三维物体的任意方向二维断面图像提取

医学三维数据场可视化是当前科学计算可视化应用的重点。在Visual C＋＋平台下,结合可视化工具包VTK,对DICOM格式的CT图像序列进行三维重建。用VTK对CT图像序列进行处理,使其在屏幕上能够显示任意方向的二维断面图像,并且可以用鼠标对断面图像进行缩放、平移、旋转等实时交互操作,从而弥补了CT不能按任意角度扫描的缺憾。     

基于AutoCAD软件的光栅图像处理技术

人类在长期的生产实践中积累了大量的纸质工程图纸,这给异地查阅和管理文件带来了诸多不便,如何将这些旧图纸转成CAD电子文档,使图形具有可测量性、修改性,便于保管与存储,提高其在工程上的应用价值,实践证明,利用扫描仪及AutoCAD软件可以轻松解决上述问题,具有实际的应用价值.     

基于分离字符的变速器壳体号码图像二值化算法

在分析几种典型的文本图像二值化算法的基础上,结合变速器装配线上获取的壳体号码图像的特点,提出了基于图像灰度梯度分布的单个字符分离算法,实现了对单个字符图像的小区域二值化处理。     

电梯的溜梯事故分析

对因电梯溜梯所造成的人员伤亡事故原因进行分析，指出曳引电机失电后制动器不能制动及制动器线圈回路触点粘连是事故的主要原因，并提出防止溜梯，保证可靠制动的办法。     

合成孔径雷达(SAR)图像编码压缩系统

论述了合成孔径雷达(SAR)图像准实时编码压缩的原理以及在工程上实现的方法。文章依据信息理论,根据SAR图像特点,阐述了三种编码压缩的设计方法,并从中选出采用数字信号处理器的硬一软件相结合的最佳编码压缩方案,实践表明,该方法可在80秒时间内对一幅2048×2048的SAR图像进行编码压缩,压缩比大于10,系统信噪比大于35db,很好地满足了工程任务需要。     

Experimental investigation of relative velocity field based on image rotation method in pump impeller

The continuous instantaneous flow field in pump impeller is vital for studying the mechanism of some complex flow phenomenon. In this paper, a high frequency PIV system with maximum sampling frequency 10 k Hz is built and used to measure the continuous flow field in impeller. In order to reduce the minimum sampling frequency required for PIV while ensuring the accuracy of flow field measurement, an image rotation method was proposed for calculating the relative velocity flow field in impeller. This method removed the particle displacement caused by impeller rotation in circumferential direction before the FFT calculation was performed. The relative velocity value calculated by velocity triangle method and image rotation method are compared and analyzed at different sampling line positions for different experimental conditions. The results show the image rotation method can not only obtain a more accurate velocity field near the blade area, but also has a lower requirement for the sampling frequency of the PIV system. The relative velocity error between two methods shows a trend of decreasing and then increasing when the sampling frequency decreases from 10 k Hz to 1 k Hz. Meanwhile, the relationship between the impeller speed and optimal sampling frequency range is established, which provides guidance for the selection of the appropriate PIV sampling frequency used for the measurement of the flow field in impeller.     

一种超声诊断仪的USB接口方案

本文介绍了一种便携式超声诊断仪的USB接口设计方案。该方案主要应用在以51系列单片机为主控器的医用超声显像诊断仪上。     

The Measurement of Anisotropic Magnetic Susceptibilities Using the Faraday Method

Apparatus of the Faraday type to measure crystal magnetic susceptibilities is described in conjunction with the method of analysis to deduce the anisotropic molecular magnetic susceptibilities. The relative merits of the Faraday and torsion methods to measure anisotropic susceptibilities are discussed. The principal molecular susceptibilities^* which were determined at 293 K for the cesium, potassium, and ammonium copper Tutton's salts indicate orthorhombic distortion in the crystal fields around the copper ion.     

Effects of prebuckling deformations on the elastic flexural-torsional buckling of laterally fixed arches

The effect of the prebuckling in-plane deformations on the elastic flexural-torsional buckling of laterally fixed circular arches is studied in this paper. The finite strains and the energy equation for the flexural-torsional buckling of arches have been derived based on an accurate orthogonal rotation matrix. A closed form solution for the elastic flexural-torsional buckling resistance of laterally fixed arches in uniform bending, including the effects of the prebuckling deformations, is obtained. It is found that the notion that the prebuckling deformations increase the flexural-torsional buckling moment of an arch or of a beam is not necessarily correct for a laterally fixed arch or beam in uniform bending, in deference to a laterally pinned arch. When a laterally fixed arch is subjected to positive uniform bending, the effects of the prebuckling deformations decrease the buckling moment, and the reduction of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When a laterally fixed arch is subjected to negative uniform bending, the effects of the prebuckling deformations decrease the absolute value of its buckling moment when the included angle is very small, but increase the absolute value of the buckling moment when the included angle exceeds a certain value. The increase in the absolute value of the buckling moment increases with an increase of the included angle and of the out-of-plane slenderness ratio of the arch. When the ratio of the out-of-plane to the in-plane second moments of area of the cross-section is not small, both the reduction of the buckling moment of a laterally fixed arch in positive uniform bending and the increase of the buckling moment of a laterally fixed arch in negative uniform bending, are substantial.     

PHENOMENON OF CARVED DRIVING WHEELS

A newly found phenomenon of carved driving wheels of a rear-wheel-drive tractor used in an airport is discussed. The circum of every driving wheel is damaged at three regions,which distribute regularly and uniformly. Everyday,the tractor tows a trailer which are times heavier than the tractor,and moves on the same road in the airport. The phenomenon is explained by the torsional self-excited vibration system of the powertrain. The simplified torsional vibration system is discribed by a 2-order ordinary differential equation,which has a limit circle. Experiments and numerical simulations show the followings: Because of the heavy trailer,the slip ratio of the tractor’s driving wheels is very large. Therefore,there is severe torsional self-excited vibration in the tractor’s drivetrain,and the self-excited vibration results in severe and regular fluctuations of the rear wheel’s velocity. The severe fluctuations in velocity fastens the damage of the driving wheels. At the same time,the time interval in which an arbitrary point in the circum of the driving wheel contacts with the road twice is two times more than the period of the torsional self-excited vibration,and this times explained the existence of three damaged regions. At last,it points out that the phenomenon can be avoided when the torsional damping is large enough.     

DESIGN AND CAD SYSTEM OF THE FOOL FOR DRILL FLUTE

Based on the principles of differential geometry and kinematics, a mathematical model is developed to describe the grinding wheel axial cross-section with the radial cross-section of the flute in a given drill under the basic engagement condition between the generating flute and the generated grinding wheel (or disk milling tool). The mathematical model is good for the flute in the radial cross-section consisting of three arcs. Furthermore, a CAD system is also developed to represent the axial cross-section of the grinding wheel (or disk milling tool). With the system, the grinding wheel (or disk milling tool) axial cross-section that corresponds to the three-arc flute cross section can be conveniently simulated. Through the grinding experiment of drill flutes, the method and the CAD system are proved to be feasible and reasonable.     

孔隙阀式磁流变阻尼器准静力分析

建立了孔隙阀式磁流变阻尼器的轴对称模型.推导了孔隙阀内磁流变液压力梯度方程.对Herschel-Bulkley模型的磁流变阻尼器压力梯度进行了数值求解.应用代数方程理论,得到了Bingham模型的磁流变阻尼器压力梯度的解析解.最后,结合算例计算了孔隙阀内磁流变液的流速分布及阻尼器的阻尼力.     

车门静态强度的有限元分析模拟

轿车门系统结构设计与优化是整车开发过程中的重要环节。车门的强度直接关系到整车在冲击、碰撞等载荷下的安全问题,车门结构静态强度的计算分析,在车门结构设计进程中非常重要。文中首先简要介绍了静态强度所涉及到的非线性有限元的基本理论,然后以某中高级轿车前车门为例,利用计算机辅助分析车门的静态强度,考虑变形的非线性因素,通过对车门的非线性有限元求解来分析车门强度,由计算所得到的车门强度性能指标来指导车门的结构设计。     

气化炉三维扫描测量与数据处理

以德士古气化炉耐火砖的内壁蚀损检测设备为基础,对采集到的点云数据做了进一步处理.通过对数据的筛选和剔除,实现了数据点的平滑降噪细化和精简.然后利用点云对整、网格划分和分色显示等方法,最终完成了内壁腐蚀情况的三维建模.重点讨论了点云数据的预处理及后处理的方法,并根据内壁耐火砖的腐蚀阈值,提出了一种气化炉内壁腐蚀区域的识别与分割方法.对耐火砖的腐蚀分析、气化炉的生产与维修提供了可靠依据,并在工程应用中获得了一致认可.     

OPTIMIZING DESIGN OF MECHANICAL SELF-CENTERING DEVICE FOR SUSPENSION HEIGHT

Firstly, in view of the respective defects of existing self-centering devices for vehicle suspension height, the design scheme of the proposed mechanical self-centering device for suspension height is described. Taking the rear suspension of a certain light bus as a research example, the structures and parameters of the novel device are designed and ascertained. Then, the road excitation models, the performance evaluation indexes and the half-vehicle model are built, the simulation outputs of time and frequency domain are obtained with the road excitations of random and pulse by using MATLAB/Simulink software. So the main characteristics of the self-centering suspension are presented preliminarily. Finally, a multi-objective parameter design optimization model for the self-centering device is built by weighted sum approach, and optimal solution is obtained by adopting complex approach. The relevant choosing-type parameters for self-centering device components are deduced by using discrete variable optimal method, and the optimal results are verified and analyzed. So the performance potentials of the self-centering device are exerted fully in condition of ensuring overall suspension performances.     

平面应变颈缩扩展与剪切断裂的数值模拟

采用虚功率增率有限元法及Ｊ２形变理论，模拟韧性金属平面应变颈缩扩展，剪切断裂演化过程。运用载荷控制的自动识别方法以及各增量步间Ｅｕｌｅｒ控制方法，实现了均匀变形与非均匀变形临界状态的稳定过渡，采用本构方程的Ｅｕｌｅｒ显式积分，对Ｊ２形变理论塑性加载与弹性卸载的不连续性进行了改进，保证了变形局部化模拟过程的可靠性，最后，讨论了不同硬化指数及初始几何不均匀性对局部化力学行为的影响。     

IMPROVED METHOD FOR HILBERT INSTANTANEOUS FREQUENCY ESTIMATION

In the mechanical fault detection and diagnosis field, it is more and more important to analyze the instantaneous frequency (IF) character of complex vibration signal. The improved IF estimation method is put forward aiming at the shortage of traditional Hilbert transform. It is based on Hilbert transform in wavelet domain. With the help of relationship between the real part and the imaginary part obtained from the complex coefficient of continuous wavelet transform or the analytical signal reconstructed in wavelet packet decomposition, the instantaneous phase function of the subcomponent is extracted. In order to improve the precise of IF estimated out, some means such as Linear regression, adaptive filtering, resampling are applied into the instantaneous phase obtained, then, the central differencing operator is used to get desired IF. Simulation results with synthetic and gearbox fault signals are included to illustrate the proposed method.     

The effect of basic nitrogen compounds on the tribological performance of sulphurised olefin

The effect of the molecular structure of basic nitrogen compounds on the lubricating properties of sulphurised olefin has been investigated using a Timken tester. X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Analysis (EDAX) were used to study the chemical states of sulphur and nitrogen on the rubbed surfaces and the reaction rates of sulphur and iron separately. It was found that the antiwear and friction reduction properties of sulphurised olefin are greatly influenced by the different molecular structures of the basic nitrogen compounds. A composite additive package containing basic nitrogen compounds with sulphurised olefin can produce either synergistic or antagonistic effects, due to the influence of the different molecular structures of the basic nitrogen compounds. XPS analysis revealed that a tribochemical protective film containing nitrogen and sulphur was formed on the rubbed surface. EDAX analysis indicated that the reaction rates between elemental sulphur and iron were influenced by the different molecular structures of the basic nitrogen compounds. It was found that the apparent reaction rates of elemental sulphur and iron are related to the tribological characteristics of the additive package.     

Adaptive stochastic resonance method for weak signal detection based on particle swarm optimization

In order to solve the parameter adjustment problems of adaptive stochastic resonance system in the areas of weak signal detection,this article presents a new method to enhance the detection efficiency and availability in the system of two-dimensional Duffing based on particle swarm optimization.First,the influence of different parameters on the detection performance is analyzed respectively.The correlation between parameter adjustment and stochastic resonance effect is also discussed and converted to the problem of multi-parameter optimization.Second,the experiments including typical system and sea clutter data are conducted to verify the effect of the proposed method.Results show that the proposed method is highly effective to detect weak signal from chaotic background,and enhance the output SNR greatly.     

INFLUENCE OF ROLL DIAMETERS ON DEFORMATION BEHAVIOUR OF HIGH TEMPERATURE SUPERCONDUCTING TAPE

During plastic process,the material flow is strongly influenced by the contact area between deformed workpiece and die.In rolling process,difference of roll diameter makes the contact area between roll and deformed tape different,which leads to different material flow and the distribution of powder density.A numerical modelling of the first rolling process for 61-filament high temperature superconducting tape is constructed and the influences of roll diameters on deformation behavior of the tape are discussed.It can be found that the BiSrCaCuO(BSCCO)powder in the center of the tape has higher relative density than those in the periphery of the tape during rolling process.With the increase of roll diameter,the length of the contact arc in the roll gap expands which lead to the in- creasing of transversal strain and the decreasing of the related longitudinal strain.It makes the value of longitudinal strain ratio decrease gradually,which decreases the possibility of occurrence of the transversal shear band,simultaneously it increases the risk of occurrence of longitudinal crack.