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5th European Conference on computer Vision, ECCV 1998

作者： Irani, M. Anandan, P. Weinshall, D. Dept. of Applied Math and CS The Weizmann Inst. of Science Rehovot Israel Microsoft Research One Microsoft Way RedmondWA98052 United States Institute of Computer Science Hebrew University Jerusalem91904 Israel

ISBN: (纸本)3540646132

This paper presents a new framework for analyzing the geometry of multiple 3D scene points from multiple uncalibrated images, based on decomposing the projection of these points on the images into two stages: (i) the projection of the scene points onto a (real or virtual) physical reference planar surface in the scene;this creates a virtual "image" on the reference plane, and (ii) the re-projection of the virtual image onto the actual image plane of the camera. The positions of the virtual image points are directly related to the 3D locations of the scene points and the camera centers relative to the reference plane alone. All dependency on the internal camera calibration parameters and the orientation of the camera are folded into homographies relating each image plane to the reference plane. Bi-linear and tri-linear constraints involving multiple points and views are given a concrete physical interpretation in terms of geometric relations on the physical reference plane. In particular, the possible dualities in the relations between scene points and camera centers are shown to have simple and symmetric mathematical forms. In contrast to the plane+parallax (p+p) representation, which also uses a reference plane, the approach described here removes the dependency on a reference image plane and extends the analysis to multiple views. This leads to simpler geometric relations and complete symmetry in multi-point multiview duality. The simple and intuitive expressions derived in the reference-plane based formulation lead to useful applications in 3D scene analysis. In particular, simpler tri-focal constraints are derived that lead to simple methods for New View Synthesis. Moreover, the separation and compact packing of the unknown camera calibration and orientation into the 2D projection transformation (a homography) allows also partial reconstruction using partial calibration information. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Geometry

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From ordinal to euclidean reconstruction with partial scene calibration

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Workshop on 3D Structure from Multiple Images of Large-Scale Environments, SMILE 1998

作者： Weinshall, Daphna Anandan, P. Irani, Michal Institute of Computer Science Hebrew University Jerusalem91904 Israel Microsoft Research One Microsoft Way RedmondWA98052 United States Dept. of Applied Math and CS The Weizmann Inst. of Science Rehovot Israel

ISBN: (纸本)3540653104

Since uncalibrated images permit only projective reconstruction, metric information requires either camera or scene calibration. We propose a stratiﬁed approach to projective reconstruction, in which gradual increase in domain information for scene calibration leads to gradual increase in 3D information. Our scheme includes the following steps: (1) Register the images with respect to a reference plane;this can be done using limited scene information, e.g., the knowledge that two pairs of lines on the plane are parallel. We show that this calibration is suﬁcient for ordinal reconstruction - sorting the points by their height over the reference plane. (2) If available, use the relative height of two additional out-of-plane points to compute the height of the remaining points up to constant scaling. Our scheme is based on the dual epipolar geometry in the reference frame, which we develop below. We show good results with ﬁve sequences of real images, using mostly scene calibration that can be inferred directly from the images themselves. © Springer-Verlag Berlin Heidelberg 1998.

关键词： Calibration

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A precise characterization of the class of languages recognized by neural nets under Gaussian and other common noise distributions 98

A precise characterization of the class of languages recogni...

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Proceedings of the 12th International Conference on Neural Information Processing Systems

作者： Wolfgang Maass Eduardo D. Sontag Inst. for Theoretical Computer Science Technische Universität Graz Graz Austria Dep. of Mathematics Rutgers University New Brunswick NJ

We consider recurrent analog neural nets where each gate is subject to Gaussian noise, or any other common noise distribution whose probability density function is nonzero on a large set. We show that many regular languages cannot be recognized by networks of this type, for example the language {w ε {O, I}*| w begins with O}, and we give a precise characterization of those languages which can be recognized. This result implies severe constraints on possibilities for constructing recurrent analog neural nets that are robust against.realistic types of analog noise. On the other hand we present a method for constructing feed forward analog neural nets that are robust with regard to analog noise of this type.

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Multext-east: Parallel and comparable corpora and lexicons for six central and Eastern European languages 36

Multext-east: Parallel and comparable corpora and lexicons f...

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36th Annual Meeting of the Association for Computational Linguistics and 17th International Conference on Computational Linguistics, COLING-ACL 1998

作者： Dimitrova, Ludmila Erjavec, Tomaz Ide, Nancy Kaalep, Heiki Jaan Petkevic, Vladimir Tufts, Dan Institute of Mathematics and Informatics Sofia Bulgaria Institute Jozef Stefan Ljubljana Slovenia Dept. of Computer Science Vassar College PoughkeepsieNY United States Dept. of General Linguistics University of Tartu Tartu Estonia Inst. of Theoretical and Computational Linguistics Charles University Prague Czech Republic Romanian Academy Center for Artificial Intelligence Bucharest Romania

The EU Copernicus project Multext-East has created a multi-lingual corpus of text and speech data, covering the six languages of the project: Bulgarian, Czech, Estonian, Hungarian, Romanian, and Slovene. In addition, wordform lexicons for each of the languages were developed. The corpus includes a parallel component consisting of Orwell's Nineteen Eighty-Four, with versions in all six languages tagged for part-of-speech and aligned to English (also tagged for POS). We describe the encoding format and data architecture designed especially for this corpus, which is generally usable for encoding linguistic corpora. We also describe the methodology for the development of a harmonized set of morphosyntactic descriptions (MSDs), which builds upon the scheme for western European languages developed within the EAGLES project. We discuss the special concerns for handling the six project languages, which cover three distinct language families. © COLING-ACL *** right reserved.

关键词： Signal encoding

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Atmospheric optical properties over the Russian Steppe during summer

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Remote Sensing Reviews 1998年第1-4期17卷 221-238页

作者： Halthore, Rangasayi N. Kozoderov, Vladimir V. Nezval, Eleana I. Chubarova, Natalia E. Shljakhova, Ludmila A. Markham, Brian L. Department of Applied Science Brookhaven National Laboratory Upton NY 11973-5000 United States Inst. of Computational Mathematics Russian Academy of Sciences Leninsky Prospect 32A Moscow 117334 Russia Meteorol. Observ. Moscow Stt. Univ. Leninskiye Gory Moscow 119899 Russia Regional Donecocenter Prospect Sokolova 52 Rostov-on-Don 344700 Russia Biospheric Sciences Branch NASA Goddard Space Flight Center Greenbelt MD 20771 United States

Atmospheric transmittance is estimated by measuring the direct-normal solar irradiance at the surface by a sun-photometer or a spectro-radiometer. Both of these types of inst.uments were used to determine the most variable components of the atmospheric transmission, aerosol optical thickness (AOT) and precipitable water vapor (PW) in cm, during an international field experiment, KUREX'91, held in July, 1991 in the Streletskaya Steppe Biospheric Reserve near Kursk, Russia. A narrow field of view sun-photometer provided AOT in 7 discrete spectral channels from 440-nm to 1030-nm and PW from observations in the 940-nm channel. A spectro-radiometer provided AOT at 70 spectral intervals in the 380-nm to 550-nm range. The latter also provided measurements of diffuse sky irradiance at the surface. Both the inst.uments were calibrated by the Langley plot method or the long-Bouguer method as it is known in the Russian literature. The derived AOT are inverted to obtain aerosol size distribution with the help of an algorithm based on Twitty's method. Size distributions derived by extinction measurements are compared with those derived from aureole measurements. Results from KUREX'91 show that on some days a significant portion of aerosols may be mono-disperse, indicating their anthropogenic origin.

关键词： Remote sensing

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Unitals and unitary polarities in symmetric designs

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Designs, Codes, and Cryptography 1997年第2期10卷 237-237页

作者： Mathon, Rudolf van Trung, Tran Department of Computer Science University of Toronto Toronto Ont. M5S1A4 Canada Inst. for Experimental Mathematics University of Essen 45326 Essen Ellernstrasse 29 Germany

We extend the notion of unital as well as unitary polarity from finite projective planes to arbitrary symmetric designs. The existence of unitals in several families of symmetric designs has been proved. It is shown that if a unital in a point-hyperplane design PG d-1(d,q) exists, then d = 2 or 3; in particular, unitals and ovoids are equivalent in case d = 3. Moreover, unitals have been found in two designs having the same parameters as the PG 4(5,2), although the latter does not have a unital. It had been not known whether or not a nonclassical design exists, which has a unitary polarity. Fortunately, we have discovered a unitary polarity in a symmetric 2-(45,12,3) design. To a certain extent this example seems to be exceptional for designs with these parameters.

关键词： Symmetric design Unital Unitary polarity

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Visibility Computations on Hierarchical Triangulated Terrain Models

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GeoInformatica 1997年第3期1卷 219-250页

作者： De Floriani, Leila Magillo, Paola Dipto. Info. Sci. dell'Informazione Università di Genova 16146 Genova Via Dodecanese 35 Italy Department of Computer Science University of Genova Italy University of Genova Italy Institute for Applied Mathematics Italian National Research Council Genova Italy Department of Mathematics University of Genova Italy Institute of Applied Mathematics Italian National Research Council Italy ACM IEEE Computer Society Intl. Assoc. for Pattern Recognition Italy University of Genova Italy Inst. Natl. Rech. Info. et Automat. Sophia Antipolis France Dept. of Comp. and Info. Sciences University of Genova Italy Intl. Assoc. for Pattern Recognition Italy

Hierarchical terrain models provide a multiresolution description of a topographic surface based on a nested partition of the domain. The tree-like structure of these models is an effective support to processing spatial operations. In this paper, we consider visibility computations on hierarchical terrain models based on triangular subdivisions, called Hierarchical Triangulated Irregular Networks (HTINs). We address two basic problems in visibility computation, namely determining the visibility of a query object, and computing the viewshed of a given viewpoint. We propose algorithms for performing such operations on an HTIN at variable resolution. A general drawback of hierarchical models is in the inconsistency of representations at variable resolution obtained from them, since vertical gaps may occur at edges where different resolutions meet. The algorithms proposed here avoid this undesired effect. A related, but independent, contribution of this paper is also a new algorithm for extracting a consistent terrain representation at variable resolution from an HTIN.

关键词： Data structures and algorithms Hierarchical terrain models Multiresolution representations Visibility computation

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RSN1-tt (NP) distinguishes robust many-one and Turing completeness 3rd

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3rd Italian Conference on Algorithms and Complexity, CIAC 1997

作者： Hemaspaandra, Edith Hemaspaandra, Lane A. Hempel, Harald Department of Mathematics Le Moyne College SyracuseNY13214 United States Department of Computer Science University of Rochester RochesterNY14627 United States Inst. für Informatik Friedrich-Schiller-Universität Jena Jena07743 Germany

ISBN: (纸本)3540625925

Do complexity classes have many-one complete sets if and only if they have Turing-complete sets? We prove that there is a relativized world in which a relatively natural complexity class—namely a downward closure of NP, RSN1-tt (NP)—has Turing-complete sets but has no many-one complete sets. In fact, we show that in the same relativized world this class has 2-truth-table complete sets but lacks 1-truth-table complete sets. As part of the groundwork for our result, we prove that RSN1-tt (NP) has many equivalent forms having to do with ordered and parallel access to NP and NP ∩ coNP. © Springer-Verlag Berlin Heidelberg 1997.

关键词： Computational complexity

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A downward translation in the polynomial hierarchy 14th

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14th Annual Symposium on Theoretical Aspects of computer science, STACS 1997

ISBN: (纸本)9783540626169

Downward translation (a.k.a. upward separation) refers to cases where the equality of two larger classes implies the equality of two smaller classes. We provide the first unqualified downward translation result completely within the polynomial hierarchy. In particular, we prove that, for k>2, where the "[1]" (respectively, "[2]") denotes that at most one query is (respectively, two queries are) allowed. We also extend this to obtain a more general downward translation result. © Springer-Verlag Berlin Heidelberg 1997.

关键词： Artificial intelligence

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Query order in the polynomial hierarchy 11th

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11th International Symposium on Fundamentals of Computation Theory, FCT 1997

作者： Hemaspaandra, Edith Hemaspaandra, Lane A. Hempel, Harald Department of Mathematics Le Moyne College SyracuseNY13214 United States Department of Computer Science University of Rochester RochesterNY14627 United States Inst. für Informatik Eriedrich-Schiller-Universität Jena Jena07743 Germany

ISBN: (纸本)3540633863

The study of query order was initiated by Hemaspaandra, Hempel, and Wechsung [HHW]. Their goal was to learn whether the order of access to information sources affects the class of problems that can be solved. They showed that in the boolean hierarchy over NP, order matters. In the present paper, we study the power of query order when accessing levels of the polynomial hierarchy, and we show that here order does not matter. In particular, let PC:D denote the class of languages computable by a polynomial-time machine that is allowed one query to C followed by one query to V [HHW]. We prove that the levels of the polynomial hierarchy are order-oblivious: PΣpj:Σpk=PΣpj:Σpj. Yet, we also show that these ordered query classes form new levels in the polynomial hierarchy unless the polynomial hierarchy collapses. We prove that a wide range of other classes (UP, BPP, ⊕P, PP, etc.) inherit all order-obliviousness results that hold for deterministic polynomialtime transducers. © Springer-Verlag Berlin Heidelberg 1997.

关键词： Polynomial approximation

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