ALBERT

Description: Author(s): P. K. Biswas, D. G. Mazzone, R. Sibille, E. Pomjakushina, K. Conder, H. Luetkens, C. Baines, J. L. Gavilano, M. Kenzelmann, A. Amato, and E. Morenzoni The recent discovery of the topologically protected surface states in the β phase of PdBi 2 has reignited the research interest in this class of superconductors. Here, we show results of our muon spin relaxation and rotation ( μ SR ) measurements carried out to investigate the superconducting and magnet… [Phys. Rev. B 93, 220504(R)] Published Mon Jun 13, 2016

Description: Author(s): Soham Biswas, Hernán Larralde, and Francois Leyvraz We consider a one-dimensional system with particles having either positive or negative velocity, and these particles annihilate on contact. Diffusion is superimposed on the ballistic motion of the particle. The annihilation may represent a reaction in which the two particles yield an inert species. … [Phys. Rev. E 93, 022136] Published Wed Feb 24, 2016

Description: Author(s): Z. Guguchia, R. Khasanov, Z. Bukowski, F. von Rohr, M. Medarde, P. K. Biswas, H. Luetkens, A. Amato, and E. Morenzoni We report muon spin rotation experiments on the magnetic penetration depth λ and the temperature dependence of λ − 2 in the over-doped Fe-based high-temperature superconductor (Fe-HTS) Ba 1 − x Rb x Fe 2 As 2 ( x  = 0.65) studied at ambient and under hydrostatic pressures up to p = 2.3 GPa. We find that in this sy… [Phys. Rev. B 93, 094513] Published Fri Mar 11, 2016

Description: Author(s): A. Gauzzi, Y. Klein, M. Nisula, M. Karppinen, P. K. Biswas, H. Saadaoui, E. Morenzoni, P. Manuel, D. Khalyavin, M. Marezio, and T. H. Geballe By means of magnetization, specific heat, and muon-spin relaxation measurements, we investigate newly synthesized high-pressure oxidized Cu 0.75 Mo 0.25 Sr 2 YCu 2 O 7.54 , in which overdoping is achieved up to p ∼ 0.46 hole/Cu, well beyond the T c − p superconducting dome of cuprates, where Fermi-liquid behavior … [Phys. Rev. B 94, 180509(R)] Published Tue Nov 22, 2016

Description: Author(s): G. Lamura, T. Shiroka, S. Bordignon, S. Sanna, M. Moroni, R. De Renzi, P. Carretta, P. K. Biswas, F. Caglieris, M. Putti, S. Wurmehl, S. J. Singh, J. Shimoyama, M. N. Gastiasoro, and B. M. Andersen The deliberate insertion of magnetic Mn dopants in the Fe sites of the optimally doped SmFeAsO 0.88 F 0.12 iron-based superconductor can modify in a controlled way its electronic properties. The resulting phase diagram was investigated across a wide range of manganese contents ( x ) by means of muon-spin… [Phys. Rev. B 94, 214517] Published Fri Dec 23, 2016

Description: High order methods are frequently used in computational simulation for their high accuracy. An efficient way to avoid unnecessary computation in smooth regions of the solution is to use adaptive meshes which employ fine grids only in areas where they are needed. Nonconforming spectral elements allow the grid to be flexibly adjusted to satisfy the computational accuracy requirements. The method is suitable for computational simulations of unsteady problems with very disparate length scales or unsteady moving features, such as heat transfer, fluid dynamics or flame combustion. In this work, we select the Mark Element Method (MEM) to handle the non-conforming interfaces between elements. A new technique is introduced to efficiently implement MEM in 3-D nonconforming meshes. By introducing an "intermediate mortar", the proposed method decomposes the projection between 3-D elements and mortars into two steps. In each step, projection matrices derived in 2-D are used. The two-step method avoids explicitly forming/deriving large projection matrices for 3-D meshes, and also helps to simplify the implementation. This new technique can be used for both h- and p-type adaptation. This method is applied to an unsteady 3-D moving heat source problem. With our new MEM implementation, mesh adaptation is able to efficiently refine the grid near the heat source and coarsen the grid once the heat source passes. The savings in computational work resulting from the dynamic mesh adaptation is demonstrated by the reduction of the the number of elements used and CPU time spent. MEM and mesh adaptation, respectively, bring irregularity and dynamics to the computer memory access pattern. Hence, they provide a good way to gauge the performance of computer systems when running scientific applications whose memory access patterns are irregular and unpredictable. We select a 3-D moving heat source problem as the Unstructured Adaptive (UA) grid benchmark, a new component of the NAS Parallel Benchmarks (NPB). In this paper, we present some interesting performance results of ow OpenMP parallel implementation on different architectures such as the SGI Origin2000, SGI Altix, and Cray MTA-2.

Description: Using a collection of benchmark problems of increasing levels of realism and computational effort, we will characterize the strengths and limitations of the 10,240 processor Columbia system to deliver supercomputing value to application scientists. Scientists need to be able to determine if and how they can utilize Columbia to carry extreme workloads, either in terms of ultra-large applications that cannot be run otherwise (capability), or in terms of very large ensembles of medium-scale applications to populate response matrices (capacity). We select existing application benchmarks that scale from a small number of processors to the entire machine, and that highlight different issues in running supercomputing-calss applicaions, such as the various types of memory access, file I/O, inter- and intra-node communications and parallelization paradigms. http://www.nas.nasa.gov/Software/NPB/