一类二阶线性脉冲微分方程解的渐近性态

研究一类二阶线性脉冲微分方程解的结构和解的渐近性态,其中δ(t)是δ-函数,且对n∈N有an>0,r(t)>0是[t0, ∞) 上的连续函数,0≤t0相似文献   

一类二阶脉冲线性非振动微分方程解的渐近性态

研究了一类二阶线性非振动脉冲微分方程(a(t)x′)′=p(t)x ∑n=1^∞anδ(t-tn)x解的有界性和趋零性,其中a(t)为正的连续可微函数,p(t)为非负连续函数,且不最终恒为零,an≥0(n∈N),δ(t)是δ-函数．充分考虑脉冲的影响,通过建立脉冲微分方程与相应的常微分方程解的比较不等式,得到了判断脉冲微分方程解有界和趋零的充要条件。     

近似函数高阶导数的高精度积分逼近方法

主要研究稳定计算近似函数的高阶导数的积分逼近方法,方法因由Lanczos提出故也称为Lanczos算法.利用Legendre多项式的正交性,提出了一类逼近近似函数高阶导数的高精度积分方法,即构造出一系列积分算子Dn,h(m)去逼近噪声函数的高阶导数,且这些积分算子具有O(δ(2n+2)/(2n+m+2))的收敛速度,其中δ为近似函数的噪声水平.数值模拟结果表明提出的方法是稳定而有效的.     

r-一致超图Ramsey函数的渐近下界(英文)

本文利用Lovasz局部引理的Spencer形式和对称形式给出r-一致超图Ramsey函数的渐近下界.证明了:对于任意取定的正整数f0,使得当n→∞时,有R~((r))(m~l,n~(k-l))≥(c-o(1))(n~(r-1)/logn)~■.特别地,R~((r))_k(n)≥(1-o(1))n/e k~■(n→∞).对于任意取定的正整数s≥r+1和常数δ>0,α≥0,如果F表示阶为s的r-一致超图,■表示阶为t的r-一致超图,且■的边数满足m(■)≥(δ-o(1))t~r/(logt)α(t→∞),则存在c=c(s,δ,α)>0,使得R~((r))(F,■)≥(c-o(1))(t~(r-1)/(logt)~l+(r-l)α)~(m(F)-l/s-r).     

关于平稳随机场的强正则性

设{X(s,t)}_(s,t=0,±1,…)为平稳随机场,H_x 为一切 X(s,t),s,t=0,±1,…所产生的线性闭子空间,即 H_x={X(m,n),m,n=0,±1,…}.令 H_x=(s,t)={X(m,n),m≤s 或n≤t},_x=H_x(s,t).当_x=φ时,平稳随机场称为强正则的;_x=H_x 时,平稳随机场称为强奇异的.已经知道,强正则平稳随机场具有下列性质:     

爵克松奇异积分对连续函数逼近的准确常数

<正> 1.设 C_(2x)是周期2π的连续函数的全体,E_n(f)表示阶数不超过 n 的三角多项式对函数 f(x)的最佳逼近,ω(f;δ)表示函数 f(π)的连续模.(?)证明:如果f(x)∈C_(2π)的话,     

SL(2,R)上一类极大算子的(H1∞,s,L1)型

本文我们引入了函数类Bδ(G//K)={ψ∈L1(G//K)‖ψ(t)|≤△-1(t)(1+t)1-δ,δ＞0},对f∈Lp(G//K),1≤p≤∞,和极大算子Mδf(x)=sup ε＞0 ψ∈Bδ(G//K) |ψε*f(x)|,证明了这类算子是(H1∞,s,L1)型的.     

ON THE EQUATION □φ=｜↓△φ｜^2 IN FOUR SPACE DIMENSIONS

This paper considers the following Cauchy problem for semilinear wave equations in n space dimensions □φ=F(δφ),φ(0,x)=f(x),δtφ(0,x)=g(x),whte □=δt^2-△ is the wave operator,F is quadratic in δεφ with δ=(δt,δx1,…,δxn).The minimal value of s is determined such that the above Cauchy problem is locally wellposed in H^s.It turns out that for the general equation s must satisfy s&gt;max(n/2,n+5/4).This is due to Ponce and Sideris (when n=3)and Tataru (when n≥5).The purpose of this paper is to supplement with a proof in the case n=2,4.     

自由树的端点数问题(英文)

本文研究具有 n 个节点的、所有结构不同的自由树的端点总数,得到了关于这些数的计算公式,给出了其生成函数与 n 节点有向树个数的生成函数和 n 节点有向数总叶数生成函数之间的一个简明关系.主要结果是:定理 设 E_n为具有 n 个节点的、所有结构不同的自由树的端点总数,则 E_n 的生成函数E(z)=sum from n=1 to ∞ E_n~z~n 满足E(z)=L(z)+zA(z)-A(z)L(z)+L(z~2),其中 A(z)和 L(z)分别是 n 节点有向树的个数 a_n 和总叶数 L_n 的生成函数.此外,E_n=(?)计算结果如正文中的数表所示.     

一类微分方程組在一个临界情形中的解的稳定条件

<正> 其中γ及p_(sσ)(s,σ=1,…,n)为实常数,且γ>0,而q_(sσ)(t)(s,σ=1,…,n)为实变数t之实函数,当一切t≥T>0时定义、連續及有界;X_s~((1))(s=1,…,n)为x_1,…,x_n之正則函数,其展开式不含低于二次之項,并具实常数系数;至于X_s~((2))(s=1,…,n)为x_1,…,x_n之正則函数,其按x_1,…,x_n之冪的展开式为:     

Estimation of Regression Coefficient in General Regression Model

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Gromov–Wasserstein Distances and the Metric Approach to Object Matching

This paper discusses certain modifications of the ideas concerning the Gromov–Hausdorff distance which have the goal of modeling and tackling the practical problems of object matching and comparison. Objects are viewed as metric measure spaces, and based on ideas from mass transportation, a Gromov–Wasserstein type of distance between objects is defined. This reformulation yields a distance between objects which is more amenable to practical computations but retains all the desirable theoretical underpinnings. The theoretical properties of this new notion of distance are studied, and it is established that it provides a strict metric on the collection of isomorphism classes of metric measure spaces. Furthermore, the topology generated by this metric is studied, and sufficient conditions for the pre-compactness of families of metric measure spaces are identified. A second goal of this paper is to establish links to several other practical methods proposed in the literature for comparing/matching shapes in precise terms. This is done by proving explicit lower bounds for the proposed distance that involve many of the invariants previously reported by researchers. These lower bounds can be computed in polynomial time. The numerical implementations of the ideas are discussed and computational examples are presented.     

用L_1-罚函数作线性搜索函数的一种修正约束变尺度算法

本文对用Ｌ１－罚函数作线性搜索的约束变尺度算法，提出了一种新的修正方法，该方法的计算量小，可行性较好，并且仍能保持原有算法的收敛性．     

Channel metrization

We present an algorithm that, given a channel, determines if there is a distance for it such that the maximum likelihood decoder coincides with the minimum distance decoder.We also show that any metric, up to a decoding equivalence, can be isometrically embedded into the hypercube with the Hamming metric, and thus, in terms of decoding, the Hamming metric is universal.     

Computational topology-based characterization of pore space changes due to chemical dissolution of rocks

In this paper, we present an algorithm for the numerical simulation of reactive transport at the pore scale to facilitate observation of pore space and rock matrix evolution. Moreover, simulation at the pore scale opens up the possibility of estimating changes in the transport properties of rocks, such as permeability and tortuosity. To quantitatively analyze pore space evolution, we developed a numerical algorithm that can be used to construct persistence diagrams of the connectivity components for pore space and the rock matrix, which characterize the topology evolution during rock matrix dissolution. Introducing the “bottle-neck” metric in the space of the persistence diagrams, we cluster the numerical experiments in terms of similarities in topology evolution. We demonstrate that the application of this metric to the persistence diagrams allowed us to distinguish topologically different dissolution scenarios, for instance, the formation of a dissolution front near the inlet, homogeneous dissolution of the matrix inside the core sample, and formation of wormholes. We illustrate that the differences in topology evolution lead to cross-correlations among the transport properties of rocks (porosity-permeability-tortuosity).     

基于Ohlson模型的企业权益价值自适应估计

企业价值估计是投资的基础.1995年,J.Ohlson将超额收益RI（Residual Income）用于企业价值估价,形成了企业价值估价的一个分支.然而,Ohlson模型要求正确估计收益率和未来各期的超额收益,在应用上有明显的局限性.本文以Ohlson超额收益估价模型为基础,结合Gordon增长模型,建立了一个企业权益资本价值估价新模型.对该模型的参数估计,我们采取逐步迭代的方法,逐步吸收企业成长过程中的信息,不断修正模型参数,直至得到“满意”的参数.我们证明了这个参数估计过程是收敛的,因此新模型有更好的可操作性.     

Evaluating credal classifiers by utility-discounted predictive accuracy

Predictions made by imprecise-probability models are often indeterminate (that is, set-valued). Measuring the quality of an indeterminate prediction by a single number is important to fairly compare different models, but a principled approach to this problem is currently missing. In this paper we derive, from a set of assumptions, a metric to evaluate the predictions of credal classifiers. These are supervised learning models that issue set-valued predictions. The metric turns out to be made of an objective component, and another that is related to the decision-maker’s degree of risk aversion to the variability of predictions. We discuss when the measure can be rendered independent of such a degree, and provide insights as to how the comparison of classifiers based on the new measure changes with the number of predictions to be made. Finally, we make extensive empirical tests of credal, as well as precise, classifiers by using the new metric. This shows the practical usefulness of the metric, while yielding a first insightful and extensive comparison of credal classifiers.     

Heat kernel fluctuations for a resistance form with non-uniform volume growth

In this article, we consider the problem of estimating the heatkernel on measure-metric spaces equipped with a resistance form.Such spaces admit a corresponding resistance metric that reflectsthe conductivity properties of the set. In this situation, ithas been proved that when there is uniform polynomial volumegrowth with respect to the resistance metric the behaviour ofthe on-diagonal part of the heat kernel is completely determinedby this rate of volume growth. However, recent results haveshown that for certain random fractal sets, there are globaland local (point-wise) fluctuations in the volume as r 0 andso these uniform results do not apply. Motivated by these examples,we present global and local on-diagonal heat kernel estimateswhen the volume growth is not uniform, and demonstrate thatwhen the volume fluctuations are non-trivial, there will benon-trivial fluctuations of the same order (up to exponents)in the short-time heat kernel asymptotics. We also provide boundsfor the off-diagonal part of the heat kernel. These resultsapply to deterministic and random self-similar fractals, andmetric space dendrites (the topological analogues of graph trees).     

Metric Regularity of the Sum of Multifunctions and Applications

The metric regularity of multifunctions plays a crucial role in modern variational analysis and optimization. This property is a key to study the stability of solutions of generalized equations. Many practical problems lead to generalized equations associated to the sum of multifunctions. This paper is devoted to study the metric regularity of the sum of multifunctions. As the sum of closed multifunctions is not necessarily closed, almost all known results in the literature on the metric regularity for one multifunction (which is assumed usually to be closed) fail to imply regularity properties of the sum of multifunctions. To avoid this difficulty, we use an approach based on the metric regularity of so-called epigraphical multifunctions and the theory of error bounds to study the metric regularity of the sum of two multifunctions, as well as some related important properties of variational systems. Firstly, we establish the metric regularity of the sum of a regular multifunction and a pseudo-Lipschitz multifunction with a suitable Lipschitz modulus. These results subsume some recent results by Durea and Strugariu. Secondly, we derive coderivative characterizations of the metric regularity of epigraphical multifunctions associated with the sum of multifunctions. Applications to the study of the behavior of solutions of variational systems are reported.     

Metric Lie algebras with maximal isotropic centre

A metric Lie algebra is a Lie algebra equipped with an invariant non-degenerate symmetric bilinear form. It is called indecomposable if it is not the direct sum of two metric Lie algebras. We are interested in describing the isomorphism classes of indecomposable metric Lie algebras. In the present paper we restrict ourselves to a certain class of solvable metric Lie algebras which includes all indecomposable metric Lie algebras with maximal isotropic centre. We will see that each metric Lie algebra belonging to this class is a twofold extension associated with an orthogonal representation of an abelian Lie algebra. We will describe equivalence classes of such extensions by a certain cohomology set. In particular we obtain a classification scheme for indecomposable metric Lie algebras with maximal isotropic centre and the classification of metric Lie algebras of index 2.