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Fluctuation spectrum in an exactly solvable model with dissipation: A new model of the Flicker noise


General expressions have been derived for the phase fluctuation spectrum of a shortwave signal reflected at the ionospheric layer with an arbitrary regular permittivity profile and given spectrum of inhomogeneities.


Determination of frequency instability on the basis of the signal phase fluctuation spectrum


We also show how the fluctuation spectrum of two quantities such as the saturation and the reaction rate can be drastically different, the first being universal and the other sensitive to the geometry of the substrate.


The predictions for the oneelectron density, the static structure factor, and the longwavelength charge fluctuation spectrum are compared to the results of extensive molecular dynamics simulations.

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 The spectrum width of photocurrent of LDA includes several different kinds of Doppler ambiguity broadening. The velocity fluctuation spectrum of turbulent flow can not be obtained from the photocurrent spectrum with broadening, unless all the Doppler ambiguity broadening can be determined or estimated. The mutualbeating contributions from two scattering particles play an important role in spectrum broadening, which varies with the spatial coherence condition. The broadening from mutualbeating... The spectrum width of photocurrent of LDA includes several different kinds of Doppler ambiguity broadening. The velocity fluctuation spectrum of turbulent flow can not be obtained from the photocurrent spectrum with broadening, unless all the Doppler ambiguity broadening can be determined or estimated. The mutualbeating contributions from two scattering particles play an important role in spectrum broadening, which varies with the spatial coherence condition. The broadening from mutualbeating is called coherence broadening △Vcoh. If the particle pairs are situated in the "coherence volume", the mutualbeating will give a beat frequency in the output of the photodetector. The lasting time of the mutualbeating is called the effectivetransit time of the scattering particle pairs, △teff, which is corresponding to the coherence broadening. The mutualbeating contributions and the relationship between the mutualbeating and the detection mode can be shown by a special optical system with a threedimentional scattering model composed of two fwodimentional models. They are varied with the expansion and the construction of the coherence volume. The experimental results show that the coherence broadening reaches its minimum value when the coherence volume and the illuminated volume are of the same magnitude.  LDA(激光多普勒流速计)的光电流谱宽中包含各种不同的多普勒模糊展宽,当多普勒模糊展宽还不能确定时,就无法由光电流谱来得到湍流脉动速度的谱。由两个散射粒子产生的互差拍在谱展宽中起重要作用,当散射粒子对处于“相干体”内时,互差拍将在光电检测器的输出中产生差拍频率信号,与相干体尺度有关的互差拍持续时间是散射粒子的有效泼越时间,它所对应的谱宽称为相干性展宽,此展宽与空间相干条件是密切相关的.互差拍项以及它与检测模式的关系可以用组合三元散射模型及特殊光学系统来显示,实验研究结果指出:当相干体和测量体的尺度是同量级时,相干性展宽达到最小值。  A convective turbulence system with a liquid medium (water or ethanol) that can be used for simulation tubulent atmospher for wavefront distortion compensation is described. After using the improved plate heater and cooler, a convective turbulence with wide intertial range similar to the spectra of atmospheric turbulence was obtained. Its turbulent intensity can be easily controlled and the optical characteristics of turbulence, such as stability, statistucs feature of turbulent and index of refraction fluctuation... A convective turbulence system with a liquid medium (water or ethanol) that can be used for simulation tubulent atmospher for wavefront distortion compensation is described. After using the improved plate heater and cooler, a convective turbulence with wide intertial range similar to the spectra of atmospheric turbulence was obtained. Its turbulent intensity can be easily controlled and the optical characteristics of turbulence, such as stability, statistucs feature of turbulent and index of refraction fluctuation spectrum are better than that in the real atmosphere and can be repeated easy. So the system can be used for the experiments of adaptive optical compensation and for studying the interaction of turbulent and blooming, and light propagation through turbulent atmosphere.  描述一种用于波前补偿实验的对流湍流系统。它用水或乙醇为介质，在采用了自行研制的平板式加热和冷却器后，不仅湍流强度易于控制，温度起伏谱和大气相似，具有较宽的惯性区和较好的重复性，而且比实际大气湍流更平稳。本系统除可用于自适应光学系统的波前补偿试验和湍流与热晕相互作用的研究外，还可用于其它激光通过湍流大气的模拟实验研究。  An experimental study is presented on TBL (turbulellt boundary layer) pressure fluctuation frequency spectrum of a revolution body in water. According to results of the experiment, a relation of convective frequency f0, correspond the models of the study, is given. Relations of turbulent wallpressure fluctuation spectrum on stagnation region and development region to frequency and speed are obtained.  本工作对水中回转体TBL（湍流边界展）压力起伏频谱特性进行了分析研究．将TBL压力起伏谱分频率高于迁移频率f0和低于f0的两个频段描述，给出与实验用模型相应的f0计算关系；由实验结果的分析得到TBL转捩区和发展区压力起伏频谱与频率、速度间的关系。   << 更多相关文摘 
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