• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.631-639
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• 2015

Extraction/separation of cobalt by solvent extraction is reviewed. Separation of cobalt using various reagents and also cobalt recovery from scrap using commercial extractant were analyzed. The separation ability for cobalt followed the order of phosphinic > phosphonic > phosphoric acid due to the increasing stabilization of tetrahedral coordination of cobalt complexes with the extractant in the organic phase. Depending upon the solution composition, commercial extractants like Cyanex 272, D2EPHA and PC 88A should primarily be used for commercial extraction processes and also the efficient management of their combination could address various separation issues associated with cobalt bearing scrap.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.1
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• pp.91-97
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• 2016

This study is concerned about the process capability index in single process. Previous process capability indices have been developed for the consistency with the nonconforming rate due to the process target value and skewness. These indices calculate the process capability by measuring one spot in an item. But the only one datum in an item reduces the representativeness of the item. In addition to the lack of representativeness, there are many cases that the uniformity of the item such as flatness of panel is absolutely important. In these cases, we have to measure several spots in an item. Also the nonconforming judgment to an item is mainly due to the range not due to the standard variation or the shift from the specifications. To imply the uniformity concept to the process capability index, we should consider only the variation in an item. It is the within subgroup variation. When the universe is composed of several subgroups, the sample standard deviation is the sum of the within subgroup variation and the between subgroup variation. So the range R which represents only the within subgroup variation is the much better measure than that of the sample standard deviation. In general, a subgroup contains a couple of individual items. But in our cases, a subgroup is an item and R is the difference between the maximum and the minimum among the measured data in an item. Even though our object is a single process index, causing by the subgroups, its analytic structure looks like a system process capability index. In this paper we propose a new process capability index considering the representativeness and uniformity.

• The Journal of the Korea Contents Association
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• v.15 no.6
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• pp.62-72
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• 2015

The purpose of this study is to discuss new entrants' role in a business ecosystem and to analyze growth strategies of a new entrant in the movie industry. When participants of a business ecosystem complement one another with their own unique capabilities, they can coevolve and develop the business ecosystem. Especially, new entrants armed with competitive advantages are the key success factor for improving robustness of business ecosystem. Korean movie industry is dominated by a few large enterprises and thereby threatening fair trade. In an effort to encourage new entrants in the industry, this study analyzed success factors of a film distributor, Next Entertainment World(NEW). The success factors include unique criteria in selecting scenarios, quality management, rapid decision making process, and competent management team. Implications for the results and the future study are discussed.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.213-216
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• 2009

WGS(Water Gas Shift)반응은 일산화탄소(CO)를 이산화탄소($CO_2$)로 전환하는 반응으로 일체형 수소생산시스템의 실현을 위한 고순도 수소생산에 있어서 중요한 단계이다. WGS 반응은 열역학적 평형을 고려하여 고온전이반응(HTS: High Temperature Shift)과 저온전이반응(LTS: Low Temperature Shift) 두 단계 반응으로 진행된다. 두 단계 공정의 통합을 위해 낮은 온도에서 높은 활성을 갖는 WGS 반응용 촉매 개발이 필요하다. 최근 낮은 온도에서 높은 활성을 갖는 귀금속 촉매에 다양한 담체를 적용시킨 연구가 활발히 진행되고 있다. 선행 연구 결과, Ce-$ZrO_2$ 구조는 Ce/Zr 비에 따라 다양한 특성 변화를 관찰하였다. 따라서 낮은 온도에서 높은 활성을 갖는 WGS 반응용 촉매 제조를 위해 환원성 담체인 $CeZrO_2$에 Pt 을 담지시켜 성능을 평가하였다. 제조된 모든 담체는 공침법(Co-precipitation)으로 제조 하였으며 $500^{\circ}C$에서 6시간 소성하였다. 제조된 담체에 백금(Pt)을 함침법(Incipient Wetness Impregnate)으로 담지시켰다. 특성분석은 BET를 이용하여 표면적을 측정하였다. 촉매 반응 실험조건은 $200^{\circ}C{\sim}400^{\circ}C$ 온도범위에서 기체공간속도(GHSV: Gas Hourly Space Velocity) 45,000 ml/$h{\cdot}g-cat$ 으로 혼합가스($H_2$:60%, $N_2$:20%,$CH_4$:1%,CO:9%,$CO_2$:10%)를 흘려 반응 후 배출되는 가스를 Micro-Gas Chromatography 를 이용하여 측정하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.338-338
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• 2012

유기물을 이용하여 제작한 비휘발성 메모리 소자는 저전력으로 구동하고 공정이 간단할 뿐만아니라 구부림이 가능한 소자를 만들 수 있다는 장점 때문에 많은 연구가 진행되고 있다. 비록 다양한 유기물 나노 클러스터를 포함한 고분자 박막을 사용한 비휘발성 메모리 소자에 대한 연구가 많이 진행되었으나 [6,6]- phenyl-C85 butyric acid methyl ester (PCBM) 나노 클러스터가 고분자 박막에 분산되어 있는 메모리 소자의 휘어짐에 따른 전기적 특성의 변화에 대한 것은 연구되지 않았다. 본 연구에서는 스핀코팅 방법으로 PCBM 나노 클러스터가 polymethyl methacrylate (PMMA) 박막에 분산되어 있는 소자를 제작하여 휘어짐에 따른 전기적 특성의 변화에 대한 관찰을 수행하였다. 소자를 제작하기 위해서 PCBM 나노 클러스터와 PMMA를 클로로벤젠에 용해시킨 후에 초음파 교반기를 사용하여 PCBM 나노 클러스터와 PMMA가 고르게 섞인 용액을 형성하였다. 전극이 되는 Indium Tin Oxide (ITO) 유리기판 위에 PCBM 나노 클러스터와 PMMA가 섞인 용액을 스핀 코팅하고, 열을 가해 용매를 제거하여 PCBM 나노 클러스터가 PMMA에 분산되어 있는 박막을 형성하였다. PCBM 나노 클러스터가 분산된 PMMA 박막 위에 Al을 상부전극으로 열증착하여 메모리 소자를 완성하였다. 제작한 소자의 휘어짐에 따른 전기적 특성을 알아보기 위해서 10 mm 의 반지름을 갖는 휘어진 홀더를 제작 한 후에 소자를 구부리기 전과 후의 전류-전압 (I-V)을 각각 측정하였다. 또한 소자의 휘어짐에 따른 포획된 전하유지능력과 안정성을 알아보기 위해 $1{\times}105$번의 반복적인 읽기 전압을 가한 후 전기적 특성을 측정하였다. 실험 결과들을 토대로 메모리 소자의 휘어짐에 따른 전기적 특성 변화에 대해서 분석하고 그 원인에 대해서 규명하였다.

• Journal of Engineering Education Research
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• v.3 no.2
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• pp.3-13
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• 2000

The paper has analyzed and summarized about the theoretical problem occurred in the CAQC, and has developed the learning model focused on the histogram as a case study. The range of study is to systematize the basic method of histogram generally used, and to make step by step procedures under the interactive relation with the improvement of the theory that must be added in case of the calculation by the aided of MS-Excel software. A histogram is the theory to understand the population distribution from which samples are extracted, so alternative methods are presented to estimate the population shape through an experiment and a practice. In order to enlarge the application area of the histogram in the factory, the theory of normal test, the criteria of process capability index and the probability calculation of PPM are added to the histogram. The learning model of CAQC education is proposed that is consistent with the target of histogram to control and search the cause of item defectives fast and correctly.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.05a
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• pp.143-143
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• 2001

조선 산업에서의 이익 극대화를 위해서는, 공기 단축을 통한 매출 증대, 주어진 생산 자원(인력, 설비 등)의 효율적인 이용을 통한 생산비 절감이 필수적인 사안이다. 다시 말하면, 효율적인 자원의 이용으로 선박의 건조 공기를 줄임으로써 조선 산업에서의 이익 극대화를 도모할 수 있고 이는 효과적인 생산 계획과 관리를 통해 얻을 수 있다. 조선 산업에서의 생산 계획과 관리는 내업, 선행, 선내 등 선박 건조의 전 과정에서 이루어지고 있는데, 조선 산업은 타 산업에 비해 환경변화에 따른 단기간의 불확실성은 비교적 적은 반면에, 가공, 절단, 조립, 의장, 도장, 선행탑재, 탑재, 안벽 작업 등 다단계 제조 프로세스가 장기간에 걸쳐 상당히 복잡하게 구성되어 있다. 또한, 유연하게 적용할 수 있는 인적자원과 공정순서, 그리고 각종 시간적 공간적 자원 제약 등으로 인하여 효과적이고 일관된 생산 계획을 신속하게 수립하기가 어려울 뿐만 아니라, 주문 생산 방식이기 때문에 정확한 일정계획 데이터의 생성도 어려운 실정이다. 본 연구는, 조선의 혁신적인 생산관리 능력 향상을 지원하기 위한 "조선 통합 생산계획 시스템 개발" 에 관련된 연구이다. 본 연구에서는 조선 생산계획에 적합한 일정계획 방법론 및 엔진 소프트웨어를 활용하고 총체적인 생산계획 및 일정계획 업무의 개념 재정립을 통하여, 통합 최적화를 실시간에 지원하는 조선 최적 일정계획 시스템 구축에 궁극적인 목적을 두고 있다. 이를 위해 본 연구에서는 조선 프로세스와 일정계획 업무규칙을 분석하고 이를 바탕으로 "조선 최적 일정계획 시스템"을 개발하였다. 조선 최적 일정계획 시스템은 블록, PE, 탑재, 선내 단계의 일정계획 최적화와 What-if Simulation을 지원하기 위하여 ILOG Solver/scheduler로 구현하였으며, 구현된 시스템에 대해 실제 계획에서 사용하는 데이터를 대상으로 다양한 최적화 기능에 대한 실험을 실시하였다. 실제 데이터를 이용한 실험결과, 풀이시간과 최적해 측면 모두에서 비교적 만족할 만한 결과를 보여주었다.교적 만족할 만한 결과를 보여주었다.

• Communications of Mathematical Education
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• v.22 no.4
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• pp.489-503
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• 2008

It is not an easy matter to develop problems which help students understand mathematical concepts correctly and precisely. The aim of this paper is to review the merits and demerits of three problem types (i.e. one answer problems, multiple choice problems and proof problems) and to suggest some points that should be taken into consideration in problem making. First, we presented the merits and demerits of three types of problems by examining actual examples. Second, we discussed some examples of misleading problems and the ways to make desirable ones. Finally, on the basis of our examination and discussion, we suggested some points that should be kept in mind in problem making. The major suggestions are as follows; i) In making one answer problems, we should consider the possibility of sitting a solution by wrong precesses, ii) In formulating multiple choice tests which are layered for their easiness of grading, we should take into account the importance of checking whether the students are fully understanding the concepts, iii) We may depend on the previous research result that multiple choice tests for proof problems can be helpful for the students who have insufficient math background. Besides those suggestions, we made an overall proposal that we should endeavor to find ways to implement the demerits of each problem type and to develop instructive problems that can help students understanding of math.

• Journal of Korean Society for Quality Management
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• v.49 no.3
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• pp.327-340
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• 2021

Purpose: The purpose of this study is to propose a system predicting whether an electricity distribution system is abnormal by analyzing the temperature of the deteriorated system. Traditional electricity distribution system abnormality diagnosis was mainly limited to post-inspection. This research presents a remote monitoring system for detecting thermal images of the deteriorated electricity distribution system efficiently hereby providing safe and efficient abnormal diagnosis to electricians. Methods: In this study, an object detection algorithm (YOLOv5) is performed using 16,866 thermal images of electricity distribution systems provided by KEPCO(Korea Electric Power Corporation). Abnormality/Normality of the extracted system images from the algorithm are classified via the limit temperature. Each classification model, Random Forest, Support Vector Machine, XGBOOST is performed to explore 463,053 temperature datasets. The process capability index is employed to indicate the quality of the electricity distribution system. Results: This research performs case study with transformers representing the electricity distribution systems. The case study shows the following states: accuracy 100%, precision 100%, recall 100%, F1-score 100%. Also the case study shows the process capability index of the transformers with the following states: steady state 99.47%, caution state 0.16%, and risk state 0.37%. Conclusion: The sum of caution and risk state is 0.53%, which is higher than the actual failure rate. Also most transformer abnormalities can be detected through this monitoring system.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.2
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• pp.18-27
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• 2019

The process control methods based on the statistical analysis apply the analysis method or mathematical model under the assumption that the process characteristic is normally distributed. However, the distribution of data collected by the automatic measurement system in real time is often not followed by normal distribution. As the statistical analysis tools, the process capability index (PCI) has been used a lot as a measure of process capability analysis in the production site. However, PCI has been usually used without checking the normality test for the process data. Even though the normality assumption is violated, if the analysis method under the assumption of the normal distribution is performed, this will be an incorrect result and take a wrong action. When the normality assumption is violated, we can transform the non-normal data into the normal data by using an appropriate normal transformation method. There are various methods of the normal transformation. In this paper, we consider the Box-Cox transformation among them. Hence, the purpose of the study is to expand the analysis method for the multivariate process capability index using Box-Cox transformation. This study proposes the multivariate process capability index to be able to use according to both methodologies whether data is normally distributed or not. Through the computational examples, we compare and discuss the multivariate process capability index between before and after Box-Cox transformation when the process data is not normally distributed.