High-current adaptive impedance matching in narrowband power-line communication systems

This paper proposes a high current impedance matching method for narrowband power-line communication (NPLC) systems. The impedance of the power-line channel is time and location variant; therefore, coupling circuitry and the channel are not usually matched. This not only results in poor signal integrity at the receiving end, but also leads to a higher transmission power requirement to secure the communication process. To offset this negative effect, a high-current adaptive impedance circuit to enable impedance matching in power-line networks is reported. The approach taken is to match the channel impedance of N-PLC systems is based on the General Impedance Converter (GIC). In order to achieve high current a special coupler in which the inductive impedance can be altered by adjusting a microcontroller controlled digital resistor is demonstrated. It is shown that the coupler works well with heavy load current in power line networks. It works in both low and high transmitting current modes, a current as high as 760 mA has been obtained. Besides, compared with other adaptive impedance couplers, the advantages include higher matching resolution and a simple control interface. Experimental results are presented to demonstrate the operation of the coupler. © 2011 IEEE.

Single sensor boost converter-based maximum power point tracking algorithms

Two new maximum power point tracking algorithms are presented: the input voltage sensor, and duty ratio maximum power point tracking algorithm (ViSD algorithm); and the output voltage sensor, and duty ratio maximum power point tracking algorithm (VoSD algorithm). The ViSD and VoSD algorithms have the features, characteristics and advantages of the incremental conductance algorithm (INC); but, unlike the incremental conductance algorithm which requires two sensors (the voltage sensor and current sensor), the two algorithms are more desirable because they require only one sensor: the voltage sensor. Moreover, the VoSD technique is less complex; hence, it requires less computational processing. Both the ViSD and the VoSD techniques operate by maximising power at the converter output, instead of the input. The ViSD algorithm uses a voltage sensor placed at the input of a boost converter, while the VoSD algorithm uses a voltage sensor placed at the output of a boost converter. © 2011 IEEE.

On-line learning of mutually orthogonal subspaces for face recognition by image sets.

We address the problem of face recognition by matching image sets. Each set of face images is represented by a subspace (or linear manifold) and recognition is carried out by subspace-to-subspace matching. In this paper, 1) a new discriminative method that maximises orthogonality between subspaces is proposed. The method improves the discrimination power of the subspace angle based face recognition method by maximizing the angles between different classes. 2) We propose a method for on-line updating the discriminative subspaces as a mechanism for continuously improving recognition accuracy. 3) A further enhancement called locally orthogonal subspace method is presented to maximise the orthogonality between competing classes. Experiments using 700 face image sets have shown that the proposed method outperforms relevant prior art and effectively boosts its accuracy by online learning. It is shown that the method for online learning delivers the same solution as the batch computation at far lower computational cost and the locally orthogonal method exhibits improved accuracy. We also demonstrate the merit of the proposed face recognition method on portal scenarios of multiple biometric grand challenge.

Comparing autonomous underwater vehicle (AUV) and vessel-based tracking performance for locating acoustically tagged fish

Autonomous underwater vehicles (AUV’s) are increasingly used to collect physical, chemical, and biological information in the marine environment. Recent efforts include merging AUV technology with acoustic telemetry to provide information on the distribution and movements of marine fish. We compared surface vessel and AUV tracking capabilities under rigorous conditions in coastal waters near Juneau, Alaska. Tracking surveys were conducted with a REMUS 100 AUV equipped with an integrated acoustic receiver and hydrophone. The AUV was programmed to navigate along predetermined routes to detect both reference transmitters at 20–500 m depths and tagged fish and crabs in situ. Comparable boat surveys were also conducted. Transmitter depth had a major impact on tracking performance. The AUV was equally effective or better than the boat at detecting reference transmitters in shallow water, and significantly better for transmitters at deeper depths. Similar results were observed for tagged animals. Red king crab, Paralithodes camtschaticus, at moderate depths were recorded by both tracking methods, while only the AUV detected Sablefish, Anoplopoma fimbria, at depths exceeding 500 m. Strong currents and deep depths caused problems with AUV navigation, position estimation, and operational performance, but reflect problems encountered by other AUV applications that will likely diminish with future advances, enhanced methods, and increased use.

A pilot study to determine the movements of buoy line used in the crab pot fishery to assess bottlenose dolphin entanglement

A pilot study on the characteristics of crab pot buoy line movements to assess bottlenose dolphin entanglement was conducted from 19 September to 30 September 2005 in the Charleston Harbor, Charleston, South Carolina. The objectives of this study were to determine: 1) the movements of the buoy line in the water at various tidal stages, current strengths, lengths of line, and water depth, 2) if lead-core rope was a better alternative to nylon rope, 3) and if the manner of deployment of the gear affected the suspension of the line in the water and on the bottom. Diamond braided nylon (#10) rope of varying length (20 ft. – 80 ft.) were used during 31 trials and stiffened (polypropylene lead-core) rope was used in four trials. Observations of the buoy line movements were captured with an Atlantis underwater camera attached to a Digital DPC-1000 video recorder. Results from this study showed that: 1) the method used for deployment was important in keeping the buoy line from arcing or coiling, 2) little to no arcing occurred in water current velocities of >0.20 m/s, 3) rope lengths of ≥50 ft. deployed in <10 ft. of water produced waving in the water column and arcing on the bottom, 4) slack tide was a period of increased risk of entanglement for bottlenose dolphins, and 5) poly lead-core rope was not a good alternative to nylon rope unless in deep water with strong water current velocities. This pilot study produced questions that can be used for future studies on the characteristics of buoy line movements in the crab pot fishery as it relates to bottlenose dolphin entanglements.

Acoustic tracking of reef fishes to elucidate habitat utilization patterns and residence times inside and outside marine protected areas around the island of St. John, USVI

This technical memorandum describes a developing project under the direction of NOAA’s Biogeography Branch in consultation with the National Park Service and US Geological Survey to understand and quantify spatial patterns and habitat affinities of reef fishes in the US Virgin Islands. The purpose of this report is to describe and disseminate the initial results from the project and to share information on the location of acoustic receivers and species electronic tag ID codes. The Virgin Islands Coral Reef National Monument (VICRNM), adjacent to Virgin Islands National Park (VIIS), was established by Executive Order in 2000, but resources within the monument are poorly documented and the degree of connectivity to VIIS is unknown. Whereas, VICRNM was established with full protection from resource exploitation, VIIS has incurred resource harvest by fishers since 1956 as allowed in its enabling legislation. Large changes in local reef communities have occurred over the past several decades, in part due to overexploitation. In order to better understand the habitat utilization patterns and movement of fishes among management regimes and areas open to fishing around St, John, an array of hydroacoustic receivers was deployed while a variety of reef fish species were acoustically tagged. In July 2006, nine receivers with a detection range of ca. 350 m were deployed in Lameshur Bay on the south shore of St. John, within VIIS. Receivers were located adjacent to reefs and in seagrass beds, inshore and offshore of these reefs. It was found that lane snappers and bluestriped grunts showed diel movement from reef habitats during daytime hours to offshore seagrass bed at night. Timing of migrations was highly predictable and coincided with changes in sunrise and sunset over the course of the year. Fish associated with reefs that did not have adjacent seagrass beds made more extensive movements than those fishes associated with reefs that had adjacent seagrass habitats. In April 2007, 21 additional receivers were deployed along much of the south shore of St. John (ca. 20 km of shoreline). This current array will address broader-scale movement among management units and examine the potential benefits of the VICRNM to provide adult “spillover” into VIIS and adjacent harvested areas. The results from this work will aid in defining fine to moderate spatial scales of reef fish habitat affinities and in designing and evaluating marine protected areas.

Preliminary results from the Caribbean Acoustic Tracking Network (CATn): a data sharing partnership for acoustic tracking and movement ecology of marine animals in the Caribbean Sea

We have recently exchanged and integrated into a single database tag detections for conch, teleost and elasmobranch fish from four separately maintained arrays in the U.S. Virgin Islands including the NMFS queen conch array (St. John nearshore), NOAA’s Biogeography Branch array (St. John nearshore & midshelf reef); UVI shelf edge arrays (Marine Conservation District, Grammanik & other shelf edge); NOAA NMFS Apex Predator array COASTSPAN (St. John nearshore). The integrated database has over 7.5 million hits. Data is shared only with consent of partners and full acknowledgements. Thus, the summary of integrated data here uses data from NOAA and UVI arrays under a cooperative agreement. The benefits of combining and sharing data have included increasing the total area of detection resulting in an understanding of broader scale connectivity than would have been possible with a single array. Partnering has also been cost-effectiveness through sharing of field work, staff time and equipment and exchanges of knowledge and experience across the network. Use of multiple arrays has also helped in optimizing the design of arrays when additional receivers are deployed. The combined arrays have made the USVI network one of the most extensive acoustic arrays in the world with a total of 150+ receivers available, although not necessarily all deployed at all times. Currently, two UVI graduate student projects are using acoustic array data.

Small-boat surveys for coastal dolphins: line-transect surveys of Hector’s dolphins (Cephalorhynchus hectori)

Management of coastal species of small cetaceans is often impeded by a lack of robust estimates of their abundance. In the Austral summers of 1997−98, 1998−99, and 1999−2000 we conducted line-transect surveys of Hector’s dolphin (Cephalorhynchus hectori) abundance off the north, east, and south coasts of the South Island of New Zealand. Survey methods were modified for the use of a 15-m sailing catamaran, which was equipped with a collapsible sighting platform giving observers an eye-height of 6 m. Eighty-six percent of 2061 km of survey effort was allocated to inshore waters (4 nautical miles [nmi] or 7.4 km from shore), and the remainder to offshore waters (4−10 nmi or 7.4–18.5 km from shore). Transects were placed at 45° to the shore and spaced apart by 1, 2, 4, or 8 nmi according to pre-existing data on dolphin density. Survey effort within strata was uniform. Detection functions for sheltered waters and open coasts were fitted separately for each survey. The effect of attraction of dolphins to the survey vessel and the fraction of dolphins missed on the trackline were assessed with simultaneous boat and helicopter surveys in January 1999. Hector’s dolphin abundance in the coastal zone to 4 nmi offshore was calculated at 1880 individuals (CV=15.7%, log-normal 95% CI=1384−2554). These surveys are the first line-transect surveys for cetaceans in New Zealand’s coastal waters.

The effect of intensive line fishing on the virgin biomass of a tropical deepwater snapper, the crimson jobfish (Pristipomoides filamentosus)

An intensive commercial hook-and-line fishing operation targeted the demersal fisheries resources at Saya de Malha Bank in the Southwest Indian Ocean. Fishing was conducted with 12 dories that were equipped with echo sounders and electric fishing reels and supported by a refrigerated mothership. Over a 13-day period in the 55–130 m depth range, a total of 74.3 metric tons (t) of fish were caught, of which the crimson jobfish (Pristipomoides filamentosus) represented 80%. Catch rates decreased with time and could not be attributed to changes in location, climatic conditions, fishing depth, fishing method, or bait type. The initial virgin biomass of P. filamentosus available to a line fishery at the North Western promontory of Saya de Malha Bank was estimated at 72.6 t through application of the Leslie model to daily catch and effort data. Biomass densities of 2364 kg/km2 and 1206 kg/km were obtained by applying the initial biomass estimates to the surface area and to the length of the dropoff that was fished. The potential sustainable yield prior to exploitation was estimated at 567 kg/km2 per year. The quantity of P. filamentosus caught by the mother-ship-dory fishing operation represented 82% of the initial biomass available to a hook-and-line fishery, equivalent to more that three times the estimated maximum sustainable yield. The results of the study are important to fisheries managers because they demonstrate that intensive line fishing operations have the potential to rapidly deplete demersal fisheries resources.