UVaDoc Comunidad: Documentos con Financiación programa OpenAireDocumentos con Financiación programa OpenAirehttp://uvadoc.uva.es/handle/10324/9192018-02-19T15:37:05Z2018-02-19T15:37:05ZRobust integrated production-maintenance scheduling for an evaporation networkGómez Palacín, CarlosPitarch Pérez, José LuisJasch, ChristianMéndez, Carlos Albertode Prada, Césarhttp://uvadoc.uva.es/handle/10324/279402018-01-08T14:05:47Z2018-01-01T00:00:00ZResumen: This work aims to reduce the global resource consumption in an industrial evaporation network by better tasks management and coordination. The network works in continuous, processing some products in several evaporation plants, so optimal load allocation and product-plant assignment problems appear. The plants have different features (capacity, equipment, etc.) and their performance is affected by fouling inside the heat exchangers and external factors. Hereby, the optimizer has to decide when maintenance operations have to be triggered. Therefore, a mixed production/maintenance scheduling problem arises. The plant behavior is approximated by surrogate linear models obtained experimentally, allowing thus the use of mixed-integer linear optimization routines to obtain solutions in acceptable time. Furthermore, uncertainty in the weather forecast and in the production plan is also considered via a two-stage stochastic programming approach. Finally, a trade-off analysis between other objectives of interest is given to support the decision maker.2018-01-01T00:00:00ZRobust multi-objective scheduling in an evaporation networkGómez Palacín, CarlosPitarch, José Luisde Prada, CésarMéndez, Carlos Albertohttp://uvadoc.uva.es/handle/10324/262382017-10-17T10:08:18Z2017-01-01T00:00:00ZResumen: Considering uncertainty in continuous production processes is key to compute short-time optimal schedules which can be trusted in practice. This paper proposes a two-step stochastic approach to the robust scheduling of several evaporation plants. This approach considers the possibility of reacting in the future once the uncertainty materializes. Each evaporator has different features (capacity, equipment, etc.) and the individual performance is affected by external factors and fouling effects. Moreover, a multi-objective analysis has been carried out to provide a decision support for the operator who must take the concrete decisions about load allocation and cleaning tasks along a time horizon. The problem has been solved by discretizing the time horizon and adapting the general-precedence method to deal with an unknown number of tasks. The nonlinear behavior of each plant is approximated by surrogate linear models obtained experimentally, providing thus solutions in acceptable time.2017-01-01T00:00:00ZRigid polyurethane foams with infused nanoclays: Relationship between cellular structure and thermal conductivityEstravis, SergioTirado Mediavilla, JosiasSantiago Calvo, MercerdesRuiz Herrero, José LuizVillafañe, FernandoRodriguez Pérez, Miguel Angelhttp://uvadoc.uva.es/handle/10324/258862017-10-19T12:22:35Z2016-01-01T00:00:00ZResumen: A water blown rigid polyurethane (PU) formulation has been used to manufacture cellular
nanocomposites containing different concentrations of montmorillonite nanoclays. The PU
foams have been produced using a low shear mixing technique for dispersing the nanoclays
and by reactive foaming to generate the cellular structure. A detailed characterization
of the cellular structure has been performed. The effect of the nanoparticles on the
reaction kinetics and the state of intercalation of the nanoparticles in the foams has been
analyzed. The thermal conductivity and extinction coefficient of the different materials has
been measured and the results obtained have been correlated with the materials structure.
A strong reduction of cell size and modifications on cell size distribution, anisotropy ratio
and fraction of material in the struts has been detected when the clays are added. In addition,
a reduction of the thermal conductivity has been observed. Different theoretical models
have been employed to explain thermal conductivity changes in terms of structural
features. It has been found that, in addition to the modifications in the cellular structure,
changes in the extinction coefficient and thermal conductivity of the matrix polymer play
an important role on the final values of the thermal conductivity for these materials.2016-01-01T00:00:00ZOscillation theory for non-autonomous linear Hamiltonian systemsNovo, SylviaNúñez, CarmenObaya, RafaelFabbri, RobertaJohnson, Russellhttp://uvadoc.uva.es/handle/10324/258052017-10-03T13:10:09Z2017-01-01T00:00:00ZResumen: This talk will be devoted to study oscillation properties of nonautonomous linear Hamiltonian systems applying some fundamental methods of topological dynamics and of ergodic theory. In particular, we will define and characterize the uniform weak disconjugacy concept and we will analyze the connections between disconjugacy, uniform weak disconjugacy, weak disconjugacy, and nonoscillation. A formula for the rotation number in terms of the multiplicity
of the proper focal points of a conjoined basis will also be shown.2017-01-01T00:00:00ZCharacterization of cocycles attractors for nonautonomous reaction-diffusion equationsCardoso, CarlosLanga, JuanObaya, Rafaelhttp://uvadoc.uva.es/handle/10324/258012017-10-04T08:48:30Z2016-01-01T00:00:00ZResumen: In this paper, we describe in detail the global and cocycle attractors related to nonautonomous scalar differential equations with diffusion. In particular, we investigate reaction–diffusion equations with almost-periodic coefficients. The associated semiflows are strongly monotone which allow us to give a full characterization of the cocycle attractor. We prove that, when the upper Lyapunov exponent associated to the linear part of the equations is positive, the flow is persistent in the positive cone, and we study the stability and the set of continuity points of the section of each minimal set in the global attractor for the skew product semiflow. We illustrate our result with some nontrivial examples showing the richness of the dynamics on this attractor, which in some situations shows internal chaotic dynamics in the Li–Yorke sense. We also include the sublinear and concave cases in order to go further in the characterization of the attractors, including, for instance, a nonautonomous version of the Chafee–Infante equation. In this last case we can show exponentially forward attraction to the cocycle (pullback) attractors in the positive cone of solutio2016-01-01T00:00:00ZAsymptotic Behaviour for a Class of Non-monotone Delay Differential Systems with ApplicationsFaria, TeresaObaya, RafaelSanz, Ana Maríahttp://uvadoc.uva.es/handle/10324/257612017-09-28T12:18:28Z2017-01-01T00:00:00ZResumen: The paper concerns a class of n-dimensional non-autonomous delay differential equations obtained by adding a non-monotone delayed perturbation to a linear homogeneous cooperative system of ordinary differential equations. This family covers a wide set of models used in structured population dynamics. By exploiting the stability and the monotone character of the linear ODE, we establish sufficient conditions for both the extinction of all the populations and the permanence of the system. In the case of DDEs with autonomous coefficients (but possible time-varying delays), sharp results are obtained, even in the case of a reducible community matrix. As a sub-product, our results improve some criteria for autonomous systems published in recent literature. As an important illustration, the extinction, persistence and permanence of a non-autonomous Nicholson system with patch structure and multiple time-dependent delays are analysed.2017-01-01T00:00:00ZExponential stability for nonautonomous functional differential equations with state-dependent delayMaroto, IsmaelNúñez, CarmenObaya, Rafaelhttp://uvadoc.uva.es/handle/10324/257592017-09-28T10:18:15Z2017-01-01T00:00:00ZResumen: The properties of stability of a compact set $K$ which is positively invariant for a semiflow $(\W\times W^{1,\infty}([-r,0],\mathbb{R}^n),\Pi,\mathbb{R}^+)$ determined by a family of nonautonomous FDEs with state-dependent delay taking values in $[0,r]$ are analyzed. The solutions of the variational equation through the orbits of $K$ induce linear skew-product semiflows on the bundles $K\times W^{1,\infty}([-r,0],\mathbb{R}^n)$ and $\mK\times C([-r,0],\mathbb{R}^n)$. The coincidence of the upper-Lyapunov exponents for both semiflows is checked, and it is a fundamental tool to prove that the strictly negative character of this upper-Lyapunov exponent is equivalent to the exponential stability of $K$ in
$\W\times W^{1,\infty}([-r,0],\mathbb{R}^n)$ and also to the exponential stability of this compact set when the supremum norm is taken in $W^{1,\infty}([-r,0],\mathbb{R}^n)$. In particular, the existence of a uniformly exponentially stable solution of a uniformly almost periodic FDE ensures the existence of exponentially stable almost periodic solutions.2017-01-01T00:00:00ZDynamical properties of nonautonomous functional differential equations with state-dependent delayMaroto, IsmaelNúñez, CarmenObaya, Rafaelhttp://uvadoc.uva.es/handle/10324/257572017-09-28T10:15:39Z2017-01-01T00:00:00ZResumen: The properties of stability of a compact set $K$ which is positively invariant for a semiflow $(\W\times W^\infty([-r,0],\mathbb{R}^n),\Pi,\mathbb{R}^+)$ determined by a family of nonautonomous FDEs with state-dependent delay taking values in $[0,r]$ are analyzed.
The solutions of the variational equation through the orbits of $K$ induce linear skew-product semiflows on the bundles $K\times W^\infty([-r,0],\R^n)$ and $K\times C([-r,0],\R^n)$. The coincidence of the upper-Lyapunov exponents for both semiflows is checked, and it is a fundamental tool to prove that the strictly negative character of this upper-Lyapunov exponent is equivalent to the exponential stability of $\mK$ in $\W\times W^\infty([-r,0],\R^n)$ and also to the exponential stability of this compact set when the supremum norm is taken in $W^\infty([-r,0],\R^n)$. In particular, the existence of a uniformly exponentially stable solution of a uniformly almost periodic FDE ensures the existence of exponentially stable almost periodic solutions.2017-01-01T00:00:00ZPullback, forward and chaotic dynamics in 1d nonautonomous linear-dissipative equationsCaraballo, TomásLanga, JoséObaya, Rafaelhttp://uvadoc.uva.es/handle/10324/257482017-10-04T08:51:01Z2017-01-01T00:00:00ZResumen: The global attractor of a skew product semiflow for a non-autonomous differential equation describes the asymptotic behaviour of the model. This attractor is usually characterized as the union, for all the parameters in the base space, of the associated cocycle attractors in the product space. The continuity of the cocycle attractor in the parameter is usually a difficult question. In this paper we develop in detail a 1D non-autonomous linear differential equation and show the richness of non-autonomous dynamics by focusing on the continuity, characterization and chaotic dynamics of the cocycle attractors. In particular, we analyse the sets of continuity and discontinuity for the parameter of the attractors, and relate them with the eventually forward behaviour of the processes. We will also find chaotic behaviour on the attractors in the Li–Yorke and Auslander–Yorke senses. Note that they hold for linear 1D equations, which shows a crucial difference with respect to the presence of chaotic dynamics in autonomous systems.2017-01-01T00:00:00ZFavard Theory and fredholm alternative for disconjugate recurrent second order equationsCampos, JuanObaya, RafaelTarallo, Massimohttp://uvadoc.uva.es/handle/10324/257452017-10-03T13:08:29Z2017-01-01T00:00:00ZResumen: We discuss the existence of a Fredholm--type Alternative for a recurrent second order linear equation, which is disconjugate in a strong sense. The basic result is about bounded solutions of equations with bounded coefficients: it depends on kinematic similarities that allow to reduce the problem to a pair of very simple normal forms. Then the result is specialized to recurrent equations, by means of Favard theory.2017-01-01T00:00:00ZFavard theory for the adjoint equation and Fredholm alternativeCampos, JuanObaya, RafaelTarallo, Massimohttp://uvadoc.uva.es/handle/10324/257422017-10-04T07:01:42Z2017-01-01T00:00:00ZResumen: Fredholm Alternative is a classical tool of periodic linear equations, allowing to describe the existence of periodic solutions of an inhomogeneous equation in terms of the adjoint equation. A few partial extensions have been proposed in the literature for recurrent equations: our aim is to point out that they have a common root and discuss whether such a root gives rise to a general Fredholm-type Alternative. Sacker–Sell spectral theory and Favard theory are main ingredients in this discussion: a considerable effort is devoted to understand how Favard theory is affected by adjunction, at least for planar equations.2017-01-01T00:00:00ZUniform and strict persistence in monotone skew-product semiflows with applications to non-autonomous Nicholson systemsObaya, RafaelSanz, Ana Maríahttp://uvadoc.uva.es/handle/10324/256882017-10-04T07:03:53Z2016-01-01T00:00:00ZResumen: We determine sufficient conditions for uniform and strict persistence in the case of skew-product semiflows generated by solutions of non-autonomous families of cooperative systems of ODEs or delay FDEs in terms of the principal spectrums of some associated linear skew-product semiflows which admit a continuous separation. Our conditions are also necessary in the linear case. We apply our results to a noncooperative almost periodic Nicholson system with a patch structure, whose persistence turns out to be equivalent to the persistence of the linearized system along the null solution.2016-01-01T00:00:00ZTopologies of Llocp type for Carathéodory functions with applications in non-autonomous differential equationsLongo, Iacopo P.Novo, SylviaObaya, Rafaelhttp://uvadoc.uva.es/handle/10324/255792017-10-04T08:45:47Z2017-01-01T00:00:00ZResumen: Metric topological vector spaces of Carathéodory functions and topologies of Llocp type are introduced, depending on a suitable set of moduli of continuity. Theorems of continuous dependence on initial data for the solutions of non-autonomous Carathéodory differential equations are proved in such new topological structures. As a consequence, new families of continuous linearized skew-product semiflows are provided in the Carathéodory spaces.2017-01-01T00:00:00ZNull controllable sets and reachable sets for nonautonomous linear control systemsFabbri, RobertaNovo, SylviaNúñez, CarmenObaya, Rafaelhttp://uvadoc.uva.es/handle/10324/255032017-09-28T10:13:04Z2016-01-01T00:00:00ZResumen: Under the assumption of lack of uniform controllability for a family of time-dependent linear control systems, we study the dimension, topological structure and other dynamical properties of the sets of null controllable points and of the sets of reachable points. In particular, when the space of null controllable vectors has constant dimension for all the systems of the family, we find a closed invariant subbundle where the uniform null controllability holds. Finally, we associate a family of linear Hamiltonian systems to the control family and assume that it has an exponential dichotomy in order to relate the space of null controllable vectors to one of the Lagrange planes of the continuous splitting.2016-01-01T00:00:00ZToward Multimodal Analytics in Ubiquitous Learning EnvironmentsMuñoz Cristóbal, Juan A.Rodríguez Triana, Aría JesúsBote Lorenzo, Miguel L.Villagrá Sobrino, Sara LorenaAsensio Pérez, Juan IgnacioMartínez Monés, Alejandrahttp://uvadoc.uva.es/handle/10324/248952017-08-20T18:32:23Z2017-01-01T00:00:00ZResumen: While Ubiquitous Learning Environments (ULEs) have shown several benefits for learning, they pose challenges for orchestration. Teachers need to be aware of the learning process, which is difficult to achieve when it occurs across a heterogeneous set of spaces, resources and devices. In addition, ULEs can benefit from multimodal analyses due to the heterogeneity of the data sources available (e.g., logs, geolocation, sensor information, learning artifacts). In previous works, we proposed an orchestration system with some analytics features that can gather multimodal datasets during the learning process. Based on this experience, in this paper we describe the technological support provided by the system to collect data from multiple spaces and sources as well as the structure of the generated dataset. We also reflect about the challenges of multimodal learning analytics (MMLA) in ULEs, and we pose some ideas about how the system could better support MMLA in the future to mitigate those challenges.2017-01-01T00:00:00ZElastin-like-recombinamers multilayered nanofibrous scaffolds for cardiovascular applicationsPutzu, M.González de Torre, IsraelRodríguez Cabello, José CarlosCausa, F.Netti, P.A.http://uvadoc.uva.es/handle/10324/248112017-07-30T18:33:24Z2016-01-01T00:00:00ZResumen: Coronary angioplasty is the most widely used technique for removing atherosclerotic plaques in blood vessels. The regeneration of the damaged intima layer after this treatment is still one of the major challenges in the field of cardiovascular tissue engineering. Different polymers have been used in scaffold manufacturing in order to improve tissue regeneration. Elastin-mimetic polymers are a new class of molecules that have been synthesized and used to obtain small diameter fibers with specific morphological characteristics. Elastin-like polymers produced by recombinant techniques and called elastin-like recombinamers (ELRs) are particularly promising due to their high degree of functionalization. Generally speaking, ELRs can show more complex molecular designs and a tighter control of their sequence than other chemically synthetized polymers Rodriguez Cabello et al (2009 Polymer 50 5159–69, 2011 Nanomedicine 6 111–22). For the fabrication of small diameter fibers, different ELRs were dissolved in 2,2,2-fluoroethanol (TFE). Dynamic light scattering was used to identify the transition temperature and get a deep characterization of the transition behavior of the recombinamers. In this work, we describe the use of electrospinning technique for the manufacturing of an elastic fibrous scaffold; the obtained fibers were characterized and their cytocompatibility was tested in vitro. A thorough study of the influence of voltage, flow rate and distance was carried out in order to determine the appropriate parameters to obtain fibrous mats without beads and defects. Moreover, using a rotating mandrel, we fabricated a tubular scaffold in which ELRs containing different cell adhesion sequences (mainly REDV and RGD) were collected. The stability of the scaffold was improved by using genipin as a crosslinking agent. Genipin-ELRs crosslinked scaffolds show a good stability and fiber morphology. Human umbilical vein endothelial cells were used to assess the in vitro bioactivity of the cell adhesion domains within the backbone of the ELRs.2016-01-01T00:00:00Z