420 research outputs found
Coronal Mass Ejection Detection using Wavelets, Curvelets and Ridgelets: Applications for Space Weather Monitoring
Coronal mass ejections (CMEs) are large-scale eruptions of plasma and
magnetic feld that can produce adverse space weather at Earth and other
locations in the Heliosphere. Due to the intrinsic multiscale nature of
features in coronagraph images, wavelet and multiscale image processing
techniques are well suited to enhancing the visibility of CMEs and supressing
noise. However, wavelets are better suited to identifying point-like features,
such as noise or background stars, than to enhancing the visibility of the
curved form of a typical CME front. Higher order multiscale techniques, such as
ridgelets and curvelets, were therefore explored to characterise the morphology
(width, curvature) and kinematics (position, velocity, acceleration) of CMEs.
Curvelets in particular were found to be well suited to characterising CME
properties in a self-consistent manner. Curvelets are thus likely to be of
benefit to autonomous monitoring of CME properties for space weather
applications.Comment: Accepted for publication in Advances in Space Research (3 April 2010
ATP-Stimulated ATP release and metabolic acid production:-regulating life and death decisions in articular chondrocytes
Signature inversion in axially deformed Tm
The microscopic analysis of experimental data in Tm is presented
within the two-quasiparticle-phonon model. The model includes the interaction
between odd quasiparticles and their coupling with core vibrations. The
coupling explains naturally the attenuation of the Coriolis interaction in
rotating odd-odd nuclei. It is shown that the competition between the Coriolis
and neutron-proton interactions is responsible for the signature inversion
phenomenon.Comment: 10 pages, 1 figure, corrected some typo
Shear testing and failure modelling of calcium phosphate coated AZ31 magnesium alloys for orthopaedic applications
Non-leftmost Unfolding in Partial Evaluation of Logic Programs with Impure Predicates
Abstract. Partial evaluation of logic programs which contain impure predicates poses non-trivial challenges. Impure predicates include those which produce side-effects, raise errors (or exceptions), and those whose truth value varies according to the degree of instantiation of arguments 4. In particular, non-leftmost unfolding steps can produce incorrect results since the independence of the computation rule no longer holds in the presence of impure predicates. Existing proposals allow non-leftmost unfolding steps, but at the cost of accuracy: bindings and failure are not propagated backwards to predicates which are potentially impure. In this work we propose a partial evaluation scheme which substantially reduces the situations in which such backpropagation has to be avoided. With this aim, our partial evaluator takes into account the information about purity of predicates expressed in terms of assertions. This allows achieving some optimizations which are not feasible using existing partial evaluation techniques. We argue that our proposal goes beyond existing ones in that it is a) accurate, since the classification of pure vs impure is done at the level of atoms instead of predicates, b) extensible, as the information about purity can be added to programs using assertions without having to modify the partial evaluator itself, and c) automatic, since (backwards) analysis can be used to automatically infer the required assertions. Our approach has been implemented in the context of CiaoPP, the abstract interpretation-based preprocessor of the Ciao logic programming system.
Automated Coronal Hole Detection using Local Intensity Thresholding Techniques
We identify coronal holes using a histogram-based intensity thresholding
technique and compare their properties to fast solar wind streams at three
different points in the heliosphere. The thresholding technique was tested on
EUV and X-ray images obtained using instruments onboard STEREO, SOHO and
Hinode. The full-disk images were transformed into Lambert equal-area
projection maps and partitioned into a series of overlapping sub-images from
which local histograms were extracted. The histograms were used to determine
the threshold for the low intensity regions, which were then classified as
coronal holes or filaments using magnetograms from the SOHO/MDI. For all three
instruments, the local thresholding algorithm was found to successfully
determine coronal hole boundaries in a consistent manner. Coronal hole
properties extracted using the segmentation algorithm were then compared with
in situ measurements of the solar wind at 1 AU from ACE and STEREO. Our results
indicate that flux tubes rooted in coronal holes expand super-radially within 1
AU and that larger (smaller) coronal holes result in longer (shorter) duration
high-speed solar wind streams
Structure and play: rethinking regulation in the higher education sector
This paper explores possible tactics for academics working within a context of increasing regulation and constraint. One suggested tactic is to move outside of a creativity-conformity binary. Rather than understanding creativity and conformity as separable, where one is seen as excluding the other, the authors consider the potential of examining the relationships between them. The theme of 'structure and play' illustrates the argument. In the first part of the paper, using various examples from art and design - fields generally associated with creativity - the authors explore the interrelatedness of creativity and conformity. For example, how might design styles, which are generally understood as creative outcomes, constrain creativity and lead to conformity within the design field? Is fashion producing creativity or conformity? Conversely, the ways in which conformity provides the conditions for creativity are also examined. For example, the conformity imposed by the state on artists in the former communist bloc contributed to a thriving underground arts movement which challenged conformity and state regulation. Continuing the theme of 'structure and play', the authors recount a story from an Australian university which foregrounds the ongoing renegotiation of power relations in the academy. This account illustrates how programmatic government in a university, with its aim of regulating conduct, can contribute to unanticipated outcomes. The authors propose that a Foucauldian view of distributed power is useful for academics operating in a context of increasing regulation, as it brings into view sites where power might begin to be renegotiated
Inference of Well-Typings for Logic Programs with Application to Termination Analysis
This paper develops a method to infer a polymorphic well-typing for a logic program. One of the main motivations is to contribute to a better automation of termination analysis in logic programs, by deriving types from which norms can automatically be constructed. Previous work on type-based termination analysis used either types declared by the user, or automatically generated monomorphic types describing the success set of predicates. Declared types are typically more precise and result in stronger termination conditions than those obtained with inferred types. Our type inference procedure involves solving set constraints generated from the program and derives a well-typing in contrast to a success-set approximation. Experiments show that our automatically inferred well-typings are close to the declared types and thus result in termination conditions that are as good as those obtained with declared types for all our experiments to date. We describe the method, its implementation and experiments with termination analysis based on the inferred types
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