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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

An Integrated Planning Representation Using Macros, Abstractions, and Cases

Planning will be an essential part of future autonomous robots and integrated intelligent systems. This paper focuses on learning problem solving knowledge in planning systems. The system is based on a common representation for macros, abstractions, and cases. Therefore, it is able to exploit both classical and case based techniques. The general operators in a successful plan derivation would be assessed for their potential usefulness, and some stored. The feasibility of this approach was studied through the implementation of a learning system for abstraction. New macros are motivated by trying to improve the operatorset. One heuristic used to improve the operator set is generating operators with more general preconditions than existing ones. This heuristic leads naturally to abstraction hierarchies. This investigation showed promising results on the towers of Hanoi problem. The paper concludes by describing methods for learning other problem solving knowledge. This knowledge can be represented by allowing operators at different levels of abstraction in a refinement.

Baltes, Jacky↗
DOE OSTI2017

Understanding the structure–property relationships of the ferroelectric to relaxor transition of the (1-x)BaTiO3–(x)BiInO3 lead-free piezoelectric system

A structural and electromechanical investigation has been performed on (1-x)BaTiO 3 –(x)BiInO 3 in the region 0.03 ≤ x ≤ 0.12. A gradual structural phase transition has been observed where the structure changes from tetragonal (P4mm) and passes through two regions of coexisting phases: (1) P4mm + R3m in the range 0.03 ≤ x ≤ 0.075 and (2) Pm$\bar{3}$m + R3m for 0.10 ≤ x ≤ 0.12. The properties also transition from ferroelectric (x ≤ 0.03) to relaxor ferroelectric (x ≥ 0.05) as the dielectric permittivity maximum becomes temperature and frequency dependent. This transition was also confirmed via polarization-electric field measurements as well as strain-electric field measurements. At the critical composition of x = 0.065, a moderate strain of ~0.104% and an effective piezoelectric coefficient (d$*\atop{33}$) of 260 pm/V were observed. Finally, the original purpose of this study was to demonstrate the polarization extension mechanism as predicted in the literature, but due to the ferroelectric to relaxor transition, this mechanism was not found to be present in this system. However, this demonstrates that BaTiO 3 -based lead-free ceramics could be modified to obtain enhanced electromechanical properties for actuator applications.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Expanded Analogs of Three‐Dimensional Lead‐Halide Hybrid Perovskites

Abstract Replacing the Pb−X octahedral building unit of A I PbX 3 perovskites (X=halide) with a pair of edge‐sharing Pb−X octahedra affords the expanded perovskite analogs: A II Pb 2 X 6 . We report seven members of this new family of materials. In 3D hybrid perovskites, orbitals from the organic molecules do not participate in the band edges. In contrast, the more spacious inorganic sublattice of the expanded analogs accommodates larger pyrazinium‐based cations with low‐lying π* orbitals that form the conduction band, substantially decreasing the band gap of the expanded lattice. The molecular nature of the conduction band allows us to electronically dope the materials by reducing the organic molecules. By synthesizing derivatives with A II =pyridinium and ammonium, we can isolate the contributions of the pyrazinium‐based orbitals in the band gap transition of A II Pb 2 X 6 . The organic‐molecule‐based conduction band and the inorganic‐ion‐based valence band provide an unusual electronic platform with localized states for electrons and more disperse bands for holes upon optical or thermal excitation.

Umeyama, Daiki↗
DOE OSTI2022

Effects of Lead and Arsenic in Soils from Former Orchards on Growth of Three Plant Species

Abstract Historical use of lead arsenate as a pesticide in former orchards of eastern Washington State (USA) has resulted in legacy lead (Pb) and arsenic (As) soil contamination. However, the impacts on plant growth in soils with residual Pb and As contamination have not yet been quantified. To this end, a comparative study of plant growth impacts was performed for native bluegrass ( Poa secunda ), invasive cheatgrass ( Bromus tectorum ), and buttercrunch lettuce ( Lactuca sativa ). Using standard plant growth protocols, germination frequency and biomass growth were measured over a wide range of Pb and arsenate concentrations, with maximum concentrations of 3400 and 790 mg kg −1 for Pb and As, respectively. Results indicated that only the biomass growth for all species decreased in soils with the highest concentrations of Pb and As in the soil, with no impacts on soils with lower residual Pb and arsenate concentrations. No impact on percentage of germination was observed at any soil concentration. These results can be used to determine site‐specific soil screening levels for use in ecological risk assessments for Pb and arsenate in soils. Environ Toxicol Chem 2022;41:1459–1465. © 2022 Battelle Memorial Institute. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

54 ENVIRONMENTAL SCIENCES↗