This project consists of analyzing and finding solutions to the effect of non-linear distortionon the performance of a Massive Multiple Input Multiple Output (MIMO) system interms of Spectral Efficiency (SE) and Symbol Error Rate (SER). Massive MIMO is one ofthe technologies that are considered the backbone of the 5th generation of wireless communicationsand therefore this technology has gathered much interest from researchersand companies alike [19], as it is proven that this kind of system greatly improves thecapacity of the wireless connection [8]. Since Massive MIMO is still a relatively newtechnology and it is yet to be implemented for commercial use, there are several challengesthat arise when trying to implement such a system. One of these problems arisefrom the fact that the Power Amplifiers (PAs) in the transmitters of Massive MIMO systemsare non-linear and thus impose a distortion on the transmitted signals of the system[12]. The thesis aims to study this non-linear effect on the performance of massive MIMOsystems by first modelling the distortion effect on the transmitted signals using two differentnon-linear models. Moreover, closed-form expressions for one of the models areformed to facilitate the simulation of the non-linear model and facilitate the analysis ofthe distortion effect on the performance metrics. Then the established system model issimulated and based on the results, the effect of each of the power amplifier non-lineardistortion models on the performance metrics of the Massive MIMO system is studied.Furthermore, based on the analysis of the simulation results, a compensation mechanismis introduced to the Massive MIMO system in order to mitigate the distortion effect onthe system performance in terms of SER and SE.

With the increasing pace of technological changes in the modern society, there has been a growing interest from educators, business leaders, and policymakers in teaching important higher-order skills which were identified as necessary for thriving in the present-day globalized economy. In this regard, one of the most widely discussed higher order skills is critical thinking, whose importance in shaping problem solving, decision making, and logical thinking has been recognized. Within the domain of distance and online education, the Community of Inquiry (CoI) model provides a pedagogical framework for understanding the critical dimensions of student learning and factors which impact the development of student critical thinking. The CoI model follows the social-constructivist perspective on learning in which learning is seen as happening in both individual minds of learners and through the discourse within the group of learners. Central to the CoI model is the construct of cognitive presence, which captures the student cognitive engagement and the development of critical thinking and deep thinking skills. However, the assessment of cognitive presence is challenging task, particularly given its latent nature and the inherent physical and time separation between students and instructors in distance education settings. One way to address this problem is to make use of the vast amounts of learning data being collected by learning systems. This thesis presents novel methods for understanding and assessing the levels of cognitive presence based on learning analytics techniques and the data collected by learning environments. We first outline a comprehensive model for cognitive presence assessment which builds on the well-established evidence-cantered design (ECD) assessment framework. The proposed assessment model provides a foundation of the thesis, showing how the developed analytical models and their components fit together and how they can be adjusted for new learning contexts. The thesis shows two distinct and complementary analytical methods for assessing students’ cognitive presence and its development. The first method is based on the automated classification of student discussion messages and captures learning as it is observed in the student dialogue. The second analytics method relies on the analysis of log data of students’ use of the learning platform and captures the individual dimension of the learning process. The developed analytics also extend current theoretical understanding of the cognitive presence construct through data-informed operationalization of cognitive presence with different quantitative measures extracted from the student use of online discussions. We also examine methodological challenges of assessing cognitive presence and other forms of cognitive engagement through the analysis of trace data. Finally, with the intent of enabling for the wider adoption of the CoI model for new online learning modalities, the last two chapters examine the use of developed analytics within the context of Massive Open Online Courses (MOOCs). Given the substantial differences between traditional online and MOOC contexts, we first evaluate the suitability of the CoI model for MOOC settings and then assess students’ cognitive presence using the data collected by the MOOC platform. We conclude the thesis with the discussion of practical application and impact of the present work and the directions for the future research.

Introduction: There is proven therapeutic benefit in bariatric surgery for obese patients. Consequently the National Institute of Clinical Excellence UK has provided referral guidelines for bariatric surgery. Successful bariatric surgery will result in massive weight loss and ptotic skin, which can cause significant functional and psychological problems. As the number of cases of bariatric surgery increases, a corresponding number of massive weight loss patients will require plastic surgery. In this novel field of post massive weight loss surgery there is a lack of understanding of the demographics, physical symptoms and psychological health of this new group of patients. The tools to assess them are few and not validated, the patient pathway is disjointed and there is no consensus on standardised provision. Method: A prospective multicentre, observational study of outcomes in 100 patients undergoing bariatric and post massive weight loss plastic surgery at 2 clinical sites was performed. Each patient followed a standard operating protocol. This included undergoing a semi structured interview, completing five patient-report outcome measures, having anthropometric measurements and clinical photographs taken. Conclusion: This observational study identified key psychosocial themes prevalent in massive weight loss patients, during their weight loss journey. It identified there are no validated patient reported outcome measures available specific to this cohort of patients. This work led to the development of a new validated tool for massive weight loss body contouring.

Recently, massive multiple-input multiple-output (MIMO) systems have gained significant attention as a new network architecture to not only achieving unprecedented spectral and energy efficiencies, but also to alleviating propagation losses and inter-user/inter-cell interference. Therefore, massive MIMO has been identified as one of the key candidate technologies for the 5th generation wireless standard. This dissertation thus focuses on (1) developing a performance analysis framework for cognitive massive MIMO systems by investigating the uplink transmissions of multi-cell multi-user massive MIMO secondary systems, which are underlaid in multi-cell multi-user primary massive MIMO systems, with taking into consideration the detrimental effects of practical transmission impairments, (2) proposing a new wireless-powered underlay cognitive massive MIMO system model, as the secondary user nodes is empowered by the ability to efficiently harvest energy from the primary user transmissions, and then access and utilize the primary network spectrum for information transmission, and (3) developing a secure communication strategy for cognitive multi-user massive MIMO systems, where physical layer secure transmissions are provisioned for both primary and secondary systems by exploiting linear precoders and artificial noise (AN) generation in order to degrade the signal decodability at eavesdropper. The key design feature of the proposed cognitive systems is to leverage the spatial multiplexing strategies to serve a large number of spatially distributed user nodes by using very large numbers of antennas at the base-stations. Moreover, the fundamental performance metrics, the secondary transmit power constraints, which constitute the underlay secondary transmissions subject to a predefined primary interference temperature, and the achievable sum rates of the primary and secondary systems, are characterized under different antenna array configurations. Additionally, the detrimental impact of practical wireless transmission impairments on the performance of the aforementioned systems are quantified. The important insights obtained throughout these analyses can be used as benchmarks for designing practical cognitive spectrum sharing networks.

The broadcast nature of wireless medium has made information security as one of the most important and critical issues in wireless systems. Physical layer security, which is based on information-theoretic secrecy concepts, can be used to secure the wireless channels by exploiting the noisiness and imperfections of the channels. Massive multiple-input multiple-output (MIMO) systems, which are equipped with very large antenna arrays at the base stations, have a great potential to boost the physical layer security by generating the artificial noise (AN) with the exploitation of excess degrees-of-freedom available at the base stations. In this thesis, we investigate physical layer security provisions in the presence of passive/active eavesdroppers for single-hop massive MIMO, dual-hop relay-assisted massive MIMO and underlay spectrum-sharing massive MIMO systems. The performance of the proposed security provisions is investigated by deriving the achievable rates at the user nodes, the information rate leaked into the eavesdroppers, and the achievable secrecy rates. Moreover, the effects of active pilot contamination attacks, imperfect channel state information (CSI) acquisition at the base-stations, and the availability of statistical CSI at the user nodes are quantified. The secrecy rate/performance gap between two AN precoders, namely the random AN precoder and the null-space based AN precoder, is investigated. The performance of hybrid analog/digital precoding is compared with the full-dimensional digital precoding. Furthermore, the physical layer security breaches in underlay spectrum-sharing massive MIMO systems are investigated, and thereby, security provisions are designed/analyzed against active pilot contamination attacks during the channel estimation phase. A power-ratio based active pilot attack detection scheme is investigated, and thereby, the probability of detection is derived. Thereby, the vulnerability of uplink channel estimation based on the pilots transmitted by the user nodes in time division duplexing based massive MIMO systems is revealed, and the fundamental trade-offs among physical layer security provisions, implementation complexity and performance gains are discussed.

Massive multiple-input multiple-output is a promising technique for the next generation of wireless communication systems which addresses most of the critical challenges associated with concurrent relaying systems, such as digital signal processing complexity, long processing delay, and low latency wireless communications. However, the deployment of conventional fully digital beamforming methods, dedicates one radio frequency (RF) chain to each antenna, is not viable enough due to the high fabrication/implementation cost and power consumption. In this thesis, we envision to address this critical issue by reducing the number of RF chains in a viable analog/digital configuration paradigm which is usually referred to hybrid structure. From another viewpoint, the development of fifth generation enabling technologies brings new challenges to the design of power amplifiers (PAs). In particular, there is a strong demand for low-cost, nonlinear PAs which, however, introduce nonlinear distortions. On the other hand, contemporary expensive PAs show great power efficiency in their nonlinear region. Inspired by this trade-off between nonlinearity distortions and efficiency, finding an optimal operating point is highly desirable, and this is the second key contribution of this thesis.

Dissertação (mestrado)—Universidade de Brasília, Instituto de Artes, Departamento de Música, Programa de Pós-Graduação Música em Contexto, 2017. / Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2018-04-13T20:05:32Z No. of bitstreams: 1 2017_TomásTeixeiradeSouza.pdf: 3828640 bytes, checksum: b0c7897c510e546308e18c7e9cc20b0b (MD5) / Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2018-05-08T20:42:10Z (GMT) No. of bitstreams: 1 2017_TomásTeixeiradeSouza.pdf: 3828640 bytes, checksum: b0c7897c510e546308e18c7e9cc20b0b (MD5) / Made available in DSpace on 2018-05-08T20:42:10Z (GMT). No. of bitstreams: 1 2017_TomásTeixeiradeSouza.pdf: 3828640 bytes, checksum: b0c7897c510e546308e18c7e9cc20b0b (MD5) Previous issue date: 2018-05-08 / Fundação de Apoio à Pesquisa do Distrito Federal (FAP-DF). / MOOCs (Massive Open Online Course) são cursos online, abertos e massivos. O objetivo da presente pesquisa é planejar e implementar o MOOC Laboratório Online de Música e Tecnologia (LOMT), um ambiente virtual de aprendizagem (AVA) criado para os alunos do curso de Licenciatura em Música da UnB, na modalidade à distância. O referencial teórico é o modelo C(L)A(S)P, uma proposta de educação musical do educador Keith Swanwick. Foram associados módulos do MOOC LOMT a cada uma das atividades do modelo C(L)A(S)P (composição, literatura, apreciação musical, desenvolvimento da técnica e performance/execução) para avaliar como essas atividades poderiam ser aplicadas online de forma integrada. O estudo foi desenvolvido através de uma pesquisa-ação que, a partir de uma abordagem qualitativa, teve como técnicas de coleta de dados a observação participante, um questionário e a extração de dados textuais do sistema de postagem do MOOC LOMT. Como resultado, com o uso de recursos como os softwares online, o Gráfico de Percepção Espacial e o MOOC LOMT, associados às atividades de composição, leitura, apreciação, técnica e performance, foi possível planejar e implementar o MOOC LOMT com base na proposta pedagógica integrada do modelo C(L)A(S)P. Com o resultado da pesquisa, espera-se, que sejam trabalhadas novas formas de aplicar o modelo C(L)A(S)P no ensino musical online; novas tecnologias musicais sejam exploradas para desenvolver as competências e habilidades musicais online, programas de capacitação de professores possam ser atualizados prevendo o uso de ferramentas online e tecnologias digitais para o ensino da música. / MOOCs (Massive open online course) are online, open and massive courses. The objective of this research is to plan and implement the MOOC Online Laboratory of Music and Technology (LOMT), a virtual learning environment (AVA) created for students of the undergraduate course in music of the University of Brasília, in the distance mode. The theoretical reference is the C(L)A(S)P model, a proposal of musical education of the educator Keith Swanwick. Modules of the MOOC LOMT were associated with each of the activities of the C(L)A(S)P model (composition, literature, musical appreciation, development of the technique and performance/execution) to evaluate how these activities could be applied online in an integrated way. The study was developed through a research-action that, from a qualitative approach, had as techniques of data collection the participant observation, a questionnaire and the extraction of textual data from the postage system of MOOC LOMT. As a result, with the use of resources such as online software, the spatial perception chart and the MOOC LOMT, associated with the activities of composition, reading, appreciation, technique and performance, it was possible to plan and implement the MOOC LOMT based on the C(L)A(S)P model integrated proposal. With the result of the research, it is hoped that new ways of applying the C(L)A(S)P in the online music education are expected to be worked, new musical technologies are explored to develop online music skills, teacher training programs can be upgraded by predicting the use of online tools and digital technologies for teaching music.

abstract: Long before “fake news” dominated the conversation within and about the media, media literacy advocates have championed the need for media literacy education that provides the tools for people to understand, analyze, and evaluate media messages. That the majority of U.S. adults now consume news on social media underscores the importance for students of all ages to be critical users of media. Furthermore, the affordances of social media to like, comment, and share news items within one’s network increases an individual’s responsibility to ascertain the veracity of news before using a social media megaphone to spread false information. Social media’s shareability can dictate how information spreads, increasing news consumers’ role as a gatekeeper of information and making media literacy education more important than ever. This research examines the media literacy practices that news consumers use to inform their gatekeeping decisions. Using a constant comparative coding method, the author conducted a qualitative analysis of hundreds of discussion board posts from adult participants in a digital media literacy Massive Open Online Course (MOOC) to identify major themes and examine growth in participants’ sense of responsibility related to sharing news information, their feeling of empowerment to make informed decisions about the media messages they receive, and how the media literacy tools and techniques garnered from the MOOC have affected their daily media interactions. Findings emphasize the personal and contextual nature of media literacy, and that those factors must be addressed to ensure the success of a media literacy education program. / Dissertation/Thesis / Doctoral Dissertation Journalism and Mass Communication 2018

Submitted by Douglas Benndorf Rodrigues null (dbenndorf@yahoo.com.br) on 2017-01-17T06:06:36Z No. of bitstreams: 1 HamiltVincSpin2_V7.pdf: 644680 bytes, checksum: 7826f04e2072b12f1597892b97b67791 (MD5) / Approved for entry into archive by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br) on 2017-01-20T13:54:02Z (GMT) No. of bitstreams: 1 rodrigues_db_me_guara.pdf: 644680 bytes, checksum: 7826f04e2072b12f1597892b97b67791 (MD5) / Made available in DSpace on 2017-01-20T13:54:02Z (GMT). No. of bitstreams: 1 rodrigues_db_me_guara.pdf: 644680 bytes, checksum: 7826f04e2072b12f1597892b97b67791 (MD5) Previous issue date: 2016-12-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho abordamos de forma introdutória o tratamento de sistemas singulares, em especial as teorias de Maxwell, Proca e Fierz-Pauli, e obtemos resultados originais para a família de modelos de spin-2 massivos do tipo não-Fierz-Pauli. Tendo como ferramenta principal o método de Dirac para sistemas vinculados, escrevemos a densidade de hamiltoniana primária do modelo LnF P , obtemos seus vínculos primários, secundários, terciários e quartenários, assim como os multiplicadores de Lagrange. Calculamos também o número de graus de liberdade independentes e mostramos a positividade da hamiltoniana reduzida. / In this work, we approach in an introductory way the treatment of singular systems, especially the theories of Maxwell, Proca and Fierz-Pauli, and obtain original results for the non-Fierz-Pauli family of massive spin-2 models. Having as main tool the Dirac method for constrained systems, we write the primary Hamiltonian density of the LnF P model, obtain their primary, secondary, tertiary and quaternary constraints, as well as Lagrange multipliers. We calculate the number of independent degrees of freedom of the model and demonstrate the positivity of the reduced Hamiltonian.

Nesta dissertação são apresentados os resultados obtidos da espectroscopia de campo integral da nebulosa do Homúnculo. As observações foram feitas na banda J, no intervalo de 10620 Å até 12960 Å, utilizando o IFU (Integral Field Unit) do espectrógrafo CIRPASS (Cambridge Infrared Panoramic Survey Spectrograph), que possui 499 lentes hexagonais. A amostragem espacial é de 0,25"/lente e a resolução espectral, R=3200. A linha do [Fe II] λ12567 permitiu a identificação de duas estruturas no lóbulo NW que ainda não haviam sido relatadas. Através da tomografia Doppler, essas estruturas indicaram a existência de uma região de baixa densidade localizada no lóbulo NW e que não é visível nas imagens feitas na região óptica. Além disso, o Pequeno Homúnculo também foi identificado através do mapeamento das componentes e também nos mapas de velocidade da linha do [Fe II] λ12567. As regiões polares da nebulosa do Homúnculo (onde ocorre a colisão mais intensa entre o vento da fonte central e a região interna dos lóbulos) são mais opacas do que as paredes dos mesmos. Isso é verificado pela diminuição na intensidade da linha do [Fe II] λ12567 no lóbulo SE e pelo aumento desta na linha de visada do lóbulo NW. O disco equatorial foi observado nas linhas da série do H (Paβ e Paγ) e na linha do He I λ10830 como uma componente devido à emissões intrínsecas até distâncias superiores às dimensões aparentes do disco que é observado nas imagens feitas na faixa óptica. A linha do [Fe II] λ12567 também apresenta uma componente associada ao disco equatorial. Regiões de baixa densidade localizadas no toro que envolve a fonte central permitem que a radiação ultravioleta escape e excite o gás contido no disco equatorial. O melhor exemplo desse efeito foi detectado pela tomografia Doppler da linha do He I λ10830, que revelou uma componente de emissão intrínseca que atinge distâncias superiores à borda aparente do lóbulo NW do Homúnculo, e que foi completamente mapeada pela primeira vez nesta dissertação. / The Homunculus nebula was mapped using the integral field technique and the results are presented in this dissertation. The observations were obtained in the J band in the range from 10620 Å to 12960 Å using the CIRPASS's IFU, which contains 499 hexagonal lenses. The spatial sampling is 0,25"/lens and the spectral resolution, set to R=3200. The [Fe II] λ12567 line allowed the identification of two structures in the NW lobe that had not been reported yet. Doppler tomography of this structures revealed a low density region placed in the NW lobe that is not seen in the optical images. Besides, the Little Homunculus was also detected both in the mapping of components of the [Fe II] λ12567 and in its velocity maps. In the Homunculus nebula, the polar regions (where the shock between the stellar bipolar wind and the internal wall of the lobes is stronger) are more opaque than the lobe walls. This can be verified by the decrease in the intensity of the [Fe II] λ12567 in the SE lobe and the enhancement of this line emission in the NW lobe. Emissions due to the equatorial disc were detected both in the H series (Paβ and Paγ) and the He I λ10830 as an intrinsic component up to distances greater than the aparent dimensions of the disc seen in the images taken in the optical range. The [Fe II] λ12567 also presents the component due to the equatorial emission. Low density regions in the torus involving the central source allow a beam of radiation to escape to large radii and thereby excite the gas contained in the equatorial disc. The best example of this effect was detected in the Doppler tomography of the He I λ10830 line, that revealed an intrinsic emission component which reaches distances larger than the aparent boundary of the NW lobe and was firstly mapped in this dissertation.