• 한국전산구조공학회논문집
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• 제19권4호
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• pp.347-356
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• 2006

본 논문에서는 단면상의 화이버 요소를 사용하여 3차원 강구조물의 점진적인 소성화를 고려하는 실용적인 비선형 비탄성 해석방법을 개발하였다. 부재의 p-$\delta$, p-$\Delta$ 등의 기하비선형은 안정함수로 고려하였다. 잔류응력은 단면상에 있는 화이버 요소에 초기응력을 가하여 고려하였다. 각 하중 단계에서 탄성상태인 단면을 계산하여 축강성과 휨강성을 직접 결정함으로서 점진적인 소성화를 고려하였다. 각 화이버 요소의 응력 변화를 계산하여 변형률 반전효과를 고려하였다. 제안된 해석 방법은 3차원 강구조물의 실용적인 해석 및 설계에 유용하게 사용될 것이라 판단한다.

• 한국전산구조공학회논문집
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• 제17권2호
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• pp.95-104
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• 2004

최근 건설이 증가하고 있는 곡선교는 1960년대 까지는 직선 거더의 조합으로 구성하여 건설되어 왔으나, 현재 곡선 거더의 사용이 증대되고 있는 추세이다. 곡선 거더를 사용하는 경우에는 시간과 건설비용의 절감 뿐 아니라 미관상으로도 유리하다. 판형교에서는 전단좌굴을 방지하기 위하여 전단 좌굴강도의 검토와 보강재의 설계가 반드시 필요하다. 직선 복부판과 비교하여 곡선 복부판은 형상비와 곡률에 따라 전단좌굴 강도가 변화하나, 현재까지 곡선 복부판의 전단좌굴강도에 대한 연구는 그다지 이루어지지 않은 실정이다. 따라서 본 연구에서는 곡선복부판의 선단좌굴 강도를 유한요소해석을 통하여 알아보고 이론 산정하는 간략식을 제시하였다.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2006년도 학술발표대회 논문집
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• pp.27-31
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• 2006

Rubber hoses for automobile radiators are apt to degraded and thus failed due to the influence of contacting stresses of air and coolant liquid under thermal and mechanical loadings. The aging behaviors of the skin part of the hoses due to thermo-oxidative and electro-chemical stresses were experimentally analyzed. Through the thermo-oxidative aging test, it was shown that the surface hardness IRHD(International Rubber Hardness Degrees) of the rubber increased with a considerable reduction of failure strain as the aging time and temperature were large. On account of the penetration of coolant liquid into the skin part the weight of rubber specimens influenced by electro-chemical degradation (ECD) test increased, whereas their failure strain and IRHD hardness decreased. The hardness decreased further as the test site on the hose skin approached to the negative pole.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2002년도 봄 학술발표회 논문집
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• pp.321-328
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• 2002

Various geosynthetics used as liners or the Protection layers are installed in the solid waste landfill. The interface shear strength between geosynthetics installed at the slope of the landfill is a very important variable for the safe design of bottom and cover systems in the solid waste landfill. The interface shear strengths between (1) Geomembrane(GM)/Geotexile(GT) and (2) Geomembrane(GM)/Geosynthetic Clay Liner(GCL) were estimated by a large direct shear test in this study and were evaluated by the Mohr-Coulomb failure criterion. Especially, this research is focused on the effect of water which exists between geosynthetics because interfaces become easily wet or hydrated by rain, leachate and groundwater beneath liners. The strength reduction at large displacement and the effects of the magnitude of normal stresses and GCL hydration methods also investigated. The test results showed that the interface shear strength and shear behavior varied depending upon the magnitude of normal stresses, water at the interface, and hydration methods. Summary of secant friction angles, which could be used as reference values at a site where similar geosynthetics are installed, together with normal stress and hydration condition are presented.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.201-204
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• 2008

In this paper, several process parameter studies of the manufacturing process of the steel cords are carried out to verify the relation between the process parameters and the residual stresses on the steel cords. At first, the finite element analysis of the drawing process is performed and the residual stress distributions with respect to the wire material and the area reduction ratio are obtained. The residual stress of the drawn wire is imported the finite element analysis of the twisting process as an initial stress. After that a parameter study of the twisting process is carried out. The process parameters are the applied tension, the over-twisting angle and the tensile strength of the drawn wire. Based on these studies, the optimum values of the process parameters which can remove or reduce the undesired residual stresses are determined. The optimum value of the process parameters are confirmed by the finite element analysis of the elastic recovery process of the steel cords. Finally, the finite element analysis of the roller straightening process is done to study the variation of the distribution of the residual stress before and after the process.

• 한국약용작물학회지
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• 제17권4호
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• pp.266-272
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• 2009

Cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.95), catalyzes the reduction of hydroxycinnamaldehydes to give hydroxycinnamyl alcohols, or "monolignols," the monomeric precursors of lignin. Lignins are important components of cell walls and lignified secondary cell walls play crucial roles in long distance transport of water and nutrients during plant growth and development and in plant defense against biotic and abiotic stresses. Here a cDNA clone containing a CAD gene, named as PgCAD, was isolated from a commercial medicinal plant Panax ginseng. PgCAD is predicted to encode a precursor protein of 177 amino acid residues, and its sequence shares high homology with a number of other plant CADS. The expression of PgCAD in adventitious roots and hairy roots of P. ginseng was analyzed using reverse transcriptase (RT)-PCR under various abiotic stresses such as salt, salicylic acid, wounding and chilling treatment that triggered a significant induction of PgCAD at different time points within 2-48 h post-treatment. This study revealed that PgCAD may help the plants to survive against various abiotic stresses.

• 한국작물학회지
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• 제34권s02호
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• pp.96-114
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• 1989

There are several meterorolgical stresses in the winter cereal crops. Among these stresses, cold injury is one of the most important stresses for wheat and barley production in Korea. The reduction in grain yield of the wheat and barley due to cold injury has occurred almost every year in Korea. The objective of the study was to get the basic information in relation to the cold injury and to detect the method minimizing the damage of cold injury. When the air temperature was the ranges of -13$^{\circ}C$ to -15$^{\circ}C$, the soil temperature at the crown part of the plant was very stable, whereas in the ranges of -2$^{\circ}C$ to -3$^{\circ}C$ the soil surface temperature was more unstable and cold than air and subterranean temperatures. The different parts of the plant in wheat and barley possess the different levels of cold hardiness. In comparison to the cold hardiness of plant parts, the leaf and crown are the less sensitive to cold injury than root and vascular transitional zone. The type and extent of stress is determined by the redistribution pattern of water during freezing. These types from freezing processes were three types: a) Equilibrium freezing pattern b) Non -equilibrium freezing pattern, c) Non-equilibrium freezing pattern typical of tender tissues. Cold hardiness in wheat plants were more harder than barley plants at vegitative stage, but inverted at the reproductive stage. Injuries by low temperature during the seasons of barley cultivation in Korea were occured mainly in four stage; in the first and third stage, frost injury occurs, the second stage, freezing injury, and the fourth stage, chilling injury.

• Journal of Ginseng Research
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• 제32권3호
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• pp.232-237
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• 2008

Cinnamoyl-CoA reductase (CCR, EC 1.2.1.44) catalyses the reduction of cinnamic acid CoA esters into their corresponding aldehydes, the first step of the phenylpropanoid pathway specially dedicated to monolignol biosynthesis. A cDNA clones encoding CCR have been isolated from Panax ginseng C.A. Meyer and its expression was investigated in response to abiotic stresses. The cDNA, designated PgCCR which is 865 nucleotides long and has an open reading frame of 590 bp with a deduced amino acid sequence of 176 residues. The PgCCR encoded protein possesses substantial homology with CCRs isolated and cloned from other sources; the highest identity (51.8%) was observed with CCR from Tomato (Lycopersicon esculentum). Under various stress conditions, expression patterns of the PgCCR were highly induced in adventitious and hairy roots by several abiotic stresses. These results indicated that PgCCR plays protective role against diverse environmental stresses.

• International Journal of Oncology
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• 제54권6호
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• pp.2117-2126
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• 2019

Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine that functions as a growth suppressor in normal epithelial cells and early stage tumors, but acts as a tumor promoter during malignant progression. However, the molecular basis underlying the conversion of TGF-β1 function remains largely undefined. X-linked inhibitor of apoptosis-associated factor 1 (XAF1) is a pro-apoptotic tumor suppressor that frequently displays epigenetic inactivation in various types of human malignancies, including colorectal cancer. The present study explored whether the anti-apoptotic effect of TGF-β1 is linked to its regulatory effect on XAF1 induction in human colon cancer cells under stressful conditions. The results revealed that TGF-β1 treatment protected tumor cells from various apoptotic stresses, including 5-fluorouracil, etoposide and γ-irradiation. XAF1 expression was activated at the transcriptional level by these apoptotic stresses and TGF-β1 blocked the stress-mediated activation of the XAF1 promoter. The study also demonstrated that mitogen-activated protein kinase kinase inhibition or extracellular signal-activated kinase (Erk)1/2 depletion induced XAF1 induction, while the activation of K-Ras (G12C) led to its reduction. In addition, TGF-β1 blocked the stress-mediated XAF1 promoter activation and induction of apoptosis. This effect was abrogated if Erk1/2 was depleted, indicating that TGF-β1 represses XAF1 transcription through Erk activation, thereby protecting tumor cells from apoptotic stresses. These findings point to a novel molecular mechanism underlying the tumor-promoting function of TGF-β1, which may be utilized in the development of a novel therapeutic strategy for the treatment of colorectal cancer.

• 한국전산구조공학회논문집
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• 제20권5호
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• pp.593-604
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• 2007

합성형 사교는 비합성형 사교에 비해 역학적 측면에서 큰 장점을 지니고 있는 것이 사실이지만 사각이 심한 사교들의 경우 합성형 사교에 매우 큰 상판응력이 유발될 가능성이 있어 종종 이들 사교들에 대한 비합성형 설계가 검토되어지곤 한다. 본 연구에서는 동적해석이 가능한 비합성형 사교의 해석모델을 제안하고 이 해석모델들을 이용하여 사교들에 대한 비합성형의 적용 타당성을 검토하였다. 또한 주형과 상판과의 세 가지 상호작용(합성작용, 부분합성작용, 비합성작용)이 단순 판형사교들의 동적특성과 동적거동에 미치는 영향을 조사하였다. 주형간격, 사각, 상판 종횡비를 매개변수로 총 27개의 판형 사교들에 대한 일련의 연구를 수행하였다. 상판과 주형 경계면에서의 미끄러짐은 고유진동주기가 길어지는 현상을 유발하여 사교의 교축직각방향에 작용하는 전체밑면전단력의 크기를 감소시킬 수도 있지만 모드형장과 강성분포에 큰 영향을 미쳐 바람직하지 않은 사교 거동을 유발할 수도 있다. 부분합성작용의 최소 규정에 따라 설치된 전단연결재는 주형응력과 상판응력을 감소시키는 효과가 있다. 즉, 몇몇 사교의 경우를 제외하고는 전반적으로 부분합성형으로부터 구한 주형응력과 상판응력의 크기는 합성형 사교로부터 구한 관련 응력들의 크기와 유사하거나 약간 크게 나타난다.