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Ticconi F.,University of Leeds | Levinsen J.F.,Technical University of Denmark | Khvorostovsky K.,NERSC Inc | Forsberg R.,Technical University of Denmark | Shepherd A.,University of Leeds
International Geoscience and Remote Sensing Symposium (IGARSS)

This work presents the first results of a research activity aiming to compare estimates of Surface Elevation Changes (SEC) over the Jakobshavn Isbræ basin (Greenland) using different repeat altimetry techniques and different sensors (laser vs. radar altimetry). The goal of this comparison is the identification of the best performing algorithm, in terms of accuracy, coverage and processing effort, for the generation of surface elevation change maps. The methods investigated here are the cross-over and repeat-track. The results of the inter-comparison are here reported and, from a first analysis, it is found that both radar and laser altimetry resolve the surface elevation changes quite well, and that the problems found mainly in the coastal region and along the main trunk can be solved by combining the two methods. The comparison with airborne lidar data from the NASA ICEBridge and the ESA CryoVex campaigns is in progress. © 2013 IEEE. Source

Lee J.H.,University of North Carolina at Chapel Hill | Yao Y.,NERSC Inc | Shrestha U.,University of California at San Francisco | Gullberg G.T.,Lawrence Berkeley National Laboratory | Seo Y.,University of North Carolina at Chapel Hill
2014 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2014

The primary goal of this project is to implement the iterative statistical image reconstruction algorithm, in this case maximum likelihood expectation maximum (MLEM) used for dynamic cardiac single photon emission computed tomography, on Spark/GraphX. This involves porting the algorithm to run on large-scale parallel computing systems. Spark is an easy-toprogram software platform that can handle large amounts of data in parallel. GraphX is a graph analytic system running on top of Spark to handle graph and sparse linear algebra operations in parallel. The main advantage of implementing MLEM algorithm in Spark/GraphX is that it allows users to parallelize such computation without any expertise in parallel computing or prior knowledge in computer science. In this paper we demonstrate a successful implementation of MLEM in Spark/GraphX and present the performance gains with the goal to eventually make it useable in clinical setting. © 2014 IEEE. Source

Thorne P.,NERSC Inc | Thorne P.,National University of Ireland
Proceedings of the Institution of Civil Engineers: Forensic Engineering

This briefing outlines the evidence from instrumental records that leads to an unequivocal finding that the world has warmed. It then goes on to address the underlying causes, showing that only through invoking the effects of humans can the last 50 years be adequately explained. Finally, it addresses the recent hiatus/pause in warming of global surface temperatures and the implications. © Thomas Telford Services Ltd. All rights reserved. Source

Gray M.,Aix - Marseille University | Petit C.,ONERA | Rodionov S.,Aix - Marseille University | Bocquet M.,ParisTech National School of Bridges and Roads | And 5 more authors.
Optics Express

We propose a new algorithm for an adaptive optics system control law, based on the Linear Quadratic Gaussian approach and a Kalman Filter adaptation with localizations. It allows to handle non-stationary behaviors, to obtain performance close to the optimality defined with the residual phase variance minimization criterion, and to reduce the computational burden with an intrinsically parallel implementation on the Extremely Large Telescopes (ELTs). © 2014 Optical Society of America. Source

Wasserman H.J.,Lawrence Berkeley National Laboratory | Gerber R.A.,Lawrence Berkeley National Laboratory | Gerber R.A.,NERSC Inc
Computing in Science and Engineering

The oil embargo of the early 1970s stalled cars but began a supercomputing story that continues to this day. The National Energy Research Scientific Computing Center, the state-of-the-art national facility that serves government, industry, and academic users today, celebrated its 40th anniversary in 2014. The guest editors of this special issue document that history and describe the articles they selected to highlight it. © 2015 IEEE. Source

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