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See detailMerging DEMs from VHR Optical Imagery with Drone Data - A High-resolution DEM for Tristan da Cunha
Backes, Dietmar UL; Teferle, Felix Norman UL

Scientific Conference (2018, December 12)

The extraction of high-resolution, Digital Elevation Models (DEM) from very high-resolution (VHR) optical satellite imagery, as well as low altitude drone images by Photogrammetric methods or modern ... [more ▼]

The extraction of high-resolution, Digital Elevation Models (DEM) from very high-resolution (VHR) optical satellite imagery, as well as low altitude drone images by Photogrammetric methods or modern Structure from Motion (SFM) engines, has rapidly matured. Today both data sources are representing cost-effective alternatives to dedicated airborne sensors, especially for remote and difficult to access regions. Ever-growing archives of high-resolution Satellite imagery, are providing a rich data source which covers even the most remote locations with high-resolution imagery up to 0.30m ground sample distance multiple times enabling the generation of high-resolution DEMS. Furthermore, low-cost, low weight and easy to use drones can easily be deployed in remote regions and capture limited areas with very high resolution. Dense point clouds derived from this method provide an invaluable data source to fill the gap between globally available low-resolution DEMs and highly accurate terrestrial surveys. The presented case study investigates the use of VHR archive imagery as well as low-cost drone imagery to generate high-quality DEMs using photogrammetric tools over a remote region which is difficult to access by manned airborne platforms. We highlight the potential and limitations of both data sources to provide high resolution, accurate elevation data. [less ▲]

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See detailNonlinear Model Predictive Control for Ecological Driver Assistance Systems in Electric Vehicles
Sajadi Alamdari, Seyed Amin UL; Voos, Holger UL; Darouach, Mohamed

in Robotics and Autonomous Systems (2018)

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See detailEcological Advanced Driver Assistance System for Optimal Energy Management in Electric Vehicles
Sajadi Alamdari, Seyed Amin UL; Voos, Holger UL; Darouach, Mohamed

in IEEE Intelligent Transportation Systems Magazine (2018)

Battery Electric Vehicles have a high potential in modern transportation, however, they are facing limited cruising range. The driving style, the road geometries including slopes, curves, the static and ... [more ▼]

Battery Electric Vehicles have a high potential in modern transportation, however, they are facing limited cruising range. The driving style, the road geometries including slopes, curves, the static and dynamic traffic conditions such as speed limits and preceding vehicles have their share of energy consumption in the host electric vehicle. Optimal energy management based on a semi-autonomous ecological advanced driver assistance system can improve the longitudinal velocity regulation in a safe and energy-efficient driving strategy. The main contribution of this paper is the design of a real-time risk-sensitive nonlinear model predictive controller to plan the online cost-effective cruising velocity in a stochastic traffic environment. The basic idea is to measure the relevant states of the electric vehicle at runtime, and account for the road slopes, the upcoming curves, and the speed limit zones, as well as uncertainty in the preceding vehicle behavior to determine the energy-efficient velocity profile. Closed-loop Entropic Value-at-Risk as a coherent risk measure is introduced to quantify the risk involved in the system constraints violation. The obtained simulation and field experimental results demonstrate the effectiveness of the proposed method for a semi-autonomous electric vehicle in terms of safe and energy-efficient states regulation and constraints satisfaction. [less ▲]

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See detailAn Interdisciplinary Methodology to Validate Formal Representations of Legal Text Applied to the GDPR
Bartolini, Cesare UL; Lenzini, Gabriele UL; Santos, Cristiana

Scientific Conference (2018, November 12)

The modelling of a legal text into a machine-processable form, such as a list of logic formulæ, enables a semi-automatic reasoning about legal compliance but might entail some anticipation of legal ... [more ▼]

The modelling of a legal text into a machine-processable form, such as a list of logic formulæ, enables a semi-automatic reasoning about legal compliance but might entail some anticipation of legal interpretation in the modelling. The formulæ need therefore to be validated by legal experts, but it is unlikely that they are familiar with the formalism used. This calls for an interdisciplinary validation methodology to ensure that the model is legally coherent with the text it aims to represent but that could also close the communication gap between formal modellers and legal evaluators. This paper discusses such a methodology, providing an human-readable representation that preserves the formulæ's meaning but that presents them in a way that is usable by non-experts. We exemplify the methodology on a use case where Articles of the GDPR are translated in the Reified I/O logic encoded in LegalRuleML. [less ▲]

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See detailA volume-averaged nodal projection method for the Reissner-Mindlin plate model
Ortiz-Bernardin, Alejandro; Köbrich, Philip; Hale, Jack UL et al

in Computer Methods in Applied Mechanics & Engineering (2018), 341

We introduce a novel meshfree Galerkin method for the solution of Reissner-Mindlin plate problems that is written in terms of the primitive variables only (i.e., rotations and transverse displacement) and ... [more ▼]

We introduce a novel meshfree Galerkin method for the solution of Reissner-Mindlin plate problems that is written in terms of the primitive variables only (i.e., rotations and transverse displacement) and is devoid of shear-locking. The proposed approach uses linear maximum-entropy approximations and is built variationally on a two-field potential energy functional wherein the shear strain, written in terms of the primitive variables, is computed via a volume-averaged nodal projection operator that is constructed from the Kirchhoff constraint of the three-field mixed weak form. The stability of the method is rendered by adding bubble-like enrichment to the rotation degrees of freedom. Some benchmark problems are presented to demonstrate the accuracy and performance of the proposed method for a wide range of plate thicknesses. [less ▲]

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See detailIndustry 4.0 – Implementation of an automated assembly line in a wooden modular house production plant: The case Leko Labs
de Vincenzo, Vincenzo UL; Hichri, Bassem UL; Plapper, Peter UL

in De vincenzo, Vincenzo; Hichri, Bassem; Plapper, Peter (Eds.) Robotix-Academy Conference for Industrial Robotics (RACIR) 2018 (2018, November)

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See detailFLEXCAP – Cost competitive flexible process for highly aesthetic closures manufacturing
Kakogiannos, Ioannis UL; Hichri, Bassem UL; Plapper, Peter UL

in Kakogiannos, Ioannis; Hichri, Bassem; Plapper, Peter (Eds.) Robotix-Academy Conference for Industrial Robotics (RACIR) 2018 (2018, November)

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See detailOptimal dispatching of electric and hybrid buses subject to scheduling and charging constraints
Rinaldi, Marco UL; Parisi, Federico; Laskaris, Georgios UL et al

Scientific Conference (2018, November)

We consider the problem of optimally determining the sequence of electric and hybrid buses departing from a multi-line bus terminal, considering both service constraints (schedule adherence) and energy ... [more ▼]

We consider the problem of optimally determining the sequence of electric and hybrid buses departing from a multi-line bus terminal, considering both service constraints (schedule adherence) and energy constraints (electric bus charging status, bus recharging scheduling in capacitated facilities). The problem is formulated as a Mixed Integer Linear Program, with the objective of minimizing the total operational cost for the bus lines in question. System dynamics are captured by practical sets of constraints, ranging from scheduling adherence to discharge- recharge dynamics. Individual operational costs at the bus level and at the trip level are fully parametrized, allowing for extensive sensitivity analysis. We investigate a real-life case study based on the city of Luxembourg, where two charging stations have been installed in the central station’s bus terminal. Experimental results show that, while full electrification is indeed possible, the required fleet size depends strongly on the given line(s) timetable. [less ▲]

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See detailRobotix-Academy Conference for Industrial Robotics (RACIR) 2018
Müller, Rainer; Plapper, Peter UL; Brüls, Olivier et al

Book published by Shaker Verlag - 1st ed (2018)

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See detailControllability of transportation networks
Rinaldi, Marco UL

in Transportation Research. Part B, Methodological (2018), 118

Network-wide traffic control policies determine the optimal values for the different kinds of controllers equipped on a transportation network, with the objective of reducing de- lays and congestion ... [more ▼]

Network-wide traffic control policies determine the optimal values for the different kinds of controllers equipped on a transportation network, with the objective of reducing de- lays and congestion, improving safety and reaching a target Level of Service. While models and algorithms for these problems have been extensively studied in literature, little at- tention has been devoted to investigating whether/how different locations, kinds (pricing controllers, traffic lights, ...) and amounts of controllers in a network affect the overall performance of network-wide schemes. In this work, we adapt the control-theoretical approach of controllability of complex networks to the specific instance of transportation networks, considering both propaga- tion/spillback dynamics and users’ behavior in terms of route choice. Thanks to the newly developed methodology, we then provide exact solutions to the Full Controllability Pric- ing Controller Location Problem for transportation networks. Comparing different pricing controller location policies through two artificial test cases, we empirically demonstrate how indeed the amount and kind of controllers in a network strongly affect the level of performance reachable by network-wide control policies, specifically in terms of Total Cost minimization. [less ▲]

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See detailLink Optimization in Future Generation Satellite Systems
Mengali, Alberto UL

Doctoral thesis (2018)

In recent years, communication networks have seen a huge growth in the amount of requested throughput, pushed from the combination of two main drivers: the introduction of new services and the improvement ... [more ▼]

In recent years, communication networks have seen a huge growth in the amount of requested throughput, pushed from the combination of two main drivers: the introduction of new services and the improvement of existing ones, requiring increased amount of traffic (e.g. higher quality of video content). These effects mandate the constant evolution of current systems in order to cope with the growing user demand and should be tackled from multiple angles. On the one hand, better utilization of available resources might help in the short term to keep up with the market and has always been an important priority for operators of terrestrial and satellite networks alike. On the other hand, acquisition and exploitation of currently unused resources might fuel the growth for a significantly longer period of time, ensuring longevity and thus enabling future-proofing of current systems. Both these topics are addressed in this thesis with specific applications relevant to satellite communication networks. In the first part, this thesis focuses on maximization of the user capacity by better exploiting the available radio resources. Motivated by the substantial capacity gains enabled by a higher bandwidth allocation, we investigate the optimization of satellite systems employing full-frequency reuse on the user downlink. Unlike most of the literature on the subject, usually resorting to precoding techniques to mitigate the interference, we propose a combination of predistortion and precoding to jointly counteract on-board non-linear distortions and multi-user interference. First, a flexible framework for the optimization of transmit processing schemes in communication chains is presented. This framework expands on the application of the well known gradient descent technique by applying it to the maximization of the received Signal to Noise plus Interference ratio in complex communication systems. To do so, it identifies a suitable mathematical representation of various key blocks of the system and exploits the chain rule of the derivative to compute the overall gradient as a cascade of the single components. Afterwards, this framework is validated by optimizating the coefficients of the proposed predistortion architecture for the satellite system in analysis. The obtained results highlight the flexibility of the developed optimization framework and the benefits of the suggested predistortion strategy compared to existing state of the art solutions. In the second part of the thesis, the focus is shifted towards investigating the exploitation of novel resources by looking at the use of optical frequencies for ground-to-space feeder links. The topic is introduced by a survey of existing benefits and limitations of free space optical communications. Subsequently, the implications of employing optical frequencies in long distance ground-to-space feeder links with transparent satellites are addressed. Furthermore, a powerful and flexible simulation tool was developed and exploited during the course of this thesis to model and assess the Physical (PHY) layer performance of hybrid optical/Radio Frequencies (RF) satellite networks. This tool is presented together with the scenarios and results obtained as part of the project ONSET (Optical Feeder Links Study for Satellite Networks - ESA Contract No. 40000113462/15/NL/NDe). Finally, the thesis investigates a scenario that combines the transmit processing techniques analyzed in the first part and the context of optical feeder links evaluated in the second part. A hybrid optical/RF system is considered with an electrical predistorter in place to counteract the impairments induced by the combined effects of electrical and optical non-linearities encountered along the end-to-end chain. The developed mathematical framework is exploited to jointly optimize the predistortion coefficients and the working point for the electro-optical modulator. The performance results obtained after the optimization procedure demonstrate the efficacy of the proposed approach for hybrid optical/RF systems with analog modulations. [less ▲]

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See detailThe provision of urban green space and its accessibility: Spatial data effects in Brussels
Le Texier, Marion UL; Schiel, Kerry UL; Caruso, Geoffrey UL

in PLoS ONE (2018), 13(10), 0204684

Urban green space (UGS) has many environmental and social benefits. UGS provision and access are increasingly considered in urban policies and must rely on data and indicators that can capture variations ... [more ▼]

Urban green space (UGS) has many environmental and social benefits. UGS provision and access are increasingly considered in urban policies and must rely on data and indicators that can capture variations in the distribution of UGS within cities. There is no consensus about how UGS, and their provision and access, must be defined from different land use data types. Here we identify four spatial dimensions of UGS and critically examine how different data sources affect these dimensions and our understanding of their variation within a city region (Brussels). We compare UGS indicators measured from an imagery source (NDVI from Landsat), an official cadastre-based map, and the voluntary geographical information provided by OpenStreetMap (OSM). We compare aggregate values of provision and access to UGS as well as their spatial distribution along a centrality gradient and at neighbourhood scale. We find that there are strong differences in the value of indicators when using the different datasets, especially due to their ability to capture private and public green space. However we find that the interpretation of intra-urban spatial variations is not affected by changes in data source. Centrality in particular is a strong determinant of the relative values of UGS availability, fragmentation and accessibility, irrespective of datasets. [less ▲]

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See detailSimple and extensible plate and shell finite element models through automatic code generation tools
Hale, Jack UL; Brunetti, Matteo; Bordas, Stéphane UL et al

in Computers & Structures (2018), 209

A large number of advanced finite element shell formulations have been developed, but their adoption is hindered by complexities of transforming mathematical formulations into computer code. Furthermore ... [more ▼]

A large number of advanced finite element shell formulations have been developed, but their adoption is hindered by complexities of transforming mathematical formulations into computer code. Furthermore, it is often not straightforward to adapt existing implementations to emerging frontier problems in thin structural mechanics including nonlinear material behaviour, complex microstructures, multi-physical couplings, or active materials. We show that by using a high-level mathematical modelling strategy and automatic code generation tools, a wide range of advanced plate and shell finite element models can be generated easily and efficiently, including: the linear and non-linear geometrically exact Naghdi shell models, the Marguerre-von K ́arm ́an shallow shell model, and the Reissner-Mindlin plate model. To solve shear and membrane-locking issues, we use: a novel re-interpretation of the Mixed Interpolation of Tensorial Component (MITC) procedure as a mixed-hybridisable finite element method, and a high polynomial order Partial Selective Reduced Integration (PSRI) method. The effectiveness of these approaches and the ease of writing solvers is illustrated through a large set of verification tests and demo codes, collected in an open-source library, FEniCS-Shells, that extends the FEniCS Project finite element problem solving environment. [less ▲]

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See detailA17044 Community health workers for non-communicable disease interventions in the digital age
Mishra, Shiva Raj; Lygidakis, Charilaos UL; Neupane, Dinesh et al

in Journal of Hypertension (2018, October)

Objectives: In this study, we review the evidence and discuss how the digitalization affects the CHWs programs for tackling non-communicable diseases (NCDs) in low-and-middle income countries (LMICs ... [more ▼]

Objectives: In this study, we review the evidence and discuss how the digitalization affects the CHWs programs for tackling non-communicable diseases (NCDs) in low-and-middle income countries (LMICs). Methods: We conducted a review of literature covering two databases: PubMED and Embase. A total of 97 articles were abstracted for full text review of which 21 are included in the analysis. Existing theories were used to construct a conceptual framework for understanding how digitalization affects the prospects of CHW programs for NCDs. Results: We identified three benefits and three challenges of digitalization. Firstly, it will help improve the access and quality of services, notwithstanding its higher establishment and maintenance costs. Secondly, it will add efficiency in training and personnel management. Thirdly, it will leverage the use of data generated across grass-roots platforms to further research and evaluation. The challenges posed are related to funding, health literacy of CHWs, and systemic challenges related to motivating CHWs. More than 60 digital platforms were identified, including mobile based networking devices (used for behavioral change communication), Web-applications (used for contact tracking, reminder system, adherence tracing, data collection, and decision support), videoconference (used for decision support) and mobile applications (used for reminder system, supervision, patients’ management, hearing screening, and tele-consultation). Conclusion: The digitalization efforts of CHW programs are afflicted by many challenges, yet the rapid technological penetration and acceptability coupled with the gradual fall in costs constitute encouraging signals for the LMICs. Both CHWs interventions and digital technologies are not inexpensive, but they may provide better value for the money. [less ▲]

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See detailThe elastic properties of composites reinforced by a transversely isotropic random fibre-network
Lin, Xiude; Zhu, Hanxing; Yuan, Xiaoli et al

in Composite Structures (2018), 208

This research stems from the idea of introducing a fibre-network structure into composites aiming to enhance the stiffness and strength of the composites. A novel new type of composites reinforced by a ... [more ▼]

This research stems from the idea of introducing a fibre-network structure into composites aiming to enhance the stiffness and strength of the composites. A novel new type of composites reinforced by a tranversely isotropic fibre-network in which the fibres are devided into continuous segments and randomly distributed has been proposed and found to have improved elastic properties compared to other conventional fibre or particle composites mainly due to the introduction of cross linkers among the fibres. Combining with the effects of Poisson’s ratio of the constituent materials, the fibre network composite can exhibit extraordinary stiffness. A simplified analytical model has also been proposed for comparison with the numerical results, showing close prediction of the stiffness of the fibre-network composites. Moreover, as a plate structure, the thickness of the fibre network composite is adjustable and can be tailored according to the dimensions and mechanical properties as demanded in industry. [less ▲]

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See detailCollision-Free Navigation of Small UAVs in Complex Urban Environment
Annaiyan, Arun UL

Doctoral thesis (2018)

Small unmanned aerial vehicles (UAVs) are expected to become highly innovative solutions for all kind of tasks such as transport, surveillance, inspection or guidance, and many commercial ideas already ... [more ▼]

Small unmanned aerial vehicles (UAVs) are expected to become highly innovative solutions for all kind of tasks such as transport, surveillance, inspection or guidance, and many commercial ideas already exist. Herein, small multi rotor UAVs are preferred since they are easy to construct and to fly, at least in wide open spaces. However, many UAV business cases are foreseen in complex urban environments which are very challenging from the perspective of UAV flight. Our work focuses on the autonomous flight and collision-free navigation in an urban environment, where GPS is still considered for localization but where variations in the accuracy or temporary unavailability of GPS position data is explicitly considered. Herein, urban environments are challenging because they require flight nearby large structures and also nearby moving obstacles such as humans and other moving objects, at low altitudes or in very narrow spaces and thus also in areas where GPS (global positioning system) position data might temporarily be very inaccurate or even not available. Therefore we designed a custom stereo camera with adjustable base length for the perception of the possible potential obstacles in the unknown outdoor environment. In this context the optimal design and sensitivity parameters are investigated in outdoor experiments. Using the stereo images, graph based SLAM approach is used for online three dimensional mapping of the static and dynamic environment. For the memory efficiency incremental online loop closure detection using bag of words method is implemented here. By having the three dimensional map, the cost of the cell and its transition calculated in real time by the modified D* lite which will search and generate three dimensional collision free path planning. Experiments of the 3D mapping and collision free path planning are conducted using small UAV in outdoor scenario. The combined experimental results of real time mapping and path planning demonstrated that the three dimensional collision free path planning is able to handle the real time computational constraints while maintaining safety distance. [less ▲]

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See detailA Dual-Grid Multiscale Approach to CFD-DEM Couplings for Multiphase Flow
Pozzetti, Gabriele UL

Doctoral thesis (2018)

This thesis focuses on a novel dual-grid multiscale approach to CFD- DEM1 couplings, proposes its advantages in terms of numerical proper- ties and performance, and provides examples of engineering ... [more ▼]

This thesis focuses on a novel dual-grid multiscale approach to CFD- DEM1 couplings, proposes its advantages in terms of numerical proper- ties and performance, and provides examples of engineering applications that can benefit from it. In recent years, CFD-DEM couplings are be- coming a more and more adopted solution for the numerical simulation of particle-laden flows. In particular, couplings based on the volume av- eraging technique have become a standard for numerical simulations in chemical and process engineering. Furthermore, they are rapidly spread- ing to civil, geotechnical and mechanical applications due to their ability in dealing with arbitrarily complex mixtures of continuum and granular media. Despite the several advantages that these Eulerian-Lagrangian cou- plings provide, their rigorous application to complex scenarios is currently limited by two main factors. First, the computational traceability of the solutions can become problematic due to the lack of a general theory on the subject. In particular, grid-convergence studies for the solution of the continuous phases are often not feasible due to the averaging procedure that imposes limitations on the grid structure and refinement. Second, the parallel implementation of these numerical schemes holds important disadvantages in terms of memory consumption and inter-physics com- munication load. These disadvantages are significantly limiting the ex- tension of these approaches to large-scale scenarios. This thesis collects some of the most significant works published in the last years on a novel approach that allows solving the two above- mentioned problems, and, therefore, tackling more complex and expen- sive scenarios. I refer to this approach as dual-grid multiscale approach for CFD-DEM couplings. It consists in using two different computational grids, one for the coupling between continuum and discrete entities and one for the solution of the so-obtained continuum equations. The two grids, i.e. the two problems, are in this way resolved on two different scales. The first scale or “bulk” scale is chosen to optimize the averag- ing operation. At this length-scale, the discrete entities are considered as zero-dimensional, and interact with the fluid with local exchanges of momentum, mass, and energy. The second scale or “fluid-fine” scale is identified as the one at which a unique solution for the averaged equa- tions can be provided. In practice, this is chosen as the one at which the solution of the fluid equations becomes grid-independent. An inter-scale communication is adopted by interpolating fields from the fluid-fine scale to the bulk one and vice-versa. The theoretical description of the method is first provided with par- ticular reference to the DEM-VOF coupling. Even in its simplest version, the multiscale approach is shown to generate grid-convergent solutions and significantly higher accuracy than a standard CFD-DEM coupling. This shows how the new approach is able to overcome the first main limitation described above. Then, an optimized parallel implementation of the method is pro- posed to show how this multiscale approach can provide significant ben- efits also for what concerns the execution time. Technically, this is made possible by moving the communication cost of the coupling from the inter-physics communication that characterized the standard CFD-DEM couplings to an optimized inter-scale communication routine. This en- ables the method to overcome a major bottleneck of the parallel execution of CFD-DEM couplings and therefore the second main limitation of those schemes. Finally, the dual-grid multiscale method is applied to approach in- dustrially relevant problems that were till now out-of-reach for standard CFD-DEM couplings, proving how this technique can have direct real- case application and produce immediate benefits for practitioners willing to adopt it. [less ▲]

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See detailModel and parameter identification through Bayesian inference in solid mechanics
Rappel, Hussein UL

Doctoral thesis (2018)

Predicting the behaviour of various engineering systems is commonly performed using mathematical models. These mathematical models include application-specific parameters that must be identified from ... [more ▼]

Predicting the behaviour of various engineering systems is commonly performed using mathematical models. These mathematical models include application-specific parameters that must be identified from measured data. The identification of model parameters usually comes with uncertainties due to model simplifications and errors in the experimental measurements. Quantifying these uncertainties can effectively improve the predictions as well as the performance of the engineering systems. Bayesian inference provides a probabilistic framework for quantifying these uncertainties in parameter identification problems. In a Bayesian framework, the user's initial knowledge, which is represented by a probability distribution, is updated by measurement data through Bayes' theorem. In the first two chapters of this thesis, Bayesian inference is developed for the identification of material parameters in elastoplasticity and viscoelasticity. The effect of the user's prior knowledge is systematically studied with respect to the number of measurements available. In addition, the influence of different types of experiments on the uncertainty is studied. Since all mathematical models are simplifications of reality, uncertainties of the model itself may also be incorporated. The third chapter of this thesis presents a Bayesian framework for parameter identification in elastoplasticity in which not only the uncertainty of the experimental output is included (i.e. stress measurements), but also the uncertainty of the model and the uncertainty of the experimental input (i.e. strain). Three different formulations for describing the model uncertainty are considered: (1) a random variable which is taken from a normal distribution with constant parameters, (2) a random variable which is taken from a normal distribution with an input-dependent mean, and (3) a Gaussian random process with a stationary covariance function. In the fourth chapter of this thesis, a Bayesian scheme is proposed to identify material parameter distributions, instead of material parameters. The application in this chapter are random fibre networks, in which the set of material parameters of each fibre is assumed to be a realisation from a material parameter distribution. The fibres behave either elastoplastically or in a perfectly brittle manner. The goal of the identification scheme is to avoid the experimentally demanding task of testing hundreds of constituents. Instead, only 20 fibres are considered. In addition to their material randomness, the macroscale behaviours of these fibre networks are also governed by their geometrical randomness. Another question aimed to be answered in this chapter is therefore is `how precise the material randomness needs to be identified, if the geometrical randomness will also influence the macroscale behaviour of these discrete networks'. [less ▲]

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