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Carreon H.,University of Morelia
AIP Advances | Year: 2017

The detectability of small inclusions and subtle imperfections by magnetic measurements that senses thermoelectric currents produced by a temperature gradient is ultimately limited by the intrinsic thermoelectric anisotropy and inhomogeneity of the material to be inspected. The probability of detection (POD) of a given material flaw is determined by the resulting signal-to-noise ratio rather than by the absolute magnitude of the signal itself. The strength of the magnetic field to be detected greatly depends on the physical nature of the host medium and dimensions of the imperfection. This paper presents experimental data for the magnetic field produced by thermoelectric currents around tin inclusions in different host medium such as 316LVM stainless steel and Ti-6Al-4V titanium alloy under external thermal excitation. The diameter of the inclusions and the lift-off distance varied from 0.39 to 3.175 mm and from 1 to 10 mm, respectively. A 0.6 °C/cm temperature gradient in the samples produced peak magnetic flux densities ranging from 0.1 to 280 nT, that was measured by a fluxgate magnetometer. The numerical results were found to be in good agreement with theoretical predictions and demonstrated that both property anisotropy and gradient in thermoelectric materials can significantly influence the induced thermoelectric currents and magnetic fields. © 2016 Author(s).

Garcia N.,University of Morelia | Acha E.,Tampere University of Technology
IEEE Transactions on Sustainable Energy | Year: 2017

This paper presents a new power systems simulation environment suitable for the swift calculation of the periodic steady-state response of large power networks with large wind parks. In order to achieve the greatest computational efficiency and solution reliability, the wind generator model uses the state-of-the-art voltage-behind-reactance model of the induction generator; in this first part of the paper, the fixed-speed wind generator model is presented. The overall solving environment for the nonlinear system of differential equations representing the power system is the so-called Poincare map method. A rather useful feature to reduce further the calculation times is the availability of an equivalent wind farm model based on multiple wakes. The Poincare acceleration yields a vastly improved numerical solution compared to existing models of fixed-speed wind parks. The application of equivalent wind farm models yields a staggering reduction in the elapsed time to only 1.16% of the time demanded by the detailed model, while retaining a good approximation of the response of the wind farm. Full comparisons of the detailed and equivalent wind park models with PSCAD/EMTDC, are carried out and the agreement of the results is excellent. In this paper the emphasis is on harmonic generation. © 2016 IEEE.

Das A.K.,University of Rochester | Das A.K.,Saha Institute of Nuclear Physics | Frenkel J.,University of Sao Paulo | Schubert C.,University of Morelia
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We study the behavior of the dynamical fermion mass when infrared divergences and mass shell singularities are present in a gauge theory. In particular, in the massive Schwinger model in covariant gauges we find that the pole of the fermion propagator is divergent and gauge dependent at one loop, but the leading singularities cancel in the quenched rainbow approximation. On the other hand, in physical gauges, we find that the dynamical fermion mass is finite and gauge independent at least up to one loop. © 2013 Elsevier B.V.

Verma M.P.,Electric Research Institute of Mexico | Mario Cesar Suarez A.,University of Morelia
Journal of Statistical Software | Year: 2014

The computer program DixonText.CriticalValues is written in VB.NET to extend the quadrature approach to calculate the critical values with accuracy up to 6 significant digits for Dixon's ratios. Its use in creating the critical values tables in Excel is illustrated.

Arteaga-Velazquez J.C.,University of Morelia
Journal of Physics: Conference Series | Year: 2015

The High Altitude Water Cherenkov (HAWC) observatory is a ground-based air- shower detector designed to study cosmic rays and gamma rays with energies from 100 GeV up to 100 TeV. HAWC simultaneously surveys 2sr of the northern sky with a high duty cycle > 90% in search for photons from point and extended sources, diffuse emission, transient events and other astrophysical phenomena at multi-TeV scales against the background of cosmic rays. In fact, the study of this background will open also the possibility of doing cosmic ray physics in the GeV - TeV regime and even to perform solar studies at HAWC. The observatory will consist of a densely packed array of 300 water Cherenkov tanks (4.5 m tall and 7.3 m diameter with 4 photomultipliers each) distributed on a 22 000 m2 surface. Deployment started in March 2012 on a plateau situated on the Sierra Negra Volcano in the state of Puebla, Mexico, at an altitude of 4100 m. Construction is expected to be finished by the first months of 2015. In the mean time, HAWC has been taking data with a partial array and preliminary results have been already obtained. In this contribution, the results from the latest HAWC observations will be presented. © Published under licence by IOP Publishing Ltd.

Wagner E.,University of Morelia
Journal of Physics: Conference Series | Year: 2016

Hilbert space representations of quantum SU(2) by multiplication operators on a local chart are constructed, where the local chart is given by tensor products of square integrable functions on a quantum disc and on the classical unit circle. The actions of generators of quantum SU(2), generators of the opposite algebra, and noncommutative partial derivatives are computed on a Hilbert space basis. © Published under licence by IOP Publishing Ltd.

Almaraz G.M.D.,University of Morelia
Materials Performance and Characterization | Year: 2015

Ultrasonic fatigue tests were carried out on the aluminum alloy AISI 6061-T6, presenting different values for the principal surface roughness parameters: Ra, Rq, and Rz. For fatigue life comprised between 3 × 105 ∼ 6 × 106 cycles, crack initiates at the specimen surface induced by stress-concentration and micro-plastic deformation (micro-void coalescence); whereas for the very high cycle fatigue (>107 cycles), the mechanism of crack initiation moves to subsurface or inside the specimen and is associated with internal imperfections such as micro-porosities or nonmetallic inclusions. For the first fatigue life regime, compression residual stresses induced by the work-hardening machining process and the associated micro-plastic deformation are the principal factors controlling the fatigue endurance on this aluminum alloy. Experimental results show that fatigue endurance is higher for the high surface roughness in the 3 × 105 ∼ 6 × 106 cycles of fatigue life, whereas this behavior is inversed in the very high-cycle fatigue regime. These results are analyzed in terms of residual compression stresses induced by the work-hardening machining process, the surface roughness, and the reverse yielding or Bauschinger effect. © 2015 by ASTM International.

In recent years eating disorders have increased their presence in Mexico. It has been suggested that internet and social network which promote restrictive behavior influence and may be responsible for this increment. Nowadays, internet plays a fundamental roll in the teaching-learning process and a very important tool in informal education, however, the use of internet and social network haven't been significantly related to the development of those eating disorders. On the other hand, one of the most accepted models about influential factors of the mentioned disorders leaves out the possibility that constant contact with these technology tools favors the development of anorexia and bulimia and other unspecified problems if we do not have the presence of other important factors.

Gonzalez-A G.,University of Morelia
Proceedings of the Institution of Mechanical Engineers. Part I: Journal of Systems and Control Engineering | Year: 2016

A bond graph model for a closed-loop linear time invariant multiple input multiple output system with singular perturbations is presented. This system is formed by a plant, an observer and the feedback. Hence, the storage elements that represent the slow dynamics of the observer determine the feedback control. Also, a junction structure of the bond graph model for the closed-loop system with singular perturbations is proposed. A new bond graph to obtain the observer and controller gains of the closed-loop system is presented. This new bond graph has the characteristic that storage elements of the fast dynamics and slow dynamics have a derivative and integral causality assignment, respectively. Thus, a quasi-steady state model of a singularly perturbed system with a slow state estimated feedback is obtained. Finally, the proposed methodology is applied to an illustrative example. © Institution of Mechanical Engineers 2016.

Arteaga-Velazquez J.C.,University of Morelia
Astroparticle Physics | Year: 2012

The diffuse neutrino flux from FRI and BL Lac type galaxies generated from interactions of their own γ radiation with the gas and dust at the sources is reported. This ν-production channel has not been studied in detail up to now. The calculations are based on individual estimations of the neutrino flux in two nearby AGN's: Centaurus A and M87, assuming the validity of the AGN unification model. The predictions for Centaurus A and M87 involved the parameterization of the measured gamma-ray luminosities and the modeling of the material of the galaxies both based on observations performed by several detectors. No hadronic origin for the TeV photons is assumed. The results show that, although the corresponding ν flux ( E2Φν+ ν̄≲10 -13s- 1sr- 1GeVcm- 2) is not competitive at high-energies ( ν≳1TeV) with that from hadronic models, FRI and BL Lac galaxies with γ emission should be already contributing to the diffuse flux of neutrinos in the universe. © 2012 Elsevier B.V. All rights reserved.

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