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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 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

CrossCheck: Rapid, Reproducible, and Interpretable Model Evaluation

Evaluation beyond aggregate performance metrics, e.g. F1-score, is crucial to both establish an appropriate level of trust in machine learning models and identify future model improvements. In this paper we demonstrate CrossCheck, an interactive visualization tool for rapid crossmodel comparison and reproducible error analysis. We describe the tool and discuss design and implementation details. We then present three use cases (named entity recognition, reading comprehension, and clickbait detection) that show the benefits of using the tool for model evaluation. CrossCheck allows data scientists to make informed decisions to choose between multiple models, identify when the models are correct and for which examples, investigate whether the models are making the same mistakes as humans, evaluate models’ generalizability and highlight models’ limitations, strengths and weaknesses. Furthermore, CrossCheck is implemented as a Jupyter widget, which allows rapid and convenient integration into data scientists’ model development workflows.

Arendt, Dustin L.↗
DOE OSTI2025

Digital Twin Framework for PIP-II Linac: AI-Driven Multi-Scale Modeling from Ion Source to 800 MeV

The PIP-II linac will enable >1.2 MW beam power for DUNE, requiring unprecedented operational reliability across its warm front-end (RFQ, MEBT) and five distinct SRF sections operating at 162.5/325/650 MHz. We present a comprehensive digital twin framework uniquely combining a fully differentiable fast beam transport code with neural network surrogates trained on high-fidelity PIC simulations, capturing space charge and nonlinear dynamics beyond traditional envelope codes while achieving 10⁴ speedup at <1% accuracy. End-to-end differentiability enables gradient-based optimization across 500+ parameters simultaneously previously impossible with conventional tools while the model incorporates static/dynamic errors and serves as a virtual commissioning platform for diverse hardware integration. The framework facilitates reinforcement learning for pulsed/CW mode transitions, predictive maintenance through anomaly detection, and autonomous tuning algorithm development with real-time execution capability. Validation against physics simulations shows excellent agreement for the front-end, with initial results demonstrating potential for 30% commissioning time reduction and proactive fault mitigation, providing a scalable blueprint for operating next-generation high-intensity accelerators.

Pathak, Abhishek [Fermilab] (ORCID:000000021704208↗
NASA NTRS1971

Noncommuting observables in quantum detection and estimation theory

In quantum detection theory, the optimum detection operators must commute; admitting simultaneous approximate measurement of noncommuting observables cannot yield a lower Bayes cost. In addition, the lower bounds on mean square errors of parameter estimates, predicted by the quantum mechanical Cramer-Rao inequality, cannot be reduced by such means.

Helstrom, C. W.↗
NASA NTRS1973

Decision-directed detector for overlapping PCM/NRZ signals.

A decision-directed (DD) technique for the detection of overlapping PCM/NRZ signals in the presence of white Gaussian noise is investigated. The performance of the DD detector is represented by probability of error Pe versus input signal-to-noise ratio (SNR). To examine how much improvement in performance can be achieved with this technique, Pe's with and without DD feedback are evaluated in parallel. Further, analytical results are compared with those found by Monte Carlo simulations. The results are in good agreement.

Wang, C. D.↗
NASA NTRS1974

Polarimetric observations of Comet Kohoutek (1973f)

Radio, optical, and visual observations were made of Comet Kohoutek (1973f) using facilities of the National Radio Astronomy Observatory (NRAO) and of the Hawaii Night Sky Observatory, State University of New York at Albany (SUNYA). Transit observations were made using the NRAO 300 ft radio telescope on six consecutive days beginning November 24, 1973. Observations were carried out in the continuum at 11 cm using the 4-feed system at different position angles. The data were recorded on magnetic tape and were computer reduced. Results were negative, with an rms error of 62 milli flux units, giving an upper limit of 180 mfu for the 11 cm continuum emission from the Comet. This relatively high detection limit resulted from a combination of interference and bad weather that affected these pre-perihelion observations. No observations could be scheduled near or after perihelion.

Weinberg, J. L.↗
NASA NTRS1974

The reliability impact of mission abort strategies on redundant flight computer systems

This correspondence presents a reliability model for a redundant flight computer system with standby sparing, taking into account various mission abort strategies. A mission rule to initiate a mission abort after a predetermined number of detected computer failures and to return to earth with the remaining computers is shown to result in: (1) little improvement of crew safety unless computer error coverage is nearly perfect, and (2) significant degradation in mission success whenever coverage is high.

Filene, R. J.↗
NASA NTRS1976

An intense extreme-ultraviolet source in Cetus

The detection of a second EUV (100-1000 A) probable white dwarf star with the EUV telescope aboard the Apollo Soyuz mission is reported. The positional error box includes Feige 24, a binary system consisting of a very blue white dwarf and a dMe star. A grid of LTE pure-hydrogen, high-surface-gravity model atmospheres, is used, in combination with the EUV data and optical spectrophotometry, to derive the stellar parameters, yielding an effective temperature of 60,000 K, a radius of 17,000 km at 100 pc, and a luminosity of 7(d/100 pc) squared solar luminosities. The Feige 24 models appear to rule out white dwarfs with pure hydrogen atmospheres if the interstellar helium abundance and ionization are not anomalous.

Margon, B.↗
NASA NTRS1977

Triaxial digital fluxgate magnetometer for NASA applications explorer mission: Results of tests of critical elements

Tests performed to prove the critical elements of the triaxial digital fluxgate magnetometer design were described. A method for improving the linearity of the analog to digital converter portion of the instrument was studied in detail. A sawtooth waveform was added to the signal being measured before the A/D conversion, and averaging the digital readings over one cycle of the sawtooth. It was intended to reduce bit error nonlinearities present in the A/D converter which could be expected to be as much as 16 gamma if not reduced. No such nonlinearities were detected in the output of the instrument which included the feature designed to reduce these nonlinearities. However, a small scale nonlinearity of plus or minus 2 gamma with a 64 gamma repetition rate was observed in the unit tested. A design improvement intended to eliminate this small scale nonlinearity was examined.

Mcleod, M. G.↗
NASA NTRS1982

Planning assistance for the NASA 30/20 GHz program. Network control architecture study.

Network Control Architecture for a 30/20 GHz flight experiment system operating in the Time Division Multiple Access (TDMA) was studied. Architecture development, identification of processing functions, and performance requirements for the Master Control Station (MCS), diversity trunking stations, and Customer Premises Service (CPS) stations are covered. Preliminary hardware and software processing requirements as well as budgetary cost estimates for the network control system are given. For the trunking system control, areas covered include on board SS-TDMA switch organization, frame structure, acquisition and synchronization, channel assignment, fade detection and adaptive power control, on board oscillator control, and terrestrial network timing. For the CPS control, they include on board processing and adaptive forward error correction control.

Inukai, T.↗
NASA NTRS1986

Experiments in software reliability - Life-critical applications

The paper discusses four reliability data gathering experiments which were conducted using a small sample of programs for two problems having ultrareliability requirements, n-version programming for fault detection, and repetitive run modeling for failure and fault rate estimation. The experimental results agree with those of Nagel and Skrivan in that the program error rates suggest an approximate log-linear pattern and the individual faults occurred with significantly different error rates. Additional analysis of the experimental data raises new questions concerning the phenomenon of interacting faults. This phenomenon may provide one explanation for software reliability decay. The fourth experiment underscored the difficulty in distinguishing between observations of deficiencies in the design of the algorithm and observations of software faults for real-time process control software. These experiments are a part of a program of serial experiments being pursued by the System Validation Methods of NASA-Langley Research Center to find a means of credibly performing reliability evaluations of flight control software.

Dunham, J. R.↗
NASA NTRS1989

Tests of general relativity in earth orbit using a superconducting gravity gradiometer

Interesting new tests of general relativity could be performed in earth orbit using a sensitive superconducting gravity gradiometer under development. Two such experiments are discussed here: a null test of the tracelessness of the Riemann tensor and detection of the Lense-Thirring term in the earth's gravity field. The gravity gradient signals in various spacecraft orientations are derived, and dominant error sources in each experimental setting are discussed. The instrument, spacecraft, and orbit requirements imposed by the experiments are derived.

Paik, H. J.↗
NASA NTRS1995

Two-Photon Laser-Induced Fluorescence O and N Atoms for the Study of Heterogeneous Catalysis in a Diffusion Reactor

Advanced laser-based diagnostics have been developed to examine catalytic effects and atom/surface interactions on thermal protection materials. This study establishes the feasibility of using laser-induced fluorescence for detection of O and N atom loss in a diffusion tube to measure surface catalytic activity. The experimental apparatus is versatile in that it allows fluorescence detection to be used for measuring species selective recombination coefficients as well as diffusion tube and microwave discharge diagnostics. Many of the potential sources of error in measuring atom recombination coefficients by this method have been identified and taken into account. These include scattered light, detector saturation, sample surface cleanliness, reactor design, gas pressure and composition, and selectivity of the laser probe. Recombination coefficients and their associated errors are reported for N and O atoms on a quartz surface at room temperature.

Pallix, Joan B.↗
NASA NTRS2003

Hybrid Network Architectures for the Next Generation NAS

To meet the needs of the 21st Century NAS, an integrated, network-centric infrastructure is essential that is characterized by secure, high bandwidth, digital communication systems that support precision navigation capable of reducing position errors for all aircraft to within a few meters. This system will also require precision surveillance systems capable of accurately locating all aircraft, and automatically detecting any deviations from an approved path within seconds and be able to deliver high resolution weather forecasts - critical to create 4- dimensional (space and time) profiles for up to 6 hours for all atmospheric conditions affecting aviation, including wake vortices. The 21st Century NAS will be characterized by highly accurate digital data bases depicting terrain, obstacle, and airport information no matter what visibility conditions exist. This research task will be to perform a high-level requirements analysis of the applications, information and services required by the next generation National Airspace System. The investigation and analysis is expected to lead to the development and design of several national network-centric communications architectures that would be capable of supporting the Next Generation NAS.

Madubata, Christian↗
NASA NTRS1977

Microbe Detector

The AutoMicrobic System (AMS) represents years of intensive research and development by McDonnell Douglas Corp. that originated with a NASA study aimed at development of a fully automated microbial detection and identification system for spacecraft use. A urine specimen is placed into the system, where it is subjected to different freeze-dried microbe nutrients for the nine most common pathogens. An electro-optical scanner studies each specimen once an hour through a 4-to-13 hour cycle, operating automatically. Changes in cell growths on each culture are monitored by computer. The presence of pathogens is indicated when growth reaches a predetermined level. The system also enumerates the pathogens and specifies the type. Developed initially to handle urine testing, AMS soon is expected to allow analyses of blood, spinal fluid, and other body fluids. An additional capability under development is "susceptibility testing," or the determination of which microbe-killing agents-such as penicillin or other antibiotics-would be most effective in eliminating the pathogens. The whole process of detecting, identifying, and enumerating the pathogens and determining susceptibility is accomplished in less half the time required for the manual procedure. The AMS minimizes human error, reduces technician time , and increases laboratory output.

Source record↗
NASA NTRS2012

The Algorithm Theoretical Basis Document for Tidal Corrections

This Algorithm Theoretical Basis Document deals with the tidal corrections that need to be applied to range measurements made by the Geoscience Laser Altimeter System (GLAS). These corrections result from the action of ocean tides and Earth tides which lead to deviations from an equilibrium surface. Since the effect of tides is dependent of the time of measurement, it is necessary to remove the instantaneous tide components when processing altimeter data, so that all measurements are made to the equilibrium surface. The three main tide components to consider are the ocean tide, the solid-earth tide and the ocean loading tide. There are also long period ocean tides and the pole tide. The approximate magnitudes of these components are illustrated in Table 1, together with estimates of their uncertainties (i.e. the residual error after correction). All of these components are important for GLAS measurements over the ice sheets since centimeter-level accuracy for surface elevation change detection is required. The effect of each tidal component is to be removed by approximating their magnitude using tidal prediction models. Conversely, assimilation of GLAS measurements into tidal models will help to improve them, especially at high latitudes.

Fricker, Helen A.↗
NASA NTRSDate not supplied

Estimation With Range Depended Sensor Model

This paper focuses on the improvement of object detection accuracy taking into account the sensor’s reading degradation as the relative range increases. The approach is based on the assumption that range measurement error depends on the actual range. Specifically, we model the measurement error as a proportional to the actual range term plus a zero-mean, Gaussian distributed, and uncorrelated process. The tracking problem is considered in a mixed continuous-discrete time domain, where the target dynamics is in continuous-time and the measurements are in discrete-time, which is an optimal choice in many tracking and navigation applications. We adopt a commonly used continuous time coordinate-uncoupled white-noise acceleration model for a point object to describe the target motion, and use Extended Kalman Filter (EKF) framework to estimate the target's state and the unknown proportionality coefficient.

Vahram Stepanyan↗
NASA NTRS2022

Modeling and Performance Analysis of the LUVOIR Coronagraph Instrument

Future space missions such as the Large UV/Optical/Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Observatory, when equipped with coronagraphs with active wavefront control to suppress starlight, will allow the discovery and characterization of habitable exoplanets. The Extreme Coronagraph for Living Planetary Systems (ECLIPS) is the coronagraph instrument on the LUVOIR Surveyor mission concept, an 8- to 15-m segmented telescope. ECLIPS is split into three channels, namely, UV (200 to 400 nm), optical (400 to 850 nm), and near IR (850 nm to 2 μm), with each channel equipped with two deformable mirrors for wavefront control, a suite of coronagraph masks, a low-order/out-of-band wavefront sensor, and separate science imagers and spectrographs. The apodized pupil Lyot coronagraph and the vector vortex coronagraph are the baselined mask technologies for ECLIPS to enable the required 10−10 contrast for observations in the habitable zones of nearby stars for LUVOIR-A (15-m telescope) and LUVOIR-B (8-m telescope), respectively. Their performance depends on active wavefront sensing and control, as well as metrology subsystems to compensate for aberrations induced by segment errors (e.g., piston and tip/tilt), secondary mirror misalignment, and global low-order wavefront errors. Here, we present the latest results of the simulation of these effects for the LUVOIR coronagraph instrument and discuss the achieved contrast for exoplanet detection and characterization after closed-loop wavefront estimation and control algorithms have been applied. Finally, we show simulated observations using high-fidelity spatial and spectral input models of complete planetary systems generated with the Haystacks code framework.

Roser Juanola-Parramon↗
DOE OSTI2025

Digital Twin Framework for PIP-II Linac: AI-Driven Multi-Scale Modeling from Ion Source to 800 MeV

The PIP-II linac will enable >1.2 MW beam power for DUNE, requiring unprecedented operational reliability across its warm front-end (RFQ, MEBT) and five distinct SRF sections operating at 162.5/325/650 MHz. We present a comprehensive digital twin framework uniquely combining a fully differentiable fast beam transport code with neural network surrogates trained on high-fidelity PIC simulations, capturing space charge and nonlinear dynamics beyond traditional envelope codes while achieving 10⁴× speedup at <1% accuracy. End-to-end differentiability enables gradient-based optimization across 500+ parameters simultaneously—previously impossible with conventional tools—while the model incorporates static/dynamic errors and serves as a virtual commissioning platform for diverse hardware integration. The framework facilitates reinforcement learning for pulsed/CW mode transitions, predictive maintenance through anomaly detection, and autonomous tuning algorithm development with real-time execution capability. Validation against physics simulations shows excellent agreement for the front-end, with initial results demonstrating potential for 30% commissioning time reduction and proactive fault mitigation, providing a scalable blueprint for operating next-generation high-intensity accelerators.

Pathak, Abhishek [Fermilab] (ORCID:000000021704208↗