• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1215-1220
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• 2008

To obtain the shape of the free surface more accurately, computations are carried out by a finite volume method using unstructured meshes and an interface capturing method. Free-surface flow, which is very important in the fields of ship and marine engineering, is numerically simulated for flows of both water and air. Control volumes are used with an arbitrary number of faces and allows a local mesh refinement. The integration is of second order, with a midpoint rule integration and linear interpolation. The method is fully implicit and uses quadratic interpolation. The solution method of pressure-correction type solves sequentially equations of momentum, continuity, conservation, and two-equations turbulence model. Comparison are quantitatively made between the computation and experiment in order to confirm the solution method.

• 한국세라믹학회지
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• 제42권1호
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• pp.1-6
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• 2005

In aqueous alumina tape casting, the effects of altering the composition of the suspensions, the binders and the casting thickness were studied. The rheological behavior of the suspensions and the defects of the dried tapes were examined and the relationships between them are discussed. The changes in the defect regions reported in the previous paper were related with the rheological properties with variations of the binder, the composition and the casting thickness. The shear thinning factor increased with the organic content and the solid content (the decrease of water content). The apparent viscosity increased with the shear thinning factor. The relation between the shear thinning factor and the log apparent viscosity was similar for all binder types. In the relation between the defect free region and the rheological properties, the defect free region became narrower with increasing casting thickness. The defect free region is independent of binder type. Therefore, the thicker tape is more difficult to produce in aqueous alumina tape casting. Knowledge of the rheological properties of the suspensions could help Predict the defect type and the possibility of defect free dried tapes.

• 설비공학논문집
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• 제7권1호
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• pp.89-97
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• 1995

Experimental study was performed for free convection and ice formation around two horizontal circular tubes which were placed vertically. Temperature and velocity distributions were visualized with real time holographic interferometry technique and tracer method. When water was cooled, super cooled region was formed around cooling pipe. It was found that flow induced by free convection always directed downwards when the coolant temperature was low, while it directed upwards when the coolant temperature was comparably high though it directed downwards initially. Flow phenomena with free convection were investigated in detail with varying cooling rate and length between cooling pipes. And growing process of dense ice was also investigated. Dendritic ice is suddenly formed within a supercooled region, and a dense ice layer begins to develop from the cooling wall.

• Bulletin of the Korean Chemical Society
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• 제22권8호
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• pp.877-882
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• 2001

The solvent effects on the relative free energies of Eu3+ to Yb3+ ion mutation in solution have been investigated using a Monte Carlo simulation of statistical perturbation theory (SPT). Our results agree well with available data that were obtained by others. Particularly, the results of water (SPC/E) solvent are almost identical with experimental data. For the present Eu3+ and Yb3+ ions, the relative free energies of solvation vs. Born’s function of bulk solvents decrease with increasing Born’s function of bulk solvents. There is also good agreement between the calculated structural properties in this study and the published works obtained by computer simulation and experimental work.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.385-392
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• 2005

The restriction of the use of hazardous substances in electrical and electronic equipment legislation mandates the substitution of lead and other hazardous substances in electronics products by July 2006. Due to this legislative pressure, the electronics industry is moving to adoption of lead free solders. In this paper, we investigated a flux to restrict generating electrochemical migration in lead-free solder. The lead-free solders used in this study were Sn-0.7Cu-0.01P and Sn-3.0Ag-0.5Cu. To measure the resistance of electrochemical migration, the dew-cycle test and water drop test were adopted. As the result, now flux having high durable of electrochemical migration was developed.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1027-1031
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• 2014

외기냉수냉방 시스템은 공조나 산업공정에 사용되는 냉수를 저온의 외기를 이용하여 냉각하는 시스템으로 에너지를 절감하기위해 사용되며, 냉각시스템과 외기와 냉수가 열교환을 하는 드라이쿨러로 구성되어있다. 외기냉수냉방 시스템은 지속적인 냉방이 필요한 곳에 에너지절감효과가 뛰어나나 국내의 경우, 외기냉수냉방 시스템에 설계 기준과 자료가 미비하다. 따라서 본 연구에서는 상용프로그램 HYSYS를 이용하여, 드라이쿨러를 이용한 외기냉수냉방 시스템의 요소변화에 따른 성능을 비교 분석했으며 그 결과는 다음과 같다. 드라이쿨러의 냉각능력은 외기온도, 요구냉수온도, 열교환기의 LMTD (Logarithmic Mean Temperature Difference, 대수평균온도차)에 따라 변한다. 드라이쿨러는 외기온도가 낮을 수록 그 냉각능력이 증가하며, LMTD가 낮은 드라이쿨러가 LMTD가 높은 것에 비하여 고온의 외기온도에서 사용이 가능하였다. 외기온도가 극히 낮은 지역에서는 글리콜이 함유된 부동액을 사용해야하며 국내의 외기온도를 고려하였을 때, 글리콜농도 34%의 부동액이 적절한 것으로 판단된다. 냉동기에 적용될 작동유체의 경우, R22, R134a, R407C의 압축일을 비교했으며, R134a가 환경관련 규제와 에너지 사용측면에서 우수한 냉매로 사료된다.

• 한국버섯학회지
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• 제12권2호
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• pp.107-116
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• 2014

본 연구에서는 느릅나무버섯의 자실체에서 메탄올과 열수를 이용해 추출한 물질의 항산화, 항염증 및 Melanoma B16/F10 세포에서의 멜라닌 생성 저해 효과를 탐색하였다. DPPH 라디칼 소거능과 환원력을 이용해 항산화 효과를 측정한 결과 양성대조군으로 사용한 BHT에 비해 항산화 효과는 낮았지만 다른 종류의 버섯에 비해 효과가 우수한 것으로 나타났으며, 철 이온 제거 항산화 실험에서 느릅나무버섯의 열수 추출물은 양성대조군인 BHT에 비해 철 이온을 효율적으로 제거하여 항산화 효과가 높게 나타났다. 느릅나무버섯 자실체의 염증 저해 실험에서는 배양 중인 RAW 264.7 대식세포에 자실체의 메탄올과 열수추출물을 각각 처리 한 후 염증 유도 물질인 LPS를 투여하여 추출물의 NO 생성 저해효과를 조사한 결과, 처리한 추출물의 농도 의존적으로 염증 유발의 주요 인자인 NO의 양이 현저하게 감소하는 우수한 소염효과를 보였으며, carrageenan에 의해 흰쥐 뒷발에 유도된 부종을 저해하는 실험에서는 투여한 추출물의 농도가 증가함에 따라 흰쥐의 뒷발에 유도된 부종의 용적도 비례적으로 감소하여 항염증 효과가 높은 것으로 나타났다. Melanoma 세포에 버섯추출물을 처리하고 생합성된 멜라닌의 양을 측정한 결과 농도 의존적으로 melanoma 세포내 멜라닌의 양이 감소하여 멜라닌 저해 효과가 높은 것으로 나타났다. 따라서 느릅나무버섯 자실체의 항산화, 항염증 및 멜라닌 생성 저해 선분은 앞으로 항산화제, 소염제 및 미백제로의 이용이 가능할 것으로 사료된다.

• 디지털융복합연구
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• 제18권7호
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• pp.397-403
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• 2020

이 연구에서는 백모근의 열수와 95% 에탄올 추출물의 유리아미노산과 유도체, phenolic acid와 flavonoid의 조성 및 함량을 분석하였다. 연구의 목적은 추출물에 대한 기조자료를 확보하고, 기능성화장품과 기능성식품 성분으로서의 활용 가능성을 확인하고자 하는 것이다. 유리아미노산은 열수 추출물 15종, 95% 에탄올 추출물 9종이 나타났다. 단백질 비구성 아미노산 유도체는 열수 추출물 5종, 95% 에탄올 추출물 4종이 나타났다. 총 polyphenol은 열수 추출물 116.50 ± 0.06 mg%, 95% 에탄올 추출물 140.10 ± 0.04 mg%이었다. 총 flavonoid 함량은 열수 추출물 31.80 ± 0.03 mg%, 95% 에탄올 추출물 43.90 ± 0.05 mg%로 나타났다. Phenolic acid는 열수 추출물 5종, 95% 에탄올 추출물 6종이 나타났다. Flavonoid는 열수 추출물의 경우 나타나지 않았으나, 95% 에탄올 추출물은 taxifolin 1종이 나타났다. 따라서 이상과 같은 결과들로 볼 때 백모근의 열수와 95% 에탄올 추출물은 코스메슈티컬, 뉴트리코스메틱 및 기능성식품 성분으로서의 활용 가치가 있을 것으로 사료되어진다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 춘계 학술대회논문집
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• pp.119-125
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• 2004

Unsteady nonlinear wave motions on the free surface over a plane beach of constant slope are numerically simulated using a finite difference method in rectangular grid system. Two-dimensional Navier-Stokes equations and the continuity equation are used for the computations. Irregular leg lengths and stars are employed near the boundaries of body and free surface to satisfy the boundary conditions. Also, the free surface which consists of markers or segments is determined every time step with the satisfaction of kinematic and dynamic free surface conditions. Moreover, marker-density method is also adopted to allow plunging jets impinging on the free surface. The second-order Stokes wave theory and solitary wave theory are employed for the generation of waves on the inflow boundary. For the simulation of wave breaking phenomena, the computations are carried out with the plane beach of constant slope in surf zone. The results are compared with each other. The marker-density method is better then the hybrid method. Also they are compared with other existing experimental results. The Agreement between the experimental data and the computation results is good.

• Journal of Advanced Research in Ocean Engineering
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• 제2권2호
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• pp.48-60
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• 2016

Accurate simulation of free-surface wave flows around a ship is very important for better hull-form design. In this paper, a computational fluid dynamics (CFD) code which is based on the open source libraries, OpenFOAM, was developed to predict the wave patterns around a ship. Additional anti-diffusion source term for minimizing a numerical diffusion, which was caused by convection differencing scheme, was considered in the volume-fraction transport equation. The influence of the anti-diffusion source term was tested by applying it to free-surface wave flow around the Wigley and KCS model ships. In results, the wave patterns and hull wave profiles of the Wigley and KCS model ships for various anti-diffusion coefficients showed quite close patterns. While, the band width of the water volume-fraction values between 0.1 to 0.9 at the Wigley and KCS model hull surfaces was narrowed by considering the anti-diffusion term. From the results, anti-diffusion source term decreased free-surface smearing.