共查询到18条相似文献,搜索用时 281 毫秒
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根据动态光散射装置测量纳米粒径原理,开发了一套基于现场可编程门阵列(FPGA)的纳米粒径测量系统。该系统通过光电倍增管(PMT)输出光子脉冲信号,利用FPGA实现高速脉冲采集及自相关运算,采用双脉冲计数器实现高精度可控的连续计数,并实现DDR3异步存储以及USB通信交互等接口功能。自研板卡既可实现自相关函数实时采集运算,又可无丢失地保存海量原始数据信号。采用该系统对200nm聚苯乙烯颗粒进行了测量,分析了不同采样时间及延迟时间等参数对粒径测量结果的影响。实验结果表明:自研FPGA采集板卡测量重复性为1.2%,具有很好的稳定性和重复性。 相似文献
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互信息函数反映的是系统中的非线性关联,是将线性的关联函数对非线性系统的一种推广,动态光散射领域目前未见到用计算互信息函数进行分析的报道.本文中通过计算互信息函数,对动态光散射检测电机转速的时间序列进行分析,研究表明,互信息函数法能准确地测出电机转速.同时,由于互信息函数自身的优点--能实际地反映出数据之间的相互关联,因此,与自相关函数法比较,互信息函数法反映出了更多的动力学信息.目前正在把互信息函数分析法用于检测颗粒粒径的实验当中.希望利用互信息函数分析的方法,在动态光散射检测颗粒粒径的实验当中得到更多的动力学信息.并进一步应用于纳米颗粒粒径的动态光散射检测中. 相似文献
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雨滴粒子直径和速度实时测量是雨滴谱参数计算的关键,为了实时、连续得到精确、可靠的统计雨滴样本数据,采用基于高速线阵CCD的光阵排列法对雨滴速度和直径进行非接触测量,通过FPGA构造雨滴图像乒乓操作缓存单元,存储两行连续一维动态雨滴图像,发挥FPGA的并行运算能力,利用FPGA快速实现雨滴动态图像连通域检测及连通域标记算法,进而实现雨滴粒子的直径和速度检测.实验证明,该方法能自动连续测量记录雨滴数量、粒径大小和收尾速度,为雨滴谱参数计算提供可靠样本数据. 相似文献
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简要介绍了散射型光电感烟探测器的光散射原理及粉尘、烟雾颗粒的分布。根据不同波长对相同颗粒的散射特性的差异,通过无因次粒径参量简单计算分析,采用双波长比较方式,对不同散射区特性进行分析。说明利用双波长比较方式,实现光电散射型感烟探测器抗粉尘颗粒干扰成为可能。 相似文献
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Luis A. Clementi Jorge R. Vega Luis M. Gugliotta 《Chemometrics and Intelligent Laboratory Systems》2011,107(1):165-173
A statistical Bayesian method is proposed for estimating the particle size distribution (PSD) of polymeric latexes from multiangle dynamic light scattering (MDLS) measurements. The procedure includes two main steps: 1) the calculation of the angle-dependent average diameters of the PSD from the MDLS autocorrelation measurements, and 2) the PSD estimation through a Bayesian method (that is solved with a Markov chain Monte Carlo sampling strategy implemented in the form of a Metropolis-Hasting algorithm). First, the method was evaluated through two simulated examples that involved unimodal and bimodal PSDs of different shapes. Then, the method was employed for estimating two bimodal PSDs obtained by mixing two narrow polystyrene standards. For comparison, all examples were also solved by numerical inversion of the raw MDLS autocorrelation measurements through a classical regularization technique typically used for inverting ill-conditioned linear problems. The proposed method appears as an effective and robust tool for characterizing unimodal or multimodal PSDs without requiring any a priori assumption on the number of modes or on their shapes. For unimodal PSDs exhibiting high asymmetries and for bimodal PSDs with modes of different particle concentration, the Bayesian method produced more accurate results than those obtained with the classical regularization technique. 相似文献
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Multiangle dynamic light scattering (MDLS) can provide better results for particle size distribution (PSD) determination than single-angle dynamic light scattering. Proper analysis of MDLS data requires data from each measurement angle to be appropriately weighted according to the intensity scattered by the particles at each scattering angle. The angular weighting coefficients may be determined by measuring the angular dependence of the scattered light intensity or estimated in various ways. In either case, any noise on the weighting coefficients will adversely affect the PSD determination. We propose a new iterative recursion method for estimating the weighting coefficients and demonstrate its effectiveness for recovering PSDs from both simulated and real experimental data. The new method gives better PSD results than those found using other weighting estimates. 相似文献
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高精度的角度采集和测量是激光跟踪仪实现跟踪和精密测量的关键。针对激光跟踪仪中采用的圆光栅编码器,本文介绍了一种基于FPGA的数据采集系统的设计与实现方法。该采集系统分为滤波、计数、通信三大模块。数字滤波模块用于消除跟踪控制过程中跟踪头振动、抖动产生的信号干扰;计数模块实现方波脉冲的倍频、辨向及计数;通信模块实现跨时钟域的数据传输。系统通过Modelsim仿真及实验测试验证了方法的可行性与可靠性。采用谐波分析方法对角度误差进行了修正,测量误差由3.5″降低到1.5″。本文设计的角度采集系统及谐波分析误差修正方法具有一定的通用性,可广泛应用于相关领域。 相似文献
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We describe the implementation of precision laser transmission spectroscopy for sizing and counting nanoparticles in suspension. Our apparatus incorporates a tunable laser and balanced optical system that measures light transmission over a wide (210-2300 nm) wavelength range with high precision and sensitivity. Spectral inversion is employed to determine both the particle size distribution and absolute particle density. In this paper we discuss results for particles with sizes (diameters) in the range from 5 to 3000 nm. For polystyrene particles 404 to 1025 nm in size, uncertainties of ±0.5% in size and ±4% in density were obtained. For polystyrene particles from 46 to 3000 nm in size, the dynamic range of the system spans densities from ~10(3)/ml to ~10(10)/ml (5 × 10(-8) to 0.5 vol. %), implying a sensitivity 5 orders of magnitude higher than dynamic light scattering. 相似文献
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We describe a dynamic light scattering experiment designed in order to study creep motion in granular materials. This method
is based on the recording of the speckle pattern with a charge coupled device (CCD) camera. The autocorrelation function of
the scattered electric field is calculated and related to the displacement field of the beads. As an application, the measurement
of the thermal expansion of a granular material subjected to temperature variations is presented. 相似文献
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Optical measurements of particle size and composition in granular samples are difficult to make due to complex light scattering from particles. These multiple scattering events bias absorption estimates and complicate the calculation of scattering and absorption coefficients used to estimate sample properties. Time series data, such as chromatograms and photon time-of-flight (TOF) profiles, contain self-repeating (fractal) characteristics. Power law analysis of photon TOF profiles allows the determination of absorption coefficients and particle sizes in a single experiment. A correlation dimension algorithm was used on photon TOF data from scattering samples. MLR models were then obtained from correlation dimension plots for the estimation of sample properties. Estimates of particle sizes and absorption coefficients were shown to agree well with theoretical values when compared using independent validation sets. Results show close to a 3-fold and up to a 5-fold decrease in the errors of estimation of dye concentration and particle size, respectively, as compared to steady-state measurements. The power law approach provides a useful means of determining sample properties in highly scattering media. 相似文献
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在将散射粒子间的相互作用看作简谐力、入射光为准直高斯光束、散射光为理想平面光波的模型下研究了胶体溶液中布朗粒子的统计特征并求解了动态光散射的散射光电场强度的自相关函数; 相似文献