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An ultrasonic method to determine bladder volumes could help eliminate some of the risk and discomfort resulting from catheterizations. A system using "A" mode ultra-sound correctly estimates bladder volumes to within 50 cc's. Near and far walls of bladder sections found at various positions define the bladder, and volumes calculated from these sections are added together for a bladder volume estimate. Accurate volume estimates (mean error of -1.9 cc.'s with standard deviation of 28 cc.'s) were obtained when bladder section characteristics such as: depth of the near wall of the bladder, thickness of the far wall echo, distance between near and far bladder walls, and amplitude of the far bladder wall echo, were considered. Most bladders were completely scanned with the transducer placed at the bodies midline, approximately 5 to 7.5 cm. above the pubic bone.

A versatile solar spectroradiometer has been designed which is capable of measuring direct solar radiation, the solar aureole, and sky radiance far from the sun. An active tracker consisting of a quadrant detector, telescope and stepper-motor driven alt-azimuth mount is used to position the spectroradiometer by computer control for solar tracking and almucantur scans. An internally baffled telescope designed to suppress stray light is employed as the optical receiver, and a photodiode serves to convert the collected flux to an electrical signal. A digitally controlled gain-switching transimpedance amplifier is used to scale the photodiode output to accommodate the large signal range encountered between measuring direct solar radiation and sky radiance well away from the sun. Example measurements are presented which demonstrate the system's capabilities.

In this thesis we determine the electromagnetic fields of a current distribution located, in free space, above a perfectly conducting plane earth. Then we consider the inverse problem of determining the source distribution from the fields. Formulae are obtained for the volume integral (dipole moment) of the current density of a small current source in terms of the fields and known functions. If field data are measured (from lightning over sea water for example) the dipole moment of the current density producing the fields may be found. The validity of the small source approximation used in this work is also established. Finally, a method is developed for determining the average current at points on a vertical line current source, a common model for a lightning return stroke. We treat the source as a string of dipoles and apply a method of constrained inversion.

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