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퍼지논리를 이용한 수평 머시닝 센터의 열변형 오차 모델링
이재하,이진현,양승한,Lee, Jae-Ha,Lee, Jin-Hyeon,Yang, Seung-Han 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.10
As current manufacturing processes require high spindle speed and precise machining, increasing accuracy by reducing volumetric errors of the machine itself, particularly thermal errors, is very important. Thermal errors can be estimated by many empirical models, for example, an FEM model, a neural network model, a linear regression model, an engineering judgment model, etc. This paper discusses to make a modeling of thermal errors efficiently through backward elimination and fuzzy logic strategy. The model of a thermal error using fuzzy logic strategy overcomes limitation of accuracy in the linear regression model or the engineering judgment model. It shows that the fuzzy model has more better performance than linear regression model, though it has less number of thermal variables than the other. The fuzzy model does not need to have complex procedure such like multi-regression and to know the characteristics of the plant, and the parameters of the model can be mathematically calculated. Also, the fuzzy model can be applied to any machine, but it delivers greater accuracy and robustness.
이재하 ( Lee Jae Ha ),한덕희 ( Han Deog Hui ) 한국파생상품학회 2002 선물연구 Vol.10 No.2
This study explores hedging strategies that use the KTB futures to hedge the price risk of the KTB spot portfolio. The study establishes the price sensitivity, risk-minimization, bivariate GARCH(1,1) models as hedging models, and analyzes their hedging performances. The sample period covers from September 29, 1999 to September 18, 2001. Time-matched prices at 11:00(11:30) of the KTB futures and spot were used in the analysis. The most important findings may be summarized as follows. First, while the average hedge ration of the price sensitivity model is close to one, both the risk-minimization and GARCH model exhibit hedge ratios that are substantially lower than one. Hedge rarios tend to be greater for daily data than for weekly data. Second, for the daily in-sample data, hedging effectiveness is the highest for the GARCH model with time-varying hedge ratios, but the risk-minimization model with constant hedge ratios is not far behind the GARCH model in its hedging performance. In the case of out-of-sample hedging effectiveness, the GARCH model is the best for the KTB spot portfolio, and the risk-minimization model is the best for the corporate bond portfolio. Third, for daily data, the in-sample hedge shows a better performance than the out-of-sample hedge, except for the risk-minimization hedge against the corporate bond portfolio. Fourth, for the weekly in-sample hedges, the price sensitivity model is the worst and the risk-minimization model is the best in hedging the KTB spot portfolio. While the GARCH model is the best against the KTB +corporate bond portfolio, the risk-minimization model is generally as good as the GARCH model. The risk-minimization model performs the best for the weekly out-of-sample data, and the out-of-sample hedges are better than the in-sample hedges. Fifth, while the hedging performance of the risk-minimization model with daily moving window seems somewhat superior to the traditional risk-minimization model when the trading volume increased one year after the inception of the KTB futures, on the average the traditional model is better than the moving-window model. For weekly data, the traditional model exhibits a better performance. Overall, in the Korean bond markets, investors are encouraged to use th simple risk-minimization model to hedge the price risk of the KTB spot and corporate bond portfolios.
뷰티서비스 종사자들의 감정노동과 레포형성이 직무만족에 미치는 영향
이재하(Jae Ha Lee),박서연(Seo Yeon Park) 한국인체미용예술학회 2015 한국인체미용예술학회지 Vol.16 No.2
Recently, many individuals have shown a great interest in Emotional Labor. People have begun to think that we did not show enough consideration to other people, especially for the emotional labor in the service sector. The purpose of this study is to examine the causal correlation between Emotional Labor, Rapport and Job satisfaction of beauty service workers. The research model for this study is used several variables as a parameter and established three hypotheses. In order to verify the hypotheses based on the research model, 251 people who work in beauty service salons were surveyed. A variety of statistical methods - correlation analysis, factor analysis, regression analysis- were used to verify the hypothesis. Analyzing the hypothesized model and following the statistical procedure, it could be assured that there was a positive correlation with emotional labor, rapport, and job satisfaction. Among the parameters, the factor of Rapport had a greater effect than Emotional labor on Job Satisfaction. However, the coefficient of correlation between those variables was not higher than the existing research results.