4,903 research outputs found
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 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 supported on one irreducible component. We also
prove that the connected component of the moduli space that contains vector
bundles of rank is isomorphic to the -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
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