IOSR-JAP   Volume-6 ~ Issue-6 ~ Nov-Dec 2014

ABSTRACT: In this paper we report a study on acoustic properties of coir mats –a biofibremat of various weaving patterns. In this study coir-mat has been introduced as one of the sound absorbing materials.There are many advantages of coconut fibres because they are moth-proof,non-hazardous,resistant to fungi and ecofriendly with good sound absorption.The study reveals the effectiveness of coir mats as sound absorber and its applications in building acoustics and automotive applications . Coir mats of different weaving were selected for the study viz;Panama, Herringbone, Boucle weaving,mesh matting,Twill weave matting,Diamond weave matting,PVC tufted mat,Lovers Knot,VC2 mat etc.The experiment is performed on an impedance tube apparatus as per ASTM E 1050/ISO 10534-2. The experimental analysis is made for the frequency range 100 Hz-6300 Hz.The results reveal that the mats show good sound absorption coefficient at high frequencies and also the mats with latex backing and increased thickness exhibit appreciable absorption of coir mats. Keywords: coir mats,panama weave,Herringbone weave,Boucle weave mesh matting,Twill weave matting,Diamond weave matting,PVC tufted mat,Lovers knot,VC2 mat,Absorption coefficient,NRC,boimats,biofibre

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ABSTRACT: GaAs:Zn films with different thickness (0.25, 0.5, 0.75 and 1.0) μm have been prepared by flash evaporation technique on glass substrate at substrate room temperature under vacuum of 10-5 mbar. These films have been annealed at different annealing temperatures Ta (373and 473) K. The d.c. conductivity for all deposited films decreases with increases of annealing temperatures. The electrical activation energies (Ea1and Ea2) increase with increasing of annealing temperatures. Hall measurements showed that all the films are p-type with carrier's concentration increase with thickness increase and decreases from with increasing of annealing temperature from RT to 473K. Also we observe that the mobility increase with increasing of annealing temperature and decreasing with thickness. the structural characteristic of GaAs:Zn have been studied by using X-ray diffraction which show that the films have amorphous structure for sample annealed at Ta> 473K.The samples were annealed at 473 K showed a polycrystalline with Face-center cubic system preferred orientation along (111).

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ABSTRACT: Nanoparticles of magnetite were synthesized usingaqueous chlorides solutions via coprecipitation technique. The structure and crystallite size of the precipitate were inspected and analyzedregarding X-ray diffraction. Cation distribution of magnetite of the form (Fe3+(2-x) Fe2+y) {Fe2+(1-y) Fe3+x}has been proved and optimized where the cation parameters X and ywere determined using the experimental value of magnetite magnetic moment.Spin-Orbit coupling calculations based on density functional theory were applied.Full optimization was considered and the most stable configuration was proffered.The density of states of magnetite was calculated.The inclination of half metallicity of magnetite was scrutinized. DC electrical resistanceofpressed disk shape magnetite nanoparticles was measured at room and elevated temperatures. The results are discussed andanalyzed in terms of DOS and cation distribution.

Key Words: Half metallic, Magnetite, Electrical resistance, Nano-crystals, DOS.

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ABSTRACT: In this study, a modified Angstrom model for the estimation of global solar radiation in Kano, Nigeria using maximum/minimum temperature and relative humidity based on meteorological data were used. Two new models were developed for estimating the monthly-average daily global solar radiation. Regression coefficients a and b of(1.2577,−1.0167 ) and( 0.8317 ,−0.0043) were obtained from the models based on temperature ratios and relative humidity respectively. In order to evaluate the results, three statistical methods have been used namely; Mean bias, root mean square, and mean percentage errors. The temperature based models which has a lower root mean square error is an indication of good agreement between the measured and estimated global solar radiation. Base on the statistical results a new temperature base model is recommended to estimate monthly global solar radiation for Kano state and other locations with similar climate conditions where the radiation data is unavailable.

Keywords: clearness index, day length, global solar radiation, extraterrestrial radiation

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[4]. NamrataK., S. P. Sharma, and S. B. L. Saksena, Estimation of global and diffuse solar radiation for Jamshedpur, India, International Journal of Science and Technology, 2(1): 2012, 44-47.
[5]. E. O. Falayi, J. O. Adepitan, and A. B. Rabiu, Empirical models for the correlation of global solar radiation with meteorological data for Iseyin, Nigeria,Pacific Journal of Science and Technology, 9(2),2008, 583-591.