Showing papers in "Technical Physics Letters in 1997"
TL;DR: In this paper, the effect of non-locality of the electron energy distribution near the head of a streamer in air was studied and it was shown that taking into account the nonlocality increases the electron field strength and the electron density in the channel.
Abstract: Computer simulation is used to study the effect on the parameters of the streamer plasma due to the nonlocality of the electron energy distribution near the head of a streamer in air. Taking into account the nonlocality increases the electron field strength in the head and the electron density in the channel. The streamer radius decreases, while the streamer velocity and current as well as the efficiency of generating chemically active particles remain essentially the same as in the local approach.
47 citations
TL;DR: The existence of large-scale structures in the form of a vortical double helix in a swirling Ranque flow is observed for the first time in this paper, where the structure of the vortial double helike is visualized in real time by the method of Hilbert bichromatic filtering.
Abstract: The existence of large-scale structures in the form of a vortical double helix in a swirling Ranque flow is observed for the first time. The structure of the vortical double helix is visualized in real time by the method of Hilbert bichromatic filtering. The experimental result is interpreted on the basis that the most probable physical mechanism for the spatial energy separation in the gas flow (i.e., for the so-called Ranque effect) is viscous heating of the gas in a thin boundary layer at the walls of the vortex chamber and the adiabatic cooling at the center owing to the formation of an intense vortex braid near the axis.
44 citations
TL;DR: In this paper, the influence of an external, pulse-periodic, energy supply source on the aerodynamic characteristics of a hemisphere positioned downstream is simulated, and the effects of the external energy supply on aerodynamic properties are investigated.
Abstract: The influence of an external, pulse-periodic, energy supply source on the aerodynamic characteristics of a hemisphere positioned downstream is simulated.
38 citations
TL;DR: In this paper, an iterative algorithm is presented for calculating diffractive phase optical elements that form light beams which are an effective superposition of a small number of nonradially symmetric Gauss-Laguerre modes with a prescribed energy contribution from each mode.
Abstract: An iterative algorithm is presented for calculating diffractive phase optical elements that form light beams which are an effective superposition of a small number of nonradially symmetric Gauss-Laguerre modes with a prescribed energy contribution from each mode.
29 citations
TL;DR: In this paper, it was shown that electrode erosion in pulsed discharges in water is governed by a thermal cavitation effect, and it has been shown that blowing gas through the water modifies the cavity effect, simplifies breakdown, and allows solid electrodes to be used.
Abstract: It has been shown that electrode erosion in pulsed discharges in water is governed by a thermal cavitation effect. Blowing gas through the water modifies the cavitation effect, simplifies breakdown, and allows solid electrodes to be used.
29 citations
TL;DR: In this article, it was shown that for a medium with the dielectric function given by the expression e=e1+e2−e1)tanh(E2/Es2), where e1 and e2 are constants and Es is the saturation field, there is a threshold value of the power density at which a nonlinear surface wave can be excited.
Abstract: It is shown that for a medium with the dielectric function given by the expression e=e1+(e2−e1)tanh(E2/Es2), where e1 and e2 are constants and Es is the saturation field, there is a threshold value of the power density at which a nonlinear surface wave can be excited.
25 citations
TL;DR: In this paper, the possibility of using amorphous silicon and germanium films prepared by magnetron sputtering as components in uncooled microbolometers has been analyzed experimentally and results are presented.
Abstract: The possibility of using amorphous silicon and germanium films prepared by magnetron sputtering as components in uncooled microbolometers has been analyzed experimentally and results are presented. Amorphous silicon and germanium films having activation energies of 0.135 and 0.2 eV, and resistivities of 50 and 0.4 kΩ·cm, respectively, were fabricated.
24 citations
TL;DR: In this article, a study of the change in the structure of a shock wave in a decaying discharge plasma with Mach numbers between 1.2 and 2 was made, and the times of the main processes responsible for this effect were determined.
Abstract: A study has been made of the change in the structure of a shock wave in a decaying discharge plasma with Mach numbers between 1.2 and 2. A novel method is proposed to investigate the rearrangement of the shock wave structure under transient conditions. The times of the main processes responsible for this effect are determined.
23 citations
TL;DR: In this paper, the feasibility of using photodeflection and photoacoustic microscopy to detect subsurface lateral and vertical cracks, as well as residual internal stresses induced by Vickers indentation in silicon nitride ceramic has been investigated.
Abstract: The feasibility of using photodeflection and photoacoustic microscopy to detect subsurface lateral and vertical cracks, as well as residual internal stresses induced by Vickers indentation in silicon nitride ceramic has been investigated. It is shown that the normal component of the photodeflection signal can be used to detect lateral subsurface cracks and the tangential component to detect vertical cracks. It is established that the sensitivity of the photoacoustic method to residual internal stresses arises from the dependence of the elastic parameters or the coefficient of thermal expansion of the silicon nitride ceramic on the internal stresses.
21 citations
TL;DR: In this paper, a 2.5-dimensional particle-in-cell code was used to simulate different scenarios for the establishment of an electron beam "squeezed state" in a magnetically insulated vircator.
Abstract: A 2.5-dimensional particle-in-cell code was used to simulate different scenarios for the establishment of an electron beam “squeezed state” in a magnetically insulated vircator. Vircators with and without anode foils were compared. It was found that the squeezed state is established in both cases but the dynamics of establishment differ.
19 citations
TL;DR: In this article, a series of thermoelements and thermoelectric generators having wide-ranging applications were developed for a variety of applications, such as switching and antidiffusion metal coatings.
Abstract: Semiconducting compounds based on silicides of 3d transition metals (MnSi1.75 and CoSi) are promising thermoelectric materials for mass-produced thermoelectric generators. Their practical use has been delayed so far by the lack of reliable switching. Electrochemical surface treatment technology and metal deposition were used to obtain thermal-cycling-resistant, switching and antidiffusion metal coatings (Ni, Co, Fe, Cr) with an electrical resistivity up to 10−6 Ω·cm2 in the metal-semiconductor region. This technology was applied to develop a series of thermoelements and thermoelectric generators having wide-ranging applications.
TL;DR: In this paper, a computer simulation is made of the grain boundary behavior in an aluminum sample under conditions of fast shear loading, and the calculations are made using a molecular dynamics method and pseudopotential theory.
Abstract: A computer simulation is made of the grain boundary behavior in an aluminum sample under conditions of fast shear loading. The calculations are made using a molecular dynamics method and pseudopotential theory. It is observed that under these loading conditions, the grain boundaries may undergo displacement at an anomalously high speed, even exceeding the rate of the applied shear. The atomic mechanisms responsible for this effect are investigated.
TL;DR: In this article, the authors describe a new cw laser with tunnel-coupled vertically aligned InGaAs quantum dots in an AlGaAs matrix with a room-temperature output power of ∼ 1 W at both mirrors.
Abstract: This paper describes a new cw laser with tunnel-coupled vertically aligned InGaAs quantum dots in an AlGaAs matrix with a room-temperature output power of ∼ 1 W at both mirrors. The maximum operating temperature of the heat sink is ∼ 75 °C.
TL;DR: In this article, a design for a device consisting of two optically coupled vertical microcavities was proposed, and the feasibility of using this design to develop optoelectronic devices was analyzed.
Abstract: A design is proposed for a device consisting of two optically coupled vertical microcavities. It is shown that interaction between two localized optical modes in the coupled microcavities induces mode splitting. The feasibility of using this design to develop optoelectronic devices is analyzed.
TL;DR: In this paper, the adsorption of C60 molecules on the surface of a rhenium ibbon heated to 1800 K is investigated quantitatively, and it is found that the C60 molecule are adsorbed without reflection and then dissociate, and the carbon formed in the process is dissolved in the bulk of the rheniam to the limit of solubility.
Abstract: The adsorption of C60 molecules on the surface of a rhenium ibbon heated to 1800 K is investigated quantitatively. It is found that the C60 molecules are adsorbed without reflection and then dissociate, and the carbon formed in the process is dissolved in the bulk of the rhenium to the limit of solubility. Then a graphite monolayer forms on the rhenium surface, and the dissociation of the C60 molecules stops. It is shown that the C60 molecules can be used as an effective carbonizing object on metals in ultrahigh vacuum.
TL;DR: In this article, experimental data are obtained which indicate some characteristic features of the plasma-surface interaction leading to the emission of electrons from the walls of the accelerating channel and the evolution of a specific beam instability.
Abstract: Experimental data are obtained which indicate some characteristic features of the plasma-surface interaction leading to the emission of electrons from the walls of the accelerating channel and the evolution of a specific beam instability of the plasma flux.
TL;DR: Cadmium oxide films obtained by magnetron sputtering of a cadmium target in a nitrogenoxygen mixture are investigated in this paper, and it is concluded that the practical utilization of CdO films as transparent electrodes would be worthwhile.
Abstract: Cadmium oxide films obtained by magnetron sputtering of a cadmium target in a nitrogenoxygen mixture are investigated. It is established that these films have a lower resistivity than do films obtained by other methods. It is concluded that the practical utilization of CdO films as transparent electrodes would be worthwhile.
TL;DR: Laser cooling of resonant ions is shown to be applicable to the effective control of the temperature of charged particles in a low-temperature electron-ion plasma confined in a magnetic trap as mentioned in this paper.
Abstract: Laser cooling of resonant ions is shown to be applicable to the effective control of the temperature of charged particles in a low-temperature electron-ion plasma confined in a magnetic trap.
TL;DR: In this paper, double-heterostructures based on the solid solution GaInAsSb were studied and continuous-wave optical power of 1.2 mW was achieved.
Abstract: GaAlAsSb/GaInAsSb/GaAlAsSb double-heterostructure LEDs emitting in the region of the 2.35 μm absorption band of methane have been developed for fast gas analyzers. Different designs of double heterostructures based on the solid solution GaInAsSb were studied. Continuous-wave optical power of 1.2 mW was achieved. The methane absorption spectrum for the LED radiation is presented.
TL;DR: In this article, it was shown that intense ultrasound gives rise to the experimentally observed nonlocality of the acoustodislocation interaction, manifested as a hysteretetic dependence of the damping coefficient of an acoustic wave on the wave amplitude, including a decrease in damping.
Abstract: It is shown that intense ultrasound gives rise to the experimentally observed nonlocality of the acoustodislocation interaction, manifested as a hysteretetic dependence of the damping coefficient of an acoustic wave on the wave amplitude, including a decrease in damping
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TL;DR: In this paper, the first experiments on the production of zinc oxide whiskers in air without crystallization chambers or reactors, using CO2-laser radiation, were described, and the features of their exciton luminescence were studied, and compared with bulk single crystals and epitaxial layers of Zno.
Abstract: This paper describes the first experiments on the production of zinc oxide whiskers in air without crystallization chambers or reactors, using CO2-laser radiation. The features of their exciton luminescence are studied, and they are compared with bulk single crystals and epitaxial layers of Zno.
TL;DR: In this article, an investigation is made of the generation and relaxation of an electric field in natural dielectrics exposed to mechanical loading and applied electric potentials, and it is shown that these processes are identical.
Abstract: An investigation is made of the generation and relaxation of an electric field in natural dielectrics exposed to mechanical loading and applied electric potentials It is shown that these processes are identical
TL;DR: In this paper, a light-sensitive material consisting of glycerin-containing bichromated gelatin has been prepared and used to record real-time volume holograms with 0.44 μm helium-cadmium laser radiation.
Abstract: A thick-layer light-sensitive material consisting of glycerin-containing bichromated gelatin has been prepared and used to record real-time volume holograms with 0.44 μm helium-cadmium laser radiation. The thickness of the layers is 400–600 μm. The holographic sensitivity of the material is 1 J/cm2. The highest diffraction efficiency of holograms recorded using a symmetric system with parallel beams is 32%.
TL;DR: In this article, the thermal degradation of polymethyl methacrylate, synthesized by the method of free-radical polymerization, in a mixture with C60 fullerene has been investigated by mass-spectrometric thermal analysis.
Abstract: The thermal degradation of polymethyl methacrylate, synthesized by the method of free-radical polymerization, in a mixture with C60 fullerene has been investigated by mass-spectrometric thermal analysis. C60 suppresses the first two, low-temperature, stages in the thermal degradation of polymethyl methacrylate and thereby increases its thermal stability.
TL;DR: In this paper, a two-section InGaAsP/InP Fabry-Perot laser was used to obtain wavelength tuning over a 12 nm range for a 2D laser.
Abstract: Wavelength tuning over a 12 nm range is obtained for a two-section InGaAsP/InP Fabry-Perot laser (λ=1.55 μm). The method used to vary the gain profile of the laser allows one to predict the range of possible wavelength tuning.
TL;DR: In this article, a new hysteresis effect is described in metal-porous-silicon-p-type silicon structures and a new model is proposed to describe current flow in these structures.
Abstract: A new hysteresis effect is described in metal-porous-silicon-p-type silicon structures and a new model is proposed to describe current flow in these structures.
TL;DR: In this paper, it was shown that the kinetics of change in the concentration of air bubbles can be observed from the change in spin-spin relaxation time, which can be used to determine the mean radius of air bubble in distilled water.
Abstract: Nuclear magnetic resonance has been used to determine the mean radius of air bubbles in distilled water that has stood for a long time and the volume concentration of these “reduced to mean radius” bubbles. It is shown that the kinetics of the change in the concentration of these bubbles can be observed from the change in the spin-spin relaxation time.
TL;DR: In this paper, a method for investigating the dynamic adiabatic compression curves of powders by measuring of the pulsed pressure in a powder pressed uniaxially by an elastic instrument is described.
Abstract: A method is described for investigating the dynamic adiabatic compression curves of powders by measuring of the pulsed pressure in a powder pressed uniaxially by an elastic instrument. The instantaneous powder density is determined by numerical solution of a pulsed spectral problem using the pressing pressure pulse and the known characteristics of the pressing instrument and the external force.
TL;DR: In this article, a statistical foundation is given for the evolution equations for the tensor order parameter, which characterizes an ensemble of such defects and has the meaning of nonequilibrium fluctuations of the strain rate.
Abstract: A possible mechanism for turbulence is proposed and substantiated for the first time, whereby turbulence is considered as a nonequilibrium transition in ensembles of defects of the microscopic shear type, which are treated as real defects in the molecular structure of liquids. A statistical foundation is given for the evolution equations for the tensor order parameter, which characterizes an ensemble of such defects and has the meaning of nonequilibrium fluctuations of the strain rate. The types of macroscopic fluctuation modes of the strain rate are determined as self-similar solutions of the evolution equations for this tensor order parameter under conditions of nonequilibrium transitions, and qualitative correspondences are established between these solutions and real scenarios for the transition to turbulence. The Kolmogorov scaling laws (the natures of the “viscous” and “ inertial” intervals) are explained for fully developed turbulence.
TL;DR: The most accurate expressions for determining stresses in coatings, for example, in aluminum nitride on molybdenum, are derived in this article, where it is shown that Stoney's formula is of limited applicability, over-or underestimating the true values of the stresses.
Abstract: The most accurate expressions for determining stresses in coatings, for example, in aluminum nitride on molybdenum, are derived. The stress curve has a characteristic shape, and for this reason it is proposed that the entire system be called a “z system.” It is shown that Stoney’s formula is of limited applicability, over-or underestimating the true values of the stresses.