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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Glancing incidence telescopes for space astronomy

A technique for determining the state of polarization of a light source by evaluating its image at the focus of a glancing telescope is reported. An analysis of the central disc of the diffraction image reveals if the light source is polarized, the plane of polarization, and the degree of polarization. When polarized light is incident at the aperture of a diffraction limited glancing telescope, the central disc of the diffraction pattern takes on an elliptical configuration. This ellipticity is caused by the tendency of the electric vector component in the plane of incidence to be absorbed by the reflecting material. As the state of polarization goes from plane polarized to decreasing degrees of elliptically polarized light, the ellipticity of the central disc goes from a maximum at plane polarization to zero at circular polarization. These curves give a direct relationship between the degree of polarization of a light source and the ellipticity of the central disc for this particular telescope, independent of the light source wavelength.

Alonso, J., Jr.↗
NASA NTRS2001

A Single-Vector Force Calibration Method Featuring the Modern Design of Experiments

This paper proposes a new concept in force balance calibration. An overview of the state-of-the-art in force balance calibration is provided with emphasis on both the load application system and the experimental design philosophy. Limitations of current systems are detailed in the areas of data quality and productivity. A unique calibration loading system integrated with formal experimental design techniques has been developed and designated as the Single-Vector Balance Calibration System (SVS). This new concept addresses the limitations of current systems. The development of a quadratic and cubic calibration design is presented. Results from experimental testing are compared and contrasted with conventional calibration systems. Analyses of data are provided that demonstrate the feasibility of this concept and provide new insights into balance calibration.

Parker, P. A.↗
DOE OSTI2025

Machine learning approaches for integrating multi-omics data to expand microbiome annotation (Final Technical Report)

We fulfilled all original three aims of the proposal. Following the earlier release (during the first phase of the project at Montana) of software that identifies and fills gaps in the annotation of metabolic proteins within bacterial genomes, we have nearly completed a second gap-filling tool that improves accuracy and explainability. We completed software for alignment-based annotation of protein coding DNA, allowing for coding frameshifts caused by sequencing error. Finally, we completed a neural embedding model for identifying similarities between protein sequences based on amino-wise latent vectors.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1984

Fast solutions to the steady state compressible and incompressible fluid dynamic equations

For low speed flows the use of the compressible fluid dynamic equations is inefficient. The use of an explicit scheme requires delta t to be bounded by 1/c. However, the physical parameters change over time scales of order 1/u which is much larger. Hence, it is not appropriate to use explicit schemes for very subsonic flows. Implicit schemes are hard to vectorize and frequently do not converge quickly for very subsonic flows. If one is only interested in the steady state then a minor change to an existing code can greatly increase the efficiency of an explicit method. Even when using an implicit method the proposed changes increase the efficiency of the scheme. The Euler equations for low speed flows will be considered first and then incompressible flows. The method is generalized to include viscous effects. Supersonic flow is accelerated by essentially decoupling the equations.

Turkel, E.↗
NASA NTRS1995

Visualizing turbulent mixing of gases and particles

A physical model and interactive computer graphics techniques have been developed for the visualization of the basic physical process of stochastic dispersion and mixing from steady-state CFD calculations. The mixing of massless particles and inertial particles is visualized by transforming the vector field from a traditionally Eulerian reference frame into a Lagrangian reference frame. Groups of particles are traced through the vector field for the mean path as well as their statistical dispersion about the mean position by using added scalar information about the root mean square value of the vector field and its Lagrangian time scale. In this way, clouds of particles in a turbulent environment are traced, not just mean paths. In combustion simulations of many industrial processes, good mixing is required to achieve a sufficient degree of combustion efficiency. The ability to visualize this multiphase mixing can not only help identify poor mixing but also explain the mechanism for poor mixing. The information gained from the visualization can be used to improve the overall combustion efficiency in utility boilers or propulsion devices. We have used this technique to visualize steady-state simulations of the combustion performance in several furnace designs.

Ma, Kwan-Liu↗
NASA NTRS2010

Reducing Tick-Borne Disease in Alabama: Linking Health Risk Perception with Spatial Analysis Using the NASA Earth Observing System

Lyme disease (LD) accounts for most vector-borne disease reports in the U.S., and although its existence in Alabama remains controversial, other tick-borne illnesses (TBI) such as Southern Tick-Associated Rash Illness (STARI) pose a health concern in the state. Phase One of the Marshall Space Flight Center-UAB DEVELOP study of TBI identified the presence of the chain of infection for LD (Ixodes scapularis ticks carrying Borrelia burgdorferi bacteria) and STARI (Amblyomma americanum ticks and an as-yet-unconfirmed agent) in Alabama. Both LD and STARI are associated with the development of erythema migrans rashes around an infected tick bite, and while treatable with oral antibiotics, a review of educational resources available to state residents revealed low levels of prevention information. To improve prevention, recognition, and treatment of TBI in Alabama, Phase Two builds a health communication campaign based on vector habitat mapping and risk perception assessment. NASA Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery identified likely tick habitats using remotely sensed measurements of vegetation vigor (Normalized Difference Vegetation Index) and soil moisture. Likely tick habitats, identified as those containing both high vegetation density and soil moisture, included Oak Mountain State Park, Bankhead National Forest, and Talladega National Forest. To target a high-risk group -- outdoor recreation program participants at Alabama universities -- the study developed a behavior survey instrument based on existing studies of LD risk factors and theoretical constructs from the Social Ecological Model and Health Belief Model. The survey instrument was amended to include geographic variables in the assessment of TBI knowledge, attitudes, and prevention behaviors, and the vector habitat model will be expanded to incorporate additional environmental variables and in situ data. Remotely sensed environmental data combined with risk perception assessments inform an ongoing outreach campaign consisting of stakeholder meetings and educational seminars.

Hemmings, S.↗
DOE OSTI2024

Exciting DeePMD: Learning excited-state energies, forces, and non-adiabatic couplings

We extend the DeePMD neural network architecture to predict electronic structure properties necessary to perform non-adiabatic dynamics simulations. While learning the excited state energies and forces follows a straightforward extension of the DeePMD approach for ground-state energies and forces, how to learn the map between the non-adiabatic coupling vectors (NACV) and the local chemical environment descriptors of DeePMD is less trivial. Most implementations of machine-learning-based non-adiabatic dynamics inherently approximate the NACVs, with an underlying assumption that the energy-difference-scaled NACVs are conservative fields. We overcome this approximation, implementing the method recently introduced by Richardson [J. Chem. Phys. 158, 011102 (2023)], which learns the symmetric dyad of the energy-difference-scaled NACV. Furthermore, the efficiency and accuracy of our neural network architecture are demonstrated through the example of the methaniminium cation CH 2 NH 2 + .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Spin-Density Matrix Elements in K∗(892) Photoproduction with Recoiling Λ at GlueX

We report on the measurement of spin-density matrix elements for the K∗(892) → K+π0 photoproduction process with a recoiling Λ hyperon. The measurement used high-statistics GlueX data from photoproduction off a proton target at photon energies between 8.2 and 8.8 GeV, in a kinematic regime dominated by t-channel exchange processes. GlueX is a fixed-target experiment with a linearly polarized photon beam and a nearly 4π hermetic detector, allowing extraction of the full spin observ- ables from both the K+π0 and Λ → π−p systems. The GlueX data show clear evidence of the K∗(892) resonance in the K+π0 mass spectrum, along with additional structures at higher masses that may correspond to K∗0 or K∗2 resonances. The precise measurement of the spin-density matrix elements of the K∗(892) could serve as a standard candle for con- tinuing studies of higher-mass excited K∗ states. In addition, t-channel K∗ photoproduction differs from previous measurements of non-strange vector meson photoproduction, as it is free from Pomeron exchange and is virtually unexplored in this energy regime. Furthermore, the unprece- dented data collected by GlueX allow for investigations of correlations between the Λ polarization and the spin-density matrix elements of K∗ production, paving the way for future partial-wave analyses with full spin information involving the recoil hyperon.

Li, Hao [College of William and Mary, Williamsburg↗
DOE OSTI2025

Multi-top signals of vectorlike quarks at the LHC

We point out that events with 6 or more top quarks may be observed at the LHC if certain particles exist at the TeV scale. In a model where a vectorlike quark of charge 2/3 decays into a top quark and a pseudoscalar particle, which subsequently decays into a top-antitop pair, the LHC production cross section for events with 6 top quarks may be above 10 fb. If the pseudoscalar is part of a complex scalar field, then longer cascade decays, involving the scalar partner, may lead to events with 8 or even 10 top quarks. We show that for a region of parameter space the dominant LHC signal in this model is 8 top quarks (i.e., four $t\bar{t}$ pairs). The ensuing signals would be spectacular, including many leptons and b jets. A discovery in that case would allow several cross section measurements that may determine the masses of all three new particles.

Specific BSM Phenomenology↗
DOE OSTI2024

Modern nuclear and astrophysical constraints of dense matter in a redefined chiral approach

Here, we explore the quantum chromodynamics (QCD) phase diagram’s complexities, including quark deconfinement transitions, liquid-gas phase changes, and critical points by using the chiral mean-field (CMF) model that is able to capture all these features. We introduce a vector meson field redefinition within the CMF framework, enabling precise adjustments of meson masses and coupling strengths related to vector meson interactions. Performing a new fit to the deconfinement potential, we are able to replicate recent lattice QCD results, low-energy nuclear physics properties, neutron star observational data, and key phase diagram features as per modern constraints. This approach enhances our understanding of vector mesons’ roles in mediating nuclear interactions and their impact on the equation of state, contributing to a more comprehensive understanding of the QCD phase diagram and its implications for nuclear and astrophysical phenomena.

QCD phase transitions↗
DOE OSTI2024

Constraints on simplified dark matter models involving an s -channel mediator with the ATLAS detector in pp collisions at $\sqrt{s} = 13$ TeV

This paper reports a summary of searches for a fermionic dark matter candidate in the context of theoretical models characterised by a mediator particle exchange in the s-channel. The data sample considered consists of pp collisions delivered by the Large Hadron Collider during its Run 2 at a centre-of-mass energy of $\sqrt{s} = 13$ TeV and recorded by the ATLAS detector, corresponding to up to 140 fb -1 . The interpretations of the results are based on simplified models where the new mediator particles can be spin-0, with scalar or pseudo-scalar couplings to fermions, or spin-1, with vector or axial-vector couplings to fermions. Exclusion limits are obtained from various searches characterised by final states with resonant production of Standard Model particles, or production of Standard Model particles in association with large missing transverse momentum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1973

Solar aspect determination system

Sensor containing commercially available solid-state position-sensitive light detector provides complete space-vehicle sun or moon vector information.

Farthing, W. H.↗
NASA NTRS1975

Hydrogen as an energy vector

The feasibility of utilizing hydrogen as an energy vector is considered, with special attention given to means of hydrogen production. The state-of-the-art in thermochemical processes is reviewed, and criteria for the technical and economic feasibility of large-scale thermochemical water splitting processes are presented. The production of hydrogen from coal and from photolysis of water is discussed.

Powers, W. D.↗
NASA NTRS1983

The use of laterally vectored thrust to counter thrust asymmetry in a tactical jet aircraft

A nonlinear, six degree-of-freedom flight simulator for a twin engine tactical jet was built on a hybrid computer to investigate lateral vectoring of the remaining thrust component for the case of a single engine failure at low dynamic pressures. Aircraft control was provided by an automatic controller rather than a pilot, and thrust vector control was provided by an open-loop controller that deflected a vane (located on the periphery of each exhaust jet and normally streamlined for noninterference with the flow). Lateral thrust vectoring decreased peak values of lateral control deflections, eliminated the requirement for steady-state lateral aerodynamic control deflections, and decreased the amount of altitude lost for a single engine failure.

Source record↗
NASA NTRS1986

Accurate solutions for transonic viscous flow over finite wings

An explicit multistage Runge-Kutta type time-stepping scheme is used for solving the three-dimensional, compressible, thin-layer Navier-Stokes equations. A finite-volume formulation is employed to facilitate treatment of complex grid topologies encountered in three-dimensional calculations. Convergence to steady state is expedited through usage of acceleration techniques. Further numerical efficiency is achieved through vectorization of the computer code. The accuracy of the overall scheme is evaluated by comparing the computed solutions with the experimental data for a finite wing under different test conditions in the transonic regime. A grid refinement study ir conducted to estimate the grid requirements for adequate resolution of salient features of such flows.

Vatsa, V. N.↗
NASA NTRS1990

Performance characteristics of a one-third-scale, vectorable ventral nozzle for SSTOVL aircraft

Several proposed configurations for supersonic short takeoff, vertical landing aircraft will require one or more ventral nozzles for lift and pitch control. The swivel nozzle is one possible ventral nozzle configuration. A swivel nozzle (approximately one-third scale) was built and tested on a generic model tailpipe. This nozzle was capable of vectoring the flow up to + or - 23 deg from the vertical position. Steady-state performance data were obtained at pressure ratios to 4.5, and pitot-pressure surveys of the nozzle exit plane were made. Two configurations were tested: the swivel nozzle with a square contour of the leading edge of the ventral duct inlet, and the same nozzle with a round leading edge contour. The swivel nozzle showed good performance overall, and the round-leading edge configuration showed an improvement in performance over the square-leading edge configuration.

Esker, Barbara S.↗
NASA NTRS1990

Performance characteristics of a one-third-scale, vectorable ventral nozzle for SSTOVL aircraft

Several proposed configurations for supersonic short takeoff, vertical landing aircraft will require one or more ventral nozzles for lift and pitch control. The swivel nozzle is one possible ventral nozzle configuration. A swivel nozzle (approximately one-third scale) was built and tested on a generic model tailpipe. This nozzle was capable of vectoring the flow up to + or - 23 deg from the vertical position. Steady-state performance data were obtained at pressure ratios to 4.5, and pitot-pressure surveys of the nozzle exit plane were made. Two configurations were tested: the swivel nozzle with a square contour of the leading edge of the ventral duct inlet, and the same nozzle with a round leading edge contour. The swivel nozzle showed good performance overall, and the round-leading-edge configuration showed an improvement in performance over the square-leading-edge configuration.

Esker, Barbara S.↗
NASA NTRS1993

Development of a large field-of-view KD potassium di-deuterium phosphate modulator: Center Director's Discretionary Fund

Magnetographs, which measure polarized light, allow solar astronomers to infer the magnetic field intensity on the Sun. The Marshall Space Flight Center (MSFC) Vector Magnetograph is such an imaging instrument. The instrument requires rapid modulation between polarization states to minimize seeing effects. The accuracy of those polarization measurements is dependent on stable modulators with small field-of-view errors. Although these devices are very important in ground-based telescopes, extending the field of view of electro-optical crystals such as KD*Ps (potassium di-deuterium phosphate) could encourage the development of these devices for other imaging applications. The work that was done at MSFC as part of the Center Director's Discretionary Fund (CDDF) to reduce the field-of-view errors of instruments that use KD*P modulators in their polarimeters is described.

West, E. A.↗