PROPERTIES OF FERROELECTRIC P(VDF-TrFE) 70/30 COPOLYMER FILMS AS A GATE DIELECTRIC

ABSTRACT

We directly formed the organic ferroelectric P(VDF-TrFE) 70/30 copolymer film by the spin coating for making the MFS structure in the silicon wafer. To understand the crystallization behavior of P(VDF-TrFE) 70/30 copolymer, the morphologies of copolymer thin films were studied by AFM and XRD. AFM studies revealed that as grown and annealed films showed surface roughness greater than amorphous films due to crystallization. The XRD spectrum of the films subjected to various annealing temperatures showed β -phase and this phase content was maximum at 140°C annealing. The capacitance shows hysteresis behavior like a buttery shape due to the polarization reversal in the film and this result indicates clearly that the film has a ferroelectric property. The dielectric constants of the P(VF₂-TrFE) copolymer films calculated from the capacitance at the two peak points of the C-V characteristics were about 8.7.     

Context-aware BPEL workflow system using aspect-oriented programming

Business process execution language(BPEL)is a most recognized standard workflow language.However,it is difficult to be used in the ubiquitous system computing environment because it is difficult to describe the context information in the selection of the flow through the branch.To solve this problem,we propose a new BPEL workflow system with context-awareness by using aspect-oriented programming(AOP).This system is composed of a BPEL system module and a weaving module using AOP for context-aware.The BPEL system module generates a BPEL workflow program.And the weaving module converts a context-aware mark-up language(CAML)document to the aspect-oriented program that is applied to context-aware code without modification of the existing BPEL document.We also define a new document form that is called CAML,which provides a context-aware that is not available in BPEL.The system can generate a context-aware workflow program.It is developed in a way that inserts context information using AOP to provide context-aware services.     

含垂直裂纹的厚热障涂层的热稳定性及力学性能(英文)

采用循环热暴露及热震试验研究含或不含垂直裂纹的厚热障涂层的热稳定性和失效机制。先采用空气等离子喷涂技术在基体表面制备150μm厚的连接涂层,再在该涂层上采用空气等离子喷涂技术制备2000μm厚的热障涂层。含或不含垂直裂纹的热障涂层的粘附强度分别为24.7和11.0 MPa,表明含垂直裂纹的热障涂层的界面稳定性更高。循环热暴露及热震试验表明其热稳定性更高。含或不含垂直裂纹的热障涂层的硬度分别为6.6和5.3GPa,经循环热暴露试验后分别升高至9.5和5.5 GPa。实验表明上层涂层中垂直裂纹的存在有利于延长热障涂层高温环境的寿命。     

Mechanical alloying of platinum with 5% ZrO2 nanoparticles for glass making tools

Synthesis and characterization of mechanically alloyed Pt–5%ZrO₂ (volume fraction) for structural components in the glass industry were described. Zirconia (ZrO₂) nanoparticles (<100 nm) were produced by the electrical explosion of zirconium (Zr) wires, and blended with platinum (Pt) powders (<44 μm) for 2–72 h in ambient atmosphere. The Pt particle size followed the typical decreasing trend of the normal ball milling process up to 48 h, but particle agglomeration was observed at 72 h. The grain size evolution was similar to that of the particle size, dropping down to around 50 nm at 48 h. The root mean square strain of the Pt crystallites showed the opposite behavior, maximizing at 48 h with a subsequent relaxation process. For the 48 h ball milled powders, spark plasma sintering was carried out to form a bulk disk. The measured mass loss of the sintered bulk sample shows a decent thermal stability despite its relatively low density.     

Fabrication of SiC_p/AA5083 composite via friction stir welding

Microstructure and mechanical properties of SiCp /AA5083 composite fabricated by friction stir welding (FSW) were investigated.The influence of the number of FSW passes on the distribution of SiC particles and mechanical properties in the joint was studied.After one pass,the SiC particles were entangled in the upper side of the stir zone (SZ).However,the particle distribution became more uniform after two passes due to the repeated stirring of the joint.As the SiC particles facilitate the grain refinement in the SZ by the pinning effect,the particle including region has much smaller grain size than the SZ without SiC particles.The SiCp /AA5083 composite region exhibits a Vickers hardness of HV90,which is much higher than the value of HV80 in the SZ produced by FSW without SiC particles.     

A fatigue life prediction model for Chopped Strand Mat GRP at elevated temperatures

Experimental and analytical investigations for the low cycle‐fatigue life prediction of Glass‐Reinforced Polymer (GRP) in Chopped Strand Mat (CSM) form are studied. Based on the theories of modulus degradation and residual strength degradation, a novel model is proposed for the prediction of progressive stiffness loss in terms of tension–tension fatigue load and the number of cycles. The proposed model involves various loadings and environmental variables, which makes the reliable predictions suitable for structural analysts. Experiments were carried out at room and elevated temperatures to evaluate the validity of the proposed prediction model for the characterisation of temperature‐dependent behaviour in fatigue. Predictions using the proposed model are in good agreement with the experiments that justify the use of the model to determine the extent of low‐cycle fatigue damage accumulation in GRP–CSM at room and elevated temperatures.     

THE ROLE OF MUNICIPAL‐LEVEL FACTORS IN NEIGHBORHOOD ECONOMIC CHANGE

Despite extensive studies on neighborhood change, the role of municipal‐level factors in neighborhood economic change has been underexplored. This article reviews diverse social science literature and makes theoretical connections between city size and homogeneity of city population and municipal performance, which is accordingly associated with neighborhood economic health. Building on the insights from the literature, this study hypothesizes that neighborhoods stay economically healthier in smaller cities and more homogeneous cities. This study presents a multilevel analysis of neighborhood economic change in 35 U.S. metropolitan areas between 1990 and 2000 and finds empirical evidence to support the proposed hypothesis.     

SIMULATING DIFFUSION MODEL AND DETERMINING DIFFUSIVITY OF POTASSIUM SORBATE THROUGH PLASTICS TO DEVELOP ANTIMICROBIAL PACKAGING FILMS

A diffusion model was simulated by computer programming and diffusivities of potassium sorbate through various plastic films were determined by a lag time method. The simulation showed that partition coefficient affected the flux of total penetration but did not affect the lag time. Therefore, the lag time method is appropriate in determining diffusivity, using any value for the partition coefficient. The diffusivities of potassium sorbate were 1.83 × 10⁻⁸ cm²/s, 4.26 × 10⁻¹³ cm²/s, 4.65 × 10⁻¹³ cm²/s, and 5.47 × 10⁻¹³ cm²/s through low density polyethylene (LDPE), high density polyethylene, polypropylene, and polyethylene terephthalate, respectively at 25 C. Arrhenius equation shows very good fit between the diffusivity and the temperature by the linear regression analysis. D₀ and E_a of potassium sorbate through LDPE film resulted in 1.98 × 10⁻⁶ cm²/s, and 11.83 KJ/mole K. The concentration of potassium sorbate was insignificant and did not contribute to the statistical model. This result verifies that the diffusion of potassium sorbate in LDPE film is typical case ofFickian diffusion.