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  • Artikel  (10)
  • Springer  (10)
  • 1995-1999  (4)
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  • 1996  (4)
  • 1992  (6)
  • Informatik  (10)
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  • 1995-1999  (4)
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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 57 (1992), S. 193-202 
    ISSN: 1436-4646
    Schlagwort(e): Steiner trees ; approximation performance ratio
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract Finding a shortest network interconnecting a given set of points in a metric space is called the Steiner minimum tree problem. The Steiner ratio is the largest lower bound for the ratio between lengths of a Steiner minimum tree and a minimum spanning tree for the same set of points. In this paper, we show that in a metric space, if the Steiner ratio is less than one and finding a Steiner minimum tree for a set of size bounded by a fixed number can be performed in polynomial time, then there exists a polynomialtime heuristic for the Steiner minimum tree problem with performance ratio bigger than the Steiner ratio. It follows that in the Euclidean plane, there exists a polynomial-time heuristic for Steiner minimum trees with performance ratio bigger than $${\textstyle{1 \over 2}}\sqrt 3 $$ . This solves a long-standing open problem.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Algorithmica 7 (1992), S. 121-135 
    ISSN: 1432-0541
    Schlagwort(e): Steiner trees ; Spanning trees ; Steiner ratio ; Convexity ; Hexagonal trees
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract LetP be a set ofn points on the euclidean plane. LetL s(P) andL m (P) denote the lengths of the Steiner minimum tree and the minimum spanning tree onP, respectively. In 1968, Gilbert and Pollak conjectured that for anyP,L s (P)≥(√3/2)L m (P). We provide a proof for their conjecture in this paper.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Algorithmica 7 (1992), S. 179-191 
    ISSN: 1432-0541
    Schlagwort(e): Steiner trees ; Spanning trees ; Steiner ratio ; L p distance ; Bounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract LetL p be the plane with the distanced p (A 1 ,A 2 ) = (¦x 1 −x 2¦ p + ¦y1 −y 2¦p)/1p wherex i andy i are the cartesian coordinates of the pointA i . LetP be a finite set of points inL p . We consider Steiner minimal trees onP. It is proved that, for 1 〈p 〈 ∞, each Steiner point is of degree exactly three. Define the Steiner ratio ϱ p to be inf{L s (P)/L m (P)¦P⊂L p } whereL s (P) andL m (P) are lengths of the Steiner minimal tree and the minimal spanning tree onP, respectively. Hwang showed ϱ1 = 2/3. Chung and Graham proved ϱ2 〉 0.842. We prove in this paper that ϱ{∞} = 2/3 and √(√2/2)ϱ1ϱ2 ≤ ϱp ≤ √3/2 for anyp.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Applicable algebra in engineering, communication and computing 7 (1996), S. 211-219 
    ISSN: 1432-0622
    Schlagwort(e): Coxeter groups ; Kazhdan-Lusztig polynomials ; Finite-state automata
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik , Technik allgemein
    Notizen: Abstract We present the different approaches available today for the computation of Kazhdan-Lusztig polynomials by computer, and describe the scope of the existing programs in this area. We also outline some possible directions for future developments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Applicable algebra in engineering, communication and computing 7 (1996), S. 211-219 
    ISSN: 1432-0622
    Schlagwort(e): Key words Coxeter groups ; Kazhdan-Lusztig polynomials ; Finite-state automata.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik , Technik allgemein
    Notizen: Abstract  We present the different approaches available today for the computation of Kazhdan-Lusztig polynomials by computer, and describe the scope of the existing programs in this area. We also outline some possible directions for future developments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Multimedia systems 4 (1996), S. 157-171 
    ISSN: 1432-1882
    Schlagwort(e): Key Words:Asynchronous transfer mode (ATM) – Distributed multimedia systems – Traffic smoothing – Network transport protocols – Video transmission
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract. We present end-to-end performance of digital coded video (JPEG, MPEG-1, and MPEG-2) over a local asynchronuous transfer mode (ATM) network. We discuss performance in terms of both delay (jitter) and frame loss as a function of load. The experimental data reveal that the burstiness of the variable bit-rate-coded video streams degrades the performance significantly when the hosts and the network are stressed. Our results show that traffic smoothing decreases frame loss significantly while maintaining acceptable jitter and loss bounds. We also discuss requirements for system components, such as the network interface and switch, which are necessary to support video services efficiently.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Journal of systems integration 6 (1996), S. 93-134 
    ISSN: 1573-8787
    Schlagwort(e): Component search ; retrieval ; software library ; reuse ; computer aided prototyping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract An important problem in software development is to make better use of software libraries by improving the search and retrieval process, that is, by making it easier to find the few components you may want among the many you do not want. This paper suggests some ideas to improve this process: (1) Associate analgebraic specification with each software component; these specifications should include complete syntactic information, but need have onlypartial semantic information. (2) User queries consist of syntactic declarations plus results forsample executions. (3) User queries may be posed in standard programming notation, which is then automatically translated into algebraic notation. (4) Search is organized asranked multi-level filtering, where each level yields aranked set of partial matches. (5) Early stages of filtering narrow the search space by using computationally simple procedures, such as checking that the number of types is adequate. (6) Middle levels may findpartial signature matches. (7) Pre-computedcatalogues (i.e., indexes) can speed up early and middle level filtering. (8) Semantic information is used in a final filter withterm rewriting, but complete verification is not attempted. (9) The series of filters is implementedincrementally, so as to backtrack to lower ranked components in case of failure. This approach avoids the need for complex theorem proving, and does not require any knowledge of algebraic specification from the user. Moreover, it does not require either specifications or queries to be complete or even fully correct, because it yields partial matches ranked by how well they fit the query. The paper concludes with a description of some preliminary experiments and some suggestions for further experiments.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Acta informatica 29 (1992), S. 281-302 
    ISSN: 1432-0525
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract A new model for multiple errors spelling correction is proposed. The model handles insert, delete, change, and transpose errors. In the new model, we put constraints on possible editing sequences to reflect the error occurrence phenomenon in spelling, resulting in an error measure different from the traditional editing distance error measure. Properties of the “error distance matrix” between two character strings are studied under the assumptions of the new model. A cut-off criterion has been discovered, which can detect whether the error distance between two character strings is greater than a prespecified value during the calculation. Based on this cut-off criterion, a fast algorithm has been developed to find the nearest neighbors of a given character string in a dictionary. Experiments have been conducted with results showing that the cut-off criterion can greatly cut down the computation time needed for the nearest neighbor searching.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Publikationsdatum: 1992-06-01
    Print ISSN: 0178-4617
    Digitale ISSN: 1432-0541
    Thema: Informatik , Mathematik
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Publikationsdatum: 1992-06-01
    Print ISSN: 0178-4617
    Digitale ISSN: 1432-0541
    Thema: Informatik , Mathematik
    Publiziert von Springer
    Standort Signatur Erwartet Verfügbarkeit
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