37,471 research outputs found
Handbook of noise ratings
Handbook announced in Tech Brief is compendium of information describing multifarious noise methods now in use. Reference material gives user better access to definitions, application, and calculation procedures of current noise rating methods
Effects of interior aircraft noise on speech intelligibility and annoyance
Recordings of the aircraft ambiance from ten different types of aircraft were used in conjunction with four distinct speech interference tests as stimuli to determine the effects of interior aircraft background levels and speech intelligibility on perceived annoyance in 36 subjects. Both speech intelligibility and background level significantly affected judged annoyance. However, the interaction between the two variables showed that above an 85 db background level the speech intelligibility results had a minimal effect on annoyance ratings. Below this level, people rated the background as less annoying if there was adequate speech intelligibility
The NASA low thrust propulsion program
The NASA OAST Propulsion, Power, and Energy Division supports a low thrust propulsion program aimed at providing high performance options for a broad range of near-term and far-term mission and vehicles. Low thrust propulsion has a major impact on the mission performance of essentially all spacecraft and vehicles. On-orbit lifetimes, payloads, and trip times are significantly impacted by low thrust propulsion performance and integration features for Earth-to-orbit (ETO) vehicles, Earth-orbit and planetary spacecraft, and large platforms in Earth orbit. Major emphases are on low thrust chemical propulsion, both storables and hydrogen/oxygen; low-power (auxiliary) electric arcjects and resistojets; and high-power (primary) electric propulsion, including ion, magnetoplasmadynamic (MPD), and electrodeless concepts. The major recent accomplishments of the program are presented and their impacts discussed
Handbook of aircraft noise metrics
Information is presented on 22 noise metrics that are associated with the measurement and prediction of the effects of aircraft noise. Some of the instantaneous frequency weighted sound level measures, such as A-weighted sound level, are used to provide multiple assessment of the aircraft noise level. Other multiple event metrics, such as day-night average sound level, were designed to relate sound levels measured over a period of time to subjective responses in an effort to determine compatible land uses and aid in community planning. The various measures are divided into: (1) instantaneous sound level metrics; (2) duration corrected single event metrics; (3) multiple event metrics; and (4) speech communication metrics. The scope of each measure is examined in terms of its: definition, purpose, background, relationship to other measures, calculation method, example, equipment, references, and standards
Electrodynamics of Bose-Einstein condensates in angular motion
A theory determining the electric and magnetic properties of vortex states in
Bose-Einstein condensates (BECs) is presented. The principal ingredient is the
Lagrangian of the system which we derive correct to the first order in the
atomic centre of mass velocity. For the first time using centre of mass
coordinates, a gauge transformation is performed and relevant relativistic
corrections are included. The Lagrangian is symmetric in the electric and
magnetic aspects of the problem and includes two key interaction terms, namely
the Aharanov-Casher and the Roentgen interaction terms. The constitutive
relations, which link the electromagnetic fields to the matter fields via their
electric polarisation and magnetisation, follow from the Lagrangian as well as
the corresponding Hamiltonian. These relations, together with a generalised
Gross-Pitaevskii equation, determine the magnetic (electric) monopole charge
distributions accompanying an order n vortex state when the constituent atoms
are characterised by an electric dipole (magnetic dipole). Field distributions
associated with electric dipole active (magnetic dipole active) BECs in a
vortex state are evaluated for an infinite- and a finite-length cylindrical
BEC. The predictd monopole charge distributions, both electric and magnetic,
automatically satisfy the requirement of global charge neutrality and the
derivations highlight the exact symmetry between the electric and magnetic
properties. Order of magnitude estimates of the effects are given for an atomic
gas BEC, superfluid helium and a spin-polarised hydrogen BEC.Comment: 23 pages, 2 figures, submitted to Journal of Optics
The Initial Value Problem For Maximally Non-Local Actions
We study the initial value problem for actions which contain non-trivial
functions of integrals of local functions of the dynamical variable. In
contrast to many other non-local actions, the classical solution set of these
systems is at most discretely enlarged, and may even be restricted, with
respect to that of a local theory. We show that the solutions are those of a
local theory whose (spacetime constant) parameters vary with the initial value
data according to algebraic equations. The various roots of these algebraic
equations can be plausibly interpreted in quantum mechanics as different
components of a multi-component wave function. It is also possible that the
consistency of these algebraic equations imposes constraints upon the initial
value data which appear miraculous from the context of a local theory.Comment: 8 pages, LaTeX 2 epsilo
Thermodynamics and the Measure of Entanglement
We point out formal correspondences between thermodynamics and entanglement.
By applying them to previous work, we show that entropy of entanglement is the
unique measure of entanglement for pure states.Comment: 8 pages, RevTeX; edited for clarity, additional references, to appear
as a Rapid Communication in Phys. Rev.
Limits on the Halo White Dwarf Component of Baryonic Dark Matter from the {\em Hubble Deep Field}
The MACHO collaboration lensing event statistics suggest that a significant
fraction of the dark galactic halo can be comprised of baryonic matter in the
form of white dwarf stars with masses between 0.1 and 1.0 \Msun . Such a halo
white dwarf population, in order to have escaped detection by those who observe
the white dwarf luminosity function of the disk, must have formed from an old
population. The observations indicate that the number of halo white dwarfs per
cubic parsec per unit bolometric magnitude is less than at
\Lsun; the number must rise significantly at lower luminosities to
provide the needed baryonic halo mass. Such white dwarfs may easily escape
detection in most current and earlier surveys. Though it is limited in angular
extent, the {\em Hubble Deep Field} (HDF) probes a sufficient volume of the
galactic halo to provide interesting limits on the number of halo white dwarf
stars, and on the fraction of the halo mass that they can make up. If the HDF
field can be probed for stars down to then the MACHO result suggests
that there could be up to 12 faint halo white dwarfs visible in the HDF.
Finding (or not finding) these stars in turn places interesting constraints on
star formation immediately following the formation of the galaxy.Comment: 10 pages, AASTEX, 1 table, no figures, accepted for publication in
Ap.J. Letter
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