Preparation and characterization of iron nanoparticles protected by an oxide film

Iron nanopowders ranging in particle size from 20 to 100 nm have been synthesized by reducing a 1-mm-thick iron(III) hydroxide layer in flowing hydrogen at 400°C and then passivated for 6–60 min in flowing argon containing 3% air. Our results demonstrate that the passivated iron nanopowders do not oxidize in air for six months. The iron nanoparticles have been characterized by X-ray diffraction (crystallite size evaluation), Auger electron spectroscopy, and polymolecular adsorption. The passivated iron nanoparticles have been shown to consist of a metallic core and oxide shell 2–4 nm in thickness.     

Solution of the Stefan problem in a conventional modified formulation for semitransparent media with consideration of isotropic radiation scattering

Numerical simulation of radiation-conductive heat transfer with a phase transition of the first kind in a semitransparent, isotropically scattering medium is carried out. A hypothesis of zero total external energy flow in the course of the phase transition is used in the formulation of the problem. The fields of temperature and the resulting radiation fluxes over a wide range of single scattering albedo and two values of the reflection coefficient of boundaries are obtained. It is shown that there is an increase in the reflection coefficient of boundaries, the effect of the scattering albedo decreases, and the melting process in general is delayed in time.     

Use of carbonizers in open-hearth steelmaking to reduce pig-iron consumption

Il'ich Zhdanov Metallurgical Institute. Translated from Metallurg, No. 10, pp. 40–42, October, 1988.     

Heat production kinetics and the scope for thermal self-ignition in wheat drying

Heat production has been examined at various oxygen partial pressures in the oxidation and thermal destruction of grain products by the use of a DAK-1-2 differential microcalorimeter. Estimates have been made on the adiabatic induction periods and critical sizes of the grain product layers on a metal surface (boundary conditions of the first kind) in the absence of heat transfer from the other surface. It is found that thermal self-ignition will occur in degenerate mode when thermal destruction is decisive.Chemical Physics Institute at Chernogolovka, Russian Academy of Sciences 142432 Chernogolovka, Moscow Region. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 1, pp. 55–60, January–February, 1994.     

Preparation and investigation of films of (Zn1−x Cdx)3(P1−y Asy)2 solid solutions

Pulsed laser evaporation was used to prepare thin films of (Zn_1−x Cd_x)₃(P_1−y As_y)₂ solid solutions. It was shown that varying the flux density of the laser radiation and the substrate temperature allows films to be obtained whose composition, structure, and electrical properties are similar to those of the bulk samples. Pis’ma Zh. Tekh. Fiz. 24, 85–88 (October 12, 1998)     

The sociomedical prevention of chronic bronchitis in workers in the mining industry]

High frequency of risk factors for origination of chronic bronchitis resulted in a striking growth of its prevalence among miners. Employment of the system of medical and social prophylaxis, especially during the stages of evolution of the malady, involving automatic diagnosis and prognostication, correction of immune disorders, recommendations toward adapting work to suit miners and assigning them to jobs for which they are suited--all this makes for reducing morbidity, permits saving the man-power resources making possible a rational distribution thereof among mining enterprises, which facts enable a substantial social and economic effect to be achieved.     

On regular realizability problems for context-free languages

We consider regular realizability problems, which consist in verifying whether the intersection of a regular language which is the problem input and a fixed language (filter) which is a parameter of the problem is nonempty. We study the algorithmic complexity of regular realizability problems for context-free filters. This characteristic is consistent with the rational dominance relation of CF languages. However, as we prove, it is more rough. We also give examples of both P-complete and NL-complete regular realizability problems for CF filters. Furthermore, we give an example of a subclass of CF languages for filters of which the regular realizability problems can have an intermediate complexity. These are languages with polynomially bounded rational indices.