18,302 research outputs found
Optimally adapted multi-state neural networks trained with noise
The principle of adaptation in a noisy retrieval environment is extended here
to a diluted attractor neural network of Q-state neurons trained with noisy
data. The network is adapted to an appropriate noisy training overlap and
training activity which are determined self-consistently by the optimized
retrieval attractor overlap and activity. The optimized storage capacity and
the corresponding retriever overlap are considerably enhanced by an adequate
threshold in the states. Explicit results for improved optimal performance and
new retriever phase diagrams are obtained for Q=3 and Q=4, with coexisting
phases over a wide range of thresholds. Most of the interesting results are
stable to replica-symmetry-breaking fluctuations.Comment: 22 pages, 5 figures, accepted for publication in PR
A polynomial training algorithm for calculating perceptrons of optimal stability
Recomi (REpeated COrrelation Matrix Inversion) is a polynomially fast
algorithm for searching optimally stable solutions of the perceptron learning
problem. For random unbiased and biased patterns it is shown that the algorithm
is able to find optimal solutions, if any exist, in at worst O(N^4) floating
point operations. Even beyond the critical storage capacity alpha_c the
algorithm is able to find locally stable solutions (with negative stability) at
the same speed. There are no divergent time scales in the learning process. A
full proof of convergence cannot yet be given, only major constituents of a
proof are shown.Comment: 11 pages, Latex, 4 EPS figure
A Two-Player Game of Life
We present a new extension of Conway's game of life for two players, which we
call p2life. P2life allows one of two types of token, black or white, to
inhabit a cell, and adds competitive elements into the birth and survival rules
of the original game. We solve the mean-field equation for p2life and determine
by simulation that the asymptotic density of p2life approaches 0.0362.Comment: 7 pages, 3 figure
Nephelometer and current observations at the STIE site, Panama Basin
The LDGO-Thorndike film recording nephelometer was used in three modes (profiling, short-term tethered and long-term moored) to measure changes in particle concentrations on time scales of minutes to weeks and space scales of meters to 25 km while measurements were being made on production and settling rates of particles. Although the nepheloid layer had no large near-bottom increase suggestive of local resuspension, there was an unusually thick nepheloid layer due to resuspension and advection of sediment from the basin walls. The concentration of particles increased by a factor of 3 between 900 m and the seafloor at 3840 m, while the vertical flux of particles measured in traps increased by only a factor of 1.7 over that distance. The horizontal flux of particles past traps at all depths is estimated to have varied by less than 20% and, therefore, does not appear to influence the flux measured with sediment traps. Changes with time in small-particle concentrations measured by the moored nephelometer were less than 30%, but the concentration of large particles changed by 100%
Parisi Phase in a Neuron
Pattern storage by a single neuron is revisited. Generalizing Parisi's
framework for spin glasses we obtain a variational free energy functional for
the neuron. The solution is demonstrated at high temperature and large relative
number of examples, where several phases are identified by thermodynamical
stability analysis, two of them exhibiting spontaneous full replica symmetry
breaking. We give analytically the curved segments of the order parameter
function and in representative cases compute the free energy, the storage
error, and the entropy.Comment: 4 pages in prl twocolumn format + 3 Postscript figures. Submitted to
Physical Review Letter
A canonical ensemble approach to graded-response perceptrons
Perceptrons with graded input-output relations and a limited output precision
are studied within the Gardner-Derrida canonical ensemble approach. Soft non-
negative error measures are introduced allowing for extended retrieval
properties. In particular, the performance of these systems for a linear and
quadratic error measure, corresponding to the perceptron respectively the
adaline learning algorithm, is compared with the performance for a rigid error
measure, simply counting the number of errors. Replica-symmetry-breaking
effects are evaluated.Comment: 26 pages, 10 ps figure
CH 3 GHz Observations of the Galactic Center
A 3 3 map of the Galactic Center was made at 9\arcmin resolution
and 10\arcmin spacing in the CH , J=1/2, F=1-1 transition at
3335 MHz. The CH emission shows a velocity extent that is nearly that of the
CO(1-0) line, but the CH line profiles differ markedly from the CO. The 3335
MHz CH transition primarily traces low-density molecular gas and our
observations indicate that the mass of this component within 30 pc of
the Galactic Center is 9 10 M. The CO-H
conversion factor obtained for the low-density gas in the mapped region is
greater than that thought to apply to the dense molecular gas at the Galactic
Center. In addition to tracing the low-density molecular gas at the Galactic
Center, the CH spectra show evidence of emission from molecular clouds along
the line of sight both in the foreground and background. The scale height of
these clouds ranges from 27 - 109 pc, consistent with previous work based on
observations of molecular clouds in the inner Galaxy.Comment: 29 pages, 12 figure
Sinking versus suspended particle size distributions in the North Pacific Subtropical Gyre
The particle size distribution (PSD) is a fundamental property that influences all aspects of phytoplankton ecology. In particular, the size (e.g., diameter d [μm]) and sinking speed w (m/day) of individual particles are inextricable, but much remains unknown about how d and w are related quantitatively for bulk particulate matter. There is significant interest in inferring sinking mass fluxes from PSDs, but doing so requires knowing how both mass and w scale with d . To this end, using both laser diffraction and imaging, we characterized for the first time both sinking and suspended PSDs in the oligotrophic North Pacific subtropical gyre. Comparing these PSDs via a power law parameterization indicates an approximately linear w ‐to‐d scaling, suggesting particles are more fractal‐like than sphere‐like in this respect. This result is robust across multiple instruments, depths, and sediment trap deployments and is made comparatively precise by a high degree of replication
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