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Robustness and breakup of the spiral wave in a two-dimensional lattice network of neurons

Science china(Physics,Mechanics & Astronomy) 2010年第4期53卷 672-679页

作者： MA Jun 1,2, TANG Jun 2 , ZHANG AiHua 3 & JIA Ya 2 1 Department of Physics, lanzhou University of Technology, lanzhou 730050, china 2 Department of Physics, Central china Normal University, Wuhan 430079, china 3 College of Electrical and Information Engineering, lanzhou University of Technology, lanzhou 730050, china 1. Department of Physics Lanzhou University of Technology Lanzhou 730050 China2. Department of Physics Central China Normal University Wuhan 430079 China3. College of Electrical and Information Engineering Lanzhou University of Technology Lanzhou 730050 China

The robustness and breakup of spiral wave in a two-dimensional lattice networks of neurons are investigated. The effect of small- world type connection is often simplified with local regular connection and the long-range connection with certain probability. The network effect on the development of spiral wave can be better described by local regular connection and changeable long-range connection probability than fixed long-range connection probability because the long-range probability could be changeable in realistic biological system. The effect from the changeable probability for long-range connection is simplified by multiplicative noise. At first, a stable rotating spiral wave is developed by using appropriate initial values, parameters and no-flux boundary conditions, and then the effect of networks is investigated. Extensive numerical studies show that spiral wave keeps its alive and robust when the intensity of multiplicative noise is below a certain threshold, otherwise, the breakup of spiral wave occurs. A statistical factor of synchronization in two-dimensional array is defined to study the phase transition of spiral wave by checking the membrane potentials of all neurons corresponding to the critical parameters(the intensity of noise or forcing current)in the curve for factor of synchronization. The Hindmarsh-Rose model is investigated, the Hodgkin-Huxley neuron model in the presence of the channel noise is also studied to check the model independence of our conclusions. And it is found that breakup of spiral wave is easier to be induced by the multiplicative noise in presence of channel noise.

关键词： spiral wave factor of synchronization breakup multiplicative noise robustness

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Microstructure and properties of thermal-sprayed NiCrWRE coatings

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Rare Metals 2008年第3期27卷 261-265页

作者： ZHANG Zhenyu WANG Zhiping LIANG Bunv Mechanical Engineering Department Lanzhou Polytechnic College Lanzhou 730050 China State Key Laboratory of New Nonferrous Metal Materials Lanzhou University of Technology Lanzhou 730050 China

The powders of NiCrW and NiCrWRE alloys were flame sprayed on a medium-carbon steel substrate by thermal spray welding. The micro- structure and tribological behavior of coatings were studied experimentally by means of scanning electron microscopy （SEM）, field emission gun scanning electron microscope （FEGSEM）, and wear tests. The addition of CeO2 modifies the coating morphology from a needle-like structure to a roughly cubic morphology; the refining and purifying effect of rare earth elements makes the microstmcture more compact and finer. Analysis of the worn surfaces reveals that the coatings with CeO2 addition show improved abrasive wear resistance over those without CeO2. By adding CeO2, the hardness of the coatings is significantly increased, and the wear resistance of the coatings is enhanced.

关键词： NiCrWRE microstructure thermal-sprayed coatings wear resistance

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Flow of Viscous Oil in the Volute of a Centrifugal Pump

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Journal of Thermal Science 2002年第1期11卷 10-15页

作者： Wen-Guang LI (Hydraulic Machinery Division, Gansu University of Technology, lanzhou 730050, china E-mail: Liwg@***) Hydraulic Machinery Division Gansu University of Technology Lanzhou China

The flows of water as well as viscous oil in the three rectangular sections of the volute of a centrifugal pump are measured by using a two-dimensional laser Doppler velocimetry(LDV) in the best efficiency and part-loading points, respectively. The results show that the magnitude of tangential component of absolute velocity is one order larger than that of radial component. There are spiral motions in the sections of the volute. The angular momentum of liquid in the volute isn’t conservative and the viscosity of liquid is larger, this situation is more severe. The flow of water or viscous oil in the volute is diffused in both best efficiency point and part-loading points. The diffusion of the flow is weakened while pumping the viscous oil.

关键词： centrifugal pump volute flow measurement viscosity LDV.

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Effect of High-energy Ball Milling on Synthetic Reaction in Al-TiO_2-C System

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Journal of Wuhan University of Technology(Materials Science) 2005年第4期20卷 50-54页

作者：寇生中 State Key Lab of Advanced Nonferrous Materials Lanzhou University of TechnologyLanzhou 730050China

High-energy ball milling has a great influence on the temperature characters of synthetic reaction in Al-TiO2-C system by changing the size,distribution state and wet ability of *** temperature characters（reaction ignition time,ignition temperature *** maximum temperature and temperature rising rate）were changed by different milling *** longer the milling *** earlier the *** quicker the temperature rise and the higher the maximum *** the milling time exceeded 10 hours,the reactivity of reactants was so high that the synthetic reaction could take place at 850℃ directly without a long time pretreatment at 670℃.The microstructure of synthetic composites became uniform and the reinforced particles（TiC and α-Al2O3）became fine with milling time increasing.

关键词： composites synthetic reaction Al2O3p-TiCp/Al temperature character microstructure

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Microstructure and Orientation Evolution of Unidirectional Solidification Pure Copper during ECAP

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稀有金属材料与工程 2011年第S3期40卷 171-175页

作者： Guo Tingbiao, Ding Yutian, Yuan Xunfeng, Hu Yong State Key Lab. of Gansu Advanced Non-ferrous Metal Materials, lanzhou University of Technology, lanzhou 730050,china lanzhou Univ Technol State Key Lab Gansu Adv Nonferrous Met Mat Lanzhou 730050 Peoples R China

Experiment were conducted to unidirectional solidification pure copper during ECAP by route C, the samples were investigated by XRD and EBSD. The results shown that the effect of original microstructure on the subgrains orientation decrease with the increasing of strain. At low strain, in the column grain interiors first formed a band structure that the orientation quite different with the matrix. With the strain increasing, the boundaries of the band structure expanding towards to two sides, gradually partition the original column grains into subgrains, the distribution of the subgrains possesses a directional distribution characteristics and the twins occurring in subgrains. Keep on increasing strain, the original grain boundaries began to broken, low angles grain boundaries and high angles grain boundaries both occur simultaneously shows a diffusion distribution characteristics.

关键词： equal channel angular extrusion (ECAE) electron back-scattering diffraction (EBSD) grain boundaries (GBs) texture

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Effect of cooling rate on plastic deformation of Zr-based bulk metallic glasses

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Progress in Natural Science:Materials International 2012年第1期22卷 21-25页

作者： Chunyan Li a,Shengzhong Kou a,b,Yanchun Zhao a,Guangqiao Liu b,Yutian Ding a a State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials,lanzhou University of Technology,lanzhou 730050,china b Key Laboratory of Non-ferrous Metal Alloys and Processing of the Ministry of Education,lanzhou University of Technology,lanzhou 730050,china [a] State Key Laboratory of Gansu Advanced Non-ferrous Metal Materials Lanzhou University of Technology Lanzhou 730050 China [b] Key Laboratory of Non-ferrous Metal Alloys and Processing of the Ministry of Education Lanzhou University of Technology Lanzhou 730050 China

The effect of cooling rate on plastic deformation of Zr-based bulk metallic glasses has been *** specimens with the diameters of 3 mm,4 mm and 6 mm cut from the same ladder-shaped Zr 55 Al 10 Ni 5 Cu 30 BMG rod were used in the present *** experimental results indicated that the different plastic strains were induced for the three type compression *** compressive plastic strain increased with the decreasing diameter for the as-cast specimens,which means that the compressive plastic strain increased with the increasing cooling *** reason of the difference is attributed to the free volume existed in the BMGs during the rapid solidification,and the larger free volume was contained in the specimen fabricated with the higher cooling *** has been found that the prominent serrations and multiple shear bands appeared during the compressive deformation tests of the specimen with smaller diameter of 3 mm,indicating that the specimen with smaller diameter exhibits better plasticity due to more free volume content.

关键词： Bulk metallic glasses Cooling rate Serration Plastic deformation Free volume

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Friction Stir Processing of Thixoformed AZ91D Magnesium Alloy and Fabrication of Surface Composite Reinforced by SiC_ps

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Journal of Wuhan University of Technology(Materials Science) 2010年第2期25卷 223-227页

作者：陈体军 State Key Laboratory of Gansu Advanced Nonferrous Materials Lanzhou University of Technology

The microstructural evolution characteristics of the thermomechanically affected zone （TMAZ） alloy during friction stir processing （FSP） of thixoformed （TF） AZ91D alloy were investigated. Simultaneously, a surface composite layer reinforced by SiC particles （SiCps） was prepared on the alloy by FSP and the corresponding tribological properties were examined. The experimental results indicate that dynamic recrystallization and mechanical separation （including splitting and fracture of the primary grains） are the main mechanisms of grain refinement for the TMAZ. A composite surface reinforced by uniformly distributed SiCps was prepared on the alloy. Compared with the corresponding permanent mould casting alloy and the TF alloy without composite surface, the TF alloy with composite surface has the highest wear resistance and lowest friction coefficient.

关键词： friction stir processing thixoforming AZ91D alloy microstructure evolution composite surface tribological properties

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Preparation and particle size characterization of Cu nanoparticles prepared by anodic arc plasma

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Rare Metals 2006年第2期25卷 172-176页

作者： WEI Zhiqiang XIA Tiandong FENG Wangjun DAI Jianfeng WANG Qing LI Weixue YAN Pengxun School of Sciences Lanzhou University of Technology Lanzhou 730050 China College of Materials Science and Engineering Lanzhou University of Technology Lanzhou 730050 China Institute of Plasma and Metal Materials Lanzhou University Lanzhou 730000 China

Copper nanoparticles were successfully prepared in large scale by means of anodic arc discharging plasma method in inert atmosphere. The particle size, specific surface area, crystal structure, and morphology of the samples were characterized by X-ray diffraction （XRD）, BET equation, transmission electron microscopy （TEM）, and the corresponding selected area electron diffraction （SAED）. The experimental results indicate that the crystal structure of the samples is fcc structure the same as that of the bulk materials. The specific surface area is 11 m^2/g, the particle size distribution is 30 to 90 nm, and the average particle size is about 67 nm obtained from TEM and confirmed from XRD and BET results. The nanoparticles with uniform size, high purity, narrow size distribution and spherical shape can be prepared by this convenient and effective method.

关键词： metal materials Cu nanoparticles anodic arc plasma particle size structure

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Crystallization kinetics of (Ni_(0.75)Fe_(0.25)_(78-x)Nb_xSi_(10)B_(12)(x=0,5)amorphous alloys

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Rare Metals 2006年第4期25卷 342-348页

作者： CHEN Xueding WEI Hengdou WANG Xiaojun State Key Laboratory of Advanced New Non-ferrous Materials l.anzhou University of Technology l.anzhou 730050 China

Amorphous ribbons of （Ni0.75Fe0.25）78-xNbxSi10B12 （x = 0, 5） were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating, and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the （Ni0.75Fe0.25）78Si10B12 amorphous alloy was annealed at the temperatures 715 and 745 K, a single phase of γ-（Fe, Ni） solid solution with grain sizes of about 10.3 and 18.5 nm, respectively, precipitates in the amorphous matrix. The crystallized phases are γ-（Fe, Ni） solid solution, Fe2Si, Ni2Si, and Fe3B after annealing at 765 K. The （Ni0.75Fe0.25）73NbsSi10 B12 amorphous alloy was annealed at 720, 750, and 800 K; and the crystallization phases, γ（Fe, Ni） solid solution, （Fe, Ni）23B6. Ni31Si12 and Nb2NiB0.16 form simultaneously.

关键词： amorphous materials thermal analysis crystallization kinetics activation energy

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Microstructures and corrosion properties of casting in situ Al_3Ti-Al composites

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Rare Metals 2010年第1期29卷 78-85页

作者： CHEN Tijun LI Jian HAO Yuan Gansu Key Laboratory of Advanced Nonferrous Materials Lanzhou University of Technology Lanzhou 730050 China School of Material Science and Engineering Xi＇an Shiyou University Xi ＇an 710065 China

The effects of Ti content and the alloying elements of Si and Cu on the microstructures of casting in situ Al3Ti-Al composites were investigated. Simultaneously, their corrosion properties were also discussed. The results indicate that the aspect ratios of Al3Ti platelets in different Al based composites are different although all of them are in flaky shape. The morphologies of Al3Ti phase are not only determined by Ti content, but are also related to the alloying elements. The grain refining role of Al3Ti phase in the pure Al and Al-Cu based composites is more effective than that in the Al-Si based composite. The addition of Ti decreases the corrosion resistance of pure Al and Al alloys. The corrosion resistances of the composites are dependent on both the corrosion characteristics of the corresponding matrixes and the distribution of Al3Ti platelets.

关键词： metal matrix composite microstructure corrosion resistance alloying element morphology

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