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Results for “dynamic profiling”

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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Global mesoscale variability from the Geosat Exact Repeat Mission - Correlation with ocean depth

A simple derivative filter technique for extracting mesoscale variability from satellite altimeter data having large-amplitude, long-wavelength errors, with no data adjustments necessary, is presented. The method is applied to the first year of Geosat Exact Repeat Mission data. The main advantage over previous filter methods is that the derivative filter is only two points long, so that it produces no edge effects. Short profiles can thus be included in the analysis. The derivative filter also transforms a dynamic height profile into a dynamic slope profile. The dynamic slope of the sea surface is a parameter that can be measured independently. Moreover, if the ocean current is in geostrophic balance, then the dynamic gradient of the sea surface is proportional to the current velocity.

Sandwell, David T.↗
NASA NTRS1994

An Alternate Method for Estimating Dynamic Height from XBT Profiles Using Empirical Vertical Modes

A technique is presented that applies modal decomposition to estimate dynamic height (0-450 db) from Expendable BathyThermograph (XBT) temperature profiles. Salinity-Temperature-Depth (STD) data are used to establish empirical relationships between vertically integrated temperature profiles and empirical dynamic height modes. These are then applied to XBT data to estimate dynamic height. A standard error of 0.028 dynamic meters is obtained for the waters of the Gulf of Alaska- an ocean region subject to substantial freshwater buoyancy forcing and with a T-S relationship that has considerable scatter. The residual error is a substantial improvement relative to the conventional T-S correlation technique when applied to this region. Systematic errors between estimated and true dynamic height were evaluated. The 20-year-long time series at Ocean Station P (50 deg N, 145 deg W) indicated weak variations in the error interannually, but not seasonally. There were no evident systematic alongshore variations in the error in the ocean boundary current regime near the perimeter of the Alaska gyre. The results prove satisfactory for the purpose of this work, which is to generate dynamic height from XBT data for coanalysis with satellite altimeter data, given that the altimeter height precision is likewise on the order of 2-3 cm. While the technique has not been applied to other ocean regions where the T-S relation has less scatter, it is suggested that it could provide some improvement over previously applied methods, as well.

Lagerloef, Gary S. E.↗
DOE OSTI2024

Dynamic cycling enhances battery lifetime

Laboratory aging campaigns benchmark and elucidate the complex degradation behavior of lithium-ion batteries, and are critical not only for developing new battery chemistries and cell designs but also for engineering reliable battery management systems. Critically, these laboratory experiments aim to quantify and capture realistic aging mechanisms. In this study, we systematically compare dynamic discharge profiles representative of electric vehicle driving to the well-accepted constant-current profiles. Surprisingly, we discovered that dynamic discharge enhances lifetime substantially compared to constant current discharge. Specifically, for the same average current and voltage window, varying the dynamic discharge profile leads to an increase of up to 38 % in equivalent full cycles at end-of-life. Explainable machine learning reveals the importance of low-frequency current pulses as well as time-induced aging under these realistic discharge conditions. Our work quantifies the importance of evaluating new battery chemistries and designs with realistic load profiles, and highlights the opportunities to revisit our understanding of aging mechanisms at the chemistry, materials, and cell levels.

25 ENERGY STORAGE↗
NASA NTRS2005

Computational Modeling And Analysis Of Synthetic Jets

In the last report we focused on the study of 3D synthetic jets of moderate jet aspect-ratio. Jets in quiescent and cross-flow cases were investigated. Since most of the synthetic jets in practical applications are found to be of large aspect ratio, the focus was shifted to studying synthetic jets of large aspect ratio. In the current year, further progress has been made by studying jets of aspect ratio 8 and infinity. Some other aspects of the jet, like the vorticity flux is looked into apart from analyzing the vortex dynamics, velocity profiles and the other dynamical characteristics of the jet which allows us to extract some insight into the effect of these modifications on the jet performance. Also, efforts were made to qualitatively validate the simulated results with the NASA Langley test cases at higher jet Reynolds number for the quiescent jet case.

Mittal, Rajat↗
DOE OSTI2015

A dynamically driven, universal thermal profile of galaxy groups and clusters

Large scale structures such as groups and clusters of galaxies show a universal, nearly linear entropy radial profile K(r). Using deprojected 16 clusters and 12 groups from the literature, we find that K∝r{sup 0.96±0.01}, consistent with the mean power-law index (0.9–1.1) of previous studies. A similarly good fit is given by a τ∝r{sup 0.72±0.01} ratio between cooling and free-fall times. Both profiles slightly flatten at small radii, as τ becomes of order unity. The entropy profile is usually attributed to self-similar shock accretion (shown to be inconsistent with the data), to non-standard heat conduction, or to turbulent heating. We argue that a dynamical mechanism is needed to sustain such a universal profile, oblivious to the temperature peak at the edge of the core and to the virial shock at the outskirts, and robust to the presence of ongoing cooling, merger, and active galactic nucleus activity. In particular, we show that such a profile can be naturally obtained in a spiral flow, which is likely to underlie most galaxy aggregates according to the ubiquitous spiral patterns and cold fronts observed. Generalizing a two-phase spiral flow model out to the virial radius surprisingly reproduces the thermal profile. A generalized Schwarzschild criterion indicates that observed spiral patterns must involve a convective layer, which may regulate the thermal profile.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1969

Calibration standard for dynamic evaluation of a profile-plotter

Template is used for evaluation of the dynamic characteristics and accuracy of the plotter. It has a profile composed of surfaces parallel to and at known distances from a reference plane, plane, the diverse surfaces being connected by slopes of known angles and blended by cylindrical developments of known radii.

Moulton, K. S.↗
DOE OSTI2015

Comparisons between tokamak fueling of gas puffing and supersonic molecular beam injection in 2D simulations

Plasma fueling with high efficiency and deep injection is very important to enable fusion power performance requirements. It is a powerful and efficient way to study neutral transport dynamics and find methods of improving the fueling performance by doing large scale simulations. Two basic fueling methods, gas puffing (GP) and supersonic molecular beam injection (SMBI), are simulated and compared in realistic divertor geometry of the HL-2A tokamak with a newly developed module, named trans-neut, within the framework of BOUT++ boundary plasma turbulence code [Z. H. Wang et al., Nucl. Fusion 54, 043019 (2014)]. The physical model includes plasma density, heat and momentum transport equations along with neutral density, and momentum transport equations. Transport dynamics and profile evolutions of both plasma and neutrals are simulated and compared between GP and SMBI in both poloidal and radial directions, which are quite different from one and the other. It finds that the neutrals can penetrate about four centimeters inside the last closed (magnetic) flux surface during SMBI, while they are all deposited outside of the LCF during GP. It is the radial convection and larger inflowing flux which lead to the deeper penetration depth of SMBI and higher fueling efficiency compared to GP.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

The feasibility of a piecewise-linear dynamic bowtie filter

Purpose: The prepatient attenuator (or 'bowtie filter') in CT is used to modulate the flux as a function of fan angle of the x-ray beam incident on the patient. Traditional, static bowtie filters are tailored only for very generic scans and for the average patient. The authors propose a design for a dynamic bowtie that can produce a time-dependent piecewise-linear attenuation profile. This dynamic bowtie may reduce dynamic range, dose or scatter, but in this work they focus on its ability to reduce dynamic range, which may be particularly important for systems employing photon-counting detectors. Methods: The dynamic bowtie is composed of a set of triangular wedges. Each wedge is independently moved in order to produce a time-dependent piecewise-linear attenuation profile. Simulations of the bowtie are conducted to estimate the dynamic range reduction in six clinical datasets. The control of the dynamic bowtie is determined by solving a convex optimization problem, and the dose is estimated using Monte Carlo techniques. Beam hardening artifacts are also simulated. Results: The dynamic range is reduced by factors ranging from 2.4 to 27 depending on the part of the body studied. With a dynamic range minimization objective, the dose to the patient can be reduced from 6% to 33% while maintaining peak image noise. Further reduction in dose may be possible with a specific dose reduction objective. Beam hardening artifacts are suppressed with a two-pass algorithm. Conclusions: A dynamic bowtie producing a time-dependent, piecewise-linear attenuation profile is possible and can be used to modulate the flux of the scanner to the imaging task. Initial simulations show a large reduction in dynamic range. Several other applications are possible.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Live Cell Chemical Profiling of Temporal Redox Dynamics in a Photoautotrophic Cyanobacterium

Protein reduction-oxidation (redox) modification is an important mechanism that allows microorganisms to sense environmental changes and initiate cellular responses. We have developed a quantitative chemical probe approach for live cell labeling of proteins that are sensitive to redox modifications. We utilize this in vivo strategy to identify 176 proteins undergoing ~5-10 fold dynamic redox change in response to nutrient limitation and subsequent replenishment in the photoautotrophic cyanobacterium, Synechococcus sp. PCC 7002. We detect redox changes in as little as 30 seconds after nutrient perturbation, and oscillations in reduction and oxidation for 60 minutes following the perturbation. Many of the proteins undergoing dynamic redox transformations participate in the major components for the production (photosystems and electron transport chains) or consumption (Calvin-Benson cycle and protein synthesis) of reductant and/or energy in photosynthetic organisms. Thus, our in vivo approach reveals new redox-susceptible proteins, in addition to validating those previously identified in vitro.

Environmental Molecular Sciences Laboratory↗
NASA NTRS1961

The Smoke-Trail Method for Obtaining Detailed Measurements of the Vertical Wind Profile for Application to Missile-Dynamic-Response Problems

Detailed measurements of the vertical profile of the wind are urgently needed f o r studies of the response of rising missiles, but conventional wind-measuring systems cannot provide the accuracy and detail required over the necessary range of altitudes. A method is presented for obtaining a detailed, accurate profile over a large altitude range. The method utilizes photogrammetric measurement of successive positions of the t rail of an ascending rocket. Construction of a rocketborne smoke generator is discussed and the photography, film reading, and data-reduction procedures are described. The accuracy of the method i s examined and error equations are derived. Finally, some examples of wind profiles measured by this method are shown, and their implications for missile response are indicated.

Henry, Robert M.↗
NASA NTRS1987

Profile modification to minimize spur gear dynamic loading

An analytical computer simulation program for dynamic modeling of low-contact-ratio spur gear systems is presented. The procedure computes the static transmission error of the gears operating under load and uses a fast Fourier transform to generate the frequency spectrum of the static transmission error at various tooth profile modifications. The dynamic loading response of an unmodified (perfect involute) gear pair was compared with that of gears with various profile modifications. Correlations were found between various profile modifications and the resulting dynamic loads. An effective error, obtained from frequency domain analysis of the static transmission error of the gears, gave a very good indication of the optimum profile modification to reduce gear dynamic loading. Design curves generated by dynamic simulation at various profile modifications are given for gear systems operated at various loads. Optimum profile modifications can be determined from these design curves for improved gear design.

Lin, Hsiang Hsi↗
NASA NTRS1989

Profile modification to minimize spur gear dynamic loading

An analytical computer simulation program for dynamic modeling of low-contact-ratio spur gear systems is presented. The procedure computes the static transmission error of the gears operating under load and uses a fast Fourier transform to generate the frequency spectrum of the static transmission error at various tooth profile modifications. The dynamic loading response of an unmodified (perfect involute) gear pair was compared with that of gears with various profile modifications. Correlations were found between various profile modifications and the resulting dynamic loads. An effective error, obtained from frequency domain analysis of the static transmission error of the gears, gave a very good indication of the optimum profile modification to reduce gear dynamic loading. Design curves generated by dynamic simulation at various profile modifications are given for gear systems operated at various loads. Optimum profile modifications can be determined from these design curves for improved gear design.

Lin, H. H.↗
NASA NTRS1995

Influence of tooth profile modification on spur gear dynamic tooth strain

This paper presents results of dynamic strain gage measurements performed on the NASA gear-noise rig. The experiments were part of a joint research program between NASA and the U.S. Army Research Laboratory to advance the technology of rotorcraft transmissions. Tests were performed on six sets of low contact ratio spur gears with different tooth profile modifications. Results presented include static and dynamic measurements of gear tooth strain taken over a matrix of operating conditions. The results demonstrate that a well-designed tooth profile modification can significantly reduce dynamic loads in spur gears, especially for gears which operate at high speed and under high torque. The two parabolic modifications tested were not as effective as linear modifications, possibly because the modification zone was too long.

Oswald, Fred B.↗