小角前向散射偏振比法颗粒粒度分布反演

在光散射法的颗粒粒径测量方法中,传统测量模型的测量结果易受光路中颗粒杂质的影响。在Mie散射理论的基础上,将小角前向散射法与偏振比法相结合,推导了新的散射光能与粒径分布关系式,构造了传统小角前向散射法和小角前向散射偏振比法两种目标函数,并引入一种非独立模式算法人工鱼群算法对两种方法的目标函数进行反演。仿真采用服从Johnson-SB单峰分布均匀球形颗粒,分别对两种目标函数散射光能加入5%,10%,15%的随机噪声。仿真结果显示,利用人工鱼群算法对小角前向散射偏振比法目标函数反演得到的反演精度、抗噪声能力和鲁棒性都明显优于传统小角前向散射法目标函数的反演结果。     

烟雾环境中532 nm/1550 nm线偏振光前向传输实验研究

针对烟雾环境中偏振前向传输在短波红外波段是否具有偏振信号增强的问题,实验研究了烟雾环境中水平线偏振光在532 nm和1 550 nm波长下的前向传输偏振特性。烟雾环境由烟饼燃烧所制,其主要由悬浮氯化铵颗粒和水汽组成,且氯化铵颗粒在烟饼点燃7~16 min内稳定沉积。搭建了532 nm和1 550 nm两套单波长激光前向传输测试平台,用以测量水平线偏振光在烟雾环境中的前向传输偏振特性。分析测量误差主要由激光源的光强波动误差、测量时间变化误差、偏振器件的安装误差和转角误差引起,计算了532 nm和1 550 nm激光前向传输测试平台的测量误差峰值分别约为1.03%和0.89%。测试烟饼燃烧7~16 min时的偏振状态保持率RoPS,测试结果表明:相比532 nm波长,水平线偏振光在1 550 nm波长前向传输后具有更优异的偏振状态保持特性,且随着烟雾浓度降低,两者之间的偏振状态保持差异逐渐缩小。文中研究通过实验验证了所制烟雾环境中水平线偏振光在1 550 nm波长前向传输后具有优异的偏振信号,这可为短波红外偏振技术的实际应用提供一定的实验支撑。     

雨滴前向散射对光传输影响的研究

利用Mie理论和M-P雨滴谱分布，分析了粒子尺度及不同波长对消光效率因子的影响，详细推导了光波在雨中衰减的计算公式，得到了衰减与降雨率之间的确定关系，介绍了前向散射修正系数，分析了雨滴的前向散射对532nm波长光信号传播的影响，得到了经过前向散射修正后的衰减计算公式。     

多粒子散射的偏振传输特性分析

针对多因素影响下偏振光在散射介质中的一般传输特性,系统分析了入射光波长、介质厚度、粒子参数和入射光偏振态等物理属性对偏振光子传输特性的影响。采用蒙特卡罗方法,追踪每个光子的偏振态变化,通过统计分析偏振度变化曲线得到光经过多次散射后的斯托克斯矢量和偏振信息,并对偏振光在散射介质中的传输规律进行分析。仿真实验表明相对于波长比较大的粒子对入射光的偏振态改变较小;线偏振光能较好地保持自身偏振态;圆偏振光能够在较短时间内重新恢复自身偏振状态,粒子半径越大恢复能力越强,并且在向前传输的过程中其旋转方向会发生改变。     

前向神经网络的一种快速分层线性优化算法

本文利用数学分析的方法,提出了一种前向神经网络快速分层线性优化算法,其特点是:用新方法构造了各层的目标函数;无须计算Hessian矩阵,加快了算法的收敛速度.仿真实验表明,与传统算法如误差反传法或BP法和含势态因子(Momentum factor)的BP法以及现有的分层优化算法相比,新算法能加快收敛速度,并降低学习误差.     

金属目标表面温度场对后向散射偏振结构的影响

文章采用基尔霍夫法和微扰法,探讨了表面为大粗糙度表面和微粗糙表面两种情况 下,入射角、金属目标表面温度场对后向散射偏振结构的影响。根据现有条件设计了实验装置,并用该装置测量了部分实验数据,相关结论对激光探测等领域的研究具有一定的参考价值。     

前向神经网络的神经元分层逐个线性优化快速学习算法

本文提出了一种新的前向神经网络快速分层学习算法.在此学习算法中,其优化策略为对输出层和隐层神经元的连接权值交替优化.对输出层权值优化算法采用基于广义逆的最小二乘递推算法,对隐层神经元的连接权值采取则对每个神经元逐个进行优化,而且采用正交变换加快每一步学习的计算速度和提高算法的数值稳定性.当学习过程停滞时采用随机扰动的方法摆脱过早收敛.数值实验表明,与BP动量因子法、牛顿型方法和现有的分层优化算法相比,新算法不仅学习速度快学习时间短,而且当网络规模增大时仍然比较有效.     

基于凸组合算法优化的前向神经网络观测器设计

本文利用凸组合算法对单隐藏层前向神经网络进行了优化,通过迭代来更新权值以调整隐藏层的信息.同时引入了一个新的误差函数来评价误差性能,该函数通过对权值进行解耦来求解优化参数,提高了参数的计算速度.在此基础上,提出了一种非线性系统的自适应神经网络状态观测器设计方法.最后通过仿真验证了该神经网络观测器能准确并快速地观测出系统的状态值.     

基于混合遗传算法的偏振双向反射分布函数优化建模

为了表征复杂涂层表面的光学散射特性,在微面元理论的基础上,建立了典型涂层样片的偏振双向反射分布函数模型.由于实验数据与模型参数之间存在复杂的非线性关系,采用了遗传算法对模型参数进行反演.针对遗传算法收敛速度慢及易限于局部极小的特点,在传统遗传算法参数反演的基础上,在适应度计算中引入了模拟退火算法对偏振双向反射分布函数模型进行优化建模.实验结果表明:模型的计算结果与实验结果吻合较好.从误差收敛曲线来看,这种混合遗传算法优化方法不仅可以有效避免目标函数陷入局部极小,而且可以有效缩短目标函数的收敛时间.这可以为后续的目标特征提取与识别工作提供参考.     

Chahine algorithm to invert light scattering spectroscopy of epithelial dysplasia

To perceive the epithelial dysplasia from the light scattering spectroscopy (LSS) is an inverse problem, which can be transformed into the inversion of the size distribution of epithelial-cell nuclei. Based on the simulation of single polarized LSS for epithelial-cell nuclei, Chahine algorithm is adopted to retrieve the size distribution. Numerical results show that Chahine algorithm has high inversion precision for both single-peaked and bimodal models, which implies the potential to increase diagnostic resolution of LSS.     

Theory and application of wave propagation and scattering in random media

This paper presents a review of basic theories and recent advances in the studies of wave propagation and scattering in random media. Examples of the random media include the atmosphere, the ocean, and biological media whose characteristics are randomly varying in time and space. The study of electromagnetic, optical, and acoustic waves in such media has become increasingly important in recent years in the areas of communication, detection, and remote-sensing. Topics covered in this paper are divided into "waves in randomly distributed scatterers," "waves in random continua," and "remote-sensing of random media." Transport theory with various approximate solutions and multiple scattering theories are discussed and their relationships are clarified. Included in the analyses are propagation characteristics of intensities, wave fluctuations, pulse propagation and scattering, coherence bandwidth, and coherence time of communication channels through random media. Remote-sensing techniques include recent advances in the use of inversion techniques to deal with ill-posed problems.     

前向光散射粒子消光测量的校正

本文分析了消光测量中的校正方法，首先指出应用于消光方法的Ｂｏｕｇｕｅｒ定理的不足之处，推导了校正系数的表达公式。然后针对实际中，在采用消光方法测量气固两相流流场中的情况下，对校正系数的表达式进行了大量分析计算。分析表明，只有在测量装置收集角较小，且测量对象小于１μｍ时才可以避免由Ｂｏｕｇｕｅｒ定理带来的误差．。     

激光散射流式细胞仪前向光探测方法研究

流式细胞仪利用微球光散射特性对测试细胞进行分析,细胞病变将改变细胞的光学特性,而粒径和折射率是改变细胞散射光光强分布的两大因素,针对激光散射流式细胞仪前向散射光采用单个光敏元件进行一维探测,只针对细胞粒径进行分析的缺点,提出一种前向散射光线阵式探测的方法。首先,根据微粒的Mie氏散射特性建立了模型。然后根据散射模型仿真结果,对不同散射光曲线的特征权值进行了分析。最后基于K-modes聚类算法,对试验数据进行聚类分析。实验结果证明,该方法不仅能替代传统方法对不同粒径大小的颗粒进行分群,同时可以对相同粒径,不同折射率的微球进行分群,误差小于4.51%。     

激光前向散射法高速测量光导纤维直径

本文叙述以He-Ne激光器作为光源,应用光的前向散射法,测量光导纤维直径,并已研制成样机,在有关工厂得到了实际应用.     

Nondestructive determination of refractive-index profile of an optical fibre: forward light scattering method

A nondestructive technique is presented for determining the refractive-index profile of an optical fibre from its forward-scattered pattern arising from a normally incident laser beam. This method does not require any index-matching liquid and is not limited to single-mode fibres. It uses as essential information only the angular positions of the extrema in the measured pattern.     

An approach to include stochastic rough surface scattering into deterministic ray-optical wave propagation modeling

A new method to include stochastic rough surface scattering into deterministic ray-optical wave propagation modeling is derived. It can be utilized in conjunction with the concept of ray launching. Similar to the Kirchoff formulations, the approach is based on a tangential plane approximation, i.e., it is applicable to surfaces with gentle undulations, whose horizontal dimensions are large compared to the incident wavelength. However, in contrast to the Kirchoff models, which are only valid for either slightly rough or very rough surfaces, the proposed stochastic scattering approach includes both the coherent and incoherent components at the same time. The purely deterministic ray-based modeling is expanded by a "stochastic" component, allowing, for the first time, to account for nondeterministic scattering in ray-optical wave propagation modeling.     

Impact of scattering on the capacity, diversity, and propagation range of multiple-antenna channels

The impact of scattering condition and array configuration on performances are inseparable in early analyses of multiple-antenna systems. An array-independent scattering model is introduced where three basic scattering mechanisms are modeled. Performance results become more intrinsic property of the scattering channel itself. For linear arrays of length L in an environment of total angle spread |/spl Omega/|, the ergodic capacity is shown to increase linearly with L|/spl Omega/| for large arrays. When antenna arrays reduce to practical sizes, the capacity scaling depends on the signal-to-noise ratio (SNR) as well. This implies that the number of antennas used should also depend on the SNR. In terms of outage capacity, the tradeoff between spatial multiplexing gain and diversity gain is shown to be very sensitive to the underlying scattering mechanisms. Finally, as |/spl Omega/| varies with the propagation range, the tradeoff among multiplexing gain, diversity gain, and propagation range is studied.