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平均值函数列 总被引:1,自引:0,他引:1
经家麒 《数学的实践与认识》1998,(3)
本文用公理方法定义了平均值函数列.从公理定义出发,推证了平均值函数列的一系列共同性质,从而概括并推广了一些常见的平均值函数列.定理1指出了两个不同的平均值函数列的大小不会因变元的增加而改变,定理2揭示了平均值函数列与凸函数之间的内在联系,定理3则给出了多种平均值函数列的构作方法. 相似文献
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设f(二)是定义在实数集R上的实函数,从这个函数出发,我们构造新函数 F(二)~f(f(‘));显然这个函数也定义在R上.函数F通常称为函数f的迭代,从下图容易看出,借助于函数f(x)的图形,对于自变量的具体的值劣气能哆求出迭代值f(f(x釜))。 我们考虑方程 f(f(二))二二 首先注意到,x。是方程 f(x)=二 (1)如果(2)┌────┐├主──┐││}一蔺 ││└───┴┘的根,那么二。也是方程(1)的根.但方程(1)也可能有另外的根,这个根不是(2)的根(从图形可看出这个事实来)。 下面我们指出,在什么情况下方程(1)与方程(2)是等价的. 定理如果对某个数a,函数… 相似文献
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利用L-函数的性质证明了满足同一个Riemann型函数方程的扩充的Selberg类中的次数大于零的L-函数分担一个有限值的定理,并应用该定理证明了满足同一个Riemann型函数方程的涉及公共值的唯一性定理,所得结果改进了J.Steuding和李宝勤的有关结果,也是S.M.Gonek,J.Haan和H.Ki主要结果的补充. 相似文献
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从三次样条插值的定义出发,通过研究第一类积分方程中未知函数的三次样条函数逼近,给出了第一类积分方程的三次样条插值离散化.利用该离散化形式,将第一类积分方程转化成线性方程组的形式.由于第一类积分方程的求解通常是不适定的,进而引起线性方程组的病态性.最后,为克服线性方程组的病态性,通过引入未知函数的多重光滑化约束,得到第一... 相似文献
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宋春蕾陈伟张国伟 《数学的实践与认识》2022,(11):216-224
应用五泛函不动点定理,当非线性函数在几个闭区域上满足一些不等式约束条件时,证明了具有Stieltjes积分边值条件的四阶问题存在多重正解,其非线性项含有未知函数的导数.通过一个多点型和积分型混合边值条件的例子,说明结论的可应用性,例子中的多点边值条件含有变号的系数,积分边值条件中积分核是变号的超越函数. 相似文献
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一个Gauss型函数方程 总被引:3,自引:0,他引:3
刘证 《纯粹数学与应用数学》2002,18(1):53-57,62
给出了任意两个正实数的几何-调和平均值的一个积分表示式,并由此去探讨了函数方程f(ab,2ab/a+b)=f(a,b),a,b>0其中f:R+×R+→R是此方程的一个未知函数. 相似文献
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§1 引言 由具有在[0,1]上均匀分布的总体中产生的简单子样称为随机数序列,其中的每一样本称为随机数。所谓伪随机数序列,一般是指用数学递推公式所产生的随机数序列。如最常见的乘同余方法,它所产生的伪随机数序列就是对给定的正整数M和小于M的任意正整数初值β_1,用如下递推公式确定的: 相似文献
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A. A. TElzoughby S. M. Metwalli G. S. A. Shawki 《Journal of Optimization Theory and Applications》1980,30(2):161-179
A modification based on a linearization of a ridge-path optimization method is presented. The linearized ridge-path method is a nongradient, conjugate direction method which converges quadratically in half the number of search directions required for Powell's method of conjugate directions. The ridge-path method and its modification are compared with some basic algorithms, namely, univariate method, steepest descent method, Powell's conjugate direction method, conjugate gradient method, and variable-metric method. The assessment indicates that the ridge-path method, with modifications, could present a promising technique for optimization.This work was in partial fulfillment of the requirements for the MS degree of the first author at Cairo University, Cairo, Egypt. The authors would like to acknowledge the helpful and constructive suggestions of the reviewer. 相似文献
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自适应多重网格法与超松弛法的比较 总被引:4,自引:0,他引:4
欧阳洁 《应用数学与计算数学学报》1994,8(1):27-33
多重网格法(Multiple Grid Method,简称M-G方法)是近年来出现的快速方法之一,本文在M-G方法中采用自适应控制层间转换的技术,并将自适应M-G方法与G-S迭代方法及SOR迭代方,法进行了比较。其计算结果表明,自适应M-G方法的计算量比G-S迭代及SOR迭代少得多,当M-G方法所用层数为4-6层,这种优越性就更加明显,且自适应M-G方法中选取控制参数有很大的灵活性。 相似文献
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In this work, we proposed the new method for estimation of the thickness and the optical properties of the thin metal oxide film deposited on a transparent substrate. The developed method uses only transmittance spectra measured. Our method is based on the two stage optimization where the thickness is determined in the outer stage and the optical properties are determined in the inner stage. The differential evolutionary algorithm is used in solving the formulated problem. The proposed method was illustrated in the case study of Titanium dioxide film deposited on a glass substrate. The results indicate that the thickness and the optical properties estimated agree well with the experiment. Moreover, we investigated robustness of the proposed method in the case of transmittance spectra containing noises. The data were modelled by adding random noises ranging between 0 and 30% to the transmittance spectra measured. It is seen that the proposed method has better robustness and performance than the existing method based on pointwise unconstrained minimization approach. In solving the estimation problem, the performance of the proposed method was also compared with the well-known Levenberg?CMarquardt method and single stage differential evolutionary method. The results indicate that the proposed method has better performance than Levenberg?CMarquardt method and single stage differential evolutionary method. Moreover, the proposed method is more robust to random noise than Levenberg?CMarquardt method and single stage differential evolutionary method. 相似文献
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Image deconvolution problems with a symmetric point-spread function arise in
many areas of science and engineering. These problems often are solved by
the Richardson-Lucy method, a nonlinear iterative method. We first show a
convergence result for the Richardson-Lucy method. The proof sheds light on
why the method may converge slowly. Subsequently, we describe an iterative
active set method that imposes the same constraints on the computed solution
as the Richardson-Lucy method. Computed examples show the latter method to
yield better restorations than the Richardson-Lucy method and typically
require less computational effort. 相似文献
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In this paper,we present a column-secant modification of the SCC method,which is called the CSSCC method.The CSSCC method uses function values more efficiently than the SCC method,and it is shown that the CSSCC method has better local q-convergence and r-convergence rates than the SCC method.The numerical results show that the CSSCC method is competitive with some well known methods for some standard test problems. 相似文献
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W. S. Luk 《BIT Numerical Mathematics》1996,36(2):302-308
Aberth's method for finding the roots of a polynomial was shown to be robust. However, complex arithmetic is needed in this method even if the polynomial is real, because it starts with complex initial approximations. A novel method is proposed for real polynomials that does not require any complex arithmetic within iterations. It is based on the observation that Aberth's method is a systematic use of Newton's method. The analogous technique is then applied to Bairstow's procedure in the proposed method. As a result, the method needs half the computations per iteration than Aberth's method. Numerical experiments showed that the new method exhibited a competitive overall performance for the test polynomials. 相似文献
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牛顿迭代法与几种改进格式的效率指数 总被引:2,自引:1,他引:1
研究牛顿迭代、牛顿弦截法以及它们的六种改进格式的计算效率,计算了它们的效率指数,得到牛顿迭代、改进牛顿法、弦截法和改进弦截法(即所谓牛顿迭代的P.C格式)、二次插值迭代格式、推广的牛顿迭代法、调和平均牛顿法和中点牛顿法的效率指数分别为0.347/n、0.3662/n、0.4812/n、0.4812/n、0.347/n、0.3662/n、0.3662/n、0.3662/n.我们的结果显示,利用抛物插值多项式推出的迭代格式和改进弦截法并没有真正提高迭代的计算效率.此外,我们还证明了改进弦截法与牛顿弦截法等价,并利用这一结论给出了改进弦截法收敛阶为2.618的一个简化证明. 相似文献
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大密度比和大压力比可压缩流的数值计算 总被引:3,自引:0,他引:3
将WENO方法、RKDG方法、RKDG方法结合原来的Ghost Fluid方法以及RKDG方法结合改进的Ghost Fluid方法,应用到大密度比和大压力比的单相流以及气-气、气-液两相流的数值计算,并对计算结果进行了比较分析.结果表明,与其它的方法相比,RKDG方法结合改进的Ghost Fluid方法得到了高分辨率的计算结果,可以捕捉到正确的激波位置,随着网格的加密,计算解收敛到物理解. 相似文献