EDXRD安检系统衍射谱数据库的仿真研究

能量色散X射线衍射(EDXRD)系统在安检领域具有重要的应用前景。基于能量色散X射线衍射原理,以ICDD-JCPDS数据作为初始能谱信息,分析了X射线光源、系统结构、探测器分辨率及物质衰减效应对衍射能谱的影响,建立了与系统特性相对应的衍射谱仿真模型。利用该模型,仿真了不同结构参数EDXRD系统的衍射谱,仿真谱和实际测量结果吻合。在此基础上,仿真了海洛因和NH_4NO_3在不同晶体结构下的衍射能谱,为EDXRD安检系统的识别数据库提供了一种有效的构建方法。     

机电信息制药装备

<正>创刊时间2001年7月出刊日期每月15日发行,全年12期刊物性质科技期刊针对行业药厂、药机行业、化工行业、食品行业等发行总量8000册/期,展会增加发行2000册/期,全年发行10万册专辑影响力·相继入选"中国知网数据库(CNKI)全文收录期刊""中国核心期刊(遴选)数据库(万方)收录期刊""中文科技期刊数据库收录期刊""中国学术期刊综合评价数据库统计源期刊"·中国机电行业十大报刊评选位居第三     

机电信息制药装备

<正>创刊时间2001年7月出刊日期每月15日发行,全年12期刊物性质科技期刊针对行业药厂、药机行业、化工行业、食品行业等发行总量8000册/期,展会增加发行2000册/期,全年发行10万册专辑影响力·相继入选"中国知网数据库(CNKI)全文收录期刊""中国核心期刊(遴选)数据库(万方)收录期刊""中文科技期刊数据库收录期刊""中国学术期刊综合评价数据库统计源期刊"·中国机电行业十大报刊评选位居第三     

粉末X射线衍射法鉴定天然气绝热转化制氢催化剂中晶体化合物

首次详细报道采用粉末X射线衍射法(PXRD)鉴定天然气低温绝热、蒸汽转化制氢催化剂(简称天然气绝热转化制氢催化剂)中晶体化合物。其主要物相鉴定结果为:尖晶石(MgAl_2O_4)、绿镍矿(NiO)、刚玉(α-Al_2O_3)。其中还含有铝酸锶(SrAl_(12)O_(19))。PXRD鉴定数据能够满足天然气绝热转化制氢催化剂研发的要求。     

征订启事

2013年征订(双月刊)中国科技核心期刊·中国核心期刊(遴选)数据库收录期刊轻工机械国内总发行:浙江省报刊发行局(邮发代号32-39)国外总发行:中国国际图书贸易总公司(发行代号BM4555)欢迎订阅·欢迎刊登广告·欢迎赐稿     

二甲基二硫逐焦膦酸二甲酯合成样品中化合物的质谱特征、碎裂机理及其鉴定

为了掌握二甲基二硫逐焦膦酸二甲酯的质谱特征,开展了该化合物合成样品的气相色谱 质谱(GC/MS)和串联质谱(MS/MS)分析鉴定研究。利用GC/MS联用技术对混合物进行分析,得到10个组分的电子电离（EI）和化学电离（CI）全扫描质谱信息。根据CI谱图中的同位素比值,推测化合物可能的元素组成;通过EI谱图与数据库谱图比对,鉴定了其中6个组分的结构。然后,对二甲基二硫逐焦膦酸二甲酯和4个未知化合物采用MS/MS模式获得各自的裂解碎片,通过分析不同的裂解碎片,推测未知化合物可能的结构,并解释其可能的碎裂途径。实验共鉴定出合成样品中10个化合物,并总结了不同化合物的质谱特征,可为相关化合物的分析和鉴定提供参考。     

设备故障监测与诊断系统数据库设计

介绍设备监测与诊断系统及其结构特点。引入了基于状态维护(CBM)和通用关系信息架构(CRIS)两个概念,从中归纳出系统功能需求、信息需求和信息关系。根据系统的功能需求设计数据库的组织结构,将整个数据库分成4个子模块:基础数据、知识库、结果数据和系统数据。分别对这几个子模块的设计进行详细阐述,进而实现以不同设备为监测对象的系统数据库,为大多数工业设备监测与诊断提供基础,同时为今后开发通用设备的监测与诊断系统提供可靠的数据模型。     

专业数据库,为您锁定目标群——解读工业媒体发行

秉承具有百年出版历史和发行经验的德国弗戈工业媒体集团B2B杂志发行方式的精髓,自1995年以来,MM《现代制造》发行部在原机械工业部情报所(即机械工业信息研究院和机械工业出版社)第三次全国工业普查结果的基础上,建立和积累了国内领先且独具的制造业企业的读者数据库——Vogel Database(简称VDB)。VOGEL数据库现状 MM《现代制造》发行部经过8年的完善和积累,VOGEL数据库目前拥有覆盖全国制造业企业     

基于UHPLC-Q-Orbitrap/MS表征竹叶石膏汤物质基准化学成分

本研究利用超高效液相色谱-四极杆-静电场轨道阱质谱(UHPLC-Q-Orbitrap/MS)法分析竹叶石膏汤物质基准的化学成分。采用SUPELCO C18色谱柱(100 mm×4.6 mm×2.7μm)分离,以0.1%甲酸水溶液-乙腈为流动相进行梯度洗脱。在正、负离子模式下,通过高分辨质谱给出分子离子峰和碎片离子数据,结合相关文献、自建数据库和对照品,共鉴定出竹叶石膏汤物质基准中121个化合物,包括47个三萜类、34个黄酮类、10个甾体皂苷以及30个其他类化合物。通过系统分析竹叶石膏汤物质基准中多种化学成分,可为其质量控制及药效物质基础研究提供依据。     

粉末X射线衍射法定性分析一种未知催化剂中晶体化合物

催化剂研制、放大及工业应用须对其进行精确分析表征.采用粉末X射线衍射法(XRPD)定性分析了一种未知催化剂中的晶体化合物,其中晶体鉴定结果为:γ-AlO(OH)、γ-Al2O3(量少)及ZSM-23,分析数据能够满足催化剂研究开发及工业应用对XRPD分析表征数据的要求.元素测定结果证明未知催化剂还含有铂族金属.实验结果表明,本法对未知催化剂分析表征的适应性很好,因而具有一定推广应用价值.     

临床X射线相衬成像研究进展

X射线相衬成像在提高人体软组织成像的衬度分辨率及空间分辨率研究中具有潜在优势,是一项有着广阔发展前景的技术。它利用空间相干X射线投过物体后携带的相位信息进行成像,在临床上适用于软组织物体,可以减少吸收剂量,进而减轻病人的辐射损伤。本文详述了当今几种典型的X射线相衬成像方法,包括X射线干涉相衬,衍射增强相衬以及类同轴相衬的成像原理以及发展历程。通过对比表明了几种成像方法的优缺点。最后对临床X射线相衬成像有待解决的问题作了分析。     

Electron diffraction analysis of individual single-walled carbon nanotubes

We present a detailed electron diffraction study of individual single-walled carbon nanotubes. A novel sample preparation procedure provides well-separated, long and straight individual single-shell nanotubes. Diffraction experiments are carried out at 60 kV, below the threshold for knock-on damage in carbon nanotubes. We describe experimental parameters that allow single-tube electron diffraction experiments with widely available thermal emission transmission electron microscopes. Further, we review the simulation of diffraction patterns for these objects.     

The effect of exit beam phase aberrations on parallel beam coherent x-ray reconstructions

Diffraction artifacts from imperfect x-ray windows near the sample are an important consideration in the design of coherent x-ray diffraction measurements. In this study, we used simulated and experimental diffraction patterns in two and three dimensions to explore the effect of phase imperfections in a beryllium window (such as a void or inclusion) on the convergence behavior of phasing algorithms and on the ultimate reconstruction. A predictive relationship between beam wavelength, sample size, and window position was derived to explain the dependence of reconstruction quality on beryllium defect size. Defects corresponding to this prediction cause the most damage to the sample exit wave and induce signature error oscillations during phasing that can be used as a fingerprint of experimental x-ray window artifacts. The relationship between x-ray window imperfection size and coherent x-ray diffractive imaging reconstruction quality explored in this work can play an important role in designing high-resolution in situ coherent imaging instrumentation and will help interpret the phasing behavior of coherent diffraction measured in these in situ environments.     

On the peculiarities of CBED pattern formation revealed by multislice simulation

A modified multislice method has been developed for calculations of Convergent Beam Electron Diffraction (CBED) patterns. The validity of the method for HOLZ- and Kikuchi-line calculations has been proofed by comparison to Bloch-wave calculations. The application of the method leads to the new understanding of CBED patterns formation. Dynamical scattering of weak HOLZ reflections plays the key role in the appearance of deficient lines in the central CBED disk. Different HOLZ lines do have significantly different and extended scattering areas; the central 000 CBED disk, consequently, contains structural information from an area around the primary beam which is determined by the Bragg angle of HOLZ reflections and the thickness of the sample. A variation of lattice parameters, if present within this area, results in artificial symmetry violations of the pattern and in changes of line profiles.     

Channelling effects in atomic resolution STEM

A Bloch wave theory for incoherent scattering of an incident plane wave has proved successful in predicting the fine detail in 2-D zone axis channelling patterns formed by ADF, BSE and characteristic X-ray detection in beam rocking mode. A previously published example of polarity determination of GaAs by channelling contrast is compared with simulations in order to illustrate the applicability of the theory. Modification of boundary conditions for a focused coherent probe allows lattice-resolution incoherent contrast based on ADF and EELS detection as well as X-ray emissions to be catered for within a similar theoretical framework. Mixed dynamic form factors constitute an integral part of this theory, where quantum-mechanical phase is a core issue. Simulations of lattice-resolution ADF and EELS are discussed with reference to various zone axis projections of GaAs. Issues of single versus double channelling conditions, and local versus nonlocal interactions, are discussed in relation to X-ray, ADF and EELS detection.     

Complementary freeze-fracture, freeze-etch specimens

For a number of reasons, the specimens used to try to correlate the electrical and structural properties of commercial semiconductor devices often consist of a thick amorphous layer (e.g. silicon oxide) and a thinned layer of crystalline material (e.g. silicon) containing the p-n junctions. Diffraction patterns and diffraction contrast images from such specimens recorded in conventional and scanning transmission electron microscopes at 80 and 500 kV are shown. The visibility of these diffraction patterns and images depends on the mode of operation, the aperture sizes and the side on which the electrons enter the specimen. The interpretation of these results is discussed and the practical implications for imaging of such specimens are pointed out.     

Coherence in inelastic electron scattering

The origin of dynamical effects in the inelastic scattering of fast electrons is discussed with reference to an (e, 2e) model for ionization and an Einstein model for TDS. The development of Kikuchi lines and bands from these localized interactions is discussed and related to current density. It is shown why the coherent preservation of amplitude and phase relationships between partial waves in a dynamical framework is of fundamental importance. Analytic expressions, related to the “mixed dynamic form factor” S(Q₁, Q₂, E), are written for K-shell ionization and for TDS. Diffraction of fast electrons emitted from a coherent point source on the top surface of a crystal is also discussed from the unified model presented for localized inelastic scattering.     

Specimen‐thickness effects on transmission Kikuchi patterns in the scanning electron microscope

We report the effects of varying specimen thickness on the generation of transmission Kikuchi patterns in the scanning electron microscope. Diffraction patterns sufficient for automated indexing were observed from films spanning nearly three orders of magnitude in thickness in several materials, from 5 nm of hafnium dioxide to 3 μm of aluminum, corresponding to a mass‐thickness range of ～5 to 810 μg cm^–2. The scattering events that are most likely to be detected in transmission are shown to be very near the exit surface of the films. The energies, spatial distribution and trajectories of the electrons that are transmitted through the film and are collected by the detector are predicted using Monte Carlo simulations.     

Quantitative measurements of Kikuchi bands in diffraction patterns of backscattered electrons using an electrostatic analyzer

Diffraction patterns of backscattered electrons can provide important crystallographic information with high spatial resolution. Recently, the dynamical theory of electron diffraction was applied to reproduce in great detail backscattering patterns observed in the scanning electron microscope (SEM). However, a fully quantitative comparison of theory and experiment requires angle-resolved measurements of the intensity and the energy of the backscattered electrons, which is difficult to realize in an SEM. This paper determines diffraction patterns of backscattered electrons using an electrostatic analyzer, operating at energies up to 40 keV with sub-eV energy resolution. Measurements are done for different measurement geometries and incoming energies. Generally a good agreement is found between theory and experiment. This spectrometer also allows us to test the influence of the energy loss of the detected electron on the backscattered electron diffraction pattern. It is found that the amplitude of the intensity variation decreases only slowly with increasing energy loss from 0 to 60 eV.