Dynamic ultrasonic contact detection using acoustic emissions.

For a non-contact ultrasonic material removal process, the control of the standoff position can be crucial to process performance; particularly where the requirement is for a standoff of the order of <20 µm. The standoff distance relative to the surface to be machined can be set by first contacting the ultrasonic tool tip with the surface and then withdrawing the tool to the required position. Determination of this contact point in a dynamic system at ultrasonic frequencies (>20 kHz) is achieved by force measurement or by detection of acoustic emissions (AE). However, where detection of distance from a surface must be determined without contact taking place, an alternative method must be sought. In this paper, the effect of distance from contact of an ultrasonic tool is measured by detection of AE through the workpiece. At the point of contact, the amplitude of the signal at the fundamental frequency increases significantly, but the strength of the 2nd and 3rd harmonic signals increases more markedly. Closer examination of these harmonics shows that an increase in their intensities can be observed in the 10 µm prior to contact, providing a mechanism to detect near contact (<10 µm) without the need to first contact the surface in order to set a standoff.

Evaluation of T1N0M0 lung cancer with CT.

Medical records and radiologic studies of 238 patients with non-small cell lung cancer who had preoperative evaluation by chest radiography and CT were reviewed. Thirty-six patients were staged as T1N0M0 by chest radiograph. Of this group, 18 (50%) had abnormalities on CT requiring additional evaluation. Confirmation of abnormalities was by tissue sampling or clinical follow-up. Evidence for unresectable spread of disease was obtained in 12 (33%). We conclude that routine preoperative staging of T1N0M0 lung cancer with CT has a positive impact on patient management.

Comparisons of meteorological structure parameters in complex terrain using optical and acoustical techniques.

Remotely sensed wind, temperature changes with height, and turbulence have been compared with in situ instrumentation using optical and acoustic techniques across and within valleys. These comparisons have provided data useful in the interpretation of spatial averages inherent in remote sensing with spatial and temporal representativity of point meteorological measurements in complex terrain. Of particular interest in this study was comparison of the optical turbulence derived index-of-refraction structure function C(n) with the acoustically derived temperature structure function C(T) over divergent scales across and within a valley.