Mobility of electrons in SnS2−xSex

The electrical resistivities and Hall constants of the semiconducting compounds SnS_2?xSe_x have been measured at temperatures ranging from 100 to 450 K and three donor ionization energies (0.013, 0.086 and 0.25 eV) have been identified. The Hall mobilities exhibit for T> 200K a temperature dependence of the form μ～ (T/T₀)^?n separating the SnS_2?xSe_x compounds into two groups one behaving like SnS₂ and the other like SnSe₂.     

Raman investigation of the drawing effects on Ge-doped fibers

We have investigated the Raman activity of various germanosilicate fibers and their associated preforms. Our data indicate an enhancement in small rings' (3-member rings) concentration in the silica-based matrix of the fibers during the drawing process. The generation of such rings appears compatible with an increase of the sample density and fictive temperature. The data regarding the drawing effects on the fiber stress appear less clear, and it is possible to suggest that in some cases the drawing could lower the tensile stress. Finally we have also provided evidence that changing the drawing conditions within the usual range of application leads to no significant changes of the matrix structure as can be observed using Raman spectroscopy.     

Radiative heat transfer at nanoscale: Closed-form expression for silicon at different doping levels

Radiative heat transfer at the nanoscale is becoming an important technological issue with the development of nano electromechanical systems (NEMS). In this article, we derive asymptotic expressions to compute near-field radiative heat transfer between two planes of silicon. We identify two physical mechanisms that give the dominant contribution at small gaps. For intrinsic and low-doped silicon, the main contribution is due to evanescent waves coming from propagating waves undergoing frustrated total internal reflections at the interfaces. For doping levels larger than N_e=10¹⁶ cm^?3 surface mode coupling contributes to the heat transfer. Asymptotic expressions are also given in that case. In all cases, we compare analytical formulas with exact numerical calculations when varying the temperature and the doping concentration. We also give their range of validity.     

Functional nonparametric estimation of conditional extreme quantiles

We address the estimation of quantiles from heavy-tailed distributions when functional covariate information is available and in the case where the order of the quantile converges to one as the sample size increases. Such “extreme” quantiles can be located in the range of the data or near and even beyond the boundary of the sample, depending on the convergence rate of their order to one. Nonparametric estimators of these functional extreme quantiles are introduced, their asymptotic distributions are established and their finite sample behavior is investigated.     

Reachability analysis of linear systems using support functions

This work is concerned with the algorithmic reachability analysis of continuous-time linear systems with constrained initial states and inputs. We propose an approach for computing an over-approximation of the set of states reachable on a bounded time interval. The main contribution over previous works is that it allows us to consider systems whose sets of initial states and inputs are given by arbitrary compact convex sets represented by their support functions. We actually compute two over-approximations of the reachable set. The first one is given by the union of convex sets with computable support functions. As the representation of convex sets by their support function is not suitable for some tasks, we derive from this first over-approximation a second one given by the union of polyhedrons. The overall computational complexity of our approach is comparable to the complexity of the most competitive available specialized algorithms for reachability analysis of linear systems using zonotopes or ellipsoids. The effectiveness of our approach is demonstrated on several examples.