• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.714-717
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• 2017

Among the factors considered in the design stage of a space launch vehicle using liquid propellant, research has been focused out on the pogo phenomenon, longitudinal dynamic instability. The pogo phenomenon refers to the instability that the longitudinal vibration of the launch vehicle structure causes a change in the pressure and flow rate of the fluids in propulsion system, and this change re-excites the fuselage structure. This mechanism constitutes a closed system to gradually increase the vibration of the launch vehicle. This paper specifically focuses on the dynamic analysis of pressure and flow changes in the propulsion system. Based on the example study of the space shuttle, the acoustic modal analysis of the propulsion system is performed to predict the modes of the supply line causing instability of the fuselage.

• Korean Journal of Community Nutrition
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• v.5 no.2
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• pp.185-192
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• 2000

As the percentage of the elderly in the population increases, research to identify the nutritional and health status of the elderly, to understand the factors influencing on them, and to delay aging have been done actively. It is necessary for these studies to be longitudinal. This study was carried out to assess the change of health-related habits such as dietary behaviors and smoking, alcohol drinking and exercising habit, and health status between previous study(1991/1994) and post study(1998) for middle-aged men and women living in Chonju. For the present study, the data of 63 pairs(23 men and 40 women) were analyzed. They were 11 men and 12 women followed up from 82 men and 100 women surveyed in 1994. Mean ages in the 1991/4 and 1998 studies were 53.6y(range 42-63y) and 59.0y(range 46-72y) respectively. The survey was conducted with interview using a questionnaire including dietary behaviors and health-related habits, and anthropometric measurement and blood test for analyzing biochemical indices in 1991/4 and 1998. To understand these changes over time, $\chi$$^2$-statistics, t-test and paired t-test were analyzed with an SAS package program. As people age, there were significantly decreases in the proportions to eat lightly salted foods and drink alcohol. Significant longitudinal increases in triceps skin fold thickness, ${\gamma}$-GPT and HDL-cholesterol and significant decrease in hemoglobin value were noted over time in both men and women. In addition a significant decrease in blood glucose level was noted over time in women. Weight, blood glucose and total cholesterol increased significantly with age in those had had breakfast regularly or those had not used more slat at the table in the past. From this study, were found out the subjects of this study had relatively desirable health-related habits. But as improper health-related habits are likely to result in inappropriate health status(eg, increase in WHR, triglyceride, total cholesterol and LDL-cholesterol), it is recommended that nutrition education in necessary as soon as possible to meet the health elderly.

• Korean Journal of Materials Research
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• v.15 no.1
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• pp.25-30
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• 2005

The microstructural changes by hot extrusion of AZ31B magnesium alloy were observed, and the relation to the tensile property was examined. The tensile properties as oriented longitudinal(L), half transverse(HT) and long transverse(LT) to the extrusion direction were investigated at $20^{\circ}C,\;100^{\circ}C,\;200^{\circ}C,\;300^{\circ}C\;and\;400^{\circ}C$, respectively. As the results, many recrystallized small grains distributed uniformly in large banded microstructures formed along the extrusion direction. The grain size of as-extruded specimen was around $30\~150\;{\mu}m$. As increasing the test temperature the tensile and yield strength with respect to the angle between the axis of the tensile and the longitudinal direction in extrusion was decreased, but their elongation were increased and their deviation between L and LT specimens have disappeared from $300^{\circ}C$. This mechanical anisotropy was reduced at elevated temperatures and almost disappeared at $400^{\circ}C$. It was considered that the homogenization was occured by the recrystallization and the change of slip system was occurred during tensile test process in elevated temperatures.

• Anxiety and mood
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• v.17 no.2
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• pp.49-58
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• 2021

Objective : The purpose of this study was to investigate the longitudinal trajectories of life satisfaction, loneliness, and depression and to identify the factors that influence these trajectories in North Korean Defectors (NKD). Methods : NKD (n=300) who registered in the multi-regional adaptation center (Hana Center), within three years of settling in South Korea, were recruited into this study. Life satisfaction, loneliness, and depression were assessed with self-report questionnaires over a period of 4 years (7 waves of data). Latent growth modeling was conducted to assess the changes in life satisfaction, loneliness, and depression. Results : Findings from both unconditional and conditional models (with gender, South Korea settlement age, household income, marital status, and PTSD at wave 1) indicated a linear increase in loneliness and depression, and a linear decrease in life satisfaction over the 4-year period. In the conditional model, gender predicted the intercept of life satisfaction and depression. In addition, PTSD predicted the intercept of life satisfaction, loneliness, and depression and slope of depression. Conclusion : Our finding suggests that the mental health of NKD tends to deteriorate over time after settling in South Korea. Therefore, continuous support is necessary for their successful adaptation to the South Korean Society.

• Journal of the Korea Society of Computer and Information
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• v.26 no.4
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• pp.189-195
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• 2021

The point of this research is verifing the longitudinal changes in youth multicultural acceptance and to verify predictive variables of multicultural acceptance. Among the Korean Children and Youth Panal data collected by the Korea Institute for Children and Youth Policy, 1,972 data from the 3rd, 5th, and 6th data of the first-year middle school panal were used, and the data were analyzed by applying the latent growth model, and the following analysis results were obtained. First, adolescents' multicultural acceptability showed an increasing pattern, and the extent of the increase was large at the point of transition from the 3rd year(3rd year of middle school) to the 5th year. Second, predicting the change of multicultural acceptability were found to be significant in the initial values of peer communication, community consciousness and in the rate of change, life-satisfaction, peer communication, community consciousness. This study proposed some plans to improve multicultural acceptance in adolescence basing on these results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.354-361
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• 2021

This study explored whether the transition to living with a chronic disease changes the level of depression symptoms among middle-aged and older adults in South Korea. We hypothesize that the transition to living with chronic disease leads to a higher level of depressive symptoms. A nationally representative sample (N = 6,284) of adults 45 years and older from the Korean Longitudinal Study of Ageing (KLoSA) was analyzed. Multi-regression modeling was used to examine the association between the diagnosis of chronic disease and the level of depressive symptoms in patients. The findings highlight the need for policy makers, clinicians, as well as patients and their caregivers to become more aware of mental health risks in patients diagnosed with chronic diseases, particularly first-time patients. This study contributes to encouraging greater psychosocial support, including monitoring the level of depressive symptoms of patients who develop chronic conditions and providing appropriate treatments for those at the highest risk.

• Journal of Science Education
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• v.44 no.3
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• pp.318-330
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• 2020

This study has been conducted to identify the types and longitudinal changes in the career values of students in science core school. Data collected from 174 students in science core school were analyzed using 11 career value items. First, this study found that there are three types of career value shown in students in science core schools. Second, the career value of students in science core school did not differ by their track. Third, many students of science core high schools have little or no change in their career value values depending on the time of collecting data. However, some students show rapidly changing career values. These findings suggest the need for individualized career education based on the changing trend of students' career values.

• Health Policy and Management
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• v.32 no.3
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• pp.282-292
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• 2022

Background: Aging societies face social problems of increased medical expenses for older adults due to increased geriatric diseases. This study aims to analyze the relationship between the state change of multiple chronic conditions (MCC) and out-of-pocket medical expenses in the elderly aged 60 or older. Methods: The 2014-2018 Korean Longitudinal Study of Aging data were used for 2,202 elderly people. Four status change groups were established according to the change in the number of chronic diseases. The association between the change of MCC and the out-of-pocket medical cost was analyzed using the generalized estimating equation model analysis. Results: The average out-of-pocket total medical costs were 1,384,900 won for participants with MCC and 542,700 won for those without MCC, which was a statistically significant difference (p<0.0001). Compared to the reference group (simple chronic disease, SCD→SCD), the change in multiple chronic conditions significantly increased the total out-of-pocket medical expenses in MCC→MCC and SCD→MCC groups (MCC→MCC: 𝛽=0.8260, p<0.0001; SCD→MCC: 𝛽=0.6607, p<0.0001). Conclusion: In this study, it was confirmed that the prevalence of MCC increased with age, and the out-of-pocket medical cost increased in the case of MCC. Continuity of treatment can be achieved for patients with MCC, and the system and management of treatment for MCC are required to receive appropriate treatment.

• Journal of Korean Biological Nursing Science
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• v.24 no.4
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• pp.243-252
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• 2022

Purpose: The purpose of this longitudinal study was to identify the relationship between the readiness for hospital discharge and self-care changes in an early stage of liver transplantation after discharge. Methods: Data of 75 liver transplant recipients within one year of surgery from a transplantation center from May 2019 to May 2020 were collected for this study. Their readiness for discharge was measured before discharge. Self-care after liver transplantation was evaluated at one week, one month, and three months of discharge at outpatient visits. Linear mixed model was used to evaluate the statistical relationship. Results: The readiness for hospital discharge was significantly higher when the caregiver was a spouse (p=.027), with fewer post-transplantation days (p=.027), absence of acute rejection (p=.004), or high self-efficacy (p<.001). As a result of the linear mixed model analysis, the higher the discharge readiness score, the higher the self-care score (β=0.29, p<.001). However, after three months, their self-care had decreased regardless of their level of readiness for hospital discharge compared to one week after discharge. Conclusion: Improving the readiness before discharge is essential to enhance self-care. Also, active intervention at 3 months of discharge should be performed to check and promote their long-term self-care.

• Korean Journal of Radiology
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• v.22 no.7
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• pp.1142-1151
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• 2021

Objective: To evaluate microstructural damage in high myopia (HM) patients using 3T diffusion kurtosis imaging (DKI). Materials and Methods: This prospective study included 30 HM patients and 33 age- and sex-matched healthy controls (HCs) with DKI. Kurtosis parameters including kurtosis fractional anisotropy (FA), mean kurtosis (MK), axial kurtosis (AK), and radial kurtosis (RK) as well as diffusion metrics including FA, mean diffusivity, axial diffusivity (AD), and radial diffusivity derived from DKI were obtained. Group differences in these metrics were compared using tract-based spatial statistics. Partial correlation analysis was used to evaluate correlations between microstructural changes and disease duration. Results: Compared to HCs, HM patients showed significantly reduced AK, RK, MK, and FA and significantly increased AD, predominately in the bilateral corticospinal tract, right inferior longitudinal fasciculus, superior longitudinal fasciculus, inferior fronto-occipital fasciculus, and left thalamus (all p < 0.05, threshold-free cluster enhancement corrected). In addition, DKI-derived kurtosis parameters (AK, RK, and MK) had negative correlations (r = -0.448 to -0.376, all p < 0.05) and diffusion parameter (AD) had positive correlations (r = 0.372 to 0.409, all p < 0.05) with disease duration. Conclusion: HM patients showed microstructural alterations in the brain regions responsible for motor conduction and vision-related functions. DKI is useful for detecting white matter abnormalities in HM patients, which might be helpful for exploring and monitoring the pathogenesis of the disease.