664 research outputs found
Evaluation of magnetic materials for static inverters and converters
Program studies materials for use in static inverters and converters. It gives suitable data on the behavior of commonly used materials when excited with square wave power
An efficient and portable SIMD algorithm for charge/current deposition in Particle-In-Cell codes
In current computer architectures, data movement (from die to network) is by
far the most energy consuming part of an algorithm (10pJ/word on-die to
10,000pJ/word on the network). To increase memory locality at the hardware
level and reduce energy consumption related to data movement, future exascale
computers tend to use more and more cores on each compute nodes ("fat nodes")
that will have a reduced clock speed to allow for efficient cooling. To
compensate for frequency decrease, machine vendors are making use of long SIMD
instruction registers that are able to process multiple data with one
arithmetic operator in one clock cycle. SIMD register length is expected to
double every four years. As a consequence, Particle-In-Cell (PIC) codes will
have to achieve good vectorization to fully take advantage of these upcoming
architectures. In this paper, we present a new algorithm that allows for
efficient and portable SIMD vectorization of current/charge deposition routines
that are, along with the field gathering routines, among the most time
consuming parts of the PIC algorithm. Our new algorithm uses a particular data
structure that takes into account memory alignement constraints and avoids
gather/scatter instructions that can significantly affect vectorization
performances on current CPUs. The new algorithm was successfully implemented in
the 3D skeleton PIC code PICSAR and tested on Haswell Xeon processors (AVX2-256
bits wide data registers). Results show a factor of to
speed-up in double precision for particle shape factor of order to . The
new algorithm can be applied as is on future KNL (Knights Landing)
architectures that will include AVX-512 instruction sets with 512 bits register
lengths (8 doubles/16 singles).Comment: 36 pages, 5 figure
Speeding up simulations of relativistic systems using an optimal boosted frame
It can be computationally advantageous to perform computer simulations in a
Lorentz boosted frame for a certain class of systems. However, even if the
computer model relies on a covariant set of equations, it has been pointed out
that algorithmic difficulties related to discretization errors may have to be
overcome in order to take full advantage of the potential speedup. We summarize
the findings, the difficulties and their solutions, and show that the technique
enables simulations important to several areas of accelerator physics that are
otherwise problematic, including self-consistent modeling in three-dimensions
of laser wakefield accelerator stages at energies of 10 GeV and above.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July
2009, eConf C09072
Presence of New Delhi metallo-ÎČ-lactamase gene (NDM-1) in a clinical isolate of Acinetobacter junii in Argentina
Here we report the presence of a clinically significant A. junii blaNDM-1 positive in a 38-year-old woman who was admitted to the emergency department with a fever and leg ulcers with signs of infection. The NDM-1 carbapenemase has been dramatically spread among Gram-negative bacilli, thus imposing a new challenge on the health system to fight bacterial infections.These data expand the number of Acinetobacter species harbouring blaNDM-1. The wide existence of Acinetobacter harbouring and dispersing this carbapenemase emphasizes the importance of non-previously recognized pathogens as reservoirs of dangerous resistance determinants. These resistance determinants can be later easily transferred to other menacing pathogens.Fil: Montaña, Sabrina Daiana. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Houssay. Instituto de Investigaciones en MicrobiologĂa y ParasitologĂa MĂ©dica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en MicrobiologĂa y ParasitologĂa MĂ©dica; ArgentinaFil: Cittadini, Roxana. Sanatorio Mater Dei; ArgentinaFil: Del Castillo M,. Sanatorio Mater Dei; ArgentinaFil: Uong, S.. California State University; Estados UnidosFil: Lazzaro, T.. California State University; Estados UnidosFil: Almuzara, Marisa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de BioquĂmica ClĂnica; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; ArgentinaFil: Barberis, Claudia. Sanatorio Mater Dei; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de BioquĂmica ClĂnica; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; ArgentinaFil: Vay, Carlos Alberto. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y BioquĂmica. Departamento de BioquĂmica ClĂnica; Argentina. Universidad de Buenos Aires. Facultad de Medicina. Hospital de ClĂnicas General San MartĂn; ArgentinaFil: RamĂrez, M. S.. California State University; Estados Unido
Improved quantification of Chinese carbon fluxes using CO2/CO correlations in Asian outflow
[1] We use observed CO2:CO correlations in Asian outflow from the TRACE-P aircraft campaign (FebruaryâApril 2001), together with a three-dimensional global chemical transport model (GEOS-CHEM), to constrain specific components of the east Asian CO2 budget including, in particular, Chinese emissions. The CO2/CO emission ratio varies with the source of CO2 (different combustion types versus the terrestrial biosphere) and provides a characteristic signature of source regions and source type. Observed CO2/CO correlation slopes in east Asian boundary layer outflow display distinct regional signatures ranging from 10â20 mol/mol (outflow from northeast China) to 80 mol/mol (over Japan). Model simulations using best a priori estimates of regional CO2 and CO sources from Streets et al. [2003] (anthropogenic), the CASA model (biospheric), and Duncan et al. [2003] (biomass burning) overestimate CO2 concentrations and CO2/CO slopes in the boundary layer outflow. Constraints from the CO2/CO slopes indicate that this must arise from an overestimate of the modeled regional net biospheric CO2 flux. Our corrected best estimate of the net biospheric source of CO2 from China for MarchâApril 2001 is 3200 Gg C/d, which represents a 45 % reduction of the net flux from the CASA model. Previous analyses of the TRACE-P data had found that anthropogenic Chinese C
Warp-X: a new exascale computing platform for beam-plasma simulations
Turning the current experimental plasma accelerator state-of-the-art from a
promising technology into mainstream scientific tools depends critically on
high-performance, high-fidelity modeling of complex processes that develop over
a wide range of space and time scales. As part of the U.S. Department of
Energy's Exascale Computing Project, a team from Lawrence Berkeley National
Laboratory, in collaboration with teams from SLAC National Accelerator
Laboratory and Lawrence Livermore National Laboratory, is developing a new
plasma accelerator simulation tool that will harness the power of future
exascale supercomputers for high-performance modeling of plasma accelerators.
We present the various components of the codes such as the new Particle-In-Cell
Scalable Application Resource (PICSAR) and the redesigned adaptive mesh
refinement library AMReX, which are combined with redesigned elements of the
Warp code, in the new WarpX software. The code structure, status, early
examples of applications and plans are discussed
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Use of the Lorentz-Boosted Frame Transformation to Simulate Free-Electron Laser Amplifier Physics
Recently [1]it has been pointed out that numerical simulation of some systems containing charged particles with highly relativistic directed motion can by speeded up by orders of magnitude by choice of the proper Lorentz boosted frame. A particularly good example is that of short wavelength free-electron lasers (FELs) in which a high energy (E0>_ 250 MeV) electron beam interacts with a static magnetic undulator. In the optimal boost frame with Lorentz factor gamma F, the red-shifted FEL radiation and blue shifted undulator have identical wavelengths and the number of required time-steps (presuming the Courant condition applies) decreases by a factor of g2 F for fullyelectromagnetic simulation. We have adapted the WARP code [2]to apply this method to several FEL problems including coherent spontaneous emission (CSE) from pre-bunched e-beams, and strong exponential gain in a single pass amplifier configuration. We discuss our results and compare with those from the"standard" FEL simulation approach which adopts the eikonal approximation for propagation ofthe radiation field
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Carbonyl sulfide (OCS): Large-scale distributions over North America during INTEX-NA and relationship to CO2
An extensive set of carbonyl sulfide (OCS) observations were made as part of the NASA Intercontinental Chemical Transport Experiment-North America (INTEX-NA) study, flown from 1 July to 14 August 2004 mostly over the eastern United States and Canada. These data show that summertime OCS mixing ratios at low altitude were dominated by surface drawdown and were highly correlated with CO2. Although local plumes were observed on some low-altitude flight legs, anthropogenic OCS sources were small compared to this sink. These INTEX-NA observations were in marked contrast to the early springtime 2001 Transport and Chemical Evolution over the Pacific experiment, which sampled Asian outflow dominated by anthropogenic OCS emissions. To test the gridded OCS fluxes used in past models, the INTEX-NA observations were combined with the sulfur transport Eulerian model (STEM) regional atmospheric chemistry model for a top-down assessment of bottom-up OCS surface fluxes for North America. Initial STEM results suggest that the modeled fluxes underestimate the OCS plant sink by more than 200%. Copyright 2008 by the American Geophysical Union
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NMHCs and halocarbons in Asian continental outflow during the Transport and Chemical Evolution over the Pacific (TRACE-P) Field Campaign: Comparison with PEM-West B
We present an overview of the spatial distributions of nonmethane hydrocarbons (NMHCs) and halocarbons observed over the western north Pacific as part of the NASA GTE Transport and Chemical Evolution over the Pacific (TRACEâP) airborne field campaign (FebruaryâApril 2001). The TRACEâP data are compared with earlier measurements from the Pacific Rim during the Pacific Exploratory MissionâWest B (PEMâWest B), which took place in FebruaryâMarch 1994, and with emission inventory data for 2000. Despite the limited spatial and temporal data coverage inherent to airborne sampling, mean levels of the longerâlived NMHCs (including ethane, ethyne, and benzene) were remarkably similar to our results during the PEMâWest B campaign. By comparison, mixing ratios of the fire extinguisher Halonâ1211 (CF2ClBr) increased by about 50% in the period between 1994 and 2001. Southern China (south of 35°N), and particularly the Shanghai region, appears to have been a substantial source of Halonâ1211 during TRACEâP. Our previous analysis of the PEMâWest B data employed methyl chloroform (CH3CCl3) as a useful industrial tracer. However, regulations have reduced its emissions to the extent that its mixing ratio during TRACEâP was only oneâthird of that measured in 1994. Methyl chloroform mixing ratio âhot spots,â indicating regions downwind of continuing emissions, included outflow from the vicinity of Shanghai, China, but particularly high emission ratios relative to CO were observed close to Japan and Korea. Tetrachloroethene (C2Cl4) levels have also decreased significantly, especially north of 25°N, but this gas still remains a useful indicator of northern industrial emissions. Methyl bromide (CH3Br) levels were systematically 1â2 pptv lower from 1994 to 2001, in accord with recent reports. However, air masses that had been advected over Japan and/or South Korean port cities typically exhibited elevated levels of CH3Br. As a consequence, emissions of CH3Br from Japan and Korea calculated employing CH3Br/CO ratios and scaled to CO emission inventory estimates, were almost as large as for all of south China (south of 35°N). Total east Asian emissions of CH3Br and CH3Cl were estimated to be roughly 4.7 Gg/yr and 167 Gg/yr, respectively, in 2001
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