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  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5318-5328 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The systematic development of the harmonic, intermolecular, internal mode interaction energy in terms of symmetry adapted Wigner functions of the molecular orientations is given for a plastic crystal. This development is used for the study of the Raman profile of a mode with a strong induced dipole-induced dipole interaction between the vibrating molecules. An approximate form of the profile is proposed, and compared with measurements made on NF3 by Gilbert and Nectoux.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Amsterdam : Elsevier
    Solid State Communications 21 (1977), S. 1095-1096 
    ISSN: 0038-1098
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Physik
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Algorithmica 8 (1992), S. 321-342 
    ISSN: 1432-0541
    Schlagwort(e): Computational geometry ; Geometric probing ; Polyhedral scenes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We show, in this paper, how the exact shapes of a class of polyhedral scenes can be computed by means of a simple sensory device issuing probes. A scene in this class consists of disjoint polyhedra with no collinear edges, no coplanar faces, and such that no edge is contained in the supporting plane of a nonincident face. The basic step of our method is a strategy for probing a single simple polygon with no collinear edges. When each probe outcome consists of a contact point and the normal to the object at the point, we present a strategy that allows us to compute the exact shape of a simple polygon with no collinear edges by means of at most3n — 3 probes, wheren is the number of edges of the polygon. This is optimal in the worst case. This strategy can be extended to probe a family of disjoint polygons. It can also be applied in planar sections of a scene of polyhedra of the class above to find out, in turn, each edge of the scene. If the scene consists ofk polyhedra with altogethern faces andm edges, we show that $$\tfrac{{10}}{3}n\left( {m + k} \right) - 2m - 3k$$ probes are sufficient to compute the exact shapes of the polyhedra.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Algorithmica 27 (2000), S. 21-56 
    ISSN: 1432-0541
    Schlagwort(e): Key words. Computational geometry, Exact arithmetic, Precision, Robust algorithms.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract. This paper presents a theoretical and experimental study on two different methods to evaluate the sign of a determinant with integer entries. The first one is a method based on the Gram—Schmidt orthogonalization process which has been proposed by Clarkson [Cl]. We review his algorithm and propose a variant of his method, for which we give a complete analysis. The second method is an extension to n × n determinants of the ABDPY method [ABD+2] which works only for 2 × 2 and 3 × 3 determinants. Both methods compute the sign of an n× n determinant whose entries are integers on b bits, by using exact arithmetic on only b +O(n) bits. Furthermore, both methods are adaptive, dealing quickly with easy cases and resorting to full-length computation only for null determinants.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Discrete & computational geometry 19 (1998), S. 485-519 
    ISSN: 1432-0444
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract. The paper bounds the combinatorial complexity of the Voronoi diagram of a set of points under certain polyhedral distance functions. Specifically, if S is a set of n points in general position in R d , the maximum complexity of its Voronoi diagram under the L ∞ metric, and also under a simplicial distance function, are both shown to be $\Theta(n^{\lceil d/2 \rceil})$ . The upper bound for the case of the L ∞ metric follows from a new upper bound, also proved in this paper, on the maximum complexity of the union of n axis-parallel hypercubes in R d . This complexity is $\Theta(n^{\left\lceil d/2 \right\rceil})$ , for d ≥ 1 , and it improves to $\Theta(n^{\left\lfloor d/2 \right\rfloor})$ , for d ≥ 2 , if all the hypercubes have the same size. Under the L 1 metric, the maximum complexity of the Voronoi diagram of a set of n points in general position in R 3 is shown to be $\Theta(n^2)$ . We also show that the general position assumption is essential, and give examples where the complexity of the diagram increases significantly when the points are in degenerate configurations. (This increase does not occur with an appropriate modification of the diagram definition.) Finally, on-line algorithms are proposed for computing the Voronoi diagram of n points in R d under a simplicial or L ∞ distance function. Their expected randomized complexities are $O(n \log n + n ^{\left\lceil d/2 \right\rceil})$ for simplicial diagrams and $O(n ^{\left\lceil d/2 \right\rceil} \log ^{d-1} n)$ for L ∞ -diagrams.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 14 (1983), S. 166-177 
    ISSN: 0377-0486
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Polarized Raman spectra of oriented single crystals of KClO4 performed over a large temperature range (300-800 K) have been used to investigate the mechanism of the 583 K phase transition. It is shown that the transition can be described using an order parameter and a mechanism based on the reorientation of the ClO4- ions is proposed. A Raman study of the plastic phase (above 583 K), using the shape of the bands associated with the internal modes, leads to a measure of the orientational density probability and the orientational self-correlation functions of the perchlorate ions.
    Zusätzliches Material: 21 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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