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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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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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Use your hand as a 3-D mouse, or, relative orientation from extended sequences of sparse point and line correspondences using the affine trifocal tensor 5th

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5th European Conference on Computer Vision, ECCV 1998

作者： Bretzner, Lars Lindeberg, Tony Dept. of Numerical Analysis and Computing Science KTH StockholmS-100 44 Sweden

ISBN: (纸本)3540645691

This paper addresses the problem of computing three-dimensional structure and motion from an unknown rigid configuration of point and lines viewed by an affine projection model. An algebraic structure, analogous to the trilinear tensor for three perspective cameras, is defined for configurations of three centered affine cameras. This centered affine trifocal tensor contains 12 non-zero coefficients and involves linear relations between point correspondences and trilinear relations between line correspondences. It is shown how the affine trifocal tensor relates to the perspective trilinear tensor, and how three-dimensional motion can be computed from this tensor in a straightforward manner. A factorization approach is also developed to handle point features and line features simultaneously in image sequences. This theory is applied to a specific problem in human-computer interaction of capturing three-dimensional rotations from gestures of a human hand. Besides the obvious application, this test problem illustrates the usefulness of the affine trifocal tensor in a situation where sufficient information is not available to compute the perspective trilinear tensor, while the geometry requires point correspondences as well as line correspondences over at least three views. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Tensors

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Symmetry in perspective 5th

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5th European Conference on Computer Vision, ECCV 1998

作者： Carlsson, Stefan Numerical Analysis and Computing Science Royal Institute of Technology KTH StockholmS-100 44 Sweden

ISBN: (纸本)3540645691

When a symmetric object in 3D is projected to an image, the symmetry properties are lost except for specific relative viewpoints. For sufficiently complex objects however, it is still possible to infer symmetry in 3D from a single image of an uncalibrated camera. In this paper we give a general computational procedure for computing 3D structure and finding image symmetry constraints from single view projections of symmetric 3D objects. For uncalibrated cameras these constraints take the form of polynomials in brackets (determinants) and by using projectively invariant shape constraints relating 3D and image structure, the symmetry constraints can be derived easily by considering the effects of the corresponding symmetry transformation group in 3D. The constraints can also be given a useful geometric interpretation in terms of projective incidence using the Grassmann-Cayley algebra formalism. We demonstrate that in specific situations geometric intuition and the use of GC-algebra is a very simple and effective tool for finding image symmetry constraints. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Algebra

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Factors of generalized fermat numbers

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MATHEMATICS OF COMPUTATION 1998年第221期67卷 441-446页

作者： Bjorn, A Riesel, H Department of Mathematics Linköping University S-581 83 Linköping Sweden Department of Numerical Analysis and Computing Science Royal Institute of Technology S-100 44 Stockholm Sweden

Abstract: A search for prime factors of the generalized Fermat numbers $F_n(a,b)=a^{2^n}+b^{2^n}$ has been carried out for all pairs $(a,b)$ with $a,b\leq 12$ and GCD$(a,b)=1$. The search limit $k$ on the factors, which all have the form $p=k\cdot 2^m+1$, was $k=10^9$ for $m\leq 100$ and $k=3\cdot 10^6$ for $101\leq m\leq 1000$. Many larger primes of this form have also been tried as factors of $F_n(a,b)$. Several thousand new factors were found, which are given in our tables.—For the smaller of the numbers, i.e. for $n\leq 15$, or, if $a,b\leq 8$, for $n\leq 16$, the cofactors, after removal of the factors found, were subjected to primality tests, and if composite with $n\leq 11$, searched for larger factors by using the ECM, and in some cases the MPQS, PPMPQS, or SNFS. As a result all numbers with $n\leq 7$ are now completely factored.

关键词： Fermat numbers primes factorization

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Fitting points on the real line and its application to RH mapping

Fitting points on the real line and its application to RH ma...

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6th Annual European Symposium on Algorithms, ESA 1998

作者： Håstad, Johan Ivansson, Lars Lagergren, Jens Department of Numerical Analysis and Computing Science Royal Institute of Technology SE-100 44 Stockholm Sweden

ISBN: (纸本)3540648488

The Matrix-To-Line problem is that of, given an n × n symmetric matrix D, finding an arrangement of n points on the real line such that the so obtained distances agree as well as possible with the by D specified distances, w.r.t. the max-norm. The Matrix-To-Line problem has previously been shown to be NP-complete [11]. We show that it can be approximated within 2, but not within 4/3 unless P=NP. We also show tight bounds under a stronger assumption. We show that the Matrix-To-Line problem cannot be approximated within 2 - δ unless 3-colorable graphs can be colored with [4/δ] colors in polynomial time. Currently, the best polynomial time algorithm colors a 3-colorable graph with Õ(n3/14) colors [4]. We apply our Matrix-To-Line algorithm to a problem in computational biology, namely, the Radiation Hybrid (RH) problem, i.e., the algorithmic part of a physical mapping method called RH mapping. This gives us the first algorithm with a guaranteed convergence for the general RH problem. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Color

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On the power of a threshold gate at the top

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INFORMATION PROCESSING LETTERS 1997年第6期63卷 287-293页

作者： Goldmann, M Department of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden

The discriminator lemma is normally used to prove lower bounds for circuits with small-weight threshold gates. In this note we adapt the lemma to circuits with a general (large-weight) threshold gate at the top. The new lemma is used to give a new proof of a previously known lower bound for the size of a threshold of parity gates that computes inner product mod 2, and to prove that a small-depth AND-OR circuit for parity must have exponential size even if we allow a threshold gate at the top. The latter result is a generalization to large weights of a result by Green, and depends heavily on Hastad's switching-lemma. (C) 1997 Elsevier science B.V.

关键词： circuit complexity computational complexity threshold circuits

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Segmentation and classification of edges using minimum description length approximation and complementary junction cues

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COMPUTER VISION AND IMAGE UNDERSTANDING 1997年第1期67卷 88-98页

作者： Lindeberg, T Li, MX Computational Vision and Active Perception Laboratory (CVAP) Department of Numerical Analysis and Computing Science Royal Institute of Technology S-100 44 Stockholm Sweden

This article presents a method for segmenting and classifying edges using minimum description length (MDL) approximation with automatically generated break points. A scheme is proposed where junction candidates are first detected in a multiscale preprocessing step, which generates junction candidates with associated regions of interest. These junction features are matched to edges based on spatial coincidence, For each matched pair, a tentative break point is introduced at the edge point closest to the junction. Finally, these feature combinations serve as input for an MDL approximation method which tests the validity of the break point hypotheses and classifies the resulting edge segments as either ''straight'' or ''curved.'' Experiments on real world image data demonstrate the viability of the approach. (C) 1997 Academic Press.

关键词： Edge detection

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