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Van Zyl, F.J., 2017. Characterisation of the dielectric properties of rhinoceros tissue using computer simulation and physical tissue phantom models. Thesis presented to Stellenbosch University, pp. 1-182

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Location: Africa - Southern Africa
Subject: Physiology
Species: African Rhino Species


Original text on this topic:
Introduction:
Understanding the electromagnetic behaviour of in-vivo devices within rhinoceros tissue will aid existing tracking and anti-poaching endeavours and provide new insights into rhinoceros physiology and environment. The simulation and agar models proposed in this project allow the investigation of electromagnetic propagation by in-vivo and ex-vivo devices without the need for surgery. Computer simulation and agar phantom models of rhinoceros tissue based on approximated dielectric properties are designed and evaluated.
Methods:
Since the dielectric properties of rhinoceros tissue have not been documented, the conductivity and permittivity of the skin, fat, muscle, blood and other organs were approximated by means of a meta-analysis that includes animals with similar physical properties. Alternative dielectric properties of the skin (epidermis, dermis and fat) were calculated based on previously reported mechanical measurements and chemical composition. Recipes using salt, sugar and agar were designed to match the dielectric properties of each tissue within the Industrial, Scientific and Medical (ISM) frequency band by applying previously reported mathematical models. Various phantom models were designed and produced to measure the power efficiency of an in-vivo transmitter to an ex-vivo receiver for two types of antenna.
Results:
The average error between the measured and theoretically predicted dielectric values was 6.22% when measured over all recipes and 4.49% for the 2.4 GHz group specifically. The specific absorption rate (SAR) within the various tissues complied with international standards. The findings indicate that the planar inverted-F antenna (PIFA) implanted in the chest of the rhinoceros is the optimal combination in terms of power efficiency, when communication with an ex-vivo receiver attached to the hind leg of the rhinoceros is considered. The power efficiency of the PIFA was seen to improve by 16 dbm when a 10 mm air gap between the antenna and phantom was introduced. Signal penetration through the hide of the rhinoceros is possible, but communication from an in-vivo transmitter located in the back, chest or neck to an ex-vivo receiver on the hind leg is not ideal for the specified antenna size and power constraints. All practical results were compared with corresponding simulation models and found to agree to an acceptable degree. The comparability between the agar and simulated rhinoceros flank models was 67.38% when regarding the efficiency between the transmitting and receiving antennas.
Discussion:
The simulation and agar models have been demonstrated to be in substantial agreement with respects to the power efficiency of in-vivo and ex-vivo antennas. It is therefore concluded that both models represent a good basis for the design of in-vivo and ex-vivo sensors for the rhinoceros. The comparability between the simulation and agar models might be improved by including more real-world mitigation factors to the computer models. Further validation can be performed in future by analysis of the dielectric properties of actual rhinoceros tissue.

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