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Mullen L.,Command Systems | O'Connor S.,Command Systems | Cochenour B.,Command Systems | Dalgleish F.,Harbor Branch Oceanographic Institute
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

The detection and identification of underwater threats in coastal areas is of interest to the Navy. Conventional optical imaging systems are limited to scenarios where the number of attenuation lengths between the system and the object are less than 4. With a desire to operate at extended ranges and threats becoming smaller and better camouflaged, new approaches are needed. In response to these challenges, new transmitters and receivers are being developed to support the next-generation of underwater optical imaging systems. One of these systems is based on the modulated pulse concept where a pulsed laser source is encoded with a radar signal, and a range-gated, high-speed optical receiver recovers the radar modulation envelope. Subsequent processing of the radar signal provides a way to discriminate against multiply scattered light and to enhance image contrast and resolution. The challenge is developing transmitter and receiver hardware that meets the requirements of the modulated pulse technique. We report recent progress that has been made in developing modulated pulse transmitter and receiver hardware. A working prototype was demonstrated and tested in a controlled laboratory environment. The results of these initial experiments are presented. © 2013 SPIE.

Rashkin D.,Florida Atlantic University | Cardei I.,Florida Atlantic University | Cardei M.,Florida Atlantic University | Dalgleish F.,Harbor Branch Oceanographic Institute | Giddings T.,Metron Inc.
OCEANS 2012 MTS/IEEE: Harnessing the Power of the Ocean | Year: 2012

The need for midrange, high throughput data networks in the undersea environment is evident for a variety of applications, including sensor networks and remote control and telemetry for unmanned underwater vehicles. While research continues into undersea acoustic and radio frequency networks, results show that these suffer from low data rates (in the case of the former) or severe range limitations (in the case of the latter) [1]. Free space optical technology provides a good balance between data throughput and potential distance between communicating nodes; given the cost of deploying and testing these types of networks, however, it is necessary to develop accurate models that allow us to simulate digital communication between nodes, facilitating the development of optimal protocols at low cost. One important component of such a system is an accurate model for the noise in the detector output signal. This paper evaluates one such model [2] for its suitability in predicting shot noise (the random variation in the detector output signal that is caused by the random arrival times of the photons at the detector photocathode) and the noise introduced by a Photomultiplier Tube (PMT) detector. © 2012 IEEE.

Dix N.,Harbor Branch Oceanographic Institute | Phlips E.,University of Florida | Suscy P.,St. Johns River Water Management District
Estuaries and Coasts | Year: 2013

Patterns in phytoplankton biomass are essential to understanding estuarine ecosystem structure and function and are the net result of various gain and loss processes. In this study, patterns in phytoplankton biomass were explored in relation to a suite of potentially regulating factors in a well-flushed, subtropical lagoon, the Matanzas River Estuary (MRE) in northeast Florida. We examined temporal variability in water temperature, light availability, nutrient concentrations, phytoplankton productivity, and phytoplankton standing stock over 8 years (2003-2010) and explored relationships among variables through correlation analysis. Laboratory experiments in the spring and summer of 2009 quantified phytoplankton growth rates, nutrient limitation potential, and zooplankton grazing rates. The potential influence of oyster grazing was also examined by scaling up population metrics and filtration rate estimates. Results indicated that phytoplankton biomass in the study area was relatively low mainly due to a combination of low temperature and light availability in the winter and consistent tidal water exchange and bivalve grazing throughout the year. Relatively low levels of phytoplankton standing stock and small inter-annual variability within the MRE reflect a balance between gain and loss processes which provide a degree of resilience of the system to natural and anthropogenic influences. © 2013 Coastal and Estuarine Research Federation.

Bonin C.A.,University of California at San Diego | Goebel M.E.,Southwest Fisheries Science Center | O'Corry-Crowe G.M.,Harbor Branch Oceanographic Institute | Burton R.S.,University of California at San Diego
Journal of Experimental Marine Biology and Ecology | Year: 2016

Antarctic fur seals (Arctocephalus gazella) are polygynous and both sexes are typically faithful to a breeding site. These characteristics could promote remating among individuals over time, leading to increased relatedness levels and negatively affecting genetic diversity. To examine this issue, the reproductive output of 55 females was monitored annually for 12 years and their pups were sampled (n = 280) and genotyped using 17 microsatellite markers. A full likelihood pedigree inference method was used to confirm maternities inferred in the field and estimate the number of full sibling pups born across years. Relatedness coefficients were estimated for pairs of individuals in the pedigree and compared to simulated values for each relationship category. There were nine cases where a female mated with the same male twice and one case where a female mated with the same male three times over the study period. The observed relatedness coefficients estimated among the sampled pups matched the simulated distribution for half-siblings. In addition, no first order relatives were found among the fur seal mothers studied, nor did observed relatedness coefficient distributions differ significantly from simulated values. Together, these results suggest a low remating rate and a negligible effect of remating on pair-wise relatedness. Territorial male replacement over time as well as female small-scale movements, driven by suitable pupping habitat, likely contribute to the low remating frequency observed in Antarctic fur seals. © 2015 .

Russell L.M.,University of California at San Diego | Rasch P.J.,Pacific Northwest National Laboratory | MacE G.M.,Imperial College London | Jackson R.B.,Duke University | And 13 more authors.
Ambio | Year: 2012

Geoengineering methods are intended to reduce climate change, which is already having demonstrable effects on ecosystem structure and functioning in some regions. Two types of geoengineering activities that have been proposed are: carbon dioxide (CO2) removal (CDR), which removes CO2 from the atmosphere, and solar radiation management (SRM, or sunlight reflection methods), which reflects a small percentage of sunlight back into space to offset warming from greenhouse gases (GHGs). Current research suggests that SRM or CDR might diminish the impacts of climate change on ecosystems by reducing changes in temperature and precipitation. However, sudden cessation of SRM would exacerbate the climate effects on ecosystems, and some CDR might interfere with oceanic and terrestrial ecosystem processes. The many risks and uncertainties associated with these new kinds of purposeful perturbations to the Earth system are not well understood and require cautious and comprehensive research. © Royal Swedish Academy of Sciences 2012.

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