2,690 research outputs found
Complete Types in an Extension of the System AF2
International audienceIn this paper, we extend the system AF2 in order to have the subject reduction for the -reduction. We prove that the types with positive quantifiers are complete for models that are stable by weak-head expansion
Mendler-style Iso-(Co)inductive predicates: a strongly normalizing approach
We present an extension of the second-order logic AF2 with iso-style
inductive and coinductive definitions specifically designed to extract programs
from proofs a la Krivine-Parigot by means of primitive (co)recursion
principles. Our logic includes primitive constructors of least and greatest
fixed points of predicate transformers, but contrary to the common approach, we
do not restrict ourselves to positive operators to ensure monotonicity, instead
we use the Mendler-style, motivated here by the concept of monotonization of an
arbitrary operator on a complete lattice. We prove an adequacy theorem with
respect to a realizability semantics based on saturated sets and
saturated-valued functions and as a consequence we obtain the strong
normalization property for the proof-term reduction, an important feature which
is absent in previous related work.Comment: In Proceedings LSFA 2011, arXiv:1203.542
Stratified Labelings for Abstract Argumentation
We introduce stratified labelings as a novel semantical approach to abstract
argumentation frameworks. Compared to standard labelings, stratified labelings
provide a more fine-grained assessment of the controversiality of arguments
using ranks instead of the usual labels in, out, and undecided. We relate the
framework of stratified labelings to conditional logic and, in particular, to
the System Z ranking functions
Low strain, long life creep fatigue of AF2-1DA and INCO 718
Two aircraft turbine disk alloys, GATORIZED AF2-DA and INCO 718 were evaluated for their low strain long life creep-fatigue behavior. Static (tensile and creep rupture) and cyclic properties of both alloys were characterized. The cntrolled strain LCF tests were conducted at 760 C (1400 F) and 649 C (1200 F) for AF2-1DA and INCO 718, respectively. Hold times were varied for tensile, compressive and tensile/compressive strain dwell (relaxation) tests. Stress (creep) hold behavior of AF2-1DA was also evaluated. Generally, INCO 718 exhibited more pronounced reduction in cyclic life due to hold than AF2-1DA. The percent reduction in life for both alloys for strain dwell tests was greater at low strain ranges (longer life regime). Changing hold time from 0 to 0.5, 2.0 and 15.0 min. resulted in corresponding reductions in life. The continuous cycle and cyclic/dwell initiation failure mechanism was predominantly transgranular for AF2-1DA and intergranular for INCO 718
Ultra low-mass star and substellar formation in sigma Orionis
The nearby young sigma Orionis cluster (~360 pc, ~3 Ma) is becoming one of
the most important regions for the study of ultra low-mass star formation and
its extension down to the mass regimes of the brown dwarfs and planetary-mass
objects. Here, I introduce the sigma Orionis cluster and present three studies
that the JOVIAN group is developing: a pilot programme of near-infrared
adaptive-optics imaging, intermediate-resolution optical spectroscopy of a
large sample of stars of the cluster and a study of the mass function down to
the planetary-mass domain. This paper is a summary of the content of four
posters that I presented in the Ultra low-mass star formation and evolution
Workshop, as single author or on behalf of different collaborations.Comment: 4 pages, 4 figures. Proceeding at the IAC-TNG Workshop on Ultra
low-mass star formation and evolution, 28 June - 1 July 2005, La Palma,
Canary Islands, Spain. Accepted for publication in Astron. Nach
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