Artículos - Ingeniería Industrial

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    The reversibility property in a job-insertion tiebreaker for the permutational flow shop scheduling problem
    (Elsevier B.V., 2021) Benavides, A.J.; Vera, A.
    The best performing approximate methods proposed for the permutational flow shop scheduling problem with makespan minimization are the well known NEH constructive heuristic and the iterated greedy algorithm. Both methods are based on the successive insertion (or reinsertion) of jobs into a partial schedule, evaluating the makespan of the resulting schedule for all insertion positions, and selecting the insertion position that presents the shortest makespan. Frequently, there are many tied insertion positions that produce such shortest makespan. Thus, a tiebreaker must be used to discern a selection among the tied insertion positions. Many tiebreakers have been proposed in the literature for this case. These tiebreakers improve the results produced by approximate methods when embedded into them. In this paper we propose two new tiebreakers that use a weighted and an unweighted approximation of the idle time increment produced by inserting the job into each tied insertion position. They were designed considering the reversibility property of the PFSSP. Our computational experiments show that the proposed tiebreakers outperform tiebreakers from the literature when evaluated within the NEH heuristic and within the iterated greedy algorithm. The iterated greedy algorithms with the proposed tiebreakers embedded are the best approximate methods so far for the permutational flow shop scheduling problem
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    Supercooling water in cylindrical capsules
    (Scopus, 2005) Milón Guzmán, Juan José; Braga, Sergio
    An experimental apparatus was developed to investigate the supercooling phenomenon of water inside cylindrical capsules used for a cold storage process. The coolant is a water-alcohol mixture controlled by a constant temperature bath (CTB). Temperatures varying with time are measured inside and outside the capsule. Cylinders with an internal diameter and thickness of 45 and 1.5mm, respectively, were made from four different materials: acrylic, PVC, brass, and aluminum. The supercooling period of the water and the nucleation temperature were investigated for different coolant temperatures. The supercooling and nucleation probabilities are shown as a function of the coolant temperature for the four different materials. © 2005 Springer Science+Business Media, Inc.
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    A study of cooling rate of the supercooled water inside of cylindrical capsules
    (Scopus, 2009) Braga, Sergio; Milón Guzmán, Juan José; Jiménez Pacheco, Hugo
    An experimental apparatus was developed to investigate the supercooling phenomenon of pure water inside cylindrical capsules used for cold storage process. The Phase Change Material (PCM) used was distilled water. The external coolant material was a water-alcohol mixture (50% vol.), controlled by a constant temperature bath (CTB) in four fixed values (-4 °C, -6 °C, -8 °C, and -10 °C). Temperatures varying with time were measured inside and outside the capsule. Cylindrical capsules with internal diameter of 30 mm, 45 mm, and 80 mm, with 1.5 mm wall thickness were made in aluminum, bronze or acrylic materials. The Cooling Rate (CR) was investigated for different positions on the internal wall of the capsule, for different external coolant temperatures (Tc), different capsules diameters and different materials. The results showed that the cooling rate is a strong function of the angular position on the internal wall, the coolant temperature, the capsule material, and the capsule's diameter. © 2008 Elsevier Ltd and IIR.
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    Corrosion behaviour of carbon and stainless steels in biodiesel, B5 blend and S500 diesel under storage conditions
    (Scopus, 2013) Cavalcanti, E.; Pacheco, H.
    In this study the corrosion behavior and physic and chemical properties of pure soy methyl biodiesel (b100), B5 blend and Diesel S-500 fuel were monitored in carbon steel storage horizontal tanks with a capacity of 25 liters kept under unsheltered conditions for 120 days. Corrosion immersion tests using standardized coupons of AISI 1020 and AISI 316L were conducted under these conditions. On every 30 days samples of the fuels were also taken so that water content, oxidative stability index, density, viscosity and acidity were monitored in accordance to EN ISO 12937, EN ISO 14112, EN ISO 15557, EN ISO 3675, EN ISO 3104 and ASTM 664 standardized procedures. At the end of the experiment corrosion rates of the coupons were determined according to ASTM G1-03 and G31-04 standardized methodologies. Water contamination increased with storage time turning the fuels potentially more aggressive. Reduction on the oxidation induction period was found to increase with time of storage, particularly for the pure biodiesel and B5 blend, turning the pure biodiesel out of specification by 30 days of storage. The oxidation stability of the B100 samples monthly taken decreased faster than the B5 blend and Diesel S-500 samples. Irrespective of the above mentioned alterations no evidence of localized attack was noted for both AISI 1020 steel and AISI 316L coupons surfaces. Density, viscosity and acidity were however found within accepted specification limits all over the 120 days period. On top of that results in corrosion rates were found to be insignificant (<0.02 mm / year). These results demonstrated the excellent corrosion resistance of carbon steel and stainless steel, within the experimental conditions used, suggesting the suitability of these two alloys for use in biodiesel and B5 blend storage tanks.
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    Visualization of dendritic ice growth in supercooled water inside cylindrical capsules
    (Scopus, 2012) Braga, Sergio; Milón Guzmán, Juan José
    An experimental device was developed to study dendritic ice growth in supercooled water inside cylindrical capsules. The capsule materials investigated were acrylic, PVC (polyvinyl chloride), bronze and aluminum. The internal diameter of all the capsules was 45 mm. The results indicate that dendritic ice appears only in supercooled water at the start of nucleation. Blockage by dendritic ice growth was classified according to the capsule material and the coolant temperature. Total blockage (100%) and partial blockage (25%, 50% and 75%) was observed. Dendritic ice growth was shown and analyzed in photographic sequences. © 2012 Elsevier Ltd. All rights reserved.
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    Innovation and startup pathways in a university scope
    (Portland State University, 2015) Cárdenas, Jose; Rondón, Ignacio
    Entrepreneurship and startup companies are related terms, in the sense that one brings support to the other. The characteristics of a successful startup could be visible in the long term, but how about the way to develop an entrepreneurial person? This study performed a survey within a Peruvian university in order to explain the innovative mindset of the students and even their position about the real needs for performing innovative and disruptive companies (or initiatives). This survey was formerly applied to overall students but the results revealed several inconsistencies. So a new survey was enhanced and applied to senior year students. Results showed that, in the big picture, the students know the innovative and startup pathways and they are able to provide new insights in this theoretical approach. © 2014 Portland International Conference on Management of Engineering and Technology.