2013
2013
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Record 133 of
Title:Simulation of laser beam propagation through the troposphere
Author(s):Wang, Bao-Feng(1,2); Luo, Xiu-Juan(1); Zhang, Yu(1,2); Zeng, Zhi-Hong(1,2); Wang, Feng(1,2)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 8905 Issue: DOI: 10.1117/12.2032170 Published: 2013Abstract:Understanding and predicting laser beam propagation effects in the atmosphere is important for laser applications. Turbulence effects cause beam wander, beam broadening, intensity scintillations, which reducing the power in bucket and the tracking accuracy, etc. In this work, the phase screens are used to model atmosphere turbulence in the model of the laser propagation through troposphere. And according to the characteristics of the troposphere, a layered model is used. Laser propagation follows the Huygens-Fresnel principle between phase screens. Simulations with different grid point numbers were constructed, and numerical experiments were conducted. According to the simulated results including Strehl ratio, sharpness, and amplitude distribution, preceding phase screens have effect on the total energy of the receiving surface, but have little impact on amplitude distribution. And the phase screens, which are close to the receiving surface, have a significant impact on both amplitude distribution and the total receiving energy. The results suggests that in simulation one should increase grid point numbers as many as possible and needs to pay particular attention to parameters of the phase screens near the receiving surface in simulation. ? 2013 SPIE.Accession Number: 20134817032685 -
Record 134 of
Title:A new reduction technique for thermospheric wind and temperature measurement with Fabry-Perot interferometer
Author(s):Wang, Hong(1,2); Liu, Xuebin(1); Feng, Yutao(1); Bai, Qinglan(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 33 Issue: 11 DOI: 10.3788/AOS201333.1130003 Published: November 2013Abstract:The principle of measuring thermospheric wind and temperature by Fabry-Perot interferometer (FPI) is elaborated, the transfer function of FPI and the analytical response expression to the incident line is studied. Referring to the basic principle of traditional wind and temperature retrieval method with FPI, a new matrix reduction technique is proposed. This technique is based on the decompose and approximate mathematics to obtain the matrix form of analytical response expression, then a least-squares technique is employed to get the thermospheric wind and temperature. Simulation results show that when the guessed wind is less than 150 m/s and the guessed temperature is less than 80 K, the error range is ±3 m/s for wind and ±10 K for temperature. The matrix technique not only retains the accuracy of a full Fourier Series Representation method, but also avoids instrument calibration and wavelength translation, which makes it simple and fast.Accession Number: 20140317203849 -
Record 135 of
Title:The orthogonal verification model based on the on-chip coordinate rotation digital computer
Author(s):Li, Tie-Feng(1,2); Ma, Cai-Wen(1); Li, Wen-Hua(1)Source: Beijing Youdian Daxue Xuebao/Journal of Beijing University of Posts and Telecommunications Volume: 36 Issue: 3 DOI: 10.13190/jbupt.201303.36.litf Published: June 2013Abstract:In order to improve the verification efficiency of coordinate rotation digital computer (CORDIC), a new verification model that derives from orthogonal statics theory is proposed. Using this model, we set up orthogonal tables with the test factors, and choose the best optimized test method to verify according to orthogonal tables results. Moreover, the proposed model can randomly generate test vectors and automatically check the precision errors of CORDIC calculation results. Simulation results show that the orthogonal model can greatly cut down verification period and improve working efficiency.Accession Number: 20133416650702 -
Record 136 of
Title:The design of a hybrid diffractive-refractive wide-angle eyepiece with a large exit pupil distance
Author(s):Wang, Feng(1,2); Cao, Jian-Zhong(1); Qu, En-Shi(1); Yu, Deng-Qun(1,2); Yan, A. Qi(1,2); Zhang, Jian(1); Guo, Hui-Nan(1,2); Zhao, Xiao-Dong(1,2); Fan, Zhe-Yuan(1,2); Tao, Jin-You(1,2)Source: Advanced Materials Research Volume: 710 Issue: DOI: 10.4028/www.scientific.net/AMR.710.469 Published: 2013Abstract:The diffractive optical elements, with the negative dispersive characteristic and the random phase distributing to realize random phase modulation for wave-front, are not only helpful to simplify the optical system, but also improve the image quality, while putting it into the optical system. It can decrease the element numbers of the system and obtain a compact configuration that introducing diffractive optical element into the design of eyepiece. A hybrid diffractive-refractive wide-angle eyepiece, with a big exit pupil distance, is designed by using the Code V Optical Design Software. The features of the wide-angle eyepiece are 30mm effective focal length, 60°whole field-of-view (FOV), 30mm exit pupil distance and 6mm exit pupil diameter, and which consists of four lens and two diffractive elements. From the result of design, the MTF in the center field of the wide-angle eyepiece is over 0.55at 60lp/mm, at the same time, the MTFs in all fields are over 0.3 at 50lp/mm, which show that this wide-angle eyepiece has a great image quality. ? (2013) Trans Tech Publications, Switzerland.Accession Number: 20133016530649 -
Record 137 of
Title:Greedy regression in sparse coding space for single-image super-resolution
Author(s):Tang, Yi(1); Yuan, Yuan(1); Yan, Pingkun(1); Li, Xuelong(1)Source: Journal of Visual Communication and Image Representation Volume: 24 Issue: 2 DOI: 10.1016/j.jvcir.2012.02.003 Published: February 2013Abstract:Based on the assumption about the sparse representation of natural images and the theory of compressed sensing, very promising results about single-image super-resolution were obtained by an excellent algorithm introduced by Yang et al. [45]. However, their success could not be well explained theoretically. The lack of theoretical insight has hindered the further improvement of the algorithm. In this paper, Yang's algorithm is revisited in the view of learning theory. According to this point, Yang's algorithm can be considered as a linear regression method in a special feature space which is named as sparse coding space by us. In fact, it has been shown that Yang's algorithm is a result of optimal linear estimation in sparse coding space. More importantly, our theoretical analysis suggests that Yang's algorithm can be improved by using more flexible regression methods than the linear regression method. Following the idea, a novel single-image super-resolution algorithm which is designed based on the framework of L2-Boosting is proposed in the paper. The experimental results show the effectiveness of the proposed algorithm by comparing with other methods, which verify our theoretical analysis about Yang's algorithm. ? 2012 Elsevier Inc. All rights reserved.Accession Number: 20140617267198 -
Record 138 of
Title:Design of long-wave infrared scan system with rotating dual-wedge prism
Author(s):Fan, Zheyuan(1,2); Gao, Limin(1); Yang, Hongtao(1,2); Chen, Weining(1); Cao, Jianzhong(1); Zhang, Jian(1); Zhang, Zhi(1)Source: Key Engineering Materials Volume: 552 Issue: DOI: 10.4028/www.scientific.net/KEM.552.27 Published: 2013Abstract:Due to the possession of advantages of passivity working mode, good disguise, and easy observation, infrared systems are used in a wide variety of applications. This paper using 640×480 uncooled detector designed a long-wave scan optical system with large field and large aperture working at 8.0μm～12μm, the Pixel Dimensions of the detector is 30μm. The F number of this system is 1.4 and focal length is 17mm, FOV is 63.6°, which extended to 143° by adopting dual-wedge prism rotating, the paper also given the extended field theory by the dual-wedge prism. Because there are a limited number of lens materials used in LWIR spectral bands, Germanium material and three aspheric surfaces were adopted to balance sphere aberrations and chromatic aberration. All above mentioned are intending to ensure the system has good imaging quality. The results show that the optical performance approximates to the diffraction limit and the design has better achromatic performance. The modulation transfer function (MTF) is above 0.5 at spatial frequency of 20lp/mm, energy concentration ratio is greater than 70% within the sensing element of the detector and Root Mean Square (RMS) value of spot diameter is smaller than the Pixel Dimensions. The system has advantages of simple structure, large aperture, high image quality etc. ? (2013) Trans Tech Publications, Switzerland.Accession Number: 20133016543308 -
Record 139 of
Title:Design of thermal stable Fabry-Perot etalon for wind measurement
Author(s):Sun, Jian(1); Feng, Yu-Tao(1); Bai, Qing-Lan(1); Wang, Yong-Mei(2); Wen, De-Sheng(1)Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 21 Issue: 5 DOI: 10.3788/OPE.20132105.1167 Published: May 2013Abstract:In consideration of the effect of thermal stability of a Fabry-Perot(F-P) etalon in the satellite-borne F-P interferometer on wind measurement, this paper analyzes the thermal stability of the F-P etalon from its construction design including materials, shapes and fixed forms, then, it optimizes the design. With optimization design, the optical elements in the etalon are constructed, which shows that the two plates are all 25 mm thick, and the spacers are all 40° in angles. Then, the dimensions of mechanical structure of the etalon are calculated using flexible structure. Finally, the thermal distortions of optical elements and the etalon are discussed. It shows that the gap dimension changes in the centers of the optical elements and the etalon are 0.64 nm and 0.28 nm and the gap dimension change of the etalon is 0.2 nm when the temperature changes 0.1°C. Furthermore, the airglow spectral lines are ~λ/2250 and ~λ/3150 at 630 nm respectively, and the gap dimension changes of the etalon fall along the radius from the center to the verge. These results demonstrate that optimized structure parameters meet the requirements of measuring accuracy for thermal stability and mechanical stability at a wind velocity of 5 m/s.Accession Number: 20132516429250 -
Record 140 of
Title:Ultra-short pulse laser deep drilling of C/SiC composites in air
Author(s):Wang, Chunhui(1); Zhang, Litong(1); Liu, Yongsheng(1); Cheng, Guanghua(2); Zhang, Qing(1); Hua, Ke(1)Source: Applied Physics A: Materials Science and Processing Volume: 111 Issue: 4 DOI: 10.1007/s00339-012-7377-5 Published: June 2013Abstract:Ultra-short pulse laser machining is an important finishing technology for high hardness materials. In this study, it demonstrated that the ultra-short pulse laser can be used to drill the film cooling holes and square holes in aero-engine turbine blades made of C/SiC composites. Both the edges and bottoms of the drilling holes are covered with small particles. The following factors have a great effect on drilling holes according to this work: (1) circular holes can be processed only at a relative small helical lines spacing. (2) With the increase of laser scanning speed, the depth of holes reduces while the diameter rarely changes. (3) Through the holes of high aspect ratio can be obtained via high processing power. ? 2012 Springer-Verlag Berlin Heidelberg.Accession Number: 20132216369970 -
Record 141 of
Title:Fabrication of microstructures in aviation components with a femtosecond laser based on PZT scanning
Author(s):Yang, Xiaojun(1); Zhao, Wei(1); Li, Ming(1); Zhao, Hualong(2); Zhang, Huixing(3); Li, Peng(2); Yang, Yong(1); Cheng, Guanghua(1)Source: Laser Physics Volume: 23 Issue: 5 DOI: 10.1088/1054-660X/23/5/056001 Published: May 2013Abstract:Thermal defects and low precision are the main disadvantages of fabricating micro-holes, irregular holes, and micro-slots in thermostable aviation materials. We demonstrate a manufacturing method employing a femtosecond laser and piezoelectric ceramic (PZT). The production process parameters were optimized according to the metallographic and dimensional accuracy of the microstructure, which was measured by phase-contrast microscopy and scanning electron microscopy. The limitations in a conventional aeroengine, such as in the recast layer, recrystallization, and micro-cracks, which degrade the performance and service life, were resolved with a simple, controllable, and commercial method. ? 2013 Astro Ltd.Accession Number: 20132616444944 -
Record 142 of
Title:Optimization of PID parameters based on improved particle-swarm-optimization
Author(s):Fan, Xinming(1,2); Cao, Jianzhong(1); Yang, Hongtao(1); Dong, Xiaokun(1); Liu, Chen(1,2); Gong, Zhendong(1,2); Wu, Qingquan(1,2)Source: Proceedings - 2013 International Conference on Information Science and Cloud Computing Companion, ISCC-C 2013 Volume: Issue: DOI: 10.1109/ISCC-C.2013.99 Published: December 3, 2014Abstract:Because the PID parameter settings obtained by classical method fail to achieve the best control performances, this paper proposes an improved particle swarm optimization (IPSO) algorithm with non-linear inertial weight changes and border buffer. Unlike the original PSO, the inertial weight changes instead of linearly. In addition, we provide a border buffer to the slopping-over particles, making them to fall in the explored space of optima to enhance the diversity of the particle swarm. The simulation experiments show that the system whose parameters are optimized by IPSO has better performances. Meanwhile, it proves the effectiveness of the improved particle swarm optimization. ? 2013 IEEE.Accession Number: 20145200372225 -
Record 143 of
Title:Tracking vehicles as groups in airborne videos
Author(s):Cao, Xianbin(1,2); Shi, Zhengrong(3); Yan, Pingkun(4); Li, Xuelong(4)Source: Neurocomputing Volume: 99 Issue: DOI: 10.1016/j.neucom.2012.05.026 Published: January 1, 2013Abstract:Airborne vehicle tracking system is receiving increasing attention due to its high mobility, low cost and large surveillance scope. However, tracking multiple vehicles simultaneously on airborne platform is a challenging problem, owing to camera vibration, which causes visible frame-to-frame jitter in the airborne videos and uncertain vehicle motion. To address these problems, a new collaborative tracking framework is proposed in this paper. The framework consists of a two-level tracking process to track vehicles as groups. The higher level builds the relevance network and divides target vehicles into different groups, where the relevance is calculated based on the status information of vehicles obtained from the lower level. The proposed group tracking takes into account the relevance between vehicles and reduces the impact of camera vibration. Experimental results demonstrated that the proposed method has better performance in terms of tracking speed and tracking accuracy compared to other existing approaches based on particle filter and stationary grouping. ? 2012 Elsevier B.V.Accession Number: 20124415617620 -
Record 144 of
Title:Pyramid-like spikes in a single crystal superalloy produced by picosecond laser irradiation
Author(s):Zhang, Wei(1); Cui, Xiangzhong(1); Feng, Qiang(2,3); Cheng, Guanghua(4); Ma, Guojia(1); Zhang, Xiaobing(1)Source: Applied Physics A: Materials Science and Processing Volume: 113 Issue: 2 DOI: 10.1007/s00339-013-7968-9 Published: November 2013Abstract:Pyramid-like spikes in a single crystal superalloy were investigated upon irradiation with picosecond (ps) laser pulses (200 ps, 800 nm, 1 kHz) under different laser fluences and pulse numbers. Both sides and grooves of pyramid-like spikes were covered with ripples, which had a period of ～760 nm. The pyramid-like spike separation increased obviously with increasing laser fluence. Microstructural investigations indicate that the pyramid-like spikeswere initiated with subsequent pulses from a smooth surface with corrugations and ripples. The coexistence of capillary waves for spikes and capillary waves for ripples in the melted material can be used to explain the formation of the pyramid-like spikes. ? 2013 Springer-Verlag Berlin Heidelberg.Accession Number: 20141217486679