20,704 research outputs found
High-temperature bearing lubricants
Synthetic paraffinic oil lubricates ball bearings at temperatures in the 600 degrees F range. The lubricant contains antiwear and antifoam additives, is thermally stable in the high temperature range, but requires protection from oxygen
Common bearing material has highest fatigue life at moderate temperature
AISI 52100, a high carbon chromium steel, has the longest fatigue life of eight bearing materials tested. Fatigue lives of the other materials ranged from 7 to 78 percent of the fatigue life of AISI 52100 at a temperature of 340 K (150 F)
NASA five-ball fatigue tester: Over 20 years of research
Studies were conducted to determine the effect on rolling-element fatigue life of contact angle, material hardness, chemistry, heat treatment and processing, lubricant type and chemistry, elastohydrodynamic film thickness, deformation and wear, vacuum, and temperature as well as Hertzian and residual stresses. Correlation was established between the results obtained using the five-ball tester and those obtained with full scale rolling-element bearings
Relation Between Einstein And Quantum Field Equations
We show that there exists a choice of scalar field modes, such that the
evolution of the quantum field in the zero-mass and large-mass limits is
consistent with the Einstein equations for the background geometry. This choice
of modes is also consistent with zero production of these particles and thus
corresponds to a preferred vacuum state preserved by the evolution. In the
zero-mass limit, we find that the quantum field equation implies the Einstein
equation for the scale factor of a radiation-dominated universe; in the
large-mass case, it implies the corresponding Einstein equation for a
matter-dominated universe. Conversely, if the classical radiation-dominated or
matter-dominated Einstein equations hold, there is no production of scalar
particles in the zero and large mass limits, respectively. The suppression of
particle production in the large mass limit is over and above the expected
suppression at large mass. Our results hold for a certain class of conformally
ultrastatic background geometries and therefore generalize previous results by
one of us for spatially flat Robertson-Walker background geometries. In these
geometries, we find that the temporal part of the graviton equations reduces to
the temporal equation for a massless minimally coupled scalar field, and
therefore the results for massless particle production hold also for gravitons.
Within the class of modes we study, we also find that the requirement of zero
production of massless scalar particles is not consistent with a non-zero
cosmological constant. Possible implications are discussed.Comment: Latex, 24 pages. Minor changes in text from original versio
Constraining ^(26)Al+p resonances using ^(26)Al(^3He,d)^(27)Si
The ^(26)Al(^3He,d)^(27)Si reaction was measured from 0°≤θ_(c.m.)≤35° at E(^3He)=20 MeV using a quadrupole-dipole-dipole-dipole magnetic spectrometer. States in ^(27)Si were observed above the background at 7652 and 7741 keV and upper limits were set for the state at 7592 keV. Implications for the ^(26)Al(p,γ)^(27)Si stellar reaction rate are discussed
New combined PIC-MCC approach for fast simulation of a radio frequency discharge at low gas pressure
A new combined PIC-MCC approach is developed for accurate and fast simulation
of a radio frequency discharge at low gas pressure and high density of plasma.
Test calculations of transition between different modes of electron heating in
a ccrf discharge in helium and argon show a good agreement with experimental
data.
We demonstrate high efficiency of the combined PIC-MCC algorithm, especially
for the collisionless regime of electron heating.Comment: 6 paged, 8 figure
Wetting and energetics in nanoparticle etching of graphene
Molten metallic nanoparticles have recently been used to construct graphene
nanostructures with crystallographic edges. The mechanism by which this
happens, however, remains unclear. Here, we present a simple model that
explains how a droplet can etch graphene. Two factors possibly contribute to
this process: a difference between the equilibrium wettability of graphene and
the substrate that supports it, or the large surface energy associated with the
graphene edge. We calculate the etching velocities due to either of these
factors and make testable predictions for evaluating the significance of each
in graphene etching. This model is general and can be applied to other
materials systems as well. As an example, we show how our model can be used to
extend a current theory of droplet motion on binary semiconductor surfaces
Baryon asymmetry from hypermagnetic helicity in dilaton hypercharge electromagnetism
The generation of the baryon asymmetry of the Universe (BAU) from the
hypermagnetic helicity, the physical interpretation of which is given in terms
of hypermagnetic knots, is studied in inflationary cosmology, taking into
account the breaking of the conformal invariance of hypercharge electromagnetic
fields through both a coupling with the dilaton and that with a pseudoscalar
field. It is shown that if the electroweak phase transition (EWPT) is strongly
first order and the present amplitude of the generated magnetic fields on the
horizon scale is sufficiently large, a baryon asymmetry with a sufficient
magnitude to account for the observed baryon to entropy ratio can be generated.Comment: 16 pages, 2 figures, a reference added, typos correcte
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