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Vestnik NSU. Series: Physics. 2014. V9, i 2 |
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Radiophysics and Electronics |
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Mikerin S. L., Poteshkina K. D., Plekhanov A. I. Terahertz Spectrometer Based on Femtosecond Laser for a Scientific Research Terahertz (THz) spectrometer using femtosecond titanium-sapphire laser was developed. Experimental stand of the multi-purpose application was realized by using this spectrometer. It was realized to obtaining of the complex refractive index spectra of a large aperture samples and to research of the emission efficiency of THz radiation in a nonlinear optical media. It was proposed a method of spectrometer's absolute calibration by THz electrical field through an external control of polarization of the probe radiation. The threshold sensitivity to polarization changes was measured. It was 1.4 ± 0.5 ?rad. It allows to estimate the threshold of THz field strength ~ 0.1 V/cm when zinc telluride crystal is used to detection. Width of the apparatus function of spectrometer was 9 GHz and it was estimated from the width of narrow lines of the water vapor in absorption spectrum of air gap. It well agrees with the theoretical estimation. |
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High-Energy and Accelerator Physics, Physics of High-Temperature Plasma |
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Solomakhin A. L., Bagryansky P. A., Kovalenko Yu. V., Savkin V. Ya., Yakovlev D. V. Electron Cyclotron Resonance Heating of Plasma in the Gas Dynamic Trap Electron cyclotron resonance plasma heating (ECRH) system has been recently installed on the
gas dynamic trap (GDT) magnetic mirror. Two microwave beams are injected into the plasma at an
angle of 36° with respect to the machine axis in a form of extraordinary (X) waves which are subsequently
absorbed in the first harmonic cyclotron resonance. Each microwave beam is generated by a
Buran-A type 450 kW/54.5 GHz gyrotron. The article reports on the first microwave injection experiments
with limited total power of 300 kW. Adjustment of experimental conditions and magnetic
field reconfiguration resulted in an increased diamagnetic signal, electron temperature and other |
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Dzyuba A. V., Arzhannikov A. V. Superconducting Resonators: Decrease of Q-Factor at High Accelerating Field Results combining efforts of different groups on investigation of losses in superconducting radio frequency cavities made of niobium are presented. Peculiarities of such losses and of their remedies are considered for dissipation at high accelerating voltages. The main results of RF tests as well as main experiments conducted via physico-chemical research methods on samples are discussed. The role of different type of defects on losses is presented. The candidate mechanisms for dissipation are considered based on exhibited results. As a conclusion the prediction is made on possible alternative processing steps for improvement of cost, time and safety efficiency of current technological procedures. |
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Tiunov M. A. The Full Calculation of Three-Dimensional Quasi-Stationary Electromagnetic Fields in Approach of the Strong Skin Effect by the Method of the Boundary Integral Equations The efficient method of the boundary integral equations allowing to carry out the full simulation of three-dimensional quasi-stationary electromagnetic fields in approach of the strong skin effect is devised and realized. Examples of calculations of modeling and real systems of formation of quasistationary electromagnetic fields are given. The comparisons of results of simulation with analytical solutions and observed data are presented. |
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Galev R. V., Kovalev O. B. About the Use Maxwell Equations in Numerical Simulation of Interaction of Laser Radiation with Materials The following problems have formulated using Maxwell equations. These are problems of the propagation and absorption of laser radiation with respect to the modeling of processes of laser materials processing: cutting, welding, drilling metals, selective laser melting and sintering of powders. With elements of parallel computing the algorithm for numerical solution of Maxwell’s equations has been implemented in FORTRAN by Finite Difference Time Domain method (FDTD). Features of posing of a number of boundary conditions have been studied applied to the problems of laser interaction in isotropic media. |
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Physics of Field, Neutral and Ionized Gases |
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Gaponov S. A., Ermolaev Yu. G., Kosinov A. D., Lysenko V. I., Semionov N. V., Smorodsky B. V. Theoretical and Experimental Investigation of the First Instability Mode Development in Supersonic Boundary Layers on Porous Coatings In the present study we have performed combined theoretical and experimental investigation of the surface permeability influence on the linear stability of the supersonic flat-plate boundary layer at free-stream Mach number M = 2. Good quantitative agreement was obtained between the data calculated by the linear theory of stability and the data obtained in experiments with artificially generated disturbances performed on models with various porous inserts. It is shown that increase of the permeable surface pore size leads to the destabilization of the first instability modes propagating under arbitrary angles in the boundary layer. |
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Zapryagaev V. I., Kavun I. N., Kundasev S. G. An Experimental and CFD Investigation of a Supersonic Nonisobaric Jet Exhausting from a Beveled Nozzle The aim of the investigation is to understand the shock-wave structure of the supersonic jet exhausting from a beveled nozzle. Results of investigation are presented as cross section Pitotpressure fields. This data can be used for verification of CFD results. The experiment was complemented by numerical simulation with using of the program packet ANSYS Fluent. The satisfactory qualitative agreement was obtained. |
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Ivanov A. V., Kachanov Yu. S., Mischenko D. A. Quantitative Study of Excitation of Unsteady Gortler Instability Modes in Concave-Wall Boundary Layer by Free-Stream Turbulence The paper is devoted to the first experimental study of distributed excitation of Gortler instability
modes due the distributed mechanism of receptivity of a concave-wall boundary layer to streamwise
freestream vortices. Experiments are carried out in the following range of problem parameters:
Gortler numbers G* = 7,4 - 21,3, frequencies f = 15, 20, and 26 Hz (nondimensional frequency parameters
are F = 17,04; 22,72 and 29,54), and a broad range of spanwise scales of disturbances
?z = 8 - 24 ìì (nondimensional scales are ? = 149 - 774). It is found that this receptivity mechanism
is quite efficient and can lead to amplification of unsteady Gortler vortices even in regimes where |
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Zverkov I. D., Krukov A. V., Grek G. R. Prospects of Studies in Region of Low-Sized Aircraft (Review) In the given review the problem of improvement of aerodynamic characteristics of the low-sized
aircraft is considered with point of view of the fundamental phenomena of the mechanics of liquid,
gas and plasma. It is a problem of the local boundary layer separation (separated bubbles) and flow
separation from a wing forward edge at which all global structure of a flow varies. The review of
the works establishing this interrelation and methods of the influence, eliminating harmful consequences
of the separations is submitted. The method of separation elimination with help of a wavy
surface, as the most perspective and easily sold on practice is in more details allocated in this review. |
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Goldfeld M. A., Starov A. V. Scheme of Hydrogen Ignition in Duct with Shock Waves In article results of the analysis of processes of self-ignition and combustion propagation are given in the multi-injector combustion chamber with high supersonic speeds of an air flow. It is established that fuel ignition at high Mach numbers, bringing to flame propagation on all volume of combustor and combustion stabilization, happens not in recirculation area behind a step, and in the field of interaction of shock waves with an boundary layer on walls or behind this area downstream near an angular point of the combustion chamber. The scheme of development of process of combustion in the combustion chamber with significantly three-dimensional configuration is in details considered. |
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Litvinenko Ì. V., Litvinenko Yu. À., Êîz lov G. V., Vikhorev V. V. Experimental Investigation of a Free Round Jet with Dean Vortices Results of the experimental investigations of free round jet with Dean vortices formed in curved channel are presented. Hot-wire anemometry measurements of three-dimensional mean velocity profile were performed, smoke visualization pictures cross and longitudinal sections at nozzle exit and downstream were obtained. The features of jet development at acoustic excitation of 40 Hz are shown. |
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Gorelikova A. E., Kashinsky O. N., Randin V. V., Chinak A. V. Dependence of Gas Bubble Diameter from the Gas Flow Rate in Upward Two-Phase Flow in an Inclined Flat Channel Experimental study of heat transfer and wall shear stress in an upward bubbly flow in an inclined flat channel is presented. The measurements were performed in the range of superficial liquid velocities 0.3 - 1.1 m/s and different values of volumetric gas flow rate ratio. Measurements of hydrodynamic structure were carried out by electrochemical method using a miniature sensors of friction. The values of average friction and heat transfer coefficient at different orientations of the channel were determined. It is shown that there is a significant dependence of friction and heat transfer on the channel inclination angle in the gas-liquid flow. |
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Serdyukov V. S., Surtaev A. S., Volodin O. A. Investigation of the Dynamics of Nucleate Boiling in Subcooled Falling Liquid Films This paper deals with the features of nucleation dynamics at boiling in falling water films at different
subcooling, Reynolds number and heat fluxes. With the use of high-speed infrared and digital
video the local parameters of nucleate boiling in falling liquid films such as: bubbles’ diameter before
condensation, frequency of nucleation and temperature of onset of bubble appearance were received.
Analysis of the experimental data showed that bubbles’ diameter before condensation has
strong dependence on initial temperature and increases with the rise of heat flux. The main influence
on nucleation frequency has the variation of heat flux density. At the same time the experimental |
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Solid-State and Semiconductor Physics, Physics of Nanostructures |
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Rogilo D. I., Fedina L. I., Kosolobov S. S., Latyshev A. V. Formation of Two-Dimensional Islands on Si(111) Surface during Homoepitaxial Growth The nucleation of two-dimensional Si islands has been studied by in situ ultrahigh vacuum reflection
electron microscopy on extra-large (~ 10–100 ?m) atomically flat terraces of Si(111) surface.
The dependence of two-dimensional island concentration N2D on substrate temperature T and
silicon deposition rate R is found to obey relation N2D ~ R^(x)exp(E2D/kT) with x~0.58 or 0.82
and E2D ~ 1.77 eV or 1.02 eV on the Si(111) surface with (7x7) or (1x1) structure, respectively. The
critical nucleus during the growth on the extra-large terraces is found to consist of i = 1 particle at
T ~ 700°Ñ, and the critical nucleus size increases to i = 7–10 on terraces with smaller width, which |
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Alekseev A. V., Predtechensky M. R. Manufacturing of Composite Material Made of Aluminum Matrix Reinforced by Carbon Nanotubes by the Way of Hot Pressing Following by Cold Rolling The method of manufacturing Al-CNT composite by hot pressing and cold rolling was tried out. Composite with a tensile strength as well as tensile strength of middle strength aluminum alloys was made |
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Educational and Methodical Provision of Teaching of Physics |
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Bogomyagkov A. V., Dorokhov V. L., Meshkov O. I., Polygalov A. S., Shcheglov A. L. Young’s Experiment on Slits with an Angle between Them Here are proposed a modified version of Young’s experiment on slits with an arbitrary angle between
them. Also here performed mathematical analysis of the proposed scheme, showing that
the intensity distribution can be approximated by a hyperbolic function. Experimental data confirm
theoretical calculations. Analysis of the experimental results has conducted using two different
methods of processing the digital data of the interference pattern. Theoretical calculations and experimental
results established a nontrivial fact, that the interference patterns for slits with different,
but symmetrical respect to 90° angles have the same intensity distribution. This experiment may be |
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