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W J Tompkins

Publications and source records attributed to W J Tompkins.

At least 55 records · Page 3Linked to original sources
PubMed1985

Development and applications of an interactive digital filter design program.

We have implemented an interactive digital filter design program in the HP 1000 computer at the Department of Electrical Engineering of the University of Washington. This program allows users to design different types of filters interactively with both amplitude and phase responses displayed on graphic devices. The performance of each designed filter can be evaluated conveniently before the best one is chosen and implemented for any particular application. This program can design recursive filters, e.g. Butterworth, Chebyshev and elliptic, or nonrecursive filters with one out of six different windows, i.e. rectangular, triangular, Hann, Hamming, Blackman and Kaiser. The main outputs from this program are coefficients of a transfer function of an analog filter, a digital filter, or both. Therefore, the design of both analog and digital filters is facilitated by using this program. The program is very simple to use and does not require background in analog or digital filter principles in order to run it. The program is written in standard FORTRAN and is about 30 kbytes in size excluding the graphics display routines. Since it uses standard FORTRAN, it can be easily transported to minicomputer and microcomputer systems that have a FORTRAN compiler and minimal graphics capabilities. This program is available for distribution to interested institutions and laboratories.

Biometry↗
PubMed1983

Electrical impedance imaging of the thorax.

In this paper, we propose to develop a new imaging technology, computerized impedance tomography (CIT) for imaging the thorax. Our study involves reconstructing images of thoracic transverse plane impedance distributions noninvasively and nondestructively and exploring the potential of CIT. We overcome the reconstruction problem due to nonlinear and nonplanar current paths in impedance imaging by solving Laplace's equation numerically for every iteration and by using a new back-projection algorithm to modify the impedance profile. We discuss advantages and disadvantages associated with impedance imaging, the computer model, and back-projection algorithms used in reconstructing impedance images. We present reconstructed impedance images with 8 projection angles and different projection methods. We identify important variables affecting the quality of reconstructed images, and discuss the resolution and accuracy of this imaging technique. We summarize numerical aspects, computer requirement, and limitations of impedance imaging. We also discuss the future of impedance imaging.

Computers↗