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221.
Summary The optimality question for blockp-cyclic SOR iterations discussed in Young and Varga is answered under natural conditions on the spectrum of the block Jacobi matrix. In particular, it is shown that repartitioning a blockp-cyclic matrix into a blockq-cyclic form,q
, results in asymptotically faster SOR convergence for the same amount of work per iteration. As a consequence block 2-cyclic SOR is optimal under these conditions.Research supported in part by the US Air Force under Grant no. AFOSR-88-0285 and the National Science Foundation under grant no. DMS-85-21154 Present address: Boeing Computer Services, P.O. Box 24346, MS 7L-21, Seattle, WA 98124-0346, USA 相似文献
222.
Giuseppina Vannella 《Annali di Matematica Pura ed Applicata》2002,180(4):429-440
We consider a Neumann problem of the type -εΔu+F
′(u(x))=0 in an open bounded subset Ω of R
n
, where F is a real function which has exactly k maximum points.
Using Morse theory we find that, for ε suitably small, there are at least 2k nontrivial solutions of the problem and we give some qualitative information about them.
Received: October 30, 1999 Published online: December 19, 2001 相似文献
223.
The problem of analytic representation of integrable CR functions on hypersurfaces with singularities is treated. The nature of singularities does not matter while the set of singularities
has surface measure zero. For simple singularities like cuspidal points, edges, corners, etc., also the behaviour of representing
analytic functions near singular points is studied.
Received: 8 December 2000; in final form: 24 June 2001/Published online: 1 February 2002 相似文献
224.
Diem Ho 《Numerische Mathematik》1989,56(7):721-734
Summary The acceleration by Tchebychev iteration for solving nonsymmetric eigenvalue problems is dicussed. A simple algorithm is derived to obtain the optimal ellipse which passes through two eigenvalues in a complex plane relative to a reference complex eigenvalue. New criteria are established to identify the optimal ellipse of the eigenspectrum. The algorithm is fast, reliable and does not require a search for all possible ellipses which enclose the spectrum. The procedure is applicable to nonsymmetric linear systems as well. 相似文献
225.
A complete optical characterization in the visible region of thin copper oxide films has been performed by ellipsometry. Copper
oxide films of various thicknesses were grown on thick copper films by low temperature thermal oxidation at 125 °C in air
for different time intervals. The thickness and optical constants of the copper oxide films were determined in the visible
region by ellipsometric measurements. It was found that a linear time law is valid for the oxide growth in air at 125 °C.
The spectral behaviour of the optical constants and the value of the band gap in the oxide films determined by ellipsometry
in this study are in agreement with the behaviour of those of Cu2O, which have been obtained elsewhere through reflectance and transmittance methods. The band gap of copper oxide, determined
from the spectral behaviour of the absorption coefficient was about 2 eV, which is the generally accepted value for Cu2O. It was therefore concluded that the oxide composition of the surface film grown on copper is in the form of Cu2O (cuprous oxide). It was also shown that the reflectance spectra of the copper oxide–copper structures exhibit behaviour
expected from a single layer antireflection coating of Cu2O on Cu.
Received: 19 July 2001 / Accepted: 27 July 2001 / Published online: 17 October 2001 相似文献
226.
M. Esmaeelpour 《Applied Surface Science》2006,252(18):6353-6359
This research investigates the effect of ion implantation dosage level and further thermal treatment on the physical characteristics of chromium coatings on Si(1 1 1) substrates. Chromium films had been exposed to nitrogen ion fluencies of 1 × 1017, 3 × 1017, 6 × 1017 and 10 × 1017 N+ cm−2 with a 15 keV energy level. Obtained samples had been heat treated at 450 °C at a pressure of 2 × 10−2 Torr in an argon atmosphere for 30 h. Atomic force microscopy (AFM) images showed significant increase in surface roughness as a result of nitrogen ion fluence increase. Secondary ion mass spectroscopy (SIMS) studies revealed a clear increased accumulation of Cr2N phase near the surface as a result of higher N+ fluence. XRD patterns showed preferred growth of [0 0 2] and [1 1 1] planes of Cr2N phase as a result of higher ion implantation fluence. These results had been explained based on the nucleation-growth of Cr2N phase and nitrogen atoms diffusion history during the thermal treatment process. 相似文献
227.
Yuri Bilu 《Monatshefte für Mathematik》2002,137(1):1-3
We correct an inaccuracy in the papers of Le, Mignotte, and Bugeaud on the generalized Ramanujan-Nagell equation.
Received June 23, 2001 相似文献
228.
C. Devaux J.P. Chapel E. Beyou Ph. Chaumont 《The European physical journal. E, Soft matter》2002,7(4):345-352
Thin layers of polystyrene were grown from surface-grafted nitroxide initiators via controlled “living” free radical polymerization.
The “reactive” Langmuir-Blodgett deposition method allowed an effective control of the initiator layer density leading to
PS brushes with different and high grafting density and stretching. The influence of the grafting density on the layer structure
was studied. Comparison with theoretical predictions for monodispersed brushes in bad solvent was discussed. The thickness
was found to vary linearly with molecular weight and the density dependence was shown using wetting measurements. Special
features of controlled radical nitroxide polymerization from a surface were discussed. A direct comparison of the molecular
weight and polydispersity between surface and bulk polymers was made by de-grafting the brushes into a toluene/HF solution.
Finally, some evidence of a “surface Fischer” effect was shown from re-initiated layers.
Received 20 December 2001 相似文献
229.
Ion synthesis and laser annealing of Cu nanoparticles in Al2O3 总被引:1,自引:0,他引:1
A.L. Stepanov V.N. Popok D.E. Hole I.B. Khaibullin 《Applied Physics A: Materials Science & Processing》2002,74(3):441-446
Al2O3 samples with Cu nanoparticles, synthesised by ion implantation at 40 keV with a dose of 1×1017 ion/cm2 and a current density from 2.5 to 12.5 μA/cm2, were annealed using ten pulses from a KrF excimer laser with a single pulse fluence of 0.3 J/cm2. The copper depth distribution, formation and modification of metal nanoparticles under the ion implantation and laser treatment
were studied by Rutherford backscattering (RBS), energy dispersive X-ray (EDX) analysis, atomic force microscopy (AFM) and
optical spectroscopy. It was found that laser annealing leads to a reduction in the nanoparticle size without diffusion of
metal atoms into the bulk. The change in particle size and the possibility for oxidation of the copper particles are examined
in the framework of Mie theory. Calculations presented show that under excimer laser treatment, Cu nanoparticles are more
likely to be reduced in size than to undergo oxidation.
Received: 19 April 2001 / Accepted: 7 November 2001 / Published online: 23 January 2002 相似文献
230.
Cardy's formula for some dependent percolation models 总被引:2,自引:0,他引:2
F. Camia C. M. Newman V. Sidoravicius 《Bulletin of the Brazilian Mathematical Society》2002,33(2):147-156
We prove Cardy's formula for rectangular crossing probabilities in dependent site percolation models that arise from a deterministic cellular automaton with a random initial state. The cellular automaton
corresponds to the zero-temperature case of Domany's stochastic Ising ferromagnet on the hexagonal lattice (with alternating
updates of two sublattices) [7]; it may also be realized on the triangular lattice 𝕋 with flips when a site disagrees with
six, five and sometimes four of its six neighbors.
Received: 24 December 2001 相似文献