• 한국해양공학회지
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• 제24권6호
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• pp.1-6
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• 2010

A far field approximate solution of the slowly varying force on a 3 dimensional offshore structure in gravity ocean waves is presented. The first order potential, or at least the far field form of the Kochin function, of each frequency wave is assumed to be known. The momentum flux of the fluid domain is formulated to find the time variant force acting on the floating body in bichromatic waves. The second order difference frequency force is identified and extracted from the time variant force. The final solution is expressed as the circular integration of the product of Kochin functions. The limiting form of the slowly varying force is identical to the mean drift force. It shows that the slowly varying force components caused by the body disturbance potential can be evaluated at the far field.

• Journal of the Korean Wood Science and Technology
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• 제37권5호
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• pp.440-450
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• 2009

In case of wood flooring, the high emissivity would be one of the most important properties especially as the cover material of underfloor heating system. The FIR (Far Infrared) materials such as wood emit FIR energy by heating, which has been used as the medical therapy such as dry sauna. This research investigated the emissivity and the emission power of wood composites by comparing the amount of the three heat transfer modes transferred by infrared radiation which came from the increased temperature of the bottom board of the plywood box by the heater. The results showed the value of radiation mode was the highest mode for the plywood box, and the convection mode was the main mode for the aluminum box. The rate of convection was 81.8% in the aluminum box and 48.2% in the plywood box, respectively. In case of the rate of radiation, the aluminum box showed only 15.4% and the plywood box showed 51%. The emissivity and the emission power of birch plywood showed the same values as those of wood. The amount of energy required for the temperature rising of water within vial in the aluminum box and in the plywood box were 3.32 kJ and 6.70 kJ respectively, which showed that the vial temperature of the plywood box was two times higher than that of the aluminum box.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.103-106
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• 2002

This paper presents an effective numerical method for analyzing three-dimensional unsteady conjugate heat transfer problems of a curved pipe subjected to infernally thermal stratification. In the present numerical analyses, the thermally stratified flows in the pipe are simulated using the standard $k-{\varepsilon}$turbulent model and the unsteady conjugate heat transfer is treated numerically with a simple and convenient numerical technique. The unsteady conjugate heat transfer analysis method is implemented in a finite volume thermal-hydraulic computer code based on a non-staggered grid arrangement, SIMPLEC algorithm and higher-order bounded convection scheme. Numerical calculations have been performed far the two cases of thermally stratified pipe flows where the surging directions are opposite each other i.e. In-surge and out-surge. The results show that the present numerical analysis method is effective to solve the unsteady flow and conjugate heat transfer in a curved pipe subjected to infernally thermal stratification.

• 설비공학논문집
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• 제14권6호
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• pp.441-449
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• 2002

Single-phase convection and partial nucleate boiling in free-surface and submerged jet impingements of subcooled water ejected through a 2-mm-diameter circular pipe nozzle were investigated by local measurements. Effects of jet velocity and nozzle-to-imping-ing surface distance as well as heat flux on distributions of wall temperature and heat transfer coefficients were considered. Incipience of boiling began from far downstream in contrast with the cases of the planar water jets of high Reynolds numbers. Heat flux increase and velocity decrease reduced the temperature difference between stagnation and far downstream regions with the increasing influence of boiling in partial boiling regime. The chance in nozzle-to-impinging surface distance from H/d=1 to 12 had a significant effect on heat transfer around the stagnation point of the submerged jet, but not for the free-surface jet. The submerged jet provided the lower cooling performance than the free-surface jet due to the entrainment of the pool fluid of which temperature increased.

• 한국수정란이식학회:학술대회논문집
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• 한국수정란이식학회 2002년도 국제심포지엄
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• pp.56-62
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• 2002

The International Union for Conservation of Nature and Natural Resources (IUCN) considers the western/lowland bongo Tragelaphus eurycerus eurycerus to be a threatened species, and the eastern/mountain bongo Tragelaphus eurycerus isaaci an endangered species［1］. Although extinction is considered by many biologists to be a natural process during evolution, the exponential growth of the human population has drastically and prematurely reduced the numbers and genetic diversity of many species［2］. Species have evolved to adapt to a specific habitat or environment that meet their survival needs. Alteration or destruction of their habitat results in a species becoming incapable of adapting and hence becoming threatened with extinction. A widespread scientific and public consensus has emerged suggesting that governments should assign high priority to the maintenance of biological diversity via habitat preservation and management far species conservation［3］. Unfortunately, the loss of biological diversity far surpasses the available conservation resources and species are lost forever on a daily basis［4］. Notwithstanding the focus on habitat preservation and wildlife management, conservation biologists have also become increasingly interested in using the technologies of reproductive and developmental biology to help manage or rescue endangered species［5］.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.218-219
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• 2010

• 한국전자파학회논문지
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• 제30권3호
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• pp.195-201
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• 2019

위상배열 안테나는 개별 안테나의 위상을 제어함으로써 원하는 방향으로 빔 패턴을 형성할 수 있어 무선전력전송의 효율을 높이는데 효과적이다. 최적의 빔포밍을 통해 무선전력전송의 효율을 극대화하기 위해 송신기는 최적의 전송 경로를 인지해야 한다. 최적의 전파 경로 추정을 위해 일반적으로 송신기는 주기적으로 파일롯 신호를 전송하고 수신기는 이를 이용하여 최적의 경로에 해당되는 빔포밍 가중치를 계산하여 송신기로 피드백한다. 일반적으로 피드백 양이 안테나 수에 비례하여 증가하여 안테나 수가 많은 경우 피드백 오버헤드 문제가 대두된다. 본 논문에서 far-field approximation을 적용하여 피드백 양을 최소화하는 기법을 제안하고, 모의실험을 통해 간소화된 피드백 정보가 빔 패턴에 미치는 영향을 분석한다.

• 제어로봇시스템학회논문지
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• 제15권7호
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• pp.655-660
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• 2009

In many real applications, the discrepancy problem between controller outputs and plant inputs or the abrupt variation problem of controller outputs can occur. These problems have a negative effect on control performance and stability. It is well-known that two phenomena called 'windup' and 'bump' cause these problems. So far these problems have been studied separately in each side of the anti-windup and the bumpless transfer. This paper proposes a new unified method combines the anti-windup and the bumpless transfer method using the linear quadratic minimization and a proper state space model representation for the anti-windup controller. The proposed method has a feature that it takes account of both the anti-windup and the bumpless transfer in one formula. Finally, we exemplify the performance of the proposed method via numerical examples using the controller switching between the anti-windup PID controller and the anti-windup LQ controller.

• 한국수정란이식학회:학술대회논문집
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• 한국수정란이식학회 2002년도 국제심포지엄
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• pp.3-7
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• 2002

In vitro embryo culture techniques provide significant contributions not only for a basic research of fertilization and early embryogenesis, but also for a low cost mass production of bovine embryos for transfer, embryo diagnosis, nuclear cloning and the production of transgenic cows. This presentation introduces newly developed serum-free media (IVD101 and IVMD101) that are effective far high yields of transferable embryos of excellent quality from in vitro-matured and fertilized oocytes. Both serum-free media are superior to a conventional serum-containing medium on the increased rates of blastocyst formation, post-thaw embryo viability, and pregnancy after transfer. Furthermore, reduced risks of calf mortality and large calf syndrome are also observed for the serum-free-derived embryos. Serum-derived embryos contain a large number of lipid droplets and immature mitochondria in their cytoplasm that may account for the lower production of transferable embryos and poor embryo quality.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.186.1-186.1
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• 2014

Graphene, which is a 2-dimensional carbon material, has been attracting much interest due to its unique properties and potential applications. So far, many interesting experimental and theoretical works have been done concerning the electronic properties of graphene on various substrates. Especially, there are many experimental reports about doping in graphene which is caused by interaction between graphene and its supporting substrates. Here, we report the study of charge transfer between graphene and oxide substrates using density functional theory (DFT) calculations. In this study, we have investigated the charge transfer related with graphene considering various oxide substrates such as SiO2(0001) and MgO(111). Details in charge transfer between graphene and oxides are analyzed in terms of charge density difference, band structure and work function.