When a train runs at high speed, affected by the structural characteristics of catenary, contact force changes periodically with span and dropper spacing. However, as running speed increases, periodic signal owing to fluctuation catenary vibration pantograph, which directly affects stable between pantograph catenary. Therefore, based on simulation research method, this study uses time–frequency...

magnetotelluric (mt) method is an important passive surface geophysical method which uses the earth’s natural electromagnetic fields to investigate the electrical resistivity structure of the subsurface. the depth of investigation of mt is much higher than that of other electromagnetic (em) methods (vozoff, 1991). for a general conductivity distribution in the earth, the horizontal electric fie...

The Fourier transform of a signal defines the frequency domain representation of the signal in that it specifies relative amplitudes of the various frequency components of the signal. However, the Fourier transform is not always the best tool to analyze 'real-time signals' which have frequency components that change over time. Joint time-frequency techniques were developed for characterizing th...

In order to improve the time-frequency resolutions of short-time fractional Fourier transform, adaptive short-time fractional Fourier transform (ASTFRFT) method is used in this paper. The optimal order of ASTFRFT is given by maximizing kurtosis of signals in fractional domain, where the window width of ASTFRFT is searched by the maximal Shannon entropy of timefrequency distribution. Short-time ...

In this paper, we propose a simple framework for studying certain distributions of variables beyond time-frequency and time-scale. When applicable, our results turn the theory of joint distributions of arbitrary variables into an easy exercise of coordinate transformation. While straightforward, the method can generate many distributions previously attainable only by the general construction of...