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Browsing by Author "Nayfeh, Taysir H."

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    A direct on-line ultrasonic sensing method to determine tool and process conditions during turning operations
    Nayfeh, Taysir H. (Virginia Tech, 1993)
    Machining operations in automated manufacturing centers are under-performing by 20-80%. Optimizing these machining operations requires on-line knowledge about the cutting tool's condition and the process state. Currently, this information is either not reliable or not available in a timely manner. This is due to the lack of suitable sensors, which must measure on-line directly and accurately one or more of the relevant tool and process information sources in the hostile machining environment. A direct, active, ultrasonic method for on-line sensing of the tool condition and process state in turning operations was developed. Sensing is achieved by using an ultrasonic transducer operating at 10 MHz in a pulse-echo mode to send pulses through the tool. The amplitude and propagation time of the reflected pulses are modulated by the tool nose, flank, temperature, and by the material in contact with the tool. The reflected pulses are received and processed by a high speed digital signal processing system. This method has the potential to directly and accurately measure on-line several relevant processes and cutting tool parameters through the use of a single sensor. These parameters are tool-workpiece contact, tool wear, tool chipping, temperature and chatter.
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    Multi-signal processing for voice recognition in noisy environments
    Nayfeh, Taysir H. (Virginia Tech, 1991)
    One of the main input devices to computerized systems is Voice Recognition Systems (VRS). VRS is best suited for applications where job functions require more than two hands to be performed. The performance of VRS is highly dependent on the environment's noise. The higher the noise level the lower the recognition capability. Automatic lip reading through vision systems have been utilized to improve the recognition capability in noisy environments. However, this approach is costly and time-consuming. The objective of this thesis was to investigate the utilization of an Infrared sensor for automatic lip reading to improve the recognition performance of VRS. The developed system is cheaper and faster than other automatic lip readers. The test results of fifty words and eleven digits indicated that the method has good repeatability, and good character recognition, while not dependent on or sensitive to the ambient light level. Although speaker independence was tested, the results are inconclusive.