E-printshttp://hdl.handle.net/2117/285772019-01-16T08:14:57Z2019-01-16T08:14:57ZOn outindependent subgraphs of strongly regular graphsFiol Mora, Miquel Àngelhttp://hdl.handle.net/2117/1269022019-01-16T08:14:37Z2019-01-16T08:14:37ZOn 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 materialsCaner, Ferhun CemDönmez, A. AbdullahSener, SiddikKoç, Varolhttp://hdl.handle.net/2117/1268982019-01-16T08:00:06Z2019-01-16T07:52:27ZDouble 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 layerCarbonell Ventura, MontserratVirto Albert, Saturnino LuisGámez Montero, Pedro Javierhttp://hdl.handle.net/2117/1268972019-01-16T07:50:04Z2019-01-16T07:44:13ZDryout 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 graphsFiol Mora, Miquel ÀngelMazzuoccolo, GiuseppeSteffen, Eckhardhttp://hdl.handle.net/2117/1268962019-01-16T07:40:04Z2019-01-16T07:31:25ZMeasures 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.Ejection-collision orbits in the symmetric collinear four–body problemAlvarez Ramírez, MarthaBarrabés Vera, EstherMedina, M.Ollé Torner, Mercèhttp://hdl.handle.net/2117/1268952019-01-16T07:30:05Z2019-01-16T07:23:53ZEjection-collision orbits in the symmetric collinear four–body problem
Alvarez Ramírez, Martha; Barrabés Vera, Esther; Medina, M.; Ollé Torner, Mercè
In this paper, we consider the collinear symmetric four-body problem, where four masses and a¿>¿0, are aligned in this order and move symmetrically about their center of mass. We introduce regularized variables to deal with binary collisions as well as McGehee coordinates to study the quadruple collision manifold for a negative value of the energy. The paper is mainly focused on orbits that eject from (or collide to) quadruple collision. The problem has two hyperbolic equilibrium points, located in the quadruple collision manifold. We use high order parametrizations of their stable/unstable manifolds to devise a numerical procedure to compute ejection-collision orbits, for any value of a. Some results from the explorations done for are presented. Furthermore, we prove the existence of ejection-direct escape orbits, which perform a unique type of binary collisions.
2019-01-16T07:23:53ZAlvarez Ramírez, MarthaBarrabés Vera, EstherMedina, M.Ollé Torner, MercèIn this paper, we consider the collinear symmetric four-body problem, where four masses and a¿>¿0, are aligned in this order and move symmetrically about their center of mass. We introduce regularized variables to deal with binary collisions as well as McGehee coordinates to study the quadruple collision manifold for a negative value of the energy. The paper is mainly focused on orbits that eject from (or collide to) quadruple collision. The problem has two hyperbolic equilibrium points, located in the quadruple collision manifold. We use high order parametrizations of their stable/unstable manifolds to devise a numerical procedure to compute ejection-collision orbits, for any value of a. Some results from the explorations done for are presented. Furthermore, we prove the existence of ejection-direct escape orbits, which perform a unique type of binary collisions.Using the R language to manage and show statistical information in the cloudFonseca Casas, PauTormos, Raülhttp://hdl.handle.net/2117/1268942019-01-16T07:30:06Z2019-01-16T07:00:06ZUsing the R language to manage and show statistical information in the cloud
Fonseca Casas, Pau; Tormos, Raül
We present a methodology to enable users to interact with the statistical information (survey data) of a public opinion institute which is stored in Cloud infrastructure. Mainly using R, this approach was developed following the open-data philosophy. Also, as we used R, the implementation is mainly based on open-source software. R has several advantages from the point of view of data management and acquisition, as it is becoming a common framework that can be used to structure the processes involved in any statistical operation. It further simplifies the access to data and enables the use of all the power of R in Cloud infrastructure. This methodology was applied successfully to develop a tool to manage the data of the Centre d’Estudis d’Opinió, but it can be applied to other institutions to enable open access to their data. The infrastructure was also deployed to Cloud infrastructure to assure its scalability and 24/7 access.
2019-01-16T07:00:06ZFonseca Casas, PauTormos, RaülWe present a methodology to enable users to interact with the statistical information (survey data) of a public opinion institute which is stored in Cloud infrastructure. Mainly using R, this approach was developed following the open-data philosophy. Also, as we used R, the implementation is mainly based on open-source software. R has several advantages from the point of view of data management and acquisition, as it is becoming a common framework that can be used to structure the processes involved in any statistical operation. It further simplifies the access to data and enables the use of all the power of R in Cloud infrastructure. This methodology was applied successfully to develop a tool to manage the data of the Centre d’Estudis d’Opinió, but it can be applied to other institutions to enable open access to their data. The infrastructure was also deployed to Cloud infrastructure to assure its scalability and 24/7 access.Gluing and grazing bifurcations in periodically forced 2-dimensional integrate-and-fire modelsGranados Corsellas, AlbertHuguet Casades, Gemmahttp://hdl.handle.net/2117/1268932019-01-16T07:00:06Z2019-01-16T06:56:06ZGluing and grazing bifurcations in periodically forced 2-dimensional integrate-and-fire models
Granados Corsellas, Albert; Huguet Casades, Gemma
In this work we consider a general class of 2-dimensional hybrid systems. Assuming that the system possesses an attracting equilibrium point, we show that, when periodically driven with a square-wave pulse, the system possesses a periodic orbit which may undergo smooth and nonsmooth grazing bifurcations. We perform a semi-rigorous study of the existence of periodic orbits for a particular model consisting of a leaky integrate-and-fire model with a dynamic threshold. We use the stroboscopic map, which in this context is a 2-dimensional piecewise-smooth discontinuous map. For some parameter values we are able to show that the map is a quasi-contraction possessing a (locally) unique maximin periodic orbit. We complement our analysis using advanced numerical techniques to provide a complete portrait of the dynamics as parameters are varied. We find that for some regions of the parameter space the model undergoes a cascade of gluing bifurcations, while for others the model shows multistability between orbits of different periods
2019-01-16T06:56:06ZGranados Corsellas, AlbertHuguet Casades, GemmaIn this work we consider a general class of 2-dimensional hybrid systems. Assuming that the system possesses an attracting equilibrium point, we show that, when periodically driven with a square-wave pulse, the system possesses a periodic orbit which may undergo smooth and nonsmooth grazing bifurcations. We perform a semi-rigorous study of the existence of periodic orbits for a particular model consisting of a leaky integrate-and-fire model with a dynamic threshold. We use the stroboscopic map, which in this context is a 2-dimensional piecewise-smooth discontinuous map. For some parameter values we are able to show that the map is a quasi-contraction possessing a (locally) unique maximin periodic orbit. We complement our analysis using advanced numerical techniques to provide a complete portrait of the dynamics as parameters are varied. We find that for some regions of the parameter space the model undergoes a cascade of gluing bifurcations, while for others the model shows multistability between orbits of different periodsMulti-temporal analysis of morphologic changes applying geomatic techniques: 70 years of torrential activity in the Rebaixader catchment (Central pyrenees)Núñez Andrés, María AmparoBuill Pozuelo, FelipeHurlimann Ziegler, MarcelAbanco Martínez de Arenzana, Claudiahttp://hdl.handle.net/2117/1268802019-01-16T02:53:17Z2019-01-15T21:01:01ZMulti-temporal analysis of morphologic changes applying geomatic techniques: 70 years of torrential activity in the Rebaixader catchment (Central pyrenees)
Núñez Andrés, María Amparo; Buill Pozuelo, Felipe; Hurlimann Ziegler, Marcel; Abanco Martínez de Arenzana, Claudia
The monitoring of morphologic changes in high-mountain environments is an important, but complex task. Terrestrial as well as airborne laser scanning (TLS and ALS) and digital photogrammetry (DP) using Unnamed Aerial Vehicle (UAV) can determine recent variations. In contrast, changes that occurred 20 or more years ago, need generally the application of DP and historic aerial photograph. We compared these four geomatic techniques and the resulting digital elevation models (DEM) that ranged over a 70-year time span (1946–2016). The accuracy of the different models and also the effect of different cell size were analysed. The accuracy analysis of the resulting DEMs shows important drawbacks, when historic aerial photographs are used. In these DEMs, the error in elevation can be important and a detailed analysis of morphologic changes is limited. Nowadays, the combination of DP and UAV is the technique with best cost-benefit ratio, although TLS could reveal similar precision. However, the application of TLS is restrained by the complex morphology and the presence of vegetation, which produce many shadows. Finally, the erosion rate was determined in our catchment. The resulting values range between 0.06 and 0.16¿m3/m2/y, which coincides rather well with data observed in other studies.
2019-01-15T21:01:01ZNúñez Andrés, María AmparoBuill Pozuelo, FelipeHurlimann Ziegler, MarcelAbanco Martínez de Arenzana, ClaudiaThe monitoring of morphologic changes in high-mountain environments is an important, but complex task. Terrestrial as well as airborne laser scanning (TLS and ALS) and digital photogrammetry (DP) using Unnamed Aerial Vehicle (UAV) can determine recent variations. In contrast, changes that occurred 20 or more years ago, need generally the application of DP and historic aerial photograph. We compared these four geomatic techniques and the resulting digital elevation models (DEM) that ranged over a 70-year time span (1946–2016). The accuracy of the different models and also the effect of different cell size were analysed. The accuracy analysis of the resulting DEMs shows important drawbacks, when historic aerial photographs are used. In these DEMs, the error in elevation can be important and a detailed analysis of morphologic changes is limited. Nowadays, the combination of DP and UAV is the technique with best cost-benefit ratio, although TLS could reveal similar precision. However, the application of TLS is restrained by the complex morphology and the presence of vegetation, which produce many shadows. Finally, the erosion rate was determined in our catchment. The resulting values range between 0.06 and 0.16¿m3/m2/y, which coincides rather well with data observed in other studies.Guia temàtica Biblioteca ETSAB: Dipòsit d'AigüesEscola Tècnica Superior d'Arquitectura de Barcelona. Bibliotecahttp://hdl.handle.net/2117/1268732019-01-16T02:56:26Z2019-01-15T17:12:54ZGuia temàtica Biblioteca ETSAB: Dipòsit d'Aigües
Escola Tècnica Superior d'Arquitectura de Barcelona. Biblioteca
Bibliografia sobre l'edifici del Dipòsit de les Aigües (Josep Fontserè, 1874), actual seu de la Biblioteca del Campus de la Ciutadella de la Universitat Pompeu Fabra.
2019-01-15T17:12:54ZEscola Tècnica Superior d'Arquitectura de Barcelona. BibliotecaFixed grid numerical modelling of frost growth and densificationBartrons Casademont, EduardGalione, PedroPérez Segarra, Carlos Davidhttp://hdl.handle.net/2117/1268712019-01-16T03:36:59Z2019-01-15T16:33:27ZFixed grid numerical modelling of frost growth and densification
Bartrons Casademont, Eduard; Galione, Pedro; Pérez Segarra, Carlos David
A fixed-grid-porous-media method capable of simulating the growth and densification of frost sheets is here presented. A velocity field is calculated across the entire domain, in which a porous media treatment is given to the ice-containing cells. The transported temperature and vapour density are used to define the thermophysical state of each cell, which might enable phase change. As an improvement to Bartrons et al., 2017, the method hereby presented accounts for solidification and sublimation phase transitions. The explicit time step has also been increased by using a semi-implicit treatment of the energy equation. Furthermore, a special boundary condition for cold surfaces has been developed in order to overcome the averaging effect that prevents ice formation in the cells adjacent to the wall. The method is then tested with a study case of a duct flow with a non-homogeneously cooled lower boundary. Several numerical tests are carried out in order to understand the capabilities of the model. The in¿uence of accounting for the convection, as well as the enhanced diffusion resistance factors within the frost layer, is studied by means of the calculated porosity and velocity fields throughout the domain.
2019-01-15T16:33:27ZBartrons Casademont, EduardGalione, PedroPérez Segarra, Carlos DavidA fixed-grid-porous-media method capable of simulating the growth and densification of frost sheets is here presented. A velocity field is calculated across the entire domain, in which a porous media treatment is given to the ice-containing cells. The transported temperature and vapour density are used to define the thermophysical state of each cell, which might enable phase change. As an improvement to Bartrons et al., 2017, the method hereby presented accounts for solidification and sublimation phase transitions. The explicit time step has also been increased by using a semi-implicit treatment of the energy equation. Furthermore, a special boundary condition for cold surfaces has been developed in order to overcome the averaging effect that prevents ice formation in the cells adjacent to the wall. The method is then tested with a study case of a duct flow with a non-homogeneously cooled lower boundary. Several numerical tests are carried out in order to understand the capabilities of the model. The in¿uence of accounting for the convection, as well as the enhanced diffusion resistance factors within the frost layer, is studied by means of the calculated porosity and velocity fields throughout the domain.