The velocity and attenuation of ultrasonic stress waves in gabbroic rock samples (San Marcos, California) subjected to shock loading in the 2 GPa range were studied. From P wave velocity measurements we determined the damage parameter Dp and crack density e of the samples and related these to the attenuation coefficient (quality factor) under dynamic strains of 2 x 10 -? and at a frequency of 2...

  Introduction: Monte Carlo (MC) is the most common method for simulating virtual SPECT projections. It is useful for optimizing procedures, evaluating correction algorithms and more recently image reconstruction as a forward projector in iterative algorithms; however, the main drawback of MC is its long run time. We introduced a model based method considering the eff...

Ultrasonic shear-wave propagation studies have been carried out for the measurements of velocity and attenuation in some rocks, concrete and synthetic materials at room conditions. It has been found that ‘pulse broadening’, which occurs due to attenuation, can be measured quite accurately while carrying out shearwave velocity measurements in them. The pulse broadening data could be used to dete...

seismic waves when crossing the earth in heterogeneous and anisotropic environments, having interaction. recognizing the impact of these factors on the seismograms help us to find out more information about interior of the earth. coda waves are the main reason for the random heterogeneities in earth. local earthquakes in the northeast region of iran with epicentral distance less than 200 km is ...

in many seismological applications, the earth is considered as a perfectly elastic, homogeneous, and isotropic body. although this assumption is approximately valid, it is known that seismic waves pass through the real earth that is anelastic, inhomogeneous and anisotropic.  we consider four processes that can reduce wave amplitude, i.e.: geometrical spreading, scattering, multi-pathing, and an...

introduction: monte carlo (mc) is the most common method for simulating virtual spect projections. it is useful for optimizing procedures, evaluating correction algorithms and more recently image reconstruction as a forward projector in iterative algorithms; however, the main drawback of mc is its long run time. we introduced a model based method considering the effect of body attenuation and i...

in the present study, the q factor is obtained for the central alborz in iran using the lg coda method. the energy of a seismic wave decays while passing through a ‘real’ medium such as the earth which is not completely elastic. the decay in energy is due to non-elastic phenomena and is called intrinsic attenuation and is characterized with the q parameter, the large values of which represent s...

To solve noises affecting the performance of laser communication system problems, this paper studies mathematical model in atmospheric attenuation condition, sets up atmospheric attenuation coefficient of the primary factor aerosol (haze) according to the absorbing and scattering characteristics of the atmosphere, gives output SNR(Signal to Noise Ratio) models under atmosphere attenuation based...