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See detailTowards a seamless Integration of CAD and Simulation: CISM Course 2017
Bordas, Stéphane UL

Learning material (2017)

Isogeometric analysis relies on the use of the same basis functions as employed in Computer Aided Design (CAD). This offers the possibility to facilitate design and optimisation. The previous course ... [more ▼]

Isogeometric analysis relies on the use of the same basis functions as employed in Computer Aided Design (CAD). This offers the possibility to facilitate design and optimisation. The previous course “Isogeometric methods for numerical simulation” held in 2013 had the aim to give an introduction to isogeometric analysis, its advantages, drawbacks and to the range of its applications. The aim of the proposed new course will be different. The focus will be more on the connection of simulation to CAD systems and how CAD data can be used directly for simulation, leading to a seamless integration. An overview of recent advances and applications will be also presented. The course will start with an introduction to NURBS and their use in describing geometry and in simulation. This will be followed by lectures from a CAD vendor describing the current state of development. Currently available connections to simulation software will also be discussed. Next the use of NURBS for 3D structural analysis, structural optimisation and damage tolerance assessment will be presented, including such advanced topics as the treatment of discontinuities and real-time solvers. It will also be discussed when it might be advantageous to decouple the boundary discretisation from the field variable discretisation, in particular in shape optimisation. Isogeometric methods for the analysis of beam and shell structures, including shape optimisation and fluid structure interaction, will be presented. Lectures on the mathematical and algorithmic foundations of analysis-suitable geometry will follow. This includes an introduction to T-splines and multilevel spline schemes such as hierarchical B- splines. Common analysis-suitable spline algorithms will be presented in the context of Bézier extraction and projection as well as its application as a foundation for integrated engineering design and analysis. An important aspect of analysis-suitable geometry is the ability to locally adapt the smooth spline basis. Several common refinement algorithms will be reviewed as well as their application in several demanding areas of application. The emerging area of weak geometry will be introduced as well as its application to the rapid construction of complex structural assemblies. With the rapid development of isogeometric analysis in recent years, there is an urgent need for volumetric parameterization such as volumetric T-spline model construction. Several volumetric T- spline modeling techniques, that were developed in recent years will be presented. They include converting any quad/ hex meshes to standard and rational T-splines, polycube-based parametric mapping, feature preservation using eigenfunctions, Boolean operations and skeletons, truncated hierarchical Catmull-Clark subdivision, weighted T-splines, conformal T-spline modeling, as well as incorporating T-splines into commercial CAD and FEA software, will be presented. The target audience will be engineers, interested in simulation, software developers and researchers. [less ▲]

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See detailTowards consolidated methods for the design and evaluation of user experience
Lallemand, Carine UL

Doctoral thesis (2015)

In the “third wave” of Human-Computer Interaction (HCI), the emergence of User Experience (UX) as a key concept has opened up both exciting perspectives and hard challenges. The conceptual shift to a more ... [more ▼]

In the “third wave” of Human-Computer Interaction (HCI), the emergence of User Experience (UX) as a key concept has opened up both exciting perspectives and hard challenges. The conceptual shift to a more comprehensive and emotional view of human-computer interactions has been accompanied by the development of numerous methods and tools for the design and evaluation of interactive systems. UX research has thus been mainly driven by novelty and innovation and to date a majority of the developed tools lack validation and consolidation. UX research undoubtedly raises new concerns and challenges common conceptual and methodological practice. Thus the primary objective of this thesis is to contribute to UX consolidation. We addressed this objective by relying on a mixed-methods approach for the empirical part of this thesis, involving comparatively large and representative samples. This part encompasses six studies, representing a variety of perspectives related to UX research consolidation. More specifically, this dissertation includes a replication study (Paper A, N = 758), the translation and validation of a tool (Paper B, N = 381), the development of new design and evaluation methods (Paper C and D, N = 137 and 33), the empirical assessment of the relevance of established HCI methods for the evaluation of UX (Paper E, N = 103) and finally an investigation on how to bridge UX research and practice through a design approach (Paper F). The contributions of this thesis to UX research and practice regard both UX as a concept and its methodologies. Main findings inform about the benefits, challenges, and limitations of UX consolidation strategies as derived from our respective studies (papers A to F). Each study provides advances to both research and practice, while the combination of our studies pushes forward consolidation of UX. This is an essential step with regards to an emerging concept and informs an overarching research agenda aiming at a continuous interdisciplinary fostering of the UX field. [less ▲]

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See detailTowards Dynamic Zero Emission Zone Management for Plug-in Hybrid Buses
Seredynski, Marcin UL; Viti, Francesco UL

Scientific Conference (2019, November)

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See detailTowards Effective Shell Modelling with the FEniCS Project
Hale, Jack UL; Baiz, P. M.

Scientific Conference (2013, March)

Fast and efficient simulations of shell structures are required in a wide range of engineering fields such as fluid-structure interaction and structural optimisation. Because of its expressive high-level ... [more ▼]

Fast and efficient simulations of shell structures are required in a wide range of engineering fields such as fluid-structure interaction and structural optimisation. Because of its expressive high-level form language UFL the FEniCS project is in an ideal position to tackle tough problems such as large deformations of non-isotropic shells. In this talk we will discuss some aspects of achieving this goal; generalised mixed formulations, reduction and projection operators for eliminating shear and membrane locking, the general shell model vs classical models and the recent work by Rognes et al. on manifolds. [less ▲]

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See detailTowards legal compliance by correlating Standards and Laws with a semi-automated methodology
Bartolini, Cesare UL; Lenzini, Gabriele UL; Robaldo, Livio UL

in Proceedings of the 28 Benelux Conference on Artificial Intelligence (BNAIC) (2016, November)

Since legal regulations do not generally provide clear parameters to determine when their requirements are met, achieving legal compliance is not trivial. If there were a clear correspondence between the ... [more ▼]

Since legal regulations do not generally provide clear parameters to determine when their requirements are met, achieving legal compliance is not trivial. If there were a clear correspondence between the provisions of a specific standard and the regulation’s requirements, one could implement the standard to claim a presumption of compliance. However, finding those correspondences is a complex process; additionally, correlations may be overridden in time, for instance, because newer court decisions change the interpretation of certain provisions. To help solve this problem, we present a framework that supports legal experts in recognizing correlations between provisions in a standard and requirements in a given law. The framework relies on state-of-the-art Natural Language Semantics techniques to process the linguistic terms of the two documents, and maintains a knowledge base of the logic representations of the terms, together with their defeasible correlations, both formal and substantive. An application of the framework is shown by comparing a provision of the European General Data Protection Regulation against the ISO/IEC 27018:2014 standard. [less ▲]

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See detailTowards multiscale data fusion of high-resolution space borne and terrestrial datasets over Tristan da Cunha
Backes, Dietmar UL; Teferle, Felix Norman UL; Abraha, Kibrom Ebuy UL et al

Poster (2018, April 10)

Ever improving low cost, lightweight and easy to use sensing technologies are enabling the capture of rich 3D Datasets to support an unprecedented range of applications in Geosciences. Especially low-cost ... [more ▼]

Ever improving low cost, lightweight and easy to use sensing technologies are enabling the capture of rich 3D Datasets to support an unprecedented range of applications in Geosciences. Especially low-cost LiDAR systems as well as optical sensors, which can be deployed from terrestrial or low altitude aerial platforms, allow the collection of large datasets without detailed expert knowledge or training. Dense pointcloud derived from these technologies provide an invaluable source to fill the gap between highly precise and accurate terrestrial topographic surveys and large area Digital Surface Models (DSMs) derived from airborne and spaceborne sensors. However, the collection of reliable 3D pointclouds in remote and hazardous locations remains to be very difficult and costly. Establishing a reliable georeference, ensuring accuracy and data quality as well as merging such rich datasets with existing or space borne mapping provide additional challenges. The presented case study investigates the data quality and integration of a heterogeneous dataset collected over the remote island of Tristan da Cunha. High-resolution 3D pointclouds derived by TLS and drone Photogrammetry are merged with space borne imagery while preserving the accurate georeference provided by Ground Control derived from geodetic observations. The volcanic island of Tristan da Cunha located in the centre of the Southern Atlantic Ocean is one of the most remote and difficult to access locations on the planet. Its remote location, rough climatic conditions and consistent cloud coverage provides exceptional challenges for terrestrial, aerial as well as space borne data acquisition. Amongst many other scientific installations, the island also hosts a continuous GNSS station observation and monitoring facilities operated by the University of Luxembourg, which provided the opportunity to conduct a local terrestrial data acquisition campaign consistent with a terrestrial ground survey, Laserscanning and an image acquisition from a low-cost drone. The highly accurate Ground Control network, observed by GNSS and total station, provides a reliable georeference. Pointclouds were acquired around the area of the harbour using a Leica P20 terrestrial Laserscanner, as well as drone Photogrammetry based on images collected by a low-cost DJI Phantom3 drone. To produce a map of the complete island a comprehensive dataset of high-resolution space borne imagery based on the Digital Globe WorldView constellation was acquired which provided high resolution mapping information. The case study presents a cross-validation of terrestrial, low altitude airborne as well as spaceborne datasets in terms coregistration, absolute georeference, scale, resolution and overall data quality. Following the evaluation a practical approach to fuse this heterogeneous dataset is applied which aims to preserve overall data quality, local resolution and accurate georeference and avoid edge artefacts. The conclusions drawn from our preliminary results provide some good practice advice for similar projects. The final topographic dataset enables mapping and monitoring of local geohazards as, e.g. coastal erosion and recent landslides thus also supporting the local population. [less ▲]

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See detailTowards optimal positioning of surveillance UGVs
Nilsson, U.; Ögren, P.; Thunberg, Johan UL

in Optimization and Cooperative Control Strategies (2009)

Unmanned Ground Vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full ... [more ▼]

Unmanned Ground Vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full advantage of the flexibility and speed offered by a group of UGV platforms, a fast way to compute desired camera locations to cover an area or a set of buildings, e.g., in response to an alarm, is needed. Building upon earlier results in terrain guarding and sensor placement we propose a way to find candidate guard positions that satisfy a large set of view angle and range constraints simulataneously. Since the original problem is NP-complete, we do not seek to find the true optimal set of guard positions. Instead, a near optimal subset of the candidate points is chosen using a scheme with a known approximation ratio of O(log(n)). A number of examples are presented to illustrate the approach. [less ▲]

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See detailTowards Optimised Deployment of Electric Bus Systems with On-Route Charging using Cooperative ITS
Laskaris, Georgios UL; Seredynski, Marcin; Viti, Francesco UL

Scientific Conference (2018, July)

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See detailTowards Optimised Large Scale Deployments of Electric Bus Systems with On-Route Charging
Seredynski, Marcin; Khadraoui, Djamel; Viti, Francesco UL

Scientific Conference (2016, October)

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See detailTowards Optimized Deployment of Electric Bus Systems Using Cooperative ITS
Laskaris, Georgios UL; Seredynski, Marcin; Viti, Francesco UL

Poster (2019, January)

In this paper we analyze the impact of using cooperative intelligent transportation systems (C-ITS) to manage electrical bus systems. A simulation-based study is presented where three control strategies ... [more ▼]

In this paper we analyze the impact of using cooperative intelligent transportation systems (C-ITS) to manage electrical bus systems. A simulation-based study is presented where three control strategies are used to regulate the operations of a line, namely bus holding, Green Light Optimal Dwell Time Adaptation (GLODTA) and Transit Signal Priority (TSP). The results show, using a realistic scenario of a major line in Luxembourg City, that buses are efficiently operated without necessarily providing additional priority to public transport, hence without negatively affecting the capacity of the private vehicles system. Benefits in terms of headway regulations, energy consumption and travel time variance reductions are quantified. [less ▲]

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See detailTradeoffs in networks with positive and negative feedback
Goncalves, Jorge UL; Yi, T.; Doyle, J.

Scientific Conference (2005)

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See detailTrading Zones of Digital History
Kemman, Max UL

Presentation (2016)

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See detailTraffic control which maximises network throughput: Some simple examples
Smith, Michael; Iryo, Takamasa; Mounce, Richard et al

in Transportation Research. Part C, Emerging Technologies (2019), 107

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See detailTragbare und aktiv vom Parkinson-Patienten genutzte Technologie im hauslichen Umfeld: Was bringt die Zukunft?
Maetzler, W.; Krüger, Rejko UL; Muller, T. et al

in Fortschritte der Neurologie-Psychiatrie (2016), 84 Suppl 1

Parkinson’s disease (PD) is a multisystem disorder with a plethora of symptoms affecting quality of life in the home environment. Due to the rapid development of wearable technique in the health and ... [more ▼]

Parkinson’s disease (PD) is a multisystem disorder with a plethora of symptoms affecting quality of life in the home environment. Due to the rapid development of wearable technique in the health and fitness sector, an increasing number of such wearables are available to complement diagnostic strategies of PD symptoms not only in the clinical but also in the domestic environment. This development has clear advantages over clinical evaluation, as the latter is relatively subjective, time-consuming and costly, and provides only a snapshot of the condition. First results about the use of such technology for the assessment of PD symptoms (including bradykinesia, dyskinesia, tremor, daily activity and sleep behavior) in the domestic environment are promising. They suggest that these techniques can provide complementary information about the symptoms of PD patients, and have the potential to be included in future diagnostic workup concepts of routine care in PD. The use of such technique provides also the chance to more actively include patients into medical decision making processes. [less ▲]

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See detailA transformation of the position based visual servoing problem into a convex optimization problem
Wang, Y.; Thunberg, Johan UL; Yu, X.

in Proceedings of the 51th IEEE Conference on Decision and Control (2012)

Here we address the problem of moving a camera from an initial pose to a final pose. The trajectory between the two poses is subject to constraints on the camera motion and the visibility, where we have ... [more ▼]

Here we address the problem of moving a camera from an initial pose to a final pose. The trajectory between the two poses is subject to constraints on the camera motion and the visibility, where we have bounds on the allowed velocities and accelerations of the camera and require that a set of point features are visible for the camera. We assume that the pose is possible to retrieve from the observations of the point features, i.e., we have a Position Based Visual Servoing Problem with constraints. We introduce a two step method that transforms the problem into a convex optimization problem with linear constraints. In the first step the rotational motion is restricted to be of a certain type. This restriction allows us to retrieve an explicit solution of the rotational motion that is optimal in terms of minimizing geodesic distance. Furthermore, this restriction guarantees that the rotational motion satisfies the constraints. Using the explicit solution, we can formulate a convex optimization problem for the translational motion, where we include constraints on workspace and visibility. [less ▲]

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See detailTransition vers le numérique : Quelles implications pour l’évaluation des élèves et leurs apprentissages ?
Rocher, Thierry; Fischbach, Antoine UL; Klausing, Andreas et al

Scientific Conference (2016, January)

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See detailTransparency by Design in Data-Informed Research: a Collection of Information Design Patterns
Rossi, Arianna UL; Lenzini, Gabriele UL

in Computer Law and Security Report (in press)

Oftentimes information disclosures describing personal data-gathering research activities are so poorly designed that participants fail to be informed and blindly agree to the terms, without grasping the ... [more ▼]

Oftentimes information disclosures describing personal data-gathering research activities are so poorly designed that participants fail to be informed and blindly agree to the terms, without grasping the rights they can exercise and the risks derived from their cooperation. To respond to the challenge, this article presents a series of operational strategies for transparent communication in line with legal-ethical requirements. These "transparency-enhancing design patterns" can be implemented by data controllers/researchers to maximize the clarity, navigability, and noticeability of the information provided and ultimately empower data subjects/research subjects to appreciate and determine the permissible use of their data. [less ▲]

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See detailTravel-sharing in multimodal systems: a behavioural modelling approach
Viti, Francesco UL

Scientific Conference (2013)

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See detailTrefftz polygonal finite element for linear elasticity: convergence, accuracy, and properties
Hirshikesh; Natarajan, Sundararajan; Ratna Kumar, A. K. et al

in Asia Pacific Journal on Computational Engineering (2017)

In this paper, the accuracy and the convergence properties of Trefftz finite element method over arbitrary polygons are studied. Within this approach, the unknown displacement field within the polygon is ... [more ▼]

In this paper, the accuracy and the convergence properties of Trefftz finite element method over arbitrary polygons are studied. Within this approach, the unknown displacement field within the polygon is represented by the homogeneous solution to the governing differential equations, also called as the T-complete set. While on the boundary of the polygon, a conforming displacement field is independently defined to enforce the continuity of the field variables across the element boundary. An optimal number of T-complete functions are chosen based on the number of nodes of the polygon and the degrees of freedom per node. The stiffness matrix is computed by the hybrid formulation with auxiliary displacement frame. Results from the numerical studies presented for a few benchmark problems in the context of linear elasticity show that the proposed method yields highly accurate results with optimal convergence rates. [less ▲]

Detailed reference viewed: 70 (1 UL)