Active Controlled Primary Current Cutting-Off ZVZCS PWM Three-Level DC-DC Converter

Shi, Yong The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.2

A novel active controlled primary current cutting-off zero-voltage and zero-current switching (ZVZCS) PWM three-level dc-dc converter (TLC) is proposed in this paper. The proposed converter has some attractive advantages. The OFF voltage on the primary switches is only Vin/2 due to the series connected structure. The leading-leg switches can obtain zero-voltage switching (ZVS), and the lagging-leg switches can achieve zero-current switching (ZCS) in a wide load range. Two MOSFETs, referred to as cutting-off MOSFETs, with an ultra-low on-state resistance are used as active controlled primary current cutting-off components, and the added conduction loss can be neglected. The added MOSFETs are switched ON and OFF with ZCS that is irrelevant to the load current. Thus, the auxiliary switching loss can be significantly minimized. In addition, these MOSFETs are not series connected in the circuit loop of the dc input bus bar and the primary switches, which results in a low parasitic inductance. The operation principle and some relevant analyses are provided, and a 6-kW laboratory prototype is built to verify the proposed converter.

Full ZVS Load Range Diode Clamped Three-level DC-DC Converter with Secondary Modulation

Shi, Yong The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.1

A new four-primary-switch diode clamped soft switching three-level DC-DC converter (TLDC) with full zero-voltage switching (ZVS) load range and TL secondary voltage waveform is proposed. The operation principle and characteristics of the presented converter are discussed, and experimental results are consistent with theoretical predictions. The improvements of the proposed converter include a simple and compact primary structure, TL secondary rectified voltage waveform, wide load range ZVS for all primary switches, and full output-regulated range with soft switching operation. The proposed converter also has some disadvantages. The VA rating of the transformer is slightly larger than that of conventional TLDCs in variable input and constant output mode. The conduction loss of the primary coil is slightly higher because an air gap is inserted into the magnetic cores of the transformer. Finally, the secondary circuit is slightly complex.

Self-curling 3D oriented scaffolds from fish scales for skeletal muscle regeneration

Shi Yong,Zhang Xiaoxuan,Liu Rui,Shao Xiaoyan,Zhao Yuanjin,Gu Zhuxiao,Jiang Qing 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Volumetric muscle loss (VML) due to various reasons may cause motor dysfunction and tissue engineering has been proposed for muscle regeneration. However, developing three-dimensional (3D) tissue-engineered scaffolds that can mimic oriented cell growth of muscle tissues are challenging for regeneration medicine. Herein, we propose a novel self-curling 3D oriented scaffold (SCOS) composed of fish derived gelatin methacrylate (GelMA) and fish scales for repairing skeletal muscles.Fish scales of tilapia were decellularized and decalcified. Then, SCOSs were constructed by ultraviolet-coating methylated fish gelatin on the back of fish scales. C2C12 myoblasts were cultured on SCOSs, and after induction of myogenic differentiation, SCOS/C2C12 transplants were prepared for in vivo experiments.Decellularized and decalcified fish scales (DDFSs) became soft and retained the original oriented microgroove surface structure that could induce oriented cell growth. SCOSs could self-curl into 3D structures when immersing in culture medium due to different swelling properties of fish GelMA and DDFSs. Cell experiments demonstrated that SCOSs enhanced the oriented growth and myogenic differentiation of C2C12 myoblasts. By integrating SCOSs and myogenic differentiated C2C12 myoblasts, the resultant SCOS/C2C12 transplants promoted de novo muscle regeneration and functional restoration of muscle activity in the mouse model of VML.Our results suggest that SCOSs loaded with myogenic differentiated C2C12 myoblasts can promote muscle regeneration in mice with skeletal muscle injuries, indicating application prospects of such scaffolds in muscle tissue engineering and other related fields.

Female Fertility and Employment Choice under the two-Child Policy: Findings from Shanghai

Shiyong Shen 한국여성정책연구원(구 한국여성개발원) 2017 한국여성정책연구원 세미나자료 Vol.2017 No.6

Women’s reproductive behavior has an impact on their employment. A comprehensive two-child policy makes it possible for women to have more children and directly affect their labor market status in China’s mega-cities. In this study ,we used data from Female fertility and employment choice of 917 questionnaires conducted in 2016 in shanghai, and Cross Analysis Methods to examine the relationship between fertility and employment. The results not only validate correlation of reproductive responsibility with professional status, even women’s income also affects their fertility, but also show that reducing women’s parenting responsibility is conducive to women’s equal employment. Thus there is an urgent need to re-divide fertility responsibilities between family, society and government. Our findings also shed light the need to further improve the fertility supporting policy.

The Relationship between Volatility and Trading Volume in Korea’s Financial Markets

Shiyong Yoo(劉時庸) 한국공공관리학회 2019 한국공공관리학보 Vol.33 No.4

The aim of this study is to identify the cross-market relationship between trade volume and volatility among Korea’s financial markets, including the KOSPI 200 Index, KOSPI 200 options, and KOSPI 200 futures. With regards to the relationship between the trading volume of the KOSPI 200 Index and the volatility of KOSPI 200 derivatives markets, the trading volume of the underlying index is found to increase the volatilities of KOSPI 200 options and the futures markets. The expected trading volume of the underlying index has a positive relation with VKOSPI, which is the options market volatility measure; further, the unexpected components have a positive relation with the volatility of the futures market. In short, the trading volume of the underlying index is positively related with the volatilities of options and futures markets. Moreover, with regards to the relation between derivatives’ trading activities and the underlying index volatility, open interests of call and futures, trading volume of futures, and its expected and unexpected components are positively related with the volatility of the KOSPI 200 Index. On the other hand, open interests of put options and their expected components have a negative relation with the volatility of the KOSPI 200 Index. Our empirical results imply that volume and volatility relations have some cross financial markets effects in both the underlying and derivatives markets; furthermore, the trading volumes and volatilities of the underlying and derivatives markets are deeply interrelated with each other.

Is Money Smart in the Korean mutual fund marketplace?

Shiyong Yoo,S. K. Hwang 한국로고스경영학회 2009 한국로고스경영학회 학술발표대회논문집 Vol.2009 No.7월

To examine the smart money controversy, we employ a Korean data set (January 2001 to May 2008) of monthly fund inflows and outflows differentiated between individual and institutional investors. Our data allow us to conduct a stronger test for the smart money effect by using monthly data on exact fund flows, and to gain greater insight into investors' decisions by considering separately the buys and sells of individual and institutional investors. Using Carhart (1997)'s four-factors model and Keswani and Stalin (2008) 's methodology, we analyze empirical relationship between fund's risk-adjusted excess return and fund flows. The results are we can't find such evidences of smart money effect in Korean mutual fund marketplace.

TEMPLATE STRATEGY FOR THE SYNTHESIS OF Cu2O-Pt HIERARCHICAL HETEROSTRUCTURES FOR THE DEGRADATION OF METHYLENE BLUE

SHIYONG BAO,HAN ZHU,PAN WANG,MEILING ZOU,MINGLIANG DU,MING ZHANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.6

A facile and green route was introduced to synthesize Pt nanoparticles (PtNPs) immobilized on Cu2O octahedrons to form Cu2O–Pt hierarchical heterostructure. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were employed to study their morphology, chemical and crystallographic properties of the Cu2O–Pt hierarchical heterostructure. These novel Cu2O–Pt hierarchical heterostructures show fascinating degradations of methylene blue (MB), due to the suppressed electron/hole recombination phenomena and the efficient ability to capture the light.

Capital Structure and Stock Returns: Evidence from Korean Stock Markets

Shiyong Yoo,Jiani Wu 사람과세계경영학회 2019 Global Business and Finance Review Vol.24 No.4

In this paper, a structural equation model is applied to Korean firms listed in KOSPI and KOSDAQ from 1990 to 2016 to analyze the determinants of capital structure and stock returns and discern how capital structure and stock returns affect each other. We find that stock returns have a strongly negative (-) effect on capital structure in the structural equation model. However, leverage has no significant effect on stock returns in the structural equation model, perhaps because we use data from before, during, and after recent financial crises. In addition, asset structure (+) and profitability (-) have strongly significant effects on capital structure. Uniqueness and size show unstable effects on capital structure. As for the determinants of stock returns, size (-), B/M (+), investment (+), and market premium (+) show strongly significant effects on stock returns in all the models. Profitability shows no significant influence on stock returns.

Stochastic Daily Temperature Simulation in Seasonal Forecast

Shiyong Yoo(유시용),Daniel S. Wilks,Timothy Mount,Joocheol Kim(김주철) 한국기상학회 2004 Asia-Pacific Journal of Atmospheric Sciences Vol.40 No.6

Entrepreneurship and Economic Growth during China’s Economic Transformation, 1978–2008

Shiyong Zhao 서울대학교 경제연구소 2018 Seoul journal of economics Vol.31 No.3

Using China’s provincial-level panel data from 1978–2008, we examine the effects of entrepreneurship on economic growth in the context of China’s transformation from a centrally planned to a market-oriented economy. We divide entrepreneurship into two types: business creation and innovation. Our estimation results show both types of entrepreneurship have significant positive effects on China’s GDP per capita growth rate over the sample period. Specifically, the annual growth rate of the GDP per capita will increase by 1.98 percentage points if business creation entrepreneurship increases by one standard deviation. Moreover, the annual growth rate will increase by 0.134 percentage points if innovation entrepreneurship increases by ten percent. The results are robust even when we control for different sets of demographical and institutional variables. China’s experience shows a strong government does not conflict with the entrepreneurs’ role.