731 research outputs found

    CAMMUAZA, or the ceremony used at the Induction of a Birman into the Order of Priesthood, called Phonghi, or Rhahaan (1795) by Michael Symes, edited by Michael W. Charney

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    This account of the induction ceremony for Buddhist monks was included as Appendix V in Michael Symes, An Acount of an Embassy to the Kingdom of Ava, Sent by the Governor-General of India in the Year 1795 (London: W. Bulmer & Co., 496-500). Symes, then a major in the 76th Regiment, made numerous valuable observations on Burmese culture, society, government, and history. While it is clear that he did consult the accounts of other visitors to Burma, most of his material was derived from first-hand observation or from material provided by Burmese acquaintances, and the following account was likely derived from the latter

    A mathematical framework for inverse wave problems in heterogeneous media

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    This paper provides a theoretical foundation for some common formulations of inverse problems in wave propagation, based on hyperbolic systems of linear integro-differential equations with bounded and measurable coefficients. The coefficients of these time-dependent partial differential equations respresent parametrically the spatially varying mechanical properties of materials. Rocks, manufactured materials, and other wave propagation environments often exhibit spatial heterogeneity in mechanical properties at a wide variety of scales, and coefficient functions representing these properties must mimic this heterogeneity. We show how to choose domains (classes of nonsmooth coefficient functions) and data definitions (traces of weak solutions) so that optimization formulations of inverse wave problems satisfy some of the prerequisites for application of Newton's method and its relatives. These results follow from the properties of a class of abstract first-order evolution systems, of which various physical wave systems appear as concrete instances. Finite speed of propagation for linear waves with bounded, measurable mechanical parameter fields is one of the by-products of this theory

    A differential semblance algorithm for the inverse problem of reflection seismology

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    AbstractThis paper presents an analysis of stability and convergence for a special case of differential semblance optimization (DSO). This approach to model estimation for reflection seismology is a variant of the output least squares inversion of seismograms, enjoying analytical and numerical properties superior to those of more straightforward versions. We study a specialization of DSO appropriate to the inversion of convolutional-approximation planewave seismograms over layered constant-density acoustic media. We prove that the differential semblance variational principle is locally convex in suitable model classes for a range of data noise. Moreover, the structure of the convexity estimates suggest a family of quasi-Newton algorithms. We describe an implementation of one of these algorithms, and present some numerical results

    Adaptive waveform inversion for transmitted wave data

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    Adaptive Waveform Inversion applied to transient transmitted wave data yields estimates of index of refraction (or wave velocity) similar to those obtained by travel time inversion, provided that the data contain a single smooth wavefront.Comment: 11 page

    An adaptive multiscale algorithm for efficient extended waveform inversion

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    Subsurface-offset extended full-waveform inversion (FWI) may converge to kinematically accurate velocity models without the low-frequency data accuracy required for standard data-domain FWI. However, this robust alternative approach to waveform inversion suffers from a very high computational cost resulting from its use of nonlocal wave physics: The computation of strain from stress involves an integral over the subsurface offset axis, which must be performed at every space-time grid point. We found that a combination of data-fit driven offset limits, grid coarsening, and low-pass data filtering can reduce the cost of extended inversion by one to two orders of magnitude

    Does Increased Effort Compensate for Performance Debilitating Test Anxiety?

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    Objective: It is well established that test anxiety is negatively related to examination performance. Based on attentional control theory, the aim of this study was to examine whether increased effort can protect against performance debilitating test anxiety. Method: Four hundred and sixty-six participants (male = 228, 48.9%; white = 346, 74.3%; mean age = 15.7 years) completed self-report measures of test anxiety and effort that were matched to performance on a high-stakes secondary school examination. Results: The worry and bodily symptoms components of test anxiety were negatively, and effort, positively related to examination performance. Effort moderated the negative relation between bodily symptoms and examination performance. At low effort the negative relationship was amplified and at high effort was attenuated. Conclusions: Compensatory effort protects performance against bodily symptoms but not worry. It is possible that the cognitive load on working memory arising from the combination of worry and examination demands may be too high to be compensated by effort
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