Reports de recerca
http://hdl.handle.net/2117/3973
Tue, 25 Oct 2016 10:21:44 GMT2016-10-25T10:21:44ZTree-decomposable and underconstrained geometric constraint problems
http://hdl.handle.net/2117/91041
Tree-decomposable and underconstrained geometric constraint problems
Fudos, Ioannis; Hoffmann, Christoph M.; Joan Arinyo, Robert
Tue, 25 Oct 2016 08:15:05 GMThttp://hdl.handle.net/2117/910412016-10-25T08:15:05ZFudos, IoannisHoffmann, Christoph M.Joan Arinyo, RobertTriangles, ruler and compass
http://hdl.handle.net/2117/90013
Triangles, ruler and compass
Joan Arinyo, Robert
A triangle can be specified by giving three independent geometric relationships defined between its elements. Usually, these relationships are distances between two vertices, angles between two sides, and heights. For each triangle specified by a set of three of such relationships, we present a procedure that constructs the triangle using ruler and compass alone.
Informe de recerca sobre constructibilitat de triangles amb regle-i-compas
Fri, 16 Sep 2016 18:41:26 GMThttp://hdl.handle.net/2117/900132016-09-16T18:41:26ZJoan Arinyo, RobertA triangle can be specified by giving three independent geometric relationships defined between its elements. Usually, these relationships are distances between two vertices, angles between two sides, and heights. For each triangle specified by a set of three of such relationships, we present a procedure that constructs the triangle using ruler and compass alone.Self-synchronized duty-cycling for sensor networks with energy harvesting capabilities: Implementation in Wiselib
http://hdl.handle.net/2117/89839
Self-synchronized duty-cycling for sensor networks with energy harvesting capabilities: Implementation in Wiselib
Hernández, H.; Baumgartner, Tobias; Blum, Christian; Blesa Aguilera, Maria Josep; Fekete, Sandor P.; Kröller, Alexander
In this work we present a protocol for a self- synchronized duty-cycling mechanism in wireless sensor net- works with energy harvesting capabilities. The protocol is im- plemented in Wiselib, a library of generic algorithms for sensor networks. Simulations are conducted with the sensor network simulator Shawn. They are based on the specifications of real hardware known as iSense sensor nodes. The experimental results show that the proposed mechanism is able to adapt to changing energy availabilities. Moreover, it is shown that the system is very robust against packet loss.
Tue, 13 Sep 2016 07:13:53 GMThttp://hdl.handle.net/2117/898392016-09-13T07:13:53ZHernández, H.Baumgartner, TobiasBlum, ChristianBlesa Aguilera, Maria JosepFekete, Sandor P.Kröller, AlexanderIn this work we present a protocol for a self- synchronized duty-cycling mechanism in wireless sensor net- works with energy harvesting capabilities. The protocol is im- plemented in Wiselib, a library of generic algorithms for sensor networks. Simulations are conducted with the sensor network simulator Shawn. They are based on the specifications of real hardware known as iSense sensor nodes. The experimental results show that the proposed mechanism is able to adapt to changing energy availabilities. Moreover, it is shown that the system is very robust against packet loss.Towards the implementation of a preference-and uncertain-aware solver using answer set programming
http://hdl.handle.net/2117/89810
Towards the implementation of a preference-and uncertain-aware solver using answer set programming
Confalonieri, Roberto; Nieves Sánchez, Juan Carlos; Vázquez Salceda, Javier
Logic programs with possibilistic ordered disjunction (or LPPODs) are a recently defined logic-programming framework based on logic programs with ordered disjunction and possibilistic logic. The framework inherits the properties of such formalisms and merging them, it supports a reasoning which is nonmonotonic, preference-and uncertain-aware. The LPPODs syntax allows to specify 1) preferences in a qualitative way, and 2) necessity values about the certainty of program clauses. As a result at semantic level, preferences and necessity values can be used to specify an order among program solutions. This class of program therefore fits well in the representation of decision problems where a best option has to be chosen taking into account both preferences and necessity measures about information. In this paper we study the computation and the complexity of the LPPODs semantics and we describe the algorithm for its implementation following on Answer Set Programming approach. We describe some decision scenarios where the solver can be used to choose the best solutions by checking whether an outcome is possibilistically preferred over another considering preferences and uncertainty at the same time.
Mon, 12 Sep 2016 08:27:55 GMThttp://hdl.handle.net/2117/898102016-09-12T08:27:55ZConfalonieri, RobertoNieves Sánchez, Juan CarlosVázquez Salceda, JavierLogic programs with possibilistic ordered disjunction (or LPPODs) are a recently defined logic-programming framework based on logic programs with ordered disjunction and possibilistic logic. The framework inherits the properties of such formalisms and merging them, it supports a reasoning which is nonmonotonic, preference-and uncertain-aware. The LPPODs syntax allows to specify 1) preferences in a qualitative way, and 2) necessity values about the certainty of program clauses. As a result at semantic level, preferences and necessity values can be used to specify an order among program solutions. This class of program therefore fits well in the representation of decision problems where a best option has to be chosen taking into account both preferences and necessity measures about information. In this paper we study the computation and the complexity of the LPPODs semantics and we describe the algorithm for its implementation following on Answer Set Programming approach. We describe some decision scenarios where the solver can be used to choose the best solutions by checking whether an outcome is possibilistically preferred over another considering preferences and uncertainty at the same time.Process mining meets abstract interpretation
http://hdl.handle.net/2117/88077
Process mining meets abstract interpretation
Carmona Vargas, Josep; Cortadella Fortuny, Jordi
The discovery of process models out of system traces is an interesting problem that has received significant attention in the last years. In this work, a theory for the derivation of a Petri net from a set of traces is presented. The method is based on the theory of abstract interpretation, which has been applied successfully in other areas. The principal application of the theory presented is Process Mining, an area that tries to incorporate the use of formal models both in the design and use of information systems.
Thu, 16 Jun 2016 08:50:11 GMThttp://hdl.handle.net/2117/880772016-06-16T08:50:11ZCarmona Vargas, JosepCortadella Fortuny, JordiThe discovery of process models out of system traces is an interesting problem that has received significant attention in the last years. In this work, a theory for the derivation of a Petri net from a set of traces is presented. The method is based on the theory of abstract interpretation, which has been applied successfully in other areas. The principal application of the theory presented is Process Mining, an area that tries to incorporate the use of formal models both in the design and use of information systems.Comparing error minimized extreme learning machines and support vector sequential feed-forward neural networks
http://hdl.handle.net/2117/88076
Comparing error minimized extreme learning machines and support vector sequential feed-forward neural networks
Romero Merino, Enrique; Alquézar Mancho, René
Recently, error minimized extreme learning machines (EM-ELMs) have been proposed as a simple and efficient approach to build single-hidden-layer feed-forward networks (SLFNs) sequentially. They add random hidden nodes one by one (or group by group) and update the output weights incrementally to minimize the sum-of-squares error in the training set. Other very similar methods that also construct SLFNs sequentially had been reported earlier with the main difference that their hidden-layer weights are a subset of the data instead of being random. By analogy with the concept of support vectors original of support vector machines (SVMs), these approaches can be referred to as support vector sequential feed-forward neural networks (SV-SFNNs), and they are a particular case of the Sequential Approximation with Optimal Coefficients and Interacting Frequencies (SAOCIF) method. In this paper, it is firstly shown that EM-ELMs can also be cast as a particular case of SAOCIF. In particular, EM-ELMs can easily be extended to test some number of random candidates at each step and select the best of them, as SAOCIF does. Moreover, it is demonstrated that the cost of the calculation of the optimal output-layer weights in the originally proposed EM-ELMs can be improved if it is replaced by the one included in SAOCIF. Secondly, we present the results of an experimental study on 10 benchmark classification and 10 benchmark regression data sets, comparing EM-ELMs and SV-SFNNs, that was carried out under the same conditions for the two models. Although both models have the same (efficient) computational cost, a statistically significant improvement in generalization performance of SV-SFNNs vs. EM-ELMs was found in 12 out of the 20 benchmark problems.
Thu, 16 Jun 2016 08:38:58 GMThttp://hdl.handle.net/2117/880762016-06-16T08:38:58ZRomero Merino, EnriqueAlquézar Mancho, RenéRecently, error minimized extreme learning machines (EM-ELMs) have been proposed as a simple and efficient approach to build single-hidden-layer feed-forward networks (SLFNs) sequentially. They add random hidden nodes one by one (or group by group) and update the output weights incrementally to minimize the sum-of-squares error in the training set. Other very similar methods that also construct SLFNs sequentially had been reported earlier with the main difference that their hidden-layer weights are a subset of the data instead of being random. By analogy with the concept of support vectors original of support vector machines (SVMs), these approaches can be referred to as support vector sequential feed-forward neural networks (SV-SFNNs), and they are a particular case of the Sequential Approximation with Optimal Coefficients and Interacting Frequencies (SAOCIF) method. In this paper, it is firstly shown that EM-ELMs can also be cast as a particular case of SAOCIF. In particular, EM-ELMs can easily be extended to test some number of random candidates at each step and select the best of them, as SAOCIF does. Moreover, it is demonstrated that the cost of the calculation of the optimal output-layer weights in the originally proposed EM-ELMs can be improved if it is replaced by the one included in SAOCIF. Secondly, we present the results of an experimental study on 10 benchmark classification and 10 benchmark regression data sets, comparing EM-ELMs and SV-SFNNs, that was carried out under the same conditions for the two models. Although both models have the same (efficient) computational cost, a statistically significant improvement in generalization performance of SV-SFNNs vs. EM-ELMs was found in 12 out of the 20 benchmark problems.The Virtual Magic Lantern: An interaction metaphor for enhanced medical data inspection
http://hdl.handle.net/2117/88074
The Virtual Magic Lantern: An interaction metaphor for enhanced medical data inspection
Monclús Lahoya, Eva; Díaz Iriberri, José; Navazo Álvaro, Isabel; Vázquez Alcocer, Pere Pau
In Volume Rendering, it is difficult to simultaneously visualize interior and exterior structures. Several approaches have been developed to solve this problem, such as cut-away or exploded views. Nevertheless, in most cases, those algorithms usually require either a preprocess of the data, or an accurate determination of the region of interest, previous to data inspection. In this paper we present the Virtual Magic Lantern (VML), an interaction tool tailored to facilitate volumetric data inspection. It behaves like a lantern whose virtual illumination cone provides the focal region which is visualized using a secondary transfer function or rendering style. This may be used for simple visual inspection, surgery planning, or injure diagnosis. The VML is a particularly friendly and intuitive interaction tool suitable for an immersive Virtual Reality setup with a large screen, where the user moves a Wanda device, like a lantern pointing to the model. We show that this inspection metaphor can be efficiently and easily adapted to a GPU ray casting volume visualization algorithm. We also present the Virtual Magic Window (VMW) metaphor as an efficient collateral implementation of the VML, that can be seen as a restricted case where the lantern illuminates following the viewing direction, through a virtual window created as the intersection of the virtual lantern (guided by the Wanda device) and the bounding box of the volume. This approach allows better frame rates because the shader requires almost no modification with respect to the classical volume ray casting. On the other hand, the contextual information is not perceived as well as with the previous method, especially on the boundary of the inspected region. Apart from its main use, our metaphor can also be used to aid in the tedious process of transfer function selection.
Thu, 16 Jun 2016 08:27:55 GMThttp://hdl.handle.net/2117/880742016-06-16T08:27:55ZMonclús Lahoya, EvaDíaz Iriberri, JoséNavazo Álvaro, IsabelVázquez Alcocer, Pere PauIn Volume Rendering, it is difficult to simultaneously visualize interior and exterior structures. Several approaches have been developed to solve this problem, such as cut-away or exploded views. Nevertheless, in most cases, those algorithms usually require either a preprocess of the data, or an accurate determination of the region of interest, previous to data inspection. In this paper we present the Virtual Magic Lantern (VML), an interaction tool tailored to facilitate volumetric data inspection. It behaves like a lantern whose virtual illumination cone provides the focal region which is visualized using a secondary transfer function or rendering style. This may be used for simple visual inspection, surgery planning, or injure diagnosis. The VML is a particularly friendly and intuitive interaction tool suitable for an immersive Virtual Reality setup with a large screen, where the user moves a Wanda device, like a lantern pointing to the model. We show that this inspection metaphor can be efficiently and easily adapted to a GPU ray casting volume visualization algorithm. We also present the Virtual Magic Window (VMW) metaphor as an efficient collateral implementation of the VML, that can be seen as a restricted case where the lantern illuminates following the viewing direction, through a virtual window created as the intersection of the virtual lantern (guided by the Wanda device) and the bounding box of the volume. This approach allows better frame rates because the shader requires almost no modification with respect to the classical volume ray casting. On the other hand, the contextual information is not perceived as well as with the previous method, especially on the boundary of the inspected region. Apart from its main use, our metaphor can also be used to aid in the tedious process of transfer function selection.A multi-client architecture for hybrid terrain rendering on mobile devices
http://hdl.handle.net/2117/88073
A multi-client architecture for hybrid terrain rendering on mobile devices
Noguera, José María; Segura Sánchez, Rafael Jesús; Ogáyar, Carlos; Joan Arinyo, Robert
Mobile devices such as Personal Digital Assistants (PDAs) or smart phones are rapidly increasing their graphics and networking capabilities. However, real-time rendering of large terrains is still a challenging task to accomplish in such limited devices. In this paper we describe the principles involved in the design and development of a scalable client-server architecture for hybrid rendering of terrains over wireless networks on mobile devices. We have developed a hybrid adaptive streaming and rendering method based on a server-client approach. The rendering workload is distributed between a server and the clients and the terrain is partitioned into the close-range geometry and the background. The close-range geometry is downloaded from the database and rendered on the mobile client, and the background is portrayed as a view-dependent panoramic impostor and rendered by the server on demand then it is sent on request to the server for display. The system architecture is organized in three levels: the main server, the panorama server and the mobile device client. This architecture provides support for efficient delivery of geometry and impostors to mobile clients according to their capabilities. As a proof of concept, we have implemented a prototype and carried out exhaustive experiments considering different network scenarios and different number of connected clients. The analysis of the server workload and response times shows that our architecture achieves a great scalability and performance even when using low-end mobile devices.
Thu, 16 Jun 2016 07:57:00 GMThttp://hdl.handle.net/2117/880732016-06-16T07:57:00ZNoguera, José MaríaSegura Sánchez, Rafael JesúsOgáyar, CarlosJoan Arinyo, RobertMobile devices such as Personal Digital Assistants (PDAs) or smart phones are rapidly increasing their graphics and networking capabilities. However, real-time rendering of large terrains is still a challenging task to accomplish in such limited devices. In this paper we describe the principles involved in the design and development of a scalable client-server architecture for hybrid rendering of terrains over wireless networks on mobile devices. We have developed a hybrid adaptive streaming and rendering method based on a server-client approach. The rendering workload is distributed between a server and the clients and the terrain is partitioned into the close-range geometry and the background. The close-range geometry is downloaded from the database and rendered on the mobile client, and the background is portrayed as a view-dependent panoramic impostor and rendered by the server on demand then it is sent on request to the server for display. The system architecture is organized in three levels: the main server, the panorama server and the mobile device client. This architecture provides support for efficient delivery of geometry and impostors to mobile clients according to their capabilities. As a proof of concept, we have implemented a prototype and carried out exhaustive experiments considering different network scenarios and different number of connected clients. The analysis of the server workload and response times shows that our architecture achieves a great scalability and performance even when using low-end mobile devices.Geometric constraint problems and solution instances
http://hdl.handle.net/2117/88071
Geometric constraint problems and solution instances
Hidalgo Garcia, Marta; Joan Arinyo, Robert; Soto Riera, Antoni
Geometric constraint solving is a growing field devoted to solve geometric problems defined by relationships, called constraints, established between the geometric elements. In this work we show that what characterizes a geometric constraint problem is the set of geometric elements on which the problem is defined. If the problem is wellconstrained, a given solution instance to the geometric constraint problem admits different representations defined by measuring geometric relationships in the solution instance.
Thu, 16 Jun 2016 07:34:15 GMThttp://hdl.handle.net/2117/880712016-06-16T07:34:15ZHidalgo Garcia, MartaJoan Arinyo, RobertSoto Riera, AntoniGeometric constraint solving is a growing field devoted to solve geometric problems defined by relationships, called constraints, established between the geometric elements. In this work we show that what characterizes a geometric constraint problem is the set of geometric elements on which the problem is defined. If the problem is wellconstrained, a given solution instance to the geometric constraint problem admits different representations defined by measuring geometric relationships in the solution instance.Skeleton computation of an image using a geometric approach
http://hdl.handle.net/2117/88018
Skeleton computation of an image using a geometric approach
Martínez Bayona, Jonàs; Vigo Anglada, Marc; Pla García, Núria; Ayala Vallespí, M. Dolors
In this work we develop two algorithms to compute the skeleton of a binary 2D images. Both algorithms follow a geometric approach and work directly with the boundary of the image wich is an orthogonal polygon (OP). One of these algorithms processes the edges of the polygon while the other uses its vertices. Compared to a thinning method, the presented algorithms show a good performance.
Wed, 15 Jun 2016 09:21:44 GMThttp://hdl.handle.net/2117/880182016-06-15T09:21:44ZMartínez Bayona, JonàsVigo Anglada, MarcPla García, NúriaAyala Vallespí, M. DolorsIn this work we develop two algorithms to compute the skeleton of a binary 2D images. Both algorithms follow a geometric approach and work directly with the boundary of the image wich is an orthogonal polygon (OP). One of these algorithms processes the edges of the polygon while the other uses its vertices. Compared to a thinning method, the presented algorithms show a good performance.