一类2n阶次线性奇异边值问题的正解

利用单调迭代方法给出了一类2n阶次线性奇异常微分方程正解的存在性,得到C~(2n-2)[0,1]和C~(2n-1)[0,1]正解存在的充分必要条件,也得到正解的唯一性.     

一类离散$\mbox{\boldmath $m$}$点边值问题正解的存在性与多重性

本文运用锥上的不动点理论，得到了一类离散多点边值问题的一个正解及两个正解存在性.     

△2u=up+μf(x)的正解的存在性

对非线性双调和方程进行了研究,考虑了其Navier边值问题正解的存在性,不存在性以及多重性,其中Ω是RN中的有界光滑区域.在f(x)可以变号且满足一定条件的情况下证明了(i)若p＞1,则当μ充分小时,上述问题至少有一个正解,而当μ充分大时上述问题没有正解;(ii)若N≥5,1＜p≤N 5/N-5,则当μ充分小时,上述问题至少有两个正解.这些结果改进了郭真华和邓引斌的相应结论.     

一类捕食——食饵模型正平衡解的整体分歧

讨论了一类改进的Leslie-Gower和Holling-Type Ⅱ型捕食-食饵模型对应的平衡态系统正解的结构.以捕食者的出生率b为分歧参数,利用局部分歧理论和整体分歧理论,得到了此平衡态系统正解的存在性与参数b的关系,即当b适当大时,该平衡态系统具有共存正解.     

非线性二阶时滞微分方程边值问题的正解

本文讨论了一类二阶时滞微分方程边值问题的正解存在性,在不要求非线性项取值恒为非负的情形下,利用锥上不动点指数的计算得到了该问题的正解.     

奇异二阶微分方程积分边值问题正解的存在唯一性

利用上下解方法结合极值原理研究一类带积分边值条件的奇异二阶微分方程正解的存在性以及唯一性,给出了$C[0,1]$和$C^1[0,1]$正解存在唯一的一个充分条件.非线性项允许在$t=0,1$ 和$x=0$处具有奇异性.     

二阶非共振半正边值问题正解的存在性

通过将微分方程化为积分方程组,并利用锥上的不动点指数定理,研究了一类二阶边值问题正解的存在性, 其中不要求非线性项$f(t,u)$非负,得到了其正解存在的一个定理.     

一类具变号非线性项二阶m点边值问题的正解

利用一个新的不动点定理,研究一类具有变号且依赖一阶导数非线性项二阶m点边值问题正解的存在性,得到了正解存在的充分条件.     

一类反应扩散方程正解的存在性

本文使用锥映象不动点指数方法,讨论了一类反应扩散方程正解的存在性.     

一类奇异二阶系统边值问题的正解

本文利用正规锥和迭代法考察了一类奇异二阶系统边值问题的正解的存在性.我们的工作是对[1]的补充和发展.     

广义凸空间上重合点定理和极大极小不等式

利用已知的KKM型定理,在广义空间上得到若干个新的重合点定理和推广的Fan-Browder型不动点定理,并且讨论了Von Newmann-Sion型极大极小不等式.主要结果改进和推广了文献中的相应结论.     

农艺措施对蔗糖产量影响的探讨

采用五元二次回归旋转正交组合设计方法，通过１９９０—１９９１年秋植蔗试验，建立蔗糖产量与种植密度，尿素、钙镁磷、氯化钾、桐麸的施用量等主要农艺措施之间的数学模型，得出各主要农艺措施及它们相互之间的作用对蔗糖产量的影响程度，并优选甘蔗生产的最优综合栽培农艺措施方案。     

Nonnegative Linearization for Polynomials Orthogonal with Respect to Discrete Measures

We give conditions for the coefficients in three term recurrence relations implying nonnegative linearization for polynomials orthogonal with respect to measures supported on convergent sequences of points. The previous methods were unable to cover this case. January 14, 1999. Date revised: January 31, 2000. Date accepted: October 24, 2000.     

A sublogarithmic convex hull algorithm

We present a parallel algorithm for finding the convex hull of a sorted set of points in the plane. Our algorithm runs inO(logn/log logn) time usingO(n log logn/logn) processors in theCommon crcw pram computational model, which is shown to be time and cost optimal. The algorithm is based onn ^1/3 divide-and-conquer and uses a simple pointer-based data structure.Part of this work was done when the last three authors were at the Department of Computer and Information Science, Linköping University. The research of the second author was supported by the Academy of Finland.     

Modelling the bending behaviour of a new hybrid glulam beam reinforced with FRP and ultra-high-performance concrete

The main objective of this research project to develop a new type of hybrid glulam beam that will increase the performance of a timber structural element by combining it with ultra-high-performance concrete with short fibre reinforcement (UHPC-SFR). The hybrid beam is obtained is a layered structures obtained by combining a glued-laminated (glulam) wood beam with UHPC-SFR lamellae that is bonded to its top and bottom faces. The obtained hybrid beam possesses a lower bending stiffness than a glulam beam of similar overall dimensions but has a higher ultimate load capacity. Two models that were developed to validate this concept are presented in this paper. The first is an analytical model based on hypotheses related to the usual strength of materials, and the second is a finite element model. The load–displacement and moment–curvature relationships from both models are compared to the experimental results obtained from the large-scale specimens. The results show good correlation between the analytical modelling and experimental results and illustrate the potential applications of such composite beam configurations for civil engineering structures.     

A note on constructing min-max heaps

In this paper we show that to construct an implicit, double-ended priority queue organized as a min-max heap, 17/9n = 1.88 ...n comparisons suffice in the worst case (neglectng lower order terms). The algorithm improves the previously best known upper bound of 2.15 ...n comparisons.Some of the ideas given in this paper were presented in a preliminary form at the 1st Scandinavian Workshop on Algorithm Theory, Halmstad (July, 1988) [7].     

不朽的丰碑 永远的怀念

介绍分别于2005年在南开数学所建成和于2006年在美国数学研究所建成的两幢陈省身楼、国际数学联盟在2009年设立并于2010年在国际数学家大会上首次颁发的陈省身奖章、陈省身的博士生们对老师的回忆以及陈省身“上善若水”的崇高品格．     

基于BP神经网络的企业信用评估模型

本文研究了企业信用评估中的模型问题.以商业企业为例,阐述了基于BP神经网络的信用评估模型的原理,通过建立指标体系,讨论基于BP神经网络的评价模型的实现,对模型的不足进行了分析,并提出改进建议.     

Uniformly distributed sums of bernoulli variables

Sums of independent, identically distributed (iid) binomial variates have binomial distributions; yet it is possible to construct a sequence of binomial distributions over {0, 1} for variatesX ₁,X ₂, ... such that all partial sumsY _i =X ₁ + ... +X _i have uniform distributions. The price to pay is to give up the iid condition. Requiring the property of only one sum does not alleviate the situation much.It is also possible to generate on a computerm × n-matrices, of 0–1 binomial variates with uniformly distributed row and column sums of all major submatrices, but only for smallm andn. Even a three-dimensional 2 × 2 × 2 array can have a similar property.Other target distributions than the rectangular are possible, but cumbersome. An example with smaller variance is given.The results were needed for simulating the performance of some Operations Research algorithms.Dedicated to Peter Naur on the occasion of his 60th birthday     

Evaluations of Parameters for the Optimization of S.S.O.R. and A.D.I. Preconditioning

The main goal of this paper is to give two ways to estimate the needed parameters in order to obtain the condition number of S.S.O.R. preconditioned matrices, namely, the algebraic matricial formulation of convexity Riesz theorem and the tridiagonal Fourier analysis. The improvement with respect to Axelsson's approach is explicitly given. Estimations of the condition number in the case of A.D.I. preconditioning is also considered.