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Date 14-19 Oct. 2012

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Displaying Results 1 - 25 of 355
  • New frontiers for underwater acoustic modeling

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (940 KB) |  | HTML iconHTML  

    Changes in the ocean soundscape have been driven by anthropogenic activity (e.g. naval-sonar systems, seismic-exploration activity, maritime shipping and windfarm development) and by natural factors (e.g. climate change and ocean acidification). New regulatory initiatives have placed additional restrictions on uses of sound in the ocean: mitigation of marine-mammal endangerment is now an integral consideration in acoustic-system design and operation. Modeling tools traditionally used in underwater acoustics have undergone a necessary transformation to respond to the rapidly changing requirements imposed by this new soundscape. Advanced modeling techniques now include forward and inverse applications, integrated-modeling approaches, non-intrusive measurements and novel processing methods. View full abstract»

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  • Sea surface slope recovery through passive polarimetric imaging

    Page(s): 1 - 9
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1379 KB) |  | HTML iconHTML  

    The goal of this project is to develop a technique to recover sea surface slopes and orientations over a distributed area using a non-intrusive imaging polarimeter. The technique relies upon the incidence angle dependence of the Fresnel coefficients at the air/water interface. Different incidence angles will lead to different polarization states in the reflected light. This is an ill-posed problem, whose challenges include multi-valued slope solutions using the polarization measurements, resolving the impact of the sky incident radiance (and polarization of the radiance), treating upwelling light and unresolved waves. In this paper, we will discuss the optimization algorithm appropriate for this type of inverse problem, describe the sensor, and show high-resolution data from a field experiment. View full abstract»

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  • Oversampling MAVS for reduction of vortex-shedding velocity-sensing noise

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1067 KB) |  | HTML iconHTML  

    Reduction of vortex-induced velocity-sampling noise was demonstrated in an acoustic travel-time current meter, MAVS, by oversampling and averaging bursts of 20Hz measurements every 0.5s sampling interval during tows in the Woods Hole Oceanographic Institution flume. A characteristic vortex size of 7.37cm (from frequency and tow speed) translated into narrow band spectral peaks of velocity fluctuation with frequency proportional to tow speed. A selection of burst-sampling intervals during which 20Hz measurements were averaged was tuned to the profiling speed of the moored profiler upon which the MAVS was to be mounted. Burst-sampling improved the signal to noise ratio by almost a factor of 3 with a 4-point burst every 0.5s at 30cm/s tow (profiling) speed. This closely matched the dominant 4.3Hz vortex at 30cm/s tow speed. View full abstract»

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  • SENSE IT — Student created water quality sensors

    Page(s): 1 - 8
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (752 KB) |  | HTML iconHTML  

    This paper describes the structure and impact of an NSF-funded ITEST project designed to enrich science, technology, engineering, and mathematics (STEM) education using educational modules that teach students to construct, program, and test a series of sensors used to monitor water quality. During the three years of the SENSE IT project, over 60 teachers across New York, New Jersey and Washington were provided with equipment and professional development, and then implemented the modules in their classrooms with over 2,000 middle and high school students. Project evaluation results indicate that the curriculum was well received by teachers and students, could be integrated into several different subject areas and types of courses, and was effective for a wide range of students. View full abstract»

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  • Underwater 3D modelling and photosynthetic life detection

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3214 KB) |  | HTML iconHTML  

    Automatic detection of photosynthetic life underwater when combined with photorealistic 3D models of observed sites offers a powerful tool for scientific investigations. This paper describes underwater Scene Modeler (uSM) and presents results of experiments in mapping and modelling microbialites colonies conducted as part of the Pavilion Lake Research Project (PLRP). uSM can be also used for monitoring health of marine plants, such as coral and algae, and inspection of underwater structures. View full abstract»

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  • Multiresolution image registration using spatial mutual information

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1824 KB) |  | HTML iconHTML  

    The maximization of mutual information has been very successful at the registration of images. Unfortunately, mutual information takes only into account the relationship between individual pixels and not those of each pixel's neighborhood. Mutual information ignores spatial information. In this paper, we propose a new similarity metric called enhanced mutual information (EMI), which combines mutual information with a weighting function based on the absolute difference of corresponding pixel values. In order to reduce computational cost we also use multiresolution wavelet decomposition as a search data strategy. Experimental results show that the enhanced mutual information is not only more robust to noise than mutual information but more reliable in the registration of multitemporal images. View full abstract»

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  • Auto-tuning mother nature: Waves in music and water

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (647 KB) |  | HTML iconHTML  

    In the late 1990s, the application of a well known mathematical transformation revolutionized the music industry. That process, known as Auto-Tune, relies on the ability of the Fourier Transform to identify dominant frequencies within a time-series record of a signal. Mega-stars like Madonna, Cher, Britney Spears, Tim McGraw, Kanye West, and many more heavily use Auto-Tune not only to ensure perfect pitch, but often simply for the unique sounds the function produces. Perhaps unknown to these singers, wave experts were using exactly the same mathematical functions to identify ocean wave characteristics forty years prior to the first mainstream music hit (Cher's “Believe”) to use Auto-Tune. This paper presents an overview of the Fourier Transform and its application in both the music industry and the scientific study of water waves. View full abstract»

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  • Development of a deep-sea sediment long coring system based on a Jackhammer for R/V Kexue

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1241 KB) |  | HTML iconHTML  

    A long coring system for deep-sea sediment cores has been developed by the Institute of Oceanology, Chinese Academy of Sciences (IOCAS). This novel device is a hybrid of Jackhammer (pneumatic drill) and gravity sampler. The originally designed recovered length is up to 30 m in water depths of 3500 m. The hybrid corer has variable weight around 2 tons, determined by the core length. So it can be deployed as a gravity sampler for the first 0-10 m clays sample. After it been plugged by the mud, a homemade deep-sea “Jackhammer” will start to drive the system go deeper and deeper. This homemade deep-sea “Jackhammer” can drive an internal hammer up and down with 0-28kN force at 1 cycle/min by a 2.5kw/100V 1500rpm deep-water motor. It has been tested on the ground. This hybrid corer is designed for the R/V Kexue, which is a new designed 4000 tons research vessel and will be delivered to IOCAS at September, 2012. This hybrid corer is the main sediment core system for this new ship. View full abstract»

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  • Beyond data management: How to foster data exploitation and better science?

    Page(s): 1 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (986 KB) |  | HTML iconHTML  

    The advent of large scale, high-bandwidth on-line access and generously powered ocean floor observatories were predicted to transform the way ocean science is conducted. They have lived up to this promise. New cabled observatories have sometimes in excess of 100 different instruments semipermanently installed in areas of scientific interest. The instruments represent hundreds of different variables measured at a high frequency (often once per second or more) on a 24/7/365 basis, thereby generating large data volumes that accumulate in archives. Not only are we talking about large data volumes, we are also facing many different data types as instruments are often preprocessing data and assembling them in complex data structures or matrices. For practical purposes, three major data types can be described based on the duty cycles of the instruments producing them: · scalar data coming from single point measurement sensors on a periodic basis with a sampling frequency <; 10Hz; · complex data structures, often produced by active acoustic instruments such as ADCPs and current profilers that produce multi-dimensional matrices typically at a rate ≤ 1 Hz · streams that are produced by passive sensors, continuously sampling their environments at high frequencies (≥ ~20Hz) such as cameras and hydrophones, seismometers, etc. The complexity also resides in that many of the instruments are in some way mapping their wider environment and not just their immediate vicinity. Therefore the matrices they sent back represent their own specific encoding of spatial data. Examples here include ADCPs, sonars, but also vehicles moving in one, two or three dimensions (vertical profiler, crawlers, gliders, AUVs, etc.) The instruments and sensors are often of a legacy type, from different vendors, with proprietary formats and usually are not optimized to work in connected, powered environment. The stated goal of the observatories is to enable not onl- science in a particular discipline, but to foster multi-disciplinary experiments, to support real-time science as well as to provide a longitudinal view on the evolutions of the oceans. The above considerations represent significant challenges not only for the scientists, but also for data providers as they need to be in a position to support: · many different science disciplines · scientists not used to dealing with vast amounts of data · scientists not necessarily used to data from instrumentation they are not always familiar with · users still expecting to be able to just “download a couple of years of data” At Ocean Networks Canada, those challenges have been addressed in a number of ways, oftentimes creative and sometimes disruptive. With the support of CANARIE, Canada's advanced research and innovation network, we have adopted the Web 2.0 concepts of participation and contribution. Those two concepts are very powerful and are at the origin of wikipedia, FaceBook, Twitter and, to some extent, massively parallel computer games: they allow individuals to contribute/share content and to participate in groups of like-minded citizens in activities around a specific topic or theme for a period of time. In this contribution, we are describing the innovations that are now available to users of the NEPTUNE Canada cabled network access interfaces and how they contribute to address many of the challenges that scientists face in dealing with those first Big Science infrastructures for the study of the oceans. They include a data visualization utility that allows plots created to be posted and shared with other users, a data search tool that offers a multitude of data formatting and averaging/decimation options, a real-time camera control interface that allows multiple users to simultaneously use the instruments and chat among themselves, regardless of where they are each located on the planet, a tool that encourages users View full abstract»

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  • Short time variation of the marine environment and the dominant phytoplankton species in the Yodo River estuary

    Page(s): 1 - 4
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1396 KB) |  | HTML iconHTML  

    Osaka Bay is the semi-enclosed bay and one of the eutrophic bays in Japan. Various red tide species are found in Osaka Bay over the year, and diatom dominates usually in the Yodo River estuary, but other harmful species appear sometimes. The transition of dominant species can occur even in shorter time but its reasons are indistinct. To clarify the short time variation of the marine environment and dominant phytoplankton species, the field observation was carried out during the 16 days from the end of June to July. Greatly diurnal change was found in all data. Thalassiosira spp. dominated throughout the period. On the other hand other diatom species decreased, and dinoflagellate and other species increased in later period. All nutrient concentrations decreased toward July 5, but DIN and DIP concentrations recovered and DSi concentration continued the low condition after July 7. From the results based on nutrient concentrations and those mole ratio, the growth of all species was limited by DIP before 2 July. Diatom has advantage in this case because can grow under the lower DIP concentration. After that, nutrient which limits the growth of diatom changed to DSi due to the decrease of DSi concentration. Then DIP and DIN concentration increased in favor of dinoflagellate. View full abstract»

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  • Wing wave: Feasible, alternative, renewable, electrical energy producing ocean floor system

    Page(s): 1 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2105 KB) |  | HTML iconHTML  

    Wing-Wave is an ocean, alternative energy system to convert the circular motion of ocean waves as they propagate through the sea into electrical energy. The system consists of planes, called “wings”. The wings are mounted on the sea floor and move in a radial motion as a result of the passing waves. The mechanical energy is translated into electrical energy by means of an electrical generator. Three Wing-Wave prototype systems were built at Florida Institute of Technology (Florida Tech) and deployed November 17th, 2010, June 23rd, 2011, and June 6th, 2012, respectively. Each deployment provided valuable information that lead to modifications in subsequent versions and deployment techniques, culminating in the demonstration of a fully functioning and feasible alternative, renewable, electrical energy producing subsea system. View full abstract»

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  • Measurement of micro-bathymetry with a GOPRO underwater stereo camera pair

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1468 KB) |  | HTML iconHTML  

    A GO-PRO underwater stereo camera kit has been used to measure the 3D topography (bathymetry) of a patch of seafloor producing a point cloud with a spatial data density of 15 measurements per 3 mm grid square and an standard deviation of less than 1 cm A GO-PRO camera is a fixed focus, 11 megapixel, still-frame (or 1080p high-definition video) camera, whose small form-factor and water-proof housing has made it popular with sports enthusiasts. A stereo camera kit is available providing a waterproof housing (to 61 m / 200 ft) for a pair of cameras. Measures of seafloor micro-bathymetry capable of resolving seafloor features less than 1 cm in amplitude were possible from the stereo reconstruction. Bathymetric measurements of this scale provide important ground-truth data and boundary condition information for modeling of larger scale processes whose details depend on small-scale variations. Examples include modeling of turbulent water layers, seafloor sediment transfer and acoustic backscatter from bathymetric echo sounders. View full abstract»

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  • GECCO ocean energy system

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1223 KB) |  | HTML iconHTML  

    In today's world the oil and gas industries play major roles in energy consumption. Nations depend heavily on these resources despite their major disadvantage: They are not renewable. As the demand for renewable energy increases, it is necessary to identify new energy sources and to invent ways of harvesting these energies by designing new systems. The ocean is a major resource for all types of materials, supplies, as well as energy; however the exploration of wave energy as a resource is still in its infancy. The Florida Institute of Technology has constructed an alternative energy system independent of non-renewable resources, such as oil and gas. The GECCO (Green Energy Coastal Collection Operation) is a wave energy converter that extracts kinetic energy from ocean waves using a rugged, innovative mechanical multi-system. View full abstract»

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  • The Intrinsic Mode Function Time Delay Method for beamforming

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1526 KB) |  | HTML iconHTML  

    This paper presents the Intrinsic Mode Function Time Delay Method (IMFTDM) which is based on Hilbert Huang Transform (HHT) and its application in beamforming. The IMFTDM can delay the broadband Intrinsic Mode Function (IMF) by arbitrary time accurately. And in this work, the IMFTDM is performed using the simulated and real data in beamforming to test its performance. The results show that it can improve the array gain and the accuracy of Direction of Arrival (DOA) estimation. With discussion, we suggest that these advantages are attributed by the following reasons. The single IMF generally has less noise and better correlation result than original data and the IMFTDM can provide better time delay. View full abstract»

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  • Acoustic and visual instrumentation for survey of manganese crusts using an underwater vehicle

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (5587 KB) |  | HTML iconHTML  

    This paper describes the application of acoustic and visual instruments developed to survey the volumetric distribution of manganese crusts from an underwater vehicle. The instruments consist of an acoustic device, used to measure the thickness manganese crust layers, and a visual mapping system that generates three-dimensional (3D) color reconstructions of the seafloor. The information obtained by these sensors is processed to automatically identify areas of exposed crust using the 3D reconstructions, and determine the thickness of the crusts based on the acoustic measurements to measure the volumetric distribution of manganese crusts. Continuous measurements of crust distribution were achieved for the first time using the instruments described during sea trials performed at #5 Takuyo seamount using the remotely operated vehicle Hyper-Dolphin. View full abstract»

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  • A systems engineering approach for performance surface computational architectures

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1577 KB) |  | HTML iconHTML  

    The Naval Meteorology and Oceanography Command (NAVMETOCCOM) produces operational image products referred to as performance surfaces. A performance surface is the projection of numerical values that reflect the performance of a system or phenomenon into a Geographic Coordinate System layer portraying a physical representation of the earth's atmosphere, surface, or ocean. That is, a performance surface is a graphic that indicates optimal performance through visual cues. To date, performance surface algorithms exist for AntiSubmarine Warfare (ASW) and Piracy, and future performance surfaces are anticipated. A characteristic of performance surfaces is their computational complexity, which can be either deterministic or stochastic in nature. The use of stochastic processes drives a significant computational burden based on the sheer volume of individual simulations that must be run and then combined to form a probabilistic prediction. To mitigate the difficulties imposed by large volume stochastic processes, NAVMETOCCOM chartered an Integrated Product Team (IPT) to characterize a suitable computational architecture for existing and future performance surfaces. The IPT was also tasked to document an engineering process by which emergent performance surfaces could implement suitable architectures. This engineering process used tailored DoD acquisition best practices that were agile and easily repeatable for use by future NAVMETOCCOM IPT efforts. View full abstract»

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  • Observations of ocean circulation and sediment transport experiment offshore of Fire Island, NY

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1327 KB) |  | HTML iconHTML  

    Researchers from the U.S. Geological Survey (USGS) Woods Hole Coastal and Marine Science Center (WHCMSC), in collaboration with Coastal Carolina University (CCU) and University of South Carolina (USC), conducted a scientific field study to investigate the ocean circulation and sediment transport processes offshore of Fire Island, NY. Although the physical processes along the entire linear extent of Fire Island (~50 km) are of interest to the project, one particular region of focus is at the western end of the island where offshore sand ridges out to depths of 20 m extend across the inner shelf and connect to the near-shore bar system. The primary objective was to measure the physical processes around the sand ridges, including circulation patterns, wave parameters, bottom stress, and suspended sediment. Transects of instrumentation were positioned along and across the crests and troughs of the ridge field. A site at the top of a ridge and a site at the bottom of an adjacent trough were each populated with two tripods designed to provide high-resolution measurements near the sea-bed to record sediment re-suspension events. Measurements at these two sites include near bottom velocity profiles, acoustic Doppler velocimeters, pressure, optical transmission and backscatter at high sampling rates. Other measurements include upward looking velocity profiles, temperature, salinity, sonar images and profiles, and sediment size classes. Five smaller tripods were deployed to complete lines alongshore and across shore over a 5 km area to provide a regional picture. These tripods recorded upward looking velocity profiles and near bottom temperature, pressure and salinity. Surface buoys marked the position of the tripods and collected surface measurements at six of the sites. One buoy gathered meteorological measurements. The sites were occupied from January to April, 2012. This deployment was similar to previous efforts off Cape Hatteras, NC, in 2009, and is part of an ongoing - ffort to understand regional patterns in circulation and sediment transport and the interaction of inner shelf and near shore processes. New instrumentation for the USGS was introduced, including a variety of current and wave measurement equipment, acquisition and telemetry in near-realtime of the weather data, time series sonar imaging equipment, and anti-fouling wipers. Preliminary results suggest a complex and subtle relationship between wind and across shore current velocity in this region, and a more straightforward relationship between winds and alongshore currents. This paper also includes a preliminary report on the effectiveness of new measurement techniques used during this experiment. View full abstract»

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  • Using a cruise report to generate XML metadata

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1200 KB) |  | HTML iconHTML  

    Since 2005 metadata generation at the Center for Coastal and Ocean Mapping/Joint Hydrographic Center has slowly evolved from a painful and tedious process of copying and pasting, to generate hundreds of files, to using an automated system that generates 90% of the needed metadata from the data collected on cruises. However there remained one piece missing to the automated system- the wordy part of the metadata that deals with information such as the attribute accuracy report, abstract and the process description. This information cannot be mined from the raw survey data. This paper illustrates how to generate a template from a Microsoft Word based cruise report that can be used in conjunction with another template (generated from the raw data collected on a cruise) to create XML metadata ready for submission to the NOAA/National Geophysical Data Center. View full abstract»

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  • Stator winding partial discharge activity for air-cooled generators

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1271 KB) |  | HTML iconHTML  

    Partial discharge (PD) activity has long been known to be an indicator of the presence of some deterioration mechanisms at work within, or on, the solid insulation of the stator windings of high voltage rotating machines. Specifically, the test can find loose, overheated, and contaminated windings, well before these problems lead to failure. As a result, on-line PD testing has become an important tool for planning motor maintenance. On-line monitoring of partial discharge results is preferred as it provides an indication of the activity while the machine is operating under normal thermal, electrical, ambient and mechanical stresses. However, when monitoring on-line, the influence of high frequency pulses from sources external to the stator winding must be identified and separated in order to prevent erroneous interpretations. In the past, this has required the use of a human expert. By using results obtained with sophisticated noise separation techniques, 272,000 partial discharge (PD) test results have been analyzed to establish the criteria for comparing results from different machines and the expected PD levels. This paper will highlight some of the benefits of on-line PD testing using these results with case studies and signal analysis from marine vessel applications. View full abstract»

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  • Analysis of relative sea level variations and trends in the Chesapeake Bay: Is there evidence for acceleration in sea level rise?

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1104 KB) |  | HTML iconHTML  

    Over the past few decades the pace of relative sea level rise (SLR) in the Chesapeake Bay (CB) has been 2-3 times faster than that of the globally mean absolute sea level. Our study is part of ongoing research that tries to determine if this SLR trend is continuing at the same pace, slowing down (SLR deceleration) or speeding up (SLR acceleration). We introduce a new analysis method for sea level data that is based on Empirical Mode Decomposition (EMD) and Hilbert-Huang Transform (HHT); the analysis separates the SLR trend from other oscillating modes of different scales. Bootstrap calculations using thousands of iterations were used to test the robustness of the method and obtain confidence levels. The analysis shows that most sea level records in the CB have significant positive SLR acceleration, so the SLR rates today are about twice the SLR rates of 60 years ago. The acceleration rates of our calculations are larger than some past studies, but comparable to recent results [1] who show accelerated SLR “hotspots” in the coastal areas between Cape Hatteras and Cape Cod. The results have implications for projections of future SLR and the impact on flooding risks in the Hampton Roads area. The contributions to SLR from land subsidence and climate-related changes in ocean circulation need further research. View full abstract»

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  • Wave Energy Development Roadmap: Design to commercialization

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (839 KB) |  | HTML iconHTML  

    In order to promote and support development of the wave energy industry, Sandia National Laboratories (SNL) has developed a Wave Energy Development Roadmap. The Wave Energy Development Roadmap outlines the pathway from initial design to commercialization for Wave Energy Converter (WEC) technologies. Commercialization of a wave energy technology is embodied in the deployment of an array of WEC's, a WEC Farm. The development process is related to the commonly used metric of Technology Readiness Levels (TRLs). The roadmap incorporates modeling and experimental expectations at corresponding TRLs which provide a guide for the industry to pursue successful design optimizations, prototype deployments, and utility scale commercialization. The roadmap serves the additional purpose of pinpointing research gaps in the development process. View full abstract»

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  • Capacity criterion-based power allocation for OFDM cooperative underwater acoustic communications with limited feedback

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (805 KB) |  | HTML iconHTML  

    The underwater acoustic (UWA) communication has been regarded as one of the most challenging wireless communications due to the unique properties, such as limited bandwidth, extended multipath delay, medium inhomogeneities, rapid time-variation and large Doppler shifts. Cooperative relaying technique is a promising technique to provide high rate data transmission. However, literature on cooperative communications in UWA environments is very scarce. In this paper, we propose a novel UWA cooperative communication system, which involves the Deocde-and-Forward (DF) transmission protocol, Orthogonal Frequency Division Multiplexing (OFDM) and the Lloyd algorithm-based limited feedback procedure for the first time. We take capacity criterion-based power allocation strategy as an example to demonstrate the performance of our proposed system. Simulation results show the system capacity performance based on uniform allocation (non-feedback), several bits of feedback and perfect feedback. View full abstract»

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  • Optimized wave energy harvester for distributed application

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (922 KB) |  | HTML iconHTML  

    As ocean and undersea missions evolve, additional sensors, communications systems, and vehicles will need access to persistent sources of power. Battery, solar, wind and fossil fuel generators and fuel cells are currently used as sources of power, but each has issues that render it problematic to buoy manufacturers and users. More persistent power would enable longer duration missions or increased sampling rates for existing sensors and would expand the range of potential new missions. In addition, system life cycle cost reduction can be realized by extending the period between costly at-sea servicing. OceanGen™, a wave energy harvesting technology under development by Battelle and Levant Power, is intended to provide this highly sought persistent power. OceanGen™ harnesses incessant wave motion in a compact, fully sealed, hydraulic-electric apparatus that can be scaled to mission needs. OceanGen™ will enable long-term unattended deployment, enabling new concepts of operation and reducing cost by extending mission duration and service intervals. View full abstract»

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  • Bathymetry degradation causes for frequency modulated multibeam echo sounders

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (874 KB) |  | HTML iconHTML  

    FM-modulated signals with pulse compression are used in the new generation of bathymetric multibeam echo sounders in order to reach higher swath while keeping a high resolution. However, the expected performances are not reached on field data. This article discusses two different effects impacting the bathymetric measurement (Doppler effect and baseline decor-relation). Firstly, the Doppler effect from the antenna motion strongly shifts in time the FM signals processed with the matched filter, and induces measurement bias. Secondly, the pulse compression side lobes affect the final bathymetric measurements: since the instantaneous footprint appears wider because of the temporal side lobes, the interferometric signals appear less coherent (due to baseline decorrelation). This results in an increase of the noise level on the interferometric phase which proportionally impacts bathymetric measurement quality. Considering that Doppler effect measurement biases are already taken into account and corrected in the sounder system, the challenge is to improve the bathymetric measurement quality by reducing the pulse-compressed side-lobes level. View full abstract»

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  • Temporal distribution of Pseudo-nitzschia spp. along the Outer Banks of North Carolina

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    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (773 KB) |  | HTML iconHTML  

    Pseudo-nitzschia is a toxin producing species of diatom that blooms commonly along the west coast of the United States. Previously the Outer Banks of North Carolina was not documented as an area able to support routine bloom formation of Pseudo-nitzschia (Hasle 2002). However, monitoring by the NOAA Phytoplankton Monitoring Network (PMN) in this region identified four blooms having occurred since 2005. Three of these blooms occurred in consecutive years (Shuler et al. 2012). View full abstract»

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