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Lens-less Fourier-transform holography has been actively studied because of its simple optical structure and its single-shot recording.However,a low-contrast interferogram between the reference and object waves limits its signal to noise ratio.Here,multi-reference lens-less Fourier-transform holography with a Greek-ladder sieve array is proposed in the experiment and demonstrated effectively to improve the signal to noise ratio.The key technique in our proposed method is a Greek-ladder sieve array,which acts as not only a wave-front modulator but also a beam splitter.With advantages of the common path,single shot,and no need for a lens,this system has enormous potential in imaging and especially in extreme ultraviolet and soft X-ray holography. 相似文献
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In optical parametric chirped pulse amplification (OPCPA), the degradation of temporal contrast of the compressed signal pulse mainly results from spectral clipping in the grating stretcher with finite size of the optics, parametric fluorescence (PF) and the spectral variations transferred from temporal fluctuation of the pump pulse. The temporal contrast of the recompressed amplified pulse in the OPCPA system is studied numerically and a number of solutions are considered and optimized to achieve the highest temporal contrast. 相似文献
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QCD deconfinement phase transition is supposed to be the same universality class as the 3D-Ising model. According to the universality of critical behavior, the Binder-like ratios and ratios of higher cumulants of order parameter near the critical temperature in the 3D-Ising model are studied. The Binder-like ratio is shown to be a step function of temperature. The critical point is the intersection of the ratios of different system sizes between two platforms. The normalized cumulant ratios, like the Skewness and Kurtosis, do not diverge with correlation length, contrary to the corresponding cumulants. Possible applications of these characters in locating critical point in relativistic heavy ion collisions are discussed. 相似文献
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Finite-size behaviour of generalized susceptibilities in the whole phase plane of the Potts model 下载免费PDF全文
We study the sign distribution of generalized magnetic susceptibilities in the temperature-external magnetic field plane using the three-dimensional three-state Potts model. We find that the sign of odd-order susceptibility is opposite in the symmetric(disorder) and broken(order) phases, but that of the even-order one remains positive when it is far away from the phase boundary. When the critical point is approached from the crossover side, negative fourth-order magnetic susceptibility is observable. It is also demonstrated that non-monotonic behavior occurs in the temperature dependence of the generalized susceptibilities of the energy. The finite-size scaling behavior of the specific heat in this model is mainly controlled by the critical exponent of the magnetic susceptibility in the three-dimensional Ising universality class. 相似文献
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A new concept, called the row–column visibility graph, is proposed to map two-dimensional landscapes to complex networks. A cluster coverage is introduced to describe the extensive property of node clusters on a Euclidean lattice. Graphs mapped from fractals generated with the probability redistribution model behave scale-free. They have pattern-induced hierarchical organizations and comparatively much more extensive structures. The scale-free exponent has a negative correlation with the Hurst exponent, however, there is no deterministic relation between them. Graphs for fractals generated with the midpoint displacement model are exponential networks. When the Hurst exponent is large enough(e.g., H >0.5), the degree distribution decays much more slowly, the average coverage becomes significant large, and the initially hierarchical structure at H < 0.5 is destroyed completely. Hence, the row–column visibility graph can be used to detect the pattern-related new characteristics of two-dimensional landscapes. 相似文献
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Based on the universal properties of a critical point in different systems and that the QCD phase transitions fall into the same universality classes as the 3-dimensional Ising, O(2) or O(4) spin models, the critical behavior of cumulants and higher cumulant ratios of the order parameter from the three kinds of spin models is studied. We found that all higher cumulant ratios change dramatically the sign near the critical temperature. The qualitative critical behavior of the same order cumulant ratio is consistent in these three models. 相似文献
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2013年6月3日,吉林禽业公司发生大火,300多名员工中120人遇难,是我国2000年以来死亡人数最多的一次火灾.此次火灾造成巨大伤亡的一个重要原因是厂房的6个出口只有3个可用,并且员工不知道每个出口的可用性信息.本文运用经典的地面场模型对吉林禽业火灾逃生过程进行模拟,研究了厂房各出口的重要性差异以及出口的可用性对逃生效果的影响.结果表明,如果多开一个出口,最多可挽救54.3%的遇难者,如果6个出口全部可用,76.6%的遇难者能够逃离.另外,在出口可用性信息完全掌握的情况下,遇难人数也会减少21.6%.由此可见,保证人群集聚现场出口的可用性以及信息的及时流通对于保护人民的生命财产安全至关重要. 相似文献
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拍瓦激光系统中剩余的高阶色散导致了脉冲波形的振荡,影响了拍瓦激光的信噪比。为了进一步优化拍瓦激光的信噪比特性,满足激光加速电子、质子等粒子的效率提升需求,本文提出了一种基于双折射晶体的新型超短脉冲的三阶色散主动调控方法,用于信噪比的主动调控。通过数值分析模拟了双折射晶体引入的二阶色散、三阶色散,针对中心波长为1053 nm的拍瓦激光系统,选择适当的晶体厚度,可以通过调节双折射晶体的面内旋转角改变系统剩余三阶色散。同时,基于神光Ⅱ第九路拍瓦激光系统光参量啁啾脉冲放大(OPCPA)预压缩的信噪比测量值,对比了不同量级剩余三阶色散对脉冲信噪比的影响,得出通过改变拍瓦激光系统中剩余三阶色散量,可实现不同量级信噪比的主动调控的结论。该研究结果对于高能激光系统剩余三阶色散的补偿以及信噪比的优化具有重要意义。 相似文献