• Journal of Ocean Engineering and Technology
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• v.2 no.1
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• pp.116-124
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• 1988

해양구조물의 원통조인트에 대한 피로 수명 산출이 전통적으로 실험적 방법에만 의존해 왔음은,원통조인트의 구조가 복잡하여 용접부위 균열의 응력확대 계수 계산이 거의 불가능 했든 것이 주 원인이었다. 최근에 유한요소 3차원 모델을 이용한 계산방법이 개발되어 심히 구조적으로 복잡한 표면 균열의 응력확대계수 산출이 용이하게 되었다. 해양 구조물의 원통조인트에 대한 피로 수명 산출법을 개발하기 위한 연속되는 3부작의 제1부로서 본 논문은 X형 원통 조인트 용접주위 표면 균열의 응력확대 계수 거동을 분석하고 있다. 분석결과를 이용하여 응력확대계수를 엄격한 방법에 의해 계산하였다. 계산된 응력확대계수를 구조적인 관점에서 해석하고 있다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.163-171
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• 1996

For the effective analysis of two dimensional plane problems, Treffiz finite elements and cavity elements have been proposed. These element matrix equaitons were formulated on the basis of hybrid variational principle and Treffiz function sets derived consitstently from the complex theoy of plane elasticity. In order to suggest the accuracy chatacteristics of the proposed Treffiz elements typical plane problems were analyzed and these results were compared with ones obtained by using the conveintional displacement type elements. The accuracy of the proposed elements is less sensitive to the element size and shape than the conventional displacement type elements. These elements, being able to be formed with multi-nodes, give the convenient modeling of an analytic domain. The cavity elements give the comparatively exact values of stress concentration factors of stress intensity factors and can be effectively used for the analysis of mechanical stuctures containing various cavities.

• Journal of the Korean Society of School Health
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• v.33 no.3
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• pp.139-147
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• 2020

Purpose: The study aimed to identify factors affecting unintentional injuries at school focusing on violent experiences in adolescents. Methods: The study used the raw data of the Korea Youth Risk Behavior Web-based Survey (2019). A total of 60,040 students were included in the analysis. Descriptive statistics, χ2 test, and multiple logistic regression were performed, using SPSS version 25.0. General characteristics, gender, school, academic achievement, living with family, socioeconomic status, vigorous physical activity, perceived stress, sleep satisfaction, high caffeine drinking, risky alcohol drinking, smoking, sexual experience, drug use, and safety education, were adjusted for and the relationship between unintentional injuries and violence was analyzed. Results: The results showed 2.4% of the adolescents had experienced violence and 24.7% had suffered unintentional injuries. Violent experiences had a significant effect on unintentional injuries among adolescents. Injuries were 1.93 times higher among adolescents who had experienced violence. Gender, school levels, high-intensity physical activity, stress, sleep satisfaction, high caffeine drinks, dangerous drinking, drug use, and safety education were associated with unintentional injuries among adolescents. Conclusion: Adolescents at high risk of suffering violence and injuries should be identified and assessed preemptively. In addition, it is necessary to implement systematic school health-centered safety education programs in order to prevent violence and injuries.

• Journal of the Korean GEO-environmental Society
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• v.10 no.4
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• pp.65-71
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• 2009

Hydraulic fracturing technology has been widely applied in the industry for the recovery of the natural resources such as gas, oil and geothermal heat from hot dry rock. During hydraulic fracturing stimulation, multiple cracks are created resulting in mechanical interaction between cracks. Such an interaction influences obtaining hydraulic fracturing key parameters (crack opening, length, and borehole net pressure). The boundary collocation method (BCM) has been proved to be very effective in considering mechanical interaction. However, for better confidence, it needs to be verified by comparison with analytical solutions such as stress intensity factors. In this paper, three cases, single fracture in remote uniaxial tension, single fracture in remote shear stress field and two arbitrary segments in an infinite plane loaded at infinity are considered. As a result, the BCM is proved to be valid technique to consider mechanical interaction between cracks and can be used to estimate the hydraulic fracturing parameters such as opening of the fracture, and so on.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3048-3057
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• 1996

Analysis model containing two inclined surface cracks on semi-infinite elastic body is established and analyzed on the basis of linear fracture mechanics to examine mutual interference of two surface cracks. Muskhelishvili's complex stress functions are introduced and a set of singular integral equations is obtained for a dislocation density function. The stress intensity factors at crack tip are obtained by using the Gerasoulis'method. When two surface cracks are parallel and have the same length, the values of $K_1$and $\Delta K_11$(variation of $K_11$) for crack 1 and crack 2 decrease by the mutual interference of two surface cracks as the distance between the two surface cracks shortens. The effect of mutual interference is remarkable in high friction coefficient. In case that two surface cracks are parallel, the values of $K_1$and $\Delta K_11$for crack 2 decrease as the length ratio ot crack 2 to crack 1 becomes small. As the crack inclination angle rises, the value of $K_1$ and the mutual interference of $K_1$for crack 2 increase and the value of$\Delta K_11$ for crack 1 becomes smaller than that for crack 2.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.713-724
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• 2004

A fatigue crack found at the coped stringer of the old dismantled Dangsan Subway Bridge was numerically simulated. A model of a single span of the plate girder bridge with its beam elements was created and analyzed in order to obtain the nominal stress history caused by trains. A detailed FEM analysis of the coped stringer was conducted using a shell element model. A fracture mechanical model was used to estimate crack propagation. The stress intensity factors were calculated using the J-Integral method. The simulation with some reasonable assumptions showed that the calculated crack lengths were comparable to those found on the site.

• Journal of Life Science
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• v.21 no.6
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• pp.838-844
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• 2011

The purpose of this study was to investigate gender-specific changes of plasma MDA, SOD, and lymphocyte DNA damage during high intensity exercise. In this study, 17 healthy male and 18 healthy female college students ran on a treadmill at 85%$VO_{2max}$ until the point of all-out. Blood-collecting was carried out five times (Rest, Ex-Exha, R0.5h, R4h and R24h), and with the collected blood, plasma malondialdehyde (MDA), superoxide dismutase (SOD), and lymphocyte DNA damage were analyzed. Plasma MDA and SOD concentration increased significantly at the Ex-Exha (p<0.05), and there were no significant differences in gender. For the degree of lymphocyte DNA damage, all %DNA in the tail, tail length and tail moment increased significantly at the Ex-Exha (p<0.05), and %DNA in the tail and tail length were significantly higher in the male group than in the female group (p<0.05). These results suggest that acute high intensity exercise not only causes oxidative stress but also brings about lymphocyte DNA damage. In addition, it was found that males showed higher DNA damage than females in terms of oxidative stress subject to high intensity exercise. Nevertheless, further subsequent studies are required in order to better understand the mechanism behind DNA damage varying with gender, in a way that takes into consideration physical fitness, hormonal level, exercise intensity and duration - additional factors which might affect DNA damage.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.3
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• pp.57-67
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• 2023

A flash drought is a rapid-onset drought that develops over a short period of time as weather and environmental factors change rapidly, unlike general droughts, due to meteorological abnormalities. Abnormally high evapotranspiration rates and rapid declines in soil moisture increase vegetation stress. In addition, crop yields may decrease due to flash droughts during crop growth and may damage agricultural and economic ecosystems. In this study, Flash Drought Intensity Index (FDII) based on soil moisture data from Gravity Recovery Climate Experiment (GRACE) was used to analyze flash drought. FDII, which is calculated using soil moisture percentile, is expressed by multiplying two factors: the rate of intensification and the drought severity. FDII was developed for domestic flash drought events from 2014 to 2018. The flash drought that occurred in 2018, Chungcheongbuk-do showed the highest FDII. FDII was higher in heat wave flash drought than in precipitation deficit flash drought. The results of this study show that FDII is reliable flash drought analysis tool and can be applied to quantitatively analyze the characteristics of flash drought in South Korea.

• Physical Therapy Rehabilitation Science
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• v.11 no.4
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• pp.565-570
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• 2022

Objective: The purpose of this study was to investigate the correlation between activity of daily living and social psychology and work mind of office workers with non-specific chronic neck pain (NSCNP). Design: Crossed-sectional study Methods: 86 patients with NSCNP were recruited for this study. Neck disability index (NDI) and Numerical pain rating scale (NPRS) were used to check the pain intensity and disability of patients with neck pain. To find out the occupational factors of the subjects, the Korean version of Latack Coping Scale was used. And,To find out the socio-psychological factors of the subjects, the Korean version of depression anxiety stress scale (DASS-21) was used. We performed correlation for each variable. Results: The correlation between NPRS and NDI and DASS-21 Scale were clear positive correlation (p<0.05). There was no statistical significance between the LATACK control group and the pain and disability index (p>0.05). A clear positive correlation was established between the avoidance group of LATACK and pain (p<0.01). Conclusions: Through this study, it is necessary to have time to manage depression, anxiety, and stress in the treatment of neck pain in office workers who spend a lot of time sitting. In addition, it is thought that there should be the ability to control oneself about one's duties in the workplace.

• Journal of East-West Nursing Research
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• v.28 no.2
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• pp.122-131
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• 2022

Purpose: This study aimed to identify the factors related to fear of falling (FOF) in different age groups from community-dwelling mid to late-adults. Methods: To identify the factors related to FOF, data of 162,684 adults over 45 years of age from 2019 Community Health Survey was analyzed using logistic regression with complex samples. Results: Factors related to FOF found in all age groups were sex, previous experience of falls, physical activity levels over moderate intensity, subjective health status, number of chronic diseases, stress, depression, and cognitive decline. In the 45-64 age group, the FOF was significantly higher in the groups of low education level and low monthly household income. In the 65-74 and over 75 age groups, the FOF was significantly higher in the groups of not living with spouse and walking not practiced. Conclusion: We suggests that understanding of risk factors and early detection of fall risk patients in each age group are necessary to establish and apply tailored fall prevention programs for prevention and management of the FOF in community-dwelling mid to late-adults.