780 research outputs found
Improved turbine disk design to increase reliability of aircraft jet engines
An analytical study was conducted on a bore entry cooled turbine disk for the first stage of the JT8D-17 high pressure turbine which had the potential to improve disk life over existing design. The disk analysis included the consideration of transient and steady state temperature, blade loading, creep, low cycle fatigue, fracture mechanics and manufacturing flaws. The improvement in life of the bore entry cooled turbine disk was determined by comparing it with the existing disk made of both conventional and advanced (Astroloy) disk materials. The improvement in crack initiation life of the Astroloy bore entry cooled disk is 87% and 67% over the existing disk made of Waspaloy and Astroloy, respectively. Improvement in crack propagation life is 124% over the Waspaloy and 465% over the Astroloy disks. The available kinetic energies of disk fragments calculated for the three disks indicate a lower fragment energy level for the bore entry cooled turbine disk
Nonlinear Realization and Weyl Scale Invariant p=2 Brane
The action of Weyl scale invariant p=2 brane which breaks the target super
Weyl scale symmetry in the N=1, D=4 superspace down to the lower dimensional
Weyl symmetry W(1,2) is derived by the approach of nonlinear realization. The
dual form action for the Weyl scale invariant supersymmetric D2 brane is also
constructed. The interactions of localized matter fields on the brane with the
Nambu-Goldstone fields associated with the breaking of the symmetries in the
superspace and one spatial translation directions are obtained through the
Cartan one-forms of the Coset structures. The covariant derivatives for the
localized matter fields are also obtained by introducing Weyl gauge field as
the compensating field corresponding to the local scale transformation on the
brane world volume.Comment: 20 page
Fluctuating initial conditions in heavy-ion collisions from the Glauber approach
In the framework of the Glauber approach we analyze the shape parameters of
the early-formed system and their event-by-event fluctuations. We test a
variety of models: the conventional wounded nucleon model, a model admixing
binary collisions to the wounded nucleons, a model with hot spots, as well as
the hot-spot model where the deposition of energy occurs with a superimposed
probability distribution. We look in detail at the so-called participant
multipole moments, obtained by an averaging procedure where in each event the
system is translated to its center of mass and aligned with the major principal
axis of the ellipse of inertia. Quantitative comparisons indicate substantial
relative effects for eccentricity in variants of Glauber models. On the other
hand, the dependence of the scaled standard deviation of the participant
eccentricity on the chosen model is weak. For all models the values range from
about 0.5 for the central collisions to about 0.3-0.4 for peripheral
collisions, both for the gold-gold and copper-copper collisions. They are
dominated by statistics and change only by 10-15% from model to model. We
provide an approximate analytic expansion for the multipole moments and their
fluctuations given in terms of the fixed-axes moments. For central collisions
and in the absence of correlations it gives the simple formula for the scaled
standard deviation of the participant eccentricity: sqrt(4/pi-1). Similarly, we
obtain expansions for the radial profiles of the multipole distributions. We
investigate the relevance of the shape-fluctuation effects for jet quenching
and find them important only for very central events. Finally, we argue how
smooth hydro leads to the known result v_4 ~ v_2^2, and further to the
prediction Delta v_4/v_4 = 2 Delta v_2/v_2.Comment: 20 pages, 15 figures, additions include comparison to the CGC result
Superposition models and the multiplicity fluctuations in heavy ion collisions
A class of simple superposition models based on the Glauber picture of
multiple collisions is compared with the data on the centrality dependence of
the multiplicity distributions in a central rapidity bin. We show how the
results depend on the specific assumptions concerning the distributions in the
number of participants and their relations to the distributions of the number
of produced hadrons in various phase space bins. None of the versions of the
model describes satisfactorily the centrality dependence of the scaled
dispersion.Comment: 9 pages, 5 figures, a misprint in formula corrected, accepted for
publication in EPJ
Hotter, Denser, Faster, Smaller...and Nearly-Perfect: What's the matter at RHIC?
The experimental and theoretical status of the ``near perfect fluid'' at RHIC
is discussed. While the hydrodynamic paradigm for understanding collisions at
RHIC is well-established, there remain many important open questions to address
in order to understand its relevance and scope. It is also a crucial issue to
understand how the early equilibration is achieved, requiring insight into the
active degrees of freedom at early times.Comment: 10 Pages, 13 Figures, submitted to the proceedings of the Second
Meeting of the APS Topical Group on Hadronic Physics, Nashville, TN, October
22-24, 200
Towards a common origin of the elliptic flow, ridge and alignment
It is claimed that elliptic flow, ridge and alignment are effects of
azimuthal asymmetry, which have a common origin evolving with primary energy
and stemming from the general structure of field-theoretical matrix elements.
It interrelates a new ridge-phenomenon, recently found at the LHC and RHIC,
with known coplanarity feature observed in collider jet physics as well as in
cosmic ray studies.Comment: 4 pages, few typos fixed, reference added, version published in JETP
Letter
Specific Heat of Ce(1-x)La(x)RhIn(5) in Zero and Applied Magnetic Field: A Very Rich Phase Diagram
Specific heat and magnetization results as a function of field on single- and
poly-crystalline samples of Ce(1-x)La(x)RhIn(5) show 1.) a specific heat gamma
of about 100 mJ/moleK^2 (in agreement with recent dHvA results of Alvers et
al.); 2.) upturns at low temperatures in C/T and chi that fit a power law
behavior ( Griffiths phase non-Fermi liquid behavior); 3.) a field induced
anomaly in C/T as well as M vs H behavior in good agreement with the recent
Griffiths phase theory of Castro Neto and Jones, where M~H at low field, M ~
H^lambda above a crossover field, C/T ~ T^(-1+lambda) at low field, and C/T ~
(H^(2+lambda/2)/T^(3-lambda/2))*exp(-mu(eff)H/T) above the same crossover field
as determined in the magnetization and where lambda is independently determined
from the temperature dependence of chi at low temperatures, chi ~ T^(-1+lambda)
and low fields.Comment: 13 pages, 9 figures, to be published in Physical Review
High transverse momentum suppression and surface effects in Cu+Cu and Au+Au collisions within the PQM model
We study parton suppression effects in heavy-ion collisions within the Parton
Quenching Model (PQM). After a brief summary of the main features of the model,
we present comparisons of calculations for the nuclear modification and the
away-side suppression factor to data in Au+Au and Cu+Cu collisions at 200 GeV.
We discuss properties of light hadron probes and their sensitivity to the
medium density within the PQM Monte Carlo framework.Comment: Comments: 6 pages, 8 figures. To appear in the proceedings of Hot
Quarks 2006: Workshop for Young Scientists on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May
200
Wounded nucleon model with realistic nucleon-nucleon collision profile and observables in relativistic heavy-ion collisions
We investigate the influence of the nucleon-nucleon collision profile
(probability of interaction as a function of the nucleon-nucleon impact
parameter) in the wounded nucleon model and its extensions on several
observables measured in relativistic heavy-ion collisions. We find that the
participant eccentricity coefficient, , as well as the higher
harmonic coefficients, , are reduced by 10-20% for
mid-peripheral collisions when the realistic (Gaussian) profile is used, as
compared to the case with the commonly-used hard-sphere profile. Similarly, the
multiplicity fluctuations, treated as the function of the number of wounded
nucleons in one of the colliding nuclei, are reduced by 10-20%. This
demonstrates that the Glauber Monte Carlo codes should necessarily use the
realistic nucleon-nucleon collision profile in precision studies of these
observables. The Gaussian collision profile is built-in in {\tt GLISSANDO}.Comment: 8 pages, 7 figure
Simulation of Light Antinucleus-Nucleus Interactions
Creations of light anti-nuclei (anti-deuterium, anti-tritium, anti-He3 and
anti-He4) are observed by collaborations at the LHC and RHIC accelerators. Some
cosmic ray experiments are aimed to find the anti-nuclei in cosmic rays. To
support the experimental studies of the anti-nuclei a Monte Carlo simulation of
anti-nuclei interactions with matter is implemented in the Geant4 toolkit. The
implementation combines practically all known theoretical approaches to the
problem of antinucleon-nucleon interactions.Comment: 8 pages, 5 figure
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