Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 61-63). Also available via the Internet.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 105-107). Also available via the Internet.

Thesis (M.S.)--Brigham Young University. Dept. of Electrical and Computer Engineering, 2004. / Includes bibliographical references (p. 51-52).

Thesis (Ph. D.)--University of Oregon, 1999. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 129-135). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948026.

Thesis (MEng) -- University of South Australia, 1994

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 45-47). Also available via the Internet.

A noncontact two-color pyrometer, which uses an infrared (IR) transmitting rod and IR lenses to optically measure the temperature of a molten particle as it falls in an evacuated drop tube, has been designed and tested in the laboratory and in the field. The design uses a calcium fluoride (CaF₂) rod which transports optical energy radiated from the molten particle to a beam splitter, where it is split into two signals. Each signal is filtered and focused onto an indium antimonide (InSb) photodetector which is liquid nitrogen (LN₂) cooled. A ratio of the detectors' outputs indicates the temperature of the molten particle. In the laboratory, a blackbody calibrator is used as a source, and a shutter with a speed of 4 ms is used to simulate the particle dropping by the optical sensing port. The pyrometer has been calibrated for a particle temperature range of 650°C - 1200°C. / Master of Science

A new method of remote thermometry utilizing the temperature dependent optical properties of thermographic phosphors was evaluated for use in measuring high-pressure turbine blade metal temperatures in an operating turbofan engine test rig. Thermographic phosphors, ceramics doped with a rare earth metal, were bonded to the turbine blades. These phosphors exhibit fluorescence when optically excited by a laser, and both the intensity and the rate of decay of the fluorescence are temperature dependent An optical fiber probe was used to carry the excitation laser light to the blade surface, and to receive the resulting fluorescence. The blades rotated at speeds up to 30,000 rpm. Synchronization was achieved by a digital pattern recognition circuit, capable of locating a specific blade with each revolution. The investigation concentrated on thennographic phosphor characteristics, phosphor binding methods, and probe optical efficiency. Although poor performance of the selected phosphor binding methods impeded the location of the fluorescence signal in the operating gas turbine engine, many operating characteristics of the technique were determined, and the new measurement technique was established as a promising candidate for further research in the temperature measurement of rotating surfaces inside a turbine engine. / Master of Science

A liquid core fiber sensor can be used to sense both strain and temperature simultaneously. This liquid core fiber sensor is comprised of a hollow core optical fiber filled with a liquid of a known index of refraction which is slightly higher than that of the silica tube which acts as the cladding. The refractive index fluid is chosen such that the variation of its refractive index with strain and temperature is well defined and linear in the desired range of operation. The core of the sensing fiber contains a fluid which has a thermo-optic coefficient much larger in magnitude (-4.0x10⁻⁴/°C) than that of the silica cladding. This causes the fiber to be more sensitive to temperature changes than all-silica fibers. Both transmitted optical signal intensity and time-of-flight depend strongly on applied strain and temperature. Furthermore, the relative difference between the core and cladding refractive indices changes as a function of both parameters due to the inherently different material types used in the fiber construction. This results in critical strain and temperature regimes within which the refractive index difference is very small, and sensitivity is optimized. Testing of prototype sensors demonstrates these characteristics. A 0.47 m long liquid core fiber containing a liquid with a room temperature refractive index of 1.492 was analyzed. Both time- and intensity-domain behaviors around the device's critical temperature (95°C) confirm theoretical expectations. Simultaneous strain and temperature measurements were performed between 95 °C and 105 °C. Methods for multiplexing liquid core fibers for increasing the range of temperatures that can be monitored were also investigated as well as using those liquid core fibers for cooling purposes. / Master of Science

Polymer electrolyte membrane (PEM) fuel cells are being studied for use as high efficiency power plants in alternative fuel vehicles. To maintain high efficiency the operating temperatures of the membranes in these fuel cells must be closely monitored and controlled. However, the environment inside of the fuel cell is not favorable for traditional temperature sensing, so a new optical-fiber-based, distributed temperature sensor was proposed to address this need. This thesis investigates the properties of neodymium-doped optical fiber for use as a distributed temperature sensor for PEM fuel cells. The optical absorption spectrum was measured to identify the energy band structure and determine upconversion excitation schemes. The temperature coefficient of the Nd³⁺-doped silica fiber fluorescence decay time was measured for several bands of emission. Finally, two-photon upconversion was attempted from the lower excited states of Nd:YAG and Nd:silica. / Graduation date: 2012