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Record 313 of
Title:Harmonic mode locking of dark and dark-bright pluses emission from a graphene-oxide ytterbium-doped fiber laser
Author(s):Lin, Rongyong(1); Wang, Yonggang(2); Zhang, Gelin(1); Yan, Peiguang(1); Zhao, Junqing(1); Li, Huiquan(1); Huang, Shisheng(1)
Source: Guangxue Xuebao/Acta Optica Sinica Volume: 34 Issue: DOI: 10.3788/AOS201434.s114014 Published: September 10, 2014
Abstract:Generation of harmonic mode locking (HML) of dark and dark-bright pulses in an Ytterbium-doped fiber (YDF)laser based on a graphene-oxide (GO) saturable absorber (SA) is investigated experimentally. Both the bunch of dark-bright pulses and high-order HML of bright pulses can be obtained in the cavity. The above operation states are switched by changing the polarization controller (PC) and the pump power. The 56th order harmonic of dark pulses is achieved. The HML of dark-bright pulses can be generated with order up to 6th, and the HML order of bright pulses is up to 1084th.
Accession Number: 20144100087836
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Record 314 of
Title:Power line detection from optical images
Author(s):Song, Biqin(1,2); Li, Xuelong(1)
Source: Neurocomputing Volume: 129 Issue: DOI: 10.1016/j.neucom.2013.09.023 Published: April 10, 2014
Abstract:Image-based power line detection is highly important for threat avoidance when the aerial vehicles fly in low altitude. However, it is very challenging for the requirements of high detection rates, low false alarms and real-time application. In this paper, a sequential local-to-global power line detection algorithm is proposed. In the local criterion, a line segment pool is detected by morphological filtering an edge map image, which is computed based on matched filter (MF) and first-order derivative of Gaussian (FDOG). It results in over detection to guarantee high detection rates. In the next global criterion, grouping the line segments into whole power lines is formulated as a graph-cut model based on graph theory. The principal advantage of the proposed algorithm is that it can detect not only the straight power lines but also the curve ones. Experimental results demonstrate that the algorithm has good performances both in detection accuracy and in processing time. ? 2013 Elsevier B.V.
Accession Number: 20140717320603
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Record 315 of
Title:Expanded-core waveguides written by femtosecond laser irradiation in bulk optical glasses
Author(s):Liu, Xin(1,2); Zhang, Wenfu(1); Zhao, Wei(1); Stoian, Razvan(3); Cheng, Guanghua(1)
Source: Optics Express Volume: 22 Issue: 23 DOI: 10.1364/OE.22.028771 Published: November 17, 2014
Abstract:Expanded-core structures based on layered increased index (type I) waveguiding traces are fabricated by ultrafast laser photoinscription in bulk optical glasses, with examples for fused silica and chalcogenide glasses. The expanded-core waveguides can serve for large-mode-area guiding concepts and their feasibility is experimentally investigated. A parametric study of the geometry, number of traces and index contrast indicates the possibility to design guided modes characteristics as exemplified in fused silica. A specific arrangement consisting of 8 traces of guiding layers with 6μm separation exhibit single-mode transport properties with mode field area of ～805μm2. The condition of single mode operation is also discussed in the frame of the dispersion relation of light guiding in periodical dielectric structures. The supported supermode of expanded-core structures can be controlled by careful design of the refractive index change, the number of guiding layers and the thickness of the interlayers. Inspection of the propagation characteristics shows equally low loss features. A Y-branching splitter based on expanded-core concept conserving single mode characteristics is fabricated. The optical design is equally successfully tested in chalcogenide Gallium Lanthanum Sulfide glass. Ultrafast laser inscribed expanded-core waveguiding provides therefore an interesting path of fabricating large mode area waveguides usable in near infrared and mid-infrared region beneficial for applications requiring high power or large mode dimensions. ?2014 Optical Society of America
Accession Number: 20144900290652
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Record 316 of
Title:Lazy random walks for superpixel segmentation
Author(s):Shen, Jianbing(1); Du, Yunfan(1); Wang, Wenguan(1); Li, Xuelong(2)
Source: IEEE Transactions on Image Processing Volume: 23 Issue: 4 DOI: 10.1109/TIP.2014.2302892 Published: April 2014
Abstract:We present a novel image superpixel segmentation approach using the proposed lazy random walk (LRW) algorithm in this paper. Our method begins with initializing the seed positions and runs the LRW algorithm on the input image to obtain the probabilities of each pixel. Then, the boundaries of initial superpixels are obtained according to the probabilities and the commute time. The initial superpixels are iteratively optimized by the new energy function, which is defined on the commute time and the texture measurement. Our LRW algorithm with self-loops has the merits of segmenting the weak boundaries and complicated texture regions very well by the new global probability maps and the commute time strategy. The performance of superpixel is improved by relocating the center positions of superpixels and dividing the large superpixels into small ones with the proposed optimization algorithm. The experimental results have demonstrated that our method achieves better performance than previous superpixel approaches. ? 2013 IEEE.
Accession Number: 20141117456310
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Record 317 of
Title:Noise model and simulation analysis of the low noise pre-amplifier of CCD camera
Author(s):Chen, Zhi(1); Qiu, Yuehong(1); Wen, Yan(1); Jiang, Baotan(1); Yao, Dalei(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9142 Issue: DOI: 10.1117/12.2054240 Published: 2014
Abstract:The low noise video process chain design is the important guarantee of realization of CCD detection performance. While pre-amplifier locate in the front end of the video signal process of CCD camera, so the low noise preamplifier design is the important guarantee of realization of low noise CCD camera. Firstly, calculate the bandwidth and equivalent noise bandwidth of video process chain of CCD camera. Secondly, design the preamplifier circuit and build the noise model of the preamplifier. Thirdly, according to the noise model calculation the noise of the pre-amplifier. Lastly, build the noise simulation model of the preamplifier. Through theoretical calculation and PSPICE simulation result predict the noise level of the preamplifier of the CCD.The noise level of the preamplifier less than 2 electronics, it meets specification requirement. ? 2014 Copyright SPIE.
Accession Number: 20141217474309
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Record 318 of
Title:Reflective carbon nanotube as the saturable absorber for mode-locked 1064 nm laser
Author(s):Fan, Mingwen(1); Ma, Baomin(2); Liu, Jie(1); Wang, Yonggang(3)
Source: Optik Volume: 125 Issue: 19 DOI: 10.1016/j.ijleo.2014.07.051 Published: 2014
Abstract:With a reflective single-walled carbon nanotube as the saturable absorber, a laser diode-pumped passively mode-locked Nd:YVO4 laser at 1064 nm was realized for the first time. The pulse duration of 12 ps was produced with a repetition rate of 83.7 MHz. The peak power and the single pulse energy of the mode-locking laser were 1.28 kW and 15.4 nJ, respectively. ? 2014 Elsevier GmbH. All rights reserved.
Accession Number: 20150700532408
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Record 319 of
Title:Giant Kerr nonlinearity induced by tunneling in triple quantum dot molecules
Author(s):Tian, Si-Cong(1); Wan, Ren-Gang(2); Tong, Cun-Zhu(1); Ning, Yong-Qiang(1); Qin, Li(1); Liu, Yun(1)
Source: Journal of the Optical Society of America B: Optical Physics Volume: 31 Issue: 7 DOI: 10.1364/JOSAB.31.001436 Published: July 1, 2014
Abstract:A scheme for giant enhancement of the Kerr nonlinearity in linear triple quantum dot molecules is proposed. In such a system, the tunneling-induced transparency window obtained in double quantum dot molecules splits into two windows, due to the coupling with the third quantum dot. And most important, the Kerr nonlinearity can be enhanced by several orders of magnitude, compared with that generated in double quantum dot molecules. With proper detuning of the tunneling, giant Kerr nonlinearity accompanied by vanishing absorption can be realized, which opens the possibility to enhance self-phase modulation in tunneling controllable semiconductor nanostructures under conditions of low light levels. Quantitative analysis shows that the giant Kerr nonlinearity is attributed to the interacting double dark resonances induced by the tunneling between the triple quantum dots, therefore no extra laser fields are required. ? 2014 Optical Society of America.
Accession Number: 20142817923511
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Record 320 of
Title:Image esthetic assessment using both hand-crafting and semantic features
Author(s):Guo, Lihua(1); Xiong, Yangchao(1); Huang, Qinghua(1); Li, Xuelong(2)
Source: Neurocomputing Volume: 143 Issue: DOI: 10.1016/j.neucom.2014.06.029 Published: November 2, 2014
Abstract:Automatically assessing the visual esthetics of images is of great interest in high-level vision research and has drawn much attention in recent years. Traditional methods heavily depend on the performance of subject region extraction. This paper proposes to use semantic features in the esthetic assessment system because they can implicitly represent the image topic and be helpful if the subject region extraction fails. Accordingly, a framework combining the hand-crafting features with semantic features is proposed to evaluate image esthetic quality. The experimental results show that the semantic features can improve the performance of image esthetic assessment. ? 2014 Elsevier B.V.
Accession Number: 20143118007247
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Record 321 of
Title:Intracavity-frequency-doubled Q-switched and mode-locked Nd:Lu 0.15Y0.85VO4/KTP green laser with AO modulator and central SESAM
Author(s):Feng, Tianli(1); Zhao, Shengzhi(1); Yang, Kejian(1); Li, Guiqiu(1); Li, Dechun(1); Zhao, Jia(1); Zhao, Bin(2); Wang, Yonggang(3)
Source: Optik Volume: 125 Issue: 12 DOI: 10.1016/j.ijleo.2014.01.009 Published: June 2014
Abstract:By using mixed crystal Nd:Lu0.15Y0.85VO4 as laser medium, KTP as frequency-doubling crystal, a diode-pumped intracavity-frequency-doubled Q-switched and mode-locked (QML) Nd:Lu 0.15Y0.85VO4/KTP green laser with acousto-optic (AO) modulator and central semiconductor saturable absorption mirror (C-SESAM) is realized by using a V-type cavity. The QML laser characteristics such as the pulse width, single-pulse energy, have been measured for different modulation frequencies of the AO modulator. In comparison with the singly passively QML green laser with central SESAM, the doubly QML green laser can generate more stable and shorter pulses with higher peak power. Based on the coupled rate equations for a diode-pumped doubly QML green laser with AO and C-SESAM, in which the saturated absorption mechanism of C-SESAM is considered, the recurrence relation of the relative amplitude of the mode-locking pulses is given and the related numerical simulations are in good agreement with the experimental results. ? 2014 Elsevier GmbH. All rights reserved.
Accession Number: 20142217757275
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Record 322 of
Title:An improved method of edge detection based on the mean shift algorithm
Author(s):Wei, Laixing(1); Liu, Bo(1); Mou, Jiao(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 9284 Issue: DOI: 10.1117/12.2069468 Published: 2014
Abstract:This paper proposes an improved method of edge detection based on the mean shift algorithm. A pixel of an image calculated by the mean shift algorithm eventually converges to a peak point of probability density of the image. The pixel which is farther from the peak point has a greater mean shift vector and higher probability to be an edge pixel. The gradient of the mean shift vector of an edge pixel is a local maximum. During the mean shift iterations, the mean shift vector decreases by steps. Therefore, the vector of the first step is representative, while it is unnecessary to calculate each pixel to its convergence. This reduces the amount of computation and promotes the efficiency of the algorithm in a large extent. First, the image is smoothed by the mean shift filter, and the gradient of the mean shift vector is computed. Then, the local maximum is found by using non-maxima suppression on the gradient, which thins the edges detected. Finally, dual-threshold is used to detect and link edges. The edges detected have more accuracy and continuity. Experimental results show that the proposed method outperforms the conventional methods while suppressing noise and preserving edges.
Accession Number: 20150800545997
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Record 323 of
Title:Three-DOF manipulator kinematics and dynamics analysis and simulation
Author(s):Shi, Heng(1); Liang, Yan-Bing(1)
Source: Shanghai Jiaotong Daxue Xuebao/Journal of Shanghai Jiaotong University Volume: 48 Issue: DOI: Published: October 28, 2014
Abstract:A 3-DOF manipulator is modeled in ADAMS. In MATLAB, inverse kinematics is solved by geometric method. The desired trajectory, angular velocity and angular acceleration of each joint are obtained by the high order polynomial interpolation to complete the kinematics planning of the manipulator. Kinematics equations were got by D-H method and dynamics equations were obtained by Lagrangian method according to angular variables, velocity and acceleration. In ADAMS, kinematics and dynamics simulation on the model are made respectively. Simulation results are consistent with theoretical calculations to verify the correctness of each other, which can provide an effective basis for the control of the manipulator and the selection of the appropriate drive system. ?, 2014, Shanghai Jiao Tong University. All right reserved.
Accession Number: 20151500741866
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Record 324 of
Title:Calibrating tracing errors for space-used telescope by coordinate transfor
Author(s):Cui, Kai(1); Liu, Zhaohui(1); Li, Zhiguo(1); Gao, Xiong(1); Xie, Youjin(1); Wang, Zhenyu(1)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 43 Issue: DOI: Published: December 25, 2014
Abstract:For better testing and calibrating the space-used telescope, a novel calculating model was introduced to simulate tracing process of the satellite. The coordinate transform theory was used for the indoor rotating target, the result was coincident with the spherical trigonometry. A model was deduced to illustrate the relationship between the tracing errors and the position errors of detecting system and the telescope gyration centre. The result showed that, a position error of 0.2 m in the vertical axis direction simply causing a constant elevation angle tracing error of 5.658 74°, without any influence on other tracing performance. An error of 0.002 m in the horizontal axis direction caused coupling tracing errors both in azimuth and elevation measurements, the azimuth angle tracing error ranged between 0.056 78°~0.139 25°, azimuth angular velocity error was 0.007 01° per second, the azimuth angular acceleration error was 0.002 56 degree per second square, while the elevation angle tracing error was about 10-4 order of magnitude, and the angular velocity and angular acceleration was about 10-6 order of magnitude. The tracing performance was independent of position error in the collimation axis direction. This conclusion provides reference for testing and assembling space-used telescope. ?, 2014, Chinese Society of Astronautics. All right reserved.
Accession Number: 20151400699929
