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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 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Magnetostriction of some rare earth-aluminum Laves phase compounds

Measurements of the linear and volume magnetostriction of RAl2 cubic Laves compounds in which R is one of the rare earth elements Gd, Dy, Ho or Er, at temperatures between 4.2 K and the Curie temperature of each compound, are reported. Magnetic fields up to 2.5 Tesla were applied, and magnetostriction was measured using standard strain gage techniques. Saturation magnetostrictions of 17 x 10 to the -6th, -1420 x 10 to the -6th, 60 x 10 to the -6th and -920 x 10 to the -6th are determined at 4.2 K for GdAl2, DyAl2, HoAl2 and ErAl2, respectively. Large forced magnetostriction is observed in GdAl2 above the saturation field and the strain temperature dependence shows a decrease in magnitude below 40 K. A linear dependence of magnetostriction on magnetic field was observed for DyAl2 above 40 K, and the observed temperature dependence is interpreted in terms of the lowest order single-ion magnetoelastic theory. An observed decrease in the magnitude of the strain of HoAl2 below 15 K is associated with a change of the easy direction of magnetization, while in the case of ErAl2, magnetostriction is observed to occur normally up to the Curie temperature. Large volume magnetostriction is obtained for all the compounds with the exception of GdAl2.

Pourarian, F.↗
NASA NTRS2004

Starting Vortex Identified as Key to Unsteady Ejector Performance

Unsteady ejectors are currently under investigation for use in some pulse-detonation-engine-based propulsion systems. Experimental measurements made in the past, and recently at the NASA Glenn Research Center, have demonstrated that thrust augmentation can be enhanced considerably when the driver is unsteady. In ejector systems, thrust augmentation is defined as = T(sup Total)/T(sup j), where T(sup Total) is the total thrust of the combined ejector and driving jet and T(sup j) is the thrust due to the driving jet alone. There are three images in this figure, one for each of the named thrust sources. The images are color contours of measured instantaneous vorticity. Each image is an ensemble average of at least 150 phase-locked measurements. The flow is from right to left, and the shape and location of each driver is shown on the far right of each image. The emitted vortex is a clearly defined "doughnut" of highly vortical (spinning) flow. In these planar images, the vortex appears as two distorted circles, one above, and one below the axis of symmetry. Because they are spinning in the opposite direction, the two circles have vorticity of opposite sign and thus are different colors. There is also a rectangle shown in each image. Its width represents the ejector diameter that was found experimentally to yield the highest thrust augmentation. It is apparent that the optimal ejector diameter is that which just "captures" the vortex: that is, the diameter bounding the outermost edge of the vortex structure. The exact mechanism behind the enhanced performance is unclear; however, it is believed to be related to the powerful vortex emitted with each pulse of the unsteady driver. As such, particle imaging velocimetry (PIV) measurements were obtained for three unsteady drivers: a pulsejet, a resonance tube, and a speaker-driven jet. All the drivers were tested with ejectors, and all exhibited performance enhancement over similarly sized steady drivers. The characteristic starting vortices of each driver are shown in these images. The images are color contours of measured instantaneous vorticity. Each image is an ensemble average of at least 150 phase-locked measurements. The flow is from right to left. The shape and location of each driver is shown on the far right of each image. The rectangle shown in each image represents the ejector diameter that was found experimentally to yield the highest thrust augmentation. It is apparent that the optimal ejector diameter is that which just "captures" the vortex: that is, the diameter bounding the outermost edge of the vortex structure. Although not shown, it was observed that the emitted vortex spread as it traveled downstream. The spreading rate for the pulsejet is shown as the dashed lines in the top image. A tapered ejector was fabricated that matched this shape. When tested, the ejector demonstrated superior performance to all those previously tested at Glenn (which were essentially of straight, cylindrical form), achieving a remarkable thrust augmentation of 2. The measured thrust augmentation is shown as a function of ejector length. Also shown are the thrust augmentation values achieved with the straight, cylindrical ejectors of varying diameters. Here, thrust augmentation is plotted as a function of ejector length for several families of ejector diameters. It can be seen that large thrust augmentation values are indeed obtained and that they are sensitive to both ejector length and diameter, particularly the latter. Five curves are shown. Four correspond to straight ejector diameters of 2.2, 3.0, 4.0, and 6.0 in. The fifth curve corresponds to the tapered ejector contoured to bound the emitted vortex. For each curve, there are several data points corresponding to different lengths. The largest value of thrust augmentation is 2.0 for the tapered ejector and 1.81 for the straight ejectors. Regardless of their diameters, all the ejectors trend toward peak performance at a particular leng. That the cross-sectional dimensions of optimal ejectors scaled precisely with the vortex dimensions on three separate pulsed thrust sources demonstrates that the action of the vortex is responsible for the enhanced ejector performance. The result also suggests that, in the absence of a complete understanding of the entrainment and augmentation mechanisms, methods of characterizing starting vortices may be useful for correlating and predicting unsteady ejector performance.

Paxson, Daniel E.↗
NASA NTRS2010

Phased Array Noise Source Localization Measurements of an F404 Nozzle Plume at Both Full and Model Scale

A 48-microphone planar phased array system was used to acquire jet noise source localization data on both a full-scale F404-GE-F400 engine and on a 1/4th scale model of a F400 series nozzle. The full-scale engine test data show the location of the dominant noise sources in the jet plume as a function of frequency for the engine in both baseline (no chevron) and chevron configurations. Data are presented for the engine operating both with and without afterburners. Based on lessons learned during this test, a set of recommendations are provided regarding how the phased array measurement system could be modified in order to obtain more useful acoustic source localization data on high-performance military engines in the future. The data obtained on the 1/4th scale F400 series nozzle provide useful insights regarding the full-scale engine jet noise source mechanisms, and document some of the differences associated with testing at model-scale versus fullscale.

Podboy, Gary G.↗
DOE OSTI2026

Deterministic Quantum Trajectory via Imaginary Time Evolution

Stochastic quantum trajectories, such as pure state evolutions under unitary dynamics and random measurements, offer a crucial ensemble description of many-body open system dynamics. Recent studies have highlighted that individual quantum trajectories also encode essential physical information. Prominent examples include measurement-induced phase transitions, where a pure quantum state corresponding to fixed measurement outcomes (trajectories) exhibits distinct entanglement phases, depending on the measurement rate. However, direct observation of this effect is hindered by an exponential postselection barrier, whereby the probability of realizing a specific trajectory is exponentially small. We propose a deterministic method to efficiently prepare quantum trajectories in polynomial time using imaginary time evolution and, thus, overcome this fundamental challenge. Here, we demonstrate that our method applies to a certain class of quantum states, and argue that universal approaches do not exist for any quantum trajectories. Our result paves the way for experimentally exploring the physics of individual quantum trajectories at scale and enables direct observation of certain postselection-dependent phenomena.

Mittal, Shivan [Los Alamos National Laboratory (LA↗
DOE OSTI2021

Cooperative Inverters to Overcome PLL Malfunctions

This paper presents a cooperative strategy between smart inverters to overcome instability and undesired trips of inverters caused by Phase-Locked Loop (PLL) malfunctions. For the grid-interactive inverter, PLL is typically required to measure the phase angle of the AC voltage at the Point of Common Coupling (PCC) of the inverter. Accurate phase-angle measurement is critical for grid-interactive inverters to stay synchronized with the power grid. If the inverters are interconnected through a communication link, they can support each other by sharing their grid information, such as phase-angles at their PCCs. The cooperative strategy utilizes the phase-angles and voltages at PCCs in a neighborhood to identify any possible PLL malfunctions or measurement inaccuracies and then enable the inverters to make corrective decisions. The efficacy of the cooperative strategy has been verified through simulation results in MATLAB/Simulink environment in this paper.

Sadeque, Fahmid↗
DOE OSTI2026

Vanishing dynamic strength measured in a transient high-pressure phase of tin

This work reports two independent experimental estimations of the dynamic strength of the body-centered tetragonal (bct) 𝛾 phase of tin, which occurs at pressures above about 9 GPa and transforms promptly back to the ambient 𝛽 phase upon pressure release. Measuring strength in such a transient high-pressure phase is challenging. One measurement used free-surface Richtmyer-Meshkov instabilities generated with gas gun impact. Another set of measurements used ramp-release loading in a pulsed-power facility. Strength estimations came from comparison to simulations using a comprehensive multiphase modeling framework that includes equation of state, shear moduli, and strength separately for each phase, and treats mixed-phase regions. Both experimental methods found the 𝛾-phase strength to be very low, within experimental uncertainty of zero. The existing literature on other materials, by contrast, almost universally reports higher strength in transient high-pressure phases compared with ambient phases. Recent Molecular-Dynamics simulations on tin in the literature showed almost zero deviatoric strength during a deformation-induced bct → bct transformation in which one of the 𝛾-phase 𝑎 axes “flips” to the 𝑐 axis. This reorientation currently provides the most plausible explanation for the low observed strength in 𝛾-phase tin.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Characterization of protein–ligand binding interactions of enoyl-ACP reductase ( FabI ) by native MS reveals allosteric effects of coenzymes and the inhibitor triclosan

The enzyme enoyl-ACP reductase (also called FabI in bacteria) is an essential member of the fatty acid synthase II pathway in plants and bacteria. This enzyme is the target of the antibacterial drug triclosan and has been the subject of extensive studies for the past 20 years. Despite the large number of reports describing the biochemistry of this enzyme, there have been no studies that provided direct observation of the protein and its various ligands. In this paper we describe the use of native MS to characterize the protein–ligand interactions of FabI with its coenzymes NAD + and NADH and with the inhibitor triclosan. Measurements of the gas-phase affinities of the enzyme for these ligands yielded values that are in close agreement with solution-phase affinity measurements. Additionally, FabI is a homotetramer and we were able to measure the affinity of each subunit for each coenzyme, which revealed that both coenzymes exhibit a positive homotropic allosteric effect. An allosteric effect was also observed in association with the inhibitor triclosan. These observations provide new insights into this well-studied enzyme and suggest that there may still be gaps in the existing mechanistic models that explain FabI inhibition.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1981

Passive maser development at NRL

The application of passive hydrogen masers to satellites was investigated. The NRL maser is of compact design suitable for the space environment. It is based on a dielectrically loaded sapphire cavity and uses a computer optimized set of four shields. The servo design is a phase sensitive method which directly measures the phase dispersion of the interrogating signal as it passes through the cavity.

White, J. D.↗
NASA NTRS1990

Measurement and analysis of a microwave oscillator stabilized by a sapphire dielectric ring resonator for ultra-low noise

Phase-noise measurements are presented for a microwave oscillator whose frequency is stabilized by a whispering-gallery sapphire ring resonator with Q of 200,000. This mode involves little metallic conduction and allows nearly full use of the very low dielectric loss in sapphire. Several mode families have been identified, in good agreement with frequency calculations. For a 5-cm wheel resonator in a 7.6-cm container, Q values above 100,000 were found at room temperature for all of the modes in this sequence. Coupling Q-values for these same modes ranged from 10,000 (n = 5) to 100,000 (n = 10) for a WR112 waveguide port at the center of the cylinder wall of the containing can. Phase noise measurements for a transistor oscillator locked to the n = 10 (7.84-GHz) mode showed a 1/f cubed dependence for low offset frequencies, and a value of L(f) = -55 dB/Hz at an offset of 10 Hz from the carrier.

Dick, G. John↗
DOE OSTI2024

A tensor density measure of topological charge in three dimensional nematic phases

A path independent measure in order parameter space is introduced such that, when integrated along any closed contour in a three dimensional nematic phase, it yields the topological charge of any line defects encircled by the contour. A related measure, when integrated over either closed or open surfaces, reduces to known results for the charge associated with point defects (hedgehogs) or Skyrmions. We further define a tensor density, the disclination density tensor D, from which the location of a disclination line can be determined. This tensor density has a dyadic decomposition near the line into its tangent and its rotation vector, allowing a convenient determination of both. The tensor D may be nonzero in special configurations in which there are no defects (double-splay or double-twist configurations), and its behavior there is provided. The special cases of Skyrmions and hedgehog defects are also examined, including the computation of their topological charge from D.

36 MATERIALS SCIENCE↗
NASA NTRS1995

A phase-stepped point diffraction interferometer using liquid crystals

A new instrument, the liquid crystal point diffraction interferometer (LCPDI), has been developed for the measurement of phase objects. This instrument maintains the compact, robust design of Linnik's point diffraction interferometer (PDI) and adds to it phase stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wavefronts with high data density and with automated data reduction. The design of the LCPDI is briefly discussed. An algorithm is presented for eliminating phase measurement error caused by object beam intensity variation from frame-to-frame. The LCPDI is demonstrated by measuring the temperature distribution across a heated chamber filled with silicone oil. The measured results are compared to independently measured results and show excellent agreement with them. It is expected that this instrument will have application in the fluid sciences as a diagnostic tool, particularly in space based applications where autonomy, robustness, and compactness are desirable qualities. It should also be useful for the testing of optical elements, provided a master is available for comparison.

Mercer, Carolyn R.↗
DOE OSTI2020

MESOSCALE THERMAL TRANSPORT MEASUREMENTS OF MULTI-PHASE AND POROUS NUCLEAR FUELS USING A SQUARE-WAVE PULSE THERMOREFLECTANCE TECHNIQUE

The safe and efficient operation of nuclear reactors require accurate knowledge of peak temperatures in the fuel assemblies. The temperature profiles are governed by the thermal transport properties of the fuel, namely the thermal conductivities (k) and thermal diffusivities (D). These values can be very difficult to measure as they are known to vary considerably from the measured bulk values of the fresh fuel, and quickly degrade with increasing burnup [1 -3] . Laser-based techniques have been effectively used for non-destructive and non-contact thermal transport measurements of a wide variety of materials, including nuclear materials [4-6] that would otherwise prove too hazardous or difficult to measure otherwise. In this study, a new thermoreflectance technique known as square-pulse transient thermoreflectance (SPTR) is described and used to determine the mesoscale thermal diffusivity of both uranium sesquisilicide (U3Si2) and uranium nitride (UN) phases in a composite fuel with micron level spatial resolution [7]. This technique employs a rapid train of square-wave pulses from an excitation laser to create a periodic heat flux on a gold coated sample surface. Surface adsorption results in transient film temperatures and hence rapid fluctuations in thermoreflectance that can be measured via a detection laser coupled with a digital oscilloscope. The lasers are coaxially focused on the sample surface, allowing for a sample measurement area of a single convolved laser spot size (~2 µm). A sensitivity analysis was conducted to identify key measurement parameters of this technique using reference materials with a range of thermal conductivities comparable to those of both ceramic, composite, and metal nuclear fuel types (1.4 – 27.2 W/m-K). The reference materials were measured using the new technique as well as a spatial-domain thermoreflectance technique (SDTR) previously reported for a comparison [8]. Additionally, measurements of several U3Si2 and UN phase regions of a polished UN/U3Si2 (70/30 vol.%) sample were taken, and the resulting calculated D values are reported, with both techniques showing excellent agreement between samples. This technique was used to scan a multiphase region at 5 micron increments to generate a local diffusivity map, demonstrating the utility of the techniques for measuring thermal transport properties in specimens with precipitates and secondary phases. Furthermore, the technique is currently being applied to measure thermal properties of Fast Flux Test Reactor (FFTR) irradiated metal fuel specimens whose porous microstructure make it very difficult to measure using other techniques. Comparison of the local scale measurements are compared with the pre-irradiated fuel samples to show the degradation of thermal transport in fuels due to pores from fission gas bubbles and other irradiation induced defects.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1999

Thin Film Ba(x)Sr(1-x)TiO3 Ku- and K-Band Phase Shifters Grown on MgO Substrates

We report measurements of gold circuits fabricated on four Ba(x)Sr(1-x)TiO3 films doped with 1% Mn grown on MgO substrates by laser ablation. Low frequency measurements of epsilon(sub r) and tan(delta) on interdigital capacitors are compared with high frequency measurements of phase shift and insertion loss on coupled microstrip phase shifters done on the same films. The variation in temperature of both high and low frequency device parameters is compared. Annealed and unannealed films are compared. Room temperature figures of merit of phase shift per insertion loss of up to 58.4 C/dB at 18 GHz and 400 V dc bias were measured.

VanKeuls, F. W.↗
NASA NTRS1995

Liquid crystal point diffraction interferometer

A new instrument, the liquid crystal point diffraction-interferometer (LCPDI), has been developed for the measurement of phase objects. This instrument maintains the compact, robust design of Linnik's point diffraction interferometer (PDI) and adds to it phase stepping capability for quantitative interferogram analysis. The result is a compact, simple to align, environmentally insensitive interferometer capable of accurately measuring optical wavefronts with very high data density and with automated data reduction. This dissertation describes the theory of both the PDI and liquid crystal phase control. The design considerations for the LCPDI are presented, including manufacturing considerations. The operation and performance of the LCPDI are discussed, including sections regarding alignment, calibration, and amplitude modulation effects. The LCPDI is then demonstrated using two phase objects: defocus difference wavefront, and a temperature distribution across a heated chamber filled with silicone oil. The measured results are compared to theoretical or independently measured results and show excellent agreement. A computer simulation of the LCPDI was performed to verify the source of observed periodic phase measurement error. The error stems from intensity variations caused by dye molecules rotating within the liquid crystal layer. Methods are discussed for reducing this error. Algorithms are presented which reduce this error; they are also useful for any phase-stepping interferometer that has unwanted intensity fluctuations, such as those caused by unregulated lasers.

Mercer, Carolyn R.↗
NASA NTRS1993

Vortical structure in a forced plane mixing layer

The objective of this phase of an ongoing study is to obtain detailed three dimensional phase-averaged measurements of forced mixing layer vorticity development and evolution. Acoustic forcing is being used to phase-lock the initial development and subsequent pairing of the span wise vortical structures. Phase averaged measurements of the three velocity components will permit the study of three dimensional vorticity distributions without invoking Taylor's hypothesis which is known to introduce uncertainty. Currently two sine waves, one at the fundamental roll-up frequency and the second, its subharmonic, are being used to force the initial roll-up and first pairing of the span wise rollers. The two dimensional measurements described in this report were obtained in order to determine the best operating conditions for the detailed three dimensional study of the mixing layer undergoing pairing via various pairing mechanisms.

Leboeuf, Richard L.↗
NASA NTRS1974

Optical polarization measurements of the Jupiter atmosphere at 103 deg phase angle

The first measurements have been made of the linear polarization of sunlight scattered by the Jupiter atmosphere at phase angles greater than 12 deg, using the imaging photopolarimeter on Pioneer 10. The data are of high accuracy, in spite of several problems in the instrument. The polarization is positive at 440 nm. There is no direct evidence for spherical particles in the Jupiter clouds. Using a simple model of Rayleigh scattering above a Lambertian cloud layer, a unique fit is found to the observed intensity and polarization at each point on the planet. The resulting Rayleigh optical depths, if they are attributed to molecular scattering alone (i.e., no aerosols above the cloud tops), can be converted into physical altitudes of the cloud tops. The first results suggest that the north tropical zone, parts of the equatorial zone, and the red spot are all elevated regions.

Coffeen, D. L.↗