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961.
M. Van De Vel 《Topology and its Applications》1983,16(2):181-206
It is shown that two-dimensional convex structures with certain natural properties are join-hull commutative. The main intermediate step is the computation of the so-called exchange number. We also give two examples of three-dimensional convexities which are not join-hull commutative. The second one has certain additional properties showing that the main theorem is sharp in many other respects. These properties are obtained from a study of convex hyperspaces. 相似文献
962.
G. A. Margulis 《Combinatorica》1982,2(1):71-78
We give an explicit construction of regular graphs of degree 2r withn vertices and girth ≧c logn/logr. We use Cayley graphs of factor groups of free subgroups of the modular group. An application to low density codes is given. 相似文献
963.
J. Reid J. Shewchun B. K. Garside 《Applied Physics A: Materials Science & Processing》1978,17(4):349-353
We report the first accurate measurements of the transition strengths and linewidths of the 00o2 9.4 μm sequence lines of CO2. This sequence band is found to be very similar to the regular 00o1 laser band, except for an experimentally determined factor of 1.89±0.12 increase in transition strength (if the CO2 molecule is treated as a simple harmonic oscillator the theoretical increase in transition strength is 2.0). The laser absorption
spectrometer used for these measurements can detect absorption coefficients in CO2 of ≈10−7 m−1, and we discuss the feasibility of using this sensitivity to monitor rare isotopic forms of CO2.
Work supported by the Department of National Health and Welfare, Environment Canada, Ontario Ministry of the Environment,
and Atmospheric Environment Service, Environment Canada. 相似文献
964.
S.??wiok W.?DudekEmail author P.?Kaszyński W.?Nazarewicz 《The European Physical Journal A - Hadrons and Nuclei》2005,23(3):387-393
The Greens function oscillator expansion method and the generalized Strutinsky smoothing procedure are applied to shell corrections in the heaviest elements. A macroscopic-microscopic method with a finite deformed Woods-Saxon potential is used. The stability condition for the shell correction is discussed in detail and the parameters defining the smoothing procedure are carefully determined. It is demonstrated that the spurious contribution to the total binding energy due to the unphysical particle gas that appears in the standard method can be as large as 1.5 MeV for weakly bound neutron-rich superheavy nuclei, but the effect on energy differences (e.g., alpha-decay values) is fairly small. 相似文献
965.
Fawaz?S.?Al-AnziEmail author Ali?Allahverdi 《Journal of Mathematical Modelling and Algorithms》2005,4(4):435-453
This research addresses the scheduling problem of multimedia object requests, which is an important problem in information
systems, in particular, for World Wide Web applications. The performance measure considered is the variance of response time
which is crucial as end users expect fair treatment to their service requests. This problem is known to be NP-hard. The literature
survey indicates that two heuristics have been proposed to solve the problem. In this paper, we present a new heuristic, a
hybrid evolutionary heuristic, which is shown to perform much better than the two existing ones, e.g., the overall average
errors of the existing ones are 1.012 and 2.042 while the error of the proposed hybrid evolutionary heuristic is 0.154. 相似文献
966.
Elena Cordero Stevan Pilipović Luigi Rodino Nenad Teofanov 《Mediterranean Journal of Mathematics》2005,2(4):381-394
We study localization operators within the framework of ultradistributions. More precisely, given a symbol a and two windows φ1, φ2, we investigate the multilinear mapping from
to the localization operator
Results are formulated in terms of modulation spaces with weights which may have exponential growth. We give sufficient and
necessary conditions for
a to be bounded or to belong to a Schatten class. As an application, we study symbols defined by ultra-distributions with
compact support, that give trace class localization operators. 相似文献
967.
We prove the existence of positive symmetric solutions to the semilinear elliptic problem
in both the radial case N = k ≥ 3 and the cylindrical case N ≥ k + 3 ≥ 6. The potential V is measurable, positive and it is only required to satisfy a mild integrability condition. The nonlinearity is continuous
and has a doublepower behavior, super-critical near the origin and sub-critical at infinity. If f is odd, we show that the radial problem has infinitely many solutions. In proving these results we exploit the compactness
of suitable restrictions of the embedding
Supported by MIUR, project “Variational Methods and Nonlinear Differential Equations”. 相似文献
968.
J.-F. Ripoll A.A. Wray 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,93(4):473-519
We present in this paper a new 3D half-moment model for radiative transfer in a gray medium, called the model, which uses maximum entropy closure. This model is a generalization to 3D of the 1D version recently proposed in (J. Comp. Phys. 180 (2002) 584). The direction space Ω is divided into two pieces, Ω+ and Ω-, in a dynamical way by the plane perpendicular to the total radiative flux, and the half moments are defined from these subspaces. The model closure and the integrations of the radiative transfer equation performed on the moving Ω± spaces are detailed. 1D planar results, which have motivated the extension of the model of (J. Comp. Phys. 180 (2002) 584) to multi-dimensions, are shown. These results are very good. The model is thereafter derived for 3D spherically symmetric geometry, where the correctness of the non-trivial border terms can be checked. Two 3D spherically symmetric problems are numerically solved in order to show the accuracy of the closure and the role of the border terms. Once again, compared to the solution obtained with a ray tracing solver, results are very good. From the 3D half-moment model, a new moment model, called , is derived for the particular case of a 3D hot and opaque source radiating into a cold medium, for applications such as simulations of stellar atmospheres and fires. Two-dimensional numerical results are presented and compared to those obtained solving the RTE and with other moment models. They demonstrate the very good accuracy of the model, its good convergence properties, and better prediction compared to all other existing moment models in its domain of applicability. 相似文献
969.
The continuous-wave laser properties of an efficient diode-pumped Nd:GdVO4 crystal operating at formed with a simple plane-concave cavity have been studied. With the incident pump power of 21 W, an output power of 6.9 W was obtained, giving an optical conversion efficiency of 32.8% and a slope efficiency of 35.3%. The laser characterization of two different Nd3+-doped concentration of Nd:GdVO4 crystals were studied. 相似文献
970.
Anna Avallone 《Rendiconti del Circolo Matematico di Palermo》2004,53(2):195-204
We prove a Lyapunov type theorem for modular functions on complemented lattices. 相似文献