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  • Articles  (132)
  • Articles: DFG German National Licenses  (132)
  • Computational geometry  (117)
  • Molecular Sequence Data
  • Seismology
  • Computer Science  (117)
  • Geosciences  (15)
  • 1
    Electronic Resource
    Electronic Resource
    Earthquake induced damage in an historic area: the September–October 1997 seismic sequence which affected Assisi, Central Italy (1998)
    Springer
    Bulletin of engineering geology and the environment 57 (1998), S. 101-109 
    Details
    ISSN: 1435-9537
    Keywords: Key words Assisi Earthquake ; Seismology ; Historic buildings ; Umbria-Marche ; Seismic microzonation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé La sequence sismique de septembre–octobre 1997 qui a affecté l'une des régions historiques les plus importantes d'Italie Centrale a mis en évidence que l'impact économique des tremblements de terre de magnitude modérée peut être considérable. En ce qui concerne la vulnerabilité du patrimoine artistique et architectural, on a constaté que des trésors inestimables pouvaient subir des dégâts importants même lors de secousses modérées. On attire l'attention sur le fait qu'un microzonage sismique ne pourra être efficace que si l'on prend en compte non seulement l'activité sismique passée mais aussi l'historique des développements urbains.
    Notes: Abstract  The September–October 1997 seismic sequence in one of the most important historic areas of Central Italy showed that the economic impact of earthquakes of only moderate magnitude can be high. In view of the vulnerability of the artistic and architectural heritage, priceless treasures in such towns as Assisi are very susceptible to damage as a consequence of such seismic events. Attention is drawn to the fact that for seismic microzonation to be effective, it is essential that not only the past seismic activity but also the history of the urban developments is taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100640050026
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  • 2
    Electronic Resource
    Electronic Resource
    Rational parameterization of quadrics and their offsets (1996)
    Springer
    Computing 57 (1996), S. 135-147 
    Details
    ISSN: 1436-5057
    Keywords: 68U05 (14J26) ; Computational geometry ; triangular and quadrangular patches ; rational Bézier patches ; rational offsets ; quadrics ; rational parameterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Die Arbeit studiert zwei mit Quadriken in Zusammenhang stehenden Probleme. Einerseits werden quadratische Bézier Dreiecke auf Quadriken gekennzeichnet. Andererseits wird gezeigt, daß die Parallelflächen regulärer Flächen zweiter Ordnung stets rational sind, und es werden Algorithmen zur Berechnung der rationalen Parametrisierung angegeben.
    Notes: Abstract In this paper, we study two problems related to quadrics. One is the representation of triangular and quadrangular patches on quadrics: a necessary and sufficient condition is given for triangular patches on quadrics to be representable as rational quadratic triangular Bézier surfaces. The other is the rationality of the offsets to quadrics: the offsets of regular quadrics are shown to be rational and the algorithms are given for computing their rational parameterizations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276876
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  • 3
    Electronic Resource
    Electronic Resource
    Algorithm for constrained delaunay triangulation (1994)
    Springer
    The visual computer 10 (1994), S. 255-265 
    Details
    ISSN: 1432-2315
    Keywords: Delaunay triangulation ; Computational geometry ; Constrained triangulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A direct algorithm for computing constrained Delaunay triangulation in 2-D is presented. The algorithm inserts points along the constrained edges (break lines) to maintain the Delaunay criterion. Since many different insertions are possible, the algorithm computes only those that are on the Delaunay circles of each intersected triangle. A shelling procedure is applied to put triangles together in such a way that completeness and correctness are guaranteed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01901582
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  • 4
    Electronic Resource
    Electronic Resource
    Algorithms for computing the center of area of a convex polygon (1994)
    Springer
    The visual computer 10 (1994), S. 432-442 
    Details
    ISSN: 1432-2315
    Keywords: Computational geometry ; Center ; Partition ; Symmetry measure ; Winternitz
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The center of area of a convex polygonP is the unique pointp * that maximizes the minimum area overlap betweenP and any halfplane that includesp *. We show thatp * is unique and present two algorithms for its computation. The first is a combinatorial algorithm that runs in timeO (n 6 log2 n). The second is a “numerical” algorithm that runs in timeO(GK(n+K)) whereK represents the number of desired bits of precision in the output coordinates andG the number of bits used to represent the coordinates of the input polygon vertices. We conclude with a discussion of implementation issues and related results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01910633
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  • 5
    Electronic Resource
    Electronic Resource
    An algorithm for recognizing palm polygons (1994)
    Springer
    The visual computer 10 (1994), S. 443-451 
    Details
    ISSN: 1432-2315
    Keywords: Computational geometry ; Palm polygon ; Weak visibility polygon ; Visibility graph ; Kernel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A polygonP is said to be apalm polygon if there exists a pointx∈P such that the Euclidean shortest path fromx to any pointy∈P makes only left turns or only right turns. The set of all such pointsx is called thepalm kernel. In this paper we propose an O(E) time algorithm for recognizing a palm polygonP, whereE is the size of the visibility graph ofP. The algorithm recognizes the given polygonP as a palm polygon by computing the palm kernel ofP. If the palm kernel is not empty,P is a palm polygon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01910634
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  • 6
    Electronic Resource
    Electronic Resource
    Optimal algorithms for symmetry detection in two and three dimensions (1985)
    Springer
    The visual computer 1 (1985), S. 37-48 
    Details
    ISSN: 1432-2315
    Keywords: Symmetry ; Similarity ; Computational geometry ; Pattern matching ; Graph isomorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Exact algorithms for detecting all rotational and involutional symmetries in point sets, polygons and polyhedra are described. The time complexities of the algorithms are shown to be θ (n) for polygons and θ (n logn) for two- and three-dimensional point sets. θ (n logn) time is also required for general polyhedra, but for polyhedra with connected, planar surface graphs θ (n) time can be achieved. All algorithms are optimal in time complexity, within constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01901268
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  • 7
    Electronic Resource
    Electronic Resource
    Hidden-surface removal in polyhedral cross-sections (1988)
    Springer
    The visual computer 3 (1988), S. 329-343 
    Details
    ISSN: 1432-2315
    Keywords: Hidden-surface problems ; Computational geometry ; Priority orderings ; Decomposition techniques ; Dynamization techniques
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Many of the fundamental problems in computer graphics involve the notion of visibility. In one approach to the hiddensurface problem, priorities are assigned to the faces of a scene. A realistic image is then rendered by displaying the faces with the resulting priority ordering. We introduce a tree-based formalism for describing priority orderings that simplifies an existing algorithm. As well, a decompositionbased algorithm is presented for classes of scenes that do not in general admit priority orderings. The algorithm requiresO(n logn) time ift=1 andO(tn logn+n logn logm) time ift〉1, wheren andm are respectively the number of faces and polyhedra in the scene, andt is a minimum decomposition factor of the scene. Finally, the tree-based formalism is used in the development ofO(n) time insertion and deletion algorithms that solve the problem of dynamically maintaining a priority ordering.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01901191
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  • 8
    Electronic Resource
    Electronic Resource
    Visibility problems for orthogonal objects in two-or three-dimensions (1988)
    Springer
    The visual computer 4 (1988), S. 84-97 
    Details
    ISSN: 1432-2315
    Keywords: Visibility ; Hidden-line elimination ; Orthogonal objects ; Computational geometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract LetP be a set ofl points in 3-space, and letF be a set ofm opaque rectangular faces in 3-space with sides parallel tox- ory-axis. We present anO(n logn) time andO(n) space algorithm for determining all points inP which are visible from a viewpoint at (0,0,∞), wheren=l+m. We also present anO(n logn+k) time andO(n) space algorithm for the hidden-line elimination problem for the orthogonal polyhedra together with a viewpoint at (0,0,∞), wheren is the number of vertices of the polyhedra andk is the number of edge intersections in the projection plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01905560
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  • 9
    Electronic Resource
    Electronic Resource
    Applications of the 4×4 determinant method and the POLYGON ENGINE (1988)
    Springer
    The visual computer 4 (1988), S. 176-187 
    Details
    ISSN: 1432-2315
    Keywords: Interference problems ; Geometric modelling ; Computational geometry ; Solid modelling ; Hidden line and surface detections ; Geometry engine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract In the first half of the paper, various types of processing pertaining to a polygon, using the 4×4 determinant theories are explained along with a new containment test algorithm of a point in a polygon. In the latter half of the paper, a general-purpose geometric processor, the POLYGON ENGINE, is presented which can deal with various types of interference problems, such as Boolean operations in solid modelling, hidden line and surface eliminations, ray tracing and so on. It is, a successor of the TRIANGLE PROCESSOR and is also based upon the 4×4 determinant theories [4–6]. While the TRIANGLE PROCESSOR processes a triangulated polygon on a triangle-by-triangle basis, the POLYGON ENGINE can treat a polygon without triangulation. The latter is expected to be more functional, more efficient and easier to use.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01887590
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  • 10
    Electronic Resource
    Electronic Resource
    Recognizing polygons, or how to spy (1988)
    Springer
    The visual computer 3 (1988), S. 344-355 
    Details
    ISSN: 1432-2315
    Keywords: Computational geometry ; Geometric algorithms ; Complexity ; Polygon recognition ; Star-shapedness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A new class of so-called pseudo-starshaped polygons is introduced. A polygon is pseudo-star-shaped if there exists a point from which the whole interior of the polygon can be seen, provided it is possible to see through single edges. We show that the class of pseudo-star-shaped polygons unifies and generalizes the well-known classes of convex, monotone and pseudostar-sphaped polygons. We give algorithms for testing whether a polygon is pseudostar-shaped from a given point in linear time, and for constructing all regions from which the polygon is pseudo-star-shaped in quadratic time. We show the latter algorithm to be worst-case optimal. Also, we give efficient algorithms solving standard geometrical problems such as point-location and triangulation for pseudo-starshaped polygons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01901192
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