21,617 research outputs found
TEA: A Code for Calculating Thermochemical Equilibrium Abundances
We present an open-source Thermochemical Equilibrium Abundances (TEA) code
that calculates the abundances of gaseous molecular species. The code is based
on the methodology of White et al. (1958) and Eriksson (1971). It applies Gibbs
free-energy minimization using an iterative, Lagrangian optimization scheme.
Given elemental abundances, TEA calculates molecular abundances for a
particular temperature and pressure or a list of temperature-pressure pairs. We
tested the code against the method of Burrows & Sharp (1999), the free
thermochemical equilibrium code CEA (Chemical Equilibrium with Applications),
and the example given by White et al. (1958). Using their thermodynamic data,
TEA reproduces their final abundances, but with higher precision. We also
applied the TEA abundance calculations to models of several hot-Jupiter
exoplanets, producing expected results. TEA is written in Python in a modular
format. There is a start guide, a user manual, and a code document in addition
to this theory paper. TEA is available under a reproducible-research,
open-source license via https://github.com/dzesmin/TEA.Comment: 14 pages, 8 figures, article is submitted to ApJS, posted on arXiv
for public commentary, please send comments to the lead autho
A Method To Remove Fringes From Images Using Wavelets
We have developed a new method that uses wavelet analysis to remove
interference fringe patterns from images. This method is particularly useful
for flat fields in the common case where fringes vary between the calibration
and object data. We analyze the efficacy of this method by creating fake flats
with fictitious fringes and removing the fringes. We find that the method
removes 90% of the fringe pattern if its amplitude is equal to the random noise
level and 60% if the fringe amplitude is of the noise level. We
also present examples using real flat field frames. A routine written in the
Interactive Data Language (IDL) that implements this algorithm is available
from the authors and as an attachment to this paper.Comment: 7 pages, 14 figures. Accepted to the Astrophysical Journal. (The
quality of the figures in this preprint has been downgraded in order to
fulfill arXiv requirements. Check journal for the high-quality figures
Tau-aggregation inhibitor therapy for Alzheimer's disease
Article Accepted Date: 9 December 2013 Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.Peer reviewedPublisher PD
Converting energy from fusion into useful forms
If fusion power reactors are to be feasible, it will still be necessary to
convert the energy of the nuclear reaction into usable form. The heat produced
will be removed from the reactor core by a primary coolant, which might be
water, helium, molten lithium-lead, molten lithium-containing salt, or CO2. The
heat could then be transferred to a conventional Rankine cycle or Brayton (gas
turbine) cycle. Alternatively it could be used for thermochemical processes
such as producing hydrogen or other transport fuels. Fusion presents new
problems because of the high energy neutrons released. These affect the
selection of materials and the operating temperature, ultimately determining
the choice of coolant and working cycle. The limited temperature ranges allowed
by present day irradiated structural materials, combined with the large
internal power demand of the plant, will limit the overall thermal efficiency.
The operating conditions of the fusion power source, the materials, coolant,
and energy conversion system will all need to be closely integrated.Comment: 22 pages, 4 figures, Proceedings of the Institution of Mechanical
Engineers, Part A: Journal of Power and Energy December 11, 201
Experimental cold-flow evaluation of a ram air cooled plug nozzle concept for afterburning turbojet engines
A concept for plug nozzles cooled by inlet ram air is presented. Experimental data obtained with a small scale model, 21.59-cm (8.5-in.) diameter, in a static altitude facility demonstrated high thrust performance and excellent pumping characteristics. Tests were made at nozzle pressure ratios simulating supersonic cruise and takeoff conditions. Effect of plug size, outer shroud length, and varying amounts of secondary flow were investigated
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