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Current Decoupling Control for the Three-level PWM Rectifier with a Low Switching Frequency
Qing-qing YUAN,Kun XIA 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.1
Three-level PWM rectifiers applied in medium voltage applications usually operate at low switching frequency to keep the dynamic losses under permitted level. However, low switching frequency brings a heavy cross-coupling between the current components id and iq with a poor dynamic system performance and a harmonic distortion in the grid-connecting current. To overcome these problems, a mathematical model based on complex variables of the three-level voltage source PWM rectifier is firstly established, and the reasons of above issues resulted from low switching frequency have been analyzed using modern control theory. Then, a novel control strategy suitable for the current decoupling control based on the complex variables for id and iq is designed here. The comparisons between this kind of control strategy and the normal PI method have been carried out. MATLAB and experimental results are given in detail.
Song, Qing-Kun,Li, Jing,Huang, Rong,Fan, Jin-Hu,Zheng, Rong-Shou,Zhang, Bao-Ning,Zhang, Bin,Tang, Zhong-Hua,Xie, Xiao-Ming,Yang, Hong-Jian,He, Jian-Jun,Li, Hui,Li, Jia-Yuan,Qiao, You-Lin,Chen, Wan-Qin Asian Pacific Journal of Cancer Prevention 2014 Asian Pacific journal of cancer prevention Vol.15 No.22
Background: The study aimed to describe the age distribution of breast cancer diagnosis among Chinese females for comparison with the United States and the European Union, and provide evidence for the screening target population in China. Materials and Methods: Median age was estimated from hospital databases from 7 tertiary hospitals in China. Population-based data in China, United States and European Union was extracted from the National Central Cancer Registry, SEER program and GLOBOCAN 2008, respectively. Age-standardized distribution of breast cancer at diagnosis in the 3 areas was estimated based on the World Standard Population 2000. Results: The median age of breast cancer at diagnosis was around 50 in China, nearly 10 years earlier than United States and European Union. The diagnosis age in China did not vary between subgroups of calendar year, region and pathological characteristics. With adjustment for population structure, median age of breast cancer at diagnosis was 50~54 in China, but 55~59 in United States and European Union. Conclusions: The median diagnosis age of female breast cancer is much earlier in China than in the United States and the European Union pointing to racial differences in genetics and lifestyle. Screening programs should start at an earlier age for Chinese women and age disparities between Chinese and Western women warrant further studies.
Current Decoupling Control for the Three-level PWM Rectifier with a Low Switching Frequency
Yuan, Qing-Qing,Xia, Kun The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.1
Three-level PWM rectifiers applied in medium voltage applications usually operate at low switching frequency to keep the dynamic losses under permitted level. However, low switching frequency brings a heavy cross-coupling between the current components $i_d$ and $i_q$ with a poor dynamic system performance and a harmonic distortion in the grid-connecting current. To overcome these problems, a mathematical model based on complex variables of the three-level voltage source PWM rectifier is firstly established, and the reasons of above issues resulted from low switching frequency have been analyzed using modern control theory. Then, a novel control strategy suitable for the current decoupling control based on the complex variables for $i_d$ and $i_q$ is designed here. The comparisons between this kind of control strategy and the normal PI method have been carried out. MATLAB and experimental results are given in detail.
Esophageal Cancer Mortality during 2004-2009 in Yanting County, China
Song, Qing-Kun,Li, Jun,Jiang, Hai-Dong,He, Yu-Ming,Zhou, Xiao-Qiao,Huang, Cheng-Yu Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.10
Objective: Yanting County is a high risk area for esophageal cancer (EC) in China. The purpose of this study was to describe the mortality and mortality change of EC from 2004 to 2009 in Yanting County. Methods: EC mortality data from 2004 to 2009 obtained from the Cancer Registry in Yanting were analyzed. Annual percentage changes (APC) were calculated to assess the trends in EC mortality. Age-standardized mortality was calculated based on world standard population of 2000. Results: The average EC mortality was 54.7/$10^5$ in males and 31.6/$10^5$ in females over the 6 years. A decline in EC mortality with time was observed in both genders, with a rate of -8.70% per year (95% CI: -13.23%~-3.93%) in females and -4.11% per year (95%CI: -11.16%~3.50%) in males. Conclusion: EC mortality decreased over the six years in both genders, although it remained high in the Yanting area. There is still a need to carry out studies of risk factors for improved cancer prevention and further reduction in the disease burden.
Song, Qing-Kun,Zhao, Lin,Li, Jun,He, Yu-Ming,Jiang, Cui-Ping,Jiang, Hai-Dong,Qu, Chen-Xu Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.2
Introduction: Squamous cell carcinoma of esophagus (ESCC) is one of the most common cancers in China. Preserved vegetables are processed foods and consumed in high amounts in the high risk areas for ESCC. This study aimed to investigate the relationships of preserved vegetable consumption with ESCC and precancer lesions. Methods: Cases from Yanting cancer hospital with pathological diagnosis of primary cancer, along with controls and individuals diagnosed with precancer lesions by endoscopy with iodine staining were interviewed. Trained staff collected data on dietary habits 1 year before the interview. An unconditional logistic regression model was used to estimate odds ratios of preserved vegetable consumption for precancer lesions and cancer. Results: Adjusting for potential confounders, intake of preserved vegetables (OR=2.92, 95%CI 1.32~6.47) and longer intake period (OR=5.78, 95%CI 2.26~14.80) were associated with higher risk of ESCC. Compared with lowest intake frequency, the highest was associated with a 3.0-fold risk for precancer lesions and 3.59-fold risk for ESCC (both p<0.05). Conclusion: Consumption of preserved vegetables is a risk factor for esophageal lesions in high risk areas. The carcinogenicity of preserved vegetables needs investigation in further studies and the public health strategies for reducing the consumption might be initiated in high risk areas.
Research of Circuit Working Construction Elevator with Single-guide Rail and Multi-cages
Kun Zhang,Kaiqiang Wang,Di Li,Qing Sun,Zhen Ye,Wei Liu Council on Tall Building and Urban Habitat Korea 2022 International journal of high-rise buildings Vol.11 No.2
As one of the most important vertical transportation equipment in super high-rise buildings, the construction elevator directly affects the project period, cost, and effectiveness. The paper proposes a new construction elevator with single-guide rail and multi-cages. It can solve the problems of single construction elevator capacity shortage and efficacy decrease with height reduction, the occupancy of plan and elevation position of multiple construction elevators, and extension of total construction period by cycling operation of multi-cages on a single-guide rail. The paper focuses on the design and research of the main components of the equipment, such as the rotating guide rail mechanism, vertical bearing mast tie system, segmented electrical power supply system, group control scheduling system, and safety anti-collision system.
Kun Dou,Lingtao Meng,Qing Liu,Bo Liu,Yunhua Huang 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3
During continuous casting process of low carbon micro-alloyed steel containing vanadium, the evolution of strand surface microstructure and the precipitation of secondary phase particles (mainly V(C, N)) are significantly influenced by cooling rate. In this paper, influence of cooling rate on the precipitation behavior of proeutectoid α-ferrite at the γ-austenite grain boundary and in the steel matrix are in situ observed and analyzed through high temperature confocal laser scanning microscopy. The relationship between cooling rate and precipitation of V(C, N) from steel continuous casting bloom surface microstructure is further studied by scanning electron microscopy and electron dispersive spectrometer. Relative results have shown the effect of V(C, N) precipitation on α-ferrite phase transformation is mainly revealed in two aspects: (i) Precipitated V(C, N) particles act as inoculant particles to promote proeutectoid ferrite nucleation. (ii) Local carbon concentration along the γ-austenite grain boundaries is decreased with the precipitation of V(C, N), which in turn promotes α-ferrite precipitation.
Design and Application of Self-Lifting & Slewing Multi-Cranes Platform
Kun Zhang,Kaiqiang Wang,Bo Chen,Qing Sun,Hui Yang,Xin Ba,Jinming Zhao Council on Tall Building and Urban Habitat Korea 2022 International journal of high-rise buildings Vol.11 No.2
Tower crane is of great importance in the construction of high rise buildings. A self-lifting & slewing multi-cranes platform (referred to as crane slewing platform) was developed to optimize the configuration of tower cranes, as well as solve the problems of cooperative operation conflict between multiple cranes and other construction equipment and their respective climbing and occupying of construction period. The design and test of the slewing platform was introduced. By applying the slewing platform in the construction of Chengdu Greenland Center super high rise building project, some key technologies such as the configuration of cranes, the installation, construction and lifting of the slewing platform are implemented and validated. Up to now, the slewing platform has been safely lifted up 98 times in Chengdu Greenland Center project construction, and achieved good social and economic benefits.