Cansu Ulker*, Yuksel Guvenilir

Journal of Renewable Materials, Vol.6, No.6, pp. 591-598, 2018, DOI:10.7569/JRM.2017.634189

Abstract As an alternative biodegradable aliphatic polyester, poly(w-pentadecalactone-co-ε-caprolactone) copolymer was synthesized via enzymatic ring-opening polymerization. A new biocatalyst, Candida antarctica lipase B, immobilized onto rice husk ash was used for catalysis. Reactions were carried out at various temperatures and periods for varied copolymer compositions in order to obtain the highest molecular weight copolymer. The best reaction parameters were found to be 80 °C and 6 hours and molecular weights increased proportionally with the amount of w-pentadecalactone (w-PDL). The molecular structure of copolymer with 75% weight ratio of w-PDL (Mn = 19720 g/mol) was characterized by proton More >

D. Brunner¹, M. Junge¹, P. Rapp¹, M. Bebendorf², L. Gaul¹

CMES-Computer Modeling in Engineering & Sciences, Vol.58, No.2, pp. 131-160, 2010, DOI:10.3970/cmes.2010.058.131

Abstract The simulation of the hydroacoustic sound radiation of ship-like structures has an ever-growing importance due to legal regulations. Using the boundary element method, the overall dimension of the problem is reduced and only integrals over surfaces have to be considered. Additionally, the Sommerfeld radiation condition is automatically satisfied by proper choice of the fundamental solution. However, the resulting matrices are fully populated and the set-up time and memory consumption scale quadratically with respect to the degrees of freedom. Different fast boundary element methods have been introduced for the Helmholtz equation, resulting in a quasilinear complexity.… More >

Nikolay Dishovsky^1*, Petrunka Malinova¹, Ivan Uzunov²

Journal of Renewable Materials, Vol.6, No.4, pp. 402-412, 2018, DOI:10.7569/JRM.2017.634171

Abstract Natural products from agricultural wastes are finding importance in the polymer industry due to their many advantages such as being lightweight, low cost and environmentally friendly. In the present study the potential of the two types of rice husk ash (RHA) prepared under different conditions as fillers in natural rubber-based elastomer composites was investigated. The fillers were prepared by rice husks incineration and characterized by means of X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), Brunauer-Emmett-Teller (BET) specific surface area, Hg-porosimetry and N2-adsorption. The evaluation involved determining the vulcanization characteristics… More >

E. M. Ciannamea, D. C. Marin, R. A. Ruseckaite, P. M. Stefani^*

Journal of Renewable Materials, Vol.5, No.5, pp. 357-362, 2017, DOI:10.7569/JRM.2017.634125

Abstract In the development of materials based on renewable resources, the search for lignocellulosic substitutes for wood is one of the biggest challenges that academia and the particleboard and wood industries are facing. In this article, particleboards were processed using rice husk, an agricultural waste, as a substitute for wood. Rice husk without any further treatment was processed into particleboards using phenol-formaldehyde resin as binder. The effect of the processing parameters, pressure and binder content (BC) on the density, water absorption (WA), thickness swelling (TS), modulus of rupture (MOR) and modulus of elasticity (MOE) was analyzed. More >

Chein-Shan Liu¹

CMC-Computers, Materials & Continua, Vol.25, No.3, pp. 239-264, 2011, DOI:10.3970/cmc.2011.025.239

Abstract For the computational applications in several areas, we propose a single-scale and a multi-scale diagonal preconditioners to reduce the condition number of Vandermonde matrix. Then a new algorithm is given to solve the inversion of the resulting coefficient matrix after multiplying by a preconditioner to the Vandermonde matrix. We apply the new techniques to the interpolation of data by using very high-order polynomials, where the Runge phenomenon disappears even the equidistant nodes are used. In addition, we derive a new technique by employing an m-order polynomial with a multi-scale technique to interpolate 2m+1 data. Numerical results More >

Liming Yang^1,2, Junjian Bai¹, Qun Sun³

CMES-Computer Modeling in Engineering & Sciences, Vol.108, No.1, pp. 49-65, 2015, DOI:10.3970/cmes.2015.108.049

Abstract Extreme learning machine (ELM) has demonstrated great potential in machine learning and data mining fields owing to its simplicity, rapidity and good generalization performance. In this work, a general framework for ELM regression is first investigated based on least absolute deviation (LAD) estimation (called LADELM), and then we develop two regularized LADELM formulations with the l₂-norm and l₁-norm regularization, respectively. Moreover, the proposed models are posed as simple linear programming or quadratic programming problems. Furthermore, the proposed models are used directly to analyze the hard rate of licorice seeds using near-infrared spectroscopy data. Experimental results on More >

T. Gortsas¹, S.V. Tsinopoulos², D. Polyzos^1,3

CMES-Computer Modeling in Engineering & Sciences, Vol.107, No.4, pp. 321-343, 2015, DOI:10.3970/cmes.2015.107.321

Abstract An advanced Boundary Element method (BEM) accelerated via Adaptive Cross Approximation (ACA) and Hierarchical Matrices (HM) techniques is presented for the solution of large-scale elastostatic problems with multi-connected domains like in fiber reinforced composite materials. Although the proposed ACA/ BEM is demonstrated for two-dimensional (2D) problems, it is quite general and it can be used for 3D problems. Different forms of ACA technique are employed for exploring their efficiency when they combined with a BEM code. More precisely, the fully and partially pivoted ACA with and without recompression are utilized, while the solution of the More >

R. Q. Rodríguez^1,2, C. L. Tan², P. Sollero¹, E. L. Albuquerque³

CMES-Computer Modeling in Engineering & Sciences, Vol.102, No.5, pp. 359-372, 2014, DOI:10.3970/cmes.2014.102.359

Abstract The efficient evaluation of the fundamental solution for 3D general anisotropic elasticity is a subject of great interest in the BEM community due to its mathematical complexity. Recently, Tan, Shiah, andWang (2013) have represented the algebraically explicit form of it developed by Ting and Lee (Ting and Lee, 1997; Lee, 2003) by a computational efficient double Fourier series. The Fourier coefficients are numerically evaluated only once for a specific material and are independent of the number of field points in the BEM analysis. This work deals with the application of hierarchical matrices and low rank More >

R. Q. Rodríguez¹, A.F. Galvis¹, P. Sollero¹, E. L. Albuquerque²

CMES-Computer Modeling in Engineering & Sciences, Vol.96, No.4, pp. 259-274, 2013, DOI:10.3970/cmes.2013.096.259

Abstract Over recent years the rapid evolution of the computational power has motivated the development of new numerical techniques to account for engineering solutions. The Boundary Element Method (BEM) has shown to be a powerful numeric tool for the analysis and solution of many physical and engineering problems. However, BEM fully populated and non-symmetric system matrices implies in higher memory requirements and solution times. This work analyze the application of hierarchical matrices and low rank approximations, applying the Adaptive Cross Approximation - ACA, to multiple inclusion potential problems. The use of hierarchical format is aimed at More >

P. Redou¹, L. Gaubert¹, G. Desmeulles¹, P-A. Béal², C. Le Gal², V. Rodin³

CMES-Computer Modeling in Engineering & Sciences, Vol.70, No.1, pp. 11-40, 2010, DOI:10.3970/cmes.2010.070.011

Abstract Multi Interaction Systems, used in the context of Virtual Reality, are dedicated to real-time interactive simulations. They open the way to the in virtuo experimentation, especially useful in the domain of biochemical kinetics. To this purpose, chaotic and asynchronous scheduling of autonomous processes is based upon desynchronization of phenomena involved in the system. It permits interactivity, especially the capability to add or remove phenomena in the course of a simulation. It provides methods of resolution of ordinary differential systems and partial derivative equations. Proofs of convergence for these methods have been established, but the problem of More >