1,270 research outputs found
Modelling a real rockslide as a static-dynamic transition using a material instability criterion
747-757Failures at geological discontinuities often play a dominant role in the prediction of rockslides. In this study, a second order work criterion was used to analyze this type of problem by its constitutive instabilities, as it can expound all physical instabilities by divergence, except flutter instabilities. Derived from vanishing of the second order work, a matrix analysis focusing on the instability of geological discontinuities in two dimensions was performed. A real rockslide was simulated in a 2-D framework, and the second order work criterion was used to predict the occurrence of the rockslide. The numerical results were compared to monitoring data. Rockslides could be considered as processes involving a transition from a static loading to a dynamic response including a sudden burst of kinetic energy. Furthermore, a relationship existed between the second order work and second order kinetic energy. Hence, kinetic energy estimation was performed using two numerical approaches derived from this relationship and compared
A_4 flavour symmetry breaking scheme for understanding quark and neutrino mixing angles
We propose a spontaneous A_4 flavour symmetry breaking scheme to understand
the observed pattern of quark and neutrino mixing. The fermion mass eigenvalues
are arbitrary, but the mixing angles are constrained in such a way that the
overall patterns are explained while also leaving sufficient freedom to fit the
detailed features of the observed values, including CP violating phases. The
scheme realises the proposal of Low and Volkas to generate zero quark mixing
and tribimaximal neutrino mixing at tree-level, with deviations from both
arising from small corrections after spontaneous A_4 breaking. In the neutrino
sector, the breaking is A_4 --> Z_2, while in the quark and charged-lepton
sectors it is A_4 --> Z_3 = C_3. The full theory has A_4 completely broken, but
the two different unbroken subgroups in the two sectors force the dominant
mixing patterns to be as stated above. Radiative effects within each sector are
shown to deviate neutrino mixing from tribimaximal, while maintaining zero
quark mixing. Interactions between the two sectors -- "cross-talk" -- induce
nonzero quark mixing, and additional deviation from tribimaximal neutrino
mixing. We discuss the vacuum alignment challenge the scenario faces, and
suggest three generic ways to approach the problem. We follow up one of those
ways by sketching how an explicit model realising the symmetry breaking
structure may be constructed.Comment: 14 pages, no figures; v3: Section 5 rewritten to correct an error;
new section added to the appendix; added references; v4: minor change to
appendix C, version to be published by JHE
Matone's relation of N=2 super Yang-Mills and spectrum of Toda chain
In N=2 super Yang-Mills theory, the Matone's relation relates instanton
corrections of the prepotential to instanton corrections of scalar field
condensation . This relation has been proved to hold for Omega
deformed theories too, using localization method. In this paper, we first give
a case study supporting the relation, which does not rely on the localization
technique. Especially, we show that the magnetic expansion also satisfies a
relation of Matone's type. Then we discuss implication of the relation for the
spectrum of periodic Toda chain, in the context of recently proposed
Nekrasov-Shatashvili scheme.Comment: 17 pages; v2 minor changes, references added; v3 more material added
in 2nd section, clarification in 4th sectio
Gamesourcing Expert Painting Annotations
Online collections provided by museums are increasingly opened for contributions from users outside the museum. These initiatives are mostly targeted at obtaining tags describing aspects of artworks that are common knowledge. This does not require the contributors to have specific skills or knowledge. Museums, however, are also interested in obtaining very specific information about the subject matter of their artworks. We present a game that can help to collect expert knowledge by enabling non-expert users to perform an expert annotation task. This is achieved by simplifying the expert task and providing a sufficient level of annotation support to the users. In a user study we could prove the usefulness of our approach
Measuring the Effectiveness of Gamesourcing Expert Oil Painting Annotations
Tasks that require users to have expert knowledge are diffi- cult to crowdsource. They are mostly too complex to be carried out by non-experts and the available expert
Hydrodynamics of thermal granular convection
A hydrodynamic theory is formulated for buoyancy-driven ("thermal") granular
convection, recently predicted in molecular dynamic simulations and observed in
experiment. The limit of a dilute flow is considered. The problem is fully
described by three scaled parameters. The convection occurs via a supercritical
bifurcation, the inelasticity of the collisions being the control parameter.
The theory is expected to be valid for small Knudsen numbers and nearly elastic
grain collisions.Comment: 4 pages, 4 EPS figures, some details adde
Craterostigma plantagineum cell wall composition is remodelled during desiccation and the glycineârich protein CpGRP1 interacts with pectins through clustered arginines
Craterostigma plantagineum belongs to the desiccationâtolerant angiosperm plants. Upon dehydration, leaves fold and the cells shrink which is reversed during rehydration. To understand this process changes in cell wall pectin composition, and the role of the apoplastic glycineârich protein 1 (CpGRP1) were analysed. Cellular microstructural changes in hydrated, desiccated and rehydrated leaf sections were analysed using scanning electron microscopy. Pectin composition in different cell wall fractions was analysed with monoclonal antibodies against homogalacturonan, rhamnogalacturonan I, rhamnogalacturonan II and hemicellulose epitopes. Our data demonstrate changes in pectin composition during dehydration/rehydration which is suggested to affect cell wall properties. Homogalacturonan was less methylesterified upon desiccation and changes were also demonstrated in the detection of rhamnogalacturonan I, rhamnogalacturonan II and hemicelluloses. CpGRP1 seems to have a central role in cell adaptations to water deficit, as it interacts with pectin through a cluster of arginine residues and deâmethylesterified pectin presents more binding sites for the proteinâpectin interaction than to pectin from hydrated leaves. CpGRP1 can also bind phosphatidic acid (PA) and cardiolipin. The binding of CpGRP1 to pectin appears to be dependent on the pectin methylesterification status and it has a higher affinity to pectin than its binding partner CpWAK1. It is hypothesised that changes in pectin composition are sensed by the CpGRP1âCpWAK1 complex therefore leading to the activation of dehydrationârelated responses and leaf folding. PA might participate in the modulation of CpGRP1 activity
Onset of thermal convection in a horizontal layer of granular gas
The Navier-Stokes granular hydrodynamics is employed for determining the
threshold of thermal convection in an infinite horizontal layer of granular
gas. The dependence of the convection threshold, in terms of the inelasticity
of particle collisions, on the Froude and Knudsen numbers is found. A simple
necessary condition for convection is formulated in terms of the
Schwarzschild's criterion, well-known in thermal convection of (compressible)
classical fluids. The morphology of convection cells at the onset is
determined. At large Froude numbers, the Froude number drops out of the
problem. As the Froude number goes to zero, the convection instability turns
into a recently discovered phase separation instability.Comment: 6 pages, 6 figures. An extended version. A simple and universal
necessary criterion for convection presente
Web Site Metadata
The currently established formats for how a Web site can publish metadata about a site's pages, the robots.txt file and sitemaps, focus on how to provide information to crawlers about where to not go and where to go on a site. This is sufficient as input for crawlers, but does not allow Web sites to publish richer metadata about their site's structure, such as the navigational structure. This paper looks at the availability of Web site metadata on today's Web in terms of available information resources and quantitative aspects of their contents. Such an analysis of the available Web site metadata not only makes it easier to understand what data is available today; it also serves as the foundation for investigating what kind of information retrieval processes could be driven by that data, and what additional data could be provided by Web sites if they had richer data formats to publish metadata
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