检索结果-南通市图书馆

Tracking multiple people under occlusion and across cameras using probabilistic models

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第7期10卷 985-996页

作者： Xuan-he WANG ji-lin liu Institute of Information and Communication Engineering Zhejiang University Hangzhou 310027 China Zhejiang Provincial Key Laboratory of lnformation Network Technology Hangzhou 310027 China

Tracking multiple people under occlusion and across cameras is a challenging question for discussion. Furthermore, the cameras in this study are used to extend the field of view, which are distinguished from the same field of view. Such corre- spondence between multiple cameras is a burgeoning research subject in the area of computer vision. This paper effectively solves the problems of tracking multiple people who pass from one camera to another and segmenting people under occlusion using probabilistic models. The probabilistic models are composed of blob model, motion model and color model, which make the most of the space, motion and color information. First, we present a color model that uses maximum likelihood estimation based on non-parametric kernel density estimation. Second, we introduce a blob model based on mean shift, which segments the body into many regions according to the color of each person in order to spatially localize the color features corresponding to the way people are dressed. Clothes can be any mixture of colors. Third, we bring forward a motion model based on statistical probability which indicates the movement position of the same person between two successive frames in a single camera. Finally, we effectively unify the three models into a general probabilistic model and attain a maximization likelihood probability image, which is used to segment the foreground region under occlusion and to match people across multiple cameras.

关键词： Color model Motion model Blob model People occlusion People tracking Kernel density estimation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Environment map building and localization for robot navigation based on image sequences

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第4期9卷 489-499页

作者： Ye-hu SHEN ji-lin liu Xin DU Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

SLAM is one of the most important components in robot navigation. A SLAM algorithm based on image sequences captured by a single digital camera is proposed in this paper. By this algorithm, SIFT feature points are selected and matched between image pairs sequentially. After three images have been captured, the environment’s 3D map and the camera’s positions are initialized based on matched feature points and intrinsic parameters of the camera. A robust method is applied to estimate the position and orientation of the camera in the forthcoming images. Finally, a robust adaptive bundle adjustment algorithm is adopted to optimize the environment’s 3D map and the camera’s positions simultaneously. Results of quantitative and qualitative experiments show that our algorithm can reconstruct the environment and localize the camera accurately and efficiently.

关键词： Monocular vision Digital elevation map (DEM) SIFT Robust adaptive bundle adiustment SLAM algorithm

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Using concurrent lines in central catadioptric camera calibration

引用

Journal of Zhejiang University-Science C(Computers and Electronics) 2011年第3期12卷 239-249页

作者： Lei ZHANG Xin DU ji-lin liu Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

Central catadioptric cameras have been extensively adopted in robotics and surveillance due to their extensive field of *** attain precise 3D information in these applications,it is important to calibrate the catadioptric cameras *** existing calibration techniques either require prior knowledge of the mirror types,or highly depend on a conic estimation procedure,which might be ruined if there are only small portions of the conic visible on calibration *** this paper,we design a novel planar pattern with concurrent lines as a calibration rig,which is more robust in conic estimation since the relationship among lines is taken into *** on the line properties,we propose a rough-to-fine approach suitable for the new planar pattern to calibrate central catadioptric *** method divides the nonlinear optimization calibration problem into several linear sub-problems that are much more robust against *** calibration method can estimate intrinsic parameters and the mirror parameter simultaneously and accurately,without a priori knowledge of the mirror *** performance is demonstrated by both simulation and a real hyperbolic catadioptric imaging system.

关键词： Catadioptric Calibration Concurrent lines Conic estimation

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Robust water hazard detection for autonomous off-road navigation

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 786-793页

作者： Tuo-zhong YAO Zhi-yu XIANG ji-lin liu Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 310027 China

Existing water hazard detection methods usually fail when the features of water surfaces are greatly changed by the surroundings, e.g., by a change in illumination. This paper proposes a novel algorithm to robustly detect different kinds of water hazards for autonomous navigation. Our algorithm combines traditional machine learning and image segmentation and uses only digital cameras, which are usually affordable, as the visual sensors. Active learning is used for automatically dealing with problems caused by the selection, labeling and classification of large numbers of training sets. Mean-shift based image segmentation is used to refine the final classification. Our experimental results show that our new algorithm can accurately detect not only ‘common’ water hazards, which usually have the features of both high brightness and low texture, but also ‘special’ water hazards that may have lots of ripples or low brightness.

关键词： Water hazard detection Active leaming Adaboost Mean-shift

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Vision based terrain reconstruction for planet rover using a special binocular bundle adjustment

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第10期9卷 1341-1350页

作者： Min-yi SHEN Zhi-yu XIANG ji-lin liu Institute of Information and Communication Engineering Zhejiang University Hangzhou 310027 China Zhejiang Provincial Key Laboratory of Information Network Technology Zhejiang University Hangzhou 310027 China

This paper presents a pure vision based technique for 3D reconstruction of planet terrain. The reconstruction accuracy depends ultimately on an optimization technique known as 'bundle adjustment'. In vision techniques, the translation is only known up to a scale factor, and a single scale factor is assumed for the whole sequence of images if only one camera is used. If an extra camera is available, stereo vision based reconstruction can be obtained by binocular views. If the baseline of the stereo setup is known, the scale factor problem is solved. We found that direct application of classical bundle adjustment on the constraints inherent between the binocular views has not been tested. Our method incorporated this constraint into the conventional bundle adjustment method. This special binocular bundle adjustment has been performed on image sequences similar to planet terrain circumstances. Experimental results show that our special method enhances not only the localization accuracy, but also the terrain mapping quality.

关键词： 3D reconstruction Binocular bundle adjustment (BBA) Scale-invariant feature transform (SIFT) Re-projectionerror RANSAC

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Unwrapping and stereo rectification for omnidirectional images

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第8期10卷 1125-1139页

作者： jie LEI Xin DU Yun-fang ZHU ji-lin liu Institute of lnformation and Communication Engineering Zhejiang University Hangzhou 310027 China Zhejiang Provincial Key Laboratory of lnformation Network Technology Hangzhou 310027 China College of Computer and lnformation Engineering Zhejiang Gongshang University Hangzhou 310027 China

Omnidirectional imaging sensors have been used in more and more applications when a very large field of view is *** this paper,we investigate the unwrapping,epipolar geometry and stereo rectification issues for omnidirectional vision when the particular mirror model and the camera parameters are unknown in ***,the omnidirectional camera is calibrated under the Taylor model,and the parameters related to this model are *** order to make the classical computer vision algorithms of conventional perspective cameras applicable,the ring omnidirectional image is unwrapped into two kinds of panoramas:cylinder and *** the epipolar geometry of arbitrary camera configuration is analyzed and the essential matrix is deduced with its properties being indicated for ring *** that,a simple stereo rectification method based on the essential matrix and the conformal mapping is *** and real data experimental results illustrate that our methods are effective for the omnidirectional camera under the constraint of a single view point.

关键词： Single point of view Calibration Catadioptric image unwrapping Omnidirectional stereo vision Epipolar geometry Essential matrix Conformal mapping

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Stereo vision based SLAM using Rao-Blackwellised particle filter

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第4期9卷 500-509页

作者： Er-yong WU Gong-yan LI Zhi-yu XIANG ji-lin liu Department of lnformation Science and Electrical Engineering Zhejiang University Hangzhou 310027 China National Laboratory of Pattern Recognition Institute of Automation CAS Beijing 100080 China

We present an algorithm which can realize mobile robot in unknown outdoor environments, which 3D stereo vision simultaneous localization and mapping （SLAM） for means the 6-DOF motion and a sparse but persistent map of natural landmarks be constructed online only with a stereo camera. In mobile robotics research, we extend FastSLAM 2.0 like stereo vision SLAM with ＂pure vision＂ domain to outdoor environments. Unlike popular stochastic motion model used in conventional monocular vision SLAM, we utilize the ideas of structure from motion （SFM） for initial motion estimation, which is more suitable for the robot moving in large-scale outdoor, and textured environments. SIFT features are used as natural landmarks, and its 3D positions are constructed directly through triangulation. Considering the computational complexity and memory consumption, Bkd-tree and Best-Bin-First （BBF） search strategy are utilized for SIFT feature descriptor matching. Results show high accuracy of our algorithm, even in the circumstance of large translation and large rotation movements.

关键词： Robot Vision based SLAM SIFT Feature management

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Local curve fitting based Lagrange multiplier selection for Id-slice in multi-view video coding

引用

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第6期10卷 778-785页

作者： Shi-fang XU Guo-bin CHEN Hua-dong PAN ji-lin liu Department of Information Science and Electronic Engineering Zhejiang University Hangzhou 31002 7 China

The rate and distortion of Id-slice do not fit the globally linear relationship on a logarithmic scale. Lagrange multiplier selection methods based on the globally linear approximate relationship are neither efficient nor optimal for multi-view video coding (MVC). To improve the coding efficiency of MVC, a local curve fitting based Lagrange multiplier selection method is proposed in this paper, where Lagrange multipliers are selected according to the local slopes of the approximate curves. Experi-mental results showed that the proposed method improves the coding efficiency. Up to 2.5 dB gain was achieved at low bitrates.

关键词： Id-slice Lagrange multiplier Local curve fitting Multi-view video coding (MVC)

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Application of a Space-based Optical Interferometer Toward Measuring Cosmological Distances of Quasars

引用

Research in Astronomy and Astrophysics 2022年第3期22卷 100-114页

作者： Ying-Ke Huang Yue-Dong Fang Kai-Xing Lu Zhi-Xiang Zhang ji-lin liu Sha-sha Li Bao-Rui Luo Qin lin Zhuo-Xi Huo Qian Xuesen Laboratory of Space Technology China Academy of Space TechnologyBeijing 100081China Yunnan Observatories Chinese Academy of SciencesKunming 650011China Department of Astronomy Xiamen UniversityXiamenFujian 361005China

Measuring quasar distance through joint analysis of spectroastrometry and reverberation mapping observations is a new method for driving the development of *** this paper,we carry out detailed simulation and analysis to study the effect of four basic observational parameters(baseline length,exposure time,equivalent diameter and spectral resolution)on the data quality of differential phase curves(DPCs),and furthermore on the accuracy of distance *** our simulation,we adopt an axisymmetrical disk model of a broad line region(BLR)to generate differential phase *** find that the differential phases and their Poisson errors could be amplified by extending the baseline,while the influence of optical path difference errors can be reduced during fitting the BLR *** exposure time or larger equivalent diameter helps reduce the absolute Poisson ***,the relative error of DPCs could be reduced by increasing any of the above three parameters,then the accuracy of distance measurement could be *** contrast,the uncertainty of absolute angular distances(D_(A))could be improved with higher spectral resolution,although the relative error of DPCs would be *** show how the uncertainty of distance measurement varies with the relative error of *** our specific set of model parameters,without considering more complicated structures and kinematics of BLRs in our simulation,it is found that the relative error of DPCs<20%is a limit for accurate distance *** relative error of DPCs has a lower limit(roughly 5%)and the uncertainty in distance measurement can be better than 2%.

关键词： (galaxies:)quasars:emission lines techniques:interferometric (cosmology:)distance scale

来源：

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Preparation and Performance of Ternary Early Strength Agent and Quercetin Composite Cement Sealing Material

引用

Journal of Wuhan University of Technology(Materials Science) 2025年第1期40卷 130-140页

作者： liu jian CHEN Meiting ji Xiaoli XU Chao WANG Chunmei Department of Safety Science and Engineering Anhui University of Science and TechnologyHuainan 232001China Key Laboratory of Mine Safety and High Efficient Mining Jointly Built by Province and Education Ministry Anhui University of Science and TechnologyHuainan 232001China Department of Chemical Engineering and Explosives Anhui University of Science and TechnologyHuainan 232001China

A ternary early-strengthening agent consisting of calcium formate+triethanolamine+lithium sulfate was compounded with quercetin to shorten the setting time of cementitious materials while ensuring their early *** optimum ratio of the three early-strengthening agents was determined as 0.5%calcium formate+0.04%triethanolamine+0.4%lithium sulfate by response surface *** effects of the ternary early-strengthening agent composed of calcium formate+triethanolamine(TEA)+lithium sulfate on cementitious pore sealing materials under the synergistic effect of quercetin were studied by means of the performance tests of compressive strength,fluidity,and setting time,and the microstructural characterizations of X-ray powder diffractometer(XRD),thermogravimetry(TG-DSC)and scanning electron microscopy(SEM).The study shows that the synergistic effect of ternary early-strengthening agent and quercetin forms a multi-performance composite admixture for cementitious *** best performance was obtained with the compounding scheme of 0.5%calcium formate+0.04%triethanolamine+0.4%lithium sulfate ternary early-strengthening agent and 0.05%*** compressive strength of 1,3,7,and 28 d are 94.8%,39.8%,42%,and 28%higher than those of the blank group,*** initial time and final setting time are 41 and 57 minutes,*** to the microscopic analysis,the network and fibrous C-S-H gels generated by ternary early-strengthening agents are attached to the surface promoted by quercetin,which forms skeleton support while thickening and solidifying the cement slurry,which enhances the early compressive strength of the cement-based materials.

关键词： sealing material ternary early-strengthening agent quercetin synergetic effect response surface methodology

来源：

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

欢迎您,

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案：

请选择收藏分类：

通借通还

欢迎您,

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

在线全文

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：