2016
2016
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Record 229 of
Title:Polarimetric dehazing method for visibility improvement based on visible and infrared image fusion
Author(s):Liang, Jian(1,2); Zhang, Wenfei(1,2); Ren, Liyong(1); Ju, Haijuan(1,2); Qu, Enshi(1)Source: Applied Optics Volume: 55 Issue: 29 DOI: 10.1364/AO.55.008221 Published: October 10, 2016Abstract:Polarimetric dehazing methods have proven effective in enhancing the quality of chromatic hazy images. Considering that the infrared radiance has a better capacity for traveling through the haze, in this paper we propose a polarimetric dehazing method based on visible and infrared image fusion to improve the visibility of hazy images, especially for dense haze conditions. Experimental results demonstrate that the visibility of hazy images can be effectively enhanced, and the color information can be finely maintained. The visibility of dehazed images can be promoted at least 100%. This kind of dehazing method can be used widely in many dehazing applications. ? 2016 Optical Society of America.Accession Number: 20164302952950 -
Record 230 of
Title:Multilayer nested X-ray focusing optical device
Author(s):Liu, Duo(1,2); Qiang, Pengfei(1); Li, Linsen(1,2); Liu, Zhe(1); Sheng, Lizhi(1,3); Liu, Yong'an(1); Zhao, Baosheng(1)Source: Guangxue Xuebao/Acta Optica Sinica Volume: 36 Issue: 8 DOI: 10.3788/AOS201636.0834002 Published: August 10, 2016Abstract:Aiming at the demand on X-ray pulsar navigation and X-ray space communication, the multilayer nested X-ray focusing optical device is developed and tested. Theoretical design of focusing lenses is carried out according to the principle of grazing incidence, and key parameters of the focusing lenses are determined. The materials of focusing lenses and the preparation technologies such as the coating process are discussed. The performance parameters of the focusing lenses are tested respectively under the conditions of visible light and X-ray. The results show that the spot diameter of visible light is 14 mm, the spot diameter of X-ray is 20 mm, and the focusing efficiency is 30.2%. The effective area is 2400 mm2 in a 10 m vacuum pipe when the photon energy is 1.5 keV. ? 2016, Chinese Lasers Press. All right reserved.Accession Number: 20163702800375 -
Record 231 of
Title:Identification of high explosive RDX using terahertz imaging and spectral fingerprints
Author(s):Liu, Jia(1,2); Fan, Wen-Hui(1); Chen, Xu(1,2); Xie, Jun(1,2)Source: Journal of Physics: Conference Series Volume: 680 Issue: 1 DOI: 10.1088/1742-6596/680/1/012030 Published: February 3, 2016Abstract:We experimentally investigated the spectral fingerprints of high explosive cyclo-1,3,5- trimethylene-2,4,6-trinitramine (RDX) in terahertz frequency region. A home-made terahertz time-domain spectroscopy ranging from 0.2 THz-; 3.4 THz was deployed. Furthermore, two sample pellets (RDX pellet and polyethylene pellet), which were concealed in an opaque envelop, could be identified by using terahertz pulse imaging system. For the purpose of distinguishing the RDX between two pellets, we further calculated the THz frequency -domain map using its spectral fingerprints. It is demonstrated that the high explosive RDX could similarly be identified using terahertz frequency-domain imaging.Accession Number: 20161802335929 -
Record 232 of
Title:Unsupervised Band Selection Based on Evolutionary Multiobjective Optimization for Hyperspectral Images
Author(s):Gong, Maoguo(1); Zhang, Mingyang(1); Yuan, Yuan(2)Source: IEEE Transactions on Geoscience and Remote Sensing Volume: 54 Issue: 1 DOI: 10.1109/TGRS.2015.2461653 Published: January 1, 2016Abstract:Band selection is an important preprocessing step for hyperspectral image processing. Many valid criteria have been proposed for band selection, and these criteria model band selection as a single-objective optimization problem. In this paper, a novel multiobjective model is first built for band selection. In this model, two objective functions with a conflicting relationship are designed. One objective function is set as information entropy to represent the information contained in the selected band subsets, and the other one is set as the number of selected bands. Then, based on this model, a new unsupervised band selection method called multiobjective optimization band selection (MOBS) is proposed. In the MOBS method, these two objective functions are optimized simultaneously by a multiobjective evolutionary algorithm to find the best tradeoff solutions. The proposed method shows two unique characters. It can obtain a series of band subsets with different numbers of bands in a single run to offer more options for decision makers. Moreover, these band subsets with different numbers of bands can communicate with each other and have a coevolutionary relationship, which means that they can be optimized in a cooperative way. Since it is unsupervised, the proposed algorithm is compared with some related and recent unsupervised methods for hyperspectral image band selection to evaluate the quality of the obtained band subsets. Experimental results show that the proposed method can generate a set of band subsets with different numbers of bands in a single run and that these band subsets have a stable good performance on classification for different data sets. ? 2015 IEEE.Accession Number: 20153501212728 -
Record 233 of
Title:The effects of femtosecond laser processing on the surface accuracy of fibre laser clad sidewalls
Author(s):Li, R.(1,2); Yang, X.-J.(1); Zhao, W.(1,2); He, B.(1); Zhao, H.-L.(1); Zhu, W.-Y.(1)Source: Lasers in Engineering Volume: 35 Issue: 5-6 DOI: Published: 2016Abstract:To enhance the surface accuracy of laser metal direct forming pieces, a method applying femtosecond laser to fabricate the cladding sidewalls is proposed in this paper. The effects of laser fluence, scanning speed and scanning strategy on the processing accuracy are studied systematically. The experimental results show that when the laser fluence increases, the roughness of cladding sidewalls also increases. The roughness of the cladding sidewall is decreased firstly and then increased with the increasing scanning speed. When the laser fluence is between 0.12 and 0.34 J/cm2, the roughness of cladding sidewall is less than 3 μm. What is more, under single scanning strategy the sidewalls roughness is less than that when back and forth scanning method is used. ?2016 Old City Publishing, Inc.Accession Number: 20164603012830 -
Record 234 of
Title:Investigations on the photoluminescence of the iron and cobalt doped fluoride-containing phosphate-based glasses and its defects-related nature
Author(s):He, Quanlong(1,2); Wang, Pengfei(1); Lu, Min(1); Peng, Bo(1)Source: Journal of Alloys and Compounds Volume: 685 Issue: DOI: 10.1016/j.jallcom.2016.05.253 Published: November 15, 2016Abstract:The influence of doping iron and cobalt ions on the formation of defects in the fluoride-containing phosphate-based glasses was studied comprehensively by means of analyzing the absorption and photoluminescence (PL) spectra as well as the electron spin resonance (ESR) spectra. The absorption and ESR spectra show that the defects, including phosphate-related oxygen hole center (POHC), oxygen-related hole centers (OHC), Fe3+, Co2+, PO3-EC, PO4-EC and fluorine-related non-paramagnetic color (FD) centers were formed during the glass preparation process. In addition, the analysis on the PL and absorption as well as excitation (PLE) spectra indicate that PO4-EC and OHC defects which have large absorption in the UV region result in the emission band peaking at 780 nm under the excitation at 351 nm for the cobalt doped (2ω absorptive) glass. Addition of small quantities of iron causes the effectively intense absorption towards the 1ω wavelength (1053 nm) due to the presence of Fe2+, but also a distinctively observed red-shift of the UV absorption edge was dominated by the charge-transfer transition of the existence of Fe3+. The experimental results demonstrate that Fe3+ suppress the formation of FD defects in the glasses, while promotes the formation of POHC defects. Besides, introduction of Co2+ inhibits the formation of POHC and PO4-EC defects, and Fe2+ promotes forming of POHC defects. ? 2016 Elsevier B.V. All rights reserved.Accession Number: 20162302474214 -
Record 235 of
Title:High-peak-power sub-nanosecond intracavity KTiOPO4 optical parametric oscillator pumped by a dual-loss modulated laser with acousto-optic modulator and single-walled carbon nanotube
Author(s):Qiao, Junpeng(1); Zhao, Shengzhi(1); Yang, Kejian(1); Zhao, Jia(1); Li, Guiqiu(1); Li, Dechun(1); Li, Tao(1); Qiao, Wenchao(1); Lu, Jianren(1); Wang, Yonggang(2); Chu, Hongwei(1); Luan, Chao(1)Source: Applied Physics Express Volume: 9 Issue: 8 DOI: 10.7567/APEX.9.082701 Published: August 2016Abstract:A high-peak-power low-repetition-rate sub-nanosecond intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO) pumped by a doubly Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser with an acousto-optic modulator (AOM) and a single-walled carbon nanotube saturable absorber (SWCNT-SA) has been demonstrated. A maximum output power of 373mW at a signal wavelength of 1570nm was obtained. The smallest pulse width, highest pulse energy, and greatest peak power of mode-locking pulses were estimated to be 119 ps, 124 μJ, and 1.04MW, respectively, under a maximum incident pump power of 8.3W and an AOM repetition rate of 2 kHz. This OPO operation paves a simple way to produce eye-safe laser sources at 1570nm with low repetition rates, small pulse widths, and high peak powers. ? 2016 The Japan Society of Applied Physics.Accession Number: 20163302714287 -
Record 236 of
Title:Preparation and characterization of self-cleaning and anti-reflection ZnO-SiO2 nanometric films
Author(s):Guo, Zhao-Long(1,2); Zhao, Hai-Xin(1); Zhao, Wei(1)Source: Wuli Xuebao/Acta Physica Sinica Volume: 65 Issue: 6 DOI: 10.7498/aps.65.064206 Published: March 20, 2016Abstract:Unlike the general anti-reflection and self-cleaning film such as SiO2 and TiO2-SiO2, the ZnO-SiO2 nanometric film used as a substrate of excellent transparency in visible region and effective photo-catalytic self-cleaning under UV illumination is seldom studied in the application as a substrate;however, it has a lot of advantages including high transmittance and low refractivity. In this paper, a self-cleaning and anti-reflection ZnO-SiO2 nanometric film is successfully fabricated by using a sol-gel dip-coating method. The morphology, crystal structure, surface microstructure and light transmittance of the obtained products are characterized by techniques such as TEM, SAD, XRD, SEM, DTA and UV-vis. Photo-catalytic degradation of the methylene blue (MB) in aqueous solution is used as probe reaction to evaluate the photo-catalytic activity of ZnO-SiO2 nanometric film. The TEM images reveal that the as-prepared ZnO nanoparticles are spherical grains with diameters of 12-20 nm, the average grain diameter is about 14.51 nm. ZnO nanoparticles obtained are of hexagonal wurtzite structure revealed by XRD pattern and there exist no other diffraction peaks. Furthermore, the SAD results show that ZnO microstructurs have good crystallinity. In addition, the ZnO grain size is about 14.41 nm by using the Scherrer formula calculation, which is consistent with the TEM results by the Gauss simulation. The UV-vis spectra reveal that the ultraviolet characteristic absorption peak of ZnO-SiO2 composite films is located at 368 nm and 375 nm after annealing at different temperatures such as 300℃ and 450℃, corresponding to the band gaps of 3.37 eV and 3.31 eV, respectively. It is highly consistent with that obtained from pure ZnO nanoparticles. Increasing the annealing temperature results in a lower refractive index and the increases of the porosity in of the ZnO-SiO2 composite films. It has a uniformly refractive index value about 1.23-1.25 and a high porosity value about 50.3%-54.7% when the annealing temperature is 450℃. Experimental results show that the ZnO-SiO2 composite film can enhance the light transmittance of the quartz substrate, due to its lower reflective index and higher porosity. Compared with the quartz substrate, the average optical transmission rate of the quartz glass coated with ZnO-SiO2 composite films is increased by about 4.17% at 400-800 nm, which favors greatly anti-reflection characteristics in a wide spectrum range. Meanwhile, the ZnO-SiO2 composite films are found to be efficient for photo-catalytically degradation of methylene blue dye under UV illumination, which favors greatly the self-cleaning function. ? 2016, Chinese Physical Society.Accession Number: 20161602262648 -
Record 237 of
Title:Influence of Driving Frequency on the Argon Dielectric Barrier Discharge Excited by Gaussian Voltage at Atmospheric Pressure
Author(s):Xu, Yonggang(1,2); Jiang, Weiman(2); Tang, Jie(2); Zhu, Sha(2); Wang, Yishan(2); Li, Yongfang(1); Zhao, Wei(2); Duan, Yixiang(2,3)Source: IEEE Transactions on Plasma Science Volume: 44 Issue: 11 DOI: 10.1109/TPS.2016.2572733 Published: November 2016Abstract:A 1-D self-consistent fluid model was employed to investigate the effect of driving frequency on the discharge characters of a dielectric barrier discharge at atmospheric pressure in argon excited by a periodic Gaussian voltage. The simulation results indicate that there are two discharge modes: 1) Townsend and 2) glow modes in the multipulse discharge and different transitions between them during the discharge take place with the increase in driving frequency. When the driving frequency is 1 kHz, there is a tendency of transition from the Townsend mode through glow and finally back to the Townsend one during the positive half-circle of applied Gaussian voltage. However, the discharge in the half-circle can all along operate in the glow mode with the higher driving frequency. Moreover, when the driving frequency is sufficiently high, there are also distinct fluctuations of spatial performance of the charge densities in the positive column during the glow discharge. This is caused by the fact that a lot of charged particles created in the gas gap have not enough time to drift and diffuse to the dielectric barriers, and then these particles are preserved in the local discharge gap at such a high frequency. A comparison of the spatial and temporal evolutions of the electron density at different driving frequencies indicates that the increase in the driving frequency can enhance the plasma chemistry and also expand its volume. ? 2016 IEEE.Accession Number: 20162602537611 -
Record 238 of
Title:Demonstration of a stable and uniform single-wavelength erbium-doped fiber laser based on microfiber knot resonator
Author(s):Xu, Yiping(1); Ren, Liyong(2); Ma, Chengju(3); Kong, Xudong(2); Ren, Kaili(2)Source: Optical Engineering Volume: 55 Issue: 12 DOI: 10.1117/1.OE.55.12.126111 Published: December 1, 2016Abstract:We propose and demonstrate an application of microfiber knot resonator (MKR) in the generation of a stable and uniform single-wavelength erbium-doped fiber laser (EDFL). An MKR was fabricated using a microfiber a few micrometers in diameter. By embedding the MKR to the ring cavity of the EDFL, a laser with a wavelength of 1558.818 nm and a 3-dB linewidth of 0.0149 nm is demonstrated. The side mode suppression ratio of the laser is about 30 dB, and the maximum power fluctuation is about 0.85 dB. The results demonstrate that the MKR can be employed as a high-performance comb filter to realize a stable and uniform fiber laser. ? 2016 Society of Photo-Optical Instrumentation Engineers (SPIE).Accession Number: 20170203237778 -
Record 239 of
Title:Effects of gamma radiation and heat treatment on the photoluminescence of the fluoride-containing phosphate-based glasses
Author(s):He, Quanlong(1,2); Wang, Pengfei(1); Lu, Min(1); Peng, Bo(1)Source: ECS Journal of Solid State Science and Technology Volume: 5 Issue: 10 DOI: 10.1149/2.0041612jss Published: 2016Abstract:We demonstrate, for the first time to our knowledge, two different balances around fluorine-related non-paramagnetic color (FD) centers in fluoride containing phosphate based optical filter glasses at low (190°C) and higher (390°C) heat-treatment temperature, respectively. The thermal bleaching experiment results indicate the heat-treatment bleached gamma radiation induced phosphaterelated oxygen hole center (POHC) and oxygen-related hole center (OHC) to some extent due to the release and capture of the electrons in the conduction band. Through the gamma radiation and subsequent heat-treatment experiment, as well as the detailed analysis of photoluminescence and excitation spectra, a general model corresponding to the two different balances about the FD defects and the evolutionary mechanism of these existing defects in the fluoride-containing phosphate based glasses was proposed. ? 2016 The Electrochemical Society.Accession Number: 20164402958210 -
Record 240 of
Title:Theoretical and experimental analysis of excessively tilted fiber gratings
Author(s):Yan, Zhijun(1,2); Wang, Hushan(1); Wang, Changle(2); Sun, Zhongyuan(2); Yin, Guolu(2); Zhou, Kaiming(1,2); Wang, Yishan(1); Zhao, Wei(1); Zhang, Lin(2)Source: Optics Express Volume: 24 Issue: 11 DOI: 10.1364/OE.24.012107 Published: May 30, 2016Abstract:We have theoretically and experimentally investigated the dual-peak feature of tilted fiber gratings with excessively tilted structure (named as Ex-TFGs). We have explained the dual-peak feature by solving eigenvalue equations for TM0m and TE0m of a circular waveguide, in which the TE (transverse electric) and TM (transverse magnetic) core modes are coupled into TE and TM cladding modes, respectively. Meanwhile, in the experiment, we have verified that one of the dual peaks at the shorter wavelength is due to the TM mode coupling whereas the other one at the longer wavelength arises from TE mode coupling when a linearly polarized light launched into the Ex-TFG. We have also investigated the peak separation of TE and TM cladding mode for different surrounding medium refractive indexes (SRI), revealed that the dual peaks separation is decreasing as increasing of SRI, which agrees very well with the theoretical analysis results. ?2016 Optical Society of America.Accession Number: 20162402499945