Response of a Multidegree-of-Freedom System to Nonstationary Random Excitation

1978 ◽  
Vol 45 (3) ◽  
pp. 649-656 ◽  
Author(s):  
S. F. Masri
Keyword(s):  
Analytical Study ◽  
Propagation Speed ◽  
Random Excitation ◽  
Intensity Function ◽  
Spatially Correlated ◽  
Unit Step ◽  
Mean Square Response ◽  
Wave Propagation Speed ◽  
Frequency Ratios ◽  
Two Degree Of Freedom

This paper presents an analytical study of the covariance kernels of a damped linear two-degree-of-freedom system that is subjected to spatially correlated nonstationary stochastic excitation consisting of modulated white noise. A unit-step intensity function and an exponential function, resembling the envelope of a typical earthquake, are considered in conjunction with a propagating disturbance. Results of the analysis are used to determine the dependence of the peak transient mean-square response of the system on the uncoupled frequency ratios, mass ratios, wave propagation speed, shape of the intensity function, and system damping.

Proximity Spectra of Oscillators Under Random Excitation

1980 ◽  
Vol 102 (2) ◽  
pp. 329-337
Author(s):  
S. F. Masri
Keyword(s):  
Cross Correlation ◽  
Random Excitation ◽  
Intensity Function ◽  
Mean Square ◽  
System Parameters ◽  
Spatially Correlated ◽  
Mean Square Response ◽  
The Mean ◽  
Two Degree Of Freedom ◽  
Different Parts

The transient mean-square response of an uncoupled two-degree-of-freedom system under spatially correlated nonstationary random excitation is determined. The excitation is modulated white noise with an intensity function that resembles the envelopes of typical earthquakes. Results of the analysis are used to investigate the effects of (a) cross correlation, (b) shape of the intensity function, (c) delay time associated with the arrival of the excitation at different parts of the system, and (d) dimensionless system parameters on the mean-square proximity spectra.

Mean-Square Response of Simple Mechanical Systems to Nonstationary Random Excitation

1969 ◽  
Vol 36 (2) ◽  
pp. 221-227 ◽  
Author(s):  
R. L. Barnoski ◽  
J. R. Maurer
Keyword(s):  
White Noise ◽  
Random Noise ◽  
Random Excitation ◽  
Correlated Noise ◽  
Mean Square ◽  
Single Degree Of Freedom ◽  
Step Functions ◽  
Unit Step ◽  
Mean Square Response ◽  
The Mean

This paper concerns the mean-square response of a single-degree-of-freedom system to amplitude modulated random noise. The formulation is developed in terms of the frequency-response function of the system and generalized spectra of the nonstationary random excitation. Both the unit step and rectangular step functions are used for the amplitude modulation, and both white noise and noise with an exponentially decaying harmonic correlation function are considered. The time-varying mean-square response is shown not to exceed its stationary value for white noise. For correlated noise, however, it is shown that the system mean-square response may exceed its stationary value.

Influence of the applied pressure of the transducer on the propagation speed of the ultrasonic wave in wood

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Edgar V.M. Carrasco ◽  
Rejane C. Alves ◽  
Mônica A. Smits ◽  
Vinnicius D. Pizzol ◽  
Ana Lucia C. Oliveira ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Applied Pressure ◽  
Pressure Gauge ◽  
Eucalyptus Grandis ◽  
Propagation Speed ◽  
Ultrasonic Waves ◽  
Ultrasonic Speed ◽  
Wave Propagation Speed ◽  
Propagation Technique ◽  
Non Destructive

Abstract The non-destructive wave propagation technique is used to estimate the wood’s modulus of elasticity. The propagation speed of ultrasonic waves is influenced by some factors, among them: the type of transducer used in the test, the form of coupling and the sensitivity of the transducers. The objective of the study was to evaluate the influence of the contact pressure of the transducers on the ultrasonic speed. Ninety-eight tests were carried out on specimens of the species Eucalyptus grandis, with dimensions of 120 × 120 × 50 mm. The calibration of the pressure exerted by the transducer was controlled by a pressure gauge using a previously calibrated load cell. The robust statistical analysis allowed to validate the experimental results and to obtain consistent conclusions. The results showed that the wave propagation speed is not influenced by the pressure exerted by the transducer.

scholarly journals К теории рассеяния Мандельштама-Бриллюэна в плазменном слое

2020 ◽  
Vol 128 (1) ◽  
pp. 98
Author(s):  
С.А. Двинин ◽  
Д.К. Солихов ◽  
Ш.С. Нурулхаков
Keyword(s):  
Wave Propagation ◽  
Pump Wave ◽  
Plasma Layer ◽  
Brillouin Scattering ◽  
Propagation Speed ◽  
Local Source ◽  
Arbitrary Angle ◽  
Perturbation Amplitude ◽  
Wave Propagation Speed ◽  
Over Time

The evolution of a perturbation from a local source for Mandel'shtam-Brillouin scattering in a plasma layer with unlimited length is calculated. Perturbation over time in this case can either leave the scattering region through one of the two boundaries, or propagate along the layer at a speed below sound wave propagation speed, with an exponential growth, or a fall in perturbation amplitude. In the particular case of strictly backward scattering (the scattering angle is π), this propagation velocity is zero. The paper calculates the threshold instability fields and the instability increments, taking into account both convective losses and collisional attenuation of waves. It is shown that the instability threshold for scattering at an arbitrary angle can be lower than for strictly backwards scattering and when the threshold is exceeded by the intensity of the pump wave; the scattering increment at an angle can also be higher than the increment for backscattering. When the threshold is greatly exceeded, the convective losses can be neglected, and the largest increment is observed for backward scattering.

Mean-Square Response of a Second-Order System to Nonstationary, Random Excitation

1970 ◽  
Vol 37 (3) ◽  
pp. 612-616 ◽  
Author(s):  
L. L. Bucciarelli ◽  
C. Kuo
Keyword(s):  
Narrow Band ◽  
Random Excitation ◽  
Second Order ◽  
Envelope Function ◽  
Order System ◽  
Mean Square ◽  
Forcing Function ◽  
Mean Square Response ◽  
Noise Function ◽  
The Mean

The mean-square response of a lightly damped, second-order system to a type of non-stationary random excitation is determined. The forcing function on the system is taken in the form of a product of a well-defined, slowly varying envelope function and a noise function. The latter is assumed to be white or correlated as a narrow band process. Taking advantage of the slow variation of the envelope function and the small damping of the system, relatively simple integrals are obtained which approximate the mean-square response. Upper bounds on the mean-square response are also obtained.

Analytical and Optimization Study of Propagation and Reduction of Wave in Granular Sand by DEM Method

2021 ◽  
Author(s):  
Amin Moslemi Petrudi ◽  
Masoud Rahmani
Keyword(s):  
Wave Propagation ◽  
Particle Density ◽  
Propagation Speed ◽  
Granular Soils ◽  
Discrete Elements ◽  
Factors Affecting ◽  
Interparticle Force ◽  
Optimization Study ◽  
Solution Methods ◽  
Wave Propagation Speed

In this research, the discrete element method has been used to analyze wave propagation and to investigate the factors affecting wave reduction in granular soils. The method of discrete elements is important because of the possibility of preparing completely similar specimens and examining the effect of changes in a certain parameter on the Behavior of the specimens. This method also provides an understanding of the changes that have occurred at the micro-scale of granular materials that are not achievable with other laboratory and numerical methods. To model the specimens, a set of disks with specific granulation has been used for two-dimensional studies. PFC 2D software has been used to perform simulations and related analyzes such as interparticle force. The DEM code in MATLAB is used to check the wave depreciation. In this research, the optimization process was performed using experimental data and the Taguchi method using the DEM method. The results of this study show that there is a direct relationship between the number of particle set contacts and the wave propagation speed. Also, material properties such as particle density are the most important parameters affecting wave velocity. The results of the method (DEM) are done with PFC 2D software and a comparison between the results of this method with the solution methods used by other researchers is shown to be a good match.

A Hydrodynamic Efficiency Parameter as a Novel Left Ventricular Diastolic Dysfunction Diagnostic Metric

2008 ◽  
Author(s):  
Kelley C. Stewart ◽  
Rahul Kumar ◽  
John J. Charonko ◽  
Pavlos P. Vlachos ◽  
William C. Little
Keyword(s):  
Diastolic Dysfunction ◽  
Critical Role ◽  
Propagation Speed ◽  
Left Ventricular Diastolic Dysfunction ◽  
Left Ventricular ◽  
Diastolic Filling ◽  
Ventricular Diastolic Dysfunction ◽  
Efficiency Parameter ◽  
Wave Propagation Speed ◽  
The Relationship

Numerous studies have shown that cardiac diastolic dysfunction and diastolic filling play a critical role in dictating overall cardiac health and demonstrated that the filling wave propagation speed is a significant index of the severity of diastolic dysfunction [1, 2]. However, the governing flow physics underlying the relationship between propagation speed and diastolic dysfunction are poorly understood. More importantly, currently there is no reliable metric to allow clinicians the ability to diagnose cardiac dysfunction on the basis of the wave filling speed.

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