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11 results on '"Zhang Zhongming"'

3. Optimizing Converter Layer and Active Volume Thickness for Gallium Nitride Neutron Detectors

Author

Zhang, Zhongming, Aspinall, Michael, Zhang, Zhongming, and Aspinall, Michael

Abstract

Gallium nitride (GaN) is a direct energy gap semiconductor material with a wide bandgap, high thermal conductivity, high chemical stability, and strong resistance to radiation. It has broad prospects in the application of optoelectronics, high temperature and high power devices, and particle detectors. In this work, an early-stage GaN radiation-hardened neutron detector is described. Monte Carlo simulations using Geant4 10.6 are used to investigate and optimize the converter layers and active volume for the detector and the suggested thickness needed to achieve the highest detection efficiency is given. Further, the gamma rejection ability for GaN has been studied, and the spatial distribution of the partial reaction type of gamma rays with GaN are shown for the first time. This work will aid the design and fabrication of radiation-resistant GaN neutron detectors and will benefit reactor monitoring, high-energy physics experiments, and nuclear fusion research.

Published
2021

4. Analytical Model of Open-Circuit Air Gap Flux Density in High Speed Permanent Magnet Machines Accounting for Winding Eddy Current Reaction

Author

Zhiquan Deng, Zelin Wang, Xin Xu, and Zhang Zhongming

Subjects
010302 applied physics, Physics, Open-circuit voltage, business.industry, 020208 electrical & electronic engineering, Accounting, 02 engineering and technology, Atmospheric model, Computer Science::Numerical Analysis, 01 natural sciences, Finite element method, Mathematics::Numerical Analysis, law.invention, law, Electromagnetic coil, Magnet, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Eddy current, Boundary value problem, Air gap (plumbing), business, Physics::Atmospheric and Oceanic Physics
Abstract

An improved analytical subdomain model is proposed to calculate the open-circuit air gap flux density in high speed permanent magnet machines accounting for the effect of winding eddy current reaction. The analytical model accounts for four subdomains including permanent magnet, retaining sleeve, air gap and slots. By applying boundary conditions between subdomains, the analytical expression of each subdomain can be derived. Compared with the conventional subdomain model, the subdomain model accounting for winding eddy current reaction can accurately predict the open-circuit air gap flux density. The finite element method is carried out to validate the analytical model.

Published
2020

8. Reduction of Rotor Harmonic Eddy-Current Loss of High-Speed PM BLDC Motors by Using a Split-Phase Winding Method.

Author

Zhang, Zhongming, Deng, Zhiquan, Gu, Cong, Sun, Quangui, Peng, Cong, and Pang, Gucai

Subjects
*HIGH temperature (Weather), *ROTORS, *PERMANENT magnets, *PERMANENT magnet motors, *MOTORS, *WINDS
Abstract

Low-order harmonic currents in high-speed permanent magnet brushless dc (PM BLDC) motors cause large rotor eddy-current loss, resulting in high temperature rise and even overheating in the rotors, thus their application in the field of high-speed drive is limited. The rotor eddy-current loss can be reduced by using a split-phase winding method. In this paper, various time–space orders of harmonic eddy-current losses in the rotors of the PM motors with and without split-phase winding are quantified. The calculated results indicate that the rotor harmonic eddy-current losses generated by the low-order harmonic currents, which inherently exist in PM BLDC motors, are greatly reduced. Furthermore, associated with the characteristics of harmonic currents of PM BLDC motors, the mechanism of drastically reducing the rotor harmonic eddy-current loss of high-speed PM motors by using the split-phase winding method is revealed and experimentally validated. [ABSTRACT FROM AUTHOR]

Published
2019
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11. Sparsity Adaptive Estimation of Memory Polynomial Based Models for Power Amplifier Behavioral Modeling.

Author

Li, Mingyu, Yang, Zhenxing, Zhang, Zhongming, Li, Ruoyu, Dong, Qing, and Nakatake, Shigetoshi

Abstract

In this letter, a new efficient model pruning method, called regularized sparsity adaptive matching pursuit (RSAMP), is presented to prune the redundant terms of memory polynomial based models for PA behavioral modeling. Unlike other CS based model pruning techniques, RSAMP method can estimate the sparsity level of the models adaptively with a regularized stagewise backtracking process. Using this method, the dominant sparse terms can be efficiently estimated based on the chosen supports without requiring the sparity level as an input parameter. Experiment results show that the RSAMP algorithm can efficiently construct a sparse behavioral model with very few terms, but almost have the same model performance with the full model. [ABSTRACT FROM PUBLISHER]

Published
2016
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