Ingeniería y Ciencia, Vol. 15, Núm. 30 (2019)

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  • Ítem
    Critical Constants Correlation from van der Waals Equation
    (Universidad EAFIT, 2019-11-29) Martínez Vitela, Mario Alberto; Gracia Fadrique, Jesús; Universidad Nacional Autónoma de México
    The cubic van der Waals equation of state at the critical condition is reduced to a linear function (Vc vs. Tc /Pc coordinates) with one adjustable parameter. It is shown that at the critical point the relation Vc = 3Vo must not hold as van der Waals suggested, but the attractive constant α = Pc Vc2 remains. Selected values of Tc, Pc, Vc compiled by Ihmels where focused on testing the quality of several empirical equations relating critical conditions. It is shown that the obtained critical constants correlation is a general form of the empirical expressions proposed by Young, Meissner, Bird, Grigoras and Ihmels. From the resulting correlation function, a function for the critical compressibility is proposed. The critical volume Vc and the ratio Tc /Pc have been expressed in group contributions.
  • Ítem
    Thermal Conductivity Measurement of Insulating Materials under non-Stationary Heat Flow
    (Universidad EAFIT, 2019-11-29) Daza-Mafioli, C M; Coral-Escobar, E E; Plaza-Castillo, J; Universidad del Atlántico
    A device to measure thermal conductivity in thermal insulating solid materials commonly used in buildings was developed following a one-dimensional model of heat flow through a plate of the material to be evaluated. The temperature gradient between the plate faces was measured as a function of time by means of a set of type T thermocouples. A circuit with commercial microcontrollers was designed to control the instrument’s mechanisms, the acquisition and the treatment of data. In preliminary tests with some materials, thermal conductivity values similar to those reported in the literature were obtained by using a linear adjustment with R values between 0.90 and 0.98. This device turns out to be a good instrument for measuring thermal conductivity because it has several advantages, such as: easy implementation, sample size, measurement method; compared to those using traditional methods.
  • Ítem
    Planning and Sizing of Electrical Networks of Underground Distribution by Metaheuristic Method
    (Universidad EAFIT, 2019-11-29) Villacres, Fabricio; Inga, Esteban; Universidad Politécnica Salesiana
    The introduction of new loads to the traditional electrical distribution systems can lead to the overloading in the power equipment. This on the sizing makes the useful life of the power equipment decrease considerably, in addition, the reliability and stability of the system begins to be compromised. Therefore, through the present investigation it is possible to solve the problem of the planning of electrical distribution networks by integrating the possibility of migrating from the concept of traditional electric networks to smart electric networks, the same ones that only electrical distribution systems of robust networks are achieved heterogeneous bidirectional communication. The present work focused on the development of a model capable of locating the distribution transformers in the best sites to satisfy the majority of users of the electrical network and obtain the best topology by applying the theory of graphs In addition, the presented model contemplates the development of a heuristic capable of executing georeferenced planning processes through the management and use of geolocated information from OpenStreetMap through the .osm file that this free platform offers us. The heuristic proposed in the present document is modeled using the Matlab software and to validate the information, the Cymdist software is required.
  • Ítem
    Generalized Simulated Annealing Algorithm for Matlab
    (Universidad EAFIT, 2019-11-29) Wilches Visbal, Jorge Homero; Martins Da Costa, Alessandro; Universidad del Magdalena
    Many problems in biology, physics, mathematics, and engineering, demand the determination of the global optimum of multidimensional functions. Simulated annealing is a meta-heuristic method that solves global optimization problems. There are three types of simulated annealing: i) classical simulated annealing; ii) fast simulated annealing and iii) generalized simulated annealing. Among them, generalized simulated annealing is the most efficient. Matlab is one of the most widely software used in numeric simulation and scientific computation. Matlab optimization toolbox provides a variety of functions able to solve many complex problems. In this article, the generalized simulated annealing method was described, the GSA function that contains this method was applied to some mathematical problems were solved in order to evaluate the efficiency of GSA with respect to some of Matlab optimization functions. As a result, it was found that the GSA function not only manages to be effective in its convergence to the global optimum but also it does so quickly. Likewise, it was observed that, in general terms, GSA was more efficient than the functions with which it was compared. Therefore, it can be concluded that the GSA function is a novel and effective alternative for addressing optimization problems using Matlab.
  • Ítem
    Study Experimental and Numerical Simulations of the Micro-hardness Tests in AL-FE alloy in Different Laser Beam Scanning
    (Universidad EAFIT, 2019-11-29) Meza Pariona, Moises; Universidade Estadual de Ponta Grossa
    In the Al–2.0 wt.%Fe alloy the laser surface remelting (LSR) treatment was executed to investigate the treated and untreated layers areas, at different laser beam scanning, among them, 80, 100 and 120 mm/s, to respect, was presented and discussed about microstructural characteristics using the FEG and EDS techniques, and numerical experiments of pyramidal indentations of the LSR-treated systems were conducted using the FEM method. In the sample-treated cross-sectional area, the microstructure presented a columnar growth characteristic, a lot of nano-porosities and large size of the molten pool geometry in low laser beam scanning, however, in high laser beam scanning, the microstructure consisted of a cellular arrangement or fine-grained microstructure, the nano-porosities concentration and the molten pool geometry are slightly decreased. Besides, the micro-hardness in the LSR-treated area increased slightly as a function of increase of the laser beam scanning, but, the micro-hardness was much higher than the untreated sample. Meanwhile, modeling of indentation on COMSOL of the LSR-treatment by finite element method of the micro-hardness was successfully calculated. Therefore, a good agreement was found between experimental and simulated data.
  • Ítem
    A Modeling Approach for Lahar Hazard Assessment: the Case of Tamasagra Sector in the City of Pasto, Colombia
    (Universidad EAFIT, 2019-11-29) Guerrero, Alejandra; Criollo, Ruby Alicia; Cordoba, Gustavo A.; Rodríguez, Diana; Universidad de Nariño
    The computational program Titan2F, a two phase flow modeling program, is used to model several hypothetical scenarios of volcanic origin mud flows (lahars) in order to estimate the spacial and temporary evolution of this potentially destructive natural phenomena at its entrance of the city of Pasto, Colombia through the Mijitayo river basin. The predictions of the program suggest that extremely high and destructive dynamic pressures at the entrance to the city can be expected. In addition, our simulations show that half of the Tamasagra and El Bosque neighbors can be inundated with lahar depths of about 1 meter thickness. The program shows to be capable to deal with the modeling of the effect of the streets and buildings on the flow behavior, showing how the streets channelizes the flow governing the path of it. In addition, our results allow to identify regions where the flow loss most of its energy, where mitigation of risk can be suggested.
  • Ítem
    Three-Dimensional Geometric Model for Rock Masses from Photographs and the Octave Program: Cantera Santa Rita, Medellín, Colombia
    (Universidad EAFIT, 2019-11-29) Suarez-Burgos, Ludger O.; Castro-Caicedo, Alvaro J.; Universidad Nacional de Colombia
    The present article exposes the procedure to achieve the three-dimensional geometric model of a rock mass from a pair of photographic shots made with a current camera, use of free/open software such as Octave and other free libraries, construction of equipment and simple tools and the appropriation of important knowledge in artificial vision. It is described taking as an example the three-dimensional model of a blast cut of the rock mass of the Santa Rita Quarry, located southwest of the city of Medellín (Colombia). Finally, it is shown by a validation, based on field measurements, that the procedure described here is promising so that it can be established as a tool for the geometric characterization of discontinuities of rock mass.