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At least 217 records · Page 12

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DOE OSTI2022

Shocked silica aerogel radiance transition

Silica (SiO 2 ) aerogel is widely used in high-energy-density shock experiments due to its low and adjustable density. Reported here are measurements of the shock velocity, optical radiance, and reflectivity of shocked SiO 2 aerogel with initial densities of 0.1, 0.2, and 0.3 g/cm 3 . These results are compared with similar data from three solid polymorphs of SiO 2 , silica, quartz, and stishovite with initial densities 2.2, 2.65, and 4.3 g/cm 3 , respectively. Interestingly, below a brightness temperature of T bright ≈ 35,000 K, the slope of the radiance vs shock velocity is the same for each of the SiO 2 aerogels and solid polymorphs. At T bright ≈ 35000 K, there is an abrupt change in the radiance vs shock velocity slope for aerogels, but not seen in the solid polymorphs over the pressures and temperatures explored here. An empirical model of shock front radiance as a function of SiO 2 density and laser drive parameters is reported to aid in the design of experiments requiring maximum shock front radiance.

42 ENGINEERING↗

DOE OSTI2025

Hyper Spectral Anomaly Detection

The HSA is a statistics based anomaly detection model. The model performs unsupervised anomaly detection, based on a datapoint's density and similarity within a dataset. Density and similarity data are encoded into an affinity matrix. The affinity matrix is evolved to summarize the data's structure on greater topographical scales within the data's function space. The set of evolved affinity matrices and an anomaly score vector are passed to a user defined penalized objective function. The penalized objective function of anomaly scores is then minimized. Data points where the absolute value of the z-scores of anomaly scores greater than a specified threshold are predicted as anomalies. A novel multi-filter feature has also been implemented. To reduce false positive rates, the multi-filter records the indexes of the HSA predictions. A new dataset and data loader are instantiated consisting of all the initial HSA predictions and non-anomalous data points in a 10% and 90% split respectively. The HSA is then run through this data set and a count of number of times a data point is predicted is kept. In this way the initial predictions may be compared with data spanning the entire dataset. After the multi-filter is complete, all datapoints will have an associated anomaly score, as well as a multi-filter prediction count to further filter the anomalous predictions.

Rogers, DempseyD [Idaho National Laboratory (INL),↗

DOE OSTI2023

Development of Optical Fiber-Based Sensors for Nuclear Microreactor Structural Health Monitoring

This report provides an experimental assessment of two different optical fiber–based acoustic sensors that are being investigated for application in nuclear microreactors to enhance structural health monitoring capabilities. Optical fibers are resilient in high-temperature and high-radiation environments, have a small sensor footprint, are immune to electromagnetic interference, and are capable of spatially distributed sensing. The two sensors investigated here are (1) Fabry–Pérot Cavities (FPCs) between two copper-coated fibers, embedded in nickel capillary tubes and (2) type-I fiber Bragg grating (FBG) arrays contained within metal capillary tubes. These sensors can be interrogated using low-coherence interferometry or swept wavelength interferometry, respectively, to measure the resonant frequencies of the components or systems to which these sensors are bonded. The FPC developed herein has been subjected to temperatures up to nearly 800°C while tack-welded to a tubular test specimen. Even at the highest temperatures, the measured resonant frequencies compared well with those obtained using an accelerometer that was bonded to an unheated portion of the specimen. The FBG array was tested in multiple bonding configurations to a tubular test specimen, all at room temperature, with the understanding that high temperature (i.e., type II) FBGs could be used to obtain similar data at high temperatures; the FBG array data were validated with noncontact laser vibrometry, which is being used at Los Alamos National Laboratory to relate acoustic signatures to component stresses and/or structural defects. The goal of this work is to identify the most promising techniques that are also compatible with operation in a microreactor environment.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2023

HD 222925: A New Opportunity to Explore the Astrophysical and Nuclear Conditions of r-process Sites

Abstract With the most trans-iron elements detected of any star outside the solar system, HD 222925 represents the most complete chemical inventory among metal-poor stars enhanced with elements made by the rapid neutron capture (“ r ”) process. As such, HD 222925 may be a new “template” for the observational r -process, where before the (much higher-metallicity) solar r -process residuals were used. In this work, we test under which conditions a single site accounts for the entire elemental r -process abundance pattern of HD 222925. We found that several of our tests—with the single exception of the black hole–neutron star merger case—challenge the single-site assumption by producing an ejecta distribution that is highly constrained, in disagreement with simulation predictions. However, we found that ejecta distributions that are more in line with simulations can be obtained under the condition that the nuclear data near the second r -process peak are changed. Therefore, for HD 222925 to be a canonical r -process template likely as a product of a single astrophysical source, the nuclear data need to be reevaluated. The new elemental abundance pattern of HD 222925—including the abundances obtained from space-based, ultraviolet (UV) data—call for a deeper understanding of both astrophysical r -process sites and nuclear data. Similar UV observations of additional r -process–enhanced stars will be required to determine whether the elemental abundance pattern of HD 222925 is indeed a canonical template (or an outlier) for the r -process at low metallicity.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

Search for Correlations of High-energy Neutrinos Detected in IceCube with Radio-bright AGN and Gamma-Ray Emission from Blazars

The IceCube Neutrino Observatory sends realtime neutrino alerts with a high probability of being astrophysical in origin. We present a new method to correlate these events and possible candidate sources using 2089 blazars from the Fermi-LAT 4LAC-DR2 catalog and with 3413 active galactic nuclei (AGNs) from the Radio Fundamental Catalog. No statistically significant neutrino emission was found in any of the catalog searches. The result suggests that a small fraction, <1%, of the studied AGNs emit neutrinos that pass the alert criteria, and is compatible with prior evidence for neutrino emission presented by IceCube and other authors from sources such as TXS 0506 + 056 and PKS 1502 + 106. We also present cross-checks to other analyses that claim a significant correlation using similar data samples.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

CondiDiag1.0: a flexible online diagnostic tool for conditional sampling and budget analysis in the E3SM atmosphere model (EAM)

Abstract. Numerical models used in weather and climate prediction take into account a comprehensive set of atmospheric processes (i.e., phenomena) such as the resolved and unresolved fluid dynamics, radiative transfer, cloud and aerosol life cycles, and mass or energy exchanges with the Earth's surface. In order to identify model deficiencies and improve predictive skills, it is important to obtain process-level understanding of the interactions between different processes. Conditional sampling and budget analysis are powerful tools for process-oriented model evaluation, but they often require tedious ad hoc coding and large amounts of instantaneous model output, resulting in inefficient use of human and computing resources. This paper presents an online diagnostic tool that addresses this challenge by monitoring model variables in a generic manner as they evolve within the time integration cycle. The tool is convenient to use. It allows users to select sampling conditions and specify monitored variables at run time. Both the evolving values of the model variables and their increments caused by different atmospheric processes can be monitored and archived. Online calculation of vertical integrals is also supported. Multiple sampling conditions can be monitored in a single simulation in combination with unconditional sampling. The paper explains in detail the design and implementation of the tool in the Energy Exascale Earth System Model (E3SM) version 1. The usage is demonstrated through three examples: a global budget analysis of dust aerosol mass concentration, a composite analysis of sea salt emission and its dependency on surface wind speed, and a conditionally sampled relative humidity budget. The tool is expected to be easily portable to closely related atmospheric models that use the same or similar data structures and time integration methods.

58 GEOSCIENCES↗

NASA NTRS1972

Sea, ice and surface water circulation, Alaskan Continental Shelf

The author has identified the following significant results. Two cruises were conducted in Cook Inlet to obtain ground truth. Forty-seven stations during 22-23 August and 68 stations during 25-29 September 1972 were occupied and temperature, salinity, percent light transmission, and suspended load of surface waters obtained. Similar data at various depths was also obtained at selected stations. Cook Inlet is an estuary with complex mixing of river discharges and ocean water. The Upper Cook Inlet shows a gradual and systematic decrease in salinity, however, west of Kenai the mixing of waters is complex. The sediments in suspension originating at the head of the inlet generally settle out east of Kenai and Drift River. Sediment load in suspension decreased gradually from 1700 mg/1 near Anchorage to about 50 mg/1 in the Narrows. In the Lower Cook Inlet the suspended load varied between 1-10 mg/1. Surface waters with sediments in suspension and ocean water with relatively lower sediment concentration are clearly discernible in ERTS-1 images obtained during September 18, 1972 pass over Cook Inlet. The movement and mixing of these waters can also be delineated in the images.

Wright, F. F.↗

NASA NTRS1973

Reusable surface insulation thermal protection systems test evaluation status

Changes in coating morphology of mullite, silica, and ceramic mullite fiber at two heating rates are described followed by a discussion of the changes in surface chemistry that occur during convective heating tests. Subsequently, the surface chemistry changes observed are compared to similar data obtained from radiantly heated coatings and the significance of the difference between the results is discussed. Finally, the changes in chemistry of the coatings in cross section before and after convectively heated cyclic testing are discussed and the significance of surface chemistry changes are described. Results indicate that the thermal conductivity of mullite surface insulation is higher than that of silica insulation, based on thermal response data. Acoustic excitation of cracked silica tiles does not lead to catastrophic failure such as spallation or tile loss. Cracks in mullite material after thermal exposure lead to fracturing of the coating and surface insulation material after acoustic excitation.

Strouhal, G.↗

NASA NTRS1973

Martian lineaments from Mariner 6 and 7 images

Mariner 6 and 7 images are used to investigate the nature and importance of linear surface trends on Mars. Cross correlations of frequency-azimuth distributions of linear trends from different Mariner frames indicate that lineations not recognized as topographic features have a component of artifacts, probably introduced during digital reconstruction of the images. Consequently, topographic and nontopographic lineations should be treated separately prior to interpretation of the data. Similar statistical tests may aid in the analysis of surface trends from future satellites and space probes.

Schultz, P. H.↗

NASA NTRS1975

The effect of surface temperature and Reynolds number on the leeward heat-transfer for a shuttle orbiter

The effect of windward surface temperature on the heat transfer to the leeward surface of the shuttle orbiter was investigated. Heat-transfer distributions, surface-pressure distributions, and schlieren photographs were obtained for an 0.01-scale model of the 37-0 shuttle orbiter at angles-of-attack of 30 deg and of 40 deg. Similar data were obtained for a fuselage-only configuration at angles-of-attack of 30 deg and of 90 deg. Data were obtained for various Mach numbers, Reynolds numbers, and surface temperatures.

Bertin, J. J.↗

NASA NTRS1975

Experimental and theoretical study of shuttle lee-side heat transfer rates

The experimental program which was conducted in the Calspan 96-inch hypersonic shock tunnel to investigate what effect the windward surface temperature had on the heat transfer to the leeward surface of the space shuttle orbiter is discussed. Heat-transfer distributions, surface-pressure distributions, and schlieren photographs were obtained for an 0.01-scale model of the 139 configuration space shuttle orbiter at angles-of-attack of 30 and 40 deg. Similar data were obtained for an 0.01 scale wingless model of the 139 configuration at angles-of-attack of 30 and 90 deg. Data were obtained for Mach numbers from Reynolds numbers, and surface temperatures and compared with theoretical results.

Mruk, G. K.↗

NASA NTRS1975

Evaluation of ERTS multispectral signatures in relation to ground control signatures using a nested-sampling approach

The author has identified the following significant results. Ground measured spectral signatures of wavelength bands matching ERTS MSS were collected using a radiometer at several Californian and Nevadan sites, and directly compared with similar data from ERTS CCTs. The comparison was tested at the highest possible spatial resolution for ERTS, using deconvoluted MSS data, and contrasted with that of ground measured spectra, originally from 1 meter squares. In the mobile traverses of the grassland sites, these one meter fields of view were integrated into eighty meter transects along the five km track across four major rock/soil types. Suitable software was developed to read the MSS CCT tapes, to shadeprint individual bands with user-determined greyscale stretching. Four new algorithms for unsupervised and supervised, normalized and unnormalized clustering were developed, into a program termed STANSORT. Parallel software allowed the field data to be calibrated, and by using concurrently continuously collected, upward- and downward-viewing, 4 band radiometers, bidirectional reflectances could be calculated.

Lyon, R. J. P.↗

NASA NTRS1977

Acoustics measurements in normal jet impingement

The dependence of far field acoustic measurements for a uniform jet on nozzle to plate spacing for small dimensionless spacings (h/d - 0.75 to 3.0) was investigated. Spectra from a real time analyzer were read and processed by an HP 2116 minicomputer in on-line mode. Similar data was generated for a fully developed pipe flow exit condition jet to compare with other investigations. The data base for normal jet impingement was extended to smaller values of nozzle to plate spacing. The effects of slight noise heating (30 deg rise) of the jet on the far field noise produced by the impinging jet are demonstrated.

Kleis, S. J.↗

NASA NTRS1977

Microvascular pressure responses of second-generation rats chronically exposed to 2 g centrifugation

Preliminary results are presented for a study aimed at a quantitative comparison of microvascular dynamics in second-generation rats reared in a 2-g force field produced by centrifugation with similar data from animals reared in a centrifuge that produced only a 1-g force. It is shown that the pressure distribution in the mesenteric microvasculature of the second generation of rats reared in a 2-g environment, as well as the animals' blood pressure response to epinephrine, are significantly different compared to their 1-g counterparts. In particular, 1-g and 2-g chronic centrifugation enhances the arterial blood pressure, and the 2-g force field attenuates the pressor effects of norepinephrine.

Richardson, D. R.↗

NASA NTRS1976

Trace element evidence regarding a chondritic component in howardite meteorites

The concentrations of siderophiles Ni, Ge, Ru, Ir, and Au and volatiles Zn, Ga, Cd, and In in howardite meteorites were determined and are discussed along with similar data for eucrites and diogenites. The concentrations of the chondritic component in howardites are remarkably high. The concentrations in four high-siderophile howardites are comparable to those found in mature soils from the lunar highlands. The amounts of excess volatiles are roughly consistent with those expected if the chondritic component resemble CI, CM, or E4 chondrites. Evidence indicates that the howardite parent body had a radius of several hundred kilometers, and the most probable formation location was 1-2 AU from the sun.

Chou, C.-L.↗

NASA NTRS1978

Transfer of training on manual control systems differing in short period frequency and damping characteristics

Each of four groups of 16 subjects was trained on one of four compensatory tracking tasks that differed with regard to short period natural frequency and damping characteristics. After completion of the training sessions, the members of each group either transferred to a task on which they had not been trained or continued with their original task. Analysis of the training data indicated that relative task difficulty was largely determined by system damping which, however, had little effect on the amount of transfer during the transfer trials. The effect of system frequency was essentially reversed, and a marked interaction between training and transfer frequencies was observed in the transfer data. Similar results were obtained both with relative error scores and transinformation scores. Positive transfer was exhibited by most of the groups when they transferred to tasks on which they had not been trained.

Lincoln, R. S.↗

NASA NTRS1979

ATMOS Spacelab 1 science investigation

Existing infrared spectra from high speed interferometer balloon flights were analyzed and experimental analysis techniques applicable to similar data from the ATMOS experiment (Spacelab 3) were investigated. Specific techniques under investigation included line-by-line simulation of the spectra to aid in the identification of absorbing gases, simultaneous retrieval of pressure and temperature profiles using carefully chosen pairs of CO2 absorption lines, and the use of these pressures and temperatures in the retrieval of gas concentration profiles for many absorbing species. A search for a new absorption features was also carried out, and special attention was given to identification of absorbing gases in spectral bandpass regions to be measured by the halogen occultation experiment.

Park, J. H.↗

NASA NTRS1981

Load compensating reactions to perturbations at wrist joint in normal man

The electromyographic responses to step torque loads were studied in flexors and extensors at the human wrist. Based on temporal bursting patterns and functional behavior, the response was divided into four temporal components. Two early components, the myotatic (30-60 ms) late myotatic (60-120 ms) appears to be reflex response. The third postmyotatic component (120-200 ms) appear to be a triggered reaction, preceeding the fourth, stabilizing component (200-400 ms). A comparison of response at the wrist with similar data at the ankle provides the basis for a generalized classification of the response in various muscles to torque step perturbations.

Jaeger, R. J.↗