Analytic approach to the computation of the temperature distribution in multilayer structures under heating by cw scanning laser radiation

By using integral transform methods, an approach is developed to the solution of a problem on the temprature distribution in multilayer structures heated by cw scanning laser radiation, with phase transitions in the layers taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 6, pp. 1000–1010, December, 1987.     

Considerations in application and selection of unit substationtransformers

This paper discusses secondary unit substations transformers (USTs) ranging from 300 up through 2500 kVA with 34.5-kV maximum primary voltages and with secondary voltages 600 V and below. Pad-mounted (compartmentalized) transformers are not considered in this paper. The first part of this paper discusses USTs belonging to two general categories, liquid type and dry type (nonliquid type). Liquid types include a discussion of the presently available insulating fluids: mineral oil, high-temperature hydrocarbon fluid, silicone fluids, and the new vegetable-based fluids. Dry types include a discussion of vacuum pressure impregnated polyester, vacuum pressure encapsulated silicone, partial cast, and full cast insulation systems. The National Electric Code (1999) requirements as they affect both liquid- and dry-type USTs for both outdoor and indoor locations are considered. The paper discusses the relative advantages of each UST within each category with respect to the following: (1) first cost; (2) operating costs (losses); (3) overload capability; (4) fan cooling; (5) space factor; (6) environmental factors; (7) sound levels; and (8) maintenance     

“Metallisation” of oxide surfaces observed by in situ high-resolution electron microscopy

Intense irradiation (25–40 A/cm²) at intermediate energy (400 keV) has been found to cause “metallisation” of tungsten oxide and titanium niobate crystal surfaces. The possible mechanisms and the likely consequences for high-resolution imaging of clean oxide surfaces are briefly discussed.     

Half-bridge inverter using 4H-SiC gate turn-off thyristors

This paper reports on the first demonstration of a half-bridge power inverter constructed from silicon carbide gate turn-off thyristors (GTOs) operated in the conventional GTO mode. This circuit was characterized with input bus voltages of up to 600 VDC and 2 A (peak current density of 540 A/cm²) with resistive loads using a pulse-width modulated switching frequency of 2 kHz. We discuss the implications of the thyristor's electrical characteristics and the circuit topology on the overall operation of the half-bridge circuit. This work has determined the conservative critical rate of rise value of the off-state voltage to be 200 V/μs in these devices     

Two-fluid large-eddy simulation approach for particle-laden turbulent flows

In this paper, effects of particles on the subgrid scales of turbulence are properly accounted for during the modeling of subgrid scale stresses in the large-eddy simulation (LES) of fluid phase. In doing so, we propose closed filtered kinetic equations for phase space density of the particle. The various moments of these equations give the `fluid' equations which can be considered as the LES equations for the particle phase. The influence of subgrid scales motion on the particles is included in these `fluid' equations.