In the present paper, we generalize Zygmund classes of functions with two variables defined by Móricz by means of modulus of continuity, and give the necessary and sufficient conditions for double sine, sine-cosine, cosinesine and double cosine series so that their sums belong to the generalized Zygmund classes. Some new results of Fülöp [1] and [2] on double trigonometric series are extended.

Phase shift keying (PSK) is one of the most important classes of digital modulation schemes. M-ary PSK of which the value of M is other than the n-th power of 2 has not been focused on until now because it is not suitable for transmitting binary information. In a previous study, we reported that ternary PSK (TPSK) has theoretically the best error rate characteristic and the minimum instantaneou...

Based on our decomposition of stochastic processes and our asymptotic representations of Fourier cosine coefficients, we deduce an asymptotic formula of approximation errors of hyperbolic cross truncations for bivariate stochastic Fourier cosine series. Moreover we propose a kind of Fourier cosine expansions with polynomials factors such that the corresponding Fourier cosine coefficients decay ...

Neutral stability limits for wake flow behind a flat plate is studied using spectral method. First, Orr-Sommerfeld equation was changed to matrix form, covering the whole domain of solution. Next, each term of matrix was expanded using Chebyshev expansion series, a series very much equivalent to the Fourier cosine series. A group of functions and conditions are applied to start and end points i...

In this paper four different orthogonal functions have been used to approximate the optimal solution of linear time invariant (LTI) singular delayed systems. The idea is that the states and the input are expressed in terms of these orthogonal functions. The method simplifies the system of state equations into a set of algebraic equations which can be solved using a digital computer. The main ad...

Quadrature Phase Shift Keying (QPSK) and Offset Quadrature Phase Shift Keying (OQPSK) are two wellaccepted modulation techniques used in Code Division Multiple Access (CDMA) system. The Pulse-Shaping Filters play an important role in digital transmission. The type of Pulse-Shaping Filter used, and its behavior would influence the performance of the communication system. This in turn, would have...

It is a classical problem in Fourier analysis to give conditions for a single sine or cosine series to be uniformly convergent. Several authors gave conditions for this problem supposing that the coefficients are monotone, non-negative or more recently, general monotone. There are also results for the regular convergence of double sine series to be uniform in case the coefficients are monotone ...