Arnulfo Luévanos Rojas

Numerical experimentation with a human migration model

In this paper, we develop a human migration model with a conjectural variations equilibrium (CVE). In contrast to previous works we extend the model to the case where the conjectural variations coefficients may be not only constants, but also (continuously differentiable) functions of the total population at the destination and of the groups fraction in it. Moreover, we allow these functions to take distinct values at the abandoned location and at the destination. As an experimental verification of the proposed model, we develop a specific form of the model based upon relevant population data of a three-city agglomeration at the boundary of two Mexican states: Durango (Dgo.) and Coahuila (Coah.). Namely, we consider the 1980-2000 dynamics of population growth in the three cities: Torreon (Coah.), Gomez Palacio (Dgo.) and Lerdo (Dgo.), and propose utility functions of four various kinds for each of the three cities. After having collected necessary information about the average movement and transportation (i.e., migration) costs for each pair of the cities, we apply the above-mentioned human migration model to this example. Numerical experiments have been conducted with interesting results concerning the probable equilibrium states revealed.

Función objetivo en el diseño de la laguna facultativa (estudio de caso)

El sistema de tratamiento con lagunas de estabilizacion es el tipo mas usado en America Latina, ya que son faciles de operar y de construir, pero presenta una gran desventaja: el requerimiento del terreno. Estos sistemas necesitan mas area que ningun otro sistema de tratamiento. Por lo tanto, es recomendable llevar a cabo un estudio debidamente analizado de manera que los resultados arrojen la menor area requerida. El objetivo del presente documento fue aplicar la programacion no lineal con el algoritmo de gradiente reducido generalizado (GRG) con el fin de optimizar el diseno tradicional y costo del sistema de tratamiento. Se diseno una laguna facultativa, los resultados indican una disminucion en el tiempo de retencion hidraulico de 4 dias y un area menor de 14.79%. Ambos analisis satisfacen perfectamente los limites maximos permisibles en la concentracion de contaminantes que indica la norma para el vertido de agua tratada a los cuerpos receptores.

Optimization of Reinforced Concrete Beams for Rectangular Sections with Numerical Experiments

In the design of reinforced concrete rectangular beams are presented two cases: 1) Simply reinforced beams; 2) Doubly reinforced beams or reinforced by compression. This paper shows an optimal model for the design of reinforced concrete rectangular beams (general case), i.e., simply and doubly reinforced beams to obtain the minimum cost. Numerical experiments show the application of the formulas of the code (ACI 318S-14), and the model for design considers two cases: the case 1 restricts the width of the beam b, and the case 2 restricts the effective deep of the beam d. Model shows the best option to design in terms of the minimum cost for the construction of beams.

DISEÑO DE ZAPATAS COMBINADAS DE LINDERO DE FORMA RECTANGULAR UTILIZANDO UN NUEVO MODELO

This paper presents the design of boundary combined footings of rectangular shape using a new model to consider real soil pressure acting on the contact surface of the footing; such pressure is presented in terms of an axial load, moment around the “X” axis and moment around the “Y” axis to each column. The classic model considers an axial load and moment around the transverse axis applied in each column, and when the moments in two directions are taken into account, the maximum pressure throughout the contact surface of the footing is considered the same. The main part of this research is that the proposed model considers real soil pressure and the classic model takes into account the maximum pressure and uniform is considered. It is concluded that the proposed model is more suited to the real conditions and is more economical.

Design of boundary combined footings of rectangular shape using a new model

This paper presents the design of boundary combined footings of rectangular shape using a new model to consider real soil pressure acting on the contact surface of the footing; such pressure is presented in terms of an axial load, moment around the “X” axis and moment around the “Y” axis to each column. The classic model considers an axial load and moment around the transverse axis applied in each column, and when the moments in two directions are taken into account, the maximum pressure throughout the contact surface of the footing is considered the same. The main part of this research is that the proposed model considers real soil pressure and the classic model takes into account the maximum pressure and uniform is considered. It is concluded that the proposed model is more suited to the real conditions and is more economical.

Mechanical Elements of Rectangular Nonprismatic Members for Symmetrical Parabolic Haunches Subjected to a Uniformly Distributed Load

This paper presents mechanical elements of rectangular nonprismatic members for symmetrical parabolic haunches subjected to a uniformly distributed load by through analytical models, these are: fixed-end moments, carry-over factors and stiffness factors. The properties of the rectangular cross section of member vary along its axis “x”, i.e., the width “b” is constant and the height “h” varies along the beam, this variation is parabolic type. Traditional methods for nonprismatic members to obtain the deflections used the Simpson’s rule, or any other technique to perform numerical integration, and the tables showing some authors are restricted to certain relationships. Also a comparison is made between the proposed models and tables that show some authors. Besides the effectiveness and accuracy of the developed models, a significant advantage is that fixed-end moments, carry-over factors and stiffness factors are calculated for any rectangular cross section of the beam using the mathematical formulas.