Correlation between magnetic properties and the hardness of powder steels

Density and carbon content are studied for their effect on strength (hardness) and magnetic (coercive force, saturation magnetization) properties of powder steels ZhGr1 and ZhGr1D3. It is shown that the hardness of articles made of these steels may be determined indirectly by measuring two magnetic characteristics.Physicotechnical Institute, Russian Academy of Sciences, Izhevsk. Translated from Poroshkovaya Metallurgiya, Nos. 1–2, pp. 67–69, January–February, 1994.     

Hydrogen-assisted cracking

This article reviews a number of case studies involving hydrogen-assisted cracking in steels. Before the case studies are presented, the current state of understanding of hydrogen-assisted cracking is briefly reviewed. At present there are two leading approaches to the development of a mechanism of hydrogen-assisted cracking, one based upon bond weakening, and the other upon strain localization. As the case studies illustrate, hydrogen-assisted cracking can lead to failures in perhaps unexpected circumstances. The need for the wider dissemination of information about hydrogen cracking to design engineers is indicated.     

Crystallization and melting behaviour of poly(butylene terephthalate) in poly(butylene terephthalate)/polyarylate blends

Summary The crystallization and melting behaviour of poly(butylene terephthalate) has been studied in the pure state and in its blends with a polyarylate of bisphenol A and isophthalic/terephthalic acids. Differential scanning calorimetry has been used as experimental technique and the effects of different thermal treatments have been analyzed. Results show the hindrance for the crystallization of poly(butylene terephthalate) imposed by the presence of polyarylate, as well as the existence of multiple melting after isothermal crystallization. Explanations are given for the observed behaviours.     

A Study of the Dust Collection Process in the Production of Refractories

An experimental setup for studying filter-assisted dust collection is described. The role of various factors — hydraulic resistance, filtering velocity, dust concentration, pressure drop, efficiency of recovery — in the performance of filters intended for use in the production of refractory materials is considered. The dust removal method was tested under industrial conditions at the Semilukskii Refractory Plant and can be recommended for wider use in different branches of industry.     

钢的连铸用保护渣的表征

在钢的连铸过程中,结晶器保护渣的性质强烈地影响着铸造的行为、钢的质量、以及连铸工艺的环境.本研究采用高温显微技术来研究保护渣的熔化行为,采用液滴测试方法来测定保护渣的熔化速率.结果表明:自由碳是控制保护渣熔化行为的主要因素.熔化速率随碳的反应能力的增加而增加,随着碳含量的减少而增加.     

Hydrogen Resistance of Steels Alloyed with Nitrogen

We study the resistance of stainless steels with different contents of nitrogen after plasma-arc remelting to hydrogen degradation. The dependence of the mechanical properties of steels on the content of nitrogen is quite complicated, which is explained by changes in the phase composition. In the analyzed collection of steels (Kh18AN9, Kh20AN15, Kh18AG10, and Kh18AG15), Kh18AG15 steel has the best combination of the characteristics of strength and plasticity in hydrogen.     

Challenges in computer architecture evaluation

We focus on problems suited to the current evaluation infrastructure. The current limitation and trends in evaluation techniques are troublesome and could noticeably slow the rate of computer system innovation. New research has been recommended to help and make quantitative evaluations of computer systems manageable. We support research in the areas of simulation frameworks, benchmarking methodologies, analytic methods, and validation techniques.     

Temporal and radial evolution of the populations of CuI levels inthe CuBr vapor laser

Populations of CuI ground state, resonance, and metastable levels have been measured in CuBr laser with and without hydrogen additives. Temporal evolution and spatial distribution populations have been studied during the excitation pulse and also during the interpulse period of time. Addition of hydrogen results in a smaller rate of resonance and metastable levels excitation and smaller depopulation of the ground state during the excitation pulse. Repopulation of the ground state after the excitation pulse with hydrogen is much faster. CuBr molecules have been detected only in the periphery of the active zone. The density of the CuBr molecules had no noticeable change either during the excitation pulse or in the interpulse period     

Isolated DC-DC converters with high-output voltage for TWTA telecommunication satellite applications

Two alternatives for the implementation of an isolated DC-DC converter operating with a high output voltage and supplied by an unregulated low input voltage are presented in this paper. The proposed topologies are especially qualified for the implementation of travelling wave tube amplifiers (TWTA) utilized in telecommunication satellite applications due to their low mass and volume and their high-efficiency. The converters studied follow different principles and the main operational aspects of each topology are analyzed. A two-stage structure composed by a regulator connected in series with a ZVS/ZCS isolated DC-DC converter is the first topology proposed. The second topology studied is an isolated single-stage converter that continues being highly efficient even with a large input voltage variation. The experimental results obtained from two prototypes, implemented following the design procedures developed, are presented, verifying experimentally the characteristics and the analysis of the proposed structures. The prototypes are developed for an application requiring an output power of 150 W, a total output voltage of 3.2 kV and an input voltage varying from 26 V to 44 V. The minimum efficiency obtained for both converters operating at the nominal output power, is equal to 93.4% for the two-stage structure and equal to 94.1% for the single-stage converter.     

A PLL clock generator with 5 to 10 MHz of lock range formicroprocessors

A microprocessor clock generator based on an analog phase-locked loop (PLL) is described for deskewing the internal logic control lock to an external system lock. This PLL is fully generated onto a 1.2-million-transistor microprocessor in 0.8-μm CMOS technology without the need for external components. It operates with a lock range from 5 to 110 MHz. The clock skew is less than 0.1 ns, with a peak-to-peak jitter of less than 0.3 ns for a 50-MHz system clock frequency