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Superplasticity and Superplastic Bulging Behavior of ZrO_2.Ni Nanocomposite

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Journal of Wuhan University of Technology(Materials science) 2011年第1期26卷 56-60页

作者：丁水 Aerospace research institute of Materials and Processing Technology

ZrO2.Ni nanocomposite was produced by pulse electrodeposition and its superplastic properties were investigated by the tensile and bulging tests. The as-deposited nickel matrix has a narrow grain size distribution with a mean grain size of 45 nm. A maximum elongation of 605% was observed at 72. K and a strain rate of 1.67×10-3s-1 by tensile test. Superplastic bulging tests were subsequently performed using dies with diameters of 1 mm and 5 mm respectively based on the optimal superplastic forming temperature. The effects of forming temperature and gas pressure on bulging process were experimentally investigated. The results indicated that ZrO2.Ni nanocomposite samples can be readily bulged at 72. K with H/d value （defined as dome apex height over the die diameter） larger than 0.5, indicating that the nanocomposite has good bulging ability. SEM and TEM were used to examine the microstructure of the as-deposited and bulged samples. The observations showed that significant grain coarsening occurs during superplastic bulging, and the microstructure is found to depend on the forming temperature.

关键词： superplasticity bulging microstructure ZrO2.Ni nanocomposite

A Novel Stable Clustering Design Method for Hierarchical Satellite Network

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Chinese Journal of Aeronautics 2010年第1期23卷 91-102页

作者： Zhou Mu,Guo Qing,Wang Zhenyong Communication research center,School of Electronics and Information Engineering,{2. institute of Technology,{2. 150001,china [a] Communication research center School of Electronics Information Engineering Harbin Institute of Technology Harbin 150001 China

This article proposes a novel stable clustering design method for hierarchical satellite network in order to increase its stability,reduce the overhead of storage and exert effective control of the delay performances based on a 5-dimensional vector model. According to the function of stability measureinent and owing to the limitation of minimal average routing table length, the hierarchical satellite network is grouped into separate stable connected clusters to improve destruction resistance and reconstruction ability in the future integrated network. In each cluster, redundant communication links with little contribution to network stability and slight influences on delay variation are deleted to satisfy the requirements for stability and connectivity by means of optimal link resources, and, also, the idea of logical weight is introduced to select the optimal satellites used to communicate with neighboring cluster satellites. Finally, the feasibility and effectiveness of the proposed method are verified by comparing it with the simulated performances of other two typical hierarchical satellite networks, double layer satellite constellation（DLSC） and satellite over satellite（SOS）.

关键词： satellite network hierarchical structure stability analysis clustering algorithms vector measurements

Identifying heavy hitters in high-speed network monitoring

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science china(Information sciences) 2010年第3期53卷 659-676页

作者： ZHANG Yu1, FANG BinXing1,2.& ZHANG YongZheng2.1research center of Computer Network and Information Security Technology, {2. institute of Technology, {2. 150001, china 2.0} center of Information Security, institute of Computing Technology, Chinese Academy of sciences, Beijing 100190, china 1. research center of Computer Network and Information Security Technology Harbin Institute of Technology Harbin 150001 China2. Research Center of Information Security Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China

Identifying heavy hitters in a network traffic stream is important for a variety of network applications ranging from traffic engineering to anomaly detection such as detection of denial-of-service attacks. Existing methods generally examine newly arriving items in the stream, perform a small number of operations using a small amount of memory, and still provide guarantees on the identifying accuracy. In high-speed network monitoring, the update speed per item is extremely critical. However, so far as we know, there are no identifying algorithms which can provide constant update time (O(1)) in a weighted data stream. In this paper, we present an algorithm named Weighted Lossy Counting (WLC) which is able to identify heavy hitters in a high-speed weighted data stream with constant update time. WLC employs a novel efficient partially ordered data structure which is able to provide a fast per-item update speed while keeping the memory cost relatively low. We compare WLC with state-of-the-art algorithms for finding heavy hitters in real traffic traces. The experimental results show that WLC performs well in accuracy (recall, precision and average relative error) as other algorithms; moreover it has a much higher update speed at the cost of relatively larger memory space used. A theoretical worst-case memory bound of WLC is also derived in this paper; however, experiments with long real traffic traces show that WLC requires much less space than the theoretical bound in practice.

关键词： network traffic monitoring heavy hitter weighted data streams

Feedback image encryption algorithm with compound chaotic stream cipher based on perturbation

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science china(Information sciences) 2010年第1期53卷 191-202页

作者： TONG XiaoJun1 & CUI MingGen2.1School of Computer science and Technology, harbin {2. of Technology, Weihai 2.42.9, china 2.chool of science, harbin {2. of Technology, Weihai 2.42.9, china 1. School of Computer science and Technology Harbin Institute of Technology Weihai 264209 China2. School of Science Harbin Institute of Technology Weihai 264209 China

In this paper, two new one-dimensional chaotic functions are designed using Devaney chaotic definition. And a dynamically shifting compound chaotic function is constructed based on the two new one-dimensional chaotic functions. The properties of compound chaotic functions are also proved. A new feedback image encryption algorithm is designed using the new compound chaos and an image pixel permutation, 3D baker scheme is described in detail. In the scheme, a new dynamic block dividing the 3D baker is put forward using the compound chaotic map, and the key space expands. In order to produce avalanche effect and sensitivity of cipher to plaintext, the round times are designed to control the cycle. The entropy analysis, difference analysis, weak-key analysis, statistical analysis, cipher random analysis, and cipher sensibility analysis depending on key and plaintext are introduced to test the security of the new scheme of image encryption. The tests show that the image encryption method passes the random tests of NIST FIPS 140-2.2.01) and SP 800-2. standards. This paper also solves the problem of short periods and low precision of one-dimensional chaotic function by perturbation.

关键词： compound chaos stream cipher feedback image encryption 3D baker perturbation

Autonomous control of multi-fingered hand

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Progress in Natural science:Materials International 2006年第5期16卷 531-537页

作者： JIANG Li and LIU Hong (Robotics research institute, {2. institute of Technology, {2. 150001, china) [a]Robotics research Institue Harbin Institute of Technology Harbin China

This paper describes a novel autonomous control strategy of multi- fingered hand based on a modular control system of dexterous manipulation. A simple proportional-integral-derivative(PID) position control with friction compensation, which requires few friction parameters, is used to realize accurate and smooth trajectory tracking in pregrasp phase. In grasp and manipulation phases, an event-driven switcher is adopted to determine the switching between unconstrained position control and constrained torque control, and an improved explicit integral force control strategy is implemented to realize simultaneously stable contact transition and accurate force tracking. Experimental results have verified the effectiveness of the proposed autonomous control strategy of multi-fingered hand.

关键词： multi-fingered hand autonomous control position control impact control.

Effects of binders on the performance of electric double-layer capacitors of carbon nanotube electrodes

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Progress in Natural science:Materials International 2005年第5期15卷 453-457页

作者： LI Chensha1*, WANG Dazhi1, ZHANG Baoyou2. WANG Xiaofeng1, CAO Maosheng3 and LIANG Ji1(1. Department of Mechanical Engineering, Tsinghua University, Beijing 100084, china 2. center for Analysis and Measurement, {2. institute of Technology, {2. 150001, china 3. School of Material science and Engineering, Tsinghua University, Beijing 100084, china) Department of Mechanical Engineering Tsinghua University Beijing 100084 China center for Analysis and Measurement Harbin Institute of Technology Harbin 150001 China School of Material science and Engineering Tsinghua University Beijing 100084 China

Polarizable electrodes of electric double layer capacitor (EDLCs) were made from carbon nanotubes. Effects of different binders, which are phenolic resin (PF) and polytetrafluoroethylene (PTFE), on the properties of polarizable electrodes are studied. Results indicate that the microstructure, pore size distribution and specific capacitance of the electrodes with PTFE binder are superior to those electrodes with PF binder after carbonization. The suitable binder (PTFE) for carbon nanotubes electrodes is proposed.

关键词： carbon nanotubes electric double-layer capacitors phenolic resin polytetrafluoroethylene.

Performance Analysis of the Dynamic CSMA/CD Protocol in a Wireless Channel

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Journal of Systems Engineering and Electronics 2003年第3期14卷 28-32页

作者： Sha Xuejun & Zhang Naitong Communication research center, {2. institute of Technology, {2. 150001, P.R. china Communication research center Harbin Institute of Technology Harbin 150001 P. R. China

In wireless networks, packet access is a popular mode, and the key problem is how to improve throughput and access delay performance, especially the throughput for wireless channels. These results will be a reference ... 详细信息

关键词： MAC protocol CSMA/CD Dynamic parameter Wireless channel.

Pseudo-beam method for compressive buckling characteristics analysis of space inflatable load-carrying structures

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Acta Mechanica Sinica 2009年第5期25卷 659-668页

作者： Changguo Wang Huifeng Tan Xingwen Du center for Composite Materials,harbin {2. of Technology, 150001 harbin, china center for Composite Materials Harbin Institute of Technology 150001 Harbin China

This paper extends Le van＇s work to the case of nonlinear problem and the complicated configuration. The wrinkling stress distribution and the pressure effects are also included in our analysis. Pseudo-beam method is presented based on the inflatable beam theory to model the inflatable structures as a set of inflatable beam elements with a prestressed state. In this method, the discretized nonlinear equations are given based upon the virtual work principle with a 3-node Timoshenko＇s beam model. Finite element simulation is performed by using a 3-node BEAM189 element incorporating ANSYS nonlinear program. The pressure effect is equivalent included in our method by modifying beam element cross-section parameters related to pressure. A benchmark example, the bending case of an inflatable cantilever beam, is performed to verify the accuracy of our proposed method. The comparisons reveal that the numerical results obtained with our method are close to open published analytical and membrane finite element results. The method is then used to evaluate the whole buckling and the loadcarrying characteristics of an inflatable support frame subjected to a compression force. The wrinkling stress and region characteristics are also shown in the end. This method gives better convergence characteristics, and requires much less computation time. It is very effective to deal with the whole load-carrying ability analytical problems for large scale inflatable structures with complex configuration.

关键词： Inflatable structure - Pseudo-beam method Inflatable beam theory Nonlinear buckling finite element

The nonlocal theory solution of a Mode-I crack in functionally graded materials

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science china(Technological sciences) 2009年第4期52卷 1101-1111页

作者： LIANG Jun center for Composite Materials and Structures, harbin {2. of Technology, harbin 150001, china 1. center for Composite Materials and Structures Harbin Institute of Technology Harbin 150001 China

The behavior of a Mode-I finite crack in functionally graded materials is investigated using the non-local theory. To make the analysis tractable, it is assumed that the shear modulus varies exponentially with coordinate vertical to the crack. The problem in this paper can be solved through the Fourier transform with the help of two pairs of dual integral equations, in which the unknown variables are jumps of dis- placements across crack surfaces. To solve dual integral equations, the jumps of displacements across crack surfaces are directly expanded in a series of Jacobi polynomials. Unlike the classical elasticity solutions, it is found that no stress singularities are present at crack tips. The non-local elastic solu- tions yield a finite stress at crack tips, thus allowing us to use the maximum stress as a fracture crite- rion. Numerical examples are provided to show the effects of the crack length, the parameter describ- ing the functionally graded materials, the lattice parameter of materials and the materials constants upon the stress fields near crack tips.

关键词： crack functionally graded materials the non-local theory mechanics of solids