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Historically, DJJ's research interests have encompassed microwave acoustics; (PhD thesis was on the microwave acoustic properties of ferroelectrics and ferroelectric semiconductors); X-ray and neutron scattering experiments from phonons in solids; frequency-crossing phonon spectrometer experiments; non-linear acoustic propagation and chaos in piezoelectric ferroelectrics; chaos in electronic circuits and telecommunications applications; chaos in computer data networks; chaos in power electronic systems. The underlying theme is the behaviour of systems having strong non-linearity and either feedback or wave propagation. Recently he has become interested in parallel computer systems where there are problems of arbitration produced by asynchronous communications which are similar to the arbitrations due to "folding" in a classic chaotic system. DJJ has also written reports on the telecommunications applications of high temperature superconducting materials, and radar absorber advanced materials construction using a photonic band-structure arrangement. At present his research interests are:
Some Postscript papers (several are large)
DJJ is interested in naturally occurring catastrophic events in complex systems. A paper which shows how these can arise as a consequence of very simple non-linear chaotic dynamics has been written for the conference COMPLEX96 in Australia, July 1996. The paper title is
There is a follow-up paper which was presented at ECCTD97 in Budapest in September 1997. The paper title is
A previous paper at COMPLEX94 entitled
Another paper at COMPLEX96 is concerned with non-linear signal processing and propagation. See
Chaos and self-similarity may also occur in computer data networks. There is some debate about this in the community, but a simple model is reported in
An earlier report of this work found chaotic states in computer data networks and was reported at the conference COMPLEX94
Self-similarity is also observed in the traffic on networks. There is a paper on
There is a speculation on the applicability of the work on networks and on trapping systems to the wider worlds of software engineering, economics, and ecology, in the unpublished paper on
Two papers presented at Complex 98 are available here.
In 2000 DJJ has been interested in emergent fractal fixed point structures as a result of approximate image-processing computations. These structures are artefacts of the discrete nature of the computation and have no basis in reality.
He has also been investigating chaotic itinerancy in a one-dimensional lattice of harmonic potential wells. A particle traverses the lattice in an irregular way which is not a random walk, but shows strong propensities to continue to make progress to the right or to the left ("short term memory") even though there is no intrinsic bias in the direction.
He has also been investigating the chaotic motions of a Newton's Cage simulation.
He has recently been interested in the limitations of the predictive (as opposed to post-dictive) powers of the fashionable technique of "agent-based modelling". It is likely that agent based models of complex systems provide very poor foundations for policy decisions.
Initial approaches from prospective research students, visiting research fellows, and collaborators are welcome. See the pages