133 research outputs found
An efficient two-phase iterative heuristic for Collection-Disassembly problem
Closing the loop in the supply chains is one of the mandatory conditions for more sustainable development. The Collection-Disassembly Problem appears in the reverse part of the closed-loop supply chains. Its aim is to coordinate the activities of collection of end-of-life products from collection centres and their subsequent disassembly. The disassembly step is required for efficient remanufacturing and recycling of returned products. The Collection-Disassembly problem integrates such optimization problems as dynamic lot-sizing and vehicle routing in general cases. In this paper, we develop a Two-Phase Iterative Heuristic to efficiently address large size instances. The numerical tests show that the heuristic provides good solutions under acceptable computational time
Coordination of Collection and Disassembly Planning for End-of-Life Product
This work proposes a formulation for coordinating between collection and disassembly planning for an End-of-Life (EOL) product. The coordination deals with the balance between the number of products collected, the inventory level and the number of products disassembled. The objective function aims to minimize the total cost including the disassembly cost, the penalty cost, the holding cost and the running cost of vehicle. Two strategies with and without coordination were compared via numerical experiments. The results obtained show that the coordinated strategy allows total cost reducing
Collection-disassembly problem in reverse supply chain
The reverse supply chain and disassembly processes are getting more and more important for tackling the burden of waste electrical and electronic equipment. The disassembly's complexity and frequent manual operation makes this process relatively expensive compared to its potential profit. The collection of end-of-life product is also a big issue dealing with vehicle routing. Thus, the decisions taken for collection and disassembly of end-of-life products need to be optimised. In this work, an optimisation model is developed for incorporating these problems. Our experimental study shows joint optimisation of collection and disassembly with coordination between them improves the global performance of the reverse supply chain including lower total cost corresponding to the component demand satisfaction
On the validity of the reduced Salpeter equation
We adapt a general method to solve both the full and reduced Salpeter
equations and systematically explore the conditions under which these two
equations give equivalent results in meson dynamics. The effects of constituent
mass, angular momentum state, type of interaction, and the nature of
confinement are all considered in an effort to clearly delineate the range of
validity of the reduced Salpeter approximations. We find that for
the solutions are strikingly similar for all
constituent masses. For zero angular momentum states the full and reduced
Salpeter equations give different results for small quark mass especially with
a large additive constant coordinate space potential. We also show that
corrections to heavy-light energy levels can be accurately
computed with the reduced equation.Comment: Latex (uses epsf macro), 24 pages of text, 12 postscript figures
included. Slightly revised version, to appear in Phys. Rev.
gamma nu -> gamma gamma nu and crossed processes at energies below m_W
The cross sections for the processes ,
and are
calculated for a range of center of mass energies from below to
considerably above , but much less than . This enables us to treat
the neutrino--electron coupling as a four--Fermi interaction and results in
amplitudes which are electron box diagrams with three real photons and one
virtual photon at their vertices. These calculations extend our previous
low--energy effective interaction results to higher energies and enable us to
determine where the effective theory is reliable.Comment: 12 pages, RevTex, 10 postscript figures include
High energy photon-neutrino elastic scattering
The one-loop helicity amplitudes for the elastic scattering process
in the Standard Model are computed at high center of
mass energies. A general decomposition of the amplitudes is utilized to
investigate the validity of some of the key features of our results. In the
center of mass, where , the cross section grows roughly as
to near the threshold for -boson production, .
Although suppressed at low energies, we find that the elastic cross section
exceeds the cross section for when
GeV. We demonstrate that the scattered photons are circularly polarized and the
net value of the polarization is non-zero. Astrophysical implications of high
energy photon-neutrino scattering are discussed.Comment: 9 pages, 7 figures, RevTeX
Neutrinos as Source of Ultra High Energy Cosmic Rays in Extra Dimensions
If the neutrinos are to be identified with the primary source of ultra-high
energy cosmic rays(UHECR), their interaction on relic neutrinos is of great
importance in understanding their long intergalactic journey. In theories with
large compact dimensions, the exchange of a tower of massive spin-2 gravitons
(Kaluza-Klein excitations) gives extra contribution to and processes along with the opening
of a new channel for the neutrinos to annihilate with the relic cosmic neutrino
background to produce bulk gravitons in
the extra dimensions. This will affect their attenuation. We compute the
contribution of these Kaluza-Klein excitations to the above processes and find
that for parameters of the theory constrained by supernova cooling, the
contribution does indeed become the dominant contribution above GeV.Comment: 16 pages Latex2e file including 4 postscript figures. Effect of brane
fluctuation taken into accoun
Photon-Neutrino Interactions in Magnetic Field through Neutrino Magnetic Moment
We study the neutrino-photon processes like in
the presence of uniform external magnetic field for the case when neutrinos can
couple to the electromagnetic field directly through their dipole magnetic
moment and obtain the stellar energy loss. The process would be of special
relevance in astrophysical situations where standard left-handed neutrinos are
trapped and the right handed neutrinos produced through the spin flip
interaction induced by neutrino magnetic moment alone can freely stream out.Comment: LaTex2e file, 9 page
The Amplitude in an External Homogeneous Electromagnetic Field
Neutrino-photon interactions in the presence of an external homogeneous
constant electromagnetic field are studied. The amplitude is
calculated in an electromagnetic field of the general type, when the two field
invariants are nonzero.Comment: 7 pages, 1 figur
High-energy neutrino conversion and the lepton asymmetry in the universe
We study matter effects on oscillations of high-energy neutrinos in the
Universe. Substantial effect can be produced by scattering of the neutrinos
from cosmological sources (z\gta 1) on the relic neutrino background,
provided that the latter has large CP-asymmetry: \eta\equiv
(n_\nu-n_{\bar{\nu}})/n_\gamma\gta 1, where , and
are the concentrations of neutrinos, antineutrinos and photons. We
consider in details the dynamics of conversion in the expanding neutrino
background. Applications are given to the diffuse fluxes of neutrinos from
GRBs, AGN, and the decay of super-heavy relics. We find that the vacuum
oscillation probability can be modified by and in extreme cases
allowed by present bounds on the effect can reach .
Signatures of matter effects would consist (i) for both active-active and
active-sterile conversion, in a deviation of the numbers of events produced in
a detector by neutrinos of different flavours,
, and of their ratios from the values given by
vacuum oscillations; such deviations can reach , (ii) for
active-sterile conversion, in a characteristic energy dependence of the ratios
. Searches for these matter
effects will probe large CP and lepton asymmetries in the universe.Comment: 32 pages, RevTeX, 16 figures. Substantial changes in the treatment of
conversion effects in the relic neutrino background and of active-active
oscillations of high-energy neutrinos. Figures and references added;
conclusions partially modifie
- …