Evaluation of the energy characteristics of an asynchronous inverter-fed induction motor at different approximations of the magnetization curve

Results of research on the effect of magnetization-curve approximation of the electrotechnical steel and excitation frequency of an asynchronous inverter-fed induction motor (IFIM) on its energy performance with extremal control algorithms based on energy-saving criteria are presented in this article. An IFIM is a variant of a double-fed motor with static frequency converters in the stator and rotor circuits. Its application in a variable-speed drive meets to the greatest extent the main requirements for an ac machine in terms of speed regulation and providing high energy performance. It is shown that application of piecewise linear approximation by three sections and the spline function provides improved values of energy performance relative to the simple approximation by two linear sections due to becoming close to a real magnetization curve. It provides, under otherwise equal values of electromagnetic torque, a higher flux linkage with decrease in magnetization current. Control of the excitation frequency of the asynchronous inverter-fed induction motor has a significant influence on the steel losses of the machine. In the region of low loads, they are particularly important relative to the active losses in the motor windings.     

Variations in several acoustic emission parameters during testing of low-carbon steel specimens

The acoustic emissions that are formed during tension of specimens made from low-carbon steels is investigated. Interpretation of the experimental data is made from the point of view of real tests of engineering objects made from low-carbon steels in order to analyze the correlation of informative parameters with the deflected mode of a metal.     

Degradation-robust 850-nm vertical-cavity surface-emitting lasers for 25Gb/s optical data transmission

Highly efficient fast vertical-cavity surface-emitting lasers (VCSELs) for the 850-nm spectral range, promising for the development of optical interconnections with a data transmission rate of 25 Gbit/s per channel, are fabricated and studied. Lasers with a selectively oxidized current aperture 6 μm in diameter demonstrate multimode lasing with a quantum efficiency of 35–45% and a threshold current of 0.5–0.7 mA in the temperature range 20–85°C. According to the results of small-signal frequency analysis, the maximum modulation frequency of the lasers exceeds 17 GHz, with the rate of its increase with current exceeding 9 GHz/mA^1/2, which provides VCSEL operation at a rate of 25 Gbit/s in the entire working temperature range. Endurance tests for 3000 h did not reveal any sudden degradation of the lasers. The optical power at working point and the threshold current changed relative to that at the beginning of the tests by no more than 5 and 10%, respectively.     

Effect of tempering temperature on the fatigue strength of high-strength tool steel

Conclusions The use of heat treatment to obtain a high ultimate strength of machine parts operating under cyclic loading conditions is inexpedient, since raising the ultimate strength does not necessarily lead to a higher fatigue limit.I. M. Gubkin Moscow Institute of the Petrochemical and Gas Industry. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 9 pp. 30–32, September, 1974.     

Nonspecific resistance in patients with chronic gastritis undergoing treatment by drinking a calcium-sodium chloride low-mineralized mineral water

A Diabetes Care Management program was developed by PrimeCare, a network model HMO, to improve quality of life health outcomes and reduce the costs of medical care for its members with diabetes. The HMO used a systems-based approach to communicate information about appropriate self-management and standards of care to members and physicians. The focus of the program was to educate and encourage patients to self-manage their illness, and to partner with physicians, other health care providers and community organizations to achieve improved quality of life, clinical and financial results. Clinical process indicators were used to measure results of interventions. Significant increases in the percentage of participants receiving glycosylated hemoglobin (HbA1c) tests, retinal eye exams and lipid panel tests were achieved.