The Sprague-Grundy function of the game Euclid

We show that the Sprague-Grundy function of the game Euclid is given by g(x,y)=⌊|y/x-x/y|⌋ for x,y≥1.     

m重对角因子循环矩阵求逆和广义逆的Euclid算法

利用多项式Euclid算法给出了非奇异m重对角因子循环矩阵求逆的一个新算法,并将该算法推广至求m重对角因子循环矩阵的群逆和Moore-Penrose逆,及给出了具体的求逆步骤.     

Al-Kūhī's revision of Book I of Euclid's Elements

The 10th-century mathematician Abū Sahl al-Kūhī, one of the best geometers of medieval Islam, wrote several treatises on the first three books of Euclid's Elements. We present an edition and translation of al-Kūhī's revision of Book I of the Elements, in which he altered the book's focus to the theorems and rearranged the propositions. The most dramatic of the changes is the complete absence of all geometric constructions, suggesting that al-Kūhī preferred instead to use Euclid's Data, and the related procedures of analysis and synthesis, for constructions. Other novel aspects include a proof of Euclid's fourth postulate, the use of the parallel postulate early in the work, and a different proof of the Pythagorean theorem.

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一种新型区间数多属性决策算法研究

随着多属性决策问题的复杂性、不确定性日益增强，基于区间数的多属性决策理论与应用研究越来越广泛。基于算子有序性的构建思想，本文提出并构建了基于有序欧几里德算子的区间数多属性决策算法模型，证明了有序欧几里德算子的单调性、齐次性和幂等性。采用基于有序欧几里德算子的区间数多属性决策方法对某火炮采购问题进行了决策计算，证明了该方法的有效性与可行性。     

Mathematics and Her Sisters in Medieval Islam: A Selective Review of Work Done from 1985 to 1995

This paper surveys work done over the past decade, largely in Western Europe and North America, in the history of the mathematical sciences as practiced in medieval Islam from central Asia to Spain. Among the major topics covered, in addition to the usual branches of mathematics, are mathematical geography, astronomy, and optics. We have also given accounts of some current debates on the interpretation of important texts and, in addition, we have surveyed some of the literature dealing with the interrelation of mathematics and society in medieval Islam.Copyright 1997 Academic Press.Cet exposé présente un rapport de recherche fait au cours de la dernière décennie en histoire des sciences mathématiques durant le Moyen Âge. Il évalue l'influence islamique de cette période dans le territoire qui s'étend de l'Asie centrale jusqu'en Espagne. Parmi les sujets traités, on y trouve la géographie, l'astronomie, et l'optique en plus des branches habituelles des mathématiques. Nous donnons un compte rendu des débats actuels en ce qui concerne l'interprétation de publications islamiques de cette époque. De plus à partir des textes littéraires, on a examiné la relation entre les mathématiques et la société islamique du Moyen Âge.Copyright 1997 Academic Press.[FORMULA]     

On some structured inverse eigenvalue problems

This work deals with various finite algorithms that solve two special Structured Inverse Eigenvalue Problems (SIEP). The first problem we consider is the Jacobi Inverse Eigenvalue Problem (JIEP): given some constraints on two sets of reals, find a Jacobi matrix J (real, symmetric, tridiagonal, with positive off-diagonal entries) that admits as spectrum and principal subspectrum the two given sets. Two classes of finite algorithms are considered. The polynomial algorithm which is based on a special Euclid–Sturm algorithm (Householder's terminology) and has been rediscovered several times. The matrix algorithm which is a symmetric Lanczos algorithm with a special initial vector. Some characterization of the matrix ensures the equivalence of the two algorithms in exact arithmetic. The results of the symmetric situation are extended to the nonsymmetric case. This is the second SIEP to be considered: the Tridiagonal Inverse Eigenvalue Problem (TIEP). Possible breakdowns may occur in the polynomial algorithm as it may happen with the nonsymmetric Lanczos algorithm. The connection between the two algorithms exhibits a similarity transformation from the classical Frobenius companion matrix to the tridiagonal matrix. This result is used to illustrate the fact that, when computing the eigenvalues of a matrix, the nonsymmetric Lanczos algorithm may lead to a slow convergence, even for a symmetric matrix, since an outer eigenvalue of the tridiagonal matrix of order n − 1 can be arbitrarily far from the spectrum of the original matrix. This revised version was published online in August 2006 with corrections to the Cover Date.     

A note on two Erdősʼs proofs of the infinitude of primes

P. Erdős found numerous theorems, problems, results and conjectures in elementary number theory. Some of them are two Erdősʼs proofs of of the famous Euclidʼs theorem on the infinitude of primes. As noticed below, one of these proofs immediately implies the fact that the number of primes smaller than x is $⩾\log x/(2\log 2)$.     

基于灰色系统理论的工程项目评标方法研究

工程项目评标实质是多目标决策问题,为优先出合适的投标单位,建立灰色Euclid理论工程项目评标决策模型.首先,运用层次分析法(AHP)与信息熵法分别确定主客观权重.然后利用博弈集结模型对指标体系进行组合赋权,得到综合权重.最后,结合工程项目评标实例运用灰色Euclid理论评标模型进行评标决策.结果表明,运用博弈集结组合赋权和灰色Euclid理论模型选出投标单位D为最优方案,与实际评标一致,验证了模型的可操作性和适用性.     

The Sprague–Grundy function of the real game Euclid

The game Euclid, introduced and named by Cole and Davie, is played with a pair of nonnegative integers. The two players move alternately, each subtracting a positive integer multiple of one of the integers from the other integer without making the result negative. The player who reduces one of the integers to zero wins. Unfortunately, the name Euclid has also been used for a subtle variation of this game due to Grossman in which the game stops when the two entries are equal. For that game, Straffin showed that the losing positions (a,b) with a<b are precisely the same as those for Cole and Davie’s game. Nevertheless, the Sprague–Grundy functions are not the same for the two games. We give an explicit formula for the Sprague–Grundy function for the original game of Euclid and we explain how the Sprague–Grundy functions of the two games are related.