SEARCH · Engineering Papers

Results for “confidence measures”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

NASA NTRS1993

Validation of a nonintrusive optical technique for the measurement of liquid mass distribution in a two-phase spray

This work is the continuation of an optical technique development program initiated as part of the 1992 Summer Faculty Fellowship Program. The 1992 work consisted of the formulation and implementation of a technique ivolving the spatial deconvolution of fluorescence data from a uniformly illuminated, seeded densed spray to obtain quantitative measurements of the liquid density profiles. This measurement approach largely overcomes substantial scattering problems associated with other optical approaches for two-phase flows. However, to apply this measurement approach with confidence to unknown flows, the technique must be validated. Consequently, technique validation using classical grid patternator techniques has been focus of the current work. This work has included the design and construction of a patternator rig and the implementation of a test program designed for the comparison of patternator data with the deconvolved optical data. The flow field used for the validation is the plume of an axisymetric swirl coaxial LOX injector being considered for use in the Space Transportation System Main Engine. The flow facility is an improved version of the test rig which was constructed in 1992 for the initial technique development. This report includes a brief description of the optical measurement technique and the patternator rig and a presentation of the data comparisons.

Hartfield, Roy, Jr.↗

DOE OSTI2020

Planck 2018 results. VI. Cosmological parameters

In this paper, we present cosmological parameter results from the final full-mission Planck measurements of the cosmic microwave background (CMB) anisotropies, combining information from the temperature and polarization maps and the lensing reconstruction. Compared to the 2015 results, improved measurements of large-scale polarization allow the reionization optical depth to be measured with higher precision, leading to significant gains in the precision of other correlated parameters. Improved modelling of the small-scale polarization leads to more robust constraints on many parameters, with residual modelling uncertainties estimated to affect them only at the 0.5 σ level. We find good consistency with the standard spatially-flat 6-parameter ΛCDM cosmology having a power-law spectrum of adiabatic scalar perturbations (denoted “base ΛCDM” in this paper), from polarization, temperature, and lensing, separately and in combination. A combined analysis gives dark matter density Ω c h 2 = 0.120 ± 0.001, baryon density Ω b h 2 = 0.0224 ± 0.0001, scalar spectral index n s = 0.965 ± 0.004, and optical depth τ = 0.054 ± 0.007 (in this abstract we quote 68% confidence regions on measured parameters and 95% on upper limits). The angular acoustic scale is measured to 0.03% precision, with 100 θ * = 1.0411 ± 0.0003. These results are only weakly dependent on the cosmological model and remain stable, with somewhat increased errors, in many commonly considered extensions. Assuming the base-ΛCDM cosmology, the inferred (model-dependent) late-Universe parameters are: Hubble constant H 0 = (67.4 ± 0.5) km s –1 Mpc –1 ; matter density parameter Ω m = 0.315 ± 0.007; and matter fluctuation amplitude σ 8 = 0.811 ± 0.006. We find no compelling evidence for extensions to the base-ΛCDM model. Combining with baryon acoustic oscillation (BAO) measurements (and considering single-parameter extensions) we constrain the effective extra relativistic degrees of freedom to be N eff = 2.99 ± 0.17, in agreement with the Standard Model prediction N eff = 3.046, and find that the neutrino mass is tightly constrained to Σ m ν < 0.12 eV. The CMB spectra continue to prefer higher lensing amplitudes than predicted in base ΛCDM at over 2 σ , which pulls some parameters that affect the lensing amplitude away from the ΛCDM model; however, this is not supported by the lensing reconstruction or (in models that also change the background geometry) BAO data. The joint constraint with BAO measurements on spatial curvature is consistent with a flat universe, Ω K = 0.001 ± 0.002. Also combining with Type Ia supernovae (SNe), the dark-energy equation of state parameter is measured to be w 0 = –1.03 ± 0.03, consistent with a cosmological constant. We find no evidence for deviations from a purely power-law primordial spectrum, and combining with data from BAO, BICEP2, and Keck Array data, we place a limit on the tensor-to-scalar ratio r 0.002 < 0.06. Standard big-bang nucleosynthesis predictions for the helium and deuterium abundances for the base-ΛCDM cosmology are in excellent agreement with observations. The Planck base-ΛCDM results are in good agreement with BAO, SNe, and some galaxy lensing observations, but in slight tension with the Dark Energy Survey’s combined-probe results including galaxy clustering (which prefers lower fluctuation amplitudes or matter density parameters), and in significant, 3.6 σ , tension with local measurements of the Hubble constant (which prefer a higher value). Simple model extensions that can partially resolve these tensions are not favoured by the Planck data.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

Validation of process simulation workflow for thermosetting prepreg platelet molding compounds

Continuous carbon fiber prepreg slit and cut into rectangular platelets has proven to be a useful material for net shape molding of semi-structural and structural components in the aerospace and automotive industries. Furthermore, to assist the designer in use of these prepreg platelet molding compounds, sometimes called carbon fiber sheet molding compounds, simulation tools are required that can predict the as-manufactured fiber orientation state which has a significant impact on the resulting performance. Herein, an analysis workflow for design-enabling predictions is demonstrated for a double dome geometry with two different initial charge configurations. Here, the workflow is validated through comparison with experimental short shots, orientation state, and stiffness trends. Significantly, to complete the validation, a method is proposed for determining the confidence bounds on measured orientation state enhancing the results of optical microscopy which can only produce a small sample of platelet orientations.

36 MATERIALS SCIENCE↗

DOE OSTI2020

A novel method for measuring ultra-trace levels of U and Th in Au, Pt, Ir, and W matrices using ICP-QQQ-MS employing an O 2 reaction gas

A mass shift method using ICP-MS/MS with O 2 reaction gas is used for ultra-trace determinations of U and Th in samples containing W, Ir, Pt, and Au derived polyatomic interferants without the need for extensive chemical sample preprocessing.

Harouaka, Khadouja↗

DOE OSTI2023

Constraints on hadron resonance gas interactions via first-principles Lattice QCD susceptibilities

We investigate extensions of the Hadron Resonance Gas (HRG) Model beyond the ideal case by incorporating both attractive and repulsive interactions into the model. When considering additional states exceeding those measured with high confidence by the Particle Data Group, attractive corrections to the overall pressure in the HRG model are imposed. On the other hand, we also apply excluded-volume corrections, which ensure there is no overlap of baryons by turning on repulsive (anti)baryon-(anti)baryon interactions. We emphasize the complementary nature of these two extensions and identify combinations of conserved charge susceptibilities that allow us to constrain them separately. In particular, we find interesting ratios of susceptibilities that are sensitive to one correction and not the other. This allows us to constrain the excluded volume and particle spectrum effects separately. Analysis of the available lattice results suggests the presence of both the extra states in the baryonstrangeness sector and the repulsive baryonic interaction, with indications that hyperons have a smaller repulsive core than non-strange baryons. We note that these results are interesting for heavy-ion-collision systems at both the LHC and RHIC.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2026

Frequentist cosmological constraints from full-shape clustering measurements in DESI DR1

We present a frequentist analysis of clustering measurements from Data Release 1 of the Dark Energy Spectroscopic Instrument (DESI) using the standard profile likelihood method. While Bayesian inferences for effective field theory models of galaxy clustering can be highly sensitive to prior choices for extended cosmological models, frequentist inferences are not susceptible to such effects. We compare frequentist and Bayesian constraints for the parameter set {σ 8 , H 0 , Ω m , w 0 , w a } using the full-shape power spectrum multipoles, post-reconstruction baryon acoustic oscillation (BAO) measurements, and external datasets from the CMB and type Ia supernovae measurements. The frequentist confidence intervals are significantly shifted relative to the Bayesian credible intervals for the w 0 w a CDM model, unless supernovae data are included. When DESI full-shape and BAO data are fit jointly, we obtain the following 1σ frequentist confidence intervals for ΛCDM (w 0 w a CDM): σ 8 = 0.863 +0.048 -0.040 , H 0 = 68.96 +0.81 -0.80 km s -1 Mpc -1 , Ω m = 0.3034 ± 0.0110 (σ 8 = 0.782 +0.060 -0.036 , H 0 = 63.7 +4.2 -2.0 km s -1 Mpc -1 , Ω m = 0.378 +0.024 -0.047 , w 0 = -0.16 +0.10 -0.50 , w a = -3.0 +1.7 ), corresponding to 0.8σ, 0.3σ, 0.7σ (2.1σ, 4.1σ, 6.5σ, 6.3σ, 6.6σ) shifts between the maximum likelihood estimate and the Bayesian posterior mean for ΛCDM (w 0 w a CDM) respectively.

Bayesian reasoning↗

DOE OSTI2024

Constraining gravity with a new precision 𝐸 𝐺 estimator using Planck + SDSS BOSS data

The 𝐸 𝐺 statistic is a discriminating probe of gravity developed to test the prediction of general relativity (GR) for the relation between gravitational potential and clustering on the largest scales in the observable Universe. We present a novel high-precision estimator for the 𝐸 𝐺 statistic using CMB lensing and galaxy clustering correlations that carefully matches the effective redshifts across the different measurement components to minimize corrections. A suite of detailed tests is performed to characterize the estimator’s accuracy, its sensitivity to assumptions and analysis choices, and the non-Gaussianity of the estimator’s uncertainty is characterized. After finalization of the estimator, it is applied to Planck CMB lensing and SDSS CMASS and LOWZ galaxy data. We report the first harmonic space measurement of 𝐸 𝐺 using the LOWZ sample and CMB lensing and also updated constraints using the final CMASS sample and the latest Planck CMB lensing map. We find $\hat{𝐸}$$^{Planck+CMASS}_{𝐺}$ = 0.3⁢6$^{+0.06}_{−0.05}$⁢(68.27%) and $\hat{𝐸}$$^{Planck+LOWZ}_{𝐺}$ = 0.4⁢0$^{+0.11}_{−0.09}$⁢(68.27%), with additional subdominant systematic error budget estimates of 2% and 3%, respectively. Using Ω m,0 constraints from Planck and SDSS BAO observations, Λ⁢CDM-GR predicts 𝐸$^{GR}_ {𝐺}$⁡(𝑧 =0.555) = 0.401 ± 0.005 and 𝐸$^{GR}_{𝐺}$⁡(𝑧 =0.316) = 0.452 ± 0.005 at the effective redshifts of the CMASS and LOWZ based measurements. We report the measurement to be in good statistical agreement with the Λ⁢CDM-GR prediction and report that the measurement is also consistent with the more general GR prediction of scale independence for 𝐸 𝐺 . Furthermore, this work provides a carefully constructed and calibrated statistic with which 𝐸 𝐺 measurements can be confidently and accurately obtained with upcoming survey data.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

Fast-Spectrum Critical Assemblies with a Pb-HEU Core Surrounded by a Copper Reflector

The Department of Energy invests tens of millions of dollars each year to develop the next generation of nuclear engineering modeling & simulation (M&S) tools. These M&S tools are used to analyze advanced reactor designs and the safety of current nuclear operations. As computers become more powerful, we are able to enhance resolution in our calculations. This improved resolution is taking us to a point where the limitations of simulation capability are in the quality of data, including our ability to quantify the uncertainty and sensitivity of the data. In order to accurately model systems of interest, the industry must improve key nuclear data measurements and our confidence of how well we understand the data. Thus, M&S tools need evaluated and quality-assured experimental data for validation purposes. The International Criticality Safety Benchmark Evaluation Project (ICSBEP) compiles benchmark experiment data in a handbook that can be used by criticality safety engineers to validate computer codes and cross-section libraries at nuclear facilities. Both critical and subcritical experiments are included in the handbook. Figure 1 organizes all the benchmark evaluations that have been performed by the isotope of interest, in this case Pb, and the neutron energy within the system. Compared to other isotopes of interest for nuclear applications, there are few benchmark evaluations for Pb systems. This has caused the latest nuclear cross-section libraries to over/underestimate changes in the neutron population compared to experimental results. Therefore, this evaluation fills an important knowledge gap in benchmark evaluations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2024

Assessing convergence in global sensitivity analysis: a review of methods for assessing and monitoring convergence

In global sensitivity analysis (GSA) of a model, a proper convergence analysis of metrics is essential for ensuring a level of confidence or trustworthiness in sensitivity results obtained, yet is somewhat deficient in practice. The level of confidence in sensitivity measures, particularly in relation to their influence and support for decisions from scientific, social and policy perspectives, is heavily reliant on the convergence of GSA. We review the literature and summarize the available methods for monitoring and assessing convergence of sensitivity measures based on application purposes. The aim is to expose the various choices for convergence assessment and encourage further testing of available methods to clarify their level of robustness. Furthermore, the review identifies a pressing need for comparative studies on convergence assessment methods to establish a clear hierarchy of effectiveness and encourages the adoption of systematic approaches for enhanced robustness in sensitivity analysis.

54 ENVIRONMENTAL SCIENCES↗

NASA NTRS1973

Estimation of rate constants of elementary processes - A review of the state of the art.

'Thermochemical kinetics,' the codification and extrapolation of empirical observations, as applied to certain elementary reactions of importance to combustion studies, is described. This approach allows the critical scrutiny of experimental data in areas where sufficient previous data exist, while, at the same time, illuminating those key areas where more experimentation is crucial. It is shown that combination of transition-state theory with an understanding of the molecular basis of entropy puts fairly rigid constraints on the values of the Arrhenius A-factor for most reactions. This, in turn, means that the activation energy is often the key datum that is missing, and that such data can be obtained with some degree of confidence, even from measurements of rate constants at only one temperature. In complex mechanisms, it is often possible to distinguish among alternate pathways and pinpoint key processes.

Golden, D. M.↗

NASA NTRS1977

Electronic and mechanical improvement of the receiving terminal of a free-space microwave power transmission system

Significant advancements were made in a number of areas: improved efficiency of basic receiving element at low power density levels, improved resolution and confidence in efficiency measurements mathematical modelling and computer simulation of the receiving element and the design, construction, and testing of an environmentally protected two-plane construction suitable for low cost, highly automated construction of large receiving arrays.

Brown, W. C.↗

NASA NTRS1976

A reliable dual-redundant sensor FDI system for the NASA F8C-DFBW aircraft

In this paper we outline the structure of a sensor failure detection and identification (FDI) system designed for the NASA F8C DFBW aircraft. The system is for use in a dual-redundant environment, and it takes maximal advantage of all functional and kinematic relationships among the sensed variables. The technique is reliable in that we have designed the system to account for a variety of unmodeled effects and have introduced a new concept - the quality sequential probability ratio (QSPR) - that provides a useful measure of our confidence in each test. The methodology used for determining detector parameters and the 'outer loop logic' for combining the various sources of information are described.

Deckert, J. C.↗

NASA NTRS1979

A study of redundancy management strategy for tetrad strap-down inertial systems

Algorithms were developed that attempt to identify which sensor in a tetrad configuration has experienced a step failure. An algorithm is also described that provides a measure of the confidence with which the correct identification was made. Experimental results are presented from real-time tests conducted on a three-axis motion facility utilizing an ortho-skew tetrad strapdown inertial sensor package. The effects of prediction errors and of quantization on correct failure identification are discussed as well as an algorithm for detecting second failures through prediction.

Hruby, R. J.↗

NASA NTRS1986

F-106 data summary and model results relative to threat criteria and protection design analysis

The NASA F-106 has acquired considerable data on the rates-of-change of electromagnetic parameters on the aircraft surface during 690 direct lightning strikes while penetrating thunderstorms at altitudes ranging from 15,000 to 40,000 feet. These in-situ measurements have provided the basis for the first statistical quantification of the lightning electromagnetic threat to aircrat appropriate for determining lightning indirect effects on aircraft. The data are presently being used in updating previous lightning criteria and standards developed over the years from ground-based measurements. The new lightning standards will, therefore, be the first which reflect actual aircraft responses measured at flight altitudes. The modeling technique developed to interpret and understand the direct strike electromagnetic data acquired on the F-106 provides a means to model the interaction of the lightning channel with the F-106. The reasonable results obtained with the model, compared to measured responses, yield confidence that the model may be credibly applied to other aircraft types and uses in the prediction of internal coupling effects in the design of lightning protection for new aircraft.

Pitts, F. L.↗

NASA NTRS1989

Determination of longitudinal aerodynamic derivatives using flight data from an icing research aircraft

A flight test was performed with the NASA Lewis Research Center's DH-6 icing research aircraft. The purpose was to employ a flight test procedure and data analysis method, to determine the accuracy with which the effects of ice on aircraft stability and control could be measured. For simplicity, flight testing was restricted to the short period longitudinal mode. Two flights were flown in a clean (baseline) configuration, and two flights were flown with simulated horizontal tail ice. Forty-five repeat doublet maneuvers were performed in each of four test configurations, at a given trim speed, to determine the ensemble variation of the estimated stability and control derivatives. Additional maneuvers were also performed in each configuration, to determine the variation in the longitudinal derivative estimates over a wide range of trim speeds. Stability and control derivatives were estimated by a Modified Stepwise Regression (MSR) technique. A measure of the confidence in the derivative estimates was obtained by comparing the standard error for the ensemble of repeat maneuvers, to the average of the estimated standard errors predicted by the MSR program. A multiplicative relationship was determined between the ensemble standard error, and the averaged program standard errors. In addition, a 95 percent confidence interval analysis was performed for the elevator effectiveness estimates, C sub m sub delta e. This analysis identified the speed range where changes in C sub m sub delta e could be attributed to icing effects. The magnitude of icing effects on the derivative estimates were strongly dependent on flight speed and aircraft wing flap configuration. With wing flaps up, the estimated derivatives were degraded most at lower speeds corresponding to that configuration. With wing flaps extended to 10 degrees, the estimated derivatives were degraded most at the higher corresponding speeds. The effects of icing on the changes in longitudinal stability and control derivatives were adequately determined by the flight test procedure and the MSR analysis method discussed herein.

Ranaudo, R. J.↗

NASA NTRS1989

Determination of longitudinal aerodynamic derivatives using flight data from an icing research aircraft

Ranaudo, R. J.↗

NASA NTRS1991

Temperature trends in the lower mesosphere

The largest atmospheric temperature changes due to the increase of greenhouse gases are expected in the 40 to 60 km altitude region, where enhanced infrared cooling decreases the temperature. Ten-year (1980-1990) temperature trends at 55 km and 0.4 mb, derived using data from the ground-based lidar at Haute Provence, (France), and the SSU-instrument channel 47X on several satellites, are presented. These data show temperature decreases that are as large and in some cases exceed predictions based on current models. At 44 deg N, the ground-based lidar and satellite techniques give a negative trend of -0.10 + or - 0.04 percent per year and -0.14 + or - 0.02 percent per year, respectively. Agreement between these two data sets based on different measurement techniques gives confidence in the detected trends at this latitude. Further analysis of the SSU 47X satellite data between 45 deg S and 45 deg N indicates a maximum decline of 0.16 percent per year near 30 deg N. A minimum trend decrease of 0.07 percent per year is detected between 20 and 30 deg S. Based on NOAA satellite radiance observations, these long-term temperature changes are larger than changes at any of the other stratospheric levels below 55 km monitored during this period.

Aikin, A. C.↗

NASA NTRS1994

Status of the Dobson total ozone data set

During deliberations of the International Ozone Trends Panel (IOTP) it became obvious that satellite determinations of global ozone amounts by themselves could not provide the necessary confidence in the measured trends. During the time of the deliberations of the IOTP, Bojkov re-examined the records of serveral North American Dobson stations and Degorska re-examined the records of the Belsk station. They were able to improve the quality of the data sets, thus improving the precision of their total ozone data sets. These improvements showed the greater potential of the world-wide Dobson total ozone data set in two primary areas. Firstly, the improvements showed that the existing data set when evaluated will become more valuable for comparisons with satellite determinations of total ozone. Secondly, the Dobson data set covers a greater period of time than the satellite data sets thus offering the possibility of extending improved information on ozone trends further back in time. An International Dobson Workshop was convened in September, 1991, under the auspices of the NOAA Climate and Global Change Program. It was part of the Information Management element of the C&GC Program. Further, it was considered as a 'data archaeology' project under the above. Clearly if the existing Dobson data set can be improved by re-evaluating all data records, we will be able to uncover the 'true' or 'best' data and fulfill the role of archaeologists.

Planet, Walter G.↗