We study a general setting of neutral evolution in which the population is of finite, constant size and can have spatial structure. Mutation leads to different genetic types ("traits"), which can be discrete...
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Dense hard-particle packings are intimately related to the structure of low-temperature phases of matter and are useful models of heterogeneous materials and granular media. Most studies of the densest packings in thr...
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Dense hard-particle packings are intimately related to the structure of low-temperature phases of matter and are useful models of heterogeneous materials and granular media. Most studies of the densest packings in three dimensions have considered spherical shapes, and it is only more recently that nonspherical shapes (e.g., ellipsoids) have been investigated. Superballs (whose shapes are defined by |x1|2p+|x2|2p+|x3|2p≤1) provide a versatile family of convex particles (p≥0.5) with both cubic-like and octahedral-like shapes as well as concave particles (0
Advances in emission imaging detector hardware and modeling have allowed on-the-fly maximum likelihood photon event attribute estimation [1]. Such detectors lead to an infinite dimensional system model called the Phot...
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Advances in emission imaging detector hardware and modeling have allowed on-the-fly maximum likelihood photon event attribute estimation [1]. Such detectors lead to an infinite dimensional system model called the Photon Processing model [2], [3], [4]. In this work we extend the Fourier crosstalk matrix formalism [5] to photon processing systems to compare the performance of such detectors to classical pixelated photon-counting detectors for the task of estimating object Fourier coefficients. In a preliminary study we have computed crosstalk matrices for a class of 2D pinhole SPECT systems;in this setting, the photon processing detector outperforms a pixelated detector with pixel size equal to the full width half maximum of the position estimation blur.
One notion of phase for stochastic oscillators is based on the mean return-time (MRT): a set of points represents a certain phase if the mean time to return from any point in this set to this set after one rotation is...
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A generalized Reynolds analogy (GRA) is proposed for compressible wall-bounded turbulent flows (CWTFs) and validated by direct numerical simulations. By introducing a general recovery factor, a similarity between the ...
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A generalized Reynolds analogy (GRA) is proposed for compressible wall-bounded turbulent flows (CWTFs) and validated by direct numerical simulations. By introducing a general recovery factor, a similarity between the Reynolds-averaged momentum and energy equations is established for the canonical CWTFs (i.e. circular pipes, channels, and boundary layers that meet the quasi one-dimensional flow approximation), independent of Prandtl number, wall temperature, and pressure gradient. This similarity and its admitted relationships between temperature and velocity constitute the GRA. The GRA relationship between the mean temperature and the mean velocity takes the same quadratic form as Walz's equation, with the adiabatic recovery factor replaced by
Cells of mutant strains of the bacterium B. subtilis fail to separate upon dividing, and form long fibers. A given fiber is initially straight, but once it grows to around 100 microns, it buckles and writhes. Soon aft...
Cells of mutant strains of the bacterium B. subtilis fail to separate upon dividing, and form long fibers. A given fiber is initially straight, but once it grows to around 100 microns, it buckles and writhes. Soon after this initial instability the fiber rapidly braids up into a plectoneme. Modeling a fiber as a twisted elastic filament in a viscous fluid, we exploit the “natural” frame of space curves to formulate the dynamics of the filament’s shape and twist density. The resulting coupled nonlinear equations are used to display a remarkable nonlinear phenomenon: geometric untwisting of open filaments, in which twist strain relaxes through a transient writhing instability without axial rotation. Experimentally observed motions of the fibers of B. subtilis may be examples of this twisting process.
Opportunistic spectrum access (OSA) is a promising reform paradigm envisioned to address the issue of spectrum scarcity in cognitive radio networks (CRNs). While current models consider various aspects of the OSA sche...
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ISBN:
(纸本)9781509015412
Opportunistic spectrum access (OSA) is a promising reform paradigm envisioned to address the issue of spectrum scarcity in cognitive radio networks (CRNs). While current models consider various aspects of the OSA scheme, the impact of retrial phenomenon in multi-channel CRNs has not yet been analyzed. In this work, we present a continuous-time Markov chain (CTMC) model in which the blocked/preempted secondary users (SUs) enter a finite retrial group (or orbit) and re-attempt independently for service in an exponentially distributed random manner. Taking into account the inherent retrial tendency of SUs, we numerically assess the performance of the proposed scheme in terms of dropping probability and throughput of SUs.
The random batch method is advantageous in accelerating force calculations in particle simulations, but it poses a challenge of removing the artificial heating effect in application to the Langevin dynamics. We develo...
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In this paper, study function the hyperbolic augmented Lagrangian function. This function is based on the hyperbolic penalty function. We ensure the existence of a local saddle point for the hyperbolic augmented Lagra...
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Disordered stealthy hyperuniform dielectric composites exhibit novel electromagnetic wave transport properties in two and three dimensions. Here, we carry out the first study of the electromagnetic properties of one-d...
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