926 research outputs found
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Modeling patterns of hot water use in households
This report presents a detailed model of hot water use patterns in individual household. The model improves upon an existing model by including the effects of four conditions that were previously unaccounted for: the absence of a clothes washer; the absence of a dishwasher; a household consisting of seniors only; and a household that does not pay for its own hot water use. Although these four conditions can significantly affect residential hot water use, and have been noted in other studies, this is the first time that they have been incorporated into a detailed model. This model allows detailed evaluation of the impact of potential efficiency standards for water heaters and other market transformation policies. 21 refs., 3 figs., 10 tabs
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Recovery and recycling of aluminum, copper, and precious metals from dismantled weapon components
Sandia National Laboratories (SNL) is tasked to support the Department of Energy in the dismantlement and disposal of SNL designed weapon components. These components are sealed in a potting compound, and contain heavy metals, explosive, radioactive, and toxic materials in discrete sub-components. SNL developed and demonstrated a process to identify and remove the hazardous sub-components utilizing real-time radiography and abrasive water-jet cutting. The remaining components were then crushed, granulated, screened, and separated into an aluminum and a precious-and-base-metals fraction using air-tables. Plastics were further cleaned for disposal as non-hazardous waste. The New Mexico Bureau of Mines & Mineral Resources assisted SNL in investigation of size-reduction and separation technologies and in the development of a conceptual design for a mechanical separation system
On kinematical constraints in boson-boson systems
We consider the scattering of two-bosons with negative parity and spin 0 or
1. Starting from helicity partial-wave scattering amplitudes we derive
transformations that eliminate all kinematical constraints. Such amplitudes are
expected to satisfy partial-wave dispersion relations and therefore provide a
suitable basis for data analysis and the construction of effective field
theories. Our derivation relies on a decomposition of the various scattering
amplitudes into suitable sets of invariant functions. A novel algebra was
developed that permits the efficient computation of such functions in terms of
computer algebra codes.Comment: 14 pages, 8 table
Characterisation of Potential Landing Sites for the European Space Agency's Lunar Lander Project
This article describes the characterization activities of the landing sites
currently envisaged for the Lunar Lander mission of the European Space Agency.
These sites have been identified in the South Pole Region (-85{\deg} to
-90{\deg} latitude) based on favourable illumination conditions, which make it
possible to have a long-duration mission with conventional power and thermal
control subsystems, capable of enduring relatively short periods of darkness
(in the order of tens of hours), instead of utilising Radioisotope Heating
Units. The illumination conditions are simulated at the potential landing sites
based on topographic data from the Lunar Orbiter Laser Altimeter (LOLA), using
three independent tools. Risk assessment of the identified sites is also being
performed through independent studies. Long baseline slopes are assessed based
on LOLA, while craters and boulders are detected both visually and using
computer tools in Lunar Reconnaissance Orbiter Camera (LROC) images, down to a
size of less than 2 m, and size-frequency distributions are generated. Shadow
hazards are also assessed via LROC images. The preliminary results show that
areas with quasi-continuous illumination of several months exist, but their
size is small (few hundred metres); the duration of the illumination period
drops quickly to less than one month outside the areas, and some areas present
gaps with short illumination periods. Concerning hazard distributions, 50 m
slopes are found to be shallow (few degrees) based on LOLA, whereas at the
scale of the lander footprint (~5 m) they are mostly dominated by craters,
expected to be mature (from geological context) and shallow (~11{\deg}). The
preliminary conclusion is that the environment at the prospective landing sites
is within the capabilities of the Lander design
Light meson mass dependence of the positive parity heavy-strange mesons
We calculate the masses of the resonances D_{s0}^*(2317) and D_{s1}(2460) as
well as their bottom partners as bound states of a kaon and a D^*- and
B^*-meson, respectively, in unitarized chiral perturbation theory at
next-to-leading order. After fixing the parameters in the D_{s0}^*(2317)
channel, the calculated mass for the D_{s1}(2460) is found in excellent
agreement with experiment. The masses for the analogous states with a bottom
quark are predicted to be M_{B^*_{s0}}=(5696\pm 40) MeV and M_{B_{s1}}=(5742\pm
40) MeV in reasonable agreement with previous analyses. In particular, we
predict M_{B_{s1}}-M_{B_{s0}^*}=46\pm 1 MeV. We also explore the dependence of
the states on the pion and kaon masses. We argue that the kaon mass dependence
of a kaonic bound state should be almost linear with slope about unity. Such a
dependence is specific to the assumed molecular nature of the states. We
suggest to extract the kaon mass dependence of these states from lattice QCD
calculations.Comment: 10 page
Prospects for the CERN Axion Solar Telescope Sensitivity to 14.4 keV Axions
The CERN Axion Solar Telescope (CAST) is searching for solar axions using the
9.0 T strong and 9.26 m long transverse magnetic field of a twin aperture LHC
test magnet, where axions could be converted into X-rays via reverse Primakoff
process. Here we explore the potential of CAST to search for 14.4 keV axions
that could be emitted from the Sun in M1 nuclear transition between the first,
thermally excited state, and the ground state of 57Fe nuclide. Calculations of
the expected signals, with respect to the axion-photon coupling, axion-nucleon
coupling and axion mass, are presented in comparison with the experimental
sensitivity.Comment: 4 pages, 1 figure. Submitted to Nucl. Instr. and Meth.
Negative Parity 70-plet Baryon Masses in the 1/Nc Expansion
The masses of the negative parity SU(6) 70-plet baryons are analyzed in the
1/Nc expansion to order 1/Nc and to first order in SU(3) breaking. At this
level of precision there are twenty predictions. Among them there are the well
known Gell-Mann Okubo and equal spacing relations, and four new relations
involving SU(3) breaking splittings in different SU(3) multiplets. Although the
breaking of SU(6) symmetry occurs at zeroth order in 1/Nc, it turns out to be
small. The dominant source of the breaking is the hyperfine interaction which
is of order 1/Nc. The spin-orbit interaction, of zeroth order in 1/Nc, is
entirely fixed by the splitting between the singlet states Lambda(1405) and
Lambda(1520), and the spin-orbit puzzle is solved by the presence of other
zeroth order operators involving flavor exchange.Comment: 31 pages, 3 figure
The LABOCA survey of the extended Chandra Deep Field South : two modes of star formation in active galactic nucleus hosts?
We study the co-existence of star formation and active galactic nucleus (AGN) activity in Chandra X-ray-selected AGN by analyzing stacked 870 μm submillimeter emission from a deep and wide map of the Extended Chandra Deep Field South (ECDFS), obtained with the LABOCA instrument at the APEX telescope. The total X-ray sample of 895 sources with median redshift z ~ 1 drawn from the combined (E)CDFS X-ray catalogs is detected at >11σ significance at a mean submillimeter flux of 0.49 ± 0.04 mJy, corresponding to a typical star formation rate (SFR) around 30 M sun yr-1 for a T = 35 K, β = 1.5 graybody far-infrared spectral energy distribution. The good signal-to-noise ratio permits stacking analyses for major subgroups, splitting the sample by redshift, intrinsic luminosity, and AGN obscuration properties. We observe a trend of SFR increasing with redshift. An increase of SFR with AGN luminosity is indicated at the highest L 2-10 keV >~ 1044 erg s-1 luminosities only. Increasing trends with X-ray obscuration as expected in some AGN evolutionary scenarios are not observed for the bulk of the X-ray AGN sample but may be present for the highest intrinsic luminosity objects with L 2-10 keV >~ 1044 erg s-1. This behavior suggests a transition between two modes in the co-existence of AGN activity and star formation. For the bulk of the sample, the X-ray luminosity and obscuration of the AGN are not intimately linked to the global SFR of their hosts. The hosts are likely massive and forming stars secularly, at rates similar to the pervasive star formation seen in massive galaxies without an AGN at similar redshifts. In these systems, star formation is not linked to a specific state of the AGN and the period of moderately luminous AGN activity may not highlight a major evolutionary transition of the galaxy. The change indicated toward more intense star formation, and a more pronounced increase in SFRs between unobscured and obscured AGN reported in the literature at highest (L 2-10 keV >~ 1044 erg s-1) luminosities suggests that these luminous AGNs follow an evolutionary path on which obscured AGN activity and intense star formation are linked, possibly via merging. Comparison to local hard X-ray-selected AGN supports this interpretation. SFRs in the hosts of moderate luminosity AGN at z ~ 1 are an order of magnitude higher than at z ~ 0, following the increase in the non-AGN massive galaxy population. At high AGN luminosities, hosts on the evolutionary link/merger path emerge from this secular level of star formation
Charm and hidden charm scalar mesons in the nuclear medium
We study the renormalization of the properties of low lying charm and hidden
charm scalar mesons in a nuclear medium, concretely of the D_{s0}(2317) and the
theoretical hidden charm state X(3700). We find that for the D_{s0}(2317), with
negligible width at zero density, the width becomes about 100 MeV at normal
nuclear matter density, while in the case of the X(3700) the width becomes as
large as 200 MeV. We discuss the origin of this new width and trace it to
reactions occurring in the nucleus, while offering a guideline for future
experiments testing these changes. We also show how those medium modifications
will bring valuable information on the nature of the scalar resonances and the
mechanisms of the interaction of D mesons with nucleons and nuclei
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