Properties of the translucent ceramics Nd: Y<Subscript>2</Subscript>O<Subscript>3</Subscript> prepared by pulsed compaction and sintering of weakly aggregated nanopowders

A translucent cubic yttria ceramic material doped by neodymium, namely, 1Nd: Y₂O₃, with particles of micrometer size (5–17 μm) and clearly defined boundaries is synthesized from nanopowders prepared by laser-induced evaporation with the use of magnetic pulsed compaction and vacuum sintering. Owing to the high activity of nanoparticles, the sintering is performed at temperatures below 1750°C without densifying additives. An increase in the sintering temperature to 900°C leads to an increase in the visual transparency of the ceramic materials and a decrease in the radiation attenuation coefficient. The samples of the translucent ceramics are characterized by rather large values of the microhardness (11.8 GPa) and the fracture toughness as compared to those of single crystals of the same composition. The fracture toughness of the ceramic material increases by a factor of approximately 2.5 with a decrease in the average crystallite size from 5.0 to 0.6 μm.     

Use of Numerical Experiments for Optimization of Mixing of Granular Materials

The operating and geometric parameters of mixing of granular materials are optimized using numerical experiments.     

Calculation and visual displaying of the water chemistry conditions in return cooling systems at thermal power stations

Matters concerned with treatment of cooling water at thermal power stations are addressed. Problems arising during operation of return cooling systems equipped with cooling towers are analyzed. The software used for monitoring, control, and indication of the hydraulic and water chemistry operating conditions of the circulation system at the Yaivinsk district power station is considered.     

Estimating the energy of electric breakdown in air gap between electrolyte and metal electrode

The influence of induced electric charge (localized on the surface of a suspended copper rod) on the formation of a protrusion (Taylor cone) on the inducing liquid (aqueous solution) surface is considered. At an applied voltage of U ≤ 12 kV, the protrusion height in the interval of pre-breakdown voltages (U < U _P) is limited by the electric field strength. At U > U _P, the growth of protrusion is terminated by an electric discharge, which drives the liquid to oscillate in a broad range of applied voltages U at almost constant multiple frequencies f = f ₀ n, which are resonantly switched at certain fixed U values. By measuring the amount of evaporated liquid, the energy (27.8 × 10⁻³ J) and current (64.9 A) of single discharge were evaluated and the electric capacitance (7.6 × 10⁻¹⁰ F) of a system comprising the water surface and suspended copper electrode was estimated. Serial connection of an additional capacitor (100 μF) to the copper electrode with induced electric charge leads to a threefold increase in these parameters.     

Simulation of radiative properties of substances used as soft X-ray source materials for an X pinch

This article presents the results of theoretical and experimental studies of the radiative properties of materials that can serve as sources of soft X-ray radiation in an X pinch. The important features of the theoretical model used to compute the radiation characteristics of the plasma with a complex chemical compound are discussed. It is shown that the yield of X-ray radiation can be increased by changing the chemical composition of the radiation source material. Theoretical results are compared with the data from experiments on measuring the total yield of X-pinch radiation where two types of wires are used: from NiCr and from Alloy 188, respectively. The physical processes in the symmetrical multilayer X pinch with the use of wires of tungsten and molybdenum are analyzed. A possible theoretical explanation of the physical effects observed in the experiment is discussed on the basis of the radiation spectra and of the W and Mo absorption and of their Rosseland and Planck paths.     

Regenerative electrical gas heater for GDL

The heat exchange and behavior of some structural elements of the heater under natural operational conditions of the GDL are investigated.     

Method of random wave vectors in simulation of anisoplanatic effects

A generalization of the method of random wave vectors [Appl. Opt. 36, 464 (1997)] that is suitable for a simulation of turbulence-induced anisoplanatic effects is proposed. A simulation of the cross-correlated phase fluctuations produced by two initially plane waves propagating through weak turbulence is considered. The variation of C(n)(2) along a propagation path and an effect of the finite outer scale of the turbulence are included in the simulation. The validity of the simulation method is verified by comparison of theoretical and simulated results. The simulation approach developed can be used in the problems related to adaptive optics, speckle inteferometry, guide stars, and imaging through turbulence.