Universidad Tecnológica de Bolívar
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Quantification of the Synthetic Phenolic Antioxidant Cyanox 1790 in Bottled Water with SPE-HPLC/MS/MS and Determination of the Impact of the Use of Recycled Packaging on Its Generation
No full textOne route of exposure to SPAs is through bottled water since the polymers used to make
plastic bottles contain these SPAs, which migrate from the plastic to the water. Solid-phase extraction
(SPE), HPLC-MS, FTIR, and DSC are used to identify and quantify these SPAs in water. Interday
measurements of cyanox 1790 in water with HPLC showed RSD, error, and R2
lower than 3.78, 9.3,and 0.99995, respectively. For intraday measurements of cyanox 1790 in water, the RSD, error, and R2 were less than 4.1, 11.2, and 0.99995, respectively. Concentrations of Cyanox 1790 in water from non-recycled bottles ranged from 0.01 ± 0.0004 to 4.15 ± 0. 14 ppm, while the levels of cyanox 1790 in water in recycled bottles ranged between 0.01 ± 0.0005 and 11.27 ± 0.12 ppm. In the tests carried
out, an increase in the migration of Cyanox 1790 from plastic bottles to water was identified, since
the ppm of Cyanox increased in the water as the days of storage increased at 40 ◦C
In-situ imaging and electrochemical monitoring of damaged thermal spray aluminium coating in synthetic seawater
No full textThis paper presents the results of a study that combined electrochemical monitoring with in-situ imaging of Thermal Spray Aluminium (TSA) coating in synthetic seawater at room temperature in quiescent condition. The coatings were obtained by twin-wire arc spraying of 1050 aluminium alloy on S355 carbon steel substrate. TSA-coated steel samples were evaluated by analysing sequential images of the surface: (i) without defect; (ii) with defects machined before immersion (5% and 30% of exposed steel surface); (iii) with a defect machined after 35 d of immersion (10% of exposed steel surface); and (iv) after the removal of calcareous deposits formed on top of the exposed steel surface. Variations in the coating and the defect were captured and correlated with the evolution of Open Circuit Potential (OCP) during 35 days of full immersion. Determination of calcareous deposit formation time on the top of exposed steel was also carried out. The defect created before immersion impacted the cathodic reactions, resulting in a faster formation of corrosion products and calcareous deposits compared to the defect machined after exposure to synthetic seawater. The penetration time of the electrolyte in the coating and the activation of the surface are key in the protection mechanism and the kinetics of corrosion.UTB, MInciencias, Lloy's Register Foundatio
Influencia del uso pedagógico de geogebra en la apropiación del concepto de la función cuadrática. Caso: Colegio Santo Tomás de Aquino.
No full textEste estudio tuvo como objetivo general determinar cómo el uso pedagógico de GeoGebra puede influir positivamente en el proceso de apropiación del concepto de función cuadrática en estudiantes de noveno grado de la Institución Educativa Colegio Santo Tomás de Aquino. Con el propósito de lograr este objetivo, se implementó un enfoque cuantitativo con un carácter explicativo, utilizando un diseño de investigación de nivel cuasiexperimental que se desarrolló en un único grupo. Se aplicaron pruebas de pretest y postest para medir los efectos de la estrategia. La estrategia pedagógica se diseñó en torno a un tutorial que incluyó ejemplos relacionados con el concepto de función cuadrática, haciendo uso del software GeoGebra como herramienta de enseñanza. La población sujeta de estudio en esta investigación estuvo compuesta por 20 estudiantes de noveno grado, mientras que la muestra se conformó con 18 estudiantes. Finalmente, se concluyó que la estrategia pedagógica mediada por GeoGebra permitió la apropiación del concepto de función cuadrática bajo los niveles de visualización trabajados. Además, la estrategia logró motivar a los estudiantes y fomentar su participación en clase
Love Thy Neighbor: La Vida Musical De Justo Almario
No full textAl igual que Soul Song, Justo interpreta diversos instrumentos para darle color al dueto: con excepción del saxofón alto, acude a todos los instrumentos de su dominio. En esta ocasión, si bien el disco también está basado en ritmos brasileros, Justo aportó varias composiciones. Una de ellas, como es habitual en él, está dedicada a alguien de su familia, se titula Kendall’s Here, en homenaje a su nieta Kendall. Escuchémosla, para darnos una idea de la música del álbum y disfrutar de su interpretación en la flauta traversa, que hemos incluido poco en los ejemplos de audio hasta aquí seleccionados
Qué costo de deuda debe ser usado para pronosticar los flujos de caja?
No full textFrequently, analysts and teachers
use the capitalized rate of interest
for the cost of debt when forecasting
and discounting cash flows. Others
estimate the interest payments
when forecasting annual financial
statements or cash flows based on
the average of debt calculated with
the beginning and ending balance.
Others use the end of year convention
that calculates the yearly interest
multiplying the beginning balance
times its contractual cost. The use
of one or other methods is critical for the definition of the tax savings.
These approaches are illustrated
with examples and the differences
in using them. A simple proposal to
solve the problem is presented.¿Qué costo de deuda debe ser usado para pronosticar los flujos de caja? Con frecuencia analistas y profesores
utilizan la tasa de interés efectiva
para estimar el costo de la deuda
para pronosticar y descontar los flujos
de caja. Otros estiman los pagos de
interés basados en el promedio de la
deuda calculado con el saldo inicial y
final. Otros más utilizan la convención de final de período y calculan el
interés multiplicando el saldo inicial
de la deuda por su costo contractual.
El uso de uno u otro método es crítico
para el cálculo de los ahorros en impuestos. Se ilustran estos enfoques
con ejemplos y se muestran las diferencias al usarlos. Se presenta una
propuesta simple para solucionar el
problem
Optimal Selection and Integration of Batteries and Renewable Generators in DC Distribution Systems through a Mixed-Integer Convex Formulation
No full textThe problem concerning the optimal placement and sizing of renewable energy resources and battery energy storage systems in electrical DC distribution networks is addressed in this research by proposing a new mathematical formulation. The exact mixed-integer nonlinear programming (MINLP) model is transformed into a mixed-integer convex model using McCormick envelopes regarding the product between two positive variables. Convex theory allows ensuring that the global optimum is found due to the linear equivalent structure of the solution space and the quadratic structure of the objective function when all the binary variables are defined. Numerical results in the 21-bus system demonstrate the effectiveness and robustness of the proposed solution methodology when compared to the solution reached by solving the exact MINLP model. Numerical results showed that the simultaneous allocation of batteries and renewable energy resources allows for the best improvements in the daily operating costs, i.e., about 53.29% with respect to the benchmark case of the 21-bus grid, followed by the scenario where the renewable energy resources are reallocated while considering a fixed location for the batteries, with an improvement of 43.33%. In addition, the main result is that the difference between the exact modeling and the proposed formulation regarding the final objective function was less than 3.90% for all the simulation cases, which demonstrated the effectiveness of the proposed approach for operating distributed energy resources in monopolar DC networks
Optimal Integration of Distributed Generators into DC Microgrids Using a Hybrid Methodology: Genetic and Vortex Search Algorithms
No full textThis paper addresses the problem of optimal location and sizing of distributed generators (DGs) in direct current (DC) grids. To solve it, we propose an optimization approach with an objective function that aims to reduce power losses due to energy transport, while considering all the constraints that represent DC grids in a distributed generation environment. For the mathematical formulation of the problem, we used a mixed-integer nonlinear programming (MINLP) model, which allowed us to evaluate the impact of all possible configurations (i.e., location and size of DGs in the DC network) on the objective function and the constraints. The solution method proposed here is a master–slave strategy that implements a hybrid solution methodology that combines a genetic algorithm (GA) and the vortex search algorithm (VSA). The GA is in charge of solving the location problem in the master stage, and the VSA is responsible for sizing the DGs in the slave stage. To evaluate the effectiveness and robustness of the proposed GA/VSA methodology, we employed two test systems (i.e., 21 and 69 buses) considering a maximum penetration of distributed generation equal to 40% of the power generated by the slack buses. Furthermore, we also implemented nine other hybrid methodologies based on metaheuristic techniques (proposed in the literature for solving the problem addressed here) to make comparisons. All the solution methods used and proposed in this paper are based on sequential programming to avoid the need for specialized software and thus reduce the complexity and cost of the solutions. The effectiveness of the proposed solution was evaluated in two scenarios: (1) peak power demand and (2) variation in power generation and demand associated with photovoltaic generation and user demand in Medellín, Colombia. The results demonstrate that the GA/VSA methodology achieved the best results in terms of solution quality and processing times in all the test scenarios proposed in this study. © 2022, King Fahd University of Petroleum & Minerals
The state of exception due to economic, social and ecological emergency in Colombia
No full textLa Constitución Política colombiana de 1991 consagra tres estados de excepción, los cuales limitan las funciones de algunas ramas del poder público dadas las condiciones que lo ameritan. Estas situaciones son: guerra exterior, conmoción interior y emergencia económica, social y ecológica. Esta última situación fue aplicada en Colombia recientemente para atender coyunturas generadas en el contexto internacional y que tienen impacto en la realidad nacional. Sin embargo, el alcance de estos estados excepcionales no se limita al texto exegéticamente considerado desde una perspectiva legal, sino que debe ser comprendido desde los precedentes establecidos por la Corte Constitucional colombiana en su calidad de intérprete y guardiana de la norma de normas.The Colombian Political Constitution of 1991 enshrines three states of exception, which limit the functions of some branches of public power given the conditions that warrant it. These situations
are Foreign War, Internal Commotion and Economic, Social and Ecological Emergency. This last situation was recently applied in Colombia to address situations generated in the international context and that have an impact on the national reality. However, the scope of these exceptional states is not limited to the text exegetically considered from a legal perspective, but must be understood from the precedents established by the Colombian Constitutional Court in its capacity as interpreter and guardian of the rule of law. Although from a formalist perspective the States of Exception have some requirements, from an anti-formalist perspective they have been hermeneutically expanded by jurisprudence. Thus, in this article are the formal and substantial requirements that from a systematic interpretation must be applied to decree a State of Exception for economic, social and ecological Emergency in Colombia.INTRODUCCIÓN. 1. Delimitación del estado de emergencia económica, social y ecológica en el marco de la Constitución Política Colombiana de 1991. 2. Requisitos formales y materiales desde sentencias hito de la Corte Constitucional aplicables al estado de emergencia económica, social y ecológica. CONCLUSIONES. REFERENCIAS.Análisis de políticas públicasNO APLIC
Information and Communication Technologies (ICT) in the processes of distribution and use of knowledge in Higher Education Institutions (HEIs)
No full textThis research aims to relate Information and Communication Technologies (ICT) in the processes of distribution and use of knowledge in Higher Education Institutions (HEI). The methodology used was based on the quantitative approach, descriptive scope, and non-experimental cross-sectional design, the sample was non-probabilistic, convenience sampling. We used the survey as a technique for data collection, through a questionnaire with Likert and ordinal scales applied to the directors and vice-rectors of research in the research departments. The methodology developed allowed us to show that the profiles of the universities to carry out knowledge management focus on two components: distribution and use of knowledge. © 2021 Elsevier B.V.. All rights reserved
Iron Oxide Powder as Responsible for the Generation of Industrial Polypropylene Waste and as a Co-Catalyst for the Pyrolysis of Non-Additive Resins
No full textFor the synthesis of polymeric resins, it is of great importance to review the raw materials and the equipment to be used to avoid the presence of compounds that may affect the effectiveness of the polymerization and the characteristics of the plastic to be obtained. Iron oxide is a compound that can be present in reactors after maintenance due to the techniques used and the cleaning of this equipment, and it can affect the characteristics of the resins, reducing their quality. In this study, the presence of FeO in different concentrations was evaluated to determine its effects on the properties and pyrolysis of polypropylene resins by using X-ray refraction to determine the elements of the samples, evaluating thermal degradation by TGA, the variation in molecular weight by measuring the MFI, and the compounds obtained from pyrolysis by chromatography. The results showed that the thermal degradation decreased as the FeO concentration increased, while for the MFI, the relationship was directly proportional. The evaluation of the compounds obtained from pyrolysis showed an increase in the production of alcohols, alkynes, ketones, and acids, and a decrease in alkanes and alkenes, showing that FeO affects the properties of polypropylene and the compounds that are produced during pyrolysis. © 2022 by the authors