Experiments conducted on combustion at microgravity in the TEXUS-38 sounding rocket

A series of experiments linked together on combustion at microgravity have been conducted in a TEXUS-38 sounding rocket. The experiments were performed with three cylindrical hollow rods of polymethylmethacrylate. Test were carried out in O2-N2 mixtures at rest and at flow velocities ranging from 10 to 30 mm/s. O2-N2 mixture composition changed from 40% oxygen down to pure nitrogen. The sequence of experiments consisted of: 1º.- Measurement of flame temperatures in the non-visible optical range. 2º.- Determination of O2 concentrations at flame extinction at constant flow velocity, obtained by continuously reducing the O2 concentration in the test section. 3º.- Measurement of flame spreading velocities. 4º.- Some information on the influence on flammability of the ignition location and time, and fuel thickness. Main conclusions are: 1º.- Flames in the infrared, non-visible optical range have a substantially lower temperature. 2º.- O2 concentration at flame extinction depends considerably on flow velocity, especially at low velocity levels. Final conclusion is that the flow velocity field of maximum interest is the one in which flow velocities are of the same order of magnitude as typical diffusion velocities. A follow-on program in this subject will be conducted in the US Combustion Module of the International Space Station

GAMES: A new Scenario for Software and Knowledge Reuse

Games are a well-known test bed for testing search algorithms and learning methods, and many authors have presented numerous reasons for the research in this area. Nevertheless, they have not received the attention they deserve as software projects. In this paper, we analyze the applicability of software and knowledge reuse in the games domain. In spite of the need to find a good evaluation function, search algorithms and interface design can be said to be the primary concerns. In addition, we will discuss the current state of the main statistical learning methods and how they can be addressed from a software engineering point of view. So, this paper proposes a reliable environment and adequate tools, necessary in order to achieve high levels of reuse in the games domain

Moduli Spaces of Semistable Sheaves on Singular Genus One Curves

We find some equivalences of the derived category of coherent sheaves on a Gorenstein genus one curve that preserve the (semi)-stability of pure dimensional sheaves. Using them we establish new identifications between certain Simpson moduli spaces of semistable sheaves on the curve. For rank zero, the moduli spaces are symmetric powers of the curve whilst for a fixed positive rank there are only a finite number of non-isomorphic spaces. We prove similar results for the relative semistable moduli spaces on an arbitrary genus one fibration with no conditions either on the base or on the total space. For a cycle $E_N$ of projective lines, we show that the unique degree 0 stable sheaves are the line bundles having degree 0 on every irreducible component and the sheaves $\mathcal{O}(-1)$ supported on one irreducible component. We also prove that the connected component of the moduli space that contains vector bundles of rank $r$ is isomorphic to the $r$-th symmetric product of the rational curve with one node.Comment: 26 pages, 4 figures. Added the structure of the biggest component of the moduli space of sheaves of degree 0 on a cycle of projective lines. Final version; to appear en IMRS (International Mathematics Research Notices 2009

Extension-based argumentation semantics via logic programming semantics with negation as failure

Extension-based argumentation semantics have been shown to be a suitable approach for performing practical reasoning. Since extension-based argumentation semantics were formalized in terms of relationships between atomic arguments, it has been shown that extension-based argumentation semantics (such as the grounded semantics and stable semantics) can be characterized by logic programming semantics with negation as failure. Recently, it has been shown that argumentation semantics such as the preferred semantics and the CF2 semantics can be characterized in terms of logic programming semantics. In this paper, we make a short overview w.r.t. recent results in the close relationship between extension-based semantics and logic programming semantics with negation as failure. We also show that there is enough evidence to believe that the use of declarative approaches based on logic programming semantics with negation as failure is a practical approach for performing practical reasoning following an argumentation reasoning approach.Peer ReviewedPostprint (published version

Distributed formation control of multiple unmanned aerial vehicles over time-varying graphs using population games

© 2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper presents a control technique based on distributed population dynamics under time-varying communication graphs for a multi-agent system structured in a leader-follower fashion. Here, the leader agent follows a particular trajectory and the follower agents should track it in a certain organized formation manner. The tracking of the leader can be performed in the position coordinates x; y; and z, and in the yaw angle phi. Additional features are performed with this method: each agent has only partial knowledge of the position of other agents and not necessarily all agents should communicate to the leader. Moreover, it is possible to integrate a new agent into the formation (or for an agent to leave the formation task) in a dynamical manner. In addition, the formation configuration can be changed along the time, and the distributed population-games-based controller achieves the new organization goal accommodating conveniently the information-sharing graph in function of the communication range capabilities of each UAV. Finally, several simulations are presented to illustrate different scenarios, e.g., formation with time-varying communication network, and time-varying formationPeer ReviewedPostprint (author's final draft

Las paradojas de Javier Muguerza

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