2013
2013
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Record 301 of
Title:Sparse coding for image denoising using spike and slab prior
Author(s):Lu, Xiaoqiang(1); Yuan, Yuan(1); Yan, Pingkun(1)Source: Neurocomputing Volume: 106 Issue: DOI: 10.1016/j.neucom.2012.09.014 Published: 2013Abstract:Sparse coding is a challenging and promising theme in image denoising. Its main goal is to learn a sparse representation from an over-complete dictionary. How to obtain a better sparse representation from the dictionary is important for the denoising process. In this paper, starting from the classic image denoising problem, a Bayesian-based sparse coding algorithm is proposed, which learns sparse representation with the spike and slab prior. Using the spike and slab prior, the proposed algorithm can achieve accurate prediction performance and effectively enforce sparsity. Experimental results on image denoising have demonstrated that the proposed algorithm can provide better representation and obtain excellent denoising performance. ? 2012 Elsevier B.V.Accession Number: 20131416156072 -
Record 302 of
Title:Effect of turbulence on visibility and signal-to-noise ratio of lensless ghost imaging with thermal light
Author(s):Yao, Yin-Ping(1,2); Wan, Ren-Gang(1); Zhang, Shi-Wei(1,2); Zhang, Tong-Yi(1)Source: Optik Volume: 124 Issue: 24 DOI: 10.1016/j.ijleo.2013.05.184 Published: December 2013Abstract:Lensless ghost imaging with thermal light through turbulent atmosphere is investigated. Based on the extended Huygens-Fresnel integral and the classical optical coherence theory, we derive the expressions for the visibility and signal-to-noise ratio (SNR) of lensless ghost imaging through turbulence. To show the effect of turbulence on the quality of lensless ghost imaging, we numerically calculate the visibility and SNR for different propagation distances and various turbulence strengths. Though turbulence degrades the image quality, specific visibility and SNR can be obtained for ghost imaging in certain propagation distances. ? 2013 Elsevier GmbH. All rights reserved.Accession Number: 20134316878004 -
Record 303 of
Title:Flexible optical clock recovery utilizing a multi-function semiconductor fiber laser
Author(s):Feng, H.(1,2); Zhao, W.(1); Xie, X.P.(1); Qian, F.C.(1); Wang, W.(1); Huang, X.(1); Hu, H.(1)Source: Laser Physics Volume: 23 Issue: 8 DOI: 10.1088/1054-660X/23/8/085109 Published: August 2013Abstract:We demonstrate a multi-function fiber laser based on cross-gain modulation in a semiconductor optical amplifier (SOA). Depending on the input signals, the fiber cavity can emit a continuous wave (CW) laser, mode-locked pulses, or act as a clock recovery device. With an extra CW light overcoming the pattern effect in the clock recovery process, a 10-GHz synchronous clock sequence withAccession Number: 20133016544404 -
Record 304 of
Title:Numerical analysis of Ytterbium-doped double-clad fiber lasers based on the temperature-dependent rate equation
Author(s):Shao, Hongmin(1,2); Duan, Kailiang(1); Zhu, Yonggang(1); Yan, Hongwei(1); Yang, Hening(1); Zhao, Wei(1)Source: Optik Volume: 124 Issue: 20 DOI: 10.1016/j.ijleo.2013.02.017 Published: October 2013Abstract:The effects of temperature on the output power and optimal conditions of Ytterbium-doped double-cladding fiber lasers (YDDFLs) are discussed. Temperature-dependent rate equations for YDDFLs based on Boltzmann distribution are built in two-end pump model. The results show that the output power and the slope efficiency decrease with the increase of temperature. The increase of pump power results in that the effect of the temperature on the output performance increases, and the fiber length is a factor that the effect of the temperature depends on really. Moreover we combine the heat distribution formula with the rate equations and compare the numerical results considering with that not considering the temperature-dependence inside laser cavity, the effect of temperature can be ignored only when the pump power is lower, and the optimal fiber length becomes longer when considering the temperature-dependence. ? 2013 Elsevier GmbH.Accession Number: 20133616704274 -
Record 305 of
Title:Heterogeneous image transformation
Author(s):Wang, Nannan(1,2); Li, Jie(1); Tao, Dacheng(2); Li, Xuelong(3); Gao, Xinbo(1)Source: Pattern Recognition Letters Volume: 34 Issue: 1 DOI: 10.1016/j.patrec.2012.04.005 Published: January 1, 2013Abstract:Heterogeneous image transformation (HIT) plays an important role in both law enforcements and digital entertainment. Some available popular transformation methods, like locally linear embedding based, usually generate images with lower definition and blurred details mainly due to two defects: (1) these approaches use a fixed number of nearest neighbors (NN) to model the transformation process, i.e.; K-NN-based methods; (2) with overlapping areas averaged, the transformed image is approximately equivalent to be filtered by a low pass filter, which filters the high frequency or detail information. These drawbacks reduce the visual quality and the recognition rate across heterogeneous images. In order to overcome these two disadvantages, a two step framework is constructed based on sparse feature selection (SFS) and support vector regression (SVR). In the proposed model, SFS selects nearest neighbors adaptively based on sparse representation to implement an initial transformation, and subsequently the SVR model is applied to estimate the lost high frequency information or detail information. Finally, by linear superimposing these two parts, the ultimate transformed image is obtained. Extensive experiments on both sketch-photo database and near infrared-visible image database illustrates the effectiveness of the proposed heterogeneous image transformation method. ? 2012 Elsevier B.V. All rights reserved.Accession Number: 20124715687932 -
Record 306 of
Title:The factors of spontaneous parametric down conversion process in BiB 3O6 crystal with a broadband pump
Author(s):Huo, Guangwen(1,2); Zhang, Tongyi(1); Wan, Rengang(1); Cheng, Guanghua(1); Zhao, Wei(1)Source: Optik Volume: 124 Issue: 24 DOI: 10.1016/j.ijleo.2013.05.114 Published: December 2013Abstract:We investigate the spontaneous parametric down-conversion (SPDC) process in biaxial nonlinear crystal BiB3O6 (BIBO) with a broadband pump. Under the type I and type II phase-matching conditions, we numerically calculate the influencing factors on SPDC process in BIBO crystal, such as temporal and spatial walk-off, the acceptance angles, and spectral acceptance bandwidth. Comparing the two types of phase-matching, we could conclude that the type II phase-matching in BIBO crystal is better for the SPDC because of zero dispersion and bigger acceptance parameters. These results can be used to construct a system to generate ultra-fast entangled photon pairs. ? 2013 Elsevier GmbH. All rights reserved.Accession Number: 20134316878069 -
Record 307 of
Title:Dependence of ultra-short electron packet broadening on external electric field
Author(s):Wang, Chao(1); Tian, Jinshou(1); Kang, Yifan(2); Li, Hao(1,3); Liu, Hulin(1)Source: Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology Volume: 33 Issue: 2 DOI: 10.3969/j.issn.1672-7126.2013.02.04 Published: February 2013Abstract:Boersch effect of electron pulse broadening was modeled and analyzed, based on the existing results reported in literature. A theory to characterize the electron packet broadening was formulated, with the time dispersion characteristics as the major factor. The influence of the external electric field on the ultra-short electron packet broadening was evaluated, in the newly-developed theory. The results show that the external e-field, accelerating the electrons, suppresses the broadening; whereas the field, decelerating electrons, widens the broadening. In image-converter streak cameras and ultra-fast electron diffraction devices, there exist one non-equipotential and two known equi-potential regions: one situates in the vicinity of photocathode, the other lies behind the deflection plate. Our preliminary results are of much technological interest for design of high-performance electron gun, because significant time broadening originates from the transit of the photoelectron packet in the potential decreasing direction.Accession Number: 20131216136120 -
Record 308 of
Title:Low-repetition rate, nanosecond, high-power pulse amplifier system based on Yb-doped rod-type fiber
Author(s):Yu, Jia(1,2); Zhao, Wei(1); Wang, Yishan(1); Yang, Zhi(1,2); Gao, Cunxiao(1); Linquan, Niu(1,2); Zhang, Ting(1)Source: Chinese Optics Letters Volume: 11 Issue: 5 DOI: 10.3788/COL201311.050601 Published: May 2013Abstract:We report a nanosecond-pulse amplification system based on an Yb-doped, 100-μm core, rod-type photonic crystal fiber. Up to 10W of average power with pulse energy of 1 mJ and peak power of 450 kWis obtained at the repetition rate of 10 kHz. The high-power nanosecond pulse has a good pulse shape and spectral characteristics. The usage of rod-type fibers provides a novel structure for nanosecond pulse amplification. ? 2013 Chinese Optics Letters.Accession Number: 20132616449035 -
Record 309 of
Title:A new method of processing high-precision micro-hole with the femtosecond laser
Author(s):Yang, Xiaojun(1); Li, Ming(1); Wang, Li(2); Zhao, Hualong(1); Cheng, Guagnhua(1)Source: Applied Mechanics and Materials Volume: 268 Issue: PART 1 DOI: 10.4028/www.scientific.net/AMM.268-270.382 Published: 2013Abstract:Based on the femtosecond laser processing technology and PZT driving scanning technology, high-precision micro- manufacturing technology is developed. By adjusting the laser parameters and scanning parameters to get micro-hole machining on the flat or curved surface. Hole's size and surface morphology is observed by using phase contrast microscopy and scanning electron microscopy observations, and the surface roughness is analyzed by the surface profile instrument. The feasibility of diesel injector nozzle processing is verified in practical industry applications. The results show that this method of making micro hole has significant advantages, such as high precision, good consistency, without burrs, good surface roughness and high efficiency. These characteristics can meet the practical application requirements and can be used in various industrial fields. ? (2013) Trans Tech Publications, Switzerland.Accession Number: 20130415941264 -
Record 310 of
Title:Structured illumination for resolution enhancement and autofocusing in digital holographic microscopy
Author(s):Gao, Peng(1,2); Pedrini, Giancarlo(1); Osten, Wolfgang(1)Source: Optics Letters Volume: 38 Issue: 8 DOI: 10.1364/OL.38.001328 Published: April 15, 2013Abstract:In this Letter we show how resolution enhancement and autofocusing in digital holographic microscopy is obtained by using structured illumination generated by a spatial light modulator, which enables it to project fringes of different orientations and phase shift without mechanical movement. The image plane is numerically determined by searching for the minimal deviation between the reconstructed images carried by different diffraction orders of the structured illuminations. ? 2013 Optical Society of America.Accession Number: 20131816287591 -
Record 311 of
Title:The damage property of oxyfluoride glasses irradiated by a 351 nm high fluence laser
Author(s):Hou, Chaoqi(1,2); Li, Weinan(1); Wang, Pengfei(1); Guo, Haitao(1); Gao, Fei(1); Cui, Xiaoxia(1); Lu, Min(1); Peng, Bo(1)Source: Laser Physics Volume: 23 Issue: 7 DOI: 10.1088/1054-660X/23/7/076005 Published: July 2013Abstract:The laser induced damage property of oxyfluoride glasses irradiated by a 351 nm laser has been investigated. Two kinds of oxyfluoride glass (oxyfluoride1 and oxyfluoride2) have been prepared by different preparation technologies and their LIDTs (laser induced damage thresholds) are 9.0 J cm-2 and 13.6 J cm-2 respectively. It is found that the variation of LIDT in oxyfluoride glasses is associated with photoluminescence originated structural defects. Decrease of the photoluminescence intensity in an oxyfluoride glass could improve the LIDT of the material. Meanwhile, an experiment on damage growth has been presented, and the damage growth of oxyfluoride glasses develops in the longitudinal direction of laser propagation, which causes the transmittance loss to be limited once the damage growth occurs. Moreover, the damage growth stops when the laser fluence is below 70% of the LIDT. ? 2013 Astro Ltd.Accession Number: 20132516432311 -
Record 312 of
Title:Two-dimensional sub-half-wavelength atom localization via phase control of absorption and gain
Author(s):Wan, Ren-Gang(1); Zhang, Tong-Yi(1); Kou, Jun(2)Source: Physical Review A - Atomic, Molecular, and Optical Physics Volume: 87 Issue: 4 DOI: 10.1103/PhysRevA.87.043816 Published: April 15, 2013Abstract:We propose a scheme for two-dimensional atom localization based on the coherent controlled absorption and gain of a weak probe field in a four-level double-Λ system, in which the atom interacts with two orthogonal standing-wave fields. Owing to the space-dependent atom-field interaction, the position probability distribution of the atom passing through the standing waves can be directly determined by measuring the resulting absorption and gain spectra. The phase-sensitive property of the atomic system significantly reduces the uncertainty in the position measurement of the atom. It is found that, by properly varying the parameters of the system, we can achieve sub-half-wavelength atom localization with high precision. Especially the probability of finding the atom at a particular position can be 100% when a photon with certain frequency is absorbed or amplified. Numerical calculations and qualitative analyses show that the enhancement of precision in the position measurement of the atom is attributed to the interference between the one-photon excitation and the phase-dependent three-photon excitation from the closed interacting contour in the laser-driven atomic system. ? 2013 American Physical Society.Accession Number: 20131716229854