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1.
A B-spline approach for empirical mode decompositions   总被引:14,自引:0,他引:14  
We propose an alternative B-spline approach for empirical mode decompositions for nonlinear and nonstationary signals. Motivated by this new approach, we derive recursive formulas of the Hilbert transform of B-splines and discuss Euler splines as spline intrinsic mode functions in the decomposition. We also develop the Bedrosian identity for signals having vanishing moments. We present numerical implementations of the B-spline algorithm for an earthquake signal and compare the numerical performance of this approach with that given by the standard empirical mode decomposition. Finally, we discuss several open mathematical problems related to the empirical mode decomposition. Dedicated to Professor Charles A. Micchelli on the occasion of his 60th birthday with friendship and esteem Mathematics subject classification (2000) 94A12. Supported in part by National Aeronautics and Space Administration under grant NAG5-5364, and National Science Foundation under grants NSF0314742 and NSF0312113. Yuesheng Xu: Corresponding author. Supported in part by Natural Science Foundation of China under grant 10371122.  相似文献
2.
Error estimates for matrix-valued radial basis function interpolation   总被引:2,自引:0,他引:2  
We introduce a class of matrix-valued radial basis functions (RBFs) of compact support that can be customized, e.g. chosen to be divergence-free. We then derive and discuss error estimates for interpolants and derivatives based on these matrix-valued RBFs.  相似文献
3.
We present an adaptive wavelet method for the numerical solution of elliptic operator equations with nonlinear terms. This method is developed based on tree approximations for the solution of the equations and adaptive fast reconstruction of nonlinear functionals of wavelet expansions. We introduce a constructive greedy scheme for the construction of such tree approximations. Adaptive strategies of both continuous and discrete versions are proposed. We prove that these adaptive methods generate approximate solutions with optimal order in both of convergence and computational complexity when the solutions have certain degree of Besov regularity.  相似文献
4.
Group Chromatic Number of Graphs without K5-Minors   总被引:2,自引:0,他引:2  
 Let G be a graph with a fixed orientation and let A be a group. Let F(G,A) denote the set of all functions f: E(G) ↦A. The graph G is A -colorable if for any function fF(G,A), there is a function c: V(G) ↦A such that for every directed e=u vE(G), c(u)−c(v)≠f(e). The group chromatic numberχ1(G) of a graph G is the minimum m such that G is A-colorable for any group A of order at least m under a given orientation D. In [J. Combin. Theory Ser. B, 56 (1992), 165–182], Jaeger et al. proved that if G is a simple planar graph, then χ1(G)≤6. We prove in this paper that if G is a simple graph without a K 5-minor, then χ1(G)≤5. Received: August 18, 1999 Final version received: December 12, 2000  相似文献
5.
On Group Chromatic Number of Graphs   总被引:2,自引:0,他引:2  
Let G be a graph and A an Abelian group. Denote by F(G, A) the set of all functions from E(G) to A. Denote by D an orientation of E(G). For fF(G,A), an (A,f)-coloring of G under the orientation D is a function c : V(G)↦A such that for every directed edge uv from u to v, c(u)−c(v) ≠ f(uv). G is A-colorable under the orientation D if for any function fF(G, A), G has an (A, f)-coloring. It is known that A-colorability is independent of the choice of the orientation. The group chromatic number of a graph G is defined to be the least positive integer m for which G is A-colorable for any Abelian group A of order ≥m, and is denoted by χg(G). In this note we will prove the following results. (1) Let H1 and H2 be two subgraphs of G such that V(H1)∩V(H2)=∅ and V(H1)∪V(H2)=V(G). Then χg(G)≤min{max{χg(H1), maxvV(H2)deg(v,G)+1},max{χg(H2), maxuV(H1) deg (u, G) + 1}}. We also show that this bound is best possible. (2) If G is a simple graph without a K3,3-minor, then χg(G)≤5.  相似文献
6.
An Exact Riemann Solver for a Fluidized Bed Model   总被引:1,自引:0,他引:1  
We study a 2 x 2 hyperbolic system of conservation laws withsource term arising in a fluidized bed model. The system issolved numerically and results are presented to demonstratethe occurrence of ‘slugging’ in the full model equations.The numerical procedure is based on operator splitting and Godunov'smethod, for which we derive the exact solution of the Riemannproblem. A second-order improvement due to Davis (1988) mayproduce small oscillations near shocks and these can be reducedif the underlying flux limiter of the Davis method is replacedby the minmod limiter.  相似文献
7.
Degree conditions for group connectivity   总被引:1,自引:0,他引:1  
Let G be a 2-edge-connected simple graph on n≥13 vertices and A an (additive) abelian group with |A|≥4. In this paper, we prove that if for every uvE(G), max{d(u),d(v)}≥n/4, then either G is A-connected or G can be reduced to one of K2,3,C4 and C5 by repeatedly contracting proper A-connected subgraphs, where Ck is a cycle of length k. We also show that the bound n≥13 is the best possible.  相似文献
8.
The asymptotic distribution for the local linear estimator in nonparametric regression models is established under a general parametric error covariance with dependent and heterogeneously distributed regressors. A two-step estimation procedure that incorporates the parametric information in the error covariance matrix is proposed. Sufficient conditions for its asymptotic normality are given and its efficiency relative to the local linear estimator is established. We give examples of how our results are useful in some recently studied regression models. A Monte Carlo study confirms the asymptotic theory predictions and compares our estimator with some recently proposed alternative estimation procedures.  相似文献
9.
Given a nonhierarchical network and time-varying flow requirements, the problem of determining optimal capacities is termed design; that of determining optimal flows as dynamic routing. We formulate a linear program to solve both simultaneously in the case of deterministic flow requirements. A probability distribution termed the Erlang Difference Distribution is derived from a queueing model to describe random flow requirements, and this case leads to a separable convex program that has a linear programming equivalent. Both linear programs are amenable to Dantzig-Wolfe decomposition, which reveals subproblems that yield to special techniques of solution.
Zusammenfassung Gegeben sei ein nicht hierarchisches Netzwerk mit zeitabhängigen Flüssen. Das Problem, optimale Kapazitäten festzusetzen, wird als Netzwerk-Entwurf bezeichnet. Die Bestimmung optimaler Flüsse bezeichnet man als dynamische Flußführung. Es wird ein lineares Programm formuliert, das beide Probleme gleichzeitig löst, sofern deterministische Flüsse vorliegen. Sodann wird eine Wahrscheinlichkeitsverteilung namens Erlang'sche Differenzen-Verteilung aus einem Warteschlangenmodell abgeleitet, um zufällige Flüsse zu beschreiben. Dies führt auf ein separables konvexes Programm mit einem linearen Programm als Äquivalent. Bei beiden betrachteten linearen Programmen kann die Dantzig-Wolfe Dekomposition angewendet werden, wobei die auftretenden Teilprobleme durch spezielle Techniken gelöst werden können.


Research partially supported by National Science Foundation Grant ECS-8300214.  相似文献
10.
New vector operations are defined that generalize the classical harmonic and geometric means of scalars. The definition of the harmonic mean involves an explicit vector formula, whereas the geometric mean of two vectors is defined by an iterative procedure. Two special cases are described in some detail, the case of 2-vectors which are equivalent to the complex numbers, and the case of 4-vectors which are a representation of the quaternions.  相似文献
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