一种含参数的Wallis公式与Stirling公式

利用离散变量连续化的思想,得到了含参数的Wallis公式与Stirling公式,它们是对这两个经典公式的一种推广形式。     

若干个数列之间的联系及其极限

揭示了若干个数列之间的联系，找到了形成这些数列的背景，求出了这些数列的极限；而后又提供两个例子作为所获得的结论的应用，且其中的一个例子是对一道典型题的错误解法的再讨论．     

关于Wallis数列的连分式估计（英文）

给出了Wallis数列的连分式表达式.基于获得的结果,建立了Wallis数列的一个双边不等式.     

Wallis不等式的新改进

对Wallis不等式做出了新的改进.与目前掌握的文献相比,所得结果精度更高,且容易估计误差.同时还导出了(2n(2-n)1!)!!!的一个渐近展开式.     

Wallis公式的几个应用

搜集了若干与Wallis公式有关的例子，论述了Wallis公式在其上的应用     

关于含有Wallis公式的双边不等式

得到了含有 Wallis公式的一个简洁且更为精细的双边不等式 .     

一个有趣数列的单调性

利用不等式(π4(n-1)/2n 4(n+))^(1/2)1<∫_0^(π/2)sin^nxdx<(π(4n+5)/2 (n+1)(4n+3))^(1/2),对有趣数列{(n+c)^(1/2)∫_0^(π/2)sin^nxdx}的单调性再次进行了分析论证,并对已有结论进行了改进.     

关于$\Gamma$函数的一个凸性结果及其应用

利用Γ函数和它的对数微商的一些性质以及Laplace变换的卷积定理,Γ函数的一个凸性结果被获得．作为应用,著名的Wallis不等式被改进．     

与Wallis不等式有关的两个数列的单调性

利用Wallis不等式正面回答了《大学数学》2016,32(1):101-104文末提出的猜想,并证明了该猜想的一个推广形式.     

推广的Wallis数列的单调性

讨论了推广的Wallis数列{(n+c)(1/2)∫π/20sin~nxdx}(n≥1,c为非负常数)的单调性.黄永忠等(2016)证明了当0≤c≤1/2该数列严格递增;当1/2c≤1该数列对于充分大的n严格递减.本文给出了此结论的一个新的简洁证明,并对相关问题做了讨论.进一步,证明了当且仅当c2π~2-16/16-π~2=0.609945…,推广的Wallis数列为严格递减数列.     

有限元插值误差的下界估计

基于一维区域上的拟一致剖分,证明了线性元插值误差的最优下界估计.基于此并利用超收敛理论,我们得到了有限元离散误差的上、下界.     

Classroom note: Sawtooth functions

Using MAPLE enables students to consider many examples which would be very tedious to work out by hand. This applies to graph plotting as well as to algebraic manipulation. The challenge is to use these observations to develop the students’ understanding of mathematical concepts. In this note an interesting relationship arising from inverse trigonometric functions is analysed. To understand what is going on students have to develop an understanding of how to deal with inverses where a function is not 1–1, by restricting the domain. The piece of work developed here also provides some interesting exercises in proof by induction.     

伪Smarandache函数的上下界

对于正整数n,设Z(n)=min{m|m∈N,1/2m(m+1)≡0(modn)},称为n的伪Smarandache函数.设r是正整数.根据广义Ramanujan-Nagell方程的结果,运用初等数论方法证明了下列结果:i)1/2(-1+(8n+1)≤Z(n)≤2n-1.ii)当r≠1,2,3或5时,Z(2~r+1)≥1/2(-1+(2~(r+3)·5+41)).iii)当r≠1,2,3,4或12时,Z(2~r-1)≥1/2(-1+(2~(r+3)·3-23).     

Bounds on Malapportionment

Uniformly sized constituencies give voters similar influence on election outcomes. When constituencies are set up, seats are allocated to the administrative units, such as states or counties, using apportionment methods. According to the impossibility result of Balinski and Young, none of the methods satisfying basic monotonicity properties assign a rounded proportional number of seats (the Hare-quota). We study the malapportionment of constituencies and provide a simple bound as a function of the house size for an important class of divisor methods, a popular, monotonic family of techniques.     

On Eigenvector Bounds

We show under very general assumptions that error bounds for an individual eigenvector of a matrix can be computed if and only if the geometric multiplicity of the corresponding eigenvalue is one. Basically, this is true if not computing exactly like in computer algebra methods. We first show, under general assumptions, that nontrivial error bounds are not possible in case of geometric multiplicity greater than one. This result is also extended to symmetric, Hermitian and, more general, to normal matrices. Then we present an algorithm for the computation of error bounds for the (up to normalization) unique eigenvector in case of geometric multiplicity one. The effectiveness is demonstrated by numerical examples.This revised version was published online in October 2005 with corrections to the Cover Date.     

Bounds on trees

We prove a finitary version of the Halpern–Läuchli Theorem. We also prove partition results about strong subtrees. Both results give estimates on the height of trees.     

Bounds for multiplicities

Let and be a homogeneous -algebra. We establish bounds for the multiplicity of certain homogeneous -algebras in terms of the shifts in a free resolution of over . Huneke and we conjectured these bounds as they generalize the formula of Huneke and Miller for the algebras with pure resolution, the simplest case. We prove these conjectured bounds for various algebras including algebras with quasi-pure resolutions. Our proof for this case gives a new and simple proof of the Huneke-Miller formula. We also settle these conjectures for stable and square free strongly stable monomial ideals . As a consequence, we get a bound for the regularity of . Further, when is not Cohen-Macaulay, we show that the conjectured lower bound fails and prove the upper bound for almost Cohen-Macaulay algebras as well as algebras with a -linear resolution.