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Search Results: 1 - 10 of 5489 matches for " Xavier Merlhiot "
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Balanced Virtual Humans Interacting with their Environment
Antoine Rennuit,Alain Micaelli,Xavier Merlhiot,Claude Andriot,Fran?ois Guillaume,Nicolas Chevassus,Damien Chablat,Patrick Chedmail
Computer Science , 2007,
Abstract: The animation of human avatars seems very successful; the computer graphics industry shows outstanding results in films everyday, the game industry achieves exploits... Nevertheless, the animation and control processes of such manikins are very painful. It takes days to a specialist to build such animated sequences, and it is not adaptive to any type of modifications. Our main purpose is the virtual human for engineering, especially virtual prototyping. As for this domain of activity, such amounts of time are prohibitive.
Integration of a Balanced Virtual Manikin in a Virtual Reality Platform aimed at Virtual Prototyping
Antoine Rennuit,Alain Micaelli,Xavier Merlhiot,Claude Andriot,Fran?ois Guillaume,Nicolas Chevassus,Damien Chablat,Patrick Chedmail
Computer Science , 2007,
Abstract: The work presented here is aimed at introducing a virtual human controller in a virtual prototyping framework. After a brief introduction describing the problem solved in the paper, we describe the interest as for digital humans in the context of concurrent engineering. This leads us to draw a control architecture enabling to drive virtual humans in a real-time immersed way, and to interact with the product, through motion capture. Unfortunately, we show this control scheme can lead to unfeasible movements because of the lack of balance control. Introducing such a controller is a problem that was never addressed in the context of real-time. We propose an implementation of a balance controller, that we insert into the previously described control scheme. Next section is dedicated to show the results we obtained. Finally, we propose a virtual reality platform into which the digital character controller is integrated.
Passive Control Architecture for Virtual Humans
Antoine Rennuit,Alain Micaelli,Xavier Merlhiot,Claude Andriot,Fran?ois Guillaume,Nicolas Chevassus,Damien Chablat,Patrick Chedmail
Computer Science , 2007,
Abstract: In the present paper, we introduce a new control architecture aimed at driving virtual humans in interaction with virtual environments, by motion capture. It brings decoupling of functionalities, and also of stability thanks to passivity. We show projections can break passivity, and thus must be used carefully. Our control scheme enables task space and internal control, contact, and joint limits management. Thanks to passivity, it can be easily extended. Besides, we introduce a new tool as for manikin's control, which makes it able to build passive projections, so as to guide the virtual manikin when sharp movements are needed.
On the Communication Requirements for the Smart Grid  [PDF]
Mohamed Daoud, Xavier Fernando
Energy and Power Engineering (EPE) , 2011, DOI: 10.4236/epe.2011.31008
Abstract: The current power grid is facing many challenges that it was not designed or engineered to handle which range from congestions and major blackouts to the overwhelming increase in demand and security concerns. The current electric grid was established before the 1960’s. It is believed that the electric grid is the most complex and gigantic machine ever made in human history; it consists of wires, cables, towers, transformers and circuit breakers installed together in outdated manner. During the 60’s, computers and sensors were used to monitor and slightly control the grid; however, fifty years later these sensors are considered less than ideal. Presented here is a review of the smart grid communication network in terms of configuration, bandwidth and latency requirements as well as the technology used. We simulate the access layer of the smart grid net-work and show that no single available communication technology can be used for all layers of the smart grid; thus, different technologies for different layers are needed. A new protocol for optimizing the smart grid is recommended.
A Conservative Model for Nonlinear Dynamics in a Stratified, Rotating Fluid  [PDF]
Nicolas Filatoff, Xavier Carton
Open Journal of Marine Science (OJMS) , 2018, DOI: 10.4236/ojms.2018.82013
We present a set of equations describing the nonlinear dynamics of flows constrained by environmental rotation and stratification (Rossby numbers Ro∈[0.1,0.5] and Burger numbers of order unity). The fluid is assumed incompressible, adiabatic, inviscid and in hydrostatic balance. This set of equations is derived from the Navier Stokes equations (with the above properties), using a Rossby number expansion with second order truncation. The resulting model has the following properties: 1) it can represent motions with moderate Rossby numbers and a Burger number of order unity; 2) it filters inertia-gravity waves by assuming that the divergence of horizontal velocity remains small; 3) it is written in terms of a single function of space and time (pressure, generalized streamfunction or Bernoulli function); 4) it conserves total (Ertel) vorticity in a Lagrangian form, and its quadratic norm (potential enstrophy) at the model order in Rossby number; 5) it also conserves total energy at the same order if the work of pressure forces vanishes when integrated over the fluid domain. The layerwise version of the model is finally presented, written in terms of pressure. Integral properties (energy, enstrophy) are conserved by these layerwise equations. The model equations agree with the generalized geostrophy equations in the appropriate parameter regime. Application to vortex dynamics are mentioned.
On the zeros and critical points of a rational map
Xavier Buff
International Journal of Mathematics and Mathematical Sciences , 2001, DOI: 10.1155/s0161171201011589
Abstract: Let f:ℙ1→ℙ1 be a rational map of degree d. It is well known that f has d zeros and 2d−2 critical points counted with multiplicities. In this note, we explain how those zeros and those critical points are related.
How does BAFF activate B cells in patients with autoimmune diseases?
Xavier Mariette
Arthritis Research & Therapy , 2012, DOI: 10.1186/ar3729
Abstract: In a study in a recent issue of Arthritis Research & Therapy, Yoshimoto and colleagues [1] demonstrate that peripheral monocytes from patients with Sj?gren's syndrome (SS) produce significantly higher amounts of the cytokines B cell-activating factor (BAFF) (also called B-lymphocyte stimulator, or BlyS) and interleukin-6 (IL-6) in comparison with normal monocytes. Increased expression of BAFF might explain pathogenic B-cell activation in several systemic autoimmune diseases (reviewed in [2]). Interestingly, autoreactive B cells depend more on BAFF for survival than do alloreactive B cells. BAFF involvement in the pathogenesis of autoimmune diseases is well illustrated in BAFF-transgenic mice, which exhibit an autoimmune disease mimicking systemic lupus erythematosus (SLE) and primary Sj?gren's syndrome (pSS) as well as a twofold increase in frequency of B-cell lymphoma [3]. In humans, an increased serum level of BAFF was reported in different autoimmune diseases, and findings concerning SLE and pSS were more consistent (reviewed in [2]).Recent findings showed that BAFF could be expressed and secreted by resident cell targets of autoimmunity after stimulation with different cytokines: synoviocytes in rheumatoid arthritis, astrocytes in multiple sclerosis, and epithelial cells in pSS [4]. Moreover, in the context of autoimmunity, BAFF could be secreted by T [5] and B [6] lymphocytes. However, the main sources of BAFF are myeloid cells and, especially, blood monocytes, myeloid dendritic cells, and macrophages [7].It has been suggested that monocytes from patients with autoimmune diseases were more susceptible to BAFF expression and secretion after stimulation with type 1 interferon (IFN) than those from healthy controls [8]. Yoshimoto and colleagues [1] add an important point to this discussion by emphasizing the role of monocytes in the overproduction of BAFF in autoimmunity. The authors demonstrate that peripheral pSS monocytes produce significantly higher amounts of
A Phase Space Diagram for Gravity
Xavier Hernandez
Entropy , 2012, DOI: 10.3390/e14050848
Abstract: In modified theories of gravity including a critical acceleration scale a 0, a critical length scale rM = (GM/a 0 )1/2 will naturally arise with the transition from the Newtonian to the dark matter mimicking regime occurring for systems larger than rM. This adds a second critical scale to gravity, in addition to the one introduced by the criterion v < c of the Schwarzschild radius, rS = 2GM/c2. The distinct dependencies of the two above length scales give rise to non-trivial phenomenology in the (mass, length) plane for astrophysical structures, which we explore here. Surprisingly, extrapolation to atomic scales suggests gravity should be at the dark matter mimicking regime there.
Seleno-enzymes and seleno-compounds: the two faces of selenium
Xavier Forceville
Critical Care , 2006, DOI: 10.1186/cc5109
Abstract: Biological and medical advances in the area of selenium provide interest in selenium for both its antioxidant properties through seleno-enzyme incorporation, as illustrated in the previous issue of Critical Care [1], and its direct pro-oxidant toxic effect through seleno-compounds.In intensive care, and especially in septic shock adjunctive therapy, there is a growing interest in the antioxidant role of selenium [2-5]. We know that there is a very low level of selenium in the human (20 mg for the whole body) but that a severe deficiency is lethal [6]. We also know that selenium plays a crucial role in antioxidant defense, as one selenium atom is absolutely required at the active site of all seleno-enzymes in the form of the 21-amino-acid selenocystein [6,7]. Mammals largely use seleno-enzymes for antioxidant purposes, whereas bacteria do not. The seleno-enzymes are ubiquitous in mammal cells and have two main roles. Firstly, the seleno-enzymes protect cell components against oxidation: membranes, enzymes, proteins, and DNA. Secondly, seleno-enzymes inhibit proinflammatory cell metabolisms by reducing the peroxide tone of intracellular water (NF-κB, acid arachidonic and complement cascades, and mitochondria) [6,8]. As a consequence, selenium has been found to improve immunity [6,7]. In septic shock patients there is a dramatic and early decrease of the plasma selenium concentration [9].In the previous issue of Critical Care, Berger and colleagues [1] reported the results of a very interesting aggregative study on a group of 41 severely burnt patients. The authors show a significant reduction of nosocomial pneumonia by intravenous multitrace-element supplements (copper, selenium, and zinc). These results confirm Berger's research on burnt and trauma patients conducted since 1986 [4]. This particular population has lower mortality than septic shock patients [2].The approach of these studies is to increase the antioxidant defense by supplementing patients with multimicr
Bacterial genomics in Spain
Xavier Bosch
Genome Biology , 2003, DOI: 10.1186/gb-spotlight-20040405-01
Abstract: The Network of Bacterial Genomics (RGB), made up of 41 research teams at universities, hospitals, and centers of the Higher Research Council, will allow scientists to share human and technical resources in an effort to understand the genetic roots of bacterial pathogenicity and utility.The network, whose creation was announced last week (March 23), aims to create a critical mass of researchers in the field to allow them, among other things, to apply for joint research projects. Fellows and senior researchers will move freely among the different centers to build their skills not only in the lab but also in bioinformatics. It is planned to organize periodical meetings and congresses of Spanish and foreign researchers.Central to the initiative is the collaboration of five biotech companies - Biomeda, Progenika, Noraybio, Bioalma, and Newbiotech - which will provide the necessary genetic and bioinformatics tools to the scientists.The RGB idea emerged in February in a meeting at the Valencia-based Institute of Cytologic Research. In the meeting, "it became clear that Spain has the capacity to start projects of bacterial genomics," Andrés Moya, head of the University of Valencia's Institute Cavanilles for Biodiversity and Evolutionary Biology, told us. "It's a pity that, given our potential in this area, we can say that our country has contributed to the sequencing of only two microorganisms out of dozens sequenced so far."It was Moya's team that sequenced the genomes of Buchnera aphidicola and Blochmannia floridanus. Moya argues that there is the "wrong perception by managers of national research programs that work in genomics ends with the sequence of a model genome."Comparative genomics analysis, sequencing, and bioinformatics should be added to the "key words already applied to national programs," he adds.Francisco Rodríguez-Valera, at Universidad Miguel Hernández in San Juan de Alicante, notes that in Spain, sparse genomics resources have been almost exclusively devo
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