28,955 research outputs found
The mechanical properties of inconel 718 sheet alloy at 800 deg, 1000 deg, and 1200 deg f
Mechanical properties of Inconel sheet superalloy at very high temperatures for supersonic transpor
What can we infer about the underlying physics from burst distributions observed in an RMHD simulation ?
We determine that the sizes of bursts in mean-square current density in a
reduced magnetohydrodynamic (RMHD)simulation follow power-law probability
density function (PDF). The PDFs for burst durations and waiting time between
bursts are clearly not exponential and could also be power-law. This suffices
to distinguish their behaviour from the original Bak et al. sandpile model
which had exponential waiting time PDFs. However, it is not sufficient to
distinguish between turbulence, some other SOC-like models, and other red noise
sources.Comment: In press, Planetary and Space Science. Proceedings of a session at
European Geophysical Society General Assembly, Nice, 200
Power law burst and inter-burst interval distributions in the solar wind: turbulence or dissipative SOC ?
We calculate for the first time the probability density functions (PDFs) P of
burst energy e, duration T and inter-burst interval tau for a known turbulent
system in nature. Bursts in the earth-sun component of the Poynting flux at 1
AU in the solar wind were measured using the MFI and SWE experiments on the
NASA WIND spacecraft. We find P(e) and P(T) to be power laws, consistent with
self-organised criticality (SOC). We find also a power law form for P(tau) that
distinguishes this turbulent cascade from the exponential P(tau) of ideal SOC,
but not from some other SOC-like sandpile models. We discuss the implications
for the relation between SOC and turbulence.Comment: 3 pages, 1 figure. Submitted to PRL on 25th February 2000. Revised
version re-submitted on 9th May 2000. Second revised version submitted Phys.
Rev. E on 26th June, 200
The strange quark condensate in the nucleon in 2+1 flavor QCD
We calculate the "strange quark content of the nucleon", ,
which is important for interpreting the results of some dark matter detection
experiments. The method is to evaluate quark-line disconnected correlations on
the MILC lattice ensembles, which include the effects of dynamical strange
quarks. After continuum and chiral extrapolations, the result is <N |s s_bar
|N> = 0.69 +- 0.07(statistical) +- 0.09(systematic), in the modified minimal
subtraction scheme (2 GeV), or for the renormalization scheme invariant form,
m_s partial{M_N}/partial{m_s} = 59(6)(8) MeV.Comment: Added figures and references, especially for fit range choice. Other
changes for clarity. Version to appear in publicatio
The intrinsic strangeness and charm of the nucleon using improved staggered fermions
We calculate the intrinsic strangeness of the nucleon, - ,
using the MILC library of improved staggered gauge configurations using the
Asqtad and HISQ actions. Additionally, we present a preliminary calculation of
the intrinsic charm of the nucleon using the HISQ action with dynamical charm.
The calculation is done with a method which incorporates features of both
commonly-used methods, the direct evaluation of the three-point function and
the application of the Feynman- Hellman theorem. We present an improvement on
this method that further reduces the statistical error, and check the result
from this hybrid method against the other two methods and find that they are
consistent. The values for and found here, together with
perturbative results for heavy quarks, show that dark matter scattering through
Higgs-like exchange receives roughly equal contributions from all heavy quark
flavors.Comment: 17 pages, 14 figure
Finite volume study of electric polarizabilities from lattice QCD
Knowledge of the electric polarizability is crucial to understanding the
interactions of hadrons with electromagnetic fields. The neutron polarizability
is very sensitive to the quark mass and is expected to diverge in the chiral
limit. Here we present results for the electric polarizability of the neutron,
neutral pion, and neutral kaon on eight ensembles with nHYP-smeared clover
dynamical fermions with two different pion masses (227 and 306 MeV). These are
currently the lightest pion masses used in polarizability studies. For each
pion mass we compute the polarizability at four different volumes and perform
an infinite volume extrapolation for the three hadrons. Along with the infinite
volume extrapolation we conduct a chiral extrapolation for the kaon
polarizability to the physical point. We compare our results for the neutron
polarizability to predictions from chiral perturbation theory.Comment: 7 pages, 11 figure
Simulator test to study hot-flow problems related to a gas cooled reactor
An advance study of materials, fuel injection, and hot flow problems related to the gas core nuclear rocket is reported. The first task was to test a previously constructed induction heated plasma GCNR simulator above 300 kW. A number of tests are reported operating in the range of 300 kW at 10,000 cps. A second simulator was designed but not constructed for cold-hot visualization studies using louvered walls. A third task was a paper investigation of practical uranium feed systems, including a detailed discussion of related problems. The last assignment resulted in two designs for plasma nozzle test devices that could be operated at 200 atm on hydrogen
Focus Point Supersymmetry Redux
Recent results from Higgs boson and supersymmetry searches at the Large
Hadron Collider provide strong new motivations for supersymmetric theories with
heavy superpartners. We reconsider focus point supersymmetry (FP SUSY), in
which all squarks and sleptons may have multi-TeV masses without introducing
fine-tuning in the weak scale with respect to variations in the fundamental
SUSY-breaking parameters. We examine both FP SUSY and its familiar special
case, the FP region of mSUGRA/CMSSM, and show that they are beautifully
consistent with all particle, astroparticle, and cosmological data, including
Higgs boson mass limits, null results from SUSY searches, electric dipole
moments, b -> s gamma, B_s -> mu^+ mu^-, the thermal relic density of
neutralinos, and dark matter searches. The observed deviation of the muon's
anomalous magnetic moment from its standard model value may also be explained
in FP SUSY, although not in the FP region of mSUGRA/CMSSM. In light of recent
data, we advocate refined searches for FP SUSY and related scenarios with heavy
squarks and sleptons, and we present a simplified parameter space to aid such
analyses.Comment: v3: 20 pages, 20 figures, minor numerical error in relic density
calculation corrected, fixed contours in figure
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