变形文档图像的矫正方法研究

针对文档表面易发生弯曲变形从而影响文档图像识别率这一问题,通过建模恢复文档表面形状,并运用参数化插值的方法实现了变形文档图像的矫正。本文讨论了基本理论及方法,并对算法的设计及实验中开发的平台进行了介绍,实验数据表明本方法可以有效的实现文档图像的矫正。     

C^2参数曲线近似弧长参数化算法

本文讨论参数曲线的近似弧长参数化插值方法。基于保单调插值方法,用分段五次(或五次以上)Bernstein多项式构造了弧长函数的反函数局部逼近解t=T(s),且T(s)是C~2连续的。将t=T(s)代入原参数曲线,得到C~2连续的近似弧长参数化曲线。这种近似弧长参数化曲线不但插值原参数曲线上的一组点,且在这组点有着精确的弧长参数化。进一步研究表明近似弧长参数化曲线可由原参数曲线经参数变换得到,所以它们有着完全相同的几何形状。最后,导出了近似弧长参数化曲线切失模长与1有二阶误差。     

基于智能的工业锅炉CAD的开发

将智能化CAD技术引入工业锅炉设计和优化的全过程,具体探讨了工业锅炉CAD系统(IBCS)的开发思想、逻辑模型和总体框架,以面向方案的智能化技术为核心,给出了一套完整的工业锅炉CAD的开发与实现模式,实现了数据库、工程分析与计算以及绘图的一体化,达到了较高的自动化和智能化水平。     

Bézier样条曲线改进的近似弧长参数化方法

提出了Bézier样条曲线利用分割技术近似弧长参数化的一种方法，并给出了相应的算法。通过求出曲线上所谓的‘最坏点’并在相应点处进行分割。可得到两条Bézier样条曲线。让这两条Bézier样条曲线具有与它们的近似弧长成比例的权，并对所得到的新的Bézier样条曲线进行同样的工作最终可得到一条由多条Bézier样条曲线所构成的新曲线。将这多条Bézier样条曲线合并成为一条Bézier样条曲线并通过节点插入技术将所得Bézier样条曲线转化为B一样条曲线的形式可得到全局参数域，其中各条Bézier曲线在全局参数域中所占子区间的长度与它们的权成比例，这样使得到了一条近似弧长参数化曲线。     

ADAPTIVE CONTROL DESIGN FOR NONLINEARLY PARAMETERIZED SYSTEMS WITH A TRIANGULAR STRUCTURE

A novel adaptive backstepping design for a class of nonlinearly parameterized systems with a triangular structure is proposed. Under the Lipschitz condition with respect to unknown parameters of the system, an effective adaptive controller is designed without the requirement on the compactness of the unknown parametric set. Especially, the proposed adaptive control enables the advantage of “tuning function concept”, which results in only one estimation law for the unknown parameters. Our simulation with induction motor model particularly shows the viability of the obtained results.     

虚拟环境下参数化建模和运动仿真的研究与实现

在VC编程环境下,运用OpenGL实现机械齿轮的三维参数化建模,并运用有向包围盒技术实现其运动仿真.分别采用显示列表技术和双缓存技术克服了传统动态模拟显示中仿真速度慢和闪动现象,所实现的零件三维模型逼真,仿真显示速度快,为进一步设计齿轮减速器和其他多子体连接系统的三维动态仿真提供参考和借鉴.     

Four‐Dimensional Geometry Lens: A Novel Volumetric Magnification Approach

We present a novel methodology that utilizes four‐dimensional (4D) space deformation to simulate a magnification lens on versatile volume datasets and textured solid models. Compared with other magnification methods (e.g. geometric optics, mesh editing), 4D differential geometry theory and its practices are much more flexible and powerful for preserving shape features (i.e. minimizing angle distortion), and easier to adapt to versatile solid models. The primary advantage of 4D space lies at the following fact: we can now easily magnify the volume of regions of interest (ROIs) from the additional dimension, while keeping the rest region unchanged. To achieve this primary goal, we first embed a 3D volumetric input into 4D space and magnify ROIs in the fourth dimension. Then we flatten the 4D shape back into 3D space to accommodate other typical applications in the real 3D world. In order to enforce distortion minimization, in both steps we devise the high‐dimensional geometry techniques based on rigorous 4D geometry theory for 3D/4D mapping back and forth to amend the distortion. Our system can preserve not only focus region, but also context region and global shape. We demonstrate the effectiveness, robustness and efficacy of our framework with a variety of models ranging from tetrahedral meshes to volume datasets.     

带不等式路径约束最优控制问题的惩罚函数法

控制变量参数化（Control variable parameterization,CVP）方法是目前求解流程工业中最优操作问题的主流数值方法,但如果问题中包含路径约束,特别是不等式路径约束时,CVP方法则需要考虑专门的处理手段.为了克服该缺点,本文提出一种基于L1精确惩罚函数的方法,能够有效处理关于控制变量、状态变量、甚至控制变量/状态变量复杂耦合形式下的不等式路径约束.此外,为了能使用基于梯度的成熟优化算法,本文还引进了最新出现的光滑化技巧对非光滑的惩罚项进行磨光.最终得到了能高效处理不等式路径约束的改进型CVP架构,并给出相应数值算法.经典的带不等式路径约束最优控制问题上的测试结果及与国外文献报道的比较研究表明:本文所提出的改进型CVP 架构及相应算法在精度和效率上兼有良好表现.     

Near-optimal parameterization of the intersection of quadrics: III. Parameterizing singular intersections

We conclude, in this third part, the presentation of an algorithm for computing an exact and proper parameterization of the intersection of two quadrics. The coordinate functions of the parameterizations in projective space are polynomial, whenever it is possible. They are also near-optimal in the sense that the number of distinct square roots appearing in the coefficients of these functions is minimal except in a small number of cases (characterized by the real type of the intersection) where there may be an extra square root.     

等几何分析研究概述

提出等几何分析(Isogeometric analysis,IGA)是一种新的物理场数值求解方法,它可实现CAE数值分析与CAD建模工具的集成,给出一条使设计、分析和优化紧密结合的新途径。以等几何分析方法的计算框架为基础,详细介绍等几何分析方法中样条几何模型的描述方式和建模方法;并以NURBS为例,阐述了IGA中的分析模型的参数化表示以及网格模型的细化方法;结合现有的经典有限元的分析过程,简单介绍IGA的离散方法、边界条件和积分方法;系统总结等几何分析在热、流体、接触和优化方面的应用,并给出了一个简单的二维问题的IGA求解实例。