Enviament des de DRAC
http://hdl.handle.net/2117/3055
20160823T21:31:22Z

A bilevel programming formulation for modelling the location of information: points for traffic conditions
http://hdl.handle.net/2117/89379
A bilevel programming formulation for modelling the location of information: points for traffic conditions
Montero Mercadé, Lídia; Codina Sancho, Esteve; Marín, Angel
20160823T11:36:25Z
Montero Mercadé, Lídia
Codina Sancho, Esteve
Marín, Angel

A beliefbased decisionmaking framework for spectrum selection in cognitive radio networks
http://hdl.handle.net/2117/89370
A beliefbased decisionmaking framework for spectrum selection in cognitive radio networks
Pérez Romero, Jordi; Raschellà, Alessandro; Sallent Roig, José Oriol; Umbert Juliana, Anna
This paper presents a comprehensive cognitive management framework for spectrum selection in cognitive radio
networks. The framework uses a belief vector concept as a means to predict the interference affecting the different spectrum blocks and relies on a smart analysis of the scenario dynamicity to properly determine an adequate observation strategy to balance the tradeoff between achievable performance and measurement requirements. In this respect, the paper shows that the
interference dynamics in a given spectrum block can be properly characterized through the second highest eigenvalue of the
interference state transition matrix. Therefore, this indicator is retained in the proposed framework as a relevant parameter to
drive the selection of both the observation strategy and spectrum selection decisionmaking criterion. The paper evaluates the
proposed framework to illustrate the capability to properly choose among a set of possible observation strategies under
different scenario conditions. Furthermore, a comparison against other stateoftheart solutions is presented.
20160729T15:09:15Z
Pérez Romero, Jordi
Raschellà, Alessandro
Sallent Roig, José Oriol
Umbert Juliana, Anna
This paper presents a comprehensive cognitive management framework for spectrum selection in cognitive radio
networks. The framework uses a belief vector concept as a means to predict the interference affecting the different spectrum blocks and relies on a smart analysis of the scenario dynamicity to properly determine an adequate observation strategy to balance the tradeoff between achievable performance and measurement requirements. In this respect, the paper shows that the
interference dynamics in a given spectrum block can be properly characterized through the second highest eigenvalue of the
interference state transition matrix. Therefore, this indicator is retained in the proposed framework as a relevant parameter to
drive the selection of both the observation strategy and spectrum selection decisionmaking criterion. The paper evaluates the
proposed framework to illustrate the capability to properly choose among a set of possible observation strategies under
different scenario conditions. Furthermore, a comparison against other stateoftheart solutions is presented.

Performance evaluation of a distributed storage service in community network clouds
http://hdl.handle.net/2117/89369
Performance evaluation of a distributed storage service in community network clouds
Selimi, Mennan; Freitag, Fèlix; Cerdà Alabern, Llorenç; Veiga, Luis
Community networks are selforganized and decentralized communication networks built and operated by citizens, for citizens. The consolidation of today's cloud technologies offers now, for community networks, the possibility to collectively develop community clouds, building upon userprovided networks and extending toward cloud services. Cloud storage, and in particular secure and reliable cloud storage, could become a key community cloud service to enable enduser applications. In this paper, we evaluate in a real deployment the performance of Tahoe leastauthority file system (TahoeLAFS), a decentralized storage system with providerindependent security that guarantees privacy to the users. We evaluate how the TahoeLAFS storage system performs when it is deployed over distributed community cloud nodes in a real community network such as Guifi.net. Furthermore, we evaluate TahoeLAFS in the Microsoft Azure commercial cloud platform, to compare and understand the impact of homogeneous network and hardware resources on the performance of the TahoeLAFS. We observed that the write operation of TahoeLAFS resulted in similar performance when using either the community network cloud or the commercial cloud. However, the read operation achieved better performance in the Azure cloud, where the reading from multiple nodes of TahoeLAFS benefited from the homogeneity of the network and nodes. Our results suggest that TahoeLAFS can run on community network clouds with suitable performance for the needed enduser experience.
20160729T14:49:58Z
Selimi, Mennan
Freitag, Fèlix
Cerdà Alabern, Llorenç
Veiga, Luis
Community networks are selforganized and decentralized communication networks built and operated by citizens, for citizens. The consolidation of today's cloud technologies offers now, for community networks, the possibility to collectively develop community clouds, building upon userprovided networks and extending toward cloud services. Cloud storage, and in particular secure and reliable cloud storage, could become a key community cloud service to enable enduser applications. In this paper, we evaluate in a real deployment the performance of Tahoe leastauthority file system (TahoeLAFS), a decentralized storage system with providerindependent security that guarantees privacy to the users. We evaluate how the TahoeLAFS storage system performs when it is deployed over distributed community cloud nodes in a real community network such as Guifi.net. Furthermore, we evaluate TahoeLAFS in the Microsoft Azure commercial cloud platform, to compare and understand the impact of homogeneous network and hardware resources on the performance of the TahoeLAFS. We observed that the write operation of TahoeLAFS resulted in similar performance when using either the community network cloud or the commercial cloud. However, the read operation achieved better performance in the Azure cloud, where the reading from multiple nodes of TahoeLAFS benefited from the homogeneity of the network and nodes. Our results suggest that TahoeLAFS can run on community network clouds with suitable performance for the needed enduser experience.

Measuring disparities in access to water based on the normative content of the human right
http://hdl.handle.net/2117/89368
Measuring disparities in access to water based on the normative content of the human right
Flores Baquero, Óscar; Jiménez Fernandez de Palencia, Alejandro; Pérez Foguet, Agustí
Measuring access to water in the Sustainable Development Goals era involves taking into account the human rights framework. Therefore, its content should be considered to conceptualize the level of service through adequate indicators and to followup inequities reduction at global, national and local level. This research develops and tests a methodology to measure intracommunity disparities based on human right to water normative criteria through a stratified sampling, splitting households served by community based organizations and those selfprovided. This approach implies considering much reduced populations, thus special care needs to be taken with sample sizes and uncertainty of estimators. The proposed methodology is practical to locate and accurately characterize minority sectors within rural communities and allows moving beyond centraltendency estimators. It implies higher costs for field data collection than traditional approaches, but this can be assumed given the relevance of the approach from a human rights perspective, which calls for adequate tools for equityoriented policy making at local level. The research point out how results might be used to shape decisionmaking processes.
20160729T14:44:30Z
Flores Baquero, Óscar
Jiménez Fernandez de Palencia, Alejandro
Pérez Foguet, Agustí
Measuring access to water in the Sustainable Development Goals era involves taking into account the human rights framework. Therefore, its content should be considered to conceptualize the level of service through adequate indicators and to followup inequities reduction at global, national and local level. This research develops and tests a methodology to measure intracommunity disparities based on human right to water normative criteria through a stratified sampling, splitting households served by community based organizations and those selfprovided. This approach implies considering much reduced populations, thus special care needs to be taken with sample sizes and uncertainty of estimators. The proposed methodology is practical to locate and accurately characterize minority sectors within rural communities and allows moving beyond centraltendency estimators. It implies higher costs for field data collection than traditional approaches, but this can be assumed given the relevance of the approach from a human rights perspective, which calls for adequate tools for equityoriented policy making at local level. The research point out how results might be used to shape decisionmaking processes.

Absorption time of the Moran process
http://hdl.handle.net/2117/89367
Absorption time of the Moran process
Díaz Cort, Josep; Goldberg, Leslie Ann; Richerby, David; Serna Iglesias, María José
© 2016 Wiley Periodicals, Inc.
The Moran process models the spread of mutations in populations on graphs. We investigate the absorption time of the process, which is the time taken for a mutation introduced at a randomly chosen vertex to either spread to the whole population, or to become extinct. It is known that the expected absorption time for an advantageous mutation is O(n4) on an nvertex undirected graph, which allows the behaviour of the process on undirected graphs to be analysed using the Markov chain Monte Carlo method. We show that this does not extend to directed graphs by exhibiting an infinite family of directed graphs for which the expected absorption time is exponential in the number of vertices. However, for regular directed graphs, we show that the expected absorption time is O(nlogn) and O(n2). We exhibit families of graphs matching these bounds and give improved bounds for other families of graphs, based on isoperimetric number. Our results are obtained via stochastic dominations which we demonstrate by establishing a coupling in a related continuoustime model. The coupling also implies several natural domination results regarding the fixation probability of the original (discretetime) process, resolving a conjecture of Shakarian, Roos and Johnson.
20160729T13:05:23Z
Díaz Cort, Josep
Goldberg, Leslie Ann
Richerby, David
Serna Iglesias, María José
© 2016 Wiley Periodicals, Inc.
The Moran process models the spread of mutations in populations on graphs. We investigate the absorption time of the process, which is the time taken for a mutation introduced at a randomly chosen vertex to either spread to the whole population, or to become extinct. It is known that the expected absorption time for an advantageous mutation is O(n4) on an nvertex undirected graph, which allows the behaviour of the process on undirected graphs to be analysed using the Markov chain Monte Carlo method. We show that this does not extend to directed graphs by exhibiting an infinite family of directed graphs for which the expected absorption time is exponential in the number of vertices. However, for regular directed graphs, we show that the expected absorption time is O(nlogn) and O(n2). We exhibit families of graphs matching these bounds and give improved bounds for other families of graphs, based on isoperimetric number. Our results are obtained via stochastic dominations which we demonstrate by establishing a coupling in a related continuoustime model. The coupling also implies several natural domination results regarding the fixation probability of the original (discretetime) process, resolving a conjecture of Shakarian, Roos and Johnson.

ßdelayed neutron emission studies
http://hdl.handle.net/2117/89343
ßdelayed neutron emission studies
Gómez Hornillos, María Belén; Taín, J.L.; Gorlychev, V.; Calviño Tavares, Francisco; Cortés Rossell, Guillem Pere; Pretel Sánchez, Carme
The study of betadelayed neutron emission plays a major role in different fields such as nuclear technology, nuclear astrophysics and nuclear structure. However the quality of the existing experimental data nowadays is not sufficient for the various technical and scientific applications and new high precision measurements are necessary to improve the data bases. One key aspect to the success of these high precission measurements is the use of a very pure ion beam that ensures that only the ion of interest is produced. The combination of the IGISOL mass separator with the JYFLTRAP Penning trap is an excellent tool for this type of measurement because of the ability to deliver isobarically and even isomerically clean beams. Another key feature of the installation is the nonchemical selectivity of the IGISOL ion source which allows measurements in the important region of refractory elements. This paper summarises the betadelayed neutron emission studies that have been carried out at the IGISOL facility with two different neutron detectors based on 3He counters in a polyethylene moderator: the Mainz neutron detector and the BEta deLayEd Neutron detector.
20160729T06:52:32Z
Gómez Hornillos, María Belén
Taín, J.L.
Gorlychev, V.
Calviño Tavares, Francisco
Cortés Rossell, Guillem Pere
Pretel Sánchez, Carme
The study of betadelayed neutron emission plays a major role in different fields such as nuclear technology, nuclear astrophysics and nuclear structure. However the quality of the existing experimental data nowadays is not sufficient for the various technical and scientific applications and new high precision measurements are necessary to improve the data bases. One key aspect to the success of these high precission measurements is the use of a very pure ion beam that ensures that only the ion of interest is produced. The combination of the IGISOL mass separator with the JYFLTRAP Penning trap is an excellent tool for this type of measurement because of the ability to deliver isobarically and even isomerically clean beams. Another key feature of the installation is the nonchemical selectivity of the IGISOL ion source which allows measurements in the important region of refractory elements. This paper summarises the betadelayed neutron emission studies that have been carried out at the IGISOL facility with two different neutron detectors based on 3He counters in a polyethylene moderator: the Mainz neutron detector and the BEta deLayEd Neutron detector.

High stability of properties in morphotropic phase boundary Bi0.5Na0.5TiO3BaTiO3 piezoceramics
http://hdl.handle.net/2117/89339
High stability of properties in morphotropic phase boundary Bi0.5Na0.5TiO3BaTiO3 piezoceramics
Machado, Rodrigo; Ochoa Guerrero, Diego A.; dos Santos, Valdeci B.; Cerdeiras Montero, Elena; Mestres Vila, Lourdes; García García, José Eduardo
The (1x)Bi0.5Na0.5TiO3–xBaTiO3 (BNTxBT) system with composition at its morphotropic phase boundary (MPB) has received significant attention because of their attractive properties as leadfree piezoceramics. Although the basic properties of this system are wellestablished, reports about the stability of the functional properties of these piezoelectric materials are still lacking. A study on the dielectric and piezoelectric properties of BNTxBT close to their MPB, with emphasis on material response under high electric field or mechanical stress, is performed in this work. The results indicate that the BNTBT system exhibits a high stability of dielectric and piezoelectric properties, making it potentially interesting for specific applications. A direct correlation between piezoelectric properties and nonlinear response is evidenced for a wide number of piezoceramics, which is expected due to the extrinsic nature of the piezoelectric response. Finding compositions that show high electromechanical properties and low nonlinear behavior is a challenge in the search for competitive leadfree piezoceramics.
20160728T15:22:50Z
Machado, Rodrigo
Ochoa Guerrero, Diego A.
dos Santos, Valdeci B.
Cerdeiras Montero, Elena
Mestres Vila, Lourdes
García García, José Eduardo
The (1x)Bi0.5Na0.5TiO3–xBaTiO3 (BNTxBT) system with composition at its morphotropic phase boundary (MPB) has received significant attention because of their attractive properties as leadfree piezoceramics. Although the basic properties of this system are wellestablished, reports about the stability of the functional properties of these piezoelectric materials are still lacking. A study on the dielectric and piezoelectric properties of BNTxBT close to their MPB, with emphasis on material response under high electric field or mechanical stress, is performed in this work. The results indicate that the BNTBT system exhibits a high stability of dielectric and piezoelectric properties, making it potentially interesting for specific applications. A direct correlation between piezoelectric properties and nonlinear response is evidenced for a wide number of piezoceramics, which is expected due to the extrinsic nature of the piezoelectric response. Finding compositions that show high electromechanical properties and low nonlinear behavior is a challenge in the search for competitive leadfree piezoceramics.

Natural convection in a horizontal cylinder with axial rotation
http://hdl.handle.net/2117/89338
Natural convection in a horizontal cylinder with axial rotation
Sánchez Casals, Odalys de la Caridad; Mercader Calvo, María Isabel; Batiste Boleda, Oriol; Alonso Maleta, María Aránzazu
We study the problem of thermal convection in a laterally heated horizontal cylinder rotating about its axis. A cylinder of aspect ratio Gamma = H/2R = 2 containing a small Prandtl number fluid (sigma = 0.01) representative of molten metals and molten semiconductors at high temperature is considered. We focus on a slow rotation regime (Omega < 8), where the effects of rotation and buoyancy forces are comparable. The NavierStokes and energy equations with the Boussinesq approximation are solved numerically to calculate the basic states, analyze their linear stability, and compute several secondary flows originated from the instabilities. Due to the confined cylindrical geometrythe presence of lateral walls and lidsall the flows are completely three dimensional, even the basic steady states. Results characterizing the basic states as the rotation rate increases are presented. As it occurred in the nonrotating case for higher values of the Prandtl number, two curves of steady states with the same symmetric character coexist for moderate values of the Rayleigh number. In the range of Omega considered, rotation has a stabilizing effect only for very small values. As the value of the rotation rate approaches Omega = 3.5 and Omega = 4.5, the scenario of bifurcations becomes more complex due to the existence in both cases of very close bifurcations of codimension 2, which in the latter case involve both curves of symmetric solutions.
20160728T14:41:31Z
Sánchez Casals, Odalys de la Caridad
Mercader Calvo, María Isabel
Batiste Boleda, Oriol
Alonso Maleta, María Aránzazu
We study the problem of thermal convection in a laterally heated horizontal cylinder rotating about its axis. A cylinder of aspect ratio Gamma = H/2R = 2 containing a small Prandtl number fluid (sigma = 0.01) representative of molten metals and molten semiconductors at high temperature is considered. We focus on a slow rotation regime (Omega < 8), where the effects of rotation and buoyancy forces are comparable. The NavierStokes and energy equations with the Boussinesq approximation are solved numerically to calculate the basic states, analyze their linear stability, and compute several secondary flows originated from the instabilities. Due to the confined cylindrical geometrythe presence of lateral walls and lidsall the flows are completely three dimensional, even the basic steady states. Results characterizing the basic states as the rotation rate increases are presented. As it occurred in the nonrotating case for higher values of the Prandtl number, two curves of steady states with the same symmetric character coexist for moderate values of the Rayleigh number. In the range of Omega considered, rotation has a stabilizing effect only for very small values. As the value of the rotation rate approaches Omega = 3.5 and Omega = 4.5, the scenario of bifurcations becomes more complex due to the existence in both cases of very close bifurcations of codimension 2, which in the latter case involve both curves of symmetric solutions.

Computerbased cognitive rehabilitation: the CoRe system
http://hdl.handle.net/2117/89336
Computerbased cognitive rehabilitation: the CoRe system
Alloni, Anna; Sinforiani, Elena; Zuchella, Chiara; Sandrini, Giorgio; Bernini, Sara; Cattani, Barbara; Tost Pardell, Daniela; Quaglini, Silvana; Pistarini, Caterina
This work aims at providing a tool for supporting cognitive rehabilitation. This is a wide field, that includes a variety of diseases and related clinical pictures; for this reason the need arises to have a tool available that overcomes the difficulties entailed by what currently is the most common approach, that is, the socalled pen and paper rehabilitation. Methods: We first organized a big number of stimuli in an ontology that represents concepts, attributes and a set of relationships among concepts. Stimuli may be words, sounds, 2D and 3D images. Then, we developed an engine that automatically generates exercises by exploiting that ontology. The design of exercises has been carried on in synergy with neuropsychologists and speech therapists. Solutions have been devised aimed at personalizing the exercises according to both patients’ preferences and performance. Results: Exercises addressed to rehabilitation of executive functions and aphasiarelated diseases have been implemented. The system has been tested on both healthy volunteers (n 1/4 38) and patients (n 1/4 9), obtaining a favourable rating and suggestions for improvements. Conclusions: We created a tool able to automate the execution of cognitive rehabilitation tasks. We hope the variety and personalization of exercises will allow to increase compliance, particularly from elderly people, usually neither familiar with technology nor particularly willing to rely on it. The next step involves the creation of a telerehabilitation tool, to allow therapy sessions to be undergone from home, thus guaranteeing continuity of care and advantages in terms of time and costs for the patients and the National Healthcare System (NHS).
20160728T12:18:04Z
Alloni, Anna
Sinforiani, Elena
Zuchella, Chiara
Sandrini, Giorgio
Bernini, Sara
Cattani, Barbara
Tost Pardell, Daniela
Quaglini, Silvana
Pistarini, Caterina
This work aims at providing a tool for supporting cognitive rehabilitation. This is a wide field, that includes a variety of diseases and related clinical pictures; for this reason the need arises to have a tool available that overcomes the difficulties entailed by what currently is the most common approach, that is, the socalled pen and paper rehabilitation. Methods: We first organized a big number of stimuli in an ontology that represents concepts, attributes and a set of relationships among concepts. Stimuli may be words, sounds, 2D and 3D images. Then, we developed an engine that automatically generates exercises by exploiting that ontology. The design of exercises has been carried on in synergy with neuropsychologists and speech therapists. Solutions have been devised aimed at personalizing the exercises according to both patients’ preferences and performance. Results: Exercises addressed to rehabilitation of executive functions and aphasiarelated diseases have been implemented. The system has been tested on both healthy volunteers (n 1/4 38) and patients (n 1/4 9), obtaining a favourable rating and suggestions for improvements. Conclusions: We created a tool able to automate the execution of cognitive rehabilitation tasks. We hope the variety and personalization of exercises will allow to increase compliance, particularly from elderly people, usually neither familiar with technology nor particularly willing to rely on it. The next step involves the creation of a telerehabilitation tool, to allow therapy sessions to be undergone from home, thus guaranteeing continuity of care and advantages in terms of time and costs for the patients and the National Healthcare System (NHS).

On the time decay of solutions for nonsimple elasticity with voids
http://hdl.handle.net/2117/89329
On the time decay of solutions for nonsimple elasticity with voids
Liu, Zhuangyi; Magaña Nieto, Antonio; Quintanilla de Latorre, Ramón
In this work we consider the nonsimple theory of elastic material with voids and we investigate how the coupling of these two aspects of the material affects the behavior of the solutions. We analyze only two kind of different behavior, slow or exponential decay. We introduce four different dissipation mechanisms in the system and we study, in each case, the effect of this mechanism in the behavior of the solutions.
20160728T11:25:42Z
Liu, Zhuangyi
Magaña Nieto, Antonio
Quintanilla de Latorre, Ramón
In this work we consider the nonsimple theory of elastic material with voids and we investigate how the coupling of these two aspects of the material affects the behavior of the solutions. We analyze only two kind of different behavior, slow or exponential decay. We introduce four different dissipation mechanisms in the system and we study, in each case, the effect of this mechanism in the behavior of the solutions.