Electrodynamic properties of plane wire grids

The method of submillimetre BWT-spectroscopy is used to measure electrodynamic parameters of the grids wound from conductors with circular cross sections. The coefficients of transmission and reflection, reflected wave phase, and ohmic losses in conductors are measured in the range of small values of diffraction parameteræ=D/λ<1 (λ is the wavelength,D is the grid spacing) for the case where the wave vector E is directed along the conductors (E‖1). In the diffraction region (0.5<æ<2.2), transmission spectra of the grids are measured for both polarizations. The data obtained are compared to those of different theoretical methods for describing grid electrodynamics. In particular, the transmission spectra are shown to have some peculiarities in the vicinity of sliding pointsæ=1;2 (E⊥1), unpredicted by corresponding theories.     

Non-alloy Cr/Au Ohmic contacts in the technology of planar beam-lead GaAs <Emphasis Type="Italic">p-i-n</Emphasis> diodes

The characteristics of non-alloy Cr/Au ohmic contacts in planar beam-lead GaAs p-i-n diodes have been studied. The room-temperature reduced contact resistance in the structures studied was 2 × 10⁻⁶ Ω cm². The obtained parameters of p-i-n diodes allow these devices to be used as limiters in radar protection systems.     

Determination of forms of element occurrence in samples of vanadium slag and slime

Complex research of technogenic raw material samples is carried out. Using the methods of X-ray diffraction and X-ray fluorescence analysis, the chemical and phase compositions of roasted vanadium slag and slime are established. The compounds of the base elements are extracted sequentially according to a three-stage scheme recommended by the European Commission. Their low mobility is recorded. Vanadium and manganese compounds possess higher mobility in the slag than in the slime. Iron and chromium form solid oxides and silicates that are disintegrated only under the action of HNO₃. The methods of microwave plasma atomic emission spectrometry (MP-AES) and inductively coupled plasma mass spectrometry (ICP-MS) are used to determine the gross contents of V, Mn, Fe, Cr, Zn, Ni, Ba, Sr, Rb, Y, Ga, Ge, Mo, La, and Ce in the samples of slag and slime. It is shown that the total concentration of V, Mn, and Cr considerably exceeds the values of the maximum allowable concentrations (MAC) of these elements established for soils, objects with a sample base that is no less complex. Possible leaching of the forms of elements from solid samples of vanadium slime and slag with 0.1 M Na₂CO₃ solution and the mobile phase for reversed-phase high performance liquid chromatography (RP HPLC) is studied. Mostly, vanadium compounds are extracted under these conditions. Manganese compounds are extracted by 1–10%. An inconsistency is found between the time of retention during the chromatographic separation of V and Fe forms in the model mixtures and solutions obtained after the samples of vanadium slag and slime have been chemically treated.     

Dynamics of the gas phase in a fuel-rod assembly simulator with a spacing grid

An experimental study of two-phase flow in a model of assembly of 37 fuel rods in a triangular arrangement was performed. Measurements were performed with local gas supply through a unit nozzle. Distributions of the local void fraction were obtained at various values of angular coordinate and distance from a spacing grid. It was shown that most of the gas phase moves in a space produced by the walls of three nearby rods. A significant increase of gas phase concentration takes place in the flow region just after the grid.     

Formation of an ordered structure in the Cu-49 at % Pd alloy

We compare the kinetics of the formation of an ordered structure in the Cu-49 at % Pd alloy in various initial states and demonstrate that the alloy can be brought into a single-phase, B2-ordered state, at variance with the commonly accepted Cu-Pd phase diagram. The alloy in this structural state has an extremely low resistivity: ?? = 5.48 × 10^?8 ?? m.     

Application of a casting-rolling unit in a combined process of production of high-quality products from copper scrap

A highly efficient technology of processing of copper scrap is considered: it implies a combination of melting, refining, casting, and rolling to produce high-quality copper products. The characteristics and parameters of the main element of this technology (casting-rolling unit) and its most important functional element (mold), which substantially affects the unit capacity and the quality of the forming billet, are described.