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991.
A novel algorithm for bridge recognition of median synthetic aperture radar (SAR) images using histogram entropy presented by Pun is proposed. Firstly, Lee filter and histogram proportion are used to denoise the original image and to make the target evident. Then, water regions are gained through histogram segmentation and the contours of water regions axe extracted. After these, the potential bridge targets are obtained based on the space relativity between bridges and water regions using improved contour search. At last, bridges are recognized by extracting the feature of Pun histogram entropy (PHE) of these potential bridge targets. Experimental results show the good qualities of the algorithm, such as fast speed, high rate of recognition, and low rate of false target. 相似文献
992.
Sheng-Hui Chen Kai Wu Chien-Cheng Kuo Sheng-Ju Ma Cheng-Chung Lee 《Optical Review》2009,16(4):479-482
A new method based on the polarization interferometer structure has been applied to measure the optical admittance, the refractive
index and thickness of a thin film. The structure is a vibration insensitive optical system. There is one Twyman-Green interferometer
part to induce a phase difference and one Fizeau interferometer part to induce the interference in the system. The intensities
coming from four different polarizers were measured at the same time to prevent mechanical vibration influence. Using the
polarization interferometer, the optical admittance, the refractive index and thickness of a single layer of Ta2O5 thin film has been measured. The measurement results were compared with the results obtained by ellipsometer. The results
meet reasonable values in both refractive index and thickness. 相似文献
993.
Mesomorphic and dielectric properties of esters useful for formulation of nematic mixtures for dual frequency addressing system 总被引:1,自引:0,他引:1
D. Ziobro P. Kula J. Dziaduszek M. Filipowicz R. D?browski J. Parka J. Czub S. Urban S.T. Wu 《Opto-Electronics Review》2009,17(1):16-19
Mesomorphic and dielectric properties of three homologous series of two and three ring fluorosubstituted esters are described.
They are 4-cyano-3-fluorophenyl 4-alkyloxy-2-fluorobenzoates, 4-cyano-3-fluorophenyl 4-(4-alkylbenzoyloxy)-2-fluorobenzoates
and 3-fluoro-4-cyanophenyl, or 3-fluoro-4-isothiocyanatophenyl or 3,4-difluorophenyl 4′-alkyl-2,3-difluoro-biphenyl-4-carboxylates.
The compounds exhibit the nematic mesophase accompanied by the smectic A or smectic C mesophase in some cases. Most of them
show strong dependence of the dielectric anisotropy Δε upon frequency, at low frequencies Δε reaches a value ∼200, while at
high frequencies a small negative dielectric anisotropy appears. 相似文献
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995.
Yage Zhan Hua Wu Qinyu Yang Jincheng Pei Xichun Yang 《Optics and Lasers in Engineering》2009,47(11):1317-1321
A multi-parameter and multi-function, but low-cost, optical fiber grating sensor with self-interrogation and self-discrimination capabilities is presented theoretically and experimentally. The sensor bases on three fiber Bragg gratings (FBG) and one fiber long period grating (LPG). Strain, vibration, pressure, ordinary temperature (−10 to 100 °C) and high temperature (100–800 °C) can be measured by the sensor. When high temperature (100–800 °C) is measured, the LPG is used as a high temperture sensor head and FBG1 is used as an interrogation element. Alternatively, when one of the other four measurands is measured, FBG1 (or FBG2) is used as a sensor head and LPG is used as an interrogation element. When two of the other four measurands are measured simultaneously, FBG1 and FBG2 are used as sensor heads and LPG is used as a shared interrogation element. FBG3 is used as a reference element to eliminate the errors resulted from light source fluctuation and the cross-sensitivity between measurand and environmental temperature. The measurands can be interrogated according to the signals of the photodiodes (PDs), which are related to the relative wavelength shift of the LPG and the FBGs. Experimental results agree well with theoretical analyses. The interrogation scheme is immune to light source fluctuation and the cross-sensitivity between measurands and enviromental temperature, and also the dynamic range is large. 相似文献
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