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DOE OSTI2019

Materials Data on BaTb by Materials Project

BaTb crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ba is bonded to six equivalent Ba and six equivalent Tb atoms to form BaBa6Tb6 cuboctahedra that share corners with eighteen equivalent BaBa6Tb6 cuboctahedra, edges with six equivalent BaBa6Tb6 cuboctahedra, edges with twelve equivalent TbBa6Tb6 cuboctahedra, faces with eight equivalent BaBa6Tb6 cuboctahedra, and faces with twelve equivalent TbBa6Tb6 cuboctahedra. All Ba–Ba bond lengths are 3.89 Å. All Ba–Tb bond lengths are 3.94 Å. Tb is bonded to six equivalent Ba and six equivalent Tb atoms to form TbBa6Tb6 cuboctahedra that share corners with eighteen equivalent TbBa6Tb6 cuboctahedra, edges with six equivalent TbBa6Tb6 cuboctahedra, edges with twelve equivalent BaBa6Tb6 cuboctahedra, faces with eight equivalent TbBa6Tb6 cuboctahedra, and faces with twelve equivalent BaBa6Tb6 cuboctahedra. All Tb–Tb bond lengths are 3.89 Å.

36 MATERIALS SCIENCE↗

NASA NTRS1990

A model-based approach to the symbolic control of space subsystems

A multilayered approach to the symbolic control of complex electromechanical assemblies, such as spaceborne thermal, power, and life subsystems, is discussed. An example of this approach is given in some recent tests of the Thermal Expert System (TEXSYS) in control of the Boeing Aerospace Thermal Bus System (BATBS), a prototype two-phase Space Station Freedom thermal bus. The BATBS hardware requires read-update-act cycles of under a minute, and it is subject to dynamic reconfiguration while operating. These performance requirements are addressed by layering model-based expert system software on a conventional numerical data acquisition and control system. TEXSYS test results demonstrate both nominal control and fault recovery actions with the BATBS. Dynamic modification of the symbolic model used in this approach is compared to that of a classical numerical adaptive controller.

Glass, B. J.↗

NASA NTRS1991

TEXSYS - A large scale demonstration of model-based real-time control of a Space Station subsystem

A hybrid approach to qualitative and temporal reasoning, using a device-oriented model-based representation in conjunction with both consistency-based and classification diagnosis methods, can be effectively used to monitor and control a complex electromechanical system. An example of this approach is given in some recent tests of the Thermal Expert System (TEXSYS) in control of the Boeing Aerospace Thermal Bus System (BATBS), a prototype two-phase Space Station Freedom thermal bus. The constraints of realtime performance and changing target hardware led to significant changes in the initial approach, including a reduction in the use of deep structural reasoning and the addition of temporal reasoning capabilities. TEXSYS test results show the successful completion of both nominal control and fault recovery actions with the BATBS.

Glass, B. J.↗