一种基于轮廓线的三维表面模型的快速切割算法

在科学计算可视化的领域中,医学图象数据的三维重构和手术模拟是一个研究热点。该文设计并实现了一个基于轮廓线的三维表面模型的快速切割算法,称为“双面切割算法”。该算法充分利用了原始数据的几何及拓扑信息,将三维表面模型的切割操作转化到二维空间中,从而避免了一般三维物体切割算法中三角面片直接求交的大量运算。双面切割算法在进行切割运算时,同时得到切割后的模型及它们的交集模型,并维持了物体数据结构的完整性。     

面向三维剪纸的网格模型切割方法

提出了一种改进的三维网格模型切割算法,在切割每个图案时首先检查面片区域是否已被其他图案修改,并在修改之后对应的面片区域上进行切割且记录切割结果,最后将三维网格模型表面封闭剪纸图案内的顶点和面片剔除,得到像手工剪纸那样的镂空效果.三维剪纸可以广泛应用于动画、教育以及娱乐产业中.     

基于VTK的医学三维图像模型构建与切割

虚拟外科手术是医学领域的一个重要研究方向。基于面绘制和体绘制两种可视化算法实现医学图像的三维模型重建,针对不同重建模型分别实现虚拟任意切割：面切割和体切割,并讨论了虚拟切割的交互操作实现方法。用VTK(Visualization Toolkit)初步实现了模拟手术系统中的虚拟切割脊柱体功能。     

从正面侧照片合成三维人脸

实现了一具交互式人脸建模和动画的工具,用户可以从一个人正面和侧面的照片构造了出头部的三维模型,并基于这个模型实现特定表情和简单的动画。详细阐述在系统实现过程中应用到的人脸几何表示,一般人脸变化到特定人脸、弹性网格、肌肉模型、全视角巾图、表情提取等技术。     

基于三维表面模型的任意切割算法*

通过对三维表面模型进行切割,人们可以方便地观察物体的内部结构。针对三维表面模型,提出了一种任意切割算法。任意切割过程首先是交互生成切割曲线,生成切割面;然后通过切割面对表面模型进行切割,在切割面上生成交线序列;再由交线序列与切割面边界生成封闭的边界轮廓,确定各边界轮廓间的包含关系;最后对边界轮廓包围的截面区域进行Delaunay三角剖分并着色,得到完整的剖面。实验结果证明了该算法的有效性和可行性。     

基于2D轮廓线的体数据切割算法

为了方便医生从三维角度直观理解体数据的内部细节,提出一种基于2D轮廓曲线的交互式体数据切割算法,并结合可视化工具包和布尔操作实现单平面和包围盒的体数据切割。轮廓线体数据切割算法根据操作者在图像窗口任意勾画的2D轮廓曲线构建切割几何体,并将轮廓曲线和体数据通过坐标变换映射到掩膜图像内,在2D空间实现三维图像数据的切割。实验结果表明轮廓线切割算法可处理任意形状的切割几何体。     

虚拟手术中顶点复制切割算法的设计研究

为了解决虚拟内镜手术中软体组织切割模拟仿真问题,论述并实现了虚拟手术中软组织切割仿真技术.使用四面体网格模型,利用刀具移动简化模型,构造用于切割操作的切割树,设计了通过划分切割区域,复制和移动顶点,在实现切割分裂时,减少网格单元结构数量增加的切割分裂和切割细化算法.通过仿真实验,文中算法的耗时与切割长度程线性关系;使用该算法实施切割后,网格结构中单元结构数量的增加相比传统的算法有明显减少.     

基于笛卡尔切割单元法的复杂河道地理信息系统环评可视化

复杂河道中污染物扩散计算及其在地理信息系统(GIS)上的可视化,对于地表水环境影响评价(EIA)具有非常重要的意义,但在网格生成、污染物计算模型及计算结果可视化方面存在着诸多困难。针对点源岸边排放河流污染物计算及基于GIS可视化中的难点问题,提出了基于切割单元法的地面水环境影响评价可视化方法。将切割单元法应用于网格剖分,通过切割单元交点追踪算法及河道轮廓线内背景网格筛取算法,生成了复杂河道笛卡尔网格。提出了基于污染物二维稳态衰减模式的网格自适应加密与稀疏算法,在非结构化笛卡尔网格基础上采用了基于河流几何信息判断的点源岸边排放河流污染预测算法与区域填充算法,实现了环境影响评价计算结果的可视化显示。通过一个河流污染环境影响评价可视化的实例,验证了所提方法的可行性与有效性。     

基于笛卡尔切割单元法的复杂河道地理信息系统环评可视化

复杂河道中污染物扩散计算及其在地理信息系统(GIS)上的可视化,对于地表水环境影响评价(EIA)具有非常重要的意义,但在网格生成、污染物计算模型及计算结果可视化方面存在着诸多困难。针对点源岸边排放河流污染物计算及基于GIS可视化中的难点问题,提出了基于切割单元法的地面水环境影响评价可视化方法。将切割单元法应用于网格剖分,通过切割单元交点追踪算法及河道轮廓线内背景网格筛取算法,生成了复杂河道笛卡尔网格。提出了基于污染物二维稳态衰减模式的网格自适应加密与稀疏算法,在非结构化笛卡尔网格基础上采用了基于河流几何信息判断的点源岸边排放河流污染预测算法与区域填充算法,实现了环境影响评价计算结果的可视化显示。通过一个河流污染环境影响评价可视化的实例,验证了所提方法的可行性与有效性。     

正颌截骨术中的凸柱体网格切割算法研究

计算机辅助虚拟手术技术对正颌外科手术方案的制定、手术效果的预测分析发挥着重要作用。然而,现有的计算机辅助正颌截骨术只能实现少量简单的截骨操作,不能满足虚拟截骨术多样性的需要。在平面切割地基础上,提出了一种基于凸柱体网格切割算法。该算法用凸柱体模拟虚拟手术刀对三维网格模型进行切割,根据截骨术的切口类型构造柱体,用此柱体进行切割实现骨块的分离。实验结果表明,该算法能有效地实现多种复杂虚拟截骨术,为手术方案的制订提供了辅助指导作用。     

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.