4,841 research outputs found
A universal scaling law for the evolution of granular gases
Dry, freely evolving granular materials in a dilute gaseous state coalesce
into dense clusters only due to dissipative interactions. This clustering
transition is important for a number of problems ranging from geophysics to
cosmology. Here we show that the evolution of a dilute, freely cooling granular
gas is determined in a universal way by the ratio of inertial flow and thermal
velocities, that is, the Mach number. Theoretical calculations and direct
numerical simulations of the granular Navier--Stokes equations show that
irrespective of the coefficient of restitution, density or initial velocity
distribution, the density fluctuations follow a universal quadratic dependence
on the system's Mach number. We find that the clustering exhibits a scale-free
dynamics but the clustered state becomes observable when the Mach number is
approximately of . Our results provide a method to determine
the age of a granular gas and predict the macroscopic appearance of clusters
The Influence of Archaeological Evidence on the Reconstruction of Religion in Monarchical Israel
Early covenant traditions shaped much of Israel’s theological expression even after the wilderness wandering and settlement. The author examines kingship, cult, and prophecy in monarchical Israel and cites archaeological evidence to support his contentions
Critical Methodology and the Lutheran Symbols\u27 Treatment of the Genesis Creation Accounts
We must begin by specifying what lexicon we are using. What “critical methodology” in the first place? Critical is, no doubt, the usual shorthand for what is commonly labelled the historical-critical method
High Latitude Radio Emission in a Sample of Edge-On Spiral Galaxies
We have mapped 16 edge-on galaxies at 20 cm using the VLA. For 5 galaxies, we
could form spectral index, energy and magnetic field maps. We find that all but
one galaxy show evidence for non-thermal high latitude radio continuum
emission, suggesting that cosmic ray halos are common in star forming galaxies.
The high latitude emission is seen over a variety of spatial scales and in
discrete and/or smooth features. In general, the discrete features emanate from
the disk, but estimates of CR diffusion lengths suggest that diffusion alone is
insufficient to transport the particles to the high latitudes seen (> 15 kpc in
one case). Thus CRs likely diffuse through low density regions and/or are
assisted by other mechanisms (e.g. winds). We searched for correlations between
the prevalence of high latitude radio emission and a number of other
properties, including the global SFR, supernova input rate per unit star
forming, and do not find clear correlations with any of these properties.Comment: 40 pages of text, 3 figures, 6 tables, and an appendix of 21 jpeg
figures (which is a radio continuum catalogue of 17 galaxies). to appear in
A. J. (around January 1999
Experimental investigation of the flow on the suction side of a thin Delta wing
Surface oil flow patterns were photographed and pressure distribution measurements were carried out on a sharp edged delta wing of aspect ratio lambda = 1.0 in order to determine the influence of Reynolds number and of vortex breakdown on the flow on the suction side of the wing. The formation of the secondary vortex occurs due to separation of a laminar boundary layer in the front part of the wing and due to separation of a turbulent boundary layer in the rear part of the wing. In the case of turbulent separation, the secondary separation line is closer to the wing leading edge than in the laminar case. The position of the transition depends on the Reynolds number and on the angle of incidence. The breakdown of a vortex above the wing leads to a kink in the secondary separation line
Detached-Eddy Simulation of the Vortical Flowfield about the VFE-2 DeltaWing
The numerical simulation of the flow around a 65° delta wing configuration with rounded leading edges is presented. For the numerical simulation the Cobalt Code uses a cell-centered unstructured hybrid mesh approach. Several numerical results are presented for the steady RANS equations as well as for DES and DDES hybrid approaches. The simulations are done as part of the NATO RTO/AVT 113 working group focusing on experimental and numerical research on delta wing configurations with rounded leading edges. Within this paper the focus is related to the dual primary vortex flow topology, especially the sensitivity of the flow to angle of attack and Reynolds number effects. Reasonable results are obtained with both steady RANS and SA-DDES simulations. The results are compared and verified by experimental data, including surface pressure and pressure sensitive paint results. The impact of transition is assessed, and recommendations for improving future simulations are made
V-like formations in flocks of artificial birds
We consider flocks of artificial birds and study the emergence of V-like
formations during flight. We introduce a small set of fully distributed
positioning rules to guide the birds' movements and demonstrate, by means of
simulations, that they tend to lead to stabilization into several of the
well-known V-like formations that have been observed in nature. We also provide
quantitative indicators that we believe are closely related to achieving V-like
formations, and study their behavior over a large set of independent
simulations
Induced Gamma-band Activity Elicited by Visual Representation of Unattended Objects
Peer reviewedPostprin
The Radio Properties of Composite LINER/HII Galaxies
Arcsec-resolution VLA observations -- newly obtained as well as published --
of 40 nearby galaxies are discussed, completing a study of the radio properties
of a magnitude-limited sample of nearby galaxies of the composite LINER/HII
type. Our results reveal an overall detection rate of at least 25% AGN
candidates among these composite sources. The general properties of these AGN
candidates, as compared to non-AGN composite sources and HII galaxies, are
discussed.Comment: Accepted for publication in ApJ
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