17,899 research outputs found
Combustion of coal gas fuels in a staged combustor
Gaseous fuels produced from coal resources generally have heating values much lower than natural gas; the low heating value could result in unstable or inefficient combustion. Coal gas fuels may contain ammonia which if oxidized in an uncontrolled manner could result in unacceptable nitrogen oxide exhaust emission levels. Previous investigations indicate that staged, rich-lean combustion represents a desirable approach to achieve stable, efficient, low nitrogen oxide emission operation for coal-derived liquid fuels contaning up to 0.8-wt pct nitrogen. An experimental program was conducted to determine whether this fuel tolerance can be extended to include coal-derived gaseous fuels. The results of tests with three nitrogen-free fuels having heating values of 100, 250, and 350 Btu/scf and a 250 Btu/scf heating value doped to contain 0.7 pct ammonia are presented
Reversible strain effect on the magnetization of LaCoO3 films
The magnetization of ferromagnetic LaCoO3 films grown epitaxially on
piezoelectric substrates has been found to systematically decrease with the
reduction of tensile strain. The magnetization change induced by the reversible
strain variation reveals an increase of the Co magnetic moment with tensile
strain. The biaxial strain dependence of the Curie temperature is estimated to
be below 4K/% in the as-grown tensile strain state of our films. This is in
agreement with results from statically strained films on various substrates
Quantum transport through single-molecule junctions with orbital degeneracies
We consider electronic transport through a single-molecule junction where the
molecule has a degenerate spectrum. Unlike previous transport models, and
theories a rate-equations description is no longer possible, and the quantum
coherences between degenerate states have to be taken into account. We present
the derivation and application of a master equation that describes the system
in the weak-coupling limit and give an in-depth discussion of the parameter
regimes and the new phenomena due to coherent on-site dynamics
Exact solution of a 2d random Ising model
The model considered is a d=2 layered random Ising system on a square lattice
with nearest neighbours interaction. It is assumed that all the vertical
couplings are equal and take the positive value J while the horizontal
couplings are quenched random variables which are equal in the same row but can
take the two possible values J and J-K in different rows. The exact solution is
obtained in the limit case of infinite K for any distribution of the horizontal
couplings. The model which corresponds to this limit can be seen as an ordinary
Ising system where the spins of some rows, chosen at random, are frozen in an
antiferromagnetic order. No phase transition is found if the horizontal
couplings are independent random variables while for correlated disorder one
finds a low temperature phase with some glassy properties.Comment: 10 pages, Plain TeX, 3 ps figures, submitted to Europhys. Let
An introduction to spacecraft thermal control
External and internal passive and active methods for spacecraft thermal control - material insulation and structural propertie
A transient heat transfer and thermodynamic analysis of the Apollo service module propulsion system. Vol. I, phase I - Transient thermal analysis Final report, 28 Jul. 1964 - 28 Jul. 1965
Transient heat transfer and thermodynamic behavior analysis for Apollo service module propulsion system - fuel cell effect on overheatin
Measurement and Calculation of Absolute Single and Multiple Charge Exchange Cross Sections for Fe^(q+) Ions Impacting H_2O
Charge exchange (CE) plays a fundamental role in the collisions of solar- and stellar-wind ions with lunar and planetary exospheres, comets, and circumstellar clouds. Reported herein are absolute cross sections for single, double, triple, and quadruple CE of Fe^(q+) (q = 5-13) ions with H_2O at a collision energy of 7q keV. One measured value of the pentuple CE is also given for Fe^(9+) ions. An electron cyclotron resonance ion source is used to provide currents of the highly charged Fe ions. Absolute data are derived from knowledge of the target gas pressure, target path length, and incident and charge-exchanged ion currents. Experimental cross sections are compared with new results of the n-electron classical trajectory Monte Carlo approximation. The radiative and non-radiative cascades following electron transfers are approximated using scaled hydrogenic transition probabilities and scaled Auger rates. Also given are estimates of cross sections for single capture, and multiple capture followed by autoionization, as derived from the extended overbarrier model. These estimates are based on new theoretical calculations of the vertical ionization potentials of H_2O up to H_2O^(10+)
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