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Influence of steric and intramolecular inductive effects on the variable trends in R-X (R=Alkyl) bond dissociation energy

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science China Chemistry 2009年第7期52卷 943-951页

作者： CAO ChenZhong School of Chemistry and Chemical Engineering, hunan university of science and technology, Xiangtan 411201, China School of Chemistry and Chemical Engineering Hunan University of Science and Technology Xiangtan 411201 China

The question "why are the variation trends of R-X bond dissociation energy different?" is answered. The R-X bond dissociation energy (BDE) may be influenced by three main factors: the C-X intrinsic bond energy, the 1,3 geminal repulsion, and the intramolecular charge-induced dipole. In the presence of atom X, the variation trend of BDE in R-X (R= Me, Et, i-Pr, t-Bu) is dominated by two factors, the 1,3 geminal repulsion and the intramolecular charge-induced dipole. The former decreases the R-X BDE, and the latter either increases or decreases the R-X BDE. For the series of R-X with the R-C bond (such as R-Me, R-CH == CH2, R-C≡CH, and R-CN), the 1,3 geminal repulsion decreases the R-X BDE, and the variation trends of R-C BDE decrease from Me to t-Bu. As regards the series of R-X (such as R-H, R-BH2, and R-SiH2) in which the electronegativity of atom X is smaller than that of the carbon atom, the above two factors decrease the R-X BDE, and the variation trends of the R-X BDE decrease from Me to t-Bu. As to the series of R-X (such as R-F, R-OH, R-Cl, R-Br, R-I, and R-NH2) in which the electronegativity of atom X is larger than that of the carbon atom, the 1,3 geminal repulsion decreases the R-X BDE, while the intramolecular charge-induced dipole increases the R-X BDE. In this case, the variation trends of R-X BDE depend on the competition of the two factors. As a result, some of them (e. g., R-F, R-OH) increase from Me to t-Bu, some (e. g., R-I) decrease from Me to t-Bu, and some (e. g., R-Br) change very little.

关键词： bond dissociation energy charge-induced dipole geminal repulsion ionic configuration

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Novel nanoporous binary Ag-Ni electrocatalysts for hydrazine oxidation

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Rare Metals 2010年第1期29卷 26-31页

作者： YI Qingfeng, LI Lei, YU Wenqiang, LIU Xiaoping, ZHOU Zhihua, and NIE Huidong School of Chemistry and Chemical Engineering, hunan university of science and technology, Xiangtan 411201, China School of Chemistry and Chemical Engineering Hunan University of Science and Technology

From an aqueous mixture of Ag（I）-EDTA complex and Ni（II） nitrate, silver and nickel particles were co-deposited on the surface of titanium substrates by the hydrothermal method using hydrazine hydrate as a reduction agent. The prepared titanium-supported nano-scale Ag and Ag-Ni particles （nano Ag/Ti, nano Ag86Ni14/Ti, nano Ag77Ni23/Ti, and nano Ag74Ni26/Ti） exhibit nanoporous 3D network textures. Their electrocatalytic activity towards hydrazine oxidation in alkaline solutions was evaluated by cyclic voltammetry and chronoamperometry. The results show that the four samples present a low onset potential of ca. -0.60 V vs. SCE and considerably high and stable anodic current densities for hydrazine oxidation. Among them, the nano Ag86Ni14/Ti electrode exhibits the highest anodic current density towards hydrazine oxidation, showing an increment of electro-active sites on the nano Ag86Ni14/Ti due to the addition of Ni to Ag particles.

关键词： electrocatalyst silver hydrazine oxidation fuel cell

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Catalytic spectrophotometric determination of trace vanadium in fly ash and coal gangue by Triton X-100 enhancing effect

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Rare Metals 2004年第1期23卷 10-14页

作者： XIAChangbin HUANGNiandong InstituteofEnvironmentalEngineering＆ChemicalHi-tech.hunanuniversityofscienceandtechnology.Xiangtan411201.China

Trace Ⅴ(Ⅴ) catalyzes mightily the decolorization reaction of arsenazo Ⅲ(AsA Ⅲ) by oxidizing with H_2O_2 in a pH 4.0 HAc-NaAc buffer solution, and the addition of TritonX-100 can further increase the sensitivity of the reaction and its catalytic extent is linear withthe content of Ⅴ(Ⅴ). A catalytic spectrophotometric procedure for determining trace Ⅴ(Ⅴ)wasdeveloped. The results show that the maximun absorption of the color solution is at 560 nm and thedetection limit of the method for Ⅴ(Ⅴ) is 0.014 mg·L^(-1). Beer's law is obeyed for Ⅴ(Ⅴ) in therange of 0.00-0.20 mg·L^(-1). The recoveries are 99.0%-104.6%, and the relative standarddeviations (RSD) are 2.7%-3.7%. Combined with ion-exchange resin, the method has been applied to thedetermination of trace vanadium in fly ash and coal gangue with satisfactory results.

关键词： analytical chemistry vanadium fly ash coal gangue catalyticspectrophotometry arsenazo Ⅲ

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A Secure-Efficient Data Collection Algorithm Based on Self-Adaptive Sensing Model in Mobile Internet of Vehicles

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China Communications 2016年第2期13卷 121-129页

作者： LIANG Wei RUAN Zhiqiang TANG Mingdong LI Peng Department of Software Engineering Xiamen University of TechnologyXiamenFujian361024China Department of Computer science Minjiang UniversityFuzhouFujian 350108China School of Computer science and Engineering Hunan University of Science and TechnologyXiangtan 411201China

Existing research on data collection using wireless mobile vehicle network emphasizes the reliable delivery of ***,other performance requirements such as life cycle of nodes,stability and security are not set as primary design *** makes data collection ability of vehicular nodes in real application environment *** considering the features of nodes in wireless IoV,such as large scales of deployment,volatility and low time delay,an efficient data collection algorithm is proposed for mobile vehicle network *** adaptive sensing model is designed to establish vehicular data collection *** protocol adopts group management in model *** vehicular sensing node in group can adjust network sensing chain according to sensing distance threshold with surrounding *** will dynamically choose a combination of network sensing chains on basis of remaining energy and location characteristics of surrounding *** addition,secure data collection between sensing nodes is undertaken as *** simulation and experiments show that the vehicular node can realize secure and real-time data ***,the proposed algorithm is superior in vehicular network life cycle,power consumption and reliability of data collection by comparing to other algorithms.

关键词： wireless vehicle network datacollection protocol network sensing chain self'-adaptive sensing sensing distance threshold.

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On the reconstruction of Dirichlet-to-Neumann map in inverse scattering problems with stability estimates

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science China Mathematics 2010年第8期53卷 2069-2084页

作者： WANG HaiBing 1,2 & LIU JiJun 1 1 Department of Mathematics,Southeast university,Nanjing 210096,China 2 School of Mathematics and Computational science,hunan university of science and technology,Xiangtan 411201,China 1. Department of Mathematics Southeast University Nanjing 210096 China2. School of Mathematics and Computational Science Hunan University of Science and Technology Xiangtan 411201 China

Consider the determination of Dirichlet-to-Neumann(D-to-N) map from the far-field pattern in inverse scattering problems,which is the key step in some recently developed inversion schemes such as probe ***,this problem is related to the reconstruction of the scattered wave from its far-field *** firstly prove the well-known uniqueness result of the D-to-N map from the far-field pattern using a new scheme based on the mixed reciprocity *** advantage of this new proof scheme is that it provides an efficient algorithm for computing the D-to-N map,avoiding the numerical differentiation for the scattered *** combining with the classical potential theory,a simple and feasible regularizing reconstruction scheme for the D-to-N map is *** the stability estimate for the reconstruction with noisy input data is rigorously analyzed.

关键词： inverse scattering Dirichlet-to-Neumann map regularization mixed reciprocity principle stability

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Orthogonal experiment investigation on wear resistance of MoSi2

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Rare Metals 2003年第3期22卷 230-234页

作者： CHEN Ping, TANG Guoning, ZHANG Hou’an, and LIU HoucaiInstitute of Material Surface Engineering, hunan university of science and technology, Xiangtan 411201, China Institute of Material Surface Engineering Hunan University of Science and Technology Xiangtan 411201

The influence of lubricant conditions, wear loads, and counterparts on thefriction and wear characteristics of an MoSi_2 material was investigated by means of orthogonalanalysis. Orthogonal experiment results show that the order of influencing degree of the factors islubricant condition > load > counterpart. MoSi_2 has excellent friction-wear comprehensiveproperties against higher-hardness counterparts on the higher load and 20 oil lubricant conditions.

关键词： molybdenum disilicide friction and wear orthogonal analysis

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Preparation and properties of ultra-fine TiCN matrix cermets by vacuum microwave sintering

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Rare Metals 2010年第5期29卷 528-532页

作者： ZHANG Hou'an YAN Dike TANG Siwen Institute of Material Preparation and Applied technology Xiamen University of Technology Xiamen 361024 China College of Electromechanical Engineering Hunan University of Science and Technology Xiangtan 411201 China

Ultra-fine titanium carbonitride （TiCN） matrix materials with a grain size less than 1μm were successfully prepared by vacuum microwave sintering. The milling process for raw TiCN particles and the microstructure and properties of cermets produced with a composition of 15wt.%WC-17wt.%（Co＋Ni）-9wt.%Mo2C-59wt.%***0.3 and sintered by vacuum microwave were analyzed by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The results show that a ball-to-powder mass ratio of 8：1 and a milling time of 50 h provided appropriate conditions for the production of ultra-fine TiCN solid solution powders. The use of vacuum microwave sintering produced cermets with much finer grain and black core structures and higher relative density and hardness than those produced by vacuum sintering technology.

关键词： cutting tools titanium carbonitride grain size microwave sintering milling hardness

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Preparation of well-defined polystyrene/silica hybrid nanoparticles by ATRP

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science China Chemistry 2008年第1期51卷 51-57页

作者： OU BaoLi1,2 LI DuXin2 1 College of Chemistry and Chemical Engineering,hunan university of science and technology,Xiangtan 411201, China 2 State Key Laboratory of Powder Metallurgy,Central South university,Changsha 410083, China 1. College of Chemistry and Chemical Engineering Hunan University of Science and Technology Xiangtan 411201 China 2. State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China

Immobilization of the atom transfer radical polymerization (ATRP) macroinitiators at the silica nanoparticle surfaces was achieved through surface modification with excess toluene-2,4-diisocynate (TDI), after which the residual isocyanate groups were converted into ATRP macroinitiators. Structurally well-defined polystyrene chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined, densely grafted outer polystyrene by ATRP, which was initiated by the as-synthesized silica-based macroinitiator. FTIR, NMR and gel permeation chro-matography (GPC) were used to characterize the polystyrene/silica hybrid particles.

关键词： silica nanoparticles surface modification atom transfer radical polymerization polystyrene hybrid particle

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Preparation of polystyrene/silica nanocomposites by radical copolymerization of styrene with silica macromonomer

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science China Chemistry 2007年第3期50卷 385-391页

作者： OU BaoLi1,2 & LI DuXin2 1 College of Chemistry and Chemical Engineering, hunan university of science and technology, Xiangtan 411201, China 2 State Key Laboratory of Powder Metallurgy, Central South university, Changsha 410083, China 1. College of Chemistry and Chemical Engineering Hunan University of Science and Technology Xiangtan 411201 China 2. State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China

A two-stage process has been developed to generate the silica-based macromonomer through surface-modification of silica with polymerizable vinyl groups. The silica surfaces were treated with excess 2,4-toluene diisocynate (TDI), after which the residual isocyanate groups were converted into polymerizable vinyl groups by reaction with hydroxypropylacrylate (HPA). Thus, polystyrene/silica nanocomposites were prepared by conventional radical copolymerization of styrene with silica macromonomer. The main effecting factors, such as ratios of styrene to the macromonomer, together with polymerization time on the copolymerization were studied in detail. FTIR, DSC and TGA were utilized to characterize the nanocomposites. Experimental results revealed that the silica nanoparticles act as cross-linking points in the polystytene/silica nanocomposites, and the glass transition temperatures of the nanocomposites are higher than that of the corresponding pure polystyrene. The glass transition temperatures of nanocomposites increased with the increasing of silica contents, which were further ascertained by DSC.

关键词： silica nanoparticles surface modification styrene radical copolymerization nanocomposites

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EXISTENCE AND NONEXISTENCE OF GLOBAL POSITIVE SOLUTIONS FOR DEGENERATE PARABOLIC EQUATIONS IN EXTERIOR DOMAINS

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Acta Mathematica Scientia 2010年第3期30卷 713-725页

作者：曾宪忠刘振海 Department of Mathematics and Computational science Hunan University of Science and Technology Department of Mathematics Central South University

This article deals with the degenerate parabolic equations in exterior domains and with inhomogeneous Dirichlet boundary conditions. We obtain that pc = （σ ＋ m ）n / （ n-σ- 2 ） is its critical exponent provided max{-1, [ （1- m ）n- 2] / （ n ＋ l ） } 〈 σ 〈 n- 2. This critical exponent is not the same as that for the corresponding equations with the boundary value 0, but is more closely tied to the critical exponent of the elliptic type degenerate equations. Futhermore, we demonstrate that if max（1, σ ＋ m）〈 p 〈 pc, then every positive solution of the equations blows up in finite time; whereas for p 〉 pc, the equations admit global positive solutions for some boundary values and initial data. Meantime, we also demonstrate that its positive solutions blow up in finite time provided n〈σ＋2.

关键词： Degenerate parabolic equations exterior domains -inhomogeneous dirichlet boundary conditions critical exponent blow-up global existence

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