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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

A second‐generation virtual‐pinhole PET device for enhancing contrast recovery and improving lesion detectability of a whole‐body PET/CT scanner

Purpose We have developed a second‐generation virtual‐pinhole (VP) positron emission tomography (PET) device that can position a flat‐panel PET detector around a patient's body using a robotic arm to enhance the contrast recovery coefficient (CRC) and detectability of lesions in any region‐of‐interest using a whole‐body PET/computed tomography (CT) scanner. Methods We constructed a flat‐panel VP‐PET device using 32 high‐resolution detectors, each containing a 4 4 MPPC array and 16 16 LYSO crystals of 1.0 1.0 3.0 mm 3 each. The flat‐panel detectors can be positioned around a patient's body anywhere in the imaging field‐of‐view (FOV) of a Siemens Biograph 40 PET/CT scanner by a robotic arm. New hardware, firmware and software have been developed to support the additional detector signals without compromising a scanner's native functions. We stepped a 22 Na point source across the axial FOV of the scanner to measure the sensitivity profile of the VP‐PET device. We also recorded the coincidence events measured by the scanner detectors and by the VP‐PET detectors when imaging phantoms of different sizes. To assess the improvement in the CRC of small lesions, we imaged an elliptical torso phantom measuring 316 228 162 mm 3 that contains spherical tumors with diameters ranging from 3.3 to 11.4 mm with and without the VP‐PET device. Images were reconstructed using a list mode Maximum‐Likelihood Estimation‐Maximization algorithm implemented on multiple graphics processing units (GPUs) to support the unconventional geometries enabled by a VP‐PET system. The mean and standard deviation of the CRC were calculated for tumors of different sizes. Monte Carlo simulation was also conducted to image clusters of lesions in a torso phantom using a PET/CT scanner alone or the same scanner equipped with VP‐PET devices. Receiver operating characteristic (ROC) curves were analyzed for three system configurations to evaluate the improvement in lesion detectability by the VP‐PET device over the native PET/CT scanner. Results The repeatability in positioning the flat‐panel detectors using a robotic arm is better than 0.15 mm in all three directions. Experimental results show that the average CRC of 3.3, 4.3, and 6.0 mm diameter tumors was 0.82%, 2.90%, and 5.25%, respectively, when measured by the native scanner. The corresponding CRC was 2.73%, 6.21% and 10.13% when imaged by the VP‐PET insert device with the flat‐panel detector under the torso phantom. These values may be further improved to 4.31%, 9.65% and 18.01% by a future dual‐panel VP‐PET insert device if DOI detectors are employed to triple its detector efficiency. Monte Carlo simulation results show that the tumor detectability can be improved by a VP‐PET device that has a single flat‐panel detector. The improvement is greater if the VP‐PET device employs a dual‐panel design. Conclusions We have developed a prototype flat‐panel VP‐PET device and integrated it with a clinical PET/CT scanner. It significantly enhances the contrast of lesions, especially for those that are borderline detectable by the native scanner, within regions‐of‐interest specified by users. Simulation demonstrated the enhancement in lesion detectability with the VP‐PET device. This technology may become a cost‐effective solution for organ‐specific imaging tasks.

Jiang, Jianyong↗
DOE OSTI2022

A cosine-based correlation information entropy approach for building automatic fault detection baseline construction

Building automatic fault detection and diagnosis (AFDD) technologies have shown great potential for energy savings. To enable AFDD, a baseline depicting the normal operation mode is needed to detect whether the building operation deviates from normality. Existing research using physics-based knowledge and models for AFDD has mainly taken a trial-and-error approach to determine if a given baseline is sufficient via empirical experiments. A mechanism to support decisions such as how many samples and what samples should be included in the baseline is currently lacking. In this study, a data-driven method for AFDD baseline construction based on information entropy is developed. The entropy is derived based on cosine similarity among typical building automation system measurements in conjunction with outdoor weather information. The performance of the proposed method is evaluated using real building data. Evaluation results indicate that the fault detection strategy adopting the proposed method has similar or better accuracy in detecting faults compared to the same fault detection strategy using the baseline construction method from the literature. Additionally, the use of entropy enables the proposed method to automatically construct and assess the baseline consisting of information-rich samples.

42 ENGINEERING↗
DOE OSTI2019

Distributed Direction-Optimizing Label Propagation for Community Detection

Designing a scalable algorithm for community detec-tion is challenging due to the tradeoff between the performance and the quality of the result. We propose a new distributed algorithm for community detection —Direction-Optimizing Label Propagation Algorithm, based on a novel Label Propagation Algorithm in community detection. The algorithm is inspired by the direction optimization technique for graph traversal algorithms and relies on the use of frontiers and alternates between label push and label pull operations. This organization creates ?exibility and affords opportunities for balancing the performance and the quality of the solution. We implement our algorithm in distributed memory with an active-message based asynchronous many-task runtime, AM++. We experiment with two seeding strategies for initial seeding stage, namely, random seeding and degree seeding. With the Graph Challenge datasets, our distributed implementation, in conjunction with the runtime support, achieves very good performance and reasonable quality of solution.

Liu, Xu↗
DOE OSTI2019

Monitoring Aqueous Reprocessing Systems for Detection of Facility Misuse

Traditional approaches to material control and accounting at used nuclear fuel reprocessing facilities relies in large part on laboratory-based destructive assay of periodic samples taken from key stages. These techniques are highly accurate, but limited inspection frequency may limit the size and operation of a reprocessing facility. Online monitoring techniques using inline detectors can be applied to fuel reprocessing systems to improve the situational awareness as the facility is operating to provide additional indicators of the evolving state of the facility between normal inspection periods, potentially alerting regulators to the need for additional inspection. The Multi-Isotope Process (MIP) Monitor combines medium-resolution gamma detectors with statistical data analysis techniques to monitor reprocessing systems for anomalous conditions resulting from process control issues or malfeasance. Gamma spectra collected from the H-Canyon reprocessing facility were modeled using principal component analysis to demonstrate the efficacy of the MIP Monitor for detecting notional diversion scenarios.

safeguards, nuclear fuel reprocessing, gamma spect↗
DOE OSTI2015

Magnetic microparticle-based multimer detection system for the detection of prion oligomers in sheep

Transmissible spongiform encephalopathies (TSEs) are zoonotic fatal neurodegenerative diseases in animals and humans. TSEs are commonly known as bovine spongiform encephalopathy in cattle, scrapie in sheep and goats, chronic wasting disease in cervids, and Creutzfeldt–Jakob disease in humans. The putative transmissible agents are infectious prion proteins (PrPSc), which are formed by the conversion of the normal prion protein on the glycoprotein cell surface in the presence of other PrPSc. Reports of the transmission of TSEs through blood raised considerable concern about the safety of blood and blood products. To address this issue, many laboratories attempted to develop a sensitive and accurate blood diagnostic test to detect PrPSc. Previously, we reported that, compared to normal controls, the multimer detection system (MDS) was more efficient in detecting PrPSc in infected hamster brain homogenate, mouse plasma spiked with purified PrPSc from scrapie mouse brain, and scrapie-infected hamster plasmas. MDS differentiates prion multimers from the cellular monomer through the multimeric expression of epitopes on prion multimers, in contrast to the monomeric form. In this study, MDS detected PrPSc in plasma samples from scrapie-infected sheep expressing clinical symptoms, demonstrating 100% sensitivity and specificity in these samples. Plasma samples from asymptomatic lambs at the preclinical stage (8-month-old naturally infected offspring of scrapie-infected parents expressing a highly susceptible genotype) tested positive with 50% sensitivity and 100% specificity. In the first of two coded analyses using clinical scrapie-infected sheep and normal healthy samples, MDS successfully identified all but one of the clinical samples with 92% sensitivity and 100% specificity. Similar results were obtained in the second coded analysis using preclinical samples. MDS again successfully identified all but one of the samples with 87% sensitivity and 100% specificity. The false-negative sample was subjected to a protease pretreatment. In conclusion, MDS could accurately detect scrapie in plasma samples at both preclinical and clinical stages. From these studies, we conclude that MDS could be a promising tool for the early diagnosis of TSEs from blood samples.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Improving Non-Destructive Detection Technology Through SAVY Feature Detection

Surveillance of special nuclear material (SNM) storage containers is required by the DOE to assess their integrity across the Complex. This work aims to improve the task of container inspections by leveraging automation through machine learning (ML) tools to reduce the human-intensive effort and expert-level knowledge needed to assess container status. A field-deployable, non-destructive technology was designed using off-the-shelf components to collect multiple images from different perspectives of containers in storage to detect both spatial features of interest and anomalies of concern. Nine ML models were generated using unique training datasets and parameters. Learned features include SAVY surface regions including the body side wall, collar, lid, filter, and printed/etched information. Average Precision (AP) is used to calculate detection performance when both viewing previously seen environments and previously unseen environments. The application of image transformations and resolution scaling while training greatly improved the detection performance in unseen environments, and significantly increasing the number of computation iterations improved detection performance on previously seen environments. Additional capabilities were developed including the novel detection of procedural non-compliance and the ability to localize anomalies relative to SAVY surface features.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1992

In situ detection of tropospheric OH, HO2, NO2, and NO by laser-induced fluorescence in detection chambers at reduced pressures

For detection of OH and HO2, we have met or exceeded most of the goals of the proposal for this grant. We have succeeded in building a prototype instrument for the detection of OH and HO2 that has a detection sensitivity of about 2 x 10 exp 4 (OH molecules/cc)/(ct/s), about five times greater than proposed. The current minimum detectable OH of 1.4 x 10 exp 5 OH molecules/cc (S/N=2; 30 second integration) is less than half that proposed, and will be much lower once scattered light levels are reduced. The instrument displays other important properties. First, interfering signals from other gases and OH losses on the inlet appear to be small under laboratory and field conditions. Second, three different calibration methods, two external to the inlet, give similar results, to within 30 percent. Third, the chemical conversion efficiency of HO2 to OH by addition of reagent NO is better than 90 percent. All of these factors give us great confidence that this technique works. The instrument has gone through several variations that have not affected its potential performance but have affected its use. We were able to undergo the first field trials away from State College in June 1992, when we were able to participate informally in the ROSE experiment in rural Alabama, a year ahead of the proposed schedule for field studies. Because this field experiment was our first and the data analysis was complicated by instrument instabilities, we have not yet released the observations. None-the-less, we have gained insight into instrument design. We have not yet completed all of the proposed work. The calibration systems need to be improved to reduce the 50 percent to 100 percent uncertainties to less than 30 percent. Interference signals from ambient gases and possible losses on the inlet under field conditions need to be quantified. Finally, the detection of NO2 and NO with laser induced fluorescence is only now being seriously pursued.

Brune, William H.↗
DOE OSTI2015

Nucleic acid detection system and method for detecting influenza

The invention provides a rapid, sensitive and specific nucleic acid detection system which utilizes isothermal nucleic acid amplification in combination with a lateral flow chromatographic device, or DNA dipstick, for DNA-hybridization detection. The system of the invention requires no complex instrumentation or electronic hardware, and provides a low cost nucleic acid detection system suitable for highly sensitive pathogen detection. Hybridization to single-stranded DNA amplification products using the system of the invention provides a sensitive and specific means by which assays can be multiplexed for the detection of multiple target sequences.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2015

A halo-independent lower bound on the dark matter capture rate in the Sun from a direct detection signal

We show that a positive signal in a dark matter (DM) direct detection experiment can be used to place a lower bound on the DM capture rate in the Sun, independent of the DM halo. For a given particle physics model and DM mass we obtain a lower bound on the capture rate independent of the local DM density, velocity distribution, galactic escape velocity, as well as the scattering cross section. We illustrate this lower bound on the capture rate by assuming that upcoming direct detection experiments will soon obtain a significant signal. When comparing the lower bound on the capture rate with limits on the high-energy neutrino flux from the Sun from neutrino telescopes, we can place upper limits on the branching fraction of DM annihilation channels leading to neutrinos. With current data from IceCube and Super-Kamiokande non-trivial limits can be obtained for spin-dependent interactions and direct annihilations into neutrinos. In some cases also annihilations into ττ or bb start getting constrained. For spin-independent interactions current constraints are weak, but they may become interesting for data from future neutrino telescopes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Dark matter directional detection in non-relativistic effective theories

We extend the formalism of dark matter directional detection to arbitrary one-body dark matter-nucleon interactions. The new theoretical framework generalizes the one currently used, which is based on 2 types of dark matter-nucleon interaction only. It includes 14 dark matter-nucleon interaction operators, 8 isotope-dependent nuclear response functions, and the Radon transform of the first 2 moments of the dark matter velocity distribution. We calculate the recoil energy spectra at dark matter directional detectors made of CF{sub 4}, CS{sub 2} and {sup 3}He for the 14 dark matter-nucleon interactions, using nuclear response functions recently obtained through numerical nuclear structure calculations. We highlight the new features of the proposed theoretical framework, and present our results for a spherical dark matter halo and for a stream of dark matter particles. This study lays the foundations for model independent analyses of dark matter directional detection experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Detecting electron neutrinos from solar dark matter annihilation by JUNO

We explore the electron neutrino signals from light dark matter (DM) annihilation in the Sun for the large liquid scintillator detector JUNO. In terms of the spectrum features of three typical DM annihilation channels χχ→νν-bar,τ{sup +}τ{sup −},bb-bar, we take two sets of selection conditions to calculate the expected signals and atmospheric neutrino backgrounds based on the Monte Carlo simulation data. Then the JUNO sensitivities to the spin independent DM-nucleon and spin dependent DM-proton cross sections are presented. It is found that the JUNO projected sensitivities are much better than the current spin dependent direct detection experimental limits for the νν-bar and τ{sup +}τ{sup −} channels. In the spin independent case, the JUNO will give the better sensitivity to the DM-nucleon cross section than the LUX and CDMSlite limits for the νν-bar channel with the DM mass lighter than 6.5 GeV. If the νν-bar or τ{sup +}τ{sup −} channel is dominant, the future JUNO results are very helpful for us to understand the tension between the DAMA annual modulation signal and other direct detection exclusions.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Towards Real-Time Detection and Tracking of Spatio-Temporal Features: Blob-Filaments in Fusion Plasma [Spatio-Temporal Features in Large Irregular Data: Blob-Filaments in Fusion Plasma]

This work was originally motivated the need to identify and track blob filaments, a feature often associated with instability in magnetically confined fusion plasma. Understanding and mitigating such instability would improve fusion reactors and make fusion a truly inexhaustible source of clean energy. Similar spatio-temporal features are important in many other applications, for example, ignition kernels in combustion and tumor cells in a medical image. This work presents an approach for extracting these features by dividing the overall task into three steps: local identification of feature cells, grouping feature cells into extended feature, and tracking movement of feature through overlapping in space. Through our extensive work in parallelization, we demonstrate that this approach can effectively make use of a large number of compute nodes to detect and track blobs in fusion plasma. On a set of 4.3TB data, we observed linear speedup on 1024 processes and completed blob detection in less than three milliseconds using Edison, a Cray XC30 system at NERSC.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Multiparticle Simulations of Quadrupolar Ion Detection in an Ion Cyclotron Resonance Cell with Four Narrow Aperture Detection Electrodes

The current paradigm in FT-ICR cell design is to approximate the ideal three-dimensional quadratic trapping potential as closely as possible to maintain ion cloud spatial coherence and achieve long transients, either with hyperbolically shaped electrodes, shimming electrodes, or by dynamic harmonization. In sharp contrast, the FT-ICR analyzer cell with four narrow aperture detection electrodes (NADEL) introduces significant anharmonic terms to the trapping potential. This analyzer cell is capable of quadrupolar detection by which one can measure a signal that is close to the unperturbed cyclotron frequency. This is far less sensitive to trapping potential and space charge shifts than the reduced cyclotron frequency measured in conventional ICR cells. The quadrupolar mode of ion detection in NADEL cells has been examined previously by SIMION simulations of ion clouds with up to 500 ions per simulation. Here, the behavior of the NADEL analyzer cell is examined through particle-in-cell (PIC) simulations, which allows us to examine the behavior of large populations (tens of thousands) of ions with space charge considerations, and to calculate the induced charge on the NADEL detection electrodes, and thus the transient signal. PIC simulations confirm a unique spatial distribution of the ions, with a coherent motion that results in long transient signals. Dependence of the ion cloud and image current signal on cell design, ion energy, and magnetron radius are examined. Coalescence effects are compared with those found in a dynamically harmonized cell. The insensitivity of the measured cyclotron frequency to space-charge is demonstrated both with simulations and experimentally. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Comparative Neutron Detection Efficiency in He-3 Proportional Counters and Liquid Scintillators

We present new results on the neutron detection efficiency of detection systems based on He-3 proportional counters compared to organic liquid scintillators. The experiments were conducted using a well-characterized Cf-252 neutron source, measured bare, and shielded with slabs of polyethylene. The results show that the intrinsic neutron detection efficiency for the bare source is approximately 25% for the He-3 system, and 67% for the liquid scintillator system. When polyethylene sheets were used to shield the source in 2.54 cm increments, the neutron detection efficiency of both systems decreased exponentially to approximately 10% for the case of 25.4 cm. Experimental results were simulated using MCNPX-PoliMi and good agreement was found between measurement and simulation results for all the cases considered here.

Organic scintillator, He-3, neutron detection, det↗
DOE OSTI2014

High-energy gamma-ray emission from solar flares: Summary of Fermi large area telescope detections and analysis of two M-class flares

We present the detections of 18 solar flares detected in high-energy γ-rays (above 100 MeV) with the Fermi Large Area Telescope (LAT) during its first 4 yr of operation. This work suggests that particle acceleration up to very high energies in solar flares is more common than previously thought, occurring even in modest flares, and for longer durations. Interestingly, all these flares are associated with fairly fast coronal mass ejections (CMEs). We then describe the detailed temporal, spatial, and spectral characteristics of the first two long-lasting events: the 2011 March 7 flare, a moderate (M3.7) impulsive flare followed by slowly varying γ-ray emission over 13 hr, and the 2011 June 7 M2.5 flare, which was followed by γ-ray emission lasting for 2 hr. We compare the Fermi LAT data with X-ray and proton data measurements from GOES and RHESSI. We argue that the γ-rays are more likely produced through pion decay than electron bremsstrahlung, and we find that the energy spectrum of the proton distribution softens during the extended emission of the 2011 March 7 flare. This would disfavor a trapping scenario for particles accelerated during the impulsive phase of the flare and point to a continuous acceleration process at play for the duration of the flares. CME shocks are known for accelerating the solar energetic particles (SEPs) observed in situ on similar timescales, but it might be challenging to explain the production of γ-rays at the surface of the Sun while the CME is halfway to the Earth. A stochastic turbulence acceleration process occurring in the solar corona is another likely scenario. Detailed comparison of characteristics of SEPs and γ-ray-emitting particles for several flares will be helpful to distinguish between these two possibilities.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Indirect Detection Analysis: Wino Dark Matter Case Study

We perform a multichannel analysis of the indirect signals for the Wino Dark Matter, including one-loop electroweak and Sommerfeld enhancement corrections. We derive limits from cosmic ray antiprotons and positrons, from continuum galactic and extragalactic diffuse γ-ray spectra, from the absence of γ-ray line features at the galactic center above 500 GeV in energy, from γ-rays toward nearby dwarf spheroidal galaxies and galaxy clusters, and from CMB power-spectra. Additionally, we show the future prospects for neutrino observations toward the inner Galaxy and from antideuteron searches. For each of these indirect detection probes we include and discuss the relevance of the most important astrophysical uncertainties that can impact the strength of the derived limits. We find that the Wino as a dark matter candidate is excluded in the mass range bellow simeq 800 GeV from antiprotons and between 1.8 and 3.5 TeV from the absence of a γ-ray line feature toward the galactic center. Limits from other indirect detection probes confirm the main bulk of the excluded mass ranges.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗