零件图新画法探讨

介绍将模型空间中的立体图通过建立分块视图,设定投影视图,然后在图纸空间编辑视图区,从而快速生成零件各视图的方法,此法一致传统绘图习惯,可大大提高工作效率。     

AutoCAD中三维立体图的尺寸标注

通过一个典型立体图的尺寸标注叙述了三维立体图的尺寸标注方法与注意点,并介绍了用户坐标系的创建及用户坐标在标注尺寸时的应用。用例图说明了轴测图标尺寸的方法与技巧,从而使用户掌握立体图的尺寸标注方法。     

刀具标准件参数绘图技术

介绍了刀具标准件库的结构及管理方法,以可转位刀片为例,讨论了刀具标准件管理系统实现绘图程序设计时的数据传输技术,叙述了刀具标准件参数化绘图程序设计技术,阐述了ＡｕｔｏＬＩＳＰ 在刀具立体图设计中的应用,说明了三维图形与二维图形之间的变换技术和多视图的显示与输出技术。     

刀具标准件参数绘图技术

介绍了刀具标准件库的结构及管理方法,以可转位刀片为例,讨论了刀具标准件管理系统实现绘图程序设计时的数据传输技术,叙述了刀具标准件参数化绘图程序设计技术,阐述了ＡｕｔｏＬＩＳＰ在刀具立体图设计中的应用,说明了三维图形与二维图形之间的变换技术和多视图的显示与输出技术。     

基才CAD的三维实体造型方法探讨

介绍了设置图层、视口及调出工具栏等创建三维实体造型环境的方法。通过创建一个较负杂的三维实体造型的典型实例,介绍了基于CAD三维实体造型的方法与技巧,包括对象捕捉等精确绘图方法,从平面二维作图状态切换到三维视图的方法,从平面图形生成面域的方法,通过拉伸平面图形生成三维实体的方法,以及布尔运算的差、并、交集运算。介绍了用户坐标系的建立方法及用户坐标系在创建三维实体造型中的应用。     

基于CAD的三维实体造型方法探讨

介绍了设置图层、视口及调出工具栏等创建三维实体造型环境的方法。通过创建一个较复杂的三维实体造型的典型实例,介绍了基于CAD三维实体造型的方法与技巧,包括对象捕捉等精确绘图方法,从平面二维作图状态切换到三维视图的方法,从平面图形生成面域的方法,通过拉伸平面图形生成三维实体的方法,以及布尔运算的差、并、交集运算。介绍了用户坐标系的建立方法及用户坐标系在创建三维实体造型中的应用。     

二维零件图与三维实体图互生成方法探讨

探讨了在AutoCAD 2008绘图环境中,由二维组合视图生成三维实体图的一些技巧和方法,以及三维实体图重新快速生成标准二维视图的具体操作步骤。可有效提高机械制图效率和设计能力,具有一定工程实用价值。     

一种关于AutoCAD软件快速绘制三视图的作图方法

在绘制形体的三视图时,如果已知两个视图,要绘制的第三视图是左视图或者是俯视图,常用的作图方法是使用一条45°辅助线。这种作图法被习惯性地应用到Auto CAD软件绘图教学中。在Auto CAD软件绘图环境中这种传统的方法绘图效率低。文中通过实例提出一种应用于Auto CAD绘图环境下绘制三视图的作图方法,这种新的作图方法的原理是基于将传统45°辅助线作图法中俯视图、左视图相应尺寸的"宽相等",转化为相应尺寸的"长对正"或"高平齐"的过程。新方法比传统45°辅助线作图法更加简单、直接,且效率高。     

形体分析法在组合体视图中的应用研究

组合体是工程制图中具有特殊性和重要地位的立体。形体分析法在组合体视图中发挥了重要作用，应用此方法可将复杂的立体分解成基本几何体和简单体，使工程立体化繁为简、化难为易。笔者研究了组合体的概念、投影规律、形体分析法及其在组合体绘图、尺寸标注、读图中的应用。     

AutoCAD环境下基于零件图的三维造型方法

对AutoCAD环境下根据零件图进行三维造型的方法进行了分析探讨。运用形体分析法将零件形体分解成可便捷地利用AutoCAD三维功能造型的体素。某一体素在视图上的投影往往即是其特征截面。将反映该特征截面的轮廓线经复制、编辑、生成面域等操作,再利用拉伸、旋转、放样等操作即可完成体素的三维造型。将各体素的三维模型经布尔运算进行组合,即可完成零件的造型。     

Three-dimensional reconstruction of a periodic specimen from a single view of an oblique section

Methods are described for producing a three-dimensional reconstruction from a single view of an oblique section through a two- or three-dimensional crystal. The image produced by the electron microscope corresponds to a projection through the thickness of the section, which smears out the details of the structure. This projection operation can be described mathematically by sets of linear projection equations or equivalently by convolution of the density in the unit cell with the section thickness. Solution of the projection equations or other methods of deconvolution reduces the smearing and gives a three-dimensional map of the density within the crystal superior to that obtained by direct inspection of the image. The degree of improvement attainable depends on the noise level in the image but computational experiments indicate that a factor of at least four should be achievable. The method, which is most powerful when the section thickness is small, has the advantage over conventional methods involving tilted that it is not affected by changes in section thickness on electron irradiation.     

CAD在齿轮三维造型中的应用

文章对直齿圆柱齿轮的视图及空间结构进行了分析,针对齿轮的二维视图进行了三维造型,描述了CAD创建齿轮模型的思路与技巧,即将齿轮结构分解为三部分,使其作图简单直观,最后将其组合,实现了完整齿轮的外形设计。     

基于UG的水轮机叶片的逆向反求

借助三坐标测量机测量叶片原始点数据并在三维CAD软件UGS NX中用进行三维造型的逆向反求工程方法.叶片建模的点数据来自实物叶片的测量资料,包括样板曲线和叶片表面上不规则的测量点云.逆向反求过程为数据采集、数据处理转换、数据导入、创建叶片轮廓曲线、用三维数据创建叶片轴面型线、创建叶片网格曲线、创建叶片外表面曲面、创建叶...     

基于Autodesk Inventor的工程剖视图的实现方法研究

为了清晰地表达零件的内外结构形状,需绘制多种工程剖视图。使用Inventor软件创建零件模型后,再利用其三维与二维的联动功能绘制工程剖视图。探讨了常用工程剖视图的创建方法和关键技术,可充分利用该软件的剖视图工具菜单,方便、快速地创建出符合国标要求的常用工程剖视图。对系列化零件的设计表达、创新设计等具有借鉴意义。     

Computer image processing of electron micrographs of biological structures with helical symmetry

Methods are described for the analysis of electron micrographs of biological objects with helical symmetry and for the production of three-dimensional models of these structures using computer image reconstruction methods. Fourier-based processing of one- and two-dimensionally ordered planar arrays is described by way of introduction, before analysing the special properties of helices and their transforms. Conceiving helical objects as a sum of helical waves (analogous to the sum of planar waves used to describe a planar crystal) is shown to facilitate analysis and enable three-dimensional models to be produced, often from a single view of the object. The corresponding Fourier transform of such a sum of helical waves consists of a sum of Bessel function terms along layer lines. Special problems deriving from the overlapping along layer lines of terms of different Bessel order are discussed, and methods to separate these terms, based on analysing a number of different azimuthal views of the object by least squares, are described. Corrections to alleviate many technical and specimen-related problems are discussed in conjunction with a consideration of the computer methods used to actually process an image. A range of examples of helical objects, including viruses, microtubules, flagella, actin, and myosin filaments, are discussed to illustrate the range of problems that can be addressed by computer reconstruction methods.     

一种双目立体视觉技术中三维坐标点的改进求取算法

在双目立体视觉技术中,经过特征提取和立体匹配得到两两对应的像素点对,根据摄像机标定建立的物体空间坐标到像平面坐标对应的矩阵,利用最小二乘法求取物体三维空间点的坐标。但是,由于最小二乘法没有考虑所建立的超限定方程组所代表的几何意义,计算出的点坐标精度不高。本文提出一种考虑方程组所代表几何意义的方法,利用异面直线公垂线中点去逼近物体空间点。     

Contrast enhancement and depth perception in three-dimensional representations of differential interference contrast and confocal scanning laser microscope images

A commonly used three-dimensional reconstruction method in confocal scanning laser microscopy (CSLM) involves the generation of stereo views by stacking optical sections. Under certain conditions the resulting stereo pairs exhibit inferior quality with respect to contrast and depth perception. A method based on digital image processing is described in which the individual images are enhanced prior to reconstruction, thereby increasing the number of usable optical sections by a factor of up to five. Furthermore, we introduce a new contrast enhancement transformation based upon local statistics and a grey-level probability density function that provides improved depth perception. Digital image processing methods map a discrete grey scale onto a continuous, unbounded interval. Inasmuch as a closed, discrete grey scale is required for computer display purposes, we present an appropriate mapping function derived from an entropy criterion.     

Three-dimensional reconstructions from incomplete data: interpretability of density maps at "atomic" resolution

Three dimensional data collection in electron microscopy is normally limited to a range of tilt angles that is less than +/- 90 degrees. Thus, even under the best conditions, experimental values of the structure factors will be missing within a solid cone in reciprocal space. Previous work has already shown that the missing cone of data can produce serious artifacts in three-dimensional density maps at modest resolution, for example approximately 15A. We now report, however, that a missing cone as large as +/- 30 degrees appears to have no serious effect on the three-dimensional density map of a protein at 3.6 A resolution, and we attribute this result to the fact that the electron density features are quite well separated from one another at that resolution. The map calculated with a +/- 30 degree missing cone is, furthermore, no more sensitive to noise (error) than is the full (isotropic) Fourier map. This result does not seem to be unreasonable in view of the fact that less than 14% of the data (i.e., signal) is lost due to the missing cone. Our numerical simulations therefore indicate that there should be no difficulty in interpreting high-resolution Fourier maps that can be produced with data that fall within realistic estimates of achievable resolution, tilt angles, and experimental error.     

Review: Correlative microscopy of Purkinje cells

The Purkinje cell and their synaptic contacts have been described using (1) light microsocopy, (2) transmission and scanning electron microscopy, and freeze etching technique, (3) conventional and field emission scanning electron microscopy and cryofracture methods, (4) confocal laser scanning microscopy using intravital stain FM64, and (5) immunocytochemical techniques for Synapsin-I, PSD9-5, GluR1 subunit of AMPA receptors, N-cadherin, and CamKII alpha. The outer surface and inner content of plasma membrane, cell organelles, cytoskeleton, nucleus, dendritic and axonal processes have been exposed and analyzed in a three-dimensional view. The intramembrane morphology, in bi- and three-dimensional views, and immunocytochemical labeling of synaptic contacts with parallel and climbing fibers, basket and stellate cell axons have been characterized. Freeze etching technique, field emission scanning microscopy and cryofracture methods, and GluR1 immunohistochemistry showed the morphology and localization of postsynaptic receptors. Purkinje cell shows N-cadherin and CamKII alpha immunoreactivity. The correlative microscopy approach provides a deeper understanding of structure and function of the Purkinje cell, a new three-dimensional outer and inner vision, a more detailed study of afferent and intrinsic synaptic junctions, and of intracortical circuits.