Fluorescence monitoring of ultrasound degradation processes

Ultrasound-based water treatment is often applied for degradation of stable organic pollutants, such as polycyclic aromatic hydrocarbons and halogenated compounds. Monitoring the degradation process, during the application of ultrasound radiation, is of considerable economical interest. In this work, the possibility of performing on-line spectral analysis during sonication was examined and it was found that direct absorption or fluorescence readings are misleading. Optical monitoring is strongly affected by the absorption and scattering of light by cavitation micro-bubbles and ultrasound induced particulates. A model was developed to account for these effects and to allow for on-line fluorescence analysis. The model takes into account the absorption and scattering coefficients of the micro-bubbles and particulates, as well as their time dependent concentration. The model parameters are found from independent measurements where the pollutants are added to already sonicated pure water. Then, the model is tested for predicting the actual fluorescence behavior during the sonication process. It has been shown that the model allows for recovery of the true degradation data, as obtained by off-line HPLC measurements.     

Electron radiation damage in copper in the high voltage electron microscope

The various factors influencing the nucleation of radiation damage in the HVEM are reviewed. A method for obtaining quantitative information from observations is given. The effect of reirradiation at room temperature on the damage formed at elevated temperatures is shown. This effect may give experimental information concerning the strain fields surrounding large dislocation loops.     

欧姆接触中接触电阻率的计算

从欧姆接触电阻率的定义出发,先从理论上介绍了热离子发射、热离子场发射和场发射三种不同情况下欧姆接触电阻率的计算公式,然后详细地从实验上综合各种测试方法,并讨论了其利弊．     

基于LabVIEW的高分辨率光谱测试系统(英文)

提出了一种基于LabVIEW的无源器件光谱测试方案.通过LabVIEW编程控制可调谐激光器、可编程光滤波器、光功率计和数据采集平台,获得了具有不同传递函数的光谱特性.实验中激光器的扫描速度为10nm/s,扫描范围为10nm,数据采集卡的采样速率为1MS/s,结果表明:单个器件的光谱测试可以在1s内完成,光谱分辨率可达1pm;与利用宽带光源和光谱分析仪的传统光谱测试方法相比,所提方案的测试性能可达到传统方案水平,且能显示更精细的光谱细节.该方案能应用于有高分辨率、快速和高效要求的光谱测试中.     

无限包层Bragg光纤的传输模式研究

分析得到了横向电场分量和磁场分量所满足的耦合方程,对于介质折射率的不连续处,采用严格的边界条件来处理。基于全矢量模型,使用有限差分法编写了复模式的求解器,并将其应用于Bragg光纤的模式求解和分析。绘制出了Bragg光纤模式谱图,分类分析了在无限包层情况下Bragg光纤模式的基本特性。     

Sound transmission prediction by 3-D elasticity theory

The problem of sound transmission through layered panel structures is studied with the exact theory of three-dimensional (3-D) elasticity. The exact solution to the 3-D elasticity equations is obtained by the use of the Fourier spectral method. Based on this analytical solution, a transfer matrix is derived that relates the spectral displacements and stresses on the one surface of the panel to those on the opposite panel surface. The transfer matrix is then used to develop the analytical solutions for sound reflection and transmission coefficients. Explicit, concise expressions are obtained for the analytical solutions of the acoustic transmission and reflection coefficients under the general conditions of layered anisotropic panels. Examples are given for both single-layer and sandwich panels. Predictions on sound transmission from the 3-D elasticity theory are compared with available data from other methods, and the results are discussed.     

A study of the structure of G-P zones in Ti-rich TiNi shape memory melt-spun ribbons

A hybrid structure composed of ordered C11_b Ti₂Ni and Ti₅Ni₃ substructures for the G-P zones precipitated in Ti-rich Ti–Ni shape memory ribbons is proposed to explain the appearance of extra diffuse scattering streaks in transmission electron microscopy observations. The point defects of Ni vacancies and Ti antisites, resulting in the lattice fluctuant displacement, also cause the incommensurate extra diffuse scattering streaks.     

Contours of constant Δ and Ψ in the 2–4 plane for the ellipsometric functions

Contour graphs of ₂ vs ₄ for different film thicknesses and a range of angles of incidence have been plotted for the ellipsometric functions Δ and Ψ in both the reflection and transmission modes. In the case of reflection ellipsometry, when the plots for Δ_R and Ψ_R are superimposed, the two sets of contours cross nearly at right angles over a large part of the field, this being indicative of the high accuracy obtainable in using this technique to determine ₄ and ₂ and hence the optical constants, n and k, for the film material. The reflection ellipsometric technique is accurate over angles of incidence between 30° and 75° and for a range of film thicknesses between λ/30 and 5λ. Transmission ellipsometry is less useful, due to anomalies in both X_s and X_p where sudden phase changes of ±π occur in regions of interest. There is also the possibility of multiple solutions, although the use of a multiangle technique would enable the “correct” values to be more easily determined.     

Frequency dependence of the photonic noise spectrum in an absorbing or amplifying diffusive medium

A theory is presented for the frequency dependence of the power spectrum of photon current fluctuations originating from a disordered medium. Both the cases of an absorbing medium (“grey body”) and of an amplifying medium (“random laser”) are considered in a waveguide geometry. The semiclassical approach (based on a Boltzmann-Langevin equation) is shown to be in complete agreement with a fully quantum mechanical theory, provided that the effects of wave localization can be neglected. The width of the peak in the power spectrum around zero frequency is much smaller than the inverse coherence time, characteristic for black-body radiation. Simple expressions for the shape of this peak are obtained, in the absorbing case, for waveguide lengths large compared to the absorption length, and, in the amplifying case, close to the laser threshold. Received 8 August 2000     

Closed-form Analysis of Lossy Cosine-Squared Tapered Nonuniform Transmission Lines

The rigorous analytical solutions and the ABCD matrix of the lossy Cosine-Squared tapered nonuniform transmission lines (CSTNTL) are presented in this paper. According to different boundary conditions, the unique solution is obtained mathematically. Through the numerical calculations based on analytical solutions, the distributed voltages and currents in different terminated cases are shown to explain the transmission characteristics of CSTNTL. Especially in the lossy case the distributed power values are simulated to show the attenuation phenomenon.