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1.
Eero Immonen 《Journal of Mathematical Analysis and Applications》2004,300(1):79-101
In this article, we study the effect of the chosen representation of a point value (and point evaluation) on the class of periodic signals realizable using a certain type of infinite-dimensional linear system. By suitably representing the point evaluation at the origin in a Hilbert space, we are able to give a complete characterization of its extensions. These extensions involve a new concept called δ-sequence, the use of which as an observation operator of an infinite-dimensional linear system is studied in this article. In particular, we consider their use in the realization of periodic signals. We also investigate how the use of δ-sequences affects the convergence properties of such realizations; we consider the rate and character of convergence and the removal of the Gibbs phenomenon. As still a further demonstration of the significance of the chosen concept of a point value, we discuss the use of distributional point values in the realization of periodic distributions. The possible applications of this work lie in regulator problems of infinite-dimensional control theory, as is indicated by the well-known internal model principle. 相似文献
2.
P. Bonckaert 《Journal of Mathematical Analysis and Applications》2008,344(1):301-321
We study normal forms of isolated singularities of vector fields in Rn or Cn. When all eigenvalues of the linear part of the vector field are nonzero, one can eliminate all so-called nonresonant terms from the equation provided some spectral condition (like Siegel) is satisfied. In this paper, we discuss the case where there is one zero eigenvalue (in that case Siegel's condition is not satisfied), and show that the formal normalizing transformations are either convergent or divergent of at most Gevrey type. In some cases, we show the summability of the normalizing transformations, which leads to the existence of analytic normal forms in complex sectors around the singularity. 相似文献
3.
A lower triangular matrix with nonzero principal diagonal entries is called a triangle. In this paper we obtain the sufficient conditions for ∑anλn to be summable ∣A∣k whenever ∑an is summable ∣T∣k for a triangle T. 相似文献
4.
W.T. Sulaiman 《Journal of Mathematical Analysis and Applications》2006,322(2):1224-1230
Extension and improvement has been made on a recent result proved by Mazhar [S.M. Mazhar, Absolute summability factors of infinite series, Kyungpook Math. J. 39 (1999) 67-73] concerning absolute summability factors of infinite series. 相似文献
5.
Ushangi Goginava 《Journal of Mathematical Analysis and Applications》2003,287(1):90-100
We prove that for the N-dimensional Walsh-Fourier series the maximal operator of the Marcinkiewicz means is of weak type (1,1). Moreover, the Marcinkiewicz means σnf of the function f∈L1 converge a.e. to f as n→∞. 相似文献
6.
7.
Rafa? Filipów 《Journal of Mathematical Analysis and Applications》2010,362(1):64-71
We consider ideals I of subsets of the set of natural numbers such that for every conditionally convergent series ∑n∈ωan and every there is a permutation such that ∑n∈ωaπr(n)=r and
8.
Summability of spherical h-harmonic expansions with respect to the weight function ∏j=1d |xj|2κj (κj0) on the unit sphere Sd−1 is studied. The main result characterizes the critical index of summability of the Cesàro (C,δ) means of the h-harmonic expansion; it is proved that the (C,δ) means of any continuous function converge uniformly in the norm of C(Sd−1) if and only if δ>(d−2)/2+∑j=1d κj−min1jd κj. Moreover, it is shown that for each point not on the great circles defined by the intersection of the coordinate planes and Sd−1, the (C,δ) means of the h-harmonic expansion of a continuous function f converges pointwisely to f if δ>(d−2)/2. Similar results are established for the orthogonal expansions with respect to the weight functions ∏j=1d |xj|2κj(1−|x|2)μ−1/2 on the unit ball Bd and ∏j=1d xjκj−1/2(1−|x|1)μ−1/2 on the simplex Td. As a related result, the Cesàro summability of the generalized Gegenbauer expansions associated to the weight function |t|2μ(1−t2)λ−1/2 on [−1,1] is studied, which is of interest in itself. 相似文献
9.
W.T. Sulaiman 《Applied mathematics and computation》2010,216(9):2645-2648
In this note we give an improvement to a recent result obtained by Savas and Rhoade concerning ∣A∣k summability of infinite series. 相似文献
10.
We describe a general procedure for computing Stokes matrices for solutions of linear differential equations with polynomial
coefficients. The algorithms developed make an automation of the calculations possible, for a wide class of equations. We
apply our techniques to some classical holonomic functions and also for some new special functions that are interesting in
their own right: Ecalle’s accelerating functions.
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