多通道快速GPU光线投射算法

现有基于GPU加速的光线投射算法为满足实时交互的需求,通常在用户交互过程中,采用降低采样频率的方法来提高重建速度,却丢失了三维数据场的信息,极大降低了重建图像的质量.针对这一问题,在分析GPU渲染管道线和图像插值重建技术的基础上,提出多通道快速GPU光线投射算法.利用离屏渲染技术,设置比显示分辨率低4～16倍的渲染分辨率,在此渲染分辨率下进行正常采样的光线投射算法,将渲染分辨率下重建结果重新作为输入,进行高分辨率重建,并显示结果.实验结果表明,该方法可以在满足重建图像质量的前提下,有效提高重建速度.     

一种用于三维重建的形状插值算法

1.引言 随着X射线,核磁共振以及CT等医疗检测设备的迅速发展,人们能够更加准确、快速、全面地获取人体内部脏器和组织的形状以及解剖信息.目前,这些检测设备提供的绝大部分是二维断层图像,而医务人员对目标三维空间信息的需求和计算机的高速发展使得三维成像成为必然的趋势.可是,断层序列图像的层间的分辨率远低于层内的分辨率,这就严重地影响了三维目标重建的质量.为此,人们提出用插值的方法来提高层间的分辨率,常见层间插值的方法有基于灰度的方法[1,2]和基于形状的方法[3～10]等.     

CT图像三维重建体绘制算法重采样改进

CT断层影像三维重建技术是目前医学可视化研究的热点之一,为了更精准地获取病变部位的信息并使诊断过程更加方便,从一组CT切片图像中重建出三维图像就显得尤为重要.针对三维重建过程中体绘制的光线投射算法成像速度慢的问题,提出了将重采样过程中的三线性插值过程转化到二维数据场再进行插值的改进方法,在相对三线性插值法图像质量基本不变的情况下,成像时间节省约75％.     

基于距离变换的图像层间插值技术

由断层图像恢复出目标物体的三维图像应用极广，文中提出了基于距离交换的断层图像插值方法来获得三维重构时的数据场。此方法由于在插值时考虑了目标物体的整体特征，从而使得插值具有连续性。     

基于小波的三维图像频域显示方法研究

提出了一种基于小波的频域体绘制算法(FWVR)进行三维图像重构。算法首先完成三维体数据的傅里叶变换和切平面提取,然后在频域中完成小波的多分辨率分解,并在不同分辨级上进行小波系数重建,最后做傅里叶逆变换,以得到观察平面上希望得到的体绘制图像。算法是基于CT成像和小波变换的原理,时间复杂度由视平面上的二维傅里叶逆变换决定,即O(N2logN)。应用此方法对128的医学体数据进行实验,结果证明该方法有效,采用伪彩色后的绘制效果3与光线投射法绘制效果基本相同,而速度大大提高。     

三维地震数据场的并行体绘制算法

光线投射算法是一种应用广泛的体绘制基本算法,其存在的主要问题是绘制速度较慢.为了提高光线投射算法的绘制速度,利用光线间和光线内的并行性,结合三维地震数据场的特点和文件存储特性,提出了一种基于工作站机群的三维地震数据场的并行体绘制算法.地震油气解释实际应用表明本算法能满足地震解释的要求.     

一种提高计算机重构三维图像质量的方法

在全真三维场景的三维图像技术的研究中,根据计算机重构三维图像时分辨率低的问题,在基于透镜阵列模型的计算机II重构图像基础上,为提高质量和图像分辨率,提出一种基于相似像素块平滑过渡的图像后处理方法,方法对从每个元素图像中提取出的相邻像素块进行相似性判断,对相似像素块内中心像素以外的像素按照一定方法修改其灰度值,进行平滑,使图像后处理过程既缓解了从不同元素图像中提取的像素块间的灰度不连续性,又能保持重要的边缘信息,改善了重构图像的视觉效果.     

融合超像素分割技术的虚拟成像细节重建研究

虚拟成像是在三维空间中投射立体影像的技术，受采集设备、环境以及网络传输等因素的影响，图像易出现分辨率降低问题，导致虚拟成像细节重建效果不理想。为解决上述问题，提出基于VR和小波降噪的复杂虚拟成像重建方法。依据光学原理确定最小识别距离，结合摄像机采集目标物体多视点图像。利用简单线性迭代聚类(simple linear iterative clustering, SLIC)超像素分割技术优化小波降噪法，完成图像的去噪。基于此，通过VR技术获取全息三维影像重建点坐标和深度距离，并将其投射至透明介质上，实现复杂虚拟成像重建。实验结果表明，研究方法的虚拟成像超像素分割效果更优，平均峰值信噪比为25.5dB,平均结构相似度为0.83,具有较高的应用可靠性。     

三维成像声纳图像后处理与可视化

针对基于线阵合成孔径技术的三维成像声纳缺乏有效后处理与可视化方法的问题,提出一个适用于三维成像声纳图像后处理与可视化方案。鉴于水体和地层2种介质具有不同的声学特性,使用组合算法分离水体和地层数据,利用基于边缘梯度均值约束的三维自适应区域生长算法分别对水底和地层目标进行检测,融合水体和地层数据,采用光线投射法进行三维实验数据的可视化。湖试和近海海试结果表明,该方案能够适应声成像中水体与地层的不同特点,有效检测目标,提高声纳图像的表现能力。     

基于断层图像分割的三维匹配插值

CT和MRI图像断层之间的距离远大于断层内部像素间的距离,三维剂量场的计算等工作通常需要等间隔分布的三维图像数据。目前常用的基于灰度插值方法会引起图像边界模糊,而基于形状的插值方法不能得到整个图像的数据。为解决这一问题,文中提出了一种基于断层图像分割的三维匹配插值算法。通过对断层图像进行分割,获得断层图像的空气、软组织和骨骼等区域信息。对相同密度区域采用匹配插值,不同密度区域采用缩放区域大小作为插值数据,使新的图像不仅在灰度上,而且在组织形状上介于原来的断层图像之间,满足了医学图像插值要求。和线性插值方法相比,新算法提高了插值图像的质量,插值结果可有效地应用于构建三维体模型。     

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.