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An acousto-optic cell is developed that allows the polarization plane of linearly polarized light to be rotated by an angle depending on the acoustic wave frequency. The effect is based on the combining of two mutually orthogonal optical waves whose polarizations are close to circular, with the phase of one of the waves changing under the action of a sound wave. A cell made of paratellurite crystal allows the polarization plane angle of linearly polarized light with a wavelength of 0.63 μm from 0° to ∼30° to be changed by varying the sound frequency from 38 to 43 MHz. [ABSTRACT FROM AUTHOR]

Absract: We examine the features of the formation of the transfer functions of an acousto-optic spatial filter made of a uniaxial gyrotropic crystal operating in tangential diffraction geometry. It is shown that a decrease in the sound frequency is accompanied by distortions of the transfer functions on the side facing the optical axis of the crystal. The distortions are caused by the influence of the second diffraction order on the distributions of axisymmetric transfer functions. The cutoff frequency of sound below which the transfer functions become practically unsuitable for two-dimensional processing of optical images is determined. It is shown theoretically and experimentally that the cutoff frequency of sound for processing a two-dimensional image with a wavelength of 0.63 μm using a spatial frequency filter made of ТеО2 is ∼40 MHz. [ABSTRACT FROM AUTHOR]

The polarization properties of a two-channel spatial AO filter based on diffraction into two symmetric Bragg orders have been studied. A regime is demonstrated where during Fourier processing of an image, the contours in different channels are formed in different polarizations and at different acoustic frequencies. This regime was confirmed experimentally on the basis of optical Fourier processing of an image transmitted by radiation with an optical wavelength of 0.63 μm. As a spatial frequency filter, an AO cell manufactured of paratellurite was used. This made it possible to form the image contour in one channel at a sound frequency of 34 MHz and in another channel at a frequency of 42 MHz. [ABSTRACT FROM AUTHOR]

We report a theoretical and experimental investigation of two-dimensional Fourier processing of an image using two channels when the image is differentiated in one channel and integrated in the other. Both operations are carried out by one acousto-optical (AO) spatial frequency filter operating in the AO diffraction regime in two symmetrical Bragg orders. The transfer functions of the channels are analyzed and differentiation and integration operations are demonstrated. The results are confirmed experimentally through optical Fourier processing of an image formed by radiation at a wavelength of 0.63 μm. An AO cell made of TeO2, operating at a sound frequency of 44 MHz, is used as a spatial frequency filter. [ABSTRACT FROM AUTHOR]

Being necessary components of large smart systems (including the brain), commutators can be realized on the basis of a resistor array with variable resistors. The paper considers some switching (commutating) capabilities of the resistor array. A switching graph is used to describe the work of the resistor array. This sort of graph provides a visual representation of generated high-conductivity current flow channels. A two-terminal scheme is used to generate the switching graph. In the scheme a voltage is supplies to a particular couple of poles (conductors), other poles being isolated from the power sources. Changing couples of poles makes it possible to generate a series of switching graphs. We demonstrate the possibility to create an interconnection between two or more blocks connected to the appropriate poles of the array. To do this, the resistor array must have a suitable signature (resistor directions), the applied voltage must match the signature. The series we generate are defined by not only control signals, but also the prehistory of the resistor array. Given preset resistor characteristics, the competition between graph edges plays an important role in that it contributes to the thinning of the switching graph we generate. [ABSTRACT FROM AUTHOR]

SnO2 – x nanocrystal films with Gd, Tb, Yb, Lu, and Sb additives for resistive gas sensors are fabricated by the magnetron sputtering of a composite target in a mixture Ar and O2 on quartz substrates with subsequent heating in air up to 350–400°C with resistance control. Sb as a donor is introduced into the composition of all the sensors and provides the given resistance values. The resistance of the sensors upon heating in air has a minimum in the range of 180–220°C and increases with temperature as a result of the field effect associated with oxygen adsorption on the film surface and the capture of film electrons. The composition of the films and their surface properties are investigated by electron microscopy and atomic-force microscopy. The resistance of the sensors is determined by the fabrication regime and may be equal from tens of kOhm up to ten of MOhm. The optimal working temperature is in the range of 280–350°C under a heating power of 500 mW. The sensors have a high sensitivity to alcohols which increases with the molecular mass of the reagent and all the sensors have a low sensitivity to benzene and acetone. The sensors have a short time of reaction to the reagents and a long time of recovery after removal of the reagents from air. The sensors are used to monitor some reagents in air and in devices of the electronic-nose type. [ABSTRACT FROM AUTHOR]

High-quality ZnS epitaxial layers are grown on GaP semiconductor substrates by the MOCVD method. Photodetectors for the visible and UV parts of the spectrum based on interdigital Schottky metal–semiconductor–metal (MSM) barrier contacts to the ZnS/GaР semiconductor structure have been fabricated and studied. The detectors exhibit low dark currents. The dependence of the characteristics of the spectral response of the detectors on the bias voltage is established. It was found that the long-wavelength response limit of ZnS/GaP MSM detectors can shift from 355 to 450 nm when the bias voltage is changed from 10 to 30 V. At the maximum photosensitivity wavelength of 450 nm, the ampere–watt sensitivity of the detector was 0.3 A/W at a bias voltage of 60 V, and the quantum efficiency is 82%. [ABSTRACT FROM AUTHOR]

A method is proposed for controlled convergence of beams with different wavelengths by means of acousto-optical (AO) Bragg diffraction. A method for calculating the parameters of the diffraction of two beams by one acoustic wave in a uniaxial crystal, which makes it possible to determine the condition for beam convergence, is presented. Calculations are demonstrated using the example of convergence of beams with wavelengths of 0.514 and 0.633 µm in a uniaxial paratellurite crystal by means of AO interaction with a "slow" acoustic wave. Experiments were carried out that confirmed the main theoretical conclusions. [ABSTRACT FROM AUTHOR]

For amplitude modulation of two-color optical radiation at a double sound frequency, it is proposed to use a device consisting of two identical acousto-optic (AO) cells operating at the same sound frequency and providing Bragg matching of two optical beams with one acoustic wave. As an AO medium, it is proposed to use a gyrotropic crystal whose eigenwaves are circularly polarized. The modulation is caused by the interference of waves with circular polarizations. The amplitude modulation of two-color Ar laser radiation (λ1 = 0.488 µm and λ2 = 0.514 μm) at a frequency of 236 MHz was experimentally obtained using two paratellurite AO cells. [ABSTRACT FROM AUTHOR]

The results of experimental study of the metal-semiconductor-metal (MSM) photodiode based on ZnCdSe/ZnSSe/GaAs heterobarrier structure are presented. MSM-diode with 2.8 μm Ni-Au interdigitated Schottky barrier contacts, gaps between them of 3 μm, and total detector area of 100 × 100 µm2 have been fabricated and investigated. At a wavelength of 460 nm MSM-diode provides a high spectral selectivity with FWHM of spectral response 4.3 nm, high current sensitivity of 2.27 A/W and low dark current of 200 pA at 30 V bias. The spectral response of the MSM-detector was characterized under various bias conditions. A reduced Schottky barrier height model was adopted to explain the gain mechanism of the MSM-detector under illumination. [ABSTRACT FROM AUTHOR]

The possibility of formation of a 2D optical image contour during double Bragg's diffraction simultaneously in two Bragg's orders is investigated. Transfer functions of Bragg's orders of double diffraction are obtained with account for ellipticity of optical beams and the curvature of wave surfaces of the crystal. The conditions for obtaining the image contour simultaneously in the zeroth and plus second Bragg's orders are determined. This is confirmed experimentally using the example of Fourier processing of the image transferred by radiation at a wavelength of 0.63 μm. Double Bragg's diffraction is realized based on an acousto-optic cell made of a uniaxial gyrotropic paratellurite crystal, which operates at an acoustic frequency of 20.3 MHz. [ABSTRACT FROM AUTHOR]

A method is proposed for the formation of two-color optical radiation with a rotating polarization vector, the rotation frequency of which is determined by the acoustic frequency. The method is based on acousto-optic (AO) diffraction of two-color radiation by an acoustic wave and the interference of circularly polarized beams with different frequencies. The rotation of polarization of two-color radiation is experimentally demonstrated for wavelengths of 0.488 × 10–4 and 0.514 × 10–4 cm using two AO Bragg cells made of a gyrotropic TeO2 crystal. Polarization rotation with a frequency of about 109 MHz is obtained. [ABSTRACT FROM AUTHOR]

New hybrid 2,2'-bipyridinium halobismuthates ([bipyH]+) (I and II), 7,8-dihydro-6H-dipyrido[1,2-a:2',1'-c][1,4]diazepine-5,9-diium ([bipyC3]2+) (III), 6,7,8,9-tetrahydrodipyrido[1,2-a:2',1'-c][1,4]diazocin-5,10-diium ([bipyC4]2+) (IV), and 1,1'-(pentanediyl)bis(2,2'-bipyridinium) ((bipyH)2C5]4+) (V) have been isolated and characterized by X-ray diffraction. The structure of I contains a monoprotonated cation 2,2'-bipyridinium and the isolated [Bi2Br10]4– anion. 2,2'-Bipyridinium bromobismuthate II contains a polymeric anion and is isostructural to the previously described iodobismuthate. Bromobismuthate III includes [BiBr6]3– anions and water molecules. Iodobismuthate [bipyC3]2[Bi2I10] (VI) is isostructural to IV. The structure of V contains [(bipyH)2C5]4+ cations and three types of anions: [Bi2Br10]4–, [BiBr6]3–, and Br–. Compounds I, III, and VI have been isolated in pure form. The values of the optical band gap for them are 2.84, 2.88, and 2.11 eV, respectively. [ABSTRACT FROM AUTHOR]

The spectral response and quantum efficiency of the visible-range photodetectors based on ZnSe and ZnCdSe/ZnSe heterostructures are experimentally studied. The spectral response of the detectors is characterized under various bias conditions. A model of a decrease in the effective height of a reverse-biased Schottky contact under irradiation is used to interpret the internal amplification of the detectors. [ABSTRACT FROM AUTHOR]

Solutions of the problem on constant-velocity expansion of a spherical cavity into a soil medium are analyzed. The cavity expands from a point in the half-space occupied by an elastoplastic soil medium. The previously obtained linearized analytical solution of this problem that was obtained under the assumption that the medium behind the shock wave front was incompressible is presented. Having performed the comparison with the results of the numerical solution of the problem in the full formulation, it is shown that the approximate solution is reasonable for the dependence of the pressure at the boundary of the cavity on the velocity of its expansion. The linearized solution is applied to calculate the force of resistance to the penetration of a rigid sphere into soft soil. The dynamic compressibility and shear resistance are characterized by the Rankine-Hugoniot relations and the Mohr-Coulomb-Tresca yield criterion. The results of analytical and numerical calculations are compared with the known experimental data, presented in the form of dependences on the impact velocity of the force of resistance to the penetration of spheres (impactors) into water-saturated sand. A good agreement between theoretical and experimental data has been demonstrated. [ABSTRACT FROM AUTHOR]

Reduction gases are widely used in the metallurgical, chemical and other industries. In this paper, the possibility of higher-quality reduction gas production using a two-stage technology is considered. It is proposed to use air conversion of natural gas with cooling and drying of the obtained products at the first stage. At the second stage, gas mixture is heated, treated in the catalyst bed, quenched and dried. It is established that the temperature of heat treatment of the gas mixture at the second stage should be at least 850–950 °C. This allows to increase the ratio (CO − H2)/CO2 in the resulting reduction gas. The minimum gas treatment temperature at the second stage is calculated depending on the pressure in the system. By overheating the gas before it enters the catalyst bed in the second stage, it is possible to compensate for the heat required for chemical reactions in temperatures above 850 °C, the total thermal effect of chemical reactions is determined. The total heat effect of chemical reactions depending on the temperature of gas heat treatment at different pressure is defined. [ABSTRACT FROM AUTHOR]

A one-dimensional problem of a spherical cavity expanding at a constant velocity from zero initial radius in an infinite granular medium, which has the first-kind self-similar solution, is considered. We are solving this dynamic spherical cavity-expansion problem to model rigid spheres penetrating into a granular media. Elastic–plastic deformation of the granular media is described in a barotropic approximation, using the high-pressure equation of state and Mohr–Coulomb Tresca's limit yield criterion. The medium is assumed to be incompressible behind the shock wave front propagating through the unperturbed medium. The problem in this formulation was solved analytically. Besides, a generalized solution of the problem was obtained numerically, which involves transition of a continuous elastic–plastic wave into a plastic shock wave when pressure grows with the cavity expansion velocity. The comparison of the analytical and numerical solutions shows that a linearized analytical solution is a good approximation of the pressure along the boundary of the cavity as a function of its expansion, except for low velocities. The linearized rigid plastic solution can be used for analyzing resistance to a rigid sphere that penetrates into the granular media. The computational results are compared with known experimental relations for resistance to spherical projectiles penetrating dry and water-saturated sand. Good agreement between the numerical and experimental results is obtained without any correction factors. [ABSTRACT FROM AUTHOR]

A method for splitting two-color optical radiation into monochromatic components, whose planes of polarization rotate with the frequency of a sound wave, is proposed. The method is based on the double passage of two-color radiation through an acousto-optical (AO) modulator made of a gyrotropic crystal, as well as on the property of light to change the polarization to the mutually orthogonal one as a result of reflection of circularly polarized radiation from a mirror surface. Experiments were performed using an AO TeO2 cell designed to split two-color Ar laser radiation and confirmed the main conclusions of the theory: the monochromatic components of Ar-laser radiation with rotating polarization planes at a sound frequency of 61 MHz were obtained. The diffraction efficiency was 60%. [ABSTRACT FROM AUTHOR]

A generator of high-voltage bipolar pulses with adjustable values of the switching frequency (0–2000 Hz) and the output-voltage amplitude (300–3600 V) with the same magnitude for pulses of different polarities has been developed. The rise time of the output voltage pulses when operating into a capacitive load of 400 pF is no more than 3 μs. The asymmetry of the effective values of the pulse voltages of different polarities at switching frequencies of 0–200 Hz is no more than 0.02%. The generator provides synchronization of the moments of switching a high voltage with the operation of the video camera of a magnetograph and other devices. The generator can be used in various fields of experimental physics related to polarization measurements. [ABSTRACT FROM AUTHOR]

The characteristics of an acoustooptic (AO) Bragg cell of two-color radiation as a differential spatial-frequency filter, in which the first diffraction order is the working one, have been investigated. It is shown that in a general case, it is impossible to provide two-dimensional image differentiation simultaneously at two wavelengths. A regime has been found that allows one to change from one wavelength to another with preservation of the two-dimensional differentiation operation by adjusting the sound power. This variant has been confirmed experimentally by the formation of a two-dimensional contour using two-color radiation of an Ar laser at wavelengths of 0.488 × 10–4 and 0.514 × 10–4 cm, as well as a TeO2 AO cell that operates at a sound frequency of 51 MHz. [ABSTRACT FROM AUTHOR]

Polydimethyl(methylvinyl)siloxane with long-chain hydrocarbon fragments was synthesized at a sequence of chemical reactions. The resulting graft copolymer was used as a compatibilizer of ethylene propylene diene/siloxane rubbers blends of different compositions. It has been established that the introduction of reactive compatibilizer in a concentration not higher than 6 wt.% in the blend of rubbers allows to increase their compatibility due to co-vulcanization of graft copolymer with each of the components under the hydrosilylation conditions and, possibly, due to the formation of chemical bonds between rubber phases, which leads to an increase in the strength properties of the compositions. [ABSTRACT FROM AUTHOR]

New hybrid N-acetonylpyridinium, N-(ω-iodoacetonyl)pyridinium, and N-acetonyl-2,6-dimethylpyridinium halobismuthates I–VII have been synthesized and structurally characterized. A preparative method of synthesis is proposed for compounds I, III, and VII, and some individual crystals have been managed to separate and characterize for compounds II, IV–VI. A new type of {K[BiBr6] 1D-chains with K+ cations has been revealed in the structure of [C8H10NO]2K[BiBr6] (II). N-acetonyl-2,6-dimethylpyridinium bromobismuthates [C10H14NO]3[Bi2Br9] V and VI (space group P21/n) are polymorphs of similar structure. Iodobismuthates [C8H10NO]4[Bi4I16] (III) and [C10H14NO]4[Bi4I16]⋅0.69I2 (VII) are built of [Bi4I16]4– anions, and [Bi4I16] moieties in the structure of VII are linked into a 1D-anionic chain by molecules I2. [ABSTRACT FROM AUTHOR]

New methylviologen (MV2+) bromobismuthate [MV]3[BiBr6]2 · 2H2O (I) isostructural to the well-known chlorobismuthate [MV]3[BiCl6]2 · 2H2O has been prepared from an aqueous solution and cha-racterized by X-ray diffraction. The reaction between I and concentrated HBr leads to the formation of acidic methylviologen bromobismuthate-bromide [H3O]2[MV][BiBr6]Br · 4H2O (II) and a minor impurity of bromobismuthate tribromide [MV]3[Bi2Br9][Br3]3 (III). The acidic bromobismuthate of ethylviologen (EtV2+) [H3O][EtV][BiBr6] · 1.34H2O (IV) formed under similar conditions has another composition. Thermal decomposition of II yields single-phase [MV][BiBr5], which has a low optical band gap. The electrochemical characteristics of I and related iodobismuthate [MV]3[Bi2I11]I have been compared. [ABSTRACT FROM AUTHOR]

The results of experimental studies of photodiodes based on interdigital MSM (metal–semiconductor–metal) Schottky barrier contacts to a ZnCdSe/ZnSSe/GaAs heterobarrier structure are presented. The detector provides a narrowband response (FWHM = 4.3 nm) at a wavelength of 460 nm, a sharp drop in the photosensitivity in the short-wavelength part of the response signal, high ampere-watt sensitivity, and low dark current. [ABSTRACT FROM AUTHOR]

This work presents experimental data pertaining to the determination of the ultimate strength of frozen soil under uniaxial compression in the range of strain rates of 400–2700 s-1. Finite expressions are obtained for quadratic approximation coefficients that depend on the impact velocity of a stress normal to the impactor surface and the experimentally determined physical and mechanical parameters of the soil, namely shock adiabat and the dynamic strength in compression. The resulting expressions are verified by comparing them with known experimental data related to the penetration of a steel impactor into frozen sandy soil. It is shown that a difference between the results of two-sided estimates and the experiments does not exceed 15%. [ABSTRACT FROM AUTHOR]

The possibility of increasing a specific yield of carbon nanomaterial from the products of methane–air conversion through the use of spent gases recirculation is considered. The analysis of the influence of water vapor and carbon dioxide contained in the recirculated gases on the methane conversion has been performed. According to the developed calculation method, the assessment of changes in the main parameters of carbon material synthesis was done. Evaluation was performed depending on the degree of recirculation of spent gases in the transition and steady-state periods of the process. It is shown that the use of gas recirculation increases the specific yield of the carbon material, but in this case, due to the accumulation of nitrogen in the gas phase, there is a decrease in the productivity of the process for the resulting product. The evaluation of the productivity enhancing by rising of the gases pressure in the system was made. It has been established that to increase the specific yield of carbon material, the obtained converted gas and reusable recirculated gas should be subjected to deep purification from water vapor. [ABSTRACT FROM AUTHOR]

Application of the acousto-optic (AO) Bragg diffraction in the processing of 2D images is analyzed. It is shown that conventional Bragg diffraction can be used for 2D processing provided that the zero-order diffraction is supplemented with the diffraction to an additional (side) order. A 2D contour of an optical image is experimentally detected using the first-order diffraction of radiation with a wavelength of 0.63 × 10–4 cm. An AO cell made from ТеО2 single crystal is used as an AO filter of spatial frequencies. Diffraction orders are formed in such an AO cell due to AO interaction with an acoustic wave with a frequency of 26 MHz. [ABSTRACT FROM AUTHOR]

Nanocrystalline films of tin dioxide with ytterbium and antimony additives are prepared from a composite target by reactive magnetron sputtering. The electrical resistance of the films increases upon heating from 180 to 400°C due to the field effect caused by surface-adsorbed oxygen, which subsequently captures electrons from the film, and decreases because of the reaction between oxygen ions and the vapor of organic reagents. Resistive gas sensors show enhanced sensitivity and selectivity to a number of organic solvents. [ABSTRACT FROM AUTHOR]

We report on the experimental observation of excitation and detection of parametric spin waves and spin currents in the bulk acoustic wave resonator. The hybrid resonator consists of a ZnO piezoelectric film, yttrium iron garnet (YIG) films on a gallium gadolinium garnet substrate, and a heavy metal Pt layer. Shear bulk acoustic waves are electrically excited in the ZnO layer due to piezoeffect at the resonant frequencies of the resonator. The magnetoelastic interaction in the YIG film emerges magnons (spin waves) excitation by acoustic waves either on resonator's eigenfrequencies or the half-value frequencies at supercritical power. We investigate the acoustic pumping of magnons at the half-value frequencies and acoustic spin pumping from parametric magnons, using the inverse spin Hall effect in the Pt layer. The constant electric voltage in the Pt layer, depending on the frequency, the magnetic field, and the pump power, was systematically studied. We explain the low threshold obtained (∼0.4 mW) by the high efficiency of electric power transmission into the acoustic wave in the resonator. [ABSTRACT FROM AUTHOR]

The article analyzes the method of pointing a high-spatial-resolution solar telescope with an angular field of view smaller than the angular size of the solar disk using an auxiliary guide telescope with the field of view covering the entire disk of the Sun and its surroundings. The requirements for the resolution of the telescope, pointing modes, and the structural diagram of the pointing are considered. [ABSTRACT FROM AUTHOR]

Hybrid bromobismuthates of N-alkylated derivatives of 2- and 3-methylpyridine, (C15H20N2)2Bi2Br10 (I), (C17H24N2)2Bi2Br10 (II), (C18H26N2)3(Bi2Br9)2 (III), (C14H18N2)(H3O)BiBr6 ∙ 2H2O (IV), (C14H18N2)2BiBr6IBr2 (V), (C16H22N2)3(Bi2Br9)2 (VI), and (C18H26N2)3(Bi2Br9)2 (VII), are synthesized in concentrated HBr and characterized by physicochemical methods. The structures of complexes I–VII are studied by X-ray structure analysis (CIF files CCDC nos. 1946844–1946850). Complexes I and II contain anions [Bi2Br10]4–. Anions [Bi2Br9]3– are found in the structures of compounds III, VI, and VII. Bis(3-methyl-1-pyridino)ethane bromobismuthate IV contains cations H3O+ and anions [BiBr6]3– and, unlike other bromobismuthates, decomposes at low temperatures. In presence of HI vapors, double bromobismuthate V containing the [BiBr6]3– and IBr2– anions crystallizes along with compound IV. [ABSTRACT FROM AUTHOR]

The effect of a ZnSe/ZnS/GaAs distributed Bragg reflector on the spectral response of a metal–semiconductor–metal (MSM)-diode is investigated. Good agreement is obtained between the calculated and experimental reflection spectra of the ZnSe/ZnS/GaAs heterostructure forming a distributed Bragg reflector in the MSM-diode. The MSM-detector provides a two-color response at 420 and 472 nm, a sharp decrease in photosensitivity in the long-wave part of the response signal, high quantum efficiency of 53%, and low dark current of 5 × 10−10 A. The two-color response of the detector can be adjusted to the desired wavelength by appropriately selecting the heterostructure parameters. [ABSTRACT FROM AUTHOR]

A method is proposed that allows one to provide high-performance acousto-optic (AO) Bragg diffraction of two-color optical radiation at the highest possible frequency of a sound wave. The method is based on the use of AO cells together with a prism, with which two-color radiation is diluted at the required angle. The method is demonstrated based on the example of AO diffraction of a two-color Ar-laser radiation, which diffracts in a paratellurite crystal at the maximum possible frequency of a transverse "slow" sound wave, equal to ~200 MHz. [ABSTRACT FROM AUTHOR]

In this paper, we present experimental work on the temporal profiling of transversly excited atmosphere (TEA) CO2 laser pulses by using a particular kind of semiconductor photodetector. The detector exploits the combined effects of two fast sensing mechanisms, namely, the electron temperature related Seebeck and photon drag effects, and one slow mechanism, the phonon related Seebeck effect. The design of the photodetector is such that the typical emitted TEA CO2 laser pulses (100 ns peak pulses in combination with a microsecond long tail) induce a transit response between the fast and the slow sensing mechanisms. In the fast regime, the output voltage is proportional to the temporal evolution of the pulse intensity. Starting from the falling edge of the pulses, this proportionality changes its characteristics gradually such that the output voltage becomes proportional to the time dependence of the laser pulse energy. All experimental results are backed by a theoretical model and numerical simulations. [ABSTRACT FROM AUTHOR]

An analytic model describing the distribution of the electron temperature created by absorption of an optical beam with a cylindrical symmetry in a layered structure was developed. Main attention was paid to the contribution of the lattice heating in the stationary and nonstationary regimes. It was shown that both the spatial distribution of the incident stationary beam and the temporal distribution of the incident pulses can be retrieved from the spatial and temporal electron temperature dependences near the illuminated surface. Electron temperature distributions can be measured using the thermoelectric effect. Experimental results of the spatial and temporal measurements of the thermoelectric voltage were compared with the theoretical calculations and a satisfactory agreement between experimental and theoretical results was found near the incident beam center for the quasistationary regime. The experimentally derived Seebeck detector’s responsivity equals 17.5 μV/W cm-2. [ABSTRACT FROM AUTHOR]

We present results of the experimental determination of the optical nonlinearities induced by heating free electrons distributed in the multivalley conduction band of highly doped n-GaAs. We propose a very sensitive multilayer leaky waveguide structure for transverse magnetic polarized waves in order to drastically reduce the required optical intensities. We explain in depth the dependence of the optical nonlinearity on doping concentration and deformation potentials. For a doping concentration n[sub o] of 7.6 × 10[sup 18] cm[sup -3], we found a nonlinear refractive index value n[sub 2]≈ (1 ... 0.2) × 10[sup -6] cm²/W at λ = 10.6 µm, by fitting nonlinear reflection measurements with an equivalent intervalley deformation potential value Λ[sub LL] = (1.0 ± 0.30) × 10[sup 9] eV/cm. [ABSTRACT FROM AUTHOR]

The results of the verification of a model of the IVG.1M reactor based on experiments performed in 1990 and 2017 are reported. Startups of the reactor which are associated with its emergence into a critical state and measured values of the power, neutron flux density, and efficiency of the CPS [control and protection system] components were chosen for verification The isotopic composition of the fuel and the beryllium blocks formed by the time the first water-cooled process channels with high-enrichment fuel were extracted from the reactor (2017), was calculated. It was established on the basis of the verification results that the measured parameters agree well with the calculations. Currently, the model of the IVG.1M reactor is used for evaluating the post-conversion characteristics of the reactor as well as the parameters of planned experiments. [ABSTRACT FROM AUTHOR]

Abstract—A two-channel high-frequency acousto-optic (AO) modulator-splitter has been developed, which splits optical radiation into two equal optical channels and modulates the intensities of the output channels at double the sound frequency. The modulator makes it possible to simply change the polarization of the output beams. A model of a modulator made of a TeO2 single crystal was used to modulate and split radiation with a wavelength of 0.63 × 10–4 cm. Intensity modulation of the output channels at a frequency of ~200 MHz was achieved. [ABSTRACT FROM AUTHOR]

Physical structures changing their resistance in operation can serve as a basis for making elements of neural networks (synapses, neurons, etc.). The processes inducing changes of resistance are rather complicated and cannot be described readily. To demonstrate the potential of this sort of variable resistors it is possible to substitute a complex physical system by a simple mathematical model reproducing the important behavioral characteristics of the actual system. A simple resistor element whose state is defined by a single scalar variable is taken as a model unit. Equations responsible for changes of the state variable are determined. Different functions and parameters that can enter these equations are discussed. Combinations of such elements and conventional electronic components are considered. Measurement methods for variable resistors are investigated. Experimental data are used to determine characteristics of a particular type of variable resistor, metal-insulator-metal structures with amorphous titanium dioxide as insulator. Specific sets of functions defining the "voltage-current" experiment-resembling behavior of a resistor element are presented. [ABSTRACT FROM AUTHOR]

The design of a two-channel acousto-optic modulator transforming the frequency shift of optical radiation into the high-frequency amplitude modulation is presented. A large- aperture modulator with two orthogonally polarized output optical beams has been produced from a TeO2 single crystal for modulating radiation with a wavelength 0.63 µm and tested. The amplitudes of the beams are modulated at a frequency of approximately 100 MHz, and the beam modulations are in antiphase. [ABSTRACT FROM AUTHOR]

Effect of the ZnSe/ZnS/GaAs distributed Bragg reflector (DBR) on the parameters of the spectral response of a photodiode based on rectifying contacts in the metal–semiconductor–metal (MSM) system is studied. The calculated photoreflection spectra of the ZnSe/ZnS/GaAs heterostructure are in good agreement with the experimental data. It is shown that the MSM diode provides two-color response of the photodetector at wavelengths of 420 and 472 nm, a sharp decrease in the photosensitivity in the long-wavelength part of the response signal, high quantum efficiency (53%), and low dark current (5 × 10–10 A). It is demonstrated that the narrow-band two-color response of the detector can be tuned to the desired wavelength using appropriate selection of the parameters of the heterostructure that forms that Bragg reflector. [ABSTRACT FROM AUTHOR]

Motion of a substantial part of the superfast exoplanets is found to be in the close resonance with the well-known "solar" timescale P 0 ≈ 0.11 days and/or the timescale 2 P 0 / π ≈ 0.07 days (at 99.9% confidence for exoplanet periods P < 2 days). There is also a noticeable lack of the exoplanetary "unstable" orbits with P ≈ 3 π P 0 ≈ 1.05 days, which copies the famous "period gap" of the cataclysmic variables at P ≈ 0.11 days; strangely enough, the ratio of the central periods of these two gaps is equal to π 2 . The exoplanet phenomenon is supposed to be caused by a coherent, with the P 0 timescale, oscillation of gravity, operating within the extra-solar planetary systems. [ABSTRACT FROM AUTHOR]

A 1D plug flow model suitable for describing the CO2 conversion into CO in microwave plasma reactors is proposed. The model is applied together with the Antwerp data set for the CO2 reaction kinetics to calculate parameter scans for a realistic experimental set up. The energy re-distribution pathways in the model calculations are analyzed. The analysis shows that despite the input power being initially deposited mainly into vibrational states the fast vibrational-translational (VT) transfer leads to dissociation of CO2 predominantly via the thermal quenching mechanism. Solutions with mitigated VT-losses can be obtained by increasing the specific input power–power per unit volume. In this regime the energy efficiency starts to be constrained by reverse processes. [ABSTRACT FROM AUTHOR]

Abstract—For broadband modulation of the intensity of optical radiation, the tandem arrangement two acousto-optic (AO) Bragg cells are proposed in which acoustic waves propagate in opposite directions. The device allows modulation of optical radiation in the acoustic frequency band of ~6 MHz at four times the frequency of the sound. The possibility of switching the modulation frequency from 2f to 4f, where f is the frequency of sound, by simply turning the output polarizer is demonstrated. The method is experimentally tested for modulating radiation with a wavelength of 0.63 × 10–4 cm using two AO cells made of paratellurite operating at a center frequency of 22 MHz. [ABSTRACT FROM AUTHOR]

Bragg diffraction which provides effective acoustooptic interaction of three-color radiation with a single acoustic wave at a high frequency of sound is proposed and tested in a single crystal of paratellurite at the wavelengths of λ= 0.488, 0.514, and 0.633 μm. Maximal diffraction efficiency of radiation with λ=0.633 μm at acoustic frequency of 150 MHz is 88% and that with λ= 0.488 μm and λ=0.514 μm is 60%. In diffraction efficiency range from 0 to 40% the dependence of all beams on acoustic power is the same. [ABSTRACT FROM AUTHOR]

The article describes a fundamentally new one-step chlorine free mechanochemical method for the direct synthesis of alkoxysilanes. The essence of the developed method consists in the direct interaction of untreated silicon with a dispersion up to 5 mm with an appropriate aliphatic alcohol containing from 1 to 4 carbon atoms in the presence of a copper-containing catalyst at a temperature of 200–300 °C in a vibrating fluidized bed of milling bodies in a wide vibration acceleration range. The experiments proved the principal possibility of its realization in a developed vibratory reactor, whose design solutions are adaptable to industrial application. It is shown that mechanoactivation plays a major role in the developed method of direct synthesis and is in fact the basis of a fundamentally new technological process. [ABSTRACT FROM AUTHOR]

Abstract—The study investigates the possibility of generating noiselike signals in the centimeter wavelength range using antenna generators built on a log-periodic microstrip antenna integrated with a field-effect transistor. The conditions for the occurrence of noiselike generation are experimentally determined. The possibility of expanding the noiselike spectrum using low-frequency noise modulation is studied. Noiselike generation was experimentally obtained in the centimeter wavelength range with a spectral width of up to 2 GHz. [ABSTRACT FROM AUTHOR]

The technology of microelectronic resistive gas sensors is considered. Heater and thermistor contacts are formed on an oxidized silicon substrate by sputtering a nichrome film and subsequent photolithography in combination with reactive magnetron sputtering of a nanocrystalline tin dioxide film with terbium and antimony additives. A 1.5 × 1.5 mm sensor requires 90 mW for heating to optimal working temperature of 250-280°C. The sensor has very high sensitivity to alcohols and low sensitivity to benzene and acetone. [ABSTRACT FROM AUTHOR]

Spin periods of Jupiter, Saturn, Uranus and Neptune are specified by the analysis of the resonant motion of large satellites: P=0.445(2)d, 0.448(1) d, 0.673(9) d and 0.561(7) d, respectively. They occur to be near-commensurate with P0=9600.606(12)s, the period of the "cosmic" oscillation, discovered first in the Sun, then in other variable objects of the Universe. The like analysis of spin rates of the total set of the largest and fastest rotators of the Solar system (with mean diameters ≥500km and P<2d,—of planets, asteroids and satellites) resulted in the best commensurable, or "synchronizing", timescale 9594(65) s, coinciding fairly well with P0 too (the probability that the two timescales could agree by chance, is less than 10-5). True origin of this odd common resonance of our planetary system is unknown. [ABSTRACT FROM AUTHOR]