Respuesta sísmica de dos puentes metálicos construidos con 100 años de diferencia

Se presenta el análisis del comportamiento sísmico de dos puentes muy similares de acero construidos en épocas muy diferentes en Europa y en América. Las características estructurales de ambos puentes y los niveles de esfuerzo bajo condiciones normales de operación son similares, pero su construcción difiere prácticamente un siglo. El Puente Pinhão se localiza en Portugal y el Puente Infiernillo II en México. El estudio tiene como objetivo determinar la influencia de las distintas épocas en los materiales utilizados, en el tipo de secciones transversales de los elementos y en el comportamiento esperado de estos dos puentes.This paper presents a comparative numerical analysis of the structural behavior and seismic performance of two similar steel bridges built in different periods in Europe and America. Both bridges have similar general structural characteristics, but their construction is separated by one hundred years. The Pinhão Bridge and the Infiernillo II Bridge are located in Portugal and in Mexico, respectively. The study aimed at determining the influence of one century period in material properties, transverse sections and expected behavior of two quite similar bridges

Expected seismic performance of irregular isolated bridges

Bridge structures are usually built on irregular topographical surfaces which create substructures with pier heights of different lengths. Three height irregularity types of typical RC medium length bridges are analyzed aimed at determining the best strength and stiffness parameters of an isolation system. The models were located in a high seismicity zone of Mexico. The isolation system is composed by lead rubber bearings (LRB) located on each pile and abutment. The bridge and isolation parameters conducted to the nonlinear time history analysis (NLTHA) of 169 models. Ten seismic records representative of the subduction zone in the Pacific Coast in Mexico were chosen to carry out the study. The maximum drift pier demands, bending moments and shear forces were analyzed to identify the best isolation properties for improving the bridges’ structural behavior, specially focused on looking for avoiding irregularity concentrations of shear forces on piers. Additionally, the seismic response of the bridges supported on traditional neoprene bearings was carried out

Development of organic fertilizers from food market waste and urban gardening by composting in Ecuador

Currently, the management of urban waste streams in developing countries is not optimized yet, and in many cases these wastes are disposed untreated in open dumps. This fact causes serious environmental and health problems due to the presence of contaminants and pathogens. Frequently, the use of specific low-cost strategies reduces the total amount of wastes. These strategies are mainly associated to the identification, separate collection and composting of specific organic waste streams, such as vegetable and fruit refuses from food markets and urban gardening activities. Concretely, in the Chimborazo Region (Ecuador), more than 80% of municipal solid waste is dumped into environment due to the lack of an efficient waste management strategy. Therefore, the aim of this study was to develop a demonstration project at field scale in this region to evaluate the feasibility of implanting the composting technology not only for the management of the organic waste fluxes from food market and gardening activities to be scaled-up in other developing regions, but also to obtain an end-product with a commercial value as organic fertilizer. Three co-composting mixtures were prepared using market wastes mixed with pruning of trees and ornamental palms as bulking agents. Two piles were created using different proportions of market waste and prunings of trees and ornamental palms: pile 1 (50:33:17) with a C/N ratio 25; pile 2: (60:30:10) with C/N ratio 24 and pile 3 (75:0:25) with C/N ratio 33), prepared with market waste and prunings of ornamental palm. Throughout the process, the temperature of the mixtures was monitored and organic matter evolution was determined using thermogravimetric and chemical techniques. Additionally, physico-chemical, chemical and agronomic parameters were determined to evaluate compost quality. The results obtained indicated that all the piles showed a suitable development of the composting process, with a significant organic matter decomposition, reached in a shorter period of time in pile 3. At the end of the process, all the composts showed absence of phytotoxicity and suitable agronomic properties for their use as organic fertilizers. This reflects the viability of the proposed alternative to be scaled-up in developing areas, not only to manage and recycle urban waste fluxes, but also to obtain organic fertilizers, including added value in economic terms related to nutrient contents.Peer ReviewedPostprint (published version

Single-file dynamics with different diffusion constants

We investigate the single-file dynamics of a tagged particle in a system consisting of N hardcore interacting particles (the particles cannot pass each other) which are diffusing in a one-dimensional system where the particles have different diffusion constants. For the two particle case an exact result for the conditional probability density function (PDF) is obtained for arbitrary initial particle positions and all times. The two-particle PDF is used to obtain the tagged particle PDF. For the general N-particle case (N large) we perform stochastic simulations using our new computationally efficient stochastic simulation technique based on the Gillespie algorithm. We find that the mean square displacement for a tagged particle scales as the square root of time (as for identical particles) for long times, with a prefactor which depends on the diffusion constants for the particles; these results are in excellent agreement with very recent analytic predictions in the mathematics literature.Comment: 9 pages, 5 figures. Journal of Chemical Physics (in press

Hydrodynamic limit of gradient exclusion processes with conductances

Fix a strictly increasing right continuous with left limits function W: \bb R \to \bb R and a smooth function \Phi : [l,r] \to \bb R, defined on some interval $[l,r]$ of \bb R, such that $0<b \le \Phi'\le b^{-1}$. We prove that the evolution, on the diffusive scale, of the empirical density of exclusion processes, with conductances given by $W$, is described by the weak solutions of the non-linear differential equation $\partial_t \rho = (d/dx)(d/dW) \Phi(\rho)$. We derive some properties of the operator $(d/dx)(d/dW)$ and prove uniqueness of weak solutions of the previous non-linear differential equation

Language universals rely on social cognition: Computational models of the use of this and that to redirect the receiver’s attention

Demonstratives—simple referential devices like this and that—are linguistic universals, but their meaning varies cross-linguistically. In languages like English and Italian, demonstratives are thought to encode the referent’s distance from the producer (e.g., that one means “the one far away from me”), while in others, like Portuguese and Spanish, they encode relative distance from both producer and receiver (e.g., aquel means “the one far away from both of us”). Here we propose that demonstratives are also sensitive to the receiver’s focus of attention, hence requiring a deeper form of social cognition than previously thought. We provide initial empirical and computational evidence for this idea, suggesting that producers use demonstratives to redirect the receiver’s attention towards the intended referent, rather than only to indicate its physical distance