• 응용통계연구
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• 제30권5호
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• pp.665-679
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• 2017

생산성 평가를 위해서는 주어진 생산 자료를 기반으로 투입 대비 최대산출량을 나타내는 최대산출량을 나타내는 생산 프런티어 곡선에 대한 정보가 필요한 경우가 많다. 이러한 프런티어 함수를 확률프런티어 모형하에서 추정하는 경우에 초기에는 프런티어 함수의 특정한 모수적 형테를 가정하는 경우가 많았다. 그러나 최근에는 프런티어 함수를 프런티어 함수가 기본적으로 만족해야 하는 단조성이나 오목성등을 만족하도록 하면서 비모수적 방법으로 추정하는 방법들이 많이 이루어졌다. 하지만, 이러한 방법들에서 얻어지는 추정량들은 프런티어 함수를 조각적 선형함수 또는 계단함수로 추정하는 특징 때문에 추정의 효율이 떨어지나가 프런티어 함수가 해석이 용이하지 않은 불연속점을 가지는 문제를 가지게 된다. 본 논문에서는 이러한 문제를 해결하기 위해 확률프런티어 모형에서 단조증가하는 매끄러운 프런티어 함수 추정법을 제시하고 제안된 추정방법이 기존의 추정방법에 비해서 가지는 추정 효율의 장점을 시뮬레이션를 통해 예시하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제8권1호
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• pp.41-46
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• 2003

Difficulties associated with bioartificial liver (BAL) preservation limit not only the commercialization of BAL, but also its clinical trials. In this study, the possibility of cold preservation of BAL cartridges containing porcine hepatocytes was examined at 4$^{\circ}C$. In an in vitro perfusion culture System, BAL cartridges maintained cytochrome P450 metabolic function for at least 50 days. However, all BAL cartridges completely lost their ammonia eliminating ability when stored at 4$^{\circ}C$. We a1so studied the effect of cell density on the maintenance of BAL liver function In a highly differentiated and healthy state. As expected, BALs containing a larger number of hepatocytes demonstrated higher metabolic functions. When metabolic functions were compared per gram of hepatotytes, no large differences were observed between devices containing different densities of hepatocytes. Decreased cell density did not Successfully prolong BAL function. The viability and function of isolated hepatotytes highly depend on the culture conditions, such as cell density, substrata, culture media, and additives to the culture media. Perfusion culture of BAL cartridges at 4$^{\circ}C$ gave a promosing result with respect to the maintenance of P450 activity. However, as indicated by the rapid loss of ammonia metabolic activity, many factors still remain to be optimized for preservation of BAL keeping high metabolic functions for a longer time.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.685-686
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• 2007

This paper presents an application of power system fault diagnostic algorithm for the PEFP Proton Accelerator Research Center using neural network. Proposed fault diagnostic system is constructed by the radial basis function (RBF) neural network because it has the capabilities of the pattern classification and function approximation of any nonlinear function. Proposed system identifies faulted section in the power system based on information about the operation of protection devices such as relays and circuit breakers. In this paper, parameters of the RBF neural networks are tuned by the GA-TS algorithm, which has the global optimal solution searching capabilities. To show the validity of the proposed method, proposed algorithm has been tested with a practical power system in Proton Accelerator Research Center of PEFP.

• The Korean Journal of Physiology
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• 제28권1호
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• pp.1-17
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• 1994

• KDI Journal of Economic Policy
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• 제39권4호
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• pp.25-50
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• 2017

Whereas a large variety of previous studies show mixed results regarding the relationship between public investment and economic outcome, several studies have been conducted on related issues in Korea. The present study deals with the effect of public investment in Korea on economic growth and productivity. Using administrative data, it exploits three different methodologies: the total factor productivity approach, production function approach, and stochastic frontier production function approach. The results of this study show that public investment has a statistically significant effect on economic growth. However, it contributes little to enhance productivity. It is explained that there exists inefficiency of production in the Korean economy. These findings indicate that public investment has played a central role in the direct input factor and not in indirect role in Korea. Thus, it is necessary for public investment policies to concentrate on enhancing the efficiency of the Korean economy.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.147-149
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• 2003

The wetness, a function of precipitation and temperature etc, and the warmth, a function of temperature, are the dominant factor for global vegetation distribution. This paper employs the normalized difference vegetation index (NDVI), warmth index (WAI), and wetness index (WEI), and focuses on an essential climate-vegetation relationship at global scale. The NDVI was acquired from ‘Twenty-year global 4-minute AVHRR NDVI dataset.’ The WEI is defined as the fraction of the precipitation to the potential evaporation. The WAI was calculated by accumulating the monthly mean temperature of the portion exceeded 5$^{\circ}C$ throughout the year. Meteorological data for the WEI and WAI calculation were obtained from the ISLSCP CD-ROM. All analyses were conducted for 1 ${\times}$ 1 degree grid box on the terrestrial area of the Earth, and on annual value basis averaged in 1987 and 1988. The result of analyses demonstrated that there are two regimes in their relations, that is, a regime in which NDVIs vary depending on the WEI, and a regime in which NDVIs vary depending on the WAI. These two regimes appeared to correspond to the wetness dominant and warmth dominant vegetation, respectively. The geographical distributions of two regimes were mapped. Most of the world vegetation is categorized into wetness dominant, while warmth dominant vegetation is seen in the high-latitude area mainly to the north of 60$^{\circ}$N in the Northern Hemisphere and high-altitude areas.

• 수산경영론집
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• 제43권2호
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• pp.67-77
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• 2012

Based on the survey on aquaculture management status in Nohwa-eup, Bogil-myeon, Wando-eup in Wando region, this study aimed to estimate productive efficiencies of abalone aquaculture production using a stochastic frontier approach (SFA) and to find out their determinants. In the analysis, a Cobb-Douglas production function with an inefficiency term that follows an halfnormal distribution was assumed for the estimation of productive efficiencies. Then, based on the outcomes of productive efficiencies, determinants of productive efficiency were investigated using a tobit regression model. Results showed that the average inefficiency was estimated to be 10% and the production size would be a statistically significant variable for the production. In addition, it was shown that the cage installing method would be an important factor affecting to the level of productive efficiency.

• Journal of the Korean Data and Information Science Society
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• 제19권4호
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• pp.1449-1463
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• 2008

This paper considers three different models with two functional forms, Cobb-Douglas and Translog, for the stochastic frontier production function of food manufacturing industry of Bangladesh over the period 1981-1982 to 1999-2000. The models are proposed by Battese and Coelli (1992, 1995) and Huang and Liu (1994). The technical efficiency, total factor productivity, technological change and technical efficiency change have been estimated in the frontier models. The results indicate that 41.47%, 59.30% and 70.98% of the potential output are being realized in this sector. The mean increments in total factor productivity are approximately 2%, 9% and 4% respectively.

• 환경정책연구
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• 제11권1호
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• pp.75-97
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• 2012

본 논문의 목적은 OECD국가를 중심으로 온실가스 감축에 대비하여 에너지 원단위(原單位) 측정의 다른 방법으로서 에너지효율함수와 원단위의 효율함수의 추정을 통하여 에너지효율을 측정하는 것이다. 실증결과는 기존의 전통적 에너지원단위와 확률변경함수에 의한 에너지 효율이 크게 연관되어 있지 않았음을 보여준다. 에너지효율 함수와 원단위 효율함수의 효율도 다소 상이하였다. 에너지 투입효율함수에 의한 에너지효율은 GDP, 자본스톡, 노동, 에너지투입량의 순서로 민감하게 반응하는 것으로 보인다. 향후 투입요소 간 최적 결합을 통한 에너지 절감이 필요하고 에너지 소비가 작은 제품의 생산을 통한 저탄소 경제성장의 추구가 요구된다

• 농업과학연구
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• 제37권3호
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• pp.509-514
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• 2010

The purpose of this study is to analyze the technical efficiency and its determinants for Korean Apiculture farming by using from door to door and e-mail inquiry data. The analysis was implemented through the Cobb-Douglas stochastic frontier production function (SFPF) model including the technical inefficiency effect model for cross-sectional data. To measure the SFPF model, honey production was used for a dependent variable, and for input variables labor cost, preventive cost, material cost, feeding cost, depreciation cost were used. Farmer's age, farmer's career, farming scale, full-time or half-time firm and movement or fixed firm variables were used to measure the inefficiency effect model. The average technical efficiency on apiculture farming in Korea is estimated to be 0.8112. It means that there were technical inefficiency of about 18.88% in Korea apiculture farming. In this study there are some suggestions which could increase the technical efficiency of Korean apiculture farming.