A STATE-MODEL REPRESENTATION OF THE PARAMETRIC TRANSFORMER

ABSTRACT

A state model of a new passive device capable of transferring electrical energy from one circuit to another through parametric excitation is developed. The state equations of the parametric transformer under various load conditions are then solved numerically to obtain the output voltage, the currents in the input and output circuits and the variable inductance responsible for parametric oscillations. The computed values are compared with those obtained from measurements made on a small experimental unit.     

Integrated water vapour content by scanning radiometry

Abstract

Radiometry at the water vapour line with a scanning antenna beam from horizon to horizon through the zenith, in the vertical plane, was shown to be useful in estimating the integrated water vapour content from the zenith angle variation of radiometric temperature. The beam scanning may be made at a rate slower than the radiometer time constant using a Dicke type radiometer. Alternatively, a fast scanning beam may be used in a total power radiometer with a synchronous detection of the radiometer output at the scanning frequency to obtain a space domain Dicke switching for the measurements. A simultaneous scanning beam with 22.235 and 31.4GHz radiometers would allow us to separate the liquid water, if any, from the integrated water vapour content. Theoretical studies of the scanning beam radiometer performance in the estimation of integrated water vapour content from radiosonde data is presented and some typical results of Dicke type scanning beam radiometers at 22.235 and 31.4 GHz are also presented in this paper.     

Reactions of Aqueous Chlorine and Chlorine Dioxide with Tryptophan, N-Methyltryptophan, and 3-Indolelactic Acid: Kinetic and Mutagenicity Studies

Reactions of tryptophan, N-methyltryptophan and 3-indolelactic acid with aqueous chlorine or chlorine dioxide (ClO₂) in 0.1M potassium phosphate buffer, pH 6.0, were investigated to determine any structural relationships with regards to kinetics and mutagenicity. The reaction with ClO₂ followed pseudo-first order kinetics, with the half-life of the respective compounds being 36, 22, and 8 milliseconds. The formation of a dark precipitate in the reaction of tryptophan with HOCl precluded any kinetic comparison. The reaction products of tryptophan with hypochlorous acid (HOCl) or ClO₂ were mutagenic to Salmonella typhimurium TA98 and TA100; while those of N-methyltryptophan with HOCl and ClO₂ were more mutagenic toward TA98. Higher recoveries of the reaction products were achieved by passing the acidified (pH 2.5) mixture through an XAD-8/XAD-2 resin column.     

Some new results on a class of periodically varying systems

The analysis and stability properties of a special class of R-L-C network, where the energy storage elements vary periodically with time and the dissipative elements are held constant, is discussed. In the analysis, fast Fourier transform technique has been utilized to obtain rapidly an accurate response of the network when excited by any arbitrary periodic signal. In the stability results, it has been shown that the network's stability can be ensured in a very simple manner if the connection matrix of the network is in Jordan normal form.     

Microprocessor based simulation and digital logic model of gate turn-off thyristor

A digital logic model of a gate turn-off thyristor is developed considering the turn-on and turn-off mechanisms of the device. A commonly used R-C-D snubber circuit is also included in the proposed model. Relations between different delay times, e.g. storage time, Tall time, turn-off time and tail time, become apparent from the model. The model is simulated with the help of a microprocessor to establish the validity of the proposal.     

涡旋管内强旋湍流气固两相流的数值模拟

本文建立了基于一种合理考虑湍流-离心力相互作用的新的代数Peynolds应力模型和颗粒随机轨道模型的强旋湍流气固两相流动数学模型。应用该模型对新型涡旋管内的强度湍流气固两相流进行了数值模拟，揭示了涡旋管内气固两相湍流流动的基本特性以及改变切向出口气体流率对流动的影响。     

Evaluation of electron temperature in transverse and axial magnetic fields in an arc plasma by diffusion voltage measurement

The diffusion voltage in a mercury arc plasma has been measured for arc currents from 2.5 A to 5 A in transverse and axial magnetic fields from zero to 1.1 kG. Assuming the radial distribution of charged particles proposed by Ghosal et al, (1978) and utilizing the method of Sen et al. (1983), the ratio of electron temperatures with and without a magnetic field has been evaluated. It becomes a maximum in an axial field and then decreases, whereas it shows a minimum in a transverse field and then increases. An expression for the ratio of the electron temperature with and without a field has been deduced that explains these results. Quantitative agreement between experiment and theory is fairly satisfactory.     

Analysis and Significance of Tyramine in Foods

SUMMARY— The tyramine levels in different varieties of cheeses, alcoholic drinks, and other foods were determined. Many of the food samples, analyzed by an existing fluorometric method, contained large amounts (up to 2.2 mg/g) of tyramine. Synephrine and octopamine, although rarely present in food, interfered with the fluorometric analysis. A gas chromatographic method was developed in which tyramine was extracted from foods and then analyzed as its trifluoroacetyl derivative using an electron capture detector. The gas chromatographic method was more sensitive and specific than the fluorometric method, and it permitted detection of 0.1–0.2 nanogram tyramine even in the presence of synephrine and octopamine.     

Optimisation of Hydrometallurgical Circuit Performance

An optimisation technique applicable to hydrometallurgical circuits has been formulated using a two-stage search incorporating a simplified and detailed version of simulator. The technique aims at development of optimised interconnection parameters. As an example of use of this approach, results obtained during computations involving a lean nickel bearing ore have been projected in this paper. It is possible to minimise net acid addition to the circuit through control of outlet fraction of a single stream. The net savings in acid addition depend on the desired pregnant metal concentration as well as acid consumption patterns for the individual leach stages. The use of the two stage search in arriving at the desired optimum has been detailed out. Minimum net acid addition is attained when the concentration of the pregnant stream is maximised within the constraints of stage pulp density. At 30% leach pulp density, it is possible to add almost stoichiometric quantities of acid at a maximum attainable pregnant stream concentration of around 7·6 gpl. The developed approach may be extended to optimal design of any other leaching circuit employing two stages and utilising date generated at bench scale. The configurations worked out may be tested at pilot plant scale, thus minimising need of additional experiments.