Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “COMPACTS”

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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Defining a compact dry cooler design to reduce LCOE contribution in a CSP facility

Concentrating solar power (CSP), when coupled with a supercritical carbon dioxide (sCO 2 ) power cycle and sensible heat storage, presents a renewable and clean alternative for utility-scale power generation. However, in order to be competitive in the current and future markets, CSP facilities must limit their levelized cost of electricity (LCOE) by minimizing capital costs and reducing operating costs over the lifetime of the plant. Targeting this goal, this study investigates the LCOE impact of the power cycle pre-cooler. This study considers a compact dry cooler with micro-channel technology on the CO 2 side and formed fin geometry on the air side, using directly-coupled centrifugal fans and a transition duct to improve air distribution across the fins as well as protect the fins from contaminants which may cause blockage, soiling, fouling, and damage. In an effort to better understand the dry cooler impact on LCOE, a sensitivity study was conducted using various combinations of end-to-end approach temperatures, air-side pressure drop values, CO 2 -side pressure drop values, fan types, cooler turndown control schemes, cooler module sizes, and design-point ambient temperatures. Furthemore, off-design cycle performance data was calculated for each dry cooler design using NPSS simulation software; cycle performance data were then input to System Advisor Model (SAM) along with the associated capital costs for LCOE prediction of a 100 MW system over a 30 year plant lifetime. Results of this study show the LCOE is most sensitive to air-side performance, followed by heat transfer effectiveness and capital cost. It was found that a power cycle with a mid- to high-performance dry cooler will produce the most competitive power-production costs. Designing at the extreme ends for approach temperature (or effectiveness), design-point ambient temperature, and compactness (footprint) produce higher LCOE values; mid-range values for these parameters balance performance, operating costs, and associated capital cost to optimize LCOE.

14 SOLAR ENERGY↗
DOE OSTI2024

General guide concepts for compact, high-brilliance neutron moderators

The trend in neutron sciences is toward integrating compact, high-brightness moderators into new or upgraded facilities. Transporting neutrons from the source to the sample position with a phase-space distribution tailored to specific requirements is crucial to leverage high source brilliance. Here we have investigated four guide concepts using Monte Carlo ray tracing simulations: Montel beamline with nested Kirkpatrick–Baez mirrors, curved-tapered beamline with a bender and straight sections, straight-elliptical beamline, and curved-elliptical beamline. The straight-elliptical (curved-elliptical) beamline features two half-ellipse guides connected by a straight (non-straight) guide section. The neutron transport efficiency and phase space homogeneity have been quantitatively compared. Our results show that the straight-elliptical beamline performs best because of few neutron bounces on the guide surface with small reflection angles, minimizing flux loss. The Montel beamline provides the best spatial confinement of neutrons within the desired region; however, there is a high thermal-neutron loss due to large reflection angles. The curved-tapered beamline suffers from significant flux loss due to high bounces, and it shows a non-uniform angular distribution related to broad ranges of bounces and reflection angles. The non-straight guide section of the curved-elliptical beamline increases the phase space inhomogeneity, leading to a spatially non-uniform beam profile. The results apply to general neutron instruments that require transporting thermal and cold neutrons from a compact, high-brilliance moderator to the sample location with a moderate phase-space volume.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

A compact and portable gamma-ray spectrometer (GRASP) for inertial confinement fusion and basic science experiments

A compact and portable gamma-ray spectrometer has been designed to diagnose different components of the inertial confinement fusion-relevant γ-ray spectrum with energies between ∼3.7–17.9 MeV. The system is designed to be as compact as possible for convenient transportation and fielding in diagnostic ports on the OMEGA laser, the National Ignition Facility, and other photon-source facilities. The system consists of a conversion foil for Compton scattering in front of four magnetic spectrometer “arms,” each covering a different energy range and constructed out of cylindrical permanent magnet Halbach arrays. Monte Carlo simulations have been used to optimize and assess the performance of the conversion foil, and COSY INFINITY ion-optical simulations have been used to optimize the spectrometer magnets. The performance of the design is assessed for a simulated direct-drive γ-ray spectrum. Spanning its total γ-ray energy bandwidth and using a 1.7 mm thick boron conversion foil, the system’s total energy resolution and efficiency are ∼15.8%–4.5% and 5.4 × 10−7–3.7 × 10−7e−/γ, respectively, with room for improvement. Spectral γ-ray measurements will provide guidance to the inertial confinement fusion program toward achieving high-energy gain relevant to inertial fusion energy and enable new measurement capabilities for basic discovery science.

Instruments & Instrumentation↗
DOE OSTI2025

Irradiation-induced gas production in REBCO-based magnet materials used for future compact fusion reactors

Nuclear fusion is an enticing alternative to current sources of energy, with multilayered Rare-Earth Barium Copper Oxide (REBCO) coated conductors deemed pivotal in the race toward fully realized, commercially viable, and magnetic confinement fusion reactors. In this study, we simulated the ion spectrum expected to evolve from REBCO's nickel-based Hastelloy C-276 substrate and copper stabilizer in an affordable robust compact-like reactor. We then emulated this gas production through helium implantation to investigate changes in materials and superconducting properties. Our results revealed that the substrate and stabilizer are capable of producing protons energetic enough to recoil throughout the tape thickness in appreciable doses, and alphas energetic enough to deposit 7.54 × 1014 ions/cm2 or 50.1 helium appm in the superconducting layer over a 30-year reactor lifetime. The superconducting layer of SuperPower® tapes exhibited at least double the swelling rate of the other major layers, and both SuperPower and Fujikura Ltd. tapes displayed microstructural changes in the REBCO layer not observed in isotropic metals. For the estimated lifetime fluence, the Fujikura tapes showed a ∼1 K reduction in critical temperature and a 32% degradation in critical current for compact reactor-relevant conditions (16 T, 20 K). Nuclear transmutation, low-temperature solder implantations, gas-ion evolution, the influence of gas production on vortex dynamics, and other related considerations are also discussed.

Reis, Chris↗
DOE OSTI2020

Compact ultrastable laser system for spectroscopy of {sup 2}S{sub 1/2} → {sup 2}D{sub 3/2} quadrupole transition in {sup 171}Yb{sup +} ion

We report the results of studying a compact laser system designed for manipulating a quantum state of the optical qubit based on the {sup 2}S{sub 1/2} → {sup 2}D{sub 3/2} quadrupole transition in the {sup 171}Yb{sup +} ion at a wavelength of 435.5 nm. An emission power of the laser system reaches 500 μW at λ = 435.5 nm and the relative frequency instability of at most 3 × 10{sup −15} is achieved at averaging intervals from 0.5 to 50 s with a subtracted linear frequency drift. The compactness of the developed system makes it possible to employ it in transportable systems including optical clocks. (laser spectroscopy)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Variation of the equilibrium energy and the S-property of stationary compact sets

This paper studies a variation of the equilibrium energy for a certain fairly general functional which appears naturally in the solution of many rational approximation problems of multi-valued analytic functions. The main result of this work states that for the energy functional under consideration and a certain class of admissible compact sets, related to the function to be approximated, the corresponding stationary compact set is fully characterized by the so-called S-property. Bibliography: 38 titles.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Densified vertically lamellar electrode architectures for compact energy storage

As one of the most compact electrochemical energy storage systems, lithium-ion batteries (LIBs) are playing an indispensable role in the process of vehicle electrification to accelerate the shift to sustainable mobility. Making battery electrodes thicker is a promising strategy for improving the energy density of LIBs which is essential for applications with weight or volume constraints, such as electric-powered transportation; however, their power densities are often significantly restricted due to elongated and tortuous charge traveling distances. Here, we propose an effective methodology that couples bidirectional freeze-casting and compression-induced densification to create densified vertically lamellar electrode architectures for compact energy storage. The vertically lamellar architectures not only overcome the critical thickness limit for conventional electrodes but also facilitate and redistribute the lithium-ion flux enabling both high rate capability and stable cyclability. Furthermore, this proposed methodology is universal as demonstrated in various electrochemical active material systems. This study offers a facile approach that realizes simultaneous high energy and high power in high-loading battery electrodes and provides useful rationales in designing electrode architectures for scalable energy storage systems.

42 ENGINEERING↗
DOE OSTI2011

STAR CLUSTERS AS TRACERS OF INTERACTIONS IN STEPHAN'S QUINTET (HICKSON COMPACT GROUP 92)

Stephan's Quintet (SQ; also known as Hickson Compact Group 92) is a compact group of galaxies that exhibits numerous signs of interactions between its members. Using high-resolution (0.''04 per pixel) images of SQ in B{sub 438}, V{sub 606}, and I{sub 814} bands from the Early Release Science project obtained with the Wide Field Camera 3 on the Hubble Space Telescope, we identify 496 star cluster candidates (SCCs), located throughout the galaxies themselves as well as in intergalactic regions. Our photometry goes {approx}2 mag deeper and covers an additional three regions, the Old Tail, NGC 7317, and the southern debris region (SDR), compared to previous work. Through comparison of the B{sub 438} - V{sub 606} and V{sub 606} - I{sub 814} colors of the SCCs with simple stellar population synthesis models, we are able to constrain cluster ages. In particular, the most massive galaxy of SQ, NGC 7319, exhibits continuous star formation throughout its history, although at a lower rate over the past few tens of Myr. NGC 7318 A/B and the northern star burst region both show ongoing active star formation; there are a number of star clusters that are younger than 10 Myr. NGC 7318 A/B also features a peculiar gap in the color distribution of the star clusters that can be used to date the onset of the recent burst. The majority of the SCCs detected in the Young Tail were formed 150-200 Myr ago, whereas the tight distribution of star cluster colors in the Old Tail allows us to constrain its age of formation to {approx}400 Myr ago. The star clusters in the SDR are seemingly divided into two groups with ages of 50 and {approx}500 Myr, and virtually all of the SCCs detected in NGC 7317 are over 2 Gyr old. Based on these ages, we estimate time intervals for the interactions between SQ members that triggered the massive star cluster formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

DUAL-FREQUENCY OBSERVATIONS OF 140 COMPACT, FLAT-SPECTRUM ACTIVE GALACTIC NUCLEI FOR SCINTILLATION-INDUCED VARIABILITY

The 4.9 GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in interstellar scintillation (ISS) for sources at redshifts z {approx}> 2, indicating an apparent increase in angular diameter or a decrease in flux density of the most compact components of these sources relative to their extended emission. This can result from intrinsic source size effects or scatter broadening in the intergalactic medium (IGM) in excess of the expected (1 + z){sup 1/2} angular diameter scaling of brightness temperature limited sources resulting from cosmological expansion. We report here 4.9 GHz and 8.4 GHz observations and data analysis for a sample of 140 compact, flat-spectrum sources which may allow us to determine the origin of this angular diameter-redshift relation by exploiting their different wavelength dependences. In addition to using ISS as a cosmological probe, the observations provide additional insight into source morphologies and the characteristics of ISS. As in the MASIV Survey, the variability of the sources is found to be significantly correlated with line-of-sight H{alpha} intensities, confirming its link with ISS. For 25 sources, time delays of about 0.15-3 days are observed between the scintillation patterns at both frequencies, interpreted as being caused by a shift in core positions when probed at different optical depths. Significant correlation is found between ISS amplitudes and source spectral index; in particular, a large drop in ISS amplitudes is observed at {alpha} < -0.4 confirming that steep spectrum sources scintillate less. We detect a weakened redshift dependence of ISS at 8.4 GHz over that at 4.9 GHz, with the mean variance at four-day timescales reduced by a factor of 1.8 in the z > 2 sources relative to the z < 2 sources, as opposed to the factor of three decrease observed at 4.9 GHz. This suggests scatter broadening in the IGM, but the interpretation is complicated by subtle selection effects that will be explored further in a follow-up paper.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

A SPITZER-MIPS SEARCH FOR DUST IN COMPACT HIGH-VELOCITY H I CLOUDS

We employ three-band Spitzer-MIPS observations to search for cold dust emission in three neutral hydrogen compact high-velocity clouds (CHVCs) in the vicinity of the Milky Way. Far-infrared emission correlated with H I column density was previously reported in HVC Complex C, indicating that this object contains dust heated by the Galactic radiation field at its distance of {approx}10 kpc. Assuming published Spitzer, IRAS, and Planck, IR-H I correlations for Complex C, our Spitzer observations are of sufficient depth to directly detect 160 {mu}m dust emission in the CHVCs if it is present at the same level as in Complex C, but no emission is detected in any of the targets. For one of the targets (CHVC289) which has well-localized H I clumps, we therefore conclude that it is fundamentally different from Complex C, with either a lower dust-to-gas ratio or a greater distance from the Galactic disk (and consequently cooler dust temperature). Firm conclusions cannot be drawn for the other two Spitzer-observed CHVCs since their small-scale H I structures are not sufficiently well known; nonetheless, no extended dust emission is apparent despite their relatively high H I column densities. The lack of dust emission in CHVC289 suggests that at least some compact high-velocity clouds objects may exhibit very low dust-to-gas ratios and/or greater Galactocentric distances than large HVC complexes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

SOLAR SYSTEM MOONS AS ANALOGS FOR COMPACT EXOPLANETARY SYSTEMS

The field of exoplanetary science has experienced a recent surge of new systems that is largely due to the precision photometry provided by the Kepler mission. The latest discoveries have included compact planetary systems in which the orbits of the planets all lie relatively close to the host star, which presents interesting challenges in terms of formation and dynamical evolution. The compact exoplanetary systems are analogous to the moons orbiting the giant planets in our solar system, in terms of their relative sizes and semimajor axes. We present a study that quantifies the scaled sizes and separations of the solar system moons with respect to their hosts. We perform a similar study for a large sample of confirmed Kepler planets in multi-planet systems. We show that a comparison between the two samples leads to a similar correlation between their scaled sizes and separation distributions. The different gradients of the correlations may be indicative of differences in the formation and/or long-term dynamics of moon and planetary systems.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

VLA observations of NGC 247: identification of compact radio sources including three candidate UD H II regions

A high resolution, Very Large Array continuum survey of NGC 247 was undertaken in order to identify compact thermal and nonthermal radio sources, such as supernova remnants (SNRs) and H II regions. NGC 247 was observed at two frequencies, 20 cm and 6 cm, in order to calculate the spectral index, and the survey resulted in the identification of 19 compact radio sources. Using the spectral index to discriminate between source types, we identify two candidate SNRs and one H II region. Three of the radio sources have inverted spectra, indicative of ultradense H II (UD H II) regions, the short-lived, dense cores where massive stars form. Four of the sources are thermal in origin, but were not detected at 20 cm, so they could be H II regions or UD H II regions. The rest of the sources are nonthermal or undetermined. We compare the radio images with Hα, V band, and infrared archive images to look for correspondences that confirm that the sources reside in NGC 247 and are not background sources. We find that over two-thirds of the radio sources have counterparts in the Hα or V band images and are associated with NGC 247. The most luminous radio source in NGC 247 is a candidate SNR, and if confirmed as an SNR, it would be a very luminous extragalactic SNR. The H II regions and UD H II regions are calculated to have ionizing luminosities of between 4-10 × 10{sup 50} s{sup –1}; each individual source would require between 41-100 O7.5V stars to produce the corresponding ionizing luminosity. The ionizing luminosity of the UD H II regions indicates that these UD H II regions represent the lower luminosity population of the known UD H II regions and thus, they may represent a more typical population of UD H II regions that can be found and studied in the nearby galaxies as opposed to more extreme examples that have been found previously.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

LOCALIZING COMPACT BINARY INSPIRALS ON THE SKY USING GROUND-BASED GRAVITATIONAL WAVE INTERFEROMETERS

The inspirals and mergers of compact binaries are among the most promising events for ground-based gravitational-wave (GW) observatories. The detection of electromagnetic (EM) signals from these sources would provide complementary information to the GW signal. It is therefore important to determine the ability of GW detectors to localize compact binaries on the sky, so that they can be matched to their EM counterparts. We use Markov Chain Monte Carlo techniques to study sky localization using networks of ground-based interferometers. Using a coherent-network analysis, we find that the Laser Interferometer Gravitational Wave Observatory (LIGO)-Virgo network can localize 50% of their detected neutron star binaries to better than 50 deg{sup 2} with a 95% confidence interval. The addition of the Large Scale Cryogenic Gravitational Wave Telescope (LCGT) and LIGO-Australia improves this to 12 deg{sup 2}. Using a more conservative coincident detection threshold, we find that 50% of detected neutron star binaries are localized to 13 deg{sup 2} using the LIGO-Virgo network, and to 3 deg{sup 2} using the LIGO-Virgo-LCGT-LIGO-Australia network. Our findings suggest that the coordination of GW observatories and EM facilities offers great promise.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

RESOLUTION OF THE COMPACT RADIO CONTINUUM SOURCES IN Arp220

We present 2 cm and 3.6 cm wavelength very long baseline interferometry images of the compact radio continuum sources in the nearby ultra-luminous infrared galaxy Arp220. Based on their radio spectra and variability properties, we confirm these sources to be a mixture of supernovae (SNe) and supernova remnants (SNRs). Of the 17 detected sources we resolve 7 at both wavelengths. The SNe generally only have upper size limits. In contrast all the SNRs are resolved with diameters {>=}0.27 pc. This size limit is consistent with them having just entered their Sedov phase while embedded in an interstellar medium (ISM) of density 10{sup 4} cm{sup -3}. These objects lie on the diameter-luminosity correlation for SNRs (and so also on the diameter-surface brightness relation) and extend these correlations to very small sources. The data are consistent with the relation L{proportional_to}D{sup -9/4}. Revised equipartition arguments adjusted to a magnetic field to a relativistic particle energy density ratio of 1% combined with a reasonable synchrotron-emitting volume filling factor of 10% give estimated magnetic field strengths in the SNR shells of {approx}15-50 mG. The SNR shell magnetic fields are unlikely to come from compression of ambient ISM fields and must instead be internally generated. We set an upper limit of 7 mG for the ISM magnetic field. The estimated energy in relativistic particles, 2%-20% of the explosion kinetic energy, is consistent with estimates from models that fit the IR-radio correlation in compact starburst galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

COMPACT REMNANT MASS FUNCTION: DEPENDENCE ON THE EXPLOSION MECHANISM AND METALLICITY

The mass distribution of neutron stars and stellar-mass black holes provides vital clues into the nature of stellar core collapse and the physical engine responsible for supernova explosions. A number of supernova engines have been proposed: neutrino- or oscillation-driven explosions enhanced by early (developing in 10-50 ms) and late-time (developing in 200 ms) convection as well as magnetic field engines (in black hole accretion disks or neutron stars). Using our current understanding of supernova engines, we derive mass distributions of stellar compact remnants. We provide analytic prescriptions for both single-star models (as a function of initial star mass) and for binary-star models-prescriptions for compact object masses for major population synthesis codes. These prescriptions have implications for a range of observations: X-ray binary populations, supernova explosion energies, and gravitational wave sources. We show that advanced gravitational radiation detectors (like LIGO/VIRGO or the Einstein Telescope) will be able to further test the supernova explosion engine models once double black hole inspirals are detected.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

INTRAGROUP AND GALAXY-LINKED DIFFUSE X-RAY EMISSION IN HICKSON COMPACT GROUPS

Isolated compact groups (CGs) of galaxies present a range of dynamical states, group velocity dispersions, and galaxy morphologies with which to study galaxy evolution, particularly the properties of gas both within the galaxies and in the intragroup medium. As part of a large, multiwavelength examination of CGs, we present an archival study of diffuse X-ray emission in a subset of nine Hickson compact groups (HCGs) observed with the Chandra X-Ray Observatory. We find that seven of the groups in our sample exhibit detectable diffuse emission. However, unlike large-scale emission in galaxy clusters, the diffuse features in the majority of the detected groups are linked to the individual galaxies, in the form of both plumes and halos likely as a result of vigourous star formation or activity in the galaxy nucleus, as well as in emission from tidal features. Unlike previous studies from earlier X-ray missions, HCGs 31, 42, 59, and 92 are found to be consistent with the L{sub X} -T relationship from clusters within the errors, while HCGs 16 and 31 are consistent with the cluster L{sub X} -{sigma} relation, though this is likely coincidental given that the hot gas in these two systems is largely due to star formation. We find that L{sub X} increases with decreasing group H I to dynamical-mass ratio with tentative evidence for a dependence in X-ray luminosity on H I morphology whereby systems with intragroup H I indicative of strong interactions are considerably more X-ray luminous than passively evolving groups. We also find a gap in the L{sub X} of groups as a function of the total group specific star formation rate. Our findings suggest that the hot gas in these groups is not in hydrostatic equilibrium and these systems are not low-mass analogs of rich groups or clusters, with the possible exception of HCG 62.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

MULTI-EPOCH VERY LONG BASELINE ARRAY OBSERVATIONS OF THE COMPACT WIND-COLLISION REGION IN THE QUADRUPLE SYSTEM Cyg OB2 no. 5

We present multi-epoch Very Long Base Array observations of the compact wind-collision region in the Cyg OB2 no. 5 system. These observations confirm the arc-shaped morphology of the emission reported earlier. The total flux as a function of time is roughly constant when the source is 'on', but falls below the detection limit as the wind-collision region approaches periastron in its orbit around the contact binary at the center of the system. In addition, at one of the 'on' epochs, the flux drops to about a fifth of its average value. We suggest that this apparent variation could result from the inhomogeneity of the wind that hides part of the flux rather than from an intrinsic variation. We measured a trigonometrical parallax, for the most compact radio emission of 0.61 {+-} 0.22 mas, corresponding to a distance of 1.65 {sup +0.96} {sub -0.44} kpc, in agreement with recent trigonometrical parallaxes measured for objects in the Cygnus X complex. Using constraints on the total mass of the system and orbital parameters previously reported in the literature, we obtain two independent indirect measurements of the distance to the Cyg OB2 no. 5 system, both consistent with 1.3-1.4 kpc. Finally, we suggest that the companion star responsible for the wind interaction, yet undetected, is of spectral type between B0.5 and O8.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

NEAR- AND FAR-FIELD RESPONSE TO COMPACT ACOUSTIC SOURCES IN STRATIFIED CONVECTION ZONES

The role of the acoustic continuum associated with compact sources in the Sun's interior wave field is explored for a simple polytropic model. The continuum produces a near-field acoustic structure-the so-called acoustic jacket-that cannot be represented by a superposition of discrete normal modes. Particular attention is paid to monochromatic point sources of various frequency and depth, and to the surface velocity power that results, both in the discrete f- and p-mode spectrum and in the continuum. It is shown that a major effect of the continuum is to heal the surface wave field produced by compact sources, and therefore to hide them from view. It is found that the continuous spectrum is not a significant contributor to observable inter-ridge seismic power.

79 ASTRONOMY AND ASTROPHYSICS↗