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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

An International Laboratory Comparison Study on Approximating the Enthalpy of Adsorption via the Clausius‐Clapeyron Approach

Materials-based gas capture and storage is an increasingly important area of research. Robust and accurate determination of material properties is required for judicial selection of materials for specific applications and for engineering materials–based systems at scale. One key property is the strength of the adsorbate–adsorbent interaction often quantified via the isosteric enthalpy of adsorption. The heat of adsorption can be measured directly through calorimetry; however, a more widely used approach is to apply the Clausius-Clapeyron (CC) equation to adsorption isotherms collected at different temperatures. While this approach appears to be straightforward, there exist multiple variants in the application of the methodologies employed. This raises the question on how these variations may or may not affect the determined results. Presented here is a discussion of the most common methodologies and a comparison of indirect determinations (via CC) of the isosteric enthalpy of adsorption by different laboratories on identical material. Included in that comparison are discussions on the measurement and analysis reproducibility. Importantly, details of the methodologies are shown to be critical when comparing enthalpies among laboratories, and different methodologies contribute to significant discrepancies and artifacts in the results. Recommendations are provided to promote robust determination and the reporting thereof.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Ecological theory applied to environmental metabolomes reveals compositional divergence despite conserved molecular properties

Stream and river systems transport and process substantial amounts of dissolved organic matter (DOM) from terrestrial and aquatic sources to the ocean, with global biogeochemical implications. However, the underlying mechanisms affecting the spatiotemporal organization of DOM composition are under-investigated. To understand the principles governing DOM composition, we leverage the recently proposed synthesis of metacommunity ecology and metabolomics, termed ‘meta-metabolome ecology.’ Applying this novel approach to a freshwater ecosystem, we demonstrated that despite similar molecular properties across metabolomes, metabolite identity significantly diverged due to environmental filtering and variations in putative biochemical transformations. We refer to this phenomenon as ‘thermodynamic redundancy,’ which is analogous to the ecological concept of functional redundancy. We suggest that under thermodynamic redundancy, divergent metabolomes can support equivalent biogeochemical function just as divergent ecological communities can support equivalent ecosystem function. As these analyses are performed in additional ecosystems, potentially generalizable principles, like thermodynamic redundancy, can be revealed and provide insight into DOM dynamics.

Danczak, Robert E.↗
DOE OSTI2021

Long-term leaf C:N ratio change under elevated CO 2 and nitrogen deposition in China: Evidence from observations and process-based modeling

Climate change, elevating atmosphere CO 2 (eCO 2 ) and increased nitrogen deposition (iNDEP) are altering the biogeochemical interactions between plants, microbes and soils, which further modify plant leaf carbon-nitrogen (C:N) stoichiometry and their carbon assimilation capability. Many field experiments have observed large sensitivity of leaf C:N ratio to eCO 2 and iNDEP. However, the large-scale pattern of this sensitivity is still unclear, because eCO 2 and iNDEP drive leaf C:N ratio toward opposite directions, which are further compounded by the complex processes of nitrogen acquisition and plant-and-microbial nitrogen competition. Here, we attempt to map the leaf C:N ratio spatial variation in the past 5 decades in China with a combination of data-driven model and process-based modeling. These two approaches showed consistent results. Over different regions, we found that leaf C:N ratio had significant but uneven changes between 2 time periods (1960-1989 and 1990-2015): a 5% ± 8% increase for temperate grasslands in northern China, a 3% ± 6% increase for boreal grasslands in western China, and by contrast, a 7% ± 6% decrease for temperate forests in southern China, and a 3% ± 5% decrease for boreal forests in northeastern China. Additionally, the structural equation models indicated that the leaf C:N change was sensitive to ΔNDEP, ΔCO 2 and ΔMAT rather than ΔMAP and ecosystem types. In this work, process-based modeling suggested that iNDEP was the main source of soil mineral nitrogen change, dominating leaf C:N ratio change in most areas in China, while eCO 2 led to leaf C:N ratio increase in low iNDEP area. This study also indicates that the long-term leaf C:N ratio acclimation was dominated by climate constraint, especially temperature, but was constrained by soil N availability over decade scale.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Anode sensitivity calibration of photomultiplier tubes used as a readout of the ELOSS detector

We present and discuss the methodology and results for an anode sensitivity calibration of Photomultiplier Tubes (PMTs) that serve as the optical readout of the Energy Loss Optical Scintillation System (ELOSS). The ELOSS detector, under development at the Facility for Rare Isotope Beams (FRIB), is a gaseous Xe scintillation-based detector designed to identify the atomic number (Z) of nuclear reaction fragments by energy-loss measurement. Variation in the anode sensitivity from tube to tube of commercially available PMTs limits ELOSS from reaching its ultimate Z resolution. A methodical approach to calibrating PMT anode sensitivities to a single target value by systematic PMT gain corrections is presented. Although the calibration process is discussed in terms of its impact on ELOSS performance, the presented method is applicable to any optical detector system composed of a large number of PMTs needing anode sensitivity calibration.

Instrumentation for heavy-ion accelerators↗
DOE OSTI2021

Meta-analysis identifies pleiotropic loci controlling phenotypic trade-offs in sorghum

Abstract Community association populations are composed of phenotypically and genetically diverse accessions. Once these populations are genotyped, the resulting marker data can be reused by different groups investigating the genetic basis of different traits. Because the same genotypes are observed and scored for a wide range of traits in different environments, these populations represent a unique resource to investigate pleiotropy. Here, we assembled a set of 234 separate trait datasets for the Sorghum Association Panel, a group of 406 sorghum genotypes widely employed by the sorghum genetics community. Comparison of genome-wide association studies (GWAS) conducted with two independently generated marker sets for this population demonstrate that existing genetic marker sets do not saturate the genome and likely capture only 35–43% of potentially detectable loci controlling variation for traits scored in this population. While limited evidence for pleiotropy was apparent in cross-GWAS comparisons, a multivariate adaptive shrinkage approach recovered both known pleiotropic effects of existing loci and new pleiotropic effects, particularly significant impacts of known dwarfing genes on root architecture. In addition, we identified new loci with pleiotropic effects consistent with known trade-offs in sorghum development. These results demonstrate the potential for mining existing trait datasets from widely used community association populations to enable new discoveries from existing trait datasets as new, denser genetic marker datasets are generated for existing community association populations.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

EQC: Ensembled Quantum Computing for Variational Quantum Algorithms

Variational quantum algorithms (VQA), which are comprised of a classical optimizer and a parameterized quantum circuit, emerges as one of the most promising approaches of harvesting quantum power in the noisy-intermediate-scale-quantum (NISQ) era. However, the deployment of VQAs on today's NISQ devices often faces considerable system noise and prohibitively slow training speeds. On the other hand, the expensive supporting sources and infrastructure make quantum computers extremely keen on high utilization. In this paper, we propose a novel way of thinking about a quantum backend: rather than relying on one physical device which tends to introduce platform-specific noise and bias, a quantum ensemble, which distributes quantum tasks across parallel devices, can serve as a virtualized quantum computer for offering reduced noise levels through an adaptive mixture and also provide significantly improved training speeds through parallelization. With this idea, we build a distributive VQA optimization framework called DVQA, serving as the first effort in adopting parallel quantum devices for cooperative VQA training. To further constraint noise and speed-up convergence, we design a model for individual NISQ devices concerning their properties and running conditions, and propose a weighting mechanism for regularizing the returned gradients. Extensive evaluations on 10 IBM-Q quantum devices using the VQE example show that the distributive VQA training framework can substantially boost the training speed by 10.5x on average (up to 86x and at least 5.2x) with improved training accuracy.

Stein, Samuel A.↗
DOE OSTI2020

Uncertainties in Density and Simulation Parameters for Radiographic Reconstructions Using Machine Learning

We will develop new and improved methods that will enable a fuller and more extensive use of experimental data, such as from radiographic imaging, towards better characterizing and reducing uncertainties in predictive modeling of weapons performance. We will achieve this by leveraging recent developments in the areas of computational imaging, statistical and machine learning, and reduced order modeling. Key new aspects of our approach include (a) a coupling of deep learning based density reconstruction with fast hydrodynamics simulators that will permit the development of certain guarantees on extrapolatability and bounds on certain other hydrodynamics-related para- metric uncertainties and (b) a dual approach towards better characterizing uncertainties in density reconstruction using deep learning based surrogates to accelerate Bayesian reconstructions on the one hand and using variational inference and Bayesian machine learning on the other hand.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
NASA NTRS1974

Apollo experience report: Command and service module communications subsystem

The development of spacecraft communications hardware from design to operation is described. Programs, requirements, specifications, and design approaches for a variety of functions (such as voice, telemetry, television, and antennas) are reviewed. Equipment environmental problems such as vibration, extreme temperature variation, and zero gravity are discussed. A review of the development of managerial techniques used in refining the roles of prime and subcontractors is included. The hardware test program is described in detail as it progressed from breadboard design to manned flight system evaluations. Finally, a series of actions is recommended to managers of similar projects to facilitate administration.

Lattier, E. E., Jr.↗
NASA NTRS1978

Ionospheric range-rate effects in satellite-to-satellite tracking

Ionospheric range and range rate corrections in satellite-to-satellite tracking were investigated and the magnitude of errors that have to be considered for communications between satellites and related experiments was defined. The major causes of the sudden and sometimes large variations apparent in the ionospheric range and range rate corrections along the satellite arc are the geometric effects of the raypath and the curved ionosphere, and the localized perturbations in electron density along the satellite-to-satellite line of sight. Ionospheric tracking errors are greatly effected by the following parameters, whose influence was thoroughly investigated: satellite height, height of maximum electron density, localized ionospheric perturbations and gradients, and electron density variations with diurnal, day-to-day, seasonal, and solar cycle patterns. The results point to the need of using a sophisticated modeling approach incorporating daily solar data, and where possible actual ionospheric measurements as update information. Simulations were performed for satellites at various heights: Apollo, Geos, and Nimbus tracked by ATS-6; and in two different geometric configurations: coplanar and perpendicular orbits.

Bent, R. B.↗
NASA NTRS1979

Piloted simulator investigation of helicopter control systems effects on handling qualities during instrument flight

An exploratory piloted simulation was conducted to investigate the effects of the characteristics of helicopter flight control systems on instrument flight handling qualities. This joint FAA/NASA study was motivated by the need to improve instrument flight capability. A near-term objective is to assist in updating the airworthiness criteria for helicopter instrument flight. The experiment consisted of variations of single-rotor helicopter types and levels of stability and control augmentation systems (SCAS). These configurations were evaluated during an omnirange approach task under visual and instrument flight conditions. The levels of SCAS design included a simple rate damping system, collective decoupling plus rate damping, and an attitude command system with collective decoupling. A limited evaluation of stick force versus airspeed stability was accomplished. Some problems were experienced with control system mechanization which had a detrimental effect on longitudinal stability. Pilot ratings, pilot commentary, and performance data related to the task are presented.

Forrest, R. D.↗
NASA NTRS1984

Thunderstorm cloud height-rainfall rate relations for use with satellite rainfall estimation techniques

Observational studies of thunderstorm cloud height-rainfall rate and cloud height-volume rainfall rate relations are reviewed with significant variations being noted among climatological regimes. Analysis of the Florida (summer) and Oklahoma (spring) relations are made using a one-dimensional cloud model to ascertain the important factors in determining the individual cloud-rain relations and the differences between the two regimes. In general, the observed relations are well simulated by the model-based calculations. The generally lower predicted rain rates in Oklahoma (as compared to Florida) result from lower precipitation efficiencies which are due to a combination of larger entrainment (related to larger vertical wind shear) and drier environment. The generally steeper slope of the Oklahoma rain rate height curves is shown to be due to a stronger variation in maximum vertical velocity with cloud top height, which, in turn, is related to the greater static stability in the range of cloud tops. The impact of the regime-to-regime variations on empirical rain estimation schemes based on satellite-observed cloud height or cloud temperature information is discussed and a rain estimation approach based on model-generated cloud-rain relations is outlined.

Adler, R. F.↗
NASA NTRS1986

Free boundary shape of a convectively cooled solidified region

The two-dimensional steady-state shape of a solidified region, such as a frost layer, was determined analytically for formation on a plate that is convectively cooled. The nonuniform shape of the layer is produced by exposure to a spatially nonuniform distribution of radiant energy. For high convective cooling the cooled wall approaches a uniform temperature, and an exact solution is obtained for the free boundary shape. For a lesser amount of convective cooling, the variation in temperature along the cooled boundary is treated by a boundary perturbation method. Some illustrative examples are given that show the effects of nonuniform heating and the magnitude of convective heat transfer at the cooled wall. Only one boundary condition is approximated by the perturbation solution; all of the other boundary conditions are satisfied exactly. The calculated results given here were found to satisfy the approximate boundary condition within a very small error.

Siegel, R.↗
NASA NTRS1986

Laser velocimeter measurements in shrouded and unshrouded radial flow pump impellers

Shrouded and unshrouded versions of a four-vaned radial flow impeller with a design flow coefficient of 0.063 were tested in a volute pump using a two-component frequency-shifted laser velocimeter. Velocity profiles were measured at six flow rates and at four radial and six circumferential positions in the volute. The variations of the velocity from blade to blade and in the axial direction were measured and are presented. A passage vortex caused by tip leakage and relative casing wall velocity was found in the unshrouded impeller. The tip leakage did not accumulate in the suction wake region; the suction wake region was only 30 to 50 percent as large in the unshrouded impeller as compared to the shrouded impeller. The slip was 30 percent higher in the unshrouded impeller and the variation of slip with flow rate is presented. At no measured position in the impellers did the slip factor reach unity; the closest approach was 0.90. Reverse loadings of the vanes at outer radii were found for flow rates below the impeller/volute matching point for both impellers.

Hamkins, C. P.↗
NASA NTRS1986

Mass distribution of particulates measured by Giotto's Dust Impact Detection System (DIDSY) in the close encounter period

The cumulative mass distribution of the comet Halley dust efflux in the close encounter period -300 to +300 sec was analyzed. Analysis of the cumulative mass distribution index (alpha) shows considerable short time scale variation. There is clear evidence from the flux rates of passage through at least one major dust enhancement (dust jet) just after closest approach and this is associated with a steepening of the alpha. Comparison with measurements from other sources, and with preencounter predictions, is also made.

Zarnecki, J. C.↗
NASA NTRS1988

VSAERO analysis of tip planforms for the free-tip rotor

The results of a numerical analysis of two interacting lifting surfaces separated in the spanwise direction by a narrow gap are presented. The configuration consists of a semispan wing with the last 32 percent of the span structurally separated from the inboard section. The angle of attack of the outboard section is set independently from that of the inboard section. In the present study, the three-dimensional panel code VSAERO is used to perform the analysis. Computed values of tip surface lift and pitching moment coefficients are correlated with experimental data to determine the proper approach to model the gap region between the surfaces. Pitching moment data for various tip planforms are also presented to show how the variation of tip pitching moment with angle of attack may be increased easily in incompressible flow. Calculated three-dimensional characteristics in compressible flow at Mach numbers of 0.5 and 0.7 are presented for new tip planform designs. An analysis of sectional aerodynamic center shift as a function of Mach number is also included for a representative tip planform. It is also shown that the induced drag of the tip surface is reduced for negative incidence angles relative to the inboard section. The results indicate that this local drag reduction overcomes the associated increase in wing induced drag at high wing lift coefficients.

Martin, D. M.↗
NASA NTRS1988

Patched-grid computations of high-speed inlet flows

Two implicit algorithms for the compressible Navier-Stokes equations are applied to the computation of high-speed inlet flows typical of those which are encountered on propulsion systems of advanced hypersonic vehicles. A patched grid formulation is used to treat accurately the blunt cowl interaction with the forebody compression field and efficiently treat variations in inlet geometry downstream of the inlet entrance. Results from the two algorithms, each based on an upwind-biased spatial differencing approach for the convective and pressure terms within a flux-difference-splitting framework, are compared with experimental results for both inlets, and reasonable agreement is found.

Thomas, J. L.↗