Discrete quadratic curvature energies

We present a family of discrete isometric bending models (IBMs) for triangulated surfaces in 3-space. These models are derived from an axiomatic treatment of discrete Laplace operators, using these operators to obtain linear models for discrete mean curvature from which bending energies are assembled. Under the assumption of isometric surface deformations we show that these energies are quadratic in surface positions. The corresponding linear energy gradients and constant energy Hessians constitute an efficient model for computing bending forces and their derivatives, enabling fast time-integration of cloth dynamics with a two- to three-fold net speedup over existing nonlinear methods, and near-interactive rates for Willmore smoothing of large meshes.     

离散信号和图象的实数形式Gabor变换

定义了用于有限序列和图象表示的实数形式离散Ｇａｂｏｒ变换（ＲＤＧＴ）这种通过将复数形式离散Ｇａｂｏｒ变换（ＣＤＧＴ）的复数Ｇａｂｏｒ基本函数替换成实数Ｇａｂｏｒ基本函数而进行的实数变换,在算法复杂性上与ＣＤＧＴ相比,明显降低,并且由于ＲＤＧＴ与离散Ｈａｒｔｌｅｙ变换（ＤＨＴ）有着相似的形式,从而使得ＲＤＧＴ能够利用快速的ＤＨＴ加速变换,另外,ＲＤＧＴ系数与ＣＤＧＴ系数的实部和虚部之间有着非常简单的     

基于离散元法与正交试验的齿板破碎力研究

研究颚式破碎机齿板齿形对破碎力的影响与齿形参数择优问题.破碎力直接影响破碎机的碎矿功率与企业的经济效益,获得齿形对破碎力的影响规律进而得到最优齿形成为重要课题,以往的研究未将齿形参数多因素协同考虑.为解决上述问题,提出离散元法,采用Hertz-Mindlin黏结接触模型,结合正交试验设计进行数值仿真,获得齿形参数多因素对破碎力的综合影响规律,对仿真结果进行直观分析和方差分析,获得最优齿形参数组合.仿真结果表明,齿底宽是影响破碎力的主要因素,其次是齿距与齿形角,以优化的齿形齿板进行仿真,其破碎力低于正交试验的最小破碎力,为颚式破碎机的设计、改造提供了方法借鉴和数据参考.     

Discrete observability and dirichlet series

The problem of recovering the initial data of the heat equation when the output is measured at points discrete in time and space is considered. It is shown that the solution of this problem is linked to the theory of Dirichlet series and a solution is found in the case of the one dimensional problem.     

Computing upper and lower bounds of rotation angles from digital images

Rotations in the discrete plane are important for many applications such as image matching or construction of mosaic images. We suppose that a digital image A is transformed to another digital image B by a rotation. In the discrete plane, there are many angles giving the rotation from A to B, which we call admissible rotation angles from A to B. For such a set of admissible rotation angles, there exist two angles that achieve the lower and the upper bounds. To find those lower and upper bounds, we use hinge angles as used in Nouvel and Rémila [Incremental and transitive discrete rotations, in: R. Reulke, U. Eckardt, B. Flash, U. Knauer, K. Polthier (Eds.), Combinatorial Image Analysis, Lecture Notes in Computer Science, vol. 4040, Springer, Berlin, 2006, pp. 199-213]. A sequence of hinge angles is a set of particular angles determined by a digital image in the sense that any angle between two consecutive hinge angles gives the identical rotation of the digital image. We propose a method for obtaining the lower and the upper bounds of admissible rotation angles using hinge angles from a given Euclidean angle or from a pair of corresponding digital images.     

Skeleton growing and pruning with bending potential ratio

We propose a novel significance measure for skeleton pruning, called bending potential ratio (BPR), in which the decision regarding whether a skeletal branch should be pruned or not is based on the context of the boundary segment that corresponds to the branch. By considering this contextual information, we can better evaluate the contribution of the boundary segment to the overall shape, which generally depends on its particular location within the whole contour (i.e., a segment may be considered to be insignificant in one place while it may be considered as a feature elsewhere). The BPR is a measure of the significance of contour segments in such context, and depicts the bending potential of a contour segment. Unlike other significance measures that only contain local shape information, the BPR evaluates both local and global shape information. Thus, it is insensitive to local boundary deformation. In addition, we also present a scheme for skeleton growing, which integrates pruning based on the BPR measurement. Our experiments demonstrate that the skeletons obtained by the proposed algorithm are medially placed and connected. We also demonstrate that shapes reconstructed from these skeletons are very close to the original shapes. Moreover, the BPR measure yields a natural multi-scale skeletal representation.     

A finite element model for the analysis of 3D axisymmetric laminated shells with piezoelectric sensors and actuators: Bending and free vibrations

This paper addresses the bending and free vibrations of multilayered cylindrical shells with piezoelectric properties using a semi-analytical axisymmetric shell finite element model with piezoelectric layers using the 3D linear elasticity theory. In the present 3D axisymmetric model, the equations of motion are expressed by expanding the displacement field using Fourier series in the circumferential direction. Thus, the 3D elasticity equations of motion are reduced to 2D equations involving circumferential harmonics. In the finite element formulation the dependent variables, electric potential and loading are expanded in truncated Fourier series. Special emphasis is given to the coupling between symmetric and anti-symmetric terms for laminated materials with piezoelectric rings. Numerical results obtained with the present model are found to be in good agreement with other finite element solutions.     

离散数学实践教学研究与实践

本文从算法描述、实验课程体系建设、实际应用领域介绍以及实践教学模式等方面讨论了离散数学的实践教学。     

离散数学课程教改的研究与实践

离散数学是计算机科学与技术各专业的核心、骨干课程,搞好本课程的教学,对学生后续课程的学习和今后的科研工作均具有十分重要的意义。本文结合教学中的一些认识,就如何改革传统教学模式,采用现代教学手段提高教学质量作了较为深入的分析与探讨。     

离散数学课程内容及学习方法探讨

讨论工程型人才培养的课程定位,通过阐述离散数学自编教材,介绍针对工程型计算机本科专业的课程内容取舍,探讨离散数学课程的学习方法,并进行了深入的思考。     

《离散数学》研究性实验的探索与实践

针对目前离散数学教学过程中存在的问题,分析增加研究性实验内容的必要性,对研究性实验教学方法和实验内容进行探索和实践,通过研究性实验将离散数学抽象的课程内容与计算机方面的实际应用联系起来,使学生学以致用,明确该课程在计算机相关专业的重要地位,有利于激发学生的学习兴趣和提高学生的计算思维能力。     

离散数学课程教学改革探索与实践

离散数学是计算机科学的核心基础理论课,该课程不但为学生学好后续课程提供数学理论基础,而且学好该课程有利于培养学生的数学思维。本文结合教学实践,分析了当前离散数学教学中存在的问题,针对该课程的特点,从教学内容、教学手段和教学方法3个方面对离散数学的教学改革进行了探讨,力求使该课程的教学上一个新的台阶。     

圆形区域极点及方差约束下线性离散系统的控制设计

本文考虑线性离散随机系统在圆形区域极点及方差约束睛的控制器设计问题，即设计状态反馈控制器，使闭环系统同时满足预先给定的圆形区域极点约束以及预先给定的各状态分量的方差约束。文中利用代数黎卡提方程方法解决了上述问题。     

平面框架结构地震力的设计敏度和海森矩阵的计算

提出一种平面框架结构地震力的设计敏度和海森矩阵的精确计算方法.在有限单元法和纽马克-β法的基础上推导了平面框架结构地震力的设计敏度和海森矩阵的计算公式,用matlab语言编制了平面框架结构地震力的设计敏度和海森矩阵的计算程序,实现了平面框架结构地震力的设计敏度和海森矩阵的精确计算.最后给出一个二层平面框架结构算例,数值结果表明本文所提的地震力的设计敏度和海森矩阵的计算方法是有效的和高效的.     

离散制造MES在照明工厂的实施与应用

本文介绍MES的概念和功能,结合企业对生产管理系统的要求,提出在离散制造企业实施MES系统的必要性。并通过对某照明工厂的实际调研,较为详尽地分析了离散制造企业目前存在的问题。在MES系统的实施过程中,结合生产工艺,完成数字化工厂和产品的建模,采集设备运行时间和速率实现关键设备的效率管理,以及通过质量控制完成双向产品追溯。     

一种基于组合外密钥和明文的离散混沌密码算法

利用混沌信号的特性提出了一种新的对称密钥块加密算法。该算法具有如下特点,不直接使用混沌系统参数和初始条件作为密钥,而这些参数由外部密钥和明文字符通过位置加权运算得到,且外部密钥由长度可变的字符串和一正整数组合,密钥空间很大。明文的每一块加密都依赖于密钥和整个明文。仿真结果表明,密文对明文或初始密钥的任何微小变化均有强烈敏感性;密文分布均匀。故该密码系统具有强壮的抵抗攻击的能力。     

离散数学教学改革及课程建设研究

依据离散数学课程教学的特点,为了激发学生的学习热情,培养其思维能力和应用能力,笔者结合课程教学实际,对离散数学教学改革及课程建设进行了研究。文章提出改革教学方法,建设教学网站,改革考核形式等教改措施。这些措施在实际教学中起到了一定的作用,教学质量有很大提高。     

浅析计算机科学与技术专业中“离散数学”教学方法的改进

"离散数学"是计算机科学与技术专业必修的专业基础课程,学好该课程对于学习计算机专业的其他课程以及培养学生抽象思维能力和解决问题的能力十分重要。本文阐述如何培养学生学习离散数学的兴趣,强调了离散数学理论应该与计算机中的应用相结合,并从多方面对离散数学教学方法的改进进行分析和探讨。     

二维实值与复值离散GABOR变换的比较

本文介绍了作者曾提出的快速二维实值离散 Ｇａｂｏｒ变换（ＲＤＧＴ）方法，以及 ＲＤＧＴ系数与复值离散 Ｇａｂｏｒ变换（ＣＤＧＴ）系数之间的关系，并在不同的等效窗宽条件下，通过对图像的二维ＲＤＧＴ系数 与二维ＣＤＧＴ系数熵的比较，指出二维ＲＤＧＴ比二维ＣＤＧＴ更适合于图像的压缩。