2019

• Record 145 of
  
  Title:Underwater polarimetric imaging for visibility enhancement utilizing active unpolarized illumination
  
  Author(s):Yang, Liming(1); Liang, Jian(2); Zhang, Wenfei(2,3); Ju, Haijuan(2); Ren, Liyong(2); Shao, Xiaopeng(1)
  Source: Optics Communications  Volume: 438  Issue:   DOI: 10.1016/j.optcom.2018.12.022  Published: 1 May 2019  
  Abstract:Underwater imaging is attractive but challenging. Images could be severely degraded by the particles in turbid water because of backscatter generation and signal light attenuation. In this paper, we focus on the scheme of underwater imaging and study the methods of visibility enhancement of turbid underwater images based on polarimetric imaging utilizing active unpolarized illumination. Compared with traditional polarimetric imaging using linearly polarized illumination, using unpolarized illumination ensures the polarization effect of the signal light could be neglected, no matter the depolarization degree of the object is high or low, which expands the application range of underwater polarimetric imaging and makes the underwater polarimetric imaging scheme more reliable and robust. Experimentally, the visibility and the contrast of underwater images are enhanced effectively. In addition, it is demonstrated that our method is applicable for objects of different materials and different imaging distances in turbid water. The contrast of underwater images could be promoted at least 100%, meaning that this kind of technique can be potentially used in many underwater environments. © 2018 Elsevier B.V.
  Accession Number: 20190406411403
• Record 146 of
  
  Title:Robotic Arm Based Automatic Ultrasound Scanning for Three-Dimensional Imaging
  
  Author(s):Huang, Qinghua(1); Lan, Jiulong(2); Li, Xuelong(3)
  Source: IEEE Transactions on Industrial Informatics  Volume: 15  Issue: 2  DOI: 10.1109/TII.2018.2871864  Published: February 2019  
  Abstract:This paper presents a human skin inspired automatic robotic ultrasound (US) system for three-dimensional (3-D) imaging. A depth camera was adopted to capture the point cloud of the skin surface. According to the 3-D contour of the skin surface, the scan range and scan path for the US probe could be automatically determined. Then, we used a normal-vector-based method to determine the pose of the robotic arm corresponding to each scan point in the scan path. In addition, two force sensors could feedback the contact force between the scanned tissue and the emission plane of the probe for fine-tuning the pose of the robotic arm. After the scanning, the system could realize 3-D US reconstruction. Experimental results validate the feasibility of the proposed system. It is expected that the proposed system will be useful in clinical practices. © 2005-2012 IEEE.
  Accession Number: 20184105910608
• Record 147 of
  
  Title:Orthogonal sparse fractal coding algorithm based on image texture feature
  
  Author(s):Cao, Jian(1); Zhang, Aihua(1); Shi, Lei(2,3)
  Source: IET Image Processing  Volume: 13  Issue: 11  DOI: 10.1049/iet-ipr.2019.0085  Published: September 19, 2019  
  Abstract:Fractal image compression coding algorithm is a novel image compression technology; however, the long encoding time and unacceptable image reconstruction quality remain the primary obstacles in practical application. The purpose of this study is to improve the coding quality from the perspective of grey level transform and feature extraction. In this study, a novel orthogonal sparse fractal coding algorithm based on image texture feature is proposed. The authors define a normalised version as the new grey description feature of the image block so that two improved methods are scientifically combined in theory and algorithm. First, orthogonal sparse grey level transform based on sparse decomposition improves image reconstruction quality and decoding speed. Then, the similarity measure matrix, which stores the variance feature between range blocks and domain blocks, is used to reduce redundancies and encoding time. Simulation results show that the proposed algorithm in this study can obtain better image reconstruction quality and speed up encoding time significantly as compared to the conventional fractal coding schemes. © The Institution of Engineering and Technology 2019.
  Accession Number: 20193907482865
• Record 148 of
  
  Title:Investigation on the formation and regulation of yttrium aluminosilicate fiber driven by spontaneous element migration
  
  Author(s):Zhang, Yeming(1); Sun, Yue(2); Wen, Jianxiang(3); lv, Shichao(1); Xiao, Xusheng(4); Ma, Zhijun(1); Yang, L.(5); Bi, Gang(2); Guo, Haitao(4); Qiu, Jianrong(1,6)
  Source: Ceramics International  Volume: 45  Issue: 15  DOI: 10.1016/j.ceramint.2019.06.165  Published: 15 October 2019  
  Abstract:In the conventional fiber drawing process, the waveguide parameters (fiber core diameter, refractive index profile, numerical aperture) of the optical fiber are decided (with very limited perturbation range) once the optical and geometric properties of the preform are determined. In comparison, yttrium aluminosilicate (YAS) fibers prepared by "molten core method" (also termed as "melt-in-tube" method) reveal a unique fiber formation process. Although the previous works have shown that the element diffusion plays a significant role in the formation of YAS fiber, the description of this formation process is still vague and the properties of YAS fibers obtained by this method show low controllability in practice, which cannot be explained by elemental diffusion alone. Here, a new model for the formation mechanism of YAS fibers is proposed based on the experimental data, which involves the consideration of interfacial stress during the formation of YAS fibers. The relationship between the refractive index and the element distribution in the YAS fibers was studied. Structural simulation based on the molecular dynamics was also performed to demonstrate the formation mechanism of glassy YAS fiber core. © 2019 Elsevier Ltd and Techna Group S.r.l.
  Accession Number: 20192607087465
• Record 149 of
  
  Title:Process research on micro-machining diamond microgroove by femtosecond laser
  
  Author(s):Dou, Jian(1,2); Sun, Yu(1,2); Xu, Muxun(1,2); Cui, Jianlei(1,2,3); Mei, Xuesong(1,2); Wang, Wenjun(1,2); Wang, Xintian(1,2)
  Source: Integrated Ferroelectrics  Volume: 198  Issue: 1  DOI: 10.1080/10584587.2019.1592571  Published: May 4, 2019  
  Abstract:Using micro-nano processing system of 120 fs and 800 nm low-frequency femtosecond laser, the microgroove was processed on the CVD diamond. The effects of some processing parameters on the microgroove size were studied. The results showed that the depth and width of microgrooves increase with the increase of laser power, scanning times, while with the decrease of scanning speed. Moreover, the suitable scanning speed of femtosecond laser processing diamond is about 0.1 mm/s, and focusing on diamond can improve material removal efficiency and processing quality. It is indicated that these research work has certain guiding significance for processing diamond microchannels for heat dissipation of electronic chips. © 2019, © 2019 Taylor & Francis Group, LLC.
  Accession Number: 20193007223803
• Record 150 of
  
  Title:Effect of refractive index measurement error on immersion grating spectral lines
  
  Author(s):Tang, Qian(1,2,3); Zhang, Chun Min(1); Zhao, Bao Chang(4)
  Source: Proceedings of SPIE - The International Society for Optical Engineering  Volume: 11023  Issue:   DOI: 10.1117/12.2522019  Published: 2019  
  Abstract:Firstly, the effect of refractive index changes on spectral line spacing is calculated and analyzed. Because refractive index changes with wavelength-variety, theoretically, the 0.5 nm interval should be separated by 5 pixels. The spectral distribution will drift with considering the changes in refractive index. At the same time, the inversed spectral line drift caused by measurement errors(±1×10-3?1/4?±1×10-4?1/4?±1×10-5) are analyzed. The same refractive index error, the effect on long waves is greater than short waves. When the refractive index is positive, the spectral line drifts in the negative direction. When the refractive index is negative, the spectral lines drift in the positive direction, and the positive and negative drift are basically symmetrical. When the accuracy error of refractive index measurement is ±1×10-4, the spectral line drift is 0.7 pixels. When the error increases or decreases by an order of magnitude, the number of drift elements also increases or decreases by the same order of magnitude. © 2019 SPIE.
  Accession Number: 20191506748648
• Record 151 of
  
  Title:Fast spectral clustering for unsupervised hyperspectral image classification
  
  Author(s):Zhao, Yang(1,2); Yuan, Yuan(3); Wang, Qi(3)
  Source: Remote Sensing  Volume: 11  Issue: 4  DOI: 10.3390/rs11040399  Published: February 1, 2019  
  Abstract:Hyperspectral image classification is a challenging and significant domain in the field of remote sensing with numerous applications in agriculture, environmental science, mineralogy, and surveillance. In the past years, a growing number of advanced hyperspectral remote sensing image classification techniques based on manifold learning, sparse representation and deep learning have been proposed and reported a good performance in accuracy and efficiency on state-of-the-art public datasets. However, most existing methods still face challenges in dealing with large-scale hyperspectral image datasets due to their high computational complexity. In this work, we propose an improved spectral clustering method for large-scale hyperspectral image classification without any prior information. The proposed algorithm introduces two efficient approximation techniques based on Nyström extension and anchor-based graph to construct the affinity matrix. We also propose an effective solution to solve the eigenvalue decomposition problem by multiplicative update optimization. Experiments on both the synthetic datasets and the hyperspectral image datasets were conducted to demonstrate the efficiency and effectiveness of the proposed algorithm. © 2019 by the authors.
  Accession Number: 20191006613014
• Record 152 of
  
  Title:A hybrid level set with semantic shape constraint for object segmentation
  
  Author(s):Wang, Bin(1); Yuan, Xiuying(1); Gao, Xinbo(1); Li, Xuelong(2); Tao, Dacheng(3,4)
  Source: IEEE Transactions on Cybernetics  Volume: 49  Issue: 5  DOI: 10.1109/TCYB.2018.2799999  Published: May 2019  
  Abstract:This paper presents a hybrid level set method for object segmentation. The method deconstructs segmentation task into two procedures, i.e., shape transformation and curve evolution, which are alternately optimized until convergence. In this framework, only one shape prior encoded by shape context is utilized to estimate a transformation allowing the curve to have the same semantic expression as shape prior, and curve evolution is driven by an energy functional with topology-preserving and kernelized terms. In such a way, the proposed method is featured by the following advantages: 1) hybrid paradigm makes the level set framework possess the ability of incorporating other shape-related techniques about shape descriptor and distance; 2) shape context endows one single prior with semanticity, and hence leads to the competitive performance compared to the ones with multiple shape priors; and 3) additionally, combining topology-preserving and kernelization mechanisms together contributes to realizing a more reasonable segmentation on textured and noisy images. As far as we know, we propose a hybrid level set framework and utilize shape context to guide curve evolution for the first time. Our method is evaluated with synthetic, healthcare, and natural images, as a result, it shows competitive and even better performance compared to the counterparts. © 2018 IEEE.
  Accession Number: 20180804823502
• Record 153 of
  
  Title:Microwave photonic fractional Hilbert transformer with an integrated optical soliton crystal micro-comb
  
  Author(s):Tan, Mengxi(1); Xu, Xingyuan(1); Corcoran, Bill(3); Wu, Jiayang(1); Boes, Andreas(2); Nguyen, Thach G.(2); Chu, Sai T.(4); Little, Brent E.(5); Morandotti, Roberto(6,7,8); Mitchell, Arnan(2); Moss, David J.(1)
  Source: arXiv  Volume:   Issue:   DOI: null  Published: October 8, 2019  
  Abstract:We report a photonic microwave and RF fractional Hilbert transformer based on an integrated Kerr micro-comb source. The micro-comb source has a free spectral range (FSR) of 50GHz, generating a large number of comb lines that serve as a high-performance multiwavelength source for the transformer. By programming and shaping the comb lines according to calculated tap weights, we achieve both arbitrary fractional orders and a broad operation bandwidth. We experimentally characterize the RF amplitude and phase response for different fractional orders and perform system demonstrations of real-time fractional Hilbert transforms. We achieve a phase ripple of Copyright © 2019, The Authors. All rights reserved.
  Accession Number: 20200468738
• Record 154 of
  
  Title:Phase-encoded RF signal generation based on an integrated 49GHz 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: arXiv  Volume:   Issue:   DOI: 10.48550/arXiv.1912.04122  Published: December 5, 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. Copyright © 2019, The Authors. All rights reserved.
  Accession Number: 20200436140
• Record 155 of
  
  Title:Integrated Optical Filter Using Spiral-Based Cascaded Mach-Zehnder Interferometers
  
  Author(s):Ge, Zhiqiang(1,2,4); Zeng, Chao(1); Gong, Yongkang(3); Zhang, Lingxuan(1); Wang, Guoxi(1,4); Wang, Leiran(1,4); Sun, Qibing(1); Si, Jinhai(2); Zhao, Wei(1,4); Zhang, Wenfu(1,4)
  Source: IEEE Photonics Journal  Volume: 11  Issue: 5  DOI: 10.1109/JPHOT.2019.2940564  Published: October 2019  
  Abstract:We have proposed a new compact integrated optical filter based on cascaded Mach-Zehnder interferometers (MZIs), and designed corresponding coupling structures without S-bend. The wavelength dependence and fabrication tolerance of coupling structures constructed in straight waveguides and bent waveguides were sufficiently analyzed by the finite-difference time-domain (FDTD) method. The results showed that the curved coupler possesses property of broadband with large fabrication tolerance. Specifically, for the presented 3 dB coupler incorporated with the asymmetric curved waveguides, the deviation of transmission remained below 2% at wavelength from 1.5 to 1.6 μm, which is greatly helpful to broadband spectral response of cascaded MZIs. By connecting curved couplers with spiral waveguides, a filter by means of two-stages cascaded MZIs was optimally demonstrated to realize a channel spacing of 10 nm. The spiral-based MZIs filter (SBMF) provides a new reference for MZIs filter limited by footprint and wavelength dependence. © 2009-2012 IEEE.
  Accession Number: 20200207984380
• Record 156 of
  
  Title:Retrieval of Hydrothermal CH4 Based on Interference Spectroscopy and PLS Methods
  
  Author(s):Liu, Qing-Song(1,2); Hu, Bing-Liang(1); Tang, Yuan-He(3); Yu, Tao(1); Wang, Xue-Ji(1,2); Liu, Yong-Zheng(1); Yang, Peng(4); Wang, Hao-Xuan(3)
  Source: Guang Pu Xue Yu Guang Pu Fen Xi/Spectroscopy and Spectral Analysis  Volume: 39  Issue: 8  DOI: 10.3964/j.issn.1000-0593(2019)08-2415-06  Published: August 1, 2019  
  Abstract:The methane (CH4) gas released by hydrothermal enters into the ocean and atmosphere successively by diffusing and causes inestimable effect on earth in physics, chemistry and biology. The principle and environment effect of abyssal hydrothermal still require further study because limited information is available about dissolved methane. In our previous work, we propose an optical passive imaging interference system (OPIIS) for the real-time detection and long-term observation of hydrothermal methane's concentration, temperature, and pressure. To accurately, stably, and rapidly obtain the information of hydrothermal methane from OPIIS's interferogram, this paper processes OPIIS's data by combining interference spectra and partial least squares (PLS) algorithm. We built three single-dependent variable models between methane radiance spectra and gas concentration, temperature and pressure, respectively. Then we can establish the PLS prediction model between interference fringes indirectly on the basis of relationship between interference fringes and radiance spectra, which can improve the capacity of resisting disturbance and stability of prediction models in practical application. On the basis of Lorentz profile, we build the deep ocean gas emission model different from atmosphere emission and obtain the synthetic methane radiance spectrum database at any concentration, temperature and pressure by using the methane spectral parameters from HITRAN2016 molecular spectroscopy database. The six spectral lines of methane in the range of 1.64~1.66 μm are selected for the PLS regression model between methane radiance spectra and gas concentration, temperature and pressure. Furthermore, this paper analyzes the contribution of number of training samples, interval of training samples and number of principal components to the improvement of the comprehensive performance of regression model. The 96 groups of concentration, temperature and pressure regression model are built by using different groups, intervals and principal components, and those regression models are cross-validated using 25 groups of prediction samples. The comparison results of those regression models' root mean square error of prediction (RMSEP) and coefficient of determination (R2) indicate that the change of single factors such as the number of training samples, the interval of training samples and the number of principal components can not improve the prediction model's comprehensive performance about prediction accuracy, stability, application scope and computation. Finally, the optimized model with balanced performance is determined with concentration, temperature and pressure application ranges at 5~375 mmol•L-1, 580~678 K, 10~34.5 MPa, training samples of concentration, temperature and pressure are 50 groups, 25 groups, 25 groups, intervals at 5 mmol•L-1, 2 K, 0.5 MPa, principal components are 2, 2, 5. The RMSEPs of concentration, temperature and pressure are 3.082×10-6, 0.977 0, 5.052×10-3, and R2s are 0.999 9, 0.998 9, 0.999 9, respectively. The prediction errors of concentration, temperature and pressure are ±1.21×10-7, ±3.63×10-3, ±9.49×10-4, and the corresponding precisions are ±45.4 nmol•L-1, ±2.5 K, ±3.3×10-2 MPa. The results indicate that this retrieval algorithm can accurately, stably, and rapidly obtain concentration, temperature and pressure of hydrothermal methane. © 2019, Peking University Press. All right reserved.
  Accession Number: 20194107528606