平面上全局半稳定系统

平面上全局半稳定系统郑作环（海南师范学院数学系，海口５７１１００）１９９０年６月２日收到，１９９１年８月２８日收到修改稿．一、前言设函数Ｘ（ｘ，ｙ）与Ｙ（ｘ，ｙ）在平面Ｒ２上连续，又设微分方程组满足解对初始值的连续依赖性条件，记ｆ（ｐ，ｔ）为（１）式...     

Hermite型插值算子对可微函数的逼近

Ｈｅｒｍｉｔｅ型插值算子对可微函数的逼近章仁江（中国计量学院，杭州３１００３４）关键词Ｈｅｒｍｉｔｅ型插值算子，Ｊａｃｏｂｉ多项式．分类号ＡＭＳ（１９９１）４１Ａ／ＣＣＬＯ１７４设（１）＞ｘ１＞ｘ２＞…＞ｘｎ＞（－１），ｘｋ＝ｃｏｓθｋ（ｋ＝１，２，...     

关于Fourier级数的一点推广

以２ｌ为周期的函数ｆ（ｘ）也可看作周期为４ｌ．设ｆ（ｘ）满足 Ｄｉｒｉｃｈｌｅｔ充分条件,按［１］方法展开的以 ２ｌ为周期的 Ｆｏｕｒｉｅｒ 级数和以 ４ｌ为周期的 Ｆｏｕｒｉｅｒ 级数则对应于不同表达式．本文证明了这两种表达形式是一致的     

次序统计量线性函数的随机加权逼近速度

设ｘ１，ｘ２，…ｘｎ（连续未知），Ｆｎ为经验分布函数，Ｈｎ（ｘ）为随机加权经验分布函数，。ｘｎ１≤ｘｎ２≤…≤ｘｎｎ为次序统计量．记以Ｆｎ取代σ２（Ｊ，Ｆ）中的Ｆ即得σ２（Ｊ，Ｆｎ）．     

∑n—1^∞1／n^2m的一种求和法

本文通过求了函数Ｆ（ｘ）＝ｘ＾２ｍ的Ｆｏｕｒｉｅｒ级数展开式,得出了∑ｎ＝１＾∞１／ｎ＾２ｍ＝Ａｍπ＾２ｍ中Ａｍ的递推关系式。     

Hermite-Fejr插值算子的平均收敛准则

给出了一个有用的判断Ｈｅｒｍｉｔｅ－Ｆｅｊéｒ插值算子Ｈｎ（ｆ,ｘ）平均收敛准则,即Ｈｎ（ｆ,ｘ）依范数收敛于ｆ（ｘ）的充分必要条件是：Ｈｎ（ｆ,ｘ）一致有界（对一切ｎ）并且Ｈｎ（ｆ,ｘｋ）依范数收敛于ｘｋ（ｋ＝１,２）．     

数学问题解答

９９７年４月号问题解答（解答由问题提供人给出）１０６６已知ｆ（ｘ）＝ｘ－１ｘ＋１，记ｆｎ（ｘ）＝ｆ｛ｆ…［ｆ（ｘ）］｝ｎ个，求方程［ｆ１９（ｘ）＋ｆ９７（ｘ）］ｆ７１（ｘ）＝３的根．（１９９７年７月１日是香港回归祖国日，故创造此题纪念）解∵ｆ２（ｘ）...     

一类滞后生态微分方程的初值问题

对一般的滞后系统，人们采用了将滞后变量ｘ（ｔ－１）用一个Ｈｅｒｍｉｔｅ插值多项式来处理，从而把滞后系统转化为常微分方程系统来求其数值解（见文［２］，［３］）．本文根据［２］中的表Ⅰ选用了一个带有五次Ｈｅｒｍｉｔｅ插值多项式的四阶Ｒｕｎｇｅ－Ｈｕｔａ法来求两个常见的滞后初值问题．     

Hermne-Fejér插值算-T的平均收敛准则

给出了一个有用的有判断Ｈｅｒｍｉｔｅ－Ｆｅｊｅｒ插值算子Ｈｎ（ｆ,ｘ）平均收敛准则,即Ｈｎ（ｆ,ｘ）依范数收敛于ｆ（ｘ）的充分必要条件是：Ｈｎ（ｆ,ｘ）一致 有界（对一切ｎ）并且Ｈｎ（Ｆ,ｘ＾ｋ）依范数收敛于ｘ＾ｋ（ｋ＝１,２）。     

关于Hermite-Fejer插值过程的平均收敛

文［１］讨论了某些非Ｗ－过程的插值算子的加权平均逼近的收敛性和收敛阶．如记Ｈｎ（ｆ；ｘ）为以第二类Ｃｈｅｂｙｓｈｅｖ多项式Ｕｎ（ｘ）的零点作为插值节点，区间［－１，１］上的函数ｆ（ｘ）的Ｈｅｒｍｉｔｅ－Ｆｅｊｅｒ插值算子，［１］中证得：定理Ａ当０＜ｐ...     

SOME REMARKS ON HOLOMORPHIC FUNCTIONS AND TAYLOR SERIES IN Cn

Some previous results on convergence of Taylor series in Cn [3] are improved by indicating outside the domain of convergence the points where the series diverges and simplifying some proofs. These results contain the Cauchy-Hadamard theorem in C. Some Cauchy integral formulas of a holomorphic function on a closed ball in Cn are constructed and the Taylor series expansion is deduced.     

On the approximation of square-integrable functions by exponential series

The expansion of a real square-integrable function in a Legendre series is considered. Existence of best approximations from different sets of exponential functions and their mean convergence to the function in question are proved. As an extension of this result existence and mean convergence of some non-linear best approximations that have been developed by Longman are also demonstrated.     

A Condition for Convergence in Mean of Trigonometric Series

We construct an example of a trigonometric series showing that a certain condition closely related to convergence in mean of trigonometric series cannot be sharpened.     

单调性条件在Fourier级数收敛性中的最终推广:历史、发展、应用和猜想

为了对Fourier级数进行近似计算和有效应用,必须研究其收敛性,这个课题有长久的历史,形成了数学分析中吸引包括许多著名数学家在内的学者研究的一条热烈但困难的主流.其中,在三角级数(Fourier级数)一致收敛性和平均收敛性问题中人们一直关心Fourier系数的单调递减条件最终的推广.这个开始于英国Chaundy-Jollife(1916年)和Young(1913年)的工作最近出现了突破性的进展,产生了许多完善的结果.本文将对这方面的历史、发展给出综述,并重点介绍最近的应用成果,并对以后的工作给出研究思路和线索.     

ON THE PERIODIC ORTHONORMAL WAVELET SYSTEM

1IntroductionAwaveletorthonormalbasisoftheusualLebesquesquareintegrablefunctionspaceLZissuchasystem{Vjj,k}i,k,z,with'Wj,k(.)=Zany(Zi'--k)beinggeneratedfromthetranslationsanddyadicdilationsofasillglefunction,rk.It11asbeenshownthatthesystem{ioj,~}j,kezcouldbeservedasSchauderbasisorunconditionalbasisformostfunctionspaces[2].ThepurposeofthispaperistopresentsomepropertiesoftheorthonormalwaveletsystemintheperiodiccauseandtoindicatesimilarityofthissystemtoothersystemssuchasthesysemsofHaarandFI'an…     

A note on almost sure uniform and complete convergences of a sequence of random variables

The aim of this note is to introduce another way of defining the almost sure uniform convergence, which is necessary when studying some mathematical results on the existence of price bubbles in certain scenarios of trading securities. This mode of convergence of random variables' sequences is intermediate between the uniform and the almost sure ones, and, more specifically, between the uniform and the complete convergences. In this way, this paper presents some mathematical characterizations of both almost sure uniform and complete convergences, and shows that the almost sure uniform convergence is a particular case of complete convergence, when the number of summands in the series defining this mode of convergence is finite. Finally, this paper presents the relation of almost surely uniform convergence with convergence in mean when the random variable limit is integrable. Moreover, almost surely convergence and local boundedness of the sequence of random variables minus its limit are sufficient to derive convergence in mean.     

On necessary conditions for the convergence of Fourier series

We establish necessary conditions for the convergence of multiple Fourier series of integrable functions in the mean.     

關於廣義狄黎希萊級數的若干問題

<正> 導言 在本文中所謂廣義狄黎希萊級數就是指具有複指數的狄黎希萊級數.黎提在研究常係數無限級線性齊次方程時討論到有間隙的這種級數。希爾與隆茨分別獨立地研究過它的收斂區域,並且獲得了若干共同的結果.范禮隆將黎提與希爾的結果加以推廣,並且研究由這種級數所定義的整函數,特     

UNCONDITIONAL CAUCHY SERIES AND UNIFORM CONVERGENCE ON MATRICES

The authors obtain new characterizations of unconditional Cauchy series in termsof separation properties of subfamilies of P(N), and a generalization of the Orlicz-PettisTheorem is also obtained. New results on the uniform convergence on matrices anda new version of the Hahn-Schur summation theorem are proved. For matrices whoserows define unconditional Cauchy series, a better sufficient condition for the basicMatrix Theorem of Antosik and Swartz, new necessary conditions and a new proof ofthat theorem are given.     

On the Convergence of Fourier Series in the Space L1

We establish necessary and sufficient conditions for the convergence in the mean of trigonometric series whose coefficients satisfy the Boas–Telyakovskii conditions.