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Record 433 of
Title:Micromachining features of TiC ceramic by femtosecond pulsed laser
Author(s):Zhang, Ying(1); Wang, Yuqian(1); Zhang, Junzhan(1); Liu, Yongsheng(2); Yang, Xiaojun(3); Zhang, Qing(2)
Source: Ceramics International Volume: 41 Issue: 5 DOI: 10.1016/j.ceramint.2015.01.095 Published: June 1, 2015
Abstract:Femtosecond pulsed laser was employed to drill blind holes (or circle surfaces) and through holes in titanium carbide (TiC) ceramic by the helical drilling technique. The effects of spiral number, processing time, laser fluence and repetition rate on the qualities of holes (or circle surfaces) were investigated. Morphology of holes (or circle surfaces) and composition of irradiated areas were analyzed by a scanning electron microscope (SEM), a three-dimensional super depth digital microscope and energy dispersive spectroscopy (EDS), etc. The results indicated that laser fluence and repetition rate had major effects on ablation efficiency and quality. Blind holes with taper bottom were observed when the laser fluence was above 6.37×10-1 J/mm2. With the increase of laser fluence, hole depth increased firstly and then decreased. The change in hole diameter decreased when the laser fluence was above 0.51 J/mm2. The effects of repetition rate on hole depth were similar to that of laser fluence, while it showed a faint change in hole diameter at laser fluence of 1.02 J/mm2 and laser repetition rate ranging from 2 to 140 kHz. Furthermore, through holes were attained at narrowed laser fluence ranging from 0.51 to 1.53 J/mm2. The drilled holes had good circular geometry for entrance and exit. ? 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Accession Number: 20150600495513
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Record 434 of
Title:Adaptive multi-bit quantization for hashing
Author(s):Deng, Cheng(1); Deng, Huiru(1); Liu, Xianglong(2); Yuan, Yuan(3)
Source: Neurocomputing Volume: 151 Issue: P1 DOI: 10.1016/j.neucom.2014.09.033 Published: 2015
Abstract:Recently, hashing methods which try to solve similarity-preserving approximate nearest search problem have obtained widely applications in various fields such as content-based image retrieval, object recognition and pose estimation. However, how to learn effective hash codes to describe the similarities in the large-scale database still remains as a NP-hard problem. Besides, a fatal problem lying in the existing hashing methods is that they usually threshold the real values to binary codes using single-bit quantization (SBQ) at the highest point density, which may destroy the data structure seriously. Due to this problem, double-bit quantization (DBQ) is proposed to solve the problem of SBQ by adaptively learning thresholds to quantize the real values to two bits, and achieves impressive results. However, one problem in DBQ is that it neglects the amount of the information contained in different data dimensions. In this paper, we propose a multi-bit quantization method based on bit allocation to quantize each projected dimension with variable bit numbers. Besides, different from existing methods of choosing threshold, we propose an incomplete coding manner by clustering to generate binary codes. Experiments on two large datasets demonstrate the feasibility of our method. ? 2014 Elsevier B.V.
Accession Number: 20150700534153
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Record 435 of
Title:A multib and THz bandpass filter based on multiple-resonance excitation of a composite metamaterial
Author(s):Chen, Xu(1,2); Fan, Wen-Hui(1)
Source: Materials Research Express Volume: 2 Issue: 5 DOI: 10.1088/2053-1591/2/5/055801 Published: May 2015
Abstract:We present a systematic numerical study on a metal-dielectric-metal (MDM) sandwich structure for multiple resonance transmission in terahertz (THz) region. The designed structure consists of periodic square close ring array on both side of a flexible dielectric substrate, exhibits a multiband transmission, with low average insertion loss, steep skirts and high out-of-b and rejection. In addition, due to its rotationally symmetric structure, this filter is polarization-insensitive for normal incidence of the electromagnetic waves, keeping highly transmission at a wide range of incident angles for transverse electric waves and transverse magnetic waves. The metamaterial structure can be utilized as a desirable multib and filter with many practical applications, especially for THz communication, spectroscopic detection and phase imaging. ? 2015 IOP Publishing Ltd.
Accession Number: 20191306678460
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Record 436 of
Title:Optical properties of a binuclear neodymium complex in phosphorus oxychloride for liquid laser
Author(s):Zhang, Guofang(1); She, Jiangbo(2); Han, Kai(1); Nie, Rongzhi(2); Li, Dongdong(3); Peng, Bo(2)
Source: Optical Materials Volume: 49 Issue: DOI: 10.1016/j.optmat.2015.10.002 Published: November 2015
Abstract:A novel binuclear neodymium complex Nd(CF3COO)3·(Ph3PO)2 (Ph3PO: triphenylphosphine oxide) with high stimulated emission cross-section was presented. The molecular structure of the complex was characterized by single-crystal X-ray diffraction. The optical properties of the complex in liquid medium were studied. From the absorption and luminescence spectra, the Judd-Ofelt parameters of Nd(CF3COO)3·(Ph3PO)2 in phosphorus oxychloride were obtained. Based on the crystal structure, the effects of crystal field and bonding valence properties on three intensity parameters Ωt(t = 2, 4, 6) and emission cross-section were analyzed in detail. The emission cross-section of 4F3/2 → 4I11/2 fluorescence transition (2.78 × 10-20 cm2) of the new neodymium compound was higher than those of other Nd(III) complexes and even comparable with some laser glasses. ? 2015 Elsevier B.V. All rights reserved.
Accession Number: 20154301447879
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Record 437 of
Title:Polarimetric dehazing method for dense haze removal based on distribution analysis of angle of polarization
Author(s):Liang, Jian(1,2); Ren, Liyong(1); Ju, Haijuan(1); Zhang, Wenfei(1,2); Qu, Enshi(1)
Source: Optics Express Volume: 23 Issue: 20 DOI: 10.1364/OE.23.026146 Published: October 5, 2015
Abstract:Many dehazing methods have proven to be effective in removing haze out of the hazy image, but few of them are adaptive in handling the dense haze. In this paper, based on the angle of polarization (AOP) distribution analysis we propose a kind of polarimetric dehazing method, which is verified to be capable of enhancing the contrast and the range of visibility of images taken in dense haze substantially. It is found that the estimating precision of the intensity of airlight is a key factor which determines the dehazing quality, and fortunately our method involves a high precision estimation inherently. In the experiments a good dehazing performance is demonstrated, especially for dense haze removal. We find that the visibility can be enhanced at least 74%. Besides, the method can be used not only in dense haze but also in severe sea fog. ? 2015 Optical Society of America.
Accession Number: 20154201387479
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Record 438 of
Title:Scene Parsing from an MAP Perspective
Author(s):Li, Xuelong(1); Mou, Lichao(1); Lu, Xiaoqiang(1)
Source: IEEE Transactions on Cybernetics Volume: 45 Issue: 9 DOI: 10.1109/TCYB.2014.2361489 Published: September 1, 2015
Abstract:Scene parsing is an important problem in the field of computer vision. Though many existing scene parsing approaches have obtained encouraging results, they fail to overcome within-category inconsistency and intercategory similarity of superpixels. To reduce the aforementioned problem, a novel method is proposed in this paper. The proposed approach consists of three main steps: 1) posterior category probability density function (PDF) is learned by an efficient low-rank representation classifier (LRRC); 2) prior contextual constraint PDF on the map of pixel categories is learned by Markov random fields; and 3) final parsing results are yielded up to the maximum a posterior process based on the two learned PDFs. In this case, the nature of being both dense for within-category affinities and almost zeros for intercategory affinities is integrated into our approach by using LRRC to model the posterior category PDF. Meanwhile, the contextual priori generated by modeling the prior contextual constraint PDF helps to promote the performance of scene parsing. Experiments on benchmark datasets show that the proposed approach outperforms the state-of-the-art approaches for scene parsing. ? 2013 IEEE.
Accession Number: 20153401201516
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Record 439 of
Title:Dynamic response of the optical resonant cavity to light-wave
Author(s):Feng, Li-Li(1,2); Ruan, Chi(1); Wang, Yun-Tao(1)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 44 Issue: 8 DOI: 10.3788/gzxb20154408.0814001 Published: August 1, 2015
Abstract:The dynamic response of optical resonant cavity has been theoretically studied, by taking resonant cavity as a linear and time invariant system and through the approach of Signal Processing. The mathematical description obtained could fit any form of light waves. From the perspective of Signal Processing, the traditional pulse and continues wave cavity ring-down spectroscopy could be considered as observation of impulse response and step response respectively. Furthermore, the cavity response to the light-wave linearly frequency chirped has been studied, in the condition of slow chirp. The Fourier analysis of light power passed through cavity has been made and an analytic description has been given, which reveals the fact that the signal spectrum of light power is related to the absorption spectrum of material inside cavity. Based on this theoretic analysis, a new approach of cavity enhanced absorption spectroscopy has been put forward, called Frequency Domain Cavity Ring-Down Spectroscopy. The result would facilitates the research of cavity enhanced spectroscopy techniques, as well others using resonant cavity, such as P-D-H laser frequency stabilization. ?, 2015, Chinese Optical Society. All right reserved.
Accession Number: 20153901310772
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Record 440 of
Title:Selection of MCP for array X-ray pulsar navigation detector
Author(s):Song, Juan(1,2); Zhao, Bao-Sheng(1); Sheng, Li-Zhi(1); Liu, Zhe(1); Liu, Yong-An(1)
Source: Guangxue Jingmi Gongcheng/Optics and Precision Engineering Volume: 23 Issue: 2 DOI: 10.3788/OPE.20152302.0402 Published: February 1, 2015
Abstract:According to the demands of an array detector in the X-ray pulsar navigation system for Micro-channel Plate (MCP), a selection method for the MCP was explored. Four key parameters for the selection of MCPs, the uniformity of gain, impedance matching, dark count rate and the gain coefficient were determined. Based on the four key parameters, corresponding experiments were designed and the selection process of MCPs was set out. The amplitudes and counting rates of MCPs selected by proposed method were tested. The tested results show that the relative error of each detection unit is not identical. When a single channel anode is used, the ranges of the maximum relative error Δ1i and minimum relative error Δ2i of the amplitudes for output signals from the ith anode are 7%-13.5% and 3%-6.7%, respectively, and when a four-channel anode is used, Δ1i and Δ2i are 7.8% and 3.1%, respectively. Moreover, the relative error between the anode count rate n1+n2+n3+n4 from the single channel and N from the four-channel shared anode is 4.38%, less than 10%. Obtained results indicate that the MCPs with good performance have been effectively chosen by the proposed selection method. ?, 2015, Chinese Academy of Sciences. All right reserved.
Accession Number: 20151800797189
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Record 441 of
Title:A new design of seed source used in optical streak camera
Author(s):Wang, Qiaoli(1,2); Bai, Yonglin(1); Zhu, Bingli(1); Wang, Bo(1); Gou, Yongsheng(1); Jin, Jing(1,2)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 7 DOI: Published: July 25, 2015
Abstract:A new technique to generate high frequency repeated sine synchronous scan seed source was introduced, based on the method of phase locked loop and direct digital synthesize technique. Phase locked loop was used to realize synchronous track of sine scan signal and trigger light impulse. Modulation of frequency, phase, and amplitude was achieved by direct digital synthesize technique. Delay of scan time was achieved by phase modulation, while different scanning rate was achieved by amplification modulation. The circuit system can obtain stable sine synchronous scan seed signal with frequency as high as 250 MHz, and jitter lower than 10 ps. The design is confirmed to meet the expectation, and fulfill the high precision requirements of streak camera on seed source for frequency, amplitude and time jitter. ?, 2015, Chinese Society of Astronautics. All right reserved.
Accession Number: 20153501225645
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Record 442 of
Title:Theoretical and experimental study on spectral characteristics of microfiber double-knot resonator with different structures
Author(s):Xu, Yi-Ping(1,2); Ren, Li-Yong(1); Ma, Cheng-Ju(1,2); Wang, Ying-Li(1); Kong, Xu-Dong(1,2); Liang, Jian(1); Ju, Hai-Juan(1)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 44 Issue: 4 DOI: 10.3788/gzxb20154404.0406001 Published: April 1, 2015
Abstract:Based on the theories of the ring resonators and the directional coupler, the theoretical models of the microfiber double-knot resonator with a serial structure and the microfiber double-knot resonator with a parallel structure were proposed, the mathematic expressions between the output light field and the input one in the two resonators were deduced. The directions of the propagation and coupling in the two resonators were studied, the change rules of the transmission spectra under different diameter ratios of their two rings were analyzed. Numerical simulation indicates that the number of the transmission peaks of the microfiber double-knot resonator with a serial structure under the envelope of its transmission spectrum is equal to the diameter ratio of its two rings, the number of the transmission peaks of the microfiber double-knot resonator with a parallel structure increases with the increasing of the diameter ratio of its two rings and there is a narrower transmission peak per equal spacing peaks of the diameter ratio. The microfiber double-knot resonator with a serial structure for approximately equivalent diameters and the microfiber double-knot resonator with a parallel structure for a diameter ratio of approximate 2 were fabricated. The experimental transmission spectra show good agreements with the theoretical ones for each structure, indicating that the theoretical analysis is considerably correct. The microfiber double-knot resonator with a serial structure and that with a parallel structure for proper diameter ratios have significant applications in optical filters, miniature lasers, sensors, and so on. ?, 2015, Chinese Optical Society. All right reserved.
Accession Number: 20152100877440
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Record 443 of
Title:Effect of femtosecond laser micromachining on the roughness of cladding sidewalls
Author(s):Li, Rui(1,2); Yang, Xiaojun(1); Zhao, Wei(1); He, Bin(1); Li, Ming(1); Zhao, Hualong(1); Zhu, Wenyu(1); Wang, Ning(1)
Source: Hongwai yu Jiguang Gongcheng/Infrared and Laser Engineering Volume: 44 Issue: 11 DOI: Published: November 25, 2015
Abstract:In order to enhance the surface finish of Laser Direct Deposition of metallic components, a method that applies femtosecond laser to fabricate the cladding layer was proposed in this paper. The effects of the energy density, distribution, and the overlapping ratio of the laser on the sidewall quality of the cladding layer were studied in experiment. The experiment results show that the roughness of the achieved cladding side-wall layer can be smaller than 3 μm once the energy density in the region is 0.12-0.34 J/cm2 for the Gaussian-shape laser or 0.13-0.66 J/cm2 for the rectangle-shape laser. And the cladding sidewall layer fabricated by Gaussian-shape laser possessed more excellent surface quality than the product fabricated by rectangle-shape laser with same parameters. The roughness of the cladding sidewall layer decreases and then increases with the increase of the laser overlapping ratio, and the optimal region of overlapping-ratio is 78%-85%. ? 2015, Editorial Board of Journal of Infrared and Laser Engineering. All right reserved.
Accession Number: 20160101761464
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Record 444 of
Title:Passively harmonic mode-locked fiber laser with a high signal-to-noise ratio via Evanescent-light deposition of Bismuth Telluride (Bi2Te3) topological insulator based saturable absorber
Author(s):Duan, L.N.(1); Wang, Y.G.(1); Xu, C.W.(2); Li, L.(1); Wang, Y.S.(1)
Source: IEEE Photonics Journal Volume: 7 Issue: 2 DOI: 10.1109/JPHOT.2015.2404315 Published: April 1, 2015
Abstract:Passively harmonic mode locking (HML) operation had been demonstrated in an erbium-doped fiber laser with a microfiber-based topological insulator (TI) Bi2Te3 saturable absorber (SA). It was found that the pulse train possessed different orders of HML (with a tunable repetition rate from 232 to 390 MHz) due to different incident pump powers. The spectra exhibited typical features of conventional solitons (perfect Gaussian profile with Kelly sidebands) with no continuous wave component. The measured signal-to-noise ratio (SNR) reached 60 dB, whereas the pulse duration was kept around 1.32 ps without significant change. The experimental observation revealed that the microfiber-based TI device could indeed be employed as a high-performance SA for further applications in ultrafast photonics. ? 2009-2012 IEEE.
Accession Number: 20151000613088
