Engineering topics
Publications and source records attributed to Davis, G..
The author has identified the following significant results. Imagery from LANDSAT 1 and 2 was analyzed to determine the location, type, and extent of fronts and boundaries in Delaware Bay as a function of tidal conditions. This information is being used to set up a subroutine for an oil slick movement prediction model.
The author has identified the following significant results. The spectral signature of the acid waste disposal plume investigated 38 miles off the Delaware coast, is caused primarily by scattering from particles in the form of suspended ferric iron floc. In comparison, the absorption caused by the dissolved fraction of iron and other substances has a negligible effect on the spectral signature. Ocean waste disposal plumes were observed by LANDSAT-1 and -2 during dump up to 54 hours afer dump during fourteen different passes over the Delaware test site. The spatial resolution, radiometric sensitivity, and spectral band location of the LANDSAT multispectral scanner are sufficient to identify the location of ocean disposal plumes. The movement and dispersion of ocean waste disposal plumes can be estimated if the original dump location, time, and injection method are known. Operating LANDSAT in the high gain mode helps to determine plume dispersion more accurately.
The author has identified the following significant results. Remote sensing from satellites and aircraft was combined with ground truth collected from ships in an attempt to classify coastal and estuarine water types by their spectral reflectance signatures. During ocean waste disposal operations 40 miles off the Delaware coast, water samples were collected and spectroradiometric measurements conducted in the field to provide ground truth for aircraft and LANDSAT overpasses with multispectral scanners.
The author has identified the following significant results. LANDSAT, aircraft, and boats were used successfully to study estuarine and coastal fronts or boundaries. Horizontal salinity gradients of 4% in one meter and convergence velocities of the order of 0.1 m/sec were observed. Visibility improved from one meter to two meters as certain boundaries were crossed. Fronts near the mouth of the bay are associated with the tidal exchange with shelf water. By capturing and holding oil slicks, these frontal systems also significantly influence the movement and dispersion of oil slicks in Delaware Bay. Recent oil slick tracking experiments conducted to verify a predictive oil dispersion and movement model have shown that during certain parts of the tidal cycle the oil slicks tend to line up along boundaries.
The author has identified the following significant results. LANDSAT, aircraft, ships, and air-dropped current drogues were deployed to determine current circulation and to track oil slick movement on four different dates in Delaware Bay. The results were used to verify a predictive model for oil slicks given their size, location, tidal stage (current), weather (wind), and nature of crude. Both LANDSAT satellites provided valuable data on gross circulation patterns and convergent coastal fronts which by capturing oil slicks significantly influence their movement and dispersion.
The author has identified the following significant results. Acid waste plume was observed in LANDSAT imagery fourteen times ranging from during dump up to 54 hours after dump. Circulation processes at the waste disposal site are highly storm-dominated, with the majority of the water transport occurring during strong northeasterlies. There is a mean flow to the south along shore. This appears to be due to the fact that northeasterly winds produce stronger currents than those driven by southeasterly winds and by the thermohaline circulation. During the warm months (May through October), the ocean at the dump site stratifies with a distinct thermocline observed during all summer cruising at depths ranging from 10 to 21 m. During stratified conditions, the near-bottom currents were small. Surface currents responded to wind conditions resulting in rapid movement of surface drogues on windy days. Mid-depth drogues showed an intermediate behavior, moving more rapidly as wind velocities increased.
The mounting economic pressure to extract oil and other resources from the Continental Shelf and to continue using the Shelf for waste disposal is creating a need for cost-effective synoptic means of determining currents in this area. An integrated satellite-aircraft-drogue approach has been developed which employs remotely tracked expendable drogues together with satellite and aircraft observations of waste plumes and tracers, such as dyes or suspended sediment. Tests conducted on the Continental Shelf and in Delaware Bay indicate that the system provides a cost-effective means of studying current circulation, oil slick movement, and ocean waste dispersion even under severe environmental conditions.
The author has identified the following significant results. An inexpensive, integrated drogue-aircraft-satellite approach was developed which is based on the Lagrangian technique and employs remotely tracked drogues and dyes together with satellite observation of natural tracers, such as suspended sediment. Results include current circulation studies in Delaware Bay in support of an oil slick movement model; investigations of the dispersion and movement of acid wastes dumped 40 miles off the Delaware coast; and coastal current circulation. In each case, the integrated drogue-aircraft-satellite approach compares favorably with other techniques on the basis of accuracy, cost effectiveness, and performance under severe weather conditions.
The author has identified the following significant results. An ocean current drogue system was developed for use in the coastal zone and continental shelf region. The method features an extremely simple radiosonde device whose position is determined from a pair of cooperative shore stations. These ocean sondes follow the tradition of the atmospheric radiosonde in that they are economically disposable at the end of their mission. The system was successfully tested in a number of environments, including the North Atlantic in two winter coastal storms. Tracking to the edge of the Baltimore and Wilmington trenches was achieved. The drogue system is being used in conjunction with remote sensing aircraft and satellites to chart current circulation at ocean waste disposal sites 40 miles off Delaware's coast.
The author has identified the following significant results. LANDSAT, aircraft, and boats were used successfully to study estuarine and coastal fronts or boundaries. Fronts are a major hydrographic feature in Delaware Bay and in other estuaries. Horizontal salinity gradients of 4% in one meter and convergence velocities of the order of 0.1 m/sec were observed. Visibility improved from one meter to two meters as certain boundaries were crossed. Fronts near the mouth of the bay are associated with the tidal exchange with shelf water. The formation of fronts in the interior of the bay appears to be associated with velocity shears induced by differences in bottom topography with horizontal density difference in the deep water portion of the estuary. Surface slicks and foam collected at frontal convergence zones near boundaries were found to contain concentrations of Cr, Cu, Fe, Hg, Pb, and Zn higher by two to four orders of magnitude than concentrations in mean ocean water.
The author has identified the following significant results. The duPont waste disposal plume was observed in 12 NASA/LANDSAT satellite images during dump up to 54 hours after dump. The circulation processes at the acid waste disposal site are highly event-dominated, with the majority of the water transport occurring strong northeasters. There is a mean flow to the south alongshore. During the warm months, the ocean stratifies with warm water over cold water. During stratified conditions, the near-bottom drogues showed very little movement. LANDSAT, aircraft, and boats were used successfully to study estuarine and coastal fronts or boundaries. By capturing and holding oil slicks, frontal systems significantly influence the movement and dispersion of oil slicks in Delaware Bay. Recent oil slick tracking experiments conducted to verify a predictive oil dispersion and movement model have shown that during certain parts of the tidal cycle the oil slicks tend to line up along boundaries.
The author has identified the following significant results. LANDSAT, aircraft, ships, and air-dropped current drogues were deployed to determine current circulation and to track oil slick movement on four different dates in Delaware Bay. Results were used to verify a predictive model for oil slick movement and dispersion. The model predicts the behavior of oil slicks given their size, location, tidal stage (current), weather (wind), and nature of crude. Both LANDSAT satellites provided valuable data on gross circulation patterns and convergent coastal fronts which by capturing oil slicks significantly influence their movement and dispersion.
The author has identified the following significant results. Circulation processes at the acid waste disposal site are highly event-dominated, with the majority of the water transport occurring during strong northeasters. There is a mean flow to the south alongshore. This appears to be due to the fact that northeasterly winds produce stronger currents than those driven by southeasterly winds and by the thermohaline circulation. During the warm months, the ocean stratifies with warm water over cold water. A distinct thermocline was observed with expendable bathythermographs during all summer cruises at depths ranging from 10 to 21 meters. During stratified conditions, the near-bottom drogues showed very little movements. The duPont waste plume was observed in LANDSAT satellite imagery during dump up to 54 hours after dump.
The author has identified the following significant results. Satellites, such as ERTS-1, can be used to obtain a synoptic view of current circulation over large coastal areas. Since in turbid coastal regions suspended sediment acts as a natural tracer, cost is minimized by eliminating the need for expensive injections of large volumes of dye such as Rhodamine-B. One of the principal shortcomings of satellite imaging of coastal currents was its inability to determine current magnitude and to penetrate beyond the upper few meters of the water column. These objections were overcome by complementing satellite observations with drogues tracking currents at various selected depths. By combining the satellite's wide coverage with aircraft or shore stations capable of tracking expendable drogues, a cost effective, integrated system was devised for monitoring currents over large areas, various depths, and under severe environmental conditions.
The author has identified the following significant results. About forty miles off the Delaware coast is located the disposal site for waste discharged from a plant processing titanium dioxide. The discharge is a greenish-brown; 15-20% acid liquid which consists primarily of iron chlorides and sulfates. The barge which transports this waste has a 1,000,000 gallon capacity and makes approximately three trips to the disposal site per week. ERTS-1 MSS digital tapes are being used to study the dispersion patterns and drift velocities of the iron-acid plume. Careful examination of ERTS-1 imagery disclosed a fishhook-shaped plume about 40 miles east of Cape Henlopen caused by a barge disposing acid wastes. The plume shows up more strongly in the green band than in the red band. Since some acids have a strong green component during dumping and turn slowly more brownish-reddish with age, the ratio of radiance signatures between the green and red bands may give an indication of how long before the satellite overpass the acid was dumped. Enlarged enhancements of the acid waste plumes, prepared from the ERTS-1 MSS digital tapes aided considerably in studies of the dispersion of the waste plume. Currently acid dumps are being coordinated with ERTS-1 overpasses.
The author has identified the following significant results. For two years ERTS-1 has been employed to investigate current circulation patterns in Delaware Bay under different tidal, flow, and wind conditions. Since sufficient numbers of current meters and boats are not available, air-droppable drogues and dye packs have been developed and tested. The drogues consist of a styrofoam float and a line to which is attached a stainless steel biplane. The length of the line determines at what depth currents will be monitored. The floats are color coded to distinguish their movement and mark the depth of the biplanes. Simultaneously floating and anchored dye packs of fluorescein dye have been deployed from aircraft. The movement of the dye and drogues is tracked by sequential aerial photography, using fixed markers on shore or on buoys as reference points to calibrate the scale and direction of drogue movement. The current data obtained by this technique is then used to annotate current circulation maps derived from ERTS-1 imagery.
The author has identified the following significant results. In order to interpret and annotate current circulation and suspended sediment concentration maps derived from ERTS-1 digital tapes, the University of Delaware has been collecting water samples and other data from boats and helicopters. In order to increase the number of samples at the exact time of the ERTS-1 pass over Delaware Bay, pleasure craft were organized to obtain samples of the entire test site. On the ERTS-1 pass of July second, scientists were stationed at three public boat launches along the Bay to hand out sampling packets to interested boaters. The packets contained two litre sampling bottles, a map, data card, and a pen. The boaters were asked to fill the two bottles between 11 and 11:15 a.m., mark their location on the map, and fill out the data card. Forty-nine packets were handed out of which 40 were returned (82%). Only four of the 40 were not in the alloted time range. This gave 36 real time data points covering approximately 30 nautical miles. The samples are being analyzed for sediment concentration, particle size, and salinity. Participating boaters will receive a copy of an ERTS image of the Delaware Bay and a summary report of the project. Because of the success of the project, future use of pleasure boaters is being planned.
Probabilistic mathematical click model for optimal click suppressing frequency modulated noise thresholds