variation of frequency and voltage by load changes in a microgrid is a challenge in droop control method. centralized restoration frequency or voltage in a microgrid requires communication link and therefore affects the advantage of decentralized droop control such as reliability, simplicity and inexpensiveness. this paper proposes a decentralized method that restores the frequency of a microgr...

seismic waves are non-stationary due to its propagation through the earth. time-frequency transformsare suitable tools for analyzing non-stationary seismic signals. spectral decomposition can reveal thenon-stationary characteristics which cannot be easily observed in the time or frequency representationalone. various types of spectral decomposition methods have been introduced by some researche...

identification of damping parameter is usually more complicated and unreliable comparing to mass or stiffness identification in structural dynamics. there are many factors such as intermolecular friction, coulomb friction and viscous damping affecting the damping mechanisms in a structure. therefore it is difficult, and in some cases impossible, to describe the details of damping mechanisms by ...

in this paper some new applications of empirical mode decomposition (emd) and hilbert spectrum in seismic ground-roll attenuation, random noise attenuation and spectral decomposition are introduced. hilbert spectrum is a time-frequency representation for hilbert-huang transform which is obtained by combination of instantaneous frequency (if) concept and intrinsic mode function of empirical mode...

spectral decomposition is a powerful tool for analysis of seismic data. fourier transform determines the frequency contents of a signal. but for analysis of non-stationary signals, 1-d transform to frequency domain is not sufficient. in early years, transforming of seismic traces into time and frequency domain was done via windowed fourier transform, called a short time fourier transform (stft)...

nowadays, radar systems have many applications and radar imaging is one of the most important of these applications. inverse synthetic aperture radar (isar) is used to form an image from moving targets. conventional methods use fourier transform to retrieve doppler information. however, because of maneuvering of the target, the doppler spectrum becomes time-varying and the image is blurred. joi...

future design procedures for civil structures, especially those to be protected from extreme and blast relatedloads, will need to account for temporal evolution of their frequency content. there are, however, several instanceswhere acceleration time histories are required as seismic input. for example, to determine the ultimate resistance andto identify modes of structures’ failure, a nonlinear...

Abstract Fast (sub-second) spectroscopy with high spectral resolution is of vital importance for revealing quantum chemistry kinetics complex chemical and biological reactions. Fourier transform (FT) spectrometers can achieve operate at hundreds ms time scales in rapid-scan mode. However, the linear translation a scanning mirror imposes stringent time-resolution limitations to these systems, wh...