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See detailStructural shape optimization of three dimensional acoustic problems with isogeometric boundary element methods
Chen, L.L.; Lian, Haojie UL; Chen, H.B. et al

in Computer Methods in Applied Mechanics and Engineering (2019), 355

The boundary element method (BEM) is a powerful tool in computational acoustics, because the analysis is conducted only on structural surfaces, compared to the finite element method (FEM) which resorts to ... [more ▼]

The boundary element method (BEM) is a powerful tool in computational acoustics, because the analysis is conducted only on structural surfaces, compared to the finite element method (FEM) which resorts to special techniques to truncate infinite domains. The isogeometric boundary element method (IGABEM) is a recent progress in the category of boundary element approaches, which is inspired by the concept of isogeometric analysis (IGA) and employs the spline functions of CAD as basis functions to discretize unknown physical fields. As a boundary representation approach, IGABEM is naturally compatible with CAD and thus can directly perform numerical analysis on CAD models, avoiding the cumbersome meshing procedure in conventional FEM/BEM and eliminating the difficulty of volume parameterization in isogeometric finite element methods. The advantage of tight integration of CAD and numerical analysis in IGABEM renders it particularly attractive in the application of structural shape optimization because (1) the geometry and the analysis can be interacted, (2) remeshing with shape morphing can be avoided, and (3) an optimized solution returns a CAD geometry directly without postprocessing steps. In the present paper, we apply the IGABEM to structural shape optimization of three dimensional exterior acoustic problems, fully exploiting the strength of IGABEM in addressing infinite domain problems and integrating CAD and numerical analysis. We employ the Burton–Miller formulation to overcome fictitious frequency problems, in which hyper-singular integrals are evaluated explicitly. The gradient-based optimizer is adopted and shape sensitivity analysis is conducted with implicit differentiation methods. The design variables are set to be the positions of control points which directly determine the shape of structures. Finally, numerical examples are provided to verify the algorithm. [less ▲]

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See detailA Structured Argumentation Framework for Modeling Debates in the Formal Sciences
Cramer, Marcos; Dauphin, Jérémie UL

in Journal for General Philosophy of Science (2019)

Scientific research in the formal sciences comes in multiple degrees of formality: fully formal work; rigorous proofs that practitioners know to be formalizable in principle; and informal work like rough ... [more ▼]

Scientific research in the formal sciences comes in multiple degrees of formality: fully formal work; rigorous proofs that practitioners know to be formalizable in principle; and informal work like rough proof sketches and considerations about the advantages and disadvantages of various formal systems. This informal work includes informal and semi-formal debates between formal scientists, e.g. about the acceptability of foundational principles and proposed axiomatizations. In this paper, we propose to use the methodology of structured argumentation theory to produce a formal model of such informal and semi-formal debates in the formal sciences. For this purpose, we propose ASPIC-END, an adaptation of the structured argumentation framework ASPIC+ which can incorporate natural deduction style arguments and explanations. We illustrate the applicability of the framework to debates in the formal sciences by presenting a simple model of some arguments about proposed solutions to the Liar paradox, and by discussing a more extensive - but still preliminary - model of parts of the debate that mathematicians had about the Axiom of Choice in the early 20th century. [less ▲]

Detailed reference viewed: 48 (13 UL)
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See detailStudent's Perception of a Semantic Search Engine
Reichert, Monique UL; Linckels, Serge UL; Meinel, Christoph

Scientific Conference (2005)

Detailed reference viewed: 39 (0 UL)
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See detailSTUDYING COMMUTER BEHAVIOUR FOR GAMIFYING MOBILITY
Kracheel, Martin UL; McCall, Roderick UL; Koenig, Vincent UL

Presentation (2014, September 30)

Detailed reference viewed: 210 (26 UL)
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See detailSupervised learning for a Kraft recovery boiler: a data mining approach with Random Forests.
Sainlez, Matthieu UL; Heyen, Georges; Lafourcade, Sébastien

in Favrat, Daniel; Maréchal, François (Eds.) ECOS 2010 Volume IV (Power plants and Industrial processes) (2011, January 11)

A data mining methodology, the random forests, is applied to predict high pressure steam production from the recovery boiler of a Kraft pulping process. Starting from a large database of raw process data ... [more ▼]

A data mining methodology, the random forests, is applied to predict high pressure steam production from the recovery boiler of a Kraft pulping process. Starting from a large database of raw process data, the goal is to identify the input variables that explain the most significant output variations and to predict the high pressure steam flow. [less ▲]

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See detailSupply characteristics and membership choice in round-trip and free-floating carsharing systems
Cisterna, Carolina UL; Giorgione, Giulio UL; Cipriani, Ernesto et al

Scientific Conference (2019, June)

Detailed reference viewed: 66 (20 UL)
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See detailSUPPORTING INTERDISCIPLINARY SYSTEM DEVELOPMENT THROUGH INTEGRATED FUNCTION MODELLING
Eisenbart, Boris UL

Doctoral thesis (2014)

Industry is confronted with ever-changing and increasing demand of customers on global markets for integration of diverse functions into newly developed products and systems. As a consequence, companies ... [more ▼]

Industry is confronted with ever-changing and increasing demand of customers on global markets for integration of diverse functions into newly developed products and systems. As a consequence, companies increasingly often combine different engineering technologies into their products necessitating close collaboration of experts from various disciplines. New types of products, such as Product-Service Systems (PSS), which have become increasingly important in the recent past and combine (multi-disciplinary) products with associated services, extend interdisciplinary system development by including further disciplines. Problems in the (cross-disciplinary) exchange of information between the involved designers are considered one of the central risks posed to the success of interdisciplinary system development. Function modelling is expected to provide suitable means for the integration of different disciplines, as it addresses solution finding early in the design process and results in a first abstract representation of the system under consideration. However, a large variety of different and often incompatible function models can be found in the different disciplines, which hampers shared, cross-disciplinary function modelling. The research project presented in this thesis provides comprehensive insights into central barriers and enablers for cross-disciplinary function modelling in the development of mechatronic systems and PSS. Conducted research comprises comprehensive literature reviews of diverse function models and function modelling approaches proposed in disciplinary and interdisciplinary design approaches. The derived insights are complemented by empirical studies in ten companies active in diverse market areas, such as machine design, automotive, aerospace, and consumer product development. The empirical studies provide compelling insights into the actual application of function modelling in different disciplines and design departments, as well as into specific needs and preferences of practicing designers from different disciplines. A central contribution resulting from this research is the ”Integrated Function Modelling framework”, which is intended to address the identified needs and provide practicing designers with a flexible and generic modelling approach supporting interdisciplinary conceptual design. The project is concluded with an initial evaluation of the developed framework in industry and academia. [less ▲]

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See detailSupporting Security Protocols on CAN-Based Networks
Bloom, Gedare; Cena, Gianlua; Cibrario Bertolotti, Ivan et al

in 2017 IEEE 18th International Conference on Industrial Technology (ICIT2017) (2017)

The ever-increasing variety of services built on top of the Controller Area Network (CAN), along with the recent discovery of vulnerabilities in CAN-based automotive systems (some of them demonstrated in ... [more ▼]

The ever-increasing variety of services built on top of the Controller Area Network (CAN), along with the recent discovery of vulnerabilities in CAN-based automotive systems (some of them demonstrated in practice) stimulated a renewed attention to security-oriented enhancements of the CAN protocol. The issue is further compounded nowadays because, unlike in the past, security can no longer be enforced by physical bus segregation. This paper describes how CAN XR, a recently proposed extension of the CAN data-link layer, can effectively support the distributed calculation of arbitrary binary Boolean functions, which are the foundation of most security protocols, without necessarily disclosing their operands on the bus. The feasibility of the approach is then shown through experimental evaluation and by confirming its applicability to a shared key generation protocol proposed in literature. [less ▲]

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See detailSupporting the Knowledge Life Cycle
Blessing, Lucienne UL; Wallace, K. M.

in Kluwer Academic Publishers (Ed.) Knowledge Intensive CAD (1999)

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See detailA Survey of Cooperative ITS for Next Generation Public Transport Systems
Seredynski, Marcin; Viti, Francesco UL

in Intelligent Transportation Systems (ITSC), 2016 IEEE 19th International Conference on (2016, November)

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See detailSusceptibility-Weighted MRI for Deep Brain Stimulation: Potentials in Trajectory Planning
Hertel, Frank UL; Husch, Andreas UL; Dooms, Georges et al

in Stereotactic & Functional Neurosurgery (2015), 93(5), 303-308

Background: Deep brain stimulation (DBS) trajectory plan- ning is mostly based on standard 3-D T1-weighted gado- linium-enhanced MRI sequences (T1-Gd). Susceptibility- weighted MRI sequences (SWI) show ... [more ▼]

Background: Deep brain stimulation (DBS) trajectory plan- ning is mostly based on standard 3-D T1-weighted gado- linium-enhanced MRI sequences (T1-Gd). Susceptibility- weighted MRI sequences (SWI) show neurovascular struc- tures without the use of contrast agents. The aim of this study was to investigate whether SWI might be useful in DBS trajectory planning. Methods: We performed bilateral DBS planning using conventional T1-Gd images of 10 patients with different kinds of movement disorders. Afterwards, we matched SWI sequences and compared the visibility of vas- cular structures in both imaging modalities. Results: By ana- lyzing 100 possible trajectories, we found a potential vascu- lar conflict in 13 trajectories based on T1-Gd in contrast to 53 in SWI. Remarkably, all vessels visible in T1-Gd were also de- picted in SWI, whereas SWI showed many additional vascular structures which could not be identified in T1-Gd. Conclu- sion/Discussion: The sensitivity for detecting neurovascular structures for DBS planning seems to be significantly higher in SWI. As SWI does not require a contrast agent, we suggest that SWI may be a valuable alternative to T1-Gd MRI for DBS trajectory planning. Furthermore, the data analysis suggests that vascular interactions of DBS trajectories might be more frequent than expected from the very low incidence of symptomatic bleedings. The explanation for this is currently the subject of debate and merits further studies. [less ▲]

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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 ▲]

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See detailTAO4school: Generic goes specific
Fischbach, Antoine UL

Bachelor/master dissertation (2008)

Detailed reference viewed: 48 (7 UL)
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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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