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Corrosion Resistance of Plasma Sprayed Ceramic Composite Coatings on Q235 Substrate

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Journal of Materials Science & technology 2001年第1期17卷 7-8页

作者： Dianran YAN Jining HE and XiangZhi LI School of Materials Science and Engineering, hebei university of technology, Tianjin 300130, China Yangai LIU Yu ZHOU and Dechang JIA School of Materials Science and Engineering, Harbin institute of technology, Harb Sch. of Mater. Sci. Hebei Univ. of Technol. Tianjin 300130 China

The corrosion resistance of SiO2/A12O3, TiO2/Al2O3 and (SiO2+TiO2)/Al2O3 ceramic composite coatings on Q235 substrate fabricated by means of plasma spraying was investigated. The results show that A12O3+13 wt pct TiO2 ceramic coating has the highest density, the lowest connected porosity and the best corrosion resistance. The corrosion mechanism of Q235 with ceramic coating has also been studied.

关键词： Figure

A note on noncommutative moment problems

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Science China Mathematics 2005年第8期48卷 1144-1151页

作者： MA Xiujuan School of Sciences, hebei university of technology, Tianjin 300130, China Mathematics Institute, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing 100080, China School of Sciences Hebei University of Technology Tianjin China Mathematics Institute Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing China

Noncommutative moment problems for C*-algebras are studied. We generalize a result of Hadwin on tracial states to nontracial case. Our results are applied to obtain simple solutions to moment problems on the square and the circle as well as extend the positive unital functionals from a (discrete) complex group algebra to states on the group C*-algebra.

关键词： moment, free product, state, group C*-algebra.

Effect of Fe(III) impurity on the electrochemical performance of LiFePO_4 prepared by hydrothermal process

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Science China(Technological Sciences) 2009年第1期52卷 264-268页

作者： OU XiuQin, XU ShengZhao, LIANG GuangChuan, WANG Li & ZHAO Xia Institute of Power Source & Ecomaterials Science, hebei university of technology, Tianjin 300130, China Institute of Power Source & Ecomaterials Science Hebei University of Technology Tianjin China

Lithium iron phosphate (LiFePO4) was synthesized from LiOH, FeSO4 and H3PO4 by a hydrothermal process at 180℃. The samples were characterized by X-ray diffraction, scanning electron microscopy and chemical analysis. Electrochemical performance of the samples was tested in terms of charge-discharge capacity and cycling behavior. The results indicated that Fe(III) impurity had obvi- ously effect on the electrochemical properties of LiFePO4, and the formation of Fe3+ was caused by the oxidation of Fe2+ in the dissolving and feeding processes accompanying the increase of pH value. It was found that the precipitation separation was effective in decreasing the content of Fe3+ in the solu- tion of FeSO4 and the sealed feeding was useful in preventing the conversion of Fe2+ to Fe3+. When the content of Fe3+ < 0.5 wt%, the hydrothermally synthesized LiFePO4 calcined at 750℃ with sucrose as carbon source exhibited an initial discharge capacity of 154.9 mAh·g-1 at the rate of 0.1 C (1 C = 150 mA·g-1) and the cycling retention rate could reach 98% after 50 cycles at room temperature.

关键词： hydrothermal synthesis lithium iron phosphate (LiFePO4) ferric

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Science China Mathematics 2004年第2期47卷 297-310页

作者： JIANG Chunlan & HE HuaDepartment of Mathematics, hebei university of technology, Tianjin 300130, China Department of Mathematics, Universtiy of Pueto Rico, Rio Piedras San Juan, PR 00931, USA Department of Mathematics, hebei Normal university, Shijiazhuang 050016, China Department of Mathematics Hebei University of Technology Tianjin China Department of Mathematics Universtiy of Pueto Rico Rio Piedras San Juan USA Department of Mathematics Hebei Normal University Shijiazhuang China

This paper shows that every operator which is quasisimilar to strongly irreducible Cowen-Douglas operators is still strongly irreducible. This result answers a question posted by Davidson and Herrero (ref. [1]).

关键词： quasisimilar, strongly irreducible, Cowen-Douglas operators.

Enough with Motivation but Lack in Strategies-A Questionnaire of Undergraduates in College English Learning

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Chinese Journal of Applied Linguistics 2004年第3期 11-12页

作者： Diao Pei’an, hebei university of technology

A questionnaire reveals some valuable data in collegestudents’ motivation, strategies, method, anxiety in Englishlearning and their evaluation for teacher’s role in *** work of investigation was done at the end of year *** 1000 engineering majors in a university of technologyjoined in. The questionnaire contains 51 questions that aredivided into four groups for the investigation of motivation, the

关键词： Enough with Motivation but Lack in Strategies-A Questionnaire of Undergraduates in College English Learning

High Temperature Deformation of Al_2O_3/Cu Composites

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Journal of Materials Science & technology 2001年第3期17卷 325-328页

作者： Jianjun WU. Yun ZHANG, Yanfei JIANG and Meiyun XUE Department of Material Science and Engineering, hebei university of technology, Tianjin 300130, China Tingquan LEI School of Materials Science and Engineering, Harbin Institute of technology, Uarbin 15000 Dept. of Mat. Sci. and Eng. Hebei Univ. of Technol. Tianjin 300130 China

This work concerns with the high temperature deformation of internally oxidized Al2O3/Cu composites. The investigation revealed that dispersive alumina can obstruct dislocation sliding and define the subgrain size thereby improve significantly the strength of the materials at high temperature. The sliding of dislocations is a main deformation mechanism in the given temperature range. The sliding of grain boundary and diffusive creep play important roles at high temperature and low strain rate. The dispersoids can raise the recrystallization temperature to higher than 1223 K. Dynamic recovery is a main softening way under the experimental conditions. Higher deformation rate and lower deformation temperature imply a higher flow stress.

关键词： High Temperature Deformation of Al2O3/Cu Composites Cu Al

K_0-group and approximate similarity invariants of strongly irreducible operators

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Science China Mathematics 2008年第12期51卷 2231-2252页

作者： HE Hua1, SHI Rui1,2 & MA XiuJuan1 1 School of Science, hebei university of technology, Tianjin 300130, China 2 School of Mathematics and Information Science, hebei Normal university, Shijiazhuang 050016, China School of Science Hebei University of Technology Tianjin China School of Mathematics and Information Science Hebei Normal University Shijiazhuang China

Let H olenote a complex separable Hilbert space and L(H) denote the collection of bounded linear operators on H. An operator T ∈ L(H) is said to be strongly irreducible if T does not commute with any nontrivial idempotent. Herrero and Jiang showed that the norm-closure of the class of all strongly irreducible operators is the class of all operators with connected spectrum. This result can be considered as an "approximate inverse" of the Riesz decomposition theorem. In the paper, we give a more precise characterization of approximate invariants of strongly irreducible operators. The main result is: For any T ∈ L(H) with connected spectrum and ε > 0, there exists a strongly irreducible operator A, such that A - T < ε, V (A (A)) =～ N, K0(A (A)) ～= Z, and A (A)/rad A (A) is commutative, where A (A) denotes the commutant of A and rad A (A) denotes the Jacobson radical of A (A). The research is inspired by the recent similarity classification technique of Cowen-Douglas operators of Jiang Chunlan.

关键词： strongly irreducible operators Cowen-Douglas operators K0-group similarity orbit

HIGH ACCURACY ANALYSIS OF THE FINITE ELEMENT METHOD FOR NONLINEAR VISCOELASTIC WAVE EQUATIONS WITH NONLINEAR BOUNDARY CONDITIONS

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Journal of Systems Science & Complexity 2011年第4期24卷 795-802页

作者： Dongyang SHI Buying ZHANG Department of Mathematics Zhengzhou University Zhengzhou 450052 China. E & A College Hebei Normal University of Science & Technology Qinhuangdao 066004 China.

The standard finite elements of degree p over the rectangular meshes are applied to solve a kind of nonlinear viscoelastic wave equations with nonlinear boundary conditions, and the superclose property of the continuous Galerkin approximation is derived without using the nonclassical elliptic projection of the exact solution of the model problem. The global superconvergence of one order higher than the traditional error estimate is also obtained through the postprocessing technique.

关键词： Nonlinear boundary conditions nonlinear viscoelastic wave equations postprocessingoperator superclose and superconvergence.

Partitioning series-parallel multigraphs into υ*-excluding edge covers

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Science China Mathematics 2006年第8期49卷 1082-1093页

作者： LIU Guizhen, DENG Xiaotie & XU Changqing School of Mathematics and System Science, Shandong university, Jinan 250100, China Department of Computer Science, City university of Hong Kong, Kowloon, Hong Kong, China Department of Applied Mathematics, hebei university of technology, Tianjin 300130, China School of Mathematics and System Science Shandong University Jinan 250100 China Department of Computer Science City University of Hong Kong Kowloon Hong Kong Hong Kong Department of Applied Mathematics Hebei University of Technology Tianjin 300130 China

We prove that, for any given vertexν* in a series-parallel graph G, its edge set can be partitioned into k= min{k′(G) + 1,δ(G)} subsets such that each subset covers all the vertices of G possibly except forν*, whereδ(G) is the minimum degree of G and k′(G) is the edge-connectivity of G. In addition, we show that the results in this paper are best possible and a polynomial time algorithm can be obtained for actually finding such a partition by our proof.

关键词： series-parallel graph, edge-connectivity, edge cover coloring, min-max theorem.