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REACTION MECHANISM OF BENZOPHENONE-PHOTOINITIATED CROSSLINKING OF POLYETHYLENE

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Chinese Journal of Polymer science 2002年第4期20卷 291-307页

作者： Bao-jun Qu State Key Laboratory of Fire science and Department of Polymer science and Engineering{2. hefei 230026{4. Univ Sci & Technol china State Key Lab Fire Sci Hefei 230026 Peoples R China Univ Sci & Technol china Dept Polymer Sci & Engn Hefei 230026 Peoples R China

The radical intermediates, the crosslink microstructures, and the reaction mechanism of benzophenone (BP)-photoinitiated crosslinking of low-density polyethylene (LDPE) and model compounds (MD) have been reviewed in detail. The spin-trapping electron spin resonance (ESR) spectra obtained from the LDPE/BP systems with spin-trap agents show that two kinds of polymer radical intermediates are mainly formed: tertiary carbon and secondary carbon radicals. The spin-trapping ESR studies of MD/BP systems give further evidence that photocrosslinking reactions of PE predominantly take place a sites of tertiary carbon, secondary carbon, and especially allylic carbon when available. The high resolution C-13-NMR spectra obtained from LDPE and MD systems show that the crosslink microstructures have H- and Y-type links and that their concentrations are of the same order. The fluorescence, ESR, C-13 and H-1-NMR spectra from the PE and MD systems demonstrate that the main photoreduction product of BP (PPB) is benzpinacol formed by the recombination of two diphenylhydroxymethyl (K-.) radical intermediates. Two new PPB products: an isomer of benzpinacol with quinoid structure, 1-phenylhydroxymethylene-4.diphenylhydroxymethyl-2.5-cyclobexadiene and three kinds of alpha-alkyl-benzhydrols have been detected and identified. These results provide new experimental evidence for elucidating the reaction mechanism in the BP-photoinitiated crosslinking of polyethylene.

关键词： photocrosslinking mechanism polymer radical intermediates crosslink microstructures photolytic products of benzophenone polyethylene model compound

Negative Temperature Coefficient of Resistivity in Bulk Nanostructured Ag

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Journal of Materials science & technology 2000年第5期16卷 521-524页

作者： Yushuang LIU, Chimei MO+ and Weili CAI (Department of Materials science and Engineering, university of science and technology of china,{2., china) Department of Materials science and Engineering University of Science and Technology of China Hefei 230026 China

The change of the temperature coefficient of resistivity (a) with the particle size, dp, and the grain size, dc, in the nanostructured Ag bulk samples was investigated. dp and dc were controlled by heating the nano-Ag powders over the temperature range from 393 to 4.3 K. The electrical resistance measurements of the nanostructured Ag bulk samples obtained by compacting the Ag powders after heat treatments showed a change in the sign of a with dP and dc. When dp and dc are smaller or equal to 18 and 11 nm below room temperature or 2. and 12.nm above room temperature, respectively, the sign of the temperature coefficient of resistivity changes from positive to negative. The negative a arises mainly from the high resistivity induced by the particle interfaces with very lowly ordered or even disordered structure, a large volume fraction of interfaces and impurities existing in the interfaces, and the quantum size effect appearing in the nano-Ag grains.

关键词： Negative Temperature Coefficient of Resistivity in Bulk Nanostructured Ag

Optimization of the inhibition of atmospheric window emission using photonic crystals

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science china(Technological sciences) 2010年第5期53卷 1315-1319页

作者： LI Jin & YE Hong Department of Thermal science and Energy and Engineering,university of science and technology of{4.,hefei 230026,china 1. Department of Thermal science and Energy and Engineering University of Science and Technology of China Hefei 230026 China

Transfer matrix method is used to discuss the effect inhibition of photonic crystals on atmospheric window emission(ε-14.μm).According to the optical characteristics of the materials,germanium and zinc sulfide are used as the composing *** structure of the photonic crystals is optimized,and the optimal thickness values of the germanium and zinc sulfide are 0.63 and 1.11μm respectively while the ratio of optical thickness is 1:1 and the period is *** photonic crystals are prepared by evaporation coating method,and the optical properties of the photonic crystals are measured,the inhibition of the photonic crystals to atmospheric window emission is verified.

关键词： photonic crystals emission at atmospheric window inhibition

Jackknifed random weighting for Cox proportional hazards model

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science china Mathematics 2012年第4期55卷 775-786页

作者： LI Xiao 1 ,WU YaoHua 2.& TU DongSheng 1 1 Cancer Research Institute,Queen’s university,Kingston,Ontario K 7L 3N6,Canada 2.Department of Finance and statistics,university of science and technology of china,hefei 230026,china 1. Cancer Research Institute Queen’s University Kingston Ontario K7L 3N6 Canada2. Department of Finance and Statistics University of Science and Technology of China Hefei 230026 China

The Cox proportional hazards model is the most used statistical model in the analysis of survival time ***,a random weighting method was proposed to approximate the distribution of the maximum partial likelihood estimate for the regression coefficient in the Cox *** method was shown not as sensitive to heavy censoring as the bootstrap method in simulation studies but it may not be second-order accurate as was shown for the bootstrap *** this paper,we propose an alternative random weighting method based on one-step linear jackknife pseudo values and prove the second accuracy of the proposed *** Carlo simulations are also performed to evaluate the proposed method for fixed sample sizes.

关键词： Cox proportional hazards model jackknife random weighting second-order accuracy simulations survival data

EFFECT OF BIAS STRESS ON NON-LINEAR INTERNAL FRICTION OF Al-Mg ALLOY

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Acta Metallurgica Sinica(English Letters) 1992年第3期5卷 166-171页

作者： TAN Qi university of science and technology of china,hefei,{2. Univ of science and technology of China Hefei China

The influence of longitudinal and torsional bias stresses on anomalous amplitude-dependent internal friction was *** longitudinal bias stress may always weaken the anomalous amplitude-dependent effect,while the torsional one may induce different effects from differ- ent directions *** stress effect exhibits only in properly heat treated and cold worked ahoy *** anomalous amplitude-dependent internal friction peaks,P_3,P_2.and P_1, are found to be related closely to slant dislocation kink ***,the application of bias stress to internal friction would be contributed to the study on dislocation structure.

关键词： internal friction bias stress anomalous amplitude effect dislocation kink

Hamiltonian Formalism of de-Sitter Invariant Special Relativity

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Communications in Theoretical Physics 2007年第7期48卷 27-36页

作者： YAN Mu-Lin XIAO Neng-Chao HUANG Wei Interdisciplinary Center for Theoretical Study,university of science and {2. of china,{4. 230026,chinaLI Si Department of Mathematics,university of science and {2. of china,{4. 230026,china Interdisciplinary Center for Theoretical Study University of Science and Technology of China Hefei 230026 China Department of Mathematics University of Science and Technology of China Hefei 230026 China

The Lagrangian of Einstein's special relativity with universal parameter c(SR_c)is invariant under Poincarétransformation,which preserves Lorentz metric η_μν.The SR_c has been extended to be one which is invariant underde Sitter transformation that preserves so-called Beltrami metric B_(μv).There are two universal parameters,c and R,inthis Special Relativity(denoted as SR_(cR)).The Lagrangian-Hamiltonian formulism of SR_(cR) is formulated in this *** canonic energy,canonic momenta,and 10 Noether charges corresponding to the space-time's,de Sitter symmetryare *** canonical quantization of the mechanics for SR_(CR)-free particle is *** physics related to itis discussed.

关键词： de-Sitter invariance special relativity canonic energy and canonic momenta Beltrami metric

Characteristic modules of quasi-hereditary algebras with three samples

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Chinese science Bulletin 1997年第6期42卷 450-454页

作者： ZHANG Pu and LIN Yanan1. Department of Mathematics, university of science and technology of china, hefei 230026,{2. 2. Department of Mathematics, Xiamen {4., Xiamen 361005,{2. Department of Mathematics University of Science and Technology of China Hefei China Department of Mathematics Xiamen University Xiamen China

CLINE et al. have introduced the concept of quasi-hereditary algebra, which provided a

关键词： tilting module characteristic module quasi-hereditary algebra.

Bell violation for the thermal states of an XXZ spin chain with Dzialoshiski-Moriya interaction

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science china(Physics,Mechanics & Astronomy) 2010年第11期53卷 2074-2079页

作者： MA XiaoSan 1 & WANG AnMin 2.1 School of Electric Engineering and Information,Anhui university of technology,Maanshan 2.3002.{2. 2.Department of Modern Physics,university of science and technology of china,hefei 230026,{2. 1. School of Electric Engineering and Information Anhui University of Technology Maanshan 243002 China2. Department of Modern Physics University of Science and Technology of China Hefei 230026 China

The effect of Dzialoshiski-Moriya (DM) interaction on the violation of Bell inequality for thermal states of interacting qubits via a two-qubit XXZ spin chain is *** results imply that the DM interaction and anisotropy taking a large positive value can enhance the Bell violation and improve the threshold temperatures of *** the comparison between the Bell violation and thermal entanglement,we find that the threshold temperatures of thermal entanglement are higher than those of the Bell *** implies that some states are entangled but the Bell inequality is not violated.

关键词： Bell violation threshold temperatures DM interaction

CONTROLLED RADICAL COPOLYMERIZATION OF STYRENE AND MALEIC ANHYDRIDE UNDER GAMMA RADIATION IN THE PRESENCE OF BENZYL DITHIOBENZOATE

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Chinese Journal of Polymer science 2002年第6期20卷 525-530页

作者： De-cheng Wu Ying-fang Zou Cai-yuan Pan Department of Polymer science and Engineering university of science and technology of china,{2., china Univ Sci & Technol china Dept Polymer Sci & Engn Hefei 230026 Peoples R China

The copolymerization of styrene (St) with maleic anhydride (MAh) under gamma radiation at room temperature in the presence of benzyl dithiobenzoate (BDTB) was found to display 'living' nature evidenced by constant concentration of chain radicals during the copolymerization, linear evolution of molecular weights with conversion and narrow molecular weight distribution (M-w/M-n = 1.2.-1.35). The compositional analysis and the sequence structural information of the copolymers obtained from DEPT (Distortionless Enhancement by Polarization Transfer) experiments demonstrate that the copolymers obtained also possess strictly alternating structure.

关键词： controlled radical polymerization alternating copolymer maleic anhydride styrene