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941.
942.
Spreading of spatially partially coherent polychromatic beams in atmospheric turbulence 总被引:1,自引:0,他引:1
Taking the polychromatic Gaussian Schell-model (GSM) beam as a typical example of spatially partially coherent polychromatic beams, the spreading of polychromatic GSM beams in atmospheric turbulence is studied. The mean-squared width of polychromatic GSM beams in turbulence is derived by using the effective source and the strong fluctuation models. It is shown that the same result is obtained using both the models. The diffraction, atmospheric turbulence and beam polychroism result in a spreading of polychromatic GSM beams. If the scaling law fails, the spreading of polychromatic GSM beams increases with increasing bandwidth Γ, but the influence of Γ on the spreading of polychromatic GSM beams becomes small as the structure constant Cn2 of the refractive index and spatial correlation parameter α increase. The spreading of polychromatic GSM beams increases as Cn2 increases and α decreases. Spatially partially coherent polychromatic beams are less sensitive to the effects of atmospheric turbulence than spatially fully coherent polychromatic beams. 相似文献
943.
944.
Fu Ri Ling Zhi Hong He Jian Quan Yao Baio Wang Shao Ji Jiang 《Optics & Laser Technology》2008,40(7):941-945
A series of near-stoichiometric Zn:Fe:LiNbO3 crystals were grown by the high-temperature top-seed solution growth (HTTSSG) method from stoichiometric melts doped with 6 mol% K2O. Infrared (IR) transmission spectra were measured and discussed in terms of the defect structure of the near-stoichiometric Zn:Fe:LiNbO3 crystals. The results of the transmitted beam pattern distortion method show that the optical damage resistance of the near-stoichiometric Zn:Fe:LiNbO3 crystals increases rapidly when the ZnO concentration exceeds a threshold value. The threshold value concentration of ZnO of the near-stoichiometric Zn:Fe:LiNbO3 crystals is much lower than that of the congruent LiNbO3 crystals. The dependence of the optical damage resistance on the defect structure of the near-stoichiometric Zn:Fe:LiNbO3 crystals are discussed, and the holographic recording properties of the near-stoichiometric Zn:Fe:LiNbO3 crystals are investigated. 相似文献
945.
946.
将心磁信号从干扰噪声中加以提取并有效地消除噪声干扰是心磁信号处理中尤为重要的环节 .从改进算法的角度出发,提出互补型自适应滤波器结构以实现心磁信号的消噪处理.该滤波器针对心磁这类非平稳信号进行设计,有效地解决了常规自适应滤波器应用于心磁信号处理时收敛速度和稳态误差的矛盾.通过仿真实验和心磁实验结果表明,该算法能有效地消除心磁信号的背景噪声和工频干扰噪声.同时该算法也可用于其他非平稳信号的消噪处理.
关键词:
自适应滤波
心磁图
最小均方误差 相似文献
947.
We report on the formation of superhydrophobic surfaces on glass by plasma polymerization with non-polar aromatic hydrocarbon, at atmospheric pressure, in an in-line process. The glass was simply treated by radio frequency (RF) plasma with a mixture of toluene and hexamethyldisiloxane (HMDSO). The hydrophobicity of the sample surfaces increase with increasing plasma treatments; contact angles of 150° for water droplets are achieved. It is attributed mainly to its high content of non-polar hydrophobic phenyl groups and its rough surface. 相似文献
948.
949.
Dmitrij Bondarev Jiří Zedník Ivana Šloufová Ahmed Sharf Marek Procházka Jiří Pfleger Jiří Vohlídal 《Journal of polymer science. Part A, Polymer chemistry》2010,48(14):3073-3081
High‐regioregular poly{3‐[6‐(1‐methylimidazolium‐3‐yl)hexyl]thiophene‐2,5‐diyl bromide}, PMHT‐Br, has been prepared by reaction of high‐regioregular (above 92%) poly[3‐(6‐bromohexyl)thiophene‐2,5‐diyl] with 1‐methylimidazole. PMHT‐Br is soluble in water and water miscible solvents such as methanol, DMSO and shows solvatochromism; λmax (nm): 423 (H2O); 435 (MeOH); 452 (DMSO). Increased absorption band broadening observed for aqueous solution as well as NMR spectra in D2O suggests a micelle‐like structure of PMHT‐Br molecules in these solutions: poly(3‐hexylthiophene) core and 1‐methylimidazolium bromide shell. Despite the disturbing effect of ionic groups, the solid‐state PMHT‐Br shows absorption maximum at 520 nm, the band edge at 660 nm (ca. 1.9 eV), and fluorescence emission with maximum at 635 nm, in a good agreement with the polymer regioregularity. Fluorescence emission maxima: λem (nm): 598 (H2O); 562 (MeOH); 574 (DMSO), occur in a vicinity of corresponding adsorption band edges. Plot of electrical conductivity of PMHT‐Br (measured under the dynamic vacuum conditions, 5 × 10?5 Pa) versus 1/T shows a break at about 70 °C same as the temperature dependence of λmax of the solid PMHT‐Br. These breaks indicate an increase in the mobility of polymer segments and ions within PMHT‐Br; however, a thermal analysis did not provide solid evidence for it. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3073–3081, 2010 相似文献
950.