A transient technique for seismograph calibration

1962 ◽  
Vol 52 (4) ◽  
pp. 767-779
Author(s):  
A. F. Espinosa ◽  
G. H. Sutton ◽  
H. J. Miller
Keyword(s):  
Fourier Transform ◽  
Steady State ◽  
Input Pulse ◽  
Electrical Signal ◽  
Experimental Results ◽  
Response Curves ◽  
Amplitude Response ◽  
Transient Technique ◽  
Absolute Amplitude ◽  
The Fourier Transform

abstract A transient technique for seismograph calibration was developed and tested by a variety of methods. In the application of this technique a known transient in the form of an electrical signal is injected, through (a) a Willmore-type calibration bridge or (b) an independent coil, into the seismometer and the corresponding output transient of the system is recorded. The ratio of the Fourier transform of this transient to that of the input pulse yields phase and relative amplitude response of the seismograph as a function of period. Absolute amplitude response may be calculated if two easily determined constants of the seismometer are known. This technique makes practical the daily calibration of continuously-recording seismographs without disturbing the instruments more than a very few minutes. The transient technique was tested and proven satisfactory with results of more conventional steady-state methods, using both digital and analog analyses of the output transients. A variety of output transients corresponding to various theoretical response curves has been calculated for two standard input transients. By comparison of the calculated output transients with experimental results it is possible to obtain the response of the instrument with considerable precision quickly and without computation.

A PUBLIC MESH WATERMARKING ALGORITHM BASED ON ADDITION PROPERTY OF FOURIER TRANSFORM

2006 ◽  
Vol 06 (01) ◽  
pp. 35-43 ◽  
Author(s):  
LI LI ◽  
ZHIGENG PAN ◽  
DAVID ZHANG
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Spatial Domain ◽  
Experimental Results ◽  
Original Image ◽  
The Fourier Transform

This paper presents a public mesh watermarking algorithm whereby the resultant watermarked image minus the original image is the watermark information. According to the addition property of the Fourier transform, a change of spatial domain will cause a change in the frequency domain. The watermark information is then scaled down and embedded in one part of the x-coordinate of the original mesh. Finally, the x-coordinate of the test mesh is amplified before extraction. Experimental results prove that our algorithm is resistant to a variety of attacks without the need for any preprocessing.

Counterface Roughness Effect on the Dry Steady State Wear of Self-Lubricating Polyimide Composites

1984 ◽  
Vol 106 (2) ◽  
pp. 177-184 ◽  
Author(s):  
D. F. Play
Keyword(s):  
Fourier Transform ◽  
Steady State ◽  
Friction And Wear ◽  
Unit Length ◽  
Wave Length ◽  
Statistical Data Analysis ◽  
Wear Rates ◽  
Polyimide Composites ◽  
The Fourier Transform ◽  
Counterface Roughness

Initial counterface topography influences both running-in and steady state wear rates of polymers. But governing roughness parameters are difficult to isolate because of their strong dependences and their statistical natures. Distributions of RT, RA, R.M.S., Skewness, Kurtosis, profile slopes, number of peaks per unit length, radii of curvature of peak asperity and Fourier transform were considered to characterize the isotropic roughness of the abraded steel disks. Two polyimide composites with PTFE and CF x powders were chosen for the pins. Correlations between parameters, friction and linear steady state wear were obtained through statistical data analysis. Radii of curvature, profile slopes or RA, and number of peaks govern friction and wear in different ways depending on fillers. However, for both materials, wear increases with average slopes or RA and decreases with an increase of number of peaks and radii of curvature. Skewness governs also the results but Kurtosis and wave length of the maximum of the Fourier transform are useless to explain the results.

INVARIANT PATTERN RECOGNITION USING RIDGELET PACKETS AND THE FOURIER TRANSFORM

2009 ◽  
Vol 07 (02) ◽  
pp. 215-228 ◽  
Author(s):  
G. Y. CHEN ◽  
P. BHATTACHARYA
Keyword(s):  
Pattern Recognition ◽  
Fourier Transform ◽  
State Of The Art ◽  
Experimental Results ◽  
Noisy Environments ◽  
Rotation Invariant ◽  
Pattern Recognition Techniques ◽  
Orthonormal Bases ◽  
The Fourier Transform ◽  
Very High

In this paper, we propose two novel invariant algorithms for pattern recognition by using ridgelet packets and the Fourier transform. Ridgelet packets provide many orthonormal bases that can effectively capture directional features present in pattern images. The Fourier transform is good at eliminating the orientation differences. By combining these two tools, very efficient rotation invariant pattern recognition techniques are created. Experimental results show that the proposed methods achieve very high classification rates and they outperform other state-of-the-art methods for rotation invariant pattern recognition under both noise-free and noisy environments.

Eigenvalue Analysis of Identical Ladder Networks

1980 ◽  
Vol 17 (4) ◽  
pp. 359-366 ◽  
Author(s):  
C. S. Indulkar
Keyword(s):  
Fourier Transform ◽  
Steady State ◽  
Short Circuit ◽  
Open Circuit ◽  
Eigenvalue Analysis ◽  
Transform Method ◽  
Fourier Transform Method ◽  
The Fourier Transform

Identical ladder networks with open-circuit, short-circuit, and matched terminations have been analysed using the eigenvalue technique. The technique has been applied to determine the steady-state and transient potential distributions across a string of 400 KV insulators. The latter has been calculated by using this technique and the Fourier transform method.

scholarly journals 27. Intensity distribution across the Cygnus and Cassiopeia sources

1957 ◽  
Vol 4 ◽  
pp. 159-161
Author(s):  
R. C. Jennison
Keyword(s):  
Fourier Transform ◽  
Angular Distribution ◽  
Intensity Distribution ◽  
Phase Measurement ◽  
Frame Of Reference ◽  
Absolute Amplitude ◽  
A New Technique ◽  
The Fourier Transform ◽  
Aerial Systems ◽  
Phase Angles

Measurements of the angular distribution of intensity across the intense discrete sources in Cassiopeia and Cygnus have previously been handicapped by lack of knowledge of the phase of the Fourier transform at very long aerial spacings. The technical difficulties of measuring the phase of the transform and also of calibrating the absolute amplitude have been solved by a new technique involving three stations. This method enables the phase to be measured relative to a frame of reference within the source and obviates the need for retaining the phase angles accurately constant on the removal of one of the aerial systems to a new site. The phase measurement is not limited to observations of the central fringe, and useful measurements may be made on all the fringes contained within the aerial polar diagrams.

An Improved Fourier-Mellin Algorithm Based on the Image Amplitude Spectrum

2014 ◽  
Vol 687-691 ◽  
pp. 3773-3776
Author(s):  
Xiao Qiang Ji ◽  
Jie Zhang Cheng ◽  
Lei Jiang ◽  
Ting Ting Zhang ◽  
Mei Jiao Wang
Keyword(s):  
Fourier Transform ◽  
Motion Vector ◽  
Amplitude Spectrum ◽  
Phase Spectrum ◽  
Video Image ◽  
Experimental Results ◽  
Image Motion ◽  
Motion Model ◽  
Image Translation ◽  
The Fourier Transform

This paper proposes an improved amplitude spectrum based Fourier-Mellin algorithm Fourier by studying the nature of the Fourier transform image of the amplitude spectrum and the application of phase spectrum in estimation for image motion vector according to the shortcomings of traditional Fourier-Mellin algorithm when the video image translation, rotation and scaling of the situation exist. Experimental results show that the algorithm can estimate the rotation, translation and other vector parameters of a complicated motion model .The complexity of the algorithm has greatly improved comparing to the traditional Fourier-Mellin algorithm.

scholarly journals Stochastic Analysis of an Epidemic SVIR Model With Holling Type II Incidence and Treatment Rates

2021 ◽  
Author(s):  
V Madhusudanan ◽  
M N Srini ◽  
L. Amalraj
Keyword(s):  
Fourier Transform ◽  
Steady State ◽  
Stochastic Stability ◽  
Stochastic Analysis ◽  
Critical Role ◽  
Type Ii ◽  
Inhibitory Effects ◽  
The World ◽  
The Fourier Transform ◽  
Theoretical Results

Abstract In the event of an epidemic, inhibitory effects play a critical role in limiting the pandemic's influence on society. The majority of infectious diseases that affect humans are still on the verge of becoming epidemics over the world. Mathematical models have long been used to investigate the complicated dynamics of infectious illnesses. This research investigates a stochastic SVIR epidemic model with Holling type II incidence and treatment rates. The Fourier transform approach is used to analyse stochastic stability around an internal steady state. Finally, numerical simulations are presented with appropriate parameter selections in order to test the efficiency of the theoretical results.

DISTRIBUTED MULTIRESOLUTION DISCRETE FOURIER TRANSFORM AND ITS APPLICATION TO WATERMARKING

2010 ◽  
Vol 08 (02) ◽  
pp. 225-241 ◽  
Author(s):  
GAURAV BHATNAGAR ◽  
BALASUBRAMANIAN RAMAN
Keyword(s):  
Signal Processing ◽  
Fourier Transform ◽  
Discrete Fourier Transform ◽  
Digital Watermarking ◽  
Singular Values ◽  
Experimental Results ◽  
The Core ◽  
Core Idea ◽  
The Fourier Transform ◽  
Watermarking Scheme

The Fourier transform is undoubtedly one of the most valuable and frequently used tools in signal processing and analysis but it has some limitations. In this paper, we rectify these limitations by proposing a newer version of Fourier transform, namely, Distributed Multiresolution Discrete Fourier Transform (D-MR-DFT) and its application in digital watermarking. The core idea of the proposed watermarking scheme is to decompose an image into four frequency sub-bands using D-MR-DFT and then singular values of every sub-band are modified with the singular values of the watermark. The experimental results show better visual imperceptibility and resiliency of the proposed scheme against intentional or unintentional variety of attacks.

Methods for Computing 3D Steady-State Vibrations of Composites Using Green’s Functions

2010 ◽  
Author(s):  
Alexander Karmazin ◽  
Evgenia Kirillova ◽  
Wolfgang Seemann ◽  
Pavel Syromyatnikov
Keyword(s):  
Fourier Transform ◽  
Steady State ◽  
Elastic Anisotropy ◽  
Displacement Vector ◽  
Phase Method ◽  
Stationary Phase Method ◽  
Surface Load ◽  
Load Vector ◽  
Green’S Matrix ◽  
The Fourier Transform

Spatial steady-state harmonic vibrations of an infinite layered composite plate with an arbitrary elastic anisotropy of each layer are considered in this paper. The required vector of mechanical displacements of arbitrary points for a layered structure can be represented in the form of a double inverse Fourier transform of the product of the Fourier transform of the Green’s matrix and the Fourier transform of the surface load vector. An algorithm for computing the Fourier inverse transform with the given load vector is presented. Reducing of the initial double integral to the repeated one and using Jordan’s lemma make it possible to present the displacement vector in terms of residues in real and complex poles of the Green’s matrix. The stationary phase method is applied for computing asymptotic representations of the displacement field in the far-field zone. Displacements on the surface of some various composites on the basis of graphite-epoxy material for two types of surface load were computed as numerical examples.

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