Spatial and temporal distribution of ichthyoplankton during an unusual period of low flow in a tributary of the São Francisco River,Brazil

Flow‐dependent fish specialists require specific conditions for reproduction, so the success and reproductive intensity of these animals are determined by the flood regime. Thus, this study investigated the spatial and temporal reproductive patterns of fish, especially migratory Prochilodus species (flow‐dependent specialists) in an unusual period of low flow in the Pará River sub‐basin, one of the main tributaries of the upper São Francisco River. For this, ichthyoplankton collections were carried out between November 2013 and February 2014. Data were analysed considering the spatial and temporal variations in density of eggs and larvae for the upper, middle, and lower portions of the Pará River sub‐basin, and correlating this to some environmental variables. The results showed that the small headwater stretch of the Pará River is one relevant spawning area for migratory fish species. However, this area is isolated by the Cajuru reservoir, which makes it uncertain the recruitment of these embryos, due to interruption of natural drift between spawning/nursery areas caused for reservoirs. Larvae of newly hatched migratory species found in tributaries of the lower Pará River sub‐basin also indicate these species use these tributaries as spawning grounds and migratory routes. The period in which the research was conducted represented the most atypical low flow, one in the last 75 years, resulting in the low variability in the environmental parameters. Although few parameters increased briefly in this low flow period influenced by greater rainfall in December, this precipitation was possibly responsible for the final gonadal maturation and spawning of migratory species.     

Glycerol steam reforming in a bench scale continuous flow heat recovery reactor

In the present study glycerol was successfully gasified using a diesel engine waste heat recovery system obtaining hydrogen and methane rich gaseous products. The reforming reactor was equipped with a vaporization pre-chamber to ensure uniform reactants distribution and a fixed reaction bed, being mounted in countercurrent flow configuration with the engine combustion gases stream. Accordingly, the reactions were conducted at gradually increased temperature conditions; starting at around 300 °C in the top section of the reaction bed and finishing in a controlled outlet bed temperature of 600–800 °C. When compared to homogeneous temperature reactors, the configuration used here produced a syngas of higher methane and ethylene contents. With regards to the reactor performance, syngas lower heat values of more than 22 MJ/kg were achieved with glycerol feed concentrations within 50–70% and outlet bed temperatures above 700 °C, corresponding to cold gas efficiencies of around 85%. The present results indicate that glycerin can be utilized as a syngas feedstock for steam reforming processes based on waste heat recovery.     

Pt-promoted α-Al2O3-supported Ni catalysts: Effect of preparation conditions on oxi-reduction and catalytic properties for hydrogen production by steam reforming of methane

The effect of Pt addition on the oxi-reduction properties of α-Al₂O₃-supported Ni catalysts, with different degrees of interaction between NiO and the α-Al₂O₃ support, was studied using atmospheres of H₂, H₂/H₂O, and CH₄/H₂O. The effect of Pt promotion on the reduction of NiO with H₂ was significant for NiO species that interacted more strongly with the alumina surface, but was much lower when a NiAl₂O₄-like bulk phase was formed. For samples activated with H₂, although metal dispersion decreased with increasing Pt content, the activity was maintained constant by the presence of Pt sites. For samples activated with a CH₄/H₂O mixture, the activity increased with increasing Pt content, due to the higher reducibility of Ni in the Pt-promoted catalysts. The Pt promotion effect was stable; there was no important decrease in the influence of Pt on NiO reduction, even after high temperature re-oxidation of the catalysts.     

An estimate for thermal osmotic heat storage using precipitation of common salts

In this brief note, a first assessment on the possibilities for thermal osmotic storage by harnessing the thermal dependence of the solubility of common salts as an alternative method to sensible heat storage is discussed. In a recent study it was found that such a dependence could be used to run a heat powered cycle (osmotic heat engine). The question raised then is whether that approach could be suitable for thermal energy storage as well. The attractiveness of such a possibility lies in the capability to store energy for an indefinite period of time without using expensive isolation systems if one considers that osmotic energy only is released when both streams with different salinities are brought together. Utilizing a simplified model, a comparative study with sensible heat storage was performed. It is shown that thermal osmotic storage via thermal precipitation of common salts could be an attractive option when long thermal storage (days) and compactness is desired.     

An efficient approach for prediction of Warburg-type resistance under working currents

In the present study, an efficient approach for the prediction of Warburg-type element is proposed via the analysis of the anode-supported solid oxide fuel cell (SOFC) performance under various working conditions. The details of the performance, polarization curves, impedance behavior, and species distribution profiles within the electrode are investigated via the combination of equivalent circuit model (ECM) analysis and multiphysics numerical simulations. The multiphysics simulation is developed and calibrated with experimental results of SOFC button cells under various working currents. With the complete datasets generated from the calibrated simulations, the trends of the element parameters involved in equivalent circuit model are analyzed. Generalized empirical functions are proposed as well as the procedures of prediction of performance under different conditions. The verification cases show good agreement between the predicted results from proposed model and the reference results. This proposed approach can be utilized to quickly predict the properties for desired performance in the manufacturing processes, and it also has the potential of reducing the computational cost in the simulation of large SOFCs.     

FOS: a low-power cache organization for multicores

The Journal of Supercomputing - The cache hierarchy of current multicore processors typically consists of one or two levels of private caches per core and a large shared last-level cache. This...     

Higher-Order Adaptive Finite Difference Methods for Fully Nonlinear Elliptic Equations

We introduce generalised finite difference methods for solving fully nonlinear elliptic partial differential equations. Methods are based on piecewise Cartesian meshes augmented by additional points along the boundary. This allows for adaptive meshes and complicated geometries, while still ensuring consistency, monotonicity, and convergence. We describe an algorithm for efficiently computing the non-traditional finite difference stencils. We also present a strategy for computing formally higher-order convergent methods. Computational examples demonstrate the efficiency, accuracy, and flexibility of the methods.     

On the feasibility of ocean brine pool power stations

The demonstrated existence of vast brine pools in a number of places in the ocean basin around the world offers an interesting opportunity to the production of power from ocean, which has not been yet considered. The attractiveness of these vast deposits of brine lie in the fact that can be readily dissolved with the surrounding top waters extracting the spontaneous osmotic mixing energy released. In addition, osmotic engines can pumped out the brackish streams by buoyancy without the add of pressure exchangers (PEXs) as is required in current pressure retarded osmosis (PRO) technology and then simplifying significatively the overall process. Utilizing a simplified physical model, a first estimation for the density of power per unit of membrane area was calculated.