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    Electromagnetic propagation through non-dissipative and dissipative barriers : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physics at Massey University, Palmerston North, New Zealand
    (Massey University, 2002) Shalav, Avi
    A Matlab simulation was developed to help visualise and investigate electromagnetic tunnelling through particular non-dissipative and dissipative barriers within a waveguide. The theory behind the simulation is based on a transmission line model that accurately predicts experimental results and is shown to be equivalent to previous numerical and quantum tunnelling models. A few useful speeds referring to electromagnetic waves have been defined and utilised to calculate die speeds at which different incident time signals penetrate electromagnetic barriers. Due to bandwidth restrictions, the created incident time signals had wavepacket properties. The importance of resampling an oscillating signal at the appropriate frequency to avoid aliasing has been recognised. The definition and creation of matched signals that can penetrate long barriers yet remain a single pulse have been investigated. Such signals will have no practical application since the attenuation will deem the transmitted signals immeasurable. However, the speeds through these larger barrier lengths will have a smaller uncertainty since the time delays are longer. Most of the signal distortion depends only on the barrier interfaces rather than the barrier length. Penetration through dissipative barriers gives speeds below the vacuum speed of light for all barrier lengths investigated. Faster than light speeds are however predicted for penetration through non-dissipative barriers greater than about 4cm.
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    Characterization of extremely low-frequency electromagnetic sources in conducting media : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physics at Massey University
    (Massey University, 2001) Rumball, Edward Ian
    Physical fields whose sources exist within maritime vessels are of concern to ship-designers and military planners. Among the fields of most significance which have been studied intensively, are those of magnetic, acoustic and pressure sources. New technological developments now require analyses of the underwater electric and magnetic fields of onboard, extremely low-frequency electromagnetic sources. This study investigated methods by which the electromagnetic sources of maritime vessels may be characterised during normal operations in typical coastal environments. It focused on situations where both the sources and field measurement points were located in a common seawater volume. At the electromagnetic frequencies of interest such a medium acts as a thin conducting layer with significant levels of wave reflection and refraction at the media boundaries. To enhance propagation models of the electromagnetic fields over short ranges, the initial investigations aimed to characterise key parameters of the conducting media in shallow-water conditions Conductivity values of seawater can be readily established by conventional methods. However, in the case of the seabed media, direct conductivity measurements are usually highly variable along horizontal and vertical sections due to aeons of land erosion, and the long-term effects of inshore waves and currents. Procedures are described which show how electromagnetic theory and indirect measurement techniques may be used to infer the characteristic values of key seabed parameters in shallow-water areas. This element of the study utilised both analytical and numerical electromagnetic models, and the efficacy of each in this context was examined. Subsequent phases of the study analysed the nature of the electromagnetic sources. In some situations the sources were regarded as point dipoles, and in others they were assumed to have a finite length. Techniques were developed to characterise the dipole moment, length and the location of a typical ship-like source, when each is treated as an electric current dipole. This information was used in turn to demonstrate the likely accuracy in ranging operations on extremely low-frequency, electromagnetic sources over short ranges, and in shallow-water conditions.