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1

Interaction Forces Between Multiple Bodies in a Magnetic Field  

NASA Technical Reports Server (NTRS)

Some of the results from experiments to determine the interaction forces between multiple bodies in a magnetic field are presented in this paper. It is shown how the force values and the force directions depend on the configuration of the bodies, their relative positions to each other, and the vector of the primary magnetic field. A number of efficient new automatic loading and assembly machines, as well as manipulators and robots, have been created based on the relationship between bodies and magnetic fields. A few of these patented magnetic devices are presented. The concepts involved open a new way to design universal grippers for robot and other kinds of mechanisms for the manipulation of objects. Some of these concepts can be used for space applications.

Joffe, Benjamin

1996-01-01

2

Evaluation of Magnetic Force Distribution and Torque Due to Smooth Interaction Body Force Density in Permanent-Magnet Materials  

Microsoft Academic Search

A smooth interaction body force density and torque were evaluated in permanent-magnet (PM) systems by using the virtual air-gap scheme coupled with the finite-element method. The virtual air-gap method has been successfully applied to soft magnetic materials for evaluating the force density, global contact force, and optimal shape design. These force-calculating methods employing the virtual air-gap scheme have been called

Geun-Young Jeong; Hong-Soon Choi; Hong-Joon Kim; Heung-Geun Kim; Se-Hee Lee

2011-01-01

3

Magnetoelastic Deformation of Soft and Hard Magnetic Materials Using Virtual Air-Gap Scheme Generating the Magnetic Body Force  

Microsoft Academic Search

The magnetoelastic deformations of soft and hard magnetic materials are evaluated by employing the body force calculating methods incorporating the virtual air-gap concept along with the finite-element method. By introducing the virtual air-gap scheme, we have recently developed generalized methods for calculating body force field such as the generalized magnetic charge force density method, the generalized magnetizing current force density

Se-Hee Lee; Hong-Soon Choi; Hong-Kyu Kim; Kyong-Yop Park; Il-Han Park

2007-01-01

4

Faraday's law of induction and the force on a body due to change in its magnetization in an electric field  

Microsoft Academic Search

From arguments based on Faraday's Law of induction, it is shown that a body whose intensity of magnetization is changing should, in general, experience a force when situated in an electrostatic field in a manner analogous to the force experienced by a conductor carrying an electric current in a magnetic field.

K. G. Ramanathan

1962-01-01

5

Three-body forces  

SciTech Connect

Three-body forces are defined and their properties discussed. Evidence for such forces in the trinucleon bound states and scattering reactions is reviewed. The binding energy defects of the trinucleon bound states, the /sup 3/He charge density, the Phillips line for doublet n-d scattering lengths, and three-nucleon breakup reactions are discussed, together with the possible influence of three-body forces on these observables.

Friar, J.L.

1982-01-01

6

Nd-Fe-B permanent magnet electrodes. Theoretical evaluation and experimental demonstration of the paramagnetic body forces.  

PubMed

Cyclic voltammetry with Nd-Fe-B disk magnet electrodes (3.2 mm diameter) at slow sweep rates (< or = 0.01 V s(-1)) in relatively concentrated solutions (e.g., 80 mM) of diamagnetic redox-active species (e.g., TMPD) is controlled by diffusion. Under similar conditions, cyclic voltammetry with conventional noble metal disk millielectrodes is characterized by the absence of diffusion waves and the presence of density gradient driven natural convection. Although the magnetic field in the vicinity of Nd-Fe-B electrodes is relatively strong (approximately 0.5 T at the surface of the magnet electrode), the absence of magnetohydrodynamic stirring effects is attributed to the fact that the i and B vectors are almost parallel, and therefore the magnetohydrodynamic force F(B) (=i x B) is very small. On the other hand, the absence of natural convection is attributed to the two possible paramagnetic body forces, F(inverted Delta B) and F(inverted Delta C), exerted by the magnet electrode on the diffusion layer. Of those two forces, the former depends on field gradients (F(inverted Delta B) approximately B x inverted Delta B), while the latter depends on concentration gradients (F(inverted Delta C) approximately inverted Delta C(j)) and is directed toward areas with higher concentration of paramagnetic j. Through thorough analysis of the magnetic field and its gradients, it is found that the average F(inverted Delta C) force acting upon the entire diffusion layer is approximately 1.75 times stronger than F(inverted Delta B). Nevertheless, it is calculated that either force independently is strong enough and would have been able to hold the diffusion layer by itself. Further evidence suggests that, integrated over the entire solution, F(inverted Delta B) is the dominant paramagnetic force when the redox-active species is paramagnetic, e.g., [Co(bipy)(3)](ClO(4))(2) (bipy = 2,2'-bipyridine). Finally, convective behavior with diamagnetic redox-active species and magnet millielectrodes can be observed by holding closely (2-3 mm away) a repelling second magnet that bends the induction B to the point that the i x B product is not equal to 0. with Nd-Fe-B disk ma PMID:11829617

Leventis, Nicholas; Gao, Xuerong

2002-02-13

7

Tunneling magnetic force microscopy  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

8

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.

9

Analytic evaluation of magnetic force of novel sensor  

Microsoft Academic Search

This paper studied the evaluations of magnetic force of magnetic immersed body in magnetic fluids, which is the prerequisite and basis for a novel inertial sensor can achieve. The novel inertial sensor is proposed based on the levitation characteristic of magnetic fluid and can be applied to many specific areas. The analyzed and calculated of the second-order magnetic force in

Tingwan Wu; Shengmei Yin

2009-01-01

10

Evaluation of Magnetic Forces in Permanent Magnets  

Microsoft Academic Search

The numerical evaluation of magnetic forces exerted by permanent magnets is usually performed by two methods, the integration of the Maxwell stress tensor or by means of virtual displacements and energy balance. In this paper, we will review previous works on this subject, where controversy exists due to the sign of the magnetic energy stored in the magnet itself. We

Santiago Sanz; Luis Garcia-Tabares; Iván Moya; Diego Obradors; Fernando Toral

2010-01-01

11

Magnetic Fields and Forces in Permanent Magnet Levitated Bearings  

Microsoft Academic Search

Magnetic fields and magnetic forces from magnetic bearings made of circular Halbach permanent-magnet arrays are computed and analyzed. The magnetic fields are calculated using superposition of fields due to patches of magnetization charge at surfaces where the magnetization is discontinuous. The magnetic force from the magnetic bearing is computed using superposition of forces on each patch of magnetization charge. The

Kevin D. Bachovchin; James F. Hoburg; Richard F. Post

2012-01-01

12

Investigating Magnetic Force Fields  

NSDL National Science Digital Library

In this classroom activity, the students will investigate the magnetic pull of a bar magnet at varying distances with the use of paper clips. Students will hypothesize, conduct the experiment, collect the data, and draw conclusions that support their data. Each student will record the experiment and their findings in their science journals. As a class, students will compare each groups' data and their interpretation of the results.

Daryl ("Tish") Monjeau, Bancroft Elementary School, Minneapolis, MN

2012-03-18

13

An assessment of body force representations for compressor stall simulation  

E-print Network

This thesis examines an axial compressor body force representation constructed from 3D CFD calculations. The radial distribution of body forces is compared to that of a body force representation based on axisymmetric ...

Kerner, Jonathan (Jonathan H.)

2010-01-01

14

Magnetic Force Calculations Applied to Magnetic Force Microscopy  

Microsoft Academic Search

\\u000a In IC failure analysis the detection of currents is often used to indicate the presence of a defective device. One method\\u000a used for this analysis is the Magnetic Force Microscopy (MFM). Employing this technique measurement errors often occur as\\u000a for instance due to heterogeneous magnetic tip coatings, fabrication\\/abrasion errors of the MFM tips and vibrations during\\u000a a MFM scanning process.

Thomas Preisner; Wolfgang Mathis

15

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

16

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

17

Force and Stiffness of Passive Magnetic Bearings Using Permanent Magnets.  

E-print Network

1 Force and Stiffness of Passive Magnetic Bearings Using Permanent Magnets. Part 2 : Radial of the force and the stiffness between two ring permanent magnets whose polarization is radial. Such a configuration corresponds to a passive magnetic bearing. The magnetic force exerted between ring permanent

Paris-Sud XI, Université de

18

Turbulence generation by electric body forces  

Microsoft Academic Search

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

J. H. Davidson; E. J. Shaughnessy

1986-01-01

19

LABORATORY V MAGNETIC FIELDS AND FORCES  

E-print Network

's technology. Magnets are used today to image parts of the body, to explore the mysteries of the human brain to combine magnets to change the magnetic field at any point. You must determine the map of the magnetic

Minnesota, University of

20

Investigation of a cuboidal permanent magnet’s force exerted on a robotic capsule  

PubMed Central

To control and drive a robotic capsule accurately from outside a patient’s body, we present a schema in which the capsule enclosing the imaging device, circuits, batteries, etc is looped by a permanent magnet ring that acts as an actuator. A cuboidal permanent magnet situated outside the patient’s body attracts or pushes the magnet ring from different directions to make the capsule move or rotate. A mathematic model of attractive or repulsive force that the cuboidal magnet exerts on the magnet ring is presented for accurate calculation of force. The experiments showed that the measuring force was in agreement with the theoretical one, and the relations between the dimensions of the cuboidal magnet and force are useful to produce a cuboidal magnet with optimal shape to get appropriate force. PMID:25170283

Yang, Wan’an; Tang, Chengbing; Qin, Fengqing

2014-01-01

21

Calculating magnetic force of permanent magnet using Maxwell stress method  

Microsoft Academic Search

It is necessary to consider magnetic force of magnetic blocks when a large permanent magnet is constructed. This paper describes the calculation of magnetic force between magnetic bars of a permanent magnet using Maxwell Stress Method. This method is simple and convenient. The calculation result is tested and verified by experiment. The method plays an important role in the structure

Y. M. Du; P. C. Xia; L. Y. Xiao

2000-01-01

22

Distribution of electromagnetic force in permanent magnets  

Microsoft Academic Search

Two dual formulations are proposed for the calculation of the electromagnetic forces in permanent magnets. The formulations are based on the virtual work principle with the use of nodal elements. Both methods allow the calculation of global force as well as local force densities. These densities depend on the expression of the magnetic energy or co-energy of the magnet. The

L. H. de Medeiros; G. Reyne; G. Meunier; J. P. Yonnet

1998-01-01

23

Dispersive forces on bodies and atoms: A unified approach  

SciTech Connect

A unified approach to the calculation of dispersive forces on ground-state bodies and atoms is given. It is based on the ground-state Lorentz force density acting on the charge and current densities attributed to the polarization and magnetization in linearly, locally, and causally responding media. The theory is applied to dielectric macro- and micro-objects, including single atoms. Existing formulas valid for weakly polarizable matter are generalized to allow also for strongly polarizable matter. In particular when micro-objects can be regarded as single atoms, well-known formulas for the Casimir-Polder force on atoms and the van der Waals interaction between atoms are recovered. It is shown that the force acting on medium atoms - in contrast to isolated atoms - is in general screened by the other medium atoms.

Raabe, Christian; Welsch, Dirk-Gunnar [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

2006-06-15

24

LABORATORY V MAGNETIC FIELDS AND FORCES  

E-print Network

's technology. Magnets are used today to image parts of the body, to explore the mysteries of the human brain to combine magnets to change the magnetic field at any point. You decide to determine the form

Minnesota, University of

25

Force sensor using changes in magnetic flux  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

26

Three-body forces and the description of light nuclei  

SciTech Connect

It is shown that a schematic three-body force in addition to a general two-body force leads to a strongly improved description of the energies of A = 4--16 nuclei. The values of the two strength parameters of the proposed three-body force, which are obtained empirically from energies and static moments of p-shell nuclei, are found to be similar to those of a realistic three-nucleon force.

van Hees, A.G.M.; Booten, J.G.L.; Glaudemans, P.W.M.

1989-05-08

27

Phenomenon of magnetic force in permanent magnet wind turbine generators  

Microsoft Academic Search

This study presents the investigation on the magnetic force phenomenon in permanent magnet (PM) wind turbine generators. Owing to the presence of PMs, the inherent and ever-existing magnetic force between the stator and rotor becomes one of the most critical phenomena in these generators. Whether it is during the assembly process throughout the manufacturing stages or when the generator is

Y. K. Chin; P. Kanninen; P. Maki-Ontto; R. Sakki; H. Lendenmann

2009-01-01

28

A force calibration standard for magnetic tweezers  

NASA Astrophysics Data System (ADS)

To study the behavior of biological macromolecules and enzymatic reactions under force, advances in single-molecule force spectroscopy have proven instrumental. Magnetic tweezers form one of the most powerful of these techniques, due to their overall simplicity, non-invasive character, potential for high throughput measurements, and large force range. Drawbacks of magnetic tweezers, however, are that accurate determination of the applied forces can be challenging for short biomolecules at high forces and very time-consuming for long tethers at low forces below ˜1 piconewton. Here, we address these drawbacks by presenting a calibration standard for magnetic tweezers consisting of measured forces for four magnet configurations. Each such configuration is calibrated for two commonly employed commercially available magnetic microspheres. We calculate forces in both time and spectral domains by analyzing bead fluctuations. The resulting calibration curves, validated through the use of different algorithms that yield close agreement in their determination of the applied forces, span a range from 100 piconewtons down to tens of femtonewtons. These generalized force calibrations will serve as a convenient resource for magnetic tweezers users and diminish variations between different experimental configurations or laboratories.

Yu, Zhongbo; Dulin, David; Cnossen, Jelmer; Köber, Mariana; van Oene, Maarten M.; Ordu, Orkide; Berghuis, Bojk A.; Hensgens, Toivo; Lipfert, Jan; Dekker, Nynke H.

2014-12-01

29

May the Magnetic Force Be with You  

NSDL National Science Digital Library

After a demonstration of the deflection of an electron beam, students review their knowledge of the cross-product and the right-hand rule with example problems. Then they study the magnetic force on a charged particle, compared to the electric force. Provided lecture material covers the motion of a charged particle in a magnetic field with respect to the direction of the field. Finally, students apply these concepts to understand the magnetic force on a current carrying wire. Through the associated activity, students further explore the force on a current carrying wire.

VU Bioengineering RET Program, School of Engineering,

30

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

31

Permanent magnet torque\\/force transfer apparatus  

Microsoft Academic Search

There is presented a torque\\/force transfer apparatus including an annular ring having therein permanent first magnets side by side about the interior of the ring. The first magnets are arranged so as to alternate in polar orientation to present an inside circumference of alternating north and south magnetic poles. The apparatus further comprises a cylindrical central member having therein permanent

Chahee P. Cho; Ralph A. Bidingfield

1994-01-01

32

Development of a body force description for compressor stability assessment  

E-print Network

This thesis presents a methodology for a body force description of a compressor with particular application to compressor stability calculations. The methodology is based on extracting blade forces from an axisymmetric ...

Kiwada, George (George Ford)

2008-01-01

33

Magnetic forces between arrays of cylindrical permanent magnets  

Microsoft Academic Search

Permanent magnet arrays are often employed in a broad range of applications: actuators, sensors, drug targeting and delivery systems, fabrication of self-assembled particles, just to name a few. An estimate of the magnetic forces in play between arrays is required to control devices and fabrication procedures. Here, we introduce analytical expressions for calculating the attraction force between two arrays of

D. Vokoun; G. Tomassetti; M. Beleggia; I. Stachiv

2011-01-01

34

Magnetic force microscopy using tip magnetization modulated by ferromagnetic resonance  

NASA Astrophysics Data System (ADS)

In magnetic force microscopy (MFM), the tip–sample distance should be reduced to analyze the microscopic magnetic domain structure with high spatial resolution. However, achieving a small tip–sample distance has been difficult because of superimposition of interaction forces such as van der Waals and electrostatic forces induced by the sample surface. In this study, we propose a new method of MFM using ferromagnetic resonance (FMR) to extract only the magnetic field near the sample surface. In this method, the magnetization of a magnetic cantilever is modulated by FMR to separate the magnetic field and topographic structure. We demonstrate the modulation of the magnetization of the cantilever and the identification of the polarities of a perpendicular magnetic medium.

Arima, Eiji; Naitoh, Yoshitaka; Li, Yan Jun; Yoshimura, Satoru; Saito, Hitoshi; Nomura, Hikaru; Nakatani, Ryoichi; Sugawara, Yasuhiro

2015-03-01

35

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

1997-03-01

36

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

37

Magnetic force microscopy images of high-coercivity permanent magnets  

Microsoft Academic Search

The stray magnetic field distributions at the surfaces of isotropic and anisotropic NdFeB-type magnets have been imaged by magnetic force microscopy. Polished surfaces of bulk samples produced by melt-quenching, hot-rolling, and sintering were examined using two techniques which provided complementary information on the structure of the domains at the surface. For the first technique a high-coercivity magnetic tip was used,

L. Folks; R. C. Woodward; K. Babcock

1996-01-01

38

Magnetic forces produced by rectangular permanent magnets in static microsystems.  

PubMed

Finite element numerical simulations were carried out in 2D geometries to map the magnetic field and force distribution produced by rectangular permanent magnets as a function of their size and position with respect to a microchannel. A single magnet, two magnets placed in attraction and in repulsion have been considered. The goal of this work is to show where magnetic beads are preferentially captured in a microchannel. These simulations were qualitatively corroborated, in one geometrical case, by microscopic visualizations of magnetic bead plug formation in a capillary. The results show that the number of plugs is configuration dependent with: in attraction, one plug in the middle of the magnets; in repulsion, two plugs near the edges of the magnets; and with a single magnet, a plug close to the center of the magnet. The geometry of the magnets (h and l are the height and length of the magnets respectively) and their relative spacing s has a significant impact on the magnetic flux density. Its value inside a magnet increases with the h/l ratio. Consequently, bar magnets produce larger and more uniform values than flat magnets. The l/s ratio also influences the magnetic force value in the microchannel, both increasing concomitantly for all the configurations. In addition, a zero force zone in the middle appears in the attraction configuration as the l/s ratio increases, while with a single magnet, the number of maxima and minima goes from one to two, producing two focusing zones instead of only one. PMID:19636467

Gassner, Anne-Laure; Abonnenc, Mélanie; Chen, Hong-Xu; Morandini, Jacques; Josserand, Jacques; Rossier, Joel S; Busnel, Jean-Marc; Girault, Hubert H

2009-08-21

39

Treatment of body forces in boundary element design sensitivity analysis  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

40

Micromagnetic Analysis of Effective Magnetic Dipole Position in Magnetic Force Microscope Tip  

Microsoft Academic Search

An accurate micromagnetic model of the magnetic force microscope (MFM) tip has been developed to calculate the effective dipole and its position in a simple point probe model, which are important in the quantitative explanation of MFM images. The pyramid-shaped MFM tips are considered in this paper; so cuboid cells in the body, as well as triangular prism and quadrangle

Hongjia Li; Yi Wang; Sumei Wang; Hai Zhong; Dan Wei

2010-01-01

41

Levitation forces in bearingless permanent magnet motors  

SciTech Connect

Bearingless motors combine brushless AC-motors with active magnetic bearings by the integration of two separate winding systems (torque and radial levitation force windings with different pole pairs) in one housing. This paper gives an insight into the influences of the motor design on the levitation force and torque generation. It is shown that especially for machines with small air gaps it can be very important to choose the right design parameters. Increasing the permanent magnet height in order to increase the motor torque can result in a remarkable reduction of radial forces. The interrelationships are discussed on the basis of Maxwell and Lorentz forces acting upon the stator surface. The investigations are presented for a bearingless low cost motor, suited for pump, fan or blower applications. The presented motor needs only four coils for operation.

Amrhein, W.; Silber, S.; Nenninger, K.

1999-09-01

42

Dynamical friction force exerted on spherical bodies  

E-print Network

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

O. Esquivel; B. Fuchs

2007-04-30

43

Magnetic force control technique in industrial application  

NASA Astrophysics Data System (ADS)

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

Nishijima, S.

2010-11-01

44

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

45

Three-body Forces from a Classical Nonlinear Field  

NASA Astrophysics Data System (ADS)

Forces in the systems of two opposite sign and three identical charges coupled to the dynamical scalar field of the signum-Gordon model are investigated. Three-body force is present, and the exact formula for it is found. Flipping the sign of one of the two charges changes not only the sign but also the magnitude of the force. Both effects are due to nonlinearity of the field equation.

Arod?, H.; Karkowski, J.; ?wierczy?ski, Z.

46

Three-body forces from a classical nonlinear field  

E-print Network

Forces in the systems of two opposite sign and three identical charges coupled to the dynamical scalar field of the signum-Gordon model are investigated. Three-body force is present, and the exact formula for it is found. Flipping the sign of one of the two charges changes not only the sign but also the magnitude of the force. Both effects are due to nonlinearity of the field equation.

Arodz, H; Swierczynski, Z

2013-01-01

47

Three-body forces from a classical nonlinear field  

E-print Network

Forces in the systems of two opposite sign and three identical charges coupled to the dynamical scalar field of the signum-Gordon model are investigated. Three-body force is present, and the exact formula for it is found. Flipping the sign of one of the two charges changes not only the sign but also the magnitude of the force. Both effects are due to nonlinearity of the field equation.

H. Arodz; J. Karkowski; Z. Swierczynski

2013-10-02

48

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

49

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

50

Force and Stiffness of Passive Magnetic Bearings Using Permanent Magnets. Part 2: Radial Magnetization  

Microsoft Academic Search

This paper deals with the calculation of the force and the stiffness between two ring permanent magnets whose polarization is radial. Such a configuration corresponds to a passive magnetic bearing. The magnetic force exerted between ring permanent magnets is determined by using the Coulombian model. The expressions obtained are semianalytical and we show that it is not possible to find

R. Ravaud; G. Lemarquand; V. Lemarquand

2009-01-01

51

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

52

Magnetic Force and Work: An Accessible Example  

ERIC Educational Resources Information Center

Despite their physics instructors' arguments to the contrary, introductory students can observe situations in which there seems to be compelling evidence for magnetic force doing work. The counterarguments are often highly technical and require physics knowledge beyond the experience of novice students, however. A simple example is presented…

Gates, Joshua

2014-01-01

53

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

54

Cooling force on ions in a magnetized electron plasma  

NASA Astrophysics Data System (ADS)

Electron cooling is a well-established method to improve the phase space quality of ion beams in storage rings. In the common rest frame of the ion and the electron beam, the ion is subjected to a drag force and it experiences a loss or a gain of energy which eventually reduces the energy spread of the ion beam. A calculation of this process is complicated as the electron velocity distribution is anisotropic and the cooling process takes place in a magnetic field which guides the electrons. In this paper the cooling force is calculated in a model of binary collisions (BC) between ions and magnetized electrons, in which the Coulomb interaction is treated up to second order as a perturbation to the helical motion of the electrons. The calculations are done with the help of an improved BC theory which is uniformly valid for any strength of the magnetic field and where the second-order two-body forces are treated in the interaction in Fourier space without specifying the interaction potential. The cooling force is explicitly calculated for a regularized and screened potential which is both of finite range and less singular than the Coulomb interaction at the origin. Closed expressions are derived for monochromatic electron beams, which are folded with the velocity distributions of the electrons and ions. The resulting cooling force is evaluated for anisotropic Maxwell velocity distributions of the electrons and ions.

Nersisyan, Hrachya B.; Zwicknagel, Günter

2013-07-01

55

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

56

About modeling aspects for the simulation of Magnetic Force Microscopes  

Microsoft Academic Search

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

T. Preisner; W. Mathis

2011-01-01

57

A compact high field magnetic force microscope.  

PubMed

We present the design and performance of a simple and compact magnetic force microscope (MFM), whose tip-sample coarse approach is implemented by the piezoelectric tube scanner (PTS) itself. In brief, a square rod shaft is axially spring-clamped on the inner wall of a metal tube which is glued inside the free end of the PTS. The shaft can thus be driven by the PTS to realize image scan and inertial stepping coarse approach. To enhance the inertial force, each of the four outer electrodes of the PTS is driven by an independent port of the controller. The MFM scan head is so compact that it can easily fit into the 52mm low temperature bore of a 20T superconducting magnet. The performance of the MFM is demonstrated by imaging a manganite thin film at low temperature and in magnetic fields up to 15T. PMID:25189114

Zhou, Haibiao; Wang, Ze; Hou, Yubin; Lu, Qingyou

2014-12-01

58

Nonlinear gravitational self-force: Field outside a small body  

NASA Astrophysics Data System (ADS)

A small extended body moving through an external spacetime g?? creates a metric perturbation h??, which forces the body away from geodesic motion in g??. The foundations of this effect, called the gravitational self-force, are now well established, but concrete results have mostly been limited to linear order. Accurately modeling the dynamics of compact binaries requires proceeding to nonlinear orders. To that end, I show how to obtain the metric perturbation outside the body at all orders in a class of generalized wave gauges. In a small buffer region surrounding the body, the form of the perturbation can be found analytically as an expansion for small distances r from a representative worldline. Given only a specification of the body’s multipole moments, the field obtained in the buffer region suffices to find the metric everywhere outside the body via a numerical puncture scheme. Following this procedure at first and second order, I calculate the field in the buffer region around an arbitrarily structured compact body at sufficiently high order in r to numerically implement a second-order puncture scheme, including effects of the body’s spin. I also define nth-order (local) generalizations of the Detweiler-Whiting singular and regular fields and show that in a certain sense, the body can be viewed as a skeleton of multipole moments.

Pound, Adam

2012-10-01

59

A cosmological interpretation of the magnetic field of the celestial bodies  

Microsoft Academic Search

A cosmological interpretation of the empirical relation between the magnetic moment and intrinsic angular momentum of the celestial bodies is examined. From a consideration of the spin-torsion interaction Lagrangian in a Riemann-Cartan space, it is shown that torsion, inducing the alignment of the spins inside matter, can produce a magnetic field, just as a magnetic field induces torsion by forcing

V. De Sabbata; M. Gasperini

1980-01-01

60

Magnetic Force Microscopy Studies of Magnetic Features and Nanostructures  

Microsoft Academic Search

\\u000a The study of small magnetic features and nanostructures has attracted much attention due to interest in both technological\\u000a applications and fundamental research in micromagnetism. For their characterization, a visualization technique with high lateral\\u000a resolution is required. Among the wealth of techniques, magnetic force microscopy (MFM) has become a powerful tool for visualizing\\u000a submicron-sized domain structures. This is mainly due to

Lanping Yue; Sy-Hwang Liou

61

Generating Mechanism of Magnetic Force in Meshing Area of Magnetic Gear Using Permanent Magnet  

Microsoft Academic Search

A new magnetic gear using a permanent magnet has been developed by the author. The design and performance characteristics of such magnetic gears have been reported previously. In this report, the mechanism by which magnetic force is generated in the meshing area is elucidated. An experimental meshing model is used to clarify the principle of operation of the magnetic gear.

K. Tsurumoto

1991-01-01

62

Measuring the Magnetic Force on a Current-Carrying Conductor.  

ERIC Educational Resources Information Center

Describes a fast and simple method for measuring the magnetic force acting on a current-carrying conductor using a digital balance. Discusses the influence of current intensity and wire length on the magnetic force on the conductor. (JRH)

Herreman, W.; Huysentruyt, R.

1995-01-01

63

Control of the Casimir Force Using Semiconductor Test Bodies  

E-print Network

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

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

2011-04-09

64

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. PMID:20687745

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

2010-01-01

65

Chiral nuclear dynamics with three-body forces  

E-print Network

We review recent progress in implementing high-precision chiral two- and three-body forces in nuclear many-body systems beyond light nuclei. We begin with applications to finite nuclei, which we study through the nuclear shell model and self-consistent mean field theory. We then turn our attention to infinite nuclear matter treated within the framework of Landau's theory of normal Fermi liquids.

J. W. Holt; N. Kaiser; W. Weise

2011-11-25

66

Elucidation of propulsive force of microrobot using magnetic fluid  

NASA Astrophysics Data System (ADS)

Using the pattern of the peristaltic movement of an earthworm, a microrobot was developed for traveling in a tube using a magnetic fluid. In this microrobot, a cell equivalent to a segment of the earthworm is composed of a natural rubber tube into which a water-based magnetic fluid is sealed up. The cells are connected with rod-like elastic bodies of natural rubber. It was confirmed that this robot can travel in an acrylic tube (inner diameter: 12 mm, outer diameter: 14 mm) by providing a shifting magnetic field from the exterior. This article will describe how our microrobot is propelled, the mechanism of its propulsion, and the analytical results of the propulsive force.

Saga, Norihiko; Nakamura, Taro

2002-05-01

67

Forces between arrays of permanent magnets of basic geometric shapes  

NASA Astrophysics Data System (ADS)

We provide formulas for evaluating the magnetic force between two permanent magnet arrays, regularly spaced over a square lattice. We focus on three basic shapes of magnets constituting the arrays: cylinder, sphere and rectangular prism. When the lattice parameter is large, the expressions can be used to calculate the force between two single magnets in a computationally efficient way. The calculations are validated experimentally by measuring the attraction force between two single permanent magnets, where we demonstrate a fair agreement within about 15%.

Vokoun, D.; Beleggia, M.

2014-01-01

68

Magnetic-enhanced normal force of magnetorheological fluids  

NASA Astrophysics Data System (ADS)

In this study, the static and dynamic normal forces of magnetorheological (MR) fluids with and without shearing were investigated by using an advanced commercial rheometer. The effects of time history, shear rate, and temperature under sweeping magnetic field on the normal force of MR fluids were systematically studied. Moreover, the influence of shear stress, gap distance, and the comparison of static and dynamic normal force in various magnetic field were also studied. The experimental results indicated that the normal force of MR fluids largely depend on magnetic field, more than 170% normal force increased when the magnetic field increases from 0 to 1 T. This behavior can be regard as the magnetic field-dependent of normal force, moreover, the mechanism of interaction between the magnetic field and normal force was investigated by microstructure analysis. The results show that the gap distance changes step-wise with increasing the magnetic field instead of continue increase. When imposing shearing, three regions can be found in the relationship between normal forces and shear rate, the normal force first decreases to a minimum value and then increases by increasing shear rates. The temperature effect of the normal forces is also measured and the normal force would increase with increasing of temperature. Comparing between with static and dynamic normal force shows that the dynamic normal force is larger than static normal force. And the average normal force is also larger than the shear stress. Finally, a normal force was calculated based on the magnetic field energy theory.

Yao, Xing-Yan; Yu, Miao; Fu, Jie

2015-03-01

69

Collision of viscoelastic bodies: Rigorous derivation of dissipative force  

E-print Network

We report a new theory of dissipative forces acting between colliding viscoelastic bodies. The impact velocity is assumed not to be large, to avoid plastic deformations and fragmentation at the impact. The bodies may be of an arbitrary convex shape and of different materials. We develop a mathematically rigorous perturbation scheme to solve the continuum mechanics equation that deals with both displacement and displacement rate fields and accounts for the dissipation in the bulk of the material. The perturbative solution of this equation allows to go beyond the previously used quasi-static approximation and obtain the dissipative force. This force does not suffer from the physical inconsistencies of the latter approximation and depends on particle deformation and deformation rate.

Denis S. Goldobin; Eugeniy A. Susloparov; Anastasiya V. Pimenova; Nikolai V. Brilliantov

2015-01-13

70

Boosting oncolytic adenovirus potency with magnetic nanoparticles and magnetic force.  

PubMed

Oncolytic adenoviruses rank among the most promising innovative agents in cancer therapy. We examined the potential of boosting the efficacy of the oncolytic adenovirus dl520 by associating it with magnetic nanoparticles and magnetic-field-guided infection in multidrug-resistant (MDR) cancer cells in vitro and upon intratumoral injection in vivo. The virus was complexed by self-assembly with core-shell nanoparticles having a magnetite core of about 10 nm and stabilized by a shell containing 68 mass % lithium 3-[2-(perfluoroalkyl)ethylthio]propionate) and 32 mass % 25 kDa branched polyethylenimine. Optimized virus binding, sufficiently stable in 50% fetal calf serum, was found at nanoparticle-to-virus ratios of 5 fg of Fe per physical virus particle (VP) and above. As estimated from magnetophoretic mobility measurements, 3,600 to 4,500 magnetite nanocrystallites were associated per virus particle. Ultrastructural analysis by electron and atomic force microscopy showed structurally intact viruses surrounded by magnetic particles that occasionally bridged several virus particles. Viral uptake into cells at a given virus dose was enhanced 10-fold compared to nonmagnetic virus when infections were carried out under the influence of a magnetic field. Increased virus internalization resulted in a 10-fold enhancement of the oncolytic potency in terms of the dose required for killing 50% of the target cells (IC(50) value) and an enhancement of 4 orders of magnitude in virus progeny formation at equal input virus doses compared to nonmagnetic viruses. Furthermore, the full oncolytic effect developed within two days postinfection compared with six days in a nonmagnetic virus as a reference. Plotting target cell viability versus internalized virus particles for magnetic and nonmagnetic virus showed that the inherent oncolytic productivity of the virus remained unchanged upon association with magnetic nanoparticles. Hence, we conclude that the mechanism of boosting the oncolytic effect by magnetic force is mainly due to the improved internalization of magnetic virus complexes resulting in potentiated virus progeny formation. Upon intratumoral injection and application of a gradient magnetic field in a murine xenograft model, magnetic virus complexes exhibited a stronger oncolytic effect than adenovirus alone. We propose that this approach would be useful during in vivo administration to tumor-feeding blood vessels to boost the efficacy of the primary infection cycle within the tumor. For systemic application, further modification of magnetic adenovirus complexes for shielding and retargeting of the whole magnetic virus complex entity is needed. PMID:20550160

Tresilwised, Nittaya; Pithayanukul, Pimolpan; Mykhaylyk, Olga; Holm, Per Sonne; Holzmüller, Regina; Anton, Martina; Thalhammer, Stefan; Adigüzel, Denis; Döblinger, Markus; Plank, Christian

2010-08-01

71

Residual long-range pseudoscalar forces between unpolarised macroscopic bodies  

E-print Network

In this paper we survey the effects of residual long-range forces associated to $\\gamma_5$-spin dependent-couplings of fermions to massless bosons exerted by unpolarised bulk matter over macroscopic distances. We establish that such forces with behaviour proportional to $R^{-6}$ do indeed exist. They arise as a quantum mechanical effect due to simultaneous exchange of two quanta. We explore their presence in existing astronomical as well as laboratory data on non-newtonian components of the force between macroscopic bodies. Since no limits on their real existence could be found, we conclude that residual long-range pseudoscalar attractive and composition dependent forces between neutral unpolarised bulk matter extending over macroscopic distances are very efficiently shielded over a huge range of distances: from astronomical scales down to the micron scale.

J. A. Grifols; S. Tortosa

1994-04-11

72

Residual long-range pseudoscalar forces between unpolarised macroscopic bodies  

E-print Network

In this paper we survey the effects of residual long-range forces associated to .gamma.sub(5)-spin dependent-couplings of fermions to massless bosons exerted by unpolarised bulk matter over macroscopic distances. We establish that such forces with behaviour proportional to R.sup(-6) do indeed exist. They arise as a quantum mechanical effect due to simultaneous exchange of two quanta. We explore their presence in existing astronomical as well as laboratory data on non-newtonian components of the force between macroscopic bodies. Since no limits on their real existence could be found, we conclude that residual long-range pseudoscalar attractive and composition dependent forces between neutral unpolarised bulk matter extending over macroscopic distances are very efficiently shielded over a huge range of distances: from astronomical scales down to the micron scale.

Grifols, J A

1994-01-01

73

Investigation of many-body forces in krypton and xenon  

SciTech Connect

The simplicity of the state dependence at relatively high temperatures ofthe many-body potential contribution to the pressure and energy has been pointed out previously (J. Ram and P. A. Egelstaff, J. Phys. Chem. Liq. 14, 29 (1984); A. Teitsima and P. A. Egelstaff, Phys. Rev. A 21, 367 (1980)). In this paper, we investigate how far these many-body potential terms may be represented by simple models in the case of krypton on the 423-, 273-, 190-, and 150-K isotherms, and xenon on the 170-, 210-, and 270-K isotherms. At the higher temperatures the best agreement is found for the mean-field type of theory, and some consequences are pointed out. On the lower isotherms a state point is found where the many-body energy vanishes, and large departures from mean-field behavior are observed. This is attributed to the influence of short-ranged many-body forces.

Salacuse, J.J.; Egelstaff, P.A.

1988-10-15

74

Accurate Prediction of Magnetic Field and Magnetic Forces in Permanent Magnet Motors Using an Analytical Solution  

Microsoft Academic Search

This paper presents an analytical model suitable for analyzing permanent magnet motors with slotted stator core. By including the effect of the interaction between the pole transitions and slot openings, the model is able to predict the airgap field and magnetic forces with high accuracy, which cannot be achieved using the previously available analytical methods. The results of electromagnetic forces,

Z. J. Liu; J. T. Li

2008-01-01

75

Hysteresis of magnetic force-gap in static and dynamic magnetic levitation with a high-{T_c} superconductor  

NASA Astrophysics Data System (ADS)

Hysteresis behavior of magnetic force versus gap between a high-Tc superconductor and a magnet, in static and dynamic cases, is studied numerically. Differing from the previous methods, based on macro electromagnetic constitutive relation of superconductors and Maxwell equations, a numerical method with the finite element method (FEM) is established. After numerical code is examined by comparing between numerical and experimental results of the relation of magnetic force-gap, the hysteresis curves of magnetic force-gap including major and minor loops in static case are simulated, and furthermore the dependences of major loop on main parameters including the critical current density and the thickness of superconductor, the residual magnetic field of magnet, and the diameter ratio of superconductor to magnet are studied numerically. In the case of free vibration, by investigating dynamic response of levitated body at different levitation/suspension positions in this magnetic levitation system, we obtain the corresponding results of the variation of magnetic force with gap. All the numerical results of the relation between magnetic force and gap show the strongly nonlinear and highly hysteretic behavior.

Gou, X.-F.; Zhang, Z.-X.

2008-11-01

76

Cylindrical Magnets and Coils: Fields, Forces, and Inductances  

Microsoft Academic Search

This paper presents a synthesis of analytical calculations of magnetic parameters (field, force, torque, stiffness) in cylindrical magnets and coils. By using the equivalence between the amperian current model and the coulombian model of a magnet, we show that a thin coil or a cylindrical magnet axially magnetized have the same mathematical model. Consequently, we present first the analytical expressions

R. Ravaud; G. Lemarquand; S. Babic; V. Lemarquand; C. Akyel

2010-01-01

77

Forced magnetic reconnection in Tokamak plasmas  

NASA Astrophysics Data System (ADS)

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

Cole, Andrew Joseph

78

Optical fibre bragg gratings based magnetic force measurement of magnetic bearings  

Microsoft Academic Search

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

Guoping Ding; Zude Zhou; Yefa Hu; Jianhua Zhou

2008-01-01

79

Casimir force acting on magnetodielectric bodies embedded in media  

SciTech Connect

Within the framework of macroscopic quantum electrodynamics, general expressions for the Casimir force acting on linearly and causally responding magnetodielectric bodies that can be embedded in another linear and causal magnetodielectric medium are derived. Consistency with microscopic harmonic-oscillator models of the matter is shown. The theory is applied to planar structures, and proper generalizations of Casimir's and Lifshitz-type formulas are given.

Raabe, Christian; Welsch, Dirk-Gunnar [Theoretisch-Physikalisches Institut, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, D-07743 Jena (Germany)

2005-01-01

80

Nuclear matter equation of state and three-body forces  

SciTech Connect

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

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

2012-04-15

81

Numerical calculation of the dielectrophoretic force on a slender body.  

PubMed

In this paper, a model is proposed to numerically calculate the dielectrophoretic (DEP) force acting on a straight slender body in a non-uniform electric field. The induced charges are assumed to be located along the centerline of the slender body. By enforcing the boundary conditions at the interfaces of the two dielectrics, an integral equations system is obtained with the induced charge densities as unknowns. Based on the calculated induced charge densities, expressions to calculate the DEP force and torque are obtained. The calculated induced charge density of a prolate ellipsoid under a uniform electric field is compared with the analytic solution and an excellent agreement is achieved. The smaller the slenderness (the ratio of maximum radius to length of the slender body), the smaller the error is. The DEP force that a prolate ellipsoid experiences in a general electric field is numerically calculated and compared with the results obtained by the commonly accepted effective dipole moment method. The current model is expected to possess higher accuracy than the effective dipole moment method and to demand less calculation work than the Maxwell stress tensor method. PMID:19197902

Lin, Yuan; Shiomi, Junichiro; Amberg, Gustav

2009-03-01

82

Evolution of magnetic microstructure in high-coercivity permanent magnets imaged with magnetic force microscopy  

Microsoft Academic Search

Magnetic force microscopy (MFM) has been shown to give high-resolution imaging of magnetic domain structures in a variety of high-coercivity permanent magnets [Folks &etal;, J. Magn. Magn. Mater. (in press)]. We show that this technique can be extended by the application of external fields during imaging, thus allowing direct observation of submicron microstructural evolution as a function of field. Electromagnets

K. L. Babcock; L. Folks; R. C. Woodward; D. L. Bradbury

1997-01-01

83

New design of a superconducting magnet for generation of quasi-uniform magnetic force field  

Microsoft Academic Search

The generation of uniform field of magnetic forces exerted on diamagnetic or paramagnetic particles is a problem with various applications: magnetic separation of particles with small differential magnetic susceptibility, diamagnetic levitation, material processing crystallization of proteins, etc. Superconducting magnets that are usually investigated to generate uniform field of magnetic forces are solenoids but unfortunately these designs lead necessarily to a

L. Quettier; A. Mailfert

2003-01-01

84

Electric and Magnetic Forces between Parallel-Wire Conductors.  

ERIC Educational Resources Information Center

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

Morton, N.

1979-01-01

85

Solvable Many-Body Models of Goldfish Type with One-, Two- and Three-Body Forces  

NASA Astrophysics Data System (ADS)

The class of solvable many-body problems ''of goldfish type'' is extended by including (the additional presence of) three-body forces. The solvable N-body problems thereby identified are characterized by Newtonian equations of motion featuring 19 arbitrary ''coupling constants''. Restrictions on these constants are identified which cause these systems - or appropriate variants of them - to be isochronous or asymptotically isochronous, i.e. all their solutions to be periodic with a fixed period (independent of the initial data) or to have this property up to contributions vanishing exponentially as t? ?.

Bihun, Oksana; Calogero, Francesco

2013-10-01

86

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

PubMed Central

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

Neuman, Keir C.; Nagy, Attila

2012-01-01

87

Demonstration: levitating globe comparing a magnetic force with the force of gravity; Geiger counter, sources.  

E-print Network

the force between two protons separated by a distance of 1 fm: Fgrav = 6.67 x 10-11 x (1.67 x 10-27)2 / (10 of a characteristic of the objects (charge or mass) ·the force is inversely proportional to the squareDemonstration: levitating globe comparing a magnetic force with the force of gravity; Geiger

Boal, David

88

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

89

Magnetic levitation force between a superconducting bulk magnet and a permanent magnet  

Microsoft Academic Search

The current density J(rho, z) in a disc-shaped superconducting bulk magnet and the magnetic levitation force FSBMz exerted on the superconducting bulk magnet by a cylindrical permanent magnet are calculated from first principles. The effect of the superconducting parameters of the superconducting bulk is taken into account by assuming the voltage-current law E = Ec(J\\/Jc)n and the material law B

J. J. Wang; C. Y. He; L. F. Meng; C. Li; R. S. Han; Z. X. Gao

2003-01-01

90

Analysis of magnetic forces in magnetically saturated permanent magnet motors by considering mechanical and magnetic coupling effects  

Microsoft Academic Search

Vibrations of magnetically induced origins are becoming more serious with the trend of high speed use in industrial applications. Vibration of motors with the rotor eccentricity, which may result from working allowances or errors in manufacturing processes, is a coupled phenomenon between mechanical and magnetic performance and dynamic characteristics of permanent magnet motors. This article investigates magnetic forces for interior

Geun-Bae Hwang; Sang-Moon Hwang; Weui-Bong Jung; Beom-Soo Kang; I.-Cheol Hwang; Chul-U. Kim

2002-01-01

91

The force exerting on cosmic bodies in a quaternionc field  

E-print Network

The expression of a time-dependent cosmological constant $\\lambda \\propto 1/t^2$ is interpreted as the energy density of a special type of the quaternionic field. The Lorenz-like force acting on the moving body in the presence of this quaternionic field is determined. The astronomical and terrestrial effects of this field are presented, and the ways how it can be observably detected is discussed. Finally, a new mechanism of the particle creation and an alternative cosmological scenario in the presence of the cosmic quatertionic field is suggested.

V. Majernik

2003-09-03

92

Journal of Magnetism and Magnetic Materials 286 (2005) 324328 Light-free magnetic resonance force microscopy for studies of  

E-print Network

Journal of Magnetism and Magnetic Materials 286 (2005) 324­328 Light-free magnetic resonance force for Physical Sciences, College Park, MD, USA Available online 4 November 2004 Abstract Magnetic resonance force microscopy is a scanned probe technique capable of three-dimensional magnetic resonance imaging. Its

93

Effect of Radial Magnetic Forces in Permanent Magnet Motors With Rotor Eccentricity  

Microsoft Academic Search

This paper studies radial magnetic forces developed in permanent magnet motors having rotor eccentricity. Such forces represent the source of magnetically induced vibration in a disk-spindle assembly, and are of concern in design stage. A new analytical model suitable for studying the relationship between eccentricity effect and design parameters of slotted permanent magnet motors is introduced. The effectiveness of the

J. T. Li; Z. J. Liu; L. H. A. Nay

2007-01-01

94

Effects of magnetically induced vibration force in brushless permanent-magnet motors  

Microsoft Academic Search

This paper discusses magnetic force imbalance and cogging torque in permanent-magnet motors under both static and dynamic rotor eccentricity. The characteristic frequencies of magnetic force imbalance and cogging torque due to rotor eccentricity can be used for fault diagnostics and quality control of permanent-magnet motors. The paper derives analytical expressions for their characteristic frequencies. The validity of the expressions has

Ungtae Kim; Dennis K. Lieu

2005-01-01

95

Magnetic Force Microscopy Imaging of the Magnetic Domains in Co Y-branch Structures  

E-print Network

UG-23 Magnetic Force Microscopy Imaging of the Magnetic Domains in Co Y structures for permanent dual magnet exposure, and non-uniform domain structures for temporary dual magnet the various magnetic domains in the Cobalt Y-branch structure resulting from different external magnetic

96

In vivo implant forces acting on a vertebral body replacement during upper body flexion.  

PubMed

Knowledge about in vivo spinal loads is required for the identification of risk factors for low back pain and for realistic preclinical testing of spinal implants. Therefore, the aim of the present study was to measure the in vivo forces on a vertebral body replacement (VBR) during trunk flexion and to analyze in detail the typical relationship between trunk inclination and spinal load. Telemeterized VBRs were implanted in five patients. In vivo loads were measured 135 times during flexion while standing or sitting. The trunk inclination was simultaneously recorded. To reveal elementary differences between flexion while standing and sitting, the force increases at the maximal inclination, as compared to the upright position, were also determined. Approximately 90% of all standing trials showed a characteristic inclination-load relationship, with an initial increase of the resultant force followed by a plateau or even a decrease of the force at an inclination of approximately 33°. Further flexion to the average maximal inclination angle of 53° only marginally affected the implant loads (~450N). Maximal forces were measured during the return to the initial standing position (~565N). Flexion during standing led to a greater force increase (~330N) than during sitting (~200N) when compared to the respective upright positions. The force plateau at greater inclination angles might be explained by abdominal load support, complex stabilization of active and passive spinal structures or intricate load sharing within the implant complex. The data presented here aid in understanding the loads acting on an instrumented lumbar spine. PMID:25640900

Dreischarf, Marcel; Albiol, Laia; Zander, Thomas; Arshad, Rizwan; Graichen, Friedmar; Bergmann, Georg; Schmidt, Hendrik; Rohlmann, Antonius

2015-02-26

97

Lateral restoring force on a magnet levitated above a superconductor  

NASA Technical Reports Server (NTRS)

The lateral restoring force on a magnet levitated above a superconductor is calculated as a function of displacement from its original position at rest using Bean's critical-state model to describe flux pinning. The force is linear for small displacements and saturates at large displacements. In the absence of edge effects the force always attracts the magnet to its original position. Thus it is a restoring force that contributes to the stability of the levitated magnet. In the case of a thick superconductor slab, the origin of the force is a magnetic dipole layer consisting of positive and negative supercurrents induced on the trailing side of the magnet. The qualitative behavior is consistent with experiments reported to date. Effects due to the finite thickness of the superconductor slab and the granular nature of high-Tc materials are also considered.

Davis, L. C.

1990-01-01

98

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

99

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

100

Drag measurements on a body of revolution in Langley's 13-inch Magnetic Suspension and Balance System  

NASA Technical Reports Server (NTRS)

NASA Langley's 13-inch Magnetic Suspension and Balance System (MSBS) has been used to conduct low-speed wind tunnel drag force measurements on a laminar-flow body-of-revolution free of support system interference, in order to verify the drag force measurement capabilities of the MSBS. The drag force calibrations and wind-on repeatability data obtained have verified the design capabilities for this system. A drag-prediction code has been used to assess the MSBS's usefulness in body drag estimation.

Dress, David A.

1988-01-01

101

Magnetic Forces and Field Line Density  

NSDL National Science Digital Library

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

102

The measurement of Magnus force and moment using a magnetically suspended wind tunnel model  

Microsoft Academic Search

The magnetic suspension system makes an ideal facility for the measurement of the aerodynamic Magnus force acting on a wind tunnel model which is spinning about an axis inclined at an angle to the air flow. The Southampton University system was modified to allow the suspended model freedom to spin whilst retaining control of the other rigid body degrees of

M. Goodyer; R. Henderson; M. Judd

1975-01-01

103

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

104

MAGNETIC HELICITY OF SELF-SIMILAR AXISYMMETRIC FORCE-FREE FIELDS  

SciTech Connect

In this paper, we continue our theoretical studies addressing the possible consequences of magnetic helicity accumulation in the solar corona. Our previous studies suggest that coronal mass ejections (CMEs) are natural products of coronal evolution as a consequence of magnetic helicity accumulation and that the triggering of CMEs by surface processes such as flux emergence also have their origin in magnetic helicity accumulation. Here, we use the same mathematical approach to study the magnetic helicity of axisymmetric power-law force-free fields but focus on a family whose surface flux distributions are defined by self-similar force-free fields. The semi-analytical solutions of the axisymmetric self-similar force-free fields enable us to discuss the properties of force-free fields possessing a huge amount of accumulated magnetic helicity. Our study suggests that there may be an absolute upper bound on the total magnetic helicity of all bipolar axisymmetric force-free fields. With the increase of accumulated magnetic helicity, the force-free field approaches being fully opened up with Parker-spiral-like structures present around a current-sheet layer as evidence of magnetic helicity in the interplanetary space. It is also found that among the axisymmetric force-free fields having the same boundary flux distribution, the one that is self-similar is the one possessing the maximum amount of total magnetic helicity. This gives a possible physical reason why self-similar fields are often found in astrophysical bodies, where magnetic helicity accumulation is presumably also taking place.

Zhang Mei [Key Laboratory of Solar Activity, National Astronomical Observatory, Chinese Academy of Sciences, Datun Road A20, Chaoyang District, Beijing 100012 (China); Flyer, Natasha [Institute for Mathematics Applied to Geosciences, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Low, Boon Chye [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

2012-08-10

105

Interaction Magnetic Force Calculation of Ring Permanent Magnets Using Ampere's Microscopic Surface Currents and Discretization Technique  

Microsoft Academic Search

Calculation of the interaction magnetic force between two ring permanent magnets of trapezoidal cross-section and a ring permanent magnet above the infinite linear magnetic plane is presented in this article. The simple and fast analytical approach is used for these calculations based on the distribution of microscopic surface Ampere's currents and the discretization technique. The results for the interaction magnetic

Ana N. Vu?kovi?; Saša S. Ili?; Slavoljub R. Aleksi?

2012-01-01

106

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

107

Nonconservative electric and magnetic optical forces on submicron dielectric particles  

SciTech Connect

We present a study of the total force on a small lossless dielectric particle, which presents both an electric and magnetic response, in a optical vortex wave field. We show that the force is a simple combination of conservative and nonconservative steady forces that can rectify the flow of magnetodielectric particles. In a vortex lattice the electric-magnetic dipolar interaction can spin the particles either in or out of the whirl sites leading to trapping or diffusion. Specifically, we analyze force effects on submicron silicon spheres in the near infrared, proving that the results previously discussed for hypothetical magnetodielectric particles can be observed for these Si particles.

Gomez-Medina, Raquel; Nieto-Vesperinas, Manuel [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, Campus de Cantoblanco, Madrid E-28049 (Spain); Saenz, Juan Jose [Departamento de Fisica de la Materia Condensada, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Donostia International Physics Center (DIPC), Paseo Manuel Lardizabal 4, 20018 Donostia-San Sebastian (Spain)

2011-03-15

108

MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2  

E-print Network

MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value total azimuthal flux with a power-law distribution over the poloidal field. Particular attention is paid

Fornberg, Bengt

109

A vibrational model using modal shapes and magnetic forces: experimental results for a permanent magnet machine  

Microsoft Academic Search

Contents The frequency inverter current spectrum generates a complex magnetic field in the airgap producing attracting forces having a wide spectrum and leads to audible noise. A mathematical model is presented, predicting vibrations of a permanent magnet machine, based on the modal analysis technique including mechanical damping. Modal forces produced by the magnetic field, are related to the supply currents

D. Verdyck; R. Belmans

1994-01-01

110

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

111

An improved analytical solution for predicting magnetic forces in permanent magnet motors  

Microsoft Academic Search

This paper describes an analytical model for analyzing magnetic forces developed in permanent magnet motors of radial field topology. The slotting effect is taken into consideration by solving the boundary value problem of the air gap field. The solution is expressed in the form of Fourier series with which the analysis of the harmonic contents in the magnetic forces can

Z. J. Liu; J. T. Li; Q. Jiang

2008-01-01

112

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

113

Electron Spin Magnetic Resonance Force Microscopy of Nitroxide Spin Labels  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

114

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

115

Magnetic forces and magnetostriction in electrical machines and transformer cores  

Microsoft Academic Search

This paper presents an original method for computing the deformation due to both magnetic forces and magnetostriction in ferromagnetic material. The method is applied to rotating electrical machines and transformers and is compared with other methods found in literature.

Lieven Vandevelde; Jan A. A. Melkebeek

2003-01-01

116

Mitigated-force carriage for high magnetic field environments  

DOEpatents

A carriage for high magnetic field environments includes a first work-piece holding means for holding a first work-piece, the first work-piece holding means being disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla. The first work-piece holding means is further disposed in operable connection with a second work-piece holding means for holding a second work-piece so that, as the first work-piece is inserted into the magnetic field, the second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Murphy, Bart L

2014-05-20

117

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

NASA Astrophysics Data System (ADS)

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 and can lead to favourable conditions for the melt dynamics and energy coupling. Numerous welds with full and partial penetration using both CO2 and Nd:YAG lasers demonstrate that this method directly influences the seam geometry and top-bead topography as well as the penetration depth and the evolution of pores and cracks. In the case of full penetration, it is also possible to lift or to lower the weld pool. The method, therefore, can be used to shape the geometry and to enhance the quality of the weld seam. Depending on the orientation of an external magnetic field, significant impacts are achieved in CO2 welding, even without an external current: the shape of the cross-sectional area can be increased of up to 50% and also the seam width is changed. Whereas for such conditions with Nd:YAG lasers no significant effect could be observed, it turned out that, when an external electric current is applied, similar effects are present with both wavelengths. In further investigations, the effect of electromagnetic body forces resulting from the interaction of an external current and its self-induced magnetic field was studied. Hereby, the current was fed into the workpiece via a tungsten electrode or a filler wire. The resulting phenomena are the same independent from wavelength and means of current feed.

Ambrosy, Guenter; Berger, P.; Huegel, H.; Lindenau, D.

2003-11-01

118

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

119

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

120

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

2009-03-26

121

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

122

Detection of magnetic-labeled antibody specific recognition events by combined atomic force and magnetic force microscopy  

NASA Astrophysics Data System (ADS)

Atomic force (AFM) and magnetic force microscopy (MFM) were developed to detect biomolecular specific interaction. Goat anti-mouse immunoglobulin (anti-IgG) was covalently attached onto gold substrate modified by a self-assembly monolayer of thioctic acid via 1-ethyl-3-[3-(dimethylamino) propyl] carbodiimide (EDC) activation. Magnetic-labeled IgG then specifically adsorbed onto anti-IgG surface. The morphological variation was identified by AFM. MFM was proved to be a fine assistant tool to distinguish the immunorecognized nanocomposites from the impurities by detection of the magnetic signal from magnetic-labeled IgG. It would enhance the understanding of biomolecular recognition process.

Hong, Xia; Liu, Yanmei; Li, Jun; Guo, Wei; Bai, Yubai

2009-09-01

123

EXPERIMENTAL BENCHMARKING OF THE MAGNETIZED FRICTION FORCE.  

SciTech Connect

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

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

2005-09-18

124

Force measurements in magnetic bearings using fiber optic strain gauges  

E-print Network

The research presented here develops a new method for measuring forces in magnetic bearings. Fiber-optic strain gauges (FOSGs) mounted to the side of the magnet poles are used to detect the small levels of strain that the metal experiences...

Raymer, Stephen Geoffrey

2000-01-01

125

Sensitive magnetic force detection with a carbon nanotube resonator  

SciTech Connect

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

Willick, Kyle [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Haapamaki, Chris [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Baugh, Jonathan, E-mail: baugh@iqc.ca [Institute for Quantum Computing, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada)

2014-03-21

126

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

127

Critical Casimir forces in a magnetic system: An experimental protocol  

NASA Astrophysics Data System (ADS)

We numerically test an experimentally realizable method for the extraction of the critical Casimir force based on its thermodynamic definition as the derivative of the excess free energy with respect to system size. Free energy differences are estimated for different system sizes by integrating the order parameter along an isotherm. The method could be developed for experiments on magnetic systems and could give access to the critical Casimir force for any universality class. By choosing an applied field that opposes magnetic ordering at the boundaries, the Casimir force is found to increase by an order of magnitude over zero-field results.

Lopes Cardozo, David; Jacquin, Hugo; Holdsworth, Peter C. W.

2014-11-01

128

Magnetic forces in high-Tc superconducting bearings  

NASA Technical Reports Server (NTRS)

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

Moon, F. C.

1991-01-01

129

A magnetic gradient induced force in NMR restricted diffusion experiments.  

PubMed

We predict that the phase cancellation of a precessing magnetisation field carried by a diffusing species in a bounded geometry under certain nuclear magnetic resonance pulsed magnetic field gradient sequences results in a small force over typically micrometre length scales. Our calculations reveal that the total magnetisation energy in a pore under the influence of a pulsed gradient will be distance-dependent thus resulting in a force acting on the boundary. It is shown that this effect of the magnetisation of diffusing particles will appear as either an attractive or repulsive force depending on the geometry of the pore and magnetic properties of the material. A detailed analysis is performed for the case of a pulsed gradient spin-echo experiment on parallel planes. It is shown that the force decays exponentially in terms of the spin-spin relaxation. The proof is based on classical electrodynamics. An application of this effect to soft matter is suggested. PMID:24697421

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

2014-03-28

130

A magnetic gradient induced force in NMR restricted diffusion experiments  

SciTech Connect

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

Ghadirian, Bahman; Stait-Gardner, Tim; Castillo, Reynaldo; Price, William S., E-mail: w.price@uws.edu.au [Nanoscale Organisation and Dynamics Group, University of Western Sydney, Penrith, NSW 2751 (Australia)

2014-03-28

131

Many-body central force potentials for tungsten  

NASA Astrophysics Data System (ADS)

Tungsten and tungsten-based alloys are the primary candidate materials for plasma facing components in fusion reactors. The exposure to high-energy radiation, however, severely degrades the performance and lifetime limits of the in-vessel components. In an effort to better understand the mechanisms driving the materials' degradation at the atomic level, large-scale atomistic simulations are performed to complement experimental investigations. At the core of such simulations lies the interatomic potential, on which all subsequent results hinge. In this work we review 19 central force many-body potentials and benchmark their performance against experiments and density functional theory (DFT) calculations. As basic features we consider the relative lattice stability, elastic constants and point-defect properties. In addition, we also investigate extended lattice defects, namely: free surfaces, symmetric tilt grain boundaries, the 1/2<1?1?1>{1?1?0} and 1/2<1?1?1> {1?1?2} stacking fault energy profiles and the 1/2<1?1?1> screw dislocation core. We also provide the Peierls stress for the 1/2<1?1?1> edge and screw dislocations as well as the glide path of the latter at zero Kelvin. The presented results serve as an initial guide and reference list for both the modelling of atomically-driven phenomena in bcc tungsten, and the further development of its potentials.

Bonny, G.; Terentyev, D.; Bakaev, A.; Grigorev, P.; Van Neck, D.

2014-07-01

132

Visualization and characterization of prolamellar bodies with atomic force microscopy.  

PubMed

Prolamellar bodies (PLBs) isolated from etiolated wheat seedlings were studied with the use of atomic force microscopy (AFM), transmission electron microscopy (TEM) and fluorescence spectroscopy. With AFM, PLBs were seen as spherical structures about 1-2?m in diameter, more elastic than mica and poly-l-lysine substrate. TEM analyses confirmed that PLBs of wheat leaf etioplasts also had an average diameter of appr. 1?m. Illumination induced the photoreduction of photoactive protochlorophyllide (Pchlide), i.e. Pchlide bound to protochlorophyllide oxidoreductase, which was shown in fluorescence spectra. The photoreduction was followed by the disruption of PLB structures, which started with the enlargement of PLB spheres and then their fragmentation into small balls as seen with AFM. Light-induced vesicle formation and the outgrowth of lamellar (pro)thylakoid membranes on the PLB surface were also confirmed by TEM analyses, and resulted in the apparent enlargement of the PLB diameter. The blue-shift of the fluorescence emission maximum of chlorophyllide observed for PLBs at room temperature after Pchlide photoreduction was completed within 25min. However, structural changes in PLBs were still observed after the completion of the blue-shift. The incubation of PLBs in darkness with HgCl2 also resulted in PLB enlargement and a loosening of their structure. AFM provides a unique opportunity to observe PLBs at a physiological temperature without the necessity of fixation. PMID:23777838

Grzyb, Joanna M; Solymosi, Katalin; Strza?ka, Kazimierz; Mysliwa-Kurdziel, Beata

2013-09-15

133

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

134

Thermal Casimir Force between Magnetic Materials  

E-print Network

We investigate the Casimir pressure between two parallel plates made of magnetic materials at nonzero temperature. It is shown that for real magnetodielectric materials only the magnetic properties of ferromagnets can influence the Casimir pressure. This influence is accomplished through the contribution of the zero-frequency term of the Lifshitz formula. The possibility of the Casimir repulsion through the vacuum gap is analyzed depending on the model used for the description of the dielectric properties of the metal plates.

G. L. Klimchitskaya; B. Geyer; V. M. Mostepanenko

2009-11-21

135

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

NASA Technical Reports Server (NTRS)

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

Moon, F. C.

1990-01-01

136

Dual-tip magnetic force microscopy with suppressed influence on magnetically soft samples  

NASA Astrophysics Data System (ADS)

Standard magnetic force microscopy (MFM) is considered as a powerful tool used for magnetic field imaging at nanoscale. The method consists of two passes realized by the magnetic tip. Within the first one, the topography pass, the magnetic tip directly touches the magnetic sample. Such contact perturbs the magnetization of the sample explored. To avoid the sample touching the magnetic tip, we present a new approach to magnetic field scanning by segregating the topological and magnetic scans with two different tips located on a cut cantilever. The approach minimizes the disturbance of sample magnetization, which could be a major problem in conventional MFM images of soft magnetic samples. By cutting the cantilever in half using the focused ion beam technique, we create one sensor with two different tips—one tip is magnetized, and the other one is left non-magnetized. The non-magnetized tip is used for topography and the magnetized one for the magnetic field imaging. The method developed we call dual-tip magnetic force microscopy (DT-MFM). We describe in detail the dual-tip fabrication process. In the experiments, we show that the DT-MFM method reduces significantly the perturbations of the magnetic tip as compared to the standard MFM method. The present technique can be used to investigate microscopic magnetic domain structures in a variety of magnetic samples and is relevant in a wide range of applications, e.g., data storage and biomedicine.

Precner, Marián; Fedor, Ján; Šoltýs, Ján; Cambel, Vladimír

2015-02-01

137

Novel composite of magnetostrictive material and piezoelectric actuator for coil-free magnetic force control  

Microsoft Academic Search

Novel composite of magnetostrictive material and piezoelectric actuator is proposed for coil-free magnetic force control. The magnetic force control is based on the inverse magnetostrictive effect of magnetostrictive materials whereby the strain hence magnetic force is controlled by the actuator. Because the piezoelectric actuator is an electrically capacitive, this magnetic force control method has the advantages of zero power consumption

Toshiyuki Ueno; Toshiro Higuchi

2006-01-01

138

Estimate of Magnetic Forces on Beam Sweeping Kickers  

SciTech Connect

The beam sweeping magnet kickers are two pairs of conductors placed 90 degrees apart inside a circular magnetic yoke. Each pair has the same excitation current in the opposite directions, and the two currents are a sine and a cosine in phase. To estimate the magnetic forces on the kickers due to the excitation currents, we make the following simplifications: (1) The four conductors are all parallel to one another; (2) There are no relative motions within the system; and (3) the magnetic yoke has {mu} = {infinity}, and the fields are zero near the outside inner surface of the yoke.

Hu, Martin; /Nebraska U.

2000-02-23

139

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

Microsoft Academic Search

The flux density, eddy current and body force of annular-type, single-phase induction electromagnetic pump were analyzed by finite element method assuming that the secondary conductor is at standstill. The diffusion characteristics of eddy current in the secondary conductor as well as the body force characteristics are also analyzed. It is shown that the diffusion characteristics of eddy current are determined

Shinya Hasebe; Yoshi Kano

1982-01-01

140

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

Microsoft Academic Search

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

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

1998-01-01

141

On the Relationship between Solar Magnetic Forces and CME Momenta  

NASA Astrophysics Data System (ADS)

Free magnetic energy is the energy source of solar flares and CMEs. At the initiation of a CME, the free magnetic energy converts to kinetic energy and few other types of energy. Observable magnetic field sudden changes have been found at the onset of flares. The Lorentz force around the onset of a flare have been formulated in recent studies and can be estimated using photospheric vector magnetic field data. It is proposed that outward Lorentz force impulses could be related to CME momenta. We analyze about 30 CMEs and their source region magnetic fields. The best vector magnetic field data are observed for active regions near the center of the solar disk. We first select CMEs that appear to be halo or partial halo CMEs in the LASCO images, and then we use STEREO SECCHI COR2 white light images to estimate CME mass and speed. We then estimate the Lorentz forces in the source active regions at the flare onset using SDO HMI photosheric vector magnetic field data. We report our studies and describe our analyses.This study is under the support of NSF grants.

Li, Yan; Lynch, Ben; Sun, Xudong; Welsch, Brian T.; Bercik, David J.; Fisher, George H.

2015-04-01

142

Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient  

PubMed Central

Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

2014-01-01

143

Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient.  

PubMed

Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971

Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo

2014-01-01

144

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

E-print Network

a particle's magnetic state. By suitably choosing the operating mode and tip coatings, the tip induced of small magnetic elements are crucial tests of micromagnetic codes and lead to a better understandingMagnetic force microscopy study of electron-beam-patterned soft permalloy particles: Technique

Grütter, Peter

145

On the determination of the internal magnetic structure by magnetic force microscopy  

Microsoft Academic Search

In this contribution it is proven mathematically that it is in principle impossible to determine the magnetic charge distribution inside a magnetic material by a method which measures the stray field outside the sample, such as magnetic force microscopy (MFM). A general source of stray field, E?, is defined and it is shown that different solutions can be found for

Bas Vellekoop; Leon Abelmann; Steffen Porthun; Cock Lodder

1998-01-01

146

On the determination of the internal magnetic structure by magnetic force microscope  

Microsoft Academic Search

In this contribution it is proven mathematically that it is in principle impossible to determine the magnetic charge distribution inside a magnetic material by a method which measures the stray field outside the sample, such as magnetic force microscopy (MFM). A general source of stray field, E?, is defined and it is shown that different solutions can be found for

S. J. L. Vellekoop; L. Abelmann; S. Porthun; J. C. Lodder

1998-01-01

147

Calculation and analysis of high-speed permanent magnetic generator unilateral magnetic force  

Microsoft Academic Search

Taking a two-pole high-speed permanent magnetic synchronous generator (PMSG) as an example, the mathematic and physical models with generator eccentric are established. This paper presented two different methods to calculate the magnetic field distribution and unilateral magnetic force (UMF) in the whole calculating region. And then analysis of influences of the eccentricity, load current and harmonics on the UMF have

Li Weili; Tang Li; Zhang Xiaocheng; Geng Jiaming

2008-01-01

148

Force-free magnetic relaxation in driven plasmas  

NASA Astrophysics Data System (ADS)

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

Tang, Xianzhu; Boozer, Allen H.

2004-11-01

149

Magnetic forces for type II superconductors in a levitation field  

NASA Astrophysics Data System (ADS)

A complete loop of hysteretic force has been calculated for hard superconductors in an almost-constant-gradient magnetic suspension system, which consists of a pair of oppositely wound superconducting coils. The dependences of levitation forces on the sample size, critical current density, external field strength, field gradient, and the magnetic history were investigated. Dynamic spring constants as well as magnetic damping coefficients were inferred from minor loop calculations. The minor loops, similar to the Rayleigh loops for ferromagnetic materials, could be described in quadratic terms. The major loops strongly depend on the magnetic passage, a flux-trap effect which is responsible for the subtlety in obtaining reproducible hysteresis loop. The basic physics of levitation and inverse levitation will be quantitatively illustrated.

Torng, Terry; Chen, Q. Y.

1993-02-01

150

Magnetic imaging by atomic force microscope (invited) (abstract)  

NASA Astrophysics Data System (ADS)

A new method of imaging the surface of magnetic samples on a submicron scale is described and the observation of magnetic domain walls is presented. Measurements in air on a Co-Ni recording media, polycrystalline Ni foil and rapidly quenched alloys are shown. This magnetic microscope is based on the idea of measuring magnetic forces with the recently developed atomic force microscope (AFM). Forces acting on a tip are recorded by the measurement of the deflection of a lever to which this tip is attached. In order to measure ultra small forces (less than nN), the spring constant of the lever has to be small and the deflection of the lever has to be measured with great sensitivity, i.e., by using interferometry or scanning tunneling microscopy (STM). The lever is made from ferromagnetic Ni foil with an integrated, electrochemically etched tip. Different measuring modes of the AFM are described. The images obtained by the AFM using a para- or ferromagnetic tip and by the STM are compared. Furthermore, the results obtained by the magnetic AFM on Co-Ni recording media are compared with previous studies by scanning electron microscopy with polarization analysis (SEMPA).

Grütter, P.; Meyer, E.; Heinzelmann, H.; Rosenthaler, L.; Hidber, H. R.; Güntherodt, H.-J.

1988-04-01

151

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

152

Force-free magnetic relaxation in driven plasmas  

Microsoft Academic Search

J. B. Taylor (1974) postulated that the helicity-conserving minimum magnetic energy state is the consequence of plasma self-organization via turbulent relaxation bounded by a magnetic surface. The Taylor state j=lambda B is a force-free plasma with lambda a global constant. For a driven plasma with open flux intercepting the boundary B\\\\cdothat nneq 0, Taylor relaxation is constrained by the Jensen-Chu

Xianzhu Tang; Allen H. Boozer

2004-01-01

153

Force-Free Magnetic Flux Ropes in the Solar Corona  

NASA Astrophysics Data System (ADS)

In the course of an ongoing investigation of force-free magnetic fields in the spherical geometry appropriate to the solar corona, we have found solutions that represent magnetic flux ropes. The magnetic energy stored in these ropes and the surrounding field is larger than that which can be stored in simple magnetic arcades with the same boundary conditions, and in some cases exceeds slightly the Aly-Sturrock limit on the energy of a closed force-free magnetic field with all its magnetic flux connected to the coronal base. Flux-rope solutions with the highest energies tend to arise when a strong potential field overlies a region of sheared field containing field-aligned currents. These flux-rope solutions have an unusual topology; instead of a single twisted, disconnected flux system, there are two distinct rope structures. A two-dimensional slice through each rope contains an O-type magnetic neutral point, and the overall solution therefore correspondingly contains two X-type neutral points. We speculate on the relation of this unusual topology to observations of magnetic clouds as interplanetary signatures of coronal mass ejections. This work was supported by NASA grant NAG5-9733 to Middlebury College.

Wolfson, R.

2003-05-01

154

A mean electromotive force induced by magnetic buoyancy instabilities  

NASA Astrophysics Data System (ADS)

For a variety of reasons, based on results from magnetoconvection, self-consistent dynamo calculations and helioseismology, it seems plausible that the bulk of the solar magnetic field is located in the overshoot zone. Furthermore, it has also been suggested that the solar dynamo is operating in this region. The aim of this paper is then to show that it is possible to obtain a mean electromotive force (EMF), and hence an ?-effect, in the convectively stable overshoot zone, which is driven by magnetic buoyancy instabilities. By investigating the stability of a layer of magnetic field embedded between two non-magnetic layers of plasma we are able to show the following: first, that magnetic buoyancy instabilities indeed give rise to a mean EMF and, secondly, that the electromotive force is largest in the region where the magnetic layer is unstable, i.e. where the field strength decreases fastest with height. Moreover, the influence of the rotation rate and the magnetic field strength on the magnetic buoyancy instability has been investigated in order to determine for which values of these parameters dynamo action might occur.

Thelen, J.-C.

2000-06-01

155

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

PubMed

We present the realization of a mesoscopic imaging technique, namely, the Magnetoelectric Force Microscopy (MeFM), for visualization of local magnetoelectric effect. The basic principle of MeFM is the lock-in detection of local magnetoelectric response, i.e., the electric field-induced magnetization, using magnetic force microscopy. We demonstrate MeFM capability by visualizing magnetoelectric domains on single crystals of multiferroic hexagonal manganites. Results of several control experiments exclude artifacts or extrinsic origins of the MeFM signal. The parameters are tuned to optimize the signal to noise ratio. PMID:24880381

Geng, Yanan; Wu, Weida

2014-05-01

156

Local nonlinear rf forces in inhomogeneous magnetized plasmas  

SciTech Connect

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

Chen, Jiale, E-mail: chen@ipp.ac.cn [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China); Gao, Zhe [Department of Engineering Physics, Tsinghua University, Beijing 100084 (China)

2014-06-15

157

Fast contact force computation for nonpenetrating rigid bodies  

Microsoft Academic Search

A new algorithm for computing contact forces between solid objects with friction is presented. The algorithm allows a mix of contact points with static and dynamic friction. In contrast to previous approaches, the problem of computing contact forces is not transformed into an optimization problem. Because of this, the need for sophisticated optimization software packages is eliminated. For both systems

David Baraff

1994-01-01

158

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

159

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

Microsoft Academic Search

A novel in-line miniature force transducer is developed for direct measurements of the net aerodynamic forces and moments\\u000a on a bluff body. The force transducers are integrated into each of the eight mounting wires that are utilized for suspension\\u000a of an axisymmetric model in a wind tunnel having minimal wake interference. The aerodynamic forces and moments on the model\\u000a are

Philip Abramson; Bojan Vukasinovic; Ari Glezer

2011-01-01

160

Magnetic Resonance Force Microscopy Measurement of Entangled Spin States  

E-print Network

We simulate magnetic resonance force microscopy measurements of an entangled spin state. One of the entangled spins drives the resonant cantilever vibrations, while the other remote spin does not interact directly with the quasiclassical cantilever. The Schr\\"odinger cat state of the cantilever reveals two possible outcomes of the measurement for both entangled spins.

G. P. Berman; F. Borgonovi; G. Chapline; P. C. Hammel; V. I. Tsifrinovich

2001-10-10

161

Models of force-free magnetic fields in resistive media  

Microsoft Academic Search

A review is given of some of the basic properties of force-free fields under circumstances when the conductivity of the medium is finite. Then the electric current density is related not only to the magnetic field, but also by Ohm's law to the electric field and plasma velocity, which must be considered in the solutions. It is pointed out that

Rolf Boström

1973-01-01

162

Magnetic bearing control systems and adaptive forced balancing  

Microsoft Academic Search

Active magnetic bearing (AMB) actuators support rotors without friction but require feedback control for stabilization and performance. We address the application of modern control techniques such as LQG\\/LTR, H?, and QFT to AMB systems. We also introduce a novel method called adaptive forced balancing (AFB) which solves the problem of synchronous vibration caused by mass unbalance. Simulation and experimental results

B. Shafai; S. Beale; P. Larocca; E. Cusson

1994-01-01

163

Magnetic resonance imaging of nonmetallic orbital foreign bodies.  

PubMed

We studied a cadaver head model in which we inserted three orbital foreign bodies. We chose these foreign bodies because of their similarity to substances found in orbital trauma. Teflon and Lucite were used to represent synthetic materials, and dry pine was chosen as a type of organic material. Lucite is similar in radiographic density to plastics used in interior trim for automobiles and spectacle frames. While both orbital ultrasound and plain skull films failed to detect the foreign bodies consistently, both computed tomography and magnetic resonance imaging detected and localized the foreign bodies relatively well. Computed tomography was better in delineating shape and characterizing composition. PMID:3287937

Wilson, W B; Dreisbach, J N; Lattin, D E; Stears, J C

1988-06-15

164

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

165

Direct Forced Evaporative Cooling in Permanent Magnetic Microtraps  

E-print Network

We propose two simple permanent magnetic micro-structures for creating single Ioffe-Pritchard magnetic microtraps. Direct forced evaporative cooling of neutral atoms without using spin flips can be implemented in these microstructures to attain Bose-Einstein condensation (BEC). A BEC critical temperature of $\\sim 10 \\mu$K is numerically obtained for $^{87}$Rb atoms in the atom chips. A bias magnetic field is used to vary the depth of the trap, frequencies and the minimum of the potential. Even without the external magnetic field, it is possible to hold ultracold atoms in the microtraps. Therefore, after achieving the BEC in the atom chips, the bias magnetic field can be slowly removed to increase the trap barrier heights for more efficiently holding the Bose-Einstein condensate.

Mohammadi, Amir; Pariz, Aref

2010-01-01

166

Chiral nuclear forces and many-body applications  

NASA Astrophysics Data System (ADS)

Description of light nuclei and low-energy nuclear reactions can be given in a model-independent way by using chiral effective field theory of QCD. In this framework, nuclear forces are described by pion and nucleon rather than fundamental quark degrees of freedom in harmony with the symmetries of QCD. In this proceeding I discuss chiral nuclear forces derived within this framework and present our first results on the three-nucleon forces calculated up to next-to-nextto-next-to-leading order in chiral effective field theory. I will also discuss our recent lattice simulations of the 12C-spectrum where the next-to-next-to-leading order nuclear forces serve as an input. In addition to the ground state and excited spin-2 state, we find a resonance at -85(3) MeV with all of the properties of the Hoyle state and in agreement with the experimentally observed energy.

Krebs, Hermann

2012-09-01

167

Characterization of magnetic force microscopy probe tip remagnetization for measurements in external in-plane magnetic fields  

SciTech Connect

A quantitative analysis of magnetic force microscopy (MFM) images taken in external in-plane magnetic fields is difficult because of the influence of the magnetic field on the magnetization state of the magnetic probe tip. We prepared calibration samples by ion bombardment induced magnetic patterning with a topographically flat magnetic pattern magnetically stable in a certain external magnetic field range for a quantitative characterization of the MFM probe tip magnetization in point-dipole approximation.

Weis, Tanja; Engel, Dieter; Ehresmann, Arno [Institute of Physics and Centre for Interdisciplinary Nanostructure Science and Technology, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel (Germany); Krug, Ingo [DSM IRAMIS SPCSI, CEA-Saclay, 91191 Gif sur Yvette (France); Hoeink, Volker; Schmalhorst, Jan; Reiss, Guenter [Department of Physics, Thin Films and Nanostructures, Bielefeld University, P.O. Box 100131, 33501 Bielefeld (Germany)

2008-12-15

168

Residual long-range pseudoscalar forces between unpolarised macroscopic bodies  

Microsoft Academic Search

In this paper we survey the effects of residual long-range forces associated to gamma5-spin dependent-couplings of fermions to massless bosons exerted by unpolarised bulk matter over macroscopic distances. We establish that such forces with behaviour proportional to R-6 do indeed exist. They arise as a quantum mechanical effect due to simultaneous exchange of two quanta. We explore their presence in

J. A. Grifols; S. Tortosa

1994-01-01

169

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

170

Height and Body Composition Determine Arm Propulsive Force in Youth Swimmers Independent of a Maturation Stage  

PubMed Central

The aim of this study was to examine the relationship between anthropometric variables, body composition and propulsive force in swimmers aged 9–17 years. Anthropometric characteristics (body height and mass, sitting height, arm span, arm muscle area and body composition) and the propulsive force of the arm (tethered swimming test) were evaluated in 56 competitive male swimmers. Tanner’s stages of genital maturation (P1–5) were used. The data analysis included correlations and multiple linear regression. The propulsive force of the arm was correlated with body height (r = 0.34; p =0.013), arm span (r = 0.29; p =0.042), sitting height (r = 0.36; p =0.009), % body fat (r = 0.33; p =0.016), lean body mass (r = 0.34; p =0.015) and arm muscle area (r = 0.31; p =0.026). Using multiple linear regression models, the percent body fat and height were identified as significant predictors of the propulsive force of the arm after controlling for the maturation stage. This model explained 22% (R2 = 0.22) of associations. In conclusion, the propulsive force of swimmers was related to body height and percent body fat. PMID:25414760

Moura, Tatiane; Costa, Manoel; Oliveira, Saulo; Júnior, Marcos Barbosa; Ritti-Dias, Raphael; Santos, Marcos

2014-01-01

171

Three-axis force actuator for a magnetic bearing  

NASA Technical Reports Server (NTRS)

This invention features a three-axis force actuator that axially, radially and rotatably supports a bearing member for frictionless rotation about an axis of rotation generally coincident with a Z-axis. Also featured is a magnetic bearing having such an actuator. The actuator includes an inner member, a magnetic member and a pole assembly having a ring member and four pole extending therefrom. The poles are equi-angular spaced from each other and radially spaced about the Z-axis. The inner member extends along the Z-axis and is a highly magnetic permeable material. The magnetic member is formed about the inner member outer surface, extends along the Z-axis and is configured so one magnetic pole polarity is located at its outer surface and the other polarity pole is located at its inner surface. Preferably, the magnetic member is a radially magnetized permanent magnet. The inner surface of the ring member is magnetically coupled to the magnetic member and a face of each pole is coupled to the bearing member. The magnetic member, the pole assembly, the inner member and the bearing member cooperate to generate a magnetic field that radially and rotatably supports a rotating member secured to the bearing member. The actuator further includes a plurality of electromagnetic coils. Preferably, a coil is formed about each pole and at least 2 coils are formed about the inner member. When energized, the electromagnetic coils generate a modulated magnetic field that stabilizes the rotating member in the desired operational position.

Gondhalekar, Vijay (Inventor)

1998-01-01

172

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

173

Electromagnetic-force study of permanent magnet about large permanent magnet generator in wind-power  

Microsoft Academic Search

Jinfeng 62(1.2MW) permanent magnet synchronous generator (PMSG) two dimensional (2D) model constituted according to a pair of magnet pole area. Basic hypothesis and boundary condition presented. Abrupt three-phase short circuit current was calculated, including diversified electromagnetic field and electromagnetic force that exert on PM when generator operates normally and fault happened. The effect to electromagnetic force was found by calculating

Shan He; Weiqing Wang; Xinyan Zhang; Xiang Zhao; Liang Guo

2008-01-01

174

Magnetic force computation in permanent magnets using a local energy coordinate derivative method  

Microsoft Academic Search

The definition of energy\\/coenergy in permanent magnets (PMs) is still in dispute when virtual work is used to compute magnetic forces using finite-element methods. There is also no current practical method for computing forces when PMs touch objects. These problems are addressed in this paper in terms of a new definition of energy\\/coenergy in PMs and by using shell elements.

W. N. Fu; P. Zhou; D. Lin; S. Stanton; Z. J. Cendes

2004-01-01

175

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

SciTech Connect

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

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

2013-11-14

176

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

PubMed

We developed an explicit equation of state (EOS) for small non polar molecules by means of an effective two-body potential. The average effect of three-body forces was incorporated as a perturbation, which results in rescaled values for the parameters of the two-body potential. These values replace the original ones in the EOS corresponding to the two-body interaction. We applied this procedure to the heavier noble gases and used a modified Kihara function with an effective Axilrod-Teller-Muto (ATM) term to represent the two- and three-body forces. We also performed molecular dynamics simulations with two- and three-body forces. There was good agreement between predicted, simulated, and experimental thermodynamic properties of neon, argon, krypton, and xenon, up to twice the critical density and up to five times the critical temperature. In order to achieve 1% accuracy of the pressure at liquid densities, the EOS must incorporate the effect of ATM forces. The ATM factor in the rescaled two-body energy is most important at temperatures around and lower than the critical one. Nonetheless, the rescaling of two-body diameter cannot be neglected at liquid-like densities even at high temperature. This methodology can be extended straightforwardly to deal with other two- and three-body potentials. It could also be used for other nonpolar substances where a spherical two-body potential is still a reasonable coarse-grain approximation. PMID:24320280

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

2013-11-14

177

Effect of transcranial magnetic stimulation on force of finger pinch  

NASA Astrophysics Data System (ADS)

Transcranial magnetic stimulation (TMS) is used to explore many aspects of brain function, and to treat neurological disorders. Cortical motor neuronal activation by TMS over the primary motor cortex (M1) produces efferent signals that pass through the corticospinal tracts. Motor-evoked potentials (MEPs) are observed in muscles innervated by the stimulated motor cortex. TMS can cause a silent period (SP) following MEP in voluntary electromyography (EMG). The present study examined the effects of TMS eliciting MEP and SP on the force of pinching using two fingers. Subjects pinched a wooden block with the thumb and index finger. TMS was applied to M1 during the pinch task. EMG of first dorsal interosseous muscles and pinch forces were measured. Force output increased after the TMS, and then oscillated. The results indicated that the motor control system to keep isotonic forces of the muscles participated in the finger pinch was disrupted by the TMS.

Odagaki, Masato; Fukuda, Hiroshi; Hiwaki, Osamu

2009-04-01

178

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

SciTech Connect

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

Grimes, S.M.

1980-07-01

179

Prediction of forces and moments on finned bodies at high angle of attack in transonic flow  

SciTech Connect

This report describes a theoretical method for the prediction of fin forces and moments on bodies at high angle of attack in subsonic and transonic flow. The body is assumed to be a circular cylinder with cruciform fins (or wings) of arbitrary planform. The body can have an arbitrary roll (or bank) angle, and each fin can have individual control deflection. The method combines a body vortex flow model and lifting surface theory to predict the normal force distribution over each fin surface. Extensive comparisons are made between theory and experiment for various planform fins. A description of the use of the computer program that implements the method is given.

Oberkampf, W. L.

1981-04-01

180

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

181

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

182

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

Microsoft Academic Search

Pushing magnetic resonance force microscopy towards single proton sensitivity demands meeting the nanofabrication challenge of producing an attonewton-sensitivity cantilever with a magnetic tip whose diameter is 50 nm or less. At the same time, the cantilever should also experience low force noise (and force gradient noise) near the surface of technologically interesting samples. Ideally then, the magnetic tip would overhang

Sarah Wright; Steven Hickman; John Marohn

2008-01-01

183

Paramagnetic Beads and Magnetically Mediated Strain Enhance Cardiomyogenesis in Mouse Embryoid Bodies  

PubMed Central

Mechanical forces play an important role in proper embryologic development, and similarly such forces can directly impact pluripotency and differentiation of mouse embryonic stem cells (mESC) in vitro. In addition, manipulation of the embryoid body (EB) microenvironment, such as by incorporation of microspheres or microparticles, can similarly influence fate determination. In this study, we developed a mechanical stimulation regimen using permanent neodymium magnets to magnetically attract cells within an EB. Arginine-Glycine-Aspartic Acid (RGD)-conjugated paramagnetic beads were incorporated into the interior of the EBs during aggregation, allowing us to exert force on individual cells using short-term magnetization. EBs were stimulated for one hour at different magnetic field strengths, subsequently exerting a range of force intensity on the cells at different stages of early EB development. Our results demonstrated that following exposure to a 0.2 Tesla magnetic field, ESCs respond to magnetically mediated strain by activating Protein Kinase A (PKA) and increasing phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) expression. The timing of stimulation can also be tailored to guide ESC differentiation: the combination of bone morphogenetic protein 4 (BMP4) supplementation with one hour of magnetic attraction on Day 3 enhances cardiomyogenesis by increasing contractile activity and the percentage of sarcomeric ?-actin-expressing cells compared to control samples with BMP4 alone. Interestingly, we also observed that the beads alone had some impact on differentiation by increasingly slightly, albeit not significantly, the percentage of cardiomyocytes. Together these results suggest that magnetically mediated strain can be used to enhance the percentage of mouse ESC-derived cardiomyocytes over current differentiation protocols. PMID:25501004

Geuss, Laura R.; Wu, Douglas C.; Ramamoorthy, Divya; Alford, Corinne D.; Suggs, Laura J.

2014-01-01

184

Paramagnetic beads and magnetically mediated strain enhance cardiomyogenesis in mouse embryoid bodies.  

PubMed

Mechanical forces play an important role in proper embryologic development, and similarly such forces can directly impact pluripotency and differentiation of mouse embryonic stem cells (mESC) in vitro. In addition, manipulation of the embryoid body (EB) microenvironment, such as by incorporation of microspheres or microparticles, can similarly influence fate determination. In this study, we developed a mechanical stimulation regimen using permanent neodymium magnets to magnetically attract cells within an EB. Arginine-Glycine-Aspartic Acid (RGD)-conjugated paramagnetic beads were incorporated into the interior of the EBs during aggregation, allowing us to exert force on individual cells using short-term magnetization. EBs were stimulated for one hour at different magnetic field strengths, subsequently exerting a range of force intensity on the cells at different stages of early EB development. Our results demonstrated that following exposure to a 0.2 Tesla magnetic field, ESCs respond to magnetically mediated strain by activating Protein Kinase A (PKA) and increasing phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2) expression. The timing of stimulation can also be tailored to guide ESC differentiation: the combination of bone morphogenetic protein 4 (BMP4) supplementation with one hour of magnetic attraction on Day 3 enhances cardiomyogenesis by increasing contractile activity and the percentage of sarcomeric ?-actin-expressing cells compared to control samples with BMP4 alone. Interestingly, we also observed that the beads alone had some impact on differentiation by increasingly slightly, albeit not significantly, the percentage of cardiomyocytes. Together these results suggest that magnetically mediated strain can be used to enhance the percentage of mouse ESC-derived cardiomyocytes over current differentiation protocols. PMID:25501004

Geuss, Laura R; Wu, Douglas C; Ramamoorthy, Divya; Alford, Corinne D; Suggs, Laura J

2014-01-01

185

Biomechanics of pressure ulcer in body tissues interacting with external forces during locomotion.  

PubMed

Forces acting on the body via various external surfaces during locomotion are needed to support the body under gravity, control posture, and overcome inertia. Examples include the forces acting on the body via the seating surfaces during wheelchair propulsion, the forces acting on the plantar foot tissues via the insole during gait, and the forces acting on the residual-limb tissues via the prosthetic socket during various movement activities. Excessive exposure to unwarranted stresses at the body-support interfaces could lead to tissue breakdowns commonly known as pressure ulcers, often presented as deep-tissue injuries around bony prominences or as surface damage on the skin. In this article, we review the literature that describes how the involved tissues respond to epidermal loading, taking into account both experimental and computational findings from in vivo and in vitro studies. In particular, we discuss related literature about internal tissue deformation and stresses, microcirculatory responses, and histological, cellular, and molecular observations. PMID:20415590

Mak, Arthur F T; Zhang, Ming; Tam, Eric W C

2010-08-15

186

Magnetic force micropiston: an integrated force/microfluidic device for the application of compressive forces in a confined environment.  

PubMed

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging. PMID:24593368

Fisher, J K; Kleckner, N

2014-02-01

187

Magnetic force micropiston: An integrated force/microfluidic device for the application of compressive forces in a confined environment  

NASA Astrophysics Data System (ADS)

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.

Fisher, J. K.; Kleckner, N.

2014-02-01

188

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

Microsoft Academic Search

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

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

2006-01-01

189

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

190

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

E-print Network

Experimental investigation of side force control on cone-cylinder slender bodies with flexible; accepted 31 December 2004 Abstract Side forces on slender bodies of revolution at medium to high angles a slender body are believed to be the principle cause of the side forces. Under some flight conditions

Leu, Tzong-Shyng "Jeremy"

191

On transition from Alfvén resonance to forced magnetic reconnection  

SciTech Connect

We revisit the transition from Alfvén resonance to forced magnetic reconnection with a focus on the property of their singularities. As the driven frequency tends to zero, the logarithmic singularity of Alfvén resonance shifts to the power-law singularity of forced reconnection, due to merging of the two resonance layers. The transition criterion depends on either kinetic effects or dissipations that resolve the singularity. As an example, a small but finite resistivity ? is introduced to investigate the transition process. The transition threshold is then obtained as the driven frequency reaches a level of ?O((?/k){sup 1/3})

Luan, Q. [MOE Key Lab of Materials Modification by Beams and School of Physics and Optoelectrical Technology, Dalian University of Technology, Dalian 116024 (China); Wang, X., E-mail: xgwang@hit.edu.cn [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China)

2014-07-15

192

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

193

Numerical Studies of Axial and Radial Magnetic Forces Between High Temperature Superconductors and a Magnetic Rotor  

NASA Astrophysics Data System (ADS)

The magnetic bearing is considered as one of the most prospective applications of high temperature superconductors (HTSs) which can realize stable levitation in a magnetic field generated by permanent magnet devices or coils. The exploration of this kind of HTS bearing through numerical investigation is usually made by assuming the induced current circulates only within the ab-plane and thus simplifying the actual three-dimensional problem to a two-dimensional one. In this paper, on the basis of the three-dimensional model of the HTS bulk established before, we further introduce the developed finite-element software to calculate the magnetic field generated by a magnetic rotor which is composed of permanent magnet (PM) rings and ferromagnet (FM) shims, and in this way, we can investigate the magnetic forces (radial force and axial force) of a simplified HTS bearing model, i.e., two symmetric HTS bulks and a magnetic rotor, at a three-dimensional level. The investigations performed in this paper lead to the observations: the favorable configuration to construct the HTS bearing is that the axial height of each HTS element should be equivalent to the axial heights of PM ring plus FM shim; the increase of the radial thickness of PM ring will improve both the radial force and the axial force considerably, but its margin decreases; the enhancement of critical current density of HTSs due to the decrease of operating temperature can result in a higher increase of both the radial and axial force with a lower nominal gap between the HTSs and the magnetic rotor.

Ma, Guangtong; Lin, Qunxu; Jiang, Donghui; Yuan, Chunyan; Deng, Zigang

2013-08-01

194

Muscle force redistributes segmental power for body progression during walking  

Microsoft Academic Search

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,

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

2004-01-01

195

Force model identification for magnetic suspension systems via magnetic field measurement  

Microsoft Academic Search

In magnetic suspension analysis, a simplified model of the current-to-distance relationship is not sufficient to design an optimal control. Due to the nonlinearity of the magnetic field, an accurate model, which is a function of the suspended object, suspension distance, core material, and operation conditions, is difficult to obtain. An improved force-model-identification method for magnetic suspension systems establishes reliable parameters

Chin E. Lin; Huei L. Jou

1993-01-01

196

Spin motive forces due to magnetic vortices and domain walls  

NASA Astrophysics Data System (ADS)

We study spin motive forces, that is, spin-dependent forces and voltages induced by time-dependent magnetization textures, for moving magnetic vortices and domain walls. First, we consider the voltage generated by a one-dimensional field-driven domain wall. Next, we perform detailed calculations on field-driven vortex domain walls. We find that the results for the voltage as a function of magnetic field differ between the one-dimensional and vortex domain walls. For the experimentally relevant case of a vortex domain wall, the dependence of voltage on the field around Walker breakdown depends qualitatively on the ratio of the so-called ? parameter to the Gilbert damping constant and thus provides a way to determine this ratio experimentally. We also consider vortices on a magnetic disk in the presence of an ac magnetic field. In this case, the phase difference between field and voltage on the edge is determined by the ? parameter, providing another experimental method to determine this quantity.

Lucassen, M. E.; Kruis, G. C. F. L.; Lavrijsen, R.; Swagten, H. J. M.; Koopmans, B.; Duine, R. A.

2011-07-01

197

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

198

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

NASA Astrophysics Data System (ADS)

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

Yu, Jing-Jiang; Garno, Jayne

2012-02-01

199

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

200

Effects of Bose-Einstein condensation on forces among bodies sitting in a boson heat bath  

Microsoft Academic Search

We explore the consequences of Bose-Einstein condensation on two-scalar-exchange mediated forces among bodies that sit in a boson gas. We find that below the condensation temperature the range of the forces becomes infinite, while it is finite at temperatures above condensation.

F. Ferrer; J. A. Grifols

2001-01-01

201

Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath  

E-print Network

We explore the consequences of Bose-Einstein condensation on two-scalar-exchange mediated forces among bodies that sit in a boson gas. We find that below the condensation temperature the range of the forces becomes infinite while it is finite at temperatures above condensation.

Ferrer, F

2001-01-01

202

Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath  

E-print Network

We explore the consequences of Bose-Einstein condensation on two-scalar-exchange mediated forces among bodies that sit in a boson gas. We find that below the condensation temperature the range of the forces becomes infinite while it is finite at temperatures above condensation.

F. Ferrer; J. A. Grifols

2000-01-18

203

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...

204

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

PubMed Central

Magnetic drug delivery has the potential to target therapy to specific regions in the body, improving efficacy and reducing side effects for treatment of cancer, stroke, infection, and other diseases. Using stationary external magnets, which attract the magnetic drug carriers, this treatment is limited to shallow targets (<5 cm below skin depth using the strongest possible, still safe, practical magnetic fields). We consider dynamic magnetic actuation and present initial results that show it is possible to vary magnets one against the other to focus carriers between them on average. The many remaining tasks for deep targeting in-vivo are then briefly noted. PMID:20165553

Shapiro, Benjamin

2010-01-01

205

Force analysis of magnetic bearings with power-saving controls  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

206

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

207

Many-body effects in magnetic inelastic electron tunneling spectroscopy  

NASA Astrophysics Data System (ADS)

Magnetic inelastic electron tunneling spectroscopy (IETS) shows sharp increases in conductance when a new conductance channel associated with a change in magnetic structure is open. Typically, the magnetic moment carried by an adsorbate can be changed by collision with a tunneling electron; in this process the spin of the electron can flip or not. A previous one-electron theory [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.103.176601 103, 176601 (2009)] successfully explained both the conductance thresholds and the magnitude of the conductance variation. The elastic spin flip of conduction electrons by a magnetic impurity leads to the well-known Kondo effect. In the present work, we compare the theoretical predictions for inelastic magnetic tunneling obtained with a one-electron approach and with a many-body theory including Kondo-like phenomena. We apply our theories to a singlet-triplet transition model system that contains most of the characteristics revealed in magnetic IETS. We use two self-consistent treatments (noncrossing approximation and self-consistent ladder approximation). We show that, although the one-electron limit is properly recovered, new intrinsic many-body features appear. In particular, sharp peaks appear close to the inelastic thresholds; these are not localized exactly at thresholds and could influence the determination of magnetic structures from IETS experiments. Analysis of the evolution with temperature reveals that these many-body features involve an energy scale different from that of the usual Kondo peaks. Indeed, the many-body features perdure at temperatures much larger than the one given by the Kondo energy scale of the system.

Korytár, Richard; Lorente, Nicolás; Gauyacq, Jean-Pierre

2012-03-01

208

Design and construction of a magnetic force microscope  

E-print Network

is vibrated near or at its resonant frequency by means of a piezoelectric-bimorph or a small piezoelectric plate. When this vibrating cantilever is brought sufficiently close to the sample (in the range of aforementioned attractive forces), its resonance... for different values of applied fields. Also it was proposed that the orientation of the tip can be controlled and coercivity can be obtained in situ by measuring the hysteresis loop. Magnetization reversal mechanisms in individual barium ferrite particles...

Khandekar, Sameer Sudhakar

2005-08-29

209

On the Independence of Magnetic and Electric Body Surface Recordings  

Microsoft Academic Search

Recent papers have shown that the ECG depends on the flow sources of the impressed field in the heart while the MCG is a function of its vortex source distribution. It has consequently been suggested that body surface electric and magnetic recordings yield completely independent information about the physiological generators. Such independence would be of enormous significance wherever present diagnostic

Stanley Rush

1975-01-01

210

LA-UR-97-40 Magnetic Resonance Force Microscopy With a  

E-print Network

LA-UR-97-40 Magnetic Resonance Force Microscopy With a Ferromagnetic Tip Mounted on the Force Resonance Force Microscope (MRFM) presents the oppor- tunity for a magnetic resonance imaging probe- tection of nuclear magnetic, electron-spin and ferromagnetic resonance (FMR) highlights its significant

Hammel, P. Chris

211

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy  

E-print Network

Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy B. J. Suh, P of microscopic ferromagnetic resonance FMR detected using the magnetic resonance force microscope MRFM of structural and magnetic properties of materials. The mag- netic resonance force microscope MRFM can

Hammel, P. Chris

212

The Magnetic-Resonance Force Microscope: A New Tool for High-Resolution, 3-D, Subsurface  

E-print Network

The Magnetic-Resonance Force Microscope: A New Tool for High-Resolution, 3-D, Subsurface Scanned, MELISSA M. MIDZOR, AND MICHAEL L. ROUKES Invited Paper The magnetic-resonance force microscope (MRFM of magnetic-resonance imaging with the high sensitivity and resolution of atomic-force microscopy

Hammel, P. Chris

213

Application of a novel rf coil design to the magnetic resonance force microscope  

E-print Network

Application of a novel rf coil design to the magnetic resonance force microscope Z. Zhang and P. C , and demonstrate its efficacy in the magnetic resonance force microscope MRFM . The rf field of the MAGC has of Physics. S0034-6748 96 02509-9 I. INTRODUCTION The magnetic resonance force microscope MRFM , based

Hammel, P. Chris

214

Analysis of the reduction of detent force in a permanent magnet linear synchronous motor  

Microsoft Academic Search

The problem in improving the positioning precision of a permanent magnet linear synchronous motor (LSM) is the large detent force caused by the permanent magnet. The detent force is thought to arise from the difference of the position of a permanent magnet end and a tooth position. If one detent force is independent from the other, we can reduce the

T. Yoshimura; H. J. Kim; M. Watada; S. Torii; D. Ebihara

1995-01-01

215

Logarithmic relaxation in the levitation force in a magnet-high TC superconductor system  

E-print Network

response of the levitation force between a permanent magnet and a bulk YBCO superconductor when subjected the permanent magnet with moment m is small, the force is given by' F=m*VBM, (1) where B, is the flux densityLogarithmic relaxation in the levitation force in a magnet-high TC superconductor system A. B

Johansen, Tom Henning

216

Dielectrophoresis-magnetophoresis force driven magnetic nanoparticle movement in transformer oil based magnetic fluids.  

PubMed

Magnetic fluid is a stable colloidal mixture contained magnetic nanoparticles coated with a surfactant. Recently, it was found that the fluid has properties to increase heat transfer and dielectric characteristics due to the added magnetic nanoparticles in transformer oils. The magnetic nanoparticles in the fluid experience an electrical force directed toward the place of maximum electric field strength when the electric field is applied. And when the external magnetic field is applied, the magnetic nanoparticles form long chains oriented along the direction of the field. The behaviors of magnetic nanoparticles in both the fields must play an important role in changing the heat transfer and dielectric characteristics of the fluids. In this study, we visualized the movement of magnetic nanoparticles influenced by both the fields applied in-situ. It was found that the magnetic nanoparticles travel in the region near the electrode by the electric field and form long chains along the field direction by the magnetic field. It can be inferred that the movement of magnetic nanoparticles appears by both the fields, and the breakdown voltage of transformer oil based magnetic fluids might be influenced according to the dispersion of magnetic nanoparticles. PMID:24205624

Lee, Jong-Chul; Lee, Sangyoup

2013-09-01

217

The two-dimensional three-body problem in a strong magnetic field is integrable  

E-print Network

The problem of $N$ particles interacting through pairwise central forces is notoriously intractable for $N\\geq3$. Some quite remarkable specific cases have been solved in one dimension, whereas higher-dimensional exactly solved systems involve velocity-dependent or many-body forces. Here we show that the guiding center approximation---valid for charges moving in two dimensions in a strong constant magnetic field---simplifies the three-body problem for an arbitrary interparticle interaction invariant under rotations and translations and makes it solvable by quadratures. This includes a broad variety of special cases, such as that of three particles interacting through arbitrary pairwise central potentials. A spinorial representation for the system is introduced, which allows a visualization of its phase space as the corresponding Bloch sphere as well as the identification of a Berry-Hannay rotational anholonomy. Finally, a brief discussion of the quantization of the problem is presented.

A. Botero; F. Leyvraz

2014-10-23

218

Bodies of Force: The Social Organization of Force, Suffering, and Honor in Policing  

E-print Network

as opposed to the community policing, victimology, orSWAT; gang Bike cops; community policing; task force; Streetcommunity or a stigmatized member has an affective dimension. A sociology of a world like policing

Lande, Brian Jacob

2010-01-01

219

Observation of ferromagnetic resonance in a microscopic sample using magnetic resonance force microscopy  

E-print Network

Observation of ferromagnetic resonance in a microscopic sample using magnetic resonance force can be measured. Employing magnetic resonance force microscopy MRFM we have observed a strong FMR the technologically important magnetic multilayer systems. MRFM, based on mechanical detection of magnetic resonance

Hammel, P. Chris

220

The Relation Between Magnetic Force and Crystal Structure of the Barium Ferrite  

Microsoft Academic Search

In this paper, a model is presented for calculating the maximum magnetic force of magnetic ceramics based on their crystalline structure. The results of the model for magnetic force of barium ferrite is compared with experimental values. In this comparison, the experimental values underestimate the theoretical results for various magnet cross sectional area. This difference is due to presence of

A. Hossienpour; A. Zakery; H. Sadeghi

2000-01-01

221

An Observer-Based Design for Cogging Forces Cancellation in Permanent Magnet Linear Motors  

E-print Network

An Observer-Based Design for Cogging Forces Cancellation in Permanent Magnet Linear Motors Jérémy magnet (PM) linear motors, in presence of spatially periodic forces, also known as cogging. Using, made up of permanent magnets, while ironcore motors feature only one magnetic track. The excess

Paris-Sud XI, Université de

222

Superconducting magnet with self-shield for whole body magnetic resonance imaging  

SciTech Connect

The authors of this paper developed a superconducting magnet with self-shield for whole body magnetic resonance imaging (MRI) that features a magnetic field strength of 0.5 T, 1.0 T, and 1.5 T, and has the following characteristics: Low leakage magnetic field due to the directly mounted magnetic shield; very small in the 0.5 mT range. Reduced helium consumption due to the use of a high adiabatic cryostat and refrigerator; does not need liquid nitrogen. Horizontal service port reduces overhead clearance requirements. Superior mechanical strength; can even be transported in the cooled state. Fitted with an emergency run down unit.

Shimada, Y.; Matsumoto, T.; Moritsu, K.; Takechi, M.; Watanabe, T. (Mitsubishi Electric Corp., Ako Works, 651 Tenwa, Ako 678-02 (JP))

1991-03-01

223

High Force Magnetic Levitation Using Magnetized Superconducting Bulks as a Field Source for Bearing Applications  

NASA Astrophysics Data System (ADS)

The ability of high temperature superconducting bulks to trap magnetic fields of several tesla allows them to generate very high levitation force. This paper reports the development of a bulk-bulk superconducting rotary bearing design which uses superconducting bulks on both the rotor and the stator. An evaluation is made of the effectiveness of pulsed fields for magnetizing bulks. Modeling of the bulks using the perfectly trapped flux model is also reported to assess the limits of the bearing design. The results demonstrate the feasibility of a (RE)BCO-MgB2 bulk bearing capable of force densities of the order of 100N/cm2. The design and construction of a unique system capable of magnetizing a 25 mm (RE)BCO bulk and measuring levitation force between this bulk and a coaxial MgB2 hollow cylinder is outlined.

Patel, A.; Giunchi, G.; Albisetti, A. Figini; Shi, Y.; Hopkins, S. C.; Palka, R.; Cardwell, D. A.; Glowacki, B. A.

224

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

225

Multiple magnetic gastrointestinal foreign bodies in a dog.  

PubMed

Case Description-A 3-year-old castrated male Yorkshire Terrier was referred because of a 3-day history of vomiting, hyporexia, and lethargy after suspected ingestion of magnetic desk toys. Multiple metallic gastric foreign bodies were visible on radiographic views obtained 24 hours previously by the referring veterinarian. Clinical Findings-On physical examination of the dog, findings included moderate dyspnea, signs of pain in the cranial portion of the abdomen, hypothermia, and tachycardia. Repeated radiography revealed moderate pleural effusion and the presence of several round metallic foreign bodies in a linear ring formation in the distal aspect of the esophagus and gastric cardia. Treatment and Outcome-Endoscopy was performed, at which time the dog became increasingly dyspneic, tachycardic, and hypotensive. Thoracocentesis was performed, and a large volume of septic exudate was removed from the left hemithorax. Exploratory surgery of the thoracic and abdominal cavities was performed, during which the magnetic foreign bodies were removed and esophageal and gastric perforations were debrided and closed. The dog died following acute cardiac arrest 48 hours after surgery. Clinical Relevance-Ingestion of multiple magnetic foreign bodies carries a high risk of gastrointestinal tract perforation, volvulus, and obstruction. Immediate surgical intervention is recommended in such cases and would have likely improved the outcome for the dog of this report. PMID:25671286

Garneau, Mark S; McCarthy, Robert J

2015-03-01

226

Gravito-magnetism of an extended celestial body  

NASA Astrophysics Data System (ADS)

Einstein's general relativity predicts that the intrinsic rotation of an astronomical body leads to a general-relativistic contribution to its gravitational field. One of the consequences of general relativity is the so called Lense-Thirring effect, which has been a subject of many theoretical and experimental investigations during the last decades. In this article the model of a rigidly rotating, homogeneous, oblate spheroid will be analyzed with respect to its gravito-magnetic properties beyond the Lense-Thirring contribution to its gravitational field. As a consequence, a scalar, gravito-magnetic potential containing all the information about the spheroid's gravito-magnetic field will be derived. Based upon these results, general-relativistic effects like the gravito-magnetic gyroscope precession and the so called G-clock effect in the vicinity of the rotating spheroid will be treated with post-Newtonian accuracy.

Panhans, Michel; Soffel, Michael H.

2014-12-01

227

Towards optimal softening in 3D N-body codes: I. Minimizing the force error  

E-print Network

In N-body simulations of collisionless stellar systems, the forces are softened to reduce the shot noise. Softening modifies gravity at r=|x-y| smaller than softening length epsilon and the softened forces are increasingly biased for ever larger epsilon. There is, thus, some optimum between reducing the fluctuations and introducing a bias. Here, analytical relations are derived for the amplitudes of the bias and the fluctuations in the limit of small epsilon and large N. It is shown that the fluctuations of the force are generated locally, in contrast to the variations of the potential, which originate from noise in the whole system. Based on the asymptotic relations and using numerical experiments, I study the dependence of the resulting force error on N, epsilon, and on the functional form by which Newtonian gravity is replaced. The Plummer softening, where each body is replaced by a Plummer sphere of scale radius epsilon, yields significantly larger force errors than do methods in which the bodies are replaced by density kernels of finite extent. I also give special kernels, which reduce the errors even further. These kernels largely compensate the errors made with too small inter-particle forces at rforces at r epsilon. Additionally, the possibilities of locally adapting epsilon and of using unequal weights for the bodies are investigated. These various techniques allow, without increasing N, to reduce the rms force error by a factor 2 compared to Plummer softening with constant epsilon. The results of this study are directly relevant to N-body simulations using direct summation techniques or the tree code. (abridged)

Walter Dehnen

2000-11-30

228

Magnetic evidence for a partially differentiated carbonaceous chondrite parent body  

PubMed Central

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

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

2011-01-01

229

Particle energization in a chaotic force-free magnetic field  

NASA Astrophysics Data System (ADS)

A force-free field (FFF) is believed to be a reasonable description of the solar corona and in general a good approximation for low-beta plasma. The equations describing the magnetic field of FFF is similar to the ABC fluid equations which has been demonstrated to be chaotic. This implies that charged particles will experience chaotic magnetic field in the corona. Here, we study particle energization in a time-dependent FFF using a test particle approach. An inductive electric field is introduced by turbulent motions of plasma parcels. We find efficient particle acceleration with power-law like particle energy spectra. The power-law indices depend on the amplitude of plasma parcel velocity field and the spatial scales of the magnetic field fluctuation. The spectra are similar for different particle species. This model provide a possible mechanism for seed population generation for particle acceleration by, e.g., CME-driven shocks. Generalization of our results to certain non-force-free-field (NFFF) is straightforward as the sum of two or multiple FFFs naturally yield NFFF.

Li, Xiaocan; Li, Gang; Dasgupta, Brahmananda

2015-04-01

230

Magnetic force microscopy reveals meta-stable magnetic domain states that prevent reliable absolute palaeointensity experiments  

NASA Astrophysics Data System (ADS)

Obtaining reliable estimates of the absolute palaeointensity of the Earth’s magnetic field is notoriously difficult. The heating of samples in most methods induces magnetic alteration—a process that is still poorly understood, but prevents obtaining correct field values. Here we show induced changes in magnetic domain state directly by imaging the domain configurations of titanomagnetite particles in samples that systematically fail to produce truthful estimates. Magnetic force microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. For a critical temperature (250?°C), we observe major changes: distinct, blocky domains before heating change into curvier, wavy domains thereafter. These structures appeared unstable over time: after 1-year of storage in a magnetic-field-free environment, the domain states evolved into a viscous remanent magnetization state. Our observations qualitatively explain reported underestimates from otherwise (technically) successful experiments and therefore have major implications for all palaeointensity methods involving heating.

de Groot, Lennart V.; Fabian, Karl; Bakelaar, Iman A.; Dekkers, Mark J.

2014-08-01

231

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

232

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

233

Investigation of the lateral magnetic force and stiffness between a high-T" superconductor and magnet of rectangular shapes  

E-print Network

Investigation of the lateral magnetic force and stiffness between a high-T" superconductor between a permanent magnet (PM) and a high-temperature superconductor (HTSC) is currently a subject to these issuesis to investigate various aspectsof the magnetic force acting betweena PM and a HTSC. While there has

Johansen, Tom Henning

234

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

Microsoft Academic Search

Different types of ferrites are employed in the form of thin films as magnetic coating on cantilevers for magnetic force microscopy (MFM) use. This is especially needed for cantilevers employed in high-frequency MFM (HF-MFM), where stray fields of hard disk recording heads are investigated. Our experiments show that we can operate HF-MFM successfully at carrier frequencies up 2GHz using such

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

2010-01-01

235

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

2008-07-01

236

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

PubMed

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. PMID:23149438

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

2012-12-14

237

The effect of power-law body forces on a thermally driven flow between concentric rotating spheres  

NASA Technical Reports Server (NTRS)

A numerical study is conducted to determine the effect of power-law body forces on a thermally-driven axisymmetric flow field confined between concentric co-rotating spheres. This study is motivated by Spacelab geophysical fluid-flow experiments, which use an electrostatic force on a dielectric fluid to simulate gravity; this force exhibits a (1/r)sup 5 distribution. Meridional velocity is found to increase when the electrostatic body force is imposed, relative to when the body force is uniform. Correlation among flow fields with uniform, inverse-square, and inverse-quintic force fields is obtained using a modified Grashof number.

Macaraeg, M. G.

1986-01-01

238

The effect of power law body forces on a thermally-driven flow between concentric rotating spheres  

NASA Technical Reports Server (NTRS)

A numerical study is conducted to determine the effect of power-law body forces on a thermally-driven axisymmetric flow field confined between concentric co-rotating spheres. This study is motivated by Spacelab geophysical fluid-flow experiments, which use an electrostatic force on a dielectric fluid to simulate gravity; this force exhibits a (1/r)sup 5 distribution. Meridional velocity is found to increase when the electrostatic body force is imposed, relative to when the body force is uniform. Correlation among flow fields with uniform, inverse-square, and inverse-quintic force fields is obtained using a modified Grashof number.

Macaraeg, M. G.

1985-01-01

239

Study on the Levitation and Restoring Force Characteristics of the Improved HTS-permanent Magnet Hybrid Magnetic Bearing  

NASA Astrophysics Data System (ADS)

We have developed the hybrid magnetic bearing using permanent magnets and high temperature bulk super conductor (HTS). In this system, the permanent magnet has ring type structure so that the permanent magnet and the HTS can be set to the stator. The pinning force of the HTS is used for the levitation and the guidance. Repulsive force of the permanent magnets was used in the conventional hybrid system. However the restoring force in the guidance direction of the conventional hybrid system decreases by the side slip force of the permanent magnets. In this research, attractive force of permanent magnets is used for increasing the load weight in the guidance direction. In this paper, influence of the hybrid system on the static characteristics of the rotor is studied. Three-dimensional numerical analysis of the linkage flux (in the levitation and the guidance direction) in the HTS is undertaken. The stator side permanent magnet increases the linkage flux of the levitation direction. Therefore in the hybrid system the linkage flux of the levitation direction increases. The levitation and restoring force of the rotor is measured. The levitation force of the hybrid system becomes smaller than that of the non-hybrid one by attractive force. The rotor in the hybrid system is supported by the pinning force and attractive force. The restoring force of the hybrid system becomes larger than that of the non-hybrid one because of increasing the linkage flux of the levitation direction.

Sugiyama, R.; Oguni, K.; Ohashi, S.

240

Insulating helium flow tubes for force-cooled magnets  

SciTech Connect

This paper describes an insulating helium flow tube which has been designed, built and tested for the Westinghouse LCP magnet. Design and testing of flow tube is described and illustrated with typical mechanical and electrical properties for Polygon fiberglass tube itemized. A cross section of helium tube fitting is shown in diagram. Results of testing indicate that the woven fiberglass reinforced tube and special ferrule constructon appear to satisfy all of the design requirements for the Westinghouse LCP coil and offer an attractive insulating tube for other forced-flow application.

Blaughter, R.D.

1982-01-01

241

Resonantly detecting axion-mediated forces with nuclear magnetic resonance.  

PubMed

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 10(9) and 10(12) GeV or axion masses between 10(-6) and 10(-3) eV, independent of the cosmic axion abundance. PMID:25361250

Arvanitaki, Asimina; Geraci, Andrew A

2014-10-17

242

Resonant detection of axion mediated forces with Nuclear Magnetic Resonance  

E-print Network

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 10^9 and 10^12 GeV or axion masses between 10^-6 and 10^-3 eV, independent of the cosmic axion abundance.

Asimina Arvanitaki; Andrew A. Geraci

2014-03-05

243

Resonantly Detecting Axion-Mediated Forces with Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

We describe a method based on precision magnetometry that can extend the search for axion-mediated spin-dependent forces by several orders of magnitude. By combining techniques used in nuclear magnetic resonance and short-distance tests of gravity, our approach can substantially improve upon current experimental limits set by astrophysics, and probe deep into the theoretically interesting regime for the Peccei-Quinn (PQ) axion. Our method is sensitive to PQ axion decay constants between 109 and 1012 GeV or axion masses between 10-6 and 10-3 eV, independent of the cosmic axion abundance.

Arvanitaki, Asimina; Geraci, Andrew A.

2014-10-01

244

Variable force, eddy-current or magnetic damper  

NASA Technical Reports Server (NTRS)

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

Cunningham, R. E. (inventor)

1985-01-01

245

Influence of the Reynolds number on normal forces of slender bodies of revolution  

NASA Technical Reports Server (NTRS)

Comprehensive force, moment, and pressure distribution measurements as well as flow visualization experiments were carried out to determine the influence of the Reynolds number on nonlinear normal forces of slender bodies of revolution. Experiments were performed in transonic wind tunnels at angles of attack up to 90 deg in the Mach number range 0.5 to 2.2 at variable Reynolds numbers. The results were analysed theoretically and an empirical theory was developed which describes the test results satisfactory.

Hartmann, K.

1982-01-01

246

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

Microsoft Academic Search

A magnetic force microscopy based study on the formation of stripe domains in Permalloy (Ni80Fe20) thin films is presented. Our results show that the critical thickness for stripe domain initiation depended on the sputtering rate, the substrate temperature, and the film thickness. Beyond the stripe domain formation, an increase of the period of a highly ordered array of stripe domains

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

2008-01-01

247

End effect on magnetic damping force of superconducting inductive magnetic levitation system  

Microsoft Academic Search

The magnetic damping force for the vertical motion of superconducting inductive levitation system is analyzed. The ground coil current induced by the vertical motion of vehicular coil generally takes a maximum value after the first vehicular coil has passed over the ground coil. At 500 km\\/h, for instance, this current takes the maximum value around when the second vehicular coil

Yoshifumi Amemiya; Shigeru Ohkuma

1977-01-01

248

An acoustic model for a permanent magnet machine: modal shapes and magnetic forces  

Microsoft Academic Search

A modal analysis concept for calculating the vibrational level of an electrical machine stator is presented. Using this concept, the designer is freed from calculating real magnet forces, which is normally difficult and inaccurate. Only flux linkages have to be calculated which can be easily done using finite element methods and the vector potential as the unknown function. Furthermore, the

D. Verdyck; R. Belmans; W. Geysen

1992-01-01

249

Drag measurements on a laminar-flow body of revolution in the 13-inch magnetic suspension and balance system  

NASA Technical Reports Server (NTRS)

Low speed wind tunnel drag force measurements were taken on a laminar flow body of revolution free of support interference. This body was tested at zero incidence in the NASA Langley 13 in. Magnetic Suspension and Balance System (MSBS). The primary objective of these tests was to substantiate the drag force measuring capabilities of the 13 in. MSBS. The drag force calibrations and wind-on repeatability data provide a means of assessing these capabilities. Additional investigations include: (1) the effects of fixing transition; (2) the effects of fins installed in the tail; and (3) surface flow visualization using both liquid crystals and oil flow. Also two simple drag prediction codes were used to assess their usefulness in estimating overall body drag.

Dress, David A.

1989-01-01

250

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

251

Analysis of the magnetic force and the torque in a brushless DC motor  

Microsoft Academic Search

As permanent-magnet motors and generators produce torque, vibration occurs through the small air gap due to the alternating\\u000a magnetic forces created by the rotating permanent magnets and the current switching of the coils. The magnetic force can be\\u000a calculated from the flux density by finite element methods and the Maxwell stress tensor in cylindrical coordinates. The transition\\u000a of the magnetic

Gunhee Jang; Dennis K. Lieu

1996-01-01

252

The Magnetic Resonance Force Microscope P. Chris Hammel and Denis V. Pelekhov  

E-print Network

The Magnetic Resonance Force Microscope P. Chris Hammel and Denis V. Pelekhov Ohio State University of Magnetic Resonance 10 5 Applications 16 6 Conclusions 24 Acknowledgments 24 References 24 1 INTRODUCTION The emerging technique of magnetic resonance force microscopy (MRFM) (Sidles, 1991) was conceived by Sidles

Hammel, P. Chris

253

Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance force microscopy  

E-print Network

Sensitivity and spatial resolution for electron-spin-resonance detection by magnetic resonance The signal intensity of electron spin resonance in magnetic resonance force microscopy MRFM experiments that magnetic resonance force microscopy MRFM is a new 3D imaging technique8,9 with the potential of achieving

Hammel, P. Chris

254

Cogging Force Minimization in a Permanent Magnet Linear Generator for Sea Wave Energy Extraction Applications  

Microsoft Academic Search

This paper analyses the stator teeth geometry effects on cogging force of permanent magnet linear generators. The method making translator adjacent sides' permanent magnet allotropic is proposed to minimize the cogging force of four sided permanent magnet linear generators. The dynamic modeling of the generator's performance is based on finite element method. The generator is coupled to a particular mechanical

Dan Li; Baodong Bai; Qing Yu; Dezhi Chen

2009-01-01

255

How Can Magnetic Forces Do Work? Investigating the Problem with Students  

ERIC Educational Resources Information Center

We present a sequence of activities aimed at promoting both learning about magnetic forces and students' reflection about the conceptual bridge between magnetic forces on a moving charge and on a current-carrying wire in a magnetic field. The activity sequence, designed for students in high school or on introductory physics courses, has been…

Onorato, Pasquale; De Ambrosis, Anna

2013-01-01

256

Lateral force on a magnet placed above a planar YBanCusO, superconductor  

E-print Network

Lateral force on a magnet placed above a planar YBanCusO, superconductor T. H. Johansen, Z. J. Yang) The lateral force interaction betweena permanentbar magnet and a large slab of high T, superconductor has equilibrium. The levitation of a permanent magnet above a super- disk of YBa$usO, is placed on a block

Johansen, Tom Henning

257

Motion Control of Linear Permanent Magnet Motors with Force Ripple Compensation  

Microsoft Academic Search

The main problem in improving the tracking perfor- mance of linear permanent magnet motors is the presence of force ripple caused by the irregular magnetic field of the permanent magnets and inaccuracy in electronic com- mutation by the servo amplifier. In this paper a motion controller with force ripple compensation is presented. A physical model of the linear motor and

Christof Rohrig; Andreas Jochheim

258

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

2013-12-01

259

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

PubMed Central

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

2013-01-01

260

Magnetic force microscopy measurements in external magnetic fields-comparison between coated probes and an iron filled carbon nanotube probe  

Microsoft Academic Search

We performed magnetic force microscopy (MFM) measurements in external magnetic fields parallel to the sample plane to qualitatively study their effect on the magnetization of different kinds of MFM probes. As a test structure we used an array of rectangular ferromagnetic thin film elements aligned with the external magnetic field direction. MFM images were taken while the field was increased

F. Wolny; T. Mühl; U. Weissker; A. Leonhardt; U. Wolff; D. Givord; B. Büchner

2010-01-01

261

Analysis of the magnetic field and force of LSM with permanent magnet Halbach array and ironless coil  

Microsoft Academic Search

The LSM, or linear synchronous motor, with permanent magnet Halbach array and ironless coil possesses the dominant advantages of direct linear movement and being energy-saving. To analytically investigate the characteristics of this innovative LSM, its magnetic field and magnetic force are analyzed in this work. Based on the magnetic field of a single surface current, the field of a single

Xiao Zhang; Yungang Li; Hengkun Liu

2011-01-01

262

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

263

Investigation of magneto-mechanical properties of Galfenol for coil-less magnetic force control using inverse magnetostrictive effect  

Microsoft Academic Search

We have been proposing a magnetic force control method using the inverse magnetostrictive effect of magnetostrictive materials. With a parallel magnetic circuit consisting of iron yokes and permanent magnet, the magnetic force exerting on the yoke can be varied by the mechanical stress applied to the magnetostrictive material. The characteristics of the magnetic force, such as stress-sensitivity and range of

Toshiyuki Ueno; Eric Summers; Thomas Lograsso; Toshiro Higuchi

2005-01-01

264

The explosion of chiral many-body forces: How to deal with it?  

NASA Astrophysics Data System (ADS)

During the past two decades, it has been demonstrated that chiral effective field theory represents a powerful tool to deal with nuclear forces in a systematic and model- independent way. Two-, three-, and four-nucleon forces have been derived up to next-to-next-to- next-to-leading order (N3LO) and (partially) applied in nuclear few- and many-body systems– with, in general, a good deal of success. But in spite of these achievements, we are still faced with some great challenges. Among them is the problem of a proper renormalization of the two- nucleon potential. Another issue are the subleading many-body forces, where the "explosion" of the number of terms with increasing order and the order-by-order convergence are reasons for concern. In this talk, I will mainly focus on the latter topic.

Machleidt, R.

2015-02-01

265

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

266

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

PubMed

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

Chen, Youping

2006-02-01

267

Examining the Magnetic Properties of LaCoO3 Thin Films Using Magnetic Force Microscopy  

NASA Astrophysics Data System (ADS)

In contrast to the non-magnetic ground state of bulk LaCoO3 (LCO) at low temperatures, ferromagnetism has been observed in elastically strained thin film specimens. The origins of ferromagnetism in strained LCO thin films have been obscured by conflicting experimental results. Pulsed laser deposition (PLD) is the current standard of preparation techniques used to grow thin films of LCO, but results from thin film LCO samples prepared by PLD have been questioned on the basis of chemical inhomogeneity and film defects. Using magnetic force microscopy, we investigate the microscale magnetic properties of strained thin films of LCO prepared by molecular beam epitaxy and deposited on lanthanum aluminate and strontium titanate substrates. We observe these properties across a temperature range surrounding the Curie temperature (Tc˜ 80K) and compare our results to global magnetic characteristics of these films as measured by a SQUID magnetometer.

Berg, Morgann; Posadas, Agham; de Lozanne, Alex; Demkov, Alexander

2011-03-01

268

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

NASA Astrophysics Data System (ADS)

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

Chen, Mao-Wei; Sun, Mao

2014-08-01

269

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

270

Revealing bending and force in a soft body through a plant root inspired approach  

PubMed Central

An emerging challenge in soft robotics research is to reveal mechanical solicitations in a soft body. Nature provides amazing clues to develop unconventional components that are capable of compliant interactions with the environment and living beings, avoiding mechanical and algorithmic complexity of robotic design. We inspire from plant-root mechanoperception and develop a strategy able to reveal bending and applied force in a soft body with only two sensing elements of the same kind, and a null computational effort. The stretching processes that lead to opposite tissue deformations on the two sides of the root wall are emulated with two tactile sensing elements, made of soft and stretchable materials, which conform to reversible changes in the shape of the body they are built in and follow its deformations. Comparing the two sensory responses, we can discriminate the concave and the convex side of the bent body. Hence, we propose a new strategy to reveal in a soft body the maximum bending angle (or the maximum deflection) and the externally applied force according to the body's mechanical configuration. PMID:25739743

Lucarotti, Chiara; Totaro, Massimo; Sadeghi, Ali; Mazzolai, Barbara; Beccai, Lucia

2015-01-01

271

Revealing bending and force in a soft body through a plant root inspired approach  

NASA Astrophysics Data System (ADS)

An emerging challenge in soft robotics research is to reveal mechanical solicitations in a soft body. Nature provides amazing clues to develop unconventional components that are capable of compliant interactions with the environment and living beings, avoiding mechanical and algorithmic complexity of robotic design. We inspire from plant-root mechanoperception and develop a strategy able to reveal bending and applied force in a soft body with only two sensing elements of the same kind, and a null computational effort. The stretching processes that lead to opposite tissue deformations on the two sides of the root wall are emulated with two tactile sensing elements, made of soft and stretchable materials, which conform to reversible changes in the shape of the body they are built in and follow its deformations. Comparing the two sensory responses, we can discriminate the concave and the convex side of the bent body. Hence, we propose a new strategy to reveal in a soft body the maximum bending angle (or the maximum deflection) and the externally applied force according to the body's mechanical configuration.

Lucarotti, Chiara; Totaro, Massimo; Sadeghi, Ali; Mazzolai, Barbara; Beccai, Lucia

2015-03-01

272

Revealing bending and force in a soft body through a plant root inspired approach.  

PubMed

An emerging challenge in soft robotics research is to reveal mechanical solicitations in a soft body. Nature provides amazing clues to develop unconventional components that are capable of compliant interactions with the environment and living beings, avoiding mechanical and algorithmic complexity of robotic design. We inspire from plant-root mechanoperception and develop a strategy able to reveal bending and applied force in a soft body with only two sensing elements of the same kind, and a null computational effort. The stretching processes that lead to opposite tissue deformations on the two sides of the root wall are emulated with two tactile sensing elements, made of soft and stretchable materials, which conform to reversible changes in the shape of the body they are built in and follow its deformations. Comparing the two sensory responses, we can discriminate the concave and the convex side of the bent body. Hence, we propose a new strategy to reveal in a soft body the maximum bending angle (or the maximum deflection) and the externally applied force according to the body's mechanical configuration. PMID:25739743

Lucarotti, Chiara; Totaro, Massimo; Sadeghi, Ali; Mazzolai, Barbara; Beccai, Lucia

2015-01-01

273

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

274

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

275

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

Microsoft Academic Search

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

S. Ohashi; S. Kobayashi

2009-01-01

276

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

277

Distribution of resistive body-force in curved free-surface flow  

NASA Technical Reports Server (NTRS)

The customary procedure for including resistive effects in turbulent hydraulic and stratified atmospheric flows is to integrate the empirically-known boundary shears over the entire wetted boundary of a thin fluid slab. A resistive body-force is then assumed to exist everywhere in each slab to replace the boundary shearing force. For the classical Saint-Venant (1871) model, this body-force can be shown to have a constant distribution in the vertical direction, and therefore can be evaluated for use in the momentum differential equation. In the newer Dressler theory (1978), however, for unsteady flow over curved beds, it is proved here that a constant body-force distribution is not possible. Its variable distribution is determined as well as its magnitude for use in the curved-flow equations. This variable distribution acts to produce an equal resultant in every thin layer of fluid parallel to the bed in an angular wedge over the curved channel bed. The new curved-flow equations are therefore extended to include resistive effects.

Sivakumaran, N. S.; Dressler, R. F.

1986-01-01

278

The "Newton Challenge": Properties of Forced Magnetic Reconnection  

NASA Astrophysics Data System (ADS)

Inspired by the observations of thin (ion-scale) current sheets at important magnetospheric boundaries, the study of the properties of thin current sheets has become very popular in recent years. Most of these investigations, however, have ignored the question of how the sheets are formed. Instead, usually a simple Harris-type current sheet is postulated at the outset, and the resulting behavior is then determined. Recently, a collaborative effort, dubbed the "Newton Challenge" and involving J. Birn, K. Galsgaard, M. Hesse, M. Hoshino, J. Huba, G. Lapenta, P.~L. Pritchett, K. Schindler, L. Yin, J. Büchner, T. Neukirch, and E.~R. Priest, was begun to investigate the transition from thicker to thin current sheets that can occur as a result of magnetopause deformations imposed by the solar wind. A standard 2-D model problem in which current sheet thinning was forced by imposing a finite deformation of the field above and below the current sheet was studied by a variety of physical models ranging from resistive MHD to fully kinetic particle models. The aim was to determine whether differences would arise between the fluid and kinetic treatments that might affect the onset of magnetic reconnection. The initial results indicate that full-particle, hybrid, and Hall-MHD models lead to fast reconnection and similar final states despite differences in energy transfer and dissipation. Resistive MHD simulations show reduced reconnection rates that depend on the magnitude of the resistivity. These results will be reviewed, and additional features of forced reconnection, including continuous forcing, open boundaries, the presence of a normal field component, and 3-D effects, will be discussed.

Pritchett, P. L.

2005-05-01

279

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

SciTech Connect

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 allows the current density to be less than the critical value. The theoretical results show an exponential relationship between the force and the distance. Analytical expressions are developed for permanent magnets in the form of a point dipole, a tip of a magnetic force microscope, and a cylindrical magnet. In the latter case, the exponential relationship has been observed in numerous experiments but without previous interpretation.

Yang, Z.J.

1997-08-01

280

Flow and Force Equations for a Body Revolving in a Fluid  

NASA Technical Reports Server (NTRS)

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

Zahm, A F

1930-01-01

281

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

NASA Astrophysics Data System (ADS)

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

Kim, Dong Ki; Lee, Jeong Tae

282

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

NASA Astrophysics Data System (ADS)

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

Wright, Sarah; Hickman, Steven; Marohn, John

2008-03-01

283

A preliminary investigation of the dynamic force-calibration of a magnetic suspension and balance system  

NASA Technical Reports Server (NTRS)

The aerodynamic forces and moments acting upon a magnetically suspended wind tunnel model are derived from calibrations of suspension electro magnet currents against known forces. As an alternative to the conventional calibration method of applying steady forces to the model, early experiences with dynamic calibration are outlined, that is a calibration obtained by oscillating a model in suspension and deriving a force/current relationship from its inertia force and the unsteady components of currents. Advantages of dynamic calibration are speed and simplicity. The two methods of calibration applied to one force component show good agreement.

Goodyer, M. J.

1985-01-01

284

Test bodies and naked singularities: is the self-force the cosmic censor?  

PubMed

Jacobson and Sotiriou showed that rotating black holes could be spun up past the extremal limit by the capture of nonspinning test bodies, if one neglects radiative and self-force effects. This would represent a violation of the cosmic censorship conjecture in four-dimensional, asymptotically flat spacetimes. We show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities. PMID:21231640

Barausse, Enrico; Cardoso, Vitor; Khanna, Gaurav

2010-12-31

285

Numerical Pattern Formation on Magnetothermal Convection of Diamagnetic Liquids in a Cylindrical Vessel of Rayleigh–Benard Model: Effects of Axisymmetric Horizontal Magnetic Forces on Vertical Magnetic Forces  

NASA Astrophysics Data System (ADS)

We carried out three-dimensional computations of the magnetothermal convection of diamagnetic liquids (e.g., water) in a shallow cylindrical vessel of the Rayleigh–Benard model to investigate the effects of the radial components of the magnetic force (MFR) and the vertical components of the magnetic force (MFZ) on heat transfer and pattern formation. For the purpose of examining various magnitudes of radial and vertical components of the magnetic force, we used a 1800-turn coil instead of an actual conventional magnet, and a 2-turn coil as a new proposal. In the computation, the Prandtl number was constant at 6.0 (i.e., water at room temperature), and the Rayleigh number was 1.0 × 104. As a result, an axisymmetric pattern and a spokelike pattern appeared in the convection. Subsequently, we arranged all the results with a new parameter, which is the absolute ratio of the radial component of magnetic force at the vessel sidewall to the vertical resultant force at the vessel center. This parameter represents the relative contribution of MFR to the vertical resultant force (RFZ). The RFZ is the sum of the gravitational force and MFZ, and is associated with the magnetic Rayleigh number. By using this parameter, the spoke pattern convection appeared when the parameter was within 0.11 to 0.85. This result suggests that not only the MFR but also the MFZ plays an important role in determining whether the convection flow pattern transited to the axisymmetric flow or not. This parameter range is easily satisfied in a conventional superconducting magnet. We can say that the spoke pattern convection may be a common phenomenon in the magnet. On the other hand, the flow pattern had little effect on the heat transfer in convection. Thus, the effects of MFR and MFZ on the pattern formation in the magnet are much more complicated than those previously considered.

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

2014-07-01

286

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

SciTech Connect

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

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

2013-11-15

287

Does Using a Visual-Representation Tool Foster Students' Ability to Identify Forces and Construct Free-Body Diagrams?  

ERIC Educational Resources Information Center

Earlier research has shown that after physics instruction, many students have difficulties with the force concept, and with constructing free-body diagrams (FBDs). It has been suggested that treating forces as interactions could help students to identify forces as well as to construct the correct FBDs. While there is evidence that identifying…

Savinainen, Antti; Makynen, Asko; Nieminen, Pasi; Viiri, Jouni

2013-01-01

288

Role of external magnetic field and current closure in the force balance mechanism of a magnetically stabilized plasma torch  

NASA Astrophysics Data System (ADS)

Experimental investigations on the role of applied external magnetic field and return current closure in the force balance mechanism of a plasma torch are reported. The plasma torch is of low power and has wall, gas and magnetic stabilization mechanisms incorporated in it. Gas flow is divided into two parts: axial-central and peripheral-shroud, applied magnetic field is axial and return current is co-axial. Results indicate that application of large external magnetic field gives rise to not only J x B force but also, coupled with gas flow, to a new drag-cum-centrifugal force that acts on the plasma arc root and column. The magnetic field also plays a role in the return current closure dynamics and thus in the overall force balance mechanism. This in turn affects the electro-thermal efficiency of the plasma torch. Detailed experimental results, analytical calculations and physical model representing the processes will be presented and discussed.

G, Ravi; Goyal, Vidhi

2012-10-01

289

Strength of reduced two-body spin-orbit interaction from chiral three-nucleon force  

E-print Network

The contribution of a chiral three-nucleon force to the strength of an effective spin-orbit coupling is estimated. We first construct a reduced two-body interaction by folding one-nucleon degrees of freedom of the three-nucleon force in nuclear matter. The spin-orbit strength is evaluated by a Scheerbaum factor obtained by the $G$-matrix calculation in nuclear matter with the two-nucleon interaction plus the reduced two-nucleon interaction. The problem of the insufficiency of modern realistic two-nucleon interactions to account for the empirical spin-orbit strength is resolved. It is also indicated that the spin-orbit coupling is weaker in the neutron-rich environment. Because the spin-orbit component from the three-nucleon force is determined by the low-energy constants fixed in the two-nucleon sector, there is little uncertainty in the present estimation.

M. Kohno

2012-09-23

290

Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths  

E-print Network

We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems, and compute Gamow-Teller transitions in carbon-14, oxygen-22 and oxygen-24 using consistent two-body currents. We compute spectra of the daughter nuclei nitrogen-14, fluorine-22 and fluorine-24 via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q^2 ~ 0.84-0.92 of the axial-vector coupling. The half life of carbon-14 depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current.

A. Ekström; G. R. Jansen; K. A. Wendt; G. Hagen; T. Papenbrock; S. Bacca; B. Carlsson; D. Gazit

2014-06-18

291

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

E-print Network

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy Keir C Neuman1 & Attila Nagy2 Single-molecule force spectroscopy has emerged as a powerful tool and displacement generated by single molecules ranging from cells to proteins. Although there is an ever

Ritort, Felix

292

Forces and torques produced by a 640-gauss permanent magnet of ferromagnetic objects.  

PubMed

Magnetic forces and torques were measured in a 640-G permanent magnet. The forces on external objects were directed in such a way and of such a strength that the likelihood of injury from unsupported ferromagnetic objects was very small. The forces and torques on ferromagnetic objects within the subject were comparable to those produced by gravitational and inertial efforts in daily living. PMID:10171183

Sheldon, P; Kaufman, L; Carlson, J

1991-11-01

293

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

294

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

295

Relations Between Lower Body Isometric Muscle Force Characteristics and Start Performance in Elite Male Sprint Swimmers  

PubMed Central

The aim of the present study was twofold. The first aim was to examine the influence of absolute and relative lower body muscle force on kinematic component which determine the start performance. The second aim was to create multiregressional model which could use as a tool for swimming coaches with the purpose to start performance control and improvement. Twenty seven high-level trained male competitive swimmers all members of the Serbian National Youth and Senior Swimming Team (Age = 21.1 ± 4.3 yrs., Height = 1. 89 ± 0.10 m, Weight = 81.6 ± 8.4 kg, 50m freestyle - long course = 24.36 ± 0.86 s) performed two trials of standing leg extensors isometric muscle force testing and three swimming start trials corresponding to 10m distance. The average start time significantly correlated with variables of leg extensors maximum voluntary force (Fmax, r = -0.559, p = 0.002), leg extensors relative muscle voluntary force (Frel, r = -0.727, p < 0.001), leg extensors specific rate of force development (RFD50%, r = -0.338, p = 0.047) and leg extensors relative value of specific rate of force development (RFD50%rel, r = -0.402, p = 0.040). Regression equation for t10m prediction was defined by following variables: maximum voluntary isometric force of leg extensors muscles at absolute and relative level (Fmax and Frel), as well as a specific rate of force development of the same muscle groups (RFD50% and RFD50%rel) at absolute and relative level too with 74.4% of explained variance. Contractile abilities indicators of the leg extensors muscles included consideration: Fmax, RFD50%, Frel and RFD50%rel showed significant correlation with swimming start times on 10m. Additionally, the results suggest that swimmers, who possess greater isometric maximum force and specific rate of force development at absolute and relative levels, tend to be able to swim faster on initial 10m swim start perforamnce. Key Points In high-level male swimmers: Leg extensors maximum voluntary force, leg exten-sors relative value of maximum muscle voluntary force, leg extensors specific rate of force develop-ment and leg extensors relative value of specific rate of force development positively associated with the start time measured on 10m-mark. Time at 10m-mark was not associated with legs ex-tensors basic level of rate of force development at absolute and relative level. Obtained multi-regressional model is defined by variables which measure the development of maxi-mum voluntary isometric leg extensor muscle force on the absolute and relative level, as well as vari-ables which measure the development of specific explosive force of the same muscle group on abso-lute and relative level, this could use as a tool for swimming coaches to control the direction and ex-tent of development of a given force characteristics for providing conditions for start improvement in highly trained elite male sprint swimmers. PMID:24421722

Bereti?, Igor; ?urovi?, Marko; Oki?i?, Tomislav; DOPSAJ, Milivoj

2013-01-01

296

GravitoMagnetic force in modified Newtonian dynamics  

SciTech Connect

We introduce the Gauge Vector-Tensor (GVT) theory by extending the AQUAL's approach to the GravitoElectroMagnetism (GEM) approximation of gravity. GVT is a generally covariant theory of gravity composed of a pseudo Riemannian metric and two U(1) gauge connections that reproduces MOND in the limit of very weak gravitational fields while remains consistent with the Einstein-Hilbert gravity in the limit of strong and Newtonian gravitational fields. GVT also provides a simple framework to study the GEM approximation to gravity. We illustrate that the gravitomagnetic force at the edge of a galaxy can be in accord with either GVT or ?CDM but not both. We also study the physics of the GVT theory around the gravitational saddle point of the Sun and Jupiter system. We notice that the conclusive refusal of the GVT theory demands measuring either both of the gravitoelectric and gravitomagnetic fields inside the Sun-Jupiter MOND window, or the gravitoelectric field inside two different solar GVT MOND windows. The GVT theory, however, will be favored by observing an anomaly in the gravitoelectric field inside a single MOND window.

Exirifard, Qasem, E-mail: exir@theory.ipm.ac.ir [Institute for Research in Fundamental Sciences (IPM), Tehran (Iran, Islamic Republic of)

2013-08-01

297

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

SciTech Connect

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

Bouillard, J.X.

1992-12-01

298

Three-dimensional cell body shape dictates the onset of traction force generation and growth of focal adhesions  

PubMed Central

Cell shape affects proliferation and differentiation, which are processes known to depend on integrin-based focal adhesion (FA) signaling. Because shape results from force balance and FAs are mechanosensitive complexes transmitting tension from the cell structure to its mechanical environment, we investigated the interplay between 3D cell shape, traction forces generated through the cell body, and FA growth during early spreading. Combining measurements of cell-scale normal traction forces with FA monitoring, we show that the cell body contact angle controls the onset of force generation and, subsequently, the initiation of FA growth at the leading edge of the lamella. This suggests that, when the cell body switches from convex to concave, tension in the apical cortex is transmitted to the lamella where force-sensitive FAs start to grow. Along this line, increasing the stiffness resisting cell body contraction led to a decrease of the lag time between force generation and FA growth, indicating mechanical continuity of the cell structure and force transmission from the cell body to the leading edge. Remarkably, the overall normal force per unit area of FA increased with stiffness, and its values were similar to those reported for local tangential forces acting on individual FAs. These results reveal how the 3D cell shape feeds back on its internal organization and how it may control cell fate through FA-based signaling. PMID:25157134

Fouchard, Jonathan; Bimbard, Célian; Bufi, Nathalie; Durand-Smet, Pauline; Proag, Amsha; Richert, Alain; Cardoso, Olivier; Asnacios, Atef

2014-01-01

299

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

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

300

DYNAMIC FE MODEL OF SITTING MAN ADJUSTABLE TO BODY HEIGHT, BODY MASS AND POSTURE USED FOR CALCULATING INTERNAL FORCES IN THE LUMBAR VERTEBRAL DISKS  

Microsoft Academic Search

Long-term whole-body vibrations can cause degeneration of the lumbar spine. Therefore existing degeneration has to be assessed as well as industrial working places to prevent further damage. Hence, the mechanical stress in the lumbar spine—especially in the three lower vertebrae—has to be known. This stress can be expressed as internal forces. These internal forces cannot be evaluated experimentally, because force

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

1998-01-01

301

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

302

Rigid-body rotation of an electron cloud in divergent magnetic fields A. Fruchtman,1  

E-print Network

Rigid-body rotation of an electron cloud in divergent magnetic fields A. Fruchtman,1 R. Gueroult,2 of the equipotential surface with respect to the magnetic surfaces may have focusing effect on ion beams.13 annular Hall thruster. Thus, while there are many magnetic field effects such as magnetic mirroring

303

Phase combination for self-cancellation of magnetic force in undulators  

NASA Astrophysics Data System (ADS)

A simple arrangement of undulator magnets having nearly zero magnetic force between the upper and lower magnet arrays is proposed, which significantly simplifies the mechanical structure of undulators. In this arrangement, each magnet array is divided into a number of sections, half of which are phase-shifted according to a particular rule without breaking the periodic condition required for the undulator field. Calculation results show that, when the gap over period is in practical range, more than or equal to 1 /18 , the magnetic force can be reduced down to less than 1 /50 of that in the Halbach undulator by applying the proposed scheme.

Kinjo, Ryota; Tanaka, Takashi

2014-12-01

304

Pull-in control due to Casimir forces using external magnetic fields  

E-print Network

We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.

R. Esquivel-Sirvent; M. A. Palomino-Ovando; G. H. Cocoletzi

2009-07-13

305

Inversion of magnetic forces between microparticles and its effect on the magnetorheology of extremely bidisperse magnetic fluids  

E-print Network

1 Inversion of magnetic forces between microparticles and its effect on the magnetorheology are in contact and aligned in the field direction. This is the basic phenomenon underlying the magnetorheological

Paris-Sud XI, Université de

306

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

PubMed Central

Objective The purpose of this study was to investigate the body surface electromagnetic field (EMF) changes using a sensitive magnetometer before and after a specific Toftness chiropractic adjustment in asymptomatic human subjects. Method Forty-four subjects were randomly assigned into control (20 subjects) and experimental groups (24 subjects) in a pre and post-test design. The Triaxial Fluxgate Magnetometer FGM-5DTAA (Walker Scientific, Worcester, Massachusetts) with five digit display and resolution of 1 nanotesla (nT) was used for EMF detection. The EMF in the research room and on the adjustment table was monitored and recorded. The subjects’ body surface (cervical, thoracic, lumbar and sacral areas) EMF was determined in the prone position before and after the chiropractic adjustment. A low force Toftness chiropractic adjustment was applied to the cervical, thoracic, lumbar and sacral areas as determined by the practitioner. Results The EMF in the research room was recorded as 41611 nT at the Z axis (earth field), 13761 nT at the X axis and 7438 nT at the Y axis. The EMF on the adjusting table changed minimally during the 15 minute observation period. The EMF on the subjects’ body surface decreased at 4 spinal locations after chiropractic adjustment. The EMF (mean ± SD in nT) decreased significantly at the cervical region from 42449 ± 907 to 41643 ± 1165 (p < 0.01) and at the sacral regions from 43206 ± 760 to 42713 ± 552 (p < 0.01). The EMF at the lumbar and thoracic regions decreased but did not reach a statistically significant level. No significant changes of the body surface EMF were found in the control group. Conclusion A low force Toftness chiropractic adjustment in the cervical and sacral areas resulted in a significant reduction of the cervical and sacral surface EMF. No significant body surface EMF changes were observed in the lumbar and thoracic regions. The mechanisms of the EMF reduction after chiropractic adjustment are not known. PMID:17549217

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

2004-01-01

307

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

308

Magnetic microposts as an approach to apply forces to living cells  

PubMed Central

Cells respond to mechanical forces whether applied externally or generated internally via the cytoskeleton. To study the cellular response to forces separately, we applied external forces to cells via microfabricated magnetic posts containing cobalt nanowires interspersed among an array of elastomeric posts, which acted as independent sensors to cellular traction forces. A magnetic field induced torque in the nanowires, which deflected the magnetic posts and imparted force to individual adhesions of cells attached to the array. Using this system, we examined the cellular reaction to applied forces and found that applying a step force led to an increase in local focal adhesion size at the site of application but not at nearby nonmagnetic posts. Focal adhesion recruitment was enhanced further when cells were subjected to multiple force actuations within the same time interval. Recording the traction forces in response to such force stimulation revealed two responses: a sudden loss in contractility that occurred within the first minute of stimulation or a gradual decay in contractility over several minutes. For both types of responses, the subcellular distribution of loss in traction forces was not confined to locations near the actuated micropost, nor uniformly across the whole cell, but instead occurred at discrete locations along the cell periphery. Together, these data reveal an important dynamic biological relationship between external and internal forces and demonstrate the utility of this microfabricated system to explore this interaction. PMID:17804810

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

2007-01-01

309

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

NASA Astrophysics Data System (ADS)

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

Chen, Xiaowei; Wang, Wenping; Wan, Min

2013-12-01

310

Linear stability of a circular Couette flow under a radial thermoelectric body force  

NASA Astrophysics Data System (ADS)

The stability of the circular Couette flow of a dielectric fluid is analyzed by a linear perturbation theory. The fluid is confined between two concentric cylindrical electrodes of infinite length with only the inner one rotating. A temperature difference and an alternating electric tension are applied to the electrodes to produce a radial dielectrophoretic body force that can induce convection in the fluid. We examine the effects of superposition of this thermoelectric force with the centrifugal force including its thermal variation. The Earth's gravity is neglected to focus on the situations of a vanishing Grashof number such as microgravity conditions. Depending on the electric field strength and of the temperature difference, critical modes are either axisymmetric or nonaxisymmetric, occurring in either stationary or oscillatory states. An energetic analysis is performed to determine the dominant destabilizing mechanism. When the inner cylinder is hotter than the outer one, the circular Couette flow is destabilized by the centrifugal force for weak and moderate electric fields. The critical mode is steady axisymmetric, except for weak fields within a certain range of the Prandtl number and of the radius ratio of the cylinders, where the mode is oscillatory and axisymmetric. The frequency of this oscillatory mode is correlated with a Brunt-Väisälä frequency due to the stratification of both the density and the electric permittivity of the fluid. Under strong electric fields, the destabilization by the dielectrophoretic force is dominant, leading to oscillatory nonaxisymmetric critical modes with a frequency scaled by the frequency of the inner-cylinder rotation. When the outer cylinder is hotter than the inner one, the instability is again driven by the centrifugal force. The critical mode is axisymmetric and either steady under weak electric fields or oscillatory under strong electric fields. The frequency of the oscillatory mode is also correlated with the Brunt-Väisälä frequency.

Yoshikawa, H. N.; Meyer, A.; Crumeyrolle, O.; Mutabazi, I.

2015-03-01

311

3D Magnetic Force Microscopy: Light microscopy, 3D Particle Tracking,Force Application and Quantification  

Microsoft Academic Search

Most cellular processes involve movements in three dimensions (3D) and the application or generation of forces. There is much to be learned by obtaining a 3D representation of molecular-scale movements along with the timing and size of the forces involved in the movement of vesicles, organelles, chromosomes, ribosomes, and so on, as well as the forces derived from the polymerization

E. T. O'Brien; J. Fisher; J. Cummings; B. Wilde; J. Cribb; R. J. Pickles; W. Matthews; C. Davis; C. Weigle; H. Matsui; L. Vicci; G. Bishop; D. Sill; G. Welch

312

Constraint Force Equation Methodology for Modeling Multi-Body Stage Separation Dynamics  

NASA Technical Reports Server (NTRS)

This paper discusses a generalized approach to the multi-body separation problems in a launch vehicle staging environment based on constraint force methodology and its implementation into the Program to Optimize Simulated Trajectories II (POST2), a widely used trajectory design and optimization tool. This development facilitates the inclusion of stage separation analysis into POST2 for seamless end-to-end simulations of launch vehicle trajectories, thus simplifying the overall implementation and providing a range of modeling and optimization capabilities that are standard features in POST2. Analysis and results are presented for two test cases that validate the constraint force equation methodology in a stand-alone mode and its implementation in POST2.

Toniolo, Matthew D.; Tartabini, Paul V.; Pamadi, Bandu N.; Hotchko, Nathaniel

2008-01-01

313

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

314

The development and requirements of a body force database from two-dimensional and streamline curvature calculations  

E-print Network

This thesis presents a methodology for development of a body force database, from design conditions to flows below the stall point, for compressor stability analysis. The methodology is based on two-dimensional blade element ...

Walker, Thomas K., III

2009-01-01

315

IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 9, NO. 3, MAY 2010 367 Controlling a Magnetic Force Microscope to Track a  

E-print Network

IEEE TRANSACTIONS ON NANOTECHNOLOGY, VOL. 9, NO. 3, MAY 2010 367 Controlling a Magnetic Force, we in- troduce a feedback control law that steers the tip of a magnetic force microscope (MFM moving in three dimensions using a mag- netic force microscope (MFM). The stray magnetic field

316

Verification of a Constraint Force Equation Methodology for Modeling Multi-Body Stage Separation  

NASA Technical Reports Server (NTRS)

This paper discusses the verification of the Constraint Force Equation (CFE) methodology and its implementation in the Program to Optimize Simulated Trajectories II (POST2) for multibody separation problems using three specially designed test cases. The first test case involves two rigid bodies connected by a fixed joint; the second case involves two rigid bodies connected with a universal joint; and the third test case is that of Mach 7 separation of the Hyper-X vehicle. For the first two cases, the POST2/CFE solutions compared well with those obtained using industry standard benchmark codes, namely AUTOLEV and ADAMS. For the Hyper-X case, the POST2/CFE solutions were in reasonable agreement with the flight test data. The CFE implementation in POST2 facilitates the analysis and simulation of stage separation as an integral part of POST2 for seamless end-to-end simulations of launch vehicle trajectories.

Tartabini, Paul V.; Roithmayr, Carlos; Toniolo, Matthew D.; Karlgaard, Christopher; Pamadi, Bandu N.

2008-01-01

317

A Generalized Thermoelasticity Problem for a Half-Space with Heat Sources and Body Forces  

NASA Astrophysics Data System (ADS)

In this work, a two-dimensional problem of distribution of thermal stresses and temperature in a linear theory of a generalized thermoelastic half-space under the action of a body force and subjected to a thermal shock on the bounding plane is considered. Heat sources permeate the medium. The problem is in the context of the theory of generalized thermoelasticity with one relaxation time. Laplace and exponential Fourier transform techniques are used. The solution in the transformed domain is obtained by a direct approach. The inverse double transform is evaluated numerically. Numerical results are obtained and represented graphically.

El-Maghraby, Nasser Mohamed

2010-03-01

318

Collective behaviour in two-dimensional cobalt nanoparticle assemblies observed by magnetic force microscopy  

Microsoft Academic Search

The use of magnetic nanoparticles in the development of ultra-high-density recording media is the subject of intense research. Much of the attention of this research is devoted to the stability of magnetic moments, often neglecting the influence of dipolar interactions. Here, we explore the magnetic microstructure of different assemblies of monodisperse cobalt single-domain nanoparticles by magnetic force microscopy and magnetometric

Pau Gorostiza; Deborah M. Aruguete; Neus G. Bastus; A. Paul Alivisatos; Victor F. Puntes

2004-01-01

319

An efficient and robust contact algorithm for a compliant contact force model between bodies of complex geometry  

Microsoft Academic Search

Dynamic analysis of many mechanical systems often involves contacts among rigid bodies. When calculating the contact force\\u000a with a compliant contact force model, a penetration depth and a contact reference frame (a contact point and normal and tangent\\u000a directions) should be determined from the geometrical information of the rigid body surfaces. In order to improve the speed\\u000a and robustness of the

Juhwan Choi; Han Sik Ryu; Chang Wan Kim; Jin Hwan Choi

2010-01-01

320

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

321

Gravitational self-force corrections to two-body tidal interactions and the effective one-body formalism  

NASA Astrophysics Data System (ADS)

Tidal interactions have a significant influence on the late dynamics of compact binary systems, which constitute the prime targets of the upcoming network of gravitational-wave detectors. We refine the theoretical description of tidal interactions (hitherto known only to the second post-Newtonian level) by extending our recently developed analytic self-force formalism, for extreme-mass-ratio binary systems, to the computation of several tidal invariants. Specifically, we compute, to linear order in the mass ratio and to the 7.5th post-Newtonian order, the following tidal invariants: the square and the cube of the gravitoelectric quadrupolar tidal tensor, the square of the gravitomagnetic quadrupolar tidal tensor, and the square of the gravitoelectric octupolar tidal tensor. Our high-accuracy analytic results are compared to recent numerical self-force tidal data by Dolan et al. [arXiv:1406.4890 [Phys. Rev. D (to be published)] ], and, notably, provide an analytic understanding of the light ring asymptotic behavior found by them. We transcribe our kinematical tidal-invariant results in the more dynamically significant effective one-body description of the tidal interaction energy. By combining, in a synergetic manner, analytical and numerical results, we provide simple, accurate analytic representations of the global, strong-field behavior of the gravitoelectric quadrupolar tidal factor. A striking finding is that the linear-in-mass-ratio piece in the latter tidal factor changes sign in the strong-field domain, to become negative (while its previously known second post-Newtonian approximant was always positive). We, however, argue that this will be more than compensated by a probable fast growth, in the strong-field domain, of the nonlinear-in-mass-ratio contributions in the tidal factor.

Bini, Donato; Damour, Thibault

2014-12-01

322

Gravitational self-force corrections to two-body tidal interactions and the effective one-body formalism  

E-print Network

Tidal interactions have a significant influence on the late dynamics of compact binary systems, which constitute the prime targets of the upcoming network of gravitational-wave detectors. We refine the theoretical description of tidal interactions (hitherto known only to the second post-Newtonian level) by extending our recently developed analytic self-force formalism, for extreme mass-ratio binary systems, to the computation of several tidal invariants. Specifically, we compute, to linear order in the mass ratio and to the 7.5$^{\\rm th}$ post-Newtonian order, the following tidal invariants: the square and the cube of the gravitoelectric quadrupolar tidal tensor, the square of the gravitomagnetic quadrupolar tidal tensor, and the square of the gravitoelectric octupolar tidal tensor. Our high-accuracy analytic results are compared to recent numerical self-force tidal data by Dolan et al. \\cite{Dolan:2014pja}, and, notably, provide an analytic understanding of the light ring asymptotic behavior found by them. We transcribe our kinematical tidal-invariant results in the more dynamically significant effective one-body description of the tidal interaction energy. By combining, in a synergetic manner, analytical and numerical results, we provide simple, accurate analytic representations of the global, strong-field behavior of the gravitoelectric quadrupolar tidal factor. A striking finding is that the linear-in-mass-ratio piece in the latter tidal factor changes sign in the strong-field domain, to become negative (while its previously known second post-Newtonian approximant was always positive). We, however, argue that this will be more than compensated by a probable fast growth, in the strong-field domain, of the nonlinear-in-mass-ratio contributions in the tidal factor.

Donato Bini; Thibault Damour

2014-09-24

323

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

324

Lorentz force time-optimal transfer trajectory design in Jovian magnetic field  

NASA Astrophysics Data System (ADS)

In this paper, the Lorentz force in Jupiter's magnetic field is used to design the transfer trajectory between Galileo moons' Lagrange points. The equatorial orbits of charged spacecraft in three-body axis-aligned nontilted-dipole magnetic field model are analyzed and the results show that the libration point L1 and L2 become nearer or further away from Europa with the variable size and polarity of the charge. The bang-bang charge control with the variable size and polarity of the charge can be used to change orbit's direction and shape. Analytical and numerical iteration methods give the fast and accurate bang-bang charge control to send the spacecraft to the L2 point of Europa, respectively. Finally, two numerical methods, the indirect and direct methods, give the time-optimal charge controls which are similar to but different from the semi-revolution variable polarity control maneuver. The optimal results achieve the final position and the flight angle at the same time, and need less time and less magnitude of charge compared with the numerical iteration method.

Zhang, Zhiguo; Gong, Shengping; Li, Junfeng

2015-02-01

325

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

2013-04-26

326

Effect of three-body forces on the phase behavior of charged colloids J. Z. Wu,a)  

E-print Network

April 2000; accepted 24 May 2000 Statistical-thermodynamic theory for predicting the phase behavior force is attractive at all separations. The three-body force arises mainly from hard-sphere collisions concentration where charged colloids experience strong electrostatic interactions. To illustrate the effect

Wu, Jianzhong

327

Measured force on elongated bodies in a simulated low-Earth orbit environment  

NASA Astrophysics Data System (ADS)

An overview of the development of a magnetically filtered atomic oxygen plasma source and the application of the source to study low-Earth orbit drag on elongated bodies is presented. Plasma diagnostics show that the magnetic filter plasma source produces atomic oxygen ions (O+) with streaming energies equivalent to the relative orbital environment of approximately 5eV and can supply the appropriate density for LEO simulation. Previous research has demonstrated that momentum transfer between ions and metal surfaces is equivalent to the momentum transfer expected for neutral molecules with similar energy, due to charge exchange occurring prior to momentum transfer. Total drag measurements of aluminum cuboid geometries of varying length to diameter ratios immersed in the extracted plasma plume are presented as a function of streaming ion energy.

Maldonado, C. A.; Ketsdever, A. D.; Gimelshein, S. F.

2014-12-01

328

A Magnetic Resonance Force Microscopy Quantum Computer with Tellurium Donors in Silicon  

E-print Network

We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines the well-developed silicon technology with expected advances in MRFM.

G. P. Berman; G. D. Doolen; V. I. Tsifrinovich

2000-03-18

329

Identification of rotordynamic forces in a flexible rotor system using magnetic bearings  

E-print Network

Methods are presented for parameter identification of an annular gas seal on a flexiblerotor test rig. Dynamic loads are applied by magnetic bearings (MBs) that support the rotor. MB forces are measured using fiber-optic strain gauges...

Zutavern, Zachary Scott

2009-06-02

330

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

NASA Astrophysics Data System (ADS)

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

Wetter, Laura; Verosub, Ken; Russell, James

2007-06-01

331

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

2013-07-01

332

The Development of the Separation Apparatus of Phosphor by Controlling the Magnetic Force  

NASA Astrophysics Data System (ADS)

The phosphor wastes contain the multiple kinds of rare-earth phosphors with high market value. Because of increasing demand for rare-earth, the technique to recover and reuse the rare-earth in the phosphor wastes is required. In this study, we focused on the difference of physical property such as magnetic susceptibility and density for each type of phosphor and tried to separate and recover the phosphors by using the magnetic separation technique utilizing the difference of the traction force to the magnet acting on the particles. Magneto-Archimedes method is method separation technique utilizi g the difference of magnetic susceptibility and density. We developed the magnetic separation apparatus by applying this technique. To develop the practical separation apparatus, the continuous process is required. Hence the fundamental experiment utilizing High Temperature Superconducting (HTS) Bulk Magnet which can generate the strong magnetic force was conducted. As a result, we succeeded the continuous separation of the phosphor wastes.

Wada, K.; Mishima, F.; Akiyama, Y.; Nishijima, S.

333

Offensive and defensive agility: a sex comparison of lower body kinematics and ground reaction forces.  

PubMed

The aim of this study was to compare biomechanical and perceptual-cognitive variables between sexes during an offensive and defensive agility protocol. Twelve male and female (n = 24) recreational team sport athletes participated in this study, each performing 12 offensive and defensive agility trials (6 left, 6 right) changing direction in response to movements of a human stimulus. Three-dimensional motion, ground reaction force (GRF), and impulse data were recorded across plant phase for dominant leg change of direction (COD) movements, while timing gates and high-speed video captured decision time, total running time, and post COD stride velocity. Subjects also performed a unilateral isometric squat to determine lower body strength and limb dominance. Group (sex) by condition (2 × 2) MANOVAs with follow-up ANOVAs were conducted to examine differences between groups (P ? .05). Male athletes demonstrated significantly greater lower body strength, vertical braking force and impulse application, knee and spine flexion, and hip abduction, as well as faster decision time and post COD stride velocity during both agility conditions compared with females. Differences between offensive and defensive movements appear to be attributed to differences in decision time between sexes. This study demonstrates that biomechanical and perceptual-cognitive differences exist between sexes and within offensive and defensive agility movements. PMID:24615296

Spiteri, Tania; Hart, Nicolas H; Nimphius, Sophia

2014-08-01

334

Quantitative magnetic resonance (QMR) measurement of changes in body composition of neonatal pigs  

Technology Transfer Automated Retrieval System (TEKTRAN)

The survival of low birth weight pigs in particular may depend on energy stores in the body. QMR (quantitative magnetic resonance) is a new approach to measuring total body fat, lean and water. These measurements are based on quantifying protons associated with lipid and water molecules in the body...

335

Atomic-scale friction measurements using friction force microscopy. Part 2: Application to magnetic media  

Microsoft Academic Search

Atomic Force\\/Friction Force Microscopes (AFM\\/FFM) were used to study tribological properties of metal-particle tapes with two roughnesses, Co-gamma Fe2O3 tapes (unwiped and wiped), and unlubricated and lubricated thin-film magnetic rigid disks (as-polished and standard textured). Nanoindentation studies showed that the hardness of the tapes through the magnetic coating is not uniform. These results are consistent with the fact that the

Bharat Bhushan; Ju-Ai Ruan

1993-01-01

336

End-Winding Vibrations Caused by Steady-State Magnetic Forces in an Induction Machine  

Microsoft Academic Search

We conducted a 3-D electromagnetic analysis coupled with a 3-D mechanical analysis to analyze end-winding vibrations and deformation in an induction machine caused by steady-state magnetic forces on the end winding. Both the analyses were based on the finite-element method. The electromagnetic analysis was used to calculate magnetic forces. During the mechanical analysis, complex support structures in the end region

Ranran Lin; Antti Nestori Laiho; Ari Haavisto; Antero Arkkio

2010-01-01

337

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

338

Spin-selective Imaging by Magnetic Exchange Force Microscopy Using Ferromagnetic Resonance.  

PubMed

Techniques to analyze the surface of magnetic memory devices with high spatial resolution are very important to develop today's information technology. The magnetic exchange force is an interaction between spins and is very important for analyzing magnetic properties. Magnetic exchange force microscopy (MExFM), which can detect the magnetic exchange force between the magnetic tip and the magnetic surface, has achieved the atomic-resolution imaging of the spin state on anti-ferromagnetic surface of NiO(001) [1]. In MExFM, however, the separation between a structure and a magnetic state on the surface has not been performed.Here, we propose a new MExFM using ferromagnetic resonance to separate the magnetic and non-magnetic tip-sample interaction. In this method, magnetic tip apex is irradiated by the frequency-modulated microwave with the frequency of ferromagnetic resonance. The magnetization of magnetic tip apex is modulated from on resonance to off resonance. Tip-sample interaction is measured with frequency modulation method. Magnetic images are obtained by detecting the modulation component of the frequency shift of the oscillating cantilever using a lock-in amplifier. Topographic images are obtained by the feedback signal for the constant tip-sample interaction. As a magnetic tip, magnetic cantilever tip coated with FePt with a high coercivity was used to detect the magnetic exchange force without an external magnetic field [2]. We performed imaging on antiferromagnetic material NiO(001) surface (Fig. 1(a)) by MExFM using ferromagnetic resonance. We obtained spin selective image in atomic resolution (Fig. 1(b)). This is the first demonstration of magnetization modulation of the magnetic tip apex using ferromagnetic resonance as well as the separation of the magnetic and non-magnetic tip-sample interaction in MExFM.jmicro;63/suppl_1/i11-a/DFU053F1F1DFU053F1Fig. 1.(a) Structure of NiO(001) surface and (b) its image (phase) obtained with MExFM using ferromagnetic resonance. (4 nm x 4 nm). PMID:25359800

Sugawara, Yasuhiro; Arima, Eiji; Naitoh, Yoshitaka; Li, Yan Jun

2014-11-01

339

Preprocessing of vector magnetograph data for a non-linear force-free magnetic field reconstruction  

E-print Network

Knowledge regarding the coronal magnetic field is important for the understanding of many phenomena, like flares and coronal mass ejections. Because of the low plasma beta in the solar corona the coronal magnetic field is often assumed to be force-free and we use photospheric vector magnetograph data to extrapolate the magnetic field into the corona with the help of a non-linear force-free optimization code. Unfortunately the measurements of the photospheric magnetic field contain inconsistencies and noise. In particular the transversal components (say Bx and By) of current vector magnetographs have their uncertainties. Furthermore the magnetic field in the photosphere is not necessary force-free and often not consistent with the assumption of a force-free field above. We develop a preprocessing procedure to drive the observed non force-free data towards suitable boundary conditions for a force-free extrapolation. As a result we get a data set which is as close as possible to the measured data and consistent with the force-free assumption.

Thomas Wiegelmann; Bernd Inhester; Takashi Sakurai

2006-12-21

340

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

NASA Astrophysics Data System (ADS)

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

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

1998-08-01

341

Analytical Force Calculations for High-Precision Planar Actuator With Halbach Magnet Array  

Microsoft Academic Search

In this paper, an analytical approach is presented to calculate the magnetic force between the mover and the stator of an electromagnetic planar actuator. The key is to use the coenergy method to calculate the force, in such a way that the stator current can be predicted properly to offer the accurate orientation and location for the real-time control of

Hao Jiang; Xueliang Huang; Gan Zhou; Yubin Wang; Zheng Wang

2009-01-01

342

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

Microsoft Academic Search

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

Tatsuya Katou; Akira Chiba; Tadashi Fukao

2005-01-01

343

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

SciTech Connect

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 {sup '}3+1{sup '} bosonic ground state is computed as a function of the mass ratio.

Pricoupenko, Ludovic [Laboratoire de Physique Theorique de la Matiere Condensee, Universite Pierre et Marie Curie and CNRS, 4 place Jussieu, F-75252 Paris (France)

2011-06-15

344

Lift force acting on a cylindrical body in a fluid near the boundary of a cavity performing translational vibrations  

NASA Astrophysics Data System (ADS)

The averaged lift force acting on a cylindrical body near the boundary of a cavity with a fluid performing translational vibrations was studied. Experiments were performed with variation the viscosity of the fluid, the size and relative density of the body, and vibration parameters were varied. The lift force was measured by the method of dynamic suspension of a body in a gravitational field in the case where the body performed inertial vibrations without touching the walls. It was found that the vibrations generated a repulsion force which held the heavy body over the bottom of the cavity, and the light body at a certain distance from the top wall. It was shown that the effect of the repulsion forces manifested itself at a distance comparable to the thickness of the Stokes layer and increased with approach to the wall. A description of the mechanism of generation of the lift force is given. It is shown that in the case of high dimensionless frequencies, the experimental and theoretical results are in agreement.

Ivanova, A. A.; Kozlov, V. G.; Shchipitsyn, V. D.

2014-09-01

345

TRUE VARIABLE FIELD MAGNETIC FORCE MICROSCOPY FOR NANOSTRUCTURES CHARACTERIZATION  

Microsoft Academic Search

Spin structures of nanoscale magnetic elements are the subject of increasing scientific effort. As the confinement of spins, imposed by geometrical restrictions, makes these structures comparable in size to some intrinsic characteristic length of the magnet new properties emerge. Part of this effort is devoted to the development of new techniques with suitable resolution and sensitivity to characterize nano-objets. Particularly

Miriam Jaafar; Julio Gómez; Manuel Vázquez; Agustina Asenjo

2008-01-01

346

Longitudinal focusing of an atomic cloud using pulsed magnetic forces  

Microsoft Academic Search

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

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

1999-01-01

347

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

348

Alternating Magnetic Field Forces for Satellite Formation Flying  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

349

Magnetic force microscopy of epitaxial magnetite films through the Verwey transition  

Microsoft Academic Search

Magnetic force microscopy was performed on 300 nm thick magnetite films grown epitaxially on MgO (001) at temperatures ranging from well below to well above the Verwey transition temperature, TV. Frequency shift images were acquired at different locations on the sample as temperature was increased through the Verwey transition. The magnetic domain features are persistent at all temperatures, which indicates

A. K. H. Lee; P. B. Jayathilaka; C. A. Bauer; M. C. Monti; J. T. Markert; A. de Lozanne; Casey W. Miller

2010-01-01

350

Magnetic force characteristics according to the variation of asymmetric overhang ratio in brushless direct current motor  

Microsoft Academic Search

As usual, brushless dc motor (BLDCM) has the overhang structure of which permanent magnet (PM) length is longer than the stator's stack length. Specially, in case of asymmetric overhang, we have to pay attention to the choice of suitable overhang ratio of the lower to the upper overhang length because of the effect of the ratio on the magnetic forces.

Yon Do Chun; Shinji Wakao; Ju Lee

2003-01-01

351

Urethral foreign body: removal of degraded magnetic spheres using Hartmann ear forceps.  

PubMed

Lower urinary tract foreign bodies have been reported in both children and adults. It is helpful for urologists to review foreign body case reports to become familiar with alternative approaches for removal that may prove helpful during challenging cases. To our knowledge, we describe for the first time a degraded rare-earth magnet within the body and use of Hartmann ear forceps to remove a foreign body from the urethra under cystoscopic guidance through a limited urethrotomy. PMID:25443938

Chung, Paul H; Traylor, Janelle; Baker, Linda A

2014-11-01

352

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

PubMed

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

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

2014-08-01

353

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

354

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

DOEpatents

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

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

1995-11-07

355

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

356

Force.  

ERIC Educational Resources Information Center

Discusses pupil misconceptions concerning forces. Summarizes some of Assessment of Performance Unit's findings on meaning of (1) force, (2) force and motion in one dimension and two dimensions, and (3) Newton's second law. (YP)

Gamble, Reed

1989-01-01

357

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

358

Stabilization of one degree-of-freedom control type levitation table with permanent magnet repulsive forces  

Microsoft Academic Search

It is impossible to levitate an object by using only permanent magnets (PMs). Many researches have been reported to reduce the number of control degree-of-freedom (DOF) in magnetic levitation systems. This paper presents a one-DOF control type magnetic levitation table supported by repulsive forces of four sets of PMs. Each set of PMs is composed of two PMs on a

Kee-Bong Choi; Young Geun Cho; Tadahiko Shinshi; Akira Shimokohbe

2003-01-01

359

Nonlinear force-free magnetic fields: Calculation and applicatin to astrophysics. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

The problem concerned in this work is that of calculating magnetic field configurations in which the Lorentz force (vector)j x (vector)B is everywhere zero, subject to specified boundary conditions. The magnetic field is represented in terms of Clebsch variables in the form (vector)B = del alpha x del beta. These variables are constant on any field line. The most appropriate choice of boundary conditions is to specify the values of alpha and beta on the bounding surface. It is proposed that the field lines move in the direction of local Lorentz force and relax towards a force-free field configuration. This concept leads to an iteration procedure for modifying the variables alpha and beta that tends asymptotically towards the force-free state. This method is first applied to a simple problem in two rectangular dimensions; the calculation shows that the convergence of magnetic field energy to a minimum state (force-free) is close to exponential. This method is then applied to study some astrophysical force-free magnetic fields, such as the structures and evolution of magnetic fields of rotating sunspots and accretion disks. The implication of the results, as related to the mechanisms of solar flares, extragalactic radio sources and radio jets, are discussed.

Yang, Wei-Hong

1987-01-01

360

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

NASA Technical Reports Server (NTRS)

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

Aly, J. J.

1984-01-01

361

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

362

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

NASA Astrophysics Data System (ADS)

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

Garshelis, I. J.; Crevecoeur, G.

2014-05-01

363

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

364

Si nanowire probe with Nd–Fe–B magnet for attonewton-scale force detection  

NASA Astrophysics Data System (ADS)

In this study, we have developed a 210?nm-wide and 32?µm-long silicon nanowire probe with a silicon mirror using a silicon-on-insulator wafer in order to improve sensitivity of force detection for magnetic resonance force microscopy (MRFM). Additionally, a Nd–Fe–B magnet has been integrated at the end of the nanowire. The fabricated nanowire probe shows a resonance frequency of 11.256?kHz and a factor of 12?800 after annealing at 800?°C for 2?h in forming gas. The probe exhibits attonewton sensitivity, and the measurement of force mapping based on electron spin resonance is demonstrated for 3D imaging of radicals. The detected force and magnetic field gradient are approximately 82?aN and ~70.1?G??m?1 at room temperature. The radical density is calculated as 4.6? × ?1018?spins?cm?3.

Seo, Yong-Jun; Toda, Masaya; Ono, Takahito

2015-04-01

365

A magnetic vector potential corresponding to a centrally conservative current element force  

NASA Astrophysics Data System (ADS)

The magnetic vector potential (Coulomb gauge) is commonly introduced in magnetostatic chapters of electromagnetism textbooks. However, what is not typically presented are the infinite subsets of the Coulomb gauge associated with differential current elements. This work provides a comparison of various differential magnetic vector potentials, differential magnetostatic potential energies, as well as differential current element forces as a collective work not available elsewhere. The differential magnetic vector potential highlighted in this work is the Coulomb–Ampère gauge corresponding to the centrally conservative Ampère current element force. The centrally conservative force is modeled as a mean valued continual exchange of energy carrier mediators accounting for both the differential magnetostatic potential energy and Ampère current element force of two differential current elements.

Minteer, Timothy M.

2015-01-01

366

Dynamics of a Levitron under a periodic magnetic forcing  

NASA Astrophysics Data System (ADS)

The Levitron is a toy that consists of a spinning top that levitates over a magnetic base for a few minutes, until air drag decreases the spin rate below a certain limit. Stable levitation, lasting hours or even days, has been achieved for Levitrons that were externally driven by either an air jet or an alternating magnetic field. We report measurements of stable levitation for the latter case. We show that the top precession couples with the frequency of the alternating field, so that the precession period equals the period of the field. In addition, the top rotates around itself with the same period. We present numerical simulations that reproduce the essential features of this dynamics. It is also shown that the magnetic torque that drives the top is due to a misalignment between the magnetic dipole moment and the mechanical axis of the top.

Pérez, Alberto T.; García-Sánchez, Pablo

2015-02-01

367

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

368

Magnetic lines of force in a Tornado trap  

Microsoft Academic Search

Numerical methods are used to analyze the structure of the magnetic field of an ideal Tornado trap; i.e., a trap consisting\\u000a of linear currents whose magnitude and location in space are such as to produce a spherical separatrix with a radius ?\\u000a c between the helices of the trap and partition the magnetic field into two regions so that the

K. B. Abramova; A. V. Voronin; M. L. Lev; A. A. Semenov; E. M. Sklyarova

1997-01-01

369

The Inverse-Cube Law of Magnetic Forces  

NSDL National Science Digital Library

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

2012-08-03

370

Invincible DNA tethers: covalent DNA anchoring for enhanced temporal and force stability in magnetic tweezers experiments.  

PubMed

Magnetic tweezers are a powerful single-molecule technique that allows real-time quantitative investigation of biomolecular processes under applied force. High pulling forces exceeding tens of picoNewtons may be required, e.g. to probe the force range of proteins that actively transcribe or package the genome. Frequently, however, the application of such forces decreases the sample lifetime, hindering data acquisition. To provide experimentally viable sample lifetimes in the face of high pulling forces, we have designed a novel anchoring strategy for DNA in magnetic tweezers. Our approach, which exploits covalent functionalization based on heterobifunctional poly(ethylene glycol) crosslinkers, allows us to strongly tether DNA while simultaneously suppressing undesirable non-specific adhesion. A complete force and lifetime characterization of these covalently anchored DNA-tethers demonstrates that, compared to more commonly employed anchoring strategies, they withstand 3-fold higher pulling forces (up to 150 pN) and exhibit up to 200-fold higher lifetimes (exceeding 24 h at a constant force of 150 pN). This advance makes it possible to apply the full range of biologically relevant force scales to biomolecular processes, and its straightforward implementation should extend its reach to a multitude of applications in the field of single-molecule force spectroscopy. PMID:25140010

Janissen, Richard; Berghuis, Bojk A; Dulin, David; Wink, Max; van Laar, Theo; Dekker, Nynke H

2014-10-01

371

Invincible DNA tethers: covalent DNA anchoring for enhanced temporal and force stability in magnetic tweezers experiments  

PubMed Central

Magnetic tweezers are a powerful single-molecule technique that allows real-time quantitative investigation of biomolecular processes under applied force. High pulling forces exceeding tens of picoNewtons may be required, e.g. to probe the force range of proteins that actively transcribe or package the genome. Frequently, however, the application of such forces decreases the sample lifetime, hindering data acquisition. To provide experimentally viable sample lifetimes in the face of high pulling forces, we have designed a novel anchoring strategy for DNA in magnetic tweezers. Our approach, which exploits covalent functionalization based on heterobifunctional poly(ethylene glycol) crosslinkers, allows us to strongly tether DNA while simultaneously suppressing undesirable non-specific adhesion. A complete force and lifetime characterization of these covalently anchored DNA-tethers demonstrates that, compared to more commonly employed anchoring strategies, they withstand 3-fold higher pulling forces (up to 150 pN) and exhibit up to 200-fold higher lifetimes (exceeding 24 h at a constant force of 150 pN). This advance makes it possible to apply the full range of biologically relevant force scales to biomolecular processes, and its straightforward implementation should extend its reach to a multitude of applications in the field of single-molecule force spectroscopy. PMID:25140010

Janissen, Richard; Berghuis, Bojk A.; Dulin, David; Wink, Max; van Laar, Theo; Dekker, Nynke H.

2014-01-01

372

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

373

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

374

Chaotic dynamics of a periodically forced slender body in a simple shear flow  

NASA Astrophysics Data System (ADS)

The dynamics of a periodically forced slender body in a simple shear flow is analysed. This represents the simplest case of a class of problems that have not attracted attention in the literature. The system undergoes a quasiperiodic transition to chaos in the range of parameters investigated. It also exhibits chaotic transients obtained by the apparent collision of a stable nonchaotic attractor and a chaotic attractor with the transients scaling in a manner similar to that analysed by Grebogi et al. [Ergodic Theory Dynamical Systems 5 (1985) 341] with the exponent of scaling approximately equal to -0.5. The class of problems to which this paper is an introduction is technologically important and can lead to new methods of processing composites, electrorheological fluids and polymer solutions.

Ramamohan, T. R.; Savithri, S.; Sreenivasan, R.; Shekara Bhat, C. Chandra

1994-07-01

375

A discrete-forcing immersed boundary method for the fluid-structure interaction of an elastic slender body  

NASA Astrophysics Data System (ADS)

We present an immersed boundary (IB) method for the simulation of flow around an elastic slender body. The present method is based on the discrete-forcing IB method for a stationary, rigid body proposed by Kim, Kim and Choi (2001) [25]. The discrete-forcing approach is used to relieve the limitation on the computational time step size. The incompressible Navier-Stokes equations are implicitly coupled with the dynamic equation for an elastic slender body motion. The first is solved in the Eulerian coordinate and the latter is described in the Lagrangian coordinate. The elastic slender body is modeled as a thin and flexible solid and is segmented by finite number of thin blocks. Each block is moved by external and internal forces such as the hydrodynamic, elastic and buoyancy forces, where the hydrodynamic force is obtained directly from the discrete forcing used in the IB method. All the spatial derivative terms are discretized with the second-order central difference scheme. The present method is applied to three different fluid-structure interaction problems: flows around a flexible filament, a flapping flag in a free stream, and a flexible flapping wing in normal hovering, respectively. Computations are performed at maximum CFL numbers of 0.75-1. The results obtained agree very well with those from previous studies.

Lee, Injae; Choi, Haecheon

2015-01-01

376

A 2-Tesla active shield magnet for whole body imaging and spectroscopy  

SciTech Connect

This paper reports on the development and testing of a 2T superconducting Active Shield magnet, with a 0.99m diameter warm bore for whole-body Magnetic Resonance Imaging (MRI) and spectroscopy. The magnet and cryostat were designed to meet the same performance standards as existing MRI magnets, but with the volume of the stray field region reduced to less than 4% of that for an unshielded magnet. The 0.5 mT stray field contour is within 5m axially and 3m radially of the magnet center. The system weight is only 14 tonnes.

Davies, F.J.; Elliott, R.T.; Hawksworth, D.G. (Oxford Magnet Technology Ltd., Wharf Road, Eynsham, Oxford OX8 1BP (GB))

1991-03-01

377

Suitable Shape and Arrangement of HTS Bulk and Permanent Magnet for Improving Levitation Force in a Magnetic Levitation Type Superconducting Seismic Isolation Device  

Microsoft Academic Search

We have investigated levitation force characteristics of a magnetic levitation type superconducting seismic isolation device composed of HTS bulks and permanent magnets. Large levitation force at a small gap of less than 3 mm has been already obtained, while only small levitation force at a large gap of more than 5 mm. In a practical use of the superconducting device,

S. Sasaki; K. Shimada; T. Yagai; M. Tsuda; T. Hamajima; N. Kawai; K. Yasui

2010-01-01

378

Magnetism: the Driving Force of Order in CoPt. A First-Principles Study. S. Karoui,1  

E-print Network

structure which favors their strong magnetic anisotropy. Conversely magnetism can influence chemical through non-magnetic and magnetic ab initio electronic structure calculations; thus providing tangibleMagnetism: the Driving Force of Order in CoPt. A First-Principles Study. S. Karoui,1 H. Amara,1 B

Boyer, Edmond

379

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

NASA Astrophysics Data System (ADS)

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 5 mm 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.

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

2011-01-01

380

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

PubMed

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

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

2011-01-01

381

Tensile Force-Dependent Neurite Elicitation via Anti-?1 Integrin Antibody-Coated Magnetic Beads  

PubMed Central

Previous work using glass microneedles to apply calibrated, localized force to neurons showed that tensile force is a sufficient signal for neurite initiation and elongation. However, previous studies did not examine the kinetics or probability of neurite initiation as a function of force or the rate of force application. Here we report the use of a new technique—magnetic bead force application—to systematically investigate the role of force in these phenomena with better ease of use and control over force than glass microneedles. Force-induced neurite initiation from embryonic chick forebrain neurons appeared to be a first-order random process whose rate increased with increasing force, and required the presence of peripheral microtubules. In addition, the probability of initiation was more than twofold lower for neurons exposed to rapid initial force ramps (450 pN/s) than for neurons exposed to slower ramps (1.5 and 11 pN/s). We observed a low force threshold for elongation (15–100 pN), which was not previously detected in chick forebrain neurites elongated by glass microneedles. Finally, neurites subjected to constant force elongated at variable instantaneous rates, and switched abruptly between elongation and retraction, similar to spontaneous, growth-cone-mediated outgrowth and microtubule dynamic instability. PMID:12829516

Fass, Joseph N.; Odde, David J.

2003-01-01

382

An individual and dynamic Body Segment Inertial Parameter validation method using ground reaction forces.  

PubMed

Over the last decades a variety of research has been conducted with the goal to improve the Body Segment Inertial Parameters (BSIP) estimations but to our knowledge a real validation has never been completely successful, because no ground truth is available. The aim of this paper is to propose a validation method for a BSIP identification method (IM) and to confirm the results by comparing them with recalculated contact forces using inverse dynamics to those obtained by a force plate. Furthermore, the results are compared with the recently proposed estimation method by Dumas et al. (2007). Additionally, the results are cross validated with a high velocity overarm throwing movement. Throughout conditions higher correlations, smaller metrics and smaller RMSE can be found for the proposed BSIP estimation (IM) which shows its advantage compared to recently proposed methods as of Dumas et al. (2007). The purpose of the paper is to validate an already proposed method and to show that this method can be of significant advantage compared to conventional methods. PMID:24704168

Hansen, Clint; Venture, Gentiane; Rezzoug, Nasser; Gorce, Philippe; Isableu, Brice

2014-05-01

383

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

384

Mechanical Forces between Electric Currents and Saturated Magnetic Fields  

Microsoft Academic Search

The general case considered is that of N independent electric circuits placed in a medium of variable permeability and subject to saturation, in parts or as a whole. The problem is to determine the component (in a given direction) of the mechanical force acting upon one of the electric circuits, upon a group of circuits, or upon a group of

Vladimir Karapetoff

1927-01-01

385

Magnetic Force Microscopy Study of CoPtCrO Perpendicular Media With Superparamagnetic And Permanent Magnet Tips  

Microsoft Academic Search

This paper compares the images obtained by superparamagnetic and permanent magnetic force microscopy (MFM) tips, that allows us to explain the issues related to the frequency double in some of domain images of the recording media. This paper also investigates the domain structures of high density recording bits (up to 1100 kfci) written on ac and dc-erased CoPtCrO perpendicular magnetic

L. Yuan; L. Gao; L. Nicholl; S. H. Liou; M. Zheng; E. N. Abarra; B. R. Acharya; G. Choe; S. S. Malhotra; B. Han

2006-01-01

386

Ingestion of multiple magnets: hazardous foreign bodies for children  

Microsoft Academic Search

We report a case of perforation, fistula formation, and small bowel obstruction in a 2-year-old child who had ingested 32\\u000a small magnets. Multiple magnets will attract one another through the bowel wall and lead to pressure necrosis with complications.\\u000a We recommend early surgical intervention before the onset of gastrointestinal complications if ingested multiple magnets have\\u000a not moved on the follow-up

Keiichi Uchida; Kohei Otake; Takashi Iwata; Hideki Watanabe; Mikihiro Inoue; Tsuyoshi Hatada; Masato Kusunoki

2006-01-01

387

Multiple degree-of-freedom force and moment measurement for static propulsion testing using magnetic suspension technology  

Microsoft Academic Search

Innovative Information Systems (IIS), Inc. is in the process of designing and fabricating a high bandwidth force and moment measuring device (i.e. the Magnetic Thruster Test Stand). This device will use active magnetic suspension to allow direct measurements of the forces and torques generated by the rocket engines of the missile under test. The principle of operation of the Magnetic

Keith Stuart; Blake Bartosh

1993-01-01

388

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

389

Magnetic force microscopy investigation of arrays of nickel nanowires and nanotubes  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

390

Enhanced buckled-beam piezoelectric energy harvesting using midpoint magnetic force  

NASA Astrophysics Data System (ADS)

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

Zhu, Yang; Zu, Jean W.

2013-07-01

391

Approximating edges of source bodies from magnetic or gravity anomalies.  

USGS Publications Warehouse

Cordell and Grauch (1982, 1985) discussed a technique to estimate the location of abrupt lateral changes in magnetization or mass density of upper crustal rocks. The final step of their procedure is to identify maxima on a contoured map of horizontal gradient magnitudes. Attempts to automate their final step. The method begins with gridded magnetic or gravity anomaly data and produces a plan view of inferred boundaries of magnetic or gravity sources. The method applies to both local surveys and to continent-wide compilations of magnetic and gravity data.-from Authors

Blakely, R.J.; Simpson, R.W.

1986-01-01

392

An investigation on the body force modeling in a lattice Boltzmann BGK simulation of generalized Newtonian fluids  

NASA Astrophysics Data System (ADS)

Body force modeling is studied in the Generalized Newtonian (GN) fluid flow simulation using a single relaxation time lattice Boltzmann (LB) method. First, in a shear thickening Poiseuille flow, the necessity for studying body force modeling in the LB method is explained. Then, a parametric unified framework is constructed for the first time which is composed of a parametric LB model and its associated macroscopic dual equations in both steady state and transient simulations. This unified framework is used to compare the macroscopic behavior of different forcing models. Besides, using this unified framework, a new forcing model for steady state simulations is devised. Finally, by solving a number of test cases it is shown that numerical results confirm the theoretical arguments presented in this paper.

Farnoush, Somayeh; Manzari, Mehrdad T.

2014-12-01

393

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

NASA Technical Reports Server (NTRS)

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

Dress, David A.

1988-01-01

394

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

PubMed

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

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

2011-07-01

395

Models of force-free magnetic fields in resistive media  

Microsoft Academic Search

A review is given of some of the basic properties of forcefree fields ; under circumstances when the conductivity of the medium is finite. Then the ; electric current density is related not only to the magnetic field, but also by ; Ohm's law to the electric fleld and plasma velocity, which must be considered in ; the solutions. It

Bostroem

1973-01-01

396

A magnetic micro-manipulator for application of three dimensional forces  

NASA Astrophysics Data System (ADS)

Magnetic manipulation finds diverse applications in actuation, characterization, and manipulation of micro- and nano-scale samples. This paper presents the design and development of a novel magnetic micro-manipulator for application of three-dimensional forces on a magnetic micro-bead. A simple analytical model is proposed to obtain the forces of interaction between the magnetic micro-manipulator and a magnetic micro-bead. Subsequently, guidelines are proposed to perform systematic design and analysis of the micro-manipulator. The designed micro-manipulator is fabricated and evaluated. The manipulator is experimentally demonstrated to possess an electrical bandwidth of about 1 MHz. The ability of the micro-manipulator to apply both in-plane and out-of-plane forces is demonstrated by actuating permanent-magnet micro-beads attached to micro-cantilever beams. The deformations of the micro-cantilevers are also employed to calibrate the dependence of in-plane and out-of-plane forces on the position of the micro-bead relative to the micro-manipulator. The experimentally obtained dependences are found to agree well with theory.

Punyabrahma, P.; Jayanth, G. R.

2015-02-01

397

A magnetic micro-manipulator for application of three dimensional forces.  

PubMed

Magnetic manipulation finds diverse applications in actuation, characterization, and manipulation of micro- and nano-scale samples. This paper presents the design and development of a novel magnetic micro-manipulator for application of three-dimensional forces on a magnetic micro-bead. A simple analytical model is proposed to obtain the forces of interaction between the magnetic micro-manipulator and a magnetic micro-bead. Subsequently, guidelines are proposed to perform systematic design and analysis of the micro-manipulator. The designed micro-manipulator is fabricated and evaluated. The manipulator is experimentally demonstrated to possess an electrical bandwidth of about 1 MHz. The ability of the micro-manipulator to apply both in-plane and out-of-plane forces is demonstrated by actuating permanent-magnet micro-beads attached to micro-cantilever beams. The deformations of the micro-cantilevers are also employed to calibrate the dependence of in-plane and out-of-plane forces on the position of the micro-bead relative to the micro-manipulator. The experimentally obtained dependences are found to agree well with theory. PMID:25725878

Punyabrahma, P; Jayanth, G R

2015-02-01

398

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

NASA Astrophysics Data System (ADS)

In typical observations of coronal mass ejections (CMEs), a magnetic structure of a helmet-shaped closed configuration bulges out and eventually opens up. In order for this transition of field configuration to occur spontaneously, the pre-eruption closed magnetic field must have more energy than the post-eruption open field. In force-free fields, however, such a possibility is denied by 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. Here we note that the theorem implicitly assumes the existence of the maximum energy configuration. However, this may not be taken for granted because the limiting configuration of energy-increasing sequences of force-free fields does not necessarily have an energy equal to the energy supremum. 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.

Choe, G. S.; Cheng, C. Z.

2002-05-01

399

Ampere force based magnetic field sensor using dual-polarization fiber laser.  

PubMed

A magnetic field sensor is proposed by placing a dual-polarization fiber grating laser under a copper wire. With a perpendicular magnetic field applied, an electrical current flowing through the copper wire can generate Ampere force to squeeze the fiber grating laser, resulting in the birefringence change inside the laser cavity and hence the change of the beat note frequency. When an alternating current is injected into the copper wire, the magnetic field induced beat note frequency change can be discriminated from environment disturbances. A novel fiber-optic magnetic field sensor is therefore demonstrated with high sensitivity and inherent immunity to disturbances. PMID:23736594

Cheng, Linghao; Guo, Zhenzhen; Han, Jianlei; Jin, Long; Guan, Bai-Ou

2013-06-01

400

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

PubMed Central

Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 ?m paramagnetic particle and 13 nN on a 4.5 ?m paramagnetic particle, forces over the full 4? sr, and a bandwidth in excess of 3 kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4 nm), high-bandwidth (10 kHz), long-range (100 ?m xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function. PMID:16858495

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

2006-01-01

401

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

PubMed

Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 mum paramagnetic particle and 13 nN on a 4.5 mum paramagnetic particle, forces over the full 4pi sr, and a bandwidth in excess of 3 kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4 nm), high-bandwidth (10 kHz), long-range (100 mum xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function. PMID:16858495

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

2006-02-01

402

Development of forced flow cooled current leads for fusion magnets  

Microsoft Academic Search

During the past 15 years, the Institut für Technische Physik of the Forschungszentrum Karlsruhe, Germany, has developed current leads cooled by forced-flow supercritical helium in the current range from 20 to 80 kA. The design is based on a separation of the current carrying part and the heat exchanger part as well as the presence of the so-called superconductor inserts

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

2001-01-01

403

Calculation of levitation forces in permanent magnet-superconductor systems using finite element analysis  

SciTech Connect

In this paper we present calculations of levitation forces between a cylindrical permanent magnet and a cylindrical superconductor using a commercial finite element program. Force limits for zero field cooled and field cooled processes have been obtained using the Meissner effect and the perfect pinning hypothesis, respectively. Comparison of the experimentally determined forces with respect to these limits provides a simple estimation of the sample quality. The hysteretical behavior of the forces has been reproduced assuming a critical state model for the superconductor. Results are compared with experimental data. Excellent agreement has been found for forces measured after zero field cooled process thus allowing us to estimate the critical current of the samples. As a further exploitation of the software capabilities we have investigated the effects of the superconducting sample geometry and the effects of different strategies of flux conditioning to optimize the levitation forces. {copyright} {ital 1997 American Institute of Physics.}

Camacho, D.; Mora, J.; Fontcuberta, J.; Obradors, X. [Institut de Ciencia de Materials de Barcelona, CSIC, Campus Universitat Autonoma de Barcelona, Bellaterra 08193, Catalunya (Spain)] [Institut de Ciencia de Materials de Barcelona, CSIC, Campus Universitat Autonoma de Barcelona, Bellaterra 08193, Catalunya (Spain)

1997-08-01

404

Detection of secondary phases in duplex stainless steel by magnetic force microscopy and scanning Kelvin probe force microscopy  

SciTech Connect

The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite was detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a “ghosted” effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: • Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. • As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. • AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA.

Ramírez-Salgado, J. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Domínguez-Aguilar, M.A., E-mail: madoming@imp.mx [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Castro-Domínguez, B. [University of Tokyo, Department of Chemical System Engineering, Faculty of Engineering Bldg. 5, 7F 722, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113–8656 (Japan); Hernández-Hernández, P. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Newman, R.C. [University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Toronto M5S 3E5 (Canada)

2013-12-15

405

Long-lived magnetism from solidification-driven convection on the pallasite parent body.  

PubMed

Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System. PMID:25612050

Bryson, James F J; Nichols, Claire I O; Herrero-Albillos, Julia; Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan, Gerrit; Nimmo, Francis; Harrison, Richard J

2015-01-22

406

Long-lived magnetism from solidification-driven convection on the pallasite parent body  

NASA Astrophysics Data System (ADS)

Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System.

Bryson, James F. J.; Nichols, Claire I. O.; Herrero-Albillos, Julia; Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan, Gerrit; Nimmo, Francis; Harrison, Richard J.

2015-01-01

407

Quantitative nuclear magnetic resonance to measure body composition in infants and children  

Technology Transfer Automated Retrieval System (TEKTRAN)

Quantitative Nuclear Magnetic Resonance (QMR) is being used in human adults to obtain measures of total body fat (FM) with high precision. The current study assessed a device specially designed to accommodate infants and children between 3 and 50 kg (EchoMRI-AH™). Body composition of 113 infants and...

408

In vivo measurement of body composition of chickens using quantitative magnetic resonance (QMR)  

Technology Transfer Automated Retrieval System (TEKTRAN)

QMR is a nuclear magnetic resonance based method for measuring the fat, lean and water content of the total body of the live animal. The purpose of this study was to evaluate the use of QMR for measuring the body composition of chickens while comparing QMR results to those obtained by dual X-ray ab...

409

Guiding center atoms: Three-body recombination in a strongly magnetized plasma  

E-print Network

Guiding center atoms: Three-body recombination in a strongly magnetized plasma Michael E. Glinsky; accepted 29 January 1991) The three-body recombination rate is calculated for an ion introduced cyclotron frequency. Since the recombination rate is controlled by a kinetic bottleneck a few k, T, below

California at San Diego, University of

410

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

411

An implicit ghost-cell immersed boundary method for simulations of moving body problems with control of spurious force oscillations  

NASA Astrophysics Data System (ADS)

A fully-implicit ghost-cell immersed boundary method for simulations of flow over complex moving bodies on a Cartesian grid is presented. The present immersed boundary method is highly capable of controlling the generation of spurious force oscillations on the surface of a moving body, thereby producing an accurate and stable solution. Spurious force oscillations on the surface of an immersed moving body are reduced by alleviating spatial and temporal discontinuities in the pressure and velocity fields across non-grid conforming immersed boundaries. A sharp-interface ghost-cell immersed-boundary method is coupled with a mass source and sink algorithm to improve the conservation of mass across non-grid conforming immersed boundaries. To facilitate the control for the temporal discontinuity in the flow field due to a motion of an immersed body, a fully-implicit time-integration scheme is employed. A novel backward time-integration scheme is developed to effectively treat multiple layers of fresh cells generated by a motion of an immersed body at a high CFL number condition. The present backward time-integration scheme allows to impose more accurate and stable velocity vectors on fresh cells than those interpolated. The effectiveness of the present fully-implicit ghost-cell immersed boundary method coupled with a mass source and sink algorithm for reducing spurious force oscillations during simulations of moving body problems is demonstrated in a number of test cases.

Lee, Jinmo; You, Donghyun

2013-01-01

412

Magnetic energy dissipation in force-free jets  

SciTech Connect

It is shown that a magnetic pressure-dominated, supersonic jet which expands or contracts in response to variations in the confining external pressure can dissipate magnetic energy through field-line reconnection as it relaxes to a minimum-energy configuration. In order for a continuous dissipation to occur, the effective reconnection time must be a fraction of the expansion time. The dissipation rate for the axisymmetric minimum-energy field configuration is analytically derived. The results indicate that the field relaxation process could be a viable mechanism for powering the synchrotron emission in extragalactic jets if the reconnection time is substantially shorter than the nominal resistive tearing time in the jet. 23 references.

Choudhuri, A.R.; Koenigl, A.

1986-11-01

413

Force-Free Magnetic Fields of Closed Configuration Having More Energy Than Open Fields  

NASA Astrophysics Data System (ADS)

Observations of CMEs show an apparent opening of a coronal magnetic field which has assumed a closed configuration before the eruption. In order for this transition of field configuration to occur spontaneously, the pre-eruption closed field must have more energy than the open field. However, as far as force-free fields are concerned, such a transition is energetically forbidden according to the Aly-Sturrock theorem. The theorem states that the maximum energy of the closed force-free fields with the same boundary-normal field distribution and the same field topology is the energy of the corresponding open field. The force-free fields treated in Aly and Sturrock's proofs of the theorem are force-free fields that can be generated from closed potential fields by footpoint motions conserving the boundary normal field distribution and the field topology. The force-free fields investigated in this paper are force-free fields which are not governed by Aly and Sturrock's proofs. We have constructed force-free fields in weak equilibrium, which can be generated in multiple flux systems by a footpoint motion not conserving the boundary normal field distribution. It is found that there exist force-free fields having more magnetic energy than the corresponding open fields. The relevance with observations and the possible mechanisms of CMEs will be discussed.

Choe, G.; Cheng, C.

2002-05-01

414

Magnetic Evidence for a Partially Differentiated Carbonaceous Chondrite Parent Body  

E-print Network

The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. ...

Shuster, David L.

415

On Generation of magnetic field in astrophysical bodies  

E-print Network

In this letter we compute energy transfer rates from velocity field to magnetic field in MHD turbulence using field-theoretic method. The striking result of our field theoretic calculation is that there is a large energy transfer rate from the large-scale velocity field to the large-scale magnetic field. We claim that the growth of large-scale magnetic energy is primarily due to this transfer. We reached the above conclusion without any linear approximation like that in $\\alpha$-dynamo.

Mahendra K. Verma

2001-12-09

416

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

PubMed

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

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

2013-01-01

417

Simulation and Experiments on Magnetic MicroForces for Magnetic MicroRobots Applications  

E-print Network

of electromagnetic coils. To control the magnetic microrobots trajectory, it is of utmost importance to know be performed. In general, there are two ways to generate controlled magnetic fields: mobile permanent magnets [4] and fixed electromagnets. The control of the trajectory of the magnetic microrobot proves

Paris-Sud XI, Université de

418

Force measurements of a magnetic micro actuator proposed for a microvalve array  

NASA Astrophysics Data System (ADS)

Low-cost, easily-fabricated and power-efficient microvalves are necessary for many microfluidic lab-on-a-chip applications. In this study, we present a simple, low-power, scalable, CMOS-compatible magnetic actuator for microvalve applications composed of a paramagnetic bead as the ball valve over a picoliter reaction well etched into a silicon substrate. The paramagnetic bead, composed of either pure FeSi or magnetite in a SiO2 matrix, is actuated by the local magnetic field gradient generated by a microcoil in an aqueous environment, and the reaction well is situated at the microcoil center. A permanent magnet beneath the microvalve device provides an external magnetic biasing field that magnetizes the bead, enabling bidirectional actuation and reducing the current required to actuate the bead to a level below 10 mA. The vertical and radial magnetic forces exerted on the bead by the microcoil were measured for both pure FeSi and composite beads and agree well with the predictions of 2D axisymmetric finite element method models. Vertical forces were within a range of 13-80 nN, and radial forces were 11-60 nN depending on the bead type. The threshold current required to initiate bead actuation was measured as a function of bead diameter and is found to scale inversely with volume for small beads, as expected based on the magnetic force model. To provide an estimate of the stiction force acting between the bead and the passivation layer on the substrate, repeated actuation trials were used to study the bead throw distance for substrates coated with silicon dioxide, Parylene-C, and photoresist. The stiction observed was lowest for a photoresist-coated substrate, while silicon dioxide and Parylene-C coated substrates exhibited similar levels of stiction.

Chang, Pauline J.; Chang, Frank W.; Yuen, Michelle C.; Otillar, Robert; Horsley, David A.

2014-03-01

419

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

420

Domain-wall structure in thin films with perpendicular anisotropy: Magnetic force microscopy and polarized neutron reflectometry study  

E-print Network

Ferromagnetic domain patterns and three-dimensional domain-wall configurations in thin CoCrPt films with perpendicular magnetic anisotropy were studied in detail by combining magnetic force microscopy and polarized neutron ...

Navas, David

421

Simulations of energy release and particle acceleration in forced magnetic reconnection in solar flare current sheets  

NASA Astrophysics Data System (ADS)

Solar flares are a release of stored magnetic energy through magnetic reconnection. The electric fields associated with reconnection are a strong candidate for explaining the origin of the large numbers of non-thermal electrons and ions which are produces in flares. A useful model for large-scale current sheets in solar flares is forced magnetic reconnection, triggered by a boundary disturbance, in a force-free current sheet. A chain of magnetic islands is generated, where particles may be trapped, as well as remaining open field lines which allow particles to escape to the solar surface or into the heliosphere. We present results both from test particle codes coupled to magnetohydrodynamic simulations, and particle-in-cell codes, and compare the results of the two approaches with regard to the energy spectra and spatial locations of both ions and electrons.

Browning, Philippa; Gordovskyy, Mykola

422

Nonlinear force-free coronal magnetic field extrapolation scheme based on the direct boundary integral formulation  

NASA Astrophysics Data System (ADS)

The boundary integral equation (BIE) method was first proposed by Yan and Sakurai (2000) and used to extrapolate the nonlinear force-free magnetic field in the solar atmosphere. Recently, Yan and Li (2006) improved the BIE method and proposed the direct boundary integral equation (DBIE) formulation, which represents the nonlinear force-free magnetic field by direct integration of the magnetic field on the bottom boundary surface. On the basis of this new method, we devised a practical calculation scheme for the nonlinear force-free field extrapolation above solar active regions. The code of the scheme was tested by the analytical solutions of Low and Lou (1990) and was applied to the observed vector magnetogram of solar active region NOAA 9077. The results of the calculations show that the improvement of the new computational scheme to the scheme of Yan and Li (2006) is significant, and the force-free and divergence-free constraints are well satisfied in the extrapolated fields. The calculated field lines for NOAA 9077 present the X-shaped structure and can be helpful for understanding the magnetic configuration of the filament channel as well as the magnetic reconnection process during the Bastille Day flare on 14 July 2000.

He, Han; Wang, Huaning

2008-05-01

423

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

424

General Formulation for Magnetic Forces in Linear Materials and Permanent Magnets  

Microsoft Academic Search

A previous work described how a magneto-mechanical tensor can be obtained from the application of the virtual work principle to the energy density or co-energy density in any given media. This paper describes how the volume and surface force densities can be obtained from this tensor. Taking these force densities into account, we can calculate the total force over any

R. Sanchez Grandia; V. Aucejo Galindo; A. Usieto Galve; R. Vives Fos

2008-01-01

425

Force  

NSDL National Science Digital Library

Instructions: This is a webquest designed to help students understand force. It is specifically meant to teach the idea that the greater the force applied to an object the greater the change in speed or direction of the object depending on the mass. This is also known as Newton's Second Law of Motion. Lets Learn about Force! For this project your students will understand force. They will use Newton's second law to solve the problem presented. UT Core Curriculum: Science 3rd Grade. Standard 3- Students will understand the relationship between the force applied to an object and resulting motion of the ...

Mrs. Brownie

2010-04-07

426

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

Microsoft Academic Search

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

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

1992-01-01

427

Confinement of Plasma along Shaped Open Magnetic Fields from the Centrifugal Force of Supersonic Plasma Rotation  

SciTech Connect

Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic ExB rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.

Teodorescu, C.; Young, W. C.; Swan, G. W. S.; Ellis, R. F.; Hassam, A. B.; Romero-Talamas, C. A. [University of Maryland, College Park, Maryland 20742 (United States)

2010-08-20

428

Relationship between coercive force and anisotropy field for oriented barium ferrite tapes and magnets  

Microsoft Academic Search

The approximate anisotropy field (Han) has been determined for twelve experimental oriented barium ferrite recording tapes and magnets with coercive force (Hc) between 715 Oe and 5250 Oe, and squareness ratio greater than 0.80. The Han values were taken as the ratio of saturation magnetic moment (ms) to the initial hard-axis susceptibility (m\\/H). Han values were generally within the 12.6–19.8

R. E. Fayling

1978-01-01

429

Relationship between coercive force and anisotropy field for oriented barium ferrite tapes and magnets  

Microsoft Academic Search

The approximate anisotropy field (Han) has been determined for twelve experimental oriented barium ferrite recording tapes and magnets with coercive force (Hc) between 715 Oe and 5250 Oe, and squareness ratio greater than 0.80. The Han values were taken as the ratio of saturation magnetic moment (ms) to the initial hard-axis susceptibility (m\\/H). Han values were generally within the 12.6-19.8

R. E. Fayling

1978-01-01

430

Estimation of the total magnetization direction of approximately spherical bodies  

NASA Astrophysics Data System (ADS)

We have developed a fast total-field anomaly inversion to estimate the magnetization direction of multiple sources with approximately spherical shape and known centres. Our method can be applied to interpret multiple sources with different magnetization directions. It neither requires the prior computation of any transformation like reduction to the pole nor the use of regularly spaced data on a horizontal grid. The method contains flexibility to be implemented as a linear or non-linear inverse problem, which results, respectively, in a least-squares or robust estimate of the components of the magnetization vector of the sources. Applications to synthetic data show the robustness of our method against interfering anomalies and errors in the location of the sources' centre. Besides, we show the feasibility of applying the upward continuation to interpret non-spherical sources. Applications to field data over the Goiás Alkaline Province (GAP), Brazil, show the good performance of our method in estimating geological meaningful magnetization directions. The results obtained for a region of the GAP, near from the alkaline complex of Diorama, suggest the presence of non-outcropping sources marked by strong remanent magnetization with inclination and declination close to -70.35° and -19.81°, respectively. This estimated magnetization direction leads to predominantly positive reduced-to-the-pole anomalies, even for other region of the GAP, in the alkaline complex of Montes Claros de Goiás. These results show that the non-outcropping sources near from the alkaline complex of Diorama have almost the same magnetization direction of that ones in the alkaline complex of Montes Claros de Goiás, strongly suggesting that these sources have emplaced the crust almost within the same geological time interval.

Oliveira, V. C., Jr.; Sales, D. P.; Barbosa, V. C. F.; Uieda, L.

2014-09-01

431

The force acting on a superparamagnetic bead due to an applied magnetic Sergey S. Shevkoplyas,*a  

E-print Network

,3 Macroscopic permanent mag- nets and electromagnets can produce magnetic fields suffi- ciently strong (.0.5 T as permanent magnets. Microfabricated electromagnets produce magnetic fields too weak (0­10 mT) to saturateThe force acting on a superparamagnetic bead due to an applied magnetic field Sergey S. Shevkoplyas

Prentiss, Mara

432

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

433

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

434

Note on a Lagally formulation for the steady body force attendant to surface-singularity distributions  

NASA Astrophysics Data System (ADS)

In 1922, Lagally presented expressions for the overall loads in response to a steady flow of an inviscid incompressible fluid stream impinging on a shape created by isolated singularities embedded within the extended flow field interior to the body surface. The simple load expressions are a summation of terms containing the product of the local regular fluid speed (defined as the speed excluding contribution from the local singularity) and the singularity strength. In 1981, Guevel and Grekas extended the analysis to a similar case with singularities distributed on a closed surface. In 2006, Ledoux et al gave a straightforward derivation for a source surface distribution and argued that such an approach is 'less prone to numerical inaccuracies'. Herein the straightforward nonlinear formulation appropriate for surface singularities is expanded to include a surface distribution of vortices and/or doublets. Numerical results derived from both the Lagally integral for distributed singularities and the integration of the product of the inviscid pressure and unit normal are shown to have similar convergence tendencies toward exact inviscid results for the computed forces on a class of two-dimensional lifting foils.

Brockett, Terry E.

2010-08-01

435

Comparison of forced-air warming and electric heating pad for maintenance of body temperature during total knee replacement.  

PubMed

We conducted a randomised controlled trial to compare the efficacy of forced-air warming (Bair Hugger(trade mark), Augustine Medical model 500/OR, Prairie, MN) with that of an electric heating pad (Operatherm 202, KanMed, Sweden) for maintenance of intra-operative body temperature in 60 patients undergoing total knee replacement under combined spinal-epidural anaesthesia. Intra-operative tympanic and rectal temperatures and verbal analogue score for thermal comfort were recorded. There were no differences in any measurements between the two groups, with mean (SD) final rectal temperatures of 36.8 (0.4) degrees C with forced-air warming and 36.9 (0.4) degrees C with the electric pad. The heating pad is as effective as forced-air warming for maintenance of intra-operative body temperature. PMID:17042850

Ng, V; Lai, A; Ho, V

2006-11-01

436

Not all radiopaque foreign bodies shadow on ultrasound: unexpected sonographic appearance of a radiopaque magnet.  

PubMed

Foreign body ingestion is a common indication for imaging children. Ultrasound can be a useful adjunct to serial radiographs for evaluation of foreign bodies in the enteric tract. This case report describes a child who swallowed a single magnetic rock. Follow-up radiographs 4 days later could not determine progression of the foreign body beyond the stomach. Ultrasound was used to locate it, showing a structure with unexpected posterior reverberation artifact in the stomach. This was correlated with a similar magnet in a water bath demonstrating identical reverberation artifact. This report discusses the underlying factors for the different sonographic appearances and associated ultrasound artifacts of foreign bodies. This knowledge is important when performing sonography as adjunct modality for identification of foreign bodies in the gastrointestinal tract. PMID:25364959

Shiu-Cheung Chan, Sherwin; Russell, Marybeth; Ho-Fung, Victor M

2014-12-01

437

First use of synoptic vector magnetograms for global nonlinear, force-free coronal magnetic field models  

NASA Astrophysics Data System (ADS)

Context. The magnetic field permeating the solar atmosphere is generally thought to provide the energy for much of the activity seen in the solar corona, such as flares, coronal mass ejections (CMEs), etc. To overcome the unavailability of coronal magnetic field measurements, photospheric magnetic field vector data can be used to reconstruct the coronal field. Currently, there are several modelling techniques being used to calculate three-dimensional field lines into the solar atmosphere. Aims: For the first time, synoptic maps of a photospheric-vector magnetic field synthesized from the vector spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) are used to model the coronal magnetic field and estimate free magnetic energy in the global scale. The free energy (i.e., the energy in excess of the potential field energy) is one of the main indicators used in space weather forecasts to predict the eruptivity of active regions. Methods: We solve the nonlinear force-free field equations using an optimization principle in spherical geometry. The resulting three-dimensional magnetic fields are used to estimate the magnetic free energy content Efree = Enlfff - Epot, which is the difference of the magnetic energies between the nonpotential field and the potential field in the global solar corona. For comparison, we overlay the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the atmospheric imaging assembly (AIA) on board the Solar Dynamics Observatory (SDO). Results: For a single Carrington rotation 2121, we find that the global nonlinear force-free field (NLFFF) magnetic energy density is 10.3% higher than the potential one. Most of this free energy is located in active regions.

Tadesse, T.; Wiegelmann, T.; Gosain, S.; MacNeice, P.; Pevtsov, A. A.

2014-02-01

438

Collective behaviour in two-dimensional cobalt nanoparticle assemblies observed by magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The use of magnetic nanoparticles in the development of ultra-high-density recording media is the subject of intense research. Much of the attention of this research is devoted to the stability of magnetic moments, often neglecting the influence of dipolar interactions. Here, we explore the magnetic microstructure of different assemblies of monodisperse cobalt single-domain nanoparticles by magnetic force microscopy and magnetometric measurements. We observe that when the density of particles per unit area is higher than a determined threshold, the two-dimensional self-assemblies behave as a continuous ferromagnetic thin film. Correlated areas (similar to domains) of parallel magnetization roughly ten particles in diameter appear. As this magnetic percolation is mediated by dipolar interactions, the magnetic microstructure, its distribution and stability, is strongly dependent on the topological distribution of the dipoles. Thus, the magnetic structures of three-dimensional assemblies are magnetically soft, and an evolution of the magnetic microstructure is observed with consecutive scans of the microscope tip.

Puntes, Victor F.; Gorostiza, Pau; Aruguete, Deborah M.; Bastus, Neus G.; Alivisatos, A. Paul

2004-04-01

439

A new approach to scaffold fixation by magnetic forces: Application to large osteochondral defects.  

PubMed

Scaffold fixation represents one of the most serious challenges in osteochondral defect surgery. Indeed, the fixation should firmly hold the scaffold in the implanted position as well as it should guaranty stable bone/scaffold interface for efficient tissue regeneration. Nonetheless successful results have been achieved for small defect repair, the fixation remains really problematic for large defects, i.e. defects with areas exceeding 2cm(2). This paper advances an innovative magnetic fixation approach based on application of magnetic scaffolds. Finite element modeling was exploited to investigate the fixation efficiency. We considered three magnetic configurations: (1) external permanent magnet ring placed around the leg near the joint; (2) four small permanent magnet pins implanted in the bone underlying the scaffold; (3) four similarly implanted stainless steel pins which magnetization was induced by the external magnet. It was found that for most appropriate magnetic materials and optimized magnet-scaffold positioning all the considered configurations provide a sufficient scaffold fixation. In addition to fixation, we analyzed the pressure induced by magnetic forces at the bone/scaffold interface. Such pressure is known to influence significantly the bone regeneration and could be used for magneto-mechanical stimulation. PMID:22381395

Russo, Alessandro; Shelyakova, Tatiana; Casino, Daniela; Lopomo, Nicola; Strazzari, Alessandro; Ortolani, Alessandro; Visani, Andrea; Dediu, Valentin; Marcacci, Maurilio

2012-11-01

440

Magnetic Energy and Helicity Budgets in the Active-Region Solar Corona. II. Nonlinear Force-Free Approximation  

E-print Network

Expanding on an earlier work that relied on linear force-free magnetic fields, we self-consistently derive the instantaneous free magnetic energy and relative magnetic helicity budgets of an unknown three-dimensional nonlinear force-free magnetic structure extending above a single, known lower-boundary magnetic field vector. The proposed method does not rely on the detailed knowledge of the three-dimensional field configuration but is general enough to employ only a magnetic connectivity matrix on the lower boundary. The calculation yields a minimum free magnetic energy and a relative magnetic helicity consistent with this free magnetic energy. The method is directly applicable to photospheric or chromospheric vector magnetograms of solar active regions. Upon validation, it basically reproduces magnetic energies and helicities obtained by well-known, but computationally more intensive and non-unique, methods relying on the extrapolated three-dimensional magnetic field vector. We apply the method to three acti...

Georgoulis, M K; Raouafi, N -E

2012-01-01

441

Electric Charge and Magnetic Flux on Rotating Black Holes in a Force-Free Magnetosphere  

E-print Network

The electric charge on rotating black holes is calculated to be ~ BJ in the force-free configuration of Ghosh (2000), with a horizon flux of ~ BM^2. This charge is gravitationally weak for B ~ 10^{15} G, so that the Kerr metric applies. Being similar to the electric charge of a magnetar, both electric charge and magnetic flux should be, in sign and order of magnitude, continuous during stellar collapse into a black hole. Extraction of the rotational energy from newly formed black holes may proceed by interaction with the magnetic field. Keywords:black hole physics --magnetic fields

Hyun Kyu Lee; Chul H. Lee; Maurice H. P. M. van Putten

2001-02-13

442

Motion of a conducting rigid body in rotating magnetic fields  

Microsoft Academic Search

A control technique for a gyroscope with an electrostatic suspension of the conducting rotor is described. The gyroscope is controlled via rotating magnetic fields generated by three mutually perpendicular circular stators. By controlling the operation of these stators, it is possible to obtain the desired characteristics of gyroscope motion: the rotor rotation rate, the nutation angle, and the value and

V. N. Komarov

1989-01-01

443

A Procedure for the Isolation of Asbestos Bodies from Lung Tissue by Exploiting their Magnetic Properties: A New Approach to Asbestos Body Study  

Microsoft Academic Search

The role of asbestos bodies (and associated proteinacious coating) in asbestos associated diseases is not well understood. Currently employed methods of isolation of these bodies employ harsh chemicals that lead to destruction of their proteinacious coating. In this work a method was developed that enabled the purification of whole, integral, unmodified asbestos bodies (AB) by exploiting their magnetic properties. Albumin

Violetta Borelli; Cristiana Brochetta; Mauro Melato; Clara Rizzardi; Maurizio Polentarutti; Cristina Busatto; Francesca Vita; Rita Abbate; Roberto Gotter; Giuliano Zabucchi

2007-01-01

444

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

Microsoft Academic Search

Magnetite thin films grown on [001] oriented MgO substrates are analyzed by means of electron backscatter diffraction (EBSD) analysis and magnetic force microscopy in applied fields. The EBSD technique enables the crystallographic orientation of individual grains to be determined with a high spatial resolution up to 20 nm on such ceramic samples. A high image quality of the recorded Kikuchi

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

2007-01-01

445

Analysis of Three-Phase Power Transformer Short Circuit Magnetic Field and Forces  

Microsoft Academic Search

This research studies the magnetic field and forces on the windings of transformer due to short circuit. Three dimensional finite element computation of three-phase power transformer is carried out. The model developed have been applied to power transformer and the results are verified experimentally. To verify the computation results, they are compared with those obtained using ANSYS software simulation.

Hongkui Li; Gang Cheng

2010-01-01

446

Elimination of three-phase transformer inrush current through core forced magnetization and simultaneous closing  

Microsoft Academic Search

The inrush current occurs during transformer energization due to flux saturation in the core. Controlled switching connects transformer to power grid in proper phase angle derived from core remanent fluxes. The DC forced magnetization prior to transformer energization is one of simultaneous closing strategy methods. Active intervention to the transformer remanent flux was realized as a DC power supply with

Miroslav Novák

2010-01-01

447

Non-linear force-free magnetic dip models of quiescent prominence fine structures  

NASA Astrophysics Data System (ADS)

Aims: We use 3D non-linear force-free magnetic field modeling of prominence/filament magnetic fields to develop the first 2D models of individual prominence fine structures based on the 3D configuration of the magnetic field of the whole prominence. Methods: We use an iterative technique to fill the magnetic dips produced by the 3D modeling with realistic prominence plasma in hydrostatic equilibrium and with a temperature structure that contains the prominence-corona transition region. With this well-defined plasma structure the radiative transfer can be treated in detail in 2D and the resulting synthetic emission can be compared with prominence/filament observations. Results: Newly developed non-linear force-free magnetic dip models are able to produce synthetic hydrogen Lyman spectra in a qualitative agreement with a range of quiescent prominence observations. Moreover, the plasma structure of these models agrees with the gravity induced prominence fine structure models which have already been shown to produce synthetic spectra in good qualitative agreement with several observed prominences. Conclusions: We describe in detail the iterative technique which can be used to produce realistic plasma models of prominence fine structures located in prominence magnetic field configurations containing dips, obtained using any kind of magnetic field modeling.

Gunár, S.; Mackay, D. H.; Anzer, U.; Heinzel, P.

2013-03-01

448

ON THE FORCE-FREE NATURE OF PHOTOSPHERIC SUNSPOT MAGNETIC FIELDS AS OBSERVED FROM HINODE (SOT/SP)  

SciTech Connect

A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic fields (computed from the force-free parameter {alpha}), and any kind of extrapolation, heavily hinges on the force-free approximation of the photospheric sunspot magnetic fields. Thus, it is of vital importance to inspect the force-free behavior of sunspot magnetic fields. The force-free nature of sunspot magnetic fields has been examined earlier by some researchers, ending with incoherent results. Accurate photospheric vector field measurements with high spatial resolution are required to inspect the force-free nature of sunspots. For this purpose, we use several vector magnetograms of high spatial resolution obtained from the Solar Optical Telescope/Spectro-Polarimeter on board Hinode. Both the necessary and sufficient conditions for force-free nature are examined by checking the global and local nature of equilibrium magnetic forces over sunspots. We find that sunspot magnetic fields are not very far from the force-free configuration, although they are not completely force-free on the photosphere. The umbral and inner penumbral fields are more force-free than the middle and outer penumbral fields. During their evolution, sunspot magnetic fields are found to maintain their proximity to force-free field behavior. Although a dependence of net Lorentz force components is seen on the evolutionary stages of the sunspots, we do not find a systematic relationship between the nature of sunspot magnetic fields and the associated flare activity. Further, we examine whether the fields at the photosphere follow linear or nonlinear force-free conditions. After examining this in various complex and simple sunspots, we conclude that, in either case, photospheric sunspot magnetic fields are closer to satisfying the nonlinear force-free field approximation.

Tiwari, Sanjiv Kumar, E-mail: tiwari@mps.mpg.de [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur 313 001 (India)

2012-01-01

449

Calculation of cogging force in a novel slotted linear tubular brushless permanent magnet motor  

SciTech Connect

There is an increasing requirement for controlled linear motion over short and long strokes, in the factory automation and packaging industries, for example. Linear brushless PM motors could offer significant advantages over conventional actuation technologies, such as motor driven cams and linkages and pneumatic rams--in terms of efficiency, operating bandwidth, speed and thrust control, stroke and positional accuracy, and indeed over other linear motor technologies, such as induction motors. Here, a finite element/analytical based technique for the prediction of cogging force in a novel topology of slotted linear brushless permanent magnet motor has been developed and validated. The various force components, which influence cogging are pre-calculated by the finite element analysis of some basic magnetic structures, facilitate the analytical synthesis of the resultant cogging force. The technique can be used to aid design for the minimization of cogging.

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

1997-09-01

450

Critical speeds and forced response solutions for active magnetic bearing turbomachinery, part 1  

NASA Technical Reports Server (NTRS)

The prediction of critical speeds and forced response of active magnetic bearing turbomachinery is of great interest due to the increased use of this new and promising technology. Calculating the system undamped critical speeds and forced response is important to all those who are involved in the design of the active magnetic bearing system. An extended Jeffcott model which was used as an approximate solution to a more accurate transfer matrix procedure is presented. Theory behind a two-degree-of freedom extended Jeffcoat model is presented. Results of the natural frequency calculation are shown followed by the results of the forced response calculation. The system response was predicted for two types of forcing. A constant magnitude excitation with a wide frequency variation was applied at the bearings as one forcing function. The normal unbalance force at the midspan was the second source of excitation. The results of this extended Jeffcott solution gives useful design guidance for the influence of the first and third modes of a symmetric rotor system.

Keesee, J.; Rawal, D.; Kirk, R. Gordon

1991-01-01

451

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

NASA Astrophysics Data System (ADS)

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.

Choe, G. S.; Cheng, C. Z.

2002-08-01

452

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

453

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

454

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

455

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

456

Force and heat current formulas for many-body potentials in molecular dynamics simulation with applications to thermal conductivity calculations  

E-print Network

We derive expressions of interatomic force and heat current for many-body potentials such as the Tersoff, the Brenner, and the Stillinger-Weber potential used extensively in molecular dynamics simulations of covalently bonded materials. Although these potentials have a many-body nature, a pairwise force expression that follows Newton's third law can be found without referring to any partition of the potential. Based on this force formula, a stress applicable for periodic systems can be unambiguously defined. The force formula can then be used to derive the heat current formulas using a natural potential partitioning. Our heat current formulation is found to be equivalent to most of the seemingly different heat current formulas used in the literature, but to deviate from the stress-based formula derived from two-body potential. We validate our formulation numerically on various systems descried by the Tersoff potential, namely three-dimensional silicon and diamond, two-dimensional graphene, and quasi-one-dimen...

Fan, Zheyong; Wang, Hui-Qiong; Zheng, Jin-Cheng; Donadio, Davide; Harju, Ari

2015-01-01

457

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