• 한국농공학회:학술대회논문집
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• 한국농공학회 2005년도 학술발표논문집
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• pp.284-287
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• 2005

The objective of this study is to check into variation trends of design rainfall according to change of the number of years for observed data. To make comparative study of the relation between design rainfall and recorded year, this study was used maximum rainfall for 24-hr consecutive duration at Gangneung, Seoul, Incheon, Chupungnyeong, Pohang, Daegu, Jeonju, Ulsan, Gwangju, Busan, Mokpo and Yeosu rainfall stations. The tests for Independence, Homogeneity and detection of outliers were used Wald-Wolfowitz's test, Mann-Whitney's test and Grubbs and Beck test respectively. To select appopriate distribution, the distribution of genaralized pareto(GPA), generalized extreme value(GEV), generalized logistic(GLO), lognormal and pearson type 3 distribution is judged by L-moment ratio diagram and Kolmogorov-Smirnov (K-S) test. Design rainfall was estimated by at-site frequency analysis using L-moments and Generalized extreme value(GEV) distribution according to change of the number of years for observed data. Through the comparative analysis for design rainfall induced by L-moments and GEV distribution, relationship between design rainfall and recorded year is provided.

• 기술혁신학회지
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• 제17권4호
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• pp.733-762
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• 2014

정부는 과학기술 핵심 인프라인 연구시설 장비의 이용 효율화를 위해 국가 연구개발 사업예산을 통해 구축한 연구시설 장비를 국가과학기술정보서비스(NTIS)에 등록할 것을 의무화하고 있다. 본 연구는 국가연구시설 장비의 효율적 관리를 위한 연구기관 구성원의 인식도 조사를 시행하고, 식스시그마 DAMIC 방법론을 통해 국가연구시설 장비 등록 프로세스 개선에 영향을 미치는 주요 요인을 도출함으로써 국가연구시설 장비의 운영 선진화와 활용 극대화 정책에 기여하고자 하였다. 이를 위하여 A대학교 사례를 중심으로 먼저 연구시설 장비의 대학 관계자인 연구책임자, 보직교수, 대학원생, 연구원, 직원을 대상으로 설문과 인터뷰를 수행하였다. 인식도 조사 결과, 연구시설 장비의 전주기적 관리와 구체적인 절차에 대한 인식이 부족함을 확인할 수 있었다. 대학의 경우 국가연구시설 장비의 운영선진화와 활용극대화를 위해서는 대학현장의 의견을 수렴하고 대학의 고유한 특성을 반영한 정책 추진이 필요함을 알 수 있었다. 연구시설 장비 등록 프로세스 개선을 위해 식스시그마 방법을 통해 CTQ-Y로 연구시설 장비 등록기한 준수율과 연구시설 장비 등록정확도를 선정하였다. Process Map과 C&E Diagram을 통해 72개 잠재원인변수를 도출하였고, 이를 대상으로 X-Y Matrix와 Pareto Chart를 통해 최종적으로 13개 잠재원인변수를 확정하였으며 개선안의 방향을 제시하였다. 연구기관마다 연구기관의 특성에 맞게 등록프로세스 개선에 영향을 미치는 잠재원인변수를 추출하고 이를 개선하기 위한 상세개선안을 마련함으로써 국가연구시설 장비의 활용 극대화를 제고할 수 있을 것이다.

• Journal of Computational Design and Engineering
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• 제1권4호
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• pp.256-265
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• 2014

Energy efficiency is an essential consideration in sustainable manufacturing. This study presents the car fender-based injection molding process optimization that aims to resolve the trade-off between energy consumption and product quality at the same time in which process parameters are optimized variables. The process is specially optimized by applying response surface methodology and using non-dominated sorting genetic algorithm II (NSGA II) in order to resolve multi-object optimization problems. To reduce computational cost and time in the problem-solving procedure, the combination of CAE-integration tools is employed. Based on the Pareto diagram, an appropriate solution is derived out to obtain optimal parameters. The optimization results show that the proposed approach can help effectively engineers in identifying optimal process parameters and achieving competitive advantages of energy consumption and product quality. In addition, the engineering analysis that can be employed to conduct holistic optimization of the injection molding process in order to increase energy efficiency and product quality was also mentioned in this paper.

• 품질경영학회지
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• 제38권3호
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• pp.340-353
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• 2010

Properly designed and well-executed services enable e-commerce companies to capture the unique needs and preferences of customers, help them build customer loyalty, and thereby, strengthen their competitiveness in the marketplace. An object of this study is the new open-market company and it has only 3 percent of the market share. Therefore, it is needed to raise the market share by improving the service qualities. This article presents a six sigma project for service quality improvement in the open-market company. This study was carried out based on five steps of DMAIC which is six sigma technique. First, a defect rate was defined as unsatisfaction rate. In addition, 50-people data was analyzed and it was shown that the defect level was 2.5 sigma level. In this study, in order to raise the sigma level, novel eight action items were determined based on SIPOC, FDPM, cause and effect diagram, matrix chart, Pareto chart and statistical analysis.

• Industrial Engineering and Management Systems
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• 제9권3호
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• pp.251-261
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• 2010

This article demonstrated the application of the Fuzzy Data Envelopment Analytical Hierarchy Process (FDEAHP) to evaluate the root causes of critical defect problems occurring in the production of liquid medicine. The methodology of the research began by collecting the defect data by using Check Sheets, and ranking the significant problems by using a Pareto Diagram. Two types of major problems were found to occur, including glass fragments in the medicine and damaged lid threads. The causes of each problem were then analyzed by using Cause and Effect Diagrams. The significant causes were ranked by FDEAHP under three criteria, Severity (S), Occurrence (O) and Detection (D), followed by the framework of the FMEA Technique. Two causes with the highest Final Weight (FW) of each problem were selected to be improved, such as installing auxiliary equipment, using the Poka-Yoke system, setting the scale of the shaft and lathing the bushes of each bottle size. The results demonstrated a reduction in defects from 3.209% to 1.669% and showed that improving a few significant root causes, identified by an experienced decision maker, was sufficient to reduce the defect rate.

• 한국산학기술학회논문지
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• 제10권5호
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• pp.1009-1019
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• 2009

본 연구에서는 우리나라 수위관측소들 중에서 관측 유량이 검증된 총 19개 유역을 선정하고 관측된 홍수량을 사용하여 적정 설계홍수량을 유도함으로써 우리나라의 설계홍수량 특성을 분석하였다. 대상유역별로 관측개시 년도에서부터 분석 시작년을 기준으로 1년씩 증가 시키는 점진적 구성 방식으로 연최대홍수량에 대한 빈도분석을 실시하기 위해, 변동특성을 이동평균법에 의해 분석하였다. 19개 대상유역에 대한 연최대홍수량 계열 구성기간별로 기본통치를 산정하고 독립성, 동질성 및 Outiler 검정을 실시하였다. Gumbel, Generalized Extreme Value, Generalized Logistic 및 Generalized Pareto 분포의 적합도 검정을 LH-모멘트비도와 Kolmogorov-Smirnov 검정에 의해 수행하였다. 적정 확률분포로 선정된 GEV 분포의 매개변수를 확률가중모멘트의 치수 변화에 의한 L, L1, L2, L3 및 L4-모멘트법에 의해 추정하고 대상유역 및 연최대홍수량 계열 구성 기간별 설계홍수량을 유도하였다. 본 연구에서 사용한 변동률 분석에 따라 최근 지구온난화에 따른 우리나라 기후 변화를 고려한 적절한 수리구조물의 설계 조건변경시기는 2002년 전후로 하여야 할 것이다.

• 산업경영시스템학회지
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• 제41권4호
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• pp.203-212
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• 2018

Quality requirements of manufactured products or parts are given in the form of specification limits on the quality characteristics of individual units. If a product is to meet the customer's fitness for use criteria, it should be produced by a process which is stable or repeatable. In other words, it must be capable of operating with little variability around the target value or nominal value of the product's quality characteristic. In order to maintain and improve product quality, we need to apply statistical process control techniques such as histogram, check sheet, Pareto chart, cause and effect diagram, or control charts. Among those techniques, the most important one is control charting. The cumulative sum (CUSUM) control charts have been used in statistical process control (SPC) in industries for monitoring process shifts and supporting online measurement. The objective of this research is to apply Taguchi's quality loss function concept to cost based CUSUM control chart design. In this study, a modified quality loss function was developed to reflect quality loss situation where general quadratic loss curve is not appropriate. This research also provided a methodology for the design of CUSUM charts using Taguchi quality loss function concept based on the minimum cost per hour criterion. The new model differs from previous models in that the model assumes that quality loss is incurred even in the incontrol period. This model was compared with other cost based CUSUM models by Wu and Goel, According to numerical sensitivity analysis, the proposed model results in longer average run length in in-control period compared to the other two models.

• 한국농공학회논문집
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• 제46권5호
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• pp.27-39
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• 2004

In the first part of this study, five homogeneous regions in view of topographical and geographically homogeneous aspects except Jeju and Ulreung islands in Korea were accomplished by K-means clustering method. A total of 57 rain gauges were used for the regional frequency analysis with minimum rainfall series for the consecutive durations. Generalized Extreme Value distribution was confirmed as an optimal one among applied distributions. Drought rainfalls following the return periods were estimated by at-site and regional frequency analysis using L-moments method. It was confirmed that the design drought rainfalls estimated by the regional frequency analysis were shown to be more appropriate than those by the at-site frequency analysis. In the second part of this study, LH-moment ratio diagram and the Kolmogorov-Smirnov test on the Gumbel (GUM), Generalized Extreme Value (GEV), Generalized Logistic (GLO) and Generalized Pareto (GPA) distributions were accomplished to get optimal probability distribution. Design drought rainfalls were estimated by both at-site and regional frequency analysis using LH-moments and GEV distribution, which was confirmed as an optimal one among applied distributions. Design rainfalls were estimated by at-site and regional frequency analysis using LH-moments, the observed and simulated data resulted from Monte Carlotechniques. Design drought rainfalls derived by regional frequency analysis using L1, L2, L3 and L4-moments (LH-moments) method have shown higher reliability than those of at-site frequency analysis in view of RRMSE (Relative Root-Mean-Square Error), RBIAS (Relative Bias) and RR (Relative Reduction) for the estimated design drought rainfalls. Relative efficiency were calculated for the judgment of relative merits and demerits for the design drought rainfalls derived by regional frequency analysis using L-moments and L1, L2, L3 and L4-moments applied in the first report and second report of this study, respectively. Consequently, design drought rainfalls derived by regional frequency analysis using L-moments were shown as more reliable than those using LH-moments. Finally, design drought rainfalls for the classified five homogeneous regions following the various consecutive durations were derived by regional frequency analysis using L-moments, which was confirmed as a more reliable method through this study. Maps for the design drought rainfalls for the classified five homogeneous regions following the various consecutive durations were accomplished by the method of inverse distance weight and Arc-View, which is one of GIS techniques.

• 한국수자원학회논문집
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• 제49권8호
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• pp.645-656
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• 2016

본 연구에서는 금강유역에 대한 지역홍수빈도분석을 실시하고 재현기간에 따른 홍수량을 추정하는 관계식을 제안하였다. 유역 내 유량자료의 수문학적 독립성과 동질성에 대한 검증을 위하여 Lag-1 자기상관성 분석, 동질성 검정, 이상치 검정, 불일치척도 검정을 수행하였다. 검정 결과, 금강유역의 대상 관측소들은 시간에 대하여 독립적이고 동질적 모집단에 속하며 이상치는 없었다. 일반 극치 분포(GEV), 3변수 대수정규 분포(LN-III), 피어슨-III 분포(P-III), 일반 로지스틱 분포(GLO), 일반 파레토 분포(GPA) 등 5개의 3변수 확률분포함수에 대한 L-모멘트비도와 평균가중거리(AWD), 그리고 $Z^{DIST}$ 적합도 산정 결과, GLO 분포함수가 금강유역의 최적 확률분포형으로 선정되었다. GLO 분포를 바탕으로 지역홍수빈도를 추정하는 회귀모형을 제안하였고, 강경 관측소의 관측 유량을 이용하여 회귀모형의 적용성을 검증하였다.