3,164 research outputs found
InAsSbBi, a direct band-gap, III-V, LWIR material
In the last several years Dr. Stringfellow's group at the University of Utah has reported success in incorporating over 3 percent Bi in InAs and 1.5 percent in InAsSb using Organometallic Vapor Phase Epitaxy (OMVPE) growth techniques. For InAs the lattice constant increase is linear with a=6.058+0.966x (InAs(1-x)Bi(x)), and a decrease in band gap energy of dEg / dx = -55meV / at a percentage Bi. Extrapolating this to the ternary minimum band gap at InAs(0.35)Sb(0.65), an addition of 1 to 2 percent Bi should drop the band gap to the 0.1 to 0.05eV range (10 to 20 microns). These alloys are direct band gap semiconductors making them candidates for far IR detectors. The current status of the InAsSbBi alloys is that good crystal morphology and x ray diffraction data has been obtained for up to 3.4 percent Bi. The Bi is metastable at these concentrations but the OMVPE grown material has been able to withstand the 400 C growth temperature for several hours without phase separation
Uncertainty-aware Flexibility Envelope Prediction in Buildings with Controller-agnostic Battery Models
Buildings are a promising source of flexibility for the application of demand
response. In this work, we introduce a novel battery model formulation to
capture the state evolution of a single building. Being fully data-driven, the
battery model identification requires one dataset from a period of nominal
controller operation, and one from a period with flexibility requests, without
making any assumptions on the underlying controller structure. We consider
parameter uncertainty in the model formulation and show how to use risk
measures to encode risk preferences of the user in robust uncertainty sets.
Finally, we demonstrate the uncertainty-aware prediction of flexibility
envelopes for a building simulation model from the Python library Energym.Comment: 7 pages, 3 figures. Submitted to the 2023 American Control Conference
(ACC
Equality Set Projection: A new algorithm for the projection of polytopes in halfspace representation
In this paper we introduce a new algorithm called Equality Set Projection (ESP) for computing the orthogonal projection of bounded, convex polytopes. Our solution addresses the case where the input polytope is represented as the intersection of a finite number of halfplanes and its projection is given in an irredundant halfspace form. Unlike many existing approaches, the key advantage offered by ESP is its output sensitivity, i.e., its complexity is a function of the number of facets in the projection of the polytope. This feature makes it particularly suited for many problems of theoretical and practical importance in which the number of vertices far exceeds the number of facets. Further, it is shown that for non-degenerate polytopes of fixed size (dimension and number of facets) the complexity is linear in the number of facets in the projection. Numerical results are presented that demonstrate that high dimensional polytopes can be projected efficiently
Rank deficiency of Kalman error covariance matrices in linear time-varying system with deterministic evolution
We prove that for-linear, discrete, time-varying, deterministic system (perfect-model) with noisy outputs, the Riccati transformation in the Kalman filter asymptotically bounds the rank of the forecast and the analysis error covariance matrices to be less than or equal to the number of nonnegative Lyapunov exponents of the system. Further, the support of these error covariance matrices is shown to be confined to the space spanned by the unstable-neutral backward Lyapunov vectors, providing the theoretical justification for the methodology of the algorithms that perform assimilation only in the unstable-neutral subspace. The equivalent property of the autonomous system is investigated as a special case
Radio Jet Feedback and Star Formation in Heavily Obscured Quasars at Redshifts ~0.3-3, I: ALMA Observations
We present ALMA 870 micron (345 GHz) data for 49 high redshift (0.47<z<2.85),
luminous (11.7 < log L(bol) (Lsun) < 14.2) radio-powerful AGN, obtained to
constrain cool dust emission from starbursts concurrent with highly obscured
radiative-mode black hole (BH) accretion in massive galaxies which possess a
small radio jet. The sample was selected from WISE with extremely steep (red)
mid-infrared (MIR) colors and with compact radio emission from NVSS/FIRST.
Twenty-six sources are detected at 870 microns, and we find that the sample has
large mid- to far-infrared luminosity ratios consistent with a dominant and
highly obscured quasar. The rest-frame 3 GHz radio powers are 24.7 < log P3.0
GHz (W/Hz) < 27.3, and all sources are radio-intermediate or radio-loud. BH
mass estimates are 7.7 < log M(BH) (Msun) < 10.2. The rest frame 1-5 um SEDs
are very similar to the "Hot DOGs" (Hot Dust Obscured Galaxies), and steeper
(redder) than almost any other known extragalactic sources. ISM masses
estimated for the ALMA detected sources are 9.9 < log M(ISM) (Msun) < 11.75
assuming a dust temperature of 30K. The cool dust emission is consistent with
star formation rates (SFRs) reaching several thousand Msun/yr, depending on the
assumed dust temperature, however we cannot rule out the alternative that the
AGN powers all the emission in some cases. Our best constrained source has
radiative transfer solutions with ~ equal contributions from an obscured AGN
and a young (10-15 Myr) compact starburst.Comment: 29 pages, 8 figures. To appear in Astrophysical Journal. Update on
Sept 14 to correct the ALMA proposal id. to ADS/JAO.ALMA#2011.0.00397.S and
to add a missing acknowledgemen
Comparison of the Near-Threshold Production of eta- and K-Mesons in Proton-Proton Collisions
The pp -> pp eta and pp -> pLambda K^+ reactions near threshold are dominated
by the first and second S_11 resonance respectively. It is shown that a
one-pion-exchange model exciting these isobars reproduces well the ratio of the
production cross sections. The consequences for this and other channels are
discussed.Comment: 10 pages, LaTeX2e, 1 eps-figur
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The global distribution of Bacillus anthracis and associated anthrax risk to humans, livestock and wildlife.
Bacillus anthracis is a spore-forming, Gram-positive bacterium responsible for anthrax, an acute infection that most significantly affects grazing livestock and wild ungulates, but also poses a threat to human health. The geographic extent of B. anthracis is poorly understood, despite multi-decade research on anthrax epizootic and epidemic dynamics; many countries have limited or inadequate surveillance systems, even within known endemic regions. Here, we compile a global occurrence dataset of human, livestock and wildlife anthrax outbreaks. With these records, we use boosted regression trees to produce a map of the global distribution of B. anthracis as a proxy for anthrax risk. We estimate that 1.83 billion people (95% credible interval (CI): 0.59-4.16 billion) live within regions of anthrax risk, but most of that population faces little occupational exposure. More informatively, a global total of 63.8 million poor livestock keepers (95% CI: 17.5-168.6 million) and 1.1 billion livestock (95% CI: 0.4-2.3 billion) live within vulnerable regions. Human and livestock vulnerability are both concentrated in rural rainfed systems throughout arid and temperate land across Eurasia, Africa and North America. We conclude by mapping where anthrax risk could disrupt sensitive conservation efforts for wild ungulates that coincide with anthrax-prone landscapes
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