Departament de Matemàtiques
http://hdl.handle.net/2117/3917
Tue, 28 Mar 2017 07:58:50 GMT2017-03-28T07:58:50ZIntegrated design of hybrid interstory-interbuilding multi-actuation schemes for vibration control of adjacent buildings under seismic excitations
http://hdl.handle.net/2117/102918
Integrated design of hybrid interstory-interbuilding multi-actuation schemes for vibration control of adjacent buildings under seismic excitations
Palacios Quiñonero, Francisco; Rubió Massegú, Josep; Rossell Garriga, Josep Maria; Karimi, Hamid Reza
The design of vibration control systems for the seismic protection of closely adjacent buildings is a complex and challenging problem. In this paper, we consider distributed multi-actuation schemes that combine interbuilding linking elements and interstory actuation devices. Using an advanced static output-feedback H 8 approach, active and passive vibration control systems are designed for a multi-story two-building structure equipped with a selected set of linked and unlinked actuation schemes. To validate the effectiveness of the obtained controllers, the corresponding frequency responses are investigated and a proper set of numerical simulations is conducted using the full scale North–South El Centro 1940 seismic record as ground acceleration disturbance. The observed results indicate that using combined interstory-interbuilding multi-actuation schemes is an effective means of mitigating the vibrational response of the individual buildings and, simultaneously, reducing the risk of interbuilding pounding. These results also point out that passive control systems with high-performance characteristics can be designed using damping elements.
Mon, 27 Mar 2017 13:39:05 GMThttp://hdl.handle.net/2117/1029182017-03-27T13:39:05ZPalacios Quiñonero, FranciscoRubió Massegú, JosepRossell Garriga, Josep MariaKarimi, Hamid RezaThe design of vibration control systems for the seismic protection of closely adjacent buildings is a complex and challenging problem. In this paper, we consider distributed multi-actuation schemes that combine interbuilding linking elements and interstory actuation devices. Using an advanced static output-feedback H 8 approach, active and passive vibration control systems are designed for a multi-story two-building structure equipped with a selected set of linked and unlinked actuation schemes. To validate the effectiveness of the obtained controllers, the corresponding frequency responses are investigated and a proper set of numerical simulations is conducted using the full scale North–South El Centro 1940 seismic record as ground acceleration disturbance. The observed results indicate that using combined interstory-interbuilding multi-actuation schemes is an effective means of mitigating the vibrational response of the individual buildings and, simultaneously, reducing the risk of interbuilding pounding. These results also point out that passive control systems with high-performance characteristics can be designed using damping elements.The flow and solidification of a thin fluid film on an arbitrary three-dimensional surface
http://hdl.handle.net/2117/102903
The flow and solidification of a thin fluid film on an arbitrary three-dimensional surface
Myers, Timothy; Charpin, Jean P. F.; Chapman, Jonathan S
A model for the flow of a thin film, with and without solidification, on an arbitrary three-dimensional substrate is presented. The problem is reduced to two simultaneous partial differential equations for the film and solid layer thicknesses. The flow model (with the solidification rate set to zero) is the first such model to describe thin film flow on an arbitrary three-dimensional surface. Various limits are investigated to recover previous models for flow on flat, cylindrical and two-dimensional curved surfaces. With solidification a previous model for accretion on a flat substrate is retrieved. It is shown how the model may be reduced to standard forms, such as solidification on a flat surface, circular and non-circular cylinders, aerofoils and spheres. Numerical solutions are obtained by combining an ADI scheme with a shock capturing method. Results are presented for flow and accretion on a flat surface, aerofoil and sphere.
Mon, 27 Mar 2017 10:03:32 GMThttp://hdl.handle.net/2117/1029032017-03-27T10:03:32ZMyers, TimothyCharpin, Jean P. F.Chapman, Jonathan SA model for the flow of a thin film, with and without solidification, on an arbitrary three-dimensional substrate is presented. The problem is reduced to two simultaneous partial differential equations for the film and solid layer thicknesses. The flow model (with the solidification rate set to zero) is the first such model to describe thin film flow on an arbitrary three-dimensional surface. Various limits are investigated to recover previous models for flow on flat, cylindrical and two-dimensional curved surfaces. With solidification a previous model for accretion on a flat substrate is retrieved. It is shown how the model may be reduced to standard forms, such as solidification on a flat surface, circular and non-circular cylinders, aerofoils and spheres. Numerical solutions are obtained by combining an ADI scheme with a shock capturing method. Results are presented for flow and accretion on a flat surface, aerofoil and sphere.Multidimensional big data processing for damage detection in real pipelines using a smart pig tool
http://hdl.handle.net/2117/102797
Multidimensional big data processing for damage detection in real pipelines using a smart pig tool
Ruiz Ordóñez, Magda; Mujica Delgado, Luis Eduardo; Alférez Baquero, Edwin Santiago; Quintero, Mario; Villamizar Mejía, Rodolfo
The history of the hydrocarbons business in Colombia dates back to the early twentieth century where mining and energy sector has been one of the principal pillars for the its development. Thus, the pipelines currently in service have over 30 years and most of them are buried and phenomena like metal losses, corrosion, mechanical stress, strike by excavation machinery and other type of damages are presented. Since it can generate social and environmental problems, monitoring tools and programs should be developed in order to prevent catastrophic situations. However, the maintaining of these structures is very expensive and it is normally developed by foreign companies. In order to overcome this situation, recently the native research institute “Research Institute of Corrosion - CIC (Corporación para la Investigación de la Corrosión)” developed an in-line inspection tool to be operated in Colombian pipelines (especially gas) to get valuable information of their current state along of thousand kilometres. The recorded data is of big size and its processing demand a high computational cost and adequate tool analysis to determine a certain pipeline damage condition. On other hand, the author from UPC and UIS have been bringing its expertise in processing and analysing this type of big data by using mainly Principal Component Analysis (PCA) as an effective tool to detect and locate different damages. In previous papers, multidimensional data matrix was used to locate possible damages along the pipeline, however most of activated points were considered false alarms since they corresponded to weld points. Thus, in this paper it is proposed no considering piecewise weld points (tube sections) and an extension of PCA named Multiway PCA (MPCA) is applied for each each one of the tube sections that form the pipeline. Therefore, if a tube section is found outside from overall indices found by using the MPCA model, an alarm activated in that section and a precise location can be obtained by analyzing only data from that specific tube section.
Wed, 22 Mar 2017 12:43:59 GMThttp://hdl.handle.net/2117/1027972017-03-22T12:43:59ZRuiz Ordóñez, MagdaMujica Delgado, Luis EduardoAlférez Baquero, Edwin SantiagoQuintero, MarioVillamizar Mejía, RodolfoThe history of the hydrocarbons business in Colombia dates back to the early twentieth century where mining and energy sector has been one of the principal pillars for the its development. Thus, the pipelines currently in service have over 30 years and most of them are buried and phenomena like metal losses, corrosion, mechanical stress, strike by excavation machinery and other type of damages are presented. Since it can generate social and environmental problems, monitoring tools and programs should be developed in order to prevent catastrophic situations. However, the maintaining of these structures is very expensive and it is normally developed by foreign companies. In order to overcome this situation, recently the native research institute “Research Institute of Corrosion - CIC (Corporación para la Investigación de la Corrosión)” developed an in-line inspection tool to be operated in Colombian pipelines (especially gas) to get valuable information of their current state along of thousand kilometres. The recorded data is of big size and its processing demand a high computational cost and adequate tool analysis to determine a certain pipeline damage condition. On other hand, the author from UPC and UIS have been bringing its expertise in processing and analysing this type of big data by using mainly Principal Component Analysis (PCA) as an effective tool to detect and locate different damages. In previous papers, multidimensional data matrix was used to locate possible damages along the pipeline, however most of activated points were considered false alarms since they corresponded to weld points. Thus, in this paper it is proposed no considering piecewise weld points (tube sections) and an extension of PCA named Multiway PCA (MPCA) is applied for each each one of the tube sections that form the pipeline. Therefore, if a tube section is found outside from overall indices found by using the MPCA model, an alarm activated in that section and a precise location can be obtained by analyzing only data from that specific tube section.Embedded piezodiagnostics for online structural damage detection based on PCA algorithm
http://hdl.handle.net/2117/102795
Embedded piezodiagnostics for online structural damage detection based on PCA algorithm
Camacho-Navarro, Jhonatan; Ruiz Ordóñez, Magda; Villamizar Mejía, Rodolfo; Mujica Delgado, Luis Eduardo; Ariza, Fabian
This work discusses a methodology used to implement a data-driven strategy for Structural Health Monitoring. First, the instrumentation of the equipment is detailed by describing the main components to be installed in the test structure in order to produce guide d waves. Specifically, an active piezo active system is used for this purpose , which consists of piezoelectric devices attached to the test structure surface and an ac quisition system. Then, the programming procedure to embed the damage detection algorithm is defined. In particular, the mathematical foundations and software requirements for impleme nting the preprocessing stage, baseline model building, and statistical index computation are specified. As a result, the Odroid-U3 computational core has the capability t o perform online damage assessment. Finally, some validation tests are presented through videos and short real time demonstration. Experimental data are recorded from two test specimens: i.) a lab carbon steel pipe loop built to emulate leak scenarios, and ii.) an aluminum plate, where mass adding is used to emulate reversible damages. The results reported i n this work show the high feasibility of the proposal methodology for obtaining an online embedded monitoring system with several advantages such as low cost, easy configuration, expandability and few computational resources
Wed, 22 Mar 2017 12:27:24 GMThttp://hdl.handle.net/2117/1027952017-03-22T12:27:24ZCamacho-Navarro, JhonatanRuiz Ordóñez, MagdaVillamizar Mejía, RodolfoMujica Delgado, Luis EduardoAriza, FabianThis work discusses a methodology used to implement a data-driven strategy for Structural Health Monitoring. First, the instrumentation of the equipment is detailed by describing the main components to be installed in the test structure in order to produce guide d waves. Specifically, an active piezo active system is used for this purpose , which consists of piezoelectric devices attached to the test structure surface and an ac quisition system. Then, the programming procedure to embed the damage detection algorithm is defined. In particular, the mathematical foundations and software requirements for impleme nting the preprocessing stage, baseline model building, and statistical index computation are specified. As a result, the Odroid-U3 computational core has the capability t o perform online damage assessment. Finally, some validation tests are presented through videos and short real time demonstration. Experimental data are recorded from two test specimens: i.) a lab carbon steel pipe loop built to emulate leak scenarios, and ii.) an aluminum plate, where mass adding is used to emulate reversible damages. The results reported i n this work show the high feasibility of the proposal methodology for obtaining an online embedded monitoring system with several advantages such as low cost, easy configuration, expandability and few computational resourcesDifferentiability with respect to parameters in global smooth linearization
http://hdl.handle.net/2117/102779
Differentiability with respect to parameters in global smooth linearization
Rodrigues, Hildebrando M.; Solà-Morales Rubió, Joan de
Let XX be a Banach space and T¿:X¿XT¿:X¿X a family of invertible contractions, T¿=L¿+f¿T¿=L¿+f¿, where L¿L¿ is linear and f¿f¿ is nonlinear with f¿(0)=0f¿(0)=0. We give conditions for the existence of a family of global linearization maps H¿H¿, such that View the MathML sourceH¿°T¿°H¿-1=L¿, with a smooth dependence on ¿. The results depend strongly on the choice of some appropriate spaces of maps, adapted norms and the use of a specific fixed point theorem with smooth dependence on parameters
Wed, 22 Mar 2017 09:59:13 GMThttp://hdl.handle.net/2117/1027792017-03-22T09:59:13ZRodrigues, Hildebrando M.Solà-Morales Rubió, Joan deLet XX be a Banach space and T¿:X¿XT¿:X¿X a family of invertible contractions, T¿=L¿+f¿T¿=L¿+f¿, where L¿L¿ is linear and f¿f¿ is nonlinear with f¿(0)=0f¿(0)=0. We give conditions for the existence of a family of global linearization maps H¿H¿, such that View the MathML sourceH¿°T¿°H¿-1=L¿, with a smooth dependence on ¿. The results depend strongly on the choice of some appropriate spaces of maps, adapted norms and the use of a specific fixed point theorem with smooth dependence on parametersSobre la inversa de grupo de grafos distancia regulares
http://hdl.handle.net/2117/102776
Sobre la inversa de grupo de grafos distancia regulares
Carmona Mejías, Ángeles
En este trabajo estudiamos cuando la inversa de grupo del Laplacia no com- binatorio de un grafo distancia–regular es una M –matriz. Cuando esto ocurre decimos que el grafo tiene la M –propiedad. Aquí probamos que sólo grafos distancia regulares con diámetro menor que cuatro pueden tener la M –propiedad y damos una caracterización en términos del vector de intersección
Wed, 22 Mar 2017 09:38:08 GMThttp://hdl.handle.net/2117/1027762017-03-22T09:38:08ZCarmona Mejías, ÁngelesEn este trabajo estudiamos cuando la inversa de grupo del Laplacia no com- binatorio de un grafo distancia–regular es una M –matriz. Cuando esto ocurre decimos que el grafo tiene la M –propiedad. Aquí probamos que sólo grafos distancia regulares con diámetro menor que cuatro pueden tener la M –propiedad y damos una caracterización en términos del vector de intersecciónThe conjugacy problem in extensions of Thompson's group F
http://hdl.handle.net/2117/102759
The conjugacy problem in extensions of Thompson's group F
Burillo Puig, José; Matucci, Francesco; Ventura Capell, Enric
We solve the twisted conjugacy problem on Thompson’s group F. We also exhibit orbit undecidable subgroups of Aut(F), and give a proof that Aut(F) and Aut+(F) are orbit decidable provided a certain conjecture on Thompson’s group T is true. By using general criteria introduced by Bogopolski, Martino and Ventura in [5], we construct a family of free extensions of F where the conjugacy problem is unsolvable. As a byproduct of our techniques, we give a new proof of a result of Bleak–Fel’shtyn–Gonçalves in [4] showing that F has property R8, and which can be extended to show that Thompson’s group T also has property R8.
The final publication is available at Springer via http://dx.doi.org/10.1007/s11856-016-1403-9
Tue, 21 Mar 2017 17:43:46 GMThttp://hdl.handle.net/2117/1027592017-03-21T17:43:46ZBurillo Puig, JoséMatucci, FrancescoVentura Capell, EnricWe solve the twisted conjugacy problem on Thompson’s group F. We also exhibit orbit undecidable subgroups of Aut(F), and give a proof that Aut(F) and Aut+(F) are orbit decidable provided a certain conjecture on Thompson’s group T is true. By using general criteria introduced by Bogopolski, Martino and Ventura in [5], we construct a family of free extensions of F where the conjugacy problem is unsolvable. As a byproduct of our techniques, we give a new proof of a result of Bleak–Fel’shtyn–Gonçalves in [4] showing that F has property R8, and which can be extended to show that Thompson’s group T also has property R8.Report on the EGNSS competition after Y1
http://hdl.handle.net/2117/102717
Report on the EGNSS competition after Y1
Sanz Subirana, Jaume; Juan Zornoza, José Miguel; Alonso Alonso, María Teresa
Tue, 21 Mar 2017 10:30:26 GMThttp://hdl.handle.net/2117/1027172017-03-21T10:30:26ZSanz Subirana, JaumeJuan Zornoza, José MiguelAlonso Alonso, María TeresaLow-dimensional dynamics of structured random networks
http://hdl.handle.net/2117/102601
Low-dimensional dynamics of structured random networks
Aljadeff, Johnatan; Renfrew, David; Vegué Llorente, Marina; Sharpee, Tatyana O.
Using a generalized random recurrent neural network model, and by extending our recently developed mean-field approach [J. Aljadeff, M. Stern, and T. Sharpee, Phys. Rev. Lett. 114, 088101 (2015)], we study the relationship between the network connectivity structure and its low-dimensional dynamics. Each connection in the network is a random number with mean 0 and variance that depends on pre- and postsynaptic neurons through a sufficiently smooth function g of their identities. We find that these networks undergo a phase transition from a silent to a chaotic state at a critical point we derive as a function of g. Above the critical point, although unit activation levels are chaotic, their autocorrelation functions are restricted to a low-dimensional subspace. This provides a direct link between the network's structure and some of its functional characteristics. We discuss example applications of the general results to neuroscience where we derive the support of the spectrum of connectivity matrices with heterogeneous and possibly correlated degree distributions, and to ecology where we study the stability of the cascade model for food web structure.
Thu, 16 Mar 2017 16:14:42 GMThttp://hdl.handle.net/2117/1026012017-03-16T16:14:42ZAljadeff, JohnatanRenfrew, DavidVegué Llorente, MarinaSharpee, Tatyana O.Using a generalized random recurrent neural network model, and by extending our recently developed mean-field approach [J. Aljadeff, M. Stern, and T. Sharpee, Phys. Rev. Lett. 114, 088101 (2015)], we study the relationship between the network connectivity structure and its low-dimensional dynamics. Each connection in the network is a random number with mean 0 and variance that depends on pre- and postsynaptic neurons through a sufficiently smooth function g of their identities. We find that these networks undergo a phase transition from a silent to a chaotic state at a critical point we derive as a function of g. Above the critical point, although unit activation levels are chaotic, their autocorrelation functions are restricted to a low-dimensional subspace. This provides a direct link between the network's structure and some of its functional characteristics. We discuss example applications of the general results to neuroscience where we derive the support of the spectrum of connectivity matrices with heterogeneous and possibly correlated degree distributions, and to ecology where we study the stability of the cascade model for food web structure.Stabbing circles for some sets of Delaunay segments
http://hdl.handle.net/2117/102530
Stabbing circles for some sets of Delaunay segments
Claverol Aguas, Mercè; Khramtcova, Elena; Papadopoulou, Evanthia; Saumell, Maria; Seara Ojea, Carlos
Let S be a set of n segments in the plane such that, for
every segment, its two endpoints are adjacent in the Delaunay triangulation of the set of endpoints of all segments in S. Our goal is to compute all the combinatorially different stabbing circles for S, and the ones with maximum and minimum radius. We exploit a recent result to solve this problem in O(n log n) in two particular cases: (i) all segments in S are parallel; (ii) all segments in S have the same length. We also show that the problem of computing the stabbing circle of minimum radius of a set of n parallel segments of equal length (not necessarily satisfying the Delaunay condition) has an Omega(n log n) lower bound.
Wed, 15 Mar 2017 15:55:08 GMThttp://hdl.handle.net/2117/1025302017-03-15T15:55:08ZClaverol Aguas, MercèKhramtcova, ElenaPapadopoulou, EvanthiaSaumell, MariaSeara Ojea, CarlosLet S be a set of n segments in the plane such that, for
every segment, its two endpoints are adjacent in the Delaunay triangulation of the set of endpoints of all segments in S. Our goal is to compute all the combinatorially different stabbing circles for S, and the ones with maximum and minimum radius. We exploit a recent result to solve this problem in O(n log n) in two particular cases: (i) all segments in S are parallel; (ii) all segments in S have the same length. We also show that the problem of computing the stabbing circle of minimum radius of a set of n parallel segments of equal length (not necessarily satisfying the Delaunay condition) has an Omega(n log n) lower bound.