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A spatio-velocity model based semantic event detection algorithm for traffic surveillance video

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Science china(Technological Sciences) 2010年第S1期53卷 120-125页

作者： SHENG Hao 1,ZHAO HuiJie 1,HUANG Jian 2 & LI Na 1 1 School of Instrument Science and Opto-Electro engineering,beihang university,beijing 100191,china 2 School of Software,beihang university,beijing 100191,china School of Instrument Science and Opto-Electro engineering Beijing University Beijing China School of Software Beijing University Beijing China

Detection of vehicle events is a research hotspot in digital *** this paper,an approach is proposed to detect vehicle events with semantic analysis of traffic surveillance video using spatio-velocity statistic *** approach includes two successive phases:trajectory clustering and semantic events *** trajectory clustering,a statistic model of vehicle trajectories are presented,for which a spatio-velocity model is trained by analyzing the trajectories of moving vehicles in the *** on the trajectory,which represents both the position of the vehicle and its instantaneous velocity,a trajectory similarity measure is ***,an improved hierarchical clustering algorithm is adopted to cluster the trajectories according to different spatial and velocity *** each cluster,trajectories that are spatially close have similar velocities of motion and represent one type of activity *** the semantic events detection phase,statistic models of semantic regions in the scene are generated by estimating the probability density and velocity distributions of each type of activity ***,semantic events are detected by the proposed spatio-velocity statistic *** paper also presents experiments using real video sequence to verify the effectiveness of the proposed method.

关键词： trajectory clustering spatio-velocity statistic model event detection digital traffic

Simulation of three-dimensional nonideal MHD flow at high magnetic Reynolds number

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中国科学：技术科学英文版 2010年第1期53卷 206-212页

作者： LU HaoYu1 & Lee ChunHian2 1 School of Astronautics,beihang university,beijing 100191,china 2 National Laboratory for Computational Fluid Dynamics,beihang university,beijing 100191,china School of Astronautics Beihang University Beijing China National Laboratory for Computational Fluid Dynamics Beihang University Beijing China

A conservative TVD scheme is adopted to solve the equations governing the three-dimensional flow of a nonideal compressible conducting fluid in a magnetic *** eight-wave equations for magnetohydrodynamics(MHD) are proved to be a non-strict hyperbolic system,therefore it is difficult to develop its *** developed a new set of equations which cannot be numerically simulated by conservative TVD scheme directly due to its non-conservative form.A conservative TVD scheme augmented with a new set of eigenvectors is proposed in the *** validate this scheme,1-D MHD shock tube,unsteady MHD Rayleigh problem and steady MHD Hartmann problem for different flow conditions are *** simulated results are in good agreement with the existing analytical *** this scheme can be used to effectively simulate high-conductivity fluids such as cosmic MHD problem and hypersonic MHD flow over a blunt body,etc.

关键词： magnetohydrodynamics(MHD) numerical simulation TVD MHD Rayleigh flow MHD Hartmann flow

A Linear Domain System Identification for Small Unmanned Aerial Rotorcraft Based on Adaptive Genetic Algorithm

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Journal of Bionic engineering 2010年第2期7卷 142-149页

作者： Xusheng Lei,Yuhu Du School of the Instrumentation Science and Opto-electronic engineering,beihang university,beijing 100191,P.R.china School of the Instrumentation Science and Opto-electronic engineering Beihang University Beijing P. R. China

This paper proposes a new adaptive linear domain system identification method for small unmanned aerial *** the flash memory integrated into the micro guide navigation control module, system records the data sequences of flighttests as inputs (control signals for servos) and outputs (aircraft’s attitude and velocity information).After data preprocessing, thesystem constructs the horizontal and vertical dynamic model for the small unmanned aerial rotorcraft using adaptive *** identified model is verified by a series of simulations and *** between flight data and the one-stepprediction data obtained from the identification model shows that the dynamic model has a good estimation for real unmannedaerial rotorcraft *** on the proposed dynamic model, the small unmanned aerial rotorcraft can perform hovering,turning, and straight flight tasks in real flight tests.

关键词： small unmanned aerial rotorcraft dynamic space model model identification adaptive genetic algorithm

Large field of view computed laminography with the asymmetric rotational scanning geometry

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Science china(Technological Sciences) 2010年第8期53卷 2261-2271页

作者： FU Jian 1,2 ,JIANG BaiHong&LI Bin 1 School of Mechanical engineering and Automation,beihang university,beijing 100191,china 2 Research Center of Digital Radiation Imaging and Biomedical Imaging,beihang university,beijing 100191,china School of Mechanical engineering and Automation Beihang University Beijing China Research Center of Digital Radiation Imaging and Biomedical Imaging Beihang University Beijing China

X-ray computed laminography(CL)is used in the fields of industrial inspection and medical *** can provide the internal structure three-dimensional(3D)information of a region of the objects *** is important to the clinical diagnosis and the quality control of flat objects like printed circuit boards,aircraft wings and satellite solar *** the restriction that the imaging region must be within the X-ray beam formed by the X-ray source and the detector,the imaging field of view of CL is limited by the size of detector.A new CL method with an asymmetric rotational cone-beam scanning geometry,called large field of view CL,is presented to overcome the existing *** can extend the imaging region when the imaging spatial resolution keeps the same as that of the conventional *** can also improve the imaging spatial resolution when the imaging region keeps the same as that of the conventional *** asymmetric configuration can be achieved by offsetting the detector from the conventional symmetric *** does not,however,require new detectors and X-ray source nor alter the scanning mechanical *** filtered back-projection(FBP)reconstruction algorithm and the data truncation smoothing functions have been deduced to reconstruct the images directly from the data acquired with this asymmetric *** performed numerical studies and experiments to demonstrate and validate the proposed approach. Results in these studies and experiments confirm that the proposed method can enlarge the imaging region and improve the spatial *** proposed approach may find applications in the CL system with the rotational scanning geometry.

关键词： computed laminography image reconstruction reconstruction algorithm imaging field of view imaging spatial resolution

A GTD model and state space approach based method for extracting the UWB scattering center of moving target

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Science china(Information Sciences) 2011年第1期54卷 182-196页

作者： WANG Jun,WEI ShaoMing,SUN JinPing & MAO ShiYi School of electronic and Information engineering,beihang university,beijing 100191,china School of electronic and Information engineering Beihang University Beijing China

Movements of the scattering center on the condition of ultra-wideband(UWB)will impact the extraction of *** paper presents an approach for extracting the moving targets’UWB scattering center parameters based on the geometrical theory of diffraction(GTD)model and the state space approach. Firstly,the UWB GTD scattering model is transformed into state-space equations in order to estimate the range and range rate through the singular value ***,the type parameter in the whole bandwidth is indicated dimension-reducedly by orthonormalized basis and estimated by traversal algorithm and minimumnorm ***,the intensity of scattering center is worked out based on the least square *** paper provides the Cramer-Rao bound(CRB)for parameter *** effectiveness of the approach is verified by computer *** approach can estimate range,range rate,reflection intensity and type parameter simultaneously in order to improve the track of scattering centers and the target identification.

关键词： scattering center extraction GTD model state space approach ultra-wideband Doppler processing

Adaptive control for autonomous rendezvous of spacecraft on elliptical orbit

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Acta Mechanica Sinica 2009年第4期25卷 539-545页

作者： Shan Lu Shijie Xu School of Astronautics, beihang university,100191 beijing, china School of Astronautics Beihang University Beijing China

A strategy for spacecraft autonomous rendezvous on an elliptical orbit in situation of no orbit information is developed. Lawden equation is used to describe relative motion of two spacecraft. Then an adaptive gain factor is introduced, and an adaptive control law for auton- omous rendezvous on the elliptical orbit is designed using Lyapunov approach. The relative motion is proved to be ultimately bounded under this control law, and the final relative position error can achieve the expected magnitude. Simulation results indicate that the adaptive control law can realize autonomous rendezvous on the elliptical orbit with relative state information only.

关键词： Autonomous rendezvous Elliptical orbit Lyapunov approach Adaptive control Gain factor

Reliability-aware automatic composition approach for web services

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Science china(Information Sciences) 2012年第4期55卷 921-937页

作者： LI Mu 1,2,LI Bo 1,2 & HUAI JinPeng 1,2 1 State Key Laboratory of Software Development Environment,beihang university,beijing 100191,china 2 School of Computer Science and engineering,beihang university,beijing 100191,china State Key Laboratory of Software Development Environment Beihang University Beijing China School of Computer Science and engineering Beihang University Beijing China

In this paper,we study the reliability-aware synthesis problem for composing available services automatically and guaranteeing that the composed result satisfies the specification,such as temporal constraints of functionality and reliability,centered on a synthesis model for mediator of web services composition (CSM).This approach focuses on handling attributes and state relations,and permitting users and services to operate over them,i.e.,read /write their data values and compare them according to a dense state *** show that the reliability-aware synthesis problem for the specification is EXPTIME-complete and we give an exponential-time algorithm (CSM-NSA) which for a given formula ψ and a synthesis model,synthesizes available services in the library satisfying ψ over the synthesis model (if they exist) or responds with "not satisfiable" (otherwise).The specification ψ is a fragment of PCTL (probabilistic computation tree logic),obtained from "ordinary" CTL (computation tree logic) by replacing the EX,AX,EU and AU operation with their quantitative counterparts X >p,X =1,U >p,and U =1,*** opposed to NSA,we provide a more effective algorithm to replace the NSA algorithm called CSM-HSA (heuristic synthesis algorithm).Though HSA is an incomplete algorithm,the answer is *** experiments show that the HSA algorithm solves the problem of reliability-aware service synthesis effectively and efficiently.

关键词： reliability web services synthesis problem synthesis model heuristic algorithm

Radiance-based color calibration for image-based modeling with multiple cameras

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Science china(Information Sciences) 2012年第7期55卷 1509-1519页

作者： ZHAO Xu 1,2 ,ZHOU Zhong 1,2 & WU Wei 1,2 1 State Key Laboratory of Virtual Reality Technology and Systems,beihang university,beijing 100191,china 2 School of Computer Science and engineering,beihang university,beijing 100191,china State Key Laboratory of Virtual Reality Technology and Systems Beihang University Beijing China School of Computer Science and engineering Beihang University Beijing China

Photo-consistency estimation is an important part for many image-based modeling *** paper presents a novel radiance-based color calibration method to reduce the uncertainty of photo-consistency estimation across multiple *** idea behind our method is to convert colors into a uniform radiometric color space in which multiple image data are *** results demonstrate that our method can achieve comparable color calibration effect without adjusting camera parameters and is more robust than other existing ***,we obtain an auto-determined threshold for photo-consistency check,which will lead to a better performance than existing photo-consistency based reconstruction algorithms.

关键词： color calibration photo-consistency estimation multi-camera system image-based modeling

An approach to detecting abnormal vehicle events in complex factors over highway surveillance video

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Science china(Technological Sciences) 2008年第S2期51卷 199-208页

作者： SHENG Hao1,XIONG Zhang1,WENG JingNong2 & WEI Qi1 1 College of Computer,beihang university,beijing 100191,china 2 College of Software,beihang university,beijing 100191,china College of Computer Beihang University Beijing China College of Software Beihang University Beijing China

The detection of abnormal vehicle events is a research hotspot in the analysis of highway surveillance *** of the complex factors,which include different conditions of weather,illumination,noise and so on,vehicle's feature extraction and abnormity detection become *** paper proposes a Fast Constrained Delaunay Triangulation(FCDT) algorithm to replace complicated segmentation algorithms for multi-feature *** on the video frames segmented by FCDT,an improved algorithm is presented to estimate background *** the estimation,a multi-feature eigenvector is generated by Principal Component Analysis(PCA) in accordance with the static and motional features extracted through locating and tracking each *** abnormity detection,adaptive detection modeling of vehicle events(ADMVE) is presented,for which a semi-supervised Mixture of Gaussian Hidden Markov Model(MGHMM) is trained with the multi-feature eigenvectors from each video *** normal model is developed by supervised mode with manual labeling,and becomes more accurate via iterated *** abnormal models are trained through the adapted Bayesian learning with unsupervised *** paper also presents experiments using real video sequence to verify the proposed method.

关键词： background estimation abnormity detection adaptive detection modeling a semi-supervised MGHMM