An automated system based on cryogenic probe station for integrated studies of semiconductor light-emitting structures and wafers in the range of 15 to 475 K

An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented.     

Vibratory drier for the chemical industry

Modern designs are examined, and technical data presented for vibratory electric and convection driers, driers with infra-red sources, and steam driers.     

Structure of the repeating unit of acid polysaccharide from Alteromonas sp. 4MS17

An acidic polysaccharide from Alteromonas sp. 4MC17 is built up of trisaccharide repeating units containing D-glucose, D-mannose and D-galacturonic acid residues. On the basis of methylation studies, 1H and 13C NMR-spectroscopy data, including two-dimensional homonuclear correlation spectroscopy and nuclear Overhauser effects, the following structure was suggested for the polysaccharide repeating unit: -->4)-beta-D-Glcp-(1-->4)-beta-D-GalpA-(1-->4)-beta-D-Manp-( 1-->.     

Radiation–Thermal Decomposition of Nitric and Acetic Acids in a Aqueous Nitrate Solution

The kinetics of radiation, thermal, and radiation–thermal decomposition of a mixture of nitric and acetic acids in water solutions of sodium nitrate is investigated under homogeneous conditions and with a solid phase introduced in the form of sandstone. The experimental data are used to calculate the temperature dependences of the rate of radiation, thermal, and radiation–thermal decomposition of the acids. The results obtained make it possible to calculate the dynamics of decomposition of acids for the conditions of deep burial of liquid radioactive wastes.     

Surface and Biocidal Properties of Gemini Cationic Surfactants Based on Propoxylated 1,6-Diaminohexane and Alkyl Bromides

Two new classes of gemini cationic surfactants—hexanediyl-1,6-bis[(isopropylol) alkylammonium] dibromide {in the abbreviation form: C_nC₆C_n[iPr-OH] and C_nC₆C_n[iPr-OH]₂; alkyl: C_nH_{2n + 1} with n = 9, 10, 12 and 14}—have been synthesized by interaction of alkyl bromides with N,N′-di-(isopropylol)-1,6-diaminohexane and N,N,N′,N′-tetra-(isopropylol)-1,6-diaminohexane. The surface tension, electrical conductivity, and dynamic light scattering (DLS) techniques were used to investigate the aggregation properties of the gemini cationic surfactants in aqueous solution. The formation of critical aggregates at two concentrations in an aqueous solution from obtained gemini cationic surfactants were determined via the tensiometric method. Thus, these gemini cationic surfactants start to form aggregates at concentrations well below their critical micelle concentrations (CMC). The surface properties and the binding degree (β) of the opposite ion were tested against the length of the surfactant hydrocarbon chain and the number of the isopropylol groups in the head group. By applying the DLS technique, it was explored that how the number of isopropylol groups in gemini cationic surfactants with C₁₂H₂₅ chain affects the sizes of micelles at concentrations greater than CMC. It was discovered that the obtained gemini cationic surfactants have a biocidal character.     

Density distribution at the detonation front of cylindrical charges of small diameter

A synchrotron radiation based technique is use to study the density distribution at the detonation front and its neighborhood for condensed explosives. Particular data are obtained on the structure of the detonation front in TNT, RDX, and an alloy of TNT with RDX; a comparison of the data with those obtained using different techniques confirms the correctness of the technique. It is concluded that adequate information on the structure of the chemical-reaction zone can be obtained for charges of small diameter. At the same time, it is shown that the Chapman-Jouguet parameters for such charges are far from their predicted values for an infinite medium. The results of the work, including those on the curvature of the detonation front in charges of small diameter, supplement the existing knowledge of the detonation transformation in condensed explosives. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 2, pp. 91–99, March–April, 2007.     

Problem of fabrication of diamond-based high-power microwave FETs

Numerical experiments are used to plan the development of diamond-based microwave FETs with an output power of 2.5 W per 1 mm of the gate width at a frequency of 15 GHz. A family of the I–V characteristics of the Schottky-barrier FET with gate length L _G = 50 nm and width W = 1 mm is calculated. Bases on analogy with a TGF2023-20 GaN HEMT, the topology of the high-power diamond transistor (parallel cells with gate widths W = 1.2 mm and 24 elementary gates per cell) is constructed.     

Tool–workpiece interaction in deformational cutting

A method is developed for the comparison of deformational cutting and traditional cutting in terms of the force and energy consumption. The force required is less in deformational cutting than in traditional cutting.     

Neural-network simulation of diesel operation under a nonsteady load

The operation of diesel engines with nonsteady loads is considered. Numerical experiments are based on a model, a neural network, and test-bench data.