• 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.9 no.2
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• pp.83-94
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• 1996

The probability of Yut was calculated by using the physical property in previous study, but this article suggested empirical estimators for probability of Yut. In practice, physics-based probability imposes too strong assumptions, which result in the difference between the calculated probabilies and empirical relative frequencies. Experiment shows the probabilities of Yut depend on the integrated shape of Yut rather than the floor type. Maximum likelihood estimator and empirical Bayes estimators are compared and all turn out to be almost identicla for more than 40 trials. For smaller number of trials, Bayes estimators are recommended for its stability. Regression approach is also adopted as an easy-to-use method without empirical trials.

• 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.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.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.62-63
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• 2003

대기 중 입자상 및 가스상 오염물질에 대한 오염원의 영향을 확인하고 기여도를 정량화하기 위하여 수용방법론 (receptor methods)이 이용되고 있다. 수용방법론은 각종 응용통계학을 기반으로 한 계량화 학적 분석기술로서, 일반대기 중 수용체에서 가스상ㆍ입자상 오염물질의 물리ㆍ화학적 특성을 분석한 후, 대기질에 영향을 미치는 오염원을 확인하고 기여도를 정량적으로 파악하여 대기오염 관리를 합리적으로 수행할 수 있는 통계적 방법이다. 또한 수용방법론은 입자상 및 가스상 오염물질의 분석에 다각도로 응용할 수 있으며, 합리적인 대기오염 관리를 유도하는 기초기술이라 할 수 있다(황인조 등, 2001). (중략)

• Journal of the Korea Society of Computer and Information
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• v.10 no.6 s.38
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• pp.17-26
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• 2005

In this paper we propose three nonparametric tests such as Wilcoxon test, Median test and Van der Waerden test, based on linear rank statistics for detecting edges in images. The methods used herein are based on detecting changes in gray-levels obtained using an edge-height parameter between two sub-regions in a 5$\times$5 window We compare and analysis the performance of three statistical edge detectors in terms of qualitative measures with the edge maps and objective, quantitative measures.

• The Korean Journal of Applied Statistics
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• v.12 no.2
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• pp.657-670
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• 1999

공공기관에서 발간하는 공식통계자료들을 살펴보면 대부분 관찰값으로 총 빈도수나 또는 전체를 기준으로 하여 그 빈도수가 차지하는 퍼센트 그리고 지수 등으로 나타나 있다. 이러한 자료는 단순히 공무원들에게 행정용으로 활용되고는 있으나 일반인들이 자료를 이해하고 나아가 활용하기는 어렵다. 이런 자료들이 일반인을 위한 자료가 되기 위해서는 국민 한사람(또는 기본 단위)당 그 발생 확률을 구하여 제시하고 나아가 개개인의 여러 복잡한 현실 상황을 고려해도 그 확률 계산이 용이하도록 기초적인 자료를 제공하는 것이 바람직하다고 사료된다. 즉, 육하(六河)원칙을 근거로한 현상에 대하여 확률을 구하고 활용할 수 있는 방안을 제시한다. 이 논문에서는 경찰청에서 발표된 교통사고에 대한 통계자료와 대검찰청에서 발표된 범죄사건 통계자료를 통계학의 기본인 확률의 개념을 도입하여 보다 이해가 쉽고, 나아가 교통사고와 범죄 피해를 최소한으로 줄일수 있는 자료로 변환하여 설명하고자 한다.