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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Analysis Of 2h-Evaporator Scale Wall [HTF-13-82] And Pot Bottom [HTF-13-77] Samples

Savannah River Remediation (SRR) is planning to remove a buildup of sodium aluminosilicate scale from the 2H-evaporator pot by loading and soaking the pot with heated 1.5 M nitric acid solution. Sampling and analysis of the scale material has been performed so that uranium and plutonium isotopic analysis can be input into a Nuclear Criticality Safety Assessment (NCSA) for scale removal by chemical cleaning. Historically, since the operation of the Defense Waste Processing Facility (DWPF), silicon in the DWPF recycle stream combines with aluminum in the typical tank farm supernate to form sodium aluminosilicate scale mineral deposits in the 2Hevaporator pot and gravity drain line. The 2H-evaporator scale samples analyzed by Savannah River National Laboratory (SRNL) came from the bottom cone sections of the 2H-evaporator pot [Sample HTF-13-77] and the wall 2H-evaporator [sample HTF-13-82]. X-ray diffraction analysis (XRD) confirmed that both the 2H-evaporator pot scale and the wall samples consist of nitrated cancrinite (a crystalline sodium aluminosilicate solid) and clarkeite (a uranium oxy-hydroxide mineral). On “as received” basis, the bottom pot section scale sample contained an average of 2.59E+00 ± 1.40E-01 wt % total uranium with a U-235 enrichment of 6.12E-01 ± 1.48E-02 %, while the wall sample contained an average of 4.03E+00 ± 9.79E-01 wt % total uranium with a U-235 enrichment of 6.03E-01% ± 1.66E-02 wt %. The bottom pot section scale sample analyses results for Pu-238, Pu-239, and Pu-241 are 3.16E- 05 ± 5.40E-06 wt %, 3.28E-04 ± 1.45E-05 wt %, and <8.80E-07 wt %, respectively. The evaporator wall scale samples analysis values for Pu-238, Pu-239, and Pu-241 averages 3.74E-05 ± 6.01E-06 wt %, 4.38E-04 ± 5.08E-05 wt %, and <1.38E-06 wt %, respectively. The Pu-241 analyses results, as presented, are upper limit values. These results are provided so that SRR can calculate the equivalent uranium-235 concentrations for the NCSA. Results confirm that the uranium contained in the scale remains depleted with respect to natural uranium. SRNL did not calculate an equivalent U-235 enrichment, which takes into account other fissionable isotopes U-233, Pu-239 and Pu-241. The applicable method for calculation of equivalent U-235 will be determined in the NCSA.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1990

Dual-polarization airborne lidar observations of polar stratospheric cloud evolution

Dual-polarization 0.532 micron lidar data show systematic polar stratospheric cloud (PSC) evolution along a portion of the Airborne Arctic Stratospheric Expedition DC-8 flight of January 31, 1989. This flight leg was roughly aligned with air parcel motion on isentropic surfaces from 400-500 K, where the local adiabatic cooling rate was about 20 K/day. Type 1 PSCs show low depolarization ratios and scattering ratios which approach intermediate limiting values as ambient temperature decreases. These data suggest that Type 1 particles formed by rapid cooling may be nearly spherical and are restricted in size by partitioning of a limited HNO3 vapor supply among many competing growth sites. Type 2 PSCs appear at temperatures below estimated local frost points with increases in depolarization and scattering typical of larger ice crystals.

Poole, L. R.↗
NASA NTRS1983

Recent progress in the application of satellite altimetry to observing the mesoscale variability and general circulation of the oceans

The application of GEOS-3 and Seasat altimeter data to the study of mesoscale variability and general circulation in the oceans is discussed in a survey of recent investigations. Seasat provided much more accurate measurements, but lasted only 3.5 months (compared to 3.5 years for GEOS-3). General-circulation studies are shown to be strongly dependent on an accurate geoid, which has not yet been developed; hence even large-wave-length (7000-km) mapping is of limited value. Geoid-independent methods allow the global mapping of mesoscale sea-surface height and geostrophic current and the analysis of their distribution in wavenumber space, at least to the limits allowed by the accuracy of the instruments. These studies demonstrate the feasibility of future satellite-altimeter measurements of variability over a wide range of periods and wavelengths, which if combined with improved mapping of the earth's gravity field) would permit the determination of the general circulation on scales as small as 200 km.

Fu, L.-L.↗
DOE OSTI2014

Phase portraits analysis of a barothropic system: The initial value problem

In this paper, we investigate the phase portraits features of a barothropic relaxing medium under pressure perturbations. In the starting point, we show within a third-order of accuracy that the previous system is modeled by a “dissipative” cubic nonlinear evolution equation. Paying particular attention to high-frequency perturbations of the system, we solve the initial value problem of the system both analytically and numerically while unveiling the existence of localized multivalued waveguide channels. Accordingly, we find that the “dissipative” term with a “dissipative” parameter less than some limit value does not destroy the ambiguous solutions. We address some physical implications of the results obtained previously.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Mercury Dispersion Modeling and Purge Ventilation Stack Height Determination for Tank 41H

The SRNL Atmospheric Technologies Group performed an analysis of mercury emissions from H-Tank Farm – Tank 41H ventilation system exhaust to assess worst case 15-minute and 8-hour average ground level concentrations and evaluate whether the Short-Term Exposure Limit (STEL), or Threshold Limit Value (TLV) levels for mercury will be exceeded during mixing operations. This analysis was also used to establish a minimum stack height at which ambient mercury concentration would not exceed the safety limits. The American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) was used as the dispersion modelling tool for this analysis. Results indicate that a stack height of 30-ft (for the 25 mg/m 3 emissions case) or 50-ft (for the 50 mg/m 3 emissions case) stacks results in ground level concentrations that do not exceed the STEL or TLV standards.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2018

Mercury Dispersion Modeling 242-25H Evaporator Portable Backup Ventilation

The SRNL Atmospheric Technologies Group performed an analysis of mercury emissions from the H-Tank Farm 242-25H Evaporator backup ventilation system exhaust to assess worst case15-minute and 8-hour average concentrations and evaluate whether the ACIGH Short-Term Exposure Limit (STEL), or Threshold Limit Value (TLV) levels for mercury are exceeded following a seismic event. This analysis was also used to establish a minimum stack height at which ambient mercury concentration would not exceed the regulatory limits. The American Meteorological Society/Environmental Protection Agency Regulatory Model (AERMOD) was used as the dispersion modelling tool for this analysis. Results indicate that a stack height of 20 ft result in ground level concentrations that exceed the STEL or TLV standards at ground level only in the areas immediately around the stack, and generally on the slope of the hill beneath the 242-25H and 242-9H buildings.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS2003

Step Bunch Evolution on Vicinal Faces of KDP

For in-situ studies of the formation and evolution of step patterns in solution growth, we have assembled an experimental setup based on Michelson interferometry with the growing crystal surface as one of the reflective surfaces. The device allows data collection over a relatively large area (approximately 4 sq. mm) in situ and in real time during growth. The depth resolution is improved over traditional interferometry using phase-shifted images combining by a suitable algorithm. We achieve a depth resolution of approximately 50 Angstroms. Lateral resolution, dependent on the degree of magnification, is around 0.3 to 5 microns. The crystal chosen as a model in this work is potassium dihydrogen phosphate (KDP), the optically non-linear material widely used in frequency doubling applications. Kinetics of KDP crystallization is well studied so that KDP can serve as a benchmark for our investigations. We present quantitative results on the onset, initial stages and development of instabilities in moving step trains on vicinal crystal surfaces at varying supersaturation, flow rate, and flow direction. The kinetics data suggest that at low supersaturations, step bunching is caused by impurity retardation of the steps, while at higher supersaturations, we link the non-linearity during growth to interdependence of the velocity and density of the steps evidenced in independent experiments. The behavior on the surface is very dynamic, small bunches both merge and split from larger bunches as they travel across the facet. We present evidence that despite these dynamics, under steady conditions there exists a limiting value to step bunch height. This height is reached at distances between 600 and 1000 microns from the step source. In our experiments, we observed the retention of this step bunch height limit up to the path of 1500 microns.

Booth, N. A.↗
DOE OSTI2018

Creating metamaterial building blocks with directed photochemical metallization of silver onto DNA origami templates

Here, DNA origami can be used to create a variety of complex and geometrically unique nanostructures that can be further modified to produce building blocks for applications such as in optical metamaterials. We describe a method for creating metal-coated nanostructures using DNA origami templates and a photochemical metallization technique. Triangular DNA origami forms were fabricated and coated with a thin metal layer by photochemical silver reduction while in solution or supported on a surface. The DNA origami template serves as a localized photosensitizer to facilitate reduction of silver ions directly from solution onto the DNA surface. The metallizing process is shown to result in a conformal metal coating, which grows in height to a self-limiting value with increasing photoreduction steps. Although this coating process results in a slight decrease in the triangle dimensions, the overall template shape is retained. Notably, this coating method exhibits characteristics of self-limiting and defect-filling growth, which results in a metal nanostructure that maps the shape of the original DNA template with a continuous and uniform metal layer and stops growing once all available DNA sites are exhausted.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1974

Elastic moduli of precompressed pyrophyllite used in ultrahigh pressure research

The propagation of ultrasonic pulses in pyrophyllite specimens was studied to determine the effect of specimen precompression on the measured elastic moduli. Measurements were made at room pressure and, for the precompressed specimens, to pressures of 3 kbar. Pyrophyllite was found to be elastically anisotropic, apparently the result of the fabric present in our material. The room pressure adiabatic bulk modulus as measured on specimens made of isostatically compacted powered pyrophyllite was determined to be 96.1 kbar. The wave speeds of ultrasonic pulses in pyrophyllite were found to decrease with increasing specimen precompression. A limiting value of precompression was found, above which no further decrease in wave speed was observed. For the shear wave speeds this occurs at 10 kbar while for the longitudinal wave at 25 kbar. In the limit, the shear waves propagate 20% slower than in the unprecompressed samples; for the longitudinal wave the difference is 30%.

Sachse, W.↗
NASA NTRS1993

Universal characteristics of transverse momentum transfer in intermediate energy heavy ion collisions

A microscopic optical model formalism for estimating momentum transfer in intermediate energy heavy ion collisions predicts universal behavior of the transverse component. In particular, for symmetric systems heavier than niobium, it appears that values of P(perpendicular)/A are independent of the mass and charge of the colliding nuclei and vary only with impact parameter and incident beam energy. This suggests that momentum transfer per nucleon saturates to some limiting value with increasing mass.

Khan, F.↗
NASA NTRS1975

Flow field characteristics and performance limitations of quasi-steady magnetoplasmadynamic accelerators

Measurements of terminal voltage, exhaust velocity, current and potential distributions in a quasi-steady MPD arc operating over a range of currents from 3 to 25 kA countervene previous indications of basic limitations on MPD performance. Terminal voltage fluctuations, previously used as an indicator of a unique limiting value of the parameter current squared over mass flow, are shown to be related to cathode surface area rather than to interelectrode plasma phenomena. With improved electrodes and insulators, satisfactory arc operation at specific impulses somewhat beyond previously proposed limits has been demonstrated, and the significant thrust producing mechanisms in such arcs have been identified.

Boyle, M. J.↗
NASA NTRS1981

On the correlation between objective measurements and subjectively felt disturbance from traffic

Measurements of traffic noise during the day were taken at 90 measurement points over the urban area of Vienna; in addition, the vehicle frequency ascertained at the individual measurement points was also noted. Results of these objective measurements or various characteristic single values derived from them are compared with the results of the environmental survey of 1973 on the subjective noise stress experienced within buildings but caused by outside factors. Suggestions for suitable measures to describe the traffic noise and to derive limit values are given considering the relationship between number of vehicles and noise and annoyance.

Lans, J.↗
NASA NTRS1972

Particle-flux limits in the synchronous orbit.

Examination of measurements of 40- and 75-keV electrons and 60and 120-keV protons on the ATS 5 satellite in synchronous orbit in order to show that fluxes of such particles often approach but rarely exceed limiting values that agree within a factor of about 2 with the fluxes predicted by Kennel and Petschek (1966) from consideration of whistler-mode wave-particle interactions. A study is made of the proton and electron fluxes for evidence of the stably trapped flux limits in order to determine them, and to study the local-time dependences of their existence.

Mozer, F. S.↗
NASA NTRS1983

A deficiency of O III in the Io plasma torus

Evidence for a deficiency of O III ions in the Io plasma torus is reported and implications of this deficiency for the physical processes controlling the plasma are considered. Observations of the O III 5007-A as well as Cl III and S III emissions from the Io plasma torus were made by a ground-based echelle spectrograph and intensified Reticon detector in February and May, 1981. The O III observations allow an upper limit of 4/cu cm to be placed on torus O III abundance, which is inconsistent with expectations for a low density plasma controlled by electron collisions. The inclusion of ion-ion and ion-atom charge exchange reactions and a depleted high energy electron component in the model is found to suppress O III levels, however observed limiting values are only achieved if it is assumed that the O III is kinetically hot. In addition, the charge-exchange model developed is inconsistent with previous observations of the kinetics of the S II-S III system. The present observations also establish upper limits of 2 R on 5518-A and 5538-A Cl III emission, and an emission rate of 58 + or - 40 R for the S III 6312-A line in the hot torus.

Brown, R. A.↗
DOE OSTI2015

Formation of correlated states and optimization of nuclear reactions for low-energy particles at nonresonant low-frequency modulation of a potential well

A method for the formation of correlated coherent states of low-energy particles in a parabolic potential well owing to the full-scale low-frequency modulation ω(t) = ω{sub 0}sinΩt of the parameters of this well has been considered. It has been shown that such a modulation in the absence of a stochastic force acting on a particle results in the fast formation of correlated coherent states and in an increase in the correlation coefficient and transparency of the potential barrier to the limiting values vertical bar r(t) vertical bar {sub max} → 1 and D → 1. The presence of the stochastic force significantly affects the evolution of correlated coherent states, decreasing the rate of an increase in the correlation coefficient vertical bar r(t) vertical bar {sub max} (at Ω ≤ 10{sup −4}ω{sub 0}) and limiting it at the level vertical bar r(∞) vertical bar {sub max} < 1 (at Ω = (0.001–0.1)ω{sub 0}); vertical bar r(∞) vertical bar {sub max} increases with a decrease in the frequency of modulation and decreases with an increase in the intensity of the stochastic force. It has been shown that, at a realistic relation between the parameters, low-frequency modulation can ensure such vertical bar r vertical bar {sub max} value that the transparency of the potential barrier for low-energy particles increases by a factor of 10{sup 50}–10{sup 100} or larger. The mechanism of the formation of correlated coherent states for charged particles in a gas or a low-pressure plasma placed in a low-frequency magnetic field has been considered. We have determined the relation between the magnetic field strength and modulation frequency, as well as the relation between the temperature and density of the gas (plasma), at which the method under consideration can be used to optimize nuclear reactions at low energies.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2013

Adaptive Control for Linear Uncertain Systems with Unmodeled Dynamics Revisited via Optimal Control Modification

This paper presents the optimal control modification for linear uncertain plants. The Lyapunov analysis shows that the modification parameter has a limiting value depending on the nature of the uncertainty. The optimal control modification exhibits a linear asymptotic property that enables it to be analyzed in a linear time invariant framework for linear uncertain plants. The linear asymptotic property shows that the closed-loop plants in the limit possess a scaled input-output mapping. Using this property, we can derive an analytical closed-loop transfer function in the limit as the adaptive gain tends to infinity. The paper revisits the Rohrs counterexample problem that illustrates the nature of non-robustness of model-reference adaptive control in the presence of unmodeled dynamics. An analytical approach is developed to compute exactly the modification parameter for the optimal control modification that stabilizes the plant in the Rohrs counterexample. The linear asymptotic property is also used to address output feedback adaptive control for non-minimum phase plants with a relative degree 1.

Unmodeled Dynamics↗
NASA NTRS2023

Remotely Sensed Soil Moisture Can Capture Dynamics Relevant to Plant Water Uptake

A frequently expressed viewpoint across the Earth science community is that global soil moisture estimates from satellite L-band (1.4 GHz) measurements represent moisture only in a shallow surface layer (0–5 cm) and consequently are of limited value for studying global terrestrial ecosystems because plants use water from deeper rootzones. Using this argumentation, many observation-based land surface studies avoid satellite-observed soil moisture. Here, based on peer-reviewed literature across several fields, we argue that such a viewpoint is overly limiting for two reasons. First, microwave soil emission depth considerations and statistical considerations of vertically correlated soil moisture information together indicate that L-band measurements carry information about soil moisture extending below the commonly referenced 5 cm in many conditions. However, spatial variations of effective depths of representation remain uncertain. Second, in reviewing isotopic tracer field studies of plant water uptake, we find a prevalence of vegetation that primarily draws moisture from these upper soil layers. This is especially true for grasslands and croplands covering more than a third of global vegetated surfaces. Even some deeper-rooted species (i.e., shrubs and trees) preferentially or seasonally draw water from the upper soil layers. Therefore, L-band satellite soil moisture estimates are more relevant to global vegetation water uptake than commonly appreciated (i.e., relevant beyond only shallow soil processes like soil evaporation). Our commentary encourages the application of satellite soil moisture across a broader range of terrestrial hydrosphere and biosphere studies while urging more rigorous estimates of its effective depth of representation.

Andrew F. Feldman↗
DOE OSTI2012

A Comparison of "Total Dust" and Inhalable Personal Sampling for Beryllium Exposure

In 2009, the American Conference of Governmental Industrial Hygienists (ACGIH) reduced the Beryllium (Be) 8-hr Time Weighted Average Threshold Limit Value (TLV-TWA) from 2.0 μg/m 3 to 0.05 μg/m 3 with an inhalable 'I' designation in accordance with ACGIH's particle size-selective criterion for inhalable mass. Currently, per the Department of Energy (DOE) requirements, the Lawrence Livermore National Laboratory (LLNL) is following the Occupational Health and Safety Administration (OSHA) Permissible Exposure Limit (PEL) of 2.0 μg/m 3 as an 8-hr TWA, which is also the 2005 ACGIH TLV-TWA, and an Action Level (AL) of 0.2 μg/m 3 and sampling is performed using the 37mm (total dust) sampling method. Since DOE is considering adopting the newer 2009 TLV guidelines, the goal of this study was to determine if the current method of sampling using the 37mm (total dust) sampler would produce results that are comparable to what would be measured using the IOM (inhalable) sampler specific to the application of high energy explosive work at LLNL's remote experimental test facility at Site 300. Side-by-side personal sampling using the two samplers was performed over an approximately two-week period during chamber re-entry and cleanup procedures following detonation of an explosive assembly containing Beryllium (Be). The average ratio of personal sampling results for the IOM (inhalable) vs. 37-mm (total dust) sampler was 1.1:1 with a P-value of 0.62, indicating that there was no statistically significant difference in the performance of the two samplers. Therefore, for the type of activity monitored during this study, the 37-mm sampling cassette would be considered a suitable alternative to the IOM sampler for collecting inhalable particulate matter, which is important given the many practical and economic advantages that it presents. However, similar comparison studies would be necessary for this conclusion to be applied to other types of activities, where earlier studies have shown that the IOM sampler tends to collect higher concentrations of Be compared to the 37-mm cassette, which could complicate compliance with what is already an extremely low exposure limit.

99 GENERAL AND MISCELLANEOUS↗