The struggle to achieve integration of public schools in Southampton County, Virginia, has been an ongoing process that has occurred through the years since the Brown v. Board of Education, 347 U.S. 483, 493, 74 S.Ct. 686, 691 (1954) and Brown v. Board of Education, 349 U.S. 294, 75 S.Ciit. 753 (1955), and Green v. County School Board of New Kent County, Virginia, 391 U.S. 430, 88 S.Ct. 1689, 20 L.Ed.2d 716 (1968). The time frame of 1954 until 1970 is particularly significant because of happenings that took place prior to the time that Judge Robert R. Merhige, federal judge of the Fourth Circuit Court of Appeals, ruled that all school divisions which operated dual school systems for Black and White students must fully integrate. Through the use of acceptable methods of historical research including personal interviews to record the oral history, school board minutes, personal correspondence, newspaper articles, books, and other such materials available to the writer, this dissertation records information regarding the desegregation of Southampton County Schools. The purpose of this study is to examine the roles of individuals and groups in the desegregation process that took place in the public schools of this rural, southside Virginia county during the years of 1954 to 1969. This study will provide a greater understanding of leadership, local governance, racial, and social class concerns of Southampton County citizens, as well as, a documentation of an important part of the history of Southampton County, Virginia. / Ed. D.

L’évolution des communications sans fil doit répondre à la croissance exponentielle de la consommation de données. On prévoit une augmentation du débit allant jusqu’à 1000 d’ici 2020. Cependant, pour atteindre ce but, plusieurs ingrédients sont essentiels. La limitation majeure des systèmes sans fil est l’interférence à cause de la réutilisation des fréquences. C'est un problème qui existait depuis toujours et notamment à partir de la 3G. On croit que ce problème sera notamment plus grave dans la 5G, et cela à cause de la densification prévue des réseaux. L’utilisation de l’OFDM en 4G a mené à la gestion de l’interférence par coordination dynamique des blocs de ressources. Or, cela n’a permis qu’une augmentation modeste du débit. Une nouvelle technique de gestion de l’interférence fut née il y a 5 années. Cette technique s’appelle l’alignement d’interférence (IA). L’IA permet d’avoir une capacité égale à la moitié de la capacité d’un système sans interférences. Cette technique suppose que chaque transmetteur (TX) connait les canaux non seulement envers les récepteurs (RX)s mais les canaux de tous les TXs vers tous les RXs. Une technique d’interférence plus récente qui améliore l’IA, c’est le massive MIMO, ou les TXs sont équipés d’antennes à grande échelle. l’idée est motivée par plusieurs simplifications qui apparaissent en régime asymptotique ou les stations de base ont un trés grand nombre d’antennes. Le but de cette thèse est d’introduire des solutions complètes et réalistes pour la gestion d’interférence en utilisant le massive MIMO dans un scénario multi-cellules multi-utilisateurs. Notre travail traite surtout le problème de la connaissance imparfaite des canaux. / The evolution of wireless communication must meet the increasingly high demand in mobile data. It is expected to increase the maximum rates of wireless by a factor of 1000 by 2020. Meanwhile, it is clear that to reach this goal, a combination of different ingredients is necessary. The major limitation of wireless systems is the interference due to frequency reuse. This has been a long-standing impairment in cellular networks of all generations that will be further exacerbated in 5G networks, due to the expected dense cell deployment. The use of orthogonal frequency-division multiplexing (OFDM) in 4G leaded to an interference management by dynamic coordination of resource blocks. However, this allowed only modest gains in rates. A new technique of interference management was born 5 years ago, the interference alignment (IA). the IA permits to have a capacity with equals the half of the capacity of an interference-free system. This technique supposes that each transmitter (TX) knows the channels not only towards its receivers (RX)s, but the channels from all TXs to all receivers RXs. A more recent interference technique that boosts IA is massive multiple input multiple output (MIMO), where TXs use antennas at a very large scale. The idea is motivated by many simplifications, which appear in an asymptotic regime where base stations are endowed with large numbers of antennas. This thesis treats the problem of interference cancellation and capacity maximization in massive MIMO. In this context, the thesis proposes new interference management alternatives for the massive MIMO antenna regime, taking into account also the practical challenges of massive antenna arrays.

The aim of this study was to assess the durability of commercially available coatings on cross- laminated timber (CLT) during natural and artificial weathering and against wood decay fungus. The CLT samples coated with twelve coatings were tested based on their moisture exclusion, water repellency, volumetric swelling and anti-swelling efficiency. Among all the tested coatings, only five (A, C, F, I and J) were able to promote water repellency and limiting dimensional changes. The top five coatings were then tested on CLT blocks exposed to natural (Starkville-MS and Madison-WI) and artificial weathering conditions and brown-rot fungi (G. trabeum). Variables such as visual ratings, water uptake, color and gloss change were determined during both weathering procedures. Damage caused by Gloeophyllum trabeum on uncoated and coated CLT was analyzed based on visual appearance and weight loss. For the coatings C and F, the visual rakings and color change results indicated high consistency during outdoor exposure. The artificial weathering showed that coating C and F were the most resistant to chalking, lightness, color and gloss change. In the soil block test, coating C obtained satisfactory performance against G. trabeum with weight loss of 1.33%. Coatings F and J did not offer any protection to water penetration, which eventually contributed to fungal development. For future, new coatings specifically designed for the protection of high percentages of end-grain in CLT panels should be a target of research and development.

This thesis focuses a noncoherent two-user uplink system with each user having a single antenna and a base station equipped with a large number of antennas. It is assumed that small scale channel fading is Rayleigh fading and varies in every one time slot. For such massive MIMO uplink system, we consider an optimal finite-alphabet non-orthogonal multiple access (NOMA) design with each user utilizing nonnegative binary modulation. A fast noncoherent maximum likelihood (ML) detection algorithm for the sum constellation of the two users and a corresponding closed form symbol error probability (SEP) formula are derived. In addition, the lower and upper bounds on SEP are established to quantitatively characterize how quickly SEP decays when the number of base station antennas goes to infinity. Two important concepts: full receiver diversity and geometrical coding gain, are introduced. Particularly for two users and three users systems, with each user transmitting nonnegative binary constellation, we obtain an optimal closed form sum constellation that maximizes both the receiver diversity gain and geometrical coding gain. Computer simulations validateour theoretical analysis and demonstrate that our proposed optimal constellation attains significant performance gains over the currently available constellation design for the same massive MIMO upink system.\ Our future work is to develop an algorithm for devising an optimal AUDCG for the considered system in a more general case. / Thesis / Master of Applied Science (MASc)

No description available.

No description available.

This thesis aims to improve our understanding of the early stages of massive star formation and of the physical properties of interstellar clouds. To achieve this, I have used submillimeter continuum dust emission data obtained by the Balloon-borne Large Aperture submillimeter Telescope (BLAST) in the first science flight in 2005, with a 2-m telescope operating simultaneously at 250, 350, and 500 micron. Unfortunately, BLAST produced images of about 3'3 resolution due to an uncharacterized optical problem. In Chapter~2, I discuss implementation of the Lucy-Richardson (L-R) method of deconvolution to restore BLAST images to near diffraction limited resolution. Its performance and convergence have been extensively analyzed through simulations and comparison of deconvolved images with available high-resolution maps. In Chapter~3, I study diverse phenomena in the Cygnus~X region associated with high mass star-formation. To interpret the BLAST emission more fully and place the compact sources in context, archival data cubes of 13CO line emission from KOSMA, MIPS images from the Spitzer Legacy Survey of this region, and 21-cm radio continuum emission from the Canadian Galactic Plane Survey have been used. Utilizing available ancillary multi-wavelength observations, the influence of OB stars and stellar clusters on Cygnus~X has been studied,revisiting the well-known DR HII regions and their surroundings in the light of submillimeter continuum dust emission and CO line emission. An effort has been made to assess the evolutionary sequence of the compact sources (spatial extent of about 1~pc) on the basis of L-M diagram and subsequently to relate this sequence to independent empirical evidence and theory. Using multi-resolution observations, evidence for hierarchical substructures within molecular clouds has been examined. Finally, in Chapter~4, a multi-wavelength power spectrum analysis of the large scale brightness fluctuations in the Galactic plane is presented. This analysis has been used to assess the level of cirrus noise which limits the detection of faint sources. A characteristic power law exponent of about -2.7 has been obtained for sub-regions of Aquila and Cygnus~X. The observed relative amplitudes of power spectra at different wavelengths have been related through a spectral energy distribution, thereby determining a characteristic temperature for the Galactic diffuse emission.

This thesis aims to improve our understanding of the early stages of massive star formation and of the physical properties of interstellar clouds. To achieve this, I have used submillimeter continuum dust emission data obtained by the Balloon-borne Large Aperture submillimeter Telescope (BLAST) in the first science flight in 2005, with a 2-m telescope operating simultaneously at 250, 350, and 500 micron. Unfortunately, BLAST produced images of about 3'3 resolution due to an uncharacterized optical problem. In Chapter~2, I discuss implementation of the Lucy-Richardson (L-R) method of deconvolution to restore BLAST images to near diffraction limited resolution. Its performance and convergence have been extensively analyzed through simulations and comparison of deconvolved images with available high-resolution maps. In Chapter~3, I study diverse phenomena in the Cygnus~X region associated with high mass star-formation. To interpret the BLAST emission more fully and place the compact sources in context, archival data cubes of 13CO line emission from KOSMA, MIPS images from the Spitzer Legacy Survey of this region, and 21-cm radio continuum emission from the Canadian Galactic Plane Survey have been used. Utilizing available ancillary multi-wavelength observations, the influence of OB stars and stellar clusters on Cygnus~X has been studied,revisiting the well-known DR HII regions and their surroundings in the light of submillimeter continuum dust emission and CO line emission. An effort has been made to assess the evolutionary sequence of the compact sources (spatial extent of about 1~pc) on the basis of L-M diagram and subsequently to relate this sequence to independent empirical evidence and theory. Using multi-resolution observations, evidence for hierarchical substructures within molecular clouds has been examined. Finally, in Chapter~4, a multi-wavelength power spectrum analysis of the large scale brightness fluctuations in the Galactic plane is presented. This analysis has been used to assess the level of cirrus noise which limits the detection of faint sources. A characteristic power law exponent of about -2.7 has been obtained for sub-regions of Aquila and Cygnus~X. The observed relative amplitudes of power spectra at different wavelengths have been related through a spectral energy distribution, thereby determining a characteristic temperature for the Galactic diffuse emission.

The detailed observational analysis of three massive B- and O-type stars was carried out in this study in order to characterize their fundamental, magnetic, and variability properties. The bulk of the data acquired were obtained with the high-resolution ESPaDOnS spectropolarimeter at the Canada-France-Hawaii telescope, within the context of the Magnetism in Massive Stars (MiMeS) project. Two of these stars (HR5907 and HD57682) are newly detected magnetic stars, discovered from observations acquired as part of the broader survey component of the MiMeS program, while the last star, ω Ori, was previously reported as magnetic in the literature. The rotation periods of HR5907 and HD57682 were inferred from photometric, Hα emission and longitudinal field variations. A period of 0.508276 was inferred for HR5907, making this the shortest period, non-degenerate, magnetic massive star identified to date. Furthermore, ultraviolet and optical spectroscopy were combined to infer the fundamental properties of HR5907 and HD57682. Direct modelling of the Least-Squares Deconvolved line profiles and the longitudinal magnetic field measurements were used to infer the magnetic properties of HR5907, HD57682, and ω Ori. A detailed investigation of the newly obtained and archival polarimetric data of ω Ori revealed no convincing evidence for a magnetic field, despite evidence of variability in some emission quantities in this dataset, which had been previously attributed to a large-scale magnetic field. The strength and variability of the optical photospheric helium lines of HR5907 suggests that this star is He-rich, with a non-uniform distribution of its surface chemistry. Lastly, the emission variations in the hydrogen lines of HR5907 suggest this star hosts a highly-structured, rigidly-rotating, centrifugally supported magnetosphere. Similarly, line profile variations throughout the optical spectrum of HD57682 are attributed to emission variations caused by a rotationally-modulated, dynamical magnetosphere. As magnetism in massive stars is a relatively rare and poorly-studied phenomenon, these studies comprise the bulk of the detailed investigations of magnetic massive stars carried out to date. The results of these investigations are also discussed in the context of addressing the current outstanding issues related to magnetism in massive stars. / Thesis (Ph.D, Physics, Engineering Physics and Astronomy) -- Queen's University, 2012-09-28 17:22:35.115

L'affinement des grains et la réduction de la texture dans les alliages TiAl brut de coulée sont très importants pour améliorer les propriétés structurales rendre les alliages industriellement utilisables et offrir la possibilité de remplacer les superalliage à base Ni dans de nombreuse applications industrielles. Les traitements thermomécaniques ne sont pas toujours le meilleur moyen pour affiner la taille des grains, ils entrainent un coût de production élevé et une difficulté de mise en œuvre. Les traitements thermiques menant à la transformation de phase massive peuvent être un moyen d'affinement des grains mais ils nécessitent une compréhension complète des mécanismes de la transformation massive, l'évolution de la microstructure ainsi que de son rôle dans la réduction de la texture par traitements thermiques. Lors de cette thèse, des grains [gamma]-massif ont été obtenus par refroidissement rapide des alliages TiAl depuis la phase [alpha] haute température (1365°C). Différentes fractions volumiques de grains [gamma]-massif peuvent être obtenues en fonction de la composition des alliages et de la vitesse de refroidissement. Pour atteindre les différents objectifs, des échantillons avec différentes fractions volumiques de grains [gamma]-massif ont été choisis et étudiés. Après l'étude des mécanismes de transformation massive, d'autres traitements thermiques ont été appliqués à la structure massive pour étudier son évolution microstructurale et texturale. Des caractérisations morphologiques et cristallographiques ont été effectuées à l'aide de différents instruments (DSC, DRX, MEB, MET) pour comprendre les mécanismes de développement d'évolution des structures massives / Grain refinement and texture reduction in as-cast TiAl alloys are very important in order to improve their structural properties, and make them industrially viable, and offer a possible replacemen to Ni-based super alloys in many industrial applications. Thermo-mechanical route is not always preferred for grain refinement due to the high production cost and low treatability. Thermal treatment through massive phase tansformation could be a possible grain refinement route but it requires full understanding of the mechanisms of massive transformation, and of the evolution of microstructure and texture through subsequent heat treatments. In the Ph.D. research work, [gamma]-massive grains were obtained by rapid quenching of TiAl alloys from the high temperature single phase [alpha] field at 1365°C. Depending on the alloy composition and cooling rate, different volume fractions of [gamma]-massive grains were obtained. In order to address different objectives, samples with different volume fractions of the [gamma] grains were chosen and studied. After studying the mechanisns of massive transformation ( nucleation and growth), subsequent heat treatments were performed on the microstructures to study their microstructural and texture evolution. To understand the mechanisms development and evolution of these massive structures, morphological and crystallographic characterization were performed using different instruments, (DSc) and microscopy techniques (X-ray, electron microscopy)