Suely Oliveira², Fang Yang²

The International Conference on Computational & Experimental Engineering and Sciences, Vol.3, No.2, pp. 113-120, 2007, DOI:10.3970/icces.2007.003.113

Abstract In this paper we describe and compare preconditioners for saddle-point systems obtained from meshfree discretizations, using the concepts of hierarchical (or H-)matrices. Previous work by the authors using this approach did not use H-matrix techniques throughout, as is done here. Comparison shows the method described here to be better than the author's previous method, an AMG method adapted to saddle point systems, and conventional iterative methods such as JOR. More >

Bahaa T. Shawky¹, Mohammed Nagah¹, Mosad A. Ghareeb², Gamal M. El-Sherbiny³, Saad A. M. Moghannem³, Mohamed S. Abdel-Aziz^1,*

Journal of Renewable Materials, Vol.7, No.7, pp. 667-682, 2019, DOI:10.32604/jrm.2019.04524

Abstract Rice straw (RS) collected from Egyptian agricultural environment (Al-Masied village-Alsharqia Governorate-Egypt) was used as substrate for three fungal isolates namely: 4b, 1Asp, Pleurotus ostreatus NRRL 3501 and mixed culture of (4b, 1Asp). Isolates number 4b and 1Asp were identified using the molecular technique (18S rRNA). Isolate 4b and 1Asp, were identified as Trichoderma saturnisporum MN1-EGY and Aspergillus niger MN2-EGY, respectively. Trichoderma saturnisporum MN1-EGY extract exhibited the highest antimicrobial activity compared to the other fungal extracts. Total phenolic, antimicrobial and antioxidant activities were also determined from the ethyl acetate extract of rice straw inoculated by these fungi. The antioxidant scavenging concentration(SC50)… More >

V. Subrahmanian^1,*, M. Albert Noble Einstien²

Journal of Renewable Materials, Vol.7, No.2, pp. 171-192, 2019, DOI:10.32604/jrm.2019.00090

Abstract Nowadays an alternate source of filler from renewable and plant derivatives are being thought of in rubber industries due to their reliability, environmental and economic benefits. Rice Husk Ash (RHA) a byproduct of the rice milling industry is obtained on partial and as well as full combustion of the rice husks. This ash is a good source of silica, silicates and needle shaped carbon and hence can be used as filler for cements. In the present study, a detailed investigation was carried out to understand the RHA as reinforcing material using mechanical properties and fractography using SEM. The rubbers studied… More >

Yasemin Kaptan, M.Sc.^1,*, Yüksel Avcıbaşı-Güvenilir¹

Journal of Renewable Materials, Vol.6, No.6, pp. 619-629, 2018, DOI:10.32604/JRM.2018.00142

Abstract Surface-modified rice husk ash was used as an inorganic support material for immobilization of Candida antarctica lipase B. (3-aminopropyl) trimethoxysilane was used for surface modification. Immobilization of CALB was performed via both physical adsorption and cross-linking. PCL synthesis was carried out by using these immobilized enzymes, free enzyme and Novozyme 435®. Molecular weight distribution of polymer samples was obtained by gel permeation chromatography (GPC) and chain structures of the polymer samples were observed by hydrogen nuclear magnetic resonance (1H-NMR). The highest monomer conversion is generally obtained by using cross-linked enzyme, around 90%. PDI values for all polymer samples were approximately… More >

Sofía Collazo-Bigliardi^1,*, Rodrigo Ortega-Toro², Amparo Chiralt Boix¹

Journal of Renewable Materials, Vol.6, No.6, pp. 599-610, 2018, DOI:10.32604/JRM.2018.00127

Abstract Cellulosic fibres from coffee (CF) and rice (RF) husks have been obtained applying chemical treatments and characterized as to their microstructure and thermal behaviour. These materials have been incorporated into glycerol plasticised thermoplastic starch (TPS) films obtained by melt blending and compression moulding at 1 wt%, 5 wt% and 10 wt%. Microstructure, thermal behaviour and optical, tensile and barrier properties of the composites were analysed. Both kinds of micro-fibres improve the film stiffness while reduced the film stretchability. However, CF better maintained the film ductility at 1 and 5 wt%. A network of fine oriented fibres was observed on the… More >

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 and carbon nuclear magnetic resonance… 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. Two of these methods are… 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 of the compounds and their… 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. The performance of the obtained… 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 confirm the validity of… More >