Performance of self bit synchronization systems

Optimum estimator for random signal sequence derived by digital computer and evaluated by Monte Carlo metho

(110) Facet of MgTe Zinc Blende Semiconductor: A Holy Grail for Modern Spintronics

In this work, we propose mono/few layers of MgTe (110) facets of zinc-blende structure for a unique next-generation ferromagnet-free nonballistic spin-field effect transistor. The atomic arrangement in this facet exhibits a unique combination of three basic symmetries found in nature: rotation, reflection, and translation. The electronic properties based on the density functional theory (DFT) reveal momentum-independent unidirectional spin polarization known as persistent spin texture (PST) that leads to an infinite spin lifetime in this particular facet. PST in these 2D structures originating from crystal symmetry makes them an ideal alternative to quantum well structures. Although the proposed Datta-Das s-FET is applicable to nonballistic s-FET, there has been little technological progress in this rapidly growing field of research and only a trivial amount of 2D semiconductors have been identified that exhibit PST intrinsically. In this regard, this particular facet studied in this work will be a great asset. A detailed theoretical insight into the origin of PST and its application in a ferromagnet-free s-FET has been proposed combining both the spin-Hall effect and inverse spin-Hall effects, harmonizing spintronics with conventional electronics

Robust drivers of urban land surface temperature dynamics across diverse landscape characters: An augmented systematic literature review

To effectively develop strategies that address the escalating surface temperatures of cities in diverse landscape characters, various and sometimes contradicting drivers are presented in the literature. A synthesis of findings and observations in this aspect is lacking. Therefore, the main tenet of our study was to identify robust landscape metrics (LMs) that drive the dynamics of urban land surface temperature (ULST) and analyse the extent to which landscape character influences their impact. We adopted a systematic literature review protocol, augmented with different geospatial datasets (at a global scale) and applied mixed approaches for our review and analyses. A total of 101 relevant articles were identified, although skewed towards Asia; various methods were utilised in analysing the LMs – ULST relationship; about 432 unique LMs were revealed with only 11 % of these confirmed to be robust. Landscape character elements are found to exert a slight to moderate significant influence on the LMs − ULST relationship reported in the literature. This further strengthened our proposition of the need to consider landscape character elements in understanding the dynamics of ULST in different environments. To this end, we developed an interactive scheme to synthesize our findings which reveal robust LMs in diverse landscape characters. Our FAIRly-open study serves as a call to the scientific community and urban stakeholders to engage and interact with our findings as this may help rethink (current) ULST mitigation strategies. Also, combining our scheme with expert and local spatial knowledge of stakeholders can offer a practical foundation for addressing ULSTs across diverse landscapes

Celebration of Learning 2016: Full Program

Full program of the 2016 Celebration of Learning at Augustana College

Post-merger Mass Ejection of Low-mass Binary Neutron Stars

We study the post-merger mass ejection of low-mass binary neutron stars (NSs) with the system mass of $2.5\, M_\odot$, and subsequent nucleosynthesis by performing general-relativistic, neutrino-radiation viscous-hydrodynamics simulations in axial symmetry. We find that the merger remnants are long-lived massive NSs surviving more than several seconds, irrespective of the nuclear equations of state (EOSs) adopted. The ejecta masses of our fiducial models are $\sim 0.06$-$0.1\, M_\odot$ (depending on the EOS), being $\sim 30\%$ of the initial disk masses ($\sim 0.15$-$0.3\, M_\odot$). Post-processing nucleosynthesis calculations indicate that the ejecta is composed mainly of light $r$-process nuclei with small amounts of lanthanides (mass fraction $\sim 0.002$-$0.004$) and heavier species due to the modest average electron fraction ($\sim 0.32$-$0.34$) for a reasonable value of the viscous coefficient. Such abundance distributions are incompatible with the solar $r$-process-like abundance patterns found in all measured $r$-process-enhanced metal-poor stars. Therefore, low-mass binary NS mergers should be rare. If such low-mass NS mergers occur, their electromagnetic counterparts, kilonovae, will be characterized by an early bright blue emission because of the large ejecta mass as well as the small lanthanide fraction. We also show, however, that if the effective turbulent viscosity is very high, or there is an efficient mass ejection working in the early post-merger phase, the electron fraction of the ejecta could be low enough that the solar $r$-process-like abundance pattern is reproduced and the lanthanide fraction becomes so high that the kilonova would be characterized by early bright blue and late bright red emissions.Comment: 35 pages, 20 figures, 4 tables. Submitted to Ap

Aircraft and spacecraft observations of high-energy radiation associated with lightning leaders

Denne avhandlingen undersøker røntgen og gammastråling assosiert med lyn ledere, observert av instrumenter på fly og fra verdensrommet. Avhandlingen består av tre forskningsartikler, publisert i Journal of Geophysical Research: Atmospheres. I den første delen blir data av lyn initiert av fly, fra tre fly kampanjer brukt sammen med tre forskjellige modeller. Fra analyse av de initierte lynene blir begrensninger på såkalte recoil leaders bestemt. Ved å bruke data fra flere forskjellige instrumenter i verdensrommet, kombinert med radio atmospherics målt fra bakken, og optisk data fra Atmosphere-Space Interactions Monitor (ASIM) finner vi at Terrestrial Gamma-ray Flashes (TGFs) blir produsert i starten av lynet. En økning av radio atmospherics er også observert noen hundre millisekund etter TGFene. Høy energi og optisk data fra ASIM ble også brukt til å identifisere en gruppe med TGFer som var assosiert med optiske signaler. Fra en analyse av disse hendelsene bestemmes sekvensen av TGF og optisk lys. Det ble også funnet at TGFer med lengre varighet har lengre tid mellom starten av TGFene og det optiske lyset.This thesis investigates high-energy radiation associated with lightning leaders, observed by aircraft and space-borne instruments. The thesis consists of three papers published in the Journal of Geophysical Research: Atmospheres. In the first part, data of aircraft-triggered lightning from three flight campaigns were used together with three different models. From an analysis of the events, constraints to the properties of so-called recoil leaders were determined. Using data from several different space-borne instruments combined with ground-detected radio atmospherics and optical data from the Atmosphere-Space Interactions Monitor (ASIM) it is determined that Terrestrial Gamma-ray flashes (TGFs) are produced at the beginning of the lightning flash. An increase in detected radio atmospherics is also observed a few hundred milliseconds after the TGFs. High-energy and optical data from ASIM was used to identify a sample of TGFs found to be associated with observed optical pulses. From an analysis of these events, the sequence of TGF-optical light was determined. A tendency for long-duration TGFs to have longer delays between onset of TGF and optical light was also determined.Doktorgradsavhandlin

Relativistic theory of nuclear structure effects in heavy atomic systems

In this thesis, several aspects of nuclear structure effects and corrections from quantum electrodynamics (QED) in the spectra of hydrogen-like systems are investigated. The first part is concerned with the structure of bound states between a muon and an atomic nucleus, so-called muonic atoms. Here, precise calculations for transition energies and probabilities are presented, using state-of-the-art numerical methods. QED corrections, hyperfine interactions, and the interaction with atomic electrons were evaluated and finite nuclear size effects were incorporated non-perturbatively. Furthermore, new methods for the calculation of higher-order corrections for the hyperfine structure are presented, including a complete calculation of the second-order hyperfine structure and leading-order vacuum polarization corrections for extended electric quadrupole distributions inside the nucleus. In connection with recent x-ray spectroscopic measurements on muonic atoms, the nuclear quadrupole moment of Re-185 and Re-187 is extracted. The second part of this thesis is about the g factor of a bound electron and its dependence on the shape of the nuclear charge distribution. A numerical, non-perturbative approach for the calculation of the corresponding nuclear shape correction is presented and implications for the uncertainties of theoretical predictions are discussed. In particular, the model-uncertainty of the finite-nuclear-size correction to the g factor can be reduced due to the more realistic model of the nuclear charge distribution. Finally, calculations of finite-size and vacuum-polarization corrections to the g factor of a muon bound to a He-4 nucleus significantly contribute to the theoretical prediction on the 10^−9 uncertainty level. As shown in an earlier work, an experimental value of the same accuracy could give access to an improved value of the muon’s mass or magnetic moment anomaly

Estudio de la dinámica del flujo gas sólido en enfriadores de catalizador de FCC usando fluidodinámica computacional (CFD)

El craqueo catalítico fluido (FCC) es un proceso importante en la industria petrolera, ya que convierte las fracciones más pesadas en las más livianas, que son más valiosas. Las partículas de catalizador (típicamente m) se desactivan durante el proceso de reacción y necesitan regenerarse antes de regresar al reactor. La temperatura es un factor clave que promueve la formación y desactivación de coque dentro del reactor. Como consecuencia, es necesario enfriar las partículas sólidas del catalizador antes de devolverlas al reactor. El sistema de enfriamiento generalmente está fuera del regenerador en un intercambiador de calor diseñado específicamente, que usa agua como fluido frío. El enfriador de catalizador no se estudió mucho antes y se pueden hacer muchas contribuciones para mejoras e intensificación. El objetivo de este trabajo fue contribuir con este tema, utilizando la dinámica de fluidos computacional (CFD) para evaluar el comportamiento del flujo de gas sólido en las geometrías características del enfriador de catalizador. Se usó el paquete comercial Fluent de ANSYS v14.5 durante la simulación y se aplicó el modelo Eulerian para la fase sólida. Se evaluó y describió la fase de fracción de volumen para las velocidades de fase sólida, sólida y gaseosa. Los resultados se compararon en términos de flujo de sólidos gaseosos en diferentes geometrías y mostraron una explicación hidrodinámica diferente de la utilizada actualmente por los autores para justificar la intensificación del intercambio térmico en este tipo de equipos. En resumen, un mayor tiempo de contacto con la pared sólida será el principal responsable de la transferencia de calor eficiente.O craqueamento catalítico fluidizado é um processo amplamente utilizado no campo do refino de petróleo. Na unidade de craqueamento, frações pesadas são transformadas em outras mais leves e com maior valor de mercado (gasolina, diesel, naftas). Após o craqueamento, o catalisador é regenerado e retorna ao reator. A temperatura do catalisador é um parâmetro que possui forte influência sobre o processo. O resfriamento de catalisador é feito em unidades externas a fim de controlar a temperatura de entrada do catalisador no reator. O funcionamento deste sistema ainda foi pouco explorado e o objetivo deste trabalho foi o de simular o escoamento gás-sólido em geometrias características de colunas para resfriamento de catalisador com diferentes condições de operação, assim tentando contribuir com o conhecimento sobre este processo. Técnicas de Fluidodinâmica Computacional foram usadas para a simulação de diferentes geometrias com o programa comercial FLUENT do pacote ANSYS v14.5. As distribuições fração volumétrica dos sólidos e de velocidades do gás e fase particulada foram analisados como parâmetros de interesse hidrodinâmico. Os resultados foram comparados em termos de escoamento gás-sólido em diferentes geometrias e mostraram uma explicação hidrodinâmica diferente da atualmente utilizada pelos autores para justificar a intensificação de troca térmica em este tipo de equipamentos. Em suma, maior contato sólido-parede seria o principal responsável pela transferência eficiente de calor.Brasil. Beca PAEC OEA-GCUB 2014Trabajo de investigació

Motor imagery and music : the influence of music on mental rotation tasks in the light of the embodied cognition theory

The Embodied Cognition Theory (ECT) has become a hot topic in Cognitive Science, providing the investigation of cognitive phenomena with food for thought through a wide range of empirical findings. Two core claims from ECT were investigated in the present study: 1) the non-neural parts of an organism’s body play a constraining role in cognition; and 2) all concepts (strong embodiment) or some concepts (weak embodiment) are grounded in modality-specific areas of the brain. In line with 2), studies on mental imagery of bodily-related movements (henceforth: motor imagery) suggest that we use motor concepts grounded in modality-specific areas of the brain (the motor cortices) when we carry out motor simulations of our own body (Jeannerod, 2006), including in cognitive tasks such as MR of bodily-related pictures (Parsons et al., 1995). Also, studies in music perception have correlated the cortical activation of motor areas of the brain with rhythmic perception, varying in degree of activation according to the rhythmic complexity of a stimulus (Grahn & Brett, 2007). Finally, these assumptions predict the Mozart Effect, which consists of subjects’ temporary enhancement in performance at spatial-temporal reasoning tasks, including MR tasks (Rauscher, Shaw & Ky, 1993). Based on these assumptions, it was investigated whether subjects’ (N= 36) performance at a MR of bodily-related pictures would differ after exposure to musical pieces with different levels of rhythmic complexity and a control condition (silence). Results show that, although subjects’ performance was affected by the biomechanical constraints of their own bodies, suggesting that the body biomechanics play a constraining role in cognition, the Mozart Effect was not observed, suggesting that either 1) weak conceptual embodiment may not be true for motor imagery, and motor concepts are not grounded in modality-specific brain areas, 2) the musical samples used in the present study were not adequate to elicit sufficient cortical activation that would eventually result in performance enhancement, or 3) the Mozart Effect is due to reasons other than cortical activation of modality-specific brain areas, such as increase in arousal/mood levels or an artefact of subjects’ preference for a stimulus (Chabris, 1999). It is suggested that future research employs brain-mapping techniques, such as Positron Emission Tomography (PET Scan), Functional Magnetic Resonance Imaging (fMRI), or Electroencephalogram (EEG) to strengthen one or more hypotheses that account for the failure in observing the Mozart Effect in this study by identifying which brain areas were involved during the listening task and/or the MR of bodily-related pictures.A Teoria da Cognição Corporificada (ECT) tem se tornado um tópico amplamente discutido nas Ciências Cognitivas, uma vez que uma ampla gama de descobertas empíricas tem provocado reflexões a respeito da cognição. Duas fortes suposições da ECT foram investigadas no presente estudo: 1) as partes não neurais do corpo de um organismo possuem um forte papel de limitação sobre a sua cognição; e 2) todos os conceitos (corporificação forte) ou alguns conceitos (corporificação fraca) estão ancorados em regiões cerebrais de modalidade específica. Alinhado à 2), estudos em imaginação motora sugerem que nós utilizamos conceitos motores ancorados em regiões cerebrais de modalidade específica (córtices motores), para realizarmos a simulação de atos motores (Jeannerod, 2006), incluindo tarefas como rotação mental de imagens corporais (Parsons et al., 1995). Mais, estudos em percepção musical correlacionam a ativação de córtices motores com a percepção de estruturas rítmicas da música, variando em nível de ativação de acordo com o grau de complexidade rítmica do estímulo (Grahn & Brett, 2007). Essas assunções predizem o Efeito Mozart, que consiste na melhoria temporária no desempenho de sujeitos em tarefas de raciocínio espaço-temporal, incluindo tarefas de rotação mental (Rauscher, Shaw & Ky, 1993). Baseado nestas assunções, este estudo investigou se o desempenho de sujeitos (N = 36) em tarefas de rotação mental de imagens corporais teria alguma alteração após a escuta de peças musicais com diferentes níveis de complexidade rítmica e silêncio como condição controle. Os resultados demonstram que, apesar dos desempenhos dos sujeitos terem sido afetados pelas restrições biomecânicas dos seus corpos, sugerindo que a biomecânica corporal possui um papel limitador na cognição, o Efeito Mozart não foi observado, sugerindo que 1) a corporificação conceitual fraca pode não ser verdadeira para imaginação motora, e conceitos motores não estão ancorados em regiões cerebrais de modalidade-específica, 2) as amostras musicais utilizadas no presente estudo não foram adequadas para evocar ativação cortical o suficiente que resultasse em uma melhoria na performance na tarefa, ou 3) o Efeito Mozart se dá por razões distintas à ativação cortical de regiões cerebrais de modalidade-específica, como acréscimo em níveis de ativação e de humor ou por ser artefato da predileção por um estímulo (Chabris, 1999). É, por fim, sugerido que pesquisas futuras empreguem técnicas de mapeamento cerebral, como Tomografia por Emissão de Pósitrons (PET Scan), Ressonância Magnética Funcional (fMRI), ou Eletroencefalograma (EEG), fortalecendo uma ou mais hipóteses que visam explicar a falha ao observar-se o Efeito Mozart neste estudo, identificando quais áreas cerebrais foram ativadas durante a exposição aos estímulos e/ou durante a realização da tarefa de rotação mental