scholarly journals Depth Dependancy of Fourier Spectra of Catheters in Turkey Breast

2013 ◽  
Author(s):  
Anke Poelstra ◽  
Heinrich Martin Overhoff
Keyword(s):  
Fourier Spectra

scholarly journals The periodic topography of ice stream beds: Insights from the Fourier spectra of mega-scale glacial lineations

2017 ◽  
Vol 122 (7) ◽  
pp. 1355-1373 ◽  
Author(s):  
Matteo Spagnolo ◽  
Timothy C. Bartholomaus ◽  
Chris D. Clark ◽  
Chris R. Stokes ◽  
Nigel Atkinson ◽  
...  
Keyword(s):  
Ice Stream ◽  
Stream Beds ◽  
Fourier Spectra

A Study of Effect of Various Normal Force Loading Forms on Frictional Stick-Slip Vibration

2021 ◽  
Author(s):  
Xiaocui Wang ◽  
◽  
Runlan Wang ◽  
Bo Huang ◽  
Jiliang Mo ◽  
...  
Keyword(s):  
Dynamic Behaviour ◽  
Normal Force ◽  
Time Varying ◽  
Stick Slip ◽  
Vibration Signals ◽  
Theoretical Methods ◽  
Normal Forces ◽  
Frequency Domains ◽  
Amplitude Vibration ◽  
Fourier Spectra

In this work, a comparative study is performed to investigate the influence of time-varying normal forces on the friction properties and friction-induced stick-slip vibration by experimental and theoretical methods. In the experiments, constant and harmonic-varying normal forces are applied, respectively. The measured vibration signals under two loading forms are compared in both time and frequency domains. In addition, mathematical tools such as phase space reconstruction and Fourier spectra are used to reveal the science behind the complicated dynamic behaviour. It can be found that the friction system shows steady stick-slip vibration, and the main frequency does not vary with the magnitude of the constant normal force, but the size of limit cycle increases with the magnitude of the constant normal force. In contrast, the friction system harmonic normal force shows complicated behaviour, for example, higher-frequency larger-amplitude vibration occurs as the frequency of the normal force increases. The interesting findings offer a new way for controlling friction-induced stick-slip vibration in engineering applications.

Ground motion accelerogram analysis including dynamical instrumental correction

1964 ◽  
Vol 54 (6A) ◽  
pp. 2087-2098
Author(s):  
V. A. Jenschke ◽  
J. Penzien
Keyword(s):  
Ground Motion ◽  
Analytical Method ◽  
Strong Motion ◽  
Instrumental Error ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Damping Characteristics ◽  
Standard Response ◽  
Fourier Spectra

abstract Due to inertial and damping characteristics of strong motion seismographs, recorded ground motion accelerograms may in some cases be sufficiently in error to significantly affect the results obtained when generating standard response or Fourier spectra. Therefore, the objectives of this paper are to present an analytical method of generating standard spectra which will eliminate the above instrumental error and to show the significance of this error by presenting some sample results obtained from accelerograms representing both earthquakes and underground nuclear explosions.

Vibrations of beams with a breathing crack and large amplitude displacements

2015 ◽  
Vol 230 (1) ◽  
pp. 34-54 ◽  
Author(s):  
Gonçalo Neves Carneiro ◽  
Pedro Ribeiro
Keyword(s):  
Time Domain ◽  
Equations Of Motion ◽  
Shape Functions ◽  
Breathing Crack ◽  
Dimensional Theory ◽  
One Dimensional ◽  
Time Histories ◽  
Linear Effects ◽  
Fourier Spectra ◽  
The Time Domain

The vibrations of beams with a breathing crack are investigated taking into account geometrical non-linear effects. The crack is modeled via a function that reduces the stiffness, as proposed by Christides and Barr (One-dimensional theory of cracked Bernoulli–Euler beams. Int J Mech Sci 1984). The bilinear behavior due to the crack closing and opening is considered. The equations of motion are obtained via a p-version finite element method, with shape functions recently proposed, which are adequate for problems with abrupt localised variations. To analyse the dynamics of cracked beams, the equations of motion are solved in the time domain, via Newmark's method, and the ensuing displacements, velocities and accelerations are examined. For that purpose, time histories, projections of trajectories on phase planes, and Fourier spectra are obtained. It is verified that the breathing crack introduce asymmetries in the response, and that velocities and accelerations can be more affected than displacements by the breathing crack.

Strong earthquake motion and site conditions: Hollywood

1970 ◽  
Vol 60 (4) ◽  
pp. 1271-1289 ◽  
Author(s):  
C. M. Duke ◽  
J. E. Luco ◽  
A. R. Carriveau ◽  
P. J. Hradilek ◽  
R. Lastrico ◽  
...  
Keyword(s):  
Strong Earthquake ◽  
Dynamic Models ◽  
Free Field ◽  
Structural Response ◽  
Site Conditions ◽  
Field Amplification ◽  
Earthquake Motion ◽  
Fourier Spectra ◽  
Earthquake Accelerograms ◽  
East West

abstract An investigation was made to determine the feasibility of isolating the effects of site conditions on strong earthquake accelerograms. The set of accelerograms recorded simultaneously in 1952 at the roof, in the basement and on the ground outside the 14-story Hollywood Storage Building was chosen for analysis. Fourier spectra were computed for the two horizontal components at each of the three recording places and were used after smoothing to compute the ratios of spectra for adjacent points. Dynamic models of the subsurface conditions, the foundation and the building were established. Certain of the spectral ratios were also determined theoretically. The primary result is the development of a method of isolating effects of site conditions in Fourier spectra of accelerograms. Good theoretical checks were obtained on soil-structure interaction and structural response in the east-west direction. The absence of bedrock accelerograms prevented the obtaining of a theoretical check on free-field amplification, although plausible bedrock Fourier spectra were obtained. The subsurface model should be useful for further analyses.

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