PTZ自主跟踪中的全景视频生成

提出了一种在单PTZ摄像机自主跟踪过程中生成全景视频的方法。该方法在自主跟踪目标的同时,生成目标在大场景上运动的全景视频,可应用于PTZ摄像机监控场所。该方 法将全景视频看作全景背景图像和当前目标图像的叠加：首先利用Mean Shift跟踪方法逐帧获取目标区域图像并保存;然后利用相邻两帧视频图像的竖直方向投影匹配和Harris角 点匹配结果合成全景背景,与传统的配准方法相比,大大降低了匹配运算的复杂度,使全景背景的生成能够实时进行,并记录每帧图像到背景图像的变换参数;最后逐帧将目标区 域图像变换到背景图像上得到全景视频。本文方法与传统的全景视频生成方法相比,无需人工控制摄像机的转动,也无需手工对齐视频帧,整个过程全部自动完成。     

基于区域的图像拼接算法

为了在实时视频监控中能够有效地检测和跟踪目标,提出了一种基于区域的图像拼接算法.该算法根据空间几何知识建立摄像机旋转投影模型,对需要拼接的图像进行二维空间坐标变换,使所有的图像都转换到同一坐标系下.最后,根据已知的云台旋转参数来设定配准特征空间,进而对图像进行配准和拼接.算法中建立了一种新的摄像机旋转投影模型,可以有效地进行图像的空间坐标转换,并且通过设定配准特征空间,有效地改进了配准和拼接算法.在PC机上的实验结果表明了该算法的准确性和有效性.     

基于多视频的虚实融合系统

提出了一种基于多视频的虚实融合可视化系统的构建方法,旨在将真实世界中的图像和视频融合到虚拟场景中,用视频图像中的纹理和动态信息去丰富虚拟场景,提高虚拟环境的真实性,得到一种增强的虚拟环境.利用无人机采集图像来重建虚拟场景,并借助图像特征点的匹配来实现视频图像的注册.然后利用投影纹理映射技术,将图像投影到虚拟场景中.视频中的动态物体由于在虚拟环境中缺失对应的三维模型,直接投影,当视点发生变化时会产生畸变.首先检测和追踪这些物体,然后尝试使用多种显示方式来解决畸变问题.此外,系统还考虑有重叠区域的多视频之间的融合.实验结果表明,所构造的虚实融合环境是十分有益的.     

基于投影图像 SURF 特征提取的三维模型配准

针对传统三维模型配准方法存在对点云初始位置有一定要求、模型配准的精度有 时不高等问题,提出了一种基于三维模型投影图像 SURF 特征提取的三维模型配准方法。首先 通过扫描三维模型数据确定投影图像的范围,判断每个投影图像像素所隶属的模型网格,并求 解从投影图像到纹理图像的映射关系,从而获取二维投影图像;然后对这两幅投影图像分别进 行 SURF 特征点的选取与特征值的计算,并按 SURF 特征值进行特征匹配,再根据投影图像像 素点与三维网格端点的映射关系计算三维特征点对;最后通过匹配的特征点对求取模型变换矩 阵完成三维模型的配准。实验结果表明,该方法在配准时间变化不大的前提下,有效提高了配 准精度,并具有较好的鲁棒性。     

基于GPU的实时三维点云数据配准研究

在三维重建中,不同摄像机坐标系下点云配准耗时过多。为此,提出一种基于图形处理单元(GPU)的实时三维点云数据配准算法。利用投影映射法获取匹配点对,使用点到切平面距离最小化方法计算变换矩阵,通过GPU多线程并行处理大规模图像数据。实验结果表明,对于分别包含307 200个数据的2帧点云,在保持原有配准效果的基础上,该算法的最优耗时仅为基于CPU的最近邻迭代算法的11.9%。     

基于改进SURF的实时视频拼接方法

视频拼接在现实生活中具有十分重要的意义。文中实现的功能是实时地将多路视频进行拼接以形成一个大视野的视频。为了使系统具有良好的实时性,先用DirectShow分离视频流、提取图像帧,然后提出了一种改进的SURF算法进行图像配准,最后采用渐入渐出法进行图像融合。改进的算法在特征点提取时对范围作了限制,同时改进了原有特征描述符,这样可以大大加快提取速度。在特征匹配时采用基于最近邻和次近邻距离比值的方法进行粗匹配,然后采用RANSAC方法进行提纯和求取变换矩阵,最后在视频拼接中,不是对每一帧图像进行配准和融合,而是只对首帧图像进行图像配准,之后的每帧图像利用第一帧计算出的变换矩阵进行图像拼接,这样可以加快视频拼接的速度。实验结果表明,该方法可以实时地生成无缝清晰的宽场景视频。     

基于CenSurE特征的虚实配准方法研究

针对虚实配准的高精度和实时性要求, 提出了一种基于CenSurE特征的自适应虚实配准方法。该方法包括离线初始化和在线跟踪两个阶段。离线阶段系统利用CenSurE-OCT滤波器和MU-SURF描述符进行特征提取和匹配操作, 并根据特征匹配集合建立坐标系, 同时求得虚实配准的初始矩阵。在线跟踪阶段系统采用自适应跟踪方法获取当前图像特征点与参考特征点的对应关系, 然后利用误差逼近的方法求得当前图像的虚实配准矩阵。实验结果表明, 该方法的配准误差均值为1. 91　mm, 运算速度为21 fps, 其综合性能优于基于FAST、SIFT和SURF等局部特征的虚实配准方法, 具有较高的配准精度和较强的实时性。     

一种多方向感知的高实时性视频融合算法

针对多路视频融合阶段拼缝线两侧范围内出现的虚影、色彩亮度差异以及高分辨率下无法实时拼接等问题,本文提出一种多方向感知的视频融合算法。首先,在图像配准阶段,采用SIFT提取特征点与特征描述子对图像进行配准;然后,在图像融合阶段,使用指数函数构建的权值查找表指导融合过渡,结合视频帧投影位置与拼接缝之间的距离,利用形态学操作自适应地融合图像拼缝;最后,利用GPU平台大量多线程并行运算,整合投影与融合等矩阵运算从而掩盖延时达到实时目的。实验结果表明,该算法能消除重叠区域内出现的虚影、模糊现象,并且具有良好的实时拼接效果。     

三维表面与平面数据间的自适应配准

三维体数据与二维平面数据间的配准是手术导航的基础。与以往的思路有所不同,论文通过把三维表面投影到平面上,利用光照模型计算投影平面的灰度值,实现投影图像与实拍照片间的匹配,在匹配中调整投影参数使得两平面图像达到最佳相似,进而实现三维到二维的自适应配准。     

基于计算机视觉的虚实场景合成方法研究

开发了一种虚拟场景与实时视频之间的合成技术,提出了一种新的基于非定标技术的虚实配准方法,有效地解决了基于标识的三雏注册系统要求摄像机内参在系统运行过程中不能发生改变的限制.详细介绍了系统所采用的基于计算机视觉的标识识别和实时自动摄像机位置、姿态跟踪算法,并给出了系统运行结果,成功地将该技术应用于虚拟规划系统中.     

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。     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).