图元法在AutoCAD二次开发中的应用

用ObjectARX作为开发工具 ,探讨了图元法在对AutoCAD 2 0 0 0进行了二次开发时的应用。结合数据库技术 ,应用折半查找方法 ,解决了CAD中查询与管理标准数据的难题 ;进而对CAD中常用零部件与标准件的装配图与零件图的绘制 ,分别采用整体法和图元法进行了描述。该方法可推广至以AutoCAD作为平台的专业软件开发中。

基于图元法的AutoCAD参数化设计与绘图

对于结构型式多变、复杂的常用件(如轴、齿轮等)的设计,因为其应用频率高,绘图工作量大,适合于用图元法对其进行二次开发,以提高工作效率。图元法是对所开发的零件进行分析归纳,总结出高度概括的图元,用这些图元基本上可组合出该类零件的所有结构,然后对各个图元编程,并赋予相应的约束参数。机械零件设计中,对形状不相似的图形采用图形元素拼合法进行设计绘图,既简单,又方便,可以将设计人员的主要精力从繁杂的绘图工作转移到零件的结构设计上,提高产品的设计效率。本文以ObjectARX作为开发工具,以机械常用的零件为例,讨论了图元法在AutoCAD2000中二次开发的应用。用基本的图形对象创建图元,通过图元拼合法生成零件图。

纳西图形文图元输入法

纳西图形文是世界上唯一仍在使用的象形文字,对研究人类文字的进化历史有着积极的作用。通过对纳西图形文的特点及信息处理现状的分析,提出图形文图元输入方案,并对输入方案进行优化处理。在Windows XP平台下采用IMM-IME接口开发了纳西图形文图元输入法,在实际应用中取得良好的应用效益及社会效益。

嵌入式GIS提高矢量地图显示速度的软件方法实现

嵌入式GIS系统已经深入到国民经济和社会生活多个方面,并得到广泛应用,在资源受限的嵌入式平台上如何通过软件方法提高矢量地图显示速度值得研究。建立矢量地图显示数学模型后,本文从降低数据在外存定位时间、减少数据读取时间和提高矢量地图数据显示处理效率三个方面进行重点分析和阐述,测试结果表明这些方法是有效的。

基于图形单元的结构变异参数化设计方法

以图形单元的插入和置换为手段 ,介绍了一种基于图形结构单元的结构变异参数化方法 ,详细探讨了图元阵列法、图元插入与删除法、图元置换法的原理和算法 。

通用地图符号表达机制的研究

地理信息共享是地理信息系统(GIS)研究中的一大热点,其中地图符号的共享尤为重要。针对目前地图符号共享所面临的主要障碍,文中从地图符号的定义出发,利用图元参数法建立通用地图符号表达模型,并采用XML语言完成符号的描述,最后通过符号配置,生成由通用几何图形组成的符号化结果,从而实现地图符号的共享。在VC++环境下开发通用地图符号化组件和符号制作软件,通过实例符号的制作和应用,验证该地图符号表达机制的可行性和通用性,符号化效果理想。

A B-spline active contour model based on finite element method

A B-spline active contour model based on finite element method is presented, into which the advantages of a B-spline active contour attributing to its fewer parameters and its smoothness is built accompanied with reduced computational complexity and better numerical stability resulted from the finite element method. In this model, a cubic B-spline segment is taken as an element, and the finite element method is adopted to solve the energy minimization problem of the B-spline active contour, thus to implement image segmentation. Experiment results verify that this method is efficient for B-spline active contour, which attains stable, accurate and faster convergence.

Study on visualization simulation of temperature distributions in surrounding rock of tunnels in a deep mine

Based on the mathematical model for rock temperature distribution in a geo-thermal field,the properties of rock temperature distribution in geothermal field for fourkinds of surrounding rock cross-sections of tunnels in a deep mine were simulated by us-ing finite element method.It is shown that the relationship for rock temperature distributionvaried with the geothermal parameters,time and space.Namely, 2-dimensionaltime-dependent isograms clearly showed the process for rock temperature variation anddistribution in a geothermal field which has been redisplayed with visualization numericalsimulation.

Edge detection method for remote sensing image based on morphological variable structuring element

There are problems such as incomplete edges and poor noise suppression when a single fixed morphological structuring element is used to detect the edges in remote sensing images. For this reason, a morphological edge detection method for remote sensing image based on variable structuring element is proposed. Firstly, the structuring elements with different scales and multiple directions are constructed according to the diversity of remote sensing imagery targets. In order to suppress the noise of the target background and highlight the edge of the image target in the remote sensing image by adaptive Top hat and Bottom hat transform, the corresponding adaptive morphological operations are constructed based on variable structuring elements; Secondly, adaptive morphological edge detection is used to obtain multiple images with different scales and directional edge features; Finally, the image edges are obtained by weighted summation of each direction edge, and then the least square is used to fit the edges for accurate location of the edge contour of the target. The experimental results show that the proposed method not only can detect the complete edge of remote sensing image, but also has high edge detection accuracy and superior anti-noise performance. Compared with classical edge detection and the morphological edge detection with a fixed single structuring element, the proposed method performs better in edge detection effect, and the accuracy of detection can reach 95 %

Using Graphics Processing Units to Parallelize the FDK Algorithm for Tomographic Image Reconstruction

The paper presents the implementation of a parallel version of FDK （Felkamp, David e Kress） algorithm using graphics processing units. Discussion was briefly some elements the computed tomographic scan and FDK algorithm; and some ideas about GPUs （Graphics Processing Units） and its use in general purpose computing were presented. The paper shows a computational implementation of FDK algorithm and the process of parallelization of this implementation. Compare the parallel version of the algorithm with the sequential version, used speedup as a performance metric. To evaluate the performance of parallel version, two GPUs, GeForce 9400GT （16 cores） a low capacity GPU and Quadro 2000 （192 cores） a medium capacity GPU was reached speedup of 3.37.

Prediction of Fluid Velocity Distribution near a Rising Bubble

Flow and concentration fields of liquid phase in a gas-liquid contacting system are simulated to showthe Rayleigh convection by utilizing the finite-element method. The Schlieren images in CO2-ethanol system provided direct visual verification of the present simulation, and the simulated results were well consistent with theexperimental observation. The influence of the Rayleigh convection on mass transfer is analyzed qualitatively andquantitatively based on the simulated and the experimental results.

Stress based forming limit diagram for formability characterization of 6061 aluminum

Two numerical criteria of forming limit diagram（FLD） criterion and ductile fracture criterion（DFC） are presented for FLD prediction of 6061 aluminum. The numerical results are compared with the experimental FLD and also punch＇s load-displacement curve of experimental samples. Experimental FLD of this study is calculated using hemispherical punch test of Hecker. Experimental FLD is converted to FLSD and imported to the Abaqus software to predict necking of samples. Numerical results for FLSD prediction were compared with experimental FLSD. Results show that ductile fracture criterion has higher accuracy for FLD and FLSD prediction of 6061 aluminum. Comparison of numerical and experimental results for force-displacement curve of punch shows that numerical results have a good agreement with experiment.

Determination of pile failure mechanism under pullout test in loose sand

Estimating the deformation of soil around the pile contributes to reliable design of structures under pullout force. This work presents the results of a series of small-scale physical modelling tests designed to investigate the uplift resistance of piles with diameter of 5 cm and slenderness ratios of 1, 2, 3 and 4 in loose sand. Close photogrammetric technique and particle image velocimetry(PIV) were employed to observe the failure patterns due to uplift force on piles. The results show that the shear zones curve slightly outward near the ground surface. After peak resistance, the shear strain concentrates into a pair of narrow shear bands,then a flow around mechanism is formed accompanied by a reduction in the uplift resistance. The results from the laboratory tests were verified by analytical method proposed by Chattopadhyay and PLAXIS 2D and 3D finite element method software. It is found that the depth and width of the failure surface increase with the increment of the slenderness ratio. A good agreement is observed among the measured bearing capacity and obtained failure surface of the models and the results of numerical modelling. Finally, the maximum deformation of loose and dense sand respectively with densities of 25% and 75% were compared in the stage of fully removing pile. The results shows that the deformation of the soil is related to its density, therefore it depends on its dilatancy.

AN EXPANSION AND CORRECTION ALGORITHM FOR PHOTOELECTRIC IMAGE WITH GEOMETRIC DISTORTION^1

A creepy photoelectric endoscopy system with good performance is studied, and anexpansion and correction algorithm for a compressed photoelectric image with serious geometricdistortion is presented. The algorithm can not only correct the geometric distortion, but alsorestore the gray-level distribution by means of ternary convolution algorithm. The details andthe outline in the image are very clear. It is proved to be of high performance in practice.

Thermal-hydraulic modeling and analysis of hydraulic system by pseudo-bond graph

To increase the efficiency and reliability of the thermodynamics analysis of the hydraulic system, the method based on pseudo-bond graph is introduced. According to the working mechanism of hydraulic components, they can be separated into two categories: capacitive components and resistive components. Then, the thermal-hydraulic pseudo-bond graphs of capacitive C element and resistance R element were developed, based on the conservation of mass and energy. Subsequently, the connection rule for the pseudo-bond graph elements and the method to construct the complete thermal-hydraulic system model were proposed. On the basis of heat transfer analysis of a typical hydraulic circuit containing a piston pump, the lumped parameter mathematical model of the system was given. The good agreement between the simulation results and experimental data demonstrates the validity of the modeling method.

A hyperspectral image endmember extraction algorithm based on generalized morphology

Generalized morphological operator can generate less statistical bias in the output than classical morphological operator. Comprehensive utilization of spectral and spatial information of pixels, an endmember extraction algorithm based on generalized morphology is proposed. For the limitations of morphological operator in the pixel arrangement rule and replacement criteria, the reference pixel is introduced. In order to avoid the cross substitution phenomenon at the boundary of different object categories in the image, an endmember is extracted by calculating the generalized opening-closing(GOC) operator which uses the modified energy function as a distance measure. The algorithm is verified by using simulated data and real data. Experimental results show that the proposed algorithm can extract endmember automatically without prior knowledge and achieve relatively high extraction accuracy.

Constraints on the Distortion of Area Objects in the Process of Map Objects Displacement

The displacement operator is an important and still a hot topic in map generalization. In the generalization product, symbols must be unambiguous and easily perceived and readily understood, which makes space competition among features an important obstacle in the process of map objects displacement. Space conflict between objects, through propagation process, may be spread and more objects may drift into it. In order to maintain symbols equilibrium and spatial relationship between objects, some unimportant symbols or parts of symbols should be distorted under constraints according to visual graphic resolution thresholds to figure out space competition among map features. Three constraints including position, legibility and characteristics are important for the maintenance of symbols equilibrium and spatial relationship, which are discussed in this paper. The skeleton is introduced to represent area objects figure characteristic, in which an area object can be separated to parts hierarchically according to their importance in the construction. Then, the finite element method is applied to the map objects’ displacement and distortion, in which a strategy for the parameters of finite element method is discussed.