Optimum design of magnetic braking coils with special application to Lewis drop tower experiments
General analytic treatment of magnetic braking coils and braking action with numerical results computed for specific 400 foot drop facility
DROP↗
SEARCH · Search NASA
Results for “magnetic action”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Anomalous transport by Kelvin-Helmholtz instabilities
A simulation of magnetohydrodynamic Kelvin-Helmholtz instabilities has been performed for parallel and transverse configurations, modeling high latitude (or downstream flanks) and dayside low latitude magnetospheric boundaries. In the parallel configuration, a super-Alfvenic and transsonic shear flow develops into small eddies, which strongly compresses, twists, and hence amplifies the magnetic field by the dynamo action with an amplification factor of M(A)/2. In the nonlinear stage, however large the initial Alfven mach number M(A) may be, the magnetic field amplified and twisted by the hydromagnetic flow vortices reacts back upon the flow evolution, and the flow vortices cascade into smaller structures. In the transverse configuration, the instability leads to the formation of a fast shock discontinuity from an initially subfast shear flow. Anomalous tangential stress by the instability in the transverse configuration reaches 1 percent of the magnetosheath momentum flux, but for the parallel configuration, the anomalous transport is 2-3 times larger than the anomalous transport in the transverse configuration. The anomalous transport for both configurations satisfies the requirement of the viscous-like interaction at the magnetospheric boundary.
Miura, A.↗
Effect of a magnetic field of extremely low intensity on the coagulatory system of the blood
The influence of a magnetic field of 10,000 gamma on the conditions of the coagulatory system of rabbits was studied. The results from a number of experiments indicate that the action of a very weak magnetic field produces an increase in the coagulatory activity of the blood.
Zabrodina, L. V.↗
Magnetocaloric refrigerator
The invention is for an apparatus and method for a refrigerator and a heat pump based on the magnetocaloric effect (MCE) offering a simpler, lighter, robust, more compact, environmentally compatible, and energy efficient alternative to traditional vapor-compression devices. The subject magnetocaloric apparatus alternately exposes a magnetocaloric material to strong and weak magnetic field while switching heat to and from the material. Action of the heat switches is coordinated with the magnetic field strength to move heat up the thermal gradient. The invention may be practiced with multiple magnetocaloric stages to attain large differences in temperature. Key applications include thermal management of electronics, as well as industrial and home refrigeration, heating, and air conditioning. The invention offers a simpler, lighter, compact, and robust apparatus compared to magnetocaloric devices of prior art. Furthermore, the invention may be run in reverse as a thermodynamic engine, receiving low-level heat and producing mechanical energy.
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
Magnetic Field Effects on Convection and Solidification in Normal and Microgravity
It has been well understood that convective flows induced by g-jitter forces associated with spacecraft are responsible for defects formation and irregularity in product quality during melt growth of single crystals in microgravity. This research is concerned about numerical simulations and experimental measurements for the purpose of developing a fundamental understanding of the g-jitter induced fluid flows and their effects on solidification in microgravity with and without the presence of additional damping forces that are derived from the applied DC magnetic fields. The numerical models include both 2-D and 3-D transient fluid flow, heat transfer, mass transfer and solidification under the combined action of g-jitter and magnetic fields. Numerical simulations using both the 2-D and 3-D models are conducted for both idealized, synthesized and real g-jitter forces, and 2-D simulations are tested against the experimental measurements taken on the thermal oscillator. 2-D solidification models have also been developed and simulations are conducted. Results show that the numerical model predictions compare well with the measurements. Analysis of these results illustrates that an applied magnetic field can have a drastic influence on the convective flows induced by g-jitter and can be particularly useful to suppress the effects resulting from the spiking of g-jitter signatures, which are considered the most detrimental effects on quality of crystals grown in space. Work in progress includes developing 3-D numerical models for solidification phenomena with the presence of both g-jitter and magnetic fields and measurements of flow fluid and its effect on solidification in both transparent fluid and low melting point melts to verify numerical predictions.
Li, Ben Q.↗
Generation of dynamo magnetic fields in thin Keplerian disks
The combined action of nonuniform rotation and helical convection in protoplanetary disks, in the Galaxy, or in accretion disks surrounding black holes and other compact objects, enables an alpha-omega dynamo to generate a large-scale magnetic field. In this paper, the properties of such magnetic fields are investigated using a two-dimensional, partially numerical method. The structures of the lowest-order steady state and oscillatory modes are calculated for two kinds of external boundary conditions. A quadruple, steady state, highly localized mode is the most easily excited for low values of the dynamo number. The results indicate that, except under special conditions, disk dynamo modes tend to consist of relatively localized rings structures. For large values of the dynamo number, the magnetic field consists of a number of quasi-independent, spatially localized modes generated in various concentric rings filling the disk inward of a dynamo generation 'front'.
Stepinski, T. F.↗
Peripheral Nerve Magnetoneurography With Optically Pumped Magnetometers
Electrodiagnosis is routinely integrated into clinical neurophysiology practice for peripheral nerve disease diagnoses, such as neuropathy, demyelinating disorders, nerve entrapment/impingement, plexopathy, or radiculopathy. Measured with conventional surface electrodes, the propagation of peripheral nerve action potentials along a nerve is the result of ionic current flow which, according to Ampere’s Law, generates a small magnetic field that is also detected as an “action current” by magnetometers, such as superconducting quantum interference device (SQUID) Magnetoencephalography (MEG) systems. Optically pumped magnetometers (OPMs) are an emerging class of quantum magnetic sensors with a demonstrated sensitivity at the 1 fT/√Hz level, capable of cortical action current detection. But OPMs were ostensibly constrained to low bandwidth therefore precluding their use in peripheral nerve electrodiagnosis. With careful OPM bandwidth characterization, we hypothesized OPMs may also detect compound action current signatures consistent with both Sensory Nerve Action Potential (SNAP) and the Hoffmann Reflex (H-Reflex). In as much, our work confirms OPMs enabled with expanded bandwidth can detect the magnetic signature of both the SNAP and H-Reflex. Taken together, OPMs now show potential as an emerging electrodiagnostic tool.
60 APPLIED LIFE SCIENCES↗
Antibacterial activity of iron oxide, iron nitride, and tobramycin conjugated nanoparticles against Pseudomonas aeruginosa biofilms
Novel methods are necessary to reduce morbidity and mortality of patients suffering from infections with Pseudomonas aeruginosa. Being the most common infectious species of the Pseudomonas genus, P. aeruginosa is the primary Gram-negative etiology responsible for nosocomial infections. Due to the ubiquity and high adaptability of this species, an effective universal treatment method for P. aeruginosa infection still eludes investigators, despite the extensive research in this area. Results We report bacterial inhibition by iron-oxide (nominally magnetite) nanoparticles (NPs) alone, having a mean hydrodynamic diameter of ~ 16 nm, as well as alginate-capped iron-oxide NPs. Alginate capping increased the average hydrodynamic diameter to ~ 230 nm. We also investigated alginate-capped iron-oxide NP-drug conjugates, with a practically unchanged hydrodynamic diameter of ~ 232 nm. Susceptibility and minimum inhibitory concentration (MIC) of the NPs, NP-tobramycin conjugates, and tobramycin alone were determined in the PAO1 bacterial colonies. Investigations into susceptibility using the disk diffusion method were done after 3 days of biofilm growth and after 60 days of growth. MIC of all compounds of interest was determined after 60-days of growth, to ensure thorough establishment of biofilm colonies. Conclusions Positive inhibition is reported for uncapped and alginate-capped iron-oxide NPs, and the corresponding MICs are presented. We report zero susceptibility to iron-oxide NPs capped with polyethylene glycol, suggesting that the capping agent plays a major role in enabling bactericidal ability in of the nanocomposite. Our findings suggest that the alginate-coated nanocomposites investigated in this study have the potential to overcome the bacterial biofilm barrier. Magnetic field application increases the action, likely via enhanced diffusion of the iron-oxide NPs and NP-drug conjugates through mucin and alginate barriers, which are characteristic of cystic-fibrosis respiratory infections. We demonstrate that iron-oxide NPs coated with alginate, as well as alginate-coated magnetite–tobramycin conjugates inhibit P. aeruginosa growth and biofilm formation in established colonies. We have also determined that susceptibility to tobramycin decreases for longer culture times. However, susceptibility to the iron-oxide NP compounds did not demonstrate any comparable decrease with increasing culture time. These findings imply that iron-oxide NPs are promising lower-cost alternatives to silver NPs in antibacterial coatings, solutions, and drugs, as well as other applications in which microbial abolition or infestation prevention is sought.
Biotechnology & Applied Microbiology↗
Propagation of solar flare-associated interplanetary shock waves in the heliospheric meridional plane
An analysis is conducted for 149 flare-associated shock wave events based on interplanetary scintillation observational data. All of the flare-associated shock waves tend to propagate toward the low latitude region near the solar equator for flares that are located in both the solar Northern and Southern Hemispheres. Also, the fastest propagation directions tend toward the heliospheric current sheet near 1 AU. This tendency is caused by the dynamic action of near-sun magnetic forces on the ejected coronal plasma that traverses the helmet-like magnetic topologies near the sun outward to the classical topology that is essentially parallel to the heliospheric current sheet.
Wei, Fengsi↗
Compressor Has No Moving Macroscopic Parts
Compressor containing no moving macroscopic parts functions by alternating piston and valve actions of successive beds of magnetic particles. Fabricated easily because no need for precisely fitting parts rotating or sliding on each other. Also no need for lubricant fluid contaminating fluid to be compressed. Compressor operates continuously, eliminating troublesome on/off cycling of other compressors, and decreasing consumption of energy. Phased cells push fluid from bottom to top, adding increments of pressure. Each cell contains magnetic powder particles loose when electromagnet coil deenergized, but tightly packed when coil energized.
Gasser, Max↗
Universal Millimeter-Wave Radar Front End
A quasi-optical front end allows any arbitrary polarization to be transmitted by controlling the timing, amplitude, and phase of the two input ports. The front end consists of two independent channels horizontal and vertical. Each channel has two ports transmit and receive. The transmit signal is linearly polarized so as to pass through a periodic wire grid. It is then propagated through a ferrite Faraday rotator, which rotates the polarization state 45deg. The received signal is propagated through the Faraday rotator in the opposite direction, undergoing a further 45 of polarization rotation due to the non-reciprocal action of the ferrite under magnetic bias. The received signal is now polarized at 90deg relative to the transmit signal. This signal is now reflected from the wire grid and propagated to the receive port. The horizontal and vertical channels are propagated through, or reflected from, another wire grid. This design is an improvement on the state of the art in that any transmit signal polarization can be chosen in whatever sequence desired. Prior systems require switching of the transmit signal from the amplifier, either mechanically or by using high-power millimeter-wave switches. This design can have higher reliability, lower mass, and more flexibility than mechanical switching systems, as well as higher reliability and lower losses than systems using high-power millimeter-wave switches.
Perez, Raul M.↗
Planetary Magnetism
The chapter on Planetary Magnetism by Connerney describes the magnetic fields of the planets, from Mercury to Neptune, including the large satellites (Moon, Ganymede) that have or once had active dynamos. The chapter describes the spacecraft missions and observations that, along with select remote observations, form the basis of our knowledge of planetary magnetic fields. Connerney describes the methods of analysis used to characterize planetary magnetic fields, and the models used to represent the main field (due to dynamo action in the planet's interior) and/or remnant magnetic fields locked in the planet's crust, where appropriate. These observations provide valuable insights into dynamo generation of magnetic fields, the structure and composition of planetary interiors, and the evolution of planets.
Magnetospheres↗
Magnetically operated limit switch has improved reliability, minimizes arcing
Limit switch for reliable, low-travel, snap action with negligible arcing uses an electrically nonconductive permanent magnet consisting of a ferrimagnetic ceramic and ferromagnetic pole shoes which form a magnetic and electrically conductive circuit with a ferrous-metal armature.
Steiner, R.↗
Combined magnetic and gravity analysis
Efforts are made to identify methods of decreasing magnetic interpretation ambiguity by combined gravity and magnetic analysis, to evaluate these techniques in a preliminary manner, to consider the geologic and geophysical implications of correlation, and to recommend a course of action to evaluate methods of correlating gravity and magnetic anomalies. The major thrust of the study was a search and review of the literature. The literature of geophysics, geology, geography, and statistics was searched for articles dealing with spatial correlation of independent variables. An annotated bibliography referencing the Germane articles and books is presented. The methods of combined gravity and magnetic analysis techniques are identified and reviewed. A more comprehensive evaluation of two types of techniques is presented. Internal correspondence of anomaly amplitudes is examined and a combined analysis is done utilizing Poisson's theorem. The geologic and geophysical implications of gravity and magnetic correlation based on both theoretical and empirical relationships are discussed.
Hinze, W. J.↗
Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell
Convection is one of the most important mixing processes in stellar interiors. Hydrodynamic mass entrainment can bring fresh fuel from neighboring stable layers into a convection zone, modifying the structure and evolution of the star. Because flows in stellar convection zones are highly turbulent, multidimensional hydrodynamic simulations are fundamental to accurately capture the physics of mixing processes. Under some conditions, strong magnetic fields can be sustained by the action of a turbulent dynamo, adding another layer of complexity and possibly altering the dynamics in the convection zone and at its boundaries. In this study, we used our fully compressible S EVEN -L EAGUE H YDRO code to run detailed and highly resolved three-dimensional magnetohydrodynamic simulations of turbulent convection, dynamo amplification, and convective boundary mixing in a simplified setup whose stratification is similar to that of an oxygen-burning shell in a star with an initial mass of 25 M ⊙ . We find that the random stretching of magnetic field lines by fluid motions in the inertial range of the turbulent spectrum (i.e., a small-scale dynamo) naturally amplifies the seed field by several orders of magnitude in a few convective turnover timescales. During the subsequent saturated regime, the magnetic-to-kinetic energy ratio inside the convective shell reaches values as high as 0.33, and the average magnetic field strength is ∼10 10 G. Such strong fields efficiently suppress shear instabilities, which feed the turbulent cascade of kinetic energy, on a wide range of spatial scales. The resulting convective flows are characterized by thread-like structures that extend over a large fraction of the convective shell. The reduced flow speeds and the presence of magnetic fields with strengths up to 60% of the equipartition value at the upper convective boundary diminish the rate of mass entrainment from the stable layer by ≈20% as compared to the purely hydrodynamic case.
79 ASTRONOMY AND ASTROPHYSICS↗
The photospheric magnetic flux budget
The ensemble of bipolar regions and the magnetic network both contain a substantial and strongly variable part of the photospheric magnetic flux at any phase in the solar cycle. The time-dependent distribution of the magnetic flux over and within these components reflects the action of the dynamo operating in the solar interior. We perform a quantitative comparison of the flux emerging in the ensemble of magnetic bipoles with the observed flux content of the solar photosphere. We discuss the photospheric flux budget in terms of flux appearance and disappearance, and argue that a nonlinear dependence exists between the flux present in the photosphere and the rate of flux appearance and disappearance. In this context, we discuss the problem of making quantitative statements about dynamos in cool stars other than the Sun.
Schrijver, C. J.↗
Magnetic fields and dense chromospheres in dMe stars
The hypothesis is investigated that dense chromospheres of dMe stars are heated by dissipation of hydromagnetic waves which may be generated in active regions where the nonspot magnetic field strength can be as large as 5 to 10 kG. It is proposed that dMe stars are a set of magnetic stars on the lower main sequence which have strong fields generated by dynamo action in deep convective envelopes, while dM stars are nonmagnetic or weakly magnetic stars having no starspots on their surfaces. The combination of magnetic fields and dense chromospheres in dMe stars is shown to provide consistent evidence for several conclusions, including: (1) the dMe stars which are most likely to be flare stars are those with hydrogen emission lines and (2) propagation of flare-initiated coronal waves can trigger sympathetic stellar flares. It is suggested that grain formation occurs in starspots of dMe stars and that such grains in a circumstellar shell are responsible for the systematic IR excesses of dMe stars relative to dM stars.
Mullan, D. J.↗
Radio emission from binary stars
Radio emission from binary star systems; characteristics of the binary systems inferred from the radio observations; and the reasons for the activity are reviewed. Binary stars with two main sequence stars, with one normal star and a white dwarf, and those containing a neutron star or a black hole are described. Energy may be directly available as matter falls into the potential well of a compact object. Electromagnetic induction effects may occur due to relative motions of magnetic fields and matter. By enforcing rapid rotation, binaries can induce strong dynamo action and hence generate free energy in the form of intense, complex, evolving magnetic fields. Whatever the source of energy, the observations at radio and X-ray wavelengths demonstrate that electrons are accelerated to high energies (mildly relativistic and, ultrarelativistic). Observed or inferred radio brightness temperatures range up to 10 to the 15th power K or more, implying coherent emission for sources brighter than 10 billion K.
Dulk, George A.↗