Applied Mechanics and Materials Vol. 575

Abstract: An overview of modification of cerium oxide, CeO₂ which is employed in the three-way catalyst (TWCs) is presented in this article. The modifications of cerium oxide, CeO₂ incorporated with the metal oxides for the improvement of thermal stability, microstructure and oxygen storage capacity (OSC) are discussed. In view of that, the types of metal oxide are grouped into transition metals, rare earth metals, and alkaline metals and the effect of each group into cerium oxide, CeO₂ are elaborated.

Abstract: The granular materials examined in this study were some Saudian soils. The effect of water content and bulk density on the specific heat and volumetric heat capacity of two Saudian soils (sand and loam) was investigated through laboratory studies. These laboratory experiments used the calorimetric method to determine specific heat of soils. For the type of soils studied, specific heat increased with increased moisture content. Also, volumetric heat capacity increased with increased moisture content and soil density. The volumetric heat capacity and specific heat of soils observed were compared with independent estimates made using derived theoretical relations. The differences between the observed and predicted results were very small. Loam soil generally had higher specific heat and volumetric heat capacity than sandy soil for the same moisture content and soil density.

Abstract: This paper discusses the wavelet-based Finite Difference Time Domain (FDTD) method and high resolution spectral estimation with a specific problem of sound wave propagation through phononic crystals. If the band structures of a phononic crystal are calculated by the traditional FDTD method combined with the fast Fourier transform (FFT), good estimation of the eigenfrequencies can only be ensured by the postprocessing of sufficiently long time series generated by a large number of FDTD iterations. In this paper, a postprocessing method based on the high-resolution spectral estimation via the Yule-Walker method is proposed to overcome the difficulty. Numerical simulation results for two-dimensional phononic crystal show that, the wavelet-based FDTD method improves the efficiency of the time stepping algorithm, and high resolution spectral estimation shows the advantages over the classic FFT-based postprocessing.

Abstract: To study the change rule of tension modulus for nylon cord/rubber composite material, a accurate prediction method is provided. Firstly, the calculation method for relevant parameters for rubber material Mooney-Rivilin constitutive model is proposed , the amendment formula for cord tension modulus is derived. Secondly, based on composite material micromechanics, the accurate numerical model is built, the equivalent modulus is calculated and compared to the experiment results in reference. Finally, the accurate prediction formula of tension modulus for the nylon cord/rubber composite material is provided, compare the equivalent tension modulus obtained by the prediction formula and the numerical model. The results show that: the method to build the numerical model of nylon/ cord-rubber composite material is correct, the prediction formula of the tension modulus for the nylon cord/rubber composite could predict the tension modulus well.

Abstract: Grinding technology is used in this study to overcome the hard machining of ceramic with hard and brittle characteristics. The grinding machine with diamond grain size 25 and 5 , spindles speed 1720 rpm and 3450 rpm are applied. Combining the unintentional roll clamp and the grinding machine, ceramic rods can be ground to the desired size.In the research, surface profilometer is applied to measure the rod surface roughness of processing results under different conditions. The results show that the grinding wheel with finer particle, the roughness of the ground ceramic rod will be better. While the rotation speed of grinding wheel is increased, the surface roughness will have the same trend.

Abstract: In drilling and well completion operations, drilling fluid is a crucial element as it is employed for the purposes of several functions. The main functions of drilling fluid are to control formation pressure, maintain the wellbore stability, transport the cuttings up to surface to clean the borehole bottom as well as to lubricate and cool the drill bit. Moreover, it is used to minimize the drilling damage to reservoir and suspend cuttings when the pumping is stop, hence it will not falling back down the borehole. The purpose of this study is to formulate new drilling mud formulation modified with nanosilica. Six samples of water based mud (WBM) were prepared using three types of polymers, (Xanthan Gum, Hydro Zan Plus and Hydro Star HT), starch and nanosilica. Basic rheological tests such as density, viscosity and pH were carried out. The density test was carried out using mud balance meanwhile the pH test was using pH meter. The plastic viscosity, yield point and gel strength tests were carried out using viscometer. Besides that, physical observation was also performed for as the stability test. The results concluded that water based mud incorporated with polymer Hydro Zan Plus and nanosilica can be a potential candidate to be commercialized as a smart nanodrilling fluid.

Abstract: The effect of the chemical vapor deposition (CVD) process parameters on the structure of graded SiC-SiO₂ coating was studied through thermodynamic computation. The addition of enough hydrogen into the carrier gas is necessary for the synthesis of the graded SiC-SiO₂ coating. Both high deposition temperature and low deposition temperature make the change of the composition of the coating abrupt with the change of the composition of CVD atmosphere, which is harmful to the process control of the coating. A low concentration of reactants is preferred according to the thermodynamic computation but the deposition rate is too low at a low concentration of reactants. When hydrogen is the carrier gas and the concentration of SiCl₄ is between 1 – 2 vol%, the graded SiC-SiO₂ coating with a suitably graded distribution of SiC and SiO₂ can be easily obtained through gradually changing the flow rate ratio of methane and water vapor at 1100 - 1200 °C.

Abstract: According to the requirement of the bionic navigation sensitive wave band of 380nm~520nm for sub-wavelength metallic gratings, in order to achieve performance indicators under the basic structural parameters. Analyzing TM transmittance and contrast ratio is carried out by employing finite-difference time-domain (FDTD) method. The result reveals that height, slit width and dielectric of grating impact TM transmittance and contrast ratio in various extents, and the greatest influence on the TM transmittance and contrast ratio is slit dielectric and slit width respectively.

Abstract: In this paper, foam glass as thermal insulation material was prepared from alkali-free glass powder, and silicon carbide was used as foaming agent in the process. The effect of silicon carbide and sodium carbonate was investigated. Thermal performance of the batch was investigated by using the TG/DSC simultaneous thermal analyzer. The morphology of the glass foams was evaluated by the scanning electron microscopy. The phase of the sample was studied through X-ray diffraction, and chemical composition of the samples was estimated by using X-ray fluorescence spectrum. The results show that, the pore diameter of sample increases gradually at first and then stabilizes with the increasement of silicon carbide. Sodium carbonate not only improves the foaming ability by reducing the glass viscosity but also influences the crystallization of the sample. The bulk density and compressive strength are decreasing while the content of sodium carbonate increasing.

Abstract: Coconut dregs that are commonly used for animal feed have the potential for glucose production due to high carbohydrate content. Nevertheless, no study found on understanding the properties of this biomass. Hence, the main purpose of this paper was to propose appropriate operational conditions for the dilute sulfuric acid hydrolysis of coconut dregs and to investigate the chemical and thermal properties of coconut dregs. The biomass was hydrolyzed with 1% sulfuric acid (v/v) at different residence times (30 and 60 min) and temperatures (110, 120 and 130°C). Higher glucose produced (0.29 g/L ) was obtained when the coconut dregs were hydrolyzed at temperature of 130°C and a residence time of 60 min. FTIR spectra revealed the degradation of the lignocelluloses chemical structure. The changes of the chemical structure of hemicelluloses and cellulose after hydrolysis obviously showed that the degradation of the polymer of carbohydrate in coconut dregs to glucose. These results of degradation of lignocelluloses compound were consistent with those from the TGA. The result from TGA analysis revealed a reduction in thermal stability of the hydrolyzed fraction compared to raw state of coconut dregs.