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The high surface area, electrical and mechanical properties of carbon nanotube (CNT) composites has rendered them promising candidates for structural power composites. Nevertheless, it is important to understand their mechanical behaviour before they are applied in energy storage devices amid the safety concerns. This work explores the nail penetration behaviours of supercapacitor specimens consisting of CNT electrodes and pseudocapacitor specimens with carbon nanotube-polyaniline (CNT/PANI) electrodes. Specimens with and without electrolyte were tested. The dry cells without electrolyte follow a power law behaviour, while the wet cells with the electrolyte exhibit a piece-wise nonlinear relationship. The force, voltage and temperature of the supercapacitor were recorded during the nail penetration test. No temperature change or overheating was observed after short-circuit. Moreover, electrochemical testing is performed before and after the specimen penetration. The cyclic voltammetry shows the dramatic loss of capacitance, changing the cell behaviour from capacitor to resistor-like manner. Johnson-Cook model was used to predict the nail penetration behaviour. The coefficients of Johnson-Cook model are calibrated from the experimental load-displacement curves. The finite element model predictions are in a good agreement with the experimental results.

The high surface area, electrical and mechanical properties of carbon nanotube (CNT) composites has rendered them promising candidates for structural power composites. Nevertheless, it is important to understand their mechanical behaviour before they are applied in energy storage devices amid the safety concerns. This work explores the nail penetration behaviours of supercapacitor specimens consisting of CNT electrodes and pseudocapacitor specimens with carbon nanotube-polyaniline (CNT/PANI) electrodes. Specimens with and without electrolyte were tested. The dry cells without electrolyte follow a power law behaviour, while the wet cells with the electrolyte exhibit a piece-wise nonlinear relationship. The force, voltage and temperature of the supercapacitor were recorded during the nail penetration test. No temperature change or overheating was observed after short-circuit. Moreover, electrochemical testing is performed before and after the specimen penetration. The cyclic voltammetry shows the dramatic loss of capacitance, changing the cell behaviour from capacitor to resistor-like manner. Johnson-Cook model was used to predict the nail penetration behaviour. The coefficients of Johnson-Cook model are calibrated from the experimental load-displacement curves. The finite element model predictions are in a good agreement with the experimental results.

Abstract A standard mechanical engineering mass transfer analysis is adapted to obtain performance calculations for the cathode of a typical polymer electrolyte membrane fuel cell. Mathematical details are provided and sample calculations performed, based on a number of simplifying assumptions. The relative advantages of low and high-mass transfer formulations are critically appraised and compared to a highly-simplified method.

Abstract A standard mechanical engineering mass transfer analysis is adapted to obtain performance calculations for the cathode of a typical polymer electrolyte membrane fuel cell. Mathematical details are provided and sample calculations performed, based on a number of simplifying assumptions. The relative advantages of low and high-mass transfer formulations are critically appraised and compared to a highly-simplified method.

Abstract Proper water management plays an essential role in the performance and durability of Polymer Electrolyte Fuel Cells (PEFCs), but it is challenged by the variety of water transport phenomena that take place in these devices. Previous experimental work has shown the existence of fluctuations between low and high current density levels in PEFCs operated with wet hydrogen and dry air feed. The alternation between both performance states is accompanied by strong changes in the high frequency resistance, suggesting a cyclic hydration and dehydration of the membrane. This peculiar scenario is examined here considering liquid water distributions from neutron imaging and predictions from a 3D two-phase non-isothermal model. The results show that the hydration-dehydration cycles are triggered by the periodic condensation and shedding of liquid water at the anode inlet. The input of liquid water humidifies the anode channel and offsets the membrane dry-out induced by the dry air stream, thus leading to the high-performance state. When liquid water is flushed out of the anode channel, the dehydration process takes over, and the cell comes back to the low-performance state. The predicted amplitude of the current oscillations grows with decreasing hydrogen and increasing air flow rates, in agreement with previous experimental data.

Abstract Proper water management plays an essential role in the performance and durability of Polymer Electrolyte Fuel Cells (PEFCs), but it is challenged by the variety of water transport phenomena that take place in these devices. Previous experimental work has shown the existence of fluctuations between low and high current density levels in PEFCs operated with wet hydrogen and dry air feed. The alternation between both performance states is accompanied by strong changes in the high frequency resistance, suggesting a cyclic hydration and dehydration of the membrane. This peculiar scenario is examined here considering liquid water distributions from neutron imaging and predictions from a 3D two-phase non-isothermal model. The results show that the hydration-dehydration cycles are triggered by the periodic condensation and shedding of liquid water at the anode inlet. The input of liquid water humidifies the anode channel and offsets the membrane dry-out induced by the dry air stream, thus leading to the high-performance state. When liquid water is flushed out of the anode channel, the dehydration process takes over, and the cell comes back to the low-performance state. The predicted amplitude of the current oscillations grows with decreasing hydrogen and increasing air flow rates, in agreement with previous experimental data.

AbstractClimate change strongly affects the health of sub-Saharan African populations. Effective adaptation strategies are required in order to enhance their limited adaptive capacities. The DFG-funded Research Unit (RU) “Climate change and health in sub-Saharan Africa” unites nine research institutions from Burkina Faso, Kenya, Germany, and Switzerland that will design, implement, and evaluate four different adaptation projects in these two African countries from 2020 until 2022.First, the effectiveness of an agro-biodiversification and nutrition program will be established for the reduction of child undernutrition of climate-sensitive nutrients in rural Burkina Faso and Kenya. Two respective cluster-randomized controlled trials (cRCT) will be conducted, each consisting of 2 × 600 children. Second, another cRCT will be conducted among 2 × 300 households in rural Burkina Faso to investigate how sunlight-reflecting cool-roof coatings affect human health outcomes, including cardiovascular and heat-related outcomes. Further outcomes comprise indoor temperature, carbon footprint, and productivity. Third, an index-based weather insurance (IBWI) will be introduced in rural Burkina Faso. The effects of IBWI on childhood nutritional status, dietary behavior, and healthcare seeking will be determined in 2 × 20 villages. Fourth, microbial larviciding has been evaluated as a promising environmental control for malaria vectors in Burkina Faso. Here, the interactions between climatic factors and the effectiveness of the intervention will be tested using spatiotemporal models.

AbstractClimate change strongly affects the health of sub-Saharan African populations. Effective adaptation strategies are required in order to enhance their limited adaptive capacities. The DFG-funded Research Unit (RU) “Climate change and health in sub-Saharan Africa” unites nine research institutions from Burkina Faso, Kenya, Germany, and Switzerland that will design, implement, and evaluate four different adaptation projects in these two African countries from 2020 until 2022.First, the effectiveness of an agro-biodiversification and nutrition program will be established for the reduction of child undernutrition of climate-sensitive nutrients in rural Burkina Faso and Kenya. Two respective cluster-randomized controlled trials (cRCT) will be conducted, each consisting of 2 × 600 children. Second, another cRCT will be conducted among 2 × 300 households in rural Burkina Faso to investigate how sunlight-reflecting cool-roof coatings affect human health outcomes, including cardiovascular and heat-related outcomes. Further outcomes comprise indoor temperature, carbon footprint, and productivity. Third, an index-based weather insurance (IBWI) will be introduced in rural Burkina Faso. The effects of IBWI on childhood nutritional status, dietary behavior, and healthcare seeking will be determined in 2 × 20 villages. Fourth, microbial larviciding has been evaluated as a promising environmental control for malaria vectors in Burkina Faso. Here, the interactions between climatic factors and the effectiveness of the intervention will be tested using spatiotemporal models.