Analysis and design-optimization of LCC resonant inverter forhigh-frequency AC distributed power system

The analysis and design of an LCC resonant inverter for a 20 kHz AC distributed power system are presented. Several resonant converter topologies are assessed to determine their suitability for high efficiency power conversion, under resistive and reactive loads. Two LCC-resonant inverter designs were implemented. One with all switches operating with zero voltage switching (ZVS), and another with two switches operating with ZVS and two switches with zero current switching (ZCS). The experimental results are presented along with a performance comparison of the two versions     

Pyrolysis of tertiarybutylphosphine at low pressure

The pyrolysis of tertiarybutylphosphine (TBP) has been studied in the low pressure conditions used for chemical beam epitaxy (CBE). The pyrolysis studies were carried out in low pressure reactors of two different configurations, one of which is a cracker cell designed for use in a CBE system. The reaction products were studied using a quadrupole mass spectrometer. The products observed are accounted for by a reaction mechanism involving homolysis of the parent TBP molecule to produce PH₂ and C₄H₉ radicals. These undergo subsequent reactions to form the stable products C₄H₈, PH₃ and H₂, with smaller amounts of P and P₂ being produced. The production of the sub-hydride PH₂ using this cracker cell design indicates that the use of partially cracked TBP may be a promising technique for reducing the amount of carbon incorporated into the growing epitaxial layer.     

Speed control of a PV powered DC motor driving a self-excited3-phase induction generator for maximum utilization efficiency

Photovoltaic (PV) powered DC motors driving dedicated loads (e.g. water pumps) are increasingly used in the remote rural areas of many developing countries. The key to their success is simplicity (direct coupling, no DC-AC conversion, no storage batteries, etc.). Because of the relatively high cost of the PV array, the system designer is interested in maximizing its utilization efficiency. A PV powered DC motor can also be used to drive a three-phase self-excited induction generator (SEIG). This arrangement is useful as part of an integrated renewable energy system (IRES), which takes advantage of the inherent diversity of wind and solar energy in most developing countries to improve power quality. The SEIG is driven by a wind-turbine, DC motor, or both. Another advantage of this arrangement is its versatile control characteristics through the DC motor control. This paper describes a technique to maximize the utilization efficiency of the PV array by controlling the field current of the DC motor through a DC chopper     

On the broad band transmittance of direct irradiance in a cloudless sky and its application to the parameterization of atmospheric turbidity

The total atmospheric attenuation of direct irradiance is often expressed as the product of independent broad band transmittances pertaining to the different depleting materials in the atmosphere. In theory, it is clear however that the broad band transmittances of the two most important attenuating factors, aerosols and water vapour, cannot be considered independent of each other. This is most relevant when trying to isolate the effect of atmospheric aerosols from the measurement of broad band direct irradiance. These questions are addressed in an analytical approach. Several broad band direct transmittance equations and corresponding turbidity parameters are discussed with respect to the analytical results. Simulations made with the SMARTS2 spectral radiative transfer code are used to illustrate the broad band effects.     

Performance enhancement of scan converter-based transientdigitizers by digital image processing

A method for the enhancement of dynamic performance of scan converter-based transient digitizers is proposed. First, a technique for discriminating the best diode target region is illustrated. Then, by considering the digitized charge distribution on the target as a digital image, a filtering algorithm capable of recovering trace discontinuities is shown. Results of tests carried out on an actual digitizer are reported     

Oblique flow impinging on a wall with suction or blowing

Summary The oblique flow of a viscous fluid impinging on a flat wall with suction or blowing is studied. It is found that when suction is applied the fluid penetrates the wall while blowing causes the shifting of the stagnation point. It is also found that this shifting depends upon the magnitude of the blowing.     

Drug Release from Lipogels According to Gelling Conditions and Mechanical Treatment

The release rate of a drug dissolved in the liquid phase of lipogels may be greatly affected by the type and concentration of gelling agent and by processing conditions and mechanical treatment of the ointment. These differences in release rate are reduced after application of mechanical stress comparable with the strain exerted on the ointment during application to the skin. Therefore, changes in the concentration of gelling agents used to achieve suitable consistency and manufacturing and packing processes that meet industrial and marketing requirements do not appear to exert a practical influence on drug availability after application to the skin.     

Effective scattering area of a three-faced corner cube reflector

Ray representations are used to refine a model for the equivalent aperture of a three-faced corner-cube reflector in which the faces are not perpendicular. This is used in calculating the actual value of the effective scattering area for such a reflector, which gives a correction factor to exclude the error component due to the nonperpendicularity. A table is given of calculated values for the correction factor together with experimental results. Translated from Izmeritel'naya Tekhnika, No. 10, pp. 45–48, October, 1996.