In situ preparation of nano ZnO/hyperbranched polyimide hybrid film and their optical properties

Novel hybrid films of fluorinated hyperbranched polyimide (HBPI) and zinc oxide (ZnO) were prepared via the in situ sol-gel polymerization technique, in which mono-ethanolamine (MEA) was used as the coupling agent between the termini of HBPI and the precursor of ZnO. The hybrid films were characterized by transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) absorption, ultraviolet-visible (UV-vis) absorption, and fluorescent excitation/emission spectroscopy. The films, which originated from the colourless fluorinated HBPI structure and homogeneously dispersed ZnO nanoparticles, exhibited good optical transparency. Furthermore, two kinds of model compounds with and without ZnO and a HBPI film blended with ZnO microparticles were prepared to clarify the fluorescence mechanism in the pristine HBPI and in situ hybrid films. Efficient energy transfer from the ZnO nanoparticles to the aromatic HBPI main chains was observed in the in situ hybrid films, whereas energy transfer occurred only from the locally excited (LE) states to the charge-transfer (CT) state in the HBPI film. These facts demonstrate that the peripheral termini of HBPI are covalently bonded to ZnO particles via the MEA function, which operates as an effective pathway for energy transfer to give intense fluorescent emission.     

Disorders and oxygen vacancies in p-type Sn2B2O7 (B = Nb,Ta): Role of the B-site element

Sn₂Nb_2−xTa_xO₇ (x = 0.0–2.0) with pyrochlore structure is a promising material for p-type oxide semiconductors. A systematic study of its Nb/Ta ratio indicated that the hole–generation efficiency of the Nb end (Sn₂Nb₂O₇) was an order of magnitude lower than that of the Ta end (Sn₂Ta₂O₇). Although this occurs due to differences in oxygen-vacancy formation, the origins of the hole–generation efficiencies remain unclear due to limited information on local and global crystal-structure disorders in pyrochlore Sn₂Nb₂O₇ and Sn₂Ta₂O₇. In this study, the crystal structures of Sn₂B₂O₇ (B = Nb, Ta), composed of BO₆ octahedra and Sn₄O tetrahedra, were investigated using X-ray absorption spectroscopy and X-ray diffraction. A detailed investigation of the local and global crystal structures indicated a larger amount of disorder in the Sn₄O tetrahedra in Sn₂Nb₂O₇ compared to Sn₂Ta₂O₇; disorder in the BO₆ octahedra occurred only in Sn₂Ta₂O₇. This study indicates that an appropriate selection of the B-site element is vital for suppressing defect and disorder formation in Sn₄O tetrahedra and subsequently improving the hole–carrier–generation efficiency.     

Electroreductive block copolymerization of dichlorosilanes in the presence of disilane additives

The electroreductive polymerization of dichloromethylphenylsilane in the presence of triphenylsilyl group‐containing disilanes such as hexaphenyldisilane followed by the electroreductive termination with chlorotriphenylsilane afforded triphenylsilyl group‐terminated polymethylphenylsilane in 15–32% yield. The isolated polymethylphenylsilane (M_n = 3350 g mol^?1, M_w/M_n = 1.4) was found to react as a macroinitiator to copolymerize with dibutyldichlorosilane under electroreductive conditions producing the corresponding block copolymer (M_n = 4730 g mol^?1, M_w/M_n = 1.2) in 38% yield. The ratio of monomer units (? MeSiPh? to? BuSiBu? ) of the copolymer was determined to be 75:25 using ¹H NMR analysis, which was in good agreement with the calculated ratio (74:26) on the assumption that molecular weight of the macroinitiator was not changed. The block structure of the resulting copolymer, poly(methylphenylsilane)‐block‐poly(dibutylsilane), was also confirmed by comparing its ¹H NMR and UV absorption spectra with those of polymethylphenylsilane, polydibutylsilane and a statistical copolymer prepared by electroreductive polymerization of dichloromethylphenylsilane with dibutyldichlorosilane. This method is applicable to the preparation of other types of macroinitiator such as triphenylsilyl group‐terminated polydibutylsilane, and polydibutylsilane‐block‐polymethylphenylsilane was also obtained using this macroinitiator. Copyright © 2011 Society of Chemical Industry     

Chaotic transport in antidot lattices

A review is given of quantum effects and roles of chaos in transport in antidot lattices mainly from a theoretical point of view. The topics include diffusive orbits combined with a magnetic focusing effect as the origin of the commensurability peaks, semiclassical quantization of periodic orbits as the origin of the Aharonov-Bohm type oscillation superimposed, and the importance of inherent disorder in the antidot potential itself.     

A 2.5-GFLOPS, 6.5 million polygons per second, four-way VLIWgeometry processor with SIMD instructions and a software bypassmechanism

A four-way very long instruction word (VLIW), 312-MHz geometry processor with peripheral component interconnect/accelerated graphic port bus bridge was implemented in a 0.21-μm, 2.5-V, three-layer-metal CMOS process. We adopted (1) a software bypass mechanism, (2) single-instruction multiple-data stream instructions, (3) four sets of floating-point multiply add and accumulate execution units, (4) special condition code registers and a branch condition generator for a clipping operation, and (5) automatic clock delay tuning methodology. As a result of these features, we achieved a performance of 2.5 GFLOPS and 6.5 million polygons per second for a three-dimensional geometry processor, which is the highest published performance as a single geometry processor. The processor is applicable to computer-aided-design systems that require very high graphics performance     

Effects of species and moisture content on penetration of liquid in laser incised lumber by the passive impregnation method

Penetration of liquid by passive impregnation method for Douglas-fir (Pseudotsuga menziesii Franco), sugi (Cryptomeria japonica D. Don) and Japanese larch (Larix leptolepis Gordon) was studied. Effects of initial moisture content of sugi (16, 43 and 70% moisture content) on liquid penetration were also studied. Dried Douglas-fir (mc=14%) and sugi (mc=16%), and green Japanese larch (mc=45%) and sugi (mc=70%) were treated by passive impregnation method for penetration analysis. It was observed that dried sugi had the highest level of liquid penetration both in length (170 mm) and width (8 mm) for all measured sections followed by green sugi, green Japanese larch and dried Douglas-fir. In case of different initial moisture content, the highest absorption (624 kg/m³) and penetration (maximum 87 and 96% at cross and longitudinal surfaces, respectively) was observed for sugi having the lowest initial moisture content under the same passive impregnation conditions. Absorption and penetration decreased with the increase of initial moisture content for sugi. These results could help in designing incising pattern and density, as well as solving the problems related to high initial moisture content of wood for passive impregnation.     

Post-Mortem Softening of Fish Muscle During Chilled Storage as Affected by Bleeding

Bleeding caused the delay of muscle softening in yellowtail, horse mackerel, and striped jack, which are pelagic fish. Conversely, bleeding had no influence on the muscle firmness of red sea bream, flatfish, and rudder-fish, which are demersal fish. Transmission electron microscopy showed delay of degradation of pericellular collagen fibrils in bled yellowtail and horse mackerel. Striped jack showed slower weakening of the pericellular connective tissue in a compression test. However, the demersal fish had no structural difference due to bleeding. These results indicate that removal of blood could delay collagen fibril degradation and muscle softening of pelagic fish.     

Micro 3D measurement method using SEM

Three diamensional (3D) measurement method by Scanning Electron Microscope (SEM) has already been proposed by using the principle of shadow moiré. In the method, the image of original grid in shadow moiré image must be clearly removed in fringe analysis process in order to perform high resolution analysis. A new method based on the principle of projection moiré is proposed to solve the trouble concerning the grid. In this paper, the mechanism of producing some shadows of grid on the surface of the object by back scattering electron beam in the new method is discussed. Fringe image as shadow of grid is analyzed by Wavelet transform. The precise 3D measurement is realized by using the phenomenon of shadows of grid. Furthermore, a 3D micro structure on the head of a hard disk is measured. From the comparison of results obtained by Atomic Force Microscope (AFM), it is confirmed that the proposed method has high-resolution power(about 20nm).     

Fabrication of high‐strength steel fibre reinforced metal matrix composites by explosive bonding and their tensile properties

Summary

Steel fibre reinforced metal matrix composites (FRM) consisting of high‐strength ductile steel wire and aluminium or titanium foil were fabricated by explosive bonding. The strength properties were evaluated by tensile tests. The optimum explosive loading (explosive mass/driver plate mass) increases with the volume fraction of fibre. For the aluminium matrix composites, the micrographs obtained show sound bonding between the adjoining foils and non‐bonding between the foil and steel wire. The tensile strength of the aluminium matrix composites is 80% of the value predicted by the rule of mixtures. For the titanium matrix composites, the micrographs obtained show both bonded and unbonded regions between the adjoining foils or between the foil and steel wire. The tensile strength of the titanium matrix composites agrees with the value predicted by the rule of mixtures.     

Nondestructive Quantitative Evaluation of Porosity Volume Distribution in Aluminum Alloy Die Castings by Fractal Analysis

The nondestructive and three-dimensional quantitative evaluation of porosity in aluminum alloy die castings is proposed to identify whether the predominant cause of pore formation is shrinkage or entrapped gas. The validity of this method of evaluation was shown by comparing two different regions with different ratios of pores formed by shrinkage and gas. It was shown that the proposed evaluation can be used as a quantitative indication of porosity.