600,359 research outputs found
Multi-mass solvers for lattice QCD on GPUs
Graphical Processing Units (GPUs) are more and more frequently used for
lattice QCD calculations. Lattice studies often require computing the quark
propagators for several masses. These systems can be solved using multi-shift
inverters but these algorithms are memory intensive which limits the size of
the problem that can be solved using GPUs. In this paper, we show how to
efficiently use a memory-lean single-mass inverter to solve multi-mass
problems. We focus on the BiCGstab algorithm for Wilson fermions and show that
the single-mass inverter not only requires less memory but also outperforms the
multi-shift variant by a factor of two.Comment: 27 pages, 6 figures, 3 Table
Perturbation Theory for the Breakdown of Mean-Field Kinetics in Oscillatory Reaction-Diffusion Systems
Spatially-distributed, nonequilibrium chemical systems described by a Markov
chain model are considered. The evolution of such systems arises from a
combination of local birth-death reactive events and random walks executed by
the particles on a lattice. The parameter \gamma, the ratio of characteristic
time scales of reaction and diffusion, is used to gauge the relative
contributions of these two processes to the overall dynamics. For the case of
relatively fast diffusion, i.e. \gamma << 1, an approximate solution to the
Markov chain in the form of a perturbation expansion in powers of \gamma is
derived. Kinetic equations for the average concentrations differ from the
mass-action law and contain memory terms. For a reaction- diffusion system with
Willamowski-Rossler reaction mechanism, we further derive the following two
results: a) in the limit of \gamma --> 0 these memory terms vanish and the
mass-action law is recovered; b) the memory kernel is found to assume a simple
exponential form. A comparison with numerical results from lattice gas
automaton simulations is also carried out.Comment: 18 pages, 5 figures. To appear in J. Chem. Phy
EDACs and test integration strategies for NAND flash memories
Mission-critical applications usually presents several critical issues: the required level of dependability of the whole mission always implies to address different and contrasting dimensions and to evaluate the tradeoffs among them. A mass-memory device is always needed in all mission-critical applications: NAND flash-memories could be used for this goal. Error Detection And Correction (EDAC) techniques are needed to improve dependability of flash-memory devices. However also testing strategies need to be explored in order to provide highly dependable systems. Integrating these two main aspects results in providing a fault-tolerant mass-memory device, but no systematic approach has so far been proposed to consider them as a whole. As a consequence a novel strategy integrating a particular code-based design environment with newly selected testing strategies is presented in this pape
Invited Review: Recent developments in vibration control of building and bridge structures
This paper presents a state-of-the-art review of recent articles published on active, passive, semi-active and hybrid vibration control systems for structures under dynamic loadings primarily since 2013. Active control systems include active mass dampers, active tuned mass dampers, distributed mass dampers, and active tendon control. Passive systems include tuned mass dampers (TMD), particle TMD, tuned liquid particle damper, tuned liquid column damper (TLCD), eddy-current TMD, tuned mass generator, tuned-inerter dampers, magnetic negative stiffness device, resetting passive stiffness damper, re-entering shape memory alloy damper, viscous wall dampers, viscoelastic dampers, and friction dampers. Semi-active systems include tuned liquid damper with floating roof, resettable variable stiffness TMD, variable friction dampers, semi-active TMD, magnetorheological dampers, leverage-type stiffness controllable mass damper, semi-active friction tendon. Hybrid systems include shape memory alloys-liquid column damper, shape memory alloy-based damper, and TMD-high damping rubber
Slightly generalized Generalized Contagion: Unifying simple models of biological and social spreading
We motivate and explore the basic features of generalized contagion, a model
mechanism that unifies fundamental models of biological and social contagion.
Generalized contagion builds on the elementary observation that spreading and
contagion of all kinds involve some form of system memory. We discuss the three
main classes of systems that generalized contagion affords, resembling: simple
biological contagion; critical mass contagion of social phenomena; and an
intermediate, and explosive, vanishing critical mass contagion. We also present
a simple explanation of the global spreading condition in the context of a
small seed of infected individuals.Comment: 8 pages, 5 figures; chapter to appear in "Spreading Dynamics in
Social Systems"; Eds. Sune Lehmann and Yong-Yeol Ahn, Springer Natur
On Coding Efficiency for Flash Memories
Recently, flash memories have become a competitive solution for mass storage.
The flash memories have rather different properties compared with the rotary
hard drives. That is, the writing of flash memories is constrained, and flash
memories can endure only limited numbers of erases. Therefore, the design goals
for the flash memory systems are quite different from these for other memory
systems. In this paper, we consider the problem of coding efficiency. We define
the "coding-efficiency" as the amount of information that one flash memory cell
can be used to record per cost. Because each flash memory cell can endure a
roughly fixed number of erases, the cost of data recording can be well-defined.
We define "payload" as the amount of information that one flash memory cell can
represent at a particular moment. By using information-theoretic arguments, we
prove a coding theorem for achievable coding rates. We prove an upper and lower
bound for coding efficiency. We show in this paper that there exists a
fundamental trade-off between "payload" and "coding efficiency". The results in
this paper may provide useful insights on the design of future flash memory
systems.Comment: accepted for publication in the Proceeding of the 35th IEEE Sarnoff
Symposium, Newark, New Jersey, May 21-22, 201
Survey of gravitational wave memory in intermediate mass ratio binaries
The non-linear gravitational wave (GW) memory effect is a distinct prediction
in general relativity. While the effect has been well studied for comparable
mass binaries, it has mostly been overlooked for intermediate mass ratio
inspirals (IMRIs). We offer a comprehensive analysis of the phenomenology and
detectability of memory effects, including contributions from subdominant
harmonic modes, in heavy IMRIs consisting of a stellar mass black hole and an
intermediate mass black hole. When formed through hierarchical mergers, for
example when a GW190521-like remnant captures a stellar mass black hole, IMRI
systems have a large total mass, large spin on the primary, and possibly
residual eccentricity; features that potentially raise the prospect for memory
detection. We compute both the displacement and spin non-linear GW memory from
the gravitational waveforms computed within a black hole
perturbation theory framework that is partially calibrated to numerical
relativity waveforms. We probe the dependence of memory effects on mass ratio,
spin, and eccentricity and consider the detectability of a memory signal from
IMRIs using current and future GW detectors. We find that (i) while
eccentricity introduces additional features in both displacement and spin
memory, it does not appreciatively change the prospects of detectability, (ii)
including higher modes into the memory computation can increase singal-to-noise
(SNR) values by about 7\% in some cases, (iii) the SNR from displacement memory
dramatically increases as the spin approaches large, positive values, (iv) spin
memory from heavy IMRIs would, however, be difficult to detect with future
generation detectors even from highly spinning systems. Our results suggest
that hierarchical binary black hole mergers may be a promising source for
detecting memory and could favorably impact memory forecasts.Comment: 18 pages, 17 figures, matches the version published in PR
An intelligent advisory system for pre-launch processing
The shuttle system of interest in this paper is the shuttle's data processing system (DPS). The DPS is composed of the following: (1) general purpose computers (GPC); (2) a multifunction CRT display system (MCDS); (3) mass memory units (MMU); and (4) a multiplexer/demultiplexer (MDM) and related software. In order to ensure the correct functioning of shuttle systems, some level of automatic error detection has been incorporated into all shuttle systems. For the DPS, error detection equipment has been incorporated into all of its subsystems. The automated diagnostic system, (MCDS) diagnostic tool, that aids in a more efficient processing of the DPS is described
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