Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “compaction banding”

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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Structural properties of compact groups

We report the results of a systematic study of galaxies in the regions of Hickson compact groups. Our sample is composed of the 22 Hickson groups which are located in the southern hemisphere and have cz less than 9000 km/s. Making use of digitized images of IIIa-J plates that cover an area of 0.5 x 0.5 deg around each group, we were able to detect and classify images down to a magnitude limit of 19.5 in the B band. This limit is typically three magnitudes fainter than previous studies. Most groups show a statistically significant excess of fainter galaxies compared to the background. These fainter galaxies typically have a somewhat more extended spatial distribution than the brighter galaxies originally classified by Hickson. Our data suggest that Hickson groups have a wide range in density and radius, ranging from very compact structures with overdensities of the order of 10(exp 2) and crossing times of roughly 0.01 H(sub 0 sup -1), to much more diffuse structures, similar to loose groups, with overdensities of about 3 and crossing times of roughly 0.5 H(sub 0 sup -1).

De Carvalho, R. R.↗
NASA NTRS1984

Development and flight test of a helicopter compact, portable, precision landing system concept

An airborne, radar based, precision approach concept is being developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. A transponder based beacon landing system (BLS) applying state of the art X band radar technology and digital processing techniques, has been built and is being flight tested to demonstrate the concept feasibility. The BLS airborne hardware consists of an add on microprocessor, installed in conjunction with the aircraft weather/mapping radar, which analyzes the radar beacon receiver returns and determines range, localizer deviation, and glide slope derivation. The ground station is an inexpensive, portable unit which can be quickly deployed at a landing site. Results from the flight test program show that the BLS concept has a significant potential for providing rotorcraft with low cost, precision instrument approach capability in remote areas.

Bull, J. S.↗
NASA NTRS1980

The nebulosity associated with 3C 120

Spectrophotometric observations have been made of the nebulosity surrounding the Seyfert (or N) galaxy 3C 120, as well as of the nucleus. Observations of the nebulosity reveal an extensive network of H II regions characterized by a high ionization level, which, it is argued, is due to photoionizations by the nucleus. The O/H and N/O abundance ratios in this gas, at least as far out as 8 kpc from the nucleus, must be within a factor of 20 of the solar values. The velocity field of this gas is very chaotic, but the systematic gas velocities, relative to the nucleus, are mostly positive to one side of an axis passing through the nucleus at P.A. 72 deg and mostly negative on the other side. The position angle of this axis is consistent with the direction (P.A. 65 deg) along which the compact radio source in the nucleus is expanding, but it is about 45 deg away from the major or minor axes of the fainter elliptical structure visible on previously published broad-band direct plates.

Baldwin, J. A.↗
NASA NTRS1986

The U.C. Berkeley Space Sciences Laboratory and Department of Physics Submillimeter Receiver

The UCB submm heterodyne receiver is a complete system for high-resolution astronomical spectroscopy in the 350-micron and 450-micron atmospheric windows. This compact system mounts directly at the Cassegrain focus of large optical and IR telescopes. It consists of a laser local oscillator, open structure mixer, quasi-optical coupling system, a broad-band IF system, and an acoustooptical spectrometer. The local oscillator is a 1-m-long submm laser optically pumped by a CO2 laser. The mixer is a quasi-optical corner-cube antenna structure and Schottky diode. The mixer is currently operated at room temperature, and its performance at 77 K is being evaluated. The system noise temperature is less than 7000 K SSB during observations.

Harris, A. I.↗
NASA NTRS2005

An XMM-Newton Search for Crab-like Supernova Remnants

The primary goals of the study are to search for evidence of non-thermal emission that would suggest the presence of a pulsar in this compact SNR. We have performed the reduction of the EPIC data for this observation, cleaning the data to remove time intervals of enhanced particle background, and have created maps in several energy bands, and on a variety of smoothing scales. We find no evidence for emission from the SNR. Given the small angular size of the SNR, we conclude that rather than being a young remnant, it is actually fairly old, but distant. At its current stage of evolution, the remnant shell has apparently entered the radiative phase, wherein the shell temperature has cooled sufficiently to be either below X-ray-emitting temperatures or at temperatures easily absorbed the foreground interstellar material. We have thus concluded that this SNR is not a viable candidate for a young ejecta-rich or pulsar-driven SNR.

Mushotzky, Richard↗
DOE OSTI2021

New accelerator capabilities with the high-gradient C-band [Slides]

LANSCE accelerator upgrades: Applications such as pRad desire higher proton beam energy. Material science at LANL will benefit from powerful directional high repetition rate X-ray sources. As it considers itself to be the NNSA accelerator laboratory, LANL should play role in developing compact accelerators for various national security missions.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Dynamically tunable membrane metasurfaces for infrared spectroscopy and strong light-matter interactions

Mid-infrared spectroscopy enables biochemical sensing by identifying vibrational molecular fingerprints, but it faces limitations in instrumentation portability and analytical sensitivity. Optical metasurfaces with strong mid-infrared photonic resonances provide an attractive solution towards on-chip spectrometry and sensitive molecular detection, yet their static nature hinders their anticipated impact. Here, we introduce and demonstrate dynamically tunable silicon membrane metasurfaces exhibiting high-Q transmissive resonances in the fingerprint region. By harnessing silicon’s thermo-optical properties, we achieve continuous modulation of coupling-induced transparency (CIT) modes that emerge upon the interference of quasi-bound states in the continuum (q-BICs) and surface lattice modes (SLMs). We measure a spectral tuning rate of 0.06 cm −1 K −1 by continuously sweeping the sharp CIT resonances over a 23.5 cm −1 spectral range across a temperature range of 300–700 K. In the current proof‑of‑concept implementation, the dynamic transmission control enables non-contact chemical analysis of polymer films by detecting characteristic absorption bands of polystyrene (1450 and 1492 cm −1 ) and poly(methyl methacrylate) (1730 cm −1 ) without requiring conventional spectrometers. When analyte molecules fill the metasurface-generated photonic cavities, we demonstrate vibrational strong coupling between the poly(methyl methacrylate)’s carbonyl band and the CIT mode, manifested in a Rabi splitting of ~43 cm −1 . Our results establish a new photonic platform that unites spectral precision, strong field enhancement, and reconfigurability, offering diverse potential for compact mid-infrared spectroscopy, molecular sensing, and programmable polaritonic photonics.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1997

Self-Consistent Thermal Accretion Disk Corona Models for Compact Objects. I: Properties of the Corona and the Spectrum of Escaping Radiation

We present the properties of accretion disk corona (ADC) models in which the radiation field, the temperature, and the total opacity of the corona are determined self-consistently. We use a nonlinear Monte Carlo code to perform the calculations. As an example, we discuss models in which the corona is situated above and below a cold accretion disk with a plane-parallel (slab) geometry, similar to the model of Haardt & Maraschi. By Comptonizing the soft radiation emitted by the accretion disk, the corona is responsible for producing the high-energy component of the escaping radiation. Our models include the reprocessing of radiation in the accretion disk. Here the photons either are Compton-reflected or photoabsorbed, giving rise to fluorescent line emission and thermal emission. The self- consistent coronal temperature is determined by balancing heating (due to viscous energy dissipation) with Compton cooling, determined using the fully relativistic, angle-dependent cross sections. The total opacity is found by balancing pair productions with annihilations. We find that, for a disk temperature kT(sub BB) approx. less than 200 eV, these coronae are unable to have a self-consistent temperature higher than approx. 140 keV if the total optical depth is approx. less than 0.2, regardless of the compactness parameter of the corona and the seed opacity. This limitation corresponds to the angle-averaged spectrum of escaping radiation having a photon index approx. greater than 1.8 within the 5-30 keV band. Finally, all models that have reprocessing features also predict a large thermal excess at lower energies. These constraints make explaining the X-ray spectra of persistent black hole candidates with ADC models very problematic.

Dove, James B.↗
NASA NTRS2006

Bias Selective Operation of Sb-Based Two-Color Photodetectors

Multicolor detectors have a strong potential to replace conventional single-color detectors in application dealing with the simultaneous detection of more than one wavelength. This will lead to the reduction of heavy and complex optical components now required for spectral discrimination for multi-wavelengths applications. This multicolor technology is simpler, lighter, compact and cheaper with respect to the single-color ones. In this paper, Sb-based two-color detectors fabrication and characterization are presented. The color separation is achieved by fabricating dual band pn junction on a GaSb substrate. The first band consists of an InGaAsSb pn junction for long wavelength detection, while the second band consists of a GaSb pn junction for shorter wavelength detection. Three metal contacts were deposited to access the individual junctions. Surface morphology of multi-layer thin films and also device characteristics of quasi-dual band photodetector were characterized using standard optical microscope and electro-optic techniques respectively. Dark current measurements illustrated the diode behavior of both lattice-matched detector bands. Spectral response measurements indicated either independent operation of both detectors simultaneously, or selective operation of one detector, by the polarity of the bias voltage, while serially accessing both devices.

Abedin, M. N.↗
DOE OSTI2020

Acoustic Explosion Data Archive for Machine Learning

The prompt detection of explosions is a key element of the nuclear non-proliferation mission. With traditional sensors being limited in number and scale, smartphones as compact and economical multi-modal sensors are gaining traction and are being deployed. To address the flood of heterogeneous smartphone data, our team proposes a feature extraction using standardized constant-Q frequency bands across acoustic, barometric, and accelerometer data. The work in this presentation contains data collected at Idaho National Laboratory during planned detonations.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗
DOE OSTI2020

Data Fusion and Feature Extraction of Explosions Recorded on Smartphones

The prompt detection of explosions is a key element of the nuclear non-proliferation mission. With traditional sensors being limited in number and scale, smartphones as compact and economical multi-modal sensors are gaining traction and are being deployed. To address the flood of heterogeneous smartphone data, our team proposes a feature extraction using standardized constant-Q frequency bands across acoustic, barometric, and accelerometer data. The work presented in this poster utilizes three explosions collected on smartphones with Idaho National Lab. More explosions are planned in the near future at INL and NNSS. These extracted features will be used in machine learning methods in future iterations.

46 - INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AN↗
NASA NTRS1984

Development and flight test of a helicopter compact, portable, precision landing system concept

An airborne, radar-based, precision approach concept is being developed and flight tested as a part of NASA's Rotorcraft All-Weather Operations Research Program. A transponder-based beacon landing system (BLS) applying state-of-the-art X-band radar technology and digital processing techniques, was built and is being flight tested to demonstrate the concept feasibility. The BLS airborne hardware consists of an add-on microprocessor, installed in conjunction with the aircraft weather/mapping radar, which analyzes the radar beacon receiver returns and determines range, localizer deviation, and glide-slope deviation. The ground station is an inexpensive, portable unit which can be quickly deployed at a landing site. Results from the flight test program show that the BLS concept has a significant potential for providing rotorcraft with low-cost, precision instrument approach capability in remote areas.

Clary, G. R.↗
DOE OSTI2023

Wind redistribution of snow impacts the Ka- and Ku-band radar signatures of Arctic sea ice

Wind-driven redistribution of snow on sea ice alters its topography and microstructure, yet the impact of these processes on radar signatures is poorly understood. Here, we examine the effects of snow redistribution over Arctic sea ice on radar waveforms and backscatter signatures obtained from a surface-based, fully polarimetric Ka- and Ku-band radar at incidence angles between 0° (nadir) and 50°. Two wind events in November 2019 during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition are evaluated. During both events, changes in Ka- and Ku-band radar waveforms and backscatter coefficients at nadir are observed, coincident with surface topography changes measured by a terrestrial laser scanner. At both frequencies, redistribution caused snow densification at the surface and the uppermost layers, increasing the scattering at the air–snow interface at nadir and its prevalence as the dominant radar scattering surface. The waveform data also detected the presence of previous air–snow interfaces, buried beneath newly deposited snow. The additional scattering from previous air–snow interfaces could therefore affect the range retrieved from Ka- and Ku-band satellite altimeters. With increasing incidence angles, the relative scattering contribution of the air–snow interface decreases, and the snow–sea ice interface scattering increases. Relative to pre-wind event conditions, azimuthally averaged backscatter at nadir during the wind events increases by up to 8 dB (Ka-band) and 5 dB (Ku-band). Results show substantial backscatter variability within the scan area at all incidence angles and polarizations, in response to increasing wind speed and changes in wind direction. Our results show that snow redistribution and wind compaction need to be accounted for to interpret airborne and satellite radar measurements of snow-covered sea ice.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1993

The NT digital micro tape recorder

The description of an audio recorder may at first glance seem out of place in a conference which has been dedicated to the discussion of the technology and requirements of mass data storage. However, there are several advanced features of the NT system which will be of interest to the mass storage technologist. Moreover, there are a sufficient number of data storage formats in current use which have evolved from their audio counterparts to recommend a close attention to major innovative introductions of audio storage formats. While the existing analog micro-cassette recorder has been (and will continue to be) adequate for various uses, there are significant benefits to be gained through the application of digital technology. The elimination of background tape hiss and the availability of two relatively wide band channels (for stereo recording), for example, would greatly enhance listenability and speech intelligibility. And with the use of advanced high-density recording and LSI circuit technologies, a digital micro recorder can realize unprecedented compactness with excellent energy efficiency. This is what was accomplished with the NT-1 Digital Micro Recorder. Its remarkably compact size contributes to its portability. The high-density NT format enables up to two hours of low-noise digital stereo recording on a cassette the size of a postage stamp. Its highly energy-efficient mechanical and electrical design results in low power consumption; the unit can be operated up to 7 hours (for continuous recording) on a single AA alkaline battery. Advanced user conveniences include a multifunction LCD readout. The unit's compactness and energy-efficiency, in particular, are attributes that cannot be matched by existing analog and digital audio formats. The size, performance, and features of the NT format are of benefit primarily to those who desire improved portability and audio quality in a personal memo product. The NT Recorder is the result of over ten years of intensive, multi-disciplinary research and development. What follows is a discussion of the technologies that have made the NT possible: (1) NT format mechanics, (2) NT media, (3) NT circuitry and board.

Sasaki, Toshikazu↗
NASA NTRS1994

A Lyman-alpha tunable acousto-optic filter for detecting superthermal flare protons

The goal of this project was to develop and characterize a narrow-band, tunable filter for use near the Lyman-alpha line of hydrogen at 121.6 nm. Such a filter could form the critical component of an instrument to observe asymmetries in the solar Lyman-alpha line, caused by energetic protons accelerated during the impulsive phase of solar flares. Characteristic charge-exchange nonthermal emission at Lyman alpha should be produced when sub-MeV protons are injected into the chromosphere, but no instrument suitable for their detection has been developed. Such an instrument would require a narrow-band (less than 0.01 nm) tunable filter with aperture and throughput consistent with imaging a solar active region at 0.1 second intervals. The development of acousto-optic tunable filters (AOTF) suitable for use as compact, simple tunable filters for astronomical work suggested an investigation into the use of an AOTF at Lyman-alpha.

Mickey, Donald L.↗
NASA NTRS1999

The Power of SS 433's Jets

We observed SS 433 for the third time with RXTE, this time simultaneously with a Nobeyama millimeter band monitoring campaign. These observations extended the RXTE coverage of SS 433's precession phases. and once again monitored the source during a binary eclipse. Our AO-2 campaign of a joint RXTE-VLBA-VLA-MERLIN observation was delayed to little more than a month before the AO-3 observations. We also had an AO-1 observation of SS 433. In each case we observed an eclipse of the compact ob'ect by the companion star, and had contemporaneous optical observations. We are analyzing all three sets of observations together. A publication is in preparation; Its completion will be supported by the remaining AO-2 funds. Here I will summarize the general results and point out the relevant features of the AO-3 observations. The spectrum is detected to approx. 50 keV, which is entirely within the PCA energy band. We find that the HEXTE data do not add significantly to the spectrum, and most of our fits are without HEXTE. We find that the continuum can be fit with a power law with an exponential cutoff; the photon index is usually approx. 1.4. A line at approx. 6.4 keV is definitely required, and the fits improve significant, if we add a second line, also with an energy in the iron K(alpha) complex, and an absorption edge. The edge usually has an energy of approx. 5.8 keV, which does not correspond to any known physical feature. and may be an instrumental artifact. This is under further investigation.

Band, David F.↗
NASA NTRS1992

Evidence for a black hole in the X-ray binary Nova Muscae 1991

Optical photometry and spectroscopy of the X-ray Nova Muscae 1991 in quiescence reveal an orbital period of 10.398 +/- 0.014 hr and an absorption-line velocity curve consistent with a sinusoidal modulation at a half-amplitude of 409 +/- 18 km/s. The spectral type of the secondary star is in the range K0 V to K4 V. The value of the mass function, 3.1 +/- 0.4 solar mass, is a conservative lower limit on the mass of the compact primary and suggests that the primary is a black hole. Further considerations of the binary inclination angle and the mass of the secondary strengthen the black hole model. The folded light curves in the I band and the B + V band resemble ellipsoidal variations, with an additional brightening near one of the maxima in the B + V band. The orbital period is 1.4 percent shorter than the photometric period observed during outburst, as expected if the outburst modulations are analogs of 'superhumps' in dwarf novae. In quiescence, the optical properties of the X-ray binary Nova Muscae 1991 bear a striking resemblance to the black hole binary A0620-00, which extends the basis of similarity that was demonstrated during outburst at X-ray and optical wavelengths.

Remillard, Ronald A.↗