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Harmonic resonance analysis and stability improvement for grid-connected inverters
Xie, Bao,Zhou, Lin,Liu, Tiantian,Mao, Mingxuan The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.1
The traditional dual-control-loop strategy is widely used in grid-connected inverters. However, due to uncertain grid conditions, a resonance phenomenon may arise in systems and grid current can be badly distorted. In addition, the systems themselves may be unstable. In this paper, an equivalent impedance model of a grid-connected inverter is established. Based on this, two concepts of circuit resonance and harmonic resonance are proposed. By using the Nyquist stability criterion, it is revealed that harmonic resonance is induced when system stability is decreased, and the harmonic amplification in the system is enhanced. Due to the fact that the dual-control-loop strategy has poor robustness against grid impedance variations, a linear quadratic regulator (LQR) based on full-state feedback is proposed in this paper. The design procedure for selecting the full-state feedback gain is presented. Finally, both simulation and experimental results are presented to verify the effectiveness of the proposed LQR controller.
Morphology of the human xiphoid process: dissection and radiography of cadavers and MDCT of patients
Xie, Yuan-Zhong,Wang, Bao-Jian,Yun, Jae Sung,Chung, Gung Ho,Ma, Zhen-Bo,Li, Xiu Juan,Kim, Ik Seong,Chai, Ok Hee,Han, Eui-Hyeog,Kim, Hyoung Tae,Song, Chang Ho Springer-Verlag 2014 Surgical and radiologic anatomy Vol.36 No.3
Xie, Li-hua,Quan, Xin,Zhang, Jie,Yang, Yan-yan,Sun, Run-hong,Xia, Ming-cong,Xue, Bao-guo,Wu, Chao,Han, Xiao-yun,Xue, Ya-nan,Yang, Li-rong The Korean Society of Plant Pathology 2019 Plant Pathology Journal Vol.35 No.1
Gaeumannomyces graminis var. tritici is a soil borne pathogenic fungus associated with wheat roots. The accurate quantification of gene expression during the process of infection might be helpful to understand the pathogenic molecular mechanism. However, this method requires suitable reference genes for transcript normalization. In this study, nine candidate reference genes were chosen, and the specificity of the primers were investigated by melting curves of PCR products. The expression stability of these nine candidates was determined with three programs-geNorm, Norm Finder, and Best Keeper. $TUB{\beta}$ was identified as the most stable reference gene. Furthermore, the exopolygalacturonase gene (ExoPG) was selected to verify the reliability of $TUB{\beta}$ expression. The expression profile of ExoPG assessed using $TUB{\beta}$ agreed with the results of digital gene expression analysis by RNA-Seq. This study is the first systematic exploration of the optimal reference genes in the infection process of Gaeumannomyces graminis var. tritici.
Han, Bao-Lin,Xu, Xiang-Ying,Zhang, Chun-Zhi,Wu, Jian-Juan,Han, Chun-Feng,Wang, Hui,Wang, Xuan,Wang, Guang-Shun,Yang, Shu-Juan,Xie, Yao Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.6
Objective: To conduct a meta-analysis to investigate the value of EBV DNA in diagnosis of nasopharyngeal cancer (NPC) in Asian populations, and provide important evidence for screening. Methods: Prospective or respective case-control or cohort studies regarding the detection role of EBV DNA for NPC were included in our study. We conducted a comprehensive literature search in PubMed, EMBASE, and the Chinese Biomedical Database (CBM database between January 1980 and March 2012. Results: A total of 18 studies with 1492 NPC cases and 2641 health controls were included. Almost of the included studies were conducted in China, and only one other conducted in Thailand. The overall results demonstrated that the pooled sensitivity, specificity, positive likelihood (+LR) and negative likelihood (-LR) were 0.73 (0.71-0.75), 0.89 (0.88-0.90), 8.84 (5.65-13.84) and 0.19(0.11-0.32), respectively. The overall EBV DNA detection showed the largest area of 0.932 under the summary receiver operator curve (SROC). The accuracy of detection by plasma for NPC (0.86) was higher than in serum (0.81), with largest areas under the SROC of 0.97 and 0.91, respectively. Conclusion: Our results demonstrated the EBV DNA detection in plasma or serum has high sensitivity and specificity in diagnosis of NPC, especially in Chinese populations with a high risk of cancer.
Tensile behavior of stainless steel S30408 at the Arctic low temperature
Jia-Bao Yan,Zhicheng Lin,Peng Xie,Yun-Biao Luo,Yanbo Li 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.40 No.5
This paper investigated tensile behaviours of S30408 at the Arctic low temperatures (T) of -80~20℃. A cooling chamber equipped with liquid nitrogen gas was adopted to rebuild the Arctic low-temperature environment. Standard tension tests were performed on 48 coupons with different thickness at different T values of -80, -60, -30, and 20℃. Test results revealed the ductile failure mode of stainless steel S30408 even at -80℃. The tensile stress-strain (σ-ε) curves of S30408 at ambient temperatures exhibited a long strain hardening plateau. Meanwhile, the low-temperature tensile σ-ε curves of S30408 were different from those at ambient temperatures, which exhibited a second hardening stage with a larger slope than the first hardening. The decreasing T generally increased the elastic modulus, yield and ultimate strength, but reduced the ductility of S30408. Decreasing the T from 20 to -80℃ reduced the ductility of S30408 by about 28%, but improved the elastic modulus, yield and ultimate strength by about 20%, 22%, and 75%, respectively. This paper also adopted the best subset regression analysis method to develop empirical formulae on estimating influences of T on mechanical properties of S30408. Validations of the predictions by these empirical formulae against the test results in the literature proved their accuracies.
Jian Xie,Jia-Bao Yan 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.1
This paper presents the results of the tests and analysis on the coefficient of thermal expansion for the steel strand under combined low temperatures and prestressing forces. A test program was firstly carried out to study the thermal expansion behaviour of the seven-wire strand under combined different low temperatures ranging from 20 to - 165 °C and different prestressing levels ranging from 0 to 0.75 ft/ftk. The test results exhibited the thermal expansion behaviours of the steel strand under low temperatures in terms of thermal strain versus temperature curves, transit linear thermal expansion coefficient, and average thermal expansion coefficient. The influences of the low temperature and prestressing levels on the thermal expansion behaviours of the steel strand were separately discussed and analysed. Based on the test data, mathematical models were developed to predict the thermal expansion coefficients including transit and average of the steel strand. The developed regression models fully considered the influences of the low temperature and prestressing stresses acted on the strand. Finally, design equations were proposed to predict the transit and average thermal expansion coefficient of the steel strand under combined low temperature and prestressing forces.
Zero-Voltage and Zero-Current Switching Interleaved Two-Switch Forward Converter
Chu, Enhui,Bao, Jianqun,Song, Qi,Zhang, Yang,Xie, Haolin,Chen, Zhifang,Zhou, Yue The Korean Institute of Power Electronics 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.6
In this paper, a novel zero-voltage and zero-current switching (ZVZCS) interleaved two switch forward converter is proposed. By using a coupled-inductor-type smoothing filter, a snubber capacitor, the parallel capacitance of the leading switches and the transformer parasitic inductance, the proposed converter can realize soft-switching for the main power switches. This converter can effectively reduce the primary circulating current loss by using the coupled inductor and the snubber capacitor. Furthermore, this converter can reduce the reverse recovery loss, parasitic ringing and transient voltage stress in the secondary rectifier diodes caused by the leakage inductors of the transformer and the coupled inductance. The operation principle and steady state characteristics of the converter are analyzed according to the equivalent circuits in different operation modes. The practical effectiveness of the proposed converter was is illustrated by simulation and experimental results via a 500W, 100 kHz prototype using the power MOSFET.
Injection molding of ultra-fine zirconia (Y-TZP) powders
Zhi-peng Xie,Zhong-zhou Yi,Bing Xiaoc, Yan Gao,Jie-sheng Luo,Jian-bao Li,Yong Huang 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.1
Injection moldings of three types of ultra-fine zirconia powder were investigated. It was demonstrated that powder characteristics involving particle size, particle size distribution, particle shape and specific surface area significantly affect the optimal compositions of binders and ceramic powders, and the properties of sintered compacts. Investigation of the injection molding variables showed that an excessive barrel-deposited value may easily lead to defects in the debound and sintered bodies. It was also demonstrated that the microstructure of a sintered body can be affected by heating rates influencing grain growth, and that suitable heating rates to the high temperature sintering stage for the three powders are different.