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Lin H.,Chang'an University | You Y.-M.,Hanyang University | Cheon S.-R.,SNTech Co. | Kwon B.-I.,Hanyang University
Journal of Electrical Engineering and Technology | Year: 2013

This paper reports an investigation of pulse width modulation (PWM) techniques fo r two-phase brushless DC (BLDC) motors fed by a two-phase eight-switch inverter in a fan a pplication. The three-phase BLDC motor is widely applied in industry; however, a lower-cost t wo-phase BLDC motor and drive circuit has been greatly in demand in recent years. In this p aper, we introduce a mathematical model of the two-phase BLDC motor with sinusoidal back electromotive forces (EMFs) based on traditional three-phase BLDC motors. To simplify the dr ive algorithm and speed up its application, we analyze the principle of block commutation for a two-phase BLDC motor drive in the 180-electrical-degree conduction mode, and we further propose five PWM schemes to improve the commutation performance of the two-phase BLDC drive. The effectiveness of the proposed PWM methods is verified through experiments.

Eom S.-H.,Pukyong National University | Kang Y.-M.,Marinebioprocess Co. | Park J.-H.,Pukyong National University | Yu D.-U.,Pukyong National University | And 3 more authors.
Fisheries and Aquatic Science | Year: 2011

The objective of this study was to select an effective microbial strain to improve the functional qualities of Eisenia bicyclis water extract by fermentation. For this purpose, several microorganisms isolated from traditional Korean fermented foods were inoculated and cultivated in E. bicyclis water extract. Ultimately, yeast strain YM-1 was selected for further study based on its total phenolic compound (TP) content and antioxidant activity, which were enhanced by microbial fermentation. The extract fermented by YM-1 exhibited a superior TP content and 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity compared to extracts fermented by other microbes. The highest TP content and DPPH radical scavenging activity were observed after one day of YM-1 fermentation. Yeast strain YM-1 was identified as Candida utilis based on an analysis of its physiological characteristics. During fermentation of the extract by C. utilis YM-1, no significant difference was observed in the proximate composition, including moisture, crude lipid, crude protein, and crude ash. Fermentation by C. utilis YM-1 resulted in enhanced biological activity, including increases in the TP content and antioxidant activity. Thus, fermentation by C. utilis YM-1 is an attractive strategy for developing value-added food ingredients. © The Korean Society of Fisheries and Aquatic Science.

Kim D.K.,Korea University | Jang Y.R.,Korea University | Kim K.H.,Korea University | Lee M.N.,Korea University | And 7 more authors.
Fisheries and Aquatic Science | Year: 2011

An agar-degrading enzyme-producing strain was isolated from seawater. The isolate was identified as Microbulbifer sp. SD-1 by 16S rRNA sequencing analysis. The optimal pH and temperature for growth were 6.0 and 30°C, respectively, and growth was possible at pH 9.0 and 60°C. The isolate required 5% NaCl for optimal growth and showed 45% growth activity without NaCl. Agar concentrations of 0-0.4% in the medium did not affect growth. Thin-layer chromatography analysis revealed that this strain could degrade agar into a monosaccharide and oligosaccharide, which may have industrial applications. © The Korean Society of Fisheries and Aquatic Science.

Vu T.T.,Korean University of Science and Technology | Kim J.-C.,Korean University of Science and Technology | Choi Y.H.,Korea Research Institute of Chemical Technology | Choi G.J.,Korea Research Institute of Chemical Technology | And 4 more authors.
Plant Disease | Year: 2013

In the process of searching antibacterial agents from plants, we discovered that the methanol extract of Sedum takesimense showed potent antibacterial activity against Ralstonia solanacearum in vitro and in vivo. Eight antibacterial gallotannins were isolated from the aerial parts of S. takesimense and identified as gallic acid, methyl gallate, 4,6-di-O-galloylarbutin, 2,6-di-O-galloylarbutin, 2,4,6-tri-O-galloyl-glucose, 1,3,4,6-tetra-O-galloyl-β-glucose, 1,2,4,6-tetra-O-galloyl-β-glucose, and 1,2,3,6-tetra-O-galloyl-β-glucose based on electrospray ionization mass spectrometry and proton nuclear magnetic resonance spectroscopy. These gallotannins displayed broad-spectrum activity against various plant-pathogenic bacteria, and the strongest in vitro antibacterial activities of these gallotannins were against R. solanacearum minimum inhibitory concentration = 0.02 to 0.10 g/liter). Among these gallotannins, methyl gallate and 1,2,3,6-tetra-O-galloyl-β-glucose showed the strongest activities. In addition, synergistic or partial synergistic effects were observed in most combinations between major antibacterial compounds. The wettable powder formulation of the S. takesimense crude extract effectively reduced the development of tomato bacterial wilt caused by R. solanacearum under greenhouse conditions for 14 days after infection. This is the first report on the isolation of antibacterial compounds from S. takesimense. These results suggest that the extract from S. takesimense or the isolated gallotannins could be used as natural bactericides for the control of tomato bacterial wilt. © 2013 The American Phytopathological Society.

Lin H.,Hanyang University | Lipo T.A.,University of Wisconsin - Madison | Kwon B.-I.,Hanyang University | Cheon S.R.,SNTech Co.
Conference Proceedings - 2012 IEEE 7th International Power Electronics and Motion Control Conference - ECCE Asia, IPEMC 2012 | Year: 2012

This paper presents a novel three-level hysteresis current control scheme for a three-phase permanent magnet synchronous motor (PMSM) fed by two single-phase four-switch voltage source inverters. Based on two-level hysteresis current control techniques for a single-phase four-switch inverter, a novel three-level PWM method for three-phase PMSM motor is implemented to reduce the magnitude and variation of the switching frequency. To obtain better harmonic performance, an improved variable band hysteresis method for three-level three-phase voltage source inverter is further proposed. Considering three states of output average voltage of the inverter, a new hysteresis controller with variable band calculated by the motor resistance, inductance, DC-link voltage, phase current and back-emf is designed to maintain constant phase leg switching frequencies. The proposed method is simple and effective, and verified by the simulation. © 2012 IEEE.

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