Influence of crystallinity and particle size on the electrochemical properties of spray pyrolyzed Nd2NiO4+δ powders

This paper is dedicated to the study of the relationship between the Nd2NiO4+ı powder micro-structural properties (especially particle size and crystallinity) and electrochemical properties when the oxide is used as SOFC cathode deposited on 8YSZ electrolyte coated with thin doped ceria. Nano-structured particles of Nd2NiO4+ı with controlled crystallinity, size and morphology have been synthesized using ultrasonic spray pyrolysis (USP). The series and polarization resistances measured on symmetrical half cells Nd2NiO4+ı/YDC/8YSZ/YDC/Nd2NiO4+ı are both found to be dependent on the cathode microstructure and present a similar evolution with temperature. The best results are obtained for highly crystalline cathode powders combined with a small particle size

L'appropriation des espaces communautaires dans l'est des Pyrénées médiévales et modernes : enquête sur les cortals

National audienceLa Cerdagne, pensait-on, n'avait pas connu les « cortals ». Une enquête approfondie a permis d'en retrouver la trace au Moyen Âge comme à l'époque moderne. Il s'agissait pour l'essentiel de structures d'habitat implantées sur les versants intermédiaires, dans un but agricole aussi bien que pastoral. Cette étude s'intéresse particulièrement au cortal comme support de la conversion des terres communes en terres privées

Managing technology development for safety-critical systems

This paper presents a model that determines the optimal budget allocation strategy for the development of new technologies for safety-critical systems over multiple decision periods. The case of the development of a hypersonic passenger airplane is used as an illustration. The model takes into account both the probability of technology development success as a function of the allocated budget, and the probability of operational performance of the final system. It assumes that the strategy is to consider (and possibly fund) several approaches to the development of each technology to maximize the probability of development success. The model thus decomposes the system's development process into multiple technology development modules (one for each technology needed), each involving a number of alternative projects. There is a tradeoff between development speed and operational reliability when the budget must be allocated among alternative technology projects with different probabilities of development success and operational reliability (e.g., an easily and quickly developed technology may have little robustness). The probabilities of development and operational failures are balanced by a risk analysis approach which allows the decision maker to optimize the budget allocation among different projects in the development program at the beginning of each budget period. The model indicates that by considering reliability in the R&D management process, the decision maker can make better decisions, optimizing the balance between development time, cost, and robustness of safety-critical systems.Technology development; system reliability; risk analysis; project management