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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Applicability of Public Dose Limits to Individuals on the Nevada National Security Site

Historically all persons working on the Nevada National Security Site (NNSS) were considered subject to worker dose limits when calculations of potential dose from the air pathway were conducted to demonstrate compliance with Title 42 United States Code (USC) Chapter 85, “The Clean Air Act,” and Title 40 Code of Federal Regulations (CFR) Part 61, Subpart H, “National Emission Standards for Hazardous Air Pollutants (NESHAP).” Calculations were also conducted for the all-pathways potential dose to demonstrate compliance with U.S. Department of Energy (DOE) Order DOE O 458.1 Chg. 3, “Radiation Protection of the Public and the Environment.” The need to evaluate environmental air sampling locations and past regulator questions about the existence of persons potentially subject to public dose limits being on the NNSS drove this assessment (letter from EPA [U.S. Environmental Protection Agency] Region 9 to DOE/Nevada Operations Office, dated September 3, 1999). This assessment also supports determining those persons subject to public dose limits from the all pathways perspective. A person that is a member of the public is subject to public dose limits.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2024

The Delicate Balance Redux: The Role of Nuclear Forces, Damage Limitation and Uncertainty in Future U.S.-China Crises

What is the impact of damage limitation capabilities like counterforce and missile defenses on deterrence, when their efficacy in stopping an adversary nuclear attack is uncertain? This is a key unanswered question to understand “how much is enough” for the United States to deter China and Russia in future nuclear crises. In this paper we extend an established, single move game theory model to capture the dynamics of two players in a nuclear crisis having varying damage limitation capabilities with uncertain effectiveness. Our model formalizes the logic of the “delicate balance” school of deterrence, which states that leverage in a crisis is driven by the risk each player can take with their combined strategic forces, and that those risks carry uncertainty as nuclear forces are hard to deliver against technologically advanced adversaries. Our model shows that damage limitation capabilities—even those with significant uncertainty around them like cyber or electronic warfare—can drive bargaining outcomes in an array of nuclear crises. We then apply these bargaining outcomes to the expected U.S.-China strategic balance as China builds out its nuclear force through 2035. We apply published force exchange models to determine the expected damage each side will be able to deliver, and we use these values to determine the likelihood that the U.S. can prevail in crises of varying stakes. Last, we show that U.S. policymakers have an array of options to improve future bargaining outcomes, evaluating how additional nuclear forces trade against improvements in damage limitation.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗
DOE OSTI2023

Impact of Limited Degree of Freedom Drag Coefficients on a Floating Offshore Wind Turbine Simulation

The worldwide effort to design and commission floating offshore wind turbines (FOWT) is motivating the need for reliable numerical models that adequately represent their physical behavior under realistic sea states. However, properly representing the hydrodynamic quadratic damping for FOWT remains uncertain, because of its dependency on the choice of drag coefficients (dimensionless or not). It is hypothesized that the limited degree of freedom (DoF) drag coefficient formulation that uses only translational drag coefficients causes mischaracterization of the rotational DoF drag, leading to underestimation of FOWT global loads, such as tower base fore-aft shear. To address these hydrodynamic modeling uncertainties, different quadratic drag models implemented in the open-source mid-fidelity simulation tool, OpenFAST, were investigated and compared with the experimental data from the Offshore Code Comparison Collaboration, Continued, with Correlation (OC5) project. The tower base fore-aft shear and up-wave mooring line tension were compared under an irregular wave loading condition to demonstrate the effects of the different damping models. Two types of hydrodynamic quadratic drag formulations were considered: (1) member-based dimensionless drag coefficients applied only at the translational DoF (namely limited-DoF drag model) and (2) quadratic drag matrix model (in dimensional form). Based on the results, the former consistently underestimated the 95th percentile peak loads and spectral responses when compared to the OC5 experimental data. In contrast, the drag matrix models reduced errors in estimates of the tower base shear peak load by 7–10% compared to the limited-DoF drag model. The underestimation in the tower base fore-aft shear was thus inferred be related to mischaracterization of the rotational pitch drag and the heave motion/drag by the limited-DoF model.

17 WIND ENERGY↗
DOE OSTI2024

The Isotopic Limit of Recycling

Despite advances in recycling technologies and practices, the world still mostly operates on a once-through materials use cycle. The once-through approach to the materials supply chain cannot work into perpetuity. The vast majority of current recycling efforts focus on mechanical or chemical separation-based techniques and are often subsequently limited on the number of times a component can be recycled or upcycled. By looking at things from a particle physics and nuclear history perspective, we propose a thought experiment to determine the physical limit of recycling and propose subsequent limits and standards to evaluate all recycling efforts. This uncommon approach to analysis demonstrates that the current limits to recycling are not physical in nature but engineering.

Lang, Eric↗
DOE OSTI2025

Limits on the Low-energy Electron Antineutrino Flux from the Brightest Gamma-Ray Burst of All Time

The electron antineutrino flux limits are presented for the brightest gamma-ray burst (GRB) of all time, GRB221009A, over a range of 1.8–200 MeV using the Kamioka Liquid Scintillator Antineutrino Detector. Using multiple time windows ranging from minutes to days surrounding the event to search for electron antineutrinos coincident with the GRB, we set an upper limit on the flux under the assumption of several power-law neutrino source spectra, with power-law indices ranging from 1.5 to 3 in steps of 0.5. No excess was observed in any time windows ranging from seconds to days around the event trigger time T 0 . For a power-law index of 2 and a time window of T 0 ± 500 s, a flux upper limit of 2.34 × 10 9 cm −2 was calculated. The limits are compared to the results presented by IceCube.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

A General Method for Estimating Zonal Transmission Interface Limits from Nodal Network Data: Preprint

Capacity expansion models for the electric power system often employ zonal (rather than nodal) resolution, necessitating estimates of aggregate power transfer limits across the interfaces between model zones. Interface limits between planning areas are sometimes published, but they are not generalizable to arbitrary zone shapes. There is thus a need for a reproducible method for estimating interface transfer limits (ITLs) between user-defined zones directly from nodal transmission system data. Here, we present a simple method for estimating ITLs using a DC power flow approximation via the power transfer distribution factor (PTDF) matrix. Linear optimization is performed to identify the distribution of power flows that maximizes the total flow on interface-crossing lines, subject to individual line ratings, limits on bus injection/withdrawal, and the relationships among flows, injections, and withdrawals imposed by the PTDF matrix. We demonstrate the application of the method on a 134-zone ~65000-bus system, and we explore the influence of flow direction, contingency level, and zone size on the estimated ITLs. There is significant heterogeneity in the ratio of the ITL to the sum of interface-crossing line ratings, which highlights the importance of accounting for the physical constraints on power flows imposed by Kirchhoff's laws when estimating zonal ITLs.

17 WIND ENERGY↗
DOE OSTI2022

Impacts of active satellite sensors' low-level cloud detection limitations on cloud radiative forcing in the Arctic

Previous studies revealed that satellites sensors with the best detection capability identify 25 %–40 % and 0 %–25 % fewer clouds below 0.5 and between 0.5–1.0 km, respectively, over the Arctic. Quantifying the impacts of cloud detection limitations on the radiation flux are critical especially over the Arctic Ocean considering the dramatic changes in Arctic sea ice. In this study, the proxies of the space-based radar, CloudSat, and lidar, CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), cloud masks are derived based on simulated radar reflectivity with QuickBeam and cloud optical thickness using retrieved cloud properties from surface-based radar and lidar during the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. Limitations in low-level cloud detection by the space-based active sensors, and the impact of these limitations on the radiation fluxes at the surface and the top of the atmosphere (TOA), are estimated with radiative transfer model Streamer. The results show that the combined CloudSat and CALIPSO product generally detects all clouds above 1 km, while detecting 25 % (9 %) fewer in absolute values below 600 m (600 m to 1 km) than surface observations. These detection limitations lead to uncertainties in the monthly mean cloud radiative forcing (CRF), with maximum absolute monthly mean values of 2.5 and 3.4 Wm –2 at the surface and TOA, respectively. Cloud information from only CALIPSO or CloudSat lead to larger cloud detection differences compared to the surface observations and larger CRF uncertainties with absolute monthly means larger than 10.0 Wm –2 at the surface and TOA. The uncertainties for individual cases are larger – up to 30 Wm –2 . These uncertainties need to be considered when radiation flux products from CloudSat and CALIPSO are used in climate and weather studies.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1970

Remote sensing for detection of soil limitations in agricultural areas

Automatic analysis of soil limitations studied by an automatic color TV density slicing system was accomplished. This system color codes the density range of the value component of color of an image. Maps of soil limitations or other similar soil groups are produced by photographing the color coded representation of an area. The planimeter feature of the density slicing system measures the area of each soil limitation providing information on the importance of a soil limitation in an area. The results of this study suggest that an automatic color TV density slicing system has great potential not only for identifying and mapping similar soil areas, but also for indicating the percentage composition of an area.

Frazee, C. J.↗
NASA NTRS1973

Determination and evaluation of performance limit criteria of fast-response electrohydraulic servosystems

Limit criteria for determining the dynamic performance capabilities of high performance, fast-response (greater than 100 Hz) electrohydraulic servosystems are presented. A detailed analysis of the maximum load locus of these systems is used as a basis for the derivation of improved limit criteria. These criteria predict the maximum performance limits caused by system nonlinearities and physical limitations. The criteria are applied to experimental data to verify their validity. Design criteria which assist in the selection of system components for optimal performance are also discussed.

Zeller, J. R.↗
NASA NTRS1973

Signal-to-noise ratios in coherent soft limiters

Expressions for the output signal-to-noise power ratio of a bandpass soft limiter followed by a coherent detection device are presented and discussed. It is found that a significant improvement in the output signal-to-noise ratio at low input SNRs can be achieved by such soft limiters as compared to hard limiters. This indicates that the soft limiter may be of some use in the area of threshold extension. Approximation methods for determining output signal-to-noise spectral densities are also presented.

Lesh, J. R.↗
NASA NTRS1972

The performance of a noncoherent FSK receiver preceded by a bandpass limiter.

Many applications of the bandpass limiter involve either coherent or noncoherent demodulation following the limiter. In this paper we study the performance of a noncoherent frequency-shift keying (FSK) receiver when it is preceded by a bandpass limiter. In particular, we obtain expressions for signal suppression factor, output signal-to-noise ratio (SNR), and error probability from which one can assess the degradation in performance of the receiver due to the presence of the limiter.

Simon, M. K.↗
NASA NTRS1972

Kinetic theory of a two-dimensional magnetized plasma. II - Balescu-Lenard limit.

The kinetic theory of a two-dimensional one-species plasma in a uniform dc magnetic field is investigated in the small plasma parameter limit. The plasma consists of charged rods interacting through the logarithmic Coulomb potential. Vahala and Montgomery earlier (1971) derived a Fokker-Planck equation for this system, but it contained a divergent integral, which had to be cut off on physical grounds. This cutoff is compared to the standard cutoff introduced in the two-dimensional unmagnetized Fokker-Planck equation. In the small plasma parameter limit, it is shown that the Balescu-Lenard collision term is zero in the long time average limit if only two-body interactions are considered. The energy transfer from a test particle to an equilibrium plasma is discussed and is also shown to be zero in the long time average limit. This supports the unexpected result of zero Balescu-Lenard collision term.

Vahala, G.↗
NASA NTRS1974

A new upper limit for an atmosphere of CO2, CO on Mercury

High-resolution infrared spectra of Mercury (1.9-2.7 microns, resolution limit 0.134 wavelength/cm) obtained with the original 'Connes' interferometer at the Steward Observatory 90-inch telescope have provided a very sensitive test for the possible presence of a CO2, CO atmosphere. An improved upper limit of 0.12 cm-atm has been set for CO2, and a new upper limit of 0.05 cm-atm has been set for CO. Upper limits of similar magnitude can be established for CH4 and NH3. From the separation of the Mercury signal into reflected sunlight and thermal emission, we determine that the reflectivity decreases toward longer wavelengths and has a value of about 0.06 at 2.25 microns. Implications for the possible evolution of an atmosphere on Mercury are discussed.

Fink, U.↗
NASA NTRS1974

Signal-to-noise ratios in coherent soft limiters

Expressions for the output signal-to-noise power ratio of a bandpass soft limiter followed by a coherent detection device are presented and discussed. It is found that a significant improvement in the output signal-to-noise ratio (SNR) at low input SNR's can be achieved by such soft limiters as compared to hard limiters. This indicates that the soft limiter may be of some use in the area of threshold extension. Approximation methods for determining output signal-to-noise spectral densities are also presented.

Lesh, J. R.↗
NASA NTRS1976

A flight investigation of piloting techniques and crosswind limitations during visual STOL-type landing operations

A flight research program was undertaken to investigate problems concerned with landing a STOL airplane in crosswind conditions. The program included a study of piloting techniques and crosswind limitations during visual STOL type landing operations. The results indicated that the crosswind was more limiting during the ground roll out than during the airborne phases. The pilots estimated that the crosswind limit for commercial STOL type operations with the test aircraft would be approximately 15 to 20 knots. The pilots thought that the crosswind limits for ground operation might be extended by incorporating wing-lift spoilers, improved nose gear steering, and improved engine response. The pilots agreed that a crosswind landing gear would also be beneficial.

Fisher, B. D.↗
NASA NTRS1977

A description of the software analysis from flight and simulation data of the course cut limiter in the TCV b-737 area navigation computer

During automatic horizontal path captures, the (Terminal Configured Vehicle) B-737 airplane maintained smaller than designed path intercept angles and experienced a sawtooth bank angle oscillation during its turn towards the path. From flight data, it was determined that these anomalies were caused by the improper output of the course cut limiter in the horizontal path control law. The output from the course cut limiter did not obtain its full value and it was calculated stepwise discontinuously. The automatic horizontal path captures were then conducted on the TCV B-737 airplane real-time simulation. The path intercept angles were maintained properly and no bank angle oscillation was encountered. Data showed that the course cut limiter was calculated at its full value in a continuous manner. The intermediate calculations of the course cut limiter in the airplane's navigation computer were rewritten and rescaled in such a manner that truncation errors could be minimized. The horizontal path capture tests were then reflown. The airplane maintained the proper path intercept angle and no bank angle oscillations occurred on any of the tests.

Knox, C. E.↗
NASA NTRS1976

New upper limits on Jovian X rays

The paper presents results of a comprehensive search for X-ray emission from the Jovian magnetosphere, using data obtained with an X-ray telescope aboard OSO 3. This satellite scanned Jupiter for 33 days from a distance of 4.4 AU during a maximum phase of solar activity. No transient X-ray fluxes were observed to accompany decameter-wave radio bursts, but upper limits on the steady X-ray emission over the energy range from 7.7 to 210 keV are estimated. These limits are shown to be consistent with the fluxes measured by Pioneer 10 as well as with the trapped-particle fluxes predicted by recent precise modeling of the Jovian trapped radiation. Upper limits are determined for the energy dissipated on Jupiter in bremsstrahlung-producing collisions and also for the electron loss rate. The energy limit is found to be approximately equal to the total solar radiant energy intercepted by the Jovian disk. It is concluded that Jovian X-rays are unlikely to be detected by near-earth observations with sensitivities currently conceivable.

Peterson, L. E.↗