Advances in Materials Science and Engineering The latest articles from Hindawi Publishing Corporation © 2015 , Hindawi Publishing Corporation . All rights reserved. Lamb Waves in a Functionally Graded Composite Plate with Nonintegral Power Function Volume Fractions Tue, 07 Jul 2015 12:00:25 +0000 An analytical modelling is carried out to determine the Lamb wave’s propagation behavior in a thermal stress relaxation type functionally graded material (FGM) plate, which is a composite of two kinds of materials. The mechanical parameters depend on the volume fractions, which are nonintegral power functions, and the gradient coefficient is the power value. Based on the theory of elastodynamics, differential equations with variable coefficients are established. We employ variable substitution for theoretical derivations to solve the ordinary differential equations with variable coefficients using the Taylor series. The numerical results reveal that the dispersion properties in some regions are changed by the graded property, the phase velocity varies in a nonlinear manner with the gradient coefficient, nondispersion frequency exists in the first mode, and the set of cutoff frequencies is a union of two series of approximate arithmetic progressions. These results provide theoretical guidance not only for the experimental measurement of material properties but also for their nondestructive testing. Xiaoshan Cao, Zhen Qu, Junping Shi, and Yan Ru Copyright © 2015 Xiaoshan Cao et al. All rights reserved. Surface Effect on Diffractions of Elastic Waves and Stress Concentration near a Cluster of Cylindrical Nanoholes Arranged as Quadrate Shape Tue, 07 Jul 2015 11:59:14 +0000 We consider the multiple scattering of elastic waves (P-wave and SV-wave) by a cluster of nanosized cylindrical holes arranged as quadrate shape. When the radius of the holes shrinks to nanometers, the surface elasticity theory is adopted in analysis. Using the displacement potential method and wave functions expansion method, we obtain that the multiple scattering fields induced by incident P- and SV-waves around the holes are derived. The dynamic stress concentration around the holes is calculated to illustrate the effect of surface effects on the multiple scattering of P- and SV-waves. Ru Yan Copyright © 2015 Ru Yan. All rights reserved. Analysis of Influence of Temperature on Magnetorheological Fluid and Transmission Performance Tue, 07 Jul 2015 11:36:13 +0000 Magnetorheological (MR) fluid shows different performances under different temperature, which causes so many problems like the reduction of rheological properties of MR fluid under a high temperature condition, the uncontrollability of shear stress, and even failure of transmission; on that basis, the influence of temperature on the performance of MR fluid and the cause of the rise in temperature of MR transmission device are analyzed in this paper; the shearing transmission performance of the MR transmission device under the effect of an external magnetic field and the influence of temperature on the shearing stress and transmission performance are analyzed. The study results indicate that temperature highly influences the viscosity of MR fluid, and the viscosity influences the shear stress of the MR fluid. The viscosity of MR fluid gradually declines when temperature rises from 100°C. Once the temperature exceeds 100°C, the viscosity would increase and the temperature stability would decline. Temperature obviously influences the characteristics of MR transmission, and particularly, highly influences the characteristics of MR transmission once being higher than 100°C. The chaining of the material in the magnetic field is influenced, which causes the reduction of the rheological properties, the uncontrollability of the shear stress, and even the failure of transmission. Song Chen, Jin Huang, Kailin Jian, and Jun Ding Copyright © 2015 Song Chen et al. All rights reserved. Optimal Heater Control with Technology of Fault Tolerance for Compensating Thermoforming Preheating System Tue, 07 Jul 2015 11:22:12 +0000 The adjustment of heater power is very important because the distribution of thickness strongly depends on the distribution of sheet temperature. In this paper, the steady state optimum distribution of heater power is searched by numerical optimization in order to get uniform sheet temperature. In the following step, optimal heater power distribution with a damaged heater was found out using the technology of fault tolerance, which will be used to reduce the repairing time when some heaters are damaged. The merit of this work is that the design variable was the power of each heater which can be directly used in the preheating process of thermoforming. Zhen-Zhe Li, Tai-Hong Cheng, Yun-De Shen, and Dong-Ji Xuan Copyright © 2015 Zhen-Zhe Li et al. All rights reserved. Optimum Design for Mechanical Structures and Material Properties of the Dual-Elbow-Bar Mechanism Tue, 07 Jul 2015 11:21:19 +0000 According to the kinematic equation of the die-cutting machine with the dual-elbow-bar mechanism, the angular acceleration curve figure can be obtained exactly through the analysis of MATLAB program when the die-cutting machine runs at the highest speed (6000 r/h). The material properties of the cam driving mechanism are analyzed by QFD (Quality Function Deployment) method, and the optimum design project is presented based on conjugate cam driving mechanism. The reverse design and the outline of conjugate cam mechanism are obtained by MATLAB program. The kinematical form of optimized design conjugate cam driving mechanism is simulated and analyzed by ADAMS software. The results show that the optimum design mechanism could raise the highest speed of the die-cutting machine up to 7500 r/h and improve the overall performance of the machine. Weiguo Lin, Chen Zhou, and Weijun Huang Copyright © 2015 Weiguo Lin et al. All rights reserved. Stability of Axially Moving Piezolaminated Viscoelastic Plate Subjected to Follower Force Tue, 07 Jul 2015 11:16:43 +0000 The stability of the moving viscoelastic plate with the piezoelectric layer subjected to uniformly distributed tangential follower force is investigated. The force excited by the piezoelectric layer due to external voltage is modeled as the follower tensile force. The differential equation of the axially moving viscoelastic rectangular plate with piezoelectric layer subjected to uniformly distributed tangential follower force is formulated on the basis of the Kirchhoff thin plate theory and the two-dimensional viscoelastic differential constitutive relation. The complex eigenvalue equations are established by the differential quadrature method. Via numerical calculation, the curves of real parts and imaginary parts of dimensionless complex frequencies versus uniformly distributed tangential follower force and dimensionless moving speed are obtained. The effects of nonconservative force, dimensionless axially moving speed, and dimensionless applied voltages on the stability of axially moving nonconservative viscoelastic plate with piezoelectric layer are analyzed. Yan Wang, Tao Jing, Jimei Wu, and Min Xie Copyright © 2015 Yan Wang et al. All rights reserved. Nondestructive Testing of Advanced Concrete Structure during Lifetime Tue, 07 Jul 2015 11:15:32 +0000 The paper reports on measurements and analysis of the measurements during hardening and drying of specimens using selected acoustic nondestructive testing techniques. An integrated approach was created for better understanding of the relations between the lifetime cycle and the development of the mechanical properties of concrete. Acoustic emission, impact echo, and ultrasonic techniques were applied simultaneously to the same mixtures. These techniques and results are presented on alkali-activated slag mortars. The acoustic emission method detects transient elastic waves within the material, caused by the release of cumulated stress energy, which can be mechanical, thermal, or chemical. Hence, the cause is a phenomenon which releases elastic energy into the material, which then spreads in the form of an elastic wave. The impact echo method is based on physical laws of elastic stress wave propagation in solids generated by mechanical impulse. Ultrasonic testing is commonly used to find flaws in materials or to assess wave velocity spreading. Lubos Pazdera, Libor Topolar, Jaroslav Smutny, and Kristyna Timcakova Copyright © 2015 Lubos Pazdera et al. All rights reserved. Nondestructive Detection of Valves Using Acoustic Emission Technique Tue, 07 Jul 2015 11:11:42 +0000 The applications of acoustic emission (AE) technique in detection of valves are presented in this review, and the theoretical models and experimental results of nondestructive detection of valves using AE are provided. The generation of AE signals and the basic composition of AE detection system are briefly explained. The applications of AE technique in valves are focused on condition monitoring, failure, cavitation detection, and the development of portable measuring devices. All results prove that the AE technique works well in the detection of valves. Jin Yan, Yang Heng-hu, Yang Hong, Zhang Feng, Liu Zhen, Wang Ping, and Yang Yan Copyright © 2015 Jin Yan et al. All rights reserved. Development of Miniature Stewart Platform Using TiNiCu Shape-Memory-Alloy Actuators Tue, 07 Jul 2015 09:46:34 +0000 A Stewart platform is a parallel manipulator robot that is able to perform three linear movements, lateral, longitudinal, and vertical, and three rotations, pitch, yaw, and roll. This paper reports a 30 mm × 30 mm × 34 mm miniscale Stewart platform using TiNiCu shape-memory-alloy (SMA) actuators. The proposed Stewart platform possesses various advantages, such as large actuation force and high robustness with a simple mechanical structure. This Stewart platform uses four SMA actuators and four bias springs and performs a linear z-axis movement and tilting motions. The SMA actuators are activated by passing a current through the SMA wires using a heating circuit that generates a pulse width modulation (PWM) signal. This signal is varied to control the level of the displacement and tilting angle of the platform. The tilting direction depends on the SMA actuator that is activated, while all four SMA actuators are activated to achieve the linear z-axis movement. Each SMA actuator exerts a maximum force of 0.6 N at PWM duty cycle of 100%. The fabricated miniature Stewart platform yields a full actuation of 12 mm in the z-axis at 55°C, with a maximum tilting angle of 30° in 4 s. Alaa AbuZaiter, Ee Leen Ng, Suhail Kazi, and Mohamed Sultan Mohamed Ali Copyright © 2015 Alaa AbuZaiter et al. All rights reserved. Research on Radial Motion Characteristic of the Cropping Hammer in Radial-Forging Cropping Method Tue, 07 Jul 2015 09:26:39 +0000 The radial loading form applied to the bar is very important for reducing or avoiding the impact and vibration of the radial-forging cropping system and obtaining the high-quality cross section. A new radial stroke loading curve of the cropping hammer based on the cycloid form is proposed and the dynamic model of radial stroke loading mechanism is built. With the aim of obtaining the equivalent stiffness of the bar with V-shaped notch, which is a key parameter affecting the dynamic characteristic of radial stroke loading mechanism, the analytic model of the bar is built and the simulation experiments are designed by means of the orthogonal test method. The analytical results show that the diameter of the bar has the significant influence on the equivalent stiffness of the bar. Furthermore, the equivalent stiffness of the bar with V-shaped notch can be directly calculated according to the equivalent stiffness of smooth bar when and . By using the cycloid stroke curve, the cropping experimental results for 45 steel bars and 20 steel bars show that the radial impact and vibration of the cropping system are decreased and the bar cross-section qualities have been significantly improved. Lijun Zhang, Shengdun Zhao, and Zhenwei Wang Copyright © 2015 Lijun Zhang et al. All rights reserved. Effect of Wood Preservatives on Surface Properties of Coated Wood Tue, 07 Jul 2015 07:09:10 +0000 Effect of wood preservatives (waterborne and organicborne) on the performance of surface finishing properties is investigated. Sapwood of scots pine, (Pinus sylvestris L.), oriental beech (Fagus orientalis Lipsky), and chestnut (Castanea sativa Mill.) specimens (300 × 100 × 15 mm along the grain) were impregnated with aqueous solution of 2% CCA, 2% Tanalith E, 1% boric acid, and Immersol aqua. Surface roughness, dry film thickness, adhesion strength, gloss measurement, scratch, and abrasion resistance were determined according to related standards for treated and untreated samples. The results indicated that surface roughness and adhesion strength depended on wood species and the chemical composition of preservatives. Generally, waterborne wood preservatives increased the surface roughness of wood while the organic-based wood preservatives decreased it. The organic-based wood preservatives decreased adhesion but they increased gloss value. Wood preservatives did not affect the scratch resistance which was found to depend on properties of the coating. All the wood preservatives increased abrasion resistance. Turgay Ozdemir, Ali Temiz, and Ismail Aydin Copyright © 2015 Turgay Ozdemir et al. All rights reserved. A Modified Eyring Equation for Modeling Yield and Flow Stresses of Metals at Strain Rates Ranging from 10−5 to 5 × 104 s−1 Mon, 06 Jul 2015 12:03:30 +0000 In several industrial applications, metallic structures are facing impact loads. Therefore, there is an important need for developing constitutive equations which take into account the strain rate sensitivity of their mechanical properties. The Johnson-Cook equation was widely used to model the strain rate sensitivity of metals. However, it implies that the yield and flow stresses are linearly increasing in terms of the logarithm of strain rate. This is only true up to a threshold strain rate. In this work, a three-constant constitutive equation, assuming an apparent activation volume which decreases as the strain rate increases, is applied here for some metals. It is shown that this equation fits well the experimental yield and flow stresses for a very wide range of strain rates, including quasi-static, high, and very high strain rates (from 10−5 to 5 × 104 s−1). This is the first time that a constitutive equation is showed to be able to fit the yield stress over a so large strain rate range while using only three material constants. Ramzi Othman Copyright © 2015 Ramzi Othman. All rights reserved. Efficient Photoluminescence of Mn2+-Doped ZnS Quantum Dots Sensitized by Hypocrellin A Sun, 05 Jul 2015 13:49:41 +0000 Mn2+-doped ZnS semiconductor quantum dots reveal remarkably intense photoluminescence with the 4T1(4G) f6A1(6S) transition. In this study, following growth doping technique, Mn2+-doped ZnS quantum dots (ZnS:Mn2+ QDs) with high-quality optical properties and narrow size distribution were synthesized successfully. The dopant emission has been optimized with various reaction parameters, and it has been found that the percentage of introduced dopant, reaction temperature, and time as well as the pH of a reaction mixture are key factors for controlling the intensity. Photoluminescence emission (PL) measurements of ZnS:Mn2+ QDs show Mn2+ d-d orange luminescence along with band-edge blue luminescence. Moreover, the electron transfer from singlet states of hypocrellin A (HA) to colloidal ZnS:Mn2+ QDs has been examined by absorption spectra and fluorescence quenching. The absorption spectrum gave an evidence of the increases in the extinction coefficient and the red-shift of the absorption maxima in the absorption spectra of HA in the presence of ZnS:Mn2+ QDs, demonstrating the occurrence of surface interactions between the sensitizer and the particle surface. Fluorescence quenching by ZnS:Mn2+ QDs also suggested that there were a complex association between HA and ZnS:Mn2+ QDs, which was necessary for observing the heterogeneous electron-transfer process at the interface of sensitizer-semiconductor. Xianlan Chen, Wei Liu, Guowei Zhang, Na Wu, Ling Shi, and Shanqing Pan Copyright © 2015 Xianlan Chen et al. All rights reserved. Optimization of Zoom Lens with Discrete State of Liquid Lens Elements by Using Genetic Algorithm Sun, 05 Jul 2015 11:11:20 +0000 This paper is to employ liquid lens elements to design a lens with zoom function by using the genetic algorithm (GA) optimization. The liquid lens elements used in the proposal can apply voltage adjustment to generate the electrical field that induces the liquid with electric conductivity to vary the surface curvature between two different kinds of liquids. According to the voltage level, the liquid lens element makes the discrete variation of the curvature and thickness realize the zoom function without moving the lens groups so that the overall length can be reduced. However, it is difficult to design the zoom lens under the discrete variation of the curvature and thickness in the liquid lens elements and the mechanical space that is constantly limited. The GA offers a flexible way for lens optimization. We regarded the spot size as the fitness function to look for the optimum curvatures, thickness, and the corresponding statuses of liquid lens elements for the zoom lens. As a result, the zoom lens with constant space can be realized by running the selection, crossover, and mutation operation in the GA optimization. Cheng-Mu Tsai Copyright © 2015 Cheng-Mu Tsai. All rights reserved. Plasmonic Filters Based on Lithographically Patterned and Hexagonally Arranged Triangular Silver Nanoparticles Array Sun, 05 Jul 2015 10:08:49 +0000 A plasmonic filter applied in visible regime is proposed on the basis of hexagonally arranged triangular silver nanoparticle arrays. A method using discrete dipole approximation (DDA) to aid design parameters of the silver nanoparticle arrays is adopted for the filter design and optimization on the basis of computational numerical calculation. The influence of the particle’s thickness and period on the extinction spectrum is studied using the DDA-based computational analysis. Considering the nanofabrication condition, arrays with 40 nm thickness and 230 nm period are selected and fabricated by using nanosphere lithography (NSL) technique. The experimental spectrum is basically in agreement with the theoretical spectrum derived by the DDA calculation. Jing Liu, Haoyuan Cai, Kai Tang, and Lingqi Kong Copyright © 2015 Jing Liu et al. All rights reserved. Quantum Chemical Study on the Corrosion Inhibition of Some Oxadiazoles Sun, 05 Jul 2015 09:49:29 +0000 Quantum chemical calculations based on DFT method were performed on three nitrogen-bearing heterocyclic compounds used as corrosion inhibitors for the mild steel in acid media to determine the relationship between the molecular structure of inhibitors and inhibition efficiency. The structural parameters, such as energy and distribution of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), the charge distribution of the studied inhibitors, the absolute electronegativity (χ) values, and the fraction of electrons () transfer from inhibitors to mild steel were also calculated and correlated with inhibition efficiencies. The results showed that the inhibition efficiency of inhibitors increased with the increase in energy of HOMO and decrease in energy gap of frontier molecular orbital, and the areas containing N and O atoms are most possible sites for bonding the steel surface by donating electrons to the mild steel. Hong Ju, Li Ding, Can Sun, and Jie-jing Chen Copyright © 2015 Hong Ju et al. All rights reserved. The High-Temperature Synthesis of the Nanoscaled White-Light Phosphors Applied in the White-Light LEDs Sun, 05 Jul 2015 09:27:10 +0000 The white-light phosphors consisting of Dy3+ doped YPO4 and Dy3+ doped YP1-XVXO4 were prepared by the chemical coprecipitation method. After the 1200°C thermal treatment in the air atmosphere, the white-light phosphors with particle sizes around 90 nm can be obtained. In order to reduce the average particle size of phosphors, the alkaline washing method was applied to the original synthesis process, which reduces the particle sizes to 65 nm. From the PLE spectra, four absorption peaks locating at 325, 352, 366, and 390 nm can be observed in the YPO4-based phosphors. These peaks appear due to the following electron transitions: 6H15/2→4K15/2, 6H15/2→4M15/2+6P7/2, 6H15/2→4I11/2, and 6H15/2→4M19/2. Besides, the emission peaks of wavelengths 484 nm and 576 nm can be observed in the PL spectra. In order to obtain the white-light phosphors, the vanadium ions were applied to substitute the phosphorus ions to compose the YP1-XVXO4 phosphors. From the PL spectra, the strongest PL intensity can be obtained with 30% vanadium ions. As the concentration of vanadium ions increases to 40%, the phosphors with the CIE coordinates locating at the white-light area can be obtained. Hao-Ying Lu and Meng-Han Tsai Copyright © 2015 Hao-Ying Lu and Meng-Han Tsai. All rights reserved. A Turbidity Test Based Centrifugal Microfluidics Diagnostic System for Simultaneous Detection of HBV, HCV, and CMV Sun, 05 Jul 2015 07:54:58 +0000 This paper presents a LAMP- (loop-mediated isothermal amplification-) based lab-on-disk optical system that allows the simultaneous detection of hepatitis B virus, hepatitis C virus, and cytomegalovirus. The various flow stages are controlled in the proposed system using different balance among centrifugal pumping, Coriolis pumping, and the capillary force. We have implemented a servo system for positioning and speed control for the heating and centrifugal pumping. We have also successfully employed a polymer light-emitting diode section for turbidity detection. The easy-to-use one-click system can perform diagnostics in less than 1 hour. Hung-Cheng Chang, Yu-Tin Chao, Jia-Yush Yen, Ya-Lin Yu, Chun-Nan Lee, Bing-Ching Ho, Kou-Chen Liu, Jiunn Fang, Chii-Wann Lin, and Jiun-Haw Lee Copyright © 2015 Hung-Cheng Chang et al. All rights reserved. A Study on the Effect of the Contact Point and the Contact Force of a Glass Fiber under End-Face Polishing Process Thu, 02 Jul 2015 08:58:54 +0000 The offset between the center lines of the polished end-face and the fiber core has a significant effect on coupling efficiency. The initial contact point and the contact force are two of the most important parameters that induce the offset. This study proposes an image assistant method to find the initial contact point and a mathematical model to estimate the contact force when fabricating the double-variable-curvature end-face of single mode glass fiber. The repeatability of finding the initial contact point via the vision assistant program is 0.3 μm. Based on the assumption of a large deflection, a mathematical model is developed to study the relationship between the contact force and the displacement of the lapping film. In order to verify the feasibility of the mathematical model, experiments, as well as DEFORM simulations, are carried out. The results show that the contact forces are alomst linearly proportional to the feed amounts of the lapping film and the errors are less than 9%. By using the method developed in this study, the offset between the grinding end-face and the center line of the fiber core is within 0.15 to 0.35 μm. Ying-Chien Tsai, Guang-Miao Huang, Shin-Wei Cheng, Cheng-An Hsu, and Innchyn Her Copyright © 2015 Ying-Chien Tsai et al. All rights reserved. Simulation-Based Optimization of Cure Cycle of Large Area Compression Molding for LED Silicone Lens Wed, 01 Jul 2015 09:08:53 +0000 Three-dimensional heat transfer-curing simulation was performed for the curing process by introducing a large area compression molding for simultaneous forming and mass production for the lens and encapsulants in the LED molding process. A dynamic cure kinetics model for the silicone resin was adopted and cure model and analysis result were validated and compared through a temperature measurement experiment for cylinder geometry with cure model. The temperature deviation between each lens cavity could be reduced by implementing a simulation model on the large area compression mold and by optimizing the location of heat source. A two-step cure cycle was constructed to reduce excessive reaction peak at the initial stage and cycle time. An optimum cure cycle that could reduce cycle time by more than 29% compared to a one-step cure cycle by adjusting dwell temperature, heating rate, and dwell time was proposed. It was thus confirmed that an optimization of large area LED lens molding process was possible by using the present experiment and the finite element method. Min-Jae Song, Kwon-Hee Kim, Seok-Kwan Hong, Jeong-Won Lee, Jeong-Yeon Park, Gil-Sang Yoon, and Heung-Kyu Kim Copyright © 2015 Min-Jae Song et al. All rights reserved. The Microstructure and Thermal Conductivity of Pressureless Infiltrated Composites Containing Electroless Nickel Platings Mon, 29 Jun 2015 11:32:51 +0000 A nickel (Ni) coating was deposited on the surface of silicon carbide particles () through electroless plating and we characterized the morphology and phase structure of the coating and the pressureless infiltrated composites. The effect of Ni coatings on the thermal conductivity of the composites was examined and analyzed with three-dimensional video microscope, scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction microscope (XRD), and finite-element. The results show that a continuous and uniform coating with a certain thickness (around 3.5 μm) can be formed on the surface of . With the addition of the Ni layer, there are some intermetallics Ni3Al but no interfacial carbide Al4C3, which improves the wettability and the thermal conductivity of the composites. The experiments and simulations both show that Ni coatings do not substantially decrease the overall thermal conductivity of the composite, although the thermal conductivity of Ni itself is lower than Al and SiC by a factor of 1. Aihua Zou, Xianliang Zhou, Xiaozhen Hua, Duosheng Li, and Kaiyang Wu Copyright © 2015 Aihua Zou et al. All rights reserved. Equal Channel Angular Extrusion Simulation of High-Nb Containing β-γ TiAl Alloys Mon, 29 Jun 2015 09:42:39 +0000 TiAl alloys containing high Nb are significantly promising for high-temperature structural applications in aerospace and automotive industries. Unfortunately the low plasticity at room temperature limits their extensive applications. To improve the plasticity, not only optimizing the opposition, but also refining grain size through equal channel angular extrusion (ECAE) is necessary. The equal channel angular extrusion simulation of Ti-44Al-8Nb-(Cr,Mn,B,Y)(at%) alloy was investigated by using the Deform-3D software. The influences of friction coefficient, extrusion velocity, and different channel angles on effective strain, damage factor, and the load on the die were analyzed. The results indicate that, with the increasing of friction coefficient, effective strain is enhanced. The extrusion velocity has little effect on the uniformity of effective strain; in contrast it has large influence on the damage factor. Thus smaller extrusion rate is more appropriate. Under the condition of different channel angles, the larger one results in the lower effective strain magnitude and better strain distribution uniformity. Lai-qi Zhang, Xiang-ling Ma, Geng-wu Ge, Yong-ming Hou, Jun-zi Zheng, and Jun-pin Lin Copyright © 2015 Lai-qi Zhang et al. All rights reserved. Multicriteria Decision Analysis in Material Design, Selection, and Manufacturing Mon, 29 Jun 2015 06:30:17 +0000 Ali Jahan, Kevin L. Edwards, Abbas S. Milani, and Marjan Bahraminasab Copyright © 2015 Ali Jahan et al. All rights reserved. Density Functional Theory Study on the Electronic Structures of Oxadiazole Based Dyes as Photosensitizer for Dye Sensitized Solar Cells Sun, 28 Jun 2015 12:39:40 +0000 The molecular structures and UV-visible absorption spectra of complex photosensitizers comprising oxadiazole isomers as the π-bridges were analyzed by density functional theory (DFT) and time-dependent DFT. The ground state and excited state oxidation potentials, HOMOs and LUMOs energy levels, and electron injection from the dyes to semiconductor TiO2 have been computed in vacuum here. The results show that all of the dyes may potentially be good photosensitizers in DSSC. To justify the simulation basis, N3 dye was also simulated under the similar conditions. Simulated absorption spectrum, HOMO, LUMO, and band gap values of N3 were compared with the experimental values. We also computed the electronic structure properties and absorption spectra of dye/(TiO2)8 systems to elucidate the electron injection efficiency at the interface. This work is expected to give proper orientation for experimental synthesis. Umer Mehmood, Ibnelwaleed A. Hussein, Khalil Harrabi, and Shakeel Ahmed Copyright © 2015 Umer Mehmood et al. All rights reserved. Atmospheric Corrosion Behavior of 2A12 Aluminum Alloy in a Tropical Marine Environment Sun, 28 Jun 2015 07:51:06 +0000 Atmospheric corrosion behavior of 2A12 aluminum alloy exposed to a tropical marine environment for 4 years was investigated. Weight loss of 2A12 alloy in the log-log coordinates can be well fitted with two linear segments, attributing to the evolution of the corrosion products. EIS results indicate that the corrosion product layer formed on the specimens exposed for 12 months or longer presents a good barrier effect. Corrosion morphology changes from pitting corrosion to severe intergranular corrosion with the extension of exposure time, resulting in the reduction of the mechanical properties. Zhongyu Cui, Xiaogang Li, Huan Zhang, Kui Xiao, Chaofang Dong, Zhiyong Liu, and Liwei Wang Copyright © 2015 Zhongyu Cui et al. All rights reserved. Piezoelectric Nanowires in Energy Harvesting Applications Thu, 25 Jun 2015 13:07:47 +0000 Recently, the nanogenerators which can convert the mechanical energy into electricity by using piezoelectric one-dimensional nanomaterials have exhibited great potential in microscale power supply and sensor systems. In this paper, we provided a comprehensive review of the research progress in the last eight years concerning the piezoelectric nanogenerators with different structures. The fundamental piezoelectric theory and typical piezoelectric materials are firstly reviewed. After that, the working mechanism, modeling, and structure design of piezoelectric nanogenerators were discussed. Then the recent progress of nanogenerators was reviewed in the structure point of views. Finally, we also discussed the potential application and future development of the piezoelectric nanogenerators. Zhao Wang, Xumin Pan, Yahua He, Yongming Hu, Haoshuang Gu, and Yu Wang Copyright © 2015 Zhao Wang et al. All rights reserved. Asphalt Concrete Mixtures: Requirements with regard to Life Cycle Assessment Thu, 25 Jun 2015 11:15:03 +0000 Design of asphalt concrete, required properties of constituent materials and their mixing ratios, is of tremendous significance and should be implemented with consideration given to the whole life cycle of those materials and the final construction. Conformity with requirements for long term performance of embedded materials is the general objective of the Life Cycle Assessment (LCA). Therefore, within the assessment, material properties need to be evaluated with consideration given to the whole service life—from the point of embedding in the construction until their disposal or recycling. The evaluation focuses on verification of conformity with criteria set for these materials and should guarantee serviceability and performance during their whole service life. Recycling and reuse of asphalt concrete should be preferred over disposal of the material. This paper presents methodology for LCA of asphalt concrete. It was created to ensure not only applicability of the materials in the initial stage, at the point of their embedding, but their suitability in terms of normatively prescribed service performance of the final construction. Methods described and results are presented in a case study for asphalt mixture AC 11; I design. Jan Mikolaj, Frantisek Schlosser, Lubos Remek, and Aurelia Chytcakova Copyright © 2015 Jan Mikolaj et al. All rights reserved. Performance Analysis of CFRP Composite Strips Confined RC Columns under Axial Compression Thu, 25 Jun 2015 08:15:38 +0000 In an attempt to mitigate the high cost of FRP composite strengthening, an experimental investigation was carried out that sought to achieve efficient and most favorable FRP strengthening using CFRP composite strips. 50 mm wide CFRP composite strips were used in two different spacings (20 mm and 40 mm) to confine columns. The test results of the column confined with smaller spacing (20 mm) showed significant restraint of axial deformation of the column and enhanced the strength capacity to a maximum of 99.20% compared to that of reference column. In contrast, the column confined by strips with larger spacing (40 mm) failed by crushing of concrete alone, which occurred even before the CFRP strips reached their ultimate strain. In addition, the embodied energy that exists in the CFRP strips could not be utilized effectively. The stress and strength enhancement ratio of this present study was compared with the previous research that has been conducted on columns confined with full wrapping. From the obtained results, it is recommended that CFRP strips with a spacing of 20 mm be used to improve the strength capacity of the RC column; in addition, this wrapping technique provides economic benefits compared to a column confined with full wrapping. J. Raja Murugadoss, Byung Jae Lee, Jin Wook Bang, G. Ganesh Prabhu, and Yun Yong Kim Copyright © 2015 J. Raja Murugadoss et al. All rights reserved. Predicting Equivalent Static Density of Fuzzy Ball Drilling Fluid by BP Artificial Neutral Network Thu, 25 Jun 2015 06:04:20 +0000 A back-propagation artificial neutral network model is built based on 220 groups of PVT experimental data to predict the equivalent static density versus depth for fuzzy ball drilling fluid which is a kind of gas-liquid two-phase material. The model is applied in the Mo80-C well located in Sichuan Province of China; the maximum relative error between calculated results and measured data is less than 2%. By comparing with the multiple regression model, the present model has a higher precision and flexibility. The equivalent static density of fuzzy ball drilling fluid from ground to the depth of 6000 m is predicted by the present model, and the results show that the equivalent static density of fuzzy ball drilling fluid will decrease slowly with the growth of depth, which indicates that the gas cores of the fuzzy balls still can exist as deep as 6000 m. Chen Yang, Zhaohong Wang, Lihui Zheng, and Dengtian Mao Copyright © 2015 Chen Yang et al. All rights reserved. A Microstructural Study of Load Distribution in Cartilage: A Comparison of Stress Relaxation versus Creep Loading Wed, 24 Jun 2015 12:34:07 +0000 The compressive response of articular cartilage has been extensively investigated and most studies have focussed largely on the directly loaded matrix. However, especially in relation to the tissue microstructure, less is known about load distribution mechanisms operating outside the directly loaded region. We have addressed this issue by using channel indentation and DIC microscopy techniques that provide visualisation of the matrix microstructural response across the regions of both direct and nondirect loading. We hypothesise that, by comparing the microstructural response following stress relaxation and creep compression, new insights can be revealed concerning the complex mechanisms of load bearing. Our results indicate that, with stress relaxation, the initial mode of stress decay appears to primarily involve relaxation of the surface layer. In the creep loading protocol, the main mode of stress release is a lateral distribution of load via the mid matrix. While these two modes of stress redistribution have a complex relationship with the zonally differentiated tissue microstructure and the depth of strain, four mechanostructural mechanisms are proposed to describe succinctly the load responses observed. Ashvin Thambyah, V. M. van Heeswijk, C. C. van Donkelaar, and Neil Broom Copyright © 2015 Ashvin Thambyah et al. All rights reserved.