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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Comparison of dermal and inhalation routes of entry for organic chemicals

The quantitative comparison of the chemical concentration inside the body as the result of a dermal exposure versus an inhalation exposure is useful for assessing human health risks and deciding on an appropriate protective posture. In order to describe the relationship between dermal and inhalation routes of exposure, a variety of organic chemicals were evaluated. The types of chemicals chosen for the study were halogenated hydrocarbons, aromatic compounds, non-polar hydrocarbons and inhalation anesthetics. Both dermal and inhalation exposures were conducted in rats and the chemicals were in the form of vapors. Prior to the dermal exposure, rat fur was closely clipped and during the exposure rats were provided fresh breathing air through latex masks. Blood samples were taken during 4-hour exposures and analyzed for the chemical of interest. A physiologically based pharmacokinetic model was used to predict permeability constants (cm/hr) consistent with the observed blood concentrations of the chemical. The ratio of dermal exposure to inhalation exposure required to achieve the same internal dose of chemical was calculated for each test chemical. The calculated ratio in humans ranged from 18 for styrene to 1180 for isoflurane. This methodology can be used to estimate the dermal exposure required to reach the internal dose achieved by a specific inhalation exposure. Such extrapolation is important since allowable exposure standards are often set for inhalation exposures, but occupational exposures may be dermal.

Jepson, Gary W.↗
NASA NTRS1992

A pressure correction method for the calculation of compressible chemical reacting flows

A recently developed noniterative method for the solution of the transient fluid flow equations at all speed is extended to handle chemical reacting flows. The species conservation equations are loosely coupled into the predictor/multicorrector sequence of the solution procedure. A split-operator method separates the chemical kinetics terms from the fluid-dynamical terms, as well as an implicit differencing method enhance the numerical stability. The method was applied for turbulent diffusion flame calculations and for the analyses of high pressure, axisymmetric turbulent hypersonic nozzle flows. The diffusion flame results were compared with a similar pressure method for fast chemistry integration scheme without operator-splitting. Simulations of the nozzle flow indicated that the nonideal intermolecular effects must be included in the analysis and design of high pressure hypersonic nozzle.

Chen, Z. J.↗
DOE OSTI2021

PyKrev: A Python Library for the Analysis of Complex Mixture FT-MS Data

In this study, we present PyKrev, a Python library for the analysis of complex mixture Fourier transform mass spectrometry (FT-MS) data. PyKrev is a comprehensive suite of tools for analysis and visualization of FT-MS data after formula assignment has been performed. These comprise formula manipulation and calculation of chemical properties, intersection analysis between multiple lists of formulas, calculation of chemical diversity, assignment of compound classes to formulas, multivariate analysis, and a variety of visualization tools producing van Krevelen diagrams, class histograms, PCA score, and loading plots, biplots, scree plots, and UpSet plots. The library is showcased through analysis of hot water green tea extracts and Scotch whisky FT-ion cyclotron resonance-MS data sets. PyKrev addresses the lack of a single, cohesive toolset for researchers to perform FT-MS analysis in the Python programming environment encompassing the most recent data analysis techniques used in the field.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

First-Principles Surface Characterization and Water Adsorption of Fe 3 P Schreibersite

We report the meteoritic mineral schreibersite, e.g., Fe 3 P, is a proposed abiotic source of phosphorus for phosphate ion (PO 4 – ) production, needed for nucleobases, phospholipids, and other life building materials. Schreibersite could have acted as both a source of elemental phosphorus and as a catalyst, and the hostile conditions on early Earth could have accelerated its degradation in different environments. Here, we present results from quantum calculations of bulk schreibersite and of its low Miller index surfaces. We also investigate water surface adsorption and identify possible dissociation pathways on the most stable facet. Our calculations provide useful chemical insights into schreibersite interactions in aqueous environments, paving the way for further detailed investigation on more reactive surfaces. Our results help provide a “bottom-up” understanding for phosphorylated organic synthesis on the primitive planet and its role in producing life building molecules.

36 MATERIALS SCIENCE↗
NASA NTRS1967

Calculation of complex chemical equilibria.

Nonlinear equations governing complex chemical and phase equilibria derived from thermodynamic principles and supplemented by solving algorithms and practical applications

NONLINEAR EQUATION↗
NASA NTRS1992

Calculating Shocks In Chemically Reacting Flows

Total-variation-diminishing dissipation operator results in crisp shocks. Report discusses method for numerical simulation of shocks in hypersonic, chemically reacting flows. Introduces mathematical model of gas of as many as three species for which species-conservation equations coupled with gas-dynamic equations.

Eberhardt, Scott↗
NASA NTRS1996

Computer Program for Calculation of Complex Chemical Equilibrium Compositions and Applications II. Users Manual and Program Description: Users Manual and Program Description - 2

This users manual is the second part of a two-part report describing the NASA Lewis CEA (Chemical Equilibrium with Applications) program. The program obtains chemical equilibrium compositions of complex mixtures with applications to several types of problems. The topics presented in this manual are: (1) details for preparing input data sets; (2) a description of output tables for various types of problems; (3) the overall modular organization of the program with information on how to make modifications; (4) a description of the function of each subroutine; (5) error messages and their significance; and (6) a number of examples that illustrate various types of problems handled by CEA and that cover many of the options available in both input and output. Seven appendixes give information on the thermodynamic and thermal transport data used in CEA; some information on common variables used in or generated by the equilibrium module; and output tables for 14 example problems. The CEA program was written in ANSI standard FORTRAN 77. CEA should work on any system with sufficient storage. There are about 6300 lines in the source code, which uses about 225 kilobytes of memory. The compiled program takes about 975 kilobytes.

McBride, Bonnie J.↗
DOE OSTI2022

Analysis of Intermediates and Products from the Dehydrogenation of Mg(BH 4 ) 2

The thermodynamic properties of key compounds, Mg(B 3 H 8 ) 2 , MgB 2 H 6 , MgB 10 H 10 , Mg(B 11 H 14 ) 2 , Mg 3 (B 3 H 6 ) 2 , and MgB 12 H 12 , proposed to be formed in the release of hydrogen from magnesium borohydride Mg(BH 4 ) 2 and uptake of hydrogen by MgB 2 , have been investigated using solid–state density functional theory (DFT) calculations. Further, more accurate treatment of cell–size effects to the entropies were also investigated, in order to improve the accuracy of the thermodynamic properties of complex borohydrides. We find that the zero–point energy corrections can lower the electronic energies of reaction by 20–30 kJ/(mol H 2 ) for these intermediates, while adding the thermal and entropy contributions results in the total decrease up to ~50 kJ/(mol H 2 ). Although our treatment lowers the calculated formation energy of Mg(B 3 H 8 ) 2 , it is still too high to explain the experimental observation of B 3 H 8 – . We discuss possible reasons for this disparity and propose that the formation of B 3 H 8 – and H – in a disordered amorphous phase has a large energy difference compared to the phase–separated Mg(B 3 H 8 ) 2 and MgH 2 considered in calculations. Comparison of the experimental and NMR chemical shifts calculated within a DFT approach for known species Mg(BH 4 ) 2 , Mg(B 3 H 8 ) 2 , Mg(B 11 H 14 ) 2 , MgB 10 H 10 and MgB 12 H 12 provides validation for predicting the chemical shifts of the other compounds which are yet to be confirmed experimentally. These include MgB 2 H 6 and the proposed tri–anion species Mg 3 (B 3 H 6 ) 2 that both have favorable thermodynamics for reversible hydrogen storage in Mg(BH 4 ) 2 without the formation of MgH 2 as a co–product which could phase–separate and inhibit rehydrogenation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1994

Improved Optical Fiber Chemical Sensors

Calculations, based on exact theory of optical fiber, have shown how to increase optical efficiency sensitivity of active-core, step-index-profile optical-fiber fluorosensor. Calculations result of efforts to improve efficiency of optical-fiber chemical sensor of previous concept described in "Making Optical-Fiber Chemical Sensors More Sensitive" (LAR-14525). Optical fiber chemical detector of enhanced sensitivity made in several configurations. Portion of fluorescence or chemiluminescence generated in core, and launched directly into bound electromagnetic modes that propagate along core to photodetector.

Egalon, Claudio O.↗
NASA NTRS1987

An implicit flux-split algorithm to calculate hypersonic flowfields in chemical equilibrium

An implicit, finite-difference, shock-capturing algorithm that calculates inviscid, hypersonic flows in chemical equilibrium is presented. The flux vectors and flux Jacobians are differenced using a first-order, flux-split technique. The equilibrium composition of the gas is determined by minimizing the Gibbs free energy at every node point. The code is validated by comparing results over an axisymmetric hemisphere against previously published results. The algorithm is also applied to more practical configurations. The accuracy, stability, and versatility of the algorithm have been promising.

Palmer, Grant↗
DOE OSTI2026

First-principles insights into Si substitution effects in Sm 2 (Fe,Si) 17 C x magnet

The partial substitution of Fe by Si enhances the phase stability of Sm 2 Fe 17 C x magnets with x > 1.0. Here, we elucidate the Si-substitution scheme and its impact on phase stability and magnetic properties in Sm 2 (Fe,Si) 17 C 3 from first-principles calculations and chemical bonding analysis. The calculated substitution energies for Si at various Fe sites are negative, indicating improved phase stability. Si preferentially substitutes Fe atoms at the 9d site in Sm 2 (Fe,Si) 17 C 3 while it tends to enter the Fe 18h site in Sm 2 (Fe,Si) 17 . This difference in site preference is attributed to the distinct chemical environments surrounding the Fe (Si) sites in the two compounds. Si substitution favors the formation of Sm–Si bonds while minimizing the Si–C and Si–Si interactions. Crystal orbital Hamilton populations and crystal orbital bond index calculations indicate that the partial replacement of Fe with Si strengthens the chemical bonding of Sm–Fe 3 (18f) and Sm–Fe 4 (18h) and improves overall phase stability in Sm 2 (Fe,Si) 17 C 3 . Beyond the dilution effect, Si substitution also reduces the magnetic moments of neighboring Fe atoms, a phenomenon linked to the strong Fe–Si bonding. These findings highlight the dual role of Si in modifying both the structural and magnetic characteristics of Sm 2 Fe 17 -based magnetic compounds.

Chemical bonding↗
NASA NTRS1973

Computer program for calculation of thermodynamic and transport properties of complex chemical systems

Program performs calculations such as chemical equilibrium for assigned thermodynamic states, theoretical rocket performance for both equilibrium and frozen compositions during expansion, incident and reflected shock properties, and Chapman-Jouget detonation properties. Features include simplicity of input and storage of all thermodynamic and transport property data on master tape.

Svehla, R. A.↗
DOE OSTI2023

Parallel Implementation of Nonadditive Gaussian Process Potentials for Monte Carlo Simulations

A strategy is presented to implement Gaussian process potentials in molecular simulations through parallel programming. Attention is focused on the three-body nonadditive energy, though all algorithms extend straightforwardly to the additive energy. The method to distribute pairs and triplets between processes is general to all potentials. Results are presented for a simulation box of argon, including full box and atom displacement calculations, which are relevant to Monte Carlo simulation. Data on speed-up are presented for up to 120 processes across four nodes. A 4-fold speed-up is observed over five processes, extending to 20-fold over 40 processes and 30-fold over 120 processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1977

Prediction of hydrodynamics and chemistry of confined turbulent methane-air flames with attention to formation of oxides of nitrogen

A formulation of the governing partial differential equations for fluid flow and reacting chemical species in a tubular combustor is presented. A numerical procedure for the solution of the governing differential equations is described, and models for chemical equilibrium and chemical kinetics calculations are presented. The chemical equilibrium model is used to characterize the hydrocarbon reactions. The chemical kinetics model is used to predict the concentrations of the oxides of nitrogen. The combustor consists of a cylindrical duct of varying cross sections with concentric streams of gaseous fuel and air entering the duct at one end. Four sample cases with specified inlet and boundary conditions are considered, and the results are discussed

Elghobashi, S.↗
DOE OSTI2020

27 AlNMR chemical shift of Al(OH)$^{-}_{4}$ calculated from first principles: Assessment of error cancellation in chemically distinct reference and target systems

Predicting accurate nuclear magnetic resonance chemical shieldings relies upon cancellation of different types of errors between the theoretically calculated shielding constant of the analyte of interest and the reference. Often, the intrinsic error in computed shieldings due to basis sets, approximations in the Hamiltonian, description of the wave function, and dynamic effects is nearly identical between the analyte and reference, yet if the electronic structure or sensitivity to local environment differs dramatically, this cannot be taken for granted. Detailed prior work has examined the octahedral trivalent cation Al(H 2 O)$^{3+}_{6}$, accounting for ab initio intrinsic errors. However, the use of this species as a reference for the chemically distinct tetrahedral anion Al(OH)$^{-}_{4}$ requires an understanding of how these errors cancel, in order to define the limits of accurately predicting 27 Al chemical shielding in Al(OH)$^{-}_{4}$. In this work, we estimate the absolute shielding of the 27 Al nucleus in Al(OH)$^{-}_{4}$ at the coupled cluster level (515.1± 5.3 ppm). Shielding sensitivity to the choice of method approximation and atomic basis sets used has been evaluated. Solvent and thermal effects are assessed through ensemble averaging techniques using ab-initio molecular dynamics. The contribution of each type of intrinsic error is assessed for the Al(H 2 O)$^{3+}_{6}$ and Al(OH)$^{-}_{4}$ ions, revealing significant differences that fundamentally hamper the ability to accurately calculate the 27 Al chemical shift of Al(OH)$^{-}_{4}$ from first principles.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1995

Computing Properties Of Chemical Mixtures At Equilibrium

Scientists and engineers need data on chemical equilibrium compositions to calculate theoretical thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93 is general program that calculates chemical equilibrium compositions and properties of mixtures for any chemical system for which thermodynamic data are available. Includes thermodynamic data for more than 1,300 gaseous and condensed species and thermal-transport data for 151 gases. Written in FORTRAN 77.

Mcbride, B. J.↗