47,801 research outputs found
Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 2: Partially Sealed Configuration
Experimental results from a partially sealed squeeze film damper (SFD) test rig, executing a circular centered orbit are presented and discussed. A serrated piston ring is installed at the damper exit. This device involves a new sealing concept which produces high damping values while allowing for oil flow to cool the damper. In the partially sealed damper, large cavitation regions are observed in the pressure fields at orbit radii epsilon equals 0.5 and epsilon equals 0.8. The cavitated pressure distributions and the corresponding force coefficients are compared with a cavitated bearing solution. The experimental results show the significance of fluid inertia and vapor cavitation in the operation of squeeze film dampers. Squeeze film Reynolds numbers tested reach up to Re equals 50, spanning the range of contemporary applications
Measurements of Pressure Distributions and Force Coefficients in a Squeeze Film Damper. Part 1: Fully Open Ended Configuration
Measurements of pressure distributions and force coefficients were carried out in two types of squeeze film dampers, executing a circular centered orbit, an open-ended configuration, and a partially sealed one, in order to investigate the effect of fluid inertia and cavitation on pressure distributions and force coefficients. Dynamic pressure measurements were carried out for two orbit radii, epsilon 0.5 and 0.8. It was found that the partially sealed configuration was less influenced by fluid inertia than the open ended configuration
Epitaxial growth and the magnetic properties of orthorhombic YTiO3 thin films
High-quality YTiO3 thin films were grown on LaAlO3 (110) substrates at low
oxygen pressures (<10-8 Torr) using pulsed laser deposition. The in-plane
asymmetric atomic arrangements at the substrate surface allowed us to grow
epitaxial YTiO3 thin films, which have an orthorhombic crystal structure with
quite different a- and b-axes lattice constants. The YTiO3 film exhibited a
clear ferromagnetic transition at 30 K with a saturation magnetization of about
0.7 uB/Ti. The magnetic easy axis was found to be along the [1-10] direction of
the substrate, which differs from the single crystal easy axis direction, i.e.,
[001].Comment: 14 pages, 4 figure
On the distribution of career longevity and the evolution of home run prowess in professional baseball
Statistical analysis is a major aspect of baseball, from player averages to
historical benchmarks and records. Much of baseball fanfare is based around
players exceeding the norm, some in a single game and others over a long
career. Career statistics serve as a metric for classifying players and
establishing their historical legacy. However, the concept of records and
benchmarks assumes that the level of competition in baseball is stationary in
time. Here we show that power-law probability density functions, a hallmark of
many complex systems that are driven by competition, govern career longevity in
baseball. We also find similar power laws in the density functions of all major
performance metrics for pitchers and batters. The use of performance-enhancing
drugs has a dark history, emerging as a problem for both amateur and
professional sports. We find statistical evidence consistent with
performance-enhancing drugs in the analysis of home runs hit by players in the
last 25 years. This is corroborated by the findings of the Mitchell Report [1],
a two-year investigation into the use of illegal steroids in major league
baseball, which recently revealed that over 5 percent of major league baseball
players tested positive for performance-enhancing drugs in an anonymous 2003
survey.Comment: 5 pages, 5 figures, 2-column revtex4 format. Revision has change of
title, a figure added, and minor changes in response to referee comment
Dijet correlations at RHIC, leading-order -factorization approach versus next-to-leading order collinear approach
We compare results of -factorization approach and next-to-leading order
collinear-factorization approach for dijet correlations in proton-proton
collisions at RHIC energies. We discuss correlations in azimuthal angle as well
as correlations in two-dimensional space of transverse momenta of two jets.
Some -factorization subprocesses are included for the first time in the
literature. Different unintegrated gluon/parton distributions are used in the
-factorization approach. The results depend on UGDF/UPDF used. For
collinear NLO case the situation depends significantly on whether we consider
correlations of any two jets or correlations of leading jets only. In the first
case the contributions associated with soft radiations summed up in
the -factorization approach dominate at and at equal
moduli of jet transverse momenta. The collinear NLO contributions
dominate over -factorization cross section at small relative azimuthal
angles as well as for asymmetric transverse momentum configurations. In the
second case the NLO contributions vanish at small relative azimuthal angles
and/or large jet transverse-momentum disbalance due to simple kinematical
constraints. There are no such limitations for the -factorization
approach. All this makes the two approaches rather complementary. The role of
several cuts is discussed and quantified.Comment: 26 pages, 17 figure
System size resonance in coupled noisy systems and in the Ising model
We consider an ensemble of coupled nonlinear noisy oscillators demonstrating
in the thermodynamic limit an Ising-type transition. In the ordered phase and
for finite ensembles stochastic flips of the mean field are observed with the
rate depending on the ensemble size. When a small periodic force acts on the
ensemble, the linear response of the system has a maximum at a certain system
size, similar to the stochastic resonance phenomenon. We demonstrate this
effect of system size resonance for different types of noisy oscillators and
for different ensembles -- lattices with nearest neighbors coupling and
globally coupled populations. The Ising model is also shown to demonstrate the
system size resonance.Comment: 4 page
Collective dynamics of two-mode stochastic oscillators
We study a system of two-mode stochastic oscillators coupled through their
collective output. As a function of a relevant parameter four qualitatively
distinct regimes of collective behavior are observed. In an extended region of
the parameter space the periodicity of the collective output is enhanced by the
considered coupling. This system can be used as a new model to describe
synchronization-like phenomena in systems of units with two or more oscillation
modes. The model can also explain how periodic dynamics can be generated by
coupling largely stochastic units. Similar systems could be responsible for the
emergence of rhythmic behavior in complex biological or sociological systems.Comment: 4 pages, RevTex, 5 figure
Initial nucleon structure results with chiral quarks at the physical point
We report initial nucleon structure results computed on lattices with 2+1
dynamical M\"obius domain wall fermions at the physical point generated by the
RBC and UKQCD collaborations. At this stage, we evaluate only connected quark
contributions. In particular, we discuss the nucleon vector and axial-vector
form factors, nucleon axial charge and the isovector quark momentum fraction.
From currently available statistics, we estimate the stochastic accuracy of the
determination of and to be around 10%, and we expect to
reduce that to 5% within the next year. To reduce the computational cost of our
calculations, we extensively use acceleration techniques such as low-eigenmode
deflation and all-mode-averaging (AMA). We present a method for choosing
optimal AMA parameters.Comment: 7 pages, 11 figures; talk presented at the 32nd International
Symposium on Lattice Field Theory, 23-28 June, 2014, Columbia University, New
York, US
- …