退化扩散过程小扰动的平均越出时间估计

本文研究了Ｒ＾ｄ上的扩散过程｛Ｘεｔ｝，它是Ｒ＾ｄ上退化扩散过程｝Ｘｔ｝的小随机扰动，其中｛Ｘｔ｝满足随机微分方程ｄＸｔ＝ｂ（Ｘｔ）ｄｔ＋τ（Ｘｔ）ｏｄＷｔ；｛Ｘ＾εｔ｝满足随机微分方程ｄＸ＾εｔ＝ｂ（Ｘεｔ）ｄｔ＋τ（Ｘ＾εｔ）ｏｄＷｔ√εσ（Ｘ＾εｔ）ｄＢｔ，ε〉０。     

中立型时滞微分方程解的零点距估计

考虑中立型时滞微分方程〔ｘ（ｔ）＋Ｐ（ｔ）ｘ（ｔ－ｒ）‘＋Ｑ（ｔ）ｘ（ｔ－σ）＝０，其中Ｐ（ｔ），Ｑ（ｔ）∈Ｃ（│ｔ０，∞），Ｒ＾＋），ｒ，σ∈Ｒ＾＋，本文对上述方程解的相邻零点间的距离作了新的估计。     

高阶亚线性Duffing方程的周期解

在本文中，二阶亚线性Ｄｕｆｆｉｎｇ方程周期解存在的结果被推广到高阶Ｄｕｆｆｉｎｇ方：ｘ＾（２ｎ）＋ｇ（ｘ）＝ｐ（ｔ）＝ｐ（ｔ＋２π）（ｎ≥１）和ｘ＾（２ｎ＋１）＋ｇ（ｘ）－ｐ（ｔ）＝ｐ（ｔ＋２π）。     

一类具周期系数的Riccati型方程的周期解

给出Ｒｉｃｃａｔｉ型方程ｘ＾&;#183;＝Ａ（ｔ）ｘ＾２ｍ＋Ｂ（ｔ）ｘ＾２ｋ－１＋Ｃ（ｔ）（Ａ（ｔ），Ｂ（ｔ），Ｃ（ｔ）是周期为Ｔ的连续函数，ｍ，ｋ∈Ｎ且ｍ≥ｋ）无周期解及存在周期解的充分条件。     

关于МОФОНЪКО不等式的精确性

证明了如下定理：设Φ（ｚ）＝Σ↑ｎ↓ｕ＝１∏↑ｔ↓ｉ＝１ｆｉ＾ａ＾ｕｉ０…（ｆｉ＾（ｋｉ））＾ａｉｋｉ＾ｕ／Σ↑ｍ↓ｖ＝１∏↑ｔ↓ｉ＝１ｆｉ＾ｂ＾ｖｉ０…（ｆｉ＾（ｋｉ））＾ｂｉｋｉ＾ｖ其中ｆｉ（ｚ），（１≤ｉ≤ｔ）是亚纯函数，ａｉｊ＾ｕ，ｂｉｊ＾ｖ为非负整数，则有Ｔ（ｒ，Φ）≤Σ↑ｔ↓ｉ＝１｛［Ｓｉ＋ｏ（１）］ｍ（ｒ，ｆｉ）＋［△ｉ＝ｕｉ＋ｏ（１）］Ｎ（ｒ，ｆｉ）＋（△ｉ－Ｓｉ）Ｎ↑－（ｒ，ｆｉ     

变系数高阶中立型泛函数分方程的振动性与渐近性

考虑变系数高阶中立型泛函微分方程ｄ＾ｎ／ｄｔ＾ｎ（ｘ（ｔ）＋ｐ（ｔ）ｘ（ｔ－τ（ｔ））＋ｍ∑ｉ＝１Ｐｉ（ｔ）ｘ（ｔ－τｉ（ｔ）＝０，在－１＜ｐ（ｔ）≤０情形下解的振动性与渐近性，取消了Ｐｉ（ｔ）≥ｑｉ＞０的限制，改进以往的相应结果，本文结果时高阶泛函方程Ｘ＾（ｎ）（ｔ）＋ｍ∑ｉ＝１ｐｉ（ｔ）ｘ（ｔ－τｉ（ｔ））＝０也是适用的。     

两指标随机积分方程解的唯一性

在正交增量的随机积分基础上，利用Ｌｉｐｓｃｈｉｔｚ条件，讨论了下面一类两参数随机积分方程解的唯一性。Ｘ（ｓ，ｔ）＝Ｚ（ｓ，０）＋Ｚ（０，ｔ）－Ｚ（０，０）＋∫Ｒｓｔα（ｕ，ｖ，Ｘ）ｄＭｕｖ＋∫Ｒｓｔβ（ｕ，ｖ，Ｘ）ｄｍｕｖ＋∫Ｒ＾ｓｔγ１（ｕ，ｖ，ｕ＇，ｖ＇，Ｘ）ｄＭｕｖｄＭｕ＇ｖ＇＋∫Ｒ＾２ｓｔγ２（ｕ，ｖ，ｕ＇，ｖ＇，Ｘ）ｄＭｕｖｄｍｕ＇ｖ＇＋∫Ｒ＾２ｓｔγ３（ｕ，ｖ，ｕ＇，ｖ＇，Ｘ）ｄｍｕｖ     

临界状态下具渐近周期系数的一阶时滞微分方程的振动性

首先证明了在临界情形ｌｉｍｉｎｆ「ｐ（ｔ）－ｒ（ｔ）」＝０且∫ｔ－ｒｒ（ｓ）ｄｓ＝１／ｅ下一阶时滞微分方程ｘ’（ｔ）＋ｐ（ｔ）ｘ（ｔ－τ）＝０（＊）所有解振动等价于Ｒｉｃｃａｔｉ不等式ｗ（ｔ）＋ｒ（ｔ）ｗ＾２（ｔ）＋２ｅ＾２（ｐ（ｔ）＝ｒ（ｔ））≤０无最终正解,然后据此给出了方程（＊）在临界状态下两个振动及非振动准则。     

一个随机过程的小扰动的平均越出时间估计

考虑Ｒ＾ｄ（ｄ≥１）上随机过程｛Ｘ（ｔ）｝的小扰动｛Ｘ＾ε（Ｔ）｝,其中｛Ｘ（ｔ）｝和｛Ｘ＾ε（ｔ）｝分别满足随机微分方程ｄＸ（ｔ）＝ｂ（Ｘ（ｔ）,Ｚ（ｔ）ｄｔ和ｄＸ＾ε（ｔ）＝ｂ（Ｘ＾ε（Ｔ）,Ｚ（ｔ）ｄｔ＋εｄＢ（ｔ）,这里｛Ｚ（ｔ）｝是一个有限状态马氏过程,应用大偏差方法,给出了当扰动趋于零时,｛Ｘ＾ε（ｔ）｝是平均越出时间的渐近估计。     

具连续变量的线性时滞差分方程的振动性

本文研究如下具有连续变量的线性时滞差分方程ｙ（ｔ）－ｙ（ｔ－τ）＋∑ｍｊ＝１ｐｊ（ｔ）ｙ（ｔ－σｊ）＝０,ｔ≥０,其中ｐｊ（ｔ）∈ｃ（Ｒ＾＋,Ｒ＾＋）,０〈τ〈σ１≤σ２≤…≤ｍ,ｊ＝１,２,…,ｍ,获得了该方程的每个解都振动的若干充分条件,改进了现有文献中的结果。     

Estimation of the number of components of finite mixtures of multivariate distributions

An estimator of the number of components of a finite mixture ofk-dimensional distributions is given on the basis of a one-dimensional independent random sample obtained by a transformation of ak-dimensional independent random sample. A consistency of the estimator is shown. Some simulation results are given in a case of finite mixtures of two-dimensional normal distributions.     

Galois Structure of K-Groups of Rings of Integers

N/Kbe a Galois extension of number fields with finite Galois group G.We describe a new approach for constructing invariants of the G-module structure of the K groups of the ring of integers of N in the Grothendieck group of finitely generated projective Z[G]modules. In various cases we can relate these classes, and their function field counterparts, to the root number class of Fröhlich and Cassou-Noguès.     

Eigenvector p-Bases of Rings of Constants of Derivations

Let A be a UFD of characteristic p > 0, let 𝒵 be a set of some eigenvectors of a derivation of A. We prove, under some additional assumptions, a necessary and sufficient condition for 𝒵 to be a p-basis of the minimal ring of constants containing 𝒵. The main preparatory result is the unique decomposition theorem with respect to a factor from a given subalgebra containing A^p.     

有资格限制的指派问题的求解方法

在实际的指派工作中，常会遇到某个人有没有资格去承担某项工作的问题，因此，本建立了有资格限制的指派问题的数学模型。在此数学模型中，将效益矩阵转化为判定矩阵，由此给出了判定此种指派问题是否有解的方法；在有解的情况下，进一步将效益矩阵转化为求解矩阵，从而将有资格限制的指派问题化为传统的指派问题来求解。最后给出了一个数值例子来说明这样的处理方法是有效的。     

On Sums of Coefficients of Products of Polynomials

We study the nilpotency of the sums of all coefficients of some sorts of products of polynomials over reversible, IFP, and NI rings, and introduce an SCN ring as a generalization. We characterize SCN rings in relation with related ring properties, and also provide several useful properties and ring extensions of SCN rings.     

Convergence of sequences of sets of associated primes

It is a well-known result of M. Brodmann that if is an ideal of a commutative Noetherian ring , then the set of associated primes of the -th power of is constant for all large . This paper is concerned with the following question: given a prime ideal of which is known to be in for all large integers , can one identify a term of the sequence beyond which will subsequently be an ever-present? This paper presents some results about convergence of sequences of sets of associated primes of graded components of finitely generated graded modules over a standard positively graded commutative Noetherian ring; those results are then applied to the above question.

     

Rates of Convergence of Means of Euclidean Functionals

Let L be the Euclidean functional with p-th power-weighted edges. Examples include the sum of the p-th power-weighted lengths of the edges in minimal spanning trees, traveling salesman tours, and minimal matchings. Motivated by the works of Steele, Redmond and Yukich (Ann. Appl. Probab. 4, 1057–1073, 1994, Stoch. Process. Appl. 61, 289–304, 1996) have shown that for n i.i.d. sample points {X ₁,…,X _n } from [0,1] ^d , L({X ₁,…,X _n })/n ^(d−p)/d converges a.s. to a finite constant. Here we bound the rate of convergence of EL({X ₁,…,X _n })/n ^(d−p)/d . Y. Koo supported by the BK21 project of the Department of Mathematics, Sungkyunkwan University. S. Lee supported by the BK21 project of the Department of Mathematics, Yonsei University.     

图表示范畴的两个子范畴

引进图表示范畴的两个子范畴,研究它们的同调性质。     

Asymptotics of families of solutions of nonlinear difference equations

One method to determine the asymptotics of particular solutions of a difference equation is by solving an associated asymptotic functional equation. Here we study the behaviour of the solutions in an asymptotic neighbourhood of such individual solutions. We identify several types of attraction and repulsion, which range from almost orthogonality to almost parallelness. Necessary and sufficient conditions for these types of behaviour are given.     

Extreme values of the sum of squares of degrees of bipartite graphs

In this paper we determine the minimum and maximum values of the sum of squares of degrees of bipartite graphs with a given number of vertices and edges.