253 research outputs found
Ressenyes
Obra ressenyada: José ORTEGA VALCÁRCEL, Los horizontes de la geografía. Teoría de la geografía. Barcelona: Ariel, 2000
Incision and width changes caused by dam removal. Experiments and data analysis
River morphodynamics and sediment transportRiver morphology and morphodynamic
Segmentation in 2D and 3D image using Tissue-Like P System
Membrane Computing is a biologically inspired computational model. Its devices are called P systems and they perform computations by applying a finite set of rules in a synchronous, maximally parallel way. In this paper, we open a new research line: P systems are used in Computational Topology within the context of the Digital Image. We choose for this a variant of P systems, called tissue-like P systems, to obtain in a general maximally parallel manner the segmentation of 2D and 3D images in a constant number of steps. Finally, we use a software called Tissue Simulator to check these systems with some examples
Serializing the Parallelism in Parallel Communicating Pushdown Automata Systems
We consider parallel communicating pushdown automata systems (PCPA) and
define a property called known communication for it. We use this property to
prove that the power of a variant of PCPA, called returning centralized
parallel communicating pushdown automata (RCPCPA), is equivalent to that of
multi-head pushdown automata. The above result presents a new sub-class of
returning parallel communicating pushdown automata systems (RPCPA) called
simple-RPCPA and we show that it can be written as a finite intersection of
multi-head pushdown automata systems
Limits of the power of Tissue P systems with cell division
Tissue P systems generalize the membrane structure tree usual in original models of P systems to an arbitrary graph. Basic opera- tions in these systems are communication rules, enriched in some variants with cell division or cell separation. Several variants of tissue P systems were recently studied, together with the concept of uniform families of these systems. Their computational power was shown to range between P and NP ? co-NP , thus characterizing some interesting borderlines between tractability and intractability. In this paper we show that com- putational power of these uniform families in polynomial time is limited by the class PSPACE . This class characterizes the power of many clas- sical parallel computing model
PNEPs, NEPs for context free parsing: Application to natural language processing
The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-642-02478-8_59Proceedings of 10th International Work-Conference on Artificial Neural Networks, IWANN 2009, Salamanca, Spain.This work tests the suitability of NEPs to parse languages. We propose PNEP, a simple extension to NEP, and a procedure to translate a grammar into a PNEP that recognizes the same language. These parsers based on NEPs do not impose any additional constrain
to the structure of the grammar, which can contain all kinds of recursive, lambda or ambiguous rules. This flexibility makes this procedure specially suited for Natural Languge Processing (NLP). In a first proof with a simplified English grammar, we got a performance (a linear time complexity) similar to that of the most popular syntactic parsers in the NLP area (Early and its derivatives). All the possible derivations for ambiguous grammars were generatedThis work was partially supported by MEC, project TIN2008-02081/TIN and by DGUI CAM/UAM, project CCG08-UAM/TIC-4425
A linear-time tissue P system based solution for the 3-coloring problem
In the literature, several examples of the efficiency of cell-like P systems regarding the solution of NPcomplete
problems in polynomial time can be found (obviously, trading space for time). Recently, different
new models of tissue-like P systems have received important attention from the scientific community. In
this paper we present a linear-time solution to an NP-complete problem from graph theory, the 3–coloring
problem, and we discuss the suitability of tissue-like P systems as a framework to address the efficient
solution to intractable problems.Ministerio de Educación y Ciencia TIN2005-09345-C04-01Junta de Andalucía TIC-58
Qualitative modelling and analysis of regulations in multi-cellular systems using Petri nets and topological collections
In this paper, we aim at modelling and analyzing the regulation processes in
multi-cellular biological systems, in particular tissues.
The modelling framework is based on interconnected logical regulatory
networks a la Rene Thomas equipped with information about their spatial
relationships. The semantics of such models is expressed through colored Petri
nets to implement regulation rules, combined with topological collections to
implement the spatial information.
Some constraints are put on the the representation of spatial information in
order to preserve the possibility of an enumerative and exhaustive state space
exploration.
This paper presents the modelling framework, its semantics, as well as a
prototype implementation that allowed preliminary experimentation on some
applications.Comment: In Proceedings MeCBIC 2010, arXiv:1011.005
Modelling of Multi-Agent Systems: Experiences with Membrane Computing and Future Challenges
Formal modelling of Multi-Agent Systems (MAS) is a challenging task due to
high complexity, interaction, parallelism and continuous change of roles and
organisation between agents. In this paper we record our research experience on
formal modelling of MAS. We review our research throughout the last decade, by
describing the problems we have encountered and the decisions we have made
towards resolving them and providing solutions. Much of this work involved
membrane computing and classes of P Systems, such as Tissue and Population P
Systems, targeted to the modelling of MAS whose dynamic structure is a
prominent characteristic. More particularly, social insects (such as colonies
of ants, bees, etc.), biology inspired swarms and systems with emergent
behaviour are indicative examples for which we developed formal MAS models.
Here, we aim to review our work and disseminate our findings to fellow
researchers who might face similar challenges and, furthermore, to discuss
important issues for advancing research on the application of membrane
computing in MAS modelling.Comment: In Proceedings AMCA-POP 2010, arXiv:1008.314
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Am 8. November wird in den USA nicht nur ein neuer Präsident, sondern auch ein neuer Kongress gewählt. Eine erneute Blockadehaltung könnte das Land zum Stillstand bringen und den sozialen Frieden gefährden
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