The total electric field(TEF) at ground level induced by high-voltage direct current(HVDC) overhead transmission lines is one of the important indexes for evaluating the lines' electromagnetic environment.Based on...The total electric field(TEF) at ground level induced by high-voltage direct current(HVDC) overhead transmission lines is one of the important indexes for evaluating the lines' electromagnetic environment.Based on analyzing the existing TEF sensors and the measurement principle of ion-current density,the influence from ions on TEF measurements is quantitively studied.The results show that the ions generated by the corona from a HVDC transmission line in operation cause errors in the measurement of TEF.This error is determined through analyzing the component of total measuring current on the filed mill's sensing electrode: if no appropriate approach taken,the maximum measurement error reaches up to 4.3%.Furthermore,a method that can eliminate such error,and hence improve the accuracy of TEF sensors is designed.展开更多
目的:系统分析全膝关节置换术后病人恐动症的影响因素。方法:系统检索中国知网、万方数据库、维普数据库、中国生物医学文献数据库、PubMed、Web of Science、Scopus、CINAHL、EMbase中与全膝关节置换术后恐动症影响因素相关的量性及质...目的:系统分析全膝关节置换术后病人恐动症的影响因素。方法:系统检索中国知网、万方数据库、维普数据库、中国生物医学文献数据库、PubMed、Web of Science、Scopus、CINAHL、EMbase中与全膝关节置换术后恐动症影响因素相关的量性及质性研究。采用混合方法评价工具评价文献质量,并依据聚敛整合方法收集、分析和整合数据。结果:共纳入12篇文献,归纳出生理与疾病状况、心理因素、外部支持三类影响因素。结论:全膝关节置换术后病人恐动症受到疾病相关症状、个体心理反应及外部支持环境等多因素的影响。建议临床基于上述影响因素进行系统性评估,并实施综合性干预策略。展开更多
This paper is concerned with the problem of network power quality when grid connected systems are used to feed the grid. These systems use power electronic components such as inverters that produce harmonics which adv...This paper is concerned with the problem of network power quality when grid connected systems are used to feed the grid. These systems use power electronic components such as inverters that produce harmonics which adversely affect the power quality of the distribution network. Instead of using a conventional PI current controller with a fixed proportional and integral gain, development of new control method is considered to overcome the total harmonic emissions in PV inverters. It considers a modification to the controller where a random integral gain is used in the system. Experimental hardware is developed and result shows a reduced total harmonic distortion (THD) of the output current when tested with a resistive load.展开更多
Objective For the inverters used in UPS, it is important to maintain the pure sinusoidal AC output voltage waveform over all loading conditions and transients. Methods A novel sinusoidal output voltage control strat...Objective For the inverters used in UPS, it is important to maintain the pure sinusoidal AC output voltage waveform over all loading conditions and transients. Methods A novel sinusoidal output voltage control strategy is pregented in this paper. The output voltage is controlled by introducing filtering eapacitor current feedback. Two simple PI regulators are used for the current and voltage control loops. Results With the new control strategy, the inverter achieves very low output voltage distortion, good output voltage regulation and strong perturbation rejection, fast dynamic response, and good performance under nonlinear loads. The THD under capacitance rectifying load is better than 0.2%, the output voltage regulation within 0 to full load is less than 0.1%. The resting time under load transient is within 200?μ s . Conclusion The merits of the new control strategy include rapid response and good steady state stiffness.展开更多
In this work, top and back gate characteristics of partially-depleted NMOS transistors with enclosed gate fabricated on SIMOX which is hardened by silicon ions implantation were studied under X-ray total-dose irradiat...In this work, top and back gate characteristics of partially-depleted NMOS transistors with enclosed gate fabricated on SIMOX which is hardened by silicon ions implantation were studied under X-ray total-dose irradiation of three bias conditions. It has been found experimentally that back gate threshold shift and leakage current were greatly reduced during irradiation for hardened transistors, comparing to control ones. It has been confirmed that the improvement of total-dose properties of SOI devices is attributed to the silicon nanocrystals (nanoclusters) in buried oxides introduced by ion implantation.展开更多
This paper presents the comparison of various current control strategies employed for an interleaved power factor correction (PFC) boost converter for improving the power quality. The major control strategies discusse...This paper presents the comparison of various current control strategies employed for an interleaved power factor correction (PFC) boost converter for improving the power quality. The major control strategies discussed in this paper are: peak current control, average current control, hysteresis control, borderline current control and non-linear control. These strategies are implemented in MATLAB/SIMULINK and the performance of the proposed converter is compared under open loop and closed loop operation. From the results, the input current waveform was close to input voltage waveform implying improved power factor and reduced total harmonic distortion for nonlinear current control technique. Experimental results validate the proposed method.展开更多
The paper proposes a Current Source Multilevel Inverter (CSMLI) with single rating inductor topology. Multilevel inverters are most familiar with power converter’s applications due to reduced dv/dt, di/dt stress, and...The paper proposes a Current Source Multilevel Inverter (CSMLI) with single rating inductor topology. Multilevel inverters are most familiar with power converter’s applications due to reduced dv/dt, di/dt stress, and very efficient for reducing harmonic distortion in the output voltage and output current. The proposed nine-level current source inverter has been tested under symmetrical and asymmetrical modes of operation, and their activities are compared using PI and Fuzzy PI (Proportional Integral) controllers with multicarrier PWM (Pulse Width Modulation) strategy. MATLAB/Simulink simulation has been made for the proposed converter to obtain its performance measures. Some experimental results are given to verify the presented Current Source Multilevel Inverter.展开更多
基金Project supported by National Natural Science Foundation of China （61273165 51207005）.
文摘The total electric field(TEF) at ground level induced by high-voltage direct current(HVDC) overhead transmission lines is one of the important indexes for evaluating the lines' electromagnetic environment.Based on analyzing the existing TEF sensors and the measurement principle of ion-current density,the influence from ions on TEF measurements is quantitively studied.The results show that the ions generated by the corona from a HVDC transmission line in operation cause errors in the measurement of TEF.This error is determined through analyzing the component of total measuring current on the filed mill's sensing electrode: if no appropriate approach taken,the maximum measurement error reaches up to 4.3%.Furthermore,a method that can eliminate such error,and hence improve the accuracy of TEF sensors is designed.
文摘目的:系统分析全膝关节置换术后病人恐动症的影响因素。方法:系统检索中国知网、万方数据库、维普数据库、中国生物医学文献数据库、PubMed、Web of Science、Scopus、CINAHL、EMbase中与全膝关节置换术后恐动症影响因素相关的量性及质性研究。采用混合方法评价工具评价文献质量,并依据聚敛整合方法收集、分析和整合数据。结果:共纳入12篇文献,归纳出生理与疾病状况、心理因素、外部支持三类影响因素。结论:全膝关节置换术后病人恐动症受到疾病相关症状、个体心理反应及外部支持环境等多因素的影响。建议临床基于上述影响因素进行系统性评估,并实施综合性干预策略。
文摘This paper is concerned with the problem of network power quality when grid connected systems are used to feed the grid. These systems use power electronic components such as inverters that produce harmonics which adversely affect the power quality of the distribution network. Instead of using a conventional PI current controller with a fixed proportional and integral gain, development of new control method is considered to overcome the total harmonic emissions in PV inverters. It considers a modification to the controller where a random integral gain is used in the system. Experimental hardware is developed and result shows a reduced total harmonic distortion (THD) of the output current when tested with a resistive load.
文摘Objective For the inverters used in UPS, it is important to maintain the pure sinusoidal AC output voltage waveform over all loading conditions and transients. Methods A novel sinusoidal output voltage control strategy is pregented in this paper. The output voltage is controlled by introducing filtering eapacitor current feedback. Two simple PI regulators are used for the current and voltage control loops. Results With the new control strategy, the inverter achieves very low output voltage distortion, good output voltage regulation and strong perturbation rejection, fast dynamic response, and good performance under nonlinear loads. The THD under capacitance rectifying load is better than 0.2%, the output voltage regulation within 0 to full load is less than 0.1%. The resting time under load transient is within 200?μ s . Conclusion The merits of the new control strategy include rapid response and good steady state stiffness.
文摘In this work, top and back gate characteristics of partially-depleted NMOS transistors with enclosed gate fabricated on SIMOX which is hardened by silicon ions implantation were studied under X-ray total-dose irradiation of three bias conditions. It has been found experimentally that back gate threshold shift and leakage current were greatly reduced during irradiation for hardened transistors, comparing to control ones. It has been confirmed that the improvement of total-dose properties of SOI devices is attributed to the silicon nanocrystals (nanoclusters) in buried oxides introduced by ion implantation.
文摘This paper presents the comparison of various current control strategies employed for an interleaved power factor correction (PFC) boost converter for improving the power quality. The major control strategies discussed in this paper are: peak current control, average current control, hysteresis control, borderline current control and non-linear control. These strategies are implemented in MATLAB/SIMULINK and the performance of the proposed converter is compared under open loop and closed loop operation. From the results, the input current waveform was close to input voltage waveform implying improved power factor and reduced total harmonic distortion for nonlinear current control technique. Experimental results validate the proposed method.
文摘The paper proposes a Current Source Multilevel Inverter (CSMLI) with single rating inductor topology. Multilevel inverters are most familiar with power converter’s applications due to reduced dv/dt, di/dt stress, and very efficient for reducing harmonic distortion in the output voltage and output current. The proposed nine-level current source inverter has been tested under symmetrical and asymmetrical modes of operation, and their activities are compared using PI and Fuzzy PI (Proportional Integral) controllers with multicarrier PWM (Pulse Width Modulation) strategy. MATLAB/Simulink simulation has been made for the proposed converter to obtain its performance measures. Some experimental results are given to verify the presented Current Source Multilevel Inverter.
