22,653 research outputs found
Sources, control, and effects of noise from aircraft propellers and rotors
Source noise predictions are compared with measurements for conventional low-speed propellers, for new high speed propellers (propfans), and for a helicopter. Results from a light aircraft demonstration program are described, indicating that about 5-dB reduction of flyover noise can be obtained without significant performance penalty. Sidewall design studies are described for interior noise control in light general aviation aircraft and in large transports using propfan propulsion. The weight of the added acoustic treatment is estimated and tradeoffs between weight and noise reduction are discussed. A laboratory study of passenger response to combined broadband and tonal propeller like noise is described. Subject discomfort ratings of combined tone broadband noises are compared with ratings of broadband (boundary layer) noise alone, and the relative importance of the propeller tones is examined
Idea Theft: Frivolous Copyright-Lite Claims, or Hollywood Business Model?
Two facts regarding idea theft in the creative context are undeniable—first, that idea misappropriation claims against Hollywood studios and television producers are rampant, and second, that the hodge-podge legal regime surrounding idea submission claims is in disarray. Institutional entertainment industry players, such as major Hollywood studios, dismiss idea theft claims as fake and frivolous, a kind of “copyrightlite” claim brought by unsuccessful wannabe writers and producers. In contrast, non-established creators seeking entry to the elite and lucrative world of Hollywood tell another tale—that of an industry that relies on the creative ides of outsiders, and fleeces idea submitters as a routine business practice. Some of these practices no doubt feed into the narrative that represents Hollywood “as a dangerous place for filmmakers with vision and integrity and many filmmakers believe that it is important to stay out of the Hollywood studios entirely in order to maintain their artistic independence.
Extracting New Physics from the CMB
We review how initial state effects generically yield an oscillatory
component in the primordial power spectrum of inflationary density
perturbations. These oscillatory corrections parametrize unknown new physics at
a scale and are potentially observable if the ratio is
sufficiently large. We clarify to what extent present and future CMB data
analysis can distinguish between the different proposals for initial state
corrections.Comment: Invited talk by B. Greene at the XXII Texas Symposium on Relativistic
Astrophysics, Stanford University, 13-17 December 2004, (TSRA04-0001), 8
pages, LaTeX, some references added, added paragraph at the end of section 2
and an extra note added after the conclusions regarding modifications to the
large k power spectra deduced from galaxy survey
Point-contact spectroscopy in heavy-fermion superconductors
We develop a minimal model to calculate point-contact spectra between a
metallic tip and a superconducting heavy-fermion system. We apply our tunneling
model to the heavy fermion CeCoIn5, both in the normal and superconducting
state. In point-contact and scanning tunneling spectroscopy many heavy-fermion
materials, like CeCoIn5, exhibit an asymmetric differential conductance, dI/dV,
combined with a strongly suppressed Andreev reflection signal in the
superconducting state. We argue that both features may be explained in terms of
a multichannel tunneling model in the presence of localized states near the
interface. We find that it is not sufficient to tunnel into two itinerant bands
of light and heavy electrons to explain the Fano line shape of the differential
conductance. Localized states in the bulk or near the interface are an
essential component for quantum interference to occur when an electron tunnels
from the metallic tip of the point contact into the heavy-fermion system.Comment: 13 pages, 9 figures. Accepted for publication in Physical Review
Andreev Reflection in Heavy-Fermion Superconductors and Order Parameter Symmetry in CeCoIn_5
Differential conductance spectra are obtained from nanoscale junctions on the
heavy-fermion superconductor CeCoIn along three major crystallographic
orientations. Consistency and reproducibility of characteristic features among
the junctions ensure their spectroscopic nature. All junctions show a similar
conductance asymmetry and Andreev reflection-like conductance with reduced
signal (~ 10%-13%), both commonly observed in heavy-fermion superconductor
junctions. Analysis using the extended Blonder-Tinkham-Klapwijk model indicates
that our data provide the first spectroscopic evidence for
symmetry. To quantify our conductance spectra, we propose a model by
considering the general phenomenology in heavy fermions, the two-fluid
behavior, and an energy-dependent density of states. Our model fits to the
experimental data remarkably well and should invigorate further investigations.Comment: 4 pages, 4 figures; Phys. Rev. Lett., published versio
&-prolog and its performance: exploiting independent and-parallelism
An Independent And-Parallel Prolog model and implementation, &-Prolog, are described. The description includes a summary of the system's architecture, some details of its execution model (based on the RAP-WAM model), and most importantly, its performance on sequential workstations and shared memory multiprocessors as compared with state-of-the-art Prolog systems. Speedup curves are provided for a collection of benchmark programs which demónstrate significant speed advantages over state-of the art sequential systems
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