• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제6권1호
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• pp.7-14
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• 2003

The interaction of monochromatic incident waves with a submerged horizontal porous membrane is investigated in the context of two-dimensional linear hydro-elastic theory. It is assumed that the membrane is made of material with very fine pores so that the normal velocity of the fluid passing through the porous membrane is linearly proportional to the pressure difference between two sides of the membrane (e.g. Darcy's law). Using the Eigen-function expansion method, the wave-blocking performance of a submerged horizontal porous membrane is tested with various membrane tensions, porosities, lengths, and submerged depths. It is found that an optimal combination of design parameters exists for given water depth and wave characteristics.

• 대한치과보철학회지
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• 제35권1호
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• pp.144-164
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• 1997

The purpose of this study were to investigate the chemical composition, mean particle size, linear thermal expansion coefficient and metal-bonding strength of the regular opaque powder and core powder. In this study, 4 types of ceramic powders, namely Duceram Jacket Opaque powder, Duceram Opaque powder, Vita Hi-Ceram powder, Vita VMK Paint On-88 powder were used. Chemical composition was evaluated by EDS(Energy Dispersive X-ray Spectrophotometer, Oxford QX-2000, England), particle size was measured by MALVERN Instruments(MALVERN Instruments SB. OC., U.S.A.. ad linear thermal expansion coefficient was measured by dilatometer(Motoyama, Japan). Bond strength was measured by the Universal tsting machine(Istron Co., Ltd., U.S.A.). The Results were as follows : 1. Through recognition of the relative difference in chemical composition between the core powder and the regular opaque powder, the difference in the proportion of $Al_2O_3$ in each type of material is demonstrated ; Duceram Jaket Opaque powder : 30.16%, Duceram Opaque powder : 16.60%, Vita Hi-Ceram : 63.64%, Vita VMK Paint-On 88 : 16.16%. 2. There was no significant difference in the proportion of metal-bonding materials between the core powder and the regular opaque powder. 3. In the regular opaque powder, alkaline materials were incoporated in order to increase the coefficient of thermal expansion. 4. In the particle size analysis, there was no significant difference in mean particle size or in the particle size distribution between the core powder and the regular opaque powder. 5. In the thermal expansion test for temperature range of $25-600^{\circ}C$, the regular opaque powder had higher coefficient of thermal expansion than that of core powder. 6. In the 4 point flexural bending test, there was no statistically significant difference in the mean bond strength between the core powder and the opaque powder among the Duceram products.

• 폴리머
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• 제31권3호
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• pp.206-214
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• 2007

3차원적 타원체 형태 ($a_1>a_2>a_3$)를 사용하여, 2가지의 종횡비 (1차 종횡비 $\rho_{\alpha}$와 2차 종횡비 $\rho_{\beta}$)를 갖는 배열된 3차원 형태의 충전제를 포함하는 복합체의 열팽창 변화를 이론적으로 예측하는 모델을 연구하였다. Eshelby의 등가 텐서를 이용하여 배열된 타원형 충전제를 기지재의 이론에 의해 열팽창 계수를 예측할 수 있었다. 종단방향 열팽창 계수 ${\alpha}_{11}$는 두 가지 종횡비 모두 증가하면, 감소하여 충전제의 열팽창에 접근한다. 수직방향 열팽창 계수 ${\alpha}_{33}$는 충전제 함유량에 따라 초기에는 증가하여 최대값을 갖는 경향을 보인다. 1차 종횡비 $\rho_{\alpha}$가 증가하면, 횡단방향 열팽창 계수는 감소하나, 2차 종횡비 $\rho_{\beta}$가 증가하면, 같이 증가한다. 또한, 수직방향 열팽창 계수 ${\alpha}_{33}$는 $\rho_{\alpha}$가 증가하면 증가하나, $\rho_{\beta}$가 증가하면, ${\alpha}_{33}$는 반대로 감소한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 춘계학술대회 논문집
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• pp.251-252
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• 2009

• 한국해양공학회지
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• 제25권1호
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• pp.1-7
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• 2011

The radiation of water waves by a heaving truncated circular cylinder with damping plate is solved in the frame of the three-dimensional linear potential theory. The damping plate has a distinct advantage in reducing the motion response of a floating circular cylinder by increasing the added mass and the damping coefficient. Using the matched eigenfunction expansion method, the characteristics of hydrodynamic added mass and the damping coefficient are investigated with various system parameters, such as the radius and submergence depth of the damping plate. It is found that both added mass and the damping coefficient are significantly increased due to the arranged features of the larger damping plate with shallow submergence, which are positive factors as a motion reduction device of the floating offshore platform. Also the numerical results for an oscillating submerged disk show that the added mass is negative and that the damping coefficient has a peak value at resonant frequency when submergence depth is sufficiently small.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 춘계학술대회논문집
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• pp.136-142
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• 1999

The injection molded part shrinks in the process of solidification by the amount of the coefficient of linear thermal expansion multiplied by the temperature difference between the coefficient of linear thermal expansion multiplied by the temperature difference between the room temperature and the temperature at which the solid structure is formed in the mold And it is called warpage for this type of deformation that shrinkage are not uniform throughout the injection molded part. To predict warpage phenomena in the articles the results obtained theoretically from the change of mold temperature fiber content of composites have been compared with exsperimental results.

• 동력기계공학회지
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• 제2권3호
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• pp.34-40
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• 1998

Performance characteristics of a refrigeration systems with various expansion valves and superheat changes were investigated experimentally. Experimental data have been taken utilizing three different devices; a thermostatic expansion valve, a linear type electronic expansion valve and a solenoid type electronic expansion valve. The data taken from tile three types of expansion valves were discussed with the temperature distribution of each zone in the evaporator and the superheat changes of the evaporator outlet In each zone temperature distribution fluctuated larger with the thermostatic expansion valve than with the electronic expansion valves. The optimum superheat ranged from $5^{\circ}C\;to\;15^{\circ}C$, and the superheat with the thermostatic expansion valve showed hunting phenomenon, which affected the evaporating and condensing temperature.

• 터널과지하공간
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• 제17권6호
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• pp.475-483
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• 2007

에너지원으로서 LNG 수요뿐 아니라 온실가스인 이산화탄소의 처분에 대한 필요성이 점차 증가되고 있어, 이를 위한 많은 저장시설이 요구된다. 이러한 저장시설은 안전성과 국토의 효율적 이용 등으로 인하여 지하화하는 경향이 있다. 이와 같은 온도특성을 고려해야하는 물질에 대한 지하저장시설의 건설에 있어서, 암석의 열물성은 열역학적 특성과 함께 저장시설의 설계 및 유지관리를 위한 중요한 요소이다. 본 연구에서는 암석입자의 크기와 실험온도범위를 고려하여 스트레인 게이지를 이용하여 암석의 열팽창계수를 실험적으로 측정하였다. 실험결과 열팽창계수는 온도가 내려감에 따라 감소하였으며, 국내 대표암석인 화강암에 대한 선열팽창계수의 온도관계식을 제안할 수 있었다. 본 연구에서 수행된 온도변화에 따른 시험결과는 지하저장소의 열역학적 안정성 해석과 열전파 특성을 규명하기 위한 해석에 주요 자료로 활용될 수 있을 것이다.

• 한국세라믹학회지
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• 제55권1호
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• pp.67-73
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• 2018

A poled lead zirconate titanate (PZT) cube specimen that is switched by an electric field at room temperature is subject to temperature increase. Changes in polarization and thermal expansion coefficients are measured during temperature rise. The measured data are analyzed to obtain changes in pyroelectric coefficient and strain during temperature change. Empirical formulae are developed using linear or quadratic curve fitting to the data. The nonlinear behavior of the materials during temperature increase is predicted using the developed formulae. It is shown that the calculation results can be compared successfully with the measured values, which proves the accuracy and reliability of the developed formulae for the nonlinear behavior of the materials during temperature changes.

• 한국해양공학회지
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• 제17권1호
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• pp.8-15
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• 2003

본 논문에서는 투과성 유연막이 수면밑 일정한 깊이에 수평으로 잠겨있을 때 투과성 유연막에 의한 파랑제어성능을 살펴보았다. 해석 방법으로는 유체문제는 고유함수전개법 (Eigenfunction expansion method)을 사용하였고, 유연막과 파랑의 상호작용문제는 Newmann 이 제시한 유탄성 이론 (hydro-elastic theory)을 채택하였다. 막의 투과성 효과를 고려하기 위하여 수평막에서의 수직속도는 수평막 상하의 압력차에 선형적으로 비례하며 그들 사이에는 위상차가 없다고 가정한 Darcy 법칙을 사용하였다. 투과성 수평막의 설계변수 (초기장력, 길이, 잠긴 깊이, 공극율)와 입사파의 주파수를 바꿔가면서 반사율과 투과율 그리고 에너지 손실율을 살펴보았다.