7,336 research outputs found
Accurate time-domain gravitational waveforms for extreme-mass-ratio binaries
The accuracy of time-domain solutions of the inhomogeneous Teukolsky equation
is improved significantly. Comparing energy fluxes in gravitational waves with
highly accurate frequency-domain results for circular equatorial orbits in
Schwarzschild and Kerr, we find agreement to within 1% or better, which we
believe can be even further improved. We apply our method to orbits for which
frequency-domain calculations have a relative disadvantage, specifically
high-eccentricity (elliptical and parabolic) "zoom-whirl" orbits, and find the
energy fluxes, waveforms, and characteristic strain in gravitational waves.Comment: 6 pages, 9 figures, 2 tables; Changes: some errors corrected.
Comparison with Frequency-domain now done in stronger fiel
Corrosion resistant coating
A method of coating a substrate with an amorphous metal is described. A solid piece of the metal is bombarded with ions of an inert gas in the presence of a magnetic field to provide a vapor of the metal which is deposited on the substrate at a sufficiently low gas pressure so that there is formed on the substrate a thin, uniformly thick, essentially pinhole-free film of the metal
Fireside Corrosion and Erosion Problems in Coal Based Power Plant
High temperature corrosion problems in coalloil based
power plants are discussed. The main corrosion problems
in power plants are the waterlsteam side corrosion of
the inner wall tubes of the boiler and the oxidation/ sulphidation and hot corrosion of outer walls of hoiler tubes. The former is well understood and can he contro-lled by controlling the chemistry of the feed water,
the fireside corrosion is, however, least understood
and is a function of several variables, both operating
and material. These are discussed in detail with some
of the data from the failure of plants as a result of fireside corrosion and erosion
New Generation Coatings - A Combination of Thermal Spray and Organic Paint Coatings to give Enhanced Corrosion Protection in Aggressive Environments
There is a great concern about the frequent replenis-
hment of paint coatings on certain specfic structures
and installations, especially erected in aggressive marine environments. Various analysis have shown that
a best paint coating with best surface finish and pre-treatment cannot guaranty a life more than 5 years.
Hence alternative methods of protecting such structures
in aggressive environment is really the need of the
hour. Metal coatings using thermal spray is becoming
very popular. There are of course some limitations
of thermal spray coatings which can either be overcome
by modification of the process or by combining thermal spray with organic paint coatings. Such new generation coatings are now guarantying a life of more than 20
years to 40 years. Principal of thermal spray coatings
and their application to structures in highly aggressive environments is discussed in this paper
Insulator interface effects in sputter‐deposited NbN/MgO/NbN (superconductor–insulator–superconductor) tunnel junctions
All refractory, NbN/MgO/NbN (superconductor–insulator–superconductor) tunnel junctions have been fabricated by in situ sputter deposition. The influence of MgO thickness (0.8–6.0 nm) deposited under different sputtering ambients at various deposition rates on current–voltage (I–V) characteristics of small‐area (30×30 μm) tunnel junctions is studied. The NbN/MgO/NbN trilayer is deposited in situ by dc reactive magnetron (NbN), and rf magnetron (MgO) sputtering, followed by thermal evaporation of a protective Au cap. Subsequent photolithography, reactive ion etching, planarization, and top contact (Pb/Ag) deposition completes the junction structure. Normal resistance of the junctions with MgO deposited in Ar or Ar and N2 mixture shows good exponential dependence on the MgO thickness indicating formation of a pin‐hole‐free uniform barrier layer. Further, a postdeposition in situ oxygen plasma treatment of the MgO layer increases the junction resistance sharply, and reduces the subgap leakage. A possible enrichment of the MgO layer stoichiometry by the oxygen plasma treatment is suggested. A sumgap as high as 5.7 mV is observed for such a junctio
Phase transition in the massive Gross-Neveu model in toroidal topologies
We use methods of quantum field theory in toroidal topologies to study the
-component -dimensional massive Gross-Neveu model, at zero and finite
temperature, with compactified spatial coordinates. We discuss the behavior of
the large- coupling constant (), investigating its dependence on the
compactification length () and the temperature (). For all values of the
fixed coupling constant (), we find an asymptotic-freedom type of
behavior, with as and/or . At T=0, and for
(the strong coupling regime), we show that,
starting in the region of asymptotic freedom and increasing , a divergence
of appears at a finite value of , signaling the existence of a phase
transition with the system getting spatially confined. Such a spatial
confinement is destroyed by raising the temperature. The confining length,
, and the deconfining temperature, , are determined
as functions of and the mass () of the fermions, in the case of
. Taking as the constituent quark mass (), the
results obtained are of the same order of magnitude as the diameter () and the estimated deconfining temperature () of
hadrons.Comment: 14 pages, 10 figures, 1 table, to appear in Phys. Rev.
On Lorentz violation in scattering at finite temperature
Small violation of Lorentz and CPT symmetries may emerge in models unifying
gravity with other forces of nature. An extension of the standard model with
all possible terms that violate Lorentz and CPT symmetries are included. Here a
CPT-even non-minimal coupling term is added to the covariant derivative. This
leads to a new interaction term that breaks the Lorentz symmetry. Our main
objective is to calculate the cross section for the
scattering in order to
investigate any violation of Lorentz and/or CPT symmetry at finite temperature.
Thermo Field Dynamics formalism is used to consider finite temperature effects.Comment: 12 pages, 1 figure, accepted for publication in PL
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