基于纹理映射与融合的医学体数据射线跟踪法

提出一种基于2D纹理映射与纹理融合的射线跟踪法，原理是利用窗值变换将体数据转换为具有光强和不透明度信息的2D纹理序列集，将其从物体空间映射到观察空间，再沿视线方向按从后往前的次序将其融合为3D图像。该方法充分利用了现有通用微机显卡纹理映射的硬件加速技术，算法简洁、易于实现，可以生成具有X光透视效果的3D图像，降低了体绘制对计算机硬件的要求，在目前通用微机上即可获得交互的绘制速度和良好的3D图像品质。     

彩色三维体数据场的直接体绘制方法

提出基于光线投射和三维纹理映射的彩色体数据成像算法，研究如何从每个体素的R，G，B三元组映射成不透明度值，即不透明度转换函数。首先把原始的RGB色彩空间转换成LUV色彩空间；然后以亮度分量的中心差分来近似估计法向量，并应用Phong光照模型进行着色，根据亮度分量及其梯度等信息计算不透明度值；最后合成、累积颜色。对美国数字人男子照相彩色体数据分别采用两种算法进行实验。结果表明：基于光线投射的彩色体数据算法成像质量较高，可以表现体表毛细血管等细微结构，但速度较慢；基于三维纹理映射的彩色体数据成像算法速度较快，但成像质量适中。     

体素分类与Phong光照模型GPU加速体绘制

为了提高体绘制的速度和效果,研究了体数据的分类和计算及其在图形处理单元上加速实现的体绘制算法.分别采用点体素先分类和预积分后分类方法为体数据分配颜色和不透明度,改进了利用不透明度对颜色加权改善绘制效果,根据Phong光照模型对体数据进行渲染.通过查找表软件加速和图形处理单元硬件加速两个方面分别实现并进行比较,实验结果表明,采用图形硬件加速的方法达到实时交互的效果,体绘制性能大大提高.     

一个新的基于3D纹理映射及Shear—werp变换的快速体绘制方法

介绍了一个新的基于纹理映射及Ｓｈｅａｒ－ｗａｒｐ变换的快速体绘制方法。所提出的方法吸收了纹理映射方法的长处，通过纹理硬件的加速，并在纹理装载时提出了可适应性的纹理分割方法，使该算法不受纹理内存的限制。在进行纹理映射时，通过剪切（Ｓｈｅａｒ）变换和三维图象的分割，加快绘制速度。与多种经典的快速体绘制方法进行测试比较，该方法达到了交互的效果和更高的绘制速度。     

一个新的基于3D纹理映射及Shear-warp变换的快速体绘制方法

介绍了一个新的基于纹理映射及Shear-warp变换的快速体绘制方法。所提出的方法吸收了纹理映射方法的长处，通过纹理硬件的加速，并在纹理装载时提出了可适应性的纹理分割方法，使该算法不受纹理内存的限制。在进行纹理映射时，通过剪切（Shear）变换和三维图象的分割，加快给制速度。与多种经典的快速体绘制方法进行测试比较，该方法达到了交互的效果和更高的绘制速度。     

PC机上基于2D纹理映射的三维体绘制算法

体绘制技术因其卓越的图象质量而被广泛应用,尤其是在医学方面.然而传统的体绘制技术(如光线跟踪法)因计算量大、绘制时间长等不足,限制了其在PC机上的应用.本文立足于目前标准的PC硬件平台和OpenGL1.1标准,在不显著降低图象质量的前提下,采用2D纹理映射技术来提高图象的绘制速度,将大量的三次线性插值运算转换为二次线性插值运算,并充分利用PC硬件的2D纹理映能力来加速绘制速度.实验结果表明,2D纹理映方法明显提高了图象的绘制速度,并具有较好的图象质量.随着PC硬件的发展,为提高体绘制速度和改善图象质量提供了更广阔的空间.     

带材质的GPU加速体绘制算法

在体绘制过程中,为了给物质表面加入材质(光照和纹理)来提高结果的可读性,提出一种带材质的体绘制算法.通过引入2D球面光照贴图,用纹理映射替代了GPU中复杂的光照模型计算;利用物质表面单位法向量索引球面光照贴图中对应点的颜色信息,从而给物体表面赋予各种材质属性;并结合基于3D纹理的GPU光线投射算法完成绘制.实验结果表明,该算法简单易行,在增强可视化效果的同时使得绘制的效率也得到提升.     

基于相邻层间相似性和空体素跳跃的体绘制加速算法研究

Splatting是经典的基于物序的直接体绘制方法,运算数据量的多少制约着算法绘制图像的速度。为了进一步提升绘制速度,采用基于相邻层间相似性和空体素跳跃相结合的方法进行加速,在读取数据过程中对图片中的三维纹理数据进行筛选,并使用足迹表对筛选后的三维纹理数据进行二维投影,利用相邻层间相似性计算每一个点的灰度值,并根据灰度值将数据分类,算出对成像没有影响的空体素,跳过其绘制过程从而加速算法。实验结果显示,该算法能够在保证绘制图像质量的基础上,在一定程度上解决和改善Splatting算法数据的空间相关性和运算效率的问题。     

基于GPU图像直接体绘制算法分析与评价

近年来计算机图形硬件性能不断提高,利用硬件来实现体绘制过程中的某些环节以获取交互的绘制速率成为可能,是目前体绘制的研究热点。描述了基于GPU的光线投射法、2D纹理映射法和3D纹理映射法等典型算法,给出了各类算法的分析与性能评价,最后实现相关算法并得出实验结果。     

一种基于交互式多维传递函数的纹理映射体绘制算法

本文设计了一种基于空间信息的交互式多维传递函数的纹理映射体绘制算法。该算法不仅可以根据体数据的强度而且还利用体素的空间位置来设定绘制的颜色和阻光度。通过采用一种独特的空间投影变换,根据用户需求,将体数据划分为不同区域,并分别定义各自的传递函数。该特点使得本文的算法可以有效地对体数据进行交互式分析。在算法实现中,利用了通用图形硬件的可编程特性,在普通PC上可以达到理想的绘制质量和交互速度。     

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.