共查询到20条相似文献,搜索用时 62 毫秒
1.
In this article, the dependent steps of a negative drift random walk are modelled as a two-sided linear process Xn =-μ ∞∑j=-∞ψn-jεj, where {ε, εn; -∞< n < ∞}is a sequence of independent, identically distributed random variables with zero mean, μ>0 is a constant and the coefficients {ψi;-∞< i <∞} satisfy 0 <∞∑j=-∞|jψj| <∞. Under the conditions that the distribution function of |ε| has dominated variation and ε satisfies certain tail balance conditions, the asymptotic behavior of P{supn≥0(-nμ ∞∑j=-∞εjβnj) > x}is discussed. Then the result is applied to ultimate ruin probability. 相似文献
2.
Caidi Zhao Shengfan Zhou Yongsheng Li 《Journal of Computational and Applied Mathematics》2008,220(1-2):129-142
This paper discusses the incompressible non-Newtonian fluid with rapidly oscillating external forces g(x,t)=g(x,t,t/) possessing the average g0(x,t) as →0+, where 0<0<1. Firstly, with assumptions (A1)–(A5) on the functions g(x,t,ξ) and g0(x,t), we prove that the Hausdorff distance between the uniform attractors and in space H, corresponding to the oscillating equations and the averaged equation, respectively, is less than O() as →0+. Then we establish that the Hausdorff distance between the uniform attractors and in space V is also less than O() as →0+. Finally, we show for each [0,0]. 相似文献
3.
The maximum asymptotic bias of an S-estimate for regression in the linear model is evaluated over the neighborhoods (called (c,γ)-neighborhoods) defined by certain special capacities, and its lower and upper bounds are derived. As special cases, the (c,γ)-neighborhoods include those in terms of -contamination, total variation distance and Rieder's (,δ)-contamination. It is shown that when the model distribution is normal and the (,δ)-contamination neighborhood is adopted, the lower and upper bounds of an S-estimate (including the LMS-estimate) based on a jump function coincide with the maximum asymptotic bias. The tables of the maximum asymptotic bias of the LMS-estimate are given. These results are an extension of the corresponding ones due to Martin et al. (Ann. Statist. 17 (1989) 1608), who used -contamination neighborhoods. 相似文献
4.
We show how any BSP tree for the endpoints of a set of n disjoint segments in the plane can be used to obtain a BSP tree of size for the segments themselves, such that the range-searching efficiency remains almost the same. We apply this technique to obtain a BSP tree of size O(nlogn) such that -approximate range searching queries with any constant-complexity convex query range can be answered in O(min>0{(1/)+k}logn) time, where k is the number of segments intersecting the -extended range. The same result can be obtained for disjoint constant-complexity curves, if we allow the BSP to use splitting curves along the given curves.We also describe how to construct a linear-size BSP tree for low-density scenes consisting of n objects in such that -approximate range searching with any constant-complexity convex query range can be done in O(logn+min>0{(1/d−1)+k}) time. 相似文献
5.
On the reducibility of a class of nonlinear quasi-periodic system with small perturbation parameter near zero equilibrium point 总被引:1,自引:0,他引:1
This work focuses on the reducibility of the following real nonlinear analytical quasiperiodic system: where A is a real 2×2 constant matrix, and f(t,0,)=O() and ∂xf(t,0,)=O() as →0. With some non-resonant conditions of the frequencies with the eigenvalues of A and without any nondegeneracy condition with respect to , by an affine analytic quasiperiodic transformation we change the system to a suitable norm form at the zero equilibrium for most of the sufficiently small perturbation parameter . 相似文献
6.
Mirela Damian-Iordache Sriram V. Pemmaraju 《Journal of Algorithms in Cognition, Informatics and Logic》2002,42(2):255
The main result of this paper is a (2 + )-approximation scheme for the minimum dominating set problem on circle graphs. We first present an O(n2) time 8-approximation algorithm for this problem and then extend it to an
time (2 + )-approximation scheme for this problem. Here n and m are the number of vertices and the number of edges of the circle graph. We then present simple modifications to this algorithm that yield (3 + )-approximation schemes for the minimum connected and the minimum total dominating set problems on circle graphs. Keil (1993, Discrete Appl. Math.42, 51–63) shows that these problems are NP-complete for circle graphs and leaves open the problem of devising approximation algorithms for them. These are the first O(1)-approximation algorithms for domination problems on circle graphs. 相似文献
7.
The following reaction-diffusion system in spatially non-homogeneous almost-periodic media is considered in a bounded domain
: (1) ∂tu=Au−f(u)+g, u|∂Ω=0. Here u=(u1,…,uk) is an unknown vector-valued function, f is a given nonlinear interaction function and the second order elliptic operator A has the following structure: where aijl(y) are given almost-periodic functions. We prove that, under natural assumptions on the nonlinear term f(u), the longtime behavior of solutions of (1) can be described in terms of the global attractor
of the associated dynamical system and that the attractors
, 0<<01, converge to the attractor
of the homogenized problem (1) as →0. Moreover, in the particular case of periodic media, we give explicit estimates for the distance between the non-homogenized
and the homogenized
attractors in terms of the parameter . 相似文献
8.
Galerkin methods are used to approximate the singular integral equation with solution φ having weak singularity at the endpoint −1, where a, b≠0 are constants. In this case φ is decomposed as φ(x)=(1−x)α(1+x)βu(x), where β=−α, 0<α<1. Jacobi polynomials are used in the discussions. Under the conditions fHμ[−1,1] and k(t,x)Hμ,μ[−1,1]×[−1,1], 0<μ<1, the error estimate under a weighted L2 norm is O(n−μ). Under the strengthened conditions f″Hμ[−1,1] and , 2α−<μ<1, the error estimate under maximum norm is proved to be O(n2α−−μ+), where , >0 is a small enough constant. 相似文献
9.
The dimension function Dψ of a band-limited wavelet ψ is bounded by n if its Fourier transform is supported in [−(2n+2/3)π,(2n+2/3)π]. For each
and for each , 0<<δ=δ(n), we construct a wavelet ψ with supp
such that Dψ>n on a set of positive measure, which proves that [−(2n+2/3)π,(2n+2/3)π] is the largest symmetric interval for estimating the dimension function by n. This construction also provides a family of (uncountably many) wavelet sets each consisting of infinite number of intervals. 相似文献
Full-size image
10.
Florian Mehats Jean-Michel Roquejoffre 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》1999,16(6):691
This paper continues the study started in [12]. In the upper half-plane, consider the elliptic equation
, submitted to the nonlinear oblique derivative boundary condition Ux = UUz on the axis x = 0. The solution of this problem appears to be the self-similar solution of the heat equation with the same boundary condition. As goes to 0, the function U converges to the non trivial solution U of the corresponding degenerate problem. Moreover there exists z0 > 0 such that U vanishes for z ≥ z0, is C∞ on ]0, z0[×
+, is continuous on the boundary x = 0 and is discontinuous on the half-axis {z = 0, x> 0}. 相似文献
Full-size image
11.
Let G be an undirected graph with nonnegative edge lengths. Given two vertices as sources and all vertices as destinations, we investigated the problem how to construct a spanning tree of G such that the sum of distances from sources to destinations is minimum. In the paper, we show the NP-hardness of the problem and present a polynomial time approximation scheme. For any >0, the approximation scheme finds a (1+)-approximation solution in O(n1/+1) time. We also generalize the approximation algorithm to the weighted case for distances that form a metric space. 相似文献
12.
For fLp(
n), with 1p<∞, >0 and x
n we denote by T(f)(x) the set of every best constant approximant to f in the ball B(x, ). In this paper we extend the operators Tp to the space Lp−1(
n)+L∞(
n), where L0 is the set of every measurable functions finite almost everywhere. Moreover we consider the maximal operators associated to the operators Tp and we prove maximal inequalities for them. As a consequence of these inequalities we obtain a generalization of Lebesgue's Differentiation Theorem. 相似文献
13.
Hee-Kap Ahn Peter Brass Otfried Cheong Hyeon-Suk Na Chan-Su Shin Antoine Vigneron 《Computational Geometry》2006,33(3):152-164
Given a planar convex set C, we give sublinear approximation algorithms to determine approximations of the largest axially symmetric convex set S contained in C, and the smallest such set S′ that contains C. More precisely, for any >0, we find an axially symmetric convex polygon QC with area |Q|>(1−)|S| and we find an axially symmetric convex polygon Q′ containing C with area |Q′|<(1+)|S′|. We assume that C is given in a data structure that allows to answer the following two types of query in time TC: given a direction u, find an extreme point of C in direction u, and given a line ℓ, find C∩ℓ. For instance, if C is a convex n-gon and its vertices are given in a sorted array, then TC=O(logn). Then we can find Q and Q′ in time O(−1/2TC+−3/2). Using these techniques, we can also find approximations to the perimeter, area, diameter, width, smallest enclosing rectangle and smallest enclosing circle of C in time O(−1/2TC). 相似文献
14.
Donglong Li Zhengde Dai Xuhong Liu 《Journal of Mathematical Analysis and Applications》2007,330(2):934-948
In this paper, the two-dimensional generalized complex Ginzburg–Landau equation (CGL)
ut=ρu−Δφ(u)−(1+iγ)Δu−νΔ2u−(1+iμ)|u|2σu+αλ1(|u|2u)+β(λ2)|u|2