• Structural Engineering and Mechanics
• /
• v.47 no.1
• /
• pp.1-25
• /
• 2013

A combined thermal and mechanical action in roller compacted concrete (RCC) dam analysis is carried out using a three-dimensional finite element method. In this work a numerical procedure for the simulation of construction process and service life of RCC dams is presented. It takes into account the more relevant features of the behavior of concrete such as hydration, ageing and creep. A viscoelastic model, including ageing effects and thermal dependent properties is adopted for the concrete. The different isothermal temperature influence on creep and elastic modulus is taken into account by the maturity concept, and the influence of the change of temperature on creep is considered by introducing a transient thermal creep term. Crack index is used to assess the risk of occurrence of crack either at short or long term. This study demonstrates that, the increase of the elastic modulus has been accelerated due to the high temperature of hydration at the initial stage, and consequently stresses are increased.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.17 no.6
• /
• pp.68-74
• /
• 2018

Study on the Ti-6Al-4V have been carried out using cutting simulation, and researches for cutting force and chip shape prediction have been actively conducted under various conditions. However, a 3D printer application method using Ti-6Al-4V metal powder material as a high-power method has been studied for the purpose of prototyping, mold modification and product modification while lowering material removal rate. However, in the case of products / parts made of 3D printers using powder materials, problems may occur in the contact surface during tolerance management and assembly due to the degradation of the surface quality. As a result, even if a 3D printer is applied, post-processing through cutting is essential for surface quality improvement and tolerance management. In the cutting simulation, the cutting force and the chip shape were predicted based on the Johnson-Cook composition equation, but the shape of the shear type chip was not predictable. To solve this problem, we added a damaging term or strain softening term to the Johnson-Cook constitutive equation to predict chip shape. In this thesis, we applied the constant value of the S-K equations to the cutting simulation to predict the cutting force and compare with the experimental data to verify the validity of the cutting simulation and analyzed the machining characterization by considering conditions.

• Women's Health Nursing
• /
• v.24 no.3
• /
• pp.233-242
• /
• 2018

Purpose: To identify risk factors for premature birth among premature obstetric labor women. Methods: Participants were 129 hospitalized women who were diagnosed with potential premature obstetric labor with 20 weeks to 37 weeks of gestation. Data were analyzed using descriptive statistics, $x^2$ test, t-test, and binary logistic regression. Results: Of 129 women, 78(60.5%) gave premature birth and 51 (39.5%) gave full-term birth. Risk factors for premature birth were education level (${\leq}$bachelor's degree), abnormal bowel condition (constipation or diarrhea), time firstly diagnosed with a premature obstetric labor (below 28 weeks of pregnancy), and multiple pregnancy. There were also increased risks of premature birth for participants with high level of anxiety and high level of prenatal stress. In social support, there was an increased risk of premature birth for participants with low level of social support. Conclusion: Prenatal nursing programs should consider not only psychosocial factors such as anxiety, prenatal stress, and social support, but also some general and obstetric factors such as education level, abnormal bowel condition, time firstly diagnosed with a premature obstetric labor, and multiple pregnancy to increase maternal and child health.

• Nutrition Research and Practice
• /
• v.16 no.2
• /
• pp.173-193
• /
• 2022

BACKGROUND/OBJECTIVES: Alzheimer's disease (AD) is one of the most representative neurodegenerative disease mainly caused by the excessive production of amyloid beta (Aβ). Several studies on the antioxidant activity and protective effects of Populus tomentiglandulosa (PT) against cerebral ischemia-induced neuronal damage have been reported. Based on this background, the present study investigated the protective effects of PT against cognitive impairment in AD. MATERIALS/METHODS: We orally administered PT (50 and 100 mg/kg/day) for 14 days in an Aβ_25-35-induced mouse model and conducted behavioral experiments to test cognitive ability. In addition, we evaluated the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum and measured the production of lipid peroxide, nitric oxide (NO), and reactive oxygen species (ROS) in tissues. RESULTS: PT treatment improved the space perceptive ability in the T-maze test, object cognitive ability in the novel object recognition test, and spatial learning/long-term memory in the Morris water-maze test. Moreover, the levels of AST and ALT were not significantly different among the groups, indicating that PT did not show liver toxicity. Furthermore, administration of PT significantly inhibited the production of lipid peroxide, NO, and ROS in the brain, liver, and kidney, suggesting that PT protected against oxidative stress. CONCLUSIONS: Our study demonstrated that administration of PT improved Aβ_25-35-induced cognitive impairment by regulating oxidative stress. Therefore, we propose that PT could be used as a natural agent for AD improvement.

• Journal of Biomedical Engineering Research
• /
• v.23 no.2
• /
• pp.119-130
• /
• 2002

The nonlinear finite element program has been developed to analyze the design performance of an artificial hip prosthesis and long term behavior of a treated femur with stems made of composite material after cementless total hip arthroplasty(THA). The authors developed the three dimentional FEM models of femoral bone with designed composite stem which was taken with elliptic cross section of 816 brick elements under hip contact load and muscle farce in simulating single leg stand. Using the program, density changes, stress distributions and micromotions of the material femoral bone were evaluated by changing fiber orientation of stems for selected manufacturing method such as plate cut and bend mold. The results showed that the composite materials such as AS4/PEEK and T300/976 gave less bone resorption than the metallic material such as cobalt chrome alloy, titanium alloy and stainless steal. It was found that increasing the long term stability of the prosthesis in the femur could be obtained by selecting the appropriate ply orientation and stacking sequence of composite.

• Advances in concrete construction
• /
• v.5 no.3
• /
• pp.271-288
• /
• 2017

This paper aims to investigate the effects of replacing cement with ground granulated blast furnace slag (GGBFS) in self compacting concrete in the fresh and hardened state. The performance of SCC in moderate climate is well investigated but few studies are available on the effect of hot environment. In this paper, the effect of initial water-curing period and curing conditions on the performance of SCC is reported. Cement was substituted by GGBFS by weight at two different levels of substitution (15% and 25%). Concrete specimens were stored either in a standard environment (T=$20^{\circ}C$, RH=100%) or in the open air in North Africa during the summer period (T=35 to $40^{\circ}C$; R.H=50 to 60%) after an initial humid curing period of 0, 3, 7 or 28 days. Compressive strength at 28 and 90 days, capillary absorption, sorptivity, water permeability, porosity and chloride ion penetration were investigated. The results show that the viscosity and yield stress are decreased with increasing dosage of GGBFS. The importance of humid curing in hot climates in particular when GGBFS is used is also proved. The substitution of cement by GGBFS improves SCC durability at long term. The best performances were observed in concrete specimens with 25% GGBFS and for 28 days water curing.

• The Journal of Internal Korean Medicine
• /
• v.25 no.1
• /
• pp.1-15
• /
• 2004

Objective : This study was aimed to evaluate the anti-starvation stress effect of Liriopis Tuber on mice. Method : The first experiment was done to mice which have a high corticosterone level at a short term starvation. The plasma corticosterone level of each mouse was measured over time at 12, 24, 36, 48, 72 hours of starvation respectively. The second experiment was done in the two groups(LT A and LT B) of mice which were in famine for 36.5 hours after being administered Liriopis Tuber three times with different doses(LT A: 1.0 g/.kg and LT B: 3.0g/kg) for three days. The plasma corticosterone levels and rectal temperature were measured when a 36.5-hour of starvation period was finished. Results : 1. The corticosterone level in the mice was significantly increased after a 36.5-hour of starvation. (P<0.001). 2. The plasma corticosterone level was decreased significantly in the group of 3.0g/kg, compared to the control group.(P<0.05) 3. The rectal temperature in the groups of 1.0g/kg and 3.0g/kg were increased slightly in both group. But the two groups didn't show significant change. Conclusion: Based on the above results, Liriopis Tuber might have anti-starvation stress effect and it may be used as anti-starvation stress medicine and anti-stress medicine. Conclusion : Based on the above results, Liriopis Tuber might have anti-starvation stress effect and it may be used as anti-starvation stress medicine and anti-stress medicine.

• Journal of Digital Convergence
• /
• v.13 no.3
• /
• pp.137-153
• /
• 2015

Technostress- a term coined by Craig Brod- refers to a modern disease of adaptation caused by an inability to cope with new technologies. Stress is a person's adaptive response to a stimulus that places excessive psychological or physical demands on that person. In a similar vein, technostress can affect a variety of side effect such as low work productivity and resistance against new technology. The purpose of this study is thus to investigate of differences of technostressors using demographic informations such as gender, age, computer use skill, and industrial types. To do this, we conducted independence t-test and analysis of variance. We found that demographic characteristics can affect the differences of technostressors. Conclusions and implications are discussed in the last section of this paper.

• Journal of Korean Critical Care Nursing
• /
• v.15 no.3
• /
• pp.101-114
• /
• 2022

Purpose : This study aimed to identify post-traumatic stress disorder (PTSD) and burnout experienced by healthcare providers who cared for patients with Coronavirus Disease 2019 (COVID-19) and their influencing factors. Methods : Data were collected from 135 healthcare providers who cared for patients with COVID-19 in a tertiary general hospital from June 8 to September 2, 2021, using a questionnaire. Descriptive statistics, Mann-Whitney U test, Kruskal-Wallis test, t-test, ANOVA and Scheffe's test, Pearson's correlation coefficients, and multiple regression were used for analysis using SPSS/WIN 27.0. Results : Participants' average PTSD score was 9.31 ± 11.80, and 8.9% were in the high-risk group. Participants' average burnout score was 51.77±21.28, and 62.2% were at high risk. PTSD scores differed significantly according to participants' age, education, job, position, and current workplace. Burnout scores differed significantly according to their age, gender, marital status, parental status, and education. There was positive correlation between participants' PTSD and burnout. The factors influencing participants' PTSD were term of self-isolation and age (R²=.09). There were no significant influencing factors on participants' burnout. Conclusion : This study reconfirmed that healthcare providers who cared for patients with COVID-19 experienced both PTSD and burnout, suggesting that interventions are needed such as regular pre-training or simulation training and establishing a support system.

• Asian Pacific Journal of Cancer Prevention
• /
• v.13 no.11
• /
• pp.5849-5855
• /
• 2012

Objective: The purpose of this study was to determine pretreatment effects of moderate-term endurance training before the various dosages (10 and $20{_{mg.kg}}^{-1}$) of DOX on a heat shock protein ($HSP_{70kda}$) and cardiotoxicity in heart tissue. Methods: Forty-eight male rats were randomly assigned to nontraining (NT) and training (T) groups and three subgroups; $DOX{_{10mg.kg}}^{-1}$ and $DOX{_{20mg.kg}}^{-1}$ and saline treatment. The training program included treadmill running between 25-39 min/day and 15-17 m/min, 5 days/wk for 3 wk. Result: DOX administration, in particularly with $20{_{mg.kg}}^{-1}$, caused up-regulation of oxidants and cardiac damage (MDA, CK, CPK-MB and CK/CPK-MB) and down-regulation of cardioprotection ($HSP_{70}$, SOD) markers, as compared to NT+saline group. Pretreatment effect of treadmill running endurance exercise in the presence of DOX with $10{_{mg.kg}}^{-1}$ caused a significant increase in $HSP_{70}$, SOD and a significant decrease in MDA and insignificant decrease in CK, CPK-MB and CK/CPK-MB, in comparison $T+DOX_{10}$ with $NT+DOX_{10}$ group. However, there was no significant difference between $T+DOX{_{10mg.kg}}^{-1}$ and $T+DOX{_{20mg.kg}}^{-1}$ in the aforesaid markers. Conclusion: Dox-induced cardiotoxicity is related to oxidative stress. Our study suggests that pretreatment with endurance exercise may be considered as a potentially useful strategy to improve myocardial tolerance against single dose DOX-induced oxidative damage.