• Journal of the Korean Data and Information Science Society
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• 제23권6호
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• pp.1231-1239
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• 2012

An estimating procedure is introduced for kernel Poisson regression when the input variables consist of numerical and categorical variables, which is based on the penalized negative log-likelihood and the component-wise product of two different types of kernel functions. The proposed procedure provides the estimates of the mean function of the response variables, where the canonical parameter is linearly and/or nonlinearly related to the input variables. Experimental results are then presented which indicate the performance of the proposed kernel Poisson regression.

• 한국물환경학회지
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• 제23권3호
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• pp.385-390
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• 2007

Reliable flow measurement for dry season is very important to set up the in-stream flow exactly and total maximum daily load control program in the basin. Especially, in the points which tidal current effects are dominant because reliability of the low measurement decrease. The reliable measuring methods are needed. In this study, we analysis the water surface elevation difference of water surface elevation. Quantity relationship to consider tidal currents in these regions. It is known that tidal current effects from Nakdong river barrage are dominant in Samrangjin measuring station. We developed multiple regression equation with water surface elevation, quantity, and difference of water surface elevation and compared these results water measured rating curve. All of these regression equation including linear regression equation and log regression equation fits better measured data them existing water surface elevation quantity line and Among three equations, the log regression equation is best to represent the measured the rating curve in Samrangjin point. The log regression equation is useful method to obtain the quantity in the regions which tidal currents are dominant.

• Journal of the Korean Data and Information Science Society
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• 제10권1호
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• pp.193-198
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• 1999

The estimation of parameters in regression models with multiplicative errors is usually based on the gamma or log-normal likelihoods. Under reciprocal misspecification, we compare the small sample efficiencies of two sets of estimators via a Monte Carlo study. We further consider the case where the errors are a random sample from a Weibull distribution. We compute the asymptotic relative efficiency of quasi-likelihood estimators on the original scale to least squares estimators on the log-transformed scale and perform a Monte Carlo study to compare the small sample performances of quasi-likelihood and least squares estimators.

• Communications for Statistical Applications and Methods
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• 제25권6호
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• pp.633-645
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• 2018

Gaussian error distributions are a common choice in traditional regression models for the maximum likelihood (ML) method. However, this distributional assumption is often suspicious especially when the error distribution is skewed or has heavy tails. In both cases, the ML method under normality could break down or lose efficiency. In this paper, we consider the log-concave and Gaussian scale mixture distributions for error distributions. For the log-concave errors, we propose to use a smoothed maximum likelihood estimator for stable and faster computation. Based on this, we perform comparative simulation studies to see the performance of coefficient estimates under normal, Gaussian scale mixture, and log-concave errors. In addition, we also consider real data analysis using Stack loss plant data and Korean labor and income panel data.

• Communications for Statistical Applications and Methods
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• 제14권2호
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• pp.401-411
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• 2007

In this paper we propose an influence measure for detecting potentially influential observations using the infinitesimal perturbation and the local influence in the log-linear regression model. Also, we propose a goodness-of-fit measure for variable selection. A real data set are used for illustration.

• Journal of the Korean Data and Information Science Society
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• 제18권3호
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• pp.767-772
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• 2007

A kernel machine is proposed as an estimating procedure for the linear and nonlinear Poisson regression, which is based on the penalized negative log-likelihood. The proposed kernel machine provides the estimate of the mean function of the response variable, where the canonical parameter is related to the input vector in a nonlinear form. The generalized cross validation(GCV) function of MSE-type is introduced to determine hyperparameters which affect the performance of the machine. Experimental results are then presented which indicate the performance of the proposed machine.

• Journal of the Korean Data and Information Science Society
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• 제23권1호
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• pp.71-77
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• 2012

본 연구는 코호트 조성법에 의해 구성된 진학률들을 사용한 비선형 회귀모형을 이용하여 장래 초등과 중등, 고등학교의 학년별 학생수를 추계 하는데 목적이 있다. 이러한 진학률들의 모형을 분석하기 위하여 경향-외삽법 중 하나인 비선형 회귀모형의 로그모형과 거듭제곱 모형을 이용하였다. 그 결과 로그모형에 의한 예측이 거듭제곱모형에 의한 예측보다 조금 더 신뢰할 수 있고, 학생수도 적게 예측됨을 알 수 있었다.

• 한국식품과학회지
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• 제26권6호
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• pp.764-769
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• 1994

본 실험은 원유내외 세균을 빠르고, 일관성있고, 신뢰성이 있는 평가 system을 얻기 위함이며, 원유 내외 총균수와 저온성균수, 대장균군수를 malthus의 detection time과 regression equation과 상관관계를 조사하였다. Conductance method는 종래의 plate count method보다빠르고 자동적이며, 노동력을 최대한 절감할 수 있다. 그 결과는 다음과 같다. 1. Conductance detection time을 (Y), total bacterial log count를 (X)라고 할 때 regression equation Y=18.27651-2.07550X, 상관계수는 -0.95(n=201)로 나타났다. 2. Conductance detection time을 (Y), total bacterial log counts를 (X)라고 할때 regression equation Y=9.32048-1.15598X, 상관계수는 -0.90(n=207)로 나타났다. 3. Conductance dotection time을 (Y), psychrotrophic bacterial log counts를 (X)라 할때 regression equation Y=29.96008-3,02487X 상관계수는 -0.90(n=201)로나타났다.

• Educational Technology International
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• 제15권2호
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• pp.71-88
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• 2014

A variety of studies to predict students' performance have been conducted since educational data such as web-log files traced from Learning Management System (LMS) are increasingly used to analyze students' learning behaviors. However, it is still challenging to predict students' learning achievement in blended learning environment where online and offline learning are combined. In higher education, diverse cases of blended learning can be formed from simple use of LMS for administrative purposes to full usages of functions in LMS for online distance learning class. As a result, a generalized model to predict students' academic success does not fulfill diverse cases of blended learning. This study compares two blended learning classes with each prediction model. The first blended class which involves online discussion-based learning revealed a linear regression model, which explained 70% of the variance in total score through six variables including total log-in time, log-in frequencies, log-in regularities, visits on boards, visits on repositories, and the number of postings. However, the second case, a lecture-based class providing regular basis online lecture notes in Moodle show weaker results from the same linear regression model mainly due to non-linearity of variables. To investigate the non-linear relations between online activities and total score, RF (Random Forest) was utilized. The results indicate that there are different set of important variables for the two distinctive types of blended learning cases. Results suggest that the prediction models and data-mining technique should be based on the considerations of diverse pedagogical characteristics of blended learning classes.

• 한국산림과학회지
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• 제78권3호
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• pp.323-330
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• 1989

한국산(韓國産) 소나무천연림(天然林)의 효과적인 현존량(現存量) 추정식(推定式)을 파악하기 위하여 4개(個) 지역형별(地域型別) 전형적인 수형을 가지는 임분(林分)을 대상으로 임분별(林分別) 10주(株)씩 총 40주(株)의 표본목(標本木)을 선정(選定) 벌목(伐木)하여 임분별(林分別), 부위별(部位別) 현존량(現存量) 추정식(推定式)을 3개(個) 상대성장식(相對成長式)(logWt=A+BlogD, logWt=A+B $1ogD^2H$, logWt=A+BlogD+ClogH)에 의하여 유도한 결과 전반적으로 logWt=A+BlogD-ClogH 식의 적합도(適合度)가 높았다. 그러나 고사지(故死枝)와 모구(毬果)의 경우 흉고직경(胸高直徑)과 수고(樹高) 즉, 개체목(個體木)의 크기 인자와의 관계(關係)가 적은 것으로 나타났다. 실용성(實用性)을 고려하여 4개(個) 임분(林分) 전체의 표본목(標本木) 40주(株)에 대한 일괄상대성장식(一括相對成長式)을 유도하고 임분별(林分別) 회귀식간(回歸式間)의 분산(分散), 기울기, 절편(截片)의 차이 유무를 검정한 결과 흉고직경(胸高直徑)만을 독립변수(獨立變數)로 하는 경우 보다 흉고직경(胸高直徑)과 수고(樹高)를 독립변수(獨立變數)로 할 경우 지성형간(地城型間)의 차이를 어느정도 배제할 수 있었으나, 임분별(林分別) 회귀식간(回歸式間)의 분산(分散) 절편(截片)에서 유기적(有機的)인 차이를 보임으로써 4개(個) 임분(林分)에 대한 일괄상대성장식(一括相對成長式)의 작용은 적합하지 않은 것으로 나타났다.