• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.211-214
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• 2009

H.264/AVC의 인트라 예측에서 미리 현재 블록 내의 정보 및 이전 블록의 예측 모드 정보 등을 이용하여 현재 블록의 예측 부호화 블록 크기가 결정되었을 경우, 예측된 블록 크기에 적합한 예측 모드 결정이 요구된다. 이에 사전에 결정된 예측 블록 크기 정보와 주변 블록과의 화소 변화량을 계산하여 예측 모드를 결정하는 기법을 제안하고 성능을 평가한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2013.06a
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• pp.27-28
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• 2013

본 논문에서는 간섭 제한 적인 상황에서 지정된 채널을 추정해야 하는 실제적인 무선 애드혹 네트워크에서 비모수 선형 MMSE 필터 기반의 간섭 제어 채널 추정 기법을 사용하여 네트워크 성능을 개선시키는 새로운 기법을 제안한다. 제안하는 채널 추정 기법은 간섭의 정도에 따라 노드를 활성화 시키고 지정된 채널 추정을 한다. 실제적인 무선 애드혹 네트워크 모의실험을 통해 제안된 기법이 기존의 채널 추정 기법에 비해 상당한 전송 캐패시티 이득을 얻을 수 있음을 확인할 수 있다.

• The Korean Journal of Applied Statistics
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• v.30 no.1
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• pp.95-102
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• 2017

Gamma generalized linear models have received less attention than Poisson and binomial generalized linear models. Therefore, many old-established statistical techniques are still used in gamma generalized linear models. In particular, existing literature and textbooks still use approximate estimates for the dispersion parameter. In this paper we study the efficiency of various dispersion parameter estimators in gamma generalized linear models and perform numerical simulations. Numerical studies show that the maximum likelihood estimator and Cox-Reid adjusted maximum likelihood estimator are recommended and that approximate estimates should be avoided in practice.

• 한국경영정보학회:학술대회논문집
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• 2007.06a
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• pp.800-806
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• 2007

IT 벤처기업은 자본 대비 높은 수익성을 가지므로 지식기반 산업환경에서 많은 투자자들의 집중적인 관심을 받고 있다. 이러한 IT 벤처기업의 효율성을 평가하기 위한 방안으로, DEA 와 데이터마이닝 기법을 통합하는 방안을 제시하였다. 국내 코스닥 상장 기업 가운데 IT 에 주력하고 있는 벤처기업들을 대상으로 본 연구에서 제시한 효율성 평가방법을 적용 하였다. 대표적인 비모수적 분석기법인 Data Envelopment Analysis(DEA)를 이용하여 연구대상 기업들을 효율기업 및 비효율기업으로 구분한 후, DEA 의 효율성을 설명하는 모형을 logit 을 이용하여 구축하였다. DEA 는 기업의 상대적인 효율성을 측정하는 데에서 우수하지만, 효율성 정도를 설명하는 모형의 구축에는 한계가 있다. 이를 보완한 DEA 의 결과를 logit 과 통합한 효율성 모형에 대해서 데이터 마이닝 기법인 logit, 판별분석, Support Vector Machine(SVM) 등을 적용하여 IT 벤처기업의 효율성을 사전에 예측하여 평가 및 투자에 활용할 수 있는 방안을 제시하였다.

• Journal of the Korean Data and Information Science Society
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• v.22 no.2
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• pp.335-351
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• 2011

In order to resolve data scarcity problem related to crisis, Oh and Kim (2007) proposed to use stability oriented approach which focuses a base period of financial market, fits asymptotic stationary autoregressive model to the base period and then compares the fitted model with the current market situation. Based on such approach, they developed financial market instability index. However, since neural network, their major tool, depends on the base period too heavily, their instability index tends to suffer from inaccuracy. In this study, we consider linear asymptotic stationary autoregressive model and neural network to fit the base period and produce two instability indexes independently. Then the two indexes are combined into one integrated instability index via newly proposed combining method. It turns out that the combined instability performs reliably well.

• The Korean Journal of Applied Statistics
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• v.14 no.2
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• pp.321-332
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• 2001

본 논문에서는 반응변수가 두 가지의 값을 갖는 회귀분석에 적용할 수 있는 사영추적회귀를 고려하였다. 회귀모형에 필요한 설명변수들의 선형결합이 하나이고 연결함수의 형태를 사전에 알지 못한다는 가정하에서 모의담금질 기법을 이용하여 모형에 필요한 선형결합을 찾는 알고리즘을 제시하였다. 이진 반응변수의 경우에는 평활모수의 값에 따라 잔차이탈도함수의 반응표면이 단봉의 형태를 갖지 않는 경우가 있어 비동질적 마코프체인을 이용한 모의담금질 기법을 적용하면 효율적으로 선형결합을 탐색할 수 있다.

• Journal of the military operations research society of Korea
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• v.32 no.1
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• pp.51-72
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• 2006

There are many occasions that the performance of a corps is influenced not only by its own efforts but by the commander of the next higher unit in a vertical organizational structure. When the direction of the commander in the next higher organization is different from that of the actual evaluation agency, the unit under evaluation may get rated lower than what it should deserve. This study suggests an alternative method to evaluate the performance of military units in the situation that there exist critical environmental factors which affect the performance. This method employes DEA, a non parametric method, and Constrained Canonical Correlation Analysis(CCCA), a parametric method which is used to estimate a efficient frontier with multiple dependent variables and constraints. This article also exploits a set of categorical environmental variables in the CCCA to improve the fairness of performance evaluation. It is shown that the introduction of the categorical variables helps evaluating the true performance of individual units such as battalions subordinated to different next higher commanders.

• The KIPS Transactions:PartB
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• v.19B no.3
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• pp.201-208
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• 2012

Accurately segmenting lumen border in intravascular ultrasound images (IVUS) is very important to study vascular wall architecture for diagnosis of the cardiovascular diseases. After each of IVUS image is transformed to a polar coordinated image, initial points are detected using wavelet transform. Then, lumen border is initialized as the set of important points using non parametric probability density function and smoothing function by removing outlier initial points occurred by noises and artifacts. Finally, polynomial curve fitting is applied to obtain real lumen border using filtered important points. The evaluation of proposed method was performed with related method and the proposed method produced accurate lumen contour detection when compared to another method in most types of IVUS images.

• Journal of the Korean Data and Information Science Society
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• v.23 no.4
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• pp.683-691
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• 2012

In $4{\times}4$ graeco-latin square design, powers of rank transformed statistic for testing the main effect are superior to powers of parametric statistic without regard to the effect structure with equally or unequally spaced effect levels as well as the type of population distributions such as exponential, double exponential, normal and uniform distribution. As numbers of block effect or effect sizes are decreased, powers of rank transformed statistic are much higher than powers of parametric statistic. In case that block effects are smaller than a main effect or one block effect is higher than other block effects, powers of rank transformed statistic are much higher than powers of parametric statistic in $4{\times}4$ graeco-latin square design with three block effects and one main effect.

• 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.