A general linear theory is presented which describes the extension of the convolutional method to nonstationary processes. This theory can apply any linear, nonstationary filter, with arbitrary time and frequency variation, in the time, Fourier, or mixed (time-frequency) domains. The filter application equations and the expressions to move the filter between domains are all ordinary Fourier tra...

Wavelet/wavelet packet decomposition has become a very useful tool in describing nonstationary processes. Important examples of nonstationary processes encountered in practice are cyclostationary processes or almost-cyclostationary processes. In this paper, we study the statistical properties of the wavelet packet decomposition of a large class of nonstationary processes, including in particula...

A new nonstationary model is applied to represent seismic ground acceleration records. The model can be obtained by modulating both the amplitude and the frequency of a stationary process. It is not included in the class of oscillatory processes. Accelerograms recorded during the 1985 Michoacan earthquake in Mexico City are used to calibrate and evaluate the usefulness of the proposed and other...

Most research in queueing theory is typically based on the steady-state analysis. In today’s dynamically changing traffic environment, the steady-state analysis may not provide enough information to operators regarding Quality of Service (QoS) requirements and dynamic design. In addition, the steady state analysis is not practical for nonstationary arrivals. In this paper, we consider the time-...

Planetary gearbox fault diagnosis under nonstationary conditions is important for many engineering applications in general and for wind turbines in particular because of their time-varying operating conditions. This paper focuses on the identification of time-varying characteristic frequencies from complex nonstationary vibration signals for fault diagnosis of wind turbines under nonstationary ...

We show that the reduced cofinality of the nonstationary ideal NSκ on a regular uncountable cardinal κ may be less than its cofinality, where the reduced cofinality of NSκ is the least cardinality of any family F of nonstationary subsets of κ such that every nonstationary subset of κ can be covered by less than κ many members of F . For this we investigate connections of the various cofinalitie...