2,367 research outputs found
A human performance modelling approach to intelligent decision support systems
Manned space operations require that the many automated subsystems of a space platform be controllable by a limited number of personnel. To minimize the interaction required of these operators, artificial intelligence techniques may be applied to embed a human performance model within the automated, or semi-automated, systems, thereby allowing the derivation of operator intent. A similar application has previously been proposed in the domain of fighter piloting, where the demand for pilot intent derivation is primarily a function of limited time and high workload rather than limited operators. The derivation and propagation of pilot intent is presented as it might be applied to some programs
Screened Coulomb interaction in the maximally localized Wannier basis
We discuss a maximally localized Wannier function approach for constructing
lattice models from first-principles electronic structure calculations, where
the effective Coulomb interactions are calculated in the constrained
random-phase-approximation. The method is applied to the 3d transition metals
and a perovskite (SrVO_3). We also optimize the Wannier functions by unitary
transformation so that U is maximized. Such Wannier functions unexpectedly
turned out to be very close to the maximally localized ones.Comment: 22 pages, 6 figure
Tuning the electrical conductivity of nanotube-encapsulated metallocene wires
We analyze a new family of carbon nanotube-based molecular wires, formed by
encapsulating metallocene molecules inside the nanotubes. Our simulations, that
are based on a combination of non-equilibrium Green function techniques and
density functional theory, indicate that these wires can be engineered to
exhibit desirable magnetotransport effects for use in spintronics devices. The
proposed structures should also be resilient to room-temperature fluctuations,
and are expected to have a high yield.Comment: 4 pages, 6 figures. Accepted in Physical Review Letter
Solving the brachistochrone and other variational problems with soap films
We show a method to solve the problem of the brachistochrone as well as other
variational problems with the help of the soap films that are formed between
two suitable surfaces. We also show the interesting connection between some
variational problems of dynamics, statics, optics, and elasticity.Comment: 16 pages, 11 figures. This article, except for a small correction,
has been submitted to the American Journal of Physic
A priori Wannier functions from modified Hartree-Fock and Kohn-Sham equations
The Hartree-Fock equations are modified to directly yield Wannier functions
following a proposal of Shukla et al. [Chem. Phys. Lett. 262, 213-218 (1996)].
This approach circumvents the a posteriori application of the Wannier
transformation to Bloch functions. I give a novel and rigorous derivation of
the relevant equations by introducing an orthogonalizing potential to ensure
the orthogonality among the resulting functions. The properties of these,
so-called a priori Wannier functions, are analyzed and the relation of the
modified Hartree-Fock equations to the conventional, Bloch-function-based
equations is elucidated. It is pointed out that the modified equations offer a
different route to maximally localized Wannier functions. Their computational
solution is found to involve an effort that is comparable to the effort for the
solution of the conventional equations. Above all, I show how a priori Wannier
functions can be obtained by a modification of the Kohn-Sham equations of
density-functional theory.Comment: 7 pages, RevTeX4, revise
New representation of orbital motion with arbitrary angular momenta
A new formulation is presented for a variational calculation of -body
systems on a correlated Gaussian basis with arbitrary angular momenta. The
rotational motion of the system is described with a single spherical harmonic
of the total angular momentum , and thereby needs no explicit coupling of
partial waves between particles. A simple generating function for the
correlated Gaussian is exploited to derive the matrix elements. The formulation
is applied to various Coulomb three-body systems such as , and up to in order to show its usefulness and
versatility. A stochastic selection of the basis functions gives good results
for various angular momentum states.Comment: Revte
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