基于多尺度滤波和线检测算子的视网膜血管检测

视网膜血管分割在眼底图像分析中具有重要作用。结合多尺度Hessian矩阵滤波和线检测算子,提出了一种有效的血管检测方法。首先利用多尺度Hessian矩阵的特征值构建血管相似性函数,实现血管增强;然后采用改进的线检测算子,提取反映血管测度的特征;最后采用SVM实现血管检测。实验结果表明,该方法只需要较少的训练样本即可达到与其他方法相当的准确率,且在灵敏性上具有更好的性能。     

HL-2M 真空室制造工艺难点分析及优化

根据 HL-2M 真空室结构及运行工况,对 HL-2M 真空室制造过程的工艺难点进行了深入的分析。结 合前期试验段制造经验,优化了真空室制造工艺,细化了真空室产品的制造工艺方案。通过优化后工艺措施的实 施,提高了真空室的制造质量,并为后续磁约束聚变装置真空室的制造积累了大量的经验。     

HL-2M 真空室内壁螺柱焊接工艺研究与实施

针对 HL-2M 真空室内壁螺柱焊接,从焊接螺柱结构设计、焊接工艺研究、焊接工艺试验、焊接质量 评判等方面进行了详细研究,最终确定了包括焊接电流、焊接时间、伸出长度、提升高度、总提升高度等焊接参 数和接地线位置、焊枪手把方向的真空室内壁螺柱焊接工艺方案。通过大量工艺试验,有效地解决了 HL-2M 真 空室内壁(5mm,Inconel625 材质)-大直径(∅12mm,316L 材质)螺柱焊难题,焊缝成型均匀,飞溅和焊瘤少,表面 发黑明显改善,满足真空清洁度要求。焊接稳定性高,良品率高,拉伸试验和疲劳试验也满足设计要求。      

A positron beam Doppler broadening analysis of formation and recovery of defects produced by ion irradiation in Fe‒C‒Cu alloys

Mechanisms of radiation embrittlement of reactor pressure vessel steels remain to be fully understood, particularly the nature of so-called ‘matrix defects’. One possible mechanism is vacancy cluster formation, probably assisted by cascade damage. In order to investigate the effect of copper on the formation and annealing processes of vacancy clusters, ion-irradiated Fe?C and Fe?C?Cu were investigated using a variable energy positron beam. Doppler broadening analysis revealed that vacancy-type defects are produced by ion irradiation and that copper addition reduces the open volume of the defects. Post irradiation annealing suggested the vacancy clusters do not have a substantial role in irradiation hardening.     

Dynamic analysis of an offshore pipe laying operation using the reel method

A system designed for a rigid and flexible pipe laying purposes is presented in the paper.Mathematical and numerical models are developed by using the rigid finite element method(RFEM).The RFEM is an efficient solution in the time domain.Static and dynamic problems related to pipe installation are solved by taking the advantage of simple interpretation and implementation of the method.Large deformations of the pipe during spooling and when it is reeled out at sea are considered.A material model implemented is used to take into consideration nonlinear material properties.In particular,the full elasto-plastic material characteristics with hardening and Bauschinger effect are included.Dynamic analyses are performed and the results attached in this work demonstrates how the sea conditions influence the machinery and pipeline,assuming a passive reel drive system. The influence of several other operational parameters on dynamic loads is verified.An active system,implemented as a part of the mathematical model,improves the system performance.Some results are presented as well.     

承压薄壁容器应力分析的讨论

通过讲述与引伸承压薄壁圆筒的应力分析, 引导学生关联几种承力构件 的受力特征, 并展示其在日常生活中的应用实例, 可作为该部分课堂教学的补充材料.     

真空规管对低温容器残余气体影响的实验研究

以高真空多层绝热低温容器为研究对象,利用残余气体分析仪研究冷阴极真空规管、热阴极真空规管以及热阴极真空规管不同放置位置对低温容器真空夹层内残余气体的影响.结果表明:冷阴极真空规管对低温容器真空夹层内残余气体的影响几乎是可以忽略不计的;热阴极真空规管对低温容器真空夹层内残余气体的影响较大,热阴极的灯丝和残余气体之间存在化...     

Flow Injection Analysis of Mercury/Cold Vapor Atomic Fluorescence Spectrophotometry

Abstract

A new flow injection system for the determination of mercury by the cold vapor atomic fluorescence method is described. A sample solution (64 μ1) is injected into a stream of 0.1 M hydrochloric acid, which is mixed with a stream of 3% tin (II) chloride solution in a mixing joint. The combined stream is carried through a reaction coil for reduction of Hg (II) to Hg (0) and subsequently introduced into a specially designed gas-liquid separation vessel. Then the vaporized mercury is swept into a flow type fluorescence cell with a continuous flow of argon after removal of water in the gas phase through a condenser. Mercury is excited with an electrodeless discharge lamp as a source and the mercury fluorescence at both 184.9 and 253.7 nm is measured with a solar-blind photomultiplier. This method allows about 35 determinations of mercury in aqueous samples per hour. The calibration curve is linear over the 0–20 ppb range of mercury. The limit of detection (S/N = 3) is 0.008 ng (0.12 ppb × 64 μ1) and the coefficient of variation is below 1% for the 1–20 ppb solutions (n=10).     

高速水面舰船型线的数学模型

提出了一种应用数学模型构建高速水面舰船船型的设计方法.该"数学船型"方法根据舰船的应用特性确定船型曲线的几何性质及应满足的定解条件,应用定解条件确定船型曲线的形状函数或型值函数,从而生成所需船型曲面.实验表明,"数学船型"方法无需型值即可得出设计舰船的型值表、型线图和任意视向的立体船图,且能保证船体的浮性、稳性和具有最小阻力等重要性能.方法可用于舰船设计的初始阶段,在与"数学船池"连接后,易于对船型做优化设计.     

基于FLUKA计算压力容器快中子注量的可行性研究

基于知识产权的考虑,通过与蒙特卡罗程序MCNP计算结果比对,研究使用FLUKA程序替代MCNP程序进行反应堆压力容器快中子注量计算的可行性。通过修改和调用子程序对次级粒子堆栈进行操作,解决了关闭裂变中子这一关键问题,FLUKA程序的计算结果与MCNP程序的计算结果相对偏差在5%以内,符合得较好,证明使用FLUKA程序替代MCNP程序用于计算反应堆压力容器快中子注量在技术上是可行的。