Electron and Phonon Thermal Waves in Semiconductors: an Application to Photothermal Effects

The electron and phonon temperature distribution function are calculated in semiconductors. We solved the coupled one-dimensional heat-diffussion equations in the linear approximation in which the physical parameters on the sample are independent of the temperature. We also consider the heat flux at the surface of the semiconductor as a boundary condition for each electron and phonon systems instead of using a fixed temperature. From this, we obtain an expression for electron and phonon temperature respectively. The characterization of the thermal waves properties is duscussed and some practical procedures for this purpose provide us information about the electron and phonon thermal parameters.Comment: 12 pages, amstex and amssymb macro package (LaTeX2e edition

Molecular random walks and invariance group of the Bogolyubov equation

Statistics of molecular random walks in a fluid is considered with the help of the Bogolyubov equation for generating functional of distribution functions. An invariance group of solutions to this equation as functions of the fluid density is discovered. It results in many exact relations between probability distribution of the path of a test particle and its irreducible correlations with the fluid. As the consequence, significant restrictions do arise on possible shapes of the path distribution. In particular, the hypothetical Gaussian form of its long-range asymptotic proves to be forbidden (even in the Boltzmann-Grad limit). Instead, a diffusive asymptotic is allowed which possesses power-law long tail (cut off by ballistic flight length).Comment: 23 pages, no figures, LaTeX AMSART, author's translation from Russian of the paper accepted to the TMPh (``Theoretical and mathematical physics''

Efficiency of using dump trucks BELAZ-75180

A comparative analysis of operational characteristics when using a different type of chassis of BELAZ-75180 mining dump trucks was performed. It is shown that the choice of the type and means of mining transport is determined by several factors, and, first of all, the characteristics of the cargo being transported, the distance of transportation, speed of flights, and the leverage for the given period. The power of vehicles and the performance of a mining dump truck depend on the scale of work (cargo turnover). The dependence of energy consumption during transport work on a quarry on the average size of pieces of rock is disclosed. The analysis of the dependence of the number of backup dump trucks on their number operating in a specific period is given. As a result of the analysis of operational characteristics, it was found that the chassis type of the BELAZ-75180 mining dump truck significantly affects its performance. © Published under licence by IOP Publishing Ltd

Analysis of the operational characteristics of the main units of BelAZ vehicles in a coal mine

A comparative analysis of the operational characteristics of the main components of BELAZ mining vehicles has been carried out. It is shown that the choice of type and means of career transport is determined by a number of factors and, first of all, by the characteristics of the transported cargo, the distance of transportation, the scale of work and the pace of their development. The power of vehicles depends on the scale of work (freight turnover), and the pace of mining operations determines the requirements for the operational reliability of career vehicles. The dependence of the dump truck failure parameter on the service life is disclosed. The analysis of the state of metal structures of structural elements of the dump truck BELAZ-7530 based on the method of non-destructive testing is given. As a result of the analysis of thermal imaging and measurements of the thickness of the walls of the motor housing, it was established that the amount of wear depends on the heating temperature of the metal structures. © Published under licence by IOP Publishing Ltd

Calibration of Troitsk nu-mass detector readout electronics by signal digital filters

We present the results of tuning and calibration of the detector electronics in the signal digitization mode. The goal of the experiment is to search for a possible sterile neutrino signature in tritium beta-decay. The read-out electronics work in direct oscilloscope mode, which requires to optimize time frame the with the goal to minimize noise and energy resolution. We use a 7-pixel silicon drift detector (SDD) and a CMOS charge sensitive preamplifier with very low integration capacitor. Amplifier forms a slowly rising output shape and operates in pulse-reset mode. The 125 MHz ADC digitizes the signals. Using calibration data from Fe55 and Am241 gamma sources we check triangular and trapezoid digital filters to obtain the best noise and energy resolution performance. We are also examining the option to differentiate the output signal.Comment: 9 pages, 8 figure

OPTICAL DEFLECTOR CREATION FOR LASER THERAPEUTIC DEVICES

The paper deals with creation of optical deflector for management of laser radiation in physiotherapeutic devices. Design features and operation principles of electro-optical, optical-acoustic and mechanical deflectors, giving the possibility to carry out continuous or discrete scanning of a laser beam are shown. Operation mechanism of the mechanical type deflector on the example of domestic laser therapeutic scanners is described in detail. Application possibility in clinical practice for heating technique of the acupuncture points by volumetric scanning of tissues by the radiation of semiconductor lasers on wave lengths equal to 0,67 and 0,85 μm is investigated. Creation justification of the new type deflector is given. Comparison between stable and labile techniques of radiation is carried out. It is shown that more intensive warming up of a skin surface in acupuncture point projection is observed at volumetric scanning, rather than at planar scanning by laser beams. Temperature increase on a skin surface in projection of acupuncture points is detected at radiation in both the visible spectrum range (0,67 μm) and the infrared range (0,85 μm). It gives the possibility to apply this scanning method to thermal photo-activation of the point and to extend an existing arsenal of laser reflexology methods. The optical deflector is offered for medical industry, making it possible to carry out volumetric scanning of a laser beam and to facilitate the medical personnel’s work in laser therapy and reflexology consulting rooms

Mössbauer study of surface layers of high-speed steel after laser treatment

Mossbauer measurements in the backscattering geometry have been employed to determine an effect of the laser pulse duration on phase transformations and tungsten redistribution in the laser-affected area in the Tl high-speed steel. It has been found that after laser processing in the surface layer 10 μm thick the phase composition becomes homogeneous, the quantity of the retained austenite decreases with the rise in the laser pulse duration, the solid solution as a result of partial solution of carbides is saturated with tungsten up to 10 and 14 percent, the pulse durations being 1.2 and 6.0 ms respectively. © 1991 J.C. Baltzer A.G., Scientific Publishing Company

"Resonance" phenomena in thermal diffusion processes in two-layer structures

The dependence on chopper frequency of the effective thermal diffusivity and effective thermal conductivity in photoacoustic experiments is discussed. The theoretical model of a two-layer structure at rear-surface illumination in the high frequency limit is considered. It is shown that the effective thermal diffusivity presents ``resonance'' while the effective thermal conductivity sharply changes its magnitude and sign. Such ``resonant'' behavior strongly depends on the surface thermal conductivities associated with the interface thermal contacts.Comment: 13 pages, 3 figure

Minimal Work Principle and its Limits for Classical Systems

The minimal work principle asserts that work done on a thermally isolated equilibrium system, is minimal for the slowest (adiabatic) realization of a given process. This principle, one of the formulations of the second law, is operationally well-defined for any finite (few particle) Hamiltonian system. Within classical Hamiltonian mechanics, we show that the principle is valid for a system of which the observable of work is an ergodic function. For non-ergodic systems the principle may or may not hold, depending on additional conditions. Examples displaying the limits of the principle are presented and their direct experimental realizations are discussed.Comment: 4 + epsilon pages, 1 figure, revte

Fluctuation theorems for stochastic dynamics

Fluctuation theorems make use of time reversal to make predictions about entropy production in many-body systems far from thermal equilibrium. Here we review the wide variety of distinct, but interconnected, relations that have been derived and investigated theoretically and experimentally. Significantly, we demonstrate, in the context of Markovian stochastic dynamics, how these different fluctuation theorems arise from a simple fundamental time-reversal symmetry of a certain class of observables. Appealing to the notion of Gibbs entropy allows for a microscopic definition of entropy production in terms of these observables. We work with the master equation approach, which leads to a mathematically straightforward proof and provides direct insight into the probabilistic meaning of the quantities involved. Finally, we point to some experiments that elucidate the practical significance of fluctuation relations.Comment: 48 pages, 2 figures. v2: minor changes for consistency with published versio