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51.
An approximate analytical propagation formula of the elliptical Gaussian beams through a paraxial ABCD optical system with a circular aperture is obtained on the basis of the expansion of a hard-edged aperture into a finite sum of complex Gaussian functions. And the parameter characteristics of the truncated beams including the beam propagation factor and the kurtosis parameter are also studied in detail by using the second-order-moments method. 相似文献
52.
Based on the truncated second-order moments method on the cylindrical coordinate systems and the incomplete gamma function, an analytical expression of the generalized beam propagation factor (MG2 factor) of hard-edged circular apertured diffracted Bessel–Gaussian beams is derived and illustrated numerically. It is shown that the MG2 factor of hard-edged diffracted BGBs mainly depends on the truncation parameter δ and the beam parameters m and η. The results can be reduced to that for the non-truncated Bessel–Gaussian beams case and that for the truncated fundamental Gaussian beams case under certain conditions, respectively. The power fraction is also discussed analytically and numerically. 相似文献
53.
湍流大气中光波闪烁的圆环孔径平均因子 总被引:2,自引:1,他引:2
利用弱起伏条件下球面波在大气湍流中传输的光强起伏(闪烁)理论和圆环孔径滤波函数,获得了圆环孔径平均因子的精确表达式。将圆环孔径平均因子关于一个无量纲参量(孔径半径与菲涅耳尺度的比值)拟合成2阶多项式,再找出多项式系数与孔径内外径之比的函数关系,获得了圆环孔径平均因子关于该参量和孔径内外径之比的函数关系式。通过误差分析确定了拟合关系式的适用范围,在此范围内,拟合式与精确式的相对误差小于25%。分别用Tatarskii谱和修正Hill谱分析了湍流内尺度对圆环孔径平均因子的影响,结果显示:在其他条件不变的情况下,内尺度越大,孔径平均效应相对越小。 相似文献
54.
Yang Li Jian Dong Ke Chen Wei Guo 《International Journal of Infrared and Millimeter Waves》2008,29(7):663-672
This paper presents a signal-level simulation model for simulating the process that antenna array of Aperture Synthesis Radiometer
(ASR) collecting thermal radiation and transforming thermal radiation signal into radio frequency (RF) signal. By using the
equivalent complex baseband signals to represent the practical thermal radiation and RF signals, simulation efficiency is
improved significantly. The statistic characteristics of simulation results are found to match the corresponding theoretical
analysis well. Results of an imaging simulation experiment show that this model can be employed in ASR system-level simulator
design. 相似文献
55.
Clear effects criterion is an important criterion for selecting fractional factorial designs [1]. Tang et al. [2] derived upper and lower bounds on the maximum number of clear two-factor interactions (2fi's) in 2n-(n-k) designs of resolution Ⅲ and Ⅳ by constructing 2n-(n-k) designs. But the method in [2] does not perform well sometimes when the resolution is III. This article modifies the construction method for 2n-(n-k) designs of resolution Ⅲ in [2]. The modified method is a great improvement on that used in [2]. 相似文献
56.
Clear effects criterion is one of the important rules for selecting optimal fractional factorial designs, and it has become
an active research issue in recent years. Tang et al. derived upper and lower bounds on the maximum number of clear two-factor
interactions (2fi’s) in 2
n−(n−k) fractional factorial designs of resolutions III and IV by constructing a 2
n−(n−k) design for given k, which are only restricted for the symmetrical case. This paper proposes and studies the clear effects problem for the asymmetrical
case. It improves the construction method of Tang et al. for 2
n−(n−k) designs with resolution III and derives the upper and lower bounds on the maximum number of clear two-factor interaction
components (2fic’s) in 4
m
2
n
designs with resolutions III and IV. The lower bounds are achieved by constructing specific designs. Comparisons show that
the number of clear 2fic’s in the resulting design attains its maximum number in many cases, which reveals that the construction
methods are satisfactory when they are used to construct 4
m
2
n
designs under the clear effects criterion.
This work was supported by the National Natural Science Foundation of China (Grant Nos. 10571093, 10671099 and 10771123),
the Research Foundation for Doctor Programme (Grant No. 20050055038) and the Natural Science Foundation of Shandong Province
of China (Grant No. Q2007A05). Zhang’s research was also supported by the Visiting Scholar Program at Chern Institute of Mathematics. 相似文献
57.
58.
59.
针对目前许多军工仪器红外成像系统的结构简单、体积小、质量轻的无热化设计要求,采用光学被动式方法对8 μm~12 μm波段、相对孔径为1的红外光学系统进行了无热化设计。具体光学系统参数:F=1,f=60 mm,2ω=11.4°。设计结果:在-40℃~60℃工作范围内,该系统的调制传递函数(MTF)接近衍射极限,空间分辨率在20 lp/mm处,中心视场传函接近0.7,边缘视场传函大于0.6。其设计结果满足系统的无热化设计要求。 相似文献
60.