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931.
Effects of uncertainties in the domain on the solution of Dirichlet boundary value problems 总被引:1,自引:0,他引:1
Summary. A domain with possibly non-Lipschitz boundary is defined as a limit of monotonically expanding or shrinking domains with
Lipschitz boundary. A uniquely solvable Dirichlet boundary value problem (DBVP) is defined on each of the Lipschitz domains
and the limit of these solutions is investigated. The limit function also solves a DBVP on the limit domain but the problem
can depend on the sequences of domains if the limit domain is unstable with respect to the DBVP. The core of the paper consists
in estimates of the difference between the respective solutions of the DBVP on two close domains, one of which is Lipschitz
and the other can be unstable. Estimates for starshaped as well as rather general domains are derived. Their numerical evaluation
is possible and can be done in different ways.
Received October 16, 2001 / Revised version received January 16, 2002 / Published online: April 17, 2002
RID="*"
ID="*" The research was funded partially by the National Science Foundation under the grants NSF–Czech Rep. INT-9724783 and
NSF DMS-9802367
RID="**"
ID="**" Support for Jan Chleboun coming from the Grant Agency of the Czech Republic through grant 201/98/0528 is appreciated 相似文献
932.
933.
Martin Juráš 《Acta Appl Math》2001,66(1):25-39
On the equation manifold of the 2nth-order scalar ordinary differential equation, n3,
we construct a contact two-form such that d0mod, if and only if Equation (1) admits a nondegenerate Lagrangian of order n. We show that the space of all nondegenerate Lagrangians for (1) is at most one-dimensional. The necessary and sufficient conditions for sixth-order and eighth-order scalar ordinary differential equation to admit a variational multiplier are found in terms of vanishing of a certain set of functions. The exact relationship between the Lie algebra of the classical infinitesimal contact symmetries of a variational Equation (1) and its the Lie subalgebra of infinitesimal divergence symmetries is established. 相似文献
934.
This paper is a summary of our study on the superconvergence of the finite element solutions and error estimators. We will persent the analysis of %-superconvergence for finite element solutions of the Poisson equation in the interior of meshes of triangles with straight edges, as well as the analysis at the boundary. The %-superconvergence via local averaging will also be presented, and the error estimators are compared in the sense of %-superconvergence. 相似文献
935.
Roman Drnovšek 《Integral Equations and Operator Theory》2001,39(3):253-266
Let
be a collection of bounded operators on a Banach spaceX of dimension at least two. We say that
is finitely quasinilpotent at a vectorx
0X whenever for any finite subset
of
the joint spectral radius of
atx
0 is equal 0. If such collection
contains a non-zero compact operator, then
and its commutant
have a common non-trivial invariant, subspace. If in addition,
is a collection of positive operators on a Banach lattice, then
has a common non-trivial closed ideal. This result and a recent remarkable theorem of Turovskii imply the following extension of the famous result of de Pagter to semigroups. Let
be a multiplicative semigroup of quasinilpotent compact positive operators on a Banach lattice of dimension at least two. Then
has a common non-trivial invariant closed ideal.This work was supported by the Research Ministry of Slovenia. 相似文献
936.
Aleksandar Jurišić Jack Koolen Paul Terwilliger 《Journal of Algebraic Combinatorics》2000,12(2):163-197
We consider a distance-regular graph with diameter d 3 and eigenvalues k = 0 > 1 > ... >
d
. We show the intersection numbers a
1, b
1 satisfy
We say is tight whenever is not bipartite, and equality holds above. We characterize the tight property in a number of ways. For example, we show is tight if and only if the intersection numbers are given by certain rational expressions involving d independent parameters. We show is tight if and only if a
1 0, a
d = 0, and is 1-homogeneous in the sense of Nomura. We show is tight if and only if each local graph is connected strongly-regular, with nontrivial eigenvalues –1 – b
1(1 + 1)–1 and –1 – b
1(1 +
d
)–1. Three infinite families and nine sporadic examples of tight distance-regular graphs are given. 相似文献
937.
H. Herrlich asked in Topology Appl.
49 (1993), 251–264, whether there are nontrivial classes of topological spaces that are almost reflective and almost coreflective at the same time. This question was dealt with (in Huek and Tozzi, Appl. Categ. Structures
4 (1996), 57–68) in a more general setting than almost reflective and almost coreflective classes. The present paper investigates a modified question: when a nontrivial generalized reflective class of topological or uniform spaces is equivalent to a generalized coreflective class of spaces. 相似文献
938.
The iron silicides samples were prepared by annealing of iron films evaporated onto silicon wafers and capped with amorphous silicon thin overlayers. Semiconducting FeSi2 phase is formed by annealing at the temperatures from 550°C to 850°C. The optical properties of the FeSi2 layers have been deduced from reflectance and transmittance measurements carried out in the temperature range of (77–380) K. The spectral dependence of the absorption coefficient favours direct allowed transitions with forbidden energy gap of 0.87eV at the room temperature. The application of a simple three-parameter semiempirical formula to the temperature dependence of the direct energy gaps leads to the following best fit parameters: the band gap at zero temperature E
g (0) = (0.895 ± 0.004)eV, the dimensionless coupling parameter S = 2.0 ± 0.3, and the average phonon energy <hw> = (46 ± 8)meV. By examining all the reported triplets of parameters for -FeSi2 fabricated by different techniques and thermal processes, an obvious discrepancy can be found for the lattice coupling parameter and average phonon energy, although the bandgaps at 0 K are very similar. Unlike the theoretical prediction and the earlier reported result, our results do not show any evidence of a particularly strong electron-phonon interaction, which would give the lower carrier mobilities. -FeSi2 seems to be an intriguing material where states with energies near the band edges permit ambiguous interpretation of the character of transitions. From optical model for the thin film-substrate system we found the index of refraction to be (5–5.9) in the photon energy interval from 0.65 to 1.15eV. There is also indication of an additional higher-energy absorption edge at l.05eV. 相似文献
939.
M. Janda V. Martišovitš M. Morvová Z. Machala K. Hensel 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):309-315
Motivated by experimental investigations of electrical discharges in N2/CO2/H2O, Monte Carlo (MC) electron dynamics simulations in atmospheric
N2/CO2 mixtures were performed. The goal was to obtain electron energy distribution functions (EEDFs), mean free path, drift velocity,
collision frequency and mean energy of electrons,
rate coefficients of electron-impact reactions, ionisation and attachment coefficients, as functions of the reduced electric
field strength (E/N) and of the concentration of individual gas components. The results obtained by MC simulations were fitted
with polynomials of up to the 3rd order with reasonable accuracy for E/N above 80 Td.
The studied parameters below 80 Td were strongly non-linear as functions of E/N. This is mostly due to the influence of elastic
collisions of electrons with CO2 molecules prevailing in CO2-dominant mixtures for E/N < 40 Td, and vibrational excitation collisions of N2 species prevailing in N2-dominant mixtures for E/N from 40 to 80 Td. The effect of these electron-impact processes was specific for each of the studied
parameters. 相似文献
940.
J.A. Fülöp Zs. Major B. Horváth F. Tavella A. Baltuška F. Krausz 《Applied physics. B, Lasers and optics》2007,87(1):79-84
The use of temporally shaped pump pulses for optical parametric chirped-pulse amplification can increase the efficiency and
suppress possible spectral distortions in this process. With this goal in mind a novel method for shaping narrowband picosecond
pulses has been developed. The method is based on the pulse stacking principle, where replicas of the incoming pulse are created
in a specially designed four-beam interferometer. The replicas are recombined with appropriate relative delays. The interferometer
design allows for a unique flexibility in varying the pulse shape, since all relevant degrees of freedom, such as relative
intensities and delays between the pulse replicas are independently adjustable. Here we describe the design of our device
in detail and report on the experimental demonstration of its pulse-shaping capabilities.
PACS 42.65.Yj; 42.65.Re; 42.81.Gs 相似文献