http://hdl.handle.net/10016/7395 Sat, 18 May 2013 15:58:59 GMT 2013-05-18T15:58:59Z http://e-archivo.uc3m.es:80/retrieve/30628/phys_dpt.JPG http://hdl.handle.net/10016/7395 http://hdl.handle.net/10016/16619 Title: Development of oxide dispersion strengthened W alloys produced by hot isostatic pressing Author(s): Martínez Gómez, Javier; Savoini Cardiel, Begoña; Monge Alcazar, Miguel Angel; Muñoz Castellanos, Angel; Pareja Pareja, Ramiro Abstract: A powder metallurgy technique has been developed to produce oxide strengthened W-Ti and W-V alloys using elemental powders and nanosized powders of La(2)O(3) or Y(2)O(3) as starting materials. The alloys consolidated by hot isostatic pressing resulted in high-density materials having an ultrafine-grained structure and microhardness values in the range 7-13 GPa. Atom force microscopy studies show a topographic relief in the Ti and V pools that appear in the consolidated alloys. This relief is attributed to the heterogeneous nucleation of martensite plates. The preliminary transmission electron microscopy studies have revealed that a dispersion of nanoparticles can be induced in these alloys produced via the present technique. Description: Conference: 26th Symposium on Fusion Technology (SOFT) Location: Porto, Portugal. Date: 27 September-01 October, 2010 Fri, 30 Sep 2011 22:00:00 GMT http://hdl.handle.net/10016/16619 2011-09-30T22:00:00Z http://hdl.handle.net/10016/12942 Title: Analytical characterisation of oxide dispersion strengthened steels for fusion reactors Author(s): Castro, Vanessa, de; Lozano-Perez, S.; Marquis, E.A.; Auger, Mª Angustias; Leguey, Teresa; Pareja, Ramiro Abstract: Reduced activation ferritic/martensitic and ferritic steels strengthened by a dispersion of oxide nanoparticles have been considered viable structural materials for fusion applications above 550uC. However, the microstructural stability and mechanical behaviour of these steels subjected to the aggressive operating conditions of these reactors are not well known. An accelerated development of these materials is crucial if they are going to be used in future power reactors. Then, it is indispensable to understand their atomic scale evolution under high temperature and irradiation conditions. The present paper reviews how the combination of transmission electron microscopy and atom probe tomography has been successfully applied for the characterisation of these steels at the near atomic scale, to reveal the nanoparticle structure, grain boundary chemistry and void distribution. Description: Special issue article Fri, 31 Dec 2010 23:00:00 GMT http://hdl.handle.net/10016/12942 2010-12-31T23:00:00Z http://hdl.handle.net/10016/8911 Title: Parallelization in time of numerical simulations of fully-developed plasma turbulence using the parareal algorithm Author(s): Samaddar, D.; Newman, David E.; Sánchez, Raúl Abstract: It is shown that numerical simulations of fully-developed plasma turbulence can be successfully parallelized in time using the parareal algorithm. The result is far from trivial, and even unexpected, since the exponential divergence of Lagrangian trajectories as well as the extreme sensitivity to initial conditions characteristic of turbulence set these type of simulations apart from the much simpler systems to which the parareal algorithm has been applied to this day. It is also shown that the parallel gain obtainable with this method is very promising (close to an order of magnitude for the cases and implementations described), even when it scales with the number of processors quite differently to what is typical for spatial parallelization. Description: 16 pages, 12 figures. Tue, 31 Aug 2010 22:00:00 GMT http://hdl.handle.net/10016/8911 2010-08-31T22:00:00Z http://hdl.handle.net/10016/8910 Title: BCYCLIC: A parallel block tridiagonal matrix cyclic solver Author(s): Hirshman, S. P.; Perumalla, K. S.; Lynch, V. E.; Sánchez, Raúl Abstract: A block tridiagonal matrix is factored with minimal fill-in using a cyclic reduction algorithm that is easily parallelized. Storage of the factored blocks allows the application of the inverse to multiple right-hand sides which may not be known at factorization time. Scalability with the number of block rows is achieved with cyclic reduction, while scalability with the block size is achieved using multithreaded routines (OpenMP, GotoBLAS) for block matrix manipulation. This dual scalability is a noteworthy feature of this new solver, as well as its ability to efficiently handle arbitrary (non-powers-of-2) block row and processor numbers. Comparison with a state-of-the art parallel sparse solver is presented. It is expected that this new solver will allow many physical applications to optimally use the parallel resources on current supercomputers. Example usage of the solver in magneto-hydrodynamic (MHD), three-dimensional equilibrium solvers for high-temperature fusion plasmas is cited. Description: 13 pages, 6 figures. Tue, 31 Aug 2010 22:00:00 GMT http://hdl.handle.net/10016/8910 2010-08-31T22:00:00Z