• The Korean Journal of Physiology and Pharmacology
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• 제5권1호
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• pp.47-53
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• 2001

Drinking excessive alcohol has been recognized as a risk factor for hypertension. However, the mechanism by which alcohol intake causes hypertension still remains elusive. We tested the hypothesis that ethanol itself acts as a stress factor on vasculature and indirectly modulates vascular contractility. After end of exposure to 1, 2.5 and 5% ethanol for 45 min, rat aortic strips were subjected to contractile responses, immunoblot for Hsp70 and the measurement of levels of myosin light chain phosphorylation. Exposure to 5% ethanol not only augmented contractions to KCl or phenylephrine, but also increased expression of Hsp70 and the levels of myosin light chain phosphorylation. There were no significant differences in contractions produced by $1\;{\mu}mol/L$ phorbol 12,13-dibutyrate, a protein kinase C activator, whether the tissues were exposed to 5% ethanol or not. This is the first report to show that even short exposure to ethanol has a delayed effect to increase vascular smooth muscle contractility through a modulation of thick filament regulation. It may be a mechanism by which ingestion of alcohol induces hypertension.

• Journal of Photoscience
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• 제9권2호
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• pp.59-62
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• 2002

In chilling-sensitive plants, the donor side of Photosystem II is inhibited by the chilling treatment in the dark, while the acceptor side of Photosystem I is inhibited by the chilling under the moderate light. Since the addition of inhibitors of electron transfer from Photosystem II protects Photosystem I from chilling induced photoinhibition of Photosystem I, inhibition or down-regulation of Photosystem II activity in vivo may also protect Photosystem I from photoinhibition. It was revealed that dark-chilling pretreatment actually protected Photosystem I from photoinhibition. The results imply that down-regulation of Photosystem II under stress conditions may have a role to protect Photosystem I from photoinhibition.

• 대한치과의사협회지
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• 제12권2호
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• pp.113-118
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• 1974

The importance of light and stress as factors in growth has not previously been clearly delineated. As the result of using experimental environments on growth rate of incisors in 24 young rats with body weight ranging 58 Gm to 62 Gm., the author obtained following conclusions. 1) The eruption rate of normal rats incisors was 0.421mm in upper incisors and 0.592mm in lower incisors per a day respectively. 2) In light environment, growth rate of incisors in rats and body weights were found to increase more rapidly during the 8-week experimental period in comparison with any environments. 3) In stress environment, growth rate of incisors in rats and body weight were found to decrease in comparison with amy environments during the 8-week experimental period.

• 한국안전학회지
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• 제26권2호
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• pp.1-5
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• 2011

In order to evaluate fatigue endurance for an ultra-light weight inline skate frame, FEM analysis was performed. Tensile properties and a S-N curve were determined through tensile and fatigue tests on a modified Al-7075+$S_c$ alloy. The yield and ultimate tensile strengths were 553.3 MPa and 705.5 MPa, respectively. The fatigue endurance limit of this alloy was 201.2 MPa. For evaluating the fatigue endurance of the inline skate frame, the S-N data were compared with the stress analysis results through FEM analysis of the frame. The maximum Von-Mises stress of the frame was determined 106 MPa through FEM analysis of the frame, assuming that the rider weight is 75 Kg. Conclusively, on the basis of fatigue limit, the inline skate frame has a safety factor of approximately 2.0.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 추계학술대회 논문집
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• pp.285-288
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• 2007

In the recent years the using of low-density material such as high-strength Al alloy on the various industries is becoming light-weight. High strength and hollow Al alloy is good material for stiffness and recycling. Therefore the advanced manufacturing technology with Al alloy is continuously required in many industrial fields. In this study simplified hallow rectangular section of Al alloy is analyzed by FE analysis. Bending stress is affected punching and rotating of wing-die. The analysis of press bending is preformed at first. The elastic recovery value of component and stress distribution acting from the result of the bending angle of three types were obtained. The designed precesses were analyzed by the commercial FE code, Deform-3D. Forming dies for each process were designed and prototypes were manufactured by the verified forming process. Some of the important features of design parameters in the press bending were reviewed.

• 한국신뢰성학회지:신뢰성응용연구
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• 제10권2호
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• pp.137-148
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• 2010

This study deals with the accelerated life test of high power phosphor converted white Light Emitting Diodes (High power LEDs). Samples were aged at $110^{\circ}C$/85% RH and $130^{\circ}C$/85% RH up to 900 hours under non-biased condition. The stress induced a luminous flux decay on LEDs in all the conditions. Aged devices exhibited modification of package silicon color from white to yellowish brown. The instability of the package contributes to the overall degradation of optical lens and structural degradations such as generating bubbles. The degradation mechanisms of lumen decay and reduction of spectrum intensity were ascribed to hygro-mechanical stress which results in package instabilities.

• 한국환경농학회지
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• 제25권2호
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• pp.109-117
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• 2006

Photoinhibition and photoprotection of PSII in the leaves of hot pepper (Capsicum annuum L.) grown in Hoagland solution and Tap water were compared. Though changes in the rates of $O_2$ evolution as a function of photon fluence rate (PFR) were comparable, the rates of respiration in the dark was 3 times higher in the Hoagland solution grown leaves than in the Tap-water grown ones. Compared to Hoagland solution grown plane, PSIIs of Tap water grown pepper leaves were more susceptible to photoinhibitory light treatment. In order to inactivate functional PSII to the same extents, Hoagland solution grown plants required almost 2-fold high light $(1600{\mu}molm^{-2}s^-)$ treatment than those of Tap water $(900{\mu}molm^{-2}s^-)$. Interestingly, the remaining fraction of PSII in Hoagland grown pepper was able to survive under prolonged illumination in the presence of lincomycin, which probably means that the growth condition of plant seemed to have an effect on the recovery of PSII from light stress. When PSII was severly photoinactivated at a chilling temperature, recovery was observed only if the residual functional PSII were not inhibited with DCMU, Nigericin and MV during recovery. In conclusion, PSIIs grown in the Hoagland solution was more resistant to excess light than in the Tap water grown one and the recovery of PSII from photodamage was more efficient in Hoagland grown pepper leaves than Tap water grown one, which means that the increased dark respiration may play a important role in the protection of PSII from photoinhibition by helping repair photosynthetic proteins (in particular, the D1 protein of PSII) degraded by photoinhibition.

• 한국전산구조공학회논문집
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• 제25권1호
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• pp.65-71
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• 2012

본 논문에서는 수상/육상 착륙 환경에서 경항공기용 플로트의 구조적 안전성과 경량화 설계개선을 위하여 고유 진동수 및 정적 응력해석을 수행하였다. 경항공기용 플로트의 설계제원 및 형상도면을 기반으로 유한요소 모델링을 수행하였으며, 수상/육상 착륙 시점의 단순화된 하중조건을 플로트모델에 적용하였다. 먼저 알루미늄 플로트모델에 대하여 고유 진동수 및 응력해석 결과를 확인하였으며, 이를 기준으로 복합재료 적층판을 적용한 플로트모델의 구조적 안전성을 비교 검토하였다. 복합재료 플로트모델의 적층유형 및 두께 변화에 따른 무게감소와 파손지수 변화 등의 성능개선을 확인하였으며, 경량화 플로트설계에 적합한 적층유형을 제시하였다.

• 대한기계학회논문집A
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• 제20권7호
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• pp.2087-2096
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• 1996

Recentrly advantages in composite and light weight material techniques have led to the increased use of bonded dissimilar materials such as ceramics/metal bonded joints, IC package, brazing, coating and soldering in the various industries. It is required to analyze the evaluation method of fracture strength and design methodology of bonded joints in dissimilar materials. Stress singularity according to changes of scarf angles for bonded scarf joints in dissimilar materials was investigated by the boundary element method and static experiments. In this paper, effect of the stress singularity factors at the interface edges of scarf joints on various dissmilar materials combinations were investigated by analysis of its stress and stress singularity index using 2-dimensional elastic program of boundary element method. And the variations of stress singularity index by changes for Young's modulus ratios of materials and scarf angles were investigated. Also, it is found that stress singularities at bonded interface edges are disappeared for certain combination of scarf angle in a pair of bonded dissimilar materials. As the results, it is proposed that the strength evaluation by using stress singularity factors, $\Gamma$, considering stress singularity at the interface edges of bonded dissimilar materials, is very useful.

• Journal of Ecology and Environment
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• 제45권1호
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• pp.54-61
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• 2021

Background: The sunfleck is an important light environmental factor for plants that live under the shade of trees. Currently, the smartfarm has a system that can artificially create these sunfleks. Therefore, it was intended to find optimal light conditions by measuring and analyzing photosynthetic responses of Eutrema japonica (Miq.) Koidz., a plant living in shade with high economic value under artificial sunflecks. Results: For this purpose, we used LED pulsed light as the simulated sunflecks and set the light frequency levels of six chambers to 20 Hz, 60 Hz, 180 Hz, 540 Hz, 1620 Hz, and 4860 Hz of a pulsed LED grow system in a plant factory and the duty ratio of the all chambers was set to 30%, 50%, and 70% every 2 weeks. We measured the photosynthetic rate, transpiration rate, stomatal conductance, and substomatal CO2 partial pressure of E. japonica under each light condition. We also calculated the results of measurement, A/Ci, and water use efficiency. According to our results, the photosynthetic rate was not different among different duty ratios, the transpiration rate was higher at the duty ratio of 70% than 30% and 50%, and stomatal conductance was higher at 50% and 70% than at 30%. In addition, the substomatal CO2 partial pressure was higher at the duty ratio of 50% than 30% and 70%, and A/Ci was higher at 30% than 50% and 70%. Water use efficiency was higher at 30% and 50% than at 70%. While the transpiration rate and stomatal conductance generally tended to become higher as the frequency level decreased, other physiological items did not change with different frequency levels. Conclusions: Our results showed that 30% and 50% duty ratios could be better in the cultivation of E. japonica due to suffering from water stress as well as light stress in environments with the 70% duty ratio by decreasing water use efficiency. These results suggest that E. japonica is adapted under the light environment with nature sunflecks around 30-50% duty ratio and low light frequency around 20 Hz.