Engineering non-Hermitian and topological flow of sound

During the last decades, acoustic and phononic metamaterial research was focused on finding new ways to modify the flow of sound waves at will. In this project, we focus on exploring novel properties of sound by developing numerical code and theoretical methods to understand the acoustic analogy to non-Hermitian systems, topological insulators, and other exciting phenomena in condensed matter physics such as the magic angle in twisted bilayer graphene. Succinctly, we wish to translate these common notions of quantum mechanics into classical acoustics to find new properties for the case of sound. Non-Hermitian acoustic structures can be achieved by balancing acoustic loss and gain units. Commonly known as Parity-Time (PT) symmetric structures, they have neither parity symmetry nor time-reversal symmetry, but are nevertheless symmetric in the product of both. In particular, the doctoral research project aims at designing acoustic PT symmetry and demonstrating the extraordinary scattering characteristics of the acoustic PT medium based on exact theoretical predictions and numerical analysis. Hence, we investigate the possibilities to realize one-way cloaks of invisibility and broken symmetry properties with amplifying or attenuating behaviour. Topological sound combines the knowledge of topology in mathematics and electronics with sound waves. Knowing that artificial sonic lattices have been widely used to explore topological phases of sound and its properties, we propose to study the properties of Second Order Topological Insulators when non-hermiticity is involved. Deriving a semi-numerical tool that allows us to compute the spectral dependence of corner states in the presence of defects, we illustrate the limits of the topological resilience of the confined non-Hermitian acoustic states. An attractive motivation of these acoustic structures compared to their electronic counterparts, is their easy fabrication and tunability, allowing the experimental verification of this quantum analogies as well as the development of many numerical studies. Thereby, in the last part of this thesis we mimic twisted bilayer physics in a mechanical twisted bilayer configuration and also in an acoustical bilayer. Designing the mathematical models to describe the physics involved, we show how the twist angle is related to the flat band formation as happens in twisted bilayer graphene.Programa de Doctorado en Ciencia e Ingeniería de Materiales por la Universidad Carlos III de MadridPresidente: Ramón Eulalio Zaera Polo.- Secretario: Clivia Marfa Sotomayor Torres.- Vocal: José Vicente Álvarez Carrer

Martha C. Nussbaum. The Monarchy of Fear, A philosophical look at the current political crisis. Bogotá: Editorial Planeta Colombia, 2019

Martha C. Nussbaum. The Monarchy of Fear, A philosophical look at the current political crisis. Bogotá: Editorial Planeta Colombia, 2019, 303 PagesMartha C. Nussbaum. The Monarchy of Fear, A philosophical look at the current political crisis. Bogotá: Editorial Planeta Colombia, 201

Orlando Oliveros: The memory machine. Stories and conversations about the life, work and legacy of Gabriel García Márquez. Cartagena de Indias, Colombia: Gabo Foundation

Orlando Oliveros: The memory machine. Stories and conversations about the life, work and legacy of Gabriel García MárquezOrlando Oliveros: The memory machine. Stories and conversations about the life, work and legacy of Gabriel García Márque

Yuval Noah Harari, from Animals into Gods. A Brief History of Humankind. Bogotá: Penguin Random House, 2017

Yuval Noah Harari, from Animals into GodsYuval Noah Harari, from Animals into God

Thomas Piketty, A Brief History of Equality. Colombia: Editorial Ariel, 2022. 294 pages.

Thomas Piketty, A Brief History of EqualityThomas Piketty, A Brief History of Equalit

Ricardo Silva Romero, Río Muerto. Bogotá: Alfaguara. Penguin Random House. 2020, 156 pages.

Ricardo Silva Romero, Río MuertoRicardo Silva Romero, Río Muert

Effect of nitrogen gas in the agglomeration and photoluminescence of Zn-ZnO nanowires after high-temperature annealing

The effect of anti-agglomeration and enhanced photoluminescence after high-temperature annealing of Zn-ZnO nanowires in nitrogen at-mosphere is reported. The Zn-ZnO nanowires were deposited by the hot filament chemical vapor deposition technique and subsequentlyannealed at 1100±C in oxygen or nitrogen atmospheres. It was found that under both annealing atmospheres, the structure of the nanowireswas completely oxidized. Morphological studies suggest that annealing under oxygen-rich atmosphere, grain growth occurs, resulting in acontinuous surface with a micrograin-shaped structure. However, it seems that nitrogen-rich annealing partially prevents complete agglom-eration and longitudinal structures composed by nanometric grains were observed. Although photoluminescence properties of the annealednanowires are improved in both annealing atmospheres, it was observed that the PL spectrum of nanowires annealed in nitrogen showed astronger UV emission than that of the oxygen annealed nanowires

Hacia un nuevo marco conceptual de la universidad pública: ethos de la Universidad Distrital

This rationale made by the Udinex group about the real existing reason of Universities in general, and, in particular, of the university Francisco Jose de Caldas leads us to formulate a working hypothesis in the sense that the university should invert the original reason for its existence: help to train people to think by themselves. This means that research activities: enunciate a new hypothesis, formulate a research problem, construct a methodology, research among other practices, should lead to eventually thinking by ourselves.Esta reflexión, realizada en el grupo Universidad Distrital: Investigación de Extensión (UDINEX), sobre la verdadera razón de ser de la universidad en general, y en particular de la Universidad Distrital Francisco José de Caldas, nos lleva a formular una hipótesis de trabajo en el sentido que la universidad debe retomar la razón primigenia de su existencia: ayudar a formar a individuos que piensen por sí mismos. Por ese camino, se entien-de que el quehacer investigativo --enunciar una nueva hipótesis, formular un problema de investigación, construir una metodología, entre otras prácticas investigativas--, significa, a la larga, pensar por sí mismo

La Seudorrevolución Educativa. Desigualdades, capitalismo y control en la educación en Colombia

Andrés Felipe Mora Cortés Editorial Pontificia Universidad Javeriana 2016, 173 página