Backscattered polarization patterns determined by conservation of angular momentum

It is demonstrated that the occurence of backscattered polarization patterns relates to the conservation of angular momentum of light. Using the geometrical phase formalism in the spin space, we develop a model where the helicity-maintaining and the helicity-flipping multiple-scattering processes can be accounted for. The model explains practically all the symmetries present in the spatially resolved Mueller matrices.     

Backscattered electron imaging of dental amalgam

A study of the microstructure of set dental amalgams has been undertaken using techniques of back-scattered electron imaging, transmission electron microscopy and X-ray analysis. It has been demonstrated that small ( 0.2, m) particles of a copper-tin phase are present in the matrix of the conventional low-copper amalgams and that the reaction zone around the silver copper eutectic phase in the high copper dispersion type amalgams is of a duplex nature consisting of the Cu₆Sn₅, phase and an intervening layer of silver-mercury phase.     

Reversible Image Coding by the Use of Optical Fibres

We examine the possibility of using optical fibres to reversibly modify a picture in order to encode and to decode it. The decoder is to receive the coded picture in the form of a photographic transparency and the decoding process requires possession of the proper apparatus in addition to the code key. The new feature of the proposed devices lies in the greatly enhanced degree of coding security. We discuss two different methods of constructing the necessary device, and we estimate theoretically the expected degree of security for each.     

采用加权最小二乘法的恒星校正研究

针对光电探测设备恒星校正过程中的时效性问题,本文分析了产生时效性的原因以及在时效性存在的情况下,人们期待的两种方式。在此基础上,提出了基于加权最小二乘法拟合求解算法。算法能够实现两个方面的功能:提高了在局部区域内校正的精度;提高了在实时引导使用过程中的引导精度。本文依据两种情况,采用外场试验数据进行了仿真,验证了算法的可行性和有效性。     

Accuracy Analysis of a Pointing Mechanism for Communication Applications

In this paper, a detailed accuracy analysis for the orientation of an innovative open-chain pointing mechanism is carried out, employing methods for indirect measurements. The particular shape of the mechanism exhibits the advantage of high structural stiffness and different pointing accuracy in comparison with a standard orthogonal axes gimbal. With the aim of finding out advantages and drawbacks as regard the accuracy of the proposed pointing mechanism, an accuracy analysis is performed through three different methods of uncertainty expression and propagation based on the probability theory or the theory of evidence. The proposed pointing mechanism, in comparison with the standard orthogonal axes gimbal, exhibits a considerable lower uncertainty for two of the three Euler angles that are used for the end-effector orientation expression and a higher uncertainty for the third Euler angle. Thus, the proposed mechanism could be particularly suited for pointing directional antennas, allowing the employment of high-data-rate communication systems. This result is strengthened by the fact that the accuracy analysis was performed with different uncertainty expression and propagation methods, which take into account only random effects or both random and systematic effects.     

Phase Identification in a Scanning Electron Microscope Using Backscattered Electron Kikuchi Patterns

Backscattered electron Kikuchi patterns (BEKP) suitable for crystallographic phase analysis can be collected in the scanning electron microscope (SEM) with a newly developed charge coupled device (CCD) based detector. Crystallographic phase identification using BEKP in the SEM is unique in that it permits high magnification images and BEKPs to be collected from a bulk specimen. The combination of scanning electron microscope (SEM) imaging, BEKP, and energy dispersive x-ray spectrometry holds the promise of a powerful new tool for materials science.     

透射模式电子背散射衍射技术在纳米材料研究中的应用

为了提高电子背散射衍射技术的空间分辨率, 使之能够对纳米尺度的晶粒或超细粉末进行相鉴定和取向分析, 本研究通过自主设计的透射模式电子背散射衍射技术的样品台, 及调整EBSD探头位置及角度, 收集到清晰、完整的透射电子菊池衍射花样。研究了减薄块体样品厚度对透射电子菊池衍射花样的影响, 对减薄氧化锆涂层样品进行了t-EBSD面分布分析, 其结果的平均角度偏差(MAD)值仅为0.38, 成功鉴定出小于30 nm尺度的纳米氧化锆涂层立方相; 将超声分散后的纳米TiO₂粉体滴在铜网上, 采用t-EBSD对纳米颗粒进行点分析, 成功鉴定了锐钛矿相和金红石相TiO₂, 其中纳米锐钛矿TiO₂粉体的最小尺寸为20 nm左右, 使得扫描电镜中相鉴定的最小分辨率从目前的约100 nm提高到小于30 nm, 大大拓展了电子背散射衍射技术在纳米材料研究中的应用范围。     

Backscattered electron imaging of cementitious microstructures: understanding and quantification

During the last 20 years, backscattered electron imaging of polished surfaces has become well established as a method for the study of cement and concrete microstructures. The technique has many advantages, including the visualisation of representative cross-sections over a wide range of magnifications and reproducible contrast dependent on atomic number. Nevertheless the limitations of observing a two-dimensional section of a three-dimensional structure must be borne in mind.

In this paper, the general microstructural features of hydrated cement pastes are described. Although the amount of aluminate phase (“C₃A”) in cement is comparatively minor, it plays an important role in determining many of the microstructural features of cement paste microstructure, for example in the formation of “Hadley” grains.

Despite the very heterogeneous nature of cement paste, it is important to be able to derive quantitative measures if the relationships between microstructure and properties are to be understood. The possibilities to quantify BSE images are described. The interface between paste and aggregates in concrete is particularly variable, but average features can be measured, which help to understand the processes of packing cement grains, which gives rise to this region. Finally an example of the potential for BSE images to study concrete durability is given.     

Analysis of Orange Peel Defect in St14 Steel Sheet by Electron Backscattered Diffraction (EBSD)

In this paper, the orange peel defect in the surface range of the st14 steel sheet has been investigated using the electron backscattered diffraction (EBSD) technique. It has been found that the orange peel defect in the st14steel sheet was resulted from the local coarse grains which were produced during hot-rolling due to the critical deformation in dual-phase zone. During deep drawing, the coarse grains with {100}＜001＞ microtexture can slip on the {112}＜111＞ slip system to form bulging and yields orange peel defects, while the coarse grains with {112}＜110＞orientation do not form the defect as the Schmid factor of {112}＜111＞ slip system in it equals zero.     

The Use of Stereoscopic Imaging Techniques to Reduce Apparent Loss of Information Caused by Image Damage

Stereoscopic viewing techniques may often be used to reclaim data which has apparently become lost through physical or chemical degradation of images. The original to be preserved may not necessarily itself be stereoscopic but merely an identical copy.

The technique assumes that degradation of any two images is unlikely to be identical on a site for site basis and that stereoscopic viewing will always reject the lesser quality site in preference for the more perfect site in recomposing the original image.     

Modification of Pointing Performance in Altered Gravitational Environments

The Fitts’ law describes a correlation between the time needed to complete basic tasks such as pointing movements and the level of knowledge of the specific target to be reached. While it has been largely proved in normal gravity, very few experiments have been carried out in altered gravitational conditions. In our experiment, four subjects were positioned in front of a panel where round targets were placed along a circumference. They carried out pointing movements towards the targets when these were switched on. The task time was acquired and processed off-line. In all the cases, the performance of each subject have been significantly modified in the altered gravitational environment and, in particular, hypergravity seems to affect motor performance more considerably than microgravity. Even if experiments involving several subjects and more complex tasks have to be carried out in order to confirm our findings, these results show that ergonomics could be strongly affected by the modification of gravity, especially during the first phase of exposure to gravity alteration.     

卫星数字化影像输出技术及其应用效果

随着数码成像技术的发展，卫星影像图制作过程中由于光学镜头产生的几何畸变，图像边缘模糊等图像失真问题得到根本解决，可显著提高卫星图像的清晰度和几何精度；而美国圣保利克公司生产的Light-Jet-5000RS型激光数码成像仪是目前国际上图像精度最高的图像输出设备，可获得较满意的卫星图像，本文扼要介绍了其成像原理，技术参数和实际应用效果。     

利用AAPM体模对CT机图像质量检测的应用

本文简要介绍利用AAPPM体模对CT机图像质量检测在实际操作中的方法和注意事项。     

The Use of Image Analysis to Simulate Growth Kinetics of Ferrite by Carbon Diffusion in SG Cast Iron

1.IntroductionThe use of the Quantimet 900 imageanalysis system to simulate the growth kine-tics of ferrite by carbon diffusion inspheroidal graphite(SG)cast iron has beendiscussed[1].The results obtained from theQ900 agreed qualitatively with experiment.     

Nondestructive Porosity Assessment of CFRP Composites with Spectral Analysis of Backscattered Laser-Induced Ultrasonic Pulses

The laser-ultrasonic method for nondestructive quantitative local porosity assessment for CFRP composites is proposed and realized experimentally for only one available flat surface of a specimen or a product. This method combines the laser thermoelastic generation and the high-sensitivity piezoelectric detection of broadband pulses of longitudinal ultrasonic waves and does not require the detection of the backwall echo ultrasonic signal. The generation and the detection of ultrasonic pulses is carried out with the specially designed laser-ultrasonic transducer, which allows one to obtain both the temporal profile and the frequency spectrum of a part of the ultrasonic signal backscattered by gas voids in a composite specimen. The frequency spectrum of backscattered ultrasonic pulses is analyzed for three sets of CFRP specimens with different epoxy matrix fractions and porosity. The empirical relation between porosity of CFRP specimens and the spectral power (structural noise power) of ultrasonic signals backscattered by voids is obtained for porosity values up to 0.15. This relation allows one to evaluate the local porosity from measured structural noise power both for CFRP specimens and products fabricated from the same composite material. The proposed laser-ultrasonic setup demonstrates a basis for a system of CFRP porosity assessment in field conditions. It can be very useful especially for nondestructive detection of structural changes of composite materials that will allow evaluation of products during their life time.     

The Use of Correlation Analysis of the Image in Phase Optoelectronic Devices

The possibility of using phase-correlation analysis of an image in optoelectronic devices to measure small angular and linear displacements of objects is considered. It is shown that the measurement accuracy is thereby increased.__________Translated from Izmeritel’naya Tekhnika, No. 5, pp. 37–39, May, 2005.     

应用数字图像相关法测定瓦楞原纸的泊松比

对瓦楞原纸泊松比的测定存在许多困难,传统的接触式方法难以满足测定要求,还没有一种简单高效的方法能解决这个问题。针对传统位移测量方法的不足,提出以数字图像相关法测定瓦楞原纸的泊松比。通过对试样变形前后的图像进行相关性位移分析,将试验所得的实测位移与已标定位移进行对比,所得结果具高度的一致性,相对误差范围为1%～3%。试验测定面纸MD（machine direction）方向和CD（crossmachine direction）方向的泊松比分别为0.175和0.073,芯纸MD方向和CD方向的泊松比分别为0.275和0.119。测试及分析结果表明,应用数字图像相关法测定瓦楞原纸的方法是可行的,具有较佳的应用价值,能为研究纸张的泊松比提供一个新途径。