Revista de la Facultad de Ciencias Químicas

Permanent URI for this communityhttps://dspace-test.ucuenca.edu.ec/handle/123456789/23901

Browse

Now showing 1 - 20 of 69

Revista de la Facultad de Ciencias Químicas
(Universidad de Cuenca, 2002-05) Universidad de Cuenca; Facultad de Ciencias Químicas
Revista de la Facultad de Ciencias Químicas
(Universidad de Cuenca, 2003-02) Universidad de Cuenca; Facultad de Ciencias Químicas
Revista de la Facultad de Ciencias Químicas
(Universidad de Cuenca, 2004-02) Universidad de Cuenca; Facultad de Ciencias Químicas
Revista de la Facultad de Ciencias Químicas
(Universidad de Cuenca, 2006-02) Universidad de Cuenca; Facultad de Ciencias Químicas
Revista de la Facultad de Ciencias Químicas
(Universidad de Cuenca, 2007-04) Universidad de Cuenca; Facultad de Ciencias Químicas
Mejorando el desempeño de los proyectos
(Universidad de Cuenca, 2015-04-01) Figueroa, Robinson; Besnier, Sandra
In the industrial evolution continuous process, the interest on projects and its utilization to implement the organizational strategy, have greatly increased. It can be stressed out, in some cases, the results obtained on the project performance have been unsatisfactory. On such scenery, this documents, develops a proposal to improve the performance of projects, based on the guide of PMBOK by the PMI and the methodology of Cadence to manage projects. This paper presents the way of how to do, and the best practices to manage projects. An audit of the company is advised to determine the level of organizational maturity to manage project to define where are we?, where we would like to be?, and finally, to implement a Project Management Office.
Estudio experimental de la combustión de la cascarilla de arroz en una cámara de lecho fijo
(Universidad de Cuenca, 2015-04-01) Tipanluisa, Luis; Moreno, Gustavo; Guasumba, José; Celi, Santiago; Molina, Jaime
This paper shows an experimental study of the combustion of rice husk, based on an estimation of the energy density, based on a field study in the cities of Quevedo and Ventanas. The gross calorific value is determinate, and its moisture content according to the UNE-EN 14774. It was establish that rice husk must enter to the combustion chamber of fixed bed with humidity below 15% to reduce CO emissions, ash and soot. 14 kg/h of rice husk was burn and it was obtain 34.01 kW thermal per hour exceeding 650 °C temperature. Each rice husk particle remained burning during 4 seconds on average.
Desarrollo e implementación de un nuevo plan de mantenimiento para equipos de perforación diamantina
(Universidad de Cuenca, 2015-04-01) Carvajal, Jorge; Rodríguez, César; Patiño, Carmen; Guevara, Fernando
The geography of Colombia requires carrying the exploration equipment to remote places to execute the process of mineral resource exploration. For this reason, unexpected failures can cause long downtime and time to repair, production losses, besides of put in risk a safety of personnel and the physical assets. In this context, to develop modifications to the original maintenance plan looking for high availability of diamond drilling equipment could be required. This paper presents the development and implementation of maintenance plans based on an analytical method, that it begins with a functional analysis of the system, it continues with the revision and identification of current maintenance plans. Subsequently, the method does a historical fault analyzes, and finally, using the systematization of all information, it a proposal and implementation of a new plan of proper maintenance for the conditions of use of the system is performed. The application of this method has represented benefits in one of Colombia's most important mineral resource exploration companies. Similarly, the decision to generalize maintenance plans for hydraulic equipment was adequate for historical use of faults, bringing economic benefits and an increase availability. Finally, as a result of the development of this work is recommended to evaluate maintenance plans every two years and thus reassess their effectiveness.
Desgaste de aleaciones de hierro Cr-Mo-V-Ti para medios de molienda de minerales
(Universidad de Cuenca, 2015-04-01) Maldonado, Simitrio; Baltazar, Víctor; López, Enrique; Orozco, Pilar; Alonso, Omero
The effect of the chemical composition of carbide forming elements on the wear resistance of cast irons was evaluated by means of grinding balls. Four alloys for high chromium white iron grinding media with chromium content of 3.5 to 6.0% percent were melted in an induction furnace of 20 kg. It was performed in standard atmosphere and they were introduced into sand molds for producing metal ore grinding balls with a diameter of 51 mm. The alloys were subjected to dry attrition in an experimental test mill 200L×200ϕ mm. The alloy factors were: carbon alloy of 3.9 to 5.3%, molybdenum of 0.5 to 1.2%, vanadium and titanium of between 0.25 to 0.5%, manganese of 1.8 to 3.6%. It was shown their effects on the resistance wear in metallic ore conminution of silver, gold, zinc, iron and copper. The test metallic ore has large quantities of quartz up to 30%, making it difficult to be crushing and pulverizing. The purpose of these alloyings, were to produce "in situ" a large amount of massive cementite and hexagonal carbides of high chromium and titanium and vanadium refractory carbides. Alloys with a higher percentage of manganese, chromium and molybdenum, however, lower carbon percentage, had the best responses to the wear process. A composition 4C6Cr4MnMo0.5V0.5Ti obtained the best results.
Actitudes hacia la química en estudiantes universitarios conforme avanzan en la carrera
(Universidad de Cuenca, 2015-04-01) Silvina Reyes, María; Porro, Silvia; Pirovani, María Elida
The aim of this work was to estimate the change of the student attitudes towards chemistry on biology careers (“Profesorado en Biología and Licenciatura en Biodiversidad”) at Universidad Nacional del Litoral, Santa Fe, Argentina. The student attitudes were studied during three stages: at the beginning (1st year), during (3rd year) and at the end (5th year) of their careers. The instrument chose to assess the attitudes of the students was a questionnaire according to Likert scale. All the students who attended each of the analyzed years (45, 30 and 20 students respectively) were surveyed. The obtained results indicate statistically significant differences (p ≤ 0.05) between attitudes towards chemistry presented by students of 3rd and 5th with respect to 1st year. This research showed that there is a positive trend in attitudes toward chemistry as students progress through university education. It could be inferred that it is possible to improve the attitude of the early college years, whether methodologies of teaching and evaluation, both in the last years of high school, and in the first years of college, are reviewed, to improve the attitude towards the chemistry of the students of biological careers from the beginning.
Metodología de integración de un ciclo de potencia de turbina de gas a un ciclo de potencia de turbina de vapor
(Universidad de Cuenca, 2015-04-01) Ovando, Juan C.; Acosta, Israel; Martínez, Miguel; Román, Raúl; Cifuentes, Augusto
This paper exposed a repowering proposal for the Lerma Central Thermal performing the cogeneration power cycle, by integrating a gas power to a steam power cycle. Mathematical modeling was performed using the thermodynamic power cycle analysis, obtaining the equations for solution. The hybrid mode results showed 62.53 MW power with a thermal efficiency of 47.74 %, which is 60.5 % higher than the originally worked Rankine cycle. Finally, it was showed that this configuration of power generation is convenient.
Costos exergéticos de una turbina de gas considerando los gases de escape como pérdida o residuo variando la relación de presiones
(Universidad de Cuenca, 2015-04-01) Aguilar, Ignacio; Lugo, Raúl; Torres, Edgar; Lugo, Helen; Ambriz García, Juan J.
This paper presents a gas turbine engine parametric performance analysis. The aim of this work is to determine the influence of the compressor pressure ratio of the exergetic costs of all energy streams, assuming the exhaust gases as a waste or a residue. If the exhaust gases are considered as a waste, its exergetic cost is zero; and if it is treated as residue, the exergetic cost is no null. The highest exergetic cos t is associated to the exhaust gases stream of the exit of the combustion chamber. This cost is mainly affected by treating the exhaust gases as a waste or as a residue. For the optimum compressor pressure ratio related to the maximum thermal efficiency of 40.05, the exergetic cost of the stream at the exit of the combustion chamber is about 787618 kW, if the exhaust gases are assumed as a waste. If they are considered as a residue the mentioned exergetic cost presents an increment of 15.66% for the same compressor pressure ratio.
Application of multiscale entropy production theory to hydro-turbine maintenance
(Universidad de Cuenca, 2015-04-01) Jaramillo, María; Cortés, María; García, Luis; Hernández, Estefanía; Estrada, Jorge; Cano, Eduardo
Maintenance of hydro turbine would be easier if it could be measured the multi-scale of its sound and magnetic waves produced by the entropy, as an accepted indicator of the physical complexity of the system, it is proportional to the logarithm of the number of states in a thermodynamic system. The following methods were applied: Parametric solid modeling, FEA analysis, CFD simulation, CAD design & drafting, PLC & SCADA programming, protection engineering & testing, power quality testing and others techniques. This paper describes a new approach to qualify the final turbine well-working. The obtained results showed that the time sound wave series obtaines from the turbine suggests a rise of the hydro-turbine complexity with aging. As well, several concepts and techniques to quantify the magnetic and sound wave signal entropy are presented, which are aimed to assess the turbine performance. Such concepts are explored and some entropy vs age plotting are depicted to show the behavior of the sound waves taken nearby the hydro–turbines and alternators located in Manizales-Colombia.
Articulación de los actores del ecosistema emprendedor como herramienta efectiva para la transición de un proyecto emprendedor a un proyecto comercialmente viable
(Universidad de Cuenca, 2015-04-01) Zalamea Piedra, Silvana; Peña González, Silvia Alexandra
The productive matrix transformation to attain the Ecuador’s good living is an agreement point for our society. Entrepreneurs are considered to be an important part on the achievement of this change, they are importatnt to increase entrepreneurship and supporting organizations to be articulated. This research highlights the importance of a linkage among actors involved on entrepreneurship ecosystem based on “Quadruple Helix” model, which it will be possible a transition between an entrepreneur project and a commercially viable project. This investigation also studies several concepts and initiatives focus on the construction of entrepreneurship ecosystems proposed by international organisms and it is analyzed the steps through which an entrepreneurial idea which could succeed.
Diseño del proceso de una torre de vacío. Ventajas de la simulación
(Universidad de Cuenca, 2015-09) Vega, Macarena; Ale Ruiz, Liliana; Martínez, Julieta; Erdmann, Eleonora
Heavy hydrocarbons are the greatest oil resource in the world, however in the past had been put aside as an energy resource due to the difficulties and costs associated with production, [1]. Nowdays, the industry is financing this research because of the importance of production and the characterization. To analyse the vacuum tower, we need ASTMD1160 temperature at 10 mmHg and oil density, thereafter it can be obtained the curve of TBP760 (True Boiling Point). To correlate different boiling points with vaporized percentages for each change of pressure on the products, is necesary to build up a phase diagram with the EFV760 (Equilibrium Flash Vaporization) and EFV10 temperature. The simulator through internal calculations resolves the phase diagram, compared with the difficulty posed by manual calculations. In this paper a vacuum tower simulator is developed by Aspen HYSYS V8.3, and using the heavy oil as input data. The major advantage of the theoretical designed simulation process is the time resolution
Análisis de las simulaciones del proceso de deshidratación del gas natural con Aspen Hysys y Aspen Plus
(Universidad de Cuenca, 2015-09) Benitez, Leonel Alberto; Gutiérrez, Juan Pablo; Ale Ruiz, Liliana; Erdmann, Eleonora; Tarifa, Enrique
Natural gas has taken an important strategic role in world energy supply as a result of the growing global energy demand. Water is probably the most undesirable component found in raw natural gas because its presence can produce hydrate formation, and it can also lead to corrosion or erosion problems. Due to these often expensive consequences natural gas should be subjected to conditioning processes in order to achieve strict specifications for sales, transportation and final uses. In recent years, process simulation is playing an important role in the oil and gas industry as an appropriate and powerful tool for the design, characterization, optimization, and monitoring of industrial processes performance. In this paper the development of two steady state simulations of natural gas dehydration by absorption with triethylene glycol (TEG) is described, using commercial process simulators such as Aspen HYSYS V8.3 and Aspen PLUS V8.2. Natural gas composition, plant configuration and operating conditions adopted for designs and simulation are those generally used in the area in conditioning plants of natural gas in the province of Salta (Argentina).
Exposición a monóxido de carbono en trabajadores de control vehicular-Cuenca: estudio exploratorio
(Universidad de Cuenca, 2015-09) Rosas, Ruth; Ochoa, Angélica; Morillo, Diana; García, Nancy; Andrade, Susana
This exploratory study aims to evaluate the carbon monoxide exposure expressed as percentage of carboxyhemoglobin (%COHb) among the vehicle-examiners of the vehicle control centers (VCC) “DANTON”-Cuenca. All the employees (N=55) in both VCCs in Cuenca (Capulispamba and Mayancela) were included. Blood samples taken at the beginning and at the end of the journey of one day at early February, April and July 2013 were used to estimate %COHb. The results show that the %COHb increased from the beginning to the end of the journey among employees in both VCCs and among smokers and nonsmokers (P<0.001). Among non-smokers (N=42), the %COHb at the end of the journey was higher than the biological limit value (BLV) of 3.5% only for Mayancela employees (4.12%, P<0.05). Among smokers, the mean %COHb at the end of the journey was higher than the BLV in both VCCs. In general, Mayancela employees and those who smoke showed higher exposition to CO measured as a %COHb.
Análisis de ciclos fusión-solidificación de ceras de parafina
(Universidad de Cuenca, 2015-09) Reyes, Alejandro; Vásquez, José; Sepúlveda, Francisco
The global energy shortage has prompted for research of accumulate renewable energy alternatives, i.e., solar energy. Paraffin wax has a Phase Change Material (PCM) which allows to accumulate energy. Depending on their physical composition the melting temperature could be between 40° and 65° C, respectively. However, there is lack of information regarding the wax´s material chractersitcis after high number of cycles. Therefore, in the present work, a paraffin wax fusion/solidification system was designed and it further implemented. It was also used a data recording system to analyze melting, solidification cycles, and temperature profiles in the time domain. . The wax was heated and cooled in a Peltier cell. Two types of wax were analyzed for about 1000 cycles. It was analyzed periods and amplitudes of each cycle. The time cycle for PT 58 and PT Ch wax were 340 and 160 seconds, respectively. Finally, the results showed that the temperature profiles have no significant differentes, this means that the waxes do not undergo chemical or structural changes.
Validación de la simulación numérica del flujo bifásico hidrodinámico en sistemas de lecho fluido
(Universidad de Cuenca, 2015-09) Mantilla N., Irla; Gonzáles Ch., Salome
This rresearch work aims to improve the validation process of two-phase flow numerical simulations, of the fluid bed characteristic transport, through the formulation and development of a combined numerical model Finite Volumes and Finite Element methods. The simulation process, inicially, was performed by COMSOL software and the obtained results showed higher accuracy compare with Discrete Element Method implemented by MFIX. The fundamental problem of bed fluid mathematical modeling phenomenon is the domain irregularity, the coupling variables in space and nonlinearity. In this research conservative equations are formulated, such as, to produce a variational equivalent and numerically solvable problem. A state equation based on the hydrodynamic pressure and the volume fraction of solids is defined. The system was decoupled into three sub-problems, ensuring the solution existence of general problem. A comparison of obtained results showed that the model developed in this article, check more effectively optimal mixing conditions, based on the quality of bubbling and mixing speed.
Relación entre el uso efectivo de las TIC y las decisiones gerenciales en PYMES
(Universidad de Cuenca, 2015-09) Mosquera Laverde, William Eduardo; Rojas Melo, Luisa Alejandra; Grillo Torres, Camilo Mauricio
The article is based on the results of an exploratory study on Information Technologies Communication (ICT) and managerial decisions in small and medium enterprises (SMEs). The idea is to find out the reason to the company’s low permanence factors in the market. They have: inefficient models application of internal and external communication, reduced use of ICT implemented inside the company, inappropriate use of computer packages and underutilization of additional services provided by Internet operators. It was found also out the administrative organization have small organizational behavior management which is inoperative. All the above factors affects management decisions. Therefore, an analysis of weak managerial aspects, especially the information flow of the use of ICT through an exploratory qualitative research presented as a series of possible correct steps and strategies to implement design was developed to face the Free Trade Agreement (FTA) in Colombia. Finally, the advantages of efficient communication presented through operational and IT measures, showing some management tools to be taken to improve productivity.

Browse

Browsing Revista de la Facultad de Ciencias Químicas by Issue Date