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A three-dimensional, computational fluid dynamics (CFD) model of a PEM fuel cell is presented. The model consists of straight channels, porous gas diffusion layers, porous catalyst layers and a membrane. In this computational domain, most of the transport phenomena which govern the performance of the PEM fuel cell are dealt with in detail. The model solves the convective and diffusive transport of the gaseous phase in the fuel cell and allows prediction of the concentration of the species present. A special feature of the model is a method that allows detailed modelling and prediction of electrode kinetics. The transport of electrons in the gas diffusion layer and catalyst layer is accounted for, as well as the transport of protons in the membrane and catalyst layer. This provides the possibility of predicting the three-dimensional distribution of the activation overpotential in the catalyst layer. The current density dependency on the gas concentration and activation overpotential can thereby be addressed. The proposed model makes it possible to predict the effect of geometrical and material properties on the fuel cell’s performance. It is shown how the ionic conductivity and porosity of the catalyst layer affects the distribution of current density and further how this affects the polarization curve. The porosity and conductivity of the catalyst layer are some of the most difficult parameters to measure, estimate and especially control. Yet the proposed model shows how these two parameters can have significant influence on the performance of the fuel cell. The two parameters are shown to be key elements in adjusting the three-dimensional model to fit measured polarization curves. Results from the proposed model are compared to single cell measurements on a test MEA from IRD Fuel Cells.

Electric vehicle seems to go well together with the growing societal trend of becoming more self-supplying with renewable electricity produced in the household. However, aligning household electricity production and electric vehicle charging have received little attention in HCI although both areas have been pursued separately for a number of years. In this paper, we present findings from a qualitative study that explore the potential of aligning electric vehicle charging with times where renewable electricity is being produced in the household. We present an empirical qualitative study of 5 households (19 persons) that own electric vehicles and also produce their own renewable electricity. Our findings, described in five themes, reveal that aligning charging and electricity production can be a challenge and tension exist for aligning consumption such as motivation, roles, mobility patterns, and electricity producing technology. We further discuss our findings and possible directions for future HCI research in the field.

An effective controller is proposed for the 'Photovoltaic(PV) - Battery - Diesel Generator(DG)' based hybrid standalone system in this article. A bidirectional DC to DC device which can allow power in both directions is integrated among the DC-link and battery bank to maintain contact voltage by maintaining power balance in the system. Further, a bidirectional inverter is also considered between point of common coupling (PCC) and DC-link for providing supply to AC loads as well as charging the battery from diesel generator based on requirement. However, the phenomenon of partial shading condition (PSC) commonly occurring on PV modules and also generated power from PV always fluctuates according to changes in weather. To achieve a superior performance of the system, a Takagi-Sugeno Fuzzy (TSF) based controllers are implemented in proposed control schemes. The novel control schemes are implemented on a bidirectional DC to DC converter as well as three phase bidirectional inverter. However, the proper deloading process of the PV system should be incorporated into the controller of the DC to DC converter to achieve power balance during light load conditions. Balanced quality voltages (3-phase) at PCC are achieved by inverter control which forces to maintain balanced currents generated by DG during the operation of unbalanced loads. Maintaining balanced DG currents can help to reduce the oscillations on the torque of the shaft which increases the fatigue life. Further the reactive power demanded at PCC is compensated by the inverter control, hence DG need not to provide it which results can reduce the consumption of diesel. Various case studies are examined by using MATLAB to present results and Real Time Digital Simulator (RTDS) based results are also provided in this paper.

Under global warming, extreme events have been increasing in the last decade and are projected to increase in the future with every increment of global warming. The potential increase in compound drought and hot events may induce a complex web of impacts on societies, ecosystems, and economies, including crop failure, wildfires, and water scarcity. This is particularly concerning for Brazil, where it has been demonstrated to be vulnerable to recent extreme climate events. Using an ensemble of CORDEX-CORE simulations over Tropical Brazil, we investigate changes in compound events inresponse to changes in radiative forcing and their impact on climate extreme events, including drought and extreme heat. The simulations are conducted at a 25 km horizontal grid spacing using lateral and lower boundary forcing from three Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. Each model covers the period from 1980 to 2100 under two Radiative Concentration Pathways (RCP2.6 and RCP8.5) in the 21st-century projection period. We used observed data from the Brazilian Daily Weather Gridded Data (BR-DWGD) to evaluate the simulations and perform a quantitative assessment of areas affected by these compound events during the present day. The study finds a generally good agreement between RCM simulations and observed data, with moderate to high correlation coefficients for precipitation, though the strength of these correlations varies across different regions and seasons. The analysis emphasizes the prevalence of compound climate events during the Austral summer season and projects a significant increase in both extreme heat and drought events in the coming decades. These findings underscore Brazil’s vulnerability to compound climate events, highlighting the need for adaptive strategies and policy interventions to mitigate the socio-economic and environmental impacts across various sectors. Fil: Bettolli, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Instituto Franco-Argentino sobre Estudios del Clima y sus Impactos; Argentina Fil: Pereira Llopart, Marta. Universidade Estadual Paulista Julio de Mesquita Filho; Brasil Fil: Feldman Firpo, Mári Ândrea. Instituto Nacional de Pesquisas Espaciais; Brasil Fil: Chimborazo Guerron, Oscar V.. State University of New York; Estados Unidos Fil: Muniz Alves, Lincoln. Instituto Nacional de Pesquisas Espaciais; Brasil Fil: Avilés Añazco, Alex. Universidad de Cuenca; Ecuador Fil: Hasson, Shabeh. Universitat Hamburg; Alemania

Isotretinoin is effective in the treatment of severe acne and rosacea. Both parent drug and its main metabolite 4-oxo-isotretinoin are potentially teratogenic compounds and contain a carboxylic acid moiety. In the presence of ethanol, naturally occurring as well as synthetic retinoids also containing a carboxylic acid moiety are capable of undergoing an ethyl esterification with the metabolic formation of more lipophilic compounds with a much longer terminal half-life.To determine if isotretinoin (13-cis-RA), its main metabolite 4-oxo-isotretinoin (4-oxo-13-cis-RA), and other possible metabolites in the presence or absence of ethanol are converted to their corresponding ethyl derivatives in patients with severe acne or rosacea after multiple isotretinoin dosing. In addition, pharmacokinetic parameters of the parent drug and its 4-oxo metabolite were determined.Eleven patients with severe acne or rosacea were treated with isotretinoin daily for 3 months and investigated pharmacokinetically during 24 h after 1 month of treatment and for up to 28 days after discontinuation of therapy. A possible influence of ethanol was evaluated using a simple self-administered questionnaire and by measuring serum ethanol levels during treatment. The concentrations of isotretinoin, 4-oxo-isotretinoin and possible ethylated and nonethylated metabolites were measured by reverse-phase high-performance liquid chromatography.Although seven of 11 patients had a considerable weekly alcohol intake, no endogenous synthesis of ethyl derivatives of isotretinoin, the main 4-oxo metabolite or the all-trans compounds was chromatographically detectable in any of the patients' plasma samples during the treatment period. Multiple dose pharmacokinetic data for the parent drug and its main metabolite were comparable to previous studies.The metabolism and pharmacokinetics of isotretinoin and its main metabolites are not influenced by ethanol during long-term isotretinoin treatment. After ceasing long-term isotretinoin therapy the recommended period of 1 month for using anticonceptive measures in fertile women seems adequate.

Filament seals, such as brush seals and leaf seals, are investigated as a potential improved seal for gas turbine applications. As these seals operate in contact with the rotor, a good understanding of their stiffness is required in order to minimize seal wear and degradation. This paper demonstrates that the filament and complete seal stiffness is affected in comparable magnitudes by mechanical and aerodynamic forces. In certain cases, the aerodynamic forces can also lead to an overall negative seal stiffness which may affect stable seal operation. In negative stiffness, the displacement of the seal or rotor into an eccentric position causes a resultant force, which, rather than restoring the rotor to a central position, acts to amplify its displacement. Insight into the forces acting on the seal filaments is gained by investigating a leaf seal, which consists of a pack of thin planar leaves arranged around the rotor, with coverplates on either side of the leaf pack, offset from the pack surfaces. The leaf seal is chosen due to its geometry being more suitable for analysis compared to alternative filament seals such as the brush seal. Data from two experimental campaigns are presented which show a seal exhibiting negative stiffness and a seal exhibiting a stiffness reduction due to aerodynamic effects. An empirical model for the forces acting on leaf filaments is developed based on the experimental data, which allows separation of mechanical and aerodynamic forces. In addition a numerical model is developed to analyze the flow approaching the leaf pack and the interleaf flow, which gives an insight into the causes of the aerodynamic forces. Using the empirical and numerical models together, a full picture of the forces affecting leaf stiffness is created. Validation of the models is achieved by successfully predicting seal stiffness for a further data set across the full range of operating conditions. The understanding of aerodynamic forces and their impact on filament and seal stiffness allows for their consideration in leaf seal design. A qualitative assessment of how they may be used to improve seal operation in filament seals is given.

As it becomes clear that climate change is not easily within the boundaries of the 1990's, society needs to be prepared and needs to anticipate future changes due to the uncertain changes in climate. So far, extensive research has been carried out on several issues including the coastal defence or shifting ecozones. However, the role spatial design and planning can play in adapting to climate change has not yet been focussed on.This book illuminates the way adaptation to climate change is tackled in water management, ecology, coastal defence, the urban environment and energy. The question posed is how each sector can anticipate climate change by creating spatial designs and plans. The main message of this book is that spatial design and planning are a very useful tool in adapting to climate change. It offers an integral view on the issue, it is capable in dealing with uncertainties and it opens the way to creative and anticipative solutions. Dealing with adaptation to climate change requires a shift in mindset; from a technical rational way of thinking towards an integral proactive one. A new era in spatial design and planning looms on the horizon. © Springer Science+Business Media B.V. 2009.

The potential for global forest cover The restoration of forested land at a global scale could help capture atmospheric carbon and mitigate climate change. Bastin et al. used direct measurements of forest cover to generate a model of forest restoration potential across the globe (see the Perspective by Chazdon and Brancalion). Their spatially explicit maps show how much additional tree cover could exist outside of existing forests and agricultural and urban land. Ecosystems could support an additional 0.9 billion hectares of continuous forest. This would represent a greater than 25% increase in forested area, including more than 200 gigatonnes of additional carbon at maturity.Such a change has the potential to store an equivalent of 25% of the current atmospheric carbon pool. Science , this issue p. 76 ; see also p. 24