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Caicedo J.C.,University of Valle | Caicedo J.C.,Autonomous University of Occidente | Cabrera G.,University of Valle | Aperador W.,University Militar Nueva Granada | And 2 more authors.
Vacuum | Year: 2012

The erosive-corrosive effect of aqueous NaCl slurries on metals and metals coated with a multilayer system was analyzed. The erosion-corrosion experiments were performed in a test machine in which the impingement velocity, impact angle, concentration of solids and pH of the solution were controlled. Polarization curves were simultaneously obtained to correlate the electrochemical effects to the erosive wear mechanisms. The slurry used consists of silica particles suspended in a mixture of acid solution and 3.5% NaCl, with a pH value of 5.6. Electrochemical results showed the best corrosion resistance for steel coated with CrN/AlN system deposited with 50 bilayer. Additionally, the surface analysis by SEM micrograph revealed formation of cracks in CrN/AlN multilayers coating and plastic deformation in both steel substrates (AISI D3 steel and 304 stainless steel), especially when the mean impact angle is a critical value of 90°. Measurements of critical and passive current densities showed that the behavior of coated materials differed depending on the substrate that is used. Nonetheless, in a general way, by increasing the impact angle and by changing its incidence from normal to grazing, it led to an improved resistance to erosion-corrosion processes. © 2012 Elsevier Ltd. All rights reserved.

Chaves F.,Escuela Colombiana de Ingenieria Julio Garavito | Rocha C.,Escuela Colombiana de Ingenieria Julio Garavito
2015 10th Colombian Computing Conference, 10CCC 2015 | Year: 2015

The calculational style of E. W. Dijkstra and C. S. Scholten is a semi-formal style for the development, both in terms of verification and derivation, of correct programs. This calculational style heavily relies on the symbolic manipulation of expressions involving, for instance, arithmetic, quantifiers, and collections. This paper presents Calculational, an executable specification language for a broad class of calculational expressions in the style of Dijkstra & Scholten. The Calculational tool offers support for executable specifications, including: (i) quantifier expressions such as summation and universal/existential quantification, and (ii) data types such as lists, sets, and bags (i.e., multisets). The current implementation of Calculational is executable in the Haskell programming language, offering support also for higher order computation and pattern matching. This implementation is available for download as open source code and as a Haskell library too (which can be embedded in other programming languages). The main features of Calculational, some examples of its use-including the formal processing and querying of relational data-, and details of its implementation are included in this paper. © 2015 IEEE.

Garcia-Caceres R.G.,Escuela Colombiana de Ingenieria Julio Garavito | Felknor S.,Escuela Colombiana de Ingenieria Julio Garavito | Cordoba J.E.,Pontifical Xavierian University | Caballero J.P.,Pontifical Xavierian University | Barrero L.H.,Pontifical Xavierian University
International Journal of Industrial Ergonomics | Year: 2012

The use of hand tools that fit users' characteristics is essential for task productivity and prevention of musculoskeletal disorders in industry. In Colombia, workers in the floriculture industry use a wide range of hand tools in cultivation tasks. However, little is known about the correspondence between the employed tools and hand dimensions of this population. The present article studies the hand anthropometry (HA) of a sample of 120 adult female workers of the Colombian flower industry located in the Bogota plateau. In total thirty-three HA measures were studied. A survey of the tasks and hand tools used in this population was also conducted. Detailed descriptive statistics were estimated for the assessed HA measures; and a comparative statistical analysis with other worker female populations reported in the literature was conducted. We found that the surveyed floriculture workers are systematically using tools with dimensions that do not adequately fit their HA and that may impose unnecessary mechanical loads to the users. HA in the present study population appear to be significantly different from other populations' HA, which suggest the need to promote the acquisition, design or re-design of manual tools specifically thought for this working population. Relevance to industry: Hand anthropometry is a necessary input for tool design that promotes task productivity and workers' health. The detailed HA information presented in this study can be used by tool manufacturers to design tools that are suitable for workers of the Colombian floriculture industry. © 2011 Elsevier B.V.

Cabrera G.,University of Valle | Torres F.,University of Valle | Caicedo J.C.,University of Valle | Aperador W.,Escuela Colombiana de Ingenieria Julio Garavito | And 2 more authors.
Journal of Materials Engineering and Performance | Year: 2012

Improvement of corrosion properties on AISI D3 steel surfaces coated with [CrN/AlN] n multilayered system deposited for various periods (Λ) via magnetron sputtering has been studied in this work exhaustively. For practical effects compared were the latter properties with CrN and AlN single layers deposited with the same conditions as the multilayered systems. The coatings were characterized in terms of crystal phase; chemical composition, micro-structural, and electrochemical properties by x-ray diffractometry, energy dispersive x-ray, Fourier transforming infrared spectroscopy, atomic force microscopy, scanning electron microscopy, Tafel polarization curves, and electrochemical impedance spectroscopy. Corrosion evolution was observed via optical microscopy. Results from x-ray diffractometry analysis revealed that the crystal structure of [CrN/AlN] n multilayered coatings has an NaCl-type lattice structure and hexagonal structure (wurtzite-type) for CrN and AlN, respectively, i.e., it was made non-isostructural multilayered. The best behavior was obtained by the multilayered period: Λ = 60 nm (50 bilayers), showing the maximum corrosion resistance (polarization resistance of 1.18 KΩ, and corrosion rate of 1.02 mpy). Those results indicated an improvement of anticorrosive properties, compared to the CrN/AlN multilayer system with 1 bilayer at 98 and 80%, respectively. Furthermore, the corrosion resistance of steel AISI D3 is improved beyond 90%. These improvement effects in multilayered coatings could be attributed to the number of interfaces that act as obstacles for the inward and outward diffusions of ion species, generating an increment in the energy or potential required for translating the corrosive ions across the coating/substrate interface. Moreover, the interface systems affect the means free path on the ions toward the metallic substrate, due to the decreasing of the defects presented in the multilayered coatings. © 2010 ASM International.

Ramirez S.,Escuela Colombiana de Ingenieria Julio Garavito | Rocha C.,Escuela Colombiana de Ingenieria Julio Garavito
2015 10th Colombian Computing Conference, 10CCC 2015 | Year: 2015

This paper presents a case study on the formal specification of a cache coherence protocol and the verification of some of its safety properties. Cache coherence refers to the consistency between the contents of a memory resource shared by many processes, that can have read and write access, and each local copy of the memory contents. The protocol presented in this paper is based on the ESI standard in which a central controller can grant exclusive and shared access to the memory, and also invalidate access to the memory. The formal specification of the protocol is presented as a rewriting logic theory and it is fully executable in the Maude system. The safety properties presented in this paper are linear temporal logic (LTL) formulas expressing invariants about mutual exclusion among the processes accessing the shared memory resource. By using Maude's search functionality and LTL model checker, some of these invariants can be proved automatically for a finite number of processes. This paper also presents an initial exploration on the mechanical verification of an invariant for any number of processes by means of deductive techniques based on inductive reasoning. © 2015 IEEE.

Ortiz-Rodriguez O.O.,University of Pamplona | Garcia-Caceres R.G.,Escuela Colombiana de Ingenieria Julio Garavito
DYNA (Colombia) | Year: 2013

As a result of the Agenda 21, presented nearly two decades ago, the Millennium Development Goals (MDG) were set and must be met by the year 2015. Nowadays, governments, researchers, engineers, environmental scientists and other stakeholders involved in the industry are working more jointed for improving environmental and socio-economic indicators for sustainability of the Building Industry. The relevance of the residential building sector is evident for its fast growing rate during the last two decades. This paper presents an analysis on the sustainability of the residential building sector in two different countries: Colombia and Spain, by measuring and evaluating a composite indicator (CI). A factor analysis (FA) with principal components extraction was employed to calculate the CI in order to evaluate the evolution of the residential building sector in two core aspects: socio and economic conditions.

Aperador W.,University Militar Nueva Granada | Mejia A.S.,Escuela Colombiana de Ingenieria Julio Garavito | Caicedo J.,University of Valle
Informacion Tecnologica | Year: 2014

Thin films of titanium nitride/zirconium nitride were deposited on AISI 4140 steel by a multi-target magnetron sputtering system with radio frequency. The process was developed under the substrate rotation system which allowed placing the substrate against the titanium and zirconium targets, generating the super-lattice with periods of 1, 50, 100, and 200 bilayers. The multilayers were evaluated against the corrosion-erosion synergy in a solution composed by 3% NaCl and silica. The electrochemical characterization was performed by electrochemical impedance spectroscopy. After the mechanic and electrochemical tests the surface was evaluated using scanning electron microscopy. By performance analysis it was observed that the material with higher synergic effect was the substrate. It is also shown that by increasing the bilayers in the system titanium nitride/zirconium nitride the corrosive phenomenon controls the material deterioration.

Aperador W.,University Militar Nueva Granada | Delgado E.,University Militar Nueva Granada | Mejia A.,Escuela Colombiana de Ingenieria Julio Garavito
International Journal of Electrochemical Science | Year: 2013

In the present investigation was obtained electro-copper coating on steel AISI SAE 1020, electrolyte was used as an industrial waste obtained from the stripping of copper. The current densities were 2.5 A/dm2, 5 A/dm2 y 7.5 A/dm2 and concentration of 222 g / l of copper sulfate (CuSO4). The corrosion behavior of the substrate and the coatings obtained were studied by electrochemical impedance spectroscopy and potentiodynamic polarization curves. Additionally, we examined the surfaces of the coatings by scanning electron microscopy (SEM). The study shows that these coatings comply with the standards for use as ground poles. © 2013 by ESG.

Garcia-Caceres R.,Escuela Colombiana de Ingenieria Julio Garavito | Nunez-Moreno A.,Pontifical Xavierian University | Ramirez-Ortiz T.,Pontifical Xavierian University | Jaimes-Suarez S.,Escuela Colombiana de Ingenieria Julio Garavito
DYNA (Colombia) | Year: 2013

The current paper describes the upstream phase of the Colombian oil palm agribusiness, by characterizing its supply and value chain in terms of the functionality and relations between its stages and echelons. This work constitutes a pioneering effort aimed at improving the efficiency and efficacy of the palm sector in this country.

Romero Rodriguez M.I.,Escuela Colombiana de Ingenieria Julio Garavito | Zhevandrov P.,Universidad Michoacana de San Nicolás de Hidalgo
Journal of Fluid Mechanics | Year: 2014

The system describing time-harmonic motions of a two-layer fluid in the linearised shallow-water approximation is considered. It is assumed that the depth is constant, with a cylindrical protrusion (an underwater ridge) of small height. For obliquely incident waves, the system reduces to a pair of coupled ordinary differential equations. The values of frequency for which wave propagation in the unperturbed system is possible are bounded from below by a cutoff, to the left of which no propagating modes exist. Under the perturbation, a trapped mode appears to the left of the cutoff and, if a certain geometric requirement is imposed upon the shape of the perturbation (for example, if the ridge is a rectangular barrier of certain width), a trapped mode appears whose frequency is embedded in the continuous spectrum. When these geometric conditions are not satisfied, the embedded trapped mode transforms into a complex pole of the reflection and transmission coefficients of the corresponding scattering problem, and the phenomenon of almost total reflection is observed when the frequency coincides with the real part of the pole. Exact formulae for the trapped modes are obtained explicitly in the form of infinite series in powers of the small parameter characterising the perturbation. The results provide a theoretical understanding of analogous phenomena observed numerically in the literature for the full problem for the potentials in a two-layer fluid in the presence of submerged cylinders, and furnish explicit formulae for the frequencies at which total reflection occurs and the trapped modes exist. © 2014 Cambridge University Press.

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