• Journal of Environmental Policy
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• v.11 no.1
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• pp.75-97
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• 2012

The purpose of the paper is to estimate the functions of the energy input efficiency and the energy intensity efficiency, and measure their energy efficiencies for the reduction of greenhouse gases focusing on OECD countries. The efficiency of the traditional energy intensity was rarely connected with the energy efficiencies of the stochastic frontier function. It seems that the energy efficiency by the function of energy input efficiency sensitively responds to the order of GDP, capital stock, labor, and energy input quantity as explanatory variables. In the future, we need to reduce energy quantities by the optimal mix of inputs, and pursuit low-carbon economic growth through the production of the goods consuming small energy.

• Proceedings of the KOR-KST Conference
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• 1998.10a
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• pp.116-125
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• 1998

도로공사로 인해 차선의 일부가 폐쇄된 경우에 이용하는 차선에 따라서 운전자의 통행패턴은 달라진다. 공사구간이 없는 경우 운전자의 차선변경은 제한적이나마 각 차선의 밀도에 의해서 좌우되는 것으로 나타났다. 또한 차선폐쇄지점 전방에서는 차선변경할 확률은 폐쇄지점까지의 남은 거리에 따라서 음지수함수를 따르는 것으로 확인되었다. 또한 논문에서 공사구간에서의 차선변경행태와 교통량, 밀도, 속도를 산정하였으며, 공사로 인한 차선별 지체시간을 산정하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.5
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• pp.1559-1569
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• 2014

The purpose of this study is to estimate the degree of cost inefficiency for the urban railway lines of a metropolitan city operated by public institutions in Korea and identify the causes of this inefficiency. To this end, we assume that the urban railway lines produce the output of train-km by putting three production factors of labor, electric power and maintenance and set the variable cost function model with the translog function to make a stochastic cost frontier analysis. Based on estimated result, we conclude that the cost savings for 6 years of all lines are about 6,672 hundred million won and top five lines with high inefficiency are Busan Line1, Daegu Line1, Daejeon Line1, Gwangju Line1, and Daegu Line2. The causes of inefficiency are attributable to labor and maintenance factors. The results of this study can be useful in case of finding the priorities of measures and specific plans for reducing labor and maintenance costs in the urban railway operation.

• Journal of the Economic Geographical Society of Korea
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• v.15 no.4
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• pp.752-765
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• 2012

We analyze the relation empirically between regional labor market characteristics and job matching efficiency with the adaption of stochastic frontier production function. Our empirical results suggest that, as both the ratio of 50 years-old-job seekers and the level of spatial density increase, job matching efficiencies also rise. In contrast, an increase in the ratio of firms which offer permanent contracts lowers job matching efficiencies. And the job matching efficiency is relatively higher in metropolitan areas. Finally, We find a negative relation between total industrial production and job matching efficiency, which implies that job seekers tend to accept uncongenial jobs in the recessions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.381-389
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• 2017

The kernel density was determined based on sampling points obtained in a Markov chain simulation and was assumed to be an important sampling function. A Kriging metamodel was constructed in more detail in the vicinity of a limit state. The failure probability was calculated based on importance sampling, which was performed for the Kriging metamodel. A pre-existing method was modified to obtain more sampling points for a kernel density in the vicinity of a limit state. A stable numerical method was proposed to find a parameter of the kernel density. To assess the completeness of the Kriging metamodel, the possibility of changes in the calculated failure probability due to the uncertainty of the Kriging metamodel was calculated.

• Proceedings of the Korea Society for Simulation Conference
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• 1992.10a
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• pp.3-3
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• 1992

컴퓨터 시스템의 개발 및 분석에 많이 활용되는 시뮬레이션 모델을 구축하는데 있어서 SIMSCRIT, GISS, SIMAN, SLA II등과 같은 시뮬레이션 전용언어가 많이 사용되지만, 이들은 새로운 전용언어의 습득, 시스템 프로그램과의 접속, 시뮬레이션 수행 속도면에서 부담을 주어왔다. 본 연구에서는 기존의 C언어 사용자들이 손쉽게 시뮬레이션 모델을 구축할 수 있도록 기존의 smpl을 확장하여 SMPLE(smpl extended)를 개발하였다. SMPLE의 모체의 smpl은 컴퓨터 시스템의 시뮬레이션 모델을 구현하기 위해 MIT에서 C언어를 이용하여 고안되었으며, C언어의 기능적인 확장으로서 라이브러리 함수들의 집합 형태를 갖는 시뮬레이션 서브 시스템이다. 이러한 라이브러리 함수들의 집합인 smpl 시뮬레이션 서브 시스템은 C언어 자체와 더불어 사건중심(event-oriented) 시뮬레이션 언어를 구성하며, smpl 시뮬레이터는 C 언어 프로그램으로 구현되다. smpl은 시뮬레이션하기 위한 설비(facility)들을 정의, 예약, 해제하거나 상태를 알아보는 함수를 제공하며, 시간의 관점에서 보면 토큰의 흐름은 일련의 대기시간과 활동시간에 의하여 나타낼 수 있게 된다. smpl은 사건의 스케쥴링(scheduling), 확률변수의 생성, 통계자료 수집 등에 관한 함수의 제공과, 시뮬레이션 시간의 전진과 사건발생의 순서를 조절해주는 기능을 제공한다. smpl 시뮬레이션 프로그램은 초기화루틴, 제어루틴 및 결과출력루틴으로 구성된다. 기존의 smpl에서 사용되는 프로그램의 자료구조(data structure)는 배열과 인덱스 구조가 사용되었다. 이러한 구조는 이미 완성되어 있는 프로그램 내에서는 효율성 면에서 좋겠지만, 변경이나 확장하기 위해 이 프로그램을 분석한다거나 필요한 기능을 추가하기 위해서는 매우 많은 어려움이 따르게 된다. 본 논문에서는 배열을 기반으로 하고 있는 smpl의 자료구조를 C의 structure와 pointer를 기반으로 하게끔 변경시키고 이에 따르는 제반 변경 사항을 수정 보완하여 프로그램의 분석을 용이하게 하며 기능의 변경 및 추가가 수월하게 하였고 메모리를 동적으로 관리할 수 있게 하였다. 또한 기존의 smpl에 디버깅용 함수 및 설비(facility) 제어용 함수를 추가하여 시뮬레이션 프로그램 작성을 용이하게 하였다. 예를 들면 who_server(), who_queue(), pop_Q(), push_Q(), pop_server(), push_server(), we(), wf(), printfct() 같은 함수들이다. 또한 동시에 발생되는 사건들의 순서를 조종하기 위해, 동시에 발생할 수 있는 각각의 사건에 우선순위를 두어 이 우선 순위에 의하여 사건 리스트(event list)에서 자동적으로 사건들의 순서가 결정되도록 확장하였으며, 설비 제어방식에 있어서도 FIFO, LIFO, 우선 순위 방식등을 선택할 수 있도록 확장하였다. SIMPLE는 자료구조 및 프로그램이 공개되어 있으므로 프로그래머가 원하는 기능을 쉽게 추가할 수 있는 장점도 있다. 아울러 SMPLE에서 새로이 추가된 자료구조와 함수 및 설비제어 방식등을 활용하여 실제 중형급 시스템에 대한 시뮬레이션 구현과 시스템 분석의 예를 보인다.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.141-157
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• 2007

This paper evaluates the effects of privatization and deregulation on the firm-specific efficiency and total factor productivity (TFP) growth in the Korean and Japanese railways. Using a stochastic frontier approach and a generalized translog functional form, the paper specifies the equation system consisting of a multiproduct variable cost function and input share equations which is estimated with Zellner's iterative seemingly unrelated regression and the corrected least squares method. The Korean and Japanese railway firms are assumed to produce three outputs (Shinkansen passenger-kilometers, incumbent railway passenger-kilometers, ton-kilometers of freight) using three input factors (labor, fuel, maintenance and rolling stock). A monetary value of the ways and fixed installations held by the railroad firm is also included as a quasi-fixed input. The empirical results indicate that the average estimate of cost inefficiency is 2.57% for the total sample and on the average, JNR and JR Kyushu are found to be worst efficient while the most efficient railway firm in the sample is JR West. Also the cost efficiency levels of seven JRs have been improved after the reform and privatization of JNR. The findings also indicate that TFP growth of the privately-owned JRs are higher than those of the government-owned KNR and JNR. Three-island JRs and JR Freight have slightly higher TFP growth than Honshu JRs as well. Thus, the results suggest that managerial autonomy and increased competition via deregulation have improved efficiency and TFP growth.

• Journal of Korean Society of Transportation
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• v.27 no.4
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• pp.63-76
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• 2009

On the basis of a Stochastic Frontier Approach (SFA), this paper analyses revenue efficiencies for the same sample of Korean and Japanese railways in the papers which analyze cost efficiencies using a generalized translog functional form. The paper also compares the results of revenue efficiencies with cost efficiencies and evaluates the effects of managerial autonomy and privatization on the firm-specific efficiencies. The results show that the average estimate of revenue inefficiency is 7.02% when the term of inefficiency is assumed to be distributed as a half-normal and 6.98% as a exponential for the total sample. Also, standardized inefficiencies in revenues (7.5%) are greater than those in costs (2.1%). JR East and JR West are found to be most efficient on the revenue side and on the cost side respectively while JNR and JR Kyushu are worst efficient on the both sides. Finally, the correlations between efficiencies in revenues and costs also between efficiencies and privatization are positively correlated. The results suggest that the most independent companies, with increased managerial autonomy via privatization, are the most efficient in both revenues and costs.

• Journal of Korea Game Society
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• v.14 no.6
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• pp.109-118
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• 2014

We studied the creation of fractal images with polygonal rotation symmetry. As in Loocke's method[13] we start with IFS of affine functions that create polygonal fractals and extends the IFS by adding functions that create Julia sets instead of adding square root functions. The resulting images are rotationally symmetric and Julia set shaped. Also we can improve fractal images by modifying probabilistic IFS algorithm, and we suggest a method of deforming Julia set by changing exponent value.

• International Area Studies Review
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• v.22 no.4
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• pp.19-35
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• 2018

This paper is to estimate the total factor productivity(TFP) in the Korean manufacturing and service industries during the period 1975:1-2016:4 using the stochastic frontier analysis model. In order to analyze the determinants for the total factor productivity the paper estimates the industry-specific determinant elasticities of TFP using the autoregressive distributed model. The industry-specific determinants, which reflect the industrial structure and properties include markup, the ratio of capital to labor(KL), and the ratio of foreign intermediate goods (FIG) to industrial output. The average value for total factor productivity growth was estimated to be 0.0199 in manufacturing and 0.0063 in the service industry. The markup and KL elasticities of TFP were estimated to be 2.481 and 0.651 in manufacturing respectively and -1.403 and 0.042 in the service industry respectively. The empirical results suggest that the industrial markup and the ratio of capital to labor have had decisive effects on the changes in the total factor productivity in the Korean manufacturing and service industries during the period 1975:1-2016:4.