An Exploration of Power Spectral Density (PSD) Estimation, with an Introduction to iDOF™ Instant Degrees of Freedom

2015 ◽  
Author(s):  
Philip Van Baren
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Degrees Of Freedom ◽  
Power Spectral ◽  
Psd Estimation

scholarly journals Validation of theα-μModel of the Power Spectral Density of GPS Ionospheric Amplitude Scintillation

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Kelias Oliveira ◽  
Alison de Oliveira Moraes ◽  
Emanoel Costa ◽  
Marcio Tadeu de Assis Honorato Muella ◽  
Eurico Rodrigues de Paula ◽  
...  
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Degrees Of Freedom ◽  
Solar Flux ◽  
Global Navigation Satellite Systems ◽  
Ionospheric Scintillation ◽  
Parameter Distribution ◽  
Satellite Systems ◽  
Amplitude Scintillation ◽  
Power Spectral

Theα-μmodel has become widely used in statistical analyses of radio channels, due to the flexibility provided by its two degrees of freedom. Among several applications, it has been used in the characterization of low-latitude amplitude scintillation, which frequently occurs during the nighttime of particular seasons of high solar flux years, affecting radio signals that propagate through the ionosphere. Depending on temporal and spatial distributions, ionospheric scintillation may cause availability and precision problems to users of global navigation satellite systems. The present work initially stresses the importance of the flexibility provided byα-μmodel in comparison with the limitations of a single-parameter distribution for the representation of first-order statistics of amplitude scintillation. Next, it focuses on the statistical evaluation of the power spectral density of ionospheric amplitude scintillation. The formulation based on theα-μmodel is developed and validated using experimental data obtained in São José dos Campos (23.1°S; 45.8°W; dip latitude 17.3°S), Brazil, located near the southern crest of the ionospheric equatorial ionization anomaly. These data were collected between December 2001 and January 2002, a period of high solar flux conditions. The results show that the proposed model fits power spectral densities estimated from field data quite well.

Calculation of Evolutionary Power Spectral Density of Bridge Response to Earthquakes by Convolution Summation

2019 ◽  
Vol 19 (04) ◽  
pp. 1950041
Author(s):  
Xianting Du ◽  
Hong Qiao ◽  
Chaoyi Xia ◽  
He Xia
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Degrees Of Freedom ◽  
Computational Cost ◽  
Time History ◽  
Dynamic Component ◽  
Rigid Frame ◽  
Power Spectral ◽  
History Analysis ◽  
Constant Coefficients

This paper presents a method for calculating the evolutionary power spectral density (EPSD) of the seismic response of bridges using the convolution summation. With zero initial values, a formula for the dynamic component of the response of bridges to spatially varying seismic ground motions is derived as the convolution summation, by assuming the seismic acceleration to vary linearly between two adjacent time stations. The convolution summation is used for calculating the convolution integral of the dynamic component response factor in the EPSD, in which the constant coefficients are independent of the harmonically modulated excitation. The constant coefficients are obtained by the time-history analysis using triangular unit impulse acceleration excitations. The computational cost of the EPSD depends mainly on the amount of degrees-of-freedom (DOFs) numbers of bridge supports in contact. The corresponding computational scheme is proposed, and its validity is indirectly verified with a single DOF system, by comparing the results obtained with those of the existing methods. Finally, a three-span continuous rigid-frame bridge is taken as a case study to illustrate the applicability and effectiveness of the proposed scheme.

Fuzzy Modeling of Multi-Degree-of-Freedom Power Spectral Density Systems

2009 ◽  
Vol 2 (1) ◽  
pp. 40-47
Author(s):  
Montasser Tahat ◽  
Hussien Al-Wedyan ◽  
Kudret Demirli ◽  
Saad Mutasher
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Fuzzy Modeling ◽  
Degree Of Freedom ◽  
Power Spectral

Power spectral density of on-off sources

1997 ◽  
Vol 33 (7) ◽  
pp. 559 ◽  
Author(s):  
K. Laevens
Keyword(s):  
Spectral Density ◽  
Power Spectral Density ◽  
Power Spectral
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