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This work presents a newly developed "Texture" software suite for quantitative analysis of the preferred orientation of crystallites in metals and alloys by diffraction techniques. A description of the theoretical foundations of texture analysis and its instrumental implementation is provided. The software functionalities are illustrated, which are used to construct, model, and analyze direct and inverse pole figures, as well as calculate the orientation distribution function by the ADC method and reconstruct pole figures. The results of a comparative study of the complete pole figures constructed based on experimental diffraction data and those calculated based on the orientation distribution function, which has been computed from a series of incomplete unnormalized pole figures, are presented. [ABSTRACT FROM AUTHOR]

The shock compressibility of single-crystal silicon is experimentally studied in the pressure range of 280 to 510 GPa. Shock waves are created using Mach's explosive cumulative generators. The parameters of shock waves are determined by the impedance matching method, and single-crystal quartz is used as a ref-erence substance. The results agree well with the ab initio calculation results and with the data obtained using laser shock waves. [ABSTRACT FROM AUTHOR]

The thermophysical properties of shock-compressed porous iron oxide at pressures up to 1 TPa were determined for the first time. The results agree well with earlier static and dynamic measurements in the pressure range up to 0.2 TPa. An equation of state for the high-pressure phase of iron oxide was constructed and compared with data at high pressures and temperatures. [ABSTRACT FROM AUTHOR]

A method is proposed for spatially correcting an acoustic hologram recorded on an arbitrarily oriented planar area in front of an axially symmetric ultrasound transducer. The method comprises steps for determining the direction of the transducer's axis from the measured acoustic hologram, transferring the hologram data on a plane perpendicular to this axis and centering it relative to the axis by means of a correction algorithm that executes appropriate rotations and shifts of the original hologram. The corrected hologram is used for reconstructing the structure of vibrations of the emitting surface of the transducer. A simplified correction algorithm is also considered that is applicable for transducers with narrow angular spectrum and small angles of inclination of the initial hologram to the transducer axis. The accuracy of the developed algorithms is analyzed numerically for a single focusing transducer with a uniform vibrational velocity distribution on its surface and is demonstrated experimentally for an annular 12-element array. [ABSTRACT FROM AUTHOR]

The problems of monitoring the state of flowing media with a simultaneous change in temperature and flow rate of the medium by more than two orders of magnitude are considered. A design of a flow-through refractometer is proposed for monitoring the state of transparent media in laminar and turbulent flow regimes, as well as at high flow rates and changes in the temperature of the medium by more than 200°C. The developed flow-through refractometer implements a method for measuring the refractive index, based on the principle of parallelism of two beams: the incident and transmitted through a pipeline with refraction at the boundaries of several media. The piping in the form of a cylindrical Plexiglas insert is part of the refractometer design. The design of the optical part of the refractometer with a vertical section of the pipeline eliminates the influence on the measurement of the refractive index of errors caused by multiple reflections of laser radiation from optical elements, the formation of voids or vortex flows in the pipeline. For the proposed refractometer there are no restrictions on the value of the measured refractive index of the flowing liquid, in contrast to the previously used industrial flow-through refractometers, the principle of operation of which is based on the phenomenon of total internal reflection of laser radiation at the interface of two media. The results of experimental studies of various media with the proposed refractometer are presented. [ABSTRACT FROM AUTHOR]

When using elastic spherical scatterers in acoustic problems, it is necessary to know their main elastic parameters that characterize the internal resonances. In this study, it has been shown that the velocities of longitudinal and transverse waves in a solid sphere can be determined from the scattering characteristics of an ultrasound beam. Millimeter-sized steel, glass, and nylon spheres that were immersed in water were considered as scatterers. In experiments an acoustic field was created by a flat piezoelectric source operating in the megahertz frequency range in a pulsed mode. By comparing the experimental data and numerical calculations for the scattered-field amplitude, the velocities of elastic waves in the materials of spheres were determined and their absorption coefficients were estimated. [ABSTRACT FROM AUTHOR]

The article presents the results of experimental determination of the structure of surface vibrations of a two-dimensional phased ultrasound probe using transient acoustic holography in the frequency range from 0.1 to 10 MHz. It is shown that this method makes it possible to detect individual elements operating with parameter deviations from the nominal values, including inactive ones. A comparison is made with the results of echo pulse measurements for each element, as well as measurements of the electric capacitance of the elements. [ABSTRACT FROM AUTHOR]

The article discusses the possibility of using a plane piezoelectric transducer with a large wave dimension as the source of a reference plane ultrasonic wave, which can be used to calibrate hydrophones in the megahertz frequency range. In the experiment, the source was a piezoceramic disk with a diameter of 100 mm and a thickness resonance frequency of about 1 MHz. A method was developed for determining the sensitivity of the transducer in the transmit mode by measuring its electrical impedance. A methodology is proposed for finding the parameters of the plane wave component of the emitted acoustic pulse from a known electrical signal on a generator. It is shown that the acoustic pulse profile measured by a calibrated hydrophone near the source agrees well with the theoretically predicted signal. [ABSTRACT FROM AUTHOR]

The review summarizes literature data on various approaches to the synthesis of substituted imidazole-4,5-dicarboxylic acids ranging from assembly from low-molecular-weight components, to modifi cation of the parent structure, and to degradation of more complex molecules. [ABSTRACT FROM AUTHOR]

Abstract: The possibility of using neutron diffraction in quantitative analysis of residual austenite in steels is investigated. According to the obtained results, some properties of neutron diffraction by two-phase structures remain size-independent, which makes it possible to use large composite standards. It is shown that this approach ensures admissible accuracy without using a priori coefficients. [ABSTRACT FROM AUTHOR]

Graphene films were synthesized with the method of chemical vapor deposition using gaseous methane as the source of carbon and copper foil as the substrate for the deposition. The following conditions were found optimal to grow large-area high quality graphene films: preliminary annealing of the foil in the argon/hydrogen mixture at 970-990 °С for 30-40 min; simultaneous supply of the argon/hydrogen mixture (100 cm3/min) and methane (10 cm3/min) for 5-10 minutes, and subsequent cooling in an inert atmosphere. As a result, 1-10 layered graphene films were obtained to fully coat the copper foil over the area up to 50 cm2. Several methods have been developed to transfer graphene to dielectric substrates such as silicon oxide and flexible polymer films. The obtained graphene films were used to create a flexible transparent conductive touch panel and a highly sensitive resistive humidity sensor exhibiting fast response-recovery time. [ABSTRACT FROM AUTHOR]

Water-soluble forms of a series of 1-alkyl(aryl)imidazole-4,5-dicarboxylic acids were prepared. Anticonvulsant activity of 1-propylimidazole-4,5-dicarboxylic acid and its triethanolammonium salt was studied using the NMDA-induced convulsion model. The triethanolammonium salt of 1-propylimidazole-4,5-dicarboxylic acid was shown to possess anticonvulsant activity whereas the acid itself was a convulsant. The change of pharmacological profile was related to the formation of ion pairs or associates even in polar physiological media. The ability to associate was confirmed using conductivity measurements. An x-ray crystal structure analysis was performed for the triethanolammonium salt of 1-propylimidazole-4,5-dicarboxylic acid. [ABSTRACT FROM AUTHOR]

3′ H-Cyclopropa[1,9](C- I )[5,6]fullerene-3′-carboxylic acid can be synthesized in a good yield by cyclopropanation of fullerene C with 2-(dimethyl-λ-sulfanylidene)acetates provided that the ester residue is readily hydrolyzable in acid medium. [ABSTRACT FROM AUTHOR]

The key feature of optically variable elements is the appearance and disappearance of high saturation colors during shooting under different angles. The accuracy of color saturation measurement algorithms is limited by the automatic white balance correction subsystem, which uncontrollably changes the color characteristics of the image from frame to frame. In this paper, the possibility of using a priori information about color consistency of the document area to compensate for distortion of the white balance is considered using examples of document owner monochrome photographs. The proposed method of color correction increases the contrast of color saturation between the unprotected areas of the photograph and the areas covered by visually variable image on the protective film. The method is tested on reference data obtained with a mobile device. [ABSTRACT FROM AUTHOR]

Linear and nonlinear fields produced by a twelve-ring annular array with varied axial electronic focus steering distances and varied number of activated elements were simulated using wide-angle parabolic representation of the Westervelt equation. The effects of electronic adjustment of the focusing angle and/or switching off the array elements were investigated with regard to the shock-forming conditions at the focus and in the grating lobes in water. Prefocal steering was shown to result in shock formation in the postfocal grating lobe, which can occur at lower array power than that required for shock formation at the main focus. Postfocal steering resulted in shock formation at the main focus and no shock in the prefocal grating lobe at any power considered. To decrease focusing angle, switching off the outer rings was more favorable than postfocal steering with all rings enabled: a fully developed shock of the same amplitude formed at the same source pressure amplitude but with lower pressure level in the prefocal grating lobe. To increase focusing angle, prefocal steering with the outer rings switched off was less favorable than using all array elements with no steering: higher source pressure amplitude was required for a fully developed shock formation at the focus, with additional shock fronts forming in the postfocal grating lobe. [ABSTRACT FROM AUTHOR]

Two types of laser heterostructures, i.e., those without internal mechanical stress compensation, with AlGaAs-alloy emitter and waveguide layers (type 1), and laser heterostructures with stress compensation, with AlGaAsP emitter and waveguide layers (type 2) are grown by metal-organic chemical vapor deposition (MOCVD). Laser-diode bars 5 mm wide with a fill factor of 24%, emitting at a wavelength of 850 nm are fabricated. Their power parameters in the continuous-wave (cw) and pulsed lasing modes are studied. It is shown that type-2 laser diode bars exhibit better linearity of the light-current characteristics in the cw and pulsed lasing modes in comparison with laser diode bars based on the type-1 structure. [ABSTRACT FROM AUTHOR]

A new fast version of the reconstruction algorithm for computed tomography based on the simultaneous algebraic reconstruction technique (SART) is proposed. The algorithm iteration is asymptotically accelerated using the fast Hough transform from O( n) to O( nlogn). Similarly to the algebraic reconstruction technique (RegART), which was proposed by us previously, the regularization operator is applied after each iteration. A bilateral filter plays the role of this operator. The algorithm behavior is investigated using the model experiment. [ABSTRACT FROM AUTHOR]

The analytic model of the dynamics of a robot-manipulator is obtained in the infinitely indefinite dynamic and completely observable exterior medium. The unboundedness property of indefiniteness most exactly accounts for the unpredictability of the real world, in which most of the moving objects of the technical nature have to function, and considerably complicates the problem of modeling because in this case the results of the classical theory of control are inapplicable in full measure. In this work an alternative approach to the modeling is developed on the basis of idempotent mathematics, which differs from the known approaches by the possibility of representing a model in the explicit analytic form. [ABSTRACT FROM AUTHOR]

A technology for high-resolution efficient numerical modelling of bioimpedance measurements is considered that includes 3D image segmentation, adaptive unstructured tetrahedral mesh generation, finite-element discretization, and analysis of simulation data. The first-order convergence of the proposed numerical methods on a series of unmatched meshes and roughly second-order convergence on a series of nested meshes are shown. The current, potential, and sensitivity field distributions are computed for conventional schemes of bioimpedance measurements using segmented geometrical torso model of the Visible Human Project (VHP) man. Use of the adaptive tetrahedral meshes reduces significantly the number of mesh elements and, hence, the associated computational cost compared to rectangular meshes while keeping the model accuracy. [ABSTRACT FROM AUTHOR]

The method of solid phase synthesis was proposed for the preparation of monoadducts of fullerene C using 3′ H-cyclopropa[1,9](C- I)[5,6]fullerene-3′-carboxylic acid as an example. [ABSTRACT FROM AUTHOR]

Laser heterostructures with an active region consisting of a highly strained GaInAs quantum well located between GaAsP compensating layers were grown by metal-organic chemical vapor deposition on GaAs substrates. Stripe mesa-structure laser diodes of 100 μm aperture emitting at 1190 nm were fabricated. The highest emission power of these diodes in the CW mode amounted to 4.5 W per output mirror. Due to the presence of compensating GaAsP barriers, the GaInAs quantum well remains unrelaxed, which eliminates the spread in the maximum emission power of laser diodes produced from the same heterostructure. [ABSTRACT FROM AUTHOR]

InGaAs/GaAs/AlGaAs laser heterostructures are grown by MOCVD epitaxy on GaAs substrates. Mesastripe laser diodes with an aperture of 100 μm emitting at a wavelength of 1190 nm are fabricated. It is shown that, in these lasers, the active region is relaxed, which manifests itself in the spread of attainable maximal power for various lasers obtained from the same heterostructure. The maximal emission power in a CW mode of lasing for such lasers was 5.5 W per mirror. [ABSTRACT FROM AUTHOR]

The article presents a study regarding the formation of Imidazole-4,5-dicarboxylic acid in the oxidation of 2-substituted benzimidazoles with hydrogen peroxide. Also explored is the preparation of 4,5-IDC derivatives with alkyl radicals. Investigated is the oxidation of 2-phenyl-substituted analog as well as the treatment of the solution with triethanolamine.

An important application of quantitative description of textures of materials is calculation of the averaged physical properties of polycrystals. In this study, such properties are elastic parameters of materials. In recent years, the effect of crystallographic texture on the average values of elastic properties of polycrystals has been analyzed in many studies. Researchers often restrict themselves to the consideration of average values of Young’s or shear moduli, which are related to the components of the elastic compliance tensor. The simplest scheme of averaging of all components of the elastic compliance tensor is considered. Complicated (not angular) normal distributions of general character are used as the weight function. A practical example of application of these techniques to calculation of elastic compliance moduli of magnesium and titanium polycrystals is proposed. [ABSTRACT FROM AUTHOR]

The errors in measuring the crystallographic texture described by pole figures are studied. A set of diffraction spectra for a sample of the MA2-1 alloy (Mg + 4.5% Al + 1% Zn) are measured, simulation of individual spectra on the basis of which the pole figures were obtained is performed, and their errors are determined. The conclusion about the possibility of determining the effect of errors of the diffraction peak half-width on the pole figure errors that was drawn in our previous studies is confirmed. [ABSTRACT FROM AUTHOR]

The effect of total reflection of an electron wave from an interface was investigated for Al[sub x]Ga[sub 1 - x]As/AlAs structures. Analysis was performed on the basis of calculations by the pseudopotential method as well as analytically and numerically in terms of the three-valley model. The appearance of zero in the coefficient of electron transmission through the Al[sub x]Ga[sub 1 - x]As/AlAs interface was observed at a certain energy in the interval between the bottom of the X[sub 1] valley in AlAs and the bottom of the X[sub 1] valley in Al[sub x]Ga[sub 1 - x]As and was shown to be induced by the multivalley character of the electron energy spectrum. It is ascertained that this total reflection is due to the mutual compensation of contributions from various valleys and is not related to any resonance interface state. [ABSTRACT FROM AUTHOR]

The behavior of charge in a buried oxide of the silicon-on-insulator structures obtained using the Dele-Cut technology was studied by keeping the structures under a voltage with an electric-field strength of 2-5.5 MV/cm. A mobile positive charge drifting under the effect of applied voltage was detected in the oxide. The expected charge accumulation in the oxide was not detected. It may be assumed that both of the observed effects are caused by the interaction of residual hydrogen, which is present in the oxide during the preparation of the structures, with traps in the thermal oxide. As a result, the traps become passivated in the buried insulator of the structure; in addition, the charge, which is mobile at room temperature, is introduced into the insulator. [ABSTRACT FROM AUTHOR]

A new method for the direct determination of rotational angles based on 2-dimensional nutation exchange NQR spectroscopy is proposed. The method involves the detection of exchange processes through NQR nutation spectra recorded after the mixing interval. The response is analysed of a system of spins I = 3/2 in zero applied field, experiencing electric quadrupole couplings, to the three-pulse sequence with incrementing pulse widths. The systems investigated here were hexachloroethane and tetrachloroethylene, which show threefold and twofold reorientational jumps about the carbon-carbon axis, respectively. It is shown that the 2D nutation exchange NQR spectrum exhibits characteristic ridges, which reveal the motional mechanism in a model-independent fashion. The angles through which the molecule rotates can be read directly from elliptical ridges in the 2D spectrum, which are also sensitive to the value of asymmetry parameter of the electric field gradient tensor. [ABSTRACT FROM AUTHOR]

The article offers information on the structure of three-manifolds which is considered as two-dimensional. It discusses complexity of a manifold M which is defined as the number c(M) of the true vertices of its minimal almost simple spine. It mentions that a spine is simple when link of each of its point is either a circle or a circle with a diameter or three radii.

We propose a lightweight noise-canceling filtering neural network that implements the filtering stage in the algorithm for tomographic reconstruction of convolution and backprojection (Filtered BackProjection—FBP). We substantiate the neural network architecture, selected on the basis of the possibility of approximating the ramp filtering operation with sufficient accuracy. The network performance has been demonstrated using synthetic data that mimics low-exposure tomographic projections. The quantum nature of X-ray radiation, the exposure time of one frame, and the nonlinear response of the ionizing radiation detector are taken into account when generating the synthetic data. The reconstruction time using the proposed network is 11 times shorter than that of the heavy networks selected for comparison, with the reconstruction quality in the metric above 0.9. [ABSTRACT FROM AUTHOR]

The necessity of a new method for measuring the refractive index of a turbulently flowing fluid in a pipeline is substantiated. A new method for measuring refractive index n of fluids is presented. For practical implementation of this method, a new design of an in-line refractometer is developed, which makes it possible to measure n in both laminar and turbulent liquid flows. A new design of the optical part of the refractometer is considered. A new method of its positioning on the vertical pipeline section is proposed. All this allows one to diminish the influence exerted on measurements of n in flowing fluids by errors related to multiple reflections of laser radiation from optical elements, to formation of cavities or vortex flows in the pipeline, and to variations in temperature. The new refractometer design has no restrictions on the determination of n in flowing fluids in contrast to commercially available in-line refractometers, operation of which is based on total internal reflection of laser radiation at the interface between two media. The results of an experimental study of various fluids are presented. [ABSTRACT FROM AUTHOR]

The emission characteristics of single-mode lasers based on an AlGaAs/GaAs heterostructure with an ultra-narrow waveguide are studied. It is shown that using an ultra-narrow waveguide (100 nm) and thin (70 nm) wide-gap barriers at the waveguide/cladding interface makes narrower the vertical divergence of far-field emission. The lateral and vertical divergences are 5° and 18.5°, respectively, for the narrow-stripe (5.1 μm) single-mode lasers developed in the study. The lasers demonstrate efficient single-mode operation up to a power of 200 mW. Raising the current further gives rise to higher order modes, the maximum optical power in continuous-wave lasing being limited to 550 mW by overheating. Passing to the pulsed operation mode (pulse width 200 ns) makes it possible to raise the maximum peak optical power to 1500 mW. [ABSTRACT FROM AUTHOR]

The emission characteristics of narrow mesa-stripe (5.5 μm) lasers based on asymmetric AlGaAs/GaAs heterostructures are studied. It is shown that the maximum optical power achieved in the continuous-wave (CW) operation mode is limited by heating and reaches a value of 1695 mW at a current of 2350 mA at +25°C, with the maximum efficiency reaching 54.8%. Reducing the working temperature to –8°C makes it possible to raise the maximum low-mode CW power to 2 W. A peak power of 2930 mW is obtained under pumping with current pulses (width 240 ns, amplitude 4230 mA). It is shown that the power profile has in the pulsed mode an "optical dip" region in which low-efficiency lasing occurs with the generation of a train of subnanosecond pulses. [ABSTRACT FROM AUTHOR]

The new improved molding gypsums are used for casting ceramic articles by the conventional and multiple casting (spagless) technologies. Such gypsums increase casting productivity and extend the life cycle of gypsum molds and copies. [ABSTRACT FROM AUTHOR]

For the first time, a new ceramic "Ideal," a diamond-silicon carbide composite obtained in the reaction-diffusion Turing process, which makes it possible to obtain materials with the optimal set of physical and mechanical properties, is studied. An elastic-brittle fracture related to the propagation of a shock wave in a two-component system is noted. The dynamic elastic limit, determined by the properties of silicon carbide, is found to be 13.4 GPa. Its dynamic elastic limit and spall strength in the region of the elastic deformation are measured. The impact compressibility of ceramics up to a pressure of 625 GPa is determined. [ABSTRACT FROM AUTHOR]

Conditions were found which allow 2-alkyl-substituted imidazole-4,5-dicarboxylic acids to be synthesized in preparative quantities by the oxidation of 2-alkylbenzimidazoles with hydrogen peroxide. It was shown that optimal results can be obtained at the concentration of 2-alkylimidazole in sulfuric acid of 1 M and the hydrogen peroxide: 2-alkylbenzimidazole molar ratio of 11: 1. Oxidation under these conditions results in higher yields of the target 2-alkylimidazole-4,5-dicarboxylic acids, including those with a branched alkyl group. [ABSTRACT FROM AUTHOR]

The effect of ion energy in a focused ion beam in the range 12–30 keV on the formation depth of nonradiative recombination centers during etching of the Al0.18Ga0.82As/GaAs/Al0.18Ga0.82As double heterostructure has been studied. It is shown that an increase in the ion energy leads to an increase in the concentration and propagation depth of radiation defects. It was found that during etching of focused ion beam with ion energies above 15 keV, the depth of formation of radiation defects exceeds 900 nm, which does not correspond to the calculations in the Stopping and Range of Ions in Matter. [ABSTRACT FROM AUTHOR]

In this study, the brightness temperatures of silicon shock-compressed to a pressure of P = 68 GPa and the evolution of its temperature during unloading are measured. The measurements were carried out in the infrared range Δλ1 = 1.1–1.7 µm, in which silicon is optically transparent, and in the visible range Δλ2 = 0.32–1.06 µm. The isentropic unloading of shock-compressed silicon into a vacuum is accompanied by an anomalous increase in the observed temperature. [ABSTRACT FROM AUTHOR]

A solar cell on a wafer of multicrystalline silicon containing grain boundaries was studied by the induced-current method. The sample was scanned by an electron beam and by a laser beam at two wavelengths (980 and 635 nm). The recorded induced-current maps were aligned by means of a specially developed code, that enabled to analyze the same part of the grain boundary for three types of measurements. Optimization of the residual between simulated induced-current profiles and those obtained experimentally yielded quantitative estimates of the characteristics of a sample and its defects: the diffusion length of minority carriers and recombination velocity at the grain boundary. [ABSTRACT FROM AUTHOR]

The effect of temperature delocalization in semiconductor lasers (emission wavelength λ = 1060 nm) based on symmetric and asymmetric separate-confinement heterostructures fabricated by metal-organic vapor-phase epitaxy (MOVPE) is studied. Experimental and calculated estimates show that the carrier concentration in the waveguide increases by an order of magnitude when the temperature of a semiconductor laser is raised by ∼100°C. It is found that an increase in the temperature of the active zone leads to enhancement of the temperature delocalization of both electrons and holes. It is shown that the delocalization of holes begins at higher temperatures, compared with that of electrons. It is demonstrated experimentally that the onset of temperature delocalization depends on the threshold carrier concentration in the active region of a laser at room temperature. It is found that raising the energy depth of the active region by choosing the waveguide material makes it possible to fully suppress the temperature-delocalization process up to 175°C. [ABSTRACT FROM AUTHOR]

In this work we propose several techniques for personalized model adaptation, including anthropometrical scaling, control point mapping and geometrical modification of the body extremities positions.We compare our previous results of segmental bioimpedance analysis using the Visible Human Project (VHP) man model to the modified model with a corrected position of the arms. [ABSTRACT FROM AUTHOR]