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1.
<正>伦敦大学学院(University College London, UCL)应用统计学系(及优生学系)作为20世纪初到30年代末世界统计科学的中心,不仅聚集了K. Pearson、F. Galton、W. F. R.Weldon、 W. S. Gosset、 R. A. Fisher、 E. S. Pearson、 J. Neyman等世界顶尖的统计学家,而且吸引了吴定良1、唐培经2、许宝騄、徐钟济等中国学生和中国学者艾伟在此攻读学位、访学研究. 相似文献
2.
1.窗户造型 (满分 1 5分 )《中学生数学》杂志 2 0 0 0年第 1期的封面是一幅欧洲教堂的照片 ,它是一座哥特式的建筑 .建筑物上有一个窗户的造型如图 1所示 .图中弧 AB和弧 AC分别是以 C和 B为圆心 BC长为半径的圆弧 .○.O1 、○.O2 和○.O3两两相切 ,并且○.O1 、○.O2 与弧AB相切 ,○.O1 、○.O3与弧 AC相切 ,○.O2 、○.O3的半径相等 .如果使○.O2 、○.O3充分大 ,记 BC的长度为 a,请你计算出○.O1 的半径 ,并给出这个圆的作法 .图 1解 设○.O1 、○.O2 相切于点 E,○.O1 、○.O3相切于点 F ,○.O2 、○.O3相切于点 D,○.… 相似文献
3.
良好的学习习惯是有效提高学业成绩的保障,不良的学习习惯影响、制约着广大学生的学习效率.现列举24种当代中学生不良学习习惯,愿广大学生、家长对照参考,矫正不足,养成良好习惯,提高学习水平.1.学习、生活、作息不规律,无计划.2.学习用品乱堆乱放,用时又找不到.3.审题不清,随意下笔.4.课堂上不主动回答老师提出的问题. 相似文献
4.
本文是D.C.隶属函数模糊集及其应用系列研究的第二部分。指出在实际问题中普遍选用的三角形、半三角形、梯形、半梯形、高斯型、柯西型、S形、Z形、π形隶属函数模糊集等均为D.C.隶属函数模糊集,建立了D.C.隶属函数模糊集对模糊集的万有逼近性。探讨了D.C.隶属函数模糊集与模糊数之间的关系,给出了用D.C.隶属函数模糊集逼近模糊数的-εC e llina逼近形式,得到模糊数与D.C.函数之间的一个对应算子,指出了用模糊数表示D.C.函数的问题。 相似文献
5.
通过论述柏拉图(Plato,B.C.427-B.C.347)、欧几里得(Euclid,约B.C.330-B.C.275)、帕波斯(Pappus,约300-350)、帕赛利(L.Pacioli,约1445-1517)、梅文鼎(1633-1721)作正二十面体、正十二面体的作图法,指出梅氏作法最为简洁,已蕴含证明,胜于上世纪苏联别列标尔金(Д.И.Перепелкин)方法,为历来最优美解. 相似文献
6.
《高等数学研究》2002,(2)
一、选择题:(本大题满分36分,每小题3分) 1、计算(-2)2+(-1)101所得的结果是( ). A.-3 B.-2 C.3 D.4 2、下列运算①(x-6)(x+b)=x2-b2,②(am)n=amn,③(a/b)n=an/bn,④a2=a,正确的个数是( ). A.1 B.2 C.3 D.4. 3、方程组{x2+y2=6 y=5x的解的个数是( ). A.1 B.2 C.3 D.4 4、不等式组{x>-3 x>4的解集是( ). A.x>-3 B.x>4 C.x>1 D.x>-1 5、反比例函数y=-1/x的图象不经过第( )象A.一、三 B.二、四 相似文献
7.
刘作述 《数学物理学报(A辑)》1984,(1)
非线性抽象压缩原理在微分方程、规划论、控制论等学科中找到了应用,近年来已有不少数学工作者从事这一领域的工作,本文继续从事这一方面的研究,我们在较一般的条件下得到了一些更为广泛的抽象压缩映象的不动点的存在定理,此外,1942年K.Menger首先引进了所谓统计度量空间的概念,其后,A.Wald、B.Schweizer、A.Sklar、E.Thorp和R.T. 相似文献
8.
9.
《数学的实践与认识》1997,(4)
<正> 1.E. A. Bender,数学模型引论,朱尧辰、徐伟宣译,科学普及出版社,1982.2.近藤次郎,数学模型,宫荣章等译,机械工业出版社,1985.3.姜启源,数学模型,高等教育出版社,1987.4.任善强,数学模型,重庆大学出版社,1987.5.M. Braun, C. S. Coleman, D. A. Drew,微分方程模型,朱煜民、周宇虹译,国防科技大学出版社,(本书为W. P. Lucas主编的Modules in Applied Mathematics一书的第一卷),1988. 相似文献
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11.
The aim of this paper is to present a kinetic numerical scheme for the computations of transient pressurised flows in closed water pipes. Firstly, we detail the mathematical model written as a conservative hyperbolic partial differentiel system of equations, and then we recall how to obtain the corresponding kinetic formulation. Then we build the kinetic scheme ensuring an upwinding of the source term due to the topography performed in a close manner described by Perthame and Simeoni (2001) [1] and Botchorishvili et al. (2003) [2] using an energetic balance at microscopic level. The validation is lastly performed in the case of a water hammer in an uniform pipe: we compare the numerical results provided by an industrial code used at EDF-CIH (France), which solves the Allievi equation (the commonly used equation for pressurised flows in pipes) by the method of characteristics, with those of the kinetic scheme. It appears that they are in a very good agreement. 相似文献
12.
We study a coupled algorithm for solving the two-dimensional Navier–Stokes equations in the stream function–vorticity variables. The algorithm is based on a finite-difference scheme in which the inertial terms in the vortex transport equation are taken from the lower time layer and the dissipative terms, from the upper time layer. In the linear approximation, we study the stability of this algorithm and use test computations to show its advantages when modeling flows at moderate Reynolds numbers. 相似文献
13.
M. V. Buntina V. V. Ostapenko 《Computational Mathematics and Mathematical Physics》2008,48(12):2241-2253
For the shallow water equations in the first approximation (Saint-Venant equations), a TVD scheme is developed for shock-capturing computations of open channel flows with discontinuous waves. The scheme is based on a special nondivergence approximation of the total momentum equation that does not involve integrals related to the cross-section pressure force and the channel wall reaction. In standard divergence difference schemes, most of the CPU time is spent on the computation of these integrals. Test computations demonstrate that the discontinuity relations reproduced by the scheme are accurate enough for actual discontinuous wave propagation to be numerically simulated. All the qualitatively distinct solutions for a dam collapsing in a trapezoidal channel with a contraction in the tailwater area are constructed as an example. 相似文献
14.
Some applications of a galerkin-collocation method for boundary integral equations of the first kind
Here we apply the boundary integral method to several plane interior and exterior boundary value problems from conformal mapping, elasticity and fluid dynamics. These are reduced to equivalent boundary integral equations on the boundary curve which are Fredholm integral equations of the first kind having kernels with logarithmic singularities and defining strongly elliptic pseudodifferential operators of order - 1 which provide certain coercivity properties. The boundary integral equations are approximated by Galerkin's method using B-splines on the boundary curve in connection with an appropriate numerical quadrature, which yields a modified collocation scheme. We present a complete asymptotic error analysis for the fully discretized numerical equations which is based on superapproximation results for Galerkin's method, on consistency estimates and stability properties in connection with the illposedness of the first kind equations in L2. We also present computational results of several numerical experiments revealing accuracy, efficiency and an amazing asymptotical agreement of the numerical with the theoretical errors. The method is used for computations of conformal mappings, exterior Stokes flows and slow viscous flows past elliptic obstacles. 相似文献
15.
A. S. Shvedov 《Mathematical Notes》1996,60(5):562-568
The difference schemes of Richardson [1] and of Crank-Nicolson [2] are schemes providing second-order approximation. Richardson's three-time-level difference scheme is explicit but unstable and the Crank-Nicolson two-time-level difference scheme is stable but implicit. Explicit numerical methods are preferable for parallel computations. In this paper, an explicit three-time-level difference scheme of the second order of accuracy is constructed for parabolic equations by combining Richardson's scheme with that of Crank-Nicolson. Restrictions on the time step required for the stability of the proposed difference scheme are similar to those that are necessary for the stability of the two-time-level explicit difference scheme, but the former are slightly less onerous.Translated fromMatematicheskie Zametki, Vol. 60, No. 5, pp. 751–759, November, 1996.This research was supported by the Russian Foundation for Basic Research under grant No. 95-01-00489 and by the International Science Foundation under grants No. N8Q300 and No. JBR100. 相似文献
16.
Andreas Meister 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2003,54(6):1010-1049
In [43] a finite volume method for
reliable simulations of inviscid fluid flows at high as well as
low Mach numbers based on a preconditioning technique proposed by
Guillard and Viozat [14] is presented. In this paper
we describe an extension of the numerical scheme for computing
solutions of the Euler and Navier-Stokes equations. At first we
show the high resolution properties, accuracy and robustness of
the finite volume scheme in the context of a wide range of
complicated transonic and supersonic test cases whereby both
inviscid and viscous flow fields are considered. Thereafter, the
validity of the method in the low Mach number regime is proven by
means of an asymptotic analysis as well as numerical simulations.
Whereas in [43] the asymptotic analysis of the
scheme is focused on the behaviour of the continuous and discrete
pressure distribution for inviscid low speed simulations we prove
both the physical sensible discrete pressure field for viscous low
Mach number flows and the divergence free condition of the
discrete velocity field in the limit of a vanishing Mach number
with respect to the simulation of inviscid fluid flow. 相似文献
17.
Andreas Meister 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2003,41(5):1010-1049
In [43] a finite volume method for
reliable simulations of inviscid fluid flows at high as well as
low Mach numbers based on a preconditioning technique proposed by
Guillard and Viozat [14] is presented. In this paper
we describe an extension of the numerical scheme for computing
solutions of the Euler and Navier-Stokes equations. At first we
show the high resolution properties, accuracy and robustness of
the finite volume scheme in the context of a wide range of
complicated transonic and supersonic test cases whereby both
inviscid and viscous flow fields are considered. Thereafter, the
validity of the method in the low Mach number regime is proven by
means of an asymptotic analysis as well as numerical simulations.
Whereas in [43] the asymptotic analysis of the
scheme is focused on the behaviour of the continuous and discrete
pressure distribution for inviscid low speed simulations we prove
both the physical sensible discrete pressure field for viscous low
Mach number flows and the divergence free condition of the
discrete velocity field in the limit of a vanishing Mach number
with respect to the simulation of inviscid fluid flow. 相似文献
18.
The method of characteristics (MOC) has been used for a long time in open channels and pipes flows. It is based on non-conservative equations, and hence it cannot be used directly for solving discontinuous shallow flows. In this paper we develop a conservative version of the MOC scheme for 1-D shallow flows by imposing the conservation law at the interpolation step. The conservation property of the scheme ensures the production of an accurate shock modeling and enables the MOC scheme to simulate dam-break type flows. By using a proper interpolation function, the proposed method can also produce quite accurate low-oscillatory results. A number of challenging test cases show considerable improvement compared to the traditional non-conservative MOC scheme in the case of dam-break type and trans-critical flow simulations. 相似文献
19.
本文建立了解二阶双曲型方程的一种新数值方法一再生核函数法.利用再生核函数,直接给出每个离散时间层上近似解的显式表达式.此方法的优点是:计算格式绝对稳定,且可显式求解;利用显式表达式,可实现完全并行计算等文中对近似解的收敛性和稳定性进行了理论分析,并给出数值算例. 相似文献
20.
K. V. Brushlinskii N. S. Zhdanova 《Computational Mathematics and Mathematical Physics》2006,46(3):527-536
A numerical study of two-dimensional plasma flows in coaxial channels of plasma accelerators is presented. Two new results are obtained. First, for the computation of MHD problems belonging to the class under consideration, Zalesak’s method is used. It is based on an explicit finite difference scheme with flux correction. This method is free of space splitting, and, therefore, is well suited for parallel computations on multiprocessors. Second, the statement of the problem is extended so that the acceleration of the plasma by the azimuth magnetic self-field goes on in the presence of an external longitudinal field. The results of test computations demonstrate the efficiency of the method and made it possible to investigate the influence of the longitudinal field on the properties of the plasma flows. 相似文献