2015

• Record 145 of
  
  Title:Effects of Cu on properties of vitrified bond and vitrified CBN composites
  
  Author(s):Feng, Dandan(1); Wu, Weijie(1); Wang, Pengfei(2); Zhu, Yumei(1); Zhai, Chenxi(1); Li, Zhihong(1)
  Source: International Journal of Refractory Metals and Hard Materials  Volume: 50  Issue:   DOI: 10.1016/j.ijrmhm.2015.01.002  Published: May 2015  
  Abstract:In order to obtain vitrified CBN composites, which have high performance of both thermal conductivity and mechanical strength, the effects of Cu on the properties of vitrified bond and the vitrified CBN composites were comprehensively investigated in this work. The results show that the vitrified CBN composites incorporating 6 wt.% Cu display excellent comprehensive performance including the increases by about 62.1% in thermal conductivity and 16.1% in bending strength. The substantial performance improvement of the vitrified bond and the vitrified CBN composites may be attributed to the high thermal conductivity and good ductility of metal Cu and its toughening effect on the vitrified bond, as well as formation of thermal conductive path in the vitrified bond. © 2015 Elsevier Ltd. All rights reserved.
  Accession Number: 20150800562400
• Record 146 of
  
  Title:Flexible sliding windows with adaptive pixel strides
  
  Author(s):Jiang, Xiaoheng(1); Pang, Yanwei(1); Pan, Jing(2); Li, Xuelong(3)
  Source: Signal Processing  Volume: 110  Issue:   DOI: 10.1016/j.sigpro.2014.08.004  Published: May 2015  
  Abstract:Detecting humans, faces, and other objects is important for pose estimation, behaviour analysis, and recognition. Most of the existing detection methods exploit sliding-window technique that typically evaluates image patches at uniform grids, with constant pixel strides along horizontal and vertical directions in an image. This approach can lead to excessively redundant computation since target object instances are relatively rare events compared to non-objects of the background. Therefore, most of the computation is unnecessarily wasted on the background. In this paper, to deal with this problem, we propose to scan the image using adaptive instead of fixed (unchanged) strides. That is, a high response of current sliding window generates small strides for the subsequent sliding windows in both horizontal and vertical directions, which means an object instance is likely to exist around. Otherwise, a low response gives large pixel strides and results in sparse sampling on the background. As a result, the areas of potential object instances are densely sampled and the areas of non-objects are sparsely sampled, leading to the reduction of total computation cost without loss of detection accuracy. Experimental results on face detection demonstrate the high efficiency and effectiveness of the proposed method. © 2014 Elsevier B.V.
  Accession Number: 20150800540725
• Record 147 of
  
  Title:Learning multiple linear mappings for efficient single image super-resolution
  
  Author(s):Zhang, Kaibing(1,2); Tao, Dacheng(3); Gao, Xinbo(1); Li, Xuelong(4); Xiong, Zenggang(2)
  Source: IEEE Transactions on Image Processing  Volume: 24  Issue: 3  DOI: 10.1109/TIP.2015.2389629  Published: March 1, 2015  
  Abstract:Example learning-based superresolution (SR) algorithms show promise for restoring a high-resolution (HR) image from a single low-resolution (LR) input. The most popular approaches, however, are either time-or space-intensive, which limits their practical applications in many resource-limited settings. In this paper, we propose a novel computationally efficient single image SR method that learns multiple linear mappings (MLM) to directly transform LR feature subspaces into HR subspaces. In particular, we first partition the large nonlinear feature space of LR images into a cluster of linear subspaces. Multiple LR subdictionaries are then learned, followed by inferring the corresponding HR subdictionaries based on the assumption that the LR-HR features share the same representation coefficients. We establish MLM from the input LR features to the desired HR outputs in order to achieve fast yet stable SR recovery. Furthermore, in order to suppress displeasing artifacts generated by the MLM-based method, we apply a fast nonlocal means algorithm to construct a simple yet effective similarity-based regularization term for SR enhancement. Experimental results indicate that our approach is both quantitatively and qualitatively superior to other application-oriented SR methods, while maintaining relatively low time and space complexity. © 1992-2012 IEEE.
  Accession Number: 20150500479083
• Record 148 of
  
  Title:Measuring the fractional topological charge of LG beams by using interference intensity analysis
  
  Author(s):Li, Xinzhong(1,2); Tai, Yuping(3); Lv, Fangjie(1); Nie, Zhaogang(4)
  Source: Optics Communications  Volume: 334  Issue:   DOI: 10.1016/j.optcom.2014.08.020  Published: 1 January 2015  
  Abstract:We demonstrate a method to measure the fractional topological charge (TC) of Laguerre-Gaussian (LG) beams by analyzing the interference intensity patterns between the vortex beam and its conjugate beam. By this method, the magnitude of integer and fractional TCs is quantitatively measured by using a simple unified formula. The proposed method can measure TCs up to 60. © 2014 Elsevier B.V.
  Accession Number: 20144200107173
• Record 149 of
  
  Title:Truncation Error Analysis on Reconstruction of Signal from Unsymmetrical Local Average Sampling
  
  Author(s):Pang, Yanwei(1); Song, Zhanjie(2); Li, Xuelong(3); Pan, Jing(1,4)
  Source: IEEE Transactions on Cybernetics  Volume: 45  Issue: 10  DOI: 10.1109/TCYB.2014.2365513  Published: October 2015  
  Abstract:The classical Shannon sampling theorem is suitable for reconstructing a band-limited signal from its sampled values taken at regular instances with equal step by using the well-known sinc function. However, due to the inertia of the measurement apparatus, it is impossible to measure the value of a signal precisely at such discrete time. In practice, only unsymmetrically local averages of signal near the regular instances can be measured and used as the inputs for a signal reconstruction method. In addition, when implemented in hardware, the traditional sinc function cannot be directly used for signal reconstruction. We propose using the Taylor expansion of sinc function to reconstruct signal sampled from unsymmetrically local averages and give the upper bound of the reconstruction error (i.e., truncation error). The convergency of the reconstruction method is also presented. © 2014 IEEE.
  Accession Number: 20144700238032
• Record 150 of
  
  Title:Targeting accurate object extraction from an image: A comprehensive study of natural image matting
  
  Author(s):Zhu, Qingsong(1,2); Shao, Ling(3); Li, Xuelong(4); Wang, Lei(1)
  Source: IEEE Transactions on Neural Networks and Learning Systems  Volume: 26  Issue: 2  DOI: 10.1109/TNNLS.2014.2369426  Published: February 1, 2015  
  Abstract:With the development of digital multimedia technologies, image matting has gained increasing interests from both academic and industrial communities. The purpose of image matting is to precisely extract the foreground objects with arbitrary shapes from an image or a video frame for further editing. It is generally known that image matting is inherently an ill-posed problem because we need to output three images out of only one input image. In this paper, we provide a comprehensive survey of the existing image matting algorithms and evaluate their performance. In addition to the blue screen matting, we systematically divide all existing natural image matting methods into four categories: 1) color sampling-based; 2) propagation-based; 3) combination of sampling-based and propagation-based; and 4) learning-based approaches. Sampling-based methods assume that the foreground and background colors of an unknown pixel can be explicitly estimated by examining nearby pixels. Propagation-based methods are instead based on the assumption that foreground and background colors are locally smooth. Learning-based methods treat the matting process as a supervised or semisupervised learning problem. Via the learning process, users can construct a linear or nonlinear model between the alpha mattes and the image colors using a training set to estimate the alpha matte of an unknown pixel without any assumption about the characteristics of the testing image. With three benchmark data sets, the various matting algorithms are evaluated and compared using several metrics to demonstrate the strengths and weaknesses of each method both quantitatively and qualitatively. Finally, we conclude this paper by outlining the research trends and suggesting a number of promising directions for future development. © 2012 IEEE.
  Accession Number: 20150500459644
• Record 151 of
  
  Title:Stray light analysis and test of cassegrain optical antenna
  
  Author(s):Li, Ting(1); Ma, Xiao-Long(1); Li, Fu(1); Xue, Bin(1); Xu, Guang-Zhou(1); He, Ying-Hong(1); Lü, Juan(1)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 44  Issue: 8  DOI: 10.3788/gzxb20154408.0806002  Published: August 1, 2015  
  Abstract:The control target of stray light is deduced based on solar power transmission and the allowable stray light radiance at the exit pupil. Two schemes used to eliminate direct radiation were present, one way is setting primary baffle and secondary baffle, the other way is only setting primary baffle and Lyot stop near the exit pupil. Theoretial analysis indicates that by setting the secondary baffle the first scheme will increase the obscuration ratio, and by setting the Lyot stop near the exit pupil the second one will appear vignetting. Since the requirements of receiving/emission efficiency for optical antenna are very high, it's also needs to take into account the energy in the design process. The receiving/emission efficiency and stray light suppression level of the two scheme were analyzed to some cassegrain optical antenna. The emission efficiency and stray light suppression level of the second scheme is better than the first, but the receiving efficiency of edge field is slight lower. Finally the second way was used to control the stray light of the optical antenna prototype, and its stray light level was tested. The results show the extinction ratio are lower than -40 dB when the range of off-field angle is from 1° to 20°, it meets the requirement. ©, 2015, Chinese Optical Society. All right reserved.
  Accession Number: 20153901310767
• Record 152 of
  
  Title:High-order topological charges measurement of LG vortex beams with a modified Mach-Zehnder interferometer
  
  Author(s):Lv, Fangjie(1); Li, Xinzhong(1,2); Tai, Yuping(3); Zhang, Liping(1); Nie, Zhaogang(4); Chen, Qingdong(1)
  Source: Optik  Volume: 126  Issue: 23  DOI: 10.1016/j.ijleo.2015.08.145  Published: 2015  
  Abstract:We present a new method to measure the high-order topological charges (TCs) of Laguerre-Gaussian (LG) vortex beams by using a modified Mach-Zehnder interferometer. Counting the number of interference bright fringes between the LG beam and its conjugate beam determines integer and half-integer TCs through half of the bright fringe number. The proposed method can measure the order of the integer TC up to 90, which is higher than that achieved by previous methods. This technique opens up new applications for LG vortex beams. © 2015 Elsevier GmbH. All rights reserved.
  Accession Number: 20160101753613
• Record 153 of
  
  Title:Optical system design for lens with large relative aperture
  
  Author(s):Zhang, Kaisheng(1); Zhang, Zhi(1); Zhang, Zhaohui(1); Wang, Zefeng(1); Yan, Aqi(1); Fei, Jiaqi(1); Mei, Chao(1); Zhang, Gaopeng(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 9676  Issue:   DOI: 10.1117/12.2203099  Published: 2015  
  Abstract:As the space remote sensing technology progresses, the developing trend of telescope is larger and larger aperture, higher and higher resolution. An Optical system with the relative aperture of 1:2 is introduced. The primary optical properties are: focal length of 120mm, F number of 2, field angle of 7.4°. It has the advantages of large high resolution, small size and excellent image quality. Several kinds of aberration curves and the MTF curve are given. Its imaging quality is nearly diffraction limited so that the spatial frequency is greater than 70lp/mm when its modulated transfer function (MTF) value of the optical system is equal to 0.8,and the optical system distortion is less than 1%. At last, the stray light is analyzed and the baffle of the telescope is designed. The solid model of the Optical system was constructed in Tracepro software, the point sources transmittance (PST) cure was given at different off-axis angle between 7.4°∼80°ï1/4Œthe analysis result indicates that the PST values are less than 10-6 when off-axis angle are larger than soar critical angle. So the system is suitable for observation or photography of deep sky objects. © 2015 SPIE.
  Accession Number: 20155201717500
• Record 154 of
  
  Title:Restoration of motion blurred image with Lucy-Richardson algorithm
  
  Author(s):Li, Jing(1); Liu, Zhao Hui(1); Zhou, Liang(1)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 9675  Issue:   DOI: 10.1117/12.2199337  Published: 2015  
  Abstract:Images will be blurred by relative motion between the camera and the object of interest. In this paper, we analyzed the process of motion-blurred image, and demonstrated a restoration method based on Lucy-Richardson algorithm. The blur extent and angle can be estimated by Radon transform algorithm and auto-correlation function, respectively, and then the point spread function (PSF) of the motion-blurred image can be obtained. Thus with the help of the obtained PSF, the Lucy-Richardson restoration algorithm is used for experimental analysis on the motion-blurred images that have different blur extents, spatial resolutions and signal-to-noise ratios (SNR's). Further, its effectiveness is also evaluated by structural similarity (SSIM). Further studies show that, at first, for the image with a spatial frequency of 0.2 per pixel, the modulation transfer function (MTF) of the restored images can maintains above 0.7 when the blur extent is no bigger than 13 pixels. That means the method compensates low frequency information of the image, while attenuates high frequency information. At second, we fund that the method is more effective on condition that the product of the blur extent and spatial frequency is smaller than 3.75. Finally, the Lucy-Richardson algorithm is found insensitive to the Gaussian noise (of which the variance is not bigger than 0.1) by calculating the MTF of the restored image. © Copyright 2015 SPIE.
  Accession Number: 20161602266821
• Record 155 of
  
  Title:Fraunhofer diffraction of Laguerre-Gaussian beam caused by a dynamic superposed dual-triangular aperture
  
  Author(s):Li, Xinzhong(1); Tai, Yuping(2); Nie, Zhaogang(3); Wang, Hui(1); Li, Hehe(1); Wang, Jingge(1); Tang, Jie(4); Wang, Yishan(4)
  Source: Optical Engineering  Volume: 54  Issue: 12  DOI: 10.1117/1.OE.54.12.123113  Published: December 1, 2015  
  Abstract:We investigate the Fraunhofer diffraction of a Laguerre-Gaussian (LG) beam incident on a dynamic superposed dual-triangular aperture. The evolution of the diffraction pattern from this aperture is analyzed experimentally and theoretically. A special aperture, called the hex-star triangular aperture, demonstrates interesting diffraction patterns. Further, the diffraction properties of integer, half-integer, and fractional orders of topological charges at the Fraunhofer zone are studied by using the hex-star triangular aperture. This study can provide additional information to enhance the understanding of the diffraction properties of the LG beam transmitted through a complex aperture. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE).
  Accession Number: 20160301808221
• Record 156 of
  
  Title:Research and implementation of improved neural network non- uniformity correction algorithm
  
  Author(s):Duan, Chengpeng(1); Liu, Wei(1); Xie, Qingsheng(1); Leng, Hanbing(1); Yi, Bo(1); Chen, Yaohong(1)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 35  Issue: 7  DOI: 10.3788/AOS201535.0710001  Published: July 10, 2015  
  Abstract:In order to implement non-uniformity correction of infrared image, the neural network algorithm is commonly used to complete adaptive non-uniformity correction of infrared image at present, this method can update the correction factor automatically, but the algorithm is complex, and the correction output image contrast is low, the ghosting and image blurring appears. An improved neural network non-uniformity correction method is presented, the initial value of calibration coefficients are obtained by the use of high and low temperature blackbody, and the calculation of the output expect value in the iterative process is improved. The test results show that the method is simple and practical, and has a good non-uniform correction effect. ©, 2015, Chinese Optical Society. All right reserved.
  Accession Number: 20153601250769