• 천문학회지
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• 제19권1호
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• pp.33-49
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• 1986

Radial distribution of internal density has been determined for thirteen subclouds in the three giant molecular cloud complexes accompanying Mon OB1, Mon OB2 and CMa OB1 associations, We modeled their radial density structures with the density distribution of isothermal gas spheres. Most of the subclouds, nine out of the thirteen, are well described by isothermal spheres of single component; while the rest four require an additional component. Total mass and potential energy of each subcloud are also derived from the radial density structure; thermal energy and internal velocity dispersion required for sustaining the density structure are deduced from the isothermal gas model. Our derived masses of the clouds are comparable to the values determined by Blitz (1978) under LTE assumption. This agreement suggests that the correction factor for non-LTE effect on mass-estimate is not far from unity. The ratio of the gravitational potential energy to the kinetic energy of thermal motion is as large as 250; hence the thermal motion alone cannot support these clouds against the gravity. Being supported by turbulence motion with velocities of six to seven times the thermal velocity, the clouds of one-component type seem to be in equilibrium with the gravity; while the clouds of two-component type are likely to be in the stage of gravitational collapse.

• Smart Structures and Systems
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• 제18권2호
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• pp.267-291
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• 2016

In this research work, an exact analytical solution for thermal buckling analysis of functionally graded material (FGM) sandwich plates with clamped boundary condition subjected to uniform, linear, and non-linear temperature rises across the thickness direction is developed. Unlike any other theory, the number of unknown functions involved is only four, as against five in case of other shear deformation theories. The theory accounts for parabolic distribution of the transverse shear strains, and satisfies the zero traction boundary conditions on the surfaces of the plate without using shear correction factor. A power law distribution is used to describe the variation of volume fraction of material compositions. Equilibrium and stability equations are derived based on the present refined theory. The non-linear governing equations are solved for plates subjected to simply supported and clamped boundary conditions. The thermal loads are assumed to be uniform, linear and non-linear distribution through-the-thickness. The effects of aspect and thickness ratios, gradient index, on the critical buckling are all discussed.

• Steel and Composite Structures
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• 제20권3호
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• pp.571-597
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• 2016

A new unified design formula for calculating the composite compressive strength of the axially loaded circular concrete filled double steel tubular (CFDST) short and slender columns is presented in this paper. The formula is obtained from the analytic solution by using the limit equilibrium theory, the cylinder theory and the "Unified theory" under axial compression. Furthermore, the stability factor of CFDST slender columns is derived on the basis of the Perry-Robertson formula. This paper also reports the results of experiments and finite element analysis carried out on concrete filled double steel tubular columns, where the tested specimens include short and slender columns with different steel ratio and yield strength of inner tube; a new constitutive model for the concrete confined by both the outer and inner steel tube is proposed and incorporated in the finite element model developed. The comparisons among the finite element results, experimental results, and theoretical predictions show a good agreement in predicting the behavior and strength of the concrete filled steel tubular (CFST) columns with or without inner steel tubes. An important characteristic of the new formulas is that they provide a unified formulation for both the plain CFST and CFDST columns relating to the compressive strength or the stability bearing capacity and a set of design parameters.

• Nuclear Engineering and Technology
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• 제13권2호
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• pp.63-72
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• 1981

핵연료 집합체의 예기치 않은 파손으로 인하여 설계 근거 재장전 방침이 변경되면 원자로심내에서의 출력 분포 비균형을 막기 위하여 파손된 핵연로 집합체 이외에 대칭 위치의 집합체도 제거되어야 할 경우가 있다. 이와 같은 때에 제거된 핵연료 집합체가 설계연소도에 미달되는 경우 이를 다시 사용하여 핵연료 이용률을 증진시키는 것이 연구되었다. TDCORE 코드가 노심ㆍ해석을 위해 이용되었으며, 최적장전모형을 찾는 코드로는 RELOAD-II가 이용되었다. 고리 1호기에 적용한 결과, 제 1주기말에 제거된 비교적 적게 연소된 4개의 핵연료집합체를 제 3주기에서 이용할 경우 주기 연소도가 l1648 MWD/MTU(가동율 : 80%)에 이를 수 있음을 알 수 있었으며 평형주기까지의 장전모형을 추적하였다.

• Archives of Pharmacal Research
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• 제19권6호
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• pp.462-468
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• 1996

The present study was undertaken to investigate the effects of age on angiotensin II (AII) response and antagonistic activity of losartan using aortic rings and liver homogenates from rats ranging in age from 0.7 to 20 months. Whether the endothelium was present or not, the maximum contractile response to AII decreased with age. Removal of the endothelium enhanced AII-induced maximum contraction and these endothelial effects seemed to be due to endothelium-derived relaxing factor (EDRF) in all ages. Equilibrium binding studies demonstrated an age-related decrease in maximum binding $(B_{max})$ with little change in binding affinity $(K_d)$. In rat aorta, the extent of losartan-induced parallel shifts $(K_B)$ in AII concentration-response curves was not significantly different between ages. In addition, $IC_{50}$ value of losartan in competition binding was not changed with age in rat liver homogenates. These results suggest that the potency of losartan is not altered with age in rat aorta and liver, although AII-induced contractile response and the maximum AII binding decreased significantly with age.

• 한국지반공학회지:지반
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• 제6권2호
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• pp.47-54
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• 1990

사면안정해석의 정확도는 흙의 강도특성과 사면의 기하학적 조건의 파악정도와 해석방법 본말 의 정확도에 지배된다. 그리고 대부분의 사면안정해절방법은 컴퓨터 프로그랙으로작성되어 있다. 국내에서 실용되고 있는 프로그램의 정확성을 비교한 것이다. 비교적 간단한 조건의 각 프로그램으로 얻은 안전률의 차리는 5% 이내이다. 요면에 관한 정확한 타보입수가 가능한 파괴사례 연구에서도 유사한 결과를 얻었다. 그러나 컴퓨터가 찾아낸 임계파괴면과 실제 파괴면은 약간 상리한 경우도 있었다. 이 때에도 두 활동면을 해석하여 구한 안전률 값은 대차 없이 거의 동일하였다. 결국 국내에서 사용되고 있는 사면안정해석 컴퓨터 프로그램은 그 실용성이 인정된다고 할 수 있다.

• 한국해안해양공학회지
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• 제7권1호
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• pp.12-23
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• 1995

불규칙파에 의한 연안류를 수치모형으로 해석하였으며, 수치모형에 사용되는 제 경험식들을 개선하였다. 불규칙파의 쇄파조건으로 Kitaigorodskii의 평형조건식을 수정하여 사용하였으며, 실제 해저면에서의 마찰력을 계산하기 위하여 연흔의 생성과 형상에 따른 조고의 증가와 토사가 이동할 때 발생하는 에너지 손실을 고려한 조고의 증가를 동시에 고려하였다. 연흔 형상 산정식으로 Nielsen 식과 Madsen-Rogengaus 식을 사용하였는데, 연흔형상에 대한 두 식의 산정결과는 비슷하나 등가조고 산정에 도입되는 비례상수의 수치가 달라 추정된 등가조고에는 상당한 차이를 보이고 있다. 난류에너지식과 확산길이식에 사용되는 경험상수를 최적화 기법으로 결정하였으며, 이를 이용하여 불규칙파에 의한 연안류를 예측하였다.

• Journal of Animal Science and Technology
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• 제56권7호
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• pp.25.1-25.6
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• 2014

This study was carried out to investigate the association of POU1F1 (POU domain, class 1, transcription factor 1, Pit1, renamed as POU1F1) gene with backfat thickness (mm), carcass weight (kg), pH, and color values ($L^*$, $a^*$, $b^*$) in crossbred pigs (Landrace ${\times}$ Yorkshire ${\times}$ Duroc). Frequency of the AA genotype indel was at the highest level (66.67%). Frequency of A allele (0.81) was higher than that of b allele (0.19). This population followed Hardy-Weinberg equilibrium. Carcass weights and $a^*$ values of the three genotypes were all significantly different (p < 0.05), respectively. However, backfat thickness, $L^*$, $b^*$, visual color, and pH of the three genotypes were not significantly different (p > 0.05). Visual color was negatively correlated with $L^*$ (r = -0.521) and $b^*$ (r = -0.390) values, $L^*$ value was correlated with $b^*$ (r = 0.419) value, and $a^*$ value was positively correlated with $b^*$ (r = 0.612) value. These results indicate that the POU1F1 gene affected carcass weight and meat redness.

• 대한기계학회논문집A
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• 제36권9호
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• pp.985-996
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• 2012

면외 기계적하중과 면내 전기적하중을 받는 압전재료에서 비정상적으로 전파하는 전기투과형 균열에 대하여 연구하였다. 비정상적으로 전파하는 균열에 대한 평형방정식을 개발하였고 근접해법으로 투과형균열에 대한 응력장 및 변위장을 얻었다. 압전상수, 유전율 그리고 균열선단속도 및 응력확대계수의 시간 변화율이 비정상적으로 전파하는 균열선단부근의 응력 및 변위장에 미치는 영향을 명확히 나타내었다. 이러한 응력장과 변위장을 사용하여 비정상적으로 전파하는 균열선단의 응력장 및 변위장의 특성에 대하여 토론하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.582-585
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• 2004

Most of hard disk drives currently employ fluid dynamic bearing (FDB) for their rotor support. Stiffness of the FDB is affected by many design factors such as bearing clearance, fluid viscosity, and rotational speed. For the high rotating speed HDDs stiffness of the rotor is normally high enough to accomodate load disturbances. However small form factor HDDs that are to be operated in low power consumption are often designed with low stiffness rotors. Although the low stiffness rotor clearly benefits low power operation, it could damage the entire motor structure or head disk interface even by a light mechanical load disturbance such as shock or vibration. In addition, since a single channel HDD does not provide gram load equilibrium in axial direction the rotor could be tilted and make a hard contact to stator. A non-symmetric groove pattern could successfully compensate the tilted rotor angle during operation.