基于环形电极的曲孔加工方法

探讨利用直柄和弧柄环形电极电火花加工曲孔的方法,可加工任意横截面的曲孔,通过加工实例,讨论其加工原理,分析了特别影响环形电极曲孔加工的工艺因素,包括电极形式、环形部分制作、芯料支撑方式、工作液方式和加工状态等,并就其加工特点进行了总结。     

不接触电极探测方法研究

介绍不接触电极电法测量的基本原理，分析视电阻率测量与视阻抗探测方法，进行视电阻率模型试验；提出视阻抗测量的理论模型，并进行了金属和非金属异常体模型试验，验证了视阻抗测量方法的正确性，可以适用于不同环境探测，区分介质的导电性差异和介电性差异，为工程探测提供一种快速、方便、准确的多参数检测手段。     

基于二维卷积神经网络的电阻抗成像算法

电阻抗成像技术(EIT)是一种非侵入、无辐射和成本低的成像技术。其逆问题求解时,传统的解决方法存在空间分辨率差的弊端。为此,提出了二维卷积神经网络(2DCNN)的解决方法。采用该方法,在有噪声和无噪声环境下,对不同形状、大小和位置的目标物体进行仿真,并且与Tikhonov和深度学习网络(DNN)算法进行了比较。仿真结果表明2DCNN方法可以有效地提取数据特征,重建的图像相对于其他方法伪影少、分辨率高、成像质量高、抗噪声能力强。     

电容式环形微机电振动陀螺的设计

针对环形振动陀螺结构对称、模态特性参数相同与抗干扰特性好的特点,提出了一种新型的电容式环形微机电振动陀螺。设计了S形弹性支撑梁形式的硅基环形振动陀螺敏感结构,并仿真分析了陀螺的工作模态与幅频响应特性。根据环形振动陀螺的动力学特性,研究了陀螺的机电接口形式与硅基电极的设置方法,建立了硅基电极的电学参数模型与陀螺的角速度敏感模型。基于深离子刻蚀技术设计了简单可行的传感器制备流程,并成功制备了陀螺的敏感结构。实验测试结果显示,该环形微机电振动陀螺驱动与检测模态的谐振频率分别为9 028.86Hz与9 036.15Hz,品质因数分别为25 051与25 026,标度因数为0.589 7mV/((°)·s~(-1))。实验结果验证了陀螺设计与研究方法的正确性,为高性能硅基微机电陀螺的研制提供了一种可行的方案。     

基于二维卷积神经网络的电阻抗成像算法北大核心CSCD

电阻抗成像技术(EIT)是一种非侵入、无辐射和成本低的成像技术。其逆问题求解时,传统的解决方法存在空间分辨率差的弊端。为此,提出了二维卷积神经网络(2DCNN)的解决方法。采用该方法,在有噪声和无噪声环境下,对不同形状、大小和位置的目标物体进行仿真,并且与Tikhonov和深度学习网络(DNN)算法进行了比较。仿真结果表明2DCNN方法可以有效地提取数据特征,重建的图像相对于其他方法伪影少、分辨率高、成像质量高、抗噪声能力强。     

基于反求工程的动物腿骨三维实体重建与分析

本文着重介绍了反求工程技术在动物腿骨三维实体重建过程中的应用。实验借助非接触式三维激光扫描仪获得动物腿骨头的离散化三维点云数据,对采集后的点云进行型面优化、点云光顺、拟合骨头曲面并对重建模型与原始点云进行偏差分析。     

基于COMSOL的油气润滑系统ECT三维阵列电极的特性分析

利用COMSOL有限元软件搭建油气润滑系统电容层析成像(ECT)的阵列电极三维管道模型,得到阵列电极在不同阵列电极结构参数下的电势云图,并求出空场满场的三维阵列电极的电容值。根据油气润滑系统小管径的管道特点,推导出一种适合油气润滑系统阵列电极三维管道内快速计算灵敏度场的计算表达式;定义横向灵敏性和灵敏度均匀性2个评价指标,并结合传统的阵列电极的灵敏度、被测电容的变化范围2个评价指标对油气润滑系统空间ECT阵列电极进行特性分析。结果表明：经过特性分析的空间ECT阵列电极可获得比较均匀的灵敏度分布和较好的检测灵敏性。该结果将为油气润滑系统ECT阵列电极的后期加工制作提供依据。     

基于直接数字频率合成的混合频率恒流源设计

对比已有的混合频率恒流源实现方式,提出一种灵活性好、稳定性高的实现结构。从系统组成角度分别介绍直接数字频率合成、电压控制增益放大器、电压控制电流源三个模块及其实现方法。从仿真及实测结果看,设计的恒流源能够达到较高的输出阻抗。通过实测电流的时域波形图及频谱图分析,恒流源能输出混合任意两种频率正弦波形的电流,且噪声水平较低。该设计在三维多频电阻抗成像系统中得到良好的应用,可提高成像系统的测量速度及精度,并使电阻抗成像技术有效应用于阻抗变换快的检测对象。     

基于PMAC的二维搅拌摩擦焊开放式数控系统研究

介绍了基于PMAC运动控制卡的5轴控制开放式数控系统,设计了二维搅拌摩擦焊接设备的具体结构,研究了控制系统的硬件结构和软件结构,介绍了通讯软件的开发方法,设计了用户界面,实现了对5轴联动的二维搅拌摩擦焊设备的控制。     

基于PC的开放式数控系统

主要介绍基于PC的开放式数控系统的发展动态、概念以及技术特征和基于PC的开放式数控系统的几种主要结构。     

基于多图像融合的MEMS显微三维形貌重构

针对微型机电系统(MEMS)的三维测量,显微镜或光学轮廓干涉仪等传统方法存在显微测量精度低、设备成本高等问题,且当结构含有较多断裂面时,解包裹算法效果欠佳。本文提出一种基于多图像融合的MEMS显微三维测量方法。不同于多角度显微三维测量方法,本研究首先利用单目显微镜,通过单一轴向移动获取一系列测量目标深度信息的单一角度图像,并利用去雾算法对图像进行预处理,实现了去噪和有效信息提取的目的;然后通过聚焦测度算法获取待测对象的深度信息;最后利用数据处理软件进行三维拟合。基于上述原理,本文以焦平面阵列(FPA)作为待测目标进行了测量实验。本文提出的三维测量方法和图像处理算法可获得更准确的FPA形貌,可清晰显示反射面与支腿部分及反射面上的释放孔,测得FPA的支腿长度为110.6μm,每个反射面的像元尺寸为120.8μm×70.8μm,与设计值基本吻合,解决了断裂面难以测量的问题,同时降低了微结构测量的难度和成本。单目显微镜单向移动的多图像融合测量技术对MEMS的三维形貌测量具有重要意义,去雾算法在图像融合与三维测量的图像处理也有很好的应用价值。     

焊接缺陷磁光成像三维轮廓重构识别

对焊件表面及亚表面缺陷进行无损检测是保证焊接产品质量的关键.提出了一种基于法拉第磁致旋光效应的磁光成像焊接缺陷三维重构方法,实现焊接缺陷形状和大小的识别.基于磁光成像原理分析漏磁场磁感应强度与磁光成像的对应关系,以脉冲激光焊接凹坑(3 mm×0.3 mm×0.25 mm)为研究对象,建立焊接凹坑缺陷三维有限元磁场仿真模...     

基于灰度值的非对称等离子体弧形貌的三维重建

等离子体加工技术在处理各类难加工材料的成形与制备方面备受关注,其温度特性是影响加工质量的决定性因素。针对现有温度特性研究大多在弧径向对称的假设前提下间隔采样测量完成的问题,提出了一种基于灰度值的非对称等离子体弧形貌三维重建方法。首先,基于自行设计的图像采集系统,给出了CCD空间布置方案,同步获取了360°方向上加工过程中的等离子体弧数字图像;然后,对采集图像进行了灰度化、直方图均衡化、滤波去噪以及灰度等值线提取等预处理,以获得良好的视觉场和测量效果;最后,取内六层灰度等值线进行了基于立体匹配和插值重构的数值模拟,建立了与温度场存在相关性的等离子体弧形貌三维模型。研究结果定性地描述了等离子体弧温度场的分布情况,实现了等离子体弧形貌的非接触测量,得到了加工过程中等离子体弧的真实形貌。     

基于regionprops函数的并行彩色共聚焦测量系统的三维重构

针对并行彩色共聚焦测量系统在进行三维重构时质心识别效果差,处理效率低等问题,提出一种高效率、高精度的三维重构方法.该方法首先对三维重构实验得到的所有图像进行目标提取和图像拼接,得到待处理的拼接图像,通过MATLAB的regionprops函数和形态学处理提取拼接后各个被测点的质心及质心连通区域,并利用颜色转换算法进行相...     

万能工具显微镜的三维改造

随着科技的创新与进步,传统二维测量技术已经满足不了现在高效率自动化检测的需求,急需新型的三维测量技术。万能工具显微镜作为传统用途广泛、准确度较高和故障率很低的精密测量仪器,目前国内现存量很大,急需对其进行三维自动化改造。该文在万能工具显微镜的基础上,增加3个光栅位移测量系统、自动控制系统以及数据采集分析系统,使其能够实现三维自动测量。     

Three-dimensional reconstruction of imperfect two-dimensional crystals

An outline is given of the general methodology of 3D reconstruction on the basis of correlation averages of the 2D projections: this hybrid real space/Fourier space approach substantially alleviates one of the most serious limitations on obtaining high resolution 3D structures, namely crystal distortions. The paper discusses some of the technical problems involved, namely optimisation of tilt increments, a posteriori tilt angle determination, extraction of lattice line data from averaged unit cells, and stain/protein boundary determination. The approach is illustrated by application to a 2D crystal from a bacterial cell envelope.     

Three-dimensional reconstruction of the human renal glomerulus

The capillary bed of the human renal glomerulus is one of the more complex capillary structures in the human body. This paper illustrates three-dimensional reconstruction of the capillary bed from serial sections. It shows that, although traditional methods of three-dimensional rendering by computer fail to handle the complexities of the capillary structure, new methods based on filtering using three-dimensional mathematical morphology are capable of revealing previously unseen details. This is done at the expense of eliminating fine structure (small capillaries). An error analysis allows the degree to which fine details are lost to be estimated.     

Three-dimensional reconstruction of microtubule-containing structures from electron micrographs

Microtubules and associated structures are among the more difficult samples studied by 3D reconstruction techniques because of their size, complexity, and lability. Nevertheless, their importance in many cellular functions often justifies efforts to acquire 3D information up to the resolution limit of negatively stained specimens or beyond. A combined approach which utilizes methods appropriate to both helical symmetry and 2D crystal lattices seems to provide the surest route to 3D reconstruction. Images of unstained specimens obtained by newer techniques of microscopy present challenging problems in data analysis, but potentially offer higher-resolution information.     

Three-dimensional reconstruction of colon carcinoma metastases in liver

Resection of liver metastases in patients with colon cancer increases survival but success depends on removal of all tumour tissue. For this purpose, understanding of spatial relationships between metastases and liver architecture is essential. Because metastatic cancer growth is essentially a three-dimensional (3D) event, we decided to apply 3D reconstruction techniques to study these spatial relationships between metastases and liver structures such as blood vessels, stroma and the liver capsule (Glisson’s capsule). Colon carcinoma metastases were experimentally induced in rat liver by injection of colon cancer cells (CC531) into the portal vein. Three weeks later, livers from these animals and control livers were removed and immediately frozen in liquid nitrogen. Thirty-seven to 110 consecutive sections were used for each 3D reconstruction of 26 metastases in eight livers. Contours of different structures were stained by (immuno)histochemical means, traced in each section and stored in a database. From the contour model, a volume model was generated. Among the 26 metastases, seven were found to grow distantly from the liver capsule. They were small and consisted of well-differentiated cancer cells that were totally surrounded by a basement membrane and stroma which was always connected with adjacent blood vessels of a portal tract. The remaining 19 metastases showed a more advanced pattern of development. Infiltration of poorly differentiated colon cancer cells progressed through the stroma at various sites and areas of direct contact between cancer cells and hepatocytes were frequently found. This type of outgrowth of cancer cells was only found when metastases had made contact with the liver capsule. However, some areas in sections of these advanced stages still resembled small metastases. On the basis of these findings, we conclude that stroma affects the differentiation pattern of cancer cells and has at least a dual role in tumour growth. On the one hand it limits invasion of cancer cells in the surrounding host tissue. On the other hand, stroma formation at the capsule, which consists mainly of granulation tissue, facilitates outgrowth of the tumours. Furthermore, our 3D reconstructions demonstrate the spatial heterogeneity of larger metastases and the importance of a 3D approach to understand growth and development of metastases in general and colon cancer metastases in the liver in particular.     

Three-dimensional reconstruction of senile plaques in Alzheimer's disease

So far, the three-dimensional approach to senile plaques, one of the principal histopathological hallmarks in Alzheimer's disease besides neurofibrillary tangles, has been scarce. Two main problems in three-dimensional reconstruction of histological specimens are the horizontal distortion during the preparation of serial thin tissue-slides and the need for consecutive vertical readjustment. This is greatly facilitated by the reflection contrast microscope (Leica, Germany) which is a light microscopical instrument causing interference patterns and reflections along interfaces by means of circularly polarized epi-illumination. Using this technique, one can obtain distinct optical sections of a depth of 1.5 μm within specimens up to 30 μm in thickness, thus preserving the integrity of the observed object and rendering a manual alignment superfluous. We applied the reflection contrast microscope (RCM) on thick tissue-slides of the cerebral cortex of a patient suffering from Alzheimer's disease which had been dyed according to Campbell. This is a silver-based staining method detecting βA4-amyloid, the main component of senile plaques. Under the RCM, these silver-stained extracellular amyloid deposits cause reflections which allow the assessment of their three-dimensional distribution by focusing through the specimen. The optical sections obtained in this way were digitized, and the identified senile plaques reconstructed by the grey-scale image analysis system VIDAS 2.5 (Zeiss/Kontron, Germany).