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1.
Let
denote the unit sphere in
and
the geodesic distance in
. A spherical‐basis function approximant is a function of the form
, where
are real constants,
is a fixed function, and
is a set of distinct points in
. It is known that if
is a strictly positive definite function in
, then the interpolation matrix
is positive definite, hence invertible, for every choice of distinct points
and every positive integer M. The paper studies a salient subclass of such functions
, and provides stability estimates for the associated interpolation matrices.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
2.
Let Δ(1) be the uniform three direction mesh of the plane whose vertices are integer points of
.Let
(respectively
of degree d=3r (respectively d=3r+1 ) for r odd (respectively even) on the triangulation
, and of degree d=2r (respectively d=2r+1) for r odd (respectively even) on the triangulation
. Using linear combinations of translates of these splines we obtain Lagrange interpolants whose corresponding order of approximation
is optimal.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
If
converges for all
with all coefficients
, then the function
is positive definite on H×H for any inner product space H. Set K={k: a
k
>0}. We show that
is strictly positive definite if and only if K contains the index 0 plus an infinite number of even integers and an infinite number of odd integers. 相似文献
4.
Solutions
of a semilinear elliptic boundary value problem,
(with
bounded below) can be put into a one-to-one correspondence with zeros
of a function
. Often d is small. The function
is called the bifurcation function. It can also be shown that the eigenvalues of the matrix
characterize the stability properties of the solutions of the elliptic problem as rest points of
. A finite element method that can be used for computing B and B
c has recently been proposed. An overview of these results and the finite element method is given.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
5.
Let
be a group of affine transformations of the plane that contains a strict contraction and all translations. It is shown that
any two topological discs
are congruent dissection with respect to
such that only three topological discs are used as pieces of dissection. Two pieces of dissection do not suffice in general
even if
consists of all affine transformations.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
For an arbitrary variety
of groups and an arbitrary class
of groups that is closed on quotient groups, we prove that a quotient group G/N of the group G possesses an invariant system with
- and
-factors (respectively, is a residually
-group) if G possesses an invariant system with
- and
-factors (respectively, is a residually
-group) and N
(respectively, N is a maximal invariant
-subgroup of the group G). 相似文献
7.
Adem Kilicman 《Czechoslovak Mathematical Journal》2001,51(3):463-471
Let
,
be ultradistributions in
and let
and
where
is a sequence in
which converges to the Dirac-delta function
. Then the neutrix product
is defined on the space of ultradistributions
as the neutrix limit of the sequence
provided the limit
exist in the sense that
for all in
. We also prove that the neutrix convolution product
exist in
, if and only if the neutrix product
exist in
and the exchange formula
is then satisfied. 相似文献
8.
Let
be a closed orientable surface of genus
, endowed with the structure of a Riemann manifold of constant negative curvature. For the universal covering
, there is the notion of absolute, each of whose points determines an asymptotic direction of a bundle of parallel equidirected geodesics. In the paper it is proved that there is a set
on the absolute having the cardinality of the continuum and such that if an arbitrary flow on
has a semitrajectory whose covering has asymptotic direction defined by a point from
, then this flow is not analytical and has infinitely many stationary points. 相似文献
9.
We compute in this paper the distribution of the area
swept under the occupation process of an M/M/1 queue during a busy period. For this purpose, we use the expression of the Laplace transform
of the random variable
established in earlier studies as a fraction of Bessel functions. To get information on the poles and the residues of
, we take benefit of the fact that this function can be represented by a continued fraction. We then show that this continued
fraction is the even part of an S fraction and we identify its successive denominators by means of Lommel polynomials. This allows us to numerically evaluate
the poles and the residues. Numerical evidence shows that the poles are very close to the numbers
as
. This motivated us to formulate some conjectures, which lead to the derivation of the asymptotic behaviour of the poles and
the residues. This is finally used to derive the asymptotic behaviour of the probability survivor function
. The outstanding property of the random variable
is that the poles accumulate at 0 and its tail does not exhibit a nice exponential decay but a decay of the form
for some positive constants c and
, which indicates that the random variable
has a Weibull-like tail.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
G. V. Kuz'mina 《Journal of Mathematical Sciences》2003,118(1):4880-4894
We apply a variant of the method of the extremal metric to some problems concerning extremal decompositions and related problems. Let
be a system of distinct points on
and let
be the family of all systems
of nonoverlapping simply connected domains on
such that
. Let
where
is the reduced module of the domain
with respect to the point
. At present, the problem concerning the value
was solved completely for
. In this work, we continue the previous author's investigations and consider the case
. In addition, we consider the problem concerning the maximum of the sum
in the family
introduced above, where
, are arbitrary points of the circle
, and is a positive number. We prove that if
, then the maximum is attained only for systems of equidistant points of the circle
. For
, this result was obtained earlier by Dubinin who applied the method of symmetrization. It is shown that if
, where
is an even number, then equidistant points of the circle
do not realize the indicated maximum. Bibliography: 11 titles. 相似文献