血管切片的三维重建

本文讨论血管的三维重建问题.我们通过研究,证明了以下的定理.定理设C(i)是中轴线和平面Z=i的交点,那么存在以C(i)为中点且端点P1(i),P2(i)在ω(i)上的线段,并且在P1(i),P2(i)处ω(i)的切线相互平行.根据定理,我们找到利用求截面图象边界曲线的平行切线方法找到中轴线和100个截面的交点及管道的直径59.1238pixel.并用这100个交点的数据拟合出中轴线的方程:x(t)=-0.207806-0.610303t+0.206455t2-0.0144935t3+0.000517774t4-8.394241977754047×10-6t5+6.133353112035975×10-8t6-1.6673218267444805×10-10t7y(t)=158.211+1.86595t-0.266798t2+0.0141407t3-0.000325412t4+3.043275597680807×10-6t5-9.899171274615063×10-9t6z(t)=t然后我们用中轴线的方程重建了三维血管,并求出了重建血管在40个平面上的截面ω′(i)(30≤i≤69),并与原始截面ω(i)(30≤i≤69)进行比较,截面平均符合率高达96.8024%.     

血管三维重建的问题

本文介绍了2001年全国大学生数学建模竞赛A题的背景和立意,对题目的条件作了必要的分析,并对各参赛组对该问题的思路和解法进行归纳总结.     

利用 OpenGL 实现 ICT 断层图像的三维重建

基于ICT断层图像的三维重建是实现实物反求的重要途径之一．本文提出了一种基于Delaunay三角剖分思想的表面重建方法．并采用OpenGL结合VC 6．0来实现ICT图像的三维重建．最后给出了仿真结果与实际实验结果．     

司炉工操作应掌握的相关问题分析

随着我国工业发展规模的不断扩大，工业技术的不断提高，司炉工的操作规范与技术标准不断加强。司炉工对锅炉的使用进行操作时，需要考虑很多因素与重点问题，不然会造成锅炉操作的损坏或导致事故风险加剧。司炉工改善自身不合理操作行为，可以让锅炉的使用更加安全与规范，保证锅炉的使用与燃烧运行的环保程度，作者针对这些问题开展以下论述。     

基于插值矩阵技术与二维空间平滑法的近场相干声源识别研究

在研究插值矩阵技术与二维空间平滑法两种方法的基础上,将两者进行结合,提出了一种对近场相干声源进行识别的方法。首先通过插值矩阵技术把实际阵列接收到的近场信号转换为形式上的远场信号,然后通过二维空间平滑法求出阵列的平滑协方差矩阵,再由平滑协方差矩阵得到给定方向向量对应的信号功率,实现二维相干声源的识别。算例表明,该方法比传统的波束形成能更准确地定位出声源的位置。     

基于流水线的FFT快速计算方法与实现技术

针对目前CDMA快速码捕获系统对捕获速度要求越来越高,在分析快速傅里叶算法理论的基础上,结合FPGA(Field Programmable Gate Array)的独特硬件结构,提出一种基于流水线的FFT(Fast Fourier Transform)快速实现方法,并对该方法进行了matlab仿真、ISE仿真和FPGA实验.研究结果证明:相比于传统的FFT实现方法,在保证计算精度的基础上,该方法实现了FFT计算数据的连续输入与输出.减小了捕获时延,缩短了至少1/3的计算时间,在100 MHz时钟时,完成4096点的FFT运算只需要42.05μs,为高速信号处理系统提供了一种更好的时频转换方法.     

应用血管内超声与X射线造影图像融合的血管三维重建

针对X射线血管造影和血管内超声各自显示血管形态的局限以及互补性问题,提出将两种数据进行融合,准确重建血管的方法。首先从在超声导管回撤路径起点拍摄的两个角度的造影图像对中提取出导管并进行三维重建。然后采用基于snake模型的半自动方法从各帧超声图像中提取出血管壁的内外膜边缘。最后,在Frenet-Serret标架中确定各相邻帧超声图像间的相对方位后,利用非迭代的统计优化方法确定各帧超声图像沿导管轴向的绝对方位,完成两种数据的融合。采用临床数据的实验结果验证了算法的可行性,并分析了可能存在的误差和计算成本。     

微波ECR-CVD法制备a-C:F:H膜的红外吸收及其光学带隙

改变CHF3 CH4 流量比R =[CHF3] ([CHF3]+[CH4 ]) ,采用微波电子回旋共振等离子体化学气相沉积 (MWECR CVD)方法沉积a C :F :H薄膜。a C :F :H薄膜的结构和光学带隙使用傅立叶变换红外光谱和紫外 可见光谱来表征。红外结果表明 ,在低流量比R(R <6 4 % )下 ,薄膜的红外特征结构主要以 CF(10 6 0cm- 1 ) , CF2(112 0cm- 1 )以及 CHx(2 80 0～ 30 0 0cm- 1 )的伸缩振动为主 ;在高流量比R(R >6 4 % )下 ,薄膜表现为类聚四氟乙烯(PTFE)的结构特征 ,典型的红外特征峰是位于 12 2 0cm- 1 处的 -CF2 反对称伸缩振动。薄膜的光学带隙Eg 随流量比R的变化表现为先降后升。进一步研究表明 ,薄膜中的H和F浓度调制着薄膜的CC共轭双键结构 ,使光学带隙Eg 从 2 37到 3 3之间变化     

基于形态自相关和时频切片分析的轴承故障诊断方法

频率切片小波变换(Frequency Slice Wavelet Transform,FSWT)是一种新的时频分析方法,信号中的噪声会降低FSWT分析的频率分辨率。为了提高分析精度,提出了基于形态滤波和时延自相关的时频切片分析方法,并成功应用到轴承故障诊断中。该方法首先采用多结构元素差值形态滤波和时延自相关方法对信号进行降噪,采用FSWT分解降噪后的轴承振动信号,然后根据轴承故障特征频率选择时间频率切片区间,进行细化分析来提取故障特征。仿真信号与轴承故障诊断实例的分析验证了该方法的有效性。     

延时相关与斜率计算的数据位数匹配

在带像增强器的微光波前传感器中,采用延时相关算法抑制CCD输出图像的随机噪声。但 处理后,使得数据位数与斜率计算所需位数不匹配。为使位数匹配提出几种方案:开平方、近似开平方、移8位与移12位,并就输出图像、计算精度、硬件实现难易等对这几种方案展开论述,找出一种最佳方案:综合使用近似开平方与移8位。     

基于图像的启发式三维火焰重建算法

研究了火焰的重建,为改进现有稀疏视角输入下的层析成像算法的重建精度,提出了一种基于图像的启发式火焰重建方法。该重建方法通过迭代优化求解能量约束模型,实现对火焰三维温度场的重建。算法允许复杂的成像模型应用于重建过程中,使渲染过程更接近火焰真实成像过程,并对数据平滑性进行约束,以提高重建结果质量。算法在迭代过程中使用启发式规则引导温度场数据调整,使算法快速收敛,并通过使用图形处理器加速重建过程。使用模拟数据和真实捕获数据进行实验,结果表明,与现有方法相比,提出的方法有效提高了重建结果的精度及平滑性,验证了提出方法的有效性。     

Three-dimensional reconstruction and homogenization of heterogeneous materials using statistical correlation functions and FEM

In this study, a previously developed reconstruction methodology is extended to three-dimensional reconstruction of a three-phase microstructure, based on two-point correlation functions and two-point cluster functions. The reconstruction process has been implemented based on hybrid stochastic methodology for simulating the virtual microstructure. While different phases of the heterogeneous medium are represented by different cells, growth of these cells is controlled by optimizing parameters such as rotation, shrinkage, translation, distribution and growth rates of the cells. Based on the reconstructed microstructure, finite element method (FEM) was used to compute the effective elastic modulus and effective thermal conductivity. A statistical approach, based on two-point correlation functions, was also used to directly estimate the effective properties of the developed microstructures. Good agreement between the predicted results from FEM analysis and statistical methods was found confirming the efficiency of the statistical methods for prediction of thermo-mechanical properties of three-phase composites.     

On the reconstruction of polycrystalline microstructures from two-point correlation statistics

An exhaustive branching technique is introduced for reconstructing discrete microstructures from two-point statistic occurrences. It is shown that two-point statistics control microstructure, to the extent that exact replicas of discrete microstructures are produced when sufficient two-point statistic occurrences are matched. Efficiency comparisons between simulated-annealing methods and the exhaustive branching method are made on polycrystalline structures and some discussion on advancing the exhaustive branching method is given.     

Three-dimensional physics-based registration of pelvic system using 2D dynamic magnetic resonance imaging slices

This paper introduces a method for dynamic 3D registration of female pelvic organs using 2D dynamic magnetic-resonance images (MRIs). The aim is to provide a better knowledge and understanding of pathologies such as prolapsus or abnormal mobility of tissues. 2D dynamic MRI sequences are commonly used in nowadays clinical routines in order to evaluate the dynamic of organs, but due to the limited view, subjectivity related to human perception cannot be avoided in the diagnoses. A novel method for 2D/3D registration is proposed combining 3D finite element models with a priori knowledge of boundary conditions, in order to provide a 3D extrapolation of the dynamic of the organs observed in a single 2D MRI slice. The method is applied to the four main structures of the female pelvic floor (bladder, vagina, uterus and rectum), providing a full 3D visualisation of the organs' displacements. The methodology is evaluated with two patient-specific data sets of volunteers presenting no pelvic pathology, and a sensitivity study is performed using synthetic data. The resulting simulations provide an estimation of the dynamic 3D shape of the organs facilitating diagnosis compared with 2D sequences. Moreover, the method follows a protocol compatible with current clinical constraints presenting this way potential short term medical applications.     

基于图像处理的外螺纹三维模型重构

提出了一种基于多角度序列图像特征实现外螺纹的三维模型重建的方法。首先在旋转平台上采集多角度序列螺纹件图像,然后对每帧图像进行特征点提取,将序列图像的特征点进行三维变换和插值,最终生成三维模型。实验结果表明,此算法能精确高精度地实现外螺纹三维模型重构。     

Three-dimensional analysis for explosions of a propane-air mixture in cylindrical vessels

A mathematically simple spatial difference method has been applied for analysing three-dimensionally, and for illustrating graphically, the process of the development of a flame after the propane-air stoichiometric mixture is ignited. The calculated results show that the mathematical simulation can well express the process of mixture explosion in cylindrical vessels, and can evaluate the effects of laminar swirl flow on the flame development. It is concluded that the swirl motion deforms the flame front and accelerates the flame enlargement. Described also is a comparison of swirl flame calculation, with and without the centripetal effect caused by the difference in densities between burnt and unburnt gases.List of symbols A, A _f , A _K , A _W area, flame surface area, flame element area, and wall area - b _e heat penetration coefficient - C _d coefficient - C _p molar specific heat at constant pressure - G mass of gas - H cylinder height - h enthalpy and molar enthalpy - L effective length - M _j molecular weight - n, N normal unit vector and normal vector to flame surface - p pressure - q heat input per unit mass - r _c flame center location - r, R radius and vessel radius - R universal gas constant - Re Reynolds number - s _b , s _u flame speed and burning velocity - t time measured from spark-ignition - U _c inward moving velocity of flame center - u _u compression velocity of the unburnt gas just ahead of the flame front - U(u, v, w) velocity vector - v _i , V _i specific volume and volume of region-i - x _j mole fraction of specie-_j - x mass fraction of burnt gas - X(x, Y, z), X(x, r, ) orthogonal and cylindrical coordinate systems - Y _j mass fraction of specie-_j - Y mass fraction of burnt gas - small amount of change - change from the initial state Suffixes ij flame element number - i region or state - j chemical species     

模拟水体湍流环境下目标激光点云数据的三维重建与分析

水下目标三维点云重建在水底勘探和水下无人航行器避障等领域有着重要的应用。本文通过实验室模拟温度和盐度水体湍流,开展了水下目标探测实验,研究了温度差和盐度差对水下潜艇、滑翔机和锚雷的激光点云三维重建效果的影响,并对重建后的三维点云数据进行误差分析。结果表明：在水下目标三维点云重建过程中,随着水体温度湍流和盐度湍流强度的增强,重建点云数据的有效点数明显下降,均值误差明显上升。研究结果对水下三维点云重建系统的研制具有一定参考价值。

     

基于点云三维重构的配合面装配间隙分析方法研究

在大型航空复合材料零部件装配过程中难免出现装配对接间隙,由于间隙较小,当构件固定之后内部间隙不可达,难以测量。因此,为了克服这一难题,完成装配体小间隙的测量,本文提出了利用逆向重建和虚拟装配的方式进行装配间隙测量的方案。本文基于大型航空复合材料零部件测量的背景,结合双目视觉测量原理,采用视觉与激光相结合的测量方式,研究从点云获取至装配仿真模型的逆向重建技术,在CATIA的虚拟环境下完成装配间隙的测量。     

基于工程三视图三维实体重构技术的研究

提出了一种利用ObjectARX技术进行三维重构的方法。通过对工程三视图中各种二维图形特征的分类和提取,进行二维视图特征的匹配,以投影模式库为基础求得与之对应的三维基本体素。然后按一定规则将这些基本体素通过各种布尔运算及坐标变换最终形成三维实体,最后在AutoCAD上开发了一个重建系统。在算法的具体实现过程中采用了新颖的二维特征识别方法及匹配方法,比较成功的完成了一定范围内的三维实体的重建。     

Failure analysis in a vehicle accident reconstruction

A metallurgical and mechanical failure analysis was applied as part of a vehicle accident reconstruction of a multi-vehicle collision. One of these vehicles was a coal-hauling tractor-trailer. Examination of the trailer involved in the incident revealed a fatigue fracture to a primary lateral stiffener, along with a significant misalignment of the stiffener. Stress and fatigue analysis indicated that the misalignment severely degraded the fatigue life of the stiffener. Evaluation of the structural dynamics of the trailer after the fatigue fracture indicated decreased lateral stability. The decreased stability caused by fracture of the lateral stiffener allowed rollover of the trailer to occur while negotiating a curve. The failure sequence developed in this investigation proved consistent with all physical damage observed on the trailer and with witness accounts of the incident. The failure scenario developed in this investigation is compared with other conclusions made by other investigators to show that those conclusions are not consistent with all of the available evidence.