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Bakke K.,Federal University of Paraiba | Belich H.,Federal University of Espirito Santo
Annals of Physics | Year: 2015

We study a possible scenario of the Lorentz symmetry violation background that allows us to build an analogue of the Landau system for a nonrelativistic Dirac neutral particle interacting with a field configuration of crossed electric and magnetic fields. We also discuss the arising of analogues of the Rashba coupling, the Zeeman term and the Darwin term from the Lorentz symmetry breaking effects, and the influence of these terms on the analogue of the Landau system confined to a two-dimensional quantum ring. Finally, we show that this analogy with the Landau system confined to a two-dimensional quantum ring allows us to establish an upper bound for the Lorentz symmetry breaking parameters. © 2014 Elsevier Inc. Source

Amaral A.R.S.,Federal University of Espirito Santo
Computers and Operations Research | Year: 2013

In this paper, we study a problem that occurs in the row layout of facilities. Among n facilities, suppose that there are t facilities with some characteristic in common so that they should be arranged along one row, leaving the remainder (n-t) facilities to be arranged on a parallel row. The objective is to order the facilities in the two rows such that some cost function is minimized. This problem is called the parallel row ordering problem (PROP). The PROP is a generalization of the single row facility layout problem (SRFLP). Here, a mixed integer programming (MIP) formulation of the PROP is presented which extends a MIP formulation of the SRFLP. We show that a PROP with n facilities may be solved faster than a SRFLP with n facilities. Theoretical and experimental comparisons of the SRFLP and the PROP formulations are presented. © 2013 Elsevier Ltd. Source

Amaral A.R.S.,Federal University of Espirito Santo
Computers and Operations Research | Year: 2012

The corridor allocation problem (CAP) seeks an arrangement of facilities along a central corridor defined by two horizontal lines parallel to the x-axis of a Cartesian coordinate system. The objective is to minimize the total communication cost among facilities, while respecting two main conditions: (i) no space is allowed between two adjacent facilities; (ii) the left-most point of the arrangement on either line should have zero abscissa. The conditions (i) and (ii) are required in many applications such as the arrangement of rooms at office buildings or hospitals. The CAP is a NP-Hard problem. In this paper, a mixed-integer programming formulation of the CAP is proposed, which allows us to compute optimal layouts in reasonable time for problem instances of moderate sizes. Moreover, heuristic procedures are presented that can handle larger instances. © 2012 Elsevier Ltd. All rights reserved. Source

Mattos Ribeiro G.,HEC Montreal | Mattos Ribeiro G.,Federal University of Espirito Santo | Laporte G.,HEC Montreal
Computers and Operations Research | Year: 2012

The cumulative capacitated vehicle routing problem (CCVRP) is a variation of the classical capacitated vehicle routing problem in which the objective is the minimization of the sum of arrival times at customers, instead of the total routing cost. This paper presents an adaptive large neighborhood search heuristic for the CCVRP. This algorithm is applied to a set of benchmark instances and compared with two recently published memetic algorithms. © 2011 Elsevier Ltd. All rights reserved. Source

Pavon D.,Autonomous University of Barcelona | Zimdahl W.,Federal University of Espirito Santo
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

In this Letter we consider three future singularities in different Friedmann-Lemaître-Robertson-Walker scenarios and show that the universe departs more and more from thermodynamic equilibrium as the corresponding singularity is approached. Though not proven in general, this feature may characterize future singularities of homogeneous and isotropic cosmologies. © 2012 Elsevier B.V. Source

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