Until recently the determination of concentration from acoustic backscatter intensity measurements required an iterative technique due to the implicit form of the acoustic backscatter equation. In this paper, an explicit form of this equation is examined in an effort to simplify the technique of determining size from multifrequency acoustic backscatter data. By retaining the size dependence throughout the derivation for an explicit solution for concentration, a new explicit form results. This new explicit concentration solution improves the technique for determining median sediment size by incorporating sediment attenuation in the calculation. Because this new technique relies on the minimization of the variance in concentration as determined by different frequency transducers, the previous technique of pairing transducers of different frequencies is replaced by a technique making use of any number of different frequency transducers. The new size/concentration inversion technique is tested using both simulated and laboratory data. Numerical precision is shown to be the only source of error with the use of simulated data. Laboratory tests result in less than 20% error in the determination of both concentration and size over a range of nearly one meter.
Ecosystem-Based Management (EBM) requires marine monitoring in real time with high temporal frequency and high spatial density. It also requires sensors that can provide direct measurements of biological processes and the means to track water movement and evaluate water quality. These requirements can not realistically be met using huge amalgamations of the independent instruments traditionally used for marine monitoring. To do so would result in marine observatories that are prohibitively expensive, unnecessarily obtrusive, inefficient in power use, difficult to deploy and maintain, with sensors inappropriate for extended deployment and with an excessive level of redundant components. The Ocean Research & Conservation Association (ORCA), in an effort to better meet the need for marine monitoring, has designed and is testing the ORCA Kilroy Network, an observatory designed as a whole system down to the sensors at the component level. The ORCA Network consists of a wireless network of remote semiautonomous marine sensor systems created by ORCA, and a central supervisory system that directs operations of the remote systems, collects data, and relays that via the Internet through a standard SOAP web service interface to a geospatial database. The network design is based on that of industrial control systems, where a central computer coordinates remote and mostly autonomous systems using Modbus, a mature, open-standard, fieldbus protocol. In this case, the coordination and data transfer are over GSM cellular Internet connections on a wide scale and cabled RS-485 connections at the station scale.To date, four remote subsystems of the ORCA Kilroy network are in use. Each is designed to take advantage of a shared power and communications infrastructure, and is integrated at the component level to lower cost, reduce size, and improve efficiency. Mass produced off-the-shelf parts have been selected over custom machined parts where possible. Power for an entire sensor station is shared, and to date, has been provided by a solar charged battery. First, the wireless and cabled communications are bridged by a device dubbed the ORCA Kilroy Voice (KV), which includes a GPS for position and UTC synchronization and acts as a GPRS Internet gateway to a sensor string -a shared serial communications and power line on which smart sensor systems can be daisy chained. Second, ORCA developed for use on that string a battery-operated sensor suite called ORCA Kilroy that from basic measurements, determines flow speed, flow direction, speed of sound, package orientation, turbidity, conductivity, temperature, water level, wave height, and wave period. Measurements are sent out upon request from the central supervisor through Modbus and are logged locally to nonvolatile memory to ensure no data is lost in the event of a power or communication outage. Third is the ORCA Kilroy I/O (KIO) -an adaptor providing serial access to the ORCA Network for instruments from other manufacturers. A forth system, also designed for sensor string operation, is...
Bioluminescent intensities were measured August 30 th -September 4 th , 2004 in the Gulf of Maine with the HIDEX III Bathyphotometer. Empirical Orthogonal Function (EOF) analysis and Complex Empirical OrthogonalFunction (CEOF) analysis were applied to these data sets in order to determine a unique excitation response for each species of bioluminescent organism encountered in the data sets. Using the results of the analysis, a filter was designed for real-time identification of dinoflagellates.
Absmocf-This project explores the design and construction of a water ware generation facility, compteted at a very low cost.For less than $US 800, an embedded control system guiding a piston-type wavemaker in a small laboratory wave channel was designed and constructed. Wave generation presently relies on a PID position control algorithm, backed by linear wavemaker theory and paddle position feedback. Results show that the system closely tracked expected positions and velocities, but algorithm modifications to improve temporal response are needed to improve high-frequency performance. Finally, all of the necessary hardware components required for future integration of simultaneous active wave absorption have been included in the design.
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