199,245 research outputs found
Genetic algorithm and neural network hybrid approach for job-shop scheduling
Copyright @ 1998 ACTA PressThis paper proposes a genetic algorithm (GA) and constraint satisfaction adaptive neural network (CSANN) hybrid approach for job-shop scheduling problems. In the hybrid approach, GA is used to iterate for searching optimal solutions, CSANN is used to obtain feasible solutions during the iteration of genetic algorithm. Simulations have shown the valid performance of the proposed hybrid approach for job-shop scheduling with respect to the quality of solutions and the speed of calculation.This research is supported by the National Nature Science Foundation and National High
-Tech Program of P. R. China
The two dimensional antiferromagnetic Heisenberg model in the presence of an external field
We present numerical results on the zero temperature magnetization curve and
the static structure factors of the two dimensional antiferromagnetic
Heisenberg model in the presence of an external field. The impact of
frustration is also studied.Comment: 6 pages, 16 figures, REVTE
The role of triplet excitons in enhancing polymer solar cell efficiency: a photo-induced absorption study
Inclusion of heavy metal atoms in a polymer backbone allows transitions
between the singlet and triplet manifolds. Interfacial dissociation of triplet
excitons constitutes a viable mechanism for enhancing photovoltaic (PV)
efficiencies in polymer heterojunction-based solar cells. The PV efficiency
from polymer solar cells utilizing a ladder-type poly (para-phenylene) polymer
(PhLPPP) with trace quantity of Pd atoms and a fullerene derivative (PCBM) is
much higher than its counterpart (MeLPPP) with no Pd atom. Evidence is
presented for the formation of a weak ground-state charge-transfer complex
(CTC) in the blended films of the polymer and PCBM, using photo-induced
absorption (PIA) spectroscopy. The CTC state in MeLPPP:PCBM has a singlet
character to it, resulting in a radiative recombination. In contrast, the CTC
states in PhLPPP:PCBM are more localized with a triplet character. An
absorption peak at 1.65 eV is observed in PhLPPP:PCBM blend in the PIA, which
may be converted to weakly-bound polaron-pairs, contributing to the enhancement
of PV efficiency.Comment: 19 pages, 11 figure
On the Genus Expansion in the Topological String Theory
A systematic formulation of the higher genus expansion in topological string
theory is considered. We also develop a simple way of evaluating genus zero
correlation functions. At higher genera we derive some interesting formulas for
the free energy in the and models. We present some evidence that
topological minimal models associated with Lie algebras other than the A-D-E
type do not have a consistent higher genus expansion beyond genus one. We also
present some new results on the model at higher genera.Comment: 36 pages, phyzzx, UTHEP-27
Spin mapping, phase diagram, and collective modes in double layer quantum Hall systems at
An exact spin mapping is identified to simplify the recently proposed
hard-core boson description (Demler and Das Sarma, Phys. Rev. Lett., to be
published) of the bilayer quantum Hall system at filling factor 2. The
effective spin model describes an easy-plane ferromagnet subject to an external
Zeeman field. The phase diagram of this effective model is determined exactly
and found to agree with the approximate calculation of Demler and Das Sarma,
while the Goldstone-mode spectrum, order parameter stiffness and
Kosterlitz-Thouless temperature in the canted antiferromagnetic phase are
computed approximately.Comment: 4 pages with 2 figures include
Topological Field Theories and the Period Integrals
We discuss topological Landau-Ginzburg theories coupled to the 2-dimensional
topological gravity. We point out that the basic recursion relations for
correlation functions of the 2-dimesional gravity have exactly the same form as
the Gauss-Manin differential equations for the period integrals of
superpotentials. Thus the one-point functions on the sphere of the
Landau-Ginzburg theories are given exactly by the period integrals. We discuss
various examples, A-D-E minimal models and the topological theories.Comment: 12 pages, phyzzx, UT 64
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