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      • A Sensorless Switched Reluctance Drive System Based on the Improved Simplified Flux Method

        Li, Zhenguo,Song, Andong,Ahn, Jin-Woo Journal of International Conference on Electrical 2012 Journal of international Conference on Electrical Vol.1 No.4

        This paper describes a new rotor position sensorless control method for SRM drives based on an improved simplified flux linkage method. In the traditional simplified flux linkage method, every phases take turns conduction and current chopping control method is used. Every phases take turns conduction means turning on the incoming working phase while turning off the working phase. This conduction mode causes coupling between turn-on and turn-off angles, which goes against optimal efficiency or torque ripple minimization with sensorless speed control. In the improved simplified flux linkage method, turn-off angle is calculated by flux loop, the turn-on angle can be given arbitrarily and has no relations with the turn-off angle, and the current chopping control method is used. The speed and rotor position can be estimated then. Finally, a sensorless SRM speed control system and an experiment platform with DSP are built and validity of this method is confirmed.

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        Impact of Various Charge States of Hydrogen on Passivation of Dislocation in Silicon

        Lihui Song,Jingjing Lou,Jiayi Fu,Zhenguo Ji 대한금속·재료학회 2018 ELECTRONIC MATERIALS LETTERS Vol.14 No.5

        Dislocation, one of typical crystallographic defects in silicon, is detrimental to the minority carrier lifetime of silicon wafer. Hydrogen passivation is able to reduce the recombination activity of dislocation, however, the passivation efficacy is stronglydependent on the experimental conditions. In this paper, a model based on the theory of hydrogen charge state control isproposed to explain the passivation efficacy of dislocation correlated to the peak temperature of thermal annealing and illuminationintensity. Experimental results support the prediction of the model that a mix of positively charged hydrogen andnegatively charged hydrogen at certain ratio can maximise the passivation efficacy of dislocation, leading to a better powerconversion efficiency of silicon solar cell with dislocation in it.

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        Numerical analysis of Poiseuille-Rayleigh-Bénard convection in supercritical carbon dioxide

        Wang Zhipeng,Xu Hong,Chen Chong,Hong Gang,Song Zhenguo,Zhang Yaoli 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.9

        The supercritical carbon dioxide (SeCO2) Brayton cycle is an important energy conversion technology for the fourth generation of nuclear energy. Since the printed circuit heat exchanger (PCHE) used in the SeCO2 Brayton cycle has narrow channels, Rayleigh-Benard (RB) convection is likely to exist in the tiny channels. However, there are very few studies on RB convection in supercritical fluids. Current research on RB convection mainly focuses on conventional fluids such as water and air that meet the Boussinesq assumption. It is necessary to study non-Boussinesq fluids. PRB convection refers to RB convection that is affected by horizontal incoming flow. In this paper, the computational fluid dynamics simulation method is used to study the PRB convection phenomenon of non-Boussinesq fluid-supercritical carbon dioxide. The result shows that the inlet Reynolds number (Re) of the horizontal incoming flow significantly affects the PRB convection. When the inlet Re remains unchanged, with the increase of Rayleigh number (Ra), the steady-state convective pattern of the fluid layer is shown in order: horizontal flow, local traveling wave, traveling wave convection. If Ra remains unchanged, as the inlet Re increases, three convection patterns of traveling wave convection, local traveling wave, and horizontal flow will appear in sequence. To characterize the relationship between traveling wave convection and horizontal incoming flow, this paper proposes the relationship between critical Reynolds number and relative Rayleigh number (r).

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