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Results for “environment”
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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Modeling of flame extinction/re-ignition in oxygen-reduced environments
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Predicting particle deposition for flow over a circular cylinder in combustion environments
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Computational materials design of a corrosion resistant high entropy alloy for harsh environments
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MoSi2- and WSi2-based embedded ceramic composite thermocouples for high-temperature and harsh-environment sensing
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Spatiotemporal intersection control in a connected and automated vehicle environment
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Analysis of telecommuting behavior and impacts on travel demand and the environment
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Deciphering the Local Environment of Single-Atom Catalysts with X-ray Absorption Spectroscopy
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Nonequilibrium Environment Dynamics in a Frequency-Dependent Polarizable Embedding Model
Hybrid quantum mechanical/molecular mechanical (QM/MM) models are some of the most powerful and computationally feasible approaches to account for solvent effects or more general environmental perturbations on quantum chemical systems. In their more recent formulations (known as polarizable embedding) they can account for electrostatic and mutual polarization effects between the QM and the MM subsystems. In this paper, a polarizable embedding scheme based on induced dipoles that is both able to describe electron evolution of the embedded QM system in an efficient manner as well as to capture the frequency dependent behavior of the solvent, is proposed. The effects of this frequency dependent solvent on a time- dependent model system - the Rabi oscillations of H+2 in a resonant - field are considered. The solvent is shown to introduce only mild perturbations when the excitation frequencies of the solvent and the solute are off-resonant. However, the dynamics of the H+2 are fundamentally changed in the presence of a near-resonant excitation solvent.
Stability of polymeric separators in lithium metal batteries in a low voltage environment
Separators can largely affect the coulombic efficiency and cycling stability of lithium metal anode, especially when using the LiPF 6 electrolyte.
Local environment rigidity and the evolution of optical properties in the green-emitting phosphor Ba 1− x Sr x ScO 2 F:Eu 2+
(Ba 1− x Sr x ) 0.98 Eu 0.02 ScO 2 F produces a tunable emission from cyan to green upon Sr 2+ substitution. Ab initio molecular dynamics simulations revealed that Sr 2+ weakens the local rigidity lowering the efficiency and thermal stability of the phosphors.
Viscous flow properties and hydrodynamic diameter of phenothiazine-based redox-active molecules in different supporting salt environments
We report viscous flow properties of a redox-active organic molecule, N-(2-(2-methoxyethoxy)ethyl)phenothiazine (MEEPT), a candidate for non-aqueous redox flow batteries, and two of its radical cation salts. A microfluidic viscometer enabled the use of small sample volumes in determining viscosity as a function of shear rate and concentration in the non-aqueous solvent, acetonitrile, both with and without supporting salts. All solutions tested show Newtonian behavior over shear rates of up to 30 000 s−1, which was rationalized by scaling arguments for the diffusion-based relaxation time of a single MEEPT molecule without aggregation. Neat MEEPT is flowable but with a large viscosity (412 mPa⋅s at room temperature), which is ∼1000 times larger than that of acetonitrile. MEEPT solutions in acetonitrile have low viscosities; at concentrations up to 0.5 M, the viscosity increases by less than a factor of two. From concentration-dependent viscosity measurements, molecular information was inferred from intrinsic viscosity (hydrodynamic diameter) and the Huggins coefficient (interactions). Model fit credibility was assessed using the Bayesian Information Criterion. It is found that the MEEPT and its charged cations are “flowable” and do not flocculate at concentrations up to 0.5 M. MEEPT has a hydrodynamic diameter of around 8.5 Å, which is almost insensitive to supporting salt and state of charge. This size is comparable to molecular dimensions of single molecules obtained from optimized structures using density functional theory calculations. The results suggest that MEEPT is a promising candidate for redox flow batteries in terms of its viscous flow properties.