Analysis of the Effect of Spacer Layers on Nonlinear Distortions of the Current–Voltage Characteristics of GaAlAs/InGaAs pHEMTs

Semiconductors - The paper presents the results of modeling the electrophysical parameters of AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistor (pHEMT) structures via...     

Calculation of the field distribution of an ultrawideband short electromagnetic pulse in the radiating aperture of an open-ended irregular waveguide

A new approach to the numerical calculation of the field of ultrawideband electromagnetic pulses in the radiating aperture of a horn antenna is studied. The approach is based on application of the concept of virtual electromagnetic waveguide and the method of nonstationary waveguide equations. It is shown that the proposed approach enables the control of the error in the obtained results and ensures a high accuracy of these results.     

Improving the reliability of metallic structures in service in the conditions with low climatic temperatures by efficient application of advanced methods of modification of the zone of the welded joint

The concept of investigations carried out to increase the reliability of metallic structures designed for operation in the conditions of low climatic temperatures is described. The worldwide tendencies in the investigation of the processes of the formation and fracture of materials and components at low climatic temperatures are analysed. The main methodological approaches, directed at ensuring high parameters of the service reliability of structures in low carbon, low alloy steels are outlined. The experimental data obtained in this area are analysed. The directions for further experimental and theoretical studies are indicated.     

Improving the service properties of metal structures working in the conditions of low climatic temperatures by methods of adaptive pulsed-arc welding

Experimental results confirm that the application of adaptive pulsed-arc welding with regulated heat input to welded material refines the structure of the metal, lowers the degree of softening of the fusion zone of the welded joint and greatly increases the mechanical properties of the welded joints, including structures working at low temperatures.     

Sequence of phase equilibrium states in the Dy-Mn-O system during thermal dissociation of the DyMn2O5 compound

The phase equilibria attained in the Dy-Mn-O system during step-by-step removal of oxygen from the DyMn₂O₅ compound are investigated using the static method (vacuum circulation setup, T = 725?950°C) and X-ray powder diffraction analysis of quenched solid phases. It is found that dissociation of DyMn₂O₅ proceeds in three stages. The temperature dependences of the equilibrium oxygen pressure for the revealed phase equilibria are determined experimentally. The changes in the standard thermodynamic functions of the reactions of dissociation and formation of DyMn₂O₅ and DyMnO₃ from the oxides are calculated.     

The immunomodulating action of cyclosporin A in vitro and in vivo on the lymphocytes of patients with alveolitis

The effect of various concentrations of ofloxacin, ciprofloxacin and lomefloxacin on the morphokinetic parameters of the cellular elements of the lung tissue of intact animals (mice, guinea pigs and dogs) was studied under the conditions of the tissue culture. It was shown that in a concentration of 100 micrograms/ml and the exposure time of 24 hours the drugs had no effect on the mobility and structure of the lung tissue cellular elements. When the drugs were used in a concentration of 100 micrograms/ml the mobility rate of the lymphocytes and macrophages proved to by markedly retarded by the end of the 24th hour. In a concentration of 1000 micrograms/ml the drugs killed the cell culture. There were detected no specific differences in the effect of the fluoroquinolones on the cellular elements of the lung tissue of the intact animals.