Transmission Fluctuation Spectrometry in Concentrated Suspensions Part Two: Particle Overlapping

Transmission fluctuations measured on a flowing suspension of particles with a high spatial and temporal resolution can be used to measure the particle size distribution and particle concentration. The theory of transmission fluctuation spectrometry (TFS) was recently developed, whereby the statistical behavior of the entire suspension is described on the basis of a single monolayer, in combination with a layer model describing the suspension as a series of independent monolayers. As the monolayers are assumed to be statistically independent from each other, the transmission through the 3‐dimensional suspension is modeled as the product of transmissions through the monolayers.     

Transmission Fluctuation Spectrometry in Concentrated Suspensions. Part Three: Measurements

The theory of transmission fluctuation spectrometry (TFS) was developed for particle size analysis in flowing particle suspensions, whereby the statistical transmission fluctuations are used to extract the particle size distribution (PSD) and particle concentration. In the previous parts of this publication high concentration effects on TFS were investigated theoretically and by simulation. This work presents a study on TFS measurements in concentrated suspensions. By introducing an empirical correction to include the high concentration effects from both the monolayer structure and particle overlapping in the inversion algorithm, it is possible to obtain the particle size distribution and particle concentration over broad ranges of particle sizes and concentrations.     

The Fundamentals of Particle Size Analysis by Transmission Fluctuation Spectrometry.

A transmission signal measured on a flowing suspension of particles with a high spatial and temporal resolution shows significant fluctuations, which contain the complete information on particle size distribution and particle concentration. In Parts 1 and 2, the basic properties of signal fluctuations were studied for temporal averaging by a gliding time window and for spatial averaging by a circular beam of uniform intensity. However, the experimental implementation of such conditions is difficult. Now, the theory is extended for Gaussian beams of variable diameter and averaging by signal filtering in the frequency domain. This provides the basis for an experimental implementation by transmission of a laser beam and analog signal processing by an array of low pass filters.     

Measurements on Particle Size Distribution and Concentration by Transmission Fluctuation Spectrometry with Temporal Correlation

Transmission fluctuation spectrometry with temporal correlation (TFS‐TC) is a new method for particle analysis. When a narrow light beam irradiates on a particle dispersion flow, the variation of the number of particles in the small measuring zone will cause the transmitted light to fluctuate, which includes the complete information on both particle size distribution (PSD) and particle concentration. The method may be used for real‐time, inline/online applications due to its simplicity of measuring principle and experimental setup. Until recently, the theory has been limited to low particle concentrations. In this work, an experimental study of the TFS‐TC measurement is presented for a very wide range of the particle concentrations. By introducing an empirical correction including the high concentration effects and considering the effect from rheological conditions in the inversion algorithm, the particle size distribution and particle concentration are reconstructed, resulting in the coverage of a broad range of particle size and concentration.     

Transmission Fluctuation Spectrometry with Spatial Correlation

Transmission fluctuation spectrometry (TFS) is being developed as a new method of particle size analysis. In the early approaches, the particle suspension was illuminated by one beam with finite beam diameter and the transmission signals underwent a process with variable spatial and/or temporal averaging and a subsequent nonlinear operation. The transmission fluctuations were obtained as a spectrum which included the information on particle size distribution and particle concentration. A new approach presented here employs two narrow parallel beams. While changing the beam separation, the transmission fluctuations of these two beams are expressed in terms of the expectancy of the transmission product (ETP). The analytical expression of the ETP through a monolayer is derived and the ETP of a 3‐dimensional suspension is formulated based on the layer model. The deviation between the transition functions of 3‐dimensional suspensions and monolayers is found to be affected by effects from particle overlapping and monolayer structure.     

Particle Size Analysis by Transmission Fluctuation Spectrometry: Experimental Results Obtained with a Gaussian Beam and Analog Signal Processing

Transmission fluctuation spectrometry (TFS) is a method for the analysis of particle size distributions based on the statistical fluctuations of a transmission signal. Complete information on the PSD and particle concentration can be retrieved by a special transformation of the transmission signal, whereby the expectancy of the transmission square (ETS) is determined after the signal has been subjected to a procedure of spatial and temporal averaging. By varying the averaging parameters over a wide range, a spectrum of ETSs is obtained and introduced into a linear equation system, which yields the PSD. In the experimental realization presented here, variable temporal averaging is realized in the frequency domain with a series of low pass filters at different cutoff frequencies while spatial averaging inevitably occurs as the particles pass through a focused Gaussian beam of finite cross section. Experimental results on spherical particles (glass beads) and non‐spherical particles (SiC) are presented. The PSDs are resolved in 30 intervals within a particle size range from 1–1000 μm, employing a modified Chahine inversion algorithm. So far, the measurements are limited to moderate particle concentrations. Some influences affecting the measurements, especially for higher particle concentrations, are discussed in detail.     

Experimental Study on Particle Size Distribution and Concentration Using Transmission Fluctuation Spectrometry with the Autocorrelation Technique

Based on the statistical characteristics of the transmission fluctuations in the particle suspension, transmission fluctuation spectrometry with autocorrelation (TFS‐AC) is described theoretically, with the assumptions of geometric ray propagation and completely absorbent particles in the suspension. The experiments presented here are realized in a focused Gaussian beam with the TFS‐AC technique. The acquisition of transmission fluctuation signals is achieved by using a high‐resolution digital oscilloscope. The transition function of TFS‐AC is obtained by varying the autocorrelation time. With a modified iterative Chahine inversion algorithm, solving a linear equation retrieves information on the particle size distribution and particle concentration. Some experimental results on spherical and non‐spherical particles are presented and discussed. The experiments cover a particle size range from 1μm to 1000 μm and a particle concentration of up to 12 %.     

无限细光束中透射起伏时间相关频谱法高浓度效应的模拟

时间或空间相关透射起伏频谱法是近年发展起来的一种新的颗粒测量方法,它可同时测量颗粒粒径分布和浓度,并可用来进行在线、实时测量。研究表明,随着浓度增大,逐渐增强的高浓度效应会导致测量值越来越严重地偏离理论值。本文采用模拟计算方法讨论无限细光束照射下的时间相关透射起伏频谱法高浓度效应并给出部分实验验证。分析表明,无限细光束照射时的透射起伏相关频谱主要受到层结构效应的影响,颗粒交叠效应不明显,表明为随着颗粒浓度增大,转换函数(特征函数)逐渐偏离低浓度理论值并向无因次相关时间小的方向移动,阶高始终保持不变。     

基于二阶滤波器的消光起伏谱颗粒测量结果

消光起伏频谱法是一种新的测量两相流系统中颗粒粒径分布和浓度的方法,装置简单,操作方便,适合实时、在线测量。采用二阶低通滤波器对起伏的透射率信号分析,得到消光起伏频谱实验数据,并利用改进的Chahine循环方法计算得到颗粒的粒径分布和浓度信息。重点讨论高浓度情况,包括对特征函数频率响应的修正和对其阶高修正两个方面,得到修正参量并运用到反演算法中从而得到正确的测量结果。测量结果表明,通过高浓度修正,消光起伏频谱法可以在很大的颗粒浓度动态范围得到合理的测量结果,其可测颗粒最大体积分数视颗粒的大小而定。     

Scattering and Transmission by a Monolayer of Spheres: A Study on the Monolayer Structure

The angular distribution of scattered light and the transmission of radiation through a monolayer of monodisperse spherical particles at variable particle concentration are studied. The scattering of light by a single particle is calculated with the classical Lorentz‐Mie theory. For a monolayer of mono‐dispersed spherical particles, if the monolayer density is less than 0.5 and the particle size parameter is larger than 5, effects from multiple scattering and dependent scattering can be excluded so that only steric interactions are considered. It is found that the scattering pattern, especially in the forward and backward directions, and the transmission are strongly dependent on the monolayer density.     

The Fundamentals of Particle Size Analysis by Transmission Fluctuation Spectrometry. Part 1: A Theory of Temporal Transmission Fluctuations in Dilute Suspensions

The extinction of radiation in suspensions is traditionally described by the Bouger-Lambert-Beer law (BLBL). Based on a quasi-continuum approach, the BLBL does not account for the discrete nature of particles or their spatial extension and arrangement. If an extinction measurement is made with a high spatial and temporal resolution, the transmitted intensity signal shows significant fluctuations. The strength of fluctuation is related to the physical properties of the suspension and the process of spatial and temporal averaging. Exploiting this connection, it is possible to calculate the particle size distribution and the particle concentration from transmission measurements. This part of the series of papers provides a method for the temporal decomposition of the transmission's power spectrum, which permits the information on the particle size and concentration to be extracted from the seemingly irregular fluctuation of the transmission signal.     

Locally Resolving Measurements of PSD,Particle Concentration and Particle Velocity by Means of TFS with Dual Beams

Transmission fluctuation spectrometry with spatial correlation (TFS‐SC) is based on transmitting two beams of radiation through a flowing suspension, whereby the distance of the beam centers is varied. Thus, the spatial correlation of the transmission fluctuations of the two beams is determined as a function of the beam distance. By numerical modeling, the transition functions of the correlation are found as a function of beam distance, beam diameters, particle diameter and beam intersection angle. Experimentally determined spatial correlation spectra can be inverted to obtain the particle concentration and particle size distribution by using the theoretical transition functions for mono‐sized particles. In addition, time correlations can be used to extract information on particle velocity. Some experimental results obtained by TFS‐SC are presented and discussed. This method appears promising for application in the local resolving of measurements of PSD, particle concentration and particle velocity in two‐phase flows, both in the laboratory and in process control.     

透过率起伏光谱分析法测粒技术

提出的透过率起伏光谱分析法是一种新的颗粒测量方法。采用一细小光束照射匀速流动的颗粒系统,通过采集透射光起伏信号,经统计处理得到透过率的平均值与起伏谱。通过求解逆问题,从透过率的起伏谱中得到颗粒粒径分布信息,再结合透过率的平均值得到颗粒的体积分数信息。给出了关于单层颗粒透过率的平均值与起伏谱的理论表达式,并推广到三维单分散和多分散的颗粒系统。对粒径在32~425μm内的稀薄颗粒系进行了部分实验测试和模拟计算,结果表明该方法可同时对颗粒粒径分布和体积分数进行有效测量。     

Conductance Fluctuation of the Normal Metal in an SNS Structure

The conductance of a clean normal metal spanning between two superconductors (SNS structure) has been investigated. It is found that the conductance fluctuates periodically with the phase difference of two superconductors. When the pairing symmetry in one side of the superconductors is d_x²-y², the fluctuation period tends to be π instead of 2π, and the phase dependence of its conductance depends strongly on the orientation of the junction in contradistinction to the s-wave case. It can be used as a new method to determine the pairing symmetry of the high-Tc superconductors.     

激发相干态下双模介观传输线的量子效应

将介观无损耗传输线中的驻波场看成作相对运动的两列同频率的行波的叠加，此电路量子化后成为两个频率相同、不同模的光子场。计算和分析了激发相干态下电压和电流梯度的量子涨落，指出了双模传输线与一般的LC电路、双模传输线与单模传输线量子涨落的异同之处。     

湿度起伏对可见光波段折射率结构常数的影响

大气折射率起伏主要是由温度和湿度起伏引起的。提出一种研究湿度起伏对折射率结构常数影响的新方法,即从超声风速计测量的虚温信号中提取出湿度起伏的信息,可计算出湿度起伏、温湿相关项的结构常数。采用自行研制的温度脉动仪和超声风速计分别在湿度差异较大的干燥的戈壁滩和潮湿的海边进行实验,并用实验时的气象参量对湿度起伏进行了模式计算。测量和模式计算都表明：湿度起伏本身对Cn^2的贡献很小,可忽略不计,湿度起伏对Cn^2的影响主要是通过与温度起伏相结合来实现的,在一般情况下,这种贡献不到10％。但在湿度较大,特别是日落前Cn^2处于最小值附近,温湿相关项的贡献可超过10％。     

电感耦合等离子体质谱中有机试剂的基体效应研究

研究了乙醇、丙醇、丙三醇、乙酸、乙二胺和三乙醇胺等与水互溶的有机试剂对不同质量和电离曜闰元素质谱信号的影响。在优化的工作条件下,溶液中加入少量的乙醇、丙醇、丙三醇、乙酸、乙二胺或三乙醇胺对电离能在９～１１ｅＶ的元素的信号有不同程度的增强,附加乙二胺或三乙醇胺对Ｈｇ信号的增强效应显著大于乙醇、丙醇和丙三醇等试剂;探讨了乙二胺和三乙醇胺对Ｈｇ的信号增强机理。利用乙二胺或三乙醇胺对Ｈｇ的信号增强的特性,     

表面活性剂对空气-乙炔火焰原子吸收法测定铝的增感效应研究

研究了溴化十六烷基三甲基胺、氯化十六烷基吡啶等10种表面活性剂对测定铝时的增感效应。结果表明,在实验所选择的表面活性剂中,阳离子表面活性剂对铝有明显增感作用,阴离子表面活性剂对铝有抑制作用,而特殊表面活性剂对铝没有作用。以溴化十六烷基三甲基胺(CTMAB)为增感剂,研究了空气-乙炔火焰原子吸收法测定铝镍合金样品中铝的工作条件、CTMAB用量、溶液介质和浓度及共存离子干扰的影响。测定铝的线性范围为0.10～2.0g·L-1,方法的相对标准偏差为2.6%,标准加入回收率在97%～103%之间。     

Laser‐induced Breakdown Detection (LIBD) for the Highly Sensitive Quantification of Aquatic Colloids. Part II: Experimental Setup of LIBD and Applications

Laser‐induced Breakdown Detection (LIBD) enables the concentration and size of aquatic nano‐particles (colloids), in the range of 10–1000 nm and from about 1 ng/L (ppt) up to some mg/L (ppm), to be determined. Such particles, which are frequently encountered in aquatic systems, cannot be detected using methods based on laser light scattering or obscuration or if detection is possible, then only at a comparably low level of accuracy. The method of Laser‐induced Breakdown Detection uses a high‐energy pulsed laser beam to selectively generate a plasma (dielectric breakdown) on particles. The method is based on non‐linear optics and allows for the determination of both mean particle size and concentration in aqueous samples. Practically, this method is non‐invasive, sample preparation is not required, and measurement can take place online. This second part of the double publication describes the experimental basics as well as the latest developments in the field of LIBD. Furthermore, it shows examples of practical applications and compares the technology to standard methods like dynamic laser light scattering as well as laser light obscuration.     

热Fock态下量子效应对介观左手传输线负折射系数的影响

基于热场动力学理论研究了热Fock态下量子效应对介观左手传输线微波段负折射系数的影响.结果表明:负折射系数随电流涨落的增加表现出线性递增的特点,而随温度的升高、频率的增大表现出锐减特性;负折射系数的变化幅度受光子数调控.该结论可对基于左手传输线开发的微波器件的微型化、集成化研究提供参考.