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See detailSustainability Research and Interactive Knowledge Generation
JUNG ép. PRELLER, Bérénice UL; Affolderbach, Julia UL; Schulz, Christian UL et al

E-print/Working paper (2014)

Based on experiences from the GreenRegio research project that investigates framework conditions for innovations in sustainable/green building, this working paper explores the potential of interactive and ... [more ▼]

Based on experiences from the GreenRegio research project that investigates framework conditions for innovations in sustainable/green building, this working paper explores the potential of interactive and collaborative methods for knowledge generation and co-production. Engagement with local practi-tioners, private industry, academics, political decision-makers and representatives of the non-profit sector early on in the research process allows researchers to gain better understanding of the re-search object and context. It also creates a platform for (mutual) knowledge exchange. Methodologi-cally, the project incorporates interactive workshops and Delphi-based feedback and validation rounds, that – over the lifespan of the project – offer a mutual learning process further inspired by in-sights and experiences across four case studies in Europe, Australia, and Canada. The exchange and learning processes provide important insights on different forms and pathways of sustainability transi-tions in the building sector to all participants involved in the project, researchers and researched alike. [less ▲]

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See detailSystematic analysis of global and local control policies
Cantelmo, Guido UL; Viti, Francesco UL; Rinaldi, Marco et al

in Periodica Polytechnica (2015)

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See detailSystematic assessment of local & global control policies: A methodological perspective
Cantelmo, Guido UL; Viti, Francesco UL; Rinaldi, Marco et al

in Proceedings of the MT-ITS Conference (2015, June)

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See detailSystematic assessment of local & global signal control policies: A methodological perspective
Cantelmo, Guido UL; Viti, Francesco UL; Rinaldi, Marco UL et al

in Proceedings of 2015 International Conference on Models and Technologies for Intelligent Transportation Systems, MT-ITS 2015 (2015)

Traffic control performance on networks depends on the flow response to the policy adopted, which in turn contributes to determine the optimal signal settings. This paper focuses on the relationship ... [more ▼]

Traffic control performance on networks depends on the flow response to the policy adopted, which in turn contributes to determine the optimal signal settings. This paper focuses on the relationship between local and network wide traffic control policies within the combined traffic control and assignment problem. Through a full exploration of the solution space, an in depth cross comparison is performed between the well-known local policies P0 and Equisaturation, versus the global policies Maximum Throughput and Minimum Delay, to verify how the two local policies approximate the optimal settings for signalized intersections. Realistic traffic dynamics, such as congestion, multiple controllers and spillback are considered, to empirically determine the conditions under which the local policies are able to approximate global performances. After presenting the different local and global control policies, experiments are performed on simple toy networks. The complexity of the underlying network and, therefore, of the problems' boundary conditions is then increased, allowing us to showcase how the different metrics perform in different situations. Finally, conclusions on the results are drawn. © 2015 BME. [less ▲]

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See detailSystems approaches to modelling pathways and networks
Pfau, Thomas UL; Christian, Nils UL; Ebenhöh, Oliver

in Briefings in Functional Genomics (2011), 10(5), 266-279

It has become commonly accepted that systems approaches to biology are of outstanding importance to gain understanding from the vast amount of data which is presently being generated by advancing high ... [more ▼]

It has become commonly accepted that systems approaches to biology are of outstanding importance to gain understanding from the vast amount of data which is presently being generated by advancing high-throughput technologies. The diversity of methods to model pathways and networks has significantly expanded over the past two decades. Modern and traditional approaches are equally important and recent activities aim at integrating the advantages of both. While traditional methods, based on differential equations, are useful to study the dynamics of small systems, modern constraint-based models can be applied to genome-scale systems, but are not able to capture dynamic features. Integrating different approaches is important to develop consistent theoretical descriptions encompassing various scales of biological information. The rapid progress of the field of theoretical systems biology, however, demonstrates how our fundamental theoretical understanding of biology is gaining momentum. The scientific community has apparently accepted the challenge to truly understand the principles of life. [less ▲]

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See detailSystems Engineering, Systems Thinking, and Learning: a Case Study in Space Industry
Moser, Hubert UL

Doctoral thesis (2013)

Systems thinking is a prerequisite of systems engineering, which is performed in multi-disciplinary teams, i.e. software engineers, mechanical engineers, electronic engineers, and others, work together to ... [more ▼]

Systems thinking is a prerequisite of systems engineering, which is performed in multi-disciplinary teams, i.e. software engineers, mechanical engineers, electronic engineers, and others, work together to develop, build, and test technical systems such as space systems. The more team members consider a systems perspective the less rework is expected and the less effort of systems engineers is required. How systems thinking evolves in practice is not sufficiently understood. Therefore, work activity of multi-disciplinary teams has been studied in an empirical study. Data from multiple sources and of different temporal resolution has been collected over four years in four studies in space systems engineering. These studies are a concept exploration project in a summer school, two concept exploration projects in a concurrent design facility, and five projects in several lifecycle stages in a small space systems company. An analytical framework has been developed based on an activity-theoretical analysis and a theme-and-key-event analysis. Contradicting multiple roles, differences in parameter definition and impact, differences in work approaches and ways of interacting, contradicting work standards, trust and doubts in extra-disciplinary decisions, awareness of diversity and orientation towards extra-disciplinary interactors, and velocity and availability of information are identified contradictions with learning potential. These contradictions provoke initiators of multi-disciplinary interaction. These are proactive provision of extra-disciplinary advice and three types of questions: critical questioning across disciplinary boundaries, asking for extra-disciplinary advice, and questioning the current work approach. The contradictions prompt the selection of themes that comprise several key events. These themes and key events are analysed on three levels (macro, meso, and micro) with a focus on systems thinking content and discourse features. Systems thinking evolves in interaction within a broad temporal range, from minutes to years. It evolves vertically, i.e. within a discipline, and horizontally, i.e. across disciplines. The evolution of systems thinking is influenced by the multi-disciplinary quality of interaction. This quality is defined by the diversity or multi-disciplinarity of the interaction, the awareness of the diversity, the orientation towards extra-disciplinary interactors, the differences in interactional responsiveness, and the cohesion of interaction. Improving the multi-disciplinary quality of interaction to foster the evolution of systems thinking is the major goal of the developed WAVES (Work Activity for a Versatile Evolution of Systems engineering and thinking) strategy. The WAVES strategy comprises two paths. The first path focuses on the introduction of employees into professional life, (space) industry, a company, a team, and a task. The second path focuses on the continuous improvement of the work activity. The implementation and evaluation of WAVES in a small space system company is the basic contribution to industry. The implementation within systems engineering departments of large space organisations has been prepared. The developed analytical framework contributes a new approach to analyse work activity in practice. Finally, the answers to the first part of the main research question contribute to a better understanding of systems engineering, systems thinking, and its learning in practice. [less ▲]

Detailed reference viewed: 251 (10 UL)
See detailTAO4school: Generic goes specific
Fischbach, Antoine UL

Bachelor/master dissertation (2008)

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See detailTaylor-Series Expansion Based Numerical Methods: A Primer, Performance Benchmarking and New Approaches for Problems with Non-smooth Solutions
Jacquemin, Thibault Augustin Marie UL; Tomar, Satyendra UL; Agathos, Konstantinos UL et al

in Archives of Computational Methods in Engineering (2019)

We provide a primer to numerical methods based on Taylor series expansions such as generalized finite difference methods and collocation methods. We provide a detailed benchmarking strategy for these ... [more ▼]

We provide a primer to numerical methods based on Taylor series expansions such as generalized finite difference methods and collocation methods. We provide a detailed benchmarking strategy for these methods as well as all data files including input files, boundary conditions, point distribution and solution fields, so as to facilitate future benchmarking of new methods. We review traditional methods and recent ones which appeared in the last decade. We aim to help newcomers to the field understand the main characteristics of these methods and to provide sufficient information to both simplify implementation and benchmarking of new methods. Some of the examples are chosen within a subset of problems where collocation is traditionally known to perform sub-par, namely when the solution sought is non-smooth, i.e. contains discontinuities, singularities or sharp gradients. For such problems and other simpler ones with smooth solutions, we study in depth the influence of the weight function, correction function, and the number of nodes in a given support. We also propose new stabilization approaches to improve the accuracy of the numerical methods. In particular, we experiment with the use of a Voronoi diagram for weight computation, collocation method stabilization approaches, and support node selection for problems with singular solutions. With an appropriate selection of the above-mentioned parameters, the resulting collocation methods are compared to the moving least-squares method (and variations thereof), the radial basis function finite difference method and the finite element method. Extensive tests involving two and three dimensional problems indicate that the methods perform well in terms of efficiency (accuracy versus computational time), even for non-smooth solutions. [less ▲]

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See detailTemperature Fields Induced by Low Power Focused Ultrasound in Soft Tissues During Gene Therapy. Numerical Predictions and Experimental Results
Gambin, Barbara; Kujawska, Tamara; Kruglenko, Eleonora et al

in Archives of Acoustics (2009), 34(4), 445459

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See detailText entry on smart glasses A comparison of two input techniques
Mccall, Roderick UL; Popleteev, Andrei UL; Martin, Benoit et al

in 8th International Conference on Human System Interaction (HSI'2015) (2015, June)

This paper presents a comparative pilot usability study of Dasher and an on-screen keyboard on a head-mounted display. Interaction logging data was captured along with subjective responses (via the SUS ... [more ▼]

This paper presents a comparative pilot usability study of Dasher and an on-screen keyboard on a head-mounted display. Interaction logging data was captured along with subjective responses (via the SUS questionnaire). The results indicate that there is a strong need to develop text entry systems for smart glasses rather to simply adopt those that are already available. However, both approaches are useful when there is a need to enter private or sensitive data. [less ▲]

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See detailTextual Inference with Deep Learning Technique
Adebayo, Kolawole; Di Caro, Luigi; Robaldo, Livio UL et al

in Proc. of the 28th Annual Benelux Conference on Artificial Intelligence (BNAIC2016). (2016)

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See detailThermodynamically constrained averaging theory for cancer growth modelling
Albrecht, Marco UL; Sciumè, Giuseppe; Lucarelli, Philippe UL et al

in IFAC-PapersOnLine (2016), 49(26), 289-294

In Systems Biology, network models are often used to describe intracellular mechanisms at the cellular level. The obtained results are difficult to translate into three-dimensional biological systems of ... [more ▼]

In Systems Biology, network models are often used to describe intracellular mechanisms at the cellular level. The obtained results are difficult to translate into three-dimensional biological systems of higher order. The multiplicity and time dependency of cellular system boundaries, mechanical phenomena and spatial concentration gradients affect the intercellular relations and communication of biochemical networks. These environmental effects can be integrated with our promising cancer modelling environment, that is based on thermodynamically constrained averaging theory (TCAT). Especially, the TCAT parameter viscosity can be used as critical player in tumour evolution. Strong cell-cell contacts and a high degree of differentiation make cancer cells viscous and support compact tumour growth with high tumour cell density and accompanied displacement of the extracellular material. In contrast, dedifferentiation and losing of cell-cell contacts make cancer cells more fluid and lead to an infiltrating tumour growth behaviour without resistance due to the ECM. The fast expanding tumour front of the invasive type consumes oxygen and the limited oxygen availability behind the invasive front results automatically in a much smaller average tumour cell density in the tumour core. The proposed modelling technique is most suitable for tumour growth phenomena in stiff tissues like skin or bone with high content of extracellular matrix. [less ▲]

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See detailThree-dimensional crack initiation, propagation, branching and junction in non-linear materials by an extended meshfree method without asymptotic enrichment
Bordas, Stéphane UL; Rabczuk, Timon; Zi, Goangseup

in Engineering Fracture Mechanics (2008), 75(5), 943-960

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, branching, growth and coalescence of an arbitrary number of cracks in non-linear solids including large ... [more ▼]

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, branching, growth and coalescence of an arbitrary number of cracks in non-linear solids including large deformations, for statics and dynamics. The novelty of the methodology is that only an extrinsic discontinuous enrichment and no near-tip enrichment is required. Instead, a Lagrange multiplier field is added along the crack front to close the crack. This decreases the computational cost and removes difficulties involved with a branch enrichment. The results are compared to experimental data, and other simulations from the literature to show the robustness and accuracy of the method. [less ▲]

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See detailThree-Dimensional Crack Propagation with Global Enrichment XFEM and Vector Level Sets
Agathos, Konstantinos; Ventura, Giulio; Chatzi, Eleni et al

Scientific Conference (2015)

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See detailA three-dimensional meshfree method for continuous multiple-crack initiation, propagation and junction in statics and dynamics
Rabczuk, Timon; Bordas, Stéphane UL; Zi, Goangseup

in Computational Mechanics (2007), 40(3), 473-495

This paper proposes a three-dimensional meshfree method for arbitrary crack initiation and propagation that ensures crack path continuity for non-linear material models and cohesive laws. The method is ... [more ▼]

This paper proposes a three-dimensional meshfree method for arbitrary crack initiation and propagation that ensures crack path continuity for non-linear material models and cohesive laws. The method is based on a local partition of unity. An extrinsic enrichment of the meshfree shape functions is used with discontinuous and near-front branch functions to close the crack front and improve accuracy. The crack is hereby modeled as a jump in the displacement field. The initiation and propagation of a crack is determined by the loss of hyperbolicity or the loss of material stability criterion. The method is applied to several static, quasi-static and dynamic crack problems. The numerical results very precisely replicate available experimental and analytical results. [less ▲]

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See detailThree-dimensional non-linear fracture mechanics by enriched meshfree methods without asymptotic enrichment
Bordas, Stéphane UL; Zi, G.; Rabczuk, T.

in Proceedings of the IUTAM Symposium on Discretization Methods for Evolving Discontinuities (2007)

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, growth and coalescence of an arbitrary number of cracks in non-linear solids including large deformations ... [more ▼]

This paper presents a three-dimensional, extrinsically enriched meshfree method for initiation, growth and coalescence of an arbitrary number of cracks in non-linear solids including large deformations, for statics and dynamics. The novelty of the methodology fashioned in this work is that only an extrinsic discontinuous enrichment and no near-tip/asymptotic enrichment is required. Instead, a Lagrange multiplier field is added along the crack front to close the crack along the front. This decreases the computational cost and removes difficulties involved with a branch enrichment. Numerical examples treated include the pull-out of a reinforcement bar from a concrete block, and a Taylor bar impact with very large deformation and fragmentation. The results are compared to experimental results, and other simulations from the literature, which shows the robustness and accuracy of the method. © 2007 Springer. [less ▲]

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See detailThree-dimensional remeshed smoothed particle hydrodynamics for the simulation of isotropic turbulence
Obeidat, Anas UL; Bordas, Stéphane UL

in International Journal for Numerical Methods in Fluids (2017)

We present a remeshed particle-mesh method for the simulation of three-dimensional compressible turbulent flow. The method is related to the mesh free smoothed particle hydrodynamic (SPH) method, but the ... [more ▼]

We present a remeshed particle-mesh method for the simulation of three-dimensional compressible turbulent flow. The method is related to the mesh free smoothed particle hydrodynamic (SPH) method, but the present method introduces a mesh for efficient calculation of the pressure gradient, and laminar and turbulent diffusion. In addition, the mesh is used to remesh (reorganise uniformly) the particles to ensure a regular particle distribution and convergence of the method. The accuracy of the presented methodology is tested for a number of benchmark problems involving two- and three-dimensional Taylor-Green flow, thin double shear layer, and three-dimensional isotropic turbulence. Two models were implemented, direct numerical simulations, and Smagorinsky model. Taking advantage of the Lagrangian advection, and the finite difference efficiency, the method is capable of providing quality simulations while maintaining its robustness and versatility [less ▲]

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See detailTime and frequency domain analysis of piezoelectric energy harvesters by monolithic finite element modeling
Ravi, Srivathsan UL; Zilian, Andreas UL

in International Journal for Numerical Methods in Engineering (2017)

The successful design of piezoelectric energy harvesting devices relies upon the identification of optimal geometrical and material configurations to maximize the power output for a specific band of ... [more ▼]

The successful design of piezoelectric energy harvesting devices relies upon the identification of optimal geometrical and material configurations to maximize the power output for a specific band of excitation frequencies. Extendable predictive models and associated approximate solution methods are essential for analysis of a wide variety of future advanced energy harvesting devices involving more complex geometries and material distributions. Based on a holistic continuum mechanics modeling approach to the multi-physics energy harvesting problem, this article proposes a monolithic numerical solution scheme using a mixed-hybrid 3-dimensional finite element formulation of the coupled governing equations for analysis in time and frequency domain. The weak form of the electromechanical/circuit system uses velocities and potential rate within the piezoelectric structure, free boundary charge on the electrodes, and potential at the level of the generic electric circuit as global degrees of freedom. The approximation of stress and dielectric displacement follows the work by Pian, Sze, and Pan. Results obtained with the proposed model are compared with analytical results for the reduced-order model of a cantilevered bimorph harvester with tip mass reported in the literature. The flexibility of the method is demonstrated by studying the influence of partial electrode coverage on the generated power output. [less ▲]

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See detailTimeWarp: Interactive Time Travel with a Mobile Mixed Reality Game
Herbst, Iris; Braun, Anne-Kathrine; McCall, Roderick UL et al

in In the Proceedings of MobileHCI 2008, Amsterdam, Netherlands (2008)

Mobile location-aware applications have become quite popular across a range of new areas such as pervasive games and mobile edutainment applications. However it is only recently, that approaches have been ... [more ▼]

Mobile location-aware applications have become quite popular across a range of new areas such as pervasive games and mobile edutainment applications. However it is only recently, that approaches have been presented which combine gaming and education with mobile Augmented Reality systems. However they typically lack a close crossmedia integration of the surroundings, and often annotate or extend the environment rather than modifying and altering it. In this paper we present a mobile outdoor mixed reality game for exploring the history of a city in the spatial and the temporal dimension. We introduce the design and concept of the game and present a universal mechanism to define and setup multi-modal user interfaces for the game challenges. Finally we discuss the results of the user tests. [less ▲]

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See detailTowards a high-resolution drone-based 3D mapping dataset to optimise flood hazard modelling
Backes, Dietmar UL; Schumann, Guy; Teferle, Felix Norman UL et al

in International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences (2019, June), XLII-2/W13

The occurrence of urban flooding following strong rainfall events may increase as a result of climate change. Urban expansion, ageing infrastructure and an increasing number of impervious surfaces are ... [more ▼]

The occurrence of urban flooding following strong rainfall events may increase as a result of climate change. Urban expansion, ageing infrastructure and an increasing number of impervious surfaces are further exacerbating flooding. To increase resilience and support flood mitigation, bespoke accurate flood modelling and reliable prediction is required. However, flooding in urban areas is most challenging. State-of-the-art flood inundation modelling is still often based on relatively low-resolution 2.5 D bare earth models with 2-5m GSD. Current systems suffer from a lack of precise input data and numerical instabilities and lack of other important data, such as drainage networks. Especially, the quality and resolution of the topographic input data represents a major source of uncertainty in urban flood modelling. A benchmark study is needed that defines the accuracy requirements for highly detailed urban flood modelling and to improve our understanding of important threshold processes and limitations of current methods and 3D mapping data alike. This paper presents the first steps in establishing a new, innovative multiscale data set suitable to benchmark urban flood modelling. The final data set will consist of high-resolution 3D mapping data acquired from different airborne platforms, focusing on the use of drones (optical and LiDAR). The case study includes residential as well as rural areas in Dudelange/Luxembourg, which have been prone to localized flash flooding following strong rainfall events in recent years. The project also represents a cross-disciplinary collaboration between the geospatial and flood modelling community. In this paper, we introduce the first steps to build up a new benchmark data set together with some initial flood modelling results. More detailed investigations will follow in the next phases of this project. [less ▲]

Detailed reference viewed: 77 (11 UL)