2015
2015
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Record 73 of
Title:Machining parameter optimization of C/SiC composites using high power picosecond laser
Author(s):Zhang, Ruoheng(1); Li, Weinan(1); Liu, Yongsheng(2); Wang, Chunhui(2); Wang, Jing(2); Yang, Xiaojun(1); Cheng, Laifei(2)Source: Applied Surface Science Volume: 330 Issue: DOI: 10.1016/j.apsusc.2015.01.010 Published: March 1, 2015Abstract:Picosecond laser is an important machining technology for high hardness materials. In this paper, high power picosecond laser was utilized to drill micro-holes in C/SiC composites, and the effects of different processing parameters including the helical line width and spacing, machining time and scanning speed were discussed. To characterize the qualities of machined holes, scanning electron microscope (SEM) was used to analyze the surface morphology, energy dispersive spectroscopy (EDS) and X-ray photoelectric spectroscopy (XPS) were employed to describe the element composition change between the untreated and laser-treated area. The experimental results indicated that all parameters mentioned above had remarkable effects on the qualities of micro-holes such as shape and depth. Additionally, the debris consisted of C, Si and O was observed on the machined surface. The SiC bonds of the SiC matrix transformed into SiO bonds after machined. Furthermore, the physical process responsible for the mechanism of debris formation was discussed as well. ? 2015 Elsevier B.V.Accession Number: 20151000610330 -
Record 74 of
Title:Research on the high indium content InGaAs multiple quantum wells wafers for λ > 1.55 μm laser diodes
Author(s):Lin, Tao(1); Sun, Hang(1); Zhang, Haoqing(1); Wang, Yonggang(2); Lin, Nan(3); Ma, Xiaoyu(3)Source: Journal of Alloys and Compounds Volume: 631 Issue: DOI: 10.1016/j.jallcom.2015.01.120 Published: May 15, 2015Abstract:The effects of TMIn flow rate and AsH3 flow rate on the photoluminescence spectra of the high indium content InGaAs multiple quantum wells for λ > 1.55 μm laser diodes have been investigated both experimentally and theoretically. The wavelength peak red-shifted about 4.8 nm for increasing 1 sccm H2 flow rate through TMIn under a AsH3 flow rate of 150 sccm, while the wavelength shift increases to 6.5 nm at a higher AsH3 flow rate of 300 sccm. Results show that more AsH3 flow rate will promote much TMGa pyrolysis than TMIn in the high indium content InGaAs growth. Considering the influence of growth parameters, the longest wavelength of 1.889 μm among the InGaAs/InGaAsP strained MQWs samples was obtained with high crystal quality. ?2015 Elsevier B.V. All rights reserved.Accession Number: 20150700509008 -
Record 75 of
Title:Calibration method for large aperture static imaging spectrometer's detector registration error
Author(s):Zhang, Zhoufeng(1,2,3); Xie, Yongjun(1); Hu, Bingliang(1); Yin, Qinye(2); Yu, Tao(1,3)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 5 DOI: Published: May 25, 2015Abstract:As a novel type Fourier transform imaging spectrometry, large aperture static imaging spectrometry has come forth in recent years, which has many advantages such as high throughput, multichanneland so on. However, if there are certain registration error on the detector array and interferogram, it will have a greater impact on the restoring spectrum, and even affect the final application of the instrument. To solve this problem, according to the imaging prinple analysis of LASIS, a detector registration error calibration method was given, after verification, this method can well solve the problem of the detector registration error, and the accuracy of recovered spectrum was evidently improved. This study has important guiding significance for the development of large aperture static imaging spectrometer. ?, 2015, Chinese Society of Astronautics. All right reserved.Accession Number: 20153501209554 -
Record 76 of
Title:Robust Visual Tracking Using Structurally Random Projection and Weighted Least Squares
Author(s):Zhang, Shengping(1); Zhou, Huiyu(2); Jiang, Feng(3); Li, Xuelong(4)Source: IEEE Transactions on Circuits and Systems for Video Technology Volume: 25 Issue: 11 DOI: 10.1109/TCSVT.2015.2406194 Published: November 2015Abstract:Sparse representation-based visual tracking approaches have attracted increasing interests in the community in recent years. The main idea is to linearly represent each target candidate using a set of target and trivial templates, while imposing a sparsity constraint onto the representation coefficients. After we obtain the coefficients using l1-norm minimization methods, the candidate with the lowest error, when it is reconstructed using only the target templates and the associated coefficients, is considered as the tracking result. In spite of promising system performance widely reported, it is unclear if the performance of these trackers can be maximized. In addition, computational complexity caused by the dimensionality of the feature space limits these algorithms in real-time applications. In this paper, we propose a real-time visual tracking method based on structurally random projection (RP) and weighted least squares (WLS) techniques. In particular, to enhance the discriminative capability of the tracker, we introduce background templates to the linear representation framework. To handle appearance variations over time, we relax the sparsity constraint using a WLS method to obtain the representation coefficients. To further reduce the computational complexity, structurally RP is used to reduce the dimensionality of the feature space, while preserving the pairwise distances between the data points in the feature space. Experimental results show that the proposed approach outperforms several state-of-the-art tracking methods. ? 2015 IEEE.Accession Number: 20161202112806 -
Record 77 of
Title:A tunable terahertz photonic crystal narrow-band filter
Author(s):Li, Shaopeng(1); Liu, Hongjun(1); Sun, Qibing(1); Huang, Nan(1)Source: IEEE Photonics Technology Letters Volume: 27 Issue: 7 DOI: 10.1109/LPT.2015.2391127 Published: April 1, 2015Abstract:We theoretically propose and investigate a magnetically tunable narrow-band terahertz filter based on a triangular lattice silicon photonic crystal with a point and two line defects. The optical properties of the filter have been analyzed in detail. It is found that a single resonant peak with the central frequency of ～ 1 THz is existed in the transmission spectrum, which has a narrow full width at half maximum of ? 2015 IEEE.Accession Number: 20151200652715 -
Record 78 of
Title:Multi-spectral pedestrian detection
Author(s):Yuan, Yuan(1); Lu, Xiaoqiang(1); Chen, Xiao(1)Source: Signal Processing Volume: 110 Issue: DOI: 10.1016/j.sigpro.2014.08.003 Published: May 2015Abstract:Pedestrian detection is a crucial problem in human pose recovery and behavior analysis, especially in applications such as visual surveillance, robotics, and drive-assistance systems. Recently, most pedestrian detection approaches of machine learning and signal processing have achieved advanced performance in traditional natural images. However, there exists a limitation on the accuracy in pedestrian detection. The reason behind this is that supporting information for detecting pedestrian is limited. In fact, spectrum besides visible light can provide abundant discriminative information for pedestrian detection. Therefore, it is significative to exploit multi-spectral information for detection task. In this paper, a multi-spectral based pedestrian detection approach is proposed, which not only takes use of the information of red, green and blue (RGB) bands, but also incorporates the information of near-infrared spectrum into the detection process. Latent variable support vector machines (L-SVM) are employed to train the multi-spectral pedestrian detection model. Experiments are implemented on a new dataset containing 1826 multi-spectral image pairs. The experimental results illustrate that utilizing multi-spectral information achieves significant performance improvement in a pedestrian detection task compared with only using RGB information. ? 2014 Elsevier B.V.Accession Number: 20150800544786 -
Record 79 of
Title:Compact diode-pumped nanosecond Nd:YVO4 grazing-incidence slab amplifier
Author(s):Sun, Zhe(1); Li, Qiang(1); Hui, Yongling(1); Jiang, Menghua(1); Lei, Hong(2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9449 Issue: DOI: 10.1117/12.2076333 Published: 2015Abstract:A high average power and high beam quality nanosecond laser is presented that is based on CW diode side-pumped Nd:YVO4grazing-incidence slab amplifier. A TEM00, passively Q-switched diode-pumped Nd:YAG laser as the seed laser, generating a M2 1.3 beam train of 0.25W, 2.3ns pulses with adjustable repetition rate in the range 5-20kHz. After double-pass amplification, more than 20W of output power with a beam quality of M2 1.4 is obtained at an optical-optical efficiency of 35%. The high brightness of this laser system seems ideal for nonlinear optics and laser processing applications. ? 2015 SPIE.Accession Number: 20151100635555 -
Record 80 of
Title:Topology optimization design of a space mirror
Author(s):Liu, Jiazhen(1,2); Jiang, Bo(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9795 Issue: DOI: 10.1117/12.2209031 Published: 2015Abstract:As key components of the optical system of the space optical remote sensor, Space mirrors' surface accuracy had a direct impact that could't be ignored of the imaging quality of the remote sensor. In the future, large-diameter mirror would become an important trend in the development of space optical technology. However, a sharp increase in the mirror diameter would cause the deformation of the mirror and increase the thermal deformation caused by temperature variations. A reasonable lightweight structure designed to ensure the optical performance of the system to meet the requirements was required. As a new type of lightweight approach, topology optimization technology was an important direction of the current space optical remote sensing technology research. The lightweight design of rectangular mirror was studied. the variable density method of topology optimization was used. The mirror type precision of the mirror assemblies was obtained in different conditions. PV value was less than λ/10 and RMS value was less than λ/50(λ = 632.8nm). The results show that the entire The mirror assemblies can achieve a sufficiently high static rigidity, dynamic stiffness and thermal stability and has the capability of sufficient resistance to external environmental interference . ? 2015 SPIE.Accession Number: 20161702279073 -
Record 81 of
Title:Research and design of astigmatism-free for C-T imaging spectrometer under non-parallel grating illumination
Author(s):Hao, Aihua(1,2,3); Hu, Bingliang(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 7 DOI: Published: July 25, 2015Abstract:Czerny-Turner (C-T) spectrometer usually been used monochromators and spectral radiometers due to its compact structure and spherical mirrors. However, astigmatism greatly confines C-T spectrometer used in imaging spectrometers. Astigmatism-free methods were analyzed theoretically and verified experimentally under non-parallel grating illumination. As a result, astigmatism of C-T spectrometer can be corrected under convergent or divergent grating illumination. When the cosine square ratio of grating incidence to difference angle was more than 1, divergent illumination can correct astigmatism. Conversely, when it was less than 1, convergent illumination can correct astigmatism. ?, 2015, Chinese Society of Astronautics. All right reserved.Accession Number: 20153501225647 -
Record 82 of
Title:Preparation and properties of low-loss core-cladding structural Ge-Sb-Se chalcogenide glass fibers
Author(s):Xu, Yantao(1); Guo, Haitao(1); Lu, Min(1); Wei, Wei(1); Peng, Bo(1)Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 1 DOI: Published: January 25, 2015Abstract:For solving the problems about Ge system chalcogenide glass fiber's relatively high loss, etc, high- purity Ge28Sb12Se60 glass was prepared by chemical and physical methods of purification. The absorptions caused by C, H, O impurities were obviously reduced in IR band. Ge28Sb12Se58S2 chalcogenide glass tube with precision wall and fine optical properties was prepared by means of tube-rotating technique. Fibers with core-cladding structure were drawn by rod-in-tube method. The diameter of the fiber is 50±1.5 μm and the bending test showed the diameter of the circle is 5 mm. The fiber loss is 2.2 dB/m (except those at 2.87 and 4.5 μm). ?, 2015, Chinese Society of Astronautics. All right reserved.Accession Number: 20151000594576 -
Record 83 of
Title:Numerical modeling of the influence of temperature and driving current on 'smile' in high power diode laser arrays
Author(s):Wang, Shuna(1); Zhang, Pu(1); Nie, Zhiqiang(1); Wu, Dihai(1); Liu, Xingsheng(1,2)Source: 16th International Conference on Electronic Packaging Technology, ICEPT 2015 Volume: Issue: DOI: 10.1109/ICEPT.2015.7236552 Published: September 1, 2015Abstract:'Smile' in high power diode laser arrays is mainly caused by thermal stress generated during packaging processes and operation. By numerical modeling, a three-dimensional finite element model of a conduction-cooled packaged 60W high power diode laser array was established. Finite element method (FEM) was conducted to simulate and analyze the thermal and mechanical characteristic of the diode laser bar in different scenarios. According to the variation of thermal stress and displacement across the laser bar, the influence of temperature and driving current on 'smile' was analyzed and discussed. Numerical simulation results show that 'smile' will decrease with the increasing heatsink temperature and increase with the increasing driving current. In this paper, the corresponding quantitative relationships of smile with heatsink temperature and driving current were obtained. The work provides theoretical guidance for optimizing high power diode laser array design, packaging process and reducing 'smile'. ? 2015 IEEE.Accession Number: 20160701931660 -
Record 84 of
Title:Multi-position coordination algorithm for lung nodule detection based on the Gestalt theory
Author(s):Qiu, Shi(1,2); Wen, Desheng(1); Feng, Jun(3); Shang, Qiongjun(4)Source: Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument Volume: 36 Issue: 11 DOI: Published: November 1, 2015Abstract:Aiming at the problem of high miss detection rate and false positive rate in the computer aided CT image lung nodule detection, a multi-position coordination algorithm for lung nodule detection based on the Gestalt theory is proposed. The algorithm simulates the process of human visual system recognizing things, builds up an isotropic sagittal image sequence and a coronary image sequence in turn for the axial view image sequence. The average intensity projection (AIP) is conducted for the three positions in a certain sequence to obtain the AIP image, which fuses in the local 3D information from three position images. The pulmonary nodule characteristics are used to detect the AIP image and mark the lung nodule area. In order to verify the effectiveness of the algorithm, 2 professional doctors marked 372 lung nodules (diameter 2-5 mm) with independent "blind" method, which were used for the detection reference. Detection was conducted using the proposed algorithm, and the result was compared with the reference. The results show that the detection correct rate is 98%, the false positive rate is 2%. According to the reference data, there were 2 suspected areas where false detection and miss detection occurred, however after the doctors reviewed the CT image sequences, it was revealed that the detection results of the algorithm are correct. Therefore the proposed algorithm can assist doctors to detect lung nodules with low miss detection rate and false positive rate. However, there is still the risk of miss detection when the lung nodule has weak greyscale and small volume, which needs further study. ? 2015, Science Press. All right reserved.Accession Number: 20160101750498