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Your search keyword '"McNamara, Dylan E."' showing total 35 results
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35 results on '"McNamara, Dylan E."'

2. Evidence of Biological Self-Organization in Spatial Patterns of a Common Tropical Alga.

Author

Sandin, Stuart A, Edwards, Clinton B, Zgliczynski, Brian J, Pedersen, Nicole E, Smith, Jennifer E, and McNamara, Dylan E

Subjects
Biological Sciences, Ecology, Animals, Coral Reefs, Ecosystem, Anthozoa, Chlorophyta, spatial patterns, emergent patterns, Halimeda, coral reefs, Biological sciences
Abstract

AbstractTropical reef communities contain spatial patterns at multiple scales, observable from microscope and satellite alike. Many of the smaller-scale patterns are generated physiologically (e.g., skeletal structures of corals at

Published
2022

3. Variations in stability revealed by temporal asymmetries in contraction of phase space flow

Author

Williams, Zachary C and McNamara, Dylan E

Subjects
Nonlinear Sciences - Adaptation and Self-Organizing Systems, Nonlinear Sciences - Chaotic Dynamics
Abstract

Empirical diagnosis of stability has received considerable attention, mostly focused on variance metrics for early warning signals of abrupt system change. Despite this, the theoretical foundation and application has been limited to relatively simple system changes such as bifurcating fixed points where variability is extrinsic to the steady state. There is currently no foundation and associated metric for empirically exploring stability in wide ranging systems that contain variability in both internal steady state dynamics and in response to external perturbations. Utilizing connections between stability, dissipation, and phase space flow, we show that stability correlates with temporal asymmetry in a measure of phase space flow contraction. Our method is general as it reveals stability variation independent of assumptions about the nature of system variability or attractor shape. After showing efficacy in a variety of model systems, we apply our technique for measuring stability to monthly returns of the S&P 500 index in the time periods surrounding the global stock market crash of October 1987. Market stability is shown to be higher in the several years preceding and subsequent to the 1987 market crash. We anticipate our technique will have wide applicability in climate, ecological, financial, and social systems where stability is a pressing concern., Comment: 8 pages, 7 figures

Published
2020

17. Spatial pattern evolution & 2D power spectra; FNN analysis - 3 dimensions resolves dynamics; Spatio-temporal forecasting for additional pathways; Pathways in varying herbivore scenarios; Incorporating diffusion into model from Influence of aggregation on benthic coral reef spatio-temporal dynamics

Author

Brito-Millán, Marlene, B. T. Werner, Sandin, Stuart A., and McNamara, Dylan E.

Abstract

Example of pattern evolution & 2D power spectra showing duration of initial condition.; Fraction of false nearest neighbors decreases to near zero at three embedding dimensions.; Forecasting results consistently shows nonlinear dynamics in transient stages of pathways.; Pathways in herbivore-limited scenarios exhibit amplified aggregation delay.; Description of methods for incorporating CO diffusion into the model that enables clumping in the attractor, but also depresses the steady-state CO fractional cover.

Published
2019
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21. Two-dimensional polarization encoding with a phase-only liquid-crystal spatial light modulator

Author

Davis, Jeffrey A., McNamara, Dylan E., Cottrell, Don M., and Sonehara, Tomio

Subjects
Polarization (Light) -- Models, Beam optics -- Research, Astronomy, Physics
Abstract

We show how to two dimensionally encode the polarization state of an incident light beam using a parallel-aligned liquid-crystal spatial light modulator (LCSLM). Each pixel of the LCSLM acts as a voltage-controlled wave plate and can be programmed over a 2[Pi] phase range at a wavelength of 514.5 nm. Techniques are reviewed for either rotating the major axis of elliptically polarized light or for converting an input linearly polarized beam into an arbitrary elliptically polarized beam. Experimental results are demonstrated in which we generate various two-dimensional spatial patterns of polarized light. Several potential applications are suggested. We also report an unexpected edge-enhancement effect that might be useful in image processing applications. [C] 2000 Optical Society of America OCIS codes: 260.5430, 230.5440, 230.3720, 120.5410, 230.6120, 160.3710.

Published
2000

25. Understanding Human–Landscape Interactions in the “Anthropocene”

Author

Harden, Carol P., primary, Chin, Anne, additional, English, Mary R., additional, Fu, Rong, additional, Galvin, Kathleen A., additional, Gerlak, Andrea K., additional, McDowell, Patricia F., additional, McNamara, Dylan E., additional, Peterson, Jeffrey M., additional, Poff, N. LeRoy, additional, Rosa, Eugene A., additional, Solecki, William D., additional, and Wohl, Ellen E., additional

Published
2013
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31. Fractional derivatives--analysis and experimental implementation

Author

Davis, Jeffrey A., Smith, David A., McNamara, Dylan E., Cottrell, Don M., and Campos, Juan

Subjects
Spatial light modulators -- Evaluation, Image processing -- Evaluation, Optics -- Research, Astronomy, Physics
Abstract

The fractional derivative spatial-filtering operator is useful for image-processing applications, particularly for examination of phase objects. Experimental implementation is difficult because the mask function combines both amplitude and phase. We present a simple one-dimensional analysis of the fractional derivative operation and note similarities with the fractional Hilbert transform. We demonstrate how to encode these amplitude and phase masks using a phase-only liquid-crystal spatial light modulator and present experimental results. Finally, we introduce a radially symmetric extension of this operation that is more useful for objects having an arbitrary shape. OCIS codes: 070.0070, 100.0100, 200.3050, 230.3720, 230.6120, 120.2440.

Published
2001

35. Image processing with the radial Hilbert transform:?theory and experiments

Author

Davis, Jeffrey A., McNamara, Dylan E., Cottrell, Don M., and Campos, Juan

Abstract

The Hilbert transform is useful for image processing because it can select which edges of an input image are enhanced and to what degree the edge enhancement occurs. However, the transform operation is one dimensional and is not applicable for arbitrarily shaped two-dimensional objects. We introduce a radially symmetric Hilbert transform that permits two-dimensional edge enhancement. We implement one-dimensional, two-dimensional, and radial Hilbert transforms with a programmable phase-only liquid-crystal spatial light modulator. Experimental results are presented.

Published
2000

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