• Journal of Nutrition and Health
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• 제33권2호
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• pp.147-157
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• 2000

This study examined the effects of excess intake of calcium (Ca) and iron (Fe) supplement on bone loss, nephrocalcinosis and renal function in osteoporotic model rats. Seven-week-old female rats were first fed a Ca-deficient diet for four weeks after ovariectomy operation, and then one of nine experimental diets for additional eight weeks, containing three levels of Ca, normal (0.5%) or high (1.5%) or excess (2.5%) and three levels of Fe, normal (35ppm) or high (210ppm) or excess (350ppm). The osteoporotic model rats showed a remarkable increase in body weight, serum alkaline phosphatase (ALP) and decrease in breaking force, Ca, P, Mg contents of femur. Serum Ca concentration was not significantly affected by dietary Ca and Fe levles. Liver Ca content increased in rats fed a high-and excess-Ca diet. Kidney Ca content and microscopic Ca deposition remarkably increased in osteoporotic model rats compared to control group, and showed a tendency to decrease in rats fed a excess-Ca diet. Breaking force of femur increased with increasing dietary Ca levels, but Ca, P contents of femur and serum ALP were not significantly affected by dietary Ca and Fe levels. Serum total protein decreased in rats fed a excess-Ca diet, BUN increased in rats fed a excess-Ca diet, while serum uric acid and creatinine were not significantly affected by dietary Ca levels. Urinary creatinine, GFR increased in rats fed a high-and excess-Ca, diet, and GFR was highest in rats fed a excess-Ca/excess-Fe diet. These results suggest that excess intake of Ca may increase breaking force of femur, but not increase mineral contents of femur, and decrease kidney function. Furthermore, excess intake of Fe and Ca concurrently may aggravate kidney function leading to potential health problems in ovariectomized osteoporotic model rats.

• 한국해안해양공학회지
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• 제19권2호
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• pp.136-145
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• 2007

파랑이 수중 천퇴부를 넘어 쇄파하는 경우 파고는 작게 형성되나 강한 이차적 흐름 (쇄파유도류)이 발생한다. 따라서, 임의의 해양구조물이 쇄파대에 위치할 경우에는 단순히 가시적인 파고에만 근거한 파력산정은 과소설계를 초래할 가능성이 있으며 구조물의 안정설계를 위해서는 쇄파유도류의 유속이 가미된 상태에서의 유체력을 정확히 산정하여 반영할 필요가 있다. 본 연구에서는 Boussinesq 방정식 모델을 이용하여 쇄파대내에서의 파고분포와 쇄파유도류를 계산하는 기법을 수립하였으며 과거에 수행하였던 이어도 해양과학기지의 수리모형실험 (1/120)의 모델영역에 적용하였다. 이 계산결과를 이용하여 모형구조물에 작용하는 유체력을 계산하고 수리모형실험 결과와 비교함으로써 쇄파유도류의 영향을 정량적으로 평가하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.530-541
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• 2019

To improve our current understanding of tsunami-like solitary waves interacting with a row of vertical slotted piles on a sloping beach, a 3D numerical wave tank based on the CFD tool $OpenFOAM^{(R)}$ was developed in this study. The Navier-Stokes equations were employed to solve the two-phase incompressible flow, combining with an improved VOF method to track the free surface and a LES model to resolve the turbulence. The numerical model was firstly validated by our laboratory measurements of wave, flow and dynamic pressure around both a row of piles and a single pile on a slope subjected to solitary waves. Subsequently, a series of numerical experiments were conducted to analyze the breaking wave force in view of varying incident wave heights, offshore water depths, spaces between adjacent piles and beach slopes. Finally, a slamming coefficient was discussed to account for the breaking wave force impacting on the piles.

• 대한조선학회지
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• 제25권4호
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• pp.1-6
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• 1988

In this paper two-dimensional breaking waves of plunger type are numerically simulated both on an even bottom and on a sinusoidally-varying bottom within the framework of potential theory. Based on the boundary integral method derived by Vinje and Brevig, fluid particles on the free surface are treated exactly by using semi-Lagrangian time-stepping. Numerical instability, in particular when the wave front becomes vertical, is discussed and the regriding method of nodal points has been found promising. Numerical accuracy is examined in terms of the wave energy and mass conservations. It is also found that the bottom topography affects significantly and the hydrostatic pressure contributes considerably to the nonoscillating force acting on the bottom, when waves are breaking.

• 한국안전학회지
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• 제25권6호
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• pp.70-74
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• 2010

For each strand of wirerope sling, the international standards, ISO-8794, EN-13414 specify that the splice shall have five series of load carrying tucks. At least three of the load carrying tucks shall be made with the whole strand. And, the breaking force of the splice shall not be less than 70% or 80% of that of rope. But, There are no prescriptions for splicing types against different efficiency of each splicing type being used many workplace. In this study, analysis the work limit load efficiency according to variation of number of tucks and splicing types by experimental method As a result, the number of tucks 3+2 had the highest breaking efficiency.

• Journal of Advanced Marine Engineering and Technology
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• 제33권6호
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• pp.873-879
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• 2009

The steady breakers at an infant stage are investigated through the numerical simulation. The appearing condition and characteristics of the sub-breaking waves are reviewed by analysing bow waves. The instability analysis is possibly done through the relationship between the free-surface curvature and circumferential force, which is obtained from the momentum equations. Navier-Stokes equations are solved by a finite difference method where the body-fitted coordinate system, the wall function and the advanced mesh system are invoked. The numerical result shows that the gradient of M/$U_s$ is greatly influenced by the Froude number and the decrease of M/$U_s$ indicates that the flows are unstable. Additionally flows with plunging or spilling are simulated successfully, but the application of breakers to the severely broken wave still remains to be settled in the future.

• 대한화학회지
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• 제59권2호
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• pp.132-135
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• 2015

Bonding force and stiffness in amine-linked single-molecule junctions for Ag electrodes were measured using a home-built conducting atomic force microscope under ambient conditions at room temperature. For comparison, Au electrodes were used to measure the rupture force and stiffness of the molecular junctions. The traces of the force along with the conductance showed a characteristic saw-tooth pattern owing to the breaking of the metal atomic contacts or the metal-molecule- metal junctions. We found the rupture force and stiffness for Ag are smaller than those for Au electrodes. Furthermore, we observed that the force required to break the amine-Ag bond in the conjugated molecule, 1,4-benzenediamine, is smaller than in 1,4-butanediamine which is fully saturated. These results consist with the previous theoretical calculations for the binding energies of the nitrogen bonded to Ag or Au atoms.

• 한국식품영양과학회지
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• 제33권10호
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• pp.1676-1684
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• 2004

어육, 닭 가슴살 및 돼지 후지 육을 산성 및 알칼리 용액으로 추출하여 등전점 부근에서 회수하고 중성 부근의 pH로 재조절하여 회수한 단백질의 가열 젤 물성과 이들의 혼합에 따른 가열 물성 값의 변화, 최적 물성과 최소비용을 제공하는 혼합 비율을 결정하였다. 갈고등어의 근원섬유단백질은 산 및 알칼리 처리에 의해 가열 젤을 형성하지 못하였으나, 산과 알칼리 처리후 근형질 단백질을 포함한 회수 단백질은 가열 젤을 형성하였다. pH 10.5에서 처리 후 회수한 단백질의 가열 젤의 파괴강도는 갈고등어가 가장 낮았고, 변형 값은 냉동 꼬마민어>닭 가슴살>돼지 후지 육>갈고등어의 순으로 높았으며, 백색도는 냉동 꼬마민어 회수 단백질이 가장 높았다. 갈고등어 회수 단백질의 첨가는 파괴강도, 변형 값, 백색도를 감소시키고 가격을 상승시키는 반면, 닭 가슴살 회수 단백질의 첨가는 파괴 강도와 백 색도를 다소 증가시키고 가격을 현저히 감소시켰다. 냉동 꼬마민어 회수 단백질인 경우, 파괴강도 110 g 이상, 변형 값 4.5 mm 이상 및 회수 단백질의 원료 단가 2000원 이하/kg을 만족하는 최적 혼합 비율은 냉동 꼬마민어 36∼50%, 닭 가슴살 34∼40%, 돼지 후지 육 14∼25%이었다 가열 젤의 구조는 냉동 꼬마민어 회수 단백질이 가장 치밀하였다. 냉동 꼬마민어 회수 단백질을 축으로 닭 가슴살, 돼지 후지 육 회수 단백질의 적절한 혼합 비율의 조절은 물성 값이 다양화한 연제품에 활용 가능할 것으로 판단된다.

• Journal of Theoretical and Applied Mechanics
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• 제2권1호
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• pp.1-14
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• 1996

In this paper, breaking waves are generated in a 2-D wave tank and simulated by using a higher-order boundary element method. A piston-type wavemaker is operated by signals composed of elementary waves. The phase of elementary waves is determined by the linear theory such that they are focused to a prescribed position. Calculated plunging waves coincide well with experiment. A steel box with different plate thicknesses is installed at a predetermined position in the tank. Measured impulsive pressures due to breaking waves are found to be 0.8-1.2$\rho$C2, where $\rho$ corresponds to water density and C to wave celerity. The transverse displacement of the plate is described in terms of modal eigenfunctions. The natural frequencies measured by impact tests in air for thin plate coincide with the computational and theoretical values. The radiationpotential due to plate vibration is derived and the radiation force is expressed in terms of hydroelastic added mass and damping forces. Comparison of natural frequencies of plate in water proves that hydroelastic added mass and damping are properly considered. The measured strain due to regular waves supports the calculated one, but there are apparent discrepancies between theory and experiment in the impulsive case.

• 전력전자학회논문지
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• 제27권3호
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• pp.175-179
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• 2022

Magnetic arc extinguishing technology is effective as an extinguishing device for low-voltage direct current (DC) circuit breakers with a resistive load of ≤4 kW. The separation distance between the magnet and the electrical contact must be shortened to increase the magnetic arc extinguishing force. However, if the magnet is installed too close to the electrical contact points, the magnet is exposed to high temperatures due to the arc current generated when the load current is cut off and the magnetism is lost. To solve this problem, the effective magnetic flux density at the electrical contact can be maintained high by placing the arc extinguishing magnet in a tandem structure with the electrical contact point between them, and the proper separation distance between the contact points and the magnet can be maintained. In addition, an electric arc extinguishing technology that emits arc energy using a series circuit of diode and resistor is used to suppress the continuous arc voltage generated by the inductive load. For the proposed circuit breaker, the breaking characteristics are analyzed through the breaking test for the DC load of the 760 V level, the load power of 4 kW, and the time constant of 5 ms, and an appropriate arc extinguishing design guideline is proposed.