Hierarchical carrier‑based discontinuous PWM strategy for hybrid‑switch current source rectifier

Weiqi Wang,Xiangjian Meng,Xi Liang 전력전자학회 2022 JOURNAL OF POWER ELECTRONICS Vol.22 No.6

This paper proposes a hybrid-switch three-phase current source rectifi er (CSR) solution, which employs only one silicon carbide (SiC) switch and six traditional silicon (Si) switches. The corresponding hierarchical discontinuous pulse widthmodulation (HDPWM) strategy for the proposed CSR is also presented, which uses two parallel carrier-based discontinuous PWM branches to perform diff erentiated modulation operations on Si and SiC devices to endow the Si switches with zero current switching capability and conveniently make full use of the high-speed and low-loss advantages of SiC devices. Consequently, the proposed hybrid-switch CSR with HDPWM can even work as a full SiC device-switching converter with relatively lower costs, thus addressing the critical needs of effi ciency promotion of CSR applications. MATLAB simulations and experimental verifi cations were conducted to verify the performance of the proposed CSR solution.

Effect of material mechanical differences on shear properties of contact zone composite samples: Experimental and numerical studies

Weiqi Wang,Yicheng Ye,Qihu Wang,Xiaoyun Liu,Fan Yang,Wenkan Tan 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.2

Aiming at the mechanical and structural characteristics of the contact zone composite rock, the shear tests and numerical studies were carried out. The effects of the differences in mechanical properties of different materials and the normal stress on shear properties of contact zone composite samples were analyzed from a macro-meso level. The results show that the composite samples have high shear strength, and the interface of different materials has strong adhesion. The differences in mechanical properties of materials weakens the shear strength and increase the shear brittleness of the sample, while normal stress will inhibit these effect. Under low/high normal stress, the sample show two failure modes, at the meso-damage level: elastic-shearing-frictional sliding and elastic-extrusion wear. This is mainly controlled by the contact and friction state of the material after damage. The secondary failure of undulating structure under normal-shear stress is the nature of extrusion wear, which is positively correlated to the normal stress and the degree of difference in mechanical properties of different materials. The increase of the mechanical difference of the sample will enhance the shear brittleness under lower normal stress and the shear interaction under higher normal stress.

Operation and Modulation of H7 Current Source Inverter with Hybrid SiC and Si Semiconductor Switches

Weiqi Wang,Feng Gao,Shuling Rui 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

This paper proposes a H7 current source inverter (CSI) with a single shunt-connected silicon carbide (SiC) switch and traditional H6 CSI circuitry, which could employ the superior characteristics of SiC switch to significantly increase the whole switching frequency with expected low losses simultaneously. A novel modulation scheme for H7 current source inverter is then proposed, which can significantly reduce the switching counts and meanwhile realize the zero current switching (ZCS) for the rear-end CSI circuitry. The proposed H7 current source inverter can guarantee the high performance and high efficiency with a smaller DC inductor. To some extent, the H7 current source inverter circuitry could be a universal solution for all CSI systems. Matlab simulations and experimental verifications have been presented to show the performance of proposed inverter.

Analysis of Rotor Noise Characteristics in Ground Effect

Weiqi Wang,Xi Chen,Qijun Zhao 한국전산유체공학회 2022 한국전산유체공학회 학술대회논문집 Vol.2022 No.10

Effects of Differences in Mechanical Parameters of Media on Mechanical Properties and Failure Form of Composite Samples

Weiqi Wang,Yicheng Ye,Qihu Wang,Xiaoyun Liu,Zhouhao Yuan,Pengcheng Li 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.2

The deformation and failure of composite rock masses at the contact zone can cause serious safety hazards in underground engineering. Therefore, uniaxial compression experiment and numerical studies of composite samples were conducted. Combined with theoretical analysis, the effects of differences in the mechanical properties of two media on the mechanical properties and failure form of composite samples were investigated. The results show that the difference in mechanical properties of two media weakened the strength and elastic modulus of the composite sample and resulted in complex failure form of the sample. Additionally, the peaks of the AE frequencies of the two media occurred successively after the peak stress of the sample. At the macrolevel, the two media failed successively. These effects are more pronounced as the degree of difference in the mechanical properties of the two media increased. The difference in mechanical properties of the two media resulted in uncoordinated deformation and constrained stress near the contact interface, and the difference in Poisson's ratio is the main factor. The influence (enhanced or weakened) of uncoordinated deformation on the mechanical properties of the composite sample is affected by differences in the elastic modulus and Poisson's ratios of the two media.

Investigation on cavitating flow and parameter effects in a control valve with a perforated cage

Wang, Hong,Zhu, Zhimao,Zhang, Miao,Li, Jie,Huo, Weiqi Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8

Valve is widely used in the various industry areas to adjust and control the flow. Cavitation frequently takes place and sometimes is inevitable in various types of valve to cause the erosion damage. Therefore, how to control and minimize the effect of cavitation is still an important topic. This study numerically investigates the cavitating flow in a control valve with a perforated cage. The effects of some parameters on the cavitation are discussed. It also discusses to use the throttling steps to govern the cavitating flow. The results show that the opening degree of valve and the length of downstream divergent connection both influence the cavitation. The increase of the divergent length reinforces the cavitation. And the larger the opening of valve is, the intenser the cavitation is and the more vapor is present. The more throttling steps are helpful to decrease the cavitation.

Changes in fl avor-relevant compounds during vine ripening of tomato fruit and their relationship with ethylene production

Libin Wang,Weiqi Luo,Xiuxiu Sun,Chunlu Qian 한국원예학회 2018 Horticulture, Environment, and Biotechnology Vol.59 No.6

Flavor quality is import for determining consumer perception and acceptance of tomato products. In this study, ‘Fendou’tomato fruit were harvested at six ripening stages and sampled to investigate the development of fl avor-relevant compoundsduring vine ripening. Results showed that upon the initiation of ripening there was an increase in respiration rate and concomitantethylene evolution that was associated with increased membrane permeability. In accordance with these physiologicalchanges, fl avor-relevant compounds demonstrated diff erent expression patterns as fruit ripened, which contributedto ‘red-ripe’ fl avor characteristics of red-ripe fruit. Based on correlation analysis between ethylene evolution and the fl avorrelevantcompounds during ‘Fendou’ tomato ripening and the other researchers’ reports, the activation of System 2-dependentautocatalytic ethylene production plays an important role in the development of most fl avor-relevant compounds duringtomato vine ripening. Overall, our results suggested that most fl avor-relevant compounds that accumulated the most duringtomato fruit ripening at red stage could be under ethylene regulation and were among the most important contributors tothe ‘red-ripe’ fl avor. Due to the development of these compounds, the fl avor quality at late ripening stages is diff erent fromthat of fruit at early ripening stages.

The Mediating Effect of Satisfaction on the Relationship Between Event Image and Behavioral Intentions: The Case of 2019 Chengdu International Marathon

( Zhongqiang Liu ),( Zheming Hu ),( Weiqi Chai ),( Shanying Huang ),( Junke Wang ) 아시아스포츠융합과학회 2020 Asia Pacific Journal of Applied Sport Sciences Vol.1 No.1

PURPOSE The purpose of this study is to establish a behavioral intention model of marathon runners in marathon tourism and validates the relationships among sport event image, satisfaction, and behavioral intention. METHOD Based on the background of marathon tourism in China, this essay shows that marathon runners from Chengdu international marathon were selected as the main research samples. A total of 460 questionnaires were collected and 30 questionnaires were deleted due to incomplete or incorrect filling, 430 questionnaires of which were used for subsequent analysis. The collected data were analysed through descriptive statistics, exploratory factor analysis, confirmatory factor analysis, structural equation models, and Bootstrap method. RESULT (1) Satisfaction and recommendation intention of marathon runners are directly affected by the event image, but the revisit intention of the event is not affected. (2) Satisfaction is a significant predictor of marathon runner recommend intention and revisit intention. (3) Recommend intention and revisit intention are indirectly affected by the event image which has a limited influence on the behavioral intention of marathon runners through satisfaction. CONCLUSION Event image has a limited influence on the behavioral intention of marathon runners. Satisfaction is an important factor in marathon runner behavioral intentions. The result of this study provides some practical suggestions for the organization and management of marathon events, as well as provides suggestions for future research.

Enhanced recovery after surgery strategy for cirrhosis patients undergoing hepatectomy: experience in a single research center

Yiling Zheng,Liming Wang,Fan Wu,Weiqi Rong,Yunhe Liu,Kai Zhang,Jianxiong Wu 대한외과학회 2020 Annals of Surgical Treatment and Research(ASRT) Vol.98 No.5

Purpose: To evaluate the safety and effectiveness of an enhanced recovery after surgery (ERAS) programme after curative liver resection in cirrhotic hepatocellular carcinoma (HCC) patients. Methods: One hundred sixty-two patients were enrolled in the study; 80 patients whose data were collected prospectively were assigned to the ERAS group, and 82 patients whose data were collected retrospectively were assigned to the control group. Preoperative clinicopathologic factors, surgical factors, and postoperative outcomes of the 2 groups were compared. Logistic regression was applied to explore potential predictors of hospital stay and morbidity. Results: The postoperative hospital stay, postoperative complication rate, and recovery of liver function on postoperative day 5 seemed to be better in the ERAS group. The composition of complications was different in the 2 groups; pleural effusion and postoperative ascites were more common in the control group, and indocyanine green retention at 15 minutes, operation time, preoperative alanine aminotransferase, and number of liver segmentectomies were associated with postoperative complications rather than ERAS intervention. Conclusion: The ERAS programme is safe and effective for HCC patients with chronic liver disease undergoing hepatectomy, but it seems that surgical factors, such as operation type, have a greater impact on morbidity than other factors. Operative characteristics such as the method of blood loss control and the volume of liver resection should be augmented into ERAS protocol of hepatectomy.

The Dynamic Characteristics of a Small Hydraulic Poppet Safety Relief Valve

Yong Sang,Xudong Wang,Weiqi Sun 한국유체기계학회 2020 International journal of fluid machinery and syste Vol.13 No.1

Hydraulic poppet pressure relief valve, which has the advantages of fast response and good sealing performance, is extensively used in the hydraulic industry. In this paper, a two-dimensional axisymmetric geometry model of the hydraulic poppet safety relief valve with a small size is established. Dynamic mesh, along with UDF in FLUENT software, is used in this study. The dynamic characteristics of a hydraulic poppet safety relief valve using CFD are investigated under different conditions. For incompressible hydraulic oil, a sharp force rise and collapse caused by a redirection of the fluid flow due to inertia forces is depicted, and the variation of the poppet motion under the influence of the back pressure is analyzed based on the flow information. The dynamic behavior of the hydraulic poppet relief valve under different set pressure is investigated. In the end, a numerical study on the instability of the poppet relief valve supplying a constant volumetric flow rate is performed, and the chatter frequency is obtained.