• Journal of the Korean Data and Information Science Society
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• v.25 no.6
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• pp.1491-1498
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• 2014

The major criticism of optimal experimental design is that it depends heavily on the model and its accompanying assumption that often leads the number of support points equal to the number of parameters in the model. Often in the past, a polynomial model of higher degree is assumed to handle the experimental design for the polynomial regression of lower degree. In this paper we searched the possible set of designs which are robust to the departure of the assumed model. The designs are categorized with respect to D-efficiency. The approach by O'Brien (1995) was discussed in univariate polynomial regression model setting.

• Journal of Korea Technology Innovation Society
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• v.19 no.4
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• pp.711-735
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• 2016

Drug Development is very important for promoting public health and pharmaceutical industry. There has been many studies on the efficiency of drug development, but there are few studies on the drug development R&D performed by government. Since CCR model assumes unidirectional influence of input and output, it is not appropriate to analyze the efficiency of R&D due to the time-lag and spill-over effect. Also, BBC model which assumes variable returns to scale has difficulty in deriving priorities between decision making units. Recently, Range Adjusted Measure (RAM) model has been suggested in R&D efficiency analysis. RAM model measures the efficincy by eliminating inefficiencies under variable returns to scale assumption, and its strong monotonicity enables to provide clear priorities between decision making units. In this study, we analyzed the efficiency of national R&D programs for drug development using the two-step approach, including RAM model and Tobit regression analysis, and discussed major policy implications.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.668-672
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• 2009

상대오염도가 높은 초기유출수에 대한 1차 처리의 화학적인 효율성 증대에 대한 연구는 많이 진행되어온 반면 동수역학적 분석에 관한 연구는 미흡한 실정이다. 본 연구에서는 수처리 시설에 대해서 수리모형 및 수치모의의 결과를 비교 분석하였다. 연구에 사용된 수처리 시설은 내부 격벽(baffle)의 배열에 변화를 주어 흐름제어를 유도하여 초기유출수의 처리 효율에 변화를 줄 수 있도록 시설을 고안하였다. 수리모형 및 수치모의 실험을 통해 구조물 내에 복잡한 난류흐름을 관찰하였고, 주입된 염수의 농도분포 양상을 시간변화에 따라 분석하였다. 수치모의를 위해서 3차원 수치모형 프로그램인 FLOW-3D를 사용하였으며 LES 난류모형과 질량생성(mass source)모형을 적용하여 수처리 시설 내에서의 동수역학적 거동분석 및 오염원(source)의 농도분포를 모의하였다. 실험 결과 수처리 시설의 3차원 난류흐름을 통해 오염원이 지체 및 확산되고 이에 따라 배출되는 농도가 현격하게 차이 냄을 확인하였다. 또한 추후 본 연구에서 제시된 바와 같이 다양한 내부구조에 대한 수치모의 결과를 분석하게 되면 초기 유출수 처리 효율을 증가시킬 수 있는 수처리 시설모형의 최적화 방안을 고려할 수 있을 것이다.

• Convergence Security Journal
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• v.8 no.4
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• pp.115-120
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• 2008

Accurate predictions of software release times, and estimation of the reliability and availability of a software product require quantification of a critical element of the software testing process： Change-point problem. In this paper, exponential (Goel-Okumoto) model was reviewed, proposes the percentile change-point problem, which maked out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on SSE statistics, for the sake of efficient model, was employed. Using NTDS data, The numerical example of percentilechange-point problemi s presented.

• Environmental and Resource Economics Review
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• v.14 no.1
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• pp.75-100
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• 2005

This study attempts to empirically investigate the respondents' preference uncertainty involved in stating their willingness to pay (WTP). In the contingent valuation (CV) survey, we employed two approaches using two split samples. The respondents of one sample were given the opportunity to express intensity of preference through polychotomous choice (PC) WTP question. Those of the other sample were given a follow-up question of confidence measure (0~100%). By incorporating the two elicited degrees of preference uncertainty into examining the WTP responses, we take a comparison of the two approaches in terms of the goodness-of-fit of the examination and the efficiency of the mean WTP estimates. In comparing the DC model with the PC models, the DC model provides more efficient estimates. Moreover, the conventional DC model give some gains in terms of the goodness-of-fit and efficiency in comparing with the PC model most similar to this model. In this specific study, incorporating the preference uncertainty in DC model results greater estimates than conventional DC model without loss of goodness-of-fit and efficiency. This implies that the consideration of preference uncertainty on DC model could correct underestimating. We conclude that DC model provides a better estimate of WTP and preference uncertainty could be a critical information on the DC-CV estimation.

• The Journal of the Korea Contents Association
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• v.11 no.6
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• pp.302-310
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• 2011

Recently, many construction firms fall on hard times because construction business continues to stagnate. In this paper, we analyze the efficiency of the listed construction firms using a combined AHP and DEA model. In order to determine the input and output factors of DEA, the AHP model is applied to evaluate the importance of input and output factors. The benchmarking companies and efficiency value for the construction firms with inefficiency are also provided to improve the their efficiency. We analyzed the 57 listed companies consisted of 36 listed on KOSPI and 21 listed on KOSDAQ at the end of 2009. The analysis results show that eleven companies whose values of CCR are 1, and fourteen enterprises whose values of BCC efficiency are 1. In additions, the eleven firms have the scalability efficiency. Finally, we test the correlation between efficiency and the stock price and the correlation coefficient of efficiency group is 0.7 in the CCR model.

• Journal of Digital Convergence
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• v.12 no.12
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• pp.611-620
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• 2014

This research analyzed the operation efficiency and influence factors of housing facilities for the severely disabled in Jeolla region by using the DEA model. First, the analysis of efficiency for 2012 was carried out using the CCR model. As a result, 12 DMUs were proved to be efficient, and the average efficiency of CCR was 0.85, confirming that the efficiency of all DMUs were satisfactory. Second, regression analysis was carried out to analyze the factors affecting the efficiency of the DEA model by using the Tobit model. In this case, the inputs and calculated variables were set as independent variables whereas the efficiency as the dependent variable. As a result, the detailed variables had a low significance; the overall input variables showed a negative influence while the calculated variables tended to be a positive influence. In terms of operation efficiency, there was no meaningful result in input variables besides the number of workers. Instead of expanding the input variables, the following should be made for housing facilities of the severely disabled; more efforts should be put in to improve welfare service delivery system and operating environment and structure, and the program must be supplemented as well.

• KDI Journal of Economic Policy
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• v.16 no.2
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• pp.141-170
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• 1994

지금까지 사회보장제도(社會保障制度)의 경제적(經濟的) 효율성(效率性)에 대한 많은 논의가 있어 왔다. 그러나 그중 생애주기(生涯週期)(life-cycle)에 바탕을 둔 일반균형연산모형(一般均衡演算模型)(AGE : Applied General Equilibrium)에 의환 경험적 분석은 미진하였다. 본(本) 연구(硏究)의 목적(目的)은 사회보장제도(社會保障制度)의 세대내(世代內) 생애소득분위간(生涯所得分位間) 재분배효과(再分配效果)와 경제적(經濟的) 효율성(效率性)을 분석하는 데 있다. 연구방법으로서 Fullerton and Rogers(1993) 모형을 수정한 일부문(一部門), 다소비자(多消費者) 생애주기(生涯週期) 일반균형연산모형(一般均衡演算模型)을 이용하였다. 본 연구는 미국을 대상으로 한 정상상태(定常狀態)(steady state)의 분석이며, 소비자(消費者)를 생애소득별(生涯所得別)로 5분위(分位)로 나누어 기존 사회보장세(社會保障稅) 및 급여(給與)가 경제적(經濟的) 효율성(效率性)뿐만 아니라 계층간(階層間)의 분배(分配)에 어떠한 영향을 주는지를 분석하였다. 본(本) 연구(硏究)의 주요한 기여사항(寄與事項)은, 첫째 사회보장제도(社會保障制度)의 부담귀착분석(負擔歸着分析)에 새로운 연구방법(硏究方法)을 시도하였다는 점, 둘째 재정정책(財政政策)의 하나인 사회보장제도(社會保障制度)의 실질적(實質的) 부담(負擔)의 귀착문제(歸着問題)를 생애주기모형(生涯週期模型)으로 분석하였다는 점, 셋째 부담(負擔)의 귀착(歸着)은 사회보장세(社會保障稅)와 아울러 사회보장급여(社會保障給與)를 고려하여 분석하지 않으면 편향(偏向)(biased) 될 수 있다는 점을 지적한 점, 넷째 분석결과(分析結果) 기존 사회보장제도(社會保障制度)는 생애주기적(生涯週期的) 소득분배(所得分配)의 관점에서 누진적(累進的)(progressive)인 제도이지만 경제적(經濟的) 비효율성(非效率性)(efficiency cost)을 내재하고 있다는 점 등을 밝힌 것이다.

• The Korean Journal of Financial Management
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• v.7 no.1
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• pp.1-20
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• 1990

In most of studies on market efficiency, the stability of risk measures and the normality of residuals unexplained by the pricing model are presumed. This paper re-examines stock splits, taking the possible violation of two assumptions into accounts. The results does not change the previous studies. But, the size of excess returns during the 2-week period before announcements decreases by 43%. The results also support that betas change around announcements and the serial autocorrelation of residuals is caused by events. Based on the results, the existing excess returns are most likely explained as a compensation to old shareholders for unwanted risk increases in their portfolio, or by uses of incorrect betas in testing models. In addition, the model suggested in the paper provides a measure for the speed of adjustment of the market to the new information arrival and the intensity of information contents.

• The Korean Journal of Applied Statistics
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• v.27 no.2
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• pp.239-247
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• 2014

For a sensitive survey in which the population is composed by several strata with quantitative attributes, we present an additive stratified quantitative attribute randomized response model which applied stratified random sampling instead of simple random sampling to the models of Himmelfarb-Edgell's additive quantitative attribute model and Gjestvang-Singh's. We also establish theoretical grounds to estimate the stratum mean of sensitive quantitative attributes as well as the over all mean. We deal with the proportional and optimal allocation problems in each suggested model and compare the relative efficiency of the suggested two models; subsequently, Himmelfarb-Edgell's model is more efficient than Gjestvang-Singh's model under the condition of stratified random sampling.