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951.
952.
The periodic steady state of power distribution system loads is studied for electronically switched, time varying cases. Many loads of this type appear on contemporary power systems as energy saving and controllable demands. Several alternative methods of calculating the periodic steady state are discussed and a new method is proposed based on the frequency modulation property of the discrete Fourier transform. The new method is termed the gain-shift formula (GSF) because the format of the technique entails adding frequency shifted terms which represent the parameter to be calculated. An example of a triac-switched load on the distribution system is given. The main advantages of the GSF are: rapid calculation of the periodic steady state; and efficient calculation of the frequency spectrum of voltages and currents in the periodic steady state 相似文献
953.
954.
Klimova T. G. Nikolaeva O. O. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(2):296-304
Power Technology and Engineering - Anecessary requirement for automatic excitation regulation systems is ensuring the stability of the electric energy systems (EES) and the required quality of the... 相似文献
955.
V. M. Polyanskii N. I. Volkov O. M. Gorodkova Yu. N. Kopanov T. A. Frol'tsova A. N. Khailov 《Strength of Materials》1990,22(1):59-70
Direct data have been obtained for the creep of high- and medium-strength aluminum alloys in the stress range of O.6–1.2 of the nominal yield strength 0.2 in laboratory air and in aqueous NaCl solution at room temperature. On this basis using known theories approximating functions have been determined for the creep curves. Stress 0.2 serves as a natural boundary for the macroelastic and macroplastic regions in the first of which creep is only transient, and in the second there are transient, quasisteady-state, and accelerated stages. Extrapolated estimates of creep strain in the macroelastic region from data measured in the macroplastic region are not physically competent. However, a tendency towards an increase in ductility with an increase in time to failure at stresses greater than o.2 makes it possible to estimate by extrapolation the time for onset of the accelerated creep stage with low test stresses from measured values at greater stresses in the macroplastic region. Fractographic and strain indices revealed the harmful effect of moist atmospheres on the deformation and failure resistance of alloys with prolonged loading.Translated from Problemy Prochnosti, No. 1, pp. 50–58, January, 1990. 相似文献
956.
It has been found that malondialdehyde penetrates during smoking through filters and exhales with smoke from cigarettes such as: "Pall Mall", "Winston", "Camel", "Lucky Strike", "Kansas", "Mustang", "Ronson", "Chesterfield", "Rally", "Oscar" and "Marlboro". These cigarettes exhale malondialdehyde in a different way, in free form in the amount from 8.5 to 23.5 mg/kg cigarettes on an average of 13.3 mg/kg for the whole group and totally (in free and bounded form) from 9.5 to 26.5 mg/kg (average 16.9 mg/kg). Moreover, it has been found that filters retain this aldehyde in free form on an average of 9.9 mg/kg and totally (in free and bounded form) of 19.0 mg/kg. Without filters these amounts would increase aldehyde contents in smoke by 42.7 and 52.9%, respectively. Low malonalogenic properties of tobacco, high effectiveness of cigarette filters, high degree of tar deposition before inhaling into lungs and slow (6 min and longer) smoking decide about low level of exhalation of malondialdehyde in cigarette smoke. 相似文献
957.
T. R. Guilinger M. J. Kelly J. R. Scully T. M. Christensen D. Ingersoll J. A. Knapp R. I. Ewing W. H. Casey S. S. Tsao 《Journal of Fusion Energy》1990,9(3):299-304
We describe several electrochemical methods used to investigate the possibility of cold fusion phenomena in palladium and titanium tritide cathodes. We performed long-term (up to 77 days) electrolysis experiments with electrochemical cells of the University of Utah type at current densities as high as 1 A/cm2, while monitoring neutron and tritium levels. With some cells, we pulsed the current to determine if neutron bursts would result. In another cell, we used titanium tritide as the cathode to determine if D-T reactions yielding neutrons would occur. In no instance were levels of neutrons or tritium significantly above background except in the titanium tritide cell where isotopic exchange, occcurring between the electrode and the electrolyte, resulted in significant tritium levels. We also combined x-ray photoelectron spectroscopy (XPS) and electrochemical hydrogen permeation experiments to determine the effectiveness of various Pd surface treatment procedures on the resultant electrochemical hydrogen absorption efficiency. Electroanalytical and thermal desorption/gas analysis techniques indicated the maximum loading of H in Pd was to a ratio of HPd=0.8. 相似文献
958.
1. | The algorithm for the integration of the reactor kinetics equations, based on Gear's numerical methods, provides an efficient means of calculating critical-assembly accidents, in which the assembly rapidly goes into prompt-neutron supercriticality and then slowly cools down. |
2. | The maximum temperature in the assembly zones, and the energy released during the burst, are not appreciably affected by the positive reactivity insertion rate. |
3. | Accident damage is significantly reduced (the assembly remains operational) only in cases of rapid scram-rod dumping (0.3 sec delay), provided the temperature coefficient of reactivity equals or exceeds the rated value. |
959.
An Operator-integration-factor splitting method for time-dependent problems: Application to incompressible fluid flow 总被引:1,自引:1,他引:0
In this paper we present a simple, general methodology for the generation of high-order operator decomposition (splitting) techniques for the solution of time-dependent problems arising in ordinary and partial differential equations. The new approach exploits operator integration factors to reduce multiple-operator equations to an associated series of single-operator initial-value subproblems. Two illustrations of the procedure are presented: the first, a second-order method in time applied to velocity-pressure decoupling in the incompressible Stokes problem; the second, a third-order method in time applied to convection-Stokes decoupling in the incompressible Navier-Stokes equations. Critical open questions are briefly described. 相似文献
960.