In this paper, I present a modification of the Beylkin inversion operator. This modification accounts for the band-limited nature of the data and makes the role of discontinuities in the sound speed more precise. The inversion presented here partially dispenses with the small-parameter constraint of the Born approximation. This is shown by applying the proposed inversion operator to upward scat...

An analytical inversion formula for the exponential Radon transform with an imaginary attenuation coefficient was developed in 2007 (2007 Inverse Problems 23 1963-71). The inversion formula in that paper suggested that it is possible to obtain an exact MRI (magnetic resonance imaging) image without acquiring low-frequency data. However, this un-measured low-frequency region (ULFR) in the k-spac...

We propose a method to derive predictions for single-word retrieval times from a semantic space model trained on text corpora. In Experiment 1 we present a large corpus analysis demonstrating that it is the number of unique semantic contexts a word appears in across language, rather than simply the number of contexts or the frequency of the word, that is the most salient predictor of lexical de...

Introduction: Vascular-space-occupancy (VASO) MRI (1) produces cerebral blood volume (CBV)-weighted images by employing inversion recovery to null the blood signal. Depending on the TR used, the residual magnetization in tissue, however, is only about 10-20% of the equilibrium signal intensity at the time of inversion (TI), which yields a relatively low signal-to-noise ratio (SNR). It has been ...

geophysical data are always affected by different sources of anomaly. these sources are classified in to three groups: first group is relatively deep sources commonly called as regional effects, second group is near surface sources or local effects and third group is high frequency noises. the only common way to separate the anomaly is separation with respect to the signal frequency. there are ...

in this paper the inversion of gravity data using l1–norm stabilizer is considered. the inversion is an important step in the interpretation of data. in gravity data inversion, the goal is to estimate density and geometry of the unknown subsurface model from a set of known observation measured on the surface. commonly, rectangular prisms are used to model the subsurface under the survey area. t...

The finite-difference (FD) method described here is specially developed to model high-frequency Rayleigh-wave propagation in near-surface mediums. Although many FD programs existed for earthquake research and oil exploration, none has been developed to model high-frequency Rayleigh-wave propagation in near-surface elastic mediums when the source and all receivers are on the free-surface. The sc...