This thesis presents a study of several algorithms for enhancing speech degraded by additive noise in mobile cellular communications. The primary goal of this multi-stage study was to examine adaptive noise cancellation techniques in which one microphone is used to measure the speech plus noise signal and another microphone is used to form an estimate of the interfering background noise. The first stage of this research project involved the design and operation of a measurement system to gather dual channel audio samples in mobile radio environments for use in testing adaptive noise cancellation algorithms developed at Northeastern University. In the second phase of this research, several adaptive algorithms were used to implement noise cancellation systems which were applied to the measured speech signals. In the third phase of this research, several of the adaptive noise cancellation algorithms are compared and additional speech enhancement techniques are investigated. / Master of Science

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Thesis (M.Sc (Physiology)) --University of Limpopo, 2015 / Objective This study assesses whether noise levels above legal limits of 85 dB(A) that can result in noise-induced hearing loss are present in areas where employees are supposed to work and to verify that such areas are demarcated as noise zones at the Polokwane Platinum Smelter. Background and motivation Excessive noise is a global health hazard with considerable social and physiological impact, including the development of noise-induced hearing loss (NIHL). Noise is a major hazard in many workplaces. It is estimated that more than 30 million workers (almost 1 in 10) are exposed to unsafe noise in their work places. NIHL is the second most self-reported occupational illness or injury in the United States. Amongst miners, more than 90% of the population reports hearing problems by the age of 55 years. Noise exposure is prevalent in construction, foundries, agriculture, transport, industry and mining-related activities. The prevalence of NIHL has not changed much in the past two decades. Therefore, a hearing conservation programme is an important issue in the smelter as certain areas are denoted as noise areas. Study design A cross-sectional study design with a group of utility workers at the Polokwane Platinum Smelter, as the experimental group, and a group of undergraduate Bachelor of Science students at the University of Limpopo (Turfloop Campus) served as a control group. Method A sound level meter was used to measure the noise levels where the utility group performs their technical work. Data were analysed using the Statistical Package for the Social Sciences (SPSS) computer program. Results The average noise measured in various locations of the Polokwane Platinum Smelter was between 62.6 dB(A) and 105.1 dB(A). The results indicated that workers at the Polokwane Platinum Smelter are over exposed to noise in certain work areas if they work eight hours in the area. Areas where the average noise level was above noise rating limit of 85 dB(A) were demarcated as noise zones as an additional protective measure. Employees also use hearing protective devices, when they are working in noise zones, to control personal noise exposure. This is in accordance with the Occupational Health and Safety Act No. 85 of 1993 as amended eleventh edition (OHS Act 85/93). Conclusion In the present study, noise levels in certain areas exceeded the noise rating limit of 85 dB(A). However such areas are clearly demarcated as noise areas and employees accessing those area must wear earmuffs or earplugs. Possibilities of employees developing hearing loss overtime exist, if employees work for eight hours or longer in demarcated areas and do not adhere to the existing Hearing Conservation Program (HCP) implemented at the Polokwane Platinum Smelter. Noise levels at the Polokwane Platinum Smelter should be monitored regularly. / University of Limpopo

Bibliography: p. 199-207. Electronic publication; full text available in PDF format; abstract in HTML format. Describes the basis of a theoretical and experimental project, directed at the design and evaluation of a practical active noise control system suitable for a single light engine aircraft. The performance of virtual sensors were evaluated both analytically and experimentally in progressively more complex environments to identify their capabilities and limitations. Electronic reproduction.[Australia] :Australian Digital Theses Program,2001.

Electrochemical techniques have potential for use in conservation, both to evaluate the protectiveness of existing coatings on metal artefacts and to evaluate potential new conservation coatings. Three electrochemical methods have been examined in this study for their applicability to conservation problems. Corrosion Potential Measurement is simple but provides only minimal information on the corrosion processes occurring in an electrochemical system. Electrochemical Impedance Spectroscopy provides both mechanistic and predictive information on coating performance, but the data are complex to interpret and measurements require equipment that is at present too bulky for effective on-site use and beyond the budget of most conservation laboratories. Electrochemical Noise Measurement can be performed using cheap, portable instrumentation and theoretically requires relatively simple statistical processing and interpretation, making it attractive for conservation applications. This project looks at the development of a simple, low cost electrochemical noise measurement system for conservation needs, and uses it to compare Electrochemical Noise Measurement with the other two techniques.

Reliability, besides the performance, is one of the important key factors of success of any technology. While a product should perform at best as desired, it must also be capable of working for intended period of life without any degradation or wear-out failure, caused by any operational parameter. For example it does no good to manufacture a super fast microprocessor if that fails within few seconds. For the product to meet the intended reliability we must understand the mechanisms that lead to unreliability or failure of the devices. The efforts to understand the fundamental physics of the mechanisms that lead to the failure of the devices has developed a branch of physics named as “reliability physics” of “physics of failure”. On the basis of the understanding of failure mechanism, new design rule can be followed and new material can be applied to improve the reliability of the product. Microelectronic technology also, which is one of the fastest growing technology, has been facing challenges posed by the reliability issues from time to time. There are number of physical failure mechanisms that can affect the reliability of a microelectronic device. Time dependent dielectric breakdown (TDDB), hot carrier damage and current induced damage of interconnects are only to name a few common mechanisms. Among these, the failure of interconnects due to current has been the oldest and persistence reliability issue since the beginning of development of the microelectronic technology. Understanding the physics of the processes that lead to failure of a current carrying film is the main interest of this thesis work. In this investigation, we have carried out a systematic study to understand stability of metal nanowires against damage caused by current stressing and its size dependency. We observe the wires of smaller diameter, having an electronic mean free path larger than or comparable to its diameter are more stable against current stressing. In wires of larger diameter (100 nm or more) the probability of the damage is more. This probably is due to presence of grain boundary type extended defects that allow low energy diffusion path. To our knowledge this is the first experimental investigation to study the stability of nanowires against high current and in-situ measurement of noise during current stressing on them. In the previous investigations by other groups observed that the nanowires without any passivation got damaged by stressing current density which was even lower than the one we used for stressing. To our knowledge this is the first observation of long lasting stability of nanowires, of dimension down to 15 nm, when they are encapsulated in dielectric, an environment that an interconnect has to see in the real integrated circuit devices. In the second chapter we will describe the sample preparation method, characterization of samples and the experimental setups we had used. The results of in-situ noise measurement are described in the third chapter. We will describe our in-situ scanning thermal microscopy study in the fourth chapter. Then in the fifth chapter, we will present our simulation investigations on current induced damage of film. Finally, we will put the concluding remarks on this thesis work and the results in the sixth chapter. We have studied similar damage processes in metal nanowires also. In an appendix we will present our approach and major results of this investigation.

Spintronics, an abbreviation of spin based electronics and also known as magneto electronics, has attracted a lot of interest in recent years. It aims to explore the role of electrons’ spins in building next generation electric devices. Using electrons’ spins rather than electrons’ charges may allow faster, lower energy cost devices. Spin Hall Effect is an important subfield of spintronics. It studies spin current, spin transport, and spin accumulation in paramagnetic systems. It can further understanding of quantum physics, device physics, and may also provide insights for spin injection, spin detection and spin manipulation in the design of the next generation spintronics devices. In this experimental work, two sets of experiments were prepared to detect the Spin Hall Effect in metallic systems. The first set of experiments aims to extract Spin Hall Effect from Double Hall Effect in micrometer size metal thin film patterns. Our experiments proved that the Spin Hall Effect signal was much smaller than the theoretically calculated value due to higher electrical resistivity in evaporated thin films. The second set of experiments employs a multi-step process. It combines micro fabrication and electrochemical method to fabricate a perpendicular ferromagnet rod as a spin injector. Process description and various techniques to improve the measurement sensitivity are presented. Measurement results in aluminum, gold and copper are presented in Chapters III, IV and V. Some new experiments are suggested in Chapters V and VI.

Bibliography: p. 199-207. Describes the basis of a theoretical and experimental project, directed at the design and evaluation of a practical active noise control system suitable for a single light engine aircraft. The performance of virtual sensors were evaluated both analytically and experimentally in progressively more complex environments to identify their capabilities and limitations.

A escolha pela Industria da Construção Civil foi devido à sua dinâmica, exibindo diversos ramos dentro de uma obra com muitos funcionários envolvidos, estando muitas vezes expostos ao ruído de máquinas e equipamentos. O ruído é considerado como um dos maiores causadores de afastamento, lesões chegando até a causar as aposentadorias, junto ao INSS. Segundo o Ministério do Trabalho e Emprego, o setor da construção civil ocupou 1.048.251 postos de trabalhos diretos em 2003, tendo ocupado 1.118.570 postos de trabalhos em 2004. De acordo com o Ministério da Previdência Social, no ano de 2005, cerca de 492 mil acidentes do trabalho foram registrados no INSS. Comparado com o ano anterior, 2004, o número de acidentes de trabalho registrados aumentou 5,6%, por isso a importância de pesquisas nessa área. De acordo com a NR-9, o ruído é um agente físico, muitas vezes esquecido, passando despercebido nas fases de execução de uma obra, se fazendo necessário, antes do inicio de cada obra, a sua identificação, avaliação e os possíveis controles quando necessário. O ruído é considerado o terceiro maior causador da poluição ambiental, só ficando atrás da poluição das águas e do ar. A perda auditiva é uma patologia 100% evitável, mas uma vez adquirida, é permanente e irreversível. Essa pesquisa teve como objetivo, a analise através da dosimetria do nível de pressão sonora, gerado pelos equipamentos: betoneira, serra circular e/ ou manual e guincho(elevador) do ramo da indústria da construção civil. Foi realizada em 5 (cinco) obras de edificações verticais, na fase de acabamento, na Região Metropolitana do Recife (RMR). Os resultados foram satisfatórios, pois nenhum funcionário encontrava-se expostos aos diferentes níveis de pressão sonora (ruídos), gerados pelas máquinas monitoradas: guincho, betoneira e serra circular ou portátil. Apesar de alguns níveis excederem o limite de tolerância (LT) que para a norma é de 85dB (A), com uma dose de exposição de 100% para uma permanência de 8 horas diárias. Apenas 1 dos 14 funcionários, não utilizava o Equipamento de Proteção Individual (EPI), no caso específico em apreço, o protetor auricular, tipo concha ou tipo plug, o que o levou a aproximar-se mais do limite estabelecido pela norma. Foram utilizados 2 (dois) dosímetros de marca Quest, modelos Q-300 e Q-400, aparelhos estes conectados ao corpo do trabalhador. Depois de verificados esses níveis de pressão sonora e a exposição de cada funcionário a tais níveis de ruído, os resultados foram confrontados com a legislação vigente e sugeridas algumas medidas de atenuação, quando julgados necessários / The decision for the building construction industry was due to its dynamics, having diverse areas within a project, many construction workers are involved, and they are exposed to machinery and equipments noise. Machinery noise is the main cause of medical leave and injuries; it can also cause early retirements by the INSS [Brazilian National Institute of Social Security]. According to the Ministry of Labor and Employment, the civil construction sector held 1,045,251 direct job positions in 2003, and 1,118,570 direct job positions in 2004. The Ministry of Welfare points that in 2005, approximately 492,000 of work related injuries were reported to the INSS. If compared to the previous year of 2004, work related injuries increased 5.6%. The numbers show the importance of a research in that area. According to the NR-9, the noise is a physical agent, and many times do not receive the special attention required, it can go unnoticed during the implementation stages of a project. It is necessary, before the start of each job or project, the identification, evaluation and the correct control of the noise when needed. Noise is considered the third main cause of environmental pollution, only behind of water and air pollution. Hearing loss is a pathology that can be 100% prevented, but once acquired, it becomes permanent and irreversible. This research objective was the analysis by a dosimeter of the sound pressure level generated by the equipments: concrete truck mixer; the circular saw or portable and construction lift of the civil construction sector. The research took place in 5 (five) sites of vertical building projects, during the final stage, in the Metropolitan area of Recife (RMR). The results were satisfactory, as no construction worker was found exposed to the different levels of sound pressure (noise), generated by the machinery being monitored: concrete truck mixer, circular saw or portable and construction lift. Even though some levels exceeded the tolerance limit (LT) which is a standard of 85dB (A), for a 100% exposure in an 8 hours working day. Only 1 out of 14 construction workers was not equipped with the Individual Protection Equipment (EPI). In this particular case, the ear protector (protective type shell or plug type), exposed the worker to the limit set by the standard. Two (2) dosimeters from Quest brand were used in this research; models Q-300 and Q-400. The devices were connected to the body of the worker. After verifying the sound pressure levels and the exposure of each worker to such levels of noise, the results were confronted with the legislation in charge and some mitigation measures were suggested, when deemed necessary, in order to avoid possible damages to the workers health

abstract: With the growing importance of underground power systems and the need for greater reliability of the power supply, cable monitoring and accurate fault location detection has become an increasingly important issue. The presence of inherent random fluctuations in power system signals can be used to extract valuable information about the condition of system equipment. One such component is the power cable, which is the primary focus of this research. This thesis investigates a unique methodology that allows online monitoring of an underground power cable. The methodology analyzes conventional power signals in the frequency domain to monitor the condition of a power cable. First, the proposed approach is analyzed theoretically with the help of mathematical computations. Frequency domain analysis techniques are then used to compute the power spectral density (PSD) of the system signals. The importance of inherent noise in the system, a key requirement of this methodology, is also explained. The behavior of resonant frequencies, which are unique to every system, are then analyzed under different system conditions with the help of mathematical expressions. Another important aspect of this methodology is its ability to accurately estimate cable fault location. The process is online and hence does not require the system to be disconnected from the grid. A single line to ground fault case is considered and the trend followed by the resonant frequencies for different fault positions is observed. The approach is initially explained using theoretical calculations followed by simulations in MATLAB/Simulink. The validity of this technique is proved by comparing the results obtained from theory and simulation to actual measurement data. / Dissertation/Thesis / Masters Thesis Electrical Engineering 2016