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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 NTRS2011

Improvements to a Response Surface Thermal Model for Orion

A study was performed to determine if a Design of Experiments (DOE)/Response Surface Methodology could be applied to on-orbit thermal analysis and produce a set of Response Surface Equations (RSE) that predict Orion vehicle temperatures within 10 F. The study used the Orion Outer Mold Line model. Five separate factors were identified for study: yaw, pitch, roll, beta angle, and the environmental parameters. Twenty-three external Orion components were selected and their minimum and maximum temperatures captured over a period of two orbits. Thus, there are 46 responses. A DOE case matrix of 145 runs was developed. The data from these cases were analyzed to produce a fifth order RSE for each of the temperature responses. For the 145 cases in the DOE matrix, the agreement between the engineering data and the RSE predictions was encouraging with 40 of the 46 RSEs predicting temperatures within the goal band. However, the verification cases showed most responses did not meet the 10 F goal. After reframing the focus of the study to better align the RSE development with the purposes of the model, a set of RSEs for both the minimum and maximum radiator temperatures was produced which predicted the engineering model output within +/-4 F. Therefore, with the correct application of the DOE/RSE methodology, RSEs can be developed that provide analysts a fast and easy way to screen large numbers of environments and assess proposed changes to the RSE factors.

Miller, Stephen W.↗
NASA NTRS2013

An Update on the Non-Mass-Dependent Isotope Fractionation under Thermal Gradient

Mass flow and compositional gradient (elemental and isotope separation) occurs when flu-id(s) or gas(es) in an enclosure is subjected to a thermal gradient, and the phenomenon is named thermal diffusion. Gas phase thermal diffusion has been theoretically and experimentally studied for more than a century, although there has not been a satisfactory theory to date. Nevertheless, for isotopic system, the Chapman-Enskog theory predicts that the mass difference is the only term in the thermal diffusion separation factors that differs one isotope pair to another,with the assumptions that the molecules are spherical and systematic (monoatomic-like structure) and the particle collision is elastic. Our previous report indicates factors may be playing a role because the Non-Mass Dependent (NMD) effect is found for both symmetric and asymmetric, linear and spherical polyatomic molecules over a wide range of temperature (-196C to +237C). The observed NMD phenomenon in the simple thermal-diffusion experiments demands quantitative validation and theoretical explanation. Besides the pressure and temperature dependency illustrated in our previous reports, efforts are made in this study to address issues such as the role of convection or molecular structure and whether it is a transient, non-equilibrium effect only.

Sun, Tao↗
NASA NTRS2018

Microphysics and Radiation Effect of Dust on Saharan Air Layer: An HS3 Case Study

A Saharan air layer (SAL) event associated with a nondeveloping African easterly wave (AEW) over the main development region of the eastern Atlantic was sampled by the NASA Global Hawk aircraft on 24-25 August 2013 during the NASA Hurricane and Severe Storm Sentinel (HS3) campaign and was simulated with the NASA Unified Weather Research and Forecasting (NU-WRF) Model. Airborne, ground-based, and spaceborne measurements were used to evaluate the model performance. The microphysical and radiative effects of dust and other aerosols on the SAL structure and environment were investigated with the factor-separation method. The results indicate that relative to a simulation without dust-radiative and microphysical impacts, Saharan dust and other aerosols heated the SAL air mainly through shortwave heating by the direct aerosol-radiation (AR) effect, resulting in a warmer (up to 0.6 K) and drier (up to 5% RH reduction) SAL and maintaining the strong temperature inversion at the base of the SAL in the presence of predominant longwave cooling. Radiative heating of the dust accentuated a vertical circulation within the dust layer, in which air rose (sank) in the northern (southern) portions of the dust layer. Furthermore, above and to the south of the dust layer, both the microphysical and radiative impacts of dust tended to counter the vertical motions associated with the Hadley circulation, causing a small weakening and southward shift of convection in the intertropical convergence zone (ITCZ) and reduced anvil cloud to the north. Changes in moisture and cloud/precipitation hydrometeors were largely driven by the dust induced changes in vertical motion. Dust strengthened the African easterly jet by up to ~1ms(exp -1) at the southern edge of the jet, primarily through the AR effect, and produced modest increases in vertical wind shear within and in the vicinity of the dust layer. These modulations of the SAL and AEW environment clearly contributed to the nondevelopment of this AEW.

Tao, Zhining↗
NASA NTRS1975

Further analysis of the effects of baffles on combustion instability

A computerized analytical model, developed to predict the effects of baffles on combustion instability, was modified in an effort to improve the ability to properly predict stability effects. The model was modified: (1) to replace a single spatially-averaged response factor by separate values for each baffle compartment; (2) to calculate the axial component of the acoustic energy flux, and (3) to permit analysis of traveling waves in a thin annular chamber. Allowance for separate average response factors in each baffle compartment was found to significantly affect the predicted results. With this modification, an optimum baffle length was predicted which gave maximum stability.

Oberg, C. L.↗
NASA NTRS1974

Potential capabilities for compression of information of certain data processing systems

This article undertakes to study a generalized block diagram of a data collection and processing system of a spacecraft in which a number of sensors or outputs of scientific instruments are cyclically interrogated by a commutator, methods of writing the supplementary information in a frame on the example of a certain hypothetical telemetry system, and the influence of statistics of number of active channels in a frame on frame compression factor. The separation of the data compression factor of the collection and processing system of spacecraft into two parts used in this work allows determination of the compression factor of an active frame depending not only on the statistics of activity of channels in the telemetry frame, but also on the method of introduction of the additional address and time information to each frame.

Khodarev, Y. K.↗
DOE OSTI2022

Ligand-Assisted Separation of Rare Earth Elements via Capillary Electrophoresis

Rare earth elements (REEs) are a class of critical materials vital in applications such as EVs, batteries, and defense weapons systems. These elements are found primarily in ores, and due to their similar chemical behavior, the challenge remains to find an effective means of separation. The addition of ligands of varying charge, size, denticity, etc. can help to increase separation, yet the mechanistic behavior and factors influencing separation are still poorly understood. Here, iminodiacetic acid (IDA) is used to exploit and maximize differences in electrophoretic mobilities between adjacent REEs. Mobilities and diffusion coefficients of REEs in aqueous media are measured via CE and are compared to MD and FEM simulations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Modeling Isotope Separation in Electrochemical Lithium Deposition

Naturally occurring Li consists of two stable isotopes, 6 Li with an abundance of about 7.5%, and 7 Li making up the remainder with 92.5%. The development of a 6 Li enrichment technique, in terms of technical reliability and environmental safety to reach 6 Li future requirements, represents a key step in the roadmap for nuclear fusion energy supply worldwide. This paper uses finite element analysis-based models to simulate electrochemical Li isotope separation, which is an attractive method in terms of simplicity, safety, and scalability. In the model, we quantitatively analyze how different electrochemical factors including thermodynamics, charge-transfer kinetics, and diffusivities affect the separation process (separation factor), together with cell parameters, such as cell length and current density. The maximum separation factor of 1.128 could be obtained with the cell under the optimal thermodynamic, kinetic, and diffusive conditions, which is among the highest separation factors ever reported. Furthermore, these results will assist in designing the actual isotope separation setup with large separation factor and appropriate timing for sample collection.

07 ISOTOPE AND RADIATION SOURCES↗
NASA NTRS1984

Real Surface Effects in Elastohydrodynamic Lubrication

Following a general discussion of real effects in EHL, consideration is given in detail to the role played by stochastic roughness superimposed on the nominal solid boundaries. Particular attention is given to the full-film EHL regime where incipient asperity contact bears a negligible fraction of the load. Flow, from which an averaged Reynolds equation can be formed, is nonetheless modified by the amplitude and texture of the roughness patterns. In describing these effects by means of certain well-defined flow factors, it is found that only two extra parameters are needed - the rms surface height and the ratio of the correlation lengths in the two principal roughness directions. In a lowest order perturbation expansion of these flow factors in powers of the ratio of rms roughness to nominal film thickness, no other properties of the roughness appear. In most cases of practical interest, the factors describing Poiseuille flow are separable into the sum of two single-surface flow factors which means that a combination of a single equivalent rough surface versus an ideal smooth surface can always be found. For flow entrained by slip velocity the factors separate instead into a difference of single-surface factors and it becomes significant which of the two surfaces carries the equivalent roughness. Results are discussed of some applications of the averaged Reynolds equation based on the flow factor method to the EHL line contact problem. Finally, the partial EHL regime is considered where comparable load fractions are carried by the hydrodynamic film and by incipient mechanical contact. An extension of the method into this regime by combining it with asperity contact models appears most encouraging.

John H Tripp↗
DOE OSTI2021

Exploring QCD Factorization at Moderate Energy Scales

Asymptotic freedom in QCD facilitates the use of partonic degrees of freedom over short distances, but physical processes are sensitive to a wide range of scales. Thus, it is necessary in QCD calculations to utilize a factorization scheme to separate a process into perturbative and non-perturbative factors. This separation relies on an assumption that one energy scale is infinitely larger than the other scales involved in the process. However, much experimental research in areas such as nucleon structure and quark-hadron duality occur at more moderate energy scales where that basic assumption may not be true but perturbative calculations should still be useful. Thus, an exploration of the limits of factorization at more moderate energy scales is needed. This dissertation examines various aspects of factorization at these energy scales first by applying the necessary approximations to a simple model where exact calculations are possible and so the effects of these approximations can be quantified. This is followed by examining areas where corrections are known to be needed. First is an exploration of target mass corrections (TMCs) in the case of deep inelastic scattering (DIS), including a discussion of what large corrections imply about the target structure. Second, is a general examination of PDFs and FFs at moderate scales. Third, I will discuss how this fits into the long-term effort to study the transition between small transverse momentum (generated non-perturbatively) and large transverse momentum (generated in the hard process)

Moffat, Eric↗
NASA NTRS2010

A Survey of Factors Affecting Blunt Leading-Edge Separation for Swept and Semi-Slender Wings

A survey is presented of factors affecting blunt leading-edge separation for swept and semi-slender wings. This class of separation often results in the onset and progression of separation-induced vortical flow over a slender or semi-slender wing. The term semi-slender is used to distinguish wings with moderate sweeps and aspect ratios from the more traditional highly-swept, low-aspect-ratio slender wing. Emphasis is divided between a selection of results obtained through literature survey a section of results from some recent research projects primarily being coordinated through NATO s Research and Technology Organization (RTO). An aircraft context to these studies is included.

Luckring, James M.↗
NASA NTRS1985

Strategies for analyzing mixed pixels in remotely sensed imagery

Two uncalibrated synthetic aperture radar (SAR) scenes from Death Valley, California, and two uncalibrated scenes from Owens Valley, California, were used to test a technique to identify and separate the primary factors associated with multipolarized radar image sets. Unique to the technique is the concept that varied types of radar polarization signatures are a result of the interaction of a few physical factors (e.g., roughness, volume scattering, and dielectric constant). Thus, the varied signatures observed in an image reflect the interaction between these factors. The objectives are to first separate the interaction of factors directly influencing the measurement and to attempt to identify these factors. Interpretation of the SAR image sets proceeds by testing models that hypothesize the cause and effect relations between those factors directly affecting the radar measurement and those features of interest to the interpreter. The results of our analysis indicated two consistent endmember types over all four image scenes. These types are defined by a high flat polarized signature near a level of 255 DN and a low level flat signature near 0 DN for all polarizations. Four other endmember types were also isolated. The spatial distribution of these endmember types indicates possible correspondence to surface volume scattering and changes in surface dielectric. However, the shapes of these endmember types were different from scene to scene.

Smith, M.↗
NASA NTRS2009

Head Pose Estimation Using Multilinear Subspace Analysis for Robot Human Awareness

Mobile robots, operating in unconstrained indoor and outdoor environments, would benefit in many ways from perception of the human awareness around them. Knowledge of people's head pose and gaze directions would enable the robot to deduce which people are aware of the its presence, and to predict future motions of the people for better path planning. To make such inferences, requires estimating head pose on facial images that are combination of multiple varying factors, such as identity, appearance, head pose, and illumination. By applying multilinear algebra, the algebra of higher-order tensors, we can separate these factors and estimate head pose regardless of subject's identity or image conditions. Furthermore, we can automatically handle uncertainty in the size of the face and its location. We demonstrate a pipeline of on-the-move detection of pedestrians with a robot stereo vision system, segmentation of the head, and head pose estimation in cluttered urban street scenes.

Ivanov, Tonislav↗
DOE OSTI2024

Anomaly detection in collider physics via factorized observables

To maximize the discovery potential of high-energy colliders, experimental searches should be sensitive to unforeseen new physics scenarios. This goal has motivated the use of machine learning for unsupervised anomaly detection. In this paper, we introduce a new anomaly detection strategy called : factorized observables for regressing conditional expectations. Our approach is based on the inductive bias of factorization, which is the idea that the physics governing different energy scales can be treated as approximately independent. Assuming factorization holds separately for signal and background processes, the appearance of nontrivial correlations between low- and high-energy observables is a robust indicator of new physics. Under the most restrictive form of factorization, a machine-learned model trained to identify such correlations will in fact converge to the optimal new physics classifier. We test on a benchmark anomaly detection task for the Large Hadron Collider involving collimated sprays of particles called jets. By teasing out correlations between the kinematics and substructure of jets, our method can reliably extract percent-level signal fractions. This strategy for uncovering new physics adds to the growing toolbox of anomaly detection methods for collider physics with a complementary set of assumptions. Published by the American Physical Society 2024

Astronomy & Astrophysics↗
DOE OSTI2024

Physics and chemistry from parsimonious representations: image analysis via invariant variational autoencoders

Electron, optical, and scanning probe microscopy methods are generating ever increasing volume of image data containing information on atomic and mesoscale structures and functionalities. This necessitates the development of the machine learning methods for discovery of physical and chemical phenomena from the data, such as manifestations of symmetry breaking phenomena in electron and scanning tunneling microscopy images, or variability of the nanoparticles. Variational autoencoders (VAEs) are emerging as a powerful paradigm for the unsupervised data analysis, allowing to disentangle the factors of variability and discover optimal parsimonious representation. Here, we summarize recent developments in VAEs, covering the basic principles and intuition behind the VAEs. The invariant VAEs are introduced as an approach to accommodate scale and translation invariances present in imaging data and separate known factors of variations from the ones to be discovered. We further describe the opportunities enabled by the control over VAE architecture, including conditional, semi-supervised, and joint VAEs. Several case studies of VAE applications for toy models and experimental datasets in Scanning Transmission Electron Microscopy are discussed, emphasizing the deep connection between VAE and basic physical principles. Python codes and datasets discussed in this article are available at https://github.com/saimani5/VAE-tutorials and can be used by researchers as an application guide when applying these to their own datasets.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Quasielastic lepton-nucleus scattering and the correlated Fermi gas model

The neutrino research program in the coming decades will require improved precision. A major source of uncertainty is the interaction of neutrinos with nuclei that serve as targets for such experiments. Broadly speaking, this interaction often depends, e.g., for charge-current quasielastic scattering, on the combination of “nucleon physics,” expressed by form factors, and “nuclear physics,” expressed by a nuclear model. It is important to get a good handle on both. We present a fully analytic implementation of the correlated Fermi gas model for electron-nucleus and charge-current quasielastic neutrino-nucleus scattering. The implementation is used to compare separately form factors and nuclear model effects for both electron-carbon and neutrino-carbon scattering data. Published by the American Physical Society 2025

Bhattacharya, Bhubanjyoti (ORCID:000000032238321X)↗