No description available.

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No description available.

A covariant form of Hamilton's Principle of Stationary Action is formulated and used to solve the general eiconal equation describing the wave function of light in a medium carrying ultrasound. Tensor notation is reviewed and the tensor form of Maxwell's equations is developed. Boundary equation that the field quantities must satisfy in order for the variation of Hamilton's action integral to be stationary are determined and used to form the generalized eiconal equation of geometrical optics. The rays are introduced and through a canonical transformation the eiconal for the diffracted medium is solved and plotted.

Ultrasonic transducers with concentric annular ring electrodes can be used to generate various circularly symmetric acoustic field profiles. These transducers can also electronically simulate a circular phased array and generate a focused ultrasonic beam. A model which predicts the acoustic transducer output for a given scaled voltage input has been developed. Several transducers have been designed using this model. Special attention has been given to the unique case of the two-dimensional radially Gaussian amplitude profile. Fabrication techniques for these transducers have been developed and are discussed. A microprocessor-based data acquisition system is described which will characterize the two-dimensional transducer profile as well as the propagation profile along one radial axis. Example tests of some of these transducers are presented. / M.S.

Ultrasonic humidifier use is a potential source of human exposure to inhalable particulates. This paper focused on the behavior of insoluble iron oxides particles, and aluminum oxide particles in ultrasonic humidifiers. 10 mg/L Fe oxide particles and 5 mg/L Al oxide suspension solutions were added into tap water, as fill water for ultrasonic humidifiers operated for 14 hours. Denser, heavier particles of approximate 1.5 um diameter of iron or aluminum oxides accumulated in the humidifier reservoir. Smaller, suspended metal oxide particles of 0.22-0.57 um diameter were emitted as aerosols from humidifiers. Soluble anions and cations in tap water were present in the aerosols emitted from humidifiers. The results indicate that if suspended particles and dissolved minerals are present in source water, they will be transported in aerosolized waters. / M. S. / Ultrasonic humidifiers are used widely globally. However, they may cause adverse human health effects, such as respiratory damage, and even deaths. Previous work focused on the effect of soluble constituents in the fill water on the emissions of aerosols. This paper demonstrated the fate and transport of insoluble mineral particles in the ultrasonic humidifiers. The particles used were iron oxides particles powder (micro iron oxide, and nano iron oxide), and aluminum oxide particles in suspension (nano size), which have different mean particle sizes. Results showed only very small portion of iron oxides particles transported into the aerosols, and a relatively much bigger portion of aluminum oxide particles transported into the aerosols, which may be contributed by their differences in density and form. In conclusion, denser and heavier particles settled to the bottom of the humidifiers, while smaller and suspended particles were emitted in the aerosols.

Infants and young children with tracheostomies need better respiratory monitors. Mucus in the tracheostomy tube presents a serious choking hazard.  Current devices indirectly detect respiration, often yielding false or delayed alarms.  A compact ultrasonic time-of-flight (TOF) airflow sensor capable of attaching directly to the tracheostomy tube has been developed to address this need.  The ultrasonic flow sensing principle, also known as transit time ultrasound, is a robust method that correlates the timing of acoustic signals to velocity measurement.  The compact prototype developed here can non-invasively measure all airflow into and out of a patient, so that breath interruption can easily be detected. This paper concerns technical design of the sensor, including the transducers, analog/digital electronics, and embedded systems hardware/software integration.   Inside the sensor's flow chamber, two piezoelectric transducers sequentially transmit and receive ping-like acoustic pulses propagating upstream and downstream of flow.  A microcontroller orchestrates measurement cycles, which consist of the transmission, reception, and signal processing of each acoustic pulse.  The velocity and direction of airflow influence transit time of the acoustic signals.  Combining TOF measurements with the known geometry of the flow chamber, average air velocity and volumetric flow rate can be calculated.  These principles have all been demonstrated successfully by the prototype sensor developed in this research. / Master of Science

no abstract provided by author / Master of Science

no abstracts provided by author / Ph. D.