A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. Johannesburg, February 6, 2015. / We explore indirect detections of Dark Matter, focusing on deep radio observations of six dwarf spheroidal galaxies (dSph), Carina, Fornax, BootesII, Hercules, Segue2, Sculptor. We discuss the WIMP Dark Matter particle annihilation process and describe brie y the particles produced in this process. We consider the emissions, which can result from electrons and positrons produced. We describe why dSph are the best observational targets for indirect Dark Matter detection at radio frequencies. We describe the theoretical framework for predicting Dark Matter synchrotron emissions and make some predictions for the six dSph of interest to us. We discuss ATCA observations of these dSph and explore the background source subtraction process in detail. We obtain an upper limit on the WIMP mass and compare our results to various other experiments. We discuss prospects for this work towards attaining an indirect Dark Matter detection.

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The knee is the most common site of osteoarthritis (OA) and is one of the leading causes of disability in older adults affecting over 53 million people in the United States and more than 302 million people worldwide. These numbers are only expected to grow because of the rise of diseases such as obesity, demographic shifts to an older population, and a more sedentary lifestyle. The rise of obesity and a more sedentary lifestyle comes with increases in joint loading which along with the aging population creates worse outcomes in proprioception. All of which can contribute to worsening OA. Despite the great costs to quality of life and society, there is no cure for OA. Only treatments exist to treat the symptoms of OA; and since knee pain is one of the most common symptoms of OA, it is a powerful driver for treatment because of the disruptive nature it can have on quality of life. Therefore, many treatments focus on pain relief and exercise to reduce the pain and worsening of OA. Radio frequency nerve ablation (RFA) is a procedure that is increasingly being performed for those who want an alternative before resorting to or are not a good match for total knee arthroplasty (TKA). Because RFA is minimally invasive, it can be performed on an outpatient basis and has been shown to be effective in reducing pain for at least 24 months for most patients. Despite the benefits in pain reduction, little is known about the biomechanical effects of RFA and its consequences on proprioception. However, based on prior studies into the pain relieving effects of interventions such as celecoxib or HA injections, we can hypothesize that with a decrease in pain, knee loading increases. Therefore, the pain relieving effects of RFA may increase the incidence of OA. Furthermore, because the RFA procedure involves ablating nerves that carry sensory information, changes to proprioception are expected. However, currently there is no information regarding its effect on proprioception. Again, using prior research that studies the consequences of reduced proprioception on those with OA, we can hypothesize that with RFA, proprioception would be further reduced compared to the reductions experienced by people with OA already, and it may also lead to worsening OA outcomes. Despite the possible issue of worsening OA outcomes with RFA, the pain relieving effects cannot be discounted as it is one of the most disruptive symptoms of OA. Therefore, effects of RFA on knee biomechanics and proprioception should be studied to understand the long-term impacts of this procedure.

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Yes / Employing electromagnetic fields EMFs) in new wireless communication and sensing technologies has substantially increased the level of human exposure to EMF waves. This paper presents a useful insight into the interaction of electromagnetic fields with biological media that is defined by the heat generation due to induced currents and dielectric loss. The specific absorption rate (SAR) defines the heating amount in a biological medium that is irradiated by an electromagnetic field value. The paper reviews the radio frequency hazards due to the SAR based on various safety standards and organisations, including a detailed investigation of previously published work in terms of modelling and measurements. It also summarises the most common techniques utilised between 1978 and 2021, in terms of the operational frequency spectrum, bandwidth, and SAR values. / The European Union’s Horizon 2020 innovation programme under grant agreement H2020- MSCA-ITN-2016 SECRET-722424 and the U.K. Engineering and Physical Sciences Research Council (EPSRC) under grant EP/E022936/1 supported this research. This study is also sponsored by the FCT/MEC through national funds and, where applicable, co-financed by the ERDF under the PT2020 Partnership Agreement under the UID/EEA/50008/2020 project. This study is part of the POSITIONII project, which is funded by the European Commission’s Joint Undertaking under the grant number Ecsel-7831132-Postitio-II-2017-IA. Moreover, this paper is also partially funded by British Council “2019 UK-China-BRI Countries Partnership Initiative” programme, with project titled “Adapting to Industry 4.0 oriented International Education and Research Collaboration”. In addition, this project has received funding from Universidad Carlos III de Madrid and the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant 801538.

This thesis will begin with an investigation on the limitations associated with the predominate two-port stability analysis techniques with respect to multi-stage RF amplifier design. The primary focus will be to investigate and develop network analysis techniques that allow internal ports to be created within a RF circuit. This technique will facilitate the application of existing stability analysis techniques in ways that are not commonly known. Examples of situations where traditional network and stability analysis is insufficient will be presented, and the application of the newly developed techniques will be examined.

One of the main problems that affect the data integrity of passive RFID systems is the collision between the tags. A popular anticollision algorithm which dominates the standards in HF and UHF passive RFID systems is Framed Slotted Aloha (FSA) and some variations of FSA. Throughput and Average time delay of the RFID system which determines the performance/efficiency of the system are reduced rapidly when the number of tags inside the interrogation zone is increased. Using larger frame sizes is not always the solution. This thesis discusses and compares the existing protocols, and proposes a variation of FSA, called Progressing Scanning (PS) algorithm. The PS algorithm divides the tags in the interrogation zone into smaller groups, and gives the ability to the reader to communicate each time with one of them. For performance analysis, the PS algorithm was evaluated with the parameters of a typical passive RFID system at 2.45 GHz . The results showed that the PS algorithm can improve the efficiency of the RFID system and provide a reliable solution for cases with a high density of tags in the area (over 800 tags ).

米勒補償是現今最被廣泛使用的頻率補償方法之一。其極點分離現象為雙級放大器供簡易而又可靠的穏定作用。可是，隨着亞微米 CMOS 技術及低電壓電路設計的興起，高增益同時又寬頻寬的放大器設計變得愈來愈困難。雖然多階段方式能實現高增益的放大器規格，但其頻寬會隨之縮窄，頻率補償亦會變得複雜及困難。 / 在過去，很多學術硏究報告都提出了不少方法去解決多階段放大器頻寬縮窄的問題，但這些方法往往離開複雜的頻率補償技巧及電路結構。為了根本性地解決此問題，本論文會提出一個虛擬雙階段放大器的設計。此放大器設計利用了兩個低增益階段來放大進入第二階段前的訊號振幅，從而放進整個放大器的頻寬及增益。由於其簡單的結構，這個設計仍然能夠採用穏定可靠的簡易米勒補償方式來穏定整個放大器。 / 這個設計由CMOS 180nm（互補式屬-氧化層-半導體180納米）技術製成。實驗結果證實了其高增益及寬頻寬的效能。另外，這果放大器亦同時應用在一個低通濾波器的實現上，用以證明其實際應用上的用途。實驗結果證實利用該放大器實現的低通濾波器比用一般雙段放大器的功率消耗減少近 45%。 / Miller compensation is one of the most widely adopted frequency compensation techniques for two-stage amplifier design. With its pole-splitting behavior achieved by connecting a capacitor between the output nodes of the two gain stages, Miller compensation provides a simple and reliable stabilizing function to two stage amplifiers. However, with the advance of sub-micron CMOS technology and low-voltage circuit designs, high-gain and wide-bandwidth amplifier design becomes more difficult. Although multi-stage amplifiers can be used to attain high-gain specification, the bandwidth will be degraded dramatically and the frequency compensation scheme becomes much more complicated. / To solve the problem, several researches have been done to improve the frequency response of multi-stage amplifiers so as to achieve high-gain and wide-bandwidth specifications simultaneously. However, these always result in the increase of circuit complexity and more complicated frequency compensation techniques. / In this thesis, a virtual two-stage Miller compensated amplifier will be proposed. By using two small gain stages, the characteristics of a conventional two-stage Miller compensated amplifier can be retained due to the low output impedance of the two gain stages. The small gain stages boost the input signal amplitude of the second stage such that the generated small-signal output current can be increased significantly. This results in wider signal bandwidth and higher voltage gain. / The proposed design has been fabricated in UMC CMOS 0.18μm technology. Experimental results have verified the concept. From the measurement, the unity-gain frequency of the proposed design is better than the conventional design by 4 times. Moreover, the voltage gain is improved by about 20dB. The current consumption is 124.76μA which is the nearly the same as the conventional design. / In order to show the improvement in real applications, the proposed amplifier has been applied to a fifth-order low-pass filter with corner frequency of 50kHz. Under the same performance, the power consumption of the filter using the proposed amplifier can be reduced by about 45%. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Poon, Hiu Ching. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Abstracts also in Chinese. / Abstract --- p.i / Acknowledgments --- p.iv / Table of Content --- p.v / List of Figures --- p.vii / List of Tables --- p.xi / Symbols Declarations --- p.xii / Chapter Chapter 1 --- Background Information / Chapter 1.1 --- High-Gain Amplifier and its Application with Negative Feedback Configuration --- p.1-1 / Chapter 1.2 --- High-Gain Amplifier Design and the Tradeoffs --- p.1-6 / Chapter 1.3 --- High-Gain Amplifier Implementations --- p.1-8 / Chapter 1.4 --- Contribution and Outlines of the Thesis --- p.1-15 / References --- p.1-16 / Chapter Chapter 2 --- Analysis of Frequency Compensation Techniques / Chapter 2.1 --- Simple Miller Compensation --- p.2-1 / Chapter 2.2 --- Miller Compensation with Null Resistor --- p.2-10 / Chapter 2.3 --- Miller Compensation with Multipath Zero Cancellation --- p.2-13 / Chapter 2.4 --- Nested Miller Compensation --- p.2-15 / Chapter 2.5 --- Advanced Frequency Compensation Techniques --- p.2-17 / Chapter 2.6 --- Conclusion of Chapter --- p.2-20 / References --- p.2-22 / Chapter Chapter 3 --- Proposed Amplifier Design / Chapter 3.1 --- Gain Tolerance --- p.3-1 / Chapter 3.2 --- Adjustments on Simple Miller Compensated Two-Stage Amplifier --- p.3-3 / Chapter 3.3 --- Introducing the Small Gain Stage --- p.3-4 / Chapter 3.4 --- Concept of the Proposed Virtual Two-Stage Miller Compensated Amplifier --- p.3-7 / Chapter 3.5 --- Comparisons with Bandwidth Enhanced Miller Compensated Two-Stage Amplifier --- p.3-9 / Chapter 3.6 --- Proposed Virtual Two-Stage Amplifier with Simple Miller Compensation --- p.3-13 / Chapter 3.7 --- Design Considerations and Expected Performance --- p.3-15 / Chapter 3.8 --- Experimental Result --- p.3-18 / Chapter 3.9 --- Conclusions of Chapter --- p.3-31 / References --- p.3-32 / Chapter Chapter 4 --- Implementation of the Low-Pass Filter / Chapter 4.1 --- Implementation of the Low-Pass Filter --- p.4-1 / Chapter 4.2 --- Experimental Result --- p.4-4 / Chapter 4.3 --- Conclusion of Chapter --- p.4-7 / Reference --- p.4-8 / Chapter Chapter 5 --- Conclusion and Future Work / Chapter 5.1 --- Conclusion of Thesis --- p.5-1 / Chapter 5.2 --- Suggestion for Future Work --- p.5-2

Electric fencing is commonly used on New Zealand's farms. Modern technology is used in farm management systems to solve old farming problems in a more efficient and simple way. Engineers have researched the use of the electric fence as a communication medium and new technologies based on transmission line theory are used at present to monitor and troubleshoot problems occurring in electric fences. The next stage of the development is to use wireless devices to accomplish those same tasks from remote locations. This project aims to develop a prototype that provides a wireless link between an electric fence and a personal computer in a remote location. This prototype is expected to prove concepts that lead to the future design of useful, marketable products. The project was supported by Gallagher Electronics and is implemented using their existing products where possible.