• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.156-156
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• 2015

최근 화석연료의 사용으로 인한 지구온난화 등 환경파괴가 점점 증가하는 추세이며 이로 인해 신재생에너지 중 하나인 수력발전이 주목받고 있다. 수력발전은 물의 위치에너지를 기계에너지로 이를 다시 전기에너지로 변환하는 친환경적인 방식으로 운영된다. 수력발전량은 우리나라 전체 발전량의 1.5% 정도로 적은 양의 발전량을 생산하지만 가동시간이 짧아 전력수요가 급변하는 상황에 대비 가능하기 때문에 수력발전은 필수적이다. 기후변화의 영향으로 연평균강수량은 증가하는 양상을 보이나 연 강수일수는 줄어드는 등 수자원의 불확실성이 증가하고 있는 실정이다. 따라서 미래 불확실한 수자원 공급에 대비할 수 있는 수자원의 효율적 활용에 대한 연구가 필요하다. 본 연구에서는 하천의 유량이 계절에 따라 변동 폭이 크다는 점을 고려하며 월별 발전량을 최대화하기 위해 선형계획법을 적용하는 모형을 구축하였다. 선형계획법은 목적함수와 제약조건식 모두 1차식으로 비선형항을 포함할 수 없으나 초기 해가 불필요하고 최적해가 보장된다는 장점을 가진다. 일부 목적함수나 제약조건식에 비선형항이 포함되어 있을 경우 Successive Linear Programming(SLP), Piecewise Linear Programming(PLP), Taylor Expansion 등의 방법을 이용하여 선형화할 수 있다. 본 연구에서 비선형 제약조건은 Taylor Expansion을 이용하여 선형화하였으며 한강수계 9개 댐의 월간 발전량을 최대화시키는 장기 운영 모형을 구축하였다. 개발 환경은 Linux-CentOS이며 사용프로그램은 통계 분석에 많이 활용되는 R programming이다. R programming은 패키지를 이용한 개발이 용이하고 Windows 뿐만 아니라 Linux, Mac, Unix 등의 운영체제에서도 호환 가능하다는 장점이 있다.

• Journal of the Korean Data and Information Science Society
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• v.21 no.1
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• pp.21-32
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• 2010

Graphical regression is a paradigm for obtaining regression information using plots without model assumptions. The general goal of this approach is to find lowdimensional sufficient summary plots without loss of important information. Model assessments using residual plots are less likely to be successful in models that are not linear. As an alternative approach, marginal model plots provide a general graphical method for assessing the model. We apply the methods of graphical regression and model assessment using marginal model plots to the logistic regression model.

• The Korean Journal of Applied Statistics
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• v.21 no.1
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• pp.169-176
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• 2008

We explore the structure and usefulness of three dimensional CERES plot as a basic tool for dealing with curvature as a function of the new predictors in generalized linear models. If predictors have nonlinear effects and there are nonlinear relationships among the predictors, the partial residual plot is not able to display the correct functional form of the predictors. Unlike this plots, the CERES plot can show the correct form. This is illustrated by simulated data.

• Journal of the Korean Operations Research and Management Science Society
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• v.7 no.1
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• pp.5-9
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• 1982

우리나라 경영학계 내지는 기업경영에 경영과학(Management Science)의 여러가지 기법이 정식으로 소개되기 시작한 것은 70년대 후반이라고 생각된다. 경영과학의 기법에는 선형계획법·재고관리모형·대기행렬모형·모의(Simulation) 모형·네트웍(Network) 모형 등 여러가지가 있지만, 이중 선형계획법이 우리에게 가장 익숙한 모형이고 기업의 실제 문제해결에도 가장 많이 이용되고 있다. 지금 소개하고자 하는 목표계획법도 경영과학기법의 하나로 모형계획법과 매우 유사한 기법이다.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.9-26
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• 2001

In this paper. the development of a pusher-barge hull form which enables the continuous transportation along the coast and canal is performed. For the design stage of the hull forms. these are developed for Kyungin canal which is will be drawn up as the next contribution project of the Korean government are adopted. The model tests for the designed ship are carried out in the Inha University Towing Tank and the numerical simulations are done with a finite difference method based on MAC scheme. At first, the experiments are performed with designed model ships from low speed to high speed including service speed(6knots) among the corresponding designed speed. Resistance characteristics of designed ships are compared with experimental results of other several pusher-barge hull shapes. Next, the numerical simulations are performed for three cases, that is pusher only, barge only and pusher-barge condition in the designed speed. Each calculations are carried out in deep and restricted water condition. The flow characteristics around hulls in the latter condition are compared with those in the former condition.

• Journal of Korea Water Resources Association
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• v.32 no.6
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• pp.711-720
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• 1999

In this study, a various rainfall-runoff modelling approaches have been applied to the runoff response of flood hydrograph in three experimental watershed of the western part of korea. Mathematical models of runoff response also have been studied including linear system theory based on modeling techniques. Eight models were operated at the five water level gauging stations and the parameters of each model were computed by the Rosenbrock's hill climbing method to minimize the objective function. For the parameter verification of the models, a different complex rainfall-runoff event was selected in the same of the three river basins and derived IUH of the each model could be calibrated. Furthermore multiple regressions of the logarithmic transformation method between model parameters and catchment characteristics were studied in the selected five station.

• Communications for Statistical Applications and Methods
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• v.16 no.2
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• pp.265-275
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• 2009

This paper considers a linear regression model with a spatial autoregressive disturbance with ill-posed data and proposes the generalized maximum entropy(GME) estimator of regression coefficients. The performance of this estimator is investigated via Monte Carlo experiments. The results show that the GME estimator provides efficient and robust estimate for the unknown parameter.

• The Korean Journal of Applied Statistics
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• v.28 no.2
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• pp.361-369
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• 2015

A general linear mixed-effects model is often used to analyze repeated measurement experiment data of a continuous response variable. However, a general linear mixed-effects model can give improper analysis results when simultaneously detecting heteroscedasticity and the non-normality of population distribution. To achieve a more robust estimation, we used a heavy-tailed linear mixed-effects model for a more exact and reliable analysis conclusion than a general linear mixed-effects model. We also provide reliability analysis results for further research.

• The Korean Journal of Applied Statistics
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• v.34 no.6
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• pp.937-944
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• 2021

The problem of selecting variables is addressed in partial linear regression. Model selection for partial linear models is not easy since it involves nonparametric estimation such as smoothing parameter selection and estimation for linear explanatory variables. In this work, several approaches for variable selection are proposed using a fast forward selection algorithm, least angle regression (LARS). The proposed procedures use t-test, all possible regressions comparisons or stepwise selection process with variables selected by LARS. An example based on real data and a simulation study on the performance of the suggested procedures are presented.

• The Korean Journal of Applied Statistics
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• v.34 no.2
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• pp.205-223
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• 2021

In this paper, we study a method to determine the existence of unit roots by using the adaptive lasso. The previously proposed method that applied the adaptive lasso to the original time series has low power when there is an unknown trend. Therefore, we propose a modified version that fits the ADF regression model without deterministic component using the adaptive lasso to the detrended series instead of the original series. Our Monte Carlo simulation experiments show that the modified method improves the power over the original method and works well in large samples.