• Advances in environmental research
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• 제3권2호
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• pp.131-149
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• 2014

Two different model selection indices, the Akaike information criterion (AIC) and the coefficient of determination ($R^2$), are used to discriminate competing isotherm equations for aqueous pollutant removal systems. The former takes into account model accuracy and complexity while the latter considers model accuracy only. The five types of isotherm shape in the Brunauer-Deming-Deming-Teller (BDDT) classification are considered. Sorption equilibrium data taken from the literature were correlated using isotherm equations with fitting parameters ranging from two to five. For the isotherm shapes of types I (favorable) and III (unfavorable), the AIC favors two-parameter equations which can easily track these simple isotherm shapes with high accuracy. The $R^2$ indicator by contrast recommends isotherm equations with more than two parameters which can provide marginally better fits than two-parameter equations. To correlate the more intricate shapes of types II (multilayer), IV (two-plateau) and V (S-shaped) isotherms, both indices favor isotherm equations with more than two parameters.

• 한국항공우주학회지
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• 제36권2호
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• pp.115-122
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• 2008

예조건화 오일러 방정식의 수렴 특성에 미치는 특성 조건수의 영향을 조사하였다. 그리고 Choi와 Merkle 예조건화를 적용한 경우와 온도 예조건화를 적용한 경우의 수렴 특성을 분석하였다. 공간차분을 위해 예조건화 Roe의 FDS 기법을 적용하였고, 시간적분을 위해 예조건화 LU-SGS 기법을 적용하였다. 지배방정식의 수렴 특성은 특성 조건수에 크게 영향을 받는 것으로 나타났으며, 최적의 특성 조건수가 존재하는 것으로 나타났다. 그리고 최적의 특성 조건수는 Choi 와 Merkle 예조건화를 적용한 경우와 온도 예조건화를 적용한 경우가 서로 다른 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제17권6호
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• pp.789-817
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• 2004

This paper deals with the modal analysis of rotational shell structures by means of the numerical solution technique known as the Generalized Differential Quadrature (G. D. Q.) method. The treatment is conducted within the Reissner first order shear deformation theory (F. S. D. T.) for linearly elastic isotropic shells. Starting from a non-linear formulation, the compatibility equations via Principle of Virtual Works are obtained, for the general shell structure, given the internal equilibrium equations in terms of stress resultants and couples. These equations are subsequently linearized and specialized for the rotational geometry, expanding all problem variables in a partial Fourier series, with respect to the longitudinal coordinate. The procedure leads to the fundamental system of dynamic equilibrium equations in terms of the reference surface kinematic harmonic components. Finally, a one-dimensional problem, by means of a set of five ordinary differential equations, in which the only spatial coordinate appearing is the one along meridians, is obtained. This can be conveniently solved using an appropriate G. D. Q. method in meridional direction, yielding accurate results with an extremely low computational cost and not using the so-called "delta-point" technique.

• 공업화학
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• 제32권4호
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• pp.417-422
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• 2021

본 연구에서는 유기 단열재인 poly isocyanurate foam (PIR), poly urethane foam (PUR), phenol foam (PF)을 선정하여 ISO 5660-1의 기준에 따라 콘칼로리미터(cone calorimeter)를 이용하여 측정하였다. 화재위험성 평가를 표준화하기 위하여 기준물질(PMMA)을 사용하여 Chung's equations-III와 Chung's equation-IV에 의한 화재위험성을 등급화하여 평가하였다. Chung's equations-II의 화재성능지수-II 값은 PF가 14.77 s²/kW로 화재성능지수-II가 가장 높았고, PUR이 0.08 s²/kW로 화재성능지수-II가 가장 낮았다. 화재성장지수-II 값은 PF가 0.01 kW/s²로 화재성장지수-II가 가장 낮았고, PUR이 1.14 kW/s²로 화재성장지수-II가 가장 높았다. Chung's equations-III의 화재성능지수-III에서 PUR이 0.11로 화재성능지수-III가 가장 낮게 나타났고, PF가 20.23으로 화재성능지수-III가 가장 높았다. FGI-III에서는 PUR이 14.25로 화재성장지수-III가 가장 높게 나타났고, PF가 0.13으로 가장 안전한 물질로 판단하였다. 그리고 Chung's equation-IV의 화재위험성지수-IV는 PUR (130.03) >> PIR (19.13) > PMMA (1.00) > PF (0.01)의 순서로 나타났다. 따라서 PF가 화재위험성이 가장 낮고, PUR이 가장 높은 것으로 판단하였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제15권4호
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• pp.253-265
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• 2011

In this paper, we study the existence of mild solutions for double perturbed impulsive neutral functional evolution equations with infinite delay in Banach spaces. The existence of mild solutions to such equations is obtained by using the theory of the Hausdorff measure of noncompactness and Darbo fixed point theorem, without the compactness assumption on associated evolution system. An example is provided to illustrate the theory.

• 대한기계학회논문집
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• 제5권3호
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• pp.217-222
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• 1981

The stress analysis of two-orthotropic layer, adhesively bonded structures is considered. An orthotropic plate has a through-crack of finite length and is adhesively bounded by a sound orthotropic plate. The problem is resuced to a pair of Fredholm integral equations ofthe second kind. Using a numerical integration scheme to evaluate the intgrals, The integral equations are reduced to a system of algebraic equations. By solving these equations some numerical results for stress intensity factors are presented for various crack lengths.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제15권3호
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• pp.177-190
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• 2011

According to fractional calculus theory and Banach's fixed point theorem, we establish the sufficient conditions for the controllability of impulsive fractional evolution integrodifferential equations in Banach spaces. An example is provided to illustrate the theory.

• Journal of applied mathematics & informatics
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• 제29권3_4호
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• pp.847-858
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• 2011

We make use of the simplified Hirota's bilinear method with computer symbolic computation to study a variety of coupled potential KdV (pKdV) equations. Each coupled equation is completely integrable and gives multiple soliton solutions and multiple singular soliton solutions. The phase shifts for all coupled pKdV equations are identical whereas the coefficients of the obtained solitons are not identical. The four coupled pKdV equations are resonance free.

• Journal of applied mathematics & informatics
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• 제16권1_2호
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• pp.383-405
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• 2004

We study the incomprssible Navier Stokes equations for the flow inside contraction geometry. The governing equations are expressed in the vorticity-stream function formulations. A rectangular computational domain is arised by elliptic grid generation technique. The numerical solution is based on a technique of automatic numerical generation of acurvilinear coordinate system by transforming the governing equation into computational plane. The transformed equations are approximated using central differences and solved simultaneously by successive over relaxation iteration. The time dependent of the vorticity equation solved by using explicit marching procedure. We will apply the technique on several irregular-shapes.

• 충청수학회지
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• 제26권1호
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• pp.197-211
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• 2013

We study some stability properties in discrete Volterra equations by employing to change Yoshizawa's results in [13] for the nonlinear equations into results for the nonlinear discrete Volterra equations with unbounded delay.