997,797 research outputs found
Symmetries and degrees of freedom in 2-dimensional dual models
The 2-dimensional version of the Schwarz and Sen duality model (Tseytlin
model) is analyzed at the classical and quantum levels. The solutions are
obtained after removing the gauge dependent sector using the Dirac method. The
Poincar\`e invariance is verified at both levels. An extension with global
supersymmetry is also proposed.Comment: 3 pages, revtex, minor correction
Critical behavior in a cross-situational lexicon learning scenario
The associationist account for early word-learning is based on the
co-occurrence between objects and words. Here we examine the performance of a
simple associative learning algorithm for acquiring the referents of words in a
cross-situational scenario affected by noise produced by out-of-context words.
We find a critical value of the noise parameter above which learning
is impossible. We use finite-size scaling to show that the sharpness of the
transition persists across a region of order about ,
where is the number of learning trials, as well as to obtain the
learning error (scaling function) in the critical region. In addition, we show
that the distribution of durations of periods when the learning error is zero
is a power law with exponent -3/2 at the critical point
A Study of Display Integration for Hypersonic Research Vehicles First Quarterly Progress Report, 16 May - 16 Aug. 1963
Contact analog television display for X-15 pilot flight control informatio
KPD1930+2752 - a candidate Type Ia supernova progenitor
We present spectra of the pulsating sdB star KPD1930+2752 which confirm that
this star is a binary. The radial velocities measured from the H-alpha and
HeI6678 spectral lines vary sinusoidally with the same period (2h 17m) as the
ellipsoidal variability seen by Billeres et al. (2000). The amplitude of the
orbital motion (349.3+-2.7 km/s) combined with the canonical mass for sdB stars
(0.5 solar masses) implies a total mass for the binary of 1.47+-0.01 solar
masses The unseen companion star is almost certainly a white dwarf star. The
binary will merge within about 200 million years due to gravitational wave
radiation. The accretion of helium and other elements heavier than hydrogen
onto the white dwarf which then exceeds the Chandrasekhar mass (1.4 solar
masses) is a viable model for the cause of Type Ia supernovae. KPD1930+2752 is
the first star to be discovered which is a good candidate for the progenitor of
a Type Ia supernova of this type which will merge on an astrophysically
interesting timescale.Comment: Accepted for publication in MNRAS. 4 pages, 2 figures. Added
Institutio
The use of multispectral sensing techniques to detect ponderosa pine trees under stress from insect or pathogenic organisms Annual progress report
Ground and aerial imaging techniques to detect tree damage caused by bark beetles in forested area
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