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Transient Characteristics and Accommodative Current Limiting Strategy for Bidirectional Interlinking Converters in Hybrid AC/DC Microgrids

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1575-1588页

作者： xia shen Zhikang Shuai Wen Huang Chao shen Yang shen Z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410082China Department of Electrical and Computer Engineering Illinois Institute of TechnologyChicagoIL 60616 USA

Bidirectional interlinking converter(BIC)is the core equipment in a hybrid AC/DC microgrid connected between AC and DC ***,the variety of control modes and flexible bidirectional power flow complicate the influence of AC faults on BIC itself and on DC sub-grid,which potentially threaten both converter safety and system *** study first investigates AC fault influence on the BIC and DC bus voltage under different BIC control modes and different pre-fault operation states,by developing a mathematical model and equivalent sequence ***,based on the analysis results,a general accommodative current limiting strategy is proposed for BIC without limitations to specific mode or operation *** amplitude is predicted and constrained according to the critical requirements to protect the BIC and relieving the AC fault influence on the DC bus *** with conventional methods,potential current limit failure and distortions under asymmetric faults can also be ***,experiments verify feasibility of the proposed method.

关键词： Bidirectional interlinking converter current limiting fault characteristic hybrid AC/DC microgrid variation/oscillation of DC bus voltage

GaAs backside via-hole etching using ICP system

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Science China(Technological Sciences) 2007年第6期50卷 749-754页

作者： WANG HaiLing GUO xia shen GuangDi Beijing Optoelectronic Technology Laboratory Institute of Electronic Information and Control Engineering Beijing University of Technology Beijing 100022 China Beijing Optoelectronic Technology Laboratory Institute of Electronic Information and Control Engineering Beijing University of Technology Beijing 100022 China Beijing Optoelectronic Technology Laboratory Institute of Electronic Information and Control Engineering Beijing University of Technology Beijing 100022 China

A high etch rate GaAs via-hole process was studied in an inductively coupled plasma system using Cl2/BCl3 gas system. The effects of process parameters on the GaAs etch rate were investigated. The influences of photoresist SiO2; Ni masks on the resultant profiles were also studied by scanning electron microscopy. A maximum etch rate of 8.9 μm/min was obtained; the etched profiles were optimized.

关键词： via-hole, GaAs, inductively coupled plasma, etching

Experimental study on the impact of temperature on the dissipation process of supersaturated total dissolved gas

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Journal of Environmental Sciences 2014年第9期26卷 1874-1878页

作者： xia shen shengyun Liu Ran Li Yangming Ou State Key Laboratory of Hydraulics and Mountain River Engineering Sichuan University Hydrochina Chengdu Engineering Corporation

Water temperature not only affects the solubility of gas in water but can also be an important factor in the dissipation process of supersaturated total dissolved gas （TDG）. The quantitative relationship between the dissipation process and temperature has not been previously described. This relationship affects the accurate evaluation of the dissipation process and the subsequent biological effects. This article experimentally investigates the impact of temperature on supersaturated TDG dissipation in static and turbulent conditions. The results show that the supersaturated TDG dissipation coefficient increases with the temperature and turbulence intensity. The quantitative relationship was verified by straight flume experiments. This study enhances our understanding of the dissipation of supersaturated TDG. Furthermore, it provides a scientific foundation for the accurate prediction of the dissipation process of supersaturated TDG in the downstream area and the negative imp）acts of high dam projects on aquatic ecosystems.

关键词： Total dissolved gas Supersaturation Temperature Dissipation coefficient

Extremum of second-order directional derivatives

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Applied Mathematics(A Journal of Chinese Universities) 2011年第4期26卷 379-389页

作者： LU Gui-xia WU Hao shen Long-jun National Key Laboratory of Science and Technology on Computational Physics Institute of Applied Physics and Computational Mathematics Beijing 100088 China.

In this paper, the extremum of second-order directional derivatives, i.e. the gradient of first-order derivatives is discussed. Given second-order directional derivatives in three nonparallel directions, or given second-order directional derivatives and mixed directional derivatives in two nonparallel directions, the formulae for the extremum of second-order directional derivatives are derived, and the directions corresponding to maximum and minimum are perpendicular to each other.

关键词： Finite point method second-order directional derivative extremum.

Imaging atmospheric turbulence,using entropy to quantify turbulence strength

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Research in Astronomy and Astrophysics 2020年第11期20卷 259-262页

作者： Lu Feng Zhi-xia shen Jing-Yao Hu National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China

Vertical profile of turbulence strength(Cn2)is one of the most important attributes for evaluating a site’s astronomical *** seeing is commonly used for describing turbulence strength,it can only represent the integral of all layers of the turbulence above the *** techniques which can be applied to produce Cn2,such as DIMM-MASS,SCIDAR,etc.,all rely on rather complex systems to do the *** this paper,we present an idea to evaluate the relative strength of turbulence with entropies of short exposure images taken at different conjugated heights of the *** experimental results are also presented in the paper.

关键词： techniques telescope site testing

Relationship between testosterone and indexes indicating endothelial function in male coronary heart disease patients

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Asian Journal of Andrology 2008年第2期10卷 214-218页

作者： Lu Fu Qian-Ping Gao Jing-xia shen Cardiovascular Department the First Affiliated Hospital of Harbin Medical University Harbin 150001 China

Aim： To investigate the relationship between androgen level and the indexes indicating endothelial function in male patients with coronary heart disease （CHD）. Methods： We registered the following data for 106 50-70-year-old men： age, weight, blood lipid, including total cholesterol, low density lipoprotein cholesterol, high density lipoprotein cholesterol and triglyceride, whether a smoker, sugar levels, blood pressure, free testosterone （FT）, vascular cell adhesion molecule- 1 （VCAM- 1） and the intima-media thickness （IMT） of common carotid artery, common carotid diameter, maximum velocity in systolic phase, minimum velocity in diastolic phase and resistent index. Among the 106 men, 51 were patients with CHD. The relationships between FT level, VCAM-1 concentration and IMT were examined, respectively, using a stepwise linear regression technique among all the 106 men. Results： There was no statistical difference in terms of age, blood pressure, whether a smoker, sugar levels, HDL-C, minimum velocity in diastolic phase, resistent index between male CHD patients and controls; whereas results for weight, total cholesterol, low density lipoprotein cholesterol, triglyceride, VCAM- 1 and IMT of male CHD patients were higher than those of controls; FT level and maximum velocity in systolic phase were lower. It was found that among all the objects, FT level was inversely correlated with IMT and VCAM-1 concentration. Condusion： FT level was inversely correlated with VCAM-I concentration and IMT which are indicators of endothelial function. （Asian JAndro12008 Mar; 10： 214-218）

关键词： testosterone coronary heart disease endothelial function

Stability Investigation and Improvement for DC Cascade Systems with Simplified Impedance-based Stability Criterion

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CSEE Journal of Power and Energy Systems 2024年第3期10卷 1044-1052页

作者： Junbin Fang Zhikang Shuai Yang Li Zhibing Wang xiangyang Wu xia shen Z.John shen College of Electrical and Information Engineering Hunan UniversityChangsha 410082China Renewable Energy Department of China Electric Power Research Institute Beijing 100192China Department of Electrical and Computer Engineering Illinois Institute of TechnologyChicagoIL 60616USA IEEE

In DC distributed power systems(DPSs),the complex impedance interactions possibly lead to DC bus voltage oscillation or *** previous research,the stability analysis of DPSs is implemented based on mathematical analysis in control *** specific mechanisms of the instability of the cascade system have not been intuitively *** this paper,the stability analysis of DPSs based on the traditional Nyquist criterion is simplified to the resonance analysis of the seriesconnected port impedance(Z=R+jX)of source and load *** reveals that the essential reason for impedance instability of a DC cascade system is that the negative damping characteristic(R<0)of the port the overall impedance amplifies the internal resonance source at reactance zero-crossing *** simplified stability criterion for DC cascade systems can be concluded as:in the negative damping frequency ranges(R<0),there exists no zero-crossing point of the reactance component(i.e.,X=0).According to the proposed stability criterion,the oscillation modes of cascade systems are classified.A typical one is the internal impedance instability excited by the negative damping,and the other one is that the external disturbance amplified by negativity in a low stability ***,the impedance reshaping method for stability improvement of the system can be further *** validity of the simplified criterion is verified theoretically and experimentally by a positive damping reshaping method.

关键词： DC cascaded system,impedance model impedance reconstruction stability criterion

Thermal conductivity model of filled polymer composites

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International Journal of Minerals,Metallurgy and Materials 2011年第5期18卷 623-631页

作者： Ming-xia shen Yin-xin Cui Jing He Yao-ming Zhang College of Mechanics and Materials Hohai University Nanjing 210098 China

Theoretical and empirical models for predicting the thermal conductivity of polymer composites were summarized since the *** effects of particle shape,filler amount,dispersion state of fillers,and interfacial thermal barrier on the thermal conductivity of filled polymer composites were investigated,and the agreement of experimental data with theoretical models in literatures was *** with high thermal conductivity was chosen to mix with polyvinyl-acetate （EVA） copolymer to prepare SiO2/EVA *** data of the co-films＇ thermal conductivity were compared with some classical theoretical and empirical *** results show that Agari＇s model,the mixed model,and the percolation model can predict well the thermal conductivity of SiO2/EVA co-films.

关键词： polymer matrix composites thermal conductivity mathematical models polyvinyl acetates silica filled polymers.

A NOVEL CALL ADMISSION CONTROL SCHEME IN CELLULAR/WLAN INTEGRATION AND PERFORMANCE ANALYSIS

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Journal of Electronics(China) 2009年第2期26卷 168-178页

作者： xia Weiwei shen Lianfeng National Mobile Communications Research Lab Southeast University Nanjing 210096 China

In order to achieve the Quality of Service(QoS) provisioning and efficient resource utili-zation in cellular network and Wireless Local Area Network(WLAN) integration,an Integrated Ser-vice-Based Call Admission Control(ISB-CAC) scheme is proposed in this *** integrated network is modeled by using multi-dimensional Markov *** numerical analysis is presented to evaluate the important performance measures such as the blocking probability of originating calls,the dropping probability,and the average transfer time,*** steady-state probabilities of the multi-dimensional Markov chains are obtained by using an iterative approach,and the CAC pa-rameters are optimally *** analytical model is validated by the computer *** is shown that compared with the conventional WLAN-First Call Admission Control(WF-CAC) scheme,the proposed ISB-CAC scheme not only provides better QoS for mobile users but also utilizes the bandwidth resources more efficiently.

关键词： Cellular/WLAN integration Call Admission Control(CAC) Quality of Service(QoS) Vertical handoff Markov process