Table of Content

    20 October 2013
    Volume 43 Issue 5
    A novel blood perfusion construction model and its application in infrared face recognition
    XIE Zhi-hua
    Abstract ( 369 )   PDF (1396KB) ( 1205 )   Save
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    To get stable biological features from the time-delay infrared face, a new construction method of blood perfusion was proposed based on bio-heat transfer, which could applied to face recognition. According to the classic bio-heat transfer equation (Pennes equation), the blood perfusion rates in different positions were computed based on the discrete method. Then, due to the low-resolution of the infrared images, feature extraction method ‘PCA (principal component analysis)+FLD (Fisher linear discriminant analysis)’ was chosen to get the principle features in the blood perfusion image. The experiment results showed that the blood perfusion rate proposed was stable, its application in infrared face recognition was robust to the impact of the environment temperature.

    Attribute derangement in decision tables
    GAO Feng1, CHI Chun-mei2
    Abstract ( 410 )   PDF (841KB) ( 1088 )   Save
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    Attribute derangement in decision tables was proposed. Based on the redundant relations between attributes, the criteria was given for judging which kind of derangement led to rough set and which one would not. The notion of derangement roughness was proposed and then the notion of best logic attribute and the best attribute logic flow were put forward. It was shown that the best attribute logic flow reflected the causal relations between different attributes in decision tables. Numerical experiment showed that missing data could be imputed effectively by using attribute derangement.

    Distributed affinity propagation clustering algorithm based on GraphLab
    CHEN Wen-qiang1, LIN Chen1,2, CHEN Ke3, CHEN Jin-xiu1, ZOU Quan1,2*
    Abstract ( 424 )   PDF (1394KB) ( 2737 )   Save
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    A distributed affinity propagation algorithm based on GraphLab was proposed, which was named GStrAP (Graphlab based stream affinity propagation). In GraphLab′s DAG abstraction, the parallel computation was represented as a directed acyclic graph with data flowing along edges between vertices, and the “Gather-Apply-Scatter” paradigm was applied to complete data synchronization and algorithm′s iteration. The experimental results on 3D Clusters, Aggregation, Flame and Pathbased datasets with different scale and the clustering performance were compared with Kmeans, which demonstrated that the proposed GStrAP could achieve high performance on both scalability and accuracy.

    Edge detection of extruded billet based on improved Canny operator
    PAN Sheng-min1,2, ZHONG Yi1*, WANG Jian-hua2
    Abstract ( 351 )   PDF (2184KB) ( 1273 )   Save
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    To deal with  flow behavior of metal billet in plastic deforming process, an algorithm of edge detection was proposed.  Firstly, the sample image was preprocessed by used the method of gray-scale enhance combine with morphological corrosion and expansion, and then the billet deformation contour was extracted by Canny operator that is limited by double thresholds. It avoided the isolating step grayscale point on the edge. In the same amount of salt and pepper noise, the peak signal to noise ratio of this algorithm was higher than other typical algorithms. The experimental results showed that the edge of deformation zone that it be extracted by this algorithm, can meet the quantitative analysis of metal flowing characteristics.

    Splicing image tamper detection based on human face color temperature
    YANG Jian-mei1, HUANG Tian-qiang1,2*, JIANG Wei-jian1
    Abstract ( 411 )   PDF (2139KB) ( 1344 )   Save
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     Focusing on the face stitching tampering image, a splicing image tamper detection method based on human face color temperature was proposed. Using the technology of target detection, the method in question pinpointed the faces in the image, and then estimated the color temperature of all those faces and the reference color temperature. After calculating the discrepancy between human face color temperature and reference color temperature, the method could find out the detection target with abnormal color temperature discrepancy as the tampering target, and then could locate the precise position of the tampering target. The empirical study showed that the algorithm was effective.

    Research of wavelet neural network based on variable basis functions and GentleAdaBoost algorithm
    LI Xiang1, ZHU Quan-yin1, WANG Zun2
    Abstract ( 412 )   PDF (2735KB) ( 1146 )   Save
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    In view that the traditional wavelet neural network (WNN) was affected largely by the number of hidden layer nodes, easy to fall into local minimum and had unstable forecast results, a method of combining the GentleAdaBoost algorithm with WNN was put forward to improve the forecasting accuracy and generalization ability. First, this method performed the pretreatment for the historical data and initialized the distribution weights of test data. Second, different hidden layer nodes and wavelet basis functions were selected randomly to construct weak predictors of WNN and trained the sample data repeatedly. Finally, the multiple weak predictors of WNN were used to form a new strong predictor by GentleAdaBoost algorithm for regression forecasting. A simulation experiment using datasets from the UCI database was carried out. The results showed that this method had reduced the average error value by more than 40% compared to the traditional WNN, improved the forecasting accuracy of neural network, and could provide references for the WNN forecasting.

    An output power optimization method based on impedance matching for a small wind generation system
    JING Ye-fei1, ZHANG Cheng-hui1*, XU Bei-bei, LI Ke1, CHU Xiao-guang1
    Abstract ( 309 )   PDF (1675KB) ( 1209 )   Save
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    In order to solve the problem that the wind energy utilization was very low in most of small wind power generation systems, a novel method based on impedance matching for optimizing output power was proposed. The mathematic model of small wind power generation system was built and analyzed, and it was pointed out that the stable operation point of the wind power generation system would be changed by adding series impedance between the generator and rectifier. The output power would be increased if the parameter of impedance is set reasonably. Base on this principle, the parameter of impedance was confirmed by using the particle swarm optimization algorithm. And the output in a period of time considering the probability distribution of wind speed and battery voltage was used as an optimization object functions. The simulation results showed that the output power of wind generator was effectively improved if the parameter of impedance was correctly selected, and the average output power was increased by 21%.

    Maximum power point tracking control of wind energy based on pattern search
    JING Ye-fei1, XU Bei-bei2, ZHANG Cheng-hui1*, LI Ke1, CHU Xiao-guang1
    Abstract ( 243 )   PDF (1774KB) ( 1194 )   Save
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    In order to solve the problems that traditional wind energy maximum power point tracking (MPPT) approaches couldn′t achieve maximum real output power or meet both rapidity and accuracy at the same time, a novel MPPT approach was proposed. According to current wind speed and characteristic curve of wind turbine, the maximum wind power was captured by using tip speed ratio (TSR) control. Then the maximum power point was searched and acquired by using pattern search. Fuzzy PID control was adopted to make that the reference speed was fast tracked. It combined TSR control and pattern search algorithm effectively, and had the advantages in simplicity, searching speed and precision. Simulation and experimental results showed that the maximum output power could be achieved, and the wind energy conversion efficiency was increased. For example, the output power was increased by 4.8% while wind speed was 6.7m·s-1.

    An attitude estimation algorithm for human body based on
    multi-sensor information fusion
    LI Jing-hui, YANG Li-cai*
    Abstract ( 346 )   PDF (1801KB) ( 2773 )   Save
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    Aiming at the problems of poor stability and short precision in traditional attitude estimation algorithms, a method based on multi-sensor information fusion was proposed. The quaternion was used to calculate the attitude changes, and deviations between measurements and observations from the Inertial Measurement Unit(IMU) were managed by PI regulator. The complementary filtering was adopted for multi-sensor information fusion, and the realtime attitude was got. Experimental results showed that the algorithm could output the high precision attitude steadily.

    Practical tracking by output feedback for a class of nonlinearly
    parameterized systems with unknown control coefficients
    WANG Fei-fei1, YAN Xue-hua2*, LIU Yun-gang3
    Abstract ( 184 )   PDF (1156KB) ( 1118 )   Save
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    The practical tracking control by output feedback was considered for a class of nonlinearly parameterized systems with unknown control coefficients. By introducing the appropriate coordinate transformation, the original system was transformed into a new system without uncertain control coefficients. Then, a suitable highgain observer was constructed and the tracking controller by output feedback was successfully designed using the backstepping technique. The simulation result showed that if the design parameters were chosen suitably, the designed controller guaranteed  the closed-loop system states to be globally bounded, and the tracking error to converge to the prescribed small neighborhood of the origin after enough long time.

    Theoretical analysis of evaluation index for allowable
    subgrade uneven settlement
    YI Xiao-ming1,2, WANG Song-gen2, SONG Xiu-guang1*, ZANG Ya-nan1
    Abstract ( 323 )   PDF (1371KB) ( 1275 )   Save
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    In order to research the evaluation index of differential settlement, the finite element code was used to study the influence of settlement gradient on the additional stress of the base. Then the analytic solution of tensile stress at the bottom of semi-rigid base was obtained basing on the two layer of elastic continuous system, and the maclaurin expansion was adopted to simplify the analytic solution. Results showed that there were great limitations for using the settlement gradient to evaluate the allowable uneven settlement. But the first derivative settlement gradient, which was the ratio of settlement gradient to spread distance, had a well linear correspondence to the tensile stress. Therefore, the first derivative settlement gradient could be used as the key index to assess the allowable subgrade uneven settlement. For the typical semi-rigid base asphalt pavement structure, the allowable first derivative settlement gradient was 0.000161m-1, when the traffic loading was not considered.

    In situ testing and evaluation of the permeability of concrete
    WANG Jia-chun1, ZHANG Zhao-hua2, SHU Ning3
    Abstract ( 299 )   PDF (1828KB) ( 965 )   Save
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    With Permit ion migration experiments and concrete surface resistivity test the chloride ion diffusion coefficient and the concrete surface resistivity of the five concretes were measured and the relation between in situ results and ASTM C1202 electric flux for 6h in the laboratory were analyzed. The mathematical relationship between a protective layer of concrete chloride ion diffusion coefficient and surface resistivity of concrete was established, and the service life of reinforced concrete beams was calculated by in situ testing results under the marine environment. The results showed that there was good correlation between the concrete surface resistivity of the concrete cover, in the steady state the action of chloride diffusion coefficient and 6 h charge. Permit experiments and the concrete surface resistivity were tested and evaluated the permeability of the concrete in situ, and concrete surface resistivity was easy in engineering applications.

    Design and optimization of the counterforce frame for sleeper and roadbed fatigue testing machine
    LI Jian-ming, WANG Han-peng*, LI Shu-cai, ZHANG Qing-he
    Abstract ( 342 )   PDF (1953KB) ( 981 )   Save
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    The counterforce frame was systematically designed and optimized, aiming to improve its current disadvantages of small stiffness, unreasonable structures, and excessive material consumption, etc. By adopting SOLIDWORKS, the 3D models of four different kinds of counterforce frame structures were established, upon which static analysis were then conducted by ANSYS and ABAQUS. The magnitude and distribution of their stiffnesses and strengths were obtained, and after comparing the steel consumptions and mechanical properties, the style of fish-bell sill was chosen to be further optimized. As for the fish-belly sill counterforce frame, its inherent frequency and vibration modes were obtained through the modal analysis in ANSYS. The first vertical vibration took place at the frequency of 25.6Hz, satisfying the requirement that the 10Hz actuator loading could not trigger resonance. Afterwards, the transient analysis could provide the vibration response of this specific counterforce frame, when tested with the 10Hz actuator. The displacement peaked at 1.128mm, and then stabilized at 0.72mm after 5 seconds, which met the requirements of both dynamic loading accuracy and counterforce frame stiffness. In sum, the results showed that the fish-belly sill structure could offer the most stiffness compared with the other three, which was large enough to meet the dynamic loading stiffness requirement, and in the meantime was the most economical with the least steel consumption.

    Numerical simulations of a particle impacting to affect the surface
    morphology by SPH coupled FEM
    WANG Jian-ming, PEI Xin-chao, FAN Xian-hang, LIU Wei, CAO Yan-chao
    Abstract ( 250 )   PDF (1927KB) ( 1597 )   Save
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    The  smoothed particle hydrodynamics (SPH) method coupled FEM was applied to eliminate the limitations of finite element method (FEM) dealing with the chip separation and large deformation of the work piece. The SPH particles were used to model the work piece and the FEM was applied to discrete the angular particle, which  were coupled by using the contact algorithm. The influence of particle rotating effects on the crater depths and chips pile-up heights was studied under different simulation incidence conditions. The results showed that the particle would rotate forward when its rake angle bacame  large enough. The angular crater would be formed and chips would pile up at the edge of the crater without separating from the work piece. On the other hand, the particle would rotate backward when its rake angle was small. A shallow and smoothed crater would be formed and chips would separate from the work piece. The simulation model and results were validated by the existing theoretical and experimental data, which could provide an effective simulation research method to study angular particle erosion.

    Fluid dynamic performance of an oscillating airfoil
    in an energy extraction system
    LU Jian-wei, WANG Yong*, XIE Yu-dong
    Abstract ( 289 )   PDF (1615KB) ( 1030 )   Save
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    The Fluent was used to solve the unsteady incompressible 2D Navier-Stokes equations for laminar flow around the airfoil. A domain dynamic mesh strategy was used on fluid domain within sliding interface to make it move with the airfoil. The strategy could ensure the mesh quality of core zone. The influence of the location of the pitching axis on the NACA0015 oscillating airfoil in aerodynamic characteristics and energy extraction performance, and the coupled effects of the location of the pitching axis and the phase difference between the two motions on the system were investigated with a Reynolds number of 1100, a pitching amplitude of 76.33°, a heaving amplitude of one chord, a reduced frequency of 0.88. The results showed that, the location of the pitching axis would influence lift characteristics, pitching moment characteristics and energy extraction performance of an oscillating airfoil. When the energy extraction performance of the system declined for the location of the pitching axis deviating from the average center of pressure, the energy extraction performance could be improved by changing the phase difference between the pitching and heaving motions.

    Quantitative analysis method for specific effect of crosswind on
    performance of natural draft wet cooling tower
    ZHANG Lei, SUN Feng-zhong*, GAO Ming
    Abstract ( 257 )   PDF (1546KB) ( 1014 )   Save
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    Computational model of natural draft wet cooling tower (NDWCT) under no crosswind condition was built based on the coupling equations of heat and aerodynamic balance. The two equations were solved by the method of iteration using MATLAB code, so as to calculate the ideal values of airflow rate and number of transfer unit (NTU), which  neglect crosswind effect under the same meteorological and operating conditions as field tests. Then by combining the actual values of airflow rate and NTU of tests, new indexes were recommended to represent the specific effect of crosswind on tower performance. The results of a 3500m2 NDWCT showed that, at the same heat loss of model and test, the airflow rate decreased 38.5% at most by crosswind, and simultaneously 33.9% volume fraction of fill was not employed efficiently. Crosswind also increased the cooling duty of NDWCT and hence more cooling capacity was needed, which was  of great help to understand  the theory of crosswind effect on the tower performance and of significance for cooling tower design and modification.

    Numerical simulations on convective heat transfer characteristics of
     laminar flow with longitudinal vortex induced by winglets
    CHE Cui-cui, TIAN Mao-cheng*, LENG Xue-li
    Abstract ( 241 )   PDF (2225KB) ( 1275 )   Save
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    3-D numerical simulations were presented for studying the flow structures and convective heat transfer characteristics in a cylinder tube embedded with wing-finned vortex generators. In the numerical simulation, the winglet was upstream placed at an angle of 45 to the tube wall and 1/6 of channel was selected for studying due to symmetry. The results showed that two counter-rotating longitudinal vortices were induced downstream the winglet, forming a symmetric vortex pair. The flow inner vortex pair was towards the wall while the flow outer vortex pair was backwards the wall. The longitudinal vortex could improve the magnitude of velocity in the radial direction, and the maximum value in near wall region reached 80% of the average mainstream velocity downstream the winglet. As a result, the winglet booted the disturbance of the velocity boundary layer. The improved velocity field could make the temperature field in the tube more uniform. Compared with the smooth tube, the temperature gradient near the wall could improve approximately an order of magnitude. The flow induced by the longitudinal vortex rushed to the wall, which strengthened the convective heat transfer significantly. The maximum value of the local Nu on the wall surface could reach 50 times of the smooth tube. The improved convective heat transfer performance lead by longitudinal vortex enhanced with the Reynolds numbers increasing.