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A NOTE ON COMPLETELY POSITIVE GRAPHS

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Systems science and Mathematical sciences 2000年第2期13卷 121-125页

作者： xu Changqing (department of mathematics, Anhui university, hefei 230039, china) LI Jiongsheng (department of mathematics, university of science and technology of china, hefei 230026, china) 安徽大学数学系安徽合肥 230039 中国科学技术大学数学系安徽合肥 230026

A necessary and sufficient condition is given for a doubly nonnegative matrix realization of a cycle to be completely positive. Also some special non-CP graphs are investigated.

关键词： Doubly nonnegative matrix completely positive graph cycle factorization.

Jackson’s theorem in Q_p spaces

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science china mathematics 2010年第2期53卷 367-372页

作者： CHEN YingWei 1 & REN Guangbin 1, 2, 1 department of mathematics, university of science and technology of china, hefei 230026, china 2 department of mathematics, university of Aveiro, P-3810-193 Aveiro, Portugal department of mathematics University of Science and Technology of China Hefei China department of mathematics University of Aveiro Aveiro Portugal

A Jackson type inequality in Q p spaces is established, i.e., for any f (z) = Σ∞ j=0 ajzj ∈ Qp , 0≤p 1, and k-1 ∈ N,where ω(1/k, f, Q p ) is the modulus of continuity in Q p spaces and C(a) is an absolute const... 详细信息

关键词： Q p space BMOA polynomial approximation

A Class of Pseudo-Monotone Operators and its Applications in PDE

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Acta Mathematica Sinica,English Series 1997年第4期13卷 517-526页

作者： Chen Zuchi Yan Xiaodong department of mathematics, university of science and technology of china, hefei 230026, china 中国科学技术大学数学系安徽合肥

In this paper we give a criterion of pseudo-monotone operators by which a class of operators related to elliptic partial differential equations is recognized as pseudo-monotone operators. Some applications in boundary... 详细信息

关键词： Pseudo-monotone operator Leray--Lions operator Sobolev imbedding theorem

Formation of hyperbranched polymers in atom transfer radical copolymerization of MMA and DVB

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science china Chemistry 2010年第12期53卷 2440-2451页

作者： SUN Miao & PAN CaiYuan CAS Key Laboratory of Soft Matter Chemistry department of Polymer science and Engineering,university of science and technology of china,hefei 230026,china CAS Key Laboratory of Soft Matter Chemistry department of Polymer science and Engineering University of Science and Technology of China Hefei China

Hyperbranched poly(methyl methacrylate)s (HPMMAs) have been successfully prepared by atom transfer radical copolymerization of MMA and divinylbenzene (DVB).Kinetic study shows complete consumption of the initiator in 0.5 h,and relatively low polymerization rate when DVB content in the feed was *** analyzing MALDI-TOF spectra of the resulting copolymers,the linear A n B (n=0,1,2,3) oligomers were formed in 0.5 h of polymerization,and then the oligomers reacted each other to form dimers,further reactions produced *** SEC and NMR spectroscopies were used to trace the polymerization,and the results demonstrate that small amount of the branching reactions occur in the initial polymerization,and the branched polymers are significantly generated past a certain conversion depending upon the feed *** the content of DVB in the monomer mixture can increase the pendent vinyl groups of the linear oligo-inimers,leading to gelation at low MMA conversion.

关键词： atom transfer radical polymerization branching divinylbenzene hyperbranched polymers mechanism

PROPULSIVE PERFORMANCE AND VORTEX SHEDDING OF A FOIL IN FLAPPING MOTION

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Journal of Hydrodynamics 2003年第5期15卷 7-12页

作者： Yang Yan, Lu Xi yun, Yin Xie zhen department of Mechanics and Mechanical Engineering, university of science and technology of china, hefei 230026, china, Dept. of Mech. and Mech. Eng. Univ. of Sci. and Technol. of China Hefei 230026 China

The propulsive performance and vortex shedding of oscillating foil, whichmimics biological locomotion, were numerically investigated. The objectives of this study were todeal with unsteady force, in particular thrust force, exerted on the foil in pitching and plungingmotions, and to explore the relation of the propulsive performance with vortex structures near thefoil and vortex shedding in the near wake. The two-dimensional incompressible Navier-Stokesequations in the vorticity and stream-function formulation were solved by fourth-order essentiallycompact finite difference schemes for the space derivatives and a fourth-order Runge-Kutta schemefor the time advancement. To reveal the mechanism of the propulsive performance, the unsteady forceand the shedding of the trailing- and leading-edge vortices of the foil were analyzed. The effectsof some typical factors, such as the frequency and amplitude of the oscillation, the phasedifference between the pitching and plunging motions, and the thickness ratio of the foil, on thevortex shedding and unsteady force were discussed.

关键词： vortex dynamics vortex shedding thrust force unsteady flow flappingmotion

Recent progress in polymer/layered double hydroxide nanocomposites

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Progress in Natural science:Materials International 2006年第6期16卷 573-579页

作者： DING Peng, CHEN Wei and QU Baojun (State Key Laboratory of Fire science and department of Polymer science and Engineering, university of science and technology of china, hefei 230026, china) State Key Laboratory of Fire science Department of Polymer Science and Engineering University of Science and Technology of China Hefei 230026 China

New developments in the studies of nanocomposites based on polymer matrixes and layered double hydroxides (LDHs) in recent years are reviewed combining our relative research work, among which the synthesis techniques, the physicochemical characterizations, and the improved material properties are especially discussed. The possible application of polymer/LDH nanocomposites is also proposed.

关键词： nanocomposite layered double hydroxide synthesis characterization structure property.

EXISTENCE, MULTIPLICITY AND BIFURCATION FOR CRITICAL POLYHARMONIC EQUATIONS

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Systems science and Mathematical sciences 1999年第1期12卷 59-69页

作者： xuAN Benjin CHEN Zuchi (department of mathematics, university of science and technology of china, hefei 230026, china) 中国科学技术大学数学系安徽合肥

This paper is concerned with the nonexistence and existence, multiplicity and bifurcation of solutions for critical semilinear polyharmonic equations. Following the ideas due to Brezis and Nirenberg[1], we obtain the extensions of [1] and partially confirm Pucci and Serrin[2] conjecture; by employing the abstract critical point theorem, the multiple results and bifurcation for the problem are obtained.

关键词： Critical Sobolev exponent critical point mountain pass theorem (PS)c condition.

Uniform estimate for maximum of randomly weighted sums with applications to insurance risk theory

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science china mathematics 2005年第10期48卷 1379-1394页

作者： WANG Dingcheng~1 SU Chun~2 & ZENG Yong~1 1. School of Management and School of Applied mathematics,university of Electronic science and technology of china,Chengdu 610054,china 2. department of Statistics and Finance,university of science and technology of china,hefei 230026,china School of Management and School of Applied mathematics University of Electronic Science and Technology of China Chengdu China department of Statistics and Finance University of Science and Technology of China Hefei China

This paper obtains the uniform estimate for maximum of sums of independent and heavy-tailed random variables with nonnegative random weights, which can be arbitrarily dependent of each other. Then the applications to ... 详细信息

关键词： dependent stochastic return, discount factor, heavy-tails, discrete time insurance risk model, maxima of randomly weighted sums, ruin probability, tail probabilities, uniformly asymptotic estimate.

γ-Radiation synthesis of nanocrystalline nickel powder from nickel (Ⅱ ) -ammonia complex solution

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Chinese science Bulletin 1997年第8期42卷 644-648页

作者： ZHU Yingjie, QIAN Yitai and ZHANG Manwei1. department of Applied Chemistry, university of science and technology of china, hefei 230026, china 2. Structure Research Laboratory, university of science and technology of china, hefei 230026, china Departnient of Applied Chemistry University of Scirnce and Technology of China Hefei China Structure Research I.aboratory University of Science and Technology of China Hefei China

NANOCRYSTALLINE nickel is very important for its applications in the fields such as catalysis andmagnetic *** usual method used for preparing nanocrystalline nickel is inert gas e-vaporation,which requires high ***,high temperature easily leads tothe growth or oxidation of nickel *** et *** the nickel microaggre-gates dispersed in solution produced by γ-irradiating a dilute solution of Ni2+

关键词： nickel nanocrystalline powder γ-radiation.