213 research outputs found
Scattering of first and second sound waves by quantum vorticity in superfluid Helium
We study the scattering of first and second sound waves by quantum vorticity
in superfluid Helium using two-fluid hydrodynamics. The vorticity of the
superfluid component and the sound interact because of the nonlinear character
of these equations. Explicit expressions for the scattered pressure and
temperature are worked out in a first Born approximation, and care is exercised
in delimiting the range of validity of the assumptions needed for this
approximation to hold. An incident second sound wave will partly convert into
first sound, and an incident first sound wave will partly convert into second
sound. General considerations show that most incident first sound converts into
second sound, but not the other way around. These considerations are validated
using a vortex dipole as an explicitely worked out example.Comment: 24 pages, Latex, to appear in Journal of Low Temperature Physic
A Testpart for Interdisciplinary Analyses in Micro Production Engineering
AbstractIn 2011, a round robin test was initiated within the group of CIRP Research Affiliates. The aim was to establish a platform for linking interdisciplinary research in order to share the expertise and experiences of participants all over the world. This paper introduces a testpart which has been designed to allow an analysis of different manufacturing technologies, simulation methods, machinery and metrology as well as process and production planning aspects. Current investigations are presented focusing on the machining and additive processes to produce the geometry, simulation approaches, machine analysis, and a comparison of measuring technologies. Challenges and limitations regarding the manufacturing and evaluation of the testpart features by the applied methods are discussed.Video abstrac
Strangeness enhancement in the String Fusion Model Code
String Fusion Model Code results for Pb--Pb central collisions at SPS
energies including the string fusion interaction mechanism are compared to the
last experimental data. Predictions for RHIC energies are also presented. On
the other hand, the evolution of the strangeness enhancement ratio
with the energy and with the atomic
number of participant nuclei is discussed.Comment: LaTeX, 19 pages, 4 Postscript figure
Production of Secondaries in High Energy d+Au Collisions
In the framework of Quark-Gluon String Model we calculate the inclusive
spectra of secondaries produced in d+Au collisions at intermediate (CERN SPS)
and at much higher (RHIC) energies. The results of numerical calculations at
intermediate energies are in reasonable agreement with the data. At RHIC
energies numerically large inelastic screening corrections (percolation
effects) should be accounted for in calculations. We extract these effects from
the existing RHIC experimental data on minimum bias and central d+Au
collisions. The predictions for p+Au interactions at LHC energy are also given.Comment: 18 pages and 10 figure
Percolation approach to Quark Gluon Plasma and suppression
It is shown that the critical threshold for percolation of the overlapping
strings exchanged in heavy ion collisions can naturally explain the sharp
strong suppresion of shown by the experimental data on central Pb--Pb
collisions, which does not occur in central O--U and S--U collisions.Comment: 11 pages in LaTeX plus 1 postscript figur
On a Clique-Based Integer Programming Formulation of Vertex Colouring with Applications in Course Timetabling
Vertex colouring is a well-known problem in combinatorial optimisation, whose
alternative integer programming formulations have recently attracted
considerable attention. This paper briefly surveys seven known formulations of
vertex colouring and introduces a formulation of vertex colouring using a
suitable clique partition of the graph. This formulation is applicable in
timetabling applications, where such a clique partition of the conflict graph
is given implicitly. In contrast with some alternatives, the presented
formulation can also be easily extended to accommodate complex performance
indicators (``soft constraints'') imposed in a number of real-life course
timetabling applications. Its performance depends on the quality of the clique
partition, but encouraging empirical results for the Udine Course Timetabling
problem are reported
Production of secondaries in soft p+pb collisions at LHC
We calculate the inclusive spectra of secondaries produced in soft (minimum
bias) p+Pb collisions in the framework of Quark-Gluon String Model at LHC
energy, and by taking into account the inelastic screening corrections
(percolation effects). The role of these effects is expected to be very large
at very high energies, and they should decrease the spectra about 3 times in
the midrapidity region and increase them about 2 times in the fragmentation
region at the energy of LHC.Comment: 18 pages and 10 figures. arXiv admin note: text overlap with
arXiv:0802.219
Active Drumming Experience Increases Infants' Sensitivity to Audiovisual Synchrony during Observed Drumming Actions
In the current study, we examined the role of active experience on sensitivity to multisensory synchrony in six-month-old infants in a musical context. In the first of two experiments, we trained infants to produce a novel multimodal effect (i.e., a drum beat) and assessed the effects of this training, relative to no training, on their later perception of the synchrony between audio and visual presentation of the drumming action. In a second experiment, we then contrasted this active experience with the observation of drumming in order to test whether observation of the audiovisual effect was as effective for sensitivity to multimodal synchrony as active experience. Our results indicated that active experience provided a unique benefit above and beyond observational experience, providing insights on the embodied roots of (early) music perception and cognition
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