2,630 research outputs found
Birth of a Learning Law
Defense Advanced Research Projects Agency; Office of Naval Research (N00014-95-1-0409, N00014-95-1-0657, N00014-92-J-1309
Radar signal categorization using a neural network
Neural networks were used to analyze a complex simulated radar environment which contains noisy radar pulses generated by many different emitters. The neural network used is an energy minimizing network (the BSB model) which forms energy minima - attractors in the network dynamical system - based on learned input data. The system first determines how many emitters are present (the deinterleaving problem). Pulses from individual simulated emitters give rise to separate stable attractors in the network. Once individual emitters are characterized, it is possible to make tentative identifications of them based on their observed parameters. As a test of this idea, a neural network was used to form a small data base that potentially could make emitter identifications
On Submodularity and Controllability in Complex Dynamical Networks
Controllability and observability have long been recognized as fundamental
structural properties of dynamical systems, but have recently seen renewed
interest in the context of large, complex networks of dynamical systems. A
basic problem is sensor and actuator placement: choose a subset from a finite
set of possible placements to optimize some real-valued controllability and
observability metrics of the network. Surprisingly little is known about the
structure of such combinatorial optimization problems. In this paper, we show
that several important classes of metrics based on the controllability and
observability Gramians have a strong structural property that allows for either
efficient global optimization or an approximation guarantee by using a simple
greedy heuristic for their maximization. In particular, the mapping from
possible placements to several scalar functions of the associated Gramian is
either a modular or submodular set function. The results are illustrated on
randomly generated systems and on a problem of power electronic actuator
placement in a model of the European power grid.Comment: Original arXiv version of IEEE Transactions on Control of Network
Systems paper (Volume 3, Issue 1), with a addendum (located in the ancillary
documents) that explains an error in a proof of the original paper and
provides a counterexample to the corresponding resul
Subjective Evaluations with Performance Feedback
This paper models two key roles of subjective performance evaluations: their incentive role and their feedback role. The paper shows that the feedback role makes subjective pay feasible even without repeated interaction, as long as there exists some verifiable measure of performance. It also shows that while subjective pay is helpful, it cannot achieve full efficiency. However, fully efficient incentives are achievable if the firm can commit to a forced distribution of evaluations and employs a continuum of workers. With a small number of workers, a forced distribution is valuable only if the verifiable measure is poor.Subjective Evaluations, Performance Feedback, Optimal Contracts
A String-Inspired Model for the Low- CMB
We present a semi--analytic exploration of some low-- angular power
spectra inspired by "Brane Supersymmetry Breaking". This mechanism splits Bose
and Fermi excitations in String Theory, leaving behind an exponential potential
that is just too steep for the inflaton to emerge from the initial singularity
while descending it. As a result, the scalar generically bounces against the
exponential wall, which typically introduces an infrared depression and a
pre--inflationary peak in the power spectrum of scalar perturbations. We
elaborate on a possible link between this phenomenon and the low-- CMB.
For the first 32 multipoles, combining the hard exponential with a milder one
leading to and with a small gaussian bump we have attained a
reduction of to about 46% of the standard CDM setting,
with both WMAP9 and PLANCK 2013 data. This result corresponds to a
of about 0.45, to be compared with a CDM value of
about 0.85. The preferred choices combine naturally quadrupole depression, a
first peak around and a wide minimum around . We have also
gathered some evidence that similar spectra emerge if the hard exponential is
combined with more realistic models of inflation. A problem of the preferred
examples is their slow convergence to an almost scale--invariant profile.Comment: 12 pages, latex, 7 figures. Power and limitations of the models and
of the semi-analytic approach stressed, misprints corrected. Final version to
appear in Mod. Phys. Lett.
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