浅析三维重建算法

为了将二雏图纸在计算机中自动转换成三维模型并进行交互式显示和各种操作,必须首先从二维图纸中读取所有线条、标注等信息。将这些信息以合适的数据结构进行组织,然后根据这些数据识别相应的几何元素及其位置、尺寸等信息,即进行三维重建。该文对已有的多种三维重建算法进行分类和剖析,归纳出三维重建算法的主要技术难点,并给出了核心的内部数据结构。     

连续断层图像的边缘检测研究

工业CT扫描通常只能得到某一断面上的二维信息,不能得到被检测物的整体描述,技术人员只能根据获得的系列二维图像在人脑中综合复原为三维结构.因而人们希望能得到直观地、精确地展示被检测物体三维空间结构的ICT直观图像,能得到比二维图像更加丰富的信息.因此断层图像的三维重建在工业无损探伤、天体结构的观察及其它更广泛的领域有着极其重要的实用价值和研究意义.本文提出了一种基于边缘检测的按层剥离的算法,此算法是在二维图像上进行,然后再将分割后的序列图像再进行三维重建实现三维物体的按层剥离显示效果.     

基于多尺度CNN-RNN的单图三维重建网络

现有基于深度学习的三维重建算法主要从深度网络的单一层进行特征获取,二维图像特征提取不完整,造成三维重建效果不理想。为提高三维重建模型的精度及准确度,充分利用二维图像细节特征,有效转换为三维网络,提出一种基于多尺度CNN-RNN的单图三维重建网络。模型网络主要由三部分组成：二维编码器、转换器及三维编码器。模型借鉴高斯金字塔模型,构建多尺度网络,保留二维图像不同尺度上的特征值,通过RNN将其转换为三维特征。模型使用公共的ShapeNet数据集进行训练和测试,通过前后对比,发现使用多尺度特征提取的方法,模型具有更好的鲁棒性。与现有方法进行对比,本模型在飞机、柜子、汽车、显示器、灯、音响、沙发等模型的三维重建中拥有更好的重建效果。     

基于二维图像三维重建的人脸特征提取技术研究

采用基于二维图像的三维重建对人脸特征进行提取.首先应用平行双目视觉原理获取人脸的二维图像,然后对图像进行预处理,消除图像上的噪音点,增强图像,以便提取特征点,对这些二维图像上的特征点进行优化计算,最后得到整体人脸的三维特征点信息.     

脊柱外科三维重建系统设计

阐述了利用CT断层扫描影像切片数据,从二维图像中提取三维信息,并采用OpenGL开发工具进行三维重建,结合VC 的功能界面设计,实现了具有医学诊断指导意义的脊柱外科三维重建系统.     

基于LM和SVD结合的点云拼接算法研究

点云拼接是场景三维重建过程中的重要环节。针对现有的拼接算法存在耗时长、拼接效果差等问题,通过利用正交映射,获取三维点云与二维图像之间的映射关系,并在二维图像中获取匹配点对。在此基础上,提出了采用LM和SVD结合的方法来变换矩阵。首先根据正交映射,获取三维点云所对应的二维图像;其次利用SURF算法,提取图像的特征点,并通过FLANN算法以及RANSAC算法,提取两幅图像中的特征拼接点对;最后将LM和SVD两种方法相结合,求得变换矩阵。试验结果表明,无论拼接精度,还是运行速度,该算法均较直接利用LM算法或SVD算法有所提高。     

基于计算网格的图像三维重建系统的设计

在计算机视觉处理领域中,三维重建是一种将二维图像恢复成三维信息的方法。目前,由于图像的三维重建过程涉及到大量的数据,重建速度较慢。为了提高三维重建的性能,构建了基于计算网格的图像三维重建系统。利用该系统提供的Web方式,用户可以实现作业提交、作业运行状态查询和图像三维重建服务部署的功能。最后,对所构建的计算网格三维重建系统进行了测试和分析。     

三维曲面的特征描述和特征匹配

本文提出了一种新的三维曲面特征描述算法,将二维图像上的特征描述思想推广到三维网格。算法将三维网格表示成从顶点到高斯曲率的映射函数,从而获得可类比于二维图像的相似性。借助于法线和梯度建立局部球坐标系,通过二维统计直方图对特征点邻域的几何信息进行描述,使得特征描述具有平移、旋转和缩放不变性,最终生成128维的特征向量(特征描述符)。基于特征向量,我们实现了多分辨率和异拓扑网格下的特征匹配,展示并分析了实验结果。本文的研究动机来源于三维扫描建模以及多视点三维重建技术中对特征描述和特征匹配的需求,主要的应用方向包括:扫描配准、模型注册、动画跟踪、对称检测和模型检索。     

具有三维重建功能的医学影像存档与通信系统

项目实现了医学影像三维重建的体绘制算法，并在传统的二维图像采集，存储，传输、共享与处理等功能之上，附加了影像的三维重建功能，开发出一套全新的医学影像存档与通信系统，具有很高的实用价值。     

采用去抖动模糊算法的稠密三维重建

针对无人机在航拍大场景对象进行三维重建时因抖动产生的图像模糊现象,以及二维图像序列经运动恢复结构SFM后得到的点云较为稀疏,可视化差等不足,采用去抖动模糊算法恢复模糊图像的原始图像信息,然后在运动恢复结构的基础上进行基于点云的稠密三维重建,最后对稠密重建后的点云进行泊松表面重建以得到表面致密、均匀的三维模型。实验结果表明,去抖动模糊算法可以有效地提高图像的质量,大场景对象经过基于点云的稠密三维重建后得到的重建效果逼真,可视化强。     

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).