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See detailTaming Android App Crashes
Kong, Pingfan UL

Doctoral thesis (2021)

App crashes constitute an important deterrence for app adoption in the android ecosystem. Yet, Android app developers are challenged by the limitation of test automation tools to ensure that released apps ... [more ▼]

App crashes constitute an important deterrence for app adoption in the android ecosystem. Yet, Android app developers are challenged by the limitation of test automation tools to ensure that released apps are free from crashes. In recent years, researchers have proposed various automation approaches in the literature. Unfortunately, the practical value of these approaches have not yet been confirmed by practitioner adoption. Furthermore, existing approaches target a variety of test needs which are relevant to different sets of problems, without being specific to app crashes. Resolving app crashes implies a chain of actions starting with their reproduction, followed by the associated fault localization, before any repair can be attempted. Each action however, is challenged by the specificity of Android. In particular, some specific mechanisms (e.g., callback methods, multiple entry points, etc.) of Android apps require Android-tailored crash-inducing bug locators. Therefore, to tame Android app crashes, practitioners are in need of automation tools that are adapted to the challenges that they pose. In this respect, a number of building blocks must be designed to deliver a comprehensive toolbox. First, the community lacks well-defined, large-scale datasets of real-world app crashes that are reproducible to enable the inference of valuable insights, and facilitate experimental validations of literature approaches. Second, although bug localization from crash information is relatively mature in the realm of Java, state-of-the-art techniques are generally ineffective for Android apps due to the specificity of the Android system. Third, given the recurrence of crashes and the substantial burden that they incur for practitioners to resolve them, there is a need for methods and techniques to accelerate fixing, for example, towards implementing Automated Program Repair (APR). Finally, the above chain of actions is for curative purposes. Indeed, this "reproduction, localization, and repair" chain aims at correcting bugs in released apps. Preventive approaches, i.e., approaches that help developers to reduce the likelihood of releasing crashing apps, are still absent. In the Android ecosystem, developers are challenged by the lack of detailed documentation about the complex Android framework API they use to develop their apps. For example, developers need support for precisely identifying which exceptions may be triggered by APIs. Such support can further alleviate the challenge related to the fact that the condition under which APIs are triggered are often not documented. In this context, the present dissertation aims to tame Android crashes by contributing to the following four building blocks: Systematic Literature Review on automated app testing approaches: We aim at providing a clear overview of the state-of-the-art works around the topic of Android app testing, in an attempt to highlight the main trends, pinpoint the main methodologies applied and enumerate the challenges faced by the Android testing approaches as well as the directions where the community effort is still needed. To this end, we conduct a Systematic Literature Review (SLR) during which we eventually identified 103 relevant research papers published in leading conferences and journals until 2016. Our thorough examination of the relevant literature has led to several findings and highlighted the challenges that Android testing researchers should strive to address in the future. After that, we further propose a few concrete research directions where testing approaches are needed to solve recurrent issues in app updates, continuous increases of app sizes, as well as the Android ecosystem fragmentation. Locating Android app crash-inducing bugs: We perform an empirical study on 500 framework-specific crashes from an open benchmark. This study reveals that 37 percent of the crash types are related to bugs that are outside the crash stack traces. Moreover, Android programs are a mixture of code and extra-code artifacts such as the Manifest file. The fact that any artifact can lead to failures in the app execution creates the need to position the localization target beyond the code realm. We propose ANCHOR, a two-phase suspicious bug location suggestion tool. ANCHOR specializes in finding crash-inducing bugs outside the stack trace. ANCHOR is lightweight and source code independent since it only requires the crash message and the apk file to locate the fault. Experimental results, collected via cross-validation and in-the-wild dataset evaluation, show that ANCHOR is effective in locating Android framework-specific crashing faults. Mining Android app crash fix templates: We propose a scalable approach, CraftDroid, to mine crash fixes by leveraging a set of 28 thousand carefully reconstructed app lineages from app markets, without the need for the app source code or issue reports. We develop a replicative testing approach that locates fixes among app versions which output different runtime logs with the exact same test inputs. Overall, we have mined 104 relevant crash fixes, further abstracted 17 fine-grained fix templates that are demonstrated to be effective for patching crashed apks. Finally, we release ReCBench, a benchmark consisting of 200 crashed apks and the crash replication scripts, which the community can explore for evaluating generated crash-inducing bug patches. Documenting framework APIs' unchecked exceptions: We propose Afuera, an automated tool that profiles Android framework APIs and provides information on when they can potentially trigger unchecked exceptions. Afuera relies on a static-analysis approach and a dedicated algorithm to examine the entire Android framework. With Afuera, we confirmed that 26739 unique unchecked exception instances may be triggered by invoking 5467 (24%) Android framework APIs. Afuera further analyzes the Android framework to inform about which parameter(s) of an API method can potentially be the cause of the triggering of an unchecked exception. To that end, Afuera relies on fully automated instrumentation and taint analysis techniques. Afuera is run to analyze 50 randomly sampled APIs to demonstrate its effectiveness.Evaluation results suggest that Afuera has perfect true positive rate. However, Afuera is affected by false negatives due to the limitation of state-of-the-art taint analysis techniques. 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See detailEnhanced Signal Space Design for Multiuser MIMO Interference Channels
Haqiqatnejad, Alireza UL

Doctoral thesis (2021)

Multiuser precoding techniques are critical to handle the co-channel interference, also known as multiuser interference (MUI), in the downlink of multiuser multi-antenna wireless systems. The convention ... [more ▼]

Multiuser precoding techniques are critical to handle the co-channel interference, also known as multiuser interference (MUI), in the downlink of multiuser multi-antenna wireless systems. The convention in designing multiuser precoding schemes has been to treat the MUI as an undesired received signal component. Consequently, the design attempts to suppress the MUI by exploiting the channel state information (CSI), regardless of the instantaneous users’ data symbols. In contrast, it has been shown that the MUI may not always be undesired or destructive as it is possible to exploit the constructive part of the interference or even converting the interfering components into constructive interference (CI) by instantaneously exploiting the users’ intended data symbols. As a result, the MUI can be transformed into a useful source of power that constructively contributes to the users’ received signals. This observation has turned the viewpoint on multiuser precoding from conventional approaches towards more sophisticated designs that further exploit the data information (DI) in addition to the CSI, referred to as symbol-level precoding (SLP). The SLP schemes can improve the multiuser system’s overall performance in terms of various metrics, such as power efficiency, symbol error rate, and received signal power. However, such improvement comes with several practical challenges, for example, the need for setting the modulation scheme in advance, increased computational complexity at the transmitter, and sensitivity to CSI and other system uncertainties. The main goal of this thesis is to address these challenges in the design of an SLP scheme. The existing design formulations for the CI-based SLP problem consider a specific signal constellation; therefore, the design needs to set the modulation scheme in advance. In this thesis, we first elaborate on optimal and relaxed approaches to exploit the CI in a novel systematic way. This study enables us to develop a generic framework for the SLP design problem, which can be used for modulation schemes with constellations of any given shape and order. Depending on the design criterion, the proposed framework can offer significant gains in the power consumption at the transmitter side or the received signal power and the symbol error rate at the receiver side without increasing the complexity, compared to the state-of-the-art schemes. Next, to address the high computational complexity issue, we simplify the design process and propose approximate yet computationally-efficient solutions performing relatively close to the optimal design. We further propose an optimized accelerated FPGA design that allows the real-time implementation of our SLP technique in high-throughput communications systems. Remarkably, the accelerated design enjoys the same per-symbol complexity order as that of the zero-forcing (ZF) precoding scheme. Next, we address the problem of robust SLP design under system uncertainties. In particular, we focus on two sources of uncertainty, namely, the channel and the design process. The related problems are tackled by adopting worst-case and stochastic design approaches and appropriately redefining the precoding optimization problem. The resulting robust schemes can effectively deal with system uncertainties while preserving reliability and power efficiency in the multiuser communications system, at the cost of a slightly increased complexity. Finally, we broaden our scope to new technologies such as millimeter wave (mmWave) communications and massive multiple-input multiple-output (MIMO) systems and revisit the SLP problem for low-cost energy-efficient transmitter architectures. The precoding design problem is more challenging particularly in such scenarios as the related hardware restrictions impose additional (often intractable) constraints on the problem. The restrictions are typically due to the use of finite-resolution analog-to-digital converters (DAC) or analog components such as switches and/or phase shifters. Two well-known design strategies are considered in this thesis, namely, quantized (finite-alphabet) precoding and hybrid analog-digital precoding. We tackle the related problems through adopting efficient design mechanisms and optimization algorithms, which are novel for the SLP schemes. The proposed techniques are shown to improve the system’s energy efficiency compared to the state-of-the-art. [less ▲]

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See detailDirection of Arrival Estimation and Localization Exploiting Sparse and One-Bit Sampling
Sedighi, Saeid UL

Doctoral thesis (2021)

In the recent years, in order to reduce implementation costs and physical resources usage, there has been a growing tendency to exploit sparse and one-bit sampling in applications such as array processing ... [more ▼]

In the recent years, in order to reduce implementation costs and physical resources usage, there has been a growing tendency to exploit sparse and one-bit sampling in applications such as array processing, radar and wireless communication. This strategy for collecting data necessitates devising new algorithms for information retrieval in such applications. This fact has motivated further research in areas such as Directional of Arrival (DoA) estimation and source/target localization in the recent years. In this context, the first part of this thesis focuses on DoA estimation using Sparse Linear Arrays (SLAs). We consider this problem under three plausible scenarios from quantization perspective. Firstly, we assume that an SLA quantized the received signal to a large number of bits per samples such that the resulting quantization error can be neglected. Although the literature presents a variety of estimators under such circumstances, none of them are (asymptotically) statistically efficient. Motivated by this fact, we introduce a novel estimator for the DoA estimation from SLA data employing the Weighted Least Squares (WLS) method. We analytically show that the large sample performance of the proposed estimator coincides with the Cram\'{e}r-Rao Bound (CRB), thereby ensuring its asymptotic statistical efficiency. Next, we study the problem of DoA estimation from one-bit SLA measurements. The analytical performance of DoA estimation from one-bit SLA measurements has not yet been studied in the literature and performance analysis in the literature has be limited to simulations studies. Therefore, we study the performance limits of DoA estimation from one-bit SLA measurements through analyzing the identifiability conditions and the corresponding CRB. We also propose a new algorithm for estimating DoAs from one-bit quantized data. We investigate the analytical performance of the proposed method through deriving a closed-form expression for the covariance matrix of its asymptotic distribution and show that it outperforms the existing algorithms in the literature. Finally, the problem of DoA estimation from low-resolution multi-bit SLA measurements, e.g. $2$ or $4$ bit per sample, is studied. We develop a novel optimization-based framework for estimating DoAs from low-resolution multi-bit measurements. It is show that increasing the sampling resolution to $2$ or $4$ bits per samples could significantly increase the DoA estimation performance compared to the one-bit sampling case while the power consumption and implementation costs are still much lower compared to the high-resolution sampling scenario. In the second part of the thesis, the problem of target localization is addressed. Firstly, we consider the problem of passive target from one-bit data in the context of Narrowband Internet-of-Things (NB-IoT). In the recently proposed narrowband IoT (NB-IoT) standard, which trades off bandwidth to gain wide area coverage, the location estimation is compounded by the low sampling rate receivers and limited-capacity links. We address both of these NB-IoT drawbacks by consider a limiting case where each node receiver employs one-bit analog-to-digital-converters and propose a novel low-complexity nodal delay estimation method. Then, to support the low-capacity links to the fusion center (FC), the range estimates obtained at individual sensors are converted to one-bit data. At the FC, we propose a novel algorithm for target localization with the aggregated one-bit range vector. Our overall one-bit framework not only complements the low NB-IoT bandwidth but also supports the design goal of inexpensive NB-IoT location sensing. Secondly, in order to reduce bandwidth usage for performing high precision time of arrival-based localization, we developed a novel sparsity-aware target localization algorithm with application to automotive radars. The thesis concludes with summarizing the main research findings and some remarks on future directions and open problems. [less ▲]

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See detailSecuring Robots: An Integrated Approach for Security Challenges adn Monitoring for the Robotic Operating System
Rivera, Sean UL

Doctoral thesis (2021)

Robotic systems are proliferating in our society due to their capacity to carry out physical tasks on behalf of human beings, with current applications in the military, industrial, agricultural, and ... [more ▼]

Robotic systems are proliferating in our society due to their capacity to carry out physical tasks on behalf of human beings, with current applications in the military, industrial, agricultural, and domestic fields. The Robotic Operating System (ROS) is the de-facto standard for the development of modular robotic systems. Manufacturing and other industries use ROS for their robots, while larger companies such as Windows and Amazon have shown interest in supporting it, with ROS systems projected to make up most robotic systems within the next five years. However, a focus on security is needed as ROS is notorious for the absence of security mechanisms, placing people in danger both physically and digitally. This dissertation presents the security shortcomings in ROS and addresses them by developing a modular, secure framework for ROS. The research focuses on three features: internal system defense, external system verification, and automated vulnerability detection. This dissertation provides an integrated approach for the security of ROS-enabled robotic systems to set a baseline for the continual development of ROS security. Internal system defense focuses on defending ROS nodes from attacks and ensuring system safety in compromise. ROS-Defender, a firewall for ROS leveraging Software Defined Networking (SDN), and ROS-FM, an extension to ROS-Defender that uses the extended Berkely Packet Filter(eBPF), are discussed. External system verification centers on when data becomes the enemy, encompassing sensor attacks, network infrastructure attacks, and inter-system attacks. In this section, the use of machine learning to address sensor attacks is demonstrated, eBPF is utilized to address network infrastructure attacks, and consensus algorithms are leveraged to mitigate inter-system attacks. Automated vulnerability detection is perhaps the most important, focusing on detecting vulnerabilities and providing immediate mitigating solutions to avoid downtime or system failure. Here, ROSploit, an automated vulnerability scanner for ROS, and DiscoFuzzer, a fuzzing system designed for robots, are discussed. ROS-Immunity combines all the components for an integrated tool that, in conjunction with Secure-ROS, provides a suite of defenses for ROS systems against malicious attackers. [less ▲]

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See detailEssai sur les fonctions de la responsabilité contractuelle : l'éclairage du débat doctrinal par la pratique judiciaire française
Boyer, Julie Marie Suzie UL

Doctoral thesis (2021)

In French law, the debate regarding the functions of contractual damages still divides legal scholars. On the one hand, an unitarian approach argues that contractual damages should only compensate the ... [more ▼]

In French law, the debate regarding the functions of contractual damages still divides legal scholars. On the one hand, an unitarian approach argues that contractual damages should only compensate the creditor for his loss (‘réparation’). On the other hand, a dual approach argues that damages should protect the creditor’s right to performance (‘exécution par équivalent’). As a result, damages are not awarded because the debtor is liable, but because the contract guaranteed the performance of an obligation. However, some scholars take a position which aims at reconciling these conflicting positions by recognising the dual function of contractual damages. At a time when the French civil Code is being remodelled, our work tackles this debate with an innovative approach. Using both a comparative and an empirical method, our research verifies the viability of the theoretical arguments. The comparative perspective seeks to highlight the shortcomings in the structure of the debate in French law. The empirical perspective is testing the proposals put forward in the scholarly literature in order to pave the way for a renewed and structured duality of functions of contractual damages. [less ▲]

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See detailMultipath Routing on Anonymous Communication Systems: Enhancing Privacy and Performance
de La Cadena Ramos, Augusto Wladimir UL

Doctoral thesis (2021)

We live in an era where mass surveillance and online tracking against civilians and organizations have reached alarming levels. This has resulted in more and more users relying on anonymous communications ... [more ▼]

We live in an era where mass surveillance and online tracking against civilians and organizations have reached alarming levels. This has resulted in more and more users relying on anonymous communications tools for their daily online activities. Nowadays, Tor is the most popular and widely deployed anonymization network, serving millions of daily users in the entire world. Tor promises to hide the identity of users (i.e., IP addresses) and prevents that external agents disclose relationships between the communicating parties. However, the benefit of privacy protection comes at the cost of severe performance loss. This performance loss degrades the user experience to such an extent that many users do not use anonymization networks and forgo the privacy protection offered. On the other hand, the popularity of Tor has captured the attention of attackers wishing to deanonymize their users. As a response, this dissertation presents a set of multipath routing techniques, both at transport and circuit level, to improve the privacy and performance offered to Tor users. To this end, we first present a comprehensive taxonomy to identify the implications of integrating multipath on each design aspect of Tor. Then, we present a novel transport design to address the existing performance unfairness of the Tor traffic.In Tor, traffic from multiple users is multiplexed in a single TCP connection between two relays. While this has positive effects on privacy, it negatively influences performance and is characterized by unfairness as TCP congestion control gives all the multiplexed Tor traffic as little of the available bandwidth as it gives to every single TCP connection that competes for the same resource. To counter this, we propose to use multipath TCP (MPTCP) to allow for better resource utilization, which, in turn, increases throughput of the Tor traffic to a fairer extend. Our evaluation in real-world settings shows that using out-of-the-box MPTCP leads to 15% performance gain. We analyze the privacy implications of MPTCP in Tor settings and discuss potential threats and mitigation strategies. Regarding privacy, in Tor, a malicious entry node can mount website fingerprinting (WFP) attacks to disclose the identities of Tor users by only observing patterns of data flows.In response to this, we propose splitting traffic over multiple entry nodes to limit the observable patterns that an adversary has access to. We demonstrate that our sophisticated splitting strategy reduces the accuracy from more than 98% to less than 16% for all state-of-the-art WFP attacks without adding any artificial delays or dummy traffic. Additionally, we show that this defense, initially designed against WFP, can also be used to mitigate end-to-end correlation attacks. The contributions presented in this thesis are orthogonal to each other and their synergy comprises a boosted system in terms of both privacy and performance. This results in a more attractive anonymization network for new and existing users, which, in turn, increases the security of all users as a result of enlarging the anonymity set. [less ▲]

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See detailLa controverse constitutionnelle grecque sur l’article 120 § 4 en période de crise. Réflexions sur la compétence controversée du peuple en tant qu’organe de l’État
Mavrouli, Roila UL

Doctoral thesis (2021)

Cette thèse s’intéresse à l’apparition des deux discours doctrinaux grecs durant la période de crise économique de 2008 visant l’(in)constitutionnalité du premier mémorandum d’austérité, suivant les ... [more ▼]

Cette thèse s’intéresse à l’apparition des deux discours doctrinaux grecs durant la période de crise économique de 2008 visant l’(in)constitutionnalité du premier mémorandum d’austérité, suivant les politiques européennes de négociation de la dette publique. Il s’agit de faire apparaître les limites entre le discours du droit, la dogmatique juridique et la science du droit tout en identifiant trois niveaux de langage. La doctrine en tant qu’activité de compréhension, d’explication, de création et de critique du droit se distingue de la connaissance du droit positif. Mais parfois par crainte qu’une vision sociologique du droit ne prive celui-ci de toute prévisibilité, la doctrine se replie sur elle-même en fondant sa « science » et par conséquent prétend à une connaissance de son objet-droit. Ainsi, il s’agit de rechercher si le discours doctrinal pro-mémorandum autant que le discours doctrinal anti-mémorandum ne seraient pas descriptifs, mais exprimeraient des valeurs et énonceraient des prescriptions. Ou bien si la doctrine ne se limitant pas à une activité de connaissance de son objet, elle interprèterait et systématiserait le droit dans son rôle créateur de source complémentaire du droit en dialogue constant avec la jurisprudence et le législateur. Ou bien encore si elle peut être caractérisée par un élément scientifique, à savoir la description critique de l’activité scientifique ou prétendument scientifique à propos du droit. À cet égard, la démarche épistémologique de cette analyse est de montrer que la science juridique, aujourd’hui confrontée à une crise du paradigme positiviste dominant, mène à penser soit la nécessité de changer les dogmes établis soit au fait que l’« anomalie » ne sera pas parvenue à infirmer la fécondité du paradigme en place. [less ▲]

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See detailHuman Motion Analysis Using 3D Skeleton Representation in The Context of Real-World Applications: From Home-Based Rehabilitation to Sensing In The Wild
Lemos Baptista, Renato Manuel UL

Doctoral thesis (2021)

Human motion analysis using 3D skeleton representations has been a very active research area in the computer vision community. The popularity of this high-level representation mainly results from the ... [more ▼]

Human motion analysis using 3D skeleton representations has been a very active research area in the computer vision community. The popularity of this high-level representation mainly results from the large variety of possible real-world applications such as video surveillance, video conferencing, human-computer interaction, virtual reality, healthcare, and sports. Despite the effectiveness of recent 3D skeleton-based approaches, their suitability to real-world scenarios still needs to be assessed. Using these approaches in a real-world scenario can give new insights on how to improve them for reaching real-world standards. In this thesis, we propose new solutions to mitigate existing constraints for the deployment of 3D skeleton-based approaches in various real-world scenarios. For that purpose, we investigate two human motion analysis applications that are based on 3D skeletons, namely, home-based rehabilitation of functional activities and human motion analysis in the wild. In the first part of this thesis, we propose a low-cost solution designed for supporting home-based rehabilitation of stroke survivors under the remote supervision of a therapist. To that end, we introduce the concept of color-based feedback proposals for guiding the patients in real-time while exercising. More specifically, color-based codes are visualized for informing the patient on the accuracy of the movement and on the adequacy of the posture. Feedback proposals are tailored to each patient's body anthropometry. An initial clinical validation shows an improvement of the posture and of the quality of motion when using the proposed feedback proposals. In the second part of this thesis, we focus on human motion analysis in the wild in the context of cross-view action recognition. We propose and investigate different 3D human pose estimation techniques from a single RGB camera in order to take advantage of 3D skeleton-based approaches. Indeed, given their 3D nature, 3D skeletons can overcome more easily the challenge of viewpoint variability in contrast to 2D-based approaches. To show the relevance of 3D pose estimation techniques in the context of human motion analysis, two different pipelines are proposed. The first pipeline makes use of a per-frame pose estimation approach. Per-frame pose estimation shows temporal inconsistency and small fluctuations in the skeleton joint locations over time. Considering this, the second framework is then based on a sequence-to-sequence pose estimation, providing, therefore, temporally consistent skeleton sequences that are more robust to sensing in the wild. These two pipelines show an improvement in recognition accuracy as compared to state-of-the-art approaches on two different well-known datasets. However, despite their relevance, 3D human pose estimation methods present some limitations. For example, their accuracy drops significantly in the presence of unseen environments or situations, eg, challenging camera locations, and outdoor conditions. For that reason, we introduce 3DBodyTex.Pose dataset, an original dataset to address the challenges of camera locations and outdoor scenarios in the context of 3D human pose estimation. Moreover, 3DBodyTex.Pose offers to the research community new possibilities for the generalization of 3D human pose estimation from monocular in-the-wild images from arbitrary camera viewpoints. [less ▲]

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See detailMining App Lineages: A Security Perspective
Gao, Jun UL

Doctoral thesis (2021)

Direct inter-app code invocation in Android apps and its evolution: The Android ecosystem offers different facilities to enable communication among app components and across apps to ensure that rich ... [more ▼]

Direct inter-app code invocation in Android apps and its evolution: The Android ecosystem offers different facilities to enable communication among app components and across apps to ensure that rich services can be composed through functionality reuse. At the heart of this system is the Inter-component communication (ICC) scheme, which has been largely studied in the literature. Less known in the community is another powerful mechanism that allows for direct inter-app code invocation which opens up for different reuse scenarios, both legitimate or malicious. In this dissertation, we expose the general workflow for this mechanism, which beyond ICCs, enables app developers to access and invoke functionalities (either entire Java classes, methods or object fields) implemented in other apps using official Android APIs. We experimentally showcase how this reuse mechanism can be leveraged to “plagiarize" supposedly-protected functionalities. Typically, we could leverage this mechanism to bypass security guards that a popular video broadcaster has placed for preventing access to its video database from outside its provided app. We further contribute with a static analysis toolkit, named DICIDer, for detecting direct inter-app code invocations in apps. An empirical analysis of the usage prevalence and evolution of this reuse mechanism is then conducted. [less ▲]

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See detailLoad bearing mechanisms of headed stud shear connections in profiled steel sheeting transverse to the beam
Vigneri, Valentino UL

Doctoral thesis (2021)

Composite steel-concrete floor solutions have become popular in the design of buildings thanks to the efficient combination of high tensile strength and ductility of steel with reinforced concrete ... [more ▼]

Composite steel-concrete floor solutions have become popular in the design of buildings thanks to the efficient combination of high tensile strength and ductility of steel with reinforced concrete elements in compression. To ensure the longitudinal shear transfer between the downstand steel beam and the concrete slab in composite beams, headed stud shear connections are generally employed with profiled steel sheeting transverse to the supporting beam. However, whilst the steel deck enhances the bending resistance of the slab, the performance of the shear connection decreases. Based on the evaluation of a large database of push-out tests carried out in the last 40 years, several design models have been proposed in the last decades to predict the resistance of studs but none of them provides safe and reliable results. This is related to the fact that the proposed design equations do not always consider appropriately the actual resistance mechanisms activated in the shear connection. Also, as the failure modes are typically observed at high displacements, no information on the resistance components at lower displacements is given. Therefore, a deep investigation on the sequence of the load bearing resistance mechanisms of headed stud shear connections was performed with the support of an experimental campaign of 21 full scale push-out tests and numerical simulations. From the analysis of the experimental results, it was seen that all the samples experienced rib punching at low displacements followed by concrete pull-out failure or stud rupture. The influence of several structural parameters was also assessed by comparing different test series. It was found that 200 mm wide recess and slab depth have a minor impact on the performance of the connection. Instead, the addition of waveform rebars increased the resistance by 26% as well as the slip capacity whereas the different position of the wire mesh did not show an important influence. To investigate specifically the behaviour of the shear connections, the distribution of the compressive stresses in the rib and the plastic hinges developed in the stud connector were evaluated by means of a validated finite element model. From the outcomes of the experimental and numerical study, three main load bearing phases were distinguished. At low displacements (Phase 1), the concrete is not damaged until the typical cone crack initiates at the edge of the rib and the stud deforms in bending. Subsequently (Phase 2), while the cracks propagate, the internal forces in the rib redistribute and the resistance is governed by the bearing stresses of the concrete in front of the connector. At large displacements (Phase 3), the front side of the concrete rib is highly damaged whereas the tension stresses in the stud increases significantly due to pulling forces. For further slips, this can lead to concrete pull-out or stud rupture as confirmed by the experimental studies. These insights were taken as a basis for the development of three respective mechanical models: cantilever model, modified strut and tie model (MSTM), and strut and tie model (STM). Whilst the first considers the system as a cantilever beam, the other two reproduce the concrete as a system of compression struts and the steel sheeting was modelled as tie elements. All the resistance functions were analytically derived in consideration of the experimental and numerical results in order to estimate the capacity of the shear connection at different displacements. As the STM focuses on the behaviour at large deformations, only the first two models were considered to predict the actual capacity of the shear connection. The design resistance of these two proposed models was finally calibrated according to the statistical procedure of EN 1990. [less ▲]

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See detailLarge Scale Parallel Simulation For Extended Discrete Element Method
Mainassara Chekaraou, Abdoul Wahid UL

Doctoral thesis (2020)

Numerical models are commonly used to simulate or model physical processes such as weather forecasts, fluid action, rocket trajectory, building designs, or biomass combustion. These simulations are ... [more ▼]

Numerical models are commonly used to simulate or model physical processes such as weather forecasts, fluid action, rocket trajectory, building designs, or biomass combustion. These simulations are immensely complex and require a hefty amount of time and computation, making it impossible to run on a standard modern laptop in a reasonable and fair period. This research work targets large-scale and parallel simulations of DEM and DEM-CFD couplings using high-performance computing techniques and optimizations. This thesis aims to analyze, contribute, and apply the DEM approach using the XDEM multi-Physics toolbox to physical processes that have been reluctant to be used due to their required computational resources and time. The first step of this work is to analyze and investigate the performance bottlenecks of the XDEM software. Therefore, the latter has been profiled and some critical parts as the contact detection were identified as the main bottlenecks of the software. A benchmark has also been set up to assess each bottleneck part’s performance using a baseline case. This step is crucial as it defines the general guidelines to follow in optimizing any application in general. A complete framework has been developed from scratch and aims to test and compare several contact detection algorithms and implementations. The framework, which also has a parallel version, has been used to select an appropriate algorithm and implementation for the XDEM software. The link-cell approach, combined with a new Verlet list concept, proved to be the best option for significantly reducing the contact detection part’s computational time. The Verlet buffer concept developed during this thesis takes the particle flow regime into account when selecting the skin margin to enhance the algorithm’s efficiency further. In order to target the high-performance computers for large-scale simulations, a full hybrid distributed-shared memory parallelization has been introduced by adding a fine-grain OpenMP implementation layer to the existing MPI approach. A shared memory parallelization allows taking full advantage of personal workstations with modern CPU architecture. On the other hand, a hybrid approach is one of the best ways to fully exploit the computing node capacities of our modern CPU clusters that mainly have a NUMA architecture. Macro-benchmarking performance analysis showed that we could entirely exploit 80% (speed-up) of 85 computing nodes representing 2380 cores on the ULHPC supercomputer. Finally, a life-size biomass combustion furnace is developed and used as an application test to demonstrate the complex and heavy cases that the XDEM software can accommodate at this time. The furnace is the combustion chamber of a 16 MW geothermal steam super-heater, partoftheEnelGreenPower"Cornia2." powerplant located in Italy. It proves that DEM, in general, and XDEM in particular, can be used for real case applications that discourage users due to their complexity and especially the time required to deliver the outcome results. [less ▲]

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See detailUnlawful Content Online: Towards A New Regulatory Framework For Online Platforms
Ullrich, Carsten UL

Doctoral thesis (2020)

The thesis reviews the online intermediary liability framework of the E-Commerce Directive (in Articles 12 - 15) along two research questions. 1) Is the current legal framework regulating content ... [more ▼]

The thesis reviews the online intermediary liability framework of the E-Commerce Directive (in Articles 12 - 15) along two research questions. 1) Is the current legal framework regulating content liability of online platforms under the ECD still adequate when it comes to combating illegal content? 2) Are there alternative models for intermediary regulation that are better suited to include internet intermediaries in the fight against illegal content? These questions were formulated against the premises that unlawful content online has been a persisting and growing problem and that the position of online intermediaries today makes enhanced responsibilities on their part necessary. The thesis undertakes to analyse the nature of the enforcement challenges in the EU when trying to engage online platforms under the current liability framework, and charts out an alternative approach to holding online platforms responsible. Chapter 3 reviews the current intermediary framework in the EU and the horizontal challenges of holding internet intermediaries liable. This is analysed against the backdrop of the proliferation of the internet and online platforms, sketched out in the preceding Chapter 2. Due to the ambiguity and outdatedness of the ECD provisions, on the one hand, and different national secondary liability traditions, on the other hand, the liability protections of online platforms have been interpreted and applied differently by EU Member States, and most importantly courts, leading to an uneven and ineffective enforcement landscape. Chapter 4 analyses sectoral provisions that cover different kinds of offences related to unlawful content and their interactions with the ECD and national legislation on intermediary liability. The thesis evaluates enforcement efforts in the areas of defamation, hate speech, terrorist content, copyright, trademarks, product safety and food safety. While none of the national (sectoral) approaches reviewed appear to be effective when trying to enlist intermediaries in the fight against unlawful content, the latter have built up powerful own private enforcement systems that have come to rival and run counter to public interests and fundamental rights. Chapter 5 introduces case studies of online enforcement in the areas of product and food safety, based on interviews conducted with market surveillance authorities in the EU. The specific enforcement system of EU product regulation poses particular challenges, but also offers some useful lessons for the eventual framework proposed in Chapter 6. This system eschews today’s liability cornerstones and the reliance of self-regulatory tools favoured by EU and national legislators so far. Instead it proposes an enhanced responsibility system, based on harmonised technical standards as used in the EU's New Approach regulatory method. Technical standards would define duty of care obligations in the guise of risk management approaches, which focus on defined (sectoral) harms that arise from the business practices of online platforms. They incorporate prospective responsibilities, such as for example safety by design for user onboarding, user empowerment, or (algorithmic) content management, as well as specific retrospective responsibilities relating to e.g. notice and takedown or content identification system. The standard can be adapted to the type of harm/violation, thus taking account of the specific fundamental rights and public interests involved on a sectoral level. [less ▲]

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See detailTaxation, Data and Destination - An Analysis of the Compatibility of a Digitalized Destination-Based Corporate Tax and a Destination-Based Cash-Flow Tax with International and EU Tax and Data Protection Law Frameworks
Sinnig, Julia Ruth UL

Doctoral thesis (2020)

The digitalized economy poses challenges and issues to traditional corporate taxation that require modifications in the way companies are taxed under international tax law. The thesis discusses two tax ... [more ▼]

The digitalized economy poses challenges and issues to traditional corporate taxation that require modifications in the way companies are taxed under international tax law. The thesis discusses two tax proposals to face some of the main issues, such as the intangibility of business assets and operations, the lack of physical presence of businesses in market jurisdictions, as well as non-taxation under both corporate income tax and value added tax in these jurisdictions. One of the tax proposals is the destination-based cash-flow tax that has been elaborated on mainly in economic literature. The other proposal has been drafted by the author and is named "digitalized destination-based corporate tax". The thesis analyzes the business and legal context in which the two taxes would operate: beyond the testing of the two model taxes against several digitalized business models, the relevant legal frameworks known in taxation and composed by double taxation conventions, EU law and WTO law are analyzed. Moreover, considering that the place of destination is determined by reference to the place of customers or users, corporate taxpayers likely need to collect and process (personal) data of these third parties in order to determine their place of tax liability. Thus, the thesis also examines potential data protection law interferences. [less ▲]

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See detailPressure Sensing with Nematic Liquid Crystal and Carbon Nanotube Networks
Murali, Meenu UL

Doctoral thesis (2020)

The study of colloidal dispersions of nanoparticles in liquid crystals (LCs) is well known. In most of the works, the particles are mixed into the LC to form suspensions with well-dispersed particles ... [more ▼]

The study of colloidal dispersions of nanoparticles in liquid crystals (LCs) is well known. In most of the works, the particles are mixed into the LC to form suspensions with well-dispersed particles. However, when nanoparticles are physically connected to form networks, the overall macroscopic properties of the ensemble are directly linked to the specific properties of the nanoparticles. Carbon nanotubes (CNTs) are excellent electrical conductors possessing extremely high aspect ratio, which results in a very low concentration threshold needed to obtain percolation. Therefore, they form conductive networks with extremely small amounts of CNTs. Another advantage of carbon nanotubes is their capability to transport large current densities without damage by electromigration, maintaining a stable resistance, and having scattering-less paths across several microns. Moreover, the electromechanical properties of CNTs make them an ideal candidate in pressure sensing technology. The doctoral thesis presented here describes two different approaches to integrate and utilise CNTs in an LC matrix. In the first case, we show that a variety of nanoparticles that are dispersed in LC can be attracted and assembled onto a LC defect line generated in a predetermined location, thereby creating a vertical interconnect of nanoparticles. The second consists of CNT sheets mechanically drawn from a CNT forest and an LC cell is then built on top, and the second consists of a template-based assembly of dispersed CNTs onto defect lines in LCs. In this case, we study the electrical and optical properties of CNT sheets in the presence and absence of liquid crystals based on their DC electrical characterization with distributed electrical contacts. Finally, we discuss how these two approaches can be used to successfully fabricate pressure-sensing devices. The pressure response in both these sensors is achieved based on the change in resistance of the CNTs, induced by the structural variations under the external applied pressure. Both the pressure sensors developed here are easy to fabricate, cost-effective, and recoverable owing to the elasticity and softness of the LC. [less ▲]

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See detailRecycling of gravel wash mud for manufacturing CO2-reduced cement
Thapa, Vishojit Bahadur UL

Doctoral thesis (2020)

The present research project “CO2REDCEM” is carried out at the Laboratory of Solid Structures (LSS) of the University of Luxembourg, in close collaboration with Luxembourgish industrial partners (Cimalux ... [more ▼]

The present research project “CO2REDCEM” is carried out at the Laboratory of Solid Structures (LSS) of the University of Luxembourg, in close collaboration with Luxembourgish industrial partners (Cimalux S.A., Carrières Feidt S.A. and Contern S.A.). This project aims at reducing the generation of CO2 emissions during cement production by minimisation of the use of cement clinker or its complete replacement by new binder compositions and concepts, containing novel material resources derived from local unused industrial waste products. Such a potential raw material is gravel wash mud (GWM), which occurs as a waste product from gravel mining. This clayey mud is collected from a sludge reservoir, located in the North West of Luxembourg. Currently, this waste product is landfilled without any further use. However, this prime material offers very promising properties, which require a thorough characterisation and verification before its revalorisation as a viable supplementary cementitious material (SCMs). Reusing or recycling of waste elements into goods has been among the greatest ambitions of our and earlier generations, and it will take a more important role in the future economy. One primary goal of this project is to replace the “end-of-life” concept of gravel wash mud by reusing it as new raw material. This endeavour will bring double benefit to environment as the waste is prevented from landfilling, and it is revalorised as a prime resource in another system.This research work shares the outcomes from the assessment of the performance of the prime material GWM within the following binder concepts and binder reaction mechanisms: • The use of gravel wash mud (GWM) powders as a precursor material for the synthesis of alkali-activated binders: A “cementless” binder is synthesised by alkaline activation of processed and calcined GWM powders. The mitigation of the CO2 emissions is achieved by the calcination process of the clayey gravel wash mud, which requires less thermal energy and thus lower energy consumption than for cement clinker production. • Substitution of Ordinary Portland Cement (OPC) by calcined GWM powders: Cement and concrete mixtures are prepared based on partial replacement of Portland cement by calcined GWM powders. This study presents the investigations on the involved reaction mechanisms (pozzolanic and cementitious hydration reactions), the optimal mixture configurations and the optimal material treatment processes. • The development of lime-Metakaolin-GWM binder concepts: Mixtures without cement are developed using GWM and other constituents, classified as industrial by-products. This research includes the mineralogical and microstructural characterisation of the constituents, the understanding of the reaction mechanism, and the optimisation of the mixtures to enhance the performance of the novel cementitious products. This thesis allowed to assess the performance of the waste product GWM as a valid pozzolanic prime material and to understand the requirements on physical, chemical and mineralogical characteristics of any potential raw material to ensure its permissibility as an alternative supplementary cementitious material (SCM). [less ▲]

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See detailDEMAND-SIDE-MANAGEMENT MIT WÄRMEPUMPEN IN LUXEMBURG - POTENZIALE UND HERAUSFORDERUNGEN DER WÄRMEPUMPENFLEXIBILITÄT FÜR DIE SYSTEMINTEGRATION DER ERNEUERBAREN ENERGIEN
Bechtel, Steffen UL

Doctoral thesis (2020)

In 2020 the European Union introduced the “Green Deal” and declared the target of climate neutrality until 2050. The necessary measures will lead to a massive roll-out of fluctuating renewable energies ... [more ▼]

In 2020 the European Union introduced the “Green Deal” and declared the target of climate neutrality until 2050. The necessary measures will lead to a massive roll-out of fluctuating renewable energies such as wind power and photovoltaic. This in turn will lead to an increasing need for flexibility in the energy system. The design of the future European internal market for electricity intends to let end-consumers actively participate by managing their consumption based on variable electricity prices and in that way contributing to the flexibility demand. For private households, these Demand-Side-Management measures target heat pumps in particular. This work analyzes the flexibility potential of heat pumps in residential buildings and addresses challenges in the Luxembourgish context. The time horizon for the evaluation is defined as 2030. The methodology presented in this work is applicable to similar regions in Europe. The research questions are investigated by the means of thermal simulation. The software TRNSYS is used for the building models and heating systems. A Model-Predictive-Control, developed in MATLAB, is sending control signals to the heat pump that are based on variable electricity tariffs. The heat extraction of the thermal energy storage tank is determined by a neural network, so that the Model-Predictive-Control in itself works without an integrated building model. The suitability of the approach is validated by the simulation results. Based on the national developments in the building stock, there is a theoretical heat pump potential of 236-353 MWel that can offer flexibility. The band with arises because of different suppositions for the yearly refurbishment rate. The technical potential is significantly lower and is determined by the developments of the national heat pump market. As the data availability for Luxemburg was insufficient, a heat market study was initiated that investigated sales numbers for the period of 2014-2018 and derived scenarios until 2030. The technical potential in conclusion amounts to 30-73 MWel. The insights of the national context are used for the design of the simulation models. The concept of Demand-Side-Management is tested with numerous simulation cases and is then evaluated on aspects of energy efficiency, profitability and load shifting. In total there are three reference buildings, one single-family and one multi-family house, each according to the energetic standard of a new construction, and one single-family house that meets the legal requirements for energetic refurbishment in Luxembourg. In order to demonstrate the influence of the heat source there are simulations with air-to-water as well as geothermal heat pumps. The analysis furthermore considers six different thermal energy storage capacities. The influence of the predictive control strategy is demonstrated by a comparison with reference cases that work with a common control. The flexible electricity tariffs are based on real market data of the EPEX-Spot Day-Ahead auction and is completed with grid fees and taxes in Luxembourg. The simulation results confirm the suitability of the Model-Predictive-Control approach without integrated building model. Air-to-water heat pumps achieve better efficiency and cost reduction than geothermal heat pumps, as they have two ways to reduce the costs: via the variable electricity tariffs and via a performance optimization of the heat pump itself. The performance optimization is the preferred choice of the control strategy if the price profile consists of mainly static components. Buildings with high insulation level show a sharper reaction to price signals than buildings with lower insulation standard. For the latter in return the absolute cost reduction potential is better as the overall energy demand is higher. With low capacity thermal energy storage, the energy efficiency and cost reduction potential are limited since the reaction to price signals immediately leads to a temperature rise in the tank counteracting the overall objective by increasing the heat pump consumption. With increasing tank capacity, this aspect improves. Nevertheless, there is a limit where the increasing heat losses of the tank compensate the positive aspects of bigger tanks. As the heating systems are usually not equipped with larger thermal energy storage tanks, there is an extra investment for the end-consumer that needs to be compensated by the cost reduction of the Demand-Side-Management. This profitability is only given for the multi-family house and the less insulated single-family house, equipped with an air-to-water heat pump and small to medium sized storage tanks. Two alternative price profiles are tested in order to demonstrate the influence of the price signals. In the first case, a higher volatility of the prices is presumed, to reflect a higher market share of renewable energies. In the second case variable grid fees are added to the volatile prices to further increase the incentive of Demand-Side-Management. In all simulation cases the cost reduction increases so that that buildings with high thermal insulation and air-to-water heat pump are profitable with medium sized thermal energy storage. At the same time a change of behavior of the predictive controller can be observed as the price signals become more attractive than the aspect of performance optimization, leading to an increased electricity consumption in comparison to the previous price profile. An overall economic potential of 22-53 MWel can be concluded. The numerous constraints for the heat pump operation lead to an implicit load management effect that is difficult to interpret. Nevertheless, there is a clear systemic benefit of Demand-Side-Management that result from the better performance of air-to-water heat pumps and the highly probable reaction to extreme price signals. The assessment of a high number of heat pumps by the grid operator in order to stabilize the electricity grid is questionable. The main counter arguments are the limited reliability considering the constraints and the low electric power compared to the e-mobility that will be the major challenge of the low voltage grids in the nearer future. Concepts, where energy providers or direct marketers assess the flexibility to optimize procurement strategies seems more interesting. In this context the profitability is the main question that cannot be verified based on the findings, except if there is added value stemming from synergy effects that were not considered in this work. In relation to the peak demand of the Luxembourgish energy system there is a relevant heat pump potential for Demand-Side-Management. In the nearer future the subject should be further investigated, keeping in mind the findings and sensitivities presented in this work. [less ▲]

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See detailRobust Real-time Sense-and-Avoid Solutions for Remotely Piloted Quadrotor UAVs in Complex Environments
Wang, Min UL

Doctoral thesis (2020)

UAV teleoperation is a demanding task: to successfully accomplish the mission without collision requires skills and experience. In real-life environments, current commercial UAVs are to a large extent ... [more ▼]

UAV teleoperation is a demanding task: to successfully accomplish the mission without collision requires skills and experience. In real-life environments, current commercial UAVs are to a large extent remotely piloted by amateur human pilots. Due to lack of teleoperation experience or skills, they often drive UAVs into collision. Therefore, in order to ensure safety of the UAV as well as its surroundings, it is necessary for the UAV to boast the capability of detecting emergency situation and acting on its own when facing imminent threat. However, the majority of UAVs currently available in the market are not equipped with such capability. To fill in the gap, in this work we present 2D LIDAR based Sense-and-Avoid solutions which are able to actively assist unskilled human operator in obstacle avoidance, so that the operator can focus on high-level decisions and global objectives in UAV applications such as search and rescue, farming etc. Specifically, with our novel 2D LIDAR based obstacle detection and tracking algorithm, perception-assistive flight control design, progressive emergency evaluation policies and optimization based and adaptive virtual cushion force field (AVCFF) based avoidance strategies, our proposed UAV teleoperation assistance systems are capable of obstacle detection and tracking, as well as automatic obstacle avoidance in complex environment where both static and dynamic objects are present. Additionally, while the optimization based solution is validated in Matlab, the AVCFF based avoidance system has been fully integrated with sensing system, perception-assistive flight controller on the basis of the Hector Quadrotor open source framework, and the effectiveness of the complete Sense-and-Avoid solution has been demonstrated and validated on a realistic simulated UAV platform in Gazebo simulations, where the UAV is operated at a high speed. [less ▲]

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See detailBoosting Automated Program Repair for Adoption By Practitioners
Koyuncu, Anil UL

Doctoral thesis (2020)

Automated program repair (APR) attracts a huge interest from research and industry as the ultimate target in automation of software maintenance. Towards realizing this automation promise, the research ... [more ▼]

Automated program repair (APR) attracts a huge interest from research and industry as the ultimate target in automation of software maintenance. Towards realizing this automation promise, the research community has explored various ideas and techniques, which are increasingly demonstrating that APR is no longer fictional. Although literature techniques constantly set new records in fixing a significant fraction of defects within well-established benchmarks, we are not aware of large-scale adoption of APR in practice. Meanwhile, open-source and commercial organizations have started to reflect on the potential of integrating some automated steps in the software development cycle. Actually, the current practice has several development settings that use a number of tools to automate and systematize various tasks such as code style checking, bug detection, and systematic patching. Our work is motivated by this fact. We advocate that systematic and empirical exploration of the current practice that leverage tools to automate debugging tasks would provide valuable insights for rethinking and boosting the APR agenda towards its acceptability by developer communities. We have identified three investigation axes in this dissertation. First, mining software repositories towards understanding code change properties that could be valuable to guide program repair. Second, analyzing communication channels in software development in order to assess to what extent they could be relevant in a real-world program repair scenario. Third, exploring generic concepts of patching in the literature for establishing a common foundation for program repair pipelines that can be integrated with industrial settings. This dissertation makes the following contributions to the community: • An empirical study of tool support in a real development setting providing concrete insights on the acceptance, stability and the nature of bugs being fixed by manually-craft patches vs tool-supported patches and manifests opportunities for improving automated repair techniques. • A novel information retrieval based bug localization approach that learns how to compute the similarity scores of various types of features. • An automated mining strategy to infer fix pattern that can be integrated to automated program repair pipelines. • A practical bug report driven program repair pipeline. [less ▲]

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See detailTertium non datur: Various aspects of value-added (VA) models used as measures of educational effectiveness
Levy, Jessica UL

Doctoral thesis (2020)

Value-added (VA) models are used as measures of educational effectiveness which aim to find the “value” that has been added by teachers or schools to students’ achievement, independent of students’ ... [more ▼]

Value-added (VA) models are used as measures of educational effectiveness which aim to find the “value” that has been added by teachers or schools to students’ achievement, independent of students’ backgrounds. Statistically speaking, teacher or school VA scores are calculated as the part of an outcome variable that cannot be explained by the covariates that are in the VA model (i.e., the residual). Teachers or schools are classified as effective (or ineffective) if they have a positive (or negative) effect on students’ achievement compared to a previously specified norm value. Although VA models have gained popularity in recent years, there is a lack of consensus concerning various aspects of VA scores. The present dissertation aims at shedding light on these aspects, including the state of the art of VA research in the international literature, covariate choice, and model selection for the estimation of VA scores. In a first step, a systematic literature review was conducted, in which 370 studies from 26 countries were classified, focusing on methodological issues (Study 1 of the present dissertation). Results indicated no consensus concerning the applied statistical model type (the majority applied a linear regression, followed by multilevel models). Concerning the covariate choice, most studies used prior achievement as a covariate, cognitive and/or motivational student data were hardly considered, and there was no consensus on the in- or exclusion of students’ background variables. Based on these findings, it was suggested that VA models are better suited to improve the quality of teaching than for accountability and decision-making purposes. Secondly, based on one of the open questions resulting from Study 1 (i.e., covariate choice), the aim of Study 2 was to systematically compare different covariate combinations in the estimation of school VA models. Based on longitudinal data from primary school students participating in the Luxembourg School Monitoring Programme in Grades 1 and 3, three covariate sets were found to be essential when calculating school VA scores with math or language achievement as dependent variables: prior language achievement, prior math achievement, and students’ sociodemographic and sociocultural background. However, the evaluation of individual schools’ effectiveness varied widely depending on the covariate set that was chosen, casting further doubt on the use of VA scores for accountability purposes. Thirdly, the aim of Study 3 was to investigate statistical model selection, as Study 1 showed no consensus on which model types are most suitable for the estimation of VA scores, with the majority of studies applying linear regression or multilevel models. These classical linear models, along with nonlinear models and different types of machine learning models were systematically compared to each other. Covariates were kept constant (based on the results from Study 2) across models. Multilevel models led to the most accurate prediction of students’ achievement. However, as school VA scores varied depending on specific model choices and as these results can be only generalized for a Luxembourgish sample, it was suggested for future research that the model selection process should be made transparent and should include different specifications in order to obtain ranges of potential VA scores. In conclusion, all three studies imply that the application of VA models for decision-making and accountability should be critically discussed and that VA scores should not be used as the only measure for accountability or high-stakes decisions. In addition, it can be concluded that VA scores are more suitable for informative purposes. Thus, the findings from the present dissertation prepare the ground for future research, where schools with stable high VA scores can be part of further investigations (both qualitatively and quantitatively) to study their pedagogical strategies and learn from them. [less ▲]

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See detailActionable knowledge for sustainability at the water-land nexus: An inquiry into governance and social learning in two river basins in Luxembourg
Hondrila, Kristina UL

Doctoral thesis (2020)

The thesis offers in-depth empirical insights into diverse factors that foster or hinder collective capacities of actors to address sustainability challenges at the water-land nexus. It focuses on how ... [more ▼]

The thesis offers in-depth empirical insights into diverse factors that foster or hinder collective capacities of actors to address sustainability challenges at the water-land nexus. It focuses on how relations, knowledge, and practices in diverse organisations and professions engaged in governance and social learning processes in the Syr and Upper Sûre river basins in Luxembourg have changed following the entering into force of the EU Water Framework Directive in 2000. Finding that contradictions in water and land systems grow while spaces for self-organisation and meaning-making shrink, the thesis raises fundamental questions concerning both dominant supply- and productivity-oriented paradigms and managerial approaches to sustainability. New approaches are needed to foster actionable knowledge, embracing interrelations between ecological and social regeneration. [less ▲]

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See detailA newform theory for Katz modular forms
Mamo, Daniel Berhanu UL

Doctoral thesis (2020)

In this thesis, a strong multiplicity one theorem for Katz modular forms is studied. We show that a cuspidal Katz eigenform which admits an irreducible Galois representation is in the level and weight old ... [more ▼]

In this thesis, a strong multiplicity one theorem for Katz modular forms is studied. We show that a cuspidal Katz eigenform which admits an irreducible Galois representation is in the level and weight old space of a uniquely associated Katz newform. We also set up multiplicity one results for Katz eigenforms which have reducible Galois representation. [less ▲]

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See detailA newform theory for Katz modular forms
Mamo, Daniel Berhanu UL

Doctoral thesis (2020)

In this thesis, a strong multiplicity one theorem for Katz modular forms is studied. We show that a cuspidal Katz eigenform which admits an irreducible Galois representation is in the level and weight old ... [more ▼]

In this thesis, a strong multiplicity one theorem for Katz modular forms is studied. We show that a cuspidal Katz eigenform which admits an irreducible Galois representation is in the level and weight old space of a uniquely associated Katz newform. We also set up multiplicity one results for Katz eigenforms which have reducible Galois representation. [less ▲]

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See detailImmersions of surfaces into SL(2,C) and into the space of geodesics of Hyperbolic space
El Emam, Christian UL

Doctoral thesis (2020)

This thesis mainly treats two developments of the classical theory of hypersurfaces inside pseudo-Riemannian space forms. The former - a joint work with Francesco Bonsante - consists in the study of ... [more ▼]

This thesis mainly treats two developments of the classical theory of hypersurfaces inside pseudo-Riemannian space forms. The former - a joint work with Francesco Bonsante - consists in the study of immersions of smooth manifolds into holomorphic Riemannian space forms of constant curvature -1 (including SL(2,C) with a multiple of its Killing form): this leads to a Gauss-Codazzi theorem, it suggests an approach to holomorphic transitioning of immersions into pseudo-Riemannian space forms, a trick to construct holomorphic maps into the PSL(2,C)-character variety, and leads to a restatement of Bers theorem. The latter - a joint work with Andrea Seppi - consists in the study of immersions of n-manifolds inside the space of geodesics of the hyperbolic (n+1)-space. We give a characterization, in terms of the para-Kahler structure of this space of geodesics, of the Riemannian immersions which turn out to be Gauss maps of equivariant immersions into the hyperbolic space. [less ▲]

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See detailvan der Waals Dispersion Interactions in Biomolecular Systems: Quantum-Mechanical Insights and Methodological Advances
Stoehr, Martin UL

Doctoral thesis (2020)

Intermolecular interactions are paramount for the stability, dynamics and response of systems across chemistry, biology and materials science. In biomolecules they govern secondary structure formation ... [more ▼]

Intermolecular interactions are paramount for the stability, dynamics and response of systems across chemistry, biology and materials science. In biomolecules they govern secondary structure formation, assembly, docking, regulation and functionality. van der Waals (vdW) dispersion contributes a crucial part to those interactions. As part of the long-range electron correlation, vdW interactions arise from Coulomb-coupled quantum-mechanical fluctuations in the instan- taneous electronic charge distribution and are thus inherently many-body in nature. Common approaches to describe biomolecular systems (i.e., classical molecular mechanics) fail to capture the full complexity of vdW dispersion by adapting a phenomenological, atom-pairwise formalism. This thesis explores beyond-pairwise vdW forces and the collectivity of intrinsic electronic behav- iors in biomolecular systems and discusses their role in the context of biomolecular processes and function. To this end, the many-body dispersion (MBD) formalism parameterized from density-functional tight-binding (DFTB) calculations is used. The investigation of simple molecular solvents with particular focus on water gives insights into the vdW energetics and electronic response properties in liquids and solvation as well as emergent behavior for coarse-grained models. A detailed study of intra-protein and protein–water vdW interactions highlights the role of many-body forces during protein folding and provides a funda- mental explanation for the previously observed “unbalanced” description and over-compaction of disordered protein states. Further analysis of the intrinsic electronic behaviors in explicitly solvated proteins indicates a long-range persistence of electron correlation through the aque- ous environment, which is discussed in the context of protein–protein interactions, long-range coordination and biomolecular regulation and allostery. Based on the example of a restriction enzyme, the potential role of many-body vdW forces and collective electronic behavior for the long-range coordination of enzymatic activity is discussed. Introducing electrodynamic quantum fluctuations into the classical picture of allostery opens up the path to a more holistic view on biomolecular regulation beyond the traditional focus on merely local structural modifications. Building on top of the MBD framework, which describes vdW dispersion within the interatomic dipole-limit, a practical extension to higher-order terms is presented. The resulting Dipole- Correlated Coulomb Singles account for multipolar as well as dispersion-polarization-like contri- butions beyond the random phase approximation by means of first-order perturbation theory over the dipole-coupled MBD state. It is shown that Dipole-Correlated Coulomb Singles become particularly relevant for relatively larger systems and can alter qualitative trends in the long-range interaction under (nano-)confinement. Bearing in mind the frequent presence of confinement in biomolecular systems due to cellular crowding, in ion channels or for interfacial water, this so-far neglected contribution is expected to have broad implications for systems of biological relevance. Ultimately, this thesis introduces a hybrid approach of DFTB and machine learning for the accu- rate description of large-scale systems on a robust, albeit approximate, quantum-mechanical level. The developed DFTB-NN rep approach combines the semi-empirical DFTB Hamiltonian with a deep tensor neural network model for localized many-body repulsive potentials. DFTB- NN rep provides an accurate description of energetic, structural and vibrational properties of a wide range of small organic molecules much superior to standard DFTB or machine learning. Overall, this thesis aims to extend the current view of complex (bio)molecular systems being governed by local, (semi-)classical interactions and develops methodological steps towards an advanced description and understanding including non-local interaction mechanisms enabled by quantum-mechanical phenomena such as long-range correlation forces arising from collective electronic fluctuations. [less ▲]

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See detailEnd-to-end Signal Processing Algorithms for Precoded Satellite Communications
Krivochiza, Jevgenij UL

Doctoral thesis (2020)

The benefits of full frequency reuse in satellite communications consist of increased spectral efficiency, physical layer security, enhanced coverage, and improved Quality of Service. This is possible due ... [more ▼]

The benefits of full frequency reuse in satellite communications consist of increased spectral efficiency, physical layer security, enhanced coverage, and improved Quality of Service. This is possible due to novel digital signal processing techniques for interference mitigation as well as signal predistortion in non-linear high-performance amplifiers. Advanced linear precoding and symbol-level precoding can jointly address the signal processing demands in the next-generation satellite communications. The real-time signal precoding increases the computational complexity handled at the gateway, thus requiring low-complexity high-performance algorithms to be developed. Additionally, extensive in-lab and field tests are required to increase the technology readiness level and industrial adaption rate. In this thesis, we focus on low-complexity precoding design and in-lab validations. We study the state-of-the-art linear and symbol-level precoding techniques and multi-user MIMO test-beds available in the literature. First, we present a novel low-complexity algorithm for sum power minimization precoding design. This technique allows to reduce transmitted power in a multi-beam satellite system and improves the quality of the received signal at user terminals. Next, we demonstrate an FPGA accelerated high-throughput precoding design. The FPGA precoding design is scalable for a different number of beams in the systems and operates in a real-time processing regime using a commercially available software defined radio platform. One of the highlights of this research is the creation of a real-time in-lab precoding test-bed. The test-bed consists of a DVB-S2X precoding enabled gateway prototype, a MIMO channel emulator, and user terminals. By using the radio frequency for transmitting and receiving the precoded signals, we can test the performance of different precoding techniques in realistic scenarios and channel impairments. We demonstrate an end-to-end symbol-level precoded real-time transmission, in which user terminals can acquire and decode the precoded signals showing an increase in performance and throughput. The in-lab validations confirm numerical results conducted alongside in this work. [less ▲]

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See detailMICROGLIA IN PARKINSON´S DISEASE: IDENTITY, HETEROGENEITY AND THEIR CONTRIBUTION TO NEURODEGENERATION
Uriarte Huarte, Oihane UL

Doctoral thesis (2020)

Parkinson´s disease (PD) is the most common movement disorder caused by dopamine deficiency owing to a loss of dopaminergic neurons within the substantia nigra (SN). So far, there is no cure available ... [more ▼]

Parkinson´s disease (PD) is the most common movement disorder caused by dopamine deficiency owing to a loss of dopaminergic neurons within the substantia nigra (SN). So far, there is no cure available, hence understanding the mechanisms by which dopaminergic neurons degenerate is essential for the development of future treatment strategies. Recently, a potential role of neuroinflammation, and especially the activation of microglial cells in PD was suggested, not being secondary to neuronal death, but rather primarily implicated in PD pathogenesis. Hence, we have ventured in to study neuroinflammation and microglia activation in the context of PD using in vivo and in vitro mouse models. Firstly, we addressed microglial heterogeneity in the healthy nigrostriatal pathway, the primary circuit affected in PD. By using single-cell RNA sequencing, we have identified four different microglial immune subsets within the midbrain and the striatum. Notably, we were able to distinguish a microglial subset with an immune alerted phenotype, which was mainly composed of microglial cells from the midbrain. The transcriptomic identity of this subset resembled partially to the one of inflammatory microglia. Additionally, in situ morphological studies, such as 3D reconstruction, revealed that microglia located within the midbrain is less complex than microglia with a striatal origin. Secondly, we studied the potential role of neuroinflammation and microglia in PD progression by using a PD-like mouse model of a-synuclein (a-syn) seeding and spreading. In this study, pre-formed fibrils (PFF) were injected into the mice striatum, and a combined neuropathological and transcriptomic analysis was performed at two time points that have distinct and increasing levels and distribution of a-syn pathology across different brain regions (13 and 90 days post-injection). Interestingly, neuropathological quantifications at 90 days post-injection uncovered that neuroinflammation and microglial reactivity are linked to neurodegeneration. However, pathology neither correlates with neurodegeneration nor with a-syn aggregation. Importantly, at 13 days post-injection, the transcriptomic analysis of the midbrain revealed the dysregulation of several inflammatory pathways and pointed to the overexpression of neurotoxic inflammatory mediators. Furthermore, at this time point, the presence of a-syn oligomers was detected in certain areas of the brain. Subsequently, we hypothesised that at early stages of PD pathogenesis, the presence of a-syn oligomeric forms induces a robust inflammatory response of microglia, which can be further associated with neurodegeneration. Thirdly, to understand if a-syn oligomers are the main inducers of microglial activation, we examined further the microglial inflammatory response to other a-syn conformations, monomers and fibrils (PFF1 and PFF2). For that, BV2 and primary microglial cells were exposed to the a-syn moieties at different concentrations and incubations times. Electron microscopy depicted some heterogeneity across the synthetic a-syn fibrils, suggesting that PFF1 and PFF2 were composed by different structures. Then, microglial reactivity to a-syn monomers and fibrils was investigated by RT-PCR, and no specific response of microglia to a-syn was encountered. Also, only one of the a-syn fibrils, the PFF1, decreased microglial phagocytic activity and reduced the expression of Il1b by microglia after LPS stimulation. Concomitant to the findings in the a-syn seeding and spreading model, we attempted to elucidate the molecular profile of microglia associated with neurodegeneration. In this particular study, RNA-sequencing was performed in isolated microglial cells in an early stage of pathology progression. In contrast with our previous results, no differences in the microglial profile were found between the PFF and the control mice. Lastly, we have investigated potential neuroprotective mechanisms associated with microglial reactivity counter-regulation. Considering previous observations that microglia express dopaminergic receptors, we investigated further whether apomorphine, a dopamine agonist with anti-oxidant properties, could govern microglial activation. The effect of apomorphine enantiomers was analysed within primary microglia cultures that were activated by exposure to mutated A53T monomeric a-syn. Herein, we demonstrated that microglial activation can be dampened by apomorphine, via the recruitment of Nrf2 to the nucleus, which results in a decreased release of proinflammatory mediators, such as TNFa or PGE2. Taken together, this study provides an additional characterisation of neuroinflammation and microglial cells in the context of PD, which ultimately contributes to a better understanding of their relationship with neurodegeneration. [less ▲]

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See detailFoundations of an Ethical Framework for AI Entities: the Ethics of Systems
Dameski, Andrej UL

Doctoral thesis (2020)

The field of AI ethics during the current and previous decade is receiving an increasing amount of attention from all involved stakeholders: the public, science, philosophy, religious organizations ... [more ▼]

The field of AI ethics during the current and previous decade is receiving an increasing amount of attention from all involved stakeholders: the public, science, philosophy, religious organizations, enterprises, governments, and various organizations. However, this field currently lacks consensus on scope, ethico-philosophical foundations, or common methodology. This thesis aims to contribute towards filling this gap by providing an answer to the two main research questions: first, what theory can explain moral scenarios in which AI entities are participants?; and second, what theory can explain the process of moral reasoning, decision and action, for AI entities in virtual, simulated and real-life moral scenarios? This thesis answers these two research questions with its two main contributions to the field of AI ethics, a substantial (ethico-philosophical) and a methodological contribution. The substantial contribution is a coherent and novel theory named Ethics of Systems Framework, as well as a possible inception of a new field of study: ethics of systems. The methodological contribution is the creation of its main methodological tool, the Ethics of Systems Interface. The second part of the research effort was focused on testing and demonstrating the capacities of the Ethics of Systems Framework and Interface in modeling and managing moral scenarios in which AI and other entities participate. Further work can focus on building on top of the foundations of the Framework provided here, increasing the scope of moral theories and simulated scenarios, improving the level of detail and parameters to reflect real-life situations, and field-testing the Framework on actual AI systems. [less ▲]

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See detailInstruction Coverage for Android App Testing and Tuning
Pilgun, Aleksandr UL

Doctoral thesis (2020)

For many people, mobile apps have already become an indispensable part of modern life. Apps entertain, educate, assist us in our daily routines and help us connect with others. However, the advanced ... [more ▼]

For many people, mobile apps have already become an indispensable part of modern life. Apps entertain, educate, assist us in our daily routines and help us connect with others. However, the advanced capabilities of modern devices running the apps and sensitive user data make mobile devices also an attractive attack target. To get access to sensitive data, adversaries tend to conceal malicious functionality in freely distributed legitimately-looking apps. The problem of low-quality and malicious apps, spreading at an enormous scale, is especially relevant for one of the biggest software repositories – Google Play. The Android apps distributed through this platform undergo a validation process by Google. However, that is insufficient to confirm their good nature. To identify dangerous apps, novel frameworks for testing and app analysis are being developed by the Android community. Code coverage is one of the most common metrics for evaluating the effectiveness of these frameworks, and it is used as an internal metric to guide code exploration in some of them. However, when analyzing apps without source code, the Android community relies mostly on method coverage since there are no reliable tools for measuring finer-grained code coverage in 3rd-party Android app testing. Another stumbling block for testing frameworks is the inability to test an app exhaustively. While code coverage measurement can indicate an improvement in testing, it is neither possible to reach 100% coverage nor to identify the maximum reachable coverage value for the app. Despite testing, the app still contains high amounts of not executed code, which makes it impossible to confirm the absence of potentially malicious code in the part of the app that has not been tested. The existing static debloating approaches aim at app size minimization rather than security and simply debloat not reachable code. However, there is currently no approach to debloat apps based on dynamic analysis information, i.e. to cut out not-executed code. In this dissertation, we solve these two problems by, first, proposing an efficient approach and a tool to measure code coverage at the instruction level, and second, a dynamic binary shrinking methodology for deleting not executed code from the app. We support our solutions by the following contributions: - An instrumentation approach to measure code coverage at the instruction level. Our technique instruments smali representation of Android bytecode to allow code coverage measurement at the finest level. - An implementation of the instrumentation approach. ACVTool is a self-contained package containing 4K lines of Python code. It is publicly available and can be integrated into different testing frameworks. - An extensive empirical evaluation that shows the high reliability and versatility of our approach. ACVTool successfully executes on 96.9% of apps from our dataset, introduces a negligible instrumentation time and runtime overheads, and its results are complaint to the results of JaCoCo (source code coverage) and Ella (method coverage) tools. - A detailed study on the influence of code coverage metric granularity on automated testing. We demonstrate the usefulness of ACVTool for automated testing techniques that rely on code coverage data in their operation. - A dynamic debloating approach based on ACVTool instruction coverage. We propose Dynamic Binary Shrinking System, a novel methodology created to shrink 3rd-party Android apps towards observed benign functionality on executed code. - An implementation of the dynamic debloating technique incorporated into the ACVCut tool. The tool demonstrates the viability of the Dynamic Shrinking System on two examples. It allows us to cut out not executed code and, thus, provide 100% instruction coverage on explored app behaviors. [less ▲]

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See detailScalable Control of Asynchronous Boolean Networks
Su, Cui UL

Doctoral thesis (2020)

Direct cell reprogramming has been garnering attention for its therapeutic potential for treating the most devastating diseases characterised by defective cells or a deficiency of certain cells. It is ... [more ▼]

Direct cell reprogramming has been garnering attention for its therapeutic potential for treating the most devastating diseases characterised by defective cells or a deficiency of certain cells. It is capable of reprogramming any kind of abundant cells in the body into the desired cells to restore functions of the diseased organ. It has shown promising benefits for clinical applications, such as cell and tissue engineering, regenerative medicine and drug discovery. A major obstacle in the application of direct cell reprogramming lies in the identification of effective reprogramming factors. Experimental approaches are usually laborious, time-consuming and enormously expensive. Mathematical modelling of biological systems paves the way to study mechanisms of biological processes and identify therapeutic targets with computational reasoning and tools. Among several modelling frameworks, Boolean networks have apparent advantages. They provide a qualitative description of biological systems and thus evade the parametrisation problem, which often occurs in quantitative models. In this thesis, we focus on the identification of reprogramming factors based on asynchronous Boolean networks. This problem is equivalent to the control of asynchronous Boolean networks: finding a subset of nodes, whose perturbations can drive the dynamics of the network from the source state (the initial cell type) to the target attractor (the desired cell type). Before diving into the control problems, we first develop a near-optimal decomposition method and use this method to improve the scalability of the decomposition-based method for attractor detection. The new decomposition-based attractor detection method can identify all the exact attractors of the network efficiently, such that we can select the proper attractors corresponding to the initial cell type and the desired cell type as the source and target attractors and predict the key nodes for the conversion. Depending on whether the source state is given or not, we can have two control problems: source-target control and target control. We develop several methods to solve the two problems using different control strategies. All the methods are implemented in our software CABEAN. Given a control problem, CABEAN can provide a rich set of realistic solutions that manipulate the dynamics in different ways, such that biologists can select suitable ones to validate with biological experiments. We believe our works can contribute to a better understanding of the regulatory mechanisms of biological processes and greatly facilitate the development of direct cell reprogramming. [less ▲]

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See detailA multifaceted formal analysis of end-to-end encrypted email protocols and cryptographic authentication enhancements
Vazquez Sandoval, Itzel UL

Doctoral thesis (2020)

Largely owing to cryptography, modern messaging tools (e.g., Signal) have reached a considerable degree of sophistication, balancing advanced security features with high usability. This has not been the ... [more ▼]

Largely owing to cryptography, modern messaging tools (e.g., Signal) have reached a considerable degree of sophistication, balancing advanced security features with high usability. This has not been the case for email, which however, remains the most pervasive and interoperable form of digital communication. As sensitive information (e.g., identification documents, bank statements, or the message in the email itself) is frequently exchanged by this means, protecting the privacy of email communications is a justified concern which has been emphasized in the last years. A great deal of effort has gone into the development of tools and techniques for providing email communications with privacy and security, requirements that were not originally considered. Yet, drawbacks across several dimensions hinder the development of a global solution that would strengthen security while maintaining the standard features that we expect from email clients. In this thesis, we present improvements to security in email communications. Relying on formal methods and cryptography, we design and assess security protocols and analysis techniques, and propose enhancements to implemented approaches for end-to-end secure email communication. In the first part, we propose a methodical process relying on code reverse engineering, which we use to abstract the specifications of two end-to-end security protocols from a secure email solution (called pEp); then, we apply symbolic verification techniques to analyze such protocols with respect to privacy and authentication properties. We also introduce a novel formal framework that enables a system's security analysis aimed at detecting flaws caused by possible discrepancies between the user's and the system's assessment of security. Security protocols, along with user perceptions and interaction traces, are modeled as transition systems; socio-technical security properties are defined as formulas in computation tree logic (CTL), which can then be verified by model checking. Finally, we propose a protocol that aims at securing a password-based authentication system designed to detect the leakage of a password database, from a code-corruption attack. In the second part, the insights gained by the analysis in Part I allow us to propose both, theoretical and practical solutions for improving security and usability aspects, primarily of email communication, but from which secure messaging solutions can benefit too. The first enhancement concerns the use of password-authenticated key exchange (PAKE) protocols for entity authentication in peer-to-peer decentralized settings, as a replacement for out-of-band channels; this brings provable security to the so far empirical process, and enables the implementation of further security and usability properties (e.g., forward secrecy, secure secret retrieval). A second idea refers to the protection of weak passwords at rest and in transit, for which we propose a scheme based on the use of a one-time-password; furthermore, we consider potential approaches for improving this scheme. The hereby presented research was conducted as part of an industrial partnership between SnT/University of Luxembourg and pEp Security S.A. [less ▲]

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See detailEmotion Regulation and Perceived Competence in Dyslexia and ADHD: Analyzing Predictors of Academic and Mental Health Outcomes in Adolescents
Battistutta, Layla UL

Doctoral thesis (2020)

Youths with dyslexia and ADHD are at risk for developing not only academic but also mental health problems. As these negative outcomes are however not found equally among all adolescents with dyslexia or ... [more ▼]

Youths with dyslexia and ADHD are at risk for developing not only academic but also mental health problems. As these negative outcomes are however not found equally among all adolescents with dyslexia or ADHD, this dissertation aimed at getting a better understanding of certain predictors and/or consequences of two mediating self-regulating mechanisms. Whereas study 1 focused on perceived competence as an important contributor to academic success or failure, studies 2, 3 and 4 analyzed the role of emotion regulation (ER) in the development of psychopathological symptoms. Study 1 showed that within a group of adolescents with dyslexia, adolescents with a late diagnosis hold lower general and academic perceived competency beliefs, with potential negative outcomes for academia. Study 2 gave a first insight into ER in dyslexia and revealed that while dyslexia might not be directly associated with ER difficulties, higher ADHD symptoms contribute to more ER difficulties not only in youths with clinical ADHD but also in youths with dyslexia. These findings were taken a step further in study 3, which showed that ER difficulties mediate the association between ADHD symptoms and further anxiety, depression and conduct disorder symptoms for youths with dyslexia, ADHD and comorbid dyslexia/ADHD. Moreover, it was demonstrated in study 4 that underlying working memory deficits, (and to a lesser extent) attentional control and inhibitory deficits are linked with ADHD symptoms, which in turn are associated with ER difficulties and further anxiety and depression symptoms. The findings are discussed within the larger context of perceived competence, ER as well as academic and psycho-social outcomes, and potential implications for the conceptualization, diagnosis, prevention and treatment of these disorders are considered. [less ▲]

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See detailJOINT DESIGN OF USER SCHEDULING AND PRECODING IN WIRELESS NETWORKS: A DC PROGRAMMING APPROACH
Bandi, Ashok UL

Doctoral thesis (2020)

These scenarios are of relevance and are already being considered in current and upcoming standards including 4G and 5G. This thesis begins by presenting the necessity of the joint design of scheduling ... [more ▼]

These scenarios are of relevance and are already being considered in current and upcoming standards including 4G and 5G. This thesis begins by presenting the necessity of the joint design of scheduling and precoding for the aforementioned scenario in detail in chapter 1. Further, the coupled nature of scheduling and precoding that prevails in many other designs is discussed. Following this, a detailed survey of the literature dealing with the joint design is presented. In chapter 2, the joint design of scheduling and precoding in the unicast scenario for multiuser MISO downlink channels for network functionality optimization considering sum-rate, Max-min SINR, and power. Thereafter, different challenges in terms of the problem formulation and subsequent reformulations for different metrics are discussed. Different algorithms, each focusing on optimizing the corresponding metric, are proposed and their performance is evaluated through numerical results. In chapter 3, the joint design of user grouping, group scheduling, user scheduling, and precoding is considered for MGMC. Differently to chapter 2, the optimization of a novel metric called multicast energy efficiency (MEE) is considered. This new paradigm for joint design in MGMC poses several additional challenges that can not be dealt with by the design in chapter 2. Therefore, towards addressing these additional challenges, a novel algorithm is proposed for MEE maximization and its efficacy is presented through simulations. In chapters 2 and 3, the joint design is considered within a given transmit slot and temporal design is not considered. In chapter 4, the joint design scheduling and precoding are considered over a block of multiple time slots for a unicast scenario. Differently to single slot design, the multi-slot joint design facilitates to address users' latency directly in terms of time slots. Noticing this, joint design across multiple slots is considered with the objective of minimizing the number of slots to serve all the users subject to users' QoS and latency constraints. Further, this multi-slot joint design problem is modeled as a structured group sparsity problem. Finally, by rendering the problem as a DC, high-quality stationary points are obtained through an efficient CCP based algorithm. In chapter 5, the joint scheduling and precoding schemes proposed in previous chapters are applied to satellite systems. Finally, The thesis concludes with the main research findings and the identification of new research challenges in chapter 6. [less ▲]

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See detailProblems in nonequilibrium fluctuations across scales: A path integral approach
Cossetto, Tommaso UL

Doctoral thesis (2020)

In this thesis we study stochastic systems evolving with Markov jump processes. In a first work we discuss different representations of the stochastic evolution: the master equation, the generalized ... [more ▼]

In this thesis we study stochastic systems evolving with Markov jump processes. In a first work we discuss different representations of the stochastic evolution: the master equation, the generalized Langevin equation, and their path integrals. The description is used to derive the generating functions for out of equilibrium observables, together with the typical approximation techniques. In a second work the path integral is used to enforce thermodynamic consistency across scales. The description of identical units with all-to-al interactions is reduced from a micro- to a meso- to a macroscopic level. A suitable scaling of the dynamics and of the thermodynamic observables allows to preserve the thermodynamical structure at the different levels. In a third work we focus on the large deviation properties of chemical networks. The path integral allows to compute the dominant trajectories that constitute macroscopic fluctuations. For bi-stable systems the existence of multiple macroscopic contributions results in a phase transition for the macroscopic current. In a fourth work we study the response of such chemical currents to external perturbations. Out of equilibrium the system can display negative differential response, a feature that offers different strategies to minimize external or internal disturbances. Finally, in a fifth work, we start from a quantum system where part of the system can be traced out to act as multiple reservoirs at different temperatures. Using the Schwinger-Keldysh contour and Green's functions we can obtain the generating function for the different parts of the hamiltonian. The statistics of thermodynamic observables is accessible even in the strong coupling regime, while the semi-classical approximation is in agreement with the classical counterpart. [less ▲]

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See detailHomomorphic encryption and multilinear maps based on the approximate-GCD problem
Lima Pereira, Hilder Vitor UL

Doctoral thesis (2020)

Cryptographic schemes are constructed on top of problems that are believed to be hard. In particular, recent advanced schemes, as homomorphic primitives and obfuscators, use the approximate greatest ... [more ▼]

Cryptographic schemes are constructed on top of problems that are believed to be hard. In particular, recent advanced schemes, as homomorphic primitives and obfuscators, use the approximate greatest common divisor (AGCD) problem, which is simple to describe and easy to implement, since it does not require complex algebraic structures nor hard-to-sample probability distributions. However, in spite of its simplicity, the AGCD problem generally yields inefficient schemes, usually with large ciphertext expansion. In this thesis, we analyze the AGCD problem and several existing variants thereof and propose a new attack on the multi-prime AGCD problem. Then, we propose two new variants: 1. The vector AGCD problem (VAGCD), in which AGCD instances are represented as vectors and randomized with a secret random matrix; 2. The polynomial randomized AGCD problem (RAGCD), that consists of representing AGCD samples as polynomials and randomizing them with a secret random polynomial. We show that these new variants cannot be easier than the original AGCD problem and that all the known attacks, when adapted to the VAGCD and the RAGCD problem, are more expensive both in terms of time and of memory, allowing us then to chose smaller parameters and to improve the efficiency of the schemes using the AGCD as the underlying problem. Thus, by combining techniques from multilinear maps and indistinguishability obfuscation with the VAGCD problem, we provide the first implementation of a N-party non-interactive key exchange resistant against all known attacks. Still aiming to show that the VAGCD problem can lead to performance improvements in cryptographic primitives, we use it to construct a homomorphic encryption scheme that can natively and efficiently operate with vectors and matrices. For instance, for 100 bits of security, we can perform a sequence of 128 homomorphic products between 128-dimensional vectors and 128x128 matrices in less than one second. We also use our scheme in two applications: homomorphic evaluation of nondeterministic finite automata and a Naïve Bayes classifier. Finally, using the RAGCD problem, we construct a new homomorphic scheme for polynomials and we propose new fast bootstrapping procedures for fully homomorphic scheme (FHE) over the integers. Therewith, we can for the first time bootstrap AGCD-based FHE schemes in less than one second in a common personal computer. For the best of our knowledge, only FHE schemes based on the LWE problem had subsecond bootstrapping procedures, while AGCD-based schemes required several seconds or even minutes to be bootstrapped. [less ▲]

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See detailAnalysis, Detection, and Prevention of Cryptographic Ransomware
Genç, Ziya Alper UL

Doctoral thesis (2020)

Cryptographic ransomware encrypts files on a computer system, thereby blocks access to victim’s data, until a ransom is paid. The quick return in revenue together with the practical difficulties in ... [more ▼]

Cryptographic ransomware encrypts files on a computer system, thereby blocks access to victim’s data, until a ransom is paid. The quick return in revenue together with the practical difficulties in accurately tracking cryptocurrencies used by victims to perform the ransom payment, have made ransomware a preferred tool for cybercriminals. In addition, exploiting zero-day vulnerabilities found in Windows Operating Systems (OSs), the most widely used OS on desktop computers, has enabled ransomware to extend its threat and have detrimental effects at world-wide level. For instance, WannaCry and NotPetya have affected almost all countries, impacted organizations, and the latter alone caused damage which costs more than $10 billion. In this thesis, we conduct a theoretical and experimental study on cryptographic ransomware. In the first part, we explore the anatomy of a ransomware, and in particular, analyze the key management strategies employed by notable families. We verify that for a long-term success, ransomware authors must acquire good random numbers to seed Key Derivation Functions (KDFs). The second part of this thesis analyzes the security of the current anti-ransomware approaches, both in academic literature and real-world systems, with the aim to anticipate how such future generations of ransomware will work, and in order to start planning on how to stop them. We argue that among them, there will be some which will try to defeat current anti-ransomware; thus, we can speculate over their working principles by studying the weak points in the strategies that six of the most advanced anti-ransomware currently implements. We support our speculations with experiments, proving at the same time that those weak points are in fact vulnerabilities and that the future ransomware that we have imagined can be effective. Next, we analyze existing decoy strategies and discuss how they are effective in countering current ransomware by defining a set of metrics to measure their robustness. To demonstrate how ransomware can identify existing deception-based detection strategies, we implement a proof-of-concept decoy-aware ransomware that successfully bypasses decoys by using a decision engine with few rules. We also discuss existing issues in decoy-based strategies and propose practical solutions to mitigate them. Finally, we look for vulnerabilities in antivirus (AV) programs which are the de facto security tool installed at computers against cryptographic ransomware. In our experiments with 29 consumer-level AVs, we discovered two critilcal vulnerabilities. The first one consists in simulating mouse events to control AVs, namely to send them mouse “clicks” to deactivate their protection. We prove that 14 out of 29 AVs can be disabled in this way, and we call this class of attacks Ghost Control. The second one consists in controlling whitelisted applications, such as Notepad, by sending them keyboard events (such as “copy-and-paste”) to perform malicious operations on behalf of the malware. We prove that the anti-ransomware protection feature of AVs can be bypassed if we use Notepad as a “puppet” to rewrite the content of protected files as a ransomware would do. Playing with the words, and recalling the cat-and-mouse game, we call this class of attacks Cut-and-Mouse. In the third part of the thesis, we propose a strategy to mitigate cryptographic ransomware attacks. Based on our insights from the first part of the thesis, we present UShallNotPass which works by controlling access to secure randomness sources, i.e., Cryptographically Secure Pseudo-Random Number Generator (CSPRNG) Appliction Programming Interfaces (APIs). We tested UShallNotPass against 524 real-world ransomware samples, and observe that UShallNotPass stops 94% of them, including WannaCry, Locky, CryptoLocker and CryptoWall. Remarkably, it also nullifies NotPetya, the offspring of the family which so far has eluded all defenses. Next, we present NoCry, which shares the same defense strategy but implements an improved architecture. We show that NoCry is more secure (with components that are not vulnerable to known attacks), more effective (with less false negatives in the class of ransomware addressed) and more efficient (with minimal false positive rate and negligible overhead). To confirm that the new architecture works as expected, we tested NoCry against a new set of 747 ransomware samples, of which, NoCry could stop 97.1%, bringing its security and technological readiness to a higher level. Finally, in the fourth part, we present the potential future of the cryptographic ransomware. We identify new possible ransomware targets inspired by the cybersecurity incidents occurred in real-world scenarios. In this respect, we described possible threats that ransomware may pose by targeting critical domains, such as the Internet of Things and the Socio-Technical systems, which will worrisomely amplify the effectiveness of ransomware attacks. Next, we looked into whether ransomware authors re-use the work of others, available at public platforms and repositories, and produce insecure code (which might enable to build decryptors). By methodically reverse-engineering malware executables, we have found that, out of 21 ransomware samples, 9 contain copy-paste code from public resources. From this fact, we recall critical cases of code disclosure in the recent history of ransomware and, reflect on the dual-use nature of this research by arguing that ransomware are components in cyber-weapons. We conclude by discussing the benefits and limits of using cyber-intelligence and counter-intelligence strategies that could be used against this threat. [less ▲]

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See detailMachine Learning Techniques for Suspicious Transaction Detection and Analysis
Camino, Ramiro Daniel UL

Doctoral thesis (2020)

Financial services must monitor their transactions to prevent being used for money laundering and combat the financing of terrorism. Initially, organizations in charge of fraud regulation were only ... [more ▼]

Financial services must monitor their transactions to prevent being used for money laundering and combat the financing of terrorism. Initially, organizations in charge of fraud regulation were only concerned about financial institutions such as banks. However, nowadays, the Fintech industry, online businesses, or platforms involving virtual assets can also be affected by similar criminal schemes. Regardless of the differences between the entities mentioned above, malicious activities affecting them share many common patterns. This dissertation's first goal is to compile and compare existing studies involving machine learning to detect and analyze suspicious transactions. The second goal is to synthesize methodologies from the last goal for tackling different use cases in an organized manner. Finally, the third goal is to assess the applicability of deep generative models for enhancing existing solutions. In the first part of the thesis, we propose an unsupervised methodology for detecting suspicious transactions applied to two case studies. One is related to transactions from a money remittance network, and the other is related to a novel payment network based on distributed ledger technologies. Anomaly detection algorithms are applied to rank user accounts based on recency, frequency, and monetary features. The results are manually validated by domain experts, confirming known scenarios and finding unexpected new cases. In the second part, we carry out an analogous analysis employing supervised methods, along with a case study where we classify Ethereum smart contracts into honeypots and non-honeypots. We take features from the source code, the transaction data, and the funds' flow characterization. The proposed classification models proved to generalize well to unseen honeypot instances and techniques and allowed us to characterize previously unknown techniques. In the third part, we analyze the challenges that tabular data brings into the domain of deep generative models, a particular type of data used to represent financial transactions in the previous two parts. We propose a new model architecture by adapting state-of-the-art methods to output multiple variables from mixed types distributions. Additionally, we extend the evaluation metrics used in the literature to the multi-output setting, and we show empirically that our approach outperforms the existing methods. Finally, in the last part, we extend the work from the third part by applying the presented models to enhance classification tasks from the second part, commonly containing a severe class imbalance. We introduce the multi-input architecture to expand models alongside our previously proposed multi-output architecture. We compare three techniques to sample from deep generative models defining a transparent and fair large-scale experimental protocol and interesting visual analysis tools. We showed that general machine learning detection and visualization techniques could help address the fraud detection domain's many challenges. In particular, deep generative models can add value to the classification task given the imbalanced nature of the fraudulent class, in exchange for implementation and time complexity. Future and promising applications for deep generative models include missing data imputation and sharing synthetic data or data generators preserving privacy constraints. [less ▲]

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See detailAN NLP-BASED FRAMEWORK TO FACILITATE THE DERIVATION OF LEGAL REQUIREMENTS FROM LEGAL TEXTS
Sleimi, Amin UL

Doctoral thesis (2020)

Information systems in several regulated domains (e.g., healthcare, taxation, labor) must comply with the applicable laws and regulations. In order to demonstrate compliance, several techniques can be ... [more ▼]

Information systems in several regulated domains (e.g., healthcare, taxation, labor) must comply with the applicable laws and regulations. In order to demonstrate compliance, several techniques can be used for assessing that such systems meet their specified legal requirements. Since requirements analysts do not have the required legal expertise, they often rely on the advisory of legal professionals. Hence, this paramount activity is expensive as it involves numerous professionals. Add to this, the communication gap between all the involved stakeholders: legal professionals, requirements analysts and software engineers. Several techniques attempt to bridge this communication gap by streamlining this process. A promising way to do so is through the automation of legal semantic metadata extraction and legal requirements elicitation from legal texts. Typically, one has to search legal texts for the relevant information for the IT system at hand, extract the legal requirements entailed by these legal statements that are pertinent to the IT system, and validate the conclusiveness and correctness of the finalized set of legal requirements. Nevertheless, the automation of legal text processing raises several challenges, especially when applied to IT systems. Existing Natural Language Processing (NLP) techniques are not built to handle the peculiarities of legal texts. On the one hand, NLP techniques are far from perfect in handling several linguistic phenomena such as anaphora, word sense disambiguation and delineating the addressee of the sentence. Add to that, the performance of these NLP techniques decreases when applied to foreign languages (other than English). On the other hand, legal text is far from being identical to the formal language used in journalism. We note that the most prominent NLP techniques are developed and tested against a selection of newspapers articles. In addition, legal text introduces cross-references and legalese that are paramount to proper legal analysis. Besides, there is still some work to be done concerning topicalization, which we need to consider for the relevance of legal statements. Existing techniques for streamlining the compliance checking of IT systems often rely on code-like artifacts with no intuitive appeal to legal professionals. Subsequently, one has no practical way to double-check with legal professionals that the elicited legal requirements are indeed correct and complete regarding the IT system at hand. Further, manually eliciting the legal requirements is an expensive, tedious and error-prone activity. The challenge is to propose a suitable knowledge representation that can be easily understood by all the involved stakeholders but at the same time remains cohesive and conclusive enough to enable the automation of legal requirements elicitation. In this dissertation, we investigate to which extent one can automate legal processing in the Requirements Engineering context. We focus exclusively on legal requirements elicitation for IT systems that have to conform to prescriptive regulations. All our technical solutions have been developed and empirically evaluated in close collaboration with a government entity. [less ▲]

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See detailDiscursive Input/Output Logic: Deontic Modals, and Computation
Farjami, Ali UL

Doctoral thesis (2020)

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See detailLearning of Control Behaviours in Flying Manipulation
Manukyan, Anush UL

Doctoral thesis (2020)

Machine learning is an ever-expanding field of research with a wide range of potential applications. It has been increasingly used in different robotics tasks enhancing their autonomy and intelligent ... [more ▼]

Machine learning is an ever-expanding field of research with a wide range of potential applications. It has been increasingly used in different robotics tasks enhancing their autonomy and intelligent behaviour. This thesis presents how machine learning techniques can enhance the decision-making ability for control tasks in aerial robots as well as amplify the safety, thus broadly improving their autonomy levels. The work starts with the development of a lightweight approach for identifying degradations of UAV hardware-related components, using traditional machine learning methods. By analysing the flight data stream from a UAV following a predefined mission, it predicts the level of degradation of components at early stages. In that context, real-world experiments have been conducted, showing that such approach can be used as a safety system during different experiments, where the flight path of the vehicle is defined a priori. The next objective of this thesis is to design intelligent control policies for flying robots with highly nonlinear dynamics, operating in continuous state-action setting, using model-free reinforcement learning methods. To achieve this objective, first, the nuances and potentials of reinforcement learning have been investigated. As a result, numerous insights and strategies have been pointed out for crafting efficient reward functions that lead to successful learning performance. Finally, a learning-based controller is provided for controlling a hexacopter UAV with 6-DoF, to perform stable navigation and hovering actions by directly mapping observations to low-level motor commands. To increase the complexity of the given objective, the degrees of freedom of the robotic platform is upgraded to 7-DoF, using a flying manipulation as learning agent. In this case, the agent learns to perform a mission composed of take-off, navigation, hovering and end-effector positioning tasks. Later, to demonstrate the effectiveness of the proposed controller and its ability to handle higher number of degrees of freedom, the flying manipulation has been extended to a robotic platform with 8-DoF. To overcome several challenges of reinforcement learning, the RotorS Gym experimental framework has been developed, providing a safe and close to real simulated environment for training multirotor systems. To handle the increasingly growing complexity of learning tasks, the Cyber Gym Robotics platform has been designed, which extends the RotorS Gym framework by several core functionalities. For instance, it offers an additional mission controller that allows to decompose complex missions into several subtasks, thus accelerating and facilitating the learning process. Yet another advantage of the Cyber Gym Robotics platform is its modularity which allows to seamlessly switch both, learning algorithms as well as agents. To validate these claims, real-world experiments have been conducted, demonstrating that the model trained in the simulation can be transferred onto a real physical robot with only minor adaptations. [less ▲]

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See detailStaging the Nation in an Intermediate Space: Cultural Policy in Luxembourg and the State Museums (1918-1974)
Spirinelli, Fabio UL

Doctoral thesis (2020)

Cultural policy has been analysed from various perspectives, ranging from sociology over cultural studies to political science. Historians have also been interested in cultural policy, but they have ... [more ▼]

Cultural policy has been analysed from various perspectives, ranging from sociology over cultural studies to political science. Historians have also been interested in cultural policy, but they have barely reflected on a theoretical framework. In addition, cultural policy has not been thoroughly researched in Luxembourg. The present thesis aims to contribute to this gap and examines how national cultural policy in Luxembourg evolved from the 1920s to the early 1970s. It investigates the presence of the national idea in cultural policy, and possible tensions and connections between the idea of the nation and the use or inclusion of foreign cultural references. Drawing on the concept of Zwischenraum (intermediate space) coined by the historian Philip Ther, the study considers Luxembourg as a nationalised intermediate space with the tensions that this status entails. Furthermore, it investigates how the State Museums, particularly the history section, evolved in the cultural policy context. To analyse the evolution of cultural policy, three interconnected aspects are considered: structures, actors and discourses. Three main periods are considered in a chronological fashion: the interwar period marked by efforts of nation-building and an increasingly interventionist state; the Nazi occupation of Luxembourg (1940-1944), when the idea of an independent nation-state was turned into its opposite; the post-war period until the early 1970s, subdivided into an immediate post-war period marked by restitution and reconstruction, and the 1950s and the 1960s characterised by a state-administrator and a conservative cultural policy. These periods, however, are not always neatly separable and reveal continuities. For each period, the State Museums are analysed in their cultural policy context: from their construction in the age of nation-building, over their ambiguous situation during Nazi occupation, to their new missions in the post-war period. [less ▲]

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See detailAnalyzing Sustainable and Emerging Cities. The Inter-American Development Bank and Spatial Transformations
Mejia Idarraga, Santiago UL

Doctoral thesis (2020)

This research analyzes the Inter-American Development Bank’s (IDB) Emerging and Sustainable Cities Initiative (ESCI) through examination of the transfer of innovation between an influential city, Medellín ... [more ▼]

This research analyzes the Inter-American Development Bank’s (IDB) Emerging and Sustainable Cities Initiative (ESCI) through examination of the transfer of innovation between an influential city, Medellín (Colombia), and a host city, Xalapa (Mexico) which participated in the ESCI. It uses categories of quality of democracy to evaluate decision-making in the regionalization process of urban transformation initiatives. The study illustrates how Medellín’s experience of social urbanism is not exportable due to particular existing conditions which are not repeated in other Latin American cities, such as Xalapa. Furthermore, this research demonstrates the existence of a dysfunctional standardized region embodied by the processes proposed by the IDB. The Inter-American Development Bank developed the Emerging and Sustainable Cities Initiative between 2012 and 2019 in 77 cities of the American continent. This initiative is influenced by Medellín, which institutionalizes a model of spatial intervention known as 'social urbanism' or 'transformation of Medellín.' The IDB exports the publicized success of the Medellín model to intermediate cities in various countries with varying results. In the case of Xalapa, Mexico, the initiative had a negative effect because it did not go beyond the implementation stage. The causes of non-execution are symptoms of a problem in the design of the regionalization strategy that fails to homogenize urban planning techniques between diverse territorialities. The objective of the research was to analyze a transfer of urban development programs between territories at the nano-level and regional institutions at the macro-level, which create a new regional integration system through urban planning projects. The analysis of the implementation of macro-regional programs in nano urban regions was carried out through a multilevel analysis and a comparative study, combining qualitative and quantitative mixed approaches in Medellín and Xalapa. Data collection included a literature review utilizing the PRISMA method, elaboration of a map of actors, and semi-structured interviews. Data was analyzed through the categories of Quality of Democracy. As a result, I developed categories extracted from the Quality of Democracy for the analysis of urban projects. The results of a triangulation of interview-type sources, a review of indicators, and press releases yielded values that show no incidence of democratic quality in decision-making processes for the implementation of regionalized projects. This opens discussions on legality, accountability, freedom, equity, and auditing in the implementation of regional initiatives. I conclude that there is a parabola of regionalization of citizen initiatives whose origin is in nano territories. This initiative is regionalized by the Inter-American Development Bank through the Emerging and Sustainable Cities Initiative, in a dysfunctional standard regionalization process. This process fails due to structural divergences in political culture, normative design, decision-making processes, and normative incoherence among the cities participating in the parabola. [less ▲]

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See detailFrom Secure to Usable and Verifiable Voting Schemes
Zollinger, Marie-Laure UL

Doctoral thesis (2020)

Elections are the foundations of democracy. To uphold democratic principles, researchers have proposed systems that ensure the integrity of elections. It is a highly interdisciplinary field, as it can be ... [more ▼]

Elections are the foundations of democracy. To uphold democratic principles, researchers have proposed systems that ensure the integrity of elections. It is a highly interdisciplinary field, as it can be studied from a technical, legal or societal points of view. While lawyers give a legal framework to the voting procedures, security researchers translate these rules into technical properties that operational voting systems must satisfy, notably privacy and verifiability. If Privacy aims to protect vote-secrecy and provide coercion-resistance to the protocol, Verifiability allows voters to check that their vote has been taken into account in the general outcome, contributing to the assurance of the integrity of the elections. To satisfy both properties in a voting system, we rely on cryptographic primitives such as encryption, signatures, commitments schemes, or zero-knowledge proofs, etc. Many protocols, paper-based or electronic-based, have been designed to satisfy these properties. Although the security of some protocols, and their limits, have been analysed from a technical perspective, the usability has often been shown to have very low rates of effectiveness. The necessary cryptographic interactions have already shown to be one contributor to this problem, but the design of the interface could also contribute by misleading voters. As elections typically rarely happen, voters must be able to understand the system they use quickly and mostly without training, which brings the user experience at the forefront of the designed protocols. In this thesis, the first contribution is to redefine privacy and verifiability in the context of tracker-based verifiable schemes. These schemes, using a so-called tracking number for individual verification, need additional user steps that must be considered in the security evaluation. These security definitions are applied to the boardroom voting protocol F2FV used by the CNRS, and the e-voting protocol Selene, both use a tracker-based procedure for individual verifiability. We provide proofs of security in the symbolic model using the Tamarin prover. The second contribution is an implementation of the Selene protocol as a mobile and a web application, tested in several user studies. The goal is to evaluate the usability and the overall user experience of the verifiability features, as well as their understanding of the system through the evaluation of mental models. The third contribution concerns the evaluation of the voters' understanding of the coercion mitigation mechanism provided by Selene, through a unique study design using game theory for the evaluation of voters. Finally, the fourth contribution is about the design of a new voting scheme, Electryo, that is based on the Selene verification mechanisms but provides a user experience close to the standard paper-based voting protocols. [less ▲]

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See detailData Analytics and Consensus Mechanisms in Blockchains
Feher, Daniel UL

Doctoral thesis (2020)

Blockchains, and especially Bitcoin have soared in popularity since their inceptions. This thesis furthers our knowledge of blockchains and their uses. First, we analyze transaction linkability in the ... [more ▼]

Blockchains, and especially Bitcoin have soared in popularity since their inceptions. This thesis furthers our knowledge of blockchains and their uses. First, we analyze transaction linkability in the privacy preserving cryptocurrency Zcash, based on the currency minting transactions (mining). Using predictable usage patterns and clustering heuristics on mining transactions, an attacker can link to publicly visible addresses in over 84% of the privacy preserving transactions. Then, we further analyze privacy issues for the privacy-oriented cryptocurrency Zcash. We study privacy preserving transactions and show ways to fingerprint user transactions, including active attacks. We introduce two new attacks, which we call the Danaan-gift attack and the Dust attack. Then, we investigate the generic landscape and hierarchy of miners as exemplified by Ethereum and Zcash. Both chains used application-specific integrated circuit (ASIC) resistant proofs-of-work which favor GPU mining in order to keep mining decentralized. This, however, has changed with the introduction of ASIC miners for these chains. This transition allows us to develop methods that might detect hidden ASIC mining in a chain (if it exists), and to study how the introduction of ASICs affects the decentralization of mining power. Finally, we describe how an attacker might use public blockchain information to invalidate miners' privacy, deducing the mining hardware of individual miners and their mining rewards. Then, we analyze the behavior of cryptocurrency exchanges on the Bitcoin blockchain, and compare the results to the exchange volumes reported by the same exchanges. We show, that in multiple cases these two values are close to each other, which confirms the integrity of their reported volumes. Finally, we present a heuristic to try to classify large clusters of addresses in the blockchain, and whether these clusters are controlled by an exchange. Finally, we describe how to couple reputation systems with distributed consensus protocols to provide a scalable permissionless consensus protocol with a low barrier of entry, while still providing strong resistance against Sybil attacks for large peer-to-peer networks of untrusted validators. We introduce the reputation module ReCon, which can be laid on top of various consensus protocols such as PBFT or HoneyBadger. The protocol takes external reputation ranking as input and then ranks nodes based on the outcomes of consensus rounds run by a small committee, and adaptively selects the committee based on the current reputation. [less ▲]

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See detailEssays on Tax Competition
Paulus, Nora UL

Doctoral thesis (2020)

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See detailAnalyzing and Improving Very Deep Neural Networks: From Optimization, Generalization to Compression
Oyedotun, Oyebade UL

Doctoral thesis (2020)

Learning-based approaches have recently become popular for various computer vision tasks such as facial expression recognition, action recognition, banknote identification, image captioning, medical image ... [more ▼]

Learning-based approaches have recently become popular for various computer vision tasks such as facial expression recognition, action recognition, banknote identification, image captioning, medical image segmentation, etc. The learning-based approach allows the constructed model to learn features, which result in high performance. Recently, the backbone of most learning-based approaches are deep neural networks (DNNs). Importantly, it is believed that increasing the depth of DNNs invariably leads to improved generalization performance. Thus, many state-of-the-art DNNs have over 30 layers of feature representations. In fact, it is not uncommon to find DNNs with over 100 layers in the literature. However, training very DNNs that have over 15 layers is not trivial. On one hand, such very DNNs generally suffer optimization problems. On the other hand, very DNNs are often overparameterized such that they overfit the training data, and hence incur generalization loss. Moreover, overparameterized DNNs are impractical for applications that require low latency, small Graphic Processing Unit (GPU) memory for operation and small memory for storage. Interestingly, skip connections of various forms have been shown to alleviate the difficulty of optimizing very DNNs. In this thesis, we propose to improve the optimization and generalization of very DNNs with and without skip connections by reformulating their training schemes. Specifically, the different modifications proposed allow the DNNs to achieve state-of-the-art results on several benchmarking datasets. The second part of the thesis presents the theoretical analyses of DNNs without and with skip connections based on several concepts from linear algebra and random matrix theory. The theoretical results obtained provide new insights into why DNNs with skip connections are easy to optimize, and generalize better than DNNs without skip connections. Ultimately, the theoretical results are shown to agree with practical DNNs via extensive experiments. The third part of the thesis addresses the problem of compressing large DNNs into smaller models. Following the identified drawbacks of the conventional group LASSO for compressing large DNNs, the debiased elastic group least absolute shrinkage and selection operator (DEGL) is employed. Furthermore, the layer-wise subspace learning (SL) of latent representations in large DNNs is proposed. The objective of SL is learning a compressed latent space for large DNNs. In addition, it is observed that SL improves the performance of LASSO, which is popularly known not to work well for compressing large DNNs. Extensive experiments are reported to validate the effectiveness of the different model compression approaches proposed in this thesis. Finally, the thesis addresses the problem of multimodal learning using DNNs, where data from different modalities are combined into useful representations for improved learning results. Different interesting multimodal learning frameworks are applied to the problems of facial expression and object recognition. We show that under the right scenarios, the complementary information from multimodal data leads to better model performance. [less ▲]

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See detailA Systems biology approach to elucidate the contribution of alpha-synuclein to early in vitro phenotypes of Parkinson’s disease
Modamio Chamarro, Jennifer UL

Doctoral thesis (2020)

Although Parkinson's disease (PD was first described more than two hundred years ago, the clinical treatment options remain limited to symptom alleviation. Consequently, understanding the underlying ... [more ▼]

Although Parkinson's disease (PD was first described more than two hundred years ago, the clinical treatment options remain limited to symptom alleviation. Consequently, understanding the underlying molecular mechanisms is vital for the development of new therapeutic strategies. Most cases of PD are associated with toxic aggregations of the alpha-synuclein (α-syn) protein. However, the physiological and pathological mechanisms of α-syn aggregation are not entirely understood. One main reason for this knowledge gap is the lack of models that properly recapitulate the pathology in a human-midbrain-like context. Organoid models have emerged as an attractive model system that covers key aspects of in vivo tissue and organ complexity. Here, we present an optimized organoid protocol, which recapitulates features of the human midbrain. These human midbrain organoids (hMOs) present reduced levels of cell death in the core, while exhibiting reduced variability and increased viability. Their smaller size also allowed the implementation of a time-efficient image analysis technique. By using the protocol mentioned above, we generated hMOs from patient-derived induced pluripotent stem cells (iPSCs harboring a triplication of the SNCA gene (3xSNCA. 3xSNCAexhibited twice the levels of α-syn protein compared to wild type (WT) hMOs. Transcriptionalanalysis of 3xSNCA hMOs showed upregulation of PD- and SNCA-associated genes, as wellas transcriptional deregulations in neurogenesis, cell death, proliferation, and synapse formation. The analysis of cellular phenotypes in patient-specific hMOs supported these genetic observations. 3xSNCA hMOs presented reduced proliferation, cell death and reduced synapse count in mature organoids. Furthermore, 3xSNCA hMOs showed a reduced total number of neurons and impaired astrocytic differentiation. In addition, analysis of transcriptional and metabolomic data showed deregulation in metabolic pathways. To further analyze and explain our results, we used the latest human metabolic reconstruction (Recon3D) to generate an in silico model. The results presented here are a systematic analysis of patient-specific phenotypes in midbrain organoids from individuals with a triplication in the SNCA gene, which represent a starting point for further approaches to develop therapies. [less ▲]

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See detailSecurity and Privacy of Blockchain Protocols and Applications
Tikhomirov, Sergei UL

Doctoral thesis (2020)

Bitcoin is the first digital currency without a trusted third party. This revolutionary protocol allows mutually distrusting participants to agree on a single common history of transactions. Bitcoin nodes ... [more ▼]

Bitcoin is the first digital currency without a trusted third party. This revolutionary protocol allows mutually distrusting participants to agree on a single common history of transactions. Bitcoin nodes pack transactions into blocks and link those in a chain (the blockchain). Hash-based proof-of-work ensures that the blockchain is computationally infeasible to modify. Bitcoin has spawned a new area of research at the intersection of computer science and economics. Multiple alternative cryptocurrencies and blockchain projects aim to address Bitcoin's limitations. This thesis explores the security and privacy of blockchain systems. In Part I, we study the privacy of Bitcoin and the major privacy-focused cryptocurrencies. In Chapter 2, we explore the peer-to-peer (P2P) protocols underpinning cryptocurrencies. In Chapter 3, we show how a network adversary can link transactions issued by the same node. We test the efficiency of this novel attack in real networks, successfully linking our own transactions. Chapter 4 studies the privacy characteristics of mobile cryptocurrency wallets. We discover that most wallets do not follow the best practices aimed at protecting users' privacy. Part II is dedicated to the Lightning Network (LN). Bitcoin's architecture emphasizes security but severely limits transaction throughput. The LN is a prominent Bitcoin-based protocol that aims to alleviate this issue. It performs low-latency transactions off-chain but leverages Bitcoin's security guarantees for dispute resolution. We introduce the LN and outline the history of off-chain protocols in Chapter 5. Then, in Chapter 6, we introduce a probing attack that allows an adversary to discover user balances in the LN. Chapter 7 estimates the likelihood of various privacy attacks on the LN. In Chapter 8, we describe a limitation on the number of concurrent LN payments and quantify its effects on transaction throughput. Part III explores the security and privacy of Ethereum smart contracts. Bitcoin's language for defining spending conditions is intentionally restricted. Ethereum is a blockchain network allowing for more programmability. Ethereum users can write programs in a Turing-complete high-level language called Solidity. These programs, called smart contracts, are stored on-chain along with their state. Chapter 9 outlines the history of blockchain-based programming. Chapter 10 describes Findel — a Solidity-based declarative domain-specific language for financial contracts. In Chapter 11, we classify the vulnerabilities in real-world Ethereum contracts. We then present SmartCheck — a static analysis tool for bug detection in Solidity programs. Finally, Chapter 12 introduces an Ethereum-based cryptographic protocol for privacy-preserving regulation compliance. [less ▲]

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See detailFor a New Hermeneutics of Practice in Digital Public History: Thinkering with memorecord.uni.lu
Lucchesi, Anita UL

Doctoral thesis (2020)

This thesis is built upon an experimental study of doing digital public history. I aim to study the digital interferences of the digital component on the historiographic operation as a whole. While the ... [more ▼]

This thesis is built upon an experimental study of doing digital public history. I aim to study the digital interferences of the digital component on the historiographic operation as a whole. While the fields of digital and public history are advancing fast with abundant work on development and application of new methodologies, tools and approaches, the discipline of history is still lagging behind in terms of theoretical reflection on the new practices emerging from it. Researchers have been exploring alternative forms of source criticism, storytelling and publications for years now, yet the greatest attention still goes to the outputs, while little criticism, if any, is devoted to the process of doing digital work. By building and analysing a digital public history platform, this research aims to make a contribution in this direction. To do so, the research takes a fully hands-on approach and offers an evaluation of digital methods that to great extent emerge from practice and the researcher’s first-hand experience with the digital. The empirical study consisted of investigating memories of Italian and Portuguese immigrants in Luxembourg through the establishment of a collaboratively shaped digital memory platform. The process of building the Memorecord platform, activating the crowdsourcing through social media and analysing the born-digital data originated from this collection informed the theoretical reflection of this thesis. While in the more practical layer, hands-on work and collaboration were highlighted, from the more speculative layer, the main theoretical contribution verse on the hybridisation of old and practices and capacities synthesized in the emergence of a hermeneutics of practice, derived from the heuristics gesture of creative and playful experimentation, (i.e. thinkering) around the digital tools and methods. This specific hermeneutical approach may function as a visibility broker, assisting historians in the process of unveiling the unspoken and implicit aspects of historical inquiry in the digital age. Hermeneutics of practice, hence, should facilitate the identification of the digital interferences we encounter throughout the research process and improve the researcher’s readiness to face the new research conditions placed by the digital component. If a new style of reasoning of/about/in/within digital and digital public history should be stabilised, hermeneutics of practice could become an important procedure to ensure historical objectivity in 21st Century. [less ▲]

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See detailLogically Centralized Security for Software-Defined Networking
Kreutz, Diego UL

Doctoral thesis (2020)

Software-Defined Networking (SDN) decouples the control and data planes of traditional networks, logically centralizing the functional properties of the network in the SDN controller. While this ... [more ▼]

Software-Defined Networking (SDN) decouples the control and data planes of traditional networks, logically centralizing the functional properties of the network in the SDN controller. While this centralization brought advantages such as a faster pace of innovation, it also disrupted some of the natural defenses of traditional architectures against different threats. Until now, SDN research has essentially been concerned with the functional side, despite some specific works relating to non-functional properties like ‘security’, ‘dependability’, or ‘quality of service’. Security is an essential non-functional property of SDN. The lack of reliable security-by-design mechanisms can quickly lead to the compromise of the entire network. For instance, most of the current security mechanisms in SDN controllers lead to exploitable vulnerabilities that allow adversaries to easily control or even shut down the entire control plane. The growing concern regarding insider threats substantially amplifies the problem. The reason lies in the fact that current Software-Defined Networks (SDNs) (e.g., OpenFlow-enabled networks) rely on weak protection mechanisms. To address these crucial security issues in the SDN control plane, it is necessary, though not sufficient, that we start by securely identifying, authenticating, and authorizing all devices before allowing them to become part of the network. Though SDN security is the central tenet of this thesis, we believe that the problem is much more generic. In essence, there is still a lack of a systematic approach to ensuring such relevant non-functional properties as security, dependability, or quality of service. Current approaches are mostly ad-hoc and piecemeal, which has led to efficiency and effectiveness problems. This reflection led us to claim that the successful enforcement of non-functional properties as a pillar of SDN robustness calls for a systematic approach. We further advocate, for its materialization, the re-iteration of the successful formula behind SDN– ‘logical centralization’. In consequence, we propose ANCHOR, a subsystem architecture for SDN that promotes the logical centralization of non-functional properties. We start by presenting the general concept and architectural principles, suggesting how they can satisfactorily enhance the current state of the art with regard to any non-functional property (security, dependability, performance, quality of service, etc.). We claim and justify that centralizing such mechanisms is vital for their effectiveness, by allowing us to: define and enforce global policies for those properties; reduce the complexity of controllers and forwarding devices; ensure higher levels of robustness for critical services; foster interoperability of the non-functional property enforcement mechanisms; and finally, better foster the resilience of the architecture itself. We focus on ‘security’ as a use case in the rest of the thesis, discussing the specialization of the ANCHOR architecture to logically-centralized enforcement of security properties. However, by presenting a principled solution to the main problem of the thesis (SDN security), we also show the effectiveness of the general ANCHOR concept, opening avenues for further research on its extension to other desirable non-functional properties, such as dependability and Quality of Service (QoS). We identify the current security gaps in SDNs, and investigate the adequate security mechanisms that should populate the architecture middleware, globally and consistently. ANCHOR sets out to provide — in a homogeneous manner to all controllers and forwarding devices — essential security mechanisms such as strong entropy, resilient pseudo-random generators, secure device registration, association and recommendation, amongst other crucial services. We present the design of those mechanisms and protocols. With the objective of promoting generalized use of encryption and authentication in the control plane, we additionally propose and describe a secure control plane communication infrastructure, Keep It Simple and Secure (KISS), based on a novel lightweight mechanism for generating cryptographic secrets — integrated Device Verification Value (iDVV). iDVV can be used in a number of ways, in a number of protocols, and outperforms widely used alternatives. In the context of this thesis, the KISS infrastructure is set up by ANCHOR and used to ensure the security of interactions amongst it, controllers and forwarding devices. Being conceptually logically-centralized, ANCHOR presents a single-point-of-failure (SPoF) challenge, which we address, through incremental measures, some of which can be selectively present in concrete designs. As a baseline, we harden the design, by endowing it with robust functions in the different modules. We increase assurance by discussing and informally proving correctness of all mechanisms and algorithms, and we also formally verify the main algorithms through a proof-assistant. By only using symmetric cryptography, we make the system Post-Quantum Secure (PQS). We also embed measures to achieve Perfect Forward Secrecy (PFS) in all algorithms, protecting pre-compromise communications in the presence of successful attacks. Finally, for higher criticality systems, we take additional algorithmic and architectural measures to mitigate the effects of possible security failures. We provide for Post-Compromise Security (PCS) through the semi-automatic restart of operation after a full compromise of ANCHOR. We present as well a design of resilience mechanisms — the continued prevention of failure/compromise by automatic means — through fail-fast recovery techniques. The prototypes’ implementation aspects and the evaluation of the two fundamental pieces of our work (ANCHOR and KISS) are performed in the respective chapters. The above-mentioned discussion and informal proof of correctness of all mechanisms and algorithms is given in appendices. We also formally machine- verified the main algorithms. [less ▲]

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See detailHilbert modular forms modulo p of partial weight one and unramifiedness of Galois representations
de Maria, Mariagiulia UL

Doctoral thesis (2020)

This thesis studies Hilbert modular forms of arbitrary weight with coefficients over a finite field of characteristic p. In particular, we compute the action on geometric q- expansions attached to these ... [more ▼]

This thesis studies Hilbert modular forms of arbitrary weight with coefficients over a finite field of characteristic p. In particular, we compute the action on geometric q- expansions attached to these forms of Hecke operators, including at places dividing p as constructed by Emerton, Reduzzi and Xiao. As an application, we prove that the Galois representation attached to a Hilbert cuspidal eigenform mod p, which has parallel weight 1 at a place P dividing p, is unramified at P. [less ▲]

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See detailMOMENT AND LONGITUDINAL RESISTANCE FOR COMPOSITE BEAMS BASED ON STRAIN LIMITED DESIGN METHOD
Zhang, Qingjie UL

Doctoral thesis (2020)

The bending and longitudinal shear design of composite beams of steel and concrete follows often the plastic design method, which is a simplification based on rectangle stress blocks. The application of ... [more ▼]

The bending and longitudinal shear design of composite beams of steel and concrete follows often the plastic design method, which is a simplification based on rectangle stress blocks. The application of the plastic design method requires cross-section to have enough rotation capacity allowing most parts of the critical cross-section reach plastic at failure. There are different types of compact composite beams, such as the slim-floor beams. For them, the neutral axis position often gets deeper at failure, which reduces the rotation capacity and brings questions to the bending resistance and longitudinal shear design according to the plastic design resistance. For a composite beam with deep neutral axis position, advanced numerical methods such as strain-limited design and FEM simulations can provide more accurate results than the plastic cross-section resistance. However, they are challenging to perform for general design engineers. In this work, simplified non-linear strain-limited design approaches, a strain-limited design software "SL.com" and an Abaqus add-in "CivilLab" have been developed to simplify the numerical calculations. They have also been applied in other chapters of this work to check the conventional plastic design results and to provide simplified design rules through parametric studies. With full shear connection, a deep neutral axis position in composite beam under sagging bending may cause an important part of the steel section not to reach plastic at concrete failure. In this case, plastic bending resistance calculated based on rectangle stress blocks can result in an overestimation of the resistance and therefore leads to unsafe design. Thus, according to EN1994-1-1 [22], a reduction factor β on plastic bending resistance (Mpl,Rd) needs to be applied for cross-sections with steel grade S420 and S460 and the relative compression zone height (zpl/h) is over 0.15. However, with the developments in industry as well as the second generation of Eurocode, this reduction factor still needs to be updated to consider new types of composite beams and wider ranges of steel grades. While the conventional plastic design method has its limitations and only applicable when the beam cross-section has enough rotation capacity to allow full plastic development, the more advanced strain-limited numerical calculation and FEM can be used for a much wider range regardless of the position of the neutral axis. The investigations in this dissertation through comparing the plastic bending resistance with advanced numerical calculation results, have confirmed that besides the cross-sections with high steel grades (S420, S460), also certain cross-sections with lower steel grades can have an overestimated plastic bending moment resistance. At least this effect is more important for compact cross-section types such as slim-floor sections or composite beams with asymmetrical structural steel profiles or with a small concrete slab effective width. Therefore vast amount of parametric studies based on strain-limited method and FEM have been developed to check the topics, such as limitation of plastic design methods for different types of composite beams. Furthermore new reduction β functions on Mpl,Rd for engineering practice considering much wider variates of composite beam cross-sections have been deviated. For the design with partial shear connection, the partial shear diagram developed based on plastic analysis has been widely used. As discussed above, the plastic design may not be suitable when the position of neutral axis is too deep, similar problems can occur for the partial shear diagram. This problem is especially significant for slim-floor beams, for which due to the compact cross-section, the relative compression zone height (zpl/h) is usually much higher than conventional composite beams. Thus the limitation of using the partial shear diagram for slim-floor beams is provided, and additional simplified engineering design rules are proposed. Plastic development inside the cross-section increases the longitudinal shear force in the plastic zones, furthermore with ductile shear connectors and respecting the minimum degree of shear connection, the non-linear redistribution of longitudinal shear force allows equal distance arrangement of shear connectors by the conventional design. For which, the full plastic development of the cross-section allowing plastic bending moment resistance and ductile shear connectors allowing non-linear longitudinal shear force distribution are the two fundamental conditions. The deep neutral axis position brings questions directly to the first assumption, as full plastic development of crosssection may not be able to reach. Thus the impact of a deep neutral axis position in the composite beams on longitudinal shear force distribution has been analysed. For which, the influence of plastic development inside beam cross-sections on longitudinal shear force with full shear interaction is theoretically explained. The different stages of nonlinear distribution of longitudinal shear force due to shear connectors are investigated through FEM parametric studies. Based on the theoretical and numerical calculation, the design suggestions of composite beams with deep neutral axis position are given. [less ▲]

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See detailThermal conductivity enhancement of graphene nanoplatelet/epoxy composites - Covalent functionalization with nitrene chemistry for reducing the interfacial thermal resistance
Depaifve, Sébastien Fabian L UL

Doctoral thesis (2020)

Polymer composites with high thermal conductivity are in strong demand for efficient thermal management in many modern applications such as electronics, batteries, aerospace structural materials, LED ... [more ▼]

Polymer composites with high thermal conductivity are in strong demand for efficient thermal management in many modern applications such as electronics, batteries, aerospace structural materials, LED lightings, etc. Nanocarbon fillers have recently attracted a lot of interest due to their extremely high intrinsic thermal conductivity. Nevertheless, the effective thermal conductivity achieved with nanocarbon-polymer composites is below the expectations. In particular, at low fillers loading due to the large interfacial thermal resistance at the nanocarbon-polymer interface. Covalent functionalization of nanocarbons has been suggested to reduce the interfacial thermal resistance in nanocarbon-polymer composites. However, large scale covalent functionalization of nanocarbons is usually achieved with harsh oxidizing conditions, causing a dramatic decrease of the intrinsic thermal conductivity of the nanocarbon fillers. In this thesis, we developed and optimized a non-disruptive covalent functionalization for graphene nanoplatelets (GNP), based on nitrene chemistry. We achieved unprecedented functionalization yields. The fillers functionalized by nitrene chemistry produced a significant thermal conductivity enhancement (TCE) compared to pristine and oxidized fillers. However, increasing the chain length or introducing heteroatoms in the functional chain afforded reduced performances. In parallel, we developed an innovative combination of SEM and µCT analyses to afford an unprecedented description of nanocarbon-polymer composites. This allowed us to elucidate the contradictory results, reported in the literature, on the influence of the aggregation level and the geometrical parameters of the fillers on the TCE. In this thesis we propose a novel and detailed description of the parameters responsible of TCE in GNP-epoxy composites. Moreover, we demonstrate that covalent functionalization of GNP by nitrene chemistry reduces the interfacial thermal resistance in epoxy composites and improves the thermal conductivity. [less ▲]

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See detailAutomated, Requirements-based Security Testing of Web-oriented Software Systems
Mai, Xuan Phu UL

Doctoral thesis (2020)

Motivation and Context. Modern Internet-based services (e.g., home-banking, personal-training, healthcare) are delivered through Web-oriented software systems which run on multiple and different devices ... [more ▼]

Motivation and Context. Modern Internet-based services (e.g., home-banking, personal-training, healthcare) are delivered through Web-oriented software systems which run on multiple and different devices including computers, mobile devices, wearable devices, and smart TVs. They manage and exchange users’ personal data such as credit reports, locations, and health status. Therefore, the security of the system and its data are of crucial importance. Unfortunately, from security requirements elicitation to security testing, there are a number of challenges to be addressed to ensure the security of Web-oriented software systems. First, existing practices for capturing security requirements do not rely on templates that ensure the specification of requirements in a precise, structured, and unambiguous manner. Second, security testing is usually performed either manually or is only partially automated. Most of existing security testing automation approaches focus only on specific vulnerabilities (e.g., buffer overflow, code injection). In addition, they suffer from the oracle problem, i.e., they cannot determine that the software does not meet its security requirements, except when it leads to denial of service or crashes. For this reason, security test automation is usually partial and only addresses the generation of inputs and not the verification of outputs. Though, in principle, solutions for the automated verification of functional requirements might be adopted to automatically verify security requirements, a number of concerns remain to be addressed. First, there is a lack of studies that demonstrate their applicability, in the context of security testing. Second, the oracle problem remains an open problem in many aspects of software testing research, not only security testing. In the context of functional testing, metamorphic testing has shown to be a viable solution to address the oracle problem; however, it has never been studied in the context of security testing. Contributions. In this dissertation, we propose a set of approaches to address the above-mentioned challenges. (1) To model security requirements in a structured and analyzable manner, we propose a use case modeling approach that relies on a restricted natural language and a template already validated in the context of functional testing. It introduces the concepts of security use case specifications (i.e., what the system is supposed to do) and misuse case specifications (i.e., malicious user behaviours that the system is supposed to prevent). Moreover, we propose a template for capturing guidelines for the mitigation of security threats. (2) To verify that systems meet their security requirements, we propose an approach to automatically generate security test cases from misuse use case specifications. More precisely, we propose a natural language programming solution that automatically generates executable security test cases and test inputs from misuse case specifications in natural language. (3) To address the oracle problem, we propose a metamorphic testing solution for Web-oriented software systems. The solution relies on a predefined set of metamorphic relations that capture (a) how an attacker likely alters a valid input to exploit a vulnerable system and (b) how the output of the system should change as a result of the attack if the system meet its security requirements. Our solution relies on Web-crawlers to automatically identify the valid inputs to be used for testing. (4) We identify a set of testability guidelines to facilitate the adoption of the proposed approaches in software projects. The identified guidelines indicate (a) which types of vulnerabilities can be addressed through the solutions proposed in this dissertation and (b) which design solutions should be integrated into the system to enable effective test automation. [less ▲]

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See detailEnergy-efficient Mobile Crowdsensing Solutions for Smart Cities
Capponi, Andrea UL

Doctoral thesis (2020)

This thesis proposes energy-efficient mobile crowdsensing (MCS) solutions for smart cities. Specifically, it focuses on sensing and communications processes in distributed computing paradigms and complex ... [more ▼]

This thesis proposes energy-efficient mobile crowdsensing (MCS) solutions for smart cities. Specifically, it focuses on sensing and communications processes in distributed computing paradigms and complex urban dynamics in city-wide scenarios. MCS is a data collection paradigm that has gained significant attention in recent years and has become appealing for urban sensing. MCS systems rely on contributions from mobile devices of a large number of participants or a crowd. Smartphones, tablets, and wearable devices are deployed widely and already equipped with a rich set of sensors, making them an excellent source of information. Mobility and intelligence of humans guarantee higher coverage and better context awareness if compared to traditional sensor networks. At the same time, individuals may be reluctant to share data for devices’ battery drain and privacy concerns. For this reason, MCS frameworks are specifically designed to include incentive mechanisms and address privacy concerns. Despite the growing interest in the research community, MCS solutions still need a more in-depth investigation and categorization on many aspects that span from sensing and communication to system management and data storage. This Ph.D. thesis focuses not only on sustainable MCS solutions to challenging problems in urban environments but also on a comprehensive study aiming to clarify concepts, aspects, and inconsistencies in existing literature from a global perspective. Specifically, this manuscript proposes the following contributions: • Present the MCS paradigm as a four-layered architecture divided into application, data, communication, and sensing layers, proposing novel taxonomies related to each layer. The detailed taxonomy aims to shed light on the current landscape, covering all MCS aspects and allowing for a simple and clear classification of applications, methodologies, and architectures. • A significant improvement of the previously developed simulation environment CrowdSenSim by implementing a set of novel features. The novelties include easy-to-use city-wide street networks, more realistic pedestrian mobility models, and real battery drain measurements over several other features. • An analysis of energy efficiency that poses the basis for sustainable MCS data collection frameworks (DCFs). It includes both a theoretical methodology to assess different DCFs and real energy measurements conducted in a laboratory, simulated in large scale urban environments. • A study that exploits crowdsensed data for a learning-driven estimation of local businesses’ attractiveness in cities to show how MCS systems can support urban planning. • A novel efficient edge data centers deployment in real urban environments based on human mobility and traffic generated from mobile devices. The citizens’ mobility is developed by feeding CrowdSenSim with crowdsensed data. [less ▲]

Detailed reference viewed: 36 (5 UL)
See detailInvestigation of condensation process inside inclined tube
Zhang, Yu UL

Doctoral thesis (2020)

Generation III+ reactor designs partially rely on passive safety systems. It aims to increase the plant safety standards and to reduce investment costs. Passive Decay Heat Removal Systems, such as the ... [more ▼]

Generation III+ reactor designs partially rely on passive safety systems. It aims to increase the plant safety standards and to reduce investment costs. Passive Decay Heat Removal Systems, such as the Emergency Condenser (EC) of the KERENA reactor design, plays an important role in the safety in nuclear power plants. As part of the emergency cooling chain, EC removes the decay heat from the reactor pressure vessel and transfers it to the flooding pool. For the successful design of the EC, the reliable prediction of the condensation heat transfer inside inclined pipes is one of the important factors. One-dimensional (1D) codes, such as ATHLET, RELAP and TRACE, are widely used today by engineers to predict the thermal hydraulic behavior of the system in nuclear power plant. However, state-of-the-art 1D codes are mainly validated for active components, and the qualification of passive systems is still a remaining problem. The goal of this thesis therefore is to investigate the condensation phenomena in EC using current advanced 1D code ATHLET (Analysis of Thermal-hydraulics of Leaks and Transients). The performance of ATHLET for prediction of condensation in slightly inclined tube was assessed and the results showed that the standard models in ATHLET code have significant deficiencies on the prediction of the condensation heat transfer coefficients. Thus, the new empirical model has been derived using experimental data from COSMEA (COndenSation test rig for flow Morphology and hEAt transfer studies) tests, condensation experiments for flow morphology and heat transfer studies in a single slightly inclined tube conducted by HZDR (Helmholtz-Zentrum Dresden-Rossendorf) and data sourced from literature. The new model was developed using Machine Learning – Regression Analysis methodology in MATLAB, which consists of upper liquid film condensation and bottom convective condensation. It was further implemented in ATHLET with Python programming language and the modified ATHLET code was used to calculate the COSMEA experiments. The post-calculation results were compared to experiments in three aspects: heat flux, condensation rate and void fraction along the whole pipe. The outcomes showed that the modified ATHLET code can be used to recalculate the relevant heat transfer values of experiments under different pressure and mass flow rate conditions. [less ▲]

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See detailESSAYS ON ASSET PRICING AND MARKET AUCTIONS
Kaiser, Gabriel UL

Doctoral thesis (2020)

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See detailDesign and Verification of Specialised Security Goals for Protocol Families
Smith, Zachary Daniel UL

Doctoral thesis (2020)

Communication Protocols form a fundamental backbone of our modern information networks. These protocols provide a framework to describe how agents - Computers, Smartphones, RFID Tags and more - should ... [more ▼]

Communication Protocols form a fundamental backbone of our modern information networks. These protocols provide a framework to describe how agents - Computers, Smartphones, RFID Tags and more - should structure their communication. As a result, the security of these protocols is implicitly trusted to protect our personal data. In 1997, Lowe presented ‘A Hierarchy of Authentication Specifications’, formalising a set of security requirements that might be expected of communication protocols. The value of these requirements is that they can be formally tested and verified against a protocol specification. This allows a user to have confidence that their communications are protected in ways that are uniformly defined and universally agreed upon. Since that time, the range of objectives and applications of real-world protocols has grown. Novel requirements - such as checking the physical distance between participants, or evolving trust assumptions of intermediate nodes on the network - mean that new attack vectors are found on a frequent basis. The challenge, then, is to define security goals which will guarantee security, even when the nature of these attacks is not known. In this thesis, a methodology for the design of security goals is created. It is used to define a collection of specialised security goals for protocols in multiple different families, by considering tailor-made models for these specific scenarios. For complex requirements, theorems are proved that simplify analysis, allowing the verification of security goals to be efficiently modelled in automated prover tools. [less ▲]

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See detailSmart Electrical and Thermal Energy Supply for Nearly Zero Energy Buildings
Rafii-Tabrizi, Sasan UL

Doctoral thesis (2020)

The European Union (EU) intends to reduce the greenhouse gas emissions to 80-95 % below 1990 levels by 2050. To achieve this goal, the EU focuses on higher energy efficiency mainly within the building ... [more ▼]

The European Union (EU) intends to reduce the greenhouse gas emissions to 80-95 % below 1990 levels by 2050. To achieve this goal, the EU focuses on higher energy efficiency mainly within the building sector and a share of renewable energy sources (RES) of around 30 % in gross final energy consumption by 2030. In this context, the concept of nearly zero-energy buildings (nZEB) is both an emerging and relevant research area. Balancing energy consumption with on-site renewable energy production in a cost-effective manner requires to develop suitable energy management systems (EMS) using demandside management strategies. This thesis develops an EMS using certainty equivalent (CE) economic model predictive control (EMPC) to optimally operate the building energy system with respect to varying electricity prices. The proposed framework is a comprehensive mixed integer linear programming model that uses suitable linearised grey box models and purely data-driven model approaches to describe the system dynamics. For this purpose, a laboratory prototype is available, which is capable of covering most building-relevant types of energy, namely thermal and electrical energy. Thermal energy for space heating, space cooling and domestic hot water is buffered in thermal energy storage systems. A dual source heat pump provides thermal energy for space heating and domestic hot water, whereas an underground ice storage covers space cooling. The environmental energy sources of the heat pump are ice storage or wind infrared sensitive collectors. The collectors are further used to regenerate the ice storage. Photovoltaic panels produce electrical energy which can be stored in a battery storage system. The electrical energy system is capable of selling and buying electricity from the public power grid. The laboratory test bench interacts with a virtual building model which is integrated into the building simulation software TRNSYS Simulation Studio. The EMS prototype is tested and validated on the basis of various simulations and under close to real-life laboratory conditions. The different test scenarios are generated using the typical day approach for each season. [less ▲]

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See detailHealth, Well-Being and Health Behavior among Immigrant Adolescents in Social Context
Kern, Matthias Robert UL

Doctoral thesis (2020)

This dissertation is guided by an overarching interest in integrating social-environmental factors into models of immigrant adolescent health, well-being and health behavior. While such ecological models ... [more ▼]

This dissertation is guided by an overarching interest in integrating social-environmental factors into models of immigrant adolescent health, well-being and health behavior. While such ecological models are enjoying increasing popularity within health research as a whole, research concerned with immigrant adolescents in particular, has, as of yet, paid only little attention to social-environmental factors. To address this gap in the literature, informed by an ecological perspective, the current dissertation focusses on the role of social-environmental factors in immigrant adolescent health, well-being and health behavior. All of the studies compiled in this dissertation seek to exemplarily illustrate the relevance of one of the investigated social contexts (school-class, receiving country, origin country) by assessing the role that particular factors pertaining to the context play for a particular health related outcome. [less ▲]

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See detailGeneralized Langevin equations and memory effects in non-equilibrium statistical physics
Meyer, Hugues UL

Doctoral thesis (2020)

The dynamics of many-body complex processes is a challenge that many scientists from various fields have to face. Reducing the complexity of systems involving a large number of bodies in order to reach a ... [more ▼]

The dynamics of many-body complex processes is a challenge that many scientists from various fields have to face. Reducing the complexity of systems involving a large number of bodies in order to reach a simple description for observables captur- ing the main features of the process is a difficult task for which different approaches have been proposed over the past decades. In this thesis we introduce new tools to describe the coarse-grained dynamics of arbitrary observables in non-equilibrium processes. Following the projection operator formalisms introduced first by Mori and Zwanzig, and later on by Grabert, we first derive a non-stationary Generalized Langevin Equation that we prove to be valid in a wide spectrum of cases. This includes in particular driven processes as well as explicitly time-dependent observ- ables. The equation exhibits a priori memory effects, controlled by a so-called non- stationary memory kernel. Because the formalism does not provide extensive infor- mation about the memory kernel in general, we introduce a set of numerical meth- ods aimed at evaluating it from Molecular Dynamics simulation data. These proce- dures range from simple dimensionless estimations of the strength of the memory to the determination of the entire kernel. Again, the methods introduced are very general and require as input a small number of quantities directly computable from numerical of experimental timeseries. We finally conclude this thesis by using the projection operator formalisms to derive an equation of motion for work and heat in dissipative processes. This is done in two different ways, either by using well-known integral fluctuation theorems, or by explicitly splitting the dynamics into adiabatic and dissipative parts. [less ▲]

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See detailPOST-COMMUNIST EUROPE AND THE THEORY OF RECOGNITION: MODERN STRUGGLES FOR RECOGNITION OF THE CROATIAN PEOPLE
Bebić, Džoen Dominique UL

Doctoral thesis (2020)

Political Philosophy has been analysing various political scenarios and governments for centuries. It is therefore very surprising that contemporary political philosophy has not contributed much to the ... [more ▼]

Political Philosophy has been analysing various political scenarios and governments for centuries. It is therefore very surprising that contemporary political philosophy has not contributed much to the analysis of the social experiences of the Croatian people during the war and events leading up to the war from 1990 to 1995 compared to other sciences. This research thus envisions to use the philosophical theory of recognition (and reification) to fulfil the extremely difficult task of analysing the social experiences and struggles for recognition of the Croatian people from the Habsburg monarchy until the end of the war of the Former Yugoslavia. As recognition as a concept was elaborated by various philosophers, this research presents different concepts of recognition developed by Rousseau, Fichte, Hegel, and Taylor while focusing on the recognition theory conceptualised by Honneth. This allows for the reconstruction of the evolution of the theory of recognition and the presentation of the interconnectedness of these different interpretations. Through the presentations of the different interpretations and the subsequent arguments and illustrations demonstrating their inadequacies to grasp the complex social experiences of the Croatian people throughout the different time periods, only Honneth’s theory of recognition can ultimately be used to capture and contextualise all the different forms of disrespect the Croatian people faced as well as the struggles for social appreciation of the Croatian culture and language and legal recognition of their right of political participation followed as a result of the deeply felt psychological consequences of the endured long-term disrespects. The extremely violent war of the Former Yugoslavia, however, falls out of what recognition theory can offer. This is where Honneth’s interpretation of Lukács reification theory comes to the fore. Using Honneth’s interpretation of reification, the different social experiences of the Croatian people during the war on the Croatian territory (1990-1992) and the territory of Bosnia-Herzegovina (1992-1995) are analysed and examined through the three forms of reification namely intersubjective reification of people, objective reification of their environment and self-reification of the perpetrators. As the relations between the Serbian and Croatian population of Croatia and Bosnia-Herzegovina remain rather tense to this day, this research also adopts Honneth’s conditions for peace and reconciliation between two states. While taking into account the valuable and important attempts of peace and reconciliation in the region, this research tries to offer an additional path of reconciliation between the Serbian and Croatian state and people in Croatia and in Bosnia-Herzegovina. A future joint research between representatives of the nations part of the Former Yugoslavia would allow for an objectification of the existentially subjective experiences of all the different nations and subsequently also offer a new path of reconciliation in the region. [less ▲]

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See detailConstant curvature surfaces and volumes of convex co-compact hyperbolic manifolds
Mazzoli, Filippo UL

Doctoral thesis (2020)

We investigate the properties of various notions of volume for convex co-compact hyperbolic 3-manifolds, and their relations with the geometry of the Teichmüller space. We prove a first-order variation ... [more ▼]

We investigate the properties of various notions of volume for convex co-compact hyperbolic 3-manifolds, and their relations with the geometry of the Teichmüller space. We prove a first-order variation formula for the dual volume of the convex core, as a function over the space of quasi-isometric deformations of a convex co-compact hyperbolic 3-manifold. For quasi-Fuchsian manifolds, we show that the dual volume of the convex core is bounded from above by a linear function of the Weil-Petersson distance between the pair of hyperbolic structures on the boundary of the convex core. We prove that, as we vary the convex co-compact structure on a fixed hyperbolic 3-manifold with incompressible boundary, the infimum of the dual volume of the convex core coincides with the infimum of the Riemannian volume of the convex core. We study various properties of the foliation by constant Gaussian curvature surfaces (k-surfaces) of convex co-compact hyperbolic 3-manifolds. We present a description of the renormalized volume of a quasi-Fuchsian manifold in terms of its foliation by k-surfaces. We show the existence of a Hamiltonian flow over the cotangent space of Teichmüller space, whose flow lines corresponds to the immersion data of the k-surfaces sitting inside a fixed hyperbolic end, and we determine a generalization of McMullen’s Kleinian reciprocity, again by means of the constant Gaussian curvature surfaces foliation. [less ▲]

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See detailBlockchain-enabled Traceability and Immutability for Financial Applications
Khan, Nida UL

Doctoral thesis (2020)

􏰔􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁The dissertation explores the efficacy of exploiting the transparency and immutability characteristics of blockchain platforms in a financial ecosystem. It elaborates on blockchain ... [more ▼]

􏰔􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁The dissertation explores the efficacy of exploiting the transparency and immutability characteristics of blockchain platforms in a financial ecosystem. It elaborates on blockchain technology employing a succinct approach, which serves as the foundation to comprehend the contributions of the present research work. The dissertation gives a verified mathematical model, derived using Nash equilibrium, to function as a framework for blockchain governance. The work elucidates the design, implementation and evaluation of a management plane to monitor and manage blockchain-based decentralized applications. The dissertation also solves the problem of data privacy by the development and evaluation of a management plane for differential privacy preservation through smart contracts. Further, the research work discusses the compliance of the privacy management plane to GDPR using a permissioned blockchain platform. The dissertation is a pioneer in conducting an implementation-based, comparative and an exploratory analysis of tokenization of ethical investment certificates. The dissertation also verifies the utility of blockchain to solve some prevalent issues in social finance. It accomplishes this through the development and testing of a blockchain-based donation application. A qualitative review of the economic impact of blockchain-based micropayments has also been conducted. The discussion on the economic impact also includes a proposition for extending the access of blockchain-based financial services to the underbanked and unbanked people. The work concludes with a hypothetical model of a financial ecosystem, depicting the deployment of the major contributions of this dissertation. 􏰃􏰝􏰃􏰄􏰧􏰁􏰈􏰧􏰨 􏰞􏰇􏰉􏰈􏰏􏰆􏰅􏰁􏰇􏰈􏰆􏰕􏰨 􏰏􏰁􏰂􏰄􏰉􏰊􏰅􏰁􏰋􏰃 􏰅􏰃􏰖􏰓􏰈􏰇􏰕􏰇􏰧􏰛 􏰩􏰁􏰅􏰓 􏰅􏰓􏰃 􏰊􏰇􏰅􏰃􏰈􏰅􏰁􏰆􏰕 􏰅􏰇 􏰖􏰇􏰝􏰊􏰕􏰃􏰅􏰃􏰕􏰛 􏰇􏰋􏰃􏰄􏰓􏰆􏰉􏰕 􏰅􏰓􏰃 􏰃􏰪􏰁􏰂􏰅􏰁􏰈􏰧 􏰫􏰈􏰆􏰈􏰖􏰁􏰆􏰕 􏰁􏰈􏰞􏰄􏰆􏰂􏰅􏰄􏰉􏰖􏰅􏰉􏰄􏰃􏰍 􏰚􏰓􏰃 􏰫􏰈􏰆􏰈􏰖􏰃 􏰂􏰃􏰖􏰅􏰇􏰄 􏰁􏰂 􏰕􏰃􏰆􏰏􏰁􏰈􏰧 􏰁􏰈 􏰅􏰓􏰃 􏰏􏰃􏰊􏰕􏰇􏰛􏰝􏰃􏰈􏰅 􏰇􏰞 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰅􏰇 􏰄􏰃􏰂􏰇􏰕􏰋􏰃 􏰃􏰈􏰏􏰃􏰝􏰁􏰖 􏰁􏰂􏰂􏰉􏰃􏰂 􏰄􏰃􏰕􏰆􏰅􏰃􏰏 􏰅􏰇 􏰅􏰄􏰆􏰈􏰂􏰊􏰆􏰄􏰃􏰈􏰖􏰛􏰨 􏰅􏰓􏰁􏰄􏰏􏰘􏰊􏰆􏰄􏰅􏰛 􏰞􏰄􏰆􏰉􏰏 􏰆􏰂 􏰩􏰃􏰕􏰕 􏰆􏰂 􏰅􏰁􏰝􏰃􏰘 􏰖􏰇􏰈􏰂􏰉􏰝􏰁􏰈􏰧 􏰆􏰈􏰏 􏰃􏰪􏰊􏰃􏰈􏰂􏰁􏰋􏰃 􏰅􏰄􏰆􏰈􏰂􏰆􏰖􏰅􏰁􏰇􏰈􏰂􏰍 􏰚􏰓􏰃 􏰫􏰈􏰆􏰈􏰖􏰃 􏰂􏰃􏰖􏰅􏰇􏰄 􏰓􏰆􏰂 􏰈􏰇􏰅 􏰙􏰃􏰃􏰈 􏰆􏰙􏰕􏰃 􏰅􏰇 􏰂􏰃􏰄􏰋􏰃 􏰅􏰓􏰃 􏰉􏰈􏰏􏰃􏰄􏰙􏰆􏰈􏰗􏰃􏰏 􏰆􏰈􏰏 􏰉􏰈􏰙􏰆􏰈􏰗􏰃􏰏 􏰊􏰇􏰊􏰉􏰕􏰆􏰅􏰁􏰇􏰈􏰂 􏰇􏰞 􏰅􏰓􏰃 􏰩􏰇􏰄􏰕􏰏 􏰂􏰇 􏰞􏰆􏰄􏰍 􏰬􏰭􏰮􏰜􏰀􏰘􏰯􏰰 􏰁􏰈 􏰱􏰲􏰱􏰲 􏰓􏰆􏰂 􏰁􏰈􏰏􏰁􏰖􏰆􏰅􏰃􏰏 􏰅􏰓􏰆􏰅 􏰆 􏰂􏰅􏰄􏰇􏰈􏰧 􏰏􏰁􏰧􏰁􏰅􏰆􏰕 􏰁􏰈􏰞􏰄􏰆􏰂􏰅􏰄􏰉􏰖􏰅􏰉􏰄􏰃 􏰁􏰂 􏰈􏰃􏰃􏰏􏰃􏰏 􏰅􏰇 􏰙􏰃 􏰆􏰙􏰕􏰃 􏰅􏰇 􏰏􏰃􏰆􏰕 􏰙􏰃􏰅􏰅􏰃􏰄 􏰩􏰁􏰅􏰓 􏰏􏰁􏰂􏰄􏰉􏰊􏰅􏰁􏰇􏰈 􏰆􏰈􏰏 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰖􏰆􏰈 􏰊􏰕􏰆􏰛 􏰆 􏰊􏰁􏰋􏰇􏰅􏰆􏰕 􏰄􏰇􏰕􏰃 􏰁􏰈 􏰃􏰂􏰅􏰆􏰙􏰕􏰁􏰂􏰓􏰁􏰈􏰧 􏰅􏰓􏰁􏰂 􏰏􏰁􏰧􏰁􏰅􏰆􏰕 􏰁􏰈􏰞􏰄􏰆􏰂􏰅􏰄􏰉􏰖􏰅􏰉􏰄􏰃􏰍 􏰚􏰓􏰃 􏰏􏰁􏰂􏰂􏰃􏰄􏰅􏰆􏰅􏰁􏰇􏰈 􏰃􏰪􏰊􏰕􏰇􏰄􏰃􏰂 􏰅􏰓􏰃 􏰃􏰳􏰖􏰆􏰖􏰛 􏰇􏰞 􏰃􏰪􏰊􏰕􏰇􏰁􏰅􏰁􏰈􏰧 􏰅􏰓􏰃 􏰅􏰄􏰆􏰈􏰂􏰊􏰆􏰄􏰃􏰈􏰖􏰛 􏰆􏰈􏰏 􏰁􏰝􏰝􏰉􏰅􏰆􏰙􏰁􏰕􏰁􏰅􏰛 􏰖􏰓􏰆􏰄􏰆􏰖􏰅􏰃􏰄􏰁􏰂􏰅􏰁􏰖􏰂 􏰇􏰞 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰊􏰕􏰆􏰅􏰞􏰇􏰄􏰝􏰂 􏰁􏰈 􏰆 􏰫􏰈􏰆􏰈􏰖􏰁􏰆􏰕 􏰃􏰖􏰇􏰂􏰛􏰂􏰅􏰃􏰝􏰍 􏰚􏰓􏰃 􏰏􏰁􏰂􏰂􏰃􏰄􏰅􏰆􏰅􏰁􏰇􏰈 􏰃􏰕􏰆􏰙􏰇􏰄􏰆􏰅􏰃􏰂 􏰇􏰈 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰅􏰃􏰖􏰓􏰈􏰇􏰕􏰇􏰧􏰛 􏰃􏰝􏰊􏰕􏰇􏰛􏰁􏰈􏰧 􏰆 􏰂􏰉􏰖􏰖􏰁􏰈􏰖􏰅 􏰆􏰊􏰊􏰄􏰇􏰆􏰖􏰓􏰨 􏰩􏰓􏰁􏰖􏰓 􏰂􏰃􏰄􏰋􏰃􏰂 􏰆􏰂 􏰅􏰓􏰃 􏰞􏰇􏰉􏰈􏰏􏰆􏰅􏰁􏰇􏰈 􏰅􏰇 􏰖􏰇􏰝􏰊􏰄􏰃􏰓􏰃􏰈􏰏 􏰅􏰓􏰃 􏰖􏰇􏰈􏰅􏰄􏰁􏰙􏰉􏰅􏰁􏰇􏰈􏰂 􏰇􏰞 􏰅􏰓􏰃 􏰊􏰄􏰃􏰂􏰃􏰈􏰅 􏰄􏰃􏰂􏰃􏰆􏰄􏰖􏰓 􏰩􏰇􏰄􏰗􏰍 􏰔􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰧􏰇􏰋􏰘 􏰃􏰄􏰈􏰆􏰈􏰖􏰃 􏰁􏰂 􏰆􏰈 􏰉􏰈􏰄􏰃􏰂􏰇􏰕􏰋􏰃􏰏 􏰞􏰆􏰖􏰃􏰅 􏰇􏰞 􏰅􏰓􏰃 􏰅􏰃􏰖􏰓􏰈􏰇􏰕􏰇􏰧􏰛􏰨 􏰁􏰈 􏰅􏰓􏰃 􏰆􏰙􏰂􏰃􏰈􏰖􏰃 􏰇􏰞 􏰩􏰓􏰁􏰖􏰓􏰨 􏰅􏰓􏰃 􏰏􏰁􏰂􏰅􏰄􏰁􏰙􏰉􏰅􏰃􏰏 􏰈􏰃􏰅􏰩􏰇􏰄􏰗 􏰖􏰆􏰈 􏰞􏰆􏰁􏰕 􏰅􏰇 􏰞􏰉􏰈􏰖􏰅􏰁􏰇􏰈 􏰇􏰊􏰅􏰁􏰝􏰆􏰕􏰕􏰛 􏰇􏰄 􏰃􏰋􏰃􏰈 􏰂􏰅􏰆􏰕􏰕􏰍 􏰚􏰓􏰃 􏰏􏰁􏰂􏰂􏰃􏰄􏰅􏰆􏰅􏰁􏰇􏰈 􏰧􏰁􏰋􏰃􏰂 􏰆 􏰋􏰃􏰄􏰁􏰫􏰃􏰏 􏰝􏰆􏰅􏰓􏰃􏰝􏰆􏰅􏰁􏰖􏰆􏰕 􏰝􏰇􏰏􏰃􏰕􏰨 􏰏􏰃􏰘 􏰄􏰁􏰋􏰃􏰏 􏰉􏰂􏰁􏰈􏰧 􏰑􏰆􏰂􏰓 􏰃􏰴􏰉􏰁􏰕􏰁􏰙􏰄􏰁􏰉􏰝􏰨 􏰅􏰇 􏰞􏰉􏰈􏰖􏰅􏰁􏰇􏰈 􏰆􏰂 􏰆 􏰞􏰄􏰆􏰝􏰃􏰩􏰇􏰄􏰗 􏰞􏰇􏰄 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰧􏰇􏰋􏰃􏰄􏰈􏰆􏰈􏰖􏰃􏰍 􏰚􏰓􏰃 􏰉􏰂􏰆􏰧􏰃 􏰇􏰞 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰁􏰈 􏰫􏰈􏰆􏰈􏰖􏰁􏰆􏰕 􏰇􏰄􏰧􏰆􏰈􏰁􏰵􏰆􏰅􏰁􏰇􏰈􏰂 􏰃􏰈􏰅􏰆􏰁􏰕􏰂 􏰅􏰓􏰃 􏰄􏰃􏰴􏰉􏰁􏰄􏰃􏰝􏰃􏰈􏰅 􏰇􏰞 􏰆 􏰂􏰇􏰉􏰈􏰏 􏰝􏰆􏰈􏰆􏰧􏰃􏰝􏰃􏰈􏰅 􏰂􏰅􏰄􏰆􏰅􏰃􏰧􏰛 􏰅􏰇 􏰇􏰙􏰘 􏰞􏰉􏰂􏰖􏰆􏰅􏰃 􏰅􏰓􏰃 􏰖􏰇􏰝􏰊􏰕􏰃􏰪􏰁􏰅􏰁􏰃􏰂 􏰇􏰞 􏰅􏰓􏰃 􏰅􏰃􏰖􏰓􏰈􏰇􏰕􏰇􏰧􏰛 􏰆􏰈􏰏 􏰄􏰃􏰊􏰕􏰁􏰖􏰆􏰅􏰃 􏰅􏰓􏰃 􏰆􏰏􏰝􏰁􏰈􏰁􏰂􏰅􏰄􏰆􏰅􏰁􏰋􏰃 􏰞􏰉􏰈􏰖􏰅􏰁􏰇􏰈􏰂 􏰃􏰪􏰁􏰂􏰅􏰁􏰈􏰧 􏰁􏰈 􏰕􏰃􏰧􏰆􏰖􏰛 􏰂􏰛􏰂􏰅􏰃􏰝􏰂􏰍 􏰚􏰓􏰃 􏰄􏰃􏰂􏰃􏰆􏰄􏰖􏰓 􏰩􏰇􏰄􏰗 􏰃􏰕􏰉􏰖􏰁􏰏􏰆􏰅􏰃􏰂 􏰅􏰓􏰃 􏰏􏰃􏰂􏰁􏰧􏰈􏰨 􏰁􏰝􏰊􏰕􏰃􏰝􏰃􏰈􏰅􏰆􏰅􏰁􏰇􏰈 􏰆􏰈􏰏 􏰃􏰋􏰆􏰕􏰉􏰆􏰅􏰁􏰇􏰈 􏰇􏰞 􏰆 􏰝􏰆􏰈􏰆􏰧􏰃􏰝􏰃􏰈􏰅 􏰊􏰕􏰆􏰈􏰃 􏰅􏰇 􏰝􏰇􏰈􏰁􏰅􏰇􏰄 􏰆􏰈􏰏 􏰝􏰆􏰈􏰆􏰧􏰃 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈􏰘􏰙􏰆􏰂􏰃􏰏 􏰏􏰃􏰖􏰃􏰈􏰅􏰄􏰆􏰕􏰁􏰵􏰃􏰏 􏰆􏰊􏰊􏰕􏰁􏰖􏰆􏰅􏰁􏰇􏰈􏰂􏰍 􏰶􏰄􏰁􏰋􏰆􏰖􏰛 􏰇􏰞 􏰫􏰈􏰆􏰈􏰖􏰁􏰆􏰕 􏰏􏰆􏰅􏰆 􏰁􏰂 􏰃􏰪􏰅􏰄􏰃􏰝􏰃􏰕􏰛 􏰁􏰝􏰊􏰇􏰄􏰅􏰆􏰈􏰅 􏰞􏰇􏰄 􏰆􏰈􏰛 􏰫􏰈􏰆􏰈􏰖􏰁􏰆􏰕 􏰇􏰄􏰧􏰆􏰈􏰁􏰵􏰆􏰅􏰁􏰇􏰈 􏰙􏰉􏰅 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈􏰨 􏰙􏰛 􏰋􏰁􏰄􏰅􏰉􏰃 􏰇􏰞 􏰁􏰅􏰂 􏰁􏰈􏰓􏰃􏰄􏰃􏰈􏰅 􏰁􏰈􏰞􏰄􏰆􏰂􏰘 􏰅􏰄􏰉􏰖􏰅􏰉􏰄􏰃􏰨 􏰊􏰇􏰂􏰃􏰂 􏰆 􏰖􏰓􏰆􏰕􏰕􏰃􏰈􏰧􏰃 􏰁􏰈 􏰅􏰓􏰁􏰂 􏰄􏰃􏰂􏰊􏰃􏰖􏰅􏰍 􏰚􏰓􏰁􏰂 􏰁􏰂 􏰆􏰕􏰂􏰇 􏰇􏰈􏰃 􏰇􏰞 􏰅􏰓􏰃 􏰇􏰋􏰃􏰄􏰆􏰄􏰖􏰓􏰁􏰈􏰧 􏰞􏰆􏰖􏰅􏰇􏰄􏰂 􏰅􏰓􏰆􏰅 􏰝􏰆􏰗􏰃􏰂 􏰉􏰂􏰆􏰧􏰃 􏰇􏰞 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰴􏰉􏰃􏰂􏰅􏰁􏰇􏰈􏰆􏰙􏰕􏰃 􏰞􏰄􏰇􏰝 􏰅􏰓􏰃 􏰷􏰉􏰄􏰇􏰊􏰃􏰆􏰈 􏰸􏰀􏰶􏰎 􏰊􏰃􏰄􏰂􏰊􏰃􏰖􏰅􏰁􏰋􏰃􏰍 􏰶􏰄􏰁􏰋􏰆􏰖􏰛􏰘􏰊􏰄􏰃􏰂􏰃􏰄􏰋􏰁􏰈􏰧 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰊􏰕􏰆􏰅􏰞􏰇􏰄􏰝􏰂 􏰓􏰆􏰋􏰃 􏰆􏰕􏰂􏰇 􏰊􏰄􏰇􏰋􏰃􏰏 􏰅􏰇 􏰙􏰃 􏰋􏰉􏰕􏰈􏰃􏰄􏰆􏰙􏰕􏰃 􏰅􏰇 􏰏􏰆􏰅􏰆 􏰙􏰄􏰃􏰆􏰖􏰓􏰃􏰂􏰍 􏰚􏰓􏰃 􏰏􏰁􏰂􏰂􏰃􏰄􏰅􏰆􏰅􏰁􏰇􏰈 􏰂􏰇􏰕􏰋􏰃􏰂 􏰅􏰓􏰁􏰂 􏰊􏰄􏰇􏰙􏰕􏰃􏰝 􏰙􏰛 􏰁􏰋 􏰀􏰁􏰂􏰂􏰃􏰄􏰅􏰆􏰅􏰁􏰇􏰈 􏰂􏰉􏰊􏰃􏰄􏰋􏰁􏰂􏰇􏰄􏰌 􏰀􏰄􏰍 􏰎􏰆􏰏􏰉 􏰐􏰅􏰆􏰅􏰃 􏰑􏰁􏰏􏰆 􏰒􏰓􏰆􏰈 􏰅􏰓􏰃 􏰏􏰃􏰋􏰃􏰕􏰇􏰊􏰝􏰃􏰈􏰅 􏰆􏰈􏰏 􏰃􏰋􏰆􏰕􏰉􏰆􏰅􏰁􏰇􏰈 􏰇􏰞 􏰆 􏰝􏰆􏰈􏰆􏰧􏰃􏰝􏰃􏰈􏰅 􏰊􏰕􏰆􏰈􏰃 􏰞􏰇􏰄 􏰏􏰁􏰹􏰃􏰄􏰃􏰈􏰅􏰁􏰆􏰕 􏰊􏰄􏰁􏰋􏰆􏰖􏰛 􏰊􏰄􏰃􏰂􏰃􏰄􏰋􏰆􏰅􏰁􏰇􏰈 􏰅􏰓􏰄􏰇􏰉􏰧􏰓 􏰂􏰝􏰆􏰄􏰅 􏰖􏰇􏰈􏰅􏰄􏰆􏰖􏰅􏰂􏰍 􏰚􏰓􏰃 􏰄􏰃􏰂􏰃􏰆􏰄􏰖􏰓 􏰩􏰇􏰄􏰗 􏰏􏰁􏰂􏰖􏰉􏰂􏰂􏰃􏰂 􏰅􏰓􏰃 􏰖􏰇􏰝􏰊􏰕􏰁􏰆􏰈􏰖􏰃 􏰇􏰞 􏰅􏰓􏰃 􏰊􏰄􏰁􏰋􏰆􏰖􏰛 􏰝􏰆􏰈􏰆􏰧􏰃􏰝􏰃􏰈􏰅 􏰊􏰕􏰆􏰈􏰃 􏰅􏰇 􏰸􏰀􏰶􏰎 􏰉􏰂􏰁􏰈􏰧 􏰆 􏰊􏰃􏰄􏰝􏰁􏰂􏰂􏰁􏰇􏰈􏰃􏰏 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰊􏰕􏰆􏰅􏰞􏰇􏰄􏰝􏰍 􏰚􏰓􏰃 􏰈􏰃􏰩 􏰃􏰖􏰇􏰈􏰇􏰝􏰁􏰖 􏰊􏰆􏰄􏰆􏰏􏰁􏰧􏰝 􏰃􏰈􏰞􏰇􏰄􏰖􏰃􏰏 􏰙􏰛 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈􏰨 􏰏􏰃􏰖􏰃􏰈􏰅􏰄􏰆􏰕􏰁􏰵􏰃􏰏 􏰫􏰈􏰆􏰈􏰖􏰃􏰨 􏰊􏰄􏰃􏰂􏰃􏰈􏰅􏰂 􏰈􏰇􏰋􏰃􏰕 􏰖􏰓􏰆􏰕􏰘 􏰕􏰃􏰈􏰧􏰃􏰂 􏰆􏰈􏰏 􏰉􏰈􏰊􏰄􏰃􏰖􏰃􏰏􏰃􏰈􏰅􏰃􏰏 􏰂􏰅􏰄􏰆􏰅􏰃􏰧􏰁􏰖 􏰆􏰏􏰋􏰆􏰈􏰅􏰆􏰧􏰃􏰂􏰍 􏰚􏰓􏰃 􏰏􏰁􏰂􏰂􏰃􏰄􏰅􏰆􏰅􏰁􏰇􏰈 􏰁􏰂 􏰆 􏰊􏰁􏰇􏰈􏰃􏰃􏰄 􏰁􏰈 􏰖􏰇􏰈􏰏􏰉􏰖􏰅􏰁􏰈􏰧 􏰆􏰈 􏰁􏰝􏰊􏰕􏰃􏰝􏰃􏰈􏰅􏰆􏰅􏰁􏰇􏰈􏰘􏰙􏰆􏰂􏰃􏰏􏰨 􏰖􏰇􏰝􏰊􏰆􏰄􏰆􏰅􏰁􏰋􏰃 􏰆􏰈􏰏 􏰆􏰈 􏰃􏰪􏰊􏰕􏰇􏰄􏰆􏰅􏰇􏰄􏰛 􏰆􏰈􏰆􏰕􏰛􏰂􏰁􏰂 􏰇􏰞 􏰅􏰇􏰗􏰃􏰈􏰁􏰵􏰆􏰅􏰁􏰇􏰈 􏰇􏰞 􏰃􏰅􏰓􏰁􏰖􏰆􏰕 􏰁􏰈􏰋􏰃􏰂􏰅􏰝􏰃􏰈􏰅 􏰖􏰃􏰄􏰅􏰁􏰫􏰖􏰆􏰅􏰃􏰂􏰍 􏰐􏰇􏰖􏰁􏰆􏰕 􏰫􏰈􏰆􏰈􏰖􏰃 􏰝􏰆􏰄􏰗􏰃􏰅􏰂 􏰓􏰆􏰋􏰃 􏰙􏰃􏰃􏰈 􏰏􏰃􏰋􏰃􏰕􏰇􏰊􏰁􏰈􏰧 􏰁􏰈 􏰷􏰉􏰄􏰇􏰊􏰃 􏰆􏰈􏰏 􏰆􏰄􏰃 􏰋􏰁􏰃􏰩􏰃􏰏 􏰆􏰂 􏰂􏰉􏰂􏰅􏰆􏰁􏰈􏰆􏰙􏰕􏰃 􏰫􏰘 􏰈􏰆􏰈􏰖􏰃 􏰙􏰛 􏰅􏰓􏰃 􏰷􏰉􏰄􏰇􏰊􏰃􏰆􏰈 􏰬􏰇􏰝􏰝􏰁􏰂􏰂􏰁􏰇􏰈􏰍 􏰚􏰓􏰃 􏰄􏰃􏰂􏰃􏰆􏰄􏰖􏰓 􏰩􏰇􏰄􏰗 􏰋􏰃􏰄􏰁􏰫􏰃􏰂 􏰅􏰓􏰃 􏰉􏰅􏰁􏰕􏰁􏰅􏰛 􏰇􏰞 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈 􏰅􏰇 􏰂􏰇􏰕􏰋􏰃 􏰂􏰇􏰝􏰃 􏰊􏰄􏰃􏰋􏰆􏰕􏰃􏰈􏰅 􏰁􏰂􏰂􏰉􏰃􏰂 􏰁􏰈 􏰂􏰇􏰖􏰁􏰆􏰕 􏰫􏰈􏰆􏰈􏰖􏰃􏰍 􏰚􏰓􏰃 􏰩􏰇􏰄􏰗 􏰆􏰖􏰖􏰇􏰝􏰊􏰕􏰁􏰂􏰓􏰃􏰂 􏰅􏰓􏰁􏰂 􏰅􏰓􏰄􏰇􏰉􏰧􏰓 􏰅􏰓􏰃 􏰏􏰃􏰋􏰃􏰕􏰇􏰊􏰝􏰃􏰈􏰅 􏰆􏰈􏰏 􏰅􏰃􏰂􏰅􏰁􏰈􏰧 􏰇􏰞 􏰆 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈􏰘􏰙􏰆􏰂􏰃􏰏 􏰏􏰇􏰈􏰆􏰅􏰁􏰇􏰈 􏰆􏰊􏰊􏰕􏰁􏰖􏰆􏰅􏰁􏰇􏰈􏰍 􏰠 􏰴􏰉􏰆􏰕􏰁􏰅􏰆􏰅􏰁􏰋􏰃 􏰄􏰃􏰋􏰁􏰃􏰩 􏰇􏰞 􏰅􏰓􏰃 􏰃􏰖􏰇􏰈􏰇􏰝􏰁􏰖 􏰁􏰝􏰊􏰆􏰖􏰅 􏰇􏰞 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈􏰘􏰙􏰆􏰂􏰃􏰏 􏰝􏰁􏰖􏰄􏰇􏰊􏰆􏰛􏰝􏰃􏰈􏰅􏰂 􏰓􏰆􏰂 􏰆􏰕􏰂􏰇 􏰙􏰃􏰃􏰈 􏰖􏰇􏰈􏰏􏰉􏰖􏰅􏰃􏰏􏰍 􏰚􏰓􏰃 􏰏􏰁􏰂􏰖􏰉􏰂􏰂􏰁􏰇􏰈 􏰇􏰈 􏰅􏰓􏰃 􏰃􏰖􏰇􏰈􏰇􏰝􏰁􏰖 􏰁􏰝􏰊􏰆􏰖􏰅 􏰆􏰕􏰂􏰇 􏰁􏰈􏰖􏰕􏰉􏰏􏰃􏰂 􏰆 􏰊􏰄􏰇􏰊􏰇􏰂􏰁􏰅􏰁􏰇􏰈 􏰞􏰇􏰄 􏰃􏰪􏰅􏰃􏰈􏰏􏰁􏰈􏰧 􏰅􏰓􏰃 􏰆􏰖􏰖􏰃􏰂􏰂 􏰇􏰞 􏰙􏰕􏰇􏰖􏰗􏰖􏰓􏰆􏰁􏰈􏰘􏰙􏰆􏰂􏰃􏰏 􏰫􏰈􏰆􏰈􏰖􏰁􏰆􏰕 􏰂􏰃􏰄􏰋􏰁􏰖􏰃􏰂 􏰅􏰇 􏰅􏰓􏰃 􏰉􏰈􏰘 􏰏􏰃􏰄􏰙􏰆􏰈􏰗􏰃􏰏 􏰆􏰈􏰏 􏰉􏰈􏰙􏰆􏰈􏰗􏰃􏰏 􏰊􏰃􏰇􏰊􏰕􏰃􏰍 􏰚􏰓􏰃 􏰩􏰇􏰄􏰗 􏰖􏰇􏰈􏰖􏰕􏰉􏰏􏰃􏰂 􏰩􏰁􏰅􏰓 􏰆 􏰓􏰛􏰊􏰇􏰅􏰓􏰃􏰅􏰁􏰖􏰆􏰕 􏰝􏰇􏰏􏰃􏰕 􏰇􏰞 􏰆 􏰫􏰈􏰆􏰈􏰖􏰁􏰆􏰕 􏰃􏰖􏰇􏰂􏰛􏰂􏰅􏰃􏰝􏰨 􏰏􏰃􏰊􏰁􏰖􏰅􏰁􏰈􏰧 􏰅􏰓􏰃 􏰏􏰃􏰊􏰕􏰇􏰛􏰝􏰃􏰈􏰅 􏰇􏰞 􏰅􏰓􏰃 􏰝􏰆􏰺􏰇􏰄 􏰖􏰇􏰈􏰅􏰄􏰁􏰙􏰉􏰅􏰁􏰇􏰈􏰂 􏰇􏰞 􏰅􏰓􏰁􏰂 􏰏􏰁􏰂􏰂􏰃􏰄􏰅􏰆􏰅􏰁􏰇􏰈􏰍 [less ▲]

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See detailBlockchain Technology for Data Sharing in the Banking Sector
Norvill, Robert UL

Doctoral thesis (2020)

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See detailInkjet-printed piezoelectric films for transducers
Godard, Nicolas UL

Doctoral thesis (2020)

Lead zirconate titanate (PZT) thin films are a popular choice for piezoelectric devices such as microelectromechanical systems, micro-pumps, micro-mirrors or energy harvesters. Various fabrication ... [more ▼]

Lead zirconate titanate (PZT) thin films are a popular choice for piezoelectric devices such as microelectromechanical systems, micro-pumps, micro-mirrors or energy harvesters. Various fabrication techniques exist for the deposition of PZT in the form of thin films. Physical vapor deposition (PVD) methods are particularly cost-intensive, as they require vacuum conditions and expensive infrastructure. Fabrication costs can be decreased by the use of chemical solution deposition (CSD), where the metal precursors are dispersed in a solvent medium and coated onto a substrate. Thermal treatments convert the liquid precursor into a functional solid film. Spin coating is a conventional coating technique allowing for the deposition of homogeneous layers over large-area substrates. However, it is inherently wasteful, as most of the precursor material is spun off the substrate in the coating process. In addition, as spin coating results in complete coverage of the substrate, layer patterning requires lithography, which adds up extra steps and costs to the overall process. Inkjet printing is an additive manufacturing technique that has the potential to address both of these issues, thus further decreasing manufacturing costs and the associated ecological footprint. The working principle of inkjet printing can be described as the deposition of individual ink droplets at digitally determined locations on the substrate surface, which then merge into a continuous film. Inkjet printing is compatible with CSD processing of PZT thin films, as demonstrated by the previous works in the field. However, the adaptation of standard CSD processing for inkjet printing comes with several challenges, which have to be considered to obtain state-of-the-art functional PZT layers. In the present work, we explore several issues related to the processing of PZT thin films by inkjet printing and we provide possible solutions to address them, in a way that had not been described yet by the state of the art. In particular, we describe a novel strategy that uses inkjet-printed alkanethiolate-based self-assembled monolayers for direct patterning of PZT thin films on platinized silicon. Then, we present a systematic study of the pyrolysis step of the process, which enabled us to print dense and textured layers with state-of-the-art electrical properties. We also developed a proof-of-concept piezoelectric energy harvesting device based on inkjet-printed PZT films. Finally, we unveil a comparative study where we identified an alternative solvent for CSD processing of PZT thin films. [less ▲]

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See detailThe compatibility of ISDS provisions in bilateral investment treaties and the Energy Charter Treaty with EU law
de Boeck, Michael Karel Marc UL

Doctoral thesis (2020)

Since the 1960’s, EU Member States concluded a vast network of international investment agreements (IIA’s). Such treaties typically offer substantive investment protection standards and investor-state ... [more ▼]

Since the 1960’s, EU Member States concluded a vast network of international investment agreements (IIA’s). Such treaties typically offer substantive investment protection standards and investor-state arbitration provisions (ISDS). It is disputed whether those treaties conflict with EU law and whether they can still be relied on against EU Member States and by whom. It is submitted that the relationship between international investment law and EU law can only be understood by clearly separating the issues of international validity and applicability of those treaties from their effects in the EU legal order. The first is determined by international conflict norms, while the second is determined only by reference to EU law itself. The thesis therefore adopts three parts. The first approaches the interaction between EU law and the IIA’s through the lens of the conflict norms of international law. After considering the framework of “harmonious interpretation” and “successive treaty” conflicts, the thesis concludes that despite the existence of a certain overlap or conflict between the EU treaties and IIA’s, the ISDS provisions of IIA’s remain valid and applicable under international law. Investors can therefore continue to rely on them against EU Member States. In a second part, the thesis considers the status and legal value of IIA’s in the EU legal order in light of the internal developments of EU law. The post-Lisbon transfer of competence on Foreign Direct Investment to the EU raised many questions with few answers. The second part therefore sets out the framework of EU law conflict norms and the legal effect of the ECT and BITs in the EU legal order. It is concluded that the BITs enjoy only limited recognition in the EU legal order through article 351 TFEU, which is however bounded by the notion of the autonomy of EU law. In the third part, the thesis examines whether the ISDS provisions of the BITs and the ECT are compatible with the autonomy of EU law. After constructing the role, meaning and requirements of autonomy in relation to international dispute resolution, the thesis concludes that the ISDS provisions in the ECT and BITs are incompatible with the autonomy of EU law. Thus, the ISDS provisions cannot be applied in the EU legal order, but remain valid internationally. [less ▲]

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See detailA Real-World Flexible Job Shop Scheduling Problem With Sequencing Flexibility: Mathematical Programming, Constraint Programming, and Metaheuristics
Tessaro Lunardi, Willian UL

Doctoral thesis (2020)

In this work, the online printing shop scheduling problem is considered. This challenging real scheduling problem, that emerged in the nowadays printing industry, corresponds to a flexible job shop ... [more ▼]

In this work, the online printing shop scheduling problem is considered. This challenging real scheduling problem, that emerged in the nowadays printing industry, corresponds to a flexible job shop scheduling problem with sequencing flexibility that includes several complicating specificities such as resumable operations, periods of unavailability of the machines, sequence-dependent setup times, partial overlapping between operations with precedence constraints, fixed operations, among others. In the present work, a mixed integer linear programming model, a constraint programming model, and heuristic methods such as local search and metaheuristics for the minimization of the makespan are presented. Modeling the problem is twofold. On the one hand, the problem is precisely defined. On the other hand, the capabilities and limitations of a commercial software for solving the models are analyzed. Numerical experiments show that the commercial solver is able to optimally solve only a fraction of the small-sized instances when considering the mixed integer linear programming formulation. While considering the constraint programming formulation of the problem, medium-sized instances are optimally solved, and feasible solutions for large-sized instances of the problem are found. Ad-hoc heuristic methods, such as local search and metaheuristic approaches that fully exploit the structure of the problem, are proposed and evaluated. Based on a common representation scheme and neighborhood function, trajectory and populational metaheuristics are considered. Extensive numerical experiments with large-sized instances show that the proposed metaheuristic methods are suitable for solving practical instances of the problem; and that they outperform the half-heuristic-half-exact off-the-shelf constraint programming solver. Numerical experiments with classical instances of the flexible job shop scheduling problem show that the introduced methods are also competitive when applied to this particular case. [less ▲]

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See detailLehrerInnenprofessionalisierung in einer digitalen, videogestützten Lernumgebung
Arimond, Ruth Annemarie UL

Doctoral thesis (2020)

The sustainable use of digital media and the conception of effective task designs are relevant aspects for the learning outcome in the training of future teachers. To model professional action competence ... [more ▼]

The sustainable use of digital media and the conception of effective task designs are relevant aspects for the learning outcome in the training of future teachers. To model professional action competence, video-supported learning opportunities are increasingly used today to train professional perception and reflexive confrontation with new knowledge, convictions and experiences from teaching. So far, however, there is a lack of empirical studies that systematically take into account effective design elements of innovative learning environments for the promotion of reflexive practice, such as blended learning, social video learning and ePortfolio [less ▲]

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See detailFatigue and fracture of rubber: Accelerated and experimentally validated phase-field damage models
Loew, Pascal Juergen UL

Doctoral thesis (2020)

Rubbers behave very particularly. Anyone who has stretched a rubber band knows that large elastic deformations over 400% can be attained with a minimal force. In order to utilize the full potential of the ... [more ▼]

Rubbers behave very particularly. Anyone who has stretched a rubber band knows that large elastic deformations over 400% can be attained with a minimal force. In order to utilize the full potential of the material and to improve the performance of a product, it is imperative to accurately model the material's failure. This thesis focuses on the development, experimental validation and application of a fatigue damage model for rubber. Cohesive zone models or nodal enrichment strategies, which treat cracks as sharp discontinuities, require a priori knowledge of the crack path or are limited in their ability to handle complex crack phenomena like branching and coalescence. On the other hand, the results of standard continuum damage models are affected by the mesh size. Phase-field damage models avoid sharp discontinuities by adding a smooth damage process zone to the crack. The width of this zone is controlled by a length scale parameter. Because of this pure continuum description, the mentioned complex phenomena are simulated without additional effort. Furthermore, the introduction of the length scale ensures mesh-independence during strain softening. Despite these advantages, phase-field models to describe the failure of rubber parts are still limited. Firstly, most published works focus only on monotonic loading. Fatigue damage of rubber has never been considered in a phase-field model. Secondly, the computational burden is too large so that only examples with limited practical relevance can be simulated. Thirdly, there is insufficient experimental validation in the literature and the process of parameter identification is not adequately addressed. For instance, the selection of the length scale parameter is often arbitrary. This thesis collects three works that have been presented to the scientific community in an effort to overcome the mentioned problems. Because the fracture resistance of rubbers is a function of the loading rate, the first work presents a rate-dependent phase-field damage model for rubber and finite strains. Rate-dependency is considered in the constitutive description of the bulk as well as in the damage driving force. All the material parameters are identified from experiments. Particular attention is paid to the length scale parameter, which is calibrated by means of local strain measurements close to the crack tip obtained via digital image correlation. The second work extends the phase-field damage model so that fatigue failure can be predicted. For this purpose, an additional fatigue damage source depending on an accumulated load history variable is introduced. The thermodynamical consistency is demonstrated by measuring the energy storage and dissipation of the various model components. Dedicated fatigue experiments are conducted in order to identify additional (fatigue) parameters. The extended model reproduces Woehler curves and Paris theory for fatigue crack growth. Using explicit and implicit cycle jump schemes, the third work focuses on the reduction of the computation time. A finite number of load cycles is simulated and the results for the next cycles are extrapolated. By alternating simulations and jumps until the component failure is reached, the total number of simulated cycles is significantly reduced, with respect to the full simulations. As the size of the cycle jump governs the acceleration of the simulations, but also the numerical stability, an adaptive cycle jump scheme for the implicit acceleration framework is proposed. Consequently, no manual adjustment of the step size is necessary. Additional experiments validate both the numerical model and the identified material parameters. Finally, the fatigue phase-field damage model is used in two industry-relevant examples demonstrating how this technology creates immediate benefits in product development. [less ▲]

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See detailWAVEFORM DESIGN FOR AUTOMOTIVE JOINT RADAR-COMMUNICATION SYSTEM
Dokhanchi, Sayed Hossein UL

Doctoral thesis (2020)

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See detailEssays in risk and experimental finance
Xanalatou, Sotiria UL

Doctoral thesis (2020)

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See detailCultural identity and values in intergenerational movement: The multicultural case of the Grand-Duchy of Luxembourg
Barros Coimbra, Stephanie UL

Doctoral thesis (2020)

Migration flows have led to an increase in questions about the multiple cultural influences on individuals. The resulting demographic changes raise in many host societies essential questions related to ... [more ▼]

Migration flows have led to an increase in questions about the multiple cultural influences on individuals. The resulting demographic changes raise in many host societies essential questions related to national belonging, and thus to cultural identity and value systems. While migrating to a new cultural environment, migrant individuals face several challenges and they have to negotiate several developmental tasks using self-regulatory strategies, with correspondingly different psychological outcomes. These issues become even more important in a country such as Luxembourg with a high migrant proportion (47%; Statec, 2019). Little is still known about how second-generation adults who have grown up in immigrant families negotiate the double cultural identity, and about their value profiles compared to the local populations of the country of origin and receiving country. Four diverse subsamples were used out of the broader IRMA project pool, depending on the different objectives of the four studies. In total, N = 506 participants from three cultural subgroups ( LU natives, PT migrants in Luxembourg & PT natives in Portugal) participated in the quantitative part of the IRMA project ( LuN: n = 179; PtM: n = 209 & PtN: n = 118), and N = 20 took part in the qualitative part (n = 10 PtM dyads & n = LuN dyads). Study 1 highlighted the importance of the migration experience as a life-disruptive event that has impacts on individual and family cultures, as well as value systems during the life of migrant families. Study 2, looking specifically at PT migrant families, found a generational gap in terms of adult children’s higher attachment to the receiving culture as well as stronger tendencies towards a compatible identity orientation compared to their respective parents. However, the qualitative part of Study 2 revealed ambivalent feelings about double cultural belonging amongst the Portuguese second-generation adult children. Study 3 therefore focused on the latter and identified four ways of dealing with double cultural frames - blended, alternated, separated (Phinney & Devich-Navarro, 1997) - and expanded the model by identifying a fourth cluster of ambivalent cultural identity. In addition, the survey analyzed how their cultural identity profiles enabled them to achieve personally or socially meaningful goals and values. Blended biculturals used mainly primary regulatory control strategies, which were linked to the most positive psychological outcomes (higher self-esteem & well-being, and low acculturation stress). The ambivalent cluster was the least successful in terms of psychological outcomes (low self-esteem & well-being, and high acculturative stress) using both primary and secondary compensatory regulatory strategies. Study 4, an intercultural comparison between two family generations – one adult child and two elder parents – within three different cultural subgroups – LuN, PtM and PtN – aimed to better disentangle the effects of family, culture and immigration, and thus investigate the different cultural influences and messages reflected in the processes of transmission of values and value profiles. Overall, findings of Study 4 revealed the existence of an intergenerational gap between elder parents and their respective adult children; the presence of a cultural gap between the three cultural subgroups studied, which could be explained by both culture of origin and migration, with specifically an acculturation gap in the sub-sample of Portuguese migrants; and a moderate relative intergenerational transmission across cultures. The latter thus allows for a certain cultural persistence and continuity of a society and its cultural system (Trommsdorff et al., 2004) while allowing for cultural flexibility over generations that could be important for family identity and beneficial for well-being far more than a mere exact reproduction of values over generations (Barni & Donato, 2018). [less ▲]

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See detailOPTICAL DEFECT SPECTROSCOPY IN CUINS2 THIN FILMS AND SOLAR CELLS
Lomuscio, Alberto UL

Doctoral thesis (2020)

Pure-sulphide Cu(In,Ga)S2 solar cells have reached certified power conversion efficiency as high as 15.5 %. While this record performance has been achieved by growing the semiconducting absorber at very ... [more ▼]

Pure-sulphide Cu(In,Ga)S2 solar cells have reached certified power conversion efficiency as high as 15.5 %. While this record performance has been achieved by growing the semiconducting absorber at very high temperature with a copper deficient composition, all other previous records were based on chalcopyrite films deposited under Cu excess. Still, this world record is far from the theoretical power conversion achievable in single junction solar cell for this semiconductor (about 30 %), which has a tunable band gap between 1.5 and 2.4 eV. This thesis aims to gain insight into the optoelectronic properties of this semiconductor, particularly CuInS2, looking at their variation as a function of the deposition temperature and of the absorber composition. The investigations are carried out mainly by photoluminescence (PL) spectroscopy, which allows to measure the quasi Fermi level splitting (QFLS), that is an upper limit of the maximum open circuit voltage (VOC) an absorber is capable of. PL spectroscopy is used to get insights onto the electronic defects as well, both the shallow ones, which contribute to the doping, and the deep ones, which enhance non-radiative recombination. By increasing the Cu content in the as-grown compositions, the morphology and microstructure of the thin films improve, as they show larger grains and less structural defects than films deposited with Cu deficiency. The composition affects the QFLS as well, which is significantly higher for sample deposited under Cu excess, in contrast to the observations in selenide chalcopyrite. The increment of the process temperature leads to an improvement of the QFLS too, although absorbers grown in Cu deficiency are less influenced, likely because of a lower sodium content in the high-temperature glass used as substrate. The QFLS increase correlates with the lowering of a deep defect related band, which manifests itself with a peak maximum at around 0.8 eV in room temperature PL spectra. In literature, the low efficiencies exhibited by Cu(In,Ga)S2–based solar cells are often attributed to interface problems at the p-n junction, i.e. at the absorber-buffer layer interface. In this work, the comparison of the QFLS and VOC of pure sulphides CIGS with those measured on selenides clearly points out that the lower efficiencies exhibited by the former are caused also by the intrinsic lower optoelectronic quality of Cu(In,Ga)S2 films. To shed light on the electronic structure, high quality CuInS2 films are deeply investigated by means of low temperature PL. Four shallow defects are detected: one shallow donor at about 30 meV from the conduction band and three shallow acceptors at about 105, 145 and 170 meV from the valence band. The first of these acceptors dominates the band edge luminescence of sample grown with composition close to the stoichiometry, whereas the second deeper acceptor is characteristic of absorbers deposited in Cu rich regime. The deepest of these acceptors seems to be present over a wide range of compositions, although its luminescence is observable only for slight Cu-poor samples with sodium incorporation during the deposition. The quality of the examined films allows the observations of phonon coupling of these shallow defects for the first time in this semiconductor. All these observations on shallow defects and their phonon coupling behaviour allowed to revise the defect model for this semiconductor. The findings of this thesis reveal the strong similarity of the shallow defects structure with selenium based compounds. On the other hand, the presence of deep defects in CuInS2 strongly limits the optoelectronic quality of the bulk material, causing the gap in power conversion efficiencies compared to low-band gap Cu(In,Ga)Se2 solar cells, which show efficiencies above 23%. [less ▲]

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See detailCultural Psychological Re-Formulation of Ego-Defence into Ego-Construction
Mihalits, Dominik Stefan UL

Doctoral thesis (2020)

The developing self is a complex concept that recurrently occupies a variety of academic disciplines, and that is yet to be clarified from a holistically, transdisciplinary standpoint. For instance ... [more ▼]

The developing self is a complex concept that recurrently occupies a variety of academic disciplines, and that is yet to be clarified from a holistically, transdisciplinary standpoint. For instance, psychoanalytical theories offer detailed insight into the intraindividual psycho-dynamics of personal development. Cultural psychological theories, on the other hand, stress a culture’s influence on a person’s day-to-day development and advance a detailed account of semiotic, i.e., culturally mediated, sign construction that underlies psychological process-es and results from it at the same time. Importantly, and what a cultural psychological standpoint therefore offers, is a view on culture that withdraws from conceiving it as an own entity (e.g., cannot be calculated as an external factor), but views it as deeply entangled with the formation of personality development. Both theory strands thus each complexly address ‘sides of the same coin’, namely the phenomenon of the developing self, but have not yet been systematically linked with each other from a holistic perspective. Therefore, this thesis addresses the question, how an integrative perspective of psychoanalytical psychodynamics can be synthesized with cultural psychological metatheory on development. More precisely, I theoretically explore how psychoanalytical theories of ego defence mechanisms help furthering an analysis of ego construction. By using the concept of ego construction, I argue that cultural psychological construction processes that are entangled with people’s engagement with their culturally laden environments can further elaborate psychoanalytical theories on ego defence. To approach ego defence, this project departs from Freudian psychoanalytic theory. It draws on the differentiation between needs and wishes that leads to an inner tension where defence mechanisms help in understanding the tension upon delayed gratification. Pushing beyond this traditional perspective and by assuming a high entanglement of needs and wishes, the defence needs to be recognized as an ongoing process, conceptualized as a continuous and recurring process rather than as mechanisms. It is a central conclusion of this Ph.D. project that, therefore, concepts of defence must leave their descriptive level to overcome the problem of cause and effect, allowing an understanding of development as open psychodynamic and cultural system. [less ▲]

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See detailInvestigating the potential of investing in fine stringed instruments as an alternative investment asset
Ortiz-Munoz, Angela UL

Doctoral thesis (2020)

Often seen as a passion project or part of a philanthropic venture, rare and fine stringed instruments offer an exciting option to diversify one’s investment portfolio while providing an opportunity for ... [more ▼]

Often seen as a passion project or part of a philanthropic venture, rare and fine stringed instruments offer an exciting option to diversify one’s investment portfolio while providing an opportunity for an exceptional long-term investment. Though, historically rare violins have not been widely recognized as assets for investment, this category is gaining interest due to its steady increase in value, a lively international market and a finite and diminishing supply. This study demonstrates that fine stringed instruments offer a steady increase of approximately 3,7-6,9% return per annum with a dramatic percentage increase since the 80’s. In this thesis, the stringed instrument public auction and private dealer markets are reviewed, the price dynamics are studied, and some fundamental intra market specific limitations are tackled in order to observe the true underlying returns of this asset. In order to build solid conclusions, the largest fine stringed instrument auction database has been developed encompassing the period from 1850 until today, although for the analysis a focus is put in the period from the 1980’s until today, as it is when the demand and, consequently the market for violins boomed. [less ▲]

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See detailOn the practical security of white-box cryptography
Wang, Junwei UL

Doctoral thesis (2020)

Cryptography studies how to secure communications and information. The security of a cryptosystem depends on the secrecy of the underlying key. White-box cryptography explores methods to hide a ... [more ▼]

Cryptography studies how to secure communications and information. The security of a cryptosystem depends on the secrecy of the underlying key. White-box cryptography explores methods to hide a cryptographic key into some software deployed in the real world. Classical cryptography only assumes that the adversary accesses the target cryptographic primitive in a black-box manner in which she can only observe or manipulate the input and output of the primitive, but cannot know or tamper with its internal details. The gray-box model further allows an adversary to exploit key- dependent sensitive information leaked from the execution of physical implementations. All sorts of side-channel attacks exploit some physical information leakage, such as the power consumption of the device. The white-box model considers the worst-case scenario in which the adversary has complete control over the software and its execution environment. The goal of white-box cryptography is to securely implement a cryptographic primitive against such a powerful adversary. Although the scientific community has proposed some candidate solutions to build white-box cryptography, all have proven ineffective. Consequently, this problem has remained open for almost two decades since the concept was introduced. The continuous growth in market demand and the emerging potential applications have driven the industry to deploy secretly-designed proprietary solutions. Al- though this paradigm of achieving security through obscurity contradicts the widely accepted Kerckhoffs' principle in cryptography, this is currently the only option for white-box cryptography. Security experts have reported how gray-box attacks could be used to extract keys from several publicly available white-box implementations. In a gray-box attack, the adversary adapts side-channel analysis techniques to the white-box context, i.e., to target computation traces made of noise-free run- time information instead of the noisy physical leakage. Gray-box attacks are generic since they do not require any a priori knowledge of the implementation and hence avoid costly reverse engineering. Some non-publicly scrutinized industrial white- box schemes in the market are believed to be under the threat of gray-box attacks. This thesis focuses on the analysis and improvement of gray-box attacks and the associated countermeasures for white-box cryptography. We first provide an in- depth analysis of why gray-box attacks are capable of breaking the classical white- box design which is based on table encodings. Next, we introduce a new gray-box at- tack named linear decoding analysis and show that linearly encoding sensitive information is insufficient to protect the cryptographic software. Afterward, we describe how to combine state-of-the-art countermeasures to resist gray-box attacks and comprehensively elaborate on the (in)effectiveness of these combined countermeasures in terms of computation complexity. Finally, we introduce a new attack technique that exploits the data-dependency of the targeted implementation to substantially lower the complexity of the existing gray-box attacks on white-box cryptography. In addition to the theoretical analyses and new attack techniques introduced in this thesis, we report some attack experiments against practical white-box implementations. In particular, we could break the winning implementations of two consecutive editions of the well-known WhibOx white-box cryptography competition. [less ▲]

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See detailDemountable composite beams: Analytical calculation approaches for shear connections with multilinear load-slip behaviour
Kozma, Andras UL

Doctoral thesis (2020)

The work carried out throughout the thesis focused on the behaviour of demountable composite beams in order to facilitate the integration of steel-concrete composite construction into the concept of ... [more ▼]

The work carried out throughout the thesis focused on the behaviour of demountable composite beams in order to facilitate the integration of steel-concrete composite construction into the concept of circular economy. There are several hindrances in the way of reuse when considering traditional composite structures. One of them is the method that the current construction practice applies for connecting the concrete deck to the steel beam. The traditionally applied welded studs are advantageous in the terms of structural performance; however, they do not provide the ability of dismounting. In order to overcome this issue, different demountable shear connection types were investigated that use pretensioned bolted connections. The investigations included laboratory experiments in the means of push-out tests and full-scale beam-tests. The experiments were complemented by numerical simulations and parametric studies. The experiments showed that the developed shear connections have highly a nonlinear load-slip behaviour. When these types of connections are applied in a composite beam, the nonlinearity of the shear connection causes a nonlinear load-deflection response already in the elastic phase. Analytical equations were derived for the description of the elastic properties of composite beams with nonlinear shear connection. For the calculation of the elastic deflections an iterative procedure was developed. This method is capable of capturing the nonlinear load-deflection response. With the developed iterative method, the elastic deflections can be determined with a similar accuracy by using spreadsheet calculations as by using nonlinear finite element simulations. Due to the highly nonlinear behaviour of the tested shear connections the basic assumptions of Eurocode 4 for the determination of the plastic moment resistance of composite beams with partial shear connection are not valid anymore. The code does not enable the use of equidistant shear connector spacing and the design needs to be conducted using fully elastic analysis. This would make the use of demountable shear connections complicated and uneconomic. In the face of these issues, the probability of the practical application of demountable and reusable composite structures would be very low. On the other hand, experiments and numerical simulations show that composite beams can develop plasticity even if a non-ductile shear connection is applied. In order to overcome these issues, a new calculation method was developed for the prediction of the plastic moment resistance of demountable composite beams. A simplified method was proposed based on the developed procedure by defining an effective shear resistance for the demountable shear connections. The effective shear resistance allows the current calculation method to be extended for demountable shear connections. In this way, the benefits of composite construction can be maintained while providing the possibility of reuse. [less ▲]

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See detailGenetic regulators of ventral midbrain gene expression and nigrostriatal circuit integrity
Gui, Yujuan UL

Doctoral thesis (2020)

Complex traits are a fundamental feature of diverse organisms. Understanding the genetic architecture of a complex trait is arduous but paramount because heterogeneity is prevalent in populations and ... [more ▼]

Complex traits are a fundamental feature of diverse organisms. Understanding the genetic architecture of a complex trait is arduous but paramount because heterogeneity is prevalent in populations and often disease-related. Genome-wide association studies have identified many genetic variants associated with complex human traits, but they can only explain a small portion of the expected heritability. This is partially because human genomes are highly diverse with large inter-personal difference. It has been estimated that every human differs from each other by at least 5 million variants. Moreover, many common variants with small effect can contribute to complex traits, but they cannot survive from stringent statistical cutoff given the currently available sample size. Mice are an ideal substitute. They are maintained in a controlled condition to minimize the variation introduced by environment. Each mouse of an inbred strain is genetically identical, but different strains bear innate genetic heterogeneity between each other, mimicking human diversity. Hence, in this work we used inbred mouse strains to study the genetic variation of complex traits. We focused on ventral midbrain, the brain region controlling motor functions and behaviors such as anxiety and fear learning that differ profoundly between inbred mouse strains. Such phenotypic diversity is directed by differences in gene expression that is controlled by cis- and trans-acting regulatory variants. Profound understanding on the genetic variation of ventral midbrain and its related phenotypic differences could pave the way to apprehend the whole genetic makeup of its associated disease phenotypes such as Parkinson’s disease and schizophrenia. Therefore, we set out to investigate the cis- and trans-acting variants affecting mouse ventral midbrain by coupling tissue-level and cell type-specific transcriptomic and epigenomic data. Transcriptomic comparison on ventral midbrains of C57BL/6J, A/J and DBA/2J, three inbred strains segregated by ~ 6 million genetic variants, pinpointed PTTG1 was the only transcription factor significantly altered at transcriptional level between the three strains. Pttg1 ablation on C57BL/6J background led to midbrain transcriptome to shift closer to A/J and DBA/2J during aging, suggesting Pttg1 is a novel regulator for ventral midbrain transcriptome. As ventral midbrain is a mixture of cells, tissue level transcriptome cannot always reveal cell type-specific regulatory variation. Therefore, we set out to generate single nuclei chromatin accessibility profiles on ¬ventral midbrains of C57BL/6J and A/J, providing a rich resource to study the transcriptional control of cellular identity and genetic diversity in this brain region. Data integration with existing single cell transcriptomes predicted the key transcription factors controlling cell identity. Putative regulatory variants showed differential accessibility across cell types, indicating genetic variation can direct cell type-specific gene expression. Comparing chromatin accessibility between mice revealed potential trans-acting variation that can affect strain-specific gene expression in a given cell type. The diverse transcriptome profiles in ventral midbrain can lead to phenotypic variation. Nigrostriatal circuit, bridging from ventral midbrain to dorsal striatum by dopaminergic neurons, is an important pathway controlling motor activity. To search for phenotypes related to dopaminergic neurons, we measured the dopamine concentration in dorsal striatum of eight inbred mouse strains. Interestingly, dopamine levels were varied among stains, suggesting it is a complex trait linked to genetic variation in ventral midbrain. To understand the genetic variation contributing to dopamine level differences, we conducted quantitative trait locus (QTL) mapping with 32 CC strains and found a QTL significantly associated with the trait on chromosome X. As expression changes are likely to be underlying the phenotypic variation, we leveraged our previous transcriptomic data from C57BL/6J and A/J to search for genes differentially expressed in the QTL locus. Col4a6 is the most likely QTL gene because of its 9-fold expression difference between C57BL/6J and A/J. Indeed, COL4A6 has been shown to regulate axogenesis during brain development. This coincides with our observation that A/J had less axon branching in dorsal striatum than C57BL/6J, prompting us to propose that Col4a6 can regulate the axon formation of dopaminergic neurons in embryonic stages. Our study provides a comprehensive overview on cis- and trans-regulatory variants affecting expression phenotypes in ventral midbrain, and how they could possibly introduce phenotypic difference associated with this brain region. In addition, our single nuclei chromatin landscapes of ventral midbrain are a rich resource for analysis on gene regulation and cell identity. Our work paves the way to apprehend full genetic makeup on the gene expression control of ventral midbrain, the result of which is important to understand the genetic background of midbrain associated phenotypes. [less ▲]

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See detailMicrostructure-based multiscale modeling of mechanical response for materials with complex microstructures
Kabore, Brice Wendlassida UL

Doctoral thesis (2020)

Complex microstructures are found in several material especially in biological tissues, geotechnical materials and many manufactured materials including composites. These materials are difficult to handle ... [more ▼]

Complex microstructures are found in several material especially in biological tissues, geotechnical materials and many manufactured materials including composites. These materials are difficult to handle by classical numerical analysis tools and the need to incorporate more details on the microstructure have been observed. This thesis focuses on the microstructure-based multi-scale modeling of the mechanical response of materials with complex microstructures and whose mechanical properties are inherently dependent on their internal structure. The conditions of interest are large displacements and high-rate deformation. This work contributes to the understanding of the relevance of microstructure informations on the macroscopic response. A primary application of this research is the investigation and modeling of snow behavior, it has been extended to modeling the impact response in concrete and composite. In the first part, a discrete approach for fine-scale modeling is applied to study the behavior of snow under the conditions mentioned above. Also, application of the this modeling approach to concrete and composite can be found in the appendices. The fine-scale approach presented herein is based on the coupling of Discrete Element Method and aspects of beam theory. This fine-scale approach has proven to be successful in modeling micro-scale processes found in snow. The micro-scale processes are mainly intergranular friction, intergranular bond fracture, creep, sintering, cohesion, and grain rearrangement. These processes not only influence the overall response of the material but also induce permanent changes in its internal structure. Therefore, the initial geometry considered during numerical analysis should be updated after each time or loading increment before further loading. Moreover, when the material matrix is partially granular and continuum, the influence of fluctuating grains micro-inertia caused by debonding, cracking and contact have a significant effect on the macroscopic response especially under dynamic loading. Consequently, the overall rate and history dependent behavior of the material is more easily captured by discrete models. Discrete modeling has proven to be efficient approach for acquiring profound scientific insight into deformation and failure processes of many materials. While important details can be obtained using the discrete models, computational cost and intensive calibration process is required for a good prediction material behavior in the real case scenarios. Therefore, in order to extend the abovementioned fine-scale model to real engineering cases a coarse-scale continuum model based have been developed using an upscaling approach. This upscaled model is based on the macroscopic response of the material with a special regard to the microstructure information of the material. Different strategies are presented for incorporating the microstructure information in the model. Micro-scale related dissipation mechanisms have been incorporated in the coarse-scale model through viscoplasticity and fracture in finite strain formulation. The thesis is divided into nine chapters, where each is an independent paper published or submitted as a refereed journal article. [less ▲]

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See detailA Formal Approach to Ontology Recommendation for Enhanced Interoperability in Open IoT Ecosystems
Kolbe, Niklas UL

Doctoral thesis (2020)

The vision of the Internet of Things (IoT) promises novel, intelligent applications to improve services across all industries and domains. Efficient data and service discovery are crucial to unfold the ... [more ▼]

The vision of the Internet of Things (IoT) promises novel, intelligent applications to improve services across all industries and domains. Efficient data and service discovery are crucial to unfold the potential value of cross-domain IoT applications. Today, the Web is the primary enabler for integrating data from distributed networks, with more and more sensors and IoT gateways connected to the Web. However, semantic data models, standards and vocabularies used by IoT vendors and service providers are highly heterogeneous, which makes data discovery and integration a challenging task. Industrial and academic research initiatives increasingly rely on Semantic Web technologies to tackle this challenge. Ongoing research efforts emphasize the development of formal ontologies for the description of Things, sensor networks, IoT services and domain-dependent observations to annotate and link data on the Web. Within this context, there is a research gap in investigating and proposing ontology recommendation approaches that foster the reuse of most suitable ontologies relevant to semantically annotate IoT data sources. Improved ontology reuse in the IoT enhances semantic interoperability and thus facilitates the development of more intelligent and context-aware systems. In this dissertation, we show that ontology recommendation can form a key building block to achieve this consensus in the IoT. In particular, we consider large-scale IoT systems, also referred to as IoT ecosystems, in which a wide range of stakeholders and service providers have to cooperate. In such ecosystems, semantic interoperability can only be efficiently achieved when a high degree of consensus on relevant ontologies among data providers and consumers exists. This dissertation includes the following contributions. First, we conceptualize the task of ontology recommendation and evaluate existing approaches with regard to IoT ecosystem requirements. We identify several limitations in ontology recommendation, especially concerning the IoT, which motivates the main focus on ontology ranking in this dissertation. Second, we subsequently propose a novel approach to ontology ranking that offers a fairer scoring of ontologies if their popularity is unknown and thus helps in providing a better recommendation in the current state of the IoT. We employ a `learning to rank' approach to show that qualitative ranking features can improve the ranking performance and potentially substitute an explicit popularity feature. Third, we propose a novel ontology ranking evaluation benchmark to address the lack of comparison studies for ontology ranking approaches as a general issue in the Semantic Web. We develop a large, representative evaluation dataset that we derive from the collected user click logs of the Linked Open Vocabularies (LOV) platform. It is the first dataset of its kind that is capable of comparing learned ontology ranking models as proposed in the literature under real-world constraints. Fourth, we present an IoT ecosystem application to support data providers in semantically annotating IoT data streams with integrated ontology term recommendation and perform an evaluation based on a smart parking use case. In summary, this dissertation presents the advancements of the state-of-the-art in the design of ontology recommendation and its role for establishing and maintaining semantic interoperability in highly heterogeneous and evolving ecosystems of inter-related IoT services. Our experiments show that ontology ranking features that are well designed with regard to the underlying ontology collection and respective user behavior can significantly improve the ranking quality and, thus, the overall recommendation capabilities of related tools. [less ▲]

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See detailNavigating the narrow circle: Rawls and Stout on justification, discourse and institutions
Burks, Deven UL

Doctoral thesis (2020)

Life in political society unfolds within the bounds of a narrow circle, epistemic and moral. A person has only finite faculties and restricted moral motivation. When formulating projects, the person ought ... [more ▼]

Life in political society unfolds within the bounds of a narrow circle, epistemic and moral. A person has only finite faculties and restricted moral motivation. When formulating projects, the person ought to recognize these limits but also to check them. Accordingly, she seeks a deliberative ideal which is sensitive both to good epistemic practice and to respectful relations. How might the person best justify the shape of her society’s institutions, statutes and policies? What reflexive attitudes and dispositions ought she to adopt towards her justificatory resources? The person might work through the sequence of standpoints from John Rawls’s “political liberalism”: a first-person, action-guiding framework of deliberation and reflection. Alternatively, she might model the exploratory discourse and personal virtues characteristic of Jeffrey Stout’s “democratic traditionalism”. This work reconstructs Rawls’s and Stout’s approaches to justification, discourse and institutions and compares their differing methods in search of the most adequate deliberative ideal for democratic society. [less ▲]

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See detailL'accord exclusif d'élection de for à travers de la Convention de La Haye: une efficacité mitigée
Mchirgui, Zohra UL

Doctoral thesis (2020)

L'accord exclusif d'élection de for en tant que mode d'attribution de compétence dans les litiges commerciaux internationaux fait partie de l'économie du contrat international. Il constitue une composante ... [more ▼]

L'accord exclusif d'élection de for en tant que mode d'attribution de compétence dans les litiges commerciaux internationaux fait partie de l'économie du contrat international. Il constitue une composante indispensable de l'autonomie des parties en tant que principe gouvernant les rapports commerciaux internationaux. À cet égard, la promotion du commerce et des investissements internationaux nécessitent l'élaboration d'un régime international apportant la sécurité et assurant l'efficacité des accords exclusifs d'élection de for. Tel est l'objectif proclamé par les rédacteurs de la Convention de La Haye sur les accords d'élection de for. L'analyse des dispositions de la Convention révèle que cette efficacité prônée par cet instrument est mitigée. Ce constat se vérifie tant au niveau de la validité de l'accord qu'au niveau de ses effets. [less ▲]

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See detailSurface Energy Modification of Filter Media to achieve optimal Performance Characteristics in select Applications
Staudt, Johannes UL

Doctoral thesis (2020)

The surface modification of modern filter media is examined from the perspective of the energetic properties and how they influence select filtration applications. In contrast to the known mechanical ... [more ▼]

The surface modification of modern filter media is examined from the perspective of the energetic properties and how they influence select filtration applications. In contrast to the known mechanical filtration mechanisms, which are mainly applicable to the solid-liquid separations, new findings strongly suggest that direct interaction forces between the filter and the functional fluids must be taken into account in order to achieve sufficient efficiencies. Separation processes of liquid phases such as liquidliquid coalescence (LLC) or the treatment of process gases with liquid-gas coalescence (LGC) require special properties of filter media with regard to the degree of interaction with these phases. These include but are not limited to surface energy, wettability, chemical resistance, etc. The focus falls increasingly on eliminating the undesired interactions of modern filters with the fluid to be filtered. Filtration with modern fine filter media can result in undesired additive removal (ADDREM), particularly of those additives that are not fully dissolved in carrier fluid. Specifically this refers to the removal of antifoamants from gear oils, which lead to serious consequential damage of those systems. The interfacial interactions between the filter media and the functional fluids are also responsible for other effects such as the highly undesirable phenomenon of electrostatic charging/discharging (ESC/ESD) during the filtration of low-conductivity oils. In this work, the effect of the surface energy modification, in particular, is examined in greater detail. Ultimately, the surface energy of modern filter media is characterized and modified in order to optimize their performance in select applications. The work also presents some examples that illustrate the importance of surface energy in highly challenging filtration applications. [less ▲]

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See detailRouting Strategies and Content Dissemination Techniques for Software-Defined Vehicular Networks
di Maio, Antonio UL

Doctoral thesis (2020)

Over the past years, vehicular networking has enabled a wide range of new applications that improve vehicular safety, efficiency, comfort, and environmental impact. Vehicular networks, however, normally ... [more ▼]

Over the past years, vehicular networking has enabled a wide range of new applications that improve vehicular safety, efficiency, comfort, and environmental impact. Vehicular networks, however, normally operate in communication-hostile environments and are characterized by dynamic topologies and volatile links, making it challenging to guarantee Quality of Service (QoS) and reliability of vehicular applications. To this end, the present work explores how the centralized coordination offered by Software-Defined Networking can improve the Quality of Service in vehicular networks, particularly for Vehicle-to-Vehicle (V2V) unicast routing and content dissemination. With regard to V2V routing, this work motivates the case for centralized network coordination by studying the performance of traditional MANET routing protocols when applied to urban VANETs, showing that they cannot provide satisfactory performance for modern vehicular applications because of their limited global network awareness, slow convergence, and high signaling. Hence, this work proposes and validates a centralized Multi-Flow Congestion-Aware Routing (MFCAR) algorithm to allocate multiple data flows on V2V routes. The first novelty of MFCAR is the SDN-based node-busyness estimation technique. The second novelty is the enhancement of the path-cost formulation as a linear combination of path length and path congestion, allowing the user application to fine-tune its QoS requirements between throughput and delay. Concerning content dissemination, this work proposes a Fairness- and Throughput-Enhanced Scheduling for Content Dissemination in VANETs (ROADNET), a centralized strategy to improve the tradeoff between data throughput and user fairness in deterministic vehicular content dissemination. ROADNET’s main novelties are the design of a graph-based multi-channel transmission scheduler and the enforcement of a transmission-priority policy that prevents user starvation. As additional contributions, the present work proposes a heuristic for the centralized selection of opportunistic content dissemination parameters and discusses the main security issues in Software-Defined Vehicular Networking (SDVN) along with possible countermeasures. The proposed techniques are evaluated in realistic scenarios (LuST), using discrete-event network simulators (OMNeT++) and microscopic vehicular-mobility simulators (SUMO). It is shown that MFCAR can improve PDR, throughput and delay for unicast V2V routing up to a five-fold gain over traditional algorithms. ROADNET can increase content dissemination throughput by 36% and user fairness by 6% compared to state-of-the-art techniques, balancing the load over multiple channels with a variance below 1%. [less ▲]

Detailed reference viewed: 200 (13 UL)