• Journal of the Korea institute for structural maintenance and inspection
• /
• v.15 no.5
• /
• pp.75-81
• /
• 2011

Recently prestressed concrete bridges are generally used instead of reinforced concrete. PSC is more durable than RC because it can reduce crack problems, reinforcement corrosion, leakage and carbonation etc. And also PSC is more effective because there is no crack in tension area, and the entire concrete section is considered in section analysis. And it can reduce section size because vertical component by prestressing force can reduce the shear force. However, using high strength concrete can increase the self weight of bridge because of it's higher density. So the hollowed PPC girder with light weight aggregate can be a alternative. In this study the hollowed PPC girder with light weight aggregate is designed and the performance of hollowed PPC girder is evaluated by experimental tests as well as numerical analysis. As a result, The hollowed PPC girder of light aggregate behaved fully elastically under service load of 110kN, and the plastic behavior was showed after elastic behavior through experimental test, and it can be also estimated by numerical analysis.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.39 no.12
• /
• pp.1753-1760
• /
• 2010

This study was designed to investigate the protective effects of Sasa borealis leaves on high glucose-induced oxidative stress in human umbilical vein endothelial cells (HUVECs). Freeze-dried Sasa borealis leaves were extracted with 70% methanol and followed by a sequential fractionation with dicholoromethan, ethyl acetate, butanol and water. The ethyl acetate fraction from Sasa borealis leaves extract (ESLE) was used in this study because it possessed the strongest antioxidant activity among the various solvent fractions. Exposure of HUVECs to 30 mM high glucose for 48 hr resulted in a significant (p<0.05) decrease in cell viability, glutathion (GSH) concentration, activities of antioxidant enzymes including superoxide dimutase (SOD), glutathion peroxidase (GSH-px) and catalase, and a significant (p<0.05) increase in intracellular ROS and lipid peroxidation formation in comparison to the cells treated with 5.5 mM glucose. ESLE treatment decreased intracellular ROS and lipid peroxidation formation and increased cell viability, GSH concentration and expressions of SOD and catalase in HUVECs. These results suggest that ESLE may be able to protect HUVECs from high glucose-induced oxidative stress, partially through the antioxidative defense systems.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.43 no.11
• /
• pp.1674-1680
• /
• 2014

The aim of this study was to investigate the protective effects of methanolic extracts of cooked mixed grain rice samples, including grain rice (sorghum, black bean, proso millet, and Job's tears) mixed with fermented brown rice (GR), GR added with 0.5% water extract of Sanghwang mushroom (GRS) or 0.1% curry (GRK), and traditional five grain mixed rice (TMR, Ohgokbap), on $H_2O_2$-induced oxidative injury in LLC-PK1 pig renal epithelial cells. White rice (WR) was used as a positive control. Cells were first exposed to $H_2O_2$ ($250{\mu}M$) for 4 hr, followed by treatment with $100{\mu}g/mL$ of different GR extracts for 24 hr. $H_2O_2$ significantly induced cell damage (P<0.05). Cellular levels of reactive oxygen species (ROS), lipid peroxidation, and antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-px), were measured. In addition, mRNA levels of antioxidant enzymes were determined by RT-PCR assay. Mixed grain rice, particularly GRS and GRK, were able to reduce cellular levels of ROS, decrease lipid peroxidation, and also increase mRNA expression of antioxidant enzymes compared to other samples. These results suggest that mixed grain rice, specifically GRS and GRK, have strong protective effects against $H_2O_2$-induced oxidative injury in LLC-PK1 cells through inhibition of lipid peroxidation, reduction of ROS levels, and elevation of antioxidant enzyme activities.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.6
• /
• pp.942-947
• /
• 2003

The effects of anti-stress rose (Rosa mutiflora) fruit extract yoghurts (RFEY-1.0, RFEY-3.0, RFEY-5.0 containing with 1.0, 3.0 and 5.0% of rose fruit extract) were tested for the anti-stress effects. ICR male mice (20$\pm$2 g) were fed with basic experimental diets and given free access to water containing these ingredients for 18 days. Psychological stress and sociopsychological stress exposed by foot-shock for 1 hour (10 sec duration at intervals of 120 sec) every day for 3 days. RFEY-1.0, RFEY-3.0, RFEY-5.0 groups in the sociopsychological stress resulted in a significant decrease of 11.7%, 16.0% and 24.7% in plasma corticosterone (CS) secretion compared with psychological stress (control group). Noradrenaline (NA) secretions in the brain were significantly increased 15.6%, 25.0% and 40.8%, respectively, in RFEY-1.0, RFEY-3.0, RFEY-5.0 groups compared with control group. MHPG -SO$_4$ (3-methoxy-4-hydroxy-phenylethyleneglycol sulfate) levels in the brain resulted in a marked decreases of 17.0%, 25.3% and 28.4%, respectively, in RFEY-1.0, RFEY-3.0, RFEY-5.0 groups compared with control group. NA/MHPG-SO$_4$ ratios in the brain of RFEY-1.0, RFEY-3.0, RFEY-5.0 groups resulted in a significantly increase of 39.5%, 67.3% and 96.3%, respectively, compared with control group. These results suggest that rose fruit extract yoghurt may be tried to apply for human consumption such as sociopsychological stress.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.242.2-242.2
• /
• 2013

최근 산화물 반도체 박막 트랜지스터의 신뢰성(reliability) 평가에 대한 연구가 활발히 이루어지고 있다. 신뢰성 평가하는 한 방법으로 게이트에 바이어스를 지속적으로 인가하여 소자의 문턱 전압의 변화를 통해 안정성(stability)를 확인한다. 전압을 지속적으로 인가하게 되면 소자를 열화시켜 전기적 특성이 약화된다. 본 연구에선 ITZO 박막 트랜지스터의 신뢰성 평가를 위해 게이트 절연막($SiO_2$, $SiN_x$)에 따른 ITZO 소자를 제작 및 게이트 바이어스 스트레스 후 전기적 특성을 비교, 분석하였다. 제작된 소자의 게이트에 전압을 +15V로 7200초 동안 인가하였다. 스트레스 후 게이트 절연막이 $SiO_2$, $SiN_x$인 ITZO 산화물 박막 트랜지스터 모두 positive 방향으로 이동하였고, 그 결과 문턱 전압, 이동도, 아문턱 기울기의 변화가 발생하였다. $SiO_2$의 경우 아문턱 기울기의 변화가 거의 없이 문턱 전압의 변화만을 보였고, 이는 단순히 ITZO층과 게이트 절연막 계면에 전자가 포획되거나 혹은 게이트 절연막 내에 전자가 주입이 되었기 때문이다. 반면에 $SiN_x$의 경우 ITZO층과 게이트 절연막 계면에 추가적인 결함(defect)이 생성되었기 때문에 $SiO_2$보다 더 많은 전자를 포획하여 아문턱 기울기와 문턱 전압의 변화가 컸다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.4
• /
• pp.167-174
• /
• 2006

The purpose of this paper is to analyse and compare experimentally flexural behavior of RC beams strengthened with CFRP plates by different methods, which are divided into three classes: externally-bonded without end anchorage, externally-bonded with end anchorages, and anchored after prestressing of CFRP plates. Test results show that the RC beams strengthened with end anchorages have the improvement of ductility and flexural performance evaluation including ultimate strength and deflection, compared with only external bonding. Especially, RC beams with prestressed and anchored CFRP plates increase ultimate strength and ductility significantly.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.4
• /
• pp.75-82
• /
• 2021

The objective of this study is to examine the loss of prestressing stress in the developed prestressing reinforcing units using steel bar and pipe (SP). The main parameters were the reinforcing bar type, the magnitude of prestressed force, and prestressing method. The test results showed that the loss of prestressing stress for SP was highest in the initial prestressing step, which was higher for the compression introduction typed specimens than tension introduction typed specimens. The loss of prestressing stress of SP made with P800 was 1.6% for the compression introduction typed specimen with 0.8f_y, which was lowest than the other specimens. Meanwhile, the relaxation of SP with the respect to the time ranged between 0.4 and 1.9%, irrespective of SP material type, the magnitude of prestressed force, and prestressing method. These values were less than 2.5%, which is the maximum value for the relaxation of prestressed reinforcing steel bars in design codes. Consequently, considering the loss of stress developed in the initial prestressing step, the developed SP material type, prestressing introduction method, and magnitude are recommended to be P800, compression introduction type, and 0.8f_y.

• Journal of the Korea Convergence Society
• /
• v.12 no.8
• /
• pp.85-92
• /
• 2021

This study was conducted to identify the impact of adolescents' dietary behavior on their stress perception and provide basic data for education programs linked to customized nutrition education by gender. In this study, the 2019 Korea Youth Risk Behavior Web-based Survey was used, and a total of 57,303 middle·high school students were selected. Controlling adolescents' age, school record, economic status, residence type, subjective health and body type perception, and the dietary life variables designed with breakfast, fresh foods(fruit, vegetables, milk, water), processed foods(carbonate beverage, energy beverage, sweet beverage, fast food) were analyzed to have an effects on the stress recognition of adolescents. Breakfast had a negative(-) effect on stress perception in all genders of adolescents, and in the case of fresh food, water for boys and fruit for girls had the highest negative(-) effect on stress perception, and in the case of processed foods, energy drink was the dietary factor that had the highest positive(+) effect on adolescents' stress perception. These results suggest that it is necessary to develop a dietary education program tailored to the gender of adolescents to improve their stress perception, and to provide continuous guidance to form a healthy diet.

• Proceedings of the Korea Contents Association Conference
• /
• 2014.11a
• /
• pp.441-442
• /
• 2014

최근 Social Network Service를 통해 사회적 네트워크를 구축하는 등의 많은 혜택으로 인해 SNS 이용자 수가 증가하였지만, 개인 정보유출, 게시물의 과부하 등과 같은 역기능으로 SNS 이용에 피로감을 느끼고 있는 실정이다. 따라서 본 연구에서는 페이스북 이용자들을 대상으로 SNS에 따른 테크노스트레스 유발요인과 테크노스트레스에 따른 대응방식(Coping)에 대해 연구하고자 한다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.2
• /
• pp.113-120
• /
• 2014

This paper showed the behavior of the material four members under blast load, and are trying to demonstrate the effectiveness of the prestress. The prestressed concrete structures are on the rise, but there is little research in this regard explosion. Concrete panels, Reinforced concrete panels, the prestressed concrete panels, and the prestressed reinforced concrete panels was set variables. TNT 500 kg was an explosion in the distance 3m. Analysis, concrete and reinforced concrete members after an explosion occurred continuously deformed, but the including prestressed panel deformation occurs only at the beginning of the explosion were able to see the results. That is, the including prestressed member is prestressed against blast load cracking and destruction can be seen that control.