• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.59-66
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• 2001

The post-peak analysis of concrete structures is carried out using a nine-node Reissner-Mindlin(RM) shell element which is formulated by using degenerated solid concepts. In order to avoid element deficiencies inherited in the standard RM shell element, assumed strains are adopted in the present shell element. A microscopic material model is adopted to represent the inelastic characteristic of concrete material. In particular, a concrete softening model is introduced to this material model. The arc-length control method is used to trace the post-peak behaviour of concrete structures. From the numerical test of the single-edge-notched beam, the present shell element shows a reasonable agreement with experimental data.

• 대한토목학회논문집
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• 제2권3호
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• pp.75-86
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• 1982

본 연구에서는 3절점, 6자유도를 갖는, 종래의 Timoshenko 보 이론에 근거한 깊은 보(Thick beam) 요소(DB6)와 3절점, 7자유도를 갖는 3차 축방향변위를 가정한 고차 보 요소(DB7)의 3차원 연속체로부터의 Degeneration을 보여 주고 있다. DB6 보 요소는 전단변형률의 비살제적인 선형분포를 보완하기 위하여 전단계수(shear coefficient)를 도입하고 있는 반면 고차 DB7 보 요소는 보다 실제적인 전단변형률의 2차분포를 가정하고 있다. 이 들 두 보 요소를 이용하여 계산된 해(解)는 Timoshenko 방정식의 해(解), 얕은 보(Thin beam)의 해(解) 및 다른 여러 보 요소들의 해(解)와 비교된다. 본 연구의 결과는 고차 DB7 보 요소가 보의 정력화적 해석이나 자유진동 해석에 있어서 다른 보 요소들에 비해 월등히 정확함을 보여주고 있다.

• 한국전산구조공학회논문집
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• 제13권2호
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• pp.197-208
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• 2000

최 등/sup 1)/은 total lagrangian formulation에 근거한 증분 평형방정식을 적용하고, 강도행렬 산정시 회전각의 2차항을 포함시켜 기하학적 비선형 해석시 해의 수렴성을 향상시켰다. 또한 등매개 쉘 유한요소의 단점인 전단구속 현상과 제로 에너지 모드가 발생하는 문제를 극복하기 위하여 가정 변형률장을 적용하여 보강된 판 및 쉘 구조의 비선형 해석법을 개발하였다. 본 연구에서는 잔류응력을 고려한 쉘구조의 극한강도 해석을 수행하기 위하여, 대변형거동과 함께 소성붕괴거동을 추적할 수 있는 알고리즘을 제시한다. 잔류응력을 고려한 증분평형방정식에 return mapping algorithm을 이용한 탄소성 해석법을 결합시켜서 보강된 판 및 쉘구조의 극한거동을 파악한다. 수치해석 예제를 통하여 본 연구에서 제시된 유한요소 및 비선형 해석 알고리즘에 대한 효율성 및 적용성을 확인하였다.

• Composites Research
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• 제13권1호
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• pp.25-32
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• 2000

국부압축력을 받는 스트링거 보강 복합적층 만곡 판넬의 좌굴 및 후좌굴 거동을 개발한 유한요소프로그램을 이용하여 해석하였다. 후좌굴 해석은 판넬거동을 세 가지로 나누어 해석하였다. 판넬과 보강재를 모델링 하기 위하여 8절점응축 쉘요소를 도입하고 비선형유한 요소 수식화를 위해 2nd Piola-Kirchhoff 응력텐서와 Lagrangian 변형률 텐서를 채택하였다. 파손 특성을 고려하기 위해 점진적 파손해석을 도입하였다. 국부축하중을 받는 복합적층 만곡 판넬의 좌굴하중 및 좌굴후 극한하중, 국부좌굴과 전체좌굴, 그리고 보강재 영향이 인자별로 해석 비교 된다.

• Earthquakes and Structures
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• 제12권5호
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• pp.501-513
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• 2017

To investigate the seismic performance of Y-shaped eccentrically braced frames fabricated with high-strength steel (Y-HSS-EBFs), a shake table test of a 1:2 scaled three-story Y-HSS-EBF specimen was performed. The input wave for the shake table test was generated by the ground motions of El Centro, Taft, and Lanzhou waves. The dynamic properties, acceleration, displacement, and strain responses were obtained from the test specimen and compared with previous test results. In addition, a finite element model of the test specimen was established using the SAP2000 software. Results from the numerical analysis were compared with the test specimen results. During the shake table test, the specimen exhibited sufficient overall structural stiffness and safety but suffered some localized damage. The lateral stiffness of the structure degenerated during the high seismic intensity earthquake. The maximum elastic and elastoplastic interstory drift of the test specimen for different peak ground accelerations were 1/872 and 1/71, respectively. During the high seismic intensity earthquake, the links of the test specimen entered the plastic stage to dissipate the earthquake energy, while other structural members remained in the elastic stage. The Y-HSS-EBF is a safe, dual system with reliable seismic performance. The numerical analysis results were in useful agreement with the test results. This finding indicated that the finite element model in SAP2000 provided a very accurate prediction of the Y-HSS-EBF structure's behavior during the seismic loadings.

• Nuclear Engineering and Technology
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• 제33권3호
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• pp.255-260
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• 2001

In mammals, most of the follicles can not be ovulated, and instead, are degenerated throughout the entire reproductive period. However, the precise mechanism of follicle atresia is unknown. Three weeks old female mice (ICR strain) were ${\gamma}$-irradiated with a dose of LD$^{50}$ . Before irradiation (day 0) and at day 1, 2, and 3 after irradiation, the normal and atretic preantral and antral follicles of the left ovaries were morphologically observed. Atretic follicles at 2 days after irradiation had numerous cell debris, apoptotic cells and bodies, and polymorphonuclear leukocytes in the antral cavity. In severely atretic follicles, numerous polymorphonuclear leukocytes infiltrated into the follicle. The frequencies of atretic antral (58.0 $\pm$8.6) and preantral follicles (27.3$\pm$11.2) induced by ${\gamma}$-radiation increased to 94.0$\pm$3.4 and 86.9$\pm$7.6, respectively at 2 days after irradiation (p<0.05). The number of follicles with one or more neutrophils in the largest cross sections at 2 and 3 days after irradiation significantly increased (p<0.05). It can be concluded that ${\gamma}$-radiation triggers the recruitment of neutrophils into the follicles during degeneration. The ovarian follicles can make a role of informative biological end-point useful for disaster-prevention.

• 대한수의학회지
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• 제34권2호
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• pp.349-359
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• 1994

To elucidate pathogenicity to hamster of encephalomyocarditis virus $K_3$ strain that was isolated in Korea from the swine with reproductive failures, adult male syrian hamsters were experimentally infected intraperitoneally with the virus at $10^{7.0}\;TCID_{50}/0.1ml$ and pathological and immunohistochemical studies were performed. The results obtained through the experiment were as follows. 1. Clinical signs such as depression, unkempt hair and bilateral parlysis of hind limbs were observed. 2. At necropsy, mild congestion was observed in the cerebrum, liver, kidney and lung, and atrophy was evident in testis. 3. In microscopic observation, degeneration and necrosis of the nervous cells and perivascular mononuclear cell infiltration were manifested in central nerve system, and various degrees of degeneration and necrosis of parenchymal cells were detected in pancreas, lacrimal gland, liver, kidney and testis. 4. In immunohistochemical observation, strong positive reactions were observed in degenerated parenchymal cell of testis, and weak positive reactions, in hepatocytes.

• Composites Research
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• 제14권6호
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• pp.16-23
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• 2001

인발 와인딩에 의한 섬유강화 복합재료 중공 봉의 기계적 거동해석을 수행하였다. 이 목적의 수행을 위해 새롭게 제작된 와인더를 전통적 인발 시스템에 부탁하여 시편을 제작하였다. 또한 인발-와인딩된 시편을 제작할 수 있는 새로운 공법을 개발하였다. 이 연구를 위해 유한요소 해석 프로그램 POSTII를 확장 개발하였다. 비선형유한요소 수식화에는 2차 피올라-키르히호프 응력 텐서와 그린 변형률 텐서에 기초한 업데이트된 라그란지언 표현법이 사용되었다. 복합재료 중공봉의 유한요소 모델링을 위해 8절점 응축쉘요소를 사용하였다. 파손평가를 위해 모든 유한요소의 각 단층에서의 평균응력을 최대음력 판정법에 대입하였다. 수치해석 예로서 불포화 섬유강화 복합재료 중공 봉의 기계적 거동을 초기 하중상태에서 최종 붕괴가지 조사하였다. 파손에 따른 강성저하와 응력제하를 고려한 유한요소해석 결과는 극만 하중과 파손 및 변형에서 실험치와 잘 일치하였다.

• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.563-569
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• 2004

The DNA sequence of the chitosanase gene (choK) from $\beta$-Proteobacterium KNU3 showed an 1,158-bp open reading frame that encodes a protein of 386 amino acids with a novel 74 signal peptide. The degenerated primers based on the partial deduced amino acid sequences from MALDI- TOF MS analyses yielded the 820 bp of the PCR product. Based on this information, double inverse PCR cloning experiments, which use the two specific sets of PCR primers rather than single set primers, identified the unknown 1.2 kb of the choK gene. Subsequently, a 1.8 kb of full choK gene was cloned from another PCR cloning experiment and it was then subcloned into pGEM T-easy and pUC18 vectors. The recombinant E. coli clone harboring recombinant pUC18 vector produced a clear halo around the colony in the glycol chitosan plates. The recombinant ChoK protein was secreted into medium in a mature form while the intracellular ChoK was produced without signal peptide cleavage. The activity staining of PAGE showed that the recombinant ChoK protein was identical to the chitosanase of wild-type. The comparison of deduced amino acid sequences of choK revealed that there is 92% identity with that of Sphingobacterium multivorum chitosanase. Judging from the conserved module in other bacterial chitosanases, chitosanase of KNU3 strain (ChoK) belongs to the family 80 of glycoside hydrolases.

• Clinical and Experimental Reproductive Medicine
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• 제27권3호
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• pp.275-282
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• 2000

Objective: This study was to determine the effect of different concentration of calcium III medium on the preimplantational development of zygotes and early 2 cell embryos. Methods: Female mice of ICR strain ($5{\sim}8$ weeks old) were superovulated and mated with fertile males. Zygotes or early 2-cell embryos were collected by flushing the oviducts $31{\sim}32$ hours after hCG injection. The embryos were cultured in various concentrations of $Ca^{2+}$ in medium or with EDTA, EGTA and $Ni^{2+}$. Result and Conclusion: Treatment of high concentraion of $Ca^{2+}$ (3.42 mM $(2X){\sim}17.l$ mM (10X)) in medium didn't develop well compared to the control. Low concentrations of $Ca^{2+}$ (0.214mM $(1/8X){\sim}0.855$ mM (1/2X) were deterimental to development beyond 2-cell stage. EDTA, $Ca^{2+}$ chelating agent was treated with ranged concentrations of EDTA (0.014 $mM{\sim}0.107$ mM) to medium contaning 1.71 mM $Ca^{2+}$ showed beneficial effect to development to blastocyst compared to the control. EGTA, extracellular $Ca^{2+}$ chelator, was treated with ranged concentrations of EGTA ($0.014{\sim}0.107$ mM) to the medium contaning 1.71 mM $Ca^{2+}$. There is no significant difference with the control. $Ni^{2+}$ (50 ${\mu}M$), T-type $Ca^{2+}$-channel blocker was treated to medium contaning low concentration of $Ca^{2+}$. It overcame 2-cell block significantly. Rate of degenerated embryos decreased and developmental rate to morula and blastocyst increased more than low $Ca^{2+}$ concentration alone. Further studies are needed for the overcoming effect of 2-cell block by $Ni^{2+}$.