bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation and Modeling of Turbulent Plasma Jet Based on Axisymetric LBGK Model
Authors: Djebali Ridha , El Ganaoui Mohammed , Pateyron Bernard , Sammouda Habib
Published: April 2011

The coating of surfaces by plasma spraying is an important manufacturing process with many industrial applications. In the last several decades, numerical modeling of plasma spraying processes has met with considerable attention [1,2,3]. That is in order to well understand the complex phenomena the plasma spray involves, for economic constraints and to well predict the plasma-inflight-particles exchanges since this affects directly the coating formability and microstructure. This study deals with the investigation of plasma jets using an axisymmetric LB thermal model. Plasma jets have been very successful in many applications (such as spraying, cutting, welding,…). The excellent choice of high performance plasma gases and spraying materials has been the subject of several experimental and numerical efforts. An excellent choice will be the response of efficient numerical studies and the results of experimental tests. Plasma jets are high temperature flows (>8000K). Therefore, all diffusion parameters involved in conservation equations are temperature dependent. In the following, we present a plasma jet investigation in an axisymmetric LBM (Jian’s model [4]). In the context of our knowledge, it is the first attempt to tackle this field by using the LBM. Further reading on solution procedure, the model implementation and assumptions may be found in [5,6].
Soil Water Characteristic Curve for a Granite Residual Soil: Experimental and Numerical Results
Authors: Topa Gomes A. , Viana Da Fonseca A. , Silva Cardoso A.
Published: April 2011

The seepage analysis in geotechnical problems, namely in excavations, was typically performed assuming saturated conditions in the ground. It is now know that the flow in the non saturated part of the ground assumes also relevant importance and hence it is vital to characterize its behaviour. The Soil Water Characteristic Curve (SWCC) of the soil is probably the most important parameter in defining this behaviour and particularly for estimating the permeability of the soil. This paper presents the definition of the SWCC for a granite residual soil using pressure plates and the filter paper method. Based on experimental data some equations are adjusted and the results obtained are discussed. At the end of the paper some predictions of the non saturated permeability of the ground are also performed.
Experimental Investigation of the Evaporation and Stability of a Meniscus in a Flat Microchannel
Authors: Harmand Souad , Sefiane Khellil , Bennacer Rachid , Lancial Nicolas
Published: April 2011

We present the results of an experimental investigation of the evaporation of a liquid meniscus in a high aspect ratio micro-channel. The study investigates evaporation rates of a stationary liquid meniscus in a high aspect ratio microchannel, the wall of which is electrically heated using transparent resistive coating. Four different liquids are used as working fluids. We report on the dependence of the measured overall evaporation rate on the applied power. The results indicate, and consistently, that the evaporation rate increases with the applied power then peaks before declining. In order to gain insight into these results, we used thermographic infra red imaging to map the temperature field on the external wall of the microchannel. The measurements show that there is a good correlation between the maximum in the evaporative rate and the onset of instabilities of the interface. These instabilities, to our mind, are induced by an increasing temperature gradient along the microchannel wall around the three phase contact line region. These instabilities are revealed by a high speed camera used to record the behaviour of the interface during evaporation.
Diffusion of Charged Species in Metal Oxides and Polymeric Solids Using AC Impedance Technique
Authors: Kamarulzaman Norlida , Rusdi Roshidah , Aziz Nor Diyana Abdul , Widarti Zainudin Lili , Osman Zurina
Published: April 2011

The diffusion of charged species in solids is a very important part of the study of the electrical properties of materials. Electrical measurements using alternating current (ac) impedance is a powerful technique to study diffusing species in metal oxides as well as polymers. Three case studies are being presented here whereby the electrical properties of LiTaO3, Poly[2-methoxy-5-(2’-ethylhexyloxy)-(p-phenylenevinylene)] (MEH-PPV) and its composite are being studied using the same ac impedance technique. LiTaO3 is a metal oxide while MEH-PPV is a polymer. They are very different and therefore present very good examples for the versatility and power of ac impedance method. Electrical parameters such as conductivity and conduction behaviours of the conducting species can be extracted from the studies. The kinetics of the diffusing species can be elucidated by using proper analytical techniques.
Hydrodynamic Simulation of Drift Mobility in N-Hg0.8Cd0.2Te
Authors: Daoudi Mebarka , Belghachi Abderrahmane , Varani Luca , Palermo Christophe
Published: April 2011

In this paper, the transport properties of Hg0.8Cd0.2Te have been investigated at 77 K using the hydrodynamic model. We remarked that ionized impurity scattering mechanism plays a dominant role in this material at low electric field. The drift velocity, mean energy and drift mobility are determined as functions of the electric field strength. Comparison is made with Monte Carlo calculations and experimental results. The obtained velocity-field curve is in good agreement with reported experimental data.
Enhanced UHMWPE Reinforced with MWCNT through Mechanical Ball-Milling
Authors: Fonseca A. , Kanagaraj S. , Oliveira Monica S.A. , Simões José A.O.
Published: April 2011

In this work, nanocomposites of ultrahigh molecular weight polyethylene (UHMWPE) reinforced with multiwalled carbon nanotubes (MWCNTs) were evaluated for their ability to produce nanocomposites with superior mechanical properties. As homogeneity of the nanocomposite plays an important role into final mechanical properties, mechanical ball-milling is used to prepare homogeneous UHMWPE/MWCNTs powders, where special emphasis is given to milling-time optimization. Mechanical ball-milling seems to be a suitable and rather simple technique for preparing nanocomposites even outside laboratory conditions and it is presented here as an interesting technique for nanoscience industrial applications. A fact that is worth noting since the great majority of research breakthroughs fail due to lack of industrial accomplishment. The powder mixture was further processed through compression moulding in a hot plate press. The impact of milling time on mechanical properties of the nanocomposites was evaluated. Nanocomposites with different volume fractions of MWCNTs were prepared using the optimized milling time, processed via compression moulding and their mechanical properties were evaluated. It was observed an enhancement of the Young’s modulus of about 80%, for higher volume fractions of MWCNTs (1.0%), as compared with the pure UHMWPE.
Composition Dependent Diffusivities in Multi-Component Systems
Authors: Wierzba Bartek , Danielewski Marek
Published: April 2011

The modified Redlich-Kister approximation of the composition dependent intrinsic diffusivities in the multicomponent solid solution is presented. The effective computation method (the inverse problem) combines the Hierarchical Genetic Strategy with real number encoding (HGS-FP) with the modified Redlich-Kister approximation. The Cu–Ni–Fe alloys at 1271 K are analyzed. We show that the measured intrinsic diffusivities, the estimated from available diffusivity data and calculated by inverse method are in agreement. The presented method may become a very effective tool when the diffusion multiple technique is considered.
Effect of the Latent Heat on Wax Deposit in Pipelines
Authors: Boucetta Rachid , Kessal Mohand
Published: April 2011

Wax deposition continues to be a relevant problem for petroleum production and transportation pipelines. This viscous and waxy flow is theoretically modelled with a simple conservation equation system, by expressing the wax layer thickness as function of time and duct length. The flow parameters are written, depending on these independent variables but also on the Reynolds and the Peclet numbers, where effect of latent heat on the wax layer thickness deposit is investigated. A numerical simulation of the flow, for two practical cases, is performed in order to predict the pipeline obstruction.
Study of Semisolid and ECAP Processes on Al-Fe-Si Alloy - Microstructure and Kinetic Grain Growth
Authors: Azimi-Yancheshmeh D. , Aghaie-Khafri M.
Published: April 2011

ECAP (Equal Channel Angular Pressing) is one of the useful methods of Severe Plastic Deformation (SPD) to reach ultrafine grain size. ECAP was carried out on Al-Fe-Si alloy. All grains stretched along the ECAP direction. Samples were ECAPed for one pass into an ECAP mold with two equal channels (1 cm × 1 cm) with 90o between them. After ECAP, specimens were heat treated (semisolided) for different times and temperatures for achieving globular grains. Optical microscopy has been used to evaluate the microstructure. By ECAP and semisolid processes, the structure becomes fine and globular. The kinetic grain growth has been studied for this alloy by the calculation of the D = Ktn equation and log(D)-log(t) curves.
Influence of Important Nanoemulsions pH on Performance of Nanostructures Catalysts for H2 Production in Syngas Reactions
Authors: Fakhroueian Zahra , Esmaeilzadeh Pouriya , Afroukhteh Langroudi N. , Varmazyar H. , Ahmadirad M. , Zadeh Pouyan Esmaeil , Yousefi M. , Karami M. , Shafiekhani A. , Sepehriseresht S.
Published: April 2011

The synthesis of nanostructures are very various, and the most of scientists always fabricate them by the coprecipitation method at pH = 10.5-11. If we prepare these nanocatalysts for partial oxidation of methane (POM), processes to transforme methane gas into hydrogen or synthesis gas (H2 + CO) for obtaining exact green fuel H2 gas at different pH, what will be occurring, and what is the influence of pH on nanoemulsion, nanofluids, nanostructures, and finally the application in syngas process In this study we prepared many different nanoparticles containing % x (w/w) Co, Ni, Ru and La oxides over the various supports e.g. Ce-ZrO2, MgO-CeO2, AlCeO2, SiO2, SiAl2O3, SiMgO, SiO2Al-MCM-41 nano mixed oxides sized (1-2 nm) at various pH (7, 8, 9, 11) by new coprecipitation and combine with nanofluids method using different direct agent surfactant, stabilizer, binder, alcohol solvent, dispersant and variable chemical pH controllers. The prepared nanostructures were characterized by common techniques such as SEM, TEM, XRD, Raman, FTIR, BET and TPR analysis at various pH. Also many marvellous and new mixture of nanotubes-nanoclay and nanotubes-nanocomposites with high % H2 selectivity and methane conversion were fabricated by CuOx and NiOx sputtering test followed coprecipitation method at pH 9, for POM reactions used in petrochemical industry for the first time.
Thin Scandium Layer on Solid Aluminium: Thermodynamic Investigation
Authors: Shubin A.B. , Shunyaev K. Y. , Yamshchikov L.F.
Published: April 2011

Thin scandium-containing layers fabricated by different methods are good systems to investigate some properties of Al-Sc intermetallic compounds (IMC). The electrochemical deposition of a thin scandium layer onto a solid metallic surface leads to complex diffusion processes, especially if the second metal forms a number of IMC with Sc. Here, we used the electromotive force (EMF) method to study thin Al-Sc films in dynamics. Also, the Al-Sc alloy layers were prepared by direct aluminium-scandium interaction. The results of SEM and EDX investigations of these alloys are also presented in this paper. Analogue coatings (like Sc on Ni, Y on Cu, Al on Ni etc.) were also considered in order to discuss the phase sequence formation.
Effects of Mechanical Activation during the Synthesis of Tungsten Carbide Powders by Carbothermic Reduction of Tungsten Oxide
Authors: Ma J. , Zhu Shi Gen , Ding H. , Gu W.S.
Published: April 2011

In this work, the effects of mechanical milling on the extent of reduction were investigated to give an overview of potential improvements in the preparation of WC. A mixture of graphite and tungsten oxide (WO3) was mechanically milled together for 10 h. The as-milled powder and un-milled powder were investigated by thermal analysis, isothermal treatment, and X-ray diffraction to determine the effect of milling on the carbothermal reduction of WO3 to tungsten carbide (WC). The as-milled powder underwent a rapid reduction reaction at about 150°C lower than the un-milled powder. The reduction sequence to WC was illustrated to differ for the two powders. The milled powder showed complete reduction to WC in 1 h at 1215°C whereas the un-milled powder was incompletely reduced. Finally, WC powder was readily achieved by carbothermic reduction of mechanical activated WO3 and graphite, leaving its grains nano-sized.
Effect of Quincke Rotation and Taylor Circulation on Mass Transfer from a Fluid Drop in a Constant Electric Field
Authors: Elperin Tov , Fominykh A.
Published: April 2011

We consider non-stationary convective mass transfer in a binary system comprising a stationary dielectric two-dimensional fluid drop embedded into an immiscible dielectric liquid under the influence of a constant uniform electric field. The partial differential equation of diffusion is solved by means of a similarity transformation, and the solution is obtained in a closed analytical form. Dependence of Sherwood number vs. the strength of the applied electric field is analyzed. It is shown that an electric field can be used for enhancement of the rate of mass transfer in terrestrial and reduced gravity environments.
Quantitative Evaluation of the Raman Spectra of Carbon Layers
Authors: Golabczak Marcin , Konstantynowicz Andrzej
Published: April 2011

The Raman effect has been widely used for years for carbon layers analysis for qualitative analysis of samples as well as quantitative. Two main lines of attitude to the quantitative analysis of the Raman spectra have been de¬ve¬lo¬ped. The first one is applied mainly in forensic investigations when one has pre¬pa¬red comparative samples which consist of known substances with known concentration. This is the ba¬se for comparison of spectra from unknown sample. A tool used in these in¬ves¬ti¬ga¬tions is the Voigt profile based on Faddeeva function, allowing a very precise com¬pa¬rison of spectra with elimination of individuality of me¬a¬s¬u¬re¬ment equipment. This at¬ti¬tu¬de seems not to be the best solution when one has not comparative samples and the sam¬p¬le un¬der test is unique – the situations often meet in scientific investigation. Using Voigt profiles may cause a loss of in¬for¬ma¬tion car¬¬ried with the spec¬trum, especially related with small quantities of nanotubes or ful¬le¬renes generated in the process of imposing diamond layers in plas¬ma arc. Another function for approximation shape of the Raman peak based on Breit-Figner-Fano curve is frequently used but difficulties arise when iden¬ti¬fy¬ing physical meaning of parameters and subtracting idle pedestal from the ex¬pe¬ri¬men¬tal spec¬t¬rum. A different attitude based on simple Gaussian peak approximation is pre¬sen¬ted as better solution. Use of this procedure as a metrological tool has been dis¬cus¬sed leading to the conclusion that engaging more advanced and so¬p¬hi¬s¬ti¬ca¬ted me¬thods does not provide automatically better results.
Carbon Fiber-Reinforced Composites in Automotive Engine
Authors: Farsani Reza Eslami , Shokuhfar Ali
Published: April 2011

In this article the last findings of composites with polymer, metal and ceramic matrices containing carbon fibers and their applications in internal combustion engines in the world beside their advantages and superiorities in comparison with common industrial materials are investigated. Afterwards, the position of these materials in automotive engines in Iran is analyzed. Researches show that carbon fibers-reinforced composites due to unique properties (including high specific strength and specific modulus, low thermal expansion coefficient, high fatigue strength, and high thermal stability) can replace common structural materials in different engine parts (such as, casing, different components, cylinder lining, and etc.). Applying these composites will result in weight reduction and consequently fuel consumption reduction, less pollution, better function and efficiency, and more lifetimes. Of course one should consider that there is a vast potential for application and development of composites in automotive engine, which will become in practice by complementary researches through time. Due to novelty of this technology in the world and also the lack of carbon fibers production and insufficient knowledge of production and application of carbon fiber composites in Iran, this issue has not been seriously investigated.
Microstructural Changes of FSX-414 Superalloy during TLP Bonding
Authors: Bakhtiari R. , Ekrami A.
Published: April 2011

The as-cast FSX-414 Co-based superalloy samples were solution treated at 1150oC for 4h and then aged at 980oC for 4h. Specimens for joining were cut from the as-cast ingot and TLP bonding carried out at the same conditions as for the solution and solution+aging treatment, using MBF-30 interlayer. Microstructures were studied for as-cast, heat treated and TLP bonded specimens. These studies showed that the ununiform distributed carbides of MC type in the as-cast specimens replaced by M23C6 type carbides with uniform distribution in the heat treated microstructure. Due to complete isothermal solidification, no eutectic structure in the bond region were wasobserved, but some intermetallics in the diffusion affected zone (DAZ) were observed. Microhardness tests were used to compare the hardness of age hardened specimens with bonded specimens at the same heat treatment condition. Hardness profile also showed a peak in DAZ region in spite of complete isothermal solidification.
Microstructure Characterization of TBC Layers of Gd2Zr2O7 Type
Authors: Moskal Grzegorz
Published: April 2011

The paper presents microstructural assessment results of thermal barrier coatings deposited by plasma spraying of powders with the formula Gd2Zr2O7. Standard parameters of the air plasma spraying (APS) method were used. A visual assessment of layers and quantitative and qualitative characteristics of an outer ceramic layer with the laser microscopy method were performed. Roughness and other geometric parameters describing the TBC surface were determined. Phase composition analysis of the ceramic layer was also carried out. Microstructural assessment of the layers for meeting the assessment criteria of the ceramic coatings was also carried out. The bondcoat and ceramic layer porosity assessment was performed. The TBC system general quality was assessed for presence of cracks, delamination and massive porosity. It was found that the new type of layers obtained meet the quality requirements used for assessment of the conventional layers obtained by spraying 8YSZ zirconia.
Diffusion in Co-Ni System Studied by Multifoil Technique
Authors: Divya V.D. , Ramamurty U. , Paul Aloke
Published: April 2011

Diffusion couple experiments were performed in the Co-Ni binary system for determining inter-, impurity- and intrinsic-diffusion coefficients in the temperature range of 1050 - 1250°C. The activation energy and pre-exponential factor estimated for interdiffusion do not vary significantly with composition. The activation energy calculated for impurity diffusion experiments shows is higher than . Intrinsic diffusion coefficients estimated from the multifoil experiment show that Ni is the fastest diffusing species in this system.
Microstructure and Hydrogenation Property of Hyper-Eutectic Mg-Ni Alloys
Authors: Saitoh Hideyuki , Kondo M. , Nakamura H.
Published: April 2011

The microstructure and hydrogenation property of hyper-eutectic Mg-Ni alloys were investigated. The specimens were Mg-31 mass%Ni, Mg-41 mass%Ni and Mg-50 mass%Ni alloys that are composed of primary Mg2Ni crystal and Mg-Mg2Ni eutectic structure. The amount of the primary Mg2Ni phase increased as the content of Ni increased. The hydrogenation behavior strongly depended on the Ni content and the number of the hydrogenation cycle, that is, as the increase of the Ni content in the specimen, the hydrogen absorption rate increased while the hydrogen absorption weight decreased. At the first cycle measurement, hydrogen absorption was slow for the Mg-31 mass%Ni alloy while hydrogen was rapidly absorbed for the Mg-50 mass%Ni alloy at 300°C. In all the specimens, saturation of the hydrogen absorption was achieved within a few minutes after the second cycle measurement. The maximum values of the hydrogen absorption weight decreased from 5.5 mass% to 4.1 mass% as the Ni content increased.
Oxidation Behaviour of WE54 and Elektron 21 Magnesium Alloys
Authors: Kiełbus Andrzej , Rzychoń Tomasz , Przeliorz Roman
Published: April 2011

In the present study, the isothermal early oxidation behaviour of the WE54 and Elektron 21 alloys were studied at a temperature of 773 K in pure O2 up to 150 min. The results showed that the oxidation kinetics depending on the chemical composition and microstructure of the investigated alloys. The oxidation kinetics of these alloys in as-cast and T6 conditions obtained a parabolic law, while in supersaturated state these alloys exhibited a linear kinetics. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses indicated that an oxide film, composed of MgO and (Y,Dy)2O3 in WE54 alloy and (Nd,Gd)2O3 in Elektron 21 alloy, had been formed.
Analytical Solution for Solute Transport in Semi-Infinite Heterogeneous Porous Media
Authors: Deng B.Q. , Qiu Y.F. , Kim C.N.
Published: April 2011

Solute transport in porous media concerns advection, dispersion, sorption, and reaction. Since porous media is commonly heterogeneous, the properties of porous media are spatially and temporally variable. In this paper, one dimensional unsteady solute transport in semi-infinite heterogeneous porous media is investigated. Both linear and nonlinear decay is considered. Analytical solution is obtained for linear decay with spatially and temporally diffusion coefficient and velocity by using generalized integral transform technique. The inverse integral transforms are developed for the problems in semi-infinite space based on some weighted functions. Some examples are given to show the application of the method and analytical solutions.
Application of Thermo-Mechanical Process to Achieve Nanostructure in 301 Austenitic Stainless Steels
Authors: Shokohfar A. , Abbasi S. M. , Yazdani Ali , Rabiee Behnam
Published: April 2011

In this study, cold rolling and annealing are used to refine the austenite grains of 301 austenitic stainless steel. The 301 austenitic stainless steel was cold rolled for 70 and 90% strain and then annealed. Effects of cold rolling factors and temperatures and annealing times on microstructure, hardness and tensile properties have been studied.
Gas Nitriding of Sintered Austenitic Stainless Steel
Authors: Baranowska Jolanta , Amigó Vicente
Published: April 2011

The results concerning gas nitriding of sintered stainless steel are presented in the paper. The samples made of 316L steel were gas nitrided at temperatures between 400-550°C. The microstructure of the layer was investigated by means of light and atomic force microscopy. The phase composition was identified using X-ray diffraction. Moreover, tribological and corrosion properties of the samples were evaluated. It was demonstrated that in case of gas nitriding it is possible to obtain nitrided layers also inside open pores, which can be beneficial for corrosion response of nitrided sintered austenitic stainless steel applied in corrosive environments.
The Impact of Diffusion Process on the Interface Microstructure in AZ91 Magnesium Matrix Composites Reinforced with TiN Nanolayer Modified Carbon Fibres
Authors: Olszówka-Myalska Anita
Published: April 2011

A TiN nanocoating was deposited on carbon fibres before their consolidation with AZ91E magnesium alloy, provided as a matrix of the composite. The main interest was the interface microstructure. Structural investigations were performed with a FE-SEM Hitachi 3200S scanning electron microscope and a Tecnai G2 FEG high resolution electron microscope equipped with energy dispersive X-ray spectrometer (EDS) and high angle annular dark field (HAADF) detectors. The observations of the fibre-matrix interface revealed the presence of a multilayered zone around the fibres. It consisted of a regular oxide layer with a thickness of approx. 100 nm around the fibre, followed by a titanium-rich layer and a region of longitudinal sharp shaped crystals directed toward the magnesium alloy matrix. This type of interface microstructure suggests that deposition of TiN as a technological nanolayer ensures the proper wettability of fibres by the metal matrix, but does not prevent diffusion processes. It was revealed that both, i.e. diffusion of elements contained in the matrix through the TiN nanolayer and diffusion of oxygen and carbon toward the surface took place.
Numerical Simulations of Heat Transfer in Plane Channel Flow
Authors: El Gharbi Najla , Absi Rafik , Benzaoui Ahmed
Published: April 2011

Reynolds-averaged Navier–Stokes “RANS” turbulence models (such as k-ε models) are still widely used for engineering applications because of their relatively simplicity and robustness. In fully developed plane channel flow (i.e. the flow between two infinitely large plates), even if available models and near-wall treatments provide adequate mean flow velocities, they fail to predict suitable turbulent kinetic energy “TKE” profiles near walls. TKE is involved in determination of eddy viscosity/diffusivity and could therefore provide inaccurate concentrations and temperatures. In order to improve TKE a User Defined Function “UDF” based on an analytical profile for TKE was developed and implemented in FLUENT. Mean streamwise velocity and TKE profiles were compared to DNS data for friction Reynolds number Reτ = 150. Simulation results for TKE show accurate profiles. Simulation results for horizontal heated channel flows obtained with FLUENT are presented. Numerical results are validated by direct numerical simulation “DNS” data for Reτ = 150.
Augmentation of the Performance of Batch Electrocoagulation Unit by Using Gas Sparging
Authors: El Shazly Ahmed Hassan
Published: April 2011

The aim of the present work is to investigate the effect of gas sparging in improving the performance of a batch electrocoagulation unit used for the treatment of wastewater generated from dyeing industry. Monopolar cylindrical aluminum electrodes were used. Many variables were investigated such as superficial gas velocity, current density, initial dye concentration, area ratio (cathode/anode), time of operation and the effect of adding chemical coagulant as Fe (SO4). The results show that the % dye removal has been increased by a factor ranging from 2.52 to 5.14 by increasing the gas flow rate from 0.4 to 0.8 liter/min, respectively, and that about 93.5% of the dye can be removed within 60 minutes. Also it was found that using gas sparging is more efficient than adding chemical coagulant as ferrous sulphate for the removal of dye from wastewater. The power consumption for the unit was measured for different gas flow rates and different current densities; the results show that lower gas flow rate can improve the economy of the process.
Structure and Thermal Transformations of Hydrated Magnesium Silicates
Authors: Selivanov Evgeny N. , Lazareva S.V. , Udoeva L.U. , Gulyaeva R.I.
Published: April 2011

The article is devoted to an estimation of phase transformations of silicates magnesium at heating in the temperatures range from 0°C to 1100°С. The object of study is a silicates of magnesium containing oxide nickel ore. Differentially-thermal (NETZSCH 449 C - Jupiter), weights – spectrometer (QMS 403 C Aёolos), high-temperature X-ray diffraction, electron-probe microanalysis (JSM - 5900 LV) and chemical analysis methods have been used in the study. The temperature ranges of existence Mg6[(OH)8Si4O10] and Mg2Si2O6 are obtained. Parameters of an elementary cell of the above minerals and their changes with temperature and features of nickel distribution in magnesium silicates with various ration MgO/SiO2 are defined in this work.
Influence of Geometry on the Position and the Intensity of Maximum Kinetic Energy in a Combustion Chamber
Authors: Stuparu Adrian Ciprian , Holotescu Sorin
Published: April 2011

We analyzed the hydrodynamics of the flow into an axis-symmetrical combustion chamber with a central bluff body. Using an axis-symmetrical turbulent flow model we determined the extent of the recirculation region behind the bluff body as well as the location and intensity of maximum kinetic energy as a function of the cone angle of the chamber wall. We showed that by shortening the convergent conical section of the chamber we obtain a compact recirculation with higher turbulence intensity, with positive influence on gas mixing. We used the software FLUENT 6.3 for the numerical simulation of the gas flow inside the combustion chamber. The simplified geometry of the two types of combustion chambers was built using the pre-processor GAMBIT 2.4. Two structured meshes were obtained for the domains of numerical analysis with approximately 170,000 cells each. For modelling the turbulence of the flow we used three different turbulence models which were implemented in FLUENT 6.3.
An Overview of the Diffusion Studies in the V-Si System
Authors: Prasad Soma , Paul Aloke
Published: April 2011

The diffusion study in the V-Si system is reviewed. We show that the indirect method used previously to determine the diffusion parameters draws unnecessary error. Rather the method developed by Wagner should be used to calculate the diffusion parameters directly from the composition profile.
Uncertainty of the Diffusion Measurements on Scaffolds for Cell Growth
Authors: Sassi Guido , Bernocco Marco , Sassi Mariapaola
Published: April 2011

The regenerative medicine uses gel and porous solid matrices as scaffolds for the growth of the stem cells in 3D structures. The structural and fluid dynamic properties of the matrices have been recognized to highly affect the behaviour and functions of the cells. The procedures of production and the clinical use of the matrices need a reliable and reproducible characterization of their properties, this means that the concepts of metrology must be applied to the measurement and definition of all the relevant properties. This paper deals with the calculation of uncertainty for diffusivity measurement in solids and the role of uncertainty in designing the measurement. Diffusion of a solute in spherical solid particles dispersed in a limited liquid volume where considered as measurement method for a Ca-alginate polymer. The model sensitivity to the concentration measurements, the model parameters and the fitting procedures have been discussed.
Oxidation and Mechanical Behaviour of Iron Based Alloys and Nickel Based Alloy for Spring Like Interconnects of the PRODHYGE High Temperature Electrolyser
Authors: Lamazouade-Tarek Marion , Aubert Isabelle , Jumel Julien
Published: April 2011

In the field of the ANR-PROD’HYGE project an original coaxial architecture for a High Temperature Electrolyser (French Atomic Energy Commission Patented) is studied which makes use of low-cost spring-like interconnects to cope with thermal dilatation. Components and materials used for this application must ensure high long-term chemical and mechanical stability which are investigated here. Oxidation resistance of EN1.4509 and CroFer22APUI iron based alloy as well as Haynes 230 nickel based alloy is investigated with thermogravimetric analysis (TGA) in humid conditions, with or without mixing with hydrogen. Experiments reveal that oxidation kinetics is increased by 30% volume of hydrogen in moisture. Oxide layer composition and morphology are then investigated using Energy Dispersive Spectroscopy (EDS), and Auger Electron Spectroscopy (AES). Preliminary tensile tests are performed at room temperature showing embrittlement due to rough oxide layer, and CroFer22APU softening due to grain growth at elevated temperature.
Finite Element Simulation of Drying of Rough Rice
Authors: Hacıhafızoğlu Oktay , Cihan Ahmet , Kahveci Kamil
Published: April 2011

Rough rice has high moisture content at harvest, and if their moisture content is not reduced to about 12% on the dry basis they decay due to infestation and mold growth. Drying process is generally performed by heating ambient air and then sending it by forced convection over the rough rice to be dried. The aim in heating air to a certain temperature is to reduce the relative humidity of the air, which has a positive effect on the drying potential. In this study, drying behavior of single layer rough rice for different drying air temperature was simulated by means of a liquid diffusion model numerically by finite element modeling and simulation software. The results show that temperature is an effective factor on the drying rate. The results also show that as drying proceeds, a moisture gradient develops within the grain. This slows down the drying rate considerably. Therefore, it can be concluded that performing drying with an intermittent period instead of continuous drying will cause a considerable energy-saving.
Electrochemical Mass Transfer Measurements of CO2 in MDEA Solutions
Authors: Maceiras Rocío , Nóvoa Xosé R. , Cancela Angeles , Álvarez Estrella
Published: April 2011

The mass transfer coefficients at different axial positions in a bubble column have been measured using a conductivity method. Measurements of CO2 absorption in methyldiethanolamine solutions were carried out in a prismatic column 0.06 m side and 1.03 m height. Five electrode pairs were placed at various axial positions in the column. Measurements were conducted at different gas flow rates and amine concentration. It was found that the local mass transfer varied in the axial direction. An experimental model was developed to obtain the absorption rate values using the electrochemical method data. The model agrees quite well with the experimental obtained data.
Non-Isothermal Enhanced Recovery of Heavy Oils by Numerical Simulation
Authors: de Lima Cunha A. , Neto S.R.F. , de Lima Antônio Gilson Barbosa , Barbosa E.Santos
Published: April 2011

The world has been witnessing a growing interest in heavy oil fields as a result of a reduction in conventional oil reserves. In this sense, this work aims to study numerically the process of heavy oil recovering in oil reservoir via water injection. Transient three-dimensional numerical simulations, considering isothermal and non-isothermal processes, were performed using the ANSYS CFX 11 commercial code, and its effects upon the oil recovery factor evaluated. The numerical results indicated an increase of 29% (non-isothermal case) and 18% (isothermal case) in the recovery factor when water was injected on the reservoir surface as compared to the water internal injection in the reservoir.
Oxygen Diffusion in Yttria-Stabilized Zirconia Subjected to Mechanical Stress
Authors: Araki Wakako , Arai Yoshio
Published: April 2011

The oxygen diffusion in 4, 8, and 14 mol%-yttria-stabilized zirconia subjected to uniaxial stresses in the [100], [110], and [111] directions is investigated. In the case of uniaxial stress in the [100] direction, the oxygen diffusion in 4YSZ and 8YSZ is facilitated in the tensile direction and deteriorated in the compressive direction without changing the total diffusion property, which could be caused by the elastic recovery force. For 14YSZ, however, the oxygen diffusion remains unchanged regardless of the stress, probably due to high yttria concentration. In the case of tensile stress in the [110] and [111] directions, the oxygen diffusion is also increased in the tensile direction, which could be attributed to the improvement of the oxygen diffusion in the <100> direction caused by the stress component in the <100> direction.
The Effect of Stabiliser’s Molarity to the Growth of ZnO Nanorods
Authors: Khusaimi Zuraida , Mamat Mohamad Hafiz , Sahdan Mohd Zainizan , Abdullah Norbani , Rusop Mohamad
Published: April 2011

A wet chemical approach, originating from sol-gel preparation, was adopted with the intention to develop a low-temperature benign method of preparation. ZnO nanorods are successfully grown in an aqueous medium. The precursor, zinc nitrate hexahydrate (Zn(NO3)2.6H2O), is stabilized by hexamethylene tetraamine (HMTA). The effect of changing the molarity of HMTA to the structural orientation of ZnO nanorods is investigated. X-ray diffraction of the synthesized ZnO shows hexagonal zincite structure. The structural features of the nanocrystalline ZnO were studied by SEM. Structural features, surface morphology and differences in lattice orientation are seemingly influenced by varying the Zn2+: HMTA molar ratio. The formation of ZnO nanorods with blunt and sharp tips is found to be significantly affected by this ratio.
Aluminum A356 Reinforcement by Carbide Nanoparticles
Authors: Borodianskiy Konstantin , Zinigrad Michael , Gedanken Aharon
Published: April 2011

The main issue of the study is aluminum A356 alloy modification by TiC nanoparticles process. Nanoparticles of TiC were especially mechanochemically activated to remove the oxide layer on the particle surface in order to prevent its floating on the molten metal surface. Experimental results indicate that after T6 heat treatment the tensile strength of the modified alloy increased by 6.5%, yield strength increased by 9% and the elongation increased by 22%. A high resolution electron microscopy study shows that dislocation of the modified alloy concentrates near the grain boundary during the crystallization process, and these grain boundaries act as obstacles to dislocation motion. Based on these results, it was found that grain-size aluminum strengthening mechanism occurs in the nanoparticle carbide reinforcement process.
Numerical Investigation of the Overall Stiffness of Carbon Nanotube-Based Composite Materials
Authors: Mavalizadeh Seyedmehdi , Rahmandoust Moones , Öchsner Andreas
Published: April 2011

In this study, a finite element model of a representative volume element that contains a hollow and filled single-walled Carbon nanotube (SWCNT) in two case studies was generated. It was assumed that the nanocomposites have geometric periodicity with respect to local length scale and the elastic properties can be represented by those of the representative volume element (RVE). Elastic properties in agreement with existing literature values for the Carbon nanotube and the matrix were assigned. Then for the two case studies, the tensile test was simulated to find the effect of the geometry, i.e. the volume fraction of matrix and SWCNT's properties variation, on the effective Young's modulus of the structure. In another approach, by applying perpendicular loading to the tube direction, the effect of matrix volume fraction on the transverse Young's modulus was studied. The investigations showed that for both RVEs with filled SWCNT and hollow SWCNT, the effective Young's modulus of the structure decreases approximately linear as the matrix volume fraction increases. The value of Young's modulus of the RVE with a filled Carbon nanotube was obtained to be higher than the RVE with the hollow Carbon nanotube. In addition, by increasing the tube diameter, the effective Young's modulus of the structure increases and the transverse Young's modulus decreases approximately linear for filled tubes but this parameter remains rather constant in the case of the hollow tube by increasing the matrix volume fraction.
Synthesis and Characterization of Al2O3-SiC Nano Composite by Sol-Gel Method and the Effect of TiO2 on Sintering
Authors: Rezaie Hamid Reza , Mohammad-Rahimi Raheleh , Nemati Ali , Samadani M.
Published: April 2011

In the present article, α-Al2O3 nano powder was synthesized by a simple aqueous sol–gel method by using AlCl3 as precursor. It was shown that the gel calcined at 1000°C, 1100 °C and 1200 °C resulted in the formation of a crystalline α-Al2O3 nano powder. In continue TEOS and saccharose was used to prepare SiO2 xerogels containing carbon nano particles. The conversion of the gel to β-SiC nano powders was accomplished by carbothermal reduction at 1500°C for 1 h in argon atmosphere. In second pace alumina matrix composites with nano particles of 5 vol% SiC were prepared with the addition of TiO2 as sintering aid and densified by pressureless sintering method at 1600°C and 1630°C for 2 h in nitrogen atmosphere. Green pellets were obtained by uniaxial pressing of 137 MPa. Maximum density (97.3%) was achieved at 1630°C. Vickers hardness was 16.5 GPa after sintering at 1630°C. Scanning electron microscopy revealed that the SiC particles were well distributed throughout the composite matrix. The precursors and the resultant powders were characterized by X-ray diffraction (XRD), thermal analysis (STA) and scanning electron microscopy (SEM).
Numerical Study of Natural Convection in a Differentially-Heated Rectangular Cavity Filled with TiO2-Water Nanofluid
Authors: Sheikhzadeh Ghanbar Ali , Arefmanesh A. , Mahmoodi Mostafa
Published: April 2011

In this study, the buoyancy-driven fluid flow and heat transfer in a differentially-heated rectangular cavity filled with the TiO2-water nanofluid is investigated numerically. The left and the top walls of the cavity are maintained at constant temperatures Thand Tc, respectively, with Th> Tc.The enclosure’s right and bottom walls are kept insulated. The governing equations are discretized using the finite volume method. A proper upwinding scheme is employed to obtain stabilized solutions for high Rayleigh numbers. Using the developed code, a parametric study is undertaken, and the effects of pertinent parameters, such as, the Rayleigh number, the aspect ratio of the cavity and the volume fraction of the nanoparticles on the fluid flow and heat transfer inside the cavity are investigated. It is observed from the results that by increasing the volume fraction of the nanoparticles, the mean Nusselt number of the hot wall increases for the shallow cavities; while, the reverse trend occurs for the tall cavities. Moreover, the heat transfer enhancement utilizing nanofluid is more effective at Ra = 103.
Photoconductivity of Nanocomposite MEH-PPV: TiO2 Thin Films
Authors: Sarah M.S.P , Zahid F.S. , Musa M.Z. , Noor U.M. , Shaameri Z. , Hamzah A.S. , Rusop Mohamad
Published: April 2011

The photoconductivity of a nanocomposite MEH-PPV:TiO2 thin film is investigated. The nanocomposite MEH-PPV:TiO2 thin film was deposited on a glass substrate by spin coating technique. The composition of the TiO2 powder was varied from 5 wt% to 20 wt% (with 5 wt% interval). The concentration of the MEH-PPV is given by 1 mg/1 ml. The current voltage characteristics were measured in dark and under illumination. The photoconductivity showed increment in value as the composition of the TiO2 is raised in the polymer based solution. The absorption showed augmentation as the amount of TiO2 is increased. The escalation of the current voltage is then supported by the results of surface morphology.
Synthesis and Characterizations of ZnO Nanoparticles for Application in Electromagnetic Detectors
Authors: Zaid Hasnah Mohd , Yahya Noorhana , Niaz Akhtar Majid , Sallehim Ahmad Badruzzaman Ahmad
Published: April 2011

Electromagnetic (EM) waves are able to distinguish between water and hydrocarbons due to their high difference in resistivity value. The method that uses EM technology to explore hydrocarbon is called Seabed Logging (SBL). Due to high demand of hydrocarbons, improvement of this technology is needed. The paper consists of modelling of the prototype of EM transmitter and receiver for hydrocarbons exploration. EM transmitter consists of carbon nanotubes (CNT), aluminium wire with magnetic feeder in toroidal shape. ZnO-CNTs-PVDF composites are used for EM detection. The XRD analysis showed a clear diffraction peak of [101] plane at 36°C of the 2θ. Raman spectra were obtained for ZnO synthesised at 200°C and 300°C temperatures. The initial permeability, Q-factor and relative loss factor were measured using vector network analyser. Results show high value of Q-factor (~43) of the ZnO-CNTs at frequency between 20-30 MHz. The nanoparticles also show low relative loss factor for frequencies above 10 MHz. The grain size, morphology and shape of the particles were characterized using FESEM and revealed rod-like structures. The CNT dipole transmitter system using improved CNT dipole antenna and CNT-ZnO detector record an enhancement of 192% and can be used for hydrocarbon detection.
Dispersion of SiW12 Nanoparticles on Highly Oxidized Multiwalled Carbon Nanotubes and their Electrocatalytic Behavior
Authors: Cuentas-Gallegos Ana Karina , Zamudio-Flores Abraham , Casas-Cabanas Montse
Published: April 2011

Nanocomposite hybrid materials (NHM) based on the immobilization and dispersion of SiW12 polyanion (H4SiW12O40) on a highly oxidized multiwalled carbon nanobue matrix (NTS) are presented. The synthesis procedure followed is designed in order to increase the SiW12 particles concentration on the NHM. XRD, FTIR, N2 adsorption isotherms, EDS, SEM, TEM, and cyclic voltammetry confirmed the presence of SiW12 nanoparticles, whose microstructure and dispersion characteristics were correlated with their BET surface area and their electrochemical behavior. Based on these studies, SiW12 nanoparticles are successfully nanodispersed in the highly oxidized carbon nanotube matrix (NTS), obtaining the highest SiW12 concentration and best electrochemical behavior for sample MH3. The electrocatalytic properties are evaluated for this optimized hybrid (MH3) in the electroreduction of bromated ion with good results.
Improved Learning Algorithm Based on Semi-Supervised Support Vector
Authors: Peng Guo Xing , Li Bei
Published: April 2011

Improved learning algorithm for branch and bound for semi-supervised support vector machines is proposed, according to the greater difference in the optimal solution in different semi-supervised support vector machines for the same data set caused by the local optimization. The lower bound of node in IBBS3VM algorithm is re-defined, which will be pseudo-dual function value as the lower bound of node to avoid the large amount of calculation of 0-1 quadratic programming, reducing the lower bound of each node calculate the time complexity; at the same time, in determining the branch nodes, only based on the credibility of the unlabeled samples without the need to repeatedly carry out the training of support vector machines to enhance the training speed of the algorithm. Simulation analysis shows that IBBS3VM presented in this paper has faster training speed than BBS3VM algorithms, higher precision and stronger robustness than the other semi-supervised support vector machines.
Heat Buffering Property of Phase Change Materials in Textiles
Authors: Sun Yu Chai , Cheng Zhong Hao
Published: April 2011

The research reported here examines heat buffering property changes of phase change materials used in textiles. In the study, six types of fabrics with different warmth retention rate catalogued in two groups were used to determine how warmth retention rate of fabric affect heat buffering time of PCM when fabric was wrapped around PCM pouches. It was found that the greater the warmth retention rate of the wrapped fabric, the longer the heat buffering time of the PCM pouch, we also found that the heat buffering time prolonged in direct proportion to the warmth retention rate in different manners for fabrics weaved by fibers that have different heat conductivity. Greater warmth retention rate and smaller fiber conductivity lead to greater increase of the heat buffering time of PCM pouches. The results in this research suggested a possibility about how to control heat buffering time of PCM-containing textiles.