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Control of Electrically Excited Synchronous Motors with a Low Switching Frequency
Qing-qing Yuan,Xiao-jie Wu,Peng Dai,Xiao Fu 전력전자학회 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4
The switching frequency of the power electronic devices used in large synchronous motor drives is usually kept low (less than 1 kHz) to reduce the switching losses and to improve the converter power capability. However, this results in a couple of problems, e.g. an increase in the harmonic components of the stator current, and an undesired cross-coupling between the magnetization current component (im) and the torque component (it). In this paper, a novel complex matrix model of electrically excited synchronous motors (EESM) was established with a new control scheme for coping with the low switching frequency issues. First, a hybrid observer was proposed to identify the instantaneous fundamental component of the stator current, which results in an obvious reduction of both the total harmonic distortion (THD) and the low order harmonics. Then, a novel complex current controller was designed to realize the decoupling between im and it. Simulation and experimental results verify the effectiveness of this novel control system for EESM drives.
Control of Electrically Excited Synchronous Motors with a Low Switching Frequency
Yuan, Qing-Qing,Wu, Xiao-Jie,Dai, Peng,Fu, Xiao The Korean Institute of Power Electronics 2012 JOURNAL OF POWER ELECTRONICS Vol.12 No.4
The switching frequency of the power electronic devices used in large synchronous motor drives is usually kept low (less than 1 kHz) to reduce the switching losses and to improve the converter power capability. However, this results in a couple of problems, e.g. an increase in the harmonic components of the stator current, and an undesired cross-coupling between the magnetization current component ($i_m$) and the torque component ($i_t$). In this paper, a novel complex matrix model of electrically excited synchronous motors (EESM) was established with a new control scheme for coping with the low switching frequency issues. First, a hybrid observer was proposed to identify the instantaneous fundamental component of the stator current, which results in an obvious reduction of both the total harmonic distortion (THD) and the low order harmonics. Then, a novel complex current controller was designed to realize the decoupling between $i_m$ and $i_t$. Simulation and experimental results verify the effectiveness of this novel control system for EESM drives.
Cui, Yan-Hui,Liang, Hai-Jun,Zhang, Qing-Qin,Li, Si-Qing,Li, Xiao-Rui,Huo, Xiao-Qing,Yang, Qing-Hui,Li, Wei-Wei,Gu, Jian-Fa,Hua, Qin-Liang,Lu, Ping,Miao, Zhan-Hui Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.4
Objective: To explore the effect on radiosensitivity of arsenic trioxide ($As_20_3$) in conjunction with hyperthermia on the esophageal carcinoma EC-1 cell line. Method: Inhibition of EC-1 cell proliferation at different concentrations of $As_20_3$ was assessed using the methyl thiazolyl blue colorimetric method (MTT method), with calculation of $IC_{50}$ value and choice of 20% of the $IC_{50}$ as the experimental drug concentration. Blank control, $As_20_3$, hyperthermia, radiotherapy group, $As_20_3$ + hyperthermia, $As_20_3$ + radiotherapy, hyperthermia + radiotherapy and $As_20_3$ + hyperthermia + radiotherapy groups were established, and the cell survival fraction (SF) was calculated from flat panel colony forming analysis, and fitted by the 'multitarget click mathematical model'. Flow cytometry (FCM) was used to detect changes in cell apoptosis and the cell cycle. Results: $As_20_3$ exerted inhibitory effects on proliferation of esophageal carcinoma EC-1 cells, with an $IC_{50}$ of 18.7 ${\mu}mol/L$. After joint therapy of $As_20_3$ + hyperthermia + radiotherapy, the results of FCM showed that cells could be arrested in the $G_2$/M phase, and as the ratio of cells in $G_0/G_1$ and S phases decreased, cell death became more pronounced. Conclusion: $As_20_3$ and hyperthermia exert radiosensitivity effects on esophageal carcinoma EC-1 cells, with synergy in combination. Mechanistically, $As_20_3$ and hyperthermia mainly influence the cell cycle distribution of EC-1 esophageal carcinoma cells, decreasing the repair of sublethal damage and inducing apoptosis, thereby enhancing the killing effects of radioactive rays.
Qing-Feng Meng,Wei-Lin Wang,Xiao-Ting Ni,Hai-Bin Li,Gui-Zhe Yao,Xiao-Lin Sun,Wei-Li Wang,Wei Cong 대한기생충학열대의학회 2015 The Korean Journal of Parasitology Vol.53 No.6
The breeding of domestic rabbits (Oryctolagus cuniculus) for human consumption has a long tradition in China. Infections that can affect the production of meat or even be transmitted from animals to humans are important to monitor, especially for public health reasons as well as for their impact on animal health. Thus, a total of 1,132 domestic rabbit sera from 4 regions in China were collected for serological screening for Encephalitozoon cuniculi and for Toxoplasma gondii by ELISA and modified agglutination test (MAT), respectively. Antibodies to E. cuniculi were detected in 248/1,132 (21.9%) sera tested while antibodies against T. gondii revealed a seroprevalence of 51/1,132 (4.5%). We believe that the present results are of epidemiological implications and public health importance due to the acknowledged susceptibility of humans to E. cuniculi and T. gondii infections. Therefore, routine screening tests of domestic rabbits are proposed considering the zoonotic potential of these parasites.
Adsorption of Nucleotides on ${\beta}$-Cyclodextrin Derivative Grafted Chitosan
Xiao Jian-Bo,Yu Hong-Zhu,Xu Ming,Chen Xiao-Qing The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.4
A novel ${\beta}$-cyclodextrin derivative (CCD-C) was synthesized with chitosan and carboxymethyl-${\beta}$-cyclodextrin. Its structure was characterized by elemental analysis, infrared spectra analysis, and X-ray diffraction analysis. The adsorption properties for guanosine 5'-monophosphate, cytidine 5'-monophosphate and uridine 5'-monophosphate were studied. Experimental results demonstrated that CCD-C had higher adsorption capability for guanosine 5'-monophosphate, and that the adsorption capacity for guanosine 5'-monophosphate was 74.20mg/g. The adsorption capacity was greatly influenced by pH, time and temperature. The introduction of chitosan enhanced the adsorption ability and adsorption selectivity of ${\beta}$-cyclodextrin for guanosine 5'-monophosphate. This novel derivative of chitosan is expected to have wide applications in the separation, concentration and analysis of nucleotides in biological samples.
Qing-Li Yang,Ji-Qing Shen,Yan Xue,Xiao-Bing Cheng,Zhi-Hua Jiang,Yi-Chao Yang,Ying-Dan Chen,Xiao-Nong Zhou 대한기생충학열대의학회 2015 The Korean Journal of Parasitology Vol.53 No.6
The nitric oxide (NO) formation and intrinsic nitrosation may be involved in the possible mechanisms of liver fluke-associated carcinogenesis. We still do not know much about the responses of inducible NO synthase (iNOS) induced by Clonorchis sinensis infection. This study was conducted to explore the pathological lesions and iNOS expressions in the liver of mice with different infection intensity levels of C. sinensis. Extensive periductal inflammatory cell infiltration, bile duct hyperplasia, and fibrosis were commonly observed during the infection. The different pathological responses in liver tissues strongly correlated with the infection intensity of C. sinensis. Massive acute spotty necrosis occurred in the liver parenchyma after a severe infection. The iNOS activity in liver tissues increased, and iNOS-expressing cells with morphological differences were observed after a moderate or severe infection. The iNOS-expressing cells in liver tissues had multiple origins.
Rotor Initial Position Estimation Based on sDFT for Electrically Excited Synchronous Motors
Qing-qing Yuan,Xiao-jie Wu,Peng Dai 전력전자학회 2014 JOURNAL OF POWER ELECTRONICS Vol.14 No.3
Rotor initial position is an important factor affecting the control performance of electrically excited synchronous motors. This study presents a novel method for estimating rotor initial position based on sliding discrete Fourier transform (sDFT). By injecting an ac excitation into the rotor winding, an induced voltage is generated in stator windings. Through this voltage, the stator flux can be obtained using a pure integral voltage model. Considering the influence from a dc bias and an integral initial value, we adopt the sDFT to extract the fundamental flux component. A quadrant identification model is designed to realize the accurate estimation of the rotor initial position. The sDFT and high-pass filter, DFT, are compared in detail, and the contrast between dc excitation and ac injection is determined. Simulation and experimental results verify that this type of novel method can eliminate the influence of dc bias and other adverse factors, as well as provide a basis for the control of motor drives.
Qing‑Ri Cao,Xiao‑Xue Zhang,Hao‑Yan Huang,Li‑Qing Chen,Hehua Jin,Beom‑Jin Lee,Jing‑Hao Cui 한국약제학회 2019 Journal of Pharmaceutical Investigation Vol.49 No.1
The application of single-walled carbon nanotubes (SWCNTs) as drug carriers is limited by their poor dispersal in aqueous medium. This study aimed to prepare chitosan (CS)-modified SWCNTs (CS-SWCNTs) and to evaluate their physicochemical properties and cytotoxicity. Oxidized SWCNTs (O-SWCNTs) were prepared with the use of strong acid, and the effects of acidizing conditions on the oxidation degree of the O-SWCNTs were investigated. CS was then non-covalently modified on the surfaces of O-SWCNTs. O-SWCNTs and CS-SWCNTs were characterized through ultraviolet spectroscopy, Fourier transform-infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy. The cytotoxic effects of the functionalized SWCNTs were determined through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. O-SWCNTs with relatively complete structure were successfully synthesized through 5 h of treatment with 5 M acid. The amine group of the CS and the carboxyl group of O-SWCNTs interacted in CS-SWCNTs. The functionalized SWCNTs did not aggregate or precipitate in water and exerted no cytotoxic effects on A549 and MCF-7 tumor cells. The CS-SWCNTs possess the advantages of a simple preparation process, excellent water dispersibility, and biocompatibility for drug loading.