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91.
Convergence of algebraic multigrid based on smoothed aggregation 总被引:10,自引:0,他引:10
Summary. We prove an abstract convergence estimate for the Algebraic Multigrid Method with prolongator defined by a disaggregation
followed by a smoothing. The method input is the problem matrix and a matrix of the zero energy modes of the same problem
but with natural boundary conditions. The construction is described in the case of a general elliptic system. The condition
number bound increases only as a polynomial of the number of levels, and requires only a uniform weak approximation property
for the aggregation operators. This property can be a-priori verified computationally once the aggregates are known. For illustration,
it is also verified here for a uniformly elliptic diffusion equations discretized by linear conforming quasiuniform finite
elements. Only very weak and natural assumptions on the hierarchy of aggregates are needed.
Received March 1, 1998 / Revised version received January 28, 2000 / Published online: December 19, 2000 相似文献
92.
Ohne Zusammenfassung
Uebersetzt von J. Matula (Wien). Eine vorl?ufige Mitteilung der in dieser und einer vorhergehenden in dieser Zeitschrift erschienenen
Abhandlung niedergelegten Ergebnisse erschien in Science43 (1916). 相似文献
93.
94.
A method for characterizing and identifying firing patterns of neural spike trains is presented. Based on the time evolution of a neural spike train, the counting process is constructed as a time-dependent stair-like function. Three characteristic variables defined at sequential moments, including two formal derivatives and the integration of the counting process, are introduced to reflect the temporal patterns of a spike train. The reconstruction of a spike train with these variables verify the validity of this method. And a model of cold receptor is used as an example to investigate the temporal patterns under different temperature conditions. The most important contribution of our method is that it not only can reflect the features of spike train patterns clearly by using their geometrical properties, but also it can reflect the trait of time, especially the change of bursting of spike train. So it is a useful complementarity to conventional method of averaging. 相似文献
95.
96.
We prove that a finite group having a fixed-point-free automorphism in the Fitting subgroup of its automorphism group must
be abelian of rather restricted structure. As a consequence, no finite nonabelian group could have a fixed-point-free automorphism
in the Frattini subgroup of its automorphism group.
Received: 21 April 2007, Revised: 18 May 2007 相似文献
97.
Assuming elastic-plastic material behavior the slow growth of Mode III crack under both monotonic and pulsating loadings is considered. Rice's idea of universal R-curve is employed while the mathematical analysis is based on the one-dimensional plasticity model suggested by Kostrov and Nikitin. Motion of a quasi-static Mode III crack is studied and the stable/unstable transition points are found through application of the final stretch failure condition proposed in 1972 by Wnuk. A logarithmic formula for fatigue crack extension rate is derived. Results are compared to other well-known solutions. 相似文献
98.
Marian Buchlovi? 《Tetrahedron letters》2010,51(44):5801-5803
The reactivity of 2-hydroxy-3,3,5-trimethyl-3,4-dihydro-2H-pyrrole 1-oxide was investigated. The title compound showed unexpected reactivity with several different types of reagents. 相似文献
99.
Iuliu O. Marian Nicolae Bonciocat Cecilia Cristea Robert Săndulescu Monica Bucşa Mircea Vlassa 《Electroanalysis》2010,22(5):542-548
The electrochemical and spectroelectrochemical behavior of 9‐substituted with ? CN and ? COOH acridine N‐oxides with potential antitumor activity was investigated. In SER spectra of the investigated compounds, the ring stretching vibration at 1568 cm?1 for 9‐CN‐substituted compound respectively 1639 cm?1 for 9‐COOH‐substituted compound was analyzed. Cyclic voltammograms indicates that the reduction potential ?0.766 V for ? CN substituted compound increase towards ?0.745 V for ? COOH substituted compound. The proposed theoretical method in the electrochemical impedance spectroscopy uses a reference redox dielectrode and a multielectrode containing the compound. To account for the change of electrochemical impedance we have considered two theoretical quantities: a pseudocapacitance and a pseudo inductance. Two possible arrangements of them: in series, respective in parallel can be used like criteria of drug classification. 相似文献
100.
Zuzana Vasková Jan Moncol Maria Korabik Dušan Valigura Jozef Švorec Tadeusz Lis Marian Valko Milan Melník 《Polyhedron》2010
A new complex of unusual composition [Cu(3-O2Nbz)2(nia)(H2O)2] (1) (nia = nicotinamide, 3-O2Nbz = 3-nitrobenzoate) has been prepared and studied together with two other complexes of composition [Cu(4-O2Nbz)2(nia)2(H2O)2] (2) and [Cu(4-O2Nbz)2(nia)2]?(4-O2NbzH)2 (3) (4-O2Nbz = 4-nitrobenzoate). The composition of all complexes has been determined by elemental analysis, the complexes have been studied by electronic, infrared and EPR spectroscopy, as well as by magnetization measurements over the temperature range 1.8–300 K, and their structures have been solved. The structure of complex (1) consists of molecules, where Cu(II) atom is monodentately coordinated by the pair of 3-nitrobenzoato anions in trans -positions together with water and nicotinamide molecules, forming nearly tetragonal basal plane, and by another water molecule in axial position of tetragonal-pyramidal coordination polyhedron. The neighboring molecule coordination polyhedron basal planes are coplanar and allow formation of supramolecular dimers with strong H-bonds between hydrogen atoms from equatorially coordinated water molecules and uncoordinated carboxylate oxygen atoms thus giving the nearest Cu?Cu distance of 4.886(2) Å. Magnetization measurements showed that complex (1) exhibits maximum of magnetic susceptibility at 6.5 K and a fit to Bleaney-Bowers equation gave singlet–triplet energy gap 2J = −6.25 cm−1, and zJ′ = −0.03 cm−1. This might be an experimental proof that the carboxylate bridges extended with hydrogen bonds are the pathway of the spin–spin interactions. The temperature dependence of changes in EPR spectra of (1) and the spectrum at 4.2 K have confirmed its hydrogen bonded dimeric structure. The calculated Cu?Cu distance 4.8 Å is in very good agreement with the value obtained from crystal structure. The complexes (2) and (3) at 300 K exhibit magnetic moment μeff = 1.98 B.M. and μeff = 1.84 B.M., respectively. These values practically do not change with lowering the temperature up to 5 K and only small drops to μeff = 1.87 B.M. (for (2)) and μeff = 1.79 B.M. (for (3)) at 1.8 K have been observed. The EPR spectra of complex (2) at room temperature as well as at 77 K are of axial type with g⊥ = 2.062 and g|| = 2.285 and exhibit resolved parallel hyperfine splitting with A|| = 160 Gauss. The EPR spectra of complex (3) at room temperature as well as at 77 K are of axial type with g⊥ = 2.065 and g|| = 2.235 and exhibit unresolved parallel hyperfine splitting. EPR spectra of (2) and (3) are consistent with the X-ray structure. 相似文献