Receiver design for nonlinearly distorted OFDM : signals applications in radio-over-fiber systems

Tese de doutoramento. Engenharia Electrotécnica e de Computadores. Universidade do Porto. Faculdade de Engenharia. 201

Wavelet Theory

The wavelet is a powerful mathematical tool that plays an important role in science and technology. This book looks at some of the most creative and popular applications of wavelets including biomedical signal processing, image processing, communication signal processing, Internet of Things (IoT), acoustical signal processing, financial market data analysis, energy and power management, and COVID-19 pandemic measurements and calculations. The editor’s personal interest is the application of wavelet transform to identify time domain changes on signals and corresponding frequency components and in improving power amplifier behavior

News endorser influence in social media

Social networking sites have become an online realm where users are exposed to news about current affairs. People mainly encounter news incidentally because they are re-distributed by users whom they befriended or follow on social media platforms. In my dissertation project, I draw on shared reality theory in order to examine the question of how the relationship to the news endorser, the person who shares news content, determines social influence on opinion formation about shared news. The shared reality theory posits that people strive to achieve socially shared beliefs about any object and topic because of the fundamental epistemic need to establish what is real. Social verification of beliefs in interpersonal communication renders uncertain and ambiguous individual perceptions as valid and objectively true. However, reliable social verification may be provided only by others who are regarded as epistemic authority, in other words as someone whose judgment one can trust. People assign epistemic authority particularly to socially close others, such as friends and family, or to members of their in-group. I inferred from this that people should be influenced by the view of a socially close news endorser when forming an opinion about shared news content but not by the view of a socially distant news endorser. In Study 1, a laboratory experiment (N = 226), I manipulated a female news endorsers social closeness by presenting her as an in-group or out-group member. Participants opinion and memory of a news article were not affected by the news endorsers opinion in either of the conditions. I concluded that the news article did not elicit motivation to strive for shared reality because participants were confident about their own judgment. Therefore, they did not rely on the news endorsers view when forming an opinion about the news topic. Moreover, the results revealed that participants had stronger trust in the news endorser when she expressed a positive (vs. negative) opinion about the news topic, while social closeness to the news endorser did not predict trust. On the one hand, this is in line with the social norm of sharing positive thoughts and experiences on social networking sites: adherence to the positivity norm results in more favorable social ratings. On the other hand, my findings indicate that participants generally had a positive opinion about the topic of the stimulus article and thus had more trust in news endorsers who expressed a similar opinion. In Study 2, an online experiment (N = 1, 116), I exposed participants to a news post by a relational close vs. relational distant news endorser by having them name a close or distant actual Facebook friend. There was a small influence of the news endorsers opinion on participants thought and opinion valence irrespective of whether the news endorser was a close or distant friend. The finding was surprising, particularly because participants reported stronger trust in the view of the close friend than in the view of a distant friend. I concluded that in light of an ambiguity eliciting news article, people may even rely on the views of less trustworthy news endorsers in order to establish a socially shared and, therefore, valid opinion about a news topic. Drawing on shared reality theory, I hypothesized that social influence on opinion formation is mediated by news endorser congruent responses to a news post. The results indicated a tendency for the proposed indirect relation however, the effect size was small and the sample in Study 2 was not large enough to provide the necessary statistical power to detect the mediation. In conclusion, the results of my empirical studies provide first insights regarding the conditions under which a single news endorser influences opinion formation about news shared on social networking sites. I found limited support for shared reality creation as underlying mechanism of such social influence. Thus, my work contributes to the understanding of social influence on news perception happening in social networking sites and proposes theoretical refinements to shared reality theory. I suggest that future research should focus on the role of social and affiliative motivation for social influences on opinion formation about news shared on social networking sites.Soziale Netzwerkseiten haben sich zu Orten entwickelt, an denen Nutzer:innen Nachrichten über aktuelle Ereignisse begegnen. Menschen treffen vor allem deswegen auf Nachrichten, weil diese von Personen geteilt werden, mit denen sie befreundet sind. In meiner Dissertation untersuche ich aufbauend auf der Shared Reality Theorie ob die Beziehung zu Nachrichten-Endorser:innen, also denjenigen, die Nachrichten teilen, bestimmt ob deren Ansichten einen Einfluss auf die Meinungsbildung haben. Die Shared Reality Theorie geht davon aus, dass Menschen ein fundamentales epistemisches Bedürfnis danach haben richtige und wahrhaftige Ansichten zu entwickeln. Deshalb streben sie nach Ansichten, die von anderen geteilt werden. Durch interpersonale Kommunikation verifizieren sie ihre Ansichten, wobei aus einer unsicheren und ambigen Wahrnehmung ein valides und objektives Urteil werden kann. Allerdings wird eine Wahrnehmung nur dann soziale verifiziert, wenn Menschen ihr Gegenüber als epistemische Autorität ansehen, also als jemanden, dessen Urteil sie vertrauen. Epistemische Autorität wird gewöhnlich Personen zugeschrieben, die einem nahestehen, z.B. Freunden oder Mitgliedern der eigenen In-Group. Daraus leite ich ab, dass die Meinungsbildung über Nachrichten, die auf sozialen Netzwerkseiten von einer sozial nahestehenden Person geteilt werden, von deren Ansicht beeinflusst sein sollte. Die Ansicht sozial entfernter Nutzer:innen sollte hingegen keinen Einfluss auf die Meinungsbildung haben. In Studie 1, einem Laborexperiment (N=226), manipulierte ich die soziale Nähe einer weiblichen Nachrichten-Endorserin, indem ich sie als In-Group oder Out-Group Mitglied vorstellte. In keiner der Bedingungen hatte die Meinung der Nachrichten-Endorserin einen Einfluss auf die Meinungen der Teilnehmenden über einen Nachrichtenartikel und auf ihre Erinnerung an dessen Inhalt. Daraus schließe ich, dass der Artikel keine Motivation für das Streben nach geteilter Realität ausgelöst hat, sondern die Teilnehmenden sich ihres eigenen Urteils sicher waren. Daher zogen sie die Ansicht der Nachrichten-Endorserin bei der Meinungsbildung nicht in Betracht. Darüber hinaus zeigen meine Ergebnisse, dass die Teilnehmenden dem Urteil der Nachrichten-Endorserin mehr vertrauten, wenn sie eine positive (vs. negative) Meinung über das Nachrichtenthema äußerte. Die soziale Nähe hingegen hatte keinen Effekt auf das Vertrauen in das Urteil der Nachrichten-Endorserin. Dies entspricht einerseits der auf sozialen Netzwerkseiten geltenden Norm, positive Gedanken und Erfahrungen zu teilen. Das Befolgen der Norm führt folglich zu einer positiveren sozialen Bewertung. Andererseits legen meine Ergebnisse nahe, dass die Teilnehmenden generell eine eher positive Meinung über das Thema des Artikels und folglich größeres Vertrauen in die Nachrichten-Endorserin hatten, wenn diese eine ähnliche Meinung äußerte. In Studie 2, einem Onlineexperiment (N=1.116), forderte ich die Teilnehmenden auf, einen nahestehenden oder entfernten Facebook-Freund zu nennen. Anschließend präsentierte ich ihnen einen fiktiven Nachrichten-Post mit einer Meinungsäußerung (positiv vs. negativ) des genannten Freundes/der genannten Freundin. Unabhängig von der sozialen Nähe der Nachrichten-Endorser:innen zeigte sich ein kleiner Einfluss ihrer Meinung auf die Valenz der Gedanken und Meinungen der Teilnehmenden über das Nachrichtenthema. Dieses Ergebnis war überraschend, insbesondere da die Teilnehmenden angaben, größeres Vertrauen in die Ansicht eines nahestehenden Freundes/einer nahestehende Freundin zu haben. Daraus schließe ich, dass sich Menschen angesichts eines ambigen Artikels sogar auf die Ansicht weniger vertrauenswürdiger Nachrichten-Endorser:innen verlassen, um sich eine sozial geteilte und damit valide Meinung über das Thema zu bilden. Zusammenfassend liefern die Ergebnisse meiner Studien erste Erkenntnisse über die Bedingungen, unter denen einzelne Nachrichten-Endorser:innen auf sozialen Netzwerkseiten die Meinungsbildung über Nachrichten beeinflussen. Die Ergebnisse sprechen nur teilweise dafür, dass das Streben nach geteilter Realität der zugrundeliegende Mechanismus dieses sozialen Einflusses ist. Meine Arbeit trägt somit einerseits zum Verständnis sozialer Einflüsse auf die Wahrnehmung von Nachrichten auf sozialen Netzwerkseiten bei. Anderseits zeigt sie Weiterentwicklungsbedarf der Shared Reality Theorie auf. Ich schlage vor, dass zukünftige Forschung insbesondere untersuchen sollte, welche Rolle soziale und affiliative Motive für soziale Einflüsse auf die Meinungsbildung über Nachrichten spielen, die auf sozialen Netzwerkseiten geteilt werden

Wireless Localization Systems: Statistical Modeling and Algorithm Design

Wireless localization systems are essential for emerging applications that rely on context-awareness, especially in civil, logistic, and security sectors. Accurate localization in indoor environments is still a challenge and triggers a fervent research activity worldwide. The performance of such systems relies on the quality of range measurements gathered by processing wireless signals within the sensors composing the localization system. Such range estimates serve as observations for the target position inference. The quality of range estimates depends on the network intrinsic properties and signal processing techniques. Therefore, the system design and analysis call for the statistical modeling of range information and the algorithm design for ranging, localization and tracking. The main objectives of this thesis are: (i) the derivation of statistical models and (ii) the design of algorithms for different wire- less localization systems, with particular regard to passive and semi-passive systems (i.e., active radar systems, passive radar systems, and radio frequency identification systems). Statistical models for the range information are derived, low-complexity algorithms with soft-decision and hard-decision are proposed, and several wideband localization systems have been analyzed. The research activity has been conducted also within the framework of different projects in collaboration with companies and other universities, and within a one-year-long research period at Massachusetts Institute of Technology, Cambridge, MA, USA. The analysis of system performance, the derived models, and the proposed algorithms are validated considering different case studies in realistic scenarios and also using the results obtained under the aforementioned projects

A new method for measuring and calibrating cinema audio systems for optimal sound quality

The aim of this research is to utilize new methodologies and technology in order to gain insight into how the modern cinema audio system could be calibrated to provide improved audio performance. To this end, both objective and subjective measurements were developed to better understand the audio preferences of listeners, the requirements of the audio systems inclusive of the acoustic environment, and how the two are related. Part of the data for this research was derived from a survey of re-recording mixers regarding their use and opinion of the current SMPTE standard. The survey confirmed anecdotal information suggesting that re-recording mixers use high-end pre-emphasis to compensate for the severe roll-off induced by the SMPTE X-curve. It is also noted that the re-recording mixers' opinions of how well their mix translates from dub-stage to cinema is correlated to how many years they have spent in the industry. The aim of this research is to utilize new methodologies and technology in order to gain insight into how the modern cinema audio system could be calibrated to provide improved audio performance. To this end, both objective and subjective measurements were developed to better understand the audio preferences of listeners, the requirements of the audio systems inclusive of the acoustic environment, and how the two are related. Part of the data for this research was derived from a survey of re-recording mixers regarding their use and opinion of the current SMPTE standard. The survey confirmed anecdotal information suggesting that re-recording mixers use high-end pre-emphasis to compensate for the severe roll-off induced by the SMPTE X-curve. It is also noted that the re-recording mixers' opinions of how well their mix translates from dub-stage to cinema is correlated to how many years they have spent in the industry. To further understand listener preference to in-room responses curves, a series of listening tests utilizing the BRS system were conducted using various sized cinemas, seating positions within the cinemas, audio tracks (including those mixed on a SMPTE calibrated dub-stage) and target curves. The overwhelming outcome was that regardless of cinema size, seating position or audio track utilized; the "curve" that listeners preferred is a relatively flat 0.9dB/octave slope with a 6.5dB bass boost below 105Hz and a -2.5dB roll off above 2.5kHz. Of the 5 target curves presented, the SMPTE X-curve place fourth with scores very near the low-rated perceptual anchor. This calls into question the notion of the X-curve providing "ideal" translation between dub-stage and cinema and in fact, challenges the concept of translation all together. Research was completed in an effort to identifying the number of microphone positions required, along with their placement, in order to accurately capture a cinema's response for calibration purposes. A novel experiment utilizing anechoic loudspeaker data as a guideline for xxi analysis demonstrated that, with proper data, the number of microphones and their positions plays a less critical factor in determining the room response. The collected data shows that even with as few as 4 microphones at varied positions, the resultant room response will trend towards the anechoic data above 1kHz. From around 300Hz to 1kHz, there is evidence of seat effects that may be resolved through randomizing the microphone heights. Below 300Hz, the room becomes the dominating factor and more than 5 microphone positions will be required to properly identify any problems

Microaggressions, racial identity, and coping: An examination of Black graduates of elite universities

Thesis advisor: David L. BlusteinEducation is often thought of as the great equalizer that is capable of offsetting societal inequities (Holmes & Zajacova, 2014). Elite universities are characterized by the most selective admissions criteria, and attendance at these universities often provides access to the social capital necessary to pursue prestigious careers. Research shows that Black students attending elite universities experience racism while on campus (Torres & Charles, 2004; Warikoo, 2018). Scholars have also found that the experience of racism negatively impacts Black student’s well-being (Neville et al., 2004). However, little is known about what happens when Black students at elite universities graduate and enter the workforce, especially the ways in which they experience racism at work. Therefore, the purpose of this study was to better understand the ways in which experiences of racism at work impact on well-being and work-fulfillment for Black graduates at elite universities and to examine potential factors that may protect against racism. Black graduates of elite universities (N= 1,010) were invited to complete measures that assessed racial microaggressions (Racial and Ethnic Microaggressions Scale), racial identity (Black Racial Identity Attitudes Scale), racism-related coping strategies (Racism-Related Coping Scale) well-being outcomes (Mental Health Inventory and Satisfaction with Life), and work-fulfillment outcomes (Work Engagement and Job Satisfaction). The present study used structural equation modeling and findings were mixed. However, the results revealed that particular experiences of racism at work negatively impact both well-being and work-fulfillment. The results of moderation analyses showed that racial identity may serve as a protective factor against experiences of racism at work for Black graduates of elite universities. Implications for research, practice and policy, as well as study limitations are presented.Thesis (PhD) — Boston College, 2022.Submitted to: Boston College. Lynch School of Education.Discipline: Counseling, Developmental and Educational Psychology