published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

Throughout North America, many species of aerial insectivorous birds – birds that capture flying insects – have exhibited sharp declines, with tree swallows (Tachycineta bicolor) experiencing a 2.8% annual decline in Canada since 1989. The timing of these declines coincides with major changes in agriculture, perhaps signaling a potential causal link. Declines may be influenced indirectly by agriculturally-driven reductions in the abundance of the swallow’s main diet of aerial insects through increased agrochemical use, wetland drainage and cropping intensity. My objectives were to determine how aerial insect abundance and biomass vary across an agricultural landscape in the Canadian Prairies, and determine how breeding tree swallows respond in terms of (i) foraging behaviours and return rates, (ii) body condition, and (iii) selected physiological responses (i.e. oxidative stress and feather corticosterone). Artificial nest-boxes were erected at each of 5 sites with varying levels of agricultural intensification in south-central Saskatchewan, 2012-2014. Insect abundance and biomass were monitored daily using passive aerial samplers at each of the sites throughout the breeding season. Tree swallows adults (n = 596) and nestlings (n = 1107) from each nest were captured, banded, measured and blood and feather sampled to determine condition and physiological status. In 2014, radio frequency identification (RFID) technology was employed at a subset of nest-boxes to determine adult foraging rates and durations. Despite strong differences in land use characteristics among sites, insect abundance and biomass varied by year but were similar between heavily cropped and grassland references sites. Regardless, birds responded to temporal changes in prey abundance and differences were found in measurements of foraging behavior and physiological measures of oxidative stress. Adult foraging rate (number of nest visits/hour) was primarily influenced by wind and nestling age, but was also positively related to daily insect biomass. Foraging intervals (i.e., length of time spent on each trip) differed between agricultural intensities; birds on agricultural sites spent more time away from the nest box, presumably foraging, suggesting reduced nest attentiveness. Return rates were primarily predicted by body condition and brood size from the previous breeding season, but were also higher on grassland sites, suggesting that agricultural sites may be less favorable. Older adults (based on banding records) and females displayed a higher body condition than did younger individuals and males, respectively. Measures of physiology (i.e. total antioxidant counts and oxidative damage) in both adult and nestling swallows were primarily driven by temporal changes in insect biomass and abundance. Similarly, adult body mass and physiology were related to local insect availability, but not land use (agriculture/grassland). Measures of nestling feather corticosterone were unrelated to any of the explanatory variables. These results provide valuable information pertaining to components of individual quality, foraging behaviour, and return status in response to prey availability under differing agricultural land use regimes, which may help to inform conservation strategies for a variety of insectivorous bird species of conservation concern.

The main crux of this thesis was to produce a model that was capable of simulating the theoretical performance of different configurations for a spatial measurement system using radio frequency technology. It has been important to study new modalities of spatial measurement since spatial measurement systems are an enabling technology that have allowed for the creation of better medical procedures and techniques, provided valuable data for motion capture in animation and biomechanics, and have improved the quality of manufacturing processes in many industries. However, there has been room for improvement in the functional design and accuracy of spatial measurement systems that will enhance current applications and further develop new applications in medicine, research and industry. <br /><br /> In this thesis, a modelling framework for the investigation of spatial measurement based on radio frequency signals was developed. The simulation framework was designed for the purpose of investigating different position determination algorithms and sensor geomatries. A finite element model using the FEMLAB partial differential equation modelling tool was created for a time-domain model of electromagnetic wave propagation in order to simulate the radio frequency signals travelling from a transmitting source antenna to a set of receiving antenna sensors. Electronic line signals were obtained using a simple receiving infinitesimal dipole model and input into a time difference of arrival localization algorithm. The finite element model results were validated against a set of analytical solutions for the free space case. The accuracy of the localization algorithm was measured against a set of possible applications for a potential radio frequency spatial measurement system design. <br /><br /> It was concluded that the simulation framework was successful should one significant deficiency be corrected in future research endeavours. A phase error was observed in the signals extracted at the receiving antenna locations. This phase error, which can be up to 40??, was attributed to the zeroth order finite elements implemented in the finite element model. This phase error can be corrected in the future if higher order vector elements are introduced into future versions of FEMLAB or via the development of custom finite element analysis software but were not implemented in this thesis due to time constraints. Other improvements were also suggested for future work.

Radio-Frequency (RF) lesioning, or RF ablation, is a method that uses high frequency currents for thermal coagulation of pathological tissue or signal pathways. The current is delivered from an electrode, which also contains a temperature sensor permitting control of the current at a desired target temperature. In the brain, RF lesioning can e.g. be used for treatment of severe chronic pain and movement disorders such as Parkinson’s disease. This thesis focuses on modelling and simulation with the aim of gaining better understanding and predictability of the lesioning process in the central brain.   The finite element method (FEM), together with experimental comparisons, was used to study the effects of electric and thermal conductivity, blood perfusion (Paper I), and cerebrospinal fluid (CSF) filled cysts (Paper II) on resulting lesion volume and shape in brain tissue. The influence of blood perfusion was modelled as an increase in thermal conductivity in non-coagulated tissue. This model gave smaller simulated lesions with increasing blood perfusion as heat was more efficiently conducted from the rim of the lesion. If the coagulation was not taken into consideration, the lesion became larger with increasing thermal conductivity instead, as the increase in conducted heat was compensated for through an increased power output in order to maintain the target temperature. Simulated lesions corresponded well to experimental in-vivo lesions. The electric conductivity in a homogeneous surrounding had little impact but this was not true for a heterogeneous surrounding. CSF has a much higher electric conductivity than brain tissue, which focused the current to the cyst if the electrode tip was in contact with both a cyst and brain tissue. Heating of CSF could also cause considerable convective flow and as a result a very efficient heat transfer. This affected both simulated and experimental lesion sizes and shapes. As a result both very large and very small lesions could be obtained depending on whether sufficient power was supplied or if the heating was mitigated over a large volume.   Clinical (Paper IV) and experimental (Paper III) measurements were used for investigation of changes in reflected light intensity from undamaged and coagulating brain tissue respectively. Monte Carlo (MC) simulations for light transport were made for comparison (Paper V). For the optical measurements, an RF electrode with adjacent optical fibres was used and this electrode was also modelled for the optical simulations. According to the MC simulations, coagulation should make grey matter lighter and white matter darker, while thalamic light grey should remain approximately the same. Experiments in ex-vivo porcine tissue gave an increase in reflected light intensity from grey matter at approximately 50 °C but the signal was very variable and the isotherm 60 °C gave better agreement between simulated and experimental lesions. No consistent decrease in reflected light intensity could be seen during coagulation of white matter. Clinical measurements were performed during the creation of 21 trajectories for deep brain stimulation electrodes. In agreement with the simulations, reflected light intensity was found to differentiate well between undamaged grey, light grey and white matter.   In conclusion, blood perfusion and CSF in particular may greatly affect the lesioning process and can be important to consider when planning surgery. Reflected light intensity seems unreliable for the detection of coagulation in light grey brain matter such as the thalamus. However, it seems very promising for navigation in the brain and for detection of coagulation in other tissue types such as muscle.

The application of Radio Frequency Identification (RFID) technology in hospitals is modest primarily due to cost and policy issues. Similar to the evolution of other electronic technologies, unit costs for components have been dramatically reduced in the past few years. Despite the reduction in costs, RFID technology has not yet achieved the tipping point of economic rationality for adoption at most healthcare organizations. Although the technology has been primarily applied to asset management and supply chain applications, Navy Medicine stands to gain tremendous benefit if this technology could be successfully implemented for staff and patient tracking in addition to inventory management. The purpose of this thesis was to conduct a review of RFID technology and components that could fit into the Navy Medicine's structure. The study explored the implementation requirements associated with the deployment in other industries that could be used as benchmarks for Navy Medicine implementation. Different technological architectures were described to illustrate the various techniques that could be used for creating the opportunity to automate administration, reduce errors and improve security for both patients and staff.

<p>Human motion monitoring is an important function in numerous applications. In this dissertation, two systems for monitoring motions of multiple human targets in wide-area indoor environments are discussed, both of which use radio frequency (RF) signals to detect, localize, and classify different types of human motion. In the first system, a coherent monostatic multiple-input multiple-output (MIMO) array is used, and a joint spatial-temporal adaptive processing method is developed to resolve micro-Doppler signatures at each location in a wide-area for motion mapping. The downranges are obtained by estimating time-delays from the targets, and the crossranges are obtained by coherently filtering array spatial signals. Motion classification is then applied to each target based on micro-Doppler analysis. In the second system, multiple noncoherent multistatic transmitters (Tx's) and receivers (Rx's) are distributed in a wide-area, and motion mapping is achieved by noncoherently combining bistatic range profiles from multiple Tx-Rx pairs. Also, motion classification is applied to each target by noncoherently combining bistatic micro-Doppler signatures from multiple Tx-Rx pairs. For both systems, simulation and real data results are shown to demonstrate the ability of the proposed methods for monitoring patient repositioning activities for pressure ulcer prevention.</p> / Dissertation

Thesis (M. Tech. Engineering: Electrical--Vaal University of Technology / A high-power Mosfet was incorporated as a switching device into the efficient Class E configuration, where the switching device switches current through itself either completely on or completely off at high frequencies. The first objective of this project was to demonstrate the effectiveness of a phase-lock loop circuit in generating stable high frequencies when connected in an indirect frequency synthesizer configuration. The indirect frequency synthesizer has established itself as a versatile frequency generator capable of generating high frequencies based on a lower stable reference frequency. The frequency generation stage incorporates a phaselock loop circuit, a frequency divider and a stable reference frequency section. The phase-lock loop section incorporates the TTL based 74HC 4046 that is based upon the common CMOS 4046 integrated circuit. The frequency divider section is built around the CMOS-based 4526 whilst the reference frequency section incorporates the CMOS-based 4060. The frequency synthesizer produced a range of frequencies from 50 kHz to 8 MHz in 50 kHz steps. The output voltage was constant at 5,5 V. The second objective was to show that the complementary emitter follower is indeed a worthy Mosfet gate drive circuit at high frequencies. The Mosfet driver stage produced a voltage signal of at least 11 V, being able to source and sink relatively high peaks of current, especially at high frequencies. Voltage amplification occurred through the use of multiple CMOS-based 40106 inverters. The complementary emitter follower, known for its low output impedance and its ability to source and sink large amounts of current, was an important component in the final Mosfet gate section.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2017 / The scientific requirements for Radio Frequency (RF) receivers especially for Radio Astronomy have become more demanding, requiring: compact, low-profile, multi and wideband antennas and more sensitive receivers. Integration of the antenna into the receiver system is often critical to meet these demands. Noise theory to model these more complex systems is well developed but is not implemented in commercial solvers, given the niche market of the receivers it is only available using specialised software. If the system is closely coupled, it becomes necessary for design to incorporate Electromagnetic (EM) and Microwave (MW) modelling into the multi port noise modelling. CAESAR, a combined noise and EM/MW modelling code is available, but to use it requires the exclusive use of the CAESAR software, which is impractical given the utility and wide use of commercial solvers. Mathematical methods are developed to incorporate commercial solvers into the more specialised CAESAR, validated using a folded dipole and applied to a wideband Eleven antenna system, a compact form of a log periodic dipole array. The Eleven antenna consist of eight single ended or four differential ports, with a closely coupled feeding arrangement. Cryogenic measurements are done to verify the modelling, the measured sensitivity matches with the model closely in amplitude and shape, giving confidence to the approach, and allowing modelling but not system optimisation. Optimising the antenna based on receiver design and still being able to use commercial code requires the external scripting of a commercial solver. The EDITFEKO (card based) module of FEKO (a powerful and versatile solver) is used along with the meshing software GMSH and GNU Octave. Optimisation of system sensitivity is demonstrated on a choke horn fed reflector system at 1420MHz. This optimisation method is applied to a practical application, an octave band system (4:5 GHz to 9 GHz) for the Hartebeesthoek Radio Observatory. The design is split into smaller simulations using waveguide modes and the associated S–parameters, the techniques are presented and checked on a truncated system. Initial design and optimisation are given. The combining of specialised multiport noise modelling design and optimisation within commercial EM/MW solvers allows more sensitive and specialised receivers to be built. Index terms— noise modelling, wideband, multiport, corrugated horn, octave band receiver, EM/MW optimisation / MT2018

ABSTRACT The multi-disciplinary accelerator based facilities at iThemba LABS are used intensively for nuclear physics experiments, radiotherapy and the production of radioisotopes. To increase the beam intensity for radioisotope production and to improve the beam quality of the 66 MeV proton beam, a double-gap horizontal half-wave flat-topping resonator has been developed for the separated-sector cyclotron to operate at the associated fixed frequency. This type of flattopping resonator has never before been implemented in a cyclotron and this study is the first to show that it can be done, featuring a special characteristic not offered by other types. The resonator is reviewed against the other types of resonators that are already in use at other institutes around the world. The flat-topping voltage of the selected type has a sinusoidal half-wave distribution along a radial line in each of its acceleration gaps with the nodal points located on the injection and extraction orbits. The flat-topping voltage therefore progressively increases from zero at both of the two most critical orbits in a cyclotron to a maximum at about halfway between them. As a result will this resonator, apart from its basic function to reduce the energy spread in the beam, not decrease the orbit separation at the injection and extraction orbits in the cyclotron, as is the case with other types of flat-topping resonators. This advantageous feature implies that the beam pattern in the cyclotron is not affected in the regions of the delicate injection and extraction components and therefore will these components or the operational control of the beam not require any modification to accommodate the resonator. In order to design a resonator that will meet our requirements, the theory of the beam dynamics and resonator characteristics were studied to ascertain the expected improvement in beam quality and beam intensity when a flat-topping resonator is implemented with the cyclotron. All resonator types were considered and studied in terms of their power dissipation, voltage distribution, harmonic number, space requirements and influence on the beam. The horizontal half-wave resonator type, with two acceleration gaps, was selected as the most suitable for our application, because of its preferred electromagnetic characteristics and its geometric shape that permits the installation inside an existing vacuum chamber through an existing flange. Initially a half-scale resonator model was build to test the feasibility of such a resonator and also to verify the calculation methods. Transmission line methods and numerical field analysis in 3D were applied to determine the resonator characteristics. In the former method a computer program, POISSON, was used to calculate curvilinear squares on sections through a triangular-shaped transmission line and in the latter method a commercial computer program, SOPRANO, was used. SOPRANO is part of an internationally acclaimed suite of programs and the acquired knowledge and skill to use this state-of-the-art software for the studying and designing of such and other electromagnetic devices also put the institute amongst the front-runners in the world. The calculated characteristics of the half- and full-scale resonator models, the study of the different electromagnetic modes that resonate in close proximity to the required frequency, the heat transport modelling and the theory and implementation of the coupling and tuning devices are all in good agreement with their respective measured results and are reported in this document. This study lead the way to have the first-ever double-gap horizontal half-wave flat-topping resonator in a cyclotron successfully commissioned at iThemba LABS and the first tests with beam report very stable operation. Accelerator physicists now have another option to utilize for the establishing of flat-topped acceleration voltages.

This thesis proposes to estimate the speed of a moving acoustic source by either linear or non linear processing of the resulting Doppler shift present in a high-frequency pilot tone. The source is an acoustic modem (Hermes) which currently uses moving average to estimate and compensate for Doppler shift. A new auto regressive approach to Doppler estimation (labeled IIR method in the text) promises to give a better estimate. The results for a simulated peak velocity of 2 m/s in the presence of additive noise showed an RMSE of 0.23 m/s using moving average vs. 0.00018 m/s for the auto regressive approach. The SNR was 75 dB. The next objective was to compare the estimated Doppler velocity obtained using the two algorithms with the experimental values recorded in real time. The setup consisted of a receiver hydrophone attached to a towing carriage that moved with a known velocity with respect to a stationary acoustic source. The source transmitted 375 kHz pilot tone. The received pilot tone data were preprocessed using the two algorithms to estimate both Doppler shift and Doppler velocity. The accuracy of the algorithms was compared against the true velocity values of the carriage. The RMSE for a message from experiments conducted indoor for constant velocity of 0.4 m/s was 0.6055 m/s using moving average, 0.0780 m/s using auto regressive approach. The SNIR was 6.3 dB. / by Poorani Kathiroli. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.