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1

Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces  

NASA Astrophysics Data System (ADS)

We have commissioned a superconducting solenoid based apparatus designed to exert strong magnetic body forces on biological specimens and other organic materials in ambient environmental conditions for extended periods. In its room temperature bore, it can produce a maximum magnetic field-field gradient product of 16 T^2-cm-1 which is sufficient to levitate frog embryos Xenopus Laevis[1]. We will discuss how we are applying these magnetic body forces to probe the known influences of gravitational forces on frog embryos and the swimming behavior of Paramecium Caudatum. In the process, we will describe a novel method for measuring the diamagnetic susceptibilities of specimens such as paramecia.

Valles, James; Guevorkian, Karine; Wurzel, Samuel; Mihalusova, Mariana

2003-03-01

2

Exploring Magnetism: Investigating the forces of magnets  

NSDL National Science Digital Library

This activity is a classroom and lab investigation of magnetism. Students gather results of experiments involving the forces of magnets. They use this data to develop their own experiments to test properties of magnets.

3

Diamagnetic forces in superconducting magnets  

Microsoft Academic Search

We have previously reported damage to two large superconducting solenoids caused by axial expansion forces and radial compression forces. These forces, which can be greater than and are of opposite sense to the classical Lorentz forces, we have attributed to the diamagnetism of the composite superconductors. Some irregularities experienced in the operation of force cooled superconducting magnet systems appear to

R. Stevenson; D. Atherton

1975-01-01

4

High Frequency Magnetic Force Microscopy  

Microsoft Academic Search

Image magnetization dynamics on all time scales, including the ultra-short regime, is an important subject that needs to be addressed by advanced magnetic force microscopy. High frequency (microwave) and fast time-domain phenomena are fundamental properties that are also closely related to applications such as magnetic data storage. In practice, the ability to evaluate high frequency performance of magnetic recording heads

Shaoping Li

5

Three-Body Forces from n-BODY Inversion  

NASA Astrophysics Data System (ADS)

Within the context of the lowest order approximation to the calculation of the n-body bound state in the Hyperspherical Harmonic Expansion Method, the hypercentral potential may be determined from n-body spectral data. Previously, we showed how the two-body force can be determined exactly from the hypercentral potential in the absence of three-body forces. In this paper, we investigate to what extent the three-body force can be determined if the two-body force is assumed to be known. For this purpose, a three-quark system is considered.

Gavin, E. J. O.; Fiedeldey, H.; Sofianos, S. A.

6

NTNU Java: Free-Body Force Diagram  

NSDL National Science Digital Library

This applet illustrates the forces on a block on an inclined plane. A free-body diagram shows the gravitational, normal, frictional and net force vectors. The weight, angle of the plane, and coefficient of friction can be changed by the user. The user can also apply an external force to the block. The motion resulting from the forces is not shown.

Hwang, Fu-Kwun

2005-02-07

7

Secondary resonance magnetic force microscopy  

NASA Astrophysics Data System (ADS)

In this study, we have developed secondary resonance magnetic force microscopy (SR-MFM) for imaging alternating magnetic fields from a sample surface at the secondary resonant frequency of the magnetic cantilever at the same time as the topographic image. SR-MFM images of alternating magnetic fields diverging from the main pole in a driving perpendicular magnetic recording head are presented, and the divergence and convergence of the fields are discussed. The spatial resolution of SR-MFM is estimated to be 18 nm this is 2.5 times smaller than that of conventional MFM.

Tanaka, Suguru; Azuma, Yasuo; Majima, Yutaka

2012-04-01

8

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

9

Magnetic Resonance Force Microscope Development  

SciTech Connect

Our objectives were to develop the Magnetic Resonance Force Microscope (MRFM) into an instrument capable of scientific studies of buried structures in technologically and scientifically important electronic materials such as magnetic multilayer materials. This work resulted in the successful demonstration of MRFM-detected ferromagnetic resonance (FMR) as a microscopic characterization tool for thin magnetic films. Strong FMR spectra obtained from microscopic Co thin films (500 and 1000 angstroms thick and 40 x 200 microns in lateral extent) allowed us to observe variations in sample inhomogeneity and magnetic anisotropy field. We demonstrated lateral imaging in microscopic FMR for the first time using a novel approach employing a spatially selective local field generated by a small magnetically polarized spherical crystallite of yttrium iron garnet. These successful applications of the MRFM in materials studies provided the basis for our successful proposal to DOE/BES to employ the MRF M in studies of buried interfaces in magnetic materials.

Hammel, P.C.; Zhang, Z.; Suh, B.J.; Roukes, M.L.; Midzor, M.; Wigen, P.E.; Childress, J.R.

1999-06-03

10

Forced magnetic reconnection  

SciTech Connect

By studying a simple model problem, we examine the time evolution of magnetic field islands which are induced by perturbing the boundary surrounding an incompressible plasma with a resonant surface inside. We find that for sufficiently small boundary perturbations, the reconnection and island formation process occurs on the tearing mode time scale defined by Furth, Killeen, and Rosenbluth. For larger perturbations the time scale is that defined by Rutherford. The resulting asymptotic equilibrium is such that surface currents in the resonant region vanish. A detailed analytical picture of this reconnection process is presented.

Hahm, T.S.; Kulsrud, R.M.

1984-11-01

11

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

12

Simultaneous imaging of surface and magnetic forces  

NASA Astrophysics Data System (ADS)

We demonstrate quantitative force imaging of long-range magnetic forces simultaneously with near-surface van-der-Waals and contact-mechanics forces using intermodulation atomic force microscopy. Magnetic forces at the 200 pN level are separated from near-surface forces at the 30 nN level. Imaging of these forces is performed in both the contact and non-contact regimes of near-surface interactions.

Forchheimer, Daniel; Platz, Daniel; Tholén, Erik A.; Haviland, David B.

2013-07-01

13

Three dimensional force of magnet wheel with revolving permanent magnets  

Microsoft Academic Search

Lift force, thrust and lateral force characteristics of “partial overlap type magnet wheel” are presented, where “magnet wheel” is a proposed electromagnetic device for an induction repulsive type Maglev vehicle constructed with revolving permanent magnets and conducting plate, and “partial overlap type” is one type of magnet wheel. Smaller resistivity of the conducting plate induces larger lift force and lateral

Nobuo Fujii; Makoto Chida; Kokichi Ogawa

1997-01-01

14

Effect of Magnetic Dipole Moment on Magnet Forces  

Microsoft Academic Search

This paper discusses the effect of magnetic dipole moment on the ``lifting power'' of permanent magnets and on forces between magnets. To within the precision of observations, stacking identical magnets end-to-end appears to increase the dipole moment of a magnet in direct proportion to the material length of the magnet. This convenience facilitates a wide range of experiments that can

Ken Taylor; Ian Campbell; Matthew Mirochna; Robbie Stewart

2008-01-01

15

Magnetic Resonance Force Microscopy with Magnetic Tiped Cantilevers  

NASA Astrophysics Data System (ADS)

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 micron-size Alnico particle to the end of a commercial Si cantilever. We will describe the techniques and protocols used to magnetize and characterize the magnetic particles as well as the mechanical detection of electron spin resonance with these probes.

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

1998-03-01

16

Modeling solar force-free magnetic fields  

Microsoft Academic Search

A class of nonlinear force-free magnetic fields is presented, described in terms of the solutions to a second-order, nonlinear ordinary differential equation. These magnetic fields are three-dimensional, filling the infinite half-space above a plane where the lines of force are anchored. They model the magnetic fields of the sun over active regions with a striking geometric realism. The total energy

B. C. Low; Y. Q. Lou

1990-01-01

17

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

18

Effective Magnus Force on a Magnetic Vortex  

Microsoft Academic Search

In classical hydrodynamics, a Magnus force exists between a vortex and the hosting fluid acting transverse to their relative\\u000a motion. There is a quantum Magnus force acting on vortices in superfluids and superconductors and an analogous force acting\\u000a on magnetic vortices excited in spin systems. Couplings with the system quasiparticles can modify this to an effective Magnus\\u000a force by introducing

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

19

Many-Body Forces in Nuclear Shell-Model.  

National Technical Information Service (NTIS)

In the microscopic derivation of the effective Hamiltonian for the nuclear shell model many-body forces between the valence nucleons occur. These many-body forces can be discriminated in ''real'' many-body forces, which can be related to mesonic and inter...

P. K. Rath

1985-01-01

20

Superconducting magnets for whole body magnetic resonance imaging  

Microsoft Academic Search

Superconducting magnets have achieved preeminence in the magnetic resonance imaging (MRI) industry. Further growth in this market will depend on reducing system costs, extending medical applications, and easing the present siting problem. New magnet designs from Oxford address these issues. Compact magnets are economical to build and operate. Two 4 Tesla whole body magnets for research in magnetic resonance spectroscopy

M. F. Murphy

1989-01-01

21

Calculation of electromagnetic forces for magnet wheels  

SciTech Connect

The characteristics of magnet wheels for magnetic levitation and linear drives are investigated by using a three-dimensional computer simulation. Magnet wheels levitate by revolving permanent magnets over a conducting plate, in which the eddy currents are induced. The thrust is also produced by making the torque unbalance. This paper deals with the ``partial overlap type`` magnet wheels, producing the lift force and the thrust. The magnetic flux density and eddy currents are examined for the 4-pole and the 2-pole structures.

Ogawa, Kokichi; Horiuchi, Yoko [Oita Univ. (Japan). Dept. of Production Systems Engineering; Fujii, Nobuo [Kyushu Univ., Fukuoka (Japan). Dept. of Electrical and Electronics Systems Engineering

1997-03-01

22

Static forces in a superconducting magnet bearing  

SciTech Connect

Static levitation forces and stiffnesses in a superconducting bearing consisting of concentric ring magnets and a superconducting YBaCuO ring are investigated. In the field-cooled mode a levitation force of 20 N has been achieved. The axial and radial stiffnesses have values of 15 N/mm and 10 N/mm, respectively. An arrangement with two bearings supporting a high speed shaft is now under development. A possible application of superconducting magnetic bearings is flywheels for energy storage.

Stoye, P.; Fuchs, G. [Institut fuer Festkoerper- und Werkstofforschung, Dresden (Germany); Gawalek, W.; Goernert, P. [Institut fuer Physikalische Hochtechnologie, Jena (Germany); Gladun, A. [Technische Univ., Dresden (Germany)

1995-11-01

23

Force-Detected Nuclear Magnetic Resonance Probe  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy (MRFM) entails measuring the force on spins in a sample by a nearby magnetic grain as they are cyclically flipped by RF radiation in the presence of a background magnetic field. The sample is glued to a cantilever, which acts as the force detector. We have constructed a compact, LHe-cooled MRFM probe which fits in a 1'' tube, minimizing thermal drift, and allowing testing in storage dewars. The RF field is generated by a 700 ?m diameter coil in a tuned and matched tank circuit. Joule and RF heating control sample temperature. The sample is mounted on a silicon-nitride cantilever, and its magnetization is modulated at the cantilever resonance frequency by interrupted adiabatic rapid passage. Probe performance is demonstrated by measuring a 10 fN magnetic resonance signal from a sample of Nd doped Ca^19F_2.

Harrell, Lee E.; Thurber, Kent; Fainchtein, Raul; Marohn, John A.; Smith, Doran D.

2000-03-01

24

A high performance magnetic force microscope  

Microsoft Academic Search

We have constructed a high performance magnetic force microscope optimized for operation in the force gradient detection mode. The instrument incorporates a novel differential heterodyne interferometer that has a high immunity to microphonics and interference. The detection limit of the interferometer is limited by the intrinsic thermal noise of the cantilever sensor. Positioning and scanning of the sample is undertaken

M. S. Valera; A. N. Farley

1996-01-01

25

Characterization of the VIPS magnetic force actuator  

NASA Astrophysics Data System (ADS)

This paper describes the magnetic force actuation system developed for the Talon Gold program. Among the topics discussed are hardware configuration, system modelling, and the magnetic actuator performance. The actuator uses quartz crystal force sensor technology to achieve high accuracy. It is capable of + or - 18 newtons of force with accuracy better than 0.5 and bandwidth greater than 25 Hz. It has exceptional low frequency isolation characteristics over the + or - 9 millimeter range of motion. A discussion of expected performance and actual brassboard test data is included.

Hamilton, B. J.; Aldrich, J. W.; Wolke, P. J.

26

The use of electromagnetic body forces to enhance the quality of laser welds  

Microsoft Academic Search

The use of electromagnetic body forces in laser beam welding of aluminum alloys is a new method to shape the geometry and to enhance the quality of the weld seams. In this new approach, electromagnetic volume forces are utilized by applying magnetic fields and electric currents of various origins. Acting in the liquid metal, they directly affect the flow field

Guenter Ambrosy; P. Berger; H. Hügel; D. Lindenau

2003-01-01

27

Body-force stress fields defined by caustic rosettes  

Microsoft Academic Search

The method of reflected caustics was extended to the study of elastic fields due to body forces. It was shown that gage perforations create caustics under the influence of body forces which are different in shape and size than those developed in usual cases. The elastic solution of a perforated strip under the influence of an external loadp and body

P. S. Theocaris

1988-01-01

28

Light-induced attractive force between two metal bodies separated by a subwavelength slit  

NASA Astrophysics Data System (ADS)

A novel light-induced attractive force which acts as a force with negative light pressure has been revealed. The force arises by the interaction of plasmon polaritons which are excited at the surface of metal when a transverse magnetic mode propagates through a subwavelength slit between two metal bodies. The estimation of the repulsive force acting on the metal walls of the slit in the case of subwavelength TE mode propagation along the slit is presented. The explicit analytical expressions of light-induced forces between two macroscopic metal bodies or films separated by a subwavelength slit have been derived. These forces could be used to manipulate metallic macro-, micro- and nano-objects in vacuum or in a dielectric medium. Estimations of these light-induced forces show that the forces are sufficient for measurements and practical applications.

Nesterov, Vladimir; Frumin, Leonid

2011-09-01

29

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

30

Superconducting magnets for whole body magnetic resonance imaging  

SciTech Connect

Superconducting magnets have achieved preeminence in the magnetic resonance imaging (MRI) industry. Further growth in this market will depend on reducing system costs, extending medical applications, and easing the present siting problem. New magnet designs from Oxford address these issues. Compact magnets are economical to build and operate. Two 4 Tesla whole body magnets for research in magnetic resonance spectroscopy (MRS) are now in operation. Active-Shield magnets, by drastically reducing the magnetic fringe fields, will allow MRI systems with superconducting magnets to be located in previously inaccessible sites.

Murphy, M.F.

1989-03-01

31

Nuclear forces and the quantum many-body problem  

Microsoft Academic Search

1. Challenges for the nuclear many-body problem Intricate nuclear forces, which have yet to be completely determined, two different fermionic species (protons and neutrons) and the lack of an external force, generate a range and diversity of behaviours that make the nucleus a truly unique quantum many-body system. One major goal of the physics of nuclei is to develop a

B R Barrett; D J Dean; M Hjorth-Jensen; J P Vary

2005-01-01

32

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

33

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

34

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

35

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

36

Many-body dispersion forces of polarizable clusters and liquids  

Microsoft Academic Search

A system of atoms with embedded Drude dispersion oscillators interacting through dipole–dipole forces is simulated. Using path integrals it is shown that after the coordinates of the dispersion oscillators are integrated out, the atoms interact through many-body dispersion forces to all orders of the dipole–dipole interaction. Simulations are carried out on clusters to see if the presence of many-body forces

J. Cao; B. J. Berne

1992-01-01

37

Microflare Activity Driven by Forced Magnetic Reconnection  

NASA Astrophysics Data System (ADS)

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-1. After a separation distance of ?4400 km is reached, multiple Ellerman bombs are observed in both H? 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-1 and wavelength ?1000 km. The velocity oscillations are followed by an impulsive brightening visible in H? 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 ?3 minutes between the H?-wing and Ca-K observations indicates that the observed magnetic reconnection occurs at a height of ~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.; Browning, P. K.; Crockett, P. J.; Keenan, F. P.

2010-03-01

38

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

39

Thermodynamic properties of nuclear matter with three-body forces  

SciTech Connect

We calculate thermodynamic quantities in symmetric nuclear matter within the self-consistent Green's functions method including three-body forces. The thermodynamic potential is computed directly from a diagrammatic expansion, implemented with the CD-Bonn and Nijmegen nucleon-nucleon potentials and the Urbana three-body forces. We present results for entropy and pressure up to temperatures of 20 MeV and densities of 0.32 fm{sup -3}. While the pressure is sensitive to the inclusion of three-body forces, the entropy is not. The unstable spinodal region is identified and the critical temperature associated to the liquid-gas phase transition is determined. When three-body forces are added we find a strong reduction of the critical temperature, obtaining T{sub c}{approx_equal}12 MeV.

Soma, V. [Institute of Nuclear Physics PAN, PL-31-342 Krakow (Poland); Bozek, P. [Institute of Physics, Rzeszow University, PL-35-959 Rzeszow (Poland); Institute of Nuclear Physics PAN, PL-31-342 Krakow (Poland)

2009-08-15

40

Modeling Forces on the Human Body.  

ERIC Educational Resources Information Center

Presents five models of the human body as a mechanical system which can be used in introductory physics courses: human arms as levers, humans falling from small heights, a model of the human back, collisions during football, and the rotating gymnast. Gives ideas for discussions and activities, including Interactive Physics (TM) simulations. (WRM)

Pagonis, Vasilis; Drake, Russel; Morgan, Michael; Peters, Todd; Riddle, Chris; Rollins, Karen

1999-01-01

41

Modeling Forces on the Human Body.  

ERIC Educational Resources Information Center

|Presents five models of the human body as a mechanical system which can be used in introductory physics courses: human arms as levers, humans falling from small heights, a model of the human back, collisions during football, and the rotating gymnast. Gives ideas for discussions and activities, including Interactive Physics (TM) simulations. (WRM)|

Pagonis, Vasilis; Drake, Russel; Morgan, Michael; Peters, Todd; Riddle, Chris; Rollins, Karen

1999-01-01

42

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

43

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

44

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

45

Computation of unbalanced radial force in permanent magnet motors  

Microsoft Academic Search

Nonuniformity in magnet strength in permanent magnet motors results in a vibration-inducing unbalanced force acting on the rotor. This force is the difference of two large numbers and as such is difficult to determine precisely with numerical models. In this paper, a permanent magnet motor with unbalanced magnets is analyzed by the finite element method. Three different techniques for computing

S. J. Salon; M. Howe; C. J. Slavik; M. J. DeBortoli; R. J. Nevins

1998-01-01

46

Magnetic clouds and force-free fields with constant alpha  

Microsoft Academic Search

Magnetic clouds observed at 1 AU are modeled as cylindrically symmetric, constant alpha force-free magnetic fields. The model satisfactorily explains the types of variations of the magnetic field direction that are observed as a magnetic cloud moves past a spacecraft in terms of the possible orientations of the axis of a magnetic cloud. The model also explains why the magnetic

L. F. Burlaga

1988-01-01

47

Magnetic deformation of ferrogel bodies: Procrustes effect  

NASA Astrophysics Data System (ADS)

Deformation of spheroidal ferrogel bodies caused by a uniform magnetic field is investigated theoretically. The deformation is induced by two competitive mechanisms—magnetostatic and magnetostrictive. The former is due to the demagnetizing field of the sample and hence depends on its shape, while the latter originates from the magnetoelasticity of ferrogel and is shape independent. Both mechanisms are dipolar in nature and contribute—for a body of commensurate dimensions—oppositely to the effect. For an isotropic ferrogel sphere, the magnetostatic contribution still prevails and the magnetic field elongates the body. The two opposing mechanisms balance each other out for a prolate spheroidal sample with the axes aspect ratio a/b?1.3 . It determines the so-called “Procrustes point” or “Procrustes size”—the magnetic field shrinks the body if a>1.3b and stretches it when a<1.3b .

Morozov, Konstantin; Shliomis, Mark; Yamaguchi, Hiroshi

2009-04-01

48

Magnetic deformation of ferrogel bodies: Procrustes effect.  

PubMed

Deformation of spheroidal ferrogel bodies caused by a uniform magnetic field is investigated theoretically. The deformation is induced by two competitive mechanisms-magnetostatic and magnetostrictive. The former is due to the demagnetizing field of the sample and hence depends on its shape, while the latter originates from the magnetoelasticity of ferrogel and is shape independent. Both mechanisms are dipolar in nature and contribute-for a body of commensurate dimensions-oppositely to the effect. For an isotropic ferrogel sphere, the magnetostatic contribution still prevails and the magnetic field elongates the body. The two opposing mechanisms balance each other out for a prolate spheroidal sample with the axes aspect ratio a/b approximately 1.3 . It determines the so-called "Procrustes point" or "Procrustes size"-the magnetic field shrinks the body if a>1.3b and stretches it when a<1.3b . PMID:19518165

Morozov, Konstantin; Shliomis, Mark; Yamaguchi, Hiroshi

2009-04-24

49

Methods for Calculating Magnus Forces on Slender Bodies of Revolution.  

National Technical Information Service (NTIS)

Theories for predicting the Magnus force for slender, pointed bodies of revolution at small angle of attack and small spin rates are reviewed. A semi-empirical method for calculating C(Y,P) is discussed and shown to be applicable to a variety of bodies an...

J. E. Milton

1974-01-01

50

Many-body effects for critical Casimir forces  

NASA Astrophysics Data System (ADS)

Within mean-field theory we calculate the scaling functions associated with critical Casimir forces for a system consisting of two spherical colloids immersed in a binary liquid mixture near its consolute point and facing a planar, homogeneous substrate. For several geometrical arrangements and boundary conditions we analyze the normal and the lateral critical Casimir forces acting on one of the two colloids. We find interesting features such as a change of sign of these forces upon varying either the position of one of the colloids or the temperature. By subtracting the pairwise forces from the total force we are able to determine the many-body forces acting on one of the colloids. We have found that the many-body contribution to the total critical Casimir force is more pronounced for small colloid-colloid and colloid-substrate distances, as well as for temperatures close to criticality, where the many-body contribution to the total force can reach up to 25%.

Mattos, T. G.; Harnau, L.; Dietrich, S.

2013-02-01

51

Energy and force between two magnetic nanotubes  

NASA Astrophysics Data System (ADS)

The interaction energy and force between two parallel thin magnetic nanotubes is calculated using four different approaches. Although they agree for separation distances over 10 times the radius of any tube, some differences appear for shorter distances. Two exact methods giving identical results face handling difficulties in comparison with an approximate method based on a truncated expansion which produces fair enough results for distances to be found in the range of interest. Numerical calculations are done for cobalt particles of dimensions corresponding to nanotubes already manufactured and with properties reported in the literature. The force between two identical and parallel Co nanotubes (L=60?m,D=180nm), separated by a distance of 300 nm is of the order of few microdynes.

Suarez, O. J.; Vargas, P.; Vogel, E. E.

2009-11-01

52

Experiments Using Force-Detected Nuclear Magnetism  

NASA Astrophysics Data System (ADS)

We present progress on our Nuclear Magnetic Resonance Force Microscopy (NMRFM) experiments, interferometer instrumentation, and double-torsional oscillator fabrication. Our new ^3He probe is in the final stages of testing and will be utilized to perform single-spin feasibility experiments at 300 millikelvin. We are also currently scanning for the boron resonance in MgB2 using our ^4He probe. With our room-temperature probe we are currently studying double and multiple resonance effects in NH4PF6 and are preparing to study dynamics and diffusion in soft condensed matter. In addition we will present results from our fabricated double-torsional oscillators using electron beam lithography with a minimum detectable force of 1.8x10-18 N/?Hz.

Chia, Han-Jong; Lu, Wei; Guchhait, Samaresh; Cardenas, Rosa; Esteve, Isaac; Millan, Michelle; Markert, John

2007-03-01

53

Unbalanced magnetic forces in rotational unsymmetrical transverse flux machine  

Microsoft Academic Search

The torque and unbalanced magnetic forces in a small flux concentrating permanent magnet transverse flux machine (FCPM-TFM) in segmented compact structure, which are the resultants of the tangential; axial and normal magnetic forces, respectively, are in general influenced by pole-teeth-winding configuration. The paper calculates the torque and unbalanced magnetic forces using finite element (FE-) method by solving Maxwell stress tensor

Salwa Baserrah; Keno Rixen; Bernd Orlik

2010-01-01

54

Dust Transport And Force Equilibria In Magnetized Dusty DC Discharges  

SciTech Connect

We have performed experiments on magnetized dusty Argon DC discharges. Here we report on the characterization of the plasma- and the dustparameters and on the response of the dust particles and the plasma to a change in the magnetic configuration inside the discharge. Finally, we show a case in which the balance of forces acting on the dust particles differs from the classical balance (in which the electrostatic force balances the downward force of gravity). In this case the electrostatic force acts as a downward force on the dust particles. From observations we will argue that the ion drag force might be the force that balances this downward electrostatic force.

Land, Victor [FOM Institute for Plasma Physics Rijnhuizen, Association Euratom-Fom (Netherlands); Thomas, Edward Jr.; Williams, Jeremaiah [Plasma Sciences Laboratory, Auburn University (United States)

2005-10-31

55

Dust Transport And Force Equilibria In Magnetized Dusty DC Discharges  

NASA Astrophysics Data System (ADS)

We have performed experiments on magnetized dusty Argon DC discharges. Here we report on the characterization of the plasma- and the dustparameters and on the response of the dust particles and the plasma to a change in the magnetic configuration inside the discharge. Finally, we show a case in which the balance of forces acting on the dust particles differs from the classical balance (in which the electrostatic force balances the downward force of gravity). In this case the electrostatic force acts as a downward force on the dust particles. From observations we will argue that the ion drag force might be the force that balances this downward electrostatic force.

Land, Victor; Thomas, Edward; Williams, Jeremaiah

2005-10-01

56

Vertical and lateral forces when a permanent magnet above a superconductor traverses in arbitrary directions  

Microsoft Academic Search

In an actual levitation system composed of high temperature superconductors (HTSs) and permanent magnets (PMs), the levitating bodies may traverse in arbitrary directions. Many previous researchers assumed that the levitating bodies moved in a vertical direction or a lateral direction in order to simplify the problem. In this paper, the vertical and lateral forces acting on the PM are calculated

Yong Yang

2008-01-01

57

Significance of Neglected Hydrodynamic Forces on the Motion of Submerged Particles Acted on by External Body Forces  

NASA Astrophysics Data System (ADS)

Recently, the manipulation of submerged particles using electromagnetic body forces has drawn increasing interest from a variety of fields, particularly medicine, where electrophoretic manipulation in lab-on-a-chip applications and magnetic drug targeting have become important areas of interest. As a direct result of this increasing interest a large number of simulations have been performed investigating the performance of devices and systems whose operation is based upon these physics. In the vast majority of cases, these simulations are based upon a force balance of the applicable body force and Stokes drag. Such simulations neglect additional hydrodynamic forces, including the added mass, Basset, Saffman, and Magnus forces. In the current study, the full equations of motion containing all of the aforementioned terms are nondimensionalized leading to a set of nondimensional parameters governing the behavior of the particle. A parametric investigation is then performed by calculating particle trajectories for both Poiseuille and Womersley flows. This analysis reveals that in many cases, the forces neglected in previous simulations are significant and should not be neglected in future studies.

Cooper, Daniel; Charonko, John; Vlachos, Pavlos

2011-11-01

58

Induced Magnetic Fields in Solar System Bodies  

NASA Astrophysics Data System (ADS)

Electromagnetic induction is a powerful technique to study the electrical conductivity of the interior of the Earth and other solar system bodies. Information about the electrical conductivity structure can provide strong constraints on the associated internal composition of planetary bodies. Here we give a review of the basic principles of the electromagnetic induction technique and discuss its application to various bodies of our solar system. We also show that the plasma environment, in which the bodies are embedded, generates in addition to the induced magnetic fields competing plasma magnetic fields. These fields need to be treated appropriately to reliably interpret magnetic field measurements in the vicinity of solar system bodies. Induction measurements are particularly important in the search for liquid water outside of Earth. Magnetic field measurements by the Galileo spacecraft provide strong evidence for a subsurface ocean on Europa and Callisto. The induction technique will provide additional important constraints on the possible subsurface water, when used on future Europa and Ganymede orbiters. It can also be applied to probe Enceladus and Titan with Cassini and future spacecraft.

Saur, Joachim; Neubauer, Fritz M.; Glassmeier, Karl-Heinz

2010-05-01

59

Low temperature magnetic force microscope utilizing a piezoresistive cantilever  

Microsoft Academic Search

We have developed a low temperature magnetic force microscope capable of operation down to 6 K in vacuum by using piezoresistive cantilevers. We use the non-contact frequency modulation technique to detect the magnetic force gradient between an iron-coated tip and the sample. We demonstrate the operation of this new instrument by obtaining images of magnetic domains in VHS tape at

C. W. Yuan; E. Batalla; M. Zacher; A. L. de Lozanne; M. D. Kirk; M. Tortonese

1994-01-01

60

Three-body forces and shell structure in calcium isotopes  

NASA Astrophysics Data System (ADS)

Understanding and predicting the formation of shell structure from nuclear forces is a central challenge for nuclear physics. While the magic numbers N = 2, 8, 20 are generally well understood, N = 28 is the first standard magic number that is not reproduced in microscopic theories with two-nucleon forces. In this paper, we show that three-nucleon forces give rise to repulsive interactions between two valence neutrons that are key to explain 48Ca as a magic nucleus, with a high 2+ excitation energy and a concentrated magnetic dipole transition strength. The repulsive three-nucleon mechanism improves the agreement with experimental binding energies. Communicated by Professor Jacek Dobaczewski

Holt, Jason D.; Otsuka, Takaharu; Schwenk, Achim; Suzuki, Toshio

2012-08-01

61

Quantitative analysis of magnetization reversal in patterned strip wire by magnetic force microscopy  

Microsoft Academic Search

Magnetic force microscopy (MFM) was used to investigate the magnetization reversal process in a patterned strip wire of permalloy thin film. The magnitude of the phase-shift of tapping mode MFM changed with the varying interactive magnetic force between the magnetic tip and the sample. By analyzing the change in values of the phase-shift, the behaviors of magnetization reversal of different

D. C. Chen; D. P. Chiang; Y. D. Yao

2006-01-01

62

Magnetic deformation of ferrogel bodies: Procrustes effect  

Microsoft Academic Search

Deformation of spheroidal ferrogel bodies caused by a uniform magnetic field is investigated theoretically. The deformation is induced by two competitive mechanisms---magnetostatic and magnetostrictive. The former is due to the demagnetizing field of the sample and hence depends on its shape, while the latter originates from the magnetoelasticity of ferrogel and is shape independent. Both mechanisms are dipolar in nature

Konstantin Morozov; Mark Shliomis; Hiroshi Yamaguchi

2009-01-01

63

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

64

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

65

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

66

Neutron star structure with modern nucleonic three-body forces  

SciTech Connect

We provide convenient parametrizations of the high-density nuclear equation of state obtained within the Brueckner-Hartree-Fock approach using different modern nucleon-nucleon potentials together with compatible microscopic nuclear three-body forces. The corresponding neutron star mass-radius relations are also presented.

Li, Z. H. [INFN-LNS, Via Santa Sofia 62, I-95123 Catania (Italy); Schulze, H.-J. [INFN Sezione di Catania, Via Santa Sofia 64, I-95123 Catania (Italy)

2008-08-15

67

The force function of two general bodies. II  

Microsoft Academic Search

The solution to the problem of the force function of two finite bodies, proposed previously by the author (1978), contains complex Stokes constants and coefficients for the products of these constants are also complex quantities formed by the products of the complex matrices of the irreducible representations of the three-dimensional pure rotation group. This solution was not, therefore, very suitable

M. Sidlichovsky

1979-01-01

68

Three-Body Forces and Neutron-Rich Exotic Nuclei  

NASA Astrophysics Data System (ADS)

Physics of three-body forces in connection to exotic nuclei will be discussed. Three-nucleon forces (3NF), especially Fujita-Miyazawa 3NF, are shown to be the key for the solution to the long-standing problem of oxygen drip line, which deviates from basic trend towards the stability line. Three-body forces produce repulsive modifications to effective interaction between valence neutrons, and make the ground states less bound. The oxygen drip line is then located at the right place. The relation to the neutron matter is presented. Applications to Ca isotopes will be presented. The shell evolution due to the 3NF depicts the raising of single-particle energies and the widening of splitting among the orbits. This is in contrast to the so-called shell quenching. The 2+ levels are calculated for Ca isotopes, suggesting about the same sub-magic structure for N = 32 and 34.

Otsuka, Takaharu; Suzuki, Toshio

2013-08-01

69

Spin-motive force due to a gyrating magnetic vortex.  

PubMed

A change of magnetic flux through a circuit induces an electromotive force. By analogy, a recently predicted force that results from the motion of non-uniform spin structures has been termed the spin-motive force. Although recent experiments seem to confirm its presence, a direct signature of the spin-motive force has remained elusive. Here we report the observation of a real-time spin-motive force produced by the gyration of a magnetic vortex core. We find a good agreement between the experimental results, theory and micromagnetic simulations, which taken as a whole provide strong evidence in favour of a spin-motive force. PMID:22617285

Tanabe, K; Chiba, D; Ohe, J; Kasai, S; Kohno, H; Barnes, S E; Maekawa, S; Kobayashi, K; Ono, T

2012-05-22

70

Managing magnetic force applied to a magnetic device by a rotating dipole field  

NASA Astrophysics Data System (ADS)

We demonstrate that the attractive magnetic force acting on a rotating magnetic device (e.g., a magnetic microrobot), actuated using a rotating magnet dipole, can be converted into a lateral force by rotating the actuator dipole according to a specific open-loop trajectory. Results show rotating magnetic devices can be rolled and simultaneously pushed along a surface by the lateral force, resulting in significant increase in velocity. We also demonstrate that the lateral force magnitude can be sufficient to levitate the magnetic device. The results apply to rotating magnetic devices of any size provided inertia has a negligible contribution to its dynamics.

Mahoney, Arthur W.; Abbott, Jake J.

2011-09-01

71

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

72

Fluctuations of the van der Waals attraction force between macroscopic bodies  

SciTech Connect

The tliccry of the fluctuations of the van der Waals (vdW) attractive force between macroscopic bodies is developed. A general equation for the spectral density of the fluctuating surface Maxwell stress (force per unit mea.) in va,cuurn nea,r the surface of a body is derived under the assumption that, inside the bodies, the random La.ngevin sources of the electric and magnetic fields (charges, polarizations, currents) are Gaussian. This spectral density of stress is an integral over frequencies of a sum of terms each of which is a product of Fourier amplitudes of two field components' correlation functions. For metallic bodies, the contribution of free electrons to the vdW force (at frequencies up to the frequency of electron scattering) is calculated. This contribution to the force and its noise grows with temperature. Application of noiseless voltage to two interacting metals across the vacuum gap between them generates an additional force noise. This additional noise is proportional to the volta.ge squared and to the spectral density of the random electric field at the frequency of noise measurement. The theoretical qualitative conclusions are in good agreement with experirncnts.

Kogan, A. S. (Aleksandr Semenovich)

2003-01-01

73

Computation of unbalanced radial force in permanent magnet motors.  

National Technical Information Service (NTIS)

Nonuniformity in magnet strength in permanent magnet motors results in a vibration-inducing unbalanced force acting on the rotor. This force is the difference of two large numbers and as such is difficult to determine precisely with numerical models. In t...

S. J. Salon M. Howe C. J. Slavik M. J. DeBortoli R. J. Nevins

1998-01-01

74

Attitude determination and stabilization of a spherically symmetric rigid body in a magnetic field  

Microsoft Academic Search

Observation and stabilization problems for a rigid body rotating about its mass centre in a time-periodic magnetic field is considered. The moment of the applied forces about the mass centre is a vector product of the field and the vector of control. The only measurement is of the field and its time derivatives in the body co-ordinates. The model describes

Georgi V. Smirnov

2001-01-01

75

Tip-induced artifacts in magnetic force microscopy images  

NASA Astrophysics Data System (ADS)

Useful sample information can be extracted from the dissipation in frequency modulation atomic force microscopy due to its correlation to important material properties. It has been recently shown that artifacts can often be observed in the dissipation channel, due to the spurious mechanical resonances of the atomic force microscope instrument when the oscillation frequency of the force sensor changes. In this paper, we present another source of instrumental artifacts specific to magnetic force microscopy (MFM), which is attributed to a magnetization switching happening at the apex of MFM tips. These artifacts can cause a misinterpretation of the domain structure in MFM images of magnetic samples.

Iglesias-Freire, Óscar; Bates, Jeffrey R.; Miyahara, Yoichi; Asenjo, Agustina; Grütter, Peter H.

2013-01-01

76

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

77

Computation of unbalanced radial force in permanent magnet motors  

SciTech Connect

Nonuniformity in magnet strength in permanent magnet motors results in a vibration-inducing unbalanced force acting on the rotor. This force is the difference of two large numbers and as such is difficult to determine precisely with numerical models. In this paper, a permanent magnet motor with unbalanced magnets is analyzed by the finite element method. Three different techniques for computing the net force on the rotor, including a recently developed field-correction approach, are compared. Sensitivities of the techniques to computational limitations and finite element mesh characteristics are discussed.

Salon, S.J.; Howe, M. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Electric Power Engineering; Slavik, C.J.; DeBortoli, M.J.; Nevins, R.J. [Lockheed Martin Corp., Schenectady, NY (United States)

1998-10-01

78

Single molecule force spectrometer with magnetic force control and inductive detection  

Microsoft Academic Search

Mechanical investigations with single molecules have opened a rich spectrum of new experiments, ranging from molecular recognition over polymer elasticity and DNA unzipping to protein unfolding. Here we present the design of a novel instrument, where the force is applied to the molecule via magnetic fields acting on a magnetic cantilever for atomic force microscopy. The performance of this instrument

A. Schemmel; H. E. Gaub

1999-01-01

79

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

80

Static and dynamic force balancing in reciprocating active magnetic refrigerators  

Microsoft Academic Search

One of the most obvious disadvantages with a reciprocating Active Magnetic Regenerative (AMR) refrigerator is the production of large unbalanced forces. Typical reciprocating AMR geometries use a single super-conducting solenoid with two AMR beds moving along the solenoid axis and spaced some distance apart. In this configuration, net forces are generally much higher than the equivalent force needed to perform

A. M. Rowe; J. A. Barclay

2002-01-01

81

Single molecule force spectrometer with magnetic force control and inductive detection  

NASA Astrophysics Data System (ADS)

Mechanical investigations with single molecules have opened a rich spectrum of new experiments, ranging from molecular recognition over polymer elasticity and DNA unzipping to protein unfolding. Here we present the design of a novel instrument, where the force is applied to the molecule via magnetic fields acting on a magnetic cantilever for atomic force microscopy. The performance of this instrument was demonstrated by measuring the binding force of biotin/avidin complexes. A new and technically very appealing detection scheme for measurements of unbinding forces was introduced, which consists of picking up the induced voltage pulse caused by a discontinuous change of the magnet position upon bond rupture.

Schemmel, A.; Gaub, H. E.

1999-02-01

82

Varying the effective buoyancy of cells using magnetic force  

NASA Astrophysics Data System (ADS)

We introduce a magnetic force buoyancy variation (MFBV) technique that employs intense inhomogeneous magnetic fields to vary the effective buoyancy of cells and other diamagnetic systems in solution. Nonswimming Paramecia have been suspended, forced to sediment and driven to rise in solution using MFBV. Details of their response to MFBV have been used to determine the magnetic susceptibility of a single Paramecium. The use of MFBV as a means by which to suspend cell cultures indefinitely is also described.

Guevorkian, Karine; Valles, James M.

2004-06-01

83

Effect of permanent-magnet irregularities in levitation force measurements.  

SciTech Connect

In the measurement of the levitation force between a vertically magnetized permanent magnet (PM) and a bulk high-temperature superconductor (HTS), PM domains with horizontal components of magnetization are shown to produce a nonnegligible contribution to the levitation force in most systems. Such domains are typically found in all PMs, even in those that exhibit zero net horizontal magnetic moment. Extension of this analysis leads to an HTS analog of Earnshaw's theorem, in which at the field-cooling position the vertical stiffness is equal to the sum of the horizontal stiffnesses, independent of angular distribution of magnetic moments within the PM.

Hull, J. R.

1999-10-14

84

Direct observation of ferromagnetic exchange by magnetic force microscopy  

Microsoft Academic Search

In this study, the exchange coupling at the interface of two different magnetic materials remains is investigated by using an original local technique combining lithography with scanning probe microscopy. A home-made magnetic force microscopy device that allows measurements in perpendicular magnetic field up to 1.8 T, operating in noncontact mode is used. The sample used is a bilayer of thin

A. Vanhaverbeke; M. Viret; O. Klein

2005-01-01

85

Force\\/position output feedback tracking control of holonomically constrained rigid bodies  

Microsoft Academic Search

In this note a new concept of force\\/position control approach for holonomically constrained rigid body systems is introduced. With this force control approach, the forces of the mechanical constraints between the rigid bodies as well as the forces of the constraints when the system's end effector interacting with the environment are to be directly controlled to desired trajectories. Our force

Khoder Melhem; El-Kebir Boukas; Luc Baron

2005-01-01

86

Nuclear Three-Body Force from the Nijmegen Potential  

NASA Astrophysics Data System (ADS)

A nuclear three-body force based on the meson-exchange approach is constructed using the same meson parameters and the exponential form factors as in the Nijmegen potential, involving four kinds of important mesons, ?, ?, ?, and ? [f0(975) and ?(760)]. For the 2?-exchange three-nucleon component, we adopt the new expansion strength constants a, b, c consistent with the contemporary ?N-scattering data base and the corresponding dipole form factor. An effective two-body interaction is derived by averaging out the third nucleon, and is self-consistently used together with the Nijmegen potential in the Brueckner-Hartree-Fock approximation. The empirical nuclear matter saturation properties are reproduced very well. At higher density the equation of state becomes rather stiff due to the strong repulsion from the (?, ?)-N three-body contribution.

Li, Z. H.; Lombardo, U.; Schulze, H.-J.; Zuo, W.

2008-02-01

87

Many-body force and mobility measurements in colloidal systems  

NASA Astrophysics Data System (ADS)

We have extended a sensitive probe of colloidal interparticle forces, blinking optical tweezers, to allow measurements of forces among groups of more than two particles. This dissertation focuses on bridging the gap between microscopic pair interactions and bulk behavior in colloidal systems by using this technique to explore the regime of few-body interactions between micron-size polymer beads suspended in oil. Electrostatic forces and each component of the mobility tensor of small groups of colloidal particles are simultaneously measured using blinking optical tweezers. When the electrostatic screening length is longer than the inter-particle separation, forces are found to be non-pairwise additive. Both pair and multi-particle forces are well described by the linearized Poisson-Boltzmann equation with constant potential boundary conditions. These findings may play an important role in understanding the structure and stability of a wide variety of systems, from micron-sized particles in oil to aqueous nanocolloids. The measurement technique presented here should be simple to further extend to systems of heterogeneous, non-spherical particles arranged in arbitrary three dimensional geometries.

Merrill, Jason W.

88

Muscle force redistributes segmental power for body progression during walking.  

PubMed

The ankle plantar flexors were previously shown to support the body in single-leg stance to ensure its forward progression [J. Biomech. 34 (2001) 1387]. The uni- (SOL) and biarticular (GAS) plantar flexors accelerated the trunk and leg forward, respectively, with each opposing the effect of the other. Around mid-stance their net effect on the trunk and the leg was negligible, consistent with the body acting as an inverted pendulum. In late stance, their net effect was to accelerate the leg and trunk forward, consistent with an active push-off. Because other muscles are active in the beginning and end of stance, we hypothesized that their active concentric and eccentric force generation also supports the body and redistributes segmental power to enable body forward progression. Muscle-actuated forward dynamical simulations that emulated observed walking kinematics and kinetics of young adult subjects were analyzed to quantify muscle contributions to the vertical and horizontal ground reaction force, and to the acceleration and mechanical power of the leg and trunk. The eccentric uniarticular knee extensors (vasti, VAS) and concentric uniarticular hip extensors (gluteus maximus, GMAX) were found to provide critical support to the body in the beginning of stance, before the plantar flexors became active. VAS also decelerated the forward motion of both the trunk and the leg. Afterwards when VAS shortens in mid-stance, it delivered the power produced to accelerate the trunk and also redistributed segmental power to the trunk by continuing to decelerate the leg. When present, rectus femoris (RF) activity in the beginning of stance had a minimal effect. But in late stance the lengthening RF accelerated the knee and hip into extension, which opposed swing initiation. Though RF was lengthening, it still accelerated the trunk forward by decelerating the leg and redistributing the leg segmental power to the trunk, as SOL does though it is shortening instead of lengthening. Force developed from highly stretched passive hip structures and active force produced by the uniarticular hip flexors assisted GAS in swing initiation. Hamstrings (HAM) decelerated the leg in late swing while lengthening and accelerated the leg in the beginning of stance while shortening. We conclude that the uniarticular knee and hip extensor muscles are critical to body support in the beginning of stance and redistribution of segmental power by muscles throughout the gait cycle is critical to forward progression of the trunk and legs. PMID:15013508

Neptune, R R; Zajac, F E; Kautz, S A

2004-04-01

89

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

90

Is the solar chromospheric magnetic field force-free?  

NASA Astrophysics Data System (ADS)

We use observations of the Na I lambda 5896 spectral line, made with the Stokes Polarimeter at Mees Solar Observatory, to measure the chromospheric vector magnetic field in NOAA active region 7216. We compute the magnetic field from observations of the Stokes parameters at six wavelengths within this spectral line using a derivative method and calculate the height dependence of the net Lorentz force in the photosphere and low chromosphere. We conclude that the magnetic field is not force-free in the photosphere, but becomes force-free roughly 400 km above the photosphere.

Metcalf, Thomas R.; Jiao, Litao; McClymont, Alexander N.; Canfield, Richard C.; Uitenbroek, Han

1995-01-01

91

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)

1997-03-01

92

Unbalanced magnetic forces in permanent magnet brushless machines with diametrically asymmetric phase windings  

Microsoft Academic Search

A general analytical model, formulated in 2-D polar coordinates, is developed to predict the unbalanced magnetic force which results in permanent magnet brushless AC and DC machines having a diametrically asymmetric disposition of slots and phase windings. It is shown that the unbalanced magnetic force can be significant in machines having a fractional ratio of slot number to pole number,

D. Ishak; Z. Q. Zhu; D. Howe

2005-01-01

93

Unbalanced Magnetic Forces in Permanent-Magnet Brushless Machines With Diametrically Asymmetric Phase Windings  

Microsoft Academic Search

A general analytical model, formulated in 2-D polar coordinates, is developed to predict the unbalanced magnetic force, which results in permanent-magnet brushless ac and dc machines having a diametrically asymmetric disposition of slots and phase windings. It is shown that the unbalanced magnetic force can be significant in machines having a fractional ratio of slot number to pole number, particularly

Z. Q. Zhu; Dahaman Ishak; David Howe; Chen Jintao

2007-01-01

94

Classical diamagnetism, magnetic interaction energies, and repulsive forces in magnetized plasmas  

NASA Astrophysics Data System (ADS)

The Bohr-van Leeuwen theorem is often summarized as saying that there is no classical magnetic susceptibility, in particular no diamagnetism. This is seriously misleading. The theorem assumes position-dependent interactions but this is not required by classical physics. Since the work of Darwin in 1920 it has been known that the magnetism due to classical charged point particles can only be described by allowing velocity-dependent interactions in the Lagrangian. Legendre transformation to an approximate Hamiltonian can give an estimate of the Darwin diamagnetism for a system of charged point particles. Comparison with experiment, however, requires knowledge of the number of classically behaving electrons in the sample. A new repulsive effective many-body force, which should be relevant in plasmas, is predicted by the Hamiltonian.

Essén, H.

2011-05-01

95

ANALYSIS OF THE MAGNETIZED FRICTION FORCE.  

SciTech Connect

A comprehensive examination of theoretical models for the friction force, in use by the electron cooling community, was performed. Here, they present their insights about the models gained as a result of comparison between the friction force formulas and direct numerical simulations, as well as studies of the cooling process as a whole.

FEDOTOV, A.V.; BRUHWILER, D.L.; SIDORIN, A.O.

2006-05-29

96

Electromotive force and huge magnetoresistance in magnetic tunnel junctions.  

PubMed

The electromotive force (e.m.f.) predicted by Faraday's law reflects the forces acting on the charge, -e, of an electron moving through a device or circuit, and is proportional to the time derivative of the magnetic field. This conventional e.m.f. is usually absent for stationary circuits and static magnetic fields. There are also forces that act on the spin of an electron; it has been recently predicted that, for circuits that are in part composed of ferromagnetic materials, there arises an e.m.f. of spin origin even for a static magnetic field. This e.m.f. can be attributed to a time-varying magnetization of the host material, such as the motion of magnetic domains in a static magnetic field, and reflects the conversion of magnetic to electrical energy. Here we show that such an e.m.f. can indeed be induced by a static magnetic field in magnetic tunnel junctions containing zinc-blende-structured MnAs quantum nanomagnets. The observed e.m.f. operates on a timescale of approximately 10(2)-10(3) seconds and results from the conversion of the magnetic energy of the superparamagnetic MnAs nanomagnets into electrical energy when these magnets undergo magnetic quantum tunnelling. As a consequence, a huge magnetoresistance of up to 100,000 per cent is observed for certain bias voltages. Our results strongly support the contention that, in magnetic nanostructures, Faraday's law of induction must be generalized to account for forces of purely spin origin. The huge magnetoresistance and e.m.f. may find potential applications in high sensitivity magnetic sensors, as well as in new active devices such as 'spin batteries'. PMID:19270681

Pham, Nam Hai; Ohya, Shinobu; Tanaka, Masaaki; Barnes, Stewart E; Maekawa, Sadamichi

2009-03-08

97

Calculating the external magnetic force on the Earth's dipole  

NASA Astrophysics Data System (ADS)

The force exerted by the external perturbation magnetic field on the magnetic moment of a planet is related to various aspects of stress balance in the magnetosphere and its interaction with the solar wind. The total force applied by the solar wind must ultimately be exerted on the planet itself, which contains essentially all the mass of the entire system (the mass fraction in the Earth's magnetosphere is less than ~ 10-20 of the total). The force is transmitted through the magnetosphere primarily (and near the planet almost exclusively) by the magnetic field. In the simplest approximation (Siscoe, 1966), the force is applied directly as the gradient of the external perturbation field at the dipole. More recently (Siscoe and Siebert, 2006; Vasyliunas, 2007), it has been recognized that coupling by Birkeland currents between the ionosphere and the magnetosphere allows the external force to be transmitted also as a J × B-c force in the ionosphere; further transmission to the planet itself then has to proceed as a mechanical stress. Because of the converging dipole field, the force in the ionosphere is greatly amplified and much stronger than the initially imposed force from the magnetosphere or solar wind, an effect sometimes described as the mechanical advantage of the magnetosphere (Vasyliunas, 2007). Empirical estimates of the force thus provide a sensitive (albeit indirect and imprecise) indicator of stresses in the outer magnetosphere, as well as a direct measure of the global input of linear momentum into the atmosphere. The total magnetic force on the planet can be calculated from measurements of magnetic perturbations by integrating the Maxwell stress tensor over the surface. I derive the formula for the three vector components of the force in terms of the conventional geomagnetic quantities, integrated over latitude and longitude with appropriate weighting factors (which are not always intuitively obvious and in some cases reverse sign between low and high latitudes).

Vasyliunas, Vytenis M.

2010-05-01

98

Experimental studies of protozoan response to intense magnetic fields and forces  

NASA Astrophysics Data System (ADS)

Intense static magnetic fields of up to 31 Tesla were used as a novel tool to manipulate the swimming mechanics of unicellular organisms. It is shown that homogenous magnetic fields alter the swimming trajectories of the single cell protozoan Paramecium caudatum, by aligning them parallel to the applied field. Immobile neutrally buoyant paramecia also oriented in magnetic fields with similar rates as the motile ones. It was established that the magneto-orientation is mostly due to the magnetic torques acting on rigid structures in the cell body and therefore the response is a non-biological, passive response. From the orientation rate of paramecia in various magnetic field strengths, the average anisotropy of the diamagnetic susceptibility of the cell was estimated. It has also been demonstrated that magnetic forces can be used to create increased, decreased and even inverted simulated gravity environments for the investigation of the gravi-responses of single cells. Since the mechanisms by which Earth's gravity affects cell functioning are still not fully understood, a number of methods to simulate different strength gravity environments, such as centrifugation, have been employed. Exploiting the ability to exert magnetic forces on weakly diamagnetic constituents of the cells, we were able to vary the gravity from -8 g to 10 g, where g is Earth's gravity. Investigations of the swimming response of paramecia in these simulated gravities revealed that they actively regulate their swimming speed to oppose the external force. This result is in agreement with centrifugation experiments, confirming the credibility of the technique. Moreover, the Paramecium's swimming ceased in simulated gravity of 10 g, indicating a maximum possible propulsion force of 0.7 nN. The magnetic force technique to simulate gravity is the only earthbound technique that can create increased and decreased simulated gravities in the same experimental setup. These findings establish a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.

Guevorkian, Karine

99

Seed island formation by forced magnetic reconnection  

Microsoft Academic Search

Neoclassical tearing modes observed in experiments often grow from seed magnetic islands induced by triggers like sawteeth. The formation of seed islands is studied in this paper using both the reduced MHD and two-fluid equations, with the trigger being modelled by externally applied resonant magnetic perturbations. In the linear phase the growth rate of the driven mode is found to

Q. Yu; S. Günter; K. Lackner; M. Maraschek

2012-01-01

100

Assessment of shot peening uniformity by magnetic drag force measurements  

NASA Astrophysics Data System (ADS)

The effects of varying shot peening process parameters on drag force signatures are examined. The salient features of such signatures are found to compare favorably with those expected from consideration of the effects of peening on magnetic properties combined with analysis of the actual force sources. The potential utility of the drag force method for automatic assessment of peening quality and uniformity is encouraged by experimental results.

Garshelis, Ivan. J.; Tollens, Stijn P. L.; Hollander, Marnix E.; Kari, Ryan J.; Cuseo, James M.

2009-04-01

101

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

Microsoft Academic Search

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

C. J. Lee; G. H. Jang

2008-01-01

102

Localized ferromagnetic resonance using Magnetic Resonance Force Microscopy  

Microsoft Academic Search

Magnetic Resonance Force Microscopy (MRFM) is a novel approach to scanned probe imaging, combining the advantages of Magnetic Resonance Imaging (MRI) with Scanning Probe Microscopy (SPM) [1]. It has extremely high sensitivity that has demonstrated detection of individual electron spins [2] and small numbers of nuclear spins [3]. Here we describe our MRFM experiments on Ferromagnetic thin film structures. Unlike

Jongjoo Kim

2008-01-01

103

Prevalence of Magnetic Field Forces and Universal Symmetry of Nature  

Microsoft Academic Search

Prevalence and equivalence of attraction and repulsion forces of magnets were searched. The repulsion between S poles was stronger by 21.6 percent than the repulsion between N poles. Attraction of N pole was greater than S pole, and inverse relation of distance for magnetic attractions were different for two types of poles. Repulsion effects between the same types of poles

Yildirim Cinar

2003-01-01

104

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

105

Frequency domain multiplexing of force signals with application to magnetic resonance force microscopy  

NASA Astrophysics Data System (ADS)

Frequency domain multiplexing, using an actively damped micromechanical cantilever, is used to detect multiple force signals simultaneously. The measurement principle is applied to magnetic resonance force microscopy to allow concurrent measurement of nuclear spin signals originating from distinct regions of the sample, or from multiple spin species.

Oosterkamp, T. H.; Poggio, M.; Degen, C. L.; Mamin, H. J.; Rugar, D.

2010-02-01

106

Magnetic Compression in Gastrointestinal and Bilioenteric Anastomosis: How Much Force?  

PubMed

Aim. The concept of compression alimentary anastomosis is well established. Recently, magnetic axial alignment pressures have been encompassed within such device constructs. We quantify the magnetic compression force and pressure required to successfully achieve gastrointestinal and bilioenteric anastomosis by in-depth interrogation of the reported literature. Methods. Reports of successful deployment and proof of anastomotic patency on survival were scrutinized to quantify the necessary dimensions and strengths of magnetic devices in (a) gastroenteral anastomosis in live porcine models and (b) bilioenteric anastomosis in the clinical setting. Using a calculatory tool developed for this work (magnetic force determination algorithm, MAGDA), ideal magnetic force and compression pressure were quantified from successful reports with regard to their variance by intermagnet separation. Results. Optimized ranges for both compression force and pressure were determined for successful porcine gastroenteral and clinical bilioenteric anastomoses. For gastroenteral anastomoses (porcine investigations), an optimized compression force between 2.55 and 3.57 kg at 2-mm intermagnet separation is recommended. The associated compression pressure should not exceed 60 N/cm(2). Successful bilioenteric anastomoses is best clinically achieved with intermagnet compression of 18 to 31 g and associated pressures between 1 and 3.5 N/mm(2) (at 2-mm intermagnet separation). Conclusion. The creation of magnetic compression anastomoses using permanent magnets demonstrates a remarkable resilience to variations in magnetic force and pressure exertion. However, inappropriate selection of compression characteristics and magnet dimensions may incur difficulties. Recommendations of this work and the availability of the free online tool (http://magda.ucc.ie/) may facilitate a factor of robustness in the design and refinement of future devices. PMID:23592733

Lambe, Tadhg; Ríordáin, Mícheál G Ó; Cahill, Ronan A; Cantillon-Murphy, Pádraig

2013-04-16

107

Sedimentation of an oblate ellipsoid subjected to magnetic forces  

NASA Astrophysics Data System (ADS)

Recent models of sedimentation are mainly based on Stokes' approximation of body motion in a linear viscous fluid, and cannot therefore account for all effects occurring either in the laboratory or in nature. One of these effects is rotation of prolate or oblate particles perpendicular to the direction of gravity. Galdi and Vaidya (GV2001) showed that torque acting on a falling particle should be added to the Stokes description. They quantified torque in the form of an inequality and evaluated a controlling parameter, G, as a function of eccentricity for the case of a prolate ellipsoid. Their result is also relevant to clustering/flocculation that occurs during sedimentation. Clusters of inert material may capture magnetic particles, which changes the balance of magnetic and hydrodynamic forces. This idea was incorporated in some sedimentation models using spherical clusters (Tauxe et al., 2006; Jezek and Gilder, 2006). Using the results of GV2001, Heslop (2007) discussed how prolate clusters influence magnetic remanence, and in particular, the inclination. Mitra and Tauxe (2009) also used the torque of GV2001 in their models. Both Heslop (2007) and Mitra and Tauxe (2009) restricted their analyses to clusters of prolate ellipsoids, despite the fact that oblate ellipsoids are more commonly found in nature. We present an evaluation of the GV2001 torque coefficient for the oblate ellipsoid. Our approach exploits Stokesian velocity fields described in Jeffery (1922) and Oberbeck (1879). The resulting G coefficient for oblate ellipsoids complements the discussion of Heslop (2007), and the corresponding torque can be added to the model of Jezek and Gilder (2006). Other aspects of re-deposition modeling will also be discussed.

Jezek, Josef; Gilder, Stuart; Bilardello, Dario

2010-05-01

108

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

109

Detecting the gravitational sensitivity of Paramecium caudatum using magnetic forces  

NASA Astrophysics Data System (ADS)

Under normal conditions, Paramecium cells regulate their swimming speed in response to the pN level mechanical force of gravity. This regulation, known as gravikinesis, is more pronounced when the external force is increased by methods such as centrifugation. Here we present a novel technique that simulates gravity fields using the interactions between strong inhomogeneous magnetic fields and cells. We are able to achieve variable gravities spanning from 10xg to -8xg; where g is earth's gravity. Our experiments show that the swimming speed regulation of Paramecium caudatum to magnetically simulated gravity is a true physiological response. In addition, they reveal a maximum propulsion force for paramecia. This advance establishes a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.

Guevorkian, Karine; Valles, James M., Jr.

2006-03-01

110

Nanoparticles for cancer therapy using magnetic forces.  

PubMed

The term 'nanomedicine' refers to the use of nanotechnology in the treatment, diagnosis and monitoring of diseases. Magnetic drug targeting is a particularly promising application in this field. The goal of the carrier systems involved is to achieve active enrichment of effective substances in diseased tissue. Numerous nanosystems can be used as carriers, but magnetic iron oxide nanoparticles are particularly important. On the one hand, the particles serve as carriers for the active substance, while on the other hand they can also be visualized using conventional imaging techniques and can therefore be used for 'theranostic' purposes. They can also be used in hyperthermia, another important pillar of nanomedicine. Both procedures are intended to lead to specific forms of treatment, which is of medical and economic relevance in view of the increasing numbers of cancer patients worldwide. This study offers a brief overview of current developments in medical applications for magnetic nanoparticles in cancer therapy. PMID:22385201

Tietze, Rainer; Lyer, Stefan; Dürr, Stephan; Alexiou, Christoph

2012-03-01

111

The Fourier analysis of magnetic force microscopy imaging  

NASA Astrophysics Data System (ADS)

The stray field near the magnetic thin film sample surface has been calculated from the measured signal of the magnetic force microscopy (MFM) image by the method of discrete Fourier transform. It is found that the domain structure of the film cannot uniquely be determined by the MFM image because the MFM image just reflects the magnetic charges distribution at sample surface. In fact, the magnetic charges at sample surface have two sources: magnetic domain or domain wall. For the same MFM image, the different sources of the magnetic charges will result in very different domain structure. A proper way to determine the domain structure is to know the source of the magnetic charges and use the different components of the stray field to redraw the image.

Wu, Dongping; Lou, Yuanfu; Zheng, Fu; Liu, Liwang; Wei, Dan; Wei, Fulin

2012-09-01

112

Dual vibrational high frequency magnetic force microscopy  

Microsoft Academic Search

The ability to evaluate high frequency writer performance is crucial to the write-head designs for high data rate application. To quantify the write-head performance at high frequency (~1 GHz), a new high frequency detection approach has been implemented. The essence of the method is to utilize a two-step signal mixing process to produce the force harmonics, which are not only

Shaoping Li; Scott Stokes; Y. Liu; Sheryl Foss-Schroder; W. Zhu; Dean Palmer

2002-01-01

113

Magnetic Stimulation of Extrastriate Body Area Impairs Visual Processing of Nonfacial Body Parts  

Microsoft Academic Search

Functional magnetic resonance imaging indicates that observation of the human body induces a selective activation of a lateral occipitotemporal cortical area called extrastriate body area (EBA) [1]. This area is responsive to static and moving images of the human body and parts of it, but it is insensitive to faces and stimulus categories unrelated to the human body [1, 2].

Cosimo Urgesi; Giovanni Berlucchi; Salvatore M. Aglioti

2004-01-01

114

Seed island formation by forced magnetic reconnection  

NASA Astrophysics Data System (ADS)

Neoclassical tearing modes observed in experiments often grow from seed magnetic islands induced by triggers like sawteeth. The formation of seed islands is studied in this paper using both the reduced MHD and two-fluid equations, with the trigger being modelled by externally applied resonant magnetic perturbations. In the linear phase the growth rate of the driven mode is found to be the same as that of the trigger. A slowly growing trigger drives a tearing mode, while a fast one drives a kink-like mode, which becomes a tearing mode later when the trigger's growth slows down. A finite ion sound Larmor radius (ion Larmor radius by using electron temperature) and electron inertia are found to lead to a larger seed island for a given external perturbation. The electron diamagnetic drift and plasma rotation, if increasing the relative rotation between the trigger and the driven mode, decrease the seed island width.

Yu, Q.; Günter, S.; Lackner, K.; Maraschek, M.

2012-06-01

115

Magnetic-Tip Silicon Nitride Cantilevers for Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy (MRFM) has enabled magnetic resonance imaging with state-of-the-art resolution and sensitivity. However, work to date has relied upon attaching either the sample under study or a magnetic particle to a fragile silicon microcantilever. At best, these procedures are inconvenient for the most delicate force-sensitive cantilevers. As a first step in producing well-defined magnetized tips in a manner integratable with established cantilever micromachining protocols, we report the successful sputtering of permalloy onto the tips of commercial silicon nitride microcantilevers. In the presence of a polarizing magnetic field, an oscillating gradient-dipole force is applied to the tip by a magnetic field gradient coil. Analysis of the resulting cantilever motion gives the tip's magnetic dipole. Progress towards demonstration of room-temperature MRFM using this tip will be summarized. (Work supported by the U. S. Army Research Laboratory Microelectronic Research Collaboration Program under contract DAAL01-95-2-3530.)

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

1997-03-01

116

Estimating dynamic external hand forces during manual materials handling based on ground reaction forces and body segment accelerations.  

PubMed

Direct measurement of hand forces during assessment of manual materials handling is infeasible in most field studies and some laboratory studies (e.g., during patient handling). Therefore, this study proposed and evaluated the performance of a novel hand force estimation method based on ground reaction forces (GRFs) and body segment accelerations. Ten male subjects performed a manual lifting/carrying task while an optoelectronic motion tracking system measured 3D full body kinematics, a force plate measured 3D GRFs and an instrumented box measured 3D hand forces. The estimated 3D hand forces were calculated by taking the measured GRF vector and subtracting the force vectors due to weight and acceleration of all body segments. Root-mean-square difference (RMSD) between estimated and measured hand forces ranged from 11 to 27N. When ignoring the segment accelerations (just subtracting body weight from the GRFs), the hand force estimation errors were much higher, with RMSDs ranging from 21 to 101N. Future studies should verify the performance of the proposed hand force estimation method when using an ambulatory field measurement system. PMID:23992763

Faber, Gert S; Chang, Chien-Chi; Kingma, Idsart; Dennerlein, Jack T

2013-07-30

117

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

NASA Astrophysics Data System (ADS)

We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSRs), which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of the MSR of a homogeneous object to include anisotropic metamaterials and consider the most extreme case of anisotropy, where the permeability is negative in one direction but positive in the others. It is shown that deeply subwavelength objects made of such indefinite (hyperbolic) media exhibit a pronounced magnetic dipole resonance that couples strongly to uniform or weakly inhomogeneous magnetic field and provides strong enhancement of the magnetic force, enabling applications such as enhanced magnetic levitation.

Urzhumov, Yaroslav; Chen, Wenchen; Bingham, Chris; Padilla, Willie; Smith, David R.

2012-02-01

118

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

119

[Maxillary expansion with magnetic force: an animal experimental study].  

PubMed

Two adult rhesus monkeys were chosen for the experimental study of maxillary expansion with magnetic force. The duration of experiment was 70 days. The following methods were applied: 1. measuring the width between the two canines and the width between the two first molars on the casts, 2. taking occlusal radiographs for the observation of premaxillary and midpalatal sutures. 3. observing the histological sections under the microscope. The results showed the width of 3 to 3 and the width of 6 to 6 significantly increased, associating with the adaptation of periodontal tissues to the action of magnetic force. PMID:12078180

Liang, W; Xu, Y; Zhang, X

1998-02-01

120

Ferromagnetic resonance force spectroscopy of a magnetic vortex  

NASA Astrophysics Data System (ADS)

Due to its nanometer size (of the order the exchange length), probing the high frequency dynamics of a magnetic vortex core is an experimental challenge. Precessional dynamics of the magnetization of individual nano-disks of NiMnSb perpendicularly magnetized is measured in a wide range of bias magnetic fields using a magnetic resonance force microscope (MRFM). A full dynamic phase diagram, demonstrating excitation of a Kittel-type dipolar mode in the saturated disks and the gyrotropic mode of vortex core rotation in the vortex-state unsaturated disks, is established. Switching of the vortex core polarity in a negative (anti-parallel to core) bias magnetic field is registered dynamically. Analytic theory and micromagnetic simulations provide a quantitative description of the experimental results.

de Loubens, G.; Klein, O.; Riegler, A.; Lochner, F.; Schmidt, G.; Molenkamp, L. W.; Hurdequint, H.; Boust, F.; Vukadinovic, N.; Slavin, A. N.

2009-03-01

121

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

122

Perihelion precession from power law central force and magnetic-like force  

SciTech Connect

By the Laplace-Runge-Lenz (LRL) vector, we analyzed perihelion precessions of orbit with arbitrary eccentricity from perturbations of 1) power law central force and 2) fThusmagnetic-like force. Exact and analytically closed expressions for the precession rate are derived in both cases. In the central force case, we give a further expansion expression of precession rate in orders of eccentricity, and a rule judging pro- or retrograde precession is also given. We applied the result of central force to precessions of a planet in 1) Schwarzschild space-time, for which the formula for the Mercury's 43''/century is reproduced, and 2) spherically distributed dark matter, for which we find a formula that is a generalization of the result derived by others for circular orbit. In the magnetic case, the use of the LRL vector proves to be simple and efficient. An example of magnetic-like perturbation is also discussed.

Xu Feng [Department of Physics, Nanjing University, 22 Hankou Road, Nanjing, 210093 (China)

2011-04-15

123

The Biomechanical Fidelity of Slope simulation on the Sarcos Treadport Using Whole-Body Force Feedback  

Microsoft Academic Search

: This paper addresses whether whole-body force feedback ontreadmill-style locomotion interfaces can simulate the gravity forces experiencedwhen walking on smooth inclines. By applying horizontal force feedbackpossible with the active mechanical tether of the Sarcos Treadport, itis shown that the biomechanics of walking are similar under conditions ofreal slope walking versus tether force walking. These biomechanical resultscomplement previous psychophysical studies which

Rose Mills; John M. Hollerbach; William B. Thompson

2000-01-01

124

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

125

Characterization of the magnetic micro- and nanostructure in unalloyed steels by magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The formation of a cementite phase influences significantly the macroscopic mechanical and magnetic properties of steels. Based on a correlation between mechanical and magnetic properties, mechanical properties as well as the morphology and content of the cementite phase can be inspected by electromagnetic non-destructive testing methods. The influence of the carbon content on bulk magnetic properties of unalloyed steels is studied on a macroscopic scale by hysteresis loop and Barkhausen noise measurements. The micro- and nanostructure is investigated by atomic force microscopy and magnetic force microscopy. Surface topography images and magnetic images of globular cementite precipitates embedded in a ferrite matrix are presented. The size, shape, and orientation of the precipitates influence the domain configuration. Applied external magnetic fields cause magnetization processes mainly in the ferrite matrix: Bloch walls move and are pinned by the cementite precipitates. The correlation between the microscopic observations and macroscopic magnetic properties of the material is discussed.

Batista, L.; Rabe, U.; Hirsekorn, S.

2013-01-01

126

Understanding the Evolution of Three-Body Forces via Similarity Renormalization Group  

NASA Astrophysics Data System (ADS)

The Similarity Renormalization Group (SRG) is a continuous series of unitary transformations. When the relative kinetic energy (Trel) is used in the SRG generator, high- and low- momentum scales are decoupled, but at a cost of induced many-body forces. For few-body nuclei or when including only short-range initial three-body forces, the four-body (and possibly higher) forces have been kept small. However, recent evolutions with long-range initial three-body forces, indicate that induced many- body forces gain significant strength for larger nuclei. We present some novel methods for examining the SRG evolution as well as results from model calculations where we have attempted to control these induced forces.

Wendt, Kyle; Furnstahl, Richard; Perry, Robert

2011-10-01

127

Prediction and analysis of magnetic forces in permanent magnet brushless dc motor with rotor eccentricity  

NASA Astrophysics Data System (ADS)

In design of permanent magnet motors for high-precision applications, it is sometimes necessary, early in the design stage, to have a detailed analysis of the effect of rotor eccentricity that may result from manufacturing imperfectness or use of fluid dynamic or aerodynamic bearings. This paper presents an analytical model for electromagnetic torque and forces in permanent magnet motors with rotor eccentricity. The model gives an insight to the relationship between the effect of the eccentricity and the other motor design parameters on the electromagnetic forces. It is shown that the calculated magnetic forces obtained from this model agree well with those obtained from numerical simulations that are very computationally demanding.

Liu, Z. J.; Li, J. T.; Jabbar, M. A.

2006-04-01

128

Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays  

NASA Astrophysics Data System (ADS)

In this paper, the use of magnetic nanowires for the study of cellular response to force is demonstrated. High-aspect ratio Ni rods with diameter 300 nm and lengths up to 20 ?m were bound to or internalized by pulmonary artery smooth muscle cells (SMCs) cultured on arrays of flexible micropost force sensors. Forces and torques were applied to the cells by driving the nanowires with AC magnetic fields in the frequency range 0.1-10 Hz, and the changes in cellular contractile forces were recorded with the microposts. These local stimulations yield global force reinforcement of the cells’ traction forces, but this contractile reinforcement can be effectively suppressed upon addition of a calcium channel blocker, ruthenium red, suggesting the role of calcium channels in the mechanical response. The responsiveness of the SMCs to actuation depends on the frequency of the applied stimulation. These results show that the combination of magnetic nanoparticles and micropatterned, flexible substrates can provide new approaches to the study of cellular mechanotransduction.

Lin, Yi-Chia; Kramer, Corinne M.; Chen, Christopher S.; Reich, Daniel H.

2012-02-01

129

Stroboscopic imaging of an alternating magnetic field from a perpendicular magnetic recording head by frequency-modulated magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The alternating current (ac) magnetic field from perpendicular magnetic recording head was imaged by using our developed frequency-modulated magnetic force microscopy (FM-MFM), which uses the frequency modulation of cantilever oscillation caused by applying ac magnetic field to a mechanically oscillated cantilever. The amplitude and phase signals (or orthogonal X and Y signals) of the ac magnetic field can be obtained separately by using the FM-MFM technique incorporated with a lock-in amplifier. A signal transformation technique to characterize the AC magnetic field source for frequency modulated magnetic force microscopy was proposed. Two-dimensional vector analysis together with the magnetization vector rotation of the perpendicular recording head was demonstrated using the FM-MFM method combined with the signal transformation algorithm. By taking advantage of this technique, the present method opens a possibility to stroboscopic analyze the AC magnetic field source and gives a very useful feedback for the development of advanced magnetic recording heads.

Li, Zhenghua; Hatakeyama, Kodai; Egawa, Genta; Yoshimura, Satoru; Saito, Hitoshi

2012-05-01

130

Magnetic versus mechanical expansion with different force thresholds and points of force application.  

PubMed

The effects of force magnitude (high versus low) and point of force application (teeth versus direct palatal endosseous pins) on palatal expansion treatment were studied on four juvenile female Macaca fascicularis monkeys. Three subjects received one of the following appliances: (1) conventional type jackscrew maxillary plate bonded to the posterior teeth with a high force magnitude of 2033 g, (2) a similar tooth-borne appliance but with rare earth repulsive magnets having a low force of 258 g, or (3) a specially designed palatal acrylic appliance pinned directly to the palatal shelves also utilizing rare earth repulsive magnets with a low force of 258 g. A fourth animal, the control, received a passive sham appliance bonded to the abutment teeth. Spatial changes of dental markers and facial implants were studied radiographically. In the low force, magnetically induced appliances, treatment was longer (95 days for the palatally pinned appliance and 135 days for the bonded tooth-borne appliance). The force radiated superolaterally, dissipating in the zygomaticofrontal suture, and the overjet significantly increased because of the marked widening of the incisive and transverse sutures. With the conventional jackscrew high-force appliance bonded to the teeth, the treatment lasted 33 days. A diastema developed between the incisors and the force was transmitted superolaterally and then transmedially, thus causing fractures in the nasal complex and other iatrogenic sequelae. The palatally pinned magnetic appliance induced bodily tooth movement, the greatest increase in intermolar distance, and a superior repositioning of the maxillopalatine region. The latter two effects were caused by selective excitation of the transverse suture over the premaxillary suture. Symmetry decreased with remoteness from the point of application. These results suggest reduction of the conventional force by up to eightfold--a level supplied by the rare earth magnets. Extrapolating from these results, the slow palatal expansion regimen for the treatment of Class III malocclusions with maxillary transverse deficiency is preferred at an early age (not more than 6 years). In the event of a suture disorder, the use of direct forces to the palate might be considered. PMID:3318395

Vardimon, A D; Graber, T M; Voss, L R; Verrusio, E

1987-12-01

131

Using Magnetic Forces to Probe the Gravi-response of Swimming Paramecium  

NASA Astrophysics Data System (ADS)

Paramecium Caudatum, a single celled ciliate, alters its swimming behavior when subjected to different gravity environments (e.g. centrifugation and micro-gravity). To dissect the mechanisms behind this gravi-response and that of other biological systems, we are developing the use of magnetic body forces as a means of creating a rapidly tunable, simulated variable gravity environment. Since biological materials are weakly diamagnetic, we must subject them to intense inhomogeneous magnetic fields with characteristic field-field gradient products on the order of 16 T^2/cm. We will describe experiments on Paramecium Caudatum in which we adjust their net buoyancy with magnetic forces and measure the resulting changes in their swimming behavior.

Guevorkian, Karine; Valles, James M., Jr.

2004-03-01

132

On the motion of a rigid body acted upon by potential and gyroscopic forces. I - The equations of motion and their transformation. II - A new form of the equations of motion of a rigid body in an ideal incompressible fluid  

Microsoft Academic Search

The combined effects of gyroscopic and potential forces on the motion of a rigid body about a fixed point are investigated analytically, applying a generalized approach to the case where all fields acting on the body have a common axis of symmetry passing through the fixed point (e.g., the motion of a charged magnetized gyrostat in three superposed classical fields).

H. M. Yehia

1986-01-01

133

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

Microsoft Academic Search

We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSR) which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of MSR of a homogeneous object

Yaroslav Urzhumov; Wenchen Chen; Chris Bingham; Willie Padilla; David R. Smith

2011-01-01

134

Ball lightning as a force-free magnetic knot  

Microsoft Academic Search

The stability of fireballs in a recent model of ball lightning is studied. It is shown that the balls shine while relaxing in an almost quiescent expansion, and that three effects contribute to their stability: ~i! the formation in each one during a process of Taylor relaxation of a force-free magnetic field, a concept introduced in 1954 in order to

Antonio F. Ranada; Mario Soler; José Trueba

2000-01-01

135

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

136

Low temperature behavior of magnetic domains observed using a magnetic force microscope  

NASA Astrophysics Data System (ADS)

A commercial atomic force microscope/magnetic force microscope (MFM) was modified to cool magnetic samples down to around 100 K under a high vacuum while maintaining its routine imaging functionality. MFM images of a 120 nm thick La0.7Ca0.3MnO3 film on a LaAlO3 substrate at low temperature show the paramagnetic-to-ferromagnetic phase transition. Evolution of magnetic domains and magnetic ripples with decreasing temperature are also observed near the edge of a 20 nm thick patterned Co film on a Si substrate.

Chung, S. H.; Shinde, S. R.; Ogale, S. B.; Venkatesan, T.; Greene, R. L.; Dreyer, M.; Gomez, R. D.

2001-06-01

137

THE MEAN ELECTROMOTIVE FORCE RESULTING FROM MAGNETIC BUOYANCY INSTABILITY  

SciTech Connect

Motivated both by considerations of the generation of large-scale astrophysical magnetic fields and by potential problems with mean magnetic field generation by turbulent convection, we investigate the mean electromotive force (emf) resulting from the magnetic buoyancy instability of a rotating layer of stratified magnetic field, considering both unidirectional and sheared fields. We discuss why the traditional decomposition into {alpha} and {beta} effects is inappropriate in this case, and that it is only consideration of the entire mean emf that is meaningful. By considering a weighted average of the unstable linear eigenmodes, and averaging over the horizontal plane, we obtain depth-dependent emfs. For the simplified case of isothermal, ideal MHD, we are able to obtain an analytic expression for the emf; more generally, the emf has to be determined numerically. We calculate how the emf depends on the various parameters of the problem, particularly the rotation rate and the latitude of the magnetic layer.

Davies, C. R.; Hughes, D. W., E-mail: tina@maths.leeds.ac.uk, E-mail: d.w.hughes@leeds.ac.uk [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom)

2011-02-01

138

First-Order Reversal Curve (FORC) analysis of chondrule magnetism  

NASA Astrophysics Data System (ADS)

We report a rock magnetic study of the magnetic properties of chondrules from the Allende and Mokoia carbonaceous chondritic meteorites. To characterise the magnetic carriers, we have made detailed magnetic hysteresis analysis including FORC measurements. We have also conducted isothermal acquisition unmixing analysis. We have determined the ancient magnetic field intensities (paleointensities) recorded by the two meteorites. As these chondrules are highly susceptible to chemical alteration on heating, we have employed two non-heating methods of determining the ancient field intensity: (1) the calibrated REM method and (2) the newly developed Preisach-based approach that determines absolute paleointensities. Allende has been extensively studied but this is the first paleointensity estimate for the Mokoia meteorite.

Emmerton, S.; Muxworthy, A. R.

2009-12-01

139

The Mean Electromotive Force Resulting from Magnetic Buoyancy Instability  

NASA Astrophysics Data System (ADS)

Motivated both by considerations of the generation of large-scale astrophysical magnetic fields and by potential problems with mean magnetic field generation by turbulent convection, we investigate the mean electromotive force (emf) resulting from the magnetic buoyancy instability of a rotating layer of stratified magnetic field, considering both unidirectional and sheared fields. We discuss why the traditional decomposition into ? and ? effects is inappropriate in this case, and that it is only consideration of the entire mean emf that is meaningful. By considering a weighted average of the unstable linear eigenmodes, and averaging over the horizontal plane, we obtain depth-dependent emfs. For the simplified case of isothermal, ideal MHD, we are able to obtain an analytic expression for the emf; more generally, the emf has to be determined numerically. We calculate how the emf depends on the various parameters of the problem, particularly the rotation rate and the latitude of the magnetic layer.

Davies, C. R.; Hughes, D. W.

2011-02-01

140

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

141

Corroboration of magnetic forces in US Maglev design  

SciTech Connect

Four System Concept Definition (SCD) contractors to the National Maglev Initiative (NMI) developed conceptual designs of maglev systems in 1991--1992. The objective of the work reported here was to perform independent calculations of the magnetic forces and fields of these four systems to assess the reasonableness'' of the results presented to the government. Commercial computer software was used for computing forces in the system employing nonlinear ferromagnetic materials and for some calculations of induced eddy current effects in finite-sized systems. Other cases required the use of models developed at ANL and verified by experiment, or in a few cases, new computer programs that have not been validated by experiment. The magnetic forces calculated by the contractors were found to be credible in every case evaluated. The stray fields were also found to be in reasonable agreement with those calculated by the contractors, but, for lack of spice, are not reported here.

Coffey, H.; He, J.; Wang, Z.

1993-01-01

142

Corroboration of magnetic forces in US Maglev design  

SciTech Connect

Four System Concept Definition (SCD) contractors to the National Maglev Initiative (NMI) developed conceptual designs of maglev systems in 1991--1992. The objective of the work reported here was to perform independent calculations of the magnetic forces and fields of these four systems to assess the ``reasonableness`` of the results presented to the government. Commercial computer software was used for computing forces in the system employing nonlinear ferromagnetic materials and for some calculations of induced eddy current effects in finite-sized systems. Other cases required the use of models developed at ANL and verified by experiment, or in a few cases, new computer programs that have not been validated by experiment. The magnetic forces calculated by the contractors were found to be credible in every case evaluated. The stray fields were also found to be in reasonable agreement with those calculated by the contractors, but, for lack of spice, are not reported here.

Coffey, H.; He, J.; Wang, Z.

1993-06-01

143

Force prediction in permanent magnet flat linear motors (abstract)  

SciTech Connect

The advent of neodymium iron boron rare-earth permanent magnet material has afforded the opportunity to construct linear machines of high force to weight ratio. The paper describes the design and construction of an axial flux machine and rotating drum test rig. The machine occupies an arc of 45{degree} on a drum 1.22 m in diameter. The excitation is provided by blocks of NdFeB material which are skewed in order to minimize the force variations due to slotting. The stator carries a three-phase short-chorded double-layer winding of four poles. The machine is supplied by a PWM inverter the fundamental component of which is phase locked to the rotor position so that a dc brushless'' drive system is produced. Electromagnetic forces including ripple forces are measured at supply frequencies up to 100 Hz. They are compared with finite-element analysis which calculates the force variation over the time period. The paper then considers some of the causes of ripple torque. In particular, the force production due solely to the permanent magnet excitation is considered. This has two important components each acting along the line of motion of the machine, one is due to slotting and the other is due to the finite length of the primary. In the practical machine the excitation poles are skewed to minimize the slotting force and the effectiveness of this is confirmed by both results from the experiments and the finite-element analysis. The end effect force is shown to have a space period of twice that of the excitation. The amplitude of this force and its period are again confirmed by practical results.

Eastham, J.F.; Akmese, R. (School of Electrical and Electronic Engineering, University of Bath, Claverton Down, Bath BA2 7AY (England))

1991-11-15

144

Issues in Computing Contact Forces for Non-Penetrating Rigid Bodies  

Microsoft Academic Search

In rigid-body simulation it is necessary to compute the forces that arise between contacting bodies to prevent interpenetration.\\u000a This paper studies the problem of rigid-body simulation when the bodies being simulated are restricted to contact at only\\u000a finitely many points. Some theoretical and practical issues in computing contact forces for systems with large numbers of\\u000a contact points are considered. Both

David Baraff

1993-01-01

145

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

146

On the unsteady-motion theory of magnetic forces for maglev  

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 their 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 provides a useful tool to measure motion-dependent magnetic forces for the prediction and control of maglev systems.

Chen, S.S.; Zhu, S.; Cai, Y. [Argonne National Lab., IL (United States). Energy Technology Div.

1996-02-01

147

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

148

Magnetic Meckel's: an unusual case report of foreign body ingestion  

PubMed Central

Foreign body ingestion in children is common. Most items pass spontaneously, however rarer cases may result in obstruction and or perforation. Ingestion of multiple magnetic items can be more troublesome, as a consequence of the ability of the items to attract across different sections of bowel, or by coalescing to form a larger foreign body. Very few cases of foreign body ingestion have led to the presentation of a complicated Meckel's diverticulum. We present of a case of an adolescent boy with intestinal obstruction secondary to multiple magnetic foreign body ingestion and sequestration within a Meckel's diverticulum.

Lindley, S.; Pathak, S.; Mulchandani, M.; Dalton, S.; Sutton, R.

2012-01-01

149

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

150

Bld10/Cep135 stabilizes basal bodies to resist cilia-generated forces  

PubMed Central

Basal bodies nucleate, anchor, and organize cilia. As the anchor for motile cilia, basal bodies must be resistant to the forces directed toward the cell as a consequence of ciliary beating. The molecules and generalized mechanisms that contribute to the maintenance of basal bodies remain to be discovered. Bld10/Cep135 is a basal body outer cartwheel domain protein that has established roles in the assembly of nascent basal bodies. We find that Bld10 protein first incorporates stably at basal bodies early during new assembly. Bld10 protein continues to accumulate at basal bodies after assembly, and we hypothesize that the full complement of Bld10 is required to stabilize basal bodies. We identify a novel mechanism for Bld10/Cep135 in basal body maintenance so that basal bodies can withstand the forces produced by motile cilia. Bld10 stabilizes basal bodies by promoting the stability of the A- and C-tubules of the basal body triplet microtubules and by properly positioning the triplet microtubule blades. The forces generated by ciliary beating promote basal body disassembly in bld10? cells. Thus Bld10/Cep135 acts to maintain the structural integrity of basal bodies against the forces of ciliary beating in addition to its separable role in basal body assembly.

Bayless, Brian A.; Giddings, Thomas H.; Winey, Mark; Pearson, Chad G.

2012-01-01

151

Bld10/Cep135 stabilizes basal bodies to resist cilia-generated forces.  

PubMed

Basal bodies nucleate, anchor, and organize cilia. As the anchor for motile cilia, basal bodies must be resistant to the forces directed toward the cell as a consequence of ciliary beating. The molecules and generalized mechanisms that contribute to the maintenance of basal bodies remain to be discovered. Bld10/Cep135 is a basal body outer cartwheel domain protein that has established roles in the assembly of nascent basal bodies. We find that Bld10 protein first incorporates stably at basal bodies early during new assembly. Bld10 protein continues to accumulate at basal bodies after assembly, and we hypothesize that the full complement of Bld10 is required to stabilize basal bodies. We identify a novel mechanism for Bld10/Cep135 in basal body maintenance so that basal bodies can withstand the forces produced by motile cilia. Bld10 stabilizes basal bodies by promoting the stability of the A- and C-tubules of the basal body triplet microtubules and by properly positioning the triplet microtubule blades. The forces generated by ciliary beating promote basal body disassembly in bld10? cells. Thus Bld10/Cep135 acts to maintain the structural integrity of basal bodies against the forces of ciliary beating in addition to its separable role in basal body assembly. PMID:23115304

Bayless, Brian A; Giddings, Thomas H; Winey, Mark; Pearson, Chad G

2012-10-31

152

Characterization of Magnetic Particles on Cantilevers for Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Until recently, magnetic resonance force microscopy (MRFM) measured the gradient dipole force between spins in a sample, mounted to a microcantilever, and a millimeter size magnetic particle. In an effort to lift MRFM's sample-on-cantilever restriction, we have developed a technique for mounting micron-scale Alnico particles on commercial silicon microcantilevers and magnetizing the particles so their easy axis ends up perpendicular to the plane of the cantilever (a force/gradient geometry which results in easy to interpret images). It is observed that the spring constant k of the resulting cantilever depends strongly on magnetic field B. A simple model explains this magnetic field contribution to the cantilever's spring constant, and allows us to extract the B-H curve and magnetic moment of the cantilever's magnetic particle from the observed k(B). We will draw on this model to assess the utility of using magnetically tipped cantilevers, configured in various cantilever/particle geometries, to perform MRFM at high magnetic field. We will also describe an apparatus for characterizing cantilevers as a function of magnetic field.

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

1998-03-01

153

Edge effects on forces and magnetic fields produced by a conductor moving past a magnet  

SciTech Connect

Experiments have been performed to further understand the forces acting on magnets moving along and over the edge of a continuous conducting sheet and to produce a comprehensive data set for the validation of analysis methods. Mapping the magnetic field gives information about the eddy currents induced in the conductor, which agrees with numerical calculations.

Mulcahy, T.M.; Hull, J.R.; Almer, J.D. (Argonne National Lab., IL (United States)); Rossing, T.D. (Northern Illinois Univ., De Kalb, IL (United States))

1992-01-01

154

Force Ripple and Magnetic Unbalance Reduction Design for Doubly Salient Permanent Magnet Linear Synchronous Motor  

Microsoft Academic Search

Permanent magnet linear synchronous motor (PMLSM) has been successfully applied in various industry fields due mainly to excellent dynamic characteristics and accurate positioning capability. However, PMLSM suffers force ripple, which deteriorates controllability, and it is often considered to be an expensive linear drive mechanism since it requires a large amount of rare-earth permanent magnet (PM) material in the stationary part.

Shi-Uk Chung; Ji-Won Kim; Byung-Chul Woo; Do-Kwan Hong; Ji-Young Lee; Dae-Hyun Koo

2011-01-01

155

Influence of slot and pole number combinations on unbalanced magnetic force in permanent magnet machines  

Microsoft Academic Search

Unbalanced magnetic forces (UMF) exist in permanent magnet machines having pole and slot numbers differed by one and two, even when there is no rotor eccentricity. In machines having pole and slot numbers differed by two, the on-load UMF results only when the single layer winding is employed and the number of coils is odd. This paper investigates the influence

Z. Q. Zhu; M. L. Mohd Jamil; L. J. Wu

2011-01-01

156

Three-dimensional computation of magnetic fields and Lorentz forces of an LHC dipole magnet.  

National Technical Information Service (NTIS)

Magnetic fields and Lorentz forces of an LHC dipole magnet are calculated using the method of image currents to represent the effect of the iron shield. The calculation is performed for coils of finite length using a parametrization for coil heads of cons...

C. Daum D. Avest

1989-01-01

157

Edge effects on forces and magnetic fields produced by a conductor moving past a magnet  

SciTech Connect

Experiments have been performed to further understand the forces acting on magnets moving along and over the edge of a continuous conducting sheet and to produce a comprehensive data set for the validation of analysis methods. Mapping the magnetic field gives information about the eddy currents induced in the conductor, which agrees with numerical calculations.

Mulcahy, T.M.; Hull, J.R.; Almer, J.D. [Argonne National Lab., IL (United States); Rossing, T.D. [Northern Illinois Univ., De Kalb, IL (United States)

1992-04-01

158

Celebrating certification in nursing: forces of magnetism in action.  

PubMed

Professional certification in nursing is a measure of distinctive nursing practice. The rise in consumerism in the face of a compelling nursing shortage and the profession's movement to elevate nursing as a career option has given prominence to the value of certification in nursing. The value of certification is not only significant for nursing practice rather the focus on professional certification is also essential to meet multiple standards within the American Nurses Credentialing Center's Magnet Recognition Program for excellence in nursing services. This article describes one hospital's success with a critical care nurse certification drive. The article identifies ways in which an organization can take elements of a professional certification drive to show-case the forces of magnetism and to provide evidence that a Magnet-aspiring organization meets required Magnet standards. PMID:16056159

Shirey, Maria R

159

An optimal magnetic tip configuration for magnetic-resonance force microscopy of microscale buried features  

NASA Astrophysics Data System (ADS)

To date, magnetic-resonance force microscopes employing a magnetic-field gradient source mounted to a microcantilever have suffered from a deleterious dependence of the effective cantilever spring constant on the external magnetic field. A ``magnet-on-tip'' configuration is introduced in which this dependence has been decreased by at least 200 fold, making it feasible to perform arbitrary-sample micron-scale magnetic resonance force microscopy at very high magnetic field. Alternating-gradient cantilever magnetometry is used to quantify the effect and to prove that the existing model of the tip-field interaction is only qualitatively correct. A model is proposed which quantitatively describes the tip-field interaction in the traditional tip configuration.

Marohn, John A.; Fainchtein, Raúl; Smith, Doran D.

1998-12-01

160

Magnetic force microscopy of thin film media for high density magnetic recording  

NASA Astrophysics Data System (ADS)

This paper discusses various aspect of magnetic force microscopy (MFM) for use in the field of high density magnetic recording. After an introduction of the most important magnetic imaging techniques, an overview is given of the operation and theory of MFM. The developments in instrumentation, MFM tips, quantification of MFM data, high resolution imaging and application of external fields is discussed. Examples are given of the applications of MFM, such as the characterization of heads, magnetic structures (bits) in longitudinal and perpendicular recording media, bits in magneto-optic films and domain structures in soft magnetic materials.

Porthun, Steffen; Abelmann, Leon; Lodder, Cock

1998-02-01

161

Accurate and consistent force calculation for finite element magnetics  

NASA Astrophysics Data System (ADS)

Three net magnetostatic loading force formulations are commonly used for finite element based electromagnetic and electromechanical computer-aided analysis and design: the Maxwell stress method, the method of classical virtual work, and the local Jacobian derivative method. None of these seems sufficient to calculate reliable results at a reasonable cost without expert user interaction. A new, fully automatic, field-error tuned force method is presented. The formulation is based on a volume integration of the computed fields over the entire free space region enveloping the body under force. Numerical tests indicate the the new method is significantly more accurate and consistent than the other methods currently available at a comparable cost. In addition, three important benchmark force problems are introduced; these problems have been designed to model the principal characteristics found in most practical force systems. Many of the computational difficulties inherent to the currently available force methods are explained. A new restructuring of the relationships between the different force formulas is provided.

McFee, James Stephan

1989-08-01

162

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

163

The effect of many-body forces on the elastic properties of simple oxides and olivine  

Microsoft Academic Search

The single crystal elastic moduli bear evidence of non-central or many-body forces in the simple oxides with transition-metal oxides being very distinctive from alkaline-earth oxides. These features which persist in more complicated structures such as olivine, suggest that noncentral or many-body forces are important in defining the physical properties of these compounds as well.

Donald J. Weidner; Geoffery D. Price

1988-01-01

164

Study of magnetic microstructures of Nd–Fe–B casting strips by using magnetic force microscope  

Microsoft Academic Search

Dy–Al substituted Nd–Fe–B strips were produced by strip casting technique. The magnetic microstructures of the 2-14-1 and Nd2Fe17(B) phases in both as-cast strips and the strips heat-treated at 1050°C in Ar atmosphere, and the domain structures of the final sintered magnets have been revealed by using magnetic force microscope. The existence of fine Nd2Fe17(B) crystals with “plate-like” domains surrounded by

Minggang Zhu; Yikun Fang; Yongquan Guo; Wei Li; Baoshan Han

2004-01-01

165

Towards a quantitative analysis of magnetic force microscopy data matrices  

NASA Astrophysics Data System (ADS)

Fast and efficient software tools previously developed in image processing were adapted to the analysis of raw datasets consisting of multiple stacks of images taken on a sample interacting with a measuring instrument and submitted to the effect of an external parameter. Magnetic force microscopy (MFM), a follow-up of atomic force microscopy (AFM), was selected as a first testbed example. In MFM, a specifically developed ferromagnetic scanning tip probes the stray magnetic field generated from a ferromagnetic specimen. Raw scanning probe images taken on soft patterned magnetic materials and continuous thin films were used, together with synthetic patterns exploited to assess the absolute performance ability of the proposed texture analysis tools. In this case, the parameter affecting the sample-instrument interaction is the applied magnetic field. The application discussed here is just one among the many possible, including, e.g., real-time microscopy images (both optical and electronic) taken during heat treatments, phase transformations and so on. Basically any image exhibiting a texture with a characteristic spatial or angular dependence could be processed by the proposed method. Standard imaging tools such as texture mapping and novel data representation schemes such as texture analysis, feature extraction and classification are discussed. A magnetic texture stability diagram will be presented as an original output of the entropic analysis on MFM datasets.

Chiolerio, A.; Allia, P.

2012-08-01

166

Effect of guideway discontinuities on magnetic levitation and drag forces  

SciTech Connect

Transients in the lift and drag forces on a NdFeB permanent magnet were observed as the magnet passed over various discontinuities in a rotating aluminum disk at velocities of 4 to 25 m/s. For full cuts in the disk, the amplitude of the lift and drag transients and the wave form of the drag transient depend on the width, and the amplitudes are much larger than for partial cuts. The use of a backing plate to join two cut segments is ineffective.

Rossing, T.D.; Korte, R.; Hull, J.R. (Materials and Components Technology Division, Argonne National Laboratory, Argonne, Illinois (USA))

1991-11-15

167

Effect of guideway discontinuities on magnetic levitation and drag forces  

SciTech Connect

Transients in the lift and drag forces on a NdFeB permanent magnet were observed as the magnet passed over various discontinuities in a rotating aluminum disk at velocities of 4 to 25 m/s. For full cuts in the disk, the amplitude of the lift and drag transients and the waveform of the drag transient depend on the width, and the amplitudes are much larger than for partial cuts. The use of a backing plate to join two cut segments is ineffective. 2 refs., 3 figs.

Rossing, T.D.; Korte, R. (Argonne National Lab., IL (USA) Northern Illinois Univ., De Kalb, IL (USA). Dept. of Physics); Hull, J.R. (Argonne National Lab., IL (USA))

1991-01-01

168

Measurement of interaction force between small distances sandwiched with magnetic fluid under magnetic field  

NASA Astrophysics Data System (ADS)

In this contribution, the interactive force measurement between 10nm distance under magnetic field is carried out. Previous measurement of the interactive force is reported by Israelachivili et al. However, its measurement under magnetic field has not been performed. The methodology described in this paper is easier as the distance between two surfaces is not measured optically but dynamically. Therefore, it is different from the previous reported studies. Based on the results of the measurement of the interactive force, the diameter of the particle suspended in a solution under magnetic field is also estimated. Moreover, it may be predictable how the clusters have been formed. The method described will be very useful for new productions based on magnetic fluid.

Miyazaki, T.; Shibayama, A.; Sato, T.; Fujita, T.

2002-11-01

169

Effective three-body forces in the three and four nucleon systems  

Microsoft Academic Search

The equivalence of effective two-body and two-body plus three-body forces for the 4He system is investigated. Sussex matrix elements are modified to bind the A=3 and A=4 systems in both a two-body as well as three-body approach. Both approaches predict reasonably accurate binding energies and rms radii for the ground states of light systems although these methods do not accurately

J. J. Bevelacqua

1977-01-01

170

Microscopic derivation of electromagnetic force density in magnetic dielectric media  

NASA Astrophysics Data System (ADS)

Macroscopic force density imposed on a linear isotropic magnetic dielectric medium by an arbitrary electromagnetic field is derived by spatially averaging the microscopic Lorentz force density. The obtained expression differs from the commonly used expressions, but the energy-momentum tensor derived from it corresponds to a so-called Helmholtz tensor written for a medium that obeys the Clausius-Mossotti law. Thus, our microscopic derivation unambiguously proves the correctness of the Helmholtz tensor for such media. Also, the expression for the momentum density of the field obtained in our theory is different from the expressions obtained by Minkowski, Abraham, Einstein and Laub, and others. We apply the theory to particular examples of static electric, magnetic and stationary electromagnetic phenomena, and show its agreement with experimental observations. We emphasize that in contrast to a widespread belief the Abraham-Minkowski controversy cannot be resolved experimentally because of incompleteness of the theories introduced by Abraham and Minkowski.

Shevchenko, A.; Hoenders, B. J.

2010-05-01

171

Induced Magnetic Fields in Solar System Bodies  

Microsoft Academic Search

Electromagnetic induction is a powerful technique to study the electrical conductivity of the interior of the Earth and other\\u000a solar system bodies. Information about the electrical conductivity structure can provide strong constraints on the associated\\u000a internal composition of planetary bodies. Here we give a review of the basic principles of the electromagnetic induction technique\\u000a and discuss its application to various

Joachim Saur; Fritz M. Neubauer; Karl-Heinz Glassmeier

2010-01-01

172

Consistent nucleon-nucleon potentials and three-body forces  

SciTech Connect

We construct microscopic three-nucleon forces consistent with the Bonn and Nijmegen two-nucleon potentials, and including {delta}, Roper, and nucleon-antinucleon excitations. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined.

Li, Z. H.; Lombardo, U. [INFN-LNS, Via Santa Sofia 62, I-95123 Catania (Italy); Schulze, H.-J. [INFN Sezione di Catania, Via Santa Sofia 64, I-95123 Catania (Italy); Zuo, W. [Institute of Modern Physics, 730000 Lanzhou (China)

2008-03-15

173

On the unsteady-motion theory of magnetic forces for maglev  

SciTech Connect

Motion-dependent magnetic forces are the key elements in the study of magnetically levitated vehicle (maglev) system dynamics. In the past, most maglev-system designs were based on a quasisteady-motion theory of magnetic forces. This report 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 provides a useful tool to measure motion-dependent magnetic forces for the prediction and control of maglev systems.

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

1993-11-01

174

Localized Spectroscopy using a Magnetic Resonance Force Microscope.  

NASA Astrophysics Data System (ADS)

The Magnetic Resonance Force Microscope (MRFM) constitutes a promising next-generation magnetic resonance detection device at room temperature. A MRFM observes nuclear (or electron) spin magnetization as a force, which occurs when a paramagnetic sample is polarized in inhomogeneous static magnetic field (10E5 T/m) and a high frequency drives the cantilever on-resonance by a cyclic adiabatic modulation, which make able to measure T1 rho. In this contribution, we combine the MRFM with spin-echo spectroscopy to add spectral resolution to NMR signals of micro-scale objects at room temperature. First experimental spectra recorded with the amplitude detection technique from a sample of barium chlorate monohydrate and ammonium sulfate single crystals mounted on a non commercial cantilever show resolution of 2?m and a sensitivity of 10E13 spins. The new microscope, which uses the frequency detection down to m-Hz resolution and the annealed non-commercials cantilevers, which have Q factor up to 250000 at room temperature, improve the sensitivity to 10E9 spins. This new setup and a new measurement technique should make able to measure T1.

Moresi, Giorgio; Lin, Qiong; Mouaziz, Schahrazede; Hunkeler, Andreas; Degen, Christian; Meier, Urban; Brugger, Juerger; Meier, Beat

2006-03-01

175

Magnetic tweezers: micromanipulation and force measurement at the molecular level.  

PubMed Central

Cantilevers and optical tweezers are widely used for micromanipulating cells or biomolecules for measuring their mechanical properties. However, they do not allow easy rotary motion and can sometimes damage the handled material. We present here a system of magnetic tweezers that overcomes those drawbacks while retaining most of the previous dynamometers properties. Electromagnets are coupled to a microscope-based particle tracking system through a digital feedback loop. Magnetic beads are first trapped in a potential well of stiffness approximately 10(-7) N/m. Thus, they can be manipulated in three dimensions at a speed of approximately 10 microm/s and rotated along the optical axis at a frequency of 10 Hz. In addition, our apparatus can work as a dynamometer relying on either usual calibration against the viscous drag or complete calibration using Brownian fluctuations. By stretching a DNA molecule between a magnetic particle and a glass surface, we applied and measured vertical forces ranging from 50 fN to 20 pN. Similarly, nearly horizontal forces up to 5 pN were obtained. From those experiments, we conclude that magnetic tweezers represent a low-cost and biocompatible setup that could become a suitable alternative to the other available micromanipulators.

Gosse, Charlie; Croquette, Vincent

2002-01-01

176

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

177

Secular changes in body dimensions of Royal Australian Air Force aircrew (1971–2005)  

Microsoft Academic Search

The aim of this study was to quantify the secular changes in body dimensions of Royal Australian Air Force aircrew. Following corrections for methodological differences, two samples (matched for age and overall body size) of male aircrew measured in 1971 (n = 220) and 2005 (n = 220) were compared across 13 absolute and proportional body dimensions. Changes in means were expressed as standardised

Grant R. Tomkinson; Adam J. Clark; Peter Blanchonette

2010-01-01

178

Magnus force and the inertial properties of magnetic vortices in weak ferromagnets  

Microsoft Academic Search

The Magnus force (gyroscopic force) acting on magnetic vortices (Bloch lines) within domain boundaries in weak ferromagnets is discussed. A general formula is derived for the Magnus force in weak ferromagnets. The Magnus force is found to be nonzero for most types of domain boundaries and is determined by the average sublattice magnetization and the constants for the Dzyaloshinsky interaction

A. K. Zvezdin; K. A. Zvezdin

2010-01-01

179

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

PubMed

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. PMID:23843602

Rawlings, Colin; Durkan, Colm

2013-07-10

180

Flagellar hydrodynamics. A comparison between resistive-force theory and slender-body theory.  

PubMed Central

This paper investigates the accuracy of the resistive-force theory (Gray and Hancock method) which is commonly used for hydrodynamic analysis of swimming flagella. We made a comparison between the forces, bending moments, and shear moments calculated by resistive-force theory and by the more accurate slender-body theory for large-amplitude, planar wave forms computed for a flagellar model. By making an upward empirical adjustment, by about 35%, of the classical drag coefficient values used in the resistive-force theory calculations, we obtained good agreement between the distributions of the forces and moments along the length of the flagellum predicted by the two methods when the flagellum has no cell body attached. After this adjustment, we found the rate of energy expenditure calculated by the two methods for the few typical test cases to be almost identical. The resistive-force theory is thus completely satisfactory for use in analysis of mechanisms for the control of flagellar bending, at the current level of sophistication of this analysis. We also examined the effects of the presence of a cell body attached to one end of the flagellum, which modifies the flow field experienced by the flagellum. This interaction, which is not considered in resistive-force theory, is probably insignificant for small cell bodies, such as the heads of simple spermatozoa, but for larger cell bodies, or cell bodies that have large-amplitude motions transverse to the swimming direction, use of slender-body theory is required for accurate analysis.

Johnson, R E; Brokaw, C J

1979-01-01

181

Development of magnetic force-assisted gene transfer system using biopolymer-coated ferromagnetic nanoparticles  

Microsoft Academic Search

The concept of drug-accumulation in the blood vessel utilizing magnetic force was a novel concept in the cancer treatment. In the present study, calculation of the applied magnetic force for the ferromagnetic particles inside the blood vessel was performed in order to clarify the effect of magnetic field gradient on the accumulation possibility of the magnetic particles and the accuracy

Shin-ichi Takeda; Fumihito Mishima; Bungo Terazono; Yoshinobu Izumi; Shigehiro Nishijima

2006-01-01

182

Magnetic Microstructures of 2:17 Type Sm(Co, Fe, Cu, Zr) z Magnets Detected by Magnetic Force Microscopy  

Microsoft Academic Search

The magnetic microstructures of 2:17 type Sm(Co, Fe, Cu, Zr)z magnets were detected by magnetic force microscopy. Comparing the microstructures of the specimens coated with and without Ta thin film before and after heat-treatment, it is found that: (a) as a protection layer, Ta coating layer about 20 nm thick can effectively restrain Sm volatilization under high temperature; (b) the

Ailin Xia; Zhaohui Guo; Wei Li; Baoshan Han

2006-01-01

183

Magnetic Forces on Orthodontic Wires in High Field Magnetic Resonance Imaging (MRI) at 3 Tesla  

Microsoft Academic Search

\\u000a Abstract\\u000a \\u000a \\u000a Background:\\u000a   In a previous investigation we reported on magnetic forces in the static magnetic field of a 1.5 Tesla MRI system. The aim\\u000a of the present investigation was to assess forces on orthodontic wires in a high field strength MRI system at 3 Tesla.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and Methods:\\u000a   Thirty-two different orthodontic wires (21 archwires, eight ligature wires and three retainer

Arndt Klocke; Bärbel Kahl-Nieke; Gerhard Adam; Jörn Kemper

2006-01-01

184

Analysis and experiment of magnetic force in permanent magnet axial thrust balance structure for canned motor pump  

Microsoft Academic Search

This paper analyzed and calculated electromagnetic field and counterbalance force between the permanent magnet thrust plate for a novel permanent magnet axial thrust balance structure in canned motor pump using a numerical method of Ansoft software. Then constructed permanent magnet axial thrust balance experiment device and detected the characteristics of repulsion and attraction which made up of axial balancing force

Yuejun An; Guoming Liu; Zhaojun Meng; Peng Wang; Hongliang Wen

2010-01-01

185

Magnetic force analysis and experiment of novel permanent magnet axial thrust balance structure in canned motor pump  

Microsoft Academic Search

This paper analyzed and calculated electromagnetic field and counterbalance force between the permanent magnet thrust plate for a novel permanent magnet axial thrust balance structure in canned motor pump using a numerical method of Ansoft software. Then constructed permanent magnet axial thrust balance experiment device and detected the characteristics of repulsion and attraction which make up of axial balancing force

Yuejun An; Guoming Liu; Peng Wang; Hongliang Wen; Zhaojun Meng

2010-01-01

186

Analysis of radially unbalanced magnetic force acting on a large superconducting magnet with iron yoke by 'TOSCA'  

Microsoft Academic Search

A superconducting solenoid magnet for colliding beam detectors has an iron yoke which controls the magnetic field inside and behind the solenoid coil. When the center of the coil is displaced from the center of the yoke, unbalanced magnetic force will act on the coil. The radial unbalanced force must be determined using three-dimensional field calculation. The three-dimensional field analysis

T. Nomura; T. Satow; M. Ashkin

1988-01-01

187

MAGFOR: a magnetics code to calculate field and forces in twisted helical coils of constant cross section  

SciTech Connect

The machine-independent computer program MAGFOR calculates electromagnetic fields and forces in coil systems of arbitrary geometry. The coils may be modeled by using 20-node isoparametric hexahedrons; 8-node rectangular cross-sectional straight segments; rectangular cross-sectional circular arcs; and/or filamenting circular loops. A combination of analytical and numerical integration of the Biot-Savart law for a volume distribution of current is used for calculating magnetic fields. Volumetric body forces are calculated for the 20-node isoparametric brick by numerically integrating the vector product J x B over its volume, where the magnetic field at each Gauss point is obtained by interpolating the magnetic field at the node points by using shape functions. The force is distributed to the node points of the element, again using the shape functions in a consistent manner that maintains inter-element torsion. Body forces obtained from MAGFOR are compared with body forces from the computer code EFFI for several coil configurations considered in the design of the Advanced Toroidal Facility (ATF).

Cain, W.D.

1983-01-01

188

In-situ investigation of patterned magnetic domain structures using magnetic force microscope  

Microsoft Academic Search

A novel method for in-situ investigation of patterned magnetic domain structures is presented. Micron-length scales of permalloy thin film fabricated by a lift-off process using electron beam lithography were placed on the top and adjacent to an aluminum strip. A magnetic force microscope was used to take continuous images of the patterned permalloy films while an electrical current was applied

J. C. Wu; H. W. Huang; Y. W. Huang; Te-Ho Wu

1999-01-01

189

Trapped scattering with three incident channels and the evaluation of the three-body forces  

SciTech Connect

A design of trapped scattering is proposed and related theoretical calculation is performed to evaluate the weak three-body interactions among neutral atoms and molecules. Different from traditional experiments of scattering, the design has three incident channels; three-body collisions would occur in a trap repeatedly, and the number of collisions can be controlled. Hence, the effect of each collision can be accumulated and eventually enlarged. Therefore the design is particularly suitable for the cases with very weak interactions. Results of the calculation demonstrate that, once the two-body force of a species has been known, information on the three-body force can be thereby obtained.

Bao, C. G. [Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator, Lanzhou 73000 (China) and State Key Laboratory of Optoelectronic Materials and Technologies, and Department of Physics, School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275 (China)

2010-11-15

190

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

191

Magnetic anisotropy considerations in magnetic force microscopy studies of single superparamagnetic nanoparticles  

NASA Astrophysics Data System (ADS)

In recent years, superparamagnetic nanoparticles (SPNs) have become increasingly important in applications ranging from solid state memory devices to biomedical diagnostic and therapeutic tools. However, detection and characterization of the small and unstable magnetic moment of an SPN at the single particle level remains a challenge. Further, depending on their physical shape, crystalline structure or orientation, SPNs may also possess magnetic anisotropy, which can govern the extent to which their magnetic moments can align with an externally applied magnetic field. Here, we demonstrate how we can exploit the magnetic anisotropy of SPNs to enable uniform, highly-sensitive detection of single SPNs using magnetic force microscopy (MFM) in ambient air. Superconducting quantum interference device magnetometry and analytical transmission electron microscopy techniques are utilized to characterize the collective magnetic behavior, morphology and composition of the SPNs. Our results show how the consideration of magnetic anisotropy can enhance the ability of MFM to detect single SPNs at ambient room temperature with high force sensitivity and spatial resolution.

Nocera, Tanya M.; Chen, Jun; Murray, Christopher B.; Agarwal, Gunjan

2012-12-01

192

Hydrodynamic Forces on Floating Bodies Moving At Low Froude Number.  

National Technical Information Service (NTIS)

The equations of steady free-surface flow with gravity past a ship are expanded in a small Froude number perturbation series. Expressions for the vertical force and the moment (and the sinkage and trim, correspondingly) are derived up to second order. Two...

G. Dagan

1970-01-01

193

Aerodynamic Forces Acting on a Finite Rectangular Slender Body.  

National Technical Information Service (NTIS)

To estimate the nonlinear transient moment acting on spinning square cylinders in a plane normal to the flow direction, the force and moment coefficients were measured for a semi-finite square cylinder (fineness ratio 5) settled in a wind tunnel. Yaw angl...

A. Tate T. Yoshinaga

1989-01-01

194

Experimental analysis of retention forces of different magnetic devices for bone-anchored auricular facial prostheses.  

PubMed

The aim of this study was to determine which combination of differently designed magnetic abutments provides the best retention for an auricular prosthesis. The withdrawal forces of eight combinations of abutments were measured and results compared. There was a significantly higher withdrawal force in arrangements containing three magnets over only two. The highest withdrawal force was found in the combination of one telescopic magnet and two large spherical magnets (median: 7.69 N), whereas two telescopic magnets alone showed the lowest withdrawal force (3.41 N). The use of two conical magnets increased retention slightly, but the median retention force remained the same (3.41 N). The commonly used combination of two small spherical magnets and one telescopic magnet showed the lowest retention of combinations consisting of three magnets (4.94 N). There seems to be no difference in median withdrawal force if a conical magnet instead of a telescopic magnet is used. The withdrawal force at a 45 degrees angle was about 10% higher than the vertical force but the difference was not significant. The rupture force needed to tear the magnet completely out of the silicone was 240.6-519.7 N (mean 331.74 N) and therefore over 10 times higher than magnetic retention. PMID:18440779

Voigt, A; Christ, S; Klein, M

2008-04-28

195

Added Masses and Forces on Two Bodies Approaching Central Impact in an Inviscid Fluid.  

National Technical Information Service (NTIS)

In several papers, which will be referenced, a procedure based on integral equations has been developed and applied for determining the interaction forces on two bodies approaching central impact in an inviscid fluid. The present work was undertaken to ev...

A. Shahshahan L. Landweber

1991-01-01

196

Three-Body Forces and Proton-Rich Nuclei  

SciTech Connect

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.

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

2013-01-01

197

Vortex Dislocations and Body Forces in Flow-Structure Interactions  

NASA Astrophysics Data System (ADS)

DNS is used in order to simulate 3D flow past stationary, rigid or flexible cylinders subject to forced vibrations (FV) or vortex induced vibrations (VIV). Different flow and structural parameters such as shear rate, Reynolds number, cylinder aspect ratio and end-conditions are investigated in order to examine structural responses and hydrodynamic forces. The relationship of these quantities with the dynamics of the near wake flow is studied. In the case of VIV due to uniform inflow, at turbulent Reynolds number of 1000, past cylinders with a small or large aspect ratio we propose an appropriate modification to the drag coefficient empirical formula of Skop, Griffin & Ramberg (1977). For the stationary and the FV cases subject to shear inflow we obtained cells of constant frequency. These cells are correlated with significant variations in the drag coefficient along the span of the cylinder.

Lucor, Didier; Evangelinos, Constantinos; Karniadakis, George Em

1999-11-01

198

Complete Expressions for the Gravitational and Buoyancy Force Terms in the Equations of Motion of a Submerged Body.  

National Technical Information Service (NTIS)

Complete expressions are given for the forces and moments acting on a submerged body because of gravitational attraction on the mass of the body and buoyancy force acting on the body boundary. The variations of the forces and moments with changes in angul...

F. H. Imlay

1964-01-01

199

Forces on solid bodies immersed in nematic phases  

Microsoft Academic Search

A method is presented for finding, in the one-constant theory of nematics, the director field u that minimizes the free energy of a liquid crystal phase in contact with cylindrical or planar surfaces imposing appropriate boundary conditions on u. The method is employed to find the resultant forces and moments acting on a long straight rod of radius 0305-4470\\/32\\/7\\/008\\/img5 immersed

Franois Alouges; Bernard D. Coleman

1999-01-01

200

Experimental investigation of side force control on cone-cylinder slender bodies with flexible micro balloon actuators  

Microsoft Academic Search

Side forces on slender bodies of revolution at medium to high angles of attack (AOA>30°) has been known from a large number of investigations. Asymmetric vortex pairs over a slender body are believed to be the principle cause of the side forces. Under some flight conditions, this side force may be as large as the normal force acting on the

Tzong-Shyng Leu; Jeng-Ren Chang; Pong-Jeu Lu

2005-01-01

201

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

202

Body force term comparison in lattice Boltzmann method for shallow water equations  

NASA Astrophysics Data System (ADS)

We present the Lattice Boltzmann method for modelling shallow water equations with a focus on external forces. Three different approximations for modelling the body force terms are used and compared in a 1D steady flow simulation over a bump. The accuracy, the mass conservation and the CPU time are discussed in this study.

Raizer, O.; Smaoui, H.; Ouahsine, A.; Sergent, P.

2013-10-01

203

Grip force control of the elastic body utilising the incipient slip sensor  

Microsoft Academic Search

In this paper, a control of grip force using an incipient slip sensor is proposed. An object for gripping has elastic body where a frictional coefficient of the contact surface is unknown. A camera is attached inside the gripper and the incipient slip is detected from the image of the contact surface. A method of grip force control is proposed

Atsutoshi Ikeda; Yuichi Kurita; Jun Ueda; Yoshio Matsumoto; Tsukasa Ogasawara

204

REVIEW OF TERMS FOR REGULATED VERSUS FORCED, NEUROCHEMICAL-INDUCED CHANGES IN BODY TEMPERATURE  

EPA Science Inventory

Deviations of the body temperature of homeothermic animals may be regulated or forced. A regulated change in core temperature is caused by a natural or synthetic compound that displaces the set-point temperature. A forced shift occurs when an excessive environmental or endogenous...

205

Blocking of magnetic moments of magnetosomes measured by magnetorelaxometry and direct observation by magnetic force microscopy  

Microsoft Academic Search

Large magnetosomes of 40nm diameter were characterised by altogether four different methods, i.e. DC-magnetometry and magnetorelaxometry as integral tools, and atomic and magnetic force microscopy as microscopic tools. The results suggest that the integral hysteretic behaviour of magnetosomes can be understood as a superposition of their microscopic behaviour, ignoring interaction between the particle moments.

Dietmar Eberbeck; Volker Janke; Stefan Hartwig; Udo Heyen; Dirk Schüler; Martin Albrecht; Lutz Trahms

2005-01-01

206

Blocking of magnetic moments of magnetosomes measured by magnetorelaxometry and direct observation by magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Large magnetosomes of 40 nm diameter were characterised by altogether four different methods, i.e. DC-magnetometry and magnetorelaxometry as integral tools, and atomic and magnetic force microscopy as microscopic tools. The results suggest that the integral hysteretic behaviour of magnetosomes can be understood as a superposition of their microscopic behaviour, ignoring interaction between the particle moments.

Eberbeck, Dietmar; Janke, Volker; Hartwig, Stefan; Heyen, Udo; Schüler, Dirk; Albrecht, Martin; Trahms, Lutz

2005-03-01

207

Motion-Related Body-Force Functions in Two-Dimensional Low-Speed Flow  

Microsoft Academic Search

The paper examines two-dimensional force functions useful in the wind-response analysis of bluff bodies, such as bridges, that are elongated in the across-wind direction. Airfoil-type theoretical 2-D indicial, admittance, and oscillatory force functions and their interrelationships are first recalled for their analogical value. Following this, a spectral force expression is developed for the lift on a bluff section due to

R. H. Scanlan

2000-01-01

208

MOTION-RELATED BODY-FORCE FUNCTIONS IN TWO-DIMENSIONAL LOW-SPEED FLOW  

Microsoft Academic Search

The paper examines two-dimensional force functions useful in the wind-response analysis of bluff bodies, such as bridges, that are elongated in the across-wind direction. Airfoil-type theoretical 2-D indicial, admittance, and oscillatory force functions and their interrelationships are first recalled for their analogical value. Following this, a spectral force expression is developed for the lift on a bluff section due to

R. H. SCANLAN

2000-01-01

209

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

210

High resolution magnetic force microscopy: instrumentation and application for recording media  

Microsoft Academic Search

This thesis describes aspects of the use of magnetic force microscopy for the study of magnetic recording media. The maximum achievable storage density in magnetic recording is limited by the magnetic reversal behaviour of the medium and by the stability of the written information. The shape and size of the small magnetic units (bits as wen as domaiDs) in the

Steffen Porthun

1996-01-01

211

Comparison of hard magnetic electrodes for magneto-electronics by magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Both spin valve sensor elements and magnetic tunnel junctions usually consist of a magnetically fixed hard magnetic layer and a soft magnetic counter electrode which can rotate freely in an external driving field. In order to yield reliable sensor signals, the hard magnetic electrode should be magnetically rigid against small fields, i.e., must not be influenced during switching of the sensing electrode. Furthermore, in order to provide a homogeneous switching behavior, the electrodes should show uniformity in their magnetic properties, especially if scaled and patterned down to sub-micron lateral sizes. In this paper, magnetic force microscopy is used to compare the magnetic properties of different hard magnetic layer stacks commonly used in magneto-electronic device technology, i.e. an artificial antiferrimagnet (CoFe/Ru/CoFe and Co/Cu/Co) and exchange biased stacks (MnIr/CoFe/Ru/CoFe). The domain pattern of a polycrystalline artificial ferrimagnet (AFi) shows a strong magnetization ripple, i.e., local variations of the magnetization directions, which are maintained in patterned submicron elements. These statistical local fluctuations can be quantitatively correlated with a reduction of the tunneling magnetoresistance (TMR) of 3%-5% in the minor loop. In addition for small area junctions, the ripple can cause different switching fields in neighboring elements. An additional exchange biasing by a thin natural antiferromagnet is shown to rigidly pin the local magnetization fluctuations of the AFi. The process used for the preparation of this system, however, creates 360° domain walls, which again deteriorate the TMR signal.

Brückl, H.; Schmalhonst, J.; Boeve, H.; Gieres, G.; Wecker, J.

2002-05-01

212

Reduction of the unbalanced magnetic force of a transverse flux machine by using symmetric multipair cores  

Microsoft Academic Search

This paper investigates the characteristics of the magnetic force and the torque in the conventional rotatory two-phase transverse flux machine (TFM) by using the three-dimensional finite element method. This research shows that the unbalanced magnetic force is one of the dominant excitation forces in this machine, and it proposes a TFM with symmetric multipair cores in which each stator core

G. H. Jang; N. K. Park; C. I. Lee; J. H. Chang; S. W. Jeong; D. H. Kang

2008-01-01

213

Magnetic Domain Analysis of GMR Spin Valves with CoFe Electrodes via Magnetic Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic Force Microscopy (MFM) has given new insight to the emergence of magnetic domains in giant magnetoresistance (GMR) spin valves with CoFe electrodes. The MFM images, taken under application of different magnetic fields, reveal how the uniformity of magnetization varies in both the parallel state and antiparallel state. In the parallel state, the image shows uniform contrast indicating that the magnetization is uniform through the sample. In the antiparallel state, different colors are present indicating that the direction of magnetization varies. This difference in the direction of magnetization arises from the antiferromagnetic coupling between the free layer and pinned layers in the GMR stack. Additionally, high field saturation allows for the analysis of the magnetic reversal of the pinned layer. MFM images are taken during this magnetic switching to observe the location of the first domains in local structure. Multiple samples will be used with variations in thickness of the free layer, thickness of the nonmagnetic spacer layer between the free and pinned layer, and aspect ratio of the samples. Samples will be grown via dc magnetron sputtering and then patterned with photolithography and ion beam etching.

Dise, Joseph; Schmidt, Robert; Wu, Jun; Stearrett, Ryan; Haughey, Kevin; Xiao, John; Nowak, Edmund

2013-03-01

214

Body-force linear elastic stress intensity factor calculation using fractal two level finite element method  

Microsoft Academic Search

Fractal two level finite element method (F2LFEM) for the analysis of linear fracture problems subjected to body force loading is presented. The main objective here is to show that by employing the F2LFEM a highly accurate and an efficient linear analysis of fracture bodies subjected to internal loading can be obtained as it is hard to find any analytical and

A. Y. T. Leung; R. K. L. Su

1995-01-01

215

Planetary Magnetic Fields and Solar Forcing: Implications for Atmospheric Evolution  

NASA Astrophysics Data System (ADS)

The solar wind and the solar XUV/EUV radiation constitute a permanent forcing of the upper atmosphere of the planets in our solar system, thereby affecting the habitability and chances for life to emerge on a planet. The forcing is essentially inversely proportional to the square of the distance to the Sun and, therefore, is most important for the innermost planets in our solar system—the Earth-like planets. The effect of these two forcing terms is to ionize, heat, chemically modify, and slowly erode the upper atmosphere throughout the lifetime of a planet. The closer to the Sun, the more efficient are these process. Atmospheric erosion is due to thermal and non-thermal escape. Gravity constitutes the major protection mechanism for thermal escape, while the non-thermal escape caused by the ionizing X-rays and EUV radiation and the solar wind require other means of protection. Ionospheric plasma energization and ion pickup represent two categories of non-thermal escape processes that may bring matter up to high velocities, well beyond escape velocity. These energization processes have now been studied by a number of plasma instruments orbiting Earth, Mars, and Venus for decades. Plasma measurement results therefore constitute the most useful empirical data basis for the subject under discussion. This does not imply that ionospheric plasma energization and ion pickup are the main processes for the atmospheric escape, but they remain processes that can be most easily tested against empirical data. Shielding the upper atmosphere of a planet against solar XUV, EUV, and solar wind forcing requires strong gravity and a strong intrinsic dipole magnetic field. For instance, the strong dipole magnetic field of the Earth provides a “magnetic umbrella”, fending of the solar wind at a distance of 10 Earth radii. Conversely, the lack of a strong intrinsic magnetic field at Mars and Venus means that the solar wind has more direct access to their topside atmosphere, the reason that Mars and Venus, planets lacking strong intrinsic magnetic fields, have so much less water than the Earth? Climatologic and atmospheric loss process over evolutionary timescales of planetary atmospheres can only be understood if one considers the fact that the radiation and plasma environment of the Sun has changed substantially with time. Standard stellar evolutionary models indicate that the Sun after its arrival at the Zero-Age Main Sequence (ZAMS) 4.5 Gyr ago had a total luminosity of ?70% of the present Sun. This should have led to a much cooler Earth in the past, while geological and fossil evidence indicate otherwise. In addition, observations by various satellites and studies of solar proxies (Sun-like stars with different age) indicate that the young Sun was rotating more than 10 times its present rate and had correspondingly strong dynamo-driven high-energy emissions which resulted in strong X-ray and extreme ultraviolet (XUV) emissions, up to several 100 times stronger than the present Sun. Further, evidence of a much denser early solar wind and the mass loss rate of the young Sun can be determined from collision of ionized stellar winds of the solar proxies, with the partially ionized gas in the interstellar medium. Empirical correlations of stellar mass loss rates with X-ray surface flux values allows one to estimate the solar wind mass flux at earlier times, when the solar wind may have been more than 1000 times more massive. The main conclusions drawn on basis of the Sun-in-time-, and a time-dependent model of plasma energization/escape is that: 1. Solar forcing is effective in removing volatiles, primarily water, from planets,

Lundin, Rickard; Lammer, Helmut; Ribas, Ignasi

2007-03-01

216

Two-meson exchange hyperonic three-body forces and consequences for neutron stars  

NASA Astrophysics Data System (ADS)

We construct two-meson exchange three-baryon potentials between two nucleons and one hyperon (NNY) consistent with the two body nucleon-hyperon (NY) J04 potential of the Jülich group. In particular, we focus on the NN? and NN?- forces since ? and ?- are the first hyperons expected to appear in microscopic calculations of neutron star matter. Brueckner-Hartree-Fock calculations of the hyperonic matter are then performed including the effect of these three-body forces. Our results show that at high densities the total contribution of the NNY force is repulsive making the resulting equation of state stiffer, as required from neutron star mass observations.

Logoteta, D.; Vidaña, I.; Providência, C.

2013-09-01

217

Linear Step Motor Based on Magnetic Force Control Using Composite of Magnetostrictive and Piezoelectric Materials  

Microsoft Academic Search

We assemble a composite of giant magnetostrictive material (Terfenol-D) and stack piezoelectric transducer (PZT) actuator, and use it in a linear step motor. Control of the magnetic force exploits the inverse magnetostrictive effect of the Terfenol, in which the composite and a magnetic circuit in combination controls the magnetic force on a movable yoke with the voltage of the PZTs

Toshiyuki Ueno; Chee Sze Keat; Toshiro Higuchi

2007-01-01

218

Magnetic force microscopy signal of flux line above a semi-infinite type II-superconductor  

Microsoft Academic Search

We have examined a single flux line in the semi-infinite type-II superconductor. The stray magnetic field of the flux line has been calculated. We have found that the vertical force exerted on a magnetic force microscopy (MFM) tip from the flux line is measurable by currently existing MFM. Two types of magnetic tips were taken into consideration, solid and thin

A. Wadas; O. Fritz; H. J. Hug; H.-J. Güntherodt

1992-01-01

219

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

Microsoft Academic Search

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

J. J. Aly

1984-01-01

220

Electricity, magnetism and the body: some uses and abuses.  

PubMed

The human body can be regarded as an extraordinarily complex electrical machine. It will respond to externally applied electromagnetic stimuli and aspects of its functionality can be interrogated electromagnetically to aid in diagnosis. The paper describes examples of interactions between electromagnetism and the body. The hazards of electric shock are considered along with the use of the defibrillator for restarting the heart. Electromagnetic therapies are discussed in the light of the disappointing lack of objective evidence to support claims for their effectiveness. Finally, two examples of new diagnostic techniques using electromagnetic energy are described. Electrical impedance tomography produces cross-sectional images of the distribution of electrical impedance in the body and magnetic nerve stimulation uses currents induced by large magnetic field pulses to stimulate nerves and the human brain without causing pain. PMID:8021899

Barker, A T

1994-04-01

221

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

222

Localized ferromagnetic resonance using Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Force Microscopy (MRFM) is a novel approach to scanned probe imaging, combining the advantages of Magnetic Resonance Imaging (MRI) with Scanning Probe Microscopy (SPM) [1]. It has extremely high sensitivity that has demonstrated detection of individual electron spins [2] and small numbers of nuclear spins [3]. Here we describe our MRFM experiments on Ferromagnetic thin film structures. Unlike ESR and NMR, Ferromagnetic Resonance (FMR) is defined not only by local probe field and the sample structures, but also by strong spin-spin dipole and exchange interactions in the sample. Thus, imaging and spatially localized study using FMR requires an entirely new approach. In MRFM, a probe magnet is used to detect the force response from the sample magnetization and it provides local magnetic field gradient that enables mapping of spatial location into resonance field. The probe field influences on the FMR modes in a sample, thus enabling local measurements of properties of ferromagnets. When sufficiently intense, the inhomogeneous probe field defines the region in which FMR modes are stable, thus producing localized modes. This feature enables FMRFM to be important tool for the local study of continuous ferromagnetic samples and structures. In our experiments, we explore the properties of the FMR signal as the strength of the local probe field evolves from the weak to strong perturbation limit. This underlies the important new capability of Ferromagnetic resonance imaging, a powerful new approach to imaging ferromagnet. The new developed FMR imaging technique enables FMR imaging and localized FMR spectroscopy to combine spectroscopy and lateral information of ferromagnetic resonance images [4][5]. Our theoretical approach agrees well with spatially localized spectroscopy and imaging results. This approach also allows analysis and reconstruction of FMR modes in a sample. Finally we consider the effect of strong probe fields on FMR modes. In this regime the probe field significantly modifies the FMR modes. In particular we observe the complete local suppression of the FMR mode under the probe. This provides as a new tool for local study of continuous ferromagnetic thin films and microstructures.

Kim, Jongjoo

223

Compensation of magnetic disturbances improves inertial and magnetic sensing of human body segment orientation  

Microsoft Academic Search

This paper describes a complementary Kalman filter design to estimate orientation of human body segments by fusing gyroscope, accelerometer, and magnetometer signals from miniature sensors. Ferromagnetic materials or other magnetic fields near the sensor module disturb the local earth magnetic field and, therefore, the orientation estimation, which impedes many (ambulatory) applications. In the filter, the gyroscope bias error, orientation error,

Daniel Roetenberg; Henk J. Luinge; Chris T. M. Baten; Peter H. Veltink

2005-01-01

224

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

225

Magnetic force acting on a magnetic dipole over a superconducting thin film  

SciTech Connect

The magnetostatic interaction energy and corresponding magnetic force acting on a magnetic point dipole placed above a type-II thin superconducting film in the mixed state with a single vortex are calculated using electromagnetics coupled with the London theory of superconductivity. If a vortex is trapped by a circular defect of radius {ital b}{lt}{Lambda}, the magnetic forces, caused by the vortex, differ from the results of free from defect pinning by the factor (1{minus}{ital b}/{Lambda}), where {Lambda} is the effective penetration depth. The possibility of formation of the vortex in the thin film only in the field of the magnetic point dipole is investigated. The critical position of the dipole for creating the first vortex under the electromagnetic pinning of a circular defect and that position in the absence of defect pinning are obtained for comparison. In particular, in the limit of {ital a}/{Lambda}{gt}1, where {ital a} is the separation between the dipole and the thin film, the only difference between two results is in the cutoff length, i.e., in the case of a circular defect the only difference in the critical position calculation is the cutoff at radius {ital b} rather than at coherence length {xi}. The pinning force of a single vortex by a circular defect is also calculated. Further, we investigate the conditions of the vortex creation for various cases (including the first, second, and third vortices) for a free of pinning center in the examining region. It is found that the creation of a new single vortex in the thin film causes an abrupt change in vertical levitation force: the force changed discontinuously. {copyright} {ital 1996 The American Physical Society.}

Wei, J.C. [Institute of Electro-Optical Engineering, National Chiao-Tung University, Hsinchu, Taiwan, Republic of (China); Chen, J.L. [Department of Electro-Physics, National Chiao-Tung University, Hsinchu, Taiwan, Republic of (China); Horng, L. [Department of Physics, National Changhua University of Education, Changhua, Taiwan, Republic of (China); Yang, T.J. [Department of Electro-Physics, National Chiao-Tung University, Hsinchu, Taiwan, Republic of (China)

1996-12-01

226

Effect of the repulsive force in the HTSC-permanent magnet hybrid bearing system  

NASA Astrophysics Data System (ADS)

Magnetic levitation using the pinning force of the YBaCuO high-Tc bulk superconductor (HTSC) materials has an advantage to achieve stable levitation without control. To increase levitation force, the HTSC-permanent magnet hybrid magnetic bearing system is introduced. A circular shaped three phase Nd-Fe-B permanent magnet is installed on the rotor, and HTSC bulk superconductor is set on the stator. The additional permanent magnet is installed under the HTSC. Repulsive force of the permanent magnet is used for levitation, and pinning force between the HTSC and permanent magnet is used for guidance force of the bearing. In this system, relationship between permanent magnet and the HTSC is important. When repulsive force of the permanent magnet is large, pinning force of superconductor is used to keep the rotor position. As a result, stability for the lateral direction is decreased with hybrid system. For levitation force, effect of the hybrid system is not observed with column HTSC. Compared with the ring HTSC results, the following thing is considered. Because there is no space that flux of one permanent magnet acts on the other one with the column HTSC configuration, interaction between two permanent magnets becomes small.

Ohashi, S.; Kobayashi, S.

2009-10-01

227

Experimental assessment of the effects of body force, surface tension force, and inertia on flow boiling CHF  

Microsoft Academic Search

The interfacial instabilities important to the modeling of critical heat flux (CHF) in reduced-gravity systems are sensitive to even minute body forces, especially for small coolant velocities. Understanding these effects is of paramount importance to both the reliability and safety of two-phase thermal management loops proposed for future space and planetary-based thermal systems. Unfortunately, reduced gravity systems cannot be accurately

Hui Zhang; Issam Mudawar; Mohammad M. Hasan

2002-01-01

228

Self-forces on extended bodies in electrodynamics  

NASA Astrophysics Data System (ADS)

In this paper, we study the bulk motion of a classical extended charge in flat spacetime. A formalism developed by W. G. Dixon is used to determine how the details of such a particle’s internal structure influence its equations of motion. We place essentially no restrictions (other than boundedness) on the shape of the charge, and allow for inhomogeneity, internal currents, elasticity, and spin. Even if the angular momentum remains small, many such systems are found to be affected by large self-interaction effects beyond the standard Lorentz-Dirac force. These are particularly significant if the particle’s charge density fails to be much greater than its 3-current density (or vice versa) in the center-of-mass frame. Additional terms also arise in the equations of motion if the dipole moment is too large, and when the “center-of-electromagnetic mass” is far from the “center-of-bare mass” (roughly speaking). These conditions are often quite restrictive. General equations of motion were also derived under the assumption that the particle can only interact with the radiative component of its self-field. These are much simpler than the equations derived using the full retarded self-field; as are the conditions required to recover the Lorentz-Dirac equation.

Harte, Abraham I.

2006-03-01

229

Torque and unbalanced magnetic force in a rotational unsymmetric brushless DC motors  

Microsoft Academic Search

The pole-teeth-winding configuration in brushless dc motors determines torque and unbalanced magnetic force which are the resultants of the tangential and the normal magnetic force in a small air gap, respectively. This paper calculated torque and unbalanced magnetic force using FEM, Maxwell stress tensor to investigate the influence of pole-teeth-winding patterns on the performance from two common designs, i.e. the

G. H. Jang; J. W. Yoon; N. Y. Park; S. M. Jang

1996-01-01

230

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

231

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

232

High Frequency Cantilevers for Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

We are exploring the possibility of using high frequency cantilevers for detection of magnetic resonance spin signals, possibly at the Larmor frequency of nuclear spins. For this purpose we have fabricated smaller, 20 micron long cantilevers that resonate at frequencies near 1 MHz. Operating at 4K, these levers can have surprisingly high Q values, over 300,000, and can achieve force noise levels in the few attonewton range, despite their rather high stiffness of about 0.1 Newton per meter. We discuss some experimental challenges that will be increasingly important for future generations of cantilevers with even smaller dimensions. Finally we look ahead into what we might expect when such high sensitivity, nanomechanical resonators become tightly coupled to small ensembles of nuclear spins.

Degen, Christian; Poggio, Martino; Chui, Ben; Mamin, John; Rugar, Dan

2007-03-01

233

Micromagnetic studies on resolution limits of magnetic force microscopy tips with different magnetic anisotropy  

NASA Astrophysics Data System (ADS)

In magnetic force microscopy (MFM), it is effective to control the magnetic properties of the coating materials on the MFM tip to achieve higher resolution. In this work, the effect of the magnetic anisotropy of the tip-coating, such as perpendicular magnetic anisotropy (PMA), in-plane magnetic anisotropy (IMA), and random magnetic anisotropy (RMA), on the MFM image resolution are studied by micromagnetics. An accurate 3 D micromagnetic model of the CoPt pyramid MFM tip, with a cone angle of 37°, tip height of 120 nm, coating thickness of 7.6 nm, and average grain size of about 8.8 nm, was setup to calculate the domain structure and the stray field of the tip. A CoPt disk medium, with a bit size of 24 × 32 nm2 and film thickness of 8 nm, was chosen for image simulation. The PMA tip is advantageous in low scan height (SH) measurement with little tip-sample interaction due to its sharp and small stray field, while the IMA tip will disturb the magnetic moments of the medium at a low SH due to its strong stray field, and the RMA tip cannot read the bits with clear image contrast due to its broader field distribution.

Li, Hongjia; Wei, Dan; Piramanayagam, S. N.

2012-04-01

234

The substrate as a skeleton: ground reaction forces from a soft-bodied legged animal.  

PubMed

The measurement of forces generated during locomotion is essential for the development of accurate mechanical models of animal movements. However, animals that lack a stiff skeleton tend to dissipate locomotor forces in large tissue deformation and most have complex or poorly defined substrate contacts. Under these conditions, measuring propulsive and supportive forces is very difficult. One group that is an exception to this problem is lepidopteran larvae which, despite lacking a rigid skeleton, have well-developed limbs (the prolegs) that can be used for climbing in complex branched structures and on a variety of surfaces. Caterpillars therefore are excellent for examining the relationship between soft body deformation and substrate reaction forces during locomotion. In this study, we devised a method to measure the ground reaction forces (GRFs) at multiple contact points during crawling by the tobacco hornworm (Manduca sexta). Most abdominal prolegs bear similar body weight during their stance phase. Interestingly, forward reaction forces did not come from pushing off the substrate. Instead, most positive reaction forces came from anterior abdominal prolegs loaded in tension while posterior legs produced drag in most instances. The counteracting GRFs effectively stretch the animal axially during the second stage of a crawl cycle. These findings help in understanding how a terrestrial soft-bodied animal can interact with its substrate to control deformation without hydraulic actuation. The results also provide insights into the behavioral and mechanistic constraints leading to the evolution of diverse proleg arrangements in different species of caterpillar. PMID:20228350

Lin, Huai Ti; Trimmer, Barry A

2010-04-01

235

Numerical analysis on the action of centrifuge force in magnetic fluid rotating shaft seals  

Microsoft Academic Search

The magnetic fluid seal is suitable for high-speed rotating shaft seal applications. Centrifuge force will have evident influence on magnetic fluid rotating shaft seals. The seal capacity of the rotating shaft seal can be improved or increased by some measures. Through hydrodynamic analysis the moving status of the magnetic fluid is worked out. By numerical method, the magnetic field and

Jibin Zou; Xuehui Li; Yongping Lu; Jianhui Hu

2002-01-01

236

Stress and deformation in soft elastic bodies due to intermolecular forces  

NASA Astrophysics Data System (ADS)

Intermolecular interaction within one and between two incompressible, soft elastic bodies is studied at a continuous level. We show that the macroscopic effect of the interaction can be characterized by a deformation-dependent Maxwell stress. The divergence of the Maxwell stress gives the body force, while the inner product of it with the outward normal of a body generates the surface traction. Accordingly, we can replace the contribution of intermolecular forces to the deformation and stress in the body by that of either the body force or the surface traction. Both approaches are proved to be equivalent, in the sense that the resulting displacements are the same and the stresses are linked by an exact correspondence relation. If the deformation induced by the interaction is small, the equations are simplified up to the first order of the displacement gradient. Two examples are given as well to illustrate some features of local stress distribution in a body caused by self and other-body interactions.

He, L. H.

2013-06-01

237

Locating and quantifying ceramic body armor impact forces on a compliant torso using acceleration mapping  

NASA Astrophysics Data System (ADS)

This research experimentally implements a new method to identify the location and magnitude of a single impulsive excitation to ceramic body armor, which is supported on a compliant torso. The method could easily be extended to other flexibly supported components that undergo rigid body dynamics. Impact loads are identified in two steps. First, the location of the impact force is determined from time domain acceleration responses by comparing them to an array of reference acceleration time histories. Then based on the estimated location, reference frequency response functions are used to reconstruct the input force in the frequency domain through a least squares inverse problem. Experimental results demonstrate the validity of this method at both low energy excitations, which are produced by a medium modally-tuned impact hammer, and at high energy excitations, which are produced by dropping rods with masses up to 0.6 kilograms from a height of 2 meters. The maximum error in the estimated location or magnitude for the low energy excitations on the 10 cm square ceramic body armor was 7.07 mm with an average error of 1.09 mm. In comparing the estimated force for the low energy excitations to the force recorded by the transducer in the modal impact hammer, the maximum error in the predicted force amplitude was 6.78 percent and the maximum error in the predicted impulse was 6.44 percent. For the high energy excitations, which produced accelerations at the measurement locations up to 50 times greater than that of the low energy excitations, the maximum error in the predicted location of the input force was 15 mm with an average error of 6.64 mm. There was no force transducer to capture the input force on the body armor from the rod, but from non-energy-dissipative projectile motion equations the validity of the solutions was confirmed by comparing the impulses.

Cardi, Adam A.; Adams, Douglas E.; Walsh, Shawn

2006-04-01

238

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

239

Short-range repulsive three-body force and the point proton density of 3 He  

Microsoft Academic Search

Summary  We consider anad hoc short-range repulsive three-body force of the form of exp [- (x\\u000a 2 + y2 + z2)\\/r\\u000a 0\\u000a 2\\u000a ], wherex, y andz are interparticle distances andr\\u000a 0 ? 1 fm, and examine its effect on the point proton density of3He around the centre. We conclude that, no matter how strong the additional three-body force is, its

S. Azam; Y. Nogami; N. Ohtsuka

1983-01-01

240

Optical response of magnetic fluorescent microspheres used for force spectroscopy in the evanescent field.  

PubMed

Force spectroscopy based on magnetic tweezers is a powerful technique for manipulating single biomolecules and studying their interactions. The resolution in magnetic probe displacement, however, needs to be commensurate with molecular sizes. To achieve the desirable sensitivity in tracking displacements of the magnetic probe, some recent approaches have combined magnetic tweezers with total internal reflection fluorescence microscopy. In this situation, a typical force probe is a polymer microsphere containing two types of optically active components: a pure absorber (magnetic nanoparticles for providing the pulling force) and a luminophore (semiconducting nanoparticles or organic dyes for fluorescent imaging). To assess the system's capability fully with regard to tracking the position of the force probe with subnanometer accuracy, we developed a body-of-revolution formulation of the method of auxiliary sources (BOR-MAS) to simulate the absorption, scattering, and fluorescence of microscopic spheres in an evanescent electromagnetic field. The theoretical formulation uses the axial symmetry of the system to reduce the dimensionality of the modeling problem and produces excellent agreement with the reported experimental data on forward scattering intensity. Using the BOR-MAS numerical model, we investigated the probe detection sensitivity for a high numerical aperture objective. The analysis of both backscattering and fluorescence observation modes shows that the total intensity of the bead image decays exponentially with the distance from the surface (or the length of a biomolecule). Our investigations demonstrate that the decay lengths of observable optical power are smaller than the penetration depth of the unperturbed excitation evanescent wave. In addition, our numerical modeling results illustrate that the expected sensitivity for the decay length changes with the angle of incidence, tracking the theoretical penetration depth for a two-media model, and is sensitive to the bead size. The BOR-MAS methodology developed in this work for near-field modeling of bead-tracking experiments fully describes the fundamental photonic response of microscopic BOR probes at the subwavelength level and can be used for future improvements in the design of these probes or in the setup of bead-tracking experiments. PMID:20486724

Bijamov, Alex; Shubitidze, Fridon; Oliver, Piercen M; Vezenov, Dmitri V

2010-07-20

241

Optical Response of Magnetic-Fluorescent Microspheres Used for Force Spectroscopy in the Evanescent Field  

PubMed Central

Force spectroscopy based on magnetic tweezers is a powerful technique to manipulate single biomolecules and study their interactions. The resolution in a magnetic probe displacement, however, needs to be commensurate with molecular sizes. To achieve the desirable sensitivity in tracking displacements of the magnetic probe, some recent approaches have combined magnetic tweezers with total internal reflection fluorescence microscopy. In this situation, a typical force probe is a polymer microsphere containing two types of optically active components – a pure absorber (magnetic nanoparticles for providing the pulling force) and a luminophore (semiconducting nanoparticles or organic dyes for fluorescent imaging). In order to fully assess the system’s capability for tracking the position of the force probe with sub-nanometer accuracy, we developed a body-of-revolution formulation of the method of auxiliary sources (BOR-MAS) to simulate absorption, scattering, and fluorescence of microscopic spheres in an evanescent electromagnetic field. The theoretical formulation uses the axial symmetry of the system to reduce the dimensionality of the modeling problem and produces excellent agreement with the reported experimental data on forward scattering intensity. Using the BOR-MAS numerical model, we investigated the probe detection sensitivity for a high numerical aperture objective. The analysis of both backscattering and fluorescence observation modes shows that the total intensity of the bead image decays exponentially with the distance from the surface (or the length of a biomolecule). Our investigations demonstrate that the decay lengths of observable optical power are smaller than the penetration depth of the unperturbed excitation evanescent wave. In addition, our numerical modeling results illustrate that the expected sensitivity for the decay length changes with the incident angle, tracking the theoretical penetration depth for a two-media model, and is sensitive to the bead size. The BOR-MAS methodology developed in this work for near field modeling of bead tracking experiments fully describes the fundamental photonic response of microscopic BOR probes at the sub-wavelength level and can be used for future improvements in the design of these probes or in the setup of bead tracking experiments.

Bijamov, Alex; Shubitidze, Fridon; Oliver, Piercen M.; Vezenov, Dmitri V.

2010-01-01

242

Wing and body motion and aerodynamic and leg forces during take-off in droneflies.  

PubMed

Here, we present a detailed analysis of the take-off mechanics in droneflies performing voluntary take-offs. Wing and body kinematics of the insects during take-off were measured using high-speed video techniques. Based on the measured data, the inertia force acting on the insect was computed and the aerodynamic force of the wings was calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. In take-off, a dronefly increases its stroke amplitude gradually in the first 10-14 wingbeats and becomes airborne at about the 12th wingbeat. The aerodynamic force increases monotonously from zero to a value a little larger than its weight, and the leg force decreases monotonously from a value equal to its weight to zero, showing that the droneflies do not jump and only use aerodynamic force of flapping wings to lift themselves into the air. Compared with take-offs in insects in previous studies, in which a very large force (5-10 times of the weight) generated either by jumping legs (locusts, milkweed bugs and fruit flies) or by the 'fling' mechanism of the wing pair (butterflies) is used in a short time, the take-off in the droneflies is relatively slow but smoother. PMID:24132205

Chen, Mao Wei; Zhang, Yan Lai; Sun, Mao

2013-10-16

243

Experimental validation of magnetic and electric local force formulations associated to energy principle  

Microsoft Academic Search

In the design process of any device, the computation of the forces or the torque is often a decisive step. Finite element solutions give accurate solutions in terms of magnetic field or flux density. But for local force computation associated to a magnetic field, many formulations are available. They use different physical interpretations of the same phenomenon. Here, a new

Olivier Barré; Pascal Brochet; Michel Hecquet

2006-01-01

244

Design of fluid bearing spindle motors with controlled unbalanced magnetic forces  

Microsoft Academic Search

This paper discusses the beneficial and detrimental effects of unbalanced magnetic forces developed in a fluid bearing spindle motor used for hard disk drives. The analysis made in this paper shows that unbalanced forces can be useful for magnetic preloading and stabilizing the fluid bearing system of a hard disk drive spindle motor

S. X. Chen; Q. D. Zhang; Z. J. Liu; H. Lin

1997-01-01

245

Magnetic levitation force measurement on high [Tc] superconducting ceramic/polymer composites  

SciTech Connect

An experimental study of magnetic levitation force for 0--3 and 3--3 superconducting ceramic/polymer composites is presented. A simple, inexpensive force versus distance measurement technique is described. The measurements of force against distance or magnetic field show strong hysteretic behavior, which is similar to the sintered superconductor ceramics and is consistent with the hysteresis in magnetization of superconductor. The volume fraction dependence and sample thickness dependence of the levitation forces are also studied for 0--3 composites. Results suggest that the new composite materials are most suitable for levitation applications.

Unsworth, J.; Du, Jia; Crosby, B.J. (Univ. of Tech., Sydney (Australia)); Macfarlane, J.C. (CSIRO, Linfield (Australia))

1993-01-01

246

Accumulation of magnetically labeled rat mesenchymal stem cells using an external magnetic force, and their potential for bone regeneration.  

PubMed

We evaluated the effect of a novel mesenchymal stem cell (MSC) delivery system using magnetic beads and an external magnetic force, and investigated the osteogenic potential of MSCs coupled with magnetic beads in vitro. MSCs were isolated from the bone marrow of 8-week-old Sprague Dawley green fluorescent protein rats, and expanded in a monolayer culture system. Magnetic beads (Ferri Sphere 100C) with carboxyl groups on the surface were conjugated to anti-rat CD44 mouse monoclonal antibodies by an amide linkage. Expanded MSCs were then combined with the magnetic beads and the MSC-magnetic bead complexes were seeded onto phi100 mm dishes at low density (5 x 10(3) cells/dish) with or without the influence of an external magnetic force provided by a neodymium magnet and supplemented with osteogenic differentiation medium. The complexes could be accumulated effectively by the influence of the external magnetic force. Moreover, the complexes could also differentiate into the osteogenic lineage in the monolayer culture system, as verified by alizarin red staining and RT-PCR for alkaline phosphatase and osteocalcin expression. These findings clearly demonstrate the possibility of a novel cell delivery system using MSCs with magnetic beads and an external magnetic force for bone regeneration. If this treatment option is established, it will be minimally invasive when compared to conventional treatments. PMID:17806114

Sugioka, Toshihiro; Ochi, Mitsuo; Yasunaga, Yuji; Adachi, Nobuo; Yanada, Shinobu

2008-06-01

247

Optimization of perpendicular magnetic anisotropy tips for high resolution magnetic force microscopy by micromagnetic simulations  

NASA Astrophysics Data System (ADS)

Magnetic Force Microscopy (MFM) tip coated with perpendicular magnetic anisotropy film (PMA tip) is one of the choices for high resolution imaging at low scan height (SH), since it has negligible tip-sample interaction related to its stable magnetic state, sharp, and small tip stray field. In this work, detailed micromagnetic studies are carried out to understand the effect of geometrical and magnetic parameters including the cone angle ? of the PMA tip, intergrain exchange constant , saturation magnetization M s and uniaxial crystalline anisotropy constant K 1 of the tip coating on the MFM tip resolution. To evaluate the resolution performance of the optimized PMA tip, MFM images of high-density granular recording media and patterned media are simulated. We find that, for the PMA tip and its coating, a cone angle in a range of 36.9? to 53.1?, a saturation M s of 700 emu/cm3, a large uniaxial crystalline anisotropy constant K 1 (>4.9×106 erg/cm3) and a high intergrain exchange constant of (0.3-1.0)×10-6 erg/cm are optimized conditions for high resolution imaging. The optimized PMA tip has an excellent performance on imaging of high-density thin film media (bit size of 8×16 nm2) at low SH of 2-8 nm and bit pattern media with a pitch of 50 nm, edge-edge spacing of 5-15 nm at SH of 8-15 nm.

Li, Hongjia; Wei, Dan; Piramanayagam, S. N.

2013-09-01

248

Topological evolution of Parker-unstable galactic magnetic fields under the influence of Coriolis force and magnetic reconnection  

NASA Astrophysics Data System (ADS)

We investigate the influence of the Coriolis force and magnetic reconnection on the evolution of the Parker instability in galactic disks. We apply a model of a local gas cube, permeated by an azimuthal large-scale magnetic field and solve numerically resistive 3D MHD equations including the contribution of the Coriolis force. We introduce a current-dependent resistivity which switches the magnetic reconnection above a certain critical current density. We study the evolution of the magnetic field topology and the formation of large-scale poloidal magnetic fields from the initial azimuthal field. Our simulations demonstrate that the Parker instability leads to the formation of helically twisted magnetic flux tubes which are then agglomerated by magnetic reconnection forming, a significant poloidal magnetic field component on the scale of the whole cube. Such an evolution represents a kind of fast dynamo process as proposed by Parker (1992, ApJ 401, 137).

Hanasz, M.; Otmianowska-Mazur, K.; Lesch, H.

2002-04-01

249

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

250

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

251

Magnetic flux and lines of force for the Hertzian electric dipole and nonsinusoidal waves  

Microsoft Academic Search

The authors present computer plots of magnetic lines of force for the Hertzian electric dipole excited by sinusoidal currents that radiate to the far-field electromagnetic waves with the time variation of a Gaussian pulse. Plots of lines of force for sinusoidal waves are also presented for comparison. Since the density of the lines of force at any distance from the

M. G. M. Hussain; A. A. Omar

1990-01-01

252

Magnetic fields produced by steady currents in the body.  

PubMed Central

The magnetic fields produced by naturally occurring steady currents in the body were measured by using a new magnetic gradiometer in a magnetically shielded room. A field of 0.1 micro G/cm with reproducible pattern was seen over the head and over the limbs, whereas the field over the torso proper was weaker (except over the abdomen). Most of the field over the head is produced by electrical sources associated with the hair follicles of the scalp; this field is produced only as a response to touching or pressing the scalp, in regions where the hair is dense. Most of the field over the limbs is produced by electrical sources associated with the muscles. The field over the forearm, studied in detail, was often present spontaneously; when absent, it could be induced by mild twisting and rubbing. On the basis of auxiliary experiments involving electrolytes, a general mechanism for generation of steady current in the body is suggested. In this mechanism, the steady current is generated by a nonclosed or a nonuniform polarized layer across an elongated semipermeable membrane such as a muscle fiber; the nonuniform polarization is due to a gradient of extracellular K+ along the membrane.

Cohen, D; Palti, Y; Cuffin, B N; Schmid, S J

1980-01-01

253

Magnetic fields produced by steady currents in the body.  

PubMed

The magnetic fields produced by naturally occurring steady currents in the body were measured by using a new magnetic gradiometer in a magnetically shielded room. A field of 0.1 micro G/cm with reproducible pattern was seen over the head and over the limbs, whereas the field over the torso proper was weaker (except over the abdomen). Most of the field over the head is produced by electrical sources associated with the hair follicles of the scalp; this field is produced only as a response to touching or pressing the scalp, in regions where the hair is dense. Most of the field over the limbs is produced by electrical sources associated with the muscles. The field over the forearm, studied in detail, was often present spontaneously; when absent, it could be induced by mild twisting and rubbing. On the basis of auxiliary experiments involving electrolytes, a general mechanism for generation of steady current in the body is suggested. In this mechanism, the steady current is generated by a nonclosed or a nonuniform polarized layer across an elongated semipermeable membrane such as a muscle fiber; the nonuniform polarization is due to a gradient of extracellular K+ along the membrane. PMID:6929495

Cohen, D; Palti, Y; Cuffin, B N; Schmid, S J

1980-03-01

254

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

255

Magnetic force microscopy of GaSb\\/Mn digital alloy epilayers and patterned structures  

Microsoft Academic Search

Magnetic force microscopy was used to investigate the magnetic structures in epitaxial GaSb\\/Mn digital alloys and in laterally patterned structures at room temperature. For epilayers of GaSb\\/Mn digital alloys, magnetic structures of both as-grown and annealed samples were investigated. The as-grown samples are nearly featureless, except for patterns related to dislocations (verified with atomic force microscopy). The results indicate that

Miyeon Cheon; Gibum Kim; Xi Chen; Shumin Wang; Hong Luo; X. Liu; Y. Sasaki; T. Wojtowicz; J. K. Furdyna

2002-01-01

256

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

NASA Astrophysics Data System (ADS)

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.

Chen, Youping

2006-02-01

257

Estimation of the radial force using a disturbance force observer for a magnetically levitated centrifugal blood pump.  

PubMed

Evaluation of the hydraulic forces in a magnetically levitated (maglev) centrifugal blood pump is important from the point of view of the magnetic bearing design. Direct measurement is difficult due to the absence of a rotor shaft, and computational fluid dynamic analysis demands considerable computational resource and time. To solve this problem, disturbance force observers were developed, using the radial controlled magnetic bearing of a centrifugal blood pump, to estimate the radial forces on the maglev impeller. In order to design the disturbance observer, the radial dynamic characteristics of a maglev impeller were evaluated under different working conditions. It was observed that the working fluid affects the additional mass and damping, while the rotational speed affects the damping and stiffness of the maglev system. Based on these results, disturbance force observers were designed and implemented. The designed disturbance force observers present a bandwidth of 45 Hz. In non-pulsatile conditions, the magnitude of the estimated radial thrust increases in proportion to the flowrate, and the rotational speed has little effect on the force direction. At 5 l/min against 100 mmHg, the estimated radial thrust is 0.95 N. In pulsatile conditions, this method was capable of estimating the pulsatile radial thrust with good response. PMID:20839658

Pai, C N; Shinshi, T; Shimokohbe, A

2010-01-01

258

Scattering from a magnetic flux line due to the Lorentz force of the return flux  

Microsoft Academic Search

The differential cross section for the scattering of an electron by an impenetrable, infinitely long magnetic flux line with return magnetic flux uniformly distributed on the surface of a cylinder of radius a is calculated. The scattering is due to the Lorentz force from the magnetic field of the return flux. In the limit as the radius of the return

Donald H. Kobe; J. Q. Liang

1988-01-01

259

Radiative Activity of Magnetic White Dwarf Undergoing Lorentz-Force Torsional Vibrations  

Microsoft Academic Search

We study radiative activity of magnetic white dwarf undergoing torsional vibrations about axis of its own dipole magnetic moment under the action of Lorentz restoring force. It is shown that pulsating white dwarf can convert its vibration energy into the energy of magneto-dipole emission, oscillating with the frequency equal to the frequency of Alfvén torsional vibrations, provided that internal magnetic

S. I. Bastrukov; J. W. Yu; R. X. Xu; I. V. Molodtsova

2011-01-01

260

Thrust Force of Novel PM Transverse Flux Linear Oscillating Actuators With Moving Magnet  

Microsoft Academic Search

This paper investigates the thrust forces of two novel permanent magnet transverse flux linear oscillating actuators (TFLOAs), one with moving magnet and the other moving both magnet and iron core, for pump and compressor drives. Different from the conventional linear actuators, the lamination construction of the TFLOAs is similar to that of a normalrotating motor, which is easy to stack.

Qinfen Lu; Minghu Yu; Yunyue Ye; Youtong Fang; Jianguo Zhu

2011-01-01

261

Novel Microrobots and Micromotors Using Lorentz Force Driven Linear Microactuators Based on Polymer Magnets  

Microsoft Academic Search

This paper reports on the development of several novel microelectromechanical systems (MEMS) machines based on linear Lorentz force actuators. These were monolithically fabricated and include micromachined polymer magnets. Polymer magnets allow a highly flexible definition of magnetic areas, arbitrary shape, and properties. By combining these linear actuators with mechanical compliant structures using Epon SU-8, we were able to build in-plane

M. Feldmann; S. Buttgenbach

2007-01-01

262

Experimental Measurement and Simulated Verification of the Unbalanced Magnetic Force in Brushless DC Motors  

Microsoft Academic Search

This paper investigates the characteristics of the unbalanced magnetic force (UMF) of a brushless dc (BLDC) motor due to uneven magnetization of a permanent magnet (PM), rotor eccentricity, stator eccentricity, and interactions between these factors. An experimental device is developed to measure the UMF of an electric motor directly. Finite-element analysis is performed to compare experimental and simulated results. The

C. I. Lee; G. H. Jang

2008-01-01

263

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

264

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

2004-01-16

265

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

266

An Analytical Model of Unbalanced Magnetic Force in Fractional-Slot Surface-Mounted Permanent Magnet Machines  

Microsoft Academic Search

We present an analytical model of unbalanced magnetic force (UMF) in fractional-slot surface-mounted permanent magnet (PM) machines having diametrically asymmetrical winding distribution but no static\\/dynamic rotor eccentricities. It is based on a 2-D analytical field model and accounts for the influence of both the radial and tangential force waves under any load condition. It is capable of providing insight into

L. J. Wu; Z. Q. Zhu; J. T. Chen; Z. P. Xia

2010-01-01

267

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

268

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

269

Magnetically labeled human natural killer cells, accumulated in vitro by an external magnetic force, are effective against HOS osteosarcoma cells.  

PubMed

We evaluated the efficacy of a novel natural killer (NK) cell delivery system in vitro, and also investigated the antitumor effect of the accumulated cells on HOS osteosarcoma cells. Human peripheral blood mononuclear cells were isolated and co-cultured with inactivated K562 erythroleukaemic cells in the presence of IL-2 for 5 days. CD3- CD56+ NK cells were labeled with immunomagnetic beads and separated using a magnetic cell sorting system. Purity and cytotoxicity against K562 cells and HOS cells of the magnetically labeled NK cells were measured. To evaluate whether magnetically labeled NK cells could be accumulated in a specific area by magnetic force, the NK cells were placed in chamber slides in the presence, or not, of an external magnetic force of a neodymium magnet (diameter: 1.5 mm, height: 3 mm, total magnetic flux density: 0.282 T). Moreover, to investigate the antitumor effect on HOS cells, the magnetically labeled NK cells were added to HOS cells in chamber slides in the presence, or not, of an external magnetic force for various times. HOS cells were subsequently stained with Papanicolaou for histological examination. It was found that the magnetically labeled NK cells were highly purified and had cytotoxicity against target cells. The NK cells were accumulated effectively by the magnetic field and, when the NK cells were added to HOS cells in a chamber slide with a magnet placed beneath, a significantly larger number of HOS cells detached from the magnet zone than from other zones. Apoptosis was detected in most detached HOS cells. In conclusion, these findings indicate that magnetically accumulated NK cells efficiently induced apoptosis in HOS cells, suggesting that magnetic targeting therapy using magnetically labeled NK cells holds promise as an immunotherapy for osteosarcoma. PMID:16142312

Nakashima, Yuko; Deie, Masataka; Yanada, Shinobu; Sharman, Patrick; Ochi, Mitsuo

2005-10-01

270

Levitation force and magnetic stiffness in bulk high-temperature superconductors  

SciTech Connect

Levitation forces between a small permanent magnet and a disk of bulk high-temperature superconductor at 77 K were measured as a function of vertical separation for disks of composition Y-Ba-Cu-O, Ag/Y-Ba-Cu-O, (Pb,Bi)-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O. The forces were highly hysteretic; however, for all samples, on the initial descent of the magnet toward the disk, the force was unique, independent of magnet speed, and varied approximately as the negative exponential of the separation distance. Magnetic stiffness, associated with minor hysteresis loops, was found to be approximately proportional to the levitation force, and nearly independent of magnet configuration and superconductor composition.

Chang, P.Z.; Moon, F.C. (Department of Mechanical Engineering Department of Aerospace Engineering, Cornell University, Ithaca, New York 14853 (USA)); Hull, J.R.; Mulcahy, T.M. (Materials Division Components Technology Division, Argonne National Laboratory, Argonne, Illinois 60439 (USA))

1990-05-01

271

Tri-axial forces at the seat and backrest during whole-body vertical vibration  

NASA Astrophysics Data System (ADS)

During exposure of seated subjects to vertical whole-body vibration, forces in the fore-and-aft, lateral and vertical directions at the seat and backrest have been measured. The responses at the seat have been compared with those measured previously on a seat without a backrest. Twelve male subjects were exposed to random vertical vibration in the frequency range 0.25-20Hz. The subjects sat on a rigid seat with a rigid backrest and were exposed to a 16 different conditions: four vibration magnitudes (0.125, 0.25, 0.625, and 1.25ms-2 r.m.s.) and four sitting postures (with varying thigh contact with the seat). Although the excitation was vertical, considerable dynamic forces were found in the fore-and-aft direction on both the seat and the backrest. In the vertical direction on the backrest, and in the lateral direction on the seat and the backrest, the forces were low. At both the seat and the backrest, forces in all directions showed a non-linear behaviour. The presence of the backrest modified the forces on the seat in both the vertical and fore-and-aft directions: in all four postures there was an increase in the resonance frequency of the apparent mass when using the backrest. The effect of the backrest on fore-and-aft forces on the seat depended on whether the feet were supported or not. The results show the importance of considering the backrest when studying the response of the human body to whole-body vertical vibration.

Nawayseh, N.; Griffin, M. J.

2004-10-01

272

The effect of photogravitational force and oblateness in the perturbed restricted three-body problem  

NASA Astrophysics Data System (ADS)

The model of restricted three-body is generalized to include the effects of the oblateness, the radiation pressure and fictitious forces. The positions of libration points, their stability, the critical mass ratio and periodic orbits emanating from these points are analyzed under the influence of these effects. The results obtained are more generalized. In addition the locations of the out of plane equilibrium points are studied. We also observe that there is no explicit effect for the perturbation of Coriolis force on the positions of the out of plane equilibrium points. It is worth mentioning that this model can be degraded into 128 special cases.

Abouelmagd, Elbaz I.

2013-07-01

273

Triaxial forces at the seat and backrest during whole-body fore-and-aft vibration  

Microsoft Academic Search

The fore-and-aft, lateral and vertical forces on a seat and a backrest have been investigated with 12 male subjects exposed to random fore-and-aft whole-body vibration (0.25–10Hz) at four vibration magnitudes (0.125, 0.25, 0.625, and 1.25ms?2rms). Subjects sat in each of four sitting postures having varying foot heights, so as to produce differing thigh contact with the seat.The fore-and-aft forces on

Naser Nawayseh; Michael J. Griffin

2005-01-01

274

Characteristics and radial magnetic force of interior permanent magnet synchronous motor according to pole\\/slot combinations  

Microsoft Academic Search

This paper presents motor characteristics and radial magnetic force (RMF) of interior permanent magnet synchronous motors (IPMSM) according to pole\\/slot combinations. Three IPMSM of 15, 18, 24 slots with 16 poles are selected; 16 poles 15 slots and 18 slots provide high winding factor and 16 poles 24 slots is a general pole-slot combination. Using finite element analysis (FEA) and

Soon-O Kwon; Jeong-Jong Lee; Tao Sun; Jung-Pyo Hong

2009-01-01

275

Magnetic domain structures and stray fields of individual elongated magnetite grains revealed by magnetic force microscopy (MFM)  

Microsoft Academic Search

In order to clarify the relationship between microscopic and macroscopic magnetic features of a rock, we applied magnetic force microscopy (MFM) as a local probe on a sample with an intense natural remanent magnetisation, a norite from Heskestad, Norway. We studied in detail seven magnetite (Fe3O4) exsolution lamellae, five of them were about 30?m long and a few micrometers wide,

C. Frandsen; S. L. S. Stipp; S. A. McEnroe; M. B. Madsen; J. M. Knudsen

2004-01-01

276

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

277

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

278

Nuclear pairing from bare interaction: Two and three-body chiral forces  

SciTech Connect

In a recent paper the {sup 1}S{sub 0} pairing gap in isospin-symmetric nuclear matter and finite nuclei has been investigated starting from the chiral nucleon-nucleon potential at the N{sup 3}LO order in the two-body sector and the N{sup 2}LO order in the three-body sector. To include realistic nuclear forces in RHB (Relativistic Hartree Bolgoliubov) calculations we relied on a separable representation of the pairing interaction. In this paper we would like to show recent results concerning isotonic chains with N= 28,50,82.

Finelli, Paolo [Physics Department, University of Bologna, Via Irnerio 46, 40126 Bologna (Italy); INFN, Section of Bologna, Viale Berti Pichat 6/2, 40127 Bologna (Italy)

2012-10-20

279

Effect of hyperonic three-body forces on the maximum mass of neutron stars  

NASA Astrophysics Data System (ADS)

A model based on a microscopic Brueckner-Hartree-Fock approach of hyperonic matter supplemented with additional simple phenomenological density-dependent contact terms is employed to estimate the effect of hyperonic three-body forces on the maximum mass of neutron stars. Our results show that although hyperonic three-body forces can reconcile the maximum mass of hyperonic stars with the current limit of 1.4 - 1.5Modot, they are unable to provide the repulsion needed to make the maximum mass compatible with the observation of massive neutron stars, such as the recent measurements of the unusually high masses of the millisecond pulsars PSR J1614-2230 (1.97 ± 0.04Modot) and PSR J1903+0327 (1.667 ± 0.021Modot).

Logoteta, D.; Vidaña, I.; Providência, C.; Polls, A.; Bombaci, I.

2012-02-01

280

Multi-body simulation of a canine hind limb: model development, experimental validation and calculation of ground reaction forces  

PubMed Central

Background Among other causes the long-term result of hip prostheses in dogs is determined by aseptic loosening. A prevention of prosthesis complications can be achieved by an optimization of the tribological system which finally results in improved implant duration. In this context a computerized model for the calculation of hip joint loadings during different motions would be of benefit. In a first step in the development of such an inverse dynamic multi-body simulation (MBS-) model we here present the setup of a canine hind limb model applicable for the calculation of ground reaction forces. Methods The anatomical geometries of the MBS-model have been established using computer tomography- (CT-) and magnetic resonance imaging- (MRI-) data. The CT-data were collected from the pelvis, femora, tibiae and pads of a mixed-breed adult dog. Geometric information about 22 muscles of the pelvic extremity of 4 mixed-breed adult dogs was determined using MRI. Kinematic and kinetic data obtained by motion analysis of a clinically healthy dog during a gait cycle (1 m/s) on an instrumented treadmill were used to drive the model in the multi-body simulation. Results and Discussion As a result the vertical ground reaction forces (z-direction) calculated by the MBS-system show a maximum deviation of 1.75%BW for the left and 4.65%BW for the right hind limb from the treadmill measurements. The calculated peak ground reaction forces in z- and y-direction were found to be comparable to the treadmill measurements, whereas the curve characteristics of the forces in y-direction were not in complete alignment. Conclusion In conclusion, it could be demonstrated that the developed MBS-model is suitable for simulating ground reaction forces of dogs during walking. In forthcoming investigations the model will be developed further for the calculation of forces and moments acting on the hip joint during different movements, which can be of help in context with the in silico development and testing of hip prostheses.

2009-01-01

281

Torsional resonance mode magnetic force microscopy: enabling higher lateral resolution magnetic imaging without topography-related effects  

NASA Astrophysics Data System (ADS)

We present experimental work that reveals the benefits of performing magnetic force microscopy measurements employing the torsional resonance mode of cantilever oscillation. This approach provides two clear advantages: the ability of performing magnetic imaging without topography-related interference and the significant lateral resolution improvement (approximately 15%). We believe that this work demonstrates a significant improvement to a versatile magnetic imaging technique widely used in academia and in industry.

Kaidatzis, A.; García-Martín, J. M.

2013-04-01

282

Torsional resonance mode magnetic force microscopy: enabling higher lateral resolution magnetic imaging without topography-related effects.  

PubMed

We present experimental work that reveals the benefits of performing magnetic force microscopy measurements employing the torsional resonance mode of cantilever oscillation. This approach provides two clear advantages: the ability of performing magnetic imaging without topography-related interference and the significant lateral resolution improvement (approximately 15%). We believe that this work demonstrates a significant improvement to a versatile magnetic imaging technique widely used in academia and in industry. PMID:23535607

Kaidatzis, A; García-Martín, J M

2013-03-27

283

Magnetic force microscopy studies of the domain structure of Co/Pd multilayers in a magnetic field  

SciTech Connect

We have measured the magnetic domain patterns in Co/Pd multilayers of varying thickness using magnetic force microscopy in the presence of an external magnetic field applied perpendicular to the multilayers. We find that the domain patterns evolution is in qualitative agreement with existing theories for single layer thin films. Our results are in reasonable agreement with a theoretical model of domains appropriate to multilayer films. {copyright} 2001 American Institute of Physics.

Rushforth, A. W.; Main, P. C.; Gallagher, B. L.; Marrows, C. H.; Hickey, B. J.; Dahlberg, E. D.; Eames, P.

2001-06-01

284

Investigation of ripple structures of thin polycrystalline Co films by magnetic force microscopy  

NASA Astrophysics Data System (ADS)

We have studied the magnetic domain structure of thin polycrystalline Co films by magnetic force microscopy. Cross-tie walls and a magnetic ripple structure within the domains have been resolved with high lateral resolution and sensitivity. The magnetization direction of the polycrystalline Co films have been determined locally by analyzing the position of the observed transversal ripple structure. By applying an external field in the plane of the sample along the magnetically easy axis we have observed a reversible rotation process of the ripple structure, whereas for an external field along the hard axis the magnetization process is characterized by domain-wall movement.

Löhndorf, M.; Wadas, A.; Wiesendanger, R.

285

Triaxial forces at the seat and backrest during whole-body vertical vibration  

Microsoft Academic Search

During exposure of seated subjects to vertical whole-body vibration, forces in the fore-and-aft, lateral and vertical directions at the seat and backrest have been measured. The responses at the seat have been compared with those measured previously on a seat without a backrest. Twelve male subjects were exposed to random vertical vibration in the frequency range 0.25–20Hz. The subjects sat

N. Nawayseh; M. J. Griffin

2004-01-01

286

Fundamental studies on free stream acceleration effect on drag force in bluff bodies  

Microsoft Academic Search

This paper describes fundamental studies on free stream acceleration effect on drag force in bluff bodies. The flow with gradual\\u000a velocity increase assumed an accelerated flow. The wind tunnel tests were conducted in order to investigate the difference\\u000a of aerodynamic characteristics between non-accelerated flow and accelerated flow. The experimental models were a circular\\u000a cylinder and a square cylinder. In an

Yeongbin Lee; Joohyun Rho; Kyu Hong Kim; Dong-Ho Lee

2011-01-01

287

Analysis of radially unbalanced magnetic force acting on a large superconducting magnet with iron yoke by ''TOSCA''  

SciTech Connect

A superconducting solenoid magnet for colliding beam detectors has an iron yoke which controls the magnetic field inside and behind the solenoid coil. When the center of the coil is displaced from the center of the yoke, unbalanced magnetic force will act on the coil. The radial unbalanced force must be determined using three-dimensional field calculation. The three-dimensional field analysis program ''TOSCA,'' which was developed by Rutherford Appleton Lab., is applied to the analysis of the force. It is shown that the program is proper for analysing force, because the finite elements need not be adapted to the shape of coils. The method of application and its result is discussed.

Nomura, T.; Satow, T.; Ashkin, M.

1988-01-01

288

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

289

High sensitivity piezomagnetic force microscopy for quantitative probing of magnetic materials at the nanoscale.  

PubMed

Accurate scanning probing of magnetic materials at the nanoscale is essential for developing and characterizing magnetic nanostructures, yet quantitative analysis is difficult using the state of the art magnetic force microscopy, and has limited spatial resolution and sensitivity. In this communication, we develop a novel piezomagnetic force microscopy (PmFM) technique, with the imaging principle based on the detection of magnetostrictive response excited by an external magnetic field. In combination with the dual AC resonance tracking (DART) technique, the contact stiffness and energy dissipation of the samples can be simultaneously mapped along with the PmFM phase and amplitude, enabling quantitative probing of magnetic materials and structures at the nanoscale with high sensitivity and spatial resolution. PmFM has been applied to probe magnetic soft discs and cobalt ferrite thin films, demonstrating it as a powerful tool for a wide range of magnetic materials. PMID:23720016

Chen, Qian Nataly; Ma, Feiyue; Xie, Shuhong; Liu, Yuanming; Proksch, Roger; Li, Jiangyu

2013-05-29

290

Assessment of airway hyperreactivity: comparison of forced spirometry and body plethysmography for methacholine challenge tests  

PubMed Central

Introduction Bronchial challenge tests by inhalation of aerosolized methacholine (MCH) are commonly used in the clinical diagnosis of airway hyperresponsiveness (AHR). While the detection of airway narrowing relies on the patient's cooperation performing forced spirometry, body plethysmographic measurements of airway resistance are less depending on the patient's cooperation and do not alter the respiratory tract by maximal maneuvers. Hence we compared both methods concerning their clinical value and correlation during MCH challenges in patients with asthma. Materials and Methods Cumulative MCH challenges test, consisting of up to 5 steps, evaluated with body plethysmography on each step were performed in 155 patients with bronchial asthma. Airway responses were recorded at each step of MCH application (Master-Screen Body, Cardinal Health, Höchberg). At the baseline test and after crossing the provocation dose (PD) threshold in body plethysmography (PD+100 sReff), forced expirations were performed and FEV1, FVC, and FEV1 %FVC were measured. Using regression analysis of the airway parameters and taking the MCH dose as the covariate, we could extrapolate to missing spirometric values and interpolate the estimated MCH dose when crossing the PD threshold (PD-20 FEV1) between two consecutive measurements. The administered PD+100 MCH doses for specific airway resistance, sRtot, and sReff were compared with resistance parameters Rtot and Reff, and to PD-20 of FEV1 and FEV1 %FVC. Results Regarding sReff we found a mild, moderate, or severe AHR in 114 patients (75%), but only 50 (32%) according to FEV1. A statistical analysis showed strongly linear correlated parameters of airway resistance, but no significant correlation between the results of body plethysmography and forced spirometry Conclusions Using MCH challenges, we found specific airway resistance to be the most sensitive parameter to detect AHR. Raw is largely independent of height and gender facilitating the interpretation of measurements carried out longitudinally.

2009-01-01

291

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

292

Magnetic force on the walls of a square coaxial transmission line  

NASA Astrophysics Data System (ADS)

There is magnetic force acting on the wall of a square coaxial transmission line when TEM wave propagates in it. The self-inductance can be determined based on a conformal transformation for the field region, which demonstrates that the inductance only depends on the side length ratio of the two walls instead of the length of the walls. The magnetic force on each side of the walls is then calculated by employing the principle of virtual work. It is proved that the magnetic force has the same magnitude and opposite direction to the electric force. And then the electromagnetic force on the wall is zero. The general meaning of this conclusion for all kinds of coaxial transmission line is proposed.

Gao, Lili; Zhao, Dekui

2013-10-01

293

Weak coupling of magnetic and vibrational analysis using local forces  

Microsoft Academic Search

A weak coupling between magnetostatic and elasticity equations is derived from energy considerations for electric machines. The coupling term results directly into a finite element expression for the nodal electromagnetic forces, which can be used as source terms for an elasticity or vibration analysis. The relative contribution of the stator's modal shapes in the deformation excited by this force distribution

Keen Delaere; Paul Sast; Roimie Belmans; Kay Hameyer

1999-01-01

294

Accurate and consistent force calculation for finite element magnetics  

Microsoft Academic Search

Three net magnetostatic loading force formulations are commonly used for finite element based electromagnetic and electromechanical computer-aided analysis and design: the Maxwell stress method, the method of classical virtual work, and the local Jacobian derivative method. None of these seems sufficient to calculate reliable results at a reasonable cost without expert user interaction. A new, fully automatic, field-error tuned force

James Stephan McFee

1989-01-01

295

Experimental investigations into forces acting during a magnetic abrasive finishing process  

Microsoft Academic Search

A magnetic abrasive finishing (MAF) process is the one in which material is removed in such a way that surface finishing and\\u000a deburring are performed simultaneously with the applied magnetic field in the finishing zone. Knowledge of forces acting during\\u000a MAF is important to understand the mechanism of material removal. Forces have direct influence on the generation of a finished

Dhirendra K. Singh; V. K. Jain; V. Raghuram

2006-01-01

296

Force, torque, and absorbed energy for a body of arbitrary shape and constitution in an electromagnetic radiation field  

Microsoft Academic Search

The force and torque exerted on a body of arbitrary shape and constitution by a stationary radiation field are in principle given by integrals of Minkowski's stress tensor over a surface surrounding the body. Similarly the absorbed energy is given by an integral of the Poynting vector. These integrals are notoriously difficult to evaluate, and so far only spherical bodies

Ø. Farsund; B. U. Felderhof

1996-01-01

297

Non-uniform forcing of a magnetic soap film  

NASA Astrophysics Data System (ADS)

The effects of a non-uniform magnetic field on a suspension of magnetic nanoparticles in a soap film are investigated. Experiments show that a strong non-uniform field will form a two-dimensional structure of magnetic nanoparticles within the soap film. A model is developed to compare with experimental results for several different magnetic field configurations. The system is modeled with a two-dimensional thin film equation with no-flux boundary conditions. We show qualitative agreement between the model and experiments.

Back, Randy; Beckham, Regan

2012-02-01

298

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

2005-02-23

299

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux  

NASA Astrophysics Data System (ADS)

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.

2002-11-01

300

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

301

Harmonic Fluxes and Electromagnetic Forces of Concentric Winding Brushless Permanent Magnet Motor  

NASA Astrophysics Data System (ADS)

Brushless permanent magnet motors have been widely used in home applications and industrial fields. These days, high efficiency and low noise motors are demanded from the view point of environment. Electromagnetic noise and iron loss of the motor are produced by the harmonic fluxes and electromagnetic forces. However, order and space pattern of these have not been discussed in detail. In this paper, fluxes, electromagnetic forces and magneto-motive forces of brushless permanent magnet motors with concentric winding were analyzed analytically, experimentally and numerically. Time harmonic fluxes and time electromagnetic forces in the air gap were measured by search coils on the inner surface of the stator teeth and analyzed by FEM. Space pattern of time harmonic fluxes and time electromagnetic forces were worked out with experiments and FEM. Magneto motive forces due to concentric winding were analyzed with equations and checked by FEM.

Ishibashi, Fuminori; Takemasa, Ryo; Matsushita, Makoto; Nishizawa, Takashi; Noda, Shinichi

302

Magnetic force microscopy on high-[ital T][sub [ital c  

SciTech Connect

We demonstrate that magnetic force microscopy is able to detect the superconducting state and to distinguish between the Meissner and Shubnikov phase of a high temperature superconductor. In the Meissner phase we observe an increasing, repulsive force with decreasing tip-to-sample distance. The force depends on the screening current density and therefore on the London penetration depth. Indeed, we detect a decrease in the maximum force as the temperature increases. In the Shubnikov phase a different behavior is observed. If the tip is approached staircase-like to a superconductor the repulsive force first increases and then decays rapidly. The superconductor has reacted to the increased stray field of the tip by readjusting the vortex structure to lower the total energy. The experiments are discussed in relation to existing theoretical predictions. We point out that magnetic force microscopy might become an important tool to directly observe the vortex structure and its complex phase transitions.

Moser, A.; Hug, H.J.; Fritz, O.; Parashikov, I.; Guentherodt, H. (Institut fuer Physik Universitaet Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)); Wolf, T. (Kernforschungszentrum Karlsruhe Institut fuer Technische Physik, D-7500 Karlsruhe (Germany))

1994-05-01

303

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

304

Robust adaptive numerical compensation for friction and force ripple in permanent-magnet linear motors  

Microsoft Academic Search

This paper describes a robust adaptive compensation method for friction and force ripple present in the dynamics of permanent-magnet linear motors. The method is used in ultraprecise positioning applications. The compensation algorithm consists of a PID component and an adaptive component for estimating friction and force ripple. The adaptive component is continuously refined on the basis of just prevailing input

K. K. Tan; S. N. Huang; T. H. Lee

2002-01-01

305

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

National Technical Information Service (NTIS)

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 hig...

J. X. Bouillard

1992-01-01

306

Radial Forces in External Rotor Permanent Magnet Synchronous Motors With Non-Overlapping Windings  

Microsoft Academic Search

In external rotor permanent magnet synchronous motors with non-overlapping windings, the higher frequency harmonics of the radial forces generate considerable resonant vibrations and acoustic noise. Therefore, diversity of spatial and specifically frequency harmonic ordinal numbers of representative slot and pole number combinations are derived analytically with open circuit and under load. Amplitudes of radial force waves are calculated by means

Jens Krotsch; Bernhard Piepenbreier

2012-01-01

307

Measurement of internal forces in superconducting accelerator magnets with strain gauge transducers  

Microsoft Academic Search

An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the compressive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made

C. L. Goodzeit; M. D. Anerella; G. L. Ganetis

1989-01-01

308

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

309

Scaling of lifting forces in relation to object size in whole body lifting.  

PubMed

Subjects prepare for a whole body lifting movement by adjusting their posture and scaling their lifting forces to the expected object weight. The expectancy is based on visual and haptic size cues. This study aimed to find out whether lifting force overshoots related to object size cues disappear or persist over a number of repeated lifts. In addition, the influence of the degree of alternation between load sizes, and the influence of knowledge of actual object weights prior to the lifts, were investigated with regard to their effect on force overshoots. Four experiments were performed using a large and a small box, each of 8.4 kg weight, and varying degrees of alternation between boxes. In two of the experiments, subjects were informed about the weight of the objects, while in the other two experiments they were not informed about the weight of the objects. When boxes were lifted 15 times before switching to the other box, rapid diminishing of force scaling errors was observed. However, when boxes were alternated each lift or after three lifts, persisting force scaling overshoots were found in lifting the large box compared to the small one. When participants were given information regarding the actual object weight, force overshoots in the first pair of large and small box lifts were not different from overshoots in experiments where subjects were not informed about the weight of the objects. This shows that, for occupational lifting, risks related to force overshoots in lifting large objects can persist despite experience in lifting the objects and despite the use of labels indicating the weight of the objects. PMID:16147418

Kingma, Idsart; Van Dieën, Jaap H; Toussaint, Huub M

2005-06-22

310

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

311

Forces in Toroidal Magnetic Field Coils on the Current Unbalance.  

National Technical Information Service (NTIS)

Calculation values of mechanical loadings are presented, which influence the elements of construction and separate coils of the longitudinal field of the tokamak type device. These forces appear at the unbalance of currents neighbouring sectionized parts ...

A. S. Simakov

1980-01-01

312

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

313

Sensorless control of interior permanent magnet synchronous motor by estimation of an extended electromotive force  

Microsoft Academic Search

Recently, many methods have been proposed for surface permanent magnet synchronous motor (SPMSM) sensorless control based on an estimation of electromotive force (EMF), in which the motor's position information is included. However, these methods cannot be applied to internal permanent magnet synchronous motors (IPMSMs) directly, because the position information is included in not only the EMF but also the inductance

Zhiqian Chen; Mutuwo Tomita; Shinji Ichikawa; Shinji Doki; Shigeru Okuma

2000-01-01

314

Experimental and numerical analysis of lift force in magnetic levitation system  

Microsoft Academic Search

A new type of magnetic levitation system using the shielding effect of the HTS bulk is studied. The system includes a permanent magnet and three HTS bulks as a vehicle, and a ferromagnetic bar as a guide way. The simple structure of the guide way reduces large amount of construction costs. The system also provides stable lift force without any

Tomoaki Takao; Akihiro Niiro; Soichiro Suzuki; Masahiro Hashimoto; Hiroki Kamijo; Hiroyuki Fujimoto

2005-01-01

315

Levitation force on a permanent magnet over a superconducting plane: Modified critical-state model.  

National Technical Information Service (NTIS)

The authors consider a model system of a permanent magnet above a semi-infinite superconductor. They introduce a modified critical-state model, and carry out derivations of the levitation force acting on the magnet. A key feature of the modification allow...

Z. J. Yang

1997-01-01

316

Characterization of Conducting Atomic Force Microscopy for Use With Magnetic Tunnel Junctions  

Microsoft Academic Search

In this paper we quantify the electrical properties of magnetic tunnel junctions with conducting atomic force microscopy (CAFM). Using rectangular pillars patterned on a magnetic tunnel junction film with in plane anisotropy, we examine the repeatability of CAFM measurements on the same pillar. We also quantify the variability seen across over 200 different pillars of sizes ranging from 600 nm

Eric R. Evarts; Limin Cao; David S. Ricketts; Nicholas D. Rizzo; James A. Bain; Sara A. Majetich

2010-01-01

317

Submicron-Scale Tip Fabrication for Magnetic Force Microscopy by Electrolytic Polishing  

Microsoft Academic Search

An electrolytic polishing technique which exposes a portion of an insulated wire and etches that portion preferentially is described. The prepared tip's configuration immediately prior to dropping off depends on the tip's weight and mechanical properties. The tip-point curvature can be below-submicron scale. Magnetic force imaging of recorded magnetic tape using these tips is shown.

Tetsuo Iijima; Kyosuke Yasuda

1988-01-01

318

Compensation of unbalanced magnetic force in switched reluctance motor with Airgap nonuniformity  

Microsoft Academic Search

This paper proposed a method to compensate the unbalanced magnetic force in 12\\/8 switched reluctance motor. Using two-dimensional transient finite element analysis coupled with external circuits, both motor and inverter could be modeled to study the performance of motor. Airgap nonuniformity caused by eccentricity between the stator and rotor axes was found to be the main source of unbalanced magnetic

J. Li; Dawoon Choi; Y. H. Cho

2009-01-01

319

Non-force-free Extrapolation of Coronal Magnetic Field with Applications to Vector Magnetograms  

Microsoft Academic Search

Motivated by increasingly more advanced solar observations, we recently develop a method of non-force-free extrapolation of the solar coronal magnetic field from vector magnetograms, especially those for a finite active region. Based on a more complex variational principle, the principle of minimum (energy) dissipation rate (MDR), we adopt and solve a more complex equation governing the coronal magnetic field that

Q. Hu; A. Wang; B. Dasgupta; G. A. Gary; S. Wu

2009-01-01

320

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

321

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

322

Improved High-Force Magnetic Tweezers for Stretching and Refolding of Proteins and Short DNA  

PubMed Central

Although magnetic tweezers have many unique advantages in terms of specificity, throughput, and force stability, this tool has had limited application on short tethers because accurate measurement of force has been difficult for short tethers under large tension. Here, we report a method that allows us to apply magnetic tweezers to stretch short biomolecules with accurate force calibration over a wide range of up to 100 pN. We demonstrate the use of the method by overstretching of a short DNA and unfolding/refolding a protein of filamin A immunoglobulin domains 1–8. Other potential applications of this method are also discussed.

Chen, Hu; Fu, Hongxia; Zhu, Xiaoying; Cong, Peiwen; Nakamura, Fumihiko; Yan, Jie

2011-01-01

323

Spinmotive force with static and uniform magnetization induced by a time-varying electric field  

NASA Astrophysics Data System (ADS)

A new spinmotive force is predicted in ferromagnets with spin-orbit coupling. By extending the theory of spinmotive force, we show that a time-varying electric field can induce a spinmotive force with static and uniform magnetization. This spinmotive has two advantages; it can be detected free from the inductive voltage owing to the absence of dynamical magnetization and it can be tuned by electric fields. To observe the effect, we propose two experimental setups: electric voltage measurement in a single ferromagnet and spin injection from a ferromagnet into an attached nonmagnetic conductor.

Yamane, Yuta; Ieda, Jun'ichi; Maekawa, Sadamichi

2013-07-01

324

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

325

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

326

Magnetic field and electromagnetic force analysis of 3-phase air-core superconducting power transformer  

Microsoft Academic Search

The superconducting windings of the air-core superconducting power transformer have possibilities of being exposed to a higher magnetic field than those of the iron-core transformer because of no special paths for magnetic flux. Thus, in this paper, the magnetic field and electromagnetic force acting on the windings of an experimental 3-phase air-core superconducting transformer are analyzed. From the results, it

Hiroshi Yamaguchi; Teruo Kataoka; Hiroki Matsuoka; Tomohide Mouri; Shoji Nishikata; Y. Sato

2001-01-01

327

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

328

Compensation of magnetic disturbances improves inertial and magnetic sensing of human body segment orientation.  

PubMed

This paper describes a complementary Kalman filter design to estimate orientation of human body segments by fusing gyroscope, accelerometer, and magnetometer signals from miniature sensors. Ferromagnetic materials or other magnetic fields near the sensor module disturb the local earth magnetic field and, therefore, the orientation estimation, which impedes many (ambulatory) applications. In the filter, the gyroscope bias error, orientation error, and magnetic disturbance error are estimated. The filter was tested under quasi-static and dynamic conditions with ferromagnetic materials close to the sensor module. The quasi-static experiments implied static positions and rotations around the three axes. In the dynamic experiments, three-dimensional rotations were performed near a metal tool case. The orientation estimated by the filter was compared with the orientation obtained with an optical reference system Vicon. Results show accurate and drift-free orientation estimates. The compensation results in a significant difference (p < 0.01) between the orientation estimates with compensation of magnetic disturbances in comparison to no compensation or only gyroscopes. The average static error was 1.4 degrees (standard deviation 0.4) in the magnetically disturbed experiments. The dynamic error was 2.6 degrees root means square. PMID:16200762

Roetenberg, Daniel; Luinge, Henk J; Baten, Chris T M; Veltink, Peter H

2005-09-01

329

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

Microsoft Academic Search

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

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

2003-01-01

330

Separation of topographic features from magnetic force images using capacitive coupling effect.  

PubMed

Separation of topographic features from magnetic images has been an issue for the past two decades in magnetic force microscopy (MFM). The frequent pickups of the topographic features are interpreted as transitions of the tip between bistable states of the tip-sample assembly in the noncontact and tapping regions. MFM using electrostatic force modulation demonstrates the separation of the topographic features from the magnetic images by removing the tapping state from the bistable states through the introduction of a capacitive coupling. PMID:19256648

Kim, Byung I

2009-02-01

331

Increase of force in magnetic levitation by using field cooled yttrium barium copper oxide trapped field magnets instead of ferromagnets  

NASA Astrophysics Data System (ADS)

This dissertation describes how forces in magnetic levitation systems can be increased by using YBa2Cu3Oy high temperature superconductors (HTS) cooled in the uniform field of an electromagnet (2.3 T), instead of ferromagnets. The HTS, cooled in a field greater than its maximum trapped field (Bt,max), is in the fully saturated critical state (fcsat). Hence, it produces fields equal to its Bt,max, up to 1.6 T in this work. Since commonly used permanent ferromagnets (PM), of the size used in this work, produce only up to 0.5 T, replacing the PM in levitation systems with such HTS ``trapped field magnets'' significantly increases the magnetic fields and thus the levitation forces. We also cool HTS in zero field (zfc) or adjacent to a PM or fc sat HTS (fcadj). We thus study six configurations of PM - HTS or HTS - HTS levitation: a PM or a fc sat HTS opposed by either a zfc, fcsat, or fcadj HTS. Levitation forces and lateral forces, as well as their behavior in multiple cycles of approach and retreat, are investigated. Compared to levitation systems with PM, forces increase by a factor of four to ten in configurations with fcsat HTS. Up to 393 N (125 N/cm2) are obtained. In multiple cycles, forces decrease 10-40% during the first 5-10 cycles, but then stabilize at a constant level. Experimental force-distance curves were fitted to phenomenological models. Furthermore, force maxima were calculated as functions of the maximum trapped field of the HTS following Bean's model. Lateral forces were used to estimate the stability of the different configurations. Arrangements of several zfc samples with high levitation force and good stability were demonstrated.

Hennig, Wolfgang

1999-11-01

332

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

333

Testing a Force Sensor for Underwater Magnetic Particle Inspection.  

National Technical Information Service (NTIS)

Offshore oil and gas production installations require regular inspection of their underwater structures. Magnetic particle inspection (MPI) is one of the most reliable methods of detecting cracks in these parts. The use of underwater manipulators for remo...

J. Vaelttilae

1991-01-01

334

Equal sensation curves for whole-body vibration expressed as a function of driving force  

NASA Astrophysics Data System (ADS)

Previous studies have shown that the seated human is most sensitive to whole-body vertical vibration at about 5 Hz. Similarly, the body shows an apparent mass resonance at about 5 Hz. Considering these similarities between the biomechanical and subjective responses, it was hypothesized that, at low frequencies, subjective ratings of whole-body vibration might be directly proportional to the driving force. Twelve male subjects participated in a laboratory experiment where subjects sat on a rigid seat mounted on a shaker. The magnitude of a test stimulus was adjusted such that the subjective intensity could be matched to a reference stimulus, using a modified Bruceton test protocol. The sinusoidal reference stimulus was 8-Hz vibration with a magnitude of 0.5 m/s2 rms (or 0.25 m/s2 rms for the 1-Hz test); the sinusoidal test stimuli had frequencies of 1, 2, 4, 16, and 32 Hz. Equal sensation contours in terms of seat acceleration showed data similar to those in the literature. Equal sensation contours in terms of force showed a nominally linear response at 1, 2, and 4 Hz, but an increasing sensitivity at higher frequencies. This is in agreement with a model derived from published subjective and objective fitted data. .

Mansfield, Neil J.; Maeda, Setsuo

2005-06-01

335

Effect of magnetic fields on combustion electromotive force  

Microsoft Academic Search

A magnetic field is observed to affect the electrical response of a system burning under self-propagating high-temperature\\u000a synthesis conditions. With the synthesis of lithium ferrite as an example, it is shown that, depending on its strength and\\u000a direction, applying a magnetic field induces different forms of response. The greatest effect is observed in the postprocess\\u000a region. Possible reasons for the

Yu. G. Morozov; M. V. Kuznetsov

1999-01-01

336

Autonomous and forced dynamics in a spin-transfer nano-oscillator: Quantitative magnetic-resonance force microscopy  

NASA Astrophysics Data System (ADS)

In this talk, we will discuss how magnetic-resonance force microscopy, can provide quantitative measurement of the power emitted by a spin-transfer nano-oscillator, consisting of a normally magnetized Py|Cu|Py circular nanopillar, excited both in the autonomous and forced regimes.footnotetextA. Hamadeh, et al. PHYSICAL REVIEW B 85, 140408(R) (2012) From the power behavior in the subcritical region of the autonomous dynamics, one obtains a quantitative measurement of the threshold current and of the noise level. Their field dependence directly yields both the spin torque efficiency acting on the thin layer and the nature of the mode which first auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. We will then demonstrate that the observed spin-wave spectrum in the forced regime critically depends on the method of excitation. While the spatially uniform radio-frequency (RF) magnetic field excites only the axially symmetric modes having azimuthal index l=0, the RF current flowing through the nano-pillar, creating a circular RF Oersted field, excites only the modes having azimuthal index l=+1.footnotetextV.V. Naletov et al. PHYSICAL REVIEW B 84, 224423 (2011) It is then demonstrated that in order to phase lock this auto-oscillating mode, the external source must have the same spatial symmetry as the mode profile, i.e., a uniform microwave field must be used rather than a microwave current flowing through the nanopillar.

Klein, Olivier

2013-03-01

337

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

338

DNA Micromanipulation Using Novel High-Force, In-Plane Magnetic Tweezer  

NASA Astrophysics Data System (ADS)

We report the development of a magnetic force transducer that can apply piconewton forces on single DNA molecules in the focus plane allowing continuous high precision tethered-bead tracking. The DNA constructs, proteins, and buffer are introduced into a 200?L closed cell created using two glass slides separated by rigid spacers interspersed within a thin viscoelastic perimeter wall. This closed cell configuration isolates our sample and produces low-noise force-extension measurements. Specially-drawn micropipettes are used for capturing the polystyrene bead, pulling on the magnetic sphere, introducing proteins of interest, and maintaining flow. Various high-precision micromanipulators allow us to move pipettes and stage as required. The polystyrene bead is first grabbed, and held using suction; then the magnetic particle at the other end of the DNA is pulled by a force created by either two small (1mm x 2mm x 4mm) bar magnets or a micro magnet-tipped pipette. Changes in the end-to-end length of the DNA are observable in real time. We will present force extension data obtained using the magnetic tweezer.

McAndrew, Christopher; Mehl, Patrick; Sarkar, Abhijit

2010-03-01

339

Competition of magnetic and hydrodynamic forces on ellipsoidal particles under shear: Influence of the Earth's magnetic field on particle alignment in viscous media  

Microsoft Academic Search

We present a model that describes the rotation of ellipsoidal magnetic particles in a viscous fluid under the influence of hydrodynamic and magnetic forces, with an aim to better understand how sediments acquire their remanent magnetizations. Analyses of the governing equations elucidate how magnetic particles will rotate for different values of leading parameters including particle shape, remanent and induced magnetic

Josef Jezek; Stuart A. Gilder

2006-01-01

340

Measurement of internal forces in superconducting accelerator magnets with strain gauge transducers  

SciTech Connect

An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the compressive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made with a new system that eliminates sources of errors due to spurious resistance changes in interconnecting wiring and solder joints. The design of the transducers and their measurement system is presented along with a discussion of the method of compensation for thermal and magnetic effects, methods of calibration with typical calibration data, and measured effects in actual magnets of the thermal stress changes from cooldown and the Lorentz forces during magnet excitation.

Goodzeit, C.L.; Anerella, M.D.; Ganetis, G.L.

1989-03-01

341

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

342

Relaxation of N-body systems with additive r-? interparticle forces  

NASA Astrophysics Data System (ADS)

In Newtonian gravity the final states of cold dissipationless collapses are characterized by several structural and dynamical properties remarkably similar to those of observed elliptical galaxies. Are these properties a peculiarity of the Newtonian force or a more general feature of long-range forces? We study this problem by means of N-body simulations of dissipationless collapse of systems of particles interacting via additive r-? forces. We find that most of the results holding in Newtonian gravity are also valid for ? ? 2. In particular, the end-products are triaxial and never flatter than an E7 system, their surface density profiles are well described by the Sérsic law, the global density slope-anisotropy inequality is obeyed, the differential energy distribution is an exponential over a large range of energies (for ? ? 1), and the pseudo-phase-space density is a power law of radius. In addition, we show that the process of virialization takes longer (in units of the system's dynamical time) for decreasing values of ?, and becomes infinite for ? = -1 (the harmonic oscillator). This is in agreement with the results of deep Modified Newtonian Dynamics collapses (qualitatively corresponding to ? = 1) and it is due to the fact that the force becomes more and more similar to the ? = -1 case, where, as well known, no relaxation can happen and the system oscillates forever.

Di Cintio, PierFrancesco; Ciotti, Luca; Nipoti, Carlo

2013-06-01

343

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

344

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

2010-10-30

345

Prediction of ocean-induced magnetic signals in the satellite observations due to tidal forcing  

NASA Astrophysics Data System (ADS)

An increase in accuracy of the Earth's magnetic field observations by the future SWARM satellite mission strengths the interest of dealing with magnetic signals of small amplitudes but a global support. An example of such a signal is the magnetic field variation induced by global ocean dynamics. Since sea-water is a good electrical conductor, the ocean currents represent electrical currents moving in the main magnetic field. According to the Faraday's law, they induce a secondary magnetic field that is, in principle, observable by ground and satellite observations. Although they are of small amplitudes, they have recently been identified for ocean currents forced by the tidal wave M2. The identification of small magnetic components in the total magnetic signal can be helpt by their numerical prediction. The 2-D theory for computing the magnetic field generated by ocean currents that has been proposed by Tyler et al. (1997) is combined with the ocean tidal flows simulated by the numerical ocean model for circulation and tides (OMCT; Thomas 2002) and used to calculate secondary magnetic field generated by lunar-solar tidal potential for individual tidal waves. Unlike to some recent studies where the ocean currents have been deduced from altimetry data by applying the geostrophic method, the ocean flows calculated by the OMCT approach are forced directly by the lunisolar tidal potential that is deduced from analytical ephemerides. As a result, the method provides the radial component of the ocean-induced magnetic signal at the sea surface and satellite altitude. A comparison with published results by Tyler et al. (2003) and Maus et al. (2004) shows a good agreement in terms of global spatial pattern and magnitude, though some minor differences occur. This new method simplifies the calculation of ocean-induced magnetic fields and allows the prediction of the secondary magnetic fields induced by the complete lunisolar tidal forcing. This numerical approach can be used to estimate the opportunities in detecting ocean-induced magnetic signals in satellite observations.

Dostal, J.; Dobslaw, H.; Thomas, M.

2009-04-01

346

Effect of the magnetic field applied during cooling on magnetic hysteresis in the low-temperature phase of magnetite: First-order reversal curve (FORC) analysis  

Microsoft Academic Search

The strength of a magnetic field applied during cooling through the Verwey transition can control the low-temperature (LT) magnetic hysteresis properties of magnetite. This effect is investigated using the first-order reversal curve (FORC) technique. LT FORC distributions were measured at 20 K from four polycrystalline samples after cooling from 300 K in zero magnetic field or in the presence of

A. V. Smirnov

2007-01-01

347

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

348

Analog of the susceptibility spectrum for levitation forces between a superconductor and a permanent magnet  

NASA Astrophysics Data System (ADS)

We report on the measurements of both vertical and lateral levitation forces between a permanent magnet NdFeB and a polycrystalline YBa4Cu6O7-? superconductor. The analysis of the obtained results revealed an interesting correlation between the behavior of the forces in the field-cooled and zero-field-cooled regimes, resembling the structure of the so-called susceptibility spectrum ?''(?'). Such force-force diagrams can be useful for identifying flux distribution structure inside a superconducting material.

Sergeenkov, S.; Sanchez, E. S.; Salla, R. V. F.; Rivera, V. A. G.; Cichetto, L.; Araújo-Moreira, F. M.

2012-08-01

349

On force-displacement relations at contact between elastic-plastic adhesive bodies  

NASA Astrophysics Data System (ADS)

The loading-unloading of dissimilar adhesive elastic-plastic bodies is studied both analytically and numerically, including elastic-ideal plastic and deformation hardening behavior. The contacting bodies are assumed to be spherical in the region of contact and consequently the presented model is partly based on results pertinent to Brinell indentation. The problem of adhesive unloading is solved in two steps; first the unloading in the absence of adhesion is studied and then an adhesive pressure term is added. The analytical model is derived using fracture mechanics arguments and is based on one parameter, the fracture energy. The model is finally verified with finite element simulations by introducing a cohesive behavior between the modeled spheres. The analytical model shows very good agreement with the FE-simulations both during loading and unloading and also concerning the case of force and displacement at separation.

Olsson, E.; Larsson, P.-L.

2013-05-01

350

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

351

A Magnetic Resonance Force Microscope for Studying Monolayers  

Microsoft Academic Search

We describe ongoing work on force-detecting NMR from a single monolayer of nuclear spins. We report on the continuing refinement of the instrument and present simulations which show the viability of this technique. The microscope incorporates custom-fabricated cantilevers, and operates at variable temperature and field. Using direct digital rf synthesis allows multiple pulse NMR techniques to be employed, including our

Sean Garner; James Kempf; Neil Jenkins; Lauren Deflores; John Allen; Tse Nga Ng; John Marohn

2002-01-01

352

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

353

The Effect of Field Representation on Student Responses to Magnetic Force Questions  

NSDL National Science Digital Library

We examine student understanding of the magnetic force exerted on a charged particle and report three findings from a series of tests administered to introductory physics students. First, we expand on previous findings that many students believe in âchargedâ magnetic poles and find that although students may answer according to a model where a positive charge is attracted to a south pole and repulsed by a north, these students may not believe that the poles are charged. Additional models produce identical answer schemes, the primary being magnetic force parallel to magnetic field. Second, the representation format affects responses: students answer differently when the magnetic field is portrayed by a field source vs. by field lines. Third, after traditional instruction improvement in student performance is greater on questions portraying field lines than for questions portraying field sources.

Scaife, Thomas M.; Heckler, Andrew F.

2009-06-24

354

Principle and Basic Characteristics of Variable-Magnetic-Force Memory Motors  

NASA Astrophysics Data System (ADS)

A reduction in the power consumed by motors is required for energy saving in the case of electrical appliances and electric vehicles (EV). The motors used for operating these apparatus operate at variable speeds. Further, the motors operate with small load in stationary mode and with large load in start-up mode. A permanent magnet motor can operate at the rated power with a high efficiency. However, the efficiency is lower at small load or high speed because the large constant magnetic force results in substantial core loss. Furthermore, the flux-weakening current that depresses voltage at high speed leads to significant copper loss. Therefore, we have developed a new technique for controlling the magnetic force of permanent magnet on the basis of the load or speed of the motor. In this paper, we propose the novel motor that can vary magnetic flux and we clarify the principle.

Sakai, Kazuto; Yuki, Kazuaki; Hashiba, Yutaka; Takahashi, Norio; Yasui, Kazuya; Kovudhikulrungsri, Lilit

355

Force-gradient detected nuclear magnetic resonance in GaAs  

NASA Astrophysics Data System (ADS)

We have demonstrated a new type of magnetic resonance force microscopy (MRFM) in which nuclear magnetization in a sample is registered as a force gradient,causing a shift in the resonance frequency of a magnet-tipped cantilever.Using custom, low spring-constant cantilevers, we have detected magnetic resonance from ^71Ga nuclei in GaAs at 4 K, at a sensitivity of better than 10-9 N/m in a one hertz bandwidth. Unlike previously reported schemes,the method used here does not require modulating the sample magnetization at the cantilever resonance frequency, a process which destroys spin coherence in the sample in a time which can be much less than the intrinsic spin-lattice relaxation time, especially at low temperatures. For this reason the requirements on sample spin relaxation characteristics are far less stringent, giving access to a much wider array of systems.

Garner, Sean; Kuehn, Seppe; Dawlaty, Jahan; Jenkins, Neil; Marohn, John

2004-03-01

356

Aligning the forces of magnetism to achieve exemplary professional practice.  

PubMed

This clinical paper presents the evolution of a Point of Care Scholars (POCS) program, which embodies three components of the Magnet model: exemplary professional practice, new knowledge, innovations, and improvements, and empirical outcomes. The drive to achieve Magnet designation and redesignation provides a focused approach on innovation. The innovative POCS program is structured to introduce new knowledge to point-of-care staff with improvements that will lead to quality outcomes. Empirical outcomes of the POCS program include practice and policy changes, improved safety, program cost, dissemination, professional advancement, and program satisfaction. PMID:21419969

Long, Lisa English; McGee, Susan; Kinstler, Angela; Huth, Myra Martz

2011-04-01

357

Motion of small bodies in general relativity: foundations and implementations of the self-force  

NASA Astrophysics Data System (ADS)

Extreme mass-ratio inspirals, in which solar-mass compact bodies spiral into supermassive black holes, are an important potential source for gravitational wave detectors. Because of the extreme mass-ratio, one can model these systems using perturbation theory. However, in order to relate the motion of the small body to the emitted waveform, one requires a model that is accurate on extremely long timescales. Additionally, in order to avoid intractable divergences, one requires a model that treats the small body as asymptotically small rather than exactly pointlike. Both of these difficulties can be resolved by using techniques of singular perturbation theory. I begin this dissertation with an analysis of singular perturbation theory on manifolds, including the common techniques of matched asymptotic expansions and two-timescale expansions. I then formulate a systematic asymptotic expansion in which the metric perturbation due to the body is expanded while a representative worldline is held fixed, and I contrast it with a regular expansion in which both the metric and the worldline must be expanded. This results in an approximation that is potentially uniformly accurate on long timescales. The equation of motion for the body's fixed worldline is determined by performing a local-in-space expansion in the neighbourhood of the body. Using this local expansion as boundary data, I construct a global solution to the perturbative Einstein equation. To concretely characterize orbits, I next devise a relativistic generalization of the Newtonian method of osculating orbits. Making use of this method and two-timescale expansions, I examine the utility of adiabatic approximations that can forgo an explicit calculation of the force.

Pound, Adam

2010-06-01

358

Principle and Basic Characteristics of a Hybrid Variable-Magnetic-Force Motor  

NASA Astrophysics Data System (ADS)

Reduction in the power consumed by motors is important for energy saving in the case of electrical appliances and electric vehicles (EVs). The motors used for operating these devices operate at variable speeds. Further, the motors operate with a small load in the stationary mode and a large load in the starting mode. A permanent magnet motor can be operated at the rated power with a high efficiency. However, the efficiency is low at a small load or at a high speed because the large constant magnetic force results in substantial core loss. Furthermore, the flux-weakening current that decreases the voltage at a high speed leads to significant copper loss and core loss. Therefore, we have developed a new technique for controlling the magnetic force of a permanent magnet on the basis of the load or speed of the motor. In this paper, we propose a novel motor that can vary the magnetic flux of a permanent magnet and clarify the principle and basic characteristics of the motor. The new motor has a permanent magnet that is magnetized by the magnetizing coil of the stator. The analysis results show that the magnetic flux linkage of the motor can be changed from 37% to 100% that a high torque can be produced.

Sakai, Kazuto; Kuramochi, Satoru

359

Analysis of a spindle pole body mutant reveals a defect in biorientation and illuminates spindle forces.  

PubMed

The spindle pole body (SPB) is the microtubule organizing center in Saccharomyces cerevisiae. An essential task of the SPB is to ensure assembly of the bipolar spindle, which requires a proper balancing of forces on the microtubules and chromosomes. The SPB component Spc110p connects the ends of the spindle microtubules to the core of the SPB. We previously reported the isolation of a mutant allele spc110-226 that causes broken spindles and SPB disintegration 30 min after spindle formation. By live cell imaging of mutant cells with green fluorescent protein (GFP)-Tub1p or Spc97p-GFP, we show that spc110-226 mutant cells have early defects in spindle assembly. Short spindles form but do not advance to the 1.5-microm stage and frequently collapse. Kinetochores are not arranged properly in the mutant cells. In 70% of the cells, no stable biorientation occurs and all kinetochores are associated with only one SPB. Examination of the SPB remnants by electron microscopy tomography and fluorescence microscopy revealed that the Spc110-226p/calmodulin complex is stripped off of the central plaque of the SPB and coalesces to from a nucleating structure in the nucleoplasm. The central plaque components Spc42p and Spc29p remain behind in the nuclear envelope. The delamination is likely due to a perturbed interaction between Spc42p and Spc110-226p as detected by fluorescence resonance energy transfer analysis. We suggest that the force exerted on the SPB by biorientation of the chromosomes pulls the Spc110-226p out of the SPB; removal of force exerted by coherence of the sister chromatids reduced fragmentation fourfold. Removal of the forces exerted by the cytoplasmic microtubules had no effect on fragmentation. Our results provide insights into the relative contributions of the kinetochore and cytoplasmic microtubules to the forces involved in formation of a bipolar spindle. PMID:15525672

Yoder, Tennessee J; McElwain, Mark A; Francis, Susan E; Bagley, Joy; Muller, Eric G D; Pak, Brian; O'Toole, Eileen T; Winey, Mark; Davis, Trisha N

2004-11-03

360

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

Microsoft Academic Search

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

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

2002-01-01

361

Normative ground reaction force data for able-bodied and trans-tibial amputee children during running  

Microsoft Academic Search

The purpose of this investigation was to develop normative ground reaction force data for able-bodied (AB) and trans-tibial amputee (TTA) children during running. Two hundred AB (mean age 9.4 years, range 7-12) and 21 TTA (mean age 11.1 years, range 5-17) children ran (2.2 m\\/s±10%) over a force platform. Ground reaction force data were normalized, averaged within groups and plotted

J. R. ENGSBERG; A. G. LEE; K. G. TEDFORD; J. A. HARDER

1993-01-01

362

Ultrahigh vacuum magnetic force microscopy on in situ grown iron thin films  

NASA Astrophysics Data System (ADS)

Ultrahigh vacuum (UHV) magnetic force microscopy (MFM) was used to investigate the magnetic structure of 10 nm thick Fe films. The films were deposited on 50 nm thick Ag films on GaAs(100)/Fe substrates. The film structure was characterized in situ by scanning tunneling microscopy (STM) and low-energy electron diffraction (LEED), showing that the films grow (100)-oriented and that they display a distinct topographic texture. MFM shows that for the as-grown films the magnetization lies within the surface plane. A clear magnetic ripple structure could be identified. Rather irregular domains and 90° domain walls were also imaged. The wall profiles are of Néel type.

Leinenbach, P.; Lösch, J.; Memmert, U.; Hartmann, U.

363

Flow pattern and lift evolution of hydrofoil with control of electro-magnetic forces  

NASA Astrophysics Data System (ADS)

The initial responses and evolutions of the flow pattern and lift coefficient of a hydrofoil under the action of electro-magnetic (Lorentz) force have been studied experimentally and numerically, and trace particle methods are employed for them. With the introduction of BVF (boundary vortex flux), the quantitative relation among Lorentz forces, BVF and lifts is deduced. The influences of flow patterns on the hydrofoil lift coefficient have been discussed based on the BVF distribution, and the flow control mechanism of Lorentz force for a hydrofoil has been elucidated. Our results show that the flow pattern and lift of the hydrofoil vary periodically without any force. However, with the action of streamwise Lorentz forces, the separation point on the hydrofoil surface moves backward with a certain velocity, which makes the flow field steady finally. The streamwise Lorentz force raises the foil lift due to the increase of BVF intensity. On the other hand, Lorentz force also increases the hydrofoil surface pressure, which makes the lift decrease. However, the factor leading to the lift enhancement is determinant, therefore, the Lorentz force on the suction side can increase the lift, and the stronger the Lorentz force, the larger the lift enhancement. Our results also show that the localized Lorentz force can also both suppress the flow separation and increase the hydrofoil lift coefficient, furthermore, the Lorentz force located on the tail acts better than that located on the front.

Chen, Yaohui; Fan, Baochun; Chen, Zhihua; Li, Hongzhi

2009-09-01

364

Sedimentation of an oblate ellipsoid subjected to magnetic forces  

Microsoft Academic Search

Recent models of sedimentation are mainly based on Stokes' approximation of body motion in a linear viscous fluid, and cannot therefore account for all effects occurring either in the laboratory or in nature. One of these effects is rotation of prolate or oblate particles perpendicular to the direction of gravity. Galdi and Vaidya (GV2001) showed that torque acting on a

Josef Jezek; Stuart Gilder; Dario Bilardello

2010-01-01

365

Estimation of general three-dimensional motion of an unknown rigid body under no external forces and moments  

Microsoft Academic Search

This paper presents a method, which is applicable to autonomous space robotic missions, to estimate and to predict the general three-dimensional motion of an unknown rigid body under no external forces and moments using visual information. The authors assume that both geometric and inertial parameters of the rigid body are completely unknown to consider a general situation. Thus it is

Yasuhiro Masutani; Yasuhiro Okada; Takeshi Iwatsu; Hiroshi Ikeda; Fumio Miyazaki

1994-01-01

366

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

PubMed

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)/?(0)(2) where ?(2)/?(0)(2) 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. PMID:23005860

Rossi, L; Doorly, D; Kustrin, D

2012-08-22

367

Plastic changes in interhemispheric inhibition with practice of a two-hand force production task: a transcranial magnetic stimulation study  

Microsoft Academic Search

We studied the effects of practice of an unusual two-hand finger force production task on electromyographic and force responses to transcranial magnetic stimulation (TMS). Prior to practice, force production by a hand resulted in decreased TMS-induced responses in the other hand. After practice, fingers that were explicitly required to produce force during practice showed a significant drop in these inhibitory

Jae Kun Shim; Sun Wook Kim; Seung Ja Oh; Ning Kang; Vladimir M. Zatsiorsky; Mark L. Latash

2005-01-01

368

Evaluation of a Quantitative Magnetic Resonance Method for Mouse Whole Body Composition Analysis  

Microsoft Academic Search

Objective: To evaluate applicability, precision, and accuracy of a new quantitative magnetic resonance (QMR) analysis for whole body composition of conscious live mice.Research Methods and Procedures: Repeated measures of body composition were made by QMR, DXA, and classic chemical analysis of carcass using live and dead mice with different body compositions. Caloric lean and dense diets were used to produce

Frank C. Tinsley; Gersh Z. Taicher; Mark L. Heiman

2004-01-01

369

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

370

Application of finite-element models to predict forces acting on the lumbar spine during whole-body vibration  

Microsoft Academic Search

Objective. To predict forces acting on the spine during whole-body vibration for a variety of boundary conditions – body mass, height and posture.Design. Representative anthropometric data and models for an upright, relaxed and bent forward sitting posture were used to derive model families with 30 variants of a finite-element model.Background. A given exposure to whole-body vibration can cause a variable

H Seidel; R Blüthner; B Hinz

2001-01-01

371

Isotropic contact forces in arbitrary representation: Heterogeneous few-body problems and low dimensions  

NASA Astrophysics Data System (ADS)

The Bethe-Peierls asymptotic approach which models pairwise short-range forces by contact conditions is introduced in arbitrary representation for spatial dimensions less than or equal to 3. The formalism is applied in various situations and emphasis is put on the momentum representation. In the presence of a transverse harmonic confinement, dimensional reduction toward two-dimensional (2D) or one-dimensional (1D) physics is derived within this formalism. The energy theorem relating the mean energy of an interacting system to the asymptotic behavior of the one-particle density matrix illustrates the method in its second quantized form. Integral equations that encapsulate the Bethe-Peierls contact condition for few-body systems are derived. In three dimensions, for three-body systems supporting Efimov states, a nodal condition is introduced in order to obtain universal results from the Skorniakov-Ter-Martirosian equation and the Thomas collapse is avoided. Four-body bound state eigenequations are derived and the 2D '3+1' bosonic ground state is computed as a function of the mass ratio.

Pricoupenko, Ludovic

2011-06-01

372

Important role of three-body repulsive force effect in nuclear reactions  

NASA Astrophysics Data System (ADS)

The effect of three-body force (TBF) is studied in nucleus-nucleus elastic scattering on the basis of Brueckner theory for nucleon-nucleon (NN) effective interaction (complex G matrix) in the nuclear matter. A new G matrix called CEG07 proposed recently by the present authors includes the TBF effect and reproduces a realistic saturation curve in the nuclear matter, and is shown to well reproduce proton-nucleus elastic scattering. The microscopic optical potential for nucleus-nucleus system is obtained by folding the G matrix with nucleon density distributions in colliding nuclei. We first analyze the 16O + 16O elastic scattering at E/A = 70 MeV in detail. The observed cross sections are nicely reproduced up to the most backward scattering angles only when the TBF effect is included. The effects of the three-body attraction (TBA) and three-body repulsion (TBR) are also analyzed. The TBR contribution has an important role in nucleus-nucleus elastic scattering. The CEG07 G matrix is also tested in the elastic scattering of 16O by the 12C, 28Si and 40Ca targets at E/A = 93.9 MeV, and in the elastic scattering of 12C by the 12C target at E/A = 135 MeV with a great success. The decisive effect of the TBF is clearly seen also in those systems.

Furumoto, T.; Sakuragi, Y.; Yamamoto, Y.

2010-04-01

373

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

374

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

375

Effect of size on levitation force in a magnet/superconductor system  

SciTech Connect

We consider a model system consisting of an infinitely long magnetic dipole line placed symmetrically above an infinitely long superconducting strip. Using the Meissner effect of superconductors, we derive analytical expressions of the levitation forces acting on the dipole line. At lowest-order approximation, we discuss the possible application of our model system to estimate the upper limit of the levitation forces in some magnetic bearing systems. In one example, the model correctly calculated the vertical vibration frequency of an experimental superconducting bearing.

Yang, Z.J.; Hull, J.R. [Argonne National Laboratory, Argonne, Illinois 60439 (United States)

1996-03-01

376

Magnetic resonance force microscopy of paramagnetic electron spins at millikelvin temperatures  

NASA Astrophysics Data System (ADS)

Magnetic resonance force microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here we demonstrate MRFM operation at temperatures as low as 30?mK, thanks to a recently developed superconducting quantum interference device (SQUID)-based cantilever detection technique, which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centres on a silicon surface down to millikelvin temperatures. Fluctuations of such defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs, as well as in several superconducting and single spin qubits. We find evidence that spin diffusion has a key role in the low-temperature spin dynamics.

Vinante, A.; Wijts, G.; Usenko, O.; Schinkelshoek, L.; Oosterkamp, T. H.

2011-12-01

377

Magnetic resonance force microscopy of paramagnetic electron spins at millikelvin temperatures.  

PubMed

Magnetic resonance force microscopy (MRFM) is a powerful technique to detect a small number of spins that relies on force detection by an ultrasoft magnetically tipped cantilever and selective magnetic resonance manipulation of the spins. MRFM would greatly benefit from ultralow temperature operation, because of lower thermomechanical noise and increased thermal spin polarization. Here we demonstrate MRFM operation at temperatures as low as 30?mK, thanks to a recently developed superconducting quantum interference device (SQUID)-based cantilever detection technique, which avoids cantilever overheating. In our experiment, we detect dangling bond paramagnetic centres on a silicon surface down to millikelvin temperatures. Fluctuations of such defects are supposedly linked to 1/f magnetic noise and decoherence in SQUIDs, as well as in several superconducting and single spin qubits. We find evidence that spin diffusion has a key role in the low-temperature spin dynamics. PMID:22146391

Vinante, A; Wijts, G; Usenko, O; Schinkelshoek, L; Oosterkamp, T H

2011-12-06

378

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

379

An investigation on influence of magnet arc shaping upon back electromotive force waveforms for design of permanent-magnet brushless motors  

Microsoft Academic Search

This paper presents the magnet arc shaping technique to effectively produce the required sinusoidal back electromotive force (EMF) waveforms for design of permanent-magnet brushless motors. The magnet shapes to produce sinusoidal air gap flux distributions are first obtained using the Laplace's equation. A modified magnetic circuit model with \\

Min-Fu Hsieh; Yu-Sheng Hsu

2005-01-01

380

Forces and Stored Energy in Thin Cosine (n0) Accelerator Magnets  

SciTech Connect

We wish to compute Lorentz forces, equilibrium stress and stored energy in thin multipole magnets (Fig.1), that are proportional to cos(n{theta}) and whose strength varies purely as a Fourier sinusoidal series of the longitudinal coordinate z (say proportional to cos (2m-1){pi}z/L where L denotes the half-period and m = 1,2,3...). We shall demonstrate that in cases where the current is situated on such a surface of discontinuity at r = R (i.e. J = f({theta},z)), by computing the Lorentz force and solving the state of equilibrium on that surface, a closed form solution can be obtained for single function magnets as well as for any combination of interacting nested multi function magnets. The results that have been obtained, indicate that the total axial force on the end of a single multipole magnet n is independent (orthogonal) to any other multipole magnet i as long as n {ne} i. The same is true for the stored energy, the total energy of a nested set of multipole magnets is equal to the some of the energy of the individual magnets (of the same period length 2L). Finally we demonstrate our results on a nested set of magnets a dipole (n = 1) and a quadmpole (n=2) that have an identical single periodicity {omega}{sub 1}. We show that in the limiting 2D case (period 2L tends to infinity), the force reduces to the commonly known 2D case.

Caspi, S.

1996-03-18

381

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

Microsoft Academic Search

We have performed analysis and experimental measurement of the electromagnetic force loads on the hybrid rotor in a novel hybrid magnetic-bearing switched-reluctance motor (MBSRM). An MBSRM has the combined characteristics of a switched-reluctance motor and a magnetic bearing. The MBSRM discussed in this paper has an eight-pole stator and a six-pole hybrid rotor, which is composed of circular and scalloped

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

2008-01-01

382

The Mean Electromotive Force for MHD Turbulence: The Case of a Weak Mean Magnetic Field and Slow Rotation  

Microsoft Academic Search

The mean electromotive force that occurs in the framework of mean-field magnetohydrodynamics is studied for cases in which magnetic field fluctuations are not only due to the action of velocity fluctuations on the mean magnetic field. The possibility of magnetic field fluctuations independent of a mean magnetic field, as they may occur as a consequence of a small-scale dynamo, is

Karl-Heinz Rädler; Nathan Kleeorin; Igor Rogachevskii

2003-01-01

383

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

384

First-order reversal curve (FORC) diagrams of natural and cultured biogenic magnetic particles  

NASA Astrophysics Data System (ADS)

First-order reversal curve (FORC) diagrams are rapidly becoming a standard tool for characterizing magnetic particles because they simultaneously incorporate information regarding magnetostatic interaction and domain states. The simplest interpretation of FORC diagrams of single-domain (SD) particles is based on the Neel interpretation of Preisach theory, which predicts that the FORC function is the product of a coercivity and an interaction field distribution. Although the underlying assumptions of this interpretation are not correct, a strictly quantitative model of weakly interacting SD grains proves that the distributions of coercivities and interaction fields can be retrieved from a FORC diagram. To test this model, we present the possibility of a quantitative interpretation of FORC diagrams, and we present measurements of samples containing magnetosomes from cultures of magnetotactic bacteria and from a lake sediment. Two samples are investigated under the electron microscope to characterize the geometrical arrangement of the particles. We find that the clustering of otherwise similar particles has a strong influence on FORC diagrams. We also obtained a crude estimate of packing densities form the FORC diagrams, which were consistent with transmission electron microscopy observations and measurements of the anhysteretic remanent magnetization.

Chen, Amy P.; Egli, Ramon; Moskowitz, Bruce M.

2007-08-01

385

Magnetic Suspension Force in an Induction Bearingless Motor with a Squirrel Cage Rotor  

NASA Astrophysics Data System (ADS)

Theoretical equations of magnetic force in an induction bearingless motor have been reported. In the bearingless motor, both 4-pole and 2-pole windings are stored in stator slots for torque and suspension force generation. In the analysis, squirrel cage rotor currents are considered. These currents are induced by both torque and suspension winding currents. Inductance matrix is represented by four sets of three-phase windings, thus 12×12 matrix is constructed. A simplification and reasonable assumptions are introduced to obtain understandable expressions for suspension force and torque representation. The rotor flux linkages in an induction bearingless motor are derived, and then, simulation model of suspension force is constructed. It is shown that the response and the phase of suspension force are delayed in a case of cage rotors.

Katou, Tatsuya; Chiba, Akira; Fukao, Tadashi

386

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

387

Three-body problem with short-range forces: Renormalized equations and regulator-independent results  

NASA Astrophysics Data System (ADS)

We discuss effective field theory treatments of the problem of three particles interacting via short-range forces. One case of such a system is neutron-deuteron (nd) scattering at low energies. We demonstrate that in attractive channels the renormalization-group evolution of the 1+2 scattering amplitude may be complicated by the presence of eigenvalues greater than unity in the kernel. We also show that these eigenvalues can be removed from the kernel by one subtraction, resulting in an equation which is renormalization-group invariant. A unique solution for 1+2 scattering phase shifts is then obtained. We give an explicit demonstration of our procedure for both the case of three spinless bosons and the case of the doublet channel in nd scattering. After the contribution of the two-body effective range is included in the effective field theory, it gives a good description of the nd doublet phase shifts below deuteron breakup threshold.

Afnan, I. R.; Phillips, Daniel R.

2004-03-01

388

A hybrid N-body code incorporating algorithmic regularization and post-Newtonian forces  

NASA Astrophysics Data System (ADS)

We describe a novel N-body code designed for simulations of the central regions of galaxies containing massive black holes. The code incorporates Mikkola's `algorithmic' chain regularization scheme including post-Newtonian terms up to PN2.5 order. Stars moving beyond the chain are advanced using a fourth-order integrator with forces computed on a GRAPE board. Performance tests confirm that the hybrid code achieves better energy conservation, in less elapsed time, than the standard scheme and that it reproduces the orbits of stars tightly bound to the black hole with high precision. The hybrid code is applied to two sample problems: the effect of finite-N gravitational fluctuations on the orbits of the S-stars, and inspiral of an intermediate-mass black hole into the Galactic Centre.

Harfst, S.; Gualandris, A.; Merritt, D.; Mikkola, S.

2008-09-01

389

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

2012-08-16

390

In-medium T matrix for nuclear matter with three-body forces: Binding energy and single-particle properties  

SciTech Connect

We present spectral calculations of nuclear matter properties including three-body forces. Within the in-medium T-matrix approach, implemented with the CD-Bonn and Nijmegen potentials plus the three-nucleon Urbana interaction, we compute the energy per particle in symmetric and neutron matter. The three-body forces are included via an effective density dependent two-body force in the in-medium T-matrix equations. After fine tuning the parameters of the three-body force to reproduce the phenomenological saturation point in symmetric nuclear matter, we calculate the incompressibility and the energy per particle in neutron matter. We find a soft equation of state in symmetric nuclear matter but a relatively large value of the symmetry energy. We study the the influence of the three-body forces on the single-particle properties. For symmetric matter the spectral function is broadened at all momenta and all densities, while an opposite effect is found for the case of neutrons only. Noticeable modification of the spectral functions are realized only for densities above the saturation density. The modifications of the self-energy and the effective mass are not very large and appear to be strongly suppressed above the Fermi momentum.

Soma, V. [Institute of Nuclear Physics PAN, PL-31-342 Krakow (Poland); Bozek, P. [Institute of Physics, Rzeszow University, PL-35-959 Rzeszow (Poland); Institute of Nuclear Physics PAN, PL-31-342 Krakow (Poland)

2008-11-15

391

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

392

Neutron Fermi liquids under the presence of a strong magnetic field with effective nuclear forces  

NASA Astrophysics Data System (ADS)

Landau's Fermi liquid parameters are calculated for non-superfluid pure neutron matter in the presence of a strong magnetic field at zero temperature. The particle-hole interactions in the system, where a net magnetization may be present, are characterized by these parameters in the framework of a multipolar formalism. We use either zero- or finite-range effective nuclear forces to describe the nuclear interaction. Using the obtained Fermi liquid parameters, the contribution of a strong magnetic field on some bulk magnitudes such as isothermal compressibility and spin susceptibility is also investigated.

Pérez-García, M. Ángeles; Navarro, J.; Polls, A.

2009-08-01

393

Self-sensing piezoresistive cantilever and its magnetic force microscopy applications.  

PubMed

A newly developed Si self-sensing piezoresistive cantilever is presented. Si piezoresistive cantilevers for scanning microscopy are fabricated by Si micro-machining technique. The sensitivity of the piezoresistive cantilever is comparable to the current laser detecting system. Topographic images are successfully obtained with the piezoresistive cantilever and some comparisons are made with the laser detecting system. Furthermore, the magnetic film (Co-Cr-Pt) is coated on the tip of the piezoresistive cantilever for magnetic force microscopy (MFM) application. The magnetic images are successfully obtained with the self-sensing MFM piezoresistive cantilever. The self-sensing piezoresistive cantilevers have been successfully applied in scanning probe microscopy and MFM. PMID:12211485

Takahashi, Hiroshi; Ando, Kazunori; Shirakawabe, Yoshiharu

2002-05-01

394

Student understanding of the direction of the magnetic force on a charged particle  

NASA Astrophysics Data System (ADS)

We study student understanding of the direction of the magnetic force experienced by a charged particle moving through a homogeneous magnetic field in both the magnetic pole and field line representations of the magnetic field. In five studies, we administer a series of simple questions in either written or interview format. Our results indicate that although students begin at the same low level of performance in both representations, they answer correctly more often in the field line representation than in the pole representation after instruction. This difference is due in part to more students believing that charges are attracted to magnetic poles than believing that charges are pushed along magnetic field lines. Although traditional instruction is fairly effective in teaching students to answer correctly up to a few weeks following instruction, especially for the field line representation, some students revert to their initial misconceptions several months after instruction. The responses reveal persistent and largely random sign errors in the direction of the force. The sign errors are largely nonsystematic and due to confusion about the direction of the magnetic field and the execution and choice of the right-hand rule and lack of recognition of the noncommutativity of the cross product.

Scaife, Thomas M.; Heckler, Andrew F.

2010-08-01

395

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

396

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

397

Electromotive force and large-scale magnetic dynamo in a turbulent flow with a mean shear  

Microsoft Academic Search

An effect of sheared large-scale motions on a mean electromotive force in a nonrotating turbulent flow of a conducting fluid is studied. It is demonstrated that in a homogeneous divergence-free turbulent flow the alpha effect does not exist, however a mean magnetic field can be generated even in a nonrotating turbulence with an imposed mean velocity shear due to a

Igor Rogachevskii; Nathan Kleeorin

2003-01-01

398

Magnetic levitation force and penetration depth in type-II superconductors  

SciTech Connect

The superconducting levitation force [ital F] acting on a magnet placed above a type-II superconductor in both Meissner and mixed states is calculated as a function of temperature, based upon the London model. A simple relationship between the levitation force and the London penetration depth [lambda] is found. In particular, in the limit of [ital a]/[lambda][much gt]1, where [ital a] is the separation between the magnet and the superconductor, [ital F] varies linearly with [lambda], regardless of the shape of the magnet. The temperature dependences of [lambda] and [ital F] are examined for various superconducting pairing states, including [ital s]-wave, [ital d]-wave, and [ital s]+[ital id] states. It is found that, at low temperatures, both [lambda] and [ital F] show an exponential temperature dependence for [ital s]-wave, linear-[ital T] for [ital d]-wave, and [ital T][sup 2] dependence in a wide low-temperature range for the [ital s]+[ital id] state with a dominant [ital d]-wave component. The magnetic force microscope (MFM) is proposed to accurately measure the temperature-dependent levitation force. It is shown that the microscopic size of the MFM tip enables one to obtain the intrinsic temperature-dependent penetration depth of a single grain, in spite of the overall quality of the superconducting sample.

Xu, J.H.; Miller, J.H. Jr.; Ting, C.S. (Department of Physics and Texas Center for Superconductivity, University of Houston, Houston, Texas 77204 (United States))

1995-01-01

399

Contact force measurements at the head\\/disk interface for contact recording heads in magnetic recording  

Microsoft Academic Search

As the spacing between the magnetic transducer and media decreases in hard disk drives, one approaches the regime of constant contact between the head and disk. In this regime, conventional measures of the head\\/disk interface such as 'takeoff velocity' and 'fly height' become less important. Instead, the 'contact force' between the head and the disk is a more relevant parameter

S. K. Ganapathi; Mark Donovan; Yiao-Tee Hsia

1996-01-01

400

An extended electromotive force model for sensorless control of interior permanent-magnet synchronous motors  

Microsoft Academic Search

During the last decade, many sensorless control methods have been proposed for surface permanent-magnet synchronous motors (SPMSMs) based on the estimation of electromotive force (EMF) in which the motor's position information is contained. However, these methods cannot be applied to interior PMSMs (IPMSMs) directly, because the position information is contained in not only the EMF, but also the inductance of

Zhiqian Chen; Mutuwo Tomita; Shinji Doki; Shigeru Okuma

2003-01-01

401

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

402

Fictitious Forces and Simulated Magnetic Fields in Rotating Reference Frames  

NASA Astrophysics Data System (ADS)

We show that the Wigner-Bargmann program of grounding nonrelativistic quantum mechanics in the unitary projective representations of the Galilei group can be extended to include all noninertial reference frames. The key concept is the Galilean line group, the group of transformations that ties together all accelerating reference frames, and its representations. These representations are constructed under the natural constraint that they reduce to the well-known unitary, projective representations of the Galilei group when the transformations are restricted to inertial reference frames. This constraint can be accommodated only for a class of representations with a sufficiently rich cocycle structure. Unlike the projective representations of the Galilei group, these cocycle representations of the Galilean line group do not correspond to central extensions of the group. Rather, they correspond to a class of nonassociative extensions, known as loop prolongations, that are determined by three-cocycles. As an application, we show that the phase shifts due to the rotation of Earth that have been observed in neutron interferometry experiments and the rotational effects that lead to simulated magnetic fields in optical lattices can be rigorously derived from the representations of the loop prolongations of the Galilean line group.

Klink, W. H.; Wickramasekara, S.

2013-10-01

403

Ferromagnetic Resonance Investigation of an Individual Permalloy Dot Using Magnetic Resonance Force Microscopy  

NASA Astrophysics Data System (ADS)

We report Ferromagnetic Resonance (FMR) investigations of individual 5.3 micron diameter permalloy dots using low temperature (4 K) Magnetic Resonance Force Microscopy (MRFM). The dot magnetization is saturated in the external magnetic field perpendicular to the plane of the sample. The evolution of the MRFM signal as probe-sample separation and the lateral probe position are varied reveals the shape of the magnetostatic modes excited in the dot in the presence of the strongly inhomogeneous magnetic field of the MRFM probe magnet. The experimental data agree excellently with micromagnetic modeling which suggests that localized FMR modes are excited in the sample. This effect opens the way for spatially resolved studies of ferromagnetic systems.

Kim, J.; Lee, I. H.; Pelekhov, D.; Obukhov, Yu.; Banerjee, P.; Martin, I.; Wigen, P.; Hammel, P. C.

2008-03-01

404

Generation of Seed Magnetic Field Around First Stars: Effects of Radiation Force  

NASA Astrophysics Data System (ADS)

We investigate seed magnetic field generation in the early universe by the radiation force of first stars. In a previous study with the steady assumption, large amplitudes (~10-15 G for first stars, ~10-11 G for QSOs) are predicted. In this study, we formulate this issue in an unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, we (1) find that the steady assumption is not valid in realistic situations and (2) obtain a much smaller magnetic field strength than that predicted by Langer et al. In addition, we find that the momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is lsim10-19 G. This seed magnetic field will not affect subsequent star formation in the neighborhood of first stars.

Ando, Masashi; Doi, Kentaro; Susa, Hajime

2010-06-01

405

No Core CI calculations for light nuclei with chiral 2- and 3-body forces  

NASA Astrophysics Data System (ADS)

The atomic nucleus is a self-bound system of strongly interacting nucleons. In No-Core Configuration Interaction calculations, the nuclear wavefunction is expanded in Slater determinants of single-nucleon wavefunctions (Configurations), and the many-body Schrödinger equation becomes a large sparse matrix problem. The challenge is to reach numerical convergence to within quantified numerical uncertainties for physical observables using finite truncations of the infinite-dimensional basis space. We discuss strategies for constructing and solving the resulting large sparse matrices for a set of low-lying eigenvalues and eigenvectors on current multicore computer architectures. Several of these strategies have been implemented in the code MFDn, a hybrid MPI/OpenMP Fortran code for ab initio nuclear structure calculations that scales well to over 200,000 cores. We discuss how the similarity renormalization group can be used to improve the numerical convergence. We present results for excitation energies and other selected observables for 8Be and 12C using realistic 2- and 3-body forces obtained from chiral perturbation theory. Finally, we demonstrate that collective phenomena such as rotational band structures can emerge from these microscopic calculations.

Maris, Pieter; Metin Aktulga, H.; Binder, Sven; Calci, Angelo; Çatalyürek, Ümit V.; Langhammer, Joachim; Ng, Esmond; Saule, Erik; Roth, Robert; Vary, James P.; Yang, Chao

2013-08-01

406

Non-force-free Extrapolation of Coronal Magnetic Field with Applications to Vector Magnetograms  

NASA Astrophysics Data System (ADS)

Motivated by increasingly more advanced solar observations, we recently develop a method of non-force-free extrapolation of the solar coronal magnetic field from vector magnetograms, especially those for a finite active region. Based on a more complex variational principle, the principle of minimum (energy) dissipation rate (MDR), we adopt and solve a more complex equation governing the coronal magnetic field that is non-force-free in general. We describe the theoretical basis in the context of general solar atmosphere conditions, and derive the extrapolation approach utilizing vector magnetograms as bottom boundary conditions. We illustrate the approach using both MHD numerical simulation results, and real vector magnetograph measurements of solar active regions. We wish to establish the validity of our approach, especially by detailed inter-comparison with self-consistent, full MHD simulation results, and investigations of the dynamics associated with non-vanishing forces.

Hu, Q.; Wang, A.; Dasgupta, B.; Gary, G. A.; Wu, S.

2009-12-01

407

High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments.  

PubMed

We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to ?4.5 ?m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as ?1 kPa. PMID:22667631

Lin, Jun; Valentine, Megan T

2012-05-01

408

Electromagnetic force on a magnetic dipole inside an annular pipe flow  

NASA Astrophysics Data System (ADS)

We present an illuminating example of electromagnetic flow measurement in liquid metals that is easy to analyze yet displays a remarkably good agreement with laboratory experiments. Our system involves a small permanent magnet located inside an annular pipe carrying the flow of a liquid metal. We investigate the Lorentz force acting upon the magnet using a combination of laboratory experiments with liquid metal at room temperature and a simple analytical model. We demonstrate that the measured Lorentz forces are in very good agreement with the predictions of our model over a wide range of geometry parameters. By virtue of its simplicity and close relationship to the well known ``creeping magnet'' classroom experiment, our system can also serve as an educational tool for introductory courses in liquid metal magnetohydrodynamics.

Heinicke, Christiane; Thess, André

2013-09-01

409

High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments  

SciTech Connect

We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to {approx}4.5 {mu}m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as {approx}1 kPa.

Lin Jun [Department of Mechanical Engineering, University of California, Santa Barbara, California 93106 (United States); Biomolecular Science and Engineering Program, University of California, Santa Barbara, California 93106 (United States); Valentine, Megan T. [Department of Mechanical Engineering, University of California, Santa Barbara, California 93106 (United States)

2012-05-15

410

Contact force measurements at the head/disk interface for contact recording heads in magnetic recording  

NASA Astrophysics Data System (ADS)

As the spacing between the magnetic transducer and media decreases in hard disk drives, one approaches the regime of constant contact between the head and disk. In this regime, conventional measures of the head/disk interface such as 'takeoff velocity' and 'fly height' become less important. Instead, the 'contact force' between the head and the disk is a more relevant parameter to evaluate the performance and reliability of the interface. In this paper, a new contact force measurement technique that uses the acoustic emission (AE) from the interface is introduced. The contact force is modeled as a series of continuous collisions that cause the slider to vibrate at its resonant frequencies. These vibrations generate an AE signal, the magnitude of which is proportional to the contact force. The Read-Rite tripad slider, which is a contact recording head, is used for the measurements. Some intuitive expectations from contact force measurements are presented as validation of the technique. Specifically, it is shown that contact force decreases with increasing disk velocity, that the contact force varies inversely with the flying height measured on a glass disk, and that the contact force decreases with burnishing of the interface.

Ganapathi, S. K.; Donovan, Mark; Hsia, Yiao-Tee

1996-01-01

411

Energy of Force-Free Magnetic Fields in Relation to Coronal Mass Ejections  

SciTech Connect

In typical observations of coronal mass ejections (CMEs), a magnetic structure of a helmet-shaped closed configuration bulges out and eventually opens up. However, a spontaneous transition between these field configurations has been regarded to be energetically impossible in force-free fields according to the Aly-Sturrock theorem. The theorem states that the maximum energy state of force-free fields with a given boundary normal field distribution is the open field. The theorem implicitly assumes the existence of the maximum energy state, which may not be taken for granted. In this study, we have constructed force-free fields containing tangential discontinuities in multiple flux systems. These force-free fields can be generated from a potential field by footpoint motions that do not conserve the boundary normal field distribution. Some of these force-free fields are found to have more magnetic energy than the corresponding open fields. The constructed force-free configurations are compared with observational features of CME-bearing active regions. Possible mechanisms of CMEs are also discussed.

G.S. Choe; C.Z. Cheng

2002-05-09

412

Measurement method for determining the magnetic hysteresis effects of reluctance actuators by evaluation of the force and flux variation  

NASA Astrophysics Data System (ADS)

A measurement method is presented which identifies the magnetic hysteresis effects present in the force of linear reluctance actuators. The measurement method is applied to determine the magnetic hysteresis in the force of an E-core reluctance actuator, with and without pre-biasing permanent magnet. The force measurements are conducted with a piezoelectric load cell (Kistler type 9272). This high-bandwidth force measurement instrument is identified in the frequency domain using a voice-coil actuator that has negligible magnetic hysteresis and eddy currents. Specifically, the phase delay between the current and force of the voice-coil actuator is used for the calibration of the measurement instrument. This phase delay is also obtained by evaluation of the measured force and flux variation in the E-core actuator, both with and without permanent magnet on the middle tooth. The measured magnetic flux variation is used to distinguish the phase delay due to magnetic hysteresis from the measured phase delay between the current and the force of the E-core actuator. Finally, an open loop steady-state ac model is presented that predicts the magnetic hysteresis effects in the force of the E-core actuator.

Vrijsen, N. H.; Jansen, J. W.; Compter, J. C.; Lomonova, E. A.

2013-07-01

413

Health and Job-Specific Body Composition Standards for the US Air Force. Volume 1.  

National Technical Information Service (NTIS)

The Air Force Medical Service strives to deliver a fit and healthy force, which ultimately translates to sustained and enhanced mission performance. In support of these goals, the Air Force School of Aerospace Medicine's Performance Enhancement Division i...

B. Palmer J. W. Carroll M. E. Rench S. H. Constable

2000-01-01

414

Influence of two-body and three-body interatomic forces on gas, liquid, and solid phases.  

PubMed

Accurate molecular dynamics simulations are reported which quantify the contributions of two- and three-body interactions in the gas, liquid, and solid phases of argon at both subcritical and supercritical conditions. The calculations use an accurate two-body potential in addition to contributions from three-body dispersion interactions from third-order triple-dipole interactions. The number dependence of three-body interactions is quantified, indicating that a system size of at least five hundred atoms is required for reliable calculations. The results indicate that, although the contribution of three-body interaction to the overall energy is small, three-body interactions significantly affect the pressure at which vapor-liquid and solid-liquid transitions are observed. In particular, three-body interactions substantially increase the pressure of the freezing point. Unlike two-body interactions, which vary with both density and temperature, for a given density, three-body interactions have a near-constant 'background' value irrespective of the temperature. Both two-body interactions and kinetic energy have an important role in vapor-liquid equilibria whereas solid-liquid equilibria are dominated by two-body interactions. PMID:17025412

Wang, Liping; Sadus, Richard J

2006-08-25

415

Dynamic analysis of radial force density in brushless DC motor using 3-D equivalent magnetic circuit network method  

SciTech Connect

The distribution of radial force density in brushless permanent magnet DC motor is not uniform in axial direction. The analysis of radial force density has to consider the 3-D shape of teeth and overhand, because the radial force density causes vibration and acts on the surface of teeth inconstantly. For the analysis, a new 3-D equivalent magnetic circuit network method is used to account the rotor movement without remesh. The radial force density is calculated and analyzed by Maxwell stress tensor and discrete Fourier transform (DFT) respectively. The results of 3-D equivalent magnetic circuit method have been compared with the results of 3-D FEM.

Hur, J.; Chun, Y.D.; Lee, J.; Hyun, D.S. [Hanyang Univ., Seoul (Korea, Republic of). Dept. of Electrical Engineering

1998-09-01

416

Determination of radiation exposure history of common materials and computer hardware by using atomic (and magnetic force) microscopy  

NASA Astrophysics Data System (ADS)

Defects produced by ionizing radiation are smaller than a micrometer and are unobservable in an optical microscope. An atomic force microscope was utilized to reveal their counts and structure in common materials like mica, silicon, organic solids, polymers, sugar, quartz, and calcite. A magnetic force microscope has shown the damage of radiation on computer hard disks. The present work shows that exposure to radioactive material leaves a permanent record, which can be read for dosimetric or forensic purposes by using atomic force microcopy on common objects or a magnetic force microscope on magnetic media.

Sharma, J.; Teter, J. P.; Abbundi, R. J.; Guardala, N. A.

2003-04-01

417

Effect of seat surface angle on forces at the seat surface during whole-body vertical vibration  

Microsoft Academic Search

Twelve male subjects have been exposed to whole-body vertical random vibration so as to investigate the effect of seat surface angle, vibration magnitude and contact with a backrest on the ‘vertical apparent mass’ (calculated from forces normal to the seat surface and vertical acceleration) and ‘fore-and-aft cross-axis apparent mass’ (calculated from forces parallel to the seat surface and vertical acceleration).

Naser Nawayseh; Michael J. Griffin

2005-01-01

418

Additional dc magnetic field response of magnetostrictive/piezoelectric magnetoelectric Laminates by Lorentz force effect  

NASA Astrophysics Data System (ADS)

We have discovered that traditional long-type magnetoelectric laminate composite of magnetostrictive Tb1-xDyxFe2-y and piezoelectric materials possesses additional ability of detecting dc magnetic field, using the product effect of the Lorentz force effect from Terfenol-D metal strips in dc magnetic field applied with an ac electrical current and the piezoelectric effect from piezoelectric material. The output voltage between the two faces of piezoelectric (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 single crystal shows a good linear response to applied dc magnetic field of 100-1200 Oe under different ac electrical current inputs (0.4-200 mA). The magnetoelectric coefficient is about ~64.1 mV/T A. The additional dc magnetic field response of magnetostrictive/piezoelectric magnetoelectric laminates driven by Lorentz force makes this composite hopeful for application in coil-free ac/dc magnetic-sensitive sensors. At the same time, for this composite, the additional ability will not affect the primal ability for detecting ac magnetic field.

Jia, Yanmin; Tang, Yanxue; Zhao, Xiangyong; Luo, Haosu; Or, Siu Wing; Chan, Helen Lai Wa

2006-12-01

419

Nonlinear Force-free Magnetic Field Fitting to Coronal Loops with and without Stereoscopy  

NASA Astrophysics Data System (ADS)

We developed a new nonlinear force-free magnetic field (NLFFF) forward-fitting algorithm based on an analytical approximation of force-free and divergence-free NLFFF solutions, which requires as input a line-of-sight magnetogram and traced two-dimensional (2D) loop coordinates of coronal loops only, in contrast to stereoscopically triangulated three-dimensional loop coordinates used in previous studies. Test results of simulated magnetic configurations and from four active regions observed with STEREO demonstrate that NLFFF solutions can be fitted with equal accuracy with or without stereoscopy, which relinquishes the necessity of STEREO data for magnetic modeling of active regions (on the solar disk). The 2D loop tracing method achieves a 2D misalignment of ?2 = 2.°7 ± 1.°3 between the model field lines and observed loops, and an accuracy of ?1.0% for the magnetic energy or free magnetic energy ratio. The three times higher spatial resolution of TRACE or SDO/AIA (compared with STEREO) also yields a proportionally smaller misalignment angle between model fit and observations. Visual/manual loop tracings are found to produce more accurate magnetic model fits than automated tracing algorithms. The computation time of the new forward-fitting code amounts to a few minutes per active region.

Aschwanden, Markus J.

2013-02-01

420

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

421

Three and four-body intervortex forces in the Ginzburg-Landau models of single- and multicomponent superconductivity  

NASA Astrophysics Data System (ADS)

A systematic numerical study of non-pairwise vortex interaction forces in the Ginzburg-Landau model for single-and multicomponent superconductivity is presented. The interactions are obtained by highly accurate numerical free energy minimization. In particular a three-body interaction is defined as the difference between the total interaction and sum of pairwise interactions in a system of three vortices and such interactions are studied for single and two-component type-1, type-2, and type-1.5 superconductors. In the investigated regimes, the three-body interaction is found to be short-range repulsive but long-range attractive in the type-1 case, zero in the critical ? (Bogomoln'y) case, attractive in the type-2 case and repulsive in the type-1.5 case. Some systems of four vortices are also studied and results indicate that four-body forces are of substantially less significance than the three-body interactions.

Edström, Alexander

2013-04-01

422

Magnetic Field Dependence of Many-Body Enhanced Electron Tunnelling Through a Quantum Dot  

Microsoft Academic Search

We consider many-body enhanced electron tunnelling through an InAs quantum dot in magnetic field applied perpendicular to the tunneling direction. Critical exponent of Fermi edge singularity in tunneling current is calculated as a function of magnetic field. We use lowest Landau level approximation for electrons in emitter and perform scattering matrix calculation in Born approximation. Results are compared with recent

Ivan A. Larkin; E. E. Vdovin; Yu. N. Khanin; M. Henini

2009-01-01

423

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

424

Magnetization of celestial bodies with special application to the primeval Earth and Moon  

Microsoft Academic Search

The magnetic fields of celestial bodies are usually supposed to be due to a ‘hydromagnetic dynamo’. This term refers to a number of rather speculative processes which are supposed to take place in the liquid core of a celestial body. In this paper we shall follow another approach which is more closely connected with hydromagnetic processes well-known from the laboratory,

Hannes Alfvén; Lennart Lindberg

1974-01-01

425

Computation of magnetic anomalies and gradients for spatial arbitrary posture regular body  

Microsoft Academic Search

In the interaction computation for 3D gravity and magnetic anomalies due to arbitrarily shaped homogenous magnetized polyhedron\\u000a model composed of triangular facets, there are many difficult points, such as mass computing, absence of a mature computer\\u000a technique in 3D geological body modeling, inconvenient human-computer interaction, hard program coding, etc.. Based on the\\u000a formulae of the magnetic field due to horizontal

Dongming Hong; Changli Yao; Yuanman Zheng; Wei Guo; Yao Luo

2009-01-01

426

Drum-like silencers using magnetic forces in a pressurized cavity  

NASA Astrophysics Data System (ADS)

A feasibility study is carried out for utilizing magnetic force to yield a low-frequency shift of the transmission loss spectrum provided by a drum-like silencer consisting of two side-branch, rectangular cavities covered by ferromagnetic membranes. The results show that the transmission loss spectrum of the drum-like silencer is mainly controlled by the vibration of the first and second modes of the membrane. Three pairs of magnets are employed inside the cavity to promote the response of these modes. It is found that the magnetic force imposes both static and dynamic effects on the silencer. While the latter helps shift the effective region of the silencer towards lower frequencies, the former results in an increase of stiffness of the membrane which is detrimental to the operation of the silencer at low frequencies. Cavity pressurization is then proposed to neutralize the static effects of the magnetic force. A finite element model is developed to predict and optimize the performance of the proposed silencer with some of the results validated experimentally. The desired shift towards the lower frequency is validated although the silencer performance is still less than ideal due to both parametric and operational constraints of the rig.

Chiu, Y. H.; Cheng, L.; Huang, L.

2006-11-01

427

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

428

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

NASA Astrophysics Data System (ADS)

We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary surface on which only the distribution of the normal magnetic field component is given. The method relies on the theory of force-free electrodynamics and applies directly to the reconstruction of the solar coronal magnetic field for a given distribution of the photospheric radial field component. The method works as follows: we start with any initial magnetostatic global field configuration ( e.g. zero, dipole), and along the boundary surface we create an evolving distribution of tangential (horizontal) electric fields that, via Faraday's equation, give rise to a respective normal-field distribution approaching asymptotically the target distribution. At the same time, these electric fields are used as boundary condition to numerically evolve the resulting electromagnetic field above the boundary surface, modeled as a thin ideal plasma with non-reflecting, perfectly absorbing outer boundaries. The simulation relaxes to a nonlinear force-free configuration that satisfies the given normal-field distribution on the boundary. This is different from existing methods relying on a fixed boundary condition - the boundary evolves toward the a priori given one, at the same time evolving the three-dimensional field solution above it. Moreover, this is the first time that a nonlinear force-free solution is reached by using only the normal field component on the boundary. This solution is not unique, but it depends on the initial magnetic field configuration and on the evolutionary course along the boundary surface. To our knowledge, this is the first time that the formalism of force-free electrodynamics, used very successfully in other astrophysical contexts, is applied to the global solar magnetic field.

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

2011-04-01

429

Nonlinear force-free reconstruction of the global solar magnetic field  

NASA Astrophysics Data System (ADS)

We present a novel numerical method that allows the calculation of nonlinear force-free magnetostatic solutions above a boundary surface on which only the distribution of the normal magnetic field component is given. The method relies on the theory of force-free electrodynamics and applies directly to the reconstruction of the solar coronal magnetic field for a given distribution of the photospheric radial field component. The method works as follows: we start with any initial magnetostatic global field configuration (e.g. zero, dipole), and along the boundary surface we create an evolving distribution of tangential (horizontal) electric fields that, via Faraday's equation, give rise to a respective normal field distribution approaching asymptotically the target distribution. At the same time, these electric fields are used as boundary condition to numerically evolve the resulting electromagnetic field above the boundary surface, modeled as a thin ideal plasma with non-reflecting, perfectly absorbing outer boundaries. The simulation relaxes to a nonlinear force-free configuration that satisfies the given normal field distribution on the boundary. This is different from existing methods relying on a fixed boundary condition - the boundary evolves toward the a priori given one, at the same time evolving the three-dimensional field solution above it. Moreover, this is the first time a nonlinear force-free solution is reached by using only the normal field component on the boundary. This solution is not unique, but depends on the initial magnetic field configuration and on the evolutionary course along the boundary surface. To our knowledge, this is the first time that the formalism of force-free electrodynamics, used very successfully in other astrophysical contexts, is applied to the global solar magnetic field.

Contopoulos, I.

2012-01-01

430

Modeling of Axial Magnetic Force and Stiffness of Ring-Shaped Permanent-Magnet Passive Vibration Isolator and Its Vibration Isolating Experiment  

Microsoft Academic Search

Magnetic suspension vibration isolators have attracted more and more attention in the field of semiconductor industry and high precision equipments. A novel ring-shaped permanent-magnet passive vibration isolator is mainly reported in this paper. An analytical expression of axial magnetic force of the isolator is derived and validated by the finite element analysis and experiment. It proves that the analytical expression

Yu Zhu; Qiang Li; Dengfeng Xu; Ming Zhang

2012-01-01

431

Short-term effects of whole-body vibration on maximal voluntary isometric knee extensor force and rate of force rise  

Microsoft Academic Search

.   Whole-Body vibration (WBV) may lead to muscle contractions via reflex activation of the primary muscle spindle (Ia) fibres.\\u000a WBV has been reported to increase muscle power in the short term by improved muscle activation. The present study set out\\u000a to investigate the acute effects of a standard WBV training session on voluntary activation during maximal isometric force\\u000a production (MVC)

C. J. de Ruiter; R. M. van der Linden; M. J. A. van der Zijden; A. P. Hollander; A. de Haan

2003-01-01

432

Light-induced dynamics in the Lorentz oscillator model with magnetic forces  

SciTech Connect

The classical Lorentz oscillator model of bound electron motion ordinarily excludes magnetic forces at nonrelativistic intensities for the simple reason that their magnitude is small. However, perturbative and numerical results show that when the v-vectorxB-vector term is retained, dynamically enhanced terms give rise to large amplitude, magnetically induced charge displacements at zero frequency and at twice the driving frequency in the Cartesian laboratory frame. Numerical simulations of electron motion are in accord with the predictions of perturbative theory for steady-state motion in the classical picture. Direct integration shows that magnetic response which is comparable to electric dipole response can arise in transparent dielectrics at optical frequencies. Parametric instability in the equations of motion is implicated as the source of rapid energy transfer from electric to magnetic motions by reduction of the equations to a complex Mathieu equation.

Fisher, W. M.; Rand, S. C. [Applied Physics Program, University of Michigan, Ann Arbor, Ann Arbor, Michigan 48109 (United States)

2010-07-15

433

Single-shot nuclear magnetization recovery curves with force-gradient detection  

NASA Astrophysics Data System (ADS)

We measure the spin-lattice relaxation time as a function of sample temperature in GaAs in a real-time single-shot inversion recovery experiment using spin force gradients acting on a magnetic tipped cantilever. After inverting 69Ga spins localized near the magnet with a single 20 ms adiabatic rapid passage sweep, the spins' magnetization recovery was passively tracked by recording the cantilever's frequency change, which is proportional to the longitudinal component of the spins' magnetization. The cantilever's frequency was recorded for a time 3*T1 for sample temperatures ranging from 4.8 to 25 K. The temperature dependence was observed for the 69Ga quadrupolar relaxation interaction.

Alexson, Dimitri A.; Hickman, Steven A.; Marohn, John A.; Smith, Doran D.

2012-07-01

434

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

435

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

436

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

437

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

438

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

439

Radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation  

Microsoft Academic Search

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. These motors are characterized by integration of switched reluctance motors and magnetic bearings. It is essential for a control system to consider magnetic saturation in real time in order to realize stable operation at a full torque load. Thus, this paper proposes a method

Masatsugu Takemoto; Akira Chiba; Hirofumi Akagi; Tadashi Fukao

2002-01-01

440

Radial force and torque of a bearingless switched reluctance motor operating in a region of magnetic saturation  

Microsoft Academic Search

Bearingless switched reluctance motors, which can control rotor radial positions with magnetic force, have been proposed. These motors are characterized by integration of switched reluctance motors and magnetic bearings. It is essential for a control system to consider magnetic saturation in real time in order to realize stable operation at a full torque load. Thus, this paper proposes a method

Masatsugu Takemoto; Akira Chiba; Hirofumi Akagi; Tadashi Fukao

2004-01-01

441

Three-body force effect on P3 F2 neutron superfluidity in neutron matter, neutron star matter, and neutron stars  

NASA Astrophysics Data System (ADS)

We investigate the effect of microscopic three-body forces on the P3 F2 neutron superfluidity in neutron matter, ?-stable neutron star matter, and neutron stars by using the BCS theory and the Brueckner-Hartree-Fock approach. We adopt the Argonne V18 potential supplemented with a microscopic three-body force as the realistic nucleon-nucleon interaction. We have concentrated on studying the three-body force effect on the P3 F2 neutron pairing gap. It is found that the three-body force effect considerably enhances the P3 F2 neutron superfluidity in neutron star matter and neutron stars.

Zuo, W.; Cui, C. X.; Lombardo, U.; Schulze, H.-J.

2008-07-01

442

Effects of short-range correlations and three-body force on proton-3He scattering at high energy  

Microsoft Academic Search

Proton-3He elastic scattering is studied within the framework of the Glauber approximation at 1 GeV. The short-range correlations and the three-body force effects are studied. These effects are considered through a ground state wavefunction of the target nucleus. The results are discussed and compared with experimental data.

M. A. Hassan; S. S. A. Hassan

1991-01-01

443

Modeling domains using Bézier surfaces in plane boundary problems defined by the Navier–Lame equation with body forces  

Microsoft Academic Search

The paper presents an effective and powerful way of solving boundary problems modeled by the Navier–Lame equation with body forces. We considered domains of complex shapes defined using Bézier surfaces, which are well-known in computer graphics. Obtained results were compared with analytical and numerical solutions received by the boundary element method (BEM). The analysis of the results has confirmed reliability

Agnieszka Boltuc; Eugeniusz Zieniuk

2011-01-01

444

Body equilibrium at the end of gait initiation: importance of ankle muscular force as evidenced in clubfoot children  

Microsoft Academic Search

This study investigates the importance of ankle muscular force and foot shape on body equilibrium at the end of a first step by means of a comparison between healthy children and children with unilateral clubfoot who showed Triceps surae atrophy. Subjects were asked to initiate gait at different velocities and to perform a few forward-oriented steps. In healthy children, there

P. Wicart; B. Maton

2003-01-01

445

Statics and dynamics of a cylindrical droplet under an external body force.  

PubMed

We study the rolling and sliding motion of droplets on a corrugated substrate by Molecular Dynamics simulations. Droplets are driven by an external body force (gravity) and we investigate the velocity profile and dissipation mechanisms in the steady state. The cylindrical geometry allows us to consider a large range of droplet sizes. The velocity of small droplets with a large contact angle is dominated by the friction at the substrate and the velocity of the center of mass scales like the square root of the droplet size. For large droplets or small contact angles, howev