4,374 research outputs found
Accurate, rapid, temperature and liquid-level sensor for cryogenic tanks
Thermopiles measure ullage gas temperatures to within plus or minus 1.65 deg K between 20 and 300 deg K, and also serve as point liquid-level sensors. Thermopile technique measures smaller temperature differences by keeping the reference junctions inside the tank and near the temperature range of the measuring junction
Comparison of Existing Linewideth Measuring Systems to an Experimental Unit that Enables Minimization of Vibration During Measurement
An experimental unit was built to minimize vibration during measurement of linewidths on integrated circuit photomasks. Linewidths in the range of 0.522 microns to 12.076 microns were measured with the Nikon LASER scanning system. Optical Specialties Inc. VLS-I video system, Nikon Micro Pattern Analyzer slit-scanning system, and the experimental unit. Average variances of 0.0096, 0.0164, 0.0377, and 0.3627 were calculated for each system respectively. The variances were compared using an F-test with the result that each system was significantly different for each linewidth. A mathematical model was derived to predict the smallest resolvable detail given the frequency and amplitude of vibration, the exposure time of the camera, numerical aperture of the objective, magnification of the system, and the size of the elements in the imaging array
Infrared Photometry and Dust Absorption in Highly Inclined Spiral Galaxies
We present JHK surface photometry of 15 highly inclined, late-type (Sab-Sc)
spirals and investigate the quantitative effects of dust extinction. Using the
(J - H, H - K) two-color diagram, we compare the color changes along the minor
axis of each galaxy to the predictions from different models of radiative
transfer. Models in which scattering effects are significant and those with
more than a small fraction of the light sources located near the edge of the
dust distribution do not produce enough extinction to explain the observed
color gradients across disk absorption features. The optical depth in dust near
the plane as deduced from the color excess depends sensitively on the adopted
dust geometry, ranging from tau = 4 to 15 in the visual band. This suggests
that a realistic model of the dust distribution is required, even for infrared
photometry, to correct for dust extinction in the bulges of nearly edge-on
systems.Comment: Accepted for publication in the March 1996 AJ. LaTex source which
generates 27 pages of text and tables (no figures). Complete (text + figs)
compressed Postscript preprint is also available at
ftp://bessel.mps.ohio-state.edu/pub/terndrup/inclined.ps.Z (854 Mbyte
PH14-8Mo stainless steel honey comb core shear strength at elevated temperatures, 1 July 1968 - 1 July 1969
PH-8Mo stainless steel honeycomb sandwich cor
Roll diffusion bonding of titanium alloy panels
Roll diffusion bonding technique is used for fabricating T-stiffened panel assemblies from titanium alloy. The single unit fabrication exhibits excellent strength characteristics under tensile and compressive loads. This program is applied to structures in which weight/strength ratio and integral construction are important considerations
Low-Energy Effective Action in Non-Perturbative Electrodynamics in Curved Spacetime
We study the heat kernel for the Laplace type partial differential operator
acting on smooth sections of a complex spin-tensor bundle over a generic
-dimensional Riemannian manifold. Assuming that the curvature of the U(1)
connection (that we call the electromagnetic field) is constant we compute the
first two coefficients of the non-perturbative asymptotic expansion of the heat
kernel which are of zero and the first order in Riemannian curvature and of
arbitrary order in the electromagnetic field. We apply these results to the
study of the effective action in non-perturbative electrodynamics in four
dimensions and derive a generalization of the Schwinger's result for the
creation of scalar and spinor particles in electromagnetic field induced by the
gravitational field. We discover a new infrared divergence in the imaginary
part of the effective action due to the gravitational corrections, which seems
to be a new physical effect.Comment: LaTeX, 42 page
Semiclassical and Quantum Black Holes and their Evaporation, de Sitter and Anti-de Sitter Regimes, Gravitational and String Phase Transitions
An effective string theory in physically relevant cosmological and black hole
space times is reviewed. Explicit computations of the quantum string entropy,
partition function and quantum string emission by black holes (Schwarzschild,
rotating, charged, asymptotically flat, de Sitter dS and AdS space times) in
the framework of effective string theory in curved backgrounds provide an
amount of new quantum gravity results as: (i) gravitational phase transitions
appear with a distinctive universal feature: a square root branch point
singularity in any space time dimensions. This is of the type of the de Vega -
Sanchez transition for the thermal self-gravitating gas of point particles.
(ii) There are no phase transitions in AdS alone. (iii) For background,
upper bounds of the Hubble constant H are found, dictated by the quantum string
phase transition.(iv) The Hawking temperature and the Hagedorn temperature are
the same concept but in different (semiclassical and quantum) gravity regimes
respectively. (v) The last stage of black hole evaporation is a microscopic
string state with a finite string critical temperature which decays as usual
quantum strings do in non-thermal pure quantum radiation (no information
loss).(vi) New lower string bounds are given for the Kerr-Newman black hole
angular momentum and charge, which are entirely different from the upper
classical bounds. (vii) Semiclassical gravity states undergo a phase transition
into quantum string states of the same system, these states are duals of each
other in the precise sense of the usual classical-quantum (wave-particle)
duality, which is universal irrespective of any symmetry or isommetry of the
space-time and of the number or the kind of space-time dimensions.Comment: review paper, no figures. to appear in Int Jour Mod Phys
The Existence of Einstein Static Universes and their Stability in Fourth order Theories of Gravity
We investigate whether or not an Einstein Static universe is a solution to
the cosmological equations in gravity. It is found that only one class
of theories admits an Einstein Static model, and that this class is
neutrally stable with respect to vector and tensor perturbations for all
equations of state on all scales. Scalar perturbations are only stable on all
scales if the matter fluid equation of state satisfies
. This result is remarkably similar to
the GR case, where it was found that the Einstein Static model is stable for
.Comment: Minor changes, To appear in PR
Renormalized Kaluza-Klein theories
Using six-dimensional quantum electrodynamics () as an example we
study the one-loop renormalization of the theory both from the six and
four-dimensional points of view. Our main conclusion is that the properly
renormalized four dimensional theory never forgets its higher dimensional
origin. In particular, the coefficients of the neccessary extra counterterms in
the four dimensional theory are determined in a precise way. We check our
results by studying the reduction of on a two-torus.Comment: LaTeX, 36 pages. A new section added; references improved, typos
fixe
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