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Conference on Computer Vision and Pattern Recognition (CVPR)

作者： M. Bjorkman J.-O. Eklundh Computational Vision and Active Perception Laboratory CVAP Department of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden

A visually guided mobile platform acting in a dynamic environment needs information, delivered from cues such as stereo and motion. In this paper a binocular stereo system, capable of dynamic vergence and ego-motion estimation, will be presented. The ability to dynamically verge the cameras is essential for visual tasks such as tracking, recognition and manipulation, since the computation of 3D geometry will be considerably simplified at fixation. We will show that the epipolar geometry of the presented system can be estimated in real-time. The number of degrees of freedom has been minimized, without affecting the flexibility of the system. Reconstructed 3D data is used in order to determine the ego-motion of the platform, at a very low computational cost. Finally, it will be shown how disparity maps and estimated ego-motion can facilitate the localization of independently moving objects.

关键词： Real time systems Cameras Computer vision Stereo vision Robot vision systems Motion estimation Computational geometry Calibration Counting circuits numerical analysis

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Vibrational properties of the one-component σ phase

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Physical Review B 2000年第5期62卷 3223-3223页

作者： S. I. Simdyankin S. N. Taraskin M. Dzugutov S. R. Elliott Department of Numerical Analysis and Computing Science Royal Institute of Technology SE–100 44 Stockholm Sweden Department of Chemistry University of Cambridge Lensfield Road Cambridge CB2 1EW United Kingdom

A structural model of a one-component σ-phase crystal has been constructed by means of molecular dynamics simulation. The phonon dispersion curves and the vibrational density of states were computed for this model. The dependence of the vibrational properties on the thermodynamical parameters was investigated. The vibrational density of states of the σ-phase structure is found to be similar to that of a one-component glass with icosahedral local order. On the basis of this comparison it is concluded that the σ phase can be considered to be a good crystalline reference structure for this glass.

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Real-time maintenance of figure-ground segmentation 1st

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1st International Conference on Computer Vision Systems, ICVS 1999

作者： Nordlund, Peter Eklundh, Jan-Olof Department of Numerical Analysis and Computing Science Royal Institute of Technology StockholmS-100 44 Sweden

ISBN: (纸本)3540654593

An approach to figure-ground segmentation based on a 2-dimensional histogram in feature space is presented. The histogram is then analyzed with a peak-finding algorithm designed with real-time performance in mind. The most significant peaks in the histogram are back-projected to the image to produce an object mask. The method is applied to segmentation based on a 2-D color space and also on a combination of motion and stereo disparities. Experiments with a system grabbing images direct from a CCD-camera with real-time performance having typical frame-rates of about 10 Hz is presented. © Springer-Verlag Berlin Heidelberg 1999.

关键词： CCD cameras

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NLC2-decomposition in polynomial time 25th

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25th International Workshop on Graph-Theoretic Concepts in Computer science, WG 1999

作者： Johansson, Öjvind Department of Numerical Analysis and Computing Science Royal Institute of Technology StockholmSE-100 44 Sweden

ISBN: (纸本)3540667318

NLCk is a family of algebras on vertex-labeled graphs introduced by Wanke. An NLC-decomposition of a graph is a derivation of this graph from single vertices using the operations in question. The width of the decomposition is the number of labels used, and the NLC-width of the graph is the smallest width among its NLC-decompositions. Many difficult graph problems can be solved efficiently with dynamic programming if an NLC-decomposition of low width is given for the input graph. It is unknown though whether arbitrary graphs of NLC-width at most k can be decomposed with k labels in polynomial time. So far this has been possible only for k = 1, which corresponds to cographs. In this paper, an algorithm is presented that works for k = 2. It runs in O(n4log n)time and uses O(n2) space. Related concepts: clique-decomposition, clique-width. © Springer-Verlag Berlin Heidelberg 1999.

关键词： Dynamic programming

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Integration of visual cues for active tracking of an end-effector

Integration of visual cues for active tracking of an end-eff...

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IEEE International Workshop on Intelligent Robots and Systems (IROS)

作者： D. Kragic H.I. Christensen Computational Vision and Active Perception Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden Centre for Autonomous Systems Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden

We describe and test how information from multiple sources can be combined into a robust visual servoing system. The main objective is integration of visual cues to provide smooth pursuit in a cluttered environment using a minimum or no calibration. For that purpose, voting schema and fuzzy logic command fusion are investigated. It is shown that the integration permits detection and rejection of measurement outliers.

关键词： Robustness Computer vision Voting Visual servoing numerical analysis Robot sensing systems Control systems Cameras System testing Fuzzy logic

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A person following behaviour for a mobile robot

A person following behaviour for a mobile robot

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IEEE International Conference on Robotics and Automation (ICRA)

作者： H. Sidenbladh D. Kragic H.I. Christensen Computer Vision and Active Perception Lab Department of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden Centre for Autonomous Systems Department of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden

In this paper, a person following behaviour for a mobile robot is presented. The head of the person is located using skin colour detection. Then, a control loop is fed with the camera movements required to put the upper part of the person in the center of the image. The algorithm was tested in different rooms of a research lab. It performed well in all lighting conditions except in direct sunlight. Since the background and lighting cannot be controlled, the vision algorithm must be robust to such changes. However, since the computing power is quite limited, the algorithm must have as low complexity as possible.

关键词： Mobile robots Robot vision systems Cameras Computer vision Skin Image motion analysis numerical analysis Lighting control Humans Machine vision

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Design of an Internet accessible visual human brain database system

Design of an Internet accessible visual human brain database...

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IEEE International Conference on Multimedia computing and Systems (ICMCS)

作者： J. Fredriksson Department of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Division of Human Brian Research Karolinska Institute Stockholm Sweden

We present the ECHBD system as a new approach to the neuroscientific discipline of brainmapping. The complexity of the brain and the potentially vast amount of brain measurement data collected, shared, and analyzed by many different research groups make experimental brain research a key area for use of multimedia database systems in the role of environments for experimental science. The neuroscientific research community has created a demand for such a system, capable of supporting analysis of 3D images of the brain, where ease of use and visual navigation are key issues. The focus of the paper is on how to handle large raster data sets in object oriented databases, visual interaction and Internet accessible research environments.

关键词： Internet Humans Database systems Image databases Visual databases Environmental management Neuroscience numerical analysis Area measurement Multimedia databases

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Linear consistency testing 3rd

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3rd International Workshop on Randomization and Approximation Techniques in Computer science and 2nd International Workshop on Approximation Algorithms for Combinatorial Optimization Problems, RANDOM-APPROX 1999

作者： Aumann, Yonatan Håstad, Johan Rabin, Michael O. Sudany, Madhu Department of Mathematics and Computer Science Bar-Ilan University Ramat-Gan52900 Israel Department of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden DEAS Harvard University CambridgeMA02138 United States Institute of Computer Science Hebrew University Jerusalem Israel Department of Electrical Engineering and Computer Science MIT 545 Technology Square CambridgeMA02139 United States

ISBN: (纸本)3540663290

We extend the notion of linearity testing to the task of checking linear-consistency of multiple functions. Informally, functions are "linear" if their graphs form straight lines on the plane. Two such functions are "consistent" if the lines have the same slope. We propose a variant of a test of Blum, Luby and Rubinfeld [8] to check the linear- consistency of three functions f1;f2;f3 mapping a finite Abelian group G to an Abelian group H: Pick x;y ϵ G uniformly and independently at random and check if f1(x) + f2(y) = f3(x + y). We analyze this test for two cases: (1) G and H are arbitrary Abelian groups and (2) G = {formula presened} and H = F2. Questions bearing close relationship to linear-consistency testing seem to have been implicitly considered in recent work on the construction of PCPs (and in particular in the work of Håstad [9]). It is abstracted explicitly for the first time here. We give an application of this problem (and of our results): A (yet another) new and tight characterization of NP, namely 8∀ ϵ> 0;NP = MIP{formula presnted}. I.e., every language in NP has 3-prover 1-round proof systems in which the verifier tosses O(log n) coins and asks each of the three provers one question each. The provers respond with one bit each such that the verifier accepts instance of the language with probability 1–ϵ and rejects non-instances with probability at least {formula presented}. Such a result is of some interest in the study of probabilistically checkable proofs. © Springer-Verlag Berlin Heidelberg 1999.

关键词： Group theory

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The complexity of solving equations over finite groups

The complexity of solving equations over finite groups

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Annual IEEE Conference on Computational Complexity

作者： M. Goldmann A. Russell Numerical Analysis and Computer Science Royal Institute of Technology Stockholm Sweden Computer Science Division University of California Berkeley CA USA

We study the computational complexity of solving systems of equations over a finite group. An equation over a group G is an expression of the form w/sub 1//spl middot/w/sub 2//spl middot//spl middot//spl middot//spl middot//spl middot/w/sub k/=id where each w/sub i/ is either a variable, an inverted variable, or group constant and id is the identity element of G. A solution to such an equation is an assignment of the variables (to values in G) which realizes the equality. A system of equations is a collection of such equations; a solution is then an assignment which simultaneously realizes each equation. We demonstrate that the problem of determining if a (single) equation has a solution is NP-complete for all nonsolvable groups G. For nilpotent groups, this same problem is shown to be in P. The analogous problem for systems of such equations is shown to be NP-complete if G is non-Abelian, and in P otherwise. Finally, we observe some connections between these languages and the theory of nonuniform automata.

关键词： Equations Computer science numerical analysis Tellurium Reactive power Automata Machinery

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Rationale and design of the European Computerized Human Brain Database System

Rationale and design of the European Computerized Human Brai...

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International Working Conference on Scientific and Statistical Database Management

作者： J. Fredriksson P. Roland P. Svensson Dept. of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Div. of Human Brain Research Dept. of Neuroscience Karolinska Institute Stockholm Dept. of Information Systems Technology Defence Research Establishment Stockholm

The European Computerized Human Brain Database (ECHBD) is an innovative approach to neuroscience, where state-of-the-art database technology has been utilised for building a system for meta-research. Meta-research here refers to research on 3D brain images, obtained from various neuroimaging techniques. The system is built on top of the RASDAMAN rasterdata manager and the object-oriented DBMS O/sub 2/. A client/server interface allows access to the database over the Internet. The system will be open for use by the ECHBD project partners in July 1999. The ECHBD system focuses on ease of use, featuring visual navigation and query specification. We discuss basic data management problems in experimental neuroscience and describe how the ECHBD system is designed to address these problems.

关键词： Humans Image databases Object oriented databases Neuroscience Buildings Brain Neuroimaging Web server Spatial databases Visual databases

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