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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Published data on a select group of SiO maser sources have been analyzed for velocity variations as a function of phase. No apparent correlation was found to a level of about 2 km/s. This places constraints on the location of the maser molecules. Such a correlation should be present at some level. The implications for future high resolution infrared measurements are discussed.
In order to resolve the discrepancy noted in values currently used for the first dissociation constant of SO2 in water, the pertinent literature was critically examined and a value of 0.0132 M at 25 C was recommended. An expression correlating this value as a function of temperature for zero-50 C has been developed. Attention is also given to the literature for the Henry's law constant, and a value of 1.242 M/atm at 25 C is recommended. Ionic activity corrections and speciation in more concentrated solutions are discussed, and recommendations are made for estimating the activity coefficients of the various ionic species in solutions of moderate ionic strength.
Stereo viewing is a valuable tool in photointerpretation and is used for the quantitative reconstruction of the three dimensional shape of a topographical surface. Stereo viewing refers to a visual perception of space by presenting an overlapping image pair to an observer so that a three dimensional model is formed in the brain. Some of the observer's function is performed by machine correlation of the overlapping images - so called automated stereo correlation. The direct perception of space with two eyes is often called natural binocular vision; techniques of generating three dimensional models of the surface from two sets of monocular image measurements is the topic of stereology.
The performance of a 12 V, 40 ampere-hour bipolar battery during various charge current, discharge current, temperature, and pressure operating conditions is investigated. The cell voltages, temperatures, ampere-hours, and watt-hours derived from the charge/discharge cycle tests are studied. Consideration is given to battery voltage and discharge capacity as a function of discharge current, the correlation between energy delivered on a discharge and battery temperature, battery voltage response to pulse discharges, and the voltage-temperature relationship. The data reveal that the bipolar Ni-H battery is applicable to high power systems.
A statistical model of water vapor fluctuations is used to describe the effect of the dynamic wet troposphere on radio interferometric measurements. It is assumed that the spatial structure of refractivity is approximated by Kolmogorov turbulence theory, and that the temporal fluctuations are caused by spatial patterns moved over a site by the wind, and these assumptions are examined for the VLBI delay and delay rate observables. The results suggest that the delay rate measurement error is usually dominated by water vapor fluctuations, and water vapor induced VLBI parameter errors and correlations are determined as a function of the delay observable errors. A method is proposed for including the water vapor fluctuations in the parameter estimation method to obtain improved parameter estimates and parameter covariances.
The inner region of M42 has been mapped in the O III N1 forbidden line at an unprecedented combination of velocity and spatial resolution and photometric accuracy. Three separate velocity systems along the line of sight are identified. Differential mass flow is present in two of these systems. All three systems show random fluctuations in velocity well above their measurement errors. The point-by-point velocities are used to determine the diagnostic statistical parameter, the structure function. The random motions show correlation with spatial separation, as expected for turbulence; but comparison with the predictions of classical theory for nebular turbulence shows poor agreement. If Kolmogorov (1941, 1942) theory applies, then the energy must be input at many scales.
The distribution of lamins (described by Gerace, 1978, as major proteins of nuclear envelope) during gametogenesis, fertilization, and early development was investigated in germ cells of a mouse (Mus musculus), an echinoderm (Lytechinus variegatus), and the surf clam (Spisula solidissima) was investigated in order to determine whether the differences detected could be correlated with differences in the function of cells in these stages of the germ cells. In order to monitor the behavior of lamins, the gametes and embryos were labeled with antibodies to lamins A, C, and B extracted from autoimmune sera of patients with scleroderma and Lupus erythematosus. Results indicated that lamin B could be identified in nuclear envelopes on only those nuclei where chromatin is attached and where RNA synthesis takes place.
A new apparatus was developed to compress the anterior compartment selectively and reproducibly in humans. Thirty-five normal volunteers were studied to determine short-term thresholds of local tissue pressure that produce significant neuromuscular dysfunction. Local tissue fluid pressure adjacent to the deep peroneal nerve was elevated by the compression apparatus and continuously monitored for 2-3 h by the slit catheter technique. Elevation of tissue fluid pressure to within 35-40 mm Hg of diastolic blood pressure (approx. 40 mm Hg of in situ pressure in our subjects) elicited a consistent progression of neuromuscular deterioration including, in order, (a) gradual loss of sensation, as assessed by Semmes-Weinstein monofilaments, (b) subjective complaints, (c) reduced nerve conduction velocity, (d) decreased action potential amplitude of the extensor digitorum brevis muscle, and (e) motor weakness of muscles within the anterior compartment. Generally, higher intracompartment at pressures caused more rapid deterioration of neuromuscular function. In two subjects, when in situ compression levels were 0 and 30 mm Hg, normal neuromuscular function was maintained for 3 h. Threshold pressures for significant dysfunction were not always the same for each functional parameter studied, and the magnitudes of each functional deficit did not always correlate with compression level. This variable tolerance to elevated pressure emphasizes the need to monitor clinical signs and symptoms carefully in the diagnosis of compartment syndromes. The nature of the present studies was short term; longer term compression of myoneural tissues may result in dysfunction at lower pressure thresholds.
This grant seeks to analyze the Heliospheric Missions data to test current theories on the angular dependence (with respect to mean magnetic field direction) of magnetohydrodynamic (MHD) turbulence in the solar wind. Solar wind turbulence may be composed of two or more dynamically independent components. Such components include magnetic pressure-balanced structures, velocity shears, quasi-2D turbulence, and slab (Alfven) waves. We use a method, developed during the first two years of this grant, for extracting the individual reduced spectra of up to three separate turbulence components from a single spacecraft time series. The method has been used on ISEE-3 data, Pioneer Venus Orbiter, Ulysses, and Voyager data samples. The correlation of fluctuations as a function of angle between flow direction and magnetic-field direction is the focus of study during the third year.
The problem of ply lifting in composite materials is a significant issue for various aerospace and military applications. A fundamental element in the prevention or mitigation of ply lift is determination of the timing of the ply lifting event during exposure of the composite material to flight conditions. The Marshall Space Flight Center s Nondestructive Evaluation Team developed a real-time radiographic technique for the detection of ply lift in carbon phenolic ablative materials in situ during live firings of subscale test motors in support of NASA s Reusable Solid Rocket Motor program, using amorphous silicon detector panels. The radiographic method has successfully detected ply lifting in seven consecutive carbon phenolic converging cones attached to solid fuel torches, providing the time of ply lift initiation in each test. Post-processing of the radiographic images improved the accuracy of timing measurements and allowed measurement of the ply lifting height as a function of time. Radiographic data correlated well with independent pressure and temperature measurements that indicate the onset of ply lift in the nozzle material.
The control inceptor used in a vehicle simulation is an important part of adequately representing the dynamics of the vehicle. The inceptor characteristics are typically based on a second order spring mass damper system with damping, force gradient, breakout force, and natural frequency parameters. Changing these parameters can have a great effect on pilot control of the vehicle. A quasi transfer of training experiment was performed employing a high fidelity and a low fidelity control inceptor. A disturbance compensatory task was employed which involved a simple horizon line disturbed in roll by a sum of sinusoids presented in an out-the-window display. Vehicle dynamics were modeled as 1/s and 1/s2. The task was to maintain level flight. Twenty subjects were divided between the high and the low fidelity training groups. Each group was trained to a performance asymptote, and then transferred to the high fidelity simulation. RMS tracking error, a PSD analysis, and a workload analysis were performed to quantify the transfer of training effect. Quantitative results of the experiments show that there is no significant difference between the high and low fidelity training groups for 1/s plant dynamics. For 1/s2 plant dynamics there is a greater difference in tracking performance and PSD; and the subjects are less correlated with the input disturbance function
The precise nature of the heating mechanism in coronal loops is still a matter of enormous research. We present the results from a 1D hydrodynamic loop simulation of a coronal loop which was run using different parameters such as loops length (50, 200 and 500 Mm), maximum temperature reached (3MK and 10 MK0, and abundances. For each scenario the model outputs were used to calculate the corresponding lightcurves as seen by XRT/Be-thin and various EUV AIA channels. The lag time between the peak of these lightcurves was computed and tested using cross-correlation and plotted as a function of loop length.
The precise nature of the heating mechanism (location, duration) in coronal loops is still a matter of enormous research. We present results from a one-dimensional (1D) hydrodynamic loop simulation of a coronal loop which was run using different parameters such as loops length (50, 200 and 500 light-seconds), maximum temperature reached (3 million degrees Kelvin and 10 million degrees Kelvin), and abundances. For each scenario the model outputs were used to calculate the corresponding lightcurves as seen by X-ray telescope/Be-thin filter and various Extreme Ultra Violet Atmospheric Imaging Assembly channels. The lag time between the peak of these lightcurves was computed using cross-correlation and plotted as a function of loop length. Additional results were computed using the zero-dimensional Enthalpy-Based Thermal Evolution of Loops (EBTEL) code in order to test the compatibility of the two codes and to investigate additional loop lengths. Initial results indicate that the long (greater than 5000 seconds) lags observed in the approximately 100 light-seconds loops of active regions can only be reproduced using photospheric abundances and much longer loop lengths. This result suggests that the observed time lags cannot be completely explained by impulsive heating.
The precise nature of the heating mechanism (location, duration) in coronal loops is still a matter of enormous research. We present results from a 1D hydrodynamic loop simulation of a coronal loop which was run using different parameters such as loops length (50, 200, and 500 Mm), maximum temperature reached (3MK and 10MK), and abundances. For each scenario the model outputs were used to calculate the corresponding lightcurves as seen by XRT/Be-thin and various EUV AIA channels. The lag time between the peak of these lightcurves was computed using cross-correlation and plotted as a function of loop length. Additional results were computed using the 0D EBTEL code in order to test the compatibility of the two codes and to investigate additional loop lengths. Initial results indicate that the long (greater than 5000s) lags observed in the approx. 100Mm loops of active regions can only be reproduced using photospheric abundances and much longer loop lengths.
The NASA improved Ground Collision Avoidance System (iGCAS) team conducted an onsite usability study at Experimental Aircraft Association (EAA) Air Venture in Oshkosh, Wisconsin from July 19 through July 26, 2015. EAA Air Venture had approximately 550,000 attendees from which the sample pool of pilots were selected. The objectives of this study were to assess the overall appropriateness and acceptability of iGCAS as a warning system for General Aviation aircraft, usability of the iGCAS displays and audio cues, test terrain avoidance characteristics, performance, functionality, pilot response time, and correlate terrain avoidance performance and pilot response time data.
Organic and inorganic molecules, neutral and ions have been observed in the interstellar medium. A few anions of organic molecules have also been observed recently. The Cassini spacecraft in the upper atmosphere of Titan has observed anions of large organic molecules. In this project we have studied the physical and spectroscopic properties of C4H3-, C6H3-, and C6H5-. We have optimized the geometrical structures of all low-lying isomers of the anions, calculated rotational, and harmonic vibrational frequencies of the anions mentioned above using the B3LYP density functional along with the augmented correlation consistent polar valence triple zeta (aug-cc-pVTZ) basis set. We have found many low-lying isomers on the potential energy surface of these anions.
Machine learning (ML) is now used in many areas of astrophysics, from detecting exoplanets in Kepler transit signals to removing telescope systematics. Recent work demonstrated the potential of using ML algorithms for atmospheric retrieval by implementing a random forest (RF) to perform retrievals in seconds that are consistent with the traditional, computationally expensive nested-sampling retrieval method. We expand upon their approach by presenting a new ML model, plan-net, based on an ensemble of Bayesian neural networks (BNNs) that yields more accurate inferences than the RF for the same data set of synthetic transmission spectra. We demonstrate that an ensemble provides greater accuracy and more robust uncertainties than a single model. In addition to being the first to use BNNs for atmospheric retrieval, we also introduce a new loss function for BNNs that learns correlations between the model outputs. Importantly, we show that designing ML models to explicitly incorporate domain-specific knowledge both improves performance and provides additional insight by inferring the covariance of the retrieved atmospheric parameters. We apply plan-net to the Hubble Space Telescope Wide Field Camera 3 transmission spectrum for WASP-12b and retrieve an isothermal temperature and water abundance consistent with the literature. We highlight that our method is flexible and can be expanded to higher resolution spectra and a larger number of atmospheric parameters.
The reliability of the small-core Lanthanide effective core potentials (ECP) is tested using MF and MF(3), for M=Eu, Gd, Tb, and Yb and the atomic excitation energies for Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb. In some case the ECP and all-electron (AE) results are in good agreement, while in others there are significant difference. The difference are much larger when the segmented basis set is used in conjunction with the ECP than when the atomic natural orbital (ANO) basis set is used. The study of the atoms suggests that problems for lanthanide containing molecules are associated with poor atomic excitation energies in the ECP treatment and even using the ANO basis set does not completely solve the problem. We note that the problem appears to be more severe for density functional approaches than for traditional correlation methods. We suggest that additional studies and new effective core potentials may be required for the Lanthanide atoms.