Preparation and microstructure of in-situ(ZrB_2+Al_2O_3+Al_3Zr)_p/A356 composite synthesized by melt direct reaction

（ZrB2＋Al2O3＋Al3Zr）/A356 composites were synthesized by melt direct reaction from A356-（K2ZrF6＋KBF4＋Na2B4O7） system.The phase compositions and the microstructures of the as-prepared composites were investigated by XRD,SEM and TEM.The results show that the reinforcements are composed of ZrB2 and Al2O3 ceramic phase particles and Al3Zr intermetallic particles.The ZrB2 particulates are easy to join together to form some particle clusters and distribute along the α（Al） grain boundary.The morphologies of the ZrB2 particulates are in hexagon-shape with the size of about 50 nm.The TEM investigation results of Al3Zr indicate that Al3Zr grows in the form of facet with the length-diameter ratio of about 20.The morphologies of Al2O3 particles are in rectangular-shape and ellipsoidal-shape,with the size of about 0.1 μm.In addition,the interfaces of the matrix and particles are net and no interfacial outgrowth is observed.

Preparation of Al-Al_3Ti in situ composites by direct reaction method

Al-Al3Ti composites were prepared by a direct reaction method, in which Al3Ti was formed by the reaction of Ti and Al in aluminum alloy melt. The morphology of Al3Ti changes apparently from the fine particle, needle-like to large block with the increase of Al3Ti content. The addition of magnesium can markedly change the morphology of Al3Ti and reduce their size. Short rod-like Al3Ti was formed and homogeneous distribution was obtained with the addition of 3 wt.% Mg. The effect of Al3Ti and Mg on the microstructure of Al-Al3Ti composites and the mechanism were also discussed.

Kinetics of the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation

In this study,high-gravity intensified heterogeneous catalytic ozonation is utilized for treatment of phenol-containing wastewater,and the kinetics of the direct reaction between ozone and phenol in the presence of excess tertiary butanol(TBA)is investigated.It is revealed that the direct reaction between ozone and phenol in the rotating packed bed(RPB)follows the pseudo-first-order kinetics with a reaction rate constant higher than that in the conventional bubbling reactor(BR).Under different conditions of temperature,initial pH,high-gravity factor,and gaseous ozone concentration,the apparent reaction rate constant varies in the range of 0.0160–0.115 min-1.An empirical power-exponential model is established to characterize the effects of these parameters on the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation.

In-situ Preparation of Al/TiAl_3(P) Composite by Direct Reaction between Molten Al and TiO_2 Powder

TiAl3 particle reinforced pure Al composite has been made by direct reaction among molten Al, TiO2 and a flux. The composite exhibits high Synthetically properties. The strength and hardness are higher than those of pure Al matrix by 71.5% and 134% respectively However, the elongation is 20.36%, slightly lower than that of the Al matrix.

PHASES AND STRUCTURE OF PREFORM DURING PREPARING PROCESS OF Al／TiCp COMPOSITES BY DIRECT REACTION SYNTHESIS

Direct reaction synthesis(DRS), based on the principle of self-propagating hightemperature synthesis (SHS), is a new method for preparing particulate metal matrix composites (PMMCs). The effects of the temperature of the aluminum melt and the aluminum content in the preform on the phases and structure of the reacted preform have been investigated by X-ray diffraction and scanning electron microscopy.It has been shown that TiC phase is prone to be synthesized with the increasing of the temperature of the aluminum melt and the decreasing of the aluminum powder content in the preform, and that the size of TiC particle becomes fine with the increasing of the temperature and the decreasing of the aluminum powder content.

Direct Dynamics Study on CH_2O + CH_3~·→ CHO + CH_4 Reaction

It is still a formidable challenge to study CH2O ＋ CH3·→ CHO ＋ CH4 reaction in the gas phase by traditional dynamics, because of the large number of freedom degrees for the system. In this paper, direct dynamics, in which trajectories were run directly on the DFT potential energy surface, have been applied to the reaction, which gave a direct look in the reaction processes. Two sets of trajectories at different initial orientations of reactants and temperature have been simulated. And the detailed reaction mechanisms have been described.

In-situ synthesized (Al_3Zr+Al_2O_3)_p /A356 composites by direct melt reaction in Al-Zr-O system

A novel in situ reaction system Al Zr O was developed. In situ Al 3Zr and Al 2O 3 particulate reinforced A356 alloy matrix composites have been fabricated by direct melt reaction method. The results show that the maximum sizes of Al 3Zr and Al 2O 3 particulates synthesized in the system ZrOCl 2 A356 are 1 μm and 3 μm respectively, and they are well distributed in the matrix. The investigation shows that the Al 3Zr crystal is in the shape of polyhedron and rectangle. There is a faceted growth phenomenon on Al 3Zr crystal surface. It is firstly found that the Al 3Zr crystal grows in the mechanism of twinning. The twinning plane is (1 1 4), and the twinning direction is [2 2 1] . The crystal morphology of in situ α Al 2O 3 particulate is rectangle or sphere. Furthermore, (Al 3Zr+Al 2O 3) p/A356 composites have not only higher tensile strength at room temperature (376.2 MPa) but also higher yield strength (319.4 MPa) and higher tensile strength at elevated temperature (200 ℃) than those of the A356 alloy. The dry sliding wear test shows that the wear resistance of the (Al 3Zr+Al 2O 3) p/A356 composites is greatly enhanced with increasing particulate volume fraction.

Direct Electrochemical Reaction of Horseradish Peroxidase Immobilized on the Surface of Active Carbon Powders

It is reported for the first time that horseradish peroxidase (HRP) immobilized on the active carbon can undergo a direct quasi-reversible electrochemical reaction. In addition, the immobilized HRP showed the stable bioelectrocatalytic activity for the reduction of H2O2.

DFT Study on the (S)-Proline-catalyzed Direct Aldol Reaction between Acetone and 4-Nitrobenzaldehyde

DFT/6-31G^＊ calculations were applied to study the direct aldol reaction between acetone and 4-nitrobenzaldehyde catalyzed by （S）-proline. Four transition states associated with the stereo-controlling step, corresponding to syn and anti arrangements of methylene moiety related to the carboxylic acid group in enamine intermediate and re and si attacks to the aldehyde carbonyl carbon have been obtained. The solvent effect of DMSO was investigated with polarized continuum model. The computed energies of transition states reveal the stereo-selectivity of the reaction.

Direct asymmetric aldol reaction using MBHA resin-supported peptide containing L-proline unit

MBHA resin-supported tripeptide catalyst system containing L-proline unit has been developed for use in the direct asymmetric aldol reaction of acetone and aldehydes, which afford the corresponding products with satisfactory isolated yields and enantiomeric excesses. 2009 Hong Bin Zou. Published by E]sevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

Study on reaction characteristics of phenolic hydroxyl in coal by using the model compound during direct coal liquefaction

The reaction characteristics of phenolic hydroxyl group were studied under the conditions of direct coal liquefaction. 2-naphthol was used as a coal model compound in this study. Under the conditions of with and without catalysts, a series of experiments were conducted at different temperatures, pressures and reaction time. Gas chromatography-mass spectrometry and gas chromatography were used to identify and quantify the reactants and products respectively. The conversion of 2-naphthol rises with the increase of reaction temperature, initial pressure and catalyst amount. The results indicated that tem- perature had a significant effect on 2-naphthol conversion, which promoted the dehydroxylation reaction. However, initial pressure had an important influence on the hydrogenation of 2-naphthol and naphthalene. The iron catalyst plays a significant role of cracking instead of hydrogenation. It is concluded that the harsh reaction conditions of high temperature, high pressure, and more catalyst are conducive to promoting dehydroxylation of 2-naphthol. The reaction mechanism was put forward based the experimental results, in which 2-tetralone was an intermediate.

Comparison of direct fecal smear microscopy,culture,and polymerase chain reaction for the detection of Blastocystis sp.in human stool samples

Objective:To compare the sensitivity and specificity of direct fecal smear microscopy,culture,and polymerase chain reaction in the detection of Blastocystis sp.in human stool.Methods:Human stool samples were collected from a community in San Isidro,Rodriguez,Rizal,Philippines.These samples were subjected to direct fecal smear microscopy,culture and polymerase chain reaction to detect the presence of Blastocystis sp.Results:Of the 110 stool samples collected,28(25%)were detected positive for the presence of Blastocystis sp.by two or more tests.Culture method detected the highest number of Blastocystis-positive stool samples(n=36),followed by PCR of DNA extracted from culture(n=26),PCR of DNA extracted from stool(n=10),and direct fecal smear(n=9).Compared to culture,the sensitivity of the other detection methods were 66.7%for PCR from culture and 19.4%for both PCR from stool and direct fecal smear.Specificity of the methods was high,with PCR from culture and direct fecal smear having97.3%,while PCR from stool at 95.9%.Conclusions:In this study,in vitro culture is the best method for detecting Blastocystis sp.in human stool samples.

Effect of tritium reduction in determining energy gain by using R-matrix method direct laser fusion in D-T reaction

The laser fusion criterion is known as the ρR-Criterion, also called high-gain condition. This parameter is temperature dependent and can be calculated by R-matrix method. This method is applied for determining improved fusion cross-section for the reactions T(d,n)4He, 3He(d,p)4He, D(d,p)T, D(d,n)3He. In this paper the time dependent reaction rate equations for fusion reaction T(d,n)4He are solved and by using the obtained results we computed the fu- sion power density, energy gain versus temperature and ρR-parameter. The obtained results show that a suitable com- bination may be a deuterium fraction fD=0.65 and fT=0.35 which would lead 30% reduction in the tritium content of the fuel mixture, and this choice would not change the energy gain value very much. Finally, the obtained energy gain for D-T reaction by using R-matrix is in good agreement with other theories.

Reaction视频中用户弹幕信息交互行为的情感反应生成机理研究

深入挖掘Reaction视频中弹幕信息交互行为的情感反应机理有助于理解用户弹幕创作背后的情感生成原因及情感变化过程。本文基于情感反应模型,利用定向内容分析法对哔哩哔哩网站中11个热门视频的弹幕信息资源、视频内容以及reactor反应情况展开编码研究,构建了Reaction视频中用户弹幕信息交互行为的情感反应生成机理模型。研究发现,Reaction视频弹幕信息交互行为中的情感反应生成机理总体上遵循“信息刺激-情感反应”的路径,信息刺激有时会独立唤醒情绪或特定情感态度,有时也会通过唤醒特定情感态度进而影响情绪或内化情感态度的生成。该模型有助于提升情感反应理论在计算机协助交流中的情境化探索,也将为社交媒体中用户与信息交互提供优化建议。

ALTERNATING DIRECTIONFINITE ELEMENT METHOD FORSOME REACTION DIFFUSION MODELS

This paper is concerned with some nonlinear reaction - diffusion models. To solve this kind of models, the modified Laplace finite element scheme and the alternating direction finite element scheme are established for the system of patrical differential equations. Besides, the finite difference method is utilized for the ordinary differential equation in the models. Moreover, by the theory and technique of prior estimates for the differential equations, the convergence analyses and the optimal L2- norm error estimates are demonstrated.

Microstructure Evolution of Ti-47Al-2Cr-2Nb Alloy in the Liquid-Metal-Cooling (LMC) Directional-Solidification Process

The microstructure evolution of Ti-47Al-2Cr-2Nb alloy was investigated on liquid metal cooling type directional solidified apparatus at high temperature gradient.The analysis shows that it is solidified with primary β cells/dendrites,and then α phase is formed through peritectic reaction.Once the columnar grains grow into the steady state,the lamellar orientation inclined with the angle of 45° to the withdrawal direction is more favored than that with parallel to the withdrawal direction.In addition,α phase grain nucleates from β-interdendrite regions,and grows up to the dendritic trunk.If no other α grain hinders its growth,it would occupy the whole dendrite,or it would stop at the dendritic trunk for the weakened motivating drive in the β dendritic core.

Application of a Rapid ESI-MS/MS Method for Quantitative Analysis of Docetaxel in Polymeric Matrices of PLGA and PLGA-PEG Nanoparticles through Direct Injection to Mass Spectrometer

Docetaxel is a member of taxan family of antineoplastic agents widely used in cancer chemotherapy. However, application of conventional chemotherapy with commercial formulation has been accompanied with matters of concern regarding drug’s biodistribution, pharmacokinetics, and pharmacodynamics. Polymeric nanoparticles have been widely used as unique drug delivery vehicles to circumvent such problems. Docetaxel-loaded poly (lactide-co-glycolide) (PLGA) and poly (lactide-co-glycolide)-poly (ethylene glycol) (PLGA-PEG) nanoparticles fit well in modifying drug’s pharmacokinetic characteristics as intravenous (IV) sustained-release delivery vehicles. In such circumstances, characterization of nanoparticles in terms of their drug-payload would be a necessary step. The majority of studies have used HPLC analysis method for docetaxel quantitation in polymeric nanoparticles. Herein, a rapid ESI-MS/MS method for quantitative analysis of docetaxel in polymeric matrices of PLGA and PLGA-PEG nanoparticles through direct injection to mass spectrometer has been developed and validated. The assay was validated over a range of 3.9 - 1000 ng/ml and 125 - 16,000 ng/ml. Samples were directly injected to the instrument through an isocratic elution (0.1% formic acid in methanol) and detection was performed on a Hybrid Triple Quadrupole/Linear Ion trap mass spectrometer with multiple reaction monitoring (MRM) mode via positive electrospray ionization (ESI) source. The run time and retention time were 2 and 0.6 minutes respectively. The method demonstrated acceptable level of accuracy and precision and was successfully applied for quantitative analysis of docetaxel in polymeric nanoparticles of PLGA and PLGA-PEG.

Addition Reaction of Fe(CO)_n (n = 3～5) on Fullerene C_(50), C_(60), and C_(70): A Density Functional Theory Study

The electronic structure and reactivities of Fe（CO）n （n = 3~5） addition to different fullerenes have been investigated through the first-principles calculations, and the results indicate that Fe（CO）3 and Fe（CO）4 can be adsorbed to the outside network of fullerene via hollow and bridge sites, respectively. Both of them have larger binding energy, but when Fe（CO）5 is adsorbed via the top site, the binding energy is relatively smaller. According to the directional curvature theory, the reactivities of Fe（CO）3 addition to the fullerenes are determined by KM of the ring center, and those of Fe（CO）4 addition by KD of the C–C bond curvature; while for Fe（CO）5, it presents weak reactivities in the addition reaction because of the larger volume effect. No matter whether the addition reaction takes place on the hollow or bridge site, the binding energies show a linear relationship with KD. This work further enriched the directional curvature theory and applied the isolobel analogy theory in the fullerene addition reactions.

Rhodium Nanoparticle-Loaded Carbon Black Electrocatalyst for the Glycerol Oxidation Reaction in Alkaline Medium

Rhodium nanoparticle-loaded carbon black (Rh/CB) was prepared by a wet method, and its activity and durability for glycerol oxidation reaction (GOR) in alkaline medium were compared with Pt, Pd and Au nanoparticle-loaded CB (Pt/CB, Pd/CB and Au/CB). In the cyclic voltammogram of the Rh/CB electrode, the redox waves due to hydrogen adsorption/desorption and the surface OH monolayer formation/reduction were observed at more negative potentials than the Pt/CB and Pd/CB electrodes. The onset and peak potentials of the GOR current densities for the Rh/CB electrode were ca. –0.55 and –0.30 V vs. Hg/HgO, respectively, which were 0.10 and 0.20 V more negative than the Pt/CB electrode whose GOR activity was the best, indicating that Rh was a fascinating metal for reducing the overpotential for GOR. In the electrostatic electrolysis with the Rh/CB and Pt/CB electrodes, the decrease in the GOR current density in the former with time was suppressed compared to that in the latter, suggesting that the tolerance to poisoning for the Rh/CB electrode was superior to that for the Pt/CB electrode.