Browsing by Issue Date, starting with "2010-05"
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- The importance of equilibration in glacial climate simulationsPublication . Brandefelt, Jenny; Kjellström, Erik; Näslund, Jens-Ove; Strandberg, Gustav; Voelker, Antje H. L.; Wohlfarth, Barbara
- Fuel Starvation: irreversible degradation mechanisms in PEM Fuel CellsPublication . Rangel, C. M.; Travassos, Maria Antónia; Fernandes, Vitor; Silva, R. A.; Paiva Luís, TeresaPEM fuel cell operates under very aggressive conditions in both anode and cathode. Failure modes and mechanism in PEM fuel cells include those related to thermal, chemical or mechanical issues that may constrain stability, power and lifetime. In this work, the case of fuel starvation is examined. The anode potential may rise to levels compatible with the oxidization of water. If water is not available, oxidation of the carbon support will accelerate catalyst sintering. Diagnostics methods used for in-situ and ex-situ analysis of PEM fuel cells are selected in order to better categorize irreversible changes of the cell. Electrochemical Impedance Spectroscopy (EIS) is found instrumental in the identification of fuel cell flooding conditions and membrane dehydration associated to mass transport limitations / reactant starvation and protonic conductivity decrease, respectively. Furthermore, it indicates that water electrolysis might happen at the anode. Cross sections of the membrane catalyst and gas diffusion layers examined by scanning electron microscopy indicate electrode thickness reduction as a result of reactions taking place during hydrogen starvation. Catalyst particles are found to migrate outwards and located on carbon backings. Membrane degradation in fuel cell environment is analyzed in terms of the mechanism for fluoride release which is considered an early predictor of membrane degradation.
- Seafloor morphology of the Eurasia-Nubia (Africa) plate boundary between the Tore-Madeira Rise and the Straits of Gibraltar: a case of coexistent Mesozoic through present day features of tectonic, oceanographic and sedimentary originPublication . Terrinha, Pedro; Duarte, João C.; Valadares, Vasco; Batista, Luís Filipe; Zitellini, Nevio; Gràcia, Eulàlia; Lourenço, Nuno; Rosas, Filipe M.; Roque, Ana Cristina
- Non-destructive and micro-invasive techniques for cultural heritage diagnosis : a case study of glazed tiles from Portuguese historial buildings [Abstract]Publication . Prudêncio, Maria Isabel; Silva, Teresa; Dias, Maria Isabel; Marques, José Gonçalves; Pereira, Marco A. Stanojev; Figueiredo, M. Ondina; Esteves, Lurdes; Albuquerque, Maria Beatriz; Botelho, Maria Luísa; Cabo Verde, Sandra I.; Trindade, Maria José; Burbidge, Christopher Ian; Marques, Rosa
- Holocene morphologic changes offshore the Quarteira region, Algarve, south PortugalPublication . Gonçalves, João Noiva; Duarte, Henrique; Terrinha, Pedro; Gonçalves, Daniela
- Hydrographic changes along the western Iberian margin : the need to reconstruct and understand regional climate responses for glacial climate record integrationPublication . Voelker, Antje H. L.; Salgueiro, Emília; Abreu, Lúcia de
- Paleoenvironmental and paleoclimatic conditions in the Tagus River Estuary during the HolocenePublication . Santos, Célia Teresa; Abrantes, Fátima; Rodrigues, Teresa; Voelker, Antje H. L.; Vis, Geert-Jan
- Surface and deep water variations and their impact on the Meridional Overturning Circulation during the mid-Brunhes as revealed at IODP Sites U1313 and U1305Publication . Voelker, Antje H. L.; Cavaleiro, Catarina; Rebotim, Andreia; Ventura, Cristina; Hillaire-Marcel, Claude; Martin, Pamela A.
- Abrupt sea surface temperature changes during The Last Glacial-Interglacial Transition in the Iberian margin: sea level implicationsPublication . Rodrigues, Teresa; Grimalt, Joan O.; Abrantes, Fátima; Naughton, Filipa; Flores, José-Abel
- Paleo-climate changes during Termination V off Iberia as revealed by coccoliths assemblagesPublication . Palumbo, Eliana; Amore, Filomena Ornella; Flores Villarejo, José Abel; Voelker, Antje H. L.