Revista Facultad de Ingenieria

This paper describes an analytical approach to conduct an analysis of beam-column elements with generalized end-boundary conditions on a homogeneous or non-homogeneous Pasternak elastic foundation. The mathematical formulation utilized herein is that presented by the senior author in a recent work. The differential equation (DE) governing the behavior of the beam-column element is solved using the differential transformation method (DTM). The DTM offers practical advantages over other conventional approaches when solving the proposed structural model. The proposed formulation provides the flexibility to account for i) combined lateral and axial load at the ends of the element, ii) homogeneous or non-homogeneous soil, iii) Pasternak elastic foundation, and iv) an external arbitrary transverse load acting on the element. The effects of various slenderness ratios, pile-soil stiffness ratios, and classical and semirigid boundary conditions can be easily studied with the proposed formulation. Examples are presented to validate the accuracy of the model and its applicability over a wide range of analyses.

The presence of heavy metals in aqueous media represents a severe threat to ecosystems because they are non-biodegradable, toxic, and carcinogenic. In the present work, the utilization of agro-industrial residues from obtaining plantain starch for removing Ni (II) was studied, establishing the effect of temperature, adsorption dose, and initial concentration. The kinetics, equilibrium, and thermodynamic parameters that determine the process were studied. For this purpose, tests were carried out in a batch system maintaining constant stirring (200 rpm), pH (2), and solution volume (100 mL). The remaining metal concentration was determined by atomic adsorption at 237 nm. It was found that the best adsorption conditions were given at 55 ºC, 0.6775 g, and 368 mg/L obtaining a maximum adsorption capacity of 47.57 mg/g corresponding to a removal of 87%. The kinetic model that best fits the experimental data was a pseudo-second-order model, and the isotherm that describes the process is Langmuir and Freundlich, so the adsorption is given by chemisorption and multilayers. The thermodynamic parameters determined suggest that the process is favourable, not spontaneous, endothermic, and irreversible under the studied conditions. The results show that the residual biomass from the obtaining of plantain starch is a good precursor for absorbing Ni (II) in an aqueous solution.

Footwear production is subject to the variability inherent in any process, and producers often need to apply tools that allow them to make the right decisions. This work documents the process to optimize the buffer allocation in a shoe manufacturing line minimizing the cycle time in the system, applying a metamodeling approach. It was found that the Front sewing operation, and the interaction between the Lining sewing operation and the assembly operation have the greatest effect on the flow time of the product within the process; the optimum assignment of spaces follows a non-uniform arrangement on the line saturating the slower stations; the cycle time follows a non-linear behavior vs. the total number of spaces (N) in the line. For a certain value of N, the cycle time reaches a minimum value.