• 품질경영학회지
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• 제27권4호
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• pp.266-279
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• 1999

Today, Companies are facing the harsh realities of a competitive environment. This is no time for revolutionary change. Instead, Companies are instituting revolutionary change meant to have impact within a very short time frame. Bold steps are required to lead the industry into a future of improved efficiency and significant productivity gains. GE, as well as Intel, Motorola, and other companies adopted a program called Six Sigma, in order to make fundamental changes in the way the company operated to fulfill customers'expectations. Six sigma reduces the occurrence of defects from a 3 sigma level of 66,800 defects per million to a 6 sigma level-less than 4defects per million. The goals and metrics of the company's Six Sigma process clearly have had a positive effect on customer satisfaction and customer perception of the company.

• 산업경영시스템학회지
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• 제21권45호
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• pp.237-246
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• 1998

In most statistical process control(SPC), control charts are used in which samples are taken and a suitable statistic is determined and plotted. In these control charts, control limits, ${\mu}{\pm}textsc{k{\sigma}}$, from which a decision is made are mostly ${\mu}{\pm}3{\sigma}$ and current literature in control charts are mainly concerned with detecting a shift in the mean. Therefore, when $\sigma$ is increased considerably after a long time, using control limits set at the first time causes a great deal of economic loss. In this paper the solutions to determine new control limits which maximizes the profit per unit produced and reduce $\sigma$ to economically optimal level for a certain cost when $\sigma$ is increased due to process deterioration are proposed. By applying new control limits, $\alpha$ error decreases considerably compared to apply initial control limits when $\sigma$ is increased due to process deterioration. Therefore, false alarm investigation cost drops down to the level of initial a error. And also this solution provides useful information regarding replacement of a process when the process is reviewed regularly.

• Bulletin of the Korean Chemical Society
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• 제6권5호
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• pp.277-279
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• 1985

Orbital interactions of the types, ${\sigma}-{\pi},\;{\sigma}^*-{\pi},\;{\sigma}-{\pi}^*\;and\;{\sigma}^*-{\pi}^*$ are investigated for the rotamers of ${\alpha}$-X-acetones (X = F and Cl) using STO-3G method of calculation. It was found that the interactions are possible only in gauche forms, and the ${\sigma}^*-{\pi}^*$ interactions are in general greater than the $\sigma-\pi$ interactions due to the greater overlap, in spite of the greater energy gap involved; the greater ${\sigma}^*-{\pi}^*$ interaction causes greater lowering of ${\pi}^*$ level relative to the lowering of ${\sigma}$ in the ${\sigma}-{\pi}$ interaction so that both ${\sigma}-{\pi}^*$ and $n-{\pi}^*$ interactions are enhanced in the gauche forms. The extra stability of the gauche form and the red shift in the $n-{\pi}^*$ transition are thus found to be natural corollaries of the greater ${\sigma}^*-{\pi}^*$ interaction in the gauche forms.

• 한국건설관리학회논문집
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• 제6권4호
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• pp.133-141
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• 2005

본 연구는 6시그마 경영기법의 건설업에 대한 적용 성과를 분석하고자 수행하였다. 이를 위하여 S 건설업체의 조직 및 인력별 6시그마 적용 프로젝트의 품질비용을 분석하고, S 건설업체의 임직원들을 대상으로 6시그마 경영에 대한 설문조사를 실시하였다. 위와 같은 목적과 방법에 따라 진행된 본 연구의 결과를 요약하면 다음과 같다. : 1) S 건설업체의 6시그마 경영기법의 도입은 03년과 04년에 걸쳐 258건의 프로젝트를 수행하면서 품질비용 절감효과를 발생시켰다. 또한, S 건설업체는 6시그마 적용 전 시그마 수준이 업무 분야별 평균 2.8이었으나, 적용 후 평균 3.6으로 향상되었다. 특히, 공사 관리 분야는 적용 전 1.3시그마에서 적용 후 2.6시그마로 매우 높은 향상율을 보였다. 2) 6시그마 경영활동에 대한 업무수행 기대성과에 관한 분석결과 대다수의 직원들은 6시그마 경영이 비용절감 효과가 있으며, 품질향상에 도움이 되는 것으로 인식하고 있었다. 그러나 현 시점은 S 건설업체에 있어 6시그마 경영기법의 도입 초기단계이므로 업무처리의 효율성에는 큰 효과를 보이지 않는 것으로 조사되었다.

• 응용통계연구
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• 제23권6호
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• pp.1035-1045
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• 2010

기업이 제공하는 제품 서비스는 시장에 소개되기 전에 기술적 검증과 사용 환경에 대한 객관적인 검토를 거쳐야 한다. 이를 위해 각 기업에서는 경험적으로 확인된 다양한 절차와 방법을 이용하여 올바른 상품력(Power of Product Service)을 판단할 수 있는 객관적인 방법을 연구하고 있다. 상품력은 특정 기능 또는 개별 특성에 대한 평가 보다는 다양한 고객의 요구 사항에 기초한 여러 특성이나 기능들을 동시에 반영할 수 있을 때 바람직하다고 할 수 있다. 고승곤 (2008)은 품질 평가 방법인 시그마 수준(Sigma Level)을 확장하여 다양한 특성들을 종합적으로 반영할 수 있는 MSL(Multi-characteristic Sigma level)을 소개하였다. 본 논문에서는 MSL과 새로운 고객 선호 일치도를 반영하는 BOI(Blue Ocean Index)를 이용한 이동 통신 단말기의 상품력 평가 방법을 확인해 보고 이를 통해 실무적 그리고 통계적으로 고려해야 할 사항들을 검토해 보고자 한다.

• 품질경영학회지
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• 제29권3호
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• pp.166-176
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• 2001

This paper considers a six sigma project for reducing the color variation of the monitor materials in a chemical plant. The project follows a disciplined process of five macro phases: define, measure, analyze, improve, and control (DMAIC). A process map is used to identify process input variables. Three key process input variables are selected by using an input variable evaluation table; a melting pressure, a coloring agent, and a DP color variation. DOE is utilized for finding the optimal process conditions of the three key process input variables. The sigma level of defects rate becomes a 4.58 from a 2.0 at the beginning of the project.

• 품질경영학회지
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• 제31권1호
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• pp.123-131
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• 2003

This paper considers a six sigma project for reducing the defects rate of the welding process in manufacturing firms. The project follows a disciplined process of five macro phases. define, measure, analyze, improve and control(DMAIC). The need of customers is used to identify critical to quality(CTQ) of project. And a process map is used to identify process input factors of CTQ. Four key process input factors are selected by using an input factor evaluation of teams; an interval of welding, an abrasion, an electric current and a moving freely. DOE is utilized for finding the optimal process conditions of the three key process input factors. Another one key input factor improved to welding machine. The six sigma level of defects rate becomes a 2.01 from a 1.61 at the beginning of the project.

• 품질경영학회지
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• 제34권1호
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• pp.1-12
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• 2006

This paper presents a six sigma project for improving gate painting quality in a medium-sized automotive part company. The project follows a disciplined process of five macro phases: Define, Measure, Analyze, Improve, and Control. A CTQ(critical to quality) is determined based on COPQ(cost of poor quality) analysis, and a process map is utilized for identifying process input variables. Three KPIV s(key process input variable) are selected; Painting Temperature, Painting Quantity, and Painting Viscosity, and DOE(design of experiments) is utilized for finding the optimal process conditions for three KPIVs. MINITAB software is used for data analyses and DOE. The sigma level of defects rate has improved from 2.93 to 3.66.

• 한국산업정보학회논문지
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• 제8권1호
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• pp.1-8
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• 2003

There are many statistical evaluation methods, A more technical Perspective is needed in estimating the effect of the Manufacturing Process for improving the Productivity, Process network analysis is a technique which has the potentiality for a wire use to improve the manufacturing process which other techniques can't be used to analyze effectively. The concept of six sigma plan was developed and pursued by Motorola to improve the process control. The goals of six sigma plan are established on the foundation of customer satisfaction such as Quality, Cost Delivery and Service This paper presents how to improve the manufacturing process by statistical process control for the evaluation of six sigma level.

• 열처리공학회지
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• 제7권1호
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• pp.61-71
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• 1994

This study is to investigate the stress distributions, crystal orientations and magnetic properties during die-upsetting according to working temperature of Nd-Fe-B-Cu alloys. The stress distributions in the specimens during compressing process were calculated by a finite element method program(SPID). The calculated stresses were effective stress (${\sigma}_{eff}$), compression stress(${\sigma}_z$), radial direction stress(${\sigma}_r$) rotational direction stress(${\sigma}_e$) and shear stress(${\tau}_{rz}$). The stress distributions of ${\sigma}_z$, obtained by a computer simulation showed that the stress components causing the magnetic alignment during die-upsetting of the cast magnets were very high at the center-part of a specimen, and decreased toward the periphery-part of a specimen. In view of the above results the magnetic properties should be better at the center-part of a specimen than any other parts. But the measured magnetic properties were better at the mid-part. These results should be due to the fact that the specimens were casted. Normally the magnetic properties are affected by the casting process as well as by the stress levels. ${\sigma}_r$, ${\sigma}_e$ are thought to affect the liquid phase flowing and domain patterns, respectively. The influence of ${\tau}_{rz}$ was trivial, ${\sigma}_{eff}$ distributed similar throughout the specimen. The Nd-rich phase appeared at the peripheral of the specimen where the stress level of ${\sigma}_r$, ${\sigma}_z$, was low or the stress level of ${\sigma}_e$ was high. The Nd-rich phase was squeezed out during die-upsetting. This phase had an effect on the crystal orientation and grain growth. The stress distributions of alloy were irregular at the parts of the specimen where the die contacted with specimen.