7,307 research outputs found

    Reasons to Care about Reasons for Action: A Response to Paul S. Davies

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    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

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    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

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    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 ?

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    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

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    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 ÎĽ\mum. 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

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    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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