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3 results

  • Dispersion properties of glide-symmetric corrugated metasurface waveguides

  • Boris Fischer, Guido Valerio
  • Journal:
    International Journal of Microwave and Wireless Technologies / Volume 16 / Issue 1 / February 2024
    Published online by Cambridge University Press:
    02 March 2023, pp. 13-20
    • Article
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  • In this paper, a mode-matching procedure is used to prove for the first time the dispersionless behavior of glide symmetry (GS) in corrugated metasurface waveguides. Depending on their field symmetry, the Floquet harmonics have a different impact onto the frequency dispersion, which is reduced with GS when the gap between the surfaces is small. Indeed, the glide-symmetric waveguide is shown to have the same effective propagation features as a scaled mirror-symmetric waveguide with half the period and a doubled gap. We propose closed-form formulas for the effective refractive index of the glide-symmetric waveguide in the first Brillouin zone, having a small groove compared to the period. The closed-form expressions analytically prove the dispersionless behavior of GS.

  • 10 - Cohort Studies in Injury Research

  • Edited by Frederick P. Rivara, Harborview Injury Prevention and Research Center, Seattle, Peter Cummings, Harborview Injury Prevention and Research Center, Seattle, Thomas D. Koepsell, Harborview Injury Prevention and Research Center, Seattle, David C. Grossman, Harborview Injury Prevention and Research Center, Seattle, Ronald V. Maier, Harborview Injury Prevention and Research Center, Seattle
  • Book:
    Injury Control
    Published online:
    16 October 2009
    Print publication:
    27 November 2000, pp 129-138

  • Summary

    This chapter discusses a number of potentially useful measures with application to cohort studies of injuries. It reviews analytic methods for cohort studies that include crude estimates of risk and relative risk, risk difference or attributable risk, etiologic fraction percent or attributable fraction percent, and multivariate techniques. For illustration purposes, the chapter presents data from a report by Felson and associates on the Framingham Study Cohort that are used to show the effect of impaired vision on hip fracture in older adults. Cohort studies used in injury research are classified into three groups, based on the criteria for assembling the cohort: cohorts based on broad inclusion criteria that do not require an illness or injury (the cohort may represent persons in a defined population), cohorts formed from persons with a non-injury illness, and cohorts which include only persons who have been injured.