14,380 research outputs found
Statistics of Bubble Rearrangements in a Slowly Sheared Two-dimensional Foam
Many physical systems exhibit plastic flow when subjected to slow steady
shear. A unified picture of plastic flow is still lacking; however, there is an
emerging theoretical understanding of such flows based on irreversible motions
of the constituent ``particles'' of the material. Depending on the specific
system, various irreversible events have been studied, such as T1 events in
foam and shear transformation zones (STZ's) in amorphous solids. This paper
presents an experimental study of the T1 events in a model, two-dimensional
foam: bubble rafts. In particular, I report on the connection between the
distribution of T1 events and the behavior of the average stress and average
velocity profiles during both the initial elastic response of the bubble raft
and the subsequent plastic flow at sufficiently high strains
Analysis of Computer Science Communities Based on DBLP
It is popular nowadays to bring techniques from bibliometrics and
scientometrics into the world of digital libraries to analyze the collaboration
patterns and explore mechanisms which underlie community development. In this
paper we use the DBLP data to investigate the author's scientific career and
provide an in-depth exploration of some of the computer science communities. We
compare them in terms of productivity, population stability and collaboration
trends.Besides we use these features to compare the sets of topranked
conferences with their lower ranked counterparts.Comment: 9 pages, 7 figures, 6 table
Impact of boundaries on velocity profiles in bubble rafts
Under conditions of sufficiently slow flow, foams, colloids, granular matter,
and various pastes have been observed to exhibit shear localization, i.e.
regions of flow coexisting with regions of solid-like behavior. The details of
such shear localization can vary depending on the system being studied. A
number of the systems of interest are confined so as to be quasi-two
dimensional, and an important issue in these systems is the role of the
confining boundaries. For foams, three basic systems have been studied with
very different boundary conditions: Hele-Shaw cells (bubbles confined between
two solid plates); bubble rafts (a single layer of bubbles freely floating on a
surface of water); and confined bubble rafts (bubbles confined between the
surface of water below and a glass plate on top). Often, it is assumed that the
impact of the boundaries is not significant in the ``quasi-static limit'', i.e.
when externally imposed rates of strain are sufficiently smaller than internal
kinematic relaxation times. In this paper, we directly test this assumption for
rates of strain ranging from to . This
corresponds to the quoted quasi-static limit in a number of previous
experiments. It is found that the top plate dramatically alters both the
velocity profile and the distribution of nonlinear rearrangements, even at
these slow rates of strain.Comment: New figures added, revised version accepted for publication in Phys.
Rev.
Mechanism of margination in confined flows of blood and other multicomponent suspensions
Flowing blood displays a phenomenon called margination, in which leukocytes
and platelets are preferentially found near blood vessel walls, while
erythrocytes are depleted from these regions. Here margination is investigated
using direct hydrodynamic simulations of a binary suspension of stiff (s) and
floppy (f) capsules, as well as a stochastic model that incorporates the key
particle transport mechanisms in suspensions -- wall-induced hydrodynamic
migration and shear-induced pair collisions. The stochastic model allows the
relative importance of these two mechanisms to be directly evaluated and
thereby indicates that margination, at least in the dilute case, is largely due
to the differential dynamics of homogeneous (e.g. s-s) and heterogeneous (s-f)
collisionsComment: 5 Pages, 4 figure
Deep shower interpretation of the cosmic ray events observed in excess of the Greisen-Zatsepin-Kuzmin energy
We consider the possibility that the ultra-high-energy cosmic ray flux has a
small component of exotic particles which create showers much deeper in the
atmosphere than ordinary hadronic primaries. It is shown that applying the
conventional AGASA/HiRes/Auger data analysis procedures to such exotic events
results in large systematic biases in the energy spectrum measurement. SubGZK
exotic showers may be mis-reconstructed with much higher energies and mimick
superGZK events. Alternatively, superGZK exotic showers may elude detection by
conventional fluorescence analysis techniques.Comment: 22 pages, 5 figure
Criminal justice interventions with perpetrators or victims of domestic violence: a theory-informed systematic review. Protocol
Subcluster Merger and Galaxy Infall in A2151
We have obtained a 12.5 ksec image of the Hercules Cluster, A2151, with the
{\it ROSAT} PSPC. Comparison of the optical and X-ray data suggest the presence
of at least three distinct subclusters in A2151. The brightest X-ray emission
coincides with the highest-density peak in the galaxy distribution, and is
bimodal. The northern subclump, distinct in position and velocity, has {\it no}
detectable X-ray gas. The eastern subclump, apparent in the optical contour
map, is indistinguishable from the main clump in velocity space but is clearly
visible in the X-ray image. X-ray spectra derived from the central peak of
emission yield a best-fit temperature of 1.6 keV. The emission coincident with
the eastern clump of galaxies is cooler, 0.8 keV, and is outside the 90\%
confidence intervals of the central peak temperature. We suggest that the
eastern and central subclusters have recently undergone a merger event. The
lack of X-ray emission to the north suggests that those galaxies do not form a
physically-distinct structure (i.e. they are not located within a distinct
gravitational potential), but rather that they are falling into the cluster
core along the filament defined by the Hercules Supercluster.Comment: To appear in the March 1995 issue of AJ, LaTeX, PostScript text and
figures available by anonymous ftp from kula.phsx.ukans.ed
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