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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Influence of Test Procedures on the Thermomechanical Properties of a 55NiTi Shape Memory Alloy

Over the past few decades, binary NiTi shape memory alloys have received attention due to their unique mechanical characteristics, leading to their potential use in low-temperature, solid-state actuator applications. However, prior to using these materials for such applications, the physical response of these systems to mechanical and thermal stimuli must be thoroughly understood and modeled to aid designers in developing SMA-enabled systems. Even though shape memory alloys have been around for almost five decades, very little effort has been made to standardize testing procedures. Although some standards for measuring the transformation temperatures of SMA s are available, no real standards exist for determining the various mechanical and thermomechanical properties that govern the usefulness of these unique materials. Consequently, this study involved testing a 55NiTi alloy using a variety of different test methodologies. All samples tested were taken from the same heat and batch to remove the influence of sample pedigree on the observed results. When the material was tested under constant-stress, thermal-cycle conditions, variations in the characteristic material responses were observed, depending on test methodology. The transformation strain and irreversible strain were impacted more than the transformation temperatures, which only showed an affect with regard to applied external stress. In some cases, test methodology altered the transformation strain by 0.005-0.01mm/mm, which translates into a difference in work output capability of approximately 2 J/cu cm (290 in!lbf/cu in). These results indicate the need for the development of testing standards so that meaningful data can be generated and successfully incorporated into viable models and hardware. The use of consistent testing procedures is also important when comparing results from one research organization to another. To this end, differences in the observed responses will be presented, contrasted and rationalized, in hopes of eventually developing standardized testing procedures for shape memory alloys.

Padula, Santo A., II↗
DOE OSTI2017

Laser-induced breakdown spectroscopy of light water reactor simulated used nuclear fuel: Main oxide phase

We show the analysis of light water reactor simulated used nuclear fuel using laser-induced breakdown spectroscopy (LIBS) is explored using a simplified version of the main oxide phase. The main oxide phase consists of the actinides, lanthanides, and zirconium. The purpose of this study is to develop a rapid, quantitative technique for measuring zirconium in a uranium dioxide matrix without the need to dissolve the material. A second set of materials including cerium oxide is also analyzed to determine precision and limit of detection (LOD) using LIBS in a complex matrix. Two types of samples are used in this study: binary and ternary oxide pellets. The ternary oxide, (U,Zr,Ce)O 2 pellets used in this study are a simplified version the main oxide phase of used nuclear fuel. The binary oxides, (U,Ce)O 2 and (U,Zr)O 2 are also examined to determine spectral emission lines for Ce and Zr, potential spectral interferences with uranium and baseline LOD values for Ce and Zr in a UO 2 matrix. In the spectral range of 200 to 800 nm, 33 cerium lines and 25 zirconium lines were identified and shown to have linear correlation values (R 2 ) > 0.97 for both the binary and ternary oxides. The cerium LOD in the (U,Ce)O 2 matrix ranged from 0.34 to 1.08 wt% and 0.94 to 1.22 wt% in (U,Ce,Zr)O 2 for 33 of Ce emission lines. The zirconium limit of detection in the (U,Zr)O 2 matrix ranged from 0.84 to 1.15 wt% and 0.99 to 1.10 wt% in (U,Ce,Zr)O 2 for 25 Zr lines. Finally, the effect of multiple elements in the plasma and the impact on the LOD is discussed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2005

A Search for Transiting Neptune-Mass Extrasolar Planets in High-Precision Photometry of Solar-Type Stars

Tennessee State University operates several automatic photometric telescopes (APTs) at Fairborn Observatory in southern Arizona. Four 0.8 m APTs have been dedicated to measuring subtle luminosity variations that accompany magnetic cycles in solar-type stars. Over 1000 program and comparison stars have been observed every clear night in this program for up to 12 years with a precision of approximately 0.0015 mag for a single observation. We have developed a transit-search algorithm, based on fitting a computed transit template for each trial period, and have used it to search our photometric database for transits of unknown companions. Extensive simulations with the APT data have shown that we can reliably recover transits with periods under 10 days as long as the transits have a depth of at least 0.0024 mag, or about 1.6 times the scatter in the photometric observations. Thus, due to our high photometric precision, we are sensitive to transits of possible short-period Neptune-mass planets that likely would have escaped detection by current radial velocity techniques. Our search of the APT data sets for 1087 program and comparison stars revealed no new transiting planets. However, the detection of several unknown grazing eclipsing binaries from among our comparison stars, with eclipse depths of only a few millimags, illustrates the success of our technique. We have used this negative result to place limits on the frequency of Neptune-mass planets in close orbits around solar-type stars in the Sun's vicinity.

Henry, Stephen M.↗
DOE OSTI2017

Development of a thermodynamic database for a new fuel alloy design

The scope of the FY17 milestone involved the development of a thermodynamic database for the Mo-Ti-Zr ternary system to support the design of new pseudo-binary actinide-M fuel alloy, where M is a ternary metallic additive composed of Mo, Ti and Zr. Optimization of thermodynamic parameters for the three binary subsystems, Mo-Zr, Mo-Ti and Zr-Ti, has been performed using the CALPHAD (CALculation of PHAse Diagrams) approach with inputs from both experiments gathered from the literature and density functional theory (DFT) total energy calculations performed in this work. Using the present database, the stability range of the bcc phase in the Mo-Ti-Zr ternary system is predicted and the results are in very good agreement with available experimental data at 600°C and 750°C. The present work can directly contribute to the future development of a multicomponent thermodynamic database for the quaternary U-Mo-Ti-Zr system.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2014

Fifty M31 black hole candidates identified by Chandra and XMM-Newton

Over approximately the last five years, we have identified ∼35 black hole candidates (BHCs) in M31 from their X-ray spectra. Our BHCs exhibited 0.3-10 keV spectra consistent with the X-ray binary (XB) hard state at luminosities that are above the upper limit for neutron star (NS) XBs. When our BHC spectra were modeled with a disk blackbody + blackbody model for comparison with bright NS XBs, we found that the BHCs inhabited a different parameter space than the NS XBs. However, BH XBs may also exhibit a thermally dominated (TD) state that has never been seen in NS XBs; this TD state is most often observed in X-ray transients. We examined the ∼50 X-ray transients in our Chandra survey of M31 and found 13 with spectra suitable for analysis. We also examined two BHCs outside the field of view of our survey in the globular clusters B045 and B375. We have 42 strong BHCs and 8 plausible BHCs that may benefit from further observation. Of our 15 BHCs in globular clusters, 12 differ from NS spectra by >5σ. Due to improvements in our analysis, we have upgraded 10 previously identified plausible BHCs to strong BHCs. The mean maximum duty cycle of the 33 X-ray transients within 6' of M31* is 0.13; we estimate that >40% of the XBs in this region contain BH accretors. Remarkably, we estimate that BHCs contribute >90% of those XBs >10{sup 38} erg s{sup –1}.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Implications of reduced-complexity aerosol thermodynamics on organic aerosol mass concentration and composition over North America

Atmospheric organic aerosol (OA) mass concentrations can be affected by water uptake through its impact on the gas–particle partitioning of semi-volatile compounds. Current chemical transport models (CTMs) neglect this process. We have implemented the Binary Activity Thermodynamics model coupled to a volatility basis set partitioning scheme in the GEOS-Chem CTM, providing an efficient reduced-complexity OA model that predicts relative-humidity-dependent mixing and partitioning thermodynamics, while limiting the impact on computational efficiency. We provide a quantitative assessment of this water-sensitive OA treatment, focusing on a subdomain over North America. The updated OA scheme predicts a spatiotemporal mean enhancement in surface-level OA mass concentration of 145 % for January 2019 and 76 % for July 2019 compared to GEOS-Chem's most advanced OA scheme. The temporal mean surface-level OA organic mass concentration can increase by up to ∼590 % for January 2019 and ∼280 % for July 2019, with the greatest enhancements occurring over the ocean. The updated OA scheme also quantifies the OA-associated water content. The simulations show how different OA precursors and related OA surrogates contribute and respond to water uptake, including that due to changes in temperature and relative humidity over the diurnal cycle in selected winter and summer months. These results are independent of future CTM improvements involving updates to chemical reaction schemes and emission inventories. Our water-sensitive OA scheme allows for a better representation of the seasonal and regional variations in OA mass concentration in CTMs.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2019

Sodium Pumping via Condensation within a Non-Wetting Porous Structure

The transfer of liquid sodium from a low-pressure condenser to a high-pressure evaporator is required to complete the thermodynamic cycle of a sodium thermal electrochemical converter (Na-TEC). A unique capillary pump is explored in this work, whereby low-pressure sodium vapor is condensed within a non-wetting (i.e. contact angle > pi/2) stainless steel porous structure. Due to the curvature of the non-wetting liquid-vapor interface, the liquid adjacent to the interface is at a higher pressure than the vapor. This is in contrast to traditional wicks, where the liquid adjacent to the interface has a lower pressure. Conjugate heat transfer techniques are used to model the coupled momentum and thermal transport processes within this non-wetting porous structure. Due to the low mass flowrates in the Na-TEC (< 0.1 mg/s), higher order friction terms are neglected and the classical Darcy’s law is used for the non-isothermal, compressible vapor flow. At lower temperatures, the sodium vapor density becomes sufficiently small and there is a transition from classic Poiseuille flow (Kn < 0.1) to Knudsen flow (Kn > 10). Furthermore, transport due to binary diffusion is also considered for situations where there is a substantial presence of non-condensable argon in the sodium vapor plenum. Initial modeling results showing expected mass flowrates, temperature profiles, and liquid-vapor interface locations are presented for various physical conditions. The main design features of an experimental set-up used to demonstrate this capillary pumping is also described in detail, including the method used to measure the low sodium mass flowrates. Initial experimental results demonstrating sodium pumping for a range of temperatures (800K – 1100K) will be presented and compared against the model predictions. Finally, several of the challenges with this experiment will be discussed, and specific strategies used to address these are presented.

14 SOLAR ENERGY↗
DOE OSTI2020

Candidate Periodically Variable Quasars from the Dark Energy Survey and the Sloan Digital Sky Survey

Periodically variable quasars have been suggested as close binary supermassive black holes. We present a systematic search for periodic light curves in 625 spectroscopically confirmed quasars with a median redshift of 1.8 in a 4.6 deg 2 overlapping region of the Dark Energy Survey Supernova (DES-SN) fields and the Sloan Digital Sky Survey Stripe 82 (SDSS-S82). Our sample has a unique 20-year long multi-color ( griz ) light curve enabled by combining DES-SN Y6 observations with archival SDSS-S82 data. The deep imaging allows us to search for periodic light curves in less luminous quasars (down to r ~23.5 mag) powered by less massive black holes (with masses ≳ 10 8.5 M ⊙ ) at high redshift for the first time. We find five candidates with significant (at >99.74% single-frequency significance in at least two bands with a global p-value of ~7 × 10 -4 –3× 10 -3 accounting for the look-elsewhere effect) periodicity with observed periods of ~3–5 years (i.e., 1–2 years in rest frame) having ~4–6 cycles spanned by the observations. If all five candidates are periodically variable quasars, this translates into a detection rate of |${\sim }0.8^{+0.5}_{-0.3}$| % or |${\sim }1.1^{+0.7}_{-0.5}$| quasar per deg 2 . Our detection rate is 4–80 times larger than those found by previous searches using shallower surveys over larger areas. This discrepancy is likely caused by differences in the quasar populations probed and the survey data qualities. Furthermore, we discuss implications on the future direct detection of low-frequency gravitational waves. Additionally, continued photometric monitoring will further assess the robustness and characteristics of these candidate periodic quasars to determine their physical origins.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Biogeochemical cycling at the aquatic–terrestrial interface is linked to parafluvial hyporheic zone inundation history

Abstract. The parafluvial hyporheic zone combines the heightened biogeochemical and microbial interactions indicative of a hyporheic region with direct atmospheric/terrestrial inputs and the effects of wet–dry cycles. Therefore, understanding biogeochemical cycling and microbial interactions in this ecotone is fundamental to understanding biogeochemical cycling at the aquatic–terrestrial interface and to creating robust hydrobiogeochemical models of dynamic river corridors. We aimed to (i) characterize biogeochemical and microbial differences in the parafluvial hyporheic zone across a small spatial domain (6 lateral meters) that spans a breadth of inundation histories and (ii) examine how parafluvial hyporheic sediments respond to laboratory-simulated re-inundation. Surface sediment was collected at four elevations along transects perpendicular to flow of the Columbia River, eastern WA, USA. The sediments were inundated by the river 0, 13, 127, and 398 days prior to sampling. Spatial variation in environmental variables (organic matter, moisture, nitrate, glucose, % C, % N) and microbial communities (16S and internal transcribed spacer (ITS) rRNA gene sequencing, qPCR) were driven by differences in inundation history. Microbial respiration did not differ significantly across inundation histories prior to forced inundation in laboratory incubations. Forced inundation suppressed microbial respiration across all histories, but the degree of suppression was dramatically different between the sediments saturated and unsaturated at the time of sample collection, indicating a binary threshold response to re-inundation. We present a conceptual model in which irregular hydrologic fluctuations facilitate microbial communities adapted to local conditions and a relatively high flux of CO2. Upon rewetting, microbial communities are initially suppressed metabolically, which results in lower CO2 flux rates primarily due to suppression of fungal respiration. Following prolonged inundation, the microbial community adapts to saturation by shifting composition, and the CO2 flux rebounds to prior levels due to the subsequent change in respiration. Our results indicate that the time between inundation events can push the system into alternate states: we suggest (i) that, above some threshold of inundation interval, re-inundation suppresses respiration to a consistent, low rate and (ii) that, below some inundation interval, re-inundation has a minor effect on respiration. Extending reactive transport models to capture processes that govern such dynamics will provide more robust predictions of river corridor biogeochemical function under altered surface water flow regimes in both managed and natural watersheds.

58 GEOSCIENCES↗
NASA NTRS2023

Phytoplankton Diversity and Chemotaxonomy in Contrasting North Pacific Ecosystems

Background. Phytoplankton is the base of majority of ocean ecosystems. It is responsible for half of the global primary production, and different phytoplankton taxa have a unique role in global biogeochemical cycles. In addition, phytoplankton abundance and diversity are highly susceptible to climate induced changes, hence monitoring of phytoplankton and its diversity is important and necessary. Methods. Water samples for phytoplankton and photosynthetic pigment analyses were collected in boreal winter 2017, along transect in the North Pacific Subtropical Gyre (NPSG) and the California Current System (CCS). Phytoplankton community was analyzed using light and scanning electron microscopy and photosynthetic pigments by high-performance liquid chromatography. To describe distinct ecosystems, monthly average satellite data of MODIS Aqua Sea Surface temperature and Chlorophyll a concentration, as well as Apparent Visible Wavelength were used. Results. A total of 207 taxa have been determined, mostly comprised of coccolithophores (35.5%), diatoms (25.2%) and dinoflagellates (19.5%) while cryptophytes, phytoflagellates and silicoflagellates were included in the group ``others" (19.8%). Phytoplankton spatial distribution was distinct, indicating variable planktonic dispersal rates and specific adaptation to ecosystems. Dinoflagellates, and nano-scale coccolithophores dominated NPSG, while micro-scale diatoms, and cryptophytes prevailed in CCS. A clear split between CCS and NPSG is evident in dendogram visualising LINKTREE constrained binary divisive clustering analysis done on phytoplankton counts and pigment oncentrations. Of all pigments determined, alloxanthin, zeaxanthin, divinyl chlorophyll b and lutein have highest correlation to phytoplankton counts. Conclusion. Combining chemotaxonomy and microscopy is an optimal method to determine phytoplankton diversity on a large-scale transect. Distinct communities between the two contrasting ecosystems of North Pacific reveal phytoplankton groups specific adaptations to trophic state, and support the hypothesis of shift from microto nano-scale taxa due to sea surface temperatures rising, favoring stratification and oligotrophic conditions.

oceanography↗
DOE OSTI2016

Facile, ethylene glycol-promoted microwave-assisted solvothermal synthesis of high-performance LiCoPO 4 as a high-voltage cathode material for lithium-ion batteries

Olivine-type LiCoPO 4 is considered a promising high-voltage cathode material for next-generation lithium-ion batteries. However, preparing high-performance LiCoPO 4 by a simple approach has been challenging. Herein, we present a facile and rapid (30 min) one-step microwave-assisted solvothermal synthesis route using a 1 : 1 (v/v) water/ethylene glycol (EG) binary solvent mixture and a temperature of 250 °C. Here, the technique delivers high-performance LiCoPO4nanoparticles without additional post-annealing or carbon coating steps. The as-prepared powder consists of single crystalline LiCoPO 4 and features a hexagonal platelet-like morphology with dimensions of 700-800 nm × 400-600 nm × 100-220 nm. Selected area electron diffraction (SAED) experiments reveal that the platelets show the smallest dimension along [010], which is the direction of the lithium diffusion pathways in the olivine crystal structure. Furthermore, the results indicate that the EG co-solvent plays an important role in tailoring the particle size, morphology, and crystal orientation of the material. Co L-edge soft X-ray absorption spectroscopy (XAS) of LiCoPO 4 are presented for the first time and confirm that the material only consists of Co 2+ . Benefiting from the unique morphology, which facilitates Li-ion conduction, electrochemical measurements deliver an initial discharge capacity of 137 mA h g -1 at 0.1 C, a remarkably stable capacity retention of 68% after 100 cycles at 0.5 C, and a specific energy density of 658 W h kg -1 based on its capacity and voltage, which is the best performance of LiCoPO 4 obtained from microwave-assisted solvothermal synthesis to date.

36 MATERIALS SCIENCE↗
NASA NTRS1994

The X-ray selected cataclysmic variables H0459 + 246 and H0857 - 242

We report the discovery of two cataclysmic variables located with the assistance of X-ray positions from the HEAO 1 Modulation Collimator and the Large-Area Sky Survey. Each case is distinguished by evidence of two periodic modulations that appear to represent the orbital period and the spin period of the white dwarf, respectively. The first case, H0459 + 246, has been observed optically during faint states (V approximately 16), in which there are spectral features of both an accretion disk and a K star. The light curves in the V and I bands are consistent with ellipsoidal variations in the secondary stars with a binary period of 9.952 hr. X-ray observations with EXOSAT reveal a strong pulsation with a period approximately 62 minutes. This result confirms an 'intermediate polar' classification for H0459 + 246. The pulsation is observed at 63.2 minutes in the optical I band. The long orbital period opens the possibility that H0459 + 246 is a relatively young intermediate polar that might evolve into a polar. The second case, H0857--242, shows radial velocity modulations at 1.78 hr along with photometric variations at a period approximately 49 minutes. The latter are observed only during the decay phase of dwarf nova outbursts (13 less than V less than 17), which apparently recur frequently. Given the lack of X-ray monitoring observations and the absence of proof that the 49 minute periodicity is coherent over long time-scales, we regard H0857--242 as a candidate intermediate polar. Photographic records from th e Harvard Observatory Plate Library further reveal superoutbursts for H0857--242 (V approximately 11). A bright X-ray source that is both an intermediate polar and a continually cycling dwarf nova may provide an effective means of measuring the time delay for the arrival of accreting matter at the white dwarf surface, relative to the onset of optical brightening.

Remillard, R. A.↗
NASA NTRS1991

Decrease in the Orbital Period of Hercules X-1

From a pulse-timing analysis of Ginga observations of the binary X-ray pulsar Her X-1 obtained during the interval 1989 April-June we have determined local orbital parameters for a Short High state. We have also determined an orbital epoch in the adjacent Main High state. By comparing these orbital solutions with previously published results, we have detected a decrease in the orbital period for Her X-1 at an average rate of dot-P/P = (- 1.32 +/- 0.16) x 10(exp -8) yr(exp -1) over the interval 1971-1989. This is substantially larger than the value predicted from current estimates of the mass transfer rate, and motivates consideration of other mechanisms of mass transfer and/or mass loss. A second result from these observations is a close agreement between orbital parameters determined separately in Main High and Short High states. This agreement places strong constraints on the obliquity of the stellar companion, HZ Her, if undergoing forced precession with a 35 day period. As a consequence further doubt is placed on the slaved-disk model as the underlying cause of the 35 day cycle in Her X-1.

Deeter, John E.↗
NASA NTRS1997

ASCA Observations of the Barnard 209 Dark Cloud and an Intense X-Ray Flare on V773 Tauri

ASCA (Advanced Satellite for Cosmology and Astrophysics) detected an intense X-ray flare on the weak-lined T Tauri star V773 Tau (=HD 283447) during a 30 ks observation of the Barnard 209 dark cloud in 1995 September. This star is a spectroscopic binary and shows signs of strong magnetic surface activity including a spot-modulated optical light curve. The flare was seen only during its decay phase but is still one of the strongest ever recorded from a T Tauri star with a peak luminosity L(sub x) = 10(exp 32.4) ergs/s (0.5-10 keV), a maximum temperature of at least 42 million K, and energy release of greater than 10(exp 37) ergs. A shorter ASCA observation taken five months later showed V773 Tau in a quiescent state (L(sub x)= 10(exp 31.0) ergs/s) and detected variable emission from the infrared binary IRAS 04113+2758. The differential emission measure (DEM) distribution during the V773 Tau flare shows a bimodal temperature structure that is almost totally dominated by hot plasma at an average temperature of approx. 37 million K. Using information from time-resolved spectra, we examine the flare decay in terms of solar flare models (cooling loops and two-ribbon flares) and also consider possible nonsolar behavior (interbinary flares, star-disk flares, and rotational X-ray modulation). Solar models are unable to reproduce the unusual convex-shaped X-ray light curve, which decays slowly over a timespan of at least 1 day. However, the light curve decay is accurately modeled as a sinusoid with an inferred X-ray period of 2.97 days, which is nearly identical to the optical rotation period(s) of the two K-type components. This provides tantalizing evidence that the flaring region was undergoing rotational occultation, but periodic X-ray variability is not yet proven since our ASCA observation spans only one-third of a rotation cycle.

Skinner, Stephen L.↗
DOE OSTI2018

Organic Speciation and Interactions in ALSEP. One Step Partitioning Process of MinorActinides, Lanthanides, and Fission Products

Research conducted in this project focused on speciation characterization of the ALSEP extraction system (similar to the TALSPEAK-like application) which addresses recovery of minor actinides and lanthanides from PUREX raffinate. The ALSEP (Actinide-Lanthanide Separation) system proposes a trivalent minor actinide/lanthanide group extraction followed by a selective actinide strip to effectively partition minor actinides, lanthanides, and other fission products. The group extraction is achieved by a mixed organic solvent, combining acidic and neutral extracting ligands. The objective of this work is investigation the interactions of the acidic and neutral ligands with each other in the extraction organic solvent and with desired metals. Four combinations of a cation-exchange ligand (either HDEHP or HEH[EHP]) and a neutral solvating ligand (either TODGA or T2EHDGA) in n-dodecane were studied. Interligand dimers in these combinations were investigated with NMR and FTIR, the strongest interaction was observed for HDEHP+TODGA and weakest for T2EHDGA+HEH[EHP]. Complexes of the trivalent Am and lanthanides Nd, Eu, Ho, Pr in these binary ligand mixtures were probed with spectroscopic (UV–vis, time-resolved fluorescence, XAFS and SAXS-spectroscopies) and extraction (Job’s plot, slope analysis) methods; co-extracted water and nitric acid were analyzed by titration methods. Comparison of the collected spectra showed significant shifting for both DGA ligands with HDEHP, while both combinations of HEH[EHP]+DGA displayed much smaller spectral changes. Data were modeled with HypSpec program, and stability constants for extracted complexes were calculated. Aggregation in these systems were studied by SAXS (small-angle X-ray scattering) spectroscopy and interfacial tension, size of aggregates were measured. Two PhD students graduated (2017, 2018) and one student continues her PhD study.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

FY21 Status Report on the Molten Salt Thermal Properties Database (MSTDB) Development

This report describes the thermodynamic assessments for the ZrF 4 -BeF 2 , AlCl 3 -NaCl, AlCl3-KCl and the PuCl 3 -CsCl pseudo-binary subsystems. Calculation results are compared to the inputs used to optimize the adjustable model parameters. The data came from experimental studies reported in the open literature, from the MSR research community, and/or computational results generated within the NEAMS program and from collaborators. The models from the thermodynamic assessment of these salt systems are integrated into the MSTDB-TC (Molten Salt Thermal Properties Database-Thermochemical). A brief description of the companion MSTDB-TP (Molten Salt Thermal Properties Database-Thermophysical) is given along with an overview of the approach for predicting both thermodynamic and thermophysical property behavior of multicomponent systems.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS2004

Signal Design for Improved Ranging Among Multiple Transceivers

"Ultra-BOC" (where "BOC" signifies "binary offset carrier") is the name of an improved generic design of microwave signals to be used by a group of spacecraft flying in formation to measure ranges and bearings among themselves and to exchange telemetry needed for these measurements. Ultra-BOC could also be applied on Earth for diverse purposes -- for example, measuring relative positions of vehicles on highways for traffic-control purposes and determining the relative alignments of machines operating in mines and of construction machines and structures at construction sites. Ultra-BOC provides for rapid and robust acquisition of signals, even when signal-to-noise ratios are low. The design further provides that each spacecraft or other platform constantly strives to acquire and track the signals from the other platforms while simultaneously transmitting signals that provide full range, bearing, and telemetry service to the other platforms. In Ultra-BOC, unlike in other signal designs that have been considered for the same purposes, it is not necessary to maneuver the spacecraft or other platforms to obtain the data needed for resolving integer-carrier-cycle phase ambiguities.

Young, Lawrence↗