51 research outputs found
Evolution of HCl Concentrations in the Lower Stratosphere from 1991 to 1996 Following the Eruption of Mt. Pinatubo
Geophysical Research Letters, Vol. 25, No. 7, pp. 995-998, April 1, 1998.In situ measurements of hydrochloric acid in the lower stratosphere reveal that its mean abundance relative to that of total inorganic chlorine..
Fitting the integrated Spectral Energy Distributions of Galaxies
Fitting the spectral energy distributions (SEDs) of galaxies is an almost
universally used technique that has matured significantly in the last decade.
Model predictions and fitting procedures have improved significantly over this
time, attempting to keep up with the vastly increased volume and quality of
available data. We review here the field of SED fitting, describing the
modelling of ultraviolet to infrared galaxy SEDs, the creation of
multiwavelength data sets, and the methods used to fit model SEDs to observed
galaxy data sets. We touch upon the achievements and challenges in the major
ingredients of SED fitting, with a special emphasis on describing the interplay
between the quality of the available data, the quality of the available models,
and the best fitting technique to use in order to obtain a realistic
measurement as well as realistic uncertainties. We conclude that SED fitting
can be used effectively to derive a range of physical properties of galaxies,
such as redshift, stellar masses, star formation rates, dust masses, and
metallicities, with care taken not to over-interpret the available data. Yet
there still exist many issues such as estimating the age of the oldest stars in
a galaxy, finer details ofdust properties and dust-star geometry, and the
influences of poorly understood, luminous stellar types and phases. The
challenge for the coming years will be to improve both the models and the
observational data sets to resolve these uncertainties. The present review will
be made available on an interactive, moderated web page (sedfitting.org), where
the community can access and change the text. The intention is to expand the
text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics &
Space Scienc
Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF
The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described
Residual stresses in a quenched superalloy turbine disc: measurements and modeling
A series of neutron diffraction measurements have been carried out to determine the elastic residual strains deep within a large, 40-cm-diameter, forged and water-quenched IN718 aeroengine compressor disc. Neutron path lengths of up to 6 cm were necessary to probe the thickest parts of the forging, and three-dimensional strain and stress components have been derived for the first time in such a large superalloy specimen. Measurements have been compared with the results from a coupled thermal-mechanical finite-element model of the quenching process, based upon appropriate temperature-dependent material properties, with some success. The general residual stress state in the disc is one of near-surface compression, balanced by tension within the disc interior. The steepest stress and strain gradients occur in the transition region from compression to tension, about 1 cm below the surface all around the disc. The largest stress component is in the disc tangential direction and reaches a magnitude of 400 to 500 MPa near the disc surface and at its core. This exceeds the effective yield stress because of the presence of significant hydrostatic stress
Study of metal oxide-semiconductor capacitors with rf magnetron sputtering TiO(x) and TiO(x)N(y) gate dielectric layer
Metal oxide-semiconductor capacitors with TiO(x) deposited with different O(2) partial pressures (30%, 35%, and 40%) and annealed at 550, 750, and 1000 degrees C were fabricated and characterized. Fourier transform infrared, x-ray near edge spectroscopy, and elipsometry measurements were performed to characterize the TiO(x) films. TiO(x)N(y) films were also obtained by adding nitrogen to the gaseous mixture and physical results were presented. Capacitance-voltage (1 MHz) and current-voltage measurements were utilized to obtain the effective dielectric constant, effective oxide thickness, leakage current density, and interface quality. The results show that the obtained TiO(x) films present a dielectric constant varying from 40 to 170 and a leakage current density (for V(G)=-1 V, for some structures as low as 1 nA/cm(2), acceptable for complementary metal oxide semiconductor circuits fabrication), indicating that this material is a viable, in terms of leakage current density, highk substitute for current ultrathin dielectric layers. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3043537
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