Acoustic CT System for Temperature Distribution and Wind Velocity Vector Measurement
In this report, a measurement method for cross-sectional temperature and wind velocity distribution is discussed. A novel method based on an acoustic CT technique is proposed. Specifically, the temperature and the wind velocity distributions are estimated simultaneously using the time of flight data of several ultrasonic propagation paths. The temperature and the wind velocity effects can be distinguished by considering sum and difference of the time of flight (TOF) data. Two types of projection data, temperature-oriented data and wind-velocity-oriented data, components are obtained. A filtered back projection method and inverse matrix method are applied to reconstruct the temperature and the wind velocity distributions, respectively. An experimental system is designed and fabricated to realize simultaneous temperature and wind velocity distribution measurements. Through this system, the effectiveness of the proposed measurement method is confirmed.
Ultrasonic tomographic imaging of solid objects in air using an array of fan-shaped-beam electrostatic transducers
A technique capable of imaging solid object distributions in air is presented. The imaging technique is based on a tomographic method, similar in concept to those used in diagnostic computerised tomography. The reconstruction algorithm has been implemented in a software modelling package to allow the performance of the technique to be evaluated for various object distributions and array configurations. Furthermore, fan-shaped-beam (FSB) electrostatic transducers have been developed to allow experimental evaluation of the technique. Experimental and simulated results indicate the utility of the approach to provide information on the size, shape, location and orientation of solid objects.
On the Problem of Reconstructing Images of Non-Scalar Parameters from Projections. Application to Vector Fields
It is demonstrated that in some cases it is possible to reconstruct images of fields whose local values are not scalars but are instead anisotropic. The approach taken relies upon Fourier analysis of the angular dependence and separation of scalar and non-scalar contributions by symmetry, and is applicable to anisotropies that do not have even symmetry. Although there are only a limited number of cases in which the problem can be analytically solved, there appears to be a variety of applications for which good approximations are available. The proposed algorithm, a hybrid of well known image reconstruction techniques, has been applied to calculated projections of test patterns, local regions of which having been assigned either scalar or vector behavior or both.