X射线检测中的图像质量的改善

对射线实时成像的预处理技术进行了较为详细的研究,提出了图像增强处理的硬件方法并对其原理进行了介绍。从射线实时成像检测的特点出发,重点对图像的去噪处理进行了分析与比较,分别采用叠加平均、局部平滑、方向滤波、频域滤波等方法进行处理,分别给出了这些方法的数学模型及处理结果。实际表明,经过以上处理,射线实时成像的图像质量有了明显提高。     

60Co集装箱检测系统中图像的采集、传输与分配

本文阐述了＾６０Ｃｏ集装箱检测系统中数据的采集方式及图像重建方法,分析了线采集周期与成像几何失真的关系,确定了系统数据流的大小及对系统的要求。分析了各种数据通讯方式,确定了高速网络通讯方案,实现了数据流在检测系统中的自动定向与合理分派,多终端协同工作,并行处理,极大地提高了系统的检测效率。     

The role of AGFA high-energy CR in the calibration and quality control of multileaf collimators （MLC）

Linear accelerators equipped with multileaf collimators （MLC） are becoming more common and are widely used in the intensity-modulated radiotherapy （IMRT）. There is an imperative need to ensure the commissioning specification of the linear accelerators for the sake of quality assurance （QA） and quality control （QC）. This paper is aimed to investigate the role of AGFA high-energy CR （Computed Radiography） in calibrating dynamic multileaf collimators and evaluating the accuracy of the leaf position. The result shows that AGFA high-energy CR can easily and conveniently be used to calibrate MLC and verify its position. Hence, the application of AGFA high-energy CR is proved to be an accurate and time-saving method for routine MLC QC, especially when MLC calibration adjustments are required.     

数字式射线图像缺陷检测的C-V方法

数字式射线图像（DR图像）缺陷检测主要是进行缺陷区域的分割和测量,分割精度将直接影响到测量精度。C-V模型是一种新的基于曲线演化理论和水平集方法的图像分割模型,它结合区域信息使得分割结果全局最优,可以很自然地处理轮廓线拓扑结构的变化。针对工件DR图像特点,研究了一种DR图像缺陷检测的C-V方法：首先应用C-V模型进行DR图像缺陷区域的分割,在此基础上,完成缺陷区域几何参数的测量。实验表明,C-V方法能准确地分割出DR图像中的缺陷区域,并获得缺陷形心和面积等参数。     

Tracking of Particles in Froth Using Neutron Imaging

The movement of hydrophobic particles in a rising froth column is investigated. Gadolinium particles are hydrophobized and floated by means of small air bubbles. The generated froth is investigated by neutron imaging. Particles are identified by correlating the resulting radiographs with an artificial template of a typical particle and subsequent scanning for local maxima. The movement of the particles in the froth was analyzed for different froth stabilities, which resulted from various concentrations of the frother sodium oleate. Decreasing froth stability leads to lower superficial vertical particle velocity and to higher horizontal diffusion of particles due to bubble rupture.     

多层螺旋CT三维成像与DR检查在肋骨骨折中的应用对比

目的:探讨研究多层螺旋CT三维成像与DR检查在肋骨骨折中的应用对比.方法:选择符合标准的63例肋骨骨折的患者,分别依次采用多层螺旋CT三维成像诊断和DR检查诊断,对比其诊断结果.结果:多层螺旋CT三维成像检测的诊断符合率为98.86％,显著性高于DR检查法诊断符合率77.27％(P＜0.05);多层螺旋CT三维成像检测的误诊率为1.14％,显著性低于DR检查法的12.50％.结论:多层螺旋CT三维成像法要检测效果优于DR检查法,但要发挥其各自优点,结合使用.     

Pitting corrosion of stainless steel: measuring and modelling pit propagation in support of damage prediction for radioactive waste containers

Abstract

In situ synchrotron radiography has been used to observe the evolution of two-dimensional pits growing in stainless steel foils under electrochemical control in chloride solutions. A method for extracting the key kinetic parameters from radiographs is under development to provide data for validating and calibrating a two-dimensional finite element model previously developed by Laycock and White. The local current density along the boundary of a pit is directly measured from the radiographs. Then, the local metal ion concentration and potential drop inside the pit cavity are backcalculated using transport equations and the requirement to maintain charge neutrality, giving the relationship between current density, solution composition and interfacial potential. Preliminary comparisons show qualitative correlation between the model and extracted data; quantitative comparison is under way.     

In-Situ Desaturation Test by Air Injection and Its Evaluation through Field Monitoring and Multiphase Flow Simulation

Desaturation of ground by air injection attracts considerable attention in recent years as an innovative technique for a liquefaction countermeasure. Several research programs were conducted in laboratories regarding the related topics. This paper describes an in situ air-injection test that aims to examine the effectiveness of the air injection to desaturate ground and the validity of observation techniques to monitor the evolution of the unsaturated zone. In the test, air was injected from an air injector deployed in a targeted saturated-sand layer at a depth of 6?m. Observations revealed that the air-flow rate increased linearly with increasing air-injection pressure and the desaturated zone was generated within 4?m from the injection point. A 3-dimensional electric resistivity tomography technique was effective for evaluation of the desaturated zone. The degree of saturation of the in situ soil was observed by using high quality undisturbed samples obtained by the ground freezing method. The degree of saturation ranged from 68–98%, which was low enough to almost double the liquefaction resistance of the soil at the site. Numerical analyses were also conducted with a gas-liquid two-phase flow simulator to describe the evolution of the soil desaturation. Qualitatively, predictions show a relatively good agreement with the in situ measurements of the 3D electric resistivity tomography and are quantitatively compatible with the in-field degree of saturation measured indirectly by using the frozen soil samples. Actual liquefaction resistance was evaluated utilizing the undisturbed samples by conducting a triaxial test under cyclic shear conditions, which revealed that desaturated samples were indeed less susceptible to liquefaction compared with the fully saturated samples.     

Assessment of welding defects for gas pipeline radiographs using computer vision

In this paper, a novel automated vision system is introduced to detect and assess the welding defects of gas pipelines from the radiographic films. The proposed vision system was used to capture images for the radiographic films and apply various image processing and computer vision algorithms to detect the welding defects and to calculate necessary information such as length, width, area and perimeter of the defects. A developed software, named AutoWDA, has been fully written in lab using Microsoft Visual C++6 to perform the analysis process. The proposed system offers many advantages such as enhancing the captured images so that the defects appear much clear and eliminating the loss of image details, which occurs due to film deterioration by the time, by transferring the radiographic films into digitized images, which could be saved on magnetic mass storage media. The proposed system is considered quite cheap compared with commercial radiographic image enhancement systems.     

Performance of a new Micromegas detector, with woven wire mesh, in CF4

Several techniques have been investigated to achieve good amplification in gas Time Projection Chambers. The classical Micromegas detection scheme with nickel grid is compared with a new one, with a stainless steel woven wire mesh, in CF₄ at different operating pressures. The performances and the mechanical properties of the woven wire mesh make this solution attractive for low and high energy particle physics experiments and other applications like low dose radiography. A more detailed study appears in Jeanneret (Ph.D. Thesis, Neuchâtel University, 2001).