• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.72-72
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• 2011

국내 및 세계의 천연가스 수요가 증가하고, 원유가 상승에 의한 천연가스의 지속적인 가격상승이 예측됨에 따라 천연가스의 99%를 수입에 의존하는 우리나라의 에너지 안보 확보 방안을 위한 기술개발이 필요하다. 국내에서 천연가스를 확보할 수 있는 현실적인 방법중의 하나는 석탄가스화를 통해 얻어진 합성가스를 이용하여 SNG(synthetic Natural Gas, 합성천연가스)를 제조하는 것이다. 본 연구에서는 다양한 석탄, 다양한 석탄 가스화기를 적용하는 경우에 대한 CASE별 공정해석을 수행하여 각 경우의 SNG 생산 특성을 파악하였다. 석탄의 종류는 역청탄, 아역청탄, 갈탄을 대상으로 하였으며, 역청탄을 사용하는 경우는 General Electric Energy(GEE), Shell Global Solutions(Shell), ConocoPhillips(CoP)사의 가스화기를, 아역청탄을 사용하는 경우는 KBR의 TRIG$^{TM}$, Siemens사의 SFG, Shell, CoP 가스화기를, 갈탄을 사용하는 경우는 Shell, Siemens 가스화기를 적용하였다. 사용한 석탄과 석탄가스화기에서 발생된 합성가스 조성은 NETL에서 발행된 보고서에 제시된 수치들을 활용하였다. 역청탄을 사용하고 CoP 가스화기를 적용한 경우, SNG 합성공정에 유입되는 유량이 100 Nm3/h 일 때, 생산되는 SNG의 조성은 $CH_4$ 96.26%, $H_2$ 1.49%, $CO_2$ 0.69%, CO 0.004% 이고 생산유량은 24 Nm3/h 였다. SNG 효율을 SNG 합성공정에 공급되는 합성가스 열량 대비 최종 생산되는 SNG의 열량을 기준으로 하고, 각 CASE 별 SNG 효율을 살펴보면, 역청탄을 대상으로 한 경우 GEE 74.05%, CoP 76.65%였다. 아역청탄을 대상으로 한 경우 TRIG 78.14%, Siemens 71.22%, CoP 75.72%였고, 갈탄을 대상으로 하는 경우 Shell 71.48%, Siemens 71.49%였다. 역청탄을 사용하는 경우는 CoP 가스화기를 대상으로 한 경우 SNG 효율 및 생산량이 가장 높았고, 아역청탄을 사용하는 경우는 TRIG 가스화기를 대상으로 한 경우의 SNG 효율 및 생산량이 높았다. 갈탄을 사용하는 경우는 Shell 가스화기와 Siemens 가스화기가 거의 비슷한 결과를 나타내었다. $$SNG\;efficiency({\eta})={\frac{Q_B}{Q_A}}={\frac{Q_{SNG}(kcal/h)}{Q_{Syngas}(kcal/h)}}{\times}100(%)$$.

• Journal of Korean Academy of Nursing
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• v.50 no.4
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• pp.631-640
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• 2020

Purpose: This study aimed to examine premenstrual symptoms (PMS) of shift nurses and identify the association between PMS, sleep, and occupational stress. Methods: This study was conducted with a secondary data analysis that used data from the Shift Work Nurse's Health and Turnover study. The participants were 258 nurses who were working in shifts including night shifts. PMS, sleep patterns (sleep time and sleep time variability), sleep quality, and the occupational stress of each participant were measured using the Moos Menstrual Distress Questionnaire, a sleep diary, an actigraph, the Insomnia Severity Index, and the Korean Occupational Stress Scale, respectively. Data were analyzed using SPSS 23 and STATA 15.1 to obtain descriptive statistics, Pearson's correlation coefficients, multiple linear regression with generalized estimating equations (GEE) and Baron and Kenny's mediating analysis. Results: The average PMS score, average sleep time, average sleep time variability, average sleep quality score, and average occupational stress score of the participants was 53.95 ± 40.45, 7.52 ± 0.89 hours, 32.84 ± 8.43%, 12.34 ± 5.95, and 49.89 ± 8.98, respectively. A multiple linear regression analysis with GEE indicated that sleep time variability (B = 0.86, p = .001), and sleep quality (B = 2.36, p < .001) had negative effects on nurses' PMS. We also found that sleep quality had a complete mediating effect in the relationship between occupational stress and PMS. Conclusion: These findings indicate that both sleep time variability and sleep quality are important factors associated with PMS among shift work nurses. To improve shift nurses' PMS status, strategies are urgently needed to decrease sleep time variability and increase sleep quality.

• Journal of Korean Academy of Nursing
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• v.47 no.6
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• pp.828-841
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• 2017

Purpose: This study aimed to analyze the impact of increasing the supply of newly licensed nurses on improving the hospital nurse staffing grades for the period of 2009~2014. Methods: Using public administrative data, we analyzed the effect of newly licensed nurses on staffing in 1,594 hospitals using Generalized Estimating Equation (GEE) ordered logistic regression, and of supply variation on improving staffing grades in 1,042 hospitals using GEE logistic regression. Results: An increase of one newly licensed nurse per 100 beds in general units had significantly lower odds of improving staffing grades (grades 6~0 vs. 7) (odds ratio=0.95, p=.005). The supply of newly licensed nurses increased by 32% from 2009 to 2014, and proportion of hospitals whose staffing grade had improved, not changed, and worsened was 19.1%, 70.1%, and 10.8% respectively. Compared to 2009, the supply variation of newly licensed nurses in 2014 was not significantly related to the increased odds of improving staffing grades in the region (OR=1.02, p=.870). Conclusion: To achieve a balance in the regional supply and demand for hospital nurses, compliance with nurse staffing legislation and revisions in the nursing fee differentiation policy are needed. Rather than relying on increasing nurse supply, retention policies for new graduate nurses are required to build and sustain competent nurse workforce in the future.

• The Journal of Internal Korean Medicine
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• v.42 no.4
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• pp.563-571
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• 2021

Objectives: This pilot study aimed to confirm the possibility of applying our design to the main study, a retrospective medical record analysis of the diseases which have most frequently been treated with collaborations of Korean and Western medicine, and to identify what corrections and statistical models are needed to conduct the main study. Methods: Data were collected from a case report form developed for patients who received treatment in the medical institutions. Appropriate statistical techniques, like Propensity Score (PS) and Generalized Estimation Equation (GEE) models, were used to compare the indicators of collaboration and non-collaboration groups for patients in comparable diseases. Results: Using PS matching for each M and S disease group, the indicators were compared by balancing the collaboration and non-collaboration group, and the GEE models compared indicators between groups in each disease over follow-up. Through this process we identified two limitations, insufficient samples and a large deviation of the follow-up period. Conclusion: This pilot study confirmed that the study design and case report form are applicable. The main study will be conducted by collecting sufficient samples and reflecting deviation of follow-up period.

• Psychiatry investigation
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• v.15 no.12
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• pp.1162-1167
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• 2018

Objective Motor, perceptual, and cognitive functions are known to affect driving competence. Subcortical ischemic changes on brain magnetic resonance imaging (MRI) can reflect reduction in cognitive and motor performance. However, few studies have reported the relationship between subcortical ischemic changes and driving competence of the elderly. Thus, the objective of this study was to investigate the association between subcortical ischemic changes on MRI and driving abilities of the elderly. Methods Participants (n=540) were drawn from a nationwide, multicenter, hospital-based, longitudinal cohort. Each participant underwent MRI scan and interview for driving capacity categorized into 'now driving' and 'driving cessation (driven before, not driving now)'. Participants were divided into three groups (mild, n=389; moderate, n=116; and severe, n=35) depending on the degree of white matter hyperintensity (WMH) on MRI at baseline. Driving status was evaluated at follow-up. Statistical analyses were conducted using ${\chi}^2$ test, analysis of variance (ANOVA), structured equation model (SEM), and generalized estimating equation (GEE). Results In SEM, greater baseline degree of WMH was directly associated with driving cessation regardless of cognitive or motor dysfunction (${\beta}=-0.110$, p<0.001). In GEE models after controlling for age, sex, education, cognitive, and motor dysfunction, more severe change in the degree of WMH was associated with faster change from 'now driving' state to 'driving cessation' state over time in the elderly (${\beta}=-0.508$, p<0.001). Conclusion In both cross-sectional and longitudinal results, the degree of subcortical ischemic change on MRI might predict driving cessation in the elderly.

• The Journal of the Convergence on Culture Technology
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• v.4 no.4
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• pp.301-308
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• 2018

This study examined the relationship between transition in living arrangement and life satisfaction outcomes among older adults in Korea. This study utilized the secondary data of 2 waves(2005-2011) of a Korean Retirement and Income Study from the National Pension Research Institute. This study categorized living arrangement transition over time into 16 categories and used generalized the estimation equation(GEE) modeling to examine the relationship between living arrangement transition group membership and life satisfaction. The results showed that transition in living arrangement in old age was partly and significantly associated with life satisfaction in later life. In particular, the best living arrangement type in older adults in terms of life satisfaction was the coresidence with spouse compared with residence alone or residence with their children. The group of residence with their children was not related to higer satisfaction. More research is needed to explore the mechanism behind older people's trajectory in transition in living arrangement.

• Nutrition Research and Practice
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• v.13 no.3
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• pp.214-221
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• 2019

BACKGROUNDS/OBJECTIVES: Cancer treatment may lead to significant body composition changes and affect growth and disease outcomes in pediatric cancer patients. This prospective study aimed to evaluate short- and long-term body compositions changes focused on body fat during the first year of cancer treatment in children. SUBJECTS/METHODS: A prospective study was conducted in 30 pediatric cancer patients (19 hematologic malignancies and 11 solid tumors) and 30 age- and sex-matched healthy controls. Anthropometric measurements and body composition analysis using whole body dual energy X-ray absorptiometry were performed at baseline and 1, 6, and 12 month(s) of cancer treatment. Kruskal-Wallis tests, Wilcoxon paired t tests, and generalized estimation equation (GEE) were applied for statistical analysis. RESULTS: At baseline, no differences in weight, height, body mass index, abdominal circumferences, body fat, and fat-free mass were observed between 30 controls and 30 pediatric cancer patients. Total fat mass (P < 0.001) and body fat percentage (P = 0.002) increased significantly during the first month, but no changes were observed from 1 to 12 months; however, no changes in the total mass were observed during the first year of cancer treatment. Meanwhile, the total fat-free mass decreased during the first month (P = 0.008) and recovered between 6 and 12 months of follow-up (P < 0.001). According to GEE analysis, there was a significant upward trend in body fat percentage during the first year, especially the first month, of cancer treatment in children with hematologic malignancies, but not in those with solid tumors. CONCLUSIONS: Our results indicate that cancer treatment is related to significant body composition changes and rapid body fat gain, particularly during the first month after initiating cancer treatment, in children with hematologic malignancies. Therefore, individualized dietary strategies to prevent excessive fat gain are needed in pediatric cancer patients for better outcomes.

• Annals of Occupational and Environmental Medicine
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• v.35
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• pp.14.1-14.10
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• 2023

Background: Shift work is known to cause changes in the circadian rhythm of the human body and adversely affect not only physical health but also mental health. Some studies have demonstrated the correlation between shift work and thyroid stimulating hormone (TSH), a hormone that changes according to the diurnal rhythm, but few studies have reported the different TSH levels according to the shift work type. This study aimed to investigate changes in TSH according to the shift work type. Methods: This study included 1,318 female workers who had a medical checkup at a university hospital in Changwon from 2015 to 2019. Shift work types were classified as non-shift work, regular 2 shifts, and irregular three shifts, and a TSH ≥ 4.2 mIU/L was defined as abnormal. A general linear model (GLM) was used to compare the TSH levels and the risk of subclinical hypothyroidism in each year, and a binary logistic analysis was performed using a generalized estimation equation (GEE) to compare the risk of subclinical hypothyroidism over the 5-year period. Results: Of the 1,318 participants included in this study, 363, 711, and 244 were non-shift, two-shift, and irregular three-shift workers, respectively. In the GEE analysis, after adjusting for age, body mass index, smoking, and alcohol consumption, the odds ratios (ORs) were 1.81 (95% confidence interval [CI]: 1.15-2.86; p = 0.011) in 2 shifts and 2.02 (95% CI: 1.23-3.32; p = 0.006) in irregular three shifts, compared to non-shift. Conclusions: Our results showed that shift work had a higher risk of subclinical hypothyroidism than non-shift work and that there was a significant difference in the risk of subclinical hypothyroidism according to the shift work type. These findings suggest that the shift work type can be considered in future thyroid function tests and evaluations.

• Health Policy and Management
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• v.34 no.1
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• pp.38-47
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• 2024

Background: Korea's population of children and adolescents has decreased by 2.88 million over the past decade and is expected to decline further due to the unprecedented low birth rate. In the fee-for-service compensation system, the decline in the pediatric population relates directly to the profit decrease in the pediatric clinics. This study analyzed whether the worsening profits of pediatric clinics impacted their closure. Methods: We built annual data for pediatric and other department clinics (internal medicine, otolaryngology, and family medicine) using the status of medical institute and health insurance claims data from 2012 to 2022. Then, we analyzed whether institutional variables such as annual profit and regional variables (Herfindahl-Hirschman index, the number of clinics per 100,000, etc.) affected the closure of clinics. The methods used in this study are descriptive statistics and chi-square analysis. Odds ratios for each variable were estimated by generalized estimating equations (GEE). Results: The closure rate of pediatric clinics was 2.66%-7.04% in 2012-2022, which was consistently higher than those of internal medicine, otolaryngology, and family medicine clinics. The profit gap per institution between the pediatric and the other clinics grew from 126 million won in 2012 to 245 million won in 2019. In the GEE analysis, profit decrease compared to the previous year with lower profit was the main factor that increased the closure of pediatric and other department clinics. After adjusting profit-related variables, the decrease in the pediatric population itself did not relate to the closure of pediatric clinics. The number of pediatric clinics or monopolies also did not affect the closure of pediatric clinics. Conclusion: The worsening profit is the crucial factor for the closure of pediatric clinics, while the pediatric population is decreasing. For this reason, it is necessary to actively seek ways to maintain a stable treatment system for children and adolescents.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.2
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• pp.89-93
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• 2003

human renin binding protein (hRnBp), showing N-acetylglucosamine-2-epimerase activity, was over-expressed in E. coli, but was mainly present as an inclusion body. To improve its solubility and activity, ubiquitin (Ub), thioredoxin (Trx), maltose binding protein (MBP) and NusA, were used as fusion partners. The comparative solubilities of the fusion proteins were, from most to least soluble: NusA, MBP, Trx, Ub. Only the MBP fusion did not significantly reduce the activity of hRnBp, but enhanced the stability. The Origami (DE3), permitting a more oxidative environment for the cytoplasm in E. coli; helped to increase its functional activity.