基于区域能量函数的快速CBCT图像牙齿分割算法

从锥形束面计算机断层扫描图像中分割出三维牙齿模型对口腔正畸治疗和研究工作十分重要.针对邻接牙、牙周组织模糊等问题,提出一种基于区域能量函数的快速牙齿分割算法.首先通过牙髓种子点和梯度模,筛选拟合得到一条粗略的初始分割曲线;然后根据灰度分布特征确定曲线变化的搜索路径和变化区域,在此区域内构造了一个基于灰度值、梯度模和边界平滑性的区域能量函数,优化初始分割曲线得到精确的分割曲线;再将上一层的最终分割曲线作为下一层的初始分割曲线,逐层优化得到所有分割曲线;最后使用Marching Cubes算法重建得到完整牙齿网格模型.采用CBCT数据集进行测试,实验结果表明,该算法能够有效且快速地解决模糊问题,得到满足正畸治疗需要的牙齿模型.     

基于保特征调和场的交互式网格分片

网格模型分片在计算机图形学应用中具有重要意义,本文提出了一种基于网格上的调和场和图割技术的网格模型分片算法.用户可以通过划线的方式来指定网格上感兴趣的区域;算法自动构建反映该区域细节特征的调和场,进而采用图割技术,得到满足用户要求的分片结果;通过对网格分割边界的光滑处理,可有效改善锯齿型分割边界.实验结果表明,我们的算法对于特征单一或复杂的网格模型都能得到符合用户意图的分割结果.     

层次渐进的三维骨架算法

提出一种新的三维网格模型骨架抽取算法。首先基于多维标度法计算三维网格模型的特征面片,以特征面片为类心对三维网格模型进行聚类分割预处理,然后在模型的各分割块上,以特征面片为种子点、以渐次读取部域带为区域增长方式,层次推进读取该分割块;计算每个层次推进带的中心,顺次连接中心即为各分割块的骨架线;最后将各分割块的骨架连接起来,即为模型的整体骨架。实验结果表明,该算法是正确的和有效的。     

基于多核学习的快速网格分割算法

网格分割是三维几何分析的重要问题之一,它不仅在传统的建模、渲染等方面起到关键作用,同时也是高层次几何分析的基础性工作.文中提出一种基于多核学习(multiple kernel learning)的快速网格分割算法.多核学习使用多个核函数的组合代替单一核函数,能够解决网格分割特征多样性和异构性的问题.给定一组同类别带分割标签的网格模型,算法首先对网格进行过分割处理,将三角面片转化为超面片(super-face),然后使用多核超限学习机训练分割分类器,最后用该分割分类器对未分割的网格进行分割.过分割处理能够减少训练样本数量,进而提高计算效率;多核学习使分类器能够有效地发现数据间的关系,使其具有更强大的学习能力.实验表明,文中算法不仅计算精度高,并且能够满足网格分割"实时学习"的计算要求.     

对称零空间准则下的LDA特征抽取方法

网格分割在网格参数化、纹理atlas图等几何处理问题中有着重要的应用.提出一种基于顶点或面凸凹信号的简单高效的网格分割算法.基于均匀支撑半径的顶点凸凹信号分析将顶点分为平坦点、凸点、凹点和特征点,先从平坦点进行平坦区域扩展,再从剩下的凸凹点出发进行凸凹区域扩展,最后根据顶点和边界边的光滑度进行区域竞争扩展;对于未能完全分割的简化程度高的模型,基于面的凸凹信号采用类似的过程进一步完成最后的分割.该算法可以快速地进行网格分割并能较好地保持网格特征,特别适用于CAD模型的分割.     

基于调制度信息的网格重构算法

提出一种基于调制度的网格重构算法,首先对调制度进行等级量化,在调制度高的区域构造种子三角面片;然后优先选取测点调制度高的活动边进行增长,依据加权最小长度准则选择最佳候选点;在径向基函数孔洞修补之前根据三角面片几何属性对孔洞边界进行预处理.实验结果表明,该算法对平坦和高曲率区域都能有效地重构出形态比较均匀的二维流形网格,较好地保持了模型的细节尖锐特征.     

半监督的三维网格模型层次分割

提出一种半监督K均值聚类和带状区域增长的三维网格模型层次分割算法,包括显著性特征点提取、预分割和后分割3个阶段.该算法在多维标度法的基础上进行显著性特征点提取;利用半监督K均值聚类算法来对原始模型进行初步的粗分割,以提高算法的整体效率;根据预分割结果,利用离散高斯曲率逼近,以带状推进的区域增长法进行层次的后分割.与同类算法相比,文中算法得到的分割边界更有意义,具有较高的边缘准确性和分割区域一致性.     

基于凸凹信号的网格分割

网格分割在网格参数化、纹理atlas图等几何处理问题中有着重要的应用,提出一种基于顶点或面凸凹信号的简单高效的网格分割算法,基于均匀支撑半径的顶点凸凹信号分析将顶点分为平坦点、凸点、凹点和特征点,先从平坦点进行平坦区域扩展,再从剩下的凸凹点出发进行凸凹区域扩展,最后根据顶点和边界边的光滑度进行区域竞争扩展;对于未能完全分割的简化程度高的模型,基于面的凸凹信号采用类似的过程进一步完成最后的分割,该算法可以快速地进行网格分割并能较好地保持网格特征,特别适用于CAD模型的分割。     

三角网格模型的最小值边界分割

针对目前网格模型块分割算法综合效果不理想、人工干预多等问题,提出一种基于凹凸信号的最小值边界检测的三角网格模型分割算法.首先通过全局控制顶点的Laplace光顺操作对网格模型进行光顺去噪;然后通过标准化和归一化的凹度信息发现符合人眼视觉的最小值规则的凹特征点;最后结合区域中心线提取算法以及扇形探射线算法构造出闭合的分割线,并用三维主动轮廓模型方法进行优化,通过分割线将模型分割为有意义的分块.实例结果表明,该算法可以快速有效地分割模型,得到有意义的分割结果.     

基于高斯球的近似共面合并层次细节模型

构造场景多层次细节模型是加速图形显示的有效途径.给出一种基于共面合并自动生成场景多层次细节模型的算法.此算法将一单位球定义为高斯球,并按一定的规则对其进行层次分割.然后根据各景物面片的法向在高斯球上的分布,将具有近似一致法向的面片划分为面片族;在面片族内对相邻面片进行合并,生成近似共面区域;然后移去其内部点,对区域边界重新三角化.算法还结合临近边界点合并等原则,删除对表达场景几何特征重要度低的顶点.算法利用平面九叉树进行合并操作,生成具有多层次细节的场景模型.实验结果表明,算法能实现较理想的场景简化效果.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.