Publications

Our research plan is two-fold: first, we have extended our biological model of bottom-up visual attention with several recently characterized cortical interactions that are known to be responsible for human performance in certain visual tasks, and second, we have used an eyetracking system for collecting human eye movement data, from which we can calibrate the new additions to the model. We acquired an infrared video eyetracking system, which we are using to record observers' eye position with high temporal (120Hz) and spatial ({+-} 0.25 deg visual angle) accuracy. We collected eye movement scan paths from observers as they view computer-generated fractals, rural and urban outdoor scenes, and overhead satellite imagery. We found that, with very high statistical significance (10 to 12 z-scores), the saliency model accurately predicts locations that human observers will find interesting. We adopted our model of short-range interactions among overlapping spatial orientation channels to better predict bottom-up stimulus-driven attention in humans. This enhanced model is even more accurate in its predictions of human observers' eye movements. We are currently incorporating biologically plausible long-range interactions among orientation channels, which will aid in the detection of elongated contours such as rivers, roads, airstrips, and other man-made structures.

Abstract not provided.

This report provides a summary of the LDRD project titled: An Electromagnetic Imaging System for Environmental Site Reconnaissance. The major initial challenge of this LDRD was to develop a ground penetrating radar (GPR) whose peak and average radiated power surpassed that of any other in existence. Goals were set to use such a system to detect the following: (1) disrupted soil layers where there is potential for buried waste, (2) buried objects such as 55-gallon drums at depths up to 3 m, and (3) detecting contaminated soil. Initial modeling of the problem suggested that for soil conditions similar to Puerto Rican clay loam, moisture content 10 percent (conductivity = 0.01 mhos at 350 MHz), a buried 55-gallon drum could be detected in a straightforward manner by an UWB GPR system at a depth of 3 meters. From the simulations, the highest attenuation ({minus}50 dB) was the result of scattering from a 3-m deep vertically orientated drum. A system loss of {minus}100 dB is a typical limit for all kinds of radar systems (either direct time-domain or swept frequency). The modeling work also determined that the waveshape of the pulse scattered off the buried drum would be relatively insensitive to drum orientation, and thus easier to detect with the GPR system.

Abstract not provided.