Parallel performance results for the OpenMOC neutron transport code on multicore platforms

The shift toward multicore architectures has ushered in a new era of shared memory parallelism for scientific applications. This transition has introduced challenges for the nuclear engineering community, as it seeks to design high-fidelity full-core reactor physics simulation tools. This article describes the parallel transport sweep algorithm in the OpenMOC method of characteristics (MOC) neutron transport code for multicore platforms using OpenMP. Strong and weak scaling studies are performed for both Intel Xeon and IBM Blue Gene/Q (BG/Q) multicore processors. The results demonstrate 100% parallel efficiency for 12 threads on 12 cores on Intel Xeon platforms and over 90% parallel efficiency with 64 threads on 16 cores on the IBM BG/Q. These results illustrate the potential for hardware acceleration for MOC neutron transport on modern multicore and future many-core architectures. In addition, this work highlights the pitfalls of programming for multicore architectures, with a focal point on false sharing.National Science Foundation (U.S.). Graduate Research Fellowship Program (Grant 1122374)United States. Department of Energy (Center for Exascale Simulation of Advanced Reactors. Contract DE-AC02-06CH11357

Transformations among large c conformal field theories

We show that there is a set of transformations that relates all of the 24 dimensional even self-dual (Niemeier) lattices, and also leads to non-lattice objects that however cannot be interpreted as a basis for the construction of holomorphic conformal field theory. In the second part of this paper, we extend our observations to higher dimensional conformal field theories build on extremal partition functions, where we generate c=24k theories with spectra decomposable into the irreducible representations of the Fischer-Griess Monster. We observe interesting periodicities in the coefficients of extremal partition functions and characters of the extremal vertex operator algebras.Comment: 14 pages, minor corrections, new references adde

Initial State Interactions for K−K^--Proton Radiative Capture

The effects of the initial state interactions on the $K^--p$ radiative capture branching ratios are examined and found to be quite sizable. A general coupled-channel formalism for both strong and electromagnetic channels using a particle basis is presented, and applied to all the low energy $K^--p$ data with the exception of the {\it 1s} atomic level shift. Satisfactory fits are obtained using vertex coupling constants for the electromagnetic channels that are close to their expected SU(3) values.Comment: 16 pages, uses revte

A task-based parallelism and vectorized approach to 3D Method of Characteristics (MOC) reactor simulation for high performance computing architectures

In this study we present and analyze a formulation of the 3D Method of Characteristics (MOC) technique applied to the simulation of full core nuclear reactors. Key features of the algorithm include a task-based parallelism model that allows independent MOC tracks to be assigned to threads dynamically, ensuring load balancing, and a wide vectorizable inner loop that takes advantage of modern SIMD computer architectures. The algorithm is implemented in a set of highly optimized proxy applications in order to investigate its performance characteristics on CPU, GPU, and Intel Xeon Phi architectures. Speed, power, and hardware cost efficiencies are compared. Additionally, performance bottlenecks are identified for each architecture in order to determine the prospects for continued scalability of the algorithm on next generation HPC architectures. Keywords: Method of Characteristics; Neutron transport; Reactor simulation; High performance computingUnited States. Department of Energy (Contract DE-AC02-06CH11357

Influence of span-wise coherence in a cylinder wake on the acoustic radiations

In the present work the influence of the spanwise coherence of the flow structures on the acoustic emission in the case of cylinder wakes is investigated. For this purpose, the correlation between pressure fluctuations in the far field and velocity fluctuations in the wake of the cylinders of different shapes is determined experimentally by means of the so called causality correlation. 2D-2C as well as 2D-3C PIV is applied to determine the velocity fluctuations. The pressure fluctuations in the far field are measured synchronously with microphones. From the temporal and spatial distribution of the correlation results, conclusions are drawn about the dependence between the coherence of the vortex structures convecting downstream of the cylinder and the tonal components in the acoustic signature. Most interestingly, in case of a tapered cylinder geometry the temporal evolution of the correlation function shows an asymmetry, which has not been observed in previous results

Influence of span-wise coherence on the acousticradiation in a cylinder wake

The aim of this study is to detect and visualise the influence of span-wise coherence on propagating sound waves emanating from a flow around circular cylinders with span-wise variations of the local radius. Synchronous particle image velocimetry (PIV) and microphone measurements are performed in a circular wind tunnel with a nozzle size of 0:4 m × 0:4 m at a maximum flow speed of U¥ = 43ms−1. The test section is surrounded by a full anechoic chamber of approximately 9 m × 9 m × 5 m

The effects of water and microstructure on the performance of polymer electrolyte fuel cells

n this paper, we present a comprehensive non-isothermal, one-dimensional model of the cathode side of a Polymer Electrolyte Fuel Cell. We explicitly include the catalyst layer, gas diffusion layer and the membrane. The catalyst layer and gas diffusion layer are characterized by several measurable microstructural parameters. We model all three phases of water, with a view to capturing the effect that each has on the performance of the cell. A comparison with experiment is presented, demonstrating excellent agreement, particularly with regard to the effects of water activity in the channels and how it impacts flooding and membrane hydration. We present several results pertaining to the effects of water on the current density (or cell voltage), demonstrating the role of micro-structure, liquid water removal from the channel, water activity, membrane and gas diffusion layer thickness and channel temperature. These results provide an indication of the changes that are required to achieve optimal performance through improved water management and MEA-component design. Moreover, with its level of detail, the model we develop forms an excellent basis for a multi-dimensional model of the entire membrane electrode assembly

General Formulation for Proton Decay Rate in Minimal Supersymmetric SO(10) GUT

We make an explicit formulation for the proton decay rate in the minimal renormalizable supersymmetric (SUSY) SO(10) model. In this model, the Higgs fields consist of ${\bf 10}$ and ${\bf \bar{126}}$ SO(10) representations in the Yukawa interactions with matter and of ${\bf 10}$, ${\bf \bar{126}}$, ${\bf 126}$, and ${\bf 210}$ representations in the Higgs potential. We present all the mass matrices for the Higgs fields contained in this minimal SUSY SO(10) model. Finally, we discuss the threshold effects of these Higgs fields on the gauge coupling unification.Comment: 32 pages, typos are corrected, a few references and comments to the papers arXiv:hep-ph/0204097 and arXiv:hep-ph/0402122 are adde

Vortex dislocation in the near wake of a cylinder with span-wise variations in diameter

We examined the evolution of three-dimensional vortex shedding patterns induced by spanwise variations of the cylinder diameter. Two distinct types of shedding patterns have identified through flow vi sualization: continuous (in-phase) oblique shedding where vortices shed with lower frequency stay attached to the vortices with higher frequency without any discontinuity or splitting and discontinuous (out-of-phase) shedding where the lower frequency vortices have no attachment to higher frequency vortices and vortex dislocation occurs. The dislocation seen in the flow is strongly influenced by th e span wi se ir regularities. We ob served a clear and strong in-phase spanwise vortex shedding for the three smooth cylinder configurations tested in the study. The tapered, bumps and steps configurations showed sections of strong coherent spanwise vortex shedding, and we identified hardly any coherent structures for the rib, sinusoidal, and helical configurations. Depending on the geometry and number of span wise irregularities, incoherent structures make difficult to determine the occurrence and location of vortex dislocations in the cylinder wake without a method that enables a reduction in the complexity. Here, we introduce a numerical approach that obtains the dominant structures of vortex shedding patterns by reducing the complexity in noisy data. The method maps the variations in the oblique shedding angle over time and provide quantitative conclusions on the intermittent occurrence and location of vortex dislocations in the 15 000 snapshots taken for each of the different cylinder geometries regardless of turbulence

Measuring the Behavioural Component of the S&P 500 and its Relationship to Financial Stress and Aggregated Earnings Surprises

Scholars in management and economics have shown increasing interest in isolating the behavioural dimension of market evolution. Indeed, by improving forecast accuracy and precision, this exercise would certainly help firms to anticipate economic fluctuations, thus leading to more profitable business and investment strategies. Yet, how to extract the behavioural component from real market data remains an open question. By using monthly data on the returns of the constituents of the S&P 500 index, we propose a Bayesian methodology to measure the extent to which market data conform to what is predicted by prospect theory (the behavioural perspective), relative to the (standard) subjective expected utility theory baseline.We document a significant behavioural component that reaches its peaks during recession periods and is correlated to measures of financial volatility, market sentiment and financial stress with expected sign. Moreover, the behavioural component decreases around macroeconomic corporate earnings news, while it reacts positively to the number of surprising announcements