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A new technique to estimate the regularity of refinable functions.

Albert Cohen, Ingrid Daubechies (1996)

Revista Matemática Iberoamericana

We study the regularity of refinable functions by analyzing the spectral properties of special operators associated to the refinement equation; in particular, we use the Fredholm determinant theory to derive numerical estimates for the spectral radius of these operators in certain spaces. This new technique is particularly useful for estimating the regularity in the cases where the refinement equation has an infinite number of nonzero coefficients and in the multidimensional cases.

Accelerating the convergence of trigonometric series

Anry Nersessian, Arnak Poghosyan (2006)

Open Mathematics

A nonlinear method of accelerating both the convergence of Fourier series and trigonometric interpolation is investigated. Asymptotic estimates of errors are derived for smooth functions. Numerical results are represented and discussed.

Exact Kronecker constants of Hadamard sets

Kathryn E. Hare, L. Thomas Ramsey (2013)

Colloquium Mathematicae

A set S of integers is called ε-Kronecker if every function on S of modulus one can be approximated uniformly to within ε by a character. The least such ε is called the ε-Kronecker constant, κ(S). The angular Kronecker constant is the unique real number α(S) ∈ [0,1/2] such that κ(S) = |exp(2πiα(S)) - 1|. We show that for integers m > 1 and d ≥ 1, α 1 , m , . . . , m d - 1 = ( m d - 1 - 1 ) / ( 2 ( m d - 1 ) ) and α1,m,m²,... = 1/(2m).

Identification of basic thermal technical characteristics of building materials

Stanislav Šťastník, Jiří Vala, Hana Kmínová (2007)

Kybernetika

Modelling of building heat transfer needs two basic material characteristics: heat conduction factor and thermal capacity. Under some simplifications these two factors can be determined from a rather simple equipment, generating heat from one of two aluminium plates into the material sample and recording temperature on the contacts between the sample and the plates. However, the numerical evaluation of both characteristics leads to a non-trivial optimization problem. This article suggests an efficient...

Indefinite integration of oscillatory functions

Paweł Keller (1998)

Applicationes Mathematicae

A simple and fast algorithm is presented for evaluating the indefinite integral of an oscillatory function ∫ x y i f ( t ) e i ω t d t , -1 ≤ x < y ≤ 1, ω ≠ 0, where the Chebyshev series expansion of the function f is known. The final solution, expressed as a finite Chebyshev series, is obtained by solving a second-order linear difference equation. Because of the nature of the equation special algorithms have to be used to find a satisfactory approximation to the integral.

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