利用切片的二维空间相关操作实现血管的三维重建

相关(Correlation)作为两个图形相似程度的度量,被广泛的用于图形图像自动识别中.为对血管的二维切片图像进行分析并重构出血管以及血管中轴线的三维空间形貌,我们利用快速傅立叶变换(FFT)及反变换对切片进行空间相关操作,几乎一步即可确定出中轴线与切片的交点,从而给出中轴线的空间坐标.我们求出了血管的半径,利用这些结果,绘出了血管中轴线的三维曲线及其投影线,并且利用计算机软件画出了血管的三维造型,在该造型中作血管切片,结果与初始的切片数据一致.文中分析了相关法进行图像处理的优点与局限性,对利用近代光学信息处理的手段进行切片三维重建的思路进行了讨论.     

血管管道的三维重建

文章对血管管道的三维重建进行了讨论.根据题目所给信息,首先读取100张血管切面图,把它们转换成数据矩阵,然后分三步进行处理:第一步,通过搜索切面最大内切圆求出管道的半径,提出两种方案,分别是切线法和最大覆盖法;第二步,轨迹的搜索,本文提出了三种方法,分别为网格法、蒙特卡罗法和非线性规划法;第三步,中轴线在三平面上投影的精确定位,分别用最小二乘和分段最小二乘进行了曲线的拟合.最后又对三维重建的血管管道进行了检验和误差分析.利用以上算法较好地进行了管道的重建,从而得出所求半径为29.529,中轴线上100点的坐标见表1,其在XY,YZ和XZ平面上的投影分别为图8到图15.     

一种改进的血管三维数字仿真方法

为了克服目前血管三维仿真方法中普遍存在的计算量大、精确度不高、缺乏合理的理论证明等问题,更好地实现血管的三维数字仿真、提高仿真精度,本文提出了一种改进的仿真方法。将血管的平行切片图像进行二值化处理,叠加,建立数学模型,得到三维血管的半径,利用求得的半径和Bresenham算法得到每张平行切片图像的最大内切圆圆心,利用多项式拟合建立中轴线空间曲线。     

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%.     

管道切片的三维重建

文中证明了所有切片含有过轴心的大圆,该大圆直径一定与切片边界相交.通过构造连续型模型和离散型模型,从0.BMP中定出轴心为(0,160)和半径为30的最大圆,并相继在其它切片中运用最大圆必包含在切片中的先决条件,找出相应切片中所有可能的轴心坐标,进一步对每一切片待选的轴心坐标,根据其球体必在上29～下29层切片中存在相应半径的圆(在上下29层中存在半径为7.68,在24层存在半径为18的该球体的相应的截面圆)的特征,筛选上述待选轴心坐标,比较准确地定出了0到70层的轴心坐标.对于71至99层由于上29层的信息不全,还存在不少待选点,再应用切片尖端特性(在70层左下角的点只能由半径较小的圆包络而成,由此定出99层的轴心坐标)确定其余切片的轴心坐标.绘制出的三维图形和各坐标面的投影图是光滑流畅的.最后文中用所得轴心坐标重新构造各切片,与原切片比较,相异象素点误差不足3%,结果令人满意.     

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.     

球面滚子轴承内套中挡边高度的测量

球面滚子轴承内套中挡边高度hn,是其轴截面内半径为R_1、R的两圆弧交点A到相对滚道基准端面B的垂直距离(图1)。两圆弧交点A在加工油沟时被切去,所以hn无法直接测量。若在两圆弧之间放入一个已知半径r的标准钢球,测出钢球顶点到基准端面B的垂直距离K_(bn),然后通过计算,即可间接求出两圆弧交点A与基面B之垂直距离hn的数值(图2)。一、公式推导(图2) 由零件设计图纸给定了R_1、R、r、N0、OW、PD、QA及AF的尺寸,测得K_(hn),即可求出hn。     

新型热流计测量技术的探索研究

目前的热流计在测量热量时需要测量供热管道的流量以及进出口温度,然后再对其进行积分计算.其技术非常复杂,而且精度低,仪器成本高,难以普及.为了解决这一系列问题,本文主要依据能量守恒定律提出了一种新型的能量测量装置,并对该装置的测量原理进行了理论分析.通过数值模拟,在理论上对其进行了验证.数值模拟的结果证实该型热流计测量结果与系统流体的流量无关,这也是本测量方法不同于其它常规热流计的优点之一,摆脱了流量对能量测量的影响,同时也简化了计算过程,大大降低了成本.     

空间曲线型微细管道曲率检测器

研制了一种适于空间曲线型微细管道的曲率检测器。该检测器主要由激光光源、关节、PSD传感器三部分组成。在管道内壁的约束作用下,出射激光和PSD传感器的中轴线的夹角将随着管道曲率的变化而变化。根据光学三角原理,可以求出该夹角的大小,然后结合检测器的结构参数可以计算出管道相应位置的曲率半径。该曲率检测器的总长度为34mm,重约为6g。在微型管道机器人的驱动下,可以实现微细管道的曲率半径测量及其中轴线的三维描述,对管道曲率半径的相对测量精度达到±2%。     

泄漏管道中振动波波速特性研究

主要根据管道振动理论并结合泄漏管道的工程实际情况,通过管道的运动方程,得到泄漏管道周向模态下不同类型振动波波速的预测公式.并以钢管和PVC塑料管为例,分析和讨论相同频率范围内,管道的几何特性和材料特性对振动波波速的影响.结果表明管道半径和材料特性对振动波波速影响较为明显.并在上述工作的基础上,与已有的实验结果进行分析和对比,验证泄漏管道中波速预测公式的准确性和可靠性.     

Pumping speed measurement of turbomolecular pumps by a quasistationary pump-down method

The pumping speed of a turbomolecular pump is usually measured by injecting a stationary known gas flow via a standardised test dome into the pump and measuring the equilibrium pressure in the test dome. The ratio of gas throughput and pressure is just the pumping speed. In practice, the pressure can be conveniently and accurately measured, whereas the convenient and accurate throughput measurement is a challenging experimental problem. The present paper reports on a new method for measuring the pumping speed in which the throughput is generated by the pumping down of a vessel via an orifice. From the decrease of vessel pressure with time, and from known vessel volume, the throughput can be directly and accurately derived. Exploring measurements by the new method in fact give high accuracy, systematical error sources are practically negligible.     

Dynamic determination of vessel speed and selection of bunkering ports for liner shipping under stochastic environment

In this work, we study a liner shipping operational problem which considers how to dynamically determine the vessel speed and refueling decisions, for a single vessel in one service route. Our model is a multi-stage dynamic model, where the stochastic nature of the bunker prices is represented by a scenario tree structure. Also, we explicitly incorporate the uncertainty of bunker consumption rates into our model. As the model is a large-scale mixed integer programming model, we adopt a modified rolling horizon method to tackle the problem. Numerical results show that our framework provides a lower overall cost and more reliable schedule compared with the stationary model of a related work.     

基于造影图像的冠状动脉血管三维表面重建方法

在冠状动脉树骨架三维重建的基础上,研究了基于造影图像的血管表面重建方法。首先采用B样条曲线拟合血管的三维骨架,建立了骨架点的局部坐标系。同时研究了血管横截面的椭圆模型,并推导了椭圆方程。针对血管树表面重建中的自相交问题,提出一种新型顶点融合技术,给出了融合点的计算方法。最后利用两幅不同角度的临床冠脉造影图像,成功实现了血管的三维表面重建。     

Doppler angle and flow velocity estimations using the classic and transverse Doppler effects

Current clinical Doppler ultrasound systems could only measure the flow vector parallel to the ultrasound beam axis, and the knowledge of the Doppler angle (beam-to-flow angle) is needed to calculate the real flow velocity. Currently, the Doppler angle is determined visually by manually aligning a vessel axis marker along the blood vessel on the duplex scan image of the ultrasound. The application of this procedure is often limited by practical constraints; therefore, measurements are not reliable. In order to overcome this problem, the authors developed a simple Doppler angle and flow velocity estimation method using a combination of the classic and transverse Doppler effects. This method uses only a single focused annular array transducer to estimate the Doppler angle and the flow velocity. The authors have verified experimentally that this method is successful for measuring constant flow in a flow phantom between 45 degrees and 80 degrees Doppler angle. The standard deviation of the estimated Doppler angles is less than 4.5 degrees . This method could be implemented easily in medical Doppler ultrasound systems to automatically estimate the Doppler angle and the flow velocity.     

Design of a variable sampling interval exponentially weighted moving average median control chart in presence of measurement errors

In the literature, many control charts monitoring the median is designed under a perfect condition that there is no measurement error. This may make the practitioners confusing to apply these control charts because the measurement error is the true problem in practice. In this paper, we consider the effect of measurement error on the performance of the exponentially weighted moving average (EWMA) control chart combining with the variable sampling interval (VSI) strategy. A linear covariate error model is supposed to model the measurement error. The performance of the VSI EWMA median control chart is evaluated through the average time to signal. The numerical simulation shows that the measurement errors have a negative influence on the proposed chart.     

基于对偶理论的椭圆变分不等式的后验误差分析（英）

本文基于对偶理论对椭圆变分不等式的正则化方法提供一个相对全面的后验误差分析．我们分别考虑了摩擦接触问题和障碍问题,通过选取一种不同形式的有界算子和泛函,推导了其对偶形式并给出了正则化方法的 $H^1$ 范后验误差估计．最后,利用凸分析中的对偶理论建立了障碍问题的残量型后验误差估计的一般框架．同时我们选取一种特殊的对偶变量和泛函形式得到该问题的残量型误差估计及其有效性．数值解的后验误差估计是发展有效自适应算法的基础而模型误差的后验误差估计在分析问题中数据的不确定影响时是非常有用的．     

Conditioning and long-term storage of spent radium sources in Turkey

Conditioning of radium sources is required before long-term interim storage to avoid the release of radioactive material and to limit radiation exposure. In this study, containment of the radium sources was achieved by high integrity encapsulation designed to control the radon emanation problem. The capsules were made of Type 316 austenitic stainless steel with dimensions of 22mm diameter and 160mm height. The gas pressures which was caused by encapsulation of different amounts of (226)Ra were determined. The maximum gas pressure found 10atm for 900mCi of (226)Ra in one capsule at 20 degrees C. A lead shielding device was designed to limit radiation exposure. A 200l drum was used as a conditioned waste package for the radium sources and represents a Type A package under the IAEA transport regulations.     

减振器节流阀片对阀门水击力的影响研究

针对车用减振器受地面瞬态冲击阀门容易失效的特点,提出了研究阻尼阀水击压强的重要性.建立了带有环形节流阀片的阻尼阀物理模型.通过有限元软件对节流阀片受瞬态冲击的变形时间进行了研究,得出了节流阀片受冲击的最大变形时间只与结构参数和材料特性相关,并随阀片厚度增加而减小的结论.与水击理论相结合,推导了阻尼阀水击的初始和边界条件,创建了阻尼阀水击数学模型.运用节流阀片等效厚度法则,编程分析了叠加节流阀片对水击力的影响规律,得出了在等效厚度相同的情况下,随着叠加阀片物理厚度的增加水击压强增大的结论,可以作为阻尼阀的设计参考.     

Boundary element simulation of large amplitude standing waves in vessels

In this paper, a fluid in a vessel is considered and large amplitude standing waves (LASW) of the fluid are simulated directly using the boundary element method (BEM).In the simulation, two problems come out. The first problem is that the energy of the LASW increases gradually when using double nodes at corners in the BEM. The second problem is that projection-like profiles appear near the point where the free surface meets the vessel wall when regridding is not used at each time step. These projection-like profiles are not physical and indicate numerical error, and cause the simulation to break down.We found that the use of discontinuous elements solves the first problem, and the use of the ‘half shift technique’ solves the second problem.In addition, a method called RIG for highly accurate simulation using regridding is proposed and verified.     

High dynamic range measurement of linear birefringence with an electro-optic modulated circular polariscope

This paper presents a common-path electro-optic modulated circular polariscope capable of performing the sequential measurements of the principal axis and retardance of the linearly birefringent media with high accuracy by means of two phase-locked extractions, and with a high dynamic range obtained by the design of optical configuration and the derivation of an easy algorithm. There exist an absolute error of 0.10° on average in the principal axis measurement of 36 times within the range of 0°–180°, and a relative error of 1.10% in the retardance measurement of a λ/2-wave plate by this method. Consequently, the standard deviations for the principal axis angle and retardance measurements are determined to be 0.0033° and 0.086°, respectively, triple standard deviations to the average values of principal axis angle and retardance are just 0.10% and 0.14% with high repeatability, respectively, and corresponding dynamic ranges of 0°–180°.