15,400 research outputs found
Nonconservative higher-order hydrodynamic modulation instability
The modulation instability (MI) is a universal mechanism that is responsible
for the disintegration of weakly nonlinear narrow-banded wave fields and the
emergence of localized extreme events in dispersive media. The instability
dynamics is naturally triggered, when unstable energy side-bands located around
the main energy peak are excited and then follow an exponential growth law. As
a consequence of four wave mixing effect, these primary side-bands generate an
infinite number of additional side-bands, forming a triangular side-band
cascade. After saturation, it is expected that the system experiences a return
to initial conditions followed by a spectral recurrence dynamics. Much complex
nonlinear wave field motion is expected, when the secondary or successive
side-band pair that are created are also located in the finite instability gain
range around the main carrier frequency peak. This latter process is referred
to as higher-order MI. We report a numerical and experimental study that
confirm observation of higher-order MI dynamics in water waves. Furthermore, we
show that the presence of weak dissipation may counter-intuitively enhance wave
focusing in the second recurrent cycle of wave amplification. The
interdisciplinary weakly nonlinear approach in addressing the evolution of
unstable nonlinear waves dynamics may find significant resonance in other
nonlinear dispersive media in physics, such as optics, solids, superfluids and
plasma
Recycle-GAN: Unsupervised Video Retargeting
We introduce a data-driven approach for unsupervised video retargeting that
translates content from one domain to another while preserving the style native
to a domain, i.e., if contents of John Oliver's speech were to be transferred
to Stephen Colbert, then the generated content/speech should be in Stephen
Colbert's style. Our approach combines both spatial and temporal information
along with adversarial losses for content translation and style preservation.
In this work, we first study the advantages of using spatiotemporal constraints
over spatial constraints for effective retargeting. We then demonstrate the
proposed approach for the problems where information in both space and time
matters such as face-to-face translation, flower-to-flower, wind and cloud
synthesis, sunrise and sunset.Comment: ECCV 2018; Please refer to project webpage for videos -
http://www.cs.cmu.edu/~aayushb/Recycle-GA
Alkaline battery containing a separator of a cross-linked copolymer of vinyl alcohol and unsaturated carboxylic acid
A battery separator for an alkaline battery is described. The separator comprises a cross linked copolymer of vinyl alcohol units and unsaturated carboxylic acid units. The cross linked copolymer is insoluble in water, has excellent zincate diffusion and oxygen gas barrier properties and a low electrical resistivity. Cross linking with a polyaldehyde cross linking agent is preferred
Quantum study of information delay in electromagetically induced transparency
Using electromagnetically induced transparency (EIT), it is possible to delay
and store light in atomic ensembles. Theoretical modelling and recent
experiments have suggested that the EIT storage mechanism can be used as a
memory for quantum information. We present experiments that quantify the noise
performance of an EIT system for conjugate amplitude and phase quadratures. It
is shown that our EIT system adds excess noise to the delayed light that has
not hitherto been predicted by published theoretical modelling. In analogy with
other continuous-variable quantum information systems, the performance of our
EIT system is characterised in terms of conditional variance and signal
transfer.Comment: 4 pages, 4 figure
On the jets, kinks, and spheromaks formed by a planar magnetized coaxial gun
Measurements of the various plasma configurations produced by a planar
magnetized coaxial gun provide insight into the magnetic topology evolution
resulting from magnetic helicity injection. Important features of the
experiments are a very simple coaxial gun design so that all observed
geometrical complexity is due to the intrinsic physical dynamics rather than
the source shape and use of a fast multiple-frame digital camera which provides
direct imaging of topologically complex shapes and dynamics. Three key
experimental findings were obtained: (1) formation of an axial collimated jet
[Hsu and Bellan, Mon. Not. R. Astron. Soc. 334, 257 (2002)] that is consistent
with a magnetohydrodynamic description of astrophysical jets, (2)
identification of the kink instability when this jet satisfies the
Kruskal-Shafranov limit, and (3) the nonlinear properties of the kink
instability providing a conversion of toroidal to poloidal flux as required for
spheromak formation by a coaxial magnetized source [Hsu and Bellan, Phys. Rev.
Lett. 90, 215002 (2003)]. A new interpretation is proposed for how the n=1
central column instability provides flux amplification during spheromak
formation and sustainment, and it is shown that jet collimation can occur
within one rotation of the background poloidal field.Comment: Physics of Plasmas (accepted
Convergence towards an asymptotic shape in first-passage percolation on cone-like subgraphs of the integer lattice
In first-passage percolation on the integer lattice, the Shape Theorem
provides precise conditions for convergence of the set of sites reachable
within a given time from the origin, once rescaled, to a compact and convex
limiting shape. Here, we address convergence towards an asymptotic shape for
cone-like subgraphs of the lattice, where . In particular, we
identify the asymptotic shapes associated to these graphs as restrictions of
the asymptotic shape of the lattice. Apart from providing necessary and
sufficient conditions for - and almost sure convergence towards this
shape, we investigate also stronger notions such as complete convergence and
stability with respect to a dynamically evolving environment.Comment: 23 pages. Together with arXiv:1305.6260, this version replaces the
old. The main results have been strengthened and an earlier error in the
statement corrected. To appear in J. Theoret. Proba
Comparative Analysis of Aerosol Retrievals from MODIS, OMI and MISR Over Sahara Region
MODIS is a wide field-of-view sensor providing daily global observations of the Earth. Currently, global MODIS aerosol retrievals over land are performed with the main Dark Target algorithm complimented with the Deep Blue (DB) Algorithm over bright deserts. The Dark Target algorithm relies on surface parameterization which relates reflectance in MODIS visible bands with the 2.1 micrometer region, whereas the Deep Blue algorithm uses an ancillary angular distribution model of surface reflectance developed from the time series of clear-sky MODIS observations. Recently, a new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm has been developed for MODIS. MAIAC uses a time series and an image based processing to perform simultaneous retrievals of aerosol properties and surface bidirectional reflectance. It is a generic algorithm which works over both dark vegetative surfaces and bright deserts and performs retrievals at 1 km resolution. In this work, we will provide a comparative analysis of DB, MAIAC, MISR and OMI aerosol products over bright deserts of northern Africa
Cosmological Rescaling through Warped Space
We discuss a scenario where at least part of the homogeneity on a brane world
can be directly related to the hierarchy problem through warped space. We study
the dynamics of an anti-D3-brane moving toward the infrared cut-off of a warped
background. After a region described by the DBI action, the self-energy of the
anti-D3-brane will dominate over the background. Then the world-volume scale of
the anti-D3-brane is no longer comoving with the background geometry. After it
settles down in the infrared end, the world-volume inhomogeneity will appear,
to a Poincare observer, to be stretched by an exponentially large ratio. This
ratio is close to that of the hierarchy problem between the gravitational and
electroweak scales.Comment: 12 pages, 2 figures; v2, PRD version, comments and references adde
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