28,054 research outputs found
Design, implementation and evaluation of a QoS-aware transport protocol
In the context of a reconfigurable transport protocol framework, we propose a QoS-aware Transport Protocol (QSTP), specifically designed to operate over QoS-enabled networks with bandwidth guarantee. QSTP combines QoS-aware TFRC congestion control mechanism, which takes into account the network-level bandwidth reservations, with a Selective ACKnowledgment (SACK) mechanism in order to provide a QoS-aware transport service that fill the gap between QoS enabled network services and QoS constraint applications. We have developed a prototype of this protocol in the user-space and conducted a large range of measurements to evaluate this proposal under various network conditions. Our results show that QSTP allows applications to reach their negotiated QoS over bandwidth guaranteed networks, such as DiffServ/AF network, where TCP fails. This protocol appears to be the first reliable protocol especially designed for QoS network architectures with bandwidth guarantee
Flavor SU(4) breaking between effective couplings
Using a framework in which all elements are constrained by Dyson-Schwinger
equation studies in QCD, and therefore incorporates a consistent, direct and
simultaneous description of light- and heavy-quarks and the states they
constitute, we analyze the accuracy of SU(4)-flavor symmetry relations between
{\pi}{\rho}{\pi}, K{\rho}K and D{\rho}D couplings. Such relations are widely
used in phenomenological analyses of the interactions between matter and
charmed mesons. We find that whilst SU(3)-flavor symmetry is accurate to 20%,
SU(4) relations underestimate the D{\rho}D coupling by a factor of five.Comment: 5 pages, two figure
Geometrical Properties of Coupled Oscillators at Synchronization
We study the synchronization of nearest neighbors coupled oscillators in
a ring. We derive an analytic form for the phase difference among neighboring
oscillators which shows the dependency on the periodic boundary conditions. At
synchronization, we find two distinct quantities which characterize four of the
oscillators, two pairs of nearest neighbors, which are at the border of the
clusters before total synchronization occurs. These oscillators are responsible
for the saddle node bifurcation, of which only two of them have a phase-lock of
phase difference equals /2. Using these properties we build a
technique based on geometric properties and numerical observations to arrive to
an exact analytic expression for the coupling strength at full synchronization
and determine the two oscillators that have a phase-lock condition of
/2.Comment: accepted for publication in "Communications in Nonlinear Science and
Numerical Simulations
BCVEGPY: An Event Generator for Hadronic Production of the B_c Meson
We have written a Fortran programme BCVEGPY, which is an event generator for
the hadronic production of the meson through the dominant hard subprocess
. To achieve a compact programme, we have written
the amplitude of the subprocess with the particle helicity technique and made
it as symmetric as possible, by decomposing the gluon self couplings and then
applying the symmetries. To check the programme, various cross sections of the
subprocess have been computed numerically and compared with those in the
literature. BCVEGPY is written in a PYTHIA-compatible format, thus it is easy
to implement in PYTHIA.Comment: 47 pages, 12 figure
Refraction of dispersive shock waves
We study a dispersive counterpart of the classical gas dynamics problem of
the interaction of a shock wave with a counter-propagating simple rarefaction
wave often referred to as the shock wave refraction. The refraction of a
one-dimensional dispersive shock wave (DSW) due to its head-on collision with
the centred rarefaction wave (RW) is considered in the framework of defocusing
nonlinear Schr\"odinger (NLS) equation. For the integrable cubic nonlinearity
case we present a full asymptotic description of the DSW refraction by
constructing appropriate exact solutions of the Whitham modulation equations in
Riemann invariants. For the NLS equation with saturable nonlinearity, whose
modulation system does not possess Riemann invariants, we take advantage of the
recently developed method for the DSW description in non-integrable dispersive
systems to obtain main physical parameters of the DSW refraction. The key
features of the DSW-RW interaction predicted by our modulation theory analysis
are confirmed by direct numerical solutions of the full dispersive problem.Comment: 45 pages, 23 figures, minor revisio
Implications of Minimal Length Scale on the Statistical Mechanics of Ideal Gas
Several alternative approaches to quantum gravity problem suggest the
modification of the {\it fundamental volume } of the accessible
phase space for representative points. This modified fundamental volume has a
novel momentum dependence. In this paper, we study the effects of this
modification on the thermodynamics of an ideal gas within the microcanonical
ensemble and using the generalized uncertainty principle(GUP). Although the
induced modifications are important only in quantum gravity era, possible
experimental manifestation of these effects may provides strong support for
underlying quantum gravity proposal.Comment: 14 Pages, No Figures, Title Changed, Revised Versio
The meson annihilation to leptons and inclusive light hadrons
The annihilation of the meson to leptons and inclusive light hadrons is
analyzed in the framework of nonrelativistic QCD (NRQCD) factorization. We find
that the decay mode, which escapes from the helicity suppression, contributes a
sizable fraction width. According to the analysis, the branching ratio due to
the contribution from the color-singlet component of the meson can be of
order (10^{-2}). We also estimate the contributions from the color-octet
components. With the velocity scaling rule of NRQCD, we find that the
color-octet contributions are sizable too, especially, in certain phase space
of the annihilation they are greater than (or comparative to) the color-singlet
component. A few observables relevant to the spectrum of charged lepton are
suggested, that may be used as measurements on the color-octet and
color-singlet components in the future experiments. A typical long
distance contribution in the annihilation is estimated too.Comment: 26 pages, 5 figures (6 eps-files), submitted to Phys. Rev.
Decays of the Meson to a -Wave Charmonium State or
The semileptonic decays,
, and the two-body
nonleptonic decays, , (here and
denote and respectively, and
indicates a meson) were computed. All of the form factors appearing in the
relevant weak-current matrix elements with as its initial state and a
-wave charmonium state as its final state for the decays were precisely
formulated in terms of two independent overlapping-integrations of the
wave-functions of and the -wave charmonium and with proper kinematics
factors being `accompanied'. We found that the decays are quite sizable, so
they may be accessible in Run-II at Tevatron and in the foreseen future at LHC,
particularly, when BTeV and LHCB, the special detectors for B-physics, are
borne in mind. In addition, we also pointed out that the decays may potentially be used as a fresh window to look for the
charmonium state, and the cascade decays,
() with one of the radiative decays
being followed accordingly, may affect
the observations of meson through the decays () substantially.Comment: 24 pages, 3 figures, the replacement for improving the presentation
and adding reference
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