• Journal of KIISE
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• v.44 no.8
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• pp.782-790
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• 2017

The service, 'Hot Search Keywords', provides a list of the most hot search terms of different web services such as Naver or Daum. The service, bases the changes in rank of a specific search keyword on changes in its users' interest. This paper introduces a temporal modelling framework for predicting the rank change of hot search keywords using past rank data and machine learning. Past rank data shows that more than 70% of hot search keywords tend to disappear and reappear later. The authors processed missing rank value, using deletion, dummy variables, mean substitution, and expectation maximization. It is however crucial to calculate the optimal window size of the past rank data. We proposed an optimal window size selection approach based on the minimum amount of time a topic within the same or a differing context disappeared. The experiments were conducted with four different machine-learning techniques using the Naver, Daum, and Nate 'Hot Search Keywords' datasets, which were collected for 2 years.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.41
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• pp.35.1-35.7
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• 2019

Background: The purpose of this study was to measure the time of the conventional surgical planning (CSP) and virtual surgical planning (VSP) in orthognathic surgery and to compare them in terms of cost. Material and method: This is a retrospective study of the patients who underwent orthognathic surgery at the Pusan National University Dental Hospital from December 2017 to August 2018. All the patients were analyzed through both CSP and VSP, and all the surgical stents were fabricated through manual and three-dimensional (3D) printing. The predictor variables were the planning method (CSP vs. VSP) and the surgery type (group I: Le Fort I osteotomy + bilateral sagittal split osteotomy [LFI+BSSO] or group II: only bilateral sagittal split osteotomy [BSSO]), and the outcomes were the time and cost. The results were analyzed using the paired t test. Results: Thirty patients (12 females, 18 males) met the inclusion criteria, and 17 patients were excluded from the study due to missing or incomplete data. There were 20 group I patients (LFI+BSSO regardless of genioplasty) and 10 group II patients (BSSO regardless of genioplasty). The average time of CSP for group I was 385 ± 7.8 min, and that for group II was 195 ± 8.33 min. The time reduction rate of VSP compared with CSP was 62.8% in group I and 41.5% in group II. On the other hand, there was no statistically significant cost reduction. Conclusions: The time investment in VSP in this study was significantly smaller than that in CSP, and the difference was greater in group I than in group II.

• Journal of Digital Convergence
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• v.18 no.11
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• pp.31-41
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• 2020

This study analyzed parents' school satisfaction longitudinally using data from the 1st, 3rd, and 5th wave data of the Korea Education Longitudinal Study(KELS)2013. The subjects of analysis are parents who responded without dropping out in the first, third and fifth panel of the KELS2013, and 4,227 cases that had no missing values in the variables were selected for the sample to input for analysis of the latent growth modeling(LGM). As a result, it is confirmed that the parents' education, educational support, and children's academic achievement have a positive effect on the parents' school satisfaction. But the parents' educational view and education cost have a negative effect on that. The results of this study are expected to be important information to help enhance the primary function of the school.

• Korean Journal of Health Education and Promotion
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• v.26 no.1
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• pp.117-128
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• 2009

Objectives: The purpose of this study was to assess the effect of mothers education attainment on prevalence of dental caries among their preschool children. Methods: Data were obtained from the third 2006 Korea National Oral Health Survey. A total of 515 preschool children aged 2 to 7 years and their mothers were selected in this study. We used mother's education level as her socioeconomic position and controlled children's tooth brushing frequency, tooth brushing before bed, the frequency of eating snack, and the preventive dental visit. Whether children experienced dental caries or not and the number of decayed or filled or missing tooth surface they had were used as outcome variables. Results: The proportion of children affected with dental caries was 46.21%. The mother's education level affected children's caries significantly (p<0.05) and children whose mother attended less than high school had more possibility of having caries than children whose mother graduated from college or more (p<0.05). This effect was still significant and got larger(p<0.05), even after controlling children's dental health behavior. Conclusion: This study showed that mother's education level affected the prevalence of caries among their preschool children. In addition, this result indicated a need for more definite policy for children's dental health in lower socioeconomic class with general dental education.

• The Journal of the Korea Contents Association
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• v.14 no.10
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• pp.151-159
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• 2014

The purpose of this study was to empirically analyze the effect that the job satisfaction of care workers would have on the organization commitment. For this study, 230 care workers were surveyed via mail who were working at the long-term recuperation institutes for the elderly located in the eastern part of Jeollanam-do. 141 sets of questionnaires were used for analysis, excluding those with missing data. The collected data were processed by using the SPSS 18.0 to conduct the frequency analysis, reliability analysis, t/F-test, and hierarchical regression analysis. The results of analysis suggested the followings : First, the difference in organization commitment based on individual characteristics and job characteristics of care workers was found to exist, depending on the age related to individual characteristics and types of institutes and work types related to the job characteristics. Second, hierarchical regression analysis was conducted to analyze the effect that the job satisfaction of care workers would have on organization commitment. With the individual characteristics and occupation environment variables of care workers being controlled, it was found that the job satisfaction of care workers had the greatest effect on organization commitment. This implies that the extent of job satisfaction determines the commitment level of care workers for the concerned job.

• Nuclear Engineering and Technology
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• v.50 no.4
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• pp.589-598
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• 2018

To maintain safety and reliability of reactors, redundant sensors are usually used to measure critical variables and estimate their averaged time-dependency. Nonhealthy sensors can badly influence the estimation result of the process variable. Since online condition monitoring was introduced, the online cross-calibration method has been widely used to detect any anomaly of sensor readings among the redundant group. The cross-calibration method has four main averaging techniques: simple averaging, band averaging, weighted averaging, and parity space averaging (PSA). PSA is used to weigh redundant signals based on their error bounds and their band consistency. Using the consistency weighting factor (C), PSA assigns more weight to consistent signals that have shared bands, based on how many bands they share, and gives inconsistent signals of very low weight. In this article, three approaches are introduced for improving the PSA technique: the first is to add another consistency factor, so called trend consistency (TC), to include a consideration of the preserving of any characteristic edge that reflects the behavior of equipment/component measured by the process parameter; the second approach proposes replacing the error bound/accuracy based weighting factor ($W^a$) with a weighting factor based on the Euclidean distance ($W^d$), and the third approach proposes applying $W^d$, TC, and C, all together. Cold neutron source data sets of four redundant hydrogen pressure transmitters from a research reactor were used to perform the validation and verification. Results showed that the second and third modified approaches lead to reasonable improvement of the PSA technique. All approaches implemented in this study were similar in that they have the capability to (1) identify and isolate a drifted sensor that should undergo calibration, (2) identify a faulty sensor/s due to long and continuous missing data range, and (3) identify a healthy sensor.

• The Journal of Korean Society for School & Community Health Education
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• v.21 no.3
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• pp.1-19
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• 2020

Objectives: This study was attempted to examine the relationship between hand grip strength and dyslipidemia. and it was analyze the effect of hand grip strength on dyslipidemia and discuss the problems that may occur. Methods: The study focused on 'the National Health and Nutrition Survey's 7th Year 1, 2, and 3 (2016-2018)' as their primary data. Among people who measured dyslipidemia and relative hand grip strength, 12,636 people were selected as the final study after excluding missing values. Frequency analysis, mean analysis, and regression analysis was used to determine dyslipidemia and hand grip strength indices according to the subjects' characteristics study and verify the research hypothesis. Results: Outcomes show that 4,542 (35.9%) of the subjects were dyslipidemia, and when the hand grip strength of the subjects increased by 1kg, Dyslipidemia decreased by 0.217 less. The result of subdivided and analyzed dependent variables presented that every time the hand grip strength increased by 1kg, the L-HDL -C decreased by 0.325 less, but it did not affect H-LDL-C and H-TG. Conclusion: In order to reduce dyslipidemia, it is essential to recognize the necessity of muscular exercise and fulfill it. Focus on health care, such as health conditions, health behavior, and make efforts to participate in health education. If so, it is expected to help reduce the economic burden, such as the treatment of dyslipidemia and improve the quality of life free from mechanical circulatory diseases.

• Journal of Yeungnam Medical Science
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• v.37 no.3
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• pp.194-201
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• 2020

Background: Dietary polyunsaturated fatty acids (PUFA) are thought to modify systemic inflammation. The present study aimed to evaluate the relationship between PUFA intake, lung function, and health-related quality of life (HRQoL) in patients with chronic obstructive pulmonary disease (COPD). Methods: In this study, we used the dataset of 6th Korea National Health and Nutrition Examination Survey, in which, a total of 22,948 individuals including 573 participants with a high probability of developing COPD were enrolled. Participants with missing data for the investigated variables were excluded. Linear regression analyses were used to evaluate the association between PUFA intake (omega-3 [N3], omega-6 [N6], and total) with lung function, and HRQoL. HRQoL was determined according to the European Quality of Life-5 Dimensions (EQ-5D). Subgroup analysis of older patients was performed. Age, sex, body mass index, smoking, alcohol, education, residence, total calorie intake, and predicted FEV₁% were adjusted in all analyses. Results: Although lung function was not associated with PUFA intake, EQ-5D index was remarkably associated with N3, N6, and total PUFA intake in a dose-dependent manner. This association was more pronounced in elderly COPD patients. Mean levels of N3, N6, and total PUFA intake were significantly higher in patients having better HRQoL with respect to mobility, self-care, and usual activities. Conclusion: Our results suggest that N3, N6, and total PUFA intake are associated with HRQoL in COPD patients. This association may be attributed to mobility, self-care, and usual activities. Further longitudinal study is required to clarify this relationship.

• The korean journal of orthodontics
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• v.45 no.2
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• pp.89-94
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• 2015

Objective: To test the null hypothesis that SmartClip self-ligating brackets are more effective than conventional brackets for initial mandibular alignment and identify influential factors. Methods: Fifty patients were randomly allocated to two equal treatment groups by using an online randomization program: self-ligating group (SmartClip brackets) and conventional group (Gemini brackets). The archwire sequence was standardized. Changes in anterior irregularity index, intercanine width, and intermolar width were assessed on plaster models at 8th and 16th weeks. Changes in incisor position and inclination were assessed on lateral cephalometric radiographs at 16 weeks. Intragroup and intergroup comparisons were performed with paired t-test and Student's t-test, respectively. Multiple linear regression was performed to identify variables affecting improvement in anterior ambiguity. Results: Data of 46 patients were analyzed; those missing an appointment (n = 2) or showing bracket breakage (n = 2) were excluded. Incisor inclination (p < 0.05), intercanine width (p < 0.05), and intermolar width (p > 0.05) increased at 8 and 16 weeks in both the groups; no significant intergroup differences were noted (p > 0.05). Initial anterior irregularity index and intercanine width change were significantly associated with improvement in anterior irregularity (p < 0.001). Conclusions: The null hypothesis was rejected. Bracket type has little effect on improvement in anterior ambiguity during initial mandibular alignment.

• Communications for Statistical Applications and Methods
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• v.16 no.1
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• pp.103-113
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• 2009

Weighting is a common form of unit nonresponse adjustment in sample surveys where entire questionnaires are missing due to noncontact or refusal to participate. A common approach computes the response weight as the inverse of the response rate within adjustment cells based on covariate information. In this paper, we consider the efficiency and robustness of nonresponse weight adjustment bated on the response propensity and predictive mean. In the simulation study based on 2000 Fishry Census in Korea, the root mean squared errors for assessing the various ways of forming nonresponse adjustment cell s are investigated. The simulation result suggest that the most important feature of variables for inclusion in weighting adjustment is that they are predictive of survey outcomes. Though useful, prediction of the propensity to response is a secondary. Also the result suggest that adjustment cells based on joint classification by the response propensity and predictor of the outcomes is productive.