PDF417条码生成实现的优化

PDF417是一种应用最为广泛的二维条码,实现其生成优化可使其应用更加方便、高效.二维条码PDF417有多种数据压缩模式,针对各种数据压缩模式,提出了一个简便的适用于多级纠错等级的解决方法;应用VB编程处理复杂多项式计算,实现了数据压缩编码算法的优化,从而使在整体数据压缩后,码字数目得到减少.该方法可用于PDF417数据压缩生成实现,促进了二维条码的应用和普及.     

第六讲 蒙特卡洛法评定测量不确定度简介

一、什么是蒙特卡洛法 蒙特卡洛法缩写为MCM．MCM是一种概率传播的方法,即通过对输入量X的概率密度函数（PDF）离散抽样,由测量模型传播输入量的概率分布．计算获得输出量y的概率密度函数（PDF）的离散抽样值,     

《测量不确定度评定与表示》系列讲座 第六讲 蒙特卡洛法评定测量不确定度简介

正一、什么是蒙特卡洛法蒙特卡洛法缩写为MCM,MCM是一种概率传播的方法,即通过对输入量Xi的概率密度函数(PDF)离散抽样,由测量模型传播输入量的概率分布,计算获得输出量Y的概率密度函数(PDF)的离散抽样值,进而由输出量的离散分布数值获取输出量的最佳估计值、标准不确定度和包含区间。该最佳估计值、标准不确定度和包含区间的可信程度随PDF抽样数的增加而提高。图1描述了由输入量Xi(i=1,……,N)的PDF,通过模型传播,给出输出量Y的PDF的过程的示意图。图     

300MW汽轮机供热蝶阀卡涩处理

冬季供热时,因供热蝶阀经常发生卡涩,不能满足热网首站的热负荷需要。通过计算碟簧片改为38对时和供热蝶阀阀板直径车削去4mm,通过以下计算可将阀板上的平衡孔对称堵死8个。3号机供热蝶阀改造后,供热蝶阀运行正常、无卡涩现象,满足了油田供热需要,提高了机组运行可靠性,供热经济效益巨大。     

《测量不确定度评定与表示》系列讲座 第六讲 蒙特卡洛法评定测量不确定度简介

正一、什么是蒙特卡洛法蒙特卡洛法缩写为MCM,MCM是一种概率传播的方法,即通过对输入量Xi的概率密度函数(PDF)离散抽样,由测量模型传播输入量的概率分布,计算获得输出量概率密度函数(PDF)的离散抽样值,进而由输出量的离散分布数值获取输出量的最佳估计值、标准不确定度和包含区间。该最佳估计值、标准不确定度和包含区间的可信程度随PDF抽样数的增加而提高。     

OpenMP在PDF技术中的应用

目前,多核处理器被广泛应用于桌面系统,为了充分利用多核处理器的计算能力,以充分发挥多核系统的强大计算能力。本文介绍一种重要的工业标准OpenMP,并将其应用于PDF技术的图像融合中。从实验结果分析得出,将OpenMP应用于PDF技术中执行效率得到明显提高。     

典型非高斯分布假设下累积和检测方法性能研究

累积和检测方法是根据声呐目标信号出现与消失时概率密度函数（Probability Distribution Function,PDF）的变化进行有效的瞬态信号检测。以非高斯模型t分布假设替代传统的高斯分布方差变化假设作为描述瞬态信号的PDF形式,推导了累积和检验统计量的表达、更新量PDF求取的数值方法,利用快速傅里叶变换法计算了门限和自由度等检测参数。利用仿真的落水信号、船体加速信号和消声水池实验数据进行检验。结果表明,基于t分布假设的累积和方法对瞬态脉冲信号的检测效果优于常规累积和方法,能更快地响应信号变化,更好地抑制背景干扰。     

塑料卡钩的设计原理与分析

本文介绍了塑料卡钩的结构特点、应用空间和材料选择原则及计算校核方法。塑料卡钩结构类似于金属弹簧原理,由于塑料材料特点,其塑料卡钩结构又不同于金属弹性结构,可以实现其独特的功能。在结构设计上使用塑料卡钩结构,装配简单可靠,可减少螺钉使用量,减低成本和节省资源,有利于保护环境,而先进的CAE计算手段更助于复杂塑料卡钩结构件的设计制造。     

隐形加密 PDF417 条码的药品防伪系统探析

分析了目前常见药品防伪系统的不足,介绍了PDF417 条码的基本原理。探讨了采用红外隐形油墨印刷的PDF417 条码隐形方法和基于DES,ECC,RSA 的三重条码加密方法,并设计了基于隐形加密PDF417 条码的药品防伪系统,详细阐述了该防伪系统的工作原理、防伪系统结构设计和防伪系统软件设计,分析了系统的防伪能力。结果表明,该系统有较强的防伪能力,适合药品防伪,可有效杜绝假冒伪劣药品的泛滥,充分保护商家和消费者的权益。     

基于GPRS的IC卡门禁系统的设计与实现

介绍一种基于GPRS的非接触式IC卡门禁系统,该系统可以用于多校区高校的统一门禁管理,也可用于异地办公的总公司与分公司之间的统一门禁管理.详细探讨GPRS在IC卡门禁系统中的软、硬件实现方法,并给出该系统的硬件电路框图和通信软件流程图.     

JCPDS-ICDD Research Associateship (Cooperative Program with NBS/NIST)

The Research Associateship program of the Joint Committee on Powder Diffraction-International Centre for Diffraction Data (JCPDS-ICDD, now known as the ICDD) at NBS/NIST was a long standing (over 35 years) successful industry-government cooperation. The main mission of the Associateship was to publish high quality x-ray reference patterns to be included in the Powder Diffraction File (PDF). The PDF is a continuing compilation of patterns gathered from many sources, compiled and published by the ICDD. As a result of this collaboration, more than 1500 high quality powder diffraction patterns, which have had a significant impact on the scientific community, were reported. In addition, various research collaborations with NBS/NIST also led to the development of several standard reference materials (SRMs) for instrument calibration and quantitative analyses, and computer software for data collection, calibration, reduction, for the editorial process of powder pattern publication, analysis of powder data, and for quantitative analyses. This article summarizes information concerning the JCPDS-ICDD organization, the Powder Diffraction File (PDF), history and accomplishments of the JCPDS-ICDD Research Associateship.     

A neutron powder diffraction study of short range order in ferroelectric Pb(Mg(1/3)Nb(2/3))O(3)

The structure of Pb(Mg(1/3)Nb(2/3))O(3) (PMN) was investigated using pulsed neutron powder diffraction. Rietveld analysis suggests small displacements of Pb and O atoms, with anomalously large thermal factors. The pair-distribution function (PDF) derived from experiment indicates the presence of short range order. Modeling in real space by fitting to the experimental PDF suggests displacements of lead and oxygen atoms of much larger magnitude than those indicated by the Rietveld analysis. Correlation of these displacements may be related to the onset of bulk ferroelectricity in this material.     

球磨对滑石、绿泥石、菱镁石和刚玉X射线衍射峰强度的影响

采用球磨工艺,获得了不同粒度的滑石、绿泥石、菱镁石和刚玉粉末样品,用来研究球磨时间对试样衍射峰强度的影响.试验表明,采用球磨法制得的样品的X射线衍射峰严重变形,随着球磨时间的延长,变形更加严重.辽宁产滑石和绿泥石,球磨4h,其衍射强度衰减不大,可以满足X射线定量分析的精度要求.菱镁石在球磨条件下迅速粉化,X射线衍射法定量分析时不宜采用.刚玉是一种较好的耐球磨物质,宜优先用作参比物质.     

高能球磨法制备不锈钢-TiC纳米复合粉末的研究

在真空条件下采用高能球磨法以不锈钢粉末、钛粉和碳粉为原料制备了不锈钢-TiC超细复合粉末.X射线、扫描电子显微镜、比表面积评价等分析技术被用来对球磨过程中粉末的微观状态进行了分析.结果表明,随着球磨时间的增加,不锈钢复合粉末逐渐细化,用X射线衍射方法计算的最终晶粒可达到20nm.同时,钛粉和碳粉在球磨过程中发生反应形成TiC,可获得纳米级的不锈钢-TiC复合粉末.     

Ab initio phasing of X-ray powder diffraction patterns by charge flipping

Determining crystal structures from powder X-ray diffraction data remains a challenging problem in materials science. By embedding a Le-Bail-like procedure within the recently discovered charge-flipping phasing algorithm, an extremely simple, fast and effective ab initio method has been developed to determine phases directly from indexed powder diffraction patterns. The algorithm solves the degeneracy problem by applying spherical averaging for overlapping Bragg reflections, while solving the phase problem by using the Oszlányi-Süto charge-flipping algorithm. The processes of peak decomposition and phasing are integrated within the same iteration, and a dynamic support is used. The Fienup hybrid input-output algorithm is also incorporated to minimize stagnation. The ability of the algorithm to find structure-factor phases rapidly is found to assist with the fundamental problem of degeneracy (overlapping reflections) which is intrinsic to powder diffraction data. Space-group and chemical-composition information are not needed as inputs, and can be determined from the result. The method is illustrated using several experimental powder patterns of indifferent quality.     

Preparation of nanocrystalline VO<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> by high-energy ball milling

We report high-energy milling of macrocrystalline nonstoichiometric cubic vanadium monoxide (VO _y ) powder in a planetary ball mill lined with stabilized zirconia. The results indicate that milling of macrocrystalline VO _y powder at 500 rpm for more than 2 h considerably broadens diffraction line profiles, with no changes in the crystal structure of the vanadium monoxide, VO_1.00. Microstructural examination of vanadium monoxide powder by high-resolution scanning electron microscopy and X-ray diffraction indicates that high-energy ball milling can be used to produce vanadium monoxide powder with an average crystallite size within 23 nm.     

Nonuniform metallic state in manganites and cuprates

Local lattice distortions suggesting nonuniform charge distributions were found to be a common feature of manganites and cuprates in the metallic state by neutron scattering studies. The atomic pair-density function (PDF) determined by pulsed neutron powder diffraction showed that in La_1-xSr_xMnO₃ doped holes form lattice polarons which persist even in the metallic state. In La_1.85Sr_0.15CuO₄ the energy width of the LO phonons around (π,0) determined by inelastic neutron scattering reflects magnetic satellites indicative of spin charge stripe formation. The implications of such nonuniform charge distribution for metal-insulator transition and superconductivity are discussed.     

Optical properties of Bi12SiO20 (BSO) and Bi12TiO20 (BTO) obtained by mechanical alloying

Mechanical alloying has been used successfully to produce nanocrystalline powders of BTO and BSO. The milled BTO and BSO were studied by x-ray powder diffraction, DTA, infrared and Raman scattering spectroscopy. After 7 hours of milling the formation of BTO and BSO was confirmed by x-ray powder diffraction. The infrared and Raman scattering spectroscopy results suggest that the increase of the milling time lead to the formation of ferroelectric BTO and BSO, as seen by x-ray diffraction analysis. These materials are attractive for various electro-optical devices, including optical data processing. They present a number of attractive features as reversible recording materials for real-time holography and image processing applications. This milling process presents the advantage, that melting is not necessary, and the powder obtained is nanocrystalline with extraordinary mechanical properties. The material, can be compacted and transformed in solid piezoelectric ceramic samples. The high efficiency of the process, opens a way to produce commercial amount of nanocrystalline piezoelectric powders. Due to the nanocrystalline character of this powder, their mechanical properties have changed and for this reason a pressure of 1 GPa is enough to shape the sample into any geometry.     

利用Rietveld方法的多相粉末定量分析

利用Ｘ射线步长扫描衍射数据和全图谱（Ｗｈｏｌｅ－ｐａｔｔｅｒｎ）拟合技术（Ｒｉｅｔｖｅｌｄ方法），通过相含量和Ｒｉｅｔｖｅｌｄ修正中标度因子之间存在的简单关系，对包含不同重量的水晶和刚玉粉末的混合物样品进行了相含量的定量分析。求得的结果与原始配比一致，说明这一技术可以有效地用于多相粉末，尤其是衍射图谱严重重叠样品的定量分析研究。     

Three-dimensional distribution of polymorphs and magnesium in a calcified underwater attachment system by diffraction tomography

Biological materials display complicated three-dimensional hierarchical structures. Determining these structures is essential in understanding the link between material design and properties. Herein, we show how diffraction tomography can be used to determine the relative placement of the calcium carbonate polymorphs calcite and aragonite in the highly mineralized holdfast system of the bivalve Anomia simplex. In addition to high fidelity and non-destructive mapping of polymorphs, we use detailed analysis of X-ray diffraction peak positions in reconstructed powder diffraction data to determine the local degree of Mg substitution in the calcite phase. These data show how diffraction tomography can provide detailed multi-length scale information on complex materials in general and of biomineralized tissues in particular.