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Damage Assessment of civil engineering structures and bridges using nonlinear dynamic characteristics Waltering, Markus Doctoral thesis (2009) Detailed reference viewed: 87 (15 UL)Data mining in geographical contexts and texts Caruso, Geoffrey Presentation (2010) An increasing number of institutions, acting at different scales and within different sectors, create in-house geographical information systems, e.g. for regional statistics, for land and transport ... [more ▼] An increasing number of institutions, acting at different scales and within different sectors, create in-house geographical information systems, e.g. for regional statistics, for land and transport management, for local urban planning, etc. In addition, with the advent of new technologies, such as GPS's or web-mapping facilities, the use of such geographical data is being more and more popular and data is made more easily accessible (sometimes even contributed by the end-users). Geographers find themselves in rather data rich environments today (irrespective of homogeneity and quality). Also geographical objects require specific visualization and statistical methods. The application and adaptation of data mining approaches in geographical contexts is an increasingly important research topic. In this lecture we will start from theoretical considerations on data mining in geography, particularly emphasizing what is special with exploratory spatial data analysis. We will then refer to ongoing research related to geographical data mining undertaken at the University of Luxembourg in collaboration with colleagues from other institutions. A first example will refer to a large and homogeneous dataset of all dwellings within a Belgian province. Using graph theory and local spatial statistics, the data is used to identify and categorize urbanisation patterns across scales in an iterative way. A second example will depict an application of 'self-organizing maps' to understand patterns of 'territorial cohesion' in Europe using a rather small and lacunary dataset. The third example will be dedicated to a text-mining application to a rather large corpus of documents related to spatial development in Europe. This work funded under the ESPON (European Spatial Observatory Network) aims at producing a relevant thematic structure to the online regional statistics database of the ESPON network. [less ▲] Detailed reference viewed: 40 (0 UL)The DAta Protection REgulation COmpliance Model Bartolini, Cesare ; Lenzini, Gabriele ; Robaldo, Livio in IEEE Security and Privacy (2019), 17(6), 37-45 Understanding whether certain technical measures comply with the General Data Protection Regulation’s (GDPR’s) principles is complex legal work. This article describes a model of the GDPR that allows for ... [more ▼] Understanding whether certain technical measures comply with the General Data Protection Regulation’s (GDPR’s) principles is complex legal work. This article describes a model of the GDPR that allows for semiautomatic processing of legal text and the leveraging of state-of-the-art legal informatics approaches, which are useful for legal reasoning, software design, information retrieval, or compliance checking. [less ▲] Detailed reference viewed: 122 (14 UL)Data Science in Europe ; ; et al in International Journal of Data Science and Analytics (2018) Detailed reference viewed: 43 (0 UL)Data Science, Learning by Latent Structures, and Knowledge Discovery ; Krolak-Schwerdt, Sabine ; Böhmer, Matthias Book published by Springer (2015) Detailed reference viewed: 155 (12 UL)Data-driven modelling and simulation: fracture and medical simulations Bordas, Stéphane Presentation (2018, February 08) Predicting failure in aircraft structures – simulating fracture across scales and times You could fly every day of your life in a commercial aircraft for twenty thousand years without suffering a fatal ... [more ▼] Predicting failure in aircraft structures – simulating fracture across scales and times You could fly every day of your life in a commercial aircraft for twenty thousand years without suffering a fatal accident. This extraordinary level of safety is the product of decades of engineering and materials science research. Simultaneously, engineers have strived to produce lighter and stronger aircraft, with increased range and metals have thus been gradually replaced by lighter advanced composite materials which take up more than half of the structural weight of today's most advanced aircraft. Such progress has been largely enabled by modeling and simulation of materials and structures, which have revolutionized design by enabling engineers to investigate virtually various design strategies. This presentation will focus on the challenges which have been posed, are posed, and will be posed to such modeling and simulation tools in the strive to predict the durability of lighter, stronger, longer-ranging and more reliable aircraft. [less ▲] Detailed reference viewed: 223 (3 UL)Deadzone-Quadratic Penalty Function for Predictive Extended Cruise Control with Experimental Validation Sajadi Alamdari, Seyed Amin ; Voos, Holger ; in ROBOT 2017: Third Iberian Robotics Conference, Sevilla, Spain 22-24 November 2017 (2017, November) Battery Electric Vehicles have high potentials for the modern transportations, however, they are facing limited cruising range. To address this limitation, we present a semi-autonomous ecological driver ... [more ▼] Battery Electric Vehicles have high potentials for the modern transportations, however, they are facing limited cruising range. To address this limitation, we present a semi-autonomous ecological driver assistance system to regulate the velocity with energy-efficient techniques. The main contribution of this paper is the design of a real-time nonlinear receding horizon optimal controller to plan the online cost-effective cruising velocity. Instead of conventional L2-norms, a deadzone-quadratic penalty function for the nonlinear model predictive controller is proposed. Obtained field experimental results demonstrate the effectiveness of the proposed method for a semi-autonomous electric vehicle in terms of real-time energy-efficient velocity regulation and constraints satisfaction. [less ▲] Detailed reference viewed: 102 (9 UL)Dealing with interfaces in partitioned model order reduction for application to nonlinear problems ; ; Bordas, Stéphane Scientific Conference (2013) We propose a reduced order modelling technique based on a partitioning of the domain of study in the context of para- metric nonlinear problems. A formulation of the reduction of the displacement and of ... [more ▼] We propose a reduced order modelling technique based on a partitioning of the domain of study in the context of para- metric nonlinear problems. A formulation of the reduction of the displacement and of the interface tractions linking subdomains to each others will be performed in a FETI context. [less ▲] Detailed reference viewed: 282 (4 UL)Dealing with requirements: Influences on Idea Generation in the Early Stages of Product Development Gericke, Kilian ; ; Blessing, Lucienne in Proceedings of DTRS7: Design Meeting Protocols (2007) This paper aims at identifying factors which influence the number of ideas generated during a brainstorming meeting as part of an industrial mechanical engineering design project. A framework for ... [more ▼] This paper aims at identifying factors which influence the number of ideas generated during a brainstorming meeting as part of an industrial mechanical engineering design project. A framework for describing groups of influencing factors and their relationships is used. As a result of an explorative, comparative protocol analysis of two design meetings the influence of some factors is described e.g. the formulation of the design task description and the sequence of the process steps. [less ▲] Detailed reference viewed: 101 (1 UL)Decentralised minimal-time consensus ; ; et al in The proceedings of the 2011 50th IEEE Conference on Decision and Control and European Control Conference (CDC-ECC) (2011) This study considers the discrete-time dynamics of a network of agents that exchange information according to the nearest-neighbour protocol under which all agents are guaranteed to reach consensus ... [more ▼] This study considers the discrete-time dynamics of a network of agents that exchange information according to the nearest-neighbour protocol under which all agents are guaranteed to reach consensus asymptotically. We present a fully decentralised algorithm that allows any agent to compute the consensus value of the whole network in finite time using only the minimal number of successive values of its own history. We show that this minimal number of steps is related to a Jordan block decomposition of the network dynamics and present an algorithm to obtain the minimal number of steps in question by checking a rank condition on a Hankel matrix of the local observations. Furthermore, we prove that the minimal number of steps is related to other algebraic and graph theoretical notions that can be directly computed from the Laplacian matrix of the graph and from the underlying graph topology. [less ▲] Detailed reference viewed: 67 (0 UL)Decentralised minimal-time dynamic consensus ; ; et al in The proceedings of the 2012 American Control Conference (ACC) (2012) This paper considers a group of agents that aim to reach an agreement on individually measured time-varying signals by local communication. In contrast to static network averaging problem, the consensus ... [more ▼] This paper considers a group of agents that aim to reach an agreement on individually measured time-varying signals by local communication. In contrast to static network averaging problem, the consensus we mean in this paper is reached in a dynamic sense. A discrete-time dynamic average consensus protocol can be designed to allow all the agents tracking the average of their reference inputs asymptotically. We propose a minimal-time dynamic consensus algorithm, which only utilises minimal number of local observations of randomly picked node in a network to compute the final consensus signal. Our results illustrate that with memory and computational ability, the running time of distributed averaging algorithms can be indeed improved dramatically using local information as suggested by Olshevsky and Tsitsiklis. [less ▲] Detailed reference viewed: 68 (1 UL)Decentralised minimum-time consensus ; ; et al in Automatica (2013), 49(5), 1227-1235 We consider the discrete-time dynamics of a network of agents that exchange information according to a nearest-neighbour protocol under which all agents are guaranteed to reach consensus asymptotically ... [more ▼] We consider the discrete-time dynamics of a network of agents that exchange information according to a nearest-neighbour protocol under which all agents are guaranteed to reach consensus asymptotically. We present a fully decentralised algorithm that allows any agent to compute the final consensus value of the whole network in finite time using the minimum number of successive values of its own state history. We show that the minimum number of steps is related to a Jordan block decomposition of the network dynamics, and present an algorithm to compute the final consensus value in the minimum number of steps by checking a rank condition of a Hankel matrix of local observations. Furthermore, we prove that the minimum number of steps is related to graph theoretical notions that can be directly computed from the Laplacian matrix of the graph and from the minimum external equitable partition. [less ▲] Detailed reference viewed: 105 (4 UL)Decentralized final value theorem for discrete-time LTI systems with application to minimal time distributed consensus ; ; et al in The proceedings of the Joint 48th IEEE Conference on Decision and Control and 28th Chinese Control Conference (2009) In this study, we consider an unknown discrete-time, linear time-invariant, autonomous system and characterise, the minimal number of discrete-time steps necessary to compute the asymptotic final value of ... [more ▼] In this study, we consider an unknown discrete-time, linear time-invariant, autonomous system and characterise, the minimal number of discrete-time steps necessary to compute the asymptotic final value of a state. The results presented in this paper have a direct link with the celebrated final value theorem. We apply these results to the design of an algorithm for minimal-time distributed consensus and illustrate the results on an example. [less ▲] Detailed reference viewed: 43 (0 UL)Decompositions of the optimal dispatching problem of electric and electric-hybrid buses with energy constraints for Luxembourg City ; Rinaldi, Marco ; Viti, Francesco et al Scientific Conference (2018, September) We are a team of engineers working on a concrete project of Mobility in Luxembourg. We want to solve the problem of optimally determining the sequence of electric and hybrid electric buses, considering ... [more ▼] We are a team of engineers working on a concrete project of Mobility in Luxembourg. We want to solve the problem of optimally determining the sequence of electric and hybrid electric buses, considering both service constraints (schedule adherence) and energy constraints (electric bus charging status, bus recharging scheduling in capacitated facilities) and at the same time ensure a high level of quality of service for the user satisfaction. 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 twenty sets of constraints, ranging from scheduling adherence to discharge-recharge dynamics. Individual operational costs at the bus level (cost of running an electric / non-electric bus per km, cost of recharging) and at the trip level (penalty due to failed schedule adherence) are fully parametrised, allowing for extensive sensitivity analysis. We investigate a real-life case study based in the city of Luxembourg, where the objective is to reach the all-electric mode for principal urban buses network. Through the model we investigate: the minimum amount of electric buses necessary to perform a day’s schedule for two currently partially electrified lines, without resorting to conventional internal combustion alternatives; the impact of electrifying two additional lines, specifically considering the trade-offs related to either adding new buses or new charging stations at the bus terminal. Finally, we studied how to best decompose the overall problem in several smaller problems, to be able to solve also realistic scenarios and using large real data sets from the Mobility Data owner of Luxembourg. We analysed and compared two kinds of decomposition: a bus line-based decomposition, and a time-based decomposition. [less ▲] Detailed reference viewed: 57 (5 UL)A Decoupling Approach to Design Observers for Polytopic Takagi-Sugeno Models Subject to Unknown Inputs Bezzaoucha, Souad ; Voos, Holger ; et al in Proceedings of the 2018 American Control Conference (2018, June 27) A decoupling approach for state estimation of nonlinear systems represented in the polytopic Takagi-Sugeno with unmeasurable premise variables subject to unknown inputs is proposed in this paper. The idea ... [more ▼] A decoupling approach for state estimation of nonlinear systems represented in the polytopic Takagi-Sugeno with unmeasurable premise variables subject to unknown inputs is proposed in this paper. The idea consists in defining a state and unknown input transformations in order to divide the state vector into two parts, a measurable part and an observable one (decoupled from the unknown input). A classical Luenberger observer to estimate the unmeasurable part is then designed and given in terms of Linear Matrix Inequalities (LMIs) conditions. A numerical example is also presented in order to illustrate the proposed approach. [less ▲] Detailed reference viewed: 132 (6 UL)Deep neural network with high-order neuron for the prediction of foamed concrete strength ; ; et al in Computer-Aided Civil and Infrastructure Engineering (2018) The article presents a deep neural network model for the prediction of the compressive strength of foamed concrete. A new, high-order neuron was developed for the deep neural network model to improve the ... [more ▼] The article presents a deep neural network model for the prediction of the compressive strength of foamed concrete. A new, high-order neuron was developed for the deep neural network model to improve the performance of the model. Moreover, the cross-entropy cost function and rectified linear unit activation function were employed to enhance the performance of the model. The present model was then applied to predict the compressive strength of foamed concrete through a given data set, and the obtained results were compared with other machine learning methods including conventional artificial neural network (C-ANN) and second-order artificial neural network (SO-ANN). To further validate the proposed model, a new data set from the laboratory and a given data set of high-performance concrete were used to obtain a higher degree of confidence in the prediction. It is shown that the proposed model obtained a better prediction, compared to other methods. In contrast to C-ANN and SO-ANN, the proposed model can genuinely improve its performance when training a deep neural network model with multiple hidden layers. A sensitivity analysis was conducted to investigate the effects of the input variables on the compressive strength. The results indicated that the compressive strength of foamed concrete is greatly affected by density, followed by the water-to-cement and sand-to-cement ratios. By providing a reliable prediction tool, the proposed model can aid researchers and engineers in mixture design optimization of foamed concrete. [less ▲] Detailed reference viewed: 105 (5 UL)Deliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2 Colombara, Diego ; ; et al in Scientific Reports (2017), 7 Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of ... [more ▼] Alkali metal doping is essential to achieve highly efficient energy conversion in Cu(In,Ga)Se2 (CIGSe) solar cells. Doping is normally achieved through solid state reactions, but recent observations of gas phase alkali transport in the kesterite sulfide (Cu2ZnSnS4) system (re)open the way to a novel gas-phase doping strategy. However, the current understanding of gas-phase alkali transport is very limited. This work (i) shows that CIGSe device efficiency can be improved from 2% to 8% by gas-phase sodium incorporation alone, (ii) identifies the most likely routes for gas-phase alkali transport based on mass spectrometric studies, (iii) provides thermochemical computations to rationalize the observations and (iv) critically discusses the subject literature with the aim to better understand the chemical basis of the phenomenon. These results suggest that accidental alkali metal doping occurs all the time, that a controlled vapor pressure of alkali metal could be applied during growth to dope the semiconductor, and that it may have to be accounted for during the currently used solid state doping routes. It is concluded that alkali gas-phase transport occurs through a plurality of routes and cannot be attributed to one single source. [less ▲] Detailed reference viewed: 227 (8 UL)Demontage von Elektroantrieben mit Assistenzrobotern zum wirtschaftlichen Recycling Jungbluth, Jan ; Plapper, Peter ; in Tagungsband AALE 2016 (2016) Die zerstörungsfreie Demontage zum Zweck der Refrabrikation oder des höherwertigem Produktrecyclings findet nur selten im industriellen Umfeld Anwendung. Allerdings ist mit einem Anstieg dieses trennenden ... [more ▼] Die zerstörungsfreie Demontage zum Zweck der Refrabrikation oder des höherwertigem Produktrecyclings findet nur selten im industriellen Umfeld Anwendung. Allerdings ist mit einem Anstieg dieses trennenden Fertigungsverfahrens in naher Zukunft zu rechnen da die immer stärker begrenzten und zugänglichen Ressourcen durch strengere Gesetze im Rahmen der Abfallwirtschaft gesichert werden müssen. Zum Beispiel wurden durch das Kreislaufwirt-schaftsgesetz der europäischen Union [1] die Hersteller dazu verpflichtet Rücknahmesysteme für elektrische und elektronische Geräte zu schaffen um sie einer weiteren wirtschaftlichen Nutzung oder umweltgerechten Entsorgung zugänglich zu machen. Für die umweltgerechte Entsorgung ist eine wertstoffgerechte Trennung der Produktkomponenten vorgesehen. Aus wirtschaftlichen Gründen erfolgt diese Materialtrennung meist verfahrenstechnisch durch Zerkleinern und Sortieren der Wertstoffe. Die weitere wirtschaftliche Nutzung ganzer Kompo-nenten wird, trotz hoher Einsparpotenziale [2], durch den Aufwand der Refabrikation kaum in Betracht gezogen. Denn die zerstörungsfreie Trennung kann bisher meist nur manuell und damit kostenintensiv erfolgen. In der Folge werden gerade im Bereich der Elektroschrottver-wertung häufig illegale Entsorgungswege über das außereuropäische Ausland gewählt [3]. Zur Verbesserung der Wirtschaftlichkeit der Demontage bietet oft die Automatisierung Lösun-gen. Um diesen Sektor der Automatisierung zugänglich zu machen, erfolgten bereits For-schungsaktivitäten zur Automatisierung der Demontage von Fernsehgeräten [4] und PCs [5]. Das Ergebnis dieser Studien zeigt, dass durch die hohe Variation der Produktgestalt oder aufgrund von Beschädigungen der Produkte, der [less ▲] Detailed reference viewed: 198 (10 UL)denmpc Dentler, Jan Eric Software (2017) This package is providing an object oriented real-time nonlinear model predictive control (NMPC) framework which developed at the Automation & Robotics Research Group http://wwwde.uni.lu/snt/research ... [more ▼] This package is providing an object oriented real-time nonlinear model predictive control (NMPC) framework which developed at the Automation & Robotics Research Group http://wwwde.uni.lu/snt/research/automation_robotics_research_group at the University of Luxembourg. It features a modularization for multi-agent systems which allows the on-line change of agents, control objectives, constraints and couplings, triggered by ROS-messages. [less ▲] Detailed reference viewed: 156 (20 UL)Derivative recovery and a posteriori error estimate for extended finite elements Bordas, Stéphane ; in Computer Methods in Applied Mechanics & Engineering (2007), 196(35-36), 3381-3399 This paper is the first attempt at error estimation for extended finite elements. The goal of this work is to devise a simple and effective local a posteriori error estimate for partition of unity ... [more ▼] This paper is the first attempt at error estimation for extended finite elements. The goal of this work is to devise a simple and effective local a posteriori error estimate for partition of unity enriched finite element methods such as the extended finite element method (XFEM). In each element, the local estimator is the L2 norm of the difference between the raw XFEM strain field and an enhanced strain field computed by extended moving least squares (XMLS) derivative recovery obtained from the raw nodal XFEM displacements. The XMLS construction is tailored to the nature of the solution. The technique is applied to linear elastic fracture mechanics, in which near-tip asymptotic functions are added to the MLS basis. The XMLS shape functions are constructed from weight functions following the diffraction criterion to represent the discontinuity. The result is a very smooth enhanced strain solution including the singularity at the crack tip. Results are shown for two- and three-dimensional linear elastic fracture mechanics problems in mode I and mixed mode. The effectivity index of the estimator is close to 1 and improves upon mesh refinement for the studied near-tip problem. It is also shown that for the linear elastic fracture mechanics problems treated, the proposed estimator outperforms one of the superconvergent patch recovery technique of Zienkiewicz and Zhu, which is only C0. Parametric studies of the general performance of the estimator are also carried out. © 2007 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 130 (3 UL) |
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