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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 253 records · Page 14

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NASA NTRS1994

Comparison of transform coding methods with an optimal predictor for the data compression of digital elevation models

Statistical encoding techniques enable the reduction of the number of bits required to encode a set of symbols, and are derived from their probabilities. Huffman encoding is an example of statistical encoding that has been used for error-free data compression. The degree of compression given by Huffman encoding in this application can be improved by the use of prediction methods. These replace the set of elevations by a set of corrections that have a more advantageous probability distribution. In particular, the method of Lagrange Multipliers for minimization of the mean square error has been applied to local geometrical predictors. Using this technique, an 8-point predictor achieved about a 7 percent improvement over an existing simple triangular predictor.

Lewis, Michael↗

NASA NTRSDate not supplied

Application of a Bayesian Framework for Plasticity Model Selection

Interpretable Machine Learning (IML) has performed well when tasked with deriving constitutive material models. However, IML has been shown to prefer models that overfit noise in data, which tends to lead to bloat and a decrease in interpretability. Due to these issues, the ability of IML to reliably derive models that fit the data and are both interpretable and generalizable is limited. A method developed recently has shown promise to improve upon traditional IML by using a Bayesian fitness definition for the evolution of free-form models with non-deterministic parameters. This framework was developed for genetic-programming-based symbolic regression(GPSR) and involves model parameter estimation using Sequential Monte Carlo sampling (SMC).The method has demonstrated a reduction in bloat when dealing with noisy data in comparison to conventional GPSR. The results of this framework applied to stress-strain data for copper show models that more effectively predict the experimental data better than was previously shown with GPSR.

plasticity↗

NASA NTRS2010

Methodology for the Assessment of 3D Conduction Effects in an Aerothermal Wind Tunnel Test

This slide presentation reviews a method for the assessment of three-dimensional conduction effects during test in a Aerothermal Wind Tunnel. The test objectives were to duplicate and extend tests that were performed during the 1960's on thermal conduction on proturberance on a flat plate. Slides review the 1D versus 3D conduction data reduction error, the analysis process, CFD-based analysis, loose coupling method that simulates a wind tunnel test run, verification of the CFD solution, Grid convergence, Mach number trend, size trends, and a Sumary of the CFD conduction analysis. Other slides show comparisons to pretest CFD at Mach 1.5 and 2.16 and the geometries of the models and grids.

Oliver, Anthony Brandon↗

NASA NTRS1973

Multiple pure tone noise generation and control.

The generation of multiple pure tones in supersonic fans is discussed. The theoretical results of Kurasaka are reviewed and compared with experimental data obtained on a 36-in. diameter, 1550 ft/sec, 1.6 pressure ratio fan. Detailed measurements on bow shock locations taken with pressure transducers indicate that blade to blade discrepancies are the source of MPT generation. The paper presents some experimental results on an attempt to reduce the shock strength, and subsequently the MPT's, through blade modifications. Other attempts at reducing the MPT's through wall treatment, high inlet flow Mach number, acoustically treated splitters - are discussed. Experimental data is presented on the validity of these noise reduction methods.

Benzakein, M. J.↗

NASA NTRS1974

Damping synthesis from substructure tests

A new method is proposed for synthesizing structural damping from substructure test data. It utilizes the off-diagonal coupling terms in the substructure modal damping matrices as well as the diagonal terms which correspond to uncoupled modal damping. The coupling terms are evaluated from complex resonant response measured at each substructure mode. Both analytical and experimental verification of the method have been made. Accuracy requirements on experimental data and data reduction have been established.

Hasselman, T. K.↗

NASA NTRS2018

Combustion Stability Evaluation of Artificial Disturbance Dynamic Response

General guidelines are provided in CPIA Publication 6551 for evaluation of the response due to an artificial disturbance, however the guideline also allows for ambiguous interpretation. Stability rating devices that produce an artificial disturbance are traditionally explosive bombs and pulse guns. This paper reviews a recently developed objective process that can be applied consistently in the reduction of artificial disturbance dynamic data. It also examines three methods of response evaluation. The first method examines the response of a specific mode of interest and requires data filtering encompassing that mode. The second method examines the response of a specific mode of interest and its nonlinear components and requires a more complex filtering scheme. The third method examines the response of the entire dynamic system and consists of examining a wide bandwidth consisting of multiple modes of interest. The evaluation process is described and the advantages and disadvantages of the evaluation methods are discussed. Signal processing is used as a tool in quantifying the assessment, clearly as an improvement from the subjective heritage approach consisting primarily of engineering judgement. Data for several engines and components have been compiled and evaluated using these methods. A summary of these combustion devices is provided and observations are discussed.

Casiano, M. J.↗

NASA NTRSDate not supplied

Comparison of two Calibrations of NASA's MC60 Five-component Semi-span Balance

Two separate manual calibrations of NASA’s MC60 five–component semi–span balance were compared. The calibrations were performed in 1999 and 2019using CALSPAN Force Measurement System’s Large Load Rig. The Iterative Method was chosen as the load prediction algorithm and data reduction matrices were generated from both calibration data sets. Then, the applied calibration load schedules, the standard deviations of the calibration load residuals, the prime sensitivities of the five gages, and the maximum outputs at capacity of the five gages were compared. In addition, the calibration data of 1999 was used as check load data for the data reduction matrix that was obtained from the 2019 data. Overall, the agreement between the data analysis results is very good considering the facts that two different load schedules were used for the calibrations, different people performed the calibrations, different instrumentation was used to measure the loads and the outputs, the Large Load Rig was moved to a different site in between the calibrations, and no tare load corrections could be applied to the 1999 data set. Nevertheless, the calibration data of 2019 is clearly the better data set. This observation is no surprise considering that CALSPAN Force Measurement Systems made significant investments in calibration hardware and process improvements during the last 20 years.

wind tunnel balance↗

NASA NTRS1984

Somali current studied from SEASAT altimetry

Mesoscale variability has been obtained for the world ocean from satellite altimetry by using the repetitive tracks data of SEASAT. No significant results were obtained for the Somali current area for two main reasons: the repetitive tracks are too sparse to cover the expected eddy pattern and these data were obtained in late September and early October when the current is strongly decaying. The non-repetitive period of SEASAT offers the possibility to study a dozen of tracks parallel to the eddy axis or crossing it. These are used here to deduce the dynamic topography of the Somali current. Data error reduction and tide and orbit corrections are addressed. A local geoid was built using a collocation inverse method to combine surface gravity data and altimetry: the repetitive tracks show no variability (which confirms that the current is quasi-inexistent at that time) and can be used as data for the local geoid. This should provide a measure of the absolute dynamic topography of the Somali current.

Perigaud, C.↗

NASA NTRS1995

SAVS: A Space and Atmospheric Visualization Science system

The research environment faced by space and atmospheric scientists in the 1990s is characterized by unprecedented volumes of new data, by ever-increasing repositories of unexploited mission files, and by the widespread use of empirical and large-scale computational models needed for the synthesis of understanding across data sets and discipline boundaries. The effective analysis and interpretation of such massive amounts of information have become the subjects of legitimate concern. With SAVS (a Space and Atmospheric Visualization Science System), we address these issues by creating a 'push-button' software environment that mimics the logical scientific processes in data acquisition, reduction, and analysis without requiring a detailed understanding of the methods, networks, and modules that link the tools and effectively execute the functions. SAVS provides (1) a customizable framework for accessing a powerful set of visualization tools based on the popular AVS visualization software with hooks to PV-Wave and access to Khoros modules, (2) a set of mathematical and statistical tools, (3) an extensible library of discipline-specific functions and models (e.g., MSIS, IRI, Feldstein Oval, IGRF, satellite tracking with CADRE-3, etc.), and (4) capabilities for local and remote data base access. The system treats scalar, vector, and image data, and runs on most common Unix workstations. We present a description of SAVS and its components, followed by several applications based on generic research interests in interplanetary and magnetospheric physics (IMP/ISTP), active experiments in space (CRRES), and mission planning focused on the Earth's thermospheric, ionospheric, and mesospheric domains (TIMED).

Szuszczewicz, E. P.↗

NASA NTRS1973

Magnetic-field measurements for the Lewis Research Center cyclotron

The magnetic field of the Lewis Center cyclotron was mapped by using a Hall-effect magnetic-field transducer. Main-field Fourier coefficients were determined on a polar mesh of 40 radii for each of seven levels of main-field coil current. Incremental fields for eight sets of trim coils and two sets of harmonic coils were also determined at four of these main-field levels. A stored-program, digital computer was used to perform the measurements. The process was entirely automatic; all data-taking and data-reduction activities were specified by the computer programs. A new method for temperature compensation of a Hall element was used. This method required no temperature control of the element. Measurements of the Hall voltage and Hall-element resistance were sufficient to correct for temperature effects.

Fessler, T. E.↗

NASA NTRS1980

Solar rotation measurements at Mount Wilson. I - Analysis and instrumental effects

We examine the background velocity fields of the sun as observed at Mount Wilson. The method of velocity reduction of the full-disk Mount Wilson data is outlined. We describe a number of tests that have been carried out in order to find an instrumental origin for short-term rotation variations and a large-scale background line-shift - the ears. No instrumental cause can be found for this ear effect, although such a cause cannot yet be ruled out.

Howard, R.↗

NASA NTRS1982

Use of a Fourier transform spectrometer on a balloon-borne telescope and at the multiple mirror telescope (MMT)

The design and use of an infrared Fourier transform spectrometer which has been used for observations of laboratory, stratospheric, and astronomical spectra are described. The spectrometer has a spectral resolution of 0.032/cm and has operated in the mid-infrared (12 to 13 microns) as well as the far-infrared (40 to 140 microns), using both bolometer and photoconductor cryogenic detectors. The spectrometer is optically sized to accept an f/9 beam from the multi-mirror telescope (MMT). The optical and electronic design are discussed, including remote operation of the spectrometer on a balloon-borne 102-cm telescope. The performance of the laser-controlled, screw-driven moving cat's-eye mirror is discussed. Segments of typical far-infrared balloon flight spectra, lab spectra, and mid-infrared MMT spectra are presented. Data reduction, interferogram processing, artifact removal, wavelength calibration, and intensity calibration methods are discussed. Future use of the spectrometer is outlined.

Traub, W. A.↗

NASA NTRS1989

The IRAS asteroid and comet survey

Observations made by the Infrared Astronomical Satellite (IRAS) during 1983 constitute the largest, most complete, and least biased of the asteroid surveys to date. A total of 1811 asteroids and 25 comets with known orbits were measured. Thermal flux densities at 12, 25, 60, and 100 microns, as well as (in the case of asteroids) their derived radiometric albedos and diameters have been compiled in the IRAS Asteroid and Comet Survey. Useful low-resolution spectra were obtained for 47 numbered asteroids. There is evidence in the IRAS data base for a large population of asteroids with unknown orbits. The methods of observation are outlined. The survey strategy and the data reduction are discussed. The rationale is given for the various IRAS asteroid and comet data products. Some directions for future research using IRAS data are suggested.

Matson, Dennis L.↗

NASA NTRS1993

A practical approach to determining the uncertainty of a pressure measurement system

The pressure measurement systems located at three propulsion component test stands at the Marshall Space Flight Center (MSFC) were evaluated for their specific measurement uncertainty levels. An elemental error source evaluation was performed to provide an analytical estimate of uncertainty. Applied loads tests were also conducted at the different MSFC test sites to derive an empirical estimate of uncertainty for the measurement system process. The analytical results are compared to those obtained empirically. The data from MFSC was also compared to data reported from other comparable test facilities. Methods for acquiring and processing the data from calibration, acquisition, and reduction error sources are also addressed.

Fish, James E.↗

NASA NTRS2001

Input Decimated Ensembles

Using an ensemble of classifiers instead of a single classifier has been shown to improve generalization performance in many pattern recognition problems. However, the extent of such improvement depends greatly on the amount of correlation among the errors of the base classifiers. Therefore, reducing those correlations while keeping the classifiers' performance levels high is an important area of research. In this article, we explore input decimation (ID), a method which selects feature subsets for their ability to discriminate among the classes and uses them to decouple the base classifiers. We provide a summary of the theoretical benefits of correlation reduction, along with results of our method on two underwater sonar data sets, three benchmarks from the Probenl/UCI repositories, and two synthetic data sets. The results indicate that input decimated ensembles (IDEs) outperform ensembles whose base classifiers use all the input features; randomly selected subsets of features; and features created using principal components analysis, on a wide range of domains.

Tumer, Kagan↗

NASA NTRS2011

Lessons Learned from CFD Validation Study of Protuberance Heating

The objectives of this presentation are: (1) Share lessons learned from a recent exercise in CFD validation of protuberance heating (2) Impact of experimental data reduction assumptions and techniques on validation activity (3) Advanced data reduction techniques may provide useful data from non-typical test methods (4) Significance of the recovery factor for high-speed flows (5) Show typical results of the Lag turbulence model on protuberances (6) Introduce and inform the listener of a protuberance heating dataset which will soon be available for comparison

Oliver, Brandon↗

NASA NTRS2019

Reexamination of the Edge Crack Torsion Test for Determining the Mode III Delamination Toughness of Laminated Composites

The edge crack torsion (ECT) test is reexamined to address two primary concerns with this method. The first of these relates to inconsistencies in the data reduction procedure that was originally proposed and is most commonly used to compute the mode III interlaminar fracture toughness, G(sub IIIc), from the experimental data. The second relates to the observation that plies neighboring the preimplanted insert in the standard ECT layup are unable to contain initiation and growth of intralaminar cracks, and that growth of these cracks contributes to errors in the apparent values of G(sub IIIc). To address these issues, an alternative data reduction technique, which uses a polynomial expression to represent the ECT specimen’s compliance versus crack length relation, is proposed. The accuracy and potential drawbacks of this expression are investigated using FE simulations. Next, seven groups of ECT specimens are fabricated and tested. Each of these groups contains specimens with preimplanted inserts that are bounded by plies at different +q and -q orientations. The seven groups consist of values of q that vary from 0° to 90° in 15° increments. Tests on these specimens show that intralaminar cracking occurs in specimens from all batches except those for which q equals 15° or 30°. However, values of G(sub IIIc) measured using specimens with these two ply orientations were not equal and, for q = 30°, the values of G(sub IIIc) that were obtained were not completely independent of initial starter crack length. Potential issues accounting for these observations and other challenges associated with measuring G(sub IIIc) using the ECT test are discussed.

Polymer matrix composites↗

NASA NTRS1987

Autogenic-feedback training: A preventive method for space adaptation syndrome

The progress made to date on the reduction of data for Spacelab 3 Shuttle experiment, No. 3AFT23 is reported. Four astronauts participated as subjects in this experiment. Crewmen A and B served as treatment subjects (i.e., received preflight training for control of their own motion sickness symptoms) and Crewmen C and D served as control (i.e., did not receive training). A preliminary evaluation of Autogenic Feedback Training (AFT) was made from visual inspections of graphs that were generated from the preflight and inflight and inflight physiological data which included: (1) Baseline rotating chair tests for all crewmen; (2) Posttraining rotating chair tests of treatment groups subjects; (3) Preflight data from Joint Integrated Simulations for all crewmen; and (4) Flight data for all crewmen during mission days 0 through 4, and mission day 6 for treatment subjects only. A summary of the findings suggested by these data is outlined.

Cowings, Patricia S.↗