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排序方式: 共有1002条查询结果,搜索用时 0 毫秒
41.
42.
43.
Tommaso Bruno Marco M. Peloso Anita Tabacco Maria Vallarino 《Journal of Functional Analysis》2019,276(10):3014-3050
Let G be a noncompact connected Lie group, denote with ρ a right Haar measure and choose a family of linearly independent left-invariant vector fields X on G satisfying Hörmander's condition. Let χ be a positive character of G and consider the measure whose density with respect to ρ is χ. In this paper, we introduce Sobolev spaces adapted to X and (, ) and study embedding theorems and algebra properties of these spaces. As an application, we prove local well-posedness and regularity results of solutions of some nonlinear heat and Schrödinger equations on the group. 相似文献
44.
Anita Burdman Feferman 《Logica Universalis》2012,6(3-4):277-291
Leitmotifs in the life of Jean van Heijenoort. 相似文献
45.
Let G = (V, E) be an interval graph with n vertices and m edges. A positive integer R(x) is associated with every vertex x ? V{x\in V}. In the conditional covering problem, a vertex x ? V{x \in V} covers a vertex y ? V{y \in V} (x ≠ y) if d(x, y) ≤ R(x) where d(x, y) is the shortest distance between the vertices x and y. The conditional covering problem (CCP) finds a minimum cardinality vertex set C í V{C\subseteq V} so as to cover all the vertices of the graph and every vertex in C is also covered by another vertex of C. This problem is NP-complete for general graphs. In this paper, we propose an efficient algorithm to solve the CCP with nonuniform
coverage radius in O(n
2) time, when G is an interval graph containing n vertices. 相似文献
46.
The method of quasilinearization is a procedure for obtaining approximate solutions of differential equations. In this paper, this technique is applied to a differential-algebraic problem. Under some natural assumptions, monotone sequences converge quadratically to a unique solution of our problem. 相似文献
47.
A high-performance liquid chromatographic procedure is described for the quantitative determination of epinephrine, norepinephrine, and dopamine in human plasma. The method, which is based on adsorption of the catecholamines to alumina and, after liberation, separation on a microparticulate bonded strong cation-exchange resin and amperometric detection, has been optimized to give complete baseline separation of the substances of interest. Dihydroxybenzylamine, a nonendogenous catecholamine, is used as the internal standard. The detection limit is about 0.1 pmol for dopamine. Analysis of data obtained for norepinephrine and epinephrine from a total of 59 plasma samples showed a good correlation to the corresponding values obtained with a radioenzymatic method. Some results from normal and pathological conditions are compared. 相似文献
48.
Corepresentations of a coalgebra over a quadratic operad are defined, and various characterizations of them are given. Cohomology
of such an operadic coalgebra with coefficients in a corepresentation is then studied. 相似文献
49.
Angel Carocca Herbert Lange Rubí E. Rodríguez Anita M. Rojas 《Geometriae Dedicata》2009,139(1):219-231
Let X
1, ..., X
m
denote smooth projective curves of genus g
i
≥ 2 over an algebraically closed field of characteristic 0 and let n denote any integer at least equal to . We show that the product JX
1 × ... × JX
m
of the corresponding Jacobian varieties admits the structure of a Prym-Tyurin variety of exponent n
m-1. This exponent is considerably smaller than the exponent of the structure of a Prym-Tyurin variety known to exist for an
arbitrary principally polarized abelian variety. Moreover it is given by explicit correspondences.
相似文献
50.
Anita T.?LaytonEmail author Michael L.?MinionEmail author 《BIT Numerical Mathematics》2005,45(2):341-373
This paper concerns a class of deferred correction methods recently developed for initial value ordinary differential equations;
such methods are based on a Picard integral form of the correction equation. These methods divide a given timestep [tn,tn+1] into substeps, and use function values computed at these substeps to approximate the Picard integral by means of a numerical
quadrature. The main purpose of this paper is to present a detailed analysis of the implications of the location of quadrature
nodes on the accuracy and stability of the overall method. Comparisons between Gauss-Legendre, Gauss-Lobatto, Gauss-Radau,
and uniformly spaced points are presented. Also, for a given set of quadrature nodes, quadrature rules may be formulated that
include or exclude function values computed at the left-hand endpoint tn. Quadrature rules that do not depend on the left-hand endpoint (which are referred to as right-hand quadrature rules) are
shown to lead to L(α)-stable implicit methods with α≈π/2. The semi-implicit analog of this property is also discussed. Numerical results suggest
that the use of uniform quadrature nodes, as opposed to nodes based on Gaussian quadratures, does not significantly affect
the stability or accuracy of these methods for orders less than ten. In contrast, a study of the reduction of order for stiff
equations shows that when uniform quadrature nodes are used in conjunction with a right-hand quadrature rule, the form and
extent of order-reduction changes considerably. Specifically, a reduction of order to
is observed for uniform nodes as opposed to
for non-uniform nodes, where Δt denotes the time step and ε a stiffness parameter such that ε→0 corresponds to the problem becoming increasingly stiff.
AMS subject classification (2000) 65B05 相似文献