Volume 80, Issue 1, January 2009
Index of content:
- THERMOMETRY; THERMAL DIFFUSIVITY; ACOUSTIC; PHOTOTHERMAL AND PHOTOACOUSTIC
80(2009); http://dx.doi.org/10.1063/1.3070518View Description Hide Description
Nondestructive testing has been performed on a thin copper plate. Lamb waves were generated and studied with a noncontact method, using a laser ultrasonic setup. A two-dimensional Fourier transform technique has been employed to obtain the dispersion curves, revealing numerous symmetric and antisymmetric modes. The inverse problem, in other words, the determination of the thickness and the elastic constants of the tested plate, has been solved by means of a feed-forward neural network. These parameters were then evaluated simultaneously, the dispersion curves being entirely fitted. The experimental results show good agreement with the theoretical model. This inversion method was found to be prompt and easy to automate.
80(2009); http://dx.doi.org/10.1063/1.3072604View Description Hide Description
A ripplon is a thermally excited capillary wave propagating on liquid surface. Propagation of the ripplon reflects surface mechanical properties such as surface tension and viscoelasticity of the liquid. An optical beating ripplon spectroscopy technique developed by us was applied mainly to the observation of various surface phenomena on a lowly viscousliquid surface in the frequency range from 1 kHz to several 10 MHz. In this study, we carried out a light scattering observation of the highly damped ripplon on the surface of the viscousliquid. The spectral peak width of the damped ripplon was smaller for the higher viscosity and the optical beating technique could resolve such a structure. A strict description of the dynamic structure factor of the ripplon was employed to fit the experimental power spectrum of overdamped ripplon to viscosity up to 1000 cS.
80(2009); http://dx.doi.org/10.1063/1.3069292View Description Hide Description
A photoacoustic tomography imagingsystem with B-mode digital ultrasound diagnosis equipment was designed, fabricated, and tested for biomedical imaging. The system for biomedical diagnostics was designed with four parts consisting of an irradiating source, digital B-mode ultrasounddiagnostic equipment with a liner transducer array, data acquisition and transmission system, and rotation devices for imaging scanning. Multielement phase-controlled focus technique was applied to reduce the data-acquisition time and enhance signal-to-noise ratio. Under the self-designed working sequence, data-acquisition time of an image can be reduced to 12 s. A series of experiments were performed to estimate the imaging quality of the system. The lateral and elevational resolutions of the system were detected to be 0.25 and 1.4 mm, respectively. The results show that the system has the feasibility to be used as a medical imaging method, and it may provide a new rapid and noninvasive imaging modality for clinical applications.