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Soft-Switching Current-Fed Push–Pull Converter for 250-W AC Module Applications
Young-Ho Kim,Soo-Cheol Shin,Jung-Hyo Lee,Yong-Chae Jung,Chung-Yuen Won IEEE 2014 IEEE transactions on power electronics Vol.29 No.2
<P>In this paper, a soft-switching single-inductor push-pull converter is proposed. A push-pull converter is suitable for low-voltage photovoltaic ac module systems, because the step-up ratio of the high-frequency transformer is high, and the number of primary-side switches is relatively small. However, the conventional push-pull converter does not have high efficiency because of high-switching losses due to hard switching and transformer losses (copper and iron losses) as a result of the high turn ratio of the transformer. In the proposed converter, primary-side switches are turned ON at the zero-voltage switching condition and turned OFF at the zero-current switching condition through parallel resonance between the secondary leakage inductance of the transformer and a resonant capacitor. The proposed push-pull converter decreases the switching loss using soft switching of the primary switches. In addition, the turn ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.</P>
A New Control Strategy of Active Clamped Flyback Inverter for a Photovoltaic AC Module System
Young-Ho Kim,Jun-Gu Kim,Young-Hyok Ji,Chung-Yuen Won,Tae-Won Lee 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
In this paper, a new control strategy of an active clamped flyback inverter for a photovoltaic AC module system is proposed. In the flyback inverter, a voltage spike across a main switch is generated from a resonance between a leakage inductance and an output capacitance across the main switch. For reducing the voltage spike of the main switch, a snubber circuit is used. In case of the active clamp technique, the circuit has a conduction loss, switching loss and gate drive loss because the switch is turned on and off with a hard switching. Therefore, a consideration reducing the losses of the active clamp circuit is required. If the new control strategy is used, the active clamp switch is not operated during a low voltage in an utility line period. Therefore, the losses of the active clamp circuit can be reduced. In order to verify these, theoretical analysis and simulations are performed.
New integral inequalities for nonlinear functions and their applications
Young-Ho Kim,Tae-In Kwon 장전수학회 2008 Advanced Studies in Contemporary Mathematics Vol.16 No.1
In this paper, we obtained new retarded integral inequalities which can beused as tools in certain integral equations. Some applications are also given to illustratethe usefulness of our results.
U.S.-China Competition in the Indo-Pacific: A Military Dimension
Young Ho Kim 미래사회통합연구센터 2019 Journal of Conflict and Integration Vol.3 No.2
The U.S.-China relations have leaned toward overt confrontation and competition with inauguration of the Trump Administration. While this change of relations between the two countries is shown most salient in the economic area with an on-going trade war, the military realm is also another lively contesting area. This growing trend of competition and confrontation between U.S. and China, especially in the military area engenders serious concerns to many countries in the region. With increasing uncertainty and instability, it compels many not only to wonder about their necessary defense postures and capabilities but also to make choices on siding with either one of the two. To avoid such a difficult situation and make smarter security policy choices, it is important for the countries in the region to understand the nature and direction of the U.S.-China military competition more clearly. Thus, this article aims to help these regional countries by explaining the main features of the military strategies and measures that each country has pursued and employed competitively for the past ten years or so. More concretely, it attempts to analyze China’s A2/AD strategy and the U.S. JAM-GC, MDO, and JCIC. And then, as a conclusion, it will discuss three implications for the future security policy-making of the regional countries, particularly South Korea.
( Young Ho Kim ) 한국체육학회 2016 국제스포츠과학 학술대회 Vol.2016 No.1
Purpose: In every new school term in South Korean society, one of the man issues dealt with and exposed through media, is college level school violence. School violence is euphemistically understood as a form of discipline instead of a type of violence. Thus, this study examines why school violence, so-called ‘discipline,’ at the college level is consistently occurring and also what factors influence innocent bystanders to become active abusers. Method: This research will be methodologically designed by qualitative research. Qualitative data analysis will be employed. In terms of method used for this study, semi-structured interview is employed with a list of topics or questions, which will be shared with participants in advance. There will be a number of 10 participants from three different Universities that have been experienced in accusation with regards to school violence within the last five years. Result: Based on theoretical and empirical research, my assumptions on the result of this study imply two propositions. First, individuals are transformed from an innocent individual into a guilty one. In order to support this proposition, classic theory of differential association proposes that individuals learn deviated behaviors such as criminal values, motives, and attitudes through their interactions with others. In other words, an individual’s violent behavior at the college level is also socialized into a certain group where current members believe their violent behaviors are a normal discipline ingrained into the group. Also, the practices, so-called discipline, among students are institutionalized into the group since the practices are eventually considered a matter of routine in order for current members to discipline newcomers such as freshmen. That cultural circulation among students helps firm the school environment institutionalized. Conclusion: As many theoretical and empirical research point out, deviated behaviors are developed among interaction with other people who share the same culture such as conventional behaviors and ethics. Thus, the belief and behavior, which ingroup members comply with in the group they belong, eventually become normalized practices. In other words, the criteria they believe whether it is right and wrong depends on what kind of cultural environment they are socialized in and on how the cultural environment is institutionalized to ingroup members. This fact may imply if the misconducted culture realizes that their behaviors are acts of violence rather than acts of disciplines, then colleges can make the necessary cultural changes to benefit and create a better school environment for ingroup members, which in turn will give those members a more harmonious relationship with others.