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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

EMHOLE v. 2.1

Program EMHOLE is an electromagnetic (EM) forward modeling algorithm that calculates time-domain electric vector e (with SI unit V/m) and magnetic vector h (in A/m) responses generated by a variety of point body sources situated within a homogeneous and isotropic wholespace. A mathematically exact (i.e., without low-frequency or far-field approximation) numerical evaluation procedure is utilized to simulate EM responses (alternately, Green functions) observed at a set of multicomponent receivers distributed throughout the wholespace.

Aldridge, David F.↗
NASA NTRS2003

Growth and Metabolism of the Green Alga, Chlorella Pyrenoidosa, in Simulated Microgravity

The effect of microgravity on living organisms during space flight has been a topic of interest for some time, and a substantial body of knowledge on the subject has accumulated. Despite this, comparatively little information is available regarding the influence of microgravity on algae, even though it has been suggested for long duration flight or occupancy in space that plant growth systems, including both higher plants and algae, are likely to be necessary for bioregenerative life support systems. High-Aspect-Ratio Rotating-Wall Vessel or HARV bioreactors developed at Johnson Space Center provide a laboratory-based approach to investigating the effects of microgravity on cellular reactions. In this study, the HARV bioreactor was used to examine the influence of simulated microgravity on the growth and metabolism of the green alga, Chlorella pyrenoidosa. After the first 2 days of culture, cell numbers increased more slowly in simulated microgravity than in the HARV gravity control; after 7 days, growth in simulated microgravity was just over half (58%) that of the gravity control and at 14 days it was less than half (42%). Chlorophyll and protein were also followed as indices of cell competence and function; as with growth, after 2-3 days, protein and chlorophyll levels were reduced in modeled microgravity compared to gravity controls. Photosynthesis is a sensitive biochemical index of the fitness of photosynthetic organisms; thus, CO2-dependent O2 evolution was tested as a measure of photosynthetic capacity of cells grown in simulated microgravity. When data were expressed with respect to cell number, modeled microgravity appeared to have little effect on CO2 fixation. Thus, even though the overall growth rate was lower for cells cultured in microgravity, the photosynthetic capacity of the cells appears to be unaffected. Cells grown in simulated microgravity formed loose clumps or aggregates within about 2 days of culture, with aggregation increasing over time. Presently, the basis for, or significance of, the cell aggregation is unknown. The results from this study suggest that cell growth and morphological characteristics of green algae may be altered by culture in simulated microgravity. The data obtained to date should provide a solid basis for additional experimentation regarding the influence of modeled microgravity on cell morphology, physiological activity, protein production and possibly gene expression in algal and plant cell systems. The final aim of the study is to provide useful information to elucidate the underlying mechanism for the biological effects of microgravity on cells.

Mills, W. Ronald↗
DOE OSTI2016

Description of Hydration Water in Protein (Green Fluorescent Protein) Solution

The structurally and dynamically perturbed hydration shells that surround proteins and biomolecules have a substantial influence upon their function and stability. This makes the extent and degree of water perturbation of practical interest for general biological study and industrial formulation. Here, we present an experimental description of the dynamical perturbation of hydration water around green fluorescent protein in solution. Less than two shells (~5.5 Å) were perturbed, with dynamics a factor of 2–10 times slower than bulk water, depending on their distance from the protein surface and the probe length of the measurement. Furthermore, this dependence on probe length demonstrates that hydration water undergoes subdiffusive motions (τ ∝ q –2.5 for the first hydration shell, τ ∝ q –2.3 for perturbed water in the second shell), an important difference with neat water, which demonstrates diffusive behavior (τ ∝ q –2 ). Our results help clarify the seemingly conflicting range of values reported for hydration water retardation as a logical consequence of the different length scales probed by the analytical techniques used.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

New correction procedures for the fast field program which extend its range

A fast field program (FFP) algorithm was developed based on the method of Lee et al., for the prediction of sound pressure level from low frequency, high intensity sources. In order to permit accurate predictions at distances greater than 2 km, new correction procedures have had to be included in the algorithm. Certain functions, whose Hankel transforms can be determined analytically, are subtracted from the depth dependent Green's function. The distance response is then obtained as the sum of these transforms and the Fast Fourier Transformation (FFT) of the residual k dependent function. One procedure, which permits the elimination of most complex exponentials, has allowed significant changes in the structure of the FFP algorithm, which has resulted in a substantial reduction in computation time.

West, M.↗
DOE OSTI2018

Disintegration in Compost Conditions and Water Uptake of Green Composites from Poly(Lactic Acid) and Hazelnut Shell Flour

Green composites of poly(lactic acid)-PLA and hazelnut shell flour (HSF) with and without epoxidized linseed oil (ELO) as plasticizer/compatibilizer were subjected to different aging conditions such as water uptake by immersion and disintegration in compost soil. The effect of the hydrolytic degradation was analyzed by measuring the weight gain as a function of the immersion time in water and calculating the corresponding diffusion coefficients. As expected, the water diffusion coefficient increases with HSF content while no remarkable change is obtained for plasticized compositions with ELO. Differential scanning calorimetry reveals a noticeable increase in crystallinity after the degradation process by water immersion. Degradation in controlled compost soil was followed thorough measurements of weight changes. In general, the weight change for a particular degradation time is lower as the HSF content increases. In addition, presence of ELO as plasticizer/compatibilizer delays the degradation process in compost soil. Scanning electron microscopy highlighted a noticeable deterioration of aged samples after 2 weeks with multiple crack formation and high surface abrasion due to microbial activity after 4 weeks.

36 MATERIALS SCIENCE↗
DOE OSTI2016

A high-finesse Fabry-Perot cavity with a frequency-doubled green laser for precision Compton polarimetry at Jefferson Lab

Here, a high-finesse Fabry-Perot cavity with a frequency-doubled continuous wave green laser (532 nm) has been built and installed in Hall A of Jefferson Lab for high precision Compton polarimetry. The infrared (1064 nm) beam from a ytterbium-doped fiber amplifier seeded by a Nd:YAG nonplanar ring oscillator laser is frequency doubled in a single-pass periodically poled MgO:LiNbO 3 crystal. The maximum achieved green power at 5 W infrared pump power is 1.74 W with a total conversion efficiency of 34.8%. The green beam is injected into the optical resonant cavity and enhanced up to 3.7 kW with a corresponding enhancement of 3800. The polarization transfer function has been measured in order to determine the intra-cavity circular laser polarization within a measurement uncertainty of 0.7%. The PREx experiment at Jefferson Lab used this system for the first time and achieved 1.0% precision in polarization measurements of an electron beam with energy and current of 1.0 GeV and 50 μA.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

TeraChem protocol buffers ( TCPB ): Accelerating QM and QM/MM simulations with a client–server model

The routine use of electronic structures in many chemical simulation applications calls for efficient and easy ways to access electronic structure programs. Here, we describe how the graphics processing unit (GPU) accelerated electronic structure program TeraChem can be set up as an electronic structure server, to be easily accessed by third-party client programs. We exploit Google’s protocol buffer framework for data serialization and communication. The client interface, called TeraChem protocol buffers (TCPB), has been designed for ease of use and compatibility with multiple programming languages, such as C++, Fortran, and Python. To demonstrate the ease of coupling third-party programs with electronic structures using TCPB, we have incorporated the TCPB client into Amber for quantum mechanics/molecular mechanics (QM/MM) simulations. The TCPB interface saves time with GPU initialization and I/O operations, achieving a speedup of more than 2× compared to a prior file-based implementation for a QM region with ~250 basis functions. We demonstrate the practical application of TCPB by computing the free energy profile of p-hydroxybenzylidene-2,3-dimethylimidazolinone (p-HBDI - )—a model chromophore in green fluorescent proteins—on the first excited singlet state using Hamiltonian replica exchange for enhanced sampling. All calculations in this work have been performed with the non-commercial freely-available version of TeraChem, which is sufficient for many QM region sizes in common use.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Apparent Explosion Moments from Rg Waves Recorded on SPE

Seismic moments for the first four chemical tests making up phase I of the Source Physics Experiments (SPE) are estimated from 6-Hz Rg waves recorded along a single radial line of geophones under the assumption that the tests are pure explosions. These apparent explosion moments are compared with moments determined from the reduced displacement potential method applied to free-field data. Light detection and ranging (lidar) observations, strong ground motions on the free surface in the vicinity of ground zero, and moment tensor inversion results are evidence that the fourth test SPE-4P is a pure explosion, and the moments show good agreement, 8×10 10 N·m for free-field data versus 9×10 10 N·m for Rg waves. In stark contrast, apparent moments for the first three tests are smaller than near-field moments by factors of 3–4. Relative amplitudes for the three tests determined from Rg interferometry using SPE-4P as an empirical Green’s function indicate that radiation patterns are cylindrically symmetric within a factor of 1.25 (25%). This fact assures that the apparent moments are reliable even though they were measured on just one azimuth. Spallation occurred on the first three tests, and ground-based lidar detected permanent deformations. As such, the source medium suffered late-time damage. In conclusion, destructive interference between Rg waves radiated by explosion and damage sources will reduce amplitudes and explain why apparent moments are smaller than near-field moments based on compressional energy emitted directly from the source.

47 OTHER INSTRUMENTATION↗
NASA NTRS1989

On the density of Halley's comet

The density of Comet Halley is presently determined as a function of (1) its ejected material's time of visibility; (2) the angular deviation alpha of the averaged reaction force due to jets of ejected material from the sun-comet direction, and (3) the thermal inertia for a variable alpha. The averaged gas ejection rate variation from the nucleus as a function of orbital true anomaly is estimated on the basis of the Green and Morris (1987) lightcurve. While some of the densities obtained are in reasonable agreement with the expected 1 g/cu cm, uncertainties associated with both parameters and assumptions weaken the significance of these density constraints.

Peale, S. J.↗
NASA NTRS1998

AIRS PFM Pulse Tube Cooler System-level Performance

JPL's Atmospheric Infrared Sounder (AIRS) instrument is being built to make precision measurements of air temperature over the surface of the Earth as a function of elevation; the flight instrument is in the final stages of assembly and checkout at this time, and uses a pair of TRW pulse tube cryocoolers operating at 55K to cool its sensitive IR focal plane.

AIRS PFM Pulse Tube Cooler System-level JPL's Atmo↗
NASA NTRSDate not supplied

Green Run Modal Test of the NASA Space Launch System Core Stage

The Core Stage of the new NASA Space Launch System (SLS) is a 212-foot tall rocket assembly—consisting primarily of two fuel tanks, an engine section, and four RS-25 rocket engines—capable of sending crew and large payloads to the moon and beyond with 1.6 million pounds of thrust. Currently, the Core Stage is in the B2 Test Stand at Stennis Space Center, undergoing a series of structural and functional tests, designated the Green Run test series. The ultimate goal of Green Run is to verify analytical models and confirm proper subsystem operation of the Core Stage. In January 2020, Green Run testing began with an experimental modal analysis test performed by the Marshal Space Flight Center modal test team. The desired free boundary condition of the Core Stage was achieved by suspending the massive spacecraft from the B2 Test Stand crane. Modal excitation was provided by a pair of 250-lb electro-dynamic shakers for multi-shaker random vibration testing, as well as a 12-pound impact hammer for impact testing. Modal response was measured with 550 accelerometers channels distributed on both the Core Stage and the B2 Test Stand crane. Following one very long night of testing, frequency response functions were calculated from the measured time histories in the target mode frequency range of 2.5 Hz to 15 Hz, and mode shapes, frequencies, and damping values were successfully extracted. The case-study presented in this paper will discuss the SLS Core Stage, the modal test setup and procedure, as well as a brief overview of the test results. Challenges associated with testing such a large, suspended structure in an outdoor environment will be discussed as well.

Green Run↗
DOE OSTI2018

Nonequilibrium electron dynamics in pump-probe spectroscopy: Role of excited phonon populations

We study the role of excited phonon populations in the relaxation rates of nonequilibrium electrons using a nonequilibrium Green's function formalism. The transient modi cations in the phononic properties are accounted for by self-consistently solving the Dyson equation for the electron and phonon Green's functions. The pump induced changes manifest in both the electronic and phononic spectral functions. We nd that the excited phonon populations suppress the decay rates of nonequilibrium electrons due to enhanced phonon absorption. The increased phonon occupation also sets the nonequilibrium decay rates and the equilibrium scattering rates apart. The decay rates are found to be time-dependent, and this is illustrated in the experimentally observed population decay of photoexcited Bi 1.5 Sb 0.5 Te 1.7 Se 1.3 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1977

Recent developments in the Green's function method

A recent computational development on the Green's function method (the method used in the computer program SOUSSA: Steady, Oscillatory and Unsteady Subsonic and Supersonic Aerodynamics) is presented. A scheme consisting of combined numerical (Gaussian quadrature) and analytical procedures for the evaluation of the source and doublet integrals used in the program is presented. This combination results in 80 to 90% reduction in computer time.

Tseng, K.↗
DOE OSTI2016

Robust half-metallicity of hexagonal SrNiO{sub 3}

In the rich panorama of the electronic and magnetic properties of 3d transition metal oxides SrMO{sub 3} (M=Ti, V, Cr, Mn, Fe, Co, Ni, Cu), one member (SrNiO{sub 3}) is missing. In this paper we use GGA+U method based on density functional theory to examine its properties. It is found that SrNiO{sub 3} is a ferromagnetic half-metal. The charge density map shows a high degree of ionic bonding between Sr and other atoms. Meanwhile, a covalent-bonding Ni–O–Ni–O–Ni chain is observed. The spin density contour of SrNiO{sub 3} further indicates that the magnetic interaction between Ni atoms mediated by O is semicovalent exchange. The density of states are examined to explore the unusual indirect magnetic-exchange mechanism. Corresponding to the total energies results, a robust half-metallic character is observed, suggesting a promising giant magneto-optical Kerr property of the material. The partial density of states are further examined to explore the origin of ferromagnetic half-metallicity. The O atoms are observed to have larger contribution at fermi level than Ni atoms to the spin-polarized states, demonstrating that O atoms play a critical role in ferromagnetic half-metallicity of SrNiO{sub 3}. Hydrostatic pressure effect is examined to evaluate how robust the half-metallic ferromagnetism is. - Graphical abstract: (a) The total energy as a function of the lattice constant a for hexagonal SrNiO3 with various magnetic phases. (b) The total electronic density of states for hexagonal SrNiO{sub 3} with FM configuration from GGA+U calculations. (c) Total electron-density distribution in the (110) plane. The colors gradually change from cyan (through pink) to yellow corresponding to charge density value from 0 to 4.0. (d) The magnetization density map in the (110) plane. The colors range from blue (through green) to red corresponding to magnetization density value from −0.15 to 0.45. Black and white contours stand for positive and negative values, respectively. - Highlights: • Hexagonal SrNiO{sub 3} is studied using first-principles method for the first time. • It is predicted that SrNiO{sub 3} is a ferromagnetic half metal. • The half-metallic ferromagnetism survives upon a pressure up to 20 GPa.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1987

Real-time artificial intelligence issues in the development of the adaptive tactical navigator

Adaptive Tactical Navigation (ATN) is a laboratory prototype of a knowledge based system to provide navigation system management and decision aiding in the next generation of tactical aircraft. ATN's purpose is to manage a set of multimode navigation equipment, dynamically selecting the best equipment to use in accordance with mission goals and phase, threat environment, equipment malfunction status, and battle damage. ATN encompasses functions as diverse as sensor data interpretation, diagnosis, and planning. Real time issues that were identified in ATN and the approaches used to address them are addressed. Functional requirements and a global architecture for the ATN system are described. Decision making with time constraints are discussed. Two subproblems are identified; making decisions with incomplete information and with limited resources. Approaches used in ATN to address real time performance are described and simulation results are discussed.

Green, Peter E.↗
DOE OSTI2014

Electrochemical solvent reorganization energies in the framework of the polarizable continuum model

Electron transfer reactions at electrochemical interfaces play a critical role in a wide range of catalytic processes. A key parameter in the rate constant expressions for such processes is the reorganization energy, which reflects the energetic cost of the solute and solvent rearrangements upon electron transfer. In this paper, we present dielectric continuum methods for calculating the solvent reorganization energy for electrochemical processes. We extend the simple approach in which the solute is represented as a point charge located a specified distance from the electrode surface to the representation of the solute as a collection of point charges corresponding to the partial atomic charges of the molecule. We also develop a method for calculating the electrochemical solvent reorganization energies with molecular-shaped cavities within the framework of the polarizable continuum model (PCM). The electronic and inertial responses of the solvent are separated according to their respective time scales, and two limiting cases of the relation between the solute and solvent electrons are examined. The effects of the electrode are included with the integral equations formalism PCM (IEF-PCM), in which the molecule-solvent boundary is treated explicitly, but the effects of the electrode-solvent boundary are included through an external Green’s function. This approach accounts for the effects of detailed molecular charge redistribution in a molecular-shaped cavity, as well as the electronic and inertial solvent responses and the effects of the electrode. The calculated total reorganization energies are in reasonable agreement with experimental measurements for a series of electrochemical systems. Inclusion of the effects of the electrode is found to be essential for obtaining even qualitatively accurate solvent reorganization energies. These approaches are applicable to a wide range of systems and can be extended to include other types of boundaries, such as a self-assembled monolayer or double layer separating the electrode and the molecule. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

Ghosh, Soumya↗
NASA NTRS1982

Nonlinear Green's function method for unsteady transonic flows

Advantages to employing Green's function in describing unsteady three-dimensional transonic flows are explored. The development of the function for application to linear subsonic and supersonic unsteady aerodynamics is reviewed. It is shown that unique solutions are possible for external flows, with all functional expressions being defined in Prandtl-Glauert space. The development of methods of using the Green's function for transonic flows is traced, noting the necessity of including the effects of significant nonlinear terms. The steady-state problem is considered to demonstrate the shock-capturing ability of the method and the usefulness of the function in the incompressible, subsonic, transonic, and supersonic areas of potential unsteady three-dimensional flows around complex configurations. Computational time is asserted to be an order of magnitude less than with finite difference methods.

Tseng, K.↗