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See detailCollective motion, sensor networks, and ocean sampling
Leonard, Naomi Ehrich; Paley, Derek; Lekien, François et al

in Proceedings of the IEEE (2007), 95(1), 48-74

This paper addresses the design of mobile sensor networks for optimal data collection. The development is strongly motivated by the application to adaptive ocean sampling for an autonomous ocean observing ... [more ▼]

This paper addresses the design of mobile sensor networks for optimal data collection. The development is strongly motivated by the application to adaptive ocean sampling for an autonomous ocean observing and prediction system. A performance metric, used to derive optimal paths for the network of mobile sensors, defines the optimal data set as one which minimizes error in a model estimate of the sampled field. Feedback control laws are presented that stably coordinate sensors on structured tracks that have been optimized over a minimal set of parameters. Optimal, closed-loop solutions are computed in a number of low-dimensional cases to illustrate the methodology. Robustness of the performance to the influence of a steady flow field on relatively slow-moving mobile sensors is also explored. [less ▲]

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See detailCollective Motion: Bistability and Trajectory Tracking
Paley, Derek; Leonard, Naomi; Sepulchre, Rodolphe ULg

in Proceedings of the 43rd IEEE Conference on Decision and Control (2004, December)

This paper presents analysis and application of steering control laws for a network of self-propelled, planar particles. We explore together the two stably controlled group motions, parallel motion and ... [more ▼]

This paper presents analysis and application of steering control laws for a network of self-propelled, planar particles. We explore together the two stably controlled group motions, parallel motion and circular motion, for modeling and design purposes. We show that a previously considered control law simultaneously stabilizes both parallel and circular group motion, leading to bistability and hysteresis. We also present behavior primitives that enable piecewise-linear network trajectory tracking. [less ▲]

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See detailCollective optimization over average quantities
Scardovi, Luca; Sepulchre, Rodolphe ULg

in Proceedings of the 45th IEEE Conference on Decision and Control (2006)

This paper addresses the design of algorithms for the collective optimization of a cost function defined over average quantities in the presence of limited communication. We argue that several meaningful ... [more ▼]

This paper addresses the design of algorithms for the collective optimization of a cost function defined over average quantities in the presence of limited communication. We argue that several meaningful collective optimization problems can be formulated in this way. As an application of the proposed approach, we propose a novel algorithm that achieves synchronization or balancing in phase models of coupled oscillators under mild connectedness assumptions on the (possibly time-varying and unidirectional) communication graphs. [less ▲]

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See detailCollective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars
Aerts, C.; Puls, J.; Godart, Mélanie ULg et al

in Astronomy and Astrophysics (2009), 508

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains ... [more ▼]

Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains unexplained.<BR /> Methods: We computed time series of line profiles for evolved massive stars broadened by rotation and by hundreds of low-amplitude nonradial gravity-mode pulsations which are predicted to be excited for evolved massive stars.<BR /> Results: In general, line profiles based on macrotubulent broadening can mimic those subject to pulsational broadening. In several cases, though, good fits require macroturbulent velocities that pass the speed of sound for realistic pulsation amplitudes. Moreover, we find that the rotation velocity can be seriously underestimated by using a simple parameter description for macroturbulence rather than an appropriate pulsational model description to fit the line profiles.<BR /> Conclusions: We conclude that macroturbulence is a likely signature of the collective effect of pulsations. We provide line diagnostics and their typical values to decide whether or not pulsational broadening is present in observed line profiles, as well as a procedure to avoid an inaccurate estimation of the rotation velocity. [less ▲]

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See detailCollective Redress in Multiple Perspectives the challenges of integrating competition law, consumer law and the construction of a European judicial area
Sibony, Anne-Lise ULg

Scientific conference (2011, April 07)

Collective redress ought to be looked at from several different perspectives: that of competition law, that of consumer law and that of building a European judicial area. This paper looks at the ... [more ▼]

Collective redress ought to be looked at from several different perspectives: that of competition law, that of consumer law and that of building a European judicial area. This paper looks at the challengenges posed by the necessity to hold all three perspective together. [less ▲]

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See detailCollective Retrieval hy Autonomous Rohots
Meyer, Patrick ULg

Conference (2004)

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See detailCollectors of Japanese Art in belgium : between exotism and scholarship
Bawin, Julie ULg

in Oriental Fascination. 1889-1915. The Japonisme in Belgium (2008)

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See detailCollider aspects of flavor physics at high Q
Lari, T.; Pape, L.; Porod, W. et al

in European Physical Journal C -- Particles & Fields (2008), 57(1-2), 183-307

This chapter of the 'Flavor in the era of LHC' workshop report discusses flavor-related issues in the production and decays of heavy states at the LHC at high momentum transfer Q, both from the ... [more ▼]

This chapter of the 'Flavor in the era of LHC' workshop report discusses flavor-related issues in the production and decays of heavy states at the LHC at high momentum transfer Q, both from the experimental and the theoretical perspective. We review top quark physics, and discuss the flavor aspects of several extensions of the standard model, such as supersymmetry, little Higgs models or models with extra dimensions. This includes discovery aspects, as well as the measurement of several properties of these heavy states. We also present publicly available computational tools related to this topic. © Springer-Verlag / Società Italiana di Fisica 2008. [less ▲]

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See detailColliding particles carrying nonzero orbital angular momentum
Ivanov, Igor ULg

in Physical Review. D : Particles and Fields (2011), 83(9), 093001

Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested ... [more ▼]

Photons carrying nonzero orbital angular momentum (twisted photons) are well-known in optics. Recently, using Compton backscattering to boost optical twisted photons to high energies was suggested. Twisted electrons in the intermediate energy range have also been produced recently. Thus, collisions involving energetic twisted particles seem to be feasible and represent a new tool in high-energy physics. Here we discuss some generic features of scattering processes involving twisted particles in the initial and/or final state. In order to avoid additional complications arising from nontrivial polarization states, we focus here on scalar fields only. We show that processes involving twisted particles allow one to perform a Fourier analysis of the plane-wave cross section with respect to the azimuthal angles of the initial particles. In addition, using twisted states, one can probe the autocorrelation function of the amplitude, which is inaccessible in the plane-wave collisions. Finally, we discuss prospects for experimental study of these effects. [less ▲]

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See detailColliding Wind Signatures in Early-Type Binaries
Rauw, Grégor ULg

in Revista Mexicana de Astronomia y Astrofisica Conference Series (2008, August 01)

Observations of early-type binaries not only allow us to establish the fundamental properties of massive stars in a model-independent fashion, but furthermore provide important information on the ... [more ▼]

Observations of early-type binaries not only allow us to establish the fundamental properties of massive stars in a model-independent fashion, but furthermore provide important information on the interactions of their stellar winds. The signatures of wind-wind interactions have been found over a broad range of wavelengths and energies, from the radio domain to X-rays and possibly gamma-rays. In this review, I discuss some results of the study of wind interactions in Wolf-Rayet and O-star binaries. [less ▲]

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See detailColliding-wind binaries as non-thermal X-ray emitters: an observational investigation from XMM-Newton to next generation X-ray observatories
De Becker, Michaël ULg

Poster (2007, December)

The investigation of massive stars in the radio domain revealed about 25 years ago that some of them are synchrotron emitters, showing that these objects are able to accelerate particles up to ... [more ▼]

The investigation of massive stars in the radio domain revealed about 25 years ago that some of them are synchrotron emitters, showing that these objects are able to accelerate particles up to relativistic velocities. In this context, non-thermal emission processes such as inverse Compton scattering are expected to be at work in the high-energy domain. For this reason, an observational campaign devoted to the X-ray investigation of non-thermal radio emitters has been carried out with XMM-Newton. However, considering the rather strong thermal X-ray emission from these systems below 10 keV, XMM-Newton does not appear to be the ideal observatory to detect their putative non-thermal X-rays. As a consequence, the advent of next generation X-ray observatories with a bandpass extending significantly above 10 keV (SIMBOL-X, XEUS, NEXT) is expected to provide important results related to the non-thermal high-energy emission from colliding-wind binaries and their capability to accelerate particles. [less ▲]

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See detailColliding-winds in massive star binaries: expectations from radio to gamma-rays
De Becker, Michaël ULg

Conference (2010, December 02)

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See detailCollimator Effects in High Resolution X-ray Computed Tomography
Verly, Jacques ULg

in IEEE Transactions on Medical Imaging (1982), MI-1(2), 122-136

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See detailCollinear helium under periodic driving: Stabilization of the asymmetric stretch orbit
Schlagheck, Peter ULg; Pingel, D.; Schmelcher, P.

in Physical Review. A (2003), 68(5), 053410

The collinear eZe configuration of helium, with the electrons on opposite sides of the nucleus, is studied in the presence of an external electromagnetic (laser or microwave) field. We show that the ... [more ▼]

The collinear eZe configuration of helium, with the electrons on opposite sides of the nucleus, is studied in the presence of an external electromagnetic (laser or microwave) field. We show that the classically unstable "asymmetric stretch" orbit, on which doubly excited intrashell states of helium with maximum interelectronic angle are anchored, can be stabilized by means of a resonant driving where the frequency of the electromagnetic field equals the frequency of Kepler-like oscillations along the orbit. A static magnetic field, oriented parallel to the oscillating electric field of the driving, can be used to enforce the stability of the configuration with respect to deviations from collinearity. Quantum Floquet calculations within a collinear model of the driven two-electron atom reveal the existence of nondispersive wave packets localized on the stabilized asymmetric stretch orbit, for double excitations corresponding to principal quantum numbers of the order of Ngreater than or similar to10. [less ▲]

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See detailA Collision Avoidance System based on Galileo Satellite
Christen, Fréderic ULg; Wimmershoff, M.

in 17th ITS World Congress 2010 (2010, October 25)

Nowadays, collision avoidance systems (CAS) are an intensive research topic since the majority of all traffic accidents are collisions that are caused due to inattention or unadjusted driving behaviour of ... [more ▼]

Nowadays, collision avoidance systems (CAS) are an intensive research topic since the majority of all traffic accidents are collisions that are caused due to inattention or unadjusted driving behaviour of the driver. Up to date prototypic CAS are based on on-board environmental sensors, such as camera or radar systems, that scan the vehicle's surrounding in order to assess the situation's hazardousness. The functionality of the used sensors under varying environmental conditions and the limited sensor covering area require an enormous effort to ensure a reliable detection of obstacles, and thus limit the application of the systems. In order to expand the operating field of such systems, a Galileo-based CAS will be developed within the project ‘Galileo above‘ (Anwendungszentrum für bodengebundenen Verkehr / application centre for ground based traffic). This advanced driver assistance system (ADAS) detects surrounding vehicles that are on collision course and reacts autonomously, if the driver does not intervene to avoid the crash. For this purpose the system initiates an emergency stop and/or an emergency steering manoeuvre. For the development of the CAS, the Galileo test centre automotiveGATE in Aldenhoven, Germany, will be used. On this test area pseudolites will be installed which provide Galileo-like navigation signals. Thus, the development respectively tuning of Galileo-based vehicle systems will be enabled, so as to have them available on the market when the Galileo satellite system becomes operative. At the end of the project ‘Galileo above‘, first prototypes should demonstrate the potential of Galileo-based CAS. [less ▲]

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See detailCollision induced dissociation of deuterium enriched protonated 2'-deoxyguanosine
Greisch, Jean-François ULg; Leyh, Bernard ULg; De Pauw, Edwin ULg

in European Physical Journal D -- Atoms, Molecules, Clusters & Optical Physics (2009), 51(1), 89-96

Collision induced dissociation in mass spectrometry of protonated nucleosides typically yields as charged fragment the protonated nucleobase augmented by one hydrogen transferred from the 2'-deoxyribose ... [more ▼]

Collision induced dissociation in mass spectrometry of protonated nucleosides typically yields as charged fragment the protonated nucleobase augmented by one hydrogen transferred from the 2'-deoxyribose, [ bH(2)]. The origin of the hydrogen transfer for the protonated 2'-deoxyguanosine has been investigated by collision induced dissociation of deuterium enriched molecules. [ 1'-H-2] 2'-deoxyguanosine, [ 2',2aEuro(3)-H-2(2)] 2'-deoxyguanosine, and [ 5',5aEuro(3)-H-2(2)] 2'-deoxyguanosine have been studied and deuterium/hydrogen back exchange has been used following complete or partial exchange of the 2'-deoxyguanosine in solution. Based on the fragmentation of the deuterated molecular ions, the hydrogen transferred from the 2'-deoxyribose to the guanine is found to originate from the O5' atom on the 2'-deoxyribose. A fragmentation mechanism involving a hydrogen shift from the 2' position to the oxygen atom O5' and supported by the kinetic isotope effect on the survival yield curves is proposed. The influence of the 2'-deoxyguanosine conformation on the hydrogen transfer and the fragmentation mechanism is discussed. [less ▲]

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See detailCollision-induced dissociation of 16-mer DNA duplexes with various sequences: evidence for conservation of the double helix conformation in the gas phase
Gabelica, Valérie ULg; De Pauw, Edwin ULg

in International Journal of Mass Spectrometry (2002), 219(1), 151-159

The MS/MS of 11 different 16-mer non-self-complementary DNA duplexes with various sequences has been under-taken with a quadrupole-TOF hybrid instrument, The comparison of the dissociation yields for ... [more ▼]

The MS/MS of 11 different 16-mer non-self-complementary DNA duplexes with various sequences has been under-taken with a quadrupole-TOF hybrid instrument, The comparison of the dissociation yields for complexes having different amounts of GC base pairs, though complicated by side-reactions like single-strand fragmentation, confirms the effect of the number of GC base pairs. More importantly, for complexes containing the same fraction of GC and different base sequences, the fragmentation yield remarkably parallels the DeltaH(diss) in solution calculated by a nearest-neighbor model for B-DNA. In addition to specific hydrogen bonding interactions, base stacking interactions also seem to survive in the gas phase and the conformation is conserved in the gas phase. Moreover, we have studied the uneven partition of the negative charges between the single strands, which was found to be directed by the nature of the terminal bases exclusively, and correlated with the gas-phase acidities of the (sugar-phosphate-sugar-base) species. [less ▲]

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See detailCollisions entre véhicules et animaux en liberté : état des lieux à partir d'une enquête au sein de la police
Lehaire, François ULg; Morelle, Kevin ULg; Lejeune, Philippe ULg

in Forêt Wallonne (2013), 122

Les accidents de la route impliquant des animaux sauvages sont de plus en plus nombreux. En se basant sur les données recueillies par les zones de police en Wallonie, il est possible d’avoir une vision ... [more ▼]

Les accidents de la route impliquant des animaux sauvages sont de plus en plus nombreux. En se basant sur les données recueillies par les zones de police en Wallonie, il est possible d’avoir une vision plus claire de la problématique. Dans le cas du cerf et du sanglier, il apparaît clairement que la hausse des accidents est liée à l’augmentation de leurs populations. [less ▲]

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See detailColloidal gold, a useful marker for antigen localization on follicular dendritic cells.
Heinen, Ernst ULg; Radoux, D.; Kinet-Denoel, C. et al

in Journal of Immunological Methods (1983), 59(3), 361-8

Bovine serum albumin (BSA) bound to colloid gold particles (BSA-gold; 20 nm diameter) and injected into preimmunized mice was found at ultrastructural level in different locations of the lymph nodes. It ... [more ▼]

Bovine serum albumin (BSA) bound to colloid gold particles (BSA-gold; 20 nm diameter) and injected into preimmunized mice was found at ultrastructural level in different locations of the lymph nodes. It was detected particularly in the secondary lysosomes of macrophages and between the cytoplasmic processes of the follicular dendritic cells. Between these processes the gold particles were isolated or grouped in clusters; they were in close contact with cell membranes or embedded in dense material. Colloidal gold injected alone was not retained on these cells. The presence of anti-BSA antibodies in the serum was necessary for trapping of BSA-gold particles on follicular dendritic cells. Injections of BSA alone after BSA-gold had been administered to preimmunized mice eliminated most of the BSA-gold from the dendritic processes. BSA-gold is thus trapped in the form of immune complexes which behave characteristically. BSA-gold is thus a suitable marker for antigen localization. Being small and electron dense it permits more precise location than radioactive markers. [less ▲]

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