Methods of constructing suboptimal solutions of integer programming problems and successive improvement of these solutions

Two-stage methods of constructing an improved suboptimal solution of problems of integer linear programs with nonnegative coefficients are developed. A solution is constructed on the first stage on the basis of newly introduced criteria, and the indices of the intervals of the variables determined, where the coordinates of the optimal solution may differ from the suboptimal solutions already constructed. On the second stage, new solutions are constructed by varying the values of the variations only within these intervals and the best of these new solutions are selected. Computational experiments for high-dimension problems confirm the high degree of efficiency of the newly developed methods.     

Production of powders from cast iron swarf and some features of the manufacture of parts from them. II. Some features of the manufacture of P/M parts and their structure and properties

Conclusions Increasing the amount of cast iron powder in such a charge and raising the sintering temperature of compacts result in the formation in the alloy structure of a coarse cementite network among the grains and a fine cementite network along the slip lines. Consequently, what is needed to increase the strength of the synthesized alloys is either a low rate of cooling in sintering or additional heat treatment, designed to prevent the presence of structurally free cementite in the structure of the finished alloys. The optimum sintering temperatures for the iron-cast iron materials in an endothermic gas atmosphere, ensuring the highest strength properties in finished P/M parts, is 1200°C. Alloys containing 10 and 20% cast iron can be recommended for construction applications, and others, for the manufacture of parts operating under conditions of friction and increased wear without dynamic loads. These include the components of the pump unit of the rotary compressor of a domestic air conditioner.Translated from Poroshkovaya Metallurgiya, No. 9(321), pp. 4–10, September, 1989.     

Mixed MVSb oxides as oxidehydrogenation catalysts

Mixed MVSb (M = Ni, Co, Bi, Sn) oxides supported by alumina were characterized and evaluated for oxidative dehydrogenations of light paraffins, ethylbenzene and ethanol. The most selective NiVSb catalyst was the most easily reduced that was interpreted on the assumption of reaction redox mechanism. The results of kinetic measurements revealed the concentration of gas-phase oxygen to be a key parameter affecting the dehydrogenation selectivity. To maintain it an optimum along the catalyst bed, a distributed oxygen feed was used.     

Deformation potentials of the Γ(000) band extrema in CdGa2S4

For the ternary compound CdGa₂S₄ the values of the contributions to the temperature coefficient of the absorption edge due to lattice dilatation (dE/dT)_L and the electron-phonon interaction (dE/dT)_eph are found. The deformation potentials of the bottom of the conduction band (12.3 eV) and top of the valence band (−10.9 eV) are calculated. Fiz. Tekh. Poluprovodn. 32, 148–150 (February 1998)     

The energy loss spectrum in oxygen-octahedron ferroelectrics

The characteristic energy loss function spectra in oxygen-octahedron ferroelectrics up to 35 eV have been investigated by VUV spectroscopy methods. Information about the energy spectrum of electrons in these crystals has been received.     

Development of a technology for pressing high-density products using gas-draining methods

The factors that hinder the formation of high-density compacts by cold-pressing of powders are considered. The main factors are the gases present in the charge and the technological lubricant introduced to facilitate the work of the press mold. A procedure has been developed for calculating the efficiency of gas drainage from a mold and the pressure in gas pores in the compacts. Recommendations are made for increasing the density of compacts from iron powders by a single cold pressing.Scientific-Industrial FirmBakkonditsioner,Baku. Translated from Poroshkovaya Metallurgiya, No. 5–6, pp. 34–39, May–June, 1994.     

Development of a higher-density pressing technology using gas drainage. II. Device for evaluating the efficiency of gas drainage from molding dies and experimental assessment of factors affecting it

A device designed specifically to determine the efficiency of gas drainage during ejection from a molding die and the intrapore gas pressure in compacts is described. This device was used to study how the morphology of iron powder particles, the size and shape of the molded parts, the compact rate and production run, as well as amount of plasticizer affect the parameters studied. Recommendations are made for developing technologies for pressing high-density briquets.Scientific Industrial Firm Bakkonditsioner. Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 19–26, July–August, 1994.     

Anharmonicity of Lattice Vibrations in Bi2Se3 Single Crystals

Semiconductors - The temperature dependences of the Raman-active frequencies $$E_{g}^{2}$$ , $$A_{{1g}}^{2}$$ in layered Bi2Se3 single crystals are studied. The contribution of the thermal...