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2009 Vol. 35, No. 5

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Influence of wing location on rotor-wing interaction of compound helicopter
Wan Jia, Chen Ming
2009, 35(5): 519-522.
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The compound helicopter has gained more and more attentions so far, but the analysis method available is limited. Employing the free-wake arithmetic and vortex lattice method(VLM), a program for compound helicopter aerodynamic computation was developed. Using this program, interactions between the rotor and the wing were computed in different advance ratios and wing locations. From the computation results, some conclusions can be made: for the compound helicopter described, the interaction between the wing and the rotor isn-t sensitive to the wing location in high velocity, except the rotor torque; In low flight speed, the interaction is more complex, and needs more researches; Because of the dissymmetrical structure of the rotor wakes, the spanwise lift distribution of the wing is dissymmetrical, and it will cause a rolling torque.
Way to study one-dimensional numerical simulation of aero engine
Chang Zhonghong, Zhu Zhili, Tang Hailong
2009, 35(5): 523-526.
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One-dimensional aerodynamic thermodynamic mathematic models for each component of aero engine were formulated. This model can be used to estimate the components and full engine system-s performance. A full engine flow simulation was done by applying this model. Viscous effects of the gas and secondary flow losses were considered as source terms of the Euler equation. High-order Godunov-s scheme possessed TVD characteristic was used in solving the governing equation, which shows good numerical stability and shock capturing capability. The model was executed using time-marching method and alternatively explicit/implicit schemes, so that convergence was fast and the accuracy was satisfactory compared with test data. A full flow of turbofan engine simulation was done by applying this model. The simulation result includes velocity characteristics and throttle characteristics shows good accuracy compared with test data.
Cooling structure on double-web turbine disk with equal mass scheme
Zhao Xi, Xu Guoqiang, Luo Xiang, Deng Hongwu
2009, 35(5): 527-531.
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Numeration analysis was made to simulate the flow and heat transfer in the double-web turbine disk. Several cooling structures of double-web turbine disk with different radial inlet position were proposed based on the same weight as a simplified solid disk. The calculated results present that: structures, in which rotor-stator cavity resorting a center or high positioned cooling air inlet, with the rotating cavity using high positioned inlet both, show better features of heat transfer. The lower volume mean temperature and the lower radial temperature difference are obtained, however, the resistant loss will increase a little.
Approximation model for reliability analysis based on GA-BP Bayesian algorithm
Ren Yuan, Bai Guangchen
2009, 35(5): 532-535.
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The usefulness of genetic algorithm-backpropagation(GA-BP) Bayesian algorithm was studied and evaluated for reliability simulation. GA-BP Bayesian algorithm is a algorithm to train feedforward neural networks, and it is based on GA, L-M (Levenberg-Marquardt) BP, and Bayesian method. The algorithm trains a network with the purpose of obtaining the weights corresponding with maximum posterior probability, and it adopts genetic algorithm in searching process. As a result, it makes neural networks have better and steadier generalization ability. When running a reliability simulation, GA-BP Bayesian algorithm can be utilized to train neural networks to make an approximation model that can be used in Monte Carlo simulation instead of expensive numerical program. In this way, the probability distribution of random ouput variables can be obtained with efficiently-controlled computing cost.
Numerical simulation of pulverized-coal combustion
Zhang Hongbo, Qin Guotong, Ji Renshan, Wang Naiji
2009, 35(5): 536-539.
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The comparative study between CFD numerical results of pulverized coal combustion process and the experimental data is becoming an important measure for validating mathematical models and direct engineering practice. The CFD commercial software, FLUENT, was used to simulate the pulverized coal flow and combustion. Mixture-Fraction/PDF model was used to simulate turbulent combustion; P-1 radiation model was used for simulating radiation heat transfer; the Langrange/Euler-s method was used for dealing with momentum, mass and energy exchange between the solid and the gas phase; the two-competing rates model for devolatilization and the kinitics/diffusion limited combustion model for simulating surface combustion of pulverized coal particles. The result of simulation is consistent with the data from actual combustion process. The simulation results show the rules of the volatile releasing and combustion processing of coke, which could provide important references to improve the combustion of the pulverized coal.
Effects of rare-earth (RE) elements on crystallization behavior of Al-Ni-Gd-Y amorphous alloy
Song Honghai, Duan Huiping, Ma Chaoli, Zhang Tao
2009, 35(5): 540-543.
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The effects of rare-earth (RE) elements on the crystallization behavior of Al-Ni-Gd-Y amorphous alloy were investigated by differential scanning calorimetry(DSC), X-ray diffraction(XRD) and transmission electron microscopy(TEM). The first crystallization temperature of Al-Ni-Gd-Y amorphous alloy increases with RE content. In the alloy Al(88- x )Ni6Gd6Y x ( x =1,2,3,4), the crystallization phase changes from fcc-Al to fcc-Al+Al3Gd/Al3Y+unknown phase when the Y content increasing. The effect of heat-treatment on the mechanical property of Al-Ni-Gd-Y alloy was also investigated. The Al86Ni8Gd3Y3 alloy was of high microhardness and good ductility after heat-treatment at 568K for 10min and fine precipitation of fcc Al with size of 1~3nm was found in the alloy.
Unsupervised classification approach based on graph-segment for multispectral remote sensing images
Liu Nana, Li Jingwen, Li Ning
2009, 35(5): 544-546.
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To solving the noisy points and high cost problems of pixel-based multispectral image classification, a hybrid unsupervised approach with graph-based segment and fuzzy c-means clustering was presented. First, based on the relationships among neighboring pixels, image was segmented into groups of sub-regions using the graph-based algorithm. Then according to the global feature vector of sub-region, the fuzzy c-means classifier was used to obtain the classification map. Experiments turn out that the proposed approach, which considers both relationships of neighboring pixels and global feature of sub-region, can achieve better accuracy and efficiency by comparing the result with pixel-based fuzzy c-means classification.
Optimization of near-space aerocraft track for regional coverage based on greedy algorithm
Chen Rongguang, Li Chunsheng, Chen Jie, Yu Ze
2009, 35(5): 547-550.
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In order to covering any discretionary polygonal region,a novel method was proposed based on set covering problem model, which is a NP-hard problem. Random greedy algorithm strategy was applied in the method to achieve 100% regional coverage with minimum aerocrafts by designing and optimizing each aerocraft-s track and beam position. Random greedy algorithm removed some aerocrafts from the solution of greedy algorithm randomly and added some new ones based on greedy strategy again. The method extended search range for more possible optimized solutions compared with traditional greedy algorithm. Simulation result on Wenchuan area shows good effectiveness and intelligence of the method. Reliable reference can be supplied for near-space regional coverage planning.
Modeling of GPS multi-path signals and receiver testing
Yang Wei, Zhao Yun, Kou Yanhong, Huang Zhigang
2009, 35(5): 551-554.
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The multi-path effect is one of the most important sources of positioning errors for global positioning system (GPS) and other satellite navigational systems. Multi-path signal modeling and its mitigation techniques have always been hot spots in the satellite navigation research direction. According to the multi-path signals nature, a specular reflection multi-path model was proposed, due to the influence of the specular reflections on GPS positioning accuracy more noticeable in comparison with other multi-path reflections. The pseudo-range measurement error of the GPS software receiver caused by the multi-path signals was tested. In the test, the multi-path signals were generated by this specular reflection model. The test results show that the pseudo-range error changes caused by the multi-path signals act in accord with the theoretical analysis curves.
Design and implementation of IF signal modulator for GNSS signal simulator
Zhang Shuo, Kou Yanhong
2009, 35(5): 555-558.
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Global navigation satellite system(GNSS) signal simulator can simulate satellite signals received by target receivers in high fidelity according to the signal structure, dynamics of the receiver and environmental parameters defined by users, which provides an effective way for both GNSS system-level simulation and receiver test. The research of GNSS IF signal generator and digital signal processing techniques of the simulator compatible with multi-systems and multiple carrier frequencies was mainly focused on. Approaches on digital signal synthesis, power control and accurate simulation of signal phase were proposed. Functions of communication with PC, calculation and updating of waveform controlling parameters, baseband signal modulation and generation of analog IF signal were implemented on the IF signal modulator based on the architecture of PCIE+DSP+FPGA+DAC. Test results from the corresponding GNSS receivers validate the accuracy and quality of signals generated by simulator.
Novel chaotic frequency modulation circuit for class-D amplifier
Feng Wei, Li Hongge, Zhang Youguang
2009, 35(5): 559-562.
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The easy to be integrated chaotic frequency modulation circuit for class-D amplifier was proposed to solve electromagnetic interference(EMI) issue. In the circuit, an improved chaotic sequence generator was designed and its chaotic behavior was modeled by stroboscopic map. The proposed circuit only replaced fixed frequency ramp generator in conventional class-D amplifier architecture. Therefore, the spread spectrum triangular wave modulated by chaotic sequence was employed as carrier wave of pulse width modulation(PWM), instead of fixed frequency triangular wave. The circuit was designed, verified and implemented using 0.35μm CMOS process. Simulation results show that the peak power reduction can achieve to 15dB.
3D laser scanning algorithm with humanoid-eye function
Chen Weihai, Song Weiyang, Rong Lixia, Liu Jingmeng
2009, 35(5): 563-566.
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Aiming at the scanning efficiency of three dimensional (3D) laser scanning system for mobile robot all over the world, a humanoid-eye 3D laser scanning algorithm was proposed. Imitating the scanning function of human eyes from bionics, this algorithm divides the scanning process into two steps: according to the scanning information currently, the scanning scheme of the next step will be planned to reduce the gain of useless information; Through adopting the stepping interpolation location to fetch up the time consuming from stepping scan, the efficiency of the scan can be improved. To satisfy the real-time requirement for the online computing, a hardware architecture consisting of digital signal processing (DSP) and field-programmable gate array (FPGA) was proposed. Therefore, as the main controller, DSP can obtain 3D laser data; as the coprocessor, FPGA can complete the scanning algorithm. The experiment result shows the humanoid-eye scanning algorithm can improve the efficiency of the 3D scanning system greatly.
Design and realization of a prototype of software GPS receiver
Liu Jie, Fu Li, Wang Linlin
2009, 35(5): 567-571.
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A prototype of software global positioning system(GPS) receiver based on software defined radio techniques to design a flexible and reconfigurable receiver with a wide range of applications was discussed. Compared with hardware GPS receiver, there is a need for a unified platform that allows software receiver development and research for Ultra-Tightly coupled GPS/INS navigation system, speeds the design process and reduces the costs. A complete software GPS receiver was implemented using fast fourier transform(FFT) acquisition approach, delay locked loop, phase locked loop, and the receiver is able to perform acquisition, code and carrier tracking, navigation data decoding, pseudorange calculations, and position calculations. Compared with Novtel-s FlexPad hardware receiver, the results shows that software GPS receiver is effective in acquisition ,steady in tacking and it-s positioning error is less than 10 m,so it can be applied to an ultra-tightly coupled GPS/INS system.
Quadric error metrics for mesh simplification based on feature matrix
Chen Weihai, Xu Lihong, Liu Jingmeng, Wang Jianhua
2009, 35(5): 572-575.
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Contraposing the some deficiencies from the algorithm based on quadric error metrics (QEM), such as neglect of some cusp features and excessive simplification in some parts of the model, a QEM based on eigenmatrix was proposed for mesh simplification. Through introducing the curvature and edge length of a vertex into this new QEM to optimize error metrics, the eigenmatrix can easily distinguish the vertexes of a model, improve the error metrics of the vertexes in the areas with obvious geometric features. Therefore, the folding sequences of edge can be adjusted, so that some sharp features of the object can be preserved. Comparing with QEM algorithm, the simulation results show that the proposed approach can not only keep merits such as high executing speed and running efficiency, but also overcome the shortcoming to easily lose some important features of models because of mesh distribution too equality.
Model of stepped leader current for simulation of lightning
Liu Ning, Xiao Chunyan
2009, 35(5): 576-579.
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Model of stepped leader current is the basis of lightning movement simulation and strike analysis, and it is indispensable for lightning protection design, theoretical research of shielding failure for transmission lines, etc.. Physical model of stepped leader was given, which includes a main channel and a tip. Current model of stepped leader was also given, which well simulates the stepwise propagation of lightening and charge change properties of stepped leader-s tip. Electric field on the ground level produced by stepped leader was derived and calculated by charge simulation method and dipole technique, and its simulation results show that the average electric field peaks and time interval between stepped leader pulses of far-zone field agree well with the measured data. The close fields under different return strike current peaks also agree with the measurements of triggered-lightning.
Instrumentation in flight-control software testing
Li Yuefei, Guo Junhong, Bai Chenggang, Cai Kaiyuan
2009, 35(5): 580-583.
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Instrumentation is one of the important techniques in the software testing. When instrumentation was applied in the flight-control software testing, the real-time performance of the original software becomes bad even lead to failure of the software, due to the extra spending on the instrumentations. In view of this problem, a new instrumentation method which is based on the BOOL array used to storage the code information was presented. Compared with traditional methods, this new method not only optimizes the instrumentation contents but also reduces the real-time influence of the instrumentation on the original software. A simulation test platform was been set up and a certain type of flight control software was used as the test object. Then, plenty of experiments have been done to demonstrate the effect of the new instrumentation method. The result show that the method greatly reduces the run time of the instrumented program which to ensure the real-time requirements of the flight-control software.
Fuzzy guidance law for wire-guidance torpedo under condition of incomplete information
Zhang Xiaogong, Ren Zhang, Wang Xinyuan
2009, 35(5): 584-587.
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A fuzzy guidance technique under the condition of incomplete information was proposed to solve the problem that the commonly used guidance methods can not provide very good solution for the incomplete information of targets.Based on the deeply analysis of the function on artificial-intelligence(AI) guidance and the introduction mechanism of the target information including the azimuth ,distance and direction ,a new technique that the weighting revision for the direction, the threshold value limit of distance and the AI transfer on the terminal guidance can use these incomplete information effectively and be applied in the combined guidance .Simulation experiments show that the AI guidance technique can use the existing incomplete information fully and make the good progress on the optimized distance and angle entering the target wake.
Numerical aerodynamic computation of unmanned aerial vehicle
Zhao Guochen, Wang Chaozhi
2009, 35(5): 588-590.
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Numerical simulation of an unmanned aerial vehicle (UAV) was carried out by 3D modeling and computational fluid dynamics (CFD) software, and then the coefficients of lift, drag and moment with a small angle of attack (AoA) variety as well as the distribution of pressure,density and velocity on the surface of UAV were obtained. Empirical estimation was also conducted and the results of the two methods were compared with each other. It shows that CFD has a satisfactory accuracy in the small-scale, low velocity flow simulation, and it plays an important role in the development of the UAV. The simulation results can provide a theoretical reference to the further optimization development of the UAV.
Numerical simulation of three dimension viscous flow of combustion-heater used for scramjet test
Chen Chaoqun, Wei Baoxi, Zhang Chengliang, Xu Xu
2009, 35(5): 591-595.
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The combustion-heater was used to get high enthalpy, high mach number flow field in scramjet test. The injection is very important for the uniformity of the out-flow field. A three dimension numerical simulation software named Fluent was used to calculate the two injection. By examining the injection boundary, stream wise vortex etc., the mixing and combustion efficiencies of two injections were compared, and the results show that the performance of the hydrogen multi-hole oblique injection is predominated over that of the hydrogen single-hole vertical injection.
Lambert transfer based on ant colony algorithm and Powell-s method
Gao Xiaobo, Dong Yunfeng, Su Jianmin
2009, 35(5): 596-599.
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The optimization of Lambert two-impulse orbital transfer with unfixed two impulses time was studied. The goal was to find the optimal two impulses time to minimize the weighted sum of consumed fuel and transfer time. Because traditional optimization algorithms were difficult to get global optimal results of the problem, an optimization algorithm which combines ant colony algorithm (ACA) and Powell-s method was then proposed. The new algorithm combined global search capacity of ACA and local search capacity of Powell-s method. It not only provided the global search capacity, but also improved the local search capacity and reduced the search time. Two examples were computed in the end. The results indicate that the optimization algorithm is valid to solve the optimal orbital transfer problem and the optimization is accurate.
Constitutive equations of high strength aluminum alloy sheet 7B04-T6 under warm tension
Zhang Zhi, Lang Lihui, Li Tao, Liu Hejun
2009, 35(5): 600-603.
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Warm tensile tests for high strength aluminum alloy 7B04-T6 sheet were held at condition of elevated temperature and different strain rates. The range of temperature is 293~573K and the strain rate is 0.0006~0.06s-1. The warm tensile properties, relation between temperature, strain rate and the flow stress were discussed. It is concluded that flow stress decline with the increase of temperature and the decrease of strain rates; Elongation percentage increase with the increase of temperature and the decrease of strain rates. Furthermore constitutive equations under warm tension were obtained based on Fields and Backofen equation.
Experiment and analysis on sound absorption characteristics of metal rubber
Ma Yanhong, Li Haoyu, Li Yifeng, Hong Jie
2009, 35(5): 604-607.
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According to the established sound absorption model of metal rubber(MR), the measurement and research for the coefficient and acoustic impedance of MR, which is of different parameters, were carried. The influencing laws of MR-s structural parameters (such as wire diameter, thickness, porosity, cavity size and so on) on its sound absorption characteristics were investigated. With the comparative analysis between the experimental results and the calculated ones from the theoretical model, the acoustic model was proved accurate. It not only provides experiment method for the further engineering application of MR in the field of noise reduction, but also set up a basis for the theory improvement.
Key factors analysis of wall-climbing robot
Liu Rong, Tian Lin
2009, 35(5): 608-611.
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A kind of negative pressure wall-climbing robot was proposed. Analysis the relationship between speed of vacuum motor and negative pressure which based on courses of pressure form and pressure keep, and found that interspace height between airproof gasbag and wall was the key factor influencing on the stability of robot. The pressure distribution which between airproof gasbag and drive wheels shows relationship with negative pressure, pressure coefficient, weight, airproof gasbag friction coefficient and airproof gasbag friction coefficient. Analysis locomotion mechanism of robot from swerve performance. Experimental results validate the theory.
Site measuring accuracy testing of laser tracker
Gan Lin, Li Xiaoxing
2009, 35(5): 612-614.
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Laser tracker has the advantages of high precision, real-time, dynamic and easy to be moved etc. The site calibration and accuracy testing of the laser tracker are very necessary in actual measurement. The error of fixed points and the plane error of standard granite set square was measured by the LT300 laser tracker in order to verify the precision of the laser tracker. The relationship between measuring accuracy and distance can be found by changing the angle and distance between set square and the laser tracker. So the measuring accuracy of the LT300 laser tracker was obtained on the actual location.
Optimal design of shell-and-tube heat exchanger
Yang Ming, Meng Xiaofeng, Zhang Weijun
2009, 35(5): 615-617.
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The optimal design of the heat exchanger structure is a coupling problem with several parameters. Exchanger cubage and the pressure loss of the exchanger performance factors was selected as the optimal object. In the condition of moist air and water heat exchange, the heat transfer and pressure loss model and the influence factors of the structure of the shell-and-tube heat exchanger was analyzed. A mathematics model and an optimization design were built for the exchanger. A structure design method which was used to synthetically evaluate the problems of the exchanger cubage and the pressure loss was developed. Compared with common design method, this method could effectively reduce the exchanger cubage and the pressure loss.
Sensing theory of fiber optic intrusion sensor based on multimode fiber intensity modulation
Li Chenguang, Yang Dewei, Luo Guangming, Li Chen
2009, 35(5): 618-622.
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An intrusion sensor adopting a "single-mode multimode single-mode" (SMS)structure was introduced. The actual sensor element was the multimode fiber spliced to two single-mode fibers on its two ends. In order to improve the sensing sensitivity, the theory of intensity modulation was researched. High sensitive sensor structure was obtained by simulation and experiment. The sensor uses coherent light source, step-index multimode fiber, and splices the single-mode fibers and the multimode fiber along the fiber axis. This scheme can be deployed to various intrusion sensing applications such as country borders, military bases, oil pipelines, for its simple structure and long sensing distance.
Algorithm for video shot clustering based on spectral division
Zhong Lin, Li Chao, Xue Ling, Xiong Zhang
2009, 35(5): 623-626.
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A spectral-division unsupervised shot-clustering algorithm (SDUSC) was proposed. First, the keyframes were picked out to represent the shots, and the color features of keyframes were extracted to describe the video shots. In order to characterize shots optimally, a spherical gaussian model (SGM) was constructed for every shot category. Then the spectral division (SD) method was employed to divide a category into two categories, and the method was iteratively used to further divide the results of previous divisions. At the end of each iterative shot-division, bayesian information criterion (BIC) was utilized to automatically judge whether to stop further division. During the processes of shot-divisions, one category might be dissevered by mistake. In order to correct these mistakes, similar categories would be merged by calculating the similarities of all the possible category pairs. This approach was applied to three kinds of sports videos, and the experimental results shows that the proposed approach is reliable and effective.
Method of processor resources virtualization on cluster
Liu Zhonglin, Xiao Limin, Hao Qinfen, Zhu Mingfa
2009, 35(5): 627-630.
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In order to make the processor resources in multiple servers of cluster be utilized to operating system transparently, the processor resources virtualization scheme in distributed virtual machine monitor was proposed. That is to make each server provide a certain amount of virtual processors based on the hardware virtualization technology and present them to guest operating systems, to capture the sensitive instructions that would be executed in the virtual processor and make a simulation of their effect through collaboration between servers, and to ensure that all the virtual processor work exactly. Thereby the low layer resource distribution transparency to the guest operating systems was achieved, and guest operating systems and applications could make use of the process ability of multiple servers without any modification.
Coverage quality problem in wireless sensor networks
Zhang Shuo, Pu Juhua, Liu Yuheng, Xiong Zhang
2009, 35(5): 631-635.
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Extending lifetime by scheduling node state and maintaining the coverage quality are two important aspects in wireless sensor networks (WSNs). It was presented a mathematical model to compute minimum number of nodes under any given required coverage quality. Simulation results demonstrate that our approach is more accurate to compute minimum number of working nodes when the ratio of target region to sensor region is larger, and the complexity of this method is lower while the sensor-s region can be perceived as arbitrary shapes. It is an NP-hard problem that network-s coverage quality and ratio of sleeping nodes get to maximize together. It tried to solve this problem by using genetic algorithm for the experiments, which is significant in WSNs for the practical applications.
Adaptive aberrant network traffic detection algorithm based on time series forecast
Lü Junhui, Zhou Gang, Jin Yi
2009, 35(5): 636-639.
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The traditional network management tools usually detect aberrant network traffic according to the preset threshold. This method is straightforward, but it has poor adaptability. Therefore, A mature aberrant detection method called Holt-Winters based on the time series forecast was described. But it needed a long time to adapt the real network environment when the algorithm model applied. To solve these problems, based on the statistics of huge history network flow model, an increased Holt-Winter algorithm was proposed to calculate the base values and the model parameter values, which made the algorithm started faster. The result shows that the increased Holt-Winters algorithm has improved the detection accuracy and reduced the false alarm rate compared with threshold method and traditional Holt-Winters model.
Effective algorithm for mining compressed frequent patterns
Tong Yongxin, Ma Shilong, Li Yu
2009, 35(5): 640-643.
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Researches of frequent-pattern mining have recently focused on discovering representative patterns to compress a large of results within a reasonable tolerance bound. A novel heuristic algorithm, approximating mining based simulated annealing (AMSA), was proposed. The algorithm uses a method based simulated-annealing to improve efficiency and quality of the compression. Our experimental studies demonstrate the algorithm is efficient and high quality on a common dataset supported by frequent itemset mining implementations repository (FIMI). The mining result of AMSA is smaller than mining results of FPclose and RPglobal by performance study. Especially, if min_sup threshold is low, RPglobal fails to generate any result within reasonable time range, while AMSA generates a concise and succinct mining result.
Performance reliability assessment for products based on time series analysis
You Qi, Zhao Yu, Ma Xiaobing
2009, 35(5): 644-648.
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Time series model has the advantage of strong self-adjustment for stochastic process and high precision for prediction. For the high-reliability and long-life products in the field of aeronautics and astronautics, two methods based on time series model were proposed to evaluate reliability and predict lifetime using performance degradation data. Firstly, assuming that the degradation measure follows the same distribution family but its parameters may change with time. Non-stationary time series were used to fit distribution parameters. According to the relation between reliability and degradation measure distribution, the corresponding reliability functions were developed. Then, degradation paths of all samples were described by time series model. False failure interval and the false lifetime value could be predicted and reliability was obtained by statistical method from complete lifetime test data. Finally, the alloy fatigue crack data was used to evaluate reliability and predict lifetime,and the reasonable results show that the proposed method has better robustness.
Trafficability of rigid wheel on moon by model experiment
Gong Yongtao, Gao Feng, Li Wen, Sun Peng
2009, 35(5): 649-652.
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Based on a tractive performance test-bed for planetary rover wheel, remodeled lunar simulant as a medium, the interaction between the rigid lugged wheel of lunar rover vehicle and lunar simulant was studied. The influence on trafficability which are brought by rotating speed and wheel load, was analyzed. The results show that drawbar pull boosts with the increase of slip ratio as wheel runs at low speed; however, there is a critical slip ratio point for drawbar pull as wheel travels at high speed. In addition, an increase of wheel load leads to an increase of drawbar pull, whereas it influences the drawbar pull coefficient negligibly.
Theoretical analysis on sound absorption characteristics of metal rubber
Ma Yanhong, Hong Jie, Li Haoyu, Li Yifeng
2009, 35(5): 653-656.
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The theoretical research on sound absorption characteristic of metal rubber (MR) was performed. On the basis of Rayleigh model and according to the sound propagation theory in pipe and the principle of Helmholtz, the acoustic model of MR was established, and formula of absorption coefficient was derived. With the acoustic impedance pipe, the experiments for noise reduction characteristic of MR with different structural parameters were carried. The results of the test show the accuracy of this acoustic model. It provides theoretical support for the further engineering application of MR in the field of noise reduction.

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