This paper presents analytic expressions for the wave structure function, frequency spread of the temporal frequency spectrum, and the temporal frequency spectrum of optical signals propagating through a random medium, specifically the Earth’s atmosphere. The results are believed to be valid for all optical turbulence conditions. These expressions are developed using the Rytov approximation method. Generally, the validity of statistical quantities obtained via this method is restricted to conditions of weak optical turbulence. However, in this work, by using a modification of the effective atmospheric spectral model presented by Andrews et al. for scintillation index, wave structure function expressions have been derived that are valid in all turbulence conditions as evidenced by comparison to experimental data. Analytic wave structure function results are developed for plane, spherical, and Gaussian-beam waves for one-way propagation. For the special case of a spherical wave, comparisons are made with experimental data. The double pass case is also considered. Analytic expressions for the wave structure function are given that incorporate reflection from a smooth target for an incident spherical wave. Additionally, analytic expressions for the frequency spread of the temporal frequency spectrum and the temporal frequency spectrum itself, after one-way propagation for horizontal and slant paths, are derived for plane and spherical waves. These results are also based on the Rytov perturbation method . Expressions that are believed to be valid in all turbulence conditions are also developed by use of the effective atmospheric spectral model used in the wave structure function development. Finally, double pass frequency spread expressions are also presented. As in the case of the wave structure function, reflection from a smooth target with an incident spherical wave is considered.

Thesis (M.M. (ICT Policy and Regulation))--University of the Witwatersrand, Faculty of Commerce, Law and Management, Graduate School of Public and Development Management, 2013. / Radio frequency spectrum, a scarce national strategic asset, has not enjoyed the necessary attention and protection it deserves. Spectrum has been managed by the same approach over the last two decades and it is only recently that attention has been given to it due to the pressure of increased competition and technological advancements. The purpose of this study was to explore the policy and regulatory approaches to the management of radio frequency spectrum prevalent in South Africa today. Internationally there is a shift from the traditional command and control spectrum management approaches to more market-based mechanisms, such as auctions and spectrum trading. The South African approach has been marked by delays in the usage of spectrum as a result of the current institutional arrangements where there is an apparent overlap between the policy and regulatory function. The study concludes that the delays could be circumvented by separating the spectrum allocation and assignment into policy and regulatory functions respectively. Efficient spectrum management policy and regulation is important for the next stage of electronic communications revolution because of the advances in the technology such as broadband and agile radio.

When a cyclist is cycling on a suburban road, it’s a problem to notice fast rear approaching vehicles in some cases. Looking back frequently is not a good idea. Finding some technical way to help cyclist perceiving rear approaching vehicles is quite necessary. This project aims to find some proper sensor to detect rear approaching vehicles. It’s separated into three steps. First, choose the suitable sensor and capture data. Then, find proper analyzing tool to analyze the capture data. Last but not least, draw a conclusion after analyzing contrast. Microphone is chosen as the sensor to recording the sounds form rear approaching vehicles. ”iRig Recorder FREE” is the program to transfer audio format. And the analyzing tool is to be Matlab. Matlab audio analysis makes good frequency spectrum for each piece of audio data. According to the frequency spectrum, the unique amplitude change around 1000 Hz is found when there is a rear approaching vehicle. This change is always distinct with or without noise. After getting the spectrum of different audio sources, the cross-correlation coefficient between 800 Hz and 1200 Hz is computed to see the correlation level. Then according to cross-correlation coefficient between new captured data and knowledge data, we can determine if there is a rear approaching vehicle in the new data or not. So, this project proves that the cross-correlation coefficient of frequency spectrum can determine if there is rear approaching vehicles or not. The future work would be automatic computer detect depending on this method.

<p>Disertacija obuhvata opis osnovnih pojmova i metoda merenja iz oblasti muzičke akustike, detaljnije razrađeni teorijski model pona&scaron;anja zvučnog talasa u cevi frule i detaljnu analizu frekvencijskog spektra tonova odsviranih na jednodelnim i dvodelnim frulama, na glavi dvodelnih frula i tonova dobijenih upotrebom različitih vrsta prigu&scaron;ivača.</p> / <p>The dissertation presents a description of the Musical acoustics basic facts and<br />measuring methods , a profoundly developed theoretical model of behaviour of sound waves in sheperd&#39;s flute, and very detailed frequency spectrum analysis of musical tones played on simple Serbian flute, two-piece Serbian flute, tones played only on the had of the flute and musical tones played on the two-piece Serbian flute using different typesof mutes.</p>

L’étude systématique de la turbulence plasma dans les tokamaks, via une méthode de paramétrisation des spectres de fréquence extraits de la base de données de réflectométrie de Tore Supra a été effectuée. Cette base de données est constituée de 350 000 acquisitions obtenues à partir de 6 000 chocs incluant différents scénarios de chauffage. La paramétrisation consiste en une décomposition de chaque spectre en quatre composantes : la composante dite continue, les fluctuations de basse fréquence (BF), la turbulence à large bande en fréquence (BB) et le niveau de bruit où chaque composante a été approchée par une fonction prédéfinie. Pour la composante de turbulence BB, trois fonctions différentes ont été testées et comparées. La fonction gaussienne généralisée et la fonction de Taylor ont montré d’excellentes performances dans la plupart des cas. Dans les plasmas ohmiques, EBB dans le régime de confinement ohmique saturé est systématiquement plus élevé que dans le régime de confinement ohmique linéaire. Dans les plasmas en mode bas confinement L, EBB dans les plasmas chauffés par une onde à la résonance. / To systematically study the plasma turbulence in tokamaks, a parametrization method of frequency spectra from the Tore Supra reflectometry database has been developed. The database includes 350,000 acquisitions obtained from 6,000 discharges with different heating scenarios. In the parametrization, each spectrum has been decomposed into four component: the direct current component, the low-frequency (LF) fluctuations, the broadband (BB) turbulence and the noise level, and each component has been fitted by a function. Specifically for the BB turbulence component, three different functions have been tested and compared. The generalized Gaussian function and the Taylor function have shown excellent fitting performance. In Ohmic plasmas, EBB in the saturated Ohmic confinement regime is observed to be systematically higher than in the linear Ohmic confinement regime. In L-mode plasmas, EBB in the ion cyclotron resonance heating plasmas is globally much higher than in the lower hybrid heating plasmas. The collisional effects on the modifications of the spectra have also been studied. With the previous kinetic simulation results, a change of the dominating micro-instabilities, i.e., between the trapped electron modes and the ion temperature gradients modes, has been proposed to explain the behaviors of EBB, supported by database analysis of the density peaking and the LF component.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-08-04T11:51:07Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Sandra Holanda IMPRESSÃO FINAL 29ABR3.pdf: 5823364 bytes, checksum: acbe323632c3b8540b3b3a2e7ba16482 (MD5) / Made available in DSpace on 2016-08-04T11:51:07Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação Sandra Holanda IMPRESSÃO FINAL 29ABR3.pdf: 5823364 bytes, checksum: acbe323632c3b8540b3b3a2e7ba16482 (MD5) Previous issue date: 2016-02-29 / Embora a vibração nem sempre seja um problema, sendo até essencial para algumas atividades, muitos equipamentos são projetados para operar de forma regular, de modo que a vibração passa a ser um indicador de anormalidades, que caso não sejam identificadas e tratadas, provocarão riscos operacionais, financeiros e de segurança.Nas piores circunstâncias, a vibração pode danificar equipamentos com gravidade, levando à sua interrupção e acarretando em elevados prejuízos financeiros. O ponto positivo está na possibilidade de que se a vibração for medida e analisada corretamente, pode ser usada como indicador da condição da máquina, ajudando a guiar o profissional da manutenção a tomar ações corretivas que evitarão futuros transtornos. Este trabalho proporciona uma primeira abordagem na análise das vibrações em equipamentos críticos do trem da Companhia Brasileira de Trens Urbanos em Recife-PE, introduzindo a manutenção preditiva por análise de vibrações como ferramenta eficaz de diagnóstico e prevenção de falhas. Esse estudo também inclui uma proposta de implantação dessa prática preditiva na CBTU, sugerindo um plano de manutenção cuja viabilização promoverá uma melhoria significativa nos parâmetros fundamentais da manutenção: disponibilidade, confiabilidade e redução de custos. / Although the vibration is not always a problem, and even essential for some activities, much equipment are designed to operate on a regular basis, so that the vibration becomes an indicator of abnormalities, which if not identified and treated, they will cause operational risks, financial and security.In the worst circumstances, the vibration can damage equipment with gravity, leading to its disruption and resulting in significant financial losses. The plus point is the possibility that the vibration is measured and analyzed properly, can be used as an indicator of machine condition, helping to guide the professional maintenance to take corrective action to avoid future problems.This work provides a first approach to matters of vibrations in critical equipments of the Brazilian Company of Urban Trains in Recife-PE, introducing predictive maintenance by vibration analysis as an effective tool to diagnose and prevent failures. This study also includes an implementation of this proposal predictive practice in this company, suggesting a maintenance plan whose feasibility promote a significant improvement in the basic parameters of maintenance: availability, reliability and cost reduction.

This dissertation aims to evaluate the allocation of essential facilities and / or scarce resources in the telecommunication industry in terms of the abuse of dominance provisions under the Competition Act 98 of 1998. Chapter 1 sets the scene by setting out the history of competition law in South Africa, and the policy considerations that lead to the promulgation of the Competition Act 98 of 1998 in its current form. This is followed by a brief examination of the scope, purpose and application of the Act, including the conduct regulated by the Act. Chapter 1 explores the functions of the Competition Authority in South Africa, and the various enforcement bodies created under the Act. In order to provide context, and to introduce the telecommunication industry, the dissertation briefly discusses concurrent jurisdiction between the Competition Authority and the Telecommunication Regulatory Authority (ICASA). Chapter 1 concludes with a description of radio frequency spectrum; and sets out the scope of the dissertation. Chapter 2 sets out the market definition for radio frequency spectrum, which is defined broadly as the national product market for radio frequency spectrum. The dissertation is limited to the telecommunication industry, thus the market definition is defined only within the context of this industry. After setting out the market definition and identifying the key players in the market for radio frequency spectrum in the telecommunication industry, the dissertation proceeds to discuss the abuse of dominance provisions under the Competition Act, the essential facilities doctrine and scarce resources under the Act. This discussion includes a description of how the doctrine of essential facilities was introduced into our law, a discussion of the relevant case law and a comparative approach of the status in the European Union and the USA. The concept of abuse of dominance and its application in South Africa, the European Union and the USA is described. In conclusion, Chapter 3 compares essential facilities and scarce resources. It is submitted that radio frequency spectrum is a scarce resource and should be dealt with under the abuse of dominance provisions of the Competition Act. Chapter 4 analyses the allocation of radio frequency spectrum in South Africa. It describes the Regulatory Authority and the empowering provisions under the Electronic Communications Act, under which ICASA is empowered to allocate radio frequency spectrum, including the recent policy directions of the Department of Communication. A discussion of the various competition issues that could influence the allocation of radio frequency spectrum follows, specifically with regard to the recent policy directions of the Department of Communications. A brief summary of the views of some of the main industry players in South Africa on the policy directions sets out the concerns of the industry in general, and their reaction to the policy directions. In the concluding Chapter, it is submitted that the abuse of dominance provisions of the Competition Act should be applicable to the allocation of radio frequency spectrum. The reason for this statement is that ICASA often obtains a de facto dominant position with regard to the allocation of an essential facility and / or a scarce resource, such as radio frequency spectrum. Thus it is submitted that the regulator is in a position of dominance which allows it to use regulation as a tool to act anti-competitively. The final Chapter concludes that a wider interpretation of the abuse of dominance provisions is necessary to ensure fair and efficient allocation of radio frequency spectrum. A brief discussion of the policy directions suggests that although, on the face of it, the directions are in line with the provisions of the Competition Act, the method of allocation has scope for anti-competitive allocation by a de facto dominant regulatory authority. It is submitted that more attention must be paid to the actual methods of allocation of radio frequency spectrum, and that a fine balance is required to ensure that spectrum allocation is transparent and efficient. In closing, the dissertation mentions the Electronic Communications Amendment Bill (Government Gazette No. 35525 18 July 2012), which aims to introduce a Spectrum Management Agency to oversee the allocation of radio frequency spectrum in the future. / Dissertation LLM --University of Pretoria, 2014 / am2014 / Mercantile Law / Unrestricted

The following technical report describes the development and testing of an arc fault circuit interrupter (AFCI) for DC circuits operating primarily at 48 volts. We have identified an effective method for determining when arcing is occurring. Our method is primarily based on comparing the frequency spectrum of current flowing through the circuit during an arcing event to a known characteristic spectrum. Once an arc has been identified, our interrupter is capable of responding adequately to eliminate the arc. Hardware tests show the AFCI developed in this thesis responded, in all test cases, within 2 seconds of an arc fault occurrence. Commercialization and adoption of our interrupter will increase the safety of DC circuits operating at 80 volts or less.

We propose an original analog method to perform instantaneous and quantitative spectral analysis of microwave signals. An ensemble of nitrogen-vacancy (NV) centers held in a diamond plate is pumped by a 532 nm laser. Its photoluminescence is imaged through an optical microscope and monitored by a digital camera. An incoming microwave signal is converted into a microwave field in the area of the NV centers by a loop shaped antenna. The resonances induced by the magnetic component of that field are detected through a decrease of the NV centers photoluminescence. A magnetic field gradient induces a Zeeman shift of the resonances and transforms the frequency information into spatial information, which allows for the simultaneous analysis of the microwave signal in the entire frequency bandwidth of the device. The time dependent spectral analysis of an amplitude modulated microwave signal is demonstrated over a bandwidth of 600 MHz, associated to a frequency resolution of 7MHz , and a refresh rate of 4 ms. With such integration time, a field of a few hundreds of lW can be detected. Since the optical properties of NV centers can be maintained even in high magnetic field, we estimate that an optimized device could allow frequency analysis in a range of 30 GHz, only limited by the amplitude of the magnetic field gradient. In addition, an increase of the NV centers quantity could lead both to an increase of the microwave sensitivity and to a decrease of the minimum refresh rate down to a few ls.

No description available.