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Surface Nanocrystallization of Magnesium Alloy AZ91D by High-Energy Shot Peening

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Journal of wuhan University of technology(Materials {2.) 2009年第4期24卷 515-519页

作者：张津 school of Materials science & Engineering University of Science and Technology Beijing College of Materials science & Engineering Chongqing University of Technology

High-energy shot peening （HESP）, a method to produce severe plastic deformation by high velocity flying balls, was applied on die cast magnesium alloy AZ91D. Effects of surface nanocrystallization by HESP and heat treatment at different temperatures were investigated. The mi- crostructure evolution was conducted using X-ray diffraction （XRD） and field emission scanning electronic microscopy （FESEM）. The hardness was measured by microhardness tester. The experimental results show that surface nanocrystrallization of AZ91D obtained by HESP would lead to the increase of microhardness. Low temperature heated at 100℃ for 1 h do not change the property obviously. However, both the microstructure and microhardness vary greatly after heat treatment at 400℃ for 1 h.

关键词： AZ91 D surface nanocrystallization HESP microhardnss corrosion resistance

COLLECTIVELY COMPACT COMPOSITION OPERATOR SEQUENCES BETWEEN BERGMAN AND HARDY SPACES

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Acta Mathematica Scientia 2004年第2期24卷 206-212页

作者：王茂发刘培德 schoolofMathematicsandStatistics WuhanUniversityWuhan430072China

This paper studies the collective compactness of composition operator sequences between the Bergman and Hardy spaces. Some sufficient and necessary conditions involving the generalized Nevanlinna counting functions fo... 详细信息

关键词： Bergman space Hardy space composition operator collectively compact operator sequence

Second-order consensus in networks of dynamic agents with communication time-delays

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Journal of Systems Engineering and Electronics 2010年第1期21卷 88-94页

作者： Bo Yang1,2. Huajing Fang3. and Hua Wang4 1. school of Navigation, wuhan University of {2., wuhan 43.063. P. R. china 2. wuhan Second Ship Design and Research Institute, wuhan 43.064, P. R. china 3. Department of Control science and Engineering, Huazhong University of science and {2., wuhan 43.074, P. R. china 4. Department of Aerospace and Mechanical Engineering, Boston University, Boston MA02.15, USA school of Navigation Wuhan University of Technology Wuhan 430063 P. R. China wuhan Second Ship Design and Research Institute Wuhan 430064 E R. China Department of Control science and Engineering Huazhong University of Science and Technology Wuhan 430074 P. R. China Department of Aerospace and Mechanical Engineering Boston University Boston MA02215 USA

This paper proposes second-order consensus protocols with time-delays and gives the measure of the robustness of the protocols to the time-delay existing in the network of agents with second-order dynamics. By employing a frequency domain method, it is proven that the information states and their time derivatives of all the agents in the network achieve consensus asymptotically, respectively, for appropriate communication timedelay if the topology of weighted network is connected. Particularly, a tight upper bound on the communication time-delay that can be tolerated in the dynamic network is found. The consensus protocols are distributed in the sense that each agent only needs information from its neighboring agents, which reduces the complexity of connections between neighboring agents significantly. Numerical simulation results are provided to demonstrate the effectiveness and the sharpness of the theoretical results for second-order consensus in networks in the presence of communication time-delays.

关键词： second-order consensus protocols dynamic networks algebraic graph theory frequency domain analysis com-munication constraints.

Internal Curing Using Water-releasing Material for High Strength Micro-expansive Concrete

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Journal of wuhan University of technology(Materials {2.) 2009年第3期24卷 510-513页

作者：吕林女 school of science Wuhan University of Technology

Due to its low water content, it is difficult for expansive agent to have an effective expansive effect on high strength concrete to compensate its extensive shrinkage and form a certain expansion. To solve this problem, water-releasing material with water storage and releasing characteristics was incorporated into high strength micro-expansive concrete to provide internal curing, and expansive effect of expansive agent was improved. Migration of water from initially saturated water-releasing material to the surrounding hydrating cement paste was investigated. Based on a given efficient diffusion distance of water stored in water-releasing material, the mass and real water-cement ratio of cured cement paste were estimated. At the same time, the effect of internal curing of water-releasing material on the volume deformation of high strength micro-expansive concrete was investigated.

关键词： water-releasing material high strength concrete expansive internal curing

Interfacial Microstructure and Properties of Ti(C, N)/Ni Bonded by Transient Liquid-phase Diffusion

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Journal of wuhan University of technology(Materials {2.) 2009年第3期24卷 432-439页

作者：周世权熊惟皓 school of Mechanical science and Engineering Huazhong University of Science and Technology Department of Mechanical Engineering University of Waterloo school of Materials science and Engineering Huazhong University of Science and Technology

Effects of the main process parameters（temperature and time） on microstructure and properties of Ti（C, N）/Ni interface bonded by （Cu＋Nb） interlayer in a vacuum diffusion bonding device were investigated. The interfacial microstructures consisted initially of Ni3.b metallic compound and eutectic of Ni3.b ＋ CuNiss, and finally transformed to （Ti, Nb）（C, N）＋Ni3.b near Ti （C, N） and NiCuss ＋ Ni3.b near Ni when diffusion bonding temperature was 1 52.-1 573.K. It was clear that Cu was a constituent in the transient liquid phase （TLP） into which Ni was dissolved by forming Cu-Ni transition liquid. Nb was dissolved in Cu-Ni transition liquid rapidly. Ti （C, N） conld be wetted by resultant Ni-Nb-Cu transient liquid phase which was followed by a little （Ti, Nb）（C, N） solid solution formed at interface. This increased the interface combining capability. Ultimately the interface shear strength was able to reach 140 MPa. The theoretle analysis and experimental results show that the growth of interfacial reaction layer Ni3.b accords with parabola law, and the activation energy of diffusion reaction is 115.0±0.5 kJ/mol, while the diffusion reaction speed constant is 12.53.mm/s^1/2.

关键词： vacuum diffusion bonding transient liquid phase (TLP) diffusion bonding interlayer activation energy

A Hybrid Genetic Algorithm for Reduct of Attributes in Decision System Based on Rough Set Theory

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wuhan University Journal of Natural sciences 2002年第3期7卷 285-289页

作者： Dai Jian\|hua 1,2., Li Yuan\|xiang 1,2.,Liu Qun 3.1. State Key Laboratory of Software Engineering, wuhan University, wuhan 43.072. Hubei,{2. 2. school of Computer, wuhan University, wuhan 43.072. Hubei, china 3. school of Computer {13., wuhan University State Key Laboratory of Software Engineering Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) wuhan University School of Computer Wuhan Hubei China (GRID:grid.49470.3e) (ISNI:***) Chongqing University of Posts & Telecommunications School of Computer Science Chongqing China (GRID:grid.411587.e) (ISNI:***)

Knowledge reduction is an important issue when dealing with huge amounts of data. And it has been proved that computing the minimal reduct of decision system is NP-complete. By introducing heuristic information into genetic algorithm, we proposed a heuristic genetic algorithm. In the genetic algorithm, we constructed a new operator to maintaining the classification ability. The experiment shows that our algorithm is efficient and effective for minimal reduct, even for the special example that the simple heuristic algorithm can’t get the right result.

关键词： rough set reduction genetic algorithm heuristic algorithm

Indeterminate direction relation model based on fuzzy description framework

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science china(Technological sciences) 2008年第S1期51卷 72-80页

作者： LIU YaoLin1,HE JianHua1,YU Yan2.& TANG XinMing3.1 school of Resource and Environment science,{2. University,{2. 43.079,china 2.school of Resource and Environment Engineer,{2. University of technology,{2. 4.0070,china 3.Chinese Academy of Surveying and Mapping,Beijing 10083.china school of Resource and Environment science Wuhan University Wuhan 430079 China school of Resource and Environment Engineer Wuhan University of Technology Wuhan 430070 China Chinese Academy of Surveying and Mapping Beijing 10083 China

The indetermination of direction relation is a hot topic for fuzzy GIS researchers. The existing models only study the effects of indetermination of spatial objects,but ignore the uncertainty of direction reference framework. In this paper,first a for-malized representation model of indeterminate spatial objects is designed based on quadruple (x,y,A,μ),then a fuzzy direction reference framework is constructed by revising the cone method,in which the partitions of direction tiles are smooth and continuous,and two neighboring sections are overlapped in the transitional zones with fuzzy method. Grounded on these,a fuzzy description model for indeterminate direction relation is proposed in which the uncertainty of all three parts (source object,reference object and reference frame) is taken into account simultaneously. In the end,case studies are implemented to test the rationality and validity of the model.

关键词： direction relation fuzzy description framework fuzzy representation model uncertainty

Sandwich Magnetoelectric Composites of Polyvinylidene Fluoride,Tb-Dy-Fe Alloy,and Lead Zireonate Titanate

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Journal of wuhan University of technology(Materials {2.) 2007年第4期22卷 596-599页

作者：赵广辉熊传溪 State Key Laboratory of Advanced technology for Materials Synthesis and Processing school of Computer science and {2. Wuhan University of TechnologyWuhan 430070China school of Materials science and Engineering Wuhan University of TechnologyWuhan 430070China

The novel sandwich composites were prepared by sandwiching a polyvinylidene fluoride/Tb- Dy-Fe alloy composite （PVDF/Terfenol-D） between polyvinylidene fluoride/lead zirconate titanate composites （PVDF/PZT）. The maximum magnetoelectric effect voltage coefficient, （dE/dn）3.max, of the sandwich composites is higher than that of three-phase composites at their own optimal loading level of Terfenol-D. This is attributed to less interface relaxations of strain and better polarization of the sandwich composites. When the volume fraction of Terfenol-D is higher than 0.10, no coupling interaction for three-phase composites could be observed, but （dE/dn）3.max of sandwiched composites still reached 2. mV/（***）. At high magnetic field intensity, the magnetoelectric effect voltage coefficient, （dE/dn）3., of sandwich composites is higher than that of three-phase composites; at low magnetic field intensity, （dE/dn）3. of sandwich composites is lower than that of three-phase composites. At their resonance frequency, the （dE/dn）3.max of the sandwich composites and the three phase composites are 150 mV/（***） and 42.mV/（cmoOe）, respectively. This significant increase of （dE/ dn）3.max at resonance frequency confirms the improvement of maximum magnetoelectric effect coefficient via sandwich-structured composites.

关键词： magnetoelectric piezoelectric sandwiched composites

Fabrication of Ti_2.lC by Spark Plasma Sintering from Elemental Powders and Thermodynamics Analysis of Ti-Al-C System

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Journal of wuhan University of technology(Materials {2.) 2007年第2期22卷 325-328页

作者：王苹 State Key Laboratory of Advanced technology for Materials Synthesis and Processing Wuhan University of Technology

A ternary-layered carbide Ti2.lC material could be synthesized by spark plasma sintering（SPS） technology using elemental powder mixture of Ti, Al and active carbon. By means of XRD and SEM, phases were identified and microscopically evaluated. The experimental results show that the main phase in the product was fully crystallized Ti2.lC with small particle size when sintered at 12.0℃. The synthesis temperature of SPS was 2.0-400℃ lower than that of hot pressing （HP） or hot isostatic pressing （HIP）. Through thermodynamics calculations, the mechanism of Ti2.lC was studied by calculating changes of Gibbs free energy of reactions.

关键词： Ti2.lC spark plasma sintering elemental powder thermodynamics analysis