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841.
主要介绍了模拟正交调制器性能优化设计方法,推导出调制器性能与相关参数之间的关系,实现其性能优化设计的方法,并给出了调制器性能与相关参数的关系图。 相似文献
842.
The differential quadrature method (DQM) has been studied for years and it has been shown by many researchers that the DQM is an attractive numerical method with high efficiency and accuracy. The conventional DQM is mostly effective for one‐dimensional and multidimensional problems with geometrically regular domains. But to deal with problems on a triangular domain, we will meet difficulties. In this article we will study how to solve problems on a triangular domain by using DQM combined with the domain decomposition method (DDM). © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2005 相似文献
843.
Lavi Karp 《Potential Analysis》2006,24(1):1-13
In this paper we introduce the notion of multivalued analytic continuation of the Cauchy transforms. Many difficulties arise
because the continuation is not single-valued. Our main result asserts that if χΩ has a multivalued analytic continuation, then the free boundary ∂Ω has zero Lebesgue measure. Here χΩ is the characteristic function of a domain Ω and ∂Ω is its boundary. We also discuss the connections between this notion,
quadrature domains and approximations of analytic functions with single-valued integrals by rational functions. The last problem
is related to the existence of a continuous function g and a closed connected set K such that the gradient of g vanishes on K, nevertheless g is not constant on K.
Mathematics Subject Classifications (2000) Primary 31A25, 31B20; secondary 30E10, 35J05, 41A20. 相似文献
844.
狄宋珍 《电子产品可靠性与环境试验》2002,(1):54-57
主要介绍了如何利用正态分布和正态优化对现有的筛选方法进行优化,从而使优化后的筛选方法在达到预期筛选目的的情况下做到最经济,省时和有效。 相似文献
845.
846.
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.
847.
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
848.
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
849.
A direct receiver is an alternative to the well‐established super‐heterodyne receiver. It is especially attractive to highly integrated low‐cost terminals since it eliminates the need for components at intermediate frequencies. There is increasingly more interest in using it in various ground/space‐based systems. This article presents a new direct quadrature receiver that uses three channels with different phase shifts and a novel technique to derive the in‐phase and quadrature baseband signals independent of the actual gains and phases in the receiver chains. The new technique relies on the property that the in‐phase and quadrature signals are orthogonal, and its implementation involves the signal subspace decomposition and projection. Computer simulations and a 90 Mbps Ka‐band prototype receiver have demonstrated that the performance of the receiver closely matches the theory. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
850.
On the Method of Neumann Series for Highly Oscillatory Equations 总被引:2,自引:0,他引:2
A. Iserles 《BIT Numerical Mathematics》2004,44(3):473-488
The main purpose of this paper is to describe and analyse techniques for the numerical solution of highily oscillatory ordinary differential equations by exployting a Neumann expansion. Once the variables in the differential system are changed with respect to a rapidly rotating frame of reference, the Neumann method becomes very effective indeed. However, this effectiveness rests upon suitable quadrature of highly oscillatory multivariate integrals, and we devote part of this paper to describe how to accomplish this to high accuracy with a modest computational effort. 相似文献