• 품질경영학회지
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• 제48권1호
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• pp.69-86
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• 2020

Purpose: This study aims to determine the optimal conditions for the spot welding process that mechanically connects the case of a cylindrical secondary battery and the negative tab. Methods: We use 33 factorial design to derive the optimal conditions for the spot welding process. The pulling strength, the cross-sectional area of nugget, and the shock test life are selected as response variables, which can represent the resistance welding quality. The input variables are selected as the welding time, welding voltage, and pressure, which are the controllable factors in the spot welding process. Results: The main effects of welding time and welding voltage and the interaction effect of welding time and welding voltage are significant. Conclusion: The optimal conditions for the spot welding process to mechanically join the negative electrode tab of the cylindrical secondary battery and the battery case are developed. The result shows that the pulling strength is increased by 44% compared to before improvement under optimal conditions.

• 한국환경과학회지
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• 제25권6호
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• pp.767-787
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• 2016

In this study, we analyzed on-site monitoring data for 15 tributaries in Geumho watersheds for 3 years (2011-2013) in order to sort out priorities on water quality characteristics and improvement. As a result of estimating contribution to contamination of the tributary rivers, Dalseocheon showed the highest load densities, despite the smallest watershed area, with 22.7% $BOD_5$, 30.7% $COD_{Mn}$, 31.3% TOC and 47.6% TP. After conducting PCA (principal component analysis) and FA (factor analysis) to analyze water quality characteristics of the tributary rivers, the first factor was classified as $COD_{Mn}$, TOC, EC, TP and $BOD_5$, the second factor as pH, Chl-a and DO, the third factor as water temperature and TN, and the fourth factor as SS and surface flow. In addition, arithmetical sum of each factor's scores based on grading criteria revealed that Dalseocheon and Namcheon were classified into Group A for their highest scores - 96 and 93, respectively -, and selected as rivers that require water environmental management measures the most. Also, water environmental contamination inspection showed that Palgeocheon had the most number of aquatic factors to be controlled: $BOD_5$, $COD_{Mn}$, SS, TOC, T-P, Chl-a, etc.

• 대한토목학회논문집
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• 제30권5B호
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• pp.429-435
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• 2010

본 연구에서는 레이더 강우자료의 품질평가를 위해 통계학 분야의 분산분석과 유사한 방법론을 제안하였다. 이 방법은 자료가 가지고 있는 편의로 인한 오차 및 변동성으로 인한 오차를 구분하여 나타내도록 한다. 제안된 방법론은 두 개의 호우사상에 적용하여 평가하였다. 그 결과 레이더 원자료의 경우는 편의로 인한 오차가 전체 오차의 대부분을 차지하는 반면, 품질 향상된 자료의 경우에는 편의로 인한 오차가 상대적으로 크게 줄어드는 것을 확인하였다. 그러나 변동성으로 인한 오차는 품질 향상 후 오히려 증가하였음을 파악하였다. 본 연구에서 제안된 방법론은 주어진 호우사상을 품질향상 단계별로 자료의 품질을 평가하는 데는 유효하나, 여러 호우사상의 품질을 비교하는데 한계를 가짐을 확인하였다. 보다 일반적인 적용을 위해서는 이에 대한 보완이 필요한 것으로 나타났다.

• International Journal of Reliability and Applications
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• 제7권1호
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• pp.27-39
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• 2006

Many real world cases in material failure analysis do not follow perfectly the normal distribution. Forcing of the normality assumption may lead to inaccurate predictions and poor product quality. We examine the failure process of the internal bond (IB or tensile strength) of medium density fiberboard (MDF). We propose a forced censoring technique that closer fits the lower tails of strength distributions and better estimates extremely smaller percentiles, which may be valuable to continuous quality improvement initiatives. Further analyses are performed to build an accelerated common-shaped Weibull model for different product types using the $JMP^{(R)}$ Survival and Reliability platform. In this paper, a forced censoring technique is implemented for the first time as a software module, using $JMP^{(R)}$ Scripting Language (JSL) to expedite data processing, which is crucial for real-time manufacturing settings. Also, we use JSL to automate the task of fitting an accelerated Weibull model and testing model homogeneity in the shape parameter. Finally, a package script is written to readily provide field engineers customized reporting for model visualization, parameter estimation, and percentile forecasting. Our approach may be more accurate for product conformance evaluation, plus help reduce the cost of destructive testing and data management due to reduced frequency of testing. It may also be valuable for preventing field failure and improved product safety even when destructive testing is not reduced by yielding higher precision intervals at the same confidence level.

• International Journal of Quality Innovation
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• 제5권2호
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• pp.63-69
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• 2004

This is an R&D project on design optimization of the inner shield of the Omega color picture tube at Samsung SDI in Korea. This was an R&D project which basically used the IDOV (Identify, Design, Optimize, Validate) process for Six Sigma implementation. Most Six Sgima projects use the process of DMAIC (Define, Measure, Analyze, Improve, Control). However, this project introduces a new cycle, RDIDOV (Recognize, Define, and IDOV). Here CPT means Color Picture Tube. Sam sung SDI is one of the two companies which began Six Sigma in Korea. This case study shows a good example how an R&D Six Sigma project can be usefully employed in manufacturing companies using a new process cycle.

• Communications for Statistical Applications and Methods
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• 제7권3호
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• pp.773-788
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• 2000

Statistical process control (SPC) and engineering process control (EPC) are based on different strategies for processes quality improvement. SPC reduces process variability by detecting and eliminating special causes of process variation. while EPC reduces process variability by adjusting compensatory variables to keep the quality variable close to target. Recently there has been needs for a process control proceduce which combines the tow strategies. This paper considers a combined scheme which simultaneously applies SPC and EPC techniques to reduce the variation of a process. The process model under consideration is an integrated moving average(IMA) process with a step shift. The EPC part of the scheme adjusts the process back to target at every fixed monitoring intervals, which is referred to a repeated adjustment scheme. The SPC part of the scheme uses an exponentially weighted moving average(EWMA) of observed deviation from target to detect special causes. A Markov chain model is developed to relate the scheme's expected cost per unit time to the design parameters of he combined control scheme. The expected cost per unit time is composed of off-target cost, adjustment cost, monitoring cost, and false alarm cost.

• Journal of the Korean Data and Information Science Society
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• 제19권4호
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• pp.1191-1200
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• 2008

Recently classroom monitoring is becoming important since the lecture is being held in the classroom and academic institutions are interested in the quality assurance. Some institutions have adopted ISO 9000 systems and constructed monitoring system through measurement, analysis and improvement. In this study quality assurance problems in academic institutions and the requirements of ISO 9001:2000 will be briefly discussed. Next we will investigate how to monitor the lecture in the classroom(in-class) using statistical process control techniques such as control charts. Then case study will be given to illustrate the technique to use appropriate statistics. Finally how to monitor the learning process during in-class and after-class will be proposed.

• 패션비즈니스
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• 제18권4호
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• pp.125-137
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• 2014

This study aims to the recognize the importance of uniform design and provide empirical data to companies after getting the effects of uniform design in cosmetics companies on service quality perception and customer satisfaction. For this, a preliminary survey was conducted against 30 college women (aged 20s) from 'K' University, and effective samples were obtained from 250 people. In terms of a research method, collected data were coded and analyzed using SPSS. The respondents' characteristics were analyzed using descriptive statistics. For reliability analysis, Cronbach's ${\alpha}$ was used. For a validity test, factor analysis was performed. In addition, correlation analysis was carried out to examine multicollinearity among variables. The analysis results found that the characteristics of uniform design have a positive effect on service quality and customer satisfaction. Among the characteristic of uniform design, however, functionality wasn't confirmed in a relational test. This kind of result was obtained because the uniform was mostly analyzed from customers' perspective, not from the wearer's standpoint. It is expected that the study results would be helpful in establishing brand identity through the improvement of the importance of uniform design.

• 대한기계학회논문집A
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• 제30권6호
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• pp.728-733
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• 2006

The reduction of the Vehicle interior noise has been the main interest of NVH engineers. The driver's perception on the vehicle noise is affected largely by psychoacoustic characteristic of the noise as well as the SPL. In particular, the HVAC sound among the vehicle interior noise has been reflected sensitively in the side of psychology. In previous study, we have developed to verify identification of source for the vehicle HVAC system through multiple-dimensional spectral analysis. Also we carried out objective assessments on the vehicle HVAC noises and subjective assessments have been already performed with 30 subjects. In this study, the linear regression models were obtained for the subjective evaluation and the sound quality metrics. The regression procedure also allows you to produce diagnostic statistics to evaluate the regression estimates including appropriation and accuracy. Appropriation of regression model is necessary to $R^2$ value and F-value. And testing for regression model is necessary to independence, homoscedesticity and normality. Also we selected optimum layout of damping material using Taguchi method. As a result of application, sound quality is improved more quietly, powerfully, even though costly, and smoothly.

• International Journal of Quality Innovation
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• 제3권2호
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• pp.13-28
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• 2002

Higher efficiency and effectiveness of Research & Development phases can be attained using advanced statistical methodologies. In this work statistical methodologies are combined with a deterministic approach to engineering design. In order to show the potentiality of such integration, a simple but effective example is presented. It concerns the problem of optimising the performances of a paper helicopter. The design of this simple device is not new in quality engineering literature and has been mainly used for educational purposes. Taking full advantage of fundamental engineering knowledge, an aerodynamic model is originally formulated in order to describe the flight of the helicopter. Screening experiments were necessary to get first estimates of model parameters. Subsequently, deterministic evaluations based on this model were necessary to set up further experimental phases needed to search (or a better design. Thanks to this integration of statistical and deterministic phases, a significant performance improvement is obtained. Moreover, the engineering knowledge かms out to be developed since an explanation of the “why” of better performances, although approximate, is achieved. The final design solution is robust in a broader sense, being both validated by experimental evidence and closely examined by engineering knowledge.