• Structural Engineering and Mechanics
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• v.16 no.2
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• pp.219-240
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• 2003

One of the most versatile approaches for analyzing the dynamic behavior of structural systems is direct time integration of semi-discrete equations of motion. However responses computed by time integration are generally inexact and hence the corresponding errors would rather be studied in advance. In spite of the various error estimation formulations that exist in the literature, it is accepted practice to repeat the analyses with smaller time steps, followed by a comparison between the results. In this paper, after a review of this simple method and disregarding the round-off errors, a more efficient, reliable and yet simple method for estimating errors and enhancing the accuracy is proposed. The main objectives of this research are more realistic error estimation based on the concept of convergence, approximately controlling the reliability by comparing the actual rate of convergence with the integration method's order of accuracy, and enhancement of reliability by applying Richardson's extrapolation. Starting from the errors at specific time instants, the study is then generalized to cases in which the errors should be estimated and decreased at specific events e.g. peak responses. Numerical study illustrates the efficacy of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1710-1719
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• 1997

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.

• Journal of Acupuncture & Meridian Studies
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• v.11 no.6
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• pp.355-360
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• 2018

Introductions: Pneumothorax is the most frequent severe acupuncture-related adverse event occurring at the GB 21 acupoint. This study used ultrasonography (US) to measure the depth of the GB 21 acupoint in adults and assessed its applicability for ensuring safe acupuncture practices. Materials and methods: A US probe was used to measure the vertical depth from the skin to the pleural line of the apex of the lungs at the right and left GB 21 acupoints. The sex, age, body weight, height, and body mass index of each person were recorded. Student t test and generalized estimating equations were used for statistical analysis. Results: Sixty women and 41 men with a median age of 29 years were included in this study. The depth of GB 21 increased with body weight, height, and body mass index (p < 0.001). The mean depth of GB 21 in men (17.4 mm) was greater than that in women (14.6 mm; p < 0.001). The depth difference between the right and left shoulders was significant in men (p < 0.001) but not in women. Conclusions: US can be used to measure GB 21 acupoint depth. Further control studies on its use to ensure safe clinical practices, including preventing acupuncture-related pneumothorax, are warranted.

• Child Health Nursing Research
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• v.28 no.2
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• pp.132-141
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• 2022

Purpose: This study examined the effects of an educational program for fathers on improving father-infant interactions, child-rearing knowledge, and attachment. Methods: In this quasi-experimental study, the participants were recruited by convenience sampling among fathers with infants (2-6 months of age) residing in three districts of Seoul. Fifteen participants in the experimental group and 17 participants in the control group completed the follow-up investigation. A 5-week online and offline intervention program with five sessions was provided to the experimental group. The data were analyzed using generalized estimating equations (GEEs). Results: There was a significant difference in the change in father-infant interaction scores of the experimental group, especially in the caregiver aspect with a significance level of .100 in time and group-to-group interactions (B=6.46, p=.051, 95% confidence interval [CI]=-0.02-12.94). The changes between the groups and times were not statistically significant when it came to infant development knowledge and father-infant attachment. Conclusion: We conclude that hybrid online and offline education should be implemented as an effective method to improve fathers' interactions with their children based on accurate knowledge about infant development.

• The Korean Journal of Applied Statistics
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• v.23 no.1
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• pp.13-28
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• 2010

Assuming a mixture distribution for credit evaluation studies, we discuss estimating threshold methods to minimize errors that default borrowers are predicted as non defaults or non defaults are regarded as defaults. A method by using statistical hypotheses tests, the most powerful test and generalized likelihood ratio test, for the probability density functions which are defined with the score random variable and the parameter space consisted of only two elements such as the default and non default states is proposed to estimate a threshold. And anther optimal thresholds to maximize classification accuracy measures of the accuracy and the true rate for ROC and CAP curves are estimated as equations related with these probability density functions. Three kinds of optimal thresholds in terms of the hypotheses testing, the accuracy and the true rate are obtained from normal random samples with various means and variances. The sums of the type I and type II errors corresponding to each optimal threshold are obtained and compared. Finally we discuss about their efficiency and derive conclusions.

• Journal of Korean Biological Nursing Science
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• v.22 no.4
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• pp.260-270
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• 2020

Purposes: Sepsis is a critical condition in which nurses should detect clinical manifestations and provide early intervention to prevent unwanted serious conditions in the patients. The initial occurrence and management of sepsis take place in general units, but there is a lack of knowledge in nurses. The purpose of this study was to examine the effects of a case-based sepsis education program and compare the case-based education program with and without smartphone applications. Methods: A quasi-experimental pre-test-post-test design with a control group was used. We provided a case-based education program with and without smartphone applications to the nurses and tested the effects of the program on knowledge, the accuracy of sepsis assessment, and self-efficacy as outcome variables. A total of 60 nurses in general units participated. To test differences in knowledge, the accuracy of sepsis assessment, and self-efficacy regarding sepsis between the groups over time, a mixed-design ANCOVA was used for parametric analysis, and generalized estimating equations (GEE) were used for nonparametric analysis. Results: There were significant differences in knowledge, the accuracy of sepsis assessment, and self-efficacy between the groups and within the groups over time. The intervention groups treated with the case-based education program showed improved outcome variables compared to the control group. There was no difference between case-based education with the smartphone application or without the application. Conclusions: The case-based education improved knowledge, the accuracy of sepsis assessment, and self-efficacy in the care of sepsis by nurses working in the general wards. The results suggest that the case-based education program for nurses was effective and eventually improved patient health outcomes.

• The Journal of the Korea Contents Association
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• v.16 no.10
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• pp.411-419
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• 2016

This study tried to find the relationship between household income level and medical expense to household income ratio. For data analysis, it used 2010 and 2011 yearly data beta version of Korea Health Panel, co-managed by Korea Institute for Health and Social Affairs and National Health Insurance Corporation. To find out how the effect of independent variable changes in 2010 and 2011, the interaction effect between year and independent variable was examined, and separating the factors that showed interaction effect into each year, linear regression analysis was conducted using generalized estimating equations method. As a result of reviewing the factors that were related to medical expense to household income ratio among the people who used medical services, it was found that the higher the household income level, the lower the medical expense. It indicates that policy measures are needed to lessen the medical burden of low-income families.

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.5
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• pp.96-105
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• 2002

As an useful water purification system for non-point source pollution in rural watersheds, interests in constructed wetlands are growing at home and abroad. It is well known that constructed wetlands are easily installed, no special managemental needs, and more flexible at fluctuating influent loads. They have a capacity for purification against nutrient materials such as phosphorus and nitrogen causing eutrophication of lentic water bodies. The Constructed Wetland Design Model (CWDM), developed through this study is consisted mainly of Database System, Runoff-discharge Prediction Submodel, Water Quality Prediction Submodel, and Area Assessment Submodel. The Database System includes data of watershed, discharge, water quality, pollution source, and design factors for the constructed wetland. It supplies data when predicting water quality and calculating the required areas of constructed wetlands. For the assessment of design flow, the GWLF (Generalized Watershed Loading Function) is used, and for water quality prediction in streams estimating influent pollutant load, Water Quality Prediction Submodel, that is a submodel of DSS-WQMRA model developed by previous works is amended. The calculation of the required areas of constructed wetlands is achieved using effluent target concentrations and area calculation equations that developed from the monitoring results in the United States. The CWDM is applied to Bokha watershed to appraise its application by assessing design flow and predicting water quality. Its application is performed through two calculations: one is to achieve each target effluent concentrations of BOD, SS, T-N and T-P, the other is to achieve overall target effluent concentrations. To prove the validity of the model, a comparison of unit removal rates between the calculated one from this study and the monitoring result from existing wetlands in Korea, Japan and United States was made. As a result, the CWDM could be very useful design tool for the constructed wetland in rural watersheds and for the non-point source pollution management.

• Safety and Health at Work
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• v.6 no.3
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• pp.240-248
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• 2015

Background: Recovery from fatigue is important in maintaining night workers' health. This study compared the course of self-reported recovery after 2-week 12-hour schedules consisting of either night shifts or swing shifts (i.e., 7 night shifts followed by 7 day shifts) to such schedules consisting of only day work. Methods: Sixty-one male offshore employees-20 night workers, 16 swing shift workers, and 25 day workers-rated six questions on fatigue (sleep quality, feeling rested, physical and mental fatigue, and energy levels; scale 1-11) for 14 days after an offshore tour. After the two night-work schedules, differences on the $1^{st}$ day (main effects) and differences during the follow-up (interaction effects) were compared to day work with generalized estimating equations analysis. Results: After adjustment for confounders, significant main effects were found for sleep quality for night workers (1.41, 95% confidence interval 1.05-1.89) and swing shift workers (1.42, 95% confidence interval 1.03-1.94) when compared to day workers; their interaction terms were not statistically significant. For the remaining fatigue outcomes, no statistically significant main or interaction effects were found. Conclusion: After 2-week 12-hour night and swing shifts, only the course for sleep quality differed from that of day work. Sleep quality was poorer for night and swing shift workers on the $1^{st}$ day off and remained poorer for the 14-day follow-up. This showed that while working at night had no effect on feeling rested, tiredness, and energy levels, it had a relatively long-lasting effect on sleep quality.

• Journal of Periodontal and Implant Science
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• v.47 no.4
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• pp.240-250
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• 2017

Purpose: The aim of this study was to analyze the prevalence and risk indicators of peri-implantitis in Korean patients with history of periodontal disease. Methods: A total of 444 patients with 1,485 implants were selected from patients who had been treated at the Department of Periodontology, Chonbuk National University Dental Hospital between July 2014 and June 2015. A group with a history of peri-implantitis (HP) (370 patients with 1,189 implants) and a group with a current peri-implantitis (CP) (318 patients with 1,004 implants) were created based on the radiographic and clinical assessments of implants. The prevalence of peri-implantitis was calculated at both the patient and implant levels. The influence of risk variables on the occurrence of peri-implantitis was analyzed using generalized estimating equations analysis. Results: The prevalence of peri-implantitis in the HP and CP groups ranged from 6.7% to 19.7%. The cumulative peri-implantitis rate in the HP group estimated with the Kaplan-Meier method was higher than that in the CP group over the follow-up period. Among the patient-related risk variables, supportive periodontal therapy (SPT) was the only significant risk indicator for the occurrence of peri-implantitis in both groups. In the analysis of implant-related variables, implants supporting fixed dental prosthesis (FDP) and implants with subjective discomfort was associated with a higher prevalence of peri-implantitis than single implants and implants without subjective discomfort in the HP group. The presence of subjective discomfort was the only significant implant-related variable predictive of peri-implantitis in the CP group. Conclusions: Within the limitations of this study, the prevalence of peri-implantitis in Korean patients with a history of periodontal disease was similar to that reported in other population samples. Regular SPT was important for preventing peri-implantitis. Single implants were found to be less susceptible to peri-implantitis than those supporting FDP. Patients' subjective discomfort was found to be a strong risk indicator for peri-implantitis.