Thesis (MScIng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Both coaxial probe and waveguide (WG) measurement systems for electric and magnetic
material property extraction were investigated. These measurement techniques were used
to determine electrical properties of an inhomogeneous rock sample in its solid and
crushed states. A lumped element model of the probe was used and permittivity was
determined by the inversion algorithm developed by Stuchly and Stuchly. To support this
technique it was compared to a full wave inversion algorithm and referenced to properties
of the same samples but determined by a resonant cavity technique. The Nicholson, Ross
and Weir inversion algorithm was used to determine material properties from WG
measurements. As a reference, the same techniques were applied to a well defined
material. It was found that neither of the measurement techniques could measure low loss
factors or conductive materials and literature values were used in these cases. Various
simulation models of the multiphase ore in both its solid and crushed states are presented.
These models were utilised in finite-difference time-domain (FDTD) simulations of
different microwave (MW) cavities. Simulation and experimental S-parameter
comparisons are presented. The level of accuracy achieved varies as a function of the
geometrical representation and material properties. After an S-parameter comparison with
simulation results it was concluded that the electrical properties of both the solid and
crushed rocks have been well determined for MW cavity design. Predicted and measured
field distributions in cavities were also compared and it is shown that accurate models of
multiphase materials become especially important in the determination of field
distributions in and around different rock phases. Recommendations for the suggested
material property determination and verification processes are presented. A specific
application of this work is in the field of microwave assisted comminution. / AFRIKAANSE OPSOMMING: ’n Koaksiale probe en golfgeleier (WG) stelsels vir die bepaling van materiaal eienskappe
(elektries en magneties) word gebruik met die doel om ’n nie-homogene rotsmonster te
karakteriseer. Die ekstraksie algoritme van Stuchly en Stuchly word gebruik om die
materiaal eienskappe te bepaal vanaf die gemete S11-parameter. Hierdie ekstraksie
metode word vergelyk met ’n vol golf ekstraksie van permitiwiteit vanaf dieselfde
gemete data. Beide die ekstraksie metodes word dan vergelyk met resonante holte
meetings van dieselfde materiale. Die Nicholson, Ross en Weir ekstraksie algoritme word
toegepas op meetings wat gedoen is deur die golfgeleier stelsel. As ’n verwysing word
dieselfde tegnieke toegepas op ’n bekende materiaal en daar is gevind dit stem goed
ooreen behalwe dat nie een van die twee meet tegnieke lae verlies faktore kan meet nie.
Verder kan nie een van die twee sisteme geleidende materiale meet nie. Vir sulke gevalle
is waardes nageslaan. Verskeie simulasiemodelle van die rots word voorgestel vir beide
soliede en vergruisde monsters.
Hierdie modelle word gebruik in FDTD simulasies van verskeie mikrogolftoevoegers met
die oog om ’n vergelyking te tref tussen gesimuleerde en gemete S-parameters.
Verskillende vlakke van akkuraatheid is bereik en is ’n funksie van die geometrie en die
materiaaleienskappe van die model. Nadat gemete en gesimuleerde S-parameters
vergelyk is, is gevind dat die materiaal eienskappe van beide die soliede en vergruisde
rots monsters goed bepaal is vir mikrogo lf toevoeger ontwerp. Voorspelde en gemete
veldverspreidings word ook vergelyk en dit is veral hierso van belang om ’n realistiese
model van die nie-homogene monster te gebruik. Sekere voorstelle word gemaak om die
verskillende aspekte van die meet van ma teriaaleienskappe en simulasiemodelle te kan
verfyn. ’n Spesifieke toepassing van hierdie werk is in mikrogolf ondersteunde skeiding
van minerale en erts.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/21217 |
| Date | 12 1900 |
| Creators | Louw, Willem J. |
| Contributors | Reader, H. C., Bradshaw, S. M., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 162 leaves : ill. |
| Rights | Stellenbosch University |
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