Investigation of novel phantom in consideration of acoustic and optical characteristics and development of assessment technique for minute change in thickness measured by ultrasound
For measurement of minute change in thickness using ultrasound, the phase tracking method based on the constraint least-squares approach has been developed. The value measured by this method has the order of sub-micrometer, and it is difficult to verify the precision of the value. We fabricated a novel phantom, which consisted of materials in consideration of the acoustic and the optical characteristics. The thickness of the phantom changed periodically and the change was measured by the ultrasound and laser simultaneously. We evaluated the proposed ultrasound measurement system with the value measured by the laser. From the experimental results, it was obtained that our ultrasound measurement system had an accuracy of about 0.2 /spl mu/m.
Abstract A study of approach wind flow and wind-induced pressure on a 1 : 50 geometrical scale model of the Texas Tech University test building was performed in a boundary layer wind tunnel at Colorado State University. The model and full-scale flow parameters and pressure coefficients are presented for low-turbulence nominal flow. The comparison of the model and prototype building point pressure exhibits a better agreement for most of the pressure taps, including the critical corner region, than other reported wind tunnel results. The study shows a significant reduction in the extreme peak pressure at critical locations due to low-pass filtering with a relatively high-frequency cut-off. This points out to the importance of proper selection of the frequency range for low-pass filtering and sampling of the pressure signals.