The logarithmic spiral, autoisoptic curve

In the Line of Investigation that in the department of “Technical Drawing” in the School of Agriculture Engineering of Madrid, we carry out on the study of The Technical Curves and his singularities, we demonstrate an interesting property of the Logarithmic Spiral. The demonstrated property consists of which the logarithmic spiral is a autoisoptic curve, that is to say that if from a point P anyone of the spiral tangent straight lines draw up to the previous arc, these form a constant angle α. This demonstration is novel and in addition we get to contribute a method to calculate the angle α given the equation of the spiral

Network coevolution drives segregation and enhances Pareto optimal equilibrium selection in coordination games

In this work we assess the role played by the dynamical adaptation of the interactions network, among agents playing Coordination Games, in reaching global coordination and in the equilibrium selection. Specifically, we analyze a coevolution model that couples the changes in agents' actions with the network dynamics, so that while agents play the game, they are able to sever some of their current connections and connect with others. We focus on two update rules: Replicator Dynamics (RD) and Unconditional Imitation (UI). We investigate a Pure Coordination Game (PCG), in which choices are equivalent, and on a General Coordination Game (GCG), for which there is a risk-dominant action and a payoff-dominant one. The network plasticity is measured by the probability to rewire links. Changing this plasticity parameter, there is a transition from a regime in which the system fully coordinates in a single connected component to a regime in which the system fragments in two connected components, each one coordinated on a different action (either if both actions are equivalent or not). The nature of this fragmentation transition is different for different update rules. Second, we find that both for RD and UI in a GCG, there is a regime of intermediate values of plasticity, before the fragmentation transition, for which the system is able to fully coordinate in a single component network on the payoff-dominant action, i. e., coevolution enhances payoff-dominant equilibrium selection for both update rules.Comment: 13 pages, 8 figures, submitted to Scientific Report

Social imitation versus strategic choice, or consensus versus cooperation, in the networked Prisoner's Dilemma

The interplay of social and strategic motivations in human interactions is a largely unexplored topic in collective social phenomena. Whether individuals' decisions are taken in a purely strategic basis or due to social pressure without a rational background crucially influences the model outcome. Here we study a networked Prisoner's Dilemma in which decisions are made either based on the replication of the most successful neighbor's strategy (unconditional imitation) or by pure social imitation following an update rule inspired by the voter model. The main effects of the voter dynamics are an enhancement of the final consensus, i.e., asymptotic states are generally uniform, and a promotion of cooperation in certain regions of the parameter space as compared to the outcome of purely strategic updates. Thus, voter dynamics acts as an interface noise and has a similar effect as a pure random noise; furthermore, its influence is mostly independent of the network heterogeneity. When strategic decisions are made following other update rules such as the replicator or Moran processes, the dynamic mixed state found under unconditional imitation for some parameters disappears, but an increase of cooperation in certain parameter regions is still observed. Comparing our results with recent experiments on the Prisoner's Dilemma, we conclude that such a mixed dynamics may explain moody conditional cooperation among the agents.This work was supported by the PRISMA project (Grant No. PON04a2 A), within the Italian National Program for Research and Innovation. M.S.M. acknowledges support from INTENSE@COSYP (Grant No. FIS2012-30634) of the Ministerio de Economía y Competitividad (MINECO, Spain). J.J.R. also receives funding from the MINECO through the Ramón y Cajal program and through the project MODASS (Grant No. IS2011-24785). A.S. acknowledges support from grant PRODIEVO from the MINECO. In addition, funding from the EU Commission was received through project LASAGNE.Publicad

Social and strategic imitation: the way to consensus

Humans do not always make rational choices, a fact that experimental economics is putting on solid grounds. The social context plays an important role in determining our actions, and often we imitate friends or acquaintances without any strategic consideration. We explore here the interplay between strategic and social imitative behaviors in a coordination problem on a social network. We observe that for interactions in 1D and 2D lattices any amount of social imitation prevents the freezing of the network in domains with different conventions, thus leading to global consensus. For interactions in complex networks, the interplay of social and strategic imitation also drives the system towards global consensus while neither dynamics alone does. We find an optimum value for the combination of imitative behaviors to reach consensus in a minimum time, and two different dynamical regimes to approach it: exponential when social imitation predominates, and power-law when strategic considerations dominate.Comment: 13 pages, 5 figures. Submitted to Scientific Report

Ratchet behavior in nonlinear Klein-Gordon systems with point-like inhomogeneities

We investigate the ratchet dynamics of nonlinear Klein-Gordon kinks in a periodic, asymmetric lattice of point-like inhomogeneities. We explain the underlying rectification mechanism within a collective coordinate framework, which shows that such system behaves as a rocking ratchet for point particles. Careful attention is given to the kink width dynamics and its role in the transport. We also analyze the robustness of our kink rocking ratchet in the presence of noise. We show that the noise activates unidirectional motion in a parameter range where such motion is not observed in the noiseless case. This is subsequently corroborated by the collective variable theory. An explanation for this new phenomenom is given

Belt separation system under slat in fattening pig housing: Effect of belt type and extraction frequency

The efficiency of manure separation by a conveyor belt under a partially slatted floor for fattening pigs was determined for two types of belts, a flat belt with an incline of up to 6° transversely and a concave belt with an incline of up to 1° longitudinally. A 31.20% and 23.75% dry matter content of the solid fraction was obtained for the flat and concave belt, respectively. The flat belt was more efficient at 6° than other slope angles. The residence time of the manure on the two belt types influenced the separation efficiency from a live weight of 63.00 kg upwards. The quantity of residue produced with this system was reduced to 25–40% with respect to a pit system under slat. This could mean a remarkable reduction in costs of storage, transport and application of manure

Multifractal analysis of discretized X-ray CT images for the characterization of soil macropore structures

A correct statistical model of soil pore structure can be critical for understanding flow and transport processes in soils, and creating synthetic soil pore spaces for hypothetical and model testing, and evaluating similarity of pore spaces of different soils. Advanced visualization techniques such as X-ray computed tomography (CT) offer new opportunities of exploring heterogeneity of soil properties at horizon or aggregate scales. Simple fractal models such as fractional Brownian motion that have been proposed to capture the complex behavior of soil spatial variation at field scale rarely simulate irregularity patterns displayed by spatial series of soil properties. The objective of this work was to use CT data to test the hypothesis that soil pore structure at the horizon scale may be represented by multifractal models. X-ray CT scans of twelve, water-saturated, 20-cm long soil columns with diameters of 7.5 cm were analyzed. A reconstruction algorithm was applied to convert the X-ray CT data into a stack of 1480 grayscale digital images with a voxel resolution of 110 microns and a cross-sectional size of 690 × 690 pixels. The images were binarized and the spatial series of the percentage of void space vs. depth was analyzed to evaluate the applicability of the multifractal model. The series of depth-dependent macroporosity values exhibited a well-defined multifractal structure that was revealed by singularity and Rényi spectra. The long-range dependencies in these series were parameterized by the Hurst exponent. Values of the Hurst exponent close to one were observed indicating the strong persistence in variations of porosity with depth. The multifractal modeling of soil macropore structure can be an efficient method for parameterizing and simulating the vertical spatial heterogeneity of soil pore space

Adaptación de la Escala de Creencias sobre el Bienestar a la población española

The study of happiness and well-being is receiving increased attention in different fields. Recent research into well-being has focused on delving deeper into the individual’s conception about the experience of well-being. McMahan and Estes (2011a) created a scale that assesses lay conceptions of well-being (BWBS) based on four dimensions: the experience of pleasure, avoidance of negative experience, self-development and contribution to others. The goal of this study was to adapt this scale, the Beliefs about Well-Being Scale, to the Spanish population. The sample consisted of 1,024 participants from the general population ranging in age interval from 17 to 87 years old. The confirmatory factorial analysis results in a structure of four dimensions, similar to the original scale, although in the adaptation of the scale the items decrease from 16 to 12. The results of the reliability analysis reveal indexes similar to those of the original scale. These results confirm the validity of Beliefs about Well-Being Scale with general population in a cultural context different from the original study. This will allow cross-cultural studies to analyze the influence of culture in the perception of well-being.El estudio de la felicidad y el bienestar está recibiendo cada vez más atención en diferentes campos. Las investigaciones recientes sobre el bienestar se han centrado en profundizar en la concepción del individuo sobre la experiencia del bienestar. McMahan y Estes (2011a) crearon una escala que evalúa las concepciones legas del bienestar en base a cuatro dimensiones: la experiencia de placer, la evitación de la experiencia negativa, el autodesarrollo y la contribución a los demás. El objetivo de este estudio fue adaptar esta escala, Beliefs about Well-Being Scale (BWBS), a la población española. La muestra estuvo formada por 1.024 participantes de la población general con un intervalo de edad entre 17 y 87 años. El análisis factorial confirmatorio da como resultado una estructura de cuatro dimensiones, similar a la escala original, aunque en la adaptación de la escala los ítems disminuyen de 16 a 12. Los resultados del análisis de fiabilidad revelan índices similares a los de la escala original. Estos resultados confirman la validez de la Escala de Creencias sobre el Bienestar con población general en un contexto cultural diferente al del estudio original. Esto permitirá realizar estudios transculturales para analizar la influencia de la cultura en la percepción del bienesta

Laboratorio de Bienestar Porcino: Primeros Resultados y Primeras Conclusiones

La puesta en marcha del Laboratorio de Bienestar Porcino comenzó con una iniciativa de un grupo de investigadores de la E.T.S.I. Agrónomos de Madrid (UPM) que, con el apoyo y financiación de la empresa Tragsa, desarrolló un modelo de alojamiento para cebo de cerdos que incluía un sistema patentado de separación in situ de heces y orina