• 대한교통학회지
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• 제28권5호
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• pp.31-41
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• 2010

본 논문에서는 2005년 1사분기부터 2009년 3사분기까지 개별 화물자동차 운전자들의 실제 화물운송 실적자료를 이용하여 영업용 도로화물운송업의 업종 및 품목별 생산 효율성을 평가하고, 위탁관리제 및 다단계거래 등 규제적 요인을 포함하여 영업용 도로화물운송업의 생산 효율성에 영향을 미치는 요인들을 분석하였다. 구체적으로 영업용 도로화물운송업의 생산 효율성 평가를 위해 자료포락분석법을 적용하였고, 개별 화물자동차 운전자들의 생산 효율성에 미치는 영향요인을 분석하기 위해 토빗모형을 이용하였다. 분석결과, 개별화물과 용달화물보다는 일반화물 업종의 생산 효율성이 더 높은 것으로 분석되었으며, 품목별로는 철강화물의 생산 효율성이 가장 높고, 유류화물의 생산 효율성이 가장 낮은 것으로 평가되었다. 특히 시간이 지남에 따라 영업용 도로화물운송업의 생산 효율성은 소폭 증감을 보이고 있으나, 전반적으로 증가하는 추세를 보이고 있다. 아울러 본 연구에서는 실증분석결과를 토대로 영업용 도로화물운송업의 생산 효율성 증대를 위한 정책방향을 제시하였다.

• Journal of Korea Trade
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• 제27권2호
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• pp.47-60
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• 2023

Purpose - This paper assesses the trade potential and efficiency of Korea and China in the aquatic products trade. Trade efficiency and potential are the main factors that affect the growth of a country's trade. In this study, a time-varying stochastic frontier trade gravity model was constructed to analyze the trade potential and efficiency between Korea and China. By integrating the results of trade theory and empirical analysis, measures and suggestions were proposed to encourage the release of trade potential of fish exports between Korea and China. Design/methodology - In this paper, GDP per capita instead of economic size was chosen as an explanatory variable, and population size and relative distance were selected as explanatory variables to measure trade potential. For trade non-efficiency terms, regional organizations, political factors, and economic factors were mainly considered, and variables such as free trade agreements, political stability, regulatory quality, government efficiency, currency freedom, investment freedom, financial freedom, and trade freedom were selected. Panel data for South Korea and 14 aquatic products trading partners (including China) from 2002 to 2020 were used in the empirical analysis. Findings - In the past 19 years, South Korea's export trade potential of aquatic products to China has never been lower than 70%. It was above 90% from 2006 to 2018, and has been at a high level for a long time. This shows that China's aquatic product market has large potential for development. Originality/value - This study examines the effectiveness and potential of South Korea's exports of aquatic items to China in a methodical and comprehensive empirical manner. The evaluation of the export trade potential of South Korea's aquatic goods to China is more precise when the effects of regional organization, political, and economic variables are taken into account in the trade non-efficiency term of the stochastic frontier gravity model. At the same time, we propose to increase the scale of South Korea's aquatic products trade from the perspective of China's demand. This issue of trade studies is underexplored both empirically and in theory, although the issue has long been important to Korean and world trade.

• 한국유기농업학회지
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• 제21권4호
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• pp.487-500
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• 2013

The purpose of this study is to estimate efficiency of environmental-friendly agricultural product by using Data Envelopment Analysis. A proposed method employs a bootstrapping approach to generating efficiency estimates through Monte Carlo simulation resampling process. The technical efficiency, pure technical efficiency, and scale efficiency measure of strawberry by pesticide-free certification is 0.967, 0.995, 0.968 respectively. However those of bias-corrected estimates are 0.918, 0.983, 0.934. We know that the DEA estimator is an upward biased estimator. In technical efficiency, average lower and upper confidence bounds of 0.807 and 0.960. According to these results, the DEA bootstrapping model used here provides bias-corrected and confidence intervals for the point estimates, it is more preferable.

• Journal of Electrical Engineering and Technology
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• 제4권4호
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• pp.515-520
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• 2009

According to the operating characteristics of pump applications, they should exhibit high efficiency and energy saving capabilities throughout the whole operating process. A novel efficiency optimization control strategy is presented here to meet the high efficiency demand of a variable speed Permanent Magnet Synchronous Motor (PMSM). The core of this strategy is the excellent integration of mended maximum torque to the current control algorithm, based on the losses model during the dynamic and the grade search method with changed step by fuzzy logic during the steady. The performance experiments for the control system of a variable speed high efficiency PMSM have been completed. The test results verified that the system can reliably operate with a different control strategy during dynamic and steady operation, and the system exhibits better performance when using the efficiency-optimization control.

• 경영과학
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• 제27권2호
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• pp.45-54
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• 2010

In this paper we analyze the effects of loading-unloading environments on the efficiency of freight railroad stations using a two-stage procedure for efficiency model estimation. And from the results we explore a way for efficiency improvement of freight railroad stations. Two-stage procedure is composed of data envelopment analysis and regression analysis. The results show that we could expect efficiency improvement through the government"s effort to make railway stations to be strategic position. Furthermore, they advocate policy-makers that efficiency can be improved by simplifying the kinds of freight items and increasing the scale.

• 경영과학
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• 제32권3호
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• pp.37-54
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• 2015

This paper suggests energy efficiency which can be the foundation on corporate profit and effective energy management following by change of global climate and of energy-related regulations. Using comparable financial information and information related to energy use, an DEA (Data Envelopment Analysis) model has been used to identify energy efficiency with DMU (Decision Making Unit)s which are companies subjected to reduce greenhouse gas emission in 2009. Through this research, different from existing researches, environmental variables which can influence on energy efficiency are identified. The results show as follows. First, most of companies follow IRS, which means scale of economy exists among units so that they have more opportunity to increase efficiency by increasing scale of inputs. Second, this research identified that depending on the difference of environmental characters such as the emission structure and the size of companies, energy efficiency of the companies turns out differently.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권4호
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• pp.560-574
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• 2010

In this paper, the relationship between the energy efficiency and spectrum efficiency in a two-cell cellular network is obtained, and the impact of multi-antenna on the energy efficiency of cellular network is analyzed and modeled based on two-state Markovian wireless channels. Then, the energy efficiency of multi-cell cellular networks with co-channel interference is investigated. Simulation results verify the proposed model and the energy-spectrum efficiency tradeoffs in cellular networks with multi-antenna and co-channel interference.

• 한국대기환경학회지
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• 제16권6호
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• pp.633-640
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• 2000

The effects of structure modification of the vortex finder on the collection efficiency and pressure drop have been investigated. The pressure drop in a cyclone having the two stage vortex finder is higher than that in a conventional cyclone and increases proportionally with the increase of square of gas inlet velocity in both cases. The pressure drop of both conventional cyclone of friction resistance at the boundary layer. The collection efficiency of fine dust has been enhanced by addition of vortex finder in a conventional cyclone and gas inlet velocity showing maximum dust removal efficiency increase to 17 m/s(1.7 times of saltation velocity). Optimum size of two stage vortex finder has been induced to 13 cm I.D$\times$2.6cm Length from the results of overall dust collection efficiency. Previous models were tested for the simulation of collection efficiency of cyclone having two stage vortex finder and the Dietz model predict the similar value with experimental results of the present study.

• 한국데이타베이스학회:학술대회논문집
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• 한국데이타베이스학회 2008년도 연합학회학술대회
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• pp.321-338
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• 2008

Information and communication industry, which shows rapid growth rate, is now leading the global economic growth, contributing a ripple effect on general business and economic structure. It is said that information and communication industry enables swift economic growth taking a role as a basic industry of information-oriented society. Especially, rapid technical innovation promotes mutual growth of other related industries and it is technology-intensive. The purpose of this research is to analyze the management efficiency of information and communication industry using DEA method, and finally suggest numerical value for inefficient organizations to improve their efficiency. CCR-I, BCC-I efficiency and RTS(Returns to scale) of 29 companies engaged in information and communication industry was evaluated. With the results, I suggested model companies for benchmarking in information and communication industry. To summarize, 7 companies were selected with CCR-I efficiency rate 1, and 12 companies with BCC-I efficiency rate 1. RTS was finalized with 8 IRS companies, 10 DRS companies, and 11 CRS companies.

• 대한기계학회논문집B
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• 제40권3호
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• pp.139-148
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• 2016

터빈과 압축기의 1차 근사 모델을 대상으로 열역학적 해석을 하여 단열 효율의 특성을 파악하였다. 비단열 터빈과 압축기에 대해서는 엔트로피 평균 온도와 생성 엔트로피, 열원 온도, 열전달량 등의 값에 따라 단열 효율이 1보다 커질 수 있다. 즉, 단열 효율을 비단열 검사체적에 적용하면 실제보다 성능을 높게 평가하는 오류가 생길 수 있다. 이 문제를 해결하는 대안으로 실제 과정과 동일한 열이 전달되는 가역 비단열 과정을 이상 과정으로 채택하여 정의하는 비단열 효율을 제안한다. 이 비단열 효율은 항상 0과 1 사이에 있으며, 대부분의 경우 엑서지 효율보다 작음을 입증하였다. 비단열 효율은 단열 효율을 포함하는 더 일반적인 효율의 정의식으로 사용할 수 있다.