82,796 research outputs found
Lagging behind versus advancing too fast? identifying gaps research in supply chain
The objective of our work is to analyze the evolution and actual trends of research in Supply Chain Management (SCM). We pretend to show how the different topics have been methodologically studied, and to determine how the advent of the so-called 'New Economy' has influenced SCM research. To get this objective, we carry out a literature review of twelve refereed journals in the Operations Management (OM) area for the period 1995-2001. Statistical tools are used to analyze the obtained information
Chaotic oscillations in a nearly inviscid, axisymmetric capillary bridge at 2:1 parametric resonance
We consider the 2:1 internal resonances (such that Ω1>0 and Ω2 â 2Ω1 are natural frequencies) that appear in a nearly inviscid, axisymmetric capillary bridge when the slenderness Î is such that 0<Î<Ï (to avoid the Rayleigh instability) and only the first eight capillary modes are considered. A normal form is derived that gives the slow evolution (in the viscous time scale) of the complex amplitudes of the eigenmodes associated with Ω1 and Ω2, and consists of two complex ODEs that are balances of terms accounting for inertia, damping, detuning from resonance, quadratic nonlinearity, and forcing. In order to obtain quantitatively good results, a two-term approximation is used for the damping rate. The coefficients of quadratic terms are seen to be nonzero if and only if the eigenmode associated with Ω2 is even. In that case the quadratic normal form possesses steady states (which correspond to mono- or bichromatic oscillations of the liquid bridge) and more complex periodic or chaotic attractors (corresponding to periodically or chaotically modulated oscillations). For illustration, several bifurcation diagrams are analyzed in some detail for an internal resonance that appears at Î â 2.23 and involves the fifth and eighth eigenmodes. If, instead, the eigenmode associated with Ω2 is odd, and only one of the eigenmodes associated with Ω1 and Ω2 is directly excited, then quadratic terms are absent in the normal form and the associated dynamics is seen to be fairly simple
Gerbes and Heisenberg's Uncertainty Principle
We prove that a gerbe with a connection can be defined on classical phase
space, taking the U(1)-valued phase of certain Feynman path integrals as Cech
2-cocycles. A quantisation condition on the corresponding 3-form field strength
is proved to be equivalent to Heisenberg's uncertainty principle.Comment: 12 pages, 1 figure available upon reques
On spectral types of semialgebraic sets
In this work we prove that a semialgebraic set is
determined (up to a semialgebraic homeomorphism) by its ring
of (continuous) semialgebraic functions while its ring of
(continuous) bounded semialgebraic functions only determines besides a
distinguished finite subset . In addition it holds that the
rings and are isomorphic if and only if
is compact. On the other hand, their respective maximal spectra
and endowed with the Zariski topology are always homeomorphic and
topologically classify a `large piece' of . The proof of this fact requires
a careful analysis of the points of the remainder associated with formal paths.Comment: 22 page
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