Experimental study of visual corona under aeronautic pressure conditions using low-cost imaging sensors

Visual corona tests have been broadly applied for identifying the critical corona points of diverse high-voltage devices, although other approaches based on partial discharge or radio interference voltage measurements are also widely applied to detect corona activity. Nevertheless, these two techniques must be applied in screened laboratories, which are scarce and expensive, require sophisticated instrumentation, and typically do not allow location of the discharge points. This paper describes the detection of the visual corona and location of the critical corona points of a sphere-plane gap configurations under different pressure conditions ranging from 100 to 20 kPa, covering the pressures typically found in aeronautic environments. The corona detection is made with a low-cost CMOS imaging sensor from both the visible and ultraviolet (UV) spectrum, which allows detection of the discharge points and their locations, thus significantly reducing the complexity and costs of the instrumentation required while preserving the sensitivity and accuracy of the measurements. The approach proposed in this paper can be applied in aerospace applications to prevent the arc tracking phenomenon, which can lead to catastrophic consequences since there is not a clear protection solution, due to the low levels of leakage current involved in the pre-arc phenomenon.Peer ReviewedPostprint (published version

Desarrollo del pensamiento proporcional en el grado séptimo, una propuesta transversal

En el marco de la Maestría en Docencia de la Matemática de la Universidad Pedagógica Nacional cohorte 2016-01, se adelanta un trabajo de grado tipo innovación curricular; este estudio es del tipo acción–participación, de corte cualitativo; se adelanta en una Institución Educativa Distrital (IED) del sector oficial, el colegio se ubica en la zona octava de Bogotá; en este colegio se analiza el pensamiento de los estudiantes de un grado séptimo de la educación básica entorno a su comprensión de la razón y la proporción matemática. Para lo anterior, específicamente se indaga sobre el pensamiento proporcional de los niños, puesto a prueba al desarrollar una serie de actividades o tareas, diseñadas sobre contextos variados, ejercitando las diferentes competencias específicas del área, mostrando la proporcionalidad como un saber conectado y como preámbulo del futuro trabajo algebraico en años posteriores

Arc tracking control in insulation systems for aeronautic applications: challenges, opportunities, and research needs

Next generation aircrafts will use more electrical power to reduce weight, fuel consumption, system complexity and greenhouse gas emissions. However, new failure modes and challenges arise related to the required voltage increase and consequent rise of electrical stress on wiring insulation materials, thus increasing the risk of electrical arc appearance. This work performs a critical and comprehensive review concerning arc tracking effects in wiring insulation systems, underlying mechanisms, role of materials and possible mitigation strategies, with a special focus on aircraft applications. To this end an evaluation of the scientific and technological state of the art is carried out from the analysis of theses, research articles, technical reports, international standards and white papers. This review paper also reports the limitations of existing insulation materials, standard test methods and mitigation approaches, while identifying the research needs to comply with the future demands of the aircraft industryPeer ReviewedPostprint (published version

Justice Blocks and Predictability of U.S. Supreme Court Votes

Successful attempts to predict judges' votes shed light into how legal decisions are made and, ultimately, into the behavior and evolution of the judiciary. Here, we investigate to what extent it is possible to make predictions of a justice's vote based on the other justices' votes in the same case. For our predictions, we use models and methods that have been developed to uncover hidden associations between actors in complex social networks. We show that these methods are more accurate at predicting justice's votes than forecasts made by legal experts and by algorithms that take into consideration the content of the cases. We argue that, within our framework, high predictability is a quantitative proxy for stable justice (and case) blocks, which probably reflect stable a priori attitudes toward the law. We find that U.S. Supreme Court justice votes are more predictable than one would expect from an ideal court composed of perfectly independent justices. Deviations from ideal behavior are most apparent in divided 5–4 decisions, where justice blocks seem to be most stable. Moreover, we find evidence that justice predictability decreased during the 50-year period spanning from the Warren Court to the Rehnquist Court, and that aggregate court predictability has been significantly lower during Democratic presidencies. More broadly, our results show that it is possible to use methods developed for the analysis of complex social networks to quantitatively investigate historical questions related to political decision-making

Analysis and mitigation of stray capacitance effects in resistive high-voltage dividers

This work analyzes the effects of the parasitic or stray distributed capacitance to ground in high-voltage environments and assesses the effectiveness of different corrective actions to minimize such effects. To this end, the stray capacitance of a 130 kV RMS high-voltage resistive divider is studied because it can severely influence the behavior of such devices when operating under alternating current or transient conditions. The stray capacitance is calculated by means of three-dimensional finite element analysis (FEA) simulations. Different laboratory experiments under direct current (DC) and alternating current (AC) supply are conducted to corroborate the theoretical findings, and different possibilities to mitigate stray capacitance effects are analyzed and discussed. The effects of the capacitance are important in applications, such as large electrical machines including transformers, motors, and generators or in high-voltage applications involving voltage dividers, conductors or insulator strings, among others. The paper also proves the usefulness of FEA simulations in predicting the stray capacitance, since they can deal with a wide range of configurations and allow determining the effectiveness of different corrective configurations.Peer ReviewedPostprint (author's final draft

Implementation of a prototype web application development framework for a non-relational storage engine that allows the mapping of objects

El desarrollo de software bajo el paradigma de Programación Orientada a Objetos está confrontado por un modelo de almacenamiento de datos de tipo relacional ampliamente aceptado por la industria desde hace casi treinta años. Lo anterior, plantea dos escenarios diferentes para modelar la estructura de la información: para almacenarla (base de datos) y/o tenerla en memoria (objetos), lo que conlleva a que los desarrolladores de software traten de mitigar a través de conversiones entre tipos o utilizando herramientas intermedias como el mapeo de objetos relacional, lo cual traen ventajas y desventajas sobre el proceso de desarrollo, el rendimiento de las aplicaciones y la mantenibilidad. Con las consideraciones anteriores, se propuso desarrollar una implementación de software que permitiera almacenar los objetos de la aplicación bajo un motor de almacenamiento no relacional o NoSQL, para lo cual se selecciono MongoDB que gracias a su estructura dinámica de documentos basada en el formato JSON se adapto a las definiciones de los objetos. El formato de documentos (Json) utilizado por el motor de datos MongoDB permitió almacenar los objetos definidos por los usuarios del Framework de tal forma que en una sola entidad se tiene organizada toda información, y no se segmenta como en el modelo de datos relacional, se respeta la definición inicial del objeto modelado, a partir de esta premisa, consideramos que se debe generar en mejoras de rendimiento de acceso a los datos, ya que la información estará ubicada en una misma colección.Universitat Oberta de Catalunya UOCRESUMEN 10 INTRODUCCIÓN 14 1. REVISIÓN BIBLIOGRÁFICA O MARCO TEÓRICO 17 2. PLANTEAMIENTO DEL PROBLEMA Y JUSTIFICACIÓN 29 3. OBJETIVOS PLANTEADOS 34 4. MÉTODO DE INVESTIGACIÓN 35 5. RESULTADOS DE LA INVESTIGACIÓN 37 5.1. Actividades 37 5.4. Funcionamiento del Framework. 42 5.5. Diseño e implementación del Framework 42 5.5.1. Casos de Uso 44 5.5.3. Diagrama de Paquetes 48 5.5.5. Interfaz grafica de usuario 50 6. ANÁLISIS DE LA INFORMACIÓN 57 6.1. Herramientas de tipo mapeo objeto-relacional (ORM) 57 6.2. Conceptos de Bases de Datos NoSQL 61 6.3. Framework desarrollado 63 7. CONCLUSIONES 65 8. RECOMENDACIONES Y TRABAJOS FUTUROS 67 9. REFERENCIAS BIBLIOGRAFICAS 68MaestríaSoftware development under the Object-Oriented Programming paradigm is confronted by a relational-type data storage model widely accepted by the industry for almost thirty years. The above raises two different scenarios to model the structure of the information: to store it (database) and / or have it in memory (objects), which leads software developers to try to mitigate through conversions between types or using intermediate tools such as relational object mapping, which bring advantages and disadvantages to the development process, application performance and maintainability. With the above considerations, it was proposed to develop a software implementation that would allow the application's objects to be stored under a non-relational or NoSQL storage engine, for which MongoDB was selected that thanks to its dynamic document structure based on the JSON format I adapt to the definitions of the objects. The document format (Json) used by the MongoDB data engine allowed to store the objects defined by the Framework users in such a way that all information is organized in a single entity, and it is not segmented as in the relational data model, The initial definition of the modeled object is respected, based on this premise, we consider that it should be generated in performance improvements for data access, since the information will be located in the same collection.Modalidad Presencia

Masculinidades Online. La resignificación de la masculinidad en el lenguaje fotográfico de las prácticas fashion blogger y fashion influencer en Colombia.

La resignificación de la indumentaria masculina, como objeto de diseño con implicaciones que exceden a la preocupación básica por la vestimenta, desarrolló procesos de comunicación e interpelación personal que la población adoptó como formas de expresión ante la sociedad; a partir de lo anterior emerge el fenómeno social de la moda de indumentaria visto como un sistema productor de significaciones que actualmente determina las diferencias sociales en la población

Energy balance of wireless sensor nodes based on bluetooth low energy and thermoelectric energy harvesting

The internet of things (IoT) makes it possible to measure physical variables and acquire data in places that were impossible a few years ago, such as transmission lines and electrical substations. Monitoring and fault diagnosis strategies can then be applied. A battery or an energy harvesting system charging a rechargeable battery typically powers IoT devices. The energy harvesting unit and rechargeable battery supply the sensors and wireless communications modules. Therefore, the energy harvesting unit must be correctly sized to optimize the availability and reliability of IoT devices. This paper applies a power balance of the entire IoT device, including the energy harvesting module that includes two thermoelectric generators and a DC–DC converter, the battery, and the sensors and communication modules. Due to the small currents typical of the different communication phases and their fast-switching nature, it is not trivial to measure the energy in each phase, requiring very specific instrumentation. This work shows that using conventional instrumentation it is possible to measure the energy involved in the different modes of communication. A detailed energy balance of the battery is also carried out during charge and discharge cycles, as well as communication modes, from which the maximum allowable data transfer rate is determined. The approach presented here can be generalized to many other smart grid IoT devices.Postprint (published version

Memory Engram Cells Have Come of Age

The idea that memory is stored in the brain as physical alterations goes back at least as far as Plato, but further conceptualization of this idea had to wait until the 20th century when two guiding theories were presented: the “engram theory” of Richard Semon and Donald Hebb’s “synaptic plasticity theory.” While a large number of studies have been conducted since, each supporting some aspect of each of these theories, until recently integrative evidence for the existence of engram cells and circuits as defined by the theories was lacking. In the past few years, the combination of transgenics, optogenetics, and other technologies has allowed neuroscientists to begin identifying memory engram cells by detecting specific populations of cells activated during specific learning epochs and by engineering them not only to evoke recall of the original memory, but also to alter the content of the memory.RIKEN Brain Science InstituteHoward Hughes Medical InstituteJPB Foundatio