1,720,972 research outputs found
Gas crossover leakage in high temperature polymer electrolyte fuel cells: In situ quantification and effect on performance
No full textHere we report an experimental in situ analysis of internal gas crossover leakage in single high- temperature polymer electrolyte membrane fuel cells. The study is based on the analysis of the exhausts from the anode and the cathode of the fuel cell during operation. An abnormal crossover rate across the membrane of the investigated fuel cell was detected, indicating the presence of an internal leakage. The internal flux shows linear dependence on the pressure difference between fuel cell compartments, attesting for permeation as the driving force. When the average cathode pressure is higher than the anode pressure, air crossover is measured. Conversely, hydrogen crossover is measured when the anode pres- sure is higher than the cathode. The effects on fuel cell performance are evaluated under air or hydrogen crossover conditions. Under both conditions, crossover leakage causes a significant increase in hydrogen consumption that reduces fuel recovery from anode exhaust
Degradation in phosphoric acid doped polymer fuel cells: A 6000 h parametric investigation
No full textSensitivity analysis of a polybenzimidazole-based polymer fuel cell and insight into the effect of humidification
No full textExperimental analysis of mass transport in high temperature polymer electrolyte fuel cells
No full textOn the activation of polybenzimidazole-based membrane electrode assemblies doped with phosphoric acid
No full textExperimental study of water transport in a polybenzimidazole-based high temperature PEMFC
No full textExperimental analysis of water transport in the diffusion layer of a PEM fuel cell
No full textOptimization of water management in Polymer Electrolyte Fuel Cells (PEMFC) is a very important factor for the achievement of high performances. A good hydration of the electrolyte membrane is essential for correct operation in order to avoid flooding at electrodes causing severe reduction in performances. Many studies on water transport across the gas diffusion layer (GDL) have been carried out to improve these components; anyway efforts in this field are affected by the lack of an effective and shared experimental method. The present work reports an experimental investigation with the purpose to determine the global coefficient of water transport across a GDL under real operating conditions. An appropriate experimental apparatus has been built to test the single GDL under a wide range of operating conditions. Experiments have been realized by feeding on both GDL sides a humidified air flow and a dry air flow respectively and measuring the quantity of water that crosses the GDL. Both temperature and relative humidity of air fluxes as well as distributors geometries are typical of real applications. Flooding onset has been observed and a simple characterization is presented
La riorganizzazione cerebrale in pazienti con esiti di trauma cranico: analisi funzionale ed elettrofisiologica dei meccanismi di plasticità neuronale alla base del recupero clinico a distanza.
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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