163 research outputs found
Large Culvert Inspection Procedures: Guidelines for INDOT
Within the state of Indiana, there are approximately 9,000 structures with unsupported span lengths that range from 4 ft to 20 ft that the Indiana Department of Transportation (INDOT) is responsible for maintaining. These structures are referred to as large culverts by INDOT. The agency recognized the need to improve culvert inspection procedures so that inspection data that is collected can provide essential information to asset engineers who make decisions regarding culvert management. The purpose of the project described in this report was to identify best practices for the inspection and management of these structures to develop guidelines that optimize the resources allocated for the maintenance and inspection of large culvert structures. This study found that standardizing the inspection process and evaluation criteria for inspection will positively impact the overall performance of the inventory of these structures. A proposed large culvert inspection manual accompanies this report and provides a detailed guide for large culvert inspection
Large Culvert Inspection Procedures: Guidelines for INDOT
SPR-4432Within the state of Indiana, there are approximately 9,000 structures with unsupported span lengths that range from 4 ft to 20ft that the Indiana Department of Transportation (INDOT) is responsible for maintaining. These structures are referred to as large culverts by INDOT. The agency recognized the need to improve culvert inspection procedures so that inspection data that is collected can provide essential information to asset engineers who make decisions regarding culvert management. The purpose of the project described in this report was to identify best practices for the inspection and management of these structures to develop guidelines that optimize the resources allocated for the maintenance and inspection of large culvert structures. This study found that standardizing the inspection process and evaluation criteria for inspection will positively impact the overall performance of the inventory of these structures. A proposed large culvert inspection manual accompanies this report and provides a detailed guide for large culvert inspection
The Sloan Digital Sky Survey Reverberation Mapping Project : investigation of continuum lag dependence on broad-line contamination and quasar properties
Funding: H.W.S., J.R.T., M.C.D., and L.B.F. acknowledge support from NSF grant CAREER-1945546, and with C.J.G. acknowledge support from NSF grants AST-2009539 and AST-2108668. C.R. acknowledges support from Fondecyt Regular grant 1230345 and ANID BASAL project FB210003. M.L.M.-A. acknowledges financial support from Millenium Nucleus NCN19-058 (TITANs).This work studies the relationship between accretion-disk size and quasar properties, using a sample of 95 quasars from the Sloan Digital Sky Survey Reverberation Mapping Project with measured lags between the g and i photometric bands. Our sample includes disk lags that are both longer and shorter than predicted by the Shakura and Sunyaev model, requiring explanations that satisfy both cases. Although our quasars each have one lag measurement, we explore the wavelength-dependent effects of diffuse broad-line region (BLR) contamination through our sampleâs broad redshift range, 0.1 < z < 1.2. We do not find significant evidence of variable diffuse Fe ii and Balmer nebular emission in the rms spectra, nor from AndersonâDarling tests of quasars in redshift ranges with and without diffuse nebular emission falling in the observed-frame filters. Contrary to previous work, we do not detect a significant correlation between the measured continuum and BLR lags in our luminous quasar sample, similarly suggesting that our continuum lags are not dominated by diffuse nebular emission. Similar to other studies, we find that quasars with larger-than-expected continuum lags have lower 3000 Ă
luminosities, and we additionally find longer continuum lags with lower X-ray luminosities and black hole masses. Our lack of evidence for diffuse BLR contribution to the lags indicates that the anticorrelation between continuum lag and luminosity is not likely to be due to the Baldwin effect. Instead, these anticorrelations favor models in which the continuum lag increases in lower-luminosity active galactic nuclei, including scenarios featuring magnetic coupling between the accretion disk and X-ray corona, and/or ripples or rims in the disk.Publisher PDFPeer reviewe
The Sloan Digital Sky Survey Reverberation Mapping Project: Investigation of Continuum Lag Dependence on Broad-Line Contamination and Quasar Properties
This work studies the relationship between accretion-disk size and quasar
properties, using a sample of 95 quasars from the SDSS-RM project with measured
lags between the and photometric bands. Our sample includes disk lags
that are both longer and shorter than predicted by the \citet{SS73} model,
requiring explanations which satisfy both cases. Although our quasars each have
one lag measurement, we explore the wavelength-dependent effects of diffuse
broad line region (BLR) contamination through our sample's broad redshift
range, . We do not find significant evidence of variable diffuse
\FeII\ and Balmer nebular emission in the root-mean-square (RMS) spectra, nor
from Anderson-Darling tests of quasars in redshift ranges with and without
diffuse nebular emission falling in the observed-frame filters. Contrary to
previous work, we do not detect a significant correlation between measured
continuum and BLR lags in our luminous quasar sample, similarly suggesting that
our continuum lags are not dominated by diffuse nebular emission. Similar to
other studies, we find that quasars with larger-than-expected continuum lags
have lower 3000~\AA\ luminosity, and we additionally find longer continuum lags
with lower X-ray luminosity and black hole mass. Our lack of evidence for
diffuse BLR contribution to the lags indicates that the anti-correlation
between continuum lag and luminosity is not likely to be due to the Baldwin
effect. Instead, these anti-correlations favor models in which the continuum
lag increases in lower-luminosity AGN, including scenarios featuring magnetic
coupling between the accretion disk and X-ray corona, and/or ripples or rims in
the disk.Comment: 15 pages, 10 figure
Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548
We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The HÎČ and He ii λ4686 broad emission-line light curves lag that of the 5100 +-optical continuum by 4.17+0.36-0.36 and 0.79+0.35-0.34 days, respectively. The HÎČ lag relative to the 1158 ultraviolet continuum light curve measured by the Hubble Space Telescope is âŒ50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is âŒ50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for HÎČ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the HÎČ and He ii emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C iv, Lyα, He ii(+O iii]), and Si iv(+O iv]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured HÎČ lag is a factor of five shorter than the expected value implied by the R BLR-L AGN relation based on the past behavior of NGC 5548
The Fourteenth Data Release of the Sloan Digital Sky Survey: First Spectroscopic Data from the extended Baryon Oscillation Spectroscopic Survey and from the second phase of the Apache Point Observatory Galactic Evolution Experiment
The fourth generation of the Sloan Digital Sky Survey (SDSS-IV) has been in
operation since July 2014. This paper describes the second data release from
this phase, and the fourteenth from SDSS overall (making this, Data Release
Fourteen or DR14). This release makes public data taken by SDSS-IV in its first
two years of operation (July 2014-2016). Like all previous SDSS releases, DR14
is cumulative, including the most recent reductions and calibrations of all
data taken by SDSS since the first phase began operations in 2000. New in DR14
is the first public release of data from the extended Baryon Oscillation
Spectroscopic Survey (eBOSS); the first data from the second phase of the
Apache Point Observatory (APO) Galactic Evolution Experiment (APOGEE-2),
including stellar parameter estimates from an innovative data driven machine
learning algorithm known as "The Cannon"; and almost twice as many data cubes
from the Mapping Nearby Galaxies at APO (MaNGA) survey as were in the previous
release (N = 2812 in total). This paper describes the location and format of
the publicly available data from SDSS-IV surveys. We provide references to the
important technical papers describing how these data have been taken (both
targeting and observation details) and processed for scientific use. The SDSS
website (www.sdss.org) has been updated for this release, and provides links to
data downloads, as well as tutorials and examples of data use. SDSS-IV is
planning to continue to collect astronomical data until 2020, and will be
followed by SDSS-V.Comment: SDSS-IV collaboration alphabetical author data release paper. DR14
happened on 31st July 2017. 19 pages, 5 figures. Accepted by ApJS on 28th Nov
2017 (this is the "post-print" and "post-proofs" version; minor corrections
only from v1, and most of errors found in proofs corrected
The SDSS-V Black Hole Mapper Reverberation Mapping Project: Unusual Broad-Line Variability in a Luminous Quasar
We present a high-cadence multi-epoch analysis of dramatic variability of
three broad emission lines (MgII, H, and H) in the spectra of
the luminous quasar ((5100\r{A}) =
erg s) SDSS J141041.25+531849.0 at with 127 spectroscopic
epochs over 9 years of monitoring (2013-2022). We observe anti-correlations
between the broad emission-line widths and flux in all three emission lines,
indicating that all three broad emission lines "breathe" in response to
stochastic continuum variations. We also observe dramatic radial velocity
shifts in all three broad emission lines, ranging from 400 km
s to 800 km s, that vary over the course of the monitoring
period. Our preferred explanation for the broad-line variability is complex
kinematics in the broad-line region gas. We suggest a model for the broad-line
variability that includes a combination of gas inflow with a radial gradient,
an azimuthal asymmetry (e.g., a hot spot), superimposed on the stochastic
flux-driven changes to the optimal emission region ("line breathing"). Similar
instances of line-profile variability due to complex gas kinematics around
quasars are likely to represent an important source of false positives in
radial velocity searches for binary black holes, which typically lack the kind
of high-cadence data we analyze here. The long-duration, wide-field, and
many-epoch spectroscopic monitoring of SDSS-V BHM-RM provides an excellent
opportunity for identifying and characterizing broad emission-line variability,
and the inferred nature of the inner gas environment, of luminous quasars
Space Telescope and Optical Reverberation Mapping Project. V. Optical Spectroscopic Campaign and Emission-line Analysis for NGC 5548
We present the results of an optical spectroscopic monitoring program targeting NGC 5548 as part of a larger multiwavelength reverberation mapping campaign. The campaign spanned 6 months and achieved an almost daily cadence with observations from five ground-based telescopes. The HÎČ and He ii λ4686 broad emission-line light curves lag that of the 5100 +-optical continuum by 4.17+0.36-0.36 and 0.79+0.35-0.34 days, respectively. The HÎČ lag relative to the 1158 ultraviolet continuum light curve measured by the Hubble Space Telescope is âŒ50% longer than that measured against the optical continuum, and the lag difference is consistent with the observed lag between the optical and ultraviolet continua. This suggests that the characteristic radius of the broad-line region is âŒ50% larger than the value inferred from optical data alone. We also measured velocity-resolved emission-line lags for HÎČ and found a complex velocity-lag structure with shorter lags in the line wings, indicative of a broad-line region dominated by Keplerian motion. The responses of both the HÎČ and He ii emission lines to the driving continuum changed significantly halfway through the campaign, a phenomenon also observed for C iv, Lyα, He ii(+O iii]), and Si iv(+O iv]) during the same monitoring period. Finally, given the optical luminosity of NGC 5548 during our campaign, the measured HÎČ lag is a factor of five shorter than the expected value implied by the R BLR-L AGN relation based on the past behavior of NGC 5548
Natural climate solutions for the United States
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science Advances 4 (2018): eaat1869, doi:10.1126/sciadv.aat1869.Limiting climate warming to <2°C requires increased mitigation efforts, including land stewardship, whose potential in the United States is poorly understood. We quantified the potential of natural climate solutions (NCS)â21 conservation, restoration, and improved land management interventions on natural and agricultural landsâto increase carbon storage and avoid greenhouse gas emissions in the United States. We found a maximum potential of 1.2 (0.9 to 1.6) Pg CO2e yearâ1, the equivalent of 21% of current net annual emissions of the United States. At current carbon market prices (USD 10 per Mg CO2e), 299 Tg CO2e yearâ1 could be achieved. NCS would also provide air and water filtration, flood control, soil health, wildlife habitat, and climate resilience benefits.This study was made possible by funding from the Doris Duke Charitable
Foundation. C.A.W. and H.G. acknowledge financial support from NASAâs Carbon Monitoring
System program (NNH14ZDA001N-CMS) under award NNX14AR39G. S.D.B. acknowledges
support from the DOEâs Office of Biological and Environmental Research Program under the
award DE-SC0014416. J.W.F. acknowledges financial support from the Florida Coastal
Everglades Long-Term Ecological Research program under National Science Foundation grant
no. DEB-1237517
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