• 대한기계학회논문집A
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• 제23권6호
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• pp.1039-1047
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• 1999

It is necessary to evaluate the fatigue behavior of rail steel under the multi-axial stress state to assure the railway vehicle's safety. For this purpose, the stress analysis to investigate the crack initiation criteria, static failure and fatigue behavior under mixed-mode are performed. The stress analysis results show that the initiation of the transverse fissure depends on the maximum shear stress below the surface. For the mixed mode, the fatigue crack growth behavior which is represented by the projection crack length and comparative S.I.F, ${\Delta}K_v$, shows the more conservative results. Also, its rate is lower than that of the case of the mode I, and this difference decreases with increasing the stress ratio, R.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1492-1501
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• 2015

This paper analyzes the effect of voltage sag on distribution systems due to the connection of Electric Vehicles (EVs). In order to study the impact of the voltage sag on the power system, two scenarios have been selected in this paper. The distribution system and EVs are modeled using the Electro Magnetic Transients Program (EMTP). The numbers of EVs are predicted based on the number of vehicles in distribution system of Seoul. In addition, the number of EVs is set up using real-time traffic in Seoul to simulate Scenario I and II. The simulation results show that voltage sag can occur if the distribution system has more than 30% of the total number of vehicles.

• 한국강구조학회 논문집
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• 제11권1호통권38호
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• pp.33-42
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• 1999

궤도용 차량의 안전성 확보를 위한 연구의 일환으로서 레일강의 균열 발생 조건과 모재와 용접부에 대한 정적파괴거동 및 단일모드 하중하의 피로균열진전거동을 검토하였다. 레일에서 횡방향 균열의 원점은 표면하층균열이며 이는 최대전단응력에 의해 발생하였다. 또한 표면하층균열의 크기가 증가함에 따라 균열의 진전은 전단모드에서 혼합모드로 천이될 가능성이 증가하였다. 용접부의 평면변형률 파괴인성은 조직의 조대화와 경도의 상승으로 인하여 모재에 비하여 약 10% 저하하였다. 용접부의 제 2단계 영역의 피로 균열진전속도는 낮은 ${\Delta}K$ 영역에서 모재에 비하여 저하하였으나 높은 ${\Delta}K$영역에서는 이의 차이가 소멸되었으며 이러한 경향은 R=0.1의 낮은 응력비에서 현저하였다. 이는 용접부의 미시조직이 모재에 비하여 성장하였기 때문이라고 판단된다.

• Laboraroty Animal Research
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• 제34권4호
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• pp.288-294
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• 2018

A few clues about correlation between endoplasmic reticulum (ER) stress and mulberry (Morus alba) leaves were investigated in only the experimental autoimmune myocarditis and streptozotocin-induced diabetes. To investigate whether a novel extract of mulberry leaves fermented with Cordyceps militaris (EMfC) could suppress ER in fatty liver, alterations in the key parameters for ER stress response were measured in high fat diet (HFD)-induced obese C57L/6 mice treated with EMfC for 12 weeks. The area of adipocytes in the liver section were significantly decreased in the HFD+EMfC treated group as compared to the HFD+Vehicle treated group, while their level was higher in HFD+Vehicle treated group than No treated group. The level of the eukaryotic initiation factor 2 alpha ($eIF2{\alpha}$) and inositol-requiring enzyme 1 beta ($IRE1{\alpha}$) phosphorylation and CCAAT-enhancer-binding protein homologous protein (CHOP) expression were remarkably enhanced in the HFD+Vehicle treated group. However, their levels were restored in the HFD+EMfC treated group, although some differences were detected in the decrease rate. Similar recovery was observed on the ER stress-induced apoptosis. The level of Caspase-3, Bcl-2 and Bax were decreased in the HFD+EMfC and HFD+orlistat (OT) treated group compared to the HFD+Vehicle treated group. The results of the present study therefore provide first evidence that EMfC with the anti-obesity effects can be suppressed ER stress and ER stress-induced apoptosis in the hepatic steatosis of HFD-induced obesity model.

• 생명과학회지
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• 제33권11호
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• pp.887-896
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• 2023

염증반응(inflammation)은 발병, 진행, 악성 전이를 포함한 암의 진행과정(tumorigenesis)에서 중요한 역할을 수행하기 때문에 암 치료를 위한 전략으로 고려되고 있다. 감태(Ecklonia cava) 열수추출물(AEC)의 항암활성 동안 나타나는 항염증 반응을 연구하기 위하여, 비만세포(mast cells)의 분포, inducible nitric oxide synthase (iNOS)단백질, cyclooxygenase-2 (COX-2)단백질, nuclear factor (NF)-κB단백질, inflammasome 구성 단백질, inflammatory cytokines 발현의 변화는 AEC를 5주간 경구투여한 CT26 대장암을 내포하는 BALB/cKorl syngeneic 마우스에서 분석하였다. AEC를 처리한 후, 고형암의 무게와 조직 절편의 괴사 부위가 vehicle처리그룹에 비하여 감소하였다. 비만세포의 수는 vehicle처리그룹에 비하여 AEC처리그룹에서 증가했지만 COX-2와 iNOS의 발현은 AEC처리그룹에서 감소하였다. 또한, NF-κB, NLR family pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC)과 Caspase-1 (Cas-1)단백질의 발현도 유사한 감소가 관찰되었다. 더불어, tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α)와 interleukin-6 (IL-6)의 mRNA 발현이 vehicle처리그룹에 비하여 AEC처리그룹에서 감소하였다. 이러한 결과는 AEC가 CT26 고형암을 내포하는 BALB/cKorl syngeneic 마우스에서 항암활성은 염증반응과 밀접한 관련이 있음을 제시하고 있다.

• 생명과학회지
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• 제15권3호
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• pp.387-396
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• 2005

The aims of the study were to establish a short-term screening test for detecting testicular toxicity of chemicals in rats and to determine whether a 2-week administration period is sufficient to detect testicular toxicity of 2-bromopropane (2-BP) as an example. Male Sprague-Dawley rats were subcutaneously administered with 1000 mg/kg/day of 2-BP or its vehicle for 2 weeks. Ten male rats each were sacrificed on days 3, 7 and 14 after the initiation of treatment. Parameters of testicular toxicity included genital organ weights, testicular sperm head counts, epididymal sperm counts, motility and morphology, and qualitative and quantitative histopathologic examinations. The early histopathological changes observed on day 3 of treatment included degeneration of spermatogonia and spermatocytes, multinuclear giant cells, mature spermatid retention, vacuolization of Sertoli cells, and decreased number of spermatogonia in stages II and V. On day 7 of treatment, atrophy of seminiferous tubules, exfoliation of germ cells, degeneration of spermatogonia and spermatocytes, multinuclear giant cells, mature spermatid retention, vacuolization of Sertoli cells, decreased number of spermatogonia in stages II and V, and decreased number of spermatocytes in stages VII and XII. On day 14 after treatment, a significant decrease in the weights of testes and seminal vesicles was found. Atrophy of seminiferous tubules, exfoliation of germ cells, degeneration of spermatogonia and spermatocytes, mature spermatid retention, vacuolization of Sertoli cells, decreased number of spermatogonia in stages II and V, and decreased number of spermatocytes in all spermatogenic stages were also observed. In addition, a slight non-significant decrease in testicular sperm head counts, daily sperm production rate and epididymal sperm counts was found. The results showed that 2 weeks of treatment is sufficient to detect the adverse effects of 2-BP on male reproductive organs. It is considered that the short-term testicular toxicity study established in this study can be a useful tool for screening the testicular toxic potential of new drug candidates in rats.