• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.2
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• pp.767-776
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• 2014

This study estimated productivity change and RTS using Parametric and Non-Parametric approach with 5 year annual data from 2006 to 2010 of 20 public general hospitals in Vietnam collected from Ho Chi Min City Health Department of Health Database. The results could be summarized as follows; First, by the Non-Parametric approach. cumulated productivity growth of 5 years was increased by 2.8% due to regress 5.2% of technical efficiency, 0.3% of pure technical efficiency, but scale efficiency was decreased 5.1% Second, by the Non-Parametric approach, cumulated productivity growth was decreased by 12.8% to due to drop of 17.1% of technical change, 9.1% of scale efficiency. In conclusion, the common result of both approaches was that scale inefficiencies occurs in public hospitals in Vietnam, and they affected productivity change of public hospitals in Vietnam. Namely, 70% to 80% of the analyzed Vietnam public hospitals were at the status of DRS(decreased returns to scale), which suggested that they had oversupply beds relative to the number of occupied patients, it was meaningful that this study was the first study in Korea to measure efficiency and productivity change of Vietnamese public general hospitals and so it could be utilized as the basic information needed to enter hospital industry of Vietnam in the future.

• Communications for Statistical Applications and Methods
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• v.16 no.3
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• pp.463-477
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• 2009

Parameter estimation methods such as maximum likelihood estimation method, probability weighted moments method, regression method have been popularly applied to various extreme value models in numerous literature. Among three methods above, the performance of regression method has not been rigorously investigated yet. In this paper the regression method is compared with the other methods via Monte Carlo simulation studies for estimation of parameters of the Generalized Extreme Value(GEV) distribution and the Generalized Pareto(GP) distribution. Our simulation results indicate that the regression method tends to outperform other methods under small samples by providing smaller biases and root mean square errors for estimation of location parameter of the GEV model. For the scale parameter estimation of the GP model under small samples, the regression method tends to report smaller biases than the other methods. The regression method tends to be superior to other methods for the shape parameter estimation of the GEV model and GP model when the shape parameter is -0.4 under small and moderately large samples.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.610-610
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• 2015

수공구조물의 설계에서는 홍수빈도분석을 통해 산정된 특정 재현기간에서의 확률수문량이 설계기준으로 사용된다. 그러나 최근 기후변화로 인해 이상기후 현상이 심해짐에 따라 수문기상자료의 정상성을 가정하는 기존의 홍수빈도분석은 변화되는 수문현상을 적절히 표현하지 못하는 경우가 많다. 본 연구에서는 확률분포의 모수가 시간에 따라 변화하는 비정상성 빈도분석기법을 적용하였으며 확률분포의 모수들을 최우추정법으로 추정하였다. 또한, 분위수 추정과정에서도 비정상성을 고려하여 정상성 가정에서 산정된 재현기간 및 위험도와 비교분석하였다. 확률분포는 GEV 분포를 사용하여 정상성 및 비정상성 모형 4개를 구축하였다. 특히, 비정상성 모형은 위치모수만 선형 경향성을 가지는 경우, 규모모수만 선형경향성을 가지는 경우, 위치 및 규모모수가 선형경향성을 가지는 경우의 3가지로 구분하여 적용하였다. 구축된 4개의 모형 중 적합모형을 선정하기 위해 우도비 검정과 Akaike 정보기준을 사용하였으며 적합모형선정 절차를 체계적으로 구축하고 적용하여 적합모형을 선정하였다. 본 연구에서 구축된 비정상성 홍수빈도분석 기법은 우리나라의 8개 다목적댐 (충주댐, 소양강댐, 안동댐, 임하댐, 합천댐, 대청댐, 섬진강댐, 주암댐)으로부터 취득된 과거 관측 댐 유입량을 대상으로 하여 적용되었다. 우도비 검정과 Akaike 정보기준을 이용한 적합 모형 선정 결과 합천댐과 섬진강댐이 비정상성 GEV 모형에 적합한 것으로 분석되었고, 나머지 지점의 다목적댐들은 정상성 모형에 적합한 것으로 분석되었다. 합천댐과 섬진강댐의 경우 비정상성 가정에서 산정된 재현기간이 정상성 가정에서 산정된 재현기간보다 매우 작게 산정되었으며 확률수문량과 위험도는 크게 산정되었다. 적합모형으로 정상성 모형이 선정된 6개의 다목적댐 중 소양강댐은 Mann-Kendall 비모수 경향성 검정 결과 유의하지는 않지만 비교적 큰 선형경향성을 가지고 있었다. 비록 비정상성 모형이 적합모형으로 선정되지는 않았지만 소양강댐에 비정상성 모형을 가정하여 재현기간과 확률수문량, 위험도를 분석한 결과 정상성 모형 가정에서 산정한 결과와 상당한 차이가 있었다. 이와 같은 결과는 수문자료의 정상성과 비정상성을 고려한 홍수빈도분석이 향후 수공구조물의 설계에 있어서 신뢰성 있는 확률수문량을 결정하는데 도움이 될 것으로 판단된다.

• Korean Journal of Agricultural and Forest Meteorology
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• v.9 no.2
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• pp.140-148
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• 2007

The remote sensing observations of land surface properties are inevitably influenced by the landscape heterogeneity. In this paper, we introduce a geostatistical technique to provide a quantitative interpretation of landscape heterogeneity in terms of key land surface parameters. The study areas consist of the two KoFlux sites: (1) the Gwangneung site, covered with temperate mixed forests on a complex terrain, and (2) the Haenam site with mixed croplands on a relatively flat terrain. The semivariogram and fractal analyses were performed for both sites to characterize the spatial heterogeneity of two radiation parameters, i.e., land surface temperature (LST) and albedo. These parameters are the main factors affecting the reflected longwave and shortwave radiation components from the two study sites. We derived them from the high-resolution Landsat ETM+ satellite images collected on 23 Sep. 2001 and 14 Feb. 2002. The results of our analysis show that the characteristic scales of albedo was >1 km at the Gwangneung site and approximately 0.3 km at the Haenam site. For LST, the scale of heterogeneity was also >1 km at the Gwangneung site and >0.6 to 1.0 km at the Haenam site. At both sites, there was little change in the characteristic scales of the two parameters between the two different seasons.

• Journal of the Korean Regional Science Association
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• v.34 no.1
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• pp.3-17
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• 2018

This paper empirically investigates time-varying regression parameter of hedonic price model for Seoul office rental market in distinct periods of a market cycle. Office rental index is constructed and the index indicates that the global financial crisis differentiates the analysis period into decline stage and recovery stage. Pre-crisis period is classified into decline stage and post-crisis is classified into recovery stage. Structural break-point test suggests structural change of hedonic model of rent determinants occurred in 2008. Evidence indicates that individual regression parameters of hedonic price model for decline stage are significantly different from those for recovery stage. Changes in the regression parameters of land price, distance to metro, building size, building age, and conversion rate are consistent. In recovery stage, the effect of locational advantage on office rent decreases whereas the effect of building characteristics on the rent increases.

• Journal of Korea Water Resources Association
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• v.48 no.7
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• pp.567-579
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• 2015

This study performed the non-stationary flood frequency analysis considering time-varying parameters of a probability density function. Also, return period and risk under non-stationary condition were estimated. A stationary model and three non-stationary models using Generalized Extreme Value(GEV) were developed. The only location parameter was assumed as time-varying parameter in the first model. In second model, the only scale parameter was assumed as time-varying parameter. Finally, the both parameters were assumed as time varying parameter in the last model. Relative likelihood ratio test and Akaike information criterion were used to select appropriate model. The suggested procedure in this study was applied to eight multipurpose dams in South Korea. Using relative likelihood ratio test and Akaike information criterion it is shown that the inflow into the Hapcheon dam and the Seomjingang dam were suitable for non-stationary GEV model but the other six dams were suitable for stationary GEV model. Also, it is shown that the estimated return period under non-stationary condition was shorter than those estimated under stationary condition.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.148-149
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• 2010

최근 널리 보급되고 있는 IPTV의 주요 서비스인 주문형 비디오 서비스의 시청 순위는 Zipf의 법칙을 따른다고 알려져 있으며 이를 기반으로 계층형 네트워크 스토리지 구조로 서비스를 제공하여 네트워크 비용과 스토리지 비용을 절감하고 있다. 그러나, 최근 연구에 의하면 미디어 시청 순위는 stretched exponential 함수에 더 근사함이 알려졌다. 본 연구에서는 국내에서 현재 상용 서비스 중인 대규모 주문형 비디오 서비스의 시청 순위-회수 데이터를 분석하여, 시청 순위로부터 stretched exponential 함수의 모수를 추정하여 시청 순위의 분포함수를 파악하고자 한다. 특히, 콘텐츠 파일 크기, 콘텐츠 파일 전달방식, 콘텐츠 장르 등의 요인과 시청 순위 분포함수의 모수 사이에 상관관계가 있는지 분석하고자 한다.

• Korean Journal of Agricultural Science
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• v.32 no.2
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• pp.169-179
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• 2005

이 연구는 근래 한국 농가계층간에 경쟁력 수준의 격차가 확대되는 원인을 생산기술효율 측면에서 계측하고 비교분석하는 것을 목적으로 한다. 비모수적 접근방법을 사용하여 농지규모계층별 농가의 생산기술효율을 측정하고, 이는 다시 순수기술효율과 규모효율로 분리 계측되어 농가계층간 격차의 원인을 비교분석하였다. 1998-2002년 기간에 한국농가평균 순수기술효율은 0.54, 규모효율은 0.93으로 계측되었고, 대농층으로 갈수록 순수기술효율은 높은데 비해 규모효율은 낮게 나타났다. 그러나 5년(1998-2002년)기간 동안 대농층일수록 순수기술효율과 규모효율 모두 여타의 계층보다 빠르게 증가하는 추세를 보였으며, 이는 결과적으로 시간이 경과함에 따라서 대농층과 여타농과의 기술의 격차가 확대되고 있는 것으로 해석된다.

• Journal of Labour Economics
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• v.29 no.2
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• pp.145-169
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• 2006

This study analyze the effect on wage, labor mobility by using Craft II Class certification out of National skill certification. In this article, we used the parametric and nonparametric method. In the former we used IV that the fraction of certification by occupation by firm scale to solve the selection problem. In the latter, it's used matching method and kernel regression. The paper shows that certification effect on wage has about 5.1~9.9%. The result of analysis between certification and labor mobility indicates better certification effects on long term tenure to the same firm than certification effects on wage from labor mobility. Also, we knew that the employee which have no certification relative is difficult to be established in the same workplace.

• The Korean Journal of Applied Statistics
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• v.27 no.4
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• pp.605-617
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• 2014

Small area estimation is a statistical inference method to overcome large variance due to a small sample size allocated in a small area. A shrinkage estimator obtained by minimizing relative error(RE) instead of MSE has been suggested. The estimator takes advantage of good interpretation when the data range is large. A semiparametric estimator is also studied for small area estimation. In this study, we suggest a semiparametric shrinkage small area estimator and compare small area estimators using labor statistics.