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实时全息术检测透明物的一种新方法 总被引:2,自引:2,他引:0
介绍了实时全息术检测透明物的一种新方法,它采用物光再现的参考光和参考光通过全息图的直透光所形成的干涉图纹检测透明物体的变化。证明了这组干涉图纹与用参考光再现的物光和物光通过全息图的直透光所形成的干涉图纹分布规律相似,仅在相位上相差π。还讨论了这组干涉图纹的衬比和获得最佳衬比的条件。此方法可消除物光光路上某些因素带来的相位畸变,避开待测物体自发光的干扰,并可在全息图后方任意位置进行记录,这使实时全息术在实践中更具有灵活性,有助于它在更广阔领域内的应用。 相似文献
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环境问题是当今世界上面临的重大问题之一,目前各国不但致力于防治,更重要的是注重提高全民族的环境意识,尤其是在青少年中广泛地开展环境教育。我国的环境问题一直受到党和国家的十分重视,把它定为一项基本国策。环境保护知识涉及生物、化学、物理、地理、医学等知识。 相似文献
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选取赣江流域21个国家或省控水质监测断面,于赣江枯水期(11月)和丰水期(4月)进行水生植被样方调查,共发现水生植物22科46种,其中挺水植物30种,沉水植物10种,浮叶植物和漂浮植物各3种,这些水生植物在赣江流域组成28种群丛,10种群系。对枯水期和丰水期赣江流域上、中、下游水生植物的覆盖度、生物量和多样性(Patrick指数、Shannon-wiener指数)进行了比较,发现枯水期水生植物的覆盖度和多样性明显小于丰水期,赣江流域中游水生植物的覆盖度和多样性明显大于上游和下游,特别是下游。我们认为,流速、水位、基底状况、人为干扰可能是影响赣江水生植被生长和分布的关键因素。更多还原 相似文献
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A facile and atom-economic method for the synthesis of 3a,6a-dihydro-furo[2,3-b]furan derivatives and polysubstituted furans starting from furylcarbionls has been developed. This protocol involved a domino Claisen rearrangement/dearomatizing electrocyclic ring-closure/aromatizing electrocyclic ring-opening sequence. 相似文献
108.
A dual-wavelength fiber laser with a narrow-linewidth, based on a P-F fiber filter has been proposed. Polarization-maintaining fiber Bragg grating (PM-FBG) and a F-P fiber filter are introduced based on the traditional fiber laser. PM-FBG is used as the wavelength selection device. The fiber F-P filter consists of two optical couplers and a section of un-pumped erbium-doped fiber (EDF). Due to the delay of cavity and the loss generated by the EDF, the filter has comb spectral response. The incorporation of the fiber F-P filter leads to the suppression of undesirable modes. At the room temperature, under 980 nm LD pumped, the maximum output of the two wavelengths is respectively ?2.259 dBm and 0.568 dBm, with the 3-dB bandwidth separately 0.1 nm and 0.14 nm, realizing the narrow linewidth and dual-wavelength output. 相似文献
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In this paper, we investigate the generalization of the Camassa–Holm equation where is a positive constant and . The bifurcation and some explicit expressions of peakons and periodic cusp wave solutions for the equation are obtained by using the bifurcation method and qualitative theory of dynamical systems. Further, in the process of obtaining the bifurcation of phase portraits, we show that is the peakon bifurcation parameter value for the equation. From the bifurcation theory, in general, the peakons can be obtained by taking the limit of the corresponding periodic cusp waves. However, we find that in the cases of , when tends to the corresponding bifurcation parameter value, the periodic cusp waves will no longer converge to the peakons, instead, they will still be the periodic cusp waves. To the best of our knowledge, up until now, this phenomenon has not appeared in any other literature. By further studying the cause of this phenomenon, we show that this planar system has some different characters from the previous Camassa–Holm systems. What is more, we obtain some periodic cusp wave solutions in the form of polynomial functions, which are different from those in the form of exponential functions. Some previous results are extended. 相似文献
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We have demonstrated a simple ring cavity tunable multiwavelength Brillouin/Erbium fiber laser (MWBEFL), in which 70 m highly nonlinear photonic crystal fiber (HNL-PCF) is used as the Brillouin gain medium. The fiber laser utilizes recycling mechanism to enhance stimulated Brillouin scattering (SBS). The configuration that consists of only 3 optical components is easy to be integrated and improves the practicality. At the maximum 1480 nm pump power of 110 mW and the Brillouin pump power of 3 dBm, 10 stable output channels with more than 10 dB optical signal to noise ratio (OSNR) and 0.078 nm channel spacing could achieve 10 nm tuning ranges. 相似文献