Schofield S.P.,Los Alamos National Laboratory |
Christon M.A.,CTO Office
International Journal for Numerical Methods in Fluids | Year: 2012
In previous studies, the moment-of-fluid interface reconstruction method showed dramatic accuracy improvements in static and pure advection tests over existing methods, but this did not translate into an equivalent improvement in volume-tracked multimaterial incompressible flow simulation using low-order finite elements. In this work, the combined effects of the spatial discretization and interface reconstruction in flow simulation are examined. The mixed finite element pairs, Q 1Q 0 (with pressure stabilization) and Q 2P -1 are compared. Material order-dependent and material order-independent first and second-order accurate interface reconstruction methods are used. The Q 2P -1 elements show significant improvements in computed flow solution accuracy for single material flows but show reduced convergence using element-average piecewise constant density and viscosity in volume-tracked simulations. In general, a refined Q 1Q 0 grid, with better material interface resolution, provided an accuracy similar to the Q 2P -1 element grid with a comparable number of degrees of freedom. Moment-of-fluid shows more benefit from the higher-order accurate flow simulation than the LVIRA, Youngs', and power diagram interface reconstruction methods, especially on unstructured grids, but does not recover the dramatic accuracy improvements it has shown in advection tests. Published 2012. This article is a US Government work and is in the public domain in the USA. The moment-of-fluid interface reconstruction method has shown dramatic improvements in advection tests, but this did not create an equivalent improvement in the volume-tracked flow simulations using low-order elements. The effects of the spatial discretization, using Q 1 Q 0 or Q 2P -1 elements, combined with first-order and second-order interface reconstruction methods are examined. The Q 2P -1 elements show reduced convergence in volume-tracked simulations. Although momentof-fluid shows some benefit of higher-order elements, the accuracy improvements shown in the advection tests are not recovered. Published 2012. This article is a US Government work and is in the public domain in the USA. Published 2012. This article is a US Government work and is in the public domain in the USA.
Ropitault T.,Telecom Bretagne |
Pelov A.,Telecom Bretagne |
Toutain L.,Telecom Bretagne |
Vedantham R.,Texas Instruments |
Itron P.C.,CTO Office
2015 IEEE International Conference on Smart Grid Communications, SmartGridComm 2015 | Year: 2015
The new standard for narrowband PLC-based communications IEEE P1901.2 defines two mechanisms which do not exist in the majority of its wireless counterparts-dynamic frequency mapping (tone mapping), and existence of several modulations. Until now, the benefit of these mechanisms was not taken explicitly into account by the routing protocols. In this paper, we propose a novel metric for RPL-the Channel Occupancy (CO) metric. It accounts for the existence of multiple nominal throughputs over a given interface. The metric aims at minimizing the global channel occupancy time. In addition, we introduce a novel proactive link-estimation technique-COALE. This mechanism allows to fully benefit from the existence of multiple candidate parents under RPL. We evaluate the performance of a IEEE P1901.2-based Smart Meter network with RPL. We compare the performance gains of using Channel Occupancy instead of the widely popular expected transmission count (ETX). The results show that CO outperforms ETX by providing faster route formation times (up to 50%), lower end-To-end delays (up to 43%), lower signaling overhead (25%), and higher packet delivery rate (47%). © 2015 IEEE.
D'Ambrosia J.,CTO Office
2011 Optical Fiber Communication Conference and Exposition and the National Fiber Optic Engineers Conference, OFC/NFOEC 2011 | Year: 2011
IEEE Std. 802.3ba™-2010 defines 100GbE, along with a new family of physical layer specifications (PHYs). This presentation will look to the future and discuss the expansion of the 100GbE family of physical layer specifications. © 2011 Optical Society of America.
Norrman K.,SeCAM |
Teppo P.,Ericsson AB |
Mononen K.,Ericsson AB |
Nilsson M.,CTO Office
Ericsson Review (English Edition) | Year: 2014
Over the past decade, the number of attacks on IT and communications systems has risen drastically. This increase has gone hand in hand with a massive rise in the use of communications systems for everything from utilities and public health, to transportation and everyday communication. Ericsson refers to this as the Networked Society, and within it, networks serve as critical infrastructure that is fundamental for economic and social development. However, it also leaves society more vulnerable to cyber threats, both malicious and those arising from carelessness and a lack of awareness - it is this situation that needs to be addressed.
Cray is partnering with the Alan Turing Institute, the new U.K. data science research organization in London, to help the U.K. as it increases research in data science to benefit research and industry. Earlier this month Fiona Burgess, U.K. senior account manager, and I attended the launch of the institute. At the event, U.K. Minister for Science and Universities Jo Johnson paid tribute to Turing and his work. Institute director Professor Andrew Blake told the audience that the Turing Institute is about much more than just big data — it is about data science, analyzing that data and gaining a new understanding that leads to decisions and actions. Alan Turing was a pioneering British computer scientist. He has become a household name in the U.K. following publicity surrounding his role in breaking the Enigma machine ciphers during the Second World War. This was a closely guarded secret until a few years ago, but has recently become the subject of numerous books and several films. Turing was highly influential in the development of computer science, providing a formalization of the concepts of algorithm and computation with the Turing machine. After the war, he worked at the National Physical Laboratory, where he designed ACE, one of the first stored-program computers. The Alan Turing Institute is a joint venture between the universities of Cambridge, Edinburgh, Oxford, Warwick, University College London, and the U.K. Engineering and Physical Science Research Council (EPSRC). The Institute received initial funding in excess of £75 million ($110 million) from the U.K. government, the university partners and other business organizations, including the Lloyd’s Register Foundation. The Turing Institute will, among other topics, research how knowledge and predictions can be extracted from large-scale and diverse digital data. It will bring together people, organizations and technologies in data science for the development of theory, methodologies and algorithms. The U.K. government is looking to this new Institute to enable the science community, commerce and industry to realize the value of big data for the U.K. economy. Cray will be working with the Turing Institute and EPSRC to provide data analytics capability to the U.K.’s data sciences community. EPSRC’s ARCHER supercomputer, a Cray XC30 system based at the University of Edinburgh, has been chosen for this work. Much as we worked with NERSC to port Docker to Cray systems, we will be working with ATI to port analytics software to ARCHER and then XC systems generally. ARCHER is currently the largest supercomputer for scientific research in the U.K. — with its recent upgrade ARCHER’s 118,080 cores can access in excess of 300 TB of memory. What sort of problem might need that amount of processing power? Genomics England is collecting around 200 GB of DNA sequence data from each of 100,000 people. Finding patterns in all this information will be a mammoth task! ATI have put together a wide ranging programme of workshops and data science summits, details of which can be found on their Web site. Duncan Roweth is a principal engineer in the Cray CTO Office in Bristol, U.K.