abstract: This thesis mainly focuses on the study of quantum efficiency (QE) and its measurement, especially for nanowires (NWs). First, a brief introduction of nano-technology and nanowire is given to describe my initial research interest. Next various fundamental kinds of recombination mechanisms are described; both for radiative and non-radiative processes. This is an introduction for defining the internal quantum efficiency (IQE). A relative IQE measurement method is shown following that. Then it comes to the major part of the thesis discussing a procedure of quantum efficiency measurement using photoluminescence (PL) method and an integrating sphere, which has not been much applied to nanowires (NWs). In fact this is a convenient and useful approach for evaluating the quality of NWs since it considers not only the PL emission but also the absorption of NWs. The process is well illustrated and performed with both wavelength-dependent and power-dependent measurements. The measured PLQE is in the range of 0.3% ~ 5.4%. During the measurement, a phenomenon called photodegradation is observed and examined by a set of power-dependence measurements. This effect can be a factor for underestimating the PLQE and a procedure is introduced during the sample preparation process which managed to reduce this effect for some degree. / Dissertation/Thesis / M.S. Electrical Engineering 2012

110f. / Submitted by Suelen Reis (suziy.ellen@gmail.com) on 2013-04-16T16:21:13Z No. of bitstreams: 1 Dissertacao Ilca Menezesseg.pdf: 651126 bytes, checksum: 7317e68c70bdedb293ee0c1dd982092d (MD5) / Approved for entry into archive by Rodrigo Meirelles(rodrigomei@ufba.br) on 2013-05-11T15:20:56Z (GMT) No. of bitstreams: 1 Dissertacao Ilca Menezesseg.pdf: 651126 bytes, checksum: 7317e68c70bdedb293ee0c1dd982092d (MD5) / Made available in DSpace on 2013-05-11T15:20:56Z (GMT). No. of bitstreams: 1 Dissertacao Ilca Menezesseg.pdf: 651126 bytes, checksum: 7317e68c70bdedb293ee0c1dd982092d (MD5) Previous issue date: 2008 / A esfera pública é um tema polêmico. Desde sua origem na sociedade burguesa, o ideal de espaço discursivo e deliberativo, em que todos podem participar, fazendo uso de uma razão esclarecida, exercendo influência sobre o sistema político, é fundamental para a democracia. Mas há grupos excluídos, e a mídia de massa, que exerce influência sobre a opinião pública, com freqüência atende a interesses privados, provenientes de grupos, partidos políticos, e pessoas com poder econômico e de influência. Na sociedade contemporânea, essas questões críticas permanecem e a democracia precisa de seus fundamentos básicos. Em vista disso, Habermas pretende reabilitar o conceito de esfera pública, na complexa sociedade. Ele nunca abandona a questão do caráter normativo da comunicação pública esclarecida em relação à integração social e ao controle das ações políticas. As teorias da ação comunicativa e da ética do discurso, em Habermas, valorizam a racionalidade comunicativa, inerente à esfera pública. Essa racionalidade tem potencial normativo para a auto-regulação dos sujeitos e também para a manutenção da ordem social, porque as leis são fundamentadas através do discurso argumentativo. Habermas teoriza sobre a relação entre a normatividade da comunicação intersubjetiva e o sistema de direitos, do Estado democrático, que exerce controle sobre a sociedade civil e o Estado. A política democrática deliberativa surge dessa relação, e configura, na sociedade contemporânea, o ideal de esfera pública. / Salvador

This study aims to gain a fundamental understanding of the physics of triboelectri- cal charging of solid particles and the separation of the charged particles under an exter- nal DC electric field by computer simulations. A condenser model is used to implement charging mechanism and a soft sphere model is used to account for the Hertzian contact mechanics. The governing nondimensional parameters of the problem are identified and a parametric study is performed to investigate their effects on the charging efficiency and separation. The study finds relevance in a host of technologically important processes, such as recycling of plastic wastes, seed cleaning in agricultural industry and separation of coal from impurities in mining.

Reader comment forums of online newspapers, a relatively new feature of online journalism, have been called spaces of public deliberation. At their inception among large newspapers just five years ago, the forums were heralded as a new way for the public to advance public dialogue by sharing opinions in an unconstrained way, promoting the democratic principles of the newspaper institution itself. Rampant incivility, however, has since become one the forums' chief defining characteristics. By content analyzing comments from online newspapers that allow anonymity, this research confirms anecdotal evidence from journalists that Latinos are regularly debased in the forums by commenters following news on immigration. This study also compares the civility of anonymous comments following news on the Tea Party movement, a non-racialized but also controversial topic. Finally, civility is measured in the comments following news on immigration from online newspapers that have disallowed anonymity. In all, more than 22,000 comments from nearly 200 news stories in more than a dozen online newspapers were collected between 2010 and 2012, and a sample of 1,350 was coded. The analysis shows that online newspaper discussion boards that allow anonymity and that follow news about immigration predominantly contain comments by those who support tough immigration laws and who express themselves with emotionally laden, uncivil comments directed at Latinos. Similar discussion boards that disallow anonymity predominantly contain comments by those who support tough immigration laws and who express themselves with emotionally laden yet civil comments directed at Latinos. Overall, this research demonstrates that a racialized topic is apt to draw more uncivil anonymous comments than a non-racialized one and that removing anonymity elevates the level of dialogue. Building on the theories of the public sphere, reduced cues in anonymity and critical race theory, this paper demonstrates that in their new role in creating a new public square of open discussion, newspapers are sometimes creating forums for hate speech while also publishing content that is perpetuating negative portrayals of Latinos. Findings reveal that a new public sphere created by online newspapers, meant to promote democracy, is actually having the opposite effect for some minority groups.

abstract: This dissertation discusses how Twitter may function not only as a tool for planning public protest, but also as a discursive site, albeit a virtual one, for staging protest itself. Much debate exists on the value and extent that Twitter (and other social media or social networking sites) can contribute to successful activism for social justice. Previously, scholars' assessments of online activism have tended to turn on a simple binary: either the activity enjoyed complete success for a social movement (for instance, during the Arab Spring an overthrow of a regime) or else the campaign was designated as a failure. In my dissertation, I examine a Twitter public-relations campaign organized by the New York Police Department using the hashtag #MyNYPD. The campaign asked citizens to tweet pictures of themselves with police officers, and the public did, just not in the way the police department envisioned. Instead of positive photos with the police, the public organized online to share pictures of police brutality and harassment. I collected six months of tweets using #MyNYPD, and then analyzed protestors' rhetorical work through three lenses: rhetorical analysis, analysis of literacy practices, and social network analysis. These analyses show, first, the complex rhetorical work required to appropriate the police department's public-service campaign for purposes that subverted its original intent; second, the wide range of literacy practices required to mobilize and to sustain public attention on data exposing police abuse; and third, the networked activity constituting the protest online. Together, these analyses show the important work achieved within this social justice campaign beyond the binary definition of successful activism. This project shows that by increasing our analytical repertoires for studying digital rhetoric and writing, scholars can more accurately acknowledge what it takes for participants to share experiential knowledge, to construct new knowledge, and to mobilize connections when engaging online in public protest. / Dissertation/Thesis / Doctoral Dissertation English 2016

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Neste trabalho estudaremos o Ãndice de hipersuperfÃcies mÃnimas e de curvatura mÃdia constante imersas na esfera Euclidiana Sn+1. Mais precisamente, definiremos o operador de Jacobi de hipersuperfÃcies mÃnimas e de curvatura mÃdia constante usando as fÃrmulas de variaÃÃo de Ãrea, e em seguida estabeleceremos estimativas por baixo para o Ãndice de hipersuperfÃcies mÃnimas imersas em Sn+1 . AlÃm disso, caracterizaremos os toros de Clifford mÃnimos como as hipersuperfÃcies compactas, orientÃveis e mÃnimas em Sn+1 tais que a = -2n, onde a à o primeiro autovalor do operador de Jacobi. Mostraremos que as esferas totalmente umbÃlicas Sn (r) em Sn+1, com 0 < r < 1, sÃo as hipersuperfÃcies fracamente estÃveis em Sn+1. Por Ãltimo, estabeleceremos estimativas por baixo para o Ãndice fraco de hipersuperfÃcies de curvatura mÃdia constante em Sn+1 e caracterizaremos os toros de Clifford Sk (r) x Sn-k (1 - r2) de curvatura mÃdia constante como as hipersuperfÃcies de curvatura mÃdia constante tais que o Ãndice fraco à igual a n + 2, onde (k/n + 2 ) &#8804; r &#8804; (k + 2/n + 2) Â. / The aim of this work is to study the index either of compact minimal or constant mean curvature hypersurfaces immersed into the Euclidean unit sphere Sn+1. The main ingredient to do that is the Jacobi operator which appears on the second formula of variation of area. On the minimal case we shall present low estimative for the index and we shall show that the minimal Clifford tori are the unique minimal hypersurfaces over which a = -2n , where a stands for the first eigenvalue of the Jacobi operator. Moreover, it is easy to see that totally umbilical sphere Sn (r) em Sn+1 , with 0 < r < 1, are weakly stable. Finally we shall show that the index is bigger that or equal to n+2 for compact constant mean curvature hypersurfaces of Sn+1 provides they have constant scalar curvature. Moreover , Clifford tori Sk (r) x Sn-k (1 - r2) attain such index provided (k/n + 2 ) &#8804; r &#8804; (k + 2/n + 2) Â.

Neste trabalho estudaremos subconjuntos especiais da esfera unitária Sm-1 de Rm, m 2, comumente chamados na literatura de designs esféricos. Os objetivos principais são analisar várias equivalências para o conceito, suas conexões com ambos, rotações sobre Sm?1 e mergulhos em esferas de dimensão superior, e resultados sobre a cardinalidade dos designs esféricos / In this work we will study specials subsets of the unitary sphere Sm-1 of Rm, m 2, usually called in literature spherical designs. The main objectives are to analyze many equivalences for the concept, its connections with both, rotations on Sm?1 and embedded in spheres of higher dimension, and results on the cardinality of spherical designs

The thesis reports the results of the research carried out towards the development of an electrooptic sensor for DC and extra low frequency electric field measurement. Available cubic electrooptic crystals were compared from the sensor sensitivity point of view. A new figure of merit was used taking into account the attenuation of the electric field in the dielectric crystal and its shape. The effect of optical activity in 23 cubic crystals was analyzed using the concept of Poincare sphere. The cubic crystals were further characterised for the charge relaxation time constant to estimate their performance in DC field measurements. Crystals of Bismuth Germanate and Lithium Niobate were identified as suitable materials for the DC field sensor. The selected crystals were found suitable at extra-low-frequencies. DC field measurements, without the rotation of the crystal, were possible only with Lithium Niobate. However, its performance was influenced to a great extent by the effect of stimulated conductivity. The quarter-wave plate and the crystal of Lithium Niobate were identified as the main sources of temperature instability. A new method of temperature compensation of the quarter-wave plate is proposed. Due to the temperature instability of Lithium Niobate, mainly attributed to the pyroelectric effect and natural birefringence, it is difficult to use the sensor in practical applications. The performance of the sensor is significantly affected by the presence of an external space charge. The proposed method of its elimination using an artificial extension of the sensing element did not reduce the space charge effect adequately. The response of the sensor in a space charge environment was found to be linear and independent of the space charge density. This enabled measurements of static fields in a unipolar environment. The direct field measurements in bipolar environment suffered from a drift which is intolerable in practical measurements. The minimum detectable electric field of this sensor in the frequency range from 1 to 200Hz was 1V/m, with a signal to noise ratio equal to 0dB and a resolution of 1V/m. The static field measurements were limited to measurements of pulses with a duration of 200s, due to a long term drift of photodetectors. The minimum detectable level of DC electric field was 2.4kV/m.

My dissertation focuses on nineteenth-century American literature texts that engage with ruins and monuments. Traditionally, this interaction has been treated as a formal curiosity for literary critics, but this project argues interarts literature carries important implications for public sphere theory, especially in cases when an author writes about nationalist architecture and iconography.

Jürgen Habermas’ The Structural Transformation of the Public Sphere has been described as outdated and incompatible with 21st century democracies. Among other things, Habermas’ initial formulation excluded the state from the public sphere. Recently, a revised model of the public sphere has emerged that positions the state and other law-making bodies at its centre. Although some theorists have embraced this revised model, others continue to exclude the state or oversimplify its role. While some research has examined how parliaments fit into this revised model, no research has been published on this in a Canadian context. This thesis attempts to fill this gap by answering the research question: Does the Canadian House of Commons constitute a form of the public sphere? To answer this question, the Canadian House of Commons is explored along three dimensions of the public sphere – structure, representation, and interaction. This system of classification conforms to the essential function and institutional criteria of classical theory and also accounts for revised models of the public sphere. Ultimately, this work argues that the Canadian House of Commons satisfies the structural and representational dimensions of the public sphere. Its interactional dimension, however, is found to be inconsistent with public sphere theory due to a lack of real deliberation and the pervasiveness of party politics.