声辐射问题的一种新的无限元方法

声波在无限大外域中的传播和衰减问题是研究声与结构相互作用的重要基础。该文提出了一种新的声无限单元耦合有限元方法于外域声辐射问题的计算。应用加权残值法推导了声无限单元的刚度矩阵和质量矩阵,选取的形函数及权函数充分考虑了外域声传播的基本特点及无穷远辐射边界条件。计算实例表明这种方法对于求解无界域声场问题是非常有效的。     

求解外域辐射和散射声场的分形有限元方法

应用二级分形有限元方法计算了外域声场.用一人工边界把外域声场分为两部分,人工边界以内使用常规有限元方法,人工边界以外的无限大区域使用分形有限元方法.使用分形有限元方法,一方面形成几何自相似网格使得相邻层之间的单元刚度矩阵和质量矩阵具有非常简单的关系,另一方面引用自动满足无限远辐射条件的全域插值函数把节点自由度变换为一组广义坐标,因而计算量可以大大减少.数值计算结果表明:该方法对于计算无限大外域声场是有效的.     

含裂纹梁自由振动分析

研究了含常开裂纹矩形截面梁的自由振动问题.通过一计及裂纹对梁局部柔度影响的无质量扭簧模拟裂纹所在截面,建立起与含裂纹梁等效的力学模型;基于完整梁自由振动方程的基本解,推导出含裂纹梁的传递矩阵;以简支梁和悬臂梁为例,结合具体的边界条件,导出它们相应的频率方程.基于泰勒展开,给出了求解该频率方程的一种迭代算法.该文的方法能够简便地计算含裂纹梁的固有频率.     

Deformable Registration of MR Brains with Best Features

Introduction Deformable registration is very important formedical image analysis and so far various methodshave been proposed in decades[1-4]. HAMMER reg-istration algorithm[5]defines an attribute vector in-cluding intensity, edge type, and geometric mo-ment invariants as a signature of each point, to re-duce ambiguity in correspondence matching duringthe image registration. Another characteristic ofHAMMER is the hierarchical matching mecha-nism, which helps avoid the warping being trapped…     

应用微分求积法的旋转变截面梁振动分析

研究了截面高度沿纵向线性变化的旋转梁的振动特性。基于Hamilton原理导出了控制方程,该控制方程计及了向心力刚化效应,利用微分求积法将其谐和振动方程转化为代数方程。计算了前三阶固有频率并进行了对比,结果表明了该方法的精度和有效性。     

A Novel Method for Character Segmentation in Natural Scenes

Introduction Nowadays the applications of scene text recog-nition are rapidly expanding with the developmentof portable digital imaging devices[1]. However,character extraction from scene images has alwaysbeen a challenging problem due to complex back-ground, uneven illumination, shadows and noise ofimages[2]. Besides, languages also impose anotherlevel of variation in text. Characters in such lan-guages as Chinese, Japanese and Korean are usual-ly composed of several strokes, which do not n…     

立交匝道线形机动设计法

本文以直线、圆曲线、缓和曲线为基本线形元自由组合，构成适用于任何复杂的立交匝道平面线形布线基本图形。通过对整条匝道及两端控制线形元，进行设计参数自由度综合机动分析，建立了边界几何约束条件数学模型，提出了机动灵活的线形调整及边界几何闭合方法，扩大了设计适用范围，有利物线形优化设计。     

Nonlinear Dynamic Analysis of Three Dimensional Flexible Multibody Systems

The nonlinear dynamic problems of three dimensional flexible multibody systems are investigated. The elastic deformation fields of flexible space beams are decomposed into axial deformation and bending deformation, and described by each exact vibration modes in the body coordinate systems. The constrainted nonlinear dynamic equations are derived by using Lagrange multiplier method. A numerical procedure for solving the resulting differential algebraic equations is presented based on Newmark direct integration method combined with the modified Newton-Raphson iterative method. Numerical results verify the effectiveness of the proposed method.