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861.
862.
介绍一种新的分析集中元件的宽带3 dB定向耦合器的方法。该方法利用奇偶模激励得到具有正交对称平面的本征单端口模型,这种等效使得在定向耦合器的分析过程中,可以直接引用一些现有的结论,利用矢量图示直观地得到各个端口散射参数之间的关系,简化了计算过程。最后对耦合器的拓扑结构的频率特性进行了理论分析和验证,对有关文献进行了扩充。 相似文献
863.
864.
865.
The authors study the Hilbert Transform on the real line. They introduce some polynomial approximations and some algorithms for its numerical evaluation. Error estimates in uniform norm are given.
866.
Terje O. Espelid 《BIT Numerical Mathematics》2003,43(2):319-337
In this paper we test two recently published Matlab codes, adaptsim and adaptlob, using both a Lyness–Kaganove test and a battery type of test. Furthermore we modify these two codes using sequences of null rules in the error estimator with the intention to increase the reliability for both codes. In addition two new Matlab codes applying a locally and a globally adaptive strategy respectively are developed. These two new codes turn out to have very good properties both with respect to reliability and efficiency. Both algorithms are using sequences of null rules in their local error estimators. These error estimators allow us both to test if we are in the region of asymptotic behavior and thus increase reliability and to take advantage of the degree of precision of the basic quadrature rule. The new codes compare favorably to the two recently published adaptive codes both when we use a Lyness–Kaganove testing technique and by using a battery test. 相似文献
867.
The usual tools for computing special functions are power series, asymptotic expansions, continued fractions, differential equations, recursions, and so on. Rather seldom are methods based on quadrature of integrals. Selecting suitable integral representations of special functions, using principles from asymptotic analysis, we develop reliable algorithms which are valid for large domains of real or complex parameters. Our present investigations include Airy functions, Bessel functions and parabolic cylinder functions. In the case of Airy functions we have improvements in both accuracy and speed for some parts of Amos's code for Bessel functions. 相似文献
868.
869.
As usual, denote by KW
r[a, b] the Sobolev class consisting of every function whose (r − 1)th derivative is absolutely continuous on the interval [a, b] and rth derivative is bounded by K a.e. in [a, b]. For a function f ∈ KW
r [a, b], its values and derivatives up to r − 1 order at a set of nodes x are known. These values are said to be the given Hermite information. This work reports the
results on the best quadrature based on the given Hermite information for the class KW
r [a, b]. Existence and concrete construction issue of the best quadrature are settled down by a perfect spline interpolation. It
turns out that the best quadrature depends on a system of algebraic equations satisfied by a set of free nodes of the interpolation
perfect spline. From our another new result, it is shown that the system can be converted in a closed form to two single-variable
polynomial equations, each being of degree approximately r/2. As a by-product, the best interpolation formula for the class KW
r [a, b] is also obtained. 相似文献
870.
In this paper, static flexural analysis of elliptic Reissner–Mindlin plates resting on a Pasternak foundation is conducted using the triangular differential quadrature method (TDQM). A triangular serendipity transformation is proposed to map a curvilinear domain onto a unit isosceles right triangle. The applicability of the TDQM to problems on domains with curvilinear boundaries is improved significantly since no inner points are needed in the transformation. In the case of thin circular plates, the results of the present method are in excellent agreement with those of the available exact solution, demonstrating the effectiveness of the present method. Elliptic plates with various aspect ratios and thickness-to-width ratios under uniformly distributed load are studied. 相似文献