Wet oxidation of thin AlAs in cylindrical composite of GaAs/AlAs/GaAs

Lateral wet oxidation in a cylindrical composite, GaAs/AlAs/GaAs, with varying thickness of the AlAs layer has been investigated. The oxidation depth in AlAs was measured in the temperature range of 400–480 °C. At given temperature and time, the depth increases with the increase in thickness. The thickness effect was successfully interpreted based on the kinetic model of boundary layer diffusion. The results are consistent with the findings from early studies on samples of square and rectangular cross-sections with the same activation energy of the thermal process.     

Improvements on the design and implementation of DVB-S2 LDPC decoders

The architecture of a field-programmable gate-array (FPGA) implementation of a low-density parity-check (LDPC) decoder for the Digital Video Broadcasting – Second Generation via Satellite (DVB-S2) standard is presented. Algorithms are devised to systematically apply the values given in DVB-S2 to implement a memory mapping scheme, which allows for 360 functional units (FUs) to be used in decoding and supports both normal and short frames. A design of a parity-check module (PCM) is presented that verifies the parity-check equations of the LDPC codes. Furthermore, a special characteristic of five of the codes defined in DVB-S2 and their influence on the decoder design is discussed.Two versions of the LDPC decoder are synthesized for two families of FPGAs. The results show that the decoder presented uses fewer hardware resources than a DVB-S2 LDPC decoder found in the current literature that also uses FPGA, while improving the maximum frequency of the decoder.     

Synthesis and electrochemical,in situ spectroelectrochemical,electrical and gas sensing properties of ball-type homo- and hetero-dinuclear phthalocyanines with four [1a,8b-dihydronaphtho[b]naphthofuro[3,2-d]furan-7,10-diyl] bridges

The new mono-nuclear Fe^II 2 and ball-type homo-dinuclear Fe^II–Fe^II 3 phthalocyanines have been synthesized from the corresponding 4,4′-(1a,8b-dihydronaphtho[b]naphthofuro[3,2-d]-furan-7,10-diyl)bis(oxy)diphthalonitrile 1 while ball-type hetero-dinuclear Fe^II–Co^II phthalocyanine 4 was synthesized from 2. The compounds have been characterized by elemental analysis, UV–vis, IR and MALDI-TOF-mass spectroscopies. The redox behaviours of the complexes were identified by controlled-potential coulometry, cyclic voltammetry and differential pulse voltammetry measurements on Pt in dimethylsulfoxide containing tetrabutylammonium perchlorate. The assignments of the redox processes and the understanding of the interactions between the metal phthalocyanine units in 3 and 4 were achieved by the combined evaluation of the voltammetric and in situ spectroelectrochemical outcomes. Complex 3 showed ring-based mixed-valence behaviour as a result of the considerable interaction between the phthalocyanine rings. On the other hand, the interactions between the two metal phthalocyanine units of 4 were found to be much weaker than those in 3. The potential application of molecular organic semiconductors needs the control adjustment of conductivity. Ac and dc conductivity measurements were performed with the applied external electric filed. At high frequency, the conduction follows the universal power law and conduction mechanism can be explained by classical hopping barriers mechanism for the system.     

GA-based decision support systems for precast production planning

Appropriate production plans can produce effective resource utilization and minimize waste. However, most precast fabricators currently propose production plans depending on the rule of thumb, resulting in squandered resources and postponed delivery. Computerized scheduling techniques provide more precise outcomes than manual scheduling. The objective of this study is to develop GA-based Decision Support Systems (GA-DSS) to assist production managers in arranging production plans. This research first establishes a flowshop sequencing model based on the current production status by considering the buffer sizes between production stations. A multiple objective genetic algorithm is then applied to search for solutions with minimum makespan and tardiness penalties. The GA-DSS performance is verified using two examples. The results demonstrate that the proposed system can offer appropriate production plans. By taking buffer sizes into consideration more reasonable and feasible production sequences can be achieved.     

Suggestion of new methodology for evaluation of osseointegration between implant and bone based on μ-CT images

Osseointegration has been used as an index for prediction of long-term success of implant. Osseointegration has been routinely evaluated by measuring bone contact ratio on histology based on two-dimensional (2D) sections or images. However, these both methodologies have been less informative analysis of results and have several disadvantages. The aim of this study is to introduce new methodology for evaluation of a degree of osseointegration between bone and implant based on micro computed tomography (μ-CT) images. Specimen was scanned at a voxel resolution of 35 μ by μ-CT. Three-dimensional (3D) models of bone and implant were reconstructed respectively. Bone contact area (BCA) and bone contact area ratio (BCAR) were measured and calculated. Here, osseointegrated BCA between bone and implant surfaces was determined by computing areas of all bone regions existed within 35μ distance from implant surface. Osseointegration of flapless implant surgery was evaluated by new methodology, compared with that of flap implant surgery. BCA and BCAR in flapless implant surgery was significantly bigger than that in flap implant surgery (p<0.05), suggesting that flapless implant surgery was more effective than flap implant surgery consistent with previous studies. In the conclusion, new methodology for evaluation osseointegration between bone and implant based on μ-CT images was likely to be reliable, useful and more informative analysis of results.     

Image Resolution Enhancement Using Spatially Invariant Point Spread Function

<正>This paper presents an image resolution enhancement algorithm using spatially invariant point spread function.Point spread function is used to constrain the solution space.This parameter is computed at each iteration step using partially restored image at each iteration,and High pass filter is used to impose the degree of edge smoothness on the solution.The resulting iterative algorithm exhibits the increased PSNR better than Bicubic interpolation approach.     

Nanotube morphology changes for Ti-Zr alloys as Zr content increases

Nanotube morphology changes in Ti-Zr alloys as Zr content increases have been investigated. Ti-Zr (10, 20, 30 and 40 wt.%) alloys were prepared by arc melting and heat treated for 24 h at 1000 °C in an argon atmosphere. TiO₂ nanotubes were formed on the Ti-Zr alloys by anodization in H₃PO₄ containing 0.5 wt.% NaF. Electrochemical experiments were performed using a conventional three-electrode configuration with a platinum counter electrode and a saturated calomel reference electrode. Samples were embedded in epoxy resin, leaving an area of 10 mm² exposed to the electrolyte. Anodization was carried out using a scanning potentiostat, and all experiments were conducted at room temperature. Microstructures of the alloys were examined by optical microscopy (OM), field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). The Ti-Zr alloy microstructures observed by OM and FE-SEM changed from a lamellar structure to a needle-like structure with increasing Zr content. The microstructures also changed from β phase to increasing amounts of α phase as the Zr content increased. The number of large nanotubes formed by anodization decreased, and the number of small nanotubes increased, as the Zr content increased. The mean inner diameter ranged from approximately 150 to 200 nm with a tube-wall thickness of about 20 nm. The interspace between the nanotubes was approximately 60, 70, 100 and 130 nm for Zr contents of 10, 20, 30 and 40 wt.%, respectively.     

Solid‐State Conversion of Single Crystals: The Principle and the State‐of‐the‐Art

Solid‐state conversion of single crystals from polycrystalline materials has the advantages of cost‐effectiveness, chemical homogeneity, and versatility over the conventional melt growth and solution growth methods, particularly for systems with high melting points, incongruent melting, high reactivity (volatility), and phase transformations at high temperature. Nevertheless, for commercial production, this technique has only been successful in a few limited systems, in particular ferroelectric systems. This is mostly because of the difficulty in controlling the microstructure, particularly suppressing grain growth in the polycrystal during its conversion. This article describes the principle and the current status of the solid‐state conversion of single crystals. We first introduce the recently developed principle of microstructural evolution to explain the basis of the microstructure control in polycrystals for solid‐state conversion. We then report recent technical developments in fabricating single crystals by the solid‐state single crystal growth (SSCG) method and their physical properties. The SSCG method is expected to be studied and utilized more widely in fabricating single crystals with complex compositions as a strong alternative to the melt growth and solution growth methods.     

On the solid state heat transport phenomena measurement

The paper deals with theoretical and experimental aspects of lumped capacitance model (LCM) application for the study of heat transport in different materials. Patented construction of the measuring chamber together with special software the fundamental features of which are presented here allows evaluating thermal conductivity k, specific heat capacity c_p and thermal diffusivity α. Obtained results are in relatively very good agreement with those obtained from independent measurement or table values.