29,885 research outputs found
A new technique for monitoring the water vapor in the atmosphere
In the correction of satellite Doppler data for tropospheric effects the precipitable water vapor (PWV) is inferred at the tracking site. The technique depends on: (1) an ephemeris for the satellite; (2) an analytic model for the refraction range effect that is good to a few centimeters; (3) Doppler data with noise level below 10 centimeters; and (4) a surface pressure/temperature measurement at the tracking site. The PWV is a by product of the computation necessary to correct the Doppler data for tropospheric effects. A formulation of the refraction integral minimizes the necessity for explicit water vapor, temperature and pressure profiles
Complementary Ansatz for the neutrino mass matrix
We propose a simple Ansatz for the three generation neutrino mass matrix
which is motivated from an SO(10) grand unified theory. The Ansatz can
be combined with information from neutrino oscillation experiments and bounds
on neutrinoless double beta decay to determine the neutrino masses themselves
and to reconstruct, with some assumptions, the matrix .Comment: 15 pages, RevteX, submitted to Phys. Rev.
Particle Dynamics in Damped Nonlinear Quadrupole Ion Traps
We examine the motions of particles in quadrupole ion traps as a function of
damping and trapping forces, including cases where nonlinear damping or
nonlinearities in the electric field geometry play significant roles. In the
absence of nonlinearities, particles are either damped to the trap center or
ejected, while their addition brings about a rich spectrum of stable closed
particle trajectories. In three-dimensional (3D) quadrupole traps, the extended
orbits are typically confined to the trap axis, and for this case we present a
1D analysis of the relevant equation of motion. We follow this with an analysis
of 2D quadrupole traps that frequently show diamond-shaped closed orbits. For
both the 1D and 2D cases we present experimental observations of the calculated
trajectories in microparticle ion traps. We also report the discovery of a new
collective behavior in damped 2D microparticle ion traps, where particles
spontaneously assemble into a remarkable knot of overlapping, corotating
diamond orbits, self-stabilized by air currents arising from the particle
motion
Development of material specifications and qualifications of polymeric materials for the jpl spacecraft materials guidebook. ii- rtv silicone adhesives and potting compounds special report no. 2
Silicone rubber adhesives and potting compounds - polymeric materials for spacecraf
Development of material specifications and qualifications of polymeric materials for the jpl spacecraft materials guide book. iii- polyfluorocarbon films special report no. 3
Outgassing studies of polyfluorocarbon films - investigation of polymers as spacecraft construction material
Investigating the Light Scalar Mesons
We first briefly review a treatment of the scalars in meson meson scattering
based on a non-linear chiral Lagrangian, with unitarity implemented by a
"local" modification of the scalar propagators. It is shown that the main
results are confirmed by a treatment in the SU(3) linear sigma model in which
unitarity is implemented "globally". Some remarks are made on the speculative
subject of the scalars' quark structure.Comment: 9 pages,3 figures,talk at hadron2001, Protvin
Variable pitch fan system for NASA/Navy research and technology aircraft
Preliminary design of a shaft driven, variable-pitch lift fan and lift-cruise fan was conducted for a V/STOL Research and Technology Aircraft. The lift fan and lift-cruise fan employed a common rotor of 157.5 cm diameter, 1.18 pressure ratio variable-pitch fan designed to operate at a rotor-tip speed of 284 mps. Fan performance maps were prepared and detailed aerodynamic characteristics were established. Cost/weight/risk trade studies were conducted for the blade and fan case. Structural sizing was conducted for major components and weights determined for both the lift and lift-cruise fans
Macroscopic coherence effects in a mesoscopic system: Weak localization of thin silver films in an undergraduate lab
We present an undergraduate lab that investigates weak localization in thin
silver films. The films prepared in our lab have thickness, , between 60-200
\AA, a mesoscopic length scale. At low temperatures, the inelastic dephasing
length for electrons, , exceeds the thickness of the film (), and the films are then quasi-2D in nature. In this situation, theory
predicts specific corrections to the Drude conductivity due to coherent
interference between conducting electrons' wavefunctions, a macroscopically
observable effect known as weak localization. This correction can be destroyed
with the application of a magnetic field, and the resulting magnetoresistance
curve provides information about electron transport in the film. This lab is
suitable for Junior or Senior level students in an advanced undergraduate lab
course.Comment: 16 pages, 9 figures. Replaces earlier version of paper rejected by
Am. J. Phys. because of too much content on vacuum systems. New version deals
with the undergraduate experiment on weak localization onl
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