• ETRI Journal
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• v.14 no.3
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• pp.67-74
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• 1992

Discrete variable을 갖는 Mean Field Theory(MFT) neural network은 이미 많은 combinatorial optimization 문제에 적용되어져 왔다. 본 논문에서는 이를 확장하여 continuous variable을 갖는 mean field annealing을 제안하고, 이러한 network에서 integral로 표현되는 spin average를 mean field에 기초하여 어렵지 않게 구할 수 있는 one-variable stochastic simulated annealing을 제안하였다. 이런 방법으로 multi-body problem을 single-body problem으로 바꿀 수 있었다. 또한 이 방법을 이용한 응용으로서 통계학에서 잘 알려진 문제중의 하나인 quantification analysis 문제에 적용하여 타당성을 보였다.

• The Korean Journal of Applied Statistics
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• v.34 no.3
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• pp.329-345
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• 2021

Recommender systems use data from customers to suggest personalized products. The recommender systems can be categorized into three cases; collaborative filtering, contents-based filtering, and hybrid recommender system that combines the first two filtering methods. In this work, we introduce and compare deep learning-based recommender system using autoencoder. Autoencoder is an unsupervised deep learning that can effective solve the problem of sparsity in the data matrix. Five versions of autoencoder-based deep learning models are compared via three real data sets. The first three methods are collaborative filtering and the others are hybrid methods. The data sets are composed of customers' ratings having integer values from one to five. The three data sets are sparse data matrix with many zeroes due to non-responses.

• The Korean Journal of Applied Statistics
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• v.34 no.1
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• pp.9-23
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• 2021

In the following paper we introduce a variational Bayes method that approximates posterior distributions with mean-field method. In particular, we introduce automatic differentiation variation inference (ADVI), which approximates joint posterior distributions using the product of Gaussian distributions after transforming parameters into real coordinate space, and then apply it to pharmacokinetic models that are models for the study of the time course of drug absorption, distribution, metabolism and excretion. We analyze real data sets using ADVI and compare the results with those based on Markov chain Monte Carlo. We implement the algorithms using Stan.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.677-687
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• 2006

Kriging interpolation is one of the generally used interpolation techniques in Geostatistics field. This technique includes the experimental and theoretical variograms and the formulation of kriging interpolation. In contrast to the conventional least square method for stress recovery, kriging interpolation is based on the weighted least square method to obtain the estimated exact solution from the stress data at the Gauss points. The weight factor is determined by variogram modeling for interpolation of stress data apart from the conventional interpolation methods that use an equal weight factor. In addition to this, the p-level is increased non-uniformly or selectively through a posteriori error estimation based on SPR (superconvergent patch recovery) technique, proposed by Zienkiewicz and Zhu, by auto mesh p-refinement. The cut-out plate problem under tension has been tested to validate this approach. It also provides validity of kriging interpolation through comparing to existing least square method.

• The Korean Journal of Applied Statistics
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• v.15 no.2
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• pp.423-432
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• 2002

Web Based electronic texts are studied on the statistics education fields. In this paper, we discuss the current problems encountered by many statistics electronic texts. We also suggest a new design concept for the Web Based interactive material. In addition, we presented several examples to demonstrate.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.30 no.4
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• pp.76-91
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• 2022

면세점 판매 채널이 다양화되고 스마트 여객 증대 등 쇼핑 성향의 변화로 인해 인천공항 면세점 객단가는 하락하고 있다. 면세점 매출액 감소에 따라 사업 다각화 및 고도화 등 대응 노력이 필요하다. 따라서 인천공항 면세점 이용객의 쇼핑 행태 및 면세점 트렌드 변화에 적기 대응을 위한 기초자료 및 마케팅 강화 방안을 제시하는 데 궁극적인 목적이 있다. 본 연구는 인천공항 면세점 내·외국인 구매자/비구매자, 환승객을 대상으로 쇼핑실태를 심층 조사하여 행동 특성을 분석하였으며, 그 결과 내국인과 외국인, 환승객별로 인구통계학 특성, 여행 특성, 쇼핑 특성에서 차이가 나타났다. 인천공항 면세점 이용객별 중요하게 인지하는 요소와 만족하는 요소를 파악하고 개선할 부분을 파악하였다. 이로써 인천공항 면세점 운영정책 수립 및 기본방향 설정을 위한 기초자료로 활용할 수 있고, 인천공항 면세점 마케팅 강화 및 활성화를 위한 전략 방안을 제시하는 데 의의가 있다.

• The Korean Journal of Applied Statistics
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• v.32 no.1
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• pp.111-128
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• 2019

Subways are eco-friendly public transportation that can transport large numbers of passengers safely and quickly. It is necessary to predict the accurate number of passengers in order to increase public interest in subway. This study groups stations on Lines 1 to 9 of the Seoul Metropolitan Subway using clustering analysis. We propose one final prediction model for all stations and three optimal prediction models for each cluster. We found three groups of stations out of 294 total subway stations. The Group 1 area is industrial and commercial, the Group 2 ares is residential and commercial, and the Group 3 area is residential districts. Various data mining techniques were conducted for each group, as well as driving some influential factors on demand prediction. We use our model to predict the number of passengers for 8 new stations which are part of the 3rd extension plan of Seoul metro line 9 opened in October 2018. The estimated average number of passengers per hour is from 241 to 452 and the estimated maximum number of passengers per hour is from 969 to 1515. We believe our analysis can help improve the efficiency of public transportation policy.

• The Korean Journal of Applied Statistics
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• v.20 no.2
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• pp.395-407
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• 2007

Outliers distort many measures for data analysis. We can propose dandelion seed plot as a graphical tool for evaluating the effect of outliers in one-and two-variate data. We can draw mean-variance dandelion seed plots using linked curves which are made by changing weights from 1 to 0 for each datum. Similarly we can also draw covariance-correlation-coefficient dandelion seed plots. This graphical method can be a useful tool for elementary statistics education in college.

• Communications for Statistical Applications and Methods
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• v.17 no.1
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• pp.79-88
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• 2010

Introductory statistic class proposes two tests for the equality of two population means according to the homogeneity of their variances. However, in practice, the variances are also unknown and practitioners often test their homogeneity before they do two sample t-test. This is also true in many popular statistical packages such as SAS and SPSS. In this paper, we study the type I error of this two stage procedure and propose a procedure to control it at a given significance level.

• The Korean Journal of Applied Statistics
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• v.9 no.2
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• pp.73-82
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• 1996

A multimedia software for introductory education is developed based on computer simulation. Developing tools for educational software are discussed. A developed software can be used interactively in teaching of statistical basic concepts.