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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Electromagnetic field representation in inhomogeneous anisotropic media

Some of the basic developments in the theory of electromagnetic field representation in terms of Hertz vectors are reviewed. A solution for the field in an inhomogeneous anisotropic medium is given in terms of the two Hertz vectors. Conditions for presentation of the field in terms of uncoupled transverse electric and transverse magnetic modes, in a general orthogonal coordinate system, are derived when the permeability and permittivity tensors have only diagonal components. These conditions are compared with some known special cases.

Mohsen, A.↗
DOE OSTI2018

Simultaneous Removal of Silicon and Iron-Rich Phases from Coarse Al-Si Alloys Using Manganese Under Electromagnetic Field

Coarse Al-Si alloy is produced from bauxite via carbon electro-thermal reduction method. Silicon and iron-rich phases are two main detrimental impurities in coarse Al-Si alloy, and they can be simultaneously removed by adding Mn under the electromagnetic field. We focus on the influence of different Mn additions, dropping rates, and current intensity on the simultaneous removal efficiency of Si and Fe. Experimental results show that as mole ratio of Mn/Fe reaches more than 0.8, the morphology of iron-rich phases together with silicon changed from harmful acicular-like to the contributing bulks, concentrated at the bottom of Al-Si alloy as intermetallic compounds. Furthermore, when Mn/Fe reaches 1.2 and a lower dropping rate (5 to 25 μm/s) is adopted, both Si and Fe contents in the Al-Si alloy decreased drastically after electromagnetic directional solidification process, reaching 11.42 and 0.4 pct, respectively, with a desirable Fe removal efficiency of 91 pct. Finally, the principle of simultaneously separating Si and removing iron-rich phases from Al-Si alloy is studied deeply.

36 MATERIALS SCIENCE↗
DOE OSTI2020

2020 State of the Science Report, Chapter 5: Risk to Animals from Electromagnetic Fields Emitted by Electric Cables and Marine Renewable Energy Devices

Interest in the potential effects of anthropogenic electromagnetic fields (EMFs) within the marine environment has increased in recent years, in part as a result of advanced knowledge gained from conducting dedicated research studies. To understand and interpret the potential environmental interactions of marine renewable energy (MRE)-related EMF emissions, it is necessary to consider the source of the EMFs and address the source within the context of the knowledge about the electro- and magneto-sensitivity of marine species. https://tethys.pnnl.gov/publications/state-of-the-science-2020-chapter-5-electromagnetic-fields

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Results of lifespan exposure to continuous and intermittent extremely low frequency electromagnetic fields (ELFEMF) administered alone to Sprague Dawley rats

Highlights: • Carcinogenic effects of ELFEMF whole-body chronic exposure were evaluated on rats. • Exposure to ELFEMF alone does not represent risk factor for neoplastic development. • ELFEMF might act as a cancer enhancer if co-administered to other known carcinogens. Up to now, experimental studies on rodents have failed to provide definitive confirmation of the carcinogenicity of extremely low frequency electromagnetic fields (ELFEMF). Two recent studies performed in our laboratory on Sprague-Dawley rats reported a statistically significant increase in malignant tumors of different sites (mammary gland, C-cells carcinoma, hemolymphoreticular neoplasia, and malignant heart Schwannoma) when ELFEMF exposure was associated with exposure to formaldehyde (50 mg/l) or acute low dose of γ-radiation (0.1 Gy) (Soffritti et al., 2016a) (Soffritti et al., 2016b). The same doses of known carcinogenic agents (50 mg/l formaldehyde, or acute 0.1 Gy γ-radiation), when administered alone, previously failed to induce any statistically significant increase in the incidence of total and specific malignant tumors in rats of the same colony.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2023

An Alternating, Current-Induced Electromagnetic Field for Membrane Fouling and Scaling Control during Desalination of Secondary Effluent from Municipal Wastewater

Membrane treatment of secondary effluent for reuse applications is a promising approach to expand water supplies and provide flexibility to water resources management. However, effective control of membrane fouling and scaling is crucial for cost-effective treatment and system resilience. This study compared the performance of antiscalants to an alternating, current-induced electromagnetic field (EMF) as an alternative pretreatment method to reverse osmosis. Compared to the no-EMF control experiments, the EMF device resulted in 13% higher water recovery and 366% lower flux decline at 60% of water recovery, along with 2–8 times lower precipitation of fouling and scaling, as evidenced by scanning electron microscope, energy dispersive X-ray spectroscopy, and chemical extraction analysis. The combination of the EMF with antiscalant was more effective for reducing membrane fouling and scaling, increasing water recoveries up to 89.3%, as compared to the EMF (67.5%) and antiscalant-only (73.6%) configurations. This is the first study to demonstrate synergistic effects of using an EMF in combination with antiscalants and could lead to lower pretreatment costs. Additional research is required to quantify the economics of this approach and to fully understand the fundamental mechanisms governing fouling and scaling control by an EMF.

42 ENGINEERING↗
DOE OSTI2018

Assessment of long-term spatio-temporal radiofrequency electromagnetic field exposure

Highlights: • A year's worth of RF-EMF data is collected in an urban sensor network is analysed. • A full spatio-temporal model of the RF-EMF exposure in the study area is built. • Short-term variations of the RF-EMF exposure are collected in temporal profiles. • Models using data collected at different instants are improved by adjusting for time. As both the environment and telecommunications networks are inherently dynamic, our exposure to environmental radiofrequency (RF) electromagnetic fields (EMF) at an arbitrary location is not at all constant in time. In this study, more than a year's worth of measurement data collected in a fixed low-cost exposimeter network distributed over an urban environment was analysed and used to build, for the first time, a full spatio-temporal surrogate model of outdoor exposure to downlink Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) signals. Though no global trend was discovered over the measuring period, the difference in measured exposure between two instances could reach up to 42 dB (a factor 12,000 in power density). Furthermore, it was found that, taking into account the hour and day of the measurement, the accuracy of the surrogate model in the area under study was improved by up to 50% compared to models that neglect the daily temporal variability of the RF signals. However, further study is required to assess the extent to which the results obtained in the considered environment can be extrapolated to other geographic locations.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2019

A Risk Retirement Pathway for Potential Effects of Underwater Noise and Electromagnetic Fields for Marine Renewable Energy

Commercial marine renewable energy (MRE) developments can take extended periods of time to progress, in part due to complicated permitting processes that require expensive data collection and data review. Much of this delay is associated with uncertainty around potential effects of MRE on marine animals and habitats, leading regulators and stakeholders to believe that significant risks may exist. This paper acknowledges the state of scientific knowledge around MRE environmental effects and puts forward a process for risk retirement associated with early MRE developments, with a focus on the potential effects from underwater noise from wave and tidal devices, as well as potential effects of electromagnetic fields (EMF) from export power cables on marine animals and habitats. This process was developed as part of the Ocean Energy Systems (OES) OES-Environmental task.

marine renewable energy (MRE), risk retirement, un↗
DOE OSTI2018

Genotoxic and carcinogenic effects of non-ionizing electromagnetic fields

Highlights: • Public concern over the effects of EMF on cancer is growing. • In vitro and in vivo experiments concerning ELF and EMF have elicited contradictory results. • Epidemiological studies may help us to understand the genotoxic and carcinogenic effects of EMF. • Do adverse effects differ depending on the EMF frequency involved? New technologies in electronics and communications are continually emerging. An increasing use of these electronic devices such as mobile phone, computer, wireless fidelity connectors or cellular towers is raising questions concerning whether they have an adverse effect on the body. Exposure to electromagnetic fields (EMF) is frequently suggested to have adverse health effects on humans and other organisms. This idea has been reported in many studies. In contrast, the therapeutic effects of EMF on different organs have also been reported. Research findings are inconsistent. This has given rise to very profound discrepancies. The duration and frequency of mobile phone calls and the association observed with various health effects has raised serious concerns due to the frequency with which these devices are used and the way they are held close to the head. The present review assesses the results of in vitro, in vivo, experimental, and epidemiological studies. The purpose of the study is to assess data concerning the carcinogenic and genotoxic effects of non-ionizing EMF. The major genotoxic and carcinogenic effects of EMF, divided into subsections as low frequency effects and radiofrequency effects, were reviewed. The inconsistent results between similar studies and the same research groups have made it very difficult to make any comprehensive interpretation. However, evaluation of current studies suggests that EMF may represent a serious source of concern and may be hazardous to living organisms.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2018

Representativeness and repeatability of microenvironmental personal and head exposures to radio-frequency electromagnetic fields

Highlights: • First time assessment of head exposure to RF-EMF in uncontrolled environments, in 15 microenvironments in Melbourne, Australia. • We show that our measurement protocol is repeatable over time. • We show that the paths selected in our protocol are representative for the larger areas in which they are defined. • Exposure to RF-EMF is higher in more dense urban areas than in less populated suburban areas in the outskirts of the city. The aims of this study were to: i) investigate the repeatability and representativeness of personal radio frequency-electromagnetic fields (RF-EMFs) exposure measurements, across different microenvironments, ii) perform simultaneous evaluations of personal RF-EMF exposures for the whole body and the head, iii) validate the data obtained with a head-worn personal distributed exposimeter (PDE) against those obtained with an on-body worn personal exposimeter (PEM). Data on personal and head RF-EMF exposures were collected by performing measurements across 15 microenvironments in Melbourne, Australia. A body-worn PEM and a head-worn PDE were used for measuring body and head exposures, respectively. The summary statistics obtained for total RF-EMF exposure showed a high representativeness (r{sup 2} > 0.66 for two paths in the same area) and a high repeatability over time (r{sup 2} > 0.87 for repetitions of the same path). The median head exposure in the 900 MHz downlink band ranged between 0.06 V/m and 0.31 V/m. The results obtained during simultaneous measurements using the two devices showed high correlations (0.42 < r{sup 2} < 0.94). The highest mean total RF-EMF exposure was measured in Melbourne's central business district (0.89 V/m), whereas the lowest mean total exposure was measured in a suburban residential area (0.05 V/m). This study shows that personal RF-EMF microenvironmental measurements in multiple microenvironments have high representativeness and repeatability over time. The personal RF-EMF exposure levels (i.e. body and head exposures) demonstrated moderate to high correlations.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2020

An energy-conserving and asymptotic-preserving charged-particle orbit implicit time integrator for arbitrary electromagnetic fields

Here we present a new implicit asymptotic preserving time integration scheme for charged-particle orbit computation in arbitrary electromagnetic fields. The scheme is built on the Crank-Nicolson integrator and continues to recover full-orbit motion in the small time-step limit, but also recovers all the first-order guiding center drifts as well as the correct gyroradius when stepping over the gyration time-scale. In contrast to previous efforts in this direction, the new scheme also features exact energy conservation. In the derivation of the scheme, we find that a new numerical time-scale is introduced. This scale is analyzed and the resulting restrictions on time-step are derived. Based on this analysis, we develop an adaptive time-stepping strategy the respects these constraints while stepping over the gyration scale when physically justified. It is shown through numerical tests on single-particle motion that the scheme's energy conservation property results in tremendous improvements in accuracy, and that the scheme is able to transition smoothly between magnetized and unmagnetized regimes as a result of the adaptive time-stepping.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1993

Electromagnetic field strength prediction in an urban environment: A useful tool for the planning of LMSS

A model for the prediction of the electromagnetic field strength in an urban environment is presented. The ray model, that is based on the Uniform Theory of Diffraction (UTD), includes effects of the non-perfect conductivity of the obstacles and their surface roughness. The urban environment is transformed into a list of standardized obstacles that have various shapes and material properties. The model is capable of accurately predicting the field strength in the urban environment by calculating different types of wave contributions such as reflected, edge and corner diffracted waves, and combinations thereof. Also, antenna weight functions are introduced to simulate the spatial filtering by the mobile antenna. Communication channel parameters such as signal fading, time delay profiles, Doppler shifts and delay-Doppler spectra can be derived from the ray-tracing procedure using post-processing routines. The model has been tested against results from scaled measurements at 50 GHz and proves to be accurate.

Vandooren, G. A. J.↗
DOE OSTI2019

A Classical Field Theory Formulation for the Numerical Solution of Time Harmonic Electromagnetic Fields

Finite element representations of Maxwell's equations pose unusual challenges inherent to the variational representation of the “curl-curl” equation for the fields. We present a variational formulation which solves for the four-potential instead, based on classical field theory. Borrowing from quantum electrodynamics, we modify the Lagrangian by adding an implicit gauge-fixing term. This reformulation explicitly accounts for Gauss’ law through the coupling between $\phi$ and $\rho$ , and enables the use of nodal basis functions instead of edge elements for time-harmonic problems. Here, we demonstrate how this formulation, adhering to the deeper underlying symmetries of the four-dimensional covariant field description, provides a highly general, robust numerical framework.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Entropy production far from equilibrium in a chiral charged plasma in the presence of external electromagnetic fields

We report on the time evolution of a charged strongly coupled N = 4 SYM plasma with an axial anomaly subjected to strong electromagnetic fields. The evolution of this plasma corresponds to a fully backreacted asymptotically AdS 5 solution to the Einstein-Maxwell-Chern-Simons theory. We explore the evolution of the axial current and production of axial charges. As an application we show that after a sufficiently long time both the entropy and the holographic entanglement entropy of a strip-like topology (both parallel to and transverse to the flow of axial current) grow linearly in time.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1974

Electromagnetic fields due to a horizontal electric dipole antenna laid on the surface of a two-layer medium

With applications to geophysical subsurface probings, electromagnetic fields due to a horizontal electric dipole laid on the surface of a two-layer medium are solved by a combination of analytic and numerical methods. Interference patterns are calculated for various layer thickness. The results are interpreted in terms of normal modes, and the accuracies of the methods are discussed.

Tsang, L.↗
NASA NTRS1982

The interaction of radio frequency electromagnetic fields with atmospheric water droplets and applications to aircraft ice prevention

The feasibility of computerized simulation of the physics of advanced microwave anti-icing systems, which preheat impinging supercooled water droplets prior to impact, was investigated. Theoretical and experimental work performed to create a physically realistic simulation is described. The behavior of the absorption cross section for melting ice particles was measured by a resonant cavity technique and found to agree with theoretical predictions. Values of the dielectric parameters of supercooled water were measured by a similar technique at lambda = 2.82 cm down to -17 C. The hydrodynamic behavior of accelerated water droplets was studied photograhically in a wind tunnel. Droplets were found to initially deform as oblate spheroids and to eventually become unstable and break up in Bessel function modes for large values of acceleration or droplet size. This confirms the theory as to the maximum stable droplet size in the atmosphere. A computer code which predicts droplet trajectories in an arbitrary flow field was written and confirmed experimentally. The results were consolidated into a simulation to study the heating by electromagnetic fields of droplets impinging onto an object such as an airfoil. It was determined that there is sufficient time to heat droplets prior to impact for typical parameter values. Design curves for such a system are presented.

Hansman, R. J., Jr.↗
NASA NTRS1971

The calculation of electromagnetic fields in the Fresnel and Fraunhofer regions using numerical integration methods

Some results obtained with a digital computer program written at Goddard Space Flight Center to obtain electromagnetic fields scattered by perfectly reflecting surfaces are presented. For purposes of illustration a paraboloidal reflector was illuminated at radio frequencies in the simulation for both receiving and transmitting modes of operation. Fields were computed in the Fresnel and Fraunhofer regions. A dual-reflector system (Cassegrain) was also simulated for the transmitting case, and fields were computed in the Fraunhofer region. Appended results include derivations which show that the vector Kirchhoff-Kottler formulation has an equivalent form requiring only incident magnetic fields as a driving function. Satisfaction of the radiation conditions at infinity by the equivalent form is demonstrated by a conversion from Cartesian to spherical vector operators. A subsequent development presents the formulation by which Fresnel or Fraunhofer patterns are obtainable for dual-reflector systems. A discussion of the time-average Poynting vector is also appended.

Schmidt, R. F.↗