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DOE OSTI2025

Inverse kinematics study of the energy levels of 21 Ne populated with the 20 Ne +𝑑 reaction

In recent years there has been significant experimental effort aimed at studying the impact of 16 O neutron poisoning on the weak 𝑠 process in rotating massive stars. Improving the understanding of energy levels in 21 Ne is crucial to reducing uncertainties in the rates of the 𝛼-induced reactions on 17 O that determine the overall efficiency of the weak 𝑠 process. This paper reports on one such experiment: a study of the 20 Ne (𝑑,𝑝)⁢ 21 Ne reaction in inverse kinematics. Deduced spin-parity assignments were made based on adiabatic distorted-wave approximation analysis and neutron partial widths were estimated by comparison with a previous experiment. Of particular significance for nuclear astrophysics is the resulting neutron partial width for the 7820-keV energy level, estimated to be 12 200 ⁢(2900)⁢ eV, and an upper limit of ≤ 9300 eV for that of the 7749-keV energy level. These results are in tension with previous studies and therefore this paper also discusses the current state of the research into the astrophysically relevant energy levels and highlights both areas of agreement and areas of disagreement between this and various other studies that have investigated this nucleus.

direct reactions↗

NASA NTRS1991

Markov reward processes

Numerous applications in the area of computer system analysis can be effectively studied with Markov reward models. These models describe the behavior of the system with a continuous-time Markov chain, where a reward rate is associated with each state. In a reliability/availability model, upstates may have reward rate 1 and down states may have reward rate zero associated with them. In a queueing model, the number of jobs of certain type in a given state may be the reward rate attached to that state. In a combined model of performance and reliability, the reward rate of a state may be the computational capacity, or a related performance measure. Expected steady-state reward rate and expected instantaneous reward rate are clearly useful measures of the Markov reward model. More generally, the distribution of accumulated reward or time-averaged reward over a finite time interval may be determined from the solution of the Markov reward model. This information is of great practical significance in situations where the workload can be well characterized (deterministically, or by continuous functions e.g., distributions). The design process in the development of a computer system is an expensive and long term endeavor. For aerospace applications the reliability of the computer system is essential, as is the ability to complete critical workloads in a well defined real time interval. Consequently, effective modeling of such systems must take into account both performance and reliability. This fact motivates our use of Markov reward models to aid in the development and evaluation of fault tolerant computer systems.

Smith, R. M.↗

NASA NTRS1987

Biomass recycle as a means to improve the energy efficiency of CELSS algal culture systems

Algal cultures can be very rapid and efficient means to generate biomass and regenerate the atmosphere for closed environmental life support systems. However, as in the case of most higher plants, a significant fraction of the biomass produced by most algae cannot be directly converted to a useful food product by standard food technology procedures. This waste biomass will serve as an energy drain on the overall system unless it can be efficiently recycled without a significant loss of its energy content. Experiments are reported in which cultures of the alga Scenedesmus obliquus were grown in the light and at the expense of an added carbon source, which either replaced or supplemented the actinic light. As part of these experiments, hydrolyzed waste biomass from these same algae were tested to determine whether the algae themselves could be made part of the biological recycling process. Results indicate that hydrolyzed algal (and plant) biomass can serve as carbon and energy sources for the growth of these algae, suggesting that the efficiency of the closed system could be significantly improved using this recycling process.

Radmer, R.↗

NASA NTRS1972

Determination of mean surface position and sea state from the radar return of a short-pulse satellite altimeter

Using the specular point theory of scatter from a very rough surface, the average backscatter cross section per unit area per radar cell width is derived for a cell located at a given height above the mean sea surface. This result is then applied to predict the average radar cross section observed by a short-pulse altimeter as a function of time for two modes of operation: pulse-limited and beam-limited configurations. For a pulse-limited satellite altimeter, a family of curves is calculated showing the distortion of the leading edge of the receiver output signal as a function of sea state (i.e., wind speed). A signal processing scheme is discussed that permits an accurate determination of the mean surface position--even in high seas--and, as a by-product, the estimation of the significant seawave height (or wind speed above the surface). Comparison of these analytical results with experimental data for both pulse-limited and beam-limited operation lends credence to the model. Such a model should aid in the design of short-pulse altimeters for accurate determination of the geoid over the oceans, as well as for the use of such altimeters for orbital sea-state monitoring.

Barrick, D. E.↗

NASA NTRS1983

Investigation of image enhancement techniques for the development of a self-contained airborne radar navigation system

This study was devoted to an investigation of the feasibility of applying advanced image processing techniques to enhance radar image characteristics that are pertinent to the pilot's navigation and guidance task. Millimeter (95 GHz) wave radar images for the overwater (i.e., offshore oil rigs) and overland (Heliport) scenario were used as a data base. The purpose of the study was to determine the applicability of image enhancement and scene analysis algorithms to detect and improve target characteristics (i.e., manmade objects such as buildings, parking lots, cars, roads, helicopters, towers, landing pads, etc.) that would be helpful to the pilot in determining his own position/orientation with respect to the outside world and assist him in the navigation task. Results of this study show that significant improvements in the raw radar image may be obtained using two dimensional image processing algorithms. In the overwater case, it is possible to remove the ocean clutter by thresholding the image data, and furthermore to extract the target boundary as well as the tower and catwalk locations using noise cleaning (e.g., median filter) and edge detection (e.g., Sobel operator) algorithms.

Phatak, A. V.↗

NASA NTRS1994

SI (Metric) handbook

This guide provides information for an understanding of SI units, symbols, and prefixes; style and usage in documentation in both the US and in the international business community; conversion techniques; limits, fits, and tolerance data; and drawing and technical writing guidelines. Also provided is information of SI usage for specialized applications like data processing and computer programming, science, engineering, and construction. Related information in the appendixes include legislative documents, historical and biographical data, a list of metric documentation, rules for determining significant digits and rounding, conversion factors, shorthand notation, and a unit index.

Artusa, Elisa A.↗

NASA NTRS2003

The Magnetic Structure of H-Alpha Macrospicules in Solar Coronal Holes

Measurements by Ulysses in the high-speed polar solar wind have shown the wind to carry some fine-scale structures in which the magnetic field reverses direction by having a switchback fold in it. The lateral span of these magnetic switchbacks, translated to the Sun, is of the scale of the lanes and cells of the magnetic network in which the open magnetic flux of the polar coronal hole and polar solar wind are rooted. This suggests that the magnetic switchbacks might be formed from network-scale magnetic loops that erupt into the corona and then undergo reconnection with the open field. This possibility motivated us to undertake the study reported here of the structure of H-alpha macrospicules observed at the limb in polar coronal holes, to determine whether a significant fraction of these eruptions appear to be erupting loops. From a search of the polar-coronal holes in 6 days of image-processed full-disk H-alpha movies from Big Bear Solar Observatory, we found a total of 35 macrospicules. Nearly all of these (32) were of one or the other of two different forms: 15 were in the form of an erupting loop, and 17 were in the form of a single-column spiked jet. The erupting-loop macrospicules are appropriate for producing the magnetic switchbacks in the polar wind. The spiked-jet macrospicules show the appropriate structure and evolution to be driven by reconnection between network-scale closed field (a network bipole) and the open field rooted against the closed field. This evidence for reconnection in a large fraction of our macrospicules (1) suggests that many spicules may be generated by similar but smaller reconnection events, and (2) supports the view that coronal heating and solar wind acceleration in coronal holes and in quiet regions and corona are driven by explosive reconnection events in the magnetic network.

Yamauchi, Y.↗

NASA NTRS2012

Mapping the Upper Subsurface of MARS Using Radar Polarimetry

Future human exploration of Mars will require detailed knowledge of the surface and upper several meters of the subsurface in potential landing sites. Likewise, many of the Planetary Science Decadal Survey science goals, such as understanding the history of Mars climate change, determining how the surface was altered through processes like volcanism and fluvial activity, and locating regions that may have been hospitable to life in the past, would be significantly advanced through mapping of the upper meters of the surface. Synthetic aperture radar (SAR) is the only remote sensing technique capable of penetrating through meters of material and imaging buried surfaces at high (meters to tens-of-meters) spatial resolution. SAR is capable of mapping the boundaries of buried units and radar polarimetry can provide quantitative information about the roughness of surface and subsurface units, depth of burial of stratigraphic units, and density of materials. Orbital SAR systems can obtain broad coverage at a spatial scale relevant to human and robotic surface operations. A polarimetric SAR system would greatly increase the safety and utility of future landed systems including sample caching.

Carter, L. M.↗

NASA NTRS1991

Isotopic constraints on the origin of meteoritic organic matter

Salient features of the isotopic distribution of H, C and N in the organic material found in carbonaceous meteorites are noted. Most organic fractions are strongly enriched in D with respect to the D/H ratio characteristic of H2 in the protosolar system; substantial variations in C-13/C-12 ratio are found among different molecular species, with oxidised species tending to be C-13 enriched relative to reduced species; some homologous series reveal systematic decrease in C-13/C-12 with increasing C number; considerable variation in N-15/N-14 ratio is observed within organic matter, though no systematic pattern to its distribution has yet emerged; no interelement correlations have been observed between isotope enrichments for the different biogenic elements. The isotopic complexity echoes the molecular diversity observed in meteoritic organic matter and suggests that the organic matter was formed by multiple processes and/or from multiple sources. However, existence of a few systematic patterns points towards survival of isotopic signatures characteristic of one or more specific processes. The widespread D enrichment implies either survival of many species of interstellar molecule or synthesis from a reservoir containing a significant interstellar component. Several of the questions raised above can be addressed by more detailed determination of the distribution of the H, C and N isotopes among different well-characterized molecular fractions. Thus, the present study is aimed at discovering whether the different amino acids have comparable D enrichments, which would imply local synthesis from a D-enriched reservoir, or very viable D enrichments, which would imply survival of some interstellar amino acids. The same approach is also being applied to polycyclic aromatic hydrocarbons. Because the analytical technique employed (secondary ion mass spectrometry) can acquire data for all three isotopic systems from each molecular fraction, any presently obscured interelement isotopic correlation should also be revealed, which will aid in identifying pertinent synthetic processes.

Kerridge, J. F.↗

NASA NTRS2011

Sources of Variation in Creep Testing

Creep rupture is an important material characteristic for the design of rocket engines. It was observed during the characterization of GRCop-84 that the complete data set had nearly 4 orders of magnitude of scatter. This scatter likely confounded attempts to determine how creep performance was influenced by manufacturing. It was unclear if this variation was from the testing, the material, or both. Sources of variation were examined by conducting tests on identically processed specimens at the same specified stresses and temperatures. Significant differences existed between the five constant-load creep frames. The specimen temperature was higher than the desired temperature by as much as 43 C. It was also observed that the temperature gradient was up to 44 C. Improved specimen temperature control minimized temperature variations. The data from additional tests demonstrated that the results from all five frames were comparable. The variation decreased to 1/2 order of magnitude from 2 orders of magnitude for the baseline data set. Independent determination of creep rates in a reference load frame closely matched the creep rates determined after the modifications. Testing in helium tended to decrease the sample temperature gradient, but helium was not a significant improvement over vacuum.

Loewenthal, William S.↗

NASA NTRS1994

Two-sample discrimination of Poisson means

This paper presents a statistical test for detecting significant differences between two random count accumulations. The null hypothesis is that the two samples share a common random arrival process with a mean count proportional to each sample's exposure. The model represents the partition of N total events into two counts, A and B, as a sequence of N independent Bernoulli trials whose partition fraction, f, is determined by the ratio of the exposures of A and B. The detection of a significant difference is claimed when the background (null) hypothesis is rejected, which occurs when the observed sample falls in a critical region of (A, B) space. The critical region depends on f and the desired significance level, alpha. The model correctly takes into account the fluctuations in both the signals and the background data, including the important case of small numbers of counts in the signal, the background, or both. The significance can be exactly determined from the cumulative binomial distribution, which in turn can be inverted to determine the critical A(B) or B(A) contour. This paper gives efficient implementations of these tests, based on lookup tables. Applications include the detection of clustering of astronomical objects, the detection of faint emission or absorption lines in photon-limited spectroscopy, the detection of faint emitters or absorbers in photon-limited imaging, and dosimetry.

Lampton, M.↗

NASA NTRS1993

Performance evaluation of the JPL TOPSAR system: An across-track interferometric SAR system for topographic mapping

An across-track interferometric (XTI) SAR has the capability of determining the three dimensional target location from the recorded radar echos thus providing high spatial resolution both horizontally and vertically. The output of an XTI SAR will typically include both a radar backscatter map and a digital elevation model (DEM). The accuracy of the derived DEM is determined by factors such as data acquisition geometry, signal-to-noise ratio, knowledge of platform position and attitude as well as the accuracy of the processing system. In the summer of 1992 the authors acquired TOPSAR data over the Ft. Irwin area in California, a desert area with significant relief (height standard deviation 150 m). Very accurate DEM's have been derived for this area by the Topographic Engineering Center (TEC) using digital correlation methods on 1:20,000 scale digitized photographs. Corner reflectors were deployed in the area, and their locations were determined to cm accuracies by the Defense Mapping Agency (DMA) using differential GPS techniques. DEM's generated from the acquired radar data have been rotated and translated to overlay the reference DEM's provided by TEC. A detailed description of the errors and their characteristics will be given. The standard deviations of the radar data sets we acquired measured over a 5.6 by 7 km area were 1.9 and 2.3 m. The corresponding numbers for flat areas were 1.1 and 2.0 m and for mountain areas 3.3 and 2.2 m.

Madsen, Soren N.↗

DOE OSTI2025

Search for η c ( 2 S ) → ω ω and ω ϕ and measurements of χ c J → ω ω and ω ϕ in ψ ( 2 S ) radiative processes

Using ( 2712 ± 14 ) × 10 6 ψ ( 2 S ) events collected with the BESIII detector at the BEPCII collider, we search for the decays η c ( 2 S ) → ω ω and η c ( 2 S ) → ω ϕ via the process ψ ( 2 S ) → γ η c ( 2 S ) . No statistically significant signals are observed. The upper limits of their product branching fractions at the 90% confidence level are determined to be B ( ψ ( 2 S ) → γ η c ( 2 S ) , η c ( 2 S ) → ω ω ) < 1.04 × 10 − 6 and B ( ψ ( 2 S ) → γ η c ( 2 S ) , η c ( 2 S ) → ω ϕ ) < 1.85 × 10 − 7 , respectively. We also update the branching fractions of χ c J → ω ω and χ c J → ω ϕ via the ψ ( 2 S ) → γ χ c J transition. Their branching fractions are determined to be B ( χ c 0 → ω ω ) = ( 10.66 ± 0.11 ± 0.57 ) × 10 − 4 , B ( χ c 1 → ω ω ) = ( 6.43 ± 0.07 ± 0.31 ) × 10 − 4 , B ( χ c 2 → ω ω ) = ( 8.75 ± 0.08 ± 0.42 ) × 10 − 4 , B ( χ c 0 → ω ϕ ) = ( 1.18 ± 0.03 ± 0.07 ) × 10 − 4 , B ( χ c 1 → ω ϕ ) = ( 2.04 ± 0.15 ± 0.11 ) × 10 − 5 , and B ( χ c 2 → ω ϕ ) = ( 9.58 ± 1.07 ± 0.76 ) × 10 − 6 , where the first uncertainties are statistical and the second are systematic. Published by the American Physical Society 2025

Ablikim, M.↗

NASA NTRS1982

The possible role of heterogeneous aerosol processes in the chemistry of CH4 and CO in the troposphere

The effect of particle-gas interactions on the CH4 to CO oxidation sequence in the troposphere is investigated by developing rate expressions for the heterogeneous removal of gaseous species based on the absorption of the species by aerosol particles. The results of this analysis indicate that the homogeneous models describe the tropospheric chemistry of CO and CH4 more accurately than heterogeneous models, which suggests that heterogeneous processes may not be significant in this sequence of chemical reactions. Estimates of the CO and CH4 emission rates are not found to provide a conclusive basis on which to compare the significance of the homogeneous and heterogeneous processes. In addition, the time period during which an aerosol particle is effective in removing a trace gaseous species from the troposphere is determined to vary according to the tropospheric concentration and solubility of the particular gaseous species.

Luther, C. J.↗

NASA NTRS1991

Thermal and solutal conditions at the tips of a directional dendritic growth front

The line-of-sight averaged, time-dependent dendrite tip concentrations for the diffusion dominated vertical directional solidification of a metal model (ammonium chloride and water) were obtained by extrapolating exponentially fit diffusion layer profiles measured using a laser interferometer. The tip concentrations were shown to increase linearly with time throughout the diffusion dominated growth process for an initially stagnant dendritic array. The process was terminated for the cases chosen by convective breakdown suffered when the conditionally stable diffusion layer exceeded the critical Rayleigh criteria. The transient tip concentrations were determined to significantly exceed the values predicted for steady state, thus producing much larger constitutional undercoolings. This has ramifications for growth speeds, arm spacings and the dendritic structure itself.

Mccay, T. D.↗

NASA NTRS1993

Digital mammography, cancer screening: Factors important for image compression

The use of digital mammography for breast cancer screening poses several novel problems such as development of digital sensors, computer assisted diagnosis (CAD) methods for image noise suppression, enhancement, and pattern recognition, compression algorithms for image storage, transmission, and remote diagnosis. X-ray digital mammography using novel direct digital detection schemes or film digitizers results in large data sets and, therefore, image compression methods will play a significant role in the image processing and analysis by CAD techniques. In view of the extensive compression required, the relative merit of 'virtually lossless' versus lossy methods should be determined. A brief overview is presented here of the developments of digital sensors, CAD, and compression methods currently proposed and tested for mammography. The objective of the NCI/NASA Working Group on Digital Mammography is to stimulate the interest of the image processing and compression scientific community for this medical application and identify possible dual use technologies within the NASA centers.

Clarke, Laurence P.↗

NASA NTRS1998

A Study of Undercooling Behavior Of Immiscible Metal Alloys in the Absence of Crucible-Induced Nucleation

The purpose of this study is to investigate the question: Would eliminating the crucible eliminate the wall-induced nucleation of one of the liquid phases in an immiscible alloy and result in undercooling of the liquid into the metastable region thereby producing significant differences in the separation process and the microstructure upon solidification. Another primary objective of this research is to study systems with a metastable miscibility gap and to directly determine the metastable liquid miscibility gap by undercooling experiments. Nucleation and growth of droplets in these undercooled metallic liquid-liquid mixtures is also being studied. Results of this investigation indicate that containerless processing of immiscibles may not promote the undercooling of the single-phase liquid into the metastable region. Although no recalescence event was observed for this liquid-liquid transition, undercooling did occur across the miscibility gap for the solidification of the Ti phase that eventually separated.

Robinson, Michael B.↗

NASA NTRS2015

Evaluation of Solid Rocket Motor Component Data Using a Commercially Available Statistical Software Package

Commercially available software packages today allow users to quickly perform the routine evaluations of (1) descriptive statistics to numerically and graphically summarize both sample and population data, (2) inferential statistics that draws conclusions about a given population from samples taken of it, (3) probability determinations that can be used to generate estimates of reliability allowables, and finally (4) the setup of designed experiments and analysis of their data to identify significant material and process characteristics for application in both product manufacturing and performance enhancement. This paper presents examples of analysis and experimental design work that has been conducted using Statgraphics®(Registered Trademark) statistical software to obtain useful information with regard to solid rocket motor propellants and internal insulation material. Data were obtained from a number of programs (Shuttle, Constellation, and Space Launch System) and sources that include solid propellant burn rate strands, tensile specimens, sub‐scale test motors, full‐scale operational motors, rubber insulation specimens, and sub‐scale rubber insulation analog samples. Besides facilitating the experimental design process to yield meaningful results, statistical software has demonstrated its ability to quickly perform complex data analyses and yield significant findings that might otherwise have gone unnoticed. One caveat to these successes is that useful results not only derive from the inherent power of the software package, but also from the skill and understanding of the data analyst.

Stefanski, Philip L.↗