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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

A Volume Flux Approach to Cryolava Dome Emplacement on Europa

We previously modeled a subset of domes on Europa with morphologies consistent with emplacement by viscous extrusions of cryolava. These models assumed instantaneous emplacement of a fixed volume of fluid onto the surface, followed by relaxation to form domes. However, this approach only allowed for the investigation of late-stage eruptive processes far from the vent and provided little insight into how cryolavas arrived at the surface. Consideration of dome emplacement as cryolavas erupt at the surface is therefore pertinent. A volume flux approach, in which lava erupts from the vent at a constant rate, was successfully applied to the formation of steep-sided volcanic domes on Venus. These domes are believed to have formed in the same manner as candi-date cryolava domes on Europa. In order to gain a more complete understanding of the potential for the emplacement of Europa domes via extrusive volcanism, we have applied this new volume flux approach to the formation of putative cryovolcanic domes on Europa. Assuming as in that europan cryolavas are briny, aqueous solutions which may or may not contain some ice crystal fraction, we present the results of this modeling and explore theories for the formation of low-albedo moats that surround some domes.

Cryolava Dome Emplacement↗
NASA NTRS2020

Investigation of a Helicopter Individual Blade Control (IBC) System in Two Full-Scale Wind Tunnel Tests: Volume II—Tabulated Data

This volume presents the tabulated data acquired during the testing of an individual blade control (IBC) system for a full-scale BO-105 helicopter rotor in the NASA Ames 40- by 80-Foot Wind Tunnel. The data are divided into appendices according to the data type. Table 6 in Volume I presents a summary of the data acquired during the 1993 and 1994 IBC wind tunnel tests. The data have been tabulated according to test year, run number, and point number (e.g., 1993 IBC Test, Run 20, pt. 3). The 1993 and 1994 IBC tests were each started with a run number of 1. A new run number was assigned each time the wind tunnel and rotor were restarted, even if no data were acquired during the previous run. For this reason, some run numbers appear to be missing, yet all of the IBC data is included in the tabulated data, with one notable exception. The Fourier series data presented in Appendices H, L, and N are provided only for the data points identified with the ”•“ symbol in the last column of Table 6 in Volume I. This was done to keep the physical size of the data tables reasonable. The table below shows which data were included in these appendices; the data encompass the majority of the IBC inputs tested in the wind tunnel. Data for the points not included in Appendices H, L, and N have been retained in the BO-105 IBC database and are electronically available from NASA Ames Research Center.

Investigation↗
DOE OSTI2016

Damping optimization for wave energy converters with compressible volumes.

The addition of a compressible degree of freedom (CDOF) to a wave energy converter (WEC)-which results in a compressible WEC-has been shown to significantly increase power absorption compared to a rigid WEC of the same shape and mass for a variety of architectures. This study demonstrates that a compressible point absorber, with a passive power-take-off (PTO) and optimized damping, can also achieve equal or better performance levels than an optimally controlled rigid point absorber (with the same shape and mass) using reactive power from the PTO. Wave energy is converted to mechanical energy in both cases using a linear damper PTO, with the PTO coefficient optimized for each resonance frequency and compressible volume. The large compressible volume required to tune the compressible point absorber to the desired frequency is a practical limitation that needs to be addressed with further research, especially for low frequencies. While realistic, these auxiliary units would increase the CapEx and OpEx costs, potentially reducing the aforementioned benefits gained by CDOF. However, alternative approaches can be developed to implement CDOF without the large compressible volume requirements, including the development of flexible surface panels tuned with mechanical springs.

16 TIDAL AND WAVE POWER↗
DOE OSTI2023

Kernel Buffer Volume Fraction Margin of the AGR Designed Fuel Particle

Modeling results used to assess the fuel performance of the TRISO-coated fuel particles as a function of kernel/buffer volume fraction include SiC tangential stress, formation of the buffer/IPyC gap, particle temperature profile, internal particle pressure, fission gas released from the kernel, probability of fuel particle failure, and fission product diffusion. These results were evaluated at two burnup levels and irradiation temperatures to bound expected steady-state irradiation conditions. In general, increasing the kernel/buffer volume fraction increases the SiC stress and subsequently the failure probability of a fuel particle when compared to the AGR designed particle. There was little impact on the fission product diffusion through the particle as the kernel/buffer volume fraction increased.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

An index to characterize gas‐solid and solid‐solid mixing from average volume fraction fields

Abstract A mixing index based on solid volume fraction fields is developed for gas‐solid flows. Conventional mixing indices are based on particle realizations of granular mixing and are applicable to experimental data or discrete element method simulations. However, these indices cannot be used as‐is for multifluid models, and an index for characterizing mixing in gas‐solid flows from continuous fields is needed. The performance of the new mixing index is tested in two applications. The first is a 3D simulation of the mixing of biomass and sand in a fluidized bed reactor, and the second is a 2D simulation of binary particle segregation in a fluidized bed. The simulations are performed using OpenFOAM®. The mixing index is used to quantify gas‐solid mixing using solid volume fractions and solid‐solid mixing using solid fractions. The formulation of conventional mixing indices is extended to be used with solid volume fractions fields, and methods for performance improvement are presented.

09 BIOMASS FUELS↗
DOE OSTI2021

Leveraging Free Volume Manipulation to Improve the Membrane Separation Performance of Amine‐Functionalized PIM‐1

Abstract Gas‐separation polymer membranes display a characteristic permeability–selectivity trade‐off that has limited their industrial use. The most comprehensive approach to improving performance is to devise strategies that simultaneously increase fractional free volume, narrow free volume distribution, and enhance sorption selectivity, but generalizable methods for such approaches are exceedingly rare. Here, we present an in situ crosslinking and solid‐state deprotection method to access previously inaccessible sorption and diffusion characteristics in amine‐functionalized polymers of intrinsic microporosity. Free volume element (FVE) size can be increased while preserving a narrow FVE distribution, enabling below‐upper bound polymers to surpass the H 2 /N 2 , H 2 /CH 4 , and O 2 /N 2 upper bounds and improving CO 2 ‐based selectivities by 200 %. This approach can transform polymers into chemical analogues with improved performance, thereby overcoming traditional permeability–selectivity trade‐offs.

Mizrahi Rodriguez, Katherine↗
DOE OSTI2025

Linking Lattice Strain and Fractal Dimensions to Non‐monotonic Volume Changes in Irradiated Nuclear Graphite

Graphite's resilience to high temperatures and neutron damage makes it vital for nuclear reactors, yet irradiation alters its microstructure, degrading key properties. We used small- and wide-angle X-ray scattering to study neutron-irradiated fine-grain nuclear graphite (Grade G347A) across varied temperatures and fluences. Results show significant shifts in internal strain and porosity, correlating with radiation-induced volume changes. Notably, porosity volume distribution (fractal dimensions) follows non-monotonic volume changes, suggesting a link to the Weibull distribution of fracture stress.

X-ray scattering↗
DOE OSTI2014

Effect of temperature and volume on the tensile and adhesive properties of photocurable resins

ABSTRACT Knowing the mechanical properties of UV‐curable resins at cryogenic conditions is important to ongoing fusion‐energy research and to emerging aerospace applications. The tensile and interfacial shear strengths of two commercially available UV‐curable resins were measured at room‐temperature and cryogenic conditions for both bulk and reduced (subnanoliter) specimen volumes. The tensile properties of cured specimens are remarkably sensitive to both testing temperature and specimen size. For one type of resin, the cold (−150 °C) tensile strength of subnanoliter specimens is ∼9× larger (179 ± 19 MPa) than bulk values at room temperature. The interfacial shear strength between SiC fibers and small volumes of resin volumes is comparable to the bulk, room‐temperature tensile strength, but it varies over a wide range at −150 °C (15–53 MPa). All resins were fully cured, and an analysis of fractured surfaces revealed microstructural features. The enhanced strength in microscopic specimens may be related to inhomogeneous stress fields that develop during cure. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52 , 936–945

thermal properties↗
DOE OSTI2017

Moment-Volume Coupling in La(Fe 1 -x Si x ) 13

We investigate the origin of the volume change and magnetoelastic interaction observed at the magnetic first-order transition in the magnetocaloric system La(Fe 1-x Six) 13 by means of first-principles calculations combined with the fixed-spin moment approach. Here, we find that the volume of the system varies with the square of the average local Fe moment, which is significantly smaller in the spin disordered configurations compared to the ferromagnetic ground state. The vibrational density of states obtained for a hypothetical ferromagnetic state with artificially reduced spin-moments compared to a nuclear inelastic X-ray scattering measurement directly above the phase transition reveals that the anomalous softening at the transition essentially depends on the same moment-volume coupling mechanism. Finally, in the same spirit, the dependence of the average local Fe moment on the Si content can account for the occurence of first- and second-order transitions in the system.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Universality of the Volume Bound in Slow-Roll Eternal Inflation

It has recently been shown that in single field slow-roll inflation the total volume cannot grow by a factor larger than e{sup S{sub dS}/2} without becoming infinite. The bound is saturated exactly at the phase transition to eternal inflation where the probability to produce infinite volume becomes non zero. We show that the bound holds sharply also in any space-time dimensions, when arbitrary higher-dimensional operators are included and in the multi-field inflationary case. The relation with the entropy of de Sitter and the universality of the bound strengthen the case for a deeper holographic interpretation. As a spin-off we provide the formalism to compute the probability distribution of the volume after inflation for generic multi-field models, which might help to address questions about the population of vacua of the landscape during slow-roll inflation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Numerical exploration of three relativistic particles in a finite volume including two-particle resonances and bound states

In this work, we use an extension of the quantization condition, given in ref. [1], to numerically explore the finite-volume spectrum of three relativistic particles, in the case that two-particle subsets are either resonant or bound. The original form of the relativistic three-particle quantization condition was derived under a technical assumption on the two- particle K matrix that required the absence of two-particle bound states or narrow two- particle resonances. Here we describe how this restriction can be lifted in a simple way using the freedom in the definition of the K-matrix-like quantity that enters the quantization condition. With this in hand, we extend previous numerical studies of the quantization condition to explore the finite-volume signature for a variety of two- and three-particle interactions. We determine the spectrum for parameters such that the system contains both dimers (two-particle bound states) and one or more trimers (in which all three particles are bound), and also for cases where the two-particle subchannel is resonant. We also show how the quantization condition provides a tool for determining infinite-volume dimer- particle scattering amplitudes for energies below the dimer breakup. We illustrate this for a series of examples, including one that parallels physical deuteron-nucleon scattering. All calculations presented here are restricted to the case of three identical scalar particles.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Percutaneous Image-Guided Cryoablation of Challenging Mediastinal Lesions Using Large-Volume Hydrodissection: Technical Considerations and Outcomes

ObjectiveThis study was designed to describe the technique of percutaneous image-guided cryoablation with large-volume hydrodissection for the treatment of challenging mediastinal lesions.MethodsBetween March 2014 and June 2015, three patients (mean age 62.7 years) with four neoplastic anterior mediastinal lesions underwent five cryoablation procedures using large-volume hydrodissection. Procedures were performed under general anaesthesia using CT guidance. Lesion characteristics, hydrodissection and cryoablation data, technical success, complications, and clinical outcomes were assessed using retrospective chart review.ResultsLesions (mean size 2.7 cm; range 2–4.3 cm) were in contact with great vessels (n = 13), trachea (n = 3), and mediastinal nerves (n = 6). Hydrodissection was performed intercostally (n = 4), suprasternally (n = 2), transsternally (n = 1), or via the sternoclavicular joint (n = 1) using 1–3 spinal needles over 13.4 (range 7–26) minutes; 450 ml of dilute contrast was injected (range 300–600 ml) and increased mean lesion-collateral structure distance from 1.9 to 7.7 mm. Vulnerable mediastinal nerves were identified in four of five procedures. Technical success was 100 %, with one immediate complication (recurrent laryngeal nerve injury). Mean follow-up period was 15 months. One lesion demonstrated residual disease on restaging PET-CT and was retreated to achieve complete ablation. At last follow-up, two patients remained disease-free, and one patient developed distant disease after 1 year without local recurrence.ConclusionsCryoablation using large-volume hydrodissection is a feasible technique, enabling safe and effective treatment of challenging mediastinal lesions.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2016

AMOC sensitivity to surface buoyancy fluxes: Stronger ocean meridional heat transport with a weaker volume transport?

Oceanic northward heat transport is commonly assumed to be positively correlated with the Atlantic meridional overturning circulation (AMOC). For example, in numerical "water-hosing" experiments, imposing anomalous freshwater fluxes in the northern Atlantic leads to a slow-down of the AMOC and the corresponding reduction of oceanic northward heat transport. Here, we study the sensitivity of the ocean heat and volume transports to surface heat and freshwater fluxes using a generalized stability analysis. For the sensitivity to surface freshwater fluxes, we find that, while the direct relationship between the AMOC volume and heat transports holds on shorter time scales, it can reverse on timescales longer than 500 years or so. That is, depending on the model surface boundary conditions, reduction in the AMOC volume transport can potentially lead to a stronger heat transport on long timescales, resulting from the gradual increase in ocean thermal stratification. Finally, we discuss the implications of these results for the problem of steady state (statistical equilibrium) in ocean and climate GCM as well as paleoclimate problems including millennial climate variability.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Comparing datasets of volume servers to illuminate their energy use in data centers

As data centers proliferate, their energy intensity deserves close attention. Always-on operations and growing usage for cloud and other backend processes make servers the fundamental driver of data center energy use. Yet servers’ power draw under real-world conditions is poorly understood. This paper explores characteristics of volume servers that affect energy use, quantifying differences in power draw between higher-performing Standard Performance Evaluation Corporation (SPEC) and ENERGY STAR servers and that of a typical server. First, we establish general characteristics of the US installed base, before reporting hardware configurations from a major online retail website. We then compare idle power across three datasets (one unique to this paper) and explain their differences via the hardware characteristics to which power draw is most sensitive. We find idle server power demand to be significantly higher than benchmarks from ENERGY STAR and the industry-released SPEC database, and SPEC server configurations—and likely their power scaling—to be atypical of volume servers. Next, we examine power draw trends among high-performing servers across their load range to consider whether these trends are representative of volume servers, before inputting average idle power load values into a recent national server energy use model. Lastly, results from two surveys of IT professionals illustrate the incidence of more efficient equipment and operational practices in server rooms/closets. Future work should include server power field measurements in data centers of different sizes, accounting for variations in configurations and setting changes post-purchase, as well as investigating the linkage between time and server energy efficiency.

Fuchs, Heidi (ORCID:0000000300105411)↗
DOE OSTI2017

Dependence of twinned volume fraction on loading mode and Schmid factor in randomly textured magnesium

Here, the twinning activity in random textured cast magnesium during room temperature tension and compression tests was monitored by neutron diffraction (ND). Variation of integrated intensities of selected diffraction peaks, characterizing the twinned volume in particularly oriented grains was compared with calculated Schmid factors for extension twinning of these grains. It is shown that in tension there is a direct proportion between the twinned volume and the maximum value of the Schmid factor for a given grain orientation. In contrast, in compression this relation is not valid. The twinned volume in this case is influenced by both deviation of the grain from the ideal orientation and its rotation around the c-axis. The experimental results are in good agreement with those obtained from elasto-plastic self-consistent (EPSC) modeling.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Scale effects on core design, fuel costs, and spent fuel volume of pressurized water reactors

The desire to improve the economic competitiveness and deployment pace of nuclear energy through modularization, manufacturing, and series production had led to the development of smaller size reactors. As the standard 17x17 fuel technology is mainly maintained in the pressurized water reactors (PWRs) category, this translates into a lower number of fuel assemblies in the core and sometimes a reduced fuel height. To assess the impact of such scale change in core design on fuel cycle cost and spent fuel volume, a scoping analysis tool is developed based on infinite lattice calculations, leakage, fuel management reduced models, and levelized unit cost of electricity (LCOE) estimate. As such, cost dynamics driven by fuel specific power, burnup, core leakage, feed, cycle length, fuel assembly height as well as uranium market data are captured with consistent set of assumptions and analysis methods. A selection of 5 reactor designs representative of leading PWR developers is assessed and compared. Pursuing higher specific powers and optimal burnups are highlighted as the main fuel cost reduction drivers, nevertheless, practical limitations and opportunities must be evaluated to establish the feasibility of such enhanced fuel operation. In consequence, a detailed core design is performed using SIMULATE3 code for 5 PWR variations including natural and forced coolant circulation modes, two reactor scales, power densities of 73, 112, and 123 kW/l and higher discharge burnups. Design and optimization are performed at the lattice level, for the reflector, and at the core loading level. Satisfactory steady-state operation including power distribution, coolant operating limits, and reactivity requirements are analyzed and reported in this paper. The fuel economics of the detailed core designs confirm the scoping analysis findings. Despite the unlocked power uprates in small PWRs, the achievable burnup for a given fuel specific power requires more enrichment and shorter fuel height results in higher fabrication costs per mass of fuel, which makes scaling down core size a more expensive endeavor on the fuel cycle front. Spent fuel volumes are reported for the PWRs designed in this paper. Furthermore, these volumes are driven by the core average discharge burnup regardless of the scale in consideration. Additional cost and core performance aspects related to heavy reflector gains, fuel-reflector substitution, and disposal cost policy in the U.S. are examined.

42 ENGINEERING↗
DOE OSTI2013

On the relevance of volume increase for the length changes of mortar bars in sulfate solutions

The ingress of sulfate ions into cementitious materials leads to the formation of ettringite, gypsum and other phases. The increase in solid volume through the formation of these phases is often assumed to be the only reason for expansion. In this paper we systematically compare the volume increase predicted by thermodynamic modeling to macroscopic expansion for mortars made with CEM I in different sulfate solutions and for mortars made with a range of blended cements in sodium sulfate solution. It is shown that the length changes cannot be explained by simple volume increase alone. A more plausible explanation of expansion lies in the theory of crystallization pressure, in which crystals forming from a supersaturated solution may exert pressure on their surroundings. It is observed that expansion occurs in systems where thermodynamic modeling predicts the co-existence of ettringite with gypsum. In such a case, if monosulfate and gypsum are both present locally, the solution can be highly supersaturated with respect to ettringite, whose formation in confined conditions (such as within C–S–H) can then exert expansive forces.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Representative elementary volume (REV) of cementitious materials from three-dimensional pore structure analysis

The representative elementary volume (REV) is a fundamental property of a material, but no direct measurements exist for cementitious materials. In this paper, the REV of cement pastes with supplementary cementitious materials (GGBS, PFA, SF) was determined by analysing the three-dimensional pore structure (> 0.2 μm) using laser scanning confocal microscopy (LSCM). The effect of axial distortion inherent to LSCM on 3D pore structure was also investigated. A range of 3D pore parameters was measured using skeletonisation, maximal ball and random walker algorithms. Results show that axial distortion has insignificant effects on most parameters except Euler connectivity, average pore and throat volumes and directional diffusion tortuosities. Most pore parameters become independent of sampling volume at ≈ 60{sup 3} μm{sup 3} except diffusion tortuosities and formation factor. The REV for porosity calculated based on a statistical approach at eight realisations and 5% relative error was found to be ≈ 100{sup 3} μm{sup 3}.

97 MATHEMATICS AND COMPUTING↗