Abstract: The poly(lactic acid) (PLA) was modified by 4,4'-diphenylmethane diisocyanate (MDI) successfully prepared to improve the stability of PLA. The MDI and the hydroxyl terminated PLA could form PLA modified by MDI (MDI-PLA) via addition reaction. The structure of MDI-PLA was confirmed by FTIR and its degradation properties were investigated. The results showed that the pH of the aqueous media and the ion strength together played an important role in the degradation behavior of the PLA and MDI-PLA. Both of the PLA and MDI-PLA had the highest degradation rate in 0.01 M NaOH. It offers the best stability to hydrolysis resistance by adding the 0.6 wt% of MDI to the PLA materials，and have a more stable of 15 times than unmodified PLA.
Abstract: Among the proposed techniques for delivering drugs to specific locations within the human body, magnetic drug targeting (MDT) surpasses because of its noninvasive character and its high targeting efficiency. In this study, two novel arrangements of permanent magnets, Halbach array and spin-Halbach, were introduced to improve the magnetic force acting on a magnetic micro/nanoparticle. Then an approach of design and evaluate the MDT magnets was developed, which was based on three performances proposed in the paper, force parameter, evaluation variable, and transverse inhomogeneity. Corresponding parameters for Halbach-Like arrays at distance of 3 cm of application from magnetic field source were calculated and compared with the other two simple magnet arrays. According to the results, the values of performances for the Halbach-Like magnet arrays were improved obviously.
Abstract: The purpose of this study was to discuss the effects of different solvent systems for aluminum doped zinc oxide (AZO) thin film deposition by using the sol-gel method. In the conventional sol-gel method of producing AZO thin films, the solution selected as the precursor solvent was used ethylene glycol monomethylether (EGME), which in this study propylene glycol mono-methyl ether (PGME) was used. The precursor solution was observed by TGA/DSC to understand the variations while heating. The two prepared precursor solutions were then respectively spin coated onto substrates of boron silicate glass. XRD analysis indicated both showed significant c-axis preferred orientation. The surface morphology of the films was observed by FESEM, which showed that the thin film surface by PGME solvent was smoother and dense. A four-point probe was used to measure the electrical resistance of the thin films, which the measured results indicated that the thin film produced by PGME had lower resistivity than those produced by EGME. Resulting with a thin film electric resistance reaching as low as 3.474×10-3(W×cm). The visible light transparency was determined via UV-vis analysis. Results showed that the average transparency of thin films produced by the EGME solvent reached 95% and above, where the average transparency from PGME solvent still reached 90% and above. Experimental results demonstrated that PGME is a good option to synthesize AZO thin films.
Abstract: This study is mainly to control the density of zinc oxide nanowires arrays as main axis. We spin coated AZO thin film to Si/SiO2 substrate by hydrothermal method growing ZnO nanowire arrays on a substrate by spin coating a layer of zinc powder mixed with SiO2 film, and controlled the concentration of zinc. We can easily obtain a nanowire array density control. In this experiment, we investigated different centrifugation speed, time, zinc concentration, temperature and other variable parameters. Through field emission scanning electron microscopy observation of dispersive zinc oxide nanowires and dispersion situation, it was found that using different doping concentration and rotation speed, different densities can be successfully obtained for ZnO nanowires array. Dispersion of zinc oxide nanowires by hydrothermal method with increasing time, the diameter and length will increase significantly.
Abstract: This study proposes a novel sol-gel method of fabricating the two-dimensional flakes polycrystalline zinc oxide (ZnO). Apply zinc acetate dehydrate in glycerol and hydrolyzed to get the precursor zinc alkoxide particles at 160°C, and self-assemble into flakes ZnO nanostructures, and then got higer crystallinity polycrystalline ZnO after calcination for one hour at 500°C. Field-emission scanning electron microscopy (FE-SEM) was used to observe the morphology of the flakes. Its size got to a few μm2. Analyze the crystal structure and crystallinity by X-ray powder diffraction (XRD). After calcination for one hour at 500°C, we can determine it is the hexagonal wurtzite structure of ZnO. And TGA/DSC to observe the loss and phase change of the solution. The Study has successfully synthesized ZnO polycrystalline flakes by sol-gel method.
Abstract: This Study applies to Stöber method for synthesis an characterization of even-sized SiO2 micrometer sphere; and then applies to sol-gel method for encapsulation for one layer of ZnO at SiO2 spherical surface after regarded it as core so that synthesis SiO2/ZnO core-shell spheres successfully. And observe morphology by FE-SEM and crossection by TEM. The TEM specimen were cut by two-beam FIB. Besides, EDS, XRD and UV-Visible spectroscopy were using for the analysis of composition, crystallization structure, and absorption spectrum, respectively. Experimental results showed that, SiO2 spherical surface became smooth after deposition for zinc oxide. The specimen made by FIB more obviously was observed for core-shell distribution by TEM. EDS analysis made us clearly see shell signal with ZnO content, but core signal only is SiO2 content. XRD analysis indicated its core-shell sphere signal possessing ZnO content, but UV-Visible absorption spectrometer displayed ZnO has been absorbed in range of UV light, in contrast, it is not absorbed in range of visible light.
Abstract: In order to develop a Web-based style semantics database system of machining centers, this paper focuses on using Image Scale to describe the style image cognition of machining centers which is a vague psychological concept, give mathematical description of image scale. Then through a style image cognition experiment, 6 adjective pairs are chosen to link with the style image cognition of machining centers, so a 6 dimensional image scale is got. At last, this paper proposes a 5´6 matrix SNC that is called Style Description Matrix of machining centers to describe their image scale in mathematics.
Abstract: Quantitative risk analysis is a method to evaluate risk and to identify areas for risk reduction. The final goal of our study is to propose an effective method for risk assessment of explosion hazard. To achieve the goal, a phenomenon that influences the consequences of explosion is first identified: self-turbulization and resulting acceleration of expanding flame during explosion. The fractal dimension is then identified as the key parameter that characterizes the phenomenon. Since the previous method to determine fractal dimension relies on large-scale explosion experiment, it has not been easy to determine fractal dimension. This paper demonstrates the possibility of determining fractal dimension by analyzing flame images of small-scale experiment, which might significantly reduce the cost of risk assessment of explosion hazard.
Abstract: In order to investigate sub-rapid solidification behavior of semi-solid magnesium alloy metal, a novel semi-solid processing technique, called new vacuum suction casting (NVSC), is used to manufacture thin castings of AZ91D Mg-alloy directly from a liquid metal. The resulting microstructures of castings are characterized in detail and linked to the solidification behavior. In the microstructure of the sub-rapidly solidified SSM sheet, the “preexisting” primary solid particles, with the morphology of near-globules or rosettes, disperse in the homogeneous matrix consisting of fine near-equiaxed secondary α-Mg grains and fine precipitates of β-Mg17Al12 intermetallics. Owing to rapid solidification rate, the volume fraction of the β phase in the sub-rapidly solidified SSM sheets is much lower than that in the as-cast ingot. In addition, the content of alloying elements of Al and Zn was higher in the grain boundaries and the eutectic structure than that in the primary solid particles and in the second α-grains.
Abstract: Creep-Feed Grinding(CFG) is one of the none-traditional machining in which form grinding to full depth is performed in limited number of passes. One of the most significant criteria which is taken into account to display valid machining parameters, is surface integrity. Surface integrity in CFG process is influenced by four main factors including surface roughness, superficial micro-crack, burning and changes in micro-hardness. According to prior investigations in CFG process, depth of cut plays an important role in surface integrity. In this study, the influence of cutting depth on workpiece surface integrity of cast nickel-based superalloy with alummina wheels, was investigated. During this study, a sample part was machined with variable depth of cut while the other parameters were Constant. After machining, surface roughness of each specimen was measured and in order to investigate existence and dimensional situation of surface micro-cracks, Chemical Etch + FPI and Thermal shock + FPI were performed. For determining micro-structural changes in ground specimens as a clarifier criteria in measuring the level of residual stress, a set of recrystallization processes were carried out on them and average grain size were measured. The results show, however, changing in depth of cut hasn't influenced on micro-cracks, quality of surface roughness has descended in terms of increasing the cutting depth.