959 resultados para Ship roll damping


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This paper demonstrates the respective roles that combined index- and gain-coupling play in the overall link performance of distributed feedback (DFB) lasers. Their impacts on both static and dynamic properties such as slope efficiency, resonance frequency, damping rate, and chirp are investigated. Simulation results are compared with experimental data with good agreement. Transmission-oriented optimization is then demonstrated based on a targeted specification. The design tradeoffs are revealed, and it is shown that a modest combination of index- and gain-coupling enables optimum transmission at 10 Gbit/s.

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A sandwich-type plate with metal facings and felt core, fastened by bolts, was studied using both test and finite-element analysis. This type of plate is cheap, light, damping-effective and without pollution; therefore, it is widely used in astronautical engineering. The tests were conducted for different felt thicknesses, bolt numbers, and fastening forces. The results show that the damping depends on friction between the plates and the felt. As compared with an identical stiffness solid plate, the damping of laminated plates can be increased up to 30 times. A mesh with rectangular elements was adopted in the finite-element analysis. In accordance with the slipping mechanism, a rectangular plate clamped on one edge was analyzed with the foregoing elements to determine the resonant frequency and the damping. The difference between the calculated and tested results was within 5 percent for the resonant frequency.

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On April 4-5, 2002, the PICES MONITOR Task Team, the PICES Continuous Plankton Recorder (CPR) Advisory Panel, and the Exxon Valdez Oil Spill Trustee Council’s Gulf Ecosystem Monitoring (GEM) program convened a workshop in Seattle, U.S.A., to consider enhanced instrumentation for volunteer observing ships (VOS), particularly instruments to complement CPR data. (PDF contains 44 pages)

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Navassa is a small, undeveloped island in the Windward Passage between Jamaica and Haiti. It was designated a National Wildlife Refuge under the jurisdiction of the U.S. Fish and Wildlife Service in 1999, but the remote location makes management and enforcement challenging, and the area is regularly fished by artisanal fishermen from Haiti. In April 2006, the NOAA Center for Coastal Fisheries and Habitat Research conducted a research cruise to Navassa. The cruise produced the first high-resolution multibeam bathymetry for the area, which will facilitate habitat mapping and assist in refuge management. A major emphasis of the cruise was to study the impact of Haitian fishing gear on benthic habitats and fish communities; however, in 10 days on station only one small boat was observed with five fishermen and seven traps. Fifteen monitoring stations were established to characterize fish and benthic communities along the deep (28-34 m) shelf, as these areas have been largely unstudied by previous cruises. The fish communities included numerous squirrelfishes, triggerfishes, and parrotfishes. Snappers and grouper were also present but no small individuals were observed. Similarly, conch surveys indicated the population was in low abundance and was heavily skewed towards adults. Analysis of the benthic photoquadrats is currently underway. Other cruise activities included installation of a temperature logger network, sample collection for stable isotope analyses to examine trophic structure, and drop camera surveys to ground-truth habitat maps and overhead imagery. (PDF contains 58 pages)

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Summary: This cruise report is a summary of a field survey conducted within the Stellwagen Bank National Marine Sanctuary (SBNMS), located between Cape Cod and Cape Ann at the mouth of Massachusetts Bay. The survey was conducted June 14 – June 21, 2008 on NOAA Ship NANCY FOSTER Cruise NF-08-09-CCEHBR. Multiple indicators of ecological condition and human dimensions were sampled synoptically at each of 30 stations throughout SBNMS using a random probabilistic sampling design. Samples were collected for the analysis of benthic community structure and composition; concentrations of chemical contaminants (metals, pesticides, PAHs, PCBs, PBDEs) in sediments and target demersal biota; nutrient and chlorophyll levels in the water column; and other basic habitat characteristics such as depth, salinity, temperature, dissolved oxygen, turbidity, pH, sediment grain size, and organic carbon content. In addition to the fish samples that were collected for analysis of chemical contaminants relative to human-health consumption limits, other human-dimension indicators were sampled as well including presence or absence of fishing gear, vessels, surface trash, marine mammals, and noxious sediment odors. The overall purpose of the survey was to collect data to assess the status of ecosystem condition and potential stressor impacts throughout SBNMS, based on these various indicators and corresponding management thresholds, and to provide this information as a baseline for determining how such conditions may be changing with time. While sample analysis is still ongoing a few preliminary results and observations are reported here. A final report will be completed once all data have been processed. The results are anticipated to be of value in supporting goals of the SBNMS and National Marine Sanctuary Program aimed at the characterization, protection, and management of sanctuary resources (pursuant to the National Marine Sanctuary Reauthorization Act) as well as a new priority of NCCOS and NOAA to apply Ecosystem Based approaches to the Management of coastal resources (EBM) through Integrated Ecosystem Assessments (IEAs) conducted in various coastal regions of the U.S. including the Northeast Atlantic continental shelf. This was a multi-disciplinary partnership effort made possible by scientists from the following organizations:  NOAA, National Ocean Service (NOS), National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Environmental Health and Biomolecular Research (CCEHBR), Charleston, SC.  U.S. Environmental Protection Agency (EPA), National Health and Environmental Effects Research Laboratory (NHEERL), Atlantic Ecology Division (GED), Narragansett, RI.  U.S. Environmental Protection Agency (EPA), National Health and Environmental Effects Research Laboratory (NHEERL), Gulf Ecology Division (GED), Gulf Breeze, FL.  U.S. Geological Survey (USGS), National Wetlands Research Center, Gulf Breeze Project Office, Gulf Breeze, FL.  NOAA, Office of Marine and Aviation Operations (OMAO), NOAA ship Nancy Foster. (31pp) (PDF contains 58 pages)

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This cruise report is a summary of a field survey conducted in coastal-ocean waters off Florida from Anclote Key to West Palm Beach and from approximately 1 nautical mile (nm) offshore seaward to the shelf break (100 m). The survey was conducted May 15 - May 28, 2007 on NOAA Ship NANCY FOSTER Cruise NF-07-08-NCCOS. Multiple indicators of ecological condition were sampled synoptically at each of 50 stations throughout the region including 10 stations within the Florida Keys National Marine Sanctuary (FKNMS) using a random probabilistic sampling design. Samples were collected for the analysis of benthic community structure and composition; concentrations of chemical contaminants (metals, pesticides, PAHs, PCBs, PBDEs) in sediments and target demersal biota; nutrient and chlorophyll levels in the water column; and other basic habitat characteristics such as depth, salinity, temperature, dissolved oxygen, pH, sediment grain size, and organic carbon content. The overall purpose of the survey was to collect data to assess the status of ecological condition in coastal-ocean waters of the region, based on these various indicators, and to provide this information as a baseline for determining how environmental conditions may be changing with time. The results will be of value in helping to broaden our understanding of the status of ecological resources and their controlling factors, including impacts of potential ecosystem stressors, in such strategic coastal areas. (PDF contains 34 pages

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This cruise report is a summary of a field survey conducted in coastal-ocean waters of the Mid-Atlantic Bight from Nags Head, North Carolina to Cape Cod, Massachusetts and from approximately 1 nautical mile (nm) of shore seaward to the shelf break (100 m). The survey was conducted May 12 - May 21, 2006 on NOAA Ship NANCY FOSTER Cruise NF-06-06-NCCOS. Multiple indicators of ecological condition were sampled synoptically at each of 49 stations throughout the region using a random probabilistic sampling design. Samples were collected for the analysis of benthic community structure and composition; concentrations of chemical contaminants (metals, pesticides, PAHs, PCBs, PBDEs) in sediments and target demersal biota; nutrient and chlorophyll levels in the water column; and other basic habitat characteristics such as depth, salinity, temperature, dissolved oxygen, pH, sediment grain size, and organic carbon content. The overall purpose of the survey was to collect data to assess the status of ecological condition in coastal-ocean waters of the region, based on these various indicators, and to provide this information as a baseline for determining how environmental conditions may be changing with time. The results will be of value in helping to broaden our understanding of the status of ecological resources and their controlling factors, including impacts of potential ecosystem stressors, in such strategic coastal areas. (18pp.) (PDF contains 24 pages)

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Summary: The offshore shelf and canyon habitats of the OCNMS (Fig. 1) are areas of high primary productivity and biodiversity that support extensive groundfish fisheries. Recent acoustic surveys conducted in these waters have indicated the presence of hard-bottom substrates believed to harbor unique deep-sea coral and sponge assemblages. Such fauna are often associated with shallow tropical waters, however an increasing number of studies around the world have recorded them in deeper, cold-water habitats in both northern and southern latitudes. These habitats are of tremendous value as sites of recruitment for commercially important fishes. Yet, ironically, studies have shown how the gear used in offshore demersal fishing, as well as other commercial operations on the seafloor, can cause severe physical disturbances to resident benthic fauna. Due to their exposed structure, slow growth and recruitment rates, and long life spans, deep-sea corals and sponges may be especially vulnerable to such disturbances, requiring very long periods to recover. Potential effects of fishing and other commercial operations in such critical habitats, and the need to define appropriate strategies for the protection of these resources, have been identified as a high-priority management issue for the sanctuary. To begin addressing this issue, an initial pilot survey was conducted June 1-12, 2004 at six sites in offshore waters of the OCNMS (Fig. 2, average depths of 147-265 m) to explore for the presence of deep-sea coral/sponge assemblages and to look for evidence of potential anthropogenic impacts in these critical habitats. The survey was conducted on the NOAA Ship McARTHUR-II using the Navy’s Phantom DHD2+2 remotely operated vehicle (ROV), which was equipped with a video camera, lasers, and a manipulator arm for the collection of voucher specimens. At each site, a 0.1-m2 grab sampler also was used to collect samples of sediments for the analysis of macroinfauna (> 1.0 mm), total organic carbon (TOC), grain size, and chemical contaminants. Vertical profiles of salinity, dissolved oxygen (DO), temperature, and pressure were recorded at each site with a small SeaCat conductivity-temperature-depth (CTD) profiler. Niskin bottles attached to the CTD also obtained near-bottom water samples in support of a companion study of microbial indicators of coral health and general ecological condition across these sites. All samples except the sediment-contaminant samples are being analyzed with present project funds. Original cruise plans included a total of 12 candidate stations to investigate (Fig. 3). However, inclement weather and equipment failures restricted the sampling to half of these sites. In spite of the limited sampling, the work completed was sufficient to address key project objectives and included several significant scientific observations. Foremost, the cruise was successful in demonstrating the presence of target deepwater coral species in these waters. Patches of the rare stony coral Lophelia pertusa, more characteristic of deepwater coral/sponge assemblages in the North Atlantic, were observed for the first time in OCNMS at a site in 271 meters of water. A large proportion of these corals consisted of dead and broken skeletal remains, and a broken gorgonian (soft coral) also was observed nearby. The source of these disturbances is not known. However, observations from several sites included evidence of bottom trawl marks in the sediment and derelict fishing gear (long lines). Preliminary results also support the view that these areas are important reservoirs of marine biodiversity and of value as habitat for demersal fishes. For example, onboard examination of 18 bottom-sediment grabs revealed benthic infaunal species representative of 14 different invertebrate phyla. Twenty-eight species of fishes from 11 families, including 11 (possibly 12) species of ommercially important rockfishes, also were identified from ROV video footage. These initial discoveries have sparked considerable interests in follow-up studies to learn more about the spatial extent of these assemblages and magnitude of potential impacts from commercial-fishing and other anthropogenic activities in the area. It is essential to expand our knowledge of these deep-sea communities and their vulnerability to potential environmental risks in order to determine the most appropriate management strategies. The survey was conducted under a partnership between NOAA’s National Centers for Coastal Ocean Science (NCCOS) and National Marine Sanctuary Program (NMSP) and included scientists from NCCOS, OCNMS, and several other west-coast State, academic, private, and tribal research institutions (see Section 4 for a complete listing of participating scientists). (PDF contains 20 pages)

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From May 22 to June 4, 2006, NOAA scientists led a research cruise using the ROPOS Remotely Operated Vehicle (ROV) to conduct a series of dives at targeted sites in the Olympic Coast National Marine Sanctuary (OCNMS) with the goal of documenting deep coral and sponge communities. Dive sites were selected from areas for which OCNMS had side scan sonar data indicating the presence of hard or complex substrate. The team completed 11 dives in sanctuary waters ranging from six to 52 hours in length, at depths ranging from 100 to 650 meters. Transect surveys were completed at 15 pre-selected sites, with additional observations made at five other sites. The survey locations included sites both inside and outside the Essential Fish Habitat (EFH) Conservation Area, known as Olympic 2, established by the Pacific Fishery Management Council, enacted on June 12, 2006. Bottom trawling is prohibited in the Olympic 2 Conservation Area for nontribal fishermen. The Conservation Area covers 159.4 square nautical miles or about 15 percent of the sanctuary. Several species of corals and sponges were documented at 14 of the 15 sites surveyed, at sites both inside and outside the Conservation Area, including numerous gorgonians and the stony corals Lophelia pertusa and Desmophyllum dianthus, as well as small patches of the reef building sponge Farrea occa. The team also documented Lophelia sp. and Desmophyllum sp. coral rubble, dead gorgonians, lost fishing gear, and other anthropogenic debris, supporting concerns over potential risks of environmental disturbances to coral health. (PDF contains 60 pages.)

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Habitat mapping and characterization has been defined as a high-priority management issue for the Olympic Coast National Marine Sanctuary (OCNMS), especially for poorly known deep-sea habitats that may be sensitive to anthropogenic disturbance. As a result, a team of scientists from OCNMS, National Centers for Coastal Ocean Science (NCCOS), and other partnering institutions initiated a series of surveys to assess the distribution of deep-sea coral/sponge assemblages within the sanctuary and to look for evidence of potential anthropogenic impacts in these critical habitats. Initial results indicated that remotely delineating areas of hard bottom substrate through acoustic sensing could be a useful tool to increase the efficiency and success of subsequent ROV-based surveys of the associated deep-sea fauna. Accordingly, side scan sonar surveys were conducted in May 2004, June 2005, and April 2006 aboard the NOAA Ship McArthur II to: (1) obtain additional imagery of the seafloor for broader habitat-mapping coverage of sanctuary waters, and (2) help delineate suitable deep-sea coral/sponge habitat, in areas of both high and low commercial-fishing activities, to serve as sites for surveying-in more detail using an ROV on subsequent cruises. Several regions of the sea floor throughout the OCNMS were surveyed and mosaicked at 1-meter pixel resolution. Imagery from the side scan sonar mapping efforts was integrated with other complementary data from a towed camera sled, ROVs, sedimentary samples, and bathymetry records to describe geological and biological (where possible) aspects of habitat. Using a hierarchical deep-water marine benthic classification scheme (Greene et al. 1999), we created a preliminary map of various habitat polygon features for use in a geographical information system (GIS). This report provides a description of the mapping and groundtruthing efforts as well as results of the image classification procedure for each of the areas surveyed. (PDF contains 60 pages.)