• 한국항공운항학회지
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• 제26권4호
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• pp.27-35
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• 2018

Recently, Intense competition is expected to bring about continuous change with the rapid global aviation industry. In particular, domestic passenger demand has been steadily increasing over the past five years, with domestic and international shipments growing at a CAGR of 8.4% and 10.0%, respectively. In addition to the economic value of the airport, social interest due to greenhouse gas emissions is also rising. In this study, we analyzed the efficiency of airport operation by using DEA model(Directional Technology Distance Function) considering undesirable output for 14 airports in Korea. As a result of analysis, all airports except Gimhae, Yangyang, Cheongju and Yeosu were analyzed as efficient airports. However, only Gimpo, Gimhae, Jeju, Muan, Daegu and Gwangju were analyzed as efficient airports considering the undesirable output.

• 한국항해항만학회지
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• 제37권2호
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• pp.195-201
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• 2013

Recently according to increase of enlarged scale ports in conformity with increase in over size vessels and container handling service, pollutants generated from ports are increasing. In advanced countries, reduction in carbon dioxide emission assigned to them has been implemented according to the Climate Change Convention and Kyoto Protocol from 2008 to 2012 in order to lessen carbon dioxide emission. Henceforth increase in discussion on the measure of constructing Green Port and low-carbon port is expected in our nation's field of port as well, it is considered that the effort in reduction with regard to undesirable output which causes environmental problem of analysis target during measuring effectiveness. Therefore, in this study, effectiveness was estimated through directional technology distance function considering undesirable output differently from effectiveness analysis of existing container terminal, and then performed comparative analysis with the result analyzed with BCC output-oriented model. As the result of analysis, in 2007 DMU3 and DMU5, and in 2010 DMU2 and DMU4 appeared to be efficient terminals in BCC output oriented model, and in directional technology distance function model, DMU1, DMU3 in 2007, DMU3, DMU5 in 2008, DMU7 in 2009, and DMU2, DMU5 in 2010 appeared to be efficient terminals.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2018년도 공동국제학술발표회
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• pp.43-43
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• 2018

• 대한교통학회지
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• 제28권4호
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• pp.157-166
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• 2010

본 연구는 2004년 서울시 대중교통개편 이후 시내버스업체가 효율적인 운영을 하고 있는지, 사고와 대기오염을 줄이려는 노력을 하고 있는지에 대한 성과를 업체별로 비교하기 위하여 방향거리함수를 통한 효율성을 측정하였다. 2005년 6월 한달 동안의 자료로서 운전사, 정비사, 임직원수, 차량, 연료를 투입물 자료로, 차량-km(유익한 산출물), 사고비용, 대기오염 비용(유해한 산출물)을 산출물 자료로 사용하였다. 유해한 산출물 고려여부에 따른 대안별 효율성을 비교해 본 결과, 유해한 산출물을 고려한 경우가 고려하지 않은 경우보다 평균적으로 효율성은 낮았으나 효율업체 수는 더 많게 나타났다. 이유는 유해한 산출물을 고려할 경우 투입물의 감소 가능성보다 유해한 산출물의 감소 가능성이 적은 업체의 수가 증가한 반면, 업체들간의 효율성 편차는 커지기 때문이다. 한편 효율성에 영향을 미치는 요인들을 살펴 본 결과, CNG 차량의 보급을 늘리고, 운행속도를 높이며, 정비효율을 높일수록 효율성에 긍정적인 영향을 미치는 것으로 나타났다.

• 한국항해항만학회지
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• 제46권2호
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• pp.110-120
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• 2022

Spain is Europe's second-largest country with total throughput reaching 16.7 million twenty-foot equivalent units (TEU) by 2020. The purpose of this study was to measure and compare the efficiency of 17 container terminals. As a study method, the DEA-CCR model, undesirable variable, and Malmquist Index (MI) were used for data envelopment analysis (DEA). The study results are as follow: (1) DEA-CCR is used to evaluate basic efficiency. The most efficient terminals are decision-making units DMU 1 (APM Terminals (Algeciras Port)), DMU 2 (Total Terminal International Algeciras (Algeciras Port)) and DMU 5 (Barcelona Europe South Terminal (Barcelona Port)). (2) Undesirable DEA was conducted to suggest inefficiency from the undesirable output. Overall, the efficiency scores were reduced. However, DMU 1, DMU 2, and DMU 5 maintained efficiency scores regardless of the finish factor. (3) Malmquist Index was used to observe technology and efficiency changes dynamically. The changes in TCI affected Spanish container terminals more than the Technical Efficiency Change Index (TECI) in 2018-2019. However, in 2019-2020, the TECI was 2.706, higher than the TCI value, indicating that the change in TECI had more influence on the increase in productivity. This study offers a broader understanding of Spanish container terminals.

• 대한산업공학회지
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• 제37권4호
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• pp.350-357
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• 2011

In the recent, it is gradually important for airport to consider environmental aspects as sustainable development is emerged. ICAO, FAA and individual countries has tried to reduce airport noise and pollution. Thus, the effort is needed to incorporate environmental factor into productivity indicator of airport. Our paper use DEA method with the non-parametric directional output distance function(DDF) to assess productivity of 14 airports in Korea during 2008~2010. In addition to three inputs, two conventional outputs, two undesirable outputs have been considered : noise and air pollution. Results are compared from models that do not include undesirable outputs. Inclusion in the analysis of the undesirable effects of airport operations leads to greater and closer airport's efficiency scores.

• 무역학회지
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• 제47권4호
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• pp.271-292
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• 2022

In Korea, the road transport industry is pointed out as a major cause of air pollutants, so management control is needed. Existing studies used only positive input and output variables to measure regional efficiency. However, it is necessary to consider the environmental pollution problem in efficiency analysis. In this study, an undesirable SBM analysis using CO₂ was conducted to measure efficiency of domestic regions. In addition, SDM was conducted to examine the ripple effect between domestic regions. As a result of the analysis, the efficiency of the capital area such as Seoul, Gyeonggi, and Incheon was high in the road transport industry. However, the efficiency of the road transportation industry in Daegu and Gangwon was low. In the SDM analysis, it was found that the regional equipment capabilities had a great influence on efficiency. In order to improve efficiency, it is necessary to increase and improve the equipment capacity of the road transport industry.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.89-96
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• 1997

A robust speed control scheme for a brushless DC(BLDC) motor using an adaptive input-output linearization technique is presented. By using this technique, the nonlinear motor model can be linearized in Brunovski canonical form, and the desired speed dynamics can be obtained based on the linearized model. This control technique, however, gives an undesirable output performance under the mismatch of the system parameters and load conditions. For the robust output response, the controller parameters will be estimated by a model reference adaptive technique where the disturbance torque and flux linkage are estimated. The adaptation laws are derived by the Popov's hyperstability theory and positivity concept. The proposed control scheme is implemented on a BLDC motor using the software of DSP TMS320C30 and the effectiveness is verified through the comparative experiments.

• Journal of Electrical Engineering and information Science
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• 제2권3호
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• pp.113-122
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• 1997

An adaptive input-output linearization technique for a robust speed control of a brushless C(BLDC) motor is presented. By using this technique, the nonlinear moro model can be effectively linearized in Brunovski canonical form, an the desired speed dynamics can be obtained based on the linearized model. This control technique, however, gives an undesirable output performance under the mismatch of the system parameters and load conditions caused by the incomplete linearization. for the robust output response, the controller parameters will be estimated by a model reference adaptive technique where the disturbance torque and flux linkage are estimated. The adaptation laws are derived by the Popov's hyperstability theory nd positivity concept. The proposed control scheme is implemented on a BLDC motor using the software of DSP TMS320C30 and the effectiveness is verified through the comparative simualtions and experiments.

• Journal of Power Electronics
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• 제18권3호
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• pp.757-765
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• 2018

This paper deals with the instability and resonant phenomena in distribution systems with multiple grid-connected inverters with an LCL output filter. The penetration of roof-top and other types of small photovoltaic (PV) grid-connected systems is rapidly increasing in distribution grids due to the attractive incentives set forth by different governments. When the number of such grid-connected inverters increases, their interaction with the distribution grid may cause undesirable effects such as instability and resonance. In this paper, a grid system with several grid-connected inverters is studied. Since proportional-resonant (PR) controllers are becoming more popular, it is assumed that most inverters use this type of controller. An LCL filter is also considered at the inverters output to make the case as realistic as possible. A complete modeling of this system is presented. Consequently, it is shown that such a system is prone to instability due to the interactions of the inverter controllers. A modification of PR controllers is presented where the output capacitor is virtually decreased. As a result, the instability is avoided. Simulation results are presented and show a good agreement with the theoretical studies. Experimental results obtained on a laboratory setup show the validity of the analysis.