Épsilon

14

Authors: Andrés José Alfaro Castillo

This article presents a probabilistic and deterministic assessment of a seismic threat in Neiva as of 2013, using the recent and robust attenuation equations corresponding to the Next Generation Attenuation (NGA) developed in the United States. These equations were proposed by Abrahamson and Silva, Boore and Atkinson, Campbell and Bozorgnia, Chiou, Youngs and Idriss. Regarding the deterministic assessments, conservative scenarios are presented, and considering a total rupture of the fault, the PGA would be of 550, 355, 305, 400 and 375 Gal due to the La Dina fault. These values are considered as the maximum credible seism. For the probabilistic analysis, due to the fact that the NGA equations are applicable to earthquakes with magnitudes between 5 and 8, the catalogue was drastically reduced. Therefore, a statistical analysis was performed with data of magnitudes between 4 and 7.2 and the catalogue was completed, assuming a Poisson distribution. The assessed accelerations (average plus a standard deviation) were 280, 230 280, 305 and 320 Gal, respectively.

18

Authors: Laura Marcela Zárate Polanco, Nury Alejandra Otálora Santamaría, Laura Ramírez Suárez, Lena Prieto Contreras, María del Socorro Cerón Lasso, Juan Carlos Poveda Pisco

Potato starch provides high functional characteristics in the elaboration of meat products. For this reason, three native starches of promising clones of a native Colombian yellow potato (S. tuberosum Phureja group) supplied by Corpoica and harvested in the town of Sibaté (Department of Cundinamarca) were evaluated in the elaboration of standard bologna. First, the starches from the three clones were extracted and functionally characterized. Then, three bolognas were produced using a total substitution of the starch in the formula by native starches, and a standard bologna with commercial potato starch. Then, three series of physicochemical tests were performed on the bologna, two series of texture tests and a sensory evaluation control test. The extracted starches showed an average gelatinization temperature of 70.7 °C, which guaranteed a stable emulsion during the scalding process. The bologna with native starches showed average protein (15.22%), fat (13.88%), starch (4.44%) and syneresis (8.83%) values, which were aligned with Colombian Technical Standard No. 1325. The texture test resulted in 2.37 kgf of hardness and 71.96 N/mm of chewiness for the bologna that contained native starch from promising clone number 2, which showed a similar texture to the standard bologna. At a sensory level, the panelists noticed that the bolognas showed similar organoleptic characteristics, that is, native starch did not affect the flavor, color or smell of the standard bologna. Statistically, the results evaluated by a random ANOVA and multiple Tukey comparisons showed significant differences (p > 0.05) for moisture and pH content of the bolognas.

20

Authors: Carlos Felipe Urazán Bonells, Yeimi Johanna Pérez Hernández, Zulma Lorena Rey Sierra

For many years, mobility in big cities has faced ongoing issues represented in greater delays in travel times. These are more apparent when the route includes main and secondary roads, where intersections play an important role, particularly if a turn to the left is required. The projection of future main roads layout and corresponding intersections implies reviewing the impact that leftturn options, such as direct traffic light turn, turn after a u-turn, loop turn and turn going around the block, among others, would have on travel times. However, it becomes clear that there will be restrictions in some circumstances in which road infrastructure improvements are foreseen for already developed areas, mainly due to the fact that it is difficult to modify land occupied by buildings. Therefore, it is important to understand the impact that it generates in travel times. Out of 31 left turns, analyzed in 10 intersections, the conclusion is that the average time of a direct left turn with a traffic light is 23 seconds, whereas left turns going around the block increase to 219 seconds and left turns after a u-turn take up to 427 seconds. There is a considerable difference among the times, and these values can become critical when projected to a significant flow of vehicles.

22

Authors: Alejandro Mejía Sierra, Álvaro Antonio Patiño Forero

In order to showcase the impact of the technical development of micro and small entrepreneurs in Colombia regarding automation of their machines, the present article describes the landscape of the metal-mechanic industry development in Colombia, in contrast with the outstanding countries of the region, with aims to present the reasons that have driven countries like Mexico to be a production and manufacturing center for leading vehicle brands. This interest arises from the achieved competitiveness and, among others, the massive importation of numerical control machines, which makes Mexico the tenth country that imports the most machines. It is also important to highlight the relation that the Colombian manufacturing industry currently holds with the automobile industry. Finally, the article describes the process to design and build a numerical control machine required by a Colombian micro-entrepreneur dedicated to modeling pieces for the car sector.

23

Authors: Andrés Ríos, Edwin Rodríguez, Mauricio Ramírez, Jorge E. Pachón

Currently, the world’s vehicle transportation system is based on the internal combustion engine, characterized by its ineffective use of energy and constant emission of polluting gases into the atmosphere, decreasing the quality of air and affecting the population and the environment. However, private transport offers alternative technologies that have both economic and environmental advantages capable of entering the national transportation system. The present article assesses and analyzes these alternatives for the private transport system in Bogota, based on a linear model. This model compares the emission of polluting and greenhouse gasses, energy consumption, autonomy and associated costs of four different technologies (electric, hybrid, hydrogen and conventional fuel cars) in order to highlight the most critical aspects of each technology and define the best alternative for potential buyers and a future model of private transport in the capital city. Results show that there are alternatives capable of decreasing the environmental and health impacts associated to the use of conventional vehicles; said options also have the potential to mitigate the dependence on price and availability of oil at a cost that supports the feasibility of a future technology transition.

29

Authors: Adolfo Camilo Torres Prada, Fabián Augusto Lamus Báez, Sebastián Bahamón Blanco, Juan Sebastián Vesga Medina

One of the current issues in the mechanics of materials field is to perform an analytic determination of the stress state of non-deformable disc-type specimens subject to diametral compression. The present approach searches to contribute to the accurate design of new tests that allow a mechanic characterization of materials, tests required in sectors such as the concrete industry, rock mechanics and mechanics of other construction materials. One of the latest analytic proposals to solve the problem is found in the work of Markides, Kourkoulis and Chatzistergos, which shows an equation system with which to obtain the distribution of internal stress within a non-deformable disc. The present article illustrates the development of a calculation program built in Fortran programming language, with aims to study the change of stress states within the disc as the distribution of the compression varies in the perimeter of the sample, an area related to the internal angle ω0 measured from the center of the disc and reaches the limit of the contact area. Specifically, this experimental numerical stage seeks to establish the range of values of ω0 in which the stress of the disc presents primarily a compression state. The results show the distribution of radial σrr, tangential σθθ and shear τrθ stress for the geometrical case established in the present investigation. Moreover, it highlights that the state of the disc is controlled in particular by compression stress for a value of ω0 = 30º.