E-prints
http://hdl.handle.net/2117/28577
2019-01-16T09:20:51ZArnold diffusion for a complete family of perturbations with two independent harmonics
http://hdl.handle.net/2117/126910
Arnold diffusion for a complete family of perturbations with two independent harmonics
Delshams Valdés, Amadeu; Gonçalves Schaefer, Rodrigo
We prove that for any non-trivial perturbation depending on any two independent harmonics of a pendulum and a rotor there is global instability. The proof is based on the geometrical method and relies on the concrete computation of several scattering maps. A complete description of the different kinds of scattering maps taking place as well as the existence of piecewise smooth global scattering maps is also provided
2019-01-16T09:05:25ZDelshams Valdés, AmadeuGonçalves Schaefer, RodrigoWe prove that for any non-trivial perturbation depending on any two independent harmonics of a pendulum and a rotor there is global instability. The proof is based on the geometrical method and relies on the concrete computation of several scattering maps. A complete description of the different kinds of scattering maps taking place as well as the existence of piecewise smooth global scattering maps is also providedEffects of cholesterol on the binding of the precursor neurotransmitter tryptophan to zwitterionic membranes
http://hdl.handle.net/2117/126909
Effects of cholesterol on the binding of the precursor neurotransmitter tryptophan to zwitterionic membranes
Lu, Huixia; Martí Rabassa, Jordi
The characterization of the microscopical forces between the essential a-amino-acid tryptophan, precursor of the neurotransmitter serotonin and of the hormone melatonin, and the basic components of cell membranes and their environments (phospholipids, cholesterol, ionic species, and water) is of central importance to elucidate their local structure and dynamics as well as the mechanisms responsible for the access of tryptophan to the interior of the cell. We have performed nanosecond molecular dynamics simulations of tryptophan embedded in model zwitterionic bilayer membranes made by di-palmitoyl-phosphatidyl-choline and cholesterol inside aqueous sodium-chloride solution in order to systematically examine tryptophan-lipid, tryptophan-cholesterol, and tryptophan-water interactions under liquid-crystalline phase conditions. Microscopic properties such as the area per lipid, lipid thickness, radial distribution functions, hydrogen-bonding lengths, atomic spectral densities, and self-diffusion coefficients have been evaluated. Our results show that the presence of tryptophan significantly affects the structure and dynamics of the membrane. Tryptophan spends long periods of time at the water-membrane interface, and it plays a central role by bridging a few lipids and cholesterol chains by means of hydrogen-bonds. The computed spectral densities, in excellent agreement with experimental infrared and Raman data, revealed the participation of each atomic site of tryptophan to the complete spectrum of the molecule. Tryptophan self-diffusion coefficients have been found to be in between 10^(-7) and 10^(-6) cm^2/s and strongly depending of the concentration of cholesterol in the system.
2019-01-16T08:56:39ZLu, HuixiaMartí Rabassa, JordiThe characterization of the microscopical forces between the essential a-amino-acid tryptophan, precursor of the neurotransmitter serotonin and of the hormone melatonin, and the basic components of cell membranes and their environments (phospholipids, cholesterol, ionic species, and water) is of central importance to elucidate their local structure and dynamics as well as the mechanisms responsible for the access of tryptophan to the interior of the cell. We have performed nanosecond molecular dynamics simulations of tryptophan embedded in model zwitterionic bilayer membranes made by di-palmitoyl-phosphatidyl-choline and cholesterol inside aqueous sodium-chloride solution in order to systematically examine tryptophan-lipid, tryptophan-cholesterol, and tryptophan-water interactions under liquid-crystalline phase conditions. Microscopic properties such as the area per lipid, lipid thickness, radial distribution functions, hydrogen-bonding lengths, atomic spectral densities, and self-diffusion coefficients have been evaluated. Our results show that the presence of tryptophan significantly affects the structure and dynamics of the membrane. Tryptophan spends long periods of time at the water-membrane interface, and it plays a central role by bridging a few lipids and cholesterol chains by means of hydrogen-bonds. The computed spectral densities, in excellent agreement with experimental infrared and Raman data, revealed the participation of each atomic site of tryptophan to the complete spectrum of the molecule. Tryptophan self-diffusion coefficients have been found to be in between 10^(-7) and 10^(-6) cm^2/s and strongly depending of the concentration of cholesterol in the system.A branch-and-cut algorithm for the multidepot rural postman problem
http://hdl.handle.net/2117/126907
A branch-and-cut algorithm for the multidepot rural postman problem
Fernández Aréizaga, Elena; Laporte, Gilbert; Rodríguez Pereira, Jessica
This paper considers the Multidepot Rural Postman Problem, an extension of the classical Rural Postman Problem in which there are several depots instead of only one. The aim is to construct a minimum cost set of routes traversing each required edge of the graph, where each route starts and ends at the same depot. The paper makes the following scientific contributions: (i) It presents optimality conditions and a worst case analysis for the problem; (ii) It proposes a compact integer linear programming formulation containing only binary variables, as well as a polyhedral analysis; (iii) It develops a branch-and-cut algorithm that includes several new exact and heuristic separation procedures. Instances involving up to four depots, 744 vertices, and 1,315 edges are solved to optimality. These instances contain up to 140 required components and 1,000 required edges.
2019-01-16T08:55:56ZFernández Aréizaga, ElenaLaporte, GilbertRodríguez Pereira, JessicaThis paper considers the Multidepot Rural Postman Problem, an extension of the classical Rural Postman Problem in which there are several depots instead of only one. The aim is to construct a minimum cost set of routes traversing each required edge of the graph, where each route starts and ends at the same depot. The paper makes the following scientific contributions: (i) It presents optimality conditions and a worst case analysis for the problem; (ii) It proposes a compact integer linear programming formulation containing only binary variables, as well as a polyhedral analysis; (iii) It develops a branch-and-cut algorithm that includes several new exact and heuristic separation procedures. Instances involving up to four depots, 744 vertices, and 1,315 edges are solved to optimality. These instances contain up to 140 required components and 1,000 required edges.A parameterization method for Lagrangian tori of exact symplectic maps of R2r
http://hdl.handle.net/2117/126905
A parameterization method for Lagrangian tori of exact symplectic maps of R2r
Villanueva Castelltort, Jordi
We are concerned with analytic exact symplectic maps of ${\mathbb R}^{2r}$ endowed with the standard symplectic form. We study the existence of a real analytic torus of dimension $r$, invariant by the map and carrying quasi-periodic motion with a prefixed Diophantine rotation vector. Therefore, this torus is a Lagrangian manifold. We address the problem by the parameterization method in KAM theory. The main aspect of our approach is that we do not look for the parameterization of the torus as a solution of the corresponding invariance equation. Instead, we consider a set of three equations that, all together, are equivalent to the invariance equation. These equations arise from the geometric and dynamical properties of the map and the torus. Suppose that an approximate solution of these equations is known and that a suitable nondegeneracy (twist) condition is satisfied. Then, this system of equations is solved by a quasi-Newton-like method, provided that the initial error is sufficiently small. By “quasi-Newton-like” we mean that the convergence is almost quadratic but that at each iteration we have to solve a nonlinear equation. Although it is straightforward to build a quasi-Newton method for the selected set of equations, proceeding in this way we improve the convergence condition. The selected definition of error reflects the level at which the error associated with each of these three equations contributes to the total error. The map is not required to be close to integrable or expressed in action-angle variables. Suppose the map is $\varepsilon$-close to an integrable one, and consider the portion of the phase space not filled up by Lagrangian invariant tori of the map. Then, the upper bound for the Lebesgue measure of this set that we may predict from the result is of ${\mathcal O}(\varepsilon^{1/2})$. In light of the classical KAM theory for exact symplectic maps, an upper bound of ${\mathcal O}(\varepsilon^{1/2})$ for this measure is the expected estimate. The result also has some implications for finitely differentiable maps
2019-01-16T08:36:08ZVillanueva Castelltort, JordiWe are concerned with analytic exact symplectic maps of ${\mathbb R}^{2r}$ endowed with the standard symplectic form. We study the existence of a real analytic torus of dimension $r$, invariant by the map and carrying quasi-periodic motion with a prefixed Diophantine rotation vector. Therefore, this torus is a Lagrangian manifold. We address the problem by the parameterization method in KAM theory. The main aspect of our approach is that we do not look for the parameterization of the torus as a solution of the corresponding invariance equation. Instead, we consider a set of three equations that, all together, are equivalent to the invariance equation. These equations arise from the geometric and dynamical properties of the map and the torus. Suppose that an approximate solution of these equations is known and that a suitable nondegeneracy (twist) condition is satisfied. Then, this system of equations is solved by a quasi-Newton-like method, provided that the initial error is sufficiently small. By “quasi-Newton-like” we mean that the convergence is almost quadratic but that at each iteration we have to solve a nonlinear equation. Although it is straightforward to build a quasi-Newton method for the selected set of equations, proceeding in this way we improve the convergence condition. The selected definition of error reflects the level at which the error associated with each of these three equations contributes to the total error. The map is not required to be close to integrable or expressed in action-angle variables. Suppose the map is $\varepsilon$-close to an integrable one, and consider the portion of the phase space not filled up by Lagrangian invariant tori of the map. Then, the upper bound for the Lebesgue measure of this set that we may predict from the result is of ${\mathcal O}(\varepsilon^{1/2})$. In light of the classical KAM theory for exact symplectic maps, an upper bound of ${\mathcal O}(\varepsilon^{1/2})$ for this measure is the expected estimate. The result also has some implications for finitely differentiable mapsExact solution of hub network design problems with profits
http://hdl.handle.net/2117/126904
Exact solution of hub network design problems with profits
Alibeyg, Armaghan; Contreras Aguilar, Ivan; Fernández Aréizaga, Elena
This paper studies hub network design problems with profits. They consider a profit-oriented objective that measure the tradeoff between the revenue due to served commodities and the overall network design and transportation costs. An exact algorithmic framework is proposed for two variants of this class of problems, where a sophisticated Lagrangian function that exploits the structure of the problems is used to efficiently obtain bounds at the nodes of an enumeration tree. In addition, reduction tests and partial enumerations are used to considerably reduce the size of the problems and thus help decrease the computational effort. Numerical results on a set of benchmark instances with up to 100 nodes confirm the efficiency of the proposed algorithmic framework. The proposed methodology can be used as a tool to solve more complex variants of this class of problems as well as other discrete location and network design problems involving servicing decisions.
2019-01-16T08:25:49ZAlibeyg, ArmaghanContreras Aguilar, IvanFernández Aréizaga, ElenaThis paper studies hub network design problems with profits. They consider a profit-oriented objective that measure the tradeoff between the revenue due to served commodities and the overall network design and transportation costs. An exact algorithmic framework is proposed for two variants of this class of problems, where a sophisticated Lagrangian function that exploits the structure of the problems is used to efficiently obtain bounds at the nodes of an enumeration tree. In addition, reduction tests and partial enumerations are used to considerably reduce the size of the problems and thus help decrease the computational effort. Numerical results on a set of benchmark instances with up to 100 nodes confirm the efficiency of the proposed algorithmic framework. The proposed methodology can be used as a tool to solve more complex variants of this class of problems as well as other discrete location and network design problems involving servicing decisions.Composition determination of rubber blends by applying differential scanning calorimetry and SPA-PLS treatment
http://hdl.handle.net/2117/126903
Composition determination of rubber blends by applying differential scanning calorimetry and SPA-PLS treatment
Riba Ruiz, Jordi-Roger; Mansilla, Marcela Ángela; Canals, Trini; Cantero, Rosa
This paper proposes an innovative approach to determine the composition of natural rubber (NR) and styrene butadiene rubber (SBR) blends from the analysis of the data provided by the differential scanning calorimetry (DSC) technique. DSC registers are post-processed, based on a multivariate chemometric approach, consisting in the application of the successive projections algorithm (SPA) as variable selection algorithm and a further application of the partial least squares (PLS) regression method and the leave-one-out cross-validation algorithm. Results attained by applying this approach are compared with those obtained from mid-infrared spectroscopy since this last method has been widely applied during the last decades. Experimental results summarized in the paper prove that this fast and cost-effective approach is useful to determine the composition of unknown incoming NR/SBR blends
2019-01-16T08:25:30ZRiba Ruiz, Jordi-RogerMansilla, Marcela ÁngelaCanals, TriniCantero, RosaThis paper proposes an innovative approach to determine the composition of natural rubber (NR) and styrene butadiene rubber (SBR) blends from the analysis of the data provided by the differential scanning calorimetry (DSC) technique. DSC registers are post-processed, based on a multivariate chemometric approach, consisting in the application of the successive projections algorithm (SPA) as variable selection algorithm and a further application of the partial least squares (PLS) regression method and the leave-one-out cross-validation algorithm. Results attained by applying this approach are compared with those obtained from mid-infrared spectroscopy since this last method has been widely applied during the last decades. Experimental results summarized in the paper prove that this fast and cost-effective approach is useful to determine the composition of unknown incoming NR/SBR blendsOn outindependent subgraphs of strongly regular graphs
http://hdl.handle.net/2117/126902
On outindependent subgraphs of strongly regular graphs
Fiol Mora, Miquel Àngel
An outindependent subgraph of a graph G, with respect to an independent vertex subset C¿¿V, is the subgraph GC induced by the vertices in V\¿C. We study the case when G is strongly regular, where the results of de Caen [1998, The spectra of complementary subgraphs in a strongly regular graph. European Journal of Combinatorics, 19 (5), 559–565.], allow us to derive the whole spectrum of GC . Moreover, when C attains the Hoffman–Lovász bound for the independence number, GC is a regular graph (in fact, distance-regular if G is a Moore graph). This article is mainly devoted to study the non-regular case. As a main result, we characterize the structure of GC when C is the neighborhood of either one vertex or one edge.
2019-01-16T08:14:37ZFiol Mora, Miquel ÀngelAn outindependent subgraph of a graph G, with respect to an independent vertex subset C¿¿V, is the subgraph GC induced by the vertices in V\¿C. We study the case when G is strongly regular, where the results of de Caen [1998, The spectra of complementary subgraphs in a strongly regular graph. European Journal of Combinatorics, 19 (5), 559–565.], allow us to derive the whole spectrum of GC . Moreover, when C attains the Hoffman–Lovász bound for the independence number, GC is a regular graph (in fact, distance-regular if G is a Moore graph). This article is mainly devoted to study the non-regular case. As a main result, we characterize the structure of GC when C is the neighborhood of either one vertex or one edge.Double cantilever indirect tension testing for fracture of quasibrittle materials
http://hdl.handle.net/2117/126898
Double cantilever indirect tension testing for fracture of quasibrittle materials
Caner, Ferhun Cem; Dönmez, A. Abdullah; Sener, Siddik; Koç, Varol
The Double Cantilever Beam (DCB) Mode I fracture testing has been widely used in fracture testing of especially fiber reinforced polymer composites and adhesive joints. Application of classical DCB testing to plain concrete or unreinforced ceramic specimens is not straightforward and cannot be carried out as in fiber reinforced polymer composites. Instead, an indirect tension approach is proposed in this study. Tests of notched geometrically similar DCB specimens made of normal and high strength concretes loaded eccentrically at the cantilever beam-column ends in compression have been carried out. Classical Type II size effect analyses of peak loads obtained from these tests are performed. The Microplane Model M7 is calibrated independently using uniaxial compression tests and employed to predict the peak loads of both tested and virtual geometrically similar DCB specimens. The same size effect analyses are performed on the predicted peak loads and the errors in the fracture parameters of the classical size effect analysis are determined.
2019-01-16T07:52:27ZCaner, Ferhun CemDönmez, A. AbdullahSener, SiddikKoç, VarolThe Double Cantilever Beam (DCB) Mode I fracture testing has been widely used in fracture testing of especially fiber reinforced polymer composites and adhesive joints. Application of classical DCB testing to plain concrete or unreinforced ceramic specimens is not straightforward and cannot be carried out as in fiber reinforced polymer composites. Instead, an indirect tension approach is proposed in this study. Tests of notched geometrically similar DCB specimens made of normal and high strength concretes loaded eccentrically at the cantilever beam-column ends in compression have been carried out. Classical Type II size effect analyses of peak loads obtained from these tests are performed. The Microplane Model M7 is calibrated independently using uniaxial compression tests and employed to predict the peak loads of both tested and virtual geometrically similar DCB specimens. The same size effect analyses are performed on the predicted peak loads and the errors in the fracture parameters of the classical size effect analysis are determined.Dryout and replenishment of bottom-heated saturated porous media with an overlying plain water layer
http://hdl.handle.net/2117/126897
Dryout and replenishment of bottom-heated saturated porous media with an overlying plain water layer
Carbonell Ventura, Montserrat; Virto Albert, Saturnino Luis; Gámez Montero, Pedro Javier
The aim of this paper is to elucidate the influence of the physical properties of both
phases—solid matrix and saturating liquid—of bottom-heated porous media with an overlying plain
water layer. The dryout, the stability of the system’s water layer-vapor region, and the thermal
state evolution are studied. The porous media under study are a bronze powder saturated by water,
and a solution of surfactant and coarse sand saturated by the same liquids. From the experimental
data obtained, a theoretical approach is carried out to describe the dryout and rewetting process.
The influence of the nature and physical properties of the solid and liquid phases is also analyzed,
with special attention to the addition of surfactant in the saturating liquid.
2019-01-16T07:44:13ZCarbonell Ventura, MontserratVirto Albert, Saturnino LuisGámez Montero, Pedro JavierThe aim of this paper is to elucidate the influence of the physical properties of both
phases—solid matrix and saturating liquid—of bottom-heated porous media with an overlying plain
water layer. The dryout, the stability of the system’s water layer-vapor region, and the thermal
state evolution are studied. The porous media under study are a bronze powder saturated by water,
and a solution of surfactant and coarse sand saturated by the same liquids. From the experimental
data obtained, a theoretical approach is carried out to describe the dryout and rewetting process.
The influence of the nature and physical properties of the solid and liquid phases is also analyzed,
with special attention to the addition of surfactant in the saturating liquid.Measures of edge-uncolorability of cubic graphs
http://hdl.handle.net/2117/126896
Measures of edge-uncolorability of cubic graphs
Fiol Mora, Miquel Àngel; Mazzuoccolo, Giuseppe; Steffen, Eckhard
There are many hard conjectures in graph theory, like Tutte’s 5-flow conjecture, and the 5-cycle double cover conjecture, which would be true in general if they would be true for cubic graphs. Since most of them are trivially true for 3-edgecolorable cubic graphs, cubic graphs which are not 3-edge-colorable, often called snarks, play a key role in this context. Here, we survey parameters measuring how far apart a non 3-edge-colorable graph is from being 3-edge-colorable. We study their interrelation and prove some new results. Besides getting new insight into the structure of snarks, we show that such measures give partial results with respect to these important conjectures. The paper closes with a list of open problems and conjectures.
2019-01-16T07:31:25ZFiol Mora, Miquel ÀngelMazzuoccolo, GiuseppeSteffen, EckhardThere are many hard conjectures in graph theory, like Tutte’s 5-flow conjecture, and the 5-cycle double cover conjecture, which would be true in general if they would be true for cubic graphs. Since most of them are trivially true for 3-edgecolorable cubic graphs, cubic graphs which are not 3-edge-colorable, often called snarks, play a key role in this context. Here, we survey parameters measuring how far apart a non 3-edge-colorable graph is from being 3-edge-colorable. We study their interrelation and prove some new results. Besides getting new insight into the structure of snarks, we show that such measures give partial results with respect to these important conjectures. The paper closes with a list of open problems and conjectures.