6,727 research outputs found
Productivity improvement, considering legal conditions and Just In Time principles in the mixed-model Sequencing problem
A new mathematical model to solve the Mixed-Model Sequencing Problem with Work overload minimization is formulated. The model incorporates productive, social and legal aspects in order to move the theory problem closer to the actual industrial environments. Specifically, there are considered the variation of work pace of workers throughout the workday to increase the completed work; the conditions of occupancy level of workers imposed by the collective agreements; and the idea of keeping constant the production mix through the sequence leading both to a balance between the required workloads at stations and regular consumption of components. Indeed, by means of a case study linked to Nissan, a gain of over 98% is achieved in terms of regular cumulative production and required work, while performing the 100% of required work and following legal restrictions of operators’ saturation.Postprint (published version
Microwave surface resistance of reactively sputtered NbN thin films
The surface resistance of niobium nitride (NBN) thin films was measured at 7.78 and 10.14 GHz in the temperature range of 1.5 to 4.2 K. The films were reactively sputtered on sapphire substrates to a thickness of approximately 1 micron. The surface resistance was determined by measuring the quality factor (Q) of the TE sub 011 mode of a lead-plated copper cavity where the NbN served as one end-cap of the cavity
The black disk and the dip in the differential elastic cross section at asymptotic energy
We test the validity of the black disk limit in elastic scattering by
studying the evolution of the dip in the scaling variable
, where is the transverse momentum squared at
the dip and the total cross section. As
and , may consistently be approaching the black
disc value,
GeV mb.Comment: 6 pages, 2 figure
Graphene coherent states
In this paper, we will construct the coherent states for a Dirac electron in
graphene placed in a constant homogeneous magnetic field which is orthogonal to
the graphene surface. First of all, we will identify the appropriate
annihilation and creation operators. Then, we will derive the coherent states
as eigenstates of the annihilation operator, with complex eigenvalues. Several
physical quantities, as the Heisenberg uncertainty product, probability density
and mean energy value, will be as well explored.Comment: 17 pages, 32 figure
Rapidity long range correlations, parton percolation and color glass condensate
The similarities between string percolation and Glasma results are
emphasized, special attention being paid to rapidity long range correlations,
ridge structure and elliptic flow. As the string density of high multiplicity
pp collisions at LHC energies has similar value as the corresponding to Au-Au
semi-central collisions at RHIC we also expect in pp collisions long rapidity
correlations and ridge structure, extended more than 8 units in rapidity.Comment: 3 pages, 3 figures, conference Quark Confinement and the hadron
spectrum I
Elliptic flow at RHIC and LHC in the string percolation approach
The percolation of strings gives a good description of the RHIC experimental
data on the elliptic flow, v2 and predicted a rise on the integrated v2 of the
order of 25% at LHC such as it has been experimentally obtained. We show that
the dependence of v2 on pT for RHIC and LHC energies is approximately the same
as it has been observed, for all the centralities. We show the results for
different particles and the dependence of v2 on the centralities and rapidity.
Our results are compatible with an small value of the ratio eta/s in the whole
energy range such as it was expected in the percolation framework.Comment: 20 pages, 12 figure
Cryogenic, low-noise high electron mobility transistor amplifiers for the Deep Space Network
The rapid advances recently achieved by cryogenically cooled high electron mobility transistor (HEMT) low-noise amplifiers (LNA's) in the 1- to 10-GHz range are making them extremely competitive with maser amplifiers. In order to address future spacecraft navigation, telemetry, radar, and radio science needs, the Deep Space Network is investing both maser and HEMT amplifiers for its Ka-band (32-GHz) downlink capability. This article describes the current state cryogenic HEMT LNA development at Ka-band for the DSN. Noise performance results at S-band (2.3 GHz) and X-band (8.5 GHz) for HEMT's and masers are included for completeness
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