A facility for studying the spatial and temporal characteristics of a plume produced by interaction of high-power CO<Subscript>2</Subscript> laser pulses with a solid-state target in various gas environments

An experimental facility for studying the kinetics of molecular association formation from atoms produced by evaporation of the target material by powerful CO₂ laser pulses is described. First experimental results are presented for the spectral and spatial-temporal characteristics of the spread of Al atoms produced in interactions of laser radiation with aluminum oxide Al₂O₃, followed by AlO formation in various low-pressure (0.1–0.3 Torr) atmospheres. Images of structurally similar forms condensed on a glass surface have been observed with an atomic-force microscope.     

Effect of p-n junction overheating on degradation of silicon high-power pulsed IMPATT diodes

The thermal limits of the two-drift impact avalanche and transit-time (IMPATT) diode operating in the pulsed mode in the 8-mm wavelength region with a microwave power as high as 30–35 W have been estimated. It is shown that p-n junction overheat at an operating pulse length of 300 ns and a supply current amplitude of 11.3–15 A amounts to 270–430°C relative to an ambient medium. The temperature limit of junction overheating, above which IMPATT diodes rapidly degrade, was determined as 350°C. The presented results of X-ray phase analysis and depth profiles of Au-Pt-Ti-Pd-Si ohmic contact components confirm thermal limits of the IMPATT diode operating in the pulsed mode.

     

Hydrodynamic effects responsible for the modification of polysaccharides in an aqueous solution under laser irradiation

An attempt to determine factors responsible for the degradation of polysaccharide molecules in aqueous solutions under the action of laser radiation was undertaken. For this purpose, free-falling drops of water containing polysaccharides were irradiated by a laser beam and the corresponding hydrodynamical model was constructed. Laser irradiation of a drop of an aqueous solution of polysaccharides leads to the formation of oligosaccharides which can be applied in medicine.     

Reliability of Measurements of the Natural Gas Flow Rate and Volume in Gas Distribution Organizations

The proposed new approach to the procedure for measuring the flow rate and volume of gas under standard conditions in gas distribution organizations increases the reliability of the measurements. It is based on identical transformations of the Clapeyron-Mendeveleev equation, with modifications, and takes into account the composition of the natural gas and the recommendations of Federal Law No. 69-FZ (article 19) of March 31, 1999, about natural gas certification by Gosstandart of the Russian Federation. Use of the modified Clapeyron–Mendeleev equation is shown to changes the form of the transformation functions of various primary measuring transducers (turbine, rotary, vortex, ultrasonic, etc.) under the conditions of actual measurements.     

Long-Range Backup of Protection and Breaker Failures in 0.4-kV Grids

The algorithm of a digital device for solving the problem of long-range backup of protection and breaker failures in 0.4-kV grids and simultaneous reduction of the setting for actuation of the protection of the transformers and generators feeding the grids is considered. Recommendations are given for choosing the actuation settings. The device has been tested under conditions close to field ones. The economic effect consists in prevention of fires due to fault-initiated protection failures and durable disabling of substations for repair works.     

Influence of elastic stresses on the character of epitaxial crystallization of (Hg, Mn)Te

Available experimental data on the composition and conditions for crystallization of semiconductor Hg_1−z Mn_zTe solid-state solutions epitaxially grown on Cd(Zn)Te substrates reveal a number of peculiarities, which indicate that the substrate strongly affects the character of crystallization of the solid phase. In this paper we discuss data on liquid-phase epitaxy of Hg_1−z Mn_zTe which suggest the possibility that elastic stresses caused by the mismatch between the crystal lattice parameters of the substrate and the epitaxial layer can influence the composition and conditions for crystallization of these layers. An important tool in our investigation is a thermodynamic analysis of the metastable equilibrium between the stressed solid phase and the supersaturated solution of components. Fiz. Tekh. Poluprovodn. 31, 342–346 (March 1997)     

Nuclear magnetic resonance study of the electronic structure and hydrogen motion in the random b.c.c.-TaV2-H(D) system

Nuclear magnetic resonance measurements of the ¹H, ²D and ⁵¹V spin-lattice relaxation times and Knight shifts in the random b.c.c.-TaV₂H_x(D_x) system (0.1 x 2.4) have been performed over the temperature range 11–440 K. The relaxation data are analysed to obtain the parameters of H(D) diffusion, which is governed by a distribution of activation energies. The long-range diffusion of H(D) in b.c.c.-TaV₂H_x(D_x) is found to be much faster than in C15-type TaV₂H_x(D_x) with comparable H(D) contents. For all the studied samples (including those with mixed isotope composition) there is a distinct isotope effect on the average activation energy: . The measured values of the Knight shifts and the electronic (Korringa) contributions to the spin-lattice relaxation rates indicate that the density of d-electron states at the Fermi level decreases with increasing H(D) content.