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- 저자 : Qian Guo (검색결과 182 건)
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Secondary Voltage Control for Reactive Power Sharing in an Islanded Microgrid
Guo, Qian,Wu, Hongyan,Lin, Liaoyuan,Bai, Zhihong,Ma, Hao The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1
Owing to mismatched feeder impedances in an islanded microgrid, the conventional droop control method typically results in errors in reactive power sharing among distributed generation (DG) units. In this study, an improved droop control strategy based on secondary voltage control is proposed to enhance the reactive power sharing accuracy in an islanded microgrid. In a DG local controller, an integral term is introduced into the voltage droop function, in which the voltage compensation signal from the secondary voltage control is utilized as the common reactive power reference for each DG unit. Therefore, accurate reactive power sharing can be realized without any power information exchange among DG units or between DG units and the central controller. Meanwhile, the voltage deviation in the microgrid common bus is removed. Communication in the proposed strategy is simple to implement because the information of the voltage compensation signal is broadcasted from the central controller to each DG unit. The reactive power sharing accuracy is also not sensitive to time-delay mismatch in the communication channels. Simulation and experimental results are provided to validate the effectiveness of the proposed method.
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Nano-Rheology of Single Unentangled Polymeric Lubricant Films
Guo, Qian,Chung, Pil Seung,Jhon, Myung S.,Choi, Hyoung Jin WILEY-VCH Verlag 2008 Macromolecular theory and simulations Vol.17 No.9
<P>Rheology and tribology become more and more critical issues in order to satisfy the harsh requirements for ultra-small head/media spacing HDDs. In this communication, MD simulations with a bead/spring model were employed to examine the nano-rheological response of nonfunctional and functional PFPEs by analyzing the shear viscosity of nanoscale PFPE films and the relaxation processes as a function of wall interaction/separation and endgroup functionality. Our simulation results indicate that thin PFPE films show more solid-like behavior, especially under high shear rate. The film deformation and shear viscosity change by tuning the film thickness and the endgroup functionality was discussed in conjunction with the relaxation processes.</P><P> <img src='wiley_img/10221344-2008-17-9-MATS200800048-gra001.gif' alt='wiley_img/10221344-2008-17-9-MATS200800048-gra001'> </P>
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Qian, Jun,Li, Jing,Jia, Jian-Guang,Jin, Xin,Yu, Da-Jun,Guo, Chen-Xu,Xie, Bo,Qian, Li-Yu Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.4
Objectives: To observed the effects of ginsenoside -Rh2 (GS-Rh2) on proliferation and apoptosis of side population (SP) human gastric cancer SGC-7901 cells. Materials and Methods: SGC-7901 SP and Non-SP cells were sorted by flow cytometry and assessed using the cck-8 method. Expression of apoptosis-related proteins Bax and Bcl-2 of SP before and after the intervention was determined by Western-blotting. Results: It was found that the proliferation of SP was significantly faster than that of NSP (P<0.05). In addition, GS-Rh2 inhibited proliferation of gastric cancer SP cells, induced cell cycle arrest and cell apoptosis, and changed the expression of BAX/Bcl-2 proteins in a time-dependent and concentration-dependent manner (P<0.05). Conclusions: With increase of GS-Rh2 dose, GS-Rh2 gradually inhibit the proliferation of SGC-7901 SP cells, which have high proliferation rate, through G1/G0 phase arrest, followed by apoptosis which involves the up-regulation of Bax and the down-regulation of Bcl-2.
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Guo Chen,Wei Mao,Shou‑Quan Wu,Yu Wang,Gui‑Yi Ji,Miao‑Miao Zhang,Qian‑Qian Liu,Jian‑Qing He 한국유전학회 2017 Genes & Genomics Vol.39 No.11
Anti-tuberculosis drug-induced hepatotoxicity (ATDH) is the most frequent, and potentially fatal adverse effect in the treatment of tuberculosis (TB). The rs7574865 polymorphism in the signal transducer and activator of transcription 4 gene (STAT4) was reported to be associated with drug-induced liver injury. However, there was no study aimed to this association in Chinese patients. The aim of this study was to investigate the influence of STAT4 polymorphisms on the susceptibility to ATDH in a Chinese Han population. A total of 280 TB patients with the prescription of anti-TB therapy, of Chinese Han origin, were enrolled. They were followed up for 3 months and demographic, clinical, laboratory and therapeutic data at each visit were collected. Two single nucleotide polymorphisms (SNPs) (rs7574865 and rs7582694) of STAT4 were genotyped with the MassARRAY platform. The associations between SNPs and ATDH risk were analyzed by logistic regression adjusting for confounding factors. A total of 24 patients were diagnosed with ATDH and considered as the case group, and 33 patients were lost to follow-up; the remaining 223 subjects without ATDH were considered as the control group. There was strong linkage disequilibrium (LD) between rs7574865 and rs7582694 ( r2 = 0.928 and D′ = 1). No significant association was found between SNPs or haplotypes of STAT4 and ATDH after correction for confounding factors. This prospective study is the first to investigate the association of genetic polymorphisms of STAT4 and ATDH in Chinese individuals. There was no significant association between the rs7574865 of STAT4 and ATDH in a Chinese Han population.
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Highly Efficient Shoot Regeneration from Cotyledonary Nodes of Vegetable Soybean
Qian-Qian Liu,Gang Chen,Jun-Yi Gai,Yue-Lin Zhu,Li-Fei Yang,Guo-Ping Wei,Cong Wang 한국원예학회 2010 원예과학기술지 Vol.28 No.2
To establish a highly efficient system for shoot regeneration in vegetable soybean (Glycine max (L.) Merrill), explants were obtained from six genotypes and adventitious shoots were regenerated from cotyledonary nodes cultured on medium supplemented with different concentrations of N-phenyl-N′-1, 2, 3-thiadiazol-5-ylurea (thidiazuron TDZ) and 1-naphthylacetic acid (NAA). The most effective combination of plant growth regulators was selected first and then the effects of medium types, inoculation methods and genotypic differences on shoot regeneration were studied. The explants were inserted either vertically or horizontally into the medium and five basal media, including B5, ½ B5, MS, ½ MS, and MSB (MS salts and B5 organics), were tested. The shoot regeneration frequency of the six genotypes ranged from 53.5% to 88.9% and three of them reached 88.9%, 87.5% and 83.3%, respectively, on B5 medium supplemented with 1 ㎎?L<SUP>-1</SUP> TDZ, 0.05 ㎎?L<SUP>-1</SUP> NAA, and 5 ㎎?L<SUP>-1</SUP> AgNO₃. The shoot regeneration frequency of explants cultured on B5 medium was significantly higher than that of the other four basal media. The vertically inserted explants were found to yield a higher shoot regeneration frequency than that of horizontally inserted ones; the maximum difference of regenerating percentages between the two methods was 37.5%. In summary, TDZ was an efficient plant growth regulator for shoot induction. B5 medium and vertically inserted explants promoted shoot regeneration. We believe this highly efficient shoot regeneration system will provide foundation for the further transgenic studies in vegetable soybean.
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Distributed Secondary Voltage Control of Islanded Microgrids with Event-Triggered Scheme
Qian Guo,Hui Cai,Ying Wang,Weimin Chen 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6
In this study, the distributed secondary voltage control of islanded microgrids with multi-agent consensus algorithm is investigated. As an alternative to a time-triggered approach, an event-triggered scheme is proposed to reduce the communication load among inverter-based distributed generators (DGs). The proposed aperiodic control scheme reduced unnecessary utilization of limited network bandwidth without degrading control performance. By properly establishing a distributed triggering condition in DG local controller, each inverter is only required to send voltage information when its own event occurs. The compensation of voltage amplitude deviation can be realized, and redundant data exchange related to fixed high sampling rate can be avoided. Therefore, an efficient use of communication infrastructure can be realized, particularly when the system is operating in steady state. The effectiveness of the proposed scheme is verified by simulations on a microgrid test system.
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Qian Guo,Shuang Cheng,Xizheng Ke 한국광학회 2021 Current Optics and Photonics Vol.5 No.6
In a free-space coherent optical communication system, wavefront distortion is frequently beyond the correction range of the adaptive-optics system after the laser has propagated through the atmospheric turbulence. A method of residual wavefront correction is proposed, to improve the quality of coherent optical communication in free space. The relationship between the wavefront phase expanded by Zernike polynomials and the mixing efficiency is derived analytically. The influence of Zernike-polynomial distortion on the bit-error rate (BER) of a phase-modulation system is analyzed. From the theoretical analysis, the BER of the system changes periodically, due to the periodic extension of wavefront distortion. Experimental results show that the BER after correction is reduced from 10 −1 to 10 −4 ; however, when the closed-loop control algorithm with residual correction is used, the experimental results show that the BER is reduced from 10 −1 to 10 −7 .
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Qian Guo,Young-Nam Kim,Bog-Hieu Lee 대한지역사회영양학회 2017 Nutrition Research and Practice Vol.11 No.1
BACKGROUND/OBJECTIVES: Stress-induced cognitive impairment is related to the suppression of hippocampal neurogenesis that results from an increase of oxidative stress. Therefore, the aim of this study was to investigate the effects of administration of a blueberry drink, having a high antioxidant power, on the cognitive performance of adult rats exposed to chronic mild stress. MATERIALS/METHODS: Twelve-week-old male Sprague-Dawley rats (n = 48) were randomly divided into four groups: control (CO), stress (ST), control + 5% blueberry drink (CO + B), and stress + 5% blueberry drink (ST + B). After eight weeks, the cognitive performance was assessed using a multiple T-maze water test. Levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and ascorbic acid were measured in the brain, and catecholamine concentrations were measured in plasma. RESULTS: The brain weights of the rats from the ST and ST + B groups were significantly lower than those of the rats from the CO and CO + B groups. The cognitive performance of the ST group was impaired when compared to that of the CO group. This impairment was significantly improved by the blueberry drink supplementation (P < 0.05). The brain SOD and CAT concentrations were not influenced by the stress or by the blueberry drink. However, the brain levels of GPx and ascorbic acid were significantly lower in the ST group than those in the CO group and were increased by the blueberry drink supplementation. The plasma catecholamine concentrations were affected by chronic mild stress and by the blueberry drink. The plasma norepinephrine and dopamine concentrations were decreased by the chronic stress and improved by the blueberry drink supplementation. The plasma epinephrine level was only influenced by the stress. CONCLUSION: These findings suggest that the blueberry drink may protect against the cognitive impairment induced by chronic mild stress.
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