Vazquez R.,Escuela Tecnica Superior de Ingenieria |
Rivas D.,Escuela Tecnica Superior de Ingenieria |
Franco A.,Escuela Tecnica Superior de Ingenieria
Aerospace Science and Technology | Year: 2017
The effects of along-track wind uncertainty on aircraft fuel consumption are analyzed. The case of cruise flight subject to an average constant wind is considered. The average wind is modeled as a random variable, which in this paper is assumed to follow either a uniform or a beta distribution. The probability density function (pdf) of the fuel consumption is obtained using a numerical approach that is based on the Probability Transformation Method (a method that evolves the wind pdf). The dynamics of aircraft mass evolution in cruise flight is defined by a simple nonlinear equation that can be solved analytically; this exact solution is used to assess the accuracy of the method. A general analysis is performed for arbitrary along-track winds. Comparison of the numerical results with the exact analytical solution shows an excellent agreement in all cases. A linear approximation is analyzed as well, which turns out to be very accurate for this problem. The results show that the standard deviation of the fuel mass distribution varies almost linearly with the standard deviation of the wind, whereas the mean of the fuel mass is practically independent of the wind uncertainty. They also show that, for the same along-track wind uncertainty, the uncertainty in the fuel consumption is larger in the case of headwinds than in the case of tailwinds. © 2017 Elsevier Masson SAS
Orive J.,University of the Basque Country |
Balda R.,Escuela Tecnica Superior de Ingenieria |
Balda R.,Donostia International Physics Center |
Fernandez J.,Escuela Tecnica Superior de Ingenieria |
And 3 more authors.
Dalton Transactions | Year: 2013
M2(SeO3)F2 (M = Zn (1), Mn (2)) stoichiometric phases together with the Zn2-xMnx(SeO 3)F2 compound doped at various concentrations (x = 0.002-0.2) were synthesized by employing mild hydrothermal conditions. These compounds have been characterized by scanning electron microscopy (SEM), Rietveld refinement of the X-ray powder diffraction patterns, ICP-Q-MS, thermogravimetric and thermodiffractometric analyses, and IR, UV/vis and electron paramagnetic resonance (EPR) spectroscopies. Compounds 1 and 2 crystallize in the orthorhombic Pnma space group with lattice parameters: a = 7.27903(4), b = 10.05232(6) and c = 5.26954(3) Å for the zinc species and a = 7.50848(9), b = 10.3501(12) and c = 5.47697(6) Å for the manganese phase, with Z = 4. The crystal structures of these compounds are isotypic and are built up from a 3D framework constructed by (010) sheets of [MO 3F3] octahedra linked up by [SeO3] building units. Luminescence measurements of Mn2(SeO3)F2 were performed at different temperatures between 10 and 150 K. At 10 K, the emission spectrum consists of a broad band peaked at around 660 nm related to the 4T1g → 6A1g transition in octahedrically coordinated Mn2+. Moreover, the influence of temperatures up to 295 K and the Mn concentration on the luminescent properties of the Zn2-xMnx(SeO3)F2 system were systematically studied. Magnetic measurements of 2 show antiferromagnetic coupling as the major interactions exhibiting a spin canting at low temperature. © 2013 The Royal Society of Chemistry.
Gandarias I.,Escuela Tecnica Superior de Ingenieria |
Requies J.,Escuela Tecnica Superior de Ingenieria |
Arias P.L.,Escuela Tecnica Superior de Ingenieria |
Armbruster U.,Leibniz Institute for Catalysis at the University of Rostock |
Martin A.,Leibniz Institute for Catalysis at the University of Rostock
Journal of Catalysis | Year: 2012
Two series of Ni-Cu/Al 2O 3 catalysts with different Cu/Ni ratio and different total metal contents were prepared and tested in the glycerol hydrogenolysis to 1,2-propanediol under N 2 pressure and using formic acid as hydrogen donor molecule. The results from the deep characterization of the catalysts by N 2-physisorption, transmission electron microscopy (TEM), temperature-programed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programed desorption of ammonia (TPD-NH 3), together with the results from the activity tests allowed deeper understanding of the role played by Ni, Cu, and acid catalytic sites. The kinetic study performed with the optimized catalyst revealed that the OH groups of glycerol and of the target product, 1,2-propanediol, compete for adsorption on the acid sites of the Al 2O 3 support. 90% glycerol conversion and 82% 1,2-propanediol selectivity after 24 h reaction time were achieved when operating at 493 K. © 2012 Elsevier Inc. All rights reserved.
Pecoraro E.,University of Aveiro |
Garcia-Revilla S.,Escuela Tecnica Superior de Ingenieria |
Ferreira R.A.S.,University of Aveiro |
Balda R.,Escuela Tecnica Superior de Ingenieria |
And 4 more authors.
Optics Express | Year: 2010
This investigation explores, for the first time, the random laser behavior of ground powder obtained from organic-inorganic hybrid materials based on Rhodamine 6G incorporated into a di-ureasil matrix. The experimental results, both in the spectral and temporal domains, obtained by pumping with picosecond laser pulses, show the existence of efficient random laser emission in this system. Finally, the random laser performance is compared with the one of other Rhodamine-doped solid state silica compounds. © 2010 Optical Society of America.
Sarras I.,Free University of Colombia |
Acosta J.A.,Escuela Tecnica Superior de Ingenieria |
Ortega R.,Supelec |
Mahindrakar A.D.,Indian Institute of Technology Madras
Automatica | Year: 2013
A constructive approach to stabilize a desired equilibrium for a class of underactuated mechanical systems, which obviates the solution of partial differential equations, is proposed. The Immersion & Invariance methodology is adopted, with the main result formulated in the Port-Hamiltonian framework, for both model and target dynamics. The procedure is applicable to mechanical systems with under-actuation degree larger than one, extending the results recently reported by some of the authors. The approach is successfully applied to two benchmark examples and some basic connections with the interconnection and damping assignment passivity-based control are revealed. An additional contribution of this work is the identification of a class of mechanical systems whose mechanical structure remains invariant under partial feedback linearization. © 2013 Elsevier Ltd. All rights reserved.
Novaes D.D.,Autonomous University of Barcelona |
Novaes D.D.,University of Campinas |
Ponce E.,Escuela Tecnica Superior de Ingenieria
International Journal of Bifurcation and Chaos | Year: 2015
Recently Braga and Mello conjectured that for a given n ∈ N there is a piecewise linear system with two zones in the plane with exactly n limit cycles. In this paper, we prove a result from which the conjecture is an immediate consequence. Several explicit examples are given where location and stability of limit cycles are provided. © 2015 World Scientific Publishing Company.
Llibre J.,Autonomous University of Barcelona |
Ordonez M.,Escuela Tecnica Superior de Ingenieria |
Ponce E.,Escuela Tecnica Superior de Ingenieria
Nonlinear Analysis: Real World Applications | Year: 2013
Some techniques to show the existence and uniqueness of limit cycles, typically stated for smooth vector fields, are extended to continuous piecewise-linear differential systems. New results are obtained for systems with three linearity zones without symmetry and having one equilibrium point in the central region. We also revisit the case of systems with only two linear zones giving shorter proofs of known results. A relevant application to the McKean piecewise linear model of a single neuron activity is included. © 2013 Elsevier Ltd. All rights reserved.
Pizzuti T.,University of Calabria |
Mirabelli G.,University of Calabria |
Sanz-Bobi M.A.,Escuela Tecnica Superior de Ingenieria |
Gomez-Gonzalez F.,Escuela Tecnica Superior de Ingenieria
Journal of Food Engineering | Year: 2014
This paper describes a food ontology developed for traceability purposes. The Food Track&Trace Ontology (FTTO) is part of a general framework devoted to managing food traceability and it has been developed with the aim of being connected with a Global Track&Trace Information System. The main goal of the proposed FTTO Ontology is to include the most representative food concepts involved in a SC all together in a single ordered hierarchy, able to integrate and connect the main features of the food traceability domain. FTTO is formed by four modules food, service products, processes and actors involved in the supply chain. This paper describes the main features of the FTTO ontology and some examples of application. © 2013 Elsevier Ltd. All rights reserved.
Franco A.,Escuela Tecnica Superior de Ingenieria |
Rivas D.,Escuela Tecnica Superior de Ingenieria
Aerospace Science and Technology | Year: 2014
Minimum-fuel cruise at constant altitude with the constraint of a fixed arrival time is analyzed, including the effects of average horizontal winds. The analysis is made using the theory of singular optimal control. The optimal control is of the bang-singular-bang type, and the optimal trajectories are formed by a singular arc and two minimum/maximum-thrust arcs joining the singular arc with the given initial and final points. The effects of average horizontal winds on the optimal results are analyzed, both qualitatively and quantitatively. The influence of the initial aircraft weight and the given cruise altitude is analyzed as well. Two applications are studied: first, the cost of meeting the given arrival time under mismodeled winds, and, second, the cost of flight delays imposed on a nominal optimal path. The optimal results are used to assess the optimality of cruising at constant speed; the results show that the standard constant-Mach cruise is very close to optimal. Results are presented for a model of a Boeing 767-300ER. © 2013 Elsevier Masson SAS. Allrights reserved.
Freire E.,Escuela Tecnica Superior de Ingenieria |
Ponce E.,Escuela Tecnica Superior de Ingenieria |
Torres F.,Escuela Polytechnic Superior
Nonlinear Dynamics | Year: 2014
Discontinuous piecewise linear systems with two zones are considered. A general canonical form that includes all the possible configurations in planar linear systems is introduced and exploited. It is shown that the existence of a focus in one zone is sufficient to get three nested limit cycles, independently on the dynamics of the another linear zone. Perturbing a situation with only one hyperbolic limit cycle, two additional limit cycles are obtained by using an adequate parametric sector of the unfolding of a codimension-two focus-fold singularity. © 2014, Springer Science+Business Media Dordrecht.