GRIDA3 (Shared Resources Manager for Environmental Data Analysis and Applications) is a multidisciplinary project designed to deliver an integrated system to forge solutions to some environmental challenges such as the constant increase of polluted sites, the sustainability of natural resources usage and the forecast of extreme meteorological events. The GRIDA3 portal is mainly based on Web 2.0 technologies and EnginFrame framework. The portal, now at an advanced stage of development, provides end-users with intuitive Web-interfaces and tools that simplify job submission to the underneath computing resources. The framework manages the user authentication and authorization, then controls the action and job execution into the grid computing environment, collects the results and transforms them into an useful format on the client side. The GRIDA3 Portal framework will provide a problemsolving platform allowing, through appropriate access policies, the integration and the sharing of skills, resources and tools located at multiple sites across federated domains

Conventional medical ultrasound systems normally implement ray-based imaging algorithms, such as delay-and-sum beamforming, whose severest limitation derives from the implicit assumption of constantvelocity media. As a result, in the case of two or more tissues with different velocities, the image of the underlying targets appears strongly degraded both in placement and in resolution. The proposed ultrasound-imaging strategy, a value-added application of concepts developed in the context of seismic prospecting, avoids this restriction by relying on the undulatory description of the physical process and not on the geometric one. Echoes are sensed in the synthetic aperture configuration by the transducer, whose elements sequentially emit a nearly spherical wave front that covers the whole region of interest. Given a macrovelocity model, the recorded echoes become the initial condition for the downward propagator of the ultrasound wavefield. The processing is in three steps: time-reverse propagation of the sensed echoes, forward simulation of the wavefield emitted by the source element, and partial imaging by computing the zero-lag temporal correlation of the two wavefields to detect the scattering structures. The final reconstruction is obtained by stacking all the partial results on a single image. Laboratory tests, performed on experimental data acquired on a physical phantom, with and without an aberrant layer, prove the effectiveness of the proposed method even in the case of vertical and lateral velocity variations, with images of impressive spatial resolution and highly accurate target placement.

In this paper we present an algorithm for the construction of the superoptimal circulant preconditioner for a two-level Toeplitz linear system. The algorithm is fast, in the sense that it operates in FFT time. Numerical results are given to assess its performance when applied to the solution of two-level Toeplitz systems by the conjugate gradient method, compared with the Strang and optimal circulant preconditioners.

SUMMARYAlthough time-domain depth migration techniques have been successfully ported to run on modern hardware accelerators, their ultimate obstacle is the I/O overhead present during the imaging step. Frequency-domain depth migration algorithms overcome this limitation and can exploit the full potential of new computing technologies. In particular, our implementation of Phase Shift Plus Interpolation (PSPI) method is characterized by fast running time, good quality results under lowsignal-to-noise ratio conditions and excellent results for steep dips. We provide a novel computational dataflow scheme to perform acceleration of PSPI on a generic dataflow engine. We present speedup results obtained on the state-of-the-art dataflow technology for synthetic VTI datasets. Our measurements indicate that a dataflow approach can achieve high speedups despite larger and larger computational domains, increased complexity of the anisotropic approach and the I/O overhead during angle-gathers calculation.