519 research outputs found
Strong Diffusion Effect of Charm Quarks on Production in Pb-Pb collisions at the LHC
We study the production based on coalescence model at
= 2.76 and 5.02 TeV Pb-Pb collisions. With the colliding energy
increasing from 2.76 TeV to 5.02 TeV, the number of charm pairs is enhanced by
more than 50%. However, the ratio of inclusive nuclear modification
factors is only about 1.1 1.2. We
find that the regeneration of is proportional to the densities of
charm and anti-charm quarks, instead of their total numbers. The charm quark
density is diluted by the strong expansion of quark gluon plasma, which
suppresses the combination probability of heavy quarks and
regeneration. This effect is more important in higher colliding energies where
QGP expansion is strong. We also propose the ratio as a
measurement of and coalescence probability, which is only affected
by the heavy quark diffusions in QGP, and does not depend on the inputs such as
cold nuclear matter effects and cross sections of charm quark production.
Further more, we give the predictions at the energy of Future Circular Collider
( = 39 TeV)
Color Filtering Localization for Three-Dimensional Underwater Acoustic Sensor Networks
Accurate localization for mobile nodes has been an important and fundamental
problem in underwater acoustic sensor networks (UASNs). The detection
information returned from a mobile node is meaningful only if its location is
known. In this paper, we propose two localization algorithms based on color
filtering technology called PCFL and ACFL. PCFL and ACFL aim at collaboratively
accomplishing accurate localization of underwater mobile nodes with minimum
energy expenditure. They both adopt the overlapping signal region of task
anchors which can communicate with the mobile node directly as the current
sampling area. PCFL employs the projected distances between each of the task
projections and the mobile node, while ACFL adopts the direct distance between
each of the task anchors and the mobile node. Also the proportion factor of
distance is proposed to weight the RGB values. By comparing the nearness
degrees of the RGB sequences between the samples and the mobile node, samples
can be filtered out. And the normalized nearness degrees are considered as the
weighted standards to calculate coordinates of the mobile nodes. The simulation
results show that the proposed methods have excellent localization performance
and can timely localize the mobile node. The average localization error of PCFL
can decline by about 30.4% than the AFLA method.Comment: 18 pages, 11 figures, 2 table
Charmonium transport in the high- medium
We employ the transport model coupled with hydrodynamic equations to study
the charmonium dissociation and regeneration in the quark-gluon plasma (QGP)
with the large baryon chemical potential in Au-Au collisions at the energies of
(, , ) GeV. The baryon chemical potential
is encoded in both Debye mass characterizing the heavy-quark potential
and also the equation of state (EoS) of the bulk medium respectively. After
considering -corrections in both heavy quarkonium and the QGP medium, we
calculate the nuclear modification factor of charmonium. And find the
influence on charmonium production at = 39 and 14.5 GeV
is negligible, while the of charmonium is reduced clearly considering
influence at GeV Au-Au collisions. It is crucial
for studying charmonium production in low energy and also fixed-target
heavy-ion collisions.Comment: 7 pages; 9 figure
Heavy flavor production under a strong magnetic field
The magnetic field created in high energy nuclear collisions will affect the
dynamical processes in the QCD medium, especially the heavy quark production
that happens in the initial stage of the collisions. We calculate in a strong
magnetic field the heavy quark production cross section for the elementary
process gg {\rightarrow} Q{\bar Q} at leading order and the corresponding
transverse momentum distribution in nucleus-nucleus collisions. In comparison
to the QED process, the heavy quark production is dominated by the unique QCD
channel with gluon self-interaction. Due to the dimension reduction of quark
phase space in a strong magnetic field, the production is concentrated in a
very narrow energy region above the threshold. Since the translation invariance
is broken, the production becomes anisotropic in magnetic field
Hydroelastic Response of Submerged Floating Tunnel
This research investigation addresses the analysis and numerical simulation of dynamic response of submerged floating tunnels (SFTs) under the influence of surface waves. As an innovative technical solution for waterway crossings, an SFT is usually considered as a slender structure restrained by cable system due to its large aspect ratio, i.e. ratio of length to diameter. Although an SFT is usually placed at a certain depth under the water surface, it is still susceptible to wave field due to its slenderness. In this research study, a three-dimensional finite element solving technique, using both Morison’s equation and modal analysis, is formulated to construct a hydroelastic model of an SFT and to determine its deformation considering the fluid-structure interactions. Two preliminary tunnel models for China and Japan, respectively, were studied by implementing the proposed methodology.
In the first case study, a three-dimensional finite element model of the SFT prototype in Qiandao Lake (China) was built in Matlab and subsequently analyzed using mode decomposition to determine its natural frequencies and mode shapes. For each mode shape, Morison’s equation was employed to calculate fluid forces at each cross section along the tunnel for given surface wave conditions. Then in the frequency domain, a complex equation of motion was solved iteratively to address the convergence of the stiffness of the cable system. The total dynamic response of SFT was the sum of contributions from each mode component. Results obtained from Matlab were compared with findings from previous publications and numerical simulations in ABAQUS.
Next, a generic pedestrian-aimed SFT proposed for Otaru Crossing in Japan was studied. Parametric studies were performed to evaluate the influence of configuration scheme of cable system and tunnel submerged depth on the dynamic response of SFT. Results show the importance of fundamental structural parameters in the SFT global performance and several key conclusions regarding parameter selections were drawn for engineering practices in design phase
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