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In this paper, we report an investigation of adding a non-hydride forming element in the multicomponent Ti-V-Nb-M system. By the Calculation of Phase Diagrams approach (CALPHAD), the thermodynamic phase stability of the TiVNbT (T = Cr, Mn, Fe, Co, and Ni) was investigated, and Cr was selected as the fourth alloying element due its high tendency to stabilize body-centered cubic solid solutions (BCC). The (TiVNb)100−xCrx alloys (with x = 15, 25, and 35 at.% Cr) were synthesized by arc-melting. The structural characterization reveals that the three alloys were composed of a major BCC phase, which agrees with the thermodynamic calculations. The three alloys absorb hydrogen at room temperature without any activation treatment, achieving a hydrogen uptake of about H/M = 2. The Pressure-Composition-Isotherms curves (PCI) has shown that increasing the Cr amount increases the equilibrium pressures, indicating that tunable H storage properties can be achieved by controlling the alloys’ Cr content.

The aim of this work is to investigate the influence of some processes variables on the microstructure and hydrogen absorption kinetics of MgH2 - X wt.% TiFe composites. Samples were synthesized by high-energy ball milling in a planetary (X = 40, 50, 60) and shaker mill (X = 40) under high-purity argon atmosphere. Commercial MgH2 instead of Mg powder was used in order to reduce adherence on the vial and balls. TiFe powder was previously produced by ball milling a mixture of TiH2 and Fe powders followed by a reaction synthesis at 600oC. Milled composites samples were characterized by XRD and SEM analysis. Milling time was preliminary investigated (X = 40) in the planetary ball mill (6 to 36h). TiFe particle size reduction was shown to be difficult since they are surrounded by MgH2 matrix. Strong particle reduction was obtained by using a shaker mill only for 2 hours and adding cyclohexane as process control agent. No reaction between MgH2 and TiFe compound was observed in any milled sample. Hydrogen absorption kinetics measurements of the as-milled samples were conducted on an Sieverts' type apparatus at room temperature after hydrogen desorption at 350oC under vacuum. The best hydrogen kinetics (3 wt% at the first hour) was attained by the planetary milled sample (36 h). Higher hydrogen capacity was observed for the sample milled in the shaker mill (4.0 wt.%), but only after 13h.

Actualmente, el mundo está cambiando la forma en que genera energía, pasando de un sistema eléctrico basado en baja penetración de energías renovables, flujos de potencia unidireccionales y baja participación de conversores de potencia, a un sistema eléctrico con alta inclusión de energías renovables, flujos de potencia bidireccionales y alto uso de conversores de potencia.Los conversores AC-AC jugarán un rol fundamental en los sistemas del futuro, en aplicaciones como la interconexión de sistemas de potencia, sistemas de transmisión AC de baja frecuencia (LFAC), sistemas de conversión de energía eólica (WECS) y como accionamiento de motores de medio/alto voltaje para bombas, molinos, cintas transportadoras, tracción marina, entre otras aplicaciones.Chile y Australia predicen que, para el 2050, los sistemas eólicos serán una de las principales fuentes de energía para industrias y personas. Adicionalmente, ambos países presentan una actividad minera activa, aplicación que considera múltiples accionamientos para motores. Sin embargo, los futuros conversores AC-AC para las aplicaciones mencionadas anteriormente, como por ejemplo el conversor matricial modular multinivel (M3C), presentan diversos desafíos para su implementación, tales como alto acoplamiento de los estados internos, alta complejidad para el control y balance de varios capacitores flotantes, gran cantidad de señales de control y oscilaciones en el voltaje de los capacitores a frecuencias críticas, desafíos que complican su implementación en aplicaciones de alto voltaje que requieren un gran número de sub-módulos.Este proyecto de investigación apunta al desarrollo de estrategias de control predictivo para controlar un M3C, que se componen de dos partes: un controlador interno encargado del control de corrientes y del control de balance local del clúster, y un controlador externo que logra el control de balance entre clústeres y mitiga las oscilaciones de baja frecuencia del voltaje de los capacitores de los sub-módulos. Por un lado, se proponen dos estrategias como controlador interno: una basada en control predictivo por modelo con desplazamiento de fase secuencial y otra basada en control predictivo por modelo con conjunto de control finito (FCS-MPC). Por otro lado, se proponen dos generadores de referencia como controlador externo: el primero genera corrientes circulantes en función de la energía de los clústeres en un espacio transformado, y el segundo considera corrientes circulantes y voltaje de modo común para balancear la energía del M3C.Finalmente, los resultados experimentales prueban la eficacia de la estrategia de control diseñada para controlar un M3C, logrando alcanzar las referencias de corriente y energía. Más aún, todas las propuestas son comparadas con estrategias de la literatura. En estado estacionario, el error de seguimiento promedio de corrientes y voltajes es de 1.96% y 1.82%, respectivamente, reduciendo el rizado del voltaje de los capacitores para baja frecuencia en 31% y para frecuencias iguales en 36%. Durante transientes, por un lado, cambios en escalón de potencia y frecuencia son seguidos instantáneamente. Por otro lado, cambios en escalón en los controles de balance local y entre clústeres son seguidos en 80 y 200 ms, respectivamente. Finalmente, la carga computacional de todas las propuestas incrementa linealmente con el número de sub-módulos, con excepción de la estrategia basada en FCSMPC.

Friability is a property related to the brittle fracture of soil aggregates and, therefore, is considered a key to the physical quality of soils and the consumption of energy during farming. This paper contains the preliminary results of research that aimed to quantitatively determine the friability index (FI) and its relationship with other soil properties; in particular, this research focused on the relationship between the FI and the clay content and organic carbon percentage (OC) of soils with a different dominance in the fine fraction (1:1 and 2:1 clay) that were cultivated with sugar cane in the southwest region of Colombia. The FI was determined by the compressive strength method using aggregates with diameters between 9.5 and 19.0 mm taken from the surface horizon, which were air air-dried and then dried at a low-temperature in an oven. The clay type content and OC content were determined in these samples. A 98.6% of the studied samples had FI values between 0.24 and 0.80, thus, classifying them as friable (especially those having a 1:1 type clay dominance) and very friable (especially those having a 2:1 type clay dominance), suggesting a structural condition of low to moderate energy requirements for farming, low greenhouse gas emissions (GHG) and a reduced risk of damage on the physical quality if a suitable soil moisture content exists during the tilling. This study found correlations between the texture, OC, and FI of the soils, indicating that the two first properties affected the friability. However, this effect depended on the clay dominance type.

Acoustic waves below the audible frequencies (20 Hz) are called infrasound. Generated by a wide variety of sources, these signals can propagate thousands of kilometers, aided by their low attenuation as well as strong winds and high temperatures in the stratosphere and thermosphere that enable them to return to the ground. Volcanic eruptions are among the most powerful sources of infrasound, and the International Monitoring System (IMS) infrasound network, maintained by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), is capable of monitoring volcanic eruptions around the globe. However, the spatiotemporal variability of the atmosphere poses a major challenge. In particular, strong horizontal cross-winds affect the observed infrasound arrival back-azimuths, causing source mislocations up to hundreds of kilometers.This dissertation presents an automatic iterative method combining empirical climatologies (HWM14/NRLMSIS2.0) and 3D ray tracing (infraGA) to obtain rapid, robust first-order estimates of the back-azimuth deviations, producing corrections for location and characterization procedures. The results compare well with a more realistic model of the lower atmosphere using Numerical Weather Prediction (NWP) simulations. Potential applications include near real-time volcano monitoring and large-scale reanalysis of infrasound archives.To test this method, we first apply it to the eruptions of Puyehue-Cordón Caulle (2011) and Calbuco (2015) in Chile, using data from IMS stations within 5000 km. The back-azimuth corrections reduce the source mislocation by ∼84% (242 to 38.7 km) and ∼75% (366 to 93.1 km), respectively.Then, we assess the method’s temporal accuracy using data from 2003-2022 from IMS station IS22 (New Caledonia), which has recorded persistent volcanic infrasound from Yasur (∼400 km) and Ambrym (∼700 km) volcanoes (Vanuatu archipelago). We find good agreement with the seasonal variation of the dataset, showing we can provide year-long estimates of the back-azimuth deviation.Finally, we use the method to identify long-range infrasound signals recorded at the Antarctic IMS station IS27, attributable to episodes of moderate persistent eruptive activity at Mount Michael volcano, 1,670 km away on Saunders island (South Sandwich islands). Examining data from 2004-2020 reveals previously hidden candidate eruptive signals, especially from May 2005 to January 2008 and from May 2016 to April 2018.

Soil friability is a physical property that provides valuable information for minimizing energy consumption during soil tillage and for preparing the edaphic medium for plant development. Its quantitative determination is generally carried out with aggregates obtained from soil blocks taken at fixed depths of profiles without considering the superficial horizons of the soil. The objective of the this study was to determine the effect of aggregate size and superficial horizon differentiation on the friability index (FI) of some soils cultivated with sugar cane in the Geographic Valley of the Cauca River (Colombia), using univariate (CVu) and multivariate (CVm) coefficients of variation. The FI was evaluated using a compression test with four aggregate-size ranges taken from the Ap and A1 superficial horizons of 182 sampling sites located on 18 sugar cane farms. Of the five types of studied soils (Inceptisols, Mollisols, Vertisols, Alfisols and Ultisols), 7,280 aggregates were collected that were air dried and subsequently dried in a low-temperature oven before determining the tensile strength (TS), which was in turn used to calculate the FI using the coefficient of variation method. This study found that the FI varied with the aggregate size and the soil depth (first two horizons). Only three of the four size ranges initially selected were relevant. The CVm proved to be very useful for the selection of a more relevant value from the confidence interval of the TS from the CVu method for friability and established that the lower limit value (FIi) of the TS CVu was the FI value that was closest to the multivariate measurement.

Cette thèse a été développée dans le cadre d’une cotutelle entre la Pontificia Universidad Católica de Chile et l’Université Pierre et Marie Curie.Je décris les tests effectués sur deux kits d’occultation, chacun constitué d’une caméra rapide, d’un système de datation et d’un logiciel d’enregistrement. En plus, j’ai observé plusieurs occultations stellaires par des objet transneptuniens et des centaures, y compris celle qui a mené à la découverte des anneaux de Chariklo.J’utilise des occultations stellaires pour obtenir les paramètres physiques de trois objets. Pour 2007 UK126, je déduis la densité la plus probable en analysant les ajustements elliptiques du limbe sur une occultation stellaire. Pour 2003 AZ84, en analysant deux occultations stellaires, je limite la densité et l’orientation de l’objet. Pour le centaure Chariklo, j’adopte une approche statistique bayésienne pour analyser cinq occultations stellaires et je déduis une forme ellipsoïdale de demi-axes a = 148 km, b = 132 km et c = 102 km, avec des irrégularités topographiques de ∼ 6 km, comparables à celles de satellites de Saturne de taille et densité similaires. L’albédo géométrique du Chariklo est de 3.7±0.1% et la réflectivité de l’anneau est de 4.9±0.3%.En fin, j’étudie les résonances de type Lindblad entre le moyen mouvement des particules de l’anneau et la rotation d’un corps irrégulier. L’excès de masse en provenance d’un corps sphérique exerce des moments forts sur un disque collisionnel, et repousse le matériau situé au niveau du rayon de la corotation jusqu’à la résonance la plus externe. Pour Chariklo, les courtes échelles de temps (< 105 ans) expliquent l’emplacement actuel de ses anneaux.

Technological developments in nanomaterials can be tracked using patent indicators. However, the traditional International Patent Classification indicators cannot be considered conclusive, since nanotechnology is not easily defined as a field of research as well as there are different types of nanomaterials not well delineated into hierarchical codes. Therefore, text mining approaches can be used to enhance patent analysis and provide insightful trends to support research and development, competitive intelligence, and policy making. This study aims at proposing a method to classify nanomaterials into main types and mapping technological developments using an advanced text mining-based method to compile patent indicators. Patent records were provided by Derwent Innovations Index database, which indexes an enhanced bibliographic data of patents filed worldwide. A comparison between the IPC indicators and those developed here by text mining is presented. We concluded that the proposed method provides useful outcomes for decision-making, technological forecasting, and material selection process.

A Biotecnologia consolida-se como um tema recorrentemente tratado como estratégico para o desenvolvimento do Brasil. Neste contexto, há necessidade de se investigar o impacto das políticas públicas de ciência e tecnologia, como os Planos Plurianuais e a Estratégia Nacional de Ciência e Tecnologia, que visam estimular a pesquisa científica na área. O objetivo deste artigo foi elaborar e analisar um conjunto de indicadores bibliométricos sobre a produção científica em Biotecnologia. O método utilizado compreendeu o uso da Bibliometria como técnica de análise de informações. A amostra analisada foi de 517.569 registros bibliográficos referentes à produção científica sobre Biotecnologia indexada na base de dados Web of Science, no período de 2001 a 2015. Os resultados alcançados compreenderam indicadores de produção e de colaboração científica nacional e internacional e apontam para o aumento da contribuição do Brasil frente à produção científica mundial neste assunto e o crescimento da importância das pesquisas realizadas pelas instituições da região nordeste do Brasil, bem como a colaboração entre elas. Conclui-se que a implementação de políticas públicas em ciência e tecnologia visando à redução das desigualdades regionais tem surtido efeito na área de Biotecnologia.

O objetivo geral deste estudo compreendeu a elaboração e análise de indicadores baseados em dados do Sistema Nacional de Pós-Graduação (SNPG), disponíveis através dos Cadernos de Indicadores da Capes. O método utilizado foi o estudo de caso e a unidade de análise a área de conhecimento Engenharias II, subárea Engenharia de Materiais e Metalúrgica. Foi empregada a bibliometria como técnica de análise de informação em uma amostra de 5364 registros bibliográficos de artigos científicos referentes ao período de 2007 a 2012. Como resultado, foram elaborados e analisados indicadores bibliométricos sobre a colaboração entre os programas de pós-graduação e a evolução das publicações. Conclui-se que os Cadernos de Indicadores da Capes consolidam-se como uma fonte de informação pública, nacional e disponível a respeito da produção científica nacional, viabilizando a construção de indicadores adequados ao processo de tomada de decisão, visando o aperfeiçoamento do SNPG e das políticas públicas de educação, ciência e tecnologia.