增强国际合作共创图学辉煌

结合在巴西萨尔瓦多（Salvador）召开的第12届几何与图学国际会议以及近年来参加国际交流与合作的体会,论述近年来国际上几何与图学的研究与进展,特别是在理论图学,应用图学和图学教育方面的动态和最新成就。介绍南美国家特别是巴西的研究成果,表明了他们在几何,造型,图形图像处理,计算机辅助设计和图学教育改革方面与我国相似的发展和状况。这种相似性说明在科学技术上的国际影响是何等高效地改变着世界的进程。     

第10届“几何与图学”国际会议介绍

乌克兰基辅几何与图学国际会议展现了近年国际几何与图学的研究与进展，特别是在理论图学，应用图学和图学教育方面的动态和最新成就。东欧国家有较多的代表和论文，显示了他们在几何，造型，图形图像处理，计算机辅助设计方面的较深的基础和众多的研究成果。并对国际几何与图学学会(ICGG)的设置与运作作了介绍。     

一种基于几何的形计算机制

提出一种几何问题几何化的形计算机制。它综合了几何、代数、画法几何及现代计算工具等理论、方法与技术,实现“三维思维,二维图解,一维计算”多维空间的融合。从更宏观的几何角度构筑算法框架,是对常规数计算的补充,可用于相当宽泛的一类几何计算。     

图与图学

图与文字、数字一样,在人类的社会进步、经济建设和科技发展过程中起着不可替代的作用。但图与图学的定义与地位从历史和当前角度来看,仍是一个没有深刻和系统阐明的问题。现在的工程图学、计算机图形学、计算机图像学等各有自己的学科定义、定位以及各自独立的发展道路,但由于没有与图和图学相关联,致使这些学科呈现出某种分散性和局限性。从形(几何)的角度揭示图的本质,给出了形与图的科学表述。提出"大图学"概念,整合分散在其他学科中的与图相关的科学与技术。重新认识与定位图学的地位和作用,给出它的定位与定义,构建了图学学科的整体框架和三级学科分类体系。认为文学、数学、图学三者构成了科学与工程发展的基础,昭示了图学的基础性和重要性。     

中国图学投影理论及其研究

图学论证了在二维平面上绘制三维空间几何形状的图形的方法,是研究投影法绘制工程图样和解决空间几何问题、理论及方法的技术基础学科.中国是一个具有丰富图学传统的国家.中国图学的投影理论及其研究在先秦之前已有见端倪,魏晋时期已提出焦点透视的图学理论,宋元之际,图样绘制之精,投影画法的创新,使图学理论大具.中国图学的投影理论不仅为中国古代科技的发展提供了信息支撑,也为近代中国图学迅速走向近现代奠定了理论基础.     

《图学学报》征稿与征订

正《图学学报》主要刊载我国图学领域的科研、教学和应用的高质量学术论文,要求反映我国图学学科的最新研究成果、最新发展水平和发展方向。主要内容:图形学与可视化、几何设计与计算、数字化设计、工业设计、视觉与图像、交互技术与虚拟现实、医学图像与设备、BIM应用与研究、图学教育、应用与交流等。稿件篇幅5000~8000字(包括图、表、公式所占面积折合的字数)。     

《图学学报》征稿与征订

正《图学学报》主要刊载我国图学领域的科研、教学和应用的高质量学术论文,要求反映我国图学学科的最新研究成果、最新发展水平和发展方向。主要内容:图形学与可视化、几何设计与计算、数字化设计、工业设计、     

《图学学报》征稿与征订

正《图学学报》主要刊载我国图学领域的科研、教学和应用的高质量学术论文,要求反映我国图学学科的最新研究成果、最新发展水平和发展方向主要内容:图形学与可视化、几何设计与计算、数字化设计、工业设计、视觉与图像、交互技术与虚拟现实、医学图像与设备、BIM应用     

《图学学报》征稿与征订

正《图学学报》主要刊载我国图学领域的科研、教学和应用的高质量学术论文,要求反映我国图学学科的最新研究成果、最新发展水平和发展方向。主要内容:图形学与可视化、几何设计与计算、数字化设计、工业设计、视觉与图像、     

基于ARX实体驱动的方法及参数化变动设计的实现

AutoCAD系统为每个实体对象提供了唯一的标识符（ID）。笔者基于ARX技术对AutoCAD图形数据库的访问机理，通过实体标识符（ID）及实体对象的特征点、图元几何约束及图元间的约束联动，实现了图元实体驱动的参数化变动设计；通过尺寸实体对象标识符（ID）及尺寸与图元的约束关系，实现了尺寸驱动的参数化变动设计。此方法在水利工程流道CAD中加以了应用，其效果良好。     

基于“广义形体分析法”的高职图学课程改革探索与实现

"广义形体分析法"是"工程图学"课程改革的一种探索性创新思维方法,它将课程核心内容整体分解为几何元素、几何结构、功能组合、零件装配、知识与技能等5个块元。介绍了基于"广义形体分析法"的高职"工程图学"课程改革方案及其实现关键,进行了改革的初步探索和实践,取得了较好的成效。实践结果表明,该方法能有效提升图学基础与应用的教学效果,有助于职业快速适应、逻辑思维形成及创新能力提升。     

Derivation of geometrically nonlinear finite shell elements via tensor notation

To develop geometrically nonlinear, doubly curved finite shell elements the basic equations of nonlinear shell theories have to be transferred into the finite element model. As these equations in general are written in tensor notation, their implementation into the finite element matrix formulation requires considerable effort. The present paper will demonstrate how to derive the nonlinear element matrices directly from the incrementally formulated nonlinear shell equations using a tensor-oriented procedure. This enables the numerical realization of all structural responses, e.g. the calculation of pre- and post-buckling branches in snap-through analysis and especially in bifurcation analysis, including the detection of critical points and the consideration of geometric imperfections. To avoid loss of accuracy care is taken for a realistic computation of the geometric properties as well as of the external loads. Finally, the developed family of shell elements will be presented and its efficiency will be demonstrated by some applications to linear and geometrically nonlinear structural phenomena.     

一种新的非线性系统脊骨线提取方法

脊骨线对于非线性系统的判断、描述和参数识别,具有重要的意义;而现有的脊骨线提取方法大多理论上较为复杂,且有局部线性化误差较大、数据波动剧烈等问题,限制了工程应用。提出一种新的非线性系统脊骨线提取方法,该方法利用非线性系统自由振动响应的一次谐波分量,计算谐波信号峰值点的瞬时频率,可以方便地提取脊骨线;这种新的非线性系统脊骨线提取方法理论明确、简单,计算方便,易于工程应用。通过三个数值算例说明了该方法的有效性,同时将此方法应用于非线性描述,并综合讨论了非线性描述的几何方法;并基于此方法进行了非线性系统参数识别,取得了良好的效果。     

Multiquadric and its shape parameter—A numerical investigation of error estimate, condition number, and round-off error by arbitrary precision computation

Hardy’s multiquadric and its related interpolators have been found to be highly efficient for interpolating continuous, multivariate functions, as well as for the solution of partial differential equations. Particularly, the interpolation error can be dramatically reduced by varying the shape parameter to make the interpolator optimally flat. This improvement of accuracy is accomplished without reducing the fill distance of collocation points, that is, without the increase of computational cost. There exist a number of mathematical theories investigating the multiquadric family of radial basis functions. These theories are often not fully tested due to the computation difficulty associated with the ill-conditioning of the interpolation matrix. This paper overcomes this difficulty by utilizing arbitrary precision arithmetic in the computation. The issues investigated include conditional positive definiteness, error estimate, optimal shape parameter, traditional and effective condition numbers, round-off error, derivatives of interpolator, and the edge effect of interpolation.     

FSI modeling of the reefed stages and disreefing of the Orion spacecraft parachutes

Orion spacecraft main and drogue parachutes are used in multiple stages, starting with a “reefed” stage where a cable along the parachute skirt constrains the diameter to be less than the diameter in the subsequent stage. After a period of time during the descent, the cable is cut and the parachute “disreefs” (i.e. expands) to the next stage. Fluid–structure interaction (FSI) modeling of the reefed stages and disreefing involve computational challenges beyond those in FSI modeling of fully-open spacecraft parachutes. These additional challenges are created by the increased geometric complexities and by the rapid changes in the parachute geometry during disreefing. The computational challenges are further increased because of the added geometric porosity of the latest design of the Orion spacecraft main parachutes. The “windows” created by the removal of panels compound the geometric and flow complexity. That is because the Homogenized Modeling of Geometric Porosity, introduced to deal with the flow through the hundreds of gaps and slits involved in the construction of spacecraft parachutes, cannot accurately model the flow through the windows, which needs to be actually resolved during the FSI computation. In parachute FSI computations, the resolved geometric porosity is significantly more challenging than the modeled geometric porosity, especially in computing the reefed stages and disreefing. Orion spacecraft main and drogue parachutes will both have three stages, with computation of the Stage 1 shape and disreefing from Stage 1 to Stage 2 for the main parachute being the most challenging because of the lowest “reefing ratio” (the ratio of the reefed skirt diameter to the nominal diameter). We present the special modeling techniques and strategies we devised to address the computational challenges encountered in FSI modeling of the reefed stages and disreefing of the main and drogue parachutes. We report, for a single parachute, FSI computation of both reefed stages and both disreefing events for both the main and drogue parachutes. In the case of the main parachute, we also report, for a 2-parachute cluster, FSI computation of the disreefing from Stage 2 to Stage 3. With results from these computations, we demonstrate that we have to a great extent overcome one of the most formidable challenges in FSI modeling of spacecraft parachutes.     

After-Tax Equipment Replacement Analysis Using Discrete Transforms

Discrete transform theory has previously been shown to offer many operational advantages in the computation of the present worths of discrete cash-flow patterns. This paper extends its application to equipment replacement models. Terborgh's classical model is used as the basis. An after-tax analysis using the latest depreciation schedule based on the Economic Recovery Tax Act of 1982 is incorporated in the analysis. Included is an example on determining the optimal replacement life cycle.     

对工程图学学科和图学学科的若干认识

从＂形＂和＂图＂两方面对图形进行了深入的讨论。总结了＂形＂与＂图＂的三种类型,并由此指出了工程图学学科和图学学科在研究对象上的差别。在文献调查和分析的基础上,对两个学科的定义给出了新表述。探讨了学科体系的组成,给出了图学学科的7个分支及每个分支中的科目,也给出了工程图学学科的5个分支及每个分支中的科目。     

Parallel tsunami simulation and visualization on tiled display wall using OpenGL Shading Language

Tsunami simulation consists of fluid dynamics, numerical computations, and visualization techniques. Nonlinear shallow water equations are often used to model the tsunami propagation. Tsunami inundation is modeled by adding the friction slope to the conservation of momentum. The two-step second-order finite difference MacCormack numerical method can solve these equations. It is well suited for nonlinear equations and simpler for related application development. In addition, the finite difference method can be computed in parallel. The programmable graphics hardware allows general-purpose computing on graphics processing units (GPUs) to solve the MacCormack method in parallel to speed up the simulation. Tsunami simulation data can be loaded as textures data in graphics memory, the computation processes can be written as shader programs using OpenGL Shading Language so that the operations can be computed by graphics processors in parallel. We developed different versions of the tsunami simulation and visualization programs: (i) CPU-based, and (ii) CPU–GPU collaboration to implement the MacCormack numerical method. The performance results showed that graphics hardware accelerated simulation had a significant improvement in the execution time of each computation step. Real-time simulation and visualization are made possible by the programmable shaders. Furthermore, we achieved high-performance parallel visualization on a tiled display wall with a cluster of computers.     

图形开眼法在广告设计中的运用

以文学中的画龙点睛之笔为启示,分析了图形开眼方法及图形开眼原则,论述了在广告设计中如何从图形的影像、图形的叠加关系、图形的放置方式、图形的切割变化、图形的逻辑关系等方面进行变化,使图形成为整个广告设计的画龙点睛之笔。在此基础上,提出了应根据广告主题灵活运用图形开眼法来增加广告的趣味性与联想空间,为广告设计的图形处理方法提供参考和借鉴。     

对称与图形创意--基于图形组织结构的数学原理与应用

艺术家已经意识到"对称"在图形设计以及对形成有规律的从复的图形组织结构的辅助作用.所谓对称,是指设计中的部分内容(母题)在某种数学几何原理的驱动下,有规律地向整个二维平面伸展从而形成完整的设计.在二维平面,总共有四种几何变换(对称操作规程)方式,数学家称这种变换isometrics(来自希腊词isos=equal(同等)matron=measure(测度).分析从复对称的图形,研究如何遵循数学"法则"等活动,动机不在于数学本身.明显地,"对称"具有双重词义,艺术的与数学的含义是不可分离的.