2013
2013
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Record 229 of
Title:Modal characteristics analysis of a doubly clad optical fiber with semi-weakly guiding approximation
Author(s):Tan, Xuefei(1,2); Liu, Xianglian(1,2); Zhao, Wei(1); Li, Cheng(1); Wang, Yishan(1); Li, Jianfeng(3)Source: Optics Communications Volume: 294 Issue: DOI: 10.1016/j.optcom.2012.11.080 Published: May 1, 2013Abstract:Modified characteristic equations for doubly clad multimode fibers were rigorously derived under semi-weakly guiding approximation in this article. The analytical expressions of the power flows distributed in the three regions of fiber cross section are also given. Different from previous works, results in this paper elucidate that, other than the inner cladding, the refractive indices also hold a non-ignorable influence on the modal power distribution and mode behaviors. By comparing the results of two models, this article demonstrates that the singly clad fiber model may not be suitable for analyses of common doubly clad fibers. ? 2012 Elsevier B.V.Accession Number: 20131416178299 -
Record 230 of
Title:A passively Q-switched Yb:YAG laser with a single-walled carbon nanotube saturable absorber
Author(s):Chu, Hongwei(1); Zhao, Shengzhi(1); Yang, Kejian(1); Li, Yuefei(1); Li, Dechun(1); Li, Guiqiu(1); Zhao, Jia(1); Xu, Xiaodong(2); Di, Juqing(2); Zheng, Lihe(2); Xu, Jun(2); Wang, Yonggang(3)Source: Laser Physics Volume: 23 Issue: 6 DOI: 10.1088/1054-660X/23/6/065002 Published: June 2013Abstract:A diode-end-pumped passively Q-switched Yb:YAG bulk laser with a single-walled carbon nanotube saturable absorber is presented. A maximum output power of 715 mW has been obtained with a slope efficiency of 15.7%. The minimum pulse width of 88 ns was achieved at a repetition rate of 175 kHz, corresponding to a pulse energy of 4:1 μJ and a peak power of 46.2 W. ? 2013 Astro Ltd.Accession Number: 20132216369208 -
Record 231 of
Title:Low repetition rate subnanosecond pulse laser generation from a diode pumped Nd:Lu3Al5O12 laser with electro-optic modulator and transmission semiconductor saturable absorber
Author(s):Chang, L.(1); Zhao, S.Z.(1); Yang, K.J.(1); Zhao, J.(1); Zheng, L.H.(2); Xu, X.D.(2); Di, J.Q.(2); Xu, J.(2); Wang, Y.G.(3)Source: Journal of the Optical Society of America B: Optical Physics Volume: 30 Issue: 10 DOI: 10.1364/JOSAB.30.002710 Published: October 1, 2013Abstract:By using the dual-loss modulated technology, i.e., adopting the electro-optic (EO) modulator and transmission semiconductor saturable absorber (transmission SSA) simultaneously, a diode-pumped doubly Q-switched and mode-locked (QML) Nd:Lu3Al5O12 (Nd:LuAG) laser at 1.06 μm has been realized for the first time. In comparison to the singly passively QML Nd:LuAG laser with transmission SSA, the doubly QML laser can generate more stable pulses with shorter pulse widths and higher peak powers. It can also be observed that the pulse duration of the Q-switched envelope decreases with increasing pump power. When the pump power exceeds 6.52 W for the first time, there is only one mode-locked pulse underneath a Q-switched envelope for this doubly QML Nd:LuAG laser. As a result, the subnanosecond pulse laser with 1 kHz repetition rate of EO and high stability canbe generated. The shortest pulse duration generated is about 718 ps and the highest peak power reaches as high as 502 kW. The experimental results show that Nd:LuAGis an excellent alternative crystal for diode-pumped QML pulsed laser generation. ? 2013 Optical Society of America.Accession Number: 20134216867588 -
Record 232 of
Title:Design of visual light and middle infrared zoom optical system
Author(s):Du, Yujun(1); Gao, Ming(1); Xin, Weijuan(1); He, Yinghong(2)Source: Applied Mechanics and Materials Volume: 246-247 Issue: DOI: 10.4028/www.scientific.net/AMM.246-247.413 Published: 2013Abstract:In order to achieve wide range for target search and monitor in all-weather, a zoom optical system with long focus length is designed which is used for visual light and middle infrared observation in this paper. In this system, the visible and infrared optical paths share a fixed R-C mirror in the foreside, on whose image surface the parallel plates is used to separate the light beam. Then the dual wavelength band zoom is achieved by two optical transmitted systems whose aperture is 100mm, Zoom range is 300mm~900mm for visual light and 250mm~750mm for middle infrared.This system has stable image and good imaging quality, satisfies the requirements of the application. ? (2013) Trans Tech Publications, Switzerland.Accession Number: 20130515974016 -
Record 233 of
Title:Dynamic focus-position detection technique with array camera in long focal length system
Author(s):Zhao, Juanning(1,2); Dong, Xiaona(1); Da, Zhengshang(1); Li, Hongguang(1)Source: Key Engineering Materials Volume: 552 Issue: DOI: 10.4028/www.scientific.net/KEM.552.484 Published: 2013Abstract:A precise detection technique with array camera is discussed for the detection of dynamic focus position in this paper. This technique is well applicable for measuring the focal spot shifting of large and slow lens or optical systems. Two coated wedges are adopted in light path to supply bands of beams, which form the spots matrix on the detector. Focus position shifting can be indirectly obtained from position shifting of the smallest spot on the detector. The technology discussed here is simple and accurate; it also solves the problem that dynamical focal spot position shifting is immeasurable for conventional focal length measureing methods. ? (2013) Trans Tech Publications, Switzerland.Accession Number: 20133016543386 -
Record 234 of
Title:Large-scale networked multi-axis control solution using EtherCAT and soft logic
Author(s):Cheng, Zhiyuan(1); Ma, Qing(2); Yan, Minqi(1); Zhang, Yu(1)Source: Telkomnika - Indonesian Journal of Electrical Engineering Volume: 11 Issue: 9 DOI: 10.11591/telkomnika.v11i9.3271 Published: 2013Abstract:Aiming at the deficiencies of the traditional multi-axis control solution such as complex networked structure, poor clustered-control feature and unsatisfactory engineering practicability, the paper firstly optimized the existing solution in networked fieldbus, controller model, engineering reliability and maintainability. Then it proposed a novel solution combined high speed real-time EtherCAT (Ethernet for control Automation Technology) fieldbus with soft logic controller. The new solution took advantage of extraordinary real-time performance of EtherCAT and made good use of powerful clustered-control architecture of soft logic controller. Thus the new solution is concise and effective to solve the Large-scale networked controlling problem of 1100 distributed motors. Compared with the traditional schemes, the engineering practice shows that the novel solution has the advantage of perfect real-time performance, powerful clustered-control capability, flexible and variable networked structure, excellent engineering practicability. The novel solution is worth using for reference in solve similar large-scale networked controlling problems. ? 2013 Universitas Ahmad Dahlan.Accession Number: 20134016808221 -
Record 235 of
Title:Learning discriminative key poses for action recognition
Author(s):Liu, Li(1); Shao, Ling(1,2); Zhen, Xiantong(1); Li, Xuelong(3)Source: IEEE Transactions on Cybernetics Volume: 43 Issue: 6 DOI: 10.1109/TSMCB.2012.2231959 Published: December 2013Abstract:In this paper, we present a new approach for human action recognition based on key-pose selection and representation. Poses in video frames are described by the proposed extensive pyramidal features (EPFs), which include the Gabor, Gaussian, and wavelet pyramids. These features are able to encode the orientation, intensity, and contour information and therefore provide an informative representation of human poses. Due to the fact that not all poses in a sequence are discriminative and representative, we further utilize the AdaBoost algorithm to learn a subset of discriminative poses. Given the boosted poses for each video sequence, a new classifier named weighted local naive Bayes nearest neighbor is proposed for the final action classification, which is demonstrated to be more accurate and robust than other classifiers, e.g., support vector machine (SVM) and naive Bayes nearest neighbor. The proposed method is systematically evaluated on the KTH data set, the Weizmann data set, the multiview IXMAS data set, and the challenging HMDB51 data set. Experimental results manifest that our method outperforms the state-of-the-art techniques in terms of recognition rate. ? 2013 IEEE.Accession Number: 20135117094981 -
Record 236 of
Title:Embedding motion and structure features for action recognition
Author(s):Zhen, Xiantong(1); Shao, Ling(1); Tao, Dacheng(2); Li, Xuelong(3)Source: IEEE Transactions on Circuits and Systems for Video Technology Volume: 23 Issue: 7 DOI: 10.1109/TCSVT.2013.2240916 Published: July 2013Abstract:We propose a novel method to model human actions by explicitly coding motion and structure features that are separately extracted from video sequences. Firstly, the motion template (one feature map) is applied to encode the motion information and image planes (five feature maps) are extracted from the volume of differences of frames to capture the structure information. The Gaussian pyramid and center-surround operations are performed on each of the six obtained feature maps, decomposing each feature map into a set of subband maps. Biologically inspired features are then extracted by successively applying Gabor filtering and max pooling on each subband map. To make a compact representation, discriminative locality alignment is employed to embed the high-dimensional features into a low-dimensional manifold space. In contrast to sparse representations based on detected interest points, which suffer from the loss of structure information, the proposed model takes into account the motion and structure information simultaneously and integrates them in a unified framework; it therefore provides an informative and compact representation of human actions. The proposed method is evaluated on the KTH, the multiview IXMAS, and the challenging UCF sports datasets and outperforms stateof-the-art techniques on action recognition.?2013 IEEE.Accession Number: 20141117451271 -
Record 237 of
Title:Design & development of multi-mode integrated timing device
Author(s):Ke, Xizheng(1); Liu, Juanhua(1); Li, Jianxun(1,2)Source: Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument Volume: 34 Issue: 6 DOI: Published: June 2013Abstract:A multi-mode combined timing device was designed based on multi-scale data fusion theory, which can output the time frequency signal with higher precision by combining the GPS, GLONAS and Beidou timing signals. Firstly, the GPS, GLONAS and Beidou timing signals are decomposed respectively in different wavelet scales. Secondly, the wavelet coefficients of these signals in the same scale are synthesized with wavelet weighting method scale by scale. Thirdly, inverse wavelet transform is used to reconstruct the signal that represents the timescale. The new timescale is in step with UTC theoretically. Test result shows that after disciplining the local oscillators, the frequency stability of the device reaches to 10-12, which is higher than that of the single-mode device by one order of magnitude.Accession Number: 20133016534351 -
Record 238 of
Title:Research on microsphere array laser in circulating state pumped by LDA
Author(s):Ding, Jianyong(1); Gui, Luo(2); Zhao, Pengfei(3); Peng, Bo(3); Wei, Wei(1)Source: Zhongguo Jiguang/Chinese Journal of Lasers Volume: 40 Issue: 10 DOI: 10.3788/CJL201340.1002010 Published: October 2013Abstract:A novel laser gain medium, microsphere array cooled by refractive index-matched coolant, is presented in response to the thermal management of high-power solid-state lasers in this paper. Experiments on microsphere array lasers in circulating state are carried out. The emission spectra and flourescence decay curves are measured. Besides, the stable pulse output energy is achieved and its laser characteristics are studied. The maximum pulse energy of microsphere array laser with diameters of 2 mm and 4 mm are 30.2 mJ and 115.4 mJ, respectively at a repetition rate of 1 Hz, and the corresponding slope efficiencies are 4.6% and 16.2%, respectively. Output energy decreases as pumping frequency increases. Experimental results show that the microsphere array laser has relatively good thermal performance and thermal stability, and can be used in high-power laser systems.Accession Number: 20134917058169 -
Record 239 of
Title:Numerical analysis of temporal response of a large exponential-doping transmission-mode GaAs photocathode
Author(s):Cai, Zhipeng(1); Yang, Wenzheng(2); Tang, Weidong(1); Hou, Xun(1)Source: Materials Science in Semiconductor Processing Volume: 16 Issue: 2 DOI: 10.1016/j.mssp.2012.09.011 Published: April 2013Abstract:The theory of temporal response properties for a large exponential-doping transmission mode GaAs photocathode is discussed in detail. By the introduction of a new concept referred to as average decay time, the deficiency usually caused by the boundary condition in the previous calculations is effectively eliminated. The analytical results show that the response time of the new GaAs photocathode can be significantly reduced to several picoseconds in the absence of bias. In addition, the thickness of the GaAs absorption layer we obtained is much larger than that of traditional GaAs photocathodes with the same response time, which means that the novel photocathode with ultrafast time response will have higher yield, especially in near-infrared region. ? 2012 Elsevier Ltd.Accession Number: 20131316145054 -
Record 240 of
Title:Photo-thermal sensitive characters and reflective index variation of photo-thermo-reflective glass
Author(s):Li, Dancui(1,2); Li, Weinan(1); Lu, Min(1); Wang, Pengfei(1)Source: Optoelectronics and Advanced Materials, Rapid Communications Volume: 7 Issue: 1-2 DOI: Published: 2013Abstract:The photo-thermo-reflective (PTR) glass is fabricated by the high temperature and melting process. The sample is characterized by differential scanning calorimetry (DSC), Ultraviolet-visible-near infrared spectroscopy, and X-ray diffraction (XRD). The experiment results show that NaF crystalis deposited in glass, the amount and the size of crystal phase precipitation can be achieved by controlling exposure dosage and time, thermal development temperature and time. At the same time, the reflective-index variation, about 5×10-4, was measured by interference measuring method.Accession Number: 20203409072516