一种新的脑部血管重建方法

血管重建是神经外科导航软件中的重要组成部分。针对脑部血管可视化,目前存在两大问题：剔除头骨法得到的图像中血管和杂质组织并存、血管间断;血管分割法重建后的血管表面存在“失真面片”或“连接阶梯”。本工作采取对分割目标形状不敏感的阈值水平集法对血管进行分割,并结合ROI来提速,最后利用改进的二维距离场与Marching Cube算法结合进行血管表面重建。实验结果表明,该方法能很大程度消除“连接阶梯”并避免杂质组织出现和血管间断。同时,该方法可同时提取多根血管,而不需要考虑脑部血管复杂的拓扑结构,其重建结果可为医生诊断提供参考。     

APPLICATION OF SURROGATE BASED PARTICLE SWARM OPTIMIZATION TO THE RELIABILITY-BASED ROBUST DESIGN OF COMPOSITE PRESSURE VESSELS

A surrogate based particle swarm optimization （SBPSO） algorithm which combines the surrogate modeling technique and particle swarm optimization is applied to the reliability- based robust design （RBRD） of composite pressure vessels. The algorithm and efficiency of SBPSO are displayed through numerical examples. A model for filament-wound composite pressure vessels with metallic liner is then studied by netting analysis and its responses are analyzed by using Finite element method （performed by software ANSYS）. An optimization problem for maximizing the performance factor is formulated by choosing the winding orientation of the helical plies in the cylindrical portion, the thickness of metal liner and the drop off region size as the design variables. Strength constraints for composite layers and the metal liner are constructed by using Tsai-Wu failure criterion and Mises failure criterion respectively. Numerical examples show that the method proposed can effectively solve the RBRD problem, and the optimal results of the proposed model can satisfy certain reliability requirement and have the robustness to the fluctuation of design variables.     

球形容器内气体的泄爆过程

为了得到球形容器内可燃气体的泄爆强度产生机理以及燃烧火焰与压力传播的基本规律,从流体力学和化学反应动力学守恒出发,采用-湍流模型和EBU-Arrhenius燃烧模型,利用SIMPLE算法对带泄爆导管的球形容器二维空间内甲烷-空气预混气体的泄爆过程内外场进行了数值计算,获得了气体燃烧过程中火焰和压力传播特性以及气体流动特性,能够比较清晰地反映泄爆的整个过程。研究表明,燃烧火焰在泄爆过程中发生湍流,传播得到了极大的加速,泄爆导管对于容器内的高压气体泄放有很大的约束作用。     

珠形爆炸容器水压试验应力测试及分析

设计压力12MPa的球形爆炸容器内径1m,壁厚2.5×10-2m,在3,6,9,12,15和0MPa的水压试验条件下,对其外表面具有代表性的20个测点进行了应力测试.并用三维ANSYS有限元编码对12和15MPa两种工况进行了应力分析,分析结果与测试结果基本吻合,这表明爆炸容器在整个试验压力范围是处于线弹性状态,容器的强度设计是合理的.     

2000m~3在役压力容器应力状况分析

本文报道了钢制 2 0 0 0 m3球罐实际运行一年后的应力状况 ,对球罐的残余应力及工作应力进行了现场测试 ,发现球罐虽经过整体热处理 ,但局部残余应力仍较高等问题 ,并进行了对比分析 .     

车载高温超导磁悬浮系统的设计

介绍车载高温超导磁悬浮系统的设计问题。为了完成系统的设计 ,首先进行了单块和多块YBCO高温超导体块材的悬浮力的研究 ,同时考虑了 YBCO高温超导体块材的选取问题。设计的目标是稳定悬浮 350 kg,采用 8个车载液氮低温容器 ,这种容器是底壁仅 3mm厚的长方体形的。     

Buckling investigations on a nuclear reactor inner vessel model

This paper presents the results of an experimental study on the buckling of scaled-down models of the inner vessel used in nuclear reactor structures. The inner vessel, a shell of composite geometry, consists of two cylindrical shells connected by conical and torus shells. There are six stand-pipes on the conical portion of the vessel carrying heat exchangers and pumps. Scaled-down models of the inner vessel are made by the conventional fabrication methods (rolling, welding) and are tested in the present study. The test setup consists of a loading system for applying concentrated load on the stand-pipes, an air compressor for applying internal pressure and the related instrumentation. Imperfection scans are carried out in a specially fabricated experimental setup using linear variable differential transformers (LVDTs) before and during loading. Using the scanned raw data, the initial geometric imperfections and eccentricity between the LVDTs and the specimen axes at different axial locations are calculated. The results show that the maximum initial imperfections are on the order of 1.75 times the wall thickness; generally, the growth of deformation patterns with loading resembles the shapes of initial imperfections, and the growth is predominant on lower cylinder and torus regions. The general purpose, finite element-based software, ABAQUS, is used to obtain the analytical values. The initial imperfections measured on the experimental models are incorporated into the finite element models. The agreement between experimental and analytical buckling loads is within about 30 percent error.     

Problem of hydrodynamic pressure on suddenly starting vessel

In this paper,Lagrangian method is applied to discuss the problem of the hydrodynamic pressure on a suddenly starting vessel.The free surface profile and the coefficients of the hydrodynamic pressure on the vessel wall are obtained.And it is verified that the singularity of the pressure near the free surface is only logarithmic.     

水箱突然起动的水动压力问题

在本文中,应用Lagrange方法讨论水箱突然起动的水动压力问题.求得了自由面形状和作用在水箱壁上的动态压力系数.也证实了在自由面附近,压力系数的奇性仅是对数奇性.     

生物组织中的残余应变

本文综述了生物组织中残余应力和残余应变的研究历史和现状,着重分析了心血管系统的残余应变和零应力状态,讨论了残余应变对血管和心脏等器官的力学分析和组织改造的重要意义,并提出了一些有待研究的问题．