scholarly journals About one decision of the quasiclassical kinetic equation

2018 ◽  
Vol 7 (2.23) ◽  
pp. 270
Author(s):  
Gladkov S O ◽  
Bogdanova S B
Keyword(s):  
Distribution Function ◽  
Perturbation Theory ◽  
Relaxation Time ◽  
Kinetic Equation ◽  
General Solution ◽  
Time Approximation ◽  
Relaxation Time Approximation ◽  
Fermi Statistics ◽  
Non Equilibrium

It has been proved that the solution of the quasi-classical kinetic equation for Bose and Fermi statistics can be represented in the general form, using the relaxation time approximation. The general solution found for the distribution function  helps calculate any non – equilibrium characteristics of metals, magnets, and dielectrics in any order of the perturbation theory according to the relaxation time .  

scholarly journals Bulk viscosity of strongly interacting matter in the relaxation time approximation

2018 ◽  
Vol 97 (4) ◽  
Author(s):  
Alina Czajka ◽  
Sigtryggur Hauksson ◽  
Chun Shen ◽  
Sangyong Jeon ◽  
Charles Gale
Keyword(s):  
Relaxation Time ◽  
Bulk Viscosity ◽  
Time Approximation ◽  
Relaxation Time Approximation ◽  
Strongly Interacting

scholarly journals Calculations of the thermal conductivity of Si1-xGex films with nonuniform composition

2018 ◽  
Vol 19 (1) ◽  
pp. 48-52
Author(s):  
V. V. Kuryliuk ◽  
O. M. Krit
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Boltzmann Equation ◽  
Temperature Interval ◽  
Thermoelectric Properties ◽  
Bulk Material ◽  
Nonuniform Distribution ◽  
Time Approximation ◽  
Relaxation Time Approximation ◽  
Available Information

SiGe films have attracted much attention recently due to experimental demonstrations of improved thermoelectric properties over those of the corresponding bulk material. However, despite this increasing attention, available information on the thermoelectric properties of Si1-xGex films is quite limited, especially for nonuniform composition in wide temperature interval. In this paper we have used the Boltzmann equation under the relaxation-time approximation to calculate the thermal conductivity of Si1-xGex films with nonuniform composition. It is confirmed that SiGe films with nonuniform composition has significantly lower thermal conductivity than its uniform counterpart. This suggests that an improvement in thermoelectric properties is possible by using the SiGe films with nonuniform distribution of germanium.

Longitudinal magnetoresistance in silver and copper between 4.2 and 35 °K

1967 ◽  
Vol 302 (1468) ◽  
pp. 83-98 ◽  
Keyword(s):  
Relaxation Time ◽  
Electron Scattering ◽  
Small Angle ◽  
Time Approximation ◽  
Long Wavelength ◽  
Relaxation Time Approximation ◽  
Angle Scattering ◽  
Different Types ◽  
Pure Single Crystal ◽  
Longitudinal Magnetoresistance

Longitudinal magnetoresistance has been measured in a number of single crystals of silver and one very pure single crystal of copper in fields up to 65 kG and at temperatures between 4.2 and 35 °K. The purpose of the work has been to investigate the effects of different types of electron scattering, in particular small angle scattering. It has been found that at 4.2 °K impure crystals obey the relaxation time approximation fairly well, whereas crystals that have been purified (by oxidation at 800 °C) do not. Above 4.2 °K, the addition of long wavelength phonons has caused the magnetoresistance to increase substantially, as predicted by Pippard (1964), but agreement with Pippard’s theory is only qualitative. To account for the results a more detailed treatment of the scattering is required.

LATTICE THERMAL CONDUCTIVITY IN A HOLLOW SILICON NANOWIRE

2005 ◽  
Vol 19 (06) ◽  
pp. 1017-1027 ◽  
Author(s):  
WEI-QING HUANG ◽  
KE-QIU CHEN ◽  
Z. SHUAI ◽  
LINGLING WANG ◽  
WANGYU HU
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Time ◽  
Lattice Thermal Conductivity ◽  
Silicon Nanowire ◽  
Boundary Scattering ◽  
Phonon Confinement ◽  
Time Approximation ◽  
Si Nanowire ◽  
Scattering Mechanisms ◽  
Relaxation Time Approximation

We theoretically investigate the lattice thermal conductivity of a hollow Si nanowire under the relaxation time approximation. The results show that the thermal conductivity in such structure is decreased markedly below the bulk value due to phonon confinement and boundary scattering. The thermal conductivities under different scattering mechanisms are given, and it is found that the boundary scattering is dominant resistive process for the decrease of the thermal conductivity.

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