V.C. Mariani¹, V. J. Neckel², L. S. Coelho³

CMES-Computer Modeling in Engineering & Sciences, Vol.68, No.2, pp. 167-184, 2010, DOI:10.3970/cmes.2010.068.167

Abstract In this study an inverse heat conduction problem using two optimization methods to estimate apparent thermal diffusivity at different drying temperatures is solved. Temperature and moisture versus time were obtained numerically using heat and mass transfer equations with drying temperatures in the range between 20°C to 70°C. The solution of the partial differential equation is made with a finite difference method coupled to optimization techniques of Differential Evolution (DE) and Particle Swarm Optimization (PSO) used in inverse problem. Statistical analysis shows no significant differences between reported and estimated curves, and no remarkable differences between results obtained using DE and PSO… More >

Han-Taw Chen¹, Li-Shie Liu¹, Shin-Ku Lee¹

CMES-Computer Modeling in Engineering & Sciences, Vol.65, No.2, pp. 155-178, 2010, DOI:10.3970/cmes.2010.065.155

Abstract The finite difference method in conjunction with the least-squares scheme and experimental measured temperatures is proposed to solve a two-dimensional steady-state inverse heat conduction problem in order to predict the natural-convection heat transfer coefficient under the isothermal situation h^−iso from a three fin array mounted on a horizontal plate and fin efficiency η_f for various values of the fin spacing and fin height. The measured fin temperatures and ambient temperature are obtained from the present experimental apparatus conducted in a small wind tunnel. The heat transfer coefficient on a fin is non-uniform for the present problem, and its functional… More >

D. C. Knupp¹, A. J. Silva Neto², W. F. Sacco³

CMES-Computer Modeling in Engineering & Sciences, Vol.54, No.2, pp. 121-146, 2009, DOI:10.3970/cmes.2009.054.121

Abstract The inverse analysis of radiative transfer in participating media has several practical applications. In most cases, the inverse problem is formulated implicitly and the solution is given by the minimization of an objective function. Gradient based methods have largely been used for that purpose, but it has been observed in recent years an increasing interest in the use of stochastic methods. In this work, it is proposed the use of the Luus-Jaakola method and the Particle Collision Algorithm. The former is a random search optimization method that has been successfully employed mainly in chemical engineering, and the latter is a… More >

M. Irízar, L. D. Câmara, A. J. Silva Neto, O. Llanes

CMES-Computer Modeling in Engineering & Sciences, Vol.54, No.1, pp. 1-14, 2009, DOI:10.3970/cmes.2009.054.001

Abstract Modeling of Chromatography allows a better understanding and development of new techniques to be applied at industrial level, although it's relatively complex. The models of this process are represented by systems of partial differential equations with non linear parameters difficult to estimate generally, which constitutes an inverse problem. In general there aren't analytical solutions and therefore numerical methods should be used for their direct solutions. Frequently typical boundary conditions are considered, but it's convenient to study different approaches for those. Evolutionary Computation has been used successfully in many problems of diverse areas for searching in complex spaces. Considering previous works… More >

C. J. Wu¹, C. Y. Chou¹, C. N. Han¹, K. N. Chiang²

CMES-Computer Modeling in Engineering & Sciences, Vol.41, No.1, pp. 49-68, 2009, DOI:10.3970/cmes.2009.041.049

Abstract In this paper, the atomistic-continuum mechanics method (ACM) is applied for carbon nanotube modeling. The atomistic-continuum mechanics is based on the transformation of chemical bonds between atoms in molecular mechanics into appropriate elements in finite element method and continuum mechanics. Spring elements are treated as chemical bonds between carbon atoms in carbon nanotube, whose force-displacement function is determined by the Reactive Empirical Bond Order (REBO) potential model. The advantages and unique feature of ACM method is same analytical model can be used for both tensile and vibration analyses, and most importantly, there are no prior inputs such as Young's Modulus,… More >

D. S. Liu¹, C.Y. Tsai¹

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 29-48, 2009, DOI:10.3970/cmes.2009.039.029

Abstract Utilizing a thin copper substrate for illustration purposes, this study presents a novel numerical method for extracting the thermo-mechanical properties of a thin-film. In the proposed approach, molecular dynamics (MD) simulations are performed to establish the load-displacement response of a thin copper substrate nanoindented at temperatures ranging from 300~1400 K. The load data are then input to an artificial neural network (ANN), trained using a finite element model (FEM), in order to extract the material constants of the copper substrate. The material constants are then used to construct the corresponding stress-strain curve, from which the elastic modulus and the plastic… More >

F. Daghia¹, W. Hasan¹, L. Nobile¹, E. Viola^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.39, No.1, pp. 1-28, 2009, DOI:10.3970/cmes.2009.039.001

Abstract In this paper, a finite element model has been developed for analysing the flexural vibrations of a uniform Timoshenko beam-column on a two-parameter elastic foundation. The beam was discretized into a number of finite elements having four degrees of freedom each. The effect of end springs was incorporated in order to identify the end constraints. \newline The procedure for identifying geometric and mechanical parameters as well as the end restraints of a beam on two-parameter elastic foundation is based on experimentally measured natural frequencies from dynamic tests on the structure itself. \newline An iterative statistical identification method, based on the… More >

Chein-Shan Liu¹, Chih-Wen Chang², Jiang-Ren Chang^2,3

CMES-Computer Modeling in Engineering & Sciences, Vol.32, No.1, pp. 1-16, 2008, DOI:10.3970/cmes.2008.032.001

Abstract In this paper, we propose a new method to tackle of two famous boundary layer equations in fluid mechanics, namely, the Falkner-Skan and the Blasius equations. We can employ this method to find unknown initial conditions. The pivotal point is based on the erection of a one-step Lie group element$\mathbf {G}(T)$ and the formation of a generalized mid-point Lie group element$\mathbf {G}(r)$. Then, by imposing$\mathbf {G}(T) = \mathbf {G}(r)$ we can seek the missing initial conditions through a minimum discrepancy from the target in terms of a weighting factor$r \in (0, 1)$. Numerical examples are worked out to persuade that… More >

H.M. Lee¹, H.S. Park^1,2

CMES-Computer Modeling in Engineering & Sciences, Vol.29, No.1, pp. 29-44, 2008, DOI:10.3970/cmes.2008.029.029

Abstract This paper presents a computational model to estimate deformed shapes of beam structures using 3D coordinate information from terrestrial laser scanning (TLS). The model is composed of five components: 1) formulation of polynomial shape function, 2) application of boundary condition, 3) inducement of compatibility condition, 4) application of the least square method and 5) evaluation of error vector and determination of reasonable polynomial shape function. In the proposed model, the optimal degree of polynomial function is selected based on the complexity of beam structures, instead of using a specific degree of polynomial function. The chosen polynomial function for estimation is… More >

N. Osawa¹, K. Hashimoto¹, J. Sawamura¹, J. Kikuchi², Y. Deguchi², T. Yamaura²

CMES-Computer Modeling in Engineering & Sciences, Vol.20, No.1, pp. 43-54, 2007, DOI:10.3970/cmes.2007.020.043

Abstract A new hypothesis regarding heat transmission during line heating is proposed. It states that the distribution of the temperature of the gas adjacent to the plate, T_G, and the overall local heat transfer coefficient, α, depend only on the distance from the torch. An identification technique for T_G and α is developed. The validity of the employed hypothesis and the proposed technique is demonstrated by comparing the measured and identified T_G during a spot heating test. The plate temperature calculated by direct heat conduction analysis closely approximates the one measured for the spot and line heating tests, when T_G and… More >