96 research outputs found
Experimental determination of the boiling heat transfer coefficients of R-134a and R-417a on a smooth copper tube
Paper presented at the 9th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Malta, 16-18 July, 2012.Flooded evaporators are widely used as compact cooling
units so as to cool liquids. They consist of a shell-and-tube heat
exchanger, with the fluid to cool flowing inside the tube bundle
and a refrigerant that evaporates over those tubes. Pool boiling
on the external surface of the tubes is a very complex process
and, therefore, an experimental analysis is required in order to
determine the boiling heat transfer coefficients (HTCs). Copper
and copper alloys tubes are commonly employed in such heat
exchangers, due to their high thermal conductivity and low cost
when compared to other materials. On the other hand,
refrigeration and air conditioning sectors are undergoing
significant changes caused mainly by the necessity of replacing
existing refrigerants with more environmentally-friendly ones.
This paper reports the work carried out to determine pool
boiling HTCs of two HFCs refrigerants, R-134a and R-417A
blend on a smooth copper tube with and outer diameter of
18.87 mm, at two saturation temperatures of 10 ÂșC and 7 ÂșC.
This work has been done experimentally by means of a test rig
specifically designed and prepared for the study of these
processes. The experimental setup and data acquisition are
described, the experimental procedure is explained, the data
reduction methodology is detailed and the results are presented
and discussed.dc201
A meta-analysis of host specificity in Neotropical hard ticks (Acari: Ixodidae)
Host specificity of Neotropical hard ticks (Acari: Ixodidae) was analyzed by using the number of hosts species for each tick species and the index of host specificity STD*, which integrates phylogenetic and ecological information. The analyses were based on 4172 records of hard ticks collected from wild and domestic tetrapods. Most tick species included in this study were associated with three to 20 host species. No tick species has been associated either with a single species or with a single genus of host. It was found that the number of host species is sensitive to sampling effort, but not the STD*. The most frequent values of STD* were between 2.5 and 3.5, which shows that the host species more frequently used by Neotropical hard tick species belong to different families or different orders. Immature stages tend to use a broader taxonomic range of hosts than adults, and the interpretation of both measures of host specificity used in this study led to the conclusion that the impact of non-endemic hosts does not alter the patterns of host specificity in Neotropical hard ticks. The index STD* showed that a high proportion of tick species has phylogenetically unrelated species as principal hosts. The conclusion reached in this work indicates that strict host specificity is not common among Neotropical hard ticks and suggests that the influence of tick ecology and evolution of habitat specificity, tick generation time, phenology, time spent off the host and the type of life-cycle could be more important than hosts species.Fil: Nava, Santiago. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Santa Fe. Estacion Experimental Agropecuaria Rafaela; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Santa Fe; ArgentinaFil: Guglielmone, Alberto Alejandro. Instituto Nacional de Tecnologia Agropecuaria. Centro Regional Santa Fe. Estacion Experimental Agropecuaria Rafaela; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Santa Fe; Argentin
Evidence for the strangeness-changing weak decay
Using a collision data sample corresponding to an integrated luminosity
of 3.0~fb, collected by the LHCb detector, we present the first search
for the strangeness-changing weak decay . No
hadron decay of this type has been seen before. A signal for this decay,
corresponding to a significance of 3.2 standard deviations, is reported. The
relative rate is measured to be
, where and
are the and fragmentation
fractions, and is the branching
fraction. Assuming is bounded between 0.1 and
0.3, the branching fraction would lie
in the range from to .Comment: 7 pages, 2 figures, All figures and tables, along with any
supplementary material and additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-047.htm
Measurements of long-range near-side angular correlations in TeV proton-lead collisions in the forward region
Two-particle angular correlations are studied in proton-lead collisions at a
nucleon-nucleon centre-of-mass energy of TeV, collected
with the LHCb detector at the LHC. The analysis is based on data recorded in
two beam configurations, in which either the direction of the proton or that of
the lead ion is analysed. The correlations are measured in the laboratory
system as a function of relative pseudorapidity, , and relative
azimuthal angle, , for events in different classes of event
activity and for different bins of particle transverse momentum. In
high-activity events a long-range correlation on the near side, , is observed in the pseudorapidity range . This
measurement of long-range correlations on the near side in proton-lead
collisions extends previous observations into the forward region up to
. The correlation increases with growing event activity and is found
to be more pronounced in the direction of the lead beam. However, the
correlation in the direction of the lead and proton beams are found to be
compatible when comparing events with similar absolute activity in the
direction analysed.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-040.htm
flavour tagging using charm decays at the LHCb experiment
An algorithm is described for tagging the flavour content at production of
neutral mesons in the LHCb experiment. The algorithm exploits the
correlation of the flavour of a meson with the charge of a reconstructed
secondary charm hadron from the decay of the other hadron produced in the
proton-proton collision. Charm hadron candidates are identified in a number of
fully or partially reconstructed Cabibbo-favoured decay modes. The algorithm is
calibrated on the self-tagged decay modes and using of data collected by the LHCb
experiment at centre-of-mass energies of and
. Its tagging power on these samples of
decays is .Comment: All figures and tables, along with any supplementary material and
additional information, are available at
http://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-027.htm
Identification of beauty and charm quark jets at LHCb
Identification of jets originating from beauty and charm quarks is important
for measuring Standard Model processes and for searching for new physics. The
performance of algorithms developed to select - and -quark jets is
measured using data recorded by LHCb from proton-proton collisions at
TeV in 2011 and at TeV in 2012. The efficiency for
identifying a jet is about 65%(25%) with a probability for
misidentifying a light-parton jet of 0.3% for jets with transverse momentum
GeV and pseudorapidity . The dependence of
the performance on the and of the jet is also measured
Search for Bâșc decays to the ppâŸÏâș final state
A search for the decays of the B + c meson to pp-Ï + is performed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb -1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV. No signal is found and an upper limit, at 95% confidence level, is set, fcfuĂB(B + c âppÏ + ) < 3.6Ă10-8 in the kinematic region m(pp) < 2.85 GeV/c2, p T (B) < 20 GeV/c and 2.0 < y(B) < 4.5, where B is the branching fraction and f c (f u ) is the fragmentation fraction of the b quark into a B c + (B + ) meson
Measurement of CP observables in B± â D(â)K± and B± â D(â)ϱ decays
Measurements of CP observables in B ± âD (â) K ± and B ± âD (â) Ï Â± decays are presented, where D (â) indicates a neutral D or D â meson that is an admixture of D (â)0 and DÂŻ (â)0 states. Decays of the D â meson to the DÏ 0 and DÎł final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the B candidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K ± Ï â , K + K â and Ï + Ï â final states. The analysis uses a sample of charged B mesons produced in pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb â1 taken at centre-of-mass energies of s=7, 8 and 13 TeV, respectively. The study of B ± âD â K ± and B ± âD â Ï Â± decays using a partial reconstruction method is the first of its kind, while the measurement of B ± âDK ± and B ± âDÏ Â± decays is an update of previous LHCb measurements. The B ± âDK ± results are the most precise to date
Observation of the decay B0s â Ï(2S)K +Ïâ
The decay B0
s â Ï(2S)K +Ïâ is observed using a data set corresponding to an integrated luminosity of
3.0 fbâ1 collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV.
The branching fraction relative to the B0 â Ï(2S)K +Ïâ decay mode is measured to be
B(B0
s â Ï(2S)K +Ïâ)
B(B0 â Ï(2S)K +Ïâ) = 5.38 ± 0.36 (stat) ± 0.22 (syst) ± 0.31 (f s/ fd)%,
where f s/ fd indicates the uncertainty due to the ratio of probabilities for a b quark to hadronise into
a B0
s or B0 meson. Using an amplitude analysis, the fraction of decays proceeding via an intermediate
Kâ(892)0 meson is measured to be 0.645 ± 0.049 (stat) ± 0.049 (syst) and its longitudinal polarisation
fraction is 0.524 ± 0.056 (stat) ± 0.029 (syst). The relative branching fraction for this component is
determined to be
B(B0
s â Ï(2S)Kâ(892)0)
B(B0 â Ï(2S)Kâ(892)0) = 5.58 ± 0.57 (stat) ± 0.40 (syst) ± 0.32 (f s/ fd)%.
In addition, the mass splitting between the B0
s and B0 mesons is measured as
M(B0
s ) â M(B0) = 87.45 ± 0.44 (stat) ± 0.09 (syst) MeV/c2
Observation of the B0 â Ï0Ï0 decay from an amplitude analysis of B0 â (Ï+Ïâ)(Ï+Ïâ) decays
Protonâproton collision data recorded in 2011 and 2012 by the LHCb experiment, corresponding to
an integrated luminosity of 3.0 fbâ1, are analysed to search for the charmless B0 â Ï0Ï0 decay.
More than 600 B0 â (Ï+Ïâ)(Ï+Ïâ) signal decays are selected and used to perform an amplitude
analysis, under the assumption of no CP violation in the decay, from which the B0 â Ï0Ï0 decay is
observed for the first time with 7.1 standard deviations significance. The fraction of B0 â Ï0Ï0 decays
yielding a longitudinally polarised final state is measured to be fL = 0.745+0.048
â0.058(stat) ± 0.034(syst).
The B0 â Ï0Ï0 branching fraction, using the B0 â ÏKâ(892)0 decay as reference, is also reported as
B(B0 â Ï0Ï0) = (0.94 ± 0.17(stat) ± 0.09(syst) ± 0.06(BF)) Ă 10â6
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