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This paper presents a thin plate formulation with nodal integration for bending analysis using three-node triangular cells and linear interpolation functions. The formulation was based on the classic thin plate theory, in which only deflection field was required and dealt with as the field variables. They were assumed to be piecewisely linear and expressed using a set of three-node triangular cells. Based on each node, the integration domain has been further derived, where the curvature in the domain was computed using a gradient smoothing technique (GST). As a result, the curvature in each integration domain is a constant whereby the deflection is compatible in the whole problem domain. The generalized smoothed Galerkin weak form is then used to create the discretized system equations where the system stiffness is obtained using simple summation operation. The essential rotational boundary conditions are imposed in the process of constructing the curvature field in conjunction with imposing the translational boundary conditions in the same way as undertaken in the standard FEM. A number of numerical examples were studied using the present formulation, including both static and free vibration analyses. The numerical results were compared with the reference ones together with those shown in the state-of-art literatures published. Very good accuracy has been achieved using the present method.

A complex product often requires a high machining precision. This is often achieved by a close-loop machining process to be carried out in several stages, and the measurements, fixture adjustments, and feedback or feed-forward control are inserted after each of these stages. The Complex Product Machining Process (CPMP) Capability Index (CPMPCI) is affected by the control and adjustments in a CPMP, and hence the calculation results of CPMPCI can be used as references to select a proper CPMP. In this paper, we present a novel calculation method of CPMPCI as quality control and improvement technology in a CPMP. A linear model is proposed for describing the variation propagation effect throughout all stages in a CPMP, and an observation model with the pre-specified control and adjustment strategy is employed to calculate the process mean and variation during a CPMP. Finally, through application of Taguchi's quality loss function, the CPMPCI calculation method is derived. The feasibility and effectiveness of t...

In this paper, basis functions generated from B-spline or Non-Uniform Rational B-spline (NURBS), are used for approximating the boundary variables to solve the 3D linear elasticity Boundary Integral Equations (BIEs). The implementation is based on the BFM framework in which both boundary integration and variable approximation are performed in the parametric spaces of the boundary surfaces to keep the exact geometric information in the BIEs. In order to reduce the influence of tensor product of B-spline and make the discretization of a body surface easier, the basis functions defined in global intervals are translated into local form. B-spline fitting function built with the local basis functions is converted into an interpolation type of function in which the nodal values of the boundary variables are used for control points. Numerical tests for 3D linear elasticity problems show that the BFM with B-spline basis functions outperforms that with the well-known Moving Least Square (MLS) approximation.

Both nanocrystalline and amorphous phases are observed from the near surface of nickel titanium shape memory alloy (NiTi SMA) with the B2 austenite phase after surface mechanical attrition treatment (SMAT). The microstructure and phase changes are systematically studied by cross-sectional and plane-view transmission electron microscopy. The strain induces grain refinement and it is accompanied by increased strain in the surface layer triggering the onset of highly dense dislocations and dislocation tangles (DTs), formation of the martensite plate via stress-induced martensite (SIM) transformation (B2 to B19′), and dislocation lines (DLs) as well as dense dislocation walls (DDWs) inside the martensite plate leading to the subdivision of the martensite plate. In addition, reverse martensite transformation (B19′ to B2) and amorphization take place concurrently in the surface region, and successive subdivision and amorphization finally result in the formation of well separated nanocrystalline and amorphous phases in the near surface. The average grain size of the nanocrystallites is about 20 nm. Owing to the almost complete reverse martensite transformation as well as thermal stability, the strain-induced nanocrystalline structure has the B2 austenite phase in the surface layer and no transformation occurs.

In this paper, bending and vibration analysis of laminated composite plates is carried out using a novel triangular composite plate element based on an edge-based smoothing technique. The present formulation is based on the first-order shear deformation theory, and the discrete shear gap (DSG) method is employed to mitigate the shear locking. The smoothed Galerkin weak form is adopted to obtain the discretized system equations, and edge-based smoothing domains are used for the numerical integration to improve the accuracy and the convergence rate of the method. The present formulation is coded and used to solve various example problems of bending and free vibration of laminated composite plates. It is found that the present method can provide excellent results with a wide range of thickness and is free of shear locking.

A general numerical method is proposed to compute nearly singular integrals arising in the boundary integral equations (BIEs). The method provides a new implementation of the conventional distance transformation technique to make the result stable and accurate no matter where the projection point is located. The distance functions are redefined in two local coordinate systems. A new system denoted as (α,β) is introduced here firstly. Its implementation is simpler than that of the polar system and it also performs efficiently. Then a new distance transformation is developed to remove or weaken the near singularities. To perform integration on irregular elements, an adaptive integration scheme is applied. Numerical examples are presented for both planar and curved surface elements. The results demonstrate that our method can provide accurate results even when the source point is very close to the integration element, and can keep reasonable accuracy on very irregular elements. Furthermore, the accuracy of our method is much less sensitive to the position of the projection point than the conventional method.

In this paper, a meshless natural neighbour Petrov–Galerkin method (NNPG) is presented for a plate described by the Mindlin theory. The discrete model of the domain Ω consists of a set of distinct nodes N, and a polygonal description of the boundary. In the NNPG, the trial functions on a local domain are constructed using natural neighbour interpolation and the three-node triangular FEM shape functions are taken as test functions. The natural neighbour interpolants are strictly linear between adjacent nodes on the boundary of the convex hull, which facilitate imposition of essential boundary conditions. The local weak forms of the equilibrium equations and the boundary conditions are satisfied in local polygonal sub-domains in the mean surface of the plate. These sub-domains are constructed with Delaunay tessellations and domain integrals are evaluated over included Delaunay triangles by using Gaussian quadrature scheme. Both elasto-static and dynamic problems are considered. The numerical results show the presented method is easy to implement and very accurate for these problems.

The isothermal oxidation behavior of Ti-45Al-8Nb and Ti-52Al-8Nb alloys at 900 °C in air was investigated. The early oxidation behaviors were studied by using XPS and AES. And the microstructure and the composition of the oxidation scale were studied by using XRD and SEM. The results show that the oxidation behavior of TiAl alloy is significantly improved by Nb addition. Nb substitutes for Ti in TiO 2 as a cation with valence 5, and thus to suppress TiO 2 growth. The (Ti,Nb)O 2 -rich layer is a dense and chemically uniform which is more protective than the TiO 2 layer. Nb addition also lowers the critical Al content to form an external alumina. Nb 2 Al phase is formed in the metallic matrix at the oxide–metal interface on the high Nb containing TiAl alloys.

An ultrafine grain layer consisting of nanocrystallites as well as submicrometer grains is produced on NiTi shape memory alloy by surface mechanical attrition treatment (SMAT) and the effects of the ultrafine grain layer on the tribological properties are investigated under dry sliding conditions. Compared to the coarse grain (CG) NiTi, the SMAT NiTi has smaller friction coefficients and improved wear resistance at applied loads from 5 to 15 N due to the grain refinement effect. Examination of the worn surfaces indicates that materials delamination and particles co-exist on both the CG and SMAT NiTi samples. Our results indicate that delamination is the main wear mechanism on CG NiTi whereas abrasive particles dominate the wear process on SMAT NiTi.

Influence of Y addition on the long time isothermal and cyclic oxidation behaviors of Ti45Al8Nb alloys containing 0.1–1.0 at.% Y with full lamellar microstructure was investigated in air at 900 °C. Only a proper amount of Y addition (0.3 at.%) can improve the long time oxidation resistance under both isothermal and cyclic oxidation. Either excessive or deficient addition of Y was detrimental to the oxidation resistance. Under isothermal oxidation, much thinner oxide scale was formed on 0.3 at.% Y-added alloy than it on Y-free alloy. Meanwhile, Y addition can effectively suppress the outmost TiO 2 layer and enhance the protective Al 2 O 3 layer on the sample surface. Under cyclic oxidation, different from the oxide scale formed on Y-free and Y-lean (0.1 at.%) alloys, the oxide scales on higher Y-added alloys were not typical layered structure and oxide pegs protruding into the substrate were formed at the oxide scale/substrate interface. As a result, no spallation was observed in the higher Y-added alloys even after 1000 cycles while spallation occurred on Y-free alloy after 280 cycles and 0.1 at.% Y added alloy after 460 cycles. However, high Y added alloys (>0.3 at.%) suffered severe internal oxidation. Therefore, the oxidation rate on high Y added alloys was significantly high.

In automotive industry, structural optimization for crashworthiness criteria is of special importance in the early design stage. To reduce the vehicle design cycle, metamodeling techniques have become so widespread... In this study, a time-based metamodeling technique is proposed for the vehicle design. The characteristics of the proposed method are the construction of a time-based objective function and establishment of a metamodel by support vector regression (SVR). Compared with other popular metamodel-based optimization methods, the design space of the proposed method is expanded to time domain. Thus, more information and features can be extracted in the expanded time domain. To validate the performance of the time-based metamodeling technique, cylinder impacting and full vehicle frontal collision are optimized by the proposed method. The results demonstrate that the proposed method has potential capability to solve the crashworthiness vehicle design.

A cell-based smoothed radial point interpolation method (CS-RPIM) based on the generalized gradient smoothing operation is proposed for static and free vibration analysis of solids. In present method, the problem domain is first discretized using triangular background cells, and each cell is further divided into several smoothing cells. The displacement field function is approximated using RPIM shape functions which have Kronecker delta function property. Supporting node selection for shape function construction uses the efficient T2L-scheme associated with edges of the background cells. The system equations are derived using the generalized smoothed Galerkin (GS-Galerkin) weak form, and the essential boundary conditions are imposed directly as in the finite element method (FEM). The effects of the number of divisions smoothing cells on the solution properties of the CS-RPIM are investigated in detail, and preferable numbers of smoothing cells is recommended. To verify the accuracy and stability of the present formulation, a number of numerical examples are studied to demonstrate numerically the efficiency of the present CS-RPIM.

A typical fan desulphurization measuring points (failure-prone region), according to measurement data on many occasions, its failure to find the development trend of the equipment malfunction and made more accurate judgments. At the same time, the preparation of the equipment, the corresponding vibration diagnostic criteria and common fault identification intelligent system and continuously updated to facilitate site inspection personnel equipment vibration condition monitoring work and improve their equipment to grasp the operation of the accuracy and efficiency.

In this paper, an edge-based smoothed finite element method (ES-FEM) is formulated for stress field determination of elastic–plastic problems using triangular meshes, in which smoothing domains associated with the edges of the triangles are used for smoothing operations to improve the accuracy and the convergence rate of the method. The smoothed Galerkin weak form is adopted to obtain the discretized system equations, and the numerical integration becomes a simple summation over the edge-based smoothing domains. The pseudo-elastic method is employed for the determination of stress field and Hencky's total deformation theory is used to define effective elastic material parameters, which are treated as field variables and considered as functions of the final state of stress fields. The effective elastic material parameters are then obtained in an iterative manner based on the strain controlled projection method from the uniaxial material curve. Some numerical examples are investigated and excellent results have been obtained demonstrating the effectivity of the present method.

In this work, a hybrid fuzzy regression-based metamodeling technique is proposed to optimize the sheet metal forming design. Compared with other metamodeling techniques, the distinctive character of the proposed approach is to consider uncertainties and certainties in one metamodel. In order to further improve the efficiency of optimization, an intelligent scheme is incorporated to generate samples at the stage of design of experiment. Additionally, one step and incremental FE forming methods are implemented to calculate values of response functions. Finally, the proposed metamodeling technique and sampling schemes are integrated and applied to optimize sheet forming design; the corresponding optimized results demonstrate that the proposed hybrid metamodeling technique is able to produce good approximation model of sheet metal forming system.

In the present paper, a Kriging-based metamodeling technique is used to minimize the risk of failure in a sheet metal forming process. The Kriging-based models are fitted to data that are obtained for larger experimental areas than the areas used in low-order polynomial regression metamodels. Therefore, computational time and memory requirement can be an obstacle for Kriging for data sets with many observations. To improve the usability of the Kriging-based metamodeling techniques, a parallel intelligent sampling approach: boundary and best neighbor searching (BBNS) (Wang et al., J Mater Process Technol 197(1–3):77–88, 2008a) is suggested. Compared with the serial BBNS version, the sampling procedure is performed synchronously. Thus, larger sample size should be considered for real-life problems when multiple processors are available. Furthermore, the parallel strategy is prone to converge based on more samples. The performance of the parallel approached is verified by means of nonlinear test functions. Moreover, the drawbead design in sheet metal forming is successfully optimized by the parallel BBNS approach and Kriging metamodeling technique. The optimization results demonstrate that the parallel BBNS approach improves the applicability of the Kriging metamodeling technique substantially.

A meshless local radial point interpolation method (LRPIM) for the bending and free vibration analysis of a nonhomogeneous moderately thick plate is presented in this paper. It uses a radial basis function coupled with a quadratic polynomial basis function as a trail function and a quartic spline function as a test function of the weighted residual method. The shape functions obtained in the trail function have the Kronecker delta function property, and the essential boundary conditions can be easily imposed. The present method is a true meshless method as it does not need any grids and all integrals can be easily evaluated over regularly shaped domains and their boundaries. In computational procedures, variations of material properties in the considered domain are modelled by adopting proper material parameters at Gauss points in integrations. Examples show that results obtained by the presented method are found to agree well with the existing solutions in the literature and with the results obtained by the finite element method, and the presented method has a number of advantages, such as high efficiency, quite good accuracy and easy implementation.

The least square support vector regression (LS-SVR) metamodel technique is proposed for sheet metal forming optimization. The major advantage of proposed approach is to build metamodel by consideration of empirical risk minimization (ERM) and structure risk minimization (SRM). In order to construct robust and accurate metamodel based LS-SVR, suitable quantity and intervals of samples are recommended. Thus, a parallel intelligent sampling scheme based on a boundary and best neighbor searching method (BBNS) is proposed to improve the efficiency and accuracy of metamodel. The BBNS was suggested and corresponding practical engineer problems were successfully solved by Hu and Li [Hu W, Li GY, Zhong ZH. Optimization of sheet metal forming processes by adaptive response surface based on intelligent sampling method. J Mater Process Technol 2008;197(1–3):77–88; Hu Wang, Li GY, Li Enying, Zhong ZH. Development of metamodeling based optimization system for high nonlinear engineering problems. Adv Eng Software 2008;39(8)629–45]. To increase the efficiency of metamodel based optimization method, the parallel architecture is implemented for BBNS due to its drawbacks. For validation of developed method, both of serial and parallel BBNS scheme are applied for the nonlinear function. The parallel BBNS is also verified to be an accuracy and efficiency scheme. Finally, the practical nonlinear engineering problems are optimized by suggested methodology and satisfied results are also obtained.

Temperature characteristics and thermal resistance of InGaAs/GaAs laser diode (LD) is investigated from below to beyond the lasing threshold. Spectrally-resolved emission measurements show that the heat generated in the active region is induced by the radiative energy transfer of free carriers. Below the lasing threshold, nonradiative recombination induces large heat generation in the active region. Beyond the lasing threshold, Joules heating due to the series resistance of the LD dominates the heating response. The dependence of the associated thermal resistance on different bonding configurations and its correlation with the output power is also discussed. Epi-side up and epi-side down bonding of LDs reduces the device temperature by ~ 30% and ~ 50%, respectively.

A metamodeling optimization system for nonlinear problems was developed in this study. Boundaries and best neighbors searching (BBNS) intelligent sampling method and fuzzy based progressive metamodeling for space reduction were integrated and applied for this system. The BBNS scheme generates new samples derived from information of boundaries and the best samples of initial sparse distributed samples. It is easy to obtain better samples and avoid local convergence due to boundary information. In order to construct accuracy metamodel, the fuzzy based progressive metamodeling method was implemented to cluster samples generated by BBNS several patches in optimization domain. Only better sets of them are involved in construction of metamodels in each patch by response surface and kriging method. The nonlinear problems with multi-humps as test functions were used for proving accuracy and efficiency of developed system. The practical nonlinear engineering problems were also successfully optimized by this system.

A series of cyclic deformation and subsequent aging treatments at room temperature were performed on ultrafine-grained Cu processed by equal-channel angular pressing in order to investigate their influences on tensile properties. It was found that a combination of both high strength and good ductility can be achieved by means of cyclic deformation together with aging treatments. The microstructure analysis gave the explanations for these phenomena.

A modified face-down bonding technique of ridge-waveguide laser diodes (LDs) using 80Au20Sn solder has been performed. For ease of manufacturability, a bonding window with good bonding integrity and improved optical performance was determined. Metallographical investigation showed that the solder joint comprised of a layer of delta phase compound near the solder/heatsink interface, a layer of (Au,Ni)Sn intermetallic compound (IMC) at the solder/heatsink interface, and zeta' phase Au/Sn compound at the center of the solder joint. The delta phase shifted to the interfaces after reflow was postulated by its lower surface tension than zeta' phase Au/Sn compound. Good bonding integrity was observed with LD residues still adhering onto the bond pad after die shear testing. Scanning electron microscopy (SEM)/energy dispersive X-ray (EDX) analyses of the fracture surface showed that the fracture occurred within the LD, at the GaAs/SiN interface. LDs bonded with this modified bonding process achieved an optical improvement of 2.5-3X compared to the unbonded LDs due to its good thermal management. These bonded LDs further exhibited good long-term reliability with no significant degradation in optical performance and no significant microstructure evolution in the solder joint after 500 thermal cycling test.

Laser diodes (LD) are usually bonded onto heat sinks for the purposes of heat dissipation, mechanical support and electrical interconnect. In this study, energy dispersive X-ray analysis (EDX) and electron backscatter diffraction (EBSD) are employed to investigate the microstructure evolution of 80Au/20Sn solder joint in LD package. During reflow, Pt-Sn and (Au, Ni)Sn IMCs were formed at the respective LD/solder and solder/heatsink interfaces, while ?, ? and ?' phases of Au/Sn intermetallics were found in the solder joint. The Au-rich ? and ?' phases in the solder joint limit the growth of interfacial IMCs. Chip shear testing showed that the failure occurred within the LD, with partial brittle fracture at the GaAs substrate and partial interfacial delamination at the GaAs/SiN interface. The strong solder bond can be attributed to the high mechanical strength of 80Au/20Sn solder, which provides improved stability for high temperature applications.

In this study, the thermomechanical behaviour of a magnesium alloy AZ31B during extrusion through a porthole die to form a square tube was revealed. Three-dimensional numerical simulation demonstrated that metal flow into the portholes, welding chamber and die bearing of the porthole die corresponded to the stepped increases of extrusion pressure at the initial stages of an extrusion cycle. Experimental measurements of extrusion pressure and extrudate temperature were found to be in agreement with the predicted values. Extrusion pressure decreased continuously after the pressure peak while the workpiece temperature increased steadily, leading to gradual increases of the recrystallised grain sizes of the extrudate along its length. Expansion tests showed consistent quality of the longitudinal weld seams along the extrudate length, although the temperature on the welding plane increased and the maximum normal pressure in the welding chamber decreased during extrusion. It is thus the ratio of the maximum normal pressure in the welding chamber to the flow stress of the workpiece material on the welding plane that determines the weld seam quality.

The effects of bonding temperature and applied load on the mechanical integrity of 80Au-20Sn solder joints and the optical performance of laser diodes (LDs) are presented. Insufficient solder wetting at 280°C and poor joint integrity at an applied load below 0.196 MPa resulted in solder failure during die shear test. As the bonding temperature and applied load increased, the joint integrity and the optical performance improved. Shear testing further showed fracture in the LD due to the high mechanical strength of 80Au-20Sn solder and good adhesion properties of the solder joint. Microstructure studies showed good metallurgical stability with little interfacial intermetallic compound (IMC) formed. However, beyond an applied load of 0.523 MPa, the LD performances degraded due to modification of the bandgap energy in the active region. From our experimentation, a bonding window with good bonding integrity and high optical performance was, nevertheless, achieved.

Highly crystalline CaMoO4:Tb3+ phosphor layers were grown on monodisperse SiO2 particles through a simple sol-gel method, resulting in formation of core-shell structured SiO2@CaMoO4:Tb3+ submicrospheres. The resulting SiO2@CaMoO4: Tb3+ core-shell particles were fully characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), and kinetic decays. The XRD results demonstrate that the CaMoO4:Tb3+ layers begin to crystallize on the SiO2 spheres after annealing at 400 degrees C and the crystallinity increases with raising the annealing temperature. SEM and TEM analysis indicates that the obtained submicrospheres have a uniform size distribution and obvious core-shell structure. SiO2@CaMoO4:Tb3+ submicrospheres show strong green emission under short ultraviolet (260 nm) and low-voltage electron beam (1-3 kV) excitation, and the emission spectra are dominated by a D-5(4) -F-7(5) transition of Tb3+(544 nm, green) from the CaMoO4:Tb3+ shells.

A meshless method based on the local Petrov–Galerkin formulation is applied to the large deformation contact analysis of elastomeric components. Trial functions are constructed using the radial-basis function (RBF) coupled with a polynomial-basis function. The plane stress hypothesis and a pressure projection method are employed to overcome the incompressibility or nearly incompressibility in the plane stress and plane strain problems, respectively. Two different sets of equations are used for the nodes on the contact surface and nodes not on the contact surface, respectively, which is based on the meshless local Petrov–Galerkin method (MLPG) establishing equations node by node. Numerical results for several examples show that the present method is effective in dealing with large deformation contact problems.

Based on an optimized bonding technique for semiconductor lasers, parametric investigations of different bonding configurations were performed using AuSn solder. No abrupt electrical degradation was observed for both face-up and face-down bonding configurations. The typical optical output achieved for face-up and face-down bonding approach was about 100 mW/facet and 150 mW/facet, respectively. Face-up bonded LDs exhibited a steady differential quantum efficiency ηD of ∼ 0.425 mW/mA before gradual degradation at 200 mA, while face-down bonded LDs improved its performance beyond 350 mA. The characteristic temperature T0 also improved to as much as 643 K for face-down bonded LDs. Spectrally-resolved emission measurement showed that the temperature rise in unbonded, face-up bonded and face-down bonded LDs were approximately 11, 7–8 and 2–3 °C, respectively. These investigations showed that the improved performances for face-down bonding approach compared to face-up approach were due to better thermal management.

In this paper we proposed a block cryptosystem based on 1d-k5 Chain C CA, by alternatively iterating leftand right-toggle chain rules, this kind of encryption is achieved by backward iteration and decryption is realized via forward iteration. From theory proof, we can ensure the security of the cryptosystem, and make mostly confusion and diffusion function. Experimant shows that this cryptosystem has a large key space and good scrambling effect and can resist brute attack and differential attack effectively. Keywords-cellular automata (CA); Chaos, encryption; cryptanalysis

SiO2@Gd2MoO6:EU3+ core-shell phosphors were prepared by the sol-gel process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy ITEM), photoluminescence (PL) spectra as well as kinetic decays were used to characterize the resulting SiO2@Gd2MoO6:Eu3+ core-shell phosphors. The XRD results demonstrate that the Gd2MoO6:Eu3+ layers on the SiO2 spheres begin to crystallize after annealing at 600 degrees C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have a near perfect spherical shape with narrow size distribution (average size ca. 600 nm), are not agglomerated, and have a smooth surface. The thickness of the Gd2MoO6:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (50 nm for four deposition cycles). The Eu3+ shows a strong PL luminescence (dominated by D-5(0)-F-7(2) red emission at 613 nm) under the excitation of 307 nm UV light.

Europium-doped nanocrystalline GdVO4 phosphor layers were coated on the surface of preformed submicron silica spheres by sol-gel method. The resulted SiO2@Gd0.95Eu0.05VO4 core-shell particles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (FESEM), energy-dispersive X-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra, low voltage cathodoluminescence (CL), time resolved PL spectra and kinetic decays. The XRD results demonstrate that the Gd0.95Eu0.05VO4 layers begin to crystallize on the SiO2 spheres after annealing at 600 C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have spherical shape, narrow size distribution (average size ca. 600 nm), non-agglomeration. The thickness of the Gd0.95Eu0.05VO4 shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (50 nm for four deposition cycles). PL and CL show that the emissions are dominated by D-5(0)-F-7(2) transition of Eu3+ (618 nm, red).

Bulk fully nanocrystalline grain structures were successfully obtained in ultralow carbon stainless steel by means of equal channel angular pressing at room temperature. Transmission electron microscopy (TEM) and high-resolution TEM investigations indicated that two types of nanostructures were formed: nanocrystalline strain-induced martensite (body-centered cubic structure) with a mean grain size of 74 nm and nanocrystalline austenite (face-centered cubic structure) with a size of 31 nm characterized by dense deformation twins. The results about the formation of fully nanocrystalline grain structures in stainless steel suggested that a low stacking fault energy is exceptionally profitable for producing nanocrystalline materials by equal channel angular pressing.

A modified meshless local Petrov–Galerkin (MLPG) method is presented for elasticity problems using the moving least squares (MLS) approximation. It is a truly meshless method because it does not need a mesh for the interpolation of the solution variables or for the integration of the energy. In this paper, a simple Heaviside test function is chosen to overcome the computationally expensive problems in the MLPG method. Essential boundary conditions are imposed by using a direct interpolation method based on the MLPG method establishes equations node by node. Numerical results in several examples show that the present method yielded very accurate solutions. And the sensitivity of the method to several parameters is also studied in this paper.

This work investigates the effects of Sb on the tensile property of the Sn–3.5Ag–0.7Cu lead-free solder alloy and joints. Results show that the Sb-containing solder alloys and joints have higher ultimate tensile strength (UTS) than Sb-free solder alloy and solder joints due to solid solution hardening and particle hardening. UTS of solder alloys have a logarithmic increase relation with strain rate and decreases with the increase of testing temperature. The tensile strength of Sn–3.5Ag–0.7Cu solder joint reaches the highest value when 1.0 wt.% Sb is added and drops with the ageing time due to intermetallic compounds (IMC) growth at solder/IMC interface.

ZnO and ZnO:Zn powder phosphors were prepared by the polyol-method followed by annealing in air and reducing gas, respectively. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photoelectron spectra (XPS), electron paramagnetic resonance (EPR), and photoluminescence (PL) and cathodoluminescence (CL) spectra, respectively. The results indicate that all samples are in agreement with the hexagonal structure of the ZnO phase and the particle sizes are in the range of 1-2 microm. The PL and CL spectra of ZnO powders annealed at 950 degrees C in air consist of a weak ultraviolet emission band (approximately 390 nm) and a broad emission band centered at about 527 nm, exhibiting yellow emission color to the naked eyes. When the sample was reduced at the temperatures from 500 to 1050 degrees C, the yellow emission decreased gradually and disappeared completely at 800 degrees C, whereas the ultraviolet emission band became the strongest. Above this temperature, the green emission ( approximately 500 nm) appeared and increased with increasing of reducing temperatures. According to the EPR results and spectral analysis, the yellow and green emissions may arise from the transitions of photogenerated electron close to the conduction band to the deeply trapped hole in the single negatively charged interstitial oxygen ion (Oi(-)) and the single ionized oxygen vacancy (V.O) centers, respectively.

By means of Gleeble-1500 testing machine, the simulation of continuous casting process for AH32 steel was carried out and hot ductility and strength were determined. The cracking sensitivity was studied under the different temperatures and strain rates. The Precipitations of AIN at different temperatures and the fractures of high-temperature tensile samples were observed by using TEM (transmission electron microscope) and SEM (scanning electron microscope). The factors affecting the brittle temperature zone were discussed.

Deformation twins were widely observed in polycrystalline Cu with grain sizes varying from micrometers to nanometers during the process of equal channel angular pressing at room temperature and low strain rate (similar to 10(-2)s(-1)). The microstructures of deformation twins were characterized by a transmission electron microscope (TEM) and a high-resolution TEM. It was found that deformation twinning in coarse-grained Cu occurred mainly in shear bands and their intersections as a result of the very high local stress resulted from the severe plastic deformation, and followed the well known pole mechanism. With a decrease in the grain size down to submicrometer (< 1 mu m) and nanometer (< 100 nm) dimensions, twinning was observed to take place via partial dislocation emission from grain boundaries and grain boundary junctions, which is different from the pole mechanism operating in coarse-grained Cu. These observations are consistent with the predictions of recent molecular dynamic simulations for nanocrystalline face-centered cubic materials. The deformation conditions required for twinning and the formation mechanism of deformation twins varying with grain size in Cu are discussed. (c) 2005 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

A new fluorinated azobenzene chromophore and its non-fluorinated analogue have been synthesized and characterized by UV–vis spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The hyperpolarizabilities were characterized through solvatochromic method and the dispersions of hyperpolarizabilities were studied in terms of the quantum-mechanical two-level model. In contrast with its non-fluorinated analogue, the new fluorinated chromophore exhibits a considerable hypsochromic shift of the absorption maximum and cut-off absorption wavelength, which could lead to a better transparency in operating wavelength of electronic devices. The results also show that the fluorinated chromophore possesses higher thermal stability and the same order of the hyperpolarizability comparing with its non-fluorinated analogue.

This study investigates the microstructural evolution and kinetics of intermetallic (IMC) formation in Sn-3.5Ag-0.7Cu lead-free solder joints with different percentages of Sb element, namely, Sn-3.5Ag-0.7Cu-xSb (x=0, 0.2, 0.5, 0.8, 1.0, 1.5, and 2.0). To investigate the elemental interdiffusion and growth kinetics of IMC formation, isothermal aging test is performed at temperatures of 100/spl deg/C, 150/spl deg/C, and 190/spl deg/C, respectively. Scanning electron microscope (SEM) is used to measure the thickness of intermetallic layer and observe the microstructural evolution of solder joint. The IMC phases are identified by EDX and XRD. Results show that some of the antimony powders are dissolved in the /spl beta/-Sn matrix (Sn-rich phase), some of them participate in the formation of Ag/sub 3/(Sn,Sb) and the rest dissolves in the Cu/sub 6/Sn/sub 5/ IMC layer. There is a significant drop in IMC thickness when Sb is added to 0.8 wt%. Over this amount the thickness of the IMC increases slightly again. The activation energy and growth rate of the IMC formation are determined. Results reveal that adding antimony in Sn-3.5Ag-0.7Cu solder system can increase the activation energy, and thus reduce the atomic diffusion rate, so as to inhibit the excessive growth of the IMC. The solder joint containing 0.8 wt% antimony has the highest activation energy. SEM images reveal that the number of small particles precipitating in the solder matrix increases with the increase in Sb composition. Based on the observation of the microstructural evolution of the solder joints, a grain boundary pinning mechanism for inhibition of the IMC growth due to Sb addition is proposed.

Ultrafine-grained (UFG) pure Cu processed by equal channel angular pressing (ECAP) was subjected to cyclic deformation and subsequent ageing treatment at room temperature (RT) in order to investigate the stability of defects and grain size. Cyclic deformation for 1000 cycles at RT leads to a large decrease of internal stress. X-ray diffraction (XRD) shows that the stability of defects and grain size at RT in as-cyclic deformed sample is lower than that in as-processed sample and that a reduction of internal stress takes place prior to grain growth. TEM observations show that the microstructural evolution during ageing is characterized by normal grain growth accompanied with recovery within grain interior.

The influence of Sb on the soldering reaction and growth kinetics of Intermetallic compound (IMC) in Sn–3.5Ag–0.7Cu– x Sb ( x =0, 0.5, 1.0, and 1.5) lead-free solder joints is investigated in this study. Scanning electron microscope (SEM) is used to observe microstructure evolution of solder joint and to estimate the thickness and the grain size of the intermetallic layers. IMC phases are identified by energy dispersive X-ray (EDX) and X-ray diffractometer (XRD). Results show that some of the Sb powders are dissolved in the β-Sn matrix (Sn-rich phase), some of them participate in the form of Ag 3 (Sn, Sb), and the rest dissolves in the Cu 6 Sn 5 IMC layer. Both thickness and grain size of IMC decrease when Sb is added. The growth exponents for both IMC layer and grains are determined by curve-fitting. The results reveal that Sn–3.5Ag–0.7Cu with about 1.0 wt.% Sb solder system exhibits the smallest growth rate and gives the most prominent effect in retarding IMC growth and refining IMC grain size. Based on the thermodynamic and phase diagram analysis, Sb has higher affinity to Sn element, and it will reduce the activity of Sn by forming SnSb compound, resulting in a decreased driving force for Cu–Sn IMC formation. A heterogeneous nucleation effect for retarding the IMC growth due to Sb addition is proposed.

This paper presents a theoretical model to study the effects of bonding parameters on the electrostatic force in anodic wafer bonding process. The modeling results show that the temperature is the dominant factor to affect the electrostatic force which would cause the firm contact of two wafer surfaces facilitating the bonding reaction to occur. The voltage is also significant for the control of the maximum electrostatic force. The bonding temperature, applied voltage, and bonding time have an obvious complementary relationship for a certain electrostatic force needed for chemical reaction between Si and glass wafers. Based on the results achieved in this study, the reference optimum bonding process parameters can be easily selected to develop low temperature wafer bonding technology for micro-electro-mechanical systems (MEMS) packaging.

The computational details of a viscoplastic finite element analysis of three-dimensional superplastic forming (SPF) are discussed in this paper. Two typical superplastic forming shapes, conical bulging and rectangle box bulging, were analyzed and the experiment of conical bulging was performed to verify the numerical simulation. The inverse identification of superplastic material parameters incorporating the finite element method and an optimization technique was developed and an activity rule was proposed for effective selection of measurement locations in the experiment. Based on the numerical modeling, the influence of many factors such as the frictional coefficient, strain rate sensitivity and strain rate on the thickness distribution was studied and some useful conclusions were drawn.

Cyclic deformation of a copper bicrystal with perpendicular grain boundary (GB) has been performed at room temperature at a constant plastic strain amplitude of 1.5 x 10(-3). The dislocation structure evolution in typical deformation band (DB) as opposed to persistent slip bands (PSB) was observed by electron channelling contrast technique in the scanning electron microscope (SEM) at different cycles. It was found that a micro-crack nucleated preferentially at the interface between matrix and the second type of deformation band (DBII), the habit plane of which is close to the conventional kink plane {1 0 1}, in the vicinity of grain boundary (GB), and propagated along DBII. The dislocation structures of the transgranular and intergranular crack tip were also observed. The main dislocation structure near the crack tip is the cell structure. (C) 2003 Elsevier B.V. All rights reserved.

The features of surface morphology and dislocation structure of [(1) over bar 55] coplanar double-slip-oriented copper single crystal under cyclic deformation at a constant plastic shear strain amplitude of 2 x 10(-3) were studied using optical microscope (OP) and electron channelling contrast imaging (ECCI) in the scanning electron microscope (SEM). Experimental results show that there are two sets of the secondary type of deformation band (DBII) formed in the specimen. The geometry relationship of the two sets of deformation bands (DBs) and slip band (SB) are given. The habit planes of DBIIs are close to ((1) over bar 01) and ((1) over bar 10) plane, respectively. The surface dislocation structures in the specimen including vein, irregular dislocation cells and dislocation walls were also observed. The typical dislocation structure in DBII is the dislocation walls. (C) 2003 Elsevier B.V. All rights reserved.

The influence of Sb on the growth kinetics of intermetallic compound (IMC) and chemical reaction between Sn-3.5Ag-0.7Cu-xSb (x=0, 0.2, 0.5, 1.0, 1.5, and 2.0) lead-free solder and Cu during reflow soldering is investigated in this study. Scanning electron microscope (SEM) is used to measure the thickness and grain size of the intermetallic layer and observe the microstructural evolution of solder joints. Results show that both thickness and grain size of IMC decrease once Sb is added into the Sn-Ag-Cu solder system, and have a significant drop at the composition of about 1.0 wt%. Beyond this composition, the thickness and grain size of IMC increase slightly. The growth exponents for both IMC layers and grains are determined by curve-fitting to study the growth kinetics of IMC in wetting reaction. The results reveal that the growth exponents of IMC range from 0.32 to 0.35, and those of IMC grains range from 0.28 to 0.32, which suggests that the growth of IMC is controlled through combined kinetic processes of atomic interdiffusion, interfacial reaction, and grain ripening. These data also show that Sn-3.5Ag-0.7Cu with about 1.0 wt% Sb solder system exhibits the smallest growth rate and gives the most prominent effect in retarding IMC growth and refining IMC grain size. Based on the phase diagram analysis and the observation of the microstructural evolution of the solder joints, a heterogeneous nucleation mechanism for retarding the IMC growth due to Sb addition is proposed.

Identification of gene expression patterns in mangroves grown under salinity will help to reveal the molecular mechanisms of salt tolerance. Here, 10 cDNAs of genes were isolated from Kandelia candel and identified by representational difference analysis of cDNA (cDNA RDA) under different NaCl concentrations. Of five genes expressed preferentially under salt condition, two were unknown, three were two kinds of low molecular mass heat-shock proteins (sHSPs) and ADP-ribosylation factor, respectively. The expressions of other five genes were repressed under NaCl stress, two encoded cyclophilins, three were tonoplast intrinsic protein, early light-induced protein and 60S ribosomal protein, respectively.