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  • Open Access

    ARTICLE

    Generation of OAM Waves and Analysis of Mode Purity for 5G Sub-6 GHz Applications

    Shehab Khan Noor1, Arif Mawardi Ismail1, Mohd Najib Mohd Yasin1,*, Mohamed Nasrun Osman1, Nurulazlina Ramli2, Ali H. Rambe3, J. Iqbal4,5

    CMC-Computers, Materials & Continua, Vol.74, No.1, pp. 2239-2259, 2023, DOI:10.32604/cmc.2023.031170

    Abstract This article presents the generation of Orbital Angular Momentum (OAM) vortex waves with mode 1 using Uniform Circular Array (UCA) antenna. Two different designs, namely, UCA-1 (4-element array antenna) and UCA-2 (8-element array antenna), were designed and fabricated using FR-4 substrate to generate OAM mode 1 at 3.5 GHz (5G mid-band). The proposed antenna arrays comprised rectangular microstrip patch elements with inset fed technique. The elements were excited by a carefully designed feeding phase shift network to provide similar output energy at output ports with desired phase shift value. The generated OAM waves were confirmed… More >

  • Open Access

    ARTICLE

    Advances of Polyurethane Foams Derived from Lignin

    Hyoe Hatakeyama1,*, Tatsuko Hatakeyama2

    Journal of Renewable Materials, Vol.1, No.2, pp. 113-123, 2013, DOI:10.7569/JRM.2012.634111

    Abstract Lignin and saccharides are two major components of plants. Huge amounts of plant residues are obtained as by-products of large-scale industries, such as pulp and paper, bio-fuel and the food industry. In this paper, preparation of polyurethane (PU) foam directly from various kinds of industrial lignin and molasses, which have scarcely been utilized, is summarized based on our results obtained by recent investigation. A onestep reaction using hydroxyl groups of plant materials as an active site makes it possible to produce a wide variety of PU, such as foams, sheets, gels and composite matrix. In More >

  • Open Access

    ARTICLE

    Dynamic Foaming Behaviour of Polyurethane vs Tannin/ Furanic Foams

    M.C. Basso1,2, A. Pizzi1,3,*, A. Celzard4

    Journal of Renewable Materials, Vol.1, No.4, pp. 273-278, 2013, DOI:10.7569/JRM.2013.634125

    Abstract : Simultaneously monitoring the variation of temperature, foam rising rate, internal foam pressure and dielectric polarisation, the latter being a direct measure of setting and curing of a thermosetting foam, has allowed the comparison of the dynamic variation of determinant parameters of polyurethane foams and of tannin/furanic foams of different formulation and characteristics. This monitoring provides a good description of the process and possible characteristics of the prepared foam and constitutes an invaluable tool for foam formulation. Such a comparison indicates that fundamental differences, but also similarities, exist between the foaming processes of the two More >

  • Open Access

    ARTICLE

    A SEM Record of Proteins-Derived Microcellular Silicon Carbide Foams

    A. Pizzi1,2,*, C. Zollfrank3, X. Li1, M. Cangemi1, A. Celzard4

    Journal of Renewable Materials, Vol.2, No.3, pp. 230-234, 2014, DOI:10.7569/JRM.2014.634114

    Abstract Protein rigid foams based on albumin coreacted with camphor and an aldehyde were converted into silicon carbide (SiC) foams. This was carried out by putting albumin-derived template foams in contact with silicon compounds in liquid phase and calcinating the mix obtained at a relatively low temperature of 500°C to eliminate the protein and leave the SiC foam. The transformation was followed by scanning electron microscopy (SEM) from the natural albumin foams to the gel obtained by infi ltrating them with tetraethyl orthosilicate (TEOS) and to the appearance of the SiC foams after calcination. X-ray diffraction More >

  • Open Access

    ARTICLE

    Development and Characterisation of Phenolic Foams with Phenol-Formaldehyde-Chestnut Tannins Resin

    M.C. Lagel1, A. Pizzi1,2, S. Giovando3, A. Celzard4

    Journal of Renewable Materials, Vol.2, No.3, pp. 220-229, 2014, DOI:10.7569/JRM.2014.634113

    Abstract With the depletion of fossil resources, tannin extracts can be a natural alternative to some synthetic products. Hydrolysable chestnut tannin extracts have been used to partially replace phenol in PF resins for phenolic rigid foams. Phenol-formaldehyde-chestnut tannin (PFT) phenolic foams were initially made from copolymerized PFT resins of different molar ratio. The PFT foams so prepared were tested for thermal conductivity, these being slightly worse than that of pure PF foams; and for mechanical and water absorption, these two properties being better than those of pure PF foams. Indeed, PF resins represent an important part More >

  • Open Access

    ARTICLE

    Characterization and Preparation of Wood-Furanic Foams

    V. K. Srivastava1, A. Pizzi2,3,*

    Journal of Renewable Materials, Vol.2, No.3, pp. 201-206, 2014, DOI:10.7569/JRM.2014.634107

    Abstract Fine wood powder/furanic foams were prepared with a strong predominance of the wood component. Low weight and density are important properties of foamed composites. Focusing on preparing light materials, wood foam composites were made using a chemical foaming method and expanded using diethyl ether as the foaming agent. The additives were added to note their effect on the density and mechanical properties, like impact strength and Young’s moduli, of the expanded composites. Various tests and scanning electron microscopy analysis were also performed. The foaming agent resulted in closed cells with varied sizes and more or More >

  • Open Access

    ARTICLE

    Alkaline Tannin Rigid Foams

    M.C. Basso1,2, S. Giovando3, A. Pizzi2,4,*, M.C. Lagel2,3, A. Celzard5

    Journal of Renewable Materials, Vol.2, No.3, pp. 182-185, 2014, DOI:10.7569/JRM.2013.634137

    Abstract Condensed fl avonoid tannin foams were obtained under alkaline conditions. This entailed the elimination of furfuryl alcohol from these formulations, as under alkaline conditions, foam preparation could not rely on the heat generated by the self-condensation of furfuryl alcohol, which occurs only under strongly acidic conditions. The approach used to formulate the alkaline foam was: (i) the total elimination of furfuryl alcohol from the formulation, (ii) coupled with the use of an aldehyde hardener different from formaldehyde (for environmental reasons) and (iii) the application of moderate heat to allow foaming. These were not tannin/ furanic More >

  • Open Access

    ARTICLE

    Foam-Laid Thermoplastic Composites Based on Kraft Lignin and Softwood Pulp

    Antti Ojala1,*, Lisa Wikström1, Kalle Nättinen2, Jani Lehmonen3, Karita Kinnunen-Raudaskoski4

    Journal of Renewable Materials, Vol.2, No.4, pp. 278-284, 2014, DOI:10.7569/JRM.2014.634126

    Abstract This article presents a new method of producing thermomoldable nonwoven materials based on kraft lignin (KL) and softwood kraft pulp (KP). A mixture of starch acetate (SA) and triethyl citrate (TEC) was used as a water insoluble plasticizer for KL. The thermoplastic lignin (TPL) material with the optimized ratio of KL, SA and TEC was prepared in a twin-screw extruder. The TPL compound was ground and mixed with KP fi bers to produce thermoformable sheets using foam-laid technology. The formed webs were compression molded (CM) into plates and mechanically tested. The foam-laid composites had tensile More >

  • Open Access

    ARTICLE

    Photodegradation of Polyurethane Foam Obtained from Renewable Resource–Pulp Production Byproducts

    A. Paberza*, L. Stiebra, U. Cabulis

    Journal of Renewable Materials, Vol.3, No.1, pp. 19-27, 2015, DOI:10.7569/JRM.2014.634138

    Abstract Rigid polyurethane foams were obtained from pulp production byproducts. Three different polyols were used—tall oil polyol, lignopolyol and commercially available polyol for comparison. The obtained rigid polyurethane foams underwent photodegradation at 60°C temperature and at 0.89 W/m2 intensity of UV light radiation up to 1000 h. Changes in chemical structure were observed by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy was used to study changes in cell morphology. Spectrophotometery was used to determine yellowing of the foams. Results showed that the thickness of degraded layer for rigid polyurethane foams obtained from pulp production byproducts was More >

  • Open Access

    ARTICLE

    Flexible Polyurethane Foams Modifi ed with New Bio-Polyol Based on Rapeseed Oil

    Sławomir Michałowski, Aleksander Prociak*

    Journal of Renewable Materials, Vol.3, No.1, pp. 14-18, 2015, DOI:10.7569/JRM.2014.634131

    Abstract This article describes the effects of the modifi cation of polyurethane system with rapeseed oil-based polyol on the cell structure and physical-mechanical properties of conventional fl exible polyurethane foams. The foams were prepared by substituting a part of the petrochemical polyether-polyols mixture with the bio-polyol based on rapeseed oil. Selected physical-mechanical properties of these foams were examined and compared to the properties of reference foam. The properties such as apparent density, resilience, comfort factor and stress-strain characteristics were analyzed in compression tests. It was found that the modifi cation of polyurethane formulation with rapeseed oil-based More >

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