A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in ful lment of the requirements for the degree of Master of Science in Engineering, Johannesburg, September 2019 / The objective of this research was to develop an integrated Port Hamiltonian model of the human outer, middle and inner ear. The developed Port Hamiltonian model of the human ear is based on the Dirac structure. The outer, middle and inner ear are developed in segments, tested and validated prior to the system being coupled. The outer, middle and inner ear are validated against existing literature and the results are found to be comparable. The application of the developed Port Hamiltonian model is illustrated using a developed feedback based noise policy management model for mine workers. This feedback based measurement system can be used to monitor mine workers in the mines hence provide the mine administrators with the current state of hearing of the individual worker. The information obtained from the system may be used by the administration to provide an early intervention and as a result the mine workers are protected from experiencing signi cant hearing threshold shifts. A control engineering approach is then used to formulate the mining noise occupational policies as a control law. Both social and measurements aspects of this system are explored. The International Standard Organization guide ISO:1999 is used to generate data and develop a basic feedback model. The basic feedback model is further re ned into a dynamic model which includes a Port Hamiltonian integrated ear model and the mining policies. The feedback based noise policy management model is validated using real data from the mine documented in open source literature. The models are implemented using MATLAB as a modelling platform and the results are generated using the Simulink model. This research work has been given an ethical clearance certi cate by the Human Research Ethics Committee (Medical), therefore, allowing for the ndings of the investigations to be published. In conclusion,to be developed is an integrated Port Hamiltonian model of the Human outer, middle and inner ear to be used for estimation of Noise induced hearing loss. The use of this model is then illustrated using a feedback based noise policy monitoring system for mine workers. / PH2020

Low-noise operational amplifiers are an important tool in the life sciences. Biosensor measurements typically rely on low-noise transimpedance amplifiers to record biological signals. Two different techniques were used to leverage the advantages of low-noise circuitry for bioelectronics. A CMOS-integrated system for measuring redox-active substrates using electrochemical read-out at very low noise levels is presented. The system incorporates 112 amplifier channels capable of current sensing with noise levels below 1 fArms in a 3.5-Hz bandwidth. The amplifier is externally connected to a gold microelectrode with a radius of 15 µm. The amplifier enables measurement of redox-couples such as potassium ferrocyanide/ferricyanide with concentrations down to 10 nM at current levels of only 300 fA. The electrochemical noise that sets the limits of detection is also measured and analyzed based on redox mass transfer equation and electrochemical impedance spectroscopy. Secondly, CMOS-integrated low noise junction field-effect transistors (JFETs) were developed in a standard 0.18-µm CMOS process. These JFETs reduce input referred flicker noise power by more than a factor of 10 when compared with equally sized n-channel MOS devices by eliminating oxide interfaces in contact with the channel. We show that this improvement in device performance translates into a factor-of-10 reduction in the input-referred noise of integrated CMOS operational amplifiers when JFET devices are used at the input.

Philosophiae Doctor - PhD / The faint radio population consisting of star forming galaxies (SFG) and radio-quiet active galactic nuclei (AGN) is important in the study of galaxy evolution. However, the bulk of the faint population is below the detection threshold of the current radio surveys. I study this population through a Bayesian-stacking technique that I have adapted to probe the radio luminosity function (RLF) below the typical 5σ detection threshold. The technique works by fitting RLF models to radio flux densities extracted at the position of galaxies selected from an auxiliary catalogue. I test the technique by adding Gaussian noise (σ) to simulated data and the RLF models are in agreement with the simulated data for up to three orders of magnitude (3 dex) below the detection threshold (5σ). The source of radio emission from radio quiet quasars (subset of AGN) is widely debated. I apply the technique to 1.4-GHz flux densities from the Faint Images of the Radio Sky at Twenty-cm survey (FIRST) at the positions of the optical quasars from the Sloan Digital Sky Survey (SDSS). The RLF models are constrained to 2 dex below the FIRST detection threshold. I found that the radio luminosity where radio-quiet quasars emerge coincides with the luminosity where SFGs are expected to start to dominate the RLF. This Implies that the radio emission of radio-quiet quasars and radio-quiet AGN, in general, could have a significant contribution from star formation in the host galaxies.

An aeroacoustic investigation was performed to assess the effects of adding mass flow at the trailing edges of four stators upstream of an aircraft engine simulator. By using trailing edge blowing to minimize the shed wakes of the stators, the flow into the rotor was made more uniform. In these experiments a reduced number of stators (four) was used in a 1/14 scale model inlet which was coupled to a 4.1 in (10.4 cm) turbofan engine simulator with 18 rotors and 26 downstream stators. This study is a preliminary step toward a more in depth investigation of using trailing edge blowing to reduce unsteady rotor-stator interaction. Steady-state measurements of the aerodynamic flow field and acoustic far field were made in order to evaluate the aeroacoustic performance at three simulator speeds: 40%, 60%, and 88% of the design speed. The lowest test speed of 40% design speed showed the most dramatic reduction in radiated noise. Noise reductions as large as 8.9 dB in the blade passing tone were recorded at 40% design speed, while a tone reduction of 5.5 dB was recorded at 60% design speed. At 88% design speed a maximum tone reduction of 2.6 dB was recorded. In addition, trailing edge blowing reduced the overall sound pressure level in every case. For both the 40% design speed and the 60% design speed, the fan face distortion was significantly reduced due to the trailing edge blowing. The addition of trailing edge blowing from the four upstream stators did not change the total pressure ratio, and the mass flow added by the blowing was approximately 1%. The results of these experiments clearly demonstrate that blowing from the trailing edges of the stators is effective in reducing unsteady rotor-stator interaction and the subsequent forward radiated noise. / Master of Science

The problem of noise as a potential health hazard to urban man has been raised. The literature was used to establish two premises: that cities are noisy environments, and that noise-free societies have less coronary artery disease (CAD) than do industrialized sections of the world. These differences also hold for rural and urban areas of the United States. Geographical questions concerning rate differentials for CAD have been addressed by numerous disciplines. Subsequently, social, psychological, and physical explanations have been put forth. Throughout this paper the emphasis has been placed on the physical aspects of noise exposure. The conceptual frame utilizes noise-load, overload, stress and deformation. Noise was described as a force capable of eliciting a predictable physiological response from the human organism. Noise was further conceptualized as a by-product of technology which exerts a stressor effect upon the cardiovascular system of man. The investigation, from which the data were generated, was a micro-view of physiological effects, in that the only measurement taken was heart rate change in hospitalized patients in response to noise. The heart rate was calculated under low noise conditions, and comparisons subsequently made to heart rate during noise. In addition, the noise climate for each of two coronary care units (CCU) was tabulated over a 24 hour period. Generally noise levels in the CCUs were higher than might be found in a man's own home. Only between the hours of 3:00 and four in the morning, was ambient noise equal to or below the suggested levels (45 dbA) for any sustained period of time. Conditions of noise elicited heart rate change in 30 of 37 subjects (p=.001). This finding relates to the presence of a change and does not speak to the extent or meaningfulness of that change. Patients with heart attacks responded to noise conditions (11=18, P=.01) in that 17 of the eighteen patients experienced a change in heart rate when noise was introduced. No differences could be noted for categories by site of infarctions. It was further hypothesized that the extent of heart rate response (HRR) would be a function of the gap between low noise and high noise conditions. A regression analysis showed the response to be significantly correlated with noise gap for the total population (N=37, P=.05), however the correlation was minimal (r=.4528) with slightly less than 21 per cent of the variation in HRR explained by the variation in noise gap. Those subjects more than 60 years of age (n=20), also showed a significant correlation (r=.5173) with 26 per cent of the variation in HRR explained by the variation in noise gap. The highest correlation (r=.7373) was obtained for ten persons with a past history of heart disease (r2=.5436, P=.05). The implications for site planning and structure are many, particularly for hospitals, nursing, and convalescent homes where older persons with heart disease are housed. Site planning should give attention to noise environment; and structural planning, to sound-proofing. Interviews with architects and hospital builders showed this goal to be attainable mechanically, if somewhat costly. It was agreed by those interviewed that such costs as evolve from noise-reduction or noise-proofing in hospitals would most certainly be passed on to the consumer and be reflected in his health care costs. Additional research is needed which focuses on the effects of noise on the cardiovascular system over time, using standardized criteria for cardiovascular health and cardiovascular disease. Other research might focus on larger samples of patients hospitalized with CAD, in an effort to identify an index of physiological and psychological responses to noise.

This work explores the stochastic dynamics and important diagnostics of a mechanical resonator (nanobeam) used in cavity optomechanical sensors for atomic force microscopy. Atomic force microscopy (AFM) is a tool to image surface topology down to the level of individual atoms. Conventional AFM has been an essential tool for micro and nanoscale studies in physics, chemistry, and biology. Cavity optomechanical sensors for AFM extend the utility of conventional AFM into a new regime of high sensitivity k is approximately 1 N/m and high frequency f0 is approximately 10 MHz. Cavity optomechanical sensors for AFM are unique because they use near field optics to transduce the position of a nanobeam. The nanobeam is not able to be transduced by more conventional AFM techniques, such as laser interferometry, because the nanobeam is smaller than the spot size of the laser. This work determines the noise spectrum G of a nanobeam in water and in air. Also important diagnostics of the nanobeam are determined in air and in water. These important diagnostics include the quality factor Q and natural frequency in fluid omega_f. It is found that the nanobeam is overdamped in water. However, the nanobeam is underdamped in air and has quality factor of Q is approximately 4. The noise spectrum is determined from deterministic numerical calculations and the Fluctuation-Dissipation Theorem. This is possible because the same molecular processes, Brownian motion, cause both the fluctuations of the nanobeam and the dissipation of the nanobeam. / Master of Science

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With the emergence of cloud-native applications, the need to secure networks and services creates new requirements concerning automation, manageability, and scalability across data centers. Several solutions have been developed to overcome the limitations of the conventional and well established IPsec suite as a secure tunneling solution. One strategy to meet these new requirements has been the design of software-based overlay networks. In this thesis, we assess the deployment of a traditional IPsec VPN solution against a new secure overlay mesh network called Nebula. We conduct a case study by provisioning an experimental system to evaluate Nebula in four key areas: reliability, security, manageability, and performance. We discuss the strengths of Nebula and its limitations for securing inter-service communication in distributed cloud applications. In terms of reliability, the thesis shows that Nebula falls short to meet its own goals of achieving host-to-host connectivity when attempting to traverse specific firewalls and NATs. With respect to security, Nebula provides certificate-based authentication and uses current and fast cryptographic algorithms and protocols from the Noise framework. Regarding manageability, Nebula is a modern solution with a loosely coupled design that allows scalability with cloud-ready features and easier deployment than IPsec. Finally, the performance of Nebula clearly shows an overhead for being a user-space software application. However, the overhead can be considered acceptable in certain server-to-server microservice interactions and is a fair trade-off for its ease of management in comparison to IPsec. / Med framväxten av molninbyggda applikationer skapar behovet av säkra nätverk och tjänster nya krav på automatisering, hanterbarhet och skalbarhet över datacenter. Flera lösningar har utvecklats för att övervinna begränsningarna i den konventionella och väletablerade IPsec-sviten som en säker tunnellösning. En strategi för att möta dessa nya krav har varit utformningen av mjukvarubaserade överläggsnätverk. I den här avhandlingen bedömer vi implementeringen av en traditionell IPsec VPN-lösning mot ett nytt säkert överläggsmeshnätverk som kallas Nebula. Vi genomför en fallstudie genom att bygga upp ett ett experimentellt system för att utvärdera Nebula inom fyra nyckelområden: tillförlitlighet, säkerhet, hanterbarhet och prestanda. Vi diskuterar styrkan i Nebula och dess begränsningar för att säkra kommunikation mellan tjänster i distribuerade molnapplikationer. När det gäller tillförlitlighet visar avhandlingen att Nebula inte uppfyller sina egna mål om att uppnå värd-tillvärd- anslutning när man försöker korsa specifika brandväggar och NAT. När det gäller säkerhet tillhandahåller Nebula certifikatbaserad autentisering och använder aktuella och snabba kryptografiska algoritmer och protokoll från Noise-ramverket. När det gäller hanterbarhet är Nebula en modern lösning med en löst kopplad design som möjliggör skalbarhet med molnklara funktioner och enklare distribution än IPsec. Slutligen visar prestandan hos Nebula tydligt en overhead för att vara en användarutrymme-programvara. Dock kan kostnaderna anses vara acceptabla i vissa server-till-server-mikroserviceinteraktioner och är en rättvis avvägning om vi tar i betraktande dess enkla hantering jämfört med IPsec.

本論文は，従来よりも信頼性や効率が良く実用的に構造物の振動・騒音を低減することを目指して，実験および解析技術に対する新たなアプローチを確立することを目的としている．そのために，統計的エネルギー解析法と伝達経路解析法を統合することで，両者の入力を相互利用可能な手法を提案し，構造物の振動・騒音の低減を支援するための，実験および解析手法を構築した． / In this thesis, we have established new theoretical approaches as well as some basic practical applications in the development of noise and vibration analysis for structures involving transfer path and sound source from airborne noise and structure-borne noise. These new approaches were extracted from the existing experimental and analysis technique of noise and vibration for structures, which will improve their efficiency and reliability for noise and vibration reduction on industrial machineries as well as other machines. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University