Showing items related by title, author, creator and subject.

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  Satellite patches, patch expansion, and doubling time as decision metrics for invasion control: Pennisetum ciliare expansion in southwestern Arizona

  Weston, Jaron D.; McClaran, Mitchel P.; Whittle, Richard K.; Black, Christian W.; Fehmi, Jeffrey S.; Univ Arizona, Sch Nat Resources & Environm (CAMBRIDGE UNIV PRESS, 2019-03)

  Essential variables to consider for an efficient control strategy for invasive plants include dispersion pattern (i.e., satellite or invasion front) and patch expansion rate. These variables were demonstrated for buffelgrass [Pennisetum ciliare (L.) Link], a C-4 perennial grass introduced from Africa, which has invaded broadly around the world. The study site was along a roadway in southern Arizona (USA). The P. ciliare plant distributions show the pattern of clumping associated with the satellite (nascent foci) colonization pattern (average nearest neighbor test, z-score -47.2, P <0.01). The distance between patches ranged from 0.743 to 12.8 km, with an average distance between patches of 5.6 km. Median patch expansion rate was 271% over the 3-yr monitoring period versus 136% found in other studies of established P. ciliare patches. Targeting P. ciliare satellite patches as a control strategy may exponentially reduce the areal doubling time, while targeting the largest patches may have less effect on the invasion speed.
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  Creation of a new facility for measuring thermal expansion and studies on the homogeneity of Heraeus-Amersil fused silica

  Shough, Dean Miles (The University of Arizona., 1981)
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  RESONANCE AND ASYMPTOTIC SERIES BASED IDENTIFICATION OF AN ACOUSTICALLY RIGID SPHERE (SINGULARITY EXPANSION METHOD).

  Dudley, Donald G.; WEYKER, ROBERT RICHARD.; Williams, Jeffery T.; Pao, Hsueh-yaun; West, Karen F. (The University of Arizona., 1986)

  Identification of the resonances and the local determination of the radius of curvature of an acoustically rigid sphere from simulated transient input-output data is presented. The scattering from the sphere is formulated using three techniques: the classic Mie-Lorenz series, the singularity expansion method (SEM), and the asymptotic series approximation. The Mie-Lorenz series is used to provide synthetic data. The SEM and the asymptotic series are used to develop two parametric inverse models. The scattered velocity potential is separated into three components: the reflection, the first creeping wave, and the second creeping wave. The effect of removing various components of the scattered potential on the resonance identification is shown, along with the effect of adding small amounts of noise. We find that the identification of a few resonances requires a relatively high order autoregressive, moving-average model. In addition, we show that removing the reflection from the synthetic output has only a small effect on the single or multiple output identified resonances. However, we find that changing the time origin, removing the second creeping wave, or adding small amounts of noise results in large errors in the identified resonances. We find that the radius of curvature can be accurately determined from synthetic data using the asymptotic series based identification. In addition, the identification is robust in the presence of noise, and requires only a low order asymptotic series model.