An iterative algorithm that reconstructs the attenuation map and emission activity distribution from SPECT emission data is proposed. The algorithm is based on the quasilinearized attenuated Radon transform. At each iteration of the algorithm, emission activity distribution is reconstructed using the attenuation map from the previous iteration. Then, the attenuation map is estimated by using th...

We discuss a simple methodology to enable a statistical comparison of human population with the vegetation of North America over the past 13000 years. Nonparametric kernel methods are applied for temporal and spatial smoothing of point data obtained from the Neotoma Paleoecology Database and the Canadian Archaeological Radiocarbon Database, which results in sequences of maps showing the develop...

The results of a wavelet analysis of data from discrete element modelling (DEM) simulations of samples under biaxial compression are presented. We show how a wavelet technique may be used to find the strain scales on which critical events occur and to identify regions both in space and in strain when particles in the sample undergo significant activity. The wavelet analysis indicates that most ...

An iterative method is presented that allows one to retrieve the Green’s function originating from a virtual source located inside a medium using reflection data measured only at the acquisition surface. In addition to the reflection response, an estimate of the travel times corresponding to the direct arrivals is required. However, no detailed information about the heterogeneities in themedium...