60 research outputs found

    On The Phase of Least-Asymmetric Scaling and Wavelet Filters

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    When using the discrete wavelet transform it is important that the filters at each scale are suitably shifted so that energy in the output sequence is appropriately positioned. We derive the form of the advance to apply to Daubechies' least-asymmetric scaling and wavelet filters at each scale, in order to obtain nearest to zero phase. At each scale the appropriate advance depends on whether half the length of each of the original quadrature mirror filters is even or odd. The departures from zero phase of the appropriately shifted wavelet filters are illustrated. The conditions under which the phase of appropriately shifted scaling and wavelet filters is continuous across octave bands (i.e., across scales) is investigated; the shifts derived here give rise to continuous phase functions. E.J. McCoy and A.T. Walden are with the Dept. of Mathematics, Imperial College of Science, Technology and Medicine, 180 Queen's Gate, London SW7 2BZ, U.K. D.B. Percival is with the Applied Physics Lab, U..

    Multitaper Spectral Estimation of Power Law Processes

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    In many branches of science, particularly astronomy and geophysics, power spectra of the form f fi ; where fi is a negative power-law exponent, are common. This form of spectrum is characterized by a sharp increase in the spectral density as the frequency f decreases towards zero. A power spectrum analysis method which has proven very powerful wherever the spectrum of interest is detailed and/or varies rapidly with a large dynamic range is the multitaper method. With multitaper spectral estimation a set of orthogonal tapers are applied to the time series and the resulting direct spectral estimators (`eigenspectra') are averaged, thus reducing the variance. One class of processes with spectra of power-law type are fractionally differenced Gaussian white noise processes which are stationary and can model certain types of long range persistence. Spectral decay f \Gammafi can be modelled for 0 ! fi ! 1. Estimation of the spectral slope parameter by regression on multitaper spectral o..

    Multitaper spectral estimation of power law processes

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    Clinical decision support alert appropriateness: A review and proposal for improvement

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    Background: Many healthcare providers are adopting clinical decision support (CDS) systems to improve patient safety and meet meaningful use requirements. Computerized alerts that prompt clinicians about drug-allergy, drug-drug, and drugdisease warnings or provide dosing guidance are most commonly implemented. Alert overrides, which occur when clinicians do not follow the guidance presented by the alert, can hinder improved patient outcomes. Methods: We present a review of CDS alerts and describe a proposal to develop novel methods for evaluating and improving CDS alerts that builds upon traditional informatics approaches. Our proposal incorporates previously described models for predicting alert overrides that utilize retrospective chart review to determine which alerts are clinically relevant and which overrides are justifiable. Results: Despite increasing implementations of CDS alerts, detailed evaluations rarely occur because of the extensive labor involved in manual chart reviews to determine alert and response appropriateness. Further, most studies have solely evaluated alert overrides that are appropriate or justifiable. Our proposal expands the use of web-based monitoring tools with an interactive dashboard for evaluating CDS alert and response appropriateness that incorporates the predictive models. The dashboard provides 2 views, an alert detail view and a patient detail view, to provide a full history of alerts and help put the patient's events in context. Conclusion: The proposed research introduces several innovations to address the challenges and gaps in alert evaluations. This research can transform alert evaluation processes across healthcare settings, leading to improved CDS, reduced alert fatigue, and increased patient safety

    Study on lithium migration for electrochemical treatment of concrete affected by alkali-silica reaction

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    Alkali-silica reaction (ASR) is one of the major durability problems in concrete and affects many structures worldwide. Nevertheless, currently, there are no definite treatments to stop it once it has star ted. Lithium is known to have beneficial effects on ASR. Indeed, the use of lithium-based admixtures has been acknowledged as a preventive method for over 50 years. Nevertheless, in existing structures, this is no longer possible: lithium ions need to be driven into the concrete and ionic migration is the most effective transport method. Although several studies have been conducted on the use of migration to transport lithium ions into concrete, so far, there is no agreement on the conclusions. It is still necessary to fully understand lithium migration into concrete before developing a possible treatment against ASR. This study aims to investigate lithium migration through experimental testing and modelling
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