15,995 research outputs found
Numerical study of the small scale structures in Boussinesq convection
Two-dimensional Boussinesq convection is studied numerically using two different methods: a filtered pseudospectral method and a high order accurate Essentially Nonoscillatory (ENO) scheme. The issue whether finite time singularity occurs for initially smooth flows is investigated. The numerical results suggest that the collapse of the bubble cap is unlikely to occur in resolved calculations. The strain rate corresponding to the intensification of the density gradient across the front saturates at the bubble cap. We also found that the cascade of energy to small scales is dominated by the formulation of thin and sharp fronts across which density jumps
A numerical resolution study of high order essentially non-oscillatory schemes applied to incompressible flow
High order essentially non-oscillatory (ENO) schemes, originally designed for compressible flow and in general for hyperbolic conservation laws, are applied to incompressible Euler and Navier-Stokes equations with periodic boundary conditions. The projection to divergence-free velocity fields is achieved by fourth order central differences through Fast Fourier Transforms (FFT) and a mild high-order filtering. The objective of this work is to assess the resolution of ENO schemes for large scale features of the flow when a coarse grid is used and small scale features of the flow, such as shears and roll-ups, are not fully resolved. It is found that high-order ENO schemes remain stable under such situations and quantities related to large-scale features, such as the total circulation around the roll-up region, are adequately resolved
Effective equations and the inverse cascade theory for Kolmogorov flows
We study the two dimensional Kolmogorov flows in the limit as the forcing frequency goes to infinity. Direct numerical simulation indicates that the low frequency energy spectrum evolves to a universal kappa (exp -4) decay law. We derive effective equations governing the behavior of the large scale flow quantities. We then present numerical evidence that with smooth initial data, the solution to the effective equation develops a kappa (exp -4) type singularity at a finite time. This gives a convenient explanation for the kappa (exp -4) decay law exhibited by the original Kolmogorov flows
DCU linking runs at MediaEval 2012: search and hyperlinking task
We describe Dublin City University (DCU)'s participation in the Hyperlinking sub-task of the MediaEval 2012 Search and Hyperlinking Task. Our strategy involves combining textual metadata, automatic speech recognition (ASR) transcripts, and visual content analysis to create anchor summaries for each video segment available for linking. Two categories of fusion strategy, score-based and rank-based methods, were used to combine scores from different modalities to produce potential inter-item links
Toward the AdS/CFT gravity dual for High Energy Collisions: I.Falling into the AdS
In the context of the AdS/CFT correspondence we discuss the gravity dual of a
high energy collision in a strongly coupled SYM gauge theory. We
suggest a setting in which two colliding objects are made of non-dynamical
heavy quarks and antiquarks, which allows to treat the process in classical
string approximation. Collision ``debris'' consist of closed as well as open
strings. If the latter have ends on two outgoing charges, and thus are being
``stretched'' along the collision axes. We discuss motion in AdS of some simple
objects first -- massless and massive particles -- and then focus on open
strings. We study the latter in a considerable detail, concluding that they
rapidly become ``rectangular'' in proper time -spatial rapidity
coordinates with well separated fragmentation part and a near-free-falling
rapidity-independent central part. Assuming that in the collisions of ``walls''
of charges multiple stretching strings are created, we also consider the motion
of a 3d stretching membrane. We then argue that a complete solution can be
approximated by two different vacuum solutions of Einstein eqns, with matter
membrane separating them. We identify one of this solution with
Janik-Peschanski stretching black hole solution, and show that all objects
approach its (retreating) horizon in an universal manner.Comment: v2 was redone, with new material and different introduction. It now
includes introduction to the second paper of the series as well, in which we
calculate "holograms" of falling objects, namely their stress tensor on the
boundar
Non-standard interactions of solar neutrinos in dark matter experiments
Non-standard neutrino interactions (NSI) affect both their propagation
through matter and their detection, with bounds on NSI parameters coming from
various astrophysical and terrestrial neutrino experiments. In this paper, we
show that NSI can be probed in future direct dark matter detection experiments
through both elastic neutrino-electron scattering and coherent neutrino-nucleus
scattering, and that these channels provide complementary probes of NSI. We
show NSI can increase the event rate due to solar neutrinos, with a sharp
increase for lower nuclear recoil energy thresholds that are within reach for
upcoming detectors. We also identify an interference range of NSI parameters
for which the rate is reduced by approximately 40\%. Finally, we show that the
"dark side" solution for the solar neutrino mixing angle may be discovered at
forthcoming direct detection experiments.Comment: 12 pages, 5 figure
Digital learning objects: a local response to the California State University system initiative
The purpose of this paper is to present a virtual library plan created by library directors of the 23 California State University (CSU) system campuses. The information literacy portion of the project offers a repository of high quality interactive digital learning objects (DLOs) in the MERLOT repository. Therefore, DLOs created locally at the Dr Martin Luther King, Jr Library at San José State University (SJSU) focus on topics that supplement the “core” DLO collection
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