• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 춘계학술대회논문집
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• pp.971-977
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• 2005

Power Flow Analysis (PFA) is developed for the effective predictions of frequency-averaged vibrational response in medium-to-high frequency ranges. In PFA, the power coefficients of semi-infinite structure and for-field energy density are used to predict the vibrational responses of structures. Generally, at high frequencies, PFA can predict narrow-band frequency-averaged vibrational responses of built-up structures. However, in low- to medium frequency ranges, the dynamic responses obtained by PFA represent broad-band frequency-averaged vibrational energy densities. For the prediction of vibrational response variance in Power Flow Finite Element Method (PFFEM), the variances of input power and joint element matrix describing structural coupling relationship are derived. Finally, for the validity of developed formulation, numerical examples for two co-planer plates are performed and the vibrational response variance of the structure are compared with the results of classical and PFFEM solutions.

• Communications for Statistical Applications and Methods
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• 제6권2호
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• pp.565-584
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• 1999

the covariance process of two martingales provides a useful tool to capture the dependence structure for paired censored data. in this paper it is applied to modify the variances of weighted logrank tests in order to take account of dependence between paired subjects. In the process of modification a 'variance correction term' is introduced. Some variance estimators based on separate samples are considered together. Performance of the estimators are compared through simulation studies. Several independence tests for bivariate sruvival date are also proposed which are naturally reduced from the weighted logrank tests accomodating dependence structure. Simulation studies are carried out to compare the independence tests. Both the weighted logrank tests and the independence tests are illustrated by an example.

• 대한전자공학회논문지
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• 제26권8호
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• pp.1227-1237
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• 1989

In this paper, we propose a lossless progressive image transmission scheme using hierarchical pyramid structure and classified vector quantizer in DCT domain. By adopting DCT to the hierarchical pyramid signals, we can reduce the spatial redundance. Moreover, the DCT coefficients can be encoded efficiently by using classified vector quantizer in DCT domain. The classifier is simply based on the variance of a subblock. Also, the mirror set of training set of images can improve the robustness of codebooks. Progressive image transmission can be achieved through following processes: from top to bottom level of planes in a pyramid, and from high to low AC variance class in a plane. Some simulation results with real images show that the proposed coding scheme yields a good performance at below 0.3 bpp and an excellent result at 0.409 bpp. The proposed coding scheme is well suited for lossless progressive image transmission as well as image data compression.

• 한국통신학회논문지
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• 제13권6호
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• pp.510-520
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• 1988

無限誤長 상태 공간 디지틀 필터를 有限誤長 상태 공간 디지틀 필터로 실현할 때 量子化 誤差인 상태 공간 계수〔ABCD〕의 미소 변동에 기인한, 출력 오차 分散을 $\Delta$〔ABCD〕의 分散으로 正規化하였다. 즉, S=E을 統計的 感度로 정의하고 시스템 구조적 성질을 나타내는 可制御性 Gramian, 그리고 2차 모드 해석 방법을 상태 공간 디지틀 필터에 확장해서 最小 統計的 感度를 갖는 실현 구조를 합성하였으며 시뮬레이션을 통하여 최소 구조 합성의 유효성을 확인하였다.

• Communications for Statistical Applications and Methods
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• 제18권6호
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• pp.809-816
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• 2011

A tree-indexed autoregressive(AR) process is a time series defined on a tree which is generated by a branching process and/or a deterministic splitting mechanism. This short article is concerned with conditional heteroscedastic structure of the tree-indexed AR models. It has been usual in the literature to analyze conditional mean structure (rather than conditional variance) of tree-indexed AR models. This article pursues to identify quadratic conditional heteroscedasticity inherent in various tree-indexed AR models in a unified way, and thus providing some perspectives to the future works in this area. The identical conditional variance of sisters sharing the same mother will be referred to as the branching heteroscedasticity(BH, for short). A quasilikelihood but preliminary estimation of the quadratic BH is discussed and relevant limit distributions are derived.

• 한국건설관리학회논문집
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• 제10권1호
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• pp.26-35
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• 2009

건설공사 공정 공사비 통합관리시스템(EVMS, Earned Value Management System)에서 대부분의 정보들은 공사정보 분류체계(WBS, Work Breakdown Structure)를 중심으로 활용된다. 즉, 공정편차와 비용편차 등의 EVM 성과정보 역시 WBS에서 선택된 공종을 중심으로 결과물이 분석되므로, EVMS에서 WBS는 정보중심 역할을 하게 된다. 본 연구에서는 WBS 정보가 4상한의 좌표방식으로 표현되어 프로젝트의 대 중 소 공종이 용이하게 표현될 수 있는 좌표식 공사정보분류체계(WBS Map) 표현기법을 구축하였다. 또한 연구에서는 WBS Map에 근거한 EVMS를 개발하였으며, 개발된 EVMS에서는 각종 속성 지표값들을 색상기호 등으로 시각화하는 방법론을 구축하여 EVMS 정보의 실무 활용성을 높일 수 있도록 하였다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2004년도 춘계공동학술대회 논문집
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• pp.294-297
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• 2004

Mean squared error (MSE) is an effective criterion to combine the mean and the standard deviation responses in dual response surface optimization. The bias and variance components of MSE need to be weighted properly in the given problem situation. This paper proposes a systematic method to determine the relative weights of bias and variance in accordance with a decision maker's prior and posterior preference structure.

• 제어로봇시스템학회논문지
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• 제2권1호
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• pp.14-20
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• 1996

This paper presents a self tuning method of a velocity type PID controller for minimum or non-minimum phase systems with time delays. The velocity type PID control structure is determined in the process of minimizing the variance of the auxilliary output, and self tuning effect is achieved through the recursive least square algorithm at the parameter estimation stage and also through the Robbins-Monro algorithm at the stage of optimizing a design parameter. This method is simple and effective compared with other existing methods[1,2]. Numerical examples are included to illustrate the procedure and to show the performance of the control system.

• Communications for Statistical Applications and Methods
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• 제8권3호
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• pp.805-814
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• 2001

The problem of 'outliers', observations which look suspicious in some way, has long been one of the most concern in the statistical structure to experimenters and data analysts. We propose a model for outliers problem and also analyze it in linear regression model using a Bayesian approach with the variance-inflation model. We will use Geweke's(1996) ideas which is based on the data augmentation method for detecting outliers in linear regression model. The advantage of the proposed method is to find a subset of data which is most suspicious in the given model by the posterior probability The sampling based approach can be used to allow the complicated Bayesian computation. Finally, our proposed methodology is applied to a simulated and a real data.

• 정보학연구
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• 제3권2호
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• pp.23-37
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• 2000

본고는 노조부문과 비노조부문간 임금불평등에 차이가 나는 요인을 분해하여 임금분배에 대한 노동조합의 직.간접적인 효과를 추정한 것이다. 노동부의 $\ulcorner$1993년 직종별 임금실태조사자료$\lrcorner$를 이용한 실증분석 결과에 의하면, 노조부문과 비노조부문간에 임금결정 메커니즘이 상이하면서도 노조부문의 임금불평등이 비노조부문에 비해 작았다. 그러나 이것은 임금분산을 요인별로 분해한 결과에 의하면 노조의 임금표준화전략에 의한 축소효과라고는 보기 어렵고, 오히려 부문간 특성 분산도의 차이에 기인하는 것으로 나타났다.