The Experts below are selected from a list of 35481 Experts worldwide ranked by ideXlab platform
Shiva Abbaszadeh - One of the best experts on this subject based on the ideXlab platform.
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kernel based gaussian process for anomaly detection in sparse Gamma Ray data
PLOS ONE, 2020Co-Authors: Gregory R Romanchek, Zheng Liu, Shiva AbbaszadehAbstract:In radioactive source surveying protocols, a number of task-inherent features degrade the quality of collected Gamma Ray Spectra, including: limited dwell times, a fluctuating background, a large distance to the source, weak source activity, and the low sensitivity of mobile detectors. Thus, collected Gamma Ray Spectra are expected to be sparse and noise dominated. For extremely sparse Spectra, direct background subtraction is infeasible and many background estimation techniques do not apply. In this paper, we present a statistical algorithm for source estimation and anomaly detection under such conditions. We employ a fixed-hyperparameter Gaussian processes regression methodology with a linear innovation sequence scheme in order to quickly update an ongoing source distribution estimate with no prior training required. We have evaluated the effectiveness of this approach for anomaly detection using background Spectra collected with a Kromek D3S and simulated source spectrum and hyperparameters defined by detector characteristics and information derived from collected Spectra. We attained an area under the ROC curve of 0.902 for identifying sparse source peaks within a sparse Gamma Ray spectrum and achieved a true positive rate of 93% when selecting the optimum thresholding value derived from the ROC curve.
E B Norman - One of the best experts on this subject based on the ideXlab platform.
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observations of fallout from the fukushima reactor accident in san francisco bay area rainwater
PLOS ONE, 2011Co-Authors: E B Norman, C T Angell, P ChodashAbstract:We have observed fallout from the recent Fukushima Dai-ichi reactor accident in samples of rainwater collected in the San Francisco Bay area. Gamma Ray Spectra measured from these samples show clear evidence of fission products – 131,132I, 132Te, and 134,137Cs. The activity levels we have measured for these isotopes are very low and pose no health risk to the public.
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fission product Gamma Ray line pairs sensitive to fissile material and neutron energy
Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment, 2008Co-Authors: R E Marrs, E B Norman, J T Burke, R A Macri, Howard A Shugart, E Browne, A R SmithAbstract:The beta-delayed Gamma-Ray Spectra from the fission of 235 U, 238 U, and 239 Pu by thermal and near14-MeV neutrons have been measured for delay times ranging from 1 min to 14 h. Spectra at all delay times contain sets of prominent Gamma-Ray lines with intensity ratios that identify the fissile material and distinguish between fission induced by low-energy or high-energy neutrons.
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fission product Gamma Ray line pairs sensitive to fissile material and neutron energy
Journal Name: Nuclear Instruments and Methods in Physics Research A vol. 592 n a July 21 2008 pp. 463-471; Journal Volume: 592, 2007Co-Authors: R E Marrs, E B Norman, J T Burke, R A Macri, Howard A Shugart, E Browne, A R SmithAbstract:The beta-delayed Gamma-Ray Spectra from the fission of {sup 235}U, {sup 238}U, and {sup 239}Pu by thermal and near-14-MeV neutrons have been measured for delay times ranging from 1 minute to 14 hours. Spectra at all delay times contain sets of prominent Gamma-Ray lines with intensity ratios that identify the fissile material and distinguish between fission induced by low-energy or high-energy neutrons.
G Georgiev - One of the best experts on this subject based on the ideXlab platform.
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potential of prompt Gamma Ray emission studies in fast neutron induced fission a first step
European Physical Journal A, 2020Co-Authors: C Schmitt, M Lebois, A Oberstedt, S Oberstedt, J N Wilson, Ali Aladili, A Chatillon, D Choudhury, Angelique Gatera, G GeorgievAbstract:Prompt $$\Gamma $$-Ray Spectra emitted in fast-neutron induced fission of $$^{239}$$Pu have been recently measured by using the LICORNE directional neutron source at E$$_n$$ = 1.8 MeV. The results are used in parallel with the measurements of fast-neutron induced fission of $$^{238}$$U and spontaneous fission of $$^{252}$$Cf to assess the potential of such reactions and observables, in contributing to the understanding of fission. The $$\Gamma $$-Ray Spectra were measured and analyzed under similar conditions, allowing a consistent and robust comparison between the three systems. They are further compared to Monte–Carlo simulations based on two widely-used semi-empirical codes, FREYA and GEF. Differences in the low and high energy portions of the spectrum are interpreted based on simple arguments involving nuclear structure and evaporation effects. The significance and potential of experimental campaigns of this kind, as well as current limitations, are highlighted, together with straightforward but mandatory extensions.
Gary W Small - One of the best experts on this subject based on the ideXlab platform.
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Committee classifier based on linear discriminant analysis for the detection of radioisotopes from airborne Gamma-Ray Spectra.
Journal of environmental radioactivity, 2020Co-Authors: Brian W Dess, Gary W SmallAbstract:A committee classifier was developed for use in the application of real-time pattern recognition to Gamma-Ray Spectra collected from airborne surveys. This technique was designed to enhance detection performance relative to that of a single linear discriminant analysis model. The approach was based on utilizing multiple classifiers to check one another through a signal averaging method. This resulted in an ability to reject random false detections while maximizing detection sensitivity. Making use of Spectral preprocessing algorithms previously studied, the committee classifiers were applied to the detection of cesium-137 and cobalt-60 in Spectra collected in the field during airborne surveys. Applying a z-score methodology to the classification scores allowed classifiers developed with different processing parameters to operate in the same dataspace for the purpose of classifying the target Spectra. The optimized classifiers were tested over 13 diverse locations, with nine of the sites containing the respective target isotopes. Results of the committee classifiers indicated an improvement in missed and false detection performance for both radioisotopes. In addition, work was performed to confirm that several suspected false detections were actually weak target signals only visible once co-added with other similar Spectra. This result suggested the committee classifier performance may have exceeded the capabilities of the visual Spectral inspection on which the performance statistics were based.
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Background correction method for improving the automated detection of radioisotopes from airborne Gamma-Ray surveys.
Journal of environmental radioactivity, 2018Co-Authors: Brian W Dess, Robert T Kroutil, Gary W SmallAbstract:Abstract An altitude-based background correction strategy was developed for use in the application of pattern recognition methods to the classification of Gamma-Ray Spectra collected during airborne surveys. Application of this methodology helped to suppress the background Spectral variation that serves to obscure the photopeaks associated with low levels of Gamma-Ray emission. The correction method was implemented by optimizing a database of background Gamma-Ray Spectra collected at various locations and altitudes. Given this background database, a field-collected spectrum was corrected by performing linear regression onto a background spectrum from the database at a matching altitude. The residuals about the regression fit were then digitally filtered and submitted to nonparametric linear discriminant analysis for the purpose of computing classification models for targeted radioisotopes. The resulting classifiers were applied to predict the presence or absence of specific radioisotope signatures in data acquired during airborne surveys. Employing data provided by the U.S Environmental Protection Agency Airborne Spectral Photometric Environmental Collection Technology (ASPECT) program, classification models were computed to detect the presence of cesium-137 (137Cs) and cobalt-60 (60Co). The optimized classifiers were tested over 12 diverse locations, with nine of these data sets containing the target radioisotopes. Correct classification percentages of 99.4% and 99.8% were obtained for the 137Cs and 60Co classifiers, respectively, on the basis of comparisons to visual inspections of the corresponding Spectra.
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automated detection of radioisotopes from an aircraft platform by pattern recognition analysis of Gamma Ray Spectra
Journal of Environmental Radioactivity, 2018Co-Authors: Brian W Dess, John Cardarelli, Mark J Thomas, Jeff Stapleton, Robert T Kroutil, David W Miller, Timothy Curry, Gary W SmallAbstract:Abstract A generalized methodology was developed for automating the detection of radioisotopes from Gamma-Ray Spectra collected from an aircraft platform using sodium-iodide detectors. Employing data provided by the U.S Environmental Protection Agency Airborne Spectral Photometric Environmental Collection Technology (ASPECT) program, multivariate classification models based on nonparametric linear discriminant analysis were developed for application to Spectra that were preprocessed through a combination of altitude-based scaling and digital filtering. Training sets of Spectra for use in building classification models were assembled from a combination of background Spectra collected in the field and synthesized Spectra obtained by superimposing laboratory-collected Spectra of target radioisotopes onto field backgrounds. This approach eliminated the need for field experimentation with radioactive sources for use in building classification models. Through a bi-Gaussian modeling procedure, the discriminant scores that served as the outputs from the classification models were related to associated confidence levels. This provided an easily interpreted result regarding the presence or absence of the signature of a specific radioisotope in each collected spectrum. Through the use of this approach, classifiers were built for cesium-137 (137Cs) and cobalt-60 (60Co), two radioisotopes that are of interest in airborne radiological monitoring applications. The optimized classifiers were tested with field data collected from a set of six geographically diverse sites, three of which contained either 137Cs, 60Co, or both. When the optimized classification models were applied, the overall percentages of correct classifications for Spectra collected at these sites were 99.9 and 97.9% for the 60Co and 137Cs classifiers, respectively.
Luigi Costamante - One of the best experts on this subject based on the ideXlab platform.
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modeling the hard tev Spectra of blazars 1es 0229 200 and 3c 66a with an internal absorption scenario
arXiv: High Energy Astrophysical Phenomena, 2011Co-Authors: Olga Zacharopoulou, Felix Aharonian, Dmitry Khangulyan, Luigi CostamanteAbstract:We study the applicability of the idea of internal absorption of Gamma-Rays produced through synchrotron radiation of ultrarelativistic protons in highly magnetized blobs to 1ES 0229+200 and 3C 66A, the two TeV blazars which show unusually hard intrinsic Gamma-Ray Spectra after being corrected for the intergalactic absorption. We show that for certain combinations of reasonable model parameters, even with quite modest energy requirements, the scenario allows a self-consistent explanation of the non-thermal emission of these objects in the keV, GeV, and TeV energy bands.
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formation of hard very high energy Gamma Ray Spectra of blazars due to internal photon photon absorption
Monthly Notices of the Royal Astronomical Society, 2008Co-Authors: F Aharonian, Dmitry Khangulyan, Luigi CostamanteAbstract:The energy Spectra of TeV Gamma-Rays from blazars, after being corrected for intergalatic absorption in the Extragalactic Background Light (EBL), appear unusually hard, a fact that poses challenges to the conventional models of particle acceleration in TeV blazars and/or to the EBL models. In this paper we show that the internal absorption of Gamma-Rays caused by interactions with dense narrow-band radiation fields in the vicinity of compact Gamma-Ray production regions can lead to the formation of Gamma-Ray Spectra of an almost arbitrary hardness. This allows significant relaxation of the current tight constraints on particle acceleration and radiation models, although at the expense of enhanced requirements to the available nonthermal energy budget. The latter, however, is not a critical issue, as long as it can be largely compensated by the Doppler boosting, assuming very large (> 30) Doppler factors of the relativistically moving Gamma-Ray production regions. The suggested scenario of formation of hard Gamma-Ray Spectra predicts detectable synchrotron radiation of secondary electronpositron pairs which might require a revision of the current “standard paradigm” of Spectral energy distributions of Gamma-Ray blazars. If the primary Gamma-Rays are of hadronic origin related to pp or pγ interactions, the “internal Gamma-Ray absorption” model predicts neutrino fluxes close to the detection threshold of the next generation high energy neutrino detectors.
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formation of hard vhe Gamma Ray Spectra of blazars due to internal photon photon absorption
arXiv: Astrophysics, 2008Co-Authors: F Aharonian, Dmitry Khangulyan, Luigi CostamanteAbstract:The energy Spectra of TeV Gamma-Rays from blazars, after being corrected for intergalatic absorption in the Extragalactic Background Light (EBL), appear unusually hard, a fact that poses challenges to the conventional models of particle acceleration in TeV blazars and/or to the EBL models. In this paper we show that the internal absorption of Gamma-Rays caused by interactions with dense narrow-band radiation fields in the vicinity of compact Gamma-Ray production regions can lead to the formation of Gamma-Ray Spectra of an almost arbitrary hardness. This allows significant relaxation of the current tight constraints on particle acceleration and radiation models, although at the expense of enhanced requirements to the available nonthermal energy budget. The latter, however, is not a critical issue, as long as it can be largely compensated by the Doppler boosting, assuming very large ($\geq 30$) Doppler factors of the relativistically moving Gamma-Ray production regions. The suggested scenario of formation of hard Gamma-Ray Spectra predicts detectable synchrotron radiation of secondary electron-positron pairs which might require a revision of the current ``standard paradigm'' of Spectral energy distributions of Gamma-Ray blazars. If the primary Gamma-Rays are of hadronic origin related to $pp$ or $p \Gamma$ interactions, the ``internal Gamma-Ray absorption'' model predicts neutrino fluxes close to the detection threshold of the next generation high energy neutrino detectors.
