一种散乱点云空间直接剖分算法

散乱点云的三角剖分在曲面重建中发挥着重要作用。在对三角剖分基本方法深入分析的基础上对此类点云提出了一种高效的重构算法。本算法将基于动态球策略的搜索算法引入到曲面重建中,源于增量式计算的思想,结合约束准则和设计的顶点度量函数,从基础三角面片开始扩展到覆盖整个物体表面。分析及实验结果表明,该算法能有效地对点云数据进行三角网格化,同时剖分后的三角网格曲面最大限度地保持了原有曲面的特性,证明了提出的基于动态球的曲面重构算法应用于散乱点云曲面重构问题的可行性。     

多视角下的改进ICP算法

在逆向工程中,为处理庞大的三维点云数据,重建物体的表面,提出一种基于多视角的改进ICP算法。通过采集多视角下的点云数据,利用Delaunay三角剖分以及深度值信息对相邻两组点云的重合部分进行提取,根据三角面片重心与待测物体重心之间的距离将获得的点云数据进行分类配准,计算最优的旋转矩阵与平移向量,提高ICP算法的效率。实验结果表明,该算法能够提高配准精度,缩短配准时间,具有良好的稳定性。     

点云的形状与曲线重建算法

针对平面无序带噪点云的曲线重建问题,给出了点云形状的定义并提出了构造点云形状的算法.该算法基于Delaunay三角剖分,在构造好点云的Delaunay三角剖分后对三角剖分进行细化,使得在点云中的点周围形成空间上的局部均匀采样;基于集合论中的基本概念定义点云中内点、外点和边界点,并且明确地定义了点云的形状,根据Delaunay三角剖分细化时,选择不同的参数得到不同层次的点云的形状;选择合适的参数得到相应形状后,通过薄化过程得到具有流形结构的曲线.实验结果表明,采用文中算法得到的重建曲线很好地反映了点云的形状,验证了该算法的有效性.     

海量点云曲面增量拓扑重建EI北大核心CSCD

针对现有的曲面重建算法难以兼顾大规模采样数据的重建效率与重建曲面拓扑正确性的问题,提出一种基于局部Delaunay网格剖分的曲面增量重建算法.该算法采用波前扩展的策略,通过波前环的扩张、分裂、重叠面片的消除等步骤,将局部重建过程传播至每个样点的邻近区域,获得插值于采样点集的二维定向流形网格曲面,实现整个采样点集的增量拓扑重建;在曲面局部重建过程中,分别基于局部区域的Cocone算法与二维投影点集的Delaunay网格剖分方法重建曲面的尖锐区域与平坦区域,其中局部区域重建曲面网格的边界的正确性由区域之外的少量辅助样点保护.实验结果表明,文中算法具有较高的重建效率,适用于封闭和非封闭海量点云数据的重建;且在采样密度符合要求的情况下,重建的网格曲面与原表面拓扑同构.     

三维散乱点云快速曲面重建算法

提出了一种基于Delaunay三角剖分的三维散乱点云快速曲面重建算法。算法首先计算点云的Delaunay三角剖分, 从Delaunay四面体提取初始三角网格, 根据Voronoi体元的特征构造优先队列并生成种子三角网格, 然后通过区域生长的方式进行流形提取。实验结果表明, 该算法可以高效、稳定地重构具有复杂拓扑结构、非封闭曲面甚至是非均匀采样的点云数据。与传统的基于Delaunay的方法比较, 该算法仅需要进行一次Delaunay三角剖分, 无须极点的计算, 因此算法的重构速度快。     

海量点云曲面增量拓扑重建

针对现有的曲面重建算法难以兼顾大规模采样数据的重建效率与重建曲面拓扑正确性的问题,提出一种基于局部Delaunay网格剖分的曲面增量重建算法.该算法采用波前扩展的策略,通过波前环的扩张、分裂、重叠面片的消除等步骤,将局部重建过程传播至每个样点的邻近区域,获得插值于采样点集的二维定向流形网格曲面,实现整个采样点集的增量拓扑重建;在曲面局部重建过程中,分别基于局部区域的Cocone算法与二维投影点集的Delaunay网格剖分方法重建曲面的尖锐区域与平坦区域,其中局部区域重建曲面网格的边界的正确性由区域之外的少量辅助样点保护.实验结果表明,文中算法具有较高的重建效率,适用于封闭和非封闭海量点云数据的重建;且在采样密度符合要求的情况下,重建的网格曲面与原表面拓扑同构.     

机载激光雷达点云多层次建筑物的三维重建

针对城市区域中常见的多层次建筑物,提出一种基于机载LiDAR点云的三维重建方法。使用优化的随机抽样一致性算法对建筑物LiDAR点云进行面片分割,在面片分割的基础上使用delaunay三角剖分进行轮廓点的检测,对检测出的轮廓点使用新的关键点检测算法提取轮廓线关键点,最后连接关键点并进行规则化处理,完成多层次建筑物的三维重建。实验表明,该方法能有效重建多层次建筑物模型,改进的RANSAC算法能更高效地分割屋顶面片,新的轮廓线关键点提取算法能够较好地提取建筑物的关键点,并能抑制错误轮廓点的干扰,减少伪关键点的生成。     

一种基于点云数据的快速曲面重构方法

研究激光扫描中的点云数据重构技术,提出一种基于规则点云数据的快速曲面重构方法。分析相邻扫描线之间数据点的相对位置关系,在三角剖分的基础上,设计改进的扫描线剖分算法,根据激光逐行扫描的特点,对点云数据进行不规则三角网格划分,利用几何关系进行配对构网,并在所建三角模型的基础上实现三角网格的局部优化和纹理映射,得到重建模型。实验结果表明,与传统Delaunay空间三角剖分算法相比,该算法可明显提高三角构网速度和质量,消除空洞,改善重建效果。     

心内膜表面几何模型三维重建算法研究

心内膜三维表面重建是心内膜三维标测系统中的关键问题。为了满足实际应用需求, 根据采集到的散乱点云数据的特点, 提出了一种改进的泊松表面重建算法。在估计表面点云法向量的基础上, 对表面点云法向量进行法向量一致化处理, 有效地控制时间复杂度, 快速重建出平滑的心脏模型。针对泊松表面重建算法中构建MC曲面出现的二义性问题, 提出一种消除二义性的简化改进方法, 可以更加精确地获取模型逼真表面, 提高重建的速度和精度。同时, 可以根据医生的要求, 对重建出的模型实时修正, 满足临床应用。最后, 通过实验验证了算法的有效性和可行性。     

基于TIN的三维地质模型栅状图的司视化方法研究

三维地质模型的栅状图可视化方法研究是正确认识地质结构和构造复杂性的一种重要手段.本文提出一种栅状图生成方法首先针对不规则散点数据,应用基于格网划分的自适应分割-合并算法进行Delaunay三角剖分,快速高效地实现了三维地层三角面片的曲面重建在此基础上,对栅状图生成过程中需要进行的追踪三维体层剖切线、层间剖切线缝合等关键问题进行了探讨,并对其中的点定位算法进行了优化,有效提高了栅状图的生成效率.     

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.