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2008 Vol. 34, No. 03

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Forecasting method for aeroengine performance parameters
Li Xiaobai, Cui Xiuling, Lang Rongling
2008, 34(03): 253-256.
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The forecasting of aeroengine performance parameters is very important for aeroengine maintenance based on condition. To improve the forecasting accuracy, a new combination method was proposed for forecasting parameters based on analyzing the data. Firstly, the original sequence was decomposed by wavelet transform and some sub-sequences in different frequency band were obtained. Then these sub-sequences were forecasted by ARMA/ARIMA respectively. Finally, the forecasting results of all sub-sequences were reconstructed and taken as the final forecasting result. Through the test, the proposed combination model was proved to be highly effective on improving the accuracy of the short-term and long-term forecasting, and the effect of wavelet decomposition levels on forecasting accuracy was analyzed.
Sensor selection algorithm based on weighted distance in wireless sensor networks tracking
Wu Hai, Zhao Wei, Tian Bin
2008, 34(03): 257-261.
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A new sensor selection methods for bearings-only sensors, weighted-distance node selection (WNS) was proposed. Based on probability distribution function (PDF) of target estimates and sensing-model, the sensors with the minimum weighted-distance were activated in the next snapshot. Since the existing mahalanobis distance measure, though yields a good precision with low computational complexity, fits only range sensors and the algorithms based on the PDF, such as entropy method, are computationally burdensome, WNS avoids the Bayes filtering process and achieves alluring precision. Simulation results show that the computation complexity is indeed reduced while a comparable selection precision is achieved as entropy method.
FFT-based acquisition method to eliminate influence caused by data modulation
Sun Guoliang, Li Yuqi, Zhang Xiaolin
2008, 34(03): 262-266.
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To achieve higher acquisition accuracy while using FFT(fast Fourier transform)-based algorithm to acquire spread spectrum signal, integration across data bit transition boundaries is necessary. However, performance degradation due to data modulation must be eliminated. Two effects of baseband data shift on acquisition performance, amplitude attenuation and frequency offset of the detected signal in frequency domain, were analyzed. A method to solve this problem was given. This algorithm constructs a complex signal which is free from data modulation, and detects Doppler shift using this signal through FFT. Simulation in MATLAB and FPGA(field programmable gate array)-based implementation of this method was also described. The simulation and experiment results verify that, this method can overcome the problem caused by baseband data shift, and improve acquisition accuracy by one times compared with conventional method in the same predetection integration time.
Simplified method of kernel fuzzy c-means clustering for image texture classification
Yuan Yunneng, Wu Yang, Cheng Gong
2008, 34(03): 267-270.
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The fuzzy c-means clustering algorithm is a widely applied method for acquiring fuzzy pattern from data, but it is not suitable for the clustering of linear inseparable data. In mercer kernel method, the problem of nonlinear separability of classes can be tricked by projecting the input data to a higher dimensional feature space in a nonlinear manner. So the fuzzy c-means clustering method was used in the mercer kernel space. The classification experiment illustrated that the kernel fuzzy c-means clustering (KFCM) algorithm was suitable for the clustering of linear inseparable data. When KFCM clustering was used in image segmentation, the large number of classification samples always caused the computational burden. The image classification procedure was divided into two steps: firstly, the image was over-segmented into large numbers of small regions according to the input features; secondly, they were classified with KFCM. The computational burden was reduced by the decrease of classification samples, while the classification result was almost as good as KFCM-s.
Approach based on speckle reduction using SPIHT for data compression of complex SAR image
Xiang Shiyong, Li Chunsheng, Chen Jie
2008, 34(03): 271-275.
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A method based on speckle reduction using SPIHT(set partitioning in hierarchical trees) for data compression of complex SAR(synthetic aperture radar) image was presented, which could achieve both speckle reduction and image compression. According to the statistic characteristic of complex SAR image, complex SAR image was processed before wavelet transform. Soft-threshold speckle reduction and SPIHT image coding were applied to image compressing in wavelet domain. Wavelet coefficients in different subbands adopted different threshold in soft-threshold speckle reduction. The improved approach preserves the phase of the raw complex SAR image well and has a good effect of speckle reduction. It proves the efficiency of the improved approach for data compression of complex SAR image through evaluating phase error, ENL(equivalent number of looks) and complex spatial correlation efficient, comparing the intensity images of raw data and decompressed data, even at high compression ratio (64∶ 1).
Novel anti-collision algorithm in RFID system
Zhao Xi, Zhang Youguang
2008, 34(03): 276-279.
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In some radio frequency identification (RFID) systems, there are lots of tags can not be identified when tags come into and get out of the scope of the reader in a regular way, for the readers with a general algorithm do not give priority to read the leaving tags. A novel anti-collision algorithm was designed for this situation, which was called the first come first served (FCFS) algorithm. The reader grouped the tags by the order of arrival, and identified them according to the urgency of the time group. Secondly, algorithm avoided the predictable collision by setting a parameter. Thirdly, the reader set the upper value of the slots for every time group. The simulation result shows that keeping the leaking proportion less than 0.01, the arrival rate of tags which the system can bear increases by 50% and when the arrival rate of tags is 0.45, the throughput increases by 13%, compared to the prefix-randomized query-tree algorithm.
Diversity detection algorithms in laser communications
Zheng Zheng, Li Ning
2008, 34(03): 280-284.
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The likelihood ratio function in symbol-by-symbol maximum likelihood detection was calculated with the Monte Carlo method for the atmosphere laser communication systems under the weak turbulence condition. Discrete points were mass-generated according to the marginal distribution for the turbulence-induced fading. Then the accuracy of estimating the diversity performance with a relatively less number of discrete points was discussed. A practical diversity detection algorithm was presented based on an algorithm similar to the likelihood ratio function-s structure and the training sequence. This algorithm was designed to operate without any knowledge of turbulence-induced fading channel in advance. The training sequence introduced in each frame can provide the atmosphere turbulence-fading channel information for the following information sequence-s detection. Simulations were taken, and the results show the validity of this newly introduced algorithm even when strong correlation exists.
Fault-tolerant control method and characteristic analysis of hydraulic redundant EMA system
Zhou Yuanjun, Zhao Yunkun, Ge Yunhai
2008, 34(03): 285-289.
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A kind of hydraulic redundant electro-mechanical actuator (EMA) system used in the next generation more power aircraft was focused on, which is made up of two brushless DC motor with dual electrical channels. In such case, the fault-tolerant operation capability of‘fault -operation/fault-safe’ was advanced. The loss of inverter and motor and force fighting in the retarder were analyzed. A motor loss balance method by which EMA system would obtain the best synthetic performance under the situation with one channel fault was brought forward. Then the system output capability under the situation with two channels fault was analyzed. The tracking performances under different situations were simulated and analyzed. Finally a set of data of the motor temperature rise examination under fault-tolerant operation was presented.
Palmprint recognition based on ICA and BP neural network
Chen Zhi, Huang Linlin
2008, 34(03): 290-294.
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A novel method based on independent comment analysis (ICA) and back propagation neural network (BPNN) was proposed to solve palmprint recognition. First, a new method was used to detect corner points as the invariant feature points in palm images. Then the palm images were aligned by the points, and the region of interest (ROI) of the images was gotten. In the next place, palmprint features were extracted from the ROI by a fast fixed-point algorithm for ICA (FastICA). By means of this method, the original palmprint ROI images were transformed into a small set of feature space. Finally, the BPNN was trained by the feature spaces of the samples in the training set to get the appropriate weights. After the training, perform palm classification was applied. The method was tested on the Hong Kong Polytechnic University palmprint database. Experimental results show that method based on ICA achieves higher recognition rate than that based on principal components analysis (PCA).
Optimal ellipse fitting method based on least-square principle
Yan Bei, Wang Bin, Li Yuan
2008, 34(03): 295-298.
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The fragmental ellipse fitting algorithm based on least square was studied. The ellipse-constraint algebraic fitting always provides an elliptical solution, but the bias is inevitably added to result because the algorithm involves all the sample data including some much biased data. Based on this situation, the random theory was introduced. First, an ellipse was fitted by six points which were selected randomly. Then the number of points which match the ellipse was calculated. Repeating the process some times, according to the voting mechanism, the best ellipse is the ellipse whose matching point number is largest. A rapid algorithm with the ability to abandon the biased sample data was presented. The application of algorithm in a real-time image processing system demonstrates that this algorithm can efficiently fit an ellipse to experimental data including a significant percentage of gross errors and the rapidity of the algorithm can meet the requirement of real-time system.
Trajectory control and online monitoring of a parallel planar robot
Chen Weihai, Li Xiang, Yu Shouqian, Wang Jianhua
2008, 34(03): 299-303.
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Kinematic control of 3-DOF planar parallel manipulators was proposed. To realize online position trajectory planning, the inverse solution of parallel robot was discussed. Two steps were proposed to realize the online monitoring of parallel robot. The first step was using the algorithm of closed solution to analyze parallel robot-s position trajectory, and the second step was using the combination with bisection method and interpolation method to calculate the forward kinematic solution online. The control system of modular manipulators based on PC was also discussed and realized, which included the program of the algorithm of parallel robot-s kinematic control using C+ + language and the design of modular robot-s controller based on PMD(performance motion devices). The test of control system was on 3-DOF modular planar parallel manipulators, and the comparison between numerical method under MATLAB and analytical method programmed by C+ + language was done. The results of the test and the comparison demonstrate the effectiveness of kinematic algorithm and motion controllers.
Reconfigurable controller design for missile using eigenstructure assignments
Wang Qing, Sun Rui
2008, 34(03): 304-306.
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An improved reconfigurable method for spacecraft attitude control system was designed by the eigenstructure assignments. For a kind of linear system, not only the closed-loop eigenstructure was recovered but also the cost function of the reconfigurable controller was improved based on the output feedback eigenstructure assignments. The method guaranteed the stability of the reconfigured closed-loop system in the presence of output feedback which is capable of dealing with order-change problems that may occur in an after-fault system, and the performance of original system was recovered to a maximum extent. Simulation results were provided to show the effectiveness of the proposed method.
Heat transfer enhancement characteristics in nature convection along vibrant surface
Wu Hong, Meng Henghui, Luo Xiang, Xu Guoqiang
2008, 34(03): 307-310.
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Based on the idea that vibrations can destroy flow and heat boundary layer, which is the main thermal resistance for heat transfer, an experiment was investigated to study the heat transfer characteristics specialty of vibrant surface in natural convection, and to get the relationship between vibration and heat transfer. The electrical bell was used as the vibration source of the heated diaphragm. Infrared thermometer was adopted to measure the temperature field on the vibrant surface, and the temperature distribution with post treatment was gotten. Experiment results show that the effect of heat transfer on the vibrant surface is increased by 90.7% under the working condition. The increasing energy of the vibration can increase the heat transfer coefficient under the constant heat flux condition, while the decreasing heat flux can improve the heat transfer coefficient under the equal vibration energy condition. The results bring a new method for the application of enhancing heat transfer in nature convection.
Modeling and retrofit of certain turbojet
Ouyang Hui, Zhu Zhili
2008, 34(03): 311-314.
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The static performance model of certain small turbojet installed in some unmanned-air-vehicle (UAV) was established based on object-oriented component-level aero-engine simulation modules, and its fidelity was verified by data comparison between simulation and original experiment. Whereafter, according to the engine-balance principle, some practical retrofit schemes of redesigning the axial flow compressor were given using the components-matching method under the precondition of maintaining the work-line of the centrifugal compressor and within the limitation of structure-durability and heat-load of the turbojet. The simulation result demonstrates that the retrofit schemes are effective in improving the turbojet-s general performance including thrust and specific fuel consumption (SFC).
P2P network-based discovery schema for semantic Web Service
Yu Bing, Ma Shilong
2008, 34(03): 315-318.
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To solve how to find the Web Service that distribute different locations efficiently and exactly, a new discovery schema for service based on P2P network and semantic description was put forward. The peers in model dynamically registered to different peer-clusters, which were managed by broker according to their services- semantic classes, and friend peer-clusters which had the similar semantic classes came into being a virtual network, and it improved the efficiency of querying. Moreover, the schema adopted feedback to monitor the peers in net actively and splitting-converging to guarantee the abilities for available. With implementing the prototype, the reasonability and validity of the schema were proved.
Method for precisely detecting buffer overflow vulnerabilities in C programs
Li Ji, Wang Lei
2008, 34(03): 319-322.
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Buffer overflow (BO) vulnerability in C programs is one of the most crucial threats to the security of a system. Using tools to detect and eliminate this kind of vulnerability in programs will give the system sufficient ability to maintain security environment. For the scarcity of accuracy in detecting BO vulnerabilities, current bug-hunting tools can not precisely detect BO vulnerabilities. A new method was proposed, which uses model checking, to precisely detect potential BO in C programs. This method converts detecting BO vulnerabilities to verifying the reachability of certain position in programs and uses model checking tool to do the verification job. Using this method, a prototype system has been developed and been tested with some benchmarks. The early results show that this method can precisely detect BO vulnerabilities in C programs.
Routing mechanism in active Peer-to-Peer network
Li Jing, Liu Xudong, Lin Xuelian, Huang Zicheng
2008, 34(03): 323-326.
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Current routing mechanisms in unstructured Peer-to-Peer system target at locating content combined with too detailed focus on peers- need. However, these routing mechanism neglect that the peers- requirements are fuzzy and multi-faceted. Therefore, they cannot be well applied to active Peer-to-Peer. In order to solve the problem ,a routing mechanism was presented based on peers- requirements. A model of routing to evaluate peer capability was proposed in a multitude number of aspects by utilizing fuzzy mathematics. The definition of peer capability factors was given making use of degree of membership to describe the ability for peers to provide resources for users requirement. The analysis and experiment show that the mechanism meets users requirement and reduce cost of network in a good balance.
OWL-S based test case generation
Zhang Xiaoyan, Huang Ning, Yu Ying
2008, 34(03): 327-330.
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To improve the automatization and the efficiency of the Web Service interactive test process, an automated test case generation approach was proposed, based on OWL-S (OWL web ontology language for services) requirement model. Test cases were generated for the requirement properties wanted to be verified, and they were generated in three steps: the requirement property formulae were analyzed to obtain the concrete event collections related to the requirement properties; using the concrete event collections, application flow was searched to find all test paths related to the requirement properties; finally, the IOPE (inputs, outputs, preconditions, effects) properties and conditions of the test paths were analyzed to generate the test cases corresponding to test paths. The approach was experimented on an ATM(automated teller machine) prototype system. The results show that tests cases related with requirement properties are generated as designed, the test cases cover all the given requirement properties, and the system faults are detected effectively.
Octree-based blind watermarking on 3D meshes
Qi Yue, Shu Jun, Shen Xukun, Cai Su
2008, 34(03): 331-335.
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Robust blind watermarking is the important method for digital works copyright protection. A novel blind watermarking method on 3D meshes was proposed. PCA (primary component analysis) was used for 3D meshes- preprocessing to make a unique model posture. After making division of the 3D meshes based octree, octree structure could be obtained. A random scrambling was made for the RGB(red, green, blue) meaningful watermark image before embedding it into the bottom octree nodes. This method can be used directly on points-cloud, as it does nothing with the topology of the meshes. It is robust against translation, rotation, uniform scaling and random vertex reordering attacks. In addition, a method to generate ‘Zero-Watermark’ based on higher codec of octree nodes was given. The ‘Zero-watermark’ was then registered in the third-party of notarization, and it can be robust against simplification, noise addition and remeshing attacks in some extent. This method has a big volume for embedding and high popularity.
Grid service container based on SEDA
Liu Chengzhong, Liu Wantao, Hu Chunming
2008, 34(03): 336-339.
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The grid service container is a fundamental component in a service grid, which is responsible for shielding resource heterogeneity and hosting grid application services. Most current grid service container implementations adopt thread-based concurrency approach to process concurrent user requests, which has limitations in terms of performance and scalability. An event-driven architecture called SEDA (staged event driven architecture) was adopted to improve the performance of concurrent processing and scalability. It results in decoupling architecture with demarcation stages between which events asynchronous communicate and in which the non-blocking I/O mechanism can be adopted naturally. The early implementation experience and some optimistic performance evaluation results were presented, which show that the event-driven architecture can indeed raise the performance like throughput and latency and get better scalability by the asynchronous message mechanism and the reduction of the system synchronous obstruction.
Design and experiment of a underwater vehicle based on capacity of voyage
Wen Li, Liang Jianhong, Wang Tianmiao, Song Yongsheng
2008, 34(03): 340-343.
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The SPC-3 UUV prototype is an experimental platform which is especially designed to improve efficiency of propulsion and capacity of voyage based on the SPC-2 UUV robofish by Beijing University of Aeronautics and Astronautics. Based on the record of data collection computer and cameral which is used to measure the speed of SPC-3 UUV in the swimming pool, the speed-frequency and power-frequency curve were founded. After the estimating the capacity of voyage, the voyage time and voyage on condition of different frequency were calculated, the propulsion frequency could be selected according to the speed and voyage and range from 1.5Hz to 1.6Hz, and it had been testified in the long voyage experiment in Beidaihe. SPC-3 UUV achieved 22.761 kilometers, and its voyage time was 6.25 h, average speed was 1.03 m/s.
Real-time visual tracking algorithm for single moving object in clustered environment
Sun Kaipeng, Li Xinjun
2008, 34(03): 344-347.
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A visual tracking algorithm was introduced, which was completely based on image information. Several existing algorithms were integrated and improvements were made to achieve the goal of tracking one single moving object when the camera-s movements were small. A target was manually selected. Then feature points were extracted from the first and second frames and feature matching was conducted between the two frames. Using the matched features, affine motion model was established to estimate background movement and target position. With the assumption that target occupies only a few pixels, the separation of optical flow was calculated in a fixed small area around estimated target point and finally the moving object was obtained. The algorithm was applied on two consecutive images of the size of 640×480, and performed well. The experiments on PC show that with proper parameters the algorithm is able to work in the sampling frequency of 12.5Hz or 25Hz.
Kinematic modeling and analysis of variable diameter wheeled lunar rover
Cui Ying, Gao Feng
2008, 34(03): 348-352.
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According to the lunar surface environmental characteristics, a new four variable diameter wheeled lunar rover which consists of a rolling-torsion all wheel steering mechanism was developed. Through the principle analysis of the variable diameter wheel, derived the wheel equivalent radius formula. The calculation formulae based on 3-D environment of positive and inverse kinematics were derived with the method of closed chains coordinates transformation and instantaneous coordinate coincidence founded on the structural characteristic. The kinematic features were analyzed. The theoretical solution and practical solution were deduced. This practical solution can reduce the calculation load. A simplification method of adjusting the pitch angle with the charge of the equivalent radius was suggested. This method can improve the mobility and stability. The results provide the theoretical foundation for structural analysis and motion control of the four-wheeled lunar rover.
Autonomic detection method of space target orbit maneuver based on wavelet analysis
Zhang Zhenjun, Dong Yunfeng
2008, 34(03): 353-356.
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The change rate of relative distance is a character signal of orbit maneuver of space target. Relative distance was measured by laser radar, and the change rate of relative distance was calculated by difference of relative distance. The measure noise was enlarged so the character signal was submerged in the noise. The wavelet analysis in differential scale was used to keep track of time and frequency information of the character signal. With the scale zoom out, the true signal was increased and noise was decreased. The existence of orbit maneuver can be judged by wavelet analysis in differential scale. In order to meet the requirements of autonomic computing on the satellite, the detection method applied correlation coefficient threshold to identification of orbit maneuver. The feasibility and effectiveness were verified by computer numerical simulation.
Optical narrowband filter and its application to fiber lasers
Zhang Chunxi, Liu Dianjun, Ou Pan
2008, 34(03): 357-360.
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Single-mode fiber laser is a very important light sources for optical sensing and optical communication. The coupled mode function of basing on saturable absorber optical narrow-band filter using numerical analysis was soluted. The factors who effected optical narrow-band filter output response properties, for example the length of Erbium-doped-fiber,the absorption coefficient of Erbium-doped-fiber and the pump wave power was analysed. The length of Erbium-doped-fiber composing saturable absorber inversing with the response bandwidth of filter was verificated experimentally. The optical narrow-band filter to fiber laser was applied, then narrow-band single-longitudinal-mode laser output was got, and the linewidth of laser output is about hundreds of Hertz magnitude. The power of output laser is more than 1mW and the lasing time of no mode-hopping is more than 2 hours. The power instability of the fiber laser is less than 0.0287%.

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