1,543 research outputs found
PREDICTION OF TRANSIENT OSCILLATING FLOW IN CZOCHRALSKI CONVECTION
No full textA numerical study was made of transient oscillatory flow modes in Czochralski convection. The temperature oscillation was computed over a broad range of the mixed convection parameters, 0.132 less than or equal to Ra/Pr Re-2 less than or equal to 1.303. This encompasses the buoyancy- and forced-dominant convection regimes. The computed period of oscillation was shown to be in excellent agreement with the relevant experimental results. Parametric studies were performed, which led to an understanding of the transition mechanism. Computational results were presented to disclose oscillating flow patterns and thermal fields. The influences of melt level and of the size of crystal rod on the onset of oscillation were examined. The effect of crucible rotation (Re-c) was also evaluated. The oscillatory flow modes were analyzed in derail for a realistic,low value of Pr
Thermal decomposition and deformation of dye and polycarbonate in compact disc-recordables
No full textThermal decomposition and deformation of a compact disc-recordable were simulated and observed. From the calculations, the writing power for the dye melting, dye decomposition and the polycarbonate (PC) deformation was predicted, and was experimentally confirmed by atomic force microscope (AFM) observation of the dye layer and PC surfaces. The deformation effects of each layer were evaluated according to the recording characteristic, the carrier to noise ratio (CNR). In the wrting power range of 4.0-6.0 mW, the deformation of the PC substrate contributes to the CNR increase and the PC plays an important role in efficiently improving the CNR
Synthesis of chain-extended organifier and properties of polyurethane/clay nanocomposites
No full textClay organifier with hydroxyl end-group and relatively high molecular weight was synthesized. The clay treated with the organifier was suspended in DMF and the dispersibility of organoclay in polyurethane matrix was enhanced by applying the sonication to the suspension of organoclay in DMF. The d-spacing of organoclay was found to be 2.29 nm compared to 1. 18 nm of pristine montmorillonite. The polyurethane/clay nanocomposites formed an intercalated structure with some disorder and their d-spacings were about 2.6-2.7 nm. The barrier property, thermal stability and tensile properties significantly increased with increasing the dispersibility of organoclay. A 2.9-fold increase in tensile strength with 1 wt% of well-dispersed organoclay, a 41% decrease in oxygen permeability and a 1.7-fold increase in Young's modulus at 5 wt% of well-dispersed organoclay were achieved. (C) 2004 Elsevier Ltd. All rights reserved
Input test signal design and parameter estimation method for the Hammerstein-Wiener processes
No full textWe propose a new parameter estimation method for Hammerstein-Wiener-type processes composed of the input-output nonlinear static functions and a linear dynamic subsystem. A special test signal is designed to separate the identification problems of the linear dynamic subsystem and the output nonlinear static function from that of the input nonlinear static function. Then, the system identification procedure can be significantly simplified: the identification problems of the linear dynamic subsystem and the output nonlinear static function can be solved independently without considering the input nonlinear static function, and the model parameters of the input nonlinear static function can also be estimated analytically without any iterative nonlinear optimization. Furthermore, we develop a new estimation algorithm to identify the linear dynamic subsystem and the output nonlinear static function more efficiently. This algorithm does not need to initialize the model parameters of the output nonlinear static function and reduces the searching space in the iterative nonlinear optimization problem, resulting in more robust and faster convergence and easier initialization in the nonlinear optimization compared to previous approaches
Analysis of nanowire alignment in a microchannel”, 9th International Symposium on Particle Image Velocimetry
No full textModeling and analysis of an energy-efficient sleep-mode operation in IEEE 802.16e system
No full textPinworm Control and Risk Factors of Pinworm Infection among Primary-School Children in Taiwan
No full textPurification and characterization of a thermostable alkaline phosphatase produced by Thermus caldophilus GK24
No full textThe thermophilic and thermostable alkaline phosphatase was purified to near homogeneity from the osmotic lysis of Thermus caldophilus GK24. The purified enzyme had an apparent molecular mass of 108, 000 Da and consisted of two subunits of 54,000 Da. Isoelectric-focusing analysis of the purified enzyme showed a pi of 7.3. The enzyme contained two Cys residues, and its amino acids composition was quite different from that ai Thermus aquaticus YT-1 alkaline phosphatase and Escherichia coli alkaline phosphatase. The optimum pH and temperature of the enzyme were 11.0-11.5 and 80 degrees C, respectively. The enzyme was stable in the pH range of 9.0-12.0 at 25 degrees C for 36 h, and the half-life al 80 degrees C (pH 11.0) was 6 h. The enzyme was activated by MgCl2 and inhibited by EDTA. With p-nitrophenyl phosphate (pNPP) as the substrate, the enzyme had a Michaelis constant (K-m) of 3.6x10(-5) hM The enzyme preferentially hydrolyzed the phosphomonester bond of AMP in ribonucleotides and glycerophosphate
一个新的稳健ARCH检验和YJ-GARCH模型
Get PDF众所周知，Engle (1982) 的ARCH检验对于条件均值模型误设并不稳健，特别地，当条件均值是非线性过程而我们仅对之建立线性模型时，它过度地拒绝真实的原假设，导致出现严重的水平扭曲 (size distortion)。因此，本文在文献当中首次利用Yeo-Johnson变换方法来转换均值模型的因变量以排除ARCH 过程中均值部分的非线性，进而提出一个新的稳健ARCH检验以及一个新的GARCH模型——Yeo-Johnson (YJ) GARCH模型。蒙特卡罗模拟结果表明，稳健的ARCH检验在水平 (size) 和势 (power) 方面的表现要显著优于Engle (1982) 的ARCH检验。对上证综指收益率的实证研究结果表明，YJ-GARCH模型的拟合效果要显著优于线性GARCH模型。该论文已经被《统计研究》接受， 即将发表
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