Search NASA⌕ Search

SEARCH · Search NASA

Results for “double”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Double-Plate Penetration Equations

This report compares seven double-plate penetration predictor equations for accuracy and effectiveness of a shield design. Three of the seven are the Johnson Space Center original, modified, and new Cour-Palais equations. The other four are the Nysmith, Lundeberg-Stern-Bristow, Burch, and Wilkinson equations. These equations, except the Wilkinson equation, were derived from test results, with the velocities ranging up to 8 km/sec. Spreadsheet software calculated the projectile diameters for various velocities for the different equations. The results were plotted on projectile diameter versus velocity graphs for the expected orbital debris impact velocities ranging from 2 to 15 km/sec. The new Cour-Palais double-plate penetration equation was compared to the modified Cour-Palais single-plate penetration equation. Then the predictions from each of the seven double-plate penetration equations were compared to each other for a chosen shield design. Finally, these results from the equations were compared with test results performed at the NASA Marshall Space Flight Center. Because the different equations predict a wide range of projectile diameters at any given velocity, it is very difficult to choose the "right" prediction equation for shield configurations other than those exactly used in the equations' development. Although developed for various materials, the penetration equations alone cannot be relied upon to accurately predict the effectiveness of a shield without using hypervelocity impact tests to verify the design.

Hayashida, K. B.↗
NASA NTRS2003

Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes

When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms [Bezzerides et al., 1978]. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines [Barakat and Schunk, 1984]. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region [Ergun et al., 2000]. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (1) the rarefaction shocks, (2) the discontinuities in the potential distributions, and (3) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains hot and cold electron populations, the temporal evolution of the potential and the plasma distribution generates evolving multiple double layers with an ,extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature. The other DLs evolve from charge separations arising either from reflection of ions coming from the low-potential side or stemming from plasma instabilities; they support the rest of the potential drop. The instabilities forming these additional double layers involve electron-ion (e-i) Buneman or ion-ion (i-i) two-stream interactions. The electron-electron two-stream interactions on the high-potential side of the RFS generate electron-acoustic waves, which evolve into electron phase-space holes. The ion population originating from the low-potential side and trapped by the RFS is energized by the e-i and i-i instabilities and it eventually precipitates into the high-potential plasma along with an electron beam. Applications of these findings to the auroral plasma physics are discussed.

Singh, Nagendra↗
NASA NTRS1999

Lack of dependence on p53 for DNA double strand break repair of episomal vectors in human lymphoblasts

The p53 tumor suppressor gene has been shown to be involved in a variety of repair processes, and recent findings have suggested that p53 may be involved in DNA double strand break repair in irradiated cells. The role of p53 in DNA double strand break repair, however, has not been fully investigated. In this study, we have constructed a novel Epstein-Barr virus (EBV)-based shuttle vector, designated as pZEBNA, to explore the influence of p53 on DNA strand break repair in human lymphoblasts, since EBV-based vectors do not inactivate the p53 pathway. We have compared plasmid survival of irradiated, restriction enzyme linearized, and calf intestinal alkaline phosphatase (CIP)-treated pZEBNA with a Simian virus 40 (SV40)-based shuttle vector, pZ189, in TK6 (wild-type p53) and WTK1 (mutant p53) lymphoblasts and determined that p53 does not modulate DNA double strand break repair in these cell lines. Copyright 1999 Academic Press.

Non-NASA Center↗
NASA NTRS2006

A non-PRE double-peaked burst with oscillations: burning front propagation and stalling

Non-photospheric-radius-expansion (non-PRE) double-peaked bursts may be explained in terms of spreading (and temporary stalling) of thermonuclear flames from a rotational pole on the neutron star surface, as we argued in a previous study. Here we analyze Rossi X-ray Timing Explorer (RXTE) Proportional Counter Array (PCA) data of such a burst from the low mass X-ray binary (LMXB) system 4U 1636-536, and show that our model (with ignition at high latitudes) can qualitatively explain the observed burst profile, and spectral evolution. Moreover, the evolution of the source radius inferred from the data shows a strong signature of temporary stalling of the burning front, which is an essential ingredient of our model. This implies that an understanding of thermonuclear flame spreading on neutron stars can be achieved by a simultaneous study of the evolution of intensity and spectrum of these bursts. We also report the discovery of millisecond period brightness oscillations from this burst, which is the first such observation from a non-PRE double-peaked burst. Our model can explain the corresponding oscillation amplitude during the first (weaker) peak, and the absence of oscillations during the second peak. We discuss how observations of oscillations during non-PRE double-peaked bursts provide an additional t 001 for understanding thermonuclear flame spreading successfully.

Bhattacharyya, Sudip↗
NASA NTRS1979

Tracking The Double Eagle

Last summer a trio of aeronauts made aviation history. Ben Abruzzo, Maxie Anderson and Larry Newman, all of Albuquerque, New Mexico, piloted their balloon Double Eagle I1 from Presque Isle, Maine to Miserey, France, some 50 miles from Paris. They were the first to negotiate a successful Atlantic crossing in a freeflying balloon after a score of attempts over a span of more than a century. A year earlier, Abruzzo and Anderson had made an unsuccessful try in their predecessor balloon Double Eagle. On that occasion, a NASA-developed satellite beacon helped save their lives. Carried aboard the balloon, the simple, seven-pound beacon continuously transmitted signals to NASA's Nimbus-6 satellite. Nimbus relayed the signals to monitors at Goddard Space Flight Center, enabling Goddard to compute the balloon's position. Position reports were then telephoned regularly to Double Eagle's control center at Bedford, Massachusetts. This monitoring system proved invaluable when the balloon encountered trouble several days after liftoff.

Source record↗
NASA NTRS2007

Analysis and Design of a Double-Divert Spiral Groove Seal

This viewgraph presentation describes the design and analysis of a double spiral groove seal. The contents include: 1) Double Spiral Design Features; 2) Double Spiral Operational Features; 3) Mating Ring/Rotor Assembly; 4) Seal Ring Assembly; 5) Insert Segment Joints; 6) Rotor Assembly Completed Prototype Parts; 7) Seal Assembly Completed Prototype Parts; 8) Finite Element Analysis; 9) Computational Fluid Dynamics (CFD) Analysis; 10) Restrictive Orifice Design; 11) Orifice CFD Model; 12) Orifice Results; 13) Restrictive Orifice; 14) Seal Face Coning; 15) Permanent Magnet Analysis; 16) Magnetic Repulsive Force; 17) Magnetic Repulsive Test Results; 18) Spin Testing; and 19) Testing and Validation.

Zheng, Xiaoqing↗
NASA NTRS1991

Double face sealing device

A double face sealing device for mounting between two surfaces to provide an airtight and fluid-tight seal between a closure member bearing one of the surfaces and a structure or housing bearing the other surface which extends around the opening or hatchway to be closed. The double face sealing device includes a plurality of sections or segments mounted to one of the surfaces, each having a main body portion, a pair of outwardly extending and diverging, cantilever, spring arms, and a pair of inwardly extending and diverging, cantilever, spring arms, an elastomeric cover on the distal, free, ends of the outwardly extending and diverging spring arms, and an elastomeric cover on the distal, free, ends of the inwardly extending and diverging spring arms. The double face sealing device has application or use in all environments requiring a seal, but is particularly useful to seal openings or hatchways between compartments of spacecraft or aircraft.

Weddendorf, Bruce C.↗
NASA NTRS2008

Effects of Doubled CO2 on Tropical Sea-Surface Temperature (SSTs) for Onset of Deep Convection and Maximum SST-GCM Simulations Based Inferences

A primary concern of CO2-induced warming is the associated rise of tropical (10S-10N) seasurface temperatures (SSTs). GISS Model-E was used to produce two sets of simulations-one with the present-day and one with doubled CO2 in the atmosphere. The intrinsic usefulness of model guidance in the tropics was confirmed when the model simulated realistic convective coupling between SSTs and atmospheric soundings and that the simulated-data correlations between SSTs and 300 hPa moiststatic energies were found to be similar to the observed. Model predicted SST limits: (i) one for the onset of deep convection and (ii) one for maximum SST, increased in the doubled C02 case. Changes in cloud heights, cloud frequencies, and cloud mass-fractions showed that convective-cloud changes increased the SSTs, while warmer mixed-layer of the doubled CO2 contained approximately 10% more water vapor; clearly that would be conducive to more intense storms and hurricanes.

Sud, Y. C.↗
NASA NTRS2008

Broadband Microstrip-to-Coplanar Strip Double-Y Balun

A new version of the double-Y balun, transitioning from an unbalanced microstrip to a balanced coplanar strip (CPS) line, has been designed to feed a complementary spiral antenna with an input impedance of 100 Omega. The new double-Y balun transitions from a microstrip line with truncated ground plane to a CPS line. The balun does not employ CPW lines; hence, CPW bridges are not required at the junction. In addition, the balun does not exhibit CPW parasitic resonances, thereby improving passband performance. The new version of the double-Y balun is designed to feed a complementary spiral antenna. Panels on the right illustrate an expanded view of the balun junction. Preliminary voltage standing-wave ratio (VSWR) and insertion loss data are illustrated. Measured data were compared with numerical results computed using Momentum. It is seen that the balun exhibits a VSWR of less than 1.5 from 400 MHz to 8 GHz and a VSWR of less than 1.8 up to 13 GHz. The VSWR can be reduced further by reducing reflections from the balun junction and load resistor. Also, the balun is seen to exhibit an insertion loss of less than 1.5 dB up to 12 GHz. Further work involves characterizing the balun's performance when feeding a complementary spiral antenna.

Venkatesan, Jaikrishna↗
NASA NTRS2010

Novel Micro Strip-to-Waveguide Feed Employing a Double-Y Junction

Previous micro strip -to -waveguide transitions either required a hermetically sealed waveguide configuration, or a balun that needed to be tuned according to the frequency band of interest. In this design, the balun is realized using a double -Y junction to transition from microstrip to coplanar strip feeding a quasi-Yagi dipole array (see figure). The length of the feed (Lf) extending into the waveguide is 15.54 mm. The length of the ground plane below the ULTRALAM substrate is 7.75 mm. The lengths L1 , L2, and L3 are 8.50 mm, 4.38 mm, and 2.14 mm, respectively. These lengths were computed via a preliminary optimization aimed at improving the return loss at the band edges. The waveguide feed was designed to excite the TE10 mode in a WR-90 waveguide, and to operate over the recommended frequencies of 8.2 to 12.4 GHz. The feed employs a Rogers 6010 substrate (dielectric constant Er approx. equals 10.2) bonded with a Rogers ULTRALAM substrate (Er approx. equals 2.5). The ULTRALAM substrate serves to provide mechanical strength for 6010 substrate, and to mitigate loses due to parasitic modes (the ground plane is etched on the bottom of this layer due to the topology of the double -Y balun). The double-Y balun transitioning from an unbalanced microstrip line to a balanced coplanar strip (CPS) line does not provide inherent impedance transformation; hence, Klopfenstein impedance tapers were synthesized to transition from 50 to 77 Ohms in the microstrip section and from 77 to 110 Ohms in the CPS section. At the balun junction, the CPS stub lengths were chosen such that the X/ 8 resonance is pushed outside the bandwidth of operation. Also, the smallest allowable conductor width and gap spacing were chosen to meet acceptable manufacturing tolerances.

Venkatesan, Jaikrishina↗
NASA NTRS2011

Evaluating the Performance of Single and Double Moment Microphysics Schemes During a Synoptic-Scale Snowfall Event

Increases in computing resources have allowed for the utilization of high-resolution weather forecast models capable of resolving cloud microphysical and precipitation processes among varying numbers of hydrometeor categories. Several microphysics schemes are currently available within the Weather Research and Forecasting (WRF) model, ranging from single-moment predictions of precipitation content to double-moment predictions that include a prediction of particle number concentrations. Each scheme incorporates several assumptions related to the size distribution, shape, and fall speed relationships of ice crystals in order to simulate cold-cloud processes and resulting precipitation. Field campaign data offer a means of evaluating the assumptions present within each scheme. The Canadian CloudSat/CALIPSO Validation Project (C3VP) represented collaboration among the CloudSat, CALIPSO, and NASA Global Precipitation Measurement mission communities, to observe cold season precipitation processes relevant to forecast model evaluation and the eventual development of satellite retrievals of cloud properties and precipitation rates. During the C3VP campaign, widespread snowfall occurred on 22 January 2007, sampled by aircraft and surface instrumentation that provided particle size distributions, ice water content, and fall speed estimations along with traditional surface measurements of temperature and precipitation. In this study, four single-moment and two double-moment microphysics schemes were utilized to generate hypothetical WRF forecasts of the event, with C3VP data used in evaluation of their varying assumptions. Schemes that incorporate flexibility in size distribution parameters and density assumptions are shown to be preferable to fixed constants, and that a double-moment representation of the snow category may be beneficial when representing the effects of aggregation. These results may guide forecast centers in optimal configurations of their forecast models for winter weather and identify best practices present within these various schemes.

Molthan, Andrew L.↗
NASA NTRS2012

Low Temperature Double-layer Capacitors with Improved Energy Density: An Overview of Recent Development Efforts

Electrochemical double-layer capacitors are finding increased use in a wide range of energy storage applications, particularly where high pulse power capabilities are required. Double-layer capacitors store charge at a liquid/solid interface, making them ideal for low temperature power applications, due to the facile kinetic processes associated with the rearrangement of the electrochemical double-layer at these temperatures. Potential low temperature applications include hybrid and electric vehicles, operations in polar regions, high altitude aircraft and aerospace avionics, and distributed environmental and structural health monitoring. State-of-the-art capacitors can typically operate to -40 C, with a subsequent degradation in power performance below room temperature. However, recent efforts focused on advanced electrolyte and electrode systems can enable operation to temperatures as low as -70 C, with capacities similar to room temperature values accompanied by reasonably low equivalent series resistances. This presentation will provide an overview of recent development efforts to extend and improve the wide temperature performance of these devices.

energy storage↗
NASA NTRS2014

Simulation of the Formation of DNA Double Strand Breaks and Chromosome Aberrations in Irradiated Cells

The formation of DNA double-strand breaks (DSBs) and chromosome aberrations is an important consequence of ionizing radiation. To simulate DNA double-strand breaks and the formation of chromosome aberrations, we have recently merged the codes RITRACKS (Relativistic Ion Tracks) and NASARTI (NASA Radiation Track Image). The program RITRACKS is a stochastic code developed to simulate detailed event-by-event radiation track structure: [1] This code is used to calculate the dose in voxels of 20 nm, in a volume containing simulated chromosomes, [2] The number of tracks in the volume is calculated for each simulation by sampling a Poisson distribution, with the distribution parameter obtained from the irradiation dose, ion type and energy. The program NASARTI generates the chromosomes present in a cell nucleus by random walks of 20 nm, corresponding to the size of the dose voxels, [3] The generated chromosomes are located within domains which may intertwine, and [4] Each segment of the random walks corresponds to approx. 2,000 DNA base pairs. NASARTI uses pre-calculated dose at each voxel to calculate the probability of DNA damage at each random walk segment. Using the location of double-strand breaks, possible rejoining between damaged segments is evaluated. This yields various types of chromosomes aberrations, including deletions, inversions, exchanges, etc. By performing the calculations using various types of radiations, it will be possible to obtain relative biological effectiveness (RBE) values for several types of chromosome aberrations.

Plante, Ianik↗
NASA NTRS2013

WISE J233237.05-505643.5: A Double-Peaked Broad-Lined AGN with Spiral-Shaped Radio Morphology

We present radio continuum mapping, optical imaging and spectroscopy of the newly discovered double-peaked broad-lined AGN WISE J233237.05-505643.5 at redshift z = 0.3447. This source exhibits an FR-I and FR-II hybrid-morphology, characterized by bright core, jet, and Doppler-boosted lobe structures in ATCA continuum maps at 1.5, 5.6, and 9 GHz. Unlike most FR-II objects, W2332-5056 is hosted by a disk-like galaxy. The core has a projected 5" linear radio feature that is perpendicular to the curved primary jet, hinting at unusual and complex activity within the inner 25 kpc. The multi-epoch optical-near-IR photometric measurements indicate significant variability over a 3-20 year baseline from the AGN component. Gemini-South optical data shows an unusual double-peaked emission-line features: the centroids of the broad-lined components of H-alpha and H-beta are blueshifted with respect to the narrow lines and host galaxy by approximately 3800 km/s. We examine possible cases which involve single or double supermassive black holes in the system, and discuss required future investigations to disentangle the mystery nature of this system.

galaxies: individual↗
NASA NTRS2014

Airborne 2-Micron Double-Pulsed Integrated Path Differential Absorption Lidar for Column CO2 Measurement

Double-pulse 2-micron lasers have been demonstrated with energy as high as 600 millijouls and up to 10 Hz repetition rate. The two laser pulses are separated by 200 microseconds and can be tuned and locked separately. Applying double-pulse laser in DIAL system enhances the CO2 measurement capability by increasing the overlap of the sampled volume between the on-line and off-line. To avoid detection complicity, integrated path differential absorption (IPDA) lidar provides higher signal-to-noise ratio measurement compared to conventional range-resolved DIAL. Rather than weak atmospheric scattering returns, IPDA rely on the much stronger hard target returns that is best suited for airborne platforms. In addition, the IPDA technique measures the total integrated column content from the instrument to the hard target but with weighting that can be tuned by the transmitter. Therefore, the transmitter could be tuned to weight the column measurement to the surface for optimum CO2 interaction studies or up to the free troposphere for optimum transport studies. Currently, NASA LaRC is developing and integrating a double-Pulsed 2-micron direct detection IPDA lidar for CO2 column measurement from an airborne platform. The presentation will describe the development of the 2-micron IPDA lidar system and present the airborne measurement of column CO2 and will compare to in-situ measurement for various ground target of different reflectivity.

Singh, Upendra N.↗
NASA NTRS2014

J1649+2635: A Grand-Design Spiral with a Large Double-Lobed Radio Source

We report the discovery of a grand-design spiral galaxy associated with a double-lobed radio source. J1649+2635 (z = 0.0545) is a red spiral galaxy with a prominent bulge that it is associated with a L(1.4GHz) is approximately 10(exp24) W Hz(exp−1) double-lobed radio source that spans almost 100 kpc. J1649+2635 has a black hole mass of M(BH) is approximately 3-7 × 10(exp8) Solar mass and SFR is approximately 0.26 - 2.6 solar mass year(exp−1). The galaxy hosts a approximately 96 kpc diffuse optical halo, which is unprecedented for spiral galaxies. We find that J1649+2635 resides in an overdense environment with a mass of M(dyn) = 7.7(+7.9/−4.3) × 10(exp13) Solar mass, likely a galaxy group below the detection threshold of the ROSAT All-Sky Survey. We suggest one possible scenario for the association of double-lobed radio emission from J1649+2635 is that the source may be similar to a Seyfert galaxy, located in a denser-than-normal environment. The study of spiral galaxies that host large-scale radio emission is important because although rare in the local Universe, these sources may be more common at high-redshifts.

J1449↗
NASA NTRSDate not supplied

Investigating Pyroclastic Volcanism in the Taurus-Littrow Valley (TLV) Using the Station 3 Double Drive Tube 73001-73002

Well over 100 pyroclastic deposits have been identified on the Moon. Eruptive processes such as represented by these deposits transported endogenous volatiles from the Moon’s mantle to its surface. Debris from pyroclastic deposits has been identified in all Apollo and Luna samples. The high-Ti pyroclastic de- posit sampled at Shorty Crater by the Station 4 double drive tube (74001-74002) is our best sampling of these types of deposits. Samples 78500 and 78526, NAC images of fissures in the Sculptured Hills, ash identified in 70001-7, and other green volcanic glass indicate that very low-Ti basalt (VLT) erup- tions also occurred in TLV. The double drive tube core being investigated by the ANGSA initiative provides an- other view of TLV pyroclastic eruptions. The regolith in 73001-73002 and the regolith breccias therein have nu- merous pyroclastic beads. Some individual regolith brec- cia fragments have abundant pyroclastic beads (>50 in a polished surface). In this work, we address the following questions. Do these glass beads overlap in composition with those sampled elsewhere in the TLV or do they rec- ord another episode of pyroclastic eruption? Are the magmas associated with pyroclastic eruptions petroge- netically related to the crystalline mare basalts in the TLV? Finally, is the volatile record of the pyroclastic eruptions better preserved in the newly opened and spe- cially contained Station 3 double drive tube core?

C.K. Shearer↗
NASA NTRS2024

Double Power-law Formation by Sequential Particle Acceleration

Spectral double power laws are common in solar high-energy phenomena such as flares and interplanetary energetic-electron events. However, the physical mechanism that produces the changes in power-law index within a single spectrum is unclear. We developed a fully analytical method of forming single power-law spectra from sequential acceleration of particles orbiting inside and hopping between simulated large-scale magnetic islands formed by flare reconnection. Here, we extend the analytical method to the formation of double power-law spectra by assuming sequential acceleration in two successive regions with different acceleration and particle-transport rates. The resulting spectral distribution is continuous and smooth, with a flattening at low energies, two power-law regions at mid-energies, and a steep rollover at high energies. The model provides analytical expressions for the spectral indices, all energy breaks, and normalization constants as functions of just three physical parameters of each acceleration region: (1) the energy gain in each accelerator, (2) the percentage of particles transferred between accelerators, and (3) the number of accelerators visited. One of the most salient predictions of our work is that the spectral index at high (low) energies is determined by the parameters of the first "seed" (second) acceleration region. By constructing the spectral distribution through an iterative analytical process, the evolution toward a double power law is easily characterized and explained. Our analytical model provides tools to interpret space- and ground-based observations from RHESSI, FOXSI, NuSTAR, Solar Orbiter/STIX, EOVSA, and future high-energy missions.

Solar flares↗