22,723 research outputs found
The sweet spot: How people trade off size and definition on mobile devices
Mobile TV can deliver up-to-date content to users on the move. But it is currently unclear how to best adapt higher resolution TV content. In this paper, we describe a laboratory study with 35 participants who watched short clips of different content and shot types on a 200ppi PDA display at a resolution of either 120x90 or 168x128. Participants selected their preferred size and rated the acceptability of the visual experience. The preferred viewing ratio depended on the resolution and had to be at least 9.8H. The minimal angular resolution people required and which limited the up-scaling factor was 14 pixels per degree. Extreme long shots were best when depicted actors were at least 0.7° high. A second study researched the ecological validity of previous lab results by comparing them to results from the field. Image size yielded more value for users in the field than was apparent from lab results. In conclusion, current prediction models based on preferred viewing distances for TV and large displays do not predict viewing preferences on mobile devices. Our results will help to further the understanding of multimedia perception and service designers to deliver both economically viable and enjoyable experiences
S-Duality for D3-Brane in NS-NS and R-R Backgrounds
We construct the low-energy effective field theory for a D3-brane in constant
R-R 2-form potential background as the S-dual theory of a D3-brane in NS-NS
B-field background. Despite the non-Abelian algebra of the noncommutative U(1)
gauge symmetry, the electromagnetic duality transformation can be carried out
to all orders, and the dual Lagrangian is given in a compact form. The gauge
algebra is found to be a mixture of a deformed area-preserving diffeomorphism
and the usual U(1) gauge symmetry.Comment: 29 pages, minor change
Electric-Magnetic Dualities in Non-Abelian and Non-Commutative Gauge Theories
Electric-magnetic dualities are equivalence between strong and weak coupling
constants. A standard example is the exchange of electric and magnetic fields
in an abelian gauge theory. We show three methods to perform electric-magnetic
dualities in the case of the non-commutative gauge theory. The first
method is to use covariant field strengths to be the electric and magnetic
fields. We find an invariant form of an equation of motion after performing the
electric-magnetic duality. The second method is to use the Seiberg-Witten map
to rewrite the non-commutative gauge theory in terms of abelian field
strength. The third method is to use the large Neveu Schwarz-Neveu Schwarz
(NS-NS) background limit (non-commutativity parameter only has one degree of
freedom) to consider the non-commutative gauge theory or D3-brane. In
this limit, we introduce or dualize a new one-form gauge potential to get a
D3-brane in a large Ramond-Ramond (R-R) background via field redefinition. We
also use perturbation to study the equivalence between two D3-brane theories.
Comparison of these methods in the non-commutative gauge theory gives
different physical implications. The comparison reflects the differences
between the non-abelian and non-commutative gauge theories in the
electric-magnetic dualities. For a complete study, we also extend our studies
to the simplest abelian and non-abelian -form gauge theories, and a
non-commutative theory with the non-abelian structure.Comment: 55 pages, minor changes, references adde
Dimensional Reduction of the Generalized DBI
We study the generalized Dirac-Born-Infeld (DBI) action, which describes a
-brane ending on a -brane with a (+1)-form background. This action has
the equivalent descriptions in commutative and non-commutative settings, which
can be shown from the generalized metric and Nambu-Sigma model. We mainly
discuss the dimensional reduction of the generalized DBI at the massless level
on the flat spacetime and constant antisymmetric background in the case of flat
spacetime, constant antisymmetric background and the gauge potential vanishes
for all time-like components. In the case of , we can do the dimensional
reduction to get the DBI theory. We also try to extend this theory by including
a one-form gauge potential.Comment: 29 pages, minor change
Young star clusters in circumnuclear starburst rings
We analyse the cluster luminosity functions (CLFs) of the youngest star
clusters in three galaxies exhibiting prominent circumnuclear starburst rings.
We focus specifically on NGC 1512 and NGC 6951, for which we have access to
H data that allow us to unambiguously identify the youngest sample
clusters. To place our results on a firm statistical footing, we first explore
in detail a number of important technical issues affecting the process from
converting the observational data into the spectral-energy distributions of the
objects in our final catalogues. The CLFs of the young clusters in both
galaxies exhibit approximate power-law behaviour down to the 90 per cent
observational completeness limits, thus showing that star cluster formation in
the violent environments of starburst rings appears to proceed similarly as
that elsewhere in the local Universe. We discuss this result in the context of
the density of the interstellar medium in our starburst-ring galaxies.Comment: 14 pages, incl. 12 figures. Accepted for publication in MNRA
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