18,328 research outputs found
Multipole Expansions of Aggregate Charge: How Far to Go?
Aggregates immersed in a plasma or radiative environment will have charge
distributed over their extended surface. Previous studies have modeled the
aggregate charge using the monopole and dipole terms of a multipole expansion,
with results indicating that the dipole-dipole interactions play an important
role in increasing the aggregation rate and altering the morphology of the
resultant aggregates. This study examines the effect that including the
quadrupole terms has on the dynamics of aggregates interacting with each other
and the confining electric fields in laboratory experiments. Results are
compared to modeling aggregates as a collection of point charges located at the
center of each spherical monomer comprising the aggregate.Comment: 6 page
Application of adaptive antenna techniques to future commercial satellite communication
The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further sub-divided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems
Application of adaptive antenna techniques to future commercial satellite communications. Executive summary
The purpose of this contract was to identify the application of adaptive antenna technique in future operational commercial satellite communication systems and to quantify potential benefits. The contract consisted of two major subtasks. Task 1, Assessment of Future Commercial Satellite System Requirements, was generally referred to as the Adaptive section. Task 2 dealt with Pointing Error Compensation Study for a Multiple Scanning/Fixed Spot Beam Reflector Antenna System and was referred to as the reconfigurable system. Each of these tasks was further subdivided into smaller subtasks. It should also be noted that the reconfigurable system is usually defined as an open-loop system while the adaptive system is a closed-loop system. The differences between the open- and closed-loop systems were defined. Both the adaptive and reconfigurable systems were explained and the potential applications of such systems were presented in the context of commercial communication satellite systems
Magnetic Fields in Star-Forming Molecular Clouds I. The First Polarimetry of OMC-3 in Orion A
The first polarimetric images of the OMC-3 region of the Orion A filamentary
molecular cloud are presented. Using the JCMT, we have detected polarized
thermal emission at 850 microns from dust along a 6' length of the dense
filament. The polarization pattern is highly ordered and is aligned with the
filament throughout most of the region. The plane-of-sky magnetic field
direction is perpendicular to the measured polarization. The mean percentage
polarization is 4.2% with a 1 sigma dispersion of 1%. This region is part of
the integral-shaped filament, and active star formation is ongoing along its
length. The protostellar outflow directions do not appear to be consistently
correlated with the direction of the plane-of-sky field or the filament
structure itself. Depolarization toward the filament center, previously
detected in many other star-forming cores and protostars, is also evident in
our data. (abstract abridged)Comment: 9 pages plus 2 figures (1 colour); accepted for publication in the
March 10, 2000 issue (vol. 531 #2) of The Astrophysical Journa
Making it in academic psychology: Demographic and personality correlates of eminence
Citations to published work, personality, and demographic characteristics were examined in a sample of male and female academic psychologists. A large sex difference was found in citations with men receiving significantly more recognition. Reputational rankings of graduate school and current institution were significantly related to citations, as were components of achievement motivation. Mastery and work needs were positively related to citations while competitiveness was negatively associated with the criterion. A model of attainment in psychology is proposed and possible explanations for the differential recognition of women are explored
TT Arietis - Observations of a Cataclysmic Variable Star with the MOST Space Telescope
We measured the photometric flux of the cataclysmic variable TT Arietis
(BD+14 341) using the MOST space telescope. Periodic oscillations of the flux
reveal the orbital period as well as other features of this binary system. We
applied a Discrete Fourier Transform (DFT) on a reduced dataset to retrieve the
frequencies of TT Arietis. The analysis of the system revealed a photometric
period of 3.19 hours. Though the MOST data has a high cadence of 52.8 seconds,
a fine structure of the accretion disk is not obvious.Comment: 3 pages, 1 figure, JENAM 2008 proceeding
Growth adaptation to temperature in N. crassa wild-type strains
Growth adaptation to temperature in N. crassa wild-type strain
Near Infrared Imaging of the Hubble Deep Field with The Keck Telescope
Two deep K-band () images, with point-source detection limits of
mag (one sigma), taken with the Keck Telescope in subfields of the
Hubble Deep Field, are presented and analyzed. A sample of objects to K=24 mag
is constructed and and colors are measured. By
stacking visually selected objects, mean colors can be measured to
very faint levels; the mean color is constant with apparent
magnitude down to mag.Comment: Replaced with slightly revised source positions and corrected V-I
magnitudes (which were incorrect in the Tables and Figure 5). 18 pages. The
data are publicly available at http://www.cco.caltech.edu/~btsoifer/hdf.html
along with a high-resolution version of Fig.
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