1,433 research outputs found
Reaction Pathway and Potential Barrier for the CaH Product in the Reaction of Ca (4s4p1 P1+H2 -> CaH (X2U+) + H
No full text
Enhanced light extraction efficiency from organic light emitting diodes by insertion of a two-dimensional photonic crystal structure
No full textWe studied the characteristics of organic light emitting diode (OLED) devices containing two-dimensional (2D) SiO2/SiNx photonic crystal (PC) layers. The finite-difference time-domain (FDTD) method was employed for the design and analysis of the PC OLED. Based on the design parameters derived from the FDTD calculations, a 2D PC layer was introduced on the glass substrate of a typical OLED structure by two-step irradiated hologram lithography and reactive ion etching. Experiments showed that incorporation of the PC layer improved the light extraction efficiency by over 50% compared to the conventional OLED, without noticeable degradation in electrical characteristics, under typical operating conditions. This improvement originates from the liberation of the photons trapped in the high-index guiding layers. (C) 2004 American Institute of Physics.This work was supported by the new faculty research
program 2004 of Kookmin University in Korea. The authors
would like to thank the members of the electronic materials
development team of Samsung SDI, Co. Ltd. for their great
help
Direct numerical simulation of turbulent Couette-Poiseuille flow with zero skin friction
No full textThe near-wall scaling of mean velocity U(y) is addressed for the case of zero skin friction on one wall of a fully turbulent channel flow. The present DNS results can be added to the evidence in support of the conjecture that U is proportional to √yw in the region just above the wall at which the mean shear dU/dy = 0
Crashworthiness assessment of side impact of an auto-body with 60trip steel for side members
No full textThis paper is concerned with the energy absorption efficiency of auto-body side Structures for the conventional steel and 60TRIP high strength steel. In order to evaluate the energy absorption efficiency, the dynamic crash analysis is carried out with the regulation of US-SINCAP. The analysis adopts the Johnson-Cook model for the dynamic material properties, which have been obtained from dynamic material tests. For the sake of the dynamic material properties, the analysis has been accurately performed for the crashworthiness assessment. The analysis result provides deformed shapes, amounts of penetration and accelerations at several important points during crash. The result confirms that 60TRIP greatly improves the crashworthiness of the side members without sacrificing the weight and thus can be used for the light-weight design of an auto-body
High temperature load relaxation behavior of superplastic iron aluminides
No full textSuperplastic deformation and high temperature load relaxation behavior of coarse-grained iron aluminides have been investigated in this study. Iron aluminides with compositions of Fe-28 at.% Al and Fe-28 at.% A1-5 at.% Cr were prepared and thermomechanically treated to obtain an average grain size of about 500 mum A series of load relaxation tests was conducted at temperatures ranging from 600 to 850 degreesC. The flow curves obtained from load relaxation tests were found to have a sigmoidal shape and to exhibit stress vs. strain rate data in a very wide strain rate range from 10(-7)/s to 10(-2)/s. Tensile tests have been conducted at 850 degreesC and at various initial strain rates ranging from 3x10(-5)/s to 1x10(-2)/s to investigate the superplastic deformation behavior. Maximum elongation of similar to 500 % was obtained at the initial strain rate of 3x10(-5)/s and the maximum strain rate sensitivity was round to be 0.68. Microstructural observation through the optical microscopy has been carried out on the deformed specimens and it has revealed the evidences for grain boundary migration and grain refinement to occur during deformation, suggesting the dynamic recrystallization mechanism as reported earlier. The activation energy was evaluated as 387 kJ/mol in the strain rate range from 10(-4)/s to 10(-2)/s, which is very close to that for creep deformation in Fe3Al alloys.X11sciescopu
Characterization of elliptic core fiber acousto-optic tunable filters operated in the single mode and the multi-mode range
No full textelectrodeposited ni/al2o3 composite coating on ndfeb permanent magnets
No full textNdFeB permanent magnets are highly susceptible to corrosion in various environments. A new composite coating electrodeposited on NdFeB magnets was investigated in this paper. The Ni matrix film was firstly electrodeposited on NdFeB surface from watts nickel electrolyte, and then Ni/Al2O3 composite coating was successively electrodeposited on the Ni film. The microstructures of electrodeposited Ni coating and Ni/Al2O3 composite coating were observed by scanning electron microscopy (SEM), The corrosion behavior of Ni coating and Ni/Al2O3 composite coating in 3.5wt% NaCl solution was studied by polarization curves and electrochemical impedance spectroscopy (EIS). The results showed that the Ni coating and Ni/Al2O3 composite coating could both provide adequate protection to NdFeB substrate. But the free corrosion potential of Ni/Al2O3 Composite coating was more positive and the passivation region was more obvious when compared with Ni coating. Meantime, the capacitance loop diameter of Ni/Al2O3 composite coating was significantly larger than that of Ni coating which suggested that the anticorrosion resistance of Ni/Al2O3 composite coating was better than electroplated Ni coating
Planarized SiNx/spin-on-glass photonic crystal organic light-emitting diodes
No full textThe light extraction characteristics of low-index spin-on-glass (SOG)-assisted, planarized photonic crystal organic light-emitting diodes (PC OLEDs) are reported. The light extraction efficiencies of planarized two-dimensional (2D) SiNx/SOG PC OLEDs (type II) and 2D SiNx/SOG PC OLEDs with an additional high-index SiNx layer (type III) are significantly better under typical operating conditions than those of the first generation of 2D SiO2/SiNx PC OLEDs (type I). The enhancements in the extraction efficiencies of type-II and type-III PC OLEDs are about 63% and 85%, respectively, with respect to those of conventional OLEDs with indium tin oxide layers of identical thicknesses. These improvements in extraction efficiencies are attributed not only to the liberation of the photons trapped in the high-index guiding layer but also to a reduction in the surface plasmon contribution. (c) 2006 American Institute of Physics.This work was supported by Grant No. 2005-02522 of
the Nano R&D program and Grant No. R11-2005-048-
00000-0 of the ERC program from the Ministry of Science
and Technology in Korea
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