• 한국물환경학회지
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• 제31권1호
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• pp.1-11
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• 2015

In this study, the attraction efficiency of the by-pass fishway installed at Dalseong Weir in Nakdong River was assessed according to operation of the attraction waterway by using River2D which is a two-dimensional physical habitat simulation model. The model was calibrated and validated through the measured water elevation. The attraction efficiency of the fishway was evaluated at the low flow condition because the target fish, Zacco platypus (Z. platypus), have moved frequently up and downstream at the spawning season from April to June. From simulation results, it can be deduced that the attraction efficiency at situation of open attraction waterway is superior to that of close attraction waterway. Also it is shown that velocity field at inner region of the fishway is suitable for migration of the fish.

• Journal of Advanced Marine Engineering and Technology
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• 제18권2호
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• pp.104-112
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• 1994

The scavenging efficiency has a great influence on the performance of a diesel engine, especially slow two-stroke diesel engines which are usually used as a marine propulsion power plant. And this is greatly affected by the conditions in the cylinder, scavenging manifold and exhaust manifold during the gas exchange process. There are many factors to affect on the scavenging efficiency and these factors interact each other very complicatedly. Therefore the simulation program of the gas exchange process is very useful to improve and predict the scavenging efficiency, due to the high costs associated with redesign and testing. In this paper, a three-zone scavenging model for two-stroke uniflow engines was developed to link a control-volume-type engine simulation program for performance prediction of long-stroke marine engines. In this model it was attempted to simulate the three different regions perceived to exist inside the cylinder during scavenging, namely the air, mixing and combystion products regions, by modeling each region as a seperate control volume. Finally the scavenging efficiency was compared with three type of scavenging modes, that is, pure displacement, partial mixing and prefect mixing.

• 대한안전경영과학회지
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• 제9권5호
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• pp.17-25
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• 2007

All of the city gas companies in Korea must employ the gas safety patrols by law. The gas safety patrols are responsible for the various tasks including daily gas pipeline patrol to prevent gas accidents. Since the size of jurisdiction varies among the city gas companies, it is very difficult to compare their efficiency for the operations of the safety patrol each other directly. The objective of this research is to develop the methodology to analyze and compare the efficiency of the safety patrol's operations among various city gas companies. Several factors that are related to the safety patrol's duty on the gas safety factors were identified and DEA(Data Envelopment Analysis) model for efficiency analysis was developed. Finally, the DEA model was applied to the collected data from six city gas companies. The less efficient city gas companies can benchmark the higher efficient city gas companies in order to improve the safety control systems.

• 한국환경보건학회지
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• 제30권2호
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• pp.133-139
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• 2004

The objective of this study was to investigate the destruction efficiency and to determine the fundamental parameters of oxidation kinetics under the supercritical water(SCW) condition. Target material was cephradine, toxic and antibiotic material, in the pharmaceutical wastewater. For this purpose, the effect of reaction temperature and oxidant were investigated on the destruction efficiency of cephradine. And the oxidation kinetics of cephradine was derived by using a empirical power-law model. The experiment was carried out in a cylindrical batch reactor made of Hastelloy C-276 which was endurable high temperature and pressure. The destruction efficiency of cephradine increased with increment of the temperature and reaction time. Also the type of oxidants was effected and oxidants(Air and $H_2O$$_2$) were enhanced the destruction efficiency. The global oxidation kinetics for cephradine has led to two rate expressions according to type of oxidant. - In the presence of air oxidant: Rate=k. $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ( $O_2$)$^{0.51}$$\pm$0.05(k=3.27${\times}$$10^{5}$ sec. Ea=63.25 kJ/mole) - In the presence of $H_2O$$_2$ oxidant : Rate=kㆍ $e^{-Ea}$RT/(Ceph.)$^{1.0}$ ($H_2O$$_2$)$^{0.62}$$\pm$0.02(k=2.76${\times}$$10^4$/sec. Ea=47.65 kJ/mole)ole))

• 수산경영론집
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• 제39권3호
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• pp.49-65
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• 2008

In Korea, deep-sea fishing industry is faced with pressure of being thrown out of business, because of the upcoming unfavorable business conditions such as the fishing regulation of coastal countries, Korea-US Free Trade Agreement(KORUS FTA), and the other socio-economic changes. Hence, we present an evaluation of future business competitive for the deep-sea fishing industry so that the government can develop a concession plan for the deep-sea fishing industry by utilizing the results of this study. In efficiency analysis of deep-sea fishing industry, the decision maker may have two problems: (1) how to deal with multiple inputs and outputs of deep-sea fishing industry and (2) how to assign the weights on different inputs and outputs, In this paper, we proposed to use Data Envelopment Analysis (DEA) to estimate efficiency of deep-sea fishing industry with multiple inputs and outputs. In the DEA, The direct impact of KORUS FTA, fishing regulation of coastal countries, fishing charges, and competitive fishing conditions were used as input parameters while the profitability and secured fishing quarters, as outputs. The results of DEA-BCC model indicate that 6 out of 12 DUMs have better efficiency under variable return to scale assumption.

• 대한기계학회논문집B
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• 제32권8호
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• pp.636-644
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• 2008

The objective of this paper is to investigate characteristics of an autothermal reformer at various operating conditions. Numerical method has been used, and simulation model has been developed for the analysis. Pseudo-homogeneous model is incorporated because the reactor is filled with catalysts of a packed-bed type. Dominant chemical reactions are Full Combustion reaction, Steam Reforming(SR) reaction, Water-Gas Shift(WGS) reaction, and Direct Steam Reforming(DSR) reaction. Simulation results are compared with experimental results for code validation. Operating parameters of the autothermal reformer are inlet temperature, Oxygen to Carbon Ratio(OCR), Steam to Carbon Ratio(SCR), and Gas Hourly Space Velocity(GHSV). Temperature at the reactor center, fuel conversion, species at the reformer outlet, and reforming efficiency are shown as simulation results. SR reaction rate is improved by increased inlet temperature. Reforming efficiency and fuel conversion reached the maximum at 0.7 of OCR. SR reaction and WGS reaction are activated as SCR increases. When GHSV is increased, reforming efficiency increases but pressure drop from the increased GHSV may decrease the system efficiency.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 추계학술대회 논문집(제1권)
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• pp.163-170
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• 2006

본 연구에서는 국내 컨테이너 전용 터미널(부산항 8개 터미널, 광양항 6개 터미널)을 대상으로 DEA(Data Envelopment Analysis) 분석을 통해 효율성을 분석하였다. 일정 시점을 대상으로 한 분석이 아니라 1998년$^{\sim}$2005년 동안의 효율성 분석을 실시하였으며, 이를 통해 각 터미널의 효율성 변화를 살펴보았다. 본 논문의 분석 결과는 우리나라 터미널의 상대적인 효율성 값을 제시해 줄 뿐만 아니라 신규 터미널 생성, 운영사의 변화, 터미널의 통합 운영 등에 따른 터미널 생산성의 변화 등을 제시하여 줌으로써 터미널 운영사의 향후 운영전략에 시사점을 제공하고 있다.

• Journal of Power Electronics
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• 제19권5호
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• pp.1087-1098
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• 2019

In this paper, a detuning factor (DeFac) method is proposed to design the key parameters for optimizing the transfer power and efficiency of an Inductively Coupled Power Transfer (ICPT) system with primary-secondary side compensation. Depending on the robustness of the system, the DeFac method can guarantee the stability of the transfer power and efficiency of an ICPT system within a certain range of resistive-capacitive or resistive-inductive loads. A MATLAB-Simulink model of a ICPT system was built to assess the system's main evaluation criteria, namely its maximum power ratio (PR) and efficiency, in terms of different approaches. In addition, a magnetic field simulation model was built using Ansoft to specify the leakage flux and current density. Simulation results show that both the maximum PR and efficiency of the ICPT system can reach almost 70% despite the severe detuning imposed by the DeFac method. The system also exhibited low levels of leakage flux and a high current density. Experimental results confirmed the validity and feasibility of an ICPT system using DeFac-designed parameters.

• The Journal of Asian Finance, Economics and Business
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• 제9권7호
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• pp.53-62
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• 2022

Commercial banks have a significant impact on the economy of Vietnam because they provide the majority of transactional capital. Therefore, the operational efficiency of commercial banks is a viral topic for the study of the Vietnamese banking system. The research aims to examine the efficiency and inefficiency of joint-stock commercial banks in Vietnam from 2016 to 2020 and then classify them into the efficient group and inefficient group. The study employs the time series data of 29 joint-stock commercial banks during the period 2016-2020. Based on the data collected from the annual audited financial statements of 29 Vietnamese joint-stock commercial banks, the authors select input and output variables for the standard DEA models and anti-efficient DEA models. This research uses two stages, first, by applying the standard DEA model, we investigate the efficient banks; second, by employing the anti-efficient DEA model, we find out the inefficient banks. The results reveal that the average efficiency score of 29 joint-stock commercial banks tends to increase in the period 2016-2018 and decrease gradually in the period 2019-2020. The findings of this study suggest that several small and medium-sized banks in the Vietnamese banking sector have both promising and risky performances and the efficiency of state-owned commercial banks has also improved significantly during the study period.

• 한국항만경제학회지
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• 제31권1호
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• pp.85-110
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• 2015

본 논문에서는 아시아 컨테이너항만들 간의 클러스터링 추세를 분석하기 위해서 퍼지(평균지수변환)DEA모형과 교차효율성모형에 대해서 이론적으로 설명하고, 아시아 38개 컨테이너항만들의 12년간 자료를 4개의 투입요소(선석길이, 수심, 총면적, 크레인 수), 1개의 산출요소(컨테이너화물처리량)를 이용하여 국내항만(부산, 인천, 광양항)들이 어떤 항만들과 클러스터링 해야만 하는지에 대한 측정방법을 실증적으로 보여 주고 분석하였다. 실증분석의 주요한 결과는 다음과 같다. 첫째, 퍼지(평균지수변환)DEA모형에 의한 클러스터링 추세분석에서 국내항만들은 클러스터링을 통해서 효율성을 증대[부산항(56.29%), 인천항(57.96%), 광양항(66.80%)]시 킬 수 있는 것으로 나타났다. 둘째, 원자료를 이용한 교차효율성 모형을 이용한 클러스터링분석에서는 부산항(홍콩, 코오베, 마닐라, 싱가포르, 카오슝, 림찬방, 방콕항), 인천항(아카바, 담만, 카라치, 모하메드 빈 오아심, 다바오), 광양항(담만, 요코하마, 나고야, 킬롱, 카오슝, 방콕항)과 각각 클러스터링을 해야만 하는 것으로 나타났다. 셋째, 퍼지(평균지수변환)DEA모형에 교차효율성 모형을 접목시킨 모형에서는 부산항은 71.38%, 인천항은 103.89%, 광양항은 168.55% 증가가 이루어 졌다. 넷째, 효율성 순위를 검정한 윌콕슨부호순위검정에서는, 세 가지 모형사이의 효율성 순위에 대해서는 약 66%-67% 수준에서 순위에 차이가 없는 것으로 나타났다. 본 논문이 갖는 정책적인 함의는 첫째, 항만정책입안자들이 본 연구에서 사용한 두 가지 모형과 접목시킨 모형을 항만의 클러스터링 정책에 도입하여 해당항만이 발전할 수 있는 전략을 수립하고 이행해 나가야만 한다는 점이다. 둘째, 본 논문의 실증분석결과 국내항만들의 참조항만, 클러스터링항만들로서 나타난 아시아항만들에 대하여, 그들 항만들의 항만개발, 운영에 대한 내용을 정밀하게 분석하고 도입하여 실시하는 것이 필요하다.