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1

Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces  

NASA Technical Reports Server (NTRS)

At Brown University, we are developing the use of magnetic body forces as a means to simulate variable gravity body forces on biological systems. This tool promises new means to probe gravi-sensing and the gravi-response of biological systems. It also has the potential as a technique for screening future systems for space flight experiments.

Guevorkian, Karine; Wurzel, Sam; Mihalusova, Mariana; Valles, Jim

2003-01-01

2

Lorentz Body Force Induced by Traveling Magnetic Fields  

NASA Technical Reports Server (NTRS)

The Lorentz force induced by a traveling magnetic field (TMF) in a cylindrical container has been calculated. The force can be used to control flow in dectrically conducting melts and the direction of the magnetic field and resulting flow can be reversed. A TMF can be used to partially cancel flow driven by buoyancy. The penetration of the field into the cylinder decreases as the frequency increases, and there exists an optimal value of frequency for which the resulting force is a maximum. Expressions for the Lorentz force in the limiting cases of low frequency and infinite cylinder are also given and compared to the numerical calculations.

Volz, M. P.; Mazuruk, K.

2003-01-01

3

Calculation of forces on magnetized bodies using COSMIC NASTRAN  

NASA Technical Reports Server (NTRS)

The methods described may be used with a high degree of confidence for calculations of magnetic traction forces normal to a surface. In this circumstance all models agree, and test cases have resulted in theoretically correct results. It is shown that the tangential forces are in practice negligible. The surface pole method is preferable to the virtual work method because of the necessity for more than one NASTRAN run in the latter case, and because distributed forces are obtained. The derivation of local forces from the Maxwell stress method involves an undesirable degree of manipulation of the problem and produces a result in contradiction of the surface pole method.

Sheerer, John

1987-01-01

4

Installation with magnetic suspension of test bodies for measurement of small forces. Verification of equivalence of inertial and gravitational mass. Discussion of the method  

NASA Astrophysics Data System (ADS)

Torsion installation with magnetic suspension of test bodies for detection of small forces is considered. Installation application for verification of equivalence of inertial and gravitational mass in the case of test body incidence on the Earth (Etvesh experiment) and in the case of their incidence on the Sun (Dicke experiment) is discussed. The total mass of test bodies, produced in the form of cylinders with 3 cm radius, equals 50 kg (one lead body and one copper body); beam radius of test bodies equals 3 cm (the cylinders are tight against one another); ferrite cylinder with 3 cm radius and 10 cm height is used for their suspension in magnetic field. Effect of thermal noise and electromagnetic force disturbances on measurement results is considered. Conducted calculations show that suggested installation enables one to improve the accuracy of verifying mentioned equivalence at least by one order and upwards. This suggests that such installation is a matter of interest for experiments on small force detection.

Kalebin, S. M.

5

Tunneling magnetic force microscopy  

NASA Technical Reports Server (NTRS)

We have developed a powerful new tool for studying the magnetic patterns on magnetic recording media. This was accomplished by modifying a conventional scanning tunneling microscope. The fine-wire probe that is used to image surface topography was replaced with a flexible magnetic probe. Images obtained with these probes reveal both the surface topography and the magnetic structure. We have made a thorough theoretical analysis of the interaction between the probe and the magnetic fields emanating from a typical recorded surface. Quantitative data about the constituent magnetic fields can then be obtained. We have employed these techniques in studies of two of the most important issues of magnetic record: data overwrite and maximizing data-density. These studies have shown: (1) overwritten data can be retrieved under certain conditions; and (2) improvements in data-density will require new magnetic materials. In the course of these studies we have developed new techniques to analyze magnetic fields of recorded media. These studies are both theoretical and experimental and combined with the use of our magnetic force scanning tunneling microscope should lead to further breakthroughs in the field of magnetic recording.

Burke, Edward R.; Gomez, Romel D.; Adly, Amr A.; Mayergoyz, Isaak D.

1993-01-01

6

Updates of the nuclear equation of state for core-collapse supernovae and neutron stars: effects of 3-body forces, QCD, and magnetic fields  

NASA Astrophysics Data System (ADS)

We summarize several new developments in the nuclear equation of state for supernova simulations and neutron stars. We discuss an updated and improved Notre-Dame-Livermore Equation of State (NDL EoS) for use in supernovae simulations. This Eos contains many updates. Among them are the effects of 3- body nuclear forces at high densities and the possible transition to a QCD chiral and/or super-conducting color phase at densities. We also consider the neutron star equation of state and neutrino transport in the presence of strong magnetic fields. We study a new quantum hadrodynamic (QHD) equation of state for neutron stars (with and without hyperons) in the presence of strong magnetic fields. The parameters are constrained by deduced masses and radii. The calculated adiabatic index for these magnetized neutron stars exhibit rapid changes with density. This may provide a mechanism for star-quakes and flares in magnetars. We also investigate the strong magnetic field effects on the moments of inertia and spin down of neutron stars. The change of the moment of inertia associated with emitted magnetic flares is shown to match well with observed glitches in some magnetars. We also discuss a perturbative calculation of neutrino scattering and absorption in hot and dense hyperonic neutron-star matter in the presence of a strong magnetic field. The absorption cross-sections show a remarkable angular dependence in that the neutrino absorption strength is reduced in a direction parallel to the magnetic field and enhanced in the opposite direction. The pulsar kick velocities associated with this asymmetry comparable to observed pulsar velocities and may affect the early spin down rate of proto-neutron star magnetars with a toroidal field configuration.

Mathews, G. J.; Meixner, M.; Olson, J. P.; Suh, I.-S.; Kajino, T.; Maruyama, T.; Hidaka, J.; Ryu, C.-Y.; Cheoun, M.-K.; Lan, N. Q.

2013-07-01

7

Three-body forces and the trinucleons  

SciTech Connect

Three-body forces are discussed in the context of classical, atomic, solid-state and nuclear physics. The basic theoretical ingredients used in the construction of such forces are reviewed. Experimental evidence for three-nucleon forces and an overview of the three-nucleon bound states are presented. 53 refs., 9 figs.

Friar, J.L.

1987-01-01

8

Magnetic elements for switching magnetization magnetic force microscopy tips.  

SciTech Connect

Using combination of micromagnetic calculations and magnetic force microscopy (MFM) imaging we find optimal parameters for novel magnetic tips suitable for switching magnetization MFM. Switching magnetization MFM is based on two-pass scanning atomic force microscopy with reversed tip magnetization between the scans. Within the technique the sum of the scanned data with reversed tip magnetization depicts local atomic forces, while their difference maps the local magnetic forces. Here we propose the design and calculate the magnetic properties of tips suitable for this scanning probe technique. We find that for best performance the spin-polarized tips must exhibit low magnetic moment, low switching fields, and single-domain state at remanence. The switching field of such tips is calculated and optimum shape of the Permalloy elements for the tips is found. We show excellent correspondence between calculated and experimental results for Py elements.

Cambel, V.; Elias, P.; Gregusova, D.; Martaus, J.; Fedor, J.; Karapetrov, G.; Novosad, V. (Materials Science Division); (Slovak Academy of Sciences)

2010-09-01

9

High resolution magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Magnetic Force Microscopy (MFM) has become ubiquitous in both fundamental magnetics research and a variety of magnetic technologies. As would be expected for any microscopy there is a continuous push to increase the spatial resolution of MFM. We have used electron beam deposition (EBD) techniques to manufacture high resolution MFM tips. [1] These tips have sufficient resolution to image continuous magnetic field reversals on the order of 30nm (as opposed to the observation of isolated dipoles which can be accomplished with commercial MFM tips). We have used these tips to study the magnetic reversal in CoCr films with a perpendicular anisotropy using in situ applied magnetic fields MFM. This study has revealed partial magnetic reversal within Co rich grains and flux closure between grains. [2] In addition to this study, we have performed high resolution MFM and Landau Lifschitz Gilbert simulations of the magnetic domain structure in Ni dots with a perpendicular anisotropy. The magnetic state of a witness film can be characterized by a stripe domain pattern with a regular period for the magnetization reversal. In the dots, we are able to predict the magnetic state by comparing the dot diameter to the stripe period. [1] Skidmore et al., Appl. Phys. Lett. 71, 3293-95 (1997) [2]. Wastlbauer et al., Appl. Phys. Lett., to be published in Jan. 2000.

Dahlberg, E. Dan

2000-03-01

10

Electric and Magnetic Forces: Electromagnetism  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach.This Science Object is the last of three Science Objects in the Electric and Magnetic Forces SciPack.

National Science Teachers Association (NSTA)

2008-10-30

11

Magnetic Force Three Wires Model  

NSDL National Science Digital Library

The Magnetic Force Three Wires model investigates the force between long straight current-carrying wires. Initially, the simulation shows a cross-section view of three long straight parallel wires, each on the corner of an equilateral triangle. The wires carry currents that have different magnitudes, and the currents are directed either into or out of the page. The task in this simulation is to rank the wires based on the magnitude of their currents, from largest to smallest. The Magnetic Force Three Wires model was created using the Easy Java Simulations (EJS) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_bu_Three_Wires.jar file will run the program if Java is installed. This is part of a collection of similar tutorial simulations created by the author.

Duffy, Andrew

2009-10-20

12

Turbulence generation by electric body forces  

Microsoft Academic Search

The effect of an electric body force on vorticity production and turbulence generation in a gas is investigated by examination of the governing electrohydrodynamic equations. The theoretical concepts are illustrated by hot-film anemometer measurements of the electrically induced turbulence in a large scale electrostatic precipitator. The results indicate dramatic increases in turbulence and diffusivity due to the corona discharge and

J. H. Davidson; E. J. Shaughnessy

1986-01-01

13

Slender soft-magnetic body in highly viscous flows  

NASA Astrophysics Data System (ADS)

For a tilted soft-magnetic slender body in a highly viscous fluid whose motion is driven by a prescribed background rotating magnetic field, the interaction between hydrodynamic and magnetic forces must be understood in order to predict the combined motion of a rod in silicon oil. Such a system arises in an experiment emulating primary cilia-driven fluid flows in developing embryos. Using classical slender body theory, the magnetic contribution to this dynamical system results in a system of equations for the torque balance. Further, analysis of body geometry such as fixed curvature will be explored, and their influence on the fluid motion illustrated.

Martindale, James; Camassa, Roberto; McLaughlin, Richard; Vicci, Leandra; Zhao, Longhua

2010-11-01

14

Maneuvering a reentry body via magnetogasdynamic forces  

NASA Astrophysics Data System (ADS)

A two-dimensional finite difference algorithm is developed to predict supersonic magnetogasdynamic (MGD) flow of compressible, inviscid, electrically conducting gases in nonuniform magnetic fields. The algorithm is then used to determine the pitching moments generated on a reentry body by a control system based on fluid-electromagnetic interactions. It was shown that, for very-high-speed reentry vehicles, the proposed MGD system could produce moments on the same order as those produced by conventional flap systems at low deflection angles; also, that moments predicted using equilibrium gas chemistry were improved over those predicted using the frozen chemistry assumption.

O'Hare, Leo P.; Anderson, John D., Jr.

1993-07-01

15

When do magnetic forces do work?  

NASA Astrophysics Data System (ADS)

All of the introductory physics texts in my library tell me at some point that magnetic forces cannot do work, but about half go on to present examples in which it is claimed that magnetic forces can do work. One should not be surprised, therefore, if many of us are confused about what magnetic forces can and cannot do. I hope to provide clarity on this issue.

Mitschele, Jonathan

2007-10-01

16

The force on a magnetic dipole  

NASA Astrophysics Data System (ADS)

The classical magnetic force on a magnetic dipole depends upon the model for the dipole. The usual electric current loop model for a magnetic dipole leads to the force F=?(m.B) on a magnetic dipole m in a magnetic field B. The separated magnetic charge model for a magnetic dipole leads to the force F=(m.?)B on a magnetic dipole. The latter expression is analogous to the force experienced by an electric dipole in an electric field. Here, some elementary examples are given where the force expressions yield entirely different forces on a magnetic dipole. Electromagnetism textbooks usually do not emphasize the difference between these force expressions; however, occasionally the difference is important for understanding experimental results. In the 1930s and 1940s the difference in force expressions was involved in a determination of the nature of the neutron dipole moment. At present, in the 1980s, the difference in the force expressions is central to a controversy over an experiment to test the proposed Aharonov-Casher effect.

Boyer, Timothy H.

1988-08-01

17

Force sensor using changes in magnetic flux  

NASA Technical Reports Server (NTRS)

A force sensor includes a magnetostrictive material and a magnetic field generator positioned in proximity thereto. A magnetic field is induced in and surrounding the magnetostrictive material such that lines of magnetic flux pass through the magnetostrictive material. A sensor positioned in the vicinity of the magnetostrictive material measures changes in one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux.

Pickens, Herman L. (Inventor); Richard, James A. (Inventor)

2012-01-01

18

Effective Magnus Force on a Magnetic Vortex  

NASA Astrophysics Data System (ADS)

In classical hydrodynamics, a Magnus force exists between a vortex and the hosting fluid acting transverse to their relative motion. There is a quantum Magnus force acting on vortices in superfluids and superconductors and an analogous force acting on magnetic vortices excited in spin systems. Couplings with the system quasiparticles can modify this to an effective Magnus force by introducing transverse damping forces. The existence and magnitude of transverse damping forces are highly controversial and have not been settled by experiment. We derive the various damping forces on a vortex in a magnetic system, in particular, damping forces acting longitudinally and transversely to current and past motion (memory effects). In a magnetic system, we expect experiments can more accurately study vortex motion for comparison with theory. Despite the simplicity of the spin system, the results are general and should reveal quantitative behaviour for the superfluid/superconductor systems.

Thompson, L. R.; Stamp, P. C. E.

19

Magnetic Resonance Force Microscopy with Magnetic Tiped Cantilevers  

Microsoft Academic Search

Magnetic resonance force microscopy has been performed, until recently, by attaching the sample under study to a fragile microcantilever. Increasing the resolution, force-sensitivity and practicality of the technique, demands both reducing the size of the magnetic particle and measuring magnetic resonance as an excitation of magnetic-tip cantilevers. To lift the sample-on-cantilever restriction we have succesfully attached and controllably magnetized a

John A. Marohn; Raul Fainchtein; Doran D. Smith

1998-01-01

20

Verifying Magnetic Force on a Conductor  

ERIC Educational Resources Information Center

The laboratory measurement of the magnetic force acting on a straight wire of length "l" carrying a current of intensity "i" in a magnetic field "B" is usually made using current balances, which are offered by various physics apparatus suppliers' catalogues. These balances require an adequate magnet and commonly allow only the measurement of the…

Ganci, Salvatore

2011-01-01

21

Magnetization reversal of ferromagnetic nanowires studied by magnetic force microscopy  

Microsoft Academic Search

The magnetization reversal of two-dimensional arrays of parallel ferromagnetic Fe nanowires embedded in nanoporous alumina templates has been studied. By combining bulk magnetization measurements (superconducting quantum interference device magnetometry) with field-dependent magnetic force microscopy (MFM), we have been able to decompose the macroscopic hysteresis loop in terms of the irreversible magnetic responses of individual nanowires. The latter are found to

T. G. Sorop; C. Untiedt; F. Luis; M. Kröll; M. Rasa; L. J. de Jongh

2003-01-01

22

Subpiconewton Dynamic Force Spectroscopy Using Magnetic Tweezers  

PubMed Central

We introduce a simple method for dynamic force spectroscopy with magnetic tweezers. This method allows application of subpiconewton force and twist control by calibration of the applied force from the height of the magnets. Initial dynamic force spectroscopy experiments on DNA molecules revealed a large hysteresis that is caused by viscous drag on the magnetic bead and will conceal weak interactions. When smaller beads are used, this hysteresis is sufficiently reduced to reveal intramolecular interactions at subpiconewton forces. Compared with typical quasistatic force spectroscopy, a significant reduction of measurement time is achieved, allowing the real-time study of transient structures and reaction intermediates. As a proof of principle, nucleosome-nucleosome interactions on a subsaturated chromatin fiber were analyzed.

Kruithof, M.; Chien, F.; de Jager, M.; van Noort, J.

2008-01-01

23

Body forces and pressures in elastic models of the myocardium.  

PubMed Central

Tension strands are introduced to represent active myocardial fibers. They create one body force proportional to the divergence of the tension-direction vector, and a second equal to the tension divided by the radius of curvature. Explicit solutions to isotropic linearly elastic tensor equations with these body forces are found for the radially-symmetric, linearly-isotropic, elastic spherical heart with arbitrary radial body force. They confirm experiments showing supraluminal intramural pressures. Such pressures may affect coronary perfusion. A tension strand model which is a reasonable compromise between actual myofibrillar geometry and analytical simplicity is the iso-oblique, terminating, nonintersecting model. The body force from that or any other axially symmetric body force can be the forcing term for equations in which the heart is modeled as a thin, ellipsoidal, elastic membrane.

Pierce, W H

1981-01-01

24

Measurement of the body force field of plasma actuators  

Microsoft Academic Search

A novel technique is proposed and investigated for the estimation of the body force field resulting from the operation of a dielectric barrier discharge plasma actuator. The technique relies on the measurement of the spatio-temporal evolution of the induced velocity field using high-speed particle image velocimetry (PIV). The technique has the advantage of providing spatial distribution of the body force

M. Kotsonis; S. Ghaemi; L. Veldhuis; F. Scarano

2011-01-01

25

Magnetic force and work: an accessible example  

NASA Astrophysics Data System (ADS)

Despite their physics instructors’ arguments to the contrary, introductory students can observe situations in which there seems to be compelling evidence for magnetic force doing work. The counterarguments are often highly technical and require physics knowledge beyond the experience of novice students, however. A simple example is presented which can illustrate that all may not be what it seems when energy transfer and the magnetic force are involved. Excel and Python simulations of the process are also provided.

Gates, Joshua

2014-05-01

26

Current-modulating magnetic force microscope probe  

SciTech Connect

A new current-modulating probe for the magnetic force microscope (MFM) is proposed in this article. The magnetic field, which will be used to interact with a magnetic specimen{close_quote}s stray field, is induced on the sharp tip of the conical magnetic core surrounded by a microfabricated single turn conductive coil. The reciprocity principle is used to obtain the force acting on the probe due to the specimen{close_quote}s stray field when scanned over a magnetic specimen. The magnetic field intensity is adjustable by control of the applied current. Images of specimens have been modeled using this probe. The suitability to different specimens is seen to be the biggest advantage of this scheme over the conventional probe designs. {copyright} 2001 American Institute of Physics.

Wang, Frank Z.; Helian, Na; Clegg, Warwick W; Windmill, James F. C.; Jenkins, David

2001-06-01

27

Manipulation and identification of objects by magnetic forces  

NASA Technical Reports Server (NTRS)

An overview is presented of the results of research and engineering design activities over the past 20 years in the area of identification and manipulation of objects by magnetic forces. The relationship is discussed between the properties of objects and the parameters of magnetic fields, with the view toward being able to create forces for efficient manipulation and identification of different kinds of parts. Some of this information, particularly regarding nonferromagnetic materials, is relatively new and can be used to solve a variety of engineering problems by creating new types of automation systems. Topics covered include identification and orientation of bodies by magnetostatic and electrodynamic forces, electromagnetic recognition and orientation of nonsymmetric parts, and assembly and position control of parts by electromagnetic forces.

Joffe, Benjamin

1992-01-01

28

Magnetic field gradient measurement on magnetic cards using magnetic force microscopy  

Microsoft Academic Search

The magnetic field gradients of magnetic stripe cards, which are developed for classifying magnetic particles used in magnetic particle inspections, have been measured using a magnetic force microscope (MFM). The magnetic force exerted on a MFM probe by the stray field emanating from the card was measured to determine the field gradients. The results are in good agreement with the

C. C. H. Lo; J. Leib; D. C. Jiles; W. C. Chedister

2002-01-01

29

Treatment of body forces in boundary element design sensitivity analysis  

NASA Technical Reports Server (NTRS)

The inclusion of body forces has received a good deal of attention in boundary element research. The consideration of such forces is essential in the desgin of high performance components such as fan and turbine disks in a gas turbine engine. Due to their critical performance requirements, optimal shapes are often desired for these components. The boundary element method (BEM) offers the possibility of being an efficient method for such iterative analysis as shape optimization. The implicit-differentiation of the boundary integral equations is performed to obtain the sensitivity equations. The body forces are accounted for by either the particular integrals for uniform body forces or by a surface integration for non-uniform body forces. The corresponding sensitivity equations for both these cases are presented. The validity of present formulations is established through a close agreement with exact analytical results.

Saigal, Sunil; Kane, James H.; Aithal, R.; Cheng, Jizu

1989-01-01

30

Dynamical friction force exerted on spherical bodies  

NASA Astrophysics Data System (ADS)

We present a rigorous calculation of the dynamical friction force exerted on a spherical massive perturber moving through an infinite homogenous system of field stars. By calculating the shape and mass of the polarization cloud induced by the perturber in the background system, which decelerates the motion of the perturber, we recover Chandrasekhar's drag force law with a modified Coulomb logarithm. As concrete examples, we calculate the drag force exerted on a Plummer sphere or a sphere with the density distribution of a Hernquist profile. It is shown that the shape of the perturber only affects the exact form of the Coulomb logarithm. The latter converges on small scales because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm in this way the earlier results based on the impulse approximation of small angle scatterings.

Esquivel, O.; Fuchs, B.

2007-07-01

31

Magnetic wires with DNA cores: A magnetic force microscopy study  

NASA Astrophysics Data System (ADS)

Magnetic force microscopy (MFM) has been employed to study Fe3O4 nanowires containing DNA cores. The MFM experiments confirmed that long DNA molecules templated with Fe3O4 nanoparticles form a magnetic wire. The components of wires containing particles with sizes below 10 nm were recorded to behave as single domain particles with out-of-plane magnetization. The MFM study showed that one can change the magnetization states of the particles using a magnetic tip. The properties of the magnetic wires with DNA cores make them an attractive material for future magnetostatic devices.

Nyamjav, Dorjderem; Kinsella, Joseph M.; Ivanisevic, Albena

2005-02-01

32

Magnetic force control technique in industrial application  

NASA Astrophysics Data System (ADS)

Techniques of the magnetic force control have been examined for industrial application. The problems and the technique are different in dispersion medium of gas and that of liquid. In addition, the method is different depending on the magnetic characteristic of the target objects. In case of the liquid, the dispersion medium having different viscosity was examined. The separation speed is decided with the magnitude of the magnetic force because a drag force increases with the viscosity. When the water is the dispersion medium, magnetic seeding is possible and hence the nonmagnetic materials can be separated and even the dissolved material could be separated. The separation technique has been used for purifying the waste water form paper mill or wash water of drum. On the other hand when the water is not dispersion medium, mainly the ferromagnetism particle becomes the target object because the magnetic seeding becomes difficult. The iron fragments have been separated from the slurry of slicing machine of solar battery. It has been clarified high gradient magnetic separation (HGMS) can be applied for the viscous fluid of which viscosity was as high as 10 Pa s. When the dispersion medium is gaseous material, the air is important. The drag force from air depends greatly on Reynolds number. When speed of the air is small, the Reynolds number is small, and the drag force is calculated by the Stokes’ law of resistance. The study with gaseous dispersion medium is not carried out much. The magnetic separation will discuss the possibility of the industrial application of this technique.

Nishijima, S.

2010-11-01

33

Forces and moments on a slender, cavitating body  

SciTech Connect

Recently a numerical code has been developed at Sandia National Laboratories to predict the pitching moment, normal force, and axial force of a slender, supercavitating shape. The potential flow about the body and cavity is calculated using an axial distribution of source/sink elements. The cavity surface is assumed to be a constant pressure streamline, extending beyond the base of the model. Slender body approximation is used to model the crossflow for small angles of attack. A significant extension of previous work in cavitation flow is the inclusion of laminar and turbulent boundary layer solutions on the body. Predictions with this code, for axial force at zero angle of attack, show good agreement with experiments. There are virtually no published data availble with which to benchmark the pitching moment and normal force predictions. An experiment was designed to measure forces and moments on a supercavitation shape. The primary reason for the test was to obtain much needed data to benchmark the hydrodynamic force and moment predictions. Since the numerical prediction is for super cavitating shapes at very small cavitation numbers, the experiment was designed to be a ventilated cavity test. This paper describes the experimental procedure used to measure the pitching moment, axial and normal forces, and base pressure on a slender body with a ventilated cavity. Limited results are presented for pitching moment and normal force. 5 refs., 7 figs.

Hailey, C.E.; Clark, E.L.; Buffington, R.J.

1988-01-01

34

Magnetic field gradient measurement on magnetic cards using magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The magnetic field gradients of magnetic stripe cards, which are developed for classifying magnetic particles used in magnetic particle inspections, have been measured using a magnetic force microscope (MFM). The magnetic force exerted on a MFM probe by the stray field emanating from the card was measured to determine the field gradients. The results are in good agreement with the field gradients estimated from the magnetizing field strengths used in the encoding process. .

Lo, C. C. H.; Leib, J.; Jiles, D. C.; Chedister, W. C.

2002-05-01

35

Dynamical friction force exerted on spherical bodies  

NASA Astrophysics Data System (ADS)

Following a wave-mechanical treatment we calculate the drag force exerted by an infinite homogeneous background of stars on a perturber as it makes its way through the system. We recover Chandrasekhar's classical dynamical friction (DF) law with a modified Coulomb logarithm. We take into account a range of models that encompasses all plausible density distributions for satellite galaxies by considering the DF exerted on a Plummer sphere and a perturber having a Hernquist profile. It is shown that the shape of the perturber affects only the exact form of the Coulomb logarithm. The latter converges on small scales, because encounters of the test and field stars with impact parameters less than the size of the massive perturber become inefficient. We confirm this way earlier results based on the impulse approximation of small angle scatterings.

Esquivel, O.; Fuchs, B.

2008-12-01

36

Electric and Magnetic Forces: Electric Charges  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach.This Science Object is the first of three Science Objects in the Electric and Magnetic Forces SciPack.

National Science Teachers Association (NSTA)

2008-10-30

37

Measuring the Forces between Magnetic Dipoles  

ERIC Educational Resources Information Center

We describe a simple undergraduate lab in which students determine how the force between two magnetic dipoles depends on their separation. We consider the case where both dipoles are permanent and the case where one of the dipoles is induced by the field of the other (permanent) dipole. Agreement with theoretically expected results is quite good.

Gayetsky, Lisa E.; Caylor, Craig L.

2007-01-01

38

Magnetic Force Microscopy Images of Magnetic Garnet With Thin-Film Magnetic Tip  

NASA Technical Reports Server (NTRS)

We present magnetic force microscopy images of YGdTmGa/YSmTmGa magnetic garnet, usinga thin Fe film deposited on Si_3N_5 tips. We have found correlations between the topography andthe magnetic domain structure. We have observed the domain wall contrast with a iron thin-film tip. We report on domain wall imaging of garnet with magnetic force microscopy.

Wadas, A.; Moreland, J.; Rice, P.; Katti, R.

1993-01-01

39

A magnetic thrust action on small bodies orbiting a pulsar  

NASA Astrophysics Data System (ADS)

Aims: We investigate the electromagnetic interaction of a relativistic stellar wind with small bodies in orbit around the star. Methods: Based on our work on the theory of Alfvén wings to relativistic winds presented in a companion paper, we estimate the force exerted by the associated current system on orbiting bodies and evaluate the resulting orbital drift. Results: This Alfvénic structure is found to have no significant influence on planets or smaller bodies orbiting a millisecond pulsar. On the time scale of millions of years, it can however affect the orbit of bodies with a diameter of 100 km around standard pulsars with a period P ~ 1 s and a magnetic field B ~ 108 T. Kilometer-sized bodies experience drastic orbital changes on a time scale of 104 years.

Mottez, F.; Heyvaerts, J.

2011-08-01

40

About modeling aspects for the simulation of Magnetic Force Microscopes  

Microsoft Academic Search

This paper presents numerical investigations of an en- tire scanning process of a Magnetic Force Microscope. Due to the distinctly different scale of various components of this magneto- mechanical coupled system, the calculation of occurring magnetic forces needs to be done thoroughly. Magnetic Force Microscopy (MFM) has been designed to investigate the magnetic properties of different sam- ple materials on

T. Preisner; W. Mathis

2011-01-01

41

Revealing of magnetic domains of strong bulk anisotropic permanent magnets via magnetic force microscopy  

NASA Astrophysics Data System (ADS)

A novel fixture is provided for revealing magnetic domains of strong bulk permanent magnets in remanent state using magnetic force microscopy (MFM). Using this, the magnetic force lines outside the strong magnetic samples are introduced through a soft magnetic alloy with high permeability, giving rise to little perturbation between magnetic sample and MFM tips while scanning. Simulation results show that the demagnetized field over the studied surface is lowered about 300 times for a cuboid permanent magnet sample. Taking typical strong Sm2Co17-type sintered magnet as example, the true revealing of the magnetic domains via MFM further confirms that the method provided is feasible.

Fang, Yi-Kun; Li, Wei; Sun, Wei; Zhu, Ming-Gang; Guo, Zhao-Hui; Han, Bao-Shan

2013-11-01

42

Discreteness noise versus force errors in N-body simulations  

NASA Technical Reports Server (NTRS)

A low accuracy in the force calculation per time step of a few percent for each particle pair is sufficient for collisionless N-body simulations. Higher accuracy is made meaningless by the dominant discreteness noise in the form of two-body relaxation, which can be reduced only by increasing the number of particles. Since an N-body simulation is a Monte Carlo procedure in which each particle-particle force is essentially random, i.e., carries an error of about 1000 percent, the only requirement is a systematic averaging-out of these intrinsic errors. We illustrate these assertions with two specific examples in which individual pairwise forces are deliberately allowed to carry significant errors: tree-codes on supercomputers and algorithms on special-purpose machines with low-precision hardware.

Hernquist, Lars; Hut, Piet; Makino, Jun

1993-01-01

43

Control of the Casimir Force Using Semiconductor Test Bodies  

NASA Astrophysics Data System (ADS)

We describe experimental and related theoretical work on the measurement of the Casimir force using semiconductor test bodies. This field of research started in 2005 and several important and interesting results have already been obtained. Specifically, the Casimir force or its gradient was measured in the configuration of an Au-coated sphere and different semiconductor surfaces. It was found that the force magnitude depends significantly on the replacement of the metal with a semiconductor and on the concentration of charge carriers in the semiconductor material. Special attention is paid to the experiment on the optical modulation of the Casimir force. In this experiment the difference in Casimir force between an Au-coated sphere and a Si plate in the presence and in the absence of laser light was measured. Possible applications of this experiment are discussed, specifically, for the realization of the pulsating Casimir force in three-layer systems. Theoretical problems arising from the comparison of the experimental data for the difference in Casimir force with the Lifshitz theory are analyzed. We consider the possibility to control the magnitude of the Casimir force in phase transitions of semiconductor materials. Experiments on measuring the Casimir force gradient between an Au-coated sphere and a Si plate covered with rectangular corrugations of different characters are also described. Here, we discuss the interplay between the material properties and nontrivial geometry and the applicability of the proximity force approximation. The review contains comparison between different experiments and analysis of their advantages and disadvantages.

Klimchitskaya, G. L.; Mohideen, U.; Mostepanenko, V. M.

44

Magnetic dynamos in accreting planetary bodies  

NASA Astrophysics Data System (ADS)

Laboratory measurements revealed ancient remanent magnetization in meteorites [1] indicating the activity of magnetic dynamos in the corresponding meteorite parent body. To study under which circumstances dynamo activity is possible, we use a new methodology to simulate the internal evolution of a planetary body during accretion and differentiation. Using the N-body code PKDGRAV [2] we simulate the accretion of planetary embryos from an initial annulus of several thousand planetesimals. The growth history of the largest resulting planetary embryo is used as an input for the thermomechanical 2D code I2ELVIS [3]. The thermomechanical model takes recent parametrizations of impact processes [4] and of the magnetic dynamo [5] into account. It was pointed out that impacts can not only deposit heat deep into the target body, which is later buried by ejecta of further impacts [6], but also that impacts expose in the crater region originally deep-seated layers, thus cooling the interior [7]. This combination of impact effects becomes even more important when we consider that planetesimals of all masses contribute to planetary accretion. This leads occasionally to collisions between bodies with large ratios between impactor and target mass. Thus, all these processes can be expected to have a profound effect on the thermal evolution during the epoch of planetary accretion and may have implications for the magnetic dynamo activity. Results show that late-formed planetesimals do not experience silicate melting and avoid thermal alteration, whereas in early-formed bodies accretion and iron core growth occur almost simultaneously and a highly variable magnetic dynamo can operate in the interior of these bodies.

Golabek, G.; Labrosse, S.; Gerya, T.; Morishima, R.; Tackley, P. J.

2012-12-01

45

MICROFLARE ACTIVITY DRIVEN BY FORCED MAGNETIC RECONNECTION  

SciTech Connect

High cadence, multiwavelength, optical observations of a solar active region, obtained with the Swedish Solar Telescope, are presented. Two magnetic bright points are seen to separate in opposite directions at a constant velocity of 2.8 km s{sup -1}. After a separation distance of {approx}4400 km is reached, multiple Ellerman bombs are observed in both H{alpha} and Ca-K images. As a result of the Ellerman bombs, periodic velocity perturbations in the vicinity of the magnetic neutral line, derived from simultaneous Michelson Doppler Imager data, are generated with amplitude {+-}6 km s{sup -1} and wavelength {approx}1000 km. The velocity oscillations are followed by an impulsive brightening visible in H{alpha} and Ca-K, with a peak intensity enhancement of 63%. We interpret these velocity perturbations as the magnetic field deformation necessary to trigger forced reconnection. A time delay of {approx}3 minutes between the H{alpha}-wing and Ca-K observations indicates that the observed magnetic reconnection occurs at a height of {approx}200 km above the solar surface. These observations are consistent with theoretical predictions and provide the first observational evidence of microflare activity driven by forced magnetic reconnection.

Jess, D. B.; Mathioudakis, M.; Crockett, P. J.; Keenan, F. P. [Astrophysics Research Centre, School of Mathematics and Physics, Queen's University, Belfast, BT7 1NN (United Kingdom); Browning, P. K. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom)], E-mail: d.jess@qub.ac.uk

2010-03-20

46

Management of postequatorial magnetic intraretinal foreign bodies.  

PubMed

17 patients with intraretinal magnetic foreign bodies and vitreous hemorrhage are reported. 15 patients underwent a primary surgical repair consisting of a watertight wound closure and removal of the already swelling cataractous lens in 5 cases. All patients had vitrectomy during the second postinjury week. The foreign body was left in place in 2 cases and removed with intravitreal forceps in 15 patients. Total or partial retinal attachment was achieved in 12 patients (71%). Details of the surgical procedure are described. PMID:2625380

Kuhn, F; Kovacs, B

1989-09-01

47

Microrheology of cells with magnetic force modulation atomic force microscopy.  

PubMed

We propose a magnetic force modulation method to measure the stiffness and viscosity of living cells using a modified AFM apparatus. An oscillating magnetic field makes a magnetic cantilever oscillate in contact with the sample, producing a small AC indentation. By comparing the amplitude of the free cantilever motion (A0) with the motion of the cantilever in contact with the sample (A1), we determine the sample stiffness and viscosity. To test the method, the frequency-dependent stiffness of 3T3 fibroblasts was determined as a power law ks(f) = ? + ?(f/f[combining macron])(?) (? = 7.6 × 10(-4) N m(-1), ? = 1.0 × 10(-4) N m(-1), f[combining macron] = 1 Hz, ? = 0.6), where the coefficient ? = 0.6 is in good agreement with rheological data of actin solutions with concentrations similar to those in cells. The method also allows estimation of the internal friction of the cells. In particular we found an average damping coefficient of 75.1 ?N s m(-1) for indentation depths ranging between 1.0 ?m and 2.0 ?m. PMID:24651941

Rebêlo, L M; de Sousa, J S; Filho, J Mendes; Schäpe, J; Doschke, H; Radmacher, M

2014-03-01

48

Magnet polepiece design for uniform magnetic force on superparamagnetic beads  

PubMed Central

Here we report construction of a simple electromagnet with novel polepieces which apply a spatially uniform force to superparamagnetic beads in an optical microscope. The wedge-shaped gap was designed to keep ?Bx??y constant and B large enough to saturate the bead. We achieved fields of 300–600 mT and constant gradients of 67 T?m over a sample space of 0.5×4 mm2 in the focal plane of the microscope and 0.05 mm along the microscope optic axis. Within this space the maximum force on a 2.8 ?m diameter Dynabead was 12 pN with a spatial variation of approximately 10%. Use of the magnet in a biophysical experiment is illustrated by showing that gliding microtubules propelled by the molecular motor kinesin can be stopped by the force of an attached magnetic bead.

Fallesen, Todd; Hill, David B.; Steen, Matthew; Macosko, Jed C.; Bonin, Keith; Holzwarth, George

2010-01-01

49

Forces on bodies moving unsteadily in rapidly compressed flows  

NASA Astrophysics Data System (ADS)

The inviscid compressible flow generated by a rigid body of volume {cal V} moving unsteadily with a velocity {bm U} in a rapidly compressed homentropic flow is considered. The fluid is compressed isentropically at a rate {bm nabla} {bm *} {bm v}_0 uniformly over a scale much larger than the size of the body and the body moves slowly enough that the Mach number M is low. The flow is initially irrotational and remains so during compression. The perturbation to the flow generated by the body moving unsteadily is non-divergent within an evolving region {cal D} of distance int_0(t) c_1 dt from the body, where c_1 is the speed of sound. Within {cal D}, the flow is dominated by a source of strength ({bm nabla} {bm *} {bm v}_0){cal V} and a dipolar contribution which is independent of the rate of compression, while outside {cal D}, compressional waves propagate away from the body. When the body is much smaller than the characteristic distance \\|({bm nabla}{bm v}_0)|_{{bm x}_0}\\|/\\|({bm nabla} {bm nabla} {bm v}_0 )|_{{bm x}_0}\\| and the size of the region {cal D}, the separation of length scales enables the force on the body to be calculated analytically from the momentum flux far from the body (but within the region {cal D}). The contribution to the total force arising from fluid compression is rho(t) ({bm nabla} {bm *} {bm v}_0) {cal V} ({bm U}-{bm v}_0) {bm *} boldsymbol{alpha} , where {bm v}_0 is the velocity field in the absence of the particles and boldsymbol{alpha} is the virtual inertia tensor. Thus a body experiences a drag (thrust) force during fluid compression (expansion) because the density of the fluid displaced forward by the body increases (decreases) with time. The analysis indicates that the sum of the compressional and added-mass force is equal to the rate of decrease of fluid impulse {bm P} = rho(t){cal V}({bm U}-{bm v}_0) {bm *} boldsymbol{alpha}. Thus the concept of fluid impulse naturally extends to the class of flows where the fluid density changes with time, but is spatially uniform.

Eames, I.; Hunt, J. C. R.

2004-04-01

50

Magnetic force-induced damping effect for magnetic bearing motor  

NASA Astrophysics Data System (ADS)

An innovative damping induced by magnetic force was designed successfully for a totally passive magnetic bearing motor. A magnetic ring of high permeability and an annular-shaped rubber pad were mounted on the stator 0.55 mm below the permanent magnet of the rotor. Computer simulations were compared with experimental measurements to decide on the material and configuration of the critical components. The natural frequencies for lateral and rotational modes of the rotor are around 22 Hz measured by impulse method. Both the magnetic bearing motor with and without magnetic damping are rotated at a rated speed of 3840 rpm, which is far above the first critical speed of 1305 rpm. Without magnetic damping, the natural damping ratio in the radial direction of the rotor is 0.0655. After damping, it increases to 0.1401. We have demonstrated by both experimental measurement and theoretical calculation that the antishock performance is significantly improved by the innovative damping technology in a passive magnetic bearing motor.

Wang, Chien-Chang; Yao, Y. D.; Chang, Yu-Hsiu; Tung, Pi-Cheng; Xiao, Ren-Bin

2005-05-01

51

Novel magnetic tips developed for the switching magnetization magnetic force microscopy.  

PubMed

Using micromagnetic calculations we search for optimal magnetic properties of novel magnetic tips to be used for a Switching Magnetization Magnetic Force Microscopy (SM-MFM), a novel technique based on two-pass scanning with reversed tip magnetization. Within the technique the sum of two scans images local atomic forces and their difference maps the local magnetic forces. The tip magnetization is switched during the scanning by a small magnetic field. The technology of novel low-coercitive magnetic tips is proposed. For best performance the tips must exhibit low magnetic moment, low switching field, and single-domain state at remanence. Such tips are equipped with Permalloy objects of a precise shape that are defined on their tilted sides. We calculate switching fields of such tips by solving the micromagnetic problem to find the optimum shape and dimensions of the Permalloy objects located on the tips. Among them, hexagon was found as the best shape for the tips. PMID:21128443

Cambel, V; Eliás, P; Gregusová, D; Fedor, J; Martaus, J; Karapetrov, G; Novosad, V; Kostic, I

2010-07-01

52

Novel magnetic tips developed for the switching magnetization magnetic force microscopy.  

SciTech Connect

Using micromagnetic calculations we search for optimal magnetic properties of novel magnetic tips to be used for a Switching Magnetization Magnetic Force Microscopy (SM-MFM), a novel technique based on two-pass scanning with reversed tip magnetization. Within the technique the sum of two scans images local atomic forces and their difference maps the local magnetic forces. The tip magnetization is switched during the scanning by a small magnetic field. The technology of novel low-coercitive magnetic tips is proposed. For best performance the tips must exhibit low magnetic moment, low switching field, and single-domain state at remanence. Such tips are equipped with Permalloy objects of a precise shape that are defined on their tilted sides. We calculate switching fields of such tips by solving the micromagnetic problem to find the optimum shape and dimensions of the Permalloy objects located on the tips. Among them, hexagon was found as the best shape for the tips.

Cambel, V.; Elias, P.; Gregusova, D.; Fedor, J.; Martaus, J.; Karapetrov, G.; Novosad, V.; Kostic, I.; Materials Science Division; Slovak Academy of Sciences

2010-07-01

53

Magnetic resonance acoustic radiation force imaging  

PubMed Central

Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery.

McDannold, Nathan; Maier, Stephan E.

2008-01-01

54

Distinguishing magnetic and electrostatic interactions by a Kelvin probe force microscopy-magnetic force microscopy combination  

PubMed Central

Summary The most outstanding feature of scanning force microscopy (SFM) is its capability to detect various different short and long range interactions. In particular, magnetic force microscopy (MFM) is used to characterize the domain configuration in ferromagnetic materials such as thin films grown by physical techniques or ferromagnetic nanostructures. It is a usual procedure to separate the topography and the magnetic signal by scanning at a lift distance of 25–50 nm such that the long range tip–sample interactions dominate. Nowadays, MFM is becoming a valuable technique to detect weak magnetic fields arising from low dimensional complex systems such as organic nanomagnets, superparamagnetic nanoparticles, carbon-based materials, etc. In all these cases, the magnetic nanocomponents and the substrate supporting them present quite different electronic behavior, i.e., they exhibit large surface potential differences causing heterogeneous electrostatic interaction between the tip and the sample that could be interpreted as a magnetic interaction. To distinguish clearly the origin of the tip–sample forces we propose to use a combination of Kelvin probe force microscopy (KPFM) and MFM. The KPFM technique allows us to compensate in real time the electrostatic forces between the tip and the sample by minimizing the electrostatic contribution to the frequency shift signal. This is a great challenge in samples with low magnetic moment. In this work we studied an array of Co nanostructures that exhibit high electrostatic interaction with the MFM tip. Thanks to the use of the KPFM/MFM system we were able to separate the electric and magnetic interactions between the tip and the sample.

Jaafar, Miriam; Iglesias-Freire, Oscar; Serrano-Ramon, Luis; Ibarra, Manuel Ricardo; de Teresa, Jose Maria

2011-01-01

55

Magnetic dynamos in accreting planetary bodies  

NASA Astrophysics Data System (ADS)

Laboratory measurements revealed ancient remanent magnetization in meteorites [1] indicating the activity of magnetic dynamos in the corresponding meteorite parent body. To study under which circumstances dynamo activity is possible, we use a new methodology to simulate the internal evolution of a planetary body during accretion and differentiation. Using the N-body code PKDGRAV [2] we simulate the accretion of planetary embryos from an initial annulus of several thousand planetesimals. The growth history of the largest resulting planetary embryo is used as an input for the thermomechanical 2D code I2ELVIS [3]. The thermomechanical model takes recent parametrizations of impact processes [4] and of the magnetic dynamo [5] into account. It was pointed out that impacts can not only deposit heat deep into the target body, which is later buried by ejecta of further impacts [6], but also that impacts expose in the crater region originally deep-seated layers, thus cooling the interior [7]. This combination of impact effects becomes even more important when we consider that planetesimals of all masses contribute to planetary accretion. This leads occasionally to collisions between bodies with large ratios between impactor and target mass. Thus, all these processes can be expected to have a profound effect on the thermal evolution during the epoch of planetary accretion and may have implications for the magnetic dynamo activity. Results show that late-formed planetesimals do not experience silicate melting and avoid thermal alteration, whereas in early-formed bodies accretion and iron core growth occur almost simultaneously and a highly variable magnetic dynamo can operate in the interior of these bodies. [1] Weiss, B.P. et al., Science, 322, 713-716, 2008. [2] Richardson, D. C. et al., Icarus, 143, 45-59, 2000. [3] Gerya, T.V and Yuen, D.J., Phys. Earth Planet. Int., 163, 83-105, 2007. [4] Monteux, J. et al., Geophys. Res. Lett., 34, L24201, 2007. [5] Aubert, J. et al., Geophys. J. Int., 179, 1414-1428, 2009. [6] Safronov, V.S., Icarus, 33, 3-12, 1978. [7] Davies, G.F., in: Origin of the Earth, ed. H.E. Newsom, J.H. Jones, Oxford Un. Press, 175-194, 1990.

Golabek, Gregor; Labrosse, Stéphane; Gerya, Taras; Morishima, Ryuji; Tackley, Paul

2013-04-01

56

Force-Freeness of Solar Magnetic Fields in the Photosphere  

Microsoft Academic Search

It is widely believed that solar magnetic fields are force-free in the solar corona but not in the solar photosphere at all. In order to examine the force-freeness of active region magnetic fields at the photospheric level, we have calculated the integrated magnetic forces for 12 vector magnetograms of three flare-productive active regions. The magnetic field vectors are derived from

Y.-J. Moon; G. S. Choe; H. S. Yun; Y. D. Park; D. L. Mickey

2002-01-01

57

Force-Freeness of Solar Magnetic Fields in the Photosphere  

Microsoft Academic Search

It is widely believed that solar magnetic fields are force-free in the solar corona, but not in the solar photosphere. In order to examine the force-freeness of active region magnetic fields at the photospheric level, we have calculated the integrated magnetic forces for 33 vector magnetograms of four flare-productive active regions. The magnetic field vectors are derived from simultaneous Stokes

Y. Moon; G. S. Choe; H. S. Yun; Y. D. Park; D. L. Mickey

2001-01-01

58

Force?Freeness of Solar Magnetic Fields in the Photosphere  

Microsoft Academic Search

Q2 It is widely believed that solar magnetic fields are force-free in the solar corona but not in the solar photo- sphere at all. In order to examine the force-freeness of active region magnetic fields at the photospheric level, we have calculated the integrated magnetic forces for 12 vector magnetograms of three flare-productive active regions. The magnetic field vectors are

G. S. Choe; H. S. Yun; Y. D. Park; D. L. Mickey

2002-01-01

59

Nuclear matter equation of state and three-body forces  

SciTech Connect

The energy per particle, symmetry energy, pressure, and free energy are calculated for symmetric nuclear matter using BHF approach with modern nucleon-nucleon CD-Bonn, Nijm1, Argonne v{sub 18}, and Reid 93 potentials. To obtain saturation in nuclear matter we add three-body interaction terms which are equivalent to a density-dependent two-nucleon interaction a la Skyrme force. Good agreement is obtained in comparison with previous theoretical estimates and experimental data.

Mansour, H. M. M.; Algamoudi, A. M. A. [Cairo University, Physics Department, Faculty of Science (Egypt)

2012-04-15

60

Force-moment line element method for flexible slender bodies in Stokes flow.  

PubMed

The hydrodynamics of flexible slender bodies in Stokes flow is studied by taking into account the fluid-structure interaction through both forces and coupled moments. The fluid subjected to line sources of forces and moments is described by using integral equations. Meanwhile, the flexible slender body is modeled using finite beam elements. The two sides are linked through interfacial continuity conditions. Upon discretization, it results in a higher-order line element method for efficient and accurate solution of slender-body hydrodynamics. Four examples are presented to demonstrate the validity and efficiency of the present method: (a) hydrodynamics of a flexible slender rod subjected to a torque at one end, (b) hydrodynamics of a flexible slender rod subjected to a bending moment at one end, (c) hydrodynamics of a flexible slender rod subjected to a cyclic force, and (d) hydrodynamics of a flexible slender rod with a magnetized head within a rotating magnetic field. Examples (a) and (b) may serve as benchmark solutions and examples (c) and (d) show how planar and spiral waves can be excited in a slender body. PMID:24125384

Jiang, H; Yang, B

2013-09-01

61

Force-moment line element method for flexible slender bodies in Stokes flow  

NASA Astrophysics Data System (ADS)

The hydrodynamics of flexible slender bodies in Stokes flow is studied by taking into account the fluid-structure interaction through both forces and coupled moments. The fluid subjected to line sources of forces and moments is described by using integral equations. Meanwhile, the flexible slender body is modeled using finite beam elements. The two sides are linked through interfacial continuity conditions. Upon discretization, it results in a higher-order line element method for efficient and accurate solution of slender-body hydrodynamics. Four examples are presented to demonstrate the validity and efficiency of the present method: (a) hydrodynamics of a flexible slender rod subjected to a torque at one end, (b) hydrodynamics of a flexible slender rod subjected to a bending moment at one end, (c) hydrodynamics of a flexible slender rod subjected to a cyclic force, and (d) hydrodynamics of a flexible slender rod with a magnetized head within a rotating magnetic field. Examples (a) and (b) may serve as benchmark solutions and examples (c) and (d) show how planar and spiral waves can be excited in a slender body.

Jiang, H.; Yang, B.

2013-09-01

62

Forced magnetic reconnection in Tokamak plasmas  

NASA Astrophysics Data System (ADS)

This dissertation addresses two related problems in the study of forced magnetic reconnection in Tokamak plasmas. First, a recent controversy concerning a model forced magnetic reconnection problem, the Taylor problem, has been resolved. The criticisms of Ishizawa and Tokuda [21] concerning the original analysis of Hahm and Kulsrud [17] are shown to be unwarranted, both analytically and numerically. Second, one possible reason for the discrepancy between recent experimental [29] and previous theoretical [13] scaling of the critical error-field penetration threshold with device parameters is addressed. The theory in question is entirely based on a single-fluid MHD (magnetohydrodynamical) treatment of the plasma. As is well-known, high temperature plasmas are far better modeled using the drift-MHD ordering.[18] Hence we develop a drift-MHD theory of error-field penetration. Although two new drift-MHD plasma response regimes are identified, the overall threshold scaling with device parameters is not altogether different from that predicted by single-fluid MHD.

Cole, Andrew Joseph

63

Fluidic Control of Aerodynamic Forces on an Axisymmetric Body  

NASA Astrophysics Data System (ADS)

The aerodynamic forces and moments on a wind tunnel model of an axisymmetric bluff body are modified by induced local vectoring of the separated base flow. Control is effected by an array of four integrated aft-facing synthetic jets that emanate from narrow, azimuthally-segmented slots, equally distributed around the perimeter of the circular tail end within a small backward facing step that extends into a Coanda surface. The model is suspended in the wind tunnel by eight thin wires for minimal support interference with the wake. Fluidic actuation results in a localized, segmented vectoring of the separated base flow along the rear Coanda surface and induces asymmetric aerodynamic forces and moments to effect maneuvering during flight. The aerodynamic effects associated with quasi-steady and transitory differential, asymmetric activation of the Coanda effect are characterized using direct force and PIV measurements.

Abramson, Philip; Vukasinovic, Bojan; Glezer, Ari

2007-11-01

64

Application of magnetic force microscopy in nanomaterials characterization.  

PubMed

This review describes the basic technical aspects of magnetic force microscopy and how this technique has been applied to the study of colossal magnetoresistance materials, superconductors, and patterned magnetic materials. Recently, current distribution in a patterned aluminum strip has been measured by magnetic force microscopy, opening the possibility of measuring currents in buried interconnects in integrated circuits. PMID:16732543

de Lozanne, Alex

2006-07-01

65

Optical fibre bragg gratings based magnetic force measurement of magnetic bearings  

Microsoft Academic Search

Magnetic bearings are typical electromechanical systems of high performance. Current-displacement-force relationship between stator and rotor is an important research topic of magnetic bearings. The critical issue is to realize magnetic force online dynamic measurement. This paper presents a novel method on magnetic force measurement of magnetic bearings with optical fibre bragg gratings (FBG), which realizes a non-contact and online force

Guoping Ding; Zude Zhou; Yefa Hu; Jianhua Zhou

2008-01-01

66

Energy levels arising from resonant two-body forces in a three-body system  

Microsoft Academic Search

Resonant two-body forces are shown to give rise to a series of levels in three-particle systems. The number of such levels may be very large. Possibility of the existence of such levels in systems of three alpha-particles (12C nucleus) and three nucleons (3H) is discussed.

V. Efimov

1970-01-01

67

Electric and Magnetic Forces between Parallel-Wire Conductors.  

ERIC Educational Resources Information Center

Discusses electric and magnetic forces between parallel-wire conductors and derives, in a simple fashion, order of magnitude estimates of the ratio of the likely electrostatic and electromagnetic forces for a simple parallel-wire balance. (Author/HM)

Morton, N.

1979-01-01

68

May the Magnetic Force Be with You  

ERIC Educational Resources Information Center

Although most elementary students have had experiences with magnets, they generally have misconceptions about magnetism (Driver et al. 1994; Burgoon, Heddle, and Duran 2010). For example, students may think magnets can attract all metals or that larger magnets are stronger than smaller magnets. Students often confuse magnets with magnetic

Wilcox, Jesse; Richey, Lindsey R.

2012-01-01

69

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy  

Microsoft Academic Search

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.

Attila Nagy; Keir C Neuman

2008-01-01

70

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy  

PubMed Central

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations.

Neuman, Keir C.; Nagy, Attila

2012-01-01

71

Three-Body Forces and the Limit of Oxygen Isotopes  

SciTech Connect

The limit of neutron-rich nuclei, the neutron drip line, evolves regularly from light to medium-mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced in shell-model calculations derived from microscopic two-nucleon forces. Here, we present the first microscopic explanation of the oxygen anomaly based on three-nucleon forces that have been established in few-body systems. This leads to repulsive contributions to the interactions among excess neutrons that change the location of the neutron drip line from {sup 28}O to the experimentally observed {sup 24}O. Since the mechanism is robust and general, our findings impact the prediction of the most neutron-rich nuclei and the synthesis of heavy elements in neutron-rich environments.

Otsuka, Takaharu [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan, 48824 (United States); Suzuki, Toshio [Department of Physics, College of Humanities and Sciences, Nihon University, Sakurajosui 3, Tokyo 156-8550 (Japan); Holt, Jason D.; Schwenk, Achim [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Akaishi, Yoshinori [RIKEN Nishina Center, Hirosawa, Wako-shi, Saitama 351-0198 (Japan)

2010-07-16

72

Force-Free Magnetic Flux Ropes in the Solar Corona  

Microsoft Academic Search

In the course of an ongoing investigation of force-free magnetic fields in the spherical geometry appropriate to the solar corona, we have found solutions that represent magnetic flux ropes. The magnetic energy stored in these ropes and the surrounding field is larger than that which can be stored in simple magnetic arcades with the same boundary conditions, and in some

R. Wolfson

2003-01-01

73

Magnetic Forces and Field Line Density  

NSDL National Science Digital Library

This is an activity about depicting the relative strength of magnetic fields using field line density. Learners will use the magnetic field line drawing of six magnetic poles created in a previous activity and identify the areas of strong, weak, and medium magnetic intensity using the density of magnetic field lines. This is the fifth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website. How to Draw Magnetic Fields - II in the Magnetic Math booklet must be completed prior to this activity.

74

Reduction of Cogging Force in Linear Permanent-Magnet Generators  

Microsoft Academic Search

Although linear permanent-magnet generators (LPMGs) are widely used for converting wave energy into electrical energy, they suffer from large cogging force. The cogging force causes oscillatory output power, which shortens lifetime and increases the maintenance costs of the generators. To reduce this force in the generator, we have designed and simulated a three-phase LPMG for direct wave energy conversion and

Jawad Faiz; Mahdi Ebrahimi-Salari; Gh. Shahgholian

2010-01-01

75

Measured force/current relations in solid magnetic thrust bearings  

SciTech Connect

When magnetic bearings are employed in a pump, compressor, turbine, or other rotating machine, measurement of the current in the bearing coils provides knowledge of the forces imposed on the bearings. This can be a significant indicator of machine problems. Additionally, magnetic bearings can be utilized as a load cell for measuring impeller forces in test rigs. The forces supported by magnetic bearings are directly related to the currents, air gaps, and other parameters in the bearings. This paper discusses the current/force relation for magnetic thrust bearings. Force versus current measurements were made on a particular magnetic bearing in a test rig as the bearing coil currents were cycled at various time rates of change.d the quasi-static force versus current relations were measured for a variety of air gaps and currents. The thrust bearing exhibits a hysteresis effect, which creates a significant difference between the measured force when the current is increasing as compared to that when the current is decreasing. For design current loops, 0.95 A to 2.55 A, at the time rate of change of 0.1 A/s, the difference between increasing and decreasing current curves due to hysteresis ranged from 4 to 8%. If the bearing is operated in small trajectories about a fixed (nonzero) operation point on the F/I (force/current) curve, the scatter in the measurement error could be expected to be on the order of 4%. A quasi-static nonlinear current/force equation was developed to model the data and curve-fit parameters established for the measured data. The effects of coercive force and iron reluctance, obtained from conventional magnetic materials tests, were included to improve the model, but theoretically calculated values from simple magnetic circuit theory do not produce accurate results. Magnetic fringing, leakage, and other effects must be included.

Allaire, P.E.; Fittro, R.L.; Maslen, E.H. [Univ. of Virginia, Charlottesville, VA (United States). Mechanical, Aerospace, and Nuclear Engineering Dept.; Wakefield, W.C. [Proctor and Gamble, Hunt Valley, MD (United States)

1997-01-01

76

Power dissipation and magnetic forces and MAGLEV rebars  

SciTech Connect

Concrete guideways for proposed MAGLEV vehicles may be reinforced with electrically conducting and magnetizable steel rebars. Transient magnetic fields due to passing MAGLEV vehicles will then induce transient currents in the rebars leading to power dissipation and temperature rise as well as Lorentz and magnetization forces on the rebars. In order to evaluate if this heating and force on the rebars affects concrete life and performance, analysis is presented for an infinitely long conducting and magnetizable cylinder in imposed uniform axial or transverse magnetic fields. Exact and approximate solutions are presented for sinusoidal steady state and step transient magnetic fields inside and outside the cylinder, the induced current density, the vector potential for transverse magnetic fields, the time average dissipated power in the sinusoidal steady state, and the total energy dissipated for step transients. Forces are approximately calculated for imposed magnetic fields` with a weak spatial gradient. The analysis is applied to representative rebar materials.

Zahn, M. [Massachusetts Inst. of Tech., Cambridge, MA (United States)] [Massachusetts Inst. of Tech., Cambridge, MA (United States)

1997-03-01

77

Gravity Wave Radiation and Mean Responses to Local Body Forces in the Atmosphere  

Microsoft Academic Search

The authors determine the spectral linear solutions that arise in response to local 3D body forces and heatings in an idealized environment that turn on and off smoothly but not necessarily slowly over a finite interval in time. The solutions include impulsive through slowly varying body forcings. The forcings result in both a mean response, which is typically significantly broadened

Sharon L. Vadas; David C. Fritts

2001-01-01

78

The change in retentive force of magnetic attachment by abrasion  

Microsoft Academic Search

Magnets are frequently applied to removable dentures as retentive attachments. A magnet-retained removable overdenture might\\u000a be slightly shifted from side to side by eccentric movement in the mouth, and the surface of magnetic attachment may be worn\\u000a as a result. However, the relationship between the retentive force of magnetic attachment and its surface abrasion has not\\u000a been reported. The purpose

Yuanjin Huang; Yasuyuki Tawada; Yoshiaki Hata; Fumihiko Watanabe

2008-01-01

79

Forced heat loss from body surface reduces heat flow to body surface.  

PubMed

Heat stress is commonly relieved by forced evaporation from body surfaces. The mode of heat stress relief by heat extraction from the periphery is not clear, although it reduces rectal temperature. Radiant surface temperature (Ts) of the right half of the body surface was examined by thermovision in 4 lactating Holstein cows (30 kg of milk/d) during 7 repeated cycles of forced evaporation created by 30s of wetting followed by 4.5 min of forced airflow. Wetting was performed by an array of sprinklers (0.76 m(3)/h), and forced airflow (>3m/s velocity) over the right side of the body surface was produced by fans mounted at a height of 3m above the ground. Sprinkling wetted the hind legs, rump, and chest, but not the lower abdomen side, front legs, or neck. The animals were maintained in shade at an air temperature of 28 degrees C and relative humidity of 47%. Coat thickness was 1 to 2mm, so Ts closely represented skin temperature. Mean Ts of 5 x 20cm areas on the upper and lower hind and front legs, rump, chest, abdomen side, and neck were obtained by converting to temperature their respective gray intensity in single frames obtained at 10-s intervals. Little change occurred in Ts during the first wetting (0.1+/-0.6 degrees C), but it decreased rapidly thereafter (1.6+/-0.6 degrees C in the fifth wetting). The Ts also decreased, to a smaller extent, in areas that remained dry (0.7+/-1.0 degrees C). In all body sites, a plateau in Ts was reached by 2 min after wetting. The difference between dry and wet areas in the first cooling cycle was approximately 1.2 degrees C. The Ts of different body areas decreased during consecutive cooling cycles and reached a plateau by 3 cooling cycles in dry sites (front leg, neck, abdomen side), by 5 cooling cycles in the hind leg, and 7 cooling cycles in the rump and chest. The reduction in mean Ts produced by 7 cycles was 4.0 to 6.0 degrees C in wetted areas and 1.6 to 3.7 degrees C in sites that were not wetted. Initial rectal temperature was 38.9+/-0.1 degrees C; it remained unchanged during first 5 cooling cycles, decreased by 0.1 degrees C after 7 cooling cycles, and decreased to 38.4+/-0.06 degrees C after 8 to 10 cooling cycles, with no additional subsequent decrease. The concomitant reduction in Ts in dry and wet areas suggests an immediate vasoconstrictor response associated with heat extraction and later development of a cooler body shell. The reduction in rectal temperature represents a response involving transfer of heat from the body core to the body shell. This response mode requires consideration in settings of heat stress relief. PMID:20059922

Berman, A

2010-01-01

80

Distortion of magnetic field and magnetic force of a brushless dc motor due to deformed rubber magnet  

NASA Astrophysics Data System (ADS)

This paper investigates the distortion of magnetic field of a brushless dc (BLDC) motor due to deformed rubber magnet. Global or local deformation of rubber magnet in the BLDC motor is mathematically modeled by using the Fourier series. Distorted magnetic field is calculated by using the finite element method, and unbalanced magnetic force is calculated by using the Maxwell stress tensor. When the rubber magnet is globally or locally deformed, the unbalanced magnetic force has the frequencies with the first harmonic and the harmonics of slot number +/-1. However, the harmonic deformation with multiple of common divisor of pole and slot does not generate unbalanced magnetic force due to the rotational symmetry.

Lee, C. J.; Jang, G. H.

2008-04-01

81

Influence of Body Posture and Gravitational Forces on Shear Wave Propagation in the Skin  

Microsoft Academic Search

The body posture and gravitational forces govern in part the intrinsic skin tensile strength because they influence the orientation of the dermal fibre networks. Our objective was to assess changes in shear wave propagation in the skin according to the body posture and orientation of the gravitational forces. The study was performed in 30 middle-aged women with a normal body

J. L. Nizet; C. Piérard-Franchimont; G. E. Piérard

2001-01-01

82

Evolution of Nuclear Many-Body Forces with the Similarity Renormalization Group  

SciTech Connect

The first practical method to evolve many-body nuclear forces to softened form using the Similarity Renormalization Group (SRG) in a harmonic oscillator basis is demonstrated. When applied to 4He calculations, the two- and three-body oscillator matrix elements yield rapid convergence of the ground-state energy with a small net contribution of the induced four-body force.

Jurgenson, E D; Navratil, P; Furnstahl, R J

2009-05-01

83

Magnetic force improvement and parameter optimization for magnetic abrasive polishing of AZ31 magnesium alloy  

Microsoft Academic Search

The magnetic force acting on workpiece to be machined plays a significantly important role in magnetic abrasive polishing process. But in a case of polishing nonferrous materials, the strength of magnetic force is very low and it leads lower polishing efficiency. The magnesium alloy that has superior mechanical properties for industrial application such as a lightweight and high specific strength

S. O. KIM; J. S. KWAK

2008-01-01

84

Electron Spin Magnetic Resonance Force Microscopy of Nitroxide Spin Labels  

NASA Astrophysics Data System (ADS)

Nitroxide spin labels are widely used in electron spin resonance studies of biological and polymeric systems. Magnetic resonance force microscopy (MRFM) is a magnetic resonance technique that couples the high spatial resolution of a scanning probe microscope with the species selectivity of magnetic resonance. We report on our investigations of 4-amino TEMPO, a nitroxide spin label, by force-gradient MRFM. Our microscope operates at high vacuum in liquid helium, using a custom fabricated ultra-soft silicon cantilever in the magnet-on-cantilever geometry. An 18 GHz gap coupled microstripline resonator supplies the transverse field.

Moore, Eric W.; Lee, Sanggap; Hickman, Steven A.; Wright, Sarah J.; Marohn, John A.

2009-03-01

85

Energy release and plasma heating by forced magnetic reconnection  

NASA Astrophysics Data System (ADS)

A simple model of forced magnetic reconnection in a force-free magnetic field is considered, which allows the calculation of the magnetic energy release during the current sheet reconnection. The dependence of this energy on characteristics of the magnetic configuration has been studied, and it was found that the released energy becomes very large when the field is near the marginal tearing stability. A persistent plasma heating provided by ongoing external driving and internal reconnection is most efficient when the time-scales of these processes are comparable. Possible implications of the obtained results for the problem of solar coronal heating are briefly discussed.

Vekstein, G. E.; Jain, Rekha

1998-05-01

86

Optical fibre bragg gratings based magnetic force measurement of magnetic bearings  

NASA Astrophysics Data System (ADS)

Magnetic bearings are typical electromechanical systems of high performance. Current-displacement-force relationship between stator and rotor is an important research topic of magnetic bearings. The critical issue is to realize magnetic force online dynamic measurement. This paper presents a novel method on magnetic force measurement of magnetic bearings with optical fibre bragg gratings (FBG), which realizes a non-contact and online force measurement with simple configuration, good noise immunity even when the rotor is running. A novel micro force transducer is designed and fabricated, which is mounted within the stator magnetic pole. To obtain current-displacement-force relationship a FBG based magnetic force measurement test rig is setup to simulate magnetic bearing working states as the stator coils currents, air gap between stator and rotor, rotor speed is adjustable. Magnetic force is measured under three classifications of test conditions and test results are presented. The measurement data show good consistency with the theory analysis and calculation, which means that the FBG based magnetic force measurement is available and of good accuracy.

Ding, Guoping; Zhou, Zude; Hu, Yefa; Zhou, Jianhua

2008-12-01

87

EXPERIMENTAL BENCHMARKING OF THE MAGNETIZED FRICTION FORCE.  

SciTech Connect

High-energy electron cooling, presently considered as essential tool for several applications in high-energy and nuclear physics, requires accurate description of the friction force. A series of measurements were performed at CELSIUS with the goal to provide accurate data needed for the benchmarking of theories and simulations. Some results of accurate comparison of experimental data with the friction force formulas are presented.

FEDOTOV, A.V.; GALNANDER, B.; LITVINENKO, V.N.; LOFNES, T.; SIDORIN, A.O.; SMIRNOV, A.V.; ZIEMANN, V.

2005-09-18

88

Computation of the Hydrodynamic Forces and Moments on a Body of Revolution with and without Appendages.  

National Technical Information Service (NTIS)

An analytical method was developed to predict the hydrodynamic forces and moments developed on a body of revolution with and without appendages. The appendages included a bridge fairwater, sternplanes, and rudders. It was assumed that the body was either ...

Y. S. Hong

1991-01-01

89

Sensing the effect of body load in legs: responses of tibial campaniform sensilla to forces applied to the thorax in freely standing cockroaches  

Microsoft Academic Search

Sense organs in the legs that detect body weight are an important component in the regulation of posture and locomotion. We tested the abilities of tibial campaniform sensilla, receptors that can monitor forces in the cockroach leg, to encode variations in body load in freely standing animals. Small magnets were attached to the thorax and currents were applied to a

J. A. Noah; L. Quimby; S. F. Frazier; S. N. Zill

2004-01-01

90

Sensitive magnetic force detection with a carbon nanotube resonator  

NASA Astrophysics Data System (ADS)

We propose a technique for sensitive magnetic point force detection using a suspended carbon nanotube (CNT) mechanical resonator combined with a magnetic field gradient generated by a ferromagnetic gate electrode. Numerical calculations of the mechanical resonance frequency show that single Bohr magneton changes in the magnetic state of an individual magnetic molecule grafted to the CNT can translate to detectable frequency shifts, on the order of a few kHz. The dependences of the resonator response to device parameters such as length, tension, CNT diameter, and gate voltage are explored and optimal operating conditions are identified. A signal-to-noise analysis shows that, in principle, magnetic switching at the level of a single Bohr magneton can be read out in a single shot on timescales as short as 10 ?s. This force sensor should enable new studies of spin dynamics in isolated single molecule magnets, free from the crystalline or ensemble settings typically studied.

Willick, Kyle; Haapamaki, Chris; Baugh, Jonathan

2014-03-01

91

Fundamental study of phosphor separation by controlling magnetic force  

NASA Astrophysics Data System (ADS)

The phosphor wastes consist of phosphors with different emission colors, green (LAP), red (YOX), blue (BAM) and white (HP). It is required to recover and reuse the rare earth phosphors with high market value. In this study, we tried to separate the phosphor using the magnetic separation by HTS bulk magnet utilizing the differences of magnetic susceptibility by the type of phosphors. We succeeded in the successive separation of HP with low market value from YOX and BAM including the rare earth using the magnetic Archimedes method. In this method, vertical and radial components of the magnetic force were used.

Wada, Kohei; Mishima, Fumihito; Akiyama, Yoko; Nishijima, Shigehiro

2013-11-01

92

Force Measurements in Magnetic Suspension and Balance System  

NASA Technical Reports Server (NTRS)

The description of an infrared telemetry system for measurement of drag forces in Magnetic Suspension and Balance Systems (MSBS) is presented. This system includes a drag force sensor, electronic pack and transmitter placed in the model which is of special construction, and receiver with a microprocessor-based measuring device, placed outside of the test section. Piezosensitive resonators as sensitive elements and non-magnetic steel as the material for the force sensor are used. The main features of the proposed system for load measurements are discussed and the main characteristics are presented.

Kuzin, Alexander; Shapovalov, George; Prohorov, Nikolay

1996-01-01

93

Application of ferromagnetic nano-wires in porous alumina arrays for magnetic force generator  

Microsoft Academic Search

Magnetic chromatograph is a techniques that use magnetic force to separate small particles. It is interesting because the magnetic column can be used repeatedly and does not produce secondary wastes. In order to increase the efficiency of the separation, the magnetic force is desired to be as large as possible. The magnetic force increases in proportion to the magnetic field

S. Kato; H. Shinagawa; H. Okada; G. Kido; K. Mitsuhashi

2005-01-01

94

Magnetic forces in high-Tc superconducting bearings  

NASA Technical Reports Server (NTRS)

In September 1987, researchers at Cornell levitated a small rotor on superconducting bearings at 10,000 rpm. In April 1989, a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu307. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

Moon, F. C.

1991-01-01

95

Magnetic force microscopy sensors using iron-filled carbon nanotubes  

SciTech Connect

Probes for magnetic force microscopy (MFM) were prepared by pinning iron-filled multiwall carbon nanotubes to conventional scanning force microscopy probes. These nanotube MFM probes reveal a great potential for high spatial resolution of both topography and magnetic stray field. The ends of the high aspect ratio iron nanowires within the nanotubes can be considered as stationary effective magnetic monopole moments which opens the possibility of quantitative stray field measurements in a straightforward manner. The carbon shells around the iron nanowires provide wear resistance and oxidation protection.

Winkler, Andreas; Muehl, Thomas; Menzel, Siegfried; Kozhuharova-Koseva, Radinka; Hampel, Silke; Leonhardt, Albrecht; Buechner, Bernd [Leibniz Institute for Solid State and Materials Research (IFW) Dresden, Helmholtzstrasse 20, D-01069 Dresden (Germany)

2006-05-15

96

A magnetic gradient induced force in NMR restricted diffusion experiments  

NASA Astrophysics Data System (ADS)

We predict that the phase cancellation of a precessing magnetisation field carried by a diffusing species in a bounded geometry under certain nuclear magnetic resonance pulsed magnetic field gradient sequences results in a small force over typically micrometre length scales. Our calculations reveal that the total magnetisation energy in a pore under the influence of a pulsed gradient will be distance-dependent thus resulting in a force acting on the boundary. It is shown that this effect of the magnetisation of diffusing particles will appear as either an attractive or repulsive force depending on the geometry of the pore and magnetic properties of the material. A detailed analysis is performed for the case of a pulsed gradient spin-echo experiment on parallel planes. It is shown that the force decays exponentially in terms of the spin-spin relaxation. The proof is based on classical electrodynamics. An application of this effect to soft matter is suggested.

Ghadirian, Bahman; Stait-Gardner, Tim; Castillo, Reynaldo; Price, William S.

2014-03-01

97

Magnetic forces in high-T(sub c) superconducting bearings  

NASA Technical Reports Server (NTRS)

In September 1987 research at Cornell levitated a small rotor on superconducting bearing at 10,000 rpm. In April 1989 a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu3O7. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic drag forces of a magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the drag force reaches a constant value, independent of the speed. Dampling of lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

Moon, F. C.

1990-01-01

98

Magnetic forces in high-T(sub c) superconducting bearings  

NASA Astrophysics Data System (ADS)

In September 1987 research at Cornell levitated a small rotor on superconducting bearing at 10,000 rpm. In April 1989 a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu3O7. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic drag forces of a magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the drag force reaches a constant value, independent of the speed. Dampling of lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.

Moon, F. C.

1990-04-01

99

Determining large deformations and stresses of layered and graded structures to include effects of body forces  

US Patent & Trademark Office Database

Techniques for determining large deformation of layered or graded structures to include effects of body forces such as gravity, electrostatic or electromagnetic forces, and other forces that uniformly distribute over the structures, support forces, and concentrated forces. A real-time stress monitoring system is also disclosed to provide in-situ monitoring of a device based on the large deformation analytical approach. A coherent gradient sensing module, for example, may be included in such a system.

2004-08-24

100

Production of Tunguska-sized bodies by Earth's tidal forces  

Microsoft Academic Search

Tidal disruption of rubble-pile bodies (stony or icy aggregates held together by self-gravity) during close Earth encounters may produce significant numbers of Tunguska-sized (50 m) fragments. Using an N-body simulation to model encounters between strengthless, elongated, rotating, particulate bodies and the Earth, two disruption categories were found which produce small bodies: (a) ``Shoemaker-Levy-9 type'' catastrophic disruptions, where the progenitor is

William F. Bottke; Derek C. Richardson; Stanley G. Love

1998-01-01

101

A computer program to estimate the source body magnetization direction from magnetic and gravity anomalies  

Microsoft Academic Search

In this paper, a FORTRAN 77 computer program that estimates the inclination and declination of the magnetization of a body causing a magnetic anomaly is presented. The program searches for maximum correlation in between the pseudogravity anomalies at ranges of body magnetization and gravity anomalies caused by the same formations. The pseudogravity transformation is performed each time for an array

F. Bilim; A Ates

1999-01-01

102

Magnetic force microscopy on nanocrystalline Co films.  

PubMed

Pioneer works in ultrathin magnetic films have shown perpendicular magnetic domains in the demagnetized state. The source of this perpendicular anisotropy is the interface anisotropy developed at the interface. Similar domains could be observed in tetragonally distorted ultrathin films due to the magnetoelastic anisotropy. On the other hand, single-crystalline hexagonal close packed (hcp) Co films when grown epitaxially with the c-axis oriented perpendicular to the film plane may show perpendicular stripe magnetic domains even up to a thickness of about 500 nm. In that case the source of perpendicular anisotropy was the magnetocrystalline anisotropy of bulk Co, which favors the c-axis. In this work, we have grown by radio frequency magnetron sputtering Co films in the thickness range 15-4500 nm. We have used various substrates, such as Corning glass, silicon and Al-foil. The substrate temperature was about 350 K. The films have been found by X-ray diffraction experiments to present various structures and textures depending on the preparation conditions, mainly the Ar-pressure and deposition rate. Stripe- and labyrinth-like domain configurations are observed in films textured along the c-axis, and in films with a mixture of hcp and fcc grains, repectively. Films which show mainly fcc or amorphous structure do not form perpendicular domains. The results are discussed with respect to magnetization loops. PMID:21133159

Karoutsos, Vangelis; Poulopoulos, Panagiotis; Kapaklis, Vassilios; Pappas, Spiridon D; Trachylis, Dimitrios; Politis, Constantin

2010-09-01

103

Modeling complexly magnetized two-dimensional bodies of arbitrary shape  

SciTech Connect

A method has been devised for the forward computation of magnetic anomalies due to two-dimensional (2-D) polygonal bodies with heterogeneously directed magnetization. The calculations are based on the equivalent line source approach wherein the source is subdivided into discrete elements that vary spatially in their magnetic properties. This equivalent dipole line method provides a fast and convenient means of representing and computing magnetic anomalies for bodies possessing complexly varying magnitude and direction of magnetization. The algorithm has been tested and applied to several generalized cases to verify the accuracy of the computation. The technique has also been used to model observed aeromagnetic anomalies associated with the structurally deformed, remanently magnetized Keweenawan volcanic rocks in eastern Lake Superior. This method is also easily adapted to the calculation of anomalies due to two and one-half-dimensional (2.5-D) and three-dimensional (3-D) heterogeneously magnetized sources.

Mariano, J.; Hinze, W.J. (Purdue Univ., West Lafayette, IN (United States). Dept. of Earth and Atmospheric Sciences)

1993-05-01

104

The Calculation of Van Der Waals Dispersion Forces between Macroscopic Bodies  

Microsoft Academic Search

This paper aims at a simple treatment of van der Waals dispersion forces by applying classical electrostatics of two basic quantum-mechanical equations. Expressions are derived for the forces between macroscopic bodies, and the effects of adsorbed surface layers is considered both quantitatively and qualitatively. Approximate expressions are given for non-retarded dispersion forces in terms of the refractive indices and absorption

J. N. Israelachvili

1972-01-01

105

Prediction of Drift Forces on Twin Hull Bodies in Waves.  

National Technical Information Service (NTIS)

A theoretical method is presented to predict the steady mean surge and sway forces and roll and yaw moments on floating twin-hull ships in waves. The steady mean forces and moments are derived by utilizing the conservation of momentum of the fluid surroun...

C. M. Lee Y. H. Kim

1982-01-01

106

Experimental Investigation of Slenderness Effect on Side Force of Slender Body  

NASA Astrophysics Data System (ADS)

This study investigates side force of a slender body with slenderness from 4.4 to 8.0. The experimental results show that flow over a slender body experiences a significant side force at angle-of-attack (AOA) higher than 30°. The side force reaches its maximum at AOA ? 50°. The present study demonstrates that slenderness (L/D) produces obvious influence on sectional side force distribution at high AOA. To understand the mechanism, evolution of near-wall vortex structure is investigated via hot wire and surface pressure measurements. It was found that one strong vortex is situated close to body surface and the other weak vortex away from the body, inducing a significant side force. Because the weak vortex lifts off early, a new vortex forms in near-wall region. Formation and evolution of the new vortex is the major mechanism that causes local sectional side force distribution exhibiting a wavy form with an alternating sign along the body. Therefore, overall side force does not necessarily increase with increasing slenderness. Reducing overall side force by canceling the alternating vortex-induced forces over the body surface is found if the slenderness L/D > 6.8 at AOA > 40°.

Leu, Tzong-Shyng; Chang, Jeng-Ren; Kuo, Chun-Lin

107

Force-free magnetic relaxation in driven plasmas  

NASA Astrophysics Data System (ADS)

J. B. Taylor (1974) postulated that the helicity-conserving minimum magnetic energy state is the consequence of plasma self-organization via turbulent relaxation bounded by a magnetic surface. The Taylor state j=? B is a force-free plasma with ? a global constant. For a driven plasma with open flux intercepting the boundary B\\cdothat nneq 0, Taylor relaxation is constrained by the Jensen-Chu theory (1984), which predicted rigorous barriers in ? for the accessible relaxed state. Both the magnetic helicity and energy formally diverge at the eigenvalues (?_i) of linear equation nabla×B=?i B with homogeneous boundary condition B\\cdothat n=0. The Jensen-Chu-Taylor paradigm suggests that force-free magnetic relaxation in a driven plasma results in a constant ? state with ? bounded by the smallest eigenvalue ?_1. More complicated force-free solutions such as toroidal field reversal (e.g. flipped spheromak) and multiple internal magnetic islands, are not energetically accessible. In an actual driven plasma, the plasma can be force-free but only partially relaxed, i.e. ?(?)=?0 + ? sumi c_i?^i weakly depends on the magnetic flux (? ? 1). We find that the Jensen-Chu singularities are regularized and a broad range of force-free solutions become accessible, sometimes suggesting a tortured path toward relaxation. This new result contradicts an earlier work by Kitson and Browning (1990). Its implications on laboratory helicity injection experiments and the structure of astrophysical magnetic field will be explained. Work supported by DOE OFES.

Tang, Xianzhu; Boozer, Allen H.

2004-11-01

108

Body Size Changes of Royal Australian Air Force Aircrew: 1971 - 2005.  

National Technical Information Service (NTIS)

The aim of this study was to quantify the secular changes in body dimensions of Royal Australian Air Force (RAAF) aircrew between 1971 and 2005. Small secular increases were observed for most body dimensions, including height, mass and body mass indices, ...

A. Clark G. Tomkinson P. Blanchonette

2009-01-01

109

Near field magnetic induction Communication in Body Area Network  

Microsoft Academic Search

Next generation wireless communication system may be near filed magnetic induction Communication (NFMIC) which has major application in Body Area Network (BAN). Communication takes place in and around the body is called BAN. This Paper describes the working principle, power equation, its significance and application in NFMIC. It is compared with the other short range wireless technology such as Bluetooth,

Nithya Thilak; Robin Braun

2012-01-01

110

Magnetic force microscopy study of electron-beam-patterned soft permalloy particles: Technique and magnetization behavior  

Microsoft Academic Search

Electron-beam-patterned submicron permalloy elements with different aspect ratios were studied by magnetic force microscopy (MFM). The MFM tip stray field can be used to control a particle's magnetic state. By suitably choosing the operating mode and tip coatings, the tip induced distortion of the magnetic structure of soft permalloy elements can be largely reduced. The particle switching field can be

Xiaobin Zhu; P. Grütter; V. Metlushko; B. Ilic

2002-01-01

111

Measurement of Magnetic Field Produced from the Human Body  

Microsoft Academic Search

This article describes the present status of research on biomagnetism, an interdisciplinary field of research involving biology, engineering, medicine, physics, psychology and other areas. Biomagnetic fields are caused either by electric currents in conducting body tissues such as the heart, the brain and muscles, or by magnetized material in lung contamination. These magnetic fields, although measurable, are so extremely weak

Y. Uchikawa; M. Kotani

1992-01-01

112

Probing the duplex stainless steel phases via magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Duplex stainless steels are austenitic-ferritic alloys used in many applications, thanks to their excellent mechanical properties and high corrosion resistance. In this work, chemical analyses, x-ray diffraction, and magnetic force microscopy (MFM) were employed to characterize the solution annealed and aged duplex stainless steel. The samples exhibited no changes in lattice parameters and the MFM technique proved successful in clearly imaging the magnetic domain structure of the ferrite phase.

Gheno, S. M.; Santos, F. S.; Kuri, S. E.

2008-03-01

113

Design and optimization of force-reduced high field magnets  

NASA Astrophysics Data System (ADS)

High field magnets have many important applications in different areas of research, in the power industry and also for military purposes. For example, high field magnets are particularly useful in: material sciences, high energy physics, plasma physics (as fusion magnets), high power applications (as energy storage devices), and space applications (in propulsion systems). One of the main issues with high-field magnets is the presence of very large electromagnetic stresses that must be counteracted and therefore require heavy support structures. In superconducting magnets, the problems caused by Lorentz forces are further complicated by the fact that superconductors for high field applications are pressure sensitive. The current carrying capacity is greatly reduced under stress and strain (especially in the case of Nb 3Sn and the new high temperature superconductors) so the reduction of the acting forces is of even greater importance. Different force-reduced magnet concepts have been studied in the past, both numerical and analytical methods have been used to solve this problem. The developed concepts are based on such complex winding geometries that the realization and manufacturing of such coils is extremely difficult and these concepts are mainly of theoretical interest. In the presented research, a novel concept for force-reduced magnets has been developed and analyzed which is easy to realize and therefore is of practical interest. The analysis has been performed with a new methodology, which does not require the time consuming finite element calculations. The developed computer models describe the 3-dimensional winding configuration by sets of filaments (filamentary approximation). This approach is much faster than finite element analysis and therefore allows rapid optimization of concepts. The method has been extensively tested on geometries of force-reduced solenoids where even analytical solutions exist. As a further cross check, the developed computer codes have been tested against qualified finite element codes and found to be in excellent agreement. The developed concept of force-reduced coils is directly applicable to pulsed magnets and a conceptual design of a 25 Tesla magnet has been developed. Although no experimental proof was possible within the scope of this research, there is strong evidence to believe that the developed concept is also applicable to superconducting magnets operating in a constant current mode.

Rembeczki, Szabolcs

114

Magnetoelectric force microscopy based on magnetic force microscopy with modulated electric field  

NASA Astrophysics Data System (ADS)

We present the realization of a mesoscopic imaging technique, namely, the Magnetoelectric Force Microscopy (MeFM), for visualization of local magnetoelectric effect. The basic principle of MeFM is the lock-in detection of local magnetoelectric response, i.e., the electric field-induced magnetization, using magnetic force microscopy. We demonstrate MeFM capability by visualizing magnetoelectric domains on single crystals of multiferroic hexagonal manganites. Results of several control experiments exclude artifacts or extrinsic origins of the MeFM signal. The parameters are tuned to optimize the signal to noise ratio.

Geng, Yanan; Wu, Weida

2014-05-01

115

Three-body force effects in few-nucleon systems  

SciTech Connect

Possible three-nucleon forces to be considered in addition to a widely accepted two-pion exchange three-nucleon force are studied to improve the fit to experimental data of proton-deuteron scattering. Two different kinds of three-nucleon potentials: a phenomenological potential and one due to the exchange of pion and sigma bosons, are presented and compared with experimental data.

Ishikawa, Souichi [Science Research Center, Hosei University, 2-17-1 Fujimi, Chiyoda, Tokyo 102-8160 (Japan)

2010-05-12

116

Possible Mach Effects in Bodies Accelerated by Non-Uniform Magnetic Fields  

NASA Astrophysics Data System (ADS)

Transient mass fluctuations are predicted by Woodward in accelerated bodies which are subjected to a change of their internal energy. This sort of effects goes under the name of Mach effects. Proving their existence would lead to a relatively fast development of rapid space transportation systems. Several tests have been pursued by Woodward himself and others, the results being sometimes elusive and contrasting. The potential of this research field, however, justifies further investigation. Until now, the tests have been conducted using exclusively capacitors as means of energy storage, and the acceleration has been supplied by the Lorentz force or by a piezoelectric actuator. The present work explores the possibility to search for Mach effects in bodies subjected to impulsive forces caused by a nonuniform magnetic field. Such magnetic field would provide both the acceleration and the change in the internal energy of the body, required for the expression of Mach effects. It will be shown that an impulsive (bell shaped) force applied to a special sort of test body should produce an anomalous final speed of the body itself. A qualitative analysis is presented and a possible experimental setup is outlined.

Buldrini, N.

117

Local nonlinear rf forces in inhomogeneous magnetized plasmas  

NASA Astrophysics Data System (ADS)

The local nonlinear forces induced by radio frequency (rf) waves are derived in inhomogeneous magnetized plasmas, where the inhomogeneity exists in the rf fields, in the static magnetic field as well as in the equilibrium density and temperature. The local parallel force is completely resonant, but a novel component dependent on those inhomogeneities is obtained as the result of the inhomogeneous transport of parallel resonant-absorbed momentum by the nonlinear perpendicular drift flux. In the local poloidal force, the component induced by the inhomogeneity of rf power absorption is also confirmed and it can be recognized as the residual effect from the incomplete cancellation between the rate of the diamagnetic poloidal momentum gain and the Lorentz force due to the radial diffusion-like flux. The compact expression for radial force is also obtained for the first time, whose nonresonant component is expressed as the sum of the ponderomotive force on particles and the gradients of the nonresonant perpendicular pressure and of the nonresonant momentum flux due to the finite temperature effect. Numerical calculations in a 1-D slab model show that the resonant component dependent on the inhomogeneities may be significant when the ion absorption dominates the resonant wave-particle interaction. A quantitative estimation shows that the novel component in the parallel force is important to understand the experiments of the ion-cyclotron-frequency mode-conversion flow drive.

Chen, Jiale; Gao, Zhe

2014-06-01

118

Magnetic-field measurements of current-carrying devices by force-sensitive magnetic-force microscopy with potential correction  

Microsoft Academic Search

A scanning probe technique for current-carrying device imaging is proposed that combines magnetic-force microscopy with surface-potential nulling measurements. The device is ac biased at an off-resonant frequency and the current-induced magnetic field results in cantilever deflection which is detected by a lock-in amplifier. An ac bias at the resonant frequency is simultaneously applied to the tip and conventional scanning surface-potential

Tony Alvarez; Sergei V. Kalinin; Dawn A. Bonnell

2001-01-01

119

Electric and Magnetic Forces: Electrostatics and Current Electricity  

NSDL National Science Digital Library

Science Objects are two hour on-line interactive inquiry-based content modules that help teachers better understand the science content they teach.This Science Object is the second of three Science Objects in the Electric and Magnetic Forces SciPack.

National Science Teachers Association (NSTA)

1900-01-01

120

Minimization of cogging force in a linear permanent magnet motor  

SciTech Connect

A finite element/analytically based method is used to aid the minimization of cogging force, due to slotting and the finite length of the ferromagnetic core, in a tubular brushless permanent magnet motor. The method is validated against both finite element calculations and measurements on a prototype motor.

Hor, P.J.; Zhu, Z.Q.; Howe, D. [Univ. of Sheffield (United Kingdom). Dept. of Electronic and Electrical Engineering] [Univ. of Sheffield (United Kingdom). Dept. of Electronic and Electrical Engineering; Rees-Jones, J. [Unilever Research Lab., Port Sunlight Lab. (United Kingdom)] [Unilever Research Lab., Port Sunlight Lab. (United Kingdom)

1998-09-01

121

The point dipole approximation in magnetic force microscopy  

Microsoft Academic Search

Image interpretation in magnetic force microscopy (MFM) requires detailed information about the internal microstructure of the ferromagnetic tip used for probing the surface microfield of a sample. Since these informations are generally not experimentally available, image interpretation is more speculative than rigorously quantitative at the present time. This theoretical analysis confirms by a simple criterion that MFM image interpretation can

U. Hartmann

1989-01-01

122

Analytical equation of state with three-body forces: Application to noble gases  

SciTech Connect

We developed an explicit equation of state (EOS) for small non polar molecules by means of an effective two-body potential. The average effect of three-body forces was incorporated as a perturbation, which results in rescaled values for the parameters of the two-body potential. These values replace the original ones in the EOS corresponding to the two-body interaction. We applied this procedure to the heavier noble gases and used a modified Kihara function with an effective Axilrod-Teller-Muto (ATM) term to represent the two- and three-body forces. We also performed molecular dynamics simulations with two- and three-body forces. There was good agreement between predicted, simulated, and experimental thermodynamic properties of neon, argon, krypton, and xenon, up to twice the critical density and up to five times the critical temperature. In order to achieve 1% accuracy of the pressure at liquid densities, the EOS must incorporate the effect of ATM forces. The ATM factor in the rescaled two-body energy is most important at temperatures around and lower than the critical one. Nonetheless, the rescaling of two-body diameter cannot be neglected at liquid-like densities even at high temperature. This methodology can be extended straightforwardly to deal with other two- and three-body potentials. It could also be used for other nonpolar substances where a spherical two-body potential is still a reasonable coarse-grain approximation.

Río, Fernando del, E-mail: fdr@xanum.uam.mx; Díaz-Herrera, Enrique; Guzmán, Orlando; Moreno-Razo, José Antonio [Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, Apdo 55 534, México DF, 09340 (Mexico)] [Departamento de Física, Universidad Autónoma Metropolitana, Iztapalapa, Apdo 55 534, México DF, 09340 (Mexico); Ramos, J. Eloy [Colegio de Ciencia y Tecnología, Universidad Autónoma de la Ciudad de México, Mexico DF (Mexico)] [Colegio de Ciencia y Tecnología, Universidad Autónoma de la Ciudad de México, Mexico DF (Mexico)

2013-11-14

123

Analytical equation of state with three-body forces: Application to noble gases  

NASA Astrophysics Data System (ADS)

We developed an explicit equation of state (EOS) for small non polar molecules by means of an effective two-body potential. The average effect of three-body forces was incorporated as a perturbation, which results in rescaled values for the parameters of the two-body potential. These values replace the original ones in the EOS corresponding to the two-body interaction. We applied this procedure to the heavier noble gases and used a modified Kihara function with an effective Axilrod-Teller-Muto (ATM) term to represent the two- and three-body forces. We also performed molecular dynamics simulations with two- and three-body forces. There was good agreement between predicted, simulated, and experimental thermodynamic properties of neon, argon, krypton, and xenon, up to twice the critical density and up to five times the critical temperature. In order to achieve 1% accuracy of the pressure at liquid densities, the EOS must incorporate the effect of ATM forces. The ATM factor in the rescaled two-body energy is most important at temperatures around and lower than the critical one. Nonetheless, the rescaling of two-body diameter cannot be neglected at liquid-like densities even at high temperature. This methodology can be extended straightforwardly to deal with other two- and three-body potentials. It could also be used for other nonpolar substances where a spherical two-body potential is still a reasonable coarse-grain approximation.

del Río, Fernando; Díaz-Herrera, Enrique; Guzmán, Orlando; Moreno-Razo, José Antonio; Ramos, J. Eloy

2013-11-01

124

Statistical methods for including two-body forces in large system calculations  

SciTech Connect

Large systems of interacting particles are often treated by assuming that the effect on any one particle of the remaining N-1 may be approximated by an average potential. This approach reduces the problem to that of finding the bound-state solutions for a particle in a potential; statistical mechanics is then used to obtain the properties of the many-body system. In some physical systems this approach may not be acceptable, because the two-body force component cannot be treated in this one-body limit. A technique for incorporating two-body forces in such calculations in a more realistic fashion is described. 1 figure.

Grimes, S.M.

1980-07-01

125

Brief High-Intensity Exercise and Resistive Force Selection in Overweight and Obese Subjects: Body Mass or Body Composition?  

Microsoft Academic Search

The purpose of this study was to compare the maximal exercise performance of overweight and obese subjects during friction braked cycle ergometry of 10 s duration when resistive forces reflected total-body mass (TBM) or fat-free mass (FFM). Subjects were assigned at random to either protocol. Eleven healthy male university students (age 22.3 ± 2 yrs, body fat 27.1 ± 2%)

Julien S. Baker; Bruce Davies

2006-01-01

126

A Theoretical and Experimental Investigation of the Magnetic Fields and Forces Arising in Magnetic Suspension Systems.  

National Technical Information Service (NTIS)

Analytical and experimental studies have been performed to obtain the fundamental relationships governing the transverse forces between an axially active, transversely passive electro-magnetic supporting system. The basic criteria have been obtained for a...

J. Walowit P. R. Albrecht

1975-01-01

127

On unsteady-motion theory of magnetic force for maglev systems.  

SciTech Connect

Motion-dependent magnetic forces are the key elements in the study of magnetically levitated vehicle (maglev) system dynamics. This paper presents an experimental and analytical study that will enhance our understanding of the role of unsteady-motion-dependent magnetic forces and demonstrate an experimental technique that can be used to measure those unsteady magnetic forces directly. The experimental technique is a useful tool for measuring motion-dependent magnetic forces for the prediction and control of maglev systems.

Chen, S. S.; Zhu, S.; Cai, Y.; Energy Technology

1995-12-14

128

Investigation of Microscale Magnetic Forces for Magnet Array Self-Assembly  

Microsoft Academic Search

This paper focuses on quantification and optimization of micromagnetic bonding forces to enable a technique of magnet array self-assembly (MASA). MASA is envisioned to uniquely assemble different microscale components using arrays of hard micromagnets, which are pre-patterned onto the component surfaces via batch-fabrication. Finite-element (FEM) and analytical methods are used to analyze the dependence of magnetic bonding forces on the

Sheetal B. Shetye; Janhavi S. Agashe; David P. Arnold

2007-01-01

129

Three-body forces and proton-rich nuclei.  

PubMed

We present the first study of three-nucleon (3N) forces for proton-rich nuclei along the N=8 and N=20 isotones. Our results for the ground-state energies and proton separation energies are in very good agreement with experiment where available, and with the empirical isobaric multiplet mass equation. We predict the spectra for all N=8 and N=20 isotones to the proton dripline, which agree well with experiment for 18Ne, 19Na, 20Mg and 42Ti. In all other cases, we provide first predictions based on nuclear forces. Our results are also very promising for studying isospin symmetry breaking in medium-mass nuclei based on chiral effective field theory. PMID:23383896

Holt, J D; Menéndez, J; Schwenk, A

2013-01-11

130

THE NEGATIVE EFFECTIVE MAGNETIC PRESSURE IN STRATIFIED FORCED TURBULENCE  

SciTech Connect

To understand the basic mechanism of the formation of magnetic flux concentrations, we determine by direct numerical simulations the turbulence contributions to the mean magnetic pressure in a strongly stratified isothermal layer with large plasma beta, where a weak uniform horizontal mean magnetic field is applied. The negative contribution of turbulence to the effective mean magnetic pressure is determined for strongly stratified forced turbulence over a range of values of magnetic Reynolds and Prandtl numbers. Small-scale dynamo action is shown to reduce the negative effect of turbulence on the effective mean magnetic pressure. However, the turbulence coefficients describing the negative effective magnetic pressure phenomenon are found to converge for magnetic Reynolds numbers between 60 and 600, which is the largest value considered here. In all these models, the turbulent intensity is arranged to be nearly independent of height, so the kinetic energy density decreases with height due to the decrease in density. In a second series of numerical experiments, the turbulent intensity increases with height such that the turbulent kinetic energy density is nearly independent of height. Turbulent magnetic diffusivity and turbulent pumping velocity are determined with the test-field method for both cases. The vertical profile of the turbulent magnetic diffusivity is found to agree with what is expected based on simple mixing length expressions. Turbulent pumping is shown to be down the gradient of turbulent magnetic diffusivity, but it is twice as large as expected. Corresponding numerical mean-field models are used to show that a large-scale instability can occur in both cases, provided the degree of scale separation is large enough and hence the turbulent magnetic diffusivity small enough.

Brandenburg, Axel; Kemel, Koen; Kleeorin, Nathan; Rogachevskii, Igor [NORDITA, AlbaNova University Center, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

2012-04-20

131

Noncontact Friction and Force Fluctuations between Closely Spaced Bodies  

SciTech Connect

Noncontact friction between a Au(111) surface and an ultrasensitive gold-coated cantilever was measured as a function of tip-sample spacing, temperature, and bias voltage using observations of cantilever damping and Brownian motion. The importance of the inhomogeneous contact potential is discussed and comparison is made to measurements over dielectric surfaces. Using the fluctuation-dissipation theorem, the force fluctuations are interpreted in terms of near-surface fluctuating electric fields interacting with static surface charge.

Stipe, B. C.; Mamin, H. J.; Stowe, T. D.; Kenny, T. W.; Rugar, D.

2001-08-27

132

Magnetic Study of Paris Meteorite: a Partially Differentiated Parent Body?  

NASA Astrophysics Data System (ADS)

The Paris meteorite is a unique carbonaceous CM chondrite find with almost no traces of terrestrial weathering [1]. Contrary to others CM chondrites, that contain abundant magnetite formed during aqueous alteration on their parent body, Paris is characterized by the coexistence of magnetite and abundant metallic Fe-Ni. We conducted a magnetic study (magnetic properties and paleomagnetism) of several oriented samples of this meteorite, with masses ranging from several mg up to 17 g. Preliminary rock magnetism results confirm that Paris has a magnetic mineralogy that is notably different from that of other CM chondrites, with a dominant FeNi metal, and minor magnetite. This corroborate that Paris suffered less aqueous alteration than other CM chondrites. Anisotropy of magnetic susceptibility shows that Paris is also one of the most anisotropic CM chondrite, and that it has a homogeneous fabric at least at the centimeter-scale. The comparison of the remanent magnetization obtained for metal-rich and magnetite-rich samples may have provided constraints on the magnetic fields present before and after accretion respectively. Unfortunately, paleomagnetic data show that the meteorite has been exposed to strong artificial magnetic field (magnet), precluding the study of the possible soft natural magnetization carried by FeNi. However, a high-coercivity magnetization is still preserved in the meteorite. It is homogeneous in direction and intensity at the scale of the meteorite. We interpret it as a pre-terrestrial component acquired on the parent body in a field on 3 ± 1 ?T (estimated with the method described in [2]). In view of its coercivity (up to 120 mT) we suppose that this magnetization is carried by fine-grained magnetite (although thermal and chemical demagnetization experiments are needed to confirm this hypothesis). In this case, because crystallization of magnetite likely occurred several Myr after the formation of the solar system [3], i.e. after the possible existence of strong solar and nebular magnetic fields, the paleofield had to be generated by the parent body. In view of its intensity, this paleofield may have been an internally generated field, pointing to a partially differentiated parent body with a convecting metallic core. Such process has recently been proposed for the parent body of CV chondrites [4, 5]. [1] Zanda et al., 2010. Meteoritics Planetary Sci., 45, 222-222. [2] Gattacceca and Rochette, 2004. EPSL, 227, 377-393 [3] Petitat and Gounelle, 2010. LPSC, abstract #1673. [4] Carporzen et al., 2011. Proc. National Acad. Sci., 108, 6386-6389. [5] Elkins-Tanton et al., 2011. Earth Planet . Sci. Lett., 305, 1-10.

Cournède, C.; Gattacceca, J.; Rochette, P.; Zanda, B.

2011-12-01

133

Unsteady Aerodynamic Forces on a Slender Body of Revolution in Supersonic Flow  

NASA Technical Reports Server (NTRS)

Linearized slender-body theory is applied to the computation of aerodynamic forces on an oscillating, or deforming, body in supersonic flow. The undeformed body is a body of revolution and the deformed body is represented by movement of a line through the centers of the cross sections which are assumed to remain circular. The time dependence is based on sinusoidal motion. For a body of vanishing thickness the slender-body theory yields the apparent mass approximation as it is obtained for incompressible crossflow around a cylinder. Both linearized slender-body theory and the apparent mass approximation are used to calculate the pitching-moment coefficients on a rigid slender body with a parabolic arc nose cone, and these coefficients are compared with some experimental results.

Bond, Reuben; Packard, Barbara B.

1961-01-01

134

Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy achieves very high resolution three-dimensional imaging capabilities of magnetic resonance imaging by taking advantage of very high sensitivity mechanical force detection. This enables non-contacting, microscopic studies and imaging of a broad range of materials. As a consequence of the strong interactions between spins, the assumptions underlying conventional MRI are not applicable to FMR imaging. However, using a new approach to localizing the resonant volume in an FMR measurement founded on the strong, nonuniform magnetic field of the micromagnetic probe tip, we have demonstrated scanned probe Ferromagnetic Resonance (FMR) imaging [1]. The scanned probe FMR images obtained in patterned ferromagnetic films are well explained by detailed numerical modeling. In addition to illuminating the mechanisms underlying localized FMR, the model provides the basis for submicron scanned probe FMR imaging of films and buried ferromagnetic elements. This work was supported by the U.S. Department of Energy through Grant No. DE-FG02-03ER46054. [1] ``Local Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy,'' Yu. Obukhov, D.V. Pelekhov, J. Kim, P. Banerjee, I. Martin, E. Nazaretski, R. Movshovich, S. An, T.J. Gramila, S. Batra, and P. C. Hammel, Phys. Rev. Lett. 100(19), 197601 (2008).

Pelekhov, Denis

2009-03-01

135

Continuum limit of amorphous elastic bodies II: Linear response to a point source force  

Microsoft Academic Search

The linear response of two-dimensional amorphous elastic bodies to an external delta force is determined in analogy with recent experiments on granular aggregates. For the generated forces, stress and displacement fields, we find strong relative fluctuations of order one close to the source, which, however, average out readily to the classical predictions of isotropic continuum elasticity. The stress fluctuations decay

F. Leonforte; A. Tanguy; J.-L. Barrat

2004-01-01

136

Continuum limit of amorphous elastic bodies II: Linear response to a point source force  

Microsoft Academic Search

The linear response of two-dimensional amorphous elastic bodies to an external delta force is determined in analogy with recent experiments on granular aggregates. For the generated forces, stress, and displacement fields, we find strong relative fluctuations of order 1 close to the source, which, however, average out readily to the classical predictions of isotropic continuum elasticity. The stress fluctuations decay

F. Leonforte; A. Tanguy; J. P. Wittmer; J.-L. Barrat

2004-01-01

137

Faddeev equations including three-body forces in first order perturbation theory  

SciTech Connect

We propose a modification of the standard Faddeev equations which takes into account the effects of a three-body force in first order perturbation theory on the triton wave function and its binding energy. Furthermore, we report our results for the energy expectation value caused by the two-pion-exchange three-nucleon force.

Boemelburg, A.; Gloeckle, W.

1983-11-01

138

Three-body radiative heat transfer and Casimir-Lifshitz force out of thermal equilibrium for arbitrary bodies  

NASA Astrophysics Data System (ADS)

We study the Casimir-Lifshitz force and the radiative heat transfer in a system consisting of three bodies held at three independent temperatures and immersed in a thermal environment, the whole system being in a stationary configuration out of thermal equilibrium. The theory we develop is valid for arbitrary bodies, i.e., for any set of temperatures, dielectric, and geometrical properties, and describes each body by means of its scattering operators. For the three-body system we provide a closed-form unified expression of the radiative heat transfer and of the Casimir-Lifshitz force (both in and out of thermal equilibrium). This expression is thus first applied to the case of three planar parallel slabs. In this context we discuss the nonadditivity of the force at thermal equilibrium, as well as the equilibrium temperature of the intermediate slab as a function of its position between two external slabs having different temperatures. Finally, we consider the force acting on an atom inside a planar cavity. We show that, differently from the equilibrium configuration, the absence of thermal equilibrium admits one or more positions of minima for the atomic potential. While the corresponding atomic potential depths are very small for typical ground-state atoms, they may become particularly relevant for Rydberg atoms, becoming a promising tool to produce an atomic trap.

Messina, Riccardo; Antezza, Mauro

2014-05-01

139

Maneuvering a reentry body via magneto-gasdynamic forces  

NASA Astrophysics Data System (ADS)

Some of the characteristics of the interaction of an electrically conducting fluid with a non-uniform applied magnetic field and a potential magnetogasdynamic control system which may be used on future aerospace vehicles are presented. The flow through a two dimensional channel is predicted by numerically solving the magnetogasdynamic equations using a time marching technique. The fluid was modeled as a compressible, inviscid, supersonic gas with finite electrical conductivity. Development of the algorithm provided a means to predict and analyze phenomena associated with magnetogasdynamic flows which had not been previously explored using numerical methods. One such phenomena was the prediction of oblique waves resulting from the interaction of an electrically conducting fluid with a non-uniform applied magnetic field. Development of this tool provided a means to explore an application which might have potential use for future aerospace vehicle missions. In order to appreciate the significance of this technology, predictions were made of the pitching moment about a slender blunted cone, generated by a system relying on the fluid-magnetic interaction. These moments were compared to predictions of a pitching moment generated by a deflecting control surface on the same vehicle. It was shown that the proposed magnetogasdynamic system could produce moments which were on the same order as the moments produced by the flap systems at low deflection angles.

Ohare, Leo Patrick

1992-04-01

140

Horizontal radial magnetic inversion for retrieving 3D geologic bodies  

NASA Astrophysics Data System (ADS)

We present a new 3D method for inverting magnetic data to retrieve the geometry of isolated geologic bodies whose uniform magnetization and depth to the top are prescribed by the interpreter. This method uses a 3D interpretation model consisting of a set of right prisms that are juxtaposed in the vertical direction of a right-handed coordinate system. Each prism has a horizontal cross-section defined by a polygon with a fixed number of vertices that are equally spaced from 0° to 360° and described by polar coordinates referred to an origin inside the polygon. Each prism has a uniform and known magnetization and thickness. Our inversion method estimates the radii associated with the vertices of the polygon and the horizontal coordinates of the origin of each prism. The estimated radii of the ensemble of prisms vertically stacked recover the 3D geologic source. Our method recovers stable and geologically meaningful solutions by using a wide variety of constraints that are designated by the interpreter with the aim of introducing information about the shape of the body. We applied our method to the noise-corrupted synthetic data (grey scale map in Fig. 1a) produced by the simulated body shown in Fig. 1b (black wire-frame body). The results confirmed the potential of our method to retrieve the shape and to infer the depth of the simulated source (black wire-frame body in Fig. 1b). The estimated source is shown in Fig. 1b (grey prisms) and produces the predicted data shown in Fig. 1a (dashed-white lines).; Fig. 1 - Application to synthetic data. (a) Noise-corrupted magnetic anomaly (grey scale map) and predicted data (dashed-white lines). (b) Simulated body (black wire-frame body) and estimated body (grey prisms).

Oliveira, V. C., Jr.; Barbosa, V. C.

2013-05-01

141

Effect of magnet/slot combination on triple-frequency magnetic force and vibration of permanent magnet motors  

NASA Astrophysics Data System (ADS)

The relationship between magnet/slot combination and magnetic forces including unbalanced magnetic force (UMF) and cogging torque (CT) of permanent magnet (PM) motors is investigated by using superposition principle and mechanical and magnetic symmetries. The results show that magnetic force can be produced by all magnets passing a single slot, by all slots passing a single magnet, or by eccentricity, which respectively correspond to three frequency components. The results further show that net force/torque can be classified into three typical cases: UMF is suppressed and CT is excited, UMF excited and CT suppressed, and UMF and CT both suppressed, and consequently possible vibrations include three unique groups: rotational modes, translational modes, and balanced modes. The conclusion that combinations with the greatest common divisor (GCD) greater than unity can avoid UMF is mathematically verified, and at the same time lower CT harmonics are preliminarily addressed by the typical excitations. The above findings can create simple guidelines for the suppression of certain UMF and/or CT by using suitable combinations, which in turn can present approach to yield a more desirable response in high performance applications. The superposition effect and predicted relationship are verified by the transient magnetic Finite Element method. Since this work is motivated by symmetries, comparisons are made in order to give further insight into the inner force and vibration behaviors of general rotary power-transmission systems.

Huo, Mina; Wang, Shiyu; Xiu, Jie; Cao, Shuqian

2013-10-01

142

Dilation of force-free magnetic flux tubes. [solar magnetic field profiles  

NASA Technical Reports Server (NTRS)

A general study is presented of the mapping functions which relate the magnetic-field profiles across a force-free rope in segments subjected to various external pressures. The results reveal that if the external pressure falls below a certain critical level (dependent on the flux-current relation which defines the tube), the magnetic profile consists of an invariant core sheathed in a layer permeated by an azimuthal magnetic field.

Frankenthal, S.

1977-01-01

143

Force analysis of magnetic bearings with power-saving controls  

NASA Technical Reports Server (NTRS)

Most magnetic bearing control schemes use a bias current with a superimposed control current to linearize the relationship between the control current and the force it delivers. For most operating conditions, the existence of the bias current requires more power than alternative methods that do not use conventional bias. Two such methods are examined which diminish or eliminate bias current. In the typical bias control scheme it is found that for a harmonic control force command into a voltage limited transconductance amplifier, the desired force output is obtained only up to certain combinations of force amplitude and frequency. Above these values, the force amplitude is reduced and a phase lag occurs. The power saving alternative control schemes typically exhibit such deficiencies at even lower command frequencies and amplitudes. To assess the severity of these effects, a time history analysis of the force output is performed for the bias method and the alternative methods. Results of the analysis show that the alternative approaches may be viable. The various control methods examined were mathematically modeled using nondimensionalized variables to facilitate comparison of the various methods.

Johnson, Dexter; Brown, Gerald V.; Inman, Daniel J.

1992-01-01

144

Dynamic force-induced direct dissociation of protein complexes in a nuclear body in living cells.  

PubMed

Despite past progress in understanding mechanisms of cellular mechanotransduction, it is unclear whether a local surface force can directly alter nuclear functions without intermediate biochemical cascades. Here we show that a local dynamic force via integrins results in direct displacements of coilin and SMN proteins in Cajal bodies and direct dissociation of coilin-SMN associated complexes. Spontaneous movements of coilin increase more than those of SMN in the same Cajal body after dynamic force application. Fluorescence resonance energy transfer changes of coilin-SMN depend on force magnitude, an intact F-actin, cytoskeletal tension, Lamin A/C, or substrate rigidity. Other protein pairs in Cajal bodies exhibit different magnitudes of fluorescence resonance energy transfer. Dynamic cyclic force induces tiny phase lags between various protein pairs in Cajal bodies, suggesting viscoelastic interactions between them. These findings demonstrate that dynamic force-induced direct structural changes of protein complexes in Cajal bodies may represent a unique mechanism of mechanotransduction that impacts on nuclear functions involved in gene expression. PMID:22643893

Poh, Yeh-Chuin; Shevtsov, Sergey P; Chowdhury, Farhan; Wu, Douglas C; Na, Sungsoo; Dundr, Miroslav; Wang, Ning

2012-01-01

145

Atomic Force Microscopy Incorporated with Magnetic Sample Modulation: a new approach to detect the magnetic nanomaterials  

NASA Astrophysics Data System (ADS)

A new imaging strategy using atomic force microscopy (AFM) for detecting magnetic nanomaterials with much higher spatial resolution and sensitivity than the traditional magnetic force microscopy (MFM) technique is developed [1,2]. This AFM-based imaging mode is referred to as magnetic sample modulation (MSM), since the flux of an AC-generated electromagnetic field is used to induce physical movement of magnetic nanomaterials on surfaces during imaging. The AFM is operated in contact mode using a soft, nonmagnetic tip to detect the physical motion of the sample. By slowly scanning an AFM probe across a vibrating area of the sample, the frequency and amplitude of vibration induced by the magnetic field is tracked by changes in tip deflection. Thus, the AFM tip serves as a force and motion sensor for mapping the vibrational response of magnetic nanomaterials. The investigations are facilitated by nanofabrication methods combining particle lithography with organic vapor deposition and electroless deposition of iron oxide to prepare designed test platforms of magnetic materials at nanometer length scales. Examples of detecting magnetic nanoparticles and magnetic biospecies at single molecular level will be presented [3,4]. [4pt] [1] Li et al. Analytical Chemistry, 2009, 81, 4792-4802

Yu, Jing-Jiang; Garno, Jayne

2012-02-01

146

Effect of horizontal magnetization reversal of the tips on magnetic force microscopy images.  

PubMed

The effect of magnetization reversal of magnetic force microscope (MFM) tips based on low coercive thin-films on MFM images has been studied both experimentally and theoretically. By analyzing the MFM images obtained on structures with high magnetic stray fields we show that during the imaging process the magnetic state of the probe is modified anisotropically: the horizontal component of the magnetization follows the external field, whereas the vertical component of the magnetization stays almost constant. The observed complex magnetic behavior of the tip is explained theoretically based on the shape anisotropy of the tip. The obtained results are important for interpretation of MFM images of structures with high magnetic moment. Moreover, these results can be used for characterization of both laboratory-made and commercially available MFM tips. PMID:24051098

Alekseev, Alexander; Popkov, Anatoliy; Shubin, Andrey; Pudonin, Feodor; Djuzhev, Nikolay

2014-01-01

147

Apparatus having reduced mechanical forces for supporting high magnetic fields  

DOEpatents

The present invention identifies several configurations of conducting elements capable of supporting extremely high magnetic fields suitable for plasma confinement, wherein forces experienced by the conducting elements are significantly reduced over those which are present as a result of the generation of such high fields by conventional techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency.

Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)

1991-01-01

148

Distributed forcing of the flow past a blunt-based axisymmetric bluff body  

NASA Astrophysics Data System (ADS)

In this paper, we address the influence of a blowing-/suction-type distributed forcing on the flow past a blunt-based axisymmetric bluff body by means of direct numerical simulations. The forcing is applied via consecutive blowing and suction slots azimuthally distributed along the trailing edge of the bluff body. We examine the impact of the forcing wavelength, amplitude and waveform on the drag experienced by the bluff body and on the occurrence of the reflectional symmetry preserving and reflectional symmetry breaking wake modes, for Reynolds numbers 800 and 1,000. We show that forcing the flow at wavelengths inherent to the unforced flow drastically damps drag oscillations associated with the vortex shedding and vorticity bursts, up to their complete suppression. The overall parameter analysis suggests that this damping results from the surplus of streamwise vorticity provided by the forcing that tends to stabilize the ternary vorticity lobes observed at the aft part of the bluff body. In addition, conversely to a blowing-type or suction-type forcing, the blowing-/suction-type forcing involves strong nonlinear interactions between locally decelerated and accelerated regions, severely affecting both the mean drag and the frequencies representative of the vortex shedding and vorticity bursts.

Jardin, Thierry; Bury, Yannick

2013-10-01

149

Distributed forcing of the flow past a blunt-based axisymmetric bluff body  

NASA Astrophysics Data System (ADS)

In this paper, we address the influence of a blowing-/suction-type distributed forcing on the flow past a blunt-based axisymmetric bluff body by means of direct numerical simulations. The forcing is applied via consecutive blowing and suction slots azimuthally distributed along the trailing edge of the bluff body. We examine the impact of the forcing wavelength, amplitude and waveform on the drag experienced by the bluff body and on the occurrence of the reflectional symmetry preserving and reflectional symmetry breaking wake modes, for Reynolds numbers 800 and 1,000. We show that forcing the flow at wavelengths inherent to the unforced flow drastically damps drag oscillations associated with the vortex shedding and vorticity bursts, up to their complete suppression. The overall parameter analysis suggests that this damping results from the surplus of streamwise vorticity provided by the forcing that tends to stabilize the ternary vorticity lobes observed at the aft part of the bluff body. In addition, conversely to a blowing-type or suction-type forcing, the blowing-/suction-type forcing involves strong nonlinear interactions between locally decelerated and accelerated regions, severely affecting both the mean drag and the frequencies representative of the vortex shedding and vorticity bursts.

Jardin, Thierry; Bury, Yannick

2014-06-01

150

Dynamic nanomagnetism characterization of individual magnetic nanoparticles by frequency-modulated magnetic force microscopy  

NASA Astrophysics Data System (ADS)

In this study, stroboscopic imaging of an alternating magnetic field (AC magnetic field) from individual superparamagnetic Fe3O4 nanoparticles was achieved using the developed frequency modulated-magnetic force microscopy (FM-MFM) technique, which enables the imaging of the vector signals of AC magnetic fields, such as a combination of in-phase and quadrature signals or that of amplitude and phase signals. FM-MFM uses the frequency modulation of cantilever oscillation, caused by the application of an off-resonant AC magnetic field to a mechanically oscillated cantilever, and visualises the vector signals of the AC magnetic field by adding a frequency demodulator and a lock-in amplifier to a conventional magnetic force microscope. Stroboscopic imaging of an AC magnetic field was carried out by varying the phase of the measured in-phase and quadrature signals via a signal processing technique. For the superparamagnetic Fe3O4 nanoparticles, stroboscopic imaging of the time-variable AC magnetic field, caused by the rotation of the magnetic moments within the particles, was demonstrated. This article describes the present status of FM-MFM technology, with particular attention to the feasibility of detecting magnetic moments of individual nanoparticles, and the possible application of FM-MFM in biological imaging.

Li, Xiang; Li, Zhenghua; Pan, Deng; Yoshimura, Satoru; Saito, Hitoshi

2014-05-01

151

Force-free magnetic fields - The magneto-frictional method  

NASA Technical Reports Server (NTRS)

The problem under discussion is that of calculating magnetic field configurations in which the Lorentz force j x B is everywhere zero, subject to specified boundary conditions. We choose to represent the magnetic field in terms of Clebsch variables in the form B = grad alpha x grad beta. These variables are constant on any field line so that each field line is labeled by the corresponding values of alpha and beta. When the field is described in this way, the most appropriate choice of boundary conditions is to specify the values of alpha and beta on the bounding surface. We show that such field configurations may be calculated by a magneto-frictional method. We imagine that the field lines move through a stationary medium, and that each element of magnetic field is subject to a frictional force parallel to and opposing the velocity of the field line. This concept leads to an iteration procedure for modifying the variables alpha and beta, that tends asymptotically towards the force-free state. We apply the method first to a simple problem in two rectangular dimensions, and then to a problem of cylindrical symmetry that was previously discussed by Barnes and Sturrock (1972). In one important respect, our new results differ from the earlier results of Barnes and Sturrock, and we conclude that the earlier article was in error.

Yang, W. H.; Sturrock, P. A.; Antiochos, S. K.

1986-01-01

152

Towards dynamic control of magnetic fields to focus magnetic carriers to targets deep inside the body  

PubMed Central

Magnetic drug delivery has the potential to target therapy to specific regions in the body, improving efficacy and reducing side effects for treatment of cancer, stroke, infection, and other diseases. Using stationary external magnets, which attract the magnetic drug carriers, this treatment is limited to shallow targets (<5 cm below skin depth using the strongest possible, still safe, practical magnetic fields). We consider dynamic magnetic actuation and present initial results that show it is possible to vary magnets one against the other to focus carriers between them on average. The many remaining tasks for deep targeting in-vivo are then briefly noted.

Shapiro, Benjamin

2010-01-01

153

Aerodynamic forces induced by controlled transitory flow on a body of revolution  

NASA Astrophysics Data System (ADS)

The aerodynamic forces and moments on an axisymmetric body of revolution are controlled in a low-speed wind tunnel by induced local flow attachment. Control is effected by an array of aft-facing synthetic jets emanating from narrow, azimuthally segmented slots embedded within an axisymmetric backward facing step. The actuation results in a localized, segmented vectoring of the separated base flow along a rear Coanda surface and induced asymmetric aerodynamic forces and moments. The observed effects are investigated in both quasi-steady and transient states, with emphasis on parametric dependence. It is shown that the magnitude of the effected forces can be substantially increased by slight variations of the Coanda surface geometry. Force and velocity measurements are used to elucidate the mechanisms by which the synthetic jets produce asymmetric aerodynamic forces and moments, demonstrating a novel method to steer axisymmetric bodies during flight.

Rinehart, Christopher S.

154

Conductive atomic force microscopy measurements of nanopillar magnetic tunnel junctions  

NASA Astrophysics Data System (ADS)

Magnetic tunnel junctions have been studied extensively for their magnetoresistance and potential uses in magnetic logic and data storage devices, but little is known about how their performance will scale with size. Here we examined the electronic behavior of 12 nm diameter magnetic tunnel junctions fabricated by a novel nanomasking process. Scanning electron microscopy images indicated feature diameter of 12 nm, and atomic force microscopy showed a height of 5 nm suggesting that unmasked regions have been milled on average to the oxide barrier layer, and areas should have the remnants of the free layer exposed with no remaining nanoparticle. Electrical contact was made to individual nanopillars using a doped-diamond-coated atomic force microscopy probe with a 40 nm radius of curvature at the tip. Off pillar we observed a resistance of 8.1 x 10^5 ?, while on pillar we found a resistance of 2.85 x 10^6 ?. Based on the RA product for this film, 120 ?-?m^2, a 12 nm diameter cylinder with perfect contact would have a resistance of 1.06 x 10^6 ?. The larger experimental value is consistent with a smaller contact area due to damaging the pillar during the ion milling process. The magnetoresistance characteristics of these magnetic tunnel junctions will be discussed.

Evarts, E. R.; Hogg, C.; Bain, J. A.; Majetich, S. A.

2009-03-01

155

Forces on a magnet moving past figure-eight coils  

SciTech Connect

Considerable attention has been given to the magnetic levitation of vehicles over guideways consisting of periodically-spaced conducting coils. Examples of proposed guideway configurations include arrays of independent coils (''loop track''), interconnected coils (''ladder track''), two layers of coils (double-layer ''null-flux'' track), and figure-eight coils (single-layer ''null-flux'' track). Typically, widely-separated superconducting magnets are mounted in the vehicle. A system that achieves both lift and guidance from vertical figure-eight coils in the guideway sidewalls has been developed in Japan. This system, when well designed, can have a very large lift-to-drag ratio. The authors conducted an experimental and theoretical investigation of the lift, drag, and guidance forces on a permanent magnet moving close to various arrays of figure-eight coils. The measured time-histories of the forces provide a basis for the evaluation of electrodynamic models and codes developed to analyze the magnetic levitation of vehicles using the discrete suspension coils of the null-flux type. Good correlation was found between the experimental data and the predictions of the code COIL GDWY. The authors report some of the results and discuss their application to the design of maglev systems.

Mulcahy, T.M.; He, J.; Rote, D.M. (Argonne National Lab., IL (United States)); Rossing, T.D. (Northern Illinois Univ., De Kalb, IL (United States). Dept. of Physics)

1993-11-01

156

Fabrication of cobalt magnetic nanostructures using atomic force microscope lithography.  

PubMed

Cobalt nanopatterns are promising assemblies for patterned magnetic storage applications. The fabrication of cobalt magnetic nanostructures on n-tridecylamine x hydrochloride (TDA x HCl) self-assembled monolayer (SAM) modified silicon surfaces using direct writing atomic force microscope (AFM) lithography for localized electrochemical reduction of cobalt ions was demonstrated. The ions were reduced to form metal nanowires along the direction of the electricfield between the AFM tip and the substrate. In this lithography process, TDA x HCI SAMs play an important role in the lithography process for improving the resolution of cobalt nanopatterns by preventing nonspecific reduction of cobalt ions on the unwritten background. Cobalt nanowires and nanodots with width of 225 +/- 26 nm and diameter of 208 +/- 28 nm were successfully fabricated. Platinium-coated polydimethylsiloxane (PDMS) stamp was used fabricating bulk cobalt structures which can be detected by energy dispersive X-ray spectroscopy for element analysis and the physical and magnetic properties of these cobalt nanopatterns were characterized using AFM and magnetic force microscope. PMID:24266190

Chu, Haena; Yun, Seonghun; Lee, Haiwon

2013-12-01

157

The inverse problem in magnetic force microscopy—inferring sample magnetization from MFM images  

NASA Astrophysics Data System (ADS)

Nanomagnetic structures have the potential to surpass silicon’s scaling limitations both as elements in hybrid CMOS logic and as novel computational elements. Magnetic force microscopy (MFM) offers a convenient characterization technique for use in the design of such nanomagnetic structures. MFM measures the magnetic field and not the sample’s magnetization. As such the question of the uniqueness of the relationship between an external magnetic field and a magnetization distribution is a relevant one. To study this problem we present a simple algorithm which searches for magnetization distributions consistent with an external magnetic field and solutions to the micromagnetic equations’ qualitative features. The algorithm is not computationally intensive and is found to be effective for our test cases. On the basis of our results we propose a systematic approach for interpreting MFM measurements.

Rawlings, Colin; Durkan, Colm

2013-08-01

158

Many-body forces and stability of the alkaline-earth tetramers  

NASA Astrophysics Data System (ADS)

The comparative study of the interaction energy and its many-body decomposition for Be 4, Mg 4, and Ca 4 at the all-electron CCSD(T)/aug-cc-pVQZ level is performed. For study of dependence of the binding energy and the orbital population on the cluster size the corresponding dimers and trimers were also calculated at the same level of theory. In comparison with weakly bound dimers, the binding energy in trimers and, especially, in tetramers drastically increases; e.g., E b/ N in Be 3 is 7 times larger and in Be 4 is 18.4 times larger than in Be 2. This sharp increase is explained as a manifestation of many-body forces. As follows from the many-body decomposition, the tetramers, and trimers as well, are stabilized by the three-body forces, whereas the two- and four-body forces are repulsive. The attractive contribution to the three-body forces has a three-atom electron exchange origin. The latter benefits the promotion of ns-electrons to np-orbitals. The natural bond orbital (NBO) population analysis reveals a relatively large np-population in trimers and tetramers (in Be 4 it is equal to 2p 0.44). The population of the valence np-orbitals leads to the sp-hybridization providing the covalent bonding.

Díaz-Torrejón, C. C.; Kaplan, Ilya G.

2011-03-01

159

The influence of gravitational body force in meteoritic chondrule and lunar glass formation  

NASA Technical Reports Server (NTRS)

The effects of gravitational body force must be considered in the formation of extraterrestrial materials such as meteoritic chondrules and lunar glasses. Solidification experiments conducted in microgravity as well as g values greater than Earth's gravitational force have demonstrated that gravitational force can have profound and sometimes unexpected effects upon the way materials solidify and, therefore, upon their physical and mechanical properties. Solutal, thermal and sedimentation effects differ from those experienced on Earth. Because buoyancy forces are reduced, materials of different densities may remain in close proximity. The spherical morphology of chondrules and many lunar glasses may reflect the tendency for free floating liquids to form spherical droplets in a microgravity environment, a form which minimizes surface energy. Under these conditions, surface energy forces dominate gravity forces. The formation of two common chondrule textures, barred and radiating chondrules, can be explained using observations from glass science.

Budka, P. Z.

1984-01-01

160

Boundary element analysis of anisotropic bodies under thermo-mechanical body force loadings  

Microsoft Academic Search

Efficient boundary element formulations are presented for the analysis of anisotropic media due to common loadings such as inertial and centrifugal forces, and known temperature. The study is made comprehensive by considering both two- and three-dimensional behaviors. The anisotropy considered is of the most general form, viz. monoclinic for plane stress\\/strain behavior and the one with 21 independent elastic constants

A. Deb

1996-01-01

161

Development of Swimming Human Simulation Model Considering Rigid Body Dynamics and Unsteady Fluid Force for Whole Body  

NASA Astrophysics Data System (ADS)

The purpose of this study is to develop a swimming human simulation model considering rigid body dynamics and unsteady fluid force for the whole body, which will be utilized to analyze various dynamical problems in human swimming. First, the modeling methods and their formulations for the human body and the fluid force are respectively described. Second, experiments to identify the coefficients of the normal drag and the added mass are conducted by use of an experimental setup, in which a limb model rotates in the water, and its rotating angle and the bending moment at the root are measured. As the result of the identification, the present model for the fluid force was found to have satisfactory performance in order to represent the unsteady fluctuations of the experimental data, although it has 10% error. Third, a simulation for the gliding position is conducted in order to identify the tangential drag coefficient. Finally, a simulation example of standard six beat front crawl swimming is shown. The swimming speed of the simulation became a reasonable value, indicating the validity of the present simulation model, although it is 7.5% lower than the actual swimming.

Nakashima, Motomu; Satou, Ken; Miura, Yasufumi

162

Magnetic evidence for a partially differentiated carbonaceous chondrite parent body  

PubMed Central

The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. As a result, the paleomagnetism of the CV carbonaceous chondrite Allende, most of which was acquired after accretion of the parent body, has been a long-standing mystery. The possibility of a core dynamo like that known for achondrite parent bodies has been discounted because chondrite parent bodies are assumed to be undifferentiated. Resolution of this conundrum requires a determination of the age and timescale over which Allende acquired its magnetization. Here, we report that Allende’s magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a >  ? 20 ?T field up to approximately 9—10 Ma after solar system formation. This field was present too recently and directionally stable for too long to have been generated by the protoplanetary disk or young Sun. The field intensity is in the range expected for planetesimal core dynamos, suggesting that CV chondrites are derived from the outer, unmelted layer of a partially differentiated body with a convecting metallic core.

Carporzen, Laurent; Weiss, Benjamin P.; Elkins-Tanton, Linda T.; Shuster, David L.; Ebel, Denton; Gattacceca, Jerome

2011-01-01

163

The Mean Forces Exerted by Waves on Floating or Submerged Bodies with Applications to Sand Bars and Wave Power Machines  

Microsoft Academic Search

Water waves transport both energy and momentum, and any solid body which absorbs or reflects wave energy must absorb or reflect horizontal momentum also. Hence the body is subject to a mean horizontal force. In low waves, the force may be calculated immediately when the incident, reflected and transmitted wave amplitudes are known. For wave power devices the mean force

M. S. Longuet-Higgins

1977-01-01

164

Faddeev equations including three-body forces in first order perturbation theory  

Microsoft Academic Search

We propose a modification of the standard Faddeev equations which takes into account the effects of a three-body force in first order perturbation theory on the triton wave function and its binding energy. Furthermore, we report our results for the energy expectation value caused by the two-pion-exchange three-nucleon force. NUCLEAR STRUCTURE Faddeev equations, energy expectation value of the two-pion-exchange three-nucleon

A. Boemelburg; W. Gloeckle

1983-01-01

165

Magnetic force microscopy study of nanocrystalline Fe 91Zr 7B 2 soft magnetic alloy  

Microsoft Academic Search

The domain structure of the nanocrystalline Fe91Zr7B2 alloy at the optimum soft magnetic state was studied by means of magnetic force microscopy (MFM), Curved domains separated by 180 ° walls were observed. The domain wall width (?Lex, where Lex is the exchange correlation length) was estimated to be less than 2 ± 0,3 ?m from the MFM image. This result

K. Suzuki; D. Wexler; J. M. Cadogan; V. Sahajwalla; A. Inoue; T. Masumoto

1997-01-01

166

Three-nucleon bound-state calculation with meson-exchange three-body forces  

NASA Astrophysics Data System (ADS)

Triton binding energies are calculated taking into account explicit mesonic degrees of freedom. The investigation is based on a dynamical approach which classifies all contributing reaction mechanisms according to allowed transitions between asymptotic three-nucleon Hilbert spaces. In addition to the usual two-nucleon interactions, this cluster description, as a matter of course, leads to three-nucleon forces based on meson- exchange mechanisms and intermediate ? contributions. While most of the forces found in this way correspond to three-body forces well-known from other investigations, this cluster-dynamical description provides an additional, novel type of one-pion-exchange- type three-body force arising from the non-relativistic reduction of certain time-retarded one-pion exchanges between two nucleons in the presence of a third nucleon bound to one of the two nucleons. In a numerical study employing ?-, ?-, and ?-exchanges and ?'s, it is found that this new type of force is well capable of explaining the missing binding energy noticed in theoretical studies based on two-nucleon forces only. By contrast, and corroborating previous studies, the binding-energy contributions of all other three-body mechanisms are found to be very small or even negligible.

Rakei, Ali

1999-07-01

167

Magnetic resonance force microscopy with a permanent magnet on the cantilever  

SciTech Connect

The magnetic resonance force microscope (MRFM) is a microscopic 3-D imaging instrument based on a recent proposal to detect magnetic resonance signals mechanically using a micro-mechanical resonator. MRFM has been successfully demonstrated in various magnetic resonance experiments including electron spin resonance, ferromagnetic resonances and nuclear magnetic resonance. In order to apply this ultra-high, 3-D spatial resolution technique to samples of arbitrary size and shape, the magnetic particle which generates the field gradient {del}{bold B}, (and, therefore, the force {bold F = (m {center_dot} {del}B)} between itself and the spin magnetization {bold m} of the sample) will need to be mounted on the mechanical resonator. Up to the present, all experiments have been performed with the sample mounted on the resonator. This is done, in part, to avoid the spurious response of the mechanical resonator which is generated by the variation of the magnetization of the magnetic particle as the external field is varied.

Zhang, Z.; Hammel, P.C.

1997-02-01

168

A computer program to estimate the source body magnetization direction from magnetic and gravity anomalies  

NASA Astrophysics Data System (ADS)

In this paper, a FORTRAN 77 computer program that estimates the inclination and declination of the magnetization of a body causing a magnetic anomaly is presented. The program searches for maximum correlation in between the pseudogravity anomalies at ranges of body magnetization and gravity anomalies caused by the same formations. The pseudogravity transformation is performed each time for an array of inclination and declination angles. Test cases demonstrate that the method can be used with confidence. An example of aeromagnetic and gravity anomalies from Northern Central Turkey, shows maximum correlation at -22° of declination of body magnetization. This result correlates well with the previous research on palaeomagnetic and tectonic work revealing an anticlockwise rotation of Central Turkey.

Bilim, F.; Ates, A.

1999-04-01

169

Variable force, eddy-current or magnetic damper  

NASA Technical Reports Server (NTRS)

An object of the invention is to provide variable damping for resonant vibrations which may occur at different rotational speeds in the range of rpms in which a rotating machine is operated. A variable force damper in accordance with the invention includes a rotating mass carried on a shaft which is supported by a bearing in a resilient cage. The cage is attached to a support plate whose rim extends into an annular groove in a housing. Variable damping is effected by tabs of electrically conducting nonmagnetic material which extend radially from the cage. The tabs at an index position lie between the pole face of respective C shaped magnets. The magnets are attached by cantilever spring members to the housing.

Cunningham, R. E. (inventor)

1985-01-01

170

The contactless measurement of forces which affect a magnetic particle in a fluid and its manipulation  

NASA Astrophysics Data System (ADS)

The magnetic force has been used for the drug delivery, the cell/DNA manipulation, and other handlings of micro or nanoparticles. When magnetic particles are suspended in a fluid, they are influenced by the magnetic force caused by the magnetic field gradient, the gravity force, and the buoyance force. The magnetic torque also affects them to align their magnetic moments to the direction of the applied magnetic field. Furthermore, the viscous force or the force between the magnetized magnetic particles themselves cannot be neglected. In this study, methods of the quantitative measurement of these forces and the manipulation of a magnetic particle were developed. Four electromagnets were used to apply magnetic fields to ferrite particles (300nm-300?m) in a fluid in a vessel. The particle tracking velocimetry method was used to visualize the behavior of the particles. Based on the theory of the magnetic suspension and balance system, the vertical and horizontal forces affected a magnetic particle were estimated from the current in the coil of each electromagnet without any physical contact to it. And, the contactless manipulations of the magnetic particle suspended in the stagnated or flowing fluid by controlling the coil currents were demonstrated successfully.

Tokura, Susumu; Hara, Masakazu; Kawaguchi, Norihito; Izawa, Jun; Amemiya, Naoyuki

2012-02-01

171

Direct measurements of controlled aerodynamic forces on a wire-suspended axisymmetric body  

NASA Astrophysics Data System (ADS)

A novel in-line miniature force transducer is developed for direct measurements of the net aerodynamic forces and moments on a bluff body. The force transducers are integrated into each of the eight mounting wires that are utilized for suspension of an axisymmetric model in a wind tunnel having minimal wake interference. The aerodynamic forces and moments on the model are altered by induced active local attachment of the separated base flow. Fluidic control is effected by an array of four integrated aft-facing synthetic jet actuators that emanate from narrow, azimuthally segmented slots, equally distributed around the perimeter of the circular tail end. The jet orifices are embedded within a small backward-facing step that extends into a Coanda surface. The altered flow dynamics associated with both quasi-steady and transitory asymmetric activation of the flow control effect is characterized by direct force and PIV measurements.

Abramson, Philip; Vukasinovic, Bojan; Glezer, Ari

2011-06-01

172

Clock field in arrayed magnetic logic gates with a magnetic force microscope tip  

NASA Astrophysics Data System (ADS)

A magnetic logic gate (MLG), which is based on magnetic quantum dot cellular automata (MQCA), is capable of NAND/NOR logic operations. By arranging MLGs in a two-dimensional periodic array, a highly functional circuit can be created. However, NAND/NOR gates are difficult to form into a two-dimensional periodic arrangement. Here, we propose NOT/AND/ORs gate based on MLGs, which can be arranged in a two-dimensional periodic array. To demonstrate logic operations, we performed numerical simulations based on the macro-spin model. To execute logic operation in the arrayed structure, we used the stray field from a magnetic force microscope tip.

Nomura, H.; Imanaga, Y.; Hiratsuka, Y.; Nakatani, R.

2012-08-01

173

The study of the role of the two-body force in determining level densities  

NASA Astrophysics Data System (ADS)

The study of the role of the two-body force in determining level densities explored the characteristics of the two-body force and their impact on nuclear level densities. Two different theoretical approaches, the statistical mechanical model and moment expansion method, were used for the determining the impact of the two-body force on level densities. Discrete levels in the lower excitation region were compiled to provide information about level density systematics. A shell model calculation for a number of light nuclei allowed a test of the input parameters including single particle energies and two-body matrix elements. Generally good agreement was found between the calculated and observed energies of low-lying states. A comparison of the results obtained with three widely used interactions for nuclei with mass numbers 18 and 20 allowed some insight into the two-body interaction and the possibilities for improving it. For the level density calculations twenty four nuclei with mass numbers between 20 and 41 were used. Both the values from tabulations of low-lying levels and the results from previous studies of level densities at 7 Mev and at 20 Mev were included. It was found that the parameters derived from the higher energy measurements gave poor results at energies below 5 Mev. The discrepancies appeared to be related to problems in determining one of the two parameters involved. Two approaches were used in an effort to improve the precision of this parameter. Both were reasonably successful. Calculations of the level of density using a super conducting model within a statistical mechanical framework and a full two-body interaction utilizing a moment method approach were completed. Both gave a reasonably good representation of the data. An examination of the significance of the analysis for future study of the two body force and of nuclear level densities is presented.

Huang, Po-Lin

174

Characteristics of magnetic force microscopy magnetics on high moment perpendicular magnetic recording writers with high coercivity probes  

NASA Astrophysics Data System (ADS)

High resolution magnetic force microscopy (MFM) imaging with high coercivity probes on perpendicular magnetic recording (PMR) writers directly characterizes magnetic field contour for the writer main pole as well as its shields' magnetic state. Evolution of write bubble and return field was analyzed by MFM imaging in dynamic phase detection scheme. Different write field components and their out of plane second order derivatives were calculated via finite element modeling. The MFM imaged write field distribution correlates well with the PMR writer out of plane write field component. Magnetic responses of the PMR writer main pole, trailing and side shields are quantified. The trailing and side shields exhibit complicated magnetic saturation behaviors comparing with the PMR writer pole. The side shield's magnetic response is dependent upon its initial equilibrium state.

Liu, Feng; Li, Shaoping; Bai, Daniel; Wang, James; Li, Zhanjie; Han, Dehua; Pan, Tao; Mao, Sining

2012-04-01

175

Magnetic Forces Simulation of Bulk HTS over Permanent Magnetic Railway with Numerical Method  

NASA Astrophysics Data System (ADS)

Magnetic levitation forces of bulk high temperature superconductor (HTS) above two types permanent magnet railway (PMR) is simulated using finite element method (FEM). The models are formulated by H-formulation and resolving codes is developed using Finite Element Program Generator (FEPG). The E- J power law is used to describe the electrical field vs. current density nonlinear characteristic of HTS. The applied magnetic fields induced by the PMR are calculated by the standard analysis method with the equivalent surface current model. By the method, the calculation formulation of magnetic fields generated by Halbach PMR and symmetrical PMR is derived respectively. The simulation results show that the finite element dynamic mesh rebuilding problem of HTS magnetic levitation transportation system comprised of bulk HTS and PMR can be easily avoided by the methods.

Lu, Yiyun; Zhuang, Shujun

2012-10-01

176

Full-body motion control integrated with Force Error Detection for wheelchair support  

Microsoft Academic Search

We propose a full-body controller system for a humanoid robot to achieve wheelchair support. There are two main problems in pushing control. One problem is that the controller system should decide pushing strategies based on whether the humanoid robot should adapt to the reaction forces from the pushed wheelchair or resist against them. Another problem is that the arms's reachabilities

Shunichi Nozawa; Masaho Ishida; Ryohei Ueda; Youhei Kakiuchi; Kei Okada; Masayuki Inaba

2011-01-01

177

Evaluation of impulse oscillation system: comparison with forced oscillation technique and body plethysmography  

Microsoft Academic Search

The impulse oscillation system (IOS) has been developed recently to measure respiratory system resistance (Rrs) and reactance (Xrs) at different frequencies up to ¢25 Hz. IOS has, however, not been validated against established techniques. This study compared IOS with the classical pseudorandom noise forced oscillation technique (FOT) and body plethysmographic airway resistance (Raw) in 49 subjects with a variety of

J. Hellinckx; M. Cauberghs; K. De Boeck; M. Demedts

2001-01-01

178

Consideration of body forces in axisymmetric design sensitivity analysis using the BEM  

Microsoft Academic Search

For the shape design sensitivity analysis (SDSA) of the axisymmetric elasticity problem, a unified approach considering body forces is presented, covering both the adjoint variable method and the direct differentiation method. The methods are based on the axisymmetric boundary integral formulation and the material derivative concept. Accuracy of the presented methods is studied through two examples: a simple disk problem

Boo Youn Lee

1996-01-01

179

Analysis of eddy current and body force of annular type single-phase electromagnetic induction pump  

SciTech Connect

The flux density, eddy current and body force of annular-type, single-phase induction electromagnetic pump were analyzed by finite element method assuming that the secondary conductor is at standstill. The diffusion characteristics of eddy current in the secondary conductor as well as the body force characteristics are also analyzed. It is shown that the diffusion characteristics of eddy current are determined by complex wave number K which is derived from the diffusion equation. The structure of annular type single-phase induction electromagnetic pump is explained and its analytical model is presented followed by derivation of energy functional. The measured results are compared with those calculated by finite element method to demonstrate validity of the calculated results. Distributions of eddy current and body force in the secondary conductor are also analyzed. Distributions of forward and backward diffusion waves in the aluminum and mercury secondary conductors are presented. It is shown that the conventional skin depth delta can be used only when the gap length l is short. It is proven that the body force in the direction of z-axis can be decomposed into components which depend on the real part K/sub r/ and imaginary part K/sub i/ of complex wave number K. Finally the influence of the end effect is discussed.

Hasebe, S.; Kano, Y.

1982-03-01

180

Many-body theory for multipole polarizabilities and dispersion forces in helium-helium interactions  

Microsoft Academic Search

Linked cluster many-body perturbation theory has been developed for the calculation of the dynamic quadrupole polarizabilities of the helium atom in its ground state. The polarizabilities have been used to calculate the London dispersion force constants for He-He interactions. The results for the polarizabilities and the van der Waals constants compare very well with other standard values.

B. K. Rao

1984-01-01

181

Two and three-body dispersion forces with one excited molecule  

Microsoft Academic Search

The interaction between molecules and the Maxwell electromagnetic field is used to determine two- and three-body dispersion forces, taking into account retardation effects fully. The case in which one of the molecules is in an electronically excited state is contrasted with that in which all molecules are in their ground states. The very long-range, retarded, potentials involving excited molecules are

E. A. Power; T. Thirunamachandran

1995-01-01

182

Many-body theory for multipole polarizabilities and dispersion forces in helium-helium interactions  

NASA Astrophysics Data System (ADS)

Linked cluster many-body perturbation theory has been developed for the calculation of the dynamic quadrupole polarizabilities of the helium atom in its ground state. The polarizabilities have been used to calculate the London dispersion force constants for He-He interactions. The results for the polarizabilities and the van der Waals constants compare very well with other standard values.

Rao, B. K.

1984-06-01

183

Theory of Surface Force Constant Changes in Body-Centered Cubic Lattices.  

National Technical Information Service (NTIS)

A calculation has been made of force-constant changes at the (100) and (110) surfaces of body-centered cubic crystals. A model consisting of first, second and third-neighbor Lennard-Jones interactions together with harmonic angle-bending interactions is e...

D. J. Cheng R. F. Wallis L. Dobrzynski

1973-01-01

184

Predictions for water clusters from a first-principles two- and three-body force field  

NASA Astrophysics Data System (ADS)

A new rigid-monomer three-body potential has been developed for water by fitting it to more than 70 thousand trimer interaction energies computed ab initio using coupled-cluster methods and augmented triple-zeta-quality basis sets. This potential was used together with a modified form of a previously developed two-body potential and with a polarization model of four- and higher-body interactions to predict the energetics of the water trimer, hexamer, and 24-mer. Despite using the rigid-monomer approximation, these predictions agree better with flexible-monomer benchmarks than published results obtained with flexible-monomer force fields. An unexpected finding of our work is that simple polarization models predict four-body interactions to within a few percent, whereas for three-body interactions these models are known to have errors on the order of 50%.

Góra, Urszula; Cencek, Wojciech; Podeszwa, Rafa?; van der Avoird, Ad; Szalewicz, Krzysztof

2014-05-01

185

Predictions for water clusters from a first-principles two- and three-body force field.  

PubMed

A new rigid-monomer three-body potential has been developed for water by fitting it to more than 70 thousand trimer interaction energies computed ab initio using coupled-cluster methods and augmented triple-zeta-quality basis sets. This potential was used together with a modified form of a previously developed two-body potential and with a polarization model of four- and higher-body interactions to predict the energetics of the water trimer, hexamer, and 24-mer. Despite using the rigid-monomer approximation, these predictions agree better with flexible-monomer benchmarks than published results obtained with flexible-monomer force fields. An unexpected finding of our work is that simple polarization models predict four-body interactions to within a few percent, whereas for three-body interactions these models are known to have errors on the order of 50%. PMID:24852524

Góra, Urszula; Cencek, Wojciech; Podeszwa, Rafa?; van der Avoird, Ad; Szalewicz, Krzysztof

2014-05-21

186

Centrifugal Force Based Magnetic Micro-Pump Driven by Rotating Magnetic Fields  

NASA Astrophysics Data System (ADS)

This paper presents a centrifugal force based magnetic micro-pump for the pumping of blood. Most blood pumps are driven by an electrical motor with wired control. To develop a wireless and battery-free blood pump, the proposed pump is controlled by external rotating magnetic fields with a synchronized impeller. Synchronization occurs because the rotor is divided into multi-stage impeller parts and NdFeB permanent magnet. Finally, liquid is discharged by the centrifugal force of multi-stage impeller. The proposed pump length is 30 mm long and19 mm in diameter which much smaller than currently pumps; however, its pumping ability satisfies the requirement for a blood pump. The maximum pressure is 120 mmHg and the maximum flow rate is 5000ml/min at 100 Hz. The advantage of the proposed pump is that the general mechanical problems of a normal blood pump are eliminated by the proposed driving mechanism.

Kim, S. H.; Hashi, S.; Ishiyama, K.

2011-01-01

187

Novel mechanism of self-injecting magnetic fluid seal applying switch of magnetic force direction on yoke surface  

NASA Astrophysics Data System (ADS)

The magnetic force distribution on the yoke surface of a magnetic fluid seal is clarified using finite element analysis. Calculations are performed for two kinds of typical magnetic fluid shape, that is, film shape and spike shape. It is interesting to note that the magnetic force direction switches halfway the yoke length. The region wherein the magnetic fluid flows to the yoke top direction is found to be wider for a thicker magnet, thicker yoke and the case with a spindle. This leads to a new concept of magnetic fluid seal having self-injection action.

Mitsuya, Yasunaga; Abe, Tsukasa; Matsunaga, Shigeki

1993-04-01

188

Transitory Aerodynamic Forces on a Body of Revolution using Synthetic Jet Actuation  

NASA Astrophysics Data System (ADS)

The aerodynamic forces and moments on axisymmetric bodies at subsonic speeds are controlled by exploiting local flow attachment using fluidic (synthetic jet) actuation and thereby altering the apparent aerodynamic shape of the surface. Control is effected upstream of the base of the body by an azimuthal array of individually-controlled, aft-facing synthetic jets emanating along an azimuthal Coanda surface. Actuation produces asymmetric aerodynamic forces and moments, with ratios of lift to average jet momentum approaching values typical of conventional jet-based circulation control on two-dimensional airfoils. Momentary forces are achieved using transient (pulsed) actuation and are accompanied by the formation and shedding of vorticity concentrations as a precursor to the turning of the outer flow into the wake region.

Rinehart, Christopher; McMichael, James; Glezer, Ari

2002-11-01

189

Many-body effects are essential in a physically motivated CO2 force field.  

PubMed

We develop a physically motivated many-body force field for CO(2), incorporating explicit three-body interactions parameterized on the basis of two- and three-body symmetry adapted perturbation theory (SAPT) calculations. The potential is parameterized consistently with, and builds upon, our successful SAPT-based two-body CO(2) model ("Schmidt, Yu, and McDaniel" (SYM) model) [K. Yu, J. G. McDaniel, and J. R. Schmidt, J. Phys Chem B 115, 10054 (2011)]. We demonstrate that three-body interactions are essential to achieve an accurate description of bulk properties, and that previous two-body models have therefore necessarily exploited large error cancellations to achieve satisfactory results. The resulting three-body model exhibits excellent second/third virial coefficients and bulk properties over the phase diagram, yielding a nearly empirical parameter-free model. We show that this explicit three-body model can be converted into a computationally efficient, density/temperature-dependent two-body model that reduces almost exactly to our prior SYM model in the high-density limit. PMID:22280763

Yu, Kuang; Schmidt, J R

2012-01-21

190

Many-body effects are essential in a physically motivated CO2 force field  

NASA Astrophysics Data System (ADS)

We develop a physically motivated many-body force field for CO2, incorporating explicit three-body interactions parameterized on the basis of two- and three-body symmetry adapted perturbation theory (SAPT) calculations. The potential is parameterized consistently with, and builds upon, our successful SAPT-based two-body CO2 model (``Schmidt, Yu, and McDaniel'' (SYM) model) [K. Yu, J. G. McDaniel, and J. R. Schmidt, J. Phys Chem B 115, 10054 (2011)]. We demonstrate that three-body interactions are essential to achieve an accurate description of bulk properties, and that previous two-body models have therefore necessarily exploited large error cancellations to achieve satisfactory results. The resulting three-body model exhibits excellent second/third virial coefficients and bulk properties over the phase diagram, yielding a nearly empirical parameter-free model. We show that this explicit three-body model can be converted into a computationally efficient, density/temperature-dependent two-body model that reduces almost exactly to our prior SYM model in the high-density limit.

Yu, Kuang; Schmidt, J. R.

2012-01-01

191

Local stress and heat flux in atomistic systems involving three-body forces.  

PubMed

Local densities of fundamental physical quantities, including stress and heat flux fields, are formulated for atomistic systems involving three-body forces. The obtained formulas are calculable within an atomistic simulation, in consistent with the conservation equations of thermodynamics of continuum, and can be applied to systems with general two- and three-body interaction forces. It is hoped that this work may correct some misuse of inappropriate formulas of stress and heat flux in the literature, may clarify the definition of site energy of many-body potentials, and may serve as an analytical link between an atomistic model and a continuum theory. Physical meanings of the obtained formulas, their relation with virial theorem and heat theorem, and the applicability are discussed. PMID:16468857

Chen, Youping

2006-02-01

192

Structure and thermodynamics of fluid xenon using an accurate integral equation for three-body forces  

NASA Astrophysics Data System (ADS)

Recently, we proposed a new self-consistent integral equation to obtain the pair correlation function of simple fluids in the case of pairwise additive forces [J. Chem. Phys. 114, 4141 (2001)]. Here this integral equation is applied to predict the structural and thermodynamic properties of xenon at supercritical temperatures and low densities, with the aim of examining the possible effect of the three-body dispersion forces. The validity of our extended integral equation is tested against molecular dynamics, and the results are compared to recent small-angle neutron scattering measurements [Formisano et al. Phys. Rev. E 58, 2648 (1998)] and thermodynamic properties. The good agreement found between semianalytic calculations and simulation or experimental results of the structural and thermodynamic properties gives clear indication of the efficiency of the use of our integral equation conjugated with an effective pair potential consisting of the Aziz-Slaman two-body potential plus the Axilrod-Teller three-body potential.

Bomont, J. M.; Bretonnet, J. L.

2002-06-01

193

Wing/body kinematics measurement and force and moment analyses of the takeoff flight of fruitflies  

NASA Astrophysics Data System (ADS)

In the paper, we present a detailed analysis of the takeoff mechanics of fruitflies which perform voluntary takeoff flights. Wing and body kinematics of the insects during takeoff were measured using high-speed video techniques. Based on the measured data, inertia force acting on the insect was computed and aerodynamic force and moment of the wings were calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. The following has been shown. In its voluntary takeoff, a fruitfly jumps during the first wingbeat and becomes airborne at the end of the first wingbeat. When it is in the air, the fly has a relatively large "initial" pitch-up rotational velocity (more than 5 000°/s) resulting from the jumping, but in about 5 wingbeats, the pitch-up rotation is stopped and the fly goes into a quasi-hovering flight. The fly mainly uses the force of jumping legs to lift itself into the air (the force from the flapping wings during the jumping is only about 5%-10% of the leg force). The main role played by the flapping wings in the takeoff is to produce a pitch-down moment to nullify the large "initial" pitch-up rotational velocity (otherwise, the fly would have kept pitching-up and quickly fallen down).

Chen, Mao-Wei; Sun, Mao

2014-05-01

194

The magnetic wake of planets and small bodies in a pulsar's wind  

NASA Astrophysics Data System (ADS)

We investigate the electromagnetic interaction of a relativistic and magnetized stellar wind with a planet or a smaller body in orbit around a pulsar. This may be relevant to objects such as PSR B1257+12 and PSR B1620-26 that are expected to hold a planetary system, or to other pulsars with suspected asteroids or comets. Most models predict that, albeit highly relativistic, pulsar's winds are slower than Alfvén waves. In that case, a pair of stationary Alfvén waves, called Alfvén wings (AW), is expected to form on the sides of the planet. They are the magnetic wake of the body into the plasma flow, like the wake of a boat left into the sea (with a similar shape). The theory of Alfvén wings was initially developed in the context of the Io- Jupiter interaction. We have extended it to relativistic winds, and we have studied the possible consequences that could be relevant for observations : possible radio emissions from pulsar's planets, and a magnetic force configuration that can deeply modify the orbit of the smaller bodies (asteroids, comets).

Mottez, F.; Heyvaerts, J.

2012-09-01

195

Magnetic resonance force microscopy and a solid state quantum computer.  

SciTech Connect

A Quantum Computer (QC) is a device that utilizes the principles of Quantum Mechanics to perform computations. Such a machine would be capable of accomplishing tasks not achievable by means of any conventional digital computer, for instance factoring large numbers. Currently it appears that the QC architecture based on an array of spin quantum bits (qubits) embedded in a solid-state matrix is one of the most promising approaches to fabrication of a scalable QC. However, the fabrication and operation of a Solid State Quantum Computer (SSQC) presents very formidable challenges; primary amongst these are: (1) the characterization and control of the fabrication process of the device during its construction and (2) the readout of the computational result. Magnetic Resonance Force Microscopy (MRFM)--a novel scanning probe technique based on mechanical detection of magnetic resonance-provides an attractive means of addressing these requirements. The sensitivity of the MRFM significantly exceeds that of conventional magnetic resonance measurement methods, and it has the potential for single electron spin detection. Moreover, the MRFM is capable of true 3D subsurface imaging. These features will make MRFM an invaluable tool for the implementation of a spin-based QC. Here we present the general principles of MRFM operation, the current status of its development and indicate future directions for its improvement.

Pelekhov, D. V. (Denis V.); Martin, I. (Ivar); Suter, A. (Andreas); Reagor, D. W. (David W.); Hammel, P. C. (P. Chris)

2001-01-01

196

Experimental Study of Collision Motion, Contact Force and Adhesion Force of Hemispherical Sliders with Stationary Magnetic Disks  

Microsoft Academic Search

In this paper, an experimental study of measuring the dynamic meniscus force and the contact force when hemispherical glass sliders bounce on stationary magnetic disks is presented. We prepared hemispherical glass sliders with radii of 1.0 and 2.0mm supported by slender cantilever beams and magnetic disks with 0-, 1-, 2-, and 3-nm-thick lubricant layers with and without ultraviolet (UV) irradiation.

Kyosuke Ono; Kenji Nakagawa

2006-01-01

197

Magnetotelluric anomalies, computed over models having high magnetic permeability bodies  

NASA Astrophysics Data System (ADS)

In magnetotellurics it is assumed that the relative magnetic permeability is 1. We carried out systematic magnetotelluric numerical modelling studies to analyse the magnetotelluric effect due to a hypothetically high-permeability body in the subsurface, e.g. due to a thin (a few hundred meter thick) layer in state of second-order magnetic phase transition at the Curie depth (Kiss et al, GRL, 2005). In one-dimensional case, we have demonstrated that a thin, highly magnetized layer produces the same size of a magnetotelluric anomaly as a similarly thin high-conductivity layer, but with the opposite sign. Its signatures are as follows. 1) extremely thick and extremely high-resistivity layers as results of magnetotelluric inversion, and 2) consistent magnetotelluric and geomagnetic depth estimations for the top of the highly magnetized thin layer. Various two-dimensional cases (both in E and H polarisations) give further insights into this phenomenon. If the enhancement of the magnetic permeability is exceptionally high, the effect may really distort the conventional magnetotelluric results. Such indications have already been observed in some magnetotelluric field curves in Hungary. OTKA Hungarian National Research Fund, Project No 68475

Prácser, Ern?; Kiss, János; Ádám, Antal; Szarka, László

2010-05-01

198

High field-gradient dysprosium tips for magnetic resonance force microscopy  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy (MRFM) is based on measuring the attonewton-scale force between nuclear or electronic spins and a magnetic tip. The force is directly proportional to the magnetic field gradient generated by the tip, making a high moment nanoscale magnet desirable. Dysprosium, with a bulk magnetization 70% higher than iron, is a suitable candidate for such a tip. We have performed MRFM to quantitatively characterize two Dy nanomagnets. We find that magnetic field gradients as high as 6 MT/m (60 G/nm) can be generated, a 40% enhancement compared to our previous FeCo tips.

Mamin, H. J.; Rettner, C. T.; Sherwood, M. H.; Gao, L.; Rugar, D.

2012-01-01

199

Nonlinear effects on magnetic energy release by forced magnetic reconnection: Long wavelength perturbations  

SciTech Connect

Two-dimensional, nonlinear magnetohydrodynamic simulations in a compressible plasma to investigate magnetic energy release during the process of forced magnetic reconnection are carried out. This is in order to study the heating of the Sun's corona where it is believed that reconnection is induced by the photospheric motions. A sheared force-free field is perturbed by a transitory slow disturbance (pulse) at the boundary. This disturbance triggers the formation of a current sheet that subsequently releases stored magnetic energy through magnetic reconnection. Previously, it has been shown that for small boundary perturbations, the simulation results are consistent with the previous analytic theory based on a linear approach. For larger amplitude perturbations, or close to the threshold for tearing instability, the evolution shows nonlinear behavior. Solar coronal heating may arise due to a series of reconnection events, and a primary aim of this work is to study the interaction of such heating events. Thus, the perturbations are applied at the boundary by successive pulses. It is found that following the second driving pulse, the current sheet expands along the separatrix before relaxing to a reconnective equilibrium with magnetic islands and releasing even more magnetic energy for the same amplitude perturbation. Here, the previous work is extended to study long wavelength perturbations for which the system exhibits even stronger nonlinear aspects.

Jain, Rekha; Browning, Philippa; Kusano, K. [Department of Applied Mathematics, University of Sheffield, Sheffield, S3 7RH (United Kingdom); School of Physics and Astronomy, University of Manchester, Manchester M60 1QD (United Kingdom); Earth Simulator Center, JAMSTEC, Yokohama (Japan)

2006-05-15

200

Electromagnetic force motor design using rare earth-cobalt permanent magnets  

Microsoft Academic Search

A high force, long stroke force motor has been developed for use in driving control valves on hydraulic actuators which position aircraft control surfaces. The force motor replaces more conventional secondary actuators at considerable savings in cost and space with improved reliability. The force motor design concept utilizes samarium cobalt magnets to achieve a compact configuration suitable for interfacing redundant

M. F. Marx; T. D. Lewis

1977-01-01

201

Experimental Study of Collision Motion, Contact Force and Adhesion Force of Hemispherical Sliders with Stationary Magnetic Disks  

NASA Astrophysics Data System (ADS)

In this paper, an experimental study of measuring the dynamic meniscus force and the contact force when hemispherical glass sliders bounce on stationary magnetic disks is presented. We prepared hemispherical glass sliders with radii of 1.0 and 2.0mm supported by slender cantilever beams and magnetic disks with 0-, 1-, 2-, and 3-nm-thick lubricant layers with and without ultraviolet (UV) irradiation. In the case of a 1-mm-radius slider with a surface roughness of 1.7nm in Ra, we found that an adhesion force can be clearly observed at the instant of separation under any lubricant condition except the one case of 1-nm-thick lubricant with UV. Typical data of displacement, velocity and acceleration of bouncing motion prove that the adhesion force originates from meniscus force rather than from van der Waals force. We also found that the maximum dynamic adhesion force is close to the static meniscus force. However, in the case of 3-nm-thick lubricant without UV, the dynamic adhesion force increases significantly, probably because of the effect of a squeeze film acting as a viscous fluid. In contrast, the smooth 2-mm-radius slider does not show a clear adhesion force at an impact velocity higher larger than 1.5mm/s. We also found that the maximum contact force versus penetration depth can be estimated well using the Hertz contact theory for the contact between a smooth sphere and a flat.

Ono, Kyosuke; Nakagawa, Kenji

202

Model for the resistance force acting on circular bodies in the imminence of rolling  

NASA Astrophysics Data System (ADS)

The laws of friction are reasonably well understood for the case of blocks in contact with rough plane surfaces. However, as far as bodies with circular sections are concerned, the physics of friction becomes more involving and it is not possible to adopt a simple conceptual framework to explain all phenomena. In particular, there is no approach so far to the problem of the resistance force that opposes to circular bodies that remain at rest while acted upon by small forces. Here we fill this gap by introducing a mechanical model based on both the elasticity theory and Hertz contact mechanics. Our approach furnishes a quantitative expression for the critical force beyond which rest can no longer be maintained. Besides confirming the expected proportionality of the resistance force with the load, our result contains no free parameters and is expressed solely in terms of physical properties of the problem, such as the pressure of the body per unit of superficial area, a relation between the Young modulus of the surface and its Poisson ratio, and the symmetry of the contact.

Bilobran, A. L. O.; Angelo, R. M.

2013-09-01

203

Benchmarking numerical predictions with force and moment measurements on slender, supercavitating bodies  

SciTech Connect

High-speed water-entry is a very complex, dynamic process. As a first attempt at modeling the process, a numerical solution was developed at Sandia National Laboratories for predicting the forces and moments acting on a body with a steady supercavity, that is, a cavity which extends beyond the base of the body. The solution is limited to supercavities on slender, axisymmetric bodies at small angles of attack. Limited data were available with which to benchmark the axial force predictions at zero angle of attack. Even less data were available with which to benchmark the pitching moment and normal force predictions at nonzero angles of attack. A water tunnel test was conducted to obtain force and moment data on a slender shape. This test produced limited data because of waterproofing problems with the balance. A new balance was designed and a second water tunnel test was conducted at Tracor Hydronautics, Inc. This paper describes the numerical solution, the experimental equipment and test procedures, and the results of the second test. 8 refs., 11 figs.

Hailey, C.E.; Clark, E.L.; Cole, J.K.

1991-01-01

204

The role of three-nucleon forces and many-body processes in nuclear pairing  

NASA Astrophysics Data System (ADS)

We present microscopic valence-shell calculations of pairing gaps in the calcium isotopes, focusing on the role of three-nucleon (3N) forces and many-body processes. In most cases, we find a reduction in pairing strength when the leading chiral 3N forces are included, compared to results with low-momentum two-nucleon (NN) interactions only. This is in agreement with a recent energy density functional study. At the NN level, calculations that include particle-particle and hole-hole ladder contributions lead to smaller pairing gaps compared with experiment. When particle-hole contributions as well as the normal-ordered one- and two-body parts of 3N forces are consistently included to third order, we find reasonable agreement with experimental three-point mass differences. This highlights the important role of 3N forces and many-body processes for pairing in nuclei. Finally, we relate pairing gaps to the evolution of nuclear structure in neutron-rich calcium isotopes and study the predictions for the 2+ excitation energies, in particular for 54Ca.

Holt, J. D.; Menéndez, J.; Schwenk, A.

2013-07-01

205

Determination of the phase-resolved body force produced by a dielectric barrier discharge plasma actuator  

NASA Astrophysics Data System (ADS)

Dielectric barrier discharge (DBD) plasma actuators are a promissing tool for active flow control applications. In order to determine the time-resolved body force induced by a DBD plasma actuator, which was driven by a 9.5 kHz sinusoidal signal, the flow has to be captured with a high spatial and temporal resolution. For this purpose we applied a laser Doppler velocity profile sensor for the measurements of the two-component velocity field and Lagrangian acceleration. A temporal and spatial resolution of 7.3 µs and 40 µm was achieved. We present the time-resolved local flow behaviours induced by the DBD actuator. Based on these measurement data the time-resolved body force generated by the plasma actuator was derived. Experiments revealed a defined dependence of the force direction on the phase angle of the ac operating voltage. This result is a contribution to the controversy on the temporal behaviour of the body force of plasma actuators.

Neumann, Mathias; Friedrich, Christian; Czarske, Jürgen; Kriegseis, Jochen; Grundmann, Sven

2013-01-01

206

Flow and Force Equations for a Body Revolving in a Fluid  

NASA Technical Reports Server (NTRS)

Part I gives a general method for finding the steady-flow velocity relative to a body in plane curvilinear motion, whence the pressure is found by Bernoulli's energy principle. Integration of the pressure supplies basic formulas for the zonal forces and moments on the revolving body. Part II, applying this steady-flow method, finds the velocity and pressure at all points of the flow inside and outside an ellipsoid and some of its limiting forms, and graphs those quantities for the latter forms. Part III finds the pressure, and thence the zonal force and moment, on hulls in plane curvilinear flight. Part IV derives general equations for the resultant fluid forces and moments on trisymmetrical bodies moving through a perfect fluid, and in some cases compares the moment values with those found for bodies moving in air. Part V furnishes ready formulas for potential coefficients and inertia coefficients for an ellipsoid and its limiting forms. Thence are derived tables giving numerical values of those coefficients for a comprehensive range of shapes.

Zahm, A F

1930-01-01

207

Development of a Force Measurement Device for Lower-Body Muscular Strength Measuring of Skaters  

NASA Astrophysics Data System (ADS)

This paper presents a force measurement system that can measure a lower-body muscular strength of skaters. The precise measurement and analysis of the left and right lower-body strength of skaters is necessary, because a left/right lower-body strength balance is helpful to improve the athletes' performance and to protect them from injury. The system is constructed with a skate sliding board, a couple of sensor-units with load cell, indicator and control box, guard, force pad, and support bracket. The developed force measurement system is calibrated by the calibration setup, and the uncertainty of the force sensing unit on the left is within 0.087% and the uncertainty of the force sensing unit on the right is within 0.109%. In order to check the feasibility of the developed measurement device, a kinematic analysis is conducted with skater. As a result, the subject shows the deviation of left and right of 12.1 N with respect to average strength and 39.1 N with respect to the maximum strength. This evaluation results are reliable enough to make it possible to measure a lower-body muscular strength of skaters. The use of this measurement system will be expected to correct the posture of skaters and record the sports dynamics data for each athlete. It is believed that through the development of this equipment, skaters in elementary, middle, high schools, colleges, and the professional level have the systematic training to compete with world-class skaters.

Kim, Dong Ki; Lee, Jeong Tae

208

Computation of trunk muscle forces, spinal loads and stability in whole-body vibration  

NASA Astrophysics Data System (ADS)

Whole-body vibration has been indicated as a risk factor in back disorders. Proper prevention and treatment management, however, requires a sound knowledge of associated muscle forces and loads on the spine. Previous trunk model studies have either neglected or over-simplified the trunk redundancy with time-varying unknown muscle forces. Trunk stability has neither been addressed. A novel iterative dynamic kinematics-driven approach was employed to evaluate muscle forces, spinal loads and system stability in a seated subject under a random vertical base excitation with ˜±1 g peak acceleration contents. This iterative approach satisfied equations of motion in all directions/levels while accounting for the nonlinear passive resistance of the ligamentous spine. The effect of posture, co-activity in abdominal muscles and changes in buttocks stiffness were also investigated. The computed vertical accelerations were in good agreement with measurements. The input base excitation, via inertial and muscle forces, substantially influenced spinal loads and system stability. The flexed posture in sitting increased the net moment, muscle forces and passive spinal loads while improving the trunk stability. Similarly, the introduction of low to moderate antagonistic coactivity in abdominal muscles increased the passive spinal loads and improved the spinal stability. A trade-off, hence, exists between lower muscle forces and spinal loads on one hand and more stable spine on the other. Base excitations with larger peak acceleration contents substantially increase muscle forces/spinal loads and, hence, the risk of injury.

Bazrgari, B.; Shirazi-Adl, A.; Kasra, M.

2008-12-01

209

Construction of a low temperature nuclear magnetic resonance force microscope  

NASA Astrophysics Data System (ADS)

All aspects of a nuclear magnetic resonance force microscope (NM-RFM) have been constructed. The development and testing of each aspect area are discussed in detail. In particular, two sets of three-axis piezoelectric positioners based on a stick-slip motion have been successfully incorporated and tested for a wide temperature range. How each component of the microscope contributes to the signal measurement process is discussed, and possible solutions to unsuccessful attempts in detecting a spin-induced NM-RFM signal are presented. Also, a novel, two-step phase cycling technique to eliminate the contribution to the spin signal from a spurious frequency modulated (FM) radiofrequency (RF) field, which can be utilized in future experiments, is discussed in detail.

Lee, Yong J.

210

Sensing the effect of body load in legs: responses of tibial campaniform sensilla to forces applied to the thorax in freely standing cockroaches.  

PubMed

Sense organs in the legs that detect body weight are an important component in the regulation of posture and locomotion. We tested the abilities of tibial campaniform sensilla, receptors that can monitor forces in the cockroach leg, to encode variations in body load in freely standing animals. Small magnets were attached to the thorax and currents were applied to a coil below the substrate. Sensory and motor activities were monitored neurographically. The tibial sensilla could show vigorous discharges to changing forces when animals stood upon their legs and actively supported the body weight. Firing of individual afferents depended upon the orientation of the receptor's cuticular cap: proximal sensilla (oriented perpendicular to the leg axis) discharged to force increases while distal receptors (parallel to the leg) fired to decreasing forces. Proximal sensillum discharges were prolonged and could encode the level of load when increases were sustained. Firing of the trochanteral extensor motoneuron was also strongly modulated by changing load. In some postures, sensillum discharges paralleled changes in motor frequency consistent with a known interjoint reflex. These findings demonstrate that tibial campaniform sensilla can monitor the effects of body weight upon the legs and may aid in generating support of body load. PMID:14727134

Noah, J A; Quimby, L; Frazier, S F; Zill, S N

2004-03-01

211

Electromagnetic force analysis of HTS bulk in DC-magnetic fields due to electromagnet  

Microsoft Academic Search

A new type linear synchronous motor which is based on an idea considering pinning force of high temperature superconducting (HTS) bulk as synchronizing force in using current-carrying-armature winding is proposed. However, HTS bulk could not produce lift force enough to levitate the HTS bulk ship for basic experiments. To research larger lift force, DC-magnet which generates higher magnetic fields has

K. Yoshida; H. Matsumoto

2002-01-01

212

Test Bodies and Naked Singularities: Is the Self-Force the Cosmic Censor?  

NASA Astrophysics Data System (ADS)

Jacobson and Sotiriou showed that rotating black holes could be spun up past the extremal limit by the capture of nonspinning test bodies, if one neglects radiative and self-force effects. This would represent a violation of the cosmic censorship conjecture in four-dimensional, asymptotically flat spacetimes. We show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities.

Barausse, Enrico; Cardoso, Vitor; Khanna, Gaurav

2010-12-01

213

Apparatus for storing high magnetic fields having reduced mechanical forces and reduced magnetic pollution  

DOEpatents

The present invention identifies several configurations of conducting elements capable of storing extremely high magnetic fields for the purpose of energy storage or for other uses, wherein forces experienced by the conducting elements and the magnetic field pollution produced at locations away from the configuration are both significantly reduced over those which are present as a result of the generation of such high fields by currently proposed techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency. 15 figures.

Prueitt, M.L.; Mueller, F.M.; Smith, J.L.

1991-04-09

214

Apparatus for storing high magnetic fields having reduced mechanical forces and reduced magnetic pollution  

DOEpatents

The present invention identifies several configurations of conducting elements capable of storing extremely high magnetic fields for the purpose of energy storage or for other uses, wherein forces experienced by the conducting elements and the magnetic field pollution produced at locations away from the configuration are both significantly reduced over those which are present as a result of the generation of such high fields by currently proposed techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency.

Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)

1991-01-01

215

Magnetic force microscopy of iron oxide nanoparticles and their cellular uptake.  

PubMed

Magnetic force microscopy has the capability to detect magnetic domains from a close distance, which can provide the magnetic force gradient image of the scanned samples and also simultaneously obtain atomic force microscope (AFM) topography image as well as AFM phase image. In this work, we demonstrate the use of magnetic force microscopy together with AFM topography and phase imaging for the characterization of magnetic iron oxide nanoparticles and their cellular uptake behavior with the MCF7 carcinoma breast epithelial cells. This method can provide useful information such as the magnetic responses of nanoparticles, nanoparticle spatial localization, cell morphology, and cell surface domains at the same time for better understanding magnetic nanoparticle-cell interaction. It would help to design magnetic-related new imaging, diagnostic and therapeutic methods. PMID:19562741

Zhang, Yu; Yang, Mo; Ozkan, Mihrimah; Ozkan, Cengiz S

2009-01-01

216

Testing for three-body quark forces in L = 1 excited baryons  

SciTech Connect

We discuss the matching of the quark model to the effective mass operator of the 1/N{sub c} expansion using the permutation group S{sub N}. As an illustration of the general procedure we perform the matching of the Isgur-Karl model for the spectrum of the negative parity L = 1 excited baryons. Assuming the most general two-body quark Hamiltonian, we derive two correlations among the masses and mixing angles of these states which should hold in any quark model. These correlations constrain the mixing angles and can be used to test for the presence of three-body quark forces.

Pirjol, Dan [National Institute for Physics and Nuclear Engineering, Department of Particle Physics, 077125 Bucharest (Romania); Schat, Carlos [Department of Physics and Astronomy, Ohio University, Athens, Ohio 45701 (United States) and Departamento de Fisica, FCEyN, Universidad de Buenos Aires, Ciudad Universitaria, Pab.1, (1428) Buenos Aires (Argentina)

2010-11-12

217

First-Principles Theory of van der Waals Forces between Macroscopic Bodies  

SciTech Connect

We present a first-principles method for the determination of the van der Waals interactions for a collection of finite-sized macroscopic bodies. The method is based on fluctuational electrodynamics and a rigorous multiple-scattering method for the electromagnetic field. As such, the method takes fully into account retardation, many-body, multipolar, and near-fields effects. By application of the method to the case of two metallic nanoparticles, we demonstrate the breakdown of the standard 1/r{sup 2} distance law as the van der Waals force decays exponentially with distance when the nanoparticles are too close or too far apart.

Yannopapas, Vassilios [Department of Materials Science, University of Patras, GR-26504 Patras (Greece); Department of Physics, Sofia University, James Bourchier 5 blvd., 1164 Sofia (Bulgaria); Vitanov, Nikolay V. [Department of Physics, Sofia University, James Bourchier 5 blvd., 1164 Sofia (Bulgaria); Institute of Solid State Physics, Bulgarian Academy of Sciences, Tsarigradsko chaussee 72, 1784 Sofia (Bulgaria)

2007-09-21

218

Induction of electromotive force by an autonomously moving magnetic bot.  

PubMed

We report the observation of the induction of electromotive force (emf) into a Faraday coil by an autonomously moving composite magnetic particle in aqueous medium. The particle consisted of a micron-sized polymer sphere, which was decorated with catalytic Pd nanoparticles (NPs) and attached to a micron-scale (N-42 grade) rare-earth magnet. The Pd NPs catalytically decomposed H2 O2 to generate O2 , resulting in buoyancy-driven vertical motion of the particle, while the micromagnet induced emf during the flight. Because a small volume of ethanol was layered on top of the liquid, the bubble burst when the particle ascended to the top and thus nearly continuous vertical motion was achieved. Spikes of alternating electrical signal could be observed up to 20?times per minute. The signal was sufficiently strong to illuminate light-emitting diodes following appropriate amplification. This distinctive approach is expected to pave the way to developing synthetic bots which are autonomously propelled, generating their own signal for running complex circuitry. PMID:24492970

Sailapu, Sunil Kumar; Chattopadhyay, Arun

2014-02-01

219

Observation of the switching fields of individual Permalloy particles in nanolithographic arrays via magnetic force microscopy  

Microsoft Academic Search

A technique has been developed for measuring the switching fields of individual submicron magnetic particles using a magnetic force microscope (MFM) in which an in situ magnetic field can be applied. This allows the study of the evolution of the particles' magnetic states as a function of applied field and the direct observation of cooperative switching. Observations of the switching

G. A. Gibson; J. F. Smyth; S. Schultz; D. P. Kern

1991-01-01

220

Fabricating overhanging magnets for use in magnetic resonance force microscopy using a XeF2 isotropic etch.  

NASA Astrophysics Data System (ADS)

Pushing magnetic resonance force microscopy towards single proton sensitivity demands meeting the nanofabrication challenge of producing an attonewton-sensitivity cantilever with a magnetic tip whose diameter is 50 nm or less. At the same time, the cantilever should also experience low force noise (and force gradient noise) near the surface of technologically interesting samples. Ideally then, the magnetic tip would overhang the leading edge of the cantilever -- to increase the signal created by the magnet while simultaneously minimizing the noise created by the rest of the cantilever interacting with the surface. We will show that the isotropic etchant XeF2 can be used to underetch a single crystal silicon cantilever to create an overhanging magnet. This etch is a controllable etch process with high selectivity to metals that can be used not only to produce magnetic resonance force microscopy cantilevers, but other overhanging metallic structures as well.

Wright, Sarah; Hickman, Steven; Marohn, John

2008-03-01

221

Induced Magnetic Force in Human Heads Exposed to 4 T MRI  

PubMed Central

Purpose To map the distribution of the magnetic force induced in the human head during magnetic resonance imaging (MRI) at 4 T for a large group of healthy volunteers. Materials and Methods The magnetic field distribution in the head of 100 men and 18 women was mapped using phase mapping techniques. Statistical parametric mapping methods using a family-wise error (FWE) corrected threshold P < 0.05 and region-of-interest analyses were used to assess the significance of the results. Results Eyeballs, orbitofrontal and temporal cortices, subcallosal gyrus, anterior cingulate, midbrain, and brainstem (pons) are the brain regions most susceptible to magnetic force. The strength of the magnetic force density in the head was lower than 11.5 ± 5.3 N/m3 (right eyeball). The strength of the magnetic force density induced in occipital cortex varied linearly with the x-rotation (pitch) angle. Conclusion We found that the induced magnetic force is highly significant in the eyeballs, orbitofrontal and temporal cortices, subcallosal gyrus, anterior cingulate as well as midbrain and brainstem (pons), regardless of subjects' age or gender. The maximum induced magnetic force was 6 × 105 times weaker than the gravitational force; thus, biological effects of the magnetic force during imaging are not expected to be significant.

Wang, Ruiliang; Wang, Gene-Jack; Goldstein, Rita Z.; Caparelli, Elisabeth C.; Volkow, Nora D.; Fowler, Joanna S.; Tomasi, Dardo

2010-01-01

222

The magnetic resonance force microscope: A new microscopic probe of magnetic materials  

SciTech Connect

The magnetic resonance force microscope (MRFM) marries the techniques of magnetic resonance imaging (MRI) and atomic force microscopy (AFM), to produce a three-dimensional imaging instrument with high, potentially atomic-scale, resolution. The principle of the MRFM has been successfully demonstrated in numerous experiments. By virtue of its unique capabilities the MRFM shows promise to make important contributions in fields ranging from three-dimensional materials characterization to bio-molecular structure determination. Here the authors focus on its application to the characterization and study of layered magnetic materials; the ability to illuminate the properties of buried interfaces in such materials is a particularly important goal. While sensitivity and spatial resolution are currently still far from their theoretical limits, they are nonetheless comparable to or superior to that achievable in conventional MRI. Further improvement of the MRFM will involve operation at lower temperature, application of larger field gradients, introduction of advanced mechanical resonators and improved reduction of the spurious coupling when the magnet is on the resonator.

Hammel, P.C.; Zhang, Z. [Los Alamos National Lab., NM (United States); Midzor, M.; Roukes, M.L. [California Inst. of Tech., Pasadena, CA (United States); Wigen, P.E. [Ohio State Univ., Columbus, OH (United States); Childress, J.R. [Univ. of Florida, Gainesville, FL (United States)

1997-08-06

223

Real-Time Control of Humanoid Robots Considering External Forces on Upper Part of the Body  

NASA Astrophysics Data System (ADS)

Recently, the demand for the practical use of service robots has risen significantly because of acceleration of demographic aging, and a humanoid robot is one of the promising form factors of service robots. When a humanoid robot is used by a human in a real environment, the robot needs to be designed by taking into account the various external forces that act on the robot. Thus far, most of the walking humanoid robots have been mainly controlled by the conventional ZMP method to maintain a stable walking posture. However, the conventional ZMP method can not be used to handle the various external forces that act on the upper part of the humanoid robot body. To overcome these problems, in this paper, we propose a novel control method, which we called 3DZMP and pZMP, for a humanoid robot to react to the external force on the upper part of the body. The 3DZMP is defined as the point in three-dimensional space at which the moment about all axes is zero. 3DZMP can prevent the rotation of a humanoid robot. The pZMP is defined as the point corresponding to the orthographic projection of the 3DZMP on a plane. pZMP is used to evaluate the stability of 3DZMP. We implemented the proposed method on a prototype robot and verified that the robot gained the capability to react to external forces that could not be handled by the conventional ZMP method.

Inomata, Kentaro; Shigemori, Yo; Uchimura, Yutaka

224

Formation of magnetic discontinuities through superposition of force-free magnetic fields: Periodic boundaries  

SciTech Connect

In ideal magnetohydrodynamics characterized by an infinite electrical conductivity, the magnetic flux across an arbitrary fluid surface is conserved in time. The magnetofluid then can be partitioned into contiguous subvolumes of fluid, each of which entraps its own subsystem of magnetic flux. During dynamical evolution of the magnetofluid, these subvolumes press into each other; and in the process, two such subvolumes may come into direct contact while ejecting a third interstitial subvolume. Depending on the orientations of magnetic fields of the two interacting subvolumes, the magnetic field at the common surface of interaction may become discontinuous and a current sheet is formed there. This process of current sheet formation and their subsequent decay is believed to be a plausible mechanism for coronal heating and may also be responsible for various eruptive phenomena at the solar corona. In this work, we explore this theoretical concept through numerical simulations of a viscous, incompressible magnetofluid characterized by infinite electrical conductivity. In particular, we show that if the initial magnetic field is prescribed by superposition of two linear force-free fields with different torsion coefficients, then formation of current sheets are numerically realizable in the neighborhood of magnetic nulls.

Kumar, Dinesh; Bhattacharyya, R. [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India)] [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)] [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)

2013-11-15

225

Formation of magnetic discontinuities through superposition of force-free magnetic fields: Periodic boundaries  

NASA Astrophysics Data System (ADS)

In ideal magnetohydrodynamics characterized by an infinite electrical conductivity, the magnetic flux across an arbitrary fluid surface is conserved in time. The magnetofluid then can be partitioned into contiguous subvolumes of fluid, each of which entraps its own subsystem of magnetic flux. During dynamical evolution of the magnetofluid, these subvolumes press into each other; and in the process, two such subvolumes may come into direct contact while ejecting a third interstitial subvolume. Depending on the orientations of magnetic fields of the two interacting subvolumes, the magnetic field at the common surface of interaction may become discontinuous and a current sheet is formed there. This process of current sheet formation and their subsequent decay is believed to be a plausible mechanism for coronal heating and may also be responsible for various eruptive phenomena at the solar corona. In this work, we explore this theoretical concept through numerical simulations of a viscous, incompressible magnetofluid characterized by infinite electrical conductivity. In particular, we show that if the initial magnetic field is prescribed by superposition of two linear force-free fields with different torsion coefficients, then formation of current sheets are numerically realizable in the neighborhood of magnetic nulls.

Kumar, Dinesh; Bhattacharyya, R.; Smolarkiewicz, P. K.

2013-11-01

226

Transformation of body force localized near the surface of a half-space into equivalent surface stresses.  

PubMed

An electromagnetic acoustic transducer (EMAT) or a laser used to generate elastic waves in a component is often described as a source of body force confined in a layer close to the surface. On the other hand, models for elastic wave radiation more efficiently handle sources described as distributions of surface stresses. Equivalent surface stresses can be obtained by integrating the body force with respect to depth. They are assumed to generate the same field as the one that would be generated by the body force. Such an integration scheme can be applied to Lorentz force for conventional EMAT configuration. When applied to magnetostrictive force generated by an EMAT in a ferromagnetic material, the same scheme fails, predicting a null stress. Transforming body force into equivalent surface stresses therefore, requires taking into account higher order terms of the force moments, the zeroth order being the simple force integration over the depth. In this paper, such a transformation is derived up to the second order, assuming that body forces are localized at depths shorter than the ultrasonic wavelength. Two formulations are obtained, each having some advantages depending on the application sought. They apply regardless of the nature of the force considered. PMID:24116402

Rouge, Clémence; Lhémery, Alain; Ségur, Damien

2013-10-01

227

The effect of an external magnetic force on cell adhesion and proliferation of magnetically labeled mesenchymal stem cells  

Microsoft Academic Search

BACKGROUND: As the strategy for tissue regeneration using mesenchymal stem cells (MSCs) for transplantation, it is necessary that MSCs be accumulated and kept in the target area. To accumulate MSCs effectively, we developed a novel technique for a magnetic targeting system with magnetically labeled MSCs and an external magnetic force. In this study, we examined the effect of an external

Toshio Nakamae; Nobuo Adachi; Takaaki Kobayashi; Yoshihiko Nagata; Tomoyuki Nakasa; Nobuhiro Tanaka; Mitsuo Ochi

2010-01-01

228

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux  

NASA Technical Reports Server (NTRS)

The bubble coalescence and interfacial instabilities that are important to modeling critical heat flux (CHF) in reduced-gravity systems can be sensitive to even minute body forces. Understanding these complex phenomena is vital to the design and safe implementation of two-phase thermal management loops proposed for space and planetary-based thermal systems. While reduced gravity conditions cannot be accurately simulated in 1g ground-based experiments, such experiments can help isolate the effects of the various forces (body force, surface tension force and inertia) which influence flow boiling CHF. In this project, the effects of the component of body force perpendicular to a heated wall were examined by conducting 1g flow boiling experiments at different orientations. FC-72 liquid was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface at conditions approaching CHF. High-speed video imaging was employed to capture dominant CHF mechanisms. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed great sensitivity to orientation for flow velocities below 0.2 m/s, where very small CHF values where measured, especially with downflow and downward-facing heated wall orientations. High flow velocities dampened the effects of orientation considerably. Figure I shows representative images for the different CHF regimes. The Wavy Vapor Layer regime was dominant for all high velocities and most orientations, while all other regimes were encountered at low velocities, in the downflow and/or downward-facing heated wall orientations. The Interfacial Lift-off model was modified to predict the effects of orientation on CHF for the dominant Wavy Vapor Layer regime. The photographic study captured a fairly continuous wavy vapor layer travelling along the heated wall while permitting liquid contact only in wetting fronts, located in the troughs of the interfacial waves. CHF commenced when wetting fronts near the outlet were lifted off the wall. The Interfacial Lift-off model is shown to be an effective tool for predicting the effects of body force on CHF at high velocities.

Zhang, Hui; Mudawar, Issam; Hasan, Mohammad M.

2002-01-01

229

Effects of optical forces on the transmission of magnetic fluids investigated by Z-scan technique  

Microsoft Academic Search

The dependence of the transmission behavior of magnetic fluids on the incident power density of a laser beam is investigated and the conventional Z-scan technique is employed to continuously vary the optical forces induced by the laser beam. We calculate the optical forces exerted on magnetic nanoparticles and compare them with those for gold and silica nanoparticles. It is found

Zi-Ming Meng; Hai-Ying Liu; Wei-Ren Zhao; Wei Zhang; Hai-Dong Deng; Qiao-Feng Dai; Li-Jun Wu; Sheng Lan; Achanta Venu Gopal

2009-01-01

230

Measurement and calculation of forces in a magnetic journal bearing actuator  

NASA Technical Reports Server (NTRS)

Numerical calculations and experimental measurements of forces from an actuator of the type used in active magnetic journal bearings are presented. The calculations are based on solution of the scalar magnetic potential field in and near the gap regions. The predicted forces from single magnet with steady current are compared with experimental measurements in the same geometry. The measured forces are smaller than calculated ones in the principal direction but are larger than calculated in the normal direction. This combination of results indicate that material and spatial effects other than saturation play roles in determining the force available from an actuator.

Knight, Josiah; Mccaul, Edward; Xia, Zule

1991-01-01

231

A short model excitation of an asymmetric force free superconducting transmission line magnet  

SciTech Connect

A short model of asymmetric force free magnet with single beam aperture was tested at Fermilab together with the excitation test of VLHC transmission line magnet. The design concept of asymmetric force free superconducting magnet was verified by the test. The testing reached up to 104 kA current and no indication of force imbalance was observed. Since the model magnet length was only 10cm, A 0.75m model was constructed and tested at KEK with low current to ensure the validity of the design. The cool down and the excitation at KEK were also successful finding very small thermal contraction of the conductor and reasonable field homogeneity.

Wake, M.; Sato, H.; /KEK, Tsukuba; Carcagno, R.; Foster, W.; Hays, S.; Kashikhin, V.; Oleck, A.; Piekarz, H.; Rabehl, R,; /Fermilab

2005-09-01

232

Force-detected magnetic resonance in a field gradient of 250 000 Tesla per meter  

NASA Astrophysics Data System (ADS)

We report the detection of slice-selective electron spin resonance with an external magnetic field gradient comparable to local interatomic gradients, using the techniques of magnetic resonance force microscopy. An applied microwave field modulated the spin-gradient force between a paramagnetic DPPH sample and a micrometer-scale ferromagnetic tip on a force microscope cantilever. A sensitivity equivalent to 184 polarized electron moments in a one-Hertz detection bandwidth was attained. We mapped the tip magnetic field with a resonant slice thickness of order one nanometer, thereby demonstrating magnetic resonance on length scales comparable to molecular dimensions.

Bruland, K. J.; Dougherty, W. M.; Garbini, J. L.; Sidles, J. A.; Chao, S. H.

1998-11-01

233

Task III: Development of an Effective Computational Methodology for Body Force Representation of High-speed Rotor 37  

NASA Technical Reports Server (NTRS)

A framework for an effective computational methodology for characterizing the stability and the impact of distortion in high-speed multi-stage compressor is being developed. The methodology consists of using a few isolated-blade row Navier-Stokes solutions for each blade row to construct a body force database. The purpose of the body force database is to replace each blade row in a multi-stage compressor by a body force distribution to produce same pressure rise and flow turning. To do this, each body force database is generated in such a way that it can respond to the changes in local flow conditions. Once the database is generated, no hrther Navier-Stokes computations are necessary. The process is repeated for every blade row in the multi-stage compressor. The body forces are then embedded as source terms in an Euler solver. The method is developed to have the capability to compute the performance in a flow that has radial as well as circumferential non-uniformity with a length scale larger than a blade pitch; thus it can potentially be used to characterize the stability of a compressor under design. It is these two latter features as well as the accompanying procedure to obtain the body force representation that distinguish the present methodology from the streamline curvature method. The overall computational procedures have been developed. A dimensional analysis was carried out to determine the local flow conditions for parameterizing the magnitudes of the local body force representation of blade rows. An Euler solver was modified to embed the body forces as source terms. The results from the dimensional analysis show that the body forces can be parameterized in terms of the two relative flow angles, the relative Mach number, and the Reynolds number. For flow in a high-speed transonic blade row, they can be parameterized in terms of the local relative Mach number alone.

Tan, Choon-Sooi; Suder, Kenneth (Technical Monitor)

2003-01-01

234

Magnetic Force Microscopy Investigation of Magnetic Domains in Nd2Fe14B  

NASA Astrophysics Data System (ADS)

Remenance and coercivity in Nd2Fe14B materials are strongly dependent on the microstructural aspects like phases morphology and grain size. The coercivity (Hc) of a magnetic material varies inversely with the grain size (D) and there is a critical size below which Hc~D6. Domain wall pinning by grain boundaries and foreign phases is the important mechanism in explaining the improvement in coercivity and remenance. Nd2Fe14B intermetallic compound with stochiometric composition was prepared from pure elements (Nd -99.5%, Fe-99.95%, B -99.99%) by arc melting in argon atmosphere. Magnetic Force Microscope (MFM) gives high-resolution magnetic domain structural information of ferromagnetic samples. DI-3100 Scanning Probe Microscope with MESP probes was used For MFM characterization of the samples. Magnetic domains observed in cast ingots were very long (up to 40 ?m were observed) and approximately 1-5 ?m wide due to high anisotropy of the compounds. Magnetic domains have displayed different image contrast and morphologies at different locations of the samples. The domain morphologies and image contrast obtained in this analysis were explained in this paper.

Talari, Mahesh Kumar; Markandeyulu, G.; Rao, K. Prasad

2010-07-01

235

Nuclear magnetic resonance force microscopy of ammonium dihydrogen phosphate and magnetism of cobalt nanocrystals  

NASA Astrophysics Data System (ADS)

A Nuclear Magnetic Resonance Force Microscopy (NMR-FM) technique utilizing a somewhat uncommon experimental geometry has been developed. Characterization of external field effects on soft permalloy micromagnets on double torsional oscillators was performed. We showed that at high enough fields (above 1 Tesla), the quality factor for each mode is comparable to the zero field value. The changes in resonance frequency fit well with our model, and permitted high-sensitivity magnetic moment and magnetic anisotropy measurement. Effects of laser power on cantilevers used for NMR-FM has been studied in detail. The origins of the observed self-sustained oscillations has been addressed by our model. NMR-FM detection has been shown in an ammonium dihydrogen phosphate sample. Imaging and spin manipulation techniques were used for the first time to detect the nuclear spins in a sample with short relaxation times. A magnetic study of epitaxially grown cobalt nanocrystals on a Si(111) substrate has been performed. Enhancement of the magnetic moment and anisotropy energy have been observed and data are consistent with single domain model. Experimental evidence indicates small inter-nanocrystal interactions. Finally, future directions in achieving the single-spin detection limit is addressed.

Mirsaidov, Utkur

236

Radiative forces on macroscopic porous bodies in protoplanetary disks: laboratory experiments  

NASA Astrophysics Data System (ADS)

In optically thin parts of protoplanetary disks photophoresis is a significant force not just for dust grains, but also for macroscopic bodies. The absolute strength on the supposedly highly porous objects is not known in detail as yet. We set up a low pressure torsion balance and studied photophoretic forces down to 100 nN on plates at a light flux of 100 W/m2. We investigated the dependence on plate dimensions and on ambient pressure and considered the influence of channels through the plates. As samples for full (no channel) plates we used tissue with 2 mm thickness and circular shape with diameters of 10 mm, 30 mm and 50 mm. The influence of channels was probed on rectangular-shaped circuit boards of 35 mm × 35 mm area and 1.5 mm thickness. The number of channels was 169 and 352. The pressure was varied over three decades between 0.001 and 1 mbar. At low pressure, the absolute photophoretic force is proportional to the cross section of the plates. At high pressure, gas flow through the channels enhances the photophoretic force. The pressure dependence of the radiative force can (formally) be calculated by photophoresis on particles with a characteristic length. We derived two characteristic length scales l depending on the plate radius r1, the channel radius r2, and the thickness of the plate, which equals the length of the channel d as l = r0.35 × d0.65. The highest force is found at a pressure pmax = 15 × l-1 Pa mm. In total, the photophoretic force on a plate with channels can be well described by a superposition of the two components: photophoresis due to the overall size and cross section of the plate and photophoresis due to the channels, both with their characteristic pressure dependencies. We applied these results to the transport of large solids in protoplanetary disks and found that the influence of porosity on the photophoretic force can reverse the inward drift of large solids, for instance meter-sized bodies, and push them outward within the optically thin parts of the disk.

Duermann, Christoph; Wurm, Gerhard; Kuepper, Markus

2013-10-01

237

The effect of low force chiropractic adjustments on body surface electromagnetic field  

PubMed Central

Objective The purpose of this study was to investigate the body surface electromagnetic field (EMF) changes using a sensitive magnetometer before and after a specific Toftness chiropractic adjustment in asymptomatic human subjects. Method Forty-four subjects were randomly assigned into control (20 subjects) and experimental groups (24 subjects) in a pre and post-test design. The Triaxial Fluxgate Magnetometer FGM-5DTAA (Walker Scientific, Worcester, Massachusetts) with five digit display and resolution of 1 nanotesla (nT) was used for EMF detection. The EMF in the research room and on the adjustment table was monitored and recorded. The subjects’ body surface (cervical, thoracic, lumbar and sacral areas) EMF was determined in the prone position before and after the chiropractic adjustment. A low force Toftness chiropractic adjustment was applied to the cervical, thoracic, lumbar and sacral areas as determined by the practitioner. Results The EMF in the research room was recorded as 41611 nT at the Z axis (earth field), 13761 nT at the X axis and 7438 nT at the Y axis. The EMF on the adjusting table changed minimally during the 15 minute observation period. The EMF on the subjects’ body surface decreased at 4 spinal locations after chiropractic adjustment. The EMF (mean ± SD in nT) decreased significantly at the cervical region from 42449 ± 907 to 41643 ± 1165 (p < 0.01) and at the sacral regions from 43206 ± 760 to 42713 ± 552 (p < 0.01). The EMF at the lumbar and thoracic regions decreased but did not reach a statistically significant level. No significant changes of the body surface EMF were found in the control group. Conclusion A low force Toftness chiropractic adjustment in the cervical and sacral areas resulted in a significant reduction of the cervical and sacral surface EMF. No significant body surface EMF changes were observed in the lumbar and thoracic regions. The mechanisms of the EMF reduction after chiropractic adjustment are not known.

Zhang, John; Snyder, Brian J; Vernor, Lori

2004-01-01

238

Fluctuating wind forces measured on a bluff body extending from a cavity  

NASA Astrophysics Data System (ADS)

The effect of wind forces measured on a bluff body extending from a cavity was investigated. This was accomplished by measuring wind induced vibratory inputs to a plexiglas bluff body model. The model extended from a ground board cavity installed in the AFIT 5-Foot Wind Tunnel. Forces and moments were measured from an 8 element load cell unit built and installed in the base of a plexiglas model. Three different size cavity openings were tested for both a no-rotation and 45 degree rotation referenced to the wind. Data was taken at individual speed points between 55 ft/s and 180 ft/s, producing Reynolds number based on model width in the range of 1.5 x 10 to the 5th power to 5.0 x 10 to the 5th power. Baseline data for a closed cavity configuration was collected and compared to previous studies conducted at the USAF Academy. Force and moment coefficient data are presented, comparing cavity opening and model rotation effects. Results of shedding frequency analysis are presented based on transient data recorded.

King, Brian W.

1989-12-01

239

Aerodynamic force generation, performance and control of body orientation during gliding in sugar gliders (Petaurus breviceps).  

PubMed

Gliding has often been discussed in the literature as a possible precursor to powered flight in vertebrates, but few studies exist on the mechanics of gliding in living animals. In this study I analyzed the 3D kinematics of sugar gliders (Petaurus breviceps) during short glides in an enclosed space. Short segments of the glide were captured on video, and the positions of marked anatomical landmarks were used to compute linear distances and angles, as well as whole body velocities and accelerations. From the whole body accelerations I estimated the aerodynamic forces generated by the animals. I computed the correlations between movements of the limbs and body rotations to examine the control of orientation during flight. Finally, I compared these results to those of my earlier study on the similarly sized and distantly related southern flying squirrel (Glaucomys volans). The sugar gliders in this study accelerated downward slightly (1.0+/-0.5 m s(-2)), and also accelerated forward (2.1+/-0.6 m s(-2)) in all but one trial, indicating that the body weight was not fully supported by aerodynamic forces and that some of the lift produced forward acceleration rather than just balancing body weight. The gliders used high angles of attack (44.15+/-3.12 degrees ), far higher than the angles at which airplane wings would stall, yet generated higher lift coefficients (1.48+/-0.18) than would be expected for a stalled wing. Movements of the limbs were strongly correlated with body rotations, suggesting that sugar gliders make extensive use of limb movements to control their orientation during gliding flight. In addition, among individuals, different limb movements were associated with a given body rotation, suggesting that individual variation exists in the control of body rotations. Under similar conditions, flying squirrels generated higher lift coefficients and lower drag coefficients than sugar gliders, yet had only marginally shallower glides. Flying squirrels have a number of morphological specializations not shared by sugar gliders that may help to explain their greater lift generating performance. PMID:17644674

Bishop, Kristin L

2007-08-01

240

Preliminary investigation of force-reduced superconducting magnet configurations for advanced technology applications  

SciTech Connect

The feasibility of new high-field low specific weight superconducting magnet designs using force-free fields is being explored analytically and numerically. This report attempts to assess the technical viability of force-free field concepts to produce high-field, low specific weight and large bore volume magnets, which could promote the use of high temperature superconductors. Several force-free/force-reduced magnet configurations are first reviewed, then discussed and assessed. Force-free magnetic fields, fields for which the current flows parallel to the field, have well-known mathematical solutions extending upon infinite domains. These solutions, however, are no longer force-free everywhere for finite geometries. In this preliminary study, force-free solutions such as the Lundquist solutions truncated to a size where the internal field of the coil matches an externally cylindrical magnetic field (also called a Lundquist coil) are numerically modeled and explored. Significant force-reduction for such coils was calculated, which may have some importance for the design of lighter toroidal magnets used in thermonuclear fusion power generation, superconducting magnetic energy storage (SMES), and mobile MHD power generation and propulsion.

Bouillard, J.X.

1992-12-01

241

Numerical Calculation and Analysis of Suspension Force of Permanent Magnetic Bearing in Conical Spiral Blood Pump  

Microsoft Academic Search

The structure of conical blood pump is introduced, and a new hybrid-type permanent magnetic bearings(PMB) composed of axial and radial PMBs are presented. The hybrid-type PMBs can suspend the rotor in axial and radial directions by the magnetic force. The static magnetic field and the force of PMBs are also computed numerically with the software ANSYS. Study indicates that the

Dianrong Gao; Shiyuan Du

2008-01-01

242

High-frequency magnetic-force microscopy characterization of magnetic recording writer poles  

NASA Astrophysics Data System (ADS)

Measurements of longitudinal writer poles at the air bearing surface were performed using high-resolution magnetic-force microscopy (MFM) with low coercivity tips. Two-dimensional MFM maps were obtained for various write currents. The modeling results indicate that the MFM maps are related more to the field than to its second derivative. Two techniques were used, dc MFM and high-frequency (HF) MFM. The results show that the HF-MFM technique can distinguish between different writer designs. The writers with the best high-frequency performance showed gradual decrease of the maximum MFM signal with frequency up to 1.5 GHz.

Nazarov, Alexey V.; Plumer, Martin L.; Pant, Bharat B.

2005-05-01

243

Magnetically Linked Star-Disk Systems. I. Force-free Magnetospheres and Effects of Disk Resistivity  

Microsoft Academic Search

We consider the interaction between a magnetic star and its circumstellar disk under the assumption that the stellar magnetic field permeates the disk and that the system's magnetosphere is force-free. Using simplified axisymmetric models (both semianalytic and numerical), we study the time evolution of the magnetic field configuration induced by the relative rotation between the disk and the star. We

Dmitri A. Uzdensky; Arieh Königl; C. Litwin

2002-01-01

244

The Role of Three-Nucleon Forces and Many-Body Processes in Nuclear Pairing  

SciTech Connect

We present microscopic valence-shell calculations of pairing gaps in the calcium isotopes, focusing on the role of three-nucleon (3N) forces and manybody processes. In most cases, we find a reduction in pairing strength when the leading chiral 3N forces are included, compared to results with lowmomentum two-nucleon (NN) interactions only. This is in agreement with a recent energy density functional study. At the NN level, calculations that include particle particle and hole hole ladder contributions lead to smaller pairing gaps compared with experiment. When particle hole contributions as well as the normal-ordered one- and two-body parts of 3N forces are consistently included to third order, we find reasonable agreement with experimental three-point mass differences. This highlights the important role of 3N forces and manybody processes for pairing in nuclei. Finally, we relate pairing gaps to the evolution of nuclear structure in neutron-rich calcium isotopes and study the predictions for the 2+ excitation energies, in particular for 54Ca.

Holt, Jason D. [Technische Univ. Darmstadt/GSI/UTK/ORNL; Menendez, J. [Technische Univ. Darmstadt/GSI Helmholtzzentrum fur Schweionenforschung, Germany; Schwenk, A. [Technische Univ. Darmstadt/GSI Helmholtzzentrum fur Schweionenforschung, Germany

2013-01-01

245

SELF-GRAVITATING BODY WITH AN INTERNAL MAGNETIC FIELD. I. NEW ANALYTICAL EQUILIBRIA  

SciTech Connect

We construct exact analytical solutions of the equations describing the equilibrium of a self-gravitating magnetized fluid body, possibly rigidly rotating, by superposing two solutions of finite energy defined in the whole space, one describing a non-magnetized gravitating equilibrium (ST1) and the other describing a magnetized non-gravitating equilibrium (ST2). A large number of ST1s can be found in the literature and directly used for our constructions, and we thus concentrate on ST2s, which are difficult to obtain. We derive some of their general properties and exhibit two explicit classes of axisymmetric 'elementary' such equilibria. The first one is extracted from the stellar models proposed by Prendergast and by Kutvitskii and Solov'ev, respectively. The second one is constructed by using Palumbo's theory of isodynamic equilibria, for which the magnetic pressure is constant on each flux surface. Both types of ST2s have their magnetic field confined within a bounded region, respectively, of spherical and toroidal shapes. A much more general ST2 can be obtained by juxtaposing n+q elementary ST2s, with n of the first type and q of the second type, in such a way that the magnetic regions do not pairwise overlap. The specific equilibria we obtain by superposition thus have no external field extending to infinity, and may be three dimensional (3D), which invalidates a recent nonexistence conjecture. Moreover, they may be arranged to contain force-free regions. Our superposition method can be considered as a 3D generalization of the axisymmetric splitting method previously developed by Kutvitskii and Solov'ev.

Aly, J.-J. [AIM-Unite Mixte de Recherche CEA-CNRS-Universite Paris VII-UMR no. 7158, Centre d'Etudes de Saclay, F-91191 Gif sur Yvette Cedex (France); Amari, T., E-mail: jean-jacques.aly@cea.fr [CNRS, Centre de Physique Theorique de l'Ecole Polytechnique, F-91128 Palaiseau Cedex (France)

2012-05-01

246

The health and cost implications of high body mass index in Australian defence force personnel  

PubMed Central

Background Frequent illness and injury among workers with high body mass index (BMI) can raise the costs of employee healthcare and reduce workforce maintenance and productivity. These issues are particularly important in vocational settings such as the military, which require good physical health, regular attendance and teamwork to operate efficiently. The purpose of this study was to compare the incidence of injury and illness, absenteeism, productivity, healthcare usage and administrative outcomes among Australian Defence Force personnel with varying BMI. Methods Personnel were grouped into cohorts according to the following ranges for (BMI): normal (18.5???24.9?kg/m2; n?=?197), overweight (25–29.9?kg/m2; n?=?154) and obese (?30?kg/m2) with restricted body fat (?28% for females, ?24% for males) (n?=?148) and with no restriction on body fat (n?=?180). Medical records for each individual were audited retrospectively to record the incidence of injury and illness, absenteeism, productivity, healthcare usage (i.e., consultation with medical specialists, hospital stays, medical investigations, prescriptions) and administrative outcomes (e.g., discharge from service) over one year. These data were then grouped and compared between the cohorts. Results The prevalence of injury and illness, cost of medical specialist consultations and cost of medical scans were all higher (p?body fat compared with the normal cohort. Within the obese cohort, the prevalence of injury and illness, healthcare usage and productivity were not significantly greater in the obese cohort with no restriction on body fat compared with the cohort with restricted body fat. The number of restricted work days, the rate of re-classification of Medical Employment Classification and the rate of discharge from service were similar between all four cohorts. Conclusions High BMI in the military increases healthcare usage, but does not disrupt workforce maintenance. The greater prevalence of injury and illness, greater healthcare usage and lower productivity in obese Australian Defence Force personnel is not related to higher levels of body fat.

2012-01-01

247

Cluster variational method for nuclear matter with the three-body force  

SciTech Connect

We report the current status of our project to construct a new nuclear equation of state (EOS), which may be used for supernova numerical simulations, based on the cluster variational method starting from the realistic nuclear Hamiltonian. We also take into account a higher-order correction to the energy of the nuclear three-body force (TBF). The nuclear EOSs with and without the higher-order TBF correction at zero temperature are very close to each other, when parameters are readjusted so as to reproduce the empirical saturation data.

Takano, M.; Togashi, H.; Yamamuro, S.; Nakazato, K.; Suzuki, H. [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 Japan and Department of Physics and Applied Physics, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Department of Physics and Applied Physics, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Department of Physics, Faculty of Science and Technology, Tokyo University of Science, Yamazaki 2641, Noda, Chiba 278-8510 (Japan)

2012-11-12

248

Hysteresis loops of individual Co nanostripes measured by magnetic force microscopy  

PubMed Central

High-resolution magnetic imaging is of utmost importance to understand magnetism at the nanoscale. In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field. The main result is the quantitative evaluation of the coercive field of the individual nanostructures. Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field.

2011-01-01

249

Boundary Layer Control Using the Lorentz Force on an Axisymmetric Body  

NASA Astrophysics Data System (ADS)

The direct effect of modifying the turbulent boundary layer with a spatially- and temporally-varying Lorentz force for the purpose of drag reduction was explored using a buoyant axisymmetric body. The body had an elliptical nose, constant diameter midbody, and conical tail with a maximum diamter of 0.25m and overall length of 1.2m, and was launched from the center of the bottom of a circular vertical tank (1.0m diameter × 6.5m deep) which held an aqueous solution of NaOH (? = 5 S/m). The body displaced 460N, with a variable buoyancy from 0 to 110N. The midbody was covered with over 8,000 electromagnetic turbulence control (EMTC) tiles, similar to those used on prior flat plate experiments (cf. Bull APS, Vol 40, No 12, Abstract FC1, Nov 1995). EMTC effectiveness was determined from: 1. arrival time at the free surface, 2. velocity at breach, and 3. breach height. In particular, the breach height was used to determine directly the mean body drag during ascent. For appropriate operating conditions (electrode voltage, operating freqency, and tile sequencing pattern) the overall mean drag was observed to be efficiently reduced in excess of 50%. The effect of EMTC on form drag was also noted and will be discussed.

Nosenchuck, Daniel M.

1996-11-01

250

Magnetic microposts as an approach to apply forces to living cells  

PubMed Central

Cells respond to mechanical forces whether applied externally or generated internally via the cytoskeleton. To study the cellular response to forces separately, we applied external forces to cells via microfabricated magnetic posts containing cobalt nanowires interspersed among an array of elastomeric posts, which acted as independent sensors to cellular traction forces. A magnetic field induced torque in the nanowires, which deflected the magnetic posts and imparted force to individual adhesions of cells attached to the array. Using this system, we examined the cellular reaction to applied forces and found that applying a step force led to an increase in local focal adhesion size at the site of application but not at nearby nonmagnetic posts. Focal adhesion recruitment was enhanced further when cells were subjected to multiple force actuations within the same time interval. Recording the traction forces in response to such force stimulation revealed two responses: a sudden loss in contractility that occurred within the first minute of stimulation or a gradual decay in contractility over several minutes. For both types of responses, the subcellular distribution of loss in traction forces was not confined to locations near the actuated micropost, nor uniformly across the whole cell, but instead occurred at discrete locations along the cell periphery. Together, these data reveal an important dynamic biological relationship between external and internal forces and demonstrate the utility of this microfabricated system to explore this interaction.

Sniadecki, Nathan J.; Anguelouch, Alexandre; Yang, Michael T.; Lamb, Corinne M.; Liu, Zhijun; Kirschner, Stuart B.; Liu, Yaohua; Reich, Daniel H.; Chen, Christopher S.

2007-01-01

251

A symmetric transformation for 3-body potential molecular dynamics using force-decomposition in a heterogeneous distributed environment  

Microsoft Academic Search

Evaluating the Force Matrix constitutes the most computationally intensive part of a Classical Molecular Dynamics (MD) simulation. In three-body MD simulations, the total energy of the system is determined by the energy of every unique triple in the system and the force matrix is three-dimensional. The execution time of a three-body MD algorithm is thus proportional to the cube of

J. V. Sumanth; David R. Swanson; Hong Jiang

2007-01-01

252

Numerical simulation for the magnetic force distribution in electromagnetic forming of small size flat sheet  

NASA Astrophysics Data System (ADS)

It is essential to calculate magnetic force in the process of studying electromagnetic flat sheet forming. Calculating magnetic force is the basis of analyzing the sheet deformation and optimizing technical parameters. Magnetic force distribution on the sheet can be obtained by numerical simulation of electromagnetic field. In contrast to other computing methods, the method of numerical simulation has some significant advantages, such as higher calculation accuracy, easier using and other advantages. In this paper, in order to study of magnetic force distribution on the small size flat sheet in electromagnetic forming when flat round spiral coil, flat rectangular spiral coil and uniform pressure coil are adopted, the 3D finite element models are established by software ANSYS/EMAG. The magnetic force distribution on the sheet are analyzed when the plane geometries of sheet are equal or less than the coil geometries under fixed discharge impulse. The results showed that when the physical dimensions of sheet are less than the corresponding dimensions of the coil, the variation of induced current channel width on the sheet will cause induced current crowding effect that seriously influence the magnetic force distribution, and the degree of inhomogeneity of magnetic force distribution is increase nearly linearly with the variation of induced current channel width; the small size uniform pressure coil will produce approximately uniform magnetic force distribution on the sheet, but the coil is easy to early failure; the desirable magnetic force distribution can be achieved when the unilateral placed flat rectangular spiral coil is adopted, and this program can be take as preferred one, because the longevity of flat rectangular spiral coil is longer than the working life of small size uniform pressure coil.

Chen, Xiaowei; Wang, Wenping; Wan, Min

2013-12-01

253

Research and Development of Magnetic Drug Delivery System Using Bulk High Temperature Superconducting Magnet  

Microsoft Academic Search

The magnetic force control of the drug motion in the body has been studied in the current work. The calculation was made to study the possibility of the magnetic force control of the drag motion from outside of the body. The condition which enables the magnetic force control was clarified. The magnetic drug delivery system (MDDS) was demonstrated to be

Shigehiro Nishijima; Fumihito Mishima; Yasuhiko Tabata; Hiroshi Iseki; Yoshihiro Muragaki; Akira Sasaki; Norihide Saho

2009-01-01

254

Magnetic force-based tissue engineering and regenerative medicine.  

PubMed

Among other biomedical applications, magnetic nanoparticles and liposomes have a vast field of applications in tissue engineering and regenerative medicine. Magnetic nanoparticles and liposomes, when introduced into cells to be cultured, maneuver the cell's positioning by the appropriate use of magnets to create more complex tissue structures than those that are achieved by conventional culture methods. PMID:23909126

Castro, Emilio; Mano, João F

2013-07-01

255

Force-Free Magnetic Flux Ropes in the Solar Corona  

Microsoft Academic Search

Magnetic flux ropes offer a venue for storage of magnetic energy in the solar corona, energy that can contribute to eruptive events such as coronal mass ejections (CMEs). When a flux rope encircles the Sun, the associated magnetic field can store more energy than is needed to open the field fully---one of three energy-demanding tasks required for a CME. This

R. Wolfson

2004-01-01

256

Important role of three-body forces effect on nucleus-nucleus elastic scattering  

NASA Astrophysics Data System (ADS)

An analysis of nucleus-nucleus (AA) elastic scattering is made by the double-folding model (DFM) with a new complex G-matrix interactions called CEG07. The CEG07 interactions are derived from the free-space nucleon-nucleon interaction the Extended Soft Core model, including the three-body forces (TBF) contributions composed of the two parts of three-body repulsive and attractive forces. We have tested the present microscopic DFM optical potential with CEG07 in the ^16O + ^16O system at E/A = 70 MeV. The TBF effect is clearly seen in the cross section and the folding model potential (FMP) calculated with TBF well reproduces the experimental data up to the backward angles. The role of each part of TBR and TBA are also demonstrated in the same system. The effect of TBF is very important not only for nuclear saturation properties but also proper understanding of AA elastic scattering. Furthermore, the FMP with CEG07 was compared with one with CDM3Y6 that is one of the realiable and successful effective density-dependent NN interaction to be used in the DFM.

Furumoto, Takenori; Sakuragi, Yukinori; Yamamoto, Yasuo

2009-10-01

257

Effect of a magnetic field on the flow in the vicinity of the stagnation point of a blunt body with ablation of a protective layer  

Microsoft Academic Search

During hypersonic flow around a blunt-nosed body, the gas which passes through the bow shock is heated to high temperatures, where dissociation, ionization, and inverse phenomena (recombination) take place in the gas. If an ionized gas moves in a magnetic field, the ponderomotive force which is set up changes the nature of its motion close to the stagnation point, decreasing

E. A. Tropp

1966-01-01

258

Energy balance and body composition during US Army special forces training.  

PubMed

Small Unit Tactics (SUT) is a 64-day phase of the Special Forces Qualification Course designed to simulate real-world combat operations. Assessing the metabolic and physiological responses of such intense training allows greater insights into nutritional requirements of soldiers during combat. The purpose of this study was to examine energy balance around specific training events, as well as changes in body mass and composition. Data were collected from 4 groups of soldiers (n = 36) across 10-day periods. Participants were 28 ± 5 years old, 177 ± 6 cm tall, and weighed 83 ± 7 kg. Doubly labeled water (D2(18)O) was used to assess energy expenditure. Energy intake was calculated by subtracting energy in uneaten foods from known energy in distributed foods in individually packaged combat rations or in the dining facility. Body composition was estimated from skinfold thickness measurements on days 0 and 64 of the course. Simulated urban combat elicited that largest energy deficit (11.3 ± 2.3 MJ·day(-1) (2700 ± 550 kcal·day(-1)); p < 0.05), and reduction in body mass (3.3 ± 1.9 kg; p < 0.05), during SUT, while energy balance was maintained during weapons familiarization training and platoon size raids. Over the entire course body mass decreased by 4.2 ± 3.7 kg (p < 0.01), with fat mass decreasing by 2.8 ± 2.0 kg (p < 0.01) and fat-free mass decreasing by 1.4 ± 2.8 kg (p < 0.05). The overall reduction in body mass suggests that soldiers were in a negative energy balance during SUT, with high energy deficit being observed during strenuous field training. PMID:23713532

Margolis, Lee M; Rood, Jennifer; Champagne, Catherine; Young, Andrew J; Castellani, John W

2013-04-01

259

Lamination and mixing in three fundamental flow sequences driven by electromagnetic body forces  

NASA Astrophysics Data System (ADS)

This article pursues the idea that the degree of striations, called lamination, could be engineered to complement stretching and to design new sequential mixers. It explores lamination and mixing in three new mixing sequences experimentally driven by electromagnetic body forces. To generate these three mixing sequences, Lorentz body forces are dynamically controlled to vary the flow geometry produced by a pair of local jets. The first two sequences are inspired from the “tendril and whorl” and “blinking vortex” flows. The third novel sequence is called the “cat's eyes flip.” These three mixing sequences exponentially stretch and laminate material lines representing the interface between two domains to be mixed. Moreover, the mixing coefficient (defined as 1-?2/?02 where ?2/?02 is the rescaled variance) and its rate grow exponentially before saturation. This saturation of the mixing process is related to the departure of the mixing rate from an exponential growth when the striations’ thicknesses reach the diffusive length scale of the measurements or species and dyes. Incidentally, in our experiments, for the same energy or forcing input, the cat's eyes flip sequence has higher lamination, stretching, and mixing rates than the tendril and whorl and the blinking vortex sequences. These features show that bakerlike in situ mixers can be conceived by dynamically controlling a pair of local jets and by integrating lamination during stirring stages with persistent geometries. Combined with novel insights provided by the quantification of the lamination, this paper should offer perspectives for the development of new sequential mixers, possibly on all scales.

Rossi, L.; Doorly, D.; Kustrin, D.

2012-08-01

260

Force-free coronal magnetic field modeling using vector fields from Hinode and SDO  

NASA Astrophysics Data System (ADS)

Given the lack of routine direct measurements of the magnetic field in the solar corona, force-free reconstruction methods are a promising tool for the diagnostics of the magnetic structure there. Routine photospheric magnetic field measurements which monitor the temporal evolution of an active region and contain information on the non-potentiality of the field above are used as an input. Based on the assumption that magnetic forces dominate the solar atmosphere, these models allow estimates of the total and free magnetic energy content and the structure of the magnetic field above active regions. The outcome of force-free field modeling strongly depends on the vector magnetic field data used as boundary condition. We compare the model results based on simultaneously observed vector maps from the Helioseismic and Magnetic Imager (HMI) on board Solar Dynamics Observatory and from the Solar Optical Telescope Spectropolarimeter (SP) on board Hinode. We find substantial differences in the absolute estimates of the magnetic field energy but very similar relative estimates, e.g., the fraction of energy to be set free during an eruption or the fraction of flux linking distinct areas within an active region. Our study reveals that only relative estimates of coronal physical quantities from force-free models might be save and conclusions about the magnetic field topology might be drawn with caution.

Thalmann, Julia K.; Tiwari, Sanjiv K.; Wiegelmann, Thomas

2013-04-01

261

Different types of ferrite thin films as magnetic cantilever coating for magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Different types of ferrites are employed in the form of thin films as magnetic coating on cantilevers for magnetic force microscopy (MFM) use. This is especially needed for cantilevers employed in high-frequency MFM (HF-MFM), where stray fields of hard disk recording heads are investigated. Our experiments show that we can operate HF-MFM successfully at carrier frequencies up 2 GHz using such ferrite-coated cantilevers. Thin films of two ferrites, NiZnFe 2O 4 spinel ferrite and Co 2 Z-type hexaferrite (Ba 3Co 2Fe 24O 41, BCFO) were prepared by RF sputtering. As a basis for these probes, we employ commercial micromachined silicon cantilevers. Additionally, films on Si (1 0 0) and Si (1 1 1)-oriented substrates with a thickness up to 100 nm were prepared for analysis purposes, enabling the optimization of the sputter process. For a high spatial resolution of MFM, however, thinner magnetic coatings are required. Therefore, the third type, c, was prepared by laser-ablation with a thickness of 30 nm, also directly onto the Si without additional buffer layer.

Koblischka, M. R.; Kirsch, M.; Pfeifer, R.; Getlawi, S.; Rigato, F.; Fontcuberta, J.; Sulzbach, T.; Hartmann, U.

2010-05-01

262

Self-ordered growth and magnetic force microscopy study of iron nanoparticles  

NASA Astrophysics Data System (ADS)

We present atomic and magnetic force microscopy measurements on magnetic iron nanoparticles produced by a self-assembly method. The fabrication process is based on the thermal disintegration of iron nanowires deposited on faceted Al2O3 substrates. Arrangement and size of the particles depend on the annealing temperature. For iron this process yields particles with diameters in the range of 100-250 nm. The usage of the prepatterned substrates enforces a linear alignment of the particles. Magnetic force microscopy shows that the particles can be remanently magnetized with external fields of different orientations.

Sievers, S.; Albrecht, M.; Siegner, U.; Herweg, C.; Freyhardt, H. C.

2005-05-01

263

Body mass penalties in the physical fitness tests of the Army, Air Force, and Navy.  

PubMed

Recent research has empirically documented a consistent penalty against heavier service members for events identical or similar to those in the physical fitness tests of the Army, Air Force, and Navy. These penalties, which are not related to body fatness, are based on biological scaling models and have a physiological basis. Using hypothetical cases, we quantified the penalties for men, with body mass of 60 vs. 90 kg, and women, 45 vs. 75 kg, to be 15% to 20% for the fitness tests of these three services. Such penalties alone can adversely affect awards and promotions for heavier service members. To deal equitably with these penalties in a practical manner, we offer two recommendations, i.e., (1) implementation of revised fitness tests with balanced events, in which the penalties of one event for heavier service members are balanced by an equal and opposite bias against lighter service members, or (2) development of correction factors that can be multiplied by raw scores to yield adjusted scores free of body mass bias. PMID:16933817

Vanderburgh, Paul M; Crowder, Todd A

2006-08-01

264

Dynamic fe Model of Sitting Man Adjustable to Body Height, Body Mass and Posture Used for Calculating Internal Forces in the Lumbar Vertebral Disks  

NASA Astrophysics Data System (ADS)

Long-term whole-body vibrations can cause degeneration of the lumbar spine. Therefore existing degeneration has to be assessed as well as industrial working places to prevent further damage. Hence, the mechanical stress in the lumbar spine—especially in the three lower vertebrae—has to be known. This stress can be expressed as internal forces. These internal forces cannot be evaluated experimentally, because force transducers cannot be implementated in the force lines because of ethical reasons. Thus it is necessary to calculate the internal forces with a dynamic mathematical model of sitting man.A two dimensional dynamic Finite Element model of sitting man is presented which allows calculation of these unknown internal forces. The model is based on an anatomic representation of the lower lumbar spine (L3-L5). This lumber spine model is incorporated into a dynamic model of the upper torso with neck, head and arms as well as a model of the body caudal to the lumbar spine with pelvis and legs. Additionally a simple dynamic representation of the viscera is used. All these parts are modelled as rigid bodies connected by linear stiffnesses. Energy dissipation is modelled by assigning modal damping ratio to the calculated undamped eigenvalues. Geometry and inertial properties of the model are determined according to human anatomy. Stiffnesses of the spine model are derived from static in-vitro experiments in references [1] and [2]. Remaining stiffness parameters and parameters for energy dissipation are determined by using parameter identification to fit measurements in reference [3]. The model, which is available in 3 different postures, allows one to adjust its parameters for body height and body mass to the values of the person for which internal forces have to be calculated.

Pankoke, S.; Buck, B.; Woelfel, H. P.

1998-08-01

265

MEMS-based Force-clamp Analysis of the Role of Body Stiffness in C. elegans Touch Sensation  

PubMed Central

Touch is enabled by mechanoreceptor neurons in the skin and plays an essential role in our everyday lives, but is among the least understood of our five basic senses. Force applied to the skin deforms these neurons and activates ion channels within them. Despite the importance of the mechanics of the skin in determining mechanoreceptor neuron deformation and ultimately touch sensation, the role of mechanics in touch sensitivity is poorly understood. Here, we use the model organism Caenorhabditis elegans to directly test the hypothesis that body mechanics modulate touch sensitivity. We demonstrate a microelectromechanical system (MEMS)-based force clamp that can apply calibrated forces to freely crawling C. elegans worms and measure touch-evoked avoidance responses. This approach reveals that wild-type animals sense forces < 1 ?N and indentation depths < 1 ?m. We use both genetic manipulation of the skin and optogenetic modulation of body wall muscles to alter body mechanics. We find that small changes in body stiffness dramatically affect force sensitivity, while having only modest effects on indentation sensitivity. We investigate the theoretical body deformation predicted under applied force and conclude that local mechanical loads induce inward bending deformation of the skin to drive touch sensation in C. elegans.

Petzold, Bryan C.; Park, Sung-Jin; Mazzochette, Eileen A.; Goodman, Miriam B.; Pruitt, Beth L.

2013-01-01

266

MEMS-based force-clamp analysis of the role of body stiffness in C. elegans touch sensation.  

PubMed

Touch is enabled by mechanoreceptor neurons in the skin and plays an essential role in our everyday lives, but is among the least understood of our five basic senses. Force applied to the skin deforms these neurons and activates ion channels within them. Despite the importance of the mechanics of the skin in determining mechanoreceptor neuron deformation and ultimately touch sensation, the role of mechanics in touch sensitivity is poorly understood. Here, we use the model organism Caenorhabditis elegans to directly test the hypothesis that body mechanics modulate touch sensitivity. We demonstrate a microelectromechanical system (MEMS)-based force clamp that can apply calibrated forces to freely crawling C. elegans worms and measure touch-evoked avoidance responses. This approach reveals that wild-type animals sense forces <1 ?N and indentation depths <1 ?m. We use both genetic manipulation of the skin and optogenetic modulation of body wall muscles to alter body mechanics. We find that small changes in body stiffness dramatically affect force sensitivity, while having only modest effects on indentation sensitivity. We investigate the theoretical body deformation predicted under applied force and conclude that local mechanical loads induce inward bending deformation of the skin to drive touch sensation in C. elegans. PMID:23598612

Petzold, Bryan C; Park, Sung-Jin; Mazzochette, Eileen A; Goodman, Miriam B; Pruitt, Beth L

2013-06-01

267

Non-force-free extrapolation of solar coronal magnetic field using vector magnetograms  

NASA Astrophysics Data System (ADS)

We report our recent improvement in non-force-free extrapolation of coronal magnetic field, using vector magnetograms. Based on the principle of minimum (energy) dissipation rate (MDR), a generally non-force-free magnetic field solution is expressed as the superposition of one potential field and two (constant-[alpha]) linear force-free fields, with distinct [alpha] parameters. With a known potential field, the system is reduced to a second-order one that can be solved using one single-layer vector magnetogram. We devise an iteration procedure to determine the potential field, by achieving satisfactory agreement between the MDR-model computed and measured transverse magnetic field vectors on the bottom boundary. We illustrate this approach by applying it to real magnetograph measurement of solar active region AR 10953. We show that the results are satisfactory as judged from the quantitative magnetic field measurement, and the behavior of the derived Lorentz force.

Hu, Qiang; Dasgupta, B.; Derosa, M. L.; Büchner, J.; Gary, G. A.

2010-02-01

268

Detection of silica-mediated dissolution of magnetic grains in sediments using FORC diagrams  

NASA Astrophysics Data System (ADS)

Recently silica-mediated dissolution has been recognized as a potentially important factor influencing magnetic studies of marine and lacustrine sediments. Although direct evidence for the dissolution of magnetic particles in silica-rich environments is lacking, the process is expected to produce changes in the magnetic grain-size distribution, a hypothesis that is tested in this study on sediments from Lake Tanganyika, East Africa, using First Order Reversal Curves (FORCs). Results from different magnetic intensity zones within the studied samples clearly show changes in the grain-size distribution of magnetic minerals. In particular, zones with high biogenic silica content (BSi) correlated with depletion in fine-grained magnetic material, whereas zones with lower BSi showed no depletion. These results are consistent with the idea that silica-mediated dissolution results in the preferential removal of fine-grained magnetic material, and indicate that FORC diagrams are effective in characterizing silica-mediated dissolution in sediments.

Wetter, Laura; Verosub, Ken; Russell, James

2007-06-01

269

Magnetic force images of nanomagnetic domains taken with platinum-coated tips  

NASA Astrophysics Data System (ADS)

This article deals with magnetic force microscope images of nanosized domains in Co-coated films made by Pt-coated tips as well as micromagnetic images of data tracks written in recording media. Pt-coated tips have improved image delineation of the magnetic field distribution compared to images obtained by Co-coated hard magnetic tips. The force acting on Pt-coated tips in the magnetic field of the substrate was modeled assuming a paramagnetic tip. Due to the ferromagnetic nature of the interaction between the tip and substrate the spatial resolution of hard magnetic tips was shown to be inadequate to measure details of the features of nanosized domains. A comparison of the magnetic images made by Pt-coated tips with topographic images shows that magnetic domains resist thermal erasure at ambient temperature when they are formed of eight metallic grains.

Teschke, O.; Kleinke, M. U.; Dotto, M. E. R.; Soares, D. M.; Knobel, M.; de Souza, E. F.

2003-07-01

270

Aerodynamic damping during body translation in animal flight: modeling and experimental results of flapping counter force (FCF)  

NASA Astrophysics Data System (ADS)

Body movements of flying animals change their effective wing kinematics and influence aerodynamic forces. Our previous studies found that substantial aerodynamic damping was produced by flapping wings during body rotation through a passive mechanism we termed flapping counter-torque (FCT). Here we present the aerodynamic damping produced by flapping wings during body translations, which we termed flapping counter-forces (FCFs). Analytical models were derived and the aerodynamic effect of spanwise flow and wing-wake interaction were also explored. The FCFs are dependent on body velocities, wing beat amplitude and frequency. Aerodynamic force and PIV measurements were compared with the analytical models. The experiments were conducted on a pair of dynamically scaled robotic model wings in an oil tank. Experiments in air using a pair of high frequency flapping wing further validate the models. Complete 6-DOF flight dynamic model was derived.

Cheng, Bo; Hu, Zheng; Deng, Xinyan

2010-11-01

271

Nonlinear Force-Free Reconstruction of the Global Solar Magnetic Field: Methodology  

Microsoft Academic Search

We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary\\u000a surface on which only the distribution of the normal magnetic field component is given. The method relies on the theory of\\u000a force-free electrodynamics and applies directly to the reconstruction of the solar coronal magnetic field for a given distribution\\u000a of the photospheric

I. Contopoulos; C. Kalapotharakos; M. K. Georgoulis

2011-01-01

272

Determination of constant alpha force-free solar magnetic fields from magnetograph data  

Microsoft Academic Search

It is shown that a magnetic field that is force-free with alpha constant (alpha is not equal to 0) in the whole volume outside the sun cannot have a finite energy content and that such a field cannot be determined uniquely from only one magnetic field component given at the photosphere. Therefore, the extension of a global scale constant-alpha force-free

N. Seehafer

1978-01-01

273

Tunneling stabilized magnetic force microscopy; Prospects for low temperature applications to superconductors  

SciTech Connect

The authors of this paper demonstrate an imaging technique referred to as tunneling stabilized magnetic force microscopy or TSMFM. TSMFM is performed using a scanning tunneling microscope (STM) with a flexible magnetic, tunneling tip in place of the usual rigid tunneling tip. TSMFM images are therefore combinations of topography and the magnetic forces between the tip and the sample. Room temperature TSMFM images of magnetic bit tracks on a hard disk have 100 nm resolution and are comparable to Bitter patterns made using a ferrofluid. We have built a low temperature STM with the hope of getting TSMFM images of the flux lattice in superconductors. Preliminary TSMFM images of a YBa{sub 2}Cu{sub c}O{sub x} (YBCO) film (T{sub c} {minus} 88 K) in a 5Q mT field show that relatively large magnetic forces are acting on the flexible tip while scanning at 48 K.

Moreland, J.; Rice, P. (National Inst. of Standards and Technology (NEL), Boulder, CO (United States). Electromagnetic Technology Div.)

1991-03-01

274

Separation of binary granular mixtures under vibration and differential magnetic levitation force.  

PubMed

The application of both a strong magnetic field and a magnetic field gradient to a diamagnetic or paramagnetic material can produce a vertical force that acts in concert with the force of gravity. We consider a binary granular mixture in which the two components have different magnetic susceptibilities and therefore experience different effective forces of gravity when subjected to an inhomogeneous magnetic field. Under vertical vibration, such a mixture may rapidly separate into regions almost pure in the two components. We investigate the conditions for this behavior, studying the speed and completeness of separation as a function of differential effective gravity and the frequency and amplitude of vibration. The influence of the cohesive magnetic dipole-dipole interactions on the separation process is also investigated. In our studies insight is gained through the use of a molecular dynamics simulation model. PMID:15783320

Catherall, A T; López-Alcaraz, P; Sánchez, P; Swift, Michael R; King, P J

2005-02-01

275

The electrically detected magnetic resonance microscope: Combining conductive atomic force microscopy with electrically detected magnetic resonance  

NASA Astrophysics Data System (ADS)

We present the design and implementation of a scanning probe microscope, which combines electrically detected magnetic resonance (EDMR) and (photo-)conductive atomic force microscopy ((p)cAFM). The integration of a 3-loop 2-gap X-band microwave resonator into an AFM allows the use of conductive AFM tips as a movable contact for EDMR experiments. The optical readout of the AFM cantilever is based on an infrared laser to avoid disturbances of current measurements by absorption of straylight of the detection laser. Using amorphous silicon thin film samples with varying defect densities, the capability to detect a spatial EDMR contrast is demonstrated. Resonant current changes as low as 20 fA can be detected, allowing the method to realize a spin sensitivity of 8 × 10^6spins/?Hz at room temperature.

Klein, Konrad; Hauer, Benedikt; Stoib, Benedikt; Trautwein, Markus; Matich, Sonja; Huebl, Hans; Astakhov, Oleksandr; Finger, Friedhelm; Bittl, Robert; Stutzmann, Martin; Brandt, Martin S.

2013-10-01

276

Edge detection of magnetic body using horizontal gradient of pseudogravity anomaly  

Microsoft Academic Search

Potential field methods are used extensively in mineral exploration. These methods also are used as reconnaissance method in oil and gas exploration. In Contrast with gravity anomaly the magnetic surveying produces dipolar anomaly which is caused complicated interpretation rather than gravity anomaly. The observation magnetic anomaly in each location other than magnetic poles has displacement rather than causative body. Several

K. Alamdar; A. H. Ansari; A. Ghorbani

2009-01-01

277

Longitudinal focusing of an atomic cloud using pulsed magnetic forces  

Microsoft Academic Search

We report on a detailed study of the focusing properties of inhomogeneous magnetic fields. The experiment is performed using cold cesium atom clouds released from a magneto-optical trap. The sample longitudinal distributions are being compressed under the influence of a pulsed parabolic magnetic potential. Achromatic imaging potentialities are demonstrated. Analogies with usual optics are pointed out. A velocity compression is

E. Maréchal; S. Guibal; J.-L. Bossennec; R. Barbé; J.-C. Keller; O. Gorceix

1999-01-01

278

Alternating magnetic field forces for satellite formation flying  

NASA Astrophysics Data System (ADS)

Selected future space missions, such as large aperture telescopes and multi-component interferometers, will require the precise positioning of a number of isolated satellites, yet many of the suggested approaches for providing satellite positioning forces have serious limitations. In this paper we propose a new approach, capable of providing both position and orientation forces, that resolves or alleviates many of these problems. We show that by using alternating fields and currents that finely-controlled forces can be induced on the satellites, which can be individually selected through frequency allocation. We also show, through analysis and experiment, that near field operation is feasible and can provide sufficient force and the necessary degrees of freedom to accurately position and orient small satellites relative to one another. In particular, the case of a telescope with a large number of free mirrors is developed to provide an example of the concept. We also discuss the far field extension of this concept.

Youngquist, Robert C.; Nurge, Mark A.; Starr, Stanley O.

2013-03-01

279

Alternating Magnetic Field Forces for Satellite Formation Flying  

NASA Technical Reports Server (NTRS)

Selected future space missions, such as large aperture telescopes and multi-component interferometers, will require the precise positioning of a number of isolated satellites, yet many of the suggested approaches for providing satellites positioning forces have serious limitations. In this paper we propose a new approach, capable of providing both position and orientation forces, that resolves or alleviates many of these problems. We show that by using alternating fields and currents that finely-controlled forces can be induced on the satellites, which can be individually selected through frequency allocation. We also show, through analysis and experiment, that near field operation is feasible and can provide sufficient force and the necessary degrees of freedom to accurately position and orient small satellites relative to one another. In particular, the case of a telescope with a large number of free mirrors is developed to provide an example of the concept. We. also discuss the far field extension of this concept.

Youngquist, Robert C.; Nurge, Mark A.; Starr, Stnaley O.

2012-01-01

280

A force-reflecting teleoperation system with magnetically levitated master and wrist  

Microsoft Academic Search

The authors present a force-reflecting teleoperation system. The system consists of a conventional manipulator equipped with a magnetically levitated teleoperation master identical to the wrist. Aspects of mechanical, system, computational, and controller design are discussed. An approach to the design of force-reflecting teleoperation controllers is also discussed. Admittance matrices and the parameterization of all stabilizing teleoperation system controllers are used

S. E. Salcudean; N. M. Wong; R. L. Hollis

1992-01-01

281

On the relationship between coercive force Hc and magnetic viscosity parameter Sv in magnetic materials  

NASA Astrophysics Data System (ADS)

Theoretical relationships between the coercive force Hc and the magnetic viscosity parameter Sv have been obtained which give a very good explanation to the well-known phenomenological Barbier plot. For the strong pinning model, the formula obtained is l gS v = l gH c - l g{( {75}/{4})[( {4fb}/{75 kT}) {2}/{3} - 1]} , where f is maximum pinning force and b is the range of interaction between domain wall and pin. For the weak pinning model, the obtained theoretical formula is: l gS v = l gH c - l g{25[( {3 1rb 2}/{25kT}) - 1]} , where r is domain wall energy. For the unpinning (nucleation) process, the obtained formula is: l gS v = l gH c - l g{( {75}/{2})[( {4fb}/{75kT}) - 1] {2}/{3}} . For uniaxial single-domain particles, the obt ained relationship between Hc and Sv is: l gS v = l gH c - l g[( {2KV {1}/{2}p}/{kT})(V {1}/{2} - V {1}/{2}p)] , where Vp is the critical volume for superparamagnetic behaviour and V is the particle volume. At a given temperature, all the relationships obtained above can be written as: lgSv = const. + lgHc.

Liu, J. F.; Luo, H. L.

1990-05-01

282

Microscopic optical potential with two and three body forces for nucleon-nucleus scattering  

NASA Astrophysics Data System (ADS)

The proton - nucleus optical potentials generated by folding the calculated complex, density and energy dependent g- matrices (with and without three-body forces (TBF): Urbana IX (UVIX) and TNI) over the target nucleon density distributions obtained from the relativistic mean field theory, are used for the calculation of the differential cross section d? / d? , polarization Ay , spin rotation function (Q). for 65 and 200 MeV polarized proton incident on 40Ca and 208Pb . The agreement with the experiment is rather impressive. It is found that the inclusion of TBF (Urbana IX )UVIX) and TNI) reduces the strength of the central part of the optical potential in the nuclear interior and affects the calculated spin-orbit potential only marginally and leads to an improvement in the agreement with the corresponding experimental results.

Gambhir, Y. K.; Gupta, M.; Bhagwat, A.; Haider, W.; Rafi, Sayed; Sharma, M.; Pachouri, D.

2014-03-01

283

Equation of state and the nucleon optical potential with three-body forces  

NASA Astrophysics Data System (ADS)

We report microscopic calculations of the equation of state of symmetric nuclear matter and the nucleon-nucleus optical potential in the Brueckner-Hartree-Fock approach. The calculations use several internucleon (NN) potentials, such as the Hamada-Johnston, Urbana v14, Argonne v14, Argonne v18, Reid93, and Nijm II along with and without two types of three-body forces (TBFs): the Urbana IX model and the phenomenological density-dependent three-nucleon interaction model of Lagris and Pandharipande [Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(81)90241-4 359, 349 (1981)] and Friedman and Pandharipande [Nucl. Phys. ANUPABL0375-947410.1016/0375-9474(81)90649-7 361, 502 (1981)]. The inclusion of TBFs helps to reproduce the saturation properties for symmetric nuclear matter rather well as expected. The proton-nucleus optical potential has been calculated by folding the calculated reaction matrices (with and without three-body forces) over the nucleon density distributions obtained from the relativistic mean-field theory. The results show that the inclusion of TBFs reduces the strength of the central part of the optical potential in the nuclear interior and affects the calculated spin-orbit potential only marginally. As a test of the calculated potential, we have analyzed proton differential elastic scattering, analyzing power, and spin-rotation data from 40Ca and 208Pb at 65 and 200 MeV. It is observed that the inclusion of TBFs improves the agreement with the experiment especially for the polarization data.

Rafi, Syed; Sharma, Manjari; Pachouri, Dipti; Haider, W.; Gambhir, Y. K.

2013-01-01

284

Noninvasive detection of unevenly magnetized permanent magnet of a brushless dc motor by characterizing back electromotive force  

NASA Astrophysics Data System (ADS)

Uneven magnetization of permanent magnets (PMs) is one of the major sources of unbalanced magnetic force and torque ripple, which excite a brushless dc (BLDC) motor. This paper investigates the frequency contents of the back electromotive force (BEMF) due to the unevenly magnetized PMs in a BLDC motor. The magnetic field of a BLDC motor is solved by using the finite element method, and the BEMF is calculated by differentiating the flux linkage with respect to time. The characteristics of BEMF are investigated by using the spectral analysis. Magnetic flux density of the ideally magnetized PMs has the harmonics of the pole-pair number, but unevenly magnetized PMs generate the additional harmonics. This research shows numerically and experimentally that the frequency components of the BEMF are determined by the least common multiple between the frequency contents of magnetic flux density from the PMs and the slot number per phase. It also shows that the magnetized status of the PMs of a BLDC can be noninvasively identified by monitoring the frequencies and the amplitudes of BEMF.

Lee, C. I.; Jang, G. H.

2009-04-01

285

Magnetic force microscopy study of magnetic stripe domains in sputter deposited Permalloy thin films  

NASA Astrophysics Data System (ADS)

A magnetic force microscopy based study on the formation of stripe domains in Permalloy (Ni80Fe20) thin films is presented. Our results show that the critical thickness for stripe domain initiation depended on the sputtering rate, the substrate temperature, and the film thickness. Beyond the stripe domain formation, an increase of the period of a highly ordered array of stripe domains was evident with increasing film thickness. Thin films sputtered at room temperature with thickness variation between ~80 and ~350 nm exhibited square-root growth dependency on stripe domains periodicity from ~150 to ~380 nm, respectively. Above a certain thickness, the domain period decreased and the periodicity deteriorated with the array becoming more random, which is a strong indicator of relatively high structural perpendicular anisotropy. To illustrate, Permalloy sputtered at 100 °C initially showed linear dependence in stripe domain periodicity growth up until ~650 nm thick films. The magnetic stripe domain structure began breaking down for thicker Permalloy films. Our data also suggested that the perpendicular anisotropy responsible for the formation of stripe domains might have resulted from strain-caused magnetostriction and the thin-film microstructure shape effect.

Amos, Nissim; Fernandez, Robert; Ikkawi, Rabee; Lee, Beomseop; Lavrenov, Andrey; Krichevsky, Alexander; Litvinov, Dmitri; Khizroev, Sakhrat

2008-04-01

286

Many-body Interactions in Magnetic Films and Nanostructures  

SciTech Connect

We describe results supported by DOE grant DE-FG02-04ER46158, which focused on magnetic interaction at surfaces, in thin films, and in metallic nanostructures. We report on three general topics: 1) The Rashba spin splitting at magnetic surfaces of rare earth metals, 2) magnetic nanowires self-assembled on stepped tungsten single crystals, and 3) magnetic interaction in graphene films doped with hydrogen atoms.

Stephen D. Kevan

2012-12-12

287

Determination of constant ? force-free solar magnetic fields from magnetograph data  

Microsoft Academic Search

At first it is shown that a magnetic field being force-free, i.e. satisfying ? × B = aB, with a = constant (a ? 0) in the whole exterior of the Sun cannot have a finite energy content and cannot be determined uniquely from only one magnetic field component given at the photosphere. Then the boundary value problem for a

N. Seehafer

1978-01-01

288

Active H ? control of the vibration of an axially moving cantilever beam by magnetic force  

Microsoft Academic Search

An H? method for the vibration control of an iron cantilever beam with axial velocity using the noncontact force by permanent magnets is proposed in the paper. The transverse vibration equation of the axially moving cantilever beam with a tip mass is derived by D'Alembert's principle and then updated by experiments. An experimental platform and a magnetic control system are

Liang Wang; Huai-Hai Chen; Xu-Dong He

2011-01-01

289

Tunneling stabilized magnetic force microscopy: prospects for low temperature applications to superconductors  

Microsoft Academic Search

A low-temperature STM (scanning tunneling microscope) was built with the aim of getting TSMFM (tunneling stabilized magnetic force microscopy) images of the flux lattice in superconductors. The STM has been operated in a cryogenic bathysphere cryostat. The bathysphere cryostat will allow measurements from 4 K to 300 K in the bore of a high-field magnet. The STM has been operated

John Moreland; Paul Rice

1991-01-01

290

Magnetic-field-induced ferroelectric polarization reversal in magnetoelectric composites revealed by piezoresponse force microscopy.  

PubMed

Controlling electric polarization (or magnetization) in multiferroic materials with external magnetic fields (or electric fields) is very important for fundamental physics and spintronic devices. Although there has been some progress on magnetic-field-induced polarization reversal in single-phase multiferroics, such behavior has so far never been realized in composites. Here we show that it is possible to reverse ferroelectric polarization using magnetic fields in a bilayer Terfenol-D/PMN-33%PT composite. We realized this by ferroelectric domain imaging using piezoresponse force microscopy (PFM) under applied magnetic field loading. The internal electric field caused by the magnetoelectric (ME) effect in the PMN-PT crystal is considered as the driving force for the 180° polarization switching, and its existence is verified by switching spectroscopy PFM testing under a series of external magnetic fields. A quantitative method is further suggested to estimate the local ME coefficient based on the switching spectroscopy PFM testing results. PMID:24953042

Miao, Hongchen; Zhou, Xilong; Dong, Shuxiang; Luo, Haosu; Li, Faxin

2014-07-10

291

Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits  

DOEpatents

A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits are disclosed. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits. 17 figs.

Campbell, A.N.; Anderson, R.E.; Cole, E.I. Jr.

1995-11-07

292

Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits  

DOEpatents

A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits.

Campbell, Ann. N. (13170-B Central SE #188, Albuquerque, NM 87123); Anderson, Richard E. (2800 Tennessee NE, Albuquerque, NM 87110); Cole, Jr., Edward I. (2116 White Cloud NE, Albuquerque, NM 87112)

1995-01-01

293

Finite element calculation of forces on a DC magnet moving over an iron rail  

SciTech Connect

This paper describes results taken from a test rig consisting of a DC magnet over a 0.35m radius spinning iron wheel. The magnet is excited by two coils. The iron parts are unlaminated. Eddy currents are induced in the wheel by virtue of the relative motion of wheel and magnetic field. All iron parts have a nonlinear B-H characteristic. Forces on the magnet are compared with 3D finite element predictions. The results are of relevance to the design of MAGLEV vehicles which are supported by DC magnets.

Rodger, D.; Allen, N.; Coles, P.C.; Street, S.; Leonard, P.J.; Eastham, J.F. (Univ. of Bath (United Kingdom))

1994-11-01

294

The effect of perturbing body segment parameters on calculated joint moments and muscle forces during gait.  

PubMed

This study examined the effect of body segment parameter (BSP) perturbations on joint moments calculated using an inverse dynamics procedure and muscle forces calculated using computed muscle control (CMC) during gait. BSP (i.e. segment mass, center of mass location (com) and inertia tensor) of the left thigh, shank and foot of a scaled musculoskeletal model were perturbed. These perturbations started from their nominal value and were adjusted to ±40% in steps of 10%, for both individual as well as combined perturbations in BSP. For all perturbations, an inverse dynamics procedure calculated the ankle, knee and hip moments based on an identical inverse kinematics solution. Furthermore, the effect of applying a residual reduction algorithm (RRA) was investigated. Muscle excitations and resulting muscle forces were calculated using CMC. The results show only a limited effect of an individual parameter perturbation on the calculated moments, where the largest effect is found when perturbing the shank com (MS(com,shank), the ratio of absolute difference in torque and relative parameter perturbation, is maximally -7.81 N m for hip flexion moment). The additional influence of perturbing two parameters simultaneously is small (MS(mass+com,thigh) is maximally 15.2 N m for hip flexion moment). RRA made small changes to the model to increase the dynamic consistency of the simulation (after RRA MS(com,shank) is maximally 5.01 N m). CMC results show large differences in muscle forces when BSP are perturbed. These result from the underlying forward integration of the dynamic equations. PMID:24332615

Wesseling, Mariska; de Groote, Friedl; Jonkers, Ilse

2014-01-22

295

The Inverse-Cube Law of Magnetic Forces  

NSDL National Science Digital Library

This is an activity about the magnetic deflection. Learners will observe and measure the deflection that an iron mass causes in a soda bottle magnetometer and plot the data. The data should show the inverse-square cube law of change in the magnetic field. This is the twelfth activity in the guide and requires prior use and construction of a soda bottle magnetometer, as well as a six to ten pound container of iron nails (or an equivalent iron mass).

296

Direct Measurements of the Penetration Depth in a Superconducting Film using Magnetic Force Microscopy  

SciTech Connect

We report the local measurements of the magnetic penetration depth in a superconducting Nb film using magnetic force microscopy (MFM). We developed a method for quantitative extraction of the penetration depth from single-parameter simultaneous fits to the lateral and height profiles of the MFM signal, and demonstrate that the obtained value is in excellent agreement with that obtained from the bulk magnetization measurements.

E Nazaretski; J Thibodaux; I Vekhter; L Civale; J Thompson; R Movshovich

2011-12-31

297

Direct visualization and identification of biofunctionalized nanoparticles using a magnetic atomic force microscope.  

PubMed

Because of its outstanding ability to image and manipulate single molecules, atomic force microscopy (AFM) established itself as a fundamental technique in nanobiotechnology. (1) We present a new modality that distinguishes single nanoparticles by the surrounding magnetic field gradient. Diamagnetic gold and superparamagnetic iron oxide nanoparticles become discernible under ambient conditions. Images of proteins, magnetolabeled with nanoparticles, demonstrate the first steps toward a magnetic analogue to fluorescence microscopy, which combines nanoscale lateral resolution of AFM with unambiguous detection of magnetic markers. PMID:21819124

Block, Stephan; Glöckl, Gunnar; Weitschies, Werner; Helm, Christiane A

2011-09-14

298

Magnetic damping forces in figure-eight-shaped null-flux coil suspension systems  

SciTech Connect

This paper discusses magnetic damping forces in figure-eight-shaped null-flux coil suspension systems, focusing on the Holloman maglev rocket system. The paper also discusses simulating the damping plate, which is attached to the superconducting magnet by two short-circuited loop coils in the guideway. Closed-form formulas for the magnetic damping coefficient as functions of heave-and-sway displacements are derived by using a dynamic circuit model. These formulas are useful for dynamic stability studies.

He, Jianliang; Coffey, H.

1997-08-01

299

Elastic properties of a magnetic fluid with an air cavity retained by levitation forces  

NASA Astrophysics Data System (ADS)

The paper describes the process of an air cavity rising in a magnetic fluid filling a tube with a bottom, transport, and retention of the cavity by magnetic levitation forces. The elastic and dissipative properties of a vibratory system with an inertial element that is a column of a magnetic fluid over an air cavity are considered. The possibility of using a transported air cavity as a movable reflector for a sound wave is evaluated.

Polunin, V. M.; Boev, M. L.; Tan, Myo Min; Karpova, G. V.; Roslyakova, L. I.

2013-01-01

300

On the force relaxation in the magnetic levitation system with a high-Tc superconductor  

NASA Astrophysics Data System (ADS)

The effect of magnetic flux creep on the lift force in a magnet/superconductor system was studied. It was shown experimentally that in the case of real levitation (when a levitating object bears only on a magnetic field) the suspension height and consequently the lift force did not change over a long period of time. When the levitating object is fixed for some time (i.e. a rigid constraint is imposed on it), the levitation height decreases after removal of the external constraint. It is assumed that free oscillations of the levitating object slow down the flux creep process, which is activated when these oscillations are suppressed.

Smolyak, B. M.; Zakharov, M. S.

2014-05-01

301

Magnetic Circuit Model of PM Motor-Generator to Predict Radial Forces  

NASA Technical Reports Server (NTRS)

A magnetic circuit model is developed for a PM motor for flywheel applications. A sample motor is designed and modeled. Motor configuration and selection of materials is discussed, and the choice of winding configuration is described. A magnetic circuit model is described, which includes the stator back iron, rotor yoke, permanent magnets, air gaps and the stator teeth. Iterative solution of this model yields flux linkages, back EMF, torque, power, and radial force at the rotor caused by eccentricity. Calculated radial forces are then used to determine motor negative stiffness.

McLallin, Kerry (Technical Monitor); Kascak, Peter E.; Dever, Timothy P.; Jansen, Ralph H.

2004-01-01

302

On some properties of force-free magnetic fields in infinite regions of space  

NASA Technical Reports Server (NTRS)

Techniques for solving boundary value problems (BVP) for a force free magnetic field (FFF) in infinite space are presented. A priori inequalities are defined which must be satisfied by the force-free equations. It is shown that upper bounds may be calculated for the magnetic energy of the region provided the value of the magnetic normal component at the boundary of the region can be shown to decay sufficiently fast at infinity. The results are employed to prove a nonexistence theorem for the BVP for the FFF in the spatial region. The implications of the theory for modeling the origins of solar flares are discussed.

Aly, J. J.

1984-01-01

303

Characterizing local anisotropy of coercive force in motor laminations with the moving magnet hysteresis comparator  

NASA Astrophysics Data System (ADS)

Non oriented silicon steels are widely used within rotating electrical machines and are assumed to have no anisotropy. There exists a need to detect the anisotropic magnetic properties and to evaluate the local changes in magnetic material properties due to manufacturing cutting processes. In this paper, the so called moving magnet hyteresis comparator is applied to non destructively detect directional variations in coercive force in a variety of local regions of rotor and stator laminations of two materials commonly used to construct induction motors cores. Maximum to minimum coercive force ratios were assessed, varying from 1.4 to 1.7.

Garshelis, I. J.; Crevecoeur, G.

2014-05-01

304

Force detection of nuclear magnetic resonance using double-torsional micro-oscillators  

NASA Astrophysics Data System (ADS)

The nuclear magnetic resonance of a sample of ammonium sulfate has been detected by coupling the magnetic force from the spins to a double torsional micro-oscillator. A single-sweep sensitivity of 3 x 10 -15 N/Hz1/2 was observed at room temperature for a sample-on-oscillator configuration. Microelectronic fabrication techniques were employed to create the high-Q single crystal silicon multiple torsional oscillators. With no sample mounted, the upper resonances of the oscillators were found to have force sensitivities as low as 1.5 x 10-16 N/Hz1/2 at room temperature. The design, fabrication, and characterization of these novel oscillators are discussed. Also, non-adiabaitc and relaxation effects on the observed force signal in nuclear magnetic resonance force miscroscopy are considered in detail.

Chabot, Michelle Diane

305

Iseult\\/INUMAC Whole Body 11.7 T MRI Magnet Status  

Microsoft Academic Search

A Whole Body 11.7 T MRI Magnet is presently being developed at the CEA Saclay for the Iseult\\/Inumac project, a French-German initiative focused on very-high-magnetic-field molecular imaging to improve sensitivity, spatial, temporal, and spectral resolution for preclinical and\\/or clinical MR systems. The magnet will be installed at the Neurospin center, Saclay, in 2012. This actively shielded magnet system, with a

P. Vedrine; G. Aubert; F. Beaudet; J. Belorgey; C. Berriaud; P. Bredy; A. Donati; O. Dubois; G. Gilgrass; F. P. Juster; C. Meuris; F. Molinie; F. Nunio; A. Payn; T. Schild; L. Scola; A. Sinanna

2010-01-01

306

Electromagnetic Forces in a Hybrid Magnetic-Bearing Switched-Reluctance Motor  

NASA Technical Reports Server (NTRS)

Analysis and experimental measurement of the electromagnetic force loads on the hybrid rotor in a novel hybrid magnetic-bearing switched-reluctance motor (MBSRM) have been performed. A MBSRM has the combined characteristics of a switched-reluctance motor and a magnetic bearing. The MBSRM discussed in this report has an eight-pole stator and a six-pole hybrid rotor, which is composed of circular and scalloped lamination segments. The hybrid rotor is levitated using only one set of four stator poles, while a second set of four stator poles imparts torque to the scalloped portion of the rotor, which is driven in a traditional switched reluctance manner by a processor. Static torque and radial force analysis were done for rotor poles that were oriented to achieve maximum and minimum radial force loads on the rotor. The objective is to assess whether simple one-dimensional magnetic circuit analysis is sufficient for preliminary evaluation of this machine, which may exhibit strong three-dimensional electromagnetic field behavior. Two magnetic circuit geometries, approximating the complex topology of the magnetic fields in and around the hybrid rotor, were employed in formulating the electromagnetic radial force equations. Reasonable agreement between the experimental and the theoretical radial force loads predictions was obtained with typical magnetic bearing derating factors applied to the predictions.

Morrison, Carlos R.; Siebert, Mark W.; Ho, Eric J.

2008-01-01

307

Measures toward the reduction of magnetic fields produced by high-voltage overhead and cable transmission lines. Currents magnetically induced in human body  

Microsoft Academic Search

In the present work, optimal designs of overhead and cable transmission lines allowing minimization of magnetic fields along the routes of these transmission lines are considered. Currents induced in human body by powerline frequency magnetic fields are calculated. The influence of magnetic-vector orientation with respect to human body on the value of induced body currents is estimated. Currents induced in

Kadomskaya Kira Panteleimonovna; L. Y. Anatol'evich; S. I. Mikhailovich

2008-01-01

308

Detecting the magnetic response of iron oxide capped organosilane nanostructures using magnetic sample modulation and atomic force microscopy.  

PubMed

A new imaging strategy using atomic force microscopy (AFM) is demonstrated for mapping magnetic domains at size regimes below 100 nm. The AFM-based imaging mode is referred to as magnetic sample modulation (MSM), since the flux of an AC-generated electromagnetic field is used to induce physical movement of magnetic nanomaterials on surfaces during imaging. The AFM is operated in contact mode using a soft, nonmagnetic tip to detect the physical motion of the sample. By slowly scanning an AFM probe across a vibrating area of the sample, the frequency and amplitude of vibration induced by the magnetic field is tracked by changes in tip deflection. Thus, the AFM tip serves as a force and motion sensor for mapping the vibrational response of magnetic nanomaterials. Essentially, MSM is a hybrid of contact mode AFM combined with selective modulation of magnetic domains. The positional feedback loop for MSM imaging is the same as that used for force modulation and contact mode AFM; however, the vibration of the sample is analyzed using channels of a lock-in amplifier. The investigations are facilitated by nanofabrication methods combining particle lithography with organic vapor deposition and electroless deposition of iron oxide, to prepare designed test platforms of magnetic materials at nanometer length scales. Custom test platforms furnished suitable surfaces for MSM characterizations at the level of individual metal nanostructures. PMID:19453164

Li, Jie-Ren; Lewandowski, Brian R; Xu, Song; Garno, Jayne C

2009-06-15

309

Use of magnetic particles to apply mechanical forces for bone tissue engineering purposes  

NASA Astrophysics Data System (ADS)

It is possible to influence osteoblast activity by the application of mechanical forces. There is potential in using these forces for tissue engineering applications in that cell matrix production may be upregulated, resulting in a functional tissue engineered construct created in a shorter culture time. We have been developing a novel technique for applying mechanical forces directly to the cell with the use of magnetic particles. Particles attached to the cell membrane can be manipulated using an external magnetic field thus applying forces in the piconewton range. We have previously demonstrated that primary human osteoblasts respond to this type of stimulus by upregulating bone related gene expression and producing mineralized matrix at early time points. In this paper we discuss the optimization of this technique by presenting data on the effects of this type of force on osteoblast proliferation, phagocytosis and also the potential use of this technique in developing 3D tissue engineered constructs.

Cartmell, S. H.; Keramane, A.; Kirkham, G. R.; Verschueren, S. B.; Magnay, J. L.; El Haj, A. J.; Dobson, J.

2005-01-01

310

Variable Force, Eddy-Current or Magnetic Damper.  

National Technical Information Service (NTIS)

Variable damping for resonant vibrations which may occur at different rotational speeds in the range of rpms in which a rotating machine is operated is provided. A variable force damper includes a rotating mass carried on a shaft which is supported by a b...

R. E. Cunningham

1983-01-01

311

qPlus magnetic force microscopy in frequency-modulation mode with millihertz resolution  

PubMed Central

Summary Magnetic force microscopy (MFM) allows one to image the domain structure of ferromagnetic samples by probing the dipole forces between a magnetic probe tip and a magnetic sample. The magnetic domain structure of the sample depends on the alignment of the individual atomic magnetic moments. It is desirable to be able to image both individual atoms and domain structures with a single probe. However, the force gradients of the interactions responsible for atomic contrast and those causing domain contrast are orders of magnitude apart, ranging from up to 100 Nm?1 for atomic interactions down to 0.0001 Nm?1 for magnetic dipole interactions. Here, we show that this gap can be bridged with a qPlus sensor, with a stiffness of 1800 Nm?1 (optimized for atomic interaction), which is sensitive enough to measure millihertz frequency contrast caused by magnetic dipole–dipole interactions. Thus we have succeeded in establishing a sensing technique that performs scanning tunneling microscopy, atomic force microscopy and MFM with a single probe.

Wastl, Daniel; Giessibl, Franz J

2012-01-01

312

qPlus magnetic force microscopy in frequency-modulation mode with millihertz resolution.  

PubMed

Magnetic force microscopy (MFM) allows one to image the domain structure of ferromagnetic samples by probing the dipole forces between a magnetic probe tip and a magnetic sample. The magnetic domain structure of the sample depends on the alignment of the individual atomic magnetic moments. It is desirable to be able to image both individual atoms and domain structures with a single probe. However, the force gradients of the interactions responsible for atomic contrast and those causing domain contrast are orders of magnitude apart, ranging from up to 100 Nm(-1) for atomic interactions down to 0.0001 Nm(-1) for magnetic dipole interactions. Here, we show that this gap can be bridged with a qPlus sensor, with a stiffness of 1800 Nm(-1) (optimized for atomic interaction), which is sensitive enough to measure millihertz frequency contrast caused by magnetic dipole-dipole interactions. Thus we have succeeded in establishing a sensing technique that performs scanning tunneling microscopy, atomic force microscopy and MFM with a single probe. PMID:22428108

Schneiderbauer, Maximilian; Wastl, Daniel; Giessibl, Franz J

2012-01-01

313

A portable Halbach magnet that can be opened and closed without force: the NMR-CUFF.  

PubMed

Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings. PMID:21036637

Windt, Carel W; Soltner, Helmut; van Dusschoten, Dagmar; Blümler, Peter

2011-01-01

314

Induction of Rhythmic Flow with a Vertical Magnetic Force  

NASA Astrophysics Data System (ADS)

The effect of a magnetic field (\\mbi{B}? 4 T) on a salt-water oscillator composed of a paramagnetic gadolinium chloride solution (? = 1.03× 103 kg/mL; inner vessel) and a diamagnetic sodium chloride solution (? = 1.06× 103 kg/mL; outer vessel) linked by a small orifice at the bottom of the inner vessel was studied. Since the low-density solution was placed on the high-density solution, no oscillation occurred without applying a magnetic field. By applying a magnetic field (2--4 T), a rhythmic flow (periodical downward flow or upward flow) was induced under a gravitationally stable condition, the effect of which was in qualitative agreement with numerical computations.

Maki, Syou; Udagawa, Chikako; Morimoto, Shotaro; Tanimoto, Yoshifumi

2013-03-01

315

A procedure to estimate the electric field induced in human body exposed to unknown magnetic sources.  

PubMed

The paper proposes and discusses a boundary element procedure able to predict the distribution of the electric field induced in a human body exposed to a low-frequency magnetic field produced by unknown sources. As a first step, the magnetic field on the body surface is reconstructed starting from the magnetic field values detected on a closed surface enclosing the sources. Then, the solution of a boundary value problem provides the electric field distribution inside the human model. The procedure is tested and validated by considering different non-uniform magnetic field distributions generated by a Helmholtz coil system as well as different locations of the human model. PMID:22899216

Wang, Wencui; Bottauscio, Oriano; Chiampi, Mario; Giordano, Domenico; Zilberti, Luca

2013-04-01

316

Magnetic effects of large-scale impacts on airless planetary bodies  

NASA Technical Reports Server (NTRS)

The analysis of lunar orbital and sample data combined with laboratory measurements of impact-produced plasmas suggest that large-scale impacts on planetary surfaces may have had significant magnetic effects. These effects may potentially explain part of all lunar crustal magnetization and, by extension, may be responsible for producing paleomagnetism on other airless silicate bodies in the solar system. Theoretical studies are presented of the magnetic field and remanent magnetization effects of basin-scale impacts on the Moon. The specific case of a Moon exposed to the solar wind plasma flow and its embedded magnetic field is investigated. It is shown that maximum compressed field amplitudes occur antipodal to the impact point in agreement with the observed tendency for orbital magnetic anomalies to be concentrated antipodal to young large lunar basins. Generalization of these results to include magnetic effects of impacts on other airless or nearly airless bodies in the solar system is presented.

Hood, L. L.; Huang, Z.

1991-01-01

317

Magnetic Force Microscopy and Energy Loss Imaging of Superparamagnetic Iron Oxide Nanoparticles”  

NASA Astrophysics Data System (ADS)

We present quantitative, high spatially resolved magnetic force microscopy imaging of samples based on 11 nm diameter superparamagnetic iron oxide nanoparticles in air at room temperature. By a proper combination of the cantilever resonance frequency shift, oscillation amplitude and phase lag we obtain the tip-sample interaction maps in terms of force gradient and energy dissipation. These physical quantities are evaluated in the frame of a tip-particle magnetic interaction model also including the tip oscillation amplitude. Magnetic nanoparticles are characterized both in bare form, after deposition on a flat substrate, and as magnetically assembled fillers in a polymer matrix, in the form of nanowires. The latter approach makes it possible to reveal the magnetic texture in a composite sample independently of the surface topography.

Torre, Bruno; Bertoni, Giovanni; Fragouli, Despina; Falqui, Andrea; Salerno, Marco; Diaspro, Alberto; Cingolani, Roberto; Athanassiou, Athanassia

2011-12-01

318

"Magnetic force microscopy and energy loss imaging of superparamagnetic iron oxide nanoparticles".  

PubMed

We present quantitative, high spatially resolved magnetic force microscopy imaging of samples based on 11 nm diameter superparamagnetic iron oxide nanoparticles in air at room temperature. By a proper combination of the cantilever resonance frequency shift, oscillation amplitude and phase lag we obtain the tip-sample interaction maps in terms of force gradient and energy dissipation. These physical quantities are evaluated in the frame of a tip-particle magnetic interaction model also including the tip oscillation amplitude. Magnetic nanoparticles are characterized both in bare form, after deposition on a flat substrate, and as magnetically assembled fillers in a polymer matrix, in the form of nanowires. The latter approach makes it possible to reveal the magnetic texture in a composite sample independently of the surface topography. PMID:22355717

Torre, Bruno; Bertoni, Giovanni; Fragouli, Despina; Falqui, Andrea; Salerno, Marco; Diaspro, Alberto; Cingolani, Roberto; Athanassiou, Athanassia

2011-01-01

319

Magnetic force microscopy investigation of arrays of nickel nanowires and nanotubes.  

PubMed

The magnetic properties of arrays of nanowires (NWs) and nanotubes (NTs), 150 nm in diameter, electrodeposited inside nanoporous polycarbonate membranes are investigated. The comparison of the nanoscopic magnetic force microscopy (MFM) imaging and the macroscopic behavior as measured by alternating gradient force magnetometry (AGFM) is made. It is shown that MFM is a complementary technique that provides an understanding of the magnetization reversal characteristics at the microscopic scale of individual nanostructures. The local hysteresis loops have been extracted by MFM measurements. The influence of the shape of such elongated nanostructures on the dipolar coupling and consequently on the squareness of the hysteresis curves is demonstrated. It is shown that the nanowires exhibit stronger magnetic interactions than nanotubes. The non-uniformity of the magnetization states is also revealed by combining the MFM and AGFM measurements. PMID:24870297

Tabasum, M R; Zighem, F; De La Torre Medina, J; Encinas, A; Piraux, L; Nysten, B

2014-06-20

320

"Magnetic Force Microscopy and Energy Loss Imaging of Superparamagnetic Iron Oxide Nanoparticles"  

PubMed Central

We present quantitative, high spatially resolved magnetic force microscopy imaging of samples based on 11?nm diameter superparamagnetic iron oxide nanoparticles in air at room temperature. By a proper combination of the cantilever resonance frequency shift, oscillation amplitude and phase lag we obtain the tip-sample interaction maps in terms of force gradient and energy dissipation. These physical quantities are evaluated in the frame of a tip-particle magnetic interaction model also including the tip oscillation amplitude. Magnetic nanoparticles are characterized both in bare form, after deposition on a flat substrate, and as magnetically assembled fillers in a polymer matrix, in the form of nanowires. The latter approach makes it possible to reveal the magnetic texture in a composite sample independently of the surface topography.

Torre, Bruno; Bertoni, Giovanni; Fragouli, Despina; Falqui, Andrea; Salerno, Marco; Diaspro, Alberto; Cingolani, Roberto; Athanassiou, Athanassia

2011-01-01

321

Magnetic force microscopy investigation of arrays of nickel nanowires and nanotubes  

NASA Astrophysics Data System (ADS)

The magnetic properties of arrays of nanowires (NWs) and nanotubes (NTs), 150 nm in diameter, electrodeposited inside nanoporous polycarbonate membranes are investigated. The comparison of the nanoscopic magnetic force microscopy (MFM) imaging and the macroscopic behavior as measured by alternating gradient force magnetometry (AGFM) is made. It is shown that MFM is a complementary technique that provides an understanding of the magnetization reversal characteristics at the microscopic scale of individual nanostructures. The local hysteresis loops have been extracted by MFM measurements. The influence of the shape of such elongated nanostructures on the dipolar coupling and consequently on the squareness of the hysteresis curves is demonstrated. It is shown that the nanowires exhibit stronger magnetic interactions than nanotubes. The non-uniformity of the magnetization states is also revealed by combining the MFM and AGFM measurements.

Tabasum, M. R.; Zighem, F.; De La Torre Medina, J.; Encinas, A.; Piraux, L.; Nysten, B.

2014-06-01

322

Magnetic Field, Force, and Inductance Computations for an Axially Symmetric Solenoid  

NASA Technical Reports Server (NTRS)

The pumping of liquid oxygen (LOX) by magnetic fields (B field), using an array of electromagnets, is a current topic of research and development at Kennedy Space Center, FL. Oxygen is paramagnetic so that LOX, like a ferrofluid, can be forced in the direction of a B field gradient. It is well known that liquid oxygen has a sufficient magnetic susceptibility that a strong magnetic gradient can lift it in the earth's gravitational field. It has been proposed that this phenomenon can be utilized in transporting (i.e., pumping) LOX not only on earth, but on Mars and in the weightlessness of space. In order to design and evaluate such a magnetic pumping system, it is essential to compute the magnetic and force fields, as well as inductance, of various types of electromagnets (solenoids). In this application, it is assumed that the solenoids are air wrapped, and that the current is essentially time independent.

Lane, John E.; Youngquist, Robert C.; Immer, Christopher D.; Simpson, James C.

2001-01-01

323

Enhanced buckled-beam piezoelectric energy harvesting using midpoint magnetic force  

NASA Astrophysics Data System (ADS)

Aiming to improve the functionality of a buckled-beam piezoelectric energy harvester, a midpoint magnetic force is utilized to enable snap-through motions under low-frequency (<30 Hz) small-amplitude (0.2 g-0.8 g) excitations. The noncontact midpoint magnetic force is introduced through a local magnetic levitation system created by neodymium magnets and is capable of triggering the second buckling mode that helps the beam easily snap through between equilibriums when subjected to excitations. Significant enhancements, along with distinct nonlinear phenomena, are observed at low frequencies in terms of large-amplitude voltage output and extended frequency bandwidth. Frequency tuning is also achievable by adjusting the separation distance between magnets.

Zhu, Yang; Zu, Jean W.

2013-07-01

324

A Study of the Influence of Aerodynamic Forces on a Human Body near a High-Speed Train  

Microsoft Academic Search

A study of the influence of aerodynamic force on human body near the high-speed train was completed by the means of the technology\\u000a of moving grids in computational fluid dynamics method. 60 running situations, which includes 3 types of locomotive shape,\\u000a 4 running speeds of train combining 5 distances from human body to the sidewall of the train (human-train distances),

Renxian Li; Jing Zhao; Shu Zhang

325

Heat Transfer Control in Quiescent Air with Thermal Gradient by Magnetizing Force Under both Gravitational and Nongravitational Fields  

Microsoft Academic Search

Two-dimensional numerical computations were carried out to clarify the influence of magnetizing force on quiescent air with thermal gradient in a vertical cylindrical container under both gravitational and nongravitational fields. Several sizes and axial positions of a circular electric coil were tested so that the magnetizing force depended on the magnetic gradient. Under both gravitational and nongravitational fields, the convection

Masato Akamatsu; Mitsuo Higano; Yoshio Takahashi; Hiroyuki Ozoe

2005-01-01

326

Magnetic Fields Produced by Steady Currents in Human and Animal Bodies.  

National Technical Information Service (NTIS)

The progress report describes efforts to utilize magnetic field measurements of the human body in clinical applications. Engineering developments, including the superconducting magnetometer system (SQUID), shielded closets, and degaussers, are briefly des...

D. Cohen

1973-01-01

327

[Geomagnetic and artificial weak magnetic fields of superlow frequency as factors changing the body radiosensitivity].  

PubMed

Geomagnetic disturbances and experimentally generated weak variable superlow-frequency magnetic fields have either a radioprotecting or radiosensitizing effect on the mouse body depending on the time, intensity, and mode of influence. PMID:11605401

Stashkov, A M; Kopylov, A N; Gorokhov, I E

2001-01-01

328

Resolving sub-cellular force dynamics using arrays of magnetic microposts  

NASA Astrophysics Data System (ADS)

The biological response of cells to mechanical forces is integral to both normal cell function and the progression of many diseases, such as hypertensive vascular wall thickening. This likely results from the fact that mechanical stresses can directly affect many cellular processes, including signal transduction, gene expression, growth, differentiation, and survival. The need to understand the relationship between applied forces and the mechanical response of cells as a critical step towards understanding mechanotransduction calls for tools that can apply forces to cells while measuring their contractile response. This talk will describe an approach that simultaneously allows local mechanical stimulation of the adherent surface of a cell and spatially resolved measurement of the local force fields generated throughout the cell in response to this stimulation. Cells are cultured on the top surfaces of arrays of micrometer-scale posts made from a flexible elastomer (PDMS), and the contractile forces generated by an adherent cell bend the posts. Measurements of the displacement of each post allow the contractile force field of the cell to be mapped out with sub-cellular precision. To apply forces to cells, rod- shaped magnetic nanoparticles are embedded in some of the posts so that externally applied magnetic fields selectively deform these ``magnetic posts,'' thereby exerting tunable local, mechanical stresses to the adherent surface of attached cells. Alternatively, magnetic particles bound to or internalized by the cell may be employed to apply forces and torques to the cell. With either approach, measuring the deflection of the surrounding non-magnetic posts probes the full mechanical response of the cell to these stresses. Results that illustrate the temporal dynamics and spatial distribution of the non-local response of fibroblasts and smooth muscle cells to local stresses will be discussed.

Reich, Daniel

2010-03-01

329

Material dependence of magnetic force microscopy performance using carbon nanotube probes: Experiments and simulation  

NASA Astrophysics Data System (ADS)

We investigated the dependence of the performance of magnetic force microscopy (MFM) on magnetic coating materials by using carbon nanotube (CNT) probes. The magnetic structures of CNT-MFM probes with CoFe(80:20), CoFe(30:70), and CoCr(80:20) coatings were essentially the same in the simulations, but their magnetic properties, such as stability after magnetic reversal, varied slightly in the experiments. It was found that a larger saturation magnetic moment (Ms) is of advantage for attaining high spatial resolution. Although the distinction was hard to see in the MFM images, the experiments and simulations showed that CNT probes coated with high Ms materials gave stronger perturbations to soft magnetic materials than probes coated with low Ms materials.

Kuramochi, H.; Asada, H.; Uzumaki, T.; Yui, H.; Iitake, M.; Takano, F.; Akinaga, H.; Manago, T.

2014-03-01

330

Quantitative magnetic force microscopy on permalloy dots using an iron filled carbon nanotube probe.  

PubMed

An iron filled carbon nanotube (FeCNT), a 10-40 nm ferromagnetic nanowire enclosed in a protective carbon tube, is an attractive candidate for a magnetic force microscopy (MFM) probe as it provides a mechanically and chemically robust, nanoscale probe. We demonstrate the probe's capabilities with images of the magnetic field gradients close to the surface of a Py dot in both the multi-domain and vortex states. We show the FeCNT probe is accurately described by a single magnetic monopole located at its tip. Its effective magnetic charge is determined by the diameter of the iron wire and its saturation magnetization 4?M(s) ? 2.2 × 10(4)G. A magnetic monopole probe is advantageous as it enables quantitative measurements of the magnetic field gradient close to the sample surface. The lateral resolution is defined by the diameter of the iron wire and the probe-sample separation. PMID:21864777

Wolny, F; Obukhov, Y; Mühl, T; Weissker, U; Philippi, S; Leonhardt, A; Banerjee, P; Reed, A; Xiang, G; Adur, R; Lee, I; Hauser, A J; Yang, F Y; Pelekhov, D V; Büchner, B; Hammel, P C

2011-07-01

331

Fabrication of Ultrafloppy Single-Crystal Silicon Cantilevers for Use as Force Probes in Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

We have developed the first batch fabrication protocol for producing nanomagnetic tips on ultrafloppy single-crystal silicon cantilevers for use in Magnetic Resonance Force Microscopy (MRFM). These 340-nm thick cantilevers have spring constants as low as 10-5 : N/m, three orders of magnitude smaller than commercially available cantilevers and exhibit quality factors as high as 200,000 at 11 K without any heat treatment or modification of the silicon surface. This conservatively indicates that forces as small as 8 attonewtons (8 × 10-18 : N) in a 1 Hz bandwidth can be detected at 4 K using these cantilevers. Nanometer-scale ferromagnets (nickel, iron, and cobalt) have been patterned phin situ near the tips of the cantilevers by electron beam lithography and characterized by frequency-shift cantilever magnetometry. These cantilevers have been used in sample-on-cantilever MRFM of diphenylpicrylhydrazil (DPPH) and in electromechanical dissipation force studies of organic semiconductors such as the polycarbonate:TPD system. Magnet-on-cantilever MRFM experiments are underway.

Jenkins, Neil E.; Deflores, Lauren; Allen, Jack; Nga Ng, Tse; Silveira, William; Muller, Erik; Garner, Sean; Dawlaty, Jahan; Kuehn, Seppe; Marohn, John A.

2003-03-01

332

Thin-foil magnetic force system for high-numerical-aperture microscopy  

PubMed Central

Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 ?m paramagnetic particle and 13 nN on a 4.5 ?m paramagnetic particle, forces over the full 4? sr, and a bandwidth in excess of 3 kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4 nm), high-bandwidth (10 kHz), long-range (100 ?m xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function.

Fisher, J. K.; Cribb, J.; Desai, K. V.; Vicci, L.; Wilde, B.; Keller, K.; Taylor, R. M.; Haase, J.; Bloom, K.; O'Brien, E. Timothy; Superfine, R.

2006-01-01

333

In situ observation of the solution convection induced by magnetic force using photoreaction  

NASA Astrophysics Data System (ADS)

The effects of vertical magnetic fields (?1260 T2/m) on the laser-induced convection of a benzene solution were studied by using a photo-induced coloration reaction of CBr4 and diphenylamine. A green solution, photo-generated at the bottom surface of a vessel, flowed against the magnetic field center. The speed of the solution depended strongly on the intensity and direction of the magnetic force. These effects were discussed in terms of the difference in the magnetic susceptibilities of the green solution and the surrounding one.

Koyama, F.; Tanimoto, Y.

334

Superconducting microwave resonator for millikelvin magnetic resonance force microscopy  

NASA Astrophysics Data System (ADS)

We have fabricated a superconducting resonator capable of generating a strong microwave magnetic field in a small (100 ?m) volume for low temperature magnetic resonance experiments. While the resonator was specifically developed for use at millikelvin temperatures in a dilution refrigerator, where the total cooling power is limited to a few hundred microwatts, it is also useful at temperatures up to 5 K. The resonator consists of a 220 ?m diameter, 2-1/2 turn niobium coil resonating with a short section of niobium microstripline. At a resonance frequency of 3 GHz, the loaded Q of the resonator was 780. The field strength was characterized by performing electron spin nutations. Operating at 100 mK with 320 ?W of dissipated power, the resonator generated a field of 4 G at a distance of 100 ?m from the coil.

Mamin, H. J.; Budakian, R.; Rugar, D.

2003-05-01

335

Drag measurements on a laminar flow body of revolution in Langley's 13 inch magnetic suspension and balance system. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Low-speed wind tunnel drag force measurements were taken on a laminar flow body of revolution free of support interference. This body was tested at zero incidence in the NASA Langley 13 inch Magnetic Suspension and Balance System (MSBS). The primary objective of these tests was to substantiate the drag force measuring capabilities of the 13 inch MSBS. A secondary objective was to obtain support interference free drag measurements on an axisymmetric body of interest. Both objectives were met. The drag force calibrations and wind-on repeatability data provide a means of assessing the drag force measuring capabilities of the 13 inch MSBS. The measured drag coefficients for this body are of interest to researchers actively involved in designing minimum drag fuselage shapes. Additional investigations included: the effects of fixing transition; the effects of fins installed in the tail; surface flow visualizations using both liquid crystals and oil flow; and base pressure measurements using a one-channel telemetry system. Two drag prediction codes were used to assess their usefulness in estimating overall body drag. These theoretical results did not compare well with the measured values because of the following: incorrect or non-existent modeling of a laminar separation bubble on the body and incorrect of non-existent estimates of base pressure drag.

Dress, David A.

1988-01-01

336

Resistance of domain walls created by means of a magnetic force microscope in transversally magnetized epitaxial Fe wires  

SciTech Connect

Magnetic domain walls are created in a controllable way in transversally magnetized epitaxial Fe wires on GaAs(110) by approaching a magnetic force microscope (MFM) tip. The electrical resistance-change due to the addition of these domain walls is measured. The anisotropic magnetoresistance as well as the intrinsic domain wall resistance contribute to the resistance-change. The efficiency of this procedure is proven by MFM images, which are obtained subsequent to the domain wall creation at a larger sample-to-probe distance. The contribution of the anisotropic magnetoresistance is calculated using micromagnetic calculations, thus making it possible to quantify the intrinsic domain wall resistance.

Hassel, C.; Stienen, S.; Roemer, F. M.; Meckenstock, R.; Dumpich, G.; Lindner, J. [Fachbereich Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, 47048 Duisburg (Germany)

2009-07-20

337

Detection of Silica-Mediated Dissolution of Magnetic Grains in Sediments Using FORC Diagrams  

NASA Astrophysics Data System (ADS)

Recently silica-mediated dissolution has been recognized as a potentially important factor in magnetic studies of marine and lacustrine sediments. Although direct evidence for the dissolution of magnetic particles in silica-rich environments is still lacking, the process is expected to produce changes in the magnetic grain-size distribution. This hypothesis can be tested using FORC diagrams, which provide detailed information about the magnetic grain-size distributions of small quantities of material. For the present study, four cores were investigated from Lake Tanganyika in East Africa, where high levels of dissolved silica are present. Large variations in both natural and artificial remanent magnetization intensities were observed during the initial paleomagnetic investigation of the cores. These variations in magnetic intensity could not be explained by simple dilution by inert silica in the sediment, suggesting that silica-mediated dissolution might be involved. To study this phenomenon, FORC diagrams were collected from zones of both high and low magnetic intensity. Results from the different zones clearly show that changes in the magnetic intensity are associated with changes in the magnetic grain-size distribution. In particular, zones with high silica content correlated with a depletion in fine-grained magnetic material, whereas zones with lower silica content showed no depletion. These results are consistent with the idea that silica-mediated dissolution results in the preferential removal of fine-grained magnetic material. The results of this study suggest that FORC diagrams are an effective way of determining the presence of silica-mediated dissolution in sediments.

Wetter, L.; Verosub, K.; Acton, G.; Russell, J.

2005-12-01

338

Effects of long-range tip-sample interaction on magnetic force imaging: A comparative study between bimorph driven system and electrostatic force modulation  

NASA Astrophysics Data System (ADS)

Magnetic force microscopy (MFM) using electrostatic force modulation has been designed and developed to avoid the drawbacks of the bimorph driven system. The bimorph driven system has poor frequency response and overlap of the topographic features on magnetic structures of the MFM images. In the electrostatic force modulation system, the amplitude increases in the noncontact regime as the tip approaches due to the capacitive coupling between tip and sample. MFM using electrostatic force modulation has been applied to observe maze-like stripe domain structures on a CoCr film. The contrast mechanism and imaging stability of MFM using electrostatic force modulation are discussed by investigating the force distance curves obtained in two magnetic domain regions.

Kim, Byung I.

2012-05-01

339

Radial motion of a solid spherical body in a magnetic field  

Microsoft Academic Search

The object of the present paper is to investigate the radial motion of a solid spherical body, assumed to be homogeneous, isotropic and elastic, in presence of a magnetic field in the azimuthal direction. The body is assumed to be in a state of initial stress which is hydrostatic in nature. This theory of radial motion of a solid spherical

R. K. Mal; P. R. Sengupta

1980-01-01

340

Magnetic Fields Produced by Steady Currents in Human and Animal Bodies.  

National Technical Information Service (NTIS)

Magnetic fields produced by organs of the human body are being measured in the MIT shielded room, using both a SQUID magnetometer and second-derivative gradiometer. Measurements of the field around the human body can yield new information about the organs...

D. Cohen

1973-01-01

341

Nanoscale Investigation of Au Islands-Ni Film Interactions by Magnetic-Force-Controlled Atomic Force Microscopy  

NASA Astrophysics Data System (ADS)

The study of metal-metal interactions is both interesting and of technological importance for various thin-film structures. We carried out surface elemental analysis of several metal-plated films using magnetic-force-controlled atomic force microscopy (MFC-AFM) to evaluate the quality of wireless bondings and the films themselves. We reached the following two conclusions. First, the stiffness of the two types of plated metal film can be differentiated by MFC-AFM, whereby the difference in stiffness between the plated metal films can be imaged. Simultaneous imaging of the surface properties and stiffness of the samples produced by wet processes can be achieved at high resolution. Secondly, the Ni atoms that diffused to the Au-plated film surface annealed at 180 °C for 5 min can also be imaged by MFC-AFM. The relationship of these metal-metal interactions to the electronic packaging are discussed in this paper.

Yamamoto, Shin-ichi; Yamada, Hirofumi

2009-08-01

342

Large eddy simulation of forced ignition of an annular bluff-body burner  

SciTech Connect

The optimization of the ignition process is a crucial issue in the design of many combustion systems. Large eddy simulation (LES) of a conical shaped bluff-body turbulent nonpremixed burner has been performed to study the impact of spark location on ignition success. This burner was experimentally investigated by Ahmed et al. [Combust. Flame 151 (2007) 366-385]. The present work focuses on the case without swirl, for which detailed measurements are available. First, cold-flow measurements of velocities and mixture fractions are compared with their LES counterparts, to assess the prediction capabilities of simulations in terms of flow and turbulent mixing. Time histories of velocities and mixture fractions are recorded at selected spots, to probe the resolved probability density function (pdf) of flow variables, in an attempt to reproduce, from the knowledge of LES-resolved instantaneous flow conditions, the experimentally observed reasons for success or failure of spark ignition. A flammability map is also constructed from the resolved mixture fraction pdf and compared with its experimental counterpart. LES of forced ignition is then performed using flamelet fully detailed tabulated chemistry combined with presumed pdfs. Various scenarios of flame kernel development are analyzed and correlated with typical flow conditions observed in this burner. The correlations between, velocities and mixture fraction values at the sparking time and the success or failure of ignition, are then further discussed and analyzed. (author)

Subramanian, V.; Domingo, P.; Vervisch, L. [CORIA-CNRS and INSA de Rouen, Technopole du Madrillet, BP 8, 76801 Saint-Etienne-du-Rouvray (France)

2010-03-15

343

Navier-Stokes Computations of Longitudinal Forces and Moments for a Blended Wing Body  

NASA Technical Reports Server (NTRS)

The object of this paper is to investigate the feasibility of applying CFD methods to aerodynamic analyses for aircraft stability and control. The integrated aerodynamic parameters used in stability and control, however, are not necessarily those extensively validated in the state of the art CFD technology. Hence, an exploratory study of such applications and the comparison of the solutions to available experimental data will help to assess the validity of the current computation methods. In addition, this study will also examine issues related to wind tunnel measurements such as measurement uncertainty and support interference effects. Several sets of experimental data from the NASA Langley 14x22-Foot Subsonic Tunnel and the National Transonic Facility are presented. Two Navier-Stokes flow solvers, one using structured meshes and the other unstructured meshes, were used to compute longitudinal static stability derivatives for an advanced Blended Wing Body configuration over a wide range of angles of attack. The computations were performed for two different Reynolds numbers and the resulting forces and moments are compared with the above mentioned wind tunnel data.

Pao, S. Paul; Biedron, Robert T.; Park, Michael A.; Fremaux, C. Michael; Vicroy, Dan D.

2004-01-01

344

Navier-Stokes Computations of Longitudinal Forces and Moments for a Blended Wing Body  

NASA Technical Reports Server (NTRS)

The object of this paper is to investigate the feasibility of applying CFD methods to aerodynamic analyses for aircraft stability and control. The integrated aerodynamic parameters used in stability and control, however, are not necessarily those extensively validated in the state of the art CFD technology. Hence, an exploratory study of such applications and the comparison of the solutions to available experimental data will help to assess the validity of the current computation methods. In addition, this study will also examine issues related to wind tunnel measurements such as measurement uncertainty and support interference effects. Several sets of experimental data from the NASA Langley 14x22-Foot Subsonic Tunnel and the National Transonic Facility are presented. Two Navier-Stokes flow solvers, one using structured meshes and the other unstructured meshes, were used to compute longitudinal static stability derivatives for an advanced Blended Wing Body configuration over a wide range of angles of attack. The computations were performed for two different Reynolds numbers and the resulting forces and moments are compared with the above mentioned wind tunnel data.

Pao, S. Paul; Biedron, Robert T.; Park, Michael A.; Fremaux, C. Michael; Vicroy, Dan D.

2005-01-01

345

Unimolecular Dynamics in Molecular Clusters: Hydrogen Bonding, 3-body Forces and Open Shell Species  

NASA Astrophysics Data System (ADS)

The combination of i) long path supersonic slit jet expansion methods, ii) high resolution direct absorption IR spectroscopy, and iii) IR/UV photolysis with LIF/REMPI detection have proven to be a particularly versatile probe of unimolecular dynamics in molecular clusters. By way of example, this talk will provide a brief overview of experimental advances and address results from three recent studies from our laboratories. 1) Single mode tunable difference frequency IR laser methods have been used to observe all 6 inter- and intramolecular vibrational modes in supersonically cooled HF and DF dimers, which in conjunction with 4-D and 6-D quantum calculations permits direect tests of potential energy surfaces for hydrogen bonding. 2) These direct absorption methods have been used to observe high resolution near IR spectra of species such as HCl, HF, DF, and CO2 sequentially "solvated" by up to n=1-4 Ar atoms, and thereby study detailed vibrational dynamics in systems well beyond the dimer. Of particular interest has been quantitative probes of non-pairwise additive (i.e. 3-body) forces, in systems where rigorous comparison with theory is possible. 3) Novel methods for generation and study of jet cooled radicals, molecular ions and radical complexes will be discussed, based on i) long path length slit jet discharges and ii) "gentle recoil" UV photolysis of closed shell dimer and trimer precursors under collision free expansion conditions.

Nesbitt, David J.

1997-03-01

346

A reliable three?node triangular plate element satisfying rigid body rule and incremental force equilibrium condition  

Microsoft Academic Search

This paper proposes a simple method for deriving the geometric stiffness matrix (GSM) of a three?node triangular plate element (TPE). It is found that when the GSM of the element is combined into the global one of the structure, this structural stiffness matrix becomes symmetric and satisfies both the rigid body rule and incremental force and moment equilibrium (IFE) conditions,

Weichung Yeih

2006-01-01

347

A Study of the Two-body Problem with Magnetic Interactions  

Microsoft Academic Search

A first order correction is applied to Kepler's third law that takes into account the magnetic interaction between two orbiting bodies. This correction is derived by introducing a magnetic moment term in the potential energy of the system. Deviations of the period, distances, and velocities, from those implied by the classic Kepler's law (based on gravitation only) are derived which

Alberto Sadun; Masoud Asadi-Zeydabadi

2009-01-01

348

An enhanced method for estimation of body magnetization direction from pseudogravity and gravity data  

Microsoft Academic Search

Source body magnetization direction of the structures causing magnetic and gravity anomalies can be estimated with some accuracy. In this paper, a further improved method is presented for this purpose. The method searches for maximum correlation between pseudogravity and gravity anomalies. The method is successfully tested with synthetic models without error and with including some error into the data locations.

F. Bilim; A. Ates

2004-01-01

349

Bilayer properties of giant magnetic liposomes formed by cationic pyridine amphiphile and probed by active deformation under magnetic forces.  

PubMed

We synthesize giant magnetic liposomes by a reverse-phase evaporation method (REV) using a new self-assembling Cationic Pyridine Amphiphile (CPA) derived from 1,4-dihydropyridine as liposome-forming agent and a magnetic ferrofluid based on ?-Fe(2)O(3) nanoparticles. Having in view the potential interest of CPA in targeted transport by magnetic forces, the mechanical elastic properties of such bilayers are here directly investigated in vesicles loaded with magnetic nanoparticles. Bending elastic modulus K(b) ? 0.2 to 5k(B)T and pre-stress ? ? 3.2 to 12.10(-6) erg/cm(2) are deduced from the under-field deformations of the giant magnetic liposomes. The obtained K(b) values are discussed in terms of A. Wurgers's theory. PMID:23359032

Petrichenko, O; Erglis, K; C?bers, A; Plotniece, A; Pajuste, K; Béalle, G; Ménager, Ch; Dubois, E; Perzynski, R

2013-01-01

350

Computing Nonlinear Force-Free Coronal Magnetic Fields in Spherical Geometry  

Microsoft Academic Search

We describe a newly developed code for the extrapolation of nonlinear force-free coronal magnetic fields in spherical coordinates.\\u000a The program uses measured vector magnetograms on the solar photosphere as input and solves the force-free equations in the\\u000a solar corona. The method is based on an optimization principle and the heritage of the newly developed code is a corresponding\\u000a method in

T. Wiegelmann

2007-01-01

351

Characteristics and computer model simulation of magnetic damping forces in maglev systems  

SciTech Connect

This report discusses the magnetic damping force in electrodynamic suspension (EDS) maglev systems. The computer model simulations, which combine electrical system equations with mechanical motion equations on the basis of dynamic circuit theory, were conducted for a loop-shaped coil guideway. The intrinsic damping characteristics of the EDS-type guideway are investigated, and the negative damping phenomenon is confirmed by the computer simulations. The report also presents a simple circuit model to aid in understanding damping-force characteristics.

He, J.L.; Rote, D.M.; Chen, S.S.

1994-05-01

352

Size-Dependent Particle Filteration using Magnetically Driven Microtool and Centrifugal Force in Microchip  

Microsoft Academic Search

We succeeded in size-dependent filtration of microparticles by rotation of magnetically driven microtool (MMT) and centrifugal force in a microchip. Novelties of this paper are summarized as follows. (1) Filtering efficiency was improved than filtration by solely centrifugal force by MMT rotation. (2) Clogging of microparticles was avoided by swirling flow generated by rotation of 3D-MMT with fins. (3) This

H. Maruyama; S. Sakuma; Y. Yamanishi; F. Arai

2009-01-01

353

On the numerical computation of nonlinear force-free magnetic fields  

NASA Technical Reports Server (NTRS)

An algorithm has been developed to extrapolate nonlinear force-free magnetic fields from a source surface, given the proper boundary conditions. The results of this work; describing the mathematical formalism that was developed, the numerical techniques employed, and the stability criteria developed for these numerical schemes are presented. An analytical solution is used for a test case; the results show that the computational accuracy for the case of a nonlinear force-free magnetic field was on the order of a few percent ( 5%).

Wu, S. T.; Chang, H. M.; Hagyard, M. J.

1985-01-01

354

Practical limits to the performance of magnetic bearings: Peak force, slew rate, and displacement sensitivity  

NASA Technical Reports Server (NTRS)

Magnetic bearings are subject to performance limits which are quite different from those of conventional bearings. These are due in part to the inherent nonlinearity of the device and in part to its electrical nature. Three important nonideal behaviors are presented: peak force capacity, force slew rate limitation, and sensitivity to rotor motion at large displacements. The problem of identifying the dynamic requirements of a magnetic bearing when used to support a known structure subject to known loads is discussed in the context of these limitations. Several simple design tools result from this investigation.

Maslen, E.; Hermann, P.; Scott, M.; Humphris, R. R.

1993-01-01

355

Configuration of an inviscid plasma in the field of a rotating magnetized central body  

Microsoft Academic Search

The problem is considered of configurations of a strongly magnetized inviscid plasma around a rotating magnetized central\\u000a body. Strong plasma magnetization implies that the Hall conductivity is much lower than the transverse conductivity, which\\u000a in turn is much lower than the longitudinal conductivity. For such conditions, a self-consistent set of equations is derived\\u000a that describes the conduction current density, the

A. O. Soldatkin; Yu. V. Chugunov

2005-01-01

356

Misorientations in [001] magnetite thin films studied by electron backscatter diffraction and magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Magnetite thin films grown on [001] oriented MgO substrates are analyzed by means of electron backscatter diffraction (EBSD) analysis and magnetic force microscopy in applied fields. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution up to 20 nm on such ceramic samples. A high image quality of the recorded Kikuchi patterns was achieved enabling multiphase scans and high spatial resolution measurements. Upon annealing in air, the magnetic properties of the magnetite thin films were found to change considerably. Using the EBSD analysis, we find that misoriented grains remaining after the annealing step form small islands with a size of about 100 nm. The size and distribution of these islands correspond well to the observations of antiferromagnetic pinning centers within the magnetic domain structures carried out by magnetic force microscopy on the same samples.

Koblischka-Veneva, A.; Koblischka, M. R.; Wei, J. D.; Zhou, Y.; Murphy, S.; Mücklich, F.; Hartmann, U.; Shvets, I. V.

2007-05-01

357

Development of forced flow cooled current leads for fusion magnets  

NASA Astrophysics Data System (ADS)

During the past 15 years, the Institut für Technische Physik of the Forschungszentrum Karlsruhe, Germany, has developed current leads cooled by forced-flow supercritical helium in the current range from 20 to 80 kA. The design is based on a separation of the current carrying part and the heat exchanger part as well as the presence of the so-called superconductor inserts made of Nb 3Sn wires inside the conductor in the heat exchanger area which allows the operation of the current lead at minimum helium mass flow in a wide current range. The paper describes the design and construction of the current leads as well as operation results obtained during various tests performed in the coil test facility TOSKA at the Forschungszentrum Karlsruhe.

Heller, R.; Fink, S.; Friesinger, G.; Kienzler, A.; Lingor, A.; Schleinkofer, G.; Süßer, M.; Ulbricht, A.; Wüchner, F.; Zahn, G.

2001-03-01

358

Forces and moments of a small body moving in a 3-D unsteady flow (with applications to slender structures)  

SciTech Connect

Complete expressions are derived for the inertia forces and moments acting on a small body in a six-degree-of-freedom motion in a three-dimensional unsteady flow in an unbounded ideal fluid. The far-field approximation of the body motion is represented by a series of multipoles located at the origin of the body. Unsteady terms are expanded in a dual series to the multipole series. Lagally integrals are expressed in terms of multipoles as well, by using Legendre polynomial expansions. New inertia force expressions are derived by truncating the multipole series after the quadrupoles. Corresponding terms for moments are also developed. The derived formulas are still compact enough for engineering applications. Many practical problems involving fixed and oscillating cylinders, piles, and risers are studied numerically. Comparisons to the Morison equation formulation prove that the nonlinear convective terms are not negligible in multidimensional relative flows.

Foulhoux, L. (Elf Aquitaine, Pau (France). Marine Advanced Techniques Section); Bernitsas, M.M. (Univ. of Michigan, Ann Arbor (United States). Dept. of Naval Architecture and Marine Engineering)

1993-05-01

359

Mechanical characterization of journal superconducting magnetic bearings: stiffness, hysteresis and force relaxation  

NASA Astrophysics Data System (ADS)

Superconducting magnetic bearings (SMBs) can provide stable levitation without direct contact between them and a magnetic source (typically a permanent magnet). In this context, superconducting magnetic levitation provides a new tool for mechanical engineers to design non-contact mechanisms solving the tribological problems associated with contact at very low temperatures. In the last years, different mechanisms have been proposed taking advantage of superconducting magnetic levitation. Flywheels, conveyors or mechanisms for high-precision positioning. In this work the mechanical stiffness of a journal SMBs have been experimentally studied. Both radial and axial stiffness have been considered. The influence of the size and shape of the permanent magnets (PM), the size and shape of the HTS, the polarization and poles configuration of PMs of the journal SMB have been studied experimentally. Additionally, in this work hysteresis behavior and force relaxation are considered because they are essential for mechanical engineer when designing bearings that hold levitating axles.

Cristache, Cristian; Valiente-Blanco, Ignacio; Diez-Jimenez, Efren; Alvarez-Valenzuela, Marco Antonio; Pato, Nelson; Perez-Diaz, Jose Luis

2014-05-01

360

Force transmission through the juvenile idiopathic arthritic wrist: a novel approach using a sliding rigid body spring model.  

PubMed

Force transmission across the wrist during a grasping maneuver of the hand was simulated for three children with juvenile idiopathic arthritis (JIA) and for one healthy age-matched child. Joint reaction forces were estimated using a series of springs between articulating bones. This method (i.e., rigid body spring modeling) has proven useful for examining loading profiles for normally aligned wrists. A novel method (i.e., sliding rigid body spring modeling) designed specifically for studying joint reaction forces of the malaligned JIA wrist is presented in this paper. Loading profiles across the wrist for the unimpaired child were similar using both spring modeling methods. However, the traditional fixed-end method failed to converge to a solution for one of the JIA subjects indicating the sliding model may be more suitable for investigating loading profiles of the malaligned wrist. The results of this study suggest that a larger proportion of force is transferred through the ulno-carpal joint of the JIA wrist than for healthy subjects, with a less than normal proportion of force transferred through the radio-carpal joint. In addition, the ulnar directed forces along the shear axis defined in this study were greater for all three JIA children compared to values for the healthy child. These observations are what were hypothesized for an individual with JIA of the wrist. PMID:11747891

Manal, Kurt; Lu, Xiaopeng; Nieuwenhuis, Marianne K; Helders, Paul J M; Buchanan, Thomas S

2002-01-01

361

An enhanced method for estimation of body magnetization direction from pseudogravity and gravity data  

NASA Astrophysics Data System (ADS)

Source body magnetization direction of the structures causing magnetic and gravity anomalies can be estimated with some accuracy. In this paper, a further improved method is presented for this purpose. The method searches for maximum correlation between pseudogravity and gravity anomalies. The method is successfully tested with synthetic models without error and with including some error into the data locations. The method is also applied to a field data in Central Turkey, which demonstrates successful pseudogravity transformation with newly estimated angle of body magnetization.

Bilim, F.; Ates, A.

2004-03-01

362

A New Method for Reduction of Detent Force in Permanent Magnet Flux-Switching Linear Motors  

Microsoft Academic Search

The permanent magnet (PM) flux-switching linear motor, which is developed from the PM flux-switching rotary machine, possesses similar advantages such as high power density and simple structure. Furthermore, the PM flux-switching linear motor has a potential for mass production at low cost, since the expensive coils and magnets are both set on the short mover. However, the detent force which

Can-Fei Wang; Jian-Xin Shen; Yu Wang; Li-Li Wang; Meng-Jia Jin

2009-01-01

363

Numerical simulations of mass outflows driven from accretion disks by radiation and magnetic forces  

Microsoft Academic Search

We study the two-dimensional, time-dependent magnetohydrodynamics (MHD) of radiation-driven winds from luminous accretion disks initially threaded by a purely axial magnetic field. The radiation force is mediated primarily by spectral lines and is calculated using a generalized multidimensional formulation of the Sobolev approximation. We use ideal MHD to compute numerically the evolution of Keplerian disks, varying the magnetic field strengths

Daniel Proga

2002-01-01

364

Self-ordered growth and magnetic force microscopy study of iron nanoparticles  

Microsoft Academic Search

We present atomic and magnetic force microscopy measurements on magnetic iron nanoparticles produced by a self-assembly method. The fabrication process is based on the thermal disintegration of iron nanowires deposited on faceted Al2O3 substrates. Arrangement and size of the particles depend on the annealing temperature. For iron this process yields particles with diameters in the range of 100-250 nm. The

S. Sievers; M. Albrecht; U. Siegner; C. Herweg; H. C. Freyhardt

2005-01-01

365

Nonlinear force-free reconstruction of the global solar magnetic field: methodology  

Microsoft Academic Search

We present a novel numerical method that allows the calculation of nonlinear\\u000aforce-free magnetostatic solutions above a boundary surface on which only the\\u000adistribution of the normal magnetic field component is given. The method relies\\u000aon the theory of force-free electrodynamics and applies directly to the\\u000areconstruction of the solar coronal magnetic field for a given distribution of\\u000athe photospheric

Ioannis Contopoulos; Constantinos Kalapotharakos; Manolis Georgoulis

2010-01-01

366

Focal transcranial magnetic stimulation and response bias in a forced-choice task  

Microsoft Academic Search

The effects of transcranial magnetic stimulation were studied on the performance of a warned, forced-choice response time task by normal adults. The task consisted of extension of the index finger in response to the click produced by the discharge of the magnetic coil (go-signal). The subjects were asked to choose the right or left finger only after the go-signal was

J. P. Brasil-neto; A Pascual-Leone; J Valls-Solé; L G Cohen; M Hallett

1992-01-01

367

Effect of an acute bout of whole body vibration exercise on muscle force output and motor neuron excitability.  

PubMed

The purpose of the current investigation was to assess the effect of an acute bout of whole body vibration (WBV) exercise on muscle force output and motor neuron excitability. Nineteen recreationally trained college-aged males were randomly assigned to a WBV (n = 10) or a sham (S, n = 9) group. The WBV group completed a series of static, body weight squats on a vibrating platform at 30 Hz and an amplitude of approximately 3.5 mm (vertical), whereas the S group performed the same series of exercises but without vibration. Measurements were performed before (Pre) and then immediately post-exercise (Imm Post), 8 minutes post-exercise (8-Min Post), or 16 minutes post-exercise (16-Min Post) during 3 different testing sessions. The measurements involved a ballistic isometric maximum voluntary contraction (MVC) of the triceps surae muscle complex and electrical stimulation of the tibial nerve for assessment of motor neuron excitability by analyzing H-reflex and M-wave responses (H(max)/M(max) ratio). Electromyography was also obtained from the triceps surae muscle complex during the MVCs. The WBV group significantly (p < or = 0.05) increased peak force at Imm Post (9.4%) and 8-Min Post (10.4%). No significant change in peak force was observed in the S group. No significant changes were observed in either group for average integrated EMG, H(max)/M(max) ratio, or rate of force development at Imm Post, 8-Min Post, or 16-Min Post. The results from this investigation indicate that an acute bout of static, body weight squat exercises, combined with WBV, increases muscle force output up to 8 minutes post-exercise. However, this increase in muscle force is not accompanied by a significant increase in motor neuron excitability or muscle activation. Thus, it is plausible to use WBV as a method for acute increase in muscle force output for athletes immediately before competition. PMID:19816218

McBride, Jeffrey M; Nuzzo, James L; Dayne, Andrea M; Israetel, Michael A; Nieman, David C; Triplett, N Travis

2010-01-01

368

Magnetic Force on a Current-carrying Wire  

NSDL National Science Digital Library

This is an inquiry-based lab for AP or Honors high school physics, designed to let students explore the effect of an external field on a current-carrying wire in that field. Detailed background information and tips for teachers accompany the lesson, along with photos and diagrams of the lab set-up. It is expected that students would have some prior experience with the fundamentals of magnetism but would not have studied the topic prior to the lab. This resource is part of a larger collection of inquiry-based labs developed by the NSF-funded Center for Nanoscale Systems Institute for Physics Teachers. SEE RELATED ITEMS on this page for a link to the full collection.

2007-07-30

369

Experimental considerations for the development of a nuclear magnetic resonance force microscope  

NASA Astrophysics Data System (ADS)

The nuclear magnetic resonance force microscope is a non-invasive three dimensional imaging tool which is a great improvement over conventional NMR. A sample is attached to a mechanical silicon oscillator and placed in a large static magnetic field. The sample is magnetized by the static field, and a net magnetization in the z-direction is produced. An rf coil is placed near the sample to excite spins into resonance, and a permanent magnetic tip is placed along the direction of the static field to resolve the excited spins. From coupling the magnetization to the field gradient a force is produced on the mechanical oscillator. The motion of the mechanical oscillator is detected with a fiber optic interferometer. From the displacement of the mechanical oscillator a force map can be determined and a final three-dimensional image can be produced. An experiment on paraffin wax has demonstrated that the microscope can detect NMR from extremely small samples. The microscopic mechanical oscillators were tested for use in the NMRFM probe and their fabrication process was optimized. Also NMR on phosphorous and deuterium was performed to determine the strength of the rf field and to determine the rf field necessary to excite protons. Some conventional NMR was done to determine the properties of yttrium in an yttrium chloride solution for the purpose of future NMRFM studies.

Barrett, Tina Alexandra

370

Evaluation of Electromagnetic Force and Magnetic Laval Nozzle Acceleration in an Applied-Field MPD Thruster  

NASA Astrophysics Data System (ADS)

A magneto-plasma-dynamic thruster (MPDT) is expected as one of the promising electric propulsion systems owing to features of a relatively large thrust, high specific impulse that is unattainable by conventional chemical or nuclear propulsion required for space missions such as a manned Mars mission. To clarify the electromagnetic acceleration mechanism of a plasma flow in an applied-field MPDT, detailed flow field and electromagnetic force field are evaluated experimentally with spectroscopic technique and magnetic probe array. It is found that an axial drag force generated by an interaction between azimuthal plasma current and radial magnetic field cancels an acceleration force in a uniform magnetic field. A thermal energy component is much larger than a flow energy component in Bernoulli's equation and ion acoustic Mach number is limited less than unity in the muzzle region of MPD arcjet. In order to convert the thermal energy to the flow energy, magnetic Laval nozzle acceleration with a local magnetic coil is attempted. The ion Mach number after passing through the nozzle throat exceeds unity and a production of supersonic plasma flow is achieved. An optimum magnetic nozzle configuration is discussed with the experimental results.

Tobari, Hiroyuki; Sato, Ryuichi; Harata, Kenji; Hattori, Kunihiko; Ando, Akira; Inutake, Masaaki

2003-10-01

371

A microfabricated magnetic force transducer-microaspiration system for studying membrane mechanics  

NASA Astrophysics Data System (ADS)

The application of forces to cell membranes is a powerful method for studying membrane mechanics. To apply controlled dynamic forces on the piconewton scale, we designed and characterized a microfabricated magnetic force transducer (MMFT) consisting of current-carrying gold wires patterned on a sapphire substrate. The experimentally measured forces applied to paramagnetic and ferromagnetic beads as a function of applied current agree well with theoretical models. We used this device to pull tethers from microaspirated giant unilamellar vesicles and measure the threshold force for tether formation. In addition, the interlayer drag coefficient of the membrane was determined from the tether-return velocity under magnetic force-free conditions. At high levels of current, vesicles expanded as a result of local temperature changes. A finite element thermal model of the MMFT provided absolute temperature calibration, allowing determination of the thermal expansivity coefficient of stearoyl-oleoyl-phosphatidycholine vesicles (1.7 ± 0.4 × 10-3 K-1) and characterization of the Joule heating associated with current passing through the device. This effect can be used as a sensitive probe of temperature changes on the microscale. These studies establish the MMFT as an effective tool for applying precise forces to membranes at controlled rates and quantitatively studying membrane mechanical and thermo-mechanical properties.

Stark, D. J.; Killian, T. C.; Raphael, R. M.

2011-10-01

372

Fluid force predictions and experimental measurements for a magnetically levitated pediatric ventricular assist device.  

PubMed

The latest generation of artificial blood pumps incorporates the use of magnetic bearings to levitate the rotating component of the pump, the impeller. A magnetic suspension prevents the rotating impeller from contacting the internal surfaces of the pump and reduces regions of stagnant and high shear flow that surround fluid or mechanical bearings. Applying this third-generation technology, the Virginia Artificial Heart Institute has developed a ventricular assist device (VAD) to support infants and children. In consideration of the suspension design, the axial and radial fluid forces exerted on the rotor of the pediatric VAD were estimated using computational fluid dynamics (CFD) such that fluid perturbations would be counterbalanced. In addition, a prototype was built for experimental measurements of the axial fluid forces and estimations of the radial fluid forces during operation using a blood analog mixture. The axial fluid forces for a centered impeller position were found to range from 0.5 +/- 0.01 to 1 +/- 0.02 N in magnitude for 0.5 +/- 0.095 to 3.5 +/- 0.164 Lpm over rotational speeds of 6110 +/- 0.39 to 8030 +/- 0.57% rpm. The CFD predictions for the axial forces deviated from the experimental data by approximately 8.5% with a maximum difference of 18% at higher flow rates. Similarly for the off-centered impeller conditions, the maximum radial fluid force along the y-axis was found to be -0.57 +/- 0.17 N. The maximum cross-coupling force in the x direction was found to be larger with a maximum value of 0.74 +/- 0.22 N. This resulted in a 25-35% overestimate of the radial fluid force as compared to the CFD predictions; this overestimation will lead to a far more robust magnetic suspension design. The axial and radial forces estimated from the computational results are well within a range over which a compact magnetic suspension can compensate for flow perturbations. This study also serves as an effective and novel design methodology for blood pump developers employing magnetic suspensions. Following a final design evaluation, a magnetically suspended pediatric VAD will be constructed for extensive hydraulic and animal testing as well as additional validation of this design methodology. PMID:17470205

Throckmorton, Amy L; Untaroiu, Alexandrina; Lim, D Scott; Wood, Houston G; Allaire, Paul E

2007-05-01

373

Different nocturnal body temperatures and sleep with forced-air warming in men and in women taking hormonal contraceptives.  

PubMed

We studied how forced-air warming, conventionally used to control body temperature during and after anaesthesia, affected the nocturnal rectal temperatures and sleep composition of young men and women. Seven healthy women who were taking oral or injection contraceptives, and six healthy men spent 3 nights in a controlled environment: an adaptation night followed by 2 nights when they slept under either a down duvet (baseline) or a quilt perfused with warm air (hot). Repeated analysis of variance (ANOVA) revealed significant gender differences in the body temperature responses. On the baseline night, despite sleeping under the same conditions, the women did not show a nocturnal drop in body temperature as shown by the men. Forced-air warming increased body temperature to a similar extent in the men and the women, and resulted in enhanced hyperthermia in the women, and blunted the drop in body temperature in the men, compared to their baseline nights. The significant increases in body temperature had no consequences, however, for the subjective sleep quality of either the men or women, and only minor consequences for objective sleep composition. Both men and women had increased amounts of Stage 2 sleep on the hot night (P < 0.04). In addition, the women had reduced rapid eye movement (REM) sleep when compared to their baseline night (P < 0.04). Our results confirm that in a passive thermal environment, women who are taking oral or injection contraceptives have higher nocturnal body temperatures than men. Also, as sleep architecture was minimally affected by the increases in body temperature of between 0.2 and 0.3 degree C on the hot night in the men and women, and subjective sleep quality was unaffected, our results question the existence of a tight association between sleep and body temperature. PMID:9785272

Baker, F C; Selsick, H; Driver, H S; Taylor, S R; Mitchell, D

1998-09-01

374

First use of synoptic vector magnetograms for global nonlinear, force-free coronal magnetic field models  

NASA Astrophysics Data System (ADS)

The magnetic field permeating the solar atmosphere is generally thought to provide the energy for much of the activity seen in the solar corona, such as flares, coronal mass ejections (CMEs), etc. To overcome the unavailability of coronal magnetic field measurements, photospheric magnetic field vector data can be used to reconstruct the coronal field. Currently, there are several modelling techniques being used to calculate three dimensional field lines into the solar atmosphere. For the first time, synoptic maps of a photospheric vector magnetic field synthesized from the vector spectromagnetograph (VSM) on Synoptic Optical Long term Investigations of the Sun (SOLIS) are used to model the coronal magnetic field and estimate free magnetic energy in the global scale. The free energy (i.e., the energy in excess of the potential field energy) is one of the main indicators used in space weather forecasts to predict the eruptivity of active regions. We solve the nonlinear force free field equations using an optimization principle in spherical geometry. The resulting three-dimensional magnetic fields are used to estimate the magnetic free energy content, which is the difference of the magnetic energies between the nonpotential field and the potential field in the global solar corona. For comparison, we overlay the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the atmospheric imaging assembly (AIA) on board the Solar Dynamics Observatory (SDO).For a single Carrington rotation 2121, we find that the global nonlinear force free field (NLFFF) magnetic energy density is 10.3% higher than the potential one. Most of this free energy is located in active regions.

Asfaw, Tilaye Tadesse; Pevtsov, Alexei A.; Macneice, Peter J.

2014-06-01

375

A general expression of magnetic force for soft ferromagnetic plates in complex magnetic fields  

Microsoft Academic Search

The experiments of ferromagnetic plates in different magnetic environments exhibit two distinct phenomena, i.e. the magnetoelastic instability of a ferromagnetic plate in transverse magnetic fields, and the increase of natural frequency of a ferromagnetic plate with low susceptibility in an inplane magnetic field. Although these two typical phenomena can be predicted separately by two kinds of theoretical models in which

You-He Zhou; Xiaojing Zheng

1997-01-01

376

Pulsed-current-induced domain wall propagation in Permalloy patterns observed using magnetic force microscope  

Microsoft Academic Search

Pulsed-current controlled wall motion in 20 ?m wide×200 ?m long×160 nm thick patterned Permalloy strips was studied using magnetic force microscopy. By sequential imaging, the displacement of Bloch walls as far as 200 ?m along the strip was observed. The direction of motion was in the same direction as the carrier velocity, which reversed with current polarity. The displacement per

L. Gan; S. H. Chung; K. H. Aschenbach; M. Dreyer; R. D. Gomez

2000-01-01

377

Buoyant convection in an enclosure under time-periodic magnetizing force  

Microsoft Academic Search

A numerical study is made of buoyant convection of air in an enclosure under constant gravity and time-periodic magnetizing force. Buoyant convection occurs when the two vertical sidewalls are maintained at different temperatures and the horizontal walls are thermally insulated. To this basic layout, electric coils are located at the left and right sides of the cavity for case 1.

Dong Gu Kang; Jae Min Hyun

2007-01-01

378

Elimination of three-phase transformer inrush current through core forced magnetization and simultaneous closing  

Microsoft Academic Search

The inrush current occurs during transformer energization due to flux saturation in the core. Controlled switching connects transformer to power grid in proper phase angle derived from core remanent fluxes. The DC forced magnetization prior to transformer energization is one of simultaneous closing strategy methods. Active intervention to the transformer remanent flux was realized as a DC power supply with

Miroslav Novák

2010-01-01

379

Magnetic resonance force microscopy quantum computer with tellurium donors in silicon.  

PubMed

We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines well-developed silicon technology and expected advances in MRFM. Our proposal does not use electrostatic gates to realize quantum logic operations. PMID:11290066

Berman, G P; Doolen, G D; Hammel, P C; Tsifrinovich, V I

2001-03-26

380

Effect of Annealing on Coercive Force and Remanent Magnetizations in Magnetite  

Microsoft Academic Search

A series of experiments is described in which single crystals of magnetite were annealed under controlled conditions. Structural changes in the magnetite were followed by changes in the magnitudes of coercive force and saturation isothermal remanent magnetization. The structural changes were identified by comparing their activation energies as estimated from the annealing curves with those of known physical processes. It

W. Lowrie; M. Fuller

1969-01-01

381

Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon  

SciTech Connect

We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines well-developed silicon technology and expected advances in MRFM. Our proposal does not use electrostatic gates to realize quantum logic operations.

Berman, G. P.; Doolen, G. D.; Hammel, P. C.; Tsifrinovich, V. I.

2001-03-26

382

The Bloch Equations in High-Gradient Magnetic Resonance Force Microscopy: Theory and Experiment  

NASA Astrophysics Data System (ADS)

We report theory and observations of paramagnetic resonance in a measured field gradient of 44,000 T per meter by the technique of magnetic resonance force microscopy (MRFM). Resonance was induced in a dilute solid solution of diphenylpicrylhydrazyl in polystyrene at 77 and 10 K by an amplitude-modulated microwave field. This modulated the force between resonant sample spins and a micrometer-scale SmCo magnetic tip on a force microscope cantilever. The force signals were typically of order 10 fN, and were detected above a thermal noise floor of 80 aN per root hertz at 10 K, equivalent to a magnetic moment noise of 200 ? B per root hertz of bandwidth. Resonance saturation was readily observed. Starting with the Bloch equations, we derived simple analytic expressions for the predicted cantilever signal amplitudes and T1-dependent phase lags, valid at low microwave power levels. For power levels below saturation, the data were in good agreement with the Bloch equation predictions, while above saturation the measured force increased more slowly with power than predicted. Several ESR mechanisms which might lead to non-Bloch dynamics in the MRFM environment are reviewed. Spin-relaxation mechanisms are also reviewed. A detailed description of the experimental apparatus is offered.

Dougherty, W. M.; Bruland, K. J.; Chao, S. H.; Garbini, J. L.; Jensen, S. E.; Sidles, J. A.

2000-03-01

383

Investigation of thermoelectric magnetic force in solid and its effect on morphological instability in directional solidification  

NASA Astrophysics Data System (ADS)

Thermoelectric magnetic force (TEMF) imposed on the liquid/solid interface and the cell was examined numerically and experimentally during the directional solidification of the Al-Cu alloy under an axial strong magnetic field. Numerical results reveal that the TEMF is related to the magnetic field intensity, temperature gradient and liquid fraction. Indeed, it has been found that the TEMF increases as the magnetic field intensity, temperature gradient and liquid fraction increase. In particular, the value of the TEMF in directional solidification at 60 K/cm temperature gradient under the 10 T strong magnetic field is in the order of 10 5 N/m 3. This force is strong enough to induce the Asaro-Tiller-Grinfield (ATG) instability. Experimental results indicate that the application of the strong magnetic field in directional solidification has led to a dramatic change in the Mullins-Sekerka (MS) instability and the deformation of the solid. The modification amplitude of the MS instability under the magnetic field is in good agreement with the value of the TEMF imposed on the solid. Therefore, the change in the MS instability should be attributed to the occurrence of the ATG instability induced by the TEMF. Moreover, the experimental result may act as an evidence for the strong coupling between the MS and ATG instabilities in directional solidification.

Xi, LI; Gagnoud, Annie; Fautrelle, Yves; Ren, Zhongming; Cao, Guanghui; Moreau, Rene; Zhang, Yudong; Esling, Claude

2011-06-01

384

Single core-shell nanoparticle probes for non-invasive magnetic force microscopy.  

PubMed

We present an easy, fast and reliable method for the preparation of magnetic force microscopy (MFM) probes based on single Co nanoparticles (NPs). Due to their dipolar character, these magnetic probes open up a new approach for quantitative and non-invasive MFM measurements on the nanometer length scale. To guarantee long-term stability of these tips under ambient conditions, an ultrathin protecting Au shell was grown around the Co NPs through photochemical deposition. Single magnetic particles were firmly attached to standard silicon AFM tips using bifunctional self-assembling molecules. Such probes were tested on longitudinal magnetic recording media and compared to the results as recorded with conventional thin-film MFM tips. Easy data interpretation of the magnetic nanoparticle probes in a point dipole model is shown. Our nanoparticle tips provide excellent endurance for MFM recording, enable non-invasive probing while maintaining a high sensitivity, resolution, and reproducibility. PMID:24896585

Uhlig, Tino; Wiedwald, Ulf; Seidenstücker, Axel; Ziemann, Paul; Eng, Lukas M

2014-06-27

385

On the numerical computation of nonlinear force-free magnetic fields. [from solar photosphere  

NASA Technical Reports Server (NTRS)

An algorithm has been developed to extrapolate nonlinear force-free magnetic fields from the photosphere, given the proper boundary conditions. This paper presents the results of this work, describing the mathematical formalism that was developed, the numerical techniques employed, and comments on the stability criteria and accuracy developed for these numerical schemes. An analytical solution is used for a benchmark test; the results show that the computational accuracy for the case of a nonlinear force-free magnetic field was on the order of a few percent (less than 5 percent). This newly developed scheme was applied to analyze a solar vector magnetogram, and the results were compared with the results deduced from the classical potential field method. The comparison shows that additional physical features of the vector magnetogram were revealed in the nonlinear force-free case.

Wu, S. T.; Sun, M. T.; Chang, H. M.; Hagyard, M. J.; Gary, G. A.

1990-01-01

386

Calculation of cogging force in a novel slotted linear tubular brushless permanent magnet motor  

SciTech Connect

There is an increasing requirement for controlled linear motion over short and long strokes, in the factory automation and packaging industries, for example. Linear brushless PM motors could offer significant advantages over conventional actuation technologies, such as motor driven cams and linkages and pneumatic rams--in terms of efficiency, operating bandwidth, speed and thrust control, stroke and positional accuracy, and indeed over other linear motor technologies, such as induction motors. Here, a finite element/analytical based technique for the prediction of cogging force in a novel topology of slotted linear brushless permanent magnet motor has been developed and validated. The various force components, which influence cogging are pre-calculated by the finite element analysis of some basic magnetic structures, facilitate the analytical synthesis of the resultant cogging force. The technique can be used to aid design for the minimization of cogging.

Zhu, Z.Q.; Hor, P.J.; Howe, D. [Univ. of Sheffield (United Kingdom). Dept. of Electronic and Electrical Engineering] [Univ. of Sheffield (United Kingdom). Dept. of Electronic and Electrical Engineering; Rees-Jones, J. [Unilever Research Port Sunlight Lab., Bebington (United Kingdom)] [Unilever Research Port Sunlight Lab., Bebington (United Kingdom)

1997-09-01

387

On the Force-free Nature of Photospheric Sunspot Magnetic Fields as Observed from Hinode (SOT/SP)  

NASA Astrophysics Data System (ADS)

A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic fields (computed from the force-free parameter ?), and any kind of extrapolation, heavily hinges on the force-free approximation of the photospheric sunspot magnetic fields. Thus, it is of vital importance to inspect the force-free behavior of sunspot magnetic fields. The force-free nature of sunspot magnetic fields has been examined earlier by some researchers, ending with incoherent results. Accurate photospheric vector field measurements with high spatial resolution are required to inspect the force-free nature of sunspots. For this purpose, we use several vector magnetograms of high spatial resolution obtained from the Solar Optical Telescope/Spectro-Polarimeter on board Hinode. Both the necessary and sufficient conditions for force-free nature are examined by checking the global and local nature of equilibrium magnetic forces over sunspots. We find that sunspot magnetic fields are not very far from the force-free configuration, although they are not completely force-free on the photosphere. The umbral and inner penumbral fields are more force-free than the middle and outer penumbral fields. During their evolution, sunspot magnetic fields are found to maintain their proximity to force-free field behavior. Although a dependence of net Lorentz force components is seen on the evolutionary stages of the sunspots, we do not find a systematic relationship between the nature of sunspot magnetic fields and the associated flare activity. Further, we examine whether the fields at the photosphere follow linear or nonlinear force-free conditions. After examining this in various complex and simple sunspots, we conclude that, in either case, photospheric sunspot magnetic fields are closer to satisfying the nonlinear force-free field approximation.

Tiwari, Sanjiv Kumar

2012-01-01

388

Critical speeds and forced response solutions for active magnetic bearing turbomachinery, part 1  

NASA Technical Reports Server (NTRS)

The prediction of critical speeds and forced response of active magnetic bearing turbomachinery is of great interest due to the increased use of this new and promising technology. Calculating the system undamped critical speeds and forced response is important to all those who are involved in the design of the active magnetic bearing system. An extended Jeffcott model which was used as an approximate solution to a more accurate transfer matrix procedure is presented. Theory behind a two-degree-of freedom extended Jeffcoat model is presented. Results of the natural frequency calculation are shown followed by the results of the forced response calculation. The system response was predicted for two types of forcing. A constant magnitude excitation with a wide frequency variation was applied at the bearings as one forcing function. The normal unbalance force at the midspan was the second source of excitation. The results of this extended Jeffcott solution gives useful design guidance for the influence of the first and third modes of a symmetric rotor system.

Keesee, J.; Rawal, D.; Kirk, R. Gordon

1991-01-01

389

The inclusion of drag forces in the restricted problem of three bodies and the instability of the triangular points.  

NASA Astrophysics Data System (ADS)

If the restricted problem of three bodies is modified so that the third body experiences a drag force proportional to its velocity relative to a surrounding medium which is modelled so that the triangular points remain equilibria, then, in a linear analysis these points are unstable. The long-period oscillations become associated with an exponential factor eat with positive a. This has been confirmed by numerical integration of the complete nonlinear equations. Variations in the kinematics of the surrounding medium and in its density are also considered: the instability remains.

Danby, J. M. A.

390

Casimir interaction between two magnetic metals in comparison with nonmagnetic test bodies  

NASA Astrophysics Data System (ADS)

We present the complete results for the dynamic experiment on measuring the gradient of the Casimir force between magnetic (Ni-coated) surfaces of a plate and a sphere. Special attention is paid to the description of some details of the setup, its calibration, error analysis, and background effects. Computations are performed in the framework of the Lifshitz theory at nonzero temperature with an account of analytic corrections to the proximity force approximation and of surface roughness using both the Drude and the plasma model approaches. The theory of magnetic interaction between a sphere and a plate due to domain structure of their surfaces is developed for both out-of-plane and in-plane magnetizations in the absence and in the presence of spontaneous magnetization. It is shown that in all cases the magnetic contribution to the measured force gradients is much smaller than the total experimental error. The comparison between experiment and theory is done using the rigorous statistical method. It is shown that the theoretical approach taking into account dissipation of free electrons is excluded by the data at a 95% confidence level. The approach neglecting dissipation is confirmed by the data at more than 90% confidence level. We prove that the results of experiments with Ni-Ni, Ni-Au, and Au-Au surfaces taken together cannot be reconciled with the approach including free electrons dissipation by the introduction of any unaccounted background force, either attractive or repulsive.

Banishev, A. A.; Klimchitskaya, G. L.; Mostepanenko, V. M.; Mohideen, U.

2013-10-01

391

Force field development for actinyl ions via quantum mechanical calculations: an approach to account for many body solvation effects.  

PubMed

Advances in computational algorithms and methodologies make it possible to use highly accurate quantum mechanical calculations to develop force fields (pair-wise additive intermolecular potentials) for condensed phase simulations. Despite these advances, this approach faces numerous hurdles for the case of actinyl ions, AcO2(n+) (high-oxidation-state actinide dioxo cations), mainly due to the complex electronic structure resulting from an interplay of s, p, d, and f valence orbitals. Traditional methods use a pair of molecules (“dimer”) to generate a potential energy surface (PES) for force field parametrization based on the assumption that many body polarization effects are negligible. We show that this is a poor approximation for aqueous phase uranyl ions and present an alternative approach for the development of actinyl ion force fields that includes important many body solvation effects. Force fields are developed for the UO2(2+) ion with the SPC/Fw, TIP3P, TIP4P, and TIP5P water models and are validated by carrying out detailed molecular simulations on the uranyl aqua ion, one of the most characterized actinide systems. It is shown that the force fields faithfully reproduce available experimental structural data and hydration free energies. Failure to account for solvation effects when generating PES leads to overbinding between UO2(2+) and water, resulting in incorrect hydration free energies and coordination numbers. A detailed analysis of arrangement of water molecules in the first and second solvation shell of UO2(2+) is presented. The use of a simple functional form involving the sum of Lennard-Jones + Coulomb potentials makes the new force field compatible with a large number of available molecular simulation engines and common force fields. PMID:22857380

Rai, Neeraj; Tiwari, Surya P; Maginn, Edward J

2012-09-01

392

Leg intramuscular pressures and in vivo knee forces during lower body positive and negative pressure treadmill exercise.  

PubMed

Quantifying muscle and joint forces over a broad range of weight bearing loads during exercise may provide data required to improve prosthetic materials and better protect against muscle and bone loss. Collectively, leg intramuscular pressure (IMP), ground reaction force (GRF), and the instrumented tibial tray force measurements provide a comprehensive assessment of leg muscle and joint biomechanical effects of gravity during exercise. Titration of body weight (BW) by lower body negative pressure (LBNP) and lower body positive pressure (LBPP) can reproducibly modulate IMP within leg muscle compartments. In addition, previous studies document peak tibial forces during various daily activities of 2.2 to 2.5 BW. The study objective was to determine the IMPs of the leg, axial compressive force on the tibia in vivo, vertical GRF, and knee range of motion during altered BW levels using LBPP and LBNP treadmill exercise. We hypothesize that peak GRF, peak tibial forces, and peak IMPs of the leg correlate linearly with percent BW, as generated across a broad range of upright LBPP and supine LBNP exercise. When running at 2.24 m/s the leg IMPs significantly increased over the loading range of 60% to 140% BW with LBPP and LBNP (P < 0.001); as expected, leg IMPs were significantly higher when running compared with standing (P < 0.001). During upright LBPP, total axial force at the knee increased linearly as a function of BW at 0.67 m/s (R(2) = 0.90) and 1.34 m/s (R(2) = 0.98). During supine LBNP, total axial force at the knee increased linearly as a function of BW at 0.67 m/s (R(2) = 0.98) and 1.34 m/s (R(2) = 0.91). The present study is the first to measure IMPs and peak tibial forces in vivo during upright LBPP, upright LBNP, and supine LBNP exercise. These data will aid the development of rehabilitation exercise hardware and prescriptions for patients and astronauts. PMID:22539171

Macias, Brandon R; D'Lima, Darryl D; Cutuk, Adnan; Patil, Shantanu; Steklov, Nick; Neuschwander, Timothy B; Meuche, Sabine; Colwell, Clifford W; Hargens, Alan R

2012-07-01

393

The role of domain wall forces on thermal-magnetically formed marks in heat-assisted magnetic probe recording  

NASA Astrophysics Data System (ADS)

We characterize a method of heat-assisted magnetic recording (HAMR), which may be applied for high-density probe storage system. The magnetic recording medium is a CoNi/Pt multilayered film, suitable for perpendicular recording. The heating source is the field emission current from a scanning tunneling microscopy(STM) tip, with pulse voltages added between the tip and the film. Writing shows a threshold voltage of 4V. Marks with an average size of 165nm were achieved for pulses above 4V. A model of dynamic domain formation is applied to simulate the process of the formation of marks. The effect of domain wall forces is discussed. Simulation results agree with experiments well, without the need of taking domain wall forces into account.

Zhang, Li; Zu, Xiao-Tao

2006-11-01

394

Edge detection of magnetic body using horizontal gradient of pseudogravity anomaly  

NASA Astrophysics Data System (ADS)

Potential field methods are used extensively in mineral exploration. These methods also are used as reconnaissance method in oil and gas exploration. In Contrast with gravity anomaly the magnetic surveying produces dipolar anomaly which is caused complicated interpretation rather than gravity anomaly. The observation magnetic anomaly in each location other than magnetic poles has displacement rather than causative body. Several methods are used to overcome to this problem such as reduction to the pole (RTP) that an asymmetric anomaly is converted to symmetrical anomaly. Boundary analysis is another method to distinguish causative magnetic body from observed magnetic data directly. One of the applicable methods in boundary detection of local scale magnetic anomaly is total gradient of pseudogravity anomaly. In this method, pseudogravity anomaly is calculated in the first step. Pseudogravity converts the magnetic field into gravity field that would be observed if the magnetization distribution were to be replaced with an identical density distribution. This filter is a linear filter that is created in the frequency domain. Poisson's relationship between magnetic and gravity potential can be used for magnetic and gravity anomaly transformation to each other. Pseudogravity transformation is done in 3 steps (1) Fourier transform of magnetic data to frequency domain. (2) Multiplying the result of step (1) on to pseudogravity filter expression. (3) Inverse Fourier transform to space domain. It is a useful technique for the interpretation of major magneto- tectonic provinces as it simplifies anomaly patterns and focuses on large scale features rather than local details. After this process the horizontal gradient of calculated pseudogravity anomaly is computed and mapped in surveying scale. In this image maximum value of total horizontal gradient determines magnetic body edge. In this work we applied this method to synthetic magnetic data from prismatic model and also in magnetic data from Gol-Gohar mining area from Iran. This area is one of the iron ore in Iran and located in 1:250000 map in Neyriz geological block. For implementation the described method to studied area observation magnetic anomaly was transformed to pseudogravity anomaly at the first step. Then horizontal gradient of this anomaly was calculated and mapped. Maximum value of horizontal gradient of psedogravity as form of two bands located in magnetic anomaly trend direction. Field observations show an iron vein with 30m width that using described technique as a boundary detection method, confirms this feature. Keywords: Magnetization, Edge detection, Reduction to the pole, pseudogravity, Poisson's relationship, Horizontal gradient, Gol-Gohar.

Alamdar, K.; Ansari, A. H.; Ghorbani, A.

2009-04-01

395

Embedding Circular Force-Free Flux Ropes in Potential Magnetic Fields  

NASA Astrophysics Data System (ADS)

We propose a method for constructing approximate force-free equilibria in active regions that locally have a potential bipolar-type magnetic field with a thin force-free flux rope embedded inside it. The flux rope has a circular-arc axis and circular cross-section in which the interior magnetic field is predominantly toroidal (axial). Its magnetic pressure is balanced outside by that of the poloidal (azimuthal) field created at the boundary by the electric current sheathing the flux rope. To facilitate the implementation of the method in our numerical magnetohydrodynamic (MHD) code, the entire solution is described in terms of the vector potential of the magnetic field. The parameters of the flux rope can be chosen so that a subsequent MHD relaxation of the constructed configuration under line-tied conditions at the boundary provides a numerically exact equilibrium. Such equilibria are an approximation for the magnetic configuration preceding solar eruptions, which can be triggered in our model by imposing suitable photospheric flows beneath the flux rope. The proposed method is a useful tool for constructing pre-eruption magnetic fields in data-driven simulations of solar active events. Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD.

Titov, V. S.; Torok, T.; Mikic, Z.; Linker, J.

2013-12-01

396

Magnetic irreversibility and pinning force density in the Ti-V alloys  

NASA Astrophysics Data System (ADS)

We present a study of critical current density estimated through dc magnetization measurements in the superconducting alloys Ti60V40 and Ti70V30. The magnetization is irreversible below the irreversibility field (BIrr), which is different from the upper critical field for the alloys. Additionally, the alloys are found to exhibit a peak effect in magnetization below the upper critical field. The critical current densities of the alloys estimated from the magnetization results decrease strongly with increasing magnetic field. The pinning force density follows a universal scaling relation with respect to the magnetic field divided by the BIrr. The field dependence of the pinning force density is analyzed in terms of the size of the grains of the main ? phase, the possible presence of dislocation arrays within the grains of the main phase, the presence of additional metallurgical phases, and the configuration of the grain boundaries in the system. The temperature dependence of critical current density is also analyzed within the framework of existing theories.

Matin, Md.; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Meena, R. K.; Kaul, Rakesh; Singh, M. N.; Sinha, A. K.; Roy, S. B.

2013-04-01

397

Does using a visual-representation tool foster students' ability to identify forces and construct free-body diagrams?  

NASA Astrophysics Data System (ADS)

Earlier research has shown that after physics instruction, many students have difficulties with the force concept, and with constructing free-body diagrams (FBDs). It has been suggested that treating forces as interactions could help students to identify forces as well as to construct the correct FBDs. While there is evidence that identifying interactions helps students in quantitative problem solving, there is no previous research investigating the effect of a visual-representation tool—an interaction diagram (ID)—on students’ ability to identify forces, and to construct the correct FBDs. We present an empirical study conducted in 11 Finnish high schools on students (n=335, aged 16) taking their first, mandatory, introductory physics course. The study design involved groups of students having heavy, light, or no use of IDs. The heavy and light ID groups answered eight pairs of ID and FBD questions in various physical contexts and the no ID group answered two of the eight FBD questions. The results indicate that the heavy ID group outperformed both the light and the no ID groups in identifying forces and constructing the correct FBDs. The analysis of these data indicates that the use of IDs is especially beneficial in identifying forces when constructing FBDs.

Savinainen, Antti; Mäkynen, Asko; Nieminen, Pasi; Viiri, Jouni

2013-06-01

398

Measurement of the gradient of the Casimir force between a nonmagnetic gold sphere and a magnetic nickel plate  

NASA Astrophysics Data System (ADS)

We measured the gradient of the Casimir force between an Au sphere and a plate made of ferromagnetic metal (Ni). It is demonstrated that the magnetic properties influence the force magnitude. This opens prospective opportunities for the control of the Casimir force in nanotechnology and for obtaining Casimir repulsion by using ferromagnetic dielectrics.

Banishev, A. A.; Chang, C.-C.; Klimchitskaya, G. L.; Mostepanenko, V. M.; Mohideen, U.

2012-05-01

399

Few-body system of charged fermions in a strong magnetic field  

NASA Astrophysics Data System (ADS)

We consider a few-body system of interacting charged fermions in a strong magnetic field. We assume that the charged fermions interact via a Coulomb interaction potential. Additionally, there is a one-particle confining potential term that is superimposed to the two-particle interaction potential. We find out that in the limit of a high magnetic field the behavior of this system resembles that of strongly correlated electronic systems in the quantum Hall regime. Numerical results obtained via diagonalization procedures indicate that the few-body system energy spectrum is quasi-degenerate for a one-particle confining potential resembling a parabolic one.

Ciftja, Orion; Rasco, Torrance; Vargas, Guillermo; Sutton, Bradley; Njuguna, Julia

2013-04-01

400

Noninvasive Oxygen Partial Pressure Measurement of Human Body Fluids In Vivo Using Magnetic Resonance Imaging1  

Microsoft Academic Search

Rationale and Objectives. The oxygen partial pressure (pO2) of human body fluids reflects the oxygenation status of sur- rounding tissues. All existing fluid pO2 measurements are invasive, requiring either microelectrode\\/optode placement or fluid removal. The purpose of this study is to develop a noninvasive magnetic resonance imaging method to measure the pO2 of human body fluids. Materials and Methods. We

Greg Zaharchuk; Reed F. Busse; Guy Rosenthal; Geoffery T. Manley; Orit A. Glenn; William P. Dillon

401

Strength of reduced two-body spin-orbit interaction from a chiral three-nucleon force  

NASA Astrophysics Data System (ADS)

The contribution of the chiral three-nucleon force to the strength of effective spin-orbit coupling is estimated. We construct a reduced two-body interaction by folding single-nucleon degrees of freedom of the three-nucleon force in nuclear matter. The spin-orbit strength is evaluated by the Scheerbaum factor obtained by a G-matrix calculation in nuclear matter with the two-nucleon interaction plus the reduced two-nucleon interaction. The inability of modern realistic two-nucleon interactions to account for the empirical spin-orbit strength is overcome. We found that spin-orbit coupling is weaker in a neutron-rich environment. Because the spin-orbit component of the three-nucleon force is determined by low-energy constants fixed in the two-nucleon sector, the present estimation has a small uncertainty.

Kohno, M.

2012-12-01

402

A Non-Linear Force-Free Field Model for the Solar Magnetic Carpet  

NASA Astrophysics Data System (ADS)

The magnetic carpet is defined to be the small-scale photospheric magnetic field of the quiet-Sun. Recent high resolution, high cadence observations have shown that although small-scale, the magnetic carpet is far from 'quiet', it is continually evolving in a complex and dynamic manner. I will present a two-component model for the dynamic evolution of the Sun's magnetic carpet. The first component is a 2D model for the photospheric evolution of the small-scale solar magnetic field, that reproduces many observed parameters. The basic evolution of magnetic elements within the model is governed by a supergranular flow profile. In addition, magnetic elements may evolve through the processes of emergence, cancellation, coalescence and fragmentation. The synthetic magnetograms produced by the 2D model are then applied as photospheric boundary data to drive the continuous evolution of a 3D non-linear force-free coronal field. We studied the resultant complex, small-scale coronal magnetic field, in particular the energetics of the field.

Meyer, Karen; Mackay, D.; van Ballegooijen, A.; Parnell, C.

2013-07-01

403

On-chip manipulation of continuous picoliter-volume superparamagnetic droplets using a magnetic force.  

PubMed

A microfluidic device for generating monodisperse superparamagnetic droplets and rapidly manipulating desired droplets into designated sub-microchannels by an external magnetic force is described. Superparamagnetic magnetite (Fe3O4) nanoparticles are synthesized by a chemical co-precipitation method. They are well dispersed in the water-phase to form a superparamagnetic fluid that is sheared into picoliter-volume monodisperse superparamagnetic droplets by the oil-phase in a T-junction PDMS microchannel. Superparamagnetic droplets always flow into sub-microchannel 1 due only to laminar flow without a magnetic field. But they are deflected from the direction of laminar flow by a perpendicular magnetic field. The results show that the deflection is proportional to the magnetic field gradient and magnetic nanoparticle concentration, and it is closely related to the magnet position. The observed experimental results make a good match with theoretical analysis. Single or bulk superparamagnetic droplets are successfully manipulated into the designated sub-microchannels 2 and 3 respectively, only by changing the positions of the magnet. Relatively high efficiency is obtained with more than 10 superparamagnetic droplets precisely manipulated per second. This simple and robust apparatus has wide applications in high throughput drug delivery/screening, immunoassay, cell research and synthesis of magnetic microparticles due to good biological compatibility and monodispersity of superparamagnetic droplets. PMID:19789755

Zhang, Kai; Liang, Qionglin; Ma, Sai; Mu, Xuan; Hu, Ping; Wang, Yiming; Luo, Guoan

2009-10-21

404

Robust tracking control of a magnetically suspended rigid body  

NASA Technical Reports Server (NTRS)

This study is an application of H-infinity and micro-synthesis for designing robust tracking controllers for the Large Angle Magnetic Suspension Test Facility. The modeling, design, analysis, simulation, and testing of a control law that guarantees tracking performance under external disturbances and model uncertainties is investigated. The type of uncertainties considered and the tracking performance metric used is discussed. This study demonstrates the tradeoff between tracking performance at low frequencies and robustness at high frequencies. Two sets of controllers were designed and tested. The first set emphasized performance over robustness, while the second set traded off performance for robustness. Comparisons of simulation and test results are also included. Current simulation and experimental results indicate that reasonably good robust tracking performance can be attained for this system using multivariable robust control approach.

Lim, Kyong B.; Cox, David E.

1994-01-01

405

Observation of force-detected nuclear magnetic resonance in a homogeneous field  

PubMed Central

We report the experimental realization of BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient), a sensitive and general method of magnetic resonance. The prototype millimeter-scale NMR spectrometer shows signal and noise levels in agreement with the design principles. We present 1H and 19F NMR in both solid and liquid samples, including time-domain Fourier transform NMR spectroscopy, multiple-pulse echoes, and heteronuclear J spectroscopy. By measuring a 1H-19F J coupling, this last experiment accomplishes chemically specific spectroscopy with force-detected NMR. In BOOMERANG, an assembly of permanent magnets provides a homogeneous field throughout the sample, while a harmonically suspended part of the assembly, a detector, is mechanically driven by spin-dependent forces. By placing the sample in a homogeneous field, signal dephasing by diffusion in a field gradient is made negligible, enabling application to liquids, in contrast to other force-detection methods. The design appears readily scalable to ?m-scale samples where it should have sensitivity advantages over inductive detection with microcoils and where it holds great promise for application of magnetic resonance in biology, chemistry, physics, and surface science. We briefly discuss extensions of the BOOMERANG method to the ?m and nm scales.

Madsen, L. A.; Leskowitz, G. M.; Weitekamp, D. P.

2004-01-01

406

A SELF-CONSISTENT NONLINEAR FORCE-FREE SOLUTION FOR A SOLAR ACTIVE REGION MAGNETIC FIELD  

SciTech Connect

Nonlinear force-free solutions for the magnetic field in the solar corona constructed using photospheric vector magnetic field boundary data suffer from a basic problem: the observed boundary data are inconsistent with the nonlinear force-free model. Specifically, there are two possible choices of boundary conditions on vertical current provided by the data, and the two choices lead to different force-free solutions. A novel solution to this problem is described. Bayesian probability is used to modify the boundary values on current density, using field-line connectivity information from the two force-free solutions and taking into account uncertainties, so that the boundary data are more consistent with the two nonlinear force-free solutions. This procedure may be iterated until a set of self-consistent boundary data (the solutions for the two choices of boundary conditions are the same) is achieved. The approach is demonstrated to work in application to Hinode/Solar Optical Telescope observations of NOAA active region 10953.

Wheatland, M. S. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Regnier, S. [School of Mathematics and Statistics, University of St Andrews, St Andrews, Fife KY16 9SS (United Kingdom)], E-mail: m.wheatland@physics.usyd.edu.au, E-mail: stephane@mcs.st-andrews.ac.uk

2009-08-01

407

Report of the Task Force on SSC Magnet System Test Site  

SciTech Connect

The Task Force on SSC Magnet Systems test Site was appointed by Maury Tigner, Director of the SSC, Phase 1 in August 1984. In brief, the charge asked the Task Force to make a critical evaluation of potential test sites for a major SSC magnet System Test Facility (STF) with regard to: (1) availability of the needed space, utilities, staff and other requirements on the desired time scale; and (2) the cost of preparing the sites for the tests and for operating the facilities during the test period. The charge further suggests that, by virtue of existing facilities and availability of experienced staff, BNL and FNAL are the two best candidate sites and that is therefore appears appropriate to restrict the considerations of the Task Force to these sites. During the subsequent deliberations of the Task Force, no new facts were revealed that altered the assumptions of the charge in this regard. The charge does not ask for a specific site recommendation for the STF. Indeed, an agreement on such a recommendation would be difficult to achieve considering the composition of the Task Force, wherein a large fraction of the membership is drawn from the two contending laboratories. Instead, we have attempted to describe the purpose of the facility, outline a productive test program, list the major facilities required, carefully review the laboratories` responses to the facility requirements, and make objective comparisons of the specific features and capabilities offered.

NONE

1984-10-01

408

Low-temperature magnetic properties of iron-bearing sulfides and their contribution to magnetism of cometary bodies  

NASA Astrophysics Data System (ADS)

In this study we present a review of low-temperature magnetic properties of alabandite (Fe, Mn)S, daubreelite FeCr 2S 4, pyrrhotite Fe 1-xS and troilite FeS updated with new experimental data. The results indicate that besides FeNi alloys mainly daubreelite with its Curie temperature T C ˜ 150 K and strong induced and remanent magnetizations may be a significant magnetic mineral in cold environments and may complement that of FeNi or even dominate magnetic properties of sulfide rich bodies at temperatures below T C. Comets are known to contain iron-bearing sulfides within dusty fraction and their surfaces are subject to temperature variations in the range of 100-200 K down to the depth of several meters while the cometary interior is thermally stable at several tens of Kelvin which is within the temperature range where alabandite, daubreelite or troilite are "magnetic". Thus not only FeNi alloys, but also sulfides have to be considered in the interpretation of magnetic data from cometary objects such as will be delivered by Rosetta mission. Modeling indicates that magnetic interactions between cometary nucleus containing iron-bearing sulfides and interplanetary magnetic field would be difficult, but not impossible, to detect from orbit. Rosetta's Philae lander present on the surface would provide more reliable signal.

Kohout, Tomáš; Kosterov, Andrei; Haloda, Jakub; Týcová, Patricie; Zbo?il, Radek

2010-08-01

409

Forces  

NSDL National Science Digital Library

The representation depicts what forces are and how they can change the motion and shape of objects in an animated slide show. This resource also includes an interactive test and review of the material, and can be downloaded for offline use.

410

The Effect of a Tangential Force on the Contact of Metallic Bodies  

Microsoft Academic Search

When two solid bodies are brought together, they are usually very heavily deformed in their region of contact. Bowden & Tabor (1954) have discussed very fully how a consideration of this deformation may be used to explain friction. They have shown that the interaction between the two bodies in the area of contact, where they come very close together on

J. S. Courtney-Pratt; E. Eisner

1957-01-01

411

Active health monitoring in a rotating cracked shaft using active magnetic bearings as force actuators  

NASA Astrophysics Data System (ADS)

We consider the active health monitoring of rotordynamic systems in the presence of breathing shaft cracks. The shaft is assumed to be supported by conventional bearings and an active magnetic bearing (AMB) is used in a mid-shaft or outboard location as an actuator to apply specified, time-dependent forcing on the system. These forces, if properly chosen, induce a combination resonance that can be used to identify the magnitude of the time-dependent stiffness arising from the breathing mode of the shaft crack.

Mani, G.; Quinn, D. D.; Kasarda, M.

2006-06-01

412

Rotordynamic forces acting on a centrifugal open impeller in whirling motion by using active magnetic bearing  

NASA Astrophysics Data System (ADS)

Rotordynamic forces acting on a centrifugal open impeller of a rocket engine turbopump were measured using a rotordynamic test stand controlled by active magnetic bearings. The tangential rotordynamic force ft had a small constantly negative value in the measured range. The direct stiffness K had a positive value under various test conditions. In general, direct stiffness K of a closed impeller had a negative value because of the Bernoulli effect. In the case of open impellers, the Bernoulli effect is speculated to be smaller because the absence of a front shroud makes K positive.

Nagao, N.; Eguchi, M.; Uchiumi, M.; Yoshida, Y.

2013-03-01

413

On some early attempts to determine the variation of the magnetic force with distance  

NASA Astrophysics Data System (ADS)

We describe two experiments made by the 18th-century physicists Francis Hauksbee and Pieter van Musschenbroek, designed to find the dependence of the magnetic force on distance. From the experimental results, given in the form of tables, the authors did not infer any simple law. We calculated the values obtained by assuming that the force varies as the inverse square of the distance and found a good agreement with their results. It therefore appears that these remarkable experiments could have provided an experimental proof of the law.

Mussard, Mickaël; Le Mouël, Jean-Louis; Poirier, Jean-Paul

2013-05-01

414

Asymptotic analysis of force-free magnetic fields of cylindrical symmetry  

NASA Technical Reports Server (NTRS)

It is known from computer calculations that if a force-free magnetic-field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution, and, in the process, the energy of the field increases progressively. Analysis of a simple model of force-free fields of cylindrical symmetry leads to simple asymptotic expressions for the extent and energy of such a configuration. The analysis is carried through for both spherical and planar source surfaces. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

Sturrock, P. A.; Antiochos, S. K.; Roumeliotis, G.

1995-01-01

415

Hyperpolarization of human mesenchymal stem cells in response to magnetic force.  

PubMed

Magnetic particle tagging techniques are currently being applied to tissue engineering applications such as controlled differentiation of mesenchymal stem cells (MSC). In order to define key mechanotransducers underpinning these applications, the electrophysiological responses of human MSCs (hMSC) have been investigated. Ferromagnetic microparticles were coated with L-arginyl-glycyl-L-aspartic acid in order to target the application of dynamic force (6 pN) directly to cell surface integrins. Human MSCs demonstrated cell membrane hyperpolarization responses after the application of force, mediated by BK channels and intracellular calcium release. PMID:20650701

Kirkham, Glen R; Elliot, Kerry J; Keramane, Ahmed; Salter, Donald M; Dobson, Jon P; El Haj, Alicia J; Cartmell, Sarah Harriet

2010-03-01

416

Enhanced ferromagnetism in grain boundary of Co-doped ZnO films: A magnetic force microscopy study  

NASA Astrophysics Data System (ADS)

Microscopic grain structures and magnetic properties of Co-doped ZnO-patterned films were studied by combinatorial atomic force microscopy and magnetic force microscopy (MFM) imaging. Whereas Co-doped ZnO was not uniformly magnetized, Co ions were homogeneously doped in the films and substitute from the Zn sites. Most Co:ZnO grains were weakly ferromagnetic (FM) and surrounded by strong FM foamlike grain boundaries networks. No MFM contrast was observed in pure ZnO films grown under similar conditions. The findings clearly demonstrate that defective grain boundaries and magnetic doping have key roles FM properties of diluted magnetic oxides.

Lin, M. N.; Hsu, H. S.; Lai, J. Y.; Guo, M. C.; Lin, C. Y.; Li, G. Y.; Chen, F. Y.; Huang, J. J.; Chen, S. F.; Liu, C. P.; Huang, J. C. A.

2011-05-01

417

Application of a constant-alpha force-free field in a toroid to fit magnetic clouds  

NASA Astrophysics Data System (ADS)

Magnetic clouds are large interplanetary flux ropes. Commonly their magnetic field configuration is fitted by a constant-alpha force-free field in a cylinder (Lundquist solution). A characteristic feature of magnetic clouds is a large rotation of the magnetic field vector. In some cases, the rotation exceeds 180 degrees and it is interpreted as a signature that the flux rope is curved. Here fits by the above mentioned solution fail and another solution is needed, a constant-alpha force-free solution in a toroid. A rather complex exact analytical solution (Tsuji solution) is compared with approximate simpler ones and fits of several magnetic clouds are presented.

Vandas, M.; Romashets, E.

2009-12-01

418

A comparison of 60 Hz uniform magnetic and electric induction in the human body  

NASA Astrophysics Data System (ADS)

High-resolution computations of induced fields are used to assess equivalent source levels for human exposure to uniform low-frequency electric and magnetic fields. These results pertain to 60 Hz foot-to-head electric excitation of the body in three positions with respect to a ground plane, and to magnetic excitation by three orthogonal source orientations. All computations are based on an anatomically derived human body model composed of 1736 873 cubic voxels with 3.6 mm edges. The data for magnetic excitation are computed using a scalar potential finite difference (SPFD) method, while those for electric excitation are computed using a hybrid method based on the SPFD method coupled with a quasistatic finite difference time domain code. The data are analysed in two ways, using an induced current density threshold of . Firstly, the various field strengths required to produce a whole-body average current density magnitude equal to the threshold are derived for each configuration, and the associated current density levels in various organs and tissues are presented. It is found that the average current density magnitude values in at least one tissue group can be up to 3 (5) times greater than the whole-body average under electric (magnetic) excitation, and that the associated maximum values can be up to 46 (28) times greater than the whole-body average under electric (magnetic) excitation, for at least one source/body configuration. Secondly, the data are analysed from the opposite point of view, in which the source levels required to induce average or maximum induced current density magnitudes at the threshold level in specific tissue groups are determined. Evaluations such as the present one should prove useful in the development of protection standards, and are also expected to aid in the understanding of results from various animal and tissue culture studies.

Dawson, Trevor W.; Caputa, Kris; Stuchly, Maria A.

1997-12-01

419

Gender differences in vestibular modulation of body mass in altered force environments  

NASA Astrophysics Data System (ADS)

Body mass regulation is affected by the gravitational environment. Gravitational and linear acceleration information is transduced by the vestibular macular receptors. In addition, there are gender differences in the regulation of body mass and composition. This study therefore investigated the role of the vestibular system in the regulation of body mass in age-matched male and female rats. Four groups of male and female rats were established. A 1G and a 2G labyrinthectomized experimental group (Labx) and a 1G and 2G control group (Con). Labyrinthectomies were accomplished by trans-tympanic injection of sodium arsanilate to remove vestibular input. Control groups experienced the same surgical procedures, but with a saline control injection. Body mass and food and water consumption data were collected twice weekly. Baseline data were collected prior to surgery. There was a decrease in body mass following chemical labyrinthectomy in both male and female rats. A recovery period followed surgery to allow for the re-establishment of stable growth curves. Body mass of female experimental rats returned to the same levels as the female controls while male labyrinthectomized rats continued to regulate body mass at a lower level. All 2G groups were exposed to 8 weeks of 2G produced via centrifugation while all control groups remained at 1G. All 2G groups decreased body mass at the onset of centrifugation, with experimental groups having a smaller response than the controls. Males continued to maintain body mass at a lower level under 2G, while, again body mass of the females returned to levels similar to controls. At the conclusion of the eight week centrifugation period, all four female groups had a similar body mass while differences were evident between male groups. Overall, 1G males had a higher body mass than did males exposed to 2G. Within G levels, 1G controls were heavier than 1G Labx and, in contrast, at 2G Labx had a larger body mass than controls. (Supported by NASA Grant NNA07CN33G.)

Fuller, Charles; Fuller, Patrick; Hoban-Higgins, Tana; Fuller, Charles

420

The Use of Magnets for Introducing Primary School Students to Some Properties of Forces through Small-Group Pedagogy  

ERIC Educational Resources Information Center

Seventeen Grade Six students were divided into small groups to study the concept of forces in the context of magnets and their properties. The researcher, a pre-service primary school teacher, encouraged the students into conversation about magnets and it was found that, without hesitation, they talked about their prior experience of magnets. The…

Carruthers, Rebecca; de Berg, Kevin

2010-01-01