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See detailDealing with requirements: Influences on Idea Generation in the Early Stages of Product Development
Gericke, Kilian UL; Schmidt-Kretschmer, Michael; Blessing, Lucienne UL

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 ▲]

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See detailDecentralised minimal-time consensus
Yuan, Y.; Stan, G.-B.; Barahona, M. 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 ▲]

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See detailDecentralised minimal-time dynamic consensus
Yuan, Y.; Liu, J.; Murray, R. M. 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 ▲]

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See detailDecentralised minimum-time consensus
Yuan, Ye; Stan, Guy-Bart; Shi, Ling 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 ▲]

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See detailDecentralized final value theorem for discrete-time LTI systems with application to minimal time distributed consensus
Yuan, Y.; Stan, G. B. V.; Shi, L. 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 ▲]

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See detailDecompositions of the optimal dispatching problem of electric and electric-hybrid buses with energy constraints for Luxembourg City
Picarelli, Erika; Rinaldi, Marco UL; Viti, Francesco UL 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 ▲]

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See detailA Decoupling Approach to Design Observers for Polytopic Takagi-Sugeno Models Subject to Unknown Inputs
Bezzaoucha, Souad UL; Voos, Holger UL; Davila, Jorge 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 ▲]

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See detailDeep neural network with high-order neuron for the prediction of foamed concrete strength
Nguyen, Tuan; Kashani, Alireza; Ngo, Tuan 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 ▲]

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See detailDeliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2
Colombara, Diego UL; Berner, Ulrich; Ciccioli, Andrea 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 ▲]

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See detailDemontage von Elektroantrieben mit Assistenzrobotern zum wirtschaftlichen Recycling
Jungbluth, Jan UL; Plapper, Peter UL; Gerke, Wolfgang

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 ▲]

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See detaildenmpc
Dentler, Jan Eric UL

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 ▲]

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See detailDerivative recovery and a posteriori error estimate for extended finite elements
Bordas, Stéphane UL; Duflot, M.

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 ▲]

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See detailDeriving essential components of lean and industry 4.0 assessment model for manufacturing SMEs
Kolla, Sri Sudha Vijay Keshav UL; Minoufekr, Meysam UL; Plapper, Peter UL

in 52nd CIRP Conference on Manufacturing Systems (CMS) (2019), 81

Quantifying lean and ICT architecture related to Industry 4.0 is a new challenge in Small and Medium Scale Enterprises (SMEs) that needs to be addressed by both research as well as enterprises themselves ... [more ▼]

Quantifying lean and ICT architecture related to Industry 4.0 is a new challenge in Small and Medium Scale Enterprises (SMEs) that needs to be addressed by both research as well as enterprises themselves. Especially in the manufacturing sector, SMEs need to transform themselves into emerging trends such as industry 4.0 while practicing existing manufacturing philosophies such as Lean Production Systems (LPS) to be competitive in global markets. The major concern is that there are many assessment models available to measure the status of an enterprise related to either LPS or Industry 4.0. Often, these models are complex and don’t fulfill the requirements of manufacturing SMEs. On the other hand, most of the models only consider either lean or industry 4.0 elements. The outcomes of this research help to develop a hybrid model including both lean and industry 4.0 features suitable for manufacturing SMEs. The main objective of this research is to provide state of the art literature on existing assessment models and consequently map lean and industry 4.0 components to the specific characteristics of manufacturing SMEs. The paper concludes with a summary and outlook for our future research. [less ▲]

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See detailDesign and Implementation of a Reliable Distributed Energy Management System
Hoben, Ralf UL

Doctoral thesis (2011)

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See detailDesign Automation With the Characteristics Properties Model and Property Driven Design for Redesign
Qureshi, Ahmed Jawad UL; Eisenbart, Boris UL; Dantan, Jean-Yves et al

in Abramovici, Michael, Stark, Rainer (Ed.) Smart Product Engineering (2013)

This paper presents a framework consisting of a mathematical model and an algorithm for representation, analysis and exploration of the design space in redesign problems. The framework develops and ... [more ▼]

This paper presents a framework consisting of a mathematical model and an algorithm for representation, analysis and exploration of the design space in redesign problems. The framework develops and extends the existing formalism of the Characteristics Properties Model (CPM) and Property Driven Design (PDD). A platform independent quantitative model based on formal log-ic is presented to map the characteristics and properties, as well as the relations and dependencies between them, along with the necessary conditions for solu-tion evaluation. The model is based on generalization of existing mathematical design models and is supported by the development of an algorithm enabling property driven design. The resulting framework offers a rich and flexible syn-tax and vocabulary along with a mathematical and computational tool applica-ble to mechanical product redesign. [less ▲]

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See detailDesign process ingredients: a comparison between group and individual work
Dwarakanath, S.; Blessing, Lucienne UL

in Cross, N.; Christiaans, H.; Dorst, K. (Eds.) Analysing Design Activity (1994)

In this paper a comparison is made between the design processes of an individually working designer and of a group of designers based on protocol analysis. The analysis focused on the differences and ... [more ▼]

In this paper a comparison is made between the design processes of an individually working designer and of a group of designers based on protocol analysis. The analysis focused on the differences and similarities in the ingredients of the two processes. The basic ingredients used for the analysis were: Issues, Arguments, Alternatives, Criteria, Decisions, External information, and Others. Comparisons have been made between: the group as a whole and the individual designer; the individual group members; the individual group members and the individual designer. The results provide a first step towards a better understanding of the differences between group and individual work. The paper also discusses some of the limitations of this type of study. [less ▲]

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See detailDesigning collaborative scenarios on tangible tabletop interfaces - insights from the implementation of paper prototypes in the context of a multidisciplinary design workshop
Sunnen, Patrick UL; Arend, Béatrice UL; Heuser, Svenja UL et al

in Proceedings of the 17th European Conference on Computer-Supported Cooperative Work: The International Venue on Practice-centred Computing and the Design of Cooperation Technologies - Exploratory Papers, Reports of the European Society for Socially Embedded Technologies (2019, June)

Within the context of the research project ORBIT (Overcoming Breakdowns in Teams with Interactive Tabletops), we design and study a joint problem-solving activity at an interactive tabletop, that gives ... [more ▼]

Within the context of the research project ORBIT (Overcoming Breakdowns in Teams with Interactive Tabletops), we design and study a joint problem-solving activity at an interactive tabletop, that gives participants the opportunity to develop their collaboration methods. To gain design insights for the development of a scenario soliciting participants to collaborate, we set up a multidisciplinary design workshop. During the latter, we explored and discussed three different collaborative scenarios, implemented as paper prototypes. In this paper, we report on first results gained from an exploratory analysis of the video data that was recorded in the context of this workshop. [less ▲]

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See detailDesigning Meaning to Change Consumer Behaviour: An Exploration
Waltersdorfer, Gregor UL; Gericke, Kilian UL; Blessing, Lucienne UL

in Chakrabarti, Amaresh (Ed.) ICoRD’15 – Research into Design Across Boundaries Volume 1: Theory, Research Methodology, Aesthetics, Human Factors and Education (2015)

The focus of our research is to support designers in fostering a more sustainable behaviour of consumers by creating meaning in products and services. The paper describes the results of a literature study ... [more ▼]

The focus of our research is to support designers in fostering a more sustainable behaviour of consumers by creating meaning in products and services. The paper describes the results of a literature study into the process of meaning making and the mechanisms through which meaning affects consumer behaviour. Meaning is defined as a mental representation of possible relationships. An initial model, the Meaning-Behaviour Model, is presented, integrating the mechanisms found in literature. Five possible interventions, derived from the model, show how designers can use meaning as a lever to foster enduring behavioural change. The paper contributes to the discussion of introducing meaning through design by exploring the link between meaning and behaviour. [less ▲]

Detailed reference viewed: 157 (8 UL)