Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xvii, 169 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 147-155).

Thesis (Ph.D.) -- McMaster University, 2001. / Includes bibliographical references (leaves 136-143). Also available via World Wide Web.

M.Ing. / The aim of Spoornet is to provide a minimise predictable service. In order to provide a predictable service, it is necessary to move trains safely and effectively from the place of departure to their destination. The keywords here are safely and effectively. Although support functions such as infrastructure and train control procedures are vital in moving the train, the train or rolling stock as it is generally known, warrants some attention. Defects on the rolling stock are very costly to Spoornet. This is mainly due to the fact that a defect on the rolling stock that goes undetected can cause damage to the rolling stock and the infrastructure. This damage can eventually lead to derailments. Considering that a derailment can cost Spoornet millions of rand and cause delays to the services, it is only logical to spend time preventing derailments. It is for this reason that a workgroup was formed to investigate and solve the problem of defects causing derailments and delays by developing an early warning system. The need for an integrated train condition monitoring system became apparent when considering an early warning system. The objectives of the integrated train condition monitoring system are to provide train condition information to different users, and alarms on detection of emergency or dangerous conditions. Various train defects that may cause damage or derailments were identified. One of them being a flat wheel on a rail vehicle. A flat wheel is characterised by the flattening of the wheel on one or more positions on its circumference, so that the wheel does not have an even and completely round profile. Flat wheels are mostly caused by the wheels of a vehicle becoming locked during braking, and sliding along the rail track. The friction created by this action grinds a flat spot on the wheel. The flat wheel leads to a decline in the riding quality of the rolling stock and a rise in the levels of vibration and noise is evident. But more importantly, the flat spot causes the wheel to roll unevenly, creating impacts on the rail on some points. It is these impacts that can cause damage to the rail and the rolling stock. Depending on the length of the flat spot, the vehicle type and speed, the stresses may be sufficient to cause final failure of the rail or initiate fatigue cracks in the rail. Severe flat wheels are a safety hazard and can in some cases, cause derailments and consequent delays to trains. Smaller flat spots contribute to track deterioration and so increase maintenance costs by damaging the rails, sleepers and ballast. Flat wheels can thus be very costly to Spoornet and its public image. In addition to safety and economic considerations, wheel flats reduce the comfort levels in the passenger coaches and the noises they make is annoying. In an attempt to restrict the damage caused by flat wheels, most railway administrations place a limit on the length of the flats that may stay in service. But to effectively find a flat wheel on rolling stock is currently a very expensive exercise. Flat wheels can be detected by an audible knocking sound when standing next to the rail. This sound is impossible for the driver to hear and therefore goes undetected. Normally flat wheels are detected by random inspection of the rolling stock or when they are brought in for a routine service. The service cycle on rolling stock can be up to 24 months in Spoornet. Considering that a flat wheel has an impact roughly every 3m, a serious flat generates roughly 160 000 impacts on a single trip on the coal heavy haul export line. It is therefore clear that a flat wheel can cause a considerable amount of damage between service cycles. The severity of the problem is however not accurately defined in Spoornet, because up to a few months ago there was no detection system in use to determine the distribution of flat wheels. The research department of the Deutsche Bundesbahn however considers rail fractures due to the flat wheels to be a serious problem with a significant annual replacement cost. There are thus sound safety and economic reasons for wishing to understand the mechanisms of flat wheels and to develop an early warning system using an automatic detector.

No description available.

Surface acoustic wave (SAW) devices are a solution for today’s ever growing need for passive wireless sensors. Orthogonal frequency coding (OFC) together with time division multiplexing (TDM) provides a large number of codes and coding algorithms producing devices that have excellent collision properties. Novel SAW noise-like re- flector (NLR) structures with pulse position modulation (PPM) are shown to exhibit good auto- and cross-correlation, and anti-collision properties. Multi-track, multi-transducer approaches yield devices with adjustable input impedances and enhanced collision properties for OFC TDM SAW sensor devices. Each track-transducer is designed for optimum performance for loss, coding, and chip reflectivity. Experimental results and theoretical predictions confirm a constant Q for SAW transducers for a given operational bandwidth, independent of device and transducer embodiment. Results on these new NLR SAW structures and devices along with a new novel 915 MHz transceiver based on a software radio approach was designed, built, and analyzed. Passive wireless SAW temperature sensors were interrogated and demodulated in a spread spectrum correlator system using a new adaptive filter. The first-ever SAW OFC four-sensor operation was demonstrated at a distance of 1 meter and a single sensor was shown to operate up to 3 meters. Comments on future work and directions are also presented

The concept of a compact sound source driven by piezoactuators is experimentally investigated, and analytical design tools are developed. The sound source, consisting of a thin, cylindrically curved aluminum panel and a pair of collocated, surface-bonded piezoceramic actuators, was developed with the objective of employing it as a secondary sound source in the active control of turbofan blade interaction inlet noise. The sound source was fitted in an experimental duct representative of an aircraft engine inlet, and the interior and exterior sound pressure levels generated by the source were measured. The effects of excitation voltage, excitation frequency, duct length, and downstream termination of the duct were investigated. It was found that the source is capable of generating relatively high acoustic levels at its fundamental frequency (over 130 dB at maximum voltage input). Techniques for analytically predicting the acoustic levels are investigated. A commercial code for numerical modeling of structural-acoustic radiation was utilized. Results show generally good agreement with experimental measurements for the case of the short duct. It is believed that the model accuracy can be further improved through additional refinements in the modeling techniques. / Master of Science

An array of small, lightweight acoustic sources was investigated to determine how such an arrangement of sources would acoustically interact with a duct similar to that of a turbofan engine inlet. The sources were cylindrically curved aluminum panels excited in vibration by the application of a sinusoidally varying voltage to a piezoceramic actuator bonded to them. The finite element method was used as a design tool to size the panel based on desired vibration characteristics. A boundary element acoustic analysis was used to predict the acoustic output from various arrangements of sources. The central portion of the research was a series of experiments using an array of twelve sources arranged circumferentially in a duct. Measurements of the performance of each source revealed that the performance of the acoustic sources varied from source to source. This variation was assumed to have been caused by differences in the quality of the bond of each of the piezoceramic actuators to the panels. Directivity measurements were made in the far field. Measurements were also taken of the pressure field established in the duct cross-section. Modal decomposition was applied to the data. It was found that the dominant acoustic modes in the duct are those whose cut-on frequencies were near the frequency of excitation. / Master of Science

No description available.

The monitoring of harmful ambient vapors is of major concern in the industrial environment. To this end, the development of systems which detect and respond in real time to specific vapors is a highly desirable goal. Surface Acoustic Wave (SAW) devices have been used for chemical analysis since 1978. While sensitive to mass changes occurring on their surfaces, they are not selective to the mass they will detect. Their use as chemical sensors requires the development of specificity for a vapor (or class of vapors) using selective chemical reagents suspended in film media that can have their permeability easily changed. This dissertation presents the development of an automated dosimeter for the detection of phosgene using SAW devices. By changing the film media from a very permeable material to a film exhibiting less permeability, the analytical range of the device using the same suspended selective chemical reagent is expanded to concentrations which the very permeable film is incapable of accurately measuring. / Ph. D.

Micromachined gyroscopes are attractive replacements to conventional macro-mechanical and optical gyroscopes due to their small size, low power and low cost. The application domain of these devices is quickly expanding from automotive to aerospace and consumer electronics industries. As potential high volume consumer applications for micromachined gyroscopes continue to emerge, design and manufacturing techniques that improve their performance, shock survivability and reliability without driving up the cost and size become important. Today, state-of-the-art micromachined gyroscopes can achieve high performance with low frequency operation (3-30kHz) but at the cost of large form factor, large operating voltages and high vacuum packaging. At the same time, most consumer applications require gyroscopes with fast response time and high shock survivability, which are generally unavailable in low frequency gyroscopes. As a result, innovative designs and fabrication technologies that will offer more practical gyroscopes are desired. In this dissertation, capacitive bulk acoustic wave (BAW) silicon disk gyroscopes are introduced as a new class of micromachined gyroscope to investigate the operation of Coriolis-based vibratory gyroscopes at high frequency and further meet consumer electronics market demands. Capacitive BAW gyroscopes, operating in the frequency range of 1-10MHz are stationary devices with vibration amplitudes less than 20nm, resulting in high device bandwidth and high shock tolerance. They require low operating voltages, which simplifies the interface circuit design and implementation in standard CMOS technologies. They also demonstrate appropriate thermally stable performance in air, which eliminates the need both for vacuum packaging and for temperature control. A revised high aspect ratio poly- and single crystal silicon (HARPSS) process was utilized to implement these devices in thick SOI substrates with very small capacitive gap sizes (~200 nm). The prototype devices show ultra-high quality factors (Q>200,000) and large bandwidth of 15-30Hz. In addition, the design and implementation of BAW disk gyroscopes are optimized for self-matched mode operation. Operating a vibratory gyroscope in matched mode is a straightforward way to improve performance parameters but, is challenging to achieve without applying large voltages. In this work, self-matched mode operation was provided by enhanced design of the perforations of the disk structure. Furthermore, a multi-axis BAW gyroscope, an extension of the z-axis, is developed. This novel approach avoids the issues associated with integrating multiple proof masses, permitting a very small form factor. The multi-axis gyroscopes operate in out-of plane and in-plane modes to measure the rotation rate around the x- and z-axes. These gyroscopes were also optimized to achieve self-matched mode operation in their both modes.