150 research outputs found
Hit with the Truth
This paper applies the hegelian dialectic to Flannery O’Conner’s short story, “Revelation,” revealing themes of self-recognition and truth
Evolving generalist controllers to handle a wide range of morphological variations
Neuro-evolutionary methods have proven effective in addressing a wide range
of tasks. However, the study of the robustness and generalisability of evolved
artificial neural networks (ANNs) has remained limited. This has immense
implications in the fields like robotics where such controllers are used in
control tasks. Unexpected morphological or environmental changes during
operation can risk failure if the ANN controllers are unable to handle these
changes. This paper proposes an algorithm that aims to enhance the robustness
and generalisability of the controllers. This is achieved by introducing
morphological variations during the evolutionary process. As a results, it is
possible to discover generalist controllers that can handle a wide range of
morphological variations sufficiently without the need of the information
regarding their morphologies or adaptation of their parameters. We perform an
extensive experimental analysis on simulation that demonstrates the trade-off
between specialist and generalist controllers. The results show that
generalists are able to control a range of morphological variations with a cost
of underperforming on a specific morphology relative to a specialist. This
research contributes to the field by addressing the limited understanding of
robustness and generalisability in neuro-evolutionary methods and proposes a
method by which to improve these properties
Discrimination of TiO2 polymorphs in sedimentary and metamorphic rocks
Investigation by Raman spectroscopy of samples from different geological settings shows that the occurrence of TiO2 polymorphs other than rutile can hardly be predicted, and furthermore, the occurrence of anatase is more widespread than previously thought. Metamorphic pressure and temperature, together with whole rock chemistry, control the occurrence of anatase, whereas variation of mineral assemblage characteristics and/or fluid occurrence or composition takes influence on anatase trace element characteristics and re-equilibration of relict rutiles. Evaluation of trace element contents obtained by electron microprobe in anatase, brookite, and rutile shows that these vary significantly between the three TiO2 phases. Therefore, on the one hand, an appropriation to source rock type according to Nb and Cr contents, but as well application of thermometry on the basis of Zr contents, would lead to erroneous results if no phase specification is done beforehand. For the elements Cr, V, Fe, and Nb, variation between the polymorphs is systematic and can be used for discrimination on the basis of a linear discriminant analysis. Using phase group means and coefficients of linear discriminants obtained from a compilation of analyses from samples with well-defined phase information together with prior probabilities of groupings from a natural sample compilation, one is able to calculate phase grouping probabilities of any TiO2 analysis containing at least the critical elements Cr, V, Fe, and Nb. An application of this calculation shows that for the appropriation to the phase rutile, a correct-classification rate of 99.5% is obtained. Hence, phase specification by trace elements proves to be a valuable tool besides Raman spectroscopy.Postprint (published version
Shallow structure beneath the Central Volcanic Complex of Tenerife from new gravity data: implications for its evolution and recent reactivation
We present a new local Bouguer anomaly map of the Central Volcanic Complex (CVC) of Tenerife, Spain, constructed from the amalgamation of 323 new high precision gravity measurements with existing gravity data from 361 observations. The new anomaly map images the high-density core of the CVC and the pronounced gravity low centred in the Las Cañadas caldera in greater detail than previously available. Mathematical construction of a sub-surface model from the local anomaly data, employing a 3D inversion based on 'growing' the sub-surface density distribution via the aggregation of cells, enables mapping of the shallow structure beneath the complex, giving unprecedented insights into the sub-surface architecture. We find the resultant density distribution in agreement with geological and other geophysical data. The modelled sub-surface structure supports a vertical collapse origin of the caldera, and maps the headwall of the ca. 180 ka Icod landslide, which appears to lie buried beneath the Pico Viejo–Pico Teide stratovolcanic complex. The results allow us to put into context the recorded ground deformation and gravity changes at the CVC during its reactivation in spring 2004 in relation to its dominant structural building blocks. For example, the areas undergoing the most significant changes at depth in recent years are underlain by low-density material and are aligned along long-standing structural entities, which have shaped this volcanic ocean island over the past few million years
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