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Xu D.-J.,University of Chinese Academy of Sciences | Xu D.-J.,CAS Shenyang Institute of Automation | Xu D.-J.,Chinese Academy of Sciences | Xu D.-J.,Key Laboratory of Image Understanding and Computer Vision | And 8 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

Visual tracking is a critical task in many computer vision applications such as surveillance, vehicle tracking, and motion analysis. The challenges in designing a robust visual tracking algorithm are caused by the presence of background clutter, occlusion, and illumination changes. In this paper, we propose a visual tracking algorithm in a particle filter framework to overcome these three challenging issues. Particle filter is an inference technique for estimating the unknown motion state from a noisy collection of observations, so we employ particle filter to learn the trajectory of a target. The proposed algorithm depends on the learned trajectory to predict the position of a target at a new frame, and corrects the predication by a process that can be entitled field transition. At the beginning of the tracking stage, a set of disturbance templates around the target template are accurately selected and defined as particles. During tracking, a position of the tracked target is firstly predicted based on the learned motion state, and then we take the normalized cross-correlation coefficient as a level to select the most suitable field transition parameters of the predicted position from the corresponding parameters of the particles. After judging the target is not occluded, we apply the named field transition with the selected parameters to compensate the predicted position to the accurate location of the target, meanwhile, we make use of the calculated cross-correlation coefficient as a posterior knowledge to update the weights of all the particles for the next prediction. In order to evaluate the performance of the proposed tracking algorithm, we test the approach on challenging sequences involving heavy background clutter, severe occlusions, and drastic illumination changes. Comparative experiments have demonstrated that this method makes a more significant improvement in efficiency and accuracy than two previously proposed algorithms: the mean shift tracking algorithm (MS) and the covariance tracking algorithm (CT). © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

Chen D.,Nanchang Hangkong University | Xiong B.,Nanchang Hangkong University | Huang J.,China Helicopter Research and Development Institute | Zhao P.,AVIC Hongdu Aviation Industry Group Co.
Bandaoti Guangdian/Semiconductor Optoelectronics | Year: 2013

To obtain 3D coordinate of helicopter rotor rapidly and accurately, a dynamic 3D-measurement method based on marked points and stereo vision is presented. Firstly, 2D plane calibration algorithm and Bouguet algorithm are used to calibrate the cameras and rectify the images. Secondly, marked points are extracted from the images by using the methods of image thresholding, connected component labeling and other, so as to acquire the pixel coordinates of the marked points. Then, by using the scanning method, the IDs of marked points are acquired, and then the points within two images are matched according to their IDs. Finally, mapping matrix of the two cameras and the 2D coordinate in the image plane is used to determine 3D coordinates of the helicopter rotor. The simulation results show that the method realizes better precision and the practical measurement error is less than 0.3 mm, which can completely meet the requirements for dynamic 3D-measurement of helicopter rotor.

Qing-Hai D.,Research Institute of General Development and Demonstration of Equipment | Xin-Rong Y.,CAS Shenyang Institute of Automation | Xin-Rong Y.,University of Chinese Academy of Sciences | Xin-Rong Y.,Chinese Academy of Sciences | And 6 more authors.
Proceedings of the 2011 Chinese Control and Decision Conference, CCDC 2011 | Year: 2011

Automatic suitable-matching area selection is an important research in visual guidance, scene matching and local non-texture target tracking. Meanwhile, it is the major research subject in computer vision and accurate guidance. In this paper, a new characteristic quantity, i.e., the edge direction dispersion was defined. Then the computation method, parameters selection and real-time realization of this characteristic quantity were investigated. Furthermore, the application of its characteristic in automatic suitable-matching area selection was studied. With a reasonable design for calculation precision, solving method for arctan(x) function in [-∞,+∞ ] could be simplified to linearization calculations in [0, 0.25], then a fast algorithm for arctan(x) function was presented. Experimental results showed that the sub-image extracted by our fast algorithm had higher matching level and was suitable to be a matching template. All the calculations involved in the proposed matching algorithm could be done in one filed period and the real-time request could be satisfied. Moreover, this characteristic of edge direction could also be used to measure the comparability of template and real-time images, which could be widely used in automatic target recognition and target tracking. © 2011 IEEE.

Feng B.,CAS Shenyang Institute of Automation | Feng B.,University of Chinese Academy of Sciences | Feng B.,Chinese Academy of Sciences | Shi Z.-L.,CAS Shenyang Institute of Automation | And 3 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

The rotation angle of a mounted polarizer in front of a camera has a direct effect on imaging quality and therefore this paper presents a rapid computation method for a polarizer's optimal rotation angle on an airborne optical platform. The computation contains four steps. First, we construct a world coordinate system and a camera coordinate system that both adopt the center of a code disc as their common origin. Second, we take the origin of the world coordinate system as a start point, intercept a unit segment along the sunlight direction and compute the endpoint coordinates of the unit segment in the world coordinate system. Third, by mapping the relation from the world coordinate system to the camera coordinate system, we compute the above endpoint coordinates in the camera coordinate system. Fourth, we project the above segment towards a disc code plane, compute the angle between the projected line and the reference of the code disc, and take the resultant angle distance as a polarizer's optimal rotation angle of airlight rejection utilizing polarization filtering. Experiment results indicate that our computation method of a polarizer's optimal rotation angle can be applied to airlight rejection on an airborne optical platform. © 2011 SPIE.

Shi H.-H.,Zhejiang Sci-Tech University | Xiao Y.,Zhejiang Sci-Tech University | Xiao Y.,AVIC Hongdu Aviation Industry Group Company Ltd | Wu Y.,Zhejiang Sci-Tech University | And 3 more authors.
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2014

For studying the Richtmyer-Meshkov (RM) instability at gas/liquid interface, we conduct some experiments of the interaction between shock wave with single row water column and double rows water columns in a horizontal shock tube. By using nitrogen gas as the high pressure driving gas, we obtain shock waves with Mach numbers of 1.10 and 1.25.We also obtain varisized columns using different test specimens. By using a high-speed camera, the developments of spike height, bubble depth and mixing zone width are measured. The result shows that the RM instability will develop linearly when the shock wave Mach number is low.

Chen W.-W.,Nanjing University of Aeronautics and Astronautics | Fang X.-D.,Nanjing University of Aeronautics and Astronautics | Shang H.,AVIC HONGDU Aviation Industry Group CO LTD | Zhang H.-L.,Nanjing University of Aeronautics and Astronautics
Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics | Year: 2016

The calculation of heat transfer of water under supercritical pressure has been used in many industrial fields, such as fossil-fired power plants and nuclear reactors. Many evaluations of previous correlations were conducted, and inconsistent conclusions appeared owing to the limited experimental data and correlations involved, which causes difficulty in choosing the appropriate correlations. This paper compiles a database of heat transfer of water under supercritical pressure which contains 5366 experimental data points obtained from 13 independent papers. The entire database is classified into different heat transfer regimes and compared with 27 existing correlations. The results show that the best correlation proposed by the authors has a mean absolute deviation of 5.4% for all the data and is the best correlation for all the heat transfer regimes, which upgrades the calculation accuracy of heat transfer of water under supercritical pressure remarkably. Research suggests that considering both the revision of thermophysical properties and the effect of buoyancy brought by the density difference, can improve the prediction performance of a heat transfer correlation of water under supercritical pressure significantly. © 2016, Science Press. All right reserved.

Chen M.,Nanjing University of Aeronautics and Astronautics | Wang F.,Nanjing University of Aeronautics and Astronautics | Xiong J.,AVIC Hongdu Aviation Industry Group Ltd.
Advanced Materials Research | Year: 2012

The main defect of shrink flanging wing rib is wrinkling in rubber bladder hydroforming. In the aeronautical field, the side blank holder is usually used to avoid wrinkling. In order to obtain appropriate parameters of side blank holder, it be carried out that the simulation analysis for the process of the high hydraulic press rubber forming processes of high shrink flanging with side blank holder by the ABAQUS finite element software. Besides, the corresponding experiments verified also be implemented. The research results show that the sheet metal tends to wrinkle along with decrease of the blank lap width and increase of these parameters such as the distance between side blank holder and die, the dip angle and fillet radius of the side blank holder. © (2012) Trans Tech Publications.

Fang X.,Nanjing University of Aeronautics and Astronautics | Wang R.,Nanjing University of Aeronautics and Astronautics | Chen W.,Nanjing University of Aeronautics and Astronautics | Zhang H.,Nanjing University of Aeronautics and Astronautics | Ma C.,AVIC Hongdu Aviation Industry Group Ltd.
Applied Thermal Engineering | Year: 2015

The flow boiling heat transfer of nanofluids is an important research area which provides many opportunities to explore new frontiers but also poses great challenges. This paper presents a comprehensive review on the flow boiling heat transfer of nanofluids, with an emphasis on the heat transfer coefficient (HTC), critical heat flux (CHF), pressure drop, nanofluid stability, flow and heat transfer mechanism, and flow pattern and bubble dynamics. Most of the available articles have been related to the first four topics. Studies related to the last two topics are rare, which are reviewed because of their importance. The important achievements, inconsistence, and contradictions of the existing research results are identified, and several topics worthy of attention for future investigations are identified. © 2015 Elsevier Ltd. All rights reserved.

Zhang H.,Nanjing University of Aeronautics and Astronautics | Fang X.,Nanjing University of Aeronautics and Astronautics | Shang H.,AVIC HONGDU Aviation Industry Group LTD | Chen W.,Nanjing University of Aeronautics and Astronautics
International Journal of Refrigeration | Year: 2015

Condensation heat transfer in tubes is extensively used in many industrial sectors. There were a number of investigations evaluating the correlations of condensation heat transfer in tubes. However, either the data used or correlations involved were limited, resulting in inconsistent conclusions. This paper presents a comprehensive review of correlations for flow condensation heat transfer in horizontal channels. A database containing 2563 experimental data points of condensation heat transfer in horizontal channels, including 1462 data points from conventional channels and 1101 from minichannels, is compiled from 26 published papers, with which 28 correlations are evaluated and analyzed. Twelve correlations have the mean absolute deviation (MAD) less than 30% against the database, and eight have 30;lt40%. The MADs of the best predictions for the entire database, conventional channel data, and microchannel data are 17.0%, 14.4%, and 20.6%, respectively, indicating a need to improve the prediction method for microchannels. © 2015 Elsevier Ltd and International Institute of Refrigeration. All rights reserved.

Guo F.,Northwestern Polytechnical University | Wang Z.,Northwestern Polytechnical University | Kang Y.,Northwestern Polytechnical University | Li X.,Northwestern Polytechnical University | And 2 more authors.
Zhongguo Jixie Gongcheng/China Mechanical Engineering | Year: 2014

To ensure the assembly accuracy of the wing-like parts, a new positioning method was studied based on coordinating holes at the internal location assembly pattern. By comparing the traditional positioning method based on the profile of the card board, due to the superiority of the coordinating holes at the coordinating process of the wing-like parts according to the coordination routine of the shape and the dimensions of the aircraft parts, a new flexible coordinate method of the ribs was proposed. The locater unit was designed to meet all of the ribs of a certain aircraft by checking the locating process under the DELMIA environment. By analyzing the coordinate principles and calculating the coordinating errors of the skin, the theoretical results show that the assembly accuracy is improved. Flexible assembly examples show that the flexible positioning unit has a simple structure and correspending low cost. The experimental measured results also reveal the new flexible coordinating method can fully satisfy the assembly precision of the skin. ©, 2014, China Mechanical Engineering Magazine Office. All right reserved.

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