Simulation of the operation of an angle transducer with a phased array in the transmission mode

Some features in the formation of signals of an angle linear transducer with a phased array are considered. The directivity characteristic is calculated as a function of the number of radiating elements, the dimensions of an array, the reference entrance angle, etc. The manner in which the spreading of a wavefront and the changes in the transformation coefficient influence the directivity characteristic in the case of focusing a signal towards the current entrance angle is shown. The directivity characteristics of the signals of an angle phased-array transducer and an elongated element radiating into a prism are compared.     

Electrodeposition of nanocrystalline chromium coatings from Cr(III)-based electrolyte using pulsed current

The effect of the pulse ratio on the current efficiency of the chromium electrodeposition reaction and the properties of coatings obtained from sulfate-formate electrolyte based on Cr(III) salts is studied. It is shown that the dependences of the current efficiency on the relative pulse duration feature a maximum that corresponds to a relative pulse duration of 2 (at τ_pulse = τ_p = 1 s). Light chromium coatings with good adhesion to the substrate are formed under pulsed electrolysis and their thickness is several tens of μm. In order to prevent pitting formation, it is expedient to introduce a special wetting surfactant additive into the electrolyte. As follows from the data of small-angle X-ray scattering, the deposited coatings are nanocrystalline. An increase in the relative pulse duration promotes a decrease in the nanocrystal size. The application of pulsed electrolysis leads to a decrease in the anodic dissolution rate of coatings in an acidic medium. Chromium electrodeposition decrease under pulsed current results in a decrease in internal stresses and in an increase in microhardness of coating.     

Photoconductivity of PbTe:In films with variable microstructure

It is shown that the microstructure and features of formation of surface states in nanocrystalline and polycrystalline PbTe:In films most significantly affect the character of photoconductivity in the spectral range of 1–2.5 THz. We present the results of a study and comparative analysis of the character of conductivity of PbTe:In films in the temperature range from 4.2 to 300 K in a static mode and in variable electric fields with a frequency of up to 1 MHz with illumination with white light and under the effect of high-power terahertz laser pulses with a wavelength of up to 280 μm.     

Macrolocalization of plastic flow in zinc single crystals oriented for basal glide

The pattern of plastic flow macrolocalization in actively loaded zinc single crystals has been studied. The character of localization consistently varies in accordance with the stage of plastic flow. The results are compared to the analogous data for single crystals with an fcc lattice. The common features and individual peculiarities in evolution of the patterns of plastic flow localization in materials with different crystal structures are revealed.     

Selection of the parameters of a probe during immersion ultrasonic inspection

The effect of a considerable reduction in the frequency of the echo-signal-spectrum peak during loading of a normal transceiver with an immersion medium as compared to loading with steel is established experimentally and theoretically. A theoretical analysis of this phenomenon with the use of a simplified physical model of the probe’s channel is performed, and physical interpretation is presented. Recommendations for selecting certain parameters of probes, which are intended for the use in immersion testing, are suggested.     

The effect of activated macrophage products on neurite growth in an organotypic culture of chick embryo sensory ganglia]

Murine peritoneal macrophages, activated by BCG vaccine, and human peripheral blood monocytes, activated by lipopolysaccharides, exerted neurite stimulating or neurite inhibiting effects in various periods of activation. The supernatants of these preparations were active in organotypic culture of chick embryo dorsal root ganglia. The inhibition of neurite growth on the 1st day of cultivation was followed by the neurite-stimulating effect. The fluctuation of neurite-inhibition and neurite-stimulation effect of macrophage supernatants suggest the availability of certain changes in cytokine composition in different periods of macrophage activation.     

Characteristics of a far-infrared germanium hot-hole laser in the Voigt and Faraday field configurations

A far-infrared laser utilizing intersubband transitions of hot holes in germanium with a hole density of 2.5×10¹⁴ cm⁻³ is investigated in the Voigt and Faraday field configurations. New comparative data for both configurations are given on the field ranges in which lasing takes place, the emission intensity and spectra, and their dependence on the temperature of the crystal. The Voigt configuration is shown to be preferable, having a broader lasing field range, a higher working temperature, a richer emission spectrum, and a higher intensity. Prominent details of the laser characteristics are discussed, and a comparison is made with calculations. Fiz. Tekh. Poluprovodn. 31, 1474–1481 (December 1997)     

Direct observation of a plastic deformation autowave in a zirconium alloy

An analysis is made of the evolution of local deformations during the elongation of samples of fine-grained zirconium alloy. It is established that the deformation distribution patterns exhibit ordered behavior where the types of ordering are closely related to the stages of the deformation curve. The results are compared with similar data from studies of the deformation fields of single-crystal and polycrystalline materials with different types of crystal structures and deformation micromechanisms. It is noted that all these similar results, including those of the present study, may be interpreted using autowave representations. Pis’ma Zh. Tekh. Fiz. 24, 26–30 (January 12, 1998)     

A Theoretical-Experimental Method of Estimating the Nonlinearity of Precision Digital-Analog Converters

The proposed method of estimating the nonlinearity of highly accurate digital-analog converters is based on subdivision of the conversion range of the converter into several parts. It is proposed to calculate the nonlinearity at the beginning and end of each part from the measured increments of the output signal of the converter. An analysis of the error in estimating the nonlinearity of the converter is given.