矩阵方程X＋A^TX^—1A=Q存在可稳定化解的充分必要条件

１引言一般的时离散代数Ｒｉｃｃａｔｉ方程具有下面的形式：这里如果方程（１）中的系数矩阵满足：（ｎ＝ｍ）则方程（１）变为当Ｑ＝ＱＴ＞０时,Ｅｎｇｗｅｒｄａ,詹兴致等人研究了方程（２）存在正定解的充分必要条件［１］［２］［３］．本章利用方程（２）与（１）的关系,从另一角度讨论了Ｑ为对称矩阵时,方程（２）存在可稳定化解的充分必要条件．２基本概念与记号首先我们简单回顾一下以前的概念与记号．矩阵束Ｍ—Ｎ,Ｍ,Ｎ为正则的,也就是说ｄｅｔ（λＭ－Ｎ）＝０;如果λ０为ｄｅｔ（λＭ－Ｎ）的ｋ重根,则称λ０为它的ｋ…     

对流扩散方程的经济差分格式

１．引言 对流扩散方程是一类基本的运动方程,它可描述质量、热量的输运过程以及反应扩散过程等众多物理现象．寻找稳定、快速实用的数值方法,有着重要的理论和实际意义．标准的差分方法或有限元方法对它常常失效,根本原因在于“对流项”的存在．［１］提出了解对流扩散方程的特征线修正技术,这一方法考虑沿着特征线（流动方向）的离散,利用了对流扩散问题的物理力学性质,可以有效地克服数值振荡,保证数值解的稳定,尤其对“对流占优”的问题,这一方法有突出的优越性．这方面已有大量的理论和应用研究成果［２,３,７］．对大规模…     

解不适定算子方程的一个定常二步隐式迭代法

１．引言 设Ｘ,Ｙ是两个Ｈｉｌｂｅｒｔ空间,Ａ：Ｘ→Ｙ是有界线性算子,考虑算子方程 Ａｘ＝ｙ（１．１）如果Ａ的值域Ｒ（Ａ）在Ｙ中非闭,则方程（１．１）是不适定的［１］．许多应用科学中都归结出这一类方程,特别地,许多反问题是不适定的［２,３］．本文考虑方程（１．１）的 Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义解,这里Ａ是算子Ａ的Ｍｏｏｒｅ－Ｐｅｎｒｏｓｅ广义逆［１］．Ａ＋ｙ存在当且仅当本文均作这一假设．在实际中,通常代替（１．１）的是扰动方程这里右端项,为一给定的误差水平,Ｑ是Ｙ到Ｒ（Ａ）的正交投影算子．对扰…     

时滞差分方程的正解与全局渐近稳定性

本文通过研究一类一阶变系数时滞差分方程ｘｎ＋１－ｘｎ＋∑ｓｉ＝１ｐｉ，ｎｘｎ－ｋｉ＝０，ｎ＝０，１，２，…的一个正解的性质，得到了它的零解为全局渐近稳定的充分条件．     

θ-方法的非线性渐近稳定性

１引言 数值求解延迟微分方程时,方法的稳定性具有无容置疑的重要性．自１９７５年Ｂａｒｗｅｌｌ引入Ｐ－稳定性与ＧＰ－稳定性概念以来,该领域研究已获许多重要成果（如［７］［８］）．它们大多是基于下面标量线性模型方程：其中λ,μ为复数且满足延迟量τ（＞０）为常数,函数θ（ｔ）连续． 我们首先回忆Ｂａｒｗｅｌｌ［１］的定义． 定义１．１一个数值方法称为是Ｐ－稳定的,如果对任意正整数ｒ用该方法按步长ｈ＝τ／ｒ求解（１．１）时在节点ｔｎ＝ｎｈ的数值解ｙｎ满足 定义１．２一个数值方法称为是ＧＰ－稳定的,如果用该方…     

奇数阶中立型微分方程的线性化振动性(英文)

考虑奇数阶非线性中立型方程我们建立了方程（１．１）的一个线性化振动结论以及存在正解的充分条件．     

高阶非线性差分方程的振动性

本文研究了差分方程△ｄｘ（ｎ）＋ｐ（ｎ）△（ｄ－１）ｘ（ｎ）＋Ｈ（ｎ，ｘ（ｎ））＝０，（１．１）△ｄｘ（ｎ）＋ｐ（ｎ）△（ｄ－１）ｘ（ｎ，ｘ（ｎ））＝Ｑ（ｎ）．（１．２）在一定的条件下，证明了方程（１．１）与（１．２）在振动性方面的等价问题．对于方程（１．１）或（１．２），在ｎ是偶数时的每一个有界解是振动的，在ｎ是奇数时，每一个有界解是振动的或当→∞时单调趋于零的充要性定理也建立了．     

二阶差分方程非振动解的渐近性态

把二阶线性差分方程（１．１）看成非振动方程（１．２）的扰动,其中是向前差分算子,是实数序列．假设（１．２）非振动,则（１．２）有一个主解及副解．本文给出充分条件或必要条件使（１．１）也有一个主解ｘｎ和一个副解ｘｎ满足且这种渐近表示式以三种不同形式给出．     

方程 λ(1 ce~(-τλ) a be~(-τλ)= 0所有根具有负实部的充要条件

考虑方程λ（１＋ｃｅ~（－τλ）＋ａ＋ｂｅ~（－τλ）＝０,（２）其中ａ,ｂ和ｃ为任意常数,τ为正常数,ｃ≠０．方程（１）为中立型方程　　　　　　　　ｘ（ｔ）＋ｃｘ（ｔ－τ）＋ａｘ（ｔ）＋ｂｘ（ｔ－τ）＝０　（２）的特征方程．方程（１）为一常见的拟多项式方程．关于拟多项式函数, Ｐｏｎｔｒｙａｇｉｎ在 １９４２年给出了判断这类函数所有零点位于左半复平面的充要条件．但对中立型方程来说,由于这些条件往往难以验证,使得人们长期以来无法用Ｐｏｎｔｒｙａｐｉｎ定理找出方程（１）所有根具有负实部的充要条件．本文在克服了上述困难后,用Ｐｏｎｔｒｇｉｎ定理找出方程（１）所有根具有负实部的充要条件．     

求解热传导方程的一类新的加权差分格式

本文提出了数值求解热传导方程的一类新的Ｏ（ｋ,ｈ２）加权差分格式,并利用Ｆｏｕｒｉｅｒ方法讨论了格式的稳定性,证明了当１／（１＋ｅε）≤θ≤１时,格式是无条件稳定的,而当０≤θ＜１／（１＋ｅε）时,只有０＜ｒ≤ｆ（θ,ε）,格式才稳定,其中ｆ（θ,ε）对任何固定的θ是正实数ε的严格单调增函数．最后通过数值算例检验了文中格式的高稳定性．     

两类带有确定潜伏期的SEIS传染病模型的分析

通过研究两类带有确定潜伏期的SEIS传染病模型,发现对种群的常数输入和指数输入会使疾病的传播过程产生本质的差异．对于带有常数输入的情形,找到了地方病平衡点存在及局部渐近稳定的阈值,证明了地方病平衡点存在时一定局部渐近稳定,并且疾病一致持续存在．对于带有指数输入的情形,发现地方病平衡点当潜伏期充分小时是局部渐近稳定的,当潜伏期充分大时是不稳定的．     

Polynomial-time algorithms for regular set-covering and threshold synthesis

A set-covering problem is called regular if a cover always remains a cover when any column in it is replaced by an earlier column. From the input of the problem - the coefficient matrix of the set-covering inequalities - it is possible to check in polynomial time whether the problem is regular or can be made regular by permuting the columns. If it is, then all the minimal covers are generated in polynomial time, and one of them is an optimal solution. The algorithm also yields an explicit bound for the number of minimal covers. These results can be used to check in polynomial time whether a given set-covering problem is equivalent to some knapsack problem without additional variables, or equivalently to recognize positive threshold functions in polynomial time. However, the problem of recognizing when an arbitrary Boolean function is threshold is NP-complete. It is also shown that the list of maximal non-covers is essentially the most compact input possible, even if it is known in advance that the problem is regular.     

Milnor方图中的w-凝聚性

整环R称为ω-凝聚整环,是指R的每个有限型理想是有限表现型的.本文证明了ω-凝聚整环是v-凝聚整环,且若(RDTF,M)是Milnor方图,则在Ⅰ型情形,R是ω-凝聚整环当且仅当D和T都是ω-整环,且T_M是赋值环;对于Ⅱ-型情形,R是ω-凝聚整环当且仅当D是域,[F:D]<∞,M是R的有限型理想,T是ω-凝聚整环,且R_M是凝聚整环.     

覆盖下近似算子的拓扑性质

在不限制U为有限论域的情况下,研究了覆盖下近似算子XL和CL的拓扑性质。证明了覆盖下近似算子XL是内部算子,而且由XL生成的拓扑TXL为包含由覆盖C本身作为子基生成的拓扑TC的最小Alexandrov拓扑。特别地,当U为有限论域时,TXL=TC.然而,覆盖下近似算子CL不是内部算子。当覆盖C为某拓扑的基时,CL是内部算子,且此时由CL生成的拓扑TCL与TC是同一个拓扑。若进一步要求U为有限论域,则TCL=TXL=TC,进而CL=XL.     

带有反馈的因果模型中的独立性识别

在本文中,直接利用计算要概率分布的办法证明了在史包含离散变量４ 反馈系统产生的因果图中的条件独立关系可以由ｄ－分离识别出．     

On the density of the minimal subspaces generated by discrete linear Hamiltonian systems

This paper focuses on the density of the minimal subspaces generated by a class of discrete linear Hamiltonian systems. It is shown that the minimal subspace is densely defined if and only if the maximal subspace is an operator; that is, it is single valued. In addition, it is shown that, if the interval on which the systems are defined is bounded from below or above, then the minimal subspace is non-densely defined in any non-trivial case.     

递推阻尼最小二乘法的收敛性与稳定性

递推最小二乘法是参数辨识中最常用的方法,但容易产生参数爆发现象.因此对一种更稳定的辨识方法——递推阻尼最小二乘法进行了收敛特性的分析.在使用算法之前先归一化测量向量,结果表明,参数化距离收敛于一个零均值随机变量,并且在持续激励条件下,适应增益矩阵的条件数有界.参数化距离的方差有界.     

An Improved Branch & Bound Method for the Uncapacitated Competitive Location Problem

In this paper, the problem of locating new facilities in a competitive environment is considered. The problem is formulated as the firm expected profit maximization and a set of nodes is selected in a graph representing the geographical zone. Profit depends on fixed and deterministic location costs and, since customers are independent decision-makers, on the expected market share. The problem is an instance of nonlinear integer programming, because the objective function is concave and submodular. Due to this complexity a branch & bound method is developed for solving small size problems (that is, when the number of nodes is less than 50), while a heuristic is necessary for larger problems. The branch & bound is called data-correcting method, while the approximate solutions are obtained using the heuristic-concentration method.     

Chaotic synchronization with filter based on wavelet transformation

A kind of chaotic synchronization method is presented in the paper. In the transmitter, part signals are transformed by wavelet and the detail information is removed. In the receiver, the component with low frequency is reconstructed and discrete feedback is used, we show that synchronization of two identical structure chaotic systems is attained. The effect of feedback on chaotic synchronization is discussed. Using the synchronous method, the transmitting signal is transported in compressible way, system resource is saved, the component with high frequency is filtered and the effect of disturbance on synchronization is reduced. The synchronization method is illustrated by numerical simulation experiment.     

Detection of multivariate outliers with location slippage or scale inflation in left orthogonally invariant or elliptically contoured distributions

This paper is concerned with two kinds of multiple outlier problems in multivariate regression. One is a multiple location-slippage problem and the other is a multiple scale-inflation problem. A multi-decision rule is proposed. Its optimality is shown for the first problem in a class of left orthogonally invariant distributions and is also shown for the second problem in a class of elliptically contoured distributions. Thus the decision rule is robust against departures from normality. Further the null robustness of the decision statistic which the rule is based on is pointed out in each problem.