bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction Model of Solidification Structure for Electroslag Remelting Slab Ingot
Authors: Chang Li Zhong , Shi Xiao Fang
Published: April 2011

The method based on solidification mathematical model and Flemings formula was adopted to simulate electroslag remelting process. The simulation results show that the depth of the molten pool become deeper with increasing of melting speed, and when the ingot gets to the certain height, the system is in the quasi-steady state, the pool shape doesn’t change. With increasing of melting speed, secondary dendrite spacing become wider too and secondary dendrite spacing become wider gradually from the surface to center of ingot if melting speed is const. According to the simulated dendrite spacing, micro-structure of slab ingot is estimated to if meeting the demand of solidification quality, and if it can’t meeting this demand, technological conditions(melting speed)should be modified, and recalculating secondary dendrite spacing, controlling solidification structure.
On the Transitive Closure over Distributive Lattices
Authors: Jiang Jing , Shu Lan , Tian Xin An
Published: April 2011

Since the transitive closure of a lattice matrix can be used to analyze the maximum road of network of traffic control and logistics, the study of the transitive closure of a lattice matrix is valua- ble. A matrix is called a lattice matrix if its elements belong to a distributive lattice. In this paper, the transitivity of powers and the closure of a lattice matrix are studied. Also, an optimal algorithm for co- mputing the transitive closure of a lattice matrix is posed.
Classical-Quantum Correspondence in Two-Dimensional Nanomaterials
Authors: Lu Jun
Published: April 2011

Two-dimensional nanomaterials are becoming the focus of intensive research due to their novel physical properties and the potential applications in nanodevices. We define a quantum spectrum function using the eigenvalues and the eigenfunctions in the system of two-dimensional nanomaterials. We find that the Fourier transform of the quantum spectrum function reveals a lot of information of the classical orbits from one point to another for a particle in the two-dimensional nanomaterials. These results give new evidence about the classical-quantum correspondence. All the methods and results can be used in a lot of other systems, including some one-dimensional and three-dimensional systems. The researches about these systems are very important in the field of applied science.
Design of Limb of 2R2T 4-DoF Symmetrical Parallel Manipulators
Authors: Chen Qiang , Zhou Mu Gui , Zhu Da Chang
Published: April 2011

A systematic methodology is presented for design of 2R2T 4-DoF symmetrical parallel manipulators, based on the screw theory. Through analyse the given constraints of the moving platform, using the screw theory and the reciprocal screw theory. According to the reciprocal product between kinetic screw and constraint screw in screw theory, this method firstly creates possible limb structures and then generates different models of mechanism. enumerate the limb twist system. Based on the limb twist system, design the feasible limb structures and the potentially parallel manipulators.
Stability of Asphalt Binder and Asphalt Mixture Modified by Polyacrylonitrile Fibers
Authors: Yao Li Yang , Hu Yun Peng , Ma Qin , Ma Xian Wei
Published: April 2011

The research was conducted to evaluate pavement properties of polyacrylonitrile fiber asphalt binder and asphalt mixtures, including high temperature stability of binder and mixture, low temperature crack resistance and water stability of mixture. Moreover, polyacrylonitrile fibers were compared with methyl cellulose in the asphalt binder and asphalt mixtures. The result indicates that polyacrylonitrile fibers may improve clearly the high temperature stability of asphalt binder, and pavement performance of mixtures is enhanced obviously. Also polyacrylonitrile fiber binder and mixtures have better performance than methyl cellulose.
The Hydrothermal Synthesis of Nano-YSZ Crystallite and the Preparation of YSZ Electrolyte Film for SOFC
Authors: Fan Bao An
Published: April 2011

The nanometer YSZ can be synthesized by a hydrothermal method. The experimental results of XRD, BET and TEM showed that the hydrothermal powder is pure cubic phase of Y2O3 stabilized ZrO2 with the crystallite size less than 10nm. Using the slurry directly, the YSZ film can be deposited on anode substrate by a dip-coating technique. The Field Emission Scanning Electron Microscope photographs approved that the film has been densified after sintered at 950°C for 5h. The pore diameter distribution experiment confirmed that there not exist aggregates in green film. The nanometer sized crystallite and no aggregates existence endow the YSZ green film with excellent sintering ability. Consequently, the YSZ film can be sintered below 1000°C for the first time.
Birch Carbonization Surface Micrograph and Element Analyses
Authors: Liu Ling , Zhang Shi Xing , Wang Yun
Published: April 2011

There are close relationships between the surface micrograph and element contents of birch and its heating-up temperature. By using the scanning electron microscope (SEM) and the X-ray energy dispersive spectrometer (EDS), the surface micrograph and element contents of birch carbonizations prepared in the simulating fires with different heating-up temperatures were observed and compared. The results show that as the heating-up temperature rises, the surfaces of tracheids gradually become smoother, and the cross sections of tracheids change from circular or ovate shape to polygon. The external films of tracheid fibers are damaged and bordered pits are exposed gradually with the increasing of heating-up temperature. At high temperature, bordered pits change from flat eye-like pores to circular pits, at the same time, the carbon content increases from 52.46% to 90.96%, and the oxygen content decreases from 47.34% to 8.31%, while the potassium and calcium content increase. Thus, the study of connecting wood surface micrographs and element contents with heating-up temperature is useful in fire trace and evidence identification, and the result is meaningful to fire investigation.
Direct Interpolation of Tool Orientation in 5-Axis Milling
Authors: Shen Bin , Qi Dang Jin , Fan Liu Qun , Zhu Zhi Hao
Published: April 2011

By circumference milling with 5-axis machine or machining center has quite the machining efficiency and the surface quality of the products been improved. But when inclined inside surface of cavity is circumference milled with the default linear interpolation of rotation angle algorithm, it results in a serious non-linear error, which takes on over cutting or under cutting, e.g. the inclined plane will be over milled by the machine with dual swivel-head machining center. In order to resolve this problem, the direct interpolation algorithm of tool orientation is developed after analyzing the algorithm of linear interpolation of rotation angles and its non-linear error is. The algorithm is reported and tested with the object of a machine with AB-axis swivel head. The testing results proved that it can resolve the problem of non-linear error.
Numerical Simulation on Rapidly Solidified Melt Spinning CuFe10 Alloys
Authors: Zhou Zhi Ming , Huang Wei Jiu , Deng M. , Cao Min Min , Tang Li Wen , Luo Jing , Li Xiao Ping , Xia Hua
Published: April 2011

The numerical simulation model of single roller rapid solidification melt-spinning CuFe10 alloys was built in this paper. The vacuum chamber, cooling roller and sample were taken into account as a holistic heat system. Based on the heat transfer theory and liquid solidification theory, the heat transfer during the rapids solidification process of CuFe10 ribbons prepared by melt spinning can be approximately modeled by one-dimensional heat conduction equation, so that the temperature distribution and the cooling rate of the ribbon can be determined by the integration of this equation. The simulative results are coincident very well with the microstructure of rapid solidification melt spinnng CuFe10 alloys at three different wheel speeds 4, 12 and 36 m/s.
Phase Field Simulation of Parameters Affecting Dendrite Growth in a Forced Flow
Authors: Yuan Xun Feng , Ding Yu Tian
Published: April 2011

The phase-field model coupled with a flow field was used to simulate the dendrite growth in the undercooled pure metal melt. The effects of flow velocity, supercooling and anisotropy on the dendritic growth were studied. Results indicate that melt flow can enhance the emergence of side-branches, the morphology of the dendrite was composed of the principal branches and side-branches. With an increase in flow velocity and supercooling, the velocity of upstream dendritic tip increases, but the tip radius decreases first and then increases. With an increase in anisotropy values, the velocity of upstream dendritic tip increases and the tip radius decreases. The results of calculation agreed with LMK theory in the case of low flow velocity and anisotropy.
Study on Precision Cutting Titanium Alloy Thin-Walled Parts Based on Finite Element Method
Authors: Wang Ming Hai , Liu Zhong Hai , Wang Hu Jun
Published: April 2011

With the development of aviation and aerospace industry, the performance requirement and part accuracy requirement of aviation engines are increasingly enhanced, and it is difficult to ensure machining accuracy and usage requirement by traditional machining technique. Therefore, the cutting performance and cutting parameter of aviation engine thin-walled parts are researched. Based on FEM (Finite Element Method), simulate cutting of titanium alloy thin-walled parts and analyze the cutting process of a three dimensional model under different cutting parameters so as to obtain the rules of the residual stress and deformation of titanium alloy thin-walled parts. The method referred to in this paper can be used to select the machining parameters of real aero-engine thin-walled, which is helpful to control deformation of workpiece and increase the machining efficiency.
Dynamic Mechanical Properties of Porous Rock under Impact Loading
Authors: Dong Yong Xiang , Xia Chang Jing , Xiao Li Xing , Feng Shun Shan
Published: April 2011

Dynamic impact experiments of man-made rock were carried out with the Split Hopkinson Pressure Bar (SHPB) apparatus in this paper. The impact process was analyzed and the influence of rock porosity on dynamic mechanical behavior was investigated. The stress-strain curves in rock were obtained by the one-dimensional stress wave theory. The curve lays foundation for numeric simulation of rock fracture under impact loading. The damage profiles of rock specimen under the impact loading show that the man-made rock exhibits obvious shear damage under the impact loading because it is a typical porous medium containing large quantities of defects such as pores, cracks and grain boundaries at the microscale. The experimental results also indicated that rock porosity plays an important role in dynamic mechanical behavior.
Solid-State Synthesis and Optical Properties-Controlling Studies of CdO Nanoparticles
Authors: Liu Jin Song , Zhao Chuan Bao , Li Zi Quan , Yu Le , Li Yong Can , Gu Shan Qun , Cao An , Jiang Wei Na , Liu Jian Ning , Yang Cheng Tong
Published: April 2011

CdO nanoparticles with different sizes were synthesized by a simple thermal decomposition reaction of precursor obtained by room-temperature solid-state grinding reaction between Cd(CH3COO)22H2O and NaOH in the presence of PEG400. Composition, structure and morphology of the products were analyzed and characterized by X-ray diffraction technology, Transmission electron microscopy and Fourier infrared spectra. The formation of CdO nanoparticles is thought that the nucleation rate of the reactive system is far excess the growth rate of particle. Optical properties of the products were recorded, and the results show that Ultraviolet-visible (UV-vis) spectra exhibit distinct blue shift in comparison with them of the bulk CdO, which is because that the quantum confinement effect of the products is larger than the Coulomb effect. Photoluminescence (PL) spectra exhibit green and red emission bands around 520 and 720 nm respectively.
Microstructure and Toughening Mechanism of Compressive Fractured Nacre
Authors: An Yuan Lin , Liu Zhi Ming , Wang Gan , Wu Wen Jian
Published: April 2011

Nacre of molluscan shells has evolved through millions of years to a level of perfect microstructure and excellent mechanical properties. Compressive strengths of nacre parallel and vertical to the surfaces of platelets are tested as 420MPa and 500MPa, respectively. The fracture surfaces are characterized by SEM and the fracture processes are analyzed. The toughening mechanism of compressive loading parallel to the aragonite platelet mainly includes cracks deflection, platelets disengagement, platelets crunch, platelet interlock, organic matrix bridging and mineral bridge. Comparably, the toughening mechanism of compressive loading vertical to the aragonite platelet mainly includes platelets crunch, organic matrix deformation and mineral bridges collapse. Additionally, the propagation of crack deflections in compressive loading parallel to the aragonite platelet is different from that in bending fracture of cross section.
The Research of Camellia Oleifera Seed Winnowing Peel Test
Authors: Guo Chuan Zhen , Chen Hong , Yuan Qiao Xia , Ge Liang , Yang Zi Gao
Published: April 2011

On the basis of analyzing the properties of the Camellia oleifera peel and seed, for the purpose of solving the problem of the separation of peel and seed, a device has been designed based on the aerodynamic principles. The single factor experiment has been carried out to research how the feeding angle, feeding height, fan inclination and fan height can influence the seperation. The result shows that the feeding angle has a significantly effect on the separation, the suitable angle is 40°; the feeding height has a significantly effect on the separation; when the feeding height is 200mm, the peel in the seed zone is the least, but the seed in mixing zone is the most, when the feeding height is 300mm, the seed in the mixing zone is the lesat, but the peel in the seed zone is the most, so in the actual production, the feeding height need to be comprehensive considered; the fan inclination has a significantly effect on the separation, the suitable inclination is 15°; the fan height does not have a significant effect on the separation.
The Preparation and Properties Research on Lanthanum-Rich Film Cathode
Authors: Hao Shi Ming , Wang Hui Fang , Zhao Dong Hui
Published: April 2011

The surface lanthanum element plays a key role in emission mechanism of Lanthanum-contained cathodes. In order to gain insight into the relation between cathode emission properties and the cathode surface La/O ratio, lanthanum-rich film cathodes were prepared in situ by using a set of equipment, specially designed to cathode research, which connected with an Auger electron spectrometer (AES) and pulse laser deposition system. Electron emission properties and surface compositions (lanthanum and oxygen) of the cathodes are investigated experimentally. Experiment results indicate that film cathodes are lanthanum-rich film cathode, there has remained unchanged on film composition in different depth; the cathode emission properties are determined intensively by the surface atomic La/O ratios, the higher the La/O ratio gets, the better the emission property reaches. The excess active Lanthanum is crucial element to the improvement of emission properties.
The Microstructure and Erosion Wear Performance of HVOF-Sprayed Cr3C2-NiCr Coatings with Different Feedstock Powder
Authors: Wang Hong Tao , Ji Gang Chang , Chen Qing Yu , Du Xue Fei , Fu Wei
Published: April 2011

In the present study, Cr3C2-NiCr coatings have been deposited using high velocity oxy-fuel (HVOF) system from two commercially available powders with different NiCr contents (25 and 40 wt.%) and manufactured by different process (the blended and agglomerated-sintered). Coating microstructures were studied by scan electron microscopy (SEM). Hardness, erosive wear performance of the two coatings was measurement. The influence of powder characteristics on the microstructure and erosive performance of Cr3C2-NiCr coatings was investigated. The erosion mechanism of Cr3C2-NiCr coatings was examined through the surface morphology of the eroded coatings. The results indicated that Cr3C2-NiCr coating hardness decreased from 822 to 702 Hv with increasing NiCr content from 25 wt.% to 40 wt.%, however, Cr3C2-40NiCr coating exhibits better erosive wear resistance in comparison to Cr3C2-25NiCr coating.
Transient Dynamic Analysis and Optimization of Chamber
Authors: Liu Hui Min , Hou Jian
Published: April 2011

In order to make up the deficiency of traditional design theory, time-dependent load is loaded on chamber, and continuity assumption, homogenization assumption, isotropy assumption, small transmogrification assumption and plane section assumption are made, then transient dynamic analysis is adopted to analysis the chamber’s strength. Analysis result is according to the theoretical calculation perfectly. Based on the analysis result, using maximum compressive stress and the deformation of chamber as constraints, the chamber’s area is optimized. During optimization, the subproblem approximation method is adopted, while local stress concentration, strong charge are not taken into account in optimization process. Optimization result shows the chamber's thickness can be reduced to 1/3 of original. That means the chamber’s weight can be reduced to 1/9 of original. It’s a good base for the optimization of whole barrel to reduce naval gun’s weight.
Study on Blasting Driving Roadway Single Transformation Ejector Auxiliary Ventilation
Authors: Han Jian Yong , Xu Peng
Published: April 2011

Faced with the serious pollution problems of blasting smoke after blasting with the ventilation method based on pressure, using single transformation ejector auxiliary ventilation was raised in the paper, namely ventilation based on pressure was put into use when it was normal, but ejector auxiliary ventilation was used after blasting. The simulation of the condition by fluid analysis software when ejector auxiliary ventilation and ventilation method based on pressure were conducted, and a inclusion was presented that ejector auxiliary ventilation had a good effect on exhausting smoke for the long tunnel with small section, and it has an advantage of shortening exhausting smoke time and less pollution to the roadway, Ventilation can be divided into two phases, when the ejector inlet is submerged in the smoke, smoke is suck out mainly through ventiduct. when the ejector inlet is exposed to fresh air flow, the ejetor assist smoke get out through ventiduct.
The Service Quality Evaluation of Machine Tools in Manufacturing Shop
Authors: Cui Peng Ju , Li Hua
Published: April 2011

Among all the influential factors, the service quality of machine tools is the most important one for workers to decide their machine tools selection in process planning. This paper proposes an evaluation model for service quality of machine tools, aiming to help workers select machine tools on a reasonable basis. An evaluation indicator system of machine tools’ service quality is established based upon a thorough investigation into how the service quality of machine tools manifest themselves. The evaluation indicator system includes the following five aspects: processing cost, processing time, machining precision, green attributes and reliability. The least square method is used to establish an optimization model that determines the weight of indicators based on subjective weight-giving and objective Weight-giving. Finally, a grey relational analysis is conducted to evaluate the service quality of machine tools. Thus we provided an effective decision method for workers to decide their machine tools selection in process planning.
New Delay Dependent Stability Analysis for Switched Neutral Systems with Mode-Dependent Delays under Arbitrary Switching Laws
Authors: Xiong Liang Lin , Wang Xin , Yang Zhu Yuan
Published: April 2011

In this paper, the stability analysis of switched uncertain neutral systems with mode-dependent delays under arbitrary switching rules is presented. Based on common Lyapunov functional, and combined with the analysis of matrix inequalities, the delay dependent stability conditions are obtained in the form of linear matrix inequalities(LMIs)which can be easily solved by LMI toolbox in Matlab. Finally, a numerical example illustrate that the proposed criteria are effective.
The Effect of Micro Arc Oxidation Process Parameters on Surface Properties of Ti6Al4v Alloy
Authors: Gunyuz M. , Baydogan Murat , Çimenoğlu H. , Kayali E.S.
Published: April 2011

This study focuses on the effect of electrolyte concentration of the micro arc oxidation process on the surface morphology of a Ti6Al4V alloy. Micro arc oxidation was performed in “(CH3COO)2Ca.H2O + Na3PO4” containing electrolytes. Micro arc oxidation developed a porous oxide layer mainly consisted of rutile form of titanium oxide on the surface of Ti6Al4V alloy with some calcium titanate (CaTiO3) and Hydroxyapatite. The increase of CH3COO)2Ca.H2O + Na3PO4 concentration of the electrolyte caused disappearance of the pores, reduction of surface roughness and decrease of wettability.
Effect of Tube Bending on Heat Transfer Characteristics of Miniature Heat Pipe with Sintered Porous Media
Authors: Sakulchangsatjatai P. , Thuchayapong N. , Terdtoon P. , Sangsirakoup N.
Published: April 2011

Miniature heat pipe is a compact heat transfer device with very high heat transfer capability. The miniature heat pipes have been widely accepted for thermal management in laptop computer. Generating heat from chip-set is rapidly transferred to a heat sink via the miniature heat pipe which occupies small space, resulting in smaller and more attractive size of the laptop. Heat pipe bending is unavoidable in such small space. However, tube bending decreases thermal performance of heat pipe and it stops working in some cases. In this study, a computer program to simulate heat transfer characteristics of a bending water-copper-sintered-wick heat pipe has been established. Domains of heat pipe consist of three parts; vapor of working fluid in vapor core which transfer heat and mass from evaporator section to condenser section, liquid of working fluid in wick which transfer heat and mass from condenser section to evaporator section in porous media by capillary force, and container wall. In simulation, fluid flow and heat transfer were assumed to be steady, laminar and incompressible. The porous media is saturated with liquid and working fluid is assumed to be Newtonian fluid. The governing equations, i.e. continuity, Navier-Stokes, and energy equations, and boundary conditions were solved by using the Finite Element Method (FEM). Several bending angles (0 and 90; angle measured from straight pipe) with 6 mm outer diameter and 200 mm length were simulated and tested. It was found that the predicted and experimental thermal resistances of heat pipe, when bending angle increases from 0 to 90, increased from 0.47°C/W to 0.65°C/W and 0.67°C/W to 0.88°C/W respectively, due to rising of the vapor pressure drop in vapor channel. The simulation results are in agreement with experimental data with 26-29% error.
Electrical Properties of Nanostructured Titanium Dioxide Thin Films Prepared by Sol-Gel Spin-Coating Method
Authors: Asiah Mohd Noor , Basri Mat Zain , Rusop Mohamad
Published: April 2011

This paper investigated the electrical properties of nanostructured Titanium Dioxide (TiO2) thin films prepared by the sol-gel method at different annealing temperatures. The precursor used was Titanium (IV) butoxide at concentration of 0.4 M. The TiO2 thin films were deposited on the glass and silicon substrates by using the spin coating technique. The influence of annealing temperatures on the electrical, structural, surface morphology and optical properties of the films were characterized by I-V measurement, X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and UV-Vis Spectroscopy, respectively. It was found that the electrical properties of TiO2¬ thin films were changed due to the changes of annealing temperatures. As the annealing temperatures rises, the resistivity of the film found to be decreased. The result also shows that films which does not applied annealing temperature called as deposited were found to be amorphous while the films with annealing temperature T = 350oC and above became crystalline structure. The anatase phase can be obtained at annealing temperatures from T = 350oC up to T = 500oC.
Thermal Shock Damage Evaluation of Porous Refractory by Finite Element Method
Authors: Wang Chong , Jiand Yan Sheng
Published: April 2011

This work addresses damage evaluation of porous mullite refractory subjected to thermal shock. Incommunicating circular pores were distributed randomly at a volume percentage up to 40% in a cylinder of 20 cm diameter. The analysis was performed by means of the software ANSYS® combined with a pre-program that generates randomly distributed pores of given size. The analysis procedure was divided into two stages. In the first, transient thermal analysis considering temperature-dependent material property was dealt with different thermal shock temperatures under natural cooling condition. The following structure analysis ran based on the obtained temperature distribution. The material damage was defined by that the local tensile stress reached to or was over the strength of the refractory. The extent of damage was determined as the ratio of the area of the damaged regions to the section area of the cylinder. The results show that the porosity, thermal shock temperature and cooling time have a high effect on the material damage. The lower the porosity is, the larger the extent of damage. The thermal damage increases with the raise of thermal shock temperature and the cooling time. The damage develops rapidly within 10 minutes but slows down after one hour cooling. The damage difference at high shock temperature stage (≥ 1000°C) is less than at low shock temperature stage. The pore size effect gets into practice only at high shock temperature stage: the damage increases with the raise of the pore size. The present research confirms that high porosity and small pore size could decrease greatly thermal shock damage and should be considered in the micro structural design of refractory.
Synthesis of Supergrowth VACNTs and Nanostructured ZnO by Immerse Method
Authors: Muhamad Salina , Abu Bakar Suriani , Zainizan Sahdan Mohamad , Ahmad Anuar , Siran Yosri M. , Rejab Syahril Anuar M. , Asis Ahmad Jaril , Tahirruddin Syawaluddin , Abdullah Saifollah , Rusop Mohamad
Published: April 2011

In this paper, the study of supergrowth VACNTs after being immersed in zinc oxide solution were presented. Vertically aligned carbon nanotubes (VACNTs) were first deposited on silicon with the orientation of [1 0 0] before being immersed in an aqueous solution of zinc nitrate hexahydrate and hexamethylenetetramine. Physical changes have been observed by scanning electron microscopy, SEM in the VACNTs, where the significant expansion of length of up to almost 0.8 mm was achieved after the immersion of 4.5 hr. The supergrowth of VACNTs was observed and analyzed by energy dispersive x-ray spectroscopy, EDX to substantiate the incorporation of CNTs and ZnO of the sample. Raman spectroscopy and x-ray diffraction, XRD were used to inspect the crystal orientation to support our findings.
Characterization of Interaction Layer in U-Mo-X (X = Nb, Zr) and U-Nb-Zr vs. Al Diffusion Couples Annealed at 600°C for 10 Hours
Authors: Ewh Ashley , Perez E. , Keiser Dennis D. , Sohn Yong Ho
Published: April 2011

U-Mo has thus far proven to be one of the most feasible metallic fuel alloys for use in research and test reactors due to its high density and stability during irradiation. However, an adverse diffusional interaction can occur between the fuel alloy and the Al based matrix. This forms an interaction layer (IL) that has undesirable thermal properties and irradiation behavior leading to accelerated swelling and reduced fuel efficiency. This study focused on the effects of ternary alloying additions on the formation of IL between U based alloys and Al. Diffusion couples of U-8Mo-3Nb, U-7Mo-6Zr, and U-10Nb-4Zr (wt.%) vs. pure Al were assembled and annealed at 600°C for 10 hours. Both thickness and phase constituent analyses were performed via electron microscopy. The major phase constituent of the IL was determined to be the UAl3 intermetallic compound. The Nb and Zr alloying additions did not reduce growth rate of IL (1.3~1.4 m/sec1/2) as compared to couples made between binary U-Mo and Al (0.9~1.8 m/sec1/2).
Design of Multifunctional Truss-Like Periodic Materials Using a Global-Local Optimization Method
Authors: Muñoz-Rojas Pablo A. , Luersen M.A. , Carniel T.A. , Bertoti E.
Published: April 2011

Porous materials have gained wide use in high level engineering structures due to their high stiffness/weight ratio, good energy absorption properties, etc. Frequently, thermal behavior is also an issue of concern and optimized multifunctional thermo-mechanical responses are sought for. This paper presents the application of a hybrid two-stage method for achieving an optimized layout of periodic truss-like structures in order to obtain a good compromise between thermal and mechanical elastic properties. The first stage employs a derivative free optimization method, which explores the design space, not getting trapped by local minima. The second stage uses a derivative based optimization algorithm to perform a refinement of the solution obtained in the first stage.
Diffusion and Electrophoretic Transport of DNA Polymers in Microfluidic Channels Made of PDMS
Authors: Sczech Ronny , Howitz Steffen , Mertig Michael
Published: April 2011

DNA molecules can be transported through microchannels with help of electrophoresis and flow. Confinement of DNA molecules leads to elongation of their unconstrained equilibrium configuration when passing the microchannel. Application of electrical fields reduces the mobility and entails DNA trapping because of high gradients of the field due to a decrease in the channels’ magnitude. Microfluidic channels in polydimethylsiloxane (PDMS) were formed by soft replica molding technology combining micro- and nanofluidic features. The applicability of the hybrid micro- and nanofluidic PDMS structures for single molecule observation and manipulation was demonstrated by introducing single molecules of λ-DNA into the channels using optimized conditions for the applied potential and flow.
Review of Several Studies on High Temperature Oxidation Behaviour and Mechanism of Austenitic Stainless Steels
Authors: Fujikawa Hisao
Published: April 2011

Three studies on the oxidation behaviour of austenitic stainless steels were described in the present paper. (1) High temperature oxidation behaviour and its mechanism in austenitic stainless steels with high silicon: Sulfur contained as impurity in steel showed a harmful influence to the oxidation resistance of 19Cr-13Ni-3.5Si stainless steels. It was found that the abnormal oxidation was caused from the surroundings of MnS inclusions. (2) Effect of a small addition of yttrium on high temperature oxidation resistance of Si-containing austenitic stain less steels: The oxidation resistance of 19Cr-10Ni-1.5Si steels was improved remarkably even with only 0.01%Y addition, which is the same concentration as added for de-oxygenation. Y was enriched at the grain boundary of oxide scale and metal-oxide interface. It was suggested that Y-containing steels shoed good oxidation resistance, because the enriched Y at the grain boundary and metal-oxide interface prevented the diffusion of iron and oxygen ions through the oxide scale. (3) Effect of grain size on the oxidation behaviour of austenitic stainless steels: Type 304, 316 and 310 steels with finer grain size showed better oxidation resistance than those with coarser grain size at 850°C. The oxide scale of steels with coarser grain size easily spalled during the cooling process.
Hydrogen-Induced Superabundant Vacancies in Metals: Implication for Electrodeposition
Authors: Fukai Yuh
Published: April 2011

The equilibrium concentration of vacancies in metals is invariably enhanced in the presence of interstitial hydrogen atoms – a phenomenon called superabundant vacancy (SAV) formation. It has been recognized that the SAV formation occurs in electrodeposition, as M-, H-atoms and M-atom vacancies are deposited by atom-by-atom process. Effects of SAV formation are described for electrodeposited Ni, Ni-Fe alloys, Fe-C alloys and Cu. Possible implication of SAV formation for corrosion in Al and steels is also briefly described.
Modern Models of Grain Boundary Diffusion
Authors: Popov Vladimir V.
Published: April 2011

Recent models of grain-boundary diffusion are briefly reviewed. Models of diffusion along equilibrium boundaries of recrystallization origin in coarse-grained materials and along non-equilibrium boundaries in nanocrystalline materials obtained by gas condensation and compacting or by severe plastic deformation are considered separately.
Optimisation of Envelope Insulation for the Retrofit of an Educational Building
Authors: Ramos N.M.M. , Ribeiro I.M. , Santos P. , Delgado João M.P.Q. , de Freitas V.P.
Published: April 2011

This paper presents ongoing work for the definition of an optimal design strategy for retrofitting educational buildings. The term “optimal design” refers to the selection of different retrofitting solutions to ensure an energy efficient building that can be developed which will not compromise hygrothermal comfort, indoor air quality, health and durability. In this paper, a selection model of thermal insulation thickness of envelope elements is developed, aiming the control of surface condensation and upgrade of hygrothermal comfort. The mathematical formulation of this model leads to a nonlinear program with linear objective function. The software Gmas/Minos was chosen to solve the optimization problem and to develop a calculation program to solve this specific application. The software Energy-Plus developed by the US Department of Energy was used to simulate hygrothermal performance of the building, providing results for a comparison with the developed simulation tool. The paper presents an example of an optimal design problem for a specific classroom of a retrofit educational building.
Water Vapour Adsorption Study in Spherical Particles Packed in a Cylindrical Container
Authors: Delgado João M.P.Q. , Vázquez da Silva M.
Published: April 2011

In this work the water vapour adsorption was studied, during the initial states of absorption, for different piles of granules held in a cylindrical container. A diffusion model was presented for the description of the physical phenomenon whereby water vapour penetrates along the piles of cylindrical pores. The differential mass balance equation was solved numerically using a finite-difference method. The numerical solutions were tested through the measurement of water vapour mass uptake for different piles of silica gel and breakfast cereals (popcorns), being observed that they are in good agreement with the experimental values.
Performance and Modelling of Water Vapour Adsorption in Piles of Granules Using a Cylindrical Pore Model
Authors: Delgado João M.P.Q. , Vázquez da Silva M.
Published: April 2011

This paper describes the application of the cylindrical pore model to the study of water vapour adsorption in piles of spherical particles packed in cylindrical containers. The differential mass balance equations were solved numerically using a finite-difference method and the numerical solutions obtained were in good agreement with the experimental data. The experiments were carried out through the measurement of water vapour mass uptake for different piles of silica gel and popcorns (breakfast cereals).
Studies of Ionic Conductivity and Dielectric Behavior in Polyacrylonitrile Based Solid Polymer Electrolytes
Authors: Osman Zurina , Isa Khairul Bahiyah Md. , Othman Lisani , Kamarulzaman Norlida
Published: April 2011

The solid polymer electrolyte films consisting of polyacrylonitrile (PAN) as the host polymer, lithium triflate (LiCF3SO3) and sodium triflate (NaCF3SO3) as dopant salts were prepared by the solution cast technique. The pure PAN film was prepared as a reference. The films were characterized using a.c. impedance spectroscopy. At room temperature, the highest conductivity for the sample from the (PAN+LiCF3SO3) system and the (PAN+NaCF3SO3) system is 3.04 x 10-4 Scm-1 and 7.13 x 10-4 Scm-1, respectively. The temperature dependence of ionic conductivity for the highest conducting film from both systems follows the Arrhenius equation in the temperature range of 303 K to 353 K. The frequency dependence of ionic conductivity, , complex permittivity, *, and complex electrical modulus, M* were studied at different temperatures. The ionic conductivity and the dielectric behavior are described in terms of ion diffusion and polarization.
Mathemathical Model of Powder Sintering with Nano- and Microadditives
Authors: Ignatiev I.E. , Bulanov V.I. , Dmitriev Andrey N.
Published: April 2011

One of the problems of powder metallurgy still remaining is the problem of billets shrinkage at sintering. Introduction of a small impurity coating consisting of a very thin layer of the particles on the basic powder is a known method of compacting at sintering of powder materials. The mathematical modeling of such a process encounters ambiguity some issues of the sintering theory of metal powders, therefore forcedly leans on experiments. A mathematical model of powder metal sintering with nano- and microadditives is presented.
Comparison of Ionic Diffusion in Sol-Gel Derived Micron and Nano LiTaO3
Authors: Kamarulzaman Norlida , Widarti Zainudin Lili , Yahaya Subban Rihanum , Osman Zurina
Published: April 2011

LiTaO3 is an important optical material. It may also be possible to use this material as a solid electrolyte for lithium-ion batteries which may be applicable in thin film solid-state batteries. Generally, ceramics have a wide range of impedances. Many ceramics have mixed charged species consisting of electronic as well as ionic charge carriers. This work investigates the conductivity of LiTaO3 materials using ac impedance spectroscopy technique measured as a function of temperature.
Oxygen Diffusion in an Nb-Ta Alloy Measured by Mechanical Spectroscopy
Authors: Grandini Carlos Roberto , de Almeida Luciano Henrique , Rodrigues Júnior Durval
Published: April 2011

When metals that present bcc crystalline structure receive the addition of interstitial atoms as oxygen, nitrogen, hydrogen and carbon, they undergo significant changes in their physical properties because they are able to dissolve great amounts of those interstitial elements, and thus form solid solutions. Niobium and most of its alloys possess a bcc crystalline structure and, because Brazil is the largest world exporter of this metal, it is fundamental to understand the interaction mechanisms between interstitial elements and niobium or its alloys. In this study, mechanical spectroscopy (internal friction) measurements were performed on Nb-8.9wt%Ta alloys containing oxygen in solid solution. The experimental results presented complex internal friction spectra. With the addition of substitutional solute, interactions between the two types of solutes (substitutional and interstitial) were observed, considering that the random distribution of the interstitial atoms was affected by the presence of substitutional atoms. Interstitial diffusion coefficients, pre-exponential factors and activation energies were calculated for oxygen in this alloy.
Diffusion Layers with Ti and Ti+Al Formed on 316L Austenitic Steel by a Pack Cementation Procedure
Authors: Britchi Iulia Mirela , Olteanu Mircea , Ene Niculae , Nita Petru
Published: April 2011

Pack cementation procedure implies the use of a powder mixture containing the diffusive elements, which in our case are either Ti or Ti+Al, Al2O3 and NHCl as activator. In the case of titanizing the powder mixture contained 77% in weight Ti, while for alumino-titanizing Al/Ti = 1/5 ratio was employed. NH4Cl content was 3% in weight in all cases. Aluminium additions to the powder mixtures led to a decrease of the process temperature. Activation energy for the aluminizing of austenitic 316L steel is 73.87 KJ/mol, much smaller than for the titanizing, 257.86 KJ/mol. Activation energy for alumino-titanizing, in the same conditions, is 146.01 KJ/mol. All diffusion coatings, in the Ti – 316L and Ti+Al – 316L couples are formed of two layers having different structures and compositions. All couples were investigated by optical microscopy, electron microscopy (SEM and EDX), X-ray diffraction and microhardness trials.
Determination of PBP by Using a Nano SiO2/GC Modified Electrode
Authors: Shokuhi Rad A.
Published: April 2011

Recently, several metal oxide nanomaterials have been deposited on the surface of electrodes and investigated for the reduction/ oxidation and detection of some biological materials. Electrochemical Sensors with high surface area and porosity are important components in an irresistible wealth of systems for various applications. An electrochemical sensor for the sensitive determination of parabromophenol (PBP) was synthesized based on the nano-SiO2 film-modified electrode. Owing to the exceptional properties of nano-SiO2 such as successfully minimized transport limitations, huge surface area, strong adsorptive ability, subtle electronic properties and catalytic ability, the electrochemical oxidation signal of PBP significantly increases at the nano- SiO2/GC electrochemical sensor, suggesting that nano-SiO2 film exhibits obvious enhancement effect to the determination of PBP. Based on this, a sensitive electrochemical method was developed for the determination of PBP.
Diffusion of Hydrogen in Amorphous Ni-Zr Alloys
Authors: Pastukhov E.A. , Sidorov N.I. , Vostrjakov A.A. , Chentsov V.P.
Published: April 2011

Amorphous alloys Ni64Zr36 and Ni36Zr64 structure and hydrogen mobility are researched by the molecular dynamics method. The analysis of structure factors and partial distribution functions of atoms revealed hydrogen affects the short order parameters of the disordered systems. Diffusion coefficients of hydrogen are shown to depend on its concentration.
Polyol-Mediated Synthesis of TiO2 Nanoparticles
Authors: Kang Jung Won , Kim Dong Han , Mathew Vinod , Gim Ji Hyeon , Yu Insun , Woo Chul Hong , Kim Eun Joung , Choi Cheol Hoon , Kim Jae Kook
Published: April 2011

TiO2 nanoparticles were synthesized from a triethylene glycol solution of titanium isopropoxide (Ti(O-iPr)4) by refluxing at 270°C for 12 hrs. The as-prepared sample was heated at 600 °C for 3 hrs in order to study the thermal stability of the sample. The X-ray diffraction patterns of the samples were well indexed to the anatase phase. The field emission TEM images show uniform spherical morphologies with average sizes of 25 nm. The electrochemical measurements revealed that the discharge capacities of the heated sample exhibited high capacities and good rate performances without capacity fading during extended cycles, due to their electrochemically beneficial highly crystalline structures, nano-sized particles, and uniform distribution.
Phase and Amplitude Control of Optical Properties of Quantum Dot Molecules
Authors: Mahmoudi Mohammad , Goharshenasan Sahar
Published: April 2011

We investigate the optical properties of a weak probe field in an asymmetry semiconductor double QDs system. We apply a coupling and a probe field to the system and it is shown that in the presence of interdot tunneling, the dispersion and absorption properties of the system can be controlled by the amplitude and relative phase of applied fields. Moreover, it is demonstrated that just by changing the relative phase of applied fields, the slope of dispersion is changed from positive to negative, corresponding to the superluminal light propagation.
Experimental and Theoretical Research of the Shell Side Heat Transfer Coefficient and Pressure Drop in a Plastic Shell and Tube Heat Exchanger
Authors: Osorio Rita Aguilar , Cliffle K.
Published: April 2011

The aim of this work is to present an experimental research of the shell side heat transfer coefficient and pressure drop in a plastic shell and tube heat exchanger with single segmental baffle. The tube bundle consisted of 110 U-tubes constructed of high-density polyethylene, the inside diameter was 9.2 mm, the tube pitch was 1.5 the out side diameter. The shell was constructed of polypropylene with a diameter of 315 mm. Shell side heat transfer coefficients and pressure drop were determined varying the flow rates. An experimental rig for the experimental research was designed and constructed. The overall experimental rig consisted of two operation cycles. The two fluids used in this system were hot and cold water. The experimental results were compared with theoretical predictions using the Bell-Taborek and Wills and Johnston Methods. The heat transfer coefficient predictions, for Reynolds number greater than 780, showed that the Bell-Taborek and Wills-Johnston methods are in general agreement with the experimental data with only 5% difference, Wills-Johnston overpredicts it and Bell underpredicts it, except at the lower Reynolds number than 780 where there was an average underprediction of 15%. The pressure drop predictions by Wills-Johnston and Bell-Taborek methods were generally acceptable including the inlet and outlet nozzles with the highest experimental data (Reynolds number greater than 780) within a 15% overprediction, however, at the lower data the pressure drop was overpredicted up to 2 times the measured values.
Raman Spectroscopy: Mutual Diffusion Coefficient in Hydrogels
Authors: Naddaf A.A. , Bart H.J.
Published: April 2011

A hydrogel kept at its equilibrium swelling state during taking the measurements controlled in a diffusion cell. The diffusion data gained from Raman spectra were analyzed to calculate the mutual diffusion coefficient in the hydrogel as semi-infinite medium. The relation between the solute concentration and Raman intensity for poly(N-isopropylacrylamide), which is characterized by the distinct peak for the isopropyl group at 2925 cm-1 was taken into account. The determination of the mutual diffusion coefficient, Dmut for hydrogels/phenol system was achieved successfully using confocal Raman spectroscopy at different solute concentrations. At 25oC, the value of the mutual diffusion coefficient is found between 5.61845x10-11 m2/s and 3.34565x10-9 m2/s for the hydrogel loaded with phenol of an initial concentration of 0.01 mM and 0.1 mM, respectively.
Characterization of Nickel Based Alloys (Hard Facing Alloys) with Additions of Ti and Mo
Authors: Khenfer K. , Lebaili Soltane , Hamar-Thibault S.
Published: April 2011

The mechanical engineering industry is always in the search of new hardfacing alloys which nowadays make it possible to solve considerable delicate problems of abrasive wear and corrosion. These alloys are heterogeneous materials and are generally composed of a ductile matrix and a significant proportion in hard phases (carbides, borides or silicides), which give a good wear resistance and corrosion. The following studies made on alloys containing Ni, rich in Silicon and tungsten. We noted that addition of these elements (Si and W) got interesting mechanical properties. The alloys that we chose for this study contain the elements C, B, Si, Cr and W with additions in Ti and Mo. The aim of this work is the characterisation of the various phases formed during solidification, to study chemical affinities in this system poly-constitutes and to make a correlation between the chemical composition, the conditions of development and the microstructures obtained.