48,864 research outputs found
Application of conformal mapping to diffraction and scattering problems
Integral equation method based on conformal mapping applied to scattering and diffraction problems of plane waves by infinite cylinder with arbitrary cross sectio
Scientific publications of the bioscience programs division. Volume 5 - Planetary quarantine
Bibliography and indexes on planetary quarantin
NASA contract listings of publications under the behavioral biology program
Behavioral biology - bibliograph
Multiple scattering in random mechanical systems and diffusion approximation
This paper is concerned with stochastic processes that model multiple (or
iterated) scattering in classical mechanical systems of billiard type, defined
below. From a given (deterministic) system of billiard type, a random process
with transition probabilities operator P is introduced by assuming that some of
the dynamical variables are random with prescribed probability distributions.
Of particular interest are systems with weak scattering, which are associated
to parametric families of operators P_h, depending on a geometric or mechanical
parameter h, that approaches the identity as h goes to 0. It is shown that (P_h
-I)/h converges for small h to a second order elliptic differential operator L
on compactly supported functions and that the Markov chain process associated
to P_h converges to a diffusion with infinitesimal generator L. Both P_h and L
are selfadjoint (densely) defined on the space L2(H,{\eta}) of
square-integrable functions over the (lower) half-space H in R^m, where {\eta}
is a stationary measure. This measure's density is either (post-collision)
Maxwell-Boltzmann distribution or Knudsen cosine law, and the random processes
with infinitesimal generator L respectively correspond to what we call MB
diffusion and (generalized) Legendre diffusion. Concrete examples of simple
mechanical systems are given and illustrated by numerically simulating the
random processes.Comment: 34 pages, 13 figure
Advanced nickel-cadmium batteries for geosynchronous spacecraft
A nickel cadmium battery was developed that can be operated at 80 percent depth of discharge in excess of 10 years in a geosynchronous orbit application, and has about a 30 percent weight savings per spacecraft over present nickel cadmium batteries when used with a 1000 watts eclipse load. The approach used in the development was to replace nylon separators with inert polymer impregnated zirconia, use electrochemically deposited plates in place of conventional chemically precipitated ones, and use an additive to extend negative plate lifetime. The design has undergone extensive testing using both engineering and protoflight cell configurations
Enhanced dielectric response by disordered nanoscale/mesoscopic insulators
Enhancement of the dielectric response of insulators by disorder is
theoretically proposed, where the quantum interference of electronic waves
through the nanoscale/mesoscopic system and its change due to external
perturbations control the polarization. In the disordered case with all the
states being localized, the resonant tunneling, which is topologically
protected, plays a crucial role, and enhances the dielectric response by a
factor 30~40 compared with the pure case. Realization of this idea with
accessible materials/structures is also discussed.Comment: 4 pages including 3 figures; minor revision; a high-resolution figure
available at http://appi.t.u-tokyo.ac.jp/~sonoda/papers.htm
Measuring Dark Energy with Gamma-Ray Bursts and Other Cosmological Probes
It has been widely shown that the cosmological parameters and dark energy can
be constrained by using data from type-Ia supernovae (SNe Ia), the cosmic
microwave background (CMB) anisotropy, the baryon acoustic oscillation (BAO)
peak from Sloan Digital Sky Survey (SDSS), the X-ray gas mass fraction in
clusters, and the linear growth rate of perturbations at z=0.15 as obtained
from the 2dF Galaxy Redshift Survey. Recently, gamma-ray bursts (GRBs) have
also been argued to be promising standard candles for cosmography. In this
paper, we present constraints on the cosmological parameters and dark energy by
combining a recent GRB sample including 69 events with the other cosmological
probes. First, we find that for the LambdaCDM cosmology this combination makes
the constraints stringent and the best fit is close to the flat universe.
Second, we fit the flat Cardassian expansion model and find that this model is
consistent with the LambdaCDM cosmology. Third, we present constraints on
several two-parameter dark energy models and find that these models are also
consistent with the LambdaCDM cosmology. Finally, we reconstruct the dark
energy equation-of-state parameter w(z) and the deceleration parameter q(z). We
see that the acceleration could have started at a redshift from
z_T=0.40_{-0.08}^{+0.14} to z_T=0.65_{-0.05}^{+0.10}. This difference in the
transition redshift is due to different dark energy models that we adopt. The
most stringent constraint on w(z) lies in the redshift range z\sim 0.3-0.6.Comment: 28 pages, 13 figures, accepted for publication in ApJ. One reference
added, one minor change in the final paragraph of section
Hadronization Approach for a Quark-Gluon Plasma Formed in Relativistic Heavy Ion Collisions
A transport model is developed to describe hadron emission from a strongly
coupled quark-gluon plasma formed in relativistic heavy ion collisions. The
quark-gluon plasma is controlled by ideal hydrodynamics, and the hadron motion
is characterized by a transport equation with loss and gain terms. The two sets
of equations are coupled to each other, and the hadronization hypersurface is
determined by both the hydrodynamic evolution and the hadron emission. The
model is applied to calculate the transverse momentum distributions of mesons
and baryons, and most of the results agree well with the experimental data at
RHIC.Comment: 16 pages, 24 figures. Version accepted by PR
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