17,036 research outputs found
High performance low-energy buildings
The era of legislation and creditable methods towards producing sustainable buildings is upon us. Yet, a major barrier to achieving environmental responsive design is in the lack of available information at the programming or pre-design phases of a project. The review and evaluation of climate as well as energy-efficient strategies could be difficult to consider at these preliminary stages. Until recently, introducing energy simulation tools at the design stage has been difficult and perhaps next to impossible at a pre-design or programming stage. However, analysis of this sort is essential to ‘green building rating’ or performance assessment schemes such as LEED (Leadership in Energy and Environmental Design) and BREEAM (Building Research Establishment Environment Assessment Method). This paper discusses the implementation of a particular tool, ENERGY-10, where ‘basecase’ building defaults are compared to a low-energy case which has applied multiple energy-efficient strategies automatically. An annual hour-by-hour simulation provides a daylighting calculation with a subsequent thermal evaluation. Calculation results provide energy consumption, peak load equipment sizing, a RANK feature of the energy-efficient strategies, reporting of CO2, SO2 and NOx reduction, optimum glazing type as well as excellent graphic output. Consideration is given as to the approach of how such information can be introduced into the building project brief enforcing a low-energyperformance target.<br /
Fermi liquid theory of ultra-cold trapped Fermi gases: Implications for Pseudogap Physics and Other Strongly Correlated Phases
We show how Fermi liquid theory can be applied to ultra-cold Fermi gases,
thereby expanding their "simulation" capabilities to a class of problems of
interest to multiple physics sub-disciplines. We introduce procedures for
measuring and calculating position dependent Landau parameters. This lays the
ground work for addressing important controversial issues: (i) the suggestion
that thermodynamically, the normal state of a unitary gas is indistinguishable
from a Fermi liquid (ii) that a fermionic system with strong repulsive contact
interactions is associated with either ferromagnetism or localization; this
relates as well to He and its p-wave superfluidity.Comment: 4 pages, 2 figures, revised versio
W-band waveguide-packaged InP HEMT reflection grid amplifier
This letter presents a 79-GHz broadband reflection-type grid amplifier using spatial power combining to combine the power of 64 unit cells. Each unit cell uses a two-stage cascade configuration with InP HEMTs arranged as a differential pair. A broadband orthogonal mode transducer (OMT) separates two orthogonally polarized input and output signals over a 75 to 85GHz range. In conjunction with the OMT, a mode converter with quadruple-ridged apertures was designed to enhance the field uniformity over the active grid. Measurements show 5-dB small signal gain at 79GHz and an 800-MHz 3-dB bandwidth. The amplifier generates an output power of 264mW with little evidence of saturation
Higgs Triplets, Decoupling, and Precision Measurements
Electroweak precision data has been extensively used to constrain models
containing physics beyond that of the Standard Model. When the model contains
Higgs scalars in representations other than SU(2) singlets or doublets, and
hence rho not equal to one at tree level, a correct renormalization scheme
requires more inputs than the three needed for the Standard Model. We discuss
the connection between the renormalization of models with Higgs triplets and
the decoupling properties of the models as the mass scale for the scalar
triplet field becomes much larger than the electroweak scale. The requirements
of perturbativity of the couplings and agreement with electroweak data place
strong restrictions on models with Higgs triplets. Our results have important
implications for Little Higgs type models and other models with rho not equal
to one at tree level.Comment: 23 page
Electron tomography at 2.4 {\AA} resolution
Transmission electron microscopy (TEM) is a powerful imaging tool that has
found broad application in materials science, nanoscience and biology(1-3).
With the introduction of aberration-corrected electron lenses, both the spatial
resolution and image quality in TEM have been significantly improved(4,5) and
resolution below 0.5 {\AA} has been demonstrated(6). To reveal the 3D structure
of thin samples, electron tomography is the method of choice(7-11), with
resolutions of ~1 nm^3 currently achievable(10,11). Recently, discrete
tomography has been used to generate a 3D atomic reconstruction of a silver
nanoparticle 2-3 nm in diameter(12), but this statistical method assumes prior
knowledge of the particle's lattice structure and requires that the atoms fit
rigidly on that lattice. Here we report the experimental demonstration of a
general electron tomography method that achieves atomic scale resolution
without initial assumptions about the sample structure. By combining a novel
projection alignment and tomographic reconstruction method with scanning
transmission electron microscopy, we have determined the 3D structure of a ~10
nm gold nanoparticle at 2.4 {\AA} resolution. While we cannot definitively
locate all of the atoms inside the nanoparticle, individual atoms are observed
in some regions of the particle and several grains are identified at three
dimensions. The 3D surface morphology and internal lattice structure revealed
are consistent with a distorted icosahedral multiply-twinned particle. We
anticipate that this general method can be applied not only to determine the 3D
structure of nanomaterials at atomic scale resolution(13-15), but also to
improve the spatial resolution and image quality in other tomography
fields(7,9,16-20).Comment: 27 pages, 17 figure
Quark energy loss and shadowing in nuclear Drell-Yan process
The energy loss effect in nuclear matter is another nuclear effect apart from
the nuclear effects on the parton distribution as in deep inelastic scattering
process. The quark energy loss can be measured best by the nuclear dependence
of the high energy nuclear Drell-Yan process. By means of three kinds of quark
energy loss parameterizations given in literature and the nuclear parton
distribution extracted only with lepton-nucleus deep inelastic scattering
experimental data, measured Drell-Yan production cross sections are analyzed
for 800GeV proton incident on a variety of nuclear targets from FNAL E866. It
is shown that our results with considering the energy loss effect are much
different from these of the FNAL E866 who analysis the experimental data with
the nuclear parton distribution functions obtained by using the deep inelastic
lA collisions and pA nuclear Drell-Yan data . Considering the existence of
energy loss effect in Drell-Yan lepton pairs production,we suggest that the
extraction of nuclear parton distribution functions should not include
Drell-Yan experimental data.Comment: 12 page
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