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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Discriminating Uranium Isotopes Based on Fission Signatures Induced by Delayed Neutrons

The use of active interrogation to induce delayed neutron emission is a well-established technique for the characterization of special nuclear materials. Delayed neutrons have isotope-characteristic spectral and temporal signatures, which provide the basis for isotope identification. However, in bulk materials that contain an appreciable fissile (e.g., 235 U or 233 U) fraction, such as highly enriched uranium (HEU), delayed neutrons have a high probability of inducing additional fissions. As a result, the overall delayed neutron signature consists of two distinct components: the “primary” delayed neutrons (emitted directly by fission fragments) and the “secondary prompt” fission neutrons produced in fission induced by primary delayed neutrons. These prompt products differ from “primary” delayed neutrons both in their energy spectra and in the presence of coincident radiation released by the parent fission event. The presence and relative quantity of prompt products from delayed fission depend on the cross section of the material in the energy range of delayed neutrons, which may differ significantly between isotopes, thus providing an exploitable means for isotope differentiation. Here, we demonstrate two experimental approaches for discriminating between 235 U and 238 U isotopes based on the measurement of delayed neutron-induced fission products. First, HEU and depleted uranium objects are differentiated through the detection of high-energy prompt neutrons from delayed fission using both recoil-based organic liquid scintillators and thermalization spectra from a custom-built capture-gated composite detector. Secondly, coincident radiation measurements are used as the basis for discrimination by comparing the overall rates and time evolution of fission events when delayed neutrons are present.

07 ISOTOPE AND RADIATION SOURCES↗
DOE OSTI2020

The use of seismic spatial gradients in a single layer neural network for seismic source discrimination: proof of concept

This report describes a proof-of-concept method of seismic source discrimination using seismic gradiometry and a common machine learning technique. The tests described here are purely numerical, using synthetic seismic data and well understood mathematical techniques. The primary innovation described here is the application of a richer seismic data set derived from seismic gradiometry. Seismic gradiometry is a method to estimate the time variable spatial gradient of the wavefield to compute various wavefield attributes such as slowness, dynamic strain, and rotational motions. With the addition of these wavefield attributes, we are afforded up to twenty "compo- nents" of time series data measured at a single point on, or in, the Earth. This is in direct contrast to conventional three-component seismic data collected at several locations using a seismic network. Using the gradiometrically-derived wavefield components directly in a single-layer neural network, I show that it is possible to discriminate between three common seismic source types (earthquakes, explosions, and opening fractures) for various noise conditions and gradiometry configurations.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2021

Rossi Alpha Measurements – Rapid Organic (n, $\gamma$) Discrimination Detector (RAM-RODD) system capabilities

The Rossi Alpha Measurements–Rapid Organic (n, $\gamma$) Discrimination Detector (RAM-RODD) is an array organic scintillation detectors that has been optimized for use in neutron noise measurements. This report details the capability of the system including the method of energy calibration, pulse shape discrimination, and time resolution.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Discriminative analysis of schizophrenia patients using graph convolutional networks: A combined multimodal MRI and connectomics analysis

Introduction Recent studies in human brain connectomics with multimodal magnetic resonance imaging (MRI) data have widely reported abnormalities in brain structure, function and connectivity associated with schizophrenia (SZ). However, most previous discriminative studies of SZ patients were based on MRI features of brain regions, ignoring the complex relationships within brain networks. Methods We applied a graph convolutional network (GCN) to discriminating SZ patients using the features of brain region and connectivity derived from a combined multimodal MRI and connectomics analysis. Structural magnetic resonance imaging (sMRI) and resting-state functional magnetic resonance imaging (rs-fMRI) data were acquired from 140 SZ patients and 205 normal controls. Eighteen types of brain graphs were constructed for each subject using 3 types of node features, 3 types of edge features, and 2 brain atlases. We investigated the performance of 18 brain graphs and used the TopK pooling layers to highlight salient brain regions (nodes in the graph). Results The GCN model, which used functional connectivity as edge features and multimodal features (sMRI + fMRI) of brain regions as node features, obtained the highest average accuracy of 95.8%, and outperformed other existing classification studies in SZ patients. In the explainability analysis, we reported that the top 10 salient brain regions, predominantly distributed in the prefrontal and occipital cortices, were mainly involved in the systems of emotion and visual processing. Discussion Our findings demonstrated that GCN with a combined multimodal MRI and connectomics analysis can effectively improve the classification of SZ at an individual level, indicating a promising direction for the diagnosis of SZ patients. The code is available at https://github.com/CXY-scut/GCN-SZ.git .

Chen, Xiaoyi↗
DOE OSTI2022

A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production

The precise mechanism for production of quarkonium at hadron colliders is still an open question. Within non-relativistic quantum chromodynamics, quarkonium production cross sections can be factorized into short-distance, perturbative contributions and universal, non-perturbative, long-distance matrix elements, and then summed over quantum numbers of the heavy quark pair. In principle, at short-distances, the heavy quark pair can be either in a color-singlet or color-octet state, and it is desirable to establish the relative contributions to compare with data and to make predictions in different experimental environments. From the explicit form of the lowest-order perturbative matrix elements for color-singlet and color-octet production, we show that the structure of the optimal observable for discrimination on phase space, the likelihood ratio, has strong dependence on the angular momentum state of the heavy quark pair. This presents an obstruction for construction of a single, robust discrimination observable that can be applied to production of an arbitrary quarkonium state.

Larkoski, Andrew↗
NASA NTRS1966

Digitally controlled pulse-level discriminator operates over wide voltage range

Low power drain discriminator circuit generates an output pulse when an input pulse exceeds a discrete digitally controlled threshold voltage. The discriminator operates over a wide linear or nonlinear range of threshold levels. It uses several amplifier stages ahead of a fixed-reference threshold detector.

Cancro, C. A.↗
NASA NTRS1972

Average evoked potential correlates of two-flash perceptual discrimination in cats.

Average evoked potentials (AEPs) were recorded from the optic tract, lateral geniculate nucleus, and visual cortex of cats trained to discriminate between two successive flashes of light at various interflash intervals (IFI) and a single flash. The percent of correct responses to two-flash stimuli decreased sharply as IFI decreased from 100 to 20 msec. This behavioral response decrement was paralleled by a progressive overlapping of the AEPs to the two flashes and at 20 msec the AEPs resembled those to a single flash at all levels of the visual pathways. Implications for the coding of the information relevant to the discrimination of two flashes are discussed.

Peck, C. K.↗
NASA NTRS1974

Improved discrimination in photographic density contouring

Density discrimination can be accomplished through use of special photographic contouring material which has two sensitive layers (one negative, one positive) on single support. Process will be of interest to investigators who require finer discrimination of densities of original photograph for purposes such as identification of crops and analysis of energy levels of radiating objects.

Godding, R. A.↗
NASA NTRS1972

Application of frequency discrimination technique to the analysis of electroencephalographic signals

A frequency discrimination technique is realized by an inexpensive frequency discriminator for direct on-line measurement of the entrainment phenomenon in EEG as entrained by the frequency of a sensory stimulus. The use of this device for detecting the presence or absence of the stimulus effect and the measurement of the time delays in the entrainment is demonstrated. The EEG signal is first filtered by a narrow-band filter with center frequency about the alpha-rhythm of the individual. It is then reasonable to consider the alpha signal as narrow-band random process with the alpha frequency f sub alpha as the mean frequency of the spectral band.

Lai, D. C.↗
NASA NTRS1973

Characteristics of cesium iodide for use as a particle discriminator for high energy cosmic rays

The possible use of CsI to discriminate between high energy cosmic ray electrons and interacting protons has been investigated. The pulse-shape properties as a function of ionization density, temperature, and spectral response are presented for thallium-activated CsI and as a function of ionization density for sodium-activated CsI. The results are based on previously published data and on corroborative measurements from the present work. Experimental results on the response of CsI to electron-induced electromagnetic cascades and to interacting hadrons are described. Bibliographies of publications dealing with the properties of CsI and with pulse-shape discrimination techniques are presented.

Crannell, C. J.↗
NASA NTRS1972

A slope reversal video processor having amplitude and pulse width discrimination.

A timing discriminator whose output is relatively insensitive to input pulse width and amplitude is described. The video-handling technique is known as slope reversal processing and is based on tapped delay line estimation methods. The concept, design, breadboard construction, and preliminary laboratory test results are reviewed. The processor system features (1) a peak input voltage dynamic range of 80x starting at 100 microvolts; (2) a four stage preamplifier/line-driver having a voltage gain of 2400x; (3) a tapped delay-line estimator implemented for slope reversal triggering by differential comparison; (4) a nominal plus or minus 2.5 nsec shift of the output trigger leading edge over the entire input voltage range, (5) up to 7 dB discrimination against pulse widths less than 35 nsec; and (6) up to one order of magnitude reduction in the false alarm rate compared to a constant fraction system.

Hoge, F. E.↗
NASA NTRS1973

Development of a two channel linear discriminant function for detecting and identifying surface water using ERTS-1 data

A method for detecting surface water using ERTS-1 multispectral scanner digital data is described. The several computer programs for processing multispectral data are described, along with the manner in which these programs were used. The use of the LARSAA program to test and demonstrate the discriminant function is explained. The discriminant function itself was later implemented in an operational program which performs only those specific operations necessary to test each data point for an indication of surface water in the scene. Several possible sources of difficulty in the use of the function are identified, and suggestions are made for avoiding or correcting those difficulties.

Source record↗
NASA NTRS1974

An evaluation of multiband photography for rock discrimination

The ability of multiband photography to discriminate sedimentary rocks is investigated. Measurements showed that there is a large natural variation in the band reflectance of rock formations and that the differences in the contrast ratios for different Wratten filters is small, making it statistically impossible to select a set of best bands from in situ reflectance measurements. It is concluded that the designed multiband photography concept is not a practical method for improving sedimentary-rock discrimination capabilities.

Raines, G. L.↗
NASA NTRS1975

Intermodal transfer in temporal discrimination

This study determined if training for accuracy in temporal discrimination would transfer across sensory modalities. A fractionation method was used in which subjects bisected the durations of acoustic and visual signals at three standard intervals (6, 12, and 18 sec). Absolute error was the performance index. Half of the subjects were trained with acoustic stimuli and then tested in vision; the remainder were trained in vision and tested in audition. Similar negatively accelerated acquisition functions were noted for both modalities. Positive intermodal transfer, characterized by symmetry across modalities, was obtained at all standard durations. The results were considered to provide support for the notion that a common mechanism underlies temporal discriminations in different sensory systems.

Warm, J. S.↗
NASA NTRS1980

Optimum spectral bands for rock discrimination

Using stepwise discriminant analysis on spectral reflectance and spectral emissivity data collected by a Multispectral Scanner and Data System, mounted in an NC-130B aircraft and flown at an altitude of approximately 3 km, spectral bands were ranked as to their usefulness in separating specific rock types and rock alteration products in seven geologically diverse Utah sites. The optimum band for rock discrimination included the 1.18 to 1.30 micron interval, and the optimum combination of bands comprised the 1.18 to 1.30, 4.50 to 4.75, 0.46 to 0.50, 1.52 to 1.73, and 2.10 to 2.36 micron intervals. It is concluded that the spectral interval combination was more successful in differentiating geologic materials than either simulated Multispectral Scanner bands or simulated Thematic Mapper bands.

Siegrist, A. W.↗
NASA NTRS1982

Discriminator aided phase lock acquisition for suppressed carrier signals

A discriminator aided technique for acquisition of phase lock to a suppressed carrier signal utilizes a Costas loop which is initially operated open loop and control voltage for its VCXO is derived from a phase detector that compares the VCXO to a reference frequency thus establishing coarse frequency resolution with the received signal. Then the Costas loop is closed with the low-pass filter of the channel having a bandwidth much greater (by a factor of about 10) than in the I channel so that a frequency discriminator effect results to aid carrier resolution. Finally, after carrier acquisition, the Q-channel filter of the Costas loop is switched to a bandwidth substantially equal to that of the I-channel for carrier tracking.

Carson, L. M.↗
NASA NTRS1982

Radar image processing for rock-type discrimination

Image processing and enhancement techniques for improving the geologic utility of digital satellite radar images are reviewed. Preprocessing techniques such as mean and variance correction on a range or azimuth line by line basis to provide uniformly illuminated swaths, median value filtering for four-look imagery to eliminate speckle, and geometric rectification using a priori elevation data. Examples are presented of application of preprocessing methods to Seasat and Landsat data, and Seasat SAR imagery was coregistered with Landsat imagery to form composite scenes. A polynomial was developed to distort the radar picture to fit the Landsat image of a 90 x 90 km sq grid, using Landsat color ratios with Seasat intensities. Subsequent linear discrimination analysis was employed to discriminate rock types from known areas. Seasat additions to the Landsat data improved rock identification by 7%.

Blom, R. G.↗