• 방사성폐기물학회지
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• 제19권2호
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• pp.205-214
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• 2021

Currently, the interim storage pools of spent fuels in South Korea are expected to become saturated from 2024. It is required to prepare an operation plan of a domestic dry storage facility during a long-term period, with the researches on safety evaluation methods. This study modified the FRAPCON code to predict the spent fuel integrity evaluation such as the axial cladding temperature, the hoop stress and hydrogen distribution in dry storage. The cladding temperature in dry storage was calculated using the COBRA-SFS code with the burnup information which was calculated using the FRAPCON code. The hoop stress was calculated using the ideal gas equation with spent fuel information such as rod internal pressure. Numerical analysis method was used to calculate the degree of hydrogen diffusion according to the hydrogen concentration and temperature distribution during a dry storage period. Before 50 years of dry storage, the cladding temperature and hoop stress decreased rapidly. However, after 50 years, they decreased gradually and the cladding temperature was below 400 K. The initial temperature distribution and hydrogen concentration showed a parabolic line, but hydrogen was transferred by the hydrogen concentration and temperature gradient over time.

• 한국융합학회논문지
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• 제6권4호
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• pp.99-105
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• 2015

오늘날 환경오염을 방지하기 위하여 화석연료를 사용하지 않는 크루저 보드의 1인승 이동수단이 주목을 받고 있다. 본 연구에서는 안전한 크루저 보드의 설계를 위하여 구조 해석을 수행함으로서 형상에 따른 크루저 보드의 특성들을 분석하고자 한다. 기존의 크루저 보드 모델과 새로운 형상의 크루저 보드 모델 총 두 가지 형상의 모델들을 설계하고, 유한요소해석 프로그램을 이용하여 구조 해석을 수행하여 변형량, 응력 및 피로 수명에 의한 내구성을 연구하였다. 연구 결과, 새로운 형상의 크루저 보드 모델이 최대 변형량은 0.000971mm, 최대 응력은 0.936MPa, 피로 수명은 $1827.7Cycle{\sim}1.887{\times}105Cycle$로서 새로운 모델에서의 모든 연구 결과 값들이 기존의 모델보다 더 양호하게 되어 새로운 모델이 기존의 모델보다 사용하기에 더 적합한 것으로 나타났다. 본 연구 결과는 더 안전하고 내구성이 있는 크루저 보드의 설계에 기여할 수 있으며, 디자인 면에서 융합 기술로의 접목도 가능하여 미적인 감각을 나타낼 수 있다.

• 한국보건간호학회지
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• 제5권2호
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• pp.45-51
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• 1991

The purpose of this study is to investigate the stress and coping level as a result of dysmenorrhea which was experienced by girls. For the collection of data, the girls from the 1st to the 3rd grade in middle school in Seoul were selected through a random sampling technique. The survey was conducted from the 1st. to the 14th of June, 1991 by the use of questionnaires made after a pilot study. The final subjects for analysis were restricted to only those who had experienced me~arche, the number of which totaled 1,131. The stress, coping level, and other variables, were tested and analysed by descriptive statistics (eg, frequency, percentage, mean and standard deviation), t-test, ANOVA and Pearson's correlation coefficients. The obtained results are summarized as follows. 1. The chronological start for menarche was at a mean age of 13.1 The respondents who had experienced menarche numbered $70.9\%$ of the 1st grades and $96.2\%$ of the 2nd grades in middle school, otherwise the starting age for menarche was in the 4th grade in primary school. 2. Their menstrual cycle and period were longer than adult's one. The number of students studied who had experienced dysmenorrhea during their menstrual cycle were 860, and 650 of those revealed that their mothers or sisters had experienced similar problems. 3. The subjects who were late or head left early rather than being absent from school every menstruation cycle were more stressful. The results are thought to show that the girl's perception of dysmenorrhea seems to be more sensitive than adult's one. 4, A significant negative correlation was found between the perception of menstrual flow and strees level. It means that an increase in the stress of dysmenorrhea was associated with decreased menstrual bleeding. The degree of hypochondrical concern assessed by the girls was significantly correlated to stress and coping level. When the girls perceived high stress as a result of dysmenorrhea, they worried about their physical health more. The above results lead us to the suggestion that the starting point of early education with a school program is appropriate for the 4th grade in primary school. Especially if the girls in middle school should be required to give the information about correct knowledge and sufficient self -care management of menstruation monthly, if this could be implemented the loss in school days among the students due to dysmenorrhea would be minimized with more ease.

• Journal of Power Electronics
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• 제12권3호
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• pp.410-417
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• 2012

In this paper, a direct current control method based on a one-cycle controller (DCOCC) for double frequency buck converters (DF buck) is proposed. This control method can make the average current through the high frequency and low frequency inductors of a DF buck converter equal. This is similar to the average current control method. However, the design of the loop compensator is much easier when compared with the average current control. Since the average current though the high frequency and low frequency inductors is equivalent, the current stress of the high frequency switches and the switch losses are minimized. Therefore, the efficiency of the DF buck converter is improved. Firstly, the operation principle of DCOCC is described, then the small signal models of a one cycle controller and a DF buck converter are presented based on the state space average method. Eventually, a system block diagram of the DCOCC controlled DF buck is established and the compensator is designed. Finally, simulation and experiment results are given to verify the correction of the theory analysis.

• 재활간호학회지
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• 제15권2호
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• pp.73-82
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• 2012

Purpose: The purpose of this study was to identify the influencing factors on mental health related quality of life (MHRQoL) in adults across the lifespan. Methods: A total of 688 Korean adults aged 19 years and older were selected. Data were collected by personal interviews or self report using structured questionnaires. For data analysis, t-test, ANOVA, Pearson's correlation coefficients and Stepwise multiple regression were used. Results: Mental health related quality of life (MHRQoL) differed significantly according to life cycle, especially showing a lower score in the elderly than others. In addition, elderly adulthood reported the highest stress and depression. The most significant predictors of MHRQoL in young and middle aged people were stress, depression, and subjective health status. Predictors of MHQoL in the elderly were stress and religion. Conclusion: The results indicate that MHRQoL of adult is associated with stress and depression. When the programs are developed to enhance mental health in elderly adulthood, religion should be considered as well as stress.

• 동의생리병리학회지
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• 제24권6호
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• pp.1004-1011
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• 2010

This study was designed to evaluate the protective effects of Dodamtanggami-bang (DDTG) on tunicamycin induced cell death by ER stress in C6 glial cells. Cell viability was measured by MTT assay and LDH release. Apoptosis was determined by caspase activity and flow cytometry in C6 glial cells. Expression of ER stress mediators including, GRP78 and CHOP proteins were measured by Western blot analysis. Tunicamycin induced the apoptosis of C6 glial cells, which was characterized as nucleic acid and caspase-3 activation, PARP cleavage, and sub-G0/G1 fraction of cell cycle increase. However, pretreatment with DDTG protected C6 glial cells from tunicamycin. Treatment with tunicamycin resulted in the increased the expression of GRP78 and CHOP protein and produced ROS generation. However, pretreatment with DDTG inhibited the ER stress pathway, including increase of the expression of GRP78, CHOP proteins in C6 glial cells treated with tunicamycin. Taken together, these data suggest that DDTG is able to protect C6 glial cells from tunicamycin with marked inhibition of ER stress.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.393-398
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• 2001

Pulsations, vibration and stress are the basic dynamic phenomena in power plant piping systems which directly affect system reliability. These phenomena are both acoustical and mechanical in nature and are closely interrelated. It was noticed that thermodynamic parameters were changed after replacing with new type tube bundles of reheat exchanger. It was reported later that the drain piping connecting the new bundle header with the associated drain tank is regularly pulsating at about every 3 second with 13.4㎐ and 7.5mm, p-p in amplitude. This amplitude is about 6 times higher than reference level of sound piping. The results of finite element analysis of the pipeline showed that its dominant natural frequency is 13.4㎐. The soundness is predicted whether the bending dynamic stress evaluated excesses the maximum allowable high cycle fatigue stress or not by the measured amplitude of vibration.

• Composites Research
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• 제30권6호
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• pp.410-415
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• 2017

본 연구에서는 탄소섬유강화 복합재의 제작 시 열 잔류응력으로 인한 변형을 유한요소 프로그램 ABAQUS에서 User Subroutine을 이용한 유한요소 해석을 통해 예측한다. 탄소섬유강화 복합재의 변형에 영향을 주는 다양한 요인 중 온도구배, 제품 형상, 적층각 및 적층순서, 수지의 화학수축, 열 잔류응력을 고려한 복합재 성형을 해석하였다. 같은 형상의 실제 모델과 해석 모델의 결과를 비교한다. 또한 해석 결과를 분석하여 실제 제작의 오차에 적용하여 실제 제작에서의 성형 완성도를 높이는데 목적이 있다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.733-738
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• 2002

In this study, contact fatigue in wheel-rail contact is simulated. It is necessary to calculate contact stress and subsurface stresses accurately to predict fatigue behavior. Contact stresses are obtained by contact analysis of semi-infinite solid based on influence function and subsurface stress field obtained by using rectangular patch solutions. Based on these stress values, several multiaxial high-cycle fatigue criteria are used and the critical loads corresponding to fatigue limits are calculated. The simulation results show that the critical load is decreasing rapidly and the site of crack initiation also moves rapidly to the surface from the subsurface when friction coefficient exceeds a specific value for all of three fatigue criteria.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1632-1642
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• 2014

This paper presents an interleaved resonant converter to reduce the voltage stress of power MOSFETs and achieve high circuit efficiency. Two half-bridge converters are connected in series at high voltage side to limit MOSFETs at $V_{in}/2$ voltage stress. Flying capacitor is used between two series half-bridge converters to balance two input capacitor voltages in each switching cycle. Variable switching frequency scheme is used to control the output voltage. The resonant circuit is operated at the inductive load. Thus, the input current of the resonant circuit is lagging to the fundamental input voltage. Power MOSFETs can be turn on under zero voltage switching. Two resonant circuits are connected in parallel to reduce the current stress of transformer windings and rectifier diodes at low voltage side. Interleaved pulse-width modulation is adopted to decrease the output ripple current. Finally, experiments are presented to demonstrate the performance of the proposed converter.