Adsorption and emission features of collectors of thermionic energy converters in the case of mass transfer in the interelectrode gap

Translated from Atomnaya Énergiya, Vol. 69, No. 3, pp. 196–197, September, 1990.     

Manifestation of the Portevin-Le Chatelier effect in the Kh20N80 alloy

It has been found that the single-phase nickel alloy Kh20N80 demonstrates discontinuous flow in the range of deformation temperatures of 300–650°C. It is shown that the discontinuous flow of this alloy possesses signs of the Portevin-Le Chatelier effect, strong localization of deformation, and negative strain-rate sensitivity of the flow stress. Furthermore, three specific features of the discontinuous flow of the Kh20N80 alloy have been revealed: (1) the “normal” dependence of the critical degrees of the onset of the discontinuous flow of ?_cr on the strain rate; (2) the “inverse” temperature dependence of ?_cr; and (3) the positive temperature dependence of the flow stress. These special features appear to be caused by the formation of a short-range-order structure, which occurs in this alloy at temperatures of approximately 350–500°C.     

Immune clonal selection algorithm for capacitated arc routing problem

In existing metaheuristics for solving the capacitated arc routing problem, traversal local search operators are often used to explore neighbors of the current solutions. This mechanism is beneficial for finding high-quality solutions; however, it entails a large number of function evaluations, causing high computational complexity. Hence, there is a need to further enhance the efficiency of such algorithms. This paper proposes a high-efficiency immune clonal selection algorithm for capacitated arc routing instances within a limited number of function evaluations. First, an improved constructive heuristic is used to initialize the antibody population. The initial antibodies generated by this heuristic help accelerate the algorithm’s convergence. Second, we show how an immune clonal selection algorithm can select in favor of these high-quality antibodies. By adopting a variety of different strategies for different clones of the same antibody, it not only promotes cooperation and information exchanging among antibodies, but also increases diversity and speeds up convergence. Third, two different antibody repair operations are proposed for repairing various kinds of infeasible solutions. These operations cause infeasible solutions to move towards global optima. Experimental studies demonstrate improved performance over state-of-art algorithms, especially on medium-scale instances.     

Possibilities of production of nanopowders with high power ELV electron accelerator

Electron-beam evaporation of various natural and industrial materials in the atmosphere of different gases at atmospheric pressure can be used for the synthesis of nanosize powders. These powders are characterized by high purity and may exhibit unusual properties. In particular, nanopowders of silicon dioxide and oxide (SiO₂, SiO), magnesia (MgO), alumina (Al₂O₃), titania (TiO₂), gadolinium oxide (Gd₂O₃), various metals (tantalum, molybdenum, nickel, aluminium, copper, silver), semiconductor (Si), nitrides (AlN, TiN), and some other substances had been produced. The process of nanopowder synthesis is highly effective; in particular, the yield of oxides can exceed ten kilograms per hour.     

Excitons in single and double GaAs/AlGaAs/ZnSe/Zn(Cd)MnSe heterovalent quantum wells

Exciton photoluminescence spectra, photoluminescence excitation spectra, and magnetophotoluminescence spectra of single (GaAs/AlGaAs/ZnMnSe) and double (GaAs/AlGaAs/ZnSe/ZnCdMnSe) heterovalent quantum wells formed by molecular beam epitaxy are studied. It is shown that the exciton absorption spectrum of such quantum wells mainly reproduces the resonant exciton spectrum expected for usual quantum wells with similar parameters, while the radiative exciton recombination have substantial distinctions, in particular the additional localization mechanism determined by defects generated by heterovalent interface exists. The nature of these localization centers is not currently clarified; their presence leads to broadening of photoluminescence lines and to an increase in the Stokes shift between the peaks of luminescence and absorption, as well as determining the variation in the magnetic g factor of bound exciton complexes.     

Cesium vapor source based on gas-regulated heat pipe for an autonomous thermionic egc

The results of work on the development of a source of cesium vapor for a thermionic EGC based on a gasregulated heat pipe and investigations of its basic technical characteristics in the cesium vapor range 30–700 Pa are presented. It is shown that the evacuation capacity and zero response time of a gas-regulated heat pipe based vapor source and the possibility of continuously monitoring the cesium vapor pressure via the temperature in the adiabatic zone and the pressure in the gas reservoir are all effective.     

Preliminary performance results of the Cs-Ba tacitron invertor

Experiments were conducted which demonstrated that an inverter could be configured by connecting two Cs-Ba tacitrons in a push-pull mode with alternating voltage grid control. The inverter characteristics demonstrated in the thyratron mode include discharge current up to 20 A, collector voltage of 30 V, conduction voltage drop less than 2.5 V, and modulation frequencies up to 10 kHz. In the tacitron model, the invertor operated at a discharge current of up to 3.5 A, collector voltage of 25 V, conduction voltage drop of 3-3.5 V, and modulation frequencies up to 20 kHz