6,560 research outputs found
Aboutness in Imagination
I present a formal theory of the logic and aboutness of imagination. Aboutness is understood as the relation between meaningful items and what they concern, as per Yablo and Fineâs works on the notion. Imagination is understood as per Chalmersâ positive conceivability: the intentional state of a subject who conceives that p by imagining a situationâa configuration of objects and propertiesâverifying p. So far aboutness theory has been developed mainly for linguistic representation, but it is natural to extend it to intentional states. The proposed framework combines a modal semantics with a mereology of contents: imagination operators are understood as variably strict quantifiers over worlds with a content-preservation constraint
On Conceiving the Inconsistent
This work has been developed within the 2013â15 ahrc project The Metaphysical Basis of Logic: The Law of Non-Contradiction as Basic Knowledge (grant ref. ah/k001698/1). A version of the paper was presented in September 2013 at the Modal Metaphysics Workshop in Bratislava. I am grateful to the audiences there and at the Aristotelian Society meeting for many helpful comments and remarks.Peer reviewedPostprin
Knowability Relative to Information
We present a formal semantics for epistemic logic, capturing the notion of knowability relative to information (KRI). Like Dretske, we move from the platitude that what an agent can know depends on her (empirical) information. We treat operators of the form K_AB (âB is knowable on the basis of information Aâ) as variably strict quantifiers over worlds with a topic- or aboutness- preservation constraint. Variable strictness models the non-monotonicity of knowledge acquisition while allowing knowledge to be intrinsically stable. Aboutness-preservation models the topic-sensitivity of information, allowing us to invalidate controversial forms of epistemic closure while validating less controversial ones. Thus, unlike the standard modal framework for epistemic logic, KRI accommodates plausible approaches to the Kripke-Harman dogmatism paradox, which bear on non-monotonicity, or on topic-sensitivity. KRI also strikes a better balance between agent idealization and a non-trivial logic of knowledge ascriptions
Late Superhumps in WZ Sge-Type Dwarf Novae
We report on the detection of very stable modulations with periods
unexpectedly (~0.5%) longer than superhump periods during the slowly fading
stage of WZ Sge-type superoutbursts in three systems, GW Lib, V455 And and WZ
Sge. These periods are naturally explained by assuming that these modulations
are superhumps arising from matter near the tidal truncation radius. This
finding provides an additional support to the hypothetical idea of expansion of
the accretion disk well beyond the 3:1 orbital resonance in some low mass-ratio
systems. Combined with the effect of 2:1 resonance, we present an explanation
of the origin of positive period derivatives in certain short-period SU
UMa-type dwarf novae.Comment: Accepted by PASJ (Letters), 4 pages, 3 figure
Variability of the symbiotic X-ray binary GX 1+4: Enhanced activity near periastron passage
Context. GX 1+4 belongs to a rare class of X-ray binaries with red giant
donors, symbiotic X-ray binaries. The system has a history of complicated
variability on multiple timescales in the optical light and X-rays. The nature
of this variability remains poorly understood. Aims. We study variability of GX
1+4 on long time-scale in X-ray and optical bands. Methods. The presented X-ray
observations are from INTEGRAL Soft Gamma-Ray Imager and RXTE All Sky Monitor.
The optical observations are from INTEGRAL Optical Monitoring Camera. Results.
The variability of GX 1+4 both in optical light and hard X-ray emission (>17
keV) is dominated by ~50-70d quasi-periodic changes. The amplitude of this
variability is highest during the periastron passage, while during the
potential neutron star eclipse the system is always at minimum, which confirms
the 1161d orbital period that has had been proposed for the system based on
radial velocity curve. Neither the quasi-periodic variability or the orbital
period are detected in soft X-ray emission (1.3-12.2 keV), where the binary
shows no apparent periodicity.Comment: 8 pages, 7 figures, accepted for publication in A&
Effect of in-mould inoculant composition on microstructure and fatigue behaviour of heavy section ductile iron castings
In this paper, the influence of the in-mould inoculant composition on microstructure and fatigue behaviour of heavy section ductile iron (EN GJS 700-2) castings has been investigated.
Axial fatigue tests under nominal load ratio R=0 have been performed on specimens taken from the core of large casting components. Metallographic analyses have been carried out by means of optical microscopy and important microstructural parameters that affect the mechanical properties of the alloy, such as nodule count, nodularity and graphite shape, were measured. Furthermore, Scanning Electron Microscopy was used to investigate the fracture surfaces of the samples in order to identify crack initiation and propagation zones.
Cracks initiation sites have been found to be microshrinkages close to specimens\u2019 surface in most cases. It was found that in-mould inoculant composition strongly influences the alloy microstructure, such as nodule count and shrinkage porosities size, as well as the fatigue resistance of heavy section ductile iron castings
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