5,874 research outputs found
Scheduling of material through a steel plant
This paper addresses the optimal scheduling of material in a steel plant. The genetic algorithm is adapted to handle various constraints in the processing mills
Diversity of knot solitons in liquid crystals manifested by linking of preimages in torons and hopfions
Topological solitons are knots in continuous physical fields classified by
non-zero Hopf index values. Despite arising in theories that span many branches
of physics, from elementary particles to condensed matter and cosmology, they
remain experimentally elusive and poorly understood. We introduce a method of
experimental and numerical analysis of such localized structures in liquid
crystals that, similar to the mathematical Hopf maps, relates all points of the
medium's order parameter space to their closed-loop preimages within the
three-dimensional solitons. We uncover a surprisingly large diversity of
naturally occurring and laser-generated topologically nontrivial solitons with
differently knotted nematic fields, which previously have not been realized in
theories and experiments alike. We discuss the implications of the liquid
crystal's non-polar nature on the knot soliton topology and how the medium's
chirality, confinement and elastic anisotropy help to overcome the constrains
of the Hobart-Derrick theorem, yielding static three-dimensional solitons
without or with additional defects. Our findings will establish chiral nematics
as a model system for experimental exploration of topological solitons and may
impinge on understanding of such nonsingular field configurations in other
branches of physics, as well as may lead to technological application
Cirrus microphysics and radiative transfer: Cloud field study on October 28, 1986
The radiative properties of cirrus clouds present one of the unresolved problems in weather and climate research. Uncertainties in ice particle amount and size and, also, the general inability to model the single scattering properties of their usually complex particle shapes, prevent accurate model predictions. For an improved understanding of cirrus radiative effects, field experiments, as those of the Cirrus IFO of FIRE, are necessary. Simultaneous measurements of radiative fluxes and cirrus microphysics at multiple cirrus cloud altitudes allows the pitting of calculated versus measured vertical flux profiles; with the potential to judge current cirrus cloud modeling. Most of the problems in this study are linked to the inhomogeneity of the cloud field. Thus, only studies on more homogeneous cirrus cloud cases promises a possibility to improve current cirrus parameterizations. Still, the current inability to detect small ice particles will remain as a considerable handicap
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