Monte Carlo transient phonons transport in silicon and germanium at nanoscales

Heat transport at nanoscales in semiconductors is investigated with a statistical method. The Boltzmann Transport Equation (BTE) which characterize phonons motion and interaction within the crystal lattice has been simulated with a Monte Carlo technique. Our model takes into account media frequency properties through the dispersion curves for longitudinal and transverse acoustic branches. The BTE collisional term involving phonons scattering processes is simulated with the Relaxation Times Approximation theory. A new distribution function accounting for the collisional processes has been developed in order to respect energy conservation during phonons scattering events. This non deterministic approach provides satisfactory results in what concerns phonons transport in both ballistic and diffusion regimes. The simulation code has been tested with silicon and germanium thin films; temperature propagation within samples is presented and compared to analytical solutions (in the diffusion regime). The two materials bulk thermal conductivity is retrieved for temperature ranging between 100 K and 500 K. Heat transfer within a plane wall with a large thermal gradient (250 K-500 K) is proposed in order to expose the model ability to simulate conductivity thermal dependence on heat exchange at nanoscales. Finally, size effects and validity of heat conduction law are investigated for several slab thicknesses

Variational Displacement Method for Geosynthetically Reinforced Slope Stability Analysis:II. Global Stability

International audienceThis paper presents the global stability analysis of geosynthetically reinforced slopes. It is a development of the French “displacement method” for geosynthetically reinforced slope stability analysis. The global stability analysis requires the determination of the reinforcement tensions, which is presented in a companion paper. In this paper, the variational limit equilibrium method, formulated by Baker and Garber in the case of unreinforced slopes, is applied to the case of reinforced slopes. This variational analysis has shown that the results obtained by Baker and Garber are still valid in the present case. A parametric study showing the influence of different geometrical parameters on the design is presented and discussed. These results are compared with those of the original “displacement method”, in order to show the improvement of the method

Hfe : une molécule à l’interface entre immunité et métabolisme du fer ?

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