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排序方式: 共有74条查询结果,搜索用时 15 毫秒
1.
Baumgarten N. Jung H. Mehlhorn K. 《Journal of Algorithms in Cognition, Informatics and Logic》1994,17(3)
The dynamic planar point location problem is the task of maintaining a dynamic set S of n nonintersecting (except possibly at endpoints) line segments in the plane under the following operations:
- • Locate (: point): Report the segment immediately above , i.e., the first segment intersected by an upward vertical ray starting at ;
- • Insert (: segment): Add segment to the collection of segments;
- • Delete (: segment): Remove segment from the collection of segments.
2.
Zusammenfassung 42 Heterocyclen, die sich formal von alternierenden und nichtalternierenden Kohlenwasserstoffen durch Ersatz einer Doppelbindung durch die Heteroatome Sauerstoff, Stickstoff, Schwefel und Selen ableiten, werden nach dem Pariser-Parr-Pople-Verfahren berechnet und ihre Spektren im nahen Ultraviolett und Sichtbaren beschrieben. Schwefel und Selen werden dabei im LCAO-MO-Verfahren nach dem p-Modell behandelt. In den meisten Fällen können die Berechnungen nicht nur die spektralen Charakteristika gut wiedergeben, sondern auch Beziehungen in den Spektren iso--elektronischer Verbindungen gleicher Struktur verständlich machen. Berechnungen an kationischen Stickstoffheterocyclen führten dann zu falschen Ergebnissen, wenn die Stickstoffparameter vom Pyrroltyp übernommen werden.
Anmerkung: Die Arbeit wurde in dem von Prof. Dr. R. Mayer geleiteten Schwefelarbeitskreis der TU Dresden durchgeführt. 相似文献
PPP-calculations and comparison of electronic spectra of iso--electronic oxygen, nitrogen, sulfur, and selenium heterocycles
42 heterocyclic compounds, formally derived from alternant or nonalternant hydrocarbons by replacing a C=C group by an oxygen, nitrogen, sulfur or selenium atom, are studied by the Pariser-Parr-Pople-type of calculation. By means of these results the near ultraviolet and visible spectra are described. The sulfur and the selenium atoms are treated in the LCAO-MO-method using the p-model. In most cases spectral features are not only well reproduced, but interrelations of the spectra of iso--electronic compounds, possessing analogous structures are interpreted, too. On calculating cationic nitrogen heterocycles using parameters of pyrrol type nitrogen results are unsatisfactory.
Résumé 42 composés hétérocycliques, formellement dérivés d'hydrocarbures alternants ou non alternants par remplacement d'un groupement C=C par un atome d'oxygène, d'azote, de soufre ou de sélénium, sont étudiés par la méthode de Pariser-Parr-Pople. Les résultats obtenus permettent de décrire le spectre U.V. proche et visible. Soufre et sélénium sont traités en utilisant le modèle p. Dans la plupart des cas les caractères spectraux sont non seulement correctement reproduits, mais les relations entre les spectres des composés iso--électroniques à structures analogues peuvent être interprétées. Les calculs concernant les heterocycles à azote cationique sont insatisfaisants lorsqu'ils sont effectués avec des paramètres de l'azote du type pyrrole.
Anmerkung: Die Arbeit wurde in dem von Prof. Dr. R. Mayer geleiteten Schwefelarbeitskreis der TU Dresden durchgeführt. 相似文献
3.
4.
Eric Berberich Efi Fogel Dan Halperin Kurt Mehlhorn Ron Wein 《Mathematics in Computer Science》2010,4(1):45-66
We introduce a framework for the construction, maintenance, and manipulation of arrangements of curves embedded on certain
two-dimensional orientable parametric surfaces in three-dimensional space. The framework applies to planes, cylinders, spheres,
tori, and surfaces homeomorphic to them. We reduce the effort needed to generalize existing algorithms, such as the sweep
line and zone traversal algorithms, originally designed for arrangements of bounded curves in the plane, by extensive reuse
of code. We have realized our approach as the Cgal package Arrangement_on_surface_2. We define a compact and modular interface for our framework; for a given application a required small subset of the interface
can be identified. Then, only this subset must be implemented. A companion paper describes concretizations for several types
of surfaces and curves embedded on them, and applications. This is the first implementation of a generic algorithm that can
handle arrangements on a large class of parametric surfaces. 相似文献
5.
Stähler J Mehlhorn M Bovensiepen U Meyer M Kusmierek DO Morgenstern K Wolf M 《Physical review letters》2007,98(20):206105
The structure of D2O clusters on a Cu(111) surface and the femtosecond dynamics of photoexcited excess electrons are investigated by low-temperature scanning tunneling microscopy and two-photon photoemission spectroscopy. Two types of amorphous ice clusters, porous and compact, which exhibit characteristic differences in electron dynamics, are identified. By titration with Xe we show that in both structures solvated electrons preferentially bind on the cluster surface. 相似文献
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7.
Bailey JE Chandler GA Slutz SA Golovkin I Lake PW MacFarlane JJ Mancini RC Burris-Mog TJ Cooper G Leeper RJ Mehlhorn TA Moore TC Nash TJ Nielsen DS Ruiz CL Schroen DG Varnum WA 《Physical review letters》2004,92(8):085002
Hot dense capsule implosions driven by Z-pinch x rays have been measured using a approximately 220 eV dynamic Hohlraum to implode 1.7-2.1 mm diameter gas-filled CH capsules. The capsules absorbed up to approximately 20 kJ of x rays. Argon tracer atom spectra were used to measure the T(e) approximately 1 keV electron temperature and the n(e) approximately 1-4 x 10(23) cm(-3) electron density. Spectra from multiple directions provide core symmetry estimates. Computer simulations agree well with the peak emission values of T(e), n(e), and symmetry, indicating reasonable understanding of the Hohlraum and implosion physics. 相似文献
8.
J.E. Bailey G.A. Chandler G.A. Rochau Y. Maron S.A. Slutz G.S. Dunham I. Golovkin P.W. Lake R.W. Lemke J.M. Lucas J.J. MacFarlane T.A. Mehlhorn T.C. Moore D.G. Schroen E. Stambulchik K. Youngblood 《High Energy Density Physics》2005,1(1):21-30
A dynamic hohlraum is created when an annular z-pinch plasma implodes onto a cylindrical 0.014 g/cc 6-mm-diameter CH2 foam. The impact launches a radiating shock that propagates toward the axis at 350 μm/ns. The radiation trapped by the tungsten z-pinch plasma forms a 200 eV hohlraum that provides X-rays for indirect drive inertial confinement fusion capsule implosion experiments. We are developing the ability to diagnose the hohlraum interior using emission and absorption spectroscopy of Si atoms added as a tracer to the central portion of the foam. Time- and space-resolved Si spectra are recorded with an elliptical crystal spectrometer viewing the cylindrical hohlraum end-on. A rectangular aperture at the end of the hohlraum restricts the field of view so that the 1D spectrometer resolution corresponds approximately to the hohlraum radial direction. This enables distinguishing between spectra from the unshocked radiation-heated foam and from the shocked foam. Typical spectral lines observed include the Si Lyα with its He-like satellites and the He-like resonance sequence including Heα, Heβ, and Heγ, along with some of their associated Li-like satellites. Work is in progress to infer the hohlraum conditions using collisional–radiative modeling that accounts for the radiation environment and includes both opacity effects and detailed Stark broadening calculations. These 6-mm-scale radiation-heated plasmas might eventually also prove suitable for testing Stark broadening line profile calculations or for opacity measurements. 相似文献
9.
10.
Erich Müller und Kurt Mehlhorn 《Fresenius' Journal of Analytical Chemistry》1934,96(5-6):173-175
Ohne Zusammenfassung 相似文献