共查询到19条相似文献,搜索用时 484 毫秒
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画法几何综合问题是教学的难点,要求学生具有较强的空间想象能力和空间逻辑思维能力。借助AutoCAD的三维图形功能,可将平面正投影图转化为空间三维图形,在三维空间进行分析、推理和求解,然后再返回二维作图,使解题过程概念清晰,可视性强。给出两个实例说明了这种解题方法的作图步骤和作图要点,可极大地帮助学生提高空间想象能力和空间逻辑思维能力。 相似文献
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基于CAD-3D技术的画法几何图解法研究 总被引:1,自引:2,他引:1
提出了基于CAD-3D技术的计算机辅助图解画法几何问题,是在传统画法几何提供的空间分析思维方式的基础上,利用CAD-3D计算机技术,将传统画法几何的图示图解方法从二维环境转换到三维实体上进行直接求解,以弥补二维图解法作图过程繁琐、作图速度缓慢、求解精度低等缺陷。希望能为建立一个适用于现代化设计、表达及制造一体化生产方式的现代画法几何基础理论体系提供有力的理论依据。 相似文献
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在中心投影,平行投影作图理论研究的基础上,对三维笛沙格图作了进一步分析,研究,得出空间笛沙格图的一般情况,特殊情况与中心投影,平行投影二求三问题的联系,并涉及三维空间的计算问题。 相似文献
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投影制图中的逆射与相交 总被引:1,自引:0,他引:1
为了更有效地训练和提高学生的空间思维能力和三维构形能力,在画法几何与投影制图的教学过程中,有必要增加一个从二维向三维转换的教学环节,即从几何元素的二维投影表达出发,实现三维形体的重建和三维环境下的定位、测量。在画法几何与投影制图的教学过程中,应用作者开发的图形教学软件Projector,操作者可以方便地从空间点、线、面、体,得到平面投影,也可以从已知平面投影出发,求解空间几何问题。 相似文献
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用CSG树体素构造法进行三维实体造型时,对形体分析的方法与传统制图教学不同,在三维实体造型的教学中,要重点培养学生正确的空间概念,训练学生在三维空间正确分析形体、构造形体的能力。 相似文献
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《Engineering Analysis with Boundary Elements》2007,31(6):528-538
An efficient 3D multidomain boundary element method (BEM) for solving problems governed by the Laplace equation is presented. Integral boundary equations are discretized using mixed boundary elements. The field function is interpolated using a continuous linear function while its derivative in a normal direction is interpolated using a discontinuous constant function over surface boundary elements. Using a multidomain approach, also known as the subdomain technique, sparse system matrices similar to the finite element method (FEM) are obtained. Interface boundary conditions between subdomains leads to an over-determined system matrix, which is solved using a fast iterative linear least square solver. The accuracy and robustness of the developed numerical algorithm is presented on a scalar diffusion problem using simple cube geometry and various types of meshes. Efficiency is demonstrated with potential flow around the complex geometry of a fighter airplane using tetrahedral mesh with over 100,000 subdomains on a personal computer. 相似文献
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AutoCAD环境下画法几何图解与三维绘图新方法的研讨 总被引:4,自引:0,他引:4
应用AutoCAD R14计算机绘图软件进行画法几何与工程制图图形的绘制与图解。如采用传统的画法几何的一些图解方法,则不便于在计算机显示屏幕上实现其图解步骤,并且存在投影民三维立体图不能同步绘制和显示的问题,以不能清楚显示空间几何元素的空间形状及其与三投影面投影关系的问题。为此,研究开发了一种新方法,它可以在读取已知二投影图(或视图)的同时补画出第三投影图(或视图),并同步绘制出轴测图,且可以解决工程图解的一系列画法图解的问题。 相似文献
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画法几何网络答疑系统的开发与研究 总被引:2,自引:1,他引:1
针对画法几何传统教学中的答疑问题,提出了一个基于网络的解决方案。系统地分析了学生和教师在相互交流时的功能需求,为学生提高学习效率和教师进行教学研究提供了一个网络交互信息平台,并从技术和内容上进行扩展,适用于远程教育和其他课程的教学需求。 相似文献
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Alejandro R. Díaz 《International journal for numerical methods in engineering》1999,44(11):1599-1616
A wavelet–Galerkin scheme tailored to address the numerical solution of large‐scale boundary value problems defined on domains of simple geometry is presented. The variation of parameters, e.g. material properties, within the domain is arbitrary but the method is specifically designed to solve problems where parameters vary in raster‐like fashion. Boundary conditions are imposed via Lagrange multipliers using a fictitious domain approach. A preconditioner specially designed for this problem is developed to guarantee that convergence of conjugate gradient algorithms is quick and insensitive to problem size. The strategy is applied to the solution of steady state, heat conduction problems in 2‐D, but it can be generalized without conceptual changes to 3‐D problems and to problems in linear elasticity. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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画法几何3D解题方法的研究 总被引:4,自引:3,他引:4
随着计算机图形技术在工程与教学中的推广应用,在教学实践中,如何处理画法几何部分的讲授,目前出现了两种不同意见。一种意见认为,应该继承画法几何的合理内核,以适应制造业中二、三维图形表达将长期并存的现实要求;另一种意见认为,在工程制图教学的第一时间,就应该运用计算机表达和建模方法,以增强直观性,提高精度和效率,便于同后续课程衔接。基于计算机图形学构建的画法几何3D求解系统,可以综合以上两种方法的优势。为画法几何与工程制图教学提供新的技术手段。 相似文献
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立体视觉图像校正是加速立体匹配简单而常用的技术之一。采用几何法对使用棱镜的单镜头立体视觉系统图像进行校正,根据成像原理,从图像平面像素点反推到三维实体点的分析运算,利用成像光线几何关系求解虚拟相机外部参数,实现极线的校正,避免了复杂相机标定过程。同时,该算法可以从双棱镜应用推广到多面棱镜的单棱镜立体视觉系统图像校正。实验结果表明,基于几何法对使用棱镜的单镜头立体视觉系统图像校正是有效的。 相似文献
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Ashok V. Kumar Premdheepak S. Periyasamy 《International journal for numerical methods in engineering》2012,91(5):472-490
Mesh independent analysis is motivated by the desire to use accurate geometric models represented as equations rather than approximated by a mesh. The trial and test functions are approximated or interpolated on a background mesh that is independent of the geometry. This background mesh is easy to generate because it does not have to conform to the geometry. Essential boundary conditions can be applied using the implicit boundary method where the trial and test functions are constructed utilizing approximate step functions such that the boundary conditions are guaranteed to be satisfied. This approach has been demonstrated for two‐dimensional (2D) and three‐dimensional (3D) structural analysis and is extended in this paper to model shell‐like structures. The background mesh consists of 3D elements that use uniform B‐spline approximations, and the shell geometry is assumed to be defined as parametric surfaces to allow arbitrarily complex shell‐like structures to be modeled. Several benchmark problems are used to study the validity of these 3D B‐spline shell elements. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Jie Gao Liang Gao Zhen Luo Peigen Li 《International journal for numerical methods in engineering》2019,119(10):991-1017
This paper will propose a more effective and efficient topology optimization method based on isogeometric analysis, termed as isogeometric topology optimization (ITO), for continuum structures using an enhanced density distribution function (DDF). The construction of the DDF involves two steps. (1) Smoothness: the Shepard function is firstly utilized to improve the overall smoothness of nodal densities. Each nodal density is assigned to a control point of the geometry. (2) Continuity: the high-order NURBS basis functions are linearly combined with the smoothed nodal densities to construct the DDF for the design domain. The nonnegativity, partition of unity, and restricted bounds [0, 1] of both the Shepard function and NURBS basis functions can guarantee the physical meaning of material densities in the design. A topology optimization formulation to minimize the structural mean compliance is developed based on the DDF and isogeometric analysis to solve structural responses. An integration of the geometry parameterization and numerical analysis can offer the unique benefits for the optimization. Several 2D and 3D numerical examples are performed to demonstrate the effectiveness and efficiency of the proposed ITO method, and the optimized 3D designs are prototyped using the Selective Laser Sintering technique. 相似文献