6,229 research outputs found
NLO Productions of and with a Global Extraction of the Jet Transport Parameter in Heavy Ion collisions
In this work, we pave the way to calculate the productions of and
mesons at large in p+p and A+A collisions at the RHIC and
the LHC. The meson fragmentation functions (FFs) in vacuum at
next-to-leading order (NLO) are obtained by evolving NLO DGLAP evolution
equations with rescaled FFs at initial scale GeV from
a broken SU(3) model, and the FFs in vacuum are taken from AKK08
parametrization directly. Within the framework of the NLO pQCD improved parton
model, we make good descriptions of the experimental data on and
in p+p both at the RHIC and the LHC. With the higher-twist
approach to take into account the jet quenching effect by medium modified FFs,
the nuclear modification factors for meson and meson at
the RHIC and the LHC are presented with different sets of jet transport
coefficient . Then we make a global extraction of at the
RHIC and the LHC by confronting our model calculations with all available data
on 6 identified mesons: , , , , , and
. The minimum value of the total for productions of
these mesons gives the best value of for Au+Au
collisions with GeV at the RHIC, and for Pb+Pb collisions with TeV at the LHC
respectively, with the QGP spacetime evolution given by an event-by-event
viscous hydrodynamics model IEBE-VISHNU. With these global extracted values of
, the nuclear modification factors of , , ,
, , and in A+A collisions are presented, and
predictions of yield ratios such as and at
large in heavy-ion collisions at the RHIC and the LHC are provided.Comment: 9 pages, 13 figures, 1 tabl
Exploring the drive-by sensing power of bus fleet through active scheduling
Vehicle-based mobile sensing (a.k.a drive-by sensing) is an important means
of surveying urban environment by leveraging the mobility of public or private
transport vehicles. Buses, for their extensive spatial coverage and reliable
operations, have received much attention in drive-by sensing. Existing studies
have focused on the assignment of sensors to a set of lines or buses with no
operational intervention, which is typically formulated as set covering or
subset selection problems. This paper aims to boost the sensing power of bus
fleets through active scheduling, by allowing instrumented buses to circulate
across multiple lines to deliver optimal sensing outcome. We consider a fleet
consisting of instrumented and normal buses, and jointly optimize sensor
assignment, bus dispatch, and intra- or inter-line relocations, with the
objectives of maximizing sensing quality and minimizing operational costs,
while serving all timetabled trips. By making general assumptions on the
sensing utility function, we formulate the problem as a nonlinear integer
program based on a time-expanded network. A batch scheduling algorithm is
developed following linearization techniques to solve the problem efficiently,
which is tested in a real-world case study in Chengdu, China. The results show
that the proposed scheme can improve the sensing objective by 12.0%-20.5%
(single-line scheduling) and 16.3%-32.1% (multi-line scheduling), respectively,
while managing to save operational costs by 1.0%. Importantly, to achieve the
same level of sensing quality, we found that the sensor investment can be
reduced by over 33% when considering active bus scheduling. Comprehensive
comparative and sensitivity analyses are presented to generate managerial
insights and recommendations for practice.Comment: 32 pages, 13 figures, 8 table
Inverting a complex matrix
We analyze a complex matrix inversion algorithm proposed by Frobenius, which
we call the Frobenius inversion. We show that the Frobenius inversion uses the
least number of real matrix multiplications and inversions among all complex
matrix inversion algorithms. We also analyze numerical properties of the
Frobenius inversion. We prove that the Frobenius inversion runs faster than the
widely used method based on LU decomposition if and only if the ratio of the
running time of the real matrix inversion to that of the real matrix
multiplication is greater than . We corroborate this theoretical result by
numerical experiments. Moreover, we apply the Frobenius inversion to matrix
sign function, Sylvester equation, and polar decomposition. In each of these
examples, the Frobenius inversion is more efficient than inversion via
LU-decomposition
A parallel downloading algorithm for redundant networks
In this paper, we study the downloading mechanism of BitTorrent (or BT), a P2P based popular and convenient parallel downloading software tool, point out some of its limitations, and propose an algorithm to improve its performance. In particular, we address the limitations of BT by using neighbours in P2P networks to resolve the redundant copies problem and to optimise the downloading speed. Our preliminary experiments show that the proposed enhancement algorithm works well
Direct observation of magnon-phonon coupling in yttrium iron garnet
The magnetic insulator yttrium iron garnet (YIG) with a ferrimagnetic
transition temperature of 560 K has been widely used in microwave and
spintronic devices. Anomalous features in the spin Seeback effect (SSE)
voltages have been observed in Pt/YIG and attributed to the magnon-phonon
coupling. Here we use inelastic neutron scattering to map out low-energy spin
waves and acoustic phonons of YIG at 100 K as a function of increasing magnetic
field. By comparing the zero and 9.1 T data, we find that instead of splitting
and opening up gaps at the spin wave and acoustic phonon dispersion
intersecting points, magnon-phonon coupling in YIG enhances the hybridized
scattering intensity. These results are different from expectations of
conventional spin-lattice coupling, calling for new paradigms to understand the
scattering process of magnon-phonon interactions and the resulting
magnon-polarons.Comment: 5 pages, 4 figures, PRB in pres
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