• The Korean Journal of Ecology
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• 제26권2호
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• pp.53-58
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• 2003

Ever-growing recreation, tourism and ecotourism worldwide have become a significant factor of resource degradation in many protected areas. Managers of these areas are increasingly challenged to implement policies, strategies and actions that would protect the resource base while providing quality visitor experience. One major issue in managing protected area visitations is that of carrying capacity, or the question of "how much use is too much\ulcorner". Scientific studies of visitor impacts, often known as recreation ecology, has generated a knowledge base that provides valuable input to the visitor carrying capacity management process adopted by the U.S. National Park Service. This paper aims at (a) providing an overview of recreation ecology research and its application in managing visitor carrying capacity, and (b) examining the relevance of recreation ecology to East Asian protected areas with special reference to the visitor capacity issue.ity issue.

• 한국음향학회지
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• 제37권1호
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• pp.46-52
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• 2018

압전변압기에 사용되는 압전 단결정은 높은 입력 임피던스로 인하여 파워전송용량이 높지 않다는 문제점이 있다. 따라서 본 연구에서는 연산증폭기를 사용한 범용 임피던스 변환(General Impedance Convert, GIC) 회로로 구현된 정전용량 증가회로를 압전 단결정 진동자의 전기단자에 연결함으로써 입력임피던스를 저하시켜 파워전송용량을 향상시킬 수 있는 방법을 제안하였다. $128^{\circ}$회전 Y판 $LiNbO_3$ 단결정 진동자에 설계 제작된 정전용량 증가회로를 적용하여 구동 특성을 측정한 결과, 입력임피턴스는 25 % 감소, 전기-기계결합계수는 30 % 증가, 전압변환 특성에 있어서는 약 17~30배의 출력파워용량이 증가됨을 확인하였다.

• 한국항해항만학회지
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• 제27권4호
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• pp.471-478
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• 2003

신호교차로는 도로조건, 교통조건, 신호조건 능 방대한 입력자료를 바탕으로 용량분석을 시행하고 이 과정을 토대로 주요 효과척도인 지체를 산정하여 신호교차로의 서비스 수준을 판단한다. 하지만 이러한 용량 및 서비스 수준 결정에 있어 바탕이 되는 현장 데이터(회전 교통량, 도로의 기하구조, 신호시간, 접근로 구배, 중차량비, 첨두시간계수, 차량도착형태 등) 입력자료의 불확실성으로 인해 초래되는 결과의 오류에 대해서는 고려되지 않고 있는 실정이다. 이로 인해 추정된 용량 및 서비스수준에 대한 신뢰성을 검증할 수 없는 문제를 내포하고 있다. 따라서 본 연구에서는 해당 교차로 접근로의 교통량과 중차량 비율 및 도로의 기하구조 등 입력자료의 불확실성이 용량해석과 서비스수준 결정에 끼치는 영향을 고려해보고 이틀에 의한 영향을 최소화할 수 있는 방안을 제시하고자 한다.

• 한국수산과학회지
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• 제41권6호
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• pp.485-492
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• 2008

To propose proper vessel characteristics for sustainable fisheries in Korean waters, we analyzed the fishing capacity, scale efficiency and utilization of large pair-trawl vessels based on the database of catch, effort and vessel characteristics (gross tonnage and engine power) in 1990 by applying data envelopment analysis (DEA). The input factors were gross tonnage, horse power and days operated; whereas the output factor was expected catch by vessel characteristics. The optimal vessel types, selected based on the input-oriented technical efficiency and gross tonnages, was 100 GT with engine power <600 HP. The output-oriented unbiased estimate of capacity utilization (CD) decreased with increasing vessel tonnage. For the same tonnage vessels, the CD decreased with increasing engine power.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.250-253
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• 2001

This paper is proposed a sinusoidal input voltage Multi-level AC-DC Converter using transformer. In this paper Multi-level PWM Control converter which controls input current by combining buck Converters together to improve input current characteristic, and confirmed its validity throughout simulation and experiment. This method, which is multiplying and duplicating output of converter of equal capacity, is able to control unit power factor of input current, reduce the problem caused by high frequency switching, and apply to high power converter because filter is not necessary.

• 한국국방경영분석학회지
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• 제34권1호
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• pp.61-77
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• 2008

본 연구에서는 의사결정기관의 상대적 효율성을 측정할 수 있는 유용한 기법으로 알려진 DEA 모형을 이용하여 국내 6개 발전회사의 효율성을 비교 분석하였다. 투입방향 CCR 및 BCC 모형에 의해서 분석된 연구 결과로는 첫째, 총 발전설비용량을 투입변수로 사용하였을 때와 각 발전원별로 설비용량을 구분하여 투입변수로 사용하였을 때와 서로 다른 연구결과를 얻었다. 이는 각 발전설비의 고정비(발전설비)와 변동비(연료비) 특성이 감안된 결과로 생각된다. 둘째, 본 연구에서 논의된 발전원별 투입변수가 중장기 발전설비용량 확장계획 기간의 효율성 평가에 사용되면 각 발전회사의 효율성은 현재 수준보다 높아질 것이다. 본 연구는 발전회사의 효과적인 경영활동을 위한 유익한 정보를 제공할 수 있을 것으로 기대된다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.753-755
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• 1993

Full Bridge Diode Rectification and Phase Controlled SCR Rectification are the most widely used methods of power conversion($AC{\rightarrow}DC$) in Power Electronic products such as UPS systems. But using these types of converters can lead to the following problems. First, they generate harmonics on the AC input side, which can cause interference in other equipment connected to the same commercial power line. Second, they deteriorate the power factor so that the input power capacity or the equipment becomes larger than the actual rated output capacity. As a means to overcome these problems an IGBT type PWM Converter, which applies a current control algorithm, is proposed. In this paper the enhancement of the converter performance is shown through simulation.

• 한국산업융합학회 논문집
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• 제24권4_2호
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• pp.491-499
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• 2021

Batteries are widely used for energy storage, such as ESS(Energy Storage System), electric vehicles, electric aircraft, and electric powered ships. Among them, a submarine uses a high power battery for an energy storage. When the battery of a submarine is discharged, a diesel generator generates AC power, and then AC/DC power converter change AC power to DC power for charging the battery. Therefore, in order to lower the current capacity of the diesel generator, it is necessary to use an AC/DC converter with a high input power factor. And, a power converter with a large power capacity must have high stability because it can lead to a major accident when a failure occurs. However, the control algorithm using the traditional PI controller is difficult to satisfy stability and dynamic characteristics. In this paper, we design the high power AC/DC converter with high input power factor for battery charging systems. And, we propose a stable control algorithm. The validity of the proposed method is verified through simulation and experiments.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.215-218
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• 2001

This paper is proposed a sinusoidal input current multi-level ac-dc converter using transformer. The multi-level converter which controls input current by combining Buck converter to Improve input current characteristics. This method, which is multiplying and duplicating output of converter of equal capacity, is able to control unit power factor of input current, reduce the problem caused by high frequency switching, and apply to high power converter because filter is not necessary The feasibility of the circuit is verified by computer simulation using PSIM

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 1998년도 강연회 및 연구개발 발표회 논문집
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• pp.3-10
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• 1998

The situation frequently occurs in which the input torque capacity of the converter should be changed. It is known that the modification of the ou angles of the torque converter elements is suitable for such situation with diameter of flow path of the converter maintained. But so far it has been, predict correctly the converter characteristics as well as the effects of oulet torque capacity in the past numerical methods. In the present numeric introducing the interrow mixing planes, the torque capacity was satifactorily and it was shown that the torque capacity could be effectively changed by the oulet blade angles of pump and stator.