Reduction of Inter-aquifer Water Exchange by Sand-Bentonite mixture

A confined to semi-confined water-supply aquifer beneath Memphis, the Memphis aquifer is protected in most areas by an upper natural hydraulic barrier referred to as the upper Claiborne confining unit (UCCU), which acts as an aquitard and is mainly comprised of clay and silt. Studies of the UCCU have revealed breaches, which allow cross-contamination or inter-aquifer exchange of water between the unconfined (shallow) and the underlying Memphis aquifers. This study examines the possibility of filling the voids within a preferential pathway in the UCCU via sand-bentonite mixture to reduce the inter-aquifer exchange between the shallow and Memphis aquifers. The research examined the development of a sand-bentonite mixture whereby the voids of the coarse particles of the sand are filled out by adding certain percentages of small-sized particles of bentonite to arrive at a maximum or optimal mixing ratio. Two types of parent media were used in the laboratory experiments: fine, medium, and coarse glass beads; and sand extracted from a core through a known breach in the UCCU. Hydraulic conductivity was measured in 76 samples prepared with a range of bentonite from 0%, 10%, 20%, 25%, and 30%, and the flow conditions were modeled in an idealized conceptual model using MODFLOW to assess the reduction of the flux resulting from the experimentally determined ideal sand-bentonite mixtures. The experimental results show that the hydraulic conductivity is reduced by two orders of magnitude in the coarse glass beads, four orders of magnitude in the medium glass beads, and achieves the same order of magnitude of a UCCU-type clay conductivity at 6% bentonite for the fine glass beads and the sand, reaching a 2-order of magnitude further decrease at 10% bentonite (4.22 x 10-6 m/day). Modeling showed that the vertical flux (q) reached at 6% bentonite approximated the flux through the UCCU clay. As bentonite percentages increased toward 10%, the flux reduced to 0.06 m/day, plateauing thereafter over differing injection thicknesses (0.5-5 m)

Solution-processed organic devices developed by a novel cost-effective patterning technique based on electrical erosion

Application of arc erosion to the patterning of metallic contacts in organic devices is presented. A home-made systems and details of the working principles are described. Advantages and drawbacks of this novel technology are discussed

State-Uncertainty preferences and the Risk Premium in the Exchange rate market

This paper introduces state-uncertainty preferences into the Lucas (1982) economy, showing that this type of preferences helps to explain the exchange rate risk premium. Under these preferences we can distinguish between two factors driving the exchange rate risk premium: “macroeconomic risk” and “the risk associated with variation in the private agents’ perception on the level of uncertainty”. State-uncertainty preferences amount to assuming that a given level of consumption will yield a higher level of utility the lower is the level of uncertainty perceived by consumers. Furthermore, empirical evidence from three main European economies in the transition period to the euro provides empirical support for the modelForecasting, subspace methods, combining forecasts.

Enhancing smart environments with mobile robots

Sensor networks are becoming popular nowadays in the development of smart environments. Heavily relying on static sensor and actuators, though, such environments usually lacks of versatility regarding the provided services and interaction capabilities. Here we present a framework for smart environments where a service robot is included within the sensor network acting as a mobile sensor and/or actuator. Our framework integrates on-the-shelf technologies to ensure its adaptability to a variety of sensor technologies and robotic software. Two pilot cases are presented as evaluation of our proposal.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Emergence and resilience of cooperation in the spatial Prisoner's Dilemma via a reward mechanism

We study the problem of the emergence of cooperation in the spatial Prisoner's Dilemma. The pioneering work by Nowak and May showed that large initial populations of cooperators can survive and sustain cooperation in a square lattice with imitate-the-best evolutionary dynamics. We revisit this problem in a cost-benefit formulation suitable for a number of biological applications. We show that if a fixed-amount reward is established for cooperators to share, a single cooperator can invade a population of defectors and form structures that are resilient to re-invasion even if the reward mechanism is turned off. We discuss analytically the case of the invasion by a single cooperator and present agent-based simulations for small initial fractions of cooperators. Large cooperation levels, in the sustainability range, are found. In the conclusions we discuss possible applications of this model as well as its connections with other mechanisms proposed to promote the emergence of cooperation

Accurate Stereo Visual Odometry with Gamma Distributions

Point-based stereo visual odometry systems typically estimate the camera motion by minimizing a cost function of the projection residuals between consecutive frames. Under some mild assumptions, such minimization is equivalent to maximizing the probability of the measured residuals given a certain pose change, for which a suitable model of the error distribution (sensor model) becomes of capital importance in order to obtain accurate results. This paper proposes a robust probabilistic model for projection errors, based on real world data. For that, we argue that projection distances follow Gamma distributions, and hence, the introduction of these models in a probabilistic formulation of the motion estimation process increases both precision and accuracy. Our approach has been validated through a series of experiments with both synthetic and real data, revealing an improvement in accuracy while not increasing the computational burden.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech. Project "PROMOVE: Advances in mobile robotics for promoting independent life of elders", funded by the Spanish Government and the "European Regional Development Fund ERDF" under contract DPI2014-55826-R

Brane dynamics in diverse backgrounds

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