Time-harmonic shear wave elastography is capable of measuring viscoelastic parameters in living tissue. However, finite tissue boundaries and waveguide effects give rise to wave interferences which are not accounted for by standard elasticity reconstruction methods. Furthermore, the viscoelasticity of tissue causes dispersion of the complex shear modulus, rendering the recovered moduli frequenc...

This work is a study of the extension of an inverse obstacle scattering algorithm for fixed, single-frequency data to multi-frequency time-dependent settings. The inversion algorithm is based on the point source method, which reconstructs scattered fields pointwise with respect to frequency. We use Fourier transforms to obtain the time-dependent scattered fields as superpositions of single-freq...

We introduce and analyze a frequency-domain method for par-abolic partial diierential equations. The method is naturally parallelizable. After taking the Fourier transformation of given sources in the space-time domain into the space-frequency domain, we propose to solve an indeenite, complex elliptic problem for each frequency. Fourier inversion will then recover the solution in the space-time...

Fisher’s information matrix for delay (which corresponds to range), Doppler (range rate), and higher derivatives was recently presented by Schultheiss and Weinstein [l], [2]. Its inverse, which provides a lower bound on the error covariance matrix, was obtained Manuscript received March 9, 1983; revised April 29, 1983 and May 12, 1983. The author is with Tel-Aviv University, Israel, on leave at...

In order to estimate space-time spectra correctly from uneven twice-daily data sampled by a polar-orbiting satellite, the wavenumber transform method (Hayashi, 1980) is modified by the use of a nonorthogonal Fourier inversion. The space-time spectra are obtained from the time-Fourier coefficients of the space-Fourier transforms of the asynoptic field with respect to its frequency-shifted wavenu...

seismic tomography is an imaging technique which creates maps of subsurface elastic properties such as p/s wave velocity, density and attenuation, based on observed seismograms and use of sophisticated inversion algorithms. amongst different acquisition geometries, seismic cross-hole tomography has a special position in geophysical surveys with many applications in hydrocarbons, coal and other ...

magnetotelluric (mt) method is a passive electromagnetic technique that uses the natural, time varying electric and magnetic field components measured at right angles at the surface of the earth to make inferences about the earth’s electrical structure which, in turn, can be related to the geology tectonics and subsurface conditions. reflection and refraction of electromagnetic (em) signals at ...

the paper presents unified analytical solution for combining high-frequency and low-frequency economic time-series by additive and proportional denton methods with parametrical dependence on the initial values of variable and indicator in evident form. this solution spans denton’s original and cholette’s advanced benchmarking initial conditions as the subcases. computational complexity of the o...

This article presents an application of a procedure to invert the highfrequency radiation process at the source during the 1995 Hyogo-ken Nanbu earthquake using the envelopes of acceleration waveforms from 16 stations. The inversion uses genetic algorithms that compare observed ground motions with synthetic ones calculated using empirical Green’s functions. Before the inversion, the reliability...

Compressed sensing (CS) theory assures us that we can accurately reconstruct magnetic resonance images using fewer k-space measurements than the Nyquist sampling rate requires. In traditional CS-MRI inversion methods, the fact that the energy within the Fourier measurement domain is distributed non-uniformly is often neglected during reconstruction. As a result, more densely sampled low-frequen...