Michael D. Collins

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Theory predicts, and recent empirical studies have shown, that the diversity of plant species determines the diversity of associated herbivores and mediates ecosystem processes, such as aboveground net primary productivity (ANPP). However, an often-overlooked component of plant diversity, namely population genotypic diversity, may also have wide-ranging(More)
We consider the problem of establishing jam-resistant, wireless, omnidirectional communication channels when there is no initial shared secret. No existing system achieves this. We propose a general algorithm for this problem, the BBC algorithm, and give several instantiations of it. We develop and analyze this algorithm within the framework of a new type(More)
Putative audio recordings of the Ivory-billed Woodpecker (Campephilus principalis) are presented along with discussions of the videos from which they were extracted and the observations that were made when these data were obtained. On two occasions, high-pitched calls were heard coming from the direction of a bird that was identified in the field as an(More)
A tank experiment was carried out to investigate underwater sound propagation over an elastic bottom in flat and sloping configurations. The purpose of the experiment was to evaluate range-dependent propagation models with high-quality experimental data. The sea floor was modeled as an elastic medium by a polyvinyl chloride slab. The relatively high(More)
Recent improvements in the parabolic equation method are combined to extend this approach to a larger class of seismo-acoustics problems. The variable rotated parabolic equation [J. Acoust. Soc. Am. 120, 3534-3538 (2006)] handles a sloping fluid-solid interface at the ocean bottom. The single-scattering solution [J. Acoust. Soc. Am. 121, 808-813 (2007)](More)
—Improvements in the capability of handling sloping interfaces and boundaries with the parabolic equation method have been an active area of research. Recent progress in accurately treating range-dependent seismoacoustic problems has involved coordinate transformation techniques. The variable-rotated parabolic equation is among recent advances in this area.(More)
Information security is only attained when all four of the classic information assurance goals-confidentiality, integrity, authenticity, and availability – are attained. The work presented focuses exclusively on the availability goal; in particular, maintaining the availability of the physical layer link in an omnidirectional wireless communications system.(More)
— The advent of concurrent coding theory means that omnidirectional communication systems can possess a level of keyless jam-resistance comparable to that of traditional spread spectrum systems, all of which rely on shared secret keys. To achieve this, concurrent codecs possess the ability to efficiently separate multiple legitimate codewords that have been(More)
Systems-thinking requires participants to view problems, and their solutions, within the context of the overall system. When this involves participants from diverse professional communities, several barriers to effective communication can arise. As in all human communities, shorthand representations , such as specialized jargon, that aid in efficient and(More)
A series of laboratory experiments was conducted to obtain high-quality data for acoustic propagation in shallow water waveguides with sloping elastic bottoms. Accurate modeling of transmission loss in these waveguides can be performed with the variable rotated parabolic equation method. Results from an earlier experiment with a flat or sloped slab of(More)