7,407 research outputs found
Reasons to Care about Reasons for Action: A Response to Paul S. Davies
In eschewing the specialty-standards of neuro-babble and philosophical neologism, Paul S. Davies (2016) argues with courageous clarity. He connects issues in neuroscience and epistemology to problems surrounding agency. I agree with many of his claims, but I think they need more context and precision for application. This is because his argument as it stands now affects only a limited set of theories, and a hidden modality in thesis 3 tempers his argument further. And perhaps most urgently, if his theory fails to address “top-down”1 mental processes or social dimensions of knowledge, his argument fails to meet even his own goals set out in the paper
Segregation in a fluidized binary granular mixture: Competition between buoyancy and geometric forces
Starting from the hydrodynamic equations of binary granular mixtures, we
derive an evolution equation for the relative velocity of the intruders, which
is shown to be coupled to the inertia of the smaller particles. The onset of
Brazil-nut segregation is explained as a competition between the buoyancy and
geometric forces: the Archimedean buoyancy force, a buoyancy force due to the
difference between the energies of two granular species, and two geometric
forces, one compressive and the other-one tensile in nature, due to the
size-difference. We show that inelastic dissipation strongly affects the phase
diagram of the Brazil nut phenomenon and our model is able to explain the
experimental results of Breu et al. (PRL, 2003, vol. 90, p. 01402).Comment: 5 pages, 2 figure
Supporting process reuse in PROMENADE
Process reuse (the ability to construct new processes by assembling already built ones) and process harvesting (the ability to build generic processes
that may be further reused, from existing ones) are two crucial issues in
process technology. Both activities involve defining a set of mechanisms,
like abstraction, adaptation, composition, etc. which are appropriate to
achieve their goals. In this report, we define a general framework to
process reuse and harvesting that proposes a complete set of mechanisms to
deal with both activities. This general framework is particularized to the
context of a process modelling language to model software processes, called
PROMENADE. A definition of the identified reuse and harvesting mecha-nisms
is proposed in the context of PROMENADE. Finally, two process reuse case
studies which composes various reuse mechanisms are presented.Postprint (published version
Are collisions with neutral hydrogen important for modelling the Second Solar Spectrum of Ti I and Ca II ?
The physical interpretation of scattering line polarization offers a novel
diagnostic window for exploring the thermal and magnetic structure of the quiet
regions of the solar atmosphere. Here we evaluate the impact of isotropic
collisions with neutral hydrogen atoms on the scattering polarization signals
of the 13 lines of multiplet 42 of Ti I and on those of the K line and of the
IR triplet of Ca II, with emphasis on the collisional transfer rates between
nearby J-levels. To this end, we calculate the linear polarization produced by
scattering processes considering realistic multilevel models and solving the
statistical equilibrium equations for the multipolar components of the atomic
density matrix. We confirm that the lower levels of the 13 lines of multiplet
42 of Ti I are completely depolarized by elastic collisions. We find that
upper-level collisional depolarization turns out to have an unnoticeable impact
on the emergent linear polarization amplitudes, except for the {\lambda 4536
line for which it is possible to notice a rather small depolarization caused by
the collisional transfer rates. Concerning the Ca II lines, we show that the
collisional rates play no role on the polarization of the upper level of the K
line, while they have a rather small depolarizing effect on the atomic
polarization of the metastable lower levels of the Ca II IR triplet.Comment: Accepted for publication in Astronomy and Astrophysic
Detection of polarization from the E^4\Pi-A^4\Pi system of FeH in sunspot spectra
Here we report the first detection of polarization signals induced by the
Zeeman effect in spectral lines of the E^4\Pi-A^4\Pi system of FeH located
around 1.6 m. Motivated by the tentative detection of this band in the
intensity spectrum of late-type dwarfs, we have investigated the full Stokes
sunspot spectrum finding circular and linear polarization signatures that we
associate with the FeH lines of the E^4\Pi-A^4\Pi band system. We investigate
the Zeeman effect in these molecular transitions pointing out that in Hund's
case (a) coupling the effective Land\'e factors are never negative. For this
reason, the fact that our spectropolarimetric observations indicate that the
Land\'e factors of pairs of FeH lines have opposite signs, prompt us to
conclude that the E^4\Pi-A^4\Pi system must be in intermediate angular momentum
coupling between Hund's cases (a) and (b). We emphasize that theoretical and/or
laboratory investigations of this molecular system are urgently needed for
exploiting its promising diagnostic capabilities.Comment: 11 pages, 4 figures, accepted for publication in Astrophysical
Journal Letter
In-flight load testing of advanced shuttle thermal protection systems
NASA Ames Research Center has conducted in-flight airload testing of some advanced thermal protection systems (TPS) at the Dryden Flight Research Center. The two flexible TPS materials tested, felt reusable surface insulation (FRSI) and advanced flexible reusable surface insulation (AFRSI), are currently certified for use on the Shuttle orbiter. The objectives of the flight tests were to evaluate the performance of FRSI and AFRSI at simulated launch airloads and to provide a data base for future advanced TPS flight tests. Five TPS configurations were evaluated in a flow field which was representative of relatively flat areas without secondary flows. The TPS materials were placed on a fin, the Flight Test fixture (FTF), that is attached to the underside of the fuselage of an F-104 aircraft. This paper describes the test approach and techniques used and presents the results of the advanced TPS flight test. There were no failures noted during post-flight inspections of the TPS materials which were exposed to airloads 40 percent higher than the design launch airloads
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