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We consider the problem of measuring the size of a spherical inclusion in a host metal. Ultrasound is directed at the test piece, and the echo returns are detected. Among other components, the received signal contains two echoes of the incident pulse, whose time separation is a measure of the diameter of the inclusion, or defect. A modified version of cepstral processing is used to determine this time separation. Simulated data are generated using a certain scattering model, and processed with good results. Sample test pieces were also constructed, and data collected and processed. The resulting measured defect diameters agreed with the true diameters.1.

A data acquisition and qignal processing system has been designed to study the EMG (electromyogram) coordination and timing interplay of agonist and antagonist muscles during specific limb movements. The PC-based system collects EMG signals from two channels, corresponding to extensor and flexor muscles of the subject's upper arm. Six other channels are utilized for motion information obtained from two three-axis piezoelectric acceleration transducers attached to the subject's wrist.Based on the collected information, the stimulator (output) side of the system derives suitable stimulation patterns for the subject. atroductionAt present there are about two million Americans who suffer from semiparalysis subsequent to non-fatal stroke. About 160,000 additional cases occur every year.For patients who have survived a cerebrovascular accident (stroke) and have incurred limb paralysis, traditional methods of occupational and physical therapy have been unsuccessful in having had a significant effect upon the rate and duration of recovery of voluntary, coordinated movement. Our therapy is based on the "Reverse loop theoryv8, so called because a functioning part of the brain is trained and learns to compensate for the injured area. Such a method is useful only for subjects with intact and normally functioning muscle and nerve fiber bundles, as with stroke victims.In this method, the affector EMG patterns associated with fast voluntary limb movement of the unafflicted limb is used to obtain, via a computer model, the motor nerve stimulation pattern specific to that limb movement. This may then be used to determine the functional electrical stimulation (FES) pattern that may be applied to the afflicted limb of the hemiplegic subject to obtain (fast) limb movement similar to the unafflicted side [I, 21.The developed system derives suitable stimulation patterns to the subject using an adaptive controller. Svstem D escr iDtionThe block diagram of the system is presented in Fig.1. The signals of the two (each 3-axis) piezoelectric accelerometer transducers (A1 and A2)and the signals of the four electromyogram electrodes are amplified, averaged and prefiltered by the analog data acquisition channels. The schematics of the analog data acquisition channels are presented in Fig. 2. and 3.The interface card (under software control) multiplexes the signals of the above described eight analog channels and accomplishes the analog to digital conversion.The controller model, running on the personal computer outputs a stimulation control pattern (via the stimulator unit) resulting in a possible maximum crosscorrelation between the acceleration signals of transducers A1 and A2.