2019

• Record 157 of
  
  Title:Analysis and Verification of Effect of Micro-Vibration on Space Photoelectric Payload Imaging
  
  Author(s):Shi, Jinfeng(1); Cheng, Pengfei(1); Yuan, Hao(1); Ren, Guorui(1,2); Wang, Wei(1); Fan, Xuewu(1); Li, Zhiguo(3)
  Source: Guangxue Xuebao/Acta Optica Sinica  Volume: 39  Issue: 5  DOI: 10.3788/AOS201939.0520001  Published: May 10, 2019  
  Abstract:Based on the least square method, the average surface rigid-body motion equation of optical elements is derived herein using the area-weighted average motion. By analyzing the effect of micro-vibration on the modulation transfer function (MTF) of an optical system, the relevant image motion and its corresponding optical axis rotation angle are determined. The data process for the frequency response analysis is performed using the average rigid-body motion equations. The micro-vibration magnitude of the photoelectric payload mounting surface is retrieved based on the demands of optical axis rotation angles of the system. The real-time MTF testing of the system is performed using the constant-frequency micro-vibration test. The results show that the error discrepancy between the analysis results and the test data is within 20%, which meets the requirements for engineering applications and verifies the correctness of the computational method. © 2019, Chinese Lasers Press. All right reserved.
  Accession Number: 20193107246235
• Record 158 of
  
  Title:A Characteristic Extraction Algorithm Based on Blocking Star Images
  
  Author(s):Du, Yun(1,2,3); Wen, Desheng(1); Liu, Guizhong(2); Qiu, Shi(1); Li, Ni(4,5)
  Source: International Journal of Pattern Recognition and Artificial Intelligence  Volume: 33  Issue: 9  DOI: 10.1142/S0218001419540284  Published: August 1, 2019  
  Abstract:The star images obtained through the CCD camera can visually display the star structure. In order to get the wide starry image, we need to extract the characteristics of star images to achieve the star image stitching. In the star images, star points, whose characteristics are limited, are easily influenced by noise and are also difficult to extract. The number of stars is too large to stitch accurately. Thus, we propose a stitching algorithm based on blocking star images. First, we establish the maximum intensity projection model based on time sequence to locate the star points accurately. Then, according to the relative positions of star points, the block model is introduced to realize the establishment of the characteristics. Finally, the star image stitching is achieved from the perspective of the characteristic similarity. The experiments illustrate that CM (combination measure) reaches 0.87, and the proposed algorithm has better anti-noise performance and robustness. © 2019 World Scientific Publishing Company.
  Accession Number: 20191006593832
• Record 159 of
  
  Title:Label-free detecting oligonucleotide hybridization melting temperature in real-time with a reflectometric interference spectroscopy–based nanosensor system
  
  Author(s):Lu, Yao(1); Sun, Dan(1); Wang, Kaige(1); Bai, Xiaohong(2); Zhang, Chen(1); Zhao, Wei(1); Feng, Xiaoqiang(1); Bai, Jintao(1)
  Source: Optik  Volume: 192  Issue:   DOI: 10.1016/j.ijleo.2019.06.003  Published: September 2019  
  Abstract:The accurate determination of melting temperature (Tm) of oligonucleotide hybridization is the primary for various biosensors based on the technique of using surface-tethered nucleic acids as probes. In this paper, a new type of nanosensor based on the reflectometric interference spectroscopy (RIFS) was proposed to determine the Tm in real time. A composite solid nanostructure, i.e., a nanoporous anodic alumina film with a 15 nm top layer of gold sputtered on surface, was employed as the substrate of the RIFS-based nanosensor, and a 30 bp oligonucleotide molecule was bond to the inner wall of pores and hybridized, and then its Tm was detected with raising temperature. The experimental data showed that there were obvious signs of dsDNA molecules denatured and melted into ssDNA molecules at 95 ℃, which was highly consistent with the theoretical analysis. The cost-effective RIFS nanosensor has excellent thermal and physicochemical stabilities, higher determination accuracy, and great potential in the field of biomolecule research. © 2019 Elsevier GmbH
  Accession Number: 20192507071490
• Record 160 of
  
  Title:Phase control and stabilization in attosecond beamline with fast Fourier transform
  
  Author(s):Jiang, Yu-Jiao(1); Gao, Yi-Tan(2,3); Huang, Pei(3,4); Zhao, Kun(2); Xu, Si-Yuan(1); Zhu, Jiang-Feng(1); Fang, Shao-Bo(2); Teng, Hao(2); Hou, Xun(4); Wei, Zhi-Yi(2,3)
  Source: Wuli Xuebao/Acta Physica Sinica  Volume: 68  Issue: 21  DOI: 10.7498/aps.68.20191164  Published: November 5, 2019  
  Abstract:With the unveiling of molecular and atomic dynamics, scientists crave finer and faster tools to communicate with the microworld. Attosecond pump-probe enjoys its reputation as the fastest camera, hinting ultrafast movements in the delay graph. To employ this camera, the stability and delay control should have very great accuracy comparable to the camera resolution. It is also of significant importance for stabilizing the carrier envelope phase (CEP) in few-cycle laser field. When dealing with a huge quantity of data, conventional Fourier transform algorism is challenging in high-speed control. Here we put forward the efficient calculation method, fast Fourier transform (FFT) algorism in Mach-Zehnder interferometer for arm length locking and f-2f for CEP locking. In the interferometer locking, 532 nm continuous wave laser is used in the Mach-Zehnder interferometer, and the phase of the FFT term corresponding to the delay between the two arms of the interferometer serves as a feedback signal on piezo transducer (PZT) in the delay line to reduce the change of the arm length. In the CEP control experiment, data to be analyzed are the f-2f spectrum interference fringes recorded by the spectrometer. The CEP values are obtained from the first order of FFT module output of the integrated spectrum interference fringes, and a labview program examines the relative phase drift and sends a feedback voltage signal to the PZT through the proportion integration differentiation module to compensate slow CEP drift after the chirped pulse amplification system by changing the insert length of a prism pair. The results show that the root mean square (RMS) of the arm length difference is 1.24 nm (4.1 attosecond for light to travel) per meter in the interferometer locking over 12 h, and the RMS of CEP is 227 mrad under 3 ms integration time in the CEP locking over 20 min. These results are able to meet the requirement of the accuracy for attosecond pulse generation and attosecond pump-probe experiments. We also use FFT to stabilize the CEP and relative time simultaneously in the waveform synthesis for 8 h (Huang P, Fang S, Gao Y, Zhao K, Hou X, Wei Z 2019 Appl. Phys. Lett. 115 031102), the phase-locking system results in a CEP stability of 280 mrad and a relative time stability of 110 as at a repetition rate of 1 kHz. These results imply that the FFT is versatile and reliable in ultrafast control. © 2019 Chinese Physical Society.
  Accession Number: 20200208021225
• Record 161 of
  
  Title:Hyperspectral Anomaly Detection via Sparse Dictionary Learning Method of Capped Norm
  
  Author(s):Yuan, Yuan(1,2); Ma, Dandan(3,4); Wang, Qi(1,2)
  Source: IEEE Access  Volume: 7  Issue:   DOI: 10.1109/ACCESS.2019.2894590  Published: 2019  
  Abstract:Hyperspectral anomaly detection is a research hot spot in the field of remote sensing. It can distinguish abnormal targets from the scene just by utilizing the spectral differences and requiring no prior information. A series of anomaly detectors based on Reed-Xiaoli methods are very important and typical algorithms in this research area, which generally have the hypothesis about background subject to the Gaussian distribution. However, this assumption is inaccurate to describe a hyperspectral image with a complex scene in practice. Besides, due to the unavoidable existence of abnormal targets, background statistics will be affected which will reduce the detection performance. To address these problems, we propose a sparse dictionary learning method by using a capped norm to realize hyperspectral anomaly detection. Moreover, a new training data selection strategy based on clustering technique is also proposed to learn a more representative background dictionary. The main contributions are concluded in threefold: 1) neither making any assumptions on the background distribution nor computing the covariance matrix, the proposed method is more adaptive to all kinds of complex hyperspectral images in practice; 2) owing to the good qualities of the capped norm, the learned sparse background dictionary is resistant to the effect of anomalies and has stronger distinctiveness to anomalies from background; 3) without using the traditional sliding hollow window technique, the proposed method is more effective to detect different sizes of abnormal targets. The extensive experiments on four commonly used real-world hyperspectral images demonstrate the effectiveness of the proposed method and show its superiority over the benchmark methods. © 2013 IEEE.
  Accession Number: 20190806530011
• Record 162 of
  
  Title:A porous Au-Ag hybrid nanoparticle array with broadband absorption and high-density hotspots for stable SERS analysis
  
  Author(s):Li, Kuanguo(1,2); Liu, Guangju(1); Zhang, Sheng(1); Dai, Yanqiu(3); Ghafoor, Sonia(3); Huang, Wanxia(1); Zu, Zewen(1); Lu, Yonghua(3,4)
  Source: Nanoscale  Volume: 11  Issue: 19  DOI: 10.1039/c9nr01744e  Published: May 21, 2019  
  Abstract:Constructing high-density hotspots is of crucial importance in surface enhanced Raman scattering (SERS). In this paper, we present a large-area and broadband porous Au-Ag hybrid nanoparticle array which was fabricated by an ultra-thin alumina mask (UTAM) technique incorporated with annealing and galvanic replacement techniques. Experimental results and numerical simulations demonstrated that the porous Au-Ag hybrid nanoparticle array possessed enormous hotspots for high sensitivity, uniformity, and stability in SERS analysis. A large Raman enhancement factor of 2.2 × 107 was achieved with a relative standard deviation (RSD) of 7.7%, leading to excellent reliability for Raman detection. Furthermore, this novel substrate exhibited a long shelf time in an ambient environment and promising practical applications in many SERS-based quantitative analytical and biomedical sensing techniques. © 2019 The Royal Society of Chemistry.
  Accession Number: 20192106968520
• Record 163 of
  
  Title:Describing video with attention-based bidirectional LSTM
  
  Author(s):Bin, Yi(1); Yang, Yang(1); Shen, Fumin(1); Xie, Ning(1); Shen, Heng Tao(1); Li, Xuelong(2)
  Source: IEEE Transactions on Cybernetics  Volume: 49  Issue: 7  DOI: 10.1109/TCYB.2018.2831447  Published: July 2019  
  Abstract:Video captioning has been attracting broad research attention in the multimedia community. However, most existing approaches heavily rely on static visual information or partially capture the local temporal knowledge (e.g., within 16 frames), thus hardly describing motions accurately from a global view. In this paper, we propose a novel video captioning framework, which integrates bidirectional long-short term memory (BiLSTM) and a soft attention mechanism to generate better global representations for videos as well as enhance the recognition of lasting motions in videos. To generate video captions, we exploit another long-short term memory as a decoder to fully explore global contextual information. The benefits of our proposed method are two fold: 1) the BiLSTM structure comprehensively preserves global temporal and visual information and 2) the soft attention mechanism enables a language decoder to recognize and focus on principle targets from the complex content. We verify the effectiveness of our proposed video captioning framework on two widely used benchmarks, that is, microsoft video description corpus and MSR-video to text, and the experimental results demonstrate the superiority of the proposed approach compared to several state-of-the-art methods. © 2013 IEEE.
  Accession Number: 20182205264544
• Record 164 of
  
  Title:Photonic based phase-encoded RF signal generation for advanced radar systems with a 49GHz soliton crystal micro-comb optical source
  
  Author(s):Xu, Xingyuan(1); Tan, Mengxi(1); Wu, Jiayang(1); Boes, Andreas(2); Corcoran, Bill(3); Nguyen, Thach G.(2); Chu, Sai T.(4); Little, Brent E.(5); Morandotti, Roberto(6,7); Mitchell, Arnan(2); Moss, David J.(1)
  Source: TechRxiv  Volume:   Issue:   DOI: 10.36227/techrxiv.11400765  Published: December 18, 2019  
  Abstract:We demonstrate photonic RF phase encoding based on an integrated micro-comb source. By assembling single-cycle Gaussian pulse replicas using a transversal filtering structure, phase encoded waveforms can be generated by programming the weights of the wavelength channels. This approach eliminates the need for RF signal generators for RF carrier generation or arbitrary waveform generators for phase encoded signal generation. A large number of wavelengths—up to 60—were provided by the microcomb source, yielding a high pulse compression ratio of 30. Reconfigurable phase encoding rates ranging from 2 to 6 Gb/s were achieved by adjusting the length of each phase code. This work demonstrates the significant potentials of this microcomb-based approach to achieve high-speed RF photonic phase encoding with low cost and footprint. © 2019, CC BY.
  Accession Number: 20220310659
• Record 165 of
  
  Title:Ultrafast dynamics of three types of simultaneous shockwaves and filament attenuation in femtosecond laser multi-pulse ablation of PMMA
  
  Author(s):Wang, Guoyan(1); Jiang, Lan(1); Sun, Jingya(1); Hu, Jie(1); Wang, Qingsong(1); Li, Ming(2); Lu, Yongfeng(3)
  Source: Chinese Optics Letters  Volume: 17  Issue: 8  DOI: 10.3788/COL201917.081405  Published: August 10, 2019  
  Abstract:Cylindrical shockwaves inside polymethyl methacrylate (PMMA) generated simultaneously with two hemispherical shockwaves induced by a femtosecond Gaussian beam laser were investigated using an ultrafast pump-probe imaging technique. The evolutions of these three shockwaves with probe delay and incident pulse number have been systematically analyzed. The plasma intensity and filament length in the center of cylindrical shockwave both decayed with pulse number. Moreover, the self-focused filament moved downstream towards the output surface with an increased pulse number. The experimental results and mechanism illustrated that energy deposition was suppressed by a degraded nonlinear effect due to a pre-ablated structure in multi-pulse irradiation. © 2019 Chinese Optics Letters.
  Accession Number: 20193707422747
• Record 166 of
  
  Title:Research on the Spatio-temporal and Gain Performances on the Small-size Streak Tube
  
  Author(s):Tian, Li-Ping(1,2); Wen, Wen-Long(1); Wang, Xing(1); Chen, Ping(1); Hui, Dan-Dan(1,2); Lu, Yu(1); Tian, Jin-Shou(1,3); Zhao, Wei(1,3)
  Source: Guangzi Xuebao/Acta Photonica Sinica  Volume: 48  Issue: 7  DOI: 10.3788/gzxb20194807.0723002  Published: July 1, 2019  
  Abstract:Based on the small-size streak tube, the dependence of the physical temporal resolution and temporal distortion on the factors including initial energy of electrons generated from the photocathode and spherical photocathode curvature radius is numerically simulated. The simulation results show that the physical temporal resolution is greatly affected by the initial energy, which is less affected by the spherical curvature radius and off-axis distance; the temporal distortion increases with the off-axis distance. Furthermore, the streak tube with a flat photocathode has a positive temporal distortion. With the decrease of the radius of curvature of the photocathode, the temporal distortion gradually changes from positive value to negative ones. And, when the photocathode curvature radius is 70 mm, the temporal distortion can be reduced to 8 ps and the spatial resolution can reach 25 lp/mm @ MTF=10%, the curvature of the slit image can be almost neglected even though the off-axis distance is 8 mm. Besides, the static spatial resolution and luminance gain of the streak tube, the luminance photocathode sensitivity of the photocathode are tested experimentally. The experiment results show that the spatial resolution of the streak tube is higher than 28 lp/mm at the photocathode center while it is higher than 18 lp/mm at the edge. The luminance photocathode sensitivity of the small-size streak tube is 178 μA/lm and the luminance gain is higher than 12 while the luminance gain of picosecond streak tube is only 0.5. Thus, the small-size streak tube has a good weak light detection ability in the field of streak tube imaging lidar. © 2019, Science Press. All right reserved.
  Accession Number: 20193407330841
• Record 167 of
  
  Title:Wide spectrum responsivity detectors from visible to mid-infrared based on antimonide
  
  Author(s):Guo, Chunyan(1,2,4); Sun, Yaoyao(3,4); Jia, Qingxuan(3,4); Jiang, Zhi(3,4); Jiang, Dongwei(3,4); Wang, Guowei(3,4); Xu, Yingqiang(3,4); Wang, Tao(1); Tian, Jinshou(1); Wu, Zhaoxin(2); Niu, Zhichuan(3,4)
  Source: Infrared Physics and Technology  Volume: 96  Issue:   DOI: 10.1016/j.infrared.2018.10.037  Published: January 2019  
  Abstract:A kind of wide spectrum infrared detectors based on InAs/GaSb type-II superlattices (T2SLs) operating from 0.5 μm to 5 μm wavelength range is reported. The materials were grown by Molecular Beam Epitaxy (MBE) on GaSb substrates. Diverse types and sizes microstructure are fabricated on the surface of the detector to form the photon traps (PTs) array. PTs decrease the reflectivity and increase the light absorption of epitaxial material. Compared with the planar mesa detectors without antireflection (AR) film, detectors with PTs array exhibits a high responsivity of 0.86 A/W at 1160 nm and maximum D* reaches to 109 cm Hz1/2/W in visible wavelength. Also, the PTs processed on detector augment spectral response and QE in infrared wavelength. The peak responsivity of the detector with PTs is to 1.35 A/W and QE can exceed to 0.76 in the infrared wavelength. The infrared detector with PTs is attractive for numerous applications. © 2018 Elsevier B.V.
  Accession Number: 20184606067275
• Record 168 of
  
  Title:Exploiting spatial relation for fine-grained image classification
  
  Author(s):Qi, Lei(1,2); Lu, Xiaoqiang(1); Li, Xuelong(3)
  Source: Pattern Recognition  Volume: 91  Issue:   DOI: 10.1016/j.patcog.2019.02.007  Published: July 2019  
  Abstract:Fine-Grained Image Classification (FGIC) aims to distinguish the images within a subordinate category. Recently, many FGIC methods have been proposed and huge progress has been made in the aspects of part detection and feature learning for FGIC. However, FGIC still remains a challenging task due to the large intra-class variance and small inter-class variance. To classify fine-grained images accurately, this paper proposes to exploit spatial relation to capture more discriminative details for FGIC. The proposed method contains two core modules: part selection module and representation module. The part selection module utilizes intrinsic spatial relation between object parts to select object part pairs with high discrimination power. The representation module exploits the interaction between object parts to describe the selected part pairs and construct a semantic image representation for FGIC. The proposed method is evaluated on CUB-200-2011 and FGVC-Aircraft datasets. Experimental results show that the classification accuracy of the proposed method can reach 85.5% on CUB-200-2011 and 86.9% on FGVC-Aircraft respectively, which exceed comparison methods obviously. © 2019 Elsevier Ltd
  Accession Number: 20190806531148