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At least 685 records · Page 38

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NASA NTRS2005

Estimation of ZnSe Slow-Crack-Growth Properties for Design of the Flow Enclosure Accommodating Novel Investigations in Combustion of Solids (FEANICS) Windows

This report reviews some of the literature on the fracture strength, fracture toughness, and crack growth properties of chemical-vapor-deposited ZnSe. The literature was reviewed to determine if the existing data on ZnSe is adequate to design windows for the Flow Enclosure Accommodating Novel Investigations in Combustion of Solids (FEANICS) project. Unfortunately, most of the published reports do not give all of the necessary design parameters despite having measured the data to do so. Further, the original data is not available. The data tabulated herein was determined by digitizing plots in original reprints of the publications. Based on the published data, an estimate of the slow-crack-growth parameters for small cracks in 100 percent humidity was made. For 100 percent humidity, the slow-crack-growth parameters n and A for small crack (or single crystal) failure were estimated. Weibull moduli estimated from bending of beams and circular plates ranged from 4 to 9, while fracture strengths ranged from 29 MPa in water to 72 MPa in dry nitrogen. Fracture toughness measurements yielded ranges, with the lower values representing failure from small flaws within grains and the larger values representing macroscopic cracks. Much of the data analyzed exhibited significant scatter, and the standard deviations were very large.

Salem, Jonathan A.↗

DOE OSTI2023

Environmental and Social Justice Considerations in a Circular Economy

A consideration of environmental justice (EJ) and social justice (SJ) is critical to minimize the impacts of technology deployment on local communities. SJ and EJ impacts occur in specific geographic locations but can cover a wide range of effects (e.g., air pollution, access to clean water, jobs, wages, and education), making it challenging to determine which metrics are appropriate to evaluate and which data are required for qualitative or quantitative analysis. This issue is only exacerbated when the technology in question is at an early technology readiness level (TRL) without community specific data. Here, we present a framework for evaluating the human health, local environment, and job implications of processes that are at early to middle TRLs. Using a case study on enzymatic polyethylene terephthalate (PET) recycling (middle TRL), we demonstrate how to qualitatively and quantitatively assess these EJ and SJ metrics for a circular economy context and how to communicate the results in a manner beneficial to both researchers and local communities.

circular economy↗

NASA NTRS1981

Cartographic potential of a spacecraft line-array camera system - Stereosat

A study of the Stereosat mission, which may acquire analog/digital stereo image data of cartographic quality with linear array camera systems, is presented, with attention given to the Stereosat system and the mission parameters, the utilization of the Stereosat studies in order to indicate the nature and scope of the problems associated with recording image data of high geometric fidelity from spacecraft equipped with line array sensors, and the assessing of the possibilities of meeting the completeness and accuracy requirements of cartographic products. A 713-km circular, sun-synchronous, near polar orbit, with an inclination of 98.24 deg and a repeat cycle of 48 days is designed to insure global coverage of the earth's land masses during the three-year lifetime of the mission. Three cameras (fore, vertical, and aft looking), mounted so as to record stereotriplets for a 61.4 km wide swath at a nominal focal plane scale of 1:1,000,000, are considered. The IFOV of 15 m should be adequate for producing thematic and image maps at scales of 1:50,000 to 1:250,000. The value of the coverage to cartographers will be dictated by the accuracy of the digital image data, which is largely a function of satellite control.

Welch, R.↗

NASA NTRS1976

Crater dimensions from Apollo data and supplemental sources

A catalog of crater dimensions that were compiled mostly from the Apollo-based Lunar Topographic Orthophotomaps is presented in its entirety. Values of crater diameter, depth, rim height, flank width, circularity, and floor diameter (where applicable) are tabulated for a sample of 484 craters on the moon and 22 craters on earth. Systematic techniques of mensuration are detailed. The lunar craters range in size from 400 m to 300 km across and include primary impact craters of the main sequence, secondary impact craters, craterlets atop domes and cones, and dark-halo craters. The terrestrial craters are between 10 m and 22.5 km in diameter and were formed by meteorite impact.

Pike, R. J.↗

NASA NTRS1986

A comparison of computed and measured aerodynamic characteristics of a proposed aeroassist flight experiment configuration

The use of experimental or computed data to evaluate the performance of aeroassist orbital transfer vehicles (AOTVs) is discussed. Aerodynamic and surface pressure data are derived from computed flowfield solutions (the HALIS inviscid flowfield code), the Newtonian theory, and ground-based, wind tunnel studies (hypersonic He tunnel, 31-inch Mach 10 tunnel, and a hypersonic CF4 tunnel). The wind tunnel and HALIS models were tested at angles-of-attack that ranged from -10 to 10 deg. The effects of the ellipticity of the nose, the radius of the circular arc, and the angle through which the arc passes on the aerodynamic characteristics of the vehicles are examined. It is observed that the HALIS and CF4 tunnel generated surface pressure on the AOTVs produced the most useful aerodynamic data. Good correlation is obtained for the experimental and computational data; however, the Newtonian results do not correspond to the tunnel/HALIS data.

Weilmuenster, K. J.↗

DOE OSTI2025

Nature of the Reactive Biferric Peroxy Intermediate P′ in the Arylamine Oxygenases and Related Binuclear Fe Enzymes

Binuclear nonheme iron enzymes activate O 2 to perform a wide range of chemical transformations. The process of O 2 activation typically involves a biferric peroxy-level intermediate P. It has been previously found that this intermediate undergoes further activation, either protonation or rearrangement to form P′ or further oxidation to form high-valent intermediates Q or X. Here, this study defines the structure of the P′ intermediate in the N-oxygenases CmlI (and AurF based on previous data) using nuclear resonance vibrational spectroscopy (NRVS) in conjugation with density functional theory (DFT) calculations. These results, combined with variable temperature variable field (VTVH) magnetic circular dichroism (MCD) spectroscopy on the 1-electron cryoreduced P′, define the structure of the P′ intermediate as a μ-1,2-hydroxoperoxo biferric site with a second hydroxide bridge. Reaction coordinate calculations demonstrate that single electron transfer (SET) is facilitated by protonation of the peroxo, activating its reductive cleavage, and that the additional hydroxide bridge does not impact this reaction. VTVH MCD studies further reveal that the hydroxide bridge is absent in the biferrous site, suggesting that during the O 2 reaction with the biferrous site, a water molecule forms the hydroxide bridge in providing the proton that activates the peroxide in P′ for reactivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

A versatile X-ray phase retarder for lock-in XMCD measurements

X-ray magnetic circular dichroism (XMCD) is a technique commonly used to probe magnetic properties of materials with element and orbital selectivity, which requires the use of circularly polarized (CP) X-rays. It is possible to accomplish XMCD experiments with fixed CP and alternating the magnetic field orientation, but most reliable data are obtained when alternating the magnetization orientation and the polarization between right and left helicities. A versatile strategy has been developed to perform XMCD experiments using a hard X-ray quarter-wave plate, at both polychromatic dispersive and conventional monochromatic optics, in combination with synchronous data acquisition. The switching frequency waveform is fed into a lock-in amplifier to detect and amplify the XMCD signal. The results on a reference sample demonstrate an improvement in data quality and acquisition time. The instrumentation successfully generated 98% of CP X-rays switching the beam helicity at 13 Hz, with the possibility of faster helicity switching once it is installed at the new Brazilian fourth-generation source, SIRIUS.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2023

Aculeaxanthones A–E, new xanthones from the marine-derived fungus Aspergillus aculeatinus WHUF0198

Introduction Dimeric natural products are widespread in plants and microorganisms, which usually have complex structures and exhibit greater bioactivities than their corresponding monomers. In this study, we report five new dimeric tetrahydroxanthones, aculeaxanthones A−E ( 4−8 ), along with the homodimeric tetrahydroxanthone secalonic acid D ( 1 ), chrysoxanthones B and C ( 2 and 3 ), and 4−4’-secalonic acid D ( 9 ), from different fermentation batches of the title fungus. Methods A part of the culture was added to a total of 60 flasks containing 300 ml each of number II fungus liquid medium and culture 4 weeks in a static state at 28˚C. The liquid phase (18 L) and mycelia was separated from the fungal culture by filtering. A crude extract was obtained from the mycelia by ultrasound using acetone. To obtain a dry extract (18 g), the liquid phase combined with the crude extract were further extracted by EtOAc and concentrated in vacuo. The MIC of anaerobic bacteria was examined by a broth microdilution assay. To obtain MICs for aerobic bacteria, the agar dilution streak method recommended in Clinical and Laboratory Standards Institute document (CLSI) M07-A10 was used. Compounds 1−9 was tested against the Bel-7402, A-549 and HCT-116 cell lines according to MTT assay. Results and Discussion The structures of these compounds were elucidated on the base of 1D and 2D NMR and HR-ESIMS data, and the absolute configurations of the new xanthones 4−8 were determined by conformational analysis and time-dependent density functional theory-electronic circular dichroism (TDDFT-ECD) calculations. Compounds 1–9 were tested for cytotoxicity against the Bel-7402, A549, and HCT-116 cancer cell lines. Of the dimeric tetrahydroxanthone derivatives, only compound 6 provided cytotoxicity effect against Bel-7402 cell line (IC50, 1.96 µM). Additionally, antimicrobial activity was evaluated for all dimeric tetrahydroxanthones, including four Gram-positive bacteria including Enterococcus faecium ATCC 19434, Bacillus subtilis 168, Staphylococcus aureus ATCC 25923 and MRSA USA300; four Gram-negative bacteria, including Helicobacter pylori 129, G27, as well as 26,695, and multi drug-resistant strain H. pylori 159, and one Mycobacterium M. smegmatis ATCC 607. However, only compound 1 performed activities against H. pylori G27, H. pylori 26695, H. pylori 129, H. pylori 159, S. aureus USA300, and B. subtilis 168 with MIC values of 4.0, 4.0, 2.0, 2.0, 2.0 and 1.0 μg/mL, respectively.

Wu, Jun↗

NASA NTRS1972

A procedure for predicting internal and external noise fields of blowdown wind tunnels

The noise generated during the operation of large blowdown wind tunnels is considered. Noise calculation procedures are given to predict the test-section overall and spectrum level noise caused by both the tunnel burner and turbulent boundary layer. External tunnel noise levels due to the tunnel burner and circular jet exhaust flow are also calculated along with their respective cut-off frequency and spectrum peaks. The predicted values are compared with measured data, and the ability of the prediction procedure to estimate blowdown-wind-tunnel noise levels is shown.

Hosier, R. N.↗

NASA NTRS1972

Some recent observations and interpretation of the Jupiter decimeter emission

The decimetric emission consists partly of thermal radiation from the planetary disk and partly of nonthermal radiation from a region of larger angular extent and is thought to result from synchrotron emission by relativistic electrons in the magnetic field. Four topics relating to the decimetric emission are discussed. (1) A comparison is made of maps giving detailed brightness contours. One was obtained for epoch 1963.8 and was at a wavelength of 10.4 cm. The second was for epoch 1967.2 at 21.3 cm. (2) Interferometric data at 21.1 cm taken in April 1968 and May 1979 indicate that the emission centroid is fixed in Jupiter and rotates with it. (3) Circular polarization observations are described and are used to obtain a surface magnetic field strength at the equator between 3.2 and 15.2 gauss. (4) An upper limit on the Faraday rotation is used to set an upper limit on the density of thermal electrons surrounding Jupiter, and uncertainties in the results are discussed.

Berge, G. L.↗

NASA NTRS1972

Flap noise measurements for STOL configurations using external upper surface blowing

Screening tests of upper surface blowing on externally blown flaps configurations were conducted. Noise and turning effectiveness data were obtained with small-scale, engine-over-the-wing models. One large model was tested to determine scale effects. Nozzle types included circular, slot, D-shaped, and multilobed. Tests were made with and without flow attachment devices. For STOL applications the particular multilobed mixer and the D-shaped nozzles tested were found to offer little or no noise advantage over the round convergent nozzle. High aspect ratio slot nozzles provided the quietest configurations. In general, upper surface blowing was quieter than lower surface blowing for equivalent EBF models.

Dorsch, R. G.↗

NASA NTRS1973

Observations of collisionless drift waves.

Velocity distribution functions of both the electron and the proton component of the magnetospheric plasma are measured in 62 logarithmically spaced steps from 50 eV to 50 keV by an instrument carried upon the ATS-5 spacecraft in circular synchronous orbit (6.6 earth radii). Oscillations which appear to be collisionless drift waves having periods of several minutes or longer are found in this data. Linearized wave theory can be used to predict the theoretical perturbation distribution function in terms of the perturbing fields and the equilibrium distribution function. The functional dependence of the theoretical perturbation distribution function upon particle energy can then be compared with that of the measured perturbation.

Laquey, R. E.↗

NASA NTRS1975

Experimental measurements of skin friction on upper surface blown wing

An experimental investigation was conducted to obtain skin-friction measurements on a wing with a circular jet exhausting above it. A Preston tube was used to determine the local shear stress at a point on the wing's upper surface. Data were obtained for four nozzle pressures and four vertical displacements of the jet above the wing. The results indicated that the highest skin-friction values occurred with the jet closest to the wing and with the highest nozzle pressure. These data trends were validated by calculations which combined two-dimensional, turbulent boundary-layer theory with axisymmetric co-flowing jet theory.

Miner, D. D.↗

NASA NTRS1976

Direct measurements of neutral wave characteristics in the thermosphere

The elliptical and circular phases of the Atmosphere Explorer-C satellite have provided the basis for a study of the neutral wave characteristics in the thermosphere using data collected by the open source mass spectrometer used to measure both reactive (O,N) and nonreactive (O2, N2, He, Ar) constituents. The phase relationships between the constituents are discussed and the results of a wave occurrence and amplitude survey covering 338 despun orbits in which the local time and latitude characteristics of the waves are presented are discussed. Conclusions based on this survey are tested in a study of waves measured at high latitudes during a geomagnetic storm.

Potter, W. E.↗

NASA NTRS1981

Wide area, coarse resolution imaging with satellite-borne synthetic aperture radars in low-earth and geosynchronous orbits

The LEOSAR (low-earth-orbit synthetic aperture radar) can map around the earth, while the GEOSAR (geosynchronous synthetic aperture radar) can map a large global area bounded in both longitudinal and latitudinal ranges. This paper presents the mapping capabilities and power requirements of both LEOSAR and GEOSAR. For a low-earth-orbit SAR, images of swath widths of the order of 700 km are possible with 100-m resolution and 300 watts of average transmitter power at 9375 MHz. From a SAR in a 50-deg inclined geosynchronous circular orbit, the contiguous United States can be imaged in about 6.4 hours with 100-m resolution, 345 watts of average transmitter power, and a data rate of 6 megabits/sec at 2450 MHz.

Tomiyasu, K.↗

NASA NTRS1984

Sampling strategies and four-dimensional assimilation of altimetric data for ocean monitoring and prediction

Numerical experiments using simulated altimeter data were conducted in order to examine the assimilation of altimeter-derived sea surface heights into numerical ocean circulation models. A reduced-gravity, primitive equation circulation model of the Gulf of Mexico was utilized; the Gulf of Mexico was chosen because of its amenability to modeling and the ability of low vertical-mode models to reproduce the observed dynamical features of the Gulf circulation. The simulated data were obtained by flying an imaginary altimeter over the model ocean and sampling the model sea surface just as real altimeter would observe the true ocean. The data were used to initialize the numerical model and the subsequent forecast was compared to the true numerical solution. Results indicate that for a stationary, circular eddy, approximately three to four tracks (either ascending or descending) across the eddy are sufficient to ensure adequate spatial resolution.

Kindle, J. C.↗

NASA NTRS1985

Comparisons of simultaneous vector magnetograms

Simultaneous vector magnetograms were obtained with the different magnetographs of the Okayama Astrophysical Observatory and the Sayan Mountain Observatory in October 1983. The data obtained show a good correspondence in general. The comparison makes clear something on the measuring accuracy of each magnetograph. Good correspondence is shown in circular and linear polarizations, and, in and near sunspots, of the velocity field. The azimuth of the magnetic fields show good agreement.

Makita, M.↗

NASA NTRS1989

Closed loop navigation and guidance for gravity probe B orbit insertion

This paper addresses the problem of guiding the Gravity Probe B (GP-B) spacecraft from its location after initial insertion to a very precise low earth orbit. Specifically, the satellite orbit is required to be circular to within 0.001 eccentricity, polar to within 0.001 deg inclination, and aligned with the direction of the star Rigel to within 0.001 deg. Navigation data supplied by an on-board GPS receiver is used as feedback to a control algorithm designed to minimize the time to achieve the desired orbit. Translational control is provided by the proportional helium thrusters, which are used for drag-free and attitude control during the remainder of the science mission. Simulations of the guidance system are presented which give an indication of performance characteristics for several types of orbit injection errors. This research is the first reported effort to use GPS as a sensor for a closed loop space guidance system.

Axelrad, P.↗