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See detailTowards multiscale data fusion of high-resolution space borne and terrestrial datasets over Tristan da Cunha
Backes, Dietmar UL; Teferle, Felix Norman UL; Abraha, Kibrom Ebuy UL et al

Poster (2018, April 10)

Ever improving low cost, lightweight and easy to use sensing technologies are enabling the capture of rich 3D Datasets to support an unprecedented range of applications in Geosciences. Especially low-cost ... [more ▼]

Ever improving low cost, lightweight and easy to use sensing technologies are enabling the capture of rich 3D Datasets to support an unprecedented range of applications in Geosciences. Especially low-cost LiDAR systems as well as optical sensors, which can be deployed from terrestrial or low altitude aerial platforms, allow the collection of large datasets without detailed expert knowledge or training. Dense pointcloud derived from these technologies provide an invaluable source to fill the gap between highly precise and accurate terrestrial topographic surveys and large area Digital Surface Models (DSMs) derived from airborne and spaceborne sensors. However, the collection of reliable 3D pointclouds in remote and hazardous locations remains to be very difficult and costly. Establishing a reliable georeference, ensuring accuracy and data quality as well as merging such rich datasets with existing or space borne mapping provide additional challenges. The presented case study investigates the data quality and integration of a heterogeneous dataset collected over the remote island of Tristan da Cunha. High-resolution 3D pointclouds derived by TLS and drone Photogrammetry are merged with space borne imagery while preserving the accurate georeference provided by Ground Control derived from geodetic observations. The volcanic island of Tristan da Cunha located in the centre of the Southern Atlantic Ocean is one of the most remote and difficult to access locations on the planet. Its remote location, rough climatic conditions and consistent cloud coverage provides exceptional challenges for terrestrial, aerial as well as space borne data acquisition. Amongst many other scientific installations, the island also hosts a continuous GNSS station observation and monitoring facilities operated by the University of Luxembourg, which provided the opportunity to conduct a local terrestrial data acquisition campaign consistent with a terrestrial ground survey, Laserscanning and an image acquisition from a low-cost drone. The highly accurate Ground Control network, observed by GNSS and total station, provides a reliable georeference. Pointclouds were acquired around the area of the harbour using a Leica P20 terrestrial Laserscanner, as well as drone Photogrammetry based on images collected by a low-cost DJI Phantom3 drone. To produce a map of the complete island a comprehensive dataset of high-resolution space borne imagery based on the Digital Globe WorldView constellation was acquired which provided high resolution mapping information. The case study presents a cross-validation of terrestrial, low altitude airborne as well as spaceborne datasets in terms coregistration, absolute georeference, scale, resolution and overall data quality. Following the evaluation a practical approach to fuse this heterogeneous dataset is applied which aims to preserve overall data quality, local resolution and accurate georeference and avoid edge artefacts. The conclusions drawn from our preliminary results provide some good practice advice for similar projects. The final topographic dataset enables mapping and monitoring of local geohazards as, e.g. coastal erosion and recent landslides thus also supporting the local population. [less ▲]

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See detailTowards optimal positioning of surveillance UGVs
Nilsson, U.; Ögren, P.; Thunberg, Johan UL

in Optimization and Cooperative Control Strategies (2009)

Unmanned Ground Vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full ... [more ▼]

Unmanned Ground Vehicles (UGVs) equipped with surveillance cameras present a flexible complement to the numerous stationary sensors being used in security applications today. However, to take full advantage of the flexibility and speed offered by a group of UGV platforms, a fast way to compute desired camera locations to cover an area or a set of buildings, e.g., in response to an alarm, is needed. Building upon earlier results in terrain guarding and sensor placement we propose a way to find candidate guard positions that satisfy a large set of view angle and range constraints simulataneously. Since the original problem is NP-complete, we do not seek to find the true optimal set of guard positions. Instead, a near optimal subset of the candidate points is chosen using a scheme with a known approximation ratio of O(log(n)). A number of examples are presented to illustrate the approach. [less ▲]

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See detailTowards Optimised Deployment of Electric Bus Systems with On-Route Charging using Cooperative ITS
Laskaris, Georgios UL; Seredynski, Marcin; Viti, Francesco UL

Scientific Conference (2018, July)

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See detailTowards Optimised Large Scale Deployments of Electric Bus Systems with On-Route Charging
Seredynski, Marcin; Khadraoui, Djamel; Viti, Francesco UL

Scientific Conference (2016, October)

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See detailTowards Optimized Deployment of Electric Bus Systems Using Cooperative ITS
Laskaris, Georgios UL; Seredynski, Marcin; Viti, Francesco UL

Poster (2019, January)

In this paper we analyze the impact of using cooperative intelligent transportation systems (C-ITS) to manage electrical bus systems. A simulation-based study is presented where three control strategies ... [more ▼]

In this paper we analyze the impact of using cooperative intelligent transportation systems (C-ITS) to manage electrical bus systems. A simulation-based study is presented where three control strategies are used to regulate the operations of a line, namely bus holding, Green Light Optimal Dwell Time Adaptation (GLODTA) and Transit Signal Priority (TSP). The results show, using a realistic scenario of a major line in Luxembourg City, that buses are efficiently operated without necessarily providing additional priority to public transport, hence without negatively affecting the capacity of the private vehicles system. Benefits in terms of headway regulations, energy consumption and travel time variance reductions are quantified. [less ▲]

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See detailTradeoffs in networks with positive and negative feedback
Goncalves, Jorge UL; Yi, T.; Doyle, J.

Scientific Conference (2005)

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See detailTrading Zones of Digital History
Kemman, Max UL

Presentation (2016)

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See detailTraffic control which maximises network throughput: Some simple examples
Smith, Michael; Iryo, Takamasa; Mounce, Richard et al

in Transportation Research. Part C, Emerging Technologies (2019), 107

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See detailTragbare und aktiv vom Parkinson-Patienten genutzte Technologie im hauslichen Umfeld: Was bringt die Zukunft?
Maetzler, W.; Krüger, Rejko UL; Muller, T. et al

in Fortschritte der Neurologie-Psychiatrie (2016), 84 Suppl 1

Parkinson’s disease (PD) is a multisystem disorder with a plethora of symptoms affecting quality of life in the home environment. Due to the rapid development of wearable technique in the health and ... [more ▼]

Parkinson’s disease (PD) is a multisystem disorder with a plethora of symptoms affecting quality of life in the home environment. Due to the rapid development of wearable technique in the health and fitness sector, an increasing number of such wearables are available to complement diagnostic strategies of PD symptoms not only in the clinical but also in the domestic environment. This development has clear advantages over clinical evaluation, as the latter is relatively subjective, time-consuming and costly, and provides only a snapshot of the condition. First results about the use of such technology for the assessment of PD symptoms (including bradykinesia, dyskinesia, tremor, daily activity and sleep behavior) in the domestic environment are promising. They suggest that these techniques can provide complementary information about the symptoms of PD patients, and have the potential to be included in future diagnostic workup concepts of routine care in PD. The use of such technique provides also the chance to more actively include patients into medical decision making processes. [less ▲]

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See detailA transformation of the position based visual servoing problem into a convex optimization problem
Wang, Y.; Thunberg, Johan UL; Yu, X.

in Proceedings of the 51th IEEE Conference on Decision and Control (2012)

Here we address the problem of moving a camera from an initial pose to a final pose. The trajectory between the two poses is subject to constraints on the camera motion and the visibility, where we have ... [more ▼]

Here we address the problem of moving a camera from an initial pose to a final pose. The trajectory between the two poses is subject to constraints on the camera motion and the visibility, where we have bounds on the allowed velocities and accelerations of the camera and require that a set of point features are visible for the camera. We assume that the pose is possible to retrieve from the observations of the point features, i.e., we have a Position Based Visual Servoing Problem with constraints. We introduce a two step method that transforms the problem into a convex optimization problem with linear constraints. In the first step the rotational motion is restricted to be of a certain type. This restriction allows us to retrieve an explicit solution of the rotational motion that is optimal in terms of minimizing geodesic distance. Furthermore, this restriction guarantees that the rotational motion satisfies the constraints. Using the explicit solution, we can formulate a convex optimization problem for the translational motion, where we include constraints on workspace and visibility. [less ▲]

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See detailTransition vers le numérique : Quelles implications pour l’évaluation des élèves et leurs apprentissages ?
Rocher, Thierry; Fischbach, Antoine UL; Klausing, Andreas et al

Scientific Conference (2016, January)

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See detailTransparency by Design in Data-Informed Research: a Collection of Information Design Patterns
Rossi, Arianna UL; Lenzini, Gabriele UL

in Computer Law and Security Report (in press)

Oftentimes information disclosures describing personal data-gathering research activities are so poorly designed that participants fail to be informed and blindly agree to the terms, without grasping the ... [more ▼]

Oftentimes information disclosures describing personal data-gathering research activities are so poorly designed that participants fail to be informed and blindly agree to the terms, without grasping the rights they can exercise and the risks derived from their cooperation. To respond to the challenge, this article presents a series of operational strategies for transparent communication in line with legal-ethical requirements. These "transparency-enhancing design patterns" can be implemented by data controllers/researchers to maximize the clarity, navigability, and noticeability of the information provided and ultimately empower data subjects/research subjects to appreciate and determine the permissible use of their data. [less ▲]

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See detailTravel-sharing in multimodal systems: a behavioural modelling approach
Viti, Francesco UL

Scientific Conference (2013)

Detailed reference viewed: 86 (5 UL)
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See detailTrefftz polygonal finite element for linear elasticity: convergence, accuracy, and properties
Hirshikesh; Natarajan, Sundararajan; Ratna Kumar, A. K. et al

in Asia Pacific Journal on Computational Engineering (2017)

In this paper, the accuracy and the convergence properties of Trefftz finite element method over arbitrary polygons are studied. Within this approach, the unknown displacement field within the polygon is ... [more ▼]

In this paper, the accuracy and the convergence properties of Trefftz finite element method over arbitrary polygons are studied. Within this approach, the unknown displacement field within the polygon is represented by the homogeneous solution to the governing differential equations, also called as the T-complete set. While on the boundary of the polygon, a conforming displacement field is independently defined to enforce the continuity of the field variables across the element boundary. An optimal number of T-complete functions are chosen based on the number of nodes of the polygon and the degrees of freedom per node. The stiffness matrix is computed by the hybrid formulation with auxiliary displacement frame. Results from the numerical studies presented for a few benchmark problems in the context of linear elasticity show that the proposed method yields highly accurate results with optimal convergence rates. [less ▲]

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See detailtrend Analysis and interpretation of Luxembourg’s consumption Footprint NFA 2010 edition, data years 2000 – 2007
Hild, Paula UL; Takagi, Aya; Schmitt, Bianca

Report (2012)

The Ecological Footprint methodology by Global Footprint Network measures human consumption of products and services from different ecosystems in terms of the amount of bioproductive land and sea area ... [more ▼]

The Ecological Footprint methodology by Global Footprint Network measures human consumption of products and services from different ecosystems in terms of the amount of bioproductive land and sea area needed to supply these products and services. In other words, the Ecological Footprint calculates the land area needed to produce food, provide resources, produce energy, and absorb the CO2 emissions generated by the supply chains within one year at country level. For the calculations of Luxembourg’s Ecological Footprint, international statistical databases are used to identify the quantities of produced, imported and exported goods and services. Then, Global Footprint Network applies different factors to the quantities to assess the area needed to supply these products and services. Finally, the Consumption Footprint of a nation is divided by the number of inhabitants and compared to other countries at a per capita level (global hectares per capita). This means that the Ecological Footprint can be used as an indicator for the sustainability of a national consumption by assessing human land uses. In the following paragraph, Luxembourg’s Ecological Footprint is discussed in the framework of the environmental indicators of Luxembourg’s competitiveness scoreboard (see Table 9) [MECE, 2010]. Luxembourg’s ranking is rather low for all of the scoreboard indicators: number of ISO 9001 certifications per billion of inhabitants (21 out of 27); number of ISO 14001 certifications per billion of inhabitants (15 out of 27); total greenhouse gas emissions (15 out of 27); renewable energy ration (23 out of 27); quantity of municipal waste per capita per year (24 out of 27); energetic intensity (8 out of 27); transport by car (17 out of 27); Ecological Footprint in gha per capita per year (27 out of 27). Based on the environmental competiveness scoreboard indicators, it can be concluded that in general, Luxembourg’s environmental performance is low compared to the other countries of the European Union. With respect to Luxembourg’s Ecological Footprint, it can be said that Luxembourg’s consumption is not sustainable. The number of planets that would be needed if the world's population lived like the population of Luxembourg in 2007 is about six. However, per year, the biocapacity (bioproductive land) of the planet can only regenerate once. [less ▲]

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See detailA Tutorial on Bayesian Inference to Identify Material Parameters in Solid Mechanics
Rappel, Hussein UL; Beex, Lars UL; Hale, Jack UL et al

in Archives of Computational Methods in Engineering (2019)

The aim of this contribution is to explain in a straightforward manner how Bayesian inference can be used to identify material parameters of material models for solids. Bayesian approaches have already ... [more ▼]

The aim of this contribution is to explain in a straightforward manner how Bayesian inference can be used to identify material parameters of material models for solids. Bayesian approaches have already been used for this purpose, but most of the literature is not necessarily easy to understand for those new to the field. The reason for this is that most literature focuses either on complex statistical and machine learning concepts and/or on relatively complex mechanical models. In order to introduce the approach as gently as possible, we only focus on stress–strain measurements coming from uniaxial tensile tests and we only treat elastic and elastoplastic material models. Furthermore, the stress–strain measurements are created artificially in order to allow a one-to-one comparison between the true parameter values and the identified parameter distributions. [less ▲]

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See detailA tutorial on multiple crack growth and intersections with XFEM
Sutula, Danas; Bordas, Stéphane UL

Presentation (2015, May 12)

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See detailA two-dimensional Isogeometric Boundary Element Method for elastostatic analysis
Simpson, R. N.; Bordas, Stéphane UL; Trevelyan, J. et al

in Computer Methods in Applied Mechanics & Engineering (2012), 209-212

The concept of isogeometric analysis, where functions that are used to describe geometry in CAD software are used to approximate the unknown fields in numerical simulations, has received great attention ... [more ▼]

The concept of isogeometric analysis, where functions that are used to describe geometry in CAD software are used to approximate the unknown fields in numerical simulations, has received great attention in recent years. The method has the potential to have profound impact on engineering design, since the task of meshing, which in some cases can add significant overhead, has been circumvented. Much of the research effort has been focused on finite element implementations of the isogeometric concept, but at present, little has been seen on the application to the Boundary Element Method. The current paper proposes an Isogeometric Boundary Element Method (BEM), which we term IGABEM, applied to two-dimensional elastostatic problems using Non-Uniform Rational B-Splines (NURBS). We find it is a natural fit with the isogeometric concept since both the NURBS approximation and BEM deal with quantities entirely on the boundary. The method is verified against analytical solutions where it is seen that superior accuracies are achieved over a conventional quadratic isoparametric BEM implementation. © 2011 Elsevier B.V. [less ▲]

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See detailA TWO-STEP APPROACH FOR THE CORRECTION OF THE SEED MATRIX IN THE DYNAMIC DEMAND ESTIMATION
Cantelmo, Guido UL; Viti, Francesco UL; Tampère, Chris M.J. et al

in Transportation Research Record: Journal of the Transportation Research Board (2014), 2466

In this work deterministic and stochastic optimization methods are tested for solving the Dynamic Demand Estimation problem. All the adopted methods demonstrate the difficulty in reproducing the correct ... [more ▼]

In this work deterministic and stochastic optimization methods are tested for solving the Dynamic Demand Estimation problem. All the adopted methods demonstrate the difficulty in reproducing the correct traffic regime, especially if the seed matrix is not sufficiently close to the real one. Therefore, in this paper a new and intuitive procedure to specify an opportune starting seed matrix is proposed: it is a two-step procedure based on the concept of dividing the problem into small-size problems, focusing on specific OD pairs in different steps. Specifically, the first step focuses on the optimization of a subset of OD variables (the ones who generate the higher flows or the ones who generate the bottlenecks on the network). In the second step the optimization works on all the OD pairs, using as starting matrix the matrix derived from the first step. In this way is possible to use a more performance optimization method for every step, improving the performance of the method and the quality of the result with respect to the classical “one-step” approach. The procedure has been tested on the real network of Antwerp, Belgium, demonstrating its efficacy in combination with different optimization methods. [less ▲]

Detailed reference viewed: 199 (25 UL)