Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Activity detect”

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.

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

At least 1,585 records · Page 88
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

CHARACTERIZATION OF ACTIVE MAIN BELT OBJECT P/2012 F5 (GIBBS): A POSSIBLE IMPACTED ASTEROID

In this work, we characterize the recently discovered active main belt object P/2012 F5 (Gibbs), which was discovered with a dust trail >7' in length in the outer main belt, 7 months prior to aphelion. We use optical imaging obtained on UT 2012 March 27 to analyze the central condensation and the long trail. We find B-band and R-band apparent magnitudes of 20.96 {+-} 0.04 mag and 19.93 {+-} 0.02 mag, respectively, which give an upper limit on the radius of the nucleus of 2.1 km. The geometric scattering cross-section of material in the trail was {approx}4 Multiplication-Sign 10{sup 8} m{sup 2}, corresponding to a mass of {approx}5 Multiplication-Sign 10{sup 7} kg. Analysis of infrared images taken by the Wide-field Infrared Survey Explorer in 2010 September reveals that the object was below the detection limit, suggesting that it was less active than it was during 2012, or possibly inactive, just six months after it passed through perihelion. We set a 1{sigma} upper limit on its radius during this time of 2.9 km. P/2012 F5 (Gibbs) is dynamically stable in the outer main belt on timescales of {approx}1 Gyr, pointing toward an asteroidal origin. We find that the morphology of the ejected dust is consistent with it being produced by a single event that occurred on UT 2011 July 7 {+-} 20 days, possibly as the result of a collision with a small impactor.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Machine Learning for Anomaly Detection in Neural Network Security and SRF Cavities

This dissertation explores the development and deployment of machine learning approaches to address critical challenges in anomaly detection across two distinct domains: neural network security in federated learning settings and cavity behavior analysis in particle accelerator operations at Jefferson Lab in Newport News, Virginia. Anomaly detection identifies deviations from expected patterns, safeguarding systems in cybersecurity, industry, and research against malicious activities and failures. This dissertation demonstrates how our machine learning approaches enhance detection accuracy and efficiency in both neural network security and industrial applications. First, we investigate vulnerabilities in deep neural networks deployed in federated learning. Although federated learning preserves user privacy by training models locally, it remains vulnerable to backdoor attacks, in which malicious participants embed hidden triggers that induce targeted misbehavior. We propose a self-supervised contrastive learning framework to detect and mitigate such backdoor attacks. In our experiments, this method achieves higher detection accuracy and lower false positive rates than existing defenses, while operating without access to local model updates or original training data and thus preserving the privacy guarantees of the federated setting. Second, we address the operational reliability of superconducting radio-frequency (SRF) cavities at the Continuous Electron Beam Accelerator Facility (CEBAF). Our research leverages an unsupervised learning approach, combined with Principal Component Analysis (PCA) and k-means clustering, to identify anomalous behaviors in SRF cavities. Our method detects subtle anomalous behavior by analyzing SRF signal data. This knowledge allows for the early detection and resolution of potential faults, significantly improving the efficiency and reliability of operations. Third, we extend these insights to time-series anomaly detection more broadly. We design a contrastive-learning based model tailored to increasingly dynamic environments and academic research. This model improves detection accuracy in settings that require real-time monitoring and predictive maintenance. Our research underscores the broader applicability and impact of advanced machine learning techniques in anomaly detection. By extracting meaningful patterns from complex data, machine learning can significantly enhance security in distributed neural networks and improve the efficiency of particle accelerator operations. This dissertation serves as a stepping stone for future investigations into the vast possibilities of anomaly detection, inspiring further exploration and development of machine learning techniques in this field.

Ferguson, Hal [Old Dominion University]↗
NASA NTRS2006

Structure Detection of Nonlinear Aeroelastic Systems with Application to Aeroelastic Flight Test Data

This viewgraph presentation reviews the 1. Motivation for the study 2. Nonlinear Model Form 3. Structure Detection 4. Least Absolute Shrinkage and Selection Operator (LASSO) 5. Objectives 6. Results 7. Assess LASSO as a Structure Detection Tool: Simulated Nonlinear Models 8. Applicability to Complex Systems: F/A-18 Active Aeroelastic Wing Flight Test Data. The authors conclude that 1. this is a novel approach for detecting the structure of highly over-parameterised nonlinear models in situations where other methods may be inadequate 2. that it is a practical significance in the analysis of aircraft dynamics during envelope expansion and could lead to more efficient control strategies and 3. this could allow greater insight into the functionality of various systems dynamics, by providing a quantitative model which is easily interpretable

Kukreja, Sunil L.↗
NASA NTRS2006

Integrated System for Autonomous Science

The New Millennium Program Space Technology 6 Project Autonomous Sciencecraft software implements an integrated system for autonomous planning and execution of scientific, engineering, and spacecraft-coordination actions. A prior version of this software was reported in "The TechSat 21 Autonomous Sciencecraft Experiment" (NPO-30784), NASA Tech Briefs, Vol. 28, No. 3 (March 2004), page 33. This software is now in continuous use aboard the Earth Orbiter 1 (EO-1) spacecraft mission and is being adapted for use in the Mars Odyssey and Mars Exploration Rovers missions. This software enables EO-1 to detect and respond to such events of scientific interest as volcanic activity, flooding, and freezing and thawing of water. It uses classification algorithms to analyze imagery onboard to detect changes, including events of scientific interest. Detection of such events triggers acquisition of follow-up imagery. The mission-planning component of the software develops a response plan that accounts for visibility of targets and operational constraints. The plan is then executed under control by a task-execution component of the software that is capable of responding to anomalies.

Chien, Steve↗
DOE OSTI2016

On-chip, self-detected terahertz dual-comb source

We present a directly generated on-chip dual-comb source at terahertz (THz) frequencies. The multi-heterodyne beating signal of two free-running THz quantum cascade laser frequency combs is measured electrically using one of the combs as a detector, fully exploiting the unique characteristics of quantum cascade active regions. Up to 30 modes can be detected corresponding to a spectral bandwidth of 630 GHz, being the available bandwidth of the dual comb configuration. The multi-heterodyne signal is used to investigate the equidistance of the comb modes showing an accuracy of 10{sup −12} at the carrier frequency of 2.5 THz.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2025

Weakly supervised anomaly detection with event-level variables

We introduce a new topology for weakly supervised anomaly detection searches, diobject plus X. In this topology, one looks for a resonance decaying to two standard model particles produced in association with other anomalous event activity (X). This additional activity is used for classification. We demonstrate how anomaly detection techniques which have been developed for dijet searches focusing on jet substructure anomalies can be applied to event-level anomaly detection in this topology. To robustly capture event-level features of multiparticle kinematics, we employ new physically motivated variables derived from the geometric structure of a collision’s phase space manifold. As a proof of concept, we explore the application of this approach to several benchmark signals in the di-𝜏 and di-𝜇 plus X final states. We demonstrate that our anomaly detection approach can reach discovery-level significances for signals that would be missed in a conventional bump-hunt approach.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS2024

Crowd-Sourced Technology Challenge for Improving Visual Color Detection of Hydrazine and Monomethylhydrazine Vapors in Spacecraft Environments

NASA currently uses a visual colorimetric detection method for potential hydrazine, monomethylhydrazine (MMH), or unsymmetrical dimethylhydrazine (UDMH) contamination in the International Space Station. Astronauts exposed to propellants or their residues during extravehicular activities may transfer contaminants into the airlock. The colorimetric detection method employs the Contamination Detection Kit (CDK), which uses a potassium tetrachloroaurate redox reaction with the propellant hydrazine vapors and a color comparison card to determine airborne concentrations. Seeking ideas for improvement, the NASA Tournament Lab (NTL) crowdsourced a way to tackle the challenge of detecting hydrazine and MMH vapors using colorimetric detection methods. This Rid the Rocket competition drew over 200 participants and 20 submissions from around the world proposing innovative ways to develop a new chemical colorimetric detection method for hydrazine and MMH vapors on spacecraft. Using a phased approach to evaluate contestants, NASA eventually narrowed the field to five finalists from the United States, Romania, Taiwan, and India. Concept papers and hardware submissions were judged on feasibility, creativity, and ability to detect hydrazine and MMH vapors before being sent to the NASA White Sands Test Facility for laboratory evaluation. Finalists employed variations of sampling methods and color-detection chemistry using a variety of sampling pumps and indicator pads or solutions—including those employing potassium or hydrogen tetrachloroaurate, para -dimethylaminobenzaldehyde (PDAB), and modifiers including sodium metasilicate and cetyltrimethylammonium bromide—to enhance gold nanoparticle formation and surface plasmon resonance (SPR) resulting in visual blue to purple color development. This paper presents a summary of the crowdsourced submissions and results of laboratory testing.

Crowd-Sourced↗
DOE OSTI2015

Synthesis, characterizations and catalytic studies of a new two-dimensional metal−organic framework based on Co–carboxylate secondary building units

A metal–organic framework [Co{sub 3}(BDC){sub 3}(DMF){sub 2}(H{sub 2}O){sub 2}] was synthesized and structurally characterized. X-ray single crystal analysis revealed that the framework contains a 2D polymeric chain through coordination of 1,4-benzenedicarboxylic acid linker ligand to cobalt centers. The polymer crystallize in monoclinic P2{sub 1}/n space group with a=13.989(3) Å, b=9.6728(17) Å, c=16.707(3) Å, and Z=2. The polymer features a framework based on the perfect octahedral Co–O6 secondary building units. The catalytic activities of [Co{sub 3}(BDC){sub 3}(DMF){sub 2}(H{sub 2}O){sub 2}]{sub n} for olefins oxidation was conducted. The heterogeneous catalyst could be facilely separated from the reaction mixture, and reused three times without significant degradation in catalytic activity. Furthermore, no contribution from homogeneous catalysis of active species leaching into reaction solution was detected. - Graphical abstract: A metal–organic framework of [Co{sub 3}(BDC){sub 3}(DMF){sub 2}(H{sub 2}O){sub 2}] was synthesized by hydrothermal method. This 2D-periodic framework is constructed from the infinite Co–O–C secondary building units and crystallizes in the monoclinic P2{sub 1}/n space group based on Co(II)–carboxylate units. The catalytic oxidation of various olefins was effectively carried out with [Co{sub 3}(BDC){sub 3}(DMF){sub 2}(H{sub 2}O){sub 2}]{sub n} catalyst by TBHP as oxidant. - Highlights: • A metal–organic framework of [Co{sub 3}(BDC){sub 3}(DMF){sub 2}(H{sub 2}O){sub 2}] is prepared by hydrothermal method. • The [Co{sub 3}(BDC){sub 3}(DMF){sub 2}(H{sub 2}O){sub 2}]{sub n} is constructed from Co–carboxylate secondary building units. • This coordination polymer displayed high catalytic activity for olefin oxidation reactions. • The catalytic reaction is heterogeneous and catalyst can be simply separated. • The heterogeneous catalyst can be reused several times without significant loss of catalytic activity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1983

Estimates of vertical crustal movements along the coast of Greece, based on mean sea level data

Mean Annual Sea Level (MASL) data from Greek coastal stations, for the 1969-1982 period, showed crustal stability to a standard deviation of + or - 1.8 cm at 10 of the 18 useful stations, supporting the contention that crustal movements greater than 5 cm can be detected by relative MASL. A comparison of MASL data with gravity changes measured in the Peloponnese and Central regions of Greece suggests that vertical movements occurred along a gradient equal to, or larger than, the free air gradient. MASL data from active volcanic islands have high potential for the detection of uplift prior to eruption.

Lagios, E.↗
DOE OSTI2018

Single-Volume Neutron Scatter Camera for High-Efficiency Neutron Imaging and Spectroscopy

Neutron detection provides an effective method to detect, locate, and characterize sources of interest to nuclear security applications. Current neutron imaging systems based on double-scatter kinematic reconstruction provide good signal vs. background discrimination and spectral capability, but suffer from poor sensitivity due to geometrical constraints. This weakness can be overcome if both neutron-proton scattering interactions are detected and resolved within one large contiguous active detector volume. We describe here a maximum likelihood approach to event reconstruction in a single-volume system with no optical segmentation and sensitivity to individual optical photons on the surfaces of the scintillator. We present results from a Geant4-based simulation establishing the feasibility of this single-volume neutron scatter camera concept given notional performance of existing photodetector and readout technologies.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

AN ULTRAVIOLET INVESTIGATION OF ACTIVITY ON EXOPLANET HOST STARS

Using the far-UV (FUV) and near-UV (NUV) photometry from the NASA Galaxy Evolution Explorer (GALEX), we searched for evidence of increased stellar activity due to tidal and/or magnetic star-planet interactions (SPI) in the 272 known FGK planetary hosts observed by GALEX. With the increased sensitivity of GALEX, we are able probe systems with lower activity levels and at larger distances than what has been done to date with X-ray satellites. We compared samples of stars with close-in planets (a < 0.1 AU) to those with far-out planets (a > 0.5 AU) and looked for correlations of excess activity with other system parameters. This statistical investigation found no clear correlations with a, M{sub p} , or M{sub p} /a, in contrast to some X-ray and Ca II studies. However, there is tentative evidence (at a level of 1.8{sigma}) that stars with radial-velocity-(RV)-detected close-in planets are more FUV-active than stars with far-out planets, in agreement with several published X-ray and Ca II results. The case is strengthened to a level of significance to 2.3{sigma} when transit-detected close-in planets are included. This is most likely because the RV-selected sample of stars is significantly less active than the field population of comparable stars, while the transit-selected sample is similarly active. Given the factor of 2-3 scatter in fractional FUV luminosity for a given stellar effective temperature, it is necessary to conduct a time-resolved study of the planet hosts in order to better characterize their UV variability and generate a firmer statistical result.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Standoff Infrared Measurements of Chemical Plume Dynamics in Complex Terrain Using a Combination of Active Swept-ECQCL Laser Spectroscopy with Passive Hyperspectral Imaging

Chemical plume detection and modeling in complex terrain present numerous challenges. We present experimental results from outdoor releases of two chemical tracers (sulfur hexafluoride and Freon-152a) from different locations in mountainous terrain. Chemical plumes were detected using two standoff instruments collocated at a distance of 1.5 km from the plume releases. A passive long-wave infrared hyperspectral imaging system was used to show time- and space-resolved plume transport in regions near the source. An active infrared swept-wavelength external cavity quantum cascade laser system was used in a standoff configuration to measure quantitative chemical column densities with high time resolution and high sensitivity along a single measurement path. Both instruments provided chemical-specific detection of the plumes and provided complementary information over different temporal and spatial scales. The results show highly variable plume propagation dynamics near the release points, strongly dependent on the local topography and winds. Effects of plume stagnation, plume splitting, and plume mixing were all observed and are explained based on local topographic and wind conditions. Measured plume column densities at distances ~100 m from the release point show temporal fluctuations over ~1 s time scales and spatial variations over ~1 m length scales. The results highlight the need for high-speed and spatially resolved measurement techniques to provide validation data at the relevant spatial and temporal scales required for high-fidelity terrain-aware microscale plume propagation models.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

SU-F-J-196: A Prototype System for Portal Imaging for Intensity Modulated Neutron Therapy

Purpose: Fast neutron therapy is offered at the University of Washington Medical Center for treatment of selected cancers. The hardware and control systems of the UW Clinical Neutron Therapy System are undergoing upgrades to enable delivery of IMNT. To clinically implement IMNT, dose verification tools need to be developed. We propose a portal imaging system that relies on the creation of positron emitting isotopes ({sup 11}C and {sup 15}O) through (n, 2n) reactions with a PMMA plate placed below the patient. After field delivery, the plate is retrieved from the vault and imaged using a reader that detects the annihilation photons. The pattern of activity produced in the plate provides information to reconstruct the neutron fluence map that can be compared to fluence maps from Monte Carlo (MCNP) simulations to verify treatment delivery. We have previously performed Monte Carlo simulations of the portal imaging system (GATE simulations) and the beam line (MCNP simulations). In this work, initial measurements using a prototype system are presented. Methods: Custom electronics were developed for BGO detectors read out with photomultiplier tubes (previous generation PET detectors from a CTI ECAT 953 scanner). Two detectors were placed in coincidence, with a detector separation of 2 cm. Custom software was developed to create the crystal look up tables and perform a limited angle planar reconstruction with a stochastic normalization. To test the initial capabilities of the system, PMMA squares were irradiated with neutrons at a depth of 1.5 cm and read out using the prototype system. Doses ranging from 10–200 cGy were delivered. Results: Using the prototype system, dose differences in the therapeutic range could be determined. Conclusion: The prototype portal imaging system is capable of detecting neutron doses as low as 10–50 cGy and shows great promise as a patient QA tool for IMNT.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2022

Advanced antireflection for back-illuminated silicon photomultipliers to detect faint light

Silicon photomultipliers have attracted increasing attention for detecting low-density light in both scientific research and practical applications in recent years; yet the photon losses due to reflection on the light-sensitive planar silicon surface considerably limit its photon detection efficiency. Here we demonstrate an advanced light trapping feature by developing the multi-layer antireflection coatings and the textured silicon surface with upright random nano-micro pyramids, which significantly reduces the reflection of faint light in a wide spectrum, from ultraviolet to infrared. Integrating this advanced photon confinement feature into next-generation back-illuminated silicon photomultiplier would increase the photon detection efficiency with significantly lower reflection and much more active areas. This advanced design feature offers the back-illuminated silicon photomultiplier broader application opportunities exemplified in the emerging scenarios such as nuclear medical imaging, light detection and ranging for autonomous driving, detection of scintillation light in ionizing radiation, as well as high energy physics.

42 ENGINEERING↗
DOE OSTI2015

Surface and Structural Investigation of a MnO x Birnessite‐Type Water Oxidation Catalyst Formed under Photocatalytic Conditions

Abstract Catalytically active MnO x species have been reported to form in situ from various Mn‐complexes during electrocatalytic and solution‐based water oxidation when employing cerium(IV) ammonium ammonium nitrate (CAN) oxidant as a sacrificial reagent. The full structural characterization of these oxides may be complicated by the presence of support material and lack of a pure bulk phase. For the first time, we show that highly active MnO x catalysts form without supports in situ under photocatalytic conditions. Our most active 4 MnO x catalyst (∼0.84 mmol O 2 mol Mn −1 s −1 ) forms from a Mn 4 O 4 bearing a metal–organic framework. 4 MnO x is characterized by pair distribution function analysis (PDF), Raman spectroscopy, and HR‐TEM as a disordered, layered Mn‐oxide with high surface area (216 m 2 g −1 ) and small regions of crystallinity and layer flexibility. In contrast, the S MnO x formed from Mn 2+ salt gives an amorphous species of lower surface area (80 m 2 g −1 ) and lower activity (∼0.15 mmol O 2 mol Mn −1 s −1 ). We compare these catalysts to crystalline hexagonal birnessite, which activates under the same conditions. Full deconvolution of the XPS Mn2p 3/2 core levels detects enriched Mn 3+ and Mn 2+ content on the surfaces, which indicates possible disproportionation/comproportionation surface equilibria.

Deibert, Benjamin J.↗
DOE OSTI2012

THE CONNECTION BETWEEN 3.3 {mu}m POLYCYCLIC AROMATIC HYDROCARBON EMISSION AND ACTIVE GALACTIC NUCLEUS ACTIVITY

We investigate the connection between starburst and active galactic nucleus (AGN) activity by comparing 3.3 {mu}m polycyclic aromatic hydrocarbon (PAH) emission with AGN properties. Utilizing the slitless spectroscopic capability of the AKARI space telescope, we observe a moderate-luminosity Type I AGN at z {approx} 0.4 to measure global starburst activity. The 3.3 {mu}m PAH emissions are detected for 7 out of 26 target galaxies. We find no strong correlation between the 3.3 {mu}m PAH emission and AGN luminosity in the limited range of the observed AGN luminosity, suggesting that global star formation may not be closely related to AGN activity. Combining our measurements with previous 3.3 {mu}m measurements of low-redshift Type I AGNs in the literature, we investigate the connection between nuclear starburst and AGN activity. In contrast to global star formation, the 3.3 {mu}m PAH luminosity measured from the central part of galaxies correlates with AGN luminosity, implying that starburst activity and AGN activity are directly connected in the nuclear region.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

XMM-NEWTON OBSERVATIONS OF FIVE INTEGRAL SOURCES LOCATED TOWARD THE SCUTUM ARM

Results are presented for XMM-Newton observations of five hard X-ray sources discovered by INTEGRAL in the direction of the Scutum Arm. Each source received {approx}>20 ks of effective exposure time. We provide refined X-ray positions for all five targets enabling us to pinpoint the most likely counterpart in optical/infrared archives. Spectral and timing information (much of which is provided for the first time) allow us to give a firm classification for IGR J18462-0223 and to offer tentative classifications for the others. For IGR J18462-0223, we discovered a coherent pulsation period of 997 {+-} 1 s, which we attribute to the spin of a neutron star in a highly obscured (N{sub H} =2 Multiplication-Sign 10{sup 23} cm{sup -2}) high-mass X-ray binary (HMXB). This makes IGR J18462-0223 the seventh supergiant fast X-ray transient candidate with a confirmed pulsation period. IGR J18457+0244 is a highly absorbed (N{sub H} =8 Multiplication-Sign 10{sup 23} cm{sup -2}) source in which the possible detection of an iron line suggests an active galactic nucleus (AGN) of type Sey-2 situated at z = 0.07(1). A periodic signal at 4.4 ks could be a quasi-periodic oscillation which would make IGR J18457+0244 one of a handful of AGNs in which such features have been claimed, but a slowly rotating neutron star in an HMXB cannot be ruled out. IGR J18482+0049 represents a new obscured HMXB candidate with N{sub H} =4 Multiplication-Sign 10{sup 23} cm{sup -2}. We tentatively propose that IGR J18532+0416 is either an AGN or a pulsar in an HMXB system. The X-ray spectral properties of IGR J18538-0102 are consistent with the AGN classification that has been proposed for this source.

79 ASTRONOMY AND ASTROPHYSICS↗