Archivo Digital UPM: No conditions. Results ordered -Date Deposited. 2022-01-29T11:38:42ZEPrintshttps://oa.upm.es/style/images/logo-archivo-digital.pnghttps://oa.upm.es/2015-03-04T19:37:33Z2015-03-04T19:37:33Zhttps://oa.upm.es/id/eprint/33237This item is in the repository with the URL: https://oa.upm.es/id/eprint/332372015-03-04T19:37:33ZRecovery of Disruptions in Rapid Transit NetworksThis paper studies the disruption management problem of rapid transit rail networks. Besides optimizing the timetable and the rolling stock schedules, we explicitly deal with the effects of the disruption on the passenger demand.
We propose a two-step approach that combines an integrated optimization model (for the timetable and rolling stock) with a model for the passengers’ behavior.
We report our computational tests on realistic problem instances of the Spanish rail operator RENFE. The proposed approach is able to find solutions with a very good balance between various managerial goals within a few minutes.
Se estudia la gestión de las incidencias en redes de metro y cercanías. Se optimizan los horarios y la asignación del material rodante, teniendo en cuenta el comportamiento de los pasajeros. Se reallizan pruebas en varias líneas de la red de cercanías de Madrid, con resultados satisfactorios.Luis Cadarso MorgaAngel Marín GraciaGábor Maróti2014-11-14T17:57:03Z2014-11-14T17:57:03Zhttps://oa.upm.es/id/eprint/16704This item is in the repository with the URL: https://oa.upm.es/id/eprint/167042014-11-14T17:57:03ZComment on the existence of a long range correlation in the geomagnetic disturbance storm time (Dst) indexVery recently (Banerjee et al. in Astrophys. Space, doi:1007/s10509-011-0836-1, 2011) the statistics of geomagnetic Disturbance storm (Dst) index have been addressed, and the conclusion from this analysis suggests that the underlying dynamical process can be modeled as a fractional Brownian motion with persistent long-range correlations. In this comment we expose several misconceptions and flaws in the statistical analysis of that work. On the basis of these arguments, the former conclusion should be revisited.Lucas Lacasa Saiz de Arce2014-11-13T19:25:26Z2014-11-13T19:25:26Zhttps://oa.upm.es/id/eprint/16712This item is in the repository with the URL: https://oa.upm.es/id/eprint/167122014-11-13T19:25:26ZDetecting periodicity with horizontal visibility graphsThe horizontal visibility algorithm was recently introduced as a mapping between time series and networks. The challenge lies in characterizing the structure of time series (and the processes that generated those series) using the powerful tools of graph theory. Recent works have shown that the visibility graphs inherit several degrees of correlations from their associated series, and therefore such graph theoretical characterization is in principle possible. However, both the mathematical grounding of this promising theory and its applications are in its infancy. Following this line, here we address the question of detecting hidden periodicity in series polluted with a certain amount of noise. We first put forward some generic properties of horizontal visibility graphs which allow us to define a (graph theoretical) noise reduction filter. Accordingly, we evaluate its performance for the task of calculating the period of noisy periodic signals, and compare our results with standard time domain (autocorrelation) methods. Finally, potentials, limitations and applications are discussed.Ángel M. NúñezLucas Lacasa Saiz de ArceEusebio Valero SánchezJose Patricio Gómez PérezBartolome Luque Serrano2014-11-13T17:26:22Z2021-11-17T10:36:14Zhttps://oa.upm.es/id/eprint/16710This item is in the repository with the URL: https://oa.upm.es/id/eprint/167102014-11-13T17:26:22ZPhase transition in the countdown problemWe present a combinatorial decision problem, inspired by the celebrated quiz show called Countdown, that involves the computation of a given target number T from a set of k randomly chosen integers along with a set of arithmetic operations. We find that the probability of winning the game evidences a threshold phenomenon that can be understood in the terms of an algorithmic phase transition as a function of the set size k. Numerical simulations show that such probability sharply transitions from zero to one at some critical value of the control parameter, hence separating the algorithm's parameter space in different phases. We also find that the system is maximally efficient close to the critical point. We derive analytical expressions that match the numerical results for finite size and permit us to extrapolate the behavior in the thermodynamic limit.Lucas Lacasa Saiz de ArceBartolome Luque Serrano2014-11-13T16:50:34Z2014-11-13T16:50:34Zhttps://oa.upm.es/id/eprint/16708This item is in the repository with the URL: https://oa.upm.es/id/eprint/167082014-11-13T16:50:34ZTime series irreversibility: a visibility graph approachWe propose a method to measure real-valued time series irreversibility which combines two different tools: the horizontal visibility algorithm and the Kullback-Leibler divergence. This method maps a time series to a directed network according to a geometric criterion. The degree of irreversibility of the series is then estimated by the Kullback-Leibler divergence (i.e. the distinguishability) between the in and out degree distributions of the associated graph. The method is computationally efficient and does not require any ad hoc symbolization process. We find that the method correctly distinguishes between reversible and irreversible stationary time series, including analytical and numerical studies of its performance for: (i) reversible stochastic processes (uncorrelated and Gaussian linearly correlated), (ii) irreversible stochastic processes (a discrete flashing ratchet in an asymmetric potential), (iii) reversible (conservative) and irreversible (dissipative) chaotic maps, and (iv) dissipative chaotic maps in the presence of noise. Two alternative graph functionals, the degree and the degree-degree distributions, can be used as the Kullback-Leibler divergence argument. The former is simpler and more intuitive and can be used as a benchmark, but in the case of an irreversible process with null net current, the degree-degree distribution has to be considered to identify the irreversible nature of the seriesLucas Lacasa Saiz de ArceAngel Manuel Nuñez NuñezE. RoldánJ.M.R. ParrondoBartolome Luque Serrano2014-11-13T16:20:44Z2014-11-13T16:20:44Zhttps://oa.upm.es/id/eprint/16711This item is in the repository with the URL: https://oa.upm.es/id/eprint/167112014-11-13T16:20:44ZFeigenbaum graphs at the onset of chaosWe analyze the properties of networks obtained from the trajectories of unimodal maps at the transi-
tion to chaos via the horizontal visibility (HV) algorithm. We find that the network degrees fluctuate
at all scales with amplitude that increases as the size of the network grows, and can be described by a
spectrum of graph-theoretical generalized Lyapunov exponents. We further define an entropy growth rate
that describes the amount of information created along paths in network space, and find that such en-
tropy growth rate coincides with the spectrum of generalized graph-theoretical exponents, constituting a
set of Pesin-like identities for the network.Bartolome Luque SerranoLucas Lacasa Saiz de ArceAlberto Robledo2014-11-11T16:54:27Z2014-11-11T16:54:27Zhttps://oa.upm.es/id/eprint/16286This item is in the repository with the URL: https://oa.upm.es/id/eprint/162862014-11-11T16:54:27ZComputational Fluid Dynamics Expert System using Artificial Neural NetworksThe design of a modern aircraft is based on three pillars:
theoretical results, experimental test and computational simulations. As a results of this, Computational Fluid Dynamic (CFD) solvers are widely used in the aeronautical field. These solvers require the correct selection of many parameters in order to obtain successful results.
Besides, the computational time spent in the simulation depends on the proper choice of these parameters.
In this paper we create an expert system capable of making an accurate prediction of the number of iterations and time required for the convergence of a computational fluid dynamic (CFD) solver.
Artificial neural network (ANN) has been used to design the expert system. It is shown that the developed expert system is capable of making an accurate prediction the number of iterations and time required for the convergence of a CFD solver.Gonzalo Rubio CalzadoEusebio Valero SánchezSven Lanzan2014-11-05T18:58:57Z2014-11-13T18:10:26Zhttps://oa.upm.es/id/eprint/16707This item is in the repository with the URL: https://oa.upm.es/id/eprint/167072014-11-05T18:58:57ZApproximate entropy of network parametersWe study the notion of approximate entropy within the framework of network theory. Approximate entropy is an uncertainty measure originally proposed in the context of dynamical systems and time series. We first define a purely structural entropy obtained by computing the approximate entropy of the so-called slide sequence. This is a surrogate of the degree sequence and it is suggested by the frequency partition of a graph. We examine this quantity for standard scale-free and Erdös-Rényi networks. By using classical results of Pincus, we show that our entropy measure often converges with network size to a certain binary Shannon entropy. As a second step, with specific attention to networks generated by dynamical processes, we investigate approximate entropy of horizontal visibility graphs. Visibility graphs allow us to naturally associate with a network the notion of temporal correlations, therefore providing the measure a dynamical garment. We show that approximate entropy distinguishes visibility graphs generated by processes with different complexity. The result probes to a greater extent these networks for the study of dynamical systems. Applications to certain biological data arising in cancer genomics are finally considered in the light of both approaches.James WestLucas Lacasa Saiz de ArceSimone SeveriniAndrew Teschendorff2014-11-05T17:37:27Z2014-11-05T17:37:27Zhttps://oa.upm.es/id/eprint/15294This item is in the repository with the URL: https://oa.upm.es/id/eprint/152942014-11-05T17:37:27ZComparison of Mesh Adaptation Using the Adjoint Methodology and Truncation Error EstimatesMesh adaptation based on error estimation has become a key technique to improve th eaccuracy o fcomputational-fluid-dynamics computations. The adjoint-based approach for error estimation is one of the most promising techniques for computational-fluid-dynamics applications. Nevertheless, the level of implementation of this technique in the aeronautical industrial environment is still low because it is a computationally expensive method. In the present investigation, a new mesh refinement method based on estimation of truncation error is presented in the context of finite-volume discretization. The estimation method uses auxiliary coarser meshes to estimate the local truncation error, which can be used for driving an adaptation algorithm. The method is demonstrated in the context
of two-dimensional NACA0012 and three-dimensional ONERA M6 wing inviscid flows, and the results are compared against the adjoint-based approach and physical sensors based on features of the flow field.François FraysseEusebio Valero SánchezJorge Ponsin Roca2014-11-04T19:45:23Z2014-11-04T19:45:23Zhttps://oa.upm.es/id/eprint/16718This item is in the repository with the URL: https://oa.upm.es/id/eprint/167182014-11-04T19:45:23ZReply to Comment on ``Towards a large deviation theory for strongly correlated systems''The computational study commented by Touchette opens the door to a desirable generalization of standard large deviation theory for special, though ubiquitous, correlations. We focus on three interrelated aspects: (i) numerical results strongly suggest that the standard exponential probability law is asymptotically replaced by a power-law dominant term; (ii) a subdominant term appears to reinforce the thermodynamically extensive entropic nature of q-generalized rate function; (iii) the correlations we discussed, correspond to Q -Gaussian distributions, differing from Lévy?s, except in the case of Cauchy?Lorentz distributions. Touchette has agreeably discussed point (i), but, unfortunately, points (ii) and (iii) escaped to his analysis. Claiming the absence of connection with q-exponentials is unjustified.Guiomar Ruiz LopezConstantino Tsallis2014-11-03T18:54:40Z2014-11-03T18:54:40Zhttps://oa.upm.es/id/eprint/22657This item is in the repository with the URL: https://oa.upm.es/id/eprint/226572014-11-03T18:54:40ZRobust rolling stock under uncertain demand in rapid transit networksThis paper focuses on the railway rolling stock circulation problem in rapid transit networks where the known demand and train schedule must be met by a given fleet. In rapid transit networks the frequencies are high and distances are relatively short. Although the distances are not very large, service times are high due to the large number of intermediate stops required to allow proper passenger flow. The previous circumstances and the reduced capacity of the depot stations and that the rolling stock is shared between
the different lines, force the introduction of empty trains and a careful control on shunting operation.
In practice the future demand is generally unknown and the decisions must be based on uncertain forecast. We have developed a stochastic rolling stock formulation of the problem. The computational experiments were developed using a commercial line of the Madrid suburban rail network operated by RENFE (The main Spanish operator of suburban trains of passengers). Comparing the results obtained
by deterministic scenarios and stochastic approach some useful conclusions may be obtained.Luis Cadarso MorgaAngel Marín GraciaLuis Torres2014-10-27T18:44:47Z2014-10-27T18:44:47Zhttps://oa.upm.es/id/eprint/29354This item is in the repository with the URL: https://oa.upm.es/id/eprint/293542014-10-27T18:44:47ZQuasiperiodic Graphs: Structural Design, Scaling and Entropic PropertiesA novel class of graphs, here named quasiperiodic, are const
ructed via application of the Horizontal Visibility algorithm to the time series generated along the
quasiperiodic route to chaos. We show how the hierarchy of mode-locked regions represented by the Far ey tree is inherited by their associated graphs. We are able to establish, via Renormalization Group (RG) theory, the architecture of the quasiperiodic graphs produced by irrational winding numbers with pure periodic continued
fraction. And finally, we demonstrate that the RG fixed-point degree distributions are recovered via
optimization of a suitably defined graph entropyBartolome Luque SerranoFernando J. BallesterosÁngel M. NúñezAlberto Robledo2014-10-10T15:46:33Z2014-11-13T18:10:08Zhttps://oa.upm.es/id/eprint/29159This item is in the repository with the URL: https://oa.upm.es/id/eprint/291592014-10-10T15:46:33ZPhase transitions in number theory: from the birthday problem to Sidon setsIn this work, we show how number theoretical problems can be fruitfully approached with the tools of statistical physics. We focus on g-Sidon sets, which describe sequences of integers whose pairwise sums are different, and propose a random decision problem which addresses the probability of a random set of k integers to be g-Sidon. First, we provide numerical evidence showing that there is a crossover between satisfiable and unsatisfiable phases which converts to an abrupt phase transition in a properly defined thermodynamic limit. Initially assuming independence, we then develop a mean-field theory for the g-Sidon decision problem. We further improve the mean-field theory, which is only qualitatively correct, by incorporating deviations from independence, yielding results in good quantitative agreement with the numerics for both finite systems and in the thermodynamic limit. Connections between the generalized birthday problem in probability theory, the number theory of Sidon sets and the properties of q-Potts models in condensed matter physics are briefly discussedBartolome Luque SerranoIvan G. TorreLucas Lacasa Saiz de Arce2014-08-07T16:28:41Z2014-09-22T11:44:37Zhttps://oa.upm.es/id/eprint/29153This item is in the repository with the URL: https://oa.upm.es/id/eprint/291532014-08-07T16:28:41ZHorizontal visibility graphs generated by type-I intermittencyThe type-I intermittency route to (or out of) chaos is investigated within the horizontal visibility (HV) graph
theory. For that purpose, we address the trajectories generated by unimodal maps close to an inverse tangent
bifurcation and construct their associatedHVgraphs.We showhowthe alternation of laminar episodes and chaotic
bursts imprints a fingerprint in the resulting graph structure. Accordingly, we derive a phenomenological theory
that predicts quantitative values for several network parameters. In particular, we predict that the characteristic power-law scaling of the mean length of laminar trend sizes is fully inherited by the variance of the graph degree distribution, in good agreement with the numerics. We also report numerical evidence on how the characteristic power-law scaling of the Lyapunov exponent as a function of the distance to the tangent bifurcation is inherited in the graph by an analogous scaling of block entropy functionals defined on the graph. Furthermore, we are able to recast the full set of HV graphs generated by intermittent dynamics into a renormalization-group framework, where the fixed points of its graph-theoretical renormalization-group flow account for the different types of dynamics.We also establish that the nontrivial fixed point of this flow coincides with the tangency condition and
that the corresponding invariant graph exhibits extremal entropic properties.Ángel M. NúñezBartolome Luque SerranoLucas Lacasa Saiz de ArceJose Patricio Gómez PérezAlberto Robledo2014-08-07T16:10:14Z2014-09-22T11:44:37Zhttps://oa.upm.es/id/eprint/29154This item is in the repository with the URL: https://oa.upm.es/id/eprint/291542014-08-07T16:10:14ZQuasiperiodic graphs at the onset of chaosWe examine the connectivity fluctuations across networks obtained when the horizontal visibility (HV)
algorithm is used on trajectories generated by nonlinear circle maps at the quasiperiodic transition to chaos.
The resultant HV graph is highly anomalous as the degrees fluctuate at all scales with amplitude that increases
with the size of the network. We determine families of Pesin-like identities between entropy growth rates and
generalized graph-theoretical Lyapunov exponents. An irrational winding number with pure periodic continued
fraction characterizes each family. We illustrate our results for the so-called golden, silver, and bronze numbersBartolome Luque SerranoMarta Amalia Cordero GraciaAlberto RobledoMariola Gómez López2014-08-06T16:28:19Z2014-09-22T11:44:36Zhttps://oa.upm.es/id/eprint/29152This item is in the repository with the URL: https://oa.upm.es/id/eprint/291522014-08-06T16:28:19ZCorrelation Dimension of Complex NetworksWe propose a new measure to characterize the dimension of complex networks based on the ergodic theory of dynamical systems. This measure is derived from the correlation sum of a trajectory generated by a random walker navigating the network, and extends the classical Grassberger-Procaccia algorithm to the context of complex networks. The method is validated with reliable results for both synthetic networks
and real-world networks such as the world air-transportation network or urban networks, and provides a
computationally fast way for estimating the dimensionality of networks which only relies on the local
information provided by the walkers.Lucas Lacasa Saiz de ArceJesús Gómez-Gardeñes2014-06-05T18:33:11Z2016-04-21T15:19:19Zhttps://oa.upm.es/id/eprint/15270This item is in the repository with the URL: https://oa.upm.es/id/eprint/152702014-06-05T18:33:11ZColumn Generation Algorithms for Nonlinear Optimization II: Numerical InvestigationsGarcía et al. present a class of column generation (CG) algorithms for nonlinear programs. Its main
motivation from a theoretical viewpoint is that under some circumstances, finite convergence can be
achieved, in much the same way as for the classic simplicial decomposition method; the main practical
motivation is that within the class there are certain nonlinear column generation problems that can
accelerate the convergence of a solution approach which generates a sequence of feasible points. This
algorithm can, for example, accelerate simplicial decomposition schemes by making the subproblems
nonlinear. This paper complements the theoretical study on the asymptotic and finite convergence of
these methods given in
[1]
with an experimental study focused on their computational efficiency.
Three types of numerical experiments are conducted. The first group of test problems has been
designed to study the parameters involved in these methods. The second group has been designed to
investigate the role and the computation of the prolongation of the generated columns to the relative
boundary. The last one has been designed to carry out a more complete investigation of the difference
in computational efficiency between linear and nonlinear column generation approaches.
In order to carry out this investigation, we consider two types of test problems: the first one is the
nonlinear, capacitated single-commodity network flow problem of which several large-scale instances
with varied degrees of nonlinearity and total capacity are constructed and investigated, and the second
one is a combined traffic assignment modelRicardo García RódenasAngel Marín GraciaMichael Patriksson2014-04-08T18:29:38Z2016-04-21T17:04:22Zhttps://oa.upm.es/id/eprint/16705This item is in the repository with the URL: https://oa.upm.es/id/eprint/167052014-04-08T18:29:38ZAnalytical properties of horizontal visibility graphs in the Feigenbaum scenarioTime series are proficiently converted into graphs via the horizontal visibility (HV) algorithm, which prompts interest in its capability for capturing the nature of different classes of series in a network context. We have recently shown [B. Luque et al., PLoS ONE 6, 9 (2011)] that dynamical systems can be studied from a novel perspective via the use of this method. Specifically, the period-doubling and band-splitting attractor cascades that characterize unimodal maps transform into families of graphs that turn out to be independent of map nonlinearity or other particulars. Here, we provide an in depth description of the HV treatment of the Feigenbaum scenario, together with analytical derivations that relate to the degree distributions, mean distances, clustering
coefficients, etc., associated to the bifurcation cascades and their accumulation points. We describe how the resultant families of graphs can be framed into a renormalization group scheme in which fixed-point graphs reveal their scaling properties. These fixed points are then re-derived from an entropy optimization process defined for the graph sets, confirming a suggested connection between renormalization group and entropy optimization. Finally, we provide analytical and numerical
results for the graph entropy and show that it emulates the Lyapunov exponent of the map independently of its sign.Bartolome Luque SerranoLucas Lacasa Saiz de ArceFernando J. BallesterosAlberto Robledo2014-04-02T15:44:55Z2016-04-21T15:19:52Zhttps://oa.upm.es/id/eprint/15277This item is in the repository with the URL: https://oa.upm.es/id/eprint/152772014-04-02T15:44:55ZAirport Taxi Planning: Lagrangian DecompositionThe airport taxi planning (TP) module is a decision tool intended to guide airport surface management
operations. TP is defined by a flow network optimization model that represents flight ground movements and
improves aircraft taxiing routes and schedules during periods of aircraft congestion. TP is not intended to
operate as a stand‐alone tool for airport operations management: on the contrary, it must be used in
conjunction with existing departing and arriving traffic tools and overseen by the taxi planner of the airport,
also known as the aircraft ground controller. TP must be flexible in order to accommodate changing inputs
while maintaining consistent routes and schedules already delivered from past executions. Within this
dynamic environment, the execution time of TP may not exceed a few minutes. Classic methods for solving
binary multi‐commodity flow networks with side constraints are not efficient enough; therefore, a Lagrangian
decomposition methodology has been adapted to solve it. We demonstrate TP Lagrangian decomposition
using actual data from the Madrid‐Barajas AirportAngel Marín Gracia2014-04-02T14:29:20Z2016-04-21T15:19:44Zhttps://oa.upm.es/id/eprint/15274This item is in the repository with the URL: https://oa.upm.es/id/eprint/152742014-04-02T14:29:20ZDesigning Rapid Transit Network Design with Alternative routesThe aim of this paper is to propose a model for the design of a robust rapid transit network. In this paper, a
network is said to be robust when the effect of disruption on total trip coverage is minimized. The proposed
model is constrained by three different kinds of flow conditions. These constraints will yield a network that
provides several alternative routes for given origin–destination pairs, therefore increasing robustness. The
paper includes computational experiments which show how the introduction of robustness influences
network designGilbert LaporteAngel Marín GraciaJuan Antonio MesaFederico Perea2013-08-29T11:14:37Z2016-04-21T15:20:00Zhttps://oa.upm.es/id/eprint/15280This item is in the repository with the URL: https://oa.upm.es/id/eprint/152802013-08-29T11:14:37ZIntegration of Timetable Planning and Rolling Stock in Rapid Transit NetworksThe aim of this paper is to propose an integrated planning model to adequate the offered capacity and system frequencies to attend the increased passenger demand and traffic congestion around urban and suburban areas. The railway capacity is studied in line planning, however, these planned frequencies were obtained without accounting for rolling stock flows through the rapid transit network.
In order to provide the problem more freedom to decide rolling stock flows and therefore better adjusting these flows to passenger demand, a new integrated model is proposed, where frequencies are readjusted. Then, the railway timetable and rolling stock assignment are also calculated, where shunting operations are taken into account. These operations may sometimes malfunction, causing localized incidents that could propagate throughout the entire network due to cascading effects. This type of operations will be penalized with the goal of selectively avoiding them and ameliorating their high malfunction probabilities. Swapping operations will also be ensured using homogeneous rolling stock material and ensuring parkings in strategic stations.
We illustrate our model using computational experiments drawn from RENFE (the main Spanish operator of suburban passenger trains) in Madrid, Spain. The results show that through this integrated approach a greater robustness degree can be obtainedLuis Cadarso MorgaAngel Marín Gracia2013-07-22T07:53:45Z2016-04-21T15:19:56Zhttps://oa.upm.es/id/eprint/15278This item is in the repository with the URL: https://oa.upm.es/id/eprint/152782013-07-22T07:53:45ZRobust rolling stock in rapid transit networkThis paper focuses on the railway rolling stock circulation problem in rapid transit networks, in which frequencies are high and distances are relatively short. Although the distances are not very large, service times are high due to the large number of intermediate stops required to allow proper passenger flow. The main complicating issue is the fact that the available capacity at depot stations is very low, and both capacity and rolling stock are shared between different train lines. This forces the introduction of empty train movements and rotation maneuvers, to ensure sufficient station capacity and rolling stock availability.
However, these shunting operations may sometimes be difficult to perform and can easily malfunction, causing localized incidents that could propagate throughout the entire network due to cascading effects. This type of operation will be penalized with the goal of selectively avoiding them and ameliorating their high malfunction probabilities. Critic trains, defined as train services that come through stations that have a large number of passengers arriving at the platform during rush hours, are also introduced.
We illustrate our model using computational experiments drawn from RENFE (the main Spanish operator of suburban passenger trains) in Madrid, Spain. The results of the model, achieved in approximately 1 min, have been received positively by RENFE plannersLuis Cadarso MorgaAngel Marín Gracia2013-07-11T09:45:26Z2016-04-21T15:19:48Zhttps://oa.upm.es/id/eprint/15276This item is in the repository with the URL: https://oa.upm.es/id/eprint/152762013-07-11T09:45:26ZIntegrated robust airline schedule developmentIn air transportation, airline profitability is influenced by the airline's ability to build flight schedules. In order to generate operational schedules, airlines engage in a complex decision-making process, referred to as airline schedule planning. Up to now, the generation of flight schedules has been separated and optimized sequentially. The schedule design has been traditionally decomposed into two sequential steps. The frequency planning and the timetable development. The purpose of the second problem of schedule development, fleet assignment, is to assign available aircraft types to flight legs such that seating capacity on an assigned aircraft matches closely with flight demand and such that costs are minimized. Our work integrates these planning phases into one single model in order to produce more economical solutions and create fewer incompatibilities between the decisions. We propose an integrated robust approach for the schedule development step. We design the timetable ensuring that enough time is available to perform passengers’ flight connections, making the system robust avoiding misconnected passengers. An application of the model for a simplified IBERIA network is shown.Luis Cadarso MorgaAngel Marín Gracia2012-09-05T11:51:55Z2016-04-21T11:30:00Zhttps://oa.upm.es/id/eprint/12259This item is in the repository with the URL: https://oa.upm.es/id/eprint/122592012-09-05T11:51:55ZThe estimation of truncation error by tau-estimation revisitedThe aim of this paper was to accurately estimate the local truncation error of partial differential equations, that are numerically solved using a finite difference or finite volume approach on structured and unstructured meshes. In this work, we approximated the local truncation error using the @t-estimation procedure, which aims to compare the residuals on a sequence of grids with different spacing. First, we focused the analysis on one-dimensional scalar linear and non-linear test cases to examine the accuracy of the estimation of the truncation error for both finite difference and finite volume approaches on different grid topologies. Then, we extended the analysis to two-dimensional problems: first on linear and non-linear scalar equations and finally on the Euler equations. We demonstrated that this approach yields a highly accurate estimation of the truncation error if some conditions are fulfilled. These conditions are related to the accuracy of the restriction operators, the choice of the boundary conditions, the distortion of the grids and the magnitude of the iteration error.François FraysseJavier de Vicente BuendiaEusebio Valero Sánchez2011-08-29T08:22:25Z2016-04-20T17:11:24Zhttps://oa.upm.es/id/eprint/8369This item is in the repository with the URL: https://oa.upm.es/id/eprint/83692011-08-29T08:22:25ZCritical behavior of a Ginzburg-Landau model with additive quenched noiseWe address a mean-field zero-temperature Ginzburg–Landau, or 4, model subjected to quenched additive noise, which has been used recently as a framework for analyzing collective effects induced by diversity. We first make use of a self-consistent theory to calculate the phase diagram of the system, predicting the onset of an order–disorder critical transition at a critical value σc of the quenched noise intensity σ, with critical exponents that follow the Landau theory of thermal phase transitions. We subsequently perform a numerical integration of the system's dynamical variables in order to compare the analytical results (valid in the thermodynamic limit and associated with the ground state of the global Lyapunov potential) with the stationary state of the (finite-size) system. In the region of the parameter space where metastability is absent (and therefore the stationary state coincides with the ground state of the Lyapunov potential), a finite-size scaling analysis of the order parameter fluctuations suggests that the magnetic susceptibility diverges quadratically in the vicinity of the transition, which constitutes a violation of the fluctuation–dissipation relation. We derive an effective Hamiltonian and accordingly argue that its functional form does not allow one to straightforwardly relate the order parameter fluctuations to the linear response of the system, at odds with equilibrium theory. In the region of the parameter space (a > 1, a being a parameter of the Lyapunov potential) where the system is susceptible to having a large number of metastable states (and therefore the stationary state does not necessarily correspond to the ground state of the global Lyapunov potential), we numerically find a phase diagram that strongly depends on the initial conditions of the dynamical variables. Specifically, for symmetrically distributed initial conditions, the system shows a disorder–order transition for σc' < σc, yielding a reentrant transition in the full picture. The location of σc' increases with the parameter a and eventually coalesces with σc, yielding in this case the disappearance of both transitions. On the other hand, for positive-definite initial conditions the order–disorder transition is eventually smoothed for large values of a, and accordingly no critical behavior is found. At this point we conclude that structural diversity can induce both the creation and annihilation of order in a nontrivial way.Niko KominLucas Lacasa Saiz de ArceRaul Toral2011-08-29T07:46:47Z2016-04-20T17:11:30Zhttps://oa.upm.es/id/eprint/8371This item is in the repository with the URL: https://oa.upm.es/id/eprint/83712011-08-29T07:46:47ZThe roundtable: an abstract model of conversation dynamicsIs it possible to abstract a formal mechanism originating schisms and governing the size evolution of social conversations? In this work we propose a constructive solution to this problem: an abstract model of a generic N-party turn-taking conversation. The model develops from simple yet realistic assumptions derived from experimental evidence, abstracts from conversation content and semantics while including topological information, and is driven by stochastic dynamics. We find that a single mechanism, namely the dynamics of conversational party's individual fitness as related to conversation size, controls the development of the self-organized schisming phenomenon. Potential generalizations of the model - including individual traits and preferences, memory effects and more elaborated conversational topologies - may find important applications also in other fields of research, where dynamically-interacting and networked agents play a fundamental role.Massimo MastrangeliLucas Lacasa Saiz de Arce2010-05-06T08:08:14Z2016-04-20T12:36:33Zhttps://oa.upm.es/id/eprint/3015This item is in the repository with the URL: https://oa.upm.es/id/eprint/30152010-05-06T08:08:14ZStrictly and asymptotically scale invariant probabilistic models of N correlated binary random variables having q-Gaussians as N → ∞ limiting distributionsThe celebrated Leibnitz triangle has a remarkable property, namely that each of its elements equals the sum of its south-west and south-east neighbors. In probabilistic terms, this corresponds to a specific form of correlation of N equally probable binary variables which satisfy scale invariance. Indeed, the marginal probabilities of the N-system precisely coincide with the joint probabilities of the (N − 1)-system. On the other hand, the non-additive entropy Sq ≡ (1 − ∫_∞^∞▒〖p(x)]q)/(q - 1)〗 (q ∈ R; S1 = −∫_∞^∞▒〖p(x) ln p(x)〗), which grounds non-extensive statistical mechanics, is, under appropriate constraints, extremized by the (q-Gaussian) distribution pq(x) ∝ [1 − (1 − q)β x2]1/(1−q) (q < 3; p1(x) ∝ e−βx2 ). These distributions also result, as attractors, from a generalized central limit theorem for random variables which have a finite generalized variance, and are correlated in a specific way called q-independence. In order to provide physical enlightenment as regards this concept, we introduce here three types of asymptotically scale invariant probabilistic models with binary random variables, namely (i) a family, characterized by an index ν = 1, 2, 3, . . ., unifying the Leibnitz triangle (ν = 1) and the case of independent variables (ν →∞); (ii) two slightly different discretizations of q-Gaussians; (iii) a special family, characterized by the parameter χ, which generalizes the usual case of independent variables (recovered for χ = 1/2). Models (i) and (iii) are in fact strictly scale invariant. For models (i), we analytically show that the N → ∞ probability distribution is a q-Gaussian with q = (ν − 2)/(ν − 1). Models (ii) approach q-Gaussians by construction, and we numerically show that they do so with asymptotic scale invariance. Models (iii), like two other strictly scale invariant models recently discussed by Hilhorst and Schehr, approach instead limiting distributions which are not q-Gaussians. The scenario which emerges is that asymptotic (or even strict) scale invariance is not sufficient but it might be necessary for having strict (or asymptotic) q-independence, which, in turn, mandates q-Gaussian attractors.Antonio Rodríguez MesasVeit SchwämmleConstantino Tsallis2010-05-05T12:30:42Z2016-04-20T12:34:26Zhttps://oa.upm.es/id/eprint/2962This item is in the repository with the URL: https://oa.upm.es/id/eprint/29622010-05-05T12:30:42ZNetwork design: Taxi PlanningThe effect of managing aircraft movements on the airport’s ground is an important tool that can alleviate the delays of flights, specially in peak hours or congested situations. Although some strategic design decisions regarding aeronautical and safety aspects have a main impact on the airport’s topology, there exists a number of other additional factors that must be evaluated according to the on ground operations, i.e. previous to the taking-off or after landing. Among these factors one can consider capacities at waiting points and directions of some corridors. These factors are related to the demand situation of a given period and influence the aircraft’s routing on the ground or short term Taxi Planning problem (or TP-S). While the TP-S problem studies the aircraft routing and scheduling on the airport’s ground under a dynamic point of view, this paper presents a Taxi Planning network design model (or TPND), attending to these additional factors of the airport’s topology and the conflicting movements of the aircraft on them with the same modelling approach used in the TP-S problem. The TPND model is formulated as a binary multicommodity network flow problem with additional side constraints under a multiobjective approach. The side constraints included are the classical limitations due to capacity and also as a distinctive approach, constraints that restrict the interference of aircraft in order to decrease the intervention of human controllers during the operations or increase their safety margins. The multiobjective approach adopted for the TPND model balances conflicting objectives: airport’s throughput, travel times, safety of operations and costs. In the paper computational results are included on two test airports solving the TPND model by “Branch and Bound” showing the effect of the conflicting objectives in the design decisions.Angel Marín GraciaEsteve Codina Sancho2010-05-05T11:09:54Z2016-04-20T12:34:29Zhttps://oa.upm.es/id/eprint/2963This item is in the repository with the URL: https://oa.upm.es/id/eprint/29632010-05-05T11:09:54ZUrban Rapid Transit Network Capacity ExpansionThis paper examines a multi-period capacity expansion problem for rapid transit network design. The capacity expansion is realized through the location of train alignments and stations in an urban traffic context by selecting the time periods. The model maximizes the public transportation demand using a limited budget and designing lines for each period. The location problem incorporates the user decisions about mode and route. The network capacity expansion is a long-term planning problem because the network is built over several periods, in which the data (demand, resource price, etc.) are changing like the real problem changes. This complex problem cannot be solved by branch and bound, and for this reason, a heuristic approach has been defined in order to solve it. Both methods have been experimented in test networks.Angel Marín GraciaPatricia Jaramillo2010-05-03T08:51:29Z2016-04-20T12:34:31Zhttps://oa.upm.es/id/eprint/2964This item is in the repository with the URL: https://oa.upm.es/id/eprint/29642010-05-03T08:51:29ZTaxi Planner Optimization: A Management ToolThis work introduces taxi planning optimization (TPO) as a methodology to guide airport surface management operations. The optimization model represents competing aircraft using limited ground resources. TPO improves aircraft taxiing routes and their schedule in situations of congestion, minimizing overall taxiing time (TT), and helping taxi planners to meet prespecified goals such as compliance with take-off windows, TT limits, and trajectory conflicts. By considering all simultaneous trajectories during a given planning horizon, TPO's estimation of TT from the stand to the runways improves over current planning methods. The operational optimization model is a large-scale space-time multi-commodity network with capacity constraints. In addition to its natural use as a real-time taxi planning tool, a number of TPO variants can be used for design purposes, such as expansion of new infrastructure. TPO is demonstrated using Madrid-Barajas as test airport.Angel Marín GraciaJ. Salmerón2010-04-16T08:21:45Z2016-04-20T12:08:04Zhttps://oa.upm.es/id/eprint/2439This item is in the repository with the URL: https://oa.upm.es/id/eprint/24392010-04-16T08:21:45ZStable high-order finite-difference methods based on non-uniform grid point distributionsIt is well known that high-order finite-difference methods may become unstable due to the presence of boundaries and the imposition of boundary conditions. For uniform grids, Gustafsson, Kreiss, and Sundstr¨om theory and the summation-by-parts method provide sufficient conditions for stability. For non-uniform grids, clustering of nodes close to the boundaries improves the stability of the resulting finite-difference operator. Several heuristic explanations exist for the goodness of the clustering, and attempts have been made to link it to the Runge phenomenon present in polynomial interpolations of high degree. By following the philosophy behind the Chebyshev polynomials, a non-uniform grid for piecewise polynomial interpolations of degree q_N is introduced in this paper, where N + 1 is the total number of grid nodes. It is shown that when q = N, this polynomial interpolation coincides with the Chebyshev interpolation, and the resulting finite-difference schemes are equivalent to Chebyshev collocation methods. Finally, test cases are run showing how stability and correct transient behaviours are achieved for any degree q<N through the use of the proposed non-uniform grids. Discussions are complemented by spectra and pseudospectra of the finite-difference operators.Juan Antonio Hernández RamosMiguel Hermanns Navarro2010-03-05T09:07:54Z2016-04-20T12:09:46Zhttps://oa.upm.es/id/eprint/2479This item is in the repository with the URL: https://oa.upm.es/id/eprint/24792010-03-05T09:07:54ZEsquemas ENO para las ecuaciones de Euler en mallas no estructuradas. Parte 1: Descripción del métodoEn el presente trabajo, que ha sido dividido en dos partes, se desarrollan esquemas numéricos de primer y segundo orden para resolver las ecuaciones de Euler en dos dimensiones alrededor de perfiles aerodinámicos. En la primera parte, a continuación, se describe el método numérico em¬pleado. En él, el dominio espacial se discretiza utilizando una malla no estructurada donde las celdas son triángulos. El esquema hace uso de métodos de volúmenes finitos de primer orden y de segundo orden a partir de los cuales se obtienen ecuaciones de evolución para los valores me¬dios en cada celda. En una segunda parte se presentarán, como aplicación al diseño aerodinámi¬co, casos de prueba de perfiles aerodinámicos en régimen transónico y subsónico.Mario Zamecnik BarrosIgnacio Parra FabiánJuan Antonio Hernández Ramos