Decompositions of the optimal dispatching problem of electric and electric-hybrid buses with energy constraints for Luxembourg City

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 ▲]

A Deep Learning Based Acceleration of Complex Satellite Resource Management Problem

Poster (2022)

Deep neural network with high-order neuron for the prediction of foamed concrete strength

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 ▲]

Deliberate and Accidental Gas-Phase Alkali Doping of Chalcogenide Semiconductors: Cu(In,Ga)Se2

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 ▲]

Demontage von Elektroantrieben mit Assistenzrobotern zum wirtschaftlichen Recycling

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 ▲]

Derivative recovery and a posteriori error estimate for extended finite elements

in Computer Methods in Applied Mechanics and 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 ▲]

Design and Control of a Flying Gripper and Manipulator for the Assisted Disposal of Improvised Explosive Devices

Doctoral thesis (2022)

Improvised Explosive Devices (IEDs) are an ever-growing worldwide threat. The disposal of IEDs is typically performed by experts of the police or the armed forces with the help of specialized ground ... [more ▼]

Improvised Explosive Devices (IEDs) are an ever-growing worldwide threat. The disposal of IEDs is typically performed by experts of the police or the armed forces with the help of specialized ground Ordnance Disposal Robots (ODRs). Unlike aerial robots, those ODRs have poor mobility, and their deployment in complex environments can be challenging or even impossible. Endowed with manipulation capabilities, aerial robots can perform complex manipulation tasks akin to ground robots. This thesis leverages the manipulation skills and the high mobility of aerial robots to perform aerial disposal of IEDs. Being, in essence, an aerial manipulation task, this work presents numerous contributions to the broader field of aerial manipulation. This thesis presents the mechatronic concept of an aerial ODR and a high-level view of the fundamental building blocks developed throughout this thesis. Starting with the system dynamics, a new hybrid modeling approach for aerial manipulators (AMs) is proposed that provides the closed-form dynamics of any given open-chain AM. Next, a highly integrated, lightweight Universal Gripper (called TRIGGER) customized for aerial manipulation is introduced to improve grasping performance in unstructured environments. The gripper (attached to a multicopter) is tested under laboratory conditions by performing a pick-and-release task. Finally, an autonomous grasping solution is presented alongside its control architecture featuring computer vision and trajectory optimization. To conclude, the grasping concept is validated in a simulated IED disposal scenario. [less ▲]

Design Automation With the Characteristics Properties Model and Property Driven Design for Redesign

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 ▲]

Design guidelines for highly glazed office buildings in steel composite construction developed by using Trnys, optimization methods and LCA

Scientific Conference (2017, March 01)

Designing collaborative scenarios on tangible tabletop interfaces - insights from the implementation of paper prototypes in the context of a multidisciplinary design workshop

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 ▲]