1,499 research outputs found
Optimization of deliveries from distribution points
We solve an optimization problem involving the assignment of transport routes to a delivery point. The general and particular cases of the optimization problem are described. An algorithm for the simplified case and ideas for the general case is presented
The vortex state in the BEC to BCS crossover: a path-integral description
We derive a path-integral description of the vortex state of a fermionic
superfluid in the crossover region between the molecular condensate (BEC)
regime and the Cooper pairing (BCS) regime. This path-integral formalism,
supplemented by a suitable choice for the saddle point value of the pairing
field in the presence of a vortex, offers a unified description that
encompasses both the BEC and BCS limits. The vortex core size is studied as a
function of the tunable interaction strength between the fermionic atoms. We
find that in the BEC regime, the core size is determined by the molecular
healing length, whereas in the BCS regime, the core size is proportional only
to the Fermi wave length. The observation of such quantized vortices in dilute
Fermi gases would provide an unambiguous proof of the realization of
superfluidity in these gases.Comment: 10 pages, 2 figure
Marsiglio De Padua and the Defensor Pacis
The life of Marsiglio de Padua is a considerable problem in itself. Opinions concerning the details of his birth, activity, and death vary widely. Each scholar that writes on the subject refutes in some way all those that precede him. Scholz and Haller seem almost to go out of their way to contradict each other. The English and American scholars are slightly more polite to each other than their German colleagues, but they, too, disagree widely. I have tried to present the cases of the various scholars and to determine as much as possible the most plausible solution to the various problems
Does growing grain legumes or applying lime cost effectively lower greenhouse gas emissions from wheat production in a semi-arid climate?
Agriculture production contributes to global warming directly via the release of carbon dioxide (CO2), methane and nitrous oxide emissions, and indirectly through the consumption of inputs such as fertilizer, fuel and herbicides. We investigated if including a grain legume (Lupinus angustifolius) in a cropping rotation, and/or applying agricultural lime to increase the pH of an acidic soil, decreased greenhouse gas (GHG) emissions from wheat production in a semi-arid environment by conducting a streamlined life cycle assessment analysis that utilized in situ GHG emission measurements, rather than international default values. We also assessed the economic viability of each GHG mitigation strategy. Incorporating a grain legume in a two year cropping rotation decreased GHG emissions from wheat production by 56% on a per hectare basis, and 35% on a per tonne of wheat basis, primarily by lowering nitrogen fertilizer inputs. However, a large incentive ($93 per tonne of carbon dioxide equivalents reduced) was required for the inclusion of grain legumes to be financially attractive. Applying lime was profitable but increased GHG emissions by varying amounts depending upon whether the lime was assumed to dissolve over one, five or 10 years. We recommend further investigating the impact of liming on both CO2 and non-CO2 emissions to accurately account for its effect on GHG emissions from agricultural production
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Terahertz electromodulation spectroscopy of electron transport in GaN
Time-resolved terahertz (THz) electromodulation spectroscopy is applied to investigate the high-frequency
transport of electrons in gallium nitride at different doping concentrations and densities of threading dislocations.
At THz frequencies, all structures reveal Drude transport. The analysis of the spectral response
provides the fundamental transport properties, such as the electron scattering time and the electrons’ conductivity
effective mass. We observe the expected impact of ionized-impurity scattering and that scattering
at threading dislocations only marginally affects the high-frequency mobility.The research was supported by the German Science
Foundation DFG under grants Ke 516/1-2 and Ke 516/6-
1.This is the accepted manuscript. The final version is available at http://scitation.aip.org/content/aip/journal/apl/106/9/10.1063/1.4914326
Coupled-cluster theory of a gas of strongly-interacting fermions in the dilute limit
We study the ground-state properties of a dilute gas of strongly-interacting
fermions in the framework of the coupled-cluster expansion (CCE). We
demonstrate that properties such as universality, opening of a gap in the
excitation spectrum and applicability of s-wave approximations appear naturally
in the CCE approach. In the zero-density limit, we show that the ground-state
energy density depends on only one parameter which in turn may depend at most
on the spatial dimensionality of the system.Comment: 7 figure
Dispersive Waves in Microstructured Solids
The wave motion in micromorphic microstructured solids is studied. The mathematical model is based on ideas of Mindlin and governing equations are derived by making use of the Euler–Lagrange formalism. The same result is obtained by means of the internal variables approach. Actually such a model describes internal fields in microstructured solids under external loading and the interaction of these fields results in various physical effects. The emphasis of the paper is on dispersion analysis and wave profiles generated by initial or boundary conditions in a one-dimensional case
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