The Experience of Security in Human-Computer Interactions: Understanding Security Perceptions Through the Concept of User Experience

Doctoral thesis (2021)

In traditional interactions that do not rely on technology, most people are able to assess risks to their privacy and security and understand how to mitigate these risks. However, risk assessment and ... [more ▼]

In traditional interactions that do not rely on technology, most people are able to assess risks to their privacy and security and understand how to mitigate these risks. However, risk assessment and mitigation is more challenging when interacting with technology, and people’s perceptions of security and privacy risks are not always aligned with reality. It is important for those who design technologies to understand how people perceive the security of technologies in order to avoid having their designs contribute to erroneous perceptions. Instead, interactions with technology should be deliberately designed to ensure that people do not over- or underestimate the security provided by the system. This dissertation contributes to a better understanding of users’ perceptions of security in human-computer interactions. It investigates which factors induce a perception of security and privacy risks and how user-centered design can influence these factors to deliberately design for or against perceived security. I use a mixed-methods approach to address these objectives, including a systematic literature review, empirical data collection with focus groups, expert co-creation sessions, user tests in a controlled environment and a quantitative survey experiment. The first research objective is to analyze how security and privacy researchers induce a perception of security and privacy risks with research participants. We conducted a systematic literature review and focused our analysis on study methods; risk representation; the use of prototypes, scenarios, and educational interventions; the use of deception to simulate risk; and types of participants. We discuss benefits and shortcomings of the methods, and identify key methodological, ethical, and research challenges when representing and assessing security and privacy risk. We also provide guidelines for the reporting of user studies in security and privacy. The second research objective is to explore the factors that contribute to the acceptance of privacy and security risks in situations where people need to weigh the potential advantages of a technology against its associated privacy or security risks. We conducted a series of focus groups and highlighted the reasons why people accept compromises to their privacy and security, finding that perceived usefulness and the fulfilment of the psychological needs for autonomy and control were important factors. Our results suggest potential links between technology acceptance models and user experience models in the context of privacy-relevant interactions. The third research objective is to design and evaluate examples of visible representations of security mechanisms, with a focus on encryption. We studied the effects of these visual and textual representations empirically to understand the impact of these visible security mechanisms on user experience, perceptions of security and users’ understanding of encryption. We addressed this question in a series of studies, both lab studies and online experiments. In a vignette experiment, we find that more complex descriptions of encryption can lead to a better understanding and higher perceived security when designed carefully. However, we find no effect of novel visualizations of encryption on user experience (UX), perceived security or understanding of encryption. The fourth objective is to explore how we might make the link from subjective experience to more secure behaviors. We introduce a new framework of security-enhancing friction design. The framework suggests helping users behave more securely by designing for moments of negative UX in security-critical situations while also ensuring that overall UX remains at an acceptable level to avoid disuse of secure technologies. Overall, this doctoral dissertation contributes to research in the field of human-computer interaction, and more specifically, usable privacy and security. It improves our understanding of the methods used by researchers in the field of usable privacy and security use to create a perception of risk, and the factors that make people accept or reject certain privacy trade-offs. This dissertation also makes contributions to helping researchers and creators of technology understand how their designs influence perceptions of security, UX and understanding of encryption. This enables them to design for or against a perception of security, depending on the actual level of security provided by the technology. Finally, we conceptualize security-enhancing friction, a framework that suggests helping users to behave more securely by designing for moments of negative UX. [less ▲]

Learning How to Be Modern: An Ethnography of the Religious Education of L/liberal Jewish Talmud Torah Students in Luxembourg

Doctoral thesis (2021)

This dissertation is an ethnography of children and young people growing up Jewish in Luxembourg. It focuses on the students of a Talmud Torah class in a Liberal synagogue that, in recent years, has drawn ... [more ▼]

This dissertation is an ethnography of children and young people growing up Jewish in Luxembourg. It focuses on the students of a Talmud Torah class in a Liberal synagogue that, in recent years, has drawn increasing numbers of highly mobile, multilingual families from around the world. As these students learn how to be Jewish and carry on Jewish tradition, they simultaneously explore what it means to be modern and to be modern Jews. This process pushes them to confront a series of ambiguities and apparent paradoxes across the contexts of their everyday lives – in Talmud Torah, at home, and at school. Based on 31 months of fieldwork, this dissertation reveals the nuanced semiotic ideologies and competing visions of modernity that become visible through the lens of the students' Talmud Torah learning, including learning to read Hebrew, engaging with religious texts, and participating in ritual performance, and their school experiences. The students grapple with, navigate, and position themselves in relation to these different 'projects of modernity' as they work to make sense of and bring together the aims of Jewish continuity and liberal modernity and all that these entail. By exploring these processes, this dissertation aims to participate in the anthropological conversation about 'modernities' and 'the modern' as a project that is both embracing of the liberal, the secular, and inclusivity and can be powerfully normative, constraining, and exclusionary, and to encourage us as anthropologists and teachers to think about how we might leave open the possibility for nuance and alternative attachments, desires, goals, mobilities, and ways of being in the classroom and beyond. [less ▲]

Attaques et preuves de sécurité des protocoles d'échange de clés authentifiés

Doctoral thesis (2021)

The vast majority of communication on the Internet and private networks heavily relies on Public-key infrastructure (PKI). One possible solution, to avoid complexities around PKI, is to use Password ... [more ▼]

The vast majority of communication on the Internet and private networks heavily relies on Public-key infrastructure (PKI). One possible solution, to avoid complexities around PKI, is to use Password Authenticated Key-Exchange (PAKE) protocols. PAKE protocols enable a secure communication link between the two parties who only share a low-entropy secret (password). PAKEs were introduced in the 1990s, and with the introduction of the first security models and security proofs in the early 2000s, it was clear that PAKEs have a potential for wide deployment - filling the gap where PKI falls short. PAKEs' PKI-free nature, resistance to phishing attacks and forward secrecy are just some of the properties that make them interesting and important to study. This dissertation includes three works on various aspects of PAKEs: an attack on an existing PAKE proposal, an application of PAKEs in login (for password leak detection) and authentication protocols (HoneyPAKEs), and a security analysis of the J-PAKE protocol, that is used in practice, and its variants. In our first work, we provide an empirical analysis of the zkPAKE protocol proposed in 2015. Our findings show that zkPAKE is not safe against offline dictionary attacks, which is one of the basic security requirements of the PAKE protocols. Further, we demonstrate an implementation of an efficient offline dictionary attack, which emphasizes that, it is necessary to provide a rigorous security proof when proposing a new protocol. In our second contribution, we propose a combined security mechanism called HoneyPAKE. The HoneyPAKE construction aims to detect the loss of password files and ensures that PAKE intrinsically protects that password. This makes the PAKE part of the HoneyPAKE more resilient to server-compromise and pre-computation attacks which are a serious security threat in a client-server communication. Our third contribution facilitates the wider adoption of PAKEs. In this work, we revisit J-PAKE and simplify it by removing a non-interactive zero knowledge proof from the last round of the protocol and derive a lighter and more efficient version called sJ-PAKE. Furthermore, we prove sJ-PAKE secure in the indistinguishability game-based model, the so-called Real-or-Random, also satisfying the notion of perfect forward secrecy. [less ▲]

Verification of design models of cyber-physical systems specified in Simulink

Doctoral thesis (2021)

Recent advances in cyber-physical systems (CPS) have allowed highly available and approachable technologies with interconnected systems between the physical assets and the computational software ... [more ▼]

Recent advances in cyber-physical systems (CPS) have allowed highly available and approachable technologies with interconnected systems between the physical assets and the computational software components. This has resulted in more complex systems with wider capabilities. For example, they can be applied in various domains such as safe transport, efficient medical devices, integrated systems, critical infrastructure control and more. The development of such critical systems requires advanced new models, algorithms, methods and tools to verify and validate the software components and the entire system. The verification of cyber-physical systems has become challenging: (1) The complex and dynamical behaviour of systems requires resilient automated monitors and test oracles that can cope with time-varying variables of CPS. (2) Given the wide range of existing verification and testing techniques from formal to empirical methods, there is no clear guidance as to how different techniques fare in the context of CPS. (3) Due to serious issues when applying exhaustive verification to complex systems, a common practice is needed to verify system components separately. This requires adding implicit assumptions about the operational environment of system components to ensure correct verification. However, identifying environment assumptions for cyber-physical systems with complex, mathematical behaviors is not trivial. In this dissertation, we focus on addressing these challenges. In this dissertation, we propose a set of effective approaches to verify design models of CPS. The work presented in this dissertation is motivated by ESAIL maritime micro-satellite system, developed by LuxSpace, a leading provider of space systems, applications and services in Luxembourg. In addition to ESAIL, we use a benchmark of eleven public-domain Simulink models provided by Lockheed Martin, which are representative of different categories of CPS models in the aerospace and defence sector. To address the aforementioned challenges, we propose (1) an automated approach to translate CPS requirements specified in a logic-based language into test oracles specified in Simulink. The generated oracles are able to deal with CPS complex behaviours and interactions with the system environment; (2) An empirical study to evaluate the fault-finding capabilities of model testing and model checking techniques for Simulink models. We also provide a categorization of model types and a set of common logical patterns for CPS requirements; (3) An automated approach to synthesize environment assumptions for a component under analysis by combining search-based testing, machine learning and model checking procedures. We also propose a novel technique to guide the test generation based on the feedback received from the machine learning process; and (4) An extension of (3) to learn more complex assumptions with arithmetic expressions over multiple signals and numerical variables. [less ▲]

Managing migration flows within the adequate data protection instrument - Scoping exercise between general and law enforcement data protection rules applicable to third country nationals

Doctoral thesis (2021)

Structuration of piezotronic junctions for ultrasensitive strain sensors

Doctoral thesis (2021)

The piezotronic effect relies on the creation of piezoelectric polarization charges mechanically induced within a piezoelectric semiconductor to modulate the carrier dynamics across electronic contact ... [more ▼]

The piezotronic effect relies on the creation of piezoelectric polarization charges mechanically induced within a piezoelectric semiconductor to modulate the carrier dynamics across electronic contact interfaces. The field of piezotronics is a relatively new area of study, based on a mechanical signal triggering, which is one of the most common kind of interactions between the environment and electronic systems. It started to draw a considerable attention in the early 2010’s, by reaching higher electromechanical sensitivities when compared to conventional methods of sensing. The rapidly spreading Internet-of-Things is accelerating Micro-ElectroMechanical Systems (MEMS) industry to deliver highly sensitive and miniaturized self-sensing sensors with low power consumption and cost-effective production process. Within this context, strain sensors based on the piezotronic effect appear as promising candidates to address these needs. However, several crucial questions remain unanswered or need to be refined, concerning the design and integration of piezotronic junctions with its fabrication process into microsystems or MEMS, the optimal configuration for strain sensing as well as noise studies for such systems. This PhD thesis proposes to rationalize the piezotronic effect for strain sensors and presents a novel microfabrication process integrating for the first time piezotronic strain sensors in millimetre-sized cantilevers on flexible polymeric substrates by means of maskless laser lithography. The atomic layer deposition (ALD) technique was used for the deposition of ZnO polycrystalline thin films on high work function metals to obtain Schottky junctions. However, such ZnO-based Schottky junctions by ALD have never been post-processed and integrated into a strain sensor. We propose to rationalize the ALD processing to obtain wurtzite polycrystalline zinc oxide thin films with a privileged (002) orientation and to make it compatible with microfabrication processing on polymer. The difficulties linked with the integration of inorganic thin films onto a polymeric substrate within the developed microfabrication process will be highlighted. We propose appropriate adjustments of the sensor’s design and the process flow. Pt/ZnO/Pt back-to-back Schottky diode junctions have been shaped in interdigitated microelectrodes to get piezotronic strain sensing on the clamp area of the cantilever structure. The conduction mechanisms occurring within the piezotronic strain microsensors have been thoroughly studied, based on the thermionic emission model. The developed electrical model will be detailed, emphasizing the presence of interface trap states and their prominent impact on the electrical characteristics. The piezotronic strain sensors’ transducing properties will be detailed as well by the mean of force spectroscopy, leading to the expected Schottky barrier height modulation by the piezotronic effect. Furthermore, we investigated for the first time the noise figure of within strain sensors based on the piezotronic effect. These new insights about noise amplitudes and origins are promising matter of optimization to improve the signal-to-noise ratio of the sensor. Within the last section of this work, we will detail the piezotronic strain sensors size miniaturization for integration in microcantilevers in a full-SU8 body. The miniaturization of our strain sensors makes them more prone for AFM (Atomic Force Microscopy) scanning probe operations on commercial machines, with the aim of greatly improving the sensitivity to small mechanical deformations. The approach taken for the microfabrication of these miniaturized sensors is based on a reversed processing by the mean of a sacrificial layer. This raised new difficulties in terms of metal adhesion and electrical contact continuity, which will be reported. The results obtained are highly promising and pave the way towards the processing of ultrasensitive strain microsensors on MEMS structures, as well as their great potential for AFM scanning probe operations. [less ▲]

Computational guided frameworks to identify signalling perturbations for cellular transitions: application to cellular conversion, disease and regeneration

Doctoral thesis (2021)

Essays on the Economics of Forced Displacement and Conflict

Doctoral thesis (2021)

In Chapter 1, we analyze the determinants of the internal mobility of refugees in Turkey. We track down this mobility relying on geolocalized mobile phone calls data and bring these measures to a micro ... [more ▼]

In Chapter 1, we analyze the determinants of the internal mobility of refugees in Turkey. We track down this mobility relying on geolocalized mobile phone calls data and bring these measures to a micro-founded gravity model in order to estimate the main drivers of refugee mobility across 26 regions in 2017. Our results show that the movements of refugees are sensitive to income differentials and contribute therefore to a more efficient allocation of labor across space. Comparing these findings with those of individuals with a non-refugee status, we find that refugees are more sensitive to variations of income at origin and to distance, while less responsive to changes in income at destination. These findings are robust to the way mobility is inferred from phone data and to the choice of the geographical unit of investigation. Further, we provide evidence against some alternative explanations of mobility such as the propensity to leave refugee camps, transit through Turkey, social magnet effects and sensitivity to agricultural business cycles. In Chapter 2, we exploit annual variations in the presence of refugees to approximate the resulting changes in diversity in the refugee-hosting areas across 23 countries in sub-Saharan Africa. We then assess the relationship between the refugee-corrected diversity indices and the likelihood of conflict between 2005 and 2016. In line with our theoretical framework, the refugee-corrected polarization exacerbates the risk of conflict. A one standard deviation increase in the polarization index raises the incidence of violent conflict by 5 percentage points. Such an effect corresponds to a 10 percent increase, at the mean. The opposite effect is found for the fractionalization index. Our results should not be interpreted as evidence that refugees per se impact the likelihood of violence. Indeed, we do not find any significant correlation between the number of refugees and the occurrence of conflict. Instead, our results point to the risk of conflict when refugees exacerbate ethnic polarization in the hosting communities. On the contrary, a situation where refugee flows raises the level of ethnic fractionalization is likely to see an attenuated risk of violence. This certainly calls for specific interventions in refugee-hosting and polarized communities. We also conduct additional analysis based on individual data and recent COVID-related protests. Results tend to support aggregate results. Refugee-corrected polarization raises the likelihood of experiencing physical assault and interpersonal crime by 2.7 resp. 4.2 percentage points, while no effect can be found for ethnic attachment and trust. Finally, the relevance of our results in the context of the COVID-19 pandemic is explored. In Chapter 3, we study the impact of independent media networks on political accountability during the Arab Spring across the Middle East and North Africa region. The study focuses on two major media networks in the Arab world: Al Jazeera and Al Arabiya. Political accountability is proxied using principally a measure of protests. Data on both political accountability measures and the media networks derive from the Arab Barometer surveys. The regional-level analysis is based on Jordan, Lebanon and Palestine due to data availability. The study uses regional ruggedness as an instrumental variable for the non-random use of independent media among individuals. Results are estimated using a Two-Stage least Squares (2SLS) regression analysis and indicate a positive and significant impact of independent media on political accountability. Several extensions are performed. First, the analysis is replicated for the impact of state media networks and results suggest a significant negative impact on participation to protests. Second, the impact of using independent media for public sector workers' participation to protests is compared with non-public workers. While a significant positive impact of using independent media is found among non-public workers, independent media among public workers seem not to affect their participation to protests. Some channels are tested using additional outcomes such as governmental trust, political alignment, signing petitions and general trust as proxies for political accountability. [less ▲]

Kontext und Praktiken der Circular Economy in Luxemburg

Doctoral thesis (2021)

Stretching Directions in Cislunar Space: Stationkeeping and an Application to Transfer Trajectory Design

Doctoral thesis (2021)

The orbits of interest for potential missions are stable or nearly stable to maintain long-term presence for conducting scientific studies and to reduce the possibility of rapid departure. Near ... [more ▼]

The orbits of interest for potential missions are stable or nearly stable to maintain long-term presence for conducting scientific studies and to reduce the possibility of rapid departure. Near Rectilinear Halo Orbits (NRHOs) offer such stable or nearly stable orbits that are defined as part of the L1 and L2 halo orbit families in the circular restricted three-body problem. Within the Earth-Moon regime, the L1 and L2 NRHOs are proposed as long-horizon trajectories for cislunar exploration missions, including NASA's upcoming Gateway mission. These stable or nearly stable orbits do not possess well-distinguished unstable and stable manifold structures. As a consequence, existing tools for stationkeeping and transfer trajectory design that exploit such underlying manifold structures are not reliable for orbits that are linearly stable. The current investigation focuses on leveraging stretching direction as an alternative for visualizing the flow of perturbations in the neighborhood of a reference trajectory. The information supplemented by the stretching directions are utilized to investigate the impact of maneuvers for two contrasting applications; the stationkeeping problem, where the goal is to maintain a spacecraft near a reference trajectory for a long period of time, and the transfer trajectory design application, where rapid departure and/or insertion is of concern. Particularly, for the stationkeeping problem, a spacecraft incurs continuous deviations due to unmodeled forces and orbit determination errors in the complex multi-body dynamical regime. The flow dynamics in the region, using stretching directions, are utilized to identify appropriate maneuver and target locations to support a long lasting presence for the spacecraft near the desired path. The investigation reflects the impact of various factors on maneuver cost and boundedness. For orbits that are particularly sensitive to epoch time and possess distinct characteristics in the higher-fidelity ephemeris model compared to their CR3BP counterpart, an additional feedback control is applied for appropriate phasing. The effect of constraining maneuvers in a particular direction is also investigated for the 9:2 synodic resonant southern L2 NRHO, the current baseline for the Gateway mission. The stationkeeping strategy is applied to a range of L1 and L2 NRHOs, and validated in the higher-fidelity ephemeris model. For missions with potential human presence, a rapid transfer between orbits of interest is a priority. The magnitude of the state variations along the maximum stretching direction is expected to grow rapidly and, therefore, offers information to depart from the orbit. Similarly, the maximum stretching in reverse time, enables arrival with a minimal maneuver magnitude. The impact of maneuvers in such sensitive directions is investigated. Further, enabling transfer design options to connect between two stable orbits. The transfer design strategy developed in this investigation is not restricted to a particular orbit but applicable to a broad range of stable and nearly stable orbits in the cislunar space, including the Distant Retrograde Orbit (DROs) and the Lunar Orbits (LO) that are considered for potential missions. Examples for transfers linking a southern and a northern NRHO, a southern NRHO to a planar DRO, and a southern NRHO to a planar LO are demonstrated. [less ▲]

Design and synthesis of novel benzoxazines to replace traditional reinforcing resins in rubber compounds

Doctoral thesis (2021)

The mechanical performance of tires is controlled by many of the ingredients used in their production. Among them, novolac-type phenolic resins (PR) are petroleum-based materials commonly employed to ... [more ▼]

The mechanical performance of tires is controlled by many of the ingredients used in their production. Among them, novolac-type phenolic resins (PR) are petroleum-based materials commonly employed to reinforce rubber compounds. Even though overall performance is efficient, there is a growing societal need to develop alternatives to these resins as they are challenged by REACH regulations. Benzoxazine resins (Bz) are a new generation of materials that can be suitable for this purpose; they hold potential for improvement of both the mechanical properties and the sustainability of the rubber compounds. However, while PR have been extensively used and their interactions with tire compounds are well known, the use of benzoxazines in rubber compounds requires extensive studies and in-detail investigations. This thesis aims at filling this gap and designing benzoxazine resins that could be relevant alternatives to PR. For this purpose, novel sulfur containing dibenzoxazines were successfully synthesized and their interactions with rubber compounds were methodically investigated. Diphenolic compounds with either disulfide bonds (S‒S), or monosulfide bonds (‒S‒) were reacted with monoamines such as furfurylamine, a bio-based amine produced from agricultural byproducts. These partially bio-based original precursors, which were never reported before, exhibited polymerization behaviors that greatly fit the required conditions for rubber vulcanization. Indeed, the curing of these novel benzoxazine monomers occurred during rubber vulcanization, allowing the elaboration of reinforced materials at the molecular scale without detrimental side-reactions with the curing package. A fine investigation of the mechanical and thermal properties of the resulting rubber compounds indicated the reinforcing effect of these new resins at the macroscale. Therefore, the potential of each benzoxazine to act as a reinforcing resin was tested in real tire parts confirming the potential of Bz to be used as alternatives to PR resins in carbon-black filled compounds. In conclusion, the outcome of this thesis emphasizes that structural features of benzoxazines are a major parameter to be considered for their use in rubber reinforcement. Thanks to the knowledge generated, it was possible to develop novel benzoxazine resins capable of reinforcing rubber compounds in place of traditional phenolic resins. This study also paves the way to replace petroleum based resins by partially bio-based precursors, improving the sustainability of tire compounds. [less ▲]

Probabilisitic limit theorems and the geometry of random fields

Doctoral thesis (2021)

The topics presented in this thesis lie at the interface of probability theory and stochastic geometry, with emphasis on the asymptotic study of geometric objects associated with Gaussian random fields ... [more ▼]

The topics presented in this thesis lie at the interface of probability theory and stochastic geometry, with emphasis on the asymptotic study of geometric objects associated with Gaussian random fields defined on manifolds. Such a research stream has been rapidly growing in past years, resulting in a number of developments focussing on local and global geometric quantities. Our principal aim is to discuss probabilistic methods allowing one to deal with the asymptotic fluctuations of volumes of zero sets (also called nodal sets) of Gaussian Laplace eigenfunctions as the eigenvalues diverge to infinity, with a particular focus on the models of Arithmetic Random Waves on the three-dimensional torus and Berry's Random Plane Wave on the two-dimensional Euclidean space. We prove universal variance estimates and non-Gaussian limit theorems for the zero sets of multiple independent Arithmetic Random Waves, complementing several related works in the literature. Our analysis for this builds on an abstract cancellation result applicable to the setting of Gaussian Laplace eigenfunctions on manifolds, yielding in particular a formal description of the so-called Berry's Cancellation Phenomenon observed in various models of random eigenfunctions. For the Berry Random Plane Wave, we prove spatial functional limit theorems for discretized and truncated versions of the nodal length indexed by rectangular domains. Such a contribution yields a basis for proving a fully general functional limit theorem for the nodal length and opens doors to a number of novel probabilistic limit theorems involving semi-local functionals of these nodal length processes. A common technique lying at the core of our arguments for dealing with these tasks is the asymptotic analysis of the Wiener-Itô chaos expansion in Hermite polynomials of such geometric quantities, often allowing one to reduce investigations on Wiener chaoses of lower order. In this context, we discuss properties of generalized Hermite polynomials with matrix arguments, appearing in multivariate statistics and the theory of zonal polynomials. We argue that this family of orthogonal polynomials is particularly effective for deducing chaotic expansions of random variables that are symmetric functionals in the eigenvalues of underlying Gaussian random matrices, notably appearing in different applications dealing with the geometry of random fields. We furthermore present a new characterization of matrix-Hermite polynomials as the eigenfunctions of a generalized Ornstein-Uhlenbeck semigroup on matrix spaces. The above mentioned probabilistic limit theorems originate from the systematic use of the Malliavin-Stein approach on Gaussian spaces, a collection of analytic statements allowing one to deduce probabilistic limit theorems by means of variational techniques. Such a series of results typically emerges from the combination of Stein's method for probabilistic approximations and Malliavin's infinite-dimensional differential calculus. At the end of this thesis, we present preliminary computations yielding variance estimates and Central Limit Theorems for certain non-linear functionals associated with the d-dimensional Berry Random field. Also, we discuss several aspects around optimal convergence rates within Gamma approximations of functionals of Gaussian fields. [less ▲]

THE DEFAULT RULE OF THE TRANSFER BACK OF PROPERTY AS A CONSEQUENCE OF THE REAL CHARACTER OF A LUXEMBOURG FIDUCIARY CONTRACT.

Doctoral thesis (2021)

One of the objectives of the thesis is to reveal the theoretic foundations and the real character of the Luxembourg fiducie. The theoretic foundations of the Luxembourg fiducie shall support the answer to ... [more ▼]

One of the objectives of the thesis is to reveal the theoretic foundations and the real character of the Luxembourg fiducie. The theoretic foundations of the Luxembourg fiducie shall support the answer to the main question raised in the thesis regarding the (automatic) transfer of fiduciary assets to fiduciant/beneficiary as a default rule, which is not provided for by the law regulating fiducie. The (automatic) transfer of fiduciary assets to fiduciant/beneficiary after the expiration of a fiduciary agreement is supported by the real dimension of the fiduciary patrimony and the prerogatives of the parties of the fiduciary patrimony. The real dimension of the Luxembourg fiducie is demonstrated by fiduciary patrimony analysed as a patrimony by appropriation and universality. The automaticity of the transfer back of the fiduciary property is supported by the fact that transferability cannot be understood in a traditional way and a transfer by operation of law replaces a voluntary transfer of an owner. The main arguments which were exposed in the thesis in order to support the default rule of the transfer back of the property are based on the economic property, the understanding of fiduciary function as an office and fiduciary patrimony as a free-floating patrimony being at the same time the patrimony by appropriation and universality. [less ▲]

Laser Welding of Metals to Polymers Under the Special Influence of Surface Pretreatment on Interfacial Thermal Transfer

Doctoral thesis (2021)

Joining of metals to polymers is increasing among various industries because of its ability to produce lightweight hybrid products with tailored properties. Common joining methods, such as adhesive ... [more ▼]

Joining of metals to polymers is increasing among various industries because of its ability to produce lightweight hybrid products with tailored properties. Common joining methods, such as adhesive bonding and mechanical fastening, require adding a third material which might involve hazardous chemicals or add extra weight and stress concentration points to the component. On the other hand, Laser-Assisted Metal – Polymer joining (LAMP) is a contactless, rapid, highly precise and energy-efficient technique, that produces autogenous and miniaturized joints. It was already demonstrated that surface pretreatment prior to the welding process has a significant impact on the joint performance by modifying surface chemistry and topography, promoting chemical bonding and mechanical interlocking. This research aims at expanding the understanding of the effects of surface properties on the joint’s performance by investigating their influence on interfacial thermal transfer. While increased surface roughness of metallic partner is expected to improve LAMP joint performance by promoting mechanical interlocking, it is hypothesized that a smoother surface would improve the joint quality by enhancing the interfacial thermal transfer during the welding process, resulting in a larger area of molten polymer at the interface and a better joint performance. In this research, aluminum (Al1050) and titanium (Ti64) were joined with polyamide (PA6.6). Initially, laser welding parameters were optimized and kept constant during all surface pretreatments’ investigations. Preliminary surface pretreatments, using short-pulsed laser ablation and atmospheric plasma pretreatment, were conducted on Al1050 – PA6.6 to analyze the effects of surface composition and topography on joint quality and performance, and to optimize interfacial adhesion. Results show a correlation between increased surface oxidation and surface energy with improved interfacial adhesion and joint resistance to shear failure. Compared to plasma pretreated surfaces, laser ablation of metals results in a very rough surface which exhibits perfect wettability to both water and diiodomethane. This promotes mechanical interlocking and interfacial adhesion, resulting in a relatively stronger joint failing in a cohesive failure mode. Results confirm that an improvement of the assembly’s shear resistance to failure can certainly be achieved without an increase in surface roughness and interfacial interlocking, as observed in case of plasma pretreatment. Design of Experiments (DoE) techniques were utilized for both material combinations in order to optimize laser ablation process and to investigate the effects of pretreatment parameters on surface properties, interfacial thermal transfer, joint quality and resistance to failure. Laser ablation parameters influenced the surface topography with no significant effect on the surface composition, and all laser-ablated surfaces showed perfect wettability to both water and diiodomethane. While all ablated surfaces demonstrate cohesive failure mode, smoother ablated surfaces results in a better interfacial thermal transfer as indicated by the Thermal Contact Resistance (TCR) calculations and measurements, based on Cooper–Mikic–Yovanovich (CMY) model and layered Laser Flash Analysis (LFA) investigations, respectively. Results show that a smoother ablated surface results in better interfacial thermal transfer, melting a larger area of polymer which increases the joint quality and resistance to shear load. [less ▲]

Thought, Language, and Reasoning. Perspectives on the Relation Between Mind and Language

Doctoral thesis (2021)

This dissertation is an investigation into the relation between mind and language from different perspectives, split up into three interrelated but still, for the most part, self-standing parts. Parts I ... [more ▼]

This dissertation is an investigation into the relation between mind and language from different perspectives, split up into three interrelated but still, for the most part, self-standing parts. Parts I and II are concerned with the question how thought is affected by language while Part III investigates the scope covered by mind and language respectively. Part I provides a reconstruction of Ludwig Wittgenstein’s famous Private Language Argument in order to apply the rationale behind this line of argument to the relation between mind and language. This argumentative strategy yields the conclusion that reasoning – an important type of thought – is constitutively dependent on language possession and is therefore not available to non-linguistic creatures. This result is achieved by considering the preconditions for reasoning – given that it is a rule-governed activity – and eliminating competitors to language for providing reasoners with what it takes to reason. Part II provides a critical outlook on the wide and highly heterogeneous field of linguistic relativity theories. It is argued that no kind of linguistic relativity whatsoever follows from the conclusion of Part I – i.e., the claim that reasoning is constitutively dependent on having a language. While Part II does not provide a conclusive argument against the linguistic relativity hypothesis, it is argued that endorsement of linguistic relativity theories often rests on a mistaken assumption to the effect that language and culture are interwoven in a way which makes it impossible to separate culture and language, as well as their respective studies. This assumption is undermined by providing examples of languages which clearly predate their culture (Esperanto) or do not even have a culture at all (Klingon). So, the assumption that language and culture are inextricably intertwined is refuted by way of counterexample. Part III provides an in-depth examination of the Principle of Expressibility – prominently endorsed and formulated by John Searle – which claims that whatever can be thought can also be said. The domains of what can be thought and of what can be said are considered in set theoretic terms in order to determine whether one is contained in the other, so that everything we can think can also be adequately communicated. After thorough study of interpretative issues regarding the Principle of Expressibility and consideration of the most pressing potential counterexamples to the principle, we can conclude that we have good reason to believe in the truth of the Principle of Expressibility. In conclusion, the achieved results are related back to prominent positions in the discussion about thought and language which already make their appearance in the very beginning of this investigation. The final chapter of this dissertation reminds us that eminent figures in philosophy have often taken a wrongheaded perspective on the relation between language and thought, so that language has frequently appeared to be an impediment to thought. We can, however, confidently conclude that language, on the contrary, is by far our most apt means for thought and that reasoning would not even be possible without the resources language provides. [less ▲]

Studies in Luxembourgish Micro-Toponymy and Linguistic History. Phonology, Morphology, Syntax and lexical Studies

Doctoral thesis (2021)

Complex Networks in Manufacturing - Suitability and Interpretation

Doctoral thesis (2021)

The fourth industrial revolution, and the associated digitization of the manufacturing industry, has resulted in increased data generation. Industry leaders aim to leverage this data to enhance ... [more ▼]

The fourth industrial revolution, and the associated digitization of the manufacturing industry, has resulted in increased data generation. Industry leaders aim to leverage this data to enhance productivity, boost innovation and generate new manners of competition. In this work, out of the many domains within the manufacturing sector, production will be explored. To this end, the mathematical tools of network science are utilized to characterize and evaluate production networks in terms of complex networks. In a manufacturing complex network, nodes represent workstations, and directed edges abstract the material flow that occurs among pairs of workstations. These types of complex networks are known as "material flow networks" and are used to study issues associated with manufacturing systems in the domain of production at the intra-enterprise level. While some research on the subject exists, this work will demonstrate that the use of complex networks to describe and evaluate manufacturing systems constitutes a nascent research field. In fact, the limited existing literature tackles a vast number of issues raising more questions than providing answers. This work aims to answer a number of those open questions. Firstly, which complex network metrics are suitable in the context of manufacturing networks will be determined. As a consequence, unsuitable metrics will be identified as well. To accomplish this, the flow underlying assumptions of popular complex network metrics is studied and compared to those of manufacturing networks. Furthermore, other existing complex network metrics with more appropriate underlying assumptions, but not yet explored in the context of manufacturing, are proposed and evaluated. Then, the appropriate interpretation of suitable complex network metrics in terms of Operations Research is provided. Finally, shortcomings of these metrics are highlighted to caution practitioners regarding their use in industrial settings. [less ▲]

Old and New Antiferroelectrics: Experimental Studies of Phase Transitions in Model Materials

Doctoral thesis (2021)

Antiferroelectrics are a subcategory of ferroic materials that display no spontaneous polarisation due to antiparallel ionic displacements. These materials undergo an electric field-induced transition to ... [more ▼]

Antiferroelectrics are a subcategory of ferroic materials that display no spontaneous polarisation due to antiparallel ionic displacements. These materials undergo an electric field-induced transition to a polar phase accompanied by the emergence of a spontaneous polarisation. As for ferroelectrics, heating up an antiferroelectric material above a certain temperature Tc will cause another phase transition towards a paraelectric phase. Antiferroelectricity is currently the subject of a renewed interest, mostly due to a rising need of new smart materials for applications such as energy storage, electrocaloric cooling or microelectronics. The most-studied antiferroelectric is lead zirconate PbZrO3perovskite. However, the understanding of its switching mechanism is still incomplete. In this work, we will first present our study on the sol-gel synthesis and characterisation of antiferroelectric polycrystalline thin films of canonical lead zirconate PbZrO3. We will notably highlight the realisation of an in-plane switching of our antiferroelectric samples grown on transparent substrates, as well as the optical observation of this switching through birefringence changes. On a more fundamental side, the oldest and best-known model of antiferroelectricity was defined by Kittel in 1951. No real unidimensional Kittel-like model material has, to our knowledge, been identified yet. We will detail our spectroscopic study of the lattice dynamics of francisite Cu3Bi(SeO3)2O2Cl which combines several inelastic scattering experiments. We will then discuss how this study proves that francisite is, to our knowledge, the best candidate of a material displaying a displacive antiferroelectric phase transition. [less ▲]

Les reconfigurations du politique et du religieux, au prisme de la sécularisation et du bioconservatisme : La Manif pour tous en France et le Family Day en Italie.

Doctoral thesis (2021)

Tensions between politics and religion lead to a very productive scope of investigation for those interested in contemporary democratic reconfigurations. In this context, this thesis will address two ... [more ▼]

Tensions between politics and religion lead to a very productive scope of investigation for those interested in contemporary democratic reconfigurations. In this context, this thesis will address two social phenomena located at the crossroads of political and religious considerations, in a comparative perspective: ‘La Manif pour tous’ - a movement opposing gay- marriage in France – and The Family Day – opposition movement to same-sex civil partnership in Italy. This study highlights the importance of the political and religious context in the structuring, the system of values and the impact of those so-called “anti-gender” movements, through a multidisciplinary approach bringing together conceptual tools from the social movement theory, religious sociology and political philosophy, but also through semi- structured interviews and attendee observations. The comparative perspective will indeed reveal a greater empowerment process for the French case, with more pronounced efforts to distance itself from traditional political and religious institutions. Despite this, this thesis will bring up a certain convergence of these movements towards the formation of a bio-conservative block, steeped in Christian anthropology but also scientific and legal considerations that challenge the principles of contemporary liberal democracies. The bio-conservative block shakes up the opposition between modern autonomy and religious heteronomy, and works on setting up and developing new political cleavages. [less ▲]

Using the Blockchain Technology for Trust Improvement of Processes in Logistics and Transportation

Doctoral thesis (2021)

This thesis address the general problem of safe and secure transport of dangerous goods (TDG). The TDG is very complicated to manage because of risk for the environment and human life. Currently, it ... [more ▼]

This thesis address the general problem of safe and secure transport of dangerous goods (TDG). The TDG is very complicated to manage because of risk for the environment and human life. Currently, it suffers from a lack of efficiency, trust, and t ransparency. In this thesis, we propose a novel method to specify the workflow aspects of TDG by considering all TDG process stages during its entire lifecycle. This method aims to facilitate the specifications of the TDG workflow management system that is entirely based on existing regulatory frameworks ensuring the compliance, trust, and transparency of all underlying processes. The proposed system design method is based on the so-called model-driven architecture (MDA) approach and enhancing it to consider blockchain properties. The first stage is the formal analysis of the process of TDG and its alignment with the regulatory frameworks. The proposed design method aims, at this stage, to allow the formal definition and verification of the design of the system with regard to the regulatory frameworks. The next stages of the method rely strongly on the model transformation that is a salient aspect of the proposed design method. Model transformation allows to automatically discover peer system components and authorized interactions. The last stage of the whole model transformations is the specification of digital twin profiles for all potential s t akeholders. All the interactions in the real world between stakeholders are transformed into interactions in the digital world, while the interactions with the environment are achieved through the use of IoT. The proposed approach enables interactions between components of the systems (digital twins, IoT devices, etc.) only if this is compliant with the regulatory framework. Thanks to blockchain technology, our design method allows improving trust and transparency in the process of TDG from the perspective of stakeholder collaborations. Smart contract technological capabilities are also a cornerstone of the proposed solution. This thesis also contributes to improving the semantic of smart contracts to capture supply chain management specifications as well as dangerous goods specificities in terms of t ransportation. Dynamic concepts related to the supply chain management of dangerous goods such as time-related and geographic constraints, digital certification, anomaly detection and multi-party smart contract, managing emergencies, and shared responsibility have been addressed at the level of the smart contract. In particular, this thesis proposes applying temporal logic for the formal specification and verification of smart contracts. This thesis proposes an integrated approach for blockchain and IoT to support the dynamic aspects in the supply chain of dangerous goods. Data collected from various IoT devices along the physical supply chain (goods, vehicles, country borders, etc.) are transmitted to the blockchain and further processed by the system following the workflow logic that was specified and automatically triggering related smart contracts and corresponding actions. The last contribution in this thesis is the implementation of a proof-of-concept system to validate the different aspects of the contribution, namely the design method, the trust and transparency assurance, and the automatic triggering of actions and information flows. [less ▲]

Nomads’ Poetic Translingualism. Multiple voices, dialogical writing and space constructions in the work of Liliane Welch and Pierre Joris

Doctoral thesis (2021)

In the past decades, multilingualism has developed into a highly researched topic in literary studies as well as in applied linguistics. Surprisingly, two Anglophone poets, Liliane Welch and Pierre Joris ... [more ▼]

In the past decades, multilingualism has developed into a highly researched topic in literary studies as well as in applied linguistics. Surprisingly, two Anglophone poets, Liliane Welch and Pierre Joris, originally from Luxembourg, have not been included in research despite the rich and manifold perspectives on languages that their work displays. They grew up and were educated in the multilingual environment of Luxembourg before they immigrated to North America while continuing to travel widely. For their writing, they rejected their earlier languages, Luxembourgish, French and German and opted for English as the language of their writing. These observations have motivated the overall research question: What multiple facets of translingualism does a nomadic approach of writing offer? Through close references to the work of Welch and Joris the study aims to investigate the impact of multiple languages on poetic writing, with a particular attention to poets’ linguistic meta-reflections and their positioning in relation to languages. The dissertation is divided into three parts with separate yet related research aims and objectives. Part I sets out the context of the research while it also enquires into the pertinence of associating literary and linguistic dimensions with important features of nomadic theory. The definition of research aims and objectives motivates the description of a concept-based inquiry. An extensive review of relevant studies highlights the international and interdisciplinary character of recent research on multilingualism while nomadism appears as a rich resource for thinking about what moving means for writers. Both areas thus significantly contribute to the description of conceptual and textual cornerstones, which ensure the coherence of the study as a whole. Concepts need not come as abstract ideas only; the palimpsest as conceptual metaphor proves a fitting tool to investigate layers of texts, thoughts and locations. It is a golden thread that all along the dissertation functions as reminder of transformative processes. A distinction between fact-oriented and poetic writing accounts for differences in focus in Parts II and III. Primary text resources in Part II comprise documentary and autobiographical writing as well as academic pieces. These texts help draw the poets’ itineraries, inquire into how they reconstruct former language experiences and develop key elements of a poetics for their creative writing. Gradually, the specificities of each poet’s conception of the role of language multiplicity emerges. Poetry as creative and imaginative work is at the centre of Part III, which scrutinizes texts for their various uses of translingualism in dialogical writing, in translational practices and in the creation of poetic spaces marked by superimposed voices, languages and texts. Among the outcomes of the study, a few points stand out. The elaboration of an interdisciplinary framework stresses the benefits of crossing disciplinary perspectives and negotiating between terminologies in different languages. Part II shows that, contrary to widespread beliefs, both poets reject the mother tongue as language for writing; moreover, they demonstrate the rich cognitive, self- constructive and creative potential that a new self-selected language holds. The fundamental role that nomads’ ongoing reading in several languages holds for translingual writing is another crucial point that both poets constantly demonstrate. Differences, however, appear in their understanding of language multiplicity in texts. While Welch aims at a unified language, Joris is in search of new forms of writing that transgress borders of languages and genres. The analysis of poems in Part III confirms these diverse orientations and underlines the relevance of a distinction between implicit and explicit forms of heterolingualism, which account for a highly diversified range of writing across languages. For a study of all forms, the palimpsest remains a powerful conceptual metaphor to investigate the articulation of languages. The examples show that only an in-depth analysis can bring to light the nature of interactions and indicate their relevance for studies of multilingualism outside the literary context. [less ▲]

HOW TO MAKE MOTIVATION PERSIST: IMPROVING PHYSICAL ACTIVITY MOTIVATION IN YOUTH ACROSS THE SCHOOL AND LEISURE-TIME CONTEXT OVER TIME

Doctoral thesis (2021)

Worldwide, physical activity levels are decreasing over time and with age (Guthold et al., 2020), which is directly related to numerous physiological and psychological health issues (Poitras et al. 2016 ... [more ▼]

Worldwide, physical activity levels are decreasing over time and with age (Guthold et al., 2020), which is directly related to numerous physiological and psychological health issues (Poitras et al. 2016). In this regard, previous research has found that, predominantly, not the daily amount of sitting, but insufficient physical activity rates are related to higher mortality rates (Eklund et al., 2016; Van der Ploeg & Hillsdon, 2017). The purpose of the present thesis is therefore to investigate underlying factors, which are directly and indirectly related to and may foster physical activity behavior. For reasons of aiming at supporting most of children and adolescents, physical education provides a promising context to intervene. In this sense, one multi-theoretical framework, the trans-contextual model (Hagger et al., 2003), has been presented in order to investigate the transfer of motivation between the school and out-of-school context. Within this particular model, three propositions are given. First, (1) Hagger and Chatzisarantis (2016) claim that the students’ perceived support of autonomy by the physical education teacher is related to increased values of students’ autonomous motivation in physical education, which, in turn, (2) is related to autonomous motivation toward physical activity beyond the school context in leisure-time. Finally, (3) the authors suggest that autonomous motivation is related to the antecedents of the intention of getting physically active, namely attitude, subjective norm, and perceived behavioral control. In order to test and extend these assumptions, the perceived support of the three basic psychological needs for autonomy, competence, and relatedness (Deci & Ryan, 2000) by the physical education teacher, the different motivational regulation types in the physical education and leisure-time context, and the concepts of the theory of planned behavior (i.e., subjective norm, attitude, perceived behavioral control, intention, and physical activity behavior; Ajzen, 1991) were assessed. The analyses performed and results obtained are presented in three individual manuscripts, each addressing a unique research question. Within the first manuscript, the aim is to analyze the psychometric properties of our translated versions of the motivational regulation scales, the Revised Perceived Locus of Causality Scale (PLOC-R; Vlachopoulos et al., 2011) and the Behavioral Regulation in Exercise Questionnaire (BREQ-II; Markland & Tobin, 2004). In a second manuscript, the three different propositions of the trans-contextual model are tested in a longitudinal design via generalized linear mixed models, cross-lagged panels, and longitudinal mediation analyses. In a final step (manuscript three), a new yet already scientifically established concept, namely mindfulness, which has been found to be beneficial in classrooms (Zenner et al., 2014), is integrated into the trans-contextual model. As a purpose of the trans-contextual model is to foster autonomous motivation in physical education in order to increase overall physical activity, and as a recent meta-analysis has underlined the positive medium-sized impact of state mindfulness on autonomous motivation (Donald et al., 2020), a further aim of the present thesis was to implement mindfulness into the trans-contextual model. It is discussed that mindfulness may play a crucial role in the development of autonomous motivation, which may help to explain the link between mindfulness and the reduction of stress, negative affect, as well as the simultaneous promotion of well-being (Schneider et al., 2018), and the execution of a behavior. As an overarching aim of the present thesis is to discover important concepts, which are in the long term increasing overall physical activity rates of children and adolescents, the trans-contextual model, which unifies important concepts of the self-determination theory (SDT, Deci & Ryan, 1985) and the theory of planned behavior, is analyzed and extended by the concept of mindfulness in the third manuscript. More specifically, the support of autonomy, relatedness, competence, as well as the possibly beneficial impact of mindfulness, when being included into the trans-contextual model, was analyzed via path model analyses. Overall, promising results could be found for the psychometric properties of the motivational regulation questionnaires. Furthermore, partial scalar measurement invariance between the German and French version can be seen as confirmed. Thus, both translated questionnaire versions provide useful tools for further inter-cultural research in the exercise domain. Furthermore, the proposed directions of the trans-contextual model could be confirmed within a longitudinal format. We found that all three basic needs were distinctly important to be supported in physical education, as they were all found to be related to autonomous motivation. Autonomous motivation, in turn, was found to be bi-directionally related between both contexts, the school and out-of-school context, meaning that the promotion of autonomous motivation in either context might be beneficial. Finally, identified regulation was found to be directly related toward intention and intrinsic motivation to physical activity over time. Autonomous motivation was furthermore found to be related to subjective norm, perceived behavioral control, and attitude. With regard to the third manuscript, it was found that the path models including mindfulness into the trans-contextual model provided better model fit indices, compared to models without mindfulness. In addition, mindfulness was found to be positively predicted by the support of autonomy in class, while mindfulness statistically significantly predicted autonomous motivation in both contexts, namely for physical education and leisure-time physical activity. Furthermore, mindfulness was positively related to attitude, subjective norm, and perceived behavioral control. Overall, the presented results reveal that the trans-contextual model provides a strong conceptual framework, which helps to better understand the transfer of autonomous motivation beyond the school-context. Furthermore, it is discussed that, in order to promote autonomous motivation in students, further educational intervention programs should ideally rely on the four concepts of autonomy, relatedness, competence, and mindfulness support, which may, in turn, help to alleviate and redeem the diminishing physical activity rates across the globe. [less ▲]

Characterization of novel covalent and non-covalent drugs against K-Ras surrogate targets

Doctoral thesis (2021)

Mutations in the KRAS gene are associated with approximately 15% of all human cancers. This makes it one of the most frequently mutated oncogenes known. Whilst recent breakthroughs in Ras drug discovery ... [more ▼]

Mutations in the KRAS gene are associated with approximately 15% of all human cancers. This makes it one of the most frequently mutated oncogenes known. Whilst recent breakthroughs in Ras drug discovery have led to the FDA approval of the first direct and covalent inhibitor of the KRAS-G12C mutant, the majority of KRAS driven cancers are not G12C mutated. Furthermore, recent studies have identified resistance mechanisms against the new inhibitors. Consequently, research into other direct and indirect Ras inhibition strategies, as well as synergistic drug combination efforts are being vigorously pursued. In the first part of this thesis, I describe my contributions to the development and characterization of novel PDE6D inhibitors with activity against KRAS driven cancers. PDE6D is a trafficking chaperone of K-Ras that facilitates its dynamic localization to the plasma membrane. Although some progress had been made in identifying lead drug candidates against this protein, an Arl2 dependent PDE6D cargo ejection mechanism continues to hamper progress. We describe the development of Deltaflexin 1 and Deltaflexin 2, into which we engineered a ‘molecular spring’ to improve resilience to Arl2 ejection of PDE6D cargo. We show that these compounds selectively inhibit K-Ras membrane organization and exhibited K-Ras selective anti-proliferative effects against cancer cell lines from colon and breast tissues whilst blocking the 3D spheroid growth of lung and breast cancer cell lines. In the second part, I describe my main project, the identification of a novel covalent inhibitor of calmodulin (CaM) with anti-cancer activity in K-Ras mutated cancers named Calmirasone1. A relevance of the K-Ras/ CaM interaction for the promotion of cancer cell stemness has been previously suggested. We previously showed that the natural product Ophiobolin A (OphA) blocked K-Ras membrane organization in a CaM dependent manner and cancer cell spheroid formation. However, because of the broad toxicity of OphA, its suitability as a tool compound to further study this K-Ras/CaM associated stemness properties is limited. We have therefore characterized a set of benzazulenones with distant chemical similarity to OphA in a battery of assays. We identified Calmirasone1 which exhibits improved CaM affinity and a significantly lower unspecific toxicity relative to OphA. Furthermore, Calmirasone1 selectively blocked K-Ras membrane organization and inhibited the 3D spheroid growth of K-Ras dependent cancer cell lines. In the third part of this thesis, I assessed the synergistic potential of targeting CaM and protein phosphatase 2A (PP2A) in Ras-MAPK dependent cancer cell lines. PP2A is a tumor suppressor that catalyze the dephosphorylation of multiple targets in the cell. Using specific CaM inhibitors and PP2A agonists as well as the already clinically approved phenothiazines (PTZs), our results from this study suggests that synergistic targeting of CaM and PP2A improves anti-cancer effects and that PTZs combine CaM inhibitory and PP2A re-activating properties in their cancer killing activity. [less ▲]

The Intra-Party Effects of Open List Design

Doctoral thesis (2021)

Functional Analysis of Long Noncoding RNAs in Glioblastoma and Chemoresistance

Doctoral thesis (2021)

Liquid Crystal Shells: from Physics Mysteries, via Chemistry Challenges, to Biosensing Opportunities

Doctoral thesis (2021)

Liquid crystals (LCs) confined in a spherical geometry between two aqueous phases, i.e., a shell, exhibit unavoidable topological defects, real or virtual. In fact, the presence of defects, and their ... [more ▼]

Liquid crystals (LCs) confined in a spherical geometry between two aqueous phases, i.e., a shell, exhibit unavoidable topological defects, real or virtual. In fact, the presence of defects, and their configuration, on the shell are dictated by the LC alignment at the LC-water boundaries. With tangential alignment of the LC, we have a total of +2 defect strength on each interface, which can be distributed either over four +1/2 defects or a combination of +1 and +1/2 defects. In contrast, when the LC is radially aligned, the shell is defect free (but one can extrapolate the director field into a virtual point defect in the internal isotropic phase). The LC alignment can be tuned by adding a suitable solute in the aqueous phase.The vast majority of studies have used sodium dodecyl sulfate (SDS) for this purpose, with only a few studies employing other surfactants. We investigate various other surfactants with a positive and negative head group charge by varying alkyl chain length. Here, we focus on the minimum surfactant concentration required (below the critical micelle concentration (CMC)) for the stability of the shells as well as for ensuring the radial alignment. It turns out that surfactants at a low concentration do not necessarily impose radial alignment. However, they provide stability by decreasing the interfacial tension. Once the surfactant concentration is above the CMC, surfactant forms micelles in water. When these micelles are in the outer aqueous phase of the hybrid aligned shells, the LC alignment changes from hybrid to radial on cooling below the Krafft temperature (TK), below which the surfactant solubility is lower than CMC. Interestingly, on heating above TK, the LC alignment changes back to hybrid. It turns out that the adsorption and desorption of micelles as a result of changed solubility in water with temperature give rise to the change in the LC alignment. Next, we replace surfactant with lipids. We add lipids in the form of vesicles in the aqueous phase of pre-tangentially aligned LC shells. After some time these shells develop small spindle-shaped islands, and these islands merge and grow with time, and they even interact in intriguing ways across the LC, from the inside to the outside. After exploring various solutes in the aqueous phase, we change our LC phase from nematic to smectic A and C phases. In the smectic A phase, lunes on the shell occur due to the change in the shell cross section area from the inner to the outer interface. In this context, we present the first study on tangentially and hybrid aligned smectic C shells. The most studied LC mesogens in the shell geometry contain cyano and biphenyl groups. To test whether this is important, I also made shells with cyclohexane core mesogens. In contrast to the cyanobiphenyl-based LCs, this LC aligns radially regardless of solutes added into the aqueous phases. We investigate in detail and find that a cyano group at the terminal supports shell stability and while the aromatic rings in most LCs, for instance having a biphenyl core, give rise to the tangential alignment when in contact with surfactant-free water. [less ▲]

Algorithmic business and EU law on fair trading

Doctoral thesis (2021)

This thesis studies how commercial practice is developing with artificial in- telligence technologies and discusses some normative concepts of EU law on fair trading. The author argues that the mainstream ... [more ▼]

This thesis studies how commercial practice is developing with artificial in- telligence technologies and discusses some normative concepts of EU law on fair trading. The author argues that the mainstream normative debate concerning artificial intelligence has underestimated the importance of un- derstanding the socio-technical context behind its adoption, and therefore aims at amending this gap by studying artificial intelligence in the context of business-consumer marketing relationships. The "algorithmic business" phe- nomenon refers to the increased deployment of artificial intelligence tools in marketing organisations which - based on large quantities of consumer data - allow companies to optimise a number of tasks related to consumer relation- ships. The phenomenon is orienting relations with consumers towards some general observable trends that are critically affecting the power relations be- tween business and consumers. These developments do not take place in a legal vacuum but in the background of a system of norms and rules aimed at maintaining fairness and balance in market transactions. Thus, the author assesses current developments in business practice in the context of EU con- sumer law specifically aimed at regulating business practice. The analysis is critical by design and without neglecting concrete practices attempts to look at the general picture. The thesis consists of nine chapters divided in three thematic parts. The first part discusses the integration of artificial intelligence technologies in marketing organisations, a brief history, the technical foundations, and their modes of integration in business organisations. In the second part, a se- lected number of socio-technological developments in commercial practice are analysed and the main implications from the perspective of consumers discussed. In particular, the following are addressed: the monitoring and analysis of consumer behaviour based on data; the personalisation of offers and customer experience; the capture of information on consumers’ psychol- ogy and emotions, the mediation through algorithmic assistants. The third part assesses these socio-technical transformations in the context of EU fair trading law and of the broader policy debate concerning consumer protection in the algorithmic society. In particular, two normative concepts underlying the EU fairness standard are critically analysed: manipulation, as a substan- tive regulatory concept that limits commercial behaviours in order to protect consumers’ informed and free choices and vulnerability, as a concept of social policy that portrays people who are more exposed to marketing practices. [less ▲]

Enhancing Smart Grid Resilience and Reliability by Using and Combining Simulation and Optimization Methods

Doctoral thesis (2021)

Modern electrical grids include numerous digital technologies for producing, transmitting, distributing, and supplying electricity. The electrical grids that achieve the most reliable, efficient, and less ... [more ▼]

Modern electrical grids include numerous digital technologies for producing, transmitting, distributing, and supplying electricity. The electrical grids that achieve the most reliable, efficient, and less environmental impact operation using the above technologies combined with renewable energy sources are characterized as smart grids. The study of electricity networks aims at the continuous and uninterrupted production, transmission, and distribution of electricity under the safest operating conditions. Therefore, an electrical grid is designed and studied in a multifaceted way to highlight the weaknesses and reduce possible disturbances. One of the most critical disturbances that can occur in energy grids is overload. Overloads on an electrical system are dangerous, as they can cause overheating or an electric arc. Cables in an electrical grid have a maximum ampacity, i.e., current capacity, that can safely flow. If an excessive number of devices, such as electric vehicles, are connected to a circuit, the electrical current will overheat the cables. If the cable insulation melts, an electric arc can be generated and cause a fire in the overheating area, even inside a wall. In order to avoid overloads, fuses are installed in the circuits. If the current exceeds a specific value, the fuse is activated, drops, and opens the circuit, thus interrupting electricity flow. However, even if they are below the safety limits, sustained overloads could also damage the wires. Smart grid operators could change the state of each grid's fuse or could remotely curtail the over-producing/over-consuming users so that, with the minimum interruption, any potential overload could be prevented. Nevertheless, making the most appropriate decisions is a complicated decision-making task, mainly due to contractual and technical obligations. The present dissertation studies the overloading prevention problem in terms of smart grids' reliability and resilience and evaluates real-world topology in a Luxembourg city district. To this end, it suggests solution methods that can suggest optimal countermeasures to operators facing potential overloading incidents. Specifically, the dissertation has three main axes: The first axis regards the deterministic overloading prevention problem. Given the topology and the energy data of a microgrid at the current time, the potential overloading incidents are detected, and the optimal countermeasures are calculated for the next measurement interval. The grid operators can apply the proposed actions to recover the grid from the disturbance. Into the thesis, the problem is defined and formulated as a Multiobjective Mixed Integer Quadratically Constrained Program. The dissertation also suggests a solution method using a combinatorial optimization approach with a state-of-the-art exact solver. The second axis focuses on reliability analysis through simulation after a potential overloading incident. Smart grid operators would be of great use to ensure stability after a potential overload for a planning horizon, as the future electrical values are unknown. To evaluate the robustness of the topology reconfiguration after a disturbance, like an overload, reliability analysis through simulation is employed. The third axis proposes the single-stage stochastic overloading prevention problem. It differs from the deterministic problem as the optimal countermeasures are calculated for a measurement horizon, e.g., 24 h. The dissertation defines the corresponding single-stage stochastic program and proposes a simheuristic method to solve it. Overall, this thesis presents a fully-edge study on reliability optimization for smart grids to provide the appropriate countermeasures after a potential overloading disturbance. The present approach has been developed in collaboration with an industrial partner and evaluated on real-world topology. [less ▲]

Les Règles du savoir-vivre dans le théâtre de Jean-Luc Lagarce : Une lecture ethnocritique et stylistique des œuvres dernières

Doctoral thesis (2021)

The purpose of this thesis is to propose an ethnocritical reading of the dramatic works of Jean-Luc Lagarce. It involves rereading the works of a writer consecrated by the Comédie Française and the ... [more ▼]

The purpose of this thesis is to propose an ethnocritical reading of the dramatic works of Jean-Luc Lagarce. It involves rereading the works of a writer consecrated by the Comédie Française and the Institution in an ethnocritical perspective which combines a poetics of literary texts with an ethnology of the symbolic in order to study the specific cosmologies present in the works. In order to do this, we propose to use a rhetorical and stylistic approach in order to illustrate the scriptural singularity demonstrated by the generic hybridity which is characteristic of his works and by forms of speech that are both highly “oralized” and very literary, in other words very “auralized”. We will pay particular attention to his last works: Juste la fin du monde, Les Règles du savoir-vivre dans la société moderne, J’étais dans ma maison et j’attendais que la pluie vienne et Le Pays lointain because of their emblematic and testamentary value. The first part of the thesis focuses on the rules, rituals and customs that are present in the works. The second part examines a third group of characters defined by Lagarce, as in addition to the living and the dead there are those who know they are going to die. These already-dead characters found in his works are liminary characters characterized by punctuation and typography that signifies a liminal space between two worlds: quotation marks, parentheses, dashes and italics invite us to explore the margins of the heterotopic theatre of Lagarce. The third part looks at the rules of creation in his final works that illustrate the processes of re-writing and hybridization between theatre, prose fiction and poetry. Our hypothesis is that as death drew closer, Lagarce saw each work as his last and each thus represents a rite of passage meant to insure that Lagarce will enjoy the recognition that he had not obtained while alive; each work is meant to guarantee his literary posterity through an “oeuvre-legenda” meant for his readers and that ended up by encountering spectators. [less ▲]

EFFICIENT AND SCALABLE OPTIMIZATION ALGORITHMS FOR MULTIANTENNA SIGNAL PROCESSING

Doctoral thesis (2021)

Multiantenna signal processing (MASP) is indispensable in many applications like wireless communications, radar, seismology, etc. Large-scale antenna arrays (LSAAs) are envisioned for future wireless ... [more ▼]

Multiantenna signal processing (MASP) is indispensable in many applications like wireless communications, radar, seismology, etc. Large-scale antenna arrays (LSAAs) are envisioned for future wireless communication systems to improve the range, power, and spectral efficiency (SE) of existing systems. Thus, for a practical multiantenna wireless communication system, efficient and scalable signal processing (SP) algorithms are essential to optimize system operations. In this thesis, we address several facets of such system optimization including beampattern matching, SE maximization among others. These are formulated as nonconvex optimization problems and the thesis proposes novel, efficient, and scalable optimization algorithms with theoretical convergence guarantees. We first consider the problem of transmit analog beamforming (or phase-only beamforming) design by solving a beampattern matching problem. We formulate variants of the unit-modulus/constant-modulus least-squares problem. To attempt at solving these NP-hard problems, we propose efficient and scalable algorithms based on different optimization frameworks including alternating minimization, majorization-minimization (MM), and cyclic coordinate descent (CCD). The proposed algorithms are theoretically shown to converge to a Karush–Kuhn–Tucker (KKT) point of the corresponding optimization problem while offering superior performance. We also provide a use case in satellite communications where a desired two-dimensional beampattern is approximated using a planar array by designing the analog beamforming system. Building on the previous problem, we consider a joint array design and beampattern matching perspective and formulate variants of sparse unit-modulus or sparse constant-modulus least-squares. The optimization problems are solved using combinations of different optimization frameworks such as variable projection/elimination, MM, and block/alternating MM. Next, we consider the problem of hybrid transceiver design for a single user point-to-point multiple-input multiple-output (MIMO) system employing LSAAs. We solve this problem based on the variable projection/elimination and MM frameworks. The proposed algorithms are shown to converge to a stationary point. We also study the applications of the proposed algorithms for hybrid precoding design for satellite communications. We then generalize convergence proofs from the earlier sections by providing a unified convergence proof for solving a generic block-structured optimization problem over nonconvex constraints. Finally, we consider the problem of localizing sources in the far-field of a spatio-temporal array formed by a single moving sensor along a known trajectory. We provide a novel signal model capturing the incoherency in the measurements sampled by the moving sensor. We establish different Cramér-Rao bounds for the considered system model by exploiting varying degrees of information, propose and study various direction of arrival (DOA) estimators. The thesis concludes by summarizing the main contributions and some open research problems. [less ▲]

Identifying and targeting metabolic vulnerabilities of IDH mutant gliomas

Doctoral thesis (2021)

Diffuse gliomas are a group of central nervous system (CNS) tumors with a poor patient prognosis. Within these diffuse gliomas, isocitrate dehydrogenase (IDH) mutation defines the different tumor subtypes ... [more ▼]

Diffuse gliomas are a group of central nervous system (CNS) tumors with a poor patient prognosis. Within these diffuse gliomas, isocitrate dehydrogenase (IDH) mutation defines the different tumor subtypes and is considered to be an initiating event in gliomagenesis. IDH is a metabolic enzyme that in normal conditions mediates the conversion of isocitrate into α-ketoglutarate (α-KG), producing the reducing equivalent NADPH. IDH mutation (IDHm) leads to a neomorphic reaction where α-KG is consumed to generate the oncometabolite D-2-hydroxyglutarate (D-2HG), using NADPH as reducing agent. It has been reported that IDHm-dependent D-2HG synthesis has a direct impact on DNA and histone methylation, however the metabolic repercussions are not yet well defined. Due to the consumption of NADPH by IDHm reaction, some groups including us have hypothesized that IDHm cells may bear an imbalance of reducing equivalents, that may trigger a defective antioxidant defense. In the present study we made use of patient-derived cell lines and xenografts thereof as well as clinical samples in order to study the metabolic vulnerabilities of IDHm gliomas. In the first part of the thesis experimental data, we generated an integrative liquid chromatography-mass spectrometry (LCMS)-based proteomic-metabolomic characterization of IDHm metabolism. We made use of patients, cell lines and xenografts to address the direct effect of the mutation. We observed that IDHm gliomas have altered regulation of key processes in central carbon metabolism through glucose and glutamate processing as well as glutathione (GSH) metabolism and fatty acid production. In the second part of experimental data, we investigated the redox vulnerabilities of IDHm gliomas. Here we discovered that IDHm astrocytomas specifically upregulate cystathionine-γ-lyase (CSE) enabling them to synthesize GSH independently of NADPH. CSE is the only known enzyme capable of synthesizing cysteine. We found that genetic and chemical inhibition of CSE led to a decrease in cell viability upon cysteine restriction. Finally inhibition of CSE in vivo led to a delay in tumor growth rate. In conclusion, in the present PhD dissertation we expose a comprehensive study of the metabolic behavior of IDHm human gliomas, and we propose a novel therapeutic strategy that might improve patient prognosis, by inflicting oxidative damage to the tumor. [less ▲]

Higher education trajectories and social origin in Germany and the United States: A comparative sequence-analytical approach

Doctoral thesis (2021)

Students’ higher education trajectories as holistic educational processes are an underresearched aspect, particularly in the German context. This cumulative thesis fills this gap by investigating ... [more ▼]

Students’ higher education trajectories as holistic educational processes are an underresearched aspect, particularly in the German context. This cumulative thesis fills this gap by investigating students’ trajectories through bachelor’s degree courses in German and US higher education. In terms of methodology, it is based on a sequence-analytical approach using two student panel data sets (the German National Educational Panel Study (NEPS) and the US Beginning Postsecondary Students Longitudinal Study (BPS)) and comprises a literature review and three empirical research articles, each providing a different theoretical and conceptual angle. Higher education is a non-compulsory educational phase, implying students are granted more autonomy and more choice but also require more personal responsibility to plan a path through higher education. As such, it is assumed that parents’ cultural resources – defined here as higher education-specific knowledge – and economic resources shape students’ trajectories to enable them to proceed through their studies in a more continuous or linear way and prevent students from experiencing complex trajectories, such as delays, interruptions or detours. To begin with, the literature review, constructed as a narrative review with systematic elements, captured the state of research on higher education trajectories by reviewing peer-reviewed journal articles from a wide range of mainly higher education research journals. It revealed that this research area is rather heterogeneous and dominated by studies focusing on the United States. Research articles one and two employ similar research strategies – sequence analyses followed by cluster analyses. Stressing the relationship between parents’ resources and students’ trajectories, the first article concentrates exclusively on students in German research universities, whereas the second also considers students at universities of applied sciences. Overall, these studies reveal that the trajectories of students at the universities of applied sciences are more often linear, while the opposite applies to students at research universities and students of low social origin, pointing towards the hypothesised effect of parental resources. Furthermore, students of low social origin are more likely to follow a linear standard trajectory when studying at a university of applied sciences compared to at a research university. In the third paper, based on the premise that trajectories are systematically shaped by the institutional context of the higher education system, students’ trajectories in German and US higher education are compared, allowing to simultaneously a view on system-level characteristics and national idiosyncrasies. US higher education provides almost universal access, is very marketised and highly differentiated, thereby accommodating diverse demands and heterogeneous student groups. By contrast, German higher education, based on public funding and regulation, early ability tracking and low permeability, restricts access and provides an overall much less diversified study offering. Consequently, research article three revealed that students’ trajectories are overall less standardised in US higher education – but this differs greatly by higher education sector, whereas the trajectories of students in the (selective) research universities are overall more standardized. Furthermore, the social origin differences were quite pronounced in the United States, whereas the social origin effect was almost nonexistent for students in German higher education in this study (based on a different sequence-analytical approach). Remarkable, though, remains the finding that students’ trajectories are less linear at German research universities compared to the universities of applied sciences – even more so among students of low social origin – while US research universities facilitate linear trajectories. Overall, this dissertation provides an important contribution to the state of research on link between social origin, students’ trajectories and how this link is mediated by the institutional context of the respective higher education system. [less ▲]

Understanding the role of colorectal cancer-associated bacteria in colorectal cancer

Doctoral thesis (2021)

Mounting evidence from 16S rRNA-based or metagenomic analyses suggests that dysbiosis, a state of pathological microbial imbalance, is prevalent in the gut of patients with CRC. Numerous microbial taxa ... [more ▼]

Mounting evidence from 16S rRNA-based or metagenomic analyses suggests that dysbiosis, a state of pathological microbial imbalance, is prevalent in the gut of patients with CRC. Numerous microbial taxa have been identified of which representative isolate cultures can interact with cancer cells, further triggering distinct disease pathways in animal models. Nevertheless, how these complex interrelationships of a dysbiotic microbiota may be involved in the pathogenesis of CRC remains a fundamental question and requires multifaceted mechanistic studies. This thesis moves beyond observational studies, it integrates novel experimental approaches for the study of the gut microbiome in colorectal cancer. It incorporates current knowledge in the field as well as interdisciplinary approaches. My work aims at contributing to an ecosystem-level mechanistic understanding of the CRC-associated microbiome in the initiation and progression of the disease. In detail, the objective of my work comprised an integrative approach of microbiome-CRC interaction studies. We revised current knowledge on, and studied the CRC-associated bacteria, in particular Fusobacterium nucleatum (Fn) and Gemella morbillorum (Gm). We assessed their direct and indirect effects on CRC cells, their interactions with immune cells, as well as their tumor-modulating potential in vitro, in silico, and in vivo. The results presented in this thesis comprise new findings on human microbial cross-talk of Fn with CRC. We identified formate as a potential fusobacterial oncometabolite, which enhanced cancer incidence and progression via increased cancer stemness signaling. Furthermore, we discovered immune-suppressive functions of Gm in the context of CRC. With my work in collaboration projects, I contributed to the development of two novel approaches in anti-cancer therapy: First, to the establishment of a personalized in vitro model (iHuMiX) for the study of microbe-host-immune interactions in anti-cancer therapy, and second, to the validation of an in silico workflow that uses metabolic rewiring strategies for network-based drug target predictions for CRC therapy. Taken together, this thesis work broadened the mechanistic understanding of CRC-associated microbes and it contributed to potential strategies for the development of an improved CRC therapy. [less ▲]

Populismes et fabrique des droits économiques et sociaux dans le cadre des droits de l'Homme. Le Front national et l'Union démocratique du centre (1992-2013)

Doctoral thesis (2021)

Since the 1990’s, with the development of Europeanisation, globalisation and the installation of the neo-liberal paradigm, we observe in Europe the non-application of economic and social rights, despite ... [more ▼]

Since the 1990’s, with the development of Europeanisation, globalisation and the installation of the neo-liberal paradigm, we observe in Europe the non-application of economic and social rights, despite being aspired by the States of the human rights continent after the Second World War. At the same time, "national-populist" parties are gaining more and more support and are establishing themselves in the political landscape as a "right-wing third way", which would provide the answers that the governing parties do not seem to be able to find, in the context of an actual crisis of the welfare state. The aim of our research is to provide a comparative analysis of the discourses of the "Front National" in France, now Rassemblement National ("RN") and the "Union Démocratique du Centre" in Switzerland ("UDC/SVP") on economic and social rights, in order to confront them with the changes and public policies observed in our societies as a result of the neo-liberal paradigm. Using a cross-cutting analytical grid that identifies the characteristics of socio-economic discourse of a "national-populist" nature, this work is made up of numerous sources from both parties, studied over a period of twenty years : work that constitutes the boundaries between 1992, when the Maastricht Treaty developing the "European market" was signed, and 2013, with the start of negotiations for the signing of the transatlantic treaty opening the "European market" to the "US market". The research work is also based on original interviews with key figures from both parties and the creation of an online questionnaire aimed at elected representatives with responsibilities on a smaller scale (at regional level). Thus, the cross-referencing of our qualitative and quantitative data has enabled us to produce original results and to construct a new category of populist parties called : "national-populist parties opposed to human rights". Among other things, the latter develop in their socio-economic approach a will to defend economic and social rights but only for nationals, rejecting the universality of human rights. At the same time, they propose a hybrid form of capitalism with nuances between the "FN/RN" and the "UDC", combining a dose of protectionism but also a more or less sought-after integration into the "market". Furthermore, it is interesting to compare the discourses of a party outside government (the "RN") that has not yet participated in executive authority at the national level and a party associated with federal authority, the "UDC", both "inside and outside". Ultimately, in both cases, it is sovereignism and anchoring in so-called right-wing policies that seem to dominate the socio-economic DNA of the two populist parties studied. With the help of our research work, we can thus ask ourselves in what way does the "national-populist" discourse point to the failure of states on the human rights continent to implement economic and social rights as they intend ? [less ▲]

Taming Android App Crashes

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. [less ▲]

LA KORA A LA CONFLUENCE DES CULTURES : UNE ETUDE DE LA TRANSMISSION D’UN OBJET CULTUREL DANS UN CONTEXTE TRANSCULTUREL CONTEMPORAIN

Doctoral thesis (2021)

The kora is a musical instrument of West African origin. Now played by several individuals who do not necessarily come from her native background, it has been transmitted from her endogenous cultural ... [more ▼]

The kora is a musical instrument of West African origin. Now played by several individuals who do not necessarily come from her native background, it has been transmitted from her endogenous cultural circle to other exogenous circles. We ourselves are kora players and belong to this exogenous circle. In our artistic journey and in our personal history, we have felt the need to produce a hybrid game. Thus, as an artist and researcher, our first objective of a doctoral thesis was to research hybridization processes from a so-called "traditional" repertoire and another called "modern". . Our academic career made us question these categorical qualifiers: "traditional", "modern". This questioning took place through the observation of the process of transmission of the kora. It was made from the very history of the instrument which cannot be dissociated from the history of the individuals and communities who adopted it. However, given the great diversity of the stories, it was necessary to think about setting up tools for collecting knowledge related to contexts and material and immaterial objects, relating to the kora. In order to achieve the primary goal we were pursuing, we finally directed this research towards proposing a method of approach to the study of transmission. There is therefore a dialectic between the object approached and the approach used in this research work. It is this dialectic that corresponds to the main objective of this work. Thus, this doctoral thesis aims to answer the following question: "How to think about the transmission of the kora" object-witness "of the meeting of cultures? "It is a double research focusing both on the transmission of the kora and on the means to study and realize this transmission. This research subsequently led to an applied anthropology and even cultural engineering project. This present writing is the summary of an academic adventure between practice and theory. [less ▲]

Internationalisation and Multilingualism in Doctoral Education: Language Ideologies, Discourse and Positioning

Doctoral thesis (2021)

In light of the growing linguistic and cultural diversity among students and researchers, studies on multilingualism in higher education have been increasingly devoting attention to how students and ... [more ▼]

In light of the growing linguistic and cultural diversity among students and researchers, studies on multilingualism in higher education have been increasingly devoting attention to how students and academics use their plurilingual repertoire for writing academic texts. Framed by the internationalisation of higher education and its contributions towards a knowledge-based society and economy in Europe, little is known about how students and researchers conceptualise the role of the national language(s) and the linguistic repertoire(s) vis-à-vis English as the lingua franca. In particular, how academic actors negotiate voice when choosing a language for academic writing and publishing has not been closely examined. To rectify this lacuna, this study focuses on the linguistic processes of doctoral publications and outputs in the context of a multilingual university—the University of Luxembourg (UL), where next to English also German and French are official academic languages. In view of the increased usage of English for writing and publishing doctoral theses, questions arise about the mechanisms and preferences underlying doctoral researchers’ linguistic choices, and how such choices pertain to shifting academic norms. Thus, the overall aim of this exploratory study is to show how doctoral researchers in a multilingual research context—here, the University of Luxembourg—position themselves in relation to macrolevel discourses about language and academic success within their complex lingua-cultural and socio-economic setting. The data analysis is based on in-depth problemcentred interviews with five plurilingual doctoral researchers from China, Germany, Luxembourg and Russia. By applying discourse analysis to the interview transcripts, this thesis makes three substantial contributions to the research field. First, it reveals that despite the dominance of English, doctoral researchers continue to draw on their plurilingual repertoire as a resource for their research and writing processes, however, for different reasons, which are ideologically motivated. Second, the study shows that the choice for publishing in English is mostly based on shifts in academic norms that focus on economic imperatives, such as competition and hyper-performativity. Therefore, the prevalence of English and the pressure to publish in international journals seem to lead doctoral researchers towards limiting the use of the totality of their plurilingual repertoire for writing and publishing theses. And third, this research allows for a detailed understanding of underlying language ideologies of doctoral researchers in higher education. In particular, it gives insights into the value of the theoretical concepts of positioning and language ideology in discourse analysis for investigating the negotiation of voice. [less ▲]

A Study of Hiring Discrimination Using Factorial Survey Experiments: Theoretical and Methodological Insights

Doctoral thesis (2021)

This dissertation provides new insights into the study of hiring discrimination related to three dimensions of inequality: gender, ethnicity, and unemployment. Scholars within sociology of work and labor ... [more ▼]

This dissertation provides new insights into the study of hiring discrimination related to three dimensions of inequality: gender, ethnicity, and unemployment. Scholars within sociology of work and labor economics widely agree that hiring discrimination based on these dimensions exists. However, the question of who is most affected beyond the classical look at single dimensions is less clear, as are the conditions under which hiring discrimination occurs. Focusing on young labor market entrants, I address these questions with two empirical studies using factorial survey experiments. First, I study how applicants’ gender and unemployment interactively shape recruiters’ hiring intentions in sex-segregated occupations. Second, I study the role of recruiter nationality in hiring discrimination against foreigners in Luxembourg. Moreover, while factorial surveys are increasingly applied in the study of hiring discrimination, they have been criticized for exhibiting low external validity. This dissertation empirically addresses how to overcome this criticism by improving the design of factorial surveys currently applied in employer studies. Specifically, I study whether designs based on real vacancies trigger more valid judgements compared to designs based on hypothetical vacancies. Overall, the findings of this dissertation support the relevance of hiring discrimination for labor market inequalities related to gender, ethnicity, and unemployment, but suggest that the mechanisms underlying hiring discrimination related to these dimensions are more nuanced. First, this dissertation suggests that occupational sex segregation might matter for how unemployment shapes recruiters’ hiring intentions towards men and women. Second, while foreign applicants might generally have better hiring chances if the recruiter is foreign, foreign applicants having the same nationality as the recruiter might benefit less from this situation. Finally, this dissertation provides first evidence that using hypothetical vacancies constitutes a valid approach to study recruiter decision-making within the limits of factorial surveys. [less ▲]

The Influence of Language on Mathematics in a Multilingual Educational Setting

Doctoral thesis (2021)

Mathematical Approaches to Biological Complexity in Systems Biomedicine

Doctoral thesis (2021)

Living organisms represents the maybe most complex systems in the universe. This complexity is rooted in the necessity of life to be robust and adaptable. During evolution, life has therefore developed ... [more ▼]

Living organisms represents the maybe most complex systems in the universe. This complexity is rooted in the necessity of life to be robust and adaptable. During evolution, life has therefore developed diverse regulatory strategies that are implemented by interactions of a plethora of entities and driven by the indispensable non-equilibrium character of living matter. The resulting intrinsic complexity of biological systems has been a major obstacle to deeply understand the underlying principles of life. Systems biology and biomedicine address this challenge by interdisciplinary approaches where mathematical modeling represents a key element to reveal and dissect the sources of complexity from large and big data sets. In this spirit, the presented thesis applies bottom-up and top-down systems biomedicine approaches to investigate biological complexity at different levels and from different angels for metabolism and cell differentiation. First, a bottom-up approach is targeting the mathematical properties of the stoichiometric matrix, which is the essential mathematical object in biochemical reaction networks and thus of metabolism. Applying graph and hypergraph theory, we present the key mathematical properties of the stoichiometric matrix and exploit biochemical properties of such networks to obtain a moiety-based decomposition of the stoichiometric matrix and consequently of biochemical reaction networks. These insights lay the foundation for a more descriptive characterization of metabolism. Second, a novel top-down approach is presented to identify cell differentiation properties from single cell transcriptomic data by a combination of binarization, information theory and neural networks in terms of self organizing maps. This distribution-based analysis of cell fate is applied to blood cell differentiation and to the differentiation of induced pluripotent stem cells (iPSCs) into dopaminergic neurons in the context of Parkinson's disease (PD). This methodology allows for an alternative and efficient characterization of differentially expressed genes and the robust identification of critical points in cell differentiation. Comparing iPSCs with a PD-associated mutation within the LRKK2 gene to a healthy control cell line shows a faster maturation process in the disease context. By adapting concepts form non-equilibrium statistical physics, an entropy-based methodology in form of the Kullback-Leibler divergence is introduced to quantify the non-equilibrium character of cell fate, which reveals complementary essential biological processes of differentiation. Finally, a potential integrative approach in form of Bayesian networks is introduced that will eventually allow for efficient and robust mechanistic inference from big data. In particular, the optimization approach is based on Markov chain Monte Carlo methods for sampling from distributions with non-smooth potential functions and uses Langevin stochastic equations for an advanced optimization strategy. The potential of the introduced approach is demonstrated by a first application to a logistic regression function. Overall, the thesis applies complementary mathematical techniques to develop new tools for the characterization of biological complexity and the identification of underlying principles that are appearing in living systems. [less ▲]

The ITU and ICAO regulating aeronautical safety services and related radio spectrum

Doctoral thesis (2021)

The aim of the thesis is two-fold. At first it has a theoretical value, aiming at shedding light upon an unexplored area of international law – i.e. the overlap of regulatory competence of the ITU and ... [more ▼]

The aim of the thesis is two-fold. At first it has a theoretical value, aiming at shedding light upon an unexplored area of international law – i.e. the overlap of regulatory competence of the ITU and ICAO – in light of the wider phenomenon of the fragmentation of international law. Secondly, it has a practical purpose, suggesting a preventive way to deal with the legal antinomies that could arise between the ITU and ICAO legal frameworks and that could ultimately represent a hazard to the safety of air navigation and to human life and property. It takes a systematic approach, analyzing both the institutional aspects of the ITU and ICAO and the legal features of their main regulatory instruments, the Radio Regulations and the Standards and Recommended Practices. Subsequently, it explores the criticalities of such interaction in the overlapping domain of aeronautical safety services and attempts to examine the viable solutions in the next future, both at the legal and institutional level. This area of law, due to its complexity and to its connection with technical and engineering aspects, is largely unexplored by international lawyers. It thus represents an original contribution filling a gap not covered by either generalist or specialized legal literature. It also tackles potential problems that, if left unanswered, could become actual in the next future and represent a serious threat to the safety of international civil aviation. In particular, it recalls the necessity of a tighter regulatory coordination between the two international agencies in view of the increasing competition for and congestion of radio spectrum. [less ▲]

PROBABILISTIC CONTENT POPULARITY LEARNING IN PROACTIVE CACHING SYSTEMS

Doctoral thesis (2021)

Recent rapid growth of data traffic in mobile networks has stretched the capability of current network architectures. Proactively caching popular contents close to end-users has been proposed as a ... [more ▼]

Recent rapid growth of data traffic in mobile networks has stretched the capability of current network architectures. Proactively caching popular contents close to end-users has been proposed as a promising approach to mitigate the issue. A full-fledged proactive cache management mechanism encompasses two interrelated algorithms which need to be carefully designed: content popularity prediction and caching policy. Abundant research has focused on the performance of various caching policies assuming that the content popularity is perfectly known. Nonetheless, the content popularity is unknown in practice and has to be predicted from users' requests. Due to non-deterministic and time-varying nature of the requests, the prediction is nontrivial. In this thesis, the main focus is to introduce efficient prediction algorithms from Bayesian viewpoint. The Bayesian approach provides a powerful framework to construct statistical models which capture uncertainty and are robust to "over-fitting" issue. Firstly, we consider the prediction problem under stationary scenario. To enhance the accuracy of prediction, content features are leveraged and a Bayesian Poisson regressor based on a Gaussian process is proposed. The model can automatically discover hidden patterns in the feature space among the already-existing or seen contents. It also allows to predict the popularities of newly-added or unseen contents whose statistical data is not available in advance. We show that these capabilities of the model can have significant impact on caching performance. Secondly, we formulate a cooperative content caching in order to optimize the aggregated network cost for delivering contents to users. An efficient caching policy requires an accurate prediction of time varying content popularity. The requests can potentially have interactions over time, among contents, and across locations. To exploit these patterns, a probabilistic dynamical model based on a canonical tensor decomposition is developed. Additionally, an online learning method that works with streaming data where content request arrives sequentially is designed. Numerical results confirm that modeling time-content-location interactions by the proposed model can improve the cooperative caching strategy performance. Last but not least, we take one step further and develop a dynamical model, which besides time-content-location interactions, it can also uncover a non-linear temporal trend structure in content requests through which a more accurate prediction can be attained. Subsequently, a cooperative caching policy is designed which adaptively performs network resource allocation and optimizes content delivery according to the dynamic of content requests. Therefore, the policy provides a more efficient utilization of network resources. Using simulations, we show that the developed caching mechanism outperforms reference methods which ignore the temporal trend information. [less ▲]

AGILE FERTIGUNGSSTEUERUNG FÜR (RE-)FABRIKATIONSSYSTEME

Doctoral thesis (2021)

Increasing product variance and individualisation lead to increasing demands for flexibility in produc-tion and production control. In the context of remanufacturing, these demands are further intensified ... [more ▼]

Increasing product variance and individualisation lead to increasing demands for flexibility in produc-tion and production control. In the context of remanufacturing, these demands are further intensified by unknown conditions of the used products. Each product to be remanufactured may therefore require an individual route through the remanufacturing system. This process, which puts used products into an "as good as new or better" condition, is receiving increasing attention due to its high ecological and economic potential and legal regulations. In order to meet these requirements, a hybrid control archi-tecture will be presented. This consists of centralised and decentralised components. At the decentral-ised level, all physical production participants are networked with software components and controlled by these. These components can acquire the status and availability of the corresponding manufacturing participants. They can communicate with each other as well as with the central level. The central level is where the scheduling of machines and automated guided vehicle (AGVs) takes place. This is carried out simultaneously and not sequentially as is the case with the currently available control systems. A method based on Constraint Programming (CP) is being developed to optimise scheduling. Simulation results show that a simultaneous, as opposed to a sequential, scheduling enables a reduction of makespan by 35.6 %. Compared to other state of the art methods, the CP-based approach provides the best results and this in a significantly shorter computing time. The control architecture is able to react adequately to unexpected events such as machine failures or new orders. It uses real-life feedback from the shop floor for this purpose. The architecture is implemented as a multi-agent system. The approach can be validated by successfully controlling a model factory in a realistic environment. [less ▲]

Curriculumentwicklung in einer mehrsprachigen Gesellschaft: Das Beispiel Luxemburg

Doctoral thesis (2021)

The study starts by shedding light on the specific language situation in Luxembourg’s schools and society and explores the ways in which national curriculum is constructed utilizing the three official ... [more ▼]

The study starts by shedding light on the specific language situation in Luxembourg’s schools and society and explores the ways in which national curriculum is constructed utilizing the three official languages of Luxembourg, namely French, German and Luxembourgish. Against this backdrop it provides a detailed discussion of how specific ideas of a national linguistic identity have evolved in the course of history, and the extent to which they act as the basis for debates on language policy in today’s Luxembourgian school system. Identity formation and curriculum making shall therefore be considered as co-constructing processes, in the sense that the curriculum anticipates future societal ideals. In this respect, the curriculum ‘fabricates’ certain kinds of people and also different kinds of people (Popkewitz, 2008, 2020). Keeping this definition in mind, curriculum design becomes challenging when the school population is highly heterogenous and multilingual in itself: In addition to its historically and contextually determined multilingualism, the Grand Duchy of Luxembourg is home to numerous immigrant languages, and today almost 48% of the population are foreigners (STATEC, 2020a). Educational policy thus has to integrate pupils of non-Luxembourg origin and languages into the trilingual school system. While considering the different usage of languages in Luxembourgian society and the school system, I examine how certain ideas of multilingualism evolved and with it the representation of an ideal member of Luxembourg’s society. The dissertation will first give a historical and sociopolitical overview, concentrating on the interrelation of nation building during the 19th century and the creation of a national school system. Following the historical background, this dissertation focuses on the school and curriculum reform process of 2009 in Luxembourg, in the course of which the former education act of 1912 was replaced by a new law on elementary education. The reform was a response to the below-average performance results in large-scale assessments, first and foremost the PISA-study in the year 2000. Furthermore, it was as well the attempt to create a far more permeable school curriculum in the entire school system, and with it equal opportunities for pupils of different origins. The reform process of 2009 is accordingly seen as a turning point that broke up previously dominant ideas about the intertwinement of language and identity. With regard to these considerations, this study claims the process of curriculum making not only to be an explicit and implicit attempt to control school, and thus social realities. It is explicit to the extent that educational planning is used as a politically conscious mean of social intervention; and implicit because this control simultaneously correlates with cultural-historical practices which create common sense and therefore became subconsciously part of policy making. Following the theoretical approaches of Ludwik Fleck’s epistemology about thought styles (Fleck, 2017 [1935]), my research analyzes the extent to which specific ways of reasoning and acting in the context of curriculum making implicitly result from specific cultural historical conditions underlying the trilingual Luxembourgian school curriculum. Regarding the correlations between the institutional ideal of trilingualism in Luxembourg, the orientation towards international education standards and the extremely heterogeneous and multilingual structure of Luxembourgian society, the dissertation mainly focuses on the interrelation of the curricular paradigm and the challenges faced in the classroom reality. In light of these reflections, the dissertation tackles the following central questions: Which logics of argumentation do different actors within the curriculum making process pursue and how do they legitimize their positions on language policy? Which conflicts arise regarding the students’ linguistic repertoire and (supra-)national standards? To what extent do (supra)national educational agendas interfere with the shaping of a Luxembourg language(s) identity? How is the Luxembourg language(s) identity in light of curriculum making produced and thought? Methodologically, the reform process of 2009 will be historicized and the research questions will be addressed by a two folded research design. First, I conduct a historiographical evaluation of newspaper articles, parliamentary debates, minutes of curriculum meetings, publications of the ministry of education and legal texts. Second, the study contains an empirical analysis of 17 expert interviews which I conducted with key figures of the reform process and those who have been working with the reformed curriculum requirements. Based on the findings of my analyses, the dissertation will show that and why Luxembourg, as a kind of laboratory, is relevant to other multilingual contexts in general and in light of immigration processes in particular. The dissertation offers an innovative impetus by looking at the school reform of 2009 through a cultural-historical perspective. [less ▲]

Scalable computational modelling of concrete ageing and degradation

Doctoral thesis (2021)

The typical lifespan of concrete structures ranges from tens to hundreds of years. During such a long period of time many external factors including weather conditions, loading history or environmental ... [more ▼]

The typical lifespan of concrete structures ranges from tens to hundreds of years. During such a long period of time many external factors including weather conditions, loading history or environmental pollution. play a crucial role in concrete health and serviceability state. Prediction (via the means of computer simulation) of the long-term material properties of concrete can thus provide valuable insights and lead to better reusability of construction components. Several very complex multi-physics models were developed in the past decades for this purpose. While these models usually include a wide range of phenomena, the numerical problem which has to be solved poses major challenges and significantly increases required computational time. This makes a predictive simulation of any larger-scale structure non-feasible. On the other hand, commercial codes (ABAQUS, ANSYS, etc.) either lack the material models for a more accurate creep prediction or provide custom material routines which are not computationally optimised. In addition, a specific model and discretisation approach often requires a very specific choice of solvers and preconditioners in order to achieve good parallel scaling properties, so much required for execution on modern HPC infrastructures. In this thesis a 3-D material model for a reinforced concrete based on the micro-prestress solidification theory (MPS) of Bažant, continuum damage mechanics and the temperature and humidity model of Kunzel is efficiently implemented in the finite-element software FEniCS. A high-performance code for the assembly of residual and tangent operators is automatically derived using automatic differentiation capabilities (AD) of FEniCS. Seamless parallel integration with the linear algebra solvers suite PETSc then offers a wide range of solvers. The combination of AD, code generation techniques (e.g. FEniCS), and parallel performance of PETSc solvers for predictive modelling of concrete degradation is not present in the existing literature. It is believed that the results presented here allow the study of reusability and degradation of concrete components also for larger structures, where the conventional existing approaches cannot provide a reasonable computation time. [less ▲]

Direction of Arrival Estimation and Localization Exploiting Sparse and One-Bit Sampling

Doctoral thesis (2021)

Data acquisition is a necessary first step in digital signal processing applications such as radar, wireless communications and array processing. Traditionally, this process is performed by uniformly ... [more ▼]

Data acquisition is a necessary first step in digital signal processing applications such as radar, wireless communications and array processing. Traditionally, this process is performed by uniformly sampling signals at a frequency above the Nyquist rate and converting the resulting samples into digital numeric values through high-resolution amplitude quantization. While the traditional approach to data acquisition is straightforward and extremely well-proven, it may be either impractical or impossible in many modern applications due to the existing fundamental trade-off between sampling rate, amplitude quantization precision, implementation costs, and usage of physical resources, e.g. bandwidth and power consumption. Motivated by this fact, system designers have recently proposed exploiting sparse and few-bit quantized sampling instead of the traditional way of data acquisition in order to reduce implementation costs and usage of physical resources in such applications. However, before transition from the tradition data acquisition method to the sparsely sampled and few-bit quntized data acquisition approach, a study on the feasibility of retrieving information from sparsely sampled and few-bit quantized data is first required to be conducted. This study should specifically seek to find the answers to the following fundamental questions: 1-Is the problem of retrieving the information of interest from sparsely sampled and few-bit quantized data an identifiable problem? If so, what are the identifiability conditions? 2-Under the identifiability conditions: what are the fundamental performance bounds for the problem of retrieving the information of interest from sparsely sampled and few-bit quantized data? and how close are these performance bounds to those of retrieving the same information from the data acquired through the traditional approach? 3-Does there exist any computationally efficient algorithm for retrieving the information of interest from sparsely sampled and few-bit quantized data capable of achieving the corresponding performance bounds? My thesis focuses on finding the answers to the above fundamental questions for the problems of Direction of Arrival (DoA) estimation and localization, which are of the most important information retrieval problems in radar, wireless communication and array processing. Inthis regard, the first part of this thesis focuses on DoA estimation using Sparse Linear Arrays (SLAs). I consider this problem under three plausible scenarios from quantization perspective. Firstly, I 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, I introduce a novel estimator for the DoA estimation from SLA data employing the Weighted Least Squares (WLS) method. I 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, I 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, I study the performance limits of DoA estimation from one-bit SLA measurements through analyzing the identifiability conditions and the corresponding CRB. I also propose a new algorithm for estimating DoAs from one-bit quantized data. I 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. I develop a novel optimization-based framework for estimating DoAs from low-resolution multi-bit measurements. It is shown 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, I consider the problem of passive target localization 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. I 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, I propose a novel algorithm for target localization with the aggregated one-bit range vector. My 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, I 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 ▲]

Securing Robots: An Integrated Approach for Security Challenges adn Monitoring for the Robotic Operating System

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 ▲]

Multipath Routing on Anonymous Communication Systems: Enhancing Privacy and Performance

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 ▲]

Carbon nanotube films as absorber for solar thermal energy harvesting

Doctoral thesis (2021)

Implications of Blockchain-Based Smart Contracts on Contract Law

Doctoral thesis (2021)