189 research outputs found
Fast and Accurate Video PQoS Estimation over Wireless Networks
This paper proposes a curve fitting technique for fast and accurate estimation of the perceived quality of streaming media contents, delivered within a wireless network. The model accounts for the effects of various network parameters such as congestion, radio link power, and video transmission bit rate. The evaluation of the perceived quality of service (PQoS) is based on the well-known VQM objective metric, a powerful technique which is highly correlated to the more expensive and time consuming subjective metrics. Currently, PQoS is used only for offline analysis after delivery of the entire video content. Thanks to the proposed simple model, we can estimate in real time the video PQoS and we can rapidly adapt the content transmission through scalable video coding and bit rates in order to offer the best perceived quality to the end users. The designed model has been validated through many different measurements in realistic wireless environments using an ad hoc WiFi test bed
Neutron Transverse-Momentum Distributions and Polarized 3He within Light-Front Hamiltonian Dynamics
The possibility to extract the quark transverse-momentum distributions in the
neutron from semi-inclusive deep inelastic electron scattering off polarized
3He is illustrated through an impulse approximation analysis in the Bjorken
limit. The generalization of the analysis at finite momentum transfers in a
Poincare' covariant framework is outlined. The definition of the light-front
spin-dependent spectral function of a J=1/2 system allows us to show that
within the light-front dynamics only three of the six leading twist T-even
transverse-momentum distributions are independent.Comment: 4 pages, 2 figures, Presented at the 20th International IUPAP
Conference on Few-Body Problems in Physics, 20 - 25 August, 2012, Fukuoka,
Japa
Towards an improved description of SiDIS by a polarized 3He target
The possibility of improving the description of the semi-inclusive deep
inelastic electron scattering off polarized 3He, that provides information on
the neutron single spin asymmetries, is illustrated. In particular, the
analysis at finite momentum transfers in a Poincare' covariant framework is
outlined and a generalized eikonal approach to include final state interaction
is presented.Comment: 4 pages, 2 figures, presented at The 22nd European Conference on Few
Body Problems in Physics, Krakow, Poland, 9 - 13 September 201
A covariant investigation of Neutral Vector Mesons: dynamical properties and electromagnetic decay widths
A simple, but fully-covariant model for describing neutral Vector Mesons, in
both light and heavy sectors, is briefly illustrated. The main ingredients of
our relativistic constituent model are i) an Ansatz for the Bethe-Salpeter
vertex for Vector Mesons, and ii) a Mandelstam-like formula for the
electromagnetic decay widths. The free parameters of our approach are fixed
through a comparison with the valence transverse-momentum distribution,
, obtained within phenomenological Light-Front Hamiltonian Dynamics
models reproducing the mass spectra. Preliminary results for the
transverse-momentum distributions, the parton distribution and the
electromagnetic decay constants are shown.Comment: 6 pages, 4 figures. Proceedings of LC2009, to appear in Nucl. Phys. B
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