• Journal of Welding and Joining
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• v.27 no.1
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• pp.65-70
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• 2009

Ir-192 radiation sealed sources are widely employed to the therapeutic applications as well as the non-destructive testing. Production of Ir-192 sources requires a delicate but robust welding technique because it is employed in a high radioactive working environment. A GTA(Gas Tungsten Arc) welding technique is currently well established for this purpose. However, this welding method requires a frequent replacement of the electrode, which results in the delay of the production to take a preparatory action such as to isolate the radiation sources from the working place before getting access to the welding machine. Hence, a resistance welding technique is considered as an alternative method of the GTA welding technique. The advantages of resistance welding are high welding speed and high-rate production. Also it has very long life of electrode comparing to GTA welding. In this study, the resistance welding system and proper welding conditions were established for sealing Ir-192 source capsule. As a results of various experiments, it showed that electrode displacement can be employed as a indicator to predict welding quality. We proposed two mathematical models(linear and curvilinear) to estimate electrode displacement with process parameters such as applied force, welding current and welding time by using regression analysis method. Predicting results of both linear and curvilinear model were relatively good agreement with experiment.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.16 no.1
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• pp.1-8
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• 2010

Purpose : This study aimed to examine the relationships among five clinical measures for functional alignment of the lower extremity. Methods : Thirty healthy subjects (15 males and 15 females) were recruited for the study. The five clinical measures of functional alignment of the lower extremity included navicular drop, quadriceps angle, internal rotation of hip, and anterior and lateral pelvic tilt angles. The level of navicular drop was calculated by the difference between the height of the navicular bone in the sitting (non-weight bearing) and standing (weight bearing) positions. The quadriceps angle and internal rotation of hip were measured using a standard goniometer with photographic markers while the subjects were lying in a prone position on a table with their knee at $90^{\circ}$ flexion. Anterior and lateral pelvic tilt angles were determined using a inclinometer. Results : Correlation and a simple linear regression analysis were used to assess relationships between the clinical measures. There were significant correlations between navicular drop and quadriceps angle (p<.05), between navicular drop and internal rotation of hip (p<.05), and between quadriceps angle and internal rotation of hip (p<.01). In simple linear regression analysis, the navicular drop appeared to be a factor affecting the quadriceps angle and internal rotation of hip (p<.05). The findings suggest that navicular drop has a great impact on lower extremity alignment. Conclusion : This study might help us to examine lower extremity function and clarify its role as a potential injury risk factor.

• Journal of Korean Society of Transportation
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• v.29 no.2
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• pp.101-109
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• 2011

In most of the urbanized cities, socio-economic attributes tend to cluster as patterns of similarity in space, namely spatial autocorrelation, by agglomeration forces. The classical linear regression model, the most frequently adopted in the trip generation step, cannot sufficiently represent this effect. In order to take into account the effect properly, we need a model which adequately deals with the spatial dependence patterns. In this study, the Geographically Weighted Regression (GWR) model is adopted as an alternative method for the local analysis of relationships in multivariate data sets; that is GWR extends this traditional regression framework by estimating local rather than global parameters. This study shows the existence of spatial effects in the production and attraction of home base/non-home based trips through the GWR model using travel data collected in Daegu metropolitan area. Furthermore, LISA is employed to verify the fact that the local spatial autocorrelation exists.

• Journal of Korea Multimedia Society
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• v.13 no.12
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• pp.1786-1797
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• 2010

Automatic understanding of contents in document image is a very hard problem due to involvement with mathematically challenging problems originated mainly from the over-determined system induced by document segmentation process. In both academic and industrial areas, there have been incessant and various efforts to improve core parts of content retrieval technologies by the means of separating out segmentation related issues using semi-structured document, e.g., invoice,. In this paper we proposed classification models for text lines on invoice document in which text lines were clustered into the five categories in accordance with their contents: purchase order header, invoice header, summary header, surcharge header, purchase items. Our investigation was concentrated on the performance of machine learning based models in aspect of linear-discriminant-analysis (LDA) and non-LDA (logic based). In the group of LDA, na$\"{\i}$ve baysian, k-nearest neighbor, and SVM were used, in the group of non LDA, decision tree, random forest, and boost were used. We described the details of feature vector construction and the selection processes of the model and the parameter including training and validation. We also presented the experimental results of comparison on training/classification error levels for the models employed.

• Steel and Composite Structures
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• v.16 no.4
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• pp.437-454
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• 2014

The influence of spacers on the behaviour and ultimate capacity of intermediate length CFS open section columns under axial compression is investigated in this paper. The focus of the research lies in the cross- section predominantly, failed by distortional buckling. This paper made an attempt to either delay or eliminate the distortional buckling mode by the introduction of transverse elements referred herein as spacers. The cross-sections investigated have been selected by performing the elastic buckling analysis using CUFSM software. The test program considered three different columns having slenderness ratios of 35, 50 & 60. The test program consisted of 14 pure axial compression tests under hinged-hinged end condition. Models have been analysed using finite element simulations and the obtained results are compared with the experimental tests. The finite element package ABAQUS has been used to carry out non-linear analyses of the columns. The finite element model incorporates material, geometric non-linearities and initial geometric imperfection of the specimens. The work involves a wide parametric study in the column with spacers of varying depth and number of spacers. The results obtained from the study shows that the depth and number of spacers have significant influence on the behaviour and strength of the columns. Based on the nonlinear regression analysis the design equation is proposed for the selected section.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.4
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• pp.863-873
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• 2021

The purpose of this research is to examine the effect of family share ownership on the value of family companies and differences in the value of the firm - a family firm managed by family members and a family firm managed by non-family members. This research is also related to agency problems, namely share ownership and professional management can increase company value. This research uses the firm value as the dependent variable that is measured using Tobin's Q. Meanwhile the independent variable in this research is family ownership, and firm size is the control variable. The purposive sampling method was used to determine the sample for this research. The object of this research is 78 family companies listing on the Indonesian Stock Exchange in 2017. The hypothesis is tested by using multiple linear regression analysis which meets the analysis requirements test or classic assumption test. The results show that majority family ownership does not affect the value of the firm and there is no difference in the firm value of family firm led by family members and the firm value of family firm managed by non-family members.

• Journal of Intelligence and Information Systems
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• v.28 no.2
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• pp.19-31
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• 2022

In Machine learning, we usually divide the entire data into training data and test data, train the model using training data, and use test data to determine the accuracy and generalization performance of the model. In the case of models with low generalization performance, the prediction accuracy of newly data is significantly reduced, and the model is said to be overfit. This study is about a method of generating training data based on central limit theorem and combining it with existed training data to increase normality and using this data to train models and increase generalization performance. To this, data were generated using sample mean and standard deviation for each feature of the data by utilizing the characteristic of central limit theorem, and new training data was constructed by combining them with existed training data. To determine the degree of increase in normality, the Kolmogorov-Smirnov normality test was conducted, and it was confirmed that the new training data showed increased normality compared to the existed data. Generalization performance was measured through differences in prediction accuracy for training data and test data. As a result of measuring the degree of increase in generalization performance by applying this to K-Nearest Neighbors (KNN), Logistic Regression, and Linear Discriminant Analysis (LDA), it was confirmed that generalization performance was improved for KNN, a non-parametric technique, and LDA, which assumes normality between model building.

• Journal of Preventive Medicine and Public Health
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• v.38 no.4
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• pp.408-414
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• 2005

Objectives : The purpose of this study was to determine the impact of the sociodemographic and health characteristics on the out-of-pocket health spending of the individuals aged 20 and older in Korea. Methods : We used the data from the 2001 National Public Health and Nutrition Survey. The final sample size was 26,154 persons. Multiple linear regression models were used according to the age groups, that is, one model was used for those people under the age of sixty-five and the other was used for those people aged sixty-five and older. In these analyses, the expenditures were transformed to a logarithmic scale to reduce the skewness of the results. Results : Out-of-pocket health expenditures for those people under the age of 65 averaged 14,800 won per month, whereas expenditures for those people aged 65 and older averaged 27,200 won per month. In the regression analysis, the insurance type, resident area, self-reported health status, acute or chronic condition and bed-disability days were the statistically significant determinants for both age groups. Gender and age were statistically significant determinants only for the non-elderly. Conclusions : The findings from this study show that the mean out-of-pocket health expenditures varied according to the age groups and also several diverse characteristics. Thus, policymakers should consider the out-of-pocket health expenditure differential between the elderly and non-elderly persons. Improvement of the insurance coverage for the economically vulnerable subgroups that were identified in this study should be carefully considered. In addition, it is necessary to assess the impact of out-of-pocket spending on the peoples' health care utilization.

• Journal of Preventive Medicine and Public Health
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• v.56 no.3
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• pp.282-290
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• 2023

Objectives: This study aimed to evaluate the potential interaction between kidney function and the non-linear association between serum calcium levels and cardiovascular disease (CVD) mortality. Methods: This study included 8927 participants enrolled in the Dong-gu Study. Albumin-corrected calcium levels were used and categorized into 6 percentile categories: <2.5th, 2.5-25.0th, 25.0-50.0th, 50.0-75.0th, 75.0-97.5th, and >97.5th. Restricted cubic spline analysis was used to examine the non-linear association between calcium levels and CVD mortality. Cox proportional hazard regression was used to estimate hazard ratios (HRs) for CVD mortality according to serum calcium categories. All survival analyses were stratified by the estimated glomerular filtration rate. Results: Over a follow-up period of 11.9±2.8 years, 1757 participants died, of whom 219 died from CVD. A U-shaped association between serum calcium and CVD mortality was found, and the association was more evident in the low kidney function group. Compared to the 25.0-50.0th percentile group for serum calcium levels, both low and high serum calcium tended to be associated with CVD mortality (<2.5th: HR, 6.23; 95% confidence interval [CI], 1.16 to 33.56; >97.5th: HR, 2.56; 95% CI, 0.76 to 8.66) in the low kidney function group. In the normal kidney function group, a similar association was found between serum calcium levels and CVD mortality (<2.5th: HR, 1.37; 95% CI, 0.58 to 3.27; >97.5th: HR, 1.65; 95% CI, 0.70 to 3.93). Conclusions: We found a non-linear association between serum calcium levels and CVD mortality, suggesting that calcium dyshomeostasis may contribute to CVD mortality, and kidney function may modify the association.

• Journal of Korea Water Resources Association
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• v.45 no.8
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• pp.815-826
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• 2012

The underestimating trend using existing ordinary regression (OR) based trend analysis has been a well-known problem. The existing OR method based on least squares approximate the conditional mean of the response variable given certain values of the time t, and the usual assumption of the OR method is normality, that is the distribution of data are not dissimilar form a normal distribution. In this regard, this study proposed a quantile regression that aims at estimating either the conditional median or other quantiles of the response variable. This study assess trend in annual daily maximum rainfall series over 64 weather stations through both in OR and QR approach. The QR method indicates that 47 stations out of 67 weather stations are a strong upward trend at 5% significance level while OR method identifies a significant trend only at 13 stations. This is mainly because the OR method is estimating the condition mean of the response variable. Unlike the OR method, the QR method allows us flexibly to detect the trends since the OR is designed to estimate conditional quantiles of the response variable. The proposed QR method can be effectively applied to estimate hydrologic trend for either non-normal data or skewed data.