5,738 research outputs found
Preparation and characterization of a nano-sized Mo/Ti mixed photocatalyst
No full textNano-sized molybdenum-doped TiO(2) (Mo/Ti) mixed oxide photocatalysts were prepared with the Mo(5+) content varying from 0 up to 2.5 mol%, to shift the absorption onset into the visible region and to enhance the efficiency of photocatalytic activity by retarding the (e(-)-h(+)) recombination. Prepared Mo/Ti mixed oxides were characterized by ultraviolet and visible spectroscopy (UV/VIS), transmission electron microscopy-electron diffraction pattern (TEM-EDP), X-ray diffraction(XRD), energy dispersive X-ray (EDAX) and X-ray photoelectron spectroscopy (XPS). Photonic efficiency was also investigated with the degradation rate of dichloroacetate (DCA) and light intensity measured by actinometry. TEM-EDP and XRD patterns showed that particles were in the form of anatase with the diameter of ca. 4 nm. The appreciable red-shift in the UV/VIS absorption spectra was monitored at each preparation stage - aging and dialyzing. The red-shift varied with addition of Mo, in the case of 2.5% Mo/Ti the UV/VIS absorption started at around 0.22 eV less than in nano-sized pure TiO(2) (about 3.42 eV). EDAX verified that the amount of Mo in the prepared mixed oxides was as required, and XPS analysis revealed that Mo(V) existed in the TiO(2) lattice. The measured photonic efficiency increased to 0.28 with DCA at 0.5 mol% Mo, and then decreased as the Mo content increased above 0.5 mol% Mo. This could be explained in terms of the changing prevailing phenomena - electron trapping and recombination - as the amount of dopant increased in terms of the distance between the trapped sites of the charge carriers. (C) 2000 Elsevier Science B.V. All rights reserved.The authors wish to thank the Ministry of Science and Technology of Korea for financial support as a project for National Research Laboratory and Prof. J.Y. Lee at Material Engineering in Korea Advanced Institute of Science and Technology (KAIST) for the analysis by TEM–ED
Effects of microstructure on material Behaviors of solder alloys
No full textThe leading candidates for replacing lead-contained solders are near ternary eutectic Sn/Ag/Cu alloys. The electronic industry has begun to study both the process behavior and the reliability assessment of these alloys in detail to figure out their applicability to electronic devices and products. In recent publications, the solidification behavior and the fatigue life of the accelerated thermal cycle test have been reported in terms of microstructure variations such as the formation of large Ag3Sn plates and their effects. In this study, coupon type bulk specimens have been made for uniaxial tensile test by casting. To consider the effects of microstructure, casting cooling rates were controlled to 0.02-2.0 degrees C/sec. Eutectic Sn/Pb and near eutectic lead-free solder materials - Sn/Ag/Cu and Sn/Cu alloys - were used in mechanical testing. Also, nanoindentation tests were performed to measure Young's modulus of materials having different microstructures. Tensile tests were performed at 3 different strain rates and then acquired 0.2% offset proof stress, ultimate tensile strength and elongation to failure.Computer Aided Reliability Evaluation Laboratory, Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, South Kore
First-order analysis of thin-plate deformable mirrors
No full textContinuous thin-plate deformable mirrors with discrete actuators are widely used as adaptive mirrors. The performance of a thin-plate deformable mirror can be characterized by the influence functions and the layout of the actuators. This paper first derives equations that model the influence functions of thin-plate deformable mirrors based on an analytic calculation and a, finite- element analysis; then, it presents a performance analysis for the cases of triangular, rectangular, and hexagonal patterned-actuators. The results from this study may be used for first-order design and analysis of thin-plate deformable mirrors
MRP8, a new member of ABC transporter superfamily, identified by EST database mining and gene prediction program, is highly expressed in breast cancer
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