提高矿用X射线核子秤计量稳定性的研究

为提高矿用X射线核子秤的计量稳定性,从防爆型X射线源和计量零点2个方面给出了具体方法:利用X射线探测器监测X射线源输出的X射线能量和强度,通过在X射线源内加装监控网络模块接收X射线探测器监测的X射线参数,并与设定的X射线参数进行比较,从而反馈控制防爆型X射线源的管电压和管电流,保持X射线源输出的X射线参数稳定;用防爆型X射线源的管电压、管电流的平均值来定义源强零点,通过X射线探测器实时采集X射线参数并与计量零点、源强零点进行比较,从而反馈调整计量零点和源强零点,克服输送机工况变化及X射线管老化对矿用X射线核子秤计量零点的影响。测试结果表明,该方法能有效提高X射线的稳定性,保证矿用X射线核子秤的计量稳定性。     

基于连续X射线谱的CT重建算法仿真

关于提高CT图像精度的问题,传统的CT重建算法都是基于X射线源是单色源的假设,忽略了X射线的多色性.直接用多色投影数据进行图像重建易产生金属、硬化等伪影,降低图像质量,影响CT值标定,从而影响医学或工业诊断.考虑到X射线能谱的连续性,采用仿真手段实现连续X射线谱的统计重建.首先将连续X射线谱离散成若干单能谱,再根据待检工件的材质信息以及射线能量所对应的质量衰减系数,构建基于连续X射线谱的工件材质模型;最后利用多能统计重建算法对多能投影数据进行迭代重建.仿真结果表明,算法充分地利用了X射线的多能性,在一定程度上可以有效地降低图像伪影,提高CT重建图像质量.     

一种数字化X射线介质识别系统的研究

数字化X射线探测系统是由X射线发生器,准直器,非晶硅平板探测器,多道分析器,接口电路以及上位机能量谱识别系统构成。该系统的创新点在于通过对X射线源加入STM32F103控制电路,实现射线源电压,电流以及曝光时间的可控,从而依据待检物体的情况把X射线的辐射剂量做到最小,而且通过基于LABVIEW环境编写上位机系统,从而远程调控射线发生的参数,最大限度的减小对人的辐射危害;在接受部分使用非晶硅平板探测器以及数字化处理芯片使得所处理信号为数字信号,从而大大的增加了信号的精度以及探测的准确度。     

X射线成像探测器发展进展

X射线摄像探测器随着相关科技的发展,各方面的性能及综合水平都取得了巨大的进展.简单介绍了早期X射线成像探测器,对现阶段的主要应用放射成像探测器一直接数字X摄影探测器做了详细介绍,并对国内外研究作了概述.最后对X射线摄影系统发展趋势进行了展望.     

基于正则项的能谱CT投影分解方法研究

能谱CT通过探索不同X射线能量下衰减特性的差异,具有定量分析材料的能力。然而,利用光子计数探测器获得的多个投影数据在进行材料分解的过程中,会受到噪声放大的影响。本文在特定材料正则项的基础上,加入张量分解的正则项,用于降低噪声,提高分解效果。实验结果表明,本文提出的算法可以清楚地分解出不同材料的投影图,利用重建算法对材料投影图进行层析重建后,材料图像的边缘结构比较清晰,并且抑制了分解过程中的噪声,提高了图像质量。     

油田测井工程中数据采集系统的设计

本文是利用X射线对物质的分辨能力为起点,以测井领域里三相流辨别为功能需求,开发基于DSP的数据采集系统,通过探测器接收穿透过套管的X射线,并对其进行调理和放大,把采集到的信号上传到上位机软件进行频谱分析,从而得到各相的组成。本文重点讲解系统的流程与搭建,该系统对于油田测井开发有重要意义。     

基于碳纳米管 X 射线源的静态扫描系统设计

相比传统热阴极 X射线源而言,碳纳米管 X射线源具有结构紧凑、高时间分辨率、可编程式发射等优势,因此可以采用电子式的扫描方式取代传统扫描方式,提高采集图像的时间分辨率,减少运动伪影,降低辐射剂量。文章针对该新型 X射线源静态扫描系统进行软硬件平台设计。其中,硬件平台集成了多光束 X射线源及其驱动电路、高压发生器、复合真空计和数字平板探测器;下位机软件采用 Quartus II开发平台,Verilog硬件描述语言,实现多路脉冲及触发信号的产生;上位机软件平台采用 LabVIEW图形化编程工具,实现多台仪器的集成控制,完成多光束 X射线源静态扫描、高压控制、真空度监测和图像采集功能。本系统设计通过实验验证,可实现多光束碳纳米管 X射线源脉冲式静态扫描成像,为碳纳米管静态 CT的研制提供了实验和测试平台。     

基于CZT探测器的X光能谱分析设备

碲锌镉（CZT）探测器是一种新型半导体探测器,具有高的原子序数、宽的禁带和高密度（有效原子序数50、密度5．81g／cm^3,Eg=1．6eV）等优点,有利于低能X射线和g射线的探测分析。CZT探测器可以工作在室温下且具有较好的能量分辨率,     

单板机在金属含量测量中的应用

<正> 元素成份分析在探矿、冶金、公安侦破等领域得到广泛应用。本文介绍一种比较实用的检测分析系统。它是计算机技术与X射线探测技术的结合,理论上比较成熟,技术上容易实现。根据粒子探测理论,物质受一定能量的射线的激发,就会产生与该物质性质有关的X射线——特征X射线。对该特征射线的能量和强度进行测量,便可探知对应物质的名称及其含量。下面给出一套金属含量测试系统框图,见图1。电子束轰击样品,产生的特征射线     

宇航空间X射线模数混合多道设计

探测空间X射线对于研究太阳活动情况、脉冲星导航和空间X射线通信等都具有重要的意义。分别利用SDD和CdZnTe半导体探测器对宇航空间中1-20keV和15-600keV两个能量段进行探测,结合模拟和数字多道脉冲分析器的优点设计了模数混合方式的抗辐照高通过率、高分辨率多道分析器。实现了峰值幅度提取、基线扣除、堆积判弃、谱仪状态监测、谱线存储与传输等功能,利用三模冗余设计(TMR)实现软件逻辑对宇航空间中单粒子翻转事件的免疫。通过实测模数混合谱仪线性度达0.99991,采用Amptek FastSDD型探测器实现能量分辨率152eV@5.9keV;输出计数率在98kcps时峰漂小于0.23%。采用DM1500型CdZnTe探测器实现^(241)AmFWHM能量分辨率为6.5%@59.6keV;输出计数率在11kcps时峰漂小于1.3%。     

Attenuation estimation using high resolution time–frequency transforms

Wave attenuation is often measured using spectral techniques such as the spectral ratio method and the frequency shift method, comparing the spectral content of pairs of waveforms along the ray path. The recent introduction of novel highly-localized time–frequency transforms leads to high-resolution but discontinuous spectra. It prevents the use of these time–frequency transforms with conventional attenuation measurement methods. We show how three highly-localized time–frequency transforms, namely basis pursuit, the synchrosqueezing wavelet transform, and complete ensemble empirical mode decomposition, can still be used to estimate attenuation using the peak frequency method. Assuming a Ricker source wavelet, the decrease in peak frequency of a wave spectrum as it propagates in a given medium is used to estimate attenuation. When applied to a synthetic benchmarking signal corrupted by Gaussian white noise, the three transforms show different degrees of performance and robustness for different signal-to-noise ratios. The developed methodology is suitable for geophysical investigations, but may also find application in other fields such as biomedicine, acoustics and engineering.     

数字X射线图象的成象分析及校正

数字X射线图象的形成是一个X射线信息影象的形成、转换和传递的复杂过程,且通常得到的数字X射线图象的灰度值没有准确的物理意义,在实验的基础上,提出了一种基于朗伯定律的理想图象模型,用以对数字X射线图象进行灰度的校正及线性化,经过这样的处理后,图象的灰度值与吸收体厚度之间的关键近似为线性,这对于人体特征参数的定量分析（如对心脏形态、血流的分析,以及在DSA中对造影剂浓度的分析等）具有重要作用。     

InSpectr: Multi‐Modal Exploration,Visualization, and Analysis of Spectral Data

This paper addresses the increasing demand in industry for methods to analyze and visualize multimodal data involving a spectral modality. Two data modalities are used: high‐resolution X‐ray computed tomography (XCT) for structural characterization and low‐resolution X‐ray fluorescence (XRF) spectral data for elemental decomposition. We present InSpectr, an integrated tool for the interactive exploration and visual analysis of multimodal, multiscalar data. The tool has been designed around a set of tasks identified by domain experts in the fields of XCT and XRF. It supports registered single scalar and spectral datasets optionally coupled with element maps and reference spectra. InSpectr is instantiating various linked views for the integration of spatial and non‐spatial information to provide insight into an industrial component's structural and material composition: views with volume renderings of composite and individual 3D element maps visualize global material composition; transfer functions defined directly on the spectral data and overlaid pie‐chart glyphs show elemental composition in 2D slice‐views; a representative aggregated spectrum and spectra density histograms are introduced to provide a global overview in the spectral view. Spectral magic lenses, spectrum probing and elemental composition probing of points using a pie‐chart view and a periodic table view aid the local material composition analysis. Two datasets are investigated to outline the usefulness of the presented techniques: a 3D virtually created phantom with a brass metal alloy and a real‐world 2D water phantom with insertions of gold, barium, and gadolinium. Additionally a detailed user evaluation of the results is provided.     

Shadows and soft shadows with participating media using splatting

This paper describes an efficient algorithm to model the light attenuation due to a participating media with low albedo. Here, we consider the light attenuation along a ray, as well as the light attenuation emanating from a surface. The light attenuation is modeled using a splatting volume renderer for both the viewer and the light source. During the rendering, a 2D shadow buffer accumulates the light attenuation. We first summarize the basic shadow algorithm using splatting. Then, an extension of the basic shadow algorithm for projective textured light sources is described. The main part of this paper is an analytic soft shadow algorithm based on convolution techniques. We describe and discuss the soft shadow algorithm, and generate soft shadows, including umbra and penumbra, for extended light sources.     

Effect on deoxidation of doped europium in oxidized BaMgAl10O17

Abstract— We studied the effect of the deoxidation of oxidized blue‐light‐emitting europium‐doped BaMgAl₁₀O₁₇ (BAM) phosphor in a plasma‐display panel by making photoluminescence and powder X‐ray diffraction measurements and by X‐ray absorption fine structure analysis. Photoluminescence spectra, powder X‐ray diffraction, and X‐ray absorption near‐edge structure, and extended X‐ray absorption fine structure spectra of BAM at the europium L₃‐edge suggest that the oxidized BAM annealed in air is revived by heating in a H₂/N₂ (5% H₂) reducing atmosphere above 500°C.     

CT有限角度算法的比较研究

在医学临床中,C形臂X射线机的应用愈来愈广泛。由于C臂机自身的特点,且所检测物体的密度及形状存在较大差异,使得其在有限角度下所获得的投影图像断截,投影数据不完全。本文主要分析在有限角度下CT图像最优准则重建的算法。通过对迭代重建算法ART、SART以及TV-SART的比较,得知在有限角为90°的情况下,TV-SART的重建图像更为清晰,更接近原始图像,从而为基于C形臂CT的成像系统的实现提供可靠的理论支撑。     

Medical displays by using plasma‐beam‐alignment technology

Abstract— Novel anode layer plasma within minimum chamber space was developed for non‐contact alignment process. The plasma‐treated polyimide (PI) surface showed no particle contamination and no micro‐scratches. Surface morphology was investigated by using scanning electron microscope (SEM), an atomic force microscope (AFM), and X‐ray photoemission spectroscopy. The different oxygen‐to‐carbon ratio ([O]/[C] ratio) for XPS spectra indicated a composition change after plasma treatment. Surface pretilt angles were varied from 0 to 2.1° under different plasma exposure times. Finally, a prototype 20.8‐in. QXGA IPS‐mode gray‐scale medical liquid‐crystal display was successfully demonstrated with high contrast ratio, excellent uniformity, and wide viewing angle using this new plasma‐beam‐alignment technique.     

一种PCI总线的高性价比数据采集卡的研制

以低成本,高性能的设计思路实现了一种用于建筑工程材料测试的数据采集卡,系统基于PCI数据总线,8路模拟量输入,配置为不同放大系数。具有结构紧凑,高可靠性和高稳定性的特点,在生产实践中得到了广泛的应用。     

两种陶瓷湿敏元件阻湿特性的分析

通过对ZrSiNb和ZrSiNaPNb元件的X射线衍射与扫描结果的分析 ,解释两种元件的阻 -湿特性 ,并对其老化原因进行了探讨     

Multisensor integration for underwater scene classification

We describe a new approach for the classification of a seafloor that is imaged with high frequency sonar and optical sensors. Information from these sensors is combined to evaluate the material properties of the seafloor. Estimation of material properties is based on the phenomenological relationship between the acoustical image intensity, surface roughness, and intrinsic object properties in the underwater scene. The sonar image yields backscatter estimates, while the optical stereo imagery yields surface roughness parameters. These two pieces of information are combined by a composite roughness model of high-frequency bottom backscattering phenomenon. The model is based on the conservation of acoustic energy travelling across a fluid-fluid interface. The model provides estimates of material density ratio and sound velocity ratio for the seafloor. These parameters serve as physically meaningful features for classification of the seafloor. Experimental results using real data illustrate the usefulness of this approach for autonomous and/or remotely operated undersea activity.Supported by the National Science Foundation Research Initiation Award IRI-91109584.