Dissertations / Theses on the topic 'Digital discrimination'

Thesis (Ph. D.)--University of Florida, 2000.
Title from first page of PDF file. Document formatted into pages; contains xvi, 289 p.; also contains graphics. Vita. Includes bibliographical references (p. 283-287).

Satellite images have been used as a complementary information for geological studies. In order to realise the maximum potential of satillite imagery, then improvements are needed, both in the visual presentation of such images, and in their automatic classification , in order to reveal the rock differences. Methods of processing imagery, were evaluated (band ratio, principal components, decorrelated stretch and maximum likelihood) and new (canonical regression, hue-saturation-intensity HSI transform, with modified manipulation, and watershed) were evaluated with respect to their ability to reveal rock differences. It was found that the HSI method gave the best results, both for visual presentation and automatic classifcation. This method has the ability to enhance both spectral and spatial information simultaneously without any data loss which is not the case in the other image enhancement methods (band ratio, principal components or decorrelation stretch). For automatic classification, the 'hue' images produced by the HSI transformation typically gave accurate (91%) classification of all the major rock types. Further, it was shown that the watershed method of classification was superior error rate = 9% to the maximum likelihood method (error rate 14%) for the same inputs. The new method of canonical regression was evaluated and although it was not very successful, the results were encouraging and it was concluded that this method may enable the estimation of the chemical composition of exposed rocks directly from satellite imagery.

This study explores the use of digital pulse processing techniques for n/y pulse shape discrimination (PSD) in liquid scintillators, and the application of these techniques to a capture-gated fast neutron monitor developed using an enriched '°B-loaded liquid scintillator (BC523A). The motivation for this study has been to develop a computationally-fast digital PSD algorithm, which can be used to detect a weak neutron flux in the presence of a strong gamma ray background and to assess its suitability for use as a portable neutron monitor for fast neutron dosimetry. BC523A can operate as a full-energy neutron spectrometer when used in the 'capturegated' mode, where a characteristic capture time is observed between the proton recoil and neutron capture pulses, thus producing a very clean signature for those fast neutrons which are completely moderated within the detector volume. The use of digital waveform capture of this double-pulse sequence is a powerful technique that allows acquiring both the timestamped pulse amplitudes and the capture lifetime in a single data set. The capture-gated performance of a 105 cm' BC523A detector was investigated using fast neutrons from an Am-Be source. The measured mean neutron capture time in BC523A was 470±80 ns, which is a factor of 5 shorter than that reported for liquid scintillators loaded with natural boron. Due to its limited neutron detection efficiency, an extension of this technique to a large volume (685 cm) BC523A was developed, and provided an efficiency increase by a factor of 7. The efficiency enhancement was modelled using MCNP-4C. Good n/y separation was obtained using digital PSD applied to BC523A. The PSD figure of- merit (FOM) was investigated for various organic scintillators, and compared between digital and analogue pulse processing techniques. The application of digital PSD to the capture-gate detection mode was investigated, as an additional method for suppression of gamma sensitivity.

L’estudi explora el paper dels mitjans informatius en línia en el canvi en els drets sexuals i de gènere a Ucraïna, basant-se en l’anàlisi del debat sobre la prohibició de la discriminació per orientació sexual i identitat de gènere (OSIG) com a part de la reforma antidiscriminació de 2013 – 2015. El canvi en els drets sexuals i de gènere va ser conceptualitzat, com a resultat de la lluita hegemònica entre discursos en disputa, seguint la teoria del discurs d’Ernesto Laclau i Chantal Mouffe. La recerca va incloure tres fases. Durant la Fase I es van examinar a través de recerca documental les condicions de la possibilitat d’un canvi dels drets sexuals i de gènere a Ucraïna durant el període 2013 – 2015. Durant la Fase II es va analitzar el discurs polític sobre drets sexuals i de gènere a Ucraïna el 2013 – 2015 a través de l’anàlisi postfundacional del discurs i utilitzant les dades recollides per les pàgines web oficials del govern, parlament i grups d’interès involucrats en la controvèrsia sobre la reforma antidiscriminació. Es van identificar quatre coalicions discursives sobre els drets sexuals i de gènere seguint les articulacions dels significants flotants clau en el debat: orientació sexual i identitat de gènere, democràcia, identitat nacional i política exterior. Cada coalició va desenvolupar el seu propi grup de trames que associaven la prohibició de la discriminació per OSIG a les seves articulacions dels significants flotants (punts nodals). Durant la Fase III es va examinar la representació mediàtica de les coalicions discursives sobre drets sexuals i de gènere en disputa a través de l’anàlisi quantitativa de contingut i l’anàlisi postfundacional del discurs de la cobertura de la reforma antidiscriminació en els cinc mitjans informatius en línia més populars d’Ucraïna. Aquesta anàlisi va revelar que durant la primera etapa de la controvèrsia antidiscriminació (2013 – 2014), els mitjans afiliats a grans grups d’empreses propietat d’oligarques afavorien les coalicions discursives conservadores citant els seus membres més freqüentment, oferint una cobertura desequilibrada de la seva posició, i fent-se eco de supòsits conservadors sobre OSIG en comentaris periodístics. Els mitjans informatius petits i independents en línia afavorien les coalicions discursives lliberals utilitzant els mateixos mètodes. Durant la segona etapa de la controvèrsia (2015), tots els mitjans informatius en línia afavorien les coalicions discursives lliberals en la seva cobertura del debat. L’estudi suggereix que el suport ofert pels mitjans informatius en línia va contribuir a la capacitat de les coalicions discursives en disputa d’introduir canvis en les lleis de drets sexuals i de gènere. De 2013 a 2014, la cobertura favorable als mitjans afiliats a grans grups d’empreses i la presència substancial als mitjans informatius en línia independents van ajudar la coalició conservadora pro-UE a articular la prohibició de la discriminació per orientació sexual com a amenaça a la democràcia i la identitat nacional i com a obstacle de la integració europea d’Ucraïna en l’esfera pública, fet que va contribuir al fracàs de la reforma antidiscriminació. Durant el 2015, la cobertura favorable en els cinc mitjans informatius en línia més populars d’Ucraïna va ajudar les coalicions discursives lliberals sobre drets sexuals i de gènere a rearticular la prohibició de la discriminació per OSIG com a instància de protecció democràtica de la igualtat de drets civils, adheriment als valors europeus, i condició prèvia d’integració europea, fet que va ajudar a l’adopció de la reforma antidiscriminació.
El estudio explora el papel de los medios informativos en línea en el cambio en los derechos sexuales y de género en Ucrania, basándose en el análisis del debate sobre la prohibición de la discriminación por orientación sexual e identidad de género (OSIG) como parte de la reforma antidiscriminación de 2013-2015. El cambio en los derechos sexuales y de género fue conceptualizado, como resultado de la lucha hegemónica entre discursos en disputa, siguiendo la teoría del discurso de Ernesto Laclau y Chantal Mouffe. La investigación incluyó tres fases. Durante la Fase I se examinaron a través de la investigación documental las condiciones de la posibilidad de un cambio de los derechos sexuales y de género en Ucrania durante el período 2013 – 2015. Durante la Fase II se analizó el discurso político sobre derechos sexuales y de género en Ucrania en 2013 – 2015 a través del análisis posfundacional del discurso y utilizando los datos obtenidos por las páginas web oficiales del gobierno, parlamento y grupos de interés involucrados en la controversia sobre la reforma antidiscriminación. Se identificaron cuatro coaliciones discursivas sobre los derechos sexuales y de género siguiendo las articulaciones de los significantes flotantes clave en el debate: orientación sexual e identidad de género, democracia, identidad nacional y política exterior. Cada coalición desarrolló su propio grupo de tramas que asociaban la prohibición de la discriminación por OSIG a sus articulaciones de los significantes flotantes (puntos nodales). Durante la Fase III se examinó la representación mediática de las coaliciones discursivas sobre derechos sexuales y de género en disputa a través del análisis cuantitativo de contenido y el análisis posfundacional del discurso de la cobertura de la reforma antidiscriminación en los cinco medios informativos en línea más populares de Ucrania. Este análisis reveló que durante la primera etapa de la controversia antidiscriminación (2013 – 2014), los medios afiliados a grandes grupos de empresas propiedad de oligarcas favorecían las coaliciones discursivas conservadoras citando sus miembros más frecuentemente, ofreciendo una cobertura desequilibrada de su posición, y haciéndose eco de suposiciones conservadoras sobre OSIG en comentarios periodísticos. Los medios informativos pequeños e independientes en línea favorecían las coaliciones discursivas liberales utilizando los mismos métodos. Durante la segunda etapa de la controversia (2015), todos los medios informativos en línea favorecían las coaliciones discursivas liberales en su cobertura del debate. El estudio sugiere que el soporte ofrecido por los medios informativos en línea contribuyó a la capacidad de las coaliciones discursivas en disputa de introducir cambios en las leyes de derechos sexuales y de género. De 2013 a 2014, la cobertura favorable en los medios afiliados a grandes grupos de empresas y la presencia sustancial en los medios informativos independientes ayudaron a la coalición conservadora pro-UE a articular la prohibición de la discriminación por orientación sexual como amenaza a la democracia y la identidad nacional y como obstáculo de la integración europea de Ucrania en la esfera pública, hecho que contribuyó al fracaso de la reforma antidiscriminación. Durante 2015, la cobertura favorable, en los cinco medios informativos en línea más populares de Ucrania, ayudó a las coaliciones discursivas liberales sobre derechos sexuales y de género a rearticular la prohibición de la discriminación por OSIG como instancia de protección democrática de la igualdad de derechos civiles, adherencia a los valores europeos, y condición previa de integración europea, hecho que favoreció a la adopción de la reforma antidiscriminación.
The study explores the role of online news media in sexual and gender rights change in Ukraine, relying on the analysis of the debate over the prohibition of discrimination on the grounds of sexual orientation and gender identity (SOGI) as part of the anti-discrimination reform in 2013 – 2015. Sexual and gender rights change was conceptualized as an outcome of hegemonic struggle among contesting discourses on sexual and gender rights based on the discourse theory of Ernesto Laclau and Chantal Mouffe. The research included three phases. In Phase I, conditions of possibility of sexual and gender rights change in Ukraine in 2013 – 2015 were examined using desk research. Dominant public opinion on sexuality, sexual and gender rights, and European integration, as well as the established legal, political, and media discourses on sexual and gender rights in Ukraine, were considered as conditions that shaped outcomes of the anti-discrimination controversy. In Phase II, political discourse on sexual and gender rights in Ukraine in 2013 – 2015 was analyzed with the use of post-foundational discourse analysis, relying on the data collected from the official websites of government, parliament, and groups of interest involved in the controversy over the anti-discrimination reform. Four discourse coalitions on sexual and gender rights were identified according to the articulations of the key floating signifiers in the debate: sexual orientation and gender identity, democracy, national identity, and foreign policy. Each coalition developed its own set of storylines that linked the prohibition of discrimination on the grounds of SOGI to the coalitions’ articulations of the floating signifiers (nodal points). In Phase III, media representation of the contesting discourse coalitions on sexual and gender rights was examined with the use of quantitative content analysis and post-foundational discourse analysis of the anti-discrimination reform coverage in the five most popular Ukrainian online news media. This analysis revealed that during the first round of the anti-discrimination controversy (2013 – 2014), news websites affiliated with big media holdings owned by oligarchs favored conservative discourse coalitions by quoting their members more frequently, providing imbalanced coverage of their position, and echoing conservative assumptions about SOGI in journalistic comments. Small independent online news media favored liberal discourse coalitions using the same means. During the second round of the controversy (2015), all examined online news media favored liberal discourse coalitions in their coverage of the debate. The study suggests that support provided by the online news media contributed to the capacity of contesting discourse coalitions to change sexual and gender rights law. In 2013 – 2014, favorable coverage in the media affiliated with big media holdings and substantial presence in the independent online news media helped the conservative pro-EU coalition to articulate the prohibition of sexual orientation discrimination as a threat to democracy and national identity and an obstacle to the European integration of Ukraine in the public sphere, which contributed to the failure of the anti-discrimination reform. In 2015, favorable coverage in the top five Ukrainian online news media helped liberal discourse coalitions on sexual and gender rights to rearticulate the prohibition of discrimination on the grounds of SOGI as an instance of democratic protection of equal civil rights, adherence to European values, and a precondition of European integration, which contributed to the adoption of the anti-discrimination reform.

Color vision deficiency (CVD) is the inability or limited ability to recognize colors and discriminate between them. A person with this condition perceives a narrower range of colors compared to a person with a normal color vision. A growing number of researchers are striving to improve the quality of life for CVD patients. Finding cure, making rectification equipment, providing simulation tools and applying color transformation methods are among the efforts being made by researchers in this field. In this study we concentrate on recoloring digital images in such a way that users with CVD, especially dichromats, perceive more details from the recolored images compared to the original image. The main focus is to give the CVD user a chance to find information within the picture which they could not perceive before. However, this transformed image might look strange or unnatural to users with normal color vision. During this color transformation process, the goal is to keep the overall contrast of the image constant while adjusting the colors that might cause confusion for the CVD user. First, each pixel in the RGB-image is converted to HSV color space in order to be able to control hue, saturation and intensity for each pixel and then safe and problematic hue ranges need to be found. The method for recognizing these ranges was inspired by a condition called “unilateral dichromacy” in which the patient has normal color vision in one eye and dichromacy in another. A special grid-like color card is designed, having constant saturation and intensity over the entire image, while the hue smoothly changes from one block to another to cover the entire hue range. The next step is to simulate the way this color card is perceived by a dichromatic user and finally to find the colors that are perceived identically from two images and the ones that differ too much. This part makes our method highly customizable and we can apply it to other types of CVD, even personalize it for the color vision of a specific observer. The resulting problematic colors need to be dealt with by shifting the hue or saturation based on some pre-defined rules. The results for the method have been evaluated both objectively and subjectively. First, we simulated a set of images as they would be perceived by a dichromat and compared them with simulated view of our transformed images. The results clearly show that our recolored images can eliminate a lot of confusion from user and convey more details. Moreover, an online questionnaire was created and 39 users with CVD confirmed that the transformed images allow them to perceive more information compared to the original images.

Die Grundlage vieler zukünftiger Flüssigszintillator-Neutrinoexperimente (SNO+, Daya Bay, LENA) ist das Lösungsmittel Lineare-Alkyl-Benzene (LAB, C6H5CnH2n+1, n = 10 - 13). Zusammen mit dem weit verbreiteten Szintillator 2,5-Diphenyloxazole (PPO) ist es ein farb- und geruchsloses Detektormaterial mit hohem Flammpunkt. Im Vergleich zu toluol- oder xylolbasierten Szintillatoren ist LAB+PPO preiswert und nicht gesundheitsschädlich. Die Eigenschaften von LAB machen es ebenfalls interessant für die Anwendung an nELBE, die Neutronenfugzeitanlage im Helmholtz-Zentrum Dresden - Rossendorf. Ein neuer Ansatz zur Bestimmung der Lichtausbeute im niederenergetischen Bereich (bis 2 MeV) wird vorgestellt. Kombiniert wurden Messungen mit (quasi) monoenergetischen Gammastrahlungs-Prüfstrahlern und einem in dieser Arbeit aufgebauten Compton-Spektrometer. Letzteres ermöglicht die Bestimmung der Lichtausbeute bis zu 5 keVee. Der Birks-Parameter wurde für eine Lösung von LAB + 3 g/l PPO sowie für den Flüssigszintillator NE-213 bestimmt. Die relative Lichtausbeute in Bezug auf letzteren konnte mit diesen Messmethoden ebenfalls ermittelt werden. Zur spektralen Analyse des Lumineszenzlichtes wurden Messungen an Fluoreszenz- und UV/VIS- Spektrometern durchgeführt. Die Pulsformdiskriminationsfähigkeit auf LAB basierenden Szintillatoren wurde während eines Flugzeitexperiments in einem gemischten n-gamma-Feld eines Cf(252)-Prüfstrahlers ermittelt. Dabei kamen unterschiedliche Algorithmen der semi-analogen und digitalen Pulsformdiskrimination zum Einsatz
Linear alkyl benzene (LAB, C6H5CnH2n+1, n = 10 - 13) is the proposed solvent for the SNO+, the Daya Bay Neutrino and LENA experiment. In solution with the commonly used scintillator PPO it is a colourless, odourless and cheap liquid scintillator with a high fash point and low health hazard compared to toluene based ones. The properties of LAB make this scintillator interesting also for nELBE, the neutron time-of-fight facility at Helmholtz-Zentrum Dresden - Rossendorf. A new approach to measure the light yield in the low-energy range using a combination of quasi-monoenergetic photon sources and a Compton-spectrometer is described. The latter allows the measurement of the light yield down to 5 keVee (electron equivalent). The Birks- Parameter was determined for a homemade solution (LAB + 3 g/l PPO) and for NE-213. The light yield (relative to this standard scintillator) was confrmed by measurements using a fuorescence spectrometer. The ability of pulse-shape-discrimination in a mixed n-gamma- field of a Cf(252) source was tested using different digital and semi-analogue techniques

Die Grundlage vieler zukünftiger Flüssigszintillator-Neutrinoexperimente (SNO+, Daya Bay, LENA) ist das Lösungsmittel Lineare-Alkyl-Benzene (LAB, C6H5CnH2n+1, n = 10 - 13). Zusammen mit dem weit verbreiteten Szintillator 2,5-Diphenyloxazole (PPO) ist es ein farb- und geruchsloses Detektormaterial mit hohem Flammpunkt. Im Vergleich zu toluol- oder xylolbasierten Szintillatoren ist LAB+PPO preiswert und nicht gesundheitsschädlich. Die Eigenschaften von LAB machen es ebenfalls interessant für die Anwendung an nELBE, die Neutronenfugzeitanlage im Helmholtz-Zentrum Dresden - Rossendorf. Ein neuer Ansatz zur Bestimmung der Lichtausbeute im niederenergetischen Bereich (bis 2 MeV) wird vorgestellt. Kombiniert wurden Messungen mit (quasi) monoenergetischen Gammastrahlungs-Prüfstrahlern und einem in dieser Arbeit aufgebauten Compton-Spektrometer. Letzteres ermöglicht die Bestimmung der Lichtausbeute bis zu 5 keVee. Der Birks-Parameter wurde für eine Lösung von LAB + 3 g/l PPO sowie für den Flüssigszintillator NE-213 bestimmt. Die relative Lichtausbeute in Bezug auf letzteren konnte mit diesen Messmethoden ebenfalls ermittelt werden. Zur spektralen Analyse des Lumineszenzlichtes wurden Messungen an Fluoreszenz- und UV/VIS- Spektrometern durchgeführt. Die Pulsformdiskriminationsfähigkeit auf LAB basierenden Szintillatoren wurde während eines Flugzeitexperiments in einem gemischten n-gamma-Feld eines Cf(252)-Prüfstrahlers ermittelt. Dabei kamen unterschiedliche Algorithmen der semi-analogen und digitalen Pulsformdiskrimination zum Einsatz.
Linear alkyl benzene (LAB, C6H5CnH2n+1, n = 10 - 13) is the proposed solvent for the SNO+, the Daya Bay Neutrino and LENA experiment. In solution with the commonly used scintillator PPO it is a colourless, odourless and cheap liquid scintillator with a high fash point and low health hazard compared to toluene based ones. The properties of LAB make this scintillator interesting also for nELBE, the neutron time-of-fight facility at Helmholtz-Zentrum Dresden - Rossendorf. A new approach to measure the light yield in the low-energy range using a combination of quasi-monoenergetic photon sources and a Compton-spectrometer is described. The latter allows the measurement of the light yield down to 5 keVee (electron equivalent). The Birks- Parameter was determined for a homemade solution (LAB + 3 g/l PPO) and for NE-213. The light yield (relative to this standard scintillator) was confrmed by measurements using a fuorescence spectrometer. The ability of pulse-shape-discrimination in a mixed n-gamma- field of a Cf(252) source was tested using different digital and semi-analogue techniques.

Orientador: Amauri Lopes
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: Abordamos o problema de estimação de direção de chegada (DOA) de ondas planas usando um arranjo de sensores. Na literatura encontramos diversos estimadores para DOA, porém estamos considerando apenas os estimadores de Máxima Verossimilhança (ML) que geram candidatas à estimativa DOA e selecionam as melhores através do critério ML. Também estamos interessados em situações em que o espaçamento angular entre as fontes de sinal é pequeno e a relação sinal-ruído é baixa. Nesse caso temos uma degradação de desempenho associada ao efeito de limiar. Mostramos que este problema pode ser amenizado reduzindo o ruído presente na matriz de covariância dos dados recebidos (snapshots) utilizada para a seleção das candidatas. Propomos então modificar o processo de seleção de candidatas, utilizando uma nova matriz de covariância dos snapshots, calculada após uma filtragem ótima dos dados através de um filtro FIR multibanda. Propomos também modificar a função custo ML para adequá-la às dimensões da matriz de covariância filtrada e para isso apresentamos 3 opções de modificação. As simulações mostram que nossa proposta tem melhor desempenho que os métodos conhecidos, reduzindo significativamente a relação sinal-ruído de limiar.
Abstract: We approached the estimation of direction of arrival (DOA) of plane waves using an array of sensors. In the literature there are several DOA estimators, but we considered only the maximum likelihood (ML) estimators that generate candidates for DOA estimation and select the best one through an ML criterion. We also considered situations where the signal sources are spatially closely spaced and the signal-to-noise ratio is low. In these cases a performance degradation associated with the threshold effect occur. We demonstrated that we can improve the estimation performance by reducing the noise in the received data covariance matrix used to select the candidates. Then we proposed to modify the selection process using a new data covariance matrix, computed after an optimum multiband FIR filtering of the received data. We also proposed to modify the ML cost function to adapt it to the dimensions of the new covariance matrix and we considered 3 alternatives of modification. Some simulations showed that our proposal has better performance than known DOA methods, significantly reducing the threshold SNR.
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica

International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, Nevada
The unit to be described differs from present tunable discriminator products chiefly because it is designed to simultaneously demodulate all the subcarrier channels in a frequency division multiplex. In addition the demodulated output data is presented in digital format that is compatible for direct computer entry. The discriminator implementation techniques will be discussed at the block diagram level. Particular emphasis will be given to the use of “Finite Impulse Response” filters and also to the internal tape speed compensation process.

In recent years, millions of customers all over the world have been subscribing to mobile telephony services which are based on modern digital transmission. At the high transmission bit rates that these systems use, the mobile radio channel exhibits frequency-selective fading characteristics. Under such conditions, the received signal could experience significant intersymbol interference (ISI) from severe distortion to the waveform of the received baseband signal. Therefore, such techniques as adaptive waveform equalisation or adaptive maximum likelihood sequence estimation (MLSE) are used in modern digital mobile radio telephone systems to combat this undesirable ISI. These adaptive schemes have almost always been used in conjunction with coherent demodulation in the receivers.This study examines the application of noncoherent demodulation, in the form of frequency discriminator detection, as an alternative to coherent demodulation. The GSM (Global System for Mobile Communications) standard has been used as the basis for this investigation. It has been shown analytically that in the presence of frequency-selective fading, a propagation environment common to the GSM system, the use of frequency discriminator detection gives rise to nonlinear ISI in the demodulated signal. It has also been shown that frequency-selective fading could cause large unwanted "spikes" to appear in the demodulated signal, thus leading to a severe degradation in the bit-error-rate (BER) performance. Consequently, several waveform distortion cancellation schemes for combatting the nonlinear ISI have been formulated. The BER performances of these proposed schemes, under various propagation conditions, have been studied by computer simulation.Furthermore, it has been observed that the undesirable "spikes", that occur in the demodulated signal due to frequency-selective fading, could be ++
suppressed by the use of inverse-limiting in conjunction with frequency discriminator detection. As a result, an effective adaptive detection scheme has been formulated, based on modelling the combination of the GMSK modulator, the mobile channel, the frequency discriminator, and any transmit and receive fitters, as a finite-state machine. The transmitted data is then detected using an MLSE. The BER performance of this proposed adaptive detection scheme has been extensively investigated by computer simulation. This has been carried out assuming various propagation conditions, including the two-ray fading channel model with equal path powers and relative delays of up to four bit periods, the maximum relative delay considered in the GSM system. Also, the effectiveness of the proposed adaptive detection scheme in combatting IS] has been investigated by computer simulation based on the six-ray GSM empirical propagation models for typical urban (TU), hilly terrain (HT) and rural area (RA) environments. The computer simulated results confirm that the voice grade performance required for the GSM system could be achieved by the proposed adaptive detection scheme in all the recommended GSM propagation models considered. Furthermore, the BER performance of the receiver remains unaffected by a carrier frequency offset of up to 2 kHz.

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CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
A principal finalidade dos algoritmos para classificação automáica de modulacão em um receptor inteligente para rádio cognitivo ou aplicacões militares é a identificacão da modulacão de um sinal para que o receptor possa, posteriormente, realizar o processo de de modulacão e em seguida o processamento da informacão recebida. A falta de conhecimento acerca de parâmetros como, por exemplo: potência do sinal, frequência e fase da portadora, sincronismo temporal e outros; somados aos efeitos dos canais como desvanecimento de multipercurso, tornam o problema de classificação automática de modulacão desafiador e bastante investigado atualmente. Neste contexto, esta Tese apresenta uma investigação sobre algoritmos de classificação automática de modulacão baseados na aprendizagem discriminativa e avalia o desempenho dos mesmos em distintos cenários de uso. A Tese apresenta uma nova proposta de classificação baseada no extrator de parâmetro (front end) chamado de HISTO. A classificação é realizada sobre os síımbolos recebidos, onde os histogramas de magnitude e fase são calculados. Os resultados obtidos usam o extrator de parâmetro proposto e o algo- ritmo Máquina de Vetores de Suporte (MVS), os quais são comparados com outras técnicas. Na literatura, alguns dos algoritmos propostos são avaliados assumindo-se o conhecimento de parâmetros da modulacão e em cenários distintos, dificultando a comparação entre os algoritmos. Nesta Tese, algoritmos representativos do estado da arte são comparados com os propostos de maneira sistemática e uniforme, incluindo-se cenários não-ideais como os com phase jitter e offset de frequência. Os resultados das simulações mostram que proposta de classificação baseada em histogramas é eficiente com relativo baixo custo computacional.
The main purpose of the algorithms for automatic modulation classification in an in- telligent receiver for cognitive radio or military applications is to identify the modulation of a signal so that the receiver can subsequently carry out the process of demodulation and then processing the received information. The lack of knowledge of parameters such as, for exam- ple, signal power, frequency and phase of carrier and timing; added to the channel effects such as multipath fading, make the automatic modulation classification problem challenger and fairly investigated currently. In this context, this thesis presents an investigation of automatic modulation classification algorithms based on discriminative learning and evaluates their per- formance in different usage scenarios. The thesis presents a new classification proposal based on front end called HISTO. Classification is performed on the received symbols, where the magnitude and phase histogram’s are computed. The results obtained using the proposed front end and the Support Vector Machine algorithm (SVM) are compared with other tech- niques. In the literature, some of the proposed algorithms are evaluated assuming knowledge of some modulation parameters and using different scenarios, which makes difficult to compare the algorithms. In this thesis, algorithms representative of the prior art are compared with the proposed ones in a systematic and uniform manner, including non-ideal scenarios such as with phase jitter and frequency offset. The simulation results show that the proposed classification based on histograms is effective with a relatively low computational cost.

L’angiogenèse est le processus par lequel de nouveaux vaisseaux sanguins se forment à partir du réseaux préexistant. Au cours de l’angiogenèse tumorale, les cellules tumorales sécrètent des facteurs de croissance qui activent la prolifération et la migration des cellules et stimulent la surproduction du facteur de croissance endothélial vasculaire (VEGF). Le rôle fondamental de l’approvisionnement vasculaire dans la croissance tumorale et le developement des thérapies anticancéreuses rend l’évaluation de l’angiogenèse tumorale, cruciale dans l’évaluation de l’effet des thérapies anti-angiogéniques, en tant que thérapie anticancéreuse prometteuse. Dans cette étude, nous établissons un panel quantitatif et qualitatif pour évaluer les structures des vaisseaux sanguins de la tumeur sur des images de fluorescence non invasives et des images histopathologique sur toute la surface tumorale afin d’identifier les caractéristiques architecturales et les mesures quantitatives souvent associées à la réponse thérapeutique ou prédictive de celle-ci. Nous développons un pipeline formé de Markov Random Field (MFR) et Watershed pour segmenter les vaisseaux sanguins et les composants du micro-environnement tumoral afin d’évaluer quantitativement l’effet du médicament anti-angiogénique Pazopanib sur le système vasculaire tumoral et l’interaction avec le micro-environnement de la tumeur. Le pazopanib, agent anti-angiogénèse, a montré un effet direct sur le système vasculaire du réseau tumoral via les cellules endothéliales. Nos résultats montrent une relation spécifique entre la néovascularisation apoptotique et la densité de noyau dans une tumeur murine traitée par Pazopanib. Une évaluation qualitative des vaisseaux sanguins de la tumeur est réalisée dans la suite de l’étude. Nous avons développé un modèle de réseau de neurone discriminant-générateur basé sur un modele d’apprentissage : réseau de neurones convolutionnels (CNN) et un modèle de connaissance basé sur des règles Marked Point Process (MPP) permettant de segmenter les vaisseaux sanguins sur des images très hétérogènes à l’aide de très peu de données annotées. Nous détaillons l’intuition et la conception du modèle discriminatif-génératif, sa similarité avec les Réseaux antagonistes génératifs (GAN) et nous évaluons ses performances sur des données histopathologiques et synthétiques. Les limites et les perspectives de la méthode sont présentées à la fin de notre étude
Angiogenesis is the process through which new blood vessels are formed from pre-existing ones. During angiogenesis, tumour cells secrete growth factors that activate the proliferation and migration of endothelial cells and stimulate over production of the vascular endothelial growth factor (VEGF). The fundamental role of vascular supply in tumour growth and anti-cancer therapies makes the evaluation of angiogenesis crucial in assessing the effect of anti-angiogenic therapies as a promising anti-cancer therapy. In this study, we establish a quantitative and qualitative panel to evaluate tumour blood vessels structures on non-invasive fluorescence images and histopathological slide across the full tumour to identify architectural features and quantitative measurements that are often associated with prediction of therapeutic response. We develop a Markov Random Field (MFRs) and Watershed framework to segment blood vessel structures and tumour micro-enviroment components to assess quantitatively the effect of the anti-angiogenic drug Pazopanib on the tumour vasculature and the tumour micro-enviroment interaction. The anti-angiogenesis agent Pazopanib was showing a direct effect on tumour network vasculature via the endothelial cells crossing the whole tumour. Our results show a specific relationship between apoptotic neovascularization and nucleus density in murine tumor treated by Pazopanib. Then, qualitative evaluation of tumour blood vessels structures is performed in whole slide images, known to be very heterogeneous. We develop a discriminative-generative neural network model based on both learning driven model convolutional neural network (CNN), and rule-based knowledge model Marked Point Process (MPP) to segment blood vessels in very heterogeneous images using very few annotated data comparing to the state of the art. We detail the intuition and the design behind the discriminative-generative model, and we analyze its similarity with Generative Adversarial Network (GAN). Finally, we evaluate the performance of the proposed model on histopathology slide and synthetic data. The limits of this promising framework as its perspectives are shown

International Telemetering Conference Proceedings / October 13-16, 1986 / Riviera Hotel, Las Vegas, Nevada
A digital frequency discriminator (DFD) of the delay-correlator type is described. The device is shown to have an instantaneous frequency measurement capability on very short pulses. The theoretical performance of the DFD in a noisy background is derived and shown to compare favorably with measured results.

Orientador: Fabio Violaro
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-07-26T00:16:55Z (GMT). No. of bitstreams: 1 Figueiredo_FabricioLira_M.pdf: 8181706 bytes, checksum: 4b3db6624620a5cb43cd1b3304195637 (MD5) Previous issue date: 1999
Resumo: Os Modelos Ocultos de Markov constituem, atualmente, a principal abordagem para o problema de Reconhecimento de Fala, pois proporcionam bom desempenho e alto grau de flexibilidade. Infelizmente, este modelo acústico não é ideal e alguns problemas afetam sua robustez e desempenho em condições adversas. A inconsistência do modelamento temporal implícito nos HMM's é um exemplo de um sério problema sem soluções bem definidas. De fato, o Modelo de Duração de Estados com distribuição exponencial é incompatível com o comportamento estatístico das unidades lingüísticas reais. A hipótese de independência entre observações representa outra limitação dos HMM's, já que não se verifica nos experimentos práticos. De fato, existe forte dependência contextual no caso de quadros pertencentes a regiões de transição entre unidades acústicas de uma elocução. Alguns modelos e algoritmos têm sido propostos para tentar transpor estes obstáculos, tais como Modelos Segmentais e Duração Explícita de Estados. Nesta tese, uma estratégia alternativa é proposta para atenuar estes problemas, sem acréscimos significativos no custo computacional. A informação relativa às transições entre fones, ao longo de uma elocução, é obtida através de métodos de segmentação automática. Realiza-se uma ponderação no algoritmo de Viterbi, a fim de penalizar os modelos que gerarem segmentações inconsistentes. Bons resultados são obtidos, para várias condições relacionadas a uma aplicação de Dígitos Conectados. O objetivo atual é aplicar esta técnica para o caso de vocabulários extensos
Abstract: Hidden Markov Model is actually the main approach to Speech Recognition problem, because of the good performance and high degree of flexibility that can be achieved. Unfortunately, this acoustical modeling is not optimum and some problems still affect it's robustness and performance in a more realistic condition. The weakness of the temporal modeling embedded in HMM is an example of a serious problem without well defined solutions. In fact, the implicit state duration model with exponential distribution may not describe the real linguistic units distributions. The hypothesis of independence between observations is other difficult problem to solve and it is incompatible with practical experiments because there is strong correlation between frames in the same acoustic segment. Some models and algorithms have been proposed to overcome or, at lest, attenuate those problems, such as Stochastic Segment Models and Explicit State Duration. This thesis presents an alternative approach to alleviate these problems, with relatively low computational cost. The information on phoneme boundaries in time is obtained through an Automatic segmentation algorithm and it is used in a Weighted Viterbi Algorithm in order to penalize the, models that generates inconsistent segmentations. Good results were achieved for various conditions related to connected digits application. The actual objective is to expand it to continuous speech recognition
Mestrado
Mestre em Engenharia Elétrica

The topic of this thesis is AI recruitment chatbots, digital discrimination, and data feminism (D´Ignazio and F.Klein 2020), where I aim to critically analyze issues of bias in these types of human-machine interaction technologies. Coming from a professional background of theatre, performance art, and drama, I am curious to analyze how using AI and social robots as hiring tools entails a new type of “stage” (actor’s space), with a special emphasis on social acting. Humans are now required to adjust their performance and facial expressions in the search for, and approval of, a new job. I will use my “theatrical glasses” with an intersectional lens, and through a methodology of cultural analysis, reflect on various examples of conversational AI used in recruitment processes. The silver bullet syndrome is a term that points to a tendency to believe in a miraculous new technological tool that will “magically” solve human-related problems in a company or an organization. The captivating marketing message of the Swedish recruitment conversational AI tool – Tengai Unbiased – is the promise of a scientifically proven objective hiring tool, to solve the diversity problem for company management. But is it really free from bias? According to Karen Barad, agency is not an attribute, but the ongoing reconfiguration of the world influenced by what she terms intra-actions, a mutual constitution of entanglement between human and non-human agencies (2003:818). However, tech developers often disregard their entanglement of human-to-machine interferences which unfortunately generates unconscious bias. The thesis raises ethical questions of how algorithmic measurement of social competence risks holding unconscious biases, benefiting those already privileged or those acting within a normative spectrum.

The purpose of this study was to determine the test-retest reliability of digitally recorded word recognition materials. Word recognition testing is included in a complete audiological evaluation to measure an individual's ability to discriminate what they hear. A phonetically balanced list of 50 monosyllabic words was presented to each participant at four different sensation levels (SL) using the American Speech Language Hearing Association recommended protocol for word recognition score testing. Each participant took a 10 minute break before the test was readministered. Participants included 40 subjects with varying levels of hearing loss, from normal hearing to severe hearing loss. The test and retest scores of all participants were analyzed to estimate the test-retest reliability to be .65 at 10 dB SL, .87 at 20 dB SL, .88 at 30 dB SL, and .95 at 40 dB SL. It was concluded that the word lists have strong test-retest reliability at 20, 30, and 40 dB SL and that the reliability increases as the presentation level increases.

碩士
國立臺灣海洋大學
電機工程學系
102
In this thesis, TDC(time-to-digital converter, TDC) digital time logic circuit implemented in Altera’s Stratix II EP2S60F1020C3 FPGA chip has been proposed. It could measure delay time between positive edges of input pulse and internal clock by using build-in carry adder chain to translate analog delay time into digital signals. The proposed TDC circuit was designed for the time coincidence unit of the PET system. In the TDC location assignment, the lengths of the routs from the pulse input pin to the first adder of carry chain and the clock signal to the D flip-flop have to be kept the same. This design guide could avoid difference of the delay time before the input pulse and the internal clock signal transport into TDC module. If the length is different, the additional delay time will affect the statistic result. Because of the semiconductor manufacturing issue and the physic arrangement in the FPGA, the build-in adders will have different transport delay time. In this restriction, the statistic result will have non-uniform distribution. In ideal condition, every adder must have similar counts in a large amount statistic. Therefore, we have to correct the non-uniform statistic result in order to get a uniform statistic result. In this thesis, we could improve the non-uniform statistic result after the correcting calibration process. Without the correcting process, the original timemark range is only 232 and the time resolution of the TDC is 325.33 ps. After correcting, the timemark range could be extended to 292 and the time resolution is improved to 183.58 ps. Moreover, improper location of the TDC module in FPGA might increase propagation delay time. Therefore, it could reduce correction complexity if we choose suitable location of the TDC module in FPGA according to the I/O pin of the input pulse and the location of the internal system clock.

碩士
國立臺灣海洋大學
電機工程學系
98
Time accuracy is a key factor affecting the performance of a positron emission tomography (PET). A fully digital time discrimination system for PET is presented in this thesis. The digital constant fraction discriminator (dCFD) and digital interpolated techniques are used to extract event time and optimize timing resolution. Two kinds of digital interpolated algorithms deduced from linear fit method are proposed, which are respectively weighted and bisection methods. These algorithms were designed by Verilog hardware description language (HDL) and implemented on a single FPGA. In our design, 5 bits of timing-mark are used in order to obtain 32 times of original time precision. The hardware prototype for the time discrimination experiments includes a pulse generator, a Xilinx Virtex-4 field programmable gate array (FPGA) and 105-MHz, 14-bit analog to digital converters (ADC). The experiment results show that the timing resolution of 550ps Full Width Half Maximum (FWHM) can be effectively achieve for both the weighted method and bisection method.

碩士
國立臺灣海洋大學
電機工程學系
100
In this thesis, the event time discrimination method for digital Positron Emission Tomography(PET) has been constructed by digital signal processing techniques. We use digital interpolated techniques and floating point operation to describe the more exact wave of the event. The exact wave of the event conduce to time discrimination system to product time-mark with the smaller time unit, then we can effectively improve the timing resolution of digital PET. The hardware prototype includes a pulse generator、Xilinx Virtex-4 field programmable gate array(FPGA) and a OSC 105MHz, 14bit analog-to-digital converter(ADC). In our design, 8 bits of time-mark are used in order to obtain 256 times of original time precision, in order words, our design are complete for reducing the smallest time unit from 9.5ns to 37.2ps. The experiment results show that the timing resolution of 78ps Full Width Half Maximum(FWHM) can be effectively achieve for this method.

The ability to digitize information goods such as music and movies and the growing accessibility of the Internet has led to online piracy and the emergence of a new class of retailers that specialize in digital downloads. Both online piracy and digital retailers have changed the dynamics of the information goods distribution channel. In my dissertation I focus on issues related to this change.

In the first chapter, "Digital music set free: the flip side of DRM," I study the effect of Digital Rights Management (DRM) mechanisms on the competition between traditional and digital retailers and on online piracy. DRM refers to technologies designed to control how end users may access, copy, or convert digital media. In the context of music downloads, DRM makes piracy of digital music more difficult, and until recently, most legal outlets for downloadable music only sold songs with DRM protection. Recently download retailers have convinced record companies to allow them to sell DRM-free music. The introduction of DRM-free music raises several important questions: Will music piracy increase as the opponents of DRM-free music predict? Will the music industry profits go up or down? How will CD retailers be affected? Will all labels start selling the unprotected (DRM-free) content?

I address these and related questions by developing a model of a music distribution channel that allows a record label to sell through both traditional CD retailers and iTunes-like download services at different wholesale prices. Among the interesting results, the analysis indicates that the level of piracy may decline when DRM protection is removed and that the traditional retailers much prefer to compete with distributors of pirated digital music rather than with legal music download services.

The competition between online and traditional retailers has led to interesting pricing policies on which I focus in the second chapter, "Digital movies at one simple price: the effect on competition." Online retailers tend to prefer uniform pricing (e.g. iTunes Store) where all "products" carry a single price, while traditional retailers do not have a policy of uniform prices. It is important to understand why one retailer should choose a single, uniform price and what impact it has on the competing retailer who chooses multiple prices. I focus specifically on the impact that single price policy adopted by digital retailer has on the traditional retailer. I also analyze the choice of uniform vs. differentiated pricing by modeling the competition between online and traditional retailers for vertically differentiated information goods. Importantly, I demonstrate how the asymmetric equilibrium we observe in the market today can change systematically with the nature of competition between the retailers.

Dissertation

碩士
國立臺北科技大學
商業自動化與管理研究所
90
Internet Company mainly maintained enterprises operate with ad income. However, the Web service and content charge will be on target after Internet Bubble burst. That is, enterprisers have unitary charge or third-level price discrimination by providing individual service. And the studies put more emphasis upon static pricing and less emphasis upon dynamic pricing or first-level discriminated pricing. So, the author is motivated to make this study to explore the practicability of first-level pricing. The author explores the desire for purchasing information products by the first-level price discrimination from Customer Value. This study is based on Literature and categorizes Customer Value of Information Products in ten items of measurement: validity, understandability, objectiveness, availability, reliability, value, task-relevance, task-completeness, and time limitation of task. In theory, the higher Customer Value is; the higher pricing is. This study is aimed to analyze content, offer the current conditions to enterprises, and make comparison with theory frame through case study. In experiment design, this study is to adopt individual techniques based on rules to achieve individual service. Then, it takes advantage of measurement of Customer Value to carry out first-level discriminated pricing. Finally, it identifies the practicability of the first-level discriminated pricing by the degree of desire for purchase. The results of study show that the desire for purchase with the individualized and first-level discriminated pricing is stronger than the one without the individualized and first-level discriminated pricing. The first-level discriminated pricing is well carried out through individual techniques and Customer Value. According to the proved results, this study suggests that Information Providers should seek to know customer needs through individual techniques and put more emphasis upon measure of Customer Value. Also, they look for the most appropriate Customer Value Measure to themselves. Furthermore, they re-map out the total pricing system of the whole enterprise by means of individual techniques and customer value measure forms.

碩士
國立臺灣海洋大學
電機工程學系
101
In this thesis, there have two kinds of digital timing signal processing algorithms for Positron Emission tomography. The high resolution time discrimination digital circuit can be implemented by using the high-speed sampling ADC and FPGA. The development of the hardware system is based on NI PXI platform which is flexible and can support any kinds of NI hardware modules for user design. The PXI platform provides 14-bit analog-to-digital converters with 250MHz sampling rate and Xilinx Vertex-5 FPGA to achieve all the designs of digital signal processing. The circuits of this research use the parallel pipeline architectures which allow ADC in free-running mode and process the data without dead time. In this research, the classical approaches of constant fraction discriminator (CFD) and Matched Filter (MF) were modified. Integrating the linear fitting interpolation into the above-mentioned methods improved the performance of resolution in time discrimination. Finally, the time resolution of the proposed time discrimination system can be decreased to 89.4 ps by CFD method and 22.82 ps by MF method.

博士
國立臺灣師範大學
資訊教育研究所
105
In a digital age, bilingual learning is currently pervasive in globalization society and is inevitably facilitated by learning technology. In order to investigate the effectiveness of digital learning on learning Chinese as a second language (CSL) from the perspective of cognitive neuroscience, the present study integrated the interdisciplinary knowledge among digital learning, linguistics, and cognitive neuroscience by non-invasive neuroimaging technology measurement in addition to behavior assessment. The research evidences elaborate the learning effect as a result of the brain neural plasticity, in which was observed after the short-term and non-specific tonal perception training for CSL beginning learners. By using a MEG experiment of magnetic correspondent of mismatch negativity (MMNm) paradigm with within-subjects design, the present study investigated the learning effect of CSL beginning learner who enrolled in a short term digital learning program. In the experiment, the measurements of MMNm, with the contrast between large deviant T3/T1 and between small deviant T3/T2, were computed to index the patterns of processing lexical tone in the brain. Results of the MMNm data indicated that activation for large contrast T3/T1 elicited earlier and significantly larger amplitude than of the small deviant contrast T3/T2, which is in line with previous studies done on native Chinese speakers. More importantly, in the comparison of pre-test and post-test time course, the amplitude of MMNm showed a significant increase in the left hemisphere after learning. The evidence indicated clearly a learning effect in the perception of linguistic features and a left lateralized neural network of processing Mandarin lexical tones as native-like pattern. Moreover, in the source analysis, the left lateralized patterns of prefrontal generator (i.e., insula) and generator of auditory cortex (i.e., Heschl's Gyrus) were observed after learning, which is also consistent with the native Mandarin speaker's response patterns. In other words, the present study provides neural evidence for a functional reorganization in the brain of CSL learners after a short-term and non-specific training program. The functional reorganization, in line with the duplex perception mechanism and functional –dependent lateralization, is reflected in transforming from predisposed acoustic-dependent right dominance for non-tonal language to linguistic functional-dependent left lateralization, as a tonal language native-like pattern. In sum, the present study provides an innovative implication of brain neural plasticity to bridge the changes of behavioral performance and neural mechanism of digital learning on second language.

Dissertação de mestrado integrado em Engenharia Física (área de especialização em Dispositivos, Microssistemas e Nanotecnologias)
The core focus of the work reported herein is the fulfillment of a functional Light Detection and Ranging (LiDAR) sensor to validate the direct Time-of-Flight (ToF) ranging concept and the acquisition of critical knowledge regarding pivotal aspects jeopardizing the sensor’s performance, for forthcoming improvements aiming a realistic sensor targeted towards automotive applications. Hereupon, the ToF LiDAR system is implemented through an architecture encompassing both optical and electronical functions and is subsequently characterized under a sequence of test procedures usually applied in benchmarking of LiDAR sensors. The design employs a hybrid edge-emitting laser diode (pulsed at 6kHz, 46ns temporal FWHM, 7ns rise-time; 919nm wavelength with 5nm FWHM), a PIN photodiode to detect the back-reflected radiation, a transamplification stage and two Time-to-Digital Converters (TDCs), with leading-edge discrimination electronics to mark the transit time between emission and detection events. Furthermore, a flexible modular design is adopted using two separate Printed Circuit Boards (PCBs), comprising the transmitter (TX) and the receiver (RX), i.e. detection and signal processing. The overall output beam divergence is 0.4º×1º and an optical peak power of 60W (87% overall throughput) is realized. The sensor is tested indoors from 0.56 to 4.42 meters, and the distance is directly estimated from the pulses transit time. The precision within these working distances ranges from 4cm to 7cm, reflected in a Signal-to-Noise Ratio (SNR) between 12dB and 18dB. The design requires a calibration procedure to correct systematic errors in the range measurements, induced by two sources: the timing offset due to architecture-inherent differences in the optoelectronic paths and a supplementary bias resulting from the design, which renders an intensity dependence and is denoted time-walk. The calibrated system achieves a mean accuracy of 1cm. Two distinct target materials are used for characterization and performance evaluation: a metallic automotive paint and a diffuse material. This selection is representative of two extremes of actual LiDAR applications. The optical and electronic characterization is thoroughly detailed, including the recognition of a good agreement between empirical observations and simulations in ZEMAX, for optical design, and in a SPICE software, for the electrical subsystem. The foremost meaningful limitation of the implemented design is identified as an outcome of the leading-edge discrimination. A proposal for a Constant Fraction Discriminator addressing sub-millimetric accuracy is provided to replace the previous signal processing element. This modification is mandatory to virtually eliminate the aforementioned systematic bias in range sensing due to the intensity dependency. A further crucial addition is a scanning mechanism to supply the required Field-of-View (FOV) for automotive usage. The opto-electromechanical guidelines to interface a MEMS micromirror scanner, achieving a 46º×17º FOV, with the LiDAR sensor are furnished. Ultimately, a proof-of-principle to the use of polarization in material classification for advanced processing is carried out, aiming to complement the ToF measurements. The original design is modified to include a variable wave retarder, allowing the simultaneous detection of orthogonal linear polarization states using a single detector. The material classification with polarization sensing is tested with the previously referred materials culminating in an 87% and 11% degree of linear polarization retention from the metallic paint and the diffuse material, respectively, computed by Stokes parameters calculus. The procedure was independently validated under the same conditions with a micro-polarizer camera (92% and 13% polarization retention).
O intuito primordial do trabalho reportado no presente documento é o desenvolvimento de um sensor LiDAR funcional, que permita validar o conceito de medição direta do tempo de voo de pulsos óticos para a estimativa de distância, e a aquisição de conhecimento crítico respeitante a aspetos fundamentais que prejudicam a performance do sensor, ambicionando melhorias futuras para um sensor endereçado para aplicações automóveis. Destarte, o sistema LiDAR é implementado através de uma arquitetura que engloba tanto funções óticas como eletrónicas, sendo posteriormente caracterizado através de uma sequência de testes experimentais comumente aplicáveis em benchmarking de sensores LiDAR. O design tira partido de um díodo de laser híbrido (pulsado a 6kHz, largura temporal de 46ns; comprimento de onda de pico de 919nm e largura espetral de 5nm), um fotodíodo PIN para detetar a radiação refletida, um andar de transamplificação e dois conversores tempo-digital, com discriminação temporal com threshold constante para marcar o tempo de trânsito entre emissão e receção. Ademais, um design modular flexível é adotado através de duas PCBs independentes, compondo o transmissor e o recetor (deteção e processamento de sinal). A divergência global do feixe emitido para o ambiente circundante é 0.4º×1º, apresentando uma potência ótica de pico de 60W (eficiência de 87% na transmissão). O sensor é testado em ambiente fechado, entre 0.56 e 4.42 metros. A precisão dentro das distâncias de trabalho varia entre 4cm e 7cm, o que se reflete numa razão sinal-ruído entre 12dB e 18dB. O design requer calibração para corrigir erros sistemáticos nas distâncias adquiridas devido a duas fontes: o desvio no ToF devido a diferenças nos percursos optoeletrónicos, inerentes à arquitetura, e uma dependência adicional da intensidade do sinal refletido, induzida pela técnica de discriminação implementada e denotada time-walk. A exatidão do sistema pós-calibração perfaz um valor médio de 1cm. Dois alvos distintos são utilizados durante a fase de caraterização e avaliação performativa: uma tinta metálica aplicada em revestimentos de automóveis e um material difusor. Esta seleção é representativa de dois cenários extremos em aplicações reais do LiDAR. A caraterização dos subsistemas ótico e eletrónico é minuciosamente detalhada, incluindo a constatação de uma boa concordância entre observações empíricas e simulações óticas em ZEMAX e elétricas num software SPICE. O principal elemento limitante do design implementado é identificado como sendo a técnica de discriminação adotada. Por conseguinte, é proposta a substituição do anterior bloco por uma técnica de discriminação a uma fração constante do pulso de retorno, com exatidões da ordem sub-milimétrica. Esta modificação é imperativa para eliminar o offset sistemático nas medidas de distância, decorrente da dependência da intensidade do sinal. Uma outra inclusão de extrema relevância é um mecanismo de varrimento que assegura o cumprimento dos requisitos de campo de visão para aplicações automóveis. As diretrizes para a integração de um micro-espelho no sensor concebido são providenciadas, permitindo atingir um campo de visão de 46º×17º. Conclusivamente, é feita uma prova de princípio para a utilização da polarização como complemento das medições do tempo de voo, de modo a suportar a classificação de materiais em processamento avançado. A arquitetura original é modificada para incluir uma lâmina de atraso variável, permitindo a deteção de estados de polarização ortogonais com um único fotodetetor. A classificação de materiais através da aferição do estado de polarização da luz refletida é testada para os materiais supramencionados, culminando numa retenção de polarização de 87% (tinta metálica) e 11% (difusor), calculados através dos parâmetros de Stokes. O procedimento é independentemente validado com uma câmara polarimétrica nas mesmas condições (retenção de 92% e 13%).