8,268 research outputs found
PST and PARR: Plan specification tools and a planning and resource reasoning shell for use in satellite mission planning
Plan Specification Tools (PST) are tools that allow the user to specify satellite mission plans in terms of satellite activities, relevent orbital events, and targets for observation. The output of these tools is a set of knowledge bases and environmental events which can then be used by a Planning And Resource Reasoning (PARR) shell to build a schedule. PARR is a reactive planning shell which is capable of reasoning about actions in the satellite mission planning domain. Each of the PST tools and PARR are described as well as the use of PARR for scheduling computer usage in the multisatellite operations control center at Goddard Space Flight Center
Design of Predictive Controllers by Dynamic Programming and Neural Networks
This paper proposes a method for the design of predictive controllers for nonlinear systems. The method consists of two phases, a solution phase and a learning phase. In the solution phase, dynamic programming is applied to obtain a closed-loop control law. In the learning phase, neural networks are used to simulate the control law. This phase overcomes the curse of dimensionality problem that has often hindered the implementation of control laws generated by dynamic programming. Experimental results demonstrate the effectiveness of the metho
d_{xy}-Density wave in fermion-fermion cold atom mixtures
We study density wave instabilities in a doubly-degenerate Fermi-Fermi
mixture with symmetry on a square lattice. For sufficiently
large on-site inter-species repulsion, when the two species of fermions are
both at half-filling, two conventional (-wave) number density waves are
formed with a -phase difference between them to minimize the inter-species
repulsion. Upon moving one species away from half-filling, an unconventional
density wave with -wave symmetry emerges. When both species are away
from the vicinity of half-filling, superconducting instabilities dominate. We
present results of a functional renormalization-group calculation that maps out
the phase diagram at weak couplings. Also, we provide a simple explanation for
the emergence of the -density wave phase based on a four-patch model.
We find a robust and general mechanism for -density-wave formation that
is related to the shape and size of the Fermi surfaces. The density imbalance
between the two species of fermions in the vicinity of half-filling leads to
phase-space discrepancy for different inter-species Umklapp couplings. Using a
phase space argument for leading corrections in the one-loop renormalization
group approach to fermions, we show that the phase-space discrepancy in our
system causes opposite flows for the two leading intra-species Umklapp
couplings and that this triggers the -density-wave instability.Comment: revised long version; 8 pages, 7 figure
Correlated Phases of Population Imbalanced Fermi-Fermi Mixtures on an Optical Lattice
We study a two species fermion mixture with different populations on a square
lattice modeled by a Hubbard Hamiltonian with on-site inter-species repulsive
interaction. Such a model can be realized in a cold atom system with fermionic
atoms in two different hyperfine states loaded on an optical lattice and with
tunable inter-species interaction strength via external fields. For a
two-dimensional square lattice, when at least one of the fermion species is
close to half-filling, the system is highly affected by lattice effects. With
the majority species near half-filling and varying densities for the minority
species, we find that several correlated phases emerge as the ground state,
including a spin density wave state, a charge density wave state with stripe
structure, and various p-wave BCS pairing states for both species. We study
this system using a functional renormalization group method, determine its
phase diagram at weak coupling, discuss the origin and characteristics of each
phase, and provide estimates for the critical temperatures.Comment: 5 pages, 4 figures, figures update
A False Acceptance Error Controlling Method for Hyperspherical Classifiers
Controlling false acceptance errors is of critical importance in many pattern recognition applications, including signature and speaker verification problems. Toward this goal, this paper presents two post-processing methods to improve the performance of hyperspherical classifiers in rejecting patterns from unknown classes. The first method uses a self-organizational approach to design minimum radius hyperspheres, reducing the redundancy of the class region defined by the hyperspherical classifiers. The second method removes additional redundant class regions from the hyperspheres by using a clustering technique to generate a number of smaller hyperspheres. Simulation and experimental results demonstrate that by removing redundant regions these two post-processing methods can reduce the false acceptance error without significantly increasing the false rejection error
Classical Extended Conformal Algebras Associated with Constrained KP Hierarchy
We examine the conformal property of the second Hamiltonian structure of
constrained KP hierarchy derived by Oevel and Strampp. We find that it
naturallygives a family of nonlocal extended conformal algebras. We give two
examples of such algebras and find that they are similar to Bilal's V algebra.
By taking a gauge transformation one can map the constrained KP hierarchy to
Kuperschmidt's nonstandard Lax hierarchy. We consider the second Hamiltonian
structure in this representation. We show that after mapping the Lax operator
to a pure differential operator the second structure becomes the sum of the
second and the third Gelfand-Dickey brackets defined by this differential
operator. We show that this Hamiltonian structure defines the W-U(1)-Kac-Moody
algebra by working out its conformally covariant form.Comment: NHCU-HEP-94-28, 19 pages (Plain TeX
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