二维直方图阈值法分割工业CT图像的研究

高精度工业CT图像因其包含物体三维信息而被广泛重视。尤其对于某些工件的缺陷检测，可利用图像分割技术进一步识别、突显缺陷，提高检测效率。针对一类工件的缺陷，对其高精度CT图像先后采用了比特窗算法进行预处理和二维直方图阈值法进行分割，突出显示了该类缺陷。该类方法对类似问题有广泛应用。     

高精度工业CT三维图像的标的挖掘与分析

高精度工业CT三维图像中存在着一些感兴趣区（例如生产工艺造成的缺陷）。为了对这些目标区域进行有针对性的挖掘与分析,利用图像处理软件Amira对特定工件模型进行了缺陷分割、显示及缺陷量测,对缺陷结果进行了评判和归档。以实验室CT系统扫描检测台钳获取的CT图像数据为研究对象,进行了上述一系列处理,取得了较好的效果。     

工业CT技术特点及应用实例

概述了工业CT技术的主要特点及其在无损检测中的应用,介绍了工业CT在缺陷检测、焊缝质量诊断、密度分布表征、结构分析及装配质量检测等方面的应用实例.     

基于多周循环步进式插值扫描轨迹的工业CT柔性检测技术研究

为了在一次CT检测过程中同时实现被检工件的精细检测与内部缺陷快速发现的两种检测需求，提出了一种新型CT检测方案。该方案将一种改进的圆形CT投影扫描轨迹与不完全投影插值算法有效融合，实现了投影采集与最优图像实时重建的同步进行。为验证该技术的可行性，设计了相应的扇束CT仿真平台及试验模体，仿真试验结果表明，该检测技术在CT扫描过程中可及时发现被检工件的内部缺陷，扫描结束后可获得工件的精细CT图像，有效满足了工业CT用户在多种检测目的之间自由切换的柔性检测需求。     

CT图像线状伪像产生的原因和校正方法

在采用面探测器阵列进行三维直接重建CT图像的时候,经常出现大量的线状伪像,对于图像质量和真正缺陷的识别影响很大.这些伪像大多是由投影数据中的随机疵点引起的.文章在雷当域用疵点邻域的均值代替疵点数值的方法来处理CT图像的线状伪像.试验结果证明这种方法简单有效,几乎能去除所有的线状伪像,提高了图像质量,对重建的时间几乎没有影响.     

用于螺旋CT的数据采集设计方案

对于工业螺旋CT的应用,针对其实时性、数据量大的特点,提出了数据采集系统的设计和实现方法.采用双CPU的系统的设计,一块负责用DMA的方式把CT数据从前置放大器传送到FIFO,另一块负责将FIFO中的数据通过无线网络传送到主控站进行进一步处理.该设计已在现有工业CT中得到应用.     

伪彩色数字高程模型在工业CT断层图像检查中的应用

在工业CT断层图像缺陷检测应用中，提出了将数字高程模型DEM与伪彩色技术一起应用于二维灰度图像缺陷检测领域的算法流程。应用该算法流程，能够充分利用CT断层灰度图像信息，获得清晰的视觉检查效果，从而大大增强了系统检测缺陷的能力。在大型工业CT图像重建与检查分系统中采用该算法流程已经取得了较为理想的效果。     

大型工业CT中的三维显示与交互检查技术

介绍了三维显示和交互检查技术在大型工业CT图像检查中的应用，总结了目前工业CT三维图像显示领域主要应用的面绘制和体绘制方法，并分别对这两类主要的绘制算法进行了评价，重点对工业CT多断层图像数据三维显示的各个技术细节进行了具体的分析，并总结了大型工业CT图像检查分系统方案设计中存在的技术难点。     

γ射线工业CT放射卫生防护标准的制定及实施

工业CT与工业射线透视成像在成像原理、检测时间、辐射剂量、操作人员要求等方面有很大的差异。已颁发的γ射线工业探伤放射防护卫生标准,不能完全适应于γ射线工业CT设备的放射卫生防护要求。因此,及时制订γ射线工业CT放射卫生防护标准,对规范γ射线工业CT的生产和使用、保障操作人员与公众的放射安全、促进工业CT这一无损检测技术的普及和应用具有重要的意义。本文简要介绍了γ射线工业CT技术及放射防护特点,并对放射卫生防护标准GBZ175-2006的主要技术内容进行了介绍,最后就标准实施1年以来的情况进行了总结分析,为进一步贯彻落实该标准提供了实践经验。     

大型集装箱CT系统图像重建研究

研究了大型集装箱CT系统的图像重建技术,给出了卷积反投影算法的基本原理、实现过程,以及目前得到的重建图像。经实际检验,应用该算法重建的图像清晰,能够识别铸造工件中的孔及树木的年轮。     

拌摩擦焊焊缝缺陷超声检测信号特征分析与神经网络模式识别

以搅拌摩擦焊（FSW）焊缝的包铝层伸入、未焊透、隧道孔缺陷为对象，将小波分析理论应用于缺陷超声检测信号特征提取问题的研究，使用小波包分解重构节点能量、小波包分解节点系数、缺陷信号的功率谱密度小波分解这三种方法对缺陷的超声检测信号进行特征提取。利用类别可分离性判据和BP神经网络分别对提取的特征量进行评估和识别。结果表明，缺陷信号的功率谱密度小波分解这一特征提取方式具有最好的类别可分性，并且以该特征量为网络输入的BP神经网络具有85.71%缺陷识别率。      

Evaluation of toughness requirements in cracked components based on fracture-mechanics methods

Different fracture-mechanics based defect assessment procedures have been checked using results of wide-plate tests. The CTOD-Design-Curve-Approach, the CEGB-R6-routine, the EPRI-approach and methods using Finite-Element-Computations to evaluate the crack driving force lead to safe predictions of the failure behaviour of components as long as the limits of application are considered carefully. Reversing the conventional procedure of defect assessment, the CTOD-Design-Curve approach and the FEM based method can be used to derive toughness requirements. The requirements depend on the component and defect geometry, the strength of the material and the safety criterion. For practical application simple diagrams have been evaluated showing the required toughness e.g. as a function of crack length or material strength.     

A Pattern Recognition Method for Nuclear Reactor Core Surveillance

An automatic method for reactor core surveillance is described which employs pattern recognition techniques. A core vibration surveillance method for a pressurized water reactor has been developed which provides the early detection of failures. The method allows on-line application and is able to give quick surveillance decisions (in about one minute). The sensors are eight ex-core ionization chambers. The system is very flexible and adaptable to the statistical properties of the data. The algorithms used are heuristic but need only the definition of a small number of parameters. These parameters may be optimized either by automatic procedures or by explicit experimental methods. Some experimental results are presented.     

Development and Systematic Application of Surface Inspection Methods Used for In-Service Inspection of Reactor Pressure Vessel

Both from the mechanics of fracture and from actual instances of defects observed in reactor pressure vessels, it is indicated that greater importance should be attached to surface than to internal defects in the in-service inspection of these components.

In the JPDR, the reactor pressure vessel has undergone ISI three times since 1968, with emphasis placed on surface inspection, and using both remote bore scope and remote Smeck methods. The two methods gave the same results on all three occasions, so that both methods can be considered effective.

With the remote Smeck method, the lower limit of detectable defect size was found to be less than ±lmm, and the reproducibility of defect position, measured on a mock-up nozzle was better than ±3 mm. For the bore scope a newly devised “shadowing technique” is described, which appreciably enhances its ability to detect and to accurately observe surface defects.

The results of ISI in JPDR indicate that significant improvements in detection ability and accuracy could be expected by systematic application of ISI methods.     

Underwater Cutting of Reactor Core Internals by CO Laser Using Local-Dry-Zone Creating Nozzle

With a view to practical application of the CO laser to underwater cutting of thick steel plates, a nozzle for creating a local dry zone on the workpiece has been developed and tested. The nozzle directed against the workpiece surface discharges a jet of air, which forms the local dry zone, bounded by a cone of high-speed water jet discharged from a concentric annular outlet. Preliminary tests were performed to optimize the nozzle shape and operating conditions. The resulting nozzle was used with a 5 kW CO laser for actual underwater cutting tests on stainless steel plates: Entirely satisfactory cutting performance was confirmed on various workpiece geometries and working positions.     

X射线计算机断层摄影(CT)受检者剂量检测方法的研究

本文介绍了目前国际上两种通用的ＣＴ受检者剂量的表示方法和检测方法。通常用多层扫描平均剂量（ＭＳＡＤ）或ＣＴ剂量指数（ＣＴＤＩ）来表示ＣＴ受检者的剂量；用ＣＴ标准电离室（笔形电离室）或热释光剂量计（ＴＬＤ）进行检测。通过实验和数学模拟方法，找出了ＭＳＡＤ与ＣＴＤＩ之间和不同方法检测结果之间的关系，为今后推广使用这两种检测方法进行ＣＴ受检者剂量监测和推广使用国际电离辐射防护与辐射源安全基本标准（ＩＢＳＳ）推荐的ＣＴ受检者剂量指导水平打下技术基础。     

通过逆向建模实现工业部件的虚拟现实显示

首先提出一套工业CT数据处理系统的构想:通过逆向建模实现基于虚拟现实显示的工业部件检测.对逆向建模模块,提出了两条解决方案:集成医用CT建模软件与使用图形图像库进行自主开发,并对基于CT数据的逆向建模需要考虑的重要因素和开发时的关键技术进行了分析.对虚拟现实显示模块,结合CT数据特点和工业用户需求,对虚拟现实显示部分需要实现的功能和关键技术做出了阐述,并简要分析了存在的问题和发展前景.     

Candidate for Residual Defect in Silicon Surface Barrier Detector

The residual defect in the pulse height defect of a silicon surface barrier detector is investigated theoretically. An application of the model of charge collection process leads to another candidate for the residual defect than the recombination defect. The residual defect is due to incomplete charge induction by electrons and holes inside a plasma column, which has dielectricity-like property. Quantity of induced charge is shown in a ratio to the number of produced electron-hole pairs as functions of depletion layer thickness, plasma column length and resistivity of the detector. Experimental result of the residual defect of ⁵⁸Ni ion and its analysis method applying this model are presented. The residual defect is successfully explained by this model.