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An improved reduced-rank STAP interference suppression method in design of GNSS receivers

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Science china(information Sciences) 2012年第10期55卷 2329-2342页

作者： GONG WenFei & SUN Xin School of electronics and information engineering,beijing Jiaotong university,beijing 100044,china School of electronics and information engineering Beijing Jiaotong University Beijing China

In this paper,we address the problem of interference cancellation in global positioning system(GPS) receiver using an adaptive reduced-rank space-time adaptive processing(STAP) interference suppression method based on multistage nested Wiener filter(MSNWF).This improved adaptive reduced-rank method is based on the improved Gerschgorin radii ***,the cross-correlations between the desired signals of the adjacent stages of MSNWF are directly used to calculate the Gerschgorin radii instead of employing the eigenvalue decomposition of the covariance ***,a heuristic decision rule based on Gerschgorin disk estimator(GDE) is employed to estimate the rank of interference *** optimal rank can be adaptively selected without increasing the *** and results of the experiment show that the proposed method further reduces the computation of STAP and enhances its real-time property with the interference suppression performance unaffected.

关键词： global positioning system reduced-rank space-time adaptive processing multistage nested Wiener filter Gerschgorin disk estimator

Inferring playback rate and rate resets of P2P video streaming transmissions by piecewise line envelope approximation

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The Journal of china Universities of Posts and Telecommunications 2009年第2期16卷 58-62,79页

作者： LI Chun-xi CHEN Chang-jia School of electronics and information engineering,beijing Jiaotong university,beijing 100044,china School of electronics and information engineering Beijing Jiaotong University Beijing 100044 China

Conventionally, P2P video is regarded as CBR traffic. However, our measurements have shown that the rate reset cannot be neglected in a practical IPTV system because each rate reset often leads to performance degradation. Thus, addressing the problem of inferring playback rate and rate reset in a P2P video system is significant. In this article, an algorithm termed piecewise linear envelope approximation （PLEA） is proposed, in which a follow-up time is introduced to smooth rate fluctuations in a small time scale and to adapt rate jumps in a large time scale automatically. With the PLEA algorithm, discontinuity introduced by blind segmentations adopted by current methods is avoided. Furthermore, unlike existing algorithms in which both segmentation and combinations are performed in multiple runs, only a single computation path is involved in the PLEA algorithm. This makes PLEA algorithm amenable to implementation of low complexity by either software or hardware. Both theoretical analysis and experiment based on measured data show that the PLEA outperforms existing algorithms based on segmentation.

关键词： P2P video playback rate rate reset convex hull linear program

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Spotlight SAR sparse sampling and imaging method based on compressive sensing

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Science china(information Sciences) 2012年第8期55卷 1816-1829页

作者： XU HuaPing1,YOU YaNan1,LI ChunSheng1&ZHANG LvQian2 1S chool of electronics and information engineering,beihang university,beijing 100191,china 2C hinese Academy of engineering,beijing 100088,china School of electronics and information engineering Beihang University Beijing China Chinese Academy of engineering Beijing China

Spotlight synthetic aperture radar(SAR)emits a chirp signal and the echo bandwidth can be reduced through dechirp processing,where the A/D sampling rate decreases accordingly at the *** sensing allows the compressible signal to be reconstructed with a high probability using only a few samples by solving a linear program *** paper presents a novel signal sampling and imaging method for application to spotlight SAR based on compressive *** signal is randomly sampled after dechirp processing to form a low-dimensional sample set,and the dechirp basis is imported to reconstruct the dechirp *** pursuit(MP)is used as a reconstruction *** reconstructed signal uses polar format algorithm(PFA)for *** our novel mechanism increases the system complexity to an extent,the data storage requirements can be compressed *** simulations verify the feasibility and accuracy of spotlight SAR signal processing via compressive sensing,and the method still obtains acceptable imaging results with 10%of the original echo data.

关键词： spotlight SAR dechirp processing compressive sensing radar signal processing

Complexity of synthesis of composite service with correctness guarantee

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Science china(information Sciences) 2012年第3期55卷 638-649页

作者： DENG Ting1,2 , HUAI JinPeng1,3 & WO TianYu1,3 1State Key Laboratory of Software Development Environment, beihang university beijing 100191, china 2School of Mathematics and System Science, beihang university, beijing 100191, china 3School of Computer Science and engineering, beihang university, beijing 100191, china State Key Laboratory of Software Development Environment Beihang University Beijing China School of Mathematics and System Science Beihang University Beijing China School of Computer Science and engineering Beihang University Beijing China

How to compose existing web services automatically and to guarantee the correctness of the design (e.g. temporal constraints specified by temporal logic LTL, CTL or CTL*) is an important and challenging problem in web services. Most existing approaches use the process in conventional software development of design, verification, analysis and correction to guarantee the correctness of composite services, which makes the composition process both complex and time-consuming. In this paper, we focus on the synthesis problem of composite service; that is, for a given set of services and correctness constraint specified by CTL or CTL* formula, a composite service is automatically constructed which guarantees that the correctness is ensured. We prove that the synthesis problem for CTL and CTL* are complete for EXPTIME and 2EXPTIME, respectively. Moreover, for the case of synthesis failure, we discuss the problem of how to disable outputs of environment (i.e. users or services) reasonably to make synthesis successful, which are also proved complete for EXPTIME and 2EXPTIME for CTL and CTL*, respectively.

关键词： business protocol composite service synthesis environment branching temporal logic

Evolution and stability of Linux kernels based on complex networks

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Science china(information Sciences) 2012年第9期55卷 1972-1982页

作者： WANG Lei,WANG Zheng,YANG Chen & ZHANG Li School of Computer Science and engineering,beihang university,beijing 100191,china School of Computer Science and engineering Beihang University Beijing China

This paper presents a novel method to study Linux kernel evolution using complex *** investigated the node degree distribution and average path length of the call graphs corresponding to the kernel modules of 223 different versions(V1.1.0 to V2.4.35),we found that the call graphs are scale-free and smallworld *** on the relationship between average path length and nodes,we propose a method to find unusual points during Linux kernel evolution using the slope of the average path *** the unusual points we identify major structural changes in kernel modules.A stability coefficient is also proposed to describe quantitatively the stability of kernel modules during ***,we verify our result through Vasa’s metrics method.

关键词： complex networks operating system scale-free networks small-world networks average path length

Logical verification of scientific discovery

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Science china(information Sciences) 2010年第4期53卷 677-684页

作者： LI Wei State Key Laboratory of Software Development Environment, School of Computer Science and engineering, beihang university, beijing 100191, china State Key Laboratory of Software Development Environment School of Computer Science and Engineering Beihang University Beijing China

This paper shows that the discovery processes of Einstein’s special theory of relativity and Darwin’s theory of evolution of species can be formally verified by R-calculus which is a logical inference system. The aim of R-calculus is to delete the principles of scientific theories which contradict empirical evidence. The paper shows that the special theory of relativity is the only and correct choice for physics to meet the experimental evidence given at the time. As far as the biology of Darwin’s time is concerned, however, the R-calculus has derived three logically correct but different theories, which are all consistent with the empirical evidence provided by Darwin and his principle of natural selection. Darwin’s theory of evolution matches one of the three theories derived by R-calculus. This theory has a logical consequence that is "each species has been independently created is erroneous". But the other two theories support the negation of the above statement. The existence of the other two theories may be a reason of the controversies over Darwin’s theory.

关键词： R-calculus theory of relativity theory of evolution

A new approach for generating function sequences——Hybrid Bridge functions derived from Walsh functions

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Progress in Natural Science:Materials International 2009年第9期19卷 1153-1158页

作者： Yan Li, Qing Chang*, Qishan Zhang School of Electronic and information engineering, beihang university, beijing 100083, china School of Electronic and information engineering Beihang University Beijing 100083 China

This paper reviews the essence of the Walsh and Bridge functions from the point of view of the recursive relationship; it also unifies their expressions. A new kind of function-the hybrid Bridge function-is constructed from the definition of the hybrid matrix, in which the row vectors are taken from the Walsh and Bridge function matrices. We also propose a new approach for generating function sequences; one that uses the column vectors of the hybrid Bridge function matrix as the new function sequences. These sequences are able to adjust the number of zeroes flexibly; thus, resolving the constraint on the application of excessive zeroes in Bridge function sequences, while at the same time maximizing the research field for function sequences. Through strict mathematical analysis, it is proved that when the initial matrix order of the parent matrices and the similarity of the hybrid matrices meet certain conditions, the hybrid function sequences exhibit good orthogonal characteristics. This provides a theoretical basis for its further applications in communication systems.

关键词： Copy theory Walsh functions Bridge functions Hybrid Bridge functions

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

Max-Min Adaptive Ant Colony Optimization Approach to Multi-UAVs Coordinated Trajectory Replanning in Dynamic and Uncertain Environments

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Journal of Bionic engineering 2009年第2期6卷 161-173页

作者： Hai-bin Duan,Xiang-yin Zhang,Jiang Wu,Guan-jun MaSchool of Automation Science and Electrical engineering,beihang university,beijing 100191,P.R.china School of Automation Science and Electrical engineering Beihang University Beijing P. R. China

Multiple Uninhabited Aerial Vehicles (multi-UAVs) coordinated trajectory replanning is one of the most complicated global optimum problems in multi-UAVs coordinated control. Based on the construction of the basic model of multi-UAVs coordinated trajectory replanning, which includes problem description, threat modeling, constraint conditions, coordinated function and coordination mechanism, a novel Max-Min adaptive Ant Colony Optimization (ACO) approach is presented in detail. In view of the characteristics of multi-UAVs coordinated trajectory replanning in dynamic and uncertain environments, the minimum and maximum pheromone trails in ACO are set to enhance the searching capability, and the point pheromone is adopted to achieve the collision avoidance between UAVs at the trajectory planner layer. Considering the simultaneous arrival and the air-space collision avoidance, an Estimated Time of Arrival (ETA) is decided first. Then the trajectory and flight velocity of each UAV are determined. Simulation experiments are performed under the complicated combating environment containing some static threats and popup threats. The results demonstrate the feasibility and the effectiveness of the proposed approach.

关键词： Multiple Uninhabited Aerial Vehicles (multi-UAVs) Ant Colony Optimization (ACO) trajectory replanning collision avoidance Estimated Time of Arrival (ETA)

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