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Analysis of a Generalized Dispersive Model Coupled to a DGTD Method with Application to Nanophotonics
No full textInternational audienceIn this paper, we are concerned with the numerical modelling of the propagation of electromagnetic waves in dispersive materials for nanophotonics applications. We focus on a generalized model that allows for the description of a wide range of dispersive media. The underlying differential equations are recast into a generic form, and we establish an existence and uniqueness result. We then turn to the numerical treatment and propose an appropriate discontinuous Galerkin time domain framework. We obtain the semidiscrete convergence and prove the stability (and to a larger extent, convergence) of a Runge--Kutta 4 fully discrete scheme via a technique relying on energy principles. Finally, we validate our approach through two significant nanophotonics test cases
Three-dimensional Simulations and Spacecraft Observations of Sub-ion Scale Turbulence in the Solar Wind: Influence of Landau Damping
No full textInternational audienceThree-dimensional nonlinear finite Larmor radius (FLR)–Landau fluid simulations, which include some small-scale kinetic effects, are performed to explore the nature of the sub-ion scale turbulence in the solar wind and to investigate the role of Landau damping and FLR corrections. The resulting steady-state magnetic power spectrum in the dispersive range display exponents that vary within a range of values compatible with statistical results reported from in situ spacecraft measurements of solar wind turbulence as well as from gyrokinetic simulations. The spectral slopes are shown to depend on the strength of the nonlinear effects and on the scale at which turbulent fluctuations are driven in the simulations. The influence of Landau damping is addressed by comparison with simulations where the double-adiabatic closure is imposed. The role of FLR corrections is also analyzed. Comparison with in situ observations in the solar wind are performed to enlighten the influence of the fluctuations power at different scales on the spectral slopes in the sub-ion range. Using diagnosis of both magnetic compressibility and frequency-wavenumber spectra, it is shown that in spite of the evidence of the presence of fast-magnetosonic modes, the magnetic energy is mostly distributed around the kinetic Alfvén waves and the slow modes, in agreement with solar wind measurements. The observed large broadening about the linear dispersion relations may reflect the presence of coherent structures
Scheduling on power-heterogeneous processors
No full textInternational audienceWe consider the problem of scheduling a set of jobs, each one specified by its release date, its deadline and its processing volume, on a set of heterogeneous speed-scalable processors, where the energy-consumption rate is processor-dependent. Our objective is to minimize the total energy consumption when both the preemption and the migration of jobs are allowed. We propose a new algorithm based on a compact linear programming formulation. Our method approaches the value of the optimal solution within any desired accuracy for a large set of continuous power functions. Furthermore, we develop a faster combinatorial algorithm based on flows for standard power functions and jobs whose density is lower bounded by a small constant. Finally, we extend and analyze the AVerage Rate (AVR) online algorithm in the heterogeneous setting
The Irredundance-related Ramsey Numbers s(3,8) = 21 and w(3,8) = 21
No full textInternational audienceThe irredundant Ramsey number s = s(m, n) is the smallest natural number s such that in any red-blue edge colouring (R, B) of the complete graph of order s, it holds that IR(B) ≥ m or IR(R) ≥ n, where IR denotes the irredundance number of a graph. Furthermore, the mixed irredundant Ramsey number t = t(m, n) [irredundant-domination Ramsey number w = w(m, n), respectively] is the smallest natural number t [w, respectively] such that in any red-blue edge colouring (R, B) of the complete graph of order t [w, respectively], it holds that IR(B) ≥ m or α(R) ≥ n [IR(B) ≥ m or Γ(R) ≥ n, respectively], where α and Γ denote respectively the (vertex) independence number and the upper domination number of a graph. These three classes of Ramsey numbers have previously been studied in the literature. In this paper, we employ a computer search to determine complete sets of avoidance colourings for the Ramsey numbers t(3, 7) and t(3, 8). In the process the two previously unknown Ramsey numbers s(3, 8) = 21 and w(3, 8) = 21 are established
Représentations alternatives du genre : l’incorporation d’un ethos combattif dans la pratique du de l’autodéfense féministe et du karaté en non-mixité
No full textInternational audienceCet article porte sur la pratique de l’autodéfense féministe et du karaté en non-mixité comme lieu de subversion des rapports de genre. Je reviens dans un premier temps sur les activités physiques et sportives comprises comme « technologie de genre » puis m’intéresse aux modalités concrètes de l’incorporation d’un ethos combattif à l’œuvre dans ces deux pratiques afin de montrer en quoi elles contribuent à la mise à mal à de l’ordre du genre. Cela permet d’envisager le corps comme un lieu de prise de conscience tout autant que comme un lieu de déconstruction des normes de genre
Stem Cell-Like Properties of CK2β-down Regulated Mammary Cells
No full textInternational audienceThe ubiquitous protein kinase CK2 has been demonstrated to be overexpressed in a number of human tumours. This enzyme is composed of two catalytic α or α' subunits and a dimer of β regulatory subunits whose expression levels are probably implicated in CK2 regulation. Several recent papers reported that unbalanced expression of CK2 subunits is sufficient to drive epithelial to mesenchymal transition, a process involved in cancer invasion and metastasis. Herein, through transcriptomic and miRNA analysis together with comparison of cellular properties between wild type and CK2β-knock-down MCF10A cells, we show that down-regulation of CK2β subunit in mammary epithelial cells induces the acquisition of stem cell-like properties associated with perturbed polarity, CD44high/CD24low antigenic phenotype and the ability to grow under anchorage-independent conditions. These data demonstrate that a CK2β level establishes a critical cell fate threshold in the control of epithelial cell plasticity. Thus, this regulatory subunit functions as a nodal protein to maintain an epithelial phenotype and its depletion drives breast cell stemness
Transferts thermiques dans les blankets aérogels de silice
No full textInternational audienceLes aérogels de silice sont des matériaux ultra poreux constitués de nanoparticules de silice amorphes, interconnectées en un réseau 3D fractal aléatoire. Leur texture mésoporeuse en fait d'excellents isolants thermiques qui suscitent beaucoup d'intérêt pour réduire les déperditions à travers les enveloppes. Pour pallier à leur fragilité mécanique, un réseau fibreux est ajouté permettant d'obtenir un matériau composite – appelé blanket aérogel-renforcé, flexible, tout en conservant une faible conductivité thermique effective. Le transfert de chaleur dans ces matériaux est complexe et résulte de quatre contributions : transfert radiatif, conduction solide au sein des fibres et de la matrice, conduction gazeuse et couplages entre les modes de transfert précédents. Des modèles de conductivité thermique du composite sont présentés et discutés dans notre étude, et peuvent être utilisés pour aider à optimiser les paramètres de conception du matériau en cherchant à minimiser sa conductivité thermique effective
Defect-free InGaN nanowires on silicon whatever the indium composition
No full textInternational audienc
Online recognition of daily activities by color-depth sensing and knowledge models
No full textInternational audienceVisual activity recognition plays a fundamental role in several research fields as a way to extract semantic meaning of images and videos. Prior work has mostly focused on classification tasks, where a label is given for a video clip. However, real life scenarios require a method to browse a continuous video flow, automatically identify relevant temporal segments and classify them accordingly to target activities. This paper proposes a knowledge-driven event recognition 5 framework to address this problem. The novelty of the method lies in the combination of a constraint-based ontology language for event modeling with robust algorithms to detect, track and re-identify people using color-depth sensing (Kinect sensor). This combination enables to model and recognize longer and more complex events and to incorporate domain knowledge and 3D information into the same models. Moreover, the ontology-driven approach enables human understanding of system decisions and facilitates knowledge transfer across different scenes. The proposed framework is evaluated with real-world recordings of seniors carrying out unscripted, daily activities at hospital observation rooms and nursing homes. Results demonstrated that the proposed framework outperforms state-of-the-art methods in a variety of activities and datasets, and it is robust to variable and low-frame rate recordings. Further work will investigate how to extend the proposed framework with uncertainty management techniques to handle strong occlusion and ambiguous semantics, and how to exploit it to further support medicine on the timely diagnosis of cognitive disorders, such as Alzheimer's disease