Charge neutrality violation in quantum-dot lasers

Theory of quantum-dot (QD) lasers is augmented to include, in a self-consistent manner, the QD-layer charge. The electron- and hole-level occupancies in QDs are obtained through the solution of the problem for the electrostatic-field distribution across the junction. They are shown to differ from each other. As a result, the local neutrality is broken down in each QD, i.e., the QD layer is charged. The key dimensionless parameters controlling the difference of the hole- and electron-level occupancies are revealed. The detailed analysis of the gain and spontaneous radiative recombination current density is given, having regard to the fact of violation of the charge neutrality in QDs. The gain-current density dependence is calculated, The voltage dependences of the electron- and hole-level occupancies, gain, and current density are obtained. Particular emphasis is given to the transparency and lasing threshold characteristics. Optimization of the QD-laser structure is carried out. The optimum surface density of QDs, minimizing the threshold current density, is shown to be distinctly higher than that calculated without regard for the lack of the charge neutrality in QDs     

Heating of condensed particles in a gas flow

A solution is obtained for the heating of condensed particles in a gas flow, from which one derives an expression for the temperature reduction and rate of cooling of the gas.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 23, No. 6, pp. 1050–1053, December, 1972.     

Analytical control of contaminating components in wastewater from viscose manufacturing operations

Conclusions The world working level of control of the composition of natural waters and wastewater has been analyzed.A mathematical model has been proposed which characterizes the level of environment-protective standardization and the tendency for its development.The information stream of national and international standards with respect to nomenclature and quality has been analyzed. Tendencies have been disclosed which coincide with mathematical calculations.A high completeness in standardization of procedures in performing measurements of the composition of natural waters and wastewater, orderliness in standardization, a tendency toward overall standardization, automatic, and instrumentation of standardized methods of performing measurements are characteristics of the leading countries in the environmental-protective respect (as applied to the needs to viscose manufacturing).The overall model of analytical control which has been made up in the leading countries in the environmental respect can be used in the man-made fibre sub-branch upon appropriate treatment.Translated from Khimicheskie Volokna, No. 6, pp. 21–26, November–December, 1988.     

Gear pumps for the man-made fibre industry

Gear pumps for the man-made fibre industry     

A thermodynamic analysis of the formation of zirconium nitride from zirconium tetrachloride

Conclusions On the basis of a thermodynamic calculation of the heterogeneous system zirconium-nitrogen-hydrogen-chlorine the feasibility is demonstrated of obtaining zirconium nitride in the condensed state, with a virtually complete transformation of the metal into the nitride and a comparatively low expenditure of energy (about 80,000 kJ/kg), at temperatures of 2000–2400°K, a pressure of 1 bar, and a 50-fold dilution of the stoichiometric composition to a ZrNClH ratio of 1504200. Use of ammonia instead of nitrogen at the same ratio of the elements increases the amount of energy expended to 106,000 kJ/kg.Translated from Poroshkovaya Metallurgiya, No. 12 (156), pp. 1–3, December, 1975.     

Adaptive control system for the viscosity of viscose

Conclusions A structure and algorithm have been developed for an adaptive system for control of viscose viscosity in the manufacture of artificial fibres.The control system has been introduced into the ACS TP for viscose tire cord manufacture of the Svetlogorodsk Khimvolokno PO.Translated from Khimicheskie Volokna, No. 5, pp. 22–25, September–October, 1986.     

Increasing the wear-resistance of yarn-guide bend elements in liquid treatment of yarns

Conclusions The frictional force of yarns on yarn-guide bends in spinning and washing essentially does not depend on the linear density of the yarn or its rate of movement within the range 60–300 m/min.The frictional force of yarns on rings of artificial corundum is less than on rings of metal, Pyroceram, or glass.Special constructions of the elements of yarn-guid bends, which make it possible to reduce the length of contact of the yarn with the friction body, considerably reduce frictional force and, consequently, the yarn tension in the system.Translated from Khimicheskie Volokna, No. 3, pp. 43–44, May–June, 1986.