Measurement of the laser pulse width on the microscope objective plane by modulated autocorrelation method

We report on the construction details of a compact autocorrelator set‐up for the measurement of the width of infrared laser pulses at the focal plane of a microscope for two‐photon excitation fluorescence imaging. One of the novelties of the set‐up, which leads to an improved measurement accuracy, is the use of a modulation technique that is achieved by mounting one of the interferometer mirrors on a loudspeaker driven by a sinusoidal bias at low frequency. A non‐linear least‐square routine selects only that part of the fluorescence signal that is modulated at the same frequency as the loudspeaker bias. To further increase the accuracy, the laser pulse width is obtained from a series of measurements at different values of the modulation bias. The autocorrelator is a compact single bread‐board (10 × 20 cm); it is PC‐controlled both for the acquisition and the analysis of the data and can be coupled to different ports of the microscope. The increase in the pulse width measured for three different ports of the microscope is well accounted for by the group velocity dispersion and the glass thickness of the optics found along these paths.     

Polarization artefacts of an FTIR microscope and the consequences for intensity measurements on anisotropic materials

The infrared beam on both the main Nicolet Nexus bench and the attached Spectra‐Tech Continuum microscope has been shown to be partially polarized. The degree of polarization is ≈ 30%. Although the state of polarization of the infrared beam is of no consequence when measuring the spectra of isotropic materials (gases, liquids), there is a potential problem when considering the spectra of anisotropic materials. Single band intensities are particularly prone to error as small changes in sample thickness or orientation directly affect the intensity. Thickness effects can be overcome by measuring intensity ratios. However, because of the partially polarized nature of the infrared beam, even intensity ratios, illustrated here by the ratio amide I/II of collagen fibres, vary with sample orientation. If overlooked, this effect can be problematic when measuring infrared spectra with an FTIR microscope from samples that are anisotropic or contain anisotropic domains, even though they may appear isotropic on a macroscopic scale. Because dichroic ratios remain unaffected, the intensity ratio from two bands with different transition moments may be used to give a strong indication of the orientation of the sample. This work is illustrated by reference to the FTIR spectra of orientated polyethylene, collagen tape and human trabecular bone.     

Automated three-dimensional analysis of particle measurements using an optical profilometer and image analysis software

The automated collection of topographic images from an optical profilometer coupled with existing image analysis software offers the unique ability to quantify three‐dimensional particle morphology. Optional software available with most optical profilers permits automated collection of adjacent topographic images of particles dispersed onto a suitable substrate. Particles are recognized in the image as a set of continuous pixels with grey‐level values above the grey level assigned to the substrate, whereas particle height or thickness is represented in the numerical differences between these grey levels. These images are loaded into remote image analysis software where macros automate image processing, and then distinguish particles for feature analysis, including standard two‐dimensional measurements (e.g. projected area, length, width, aspect ratios) and third‐dimensional measurements (e.g. maximum height, mean height). Feature measurements from each calibrated image are automatically added to cumulative databases and exported to a commercial spreadsheet or statistical program for further data processing and presentation. An example is given that demonstrates the superiority of quantitative three‐dimensional measurements by optical profilometry and image analysis in comparison with conventional two‐dimensional measurements for the characterization of pharmaceutical powders with plate‐like particles.     

压电压杆式冲击波压力传感器

本文介绍了用于测量冲击波的气隙式带色散效应的压杆式传感器的基本原理以及制作、标定、讨论等内容.本传感器的特点是结构简单、成本低廉、工艺容易实现,有一定的发展前途.     

一种改进的解析测图法

本文提出了改进解析测图法的二点措施：１．利用ｆｘ－３６００Ｐ型计算器编制程序训计算碎部点的坐标和高程；２设计了直角坐标展点尺．采用这种改进的解析测图法能显著地提高测图的速度和精度，使该方法更具实用性．     

多变量自校正PID调节器与自校正控制器的关系分析

提出了多变量自校正ＰＩＤ调节器的控制律；并与多变量广义最小方差自校正控制器（ＳＴＣ）作了比较。发现ＳＴＣ具有ＰＩＤ的性质。预示了今后的研究方向。     

长清模拟科威特油井灭火试验中的流体力学计算问题

根据当时灭火试验提供的数据和模拟灭火现场的具体条件,从流体力学理论的角度,计算出完成水压试验和最后灭火试验所需的基本参数,为试验圆满成功提供了理论依据。     

多变量高增益反馈系统的稳定化问题

本文将高增益反馈系统的鲁棒稳定化问题作为鲁棒正实性实现问题进行研究.导出了实现鲁棒正实性的补偿器存在的条件,阐明了对象特性变动的容许范围。并通过示例对 RPR 控制及 LQ最优控制进行了比较,显示了 RPR 控制的稳定域,要比 LQ 最优控制宽广.     

Additional microstructural analysis on the samples examined in the paper ‘Are high resolution resistometric methods really useful for the early detection of electromigration damage?’

In a previous paper (A. Scorzoni, S. Franceschini, R. Balboni, M. Impronta, I. De Munari, and F. Fantini, Are high resolution resistometric methods really useful for the early detection of electromigration damage? Microelectr. Reliab. 1997;37(10/11):1479–1482), we reported largely different electromigration lifetimes and different high resolution early resistance changes measured on two nominally identical lots of 4 μm wide lines tested at moderately accelerated stress conditions. A microstructural analysis on unstressed samples was performed in order to detect the reason which induced these differences. The analysis confirmed a major defectivity of the lot with shorter lifetime: we detected the presence of TiAl₃ precipitates at the interface between the Al–Cu and the Ti-based metal barrier. This was not easily detectable by means of simple visual inspection. These additional findings confirm that a quick electrical detection of the metallization quality could be feasible by means of high resolution resistance measurements without the need of time-consuming direct examination of production lots.