• KSBB Journal
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• 제28권3호
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• pp.202-207
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• 2013

In this study, saponin content of extract from modified preconditioning process was investigated in Saponaria officinalis L. for cosmetic natural surfactant. Saponin content in steamed leaves from S. officinalis L. was about three times more than that in dried leaves (tea saponin and quillaja saponin). And saponin extracts from steamed leaves was excellently shown in both forming force and forming stability. In emulsion activity, saponin extracts from steamed leaves had a similar level to quillaja saponin and tea saponin. Saponin extracts from steamed leaves in S. officinalis L. showed nontoxic effect below in $1,000{\mu}g/mL$ of concentration and dose-dependent inhibition of NO production. From the experiment, the extracts of S. officinalis L. showed good cosmetic agent.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.7-11
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• 2003

for many years already, testing laboratories, research institutes and manufactures try to find a reliable water tree accelerated ageing test that is able to show whether a polymer Medium Voltage cable os susceptible to water treeing or not. Test on laboratory samples, model cable designs, and fell size cable are presented. Apart form aging, another important aspect of any accelerated aging test is the right choice of th preconditioning method. THTS paper is the analysis of weibull distribution method after an accelerated aging test of MV(Medium Cable) cable.

• 한국전산유체공학회지
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• 제12권4호
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• pp.74-84
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• 2007

The flowfield characteristics in a straight rectangular channel have been investigated through a numerical model to analyze the regenerative cooling system that is used in rocket engine cooling. The supercritical hydrogen coolant introduces strong property variations that have a major influence on the developing flow and heat transfer characteristics. Of particular interest is the improved understanding of the physical characteristics of such flows through parametric studies. The approach used is a numerical solution of the full Navier-Stokes equations in the three dimensional form including the arbitrary equation of state and property variations. The present study compares constant and variable property solutions for both laminar and turbulent flow. For laminar flow, the variation of aspect ratio is examined, while for turbulent flow, the effects of variation of channel length and Reynolds number are discussed.

• 한국추진공학회지
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• 제6권2호
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• pp.9-17
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• 2002

난류분무 연소해석을 위한 수치해석 코드가 개발되었다. 복잡한 형상을 다루기 위하여 일반좌표계에서 이산화되었고 낮은 마하수 유동에 대한 수렴성을 증가시키기 위하여 예조건화기법과 고유치 재규격화기법이 도입되었다. 코트의 정확성은 캐비티 유동과 평면노즐에서 검증되었다. 액체로켓 엔진의 막냉각효과가 분무연소해석에 의하여 분석되었다. 막냉각은 연소효율에 부정적인 영향을 보였다. 연소실 벽면에서 막냉각효과는 연료가 많은 지역형성에 증진됨을 보여주었다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제4권3호
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• pp.256-266
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• 2012

Cavitating flow simulation is of practical importance for many engineering systems, such as marine propellers, pump impellers, nozzles, torpedoes, etc. The present work has developed the base code to solve the cavitating flows past the axisymmetric bodies with several forebody shapes. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. The momentum is in the mixture phase while the continuity equation is solved in liquid and vapor phase, separately. The solver employs an implicit preconditioning algorithm in curvilinear coordinates. The computations have been carried out for the cylinders with hemispherical, 1-caliber, and 0-caliber forebody and, then, compared with experiments and other numerical results. Fairly good agreements with experiments and numerical results have been achieved. It has been concluded that the present numerical code has successfully accounted for the cavitating flows past axisymmetric bodies. The present code has also shown the capability to simulate ventilated cavitation.

• 대한치과의사협회지
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• 제53권3호
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• pp.178-186
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• 2015

Dental polymer-based luting materials are classified into esthetic resin cement, adhesive resin cement and self-adhesive resin cement. Due to the different component of each type of resin cement, the preconditioning method of tooth surface and the steps are different from each type of resin cement. The pre-treatment of adherend (ceramic, resin and metal) surface also varies with the type of resin cement and the manufacturer. In this study, the characteristics of each type of resin cement, mechanical properties, indication and advantages were investigated. Through these, clinical tips on using resin cements were suggested.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 B
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• pp.734-736
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• 1996

This paper presents a method of calculating a selective number of eigenvalues in power systems, which are rightmost, or are largest modulus. The modified Arnoldi method in conjunction with implicit shift OR-algorithm is used to calculate the rightmost eigenvalues. Algorithm requires neither a prior knowledge of the specified shifts nor the calculation of inverse matrix. The key advantage of the algorithm is its ability to converge to the wanted eigenvalues at once. The method is compared with the modified Arnoldi method combined with S-matrix transformation, where the eigenvalues having the largest modulus are to be determined. The two methods are applied to the reduced Kansai system. Convergence characteristics and performances are compared. Results show that both methods are robust and has good convergence properties. However, the implicit shift OR method is seen to be faster than the S-matrix method under the same condition.

• 에너지공학
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• 제4권1호
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• pp.126-139
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• 1995

저속의 압축성 유동장에서의 원형 실린더 주위의 유동 및 열전달특성을 해석하였다. 비압축성 유동장에서의 실린더 주위의 유동 및 열전달현상에 대하여는 실험과 수치해석을 포함한 광범위한 연구가 진행되어 왔으며 매우 잘 알려져 있다. 실린더 벽면과 주위 유동장의 온도차가 큰 경우, 밀도의 변화가 커지므로 유동장은 압축성 유체가 되나 지배 방정식의 복잡함과 적절한 수치해석 방법의 부족으로 실린더 주위의 유동장을 압축성유체로 해석한 경우는 매우 드물다. 현재 압축성유동 해석에 널리 사용되는 time marching algorithm은 저속의 유동장 해석시 지배방정식에 나타나는 eigenvalue들의 괴리에 의하여 수렴속도가 현저히 떨어지게 된다. 본 연구에서는 이와 같은 난점을 극복할 수 있는 time-derivative preconditioning 방법을 사용하여 온도차가 큰 유동장에서의 강제 및 혼합대류에 대한 계산을 수행하였고 이들의 열전달특성을 비교하였다. 강제대류의 경우 실린더 벽면 온도의 증가에 따른 밀도 감소의 영향은 유동장의 Re수를 감소시켜 확산의 영향을 증가시키면서, 혼합대류의 경우 부력의 영향은 가열되는 유동장의 범위와 재순환 영역을 강제대류에 비해 현저히 감소시킨다.

• Nuclear Engineering and Technology
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• 제49권6호
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• pp.1114-1124
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• 2017

Acceleration/preconditioning strategies available in the SCEPTRE radiation transport code are described. A flexible transport synthetic acceleration (TSA) algorithm that uses a low-order discrete-ordinates ($S_N$) or spherical-harmonics ($P_N$) solve to accelerate convergence of a high-order $S_N$ source-iteration (SI) solve is described. Convergence of the low-order solves can be further accelerated by applying off-the-shelf incomplete-factorization or algebraic-multigrid methods. Also available is an algorithm that uses a generalized minimum residual (GMRES) iterative method rather than SI for convergence, using a parallel sweep-based solver to build up a Krylov subspace. TSA has been applied as a preconditioner to accelerate the convergence of the GMRES iterations. The methods are applied to several problems involving electron transport and problems with artificial cross sections with large scattering ratios. These methods were compared and evaluated by considering material discontinuities and scattering anisotropy. Observed accelerations obtained are highly problem dependent, but speedup factors around 10 have been observed in typical applications.

• 대한수학회보
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• 제53권2호
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• pp.423-440
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• 2016

The bubble stabilization technique of Chebyshev-Legendre high-order element methods for one dimensional advection-diffusion equation is analyzed for the proposed scheme by Canuto and Puppo in [8]. We also analyze the finite element lower-order preconditioner for the proposed stabilized linear system. Further, the numerical results are provided to support the developed theories for the convergence and preconditioning.