Browsing
     by title


0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

or enter first few letters:   
OK
Full Text
Peer Reviewed
See detailDistributed Collaborative Design Studio : a sketch-based environment to support rich distant collaboration. Workshop.
Safin, Stéphane ULg; Delfosse, Vincent ULg; Elsen, Catherine ULg et al

Conference (2008)

An increasing number of large scale projects requires that distant teams collaborate together remotely. At the same time, the current CAD tools only offer minimal support for partial and asynchronous ... [more ▼]

An increasing number of large scale projects requires that distant teams collaborate together remotely. At the same time, the current CAD tools only offer minimal support for partial and asynchronous interactions. The application we propose enables full synchronous and remote sketch-based collaborative design. This setup is a combination of a virtual desktop (a remote meeting table), a standard videoconference system, a gesture recognition module and a networked, real-time, collaborative drawing software (SketSha). The solution as a whole is multimodal in essence (gestures, speech, drawing…) supporting immersive remote collaborative design. [less ▲]

Detailed reference viewed: 92 (19 ULg)
Full Text
See detailDistributed control of electromechanical oscillations in very large-scale electric power systems
Wang, Da ULg

Doctoral thesis (2014)

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different ... [more ▼]

Electromechanical oscillations threaten the secure operation of power systems and if not controlled efficiently can lead to generator outages, line tripping and even large-scale blackouts. Different damping devices, like Power System Stabilizers (PSSs), Thyristor Controlled Series Compensators (TCSCs), and so on, are installed to damp these oscillations. This thesis proposes a trajectory-based supplementary control to improve damping effects of existing controllers, which treats damping control as a multi-step optimization control problem with discrete dynamics and costs. At each control time, it collects current system states, solves the optimal control problem and superimposes the calculated supplementary inputs on the outputs of existing damping controllers, in order to enhance the damping. These supplementary signals are continuously updated, which allows to adaptively adjust and coordinate a subset of existing damping controllers, and eventually all of them. Two kinds of methods, Model Predictive Control (MPC) and Reinforcement Learning (RL), are used to embody the proposed supplementary damping control. Firstly, a fully centralized MPC scheme is designed based on a linearized, discrete, complete state space model. Its performances are evaluated both in ideal conditions and considering realistic state estimation errors, and computation and communication delays. The effects of the number and type of available damping controllers are also studied. This scheme is further extended into a distributed scheme with the aim of making it more viable for very large-scale or multi-area systems. Different ways of decoupling and coordinating between subsystems are analyzed. Finally, a robust hierarchical multi-area MPC scheme is proposed, introducing a second layer of MPC based controllers at the level of individual power plants and transmission lines. Secondly, a tree-based batch mode RL algorithm is applied to carry on the proposed supplementary damping control. Using a set of dynamic and reward four-tuples, it constructs an approximation of the optimal $Q$-function over a given temporal horizon. The actions greediest with respect to the $Q$-function are applied as supplementary signals to existing damping controllers. The scheme is firstly tested on a single generator, and then on multiple generators. Different reward signals and damping levels are also considered. Finally, the combined control effects of MPC and RL are investigated. [less ▲]

Detailed reference viewed: 75 (8 ULg)
Full Text
Peer Reviewed
See detailDistributed Dynamic Load Balancing for Iterative-Stencil Applications
Dethier, Gérard ULg; Marchot, Pierre ULg; de Marneffe, Pierre-Arnoul ULg

in Cracow Grid Workshop '08 Proceedings (2009, March)

In the context of jobs executed on heterogeneous clusters or Grids, load balancing is essential. Indeed, a slow machine must receive less work than a faster one otherwise the overall job termination will ... [more ▼]

In the context of jobs executed on heterogeneous clusters or Grids, load balancing is essential. Indeed, a slow machine must receive less work than a faster one otherwise the overall job termination will be delayed. This is particularly true for Iterative-Stencil Applications where tasks are run simultaneously and are interdependent. The problem of assigning coexisting tasks to machines is called mapping. With dynamic clusters (where the number of machines and their available power can change over time), dynamic mapping must be used. A new mapping must be calculated each time the cluster changes. The mapping calculation must therefore be fast. Also, a new mapping should be as close as possible to the previous mapping in order to minimize task migrations. Dynamic mapping methods exist but are based on iterative optimization algorithms. Many iterations are required to reach convergence. In the context of a distributed implementation, many communications are needed. We developed a new distributed dynamic mapping method which is not based on iterative optimization algorithms. Current results are encouraging. Load balancing execution time remains bounded for tested cluster sizes. Also, a decrease of ~20% of the global available computational power of a cluster leads to ~30% of migrated tasks during load rebalancing. A new mapping is therefore close to the previous one. [less ▲]

Detailed reference viewed: 132 (14 ULg)
Full Text
Peer Reviewed
See detailDistributed fiber-optic temperature sensing for hydrologic systems
Selker, John S.; Thévenaz, Luc; Huwald, Hendrik et al

in Water Resources Research (2006), 42(12), 12202

Instruments for distributed fiber-optic measurement of temperature are now available with temperature resolution of 0.01°C and spatial resolution of 1 m with temporal resolution of fractions of a minute ... [more ▼]

Instruments for distributed fiber-optic measurement of temperature are now available with temperature resolution of 0.01°C and spatial resolution of 1 m with temporal resolution of fractions of a minute along standard fiber-optic cables used for communication with lengths of up to 30,000 m. We discuss the spectrum of fiber-optic tools that may be employed to make these measurements, illuminating the potential and limitations of these methods in hydrologic science. There are trade-offs between precision in temperature, temporal resolution and spatial resolution, following the square root of the number of measurements made; thus brief, short measurements are less precise than measurements taken over longer spans in time and space. Five illustrative applications demonstrate configurations where the distributed temperature sensing (DTS) approach could be used: (1) lake bottom temperatures using existing communication cables, (2) temperature profile with depth in a 1400 m deep decommissioned mine shaft, (3) air-snow interface temperature profile above a snow-covered glacier (4) air-water interfacial temperature in a lake, and (5) temperature distribution along a first-order stream. In examples 3 and 4 it is shown that by winding the fiber around a cylinder, vertical spatial resolution of millimeters can be achieved. These tools may be of exceptional utility in observing a broad range of hydrologic processes including evaporation, infiltration, limnology, and the local and overall energy budget spanning scales from 0.003 to 30,000 m. This range of scales corresponds well with many of the areas of greatest opportunity for discovery in hydrologic science. [less ▲]

Detailed reference viewed: 12 (5 ULg)
Peer Reviewed
See detailDistributed GIS for sharing large scale data between public agencies. A case study in Belgium
Donnay, Jean-Paul ULg

in GIS 2002 International Conference Proceedings (2002)

Detailed reference viewed: 11 (3 ULg)
Peer Reviewed
See detailA Distributed Implementation of Fast Fourier Transforms
Verly, Jacques ULg; Kirk, Donald E.

Conference (1984, November)

Detailed reference viewed: 7 (0 ULg)
Full Text
Peer Reviewed
See detailA Distributed Lattice Boltzmann-based Flow Simulator
Dethier, Gérard ULg

Conference (2009, January 22)

The use of Lattice Boltzmann (LB) methods is interesting to describe flows through complex geometries encountered in Chemical Engineering (porous media, packed beds, multi phase flows). However, flow ... [more ▼]

The use of Lattice Boltzmann (LB) methods is interesting to describe flows through complex geometries encountered in Chemical Engineering (porous media, packed beds, multi phase flows). However, flow simulations based on LB methods can require big amounts of memory. It is not always possible to run a simulation on a single machine. Distributed computing is a solution to this problem and also accelerates the execution of the flow simulation. In the context of dynamic heterogeneous clusters, the available machines can have different computational powers. The computational power of each machine can vary during a flow simulation (because of background load). Also, the number of available machines can change. These characteristics impose the use of special technics. Dynamic Load Balancing allows the optimal use of available machines. A fault occurs when one or several machines interrupt the execution of the distributed software component they were executing. Checkpointing makes the system fault tolerant. In order to obtain a scalable software and to suppress single points of failure, a special effort is made to decentralize as much as possible the software components of the simulator. Currently, fluid flows of 400³ points (more than 9 GBytes of data) are simulated using an heterogeneous cluster of 54 machines. [less ▲]

Detailed reference viewed: 133 (28 ULg)
Full Text
Peer Reviewed
See detailDistributed load interruption and shedding against voltage delayed recovery or instability
Otomega, Bogdan; Van Cutsem, Thierry ULg

in Proc. IEEE PES 2013 PowerTech Conference (2013, June)

This paper deals with a two-part system integrity protection scheme to be installed in distribution networks, to counteract fault-induced delayed voltage recovery or even short-term voltage instability ... [more ▼]

This paper deals with a two-part system integrity protection scheme to be installed in distribution networks, to counteract fault-induced delayed voltage recovery or even short-term voltage instability due to induction motors. The first part consists of a fast triggered but temporary reduction of some loads to facilitate motor re-acceleration after fault clearing. The second part resorts to load shedding, as a back-up. The scheme relies on purely distributed controllers; each of them measures a bus voltage and interrupts/disconnects load at the same bus. Tests have been performed on a generic MV/LV system. They illustrate the benefit of load interruption and the selectivity of the proposed scheme. [less ▲]

Detailed reference viewed: 84 (9 ULg)
Full Text
Peer Reviewed
See detailDistributed Model-free Control of Photovoltaic Units for Mitigating Overvoltages in Low-Voltage Networks
Aristidou, Petros ULg; Olivier, Frédéric ULg; Hervas, Maria Emilia et al

in Proc. of CIRED 2014 workshop (2014, June)

In this paper, a distributed model-free control scheme to mitigate overvoltage problems caused by high photovoltaic generation in low-voltage feeders is proposed. The distributed controllers are ... [more ▼]

In this paper, a distributed model-free control scheme to mitigate overvoltage problems caused by high photovoltaic generation in low-voltage feeders is proposed. The distributed controllers are implemented on the photovoltaic inverters and modulate the active and reactive power injected into the network. In particular, they direct photovoltaic units first to consume reactive power and, if necessary, curtail active power generation to reduce high voltages in the feeder. [less ▲]

Detailed reference viewed: 111 (33 ULg)
Full Text
Peer Reviewed
See detailDistributed MPC of wide-area electromechanical oscillations of large-scale power systems
Wang, Da ULg; Glavic, Mevludin; Wehenkel, Louis ULg

in Proceedings of ISAP 2011 (2011, September)

We investigate distributed Model Predictive Control (MPC) to damp wide-area electromechanical oscillations. Our distributed MPC schemes are derived from and compared with a fully centralized MPC scheme ... [more ▼]

We investigate distributed Model Predictive Control (MPC) to damp wide-area electromechanical oscillations. Our distributed MPC schemes are derived from and compared with a fully centralized MPC scheme proposed in a previous publication. Based on simulations carried out using a 16-generator, 70-bus, two-area test power system, we show that simple coordination schemes based on additional local measurements’ feedback yield already a significant improvement with respect to a scheme with only implicit coordination, improve significantly with respect to purely local controls, and in this respect reach about 75% of the improvements obtained by an ideal centralized MPC scheme. [less ▲]

Detailed reference viewed: 33 (7 ULg)
See detailA Distributed Signal Processing Architecture
Filip, A. E.; Arthur, James S.; Drinan, John D. et al

Report (1983)

Detailed reference viewed: 1 (0 ULg)
Full Text
Peer Reviewed
See detailA distributed stream temperature model using high resolution temperature observations
Westhoff, Martijn ULg; Savenije, H. H. G.; Luxemburg, W. M. J. et al

in Hydrology and Earth System Sciences (2007), 11(4), 1469-1480

Detailed reference viewed: 8 (1 ULg)
Full Text
Peer Reviewed
See detailDistributed undervoltage load shedding
Otomega, Bogdan; Glavic, Mevludin; Van Cutsem, Thierry ULg

in IEEE Transactions on Power Systems (2007), 22(4), 2283-2284

A new design of load shedding against long-term voltage instability is proposed. It uses a set of distributed controllers, each monitoring a transmission voltage, controlling a group of loads, acting in ... [more ▼]

A new design of load shedding against long-term voltage instability is proposed. It uses a set of distributed controllers, each monitoring a transmission voltage, controlling a group of loads, acting in closed-loop, and adjusting its action to the voltage evolution. The whole system operates without information exchange between controllers. [less ▲]

Detailed reference viewed: 74 (2 ULg)
Full Text
See detailDe distributie van goederen en de licentieovereenkomst
Vanbrabant, Bernard ULg; Van Couter, Yves

in Bestendig Handboek Distributierecht (2007)

Detailed reference viewed: 40 (4 ULg)
Full Text
Peer Reviewed
See detailDistributing the Optical Near-Field for Efficient Field-Enhancements in Nanostructures
Valev, V; De Clercq, B; Biris, C et al

in Advanced Materials (2012), 24

Circularly polarized light imparts a sense of rotation on the electron density in ring-shaped gold nanostructures. As a consequence, the near-field enhancement becomes homogeneous on the surface of the ... [more ▼]

Circularly polarized light imparts a sense of rotation on the electron density in ring-shaped gold nanostructures. As a consequence, the near-field enhancement becomes homogeneous on the surface of the nanostructures, thereby increasing the opportunity for interaction with molecules. This type of nanostructured samples can find a broad range of applications in chemical processes where the interaction between molecules and local field enhancements play an important role. [less ▲]

Detailed reference viewed: 16 (2 ULg)
Full Text
Peer Reviewed
See detailDistribution amplitude for the photon-pion transition
Courtoy, Aurore ULg; Noguera, S.

in PoS - Proceedings of Science (2008), LC2008

Detailed reference viewed: 12 (0 ULg)
Peer Reviewed
See detailDistribution and accumulation pattern of perfluorooctane sulfonic acid (PFOs) in marine mammals from the North Sea
Van de Vijver, Kristin; Das, Krishna ULg; Van Dongen, W. et al

Poster (2002, November)

Detailed reference viewed: 14 (0 ULg)
Full Text
Peer Reviewed
See detailDistribution and air-water exchange of carbon dioxide in the Scheldt plume off the Belgian coast
Borges, Alberto ULg; Frankignoulle, Michel

in Biogeochemistry (2002), 59((1-2)), 41-67

In the present paper we report partial pressure of CO2 (pCO2) data obtained off the Belgian coast during 24 cruises. The temporal and spatial resolution of this data set allows us to discuss ... [more ▼]

In the present paper we report partial pressure of CO2 (pCO2) data obtained off the Belgian coast during 24 cruises. The temporal and spatial resolution of this data set allows us to discuss satisfactorily seasonal and inter-annual variability of pCO2 in the study area. The dynamics of pCO2 are described using two approaches: fixed reference stations and area survey cruises. The air-water fluxes of CO2 in the Scheldt estuarine plume and in the outerplume region are estimated quantitatively, showing that these areas correspond respectively to a net annual source and sink of atmospheric CO2. The annually integrated air-water fluxes for the Scheldt estuarine plume range between +1.1 and +1.9 mol m−2 year−1 as a function of the formulation of the exchange coefficient of CO2. The annual net emission of CO2 from the estuarine plume to the atmosphere is estimated to be between +2.3 to +4.0 Gmol year−1 which represents 17 to 29% of the estimate reported in the literature for the Scheldt inner estuary. [less ▲]

Detailed reference viewed: 20 (2 ULg)
Full Text
Peer Reviewed
See detailDistribution and characteristics of aquatic habitats of newts and yellow-bellied toads in the district of Ioannina (Epirus, Greece)
Denoël, Mathieu ULg

in Herpetozoa (2004), 17(1/2), 49-64

The study describes the aquatic habitats and distribution of Triturus alpestris veluchiensis Wolterstorff 1935, T. carnifex macedonicus (Karaman, 1922), T. vulgaris graecus (Wolterstorff, 1905) and ... [more ▼]

The study describes the aquatic habitats and distribution of Triturus alpestris veluchiensis Wolterstorff 1935, T. carnifex macedonicus (Karaman, 1922), T. vulgaris graecus (Wolterstorff, 1905) and Bombina variegata scabra (Küster, 1843) in the district (“nomos”) of Ioannina, Northern Greece. Bombina variegata was found to be the most common species, followed by T. alpestris and T. carnifex while T. vulgaris seemed to be rare. The four taxa differed in habitat use and geographic distribution. Records of T. alpestris were limited to the highest sites in the north and east of the district. This species inhabited alpine lakes, but also smaller habitats such as drinking troughs and ponds. Four populations contained paedomorphic individuals. Triturus vulgaris appeared to be restricted to low altitude sites in the centre of the district where it lived in reservoirs, watering basins and drinking troughs. Triturus carnifex and B. variegata had a wider distribution and occupied a broader spectrum of habitats. Bombina variegata was the only species studied which lived in running waters (small brooks). Neither newts nor yellow-bellied toads were found in large rivers and lakes. In the district of Ioannina both habitat variety and distribution range of newts and Yellow-bellied Toads turned out to be greater than previously known. Alpine lakes containing very large populations of paedomorphic individuals should be protected given the rarity of the phenomenon. [less ▲]

Detailed reference viewed: 986 (6 ULg)
See detailDistribution and composition of organic carbon in the Tana River Basin, (Kenya)
Tamooh, F.; van den Meersche, K.; Borges, Alberto ULg et al

Poster (2011)

Detailed reference viewed: 10 (1 ULg)