Observed controls on resilience of groundwater to climate variability in sub-Saharan Africa

Groundwater in sub-Saharan Africa supports livelihoods and poverty alleviation1,2, maintains vital ecosystems, and strongly influences terrestrial water and energy budgets. Yet the hydrological processes that govern groundwater recharge and sustainability—and their sensitivity to climatic variability—are poorly constrained4. Given the absence of firm observational constraints, it remains to be seen whether model-based projections of decreased water resources in dry parts of the region4 are justified. Here we show, through analysis of multidecadal groundwater hydrographs across sub-Saharan Africa, that levels of aridity dictate the predominant recharge processes, whereas local hydrogeology influences the type and sensitivity of precipitation–recharge relationships. Recharge in some humid locations varies by as little as five per cent (by coefficient of variation) across a wide range of annual precipitation values. Other regions, by contrast, show roughly linear precipitation–recharge relationships, with precipitation thresholds (of roughly ten millimetres or less per day) governing the initiation of recharge. These thresholds tend to rise as aridity increases, and recharge in drylands is more episodic and increasingly dominated by focused recharge through losses from ephemeral overland flows. Extreme annual recharge is commonly associated with intense rainfall and flooding events, themselves often driven by large-scale climate controls. Intense precipitation, even during years of lower overall precipitation, produces some of the largest years of recharge in some dry subtropical locations. Our results therefore challenge the ‘high certainty’ consensus regarding decreasing water resources in such regions of sub-Saharan Africa. The potential resilience of groundwater to climate variability in many areas that is revealed by these precipitation–recharge relationships is essential for informing reliable predictions of climate-change impacts and adaptation strategies

Numerical Simulation of Heat Removal from a Window Slab Partition of a Radiative Coil Coating Oven

In this work, fluid flow and heat transfer performance of a radiative coil coating oven is numerically investigated. In the coil coating oven concept under consideration, porous radiant burners provide the required energy to evaporate the volatile species (solvents) from the applied coating and to promote curing reactions. To avoid the mixing between burners flue gas (with a non-negligible oxygen content) and evaporated (combustible) solvents in the oven (which could lead to a catastrophic oven failure), a semi-transparent window in between both atmospheres is applied. To ensure the window thermal stability during the oven operation, window cooling by wall jets is considered. Different turbulence models were compared against available wall jet heat transfer correlations to select the most suitable for three-dimensional (3D) numerical simulations. Convective heat transfer correlations purposefully developed were embedded in a one-dimensional (1D) window energy model for fast performance characterization, analysing the most influencing parameters—window radiative properties, thickness, inlet temperature and velocity of wall jets, and cooling strategy. The 1D window thermal performance is compared with literature and 3D results considering the full coil coating oven, providing satisfactory confidence on the developed strategy. The 1D model is used for an optimisation study to find the minimum energy consumption while ensuring the safety requirements (maximum window temperature and thermal gradient) are met

Mortar Made of Recycled Sand from C&D

AbstractInthe production of coarse recycled aggregates (RA), the fine fraction is involuntarily produced, representing a large amount of the weight of the crushed C&D waste. In this work the mortar has been analyzed, by replacing standardized sand (SS) with recycled sand (RS) and by using a fixed w/c ratio equal to 0,5. The most relevant problem has been occurred during the mixing phase: in fact, RS induced a high water demand which made the mechanical properties worst. The results show that, by adding the optimum dose of superplasticizer, the RS mortars have the same mechanical characteristics of the SS mortar

A Psicologia como campo de conhecimento e como profissão de ajuda Psychology as a field of knowledge and a helping profession

O presente artigo discute um modelo de interpretação da Psicologia, de acordo com o qual conteúdos filosóficos/reflexivos, empíricos e aplicados imprimem uma configuração original à disciplina. Alguns aspectos históricos que estão na base dessa configuração são considerados, a fim de lançar luz sobre a heterogeneidade de objetos, métodos, objetivos e vínculos filosóficos das diferentes abordagens psicológicas. Em seguida, discutem-se algumas implicações do modelo para uma apreciação de certos fazeres (acadêmicos e não acadêmicos) psicológicos contemporâneos. Argumenta-se que o sucesso de cada abordagem psicológica depende, em alguma medida, do reconhecimento do caráter multifacetado do campo da Psicologia e da capacidade de responder de modo consistente e integrado às diferentes demandas sociais que definem esse campo.<br>The present article focuses an interpretation of psychology according to which philosophical/reflexive, empirical, and applied contents account for an original configuration of the discipline. The paper considers some historical facts that ground such configuration, which should be considered in order to achieve a better understanding of the heterogeneity of objects, methods, goals and philosophical commitments of the diverse psychological approaches. Some implications of the model to an appreciation of (academic and non academic) doings in contemporary psychology are then discussed. It is argued that the success of each psychological approach depends, to a certain extent, on its recognition of the multifold character of the psychological field and its capacity to give consistent and integrated responses to the different social demands that give rise to the field