• Journal of Power Electronics
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• 제15권5호
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• pp.1348-1357
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• 2015

Under traditional unified power quality conditioner (UPQC) control, a UPQC series converter (SC) is mainly used to handle grid-side power quality problems while its parallel converter (PC) is mainly used to handle load-side power quality problems. The SC and PC are relatively independent. The SC is usually in standby mode and it only runs when the grid voltage abruptly changes. In this paper, novel UPQC coordinated control strategies are proposed which use the SC to share the reactive power compensation function of the PC especially without grid-side power quality problems. However, in some cases, there will be a circulating current between the SC and the PC, which will probably influence the compensation fashion, the compensation capacity, or the normal work of the UPQC. Through an active power circulation analysis, strategies with and without a circulating current are presented which fuses the reactive power allocation strategy of the SC and the PC, the composite control strategy of the SC and the compensation strategy of the DC storage unit. Both of the strategies effectively solve the SC long term idle problem, limit the influence of the circulating current, optimize all of the UPQC units and reduce the production cost. An analysis, along with simulation andexperimental results, is presented to verify the feasibility and effectiveness of the proposed control strategies.

• 공학교육연구
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• 제14권3호
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• pp.45-54
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• 2011

The purpose of this study is to analyze performance problems in establishing and improving program educational objectives (PEO) and to set up action strategies for the civil engineering program at the A university. To fulfill the purpose, according to the typical needs analysis model, research problems were defined, current conditions and desired conditions were identified, discrepancies and their reasons were examined, and action strategies were derived. Current conditions and desired conditions were identified by analyzing the A civil engineering program's self study report, conducting surveys and interviews with constituents. After the discrepancies and the reasons were examined, performance problems and field force analysis were conducted to draw short term and long term action strategies to improve PEO. Short term action strategies were to announce PEO to current students, to hold faculty seminars to establish and to improve PEO, to renew the list of constituents regularly, to composite an annual milestone, to define roles of the committees, and to enforce educational opportunity toward industrial advisory board members. For the long term strategies, improvement and documentation of PEO assessment system, collection and analysis of constituents' suggestions, establishment of effective accreditation support system, and arrangement of compensation system for the faculties who are in charge of engineering education accreditation responsibility.

• 서비스연구
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• 제7권2호
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• pp.79-90
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• 2017

본 연구는 서비스R&D 전략을 현대경제사회의 본질 관점에서 연구하였다. 현대는 산업간 경계가 해체되는 시대다. 제조업과 서비스업의 구분이 없어지고, 고객을 중심으로 하나의 산업 환경에서 경쟁하고 있다. 고객의 욕구는 서비스로 구현되므로, 서비스R&D는 현대 기업과 국가들의 중심주제가 되었다. 그런데, 서비스R&D는 정의도 다양하고 각 정의에 따라 범위 차이가 커서 정책 당국자들 사이에서도 이견이 많다. 본 연구는 현대 경제사회의 특징과 서비스의 본질에 집중하여 서비스R&D의 바람직한 정책방향과 전략을 논의한다. 산업간 경계가 해체되는 현대경제의 특징을 반영하여 서비스R&D 전략을 도출하였다. 또한 서비스의 관계성, 쌍방향성, 수평성, 조화성 본질과 서비스의 무형성, 비분리성, 비일관성, 무재고성 특성을 반영하여 서비스R&D전략을 도출해내는 연구를 수행하였다. 제조업은 서비스화R&D를, 서비스업은 제조업화 R&D를 강화하는 전략, 서비스본질을 반영하는 전략, 서비스의 특성을 활용하는 전략을 도출하여 제안하였다. 본 연구의 결과는 개별 기업의 서비스R&D전략수립, 서비스산업의 발전과 전체 서비스산업의 발전, 그리고 제조업을 포함한 전체 산업의 발전 전략 수립에 공통적으로 활용될 수 있을 것이다.

• Journal of Power Electronics
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• 제19권4호
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• pp.1034-1044
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• 2019

In medium-voltage and high-voltage high-power converters, the switching devices need to operate at a low switching frequency to reduce power loss and increase the power capacity. This increases the delay of the signal sampling and PWM. It also makes the cross-couplings of the d-q current components more severe. In addition, the LCL filter has three cross-coupling loops and is prone to resonance. In order to solve these problems, this paper establishes a complex vector model of an LCL type grid-connected converter. Based on this model, two multiple decoupling current control strategies with passive damping / notch damping are proposed for the LCL type grid-connected converter. The proposed strategies can effectively eliminate the cross-couplings of the converter, achieve independent control of the d-q current components, expand the stable region and suppress the resonance of the LCL filter. Simulation and experimental results verify the correctness of the theoretical analysis and the feasibility of the proposed strategies.

• Journal of Power Electronics
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• 제16권2호
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• pp.769-777
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• 2016

This work focuses on current sharing between punch-through insulated gate bipolar transistors (IGBTs) connected in parallel and evaluates the mechanisms that allow overall current balancing. Two different control strategies are presented. These strategies are based on the modification of transistor gate-emitter control voltage V_GE by using an active gate driver circuit. The first strategy relies on the calculation of the average value of the current flowing through all parallel-connected IGBTs. The second strategy is proposed by the authors on the basis of a current cross reference control scheme. Finally, the simulation and experimental results of the application of the two current sharing control algorithms are presented.

• 한국경영과학회지
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• 제8권2호
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• pp.57-65
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• 1983

Despite the recent phenomenal growth in computer installations in business and increasing interests in Management Information Systems in Korea, there are basic questions remained: how are the computers utilized, what is the current state of MIS, and what are the strategies which will enhance the current state of MIS in Korea？ The purpose of this paper is to answer these questions. To begin, the current state of MIS is investigated from the aspects of MIS budget, manpower, hardware, and various softwares based on the survey of 30 major industries. The results show that the overall MIS in Korea is still remained in the primitive stage despite its ultra modern computer hardwares. The obstacles that hinders the MIS evolution in Korea seems intractable for quite a long period of time. Some strategies are suggested which can partially remove two big obstacles-shortage in qualified manpower and lack of softwares that fit Korean industries.

• 한국전자거래학회지
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• 제3권2호
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• pp.17-35
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• 1998

Global Electronic Commerce (EC) is currently being pursued by most of the developed countries. Domestically, EC has just started and still has lots of problems to solve in terms of both technology and institutions. EC has a great potential to affect a country's competitive advantage. For EC to be adopted and diffused early, it is necessary to analyze the current status of EC and to establish the strategies to strengthen the competitive position. Therefore, the major objectives of the study are to review the current status of EC in Korea and to propose for both public and private sectors the strategies to strengthen the competitive advantage.

• 전력전자학회논문지
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• 제25권2호
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• pp.152-155
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• 2020

This study proposes an input filter for a gallium-nitride-based direct matrix converter with a stepless current commutation technique. Various current commutation strategies have been adopted for reliable operation of switches. These strategies are complex to be implemented and require additional components. The stepless current commutation technique is simple to operate but causes overcurrent issues due to the occurrence of short circuit on input sources. In this study, to restrict the short circuit current, we utilized GaN devices with fast switching properties and modified the input filter. The proposed input filter was verified by experimental results of induction motor drive.

• Asian Pacific Journal of Cancer Prevention
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• 제17권12호
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• pp.5113-5119
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• 2016

Purpose:The present qualitative study explored adolescents' perceptions regarding effective strategies to prevent adolescents from using tobacco products (TP). Apart from the commercial TPs, there has been emerging use of alternatives such as vapes, e-cigarettes and shisha. This unfortunate phenomenon continues despite the currently available preventive strategies. Thus, understanding of the perceptions of the current generation would be valuable to provide new insights. Methods: Purposive sampling was utilized to recruit 40 adolescents between the age of 15 and 16 years old attending public daily secondary schools. Eight focus group discussions were conducted among the TP users, ex-users and non-users. Data were analyzed using a thematic content analysis procedure with NVivo. Results: Among barriers with the currently available strategies were having teachers who smoke tobacco, addiction to nicotine and self-perceptions of being healthy. The content of any program should include knowledge on negative outcomes of using tobacco products and awareness of the legislation together with ways to overcome peer and family influence including improving self-efficacy and refusal skills. Strategies were suggested to be delivered using information technology which provides interactive learning and visual effects. Conclusions: Adolescents agreed that the content and delivery of tobacco use prevention strategies need to be revised to suit the current generation to ensure sustainability.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.638-642
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• 2005

This paper presents incentive application strategies and delay prevention strategies as schematic approaches to improve time performance of highway construction contracts. This research recognizes the importance of improving time performance during highway construction. Strategic solutions of the most core issues on time performance incentive contracting are identified. The suggested incentive application strategies develop criteria for applying time classification to projects, for assigning project time classifications to contractors and designers, and for determining appropriate incentive values in A (cost) + B (time cost) and other performance incentive contracts. The suggested delay prevention strategies develop criteria for determining the appropriate subsurface utility engineering (SUE) level and to develop best practices for avoiding utility relocation delays. A schematic approach for each strategy is developed. This paper also introduces current incentive contracting practices in Florida. The researchers obtained the information from experienced persons in the highway construction industry, including key highway contractors, designers, and Department of Transportation (DOT) and Federal Highway Administration (FHWA) personnel. The major focus of this research is to develop strategies and suggest approaches to improve time performance of highway construction contracts. For future study, practical tools to facilitate implementation of the suggested strategies should be developed, so that the criteria, implementation processes, and best practices developed may contribute to the current industry-wide effort to improve time performance.