Geometrical approach for automatic detection of liquid surfaces in 3D computed tomography baggage imagery

This study presents a novel method for liquid detection within three-dimensional (3D) computed tomography (CT) baggage inspection imagery. Liquid detection within airport security is currently of significant interest due to security threats associated with liquid explosives. In this paper, we propose a robust technique based on the automatic identification of universal geometric properties of liquids within 3D space. The proposed approach is based on two stages of geometric fitting. First, we identify the 3D plane which fits to the horizontally oriented surface of the liquid recognising the universal self-levelling property of liquids in any given container. Second, we conduct two-dimensional shape analysis to highlight the shape of the liquid surface at a given level within the container using a least squares elliptical fitting approach. The proposed approach relies on the fact that occurrences of such perfectly aligned horizontal planes within a 3D CT security baggage scan are generally unlikely. Occurrences of such instance are thus indicative of liquid presence. Our results, over an extended set of complex test examples, confirm a liquid detection rate of 85–98% with a moderate processing time. Furthermore, as this proposed approach is based purely on the geometric properties of liquids and robust geometrical shape detection, this methodology is intrinsic to the 3D nature of the resulting CT data and not dependent on any exemplar training imagery.     

有限角 CT 重构压缩算法及仿真分析

研究了有限角 CT重构压缩算法中有限角度和投影幅数对重构结果的影响 .通过仿真程序 ,对不同的有限角度和投影幅数下的压缩重构结果进行分析和比较 ,得出不同的有限角度和投影幅数下重构质量有很大的不同 .当缺失角大于等于 3 0°时 ,重构质量很差 .说明压缩算法其本身具有较大的局限性     

电磁层析成像中新型归一化算法的设计与实

基于电容和电阻层析成像技术中灵敏度矩阵非线性归一化方法,提出了电磁层析成像中使用线性归一化方法的不合理性,在推导出其解析解的前提下,建立了电磁层析成像技术中的新型归一化模型,并给出了新型灵敏度模型的归一化公式。比较了原始和新型模型对于灵敏度归一化的效果,并将新型归一化模型应用到图像重建中,比较了成像质量,用相关系数比较了两种模型和原图的相关度,得出了结论：新型灵敏度归一化模型更逼近原始灵敏度的变化趋势,采用新型模型重建图像的质量更高。     

The development and evaluation of Syco3D: a real-time collaborative 3D CAD system

This paper describes the development and evaluation of a real-time collaborative 3D CAD system, Syco3D, which allows distributed designers in a small team to work together to build and edit virtual 3D models. A shared 3D workspace, Shared Stage, is incorporated in a conventional CAD interface and provides a number of real-time collaborative features in two main interface elements: Synchronised Stage View and Data Structure Diagram. This paper also reports on a usability experiment with two versions of the system, one with the Shared Stage module and the other without, and discusses the issues raised from the development and experiments with the real-time collaborative 3D CAD system.     

微细管道内表面光电检测及三维重构系统

基于位置传感器PSD和光学三角原理,开发了一种适于空间曲线型微细管孔内表面三维重构的检测系统.该系统主要由管道机器人、形貌检测器和曲率检测器等部分组成.形貌检测器可以采集管道内壁截面信息,并计算出截面环上的点在局部坐标系中的位置.曲率检测器负责测量管孔中心轴线在检测器采样位置处的局部几何性质,并完成管道中轴线的重构.在管道机器人的驱动下,根据上述两方面提供的数据以及其前进步距,可以实现管道内表面的三维重建.实验结果表明,利用该技术检测的管道时,管道曲率半径的相对检测精度可以达到±2%,内表面缺陷及内径的测量精度可以达到±0.1mm.     

Development of a lab-scale,high-resolution,tube-generated X-ray computed-tomography system for three-dimensional (3D) materials characterization

The design and construction of a modular high resolution X-ray computed tomography (XCT) system is highlighted in this paper. The design approach is detailed for meeting a specified set of instrument performance goals tailored towards experimental versatility and high resolution imaging. The XCT tool is unique in the detector and X-ray source design configuration, enabling control in the balance between detection efficiency and spatial resolution. The system package is also unique: The sample manipulation approach implemented enables a wide gamut of in situ experimentation to analyze structure evolution under applied stimulus, by optimizing scan conditions through a high degree of controllability. The component selection and design process is detailed: Incorporated components are specified, custom designs are shared, and the approach for their integration into a fully functional XCT scanner is provided. Custom designs discussed include the dual-target X-ray source cradle which maintains position and trajectory of the beam between the two X-ray target configurations with respect to a scintillator mounting and positioning assembly and the imaging sensor, as well as a novel large-format X-ray detector with enhanced adaptability. The instrument is discussed from an operational point of view, including the details of data acquisition and processing implemented for 3D imaging via micro-CT. The performance of the instrument is demonstrated on a silica-glass particle/hydroxyl-terminated-polybutadiene (HTPB) matrix binder PBX simulant. Post-scan data processing, specifically segmentation of the sample's relevant microstructure from the 3D reconstruction, is provided to demonstrate the utility of the instrument.     

High-resolution 3D imaging of microvascular architecture in human glioma tissues using X-ray phase-contrast computed tomography as a potential adjunct to histopathology

Gliomas are rich in blood vessels, and the generation of tumor-associated vessels plays an important role in glioma growth and transfer. Histology can directly depict microvascular architecture in the tumor, but it just provides two-dimensional (2D) images obtained by destroying three-dimensional (3D) tissue specimens. There is a lack of high-resolution 3D imaging methods for observing the microvasculature throughout the entire specimens. X-ray phase-contrast computed tomography (PCCT) which is an emerging imaging method has demonstrated its outstanding potential in imaging soft tissues. Thus, this study aims to evaluate the potential of PCCT as an adjunct to histopathology in nondestructive and 3D visualization of the microvascular architecture in human glioma tissues. In this study, seven resected glioma tissues were scanned via PCCT and then processed histologically. The obtained PCCT data was analyzed and compared with corresponding histological results. Significant anatomical structures of the glioma such as microvessels, thrombi inside the microvessels, and areas of vascular proliferation could be clearly presented via PCCT, confirmed by the histological findings. Moreover, PCCT data also provided additional 3D information such as morphological alterations of the microvasculature, 3D distribution of the thrombi and stenosis severity of the vessels in glioma tissues, which cannot be fully analyzed in 2D histological slices. In conclusion, this study demonstrated that PCCT can offer excellent images at a near-histological level and additional valuable information in screening gliomas, without impeding further histological investigations. Thus, this technique could be potentially used as an adjunct to conventional histopathology in 3D nondestructive characterization of glioma vasculature.     

Fast computation for generating CGH of a 3D object by employing connections between layers

An approximate method for generating computer-generated holograms (CGH) of a 3D object with six times faster speed than the conventional algorithm is presented. In the conventional algorithm, a 3D object is sliced into many layers and treated as a collection of self-illuminated point light source. The propagation process of a light ray from every point of an object to all the points on the hologram plane is simulated and interfered with by the reference beam to form a CGH. In our proposed method, under the assumption that the depth of a 3D object is much smaller than the recording distance, we just need to calculate the oblique distance between the first layer and the hologram plane, and then the oblique distances from the other layers to the hologram plane can be obtained from a simple relation, thus the computational time is much reduced. The CGH is optically reconstructed and the quality of the reconstructed image agrees well with that from the conventional algorithm.     

Flexural strength of fused filament fabricated (FFF) PLA parts on an open-source 3D printer

Fused filament fabrication (FFF) has been widely used to develop prototypes as well as functional parts owing to its capability for creating parts with complex geometries in a short time without the specific requirement of tooling. The mechanical properties of parts produced by FFF exhibit 70%-80% of the mechanical properties of parts produced by injection molding. The mechanical properties of FFF-produced parts are primarily dependent on the selection of various process variables. The mechanical properties of the part can be enhanced through the proper selection of process variables. In the present experimental investigation, the effects of the process variables, viz. raster angle, layer height, and raster width on the flexural properties of FFF-printed polylactic acid (PLA) is studied. The result shows that flexural strength is primarily influenced by layer height followed by raster angle. The sample printed with 100-μm layer height and 0° raster angle exhibits a higher tensile strength. Further, the microscopic examination of the deformed specimen is performed to understand the mode of failure. Specimens printed at different raster angles show different modes of failure.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-018-0237-6     

New opportunities for 3D materials science of polycrystalline materials at the micrometre lengthscale by combined use of X-ray diffraction and X-ray imaging

Non-destructive, three-dimensional (3D) characterization of the grain structure in mono-phase polycrystalline materials is an open challenge in material science. Recent advances in synchrotron based X-ray imaging and diffraction techniques offer interesting possibilities for mapping 3D grain shapes and crystallographic orientations for certain categories of polycrystalline materials. Direct visualisation of the three-dimensional grain boundary network or of two-phase (duplex) grain structures by means of absorption and/or phase contrast techniques may be possible, but is restricted to specific material systems. A recent extension of this methodology, termed X-ray diffraction contrast tomography (DCT), combines the principles of X-ray diffraction imaging, three-dimensional X-ray diffraction microscopy (3DXRD) and image reconstruction from projections. DCT provides simultaneous access to 3D grain shape, crystallographic orientation and local attenuation coefficient distribution. The technique applies to the larger range of plastically undeformed, polycrystalline mono-phase materials, provided some conditions on grain size and texture are fulfilled. The straightforward combination with high-resolution microtomography opens interesting new possibilities for the observation of microstructure related damage and deformation mechanisms in these materials.     

Bi_4Ti_3O_（12）铁电薄膜的I－V特性测量及导电机理

Ｂｉ＿４Ｔｉ＿３Ｏ＿（１２）薄膜是一种具有广泛应用前景的典型的铁电薄膜。本文报道了用ＭＯＣＶＤ方法制备的Ｂｉ＿４Ｔｉ＿３Ｏ＿（１２）薄膜的Ｉ－Ｖ特性测量及其导电机理。结果表明，在低场下，Ｂｉ＿４Ｔｉ＿３Ｏ＿（１２）薄膜的Ｉ－Ｖ特性表现为欧姆性质，在中强场下，薄膜的导电机理遵从ＳＣＬＣ理论。     

The high‐speed measurement of a partial area imaging system applied to photoresist development processing

Abstract

Among the parameters that affect photolithography, the most important are exposure and development time which affect the coating photoresist characteristics. This study further researches the relationship between the exposure and development time using a high speed image inspection system, and the relationship between the development time and photoresist depth using a Scanning Probe Microscope (SPM). A partial scan CCD camera and high speed frame capture card were used to obtain the photoresist development processing parameters. The experimental results verified that this imaging system provides an economical and effective method for producing a micro‐photo‐etched product. It is expected that these experiments can also offer some good references useful in the micro electro mechanical industrial field.     

一种新型的掩膜管理控制系统的研制

研制了一种与掩膜光刻机相配套的新型掩膜管理控制系统.系统硬件由1个4自由度机械手、2个版库、粗预对准机构、精细预对准机构、PLC控制器和伺服驱动器等构成;系统软件由基于VC的上层管理程序以及基于梯形图的底层流程控制程序构成,其中上掩膜版和卸掩膜版是流程控制的主要组成部分.介绍了四象限光电探测器的对准工作原理和掩膜版的粗、精细预对准方法,实验测试了上、卸掩膜版的节拍,粗、精细预对准时间和掩膜版经过精细预对准后的重复定位精度,讨论了激光器和四象限光电探测器相对 位姿的标定方法,并指出了该系统的特点.实验结果表明,该系统性能稳定,主要指标能够满足掩膜光刻机的实际生产要求.     

平面参数空间的实时三维点云配准方法

针对具有多平面结构的室内环境的三维定位和环境建模,提出了一种在平面参数空间进行配准的实时三维点云配准方法。该方法首先使用一种改进的三维霍夫变换算法快速提取点云中的平面特征,然后使用迭代算法在平面的参数空间中寻找最近平面,最后使用这些平面的对应关系来估计两帧点云之间的位姿变换关系。在一个实验室场景中进行的对比实验表明,该算法能够达到与传统迭代最近点(ICP)算法相似的精度,而且速度大大提升。在仅使用普通笔记本CPU的情况下即可实现实时的点云拼接。