Robust Covariance Adaptation in Adaptive Importance Sampling

Importance sampling (IS) is a Monte Carlo methodology that allows for approximation of a target distribution using weighted samples generated from another proposal distribution. Adaptive importance sampling (AIS) implements an iterative version of IS which adapts the parameters of the proposal distribution in order to improve estimation of the target. While the adaptation of the location (mean) of the proposals has been largely studied, an important challenge of AIS relates to the difficulty of adapting the scale parameter (covariance matrix). In the case of weight degeneracy, adapting the covariance matrix using the empirical covariance results in a singular matrix, which leads to poor performance in subsequent iterations of the algorithm. In this paper, we propose a novel scheme which exploits recent advances in the IS literature to prevent the so-called weight degeneracy. The method efficiently adapts the covariance matrix of a population of proposal distributions and achieves a significant performance improvement in high-dimensional scenarios. We validate the new method through computer simulations

The Fourteenth Amendment's protection scope over sexual orientation: a comprehensive legal analysis

This thesis provides an in-depth legal analysis of the protection status granted to minority groups by the Supreme Court under the Fourteenth Amendment. It sets forth a thorough definition of what a suspect class is and an explanation of its requirements, with the final aim of analyzing sexual orientation within the boundaries of such definition. There are four main points to consider when identifying a suspect class: a history of purposeful discrimination, political powerlessness, an immutable and uncontrollable trait, and incorrect stereotypes. If all the indicia of suspectness are met then the group is considered a suspect class and if only some of the criteria are met then it is considered a Quasi-suspect class. This thesis will prove that sexual orientation is at least a Quasi suspect class by fulfilling most of the requirements in an above satisfactory fashion, although the argument could perfectly be made for full-suspectness status if the Court were to find them all sufficient. It also comprehensively compares U.S. court cases throughout, and finally presents a side-by-side review of U.S. Supreme Court’s decisions on gender and sexual orientation

Two Versions of the Antimaternal: The Change of the Conception of Motherhood and Female Sexuality in the Late Victorian Period

Traballo Fin de Grao en Lingua e Literatura Inglesas. Curso 2020-2021In the beginning of the Victorian era, women’s role in society was still limited to the domestic sphere, with no access to the political sphere or the work place. A change for the better reading said role took place at the end of the 19th century, when a reaction against the conception of the True Womanhood rose, in the shape of the New Woman, who vindicated the right to break free from traditional boundaries. Two aspects of womanhood were specially affected by this active feminist role movement: motherhood and sexuality. Perspective changed so that many women began to oppose the view of motherhood as a duty, even rejecting it altogether to pursue a career in the public sphere. However, this change was contested not only by men but also by many women who still praised the True Womanhood ideal. The New Woman soon became, for the most conservative people, an embodiment of everything a woman should not be: sexually active, seducing, independent, rejecting their socially imposed duties such as motherhood… Another interesting topic brought to light by this struggle to change the terms of gender relations was the challenge that pregnancy and motherhood meant for women. Women who did not reject motherhood did in many cases decide to expose the hardships that conceiving, carrying, birthing and raising a child entailed, and in that way de-glorify motherhood. These women were not positively regarded either, since just like the ones who rejected motherhood entirely, they were undermining the foundations of Victorian society and the True Womanhood concept. Thus, this dissertation aims to analyse from a contrastive point of view the way these revolutionary women were viewed by Victorian society, finding a connection between both versions of the antimaternal and female sexuality through the literary works of Bram Stoker, Dracula (1897) and Charlotte Perkins Gilman “The Yellow Wallpaper” (1899), since such works articulate depictions of these new conceptions of motherhood and sexuality, both from the male and female point of view, yet not devoid of conflict

Working with student teachers in education for sustainability: knowledge and biodiversity conservation

[Resumo] O presente traballo describe unha actividade deseñada para integrar temas de educación para a sustentabilidade na formación inicial de docentes de Educación Primaria, a través da inclusión do concepto de biodiversidade na elaboración de traballos por proxectos específicos. Para promover e implementar esta metodoloxía e a aprendizaxe deste concepto centrouse a súa formación en destacar estratexias didácticas baseadas na construción dos coñecementos por medio dun proceso de indagación o investigación orientada; tamén se aplican os valores da comunicación presentes nos novos instrumentos do traballo científico. Con estas estratexias camíñase na comprensión da globalidade do concepto e posibilítanse decisións para acción claves na conservación da biodiversidade[Abstract] This paper sets out an activity designed to integrate sustainable development issues into pre-service Primary teacher training, including the biodiversity concept and following a methodology by work projects. In order to promote and implement this methodology and learn this concept their initial formation is focused at highlighting the didactic strategies based in research/inquiry processes. Communication values also apply these new tools of scientific work, These strategies allow them to understand the globality of the concept and to take decisions to conserve biodiversit

O ensino da Historia Natural no Instituto de Santiago (1850-1903). Profesorado e recursos, dependencias e influencias

[Resumo] Dado o seu carácter de instituto universitario, o Instituto de Santiago mantivo, dende a súa cre- ación, unha gran dependencia da Universidade compostelá, especialmente nas chamadas materias de ciencias. Aínda que a cátedra de Historia Natural loi creada no ano 1850, o Instituto seguiu utilizando aulas e materiais da Universidade para impartir a disciplina, ata a creación en 1863 dun gabinete propio. Neste artigo estúdiase esta relación de dependencia que se mantivo no tempo, as características dos distintos períodos de actividade, a actuación do prolesorado, a utilización que fixo dos recursos didácti- cos dispoñíbeis -especialmente das colección s do gabinete- e a incorporación das novas técnicas e dis- ciplinas ó ensino da Historia Natural.[Abstract] The High School 01 Santiago has always maintained close links with the local university, having the reputation 01 being an academic institution, especially in the sciences. Although the chair 01 Natural History was created in 1850, the Secondary School continued to use the University's c1assrooms and teaching materials until it set up its own lacilities in 1863. In this article we study the relationship between the two institutions over the years, the different kinds 01 activities carried out, the work of the teaching staff, the use made 01 the educational resources available -especially the museum collection- and the incorporation 01 new techniques and disciplines into the tea- ching 01 Natural History

Structural characterization of recombinant PrPSc prions using biochemical and biophysical techniques

Prion diseases i.e. Creutzfeldt-Jakob disease (CJD) and related disorders, are rare, fatal brain neurodegenerative ailments. Their worldwide yearly incidence is of about one case per million people, i.e., approximately 8000 new cases per year in the world. They are caused by the autopropagative misfolding of the prion protein, PrP, namely PrPSc. Despite extensive efforts, effective drugs against these disorders are still lacking, very likely due to the fact that the structure of PrPSc is still unknown.This thesis proposal aims at elucidating the structure of such prion using different biochemical and biophysical techniques. The main technique employed is solid state nuclear magnetic resonance (ssNMR) by which we analyzed for the first time recombinant BVPrPSc sample produced by the PMSA technique, along with some controls that allowed us to obtain an array of structural information. The most relevant piece of information obtained by analyzing 13CO-Phe- Het-s, a yeast prion, 13CO-Phe-PrP amyloid which is non infectious and recBVPrPSc was the secondary structure of the latter conforms to a PIRIBS (parallel-in-register-intermolecular-beta-sheets) structure contrary to our initial hypothesis that its secondary structure was that of a 4RBS (4-rung-beta-solenoid). In my thesis I present all the details of how I arrived to this conclusion along with others

Development and Validation of Turbulence Closures for Three-Dimensional Reynolds-Averaged and Partially-Averaged Navier-Sotkes Application to Open-Channel Flow in Bends and Meanders

Programa Oficial de Doutoramento en Enxeñaría Civil . 5011V01[Resumo] Desenvolvemento e validación de modelos de turbulencia para Reynolds-Averaged e Partially-Averaged Navier-Stokes en tres dimensións. Aplicación a fluxo en canais abertos curvos e meandriformes Entender e ser quen de predicir o comportamento do fluxo en canles abertos curvos e meandriformes é un elemento crucial para a enxeñería fluvial. O presente documento analiza este tipo de casos mediante a utilización de modelos computacionais tridimensionais e non hidrostáticos baseados nas ecuacións de conservación da masa e o momentum de Navier-Stokes. Dado que a turbulencia é omnipresente en fluxos ambientais e que a sua influencia é extremadamente relevante, este traballo analiza o efecto dunha variedade de modelos de peche para o termo que encapsula a aportación das fluctuacións turbulentas en tres escenarios: un canal curvo de 270°, un canal meandriforme consistente nunha sucesión de dúas curvas contrapostas e un meandro infinito. A análise céntrase específicamente na descripción do fluxo secundario, os mecanismos de xeración e regulación das estruturas coherentes e a súa influencia na distribución das tensións tanxenciais. Os modelos empregados nesta investigación pódense encadrar dentro de tres familias fundamentais que se diferenzan no xeito en que resolven ou aproximan as tensións turbulentas: URANS, PANS e LES. As prediccións obtidas nestas simulacións foron comparadas e validadas numérica e experimentalmente. A influenza nos resultados de parámetros numéricos como a condición de contorno de entrada e a discretización do termo convectivo da ecuación de momentum recibiu particular atención. Os resultados mostran que determinadas configuracións de PANS predín particularmente ben os fluxos primario e secundario e a estrutura da turbulencia con respecto aos datos experimentais e os resultados obtidos con LES. URANS combinado co modelo de turbulencia k-ε produce simulacións robustas e fiábeis para os escenarios considerados, pero manifesta deficiencias na predicción dalgúns mecanismos do fluxo secundario e a cuantificación da enerxía cinética turbulenta debido ao exceso de disipación. Implementáronse modelos non lineais baseados no concepto de viscosidade turbulenta en cobinación con URANS; os resultados foron irregulares e, en xeral, non melloraron a capacidade predictiva de k-ε. Os resultados sinalan que o desenvolvemento da turbulencia e a ‘memoria’ previa do fluxo tras percorrer sucesivas curvas alternas en canais meandriformes son cruciais para definir a estrutura e magnitude do fluxo secundario. Esta investigación amosa como estruturas coherentes formadas en curvas consecutivas interaccionan entre si e son recicladas entre un meandro e o seguinte, o cal ten importantes repercusións para o transporte de sedimentos e contaminantes en fluxos ambientais. As fluctuacións turbulentas identificadas nos canais en curva son intensamente anisotrópicas e non poden ser descritas con rigor e exclusivamente por modelos baseados en hipóteses de turbulencia isotrópica. Este traballo servirá como base a novas liñas de investigación para o desenvolvemento de modelos dinámicos inspirados en PANS que produzan ferramentas predictivas tridimensionais rápidas, fiables e precisas para enxeñería fluvial.[Resumen] Desarrollo y validación de modelos de turbulencia para Reynolds-Averaged y Partially-Averaged Navier-Stokes en tres dimensiones. Aplicación a flujo en canales abiertos curvos y meandriformes Entender y ser capaz de predecir el comportamiento del flujo en canales abiertos curvos y meandriformes es un elemento crucial en ingeniería fluvial. El presente documento analiza este tipo de casos mediante la aplicación de modelos computacionales tridimensionales y no hidrostáticos basados en las ecuaciones de conservación de masa y momentum de Navier-Stokes. Dado que la turbulencia es omnipresente en flujos ambientales y que su influencia es extremadamente relevante, se analizó el efecto producido por diferentes modelos de cierre para el término turbulento en tres escenarios: un canal curvo de 270°, un canal meandriforme consistente en una sucesión de dos curvas alternas y un meandro infinito. El análisis se centra específicamente en la descripción del flujo secundario, los mecanismos de generación y la evolución de las estructuras coherentes y la interdependencia de lo anterior con las tensiones tangenciales. Los modelos empleados en este trabajo se pueden encuadrar en tres familias principales atendiendo al modo en que resuelven o aproximan las tensiones turbulentas: URANS, PANS y LES. Las predicciones obtenidas en dichas en estas simulaciones han sido comparadas y validadas numérica y experimentalmente. La influencia de parámetros como la condición de contorno de entrada del flujo y la discretización del término convectivo de la ecuación de momentum recibió particular atención. Los resultados revelan que determinadas configuraciones de PANS predicen con acierto los flujos primario y secundario, así como la estructura de la turbulencia, con respecto a los datos experimentales y simulaciones hechas con LES. URANS combinado con el modelo de turbulencia k-ε produce simulaciones robustas y fiables para los escenarios considerados, en especial del flujo primario, pero manifiesta deficiencias en la predicción de algunos mecanismos del flujo secundario y la cuantificación de la energía cinética turbulenta debido al exceso de disipación. Se han aplicado modelos no-lineales para la predicción de la viscosidad turbulenta en combinación con URANS; los resultados son irregulares y, en general, no mejoraron la capacidad predictiva de k-ε. Los resultados señalan que el desarrollo de la turbulencia y la ‘memoria’ previa del flujo tras recorrer sucesivas curvas alternas en canales meandriformes son clave para definir la estructura y magnitud del flujo secundario. Esta investigación muestra como estructuras coherentes formadas en curvas consecutivas interactúan entre sí y son recicladas entre un meandro y el siguiente, lo cual tiene importantes repercusiones para el transporte de sedimentos y contaminantes en flujos ambientales. Las fluctuaciones turbulentas identificadas en los canales en curva son intensamente anisotrópicas y no pueden ser descritas con rigor exclusivamente por modelos basados en hipótesis de turbulencia isotrópica. Este trabajo servirá de base a nuevas líneas de investigación sobre el desarrollo de modelos dinámicos inspirados en PANS capaces de producir herramientas predictivas en tres dimensiones rápidas, fiables y precisas para la ingeniería fluvial.[Abstract] Development and validation of turbulence closures for three-dimensional Reynolds-Averaged and Partially-Averaged Navier-Stokes. Application to open-channel flow in bends and meanders Understanding and being able to predict curved and meandering flow behaviour is key to river engineering. This work analyses this kind of flows using three-dimensional, non-hydrostatic computational models. Given the ubiquitous presence of turbulence in environmental flows and its crucial importance, different turbulence closures are applied to three curved and meandering open-channel flow scenarios: a single 270° bend, a two-bends meandering channel and an infinite meander. The analysis particularly focuses on the structure of the secondary flow, the mechanisms of generation and modulation of coherent structures, and their influence on the shear stresses. The modelling approaches utilised during this research fall within three fundamental families, URANS, PANS and LES. The fundamental difference among them is their approach to solve or model the turbulence stresses. The predictions provided by these models were tested, compared and validated. The influence of several modelling parameters – besides the turbulence closure itself - on their performance is also analysed, with a special emphasis on the discretisation scheme for the convective term and the inflow conditions. The results show that some configurations of PANS remarkably match the available experimental and LES datasets regarding the prediction of primary and secondary flow and turbulence structure. URANS combined with a k-ε turbulence closure provides a very robust and consistent forecasting of the scenarios under investigation, particularly the primary flow, while lacking on the prediction of some of the mechanisms driving the secondary motion and the turbulence structure. Non-linear eddy viscosity models were tested with irregular results, and overall failing to improve k-ε performance. Turbulence development and the memory of prior bends in meandering channels seem to be key to the secondary flow structure. It was found that coherent structures of consecutive bends interact with each other, which has important repercussions to sediment and pollution transport in environmental flows. It was also found that the turbulent fluctuations within the bends are strongly anisotropic and cannot be well described by models reliant on isotropic assumptions. Future lines of work based on this research could provide dynamic PANS models and new turbulence closures that will generate quick, reliable, and accurate three-dimensional tools for river engineering modelling

Alumbrado en vehículos espaciales

Finalizándose el programa espacial Apollo, la Administración Nacional de Aeronáutica y del Espacio de los Estados Unidos de Norteamérica, NASA (National Aeronautics and Space Administration), que es la agencia gubernamental responsable de los programas espaciales, comenzó a analizar el futuro del programa espacial Norteamericano. Durante la campaña de los Apollo los cohetes impulsores utilizados, para colocar los astronautas y los equipos en el espacio exterior, se basaban en el uso de cohetes desechables. En el futuro se necesitarían cohetes fiables, menos costosos y que pudiesen ser reutilizables. La idea de un transbordador espacial reutilizable que se pudiese lanzar como un cohete, pero que su reentrada a la tierra fuera como la de un avión, era un desafío atractivo y un gran logro técnic