bluuebunny/crossref_metadata_2025 huggingface dataset:
Análisis comparativo de eficiencias de combustión en un generador de vapor cuando se utiliza gas natural y diesel de caldera
Authors: Amell-Arrieta Andrés , Vélez-Rueda Liliana
Published: July 2024

En este trabajo se comparan las eficiencias de combustión utilizando como combustible gas natural de la Guajira y diesel de caldera, con factores de aireación de 1,07, 1, 16, 1,26, 1,34, 1,45 y condiciones tubos sucios y lim­pios, como resultado de ensayos en una caldera pirotubular dual de 30 BHP. Se encontró que la eficiencia de combustión con base en el poder calorífico superior en condición de tubos sucios resultó mayor para el diesel de caldera en valores que oscilan entre el 3,2 y 4,5% dependiendo del factor de aireación. Cuando se compara la condición de tubos limpios para el gas natural y sucios para el diesel, la eficiencia sigue siendo mayor para este último pero la diferen­cia porcentual disminuye significativamente. La eficiencia con base en el poder calorífico inferior y condición tubos lim­pios, resultó mayor para el gas natural con diferencias porcentuales que osci­lan entre 3 y 5,2% dependiendo del factor de aireación. Con estos resultados se demuestra cómo la composición y naturaleza del com­bustible tiene una fuerte incidencia en la eficiencia de combustión.
Regulación del voltaje en estado estable mediante compensación reactiva controlada
Authors: Vinasco Guillermo
Published: July 2024

El presente artículo revisa el concepto de compensación paralela controlada, y desarrolla un modelo analítico simple (pero muy genérico y útil) para ella. Este modelo permitirá el estudio y análisis en estado estable, útil para problemas como el del dimensionamiento óptimo de compensación reactiva para una carga, en el cual pueden requerirse estrategias combinadas de compensación serie-paralela .
Balance energético y estimación de contaminantes atmosféricos emitidos en el Valle de aburrá, 1999: una aproximación inicial
Authors: Molina-Pérez Francisco , Saavedra-Duque Marcelena , Obregón-Cardona Mauricio
Published: July 2024

Resumen A partir de la aplicación del análisis de flujo de materiales, el trabajo realizado presenta la composición de la canasta energética del Valle de Aburrá durante 1999 y las emisiones atmosféricas generadas por el consumo de dichas sus­tancias. Globalmente, se encontró que el sistema consumió 43,2 teracalorías diarias y generó 716 toneladas de contaminantes al día. Los resultados obteni­dos indican la participación mayoritaria de los energéticos consumidos por el sector transporte (gasolina y ACPM) en el metabolismo del sistema, por tanto el sector transporte aporta la mayor carga contaminante representada por el monóxido de carbono, el cual corresponde al 77,6% de toda la contaminación emitida.
Caracterización de magnetitas sintéticas dopadas con aluminio y cerio mediante difracción de rayos X
Authors: Conrado-Suárez Luis , Barrero César , Minotas Julio
Published: July 2024

Desde el punto de vista de la corrosión, los óxidos de hierro presentan gran importancia por ser constituyentes de la capa de herrumbre que se forma sobre el acero al ser expuesto en el ambiente. La magnetita es uno de dichos productos y de allí el interés científico que tiene su conocimiento. En el presente trabajo se muestran los resultados de un estudio realizado utilizando la técnica de difracción de rayos X (DRX) sobre magnetitas obtenidas mediante síntesis hidrotermal en presencia de iones Al+3 y Ce+3 en porcentajes de 0, 1, 5 y 10% mol. Se determinó la dimensión de la celda unidad y el tamaño del dominio coherente en la dirección [311], usando la ecuación de Scherrer. Se encontró una disminución en el valor del parámetro de celda con el incremen­to de aluminio adicionado. En los patrones de los productos que fueron sinte­tizados en presencia de 5 y 10% nominal de cerio, se encontraron otras fases que fueron identificadas como goethita y óxido de cerio (CeO2), mostrando el cerio un carácter promotor de la formación de goethita.
Reducción coulométrica de productos de corrosión de cobre en ambientes de ácido acético y ácido sulfhídrico
Authors: Echavarría Alejandro , Vieira-Aoki Idalina , Vilca-Meléndez Hugo
Published: July 2024

En ambientes contaminados, es normal encontrar cantidades elevadas de com­puestos gaseosos tanto orgánicos como inorgánicos. Los compuestos orgáni­cos de ácidos volátiles (principalmente acético y fórmico) contribuyen significativamente a la agresividad del ambiente. Por su parte, el ácido sulfhí­drico es otro poderoso contaminante capaz de producir productos de corro­sión en el cobre tanto en ambientes secos como húmedos. El presente estudio muestra los resultados de la caracterización de los productos de corrosión al exponer muestras de cobre en una corriente de aire con diversos contenidos de ácido acético (HAc) y ácido sulfhídrico (H2S) a 80% de humedad relativa y 30 ºC, empleando la técnica de la reducción coulométrica. Particularmente se encontró que los productos de corrosión son cuprita (Cu2O) y tenorita (CuO) en los ambientes no contaminados o contaminados con HAc (hasta 400 ppbv). El espesor de estos compuestos crece con un aumento en el con­tenido de HAc. En el caso de la mezcla con HAc (200 ppbv) y H2S (400 ppbv) se detectaron, aparte de la cuprita y la tenorita, dos nuevos compuestos: CUiS y uno denominado X (no identificado). De todas las condiciones evaluadas en el presente estudio, esta combinación resultó ser la más agresiva.
Juicio a la Facultad de Ingeniería por sus egresados
Authors: Restrepo-González Guillermo , Mejía-Vélez Luis Fernando , Parra-Mesa Carlos Mario , Ochoa-Ángel Jaime , Muñoz-Ortíz Luz Dary
Published: July 2024

Con base en un estudio de campo, con utilización de metodologías cuantitativas y cualitativas, se presentan las percepciones sobre los programas académicos de pregrado de la Facultad de Ingeniería de la Universidad de Antioquia y sobre el desempeño de sus egresados, para una muestra de los graduados entre 1995 y 1998. No obstante el buen concepto sobre el ambiente académico de la Facultad de Ingeniería, los egresados identifican una facultad con énfasis en lo teórico, lo técnico y académico, pero con debilidades en la formación personal y en las relaciones con el sector productivo. Juicios severos sobre otros aspectos vitales en la formación de los ingenieros hacen pensar en la necesidad de estrategias innovadoras en la formación profesional de los ingenieros de la Universidad de Antioquia.
Cold production from magnetic fields. Part II: Thermodynamic analysis
Authors: Velásquez Juan Esteban , Chejne Farid , J. Hill Allan F.
Published: July 2024

In magnetic refrigeration a magnetic material undergoes temperature changes or heat interchanges with the environment when it is placed in a strong magnetic field. In this paper, a conventional cycle for magnetic refrigeration is analyzed. Expressions for the released and absorbed heat and the temperature changes at the different stages of the cycle are obtained from the first law of thermodynamics. Also, by means of the second law of the thermodynamics, equations for the work done, entropy change and ideal performance coefficient are obtained as a function of temperatures and magnetic material properties.
Measurement of electrode potential in oil in water emulsions
Authors: Echeverría Félix , Peña Darío , Vásquez Custodio
Published: July 2024

This study was performed taking into account the problems found when common reference electrode systems like SCE with a satured KCl bridge are used. Tests were carried out to establish the most appropriate reference electrodes for measurement of electrode potentials in emulsions kerosene in water. Four reference cells were tested, looking for compatibility between aqueous and oil phases inherent to the nature of these emulsion systems. The cell SCE/Sat KCl/Agar 3% + 0,1 M KCl// was taken as reference cell. The corrosion systems studied were aqueous solution of satured KCl, aqueous solution containing 1.000 ppm of anionic surfactant (GR-7M) and kerosene in water emulsions with 5, 20, 40 and 60 weight per cent. The cell //AgarGR7M (1%)/GR7M (1%)/SCE was chosen due to its long stability with time and small joining potentials.
Macroporous hydroxyapatite obtained in the Universidad de Antioquia: synthesis, characterization and comparison with the spongy calcined bovine bone
Authors: López María Esperanza , Echavarría Alejandro , Suárez Ricardo , Herrera Natalia
Published: July 2024

Macroporous blocks of hydroxyapatite were obtained and they were characterized by atomic absorption, x-rays diffraction, infrared and electronic microscopy SEM. The macroporosity was induced with three natural macroporous agents: montanoa quadrangularis, asparagus ofssicynali and zea may, An experimental design was used for hydroxyapatite synthesis with these agents. The macroporous blocks were compared with the spongy calcined bovine bone, the best results were obtained with the block elaborated with zea mays. The block presented the following characteristics: hardness in the Mohs scale of 2,5-3,0; total porosity by water absorption: 85% in volume; porosity by image analysis: 18,61% in area; maximum diameter of pore: 1.048 µm; modulus of rupture: 6,35 Kg/cm2 ; Ca/P relation: 1,65 and density: 3,11 g/cm3 .
The electricity before Faraday
Authors: Poveda-Ramos Gabriel
Published: July 2024

This document is a paper describing the appearance and development of the electrical science since the early human history until the times of Michael Faraday at the beginning of nineteenth century. It is writen with the pourpose of adding it to another paper already writen by the author on the history of magnetism in the same period.
Transformation the contunuum current vehicles actuated by a chopper in alternating current actuated by frequency converter and asynchronous power engine
Authors: Bele Ioan , Bocîi Liviu Sevastian
Published: July 2024

The present work shows the methodology and the conditions that have to be fulfilled to transform the continuum current vehicles actuated by a chopper into alternating current vehicles actuated by frequency converter and asynchronous power engine. In both systems the speed regulation is done through a programmable actuated system. But, for the first system the speed regulation is done by chopped impulses command, while for the second one the regulation is made by current tension and frequency modification.
A part of programmable automatically actuation system is unchanged, particularly: the auxiliary equipment command and surveillance for the main switch, lines and network contact devices, as wlle as the signal displays for speed, current and tension.
Other programmable actuated system tasks are totally changed: controlled rectifier diode or transistors command, current information, some components and equipment are eliminated and other could be located directly on the frequency converter.
Concluding, the passing from continuum current vehicles actuated by a chopper system to alternating current actuated by frequency converter and speed actuation by a frequency converter, could be done in a inrelatively easy manner if an exact function analysis is done of the the command and regulation equipment.
College of Engineering, University of Antioquia from 1814 to the 1980 decade
Authors: Gaviria-Ortiz Álvaro , Valencia-Giraldo Asdrúbal
Published: July 2024

In the year 2003, the College of Engineering of the University of Antioquia arrives to 60 years from its more recent foundation; this is so, because this College was the first School of Engineering in Colombia and really has a long history that goes back to the Independence times. In fact, at the end of August, 1814, in Medellín, the first Colombian Academy of Military Engineers was inaugurated, under the guidance of “coronel injeniero general”, Francisco José de Caldas, and functioned up to September 25, 1815. So, the evolution of our College is quite long and deserves to be related and kept in the common memory. For that reason, this anniversary is a good excuse for a brief presentation of the history of an entity that now enters its third century of existence. In this first issue an account is done from its very beginning up to 1980 decade.
College of Engineering, University of Antioquia from the 1980 decade up the future
Authors: Valencia-Giraldo Asdrúbal , Gaviria-Ortiz Álvaro
Published: July 2024

In the year 2003, the College of Engineering of the University of Antioquia arrives to 60 years from its more recent foundation; this is so, because this College was the first School of Engineering in Colombia and really has a long history that goes back to the Independence times. In fact, at the end of August, 1814, in Medellín, the first Colombian Academy of Military Engineers was inaugurated, under the guidance of “coronel injeniero general”, Francisco José de Caldas, and functioned up to September 25, 1815.
So, the evolution of our College is quite long and deserves to be related and kept in the common memory. For that reason, this anniversary is a good excuse for briefly present this history of an entity that now enters its third century of existence. In this second issue an account is done from the 1980 decade up to the future.
Statistic assessment of the factors that take part in the corrosion on buried pipe
Authors: Delgado Lastra Juan , Calderón Gutierrez Jorge Andrés , Peñaranda Arciniegas Sergio Luis , Restrepo Alex
Published: July 2024

Corrosion of buried pipes is a phenomenon that depends more on the corrosivity of the ground than on the nature of the metal. The evaluation of the corrosivity of the ground is a complex activity because there are many variables influencing the process. In this work a multivariate analysis of the main factors taking part in corrosion of buried structures was carried out. This analysis allows a factorial classification and permits the transformations of a set of correlated variables into a smaller set of not correlated variables. This study gives a better understanding of data of the experimental units and determines the variables of major influence over the variable response. With this information a smaller number of variables could to be measured. This paper describes the experimental techniques used and the statistics analysis realized of the 6 variables measured in the experimental units. A new set of 3 variables is obtained, which allows a classification of the soils according to corrosivity with a confidence of 90% and an error of 20%.
A proposal for semiautomatic recognition of operations using a linguistic approach
Authors: Jaramillo Franco Aldrin Fredy , Zapata Jaramillo Carlos Mario , Arango Isaza Fernando
Published: July 2024

In the context of the process of software development automated recognition of class operations from textual descriptions of a system is an open research topic. This paper presents a proposal to deal whit this problem, which is based on Sowa’s conceptual graphs and a linguistic treatment of their components; this treatment is based on verb classification identification from three features: telicity, dynamism and durability
The social and humanistic education in the undergraduate engineering programs of the Universidad de Antioquia
Authors: Valencia Giraldo Asdrúbal , Mejía Vélez Luis Fernando , Parra Mesa Carlos Mario , Ochoa Ángel Jaime , Restrepo González Guillermo
Published: July 2024

A research project was carried out in order to detect the general perception about the social and humanistic formation in the undergraduate engineering programs of Universidad de Antioquia. Quantitative and qualitative research methods were employed. This paper presents the results obtained, as well as some proposals to give an answer to the detected problem.
Occupational profile in the Telecommunications sector and the educational offer in Colombia
Authors: Teuta Gómez Guillermo
Published: July 2024

This article presents the most significant results obtained from a survey that was carried out in 26 companies (local operators, long distance operators, cellular operators, TVC operators, internet service providers and technology suppliers), intending to generate an occupational characterization of the Telecommunications sector in Colombia. It is supplemented with an analysis of the educational offer that existed in Colombia, until December 31, 2002. The purpose is to invite the academic community to begin a deep reflection regarding the policies adopted by the State and the role that the educational institutions should be play in the development of human resources in this sector.
Is biogasoline an environmentally-acceptable alternative in Colombia?
Authors: Ocampo Duque William Andrés
Published: July 2024

Colombian government is currently promoting the commercialization and use of biogasoline in the country; this process started on November 1, 2005. Biogasoline (gasohol or E10 blend) is an ethanol-gasoline blend with 10 v/v % of ethanol. Ethanol is being produced by fermentation of sugarcane, maize, wheat or cassava crops. Both the government and the ethanol manufacturers have defended the potential of biogasoline in reducing the environmental deleterious effects that result from the use of fossil fuels in the transportation sector. However, there is scarce evidence in the scientific literature of favorable environmental impacts due to the use of gasoline oxygenated with 10 v/v % ethanol. Moreover, there is a worldwide controversy about using this type of modified fuel. A detailed scientific review showing the questionable environmental benefits of ethanol-gasoline blends is presented in this work. Potential release of highly toxic pollutants, contribution to the formation of photochemical smog and greenhouse gases, environmental sustainability, and groundwater pollution risk issues resulting from the deployment of E10 fuels are widely discussed.
Hydrodynamics in stirred vessels with flat-bladed disk-style turbine
Authors: García-Cortés D. , Jáuregui-Haza U.
Published: July 2024

The flat-bladed disk-style turbines are the radial flow impellers more widely used in industry because they can be implemented to obtain this flow pattern in the in the standard geometric configuration of stirred tanks. The detailed study of the hydrodynamics in this agitation system is very important in order to obtain the basic knowledge required both for the operation and mathematical modelling of different complex processes carried out in the stirred tanks, such as the spherical crystallization. The aim of this paper is to review the published information on hydrodynamics and mathematical modelling of the fluid dynamics in stirred tanks by flat-bladed disk-style turbines, pointing out the advances as well as the topics that need further research.
Rapid manufacturing technologies. Part 1: Optimization and improvement of rapid tooling technology-Coproinmold
Authors: Serres Moliner Esther , Coba Salcedo Milton
Published: July 2024

Making pieces directly from a CAD model is considered an important method for reduction of production time and manufacturing costs of new products. Rapid prototyping techniques are a way of producing conceptual models in a quick and simple fashion. Rapid tooling is the method of producing tools of general use, aimed specifically at obtaining small and medium series of pieces. This article studies the optimization of Coproinmold technology for obtaining molds for plastic injection.
Grounding transient response of lightning protection GTIERRAS software
Authors: Gómez Montoya Héctor David , Velilla Hernández Esteban , Moreno Ospina Germán , Valencia Velásquez Jaime Alejandro
Published: July 2024

A computer program developed in Matlab (GTIERRAS) from an electromagneticbased model is used to assess grounding impedances and the behavior of grounding electrodes of arbitrary shapes under lightning impulses. Impedance, currents and voltages, or other electric variables of the grounding system can be presented as well in frequency or in time domain with the use of Fast Fourier Transform. The generality of the model allows its use for assessing lightning overvoltages, but also for other typical transients associated with electromagnetic compatibility problems. Results show the influence of some variables on the response of grounding system and shed light on some differences that must be taken into account when applying criteria based on low frequency performance to groundings stressed by surges. Calculation examples and comparison with results from other authors are presented and analyzed so as to illustrate some grounding behaviors that by no means are evident. Effects of electrode geometry and soil resistivity, as well as of wave front and number of injection points are also investigated. Results of touch and step potentials are shown. A study of a lightning protection system is presented as an extension of the model application capabilities. Some conclusions useful for grounding system design are derived.
Characterization of mechanical properties and micro-structural features of welds used for rebuilding shafts
Authors: Cerón Bolaños César , Rivas Murillo John Sandro , Coronado Marín John Jairo
Published: July 2024

Mechanical properties and micro-structural features of welded metal and heataffected zone (HAZ) of three welding processes used to rebuild worn shafts in sugar cane mills were analyzed. For two welding processes the following characteristics were observed in the HAZ: presence of ferrite in the grain boundary, higher grain growth and Widmanstaetten structure, features that reduce steel toughness. A weld ranking was established from mechanical properties obtained by both tension and Charpy impact tests.
Reliability analysis of cutting tools applied to drilling process
Authors: Patiño Rodríguez Carmen Elena , Martha de Souza Gilberto Francisco
Published: July 2024

This study presents a theoretical reliability analysis of mechanical manufacturing process of a cutting tool subject to flank wear. The process reliability is a statistical relation between cutting tool, operator and machine-tool. The cutting tool life is modeled with a probability function representing the chance that a critical wear magnitude is achieved in a given time period. Parameters for this probability function are calculated based on experimental analysis, as well as on reliability of a cutting tool.
Mathematical model for the combustion phenomena in a cupola furnace
Authors: Aristizábal Sierra Ricardo Emilio , Mejía Arango Héctor Daniel , Silva Claudia , Pineda Arango Diego Alfonso , Rojas Arango Juan Marcelo
Published: July 2024

Se presenta un modelo matemático que describe los fenómenos de combustión en un horno de cubilote. La construcción del modelo se realizó con base en las reacciones heterogéneas coque-gas más importantes; es decir, la reacción de combustión, la gasificación por CO2 y la gasificación por vapor de agua. Se usó el programa Matlab versión 5.3 y los resultados de la simulación se compararon con los datos experimentales obtenidos en el horno de cubilote de la planta ecoeficiente de la Universidad de Antioquia. El modelo proporciona los perfiles de composición de los gases en la columna del horno, la composición de los gases en chimenea y la velocidad de carga del metal durante la operación. Las desviaciones máximas obtenidas con el modelo fueron menores de 1% para CO2, 5% para CO, 7% para la relación de combustión y 9% para la velocidad de carga del metal.
Environmental impact assessment for ethanol production process using the waste reduction algorithm
Authors: Montoya Ramírez María Isabel , Quintero Suárez Julián Andrés , Sánchez Toro Oscar Julián , Cardona Alzate Carlos Ariel
Published: July 2024

The environmental performance of ethanol production from maize and sugar cane was evaluated. Process simulation was initially conducted using the commercial process simulator Aspen Plus. After mass and energy balances, analysis of the environmental impact was carried out using the waste algorithm reduction (WAR), which evaluates the environmental friendliness of each process. It was found that ethanol production from maize shows a lower potential environmental impact than that from sugar cane. The larger environmental impact of both processes occurs in the aquatic toxicity category, primarily due to high organic charge of the stillage produced.
Use of a biological additive to enhance the physical-mechanical and thermal properties of concrete
Authors: Sánchez Henao Claudia Patricia , Jiménez Castrillón Diego Andrés , Ruiz Múnera Jorge Ignacio
Published: July 2024

The effect of the addition of a biological ingredient composed primarily of calcific bacteria (T. ferroxidans, T. thioxidans, Desulfovibrio and Sulfolobus acidularios) on the properties of concrete is studied. The biological additive was synthesized based on native cultures in a nutritive medium (modified 9K medium), 2.5 ≤ pH ≤ 3.0, at room temperature in a 30 L bioreactor. Cylinders of concrete containing 30, 60, and 100% of the biological additive were prepared using different aging times (7 and 28 days) in order to determine the technical feasibility of the mixture. The mixture of concrete was prepared using a cement to sand to gravel ratio of 1:2,3:3 and a water to cement ratio of 0.56:1. The sample without biological additive was used as the reference. The main findings are: an increase of 17.2% in resistance was observed in the sample with 30% biological additive (14.63 ± 2.11 MPa and 15.17 ± 0.85 MPa at 7 and 28 days, respectively); the percentage of pores and their diameter decreased by 39% and 46%, respectively, in the sample with 30% biological additive (porosity: 0.91%, pore diameter: 144.7 µm); thermal conductivity decreased in all samples containing the biological additive (the best behavior was obtained in the sample with 30% biological which displayed a 50% reduction in thermal conductivity: 0.33W/m K); Durability to nitric acid indicates that weight lose was larger for the reference probe than
Dynamic topology generation of an artificial neural network of the multilayer perceptron type
Authors: Tabares Héctor , Branch John , Valencia Jaime
Published: July 2024

This paper deals with an approximate constructive method to find architectures of artificial neuronal network (ANN) of the type Multi-Layer Percetron (MLP) which solves a particular problem. This method is supplemented with the technique of the Forced search of better local minima. The training of the net uses an algorithm basic descending gradient (BDG). Techniques such as repetition of the training and the early stopping (cross validation) are used to improve the results. The evaluation approach is based not only on the learning abilities but also on the generalization of the specific generated architectures of a domain. Experimental results are presented in order to prove the effectiveness of the proposed method. These are compared with architectures found by other methods.
Compocasting of the ZA-27 alloy, reinforced with SiC particles
Authors: Martínez Hader Vladimir , Valencia Marco Fidel , Chejne Farid , Cruz Javier
Published: July 2024

Results obtained during the synthesis of ZA-27/B-SiC/xxp metal matrix composites are reported. These results are in line with other works conducted by the authors on ZA-27/C/xxp, Pb-Sn20%wt/SiC/xxp and Al-Cu8%wt/SiC/xxp. There are many kinds of commercially-available reinforcement particles. Nevertheless, for this research β-SiC particles obtained from wastes of rice husk have been used. The technique employed for fabrication of composites was Compocasting. It consisted on the design and construction of an experimental rheocaster, useful for semi-solid as well as particulate metal matrix composites processing. The characterization by mechanical tests and optical microscopy and comparison with the base alloy, allowed validation of the effects of different process variables and improvements in mechanical properties.
Production and mechanical characterization of a reinforced polyurethane compound from castor oil and polymeric MDI using the poltrusion forming method
Authors: González Francisco , Cadavid J. G.
Published: July 2024

Polyurethane is a compound that is produced by the reaction of a diisocyanate and a polyol. Taking advantage of the high reactivity of polymeric diphenyl-methanediisociante (MDI) urethanic groups are formed with the ricinoleic acid provided by castor oil, obtaining a polyurethane with a shore D 45 hardness. This polymer forms a reinforced compound with the type E glass fiber using the poltrusion forming method. Poltrusion is a continuous forming process that is employed in the industrial scale production of polyester resins and releases high emissions of organic volatile compounds (VOC) to the environment. In this work we propose a more efficient alternative with a renewable raw material like castor oil, minimizing VOC emissions to the environment; the interaction between polyurethane and glass fiber in the production of a composite material with a high chemical resistance and excellent mechanical properties, associated with the synergy between glass fiber and polyurethane, is also studied.
Influence of ionic bombardment on cubic boron nitride (c-BN) thin film deposition by r. f. magnetron sputtering
Authors: Bejarano Gaitán Gilberto , Roque Caicedo José Manuel , Prieto Pulido Pedro , Zambrano Gustavo , Baca Miranda Eval
Published: July 2024

Thin films of cubic Boron Nitride (c-BN) were deposited by d. c. and r. f. (13,56 MHz) multi-target magnetron sputtering from high-purity (99,99 %) hexagonal boron nitride (h-BN) target, in an Ar (95%)-N2 (5%) gas mixture. Films were deposited at 300 and 900 oC, with power density of 7 and 24 W/cm2. In order to obtain the highest fraction of the c-BN phase, a d. c. substrate bias voltage between 0 and -250 V, as well as an r. f. substrate bias voltage between 0 V and 350 V were applied during the film growth. Characterization of the microstructure, composition, morphology, topography and thickness of the films was carried out by Fourier Transformed Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Atom Force Microscopy (AFM). It was found that BN films deposited at 300 oC, at a pressure of 4 x 10-3 mbar and under -150 V of r. f. bias, applied for 35 min, presented the highest c-BN fraction, close to 85%.
Electrochemical assessment of weathering steels under simulated laboratory conditions
Authors: Jaramillo Beatriz , Calderón Jorge Andrés , Castaño Juan Guillermo
Published: July 2024

In the last decades weathering steels have became important structural materials in the construction of civil works due to their low rate of corrosion when exposed to urban and industrial atmospheres. The excellent anticorrosive properties of the weathering steels have been attributed to the nature and structure of the rust formed on the material surfaces when certain favorable conditions are present. In  this work a study of the characteristics of the rust initially formed on weathering steels is presented. The study was performed on weathering steels of different nature and different surface conditions: nude, pre-rusted and galvanized, and exposed to conditions that simulate urban and industrial atmospheres. The analysis was carried out by means of electrochemical techniques, such as evaluation of the open-circuit potential and electrochemical impedance during the first two months of exposure.
Metallurgical and electrochemical properties of an Au-1,7% Ti alloy for dental applications
Authors: Sánchez Hector Darío , Calderón Jorge Andrés , Echavarría Alejandro , Morales Lina
Published: July 2024

The micro-structure and micro-hardness of an Au-1,7%Ti alloy in different condi¬tions: centrifuged, solubilized and aged at 400°C during 4 hours were evaluated. Polarization curves obtained in an artificial physiological solution (Ringer) of the Au-1,7% Ti alloy, with and without surface passivation treatment, were compared to those of an Au-Pd-Ga-In alloy and pure gold. Results indicate that the Au-1,7% Ti alloy has a good response to the aging treatment in the passivated condition the alloy alsopresents a satisfactory, although lower, corrosion resistance with respect to the Au-Pd-Ga-In alloy.
Theoretical evaluation of radio noise and audible noise in transmission lines
Authors: Velilla Hernández Esteban , Moreno Ospina Germán , Escobar Carlos A.
Published: July 2024

One of the most important effects in transmission lines (TL) is the corona effect, which is the cause of related phenomena like radio noise (RN) and audible noise (AN). The magnitude of such phenomena increment their magnitude with the increase of operating voltages, therefore rising the likelihood of affecting or interfering with human beings or equipment. It is possible that, due to the electromagnetic properties of the environment surrounding TL’s, problems of electromagnetic compatibility arise. A software (CERARI) that allows the evaluation of noise levels generated in the vicinity of the transmission lines was developed using Matlab and is presented in this paper.
Oxidative Dehydrogenation of Propane using a Manganese Molybdate
Authors: Echavarría Vera Juan Carlos , Palacio Santos Luz Amparo
Published: July 2024

A manganese molybdate (MnMoO4) was synthesized, characterized and used in the oxidative dehydrogenation of propane. It was found that the crystalline structure is the same before and after the reaction. The reaction was carried out in the 400-600 o C temperature range, with a space velocity between 50 and 150 ml/g.min. Propane conversion of 29,4%, with 25% selectivity to propene, was observed when the reaction was conducted at a space velocity of 150 ml/g.min and temperature of 600 ºC. Reaction products were the corresponding unsaturated hydrocarbons, CO, and CO2. Only a small part of the propane was cracked to ethylene and methane.
Mechanical, thermo dynamical and environmental comparison of engines using natural gas and gasoline
Authors: Agudelo Santamaría John Ramiro , Bedoya Caro Iván Darío , Moreno Sánchez Ricardo
Published: July 2024

This paper shows experimental results of a Toyota Hilux 2400 swept volume, compression ratio 9:1 engine, operating with La Guajira natural gas and petrol. Also shows a thermodynamic study of those fuels in a normalized, variable compression ratio ASTM-CFR monocylinder engine. When using natural gas, Hilux engine increases its fuel consumption around 20% for the same power. Volumetric efficiency increases 10% and CO emissions decrease around 40%. When comparing thermodynamic parameters in CFR engine operating at a compression ratio of 9:1, it was found a 12,5% decrease in indicated power and 17% in maximum combustion pressure, which is proportional to temperature diminish of around 20%. Convective heat transfer coefficient decreases around 28% respect to petrol. First laminar combustion phase is duplicated when using the same spark advance as petrol, nevertheless this is maintained almost constant when spark is advance 15º over petrol spark advance.
Phenol hydroxylation over copper modified ZSM-5 catalysts
Authors: Caro Muñoz César Augusto , Villa Holguín Aída Luz , Montes de Correa Consuelo
Published: July 2024

Several CuZSM-5 catalysts were prepared by hydrothermal synthesis from gels containing different Si/Al and Si/Cu ratios; methylamine or sodium hydroxide were used as mineralizing agents. Catalysts were characterized by DRX, IR, BET, UVVIS and chemical analysis. Catalysts activity were evaluated in the hydroxylation of phenol with H2O2. The catechol (CAT)/(hydroquinone (HQ) + p-benzoquinone (PBQ)) ratio increased either by increasing H2O content and reaction temperature, lowering catalyst amount, or decreasing catalyst Si/Al ratio. The production of p-benzoquinone (PBQ), resulting from hydroquinone oxidation, was minimized when reaction conditions were: 80 ºC, phenol: 1 mmol, phenol/H2O2 molar ratio: 3/1, catalyst: 20 mg, and water: 5 g, reaction time: 4 h.
Dioxins and furans in fly ashes from an incinerator
Authors: Cobo Marta Isabel , Hoyos Andrés Emilio , Aristizábal Beatriz , Montes de Correa Consuelo
Published: July 2024

The amount of dioxins and furans in fly ashes from a medical waste incinerator was determined following the US EPA 8280A protocol. Dioxin emissions in both particulate matter and exit gas stream from the incinerator’s chimney were estimated. Furthermore, the role of several operating conditions: residence time, combustion temperature, metal content, and oxygen levels, as possible factors leading to dioxin formation are discussed. Some useful recommendations to improve the process of incineration of medical residues are also outlined.
Coulometric determinations on copper samples exposed to low content propionic acid vapor environments
Authors: Echavarría Alejandro , Ruiz Rodolfo , Echeverría Félix , Arroyave Carlos , Cano Emilio
Published: July 2024

In the present study the effect of three propionic acid vapor concentrations (260, 380 and 680 parts by billion in volume, ppbv) on the deterioration of copper was evaluated in an air stream at 30 °C and 90% of relative humidity, using the coulometric reduction technique for the determination of the total charge required to reduce the formed copper compounds, according to ASTM B-825-97. The electrochemical tests were performed on samples exposed during 7, 14 and 21 days. In addition, gravimetric determinations for the samples with 21 days of exposure were made, according to ASTM G1-90, in order to compare these results with the electrochemical results. The corrosive environments were performed in a climatic chamber with both temperature and relative humidity electronic controls. A constant air flow 4 of L/min was maintained during the tests. The polluting agent was added to the air stream by means of emission tubes of propionic acid vapor with different emission openings. All emission tubes were gravimetrically certificated at 2650, 3750 and 6900 ng/min. The results showed statistical differences (with 95% confidence) for the charge needed for the total reduction of oxides formed on the samples with 7 and 21 days of exposure and it was found that this charge also increases with the polluting agent level, indicating that the corrosion products grow continuously with exposure time and with the increase in the propionic acid vapor concentration. In the other hand, it was found that the coulometric reduction technique is more reliable than the gravimetric test in order to evaluate the corrosion rate in these atmospheres, typical of environments of very low aggressiveness. On the gravimetric technique, the inherent removal of base metal as a result of the acid pickling procedure was in the same order of magnitude with respect to the effect of the corrosion process, leading to a high dispersion of the results.
Effect of two heavy metals, cadmium and nickel, on the organic load removal efficiency in a laboratory UASB reactor
Authors: Forero Luis Eduardo , Sierra Jorge Humberto
Published: July 2024

Experiments were carried out in three up flow anaerobic sludge blanket, UASB, reactors each with 3 L capacity, four hours of hydraulic retention time, (HRT) and volumetric organic load of 4,8 g/L/d. After the initial start phase, which was of 4.000 hours for the three reactors, they were affected in the following way: the first reactor was continuously feed with 5 mg/L of cadmium chloride, the second one was continuously feed with 10 mg/L of nickel chloride and the last one was not affected and served as reference. Efficiency in organic load removal was measured as oxygen chemical demand (OCD), the first reactor changed from 60% in the start phase (phase one) to 18% in the cadmium affected phase (phase two), efficiency in removal (OCI) in reactor two varied from 60 to 24% and the last one did not change in a noticeable manner. Reactor one accumulated cadmium in the mud, whereas reactor two did not do that with nickel.
Influence of the configuration of conversion kit on the performance of a bifuel gasoline-vehicular natural gas spark ignition engine
Authors: Agudelo John Ramiro , Moreno Ricardo , Bedoya Iván Darío
Published: July 2024

This article presents the results of an experimental study made on a Toyota Hilux 2.400 cm3 motor, for determining the influence on environmental-mechanical performance (fuel consumption, volumetric efficiency, equivalence ratio, the concentration of CO and CH4) when the dimensions of the kit components are modified. The factors evaluated were: size of the regulator, diameter of the Venturi in a fixed mixer and its location (in the admission duct and on the carburetor). The motor was tested in five different operating conditions (secondary factor). The effect of the statistic factor on environmental-mechanical performance was determined by using a multifactor experimental design and variance analysis. The respective validation of the statistic suppositions (no autocorrelation and homoscedasticity) complements the analysis. The behavior of these variables showed a marked influence of the size of the regulator and the location for the mixer in the fuel consumption and in the concentration of CO (combustion process), while the diameter of the venturi mixer affects considerably the concentration of CH4 (incomplete combustion).
The electricity before Faraday. Part 2
Authors: Poveda Ramos Gabriel
Published: July 2024

This is the second and final part of this paper. The first part appeared in the former issue. This part deals with the period of the so-called Modern Age after the Renaissance, until the times of Faraday. Here the discoveries and inventions in the theory and practice of electricity made in that period are presented. Today they constitute a very important part of that science with the name of electrostatics. This final part reaches to Faraday because this great scientist merged in one body of knowledge two aspects: electricity and magnetism.
Training soft skills in Russian language classes with foreign students of economic specialties
Authors: Il’ina Natal’ya O.
Published: July 2024

The paper is devoted to the problem of soft skills development when working with foreign students in the course of Russian as a foreign language. It is known that soft skills are currently being actively introduced into the learning process at all levels of education. In this regard, it is necessary to include tasks for the development of soft skills in the educational process of foreign students in classes on the scientific style of speech and the language for specialty purposes. The purpose of this study is to analyze methodological approaches and develop tasks that meet the communicative needs of foreign students receiving Russian education and, therefore, acquiring soft skills in the main subjects of their field of study. The research offers options for tasks for soft skills development for foreign students studying economics. The work also analyzes the importance of teamwork, which helps to create the most comfortable atmosphere that facilitates free exchange of opinions and the active participation of all students in classroom activities. The paper draws attention to one of the most effective techniques for developing soft skills, namely, gaming technology. With the help of an educational game in classes on Russian as a foreign language, you can solve a number of complex problems that contribute to the development of the skills in question. In conclusion, the author focuses on the fact that despite the absence of Soft Skills competencies in the list of competencies listed in the federal state requirements for Russian as a foreign language, it is necessary to look for methodological techniques and forms of work, develop exercises and tasks for the formation and development of soft skills, so as dictated by the communicative needs of foreign students receiving education in the Russian Federation.
Application of the project method in foreign language teaching in the training of master’s degree students at a non-linguistic university (exemplified by «foreign language in the field of professional communication»)
Authors: Grigorieva Viktoria G. , Nazarova Natalia
Published: July 2024

Introduction of new areas of master’s programs in a non-linguistic university sets challenges for foreign language teachers to optimize the language training of the students. The article describes the experience of using a practical-oriented method in teaching the discipline «Foreign Language in the Professional Sphere» to Master’s Degree students of «Management of Museum and Exhibition Activities» at the Samara State Institute of Culture. The preparatory stage of the project activity involved updating the necessary language material based on authentic text and video sources. The next stage was introduction of the Master’s Degree students to exposition and exhibition activities and the latest technologies in museum business on the basis of the Samara «E.A. Ryazanov Museum», which was completed with an excursion conducted by the Master’s Degree students in English. During the next stage, a survey was prepared and carried out among the undergraduate Bachelor students studying museum business on the topic of the project. The final stage of the work was the assessment of the project activities in the form of the participants’ survey regarding the positive impact of the project method on the development of language skills and on the formation of universal and professional competencies.
Pedagogical culture development of the teacher of the future: scientific and practical point of view
Authors: Kochemasova Lyubov’ A.
Published: July 2024

The need for scientific understanding and rethinking of modern problems in the theory and practice of education, as well as their adequate understanding and search for their effective solutions cannot be achieved without turning to the pedagogical heritage of the American pragmatist philosopher, sociologist and political scientist, psychologist and teacher, outstanding scientist and public figure John Dewey. In 1988, UNESCO recognized him as one of the four people who defined the way of pedagogical thinking in the twentieth century. Based on the above, the goal of the study is to create an attractive and open environment for current philosophical discussion, its cultural codes and scientific rethinking of the pedagogical heritage of D. Dewey. The author of the paper focuses on the pedagogical support of the teacher of the future in the field of popularization of science, which became possible due to the organization and holding of the International Competition of Scientific Research and Creative Works of Students “In the World of the Wise Thoughts of Nikolai Aleksandrovich Berdyaev and John Dewey.” In the study, the author’s attention is focused on the key idea of John Dewey in the development of the pedagogical culture of the teacher of the future, from which all his pedagogical principles stemmed. The applied value of the conducted research is determined by the expansion of the range of scientific and professional knowledge, the field of scientific knowledge, comprehension, and free choice of “personal research action” within the framework of updating the ideas of John Dewey. In modern pedagogical science and practice, the presented results of scientific research can be used as a tool for attracting educational subjects to the field of popularization of science.