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No description available.

No description available.

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An understanding of the problems associated with a very large light weight structure orbiting in space is of utmost importance at present. A knowledge of how the structure behaves under the influence of external disturbances in space should be available for any design and deployment of a structure in space. The life, efficiency, and function of the space structure are dependent on this knowledge. A mathematical formulation has been developed for an axially flexible structure executing a planar motion in a general orbit in space in order to determine dynamic and thermal effects in the structure due to various disturbances in a space environment. The characteristic dimension of the structure is very large (of the order of a few kilometers). We have studied the influences of the differential gravitational forces, the radiation heating, and the radiation pressure forces. Effects of these factors have been studied on the structure's axial deformation, its attitude motion and its orbit simultaneously. Results are obtained for various initial conditions and physical parameter values. It is observed that the differential gravitational forces do not have any appreciable effects on the structure's axial length and its attitude motion. Thermal effects are significant in producing appreciable structural deformation, and they also affect the attitude motion of the structure considerably. The radiation pressure forces are very significant in changing attitude motion of the space structure, but it causes negligible effects in producing longitudinal deformation of the structure. All of the above factors have insignificant effects on the orbit of the structure chosen in this study. Of all the three external disturbances, the radiation pressure forces are found to be strongest in affecting the orbit of the structure.

Intermittency of energy availability from renewable energy resources is a longstanding challenge as we transition away from fossil fuels. There is a dire need for storing energy during periods of excess renewable power generation, and the ability to utilize the stored energy during periods of peak demand. Reversible solid oxide cells (RSOCs) can be an efficient solution to this societal challenge if the device can be operated reversibly between fuel cell (SOFC) and electrolysis modes (SOEC). One of the barriers to designing an efficient RSOC device is the non-availability of a highly reversible oxygen electrode material that is satisfactory under both modes of operation, i.e., SOFC and SOEC. Mixed ionic and electronic conducting (MIEC) rare earth nickelate materials, i.e., neodymium nickelate (NNO), lanthanum nickelate have high oxygen surface exchange coefficients and bulk diffusion coefficients which makes them eminently suitable as RSOC oxygen electrodes. Furthermore, the reactivity of the solid electrolyte, namely yttria-zirconia with rare-earth nickelates leads to insulating phases at the oxygen electrode-electrolyte interface. Thus an appropriate barrier layer between the zirconia-based electrolyte and the oxygen electrode is required. The influence of such a barrier layer on electrode polarization is explored in this research. In this research, RSOCs featuring NNO as the oxygen electrode are operated under various fuel and oxidant compositions in SOFC, SOEC, and mode-switching reversible conditions to characterize polarization losses. The roles of the oxygen electrode active layer and current layer thickness on electrode polarization losses are explored. Single cells with an optimized oxygen electrode architecture have been tested in reversible, and electrolysis-only conditions for 500 h to assess their long-term performance stability. Detailed analysis of the electrochemical impedance spectra using equivalent circuit modeling and distribution of relaxation time analysis, along with microstructural characterization using scanning electron microscopy, provides insights into the rate-limiting steps and degradation mechanisms of the different oxygen electrodes and barrier layer cells. Based on these studies, suggestions are made for optimum cell design and operating conditions for RSOCs. / 2025-01-16T00:00:00Z

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