The consequences for nucleus-nucleus collisions of the mvariance (Tidal Symmetry) of arbitrary but momentum-independent interactions under rotations about the relative coordinate of the interacting nuclei are examined. In conjunction with an approximate treatment of the centrifugal barrier this symmetry leads to a partial diagonalisation of the coupled-channels description of the scattering of the two nuclei. This approximation is found to give an accurate description of the tensor polarisation observables in a specific heavy-ion elastic scattenng case. A consequence of the treatment given here is that the so called 'shape effect' relations can be satisfied in strong-coupling situations.
A novel detection system for second harmonic ultrasonic pulse waves is constructed by modifying an existing system using a double-layered piezoelectric transducer (DLPT). Two unique methods are introduced into the system, namely, the switching of the electrical connection of the DLPT and the pulse inversion excitation method, in which the DLPT is excited by both inphase and out-of-phase pulses alternatively and averaged to cancel the fundamental and odd harmonic components. As a result of using these two methods, enhanced second harmonic waves are displayed on an oscilloscope in real time, and an improved sensitivity of 80 dB is obtained. Finally, drilled holes are imaged as an application of the new system and to demonstrate its usefulness.
A novel noncontact air-coupled ultrasonic system introducing a conical acoustic probe (CAP) with a pinhole is constructed at low frequency. A 40 kHz ultrasonic wave in air goes through the pinhole, which has a diameter much smaller than the ultrasonic wavelength (' 9 mm), and forms a unique sound field. The lateral À3 dB widths of both theoretical and experimental sound fields approximately coincide with the pinhole diameter. A lateral resolution of =30 (0.3 mm) beyond the diffraction limit has been achieved using this system. As an application of the system, the surface profile for a 0.5 mm (=18) drilled hole in an aluminum plate was successfully imaged. The surface topographical profile of a step difference of 1 mm (=9000) was also measured.
Second-harmonic components generated from plastic-deformed metal rods are detected in real time using a double-layered piezoelectric transducer (DLPT). The DLPT is composed of two transducers with the resonance frequency f0; its resonance frequencies are f0/2 when the transducers are connected in parallel and f0 when the transducers are connected in series. The performance of the DLPT used in this ultrasonic system is evaluated. Samples of plastic-deformed metal rods are prepared using tensile test equipment. The relative amplitude of the second-harmonic component of the metal rod increased by approximately 25 dB after the tensile tests compared with that before the tensile tests. The variation in tensile load of the second-harmonic components generated by plastic-deformed metal rods is accurately measured by our system.
The acoustic properties of composite materials used for an intermediate layer or backing of an ultrasonic transducer are studied experimentally. (0-3) composite materials are formed from a mixture of epoxy resin and tungsten powder for various weight ratios and their acoustic properties are measured. The experimental results are compared with the results predicted by different models, which are based on the elastic-wave scattering theory, to verify if the measured acoustic properties agree with theoretical estimations. For the ultrasonic velocities, the estimations of the Devaney model were closest to the experimental results. The weight fractions of tungsten powder for the composite materials, which have objective acoustic properties, can easily be estimated by theoretical calculations using the Devaney model.
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