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NASA NTRS1983

Increase and seasonal cycles of nitrous oxide in the earth's atmosphere

It is determined that nitrous oxide (N2O) is increasing at about 0.9 ppb/yr in the northern hemisphere and at about 0.7 ppb/yr in the southern hemisphere, based on about 9000 ground-level measurements at Cape Meares, Oregon (45 deg N), and Cape Grim, Tasmania (42 deg S), spanning a three-year period. It is also shown that the N2O concentrations vary with season in the northern hemisphere, where the concentrations are 0.8 ppbv higher during April, May, and June compared to the rest of the year, and in the southern hemisphere where the concentrations are about 0.5 ppbv lower during March, April, and May compared to the rest of the year. An explanation of this increase as a sizeable anthropogenically-controlled land-based source is presented, based on an examination of the existing estimates of natural and anthropogenic sources of N2O. Mass-balance calculations are also presented which suggest that a natural land-based source, peaking in spring, would explain the main features of the observed seasonal cycle. A growth model is employed to extrapolate the observed increase of N2O into the future and the results are compared with exponential extrapolations.

Khalil, M. A. K.↗

NASA NTRS1983

Variation in light intensity with height and time from subsequent lightning return strokes

Photographic measurements of relative light intensity as a function of height and time have been conducted for seven return strokes in two lightning flashes at 7.8 and 8.7 km ranges, using film which possesses an approximately constant spectral response in the 300-670 nm range. The amplitude of the initial light peak is noted to decrease exponentially with height, with a decay constant of 0.6-0.8 km. The logarithm of the peak light intensity near the ground is found to be approximately proportional to the initial peak electric field intensity, implying that the current decrease with height may be much slower than the light decrease. Absolute light intensity is presently estimated through the integration of the photographic signals from individual channel segments, in order to simulate the calibrated, all-sky photoelectric data of Guo and Krider (1982).

Jordan, D. M.↗

NASA NTRS1984

Adaptive optics

An estimation of the costs and potential resolution and sensitivity benefits of adaptive optics systems is presented. The effects of atmospheric disturbances on the peak-to-peak wavefront errors are assessed. Definitions are included of the maximum permissible controlled patch of entrance pupil of the system, the permissible response time, the permissible field radius, and the required magnitude and frequency of a reference star. It is pointed out that adaptive optics system for visible of near-visible wavelengths is likely to be very expensive, whereas operation at 2-3 microns under best seeing conditions is expected to be useful and have reasonable cost.

Woolf, N. J.↗

NASA NTRS1986

Factors influencing elastic stresses in double cantilever beam specimens

An elastic stress analysis was conducted for a double cantilever beam (DCB) specimen using finite-element methods. The purpose of this study was to identify the important parameters that influence stresses ahead of the delamination front. The study focused on an aluminum DCB specimen, typical of adhesively-bonded joints, and on a graphite/epoxy specimen representing a cocured composite. Opening mode sigma sub y stresses ahead of the crack tip were calculated and compared with those for a monolithic reference specimen. Beyond the singularity-dominated region very near the crack tip, the sigma sub y distribution was elevated compared to the monolithic case. Both the adhesive thickness and the adherend transverse (thickness-direction) stiffness were found to influence the elevation of sigma sub y. In contrast, adherend thickness and longitudinal stiffness has very little effect on this stress distribution. Estimates for adhesive yielding beyond the aluminum DCB crack tip showed that both the area and height of the plastic zone increased to a peak value for increasing adhesive thicknesses. Results from this study would provide insight for comparing data from different DCB specimens and for designing new DCB specimens.

Crews, J. H., Jr.↗

NASA NTRS1987

Infrared spectroscopy of IRC + 10420

High resolution 1.6, 3.3 and 4.6 micron spectra were obtained on the F8 supergiant star IRC + 10420 on June 9-11, 1984, using the 4 m Mayall telescope and Fourier Transform Spectrometer at Kitt Peak. IRC + 10420 is distinguished by its hydrogen maser, unusual for stars of this type. The measured column densities of CO led to an estimated isotopic carbon ratio of 7-11, supporting a model of the object as a highly evolved star. The redshift is interpreted as due to scattering by outward-moving circumstellar dust grains. The IR spectrum of IRC + 10420 suggests that the object is a post-asymptotic branch star still surrounded by the thick dust shell it produced while it was much cooler.

Fix, John D.↗

NASA NTRS1988

Factors influencing elastic stresses in double cantilever beam specimens

Crews, J. H., Jr.↗

NASA NTRS1990

The molecular spiral arms of NGC 6946

From CO-12(J=1 to 0) observations at 45 seconds resolution Tacconi and Young (1989) have found evidence for enhancements in both the CO emissivity and the massive star formation efficiency (MSFE) on optical spiral arms of the bright spiral galaxy NGC 6946. In the optically luminous and well-defined spiral arm in the NE quadrant, there are enhancements in both the H2 surface density and MSFE relative to the interarm regions. In contrast, a poorly defined arm in the SW shows no arm-interarm contrast in the MSFE. To further investigate the molecular gas content of these two spiral arms, researchers have made CO-12 J=2 to 1 and 3 to 2 observations with the James Clerk Maxwell Telescope. In the J=2 to 1 line, they made observations of the NE and SW spiral arm and interarm regions in 4 x 9 10 seconds spaced grids (36 points per grid). Because of decreased sensitivity in the J=3 to 2 line, they were limited to mapping the two arm regions in 2 x 3 10 seconds spaced grids (6 points per grid). The centers of each of the grids lie 2.4 minutes to the NE and 2.3 minutes to the SW of the nucleus of NGC 6946. With the CO J=2 to 1 data researchers are able to fully resolve the two observed spiral arms in NGC 6946. In both cases the CO emission is largely confined to the optical spiral arm regions with the peak observed T asterisk sub A being up to 4 times higher on the spiral arms than in the interarm regions. Researchers are currently estimating massive star formation efficiencies on and off the spiral arms through direct comparison of the CO maps with an H alpha image. They are also comparing the CO J=2 to 1 data with an HI map made at similar resolution. Thus, they will be able to determine structure in all components of the IS on scales of less than 20 inches.

Tacconi, L. J.↗

NASA NTRS1993

Extreme Ultraviolet Explorer deep survey observations of a large flare on AU Microscopii

We have made the first extended observation of a stellar flare in the EUV with 100 s time resolution. The flare was detected on AU Mic by the Extreme Ultraviolet Explorer satellite at 12:38 UT on 1992 July 15 during a 4 d observation from 1992 July 14 to 18. This was a large flare detected in the Lexan/boron (65-190 A) band with an observed peak count rate of 7.0 +/- 0.5 counts/s, corresponding to a peak luminosity of 10 exp 30 erg/s in the Lexan/boron bandpass. This is significantly above the measured quiescent level of 0.4 +/- 0.2 counts/s. The flare consisted of a sharp peak lasting about 2 hr, followed by a decaying tail that lasted more than a day. The total EUV energy of the event is estimated to be 3 x 10 exp 34 ergs. A second, smaller flare was also observed and is described. We conclude that the large emission measures on order of 6 x 10 exp 53/cu cm are due to large volumes with characteristic length scales of order the stellar radius. We compare these EUV observations with stellar flare observations in other bandpasses and estimate the likelihood of seeing similar flares in future observations.

Cully, Scott L.↗

NASA NTRS1994

Latitudinal variability of large-scale coronal temperature and its association with the density and the global magnetic field

In this paper we utilize the latitiude distribution of the coronal temperature during the period 1984-1992 that was derived in a paper by Guhathakurta et al, 1993, utilizing ground-based intensity observations of the green (5303 A Fe XIV) and red (6374 A Fe X) coronal forbidden lines from the National Solar Observatory at Sacramento Peak, and establish it association with the global magnetic field and the density distributions in the corona. A determination of plasma temperature, T, was estimated from the intensity ratio Fe X/Fe XIV (where T is inversely proportional to the ratio), since both emission lines come from ionized states of Fe, and the ratio is only weakly dependent on density. We observe that there is a large-scale organization of the inferred coronal temperature distribution that is associated with the large-scale, weak magnetic field structures and bright coronal features; this organization tends to persist through most of the magnetic activity cycle. These high-temperature structures exhibit time-space characteristics which are similar to those of the polar crown filaments. This distribution differs in spatial and temporal characterization from the traditional picture of sunspot and active region evolution over the range of the sunspot cycle, which are manifestations of the small-scale, strong magnetic field regions.

Guhathakurta, M.↗

NASA NTRS1999

Electrical Properties and Power Considerations of a Piezoelectric Actuator

This paper assesses the electrical characteristics of piezoelectric wafers for use in aeronautical applications such as active noise control in aircraft. Determination of capacitive behavior and power consumption is necessary to optimize the system configuration and to design efficient driving electronics. Empirical relations are developed from experimental data to predict the capacitance and loss tangent of a PZT5A ceramic as nonlinear functions of both applied peak voltage and driving frequency. Power consumed by the PZT is the rate of energy required to excite the piezoelectric system along with power dissipated due to dielectric loss and mechanical and structural damping. Overall power consumption is thus quantified as a function of peak applied voltage and driving frequency. It was demonstrated that by incorporating the variation of capacitance and power loss with voltage and frequency, satisfactory estimates of power requirements can be obtained. These relations allow general guidelines in selection and application of piezoelectric actuators and driving electronics for active control applications.

Jordan, T.↗

NASA NTRS2005

Energetics of RHESSI X-Class Flares

The thermal and nonthermal energies of several X-class flares seen with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) will be presented. The same techniques described by Emslie et al. (JGR, 109, A10104, 2004) are used to take the RHESSI imaging spectroscopic observations and compute the energies in the thermal plasma and in the nonthermal electrons as a function of time throughout the flares. Radiative and conductive cooling rates are estimated and total thermal and nonthermal energies are computed for each flare. Typically, the energy in nonthermal electrons integrated up to the time of peak soft X-ray emission is equal to or exceeds the energy in the thermal plasma at that time. This suggests that energy must have been converted into a form not visible with RHESSI and that the total energy released by the flares may be significantly greater than the sum of energies calculated from the RHESSI observations alone. This conclusion is supported by the high radiative energy seen with SORCE during the impulsive phase of the 28 October 2003 flare. The peak increase in total solar irradiance of 270 mW per square meters measured with SORCE was over two orders of magnitude higher than the peak soft X-ray flux seen with GOES or RHESSI. The implications of this new observation as compared to the energetics derived from the X-ray observations of that flare will be discussed along with the energetics analysis of most of the other X- class flares in October/November 2003.

Dennis, Brian R.↗

NASA NTRS2013

Reefing Line Tension in CPAS Main Parachute Clusters

Reefing lines are an essential feature to manage inflation loads. During each Engineering Development Unit (EDU) test of the Capsule Parachute Assembly System (CPAS), a chase aircraft is staged to be level with the cluster of Main ringsail parachutes during the initial inflation and reefed stages. This allows for capturing high-quality still photographs of the reefed skirt, suspension line, and canopy geometry. The over-inflation angles are synchronized with measured loads data in order to compute the tension force in the reefing line. The traditional reefing tension equation assumes radial symmetry, but cluster effects cause the reefed skirt of each parachute to elongate to a more elliptical shape. This effect was considered in evaluating multiple parachutes to estimate the semi-major and semi-minor axes. Three flight tests are assessed, including one with a skipped first stage, which had peak reefing line tension over three times higher than the nominal parachute disreef sequence.

Ray, Eric S.↗

NASA NTRS2012

SN 2010ay Is a Luminous and Broad-Lined Type Ic Supernova Within a Low-Metallicity Host Galaxy

We report on our serendipitous pre-discovery detection and follow-up observations of the broad-lined Type Ic supernova (SN Ic) 2010ay at z = 0.067 imaged by the Pan-STARRS1 3pi survey just approximately 4 days after explosion. The supernova (SN) had a peak luminosity, MR approx. -20.2 mag, significantly more luminous than known GRB-SNe and one of the most luminous SNe Ib/c ever discovered. The absorption velocity of SN 2010ay is v Si (is) approx. 19×10(exp 3) km s−1 at approximately 40 days after explosion, 2-5 times higher than other broad-lined SNe and similar to the GRB-SN 2010bh at comparable epochs. Moreover, the velocity declines approximately 2 times slower than other SNe Ic-BL and GRB-SNe. Assuming that the optical emission is powered by radioactive decay, the peak magnitude implies the synthesis of an unusually large mass of 56Ni, MNi = 0.9 solar mass. Applying scaling relations to the light curve, we estimate a total ejecta mass, Mej (is) approx. 4.7 solar mass, and total kinetic energy, EK (is) approx. 11 × 10(exp 51) erg. The ratio of MNi to Mej is approximately 2 times as large for SN 2010ay as typical GRB-SNe and may suggest an additional energy reservoir. The metallicity (log(O/H)PP04 + 12 = 8.19) of the explosion site within the host galaxy places SN 2010ay in the low-metallicity regime populated by GRB-SNe, and (is) approximately 0.5(0.2) dex lower than that typically measured for the host environments of normal (broad-lined) SNe Ic. We constrain any gamma-ray emission with E(gamma) (is) approximately less than 6 × 10(exp 48) erg (25-150 keV), and our deep radio follow-up observations with the Expanded Very Large Array rule out relativistic ejecta with energy E (is) approximately greater than 10(exp 48) erg. We therefore rule out the association of a relativistic outflow like those that accompanied SN 1998bw and traditional long-duration gamma-ray bursts (GRBs), but we place less-stringent constraints on a weak afterglow like that seen from XRF 060218. If this SN did not harbor a GRB, these observations challenge the importance of progenitor metallicity for the production of relativistic ejecta and suggest that other parameters also play a key role.

supernovae: individual (2010ay)↗

DOE OSTI2021

Detector Calibration to Quantify Random Summing in HPGe Spectroscopy

While calibrating a High Purity Germanium (HPGe) Radiation Detector for Xenon-133 (133Xe) the process of random summing occurs which leads to excess counts in the 160.6keV peak from random summing of the 81keV photons at the 162keV energy. Multiple samples of 133Xe with varying levels of radioactivity were assayed to determine a relationship between the occurrence of random summing and the net area of the 160.6keV peak. When the calculated efficiencies in the 160.6keV peak were compared to the theoretical efficiency obtained from a multi-energy calibration at 160.6keV, the amount of random summing could be estimated as excess observed efficiency and correlated to the sample activity. While a trend is apparent in the data, the mechanisms that contribute to the trend are still being studied so the data can be accurately correlated.

07 ISOTOPE AND RADIATION SOURCES↗

NASA NTRS1986

Spectrum and anisotropy of the cosmic infrared background

If the luminosity per mass of the universe at redshifts z = 5-1000 were at least comparable to its present luminosity, then a conspicuous cosmological infrared radiation background would be produced. A number of situations where this could arise are surveyed, and the intensity of the background is evaluated for specific types of sources (protogalaxies, pregalactic stars, quasars, black holes, and decaying relict particles) in several candidate scenarios, which are also discussed in terms of metal enrichment, dark matter, and formation of large-scale structure. The spectrum of the background radiation is estimated, both with and without dust obscuration. General features of cosmological radiative transfer with dust are discussed. It is argued that dust is expected to degrade the background to the far-infrared, 100-1000 microns, where the wavelength of the spectral peak can be predicted from the total present-day background flux and depends only weakly on properties of the dust or the redshift of emission. The statistical properties of the anisotropy expected in the radiation and its relationship to the distribution of dust at the time the dust is formed or the radiation is produced are estimated. Intensity fluctuations at the few percent level on arc minute scales are typical in current galaxy-formation scenarios.

Bond, J. R.↗

NASA NTRS1999

Satellite-Based Global Precipitation Data Sets at Monthly and Finer Time Scales

A new 20-year, monthly, globally complete precipitation analysis has been completed as part of the World Climate Research Program's (WCRP/GEWEX) Global Precipitation Climatology Project (GPCP). The global, monthly, 2.5 deg x 2.5 deg latitude-longitude product utilizes precipitation estimates from low-orbit microwave sensors (SSM/1) and geosynchronous IR sensors and raingauge information over land. The low-orbit microwave estimates are used to adjust or correct the geosynchronous IR estimates, thereby maximizing the utility of the more physically-based microwave estimates and the finer time sampling of the geosynchronous data. The 20-year climatology of the Version 2 GPCP analysis indicates the expected features of a very strong Pacific Ocean ITCZ and SPCZ with maximum 20-year means approaching 10 mm/day. A similar strength maximum over land is evident over Borneo. Weaker maxima in the tropics occur in the Atlantic ITCZ and over South America and Africa. In mid-latitudes of the Northern Hemisphere the Western Pacific and Western Atlantic maxima have values of approximately 7 mm/day, while in the Southern Hemisphere the mid-latitude maxima are located southeast of Africa, in mid-Pacific as an extension of the SPCZ and southeast of South America. In terms of global totals the GPCP analysis shows 2.7 mm/day (3.0 mm/day over ocean; 2.1 mm/day over land), similar to the Jaeger climatology, but not other climatologies. Zonal averages peak at 6 mm/day at 7 deg N with mid-latitude peaks of about 3 mm/day at 40-45 deg latitude. Poleward of 45 deg the GPCP analysis shows larger zonally-averaged values than most previous satellite-based estimates, although the values are similar to the Jaeger climatology.

Adler, Robert↗

NASA NTRS1999

Noninvasive assessment of left atrial maximum dP/dt by a combination of transmitral and pulmonary venous flow

OBJECTIVES: The study assessed whether hemodynamic parameters of left atrial (LA) systolic function could be estimated noninvasively using Doppler echocardiography. BACKGROUND: Left atrial systolic function is an important aspect of cardiac function. Doppler echocardiography can measure changes in LA volume, but has not been shown to relate to hemodynamic parameters such as the maximal value of the first derivative of the pressure (LA dP/dt(max)). METHODS: Eighteen patients in sinus rhythm were studied immediately before and after open heart surgery using simultaneous LA pressure measurements and intraoperative transesophageal echocardiography. Left atrial pressure was measured with a micromanometer catheter, and LA dP/dt(max) during atrial contraction was obtained. Transmitral and pulmonary venous flow were recorded by pulsed Doppler echocardiography. Peak velocity, and mean acceleration and deceleration, and the time-velocity integral of each flow during atrial contraction was measured. The initial eight patients served as the study group to derive a multilinear regression equation to estimate LA dP/dt(max) from Doppler parameters, and the latter 10 patients served as the test group to validate the equation. A previously validated numeric model was used to confirm these results. RESULTS: In the study group, LA dP/dt(max) showed a linear relation with LA pressure before atrial contraction (r = 0.80, p < 0.005), confirming the presence of the Frank-Starling mechanism in the LA. Among transmitral flow parameters, mean acceleration showed the strongest correlation with LA dP/dt(max) (r = 0.78, p < 0.001). Among pulmonary venous flow parameters, no single parameter was sufficient to estimate LA dP/dt(max) with an r2 > 0.30. By stepwise and multiple linear regression analysis, LA dP/dt(max) was best described as follows: LA dP/dt(max) = 0.1 M-AC +/- 1.8 P-V - 4.1; r = 0.88, p < 0.0001, where M-AC is the mean acceleration of transmitral flow and P-V is the peak velocity of pulmonary venous flow during atrial contraction. This equation was tested in the latter 10 patients of the test group. Predicted and measured LA dP/dt(max) correlated well (r = 0.90, p < 0.0001). Numerical simulation verified that this relationship held across a wide range of atrial elastance, ventricular relaxation and systolic function, with LA dP/dt(max) predicted by the above equation with r = 0.94. CONCLUSIONS: A combination of transmitral and pulmonary venous flow parameters can provide a hemodynamic assessment of LA systolic function.

NASA Discipline Cardiopulmonary↗

DOE OSTI2024

Optimal hybrid power plants for electric vehicle charging demand

Transmission constraints, increasing motivations to decarbonize, and concerns over peak electric vehicle (EV) load impacts on local grids have driven electric customers to consider behind-the-meter, hybrid power plant generation and storage at the distributed-grid level for EV charging. In this study, we develop capabilities to optimize hybrid power plant component capacities for EV charging. We then demonstrate these capabilities in a case study for Boulder, Colorado, using public EV charging data as well as wind and solar resource data. Our results show system designs that balance the cost of energy with load-meeting and peak shaving performance. Within the case study, systems designed for wind, solar photovoltaic (PV), and storage resulted in lower cost of energy than those optimized for PV and storage only. This indicates that in areas where wind resource exists, hybrid power plants that include wind, PV, and battery assets can better meet EV charging loads (including peak loads that are prone to overloading local grids) than PV and battery assets alone. Future work to address limitations in this paper include extending cost modeling to include performance losses (e.g., based on operations or weather) and charging station costs to estimate levelized cost of charging, and quantifying uncertainty and error in our aggregation methods for estimating EV charging loads at the hourly timescale.

14 SOLAR ENERGY↗