Über die Differentialgleichungu x y =f(x,y, u,u x,u y )

Ohne ZusammenfassungDiese Arbeit wurde teilweise unterstützt von der United States Air Force [Air Force Office of Scientific Research-Contract AF 49 (638)-228]. Sie besteht aus drei Teilen. Teil I ist im vorangehenden Heft dieser Zeitschrift erschienen, Teil III erscheint im folgenden Heft. Formeln und Sätze sind in jedem Teil für sich durchnumeriert. Bei Verweisen bedeutet z. B. (I. 17) die Formel (17) von Teil I, Satz I. 5 bedeutet Satz 5 von Teil I.     

关于方程(a(t,y)y′)′=f(t,y,y′)的某些边值问题的可解性

本文在假设α(t,y)为正连续函数的情形下,把Granas, Petryshyn, Schuur等关于方程y″=f(t, y, y′)在有限或无限区间上的边值问题的可解性推广到方程(α(t, y)y′)′=f(t, y, y′)所用方法是Leray-Schauder原理及Wazewski拓朴方法。     

Über die Differentialgleichungu xy =f(x,y, u,u x,u y )

Ohne ZusammenfassungDiese Arbeit wurde teilweise unterstützt von der United States Air Force [Air Force Office of Scientific Research-Contract AF 49(638)-228]. Sie wurde von der Fakultät für Natur- und Geisteswissenschaften der Technischen Hochschule Karlsruhe als Habilitationsschrift angenommen. Die beiden ersten Teile sind in Band 71 dieser Zeitschrift erschienen (S. 308–324 und 436–453).     

Über die Differentialgleichungu xy =f(x,y, u,u x,u y )

Ohne ZusammenfassungDiese Arbeit wurde teilweise unterstützt von der United States Air Force (Air Force Office of Scientific Research-Contract AF 49 (638)-228). Sie besteht aus insgesamt drei Teilen. Teil II (Existenzsätze für die charakteristische Anfangswertaufgabe) und Teil III (Die nichtcharakteristische Anfangswertaufgabe) werden in Kürze in dieser Zeitschrift erscheinen.     

Four step methods for y″=f(x,y)

A systematic investigation is undertaken here on the possible practical consequences of the fact that the linear four step methods for y″=f(x, y) form a family with a certain structure. The mentioned property is found to be surprisingly rich in consequences, and three of them are of particular importance: (i) drastic reduction in the number of iterations at each step, (ii) increased flexibility with respect to the start of integration and to the modification of the step size during the integration process, (iii) possibility of direct and simple appraisal of the local truncation error.     

关于非线性方程εy″=f(x,y,y′,ε)奇异摄动边值问题解的估计

在本文中,我们研究边值问题其中ε为小的正参数,在f_(y′)≤-k<0和其它适当的限制下,存在一个解y(x,ε)并满足其中y_0(x)为退化问题f(x,y,y′,0)=0,0相似文献   

关于集值系统x∈F(x,y),y∈G(x,y)解的存在性

Let (E, ‖·‖) be a uniformly convex Banach space, X a nonempty compact and convex subset of E. Let F be a closed mapping of X×X into 2^X, G a mapping of X×X into C(X). It is shown that if for any f∈C(X), x∈X, F(x,f(x)) is a closed and convex subset of X, and G(x,f(x)) is a continuous function and for any x,y₁,y₂∈X,H(x,G(x,y₁),G(x,y₂))≤‖y₁-y₂‖ then there exist X₀,y₀∈X such that X₀∈F(x₀,y₀) and y₀∈G(x₀, y₀).     

EXPLICIT TWO-STEP HIGH-ACCURACY METHODS FOR y" = f(x,y)

In this paper, an almost P-stable two-step sixth-order Hybrid method with phase-lag of order infinity and a class explicit eighth-order Obreckoff methods with phase-lag of order 10-24 are developed for the numerical integration of the special second-order periodic initial-value problems. These methods have the advantage of higher algebraic order and considerably smaller phase-tag compared with some methods in [1-6]. Numerical examples indicate that these new methods are more accurate than methods developed by [1-6].     

Group Laws [x,y −1] ≡ u(x,y) and Varietal Properties

Let F = ?x, y? be a free group. It is known that the commutator [x, y ^?1] cannot be expressed in terms of basic commutators, in particular in terms of Engel commutators. We show that the laws imposing such an expression define specific varietal properties. For a property 𝒫 we consider a subset U(𝒫) ? F such that every law of the form [x, y ^?1] ≡ u, u ∈ U(𝒫) provides the varietal property 𝒫. For example, we show that each subnormal subgroup is normal in every group of a variety 𝔙 if and only if 𝔙 satisfies a law of the form [x, y ^?1] ≡ u, where u ∈ [F′, ?x?].     

解初值问题y"=g(x,y)的含参数块方法

1引言对于二阶常微分方程的初值问题y″=g(x,y),y(x_0)=y_0,y′(x_0)=y_0′,x_0(?)x(?)T(1)的数值解法的研究引起人们的广泛兴趣．对于直接积分(1),自从1976年J．D．Lambert和I．A．Waston提出二阶P-稳定方法和1978年G．Dahlquist证明P-稳定常系数线性多步方法的最高相容阶不超过2的重要结论以来,截止目前,已积累了许多高于2阶的P-稳定方法．例如,修正的Numerov方法,混合法(特殊形式RK的方法),多导法,Obrechkoff方法,显式RKN方法,单隐方法和对角隐式RKN方法等(顺便指出,文献[5,16]中所说的高阶方法的相容阶均不超过4)．所有这些方法,有些相     

Study Bulletin HIGH ACCURACY HYBRIDFORMULA FOR y"=f(x,y)

1.AFamilyofSixthOrderMethodsM6(a,afl)withPhaseLagOrderSixorEightThegeneralsymmetric,tow--stepsixthorderwithtwooff-steppointmethodgiveniswhereIfweapplyformulas(l.1),(1.3)--(1.5)tothetestequationandtakeA A~aam,wehavethestabilitypolynomialRevisedSeptember3.1997.whereFOrm(1.9)(1.1l),weareabletoderiveTable1asfollows.Table1.Thetwo-parameterfamilyofsixthordermethodsac(or,crl)Thedefinitionsofp-stable,almostp-stableandthephase-laghavebeengivenby[5],[6]and18]respectively.FromTableIobtainedwecon…     

混合偏导数fyx(x,y)与fxy(x,y)相等的条件

对二元函数的两个混合偏导数fyx(x,y)及fxy(x,y)进行了进一步研究,并得出了它们相等的一个充分条件,该条件比[1]中给出的条件更弱.     

妙用坐标(x,y)解题

<正>纵观近几年的中考题目,考查数学的基本思想及活动经验的积累极为突出,考查在实际解题中能否运用数学知识、数学思想方法去发现问题、分析问题、解决问题.下面以两题中考试题为例,浅析坐标(x,y)在解题中的妙用,以供大家参考.     

A conditionally P-stable fourth-order exponential-fitting method for y″=f(x,y)

We search for the modification of the stability properties of a P-stable multistep algorithm with an order greater than two when this is reformulated on the basis of the exponential fitting. We effectively construct the exponential-fitting version of the fourth-order two-step algorithm of Chawla (BIT 21 (1981) 190–193). In order to characterize the stability properties of the new version, we first introduce the concept of the conditional P-stability of a family of exponential-fitting methods and the parameter θ_max to be associated to a conditionally P-stable family. We then show that this version is conditionally P-stable indeed, with θ_max=3.4. This means that the method can be used for stiff problems provided some typically nonsevere restrictions are imposed on the stepsize h.     

積分∫F(x,y,y′,…,y~((n)))dx的等價問题

<正> 命g為x,y平面上由所有保切變換所構成的羣。在本文內我們將定義一類廣義空間使這空間與積分∫F(x,y,y′,…y~((n)))dx對於羣g而言有不變的聯繫。所謂一空間對於羣g而言與積分∫Fdx有不變的聯繫,意義是:如我們施用羣g     

HIGH-ACCURACY EXPLICIT TWO-STEP METHODS WITH MINIMAL PHASE-LAG FOR y″= f（t,y）

In this paper, two families of high accuracy explicit two-step methods with minimal phase-lag are developed for the numerical integration of special second-order periodic initial-value problems. In comparison with some methods in [1-4,6], the advantage of these methods has a higher accuracy and minimal phase-lag. The methods proposed in this paper can be considered as a generalization of some methods in [1,3,4]. Numerical examples indicate that these new methods are generally more accurate than the methods used in [3,6]. second order periodic initial-value problems, phase-lag, local truncation error     

Nested Runge-Kutta methods for the differential equation y”=F(x,y)

Nested Runge-Kutta methods of fourth, fifth, and sixth orders of accuracy are constructed for numerical solution of the Cauchy problem for the ordinary differential equation y=f(x, y). The first two stages of the fifth- and sixth-order methods determine the fourth-order method, and the ftrst three stages of the sixth-order method determine the fifthorder method. Numerical values of the parameters for these methods are determined and two test problems are solved numerically.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 57, pp. 42–48, 1985.     

关于求解y″=f(x,y)的高精度预估—校正方法

本文分别提出了数值积分二阶常微分方程周期性初值问题,具有极小相位延迟误差O(H~(2m+4))和O(H~8)的显式与隐式预估—校正方法。文中所构造的方法与[1-5]中同类型方法相比,具有较高的代数精度;相当或较小的相位延迟误差;相同或较长的周期区间,因而文中所构造的方法是对[1-5]中方法的改进与推广。