• 한국생산제조학회지
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• 제8권1호
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• pp.21-27
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• 1999

In this study, stress intensity factors KI, KII, KIII are existing at the same time to a hollow cylindrical bar of three dimension inclination crack. In order to investigate by experimentally the effect of the inclination angle $\psi$ of crack, artificial inclination cracks in the circumferential direction are put in the surface of a hollow cylindrical bar made by the epoxy-resin. Experimentally, stress analysis methods of stress intensity factors were proposed. But, suitable method are the caustic method and the photoelastic stress freezing method. The mixed mode of KI, and KII, were determined by the photoelastic method of the classical approach method and the FORTRAN language program of the used smallest square method.

• 한국강구조학회 논문집
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• 제11권3호통권40호
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• pp.301-309
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• 1999

본 연구의 목적은 소성영역에서의 철골 부재내에 존재하는 존재응력을 추정하는 법을 개발하기 위함이다. 여기에선 선행 실험 연구를 근거로 하여 응력집중 현상에 기인한 국부 소성화를 고려하여 보정계수법이 제안되었다. 구멍주위의 응력 분포를 파악하기 위하여 유한요소 해석을 수행하였고, 그 결과를 탄 소성역에서의 구멍내기법에 의한 결과와 비교하였다. 보정계수법을 적용한 결과, 본 연구에서 제안된 방법은 실재 초기 존재응력값과 약 2% 정도의 오차를 가진 매우 좋은 결과치를 나타냈다.

• 오토저널
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• 제3권2호
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• pp.27-33
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• 1981

In the paper, it was attempted to verify how the strength around fillet area of shifted gear would be affected by variables such as number of teeth, shifted value, and diametral pitch. Thereafter, the Lewis' tooth factor of the shifted gear was computed in terms of previously mentioned variables in order to observe the characteristics of stress change related from tooth factor and tooth number with the parameter of shifted values and diametral pitches. From the results of quasi-theoretical values by Finite Element Method(F.E.M.)and experimental values through the photo-elastic tests, the followings were identified. The more the number of gear teeth increased, the more the profile of the tooth became close to that of rack, and accordingly the stresses in the fillet area decreased significantly in certain range. Furthermore, as the shifted value and pressure angle increase the stresses tend decrease. Moreover, the stresses analyzed by F.E.M. in the filled area became around 1.22 times larger than the stresses computed by Lewis' form factor, and this is supposed as on influence of the stress concentration in fillet area.

• 한국강구조학회 논문집
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• 제10권1호통권34호
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• pp.85-99
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• 1998

본 논문은 케이슨의 인양작업중 Fitting Anchor의 취성파괴로 인한 들고리의 붕괴원인을 조사하기 위한 실험적 연구이다. 또한, 본 연구에서는 응력해석을 통하여 들고리의 붕괴메카니즘을 분석하고 이를 실제 붕괴과정과 비교한다. 본 연구에서는 파괴된 강재에 대한 파면해석 뿐만아니라 화학성분시험, 인장시험 및 샤르피 V-노치 충격시험을 실시한다. 그리고 이의 시험 결과를 정상적인 강재에 대한 시험결과와 비교한다. 본 연구의 거시적, 미시적인 방법으로 결함을 관찰한 결과, Fitting Anchor 내부에 원주방향으로 나타난 표면결함은 케이슨의 진수시 발생하는 들고리의 인장응력이 작용하기 전에 발생한 것임을 확인할 수 있었다. 이는 균열선단의 응력집중이 발생하여 작용응력보다 큰 응력이 결함에 발생한 것임을 알 수 있다. 또한, 잠재한 결함의 크기가 임계값 이상으로 증가하여 본 연구대상 강재의 응력확대계수가 증가하였을 것으로 판단된다. 그래서 균열선단의 응력확대계수가 본 강재의 파괴인성보다 크게 되어 케이슨의 인양작업중에 취성파괴를 일으킨 것으로 사료된다. 본 연구결과에 따르면 케이슨 들고리의 붕괴는 Fitting Anchor의 취성파괴로 발생한 것으로 사료된다.

• 약학회지
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• 제56권1호
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• pp.14-19
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• 2012

Nonalcoholic steatohepatitis(NASH) is serious metabolic disease related to fatty acid. According to "two hit theory", fatty acid-induced oxidative stress is important factor to progress nonalcoholic steatohepatitis from steatosis. In this study, we evaluated stearic acid induced oxidative stress in human hepatocarcinoma SK-Hep-1 cell. Cell viability, reactive oxygen species (ROS) production, glutathione (GSH), malondialdehyde and expression of antioxidant enzymes were determined at various time-points and concentrations of stearic acid. At 0.2 mM, non-toxic concentration, of stearic acid, production of ROS was significantly increased at 24 hours and the level of GSH was significantly decreased. Expression of superoxide dismutase-1 and 2 was slightly increased in 0.2 mM stearic acid at 24 hours. These results represent that the non-toxic concentration of stearic acid resulted in oxidative stress, suggesting that stearic acid may play a critical role in development of steatohepatitis.

• 한국압력기기공학회 논문집
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• 제8권3호
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• pp.7-12
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• 2012

Steam generator tubes are critical boundary of the primary and secondary side in nuclear power plants. Eddy current testing is commonly used as the method of non-destructive testing for the safety and integrity of steam generator tubes in the nuclear power plants. Changes in the geometric shape act as a stress concentration factor likely to cause a defect during the steam generator operation. The mixed-signals with the geometric shape are distorted and attributes that are difficult to detect signals. An example is bending stress due to compression process at a U-bend occurring in the intrados region which has a small radius of curvature. The resulting change in the geometric shape may lead to a dent like occurrences. The dent can cause stress concentration and generates stress corrosion cracks. In this study, the steam generator tubes of nuclear power plant were selected to study for analysis of mixed-signal containing dent and stress corrosion cracks.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.1516-1523
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• 2015

본 연구는 해상풍력 강재타워의 출입문에 발생되는 응력집중에 대해 상세히 기술하고 있다. 원형강재 풍력타워에는 8종류의 하중조합이 작용하며 그 하중조합은 극한한계상태와 사용한계상태를 고려한 정상 및 이상시 운영상태를 고려하고 있다. 유한요소해석 및 변수연구에 범용해석프로그램인 ABAQUS를 사용하였으며 응력값이 변화되는 곳을 고려하여 변위 및 응력을 검토하였다. 출입문 주변의 응력집중현상을 비교분석하기 위하여 출입문이 없는 경우, 출입문은 없으나 보강재가 있는 경우, 출입문 및 보강재가 모두 적용된 경우로 구분하여 해석연구를 수행하였다. 분석내용은 본문에 자세히 기술하고 있으며, 해석결과 응력집중계수 평균값은 1.47, 최대값은 1.81로 분석되었다.

• Journal of Nutrition and Health
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• 제43권5호
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• pp.443-452
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• 2010

Elevated plasma concentration of total homocysteine (ptHcy) is known as an independent risk factor of cardiovascular disease (CVD) and oxidative stress is also commonly implicated in CVD. An association between ptHcy and oxidative stress has recently been suggested. The study objective is to examine the relationship between ptHcy and oxidative stress markers in 103 healthy college students (62 males and 41 females). Plasma levels of ptHcy, oxidative stress markers (conjugated diene, erythrocyte catalase, TRAP, lymphocyte DNA damage), antioxidant vitamins ($\alpha$-tocopherol, $\gamma$-tocopherol, carotenoids), and lipid parameters (total cholesterol, triglyceride, HDL cholesterol) were determined. The results show that the concentration of ptHcy was significantly higher in male subjects ($22.17\;{\pm}\;2.14\;{\mu}mole/L$) than in female subjects ($12.28\;{\pm}\;0.45\;{\mu}mole/L$). There was a negative association between ptHcy and plasma ${\beta}$-carotene in male subjects (p $lt; 0.05), but no correlation between ptHcy and other plasma antioxidant vitamin levels in either gender. However, there were the negative correlations between ptHcy and plasma ${\alpha}$-carotene or ${\beta}$-carotene, and a positive correlation between ptHcy and lymphocyte DNA damage. A significantly low level of ${\alpha}$-carotene or ${\beta}$-carotene was found in male subjects with elevated ptHcy (${\geq}\;15\;{\mu}mol/L$), as compared to those with lower plasma homocysteine. These study results confirmed the views on the association between plasma homocysteine and oxidative stress markers in humans and support the hypothesis that homocysteine promotes the oxidative environment by counteracting the antioxidant defense mechanism.

• 대한간호학회지
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• 제29권2호
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• pp.445-455
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• 1999

This study has been conducted on the nonequivalent control group pretest-posttest design in quasi experimental basis and newly born premature infants from intensive care unit of G Medical University Hospital in Inchon Metropolitan were selected in two groups of 21 infants each. The first group for experimental and the other for control. Data has been collected form October 30, 1997 to August 29, 1998. For the experimental group tactile and kinesthetic stimulation was applied 2 times a day for 10 days(10 : 00~11 : 00 hours in the morning and 17 : 00~18 : 00 in the afternoon). As a weight weighing instrument. electronic indicator scale(Cas Co. korea) was used. To determine urine cortisol concentration level in stress hormone, radio immune assay method was used. And high performance liquid chlomatography was used to determine urine norepinephrine, concentration level To determine behavior status, tools developed by Anderson et at(1990) and remodeled by Kim Hee-Sook(1996) were used. Collected data were analyzed with the SAS program using x$^2$-test, student t-test, repeated measures ANOVA and paired t -test. The result were as follow. 1. As for the daily weight gain. the experimental group showed first change in weight and this group also showed higher weight in the average weight than the control group. Statistically, however, there was no significant factor between the two group. 2. The cortisol concentration in urine showed decrease in the experimental group norepinephrine concentration in urine showed increase in both experimental and control groups. No statistical significance was shown between the two groups. 3. In the aspect of behavior status. the experimental group showed statistical significance by showing inactive in the state of alert and conversion to a positive state than the control group. In conclusion, the sensory stimulation in this study showed a positive aspect through there was no statistical significance in the weight gain and urine stress hormone concentration. In the behavior status, there was statistical significance in the frequency of staying inactive in the state of alert and conversion to a positive state.

• Smart Structures and Systems
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• 제19권2호
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• pp.203-211
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• 2017

This paper provides a numerical solution for multiple confocal elliptic dissimilar cylinders. In the problem, the inner elliptic notch is under the traction free condition. The medium is composed of many confocal elliptic dissimilar cylinders. The transfer matrix method is used to study the continuity condition for the stress and displacement along the interfaces. Two cases, or the infinite matrix case and the finite matrix case, are studied in this paper. In the former case, the remote tension is applied in y- direction. In the latter case, the normal loading is applied along the exterior elliptic contour. For two cases, several numerical results are provided.