bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Measurement Results of Thermal Conductivity and Heat Transfer Coefficients on the Simulation Results of Casting Process of Aircraft Engine Elements
Authors: Moskal Grzegorz , Cwajna Jan , Witala Bartosz , Cygan Rafał
Published: April 2011

The paper presents results of tests concerning influence of accuracy in measurements of selected thermal properties of materials of a ceramic mould, insulating mat and an alloy itself on effects of simulation of a casting process provided for elements of an aero-engine. A simulation process was realized by means of the PROCAST program. In initial simulations, thermal parameters were applied and they are accessible in literature and concern materials of a mould and nickel superalloys. Results of simulation revealed presence of numerous defects in a form of gaps, pores and cracks. These results were proved in trial casting. In consequence, it was impossible to select correctly right casting parameters. In order to solve this problem, a value of thermal conductivity was defined experimentally and basing on it, coefficients of heat exchange in metal – mould, mould – insulation mat systems were defined as well. A value of partial coefficients of heat exchange was used to determine values of substitute coefficient of heat exchange for the whole metal – mould, mould – insulation mat systems. By introducing the got data, one managed to define parameters of a casting process, providing improvement in a level of quality of cast elements.
Characteristics of Thermal Properties of Gd2Zr2O7 – ZrO2XY2O3 Powder Mixtures Intended for Deposition of Gradient Layers of TBC Type
Authors: Moskal Grzegorz , Swadźba Lucjan , Witala Bartosz
Published: April 2011

This article presents a study and results concerning the characteristics of selected thermal properties of the powders intended for deposition of gradient structure layers of the TBC type. The study included evaluation of the thermal diffusivity and specific heat of the powders in the initial state, and also calorimetric analysis of powder mixtures. Thermal diffusivity tests were performed with the laser-flash method. The temperature range of the tests was 25°C-1400°C. Specific heat and calorimetric analyses were performed with the heat flux method within a similar temperature range. The Gd2Zr2O7 powders obtained by spray drying method and standard ZrO2 x 8Y2O3 powder were analysed. The thermal diffusivity analysis and calorimetric analysis were performed for the samples obtained by pressing the Gd2Zr2O7 - ZrO2 x 8Y2O3 powder mixture of equal weight fractions. Specific heat measurements were taken for pure powders. The calorimetric analysis performed showed that no significant thermal effects were observed in both pure powders and their mixture within the temperature range of 800°C-1400°C. A small endothermic effect (approx.-7J/g) was observed for gadolinium powder within the temperature range of 350°C-615°C. Specific heat measurements revealed that gadolinium powder was characterized by stable values of that parameter within the whole temperature range like zirconium powder. The analyses performed showed that the powders were characterized by small mutual reactivity, and gadolinium powder showed a definitely lower thermal diffusivity, which is advantageous as regards obtaining TBC layers with a gradient structure on the basis of those two powders.
Characteristics of Phenomena in Powders Type RE2Zr2O7-Al2O3 in High Temperature Annealing Conditions
Authors: Moskal Grzegorz , Swadźba Lucjan , Hetmańczyk Marek , Witala Bartosz
Published: April 2011

The paper presents test results and characterizes the structural stability of powders, which form a mixture of aluminium oxide (Al2O3) and gadolinium, based on rare earth zirconates. This mixture is provided to create thermal barrier coatings (TBCs) by spraying. The purpose of the tests was to determine the influence of temperature on reactions, occurring between those powders within a temperature range from 25°C to 1500°C, while such conditions were to simulate the conditions, which occur during creation of TBCs and they give an answer to the question concerning mutual reactivity of the powders. The requirements for new materials, provided to spray the TBCs, indicate the necessity to prepare the materials, which do not show tendency towards reactions with the Al2O3, formed during oxidation of Ni (Co) CrAlY, while this reaction is of type bond coat. The tests included differential scanning calorimetric (DSC) analysis and differential thermal analysis (DTA) of powder mixtures. Diffraction analysis was also performed before and after the tests have been finished. The DSC analysis results, obtained at a range of high temperature, did not show any thermal effects, which indicate a low level of mutual reactivity of the powders. However, the DTA analysis suggests presence of such effects at temperature close to 1300°C, and it indicates the necessity to verify exactly the obtained results. Results of the XRD measurement showed that after annealing process already at 1100°C the perovskite oxide of GdAlO3 was present.
High-Temperature Diffusion Barrier for Ni-Cr Cast Steel
Authors: Kochmańska Agnieszka , Garbiak Małgorzata
Published: April 2011

The study describes aluminium-silicon protective coatings produced by the slurry cementation process on a substrate of creep-resistant Ni-Cr cast steel. The mechanism of the coating growth on a substrate was examined and the effect of annealing time and temperature on total thickness of the coatings and on the thickness of the individual zones was analyzed. The coating structure is composed of two zones. In the external zone, elements like Al, Ni and Fe are concentrated, forming intermetallic phases of an Al(Ni,Fe) type, while the internal zone contains an (Fe,Cr,Si) solution. The internal zone formed in a sub-surface layer of the substrate has hardness values intermediate between the hardness of the substrate and that of the external layer.
Real Time Prognostic Strategies: Application to Gas Turbines
Authors: Yadegari M.
Published: April 2011

Gas turbines are increasingly deployed throughout the world to provide electrical and mechanical power in consumer and industrial sectors. A health management system can incorporate prognostic algorithms to effectively interpret and determine the healthy working span of a gas turbine. The research project’s objective is to develop real-time monitoring and prediction algorithms for simple cycle natural gas turbines to forecast short and long term system behavior.
Investigation of the Effect of Electrospun Polyethersulfone Nanofibers in Membrane
Authors: Shahgaldi Samaneh , Yaakob Zahira , Ghasemi Mostafa , Wan Daud Wan Ramli , Khadem Dariush Jafar
Published: April 2011

One dimensional (1D) nanostructure materials such as nanowires, nanofibers, and nanorods with porous structures have potential for use in various applications. Electrospinning is one of the versatile techniques with the ability of producing cost-effective, large production, highly porous nanofibers and membrane with large surface to volume ratios. Poly ether sulfone (PES) is a kind of special engineering plastic with good processing characteristics. In this paper, synthesis of PES membrane was investigated by two main methods, i.e. phase inversion and electrospiing. For electrospining, the main effective parameters such as concentration of polymer and solvent, for finding the optimized condition of electrospun PES membrane was studied. The produced membranes were characterized by SEM for morphology and BET observation of surface area, permeability, flux, and mechanical propertise for different applications.
Weight Analysis in a Quantum Mechanical Transport Model for Nano and Bio Materials
Authors: Di Sia Paolo , Dallacasa Valerio
Published: April 2011

The charge transport is one of the most important factors for the efficiency in nanostructured devices. The detailed nature of transport processes in these systems is still not completely resolved. Starting from the Drude model, we have proposed an analytical method for describing classically the most important quantities concerning transport phenomena, i.e. the velocity correlation functions, the mean square deviation of position and the diffusion coefficient. To fully account for quantum effects arising in systems of reduced dimensions, in this work we present the quantum mechanical version of this model, comprehending the oscillator strength weights, and apply the model to single-walled carbon nanotube ﬁlms, extracting the oscillator weights from reflectivity data reported in the literature. We are able to give a complete and precise description of time correlations avoiding time-consuming numerical or simulation procedures. This method demonstrates high generality and offers perspectives even in the study of ions, like mass transfer, and solutions, so as in nano bio systems. This quantum mechanical extension allows significant applications for the nanodiffusion in nanostructured, porous and cellular materials, as for biological, medical and nanopiezotronic devices.
A New Approach for the Diffusion Coefficient Evaluation of Sulfur in CaO-SiO2-Al2O3 Slag
Authors: Muhmood Luckman , Viswanathan Nurni N. , Seetharaman Seshadri
Published: April 2011

The Diffusion coefficient of sulfur in a ternary slag with composition of 51.5% CaO- 9.6% SiO2- 38.9% Al2O3 was measured at 1723 K by chemical diffusion from the variation of concentration of sulfur in silver metal. A MATLAB program was developed to find the concentration variation of sulfur in silver metal using various critical parameters like the diffusion coefficient of sulfur in slag available in literature, sulfur partition ratio, sulfide capacity of the slag and the its density. The PS2 and PO2 pressures were calculated from the Gibbs energy of the equilibrium reaction between CaO in the slag and solid CaS and confirming the same by using ThermoCalc. The density of the slag at 1723 K was obtained from earlier experiments. Initially the order of magnitude for the diffusion coefficient was taken from the works of Saito and Kawai but later was modified so that the concentration changes of Sulfur obtained from the program agreed with the experimental results. The diffusion coefficient of sulfur in 51.5% CaO- 9.6% SiO2- 38.9% Al2O3 slag at 1723 K was estimated as 4.14x10-6 cm2/sec.
Experimental Results on Evaporation Waves
Authors: Graña-Otero José C. , Parra Ignacio E.
Published: April 2011

We address an experimental investigation of evaporation waves. They are obtained when a liquid contained in a vertical glass tube is suddenly depressurized from a high initial pressure down to the atmospheric one. After the release of pressure, the state of the liquid, which is at ambient pressure and the initial temperature, is well known to be metastable when the corresponding stable state is vapour. For moderately large evaporation rates (moderately large initial to ambient pressure ratios), the vapour-liquid interface ultimately evolves into an evaporation wave in which a highly corrugated front propagates downwards into the liquid with a well defined mean velocity. This mean velocity turns out to be a function of the ratio between the initial and the ambient pressures. In addition, attention to some new phenomena not previously reported is brought.
Modeling of Heat and Mass Transfer in an Annular Adsorber for Solar Cooling Machine: Performance Coefficients
Authors: Allouache Nadia , Bennacer Rachid , Chikh Salahs , Al Mers A. , Mimouni N.
Published: April 2011

The primary aim of this study is to simulate numerically the heat and mass transfer characteristics in the annular adsorber that is the most important component of the solar cooling machine, and to evaluate the solar and thermal coefficients of performance as an optimisation criterion of the system, for different adsorbent/adsorbate pairs. The porous medium constituted of the adsorbent/adsorbate is contained in the annular space and it is heated by solar energy. A general model equation is used for modeling the transient heat and mass transfer. The adsorption phenomenon is described by using different models of solid-adsorbate equilibrium. Effects of the key parameters on the adsorbed quantity, the generating temperature, the performance coefficients and thus on the system performances are investigated.
Characteristics of Liquid–Solid Mass Transfer in a Bubble Column Equipped with a Vertical Tube of Circular Fins
Authors: Bamufleh Hesham S. , Nosier S. A. , Daous M. A.
Published: April 2011

The solid-liquid mass transfer rate at a stack of circular fin surfaces in a bubble column was investigated. A diffusion-controlled dissolution technique of copper in an acidified chromate solution was employed. Variables studied included the number of actively exposed fins ranging from 5 to 20, pertinent physical properties of the solution, and air superficial velocity. Experimental data showed that the rate of the diffusion-controlled mass transfer increases with increasing superficial air velocity and decreases with increasing chromate solution acid concentration. Moreover, at relatively low superficial air velocity, increasing the number of actively exposed fins results into a continuous increase in the mass transfer coefficient. At relatively higher superficial air velocity, however, the mass transfer coefficient decreases in the 5 to 10 range of actively exposed fins and then reverts to increase in the 15 to 20 range.
Effect of Ti and Fe Alloying on Kirkendall Voids Feature in Ni/Ni3Al Welded Joints after the High Temperature Annealing
Authors: Losertová Monika , Drápala Jaromír , Vrbický Jiří
Published: April 2011

The study of influence of Fe and Ti alloying elements in the Ni3Al intermetallic alloy on diffusion feature in Ni/Ni3Al-Me (Me = Fe or Ti) joints was performed using the diffusion couple technique. Four sets of diffusion couples of diverse compositions prepared by means of resistance welding or electron beam welding in vacuum were used. The concentrations profiles and diffusivities of welded Ni/Ni3Al-Fe and Ni/Ni3Al-Ti joints were determined after annealing at 1050°C for 100 hours. The concentration profiles were smoothed using suitable types of polynomials. The Kirkendall voids in the area between the Matano plane and the new  interface created after annealing were observed. Metallographic study and qualitative evaluation of voids by means of AFM method revealed different feature of Kirkendall regions in Ni/Ni3Al-Fe couples unlike Ni/Ni3Al-Ti joints.
Influence of the Thermo-Piezo-Viscous Effect on the THD Lubrication in Porous Self- Lubricating Bearings
Authors: Boubendir S. , Bennacer Rachid , Larbi Salah
Published: April 2011

A numerical study of the behavior for a finite porous journal bearing lubricated with Newtonian fluid is undertaken considering both thermal and piezo-viscous effects. The modified Reynolds equation is obtained by using the thermo-hydrodynamic aspect to account for the viscous variation versus pressure and temperature where Barus law has been used for the visous formulation. To determine the flow in the porous media, the Darcy’s law has considered. The governing equations were solved numerically using a finite difference approach. Obtained results compared with the case of a thermo-viscous aspect, the piezo-viscous parameter increases the load carrying capacity significantly and improves the characteristics of the journal bearings.
Mechanisms of Microstructural Rearrangement on Two-Dimensional Aggregates under Compressive Stress
Authors: Promkotra Sarunya
Published: April 2011

Two-dimensional (2D) colloidal aggregates of polystyrene microspheres 4 μm were experimentally modeled to study the rearranged mechanisms and compression behaviors at the air-liquid interface. The aggregated models occurred due to the interaction forces between particles. The combination of mechanical testing technique and the digital video microscopy had been developed to quantitatively analyze the compressive deformation of 2D aggregates. When the compressive forces were applied to the cluster, these forces were transmitted trough the aggregated network during compression. Solid-like mechanical properties of 2D aggregated cluster were examined. Deformation mechanisms occurred within the aggregated network which presented the particle rearrangements during yield. Elastic deformation had undergone the compressive elastic stress of the elastic loading. Rearrangement mechanisms found generally were rolling-hinge, sliding mechanisms and tensile failure for a small-scale deformation. Shear failure and stick-slip mechanisms caused a large-scale plastic deformation. However, across the yield point, the tensile failures were dominated. Rearrangement mechanisms of particles affected both elastic and plastic deformations.
Improving the Diffusion Controlled Cementation of Cadmium Ions Using Reciprocating Fixed Bed of Zinc Rings
Authors: El Shazly Ahmed Hassan , Mubarak Ashraf A. , Bamufleh Hesham S.
Published: April 2011

The aim of the present work is to investigate the effect of pulsation on improving the rate of the diffusion controlled cementation of cadmium ions using reciprocating fixed bed of zinc rings. The kinetics of the cementation reaction was investigated under different conditions of initial concentration of cadmium ions, frequency and amplitude of oscillation (vibration velocity), zinc ring diameter, bed diameter, bed height and temperature. The effect of temperature was found to fit the Arrhenius equation with an activation energy of 7.58 kcal/mole which confirms the diffusion controlled nature of the reaction. A dimensionless correlation in the form of Sh = 6.9 Re0.45 Sc0.33 (Bd/Bh)0.89 was deduced. The industrial application of the obtained results was discussed.
Surface Characterization of a Nitrided Low Alloy Steel
Authors: Keddam Mourad , Kouba R. , Chegroune Redoune , Bouarour B.
Published: April 2011

The 32CrMoV13 low alloy steel was gas nitrided at 550°C, for three time durations (6.5, 13 and 20 h) and under a variable nitriding potential (1, 2.2 and 6 atm-0.5). The generated nitride layers were characterized by SEM observations, XRD and GDOS analyses as well as microhardness testing. The XRD analysis indicates that the compound layer was composed of and iron nitrides and CrN phase. The surface hardness (inside the compound layer) was found to be dependent on the nitriding potential value, its value increases as rises. It was shown by GDOS analysis that the upper and lower nitrogen concentrations at the (compound layer / diffusion zone) interface are approximatively: 4 and 0.88 wt. % N, respectively.
Heat and Mass Transfer Made Visible
Authors: Speetjens M.F.M. , Van Steenhoven A.A.
Published: April 2011

Heat and mass transfer in fluid flows traditionally is examined in terms of temperature and concentration fields and heat/mass-transfer coefficients at fluid-solid interfaces. However, heat/mass transfer may alternatively be considered as the transport of a passive scalar by the total advective-diffusive flux in a way analogous to the transport of fluid by the flow field. This Lagrangian approach facilitates heat/mass-transfer visualisation in a similar manner as flow visualisation and has great potential for transport problems in which insight into (interaction between) the scalar fluxes throughout the entire configuration is essential. This ansatz furthermore admits investigation of heat and mass transfer by well-established geometrical methods from laminar-mixing studies, which offers promising new research capabilities. The Lagrangian approach is introduced and demonstrated by way of representative examples.
Nutrients and Metabolic Secretions Transfer in Cornea
Authors: Dória Silva Humberto , Pereira Dória Luiz Cláudio , Pereira Dória Cristiana , Pereira Dória Cristiane , Dória Silva Maria do Carmo Tatiana , Dória Silva Júnior Humberto , Dória Silva Maria Tamires
Published: April 2011

This work demonstrates the need for updated review of the mechanism of mass transport in the human cornea, to understand the deterioration of visual acuity and plan your recovery. It is the conclusion of a work for ten years for recovery of presbyopia of the first author, through exercise the extra-ocular and ciliary muscles. It is shown that intraocular pressure varies according to the direction of the visual axis and that this variation is part of the mechanism of forced convection for the transport of nutrients and drainage of secretions metabolic in cornea. In both eyes, seven pressure measurements are proposed at intervals of one hour, with the non-contact tonometer: The first measurement in the initial condition; The second measurement after relaxation of the eyes; The following measurement after an activity with the attachment point near of the two eyes; The last four are proposed out after two activities, in the limit of the direction of the right border and, also, in the limit of the direction of the left border of the field of binocular vision, considering the two alternatives near and far from the eyes. The oblique muscles contraction causes a reduction in the anterior chamber volume and, consequently, the intraocular pressure increases, however, when the oblique muscles relax the opposite occurs. It is considered that, after an hour, the intraocular pressure reaches dynamic equilibrium. To measure the pressure, the equilibrium condition of the anterior chamber volume is changed, the system undergoes a new transient dynamic. There should be no change in intraocular pressure equilibrium during one day, unless because of an external factor. To collect the data, it is proposed to use the system eye of the first author who has good binocular vision.
New Use Heat Transfer Theories for the Design of Heat Setting Machines for Precise Post-Treatment of Dyed Fabrics
Authors: Ip Ralph W.L. , Wan Elvis Iok Cheong
Published: April 2011

Fabrics are needed further treatment after dyeing to restore their original mechanical properties by suitable drying/shrinkage process because of wetted and elongated fabrics cannot be used for clothes making. Heating up the dyed fabrics at suitable temperature can restore their original shapes and geometries by releasing the internal stress introduced by dyeing process. Thus, heat setting is a commonly used post-treatment process to stabilize fabric geometrical dimensions and prevent further shrinkage. Hot air jet impingement [1] and moist heat are conventional drying methods for different applications. Despite the well establishments of these drying technologies, most of the applications are for materials like clay and paper, and few on the study of textile materials. In fact that most of the developed heat setting machines used in textile industry are only designed by empirical models and lack of theoretical bases. This situation will obstruct further improvement of the drying technology. In this paper, a theoretical basis heat transfer model is developed for a precise description of a heated air flowing process for heat setting machine design. In the machine design, a better airflow circulation strategy for an efficient drying is addressed. Equations for heat and mass transfer in moist porous materials and theories on thermo- and fluid-dynamics are used to support the machine design. Outcomes from the research are to develop a heat transfer model that provides more precise and effective calculation for heat setting machine design that unavailable from the developed machine prototypes.
Diffusion of Particles Adsorbed on a Dynamically Disordered Reconstructive Surface
Authors: Tarasenko Alexander , Jastrabik Lubomir
Published: April 2011

We have considered the diffusion of particles in a dynamically disordered medium in the framework of a simple lattice-gas model of a reconstructive surface. Using kinetic Monte Carlo simulations we have investigated the diffusion of particles over the host lattice with moving atoms. The dynamic lattice reconstruction increases substantially the particle diffusion coefficient and changes its activation energy.
Sensitivity Tests of Simulation Models Used in Chosen Calculation Codes on Uncertainty of Thermo-Mechanical Parameters during Virtual Mechanical Stress Estimation for Ferrous Alloy Castings
Authors: Ignaszak Zenon , Popielarski Paweł
Published: April 2011

Simulation systems used for many years in foundry industry such as MAGMASOFT, NovaFlow&Solid and ProCAST, contain thermo-mechanical modules permitting the estimation of mechanical stresses and hot tears appearing in casting during its cooling. It is also known that these modules are rarely used because of the very limited thermo-mechanical database especially for ceramic materials such as foundry sand moulds. These technologies – castings pouring in non-permanent sand moulds, particularly iron alloys are most often applied in foundry. In our study the method of evaluating the algorithms quality applied in thermo-mechanical phenomena models based on parameters sensitivity testing from the proper database of the simulation system was used [1]. The comparative analyses of both experimental and virtual results were realized (by stress estimation). The methodology of experimental research was similar to that described where gray cast iron castings of stress bars (grid) were casted in sand mould bonded by organic resins.
Formation of Zirconia and Titania Nanotubes in Fluorine Contained Glycerol Electrochemical Bath
Authors: Lockman Zainovia , Ismail Syahriza , Kawamura Go , Matsuda Atsunori
Published: April 2011

The formation of self-aligned titania and zirconia nanotubes is achieved by the anodisation of Ti and Zr in a fluorine contained electrochemical bath. The anodic oxidation was performed at 30 V for 60 min in a two-electrode glycerol (15% water) bath containing varying amount of NH4F. Despite the fact that a self-aligned nanotubular structure is formed on both titanium and zirconium, the dimensions of zirconia and titania nanotubes are different under the same anodisation parameters. It appears that by using 30 V as the anodisation voltage, the diameter of zirconia nanotubes (30-60 nm) is much smaller compared to that of titania nanotubes (80-100 nm). The length of zirconia nanotubes in the bath consisting of 0.7 g NH4F is 3 µm whereas titania nanotubes formed in the same bath have a length of ~700 nm. The fundamental difference between the nanotubes formed on titanium and zirconium may be related to the rate of oxidation, initial oxide formation during anodisation, pits formation and rate of pits growth for pores formation and stabilisation. Moreover, investigation on the crystallinity of the nanotubes reveals that titania nanotubes are weakly crystalline with crystallite sizes of <5 nm. Whereas, zirconia nanotubes are much more crystalline in cubic modification. The stabilisation of the high temperature phase is thought to originate from the size of the nanotubes walls and the deficiency in oxygen during the growth of the anodic oxide by anodisation.
Estimation of Coupled Thermo-Physical and Thermo-Mechanical Properties of Porous Thermolabile Ceramic Material Using Hot Distortion Plus® Test
Authors: Ignaszak Zenon , Popielarski Paweł , Strek Tomasz
Published: April 2011

In the paper the thermo-mechanical phenomena which occur in thermal shocked thermolabile porous ceramic material were described. Such materials are applied in foundry industry for mould making and they are characterized the low thermal stability losing its strength above 400°C. In [3] the usefulness of Hot Distortion Plus® to estimate the thermo-physical parameters (apparent thermal conductivity, heat capacity) was discussed. These parameters are necessary in data base of simulation codes which permit to simulate the phenomena in casting-mould system. The aim of these tests is to predict the mould material phenomena influence on castings quality. Parameters applied in these thermo-mechanical models (Young's modulus, Poisson's ratio, Yield stress) and their variations with temperature are not really known for thermal unstable mould material. There is no adapted method in literature and description of such total investigations of both parameters groups: thermo-physical and thermo-mechanical. The author's method called Hot Distortion Plus® consists in acquisition of temperature curves of heated sample of material and correlation with curves of their dilatation. Following the simulation using inverse solution method to reproduce the measured parameters with experiment was applied. The tests were carried out for the new quartz sand bonded by resin (approx. 1%). The specimens (dimensions 114 × 25 × 6mm) from binder-sand mixture were made using special core-box.
Effect of Co-Doping of Nano Silver, Carbon and Nitrogen on Titania on the Visible Light Activity for Methylorange Degradation
Authors: Binitha Naraya Nan , Yaakob Zahira , Silija P.P. , Suraja P.V. , Tasirin S.M
Published: April 2011

Co-doping of nanosilver, carbon and nitrogen is done on titania to get improved photodegradation of pollutants when compared to single doping. Anion doping extends the absorption of TiO2 to the visible region; whereas noble metal NP doping prevents the recombination of photoinduced electrons and holes. Doped TiO2 prepared using sol gel method allows efficient dispersion of nano silver and thus enhances the photodegradability. X-ray Diffraction analysis shows the efficient dispersion of incorporated nano silver over anatase TiO2. The visible light absorption is confirmed from UV-Vis Diffuse Reflectance spectral studies. Photocatalytic activity is investigated by the degradation of methyl orange as a model pollutant. Efficient degradation in visible light shows the synergetic effect of carbon and nitrogen doping as well as nano silver loading on the performance of TiO2.
Microstructure and Properties of Diffusion Boride Layer on Die Steel
Authors: Beznák Matej , Chaus Alexander S. , Čaplovič Lubomír
Published: April 2011

Diffusion boride layer has been produced on the surface of a hot work tool steel. The microstructure and elemental spectra as well as depth profiles of the elements in the boride layer have been studied by scanning electron microscopy, X-ray diffraction analysis and energy dispersive X-ray spectrometry. Micro-hardness measurement was carried out using the Vickers micro-hardness test. The results showed that the boride layer is formed by boron compound Fe2B. Additionally, boron carbide B4C has been revealed embedded in the bulk of the boride layer.
Polymorphic and Morphological Transformation during the Transition from a Propagating Band to Static Bands in the Nickel Hydroxide/Ammonia Liesegang System
Authors: Al-Ghoul Mazen , Ammar Manal
Published: April 2011

We present an experimental study of the Ni+2/Ni(OH)2/NH3 reaction-diffusion system in a gel (agar). The system, which consists of a gel containing an inner electrolyte Ni+2 and a diffusing outer electrolyte (NH3/OH-), exhibits pulse propagation due to the concomitant precipitation reaction between Ni+2 and hydroxide ions and re-dissolution due to ammonia. During the propagation of the pulse, a transition to Liesegang banding is shown to take place. The bands are characterized by IR and XRD and are shown to consist of the polymorph -Ni(OH)2 whereas the pulse contains the other polymorph -Ni(OH)2. SEM measurements also reveal a morphological change accompanying the polymorphic transition between the pulse and the bands and uncovering an Ostwald ripening mechanism.
Sorptivity and Hydraulic Diffusivity of Coating Gypsum and Impact of Hemp Fibers Addition
Authors: Gassita Serge , Marmoret Laurent , Ben Hamed Haykel , Beji Hassen
Published: April 2011

This paper aims to provide a better understanding of the gypsum hydric behavior used as coating during imbibition in liquid water. Firstly, we want to describe hydric transfer by determining sorptivity and hydraulic diffusivity of coating gypsum. Secondly, we evaluate the impact of the hemp fibers addition on hydric parameters. Experimentally, hydraulic diffusivity will be obtained by an overall measure of the moisture content (mc) in a defined sample volume, and the sorptivity describes capacity absorption. Through numerical simulation, hydraulic diffusivity will be determined by a local measure of the mc.
Grain Boundary Parameters in Sandstone and Limestone
Authors: Palchik Vyacheslav
Published: April 2011

In this paper, length of grain-to-grain contact, number of contacts per grain and ratios between the length of contacts and geometric characteristics of grains in heterogeneous Berea sandstone and Indiana limestone are studied. It is shown how hydrostatic pressure up to 40 MPa influences these grain boundary parameters. Observations show that there are different types of influence of hydrostatic pressure on grain boundary parameters in the studied sandstone and limestone.
Determination of Gamma Transmittance and Density Assessment for Al Doped ZnO Thin Films by Using Gamma Transmission Technique
Authors: Karagoz B. , Ozdemir O. , Karacasu O. , Baydogan Nilgun , Çimenoğlu H. , Kayali E.S. , Tugrul A.B. , Altinsoy N. , Haciyakupoğlu S. , Kiziltas S. , Okka M. , Albayrak Gülçin , Sengel H. , Akmaz F. , Parlar A.
Published: April 2011

The aim of this study is to investigate the structural changes of Al doped ZnO thin films with gamma transmission technique with Cs-137 gamma radioisotope source. Gamma transmittance and gamma absorption coefficient, (1/mm) were investigated with the increase Al (at.%) concentration. Hence it can be possible to assess the density for Al doped ZnO thin films.
Single Layer Drying Behavior of Apple Slices in a Microwave Dryer
Authors: Çelen Soner , Kahveci Kamil , Akyol Ugur
Published: April 2011

In this study, the drying behaviour of single layer apple slices of 5mm thickness in a microwave dryer was investigated experimentally for four different microwave power levels (90 W, 180 W, 360 W and 600 W) and suitability of drying models available in the literature in simulating the drying behaviour of apple slices was determined by statistical analysis. The performance of these models was determined by comparing the coefficients of determination (R), reduced chi-squares (χ2) and root mean square errors (RMSE) of the models. The results show that drying time and energy consumption decreases considerably with increasing microwave power. The results also show that, among of the models proposed, the Verma et al. model gives the best fit with experimental data for all drying conditions considered. In order to determine the colour change of apple, a colour meter was also used in this study and found that L* and a* values were not significantly different from the values of the fresh apples.
Drying Behavior of Polyester Based Yarn Bobbins in a Hot-Air Bobbin Dryer
Authors: Cihan Ahmet , Kahveci Kamil , Akyol Ugur , Akal Dinçer
Published: April 2011

Drying behavior of polyester based yarn bobbins (67% polyester, 33% viscose) was simulated for different drying air temperatures by a simultaneous heat and mass transfer model. In the model, it was assumed that mass transfer is occurred by the diffusion mechanism. In the study, firstly drying behavior of polyester bobbins for different drying air temperatures has been determined experimentally. The experiments were conducted on an experimental hot-air bobbin dryer designed and manufactured based on hot-air bobbin dryers used in textile industry. In the experimental setup, temperatures of different points of the bobbins were measured by thermocouples placed inside the bobbins and weight of the bobbins during the drying period were determined by a load cell. Then moisture ratio and temperature values of the model have been fitted to the experimental ones. The fit was performed by selecting the values for the diffusion coefficient and the thermal diffusivity in the model in such a way that these values make the sum of the squared differences between the experimental and the model results for moisture ratio and temperature minimum. The results show that there is a good agreement between the model results and the experimental ones. The results also show that temperature has a significant effect on mass transfer and temperature dependence of the diffusion coefficient may be explained by an Arrhenius type relation.
Fluid Flow and Solid/Fluid Suspensions Flow in 3-D Packed Beds of Spheres: The Effect of Periodicity of Fixed Beds
Authors: Serrenho Ana , Miguel Antonio Ferreira
Published: April 2011

A 3-D numerical study is performed to investigate the effects of periodicity (geometry) on flow of fluid and on flow of solid/fluid suspensions in packing arrangements of fixed beds of spheres. The porosity is fixed at 0.58 and the following packing arrangements are studied: simple cubic, face-centered cubic, hexagonal, rhomboedric hexagonal and tetragonal. Simulations are carried out at Reynolds numbers ranging from 0.1 and 50, and using solid suspensions with different sizes (0.2, 2 and 10 micron) and densities (200 and 2000 kg/m3). The effect of the periodicity on fluid flow characteristics (permeability and inertia parameter) and on the penetration efficiency of solid suspensions within the packed beds is analyzed and quantified.
Micro Arc Oxidation of AZ91 Mg Alloy for Improved Corrosion Resistance
Authors: Yavuz H.G. , Gunyuz M. , Ozkara Isa Metin , Baydogan Murat , Çimenoğlu H.
Published: April 2011

AZ91 Mg alloy was subjected to the micro arc oxidation process by using different processing parameters. Following oxidation, surface topography and qualitative phase analysis were made by tabletop digital microscopy and X-ray diffraction (XRD) analysis. In order to evaluate the relative corrosion resistance of the samples that were oxidized in different parameters, the samples were immersed in a corrosive solution for 6 days and the weight losses before and after the corrosion tests were compared. Relative corrosion resistance of the samples was evaluated on the basis of surface topography.
Elaboration of Sol-Gel Derived Hydroxyapatite / Yttria Stabilized Zirconia Composite Coatings Obtained for Biomedical Application
Authors: Salehi Sahar , Fathi Mohammad Hosseien
Published: April 2011

In this study, nanostructured composite coatings of hydroxyapatite (HA)/ 30wt% yttria stabilized zirconia (YSZ) coatings containing 0, 3, 5, and 8 mol% Y2O3 (namely; HA-0YSZ, HA-3YSZ, HA-5YSZ, and HA-8YSZ) were successfully synthesized using the sol-gel method. The crystallite size of the coating was about ~44-58 nm for tetragonal and cubic zirconia grain size and 75-87 nm for hydroxyapatite grain size. Crack-free and homogeneous HA-YSZ composite coatings were obtained with no observable defects. The uniform distribution of zirconia particles in a composite would be highly beneficial for obtaining homogeneous coatings of HA-YSZ film and would hinder grain growth of HA phase during calcinations. In vitro evaluation in 0.9% NaCl showed that Ca2+ dissolution rate of composite coatings was lower than pure HA coatings.
Dispersion of Twin Inclined Fume Jets of a Variable Height within a CrossFlow
Authors: Radhouane Amina , Mahjoub Said Nejla , Mhiri Hatem , Le Palec Georges , Bournot Philippe
Published: April 2011

Twin elliptic inclined tandem jets are emitted within an oncoming cooler crossflow. The jets contain a non reactive fume whose dispersion is tracked all over the surrounding domain. Such a configuration may be found in chimney stacks, ships’ chimneys, etc. We propose to evaluate in the present paper the impact of the jets’ height on the resulting dispersion process. To reach this goal, a numerical simulation of a double jet model of variable height is carried out by means of the finite volume method together with a non uniform grid system. The model, validated by previous experimental data, allowed the tracking of the emitted fume by studying the evolution of a single particle contained within this fume, the Carbone dioxide (CO2) mass fraction. This is possible thanks to the assumption of handling a non reactive fume, which is adopted only to simplify the calculations. The CO2 mass fraction was mainly tracked between the emitting nozzles, in a try to find out the changes brought by the extension of the emitting jet nozzles on the flow trapped between them.
Simulation of VOCs Recovery Process by Absorption
Authors: Maceiras Rocío , Urrejola S. , Cancela Angeles , Sanchez A. , Díaz J.
Published: April 2011

Using a simulation program, an absorption process has been simulated of an air stream contaminated with acetone using water as absorbent and the subsequent recovery of the solvent by distillation. After verifying the effectiveness of the simulated process, the next step was to carry out an economic analysis at the level of equipment to assess the economic viability of the simulated recovery plant.
Numerical Investigation of the Thermal Properties of Irregular Foam Structures
Authors: Hossein Hosseini Seyed Mohammad , Kharaghani A. , Kirsch Christoph , Öchsner Andreas
Published: April 2011

The thermal properties of irregular open-cell and closed-cell metal foams are investigated via numerical simulation. The influence of relative density and cell irregularity on the thermal conductivity and thermal expansion of the foam structure is determined. It is concluded that the effective thermal conductivity of the foam structure depends linearly on the relative density, whereas no dependence on the degree of irregularity is observed. The effective thermal expansion coefficient of the foam structure is constant for the range of parameters considered.
3-D Finite Element Simulation of Friction Stir Welding Process of Non Similar Aluminum-Copper Sheets
Authors: Alimoradi A. , Loh-Mousavi M. , Salekrostam R.
Published: April 2011

The Friction Stir Welding (FSW), a relatively new welding process, was developed in 1991 at the Welding Institute near Cambridge, England. There are two tool speeds to be considered in friction-stir welding; how fast the tool rotates and how quickly it traverses the interface. These two parameters have considerable importance and must be chosen with care to ensure a successful and efficient welding cycle. The relationship between the welding speeds and the heat input during welding is complex. In this paper the friction stir welding (FSW) process of stainless steel alloys has been modeled using a three dimensional finite element method. A coupled thermal viscoplastic model was used for the simulation. Tool speeds and temperature distribution are coupled and solved together using this method. The relationship between the welding speeds and the heat input during welding is obtained by numerical analysis, and the stress contour occurred by temperature field and tool force is surveyed. In addition, the effects of FSW process conditions on heating mainly near the tool pin are investigated in this paper.
Flow Structure Issued from a Bent Chimney around a Cylindrical Obstacle: Effect of the Aspect Ratio
Authors: Bhouri Baouab Inès , Mahjoub Said Nejla , Mhiri Hatem , Le Palec Georges , Bournot Philippe
Published: April 2011

We present in this work a numerical study of pollutants’ dispersion resulting from a bent chimney around a cylindrical obstacle. A three-dimensional numerical model, based upon the RSM (Reynolds Stress Model) turbulence closure model was used. The adopted grid is not uniform, particularly refined near the chimney and around the cylindrical building. The domain is large enough to be able to visualize the recirculation zones and the vortices created by the building. The results obtained in three dimensional configurations make possible the description of the dynamics and mass features under different aspect rations.
Heat and Mass Diffusion Including Shrinkage and Hygrothermal Stress during Drying of Holed Ceramics Bricks
Authors: Barbosa da Silva J. , Almeida G. Silva , Barbosa de Lima W.C.P. , Neves Gelmires Araújo , de Lima Antônio Gilson Barbosa
Published: April 2011

The Aim of this Work Is to Present a Three-Dimensional Mathematical Modelling to Predict Heat and Mass Transport inside the Industrial Brick with Rectangular Holes during the Drying Including Shrinkage and Hygrothermalelastic Stress Analysis. the Numerical Solution of the Diffusion Equation, Being Used the Finite-Volume Method, Considering Constant Thermo-Physical Properties and Convective Boundary Conditions at the Surface of the Solid, it Is Presented and Analyzed. Results of the Temperature, Moisture Content and Stress Distributions, and Drying and Heating Kinetics Are Shown and Analyzed. Results of the Average Moisture Content and Surface Temperature of the Brick along the Drying Process Are Compared with Experimental Data (T = 80.0oC and RH = 4.6 %) and Good Agreement Was Obtained. it Was Verified that the Largest Temperature, Moisture Content and Stress Gradients Are Located in the Intern and External Vertexes of the Brick.
Investigation of Interatomic Potential on Chip Formation Mechanism in Nanometric Cutting Using MD Simulation
Authors: Vahid Hosseini Seyed , Vahdati Mehrdad , Shokuhfar Ali
Published: April 2011

Nowadays, the nano-machining process is used to produce high quality finished surfaces with precise form accuracy. To understand and analyze the chip formation mechanism of nano-machining process on an atomistic scale, since the experimentation is not an easy task, numerical simulation such as molecular dynamic (MD) simulation is a very useful method. In this paper, MD simulation of the nano-metric cutting of single-crystal copper was performed with a single crystal diamond tool. The model was solved with both pair wise Morse potential function and embedded atom method (EAM) potential to simulate the inter-atomic force between the work-piece and a rigid tool. The chip formation mechanism, dislocation generation, tool forces and generated temperature were investigated. Results show that the Morse potential cannot perform an appropriate defect formation and plastic deformation in nano-metric cutting of metals. Also, tool forces in Morse potential are more than the forces in EAM potential. Furthermore, the fluctuations of resultant forces in Morse potential are greater than that of EAM. In addition, using many-body interaction potentials like EAM can lead to substantial changes in surface energies, elastic-plastic properties and atomic displacement, compared with the pair-wise potentials like Morse. Finally, the atomic displacement investigation shows that in EAM potential study, only the atoms in a local region near the cutting process are displaced, but in Morse potential a large portion of atoms has affected during cutting process. Subsequently, the chip temperature in EAM potential is more than that of Morse potential.
Nano-Based Optical Chemical Sensors
Authors: Lobnik Aleksandra , Korent Urek Špela
Published: April 2011

The development of nanoscale materials for optical chemical sensing applications has emerged as one of the most important research areas of interest over the past decades. Nanomaterials exhibit highly tunable size- and shape-dependent chemical and physical properties, show unique surface chemistry, thermal and electrical properties, high surface area and large pore volume per mass unit area. Because of their unique and advantageous features they can help to improve sensitivity, response time and detection limit of sensors. In this review, recently developed photoluminescence-based optical chemical nanosensors are presented. Some future trends of the nanomaterial-based optical chemical sensors are given.