The effects of abrasive particle size and tool surface roughness on tool and work wears of a polishing process were investigated. It was aimed to obtain a polishing condition that could result in a high work wear while the tool wear was low. An analytical study was first done to examine how the various operating conditions affected the wear rates of tool and work. It was done from a wear model developed by Su and Horng [1]. This model was further extended in the study to allow the wear rate analysis for an abrasive particle with ellipsoid shape. It was shown that an enhancement of abrasive particle size or tool surface roughness would increase the work wear while decrease the tool wear. Several sets of experiments were conducted to confirm the predictions of analytical study. It was shown that the experimental trends were the same as the analytical ones. Finally, the possible causes of observed phenomena and the limitations of the study were discussed.

Thesis (M.S.)--Naval Postgraduate School, 1962. / Thesis advisor(s): Borsting, Jack R. "May 1962." Bibliography: l. 34-37. Also available online.

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The mid-latitude ionosphere is more complicated than previously thought, as it includes many different scales of wave-like structures. Recent studies reveal that the mid-latitude ionospheric irregularities are less understood due to lack of models and observations that can explain the characteristics of the observed wave structures. Since temperature and density gradients are a persistent feature in the mid-latitude ionosphere near the plasmapause, the drift mode growth rate at short wavelengths may explain the mid-latitude decameter-scale ionospheric irregularities observed by the Super Dual Auroral Radar Network (SuperDARN). In the context of this dissertation, we focus on investigating the plasma waves responsible for the mid-latitude ionospheric irregularities and studying their influence on Global Positioning System (GPS) scintillations. First, the physical mechanism of the Temperature Gradient Instability (TGI), which is a strong candidate for producing mid-latitude irregularities, is proposed. The electro- static dispersion relation for TGI is extended into the kinetic regime appropriate for High- Frequency (HF) radars by including Landau damping, finite gyro-radius effects, and tem- perature anisotropy. The kinetic dispersion relation of the Gradient Drift Instability (GDI) including finite ion gyro-radius effects is also solved to consider decameter-scale waves gen- eration. The TGI and GDI calculations are obtained over a broad set of parameter regimes to underscore limitations in fluid theory for short wavelengths and to provide perspective on the experimental observations. Joint measurements by the Millstone Hill Incoherent Scatter Radar (ISR) and the Su- perDARN HF radar located at Wallops Island, Virginia have identified the presence of decameter-scale electron density irregularities that have been proposed to be responsible for low-velocity Sub-Auroral Ionospheric Scatter (SAIS) observed by SuperDARN radars. In order to investigate the mechanism responsible for the growth of these irregularities, a time series for the growth rate of both TGI and GDI is developed. The time series is computed for both perpendicular and meridional density and temperature gradients. The growth rate comparison shows that the TGI is the most likely generation mechanism for the observed quiet-time irregularities and the GDI is expected to play a relatively minor role in irregular- ity generation. This is the first experimental confirmation that mid-latitude decameter-scale ionospheric irregularities are produced by the TGI or by turbulent cascade from primary irregularity structures produced from this instability. The quiet- and disturbed-times plasma wave irregularities are compared by investigating co-located experimental observations by the Blackstone SuperDARN radar and the Millstone Hill ISR under various sets of geomagnetic conditions. The radar observations in conjunction with growth rate calculations suggest that the TGI in association with the GDI or a cascade product from them may cause the observations of disturbed-time sub-auroral ionospheric irregularities. Following this, the nonlinear evolution of the TGI is investigated utilizing gyro-kinetic Particle-In-Cell (PIC) simulation techniques with Monte Carlo collisions for the first time. The purpose of this investigation is to identify the mechanism responsible for the nonlinear saturation as well as the associated anomalous transport. The simulation results indicate that the nonlinear E x B convection (trapping) of the electrons is the dominant TGI sat- uration mechanism. The spatial power spectra of the electrostatic potential and density fluctuations associated with the TGI are also computed and the results show wave cascad- ing of TGI from kilometer scales into the decameter-scale regime of the radar observations. This suggests that the observed mid-latitude decameter-scale ionospheric irregularities may be produced directly by the TGI or by turbulent cascade from primary longer-wavelength irregularity structures produced from this instability. Finally, the potential impact of the mid-latitude ionospheric irregularities on GPS signals is investigated utilizing modeling and observations. The recorded GPS data at mid-latitude stations are analyzed to study the amplitude and phase fluctuations of the GPS signals and to investigate the spectral index variations due to ionospheric irregularities. The GPS measurements show weak to moderate scintillations of GPS L1 signals in the presence of ionospheric irregularities during disturbed geomagnetic conditions. The GPS spectral indices are calculated and found to be in the same range of the numerical simulations of TGI and GDI. Both simulation results and GPS spectral analysis are consistent with previous in-situ satellite measurements during disturbed periods, showing that the spectral index of mid- latitude density irregularities are of the order 2. The scintillation results along with radar observations suggest that the observed decameter-scale irregularities that cause SuperDARN backscatter, co-exist with kilometer-scale irregularities that cause L-band scintillations. The alignment between the experimental, theoretical, and computational results of this study suggests that turbulent cascade processes of TGI and GDI may cause the observations of GPS scintillations that occur under disturbed conditions of the mid-latitude F-region ionosphere. The TGI and GDI wave cascading lends further support to the belief that the E-region may be responsible for shorting out the F-region TGI and GDI electric fields before and around sunset and ultimately leading to irregularity suppression. / Ph. D.

The propagation of radiowaves through ionospheric irregularities can lead to random amplitude and phase fluctuations of the signal, otherwise known as scintillation, which can severely impact the performance of Global Navigation Satellite System (GNSS) and communication systems. Research into high latitude scintillation, through statistical analysis and inverse modeling, was completed to provide insight into the temporal and spatial distribution, and irregularity parameters, which can ultimately support the development of impact mitigation techniques, and deepen our understanding of the underlying physics. The work in this dissertation focused on the statistical analysis of Global Positioning System (GPS) scintillation data, data inversion, two-dimensional (2D) and three-dimensional (3D) scintillation modeling. The statistical analysis revealed distinct trends in the distribution of scintillation, while demonstrating that for GPS signals, phase scintillation occurs most frequently and can be treated as stochastic Total Electron Content (TEC); findings which have significant implications for impact mitigation. For the first of two inversion studies, scintillation data associated with a series of Polar Cap Patches (PCPs), which are common large-scale high latitude structures, was inverted to gain insight into the composition of the underlying irregularities. The results of this study suggest that the irregularities can be modeled as rods interbedded with sheets, which is knowledge that is crucial for the anchoring of models used to develop system mitigation techniques. The final study presents the results of modeling and inversion work to identify the conditions under which a 2D analytic version of the 3D numerical Satellite-beacon Ionospheric-scintillation global model of the upper atmosphere (SIGMA) model can be used to perform modeling in high latitude regions. During the study, it was found that the analytic model tends to diverge for electron density variance times irregularity layer thickness values exceeding 2, matched reasonably well for correlation length to thickness ratios up to 0.2, and was incompatible when ratios approached 0.35. An elevation angle limitation was also identified for the 2D model, and inflated values for the electron density variance were observed overall, which are thought to result from the weak scatter limits of the analytic model. These inflated values were particularly acute in the auroral zone during elevated conditions and suggest that the analytic model used in the study is not well suited for modeling the highly elongated irregularities associated with auroral precipitation. / Doctor of Philosophy / The ionosphere is a region of the earth's atmosphere extending from approximately 90 to 1000 km in altitude. Radio wave signals which travel through irregularities in the ionosphere can be distorted in a way that can lead to random amplitude and phase fluctuations of the signal, otherwise known as scintillation, which can severely degrade the performance of navigation and communication systems. Research into high latitude scintillation, through statistical analysis, and data and model matching, was completed to provide insight into the time and space distribution, and irregularity parameters, in order to ultimately deepen our understanding of the physics and to help develop better models. The work in this dissertation focused on the statistical analysis of GPS scintillation data, data and model matching, and 2D and 3D irregularity modeling. The statistical analysis revealed distinct trends in the distribution of scintillation, while demonstrating that for GPS signals, phase scintillation occurs most frequently but the impacts can be corrected if measured; findings which have significant implications for impact mitigation. For the first of two model and data matching studies, scintillation data associated with a series of common large-scale high latitude structures called PCPs, was matched to a model to gain insight into the composition of the underlying irregularities. The results of this study suggest that the irregularities can be modeled as vertical rods oriented along the magnetic field interbedded within flat sheets, which is knowledge that is crucial for having confidence in the models used to develop system mitigation techniques. The final study presents the results of modeling and data matching work to identify the conditions under which a 2D or 3D model can be used to perform irregularity modeling in the high latitude regions. During the study, it was found that the 2D model tends to diverge from the 3D model for significant variations in the ionosphere, and when irregularity rods are highly elongated. A signal propagation path elevation angle limitation was also identified for the 2D model, and inflated values for the predicted ionospheric variations were observed overall, which are thought to result from limits of the 2D model compared to the more general 3D version. These inflated values were particularly acute in the auroral region during elevated conditions and suggest that the 2D model used in the study is not well suited for modeling the highly elongated irregularities associated with aurora effects.

The accuracy of the results from a rail vehicle dynamic model is dependent on the realism of the track input to the model. An important part of the track input is the irregularities that exist on actual track. This study analyzes the irregularities inherent in railroad track geometry data, and provides an analytical method for creating track data with the irregularities for use as the input to a dynamic model. Track data, measured from various classes of track, was examined using statistical and frequency analysis techniques to identify any similarities in the characteristics of the irregularities. The results showed that each class of track had a distinctive value for the standard deviation of the alignment and profile data. It was also determined that the frequency content of all the tracks was contained within a common bandwidth. The track irregularities could then be generated with the same characteristics as an actual track. The method for creating the track irregularities was then programmed into TRAKVU. TRAKVU is a track preprocessor used in conjunction with NUCARS, a railcar dynamic modeling program¹. TRAKVU enables users to create track data and apply the appropriate irregularities so that the track will have the characteristics of the desired class of track. A validation was then performed to determine how well track created in TRAKVU simulated actual tracks. The statistical and frequency characteristics of created tracks were compared directly with actual tracks. Created track was also used as the input to a dynamic model. The predicted vehicle response was then compared to the actual vehicle response and the predicted vehicle response using measured track data as the input. The results from the validation showed that the created track performed as well as the measured track in providing the input to the model. Although the predicted response using the created track did not compare as well with the actual vehicle response, the differences could be attributed to inaccuracies in the model. ¹NUCARS and TRAKVU are copyrighted property of the Association of American Railroads. / Master of Science

The dissertation consists of two parts. The first part is devoted to results in Discrepancy Theory. We consider geometric discrepancy in higher dimensions (d > 2) and obtain estimates in Exponential Orlicz Spaces. We establish a series of dichotomy-type results for the discrepancy function which state that if the L¹ norm of the discrepancy function is too small (smaller than the conjectural bound), then the discrepancy function has to be very large in some other function space.The second part of the thesis is devoted to results in Additive Combinatorics. For a set with small doubling an order-preserving Freiman 2-isomorphism is constructed which maps the set to a dense subset of an interval. We also present several applications.

BACKGROUND: Polycystic Ovary Syndrome (PCOS) is an endocrine disrupting disorder affecting at least 10 percent of reproductive-aged women. In many cases, women develop comorbidities such as diabetes, cardiovascular disease, and other metabolic disorders. In North America and Europe, it takes several years and multiple doctors for women to receive a diagnosis of PCOS. This results in lost time for risk-reducing interventions. Menstrual tracking applications are one potential tool to alert women of their risk for PCOS and prompt them to seek further evaluation from a medical professional. OBJECTIVE: The objective was to develop the Irregular Cycles Feature (ICF) on the mobile phone application Clue®, which generates a probability of a user’s risk for PCOS. The secondary aim was to assess the accuracy of the tool by testing the feature on virtual test subjects. METHODS: A literature review was conducted to generate a list of signs and symptoms of PCOS. Probabilities were assigned to each variable and built into a Bayesian Network. The Irregular Cycles Feature, an adaptive questionnaire, was then developed in order to detect high-risk PCOS patients. The ICF detected at risk Clue® users through self-reported menstrual cycles and answers to medical history questions. Upon completion of the questionnaire, a Result Screen is displayed to the user. The Screen is a summary of the individual’s probability of having PCOS. For each eligible user, a Doctor’s Report is also generated. This is a screen containing information regarding menstrual irregularities and a brief medical history to be used by a medical professional in order to make a final diagnosis. Both the Result Screen and Doctor’s Report disclose information about PCOS and detailed explanations for consulting a medical provider. A brief statistical validation was then performed to compare the output of the network to predictions made by a physician-scientist using a correlation coefficient, a p-value, and a Pearson’s coefficient. RESULTS: The Irregular Cycles Feature successfully predicts probability of PCOS based on eight test cases. The correlation between the network’s calculation and the assessment made by a board-certified reproductive endocrinology/infertility physician-scientist was 0.82, with a p-value of less than 0.05. The Pearson’s coefficient was calculated to be 0.69. These values indicate that the ICF made statistically significant predictions when compared to the physician-scientist. CONCLUSIONS: The ICF provides consumer-friendly ways to improve interactions between medical providers and patients. The tool can be adapted to capture other causes of menstrual irregularities and can serve as an important mechanism for drawing attention to potentially hazardous health problems. Further validation studies will be conducted to confirm the utility of the ICF with Clue® users, particularly amongst those who receive an official diagnosis from a medical professional. / 2020-06-17T00:00:00Z

Este trabalho utiliza uma metodologia simplificada de análise dinâmica para o estudo das vibrações em pontes ferroviárias, produzidas pela passagem de um trem de alta velocidade, associadas à presença de irregularidades nos trilhos. Iniciou-se o estudo a partir de um modelo do veículo composto por quinze graus de liberdade, referentes aos deslocamentos verticais e horizontais transversais, e rotações em torno dos eixos longitudinal, transversal e vertical. Os modelos dinâmicos do trem e da ponte foram tratados de forma desacoplada, sendo conectados pelas forças de interação trem-ponte. Desta forma, foram calculados os carregamentos provenientes da modelação dinâmica do trem, adotando-se inicialmente a hipótese de tabuleiro rígido e indeslocável e, ainda, considerando-se a presença de irregularidades geométricas nos trilhos no plano vertical. Neste trabalho, foi considerado um estudo de caso utilizando-se o modelo veicular Alfa Pendular, avaliando-se a resposta dinâmica do trem e da estrutura, considerando o efeito das irregularidades geométricas nos trilhos, bem como a presença do lastro. As forças de interação obtidas da modelagem do veículo foram aplicadas em um modelo estrutural de alta hierarquia da ponte, dividido em elementos finitos de casca, sendo que em cada nó do modelo da ponte foram especificados os esforços obtidos da análise dinâmica do veículo. Para representar a passagem do comboio sobre a ponte, foram utilizadas funções que descrevem as forças de interação trem-ponte em cada nó do modelo da ponte, em cada intervalo de tempo, até que todo o trem tenha percorrido o comprimento da ponte. A consideração de tabuleiro rígido indeslocável foi corrigida por meio de um processo iterativo, de forma que os deslocamentos do tabuleiro obtidos para a primeira determinação dos esforços de interação foram somados às irregularidades do trilho (excitação de suporte aplicada nas rodas do trem). Com isso, foi possível identificar a resposta dinâmica proveniente da carga em movimento e das irregularidades geométricas nos trilhos, avaliando o conforto dos passageiros no interior do vagão. Por fim, realizou-se uma análise de distribuição estatística para avaliar a probabilidade de se ultrapassar os limites estabelecidos pelo Eurocode. / This thesis resorts to a simplified methodology of dynamic analysis for the study of vibrations in railway bridges, produced by the passage of a high speed train, associated to the presence of irregularities in the rails. The study started from a vehicle model composed of fifteen degrees of freedom, namely, vertical and lateral displacements, and rotations about the longitudinal, lateral and vertical axes. The dynamic models of the train and the bridge were treated as uncoupled, yet being bound by the interaction train-bridge forces. Thus, the loads from the dynamic model of the train were calculated, adopting initially the hypothesis of rigid and fixed deck and also, considering the presence of geometric irregularities in the vertical track plane. In this work, we considered a case study using the Alfa Pendular vehicle model, evaluating the dynamic response of the train and the structure, considering the effect of the geometric irregularities at the tracks, as well as the presence of the ballast. The interaction forces obtained from the model of the vehicle were applied in a high hierarchy structural model of the bridge, divided into shell finite elements, specifying the forces obtained from the dynamic analysis of the vehicle at each node of the bridge model. To represent the train passage on the bridge, functions were used to describe the bridge-train interaction forces at each node of the bridge model at each time interval, until the entire train had travelled the bridge length. The consideration of rigid and fixed deck was corrected by means of an iterative process, so that the deck displacements obtained for a first determination of the interaction forces were added to the rail irregularities (excitation applied to the train wheels). Thus, it was possible to identify the dynamic response caused both by the moving loading and the geometrical irregularities of the tracks, evaluating the comfort of the passengers inside the wagon. Finally, a reliability study was carried out to evaluate the probability of exceeding the limits established by Eurocode.