《数学学报》外文版7卷3期文章简介(1991)

<正> 关于算术级数中的最小素数王炜以 P(q,l)表示满足条件 P≡l(modq)的素数中之最小者,本文通过一种估计 Dirichlet L-函数非零区域的一种新方法,改进了 P(q,l)的上界估计,证明了P(q,l)(?)q~8.     

本刊外文版6卷4期文章简介

<正> 设f(m)表二次不可约多项式ρf(P)是同余式f(m)≡0(modp)的解数,本文首先研究了对固定的整数a,Legendre符号(a/P)随素数p变化的规律,由此在广义Riemann假设下给出∑ν≤p<ωρf(p)logp/p新的上界,从而改进了Bantle关于f(m)表素数个数的两个上界估计.最后作为应用,我们得到了算术级数上最小素数问题的一个下界估计.     

算术级数中的华罗庚五素数平方定理

本文给出了华罗庚五素数平方定理的算术级数形式,证明了其中一个素数可 以取在大模的算术级数中.     

光滑Weyl和的分数幂均值的数值上界(Ⅱ)

通过讨论光滑Weyl和的任意幂次均值的数值上界之间的关系,给出了幂次为区间[6,7]中的值时相应均值的数值上界的一些新结果.     

光滑Weyl和的分数幂均值的数值上界

通过讨论光滑Weyl和的任意幂次均值的数值上界之间的关系,本文给出了幂次为区间[4,5]中的值时相应均值的数值上界的一些新结果.     

严格α-对角占优M-矩阵A的‖A~(-1)‖_∞的上界估计

针对逆矩阵的无穷范数的上界估计问题,利用严格对角占优M-矩阵逆的无穷范数的上界,给出了严格α-对角占优M-矩阵A的||A~(-1)||_∞的单调递减的上界序列,理论证明及数值分析均表明所得估计改进了某些现有结果.     

矩阵广义逆新的扰动上界

利用矩阵的奇异值分解方法,研究了矩阵广义逆的扰动上界,得到了在F-范数下矩阵广义逆的扰动上界定理,所得定理推广并彻底改进了近期的相关结果.相应的数值算例验证了定理的有效性.     

严格对角占优M-矩阵A的‖A~(-1)‖_∞的上界估计

针对严格对角占优M-矩阵A的‖A~(-1)‖_∞。的估计问题,利用逆矩阵元素的上界,给出了‖A~(-1)‖_∞的单调递减的上界序列,理论证明及数值算例均表明所得估计改进了某些现有结果.     

计算平面代数曲线亏格上界的符号-数值算法

亏格是代数曲线的重要不变量.文章给出计算一类平面代数曲线亏格上界的符号-数值混合算法.首先通过数值稳定的符号-数值混合算法把代数曲线的定义多项式系统约化到几何对合形式,然后考察奇点的性质.如果曲线的奇点是寻常的,那么由奇点的重数可以计算出代数曲线的亏格;否则算法仅给出亏格的一个上界.     

一类变延迟中立型微分方程梯形方法的渐近估计

该文研究了一类变延迟中立型微分方程梯形方法的稳定性,并借助于一个泛函不等式得到了数值解的渐近估计.此渐近估计对数值解的性态不仅比数值渐近稳定性描述得更加精确,而且能给出非稳定情形数值解的上界估计式.     

Error bounds for spatial discretization and waveform relaxation applied to parabolic functional differential equations

The process of semi-discretization and waveform relaxation are applied to general nonlinear parabolic functional differential equations. Two new theorems are presented, which extend and improve some of the classical results. The first of these theorems gives an upper bound for the norm of the error of finite difference semi-discretization. This upper bound is sharper than the classical error bound. The second of these theorems gives an upper bound for the norm of the error, which is caused by both semi-discretization and waveform relaxation. The focus in the paper is on estimating this error directly without using the upper bound for the error, which is caused by the process of semi-discretization and the upper bound for the error, which is caused by the waveform relaxation method. Such estimating gives sharper error bound than the bound, which is obtained by estimating both errors separately.     

Estimates of the rate of convergence of a dynamic reconstruction algorithm under incomplete information about the phase state

In this paper, we study a dynamic reconstruction algorithm which reconstructs the unknown unbounded input and all unobservable phase coordinates from the results of measurements of part of the coordinates. An upper and a lower bound for the accuracy of the reconstruction is obtained. We determine the class of inputs for which the upper bound is uniform. We give a condition for optimally matching the algorithm parameters, ensuring the highest order of the upper bound and equating the orders of the upper and lower bounds. Thus, we establish the sharpness of the upper bound.     

Maximal amplitudes of hyperelliptic solutions of the derivative nonlinear Schrödinger equation

A simple formula is proven for an upper bound for amplitudes of hyperelliptic (finite-gap or N-phase) solutions of the derivative nonlinear Schrödinger equation. The upper bound is sharp, viz, it is attained for some initial conditions. The method used to prove the upper bound is the same method, with necessary modifications, used to prove the corresponding bound for solutions of the focusing NLS equation (Wright OC, III. Sharp upper bound for amplitudes of hyperelliptic solutions of the focusing nonlinear Schrödinger equation. Nonlinearity. 2019;32:1929-1966).     

On field extensions given by periods of Drinfeld modules

In this short note, we answer a question raised by M. Papikian on a universal upper bound for the degree of the extension of $$K_\infty $$ given by adjoining the periods of a Drinfeld module of rank 2. We show that contrary to the rank 1 case such a universal upper bound does not exist, and the proof generalies to higher rank. Moreover, we give an upper and lower bound for the extension degree depending on the valuations of the defining coefficients of the Drinfeld module. In particular, the lower bound shows the non-existence of a universal upper bound.     

An upper bound for the number of matroids

An upper bound for the number of matroids is obtained. This upper bound complements the lower bound obtained by Piff and Welsh in [1].     

A new upper bound for unconstrained two-dimensional cutting and packing

A new upper bound for the unconstrained two-dimensional cutting or packing problem is proposed in this paper. The proposed upper bound can be calculated for any size of plate by solving just two knapsack problems at the beginning of the algorithm. In this research, the proposed upper bound was applied to the well known exact cutting algorithm, although it can be used for both cutting and packing applications. The experimental results demonstrate that the new upper bound is very efficient, and reduces the search time required to find an optimal solution.     

相关随机利率下的双二项模型的破产概率

研究带有相关随机利率的双二项风险模型,得到了破产概率的积分表达式,并利用鞅分析的方法得到了破产概率的经典Lundberg上界,另外给出了一个破产概率的比经典Lundberg上界更精确的上界.     

A note on construction of upper bound graphs

In this paper, we consider construction of upper bound graphs. An upper bound graph can be transformed into a nova by contractions and a nova can be transformed into an upper bound graph by splits. These results include a characterization on upper bound graphs.     

Inequality for the Moment of a Function of a Random Variable

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A degree bound for families of rational curves on surfaces

We give an upper bound for the degree of rational curves in a family that covers a given birationally ruled surface in projective space. The upper bound is stated in terms of the degree, sectional genus and arithmetic genus of the surface. We introduce an algorithm for constructing examples where the upper bound is tight. As an application of our methods we improve an inequality on lattice polygons.