Sample records for magnetic body forces

  1. Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  2. Modeling Magnetic Torque and Force for Controlled Manipulation of Soft-Magnetic Bodies

    Microsoft Academic Search

    Jake J. Abbott; Olgaç Ergeneman; Michael P. Kummer; Ann M. Hirt; Bradley J. Nelson

    2007-01-01

    We calculate the torque and force generated by an arbitrary magneticfield on an axially symmetric soft-magnetic body. We consider the magnetization of the body as a function of the applied field, using a con- tinuous model that unifies two disparate magnetic models. The continuous torque and force follow. The model is verified experimentally, and captures the often neglected region between

  3. Nonlinear oscillation of a rigid body over high- Tc superconductors supported by electro-magnetic forces

    NASA Astrophysics Data System (ADS)

    Sugiura, T.; Ogawa, S.; Ura, H.

    2005-10-01

    Characteristics of high- Tc superconducting levitation systems are no contact support and stable levitation without control. They can be applied to supporting mechanisms in machines, such as linear-drives and magnetically levitated trains. But small damping due to noncontact support and nonlinearity in the magnetic force can easily cause complicated phenomena of nonlinear dynamics. This research deals with nonlinear oscillation of a rigid bar supported at its both ends by electro-magnetic forces between superconductors and permanent magnets as a simple modeling of the above application. Deriving the equation of motion, we discussed an effect of nonlinearity in the magnetic force on dynamics of the levitated body: occurrence of combination resonance in the asymmetrical system. Numerical analyses and experiments were also carried out, and their results confirmed the above theoretical prediction.

  4. ANALYSIS AND NUMERICAL SIMULATION OF MAGNETIC FORCES BETWEEN RIGID POLYGONAL BODIES.

    E-print Network

    Popovic, Nikola

    of magnetoelastic phenomena is a field of active research. Formulae for the magnetic force in macroscopic systems. Introduction The analysis of magnetoelastic phenomena is a field of active research. In particular

  5. 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.

  6. Magnetic modelling of strongly magnetized bodies

    NASA Astrophysics Data System (ADS)

    Koppelt, U.; Abrahamsen, N.; Voss, O.

    At different prehistoric iron production sites near Varde in SW Jutland (Denmark) several thousands slag bodies remained after the smeltings and were located by magnetic surveying. Total magnetic field data measured over isolated slag bodies were inverted to determine the direction of the remanent magnetization. Palaeomagnetic investigations were carried out for dating purposes. The large scatter of palaeomagnetic directions obtained for different specimens from a single slag body was interpreted in terms of shape anisotropy (magnetic refraction). By an integral equation technique the effect of magnetic refraction was modelled. Charts were computed to correct the inversion results. The obtained directions correspond to the directions predicted by the secular variation curve for the appropriate period of time and to C 14 datings from the same archaeological site.

  7. Investigating Magnetic Force Fields

    NSDL National Science Digital Library

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

    2012-03-18

    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.

  8. Three-body critical Casimir forces.

    PubMed

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

    2015-04-01

    Within mean-field theory we calculate universal scaling functions associated with critical Casimir forces for a system consisting of three parallel cylindrical colloids immersed in a near-critical binary liquid mixture. For several geometrical arrangements and boundary conditions at the surfaces of the colloids we study the force between two colloidal particles in the direction normal to their axes, analyzing the influence of the presence of a third particle on that force. Upon changing temperature or the relative positions of the particles we observe interesting features such as a change of sign of this force caused by the presence of the third particle. We determine the three-body component of the forces acting on one of the colloids by subtracting the pairwise forces from the total force. The three-body contribution to the total critical Casimir force turns out to be more pronounced for small surface-to-surface distances between the colloids as well as for temperatures close to criticality. Moreover, we compare our results with similar ones for other physical systems such as three atoms interacting via van der Waals forces. PMID:25974488

  9. Electric and Magnetic Forces: Electromagnetism

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2008-10-30

    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.

  10. Distribution of electromagnetic force in permanent magnets

    Microsoft Academic Search

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

    1998-01-01

    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

  11. Dispersive forces on bodies and atoms: a unified approach

    E-print Network

    Raabe, C; Raabe, Christian; Welsch, Dirk-Gunnar

    2006-01-01

    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.

  12. Calculation of electromagnetic forces for magnet wheels

    Microsoft Academic Search

    Kokichi Ogawa; Yoko Horiuchi; Nobuo Fujii

    1997-01-01

    The characteristics of magnet wheels for magnetic levitation and linear drive applications are investigated by using a three-dimensional computer simulation. Magnet wheels levitate by revolving permanent magnets over a conducting plate, in which eddy currents are induced. Thrust is also produced by making the torque unbalanced. This paper deals with “partial overlap type” magnet wheels, producing a lift force and

  13. Hydrodynamic Forces on Submerged Rigid Bodies -Steady Flow

    E-print Network

    Thomann, Enrique

    Hydrodynamic Forces on Submerged Rigid Bodies - Steady Flow Ronald B. Guenther +#3; Department The evaluation of the hydrodynamic forces on a submerged rigid body requires the knowledge of the stress vector of the surface of the submerged rigid body, can be obtained that relate the velocity of the rigid body

  14. Cryogenic magnetic force microscope M. Rosemana)

    E-print Network

    Grütter, Peter

    Cryogenic magnetic force microscope M. Rosemana) and P. Gru¨tter Centre for the Physics for publication 27 June 2000 We describe our cryogenic magnetic force microscope, operating between 4.2 and 300 K. As an effective means of vibration isolation, we suspend the microscope from a soft bellows which attenuates

  15. May the Magnetic Force Be with You

    NSDL National Science Digital Library

    VU Bioengineering RET Program, School of Engineering,

    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.

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

    Microsoft Academic Search

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

    2003-01-01

    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

  17. Verifying Magnetic Force on a Conductor

    ERIC Educational Resources Information Center

    Ganci, Salvatore

    2011-01-01

    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…

  18. LABORATORY VI MAGNETIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    . · Calculate the motion of a particle with a constant acceleration. · Calculate the motion of a particle of the universe, the atomic structure of materials, and the quark structure of elementary particles. Magnetic; · Calculate the magnetic force on a charged particle moving in a uniform magnetic field and describe its

  19. On the electromagnetic force on a polarizable body

    Microsoft Academic Search

    A. Engel; R. Friedrichs

    2002-01-01

    The force on a macroscopic polarizable body in an inhomogenous electromagnetic field is calculated for three simple exactly solvable situations. By comparing different approaches, we pinpoint possible pitfalls and resolve recent confusion about the force density in ferrofluids.

  20. Development of a body force description for compressor stability assessment

    E-print Network

    Kiwada, George (George Ford)

    2008-01-01

    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 ...

  1. Magnetic force and work: an accessible example

    NASA Astrophysics Data System (ADS)

    Gates, Joshua

    2014-05-01

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

  2. Static forces in a superconducting magnet bearing

    SciTech Connect

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

    1995-11-01

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

  3. Body Force Model for the Aerodynamics of Inclined Perforated Surfaces

    E-print Network

    Papamoschou, Dimitri

    Body Force Model for the Aerodynamics of Inclined Perforated Surfaces Juntao Xiong, Andrew Johnson of perforated surfaces inclined to a freestream. The goal is to characterize the key parameters affecting coefficient Cp = pressure coefficient D = hole size on plane of freestream FB = body force H = nozzle height h

  4. Investigation of a cuboidal permanent magnet's force exerted on a robotic capsule.

    PubMed

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

    2014-01-01

    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

  5. LABORATORY V MAGNETIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    of a particle with a constant acceleration. · Calculate the motion of a particle with an acceleration structure of materials, and the quark structure of elementary particles. The magnetic interaction can best current-carrying wires, and coils of wire. · Calculate the magnetic force on a charged particle moving

  6. Magnetic wires with DNA cores: A magnetic force microscopy study

    NASA Astrophysics Data System (ADS)

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

    2005-02-01

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

  7. Treatment of body forces in boundary element design sensitivity analysis

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  8. Magnetic force microscopy: quantitative issues in biomaterials.

    PubMed

    Passeri, Daniele; Dong, Chunhua; Reggente, Melania; Angeloni, Livia; Barteri, Mario; Scaramuzzo, Francesca A; De Angelis, Francesca; Marinelli, Fiorenzo; Antonelli, Flavia; Rinaldi, Federica; Marianecci, Carlotta; Carafa, Maria; Sorbo, Angela; Sordi, Daniela; Arends, Isabel Wce; Rossi, Marco

    2014-01-01

    Magnetic force microscopy (MFM) is an atomic force microscopy (AFM) based technique in which an AFM tip with a magnetic coating is used to probe local magnetic fields with the typical AFM spatial resolution, thus allowing one to acquire images reflecting the local magnetic properties of the samples at the nanoscale. Being a well established tool for the characterization of magnetic recording media, superconductors and magnetic nanomaterials, MFM is finding constantly increasing application in the study of magnetic properties of materials and systems of biological and biomedical interest. After reviewing these latter applications, three case studies are presented in which MFM is used to characterize: (i) magnetoferritin synthesized using apoferritin as molecular reactor; (ii) magnetic nanoparticles loaded niosomes to be used as nanocarriers for drug delivery; (iii) leukemic cells labeled using folic acid-coated core-shell superparamagnetic nanoparticles in order to exploit the presence of folate receptors on the cell membrane surface. In these examples, MFM data are quantitatively analyzed evidencing the limits of the simple analytical models currently used. Provided that suitable models are used to simulate the MFM response, MFM can be used to evaluate the magnetic momentum of the core of magnetoferritin, the iron entrapment efficiency in single vesicles, or the uptake of magnetic nanoparticles into cells. PMID:25050758

  9. An unusual destination for magnetic foreign bodies.

    PubMed

    Robey, Thomas E; Kaimakliotis, Hristos Z; Hittelman, Adam B; Walsh, Susan A

    2014-09-01

    Rare earth metal magnets (Buckyballs and similar products) remain an important public health risk for children. We report the presentation, course, and treatment of a boy who inserted a string of 30 magnets through his urethra into his bladder and review the diagnostic as well as the therapeutic options for foreign bodies inserted into the pediatric urogenital tract. PMID:25186508

  10. Levitation forces in bearingless permanent magnet motors

    SciTech Connect

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

    1999-09-01

    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.

  11. Thermodynamic properties of nuclear matter with three-body forces

    SciTech Connect

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

    2009-08-15

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

  12. Body fat predicts forced vital capacity in college males

    Microsoft Academic Search

    José Moncada-jiménez

    2003-01-01

    The study was designed to determine how body fat percentage (BF%), body fat distribution (BFD), and abdominal muscular endurance (AME) relate to pul-monary function (PF) as measured by the forced vital capacity (FVC), the forced expiratory volume in 1 s (FEV1), the FEV1\\/FVC ratio, and the maximal inspiratory pressure (MIP) among college (M= 22.82,SD = 2.45 yr) males (N= 60).

  13. LABORATORY V MAGNETIC FIELDS AND FORCES

    E-print Network

    Minnesota, University of

    with a constant acceleration. · Calculate the motion of a particle with an acceleration of constant magnitude, the atomic structure of materials, and the quark structure of elementary particles. In this set of laboratory-carrying wires, and coils of wire. · Calculate the magnetic force on a charged particle moving in a uniform

  14. A compact high field magnetic force microscope.

    PubMed

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

    2014-12-01

    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

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

    E-print Network

    Degen, Christian

    Frequency domain multiplexing, using an actively damped micromechanical cantilever, is used to detect multiple force signals simultaneously. The measurement principle is applied to magnetic resonance force microscopy to ...

  16. Body force circulation and the Antarctic Ozone minimum

    NASA Technical Reports Server (NTRS)

    Dunkerton, Timothy J.

    1988-01-01

    A dynamical mechanism, which is relevant to the ozone-depletion problem and which involves a 'body force' circulation discussed by Eliassen (1951), is considered. The body force problem and its application to 'generic' upper-tropospheric wave-driving are discussed theoretically. Following a review of the interhemispheric differences in the winter and early-spring circulation, the elliptic equation governing the residual mean meridional streamfunction is derived, and its analytic-solution properties in negligible shear are discussed. Finally, a numerical solution is derived using the observed August winds under the assumption of radiative equilibrium, and the effect of diabatic heating is discussed.

  17. Magnetic Resonance Force Microscopy Detected Long-Lived Spin Magnetization

    PubMed Central

    Chen, Lei; Longenecker, Jonilyn G.; Moore, Eric W.; Marohn, John A.

    2015-01-01

    Magnetic resonance force microscopy (MRFM), which combines magnetic resonance imaging with scanning probe microscopy together, is capable of performing ultra-sensitive detection of spin magnetization. In an attempt to observe dynamic nuclear polarization (DNP) in an MRFM experiment, which could possibly further improve its sensitivity towards a single proton spin, a film of perdeuterated polystyrene doped with a nitroxide electron-spin probe was prepared. A high-compliance cantilever with a 4 ?m diameter magnetic tip was brought near the film at a temperature of 7.3 K and in a background magnetic field of ~0.6 T. The film was irradiated with 16.7 GHz microwaves while the resulting transient change in cantilever frequency was recorded in real time. In addition to observing the expected prompt change in cantilever frequency due to saturation of the nitroxide’s electron-spin magnetization, we observed a persistent cantilever frequency change. Based on its magnitude, lifetime, and field dependence, we tentatively attribute the persistent signal to polarized deuteron magnetization created via transfer of magnetization from electron spins. Further measurements of the persistent signal’s dependence on the cantilever amplitude and tip-sample separation are presented and explained by the cross-effect DNP mechanism in high magnetic field gradients. PMID:26097251

  18. Controlling a magnetic force microscope to track a magnetized nanosize particle

    E-print Network

    Andersson, Sean B.

    1 Controlling a magnetic force microscope to track a magnetized nanosize particle Dimitar Baronov moving in three-dimensions using a magnetic force microscope (MFM). The stray magnetic field a feedback control law which steers the tip of a magnetic force microscope (MFM) to remain in a neighborhood

  19. Three-body forces and shell structure in calcium isotopes

    E-print Network

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

    2012-07-02

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

  20. Magnetic dynamos in accreting planetary bodies

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  1. Forced vibrations of a body supported by viscohyperelastic shear mountings

    Microsoft Academic Search

    A. E. Zúñiga; M. F. Beatty

    2001-01-01

    The damped, finite-amplitude forced vibration of a rigid body supported symmetrically by simple shear springs and by a smooth inclined bearing surface is studied. The spring material is characterized as a compressible or incompressible, homogeneous and isotropic viscohyperelastic material for which the shear response function in a simple shear deformation is a quadratic function of the amount of shear. The

  2. Collision of viscoelastic bodies: Rigorous derivation of dissipative force.

    PubMed

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

    2015-06-01

    We report a new theory of dissipative forces acting between colliding viscoelastic bodies. The impact velocity is assumed not to be large to neglect plastic deformations in the material and propagation of sound waves. We consider the general case of bodies of an arbitrary convex shape and of different materials. We develop a mathematically rigorous perturbation scheme to solve the continuum mechanics equations that deal with both displacement and displacement rate fields and accounts for the dissipation in the bulk of the material. The perturbative solution of these equations allows to go beyond the previously used quasi-static approximation and obtain the dissipative force. The derived force does not suffer from the inconsistencies of the quasi-static approximation, like the violation of the third Newton's law for the case of different materials, and depends on particle deformation and deformation rate. PMID:26087916

  3. Collision of viscoelastic bodies: Rigorous derivation of dissipative force

    E-print Network

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

    2015-01-13

    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.

  4. Investigation of many-body forces in krypton and xenon

    SciTech Connect

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

    1988-10-15

    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.

  5. Application of magnetic force microscopy in nanomaterials characterization.

    PubMed

    de Lozanne, Alex

    2006-07-01

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

  6. Low temperature magnetic force microscopy studies of superconducting niobium films

    Microsoft Academic Search

    Mark A. Roseman

    2002-01-01

    Low temperature magnetic force microscopy studies of superconducting niobium films have been undertaken with the goal of studying the interplay between artificial pinning centers and magnetic vortices. Measurements were performed using a custom built low temperature magnetic force microscope, capable of operation at temperatures ranging from 4.2 K to room temperature. Special attention has been paid to optimizing the instrumentation

  7. Nuclear matter equation of state and three-body forces

    SciTech Connect

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

    2012-04-15

    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.

  8. Dynamics of a rigid body in an inhomogenous force field

    Microsoft Academic Search

    Andreas Resch; Claus Laemmerzahl; Dennis Lorek; Isabell Schaffer

    2008-01-01

    Extended rigid bodies do not move on geodesics but couple to the space-time curvature. We discuss this effect at the Newtonian level where the deviation from the ordinary Keplerian orbits occurs in two ways: we obtain an additional force in the equation of motion for the center-of-mass and a torque acting on the rotational degrees of freedom. We give a

  9. Magnetic forces associated with bursty bulk flows in Earth's magnetotail

    NASA Astrophysics Data System (ADS)

    Karlsson, Tomas; Hamrin, Maria; Nilsson, Hans; Kullen, Anita; Pitkänen, Timo

    2015-05-01

    We present the first direct measurements of magnetic forces acting on bursty bulk flow plasma in the magnetotail. The magnetic forces are determined using Cluster multispacecraft measurements. We analyze 67 bursty bulk flow (BBF) events and show that the curvature part of the magnetic force is consistently positive, acting to accelerate the plasma toward Earth between approximately 10 and 20 RE geocentrical distances, while the magnetic field pressure gradient increasingly brakes the plasma as it moves toward Earth. The net result is that the magnetic force accelerates the plasma at distances greater than approximately 14 RE, while it acts to decelerate it within that distance. The magnetic force, together with the thermal pressure gradient force, will determine the dynamics of the BBFs as they propagate toward the near-Earth tail region. The determination of the former provides an important clue to the ultimate fate of BBFs in the inner magnetosphere.

  10. Electric and Magnetic Forces between Parallel-Wire Conductors.

    ERIC Educational Resources Information Center

    Morton, N.

    1979-01-01

    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)

  11. Three-body forces and shell structure in calcium isotopes

    E-print Network

    Holt, Jason D; Schwenk, Achim; Suzuki, Toshio

    2010-01-01

    Understanding and predicting the formation of shell structure from nuclear forces is a central challenge for nuclear physics. While the magic numbers N=2,8,20 are generally well understood, N=28 is the first standard magic number that is not reproduced in microscopic theories with two-nucleon forces. In this Letter, we show that three-nucleon forces give rise to repulsive interactions between two valence neutrons that correctly lead to 48Ca as a magic nucleus, with a high 2+ excitation energy and a concentrated magnetic dipole transition strength. Towards the neutron drip line, we robustly predict a shell closure at N=34. The repulsive three-nucleon mechanism improves the agreement with experimental binding energies and suggests the drip line around 60Ca.

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

    PubMed Central

    Neuman, Keir C.; Nagy, Attila

    2012-01-01

    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

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

    Microsoft Academic Search

    Attila Nagy; Keir C Neuman

    2008-01-01

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

  14. May the Magnetic Force Be with You

    ERIC Educational Resources Information Center

    Wilcox, Jesse; Richey, Lindsey R.

    2012-01-01

    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

  15. Performance enhancement of a Lorentz force velocimeter using a buoyancy-compensated magnet system

    NASA Astrophysics Data System (ADS)

    Ebert, R.; Leineweber, J.; Resagk, C.

    2015-07-01

    Lorentz force velocimetry (LFV) is a highly feasible method for measuring flow rate in a pipe or a duct. This method has been established for liquid metal flows but also for electrolytes such as saltwater. A decrease in electrical conductivity of the medium causes a decrease of the Lorentz force which needs to be resolved, affecting the accuracy of the measurement. We use an electrical force compensation (EFC) balance for the determination of the tiny force signals in a test channel filled with electrolyte solution. It is used in a 90°-rotated orientation with a magnet system hanging vertically on its load bar. The thin coupling elements of its parallel guiding system limit the mass of the magnets to 1?kg. To overcome this restriction, which limits the magnetic flux density and hence the Lorentz forces, a weight force compensation mechanism is developed. Therefore, different methods such as air bearing are conceivable, but for the elimination of additional horizontal force components which would disturb the force signal, only compensation by lift force provided by buoyancy is reasonable. We present a swimming body setup that will allow larger magnet systems than before, because a large amount of the weight force will be compensated by this lift force. Thus the implementation of this concept has to be made with respect to hydrodynamical and mechanical stability. This is necessary to avoid overturning of the swimming body setup and to prevent inelastic deformation. Additionally, the issue will be presented and discussed whether thermal convection around the lifting body diminishes the signal-to-noise ratio (SNR) significantly or not.

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

    Microsoft Academic Search

    Motomu Nakashima; Ken Satou; Yasufumi Miura

    2007-01-01

    The purpose of this study is to develop a swimming human simulation model considering rigid body dynamics and unsteady fluid force for the whole body, which will be utilized to analyze various dynamical problems in human swimming. First, the modeling methods and their formulations for the human body and the fluid force are respectively described. Second, experiments to identify the

  17. Estimation of axial compressor body forces using three-dimensional flow computations

    E-print Network

    Reichstein, Georg A

    2009-01-01

    This thesis presents an examination of body force distributions in a single stage low speed compressor. The body force distributions are developed using two different computational procedures, an axisymmetric streamline ...

  18. Forced vibration of flexible body systems. A dynamic stiffness method

    NASA Astrophysics Data System (ADS)

    Liu, T. S.; Lin, J. C.

    1993-10-01

    Due to the development of high speed machinery, robots, and aerospace structures, the research of flexible body systems undergoing both gross motion and elastic deformation has seen increasing importance. The finite element method and modal analysis are often used in formulating equations of motion for dynamic analysis of the systems which entail time domain, forced vibration analysis. This study develops a new method based on dynamic stiffness to investigate forced vibration of flexible body systems. In contrast to the conventional finite element method, shape functions and stiffness matrices used in this study are derived from equations of motion for continuum beams. Hence, the resulting shape functions are named as dynamic shape functions. By applying the dynamic shape functions, the mass and stiffness matrices of a beam element are derived. The virtual work principle is employed to formulate equations of motion. Not only the coupling of gross motion and elastic deformation, but also the stiffening effect of axial forces is taken into account. Simulation results of a cantilever beam, a rotating beam, and a slider crank mechanism are compared with the literature to verify the proposed method.

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

    E-print Network

    Fornberg, Bengt

    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 to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy

  20. Body force effect on consolidation of porous elastic media due to pumping

    Microsoft Academic Search

    2006-01-01

    In this study, the linear poro?elasticity theory is applied to examine the body force effect on consolidation of porous media due to pumping. The steady?state solutions of displacement and incremental effective stress for a stratum of clay sandwiched between sandy strata are analytically given. The effect of body force could be represented by the body force number that depends on

  1. Floating body second order slow drift force spectrum

    SciTech Connect

    Aranha, J.A.P. [Univ. of Sao Paulo (Brazil). Dept. of Naval Architecture and Ocean Engineering; Fernandes, A.C. [PETROBRAS, E and P/GETINP/GESEM, Rio de Janeiro (Brazil)

    1996-12-31

    In this paper it is shown that the slow drift force spectrum of a floating body, obtained from the quadratic transfer function, can be approximated, in the range of interest ({mu} {much_lt} 1) by a white noise of the form S{sub F}({mu}) = S{sub F}(0) + O({mu}{sup 2}) where S{sub F}(0) can be computed from the known drift force coefficient in harmonic waves and the wave energy spectrum. It is also shown here that a special and normally used form of Newman`s approximation represents the spectrum S{sub F}({mu}) with an error [1 + O({mu}{sup 2})] in the low frequency regime. It is also shown that a well chosen Newman`s Approximations may be O({mu}{sup 2}) instead of only O({mu}).

  2. The force exerting on cosmic bodies in a quaternionc field

    E-print Network

    V. Majernik

    2003-09-03

    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.

  3. Three-Dimensional Approach; The Study of Three-Body Forces in Four-Body Bound State

    E-print Network

    Hadizadeh, M R

    2007-01-01

    The four-body Yakubovsky equations in a Three-Dimensional approach with the inclusion of the three-body forces is proposed. The four-body bound state with two- and three-body interactions is formulated in Three-Dimensional approach for identical particles as function of vector Jacobi momenta, specifically the magnitudes of the momenta and the angles between them. The modified three dimensional Yakubovsky integral equations is successfully solved with the scalar two-meson exchange three-body force where the Malfliet-Tjon-type two-body force is implemented. The three-body force effects on the energy eigenvalue and the four-body wave function, as well as accuracy of our numerical calculations are presented.

  4. Magnetic Forces and Field Line Density

    NSDL National Science Digital Library

    2012-08-03

    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.

  5. Power dissipation and magnetic forces and MAGLEV rebars

    SciTech Connect

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

    1997-03-01

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

  6. Nonconservative electric and magnetic optical forces on submicron dielectric particles

    SciTech Connect

    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

    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.

  7. The role of hydrodynamic forces in the confinement and assembly of magnetic dipoles

    NASA Astrophysics Data System (ADS)

    Prikockis, M.; Chen, A.; Sooryakumar, R.

    2014-03-01

    The confinement of interacting magnetic dipoles provides a means to probe the assembly of and many-body coupling within a mesoscopic system. Using a previously developed confinement method (Scientific Reports 3, 3124 (2013)), we investigate the role of hydrodynamic forces in one such mesoscopic system that supports a fluid borne suspension of microscopic beads that contain embedded superparmagnetic particles. Our confinement platform consists of a thin permalloy disk patterned on a silicon surface and a precessing magnetic field. By adjusting the orientation of the field, inter-particle dipolar and trap confinement forces are tuned - thereby enabling the plane-confined beads to repel or attract one another. At a specific field orientation, the dipolar interaction is weakened to provide a regime where the hydrodynamic forces, stemming from rotational motion of the beads, play a role in bead assembly. We investigate the dependence of dipole ordering on the hydrodynamic forces by varying the frequency of the field rotation in this special field configuration. This represents a unique system where the hydrodynamic forces of fluid borne magnets are tuned independently of the magnetic forces in a magnetic dipolar confinement scheme.

  8. The importance of spatial variability in the generation of secondary gravity waves from local body forces

    E-print Network

    Vadas, Sharon

    forces Sharon L. Vadas and David C. Fritts NorthWest Research Associates, CoRA division, Boulder, CO, USA hypothesized earlier that the zonal mean body force required to close the mesospheric jets is sporadic in time, and is composed of a large number of spatially and temporally localized body forces. To explore the effects

  9. Integrals of Motion for Planar Multi-Body Formations with Internal Forces

    E-print Network

    Peck, Mason A.

    Integrals of Motion for Planar Multi-Body Formations with Internal Forces Michael C. Norman of such a force potentially complicates the analysis of these systems, inte- grals of motion still exist, AIAA Member. 1 of 19 Integrals of Motion for Planar Multi-Body Formations with Internal Forces #12;~q

  10. Whole-body magnetic resonance imaging: assessment of skeletal metastases.

    PubMed

    Moynagh, Michael R; Colleran, Gabrielle C; Tavernaraki, Katarina; Eustace, Stephen J; Kavanagh, Eoin C

    2010-03-01

    The concept of a rapid whole-body imaging technique with high resolution and the absence of ionizing radiation for the assessment of osseous metastatic disease is a desirable tool. This review article outlines the current perspective of whole-body magnetic resonance imaging in the assessment of skeletal metastatic disease, with comparisons made to alternative whole-body imaging modalities. PMID:20229438

  11. Experimental studies of protozoan response to intense magnetic fields and forces

    NASA Astrophysics Data System (ADS)

    Guevorkian, Karine

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2003-11-01

    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.

  13. Advances in Magnetic Force Microscopy John Moreland, Chairman Magnetic dissipation force microscopy studies of magnetic

    E-print Network

    Grütter, Peter

    for magnetoelastic dissipation due to domain-wall width oscillations, and present some applications of magnetic. Magnetoelastic dissipation is caused by tip-field-induced domain-wall width oscillations through magnetostriction effects. Magnetoelastic damping is strongly correlated with micromagnetic structures and allows different

  14. Magnetohydrodynamic Flow Past Axisymmetric Bodies with Aligned Magnetic Field

    Microsoft Academic Search

    Kanwal J. Parbhakar; Mahinder S. Uberoi

    1969-01-01

    The steady axially symmetric flow of an inviscid incompressible fluid of small conductivity, embedded in a strong magnetic field, past fixed bodies is studied as a problem of finite perturbation. The magnetic Reynolds number is assumed small so that the magnetic field is unperturbed. The flow depends on the parameter ? which is proportional to the product of conductivity and

  15. Mitigated-force carriage for high magnetic field environments

    DOEpatents

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

    2014-05-20

    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.

  16. Temporary shape development in shape memory nanocomposites using magnetic force

    Microsoft Academic Search

    Atefeh Golbang; Mehrdad Kokabi

    2011-01-01

    Direct mechanical force is used to create a temporary shape in shape memory polymers. This can become difficult in situations where the sample is not directly accessible such as interior in the body. In these cases it is not possible to use a direct mechanical force to deform the sample into temporary shape; therefore other alternative routes should be proposed.

  17. Qunatum oscillations of the mechanical forces in rotating molecular magnets

    NASA Astrophysics Data System (ADS)

    Kim, Gwang-Hee

    2015-03-01

    We study a rotating nanomagnet that exhibits beat structure of the quantum forces. We show that such forces are originated from tunneling between two entangled states of spin and mechanical angular momentum. They can be observed in the presence of a static magnetic field gradient with ac magnetic field and disappear on increasing total angular momentum and parameter which depends on the moment of inertia and the tunnel splitting.

  18. Estimating the magnetic penetration depth using constant-height magnetic force

    E-print Network

    Grütter, Peter

    Estimating the magnetic penetration depth using constant-height magnetic force microscopy images to determine the relative value of the magnetic penetration depth to within 10­20% using an uncalibrated tip to obtain an absolute value of with similar accuracy. The magnetic penetration depth is one

  19. Extending the range for force calibration in magnetic tweezers.

    PubMed

    Daldrop, Peter; Brutzer, Hergen; Huhle, Alexander; Kauert, Dominik J; Seidel, Ralf

    2015-05-19

    Magnetic tweezers are a wide-spread tool used to study the mechanics and the function of a large variety of biomolecules and biomolecular machines. This tool uses a magnetic particle and a strong magnetic field gradient to apply defined forces to the molecule of interest. Forces are typically quantified by analyzing the lateral fluctuations of the biomolecule-tethered particle in the direction perpendicular to the applied force. Since the magnetic field pins the anisotropy axis of the particle, the lateral fluctuations follow the geometry of a pendulum with a short pendulum length along and a long pendulum length perpendicular to the field lines. Typically, the short pendulum geometry is used for force calibration by power-spectral-density (PSD) analysis, because the movement of the bead in this direction can be approximated by a simple translational motion. Here, we provide a detailed analysis of the fluctuations according to the long pendulum geometry and show that for this direction, both the translational and the rotational motions of the particle have to be considered. We provide analytical formulas for the PSD of this coupled system that agree well with PSDs obtained in experiments and simulations and that finally allow a faithful quantification of the magnetic force for the long pendulum geometry. We furthermore demonstrate that this methodology allows the calibration of much larger forces than the short pendulum geometry in a tether-length-dependent manner. In addition, the accuracy of determination of the absolute force is improved. Our force calibration based on the long pendulum geometry will facilitate high-resolution magnetic-tweezers experiments that rely on short molecules and large forces, as well as highly parallelized measurements that use low frame rates. PMID:25992733

  20. Forces on a magnet moving past figure-eight coils

    SciTech Connect

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

    1993-01-01

    For the first time, the lift, drag, and guidance forces acting on a permanent magnet are measured as the magnet passes over different arrays of figure-eight (null-flux) coils. The experimental results are in good agreement with the predictions of dynamic circuit theory, which is used to explain more optimal coil arrays.

  1. Forces on a magnet moving past figure-eight coils

    SciTech Connect

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

    1993-03-01

    For the first time, the lift, drag, and guidance forces acting on a permanent magnet are measured as the magnet passes over different arrays of figure-eight (null-flux) coils. The experimental results are in good agreement with the predictions of dynamic circuit theory, which is used to explain more optimal coil arrays.

  2. A 3D Magnetic Force Manipulator DC Prototype

    E-print Network

    North Carolina at Chapel Hill, University of

    force microscope (3DFM) for measurement of 3 di- mensional viscous and elastic fields at sub micrometer geometry is to be formed by using high permeability magnetic cores which are optically opaque mag- netic core material of very high permeability. In this idealization, a magnetic structure can

  3. Magnetic-force-induced long-period fiber gratings.

    PubMed

    Sakata, Hajime; Yamahata, Kosuke

    2012-04-01

    A novel formation method of a long-period fiber grating (LPFG) based on a magnetic-force-induced microbend is proposed and experimentally demonstrated. The LPFG employs a permanent magnet that exerts transversal force to the fiber by attracting a steel coil spring. The transversal force causes periodic microbending to the fiber, and therefore the transmission wave attenuates at the core-to-cladding mode resonance. This device has advantages of ease of fabrication, reconfigurability, and available for any type of fiber. PMID:22466211

  4. Local enhancement of magnetoelectric coupling observed using magnetic force microscopy

    Microsoft Academic Search

    Massimo Ghidini; Neil D. Mathur

    2010-01-01

    Poled multilayer capacitors (MLCs) show strain-mediated magnetoelectric coupling [1,2], but the microscopic details are unknown. By recording magnetic force microscopy (MFM) images at a polished surface in zero electric field, we show that the magnetic domain configuration of the Ni-based electrodes may be switched by electric-field history. By contrast, electric-field history has nominally no effect on the macroscopic magnetization measured

  5. A magnetic gradient induced force in NMR restricted diffusion experiments.

    PubMed

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

    2014-03-28

    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

  6. Spin motive force driven by skyrmion dynamics in magnetic nanodisks

    NASA Astrophysics Data System (ADS)

    Shimada, Yuhki; Ohe, Jun-ichiro

    2015-05-01

    The spin motive force driven by the dynamics of the skyrmion structure formed in a nanomagnetic disk is numerically investigated. Due to the existence of the magnetic structure along the disk edge, the collective mode of the magnetization is modified from that of the bulk skyrmion lattice obtained by using the periodic boundary condition. For a single-skyrmion disk, the dynamics of the skyrmion core and the edge magnetization induce the spin motive force, and a measurable AC voltage is obtained by two probes on the disk. For a multi-skyrmions disk, the phase-locked collective mode of skyrmions is found in the lowest resonant frequency where the amplitude of the AC voltage is enhanced by the cascade effect of the spin motive force. We also investigate the effect of the Rashba spin-orbit coupling on the spin motive force.

  7. Many-body forces, isospin asymmetry and dense hyperonic matter

    E-print Network

    R. O. Gomes; V. Dexheimer; S. Schramm; C. A. Z. Vascconcellos

    2015-04-10

    The equation of state (EoS) of asymmetric nuclear matter at high densities is a key topic for the description of matter inside neutron stars. The determination of the properties of asymmetric nuclear matter, such as the symmetry energy ($a_{sym}$) and the slope of the symmetry energy ($L_0$) at saturation density, has been exaustively studied in order to better constrain the nuclear matter EoS. However, differently from symmetric matter properties that are reasonably constrained, the symmetry energy and its slope still large uncertainties in their experimental values. Regarding this subject, some studies point towards small values of the slope of the symmetry energy, while others suggest rather higher values. Such a lack of agreement raised a certain debate in the scientific community. In this paper, we aim to analyse the role of these properties on the behavior of asymmetric hyperonic matter. Using the formalism presented in Ref. (R.O. Gomes et al 2014}, which considers many-body forces contributions in the meson-baryon coupling, we calculate the EoS of asymmetric hyperonic matter and apply it to describe hyperonic matter and hyperon stars.

  8. Current-induced magnetic field detection around fine current paths by magnetic force microscopy

    Microsoft Academic Search

    D. Saida; T. Edura; K. Tsutsui; Y. Wada; T. Takahashi

    2005-01-01

    A commercial magnetic force microscopy (MFM), combined with a potential feedback, is described. The MFM is operated in an intermittent contact mode, and a vertical displacement of the cantilever is used for observing a topography. Magnetic force images are obtained simultaneously with the topography with this setup. At total current of 200 ?A, topography, amplitude and phase difference of the

  9. Solutions and symmetries of force-free magnetic fields

    SciTech Connect

    Tassi, E. [Burning Plasma Research Group, Dipartimento di Energetica and CNISM, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy); Pegoraro, F. [Dipartimento di Fisica, E. Fermi and CNISM, Pisa (Italy); Cicogna, G. [Dipartimento di Fisica, E. Fermi and INFN, Pisa (Italy)

    2008-09-15

    New analytical results concerning force-free magnetic fields are presented. A number of examples of exact solutions for two-dimensional nonlinear force-free fields described by the Liouville equation are shown. These include classical solutions, such as, the Gold-Hoyle field and the force-free Harris sheet as special cases. The connection between these solutions and the Lie point symmetries of the Liouville equation is illustrated. Lie point symmetries of the equation describing force-free magnetic fields in helical symmetry in cylindrical geometry are also investigated and an infinitesimal generator that, in the vicinity of the cylinder axis, makes it possible to transform purely radially dependent solutions into helically symmetric solutions, is found. Finally we point out the existence of a formal analogy between the equations for the vector potential components of a class of force-free fields and the equations of motion of a charged particle in a magnetic field. This analogy makes it possible to transfer known results from the theory of the motion of a charged particle, into the context of force-free magnetic fields. Explicit examples of such application are given.

  10. The use of FORC diagrams in environmental magnetism: recent developments

    NASA Astrophysics Data System (ADS)

    Egli, Ramon

    2015-04-01

    First-order reversal curve (FORC) diagrams have proven to be a valuable tool for characterizing magnetic minerals in geologic materials, especially when ambiguous mixtures of two or more magnetic components need to be resolved. Since their introduction to the paleomagnetic community and untily very recently, FORC diagrams have been used in a qualitative manner for distinguishing magnetic contributions according to the domain state of the associated particles. However, the large amount of information provided by high-resolution FORC measurements enable fully quantitative analyses, and, at least in some cases, a precise numerical separation of magnetic components (e.g. authigenic vs. detrital/aeolic contributions). Although high-resolution FORC measurements are extremely time consuming and therefore not systematically applicable to large numbers of samples, the information provided by the analysis of few reference samples supports the calibration of much faster techniques, such as magnetic unmixing based on hysteresis loops. Quantitative analyses of FORC measurements are made possible by a dedicated software (VARIFORC, see poster EGU2015-ASC-2015-14199 in this session), as shown with examples based on the identification of magnetofossil signatures in pelagic carbonates.

  11. The indirect measurement of biomechanical forces in the moving human body

    Microsoft Academic Search

    Melanie Cluss; Kenneth Laws; Natalie Martin; T. Scott Nowicki; Allan Mira

    2006-01-01

    Inexpensive experimental techniques now exist for indirectly measuring forces within the moving human body. These techniques involve nontrivial applications of basic physical principles, have practical uses, and are appropriate for undergraduate experimentation. A two-dimensional video motion analysis is used to find the accelerations of various parts of the body, and anatomical geometry is used to determine specific biomechanical forces and

  12. Magnetic force microscopy on nanocrystalline Co films.

    PubMed

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

    2010-09-01

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

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

    PubMed Central

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

    2014-01-01

    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

  14. Quark contribution to the nucleon polarizabilities and three-body forces

    E-print Network

    Elvira Biasioli; Marco Traini; Renzo Leonardi

    1998-07-22

    We study the response of the nucleon, as a system of three bound (constituent) non relativistic quarks, to external (quasi static) electric and magnetic fields. The approach, based on a sum rule technique, is applied to a large class of two and three-body interquark potentials. Lower and upper bounds to the electric polarizability and para-magnetic susceptibility are explicitly calculated within a large variety of constituent models and their values related to the features of the interquark interaction picture. The r\\^ole of three-body forces is investigated in details as well as the effects of SU(6) breaking terms in the potential model. Our results can be used to extract the mesonic contributions to the static polarizabilty and susceptibility. The quark degrees of freedom give a quite sizeable contributions to both and the meson cloud accounts roughly for 30% and 60% of the electric proton and neutron polarizability respectively. The quark contribution to the paramagnetic susceptibility is even higher and the mesonic effects are rather uncertain.

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

    Microsoft Academic Search

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

    1998-01-01

    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

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

    Microsoft Academic Search

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

    1998-01-01

    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

  17. Seed island formation by forced magnetic reconnection

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  18. Interactions between internal forces, body stiffness, and fluid environment in a neuromechanical model of lamprey swimming.

    PubMed

    Tytell, Eric D; Hsu, Chia-Yu; Williams, Thelma L; Cohen, Avis H; Fauci, Lisa J

    2010-11-16

    Animal movements result from a complex balance of many different forces. Muscles produce force to move the body; the body has inertial, elastic, and damping properties that may aid or oppose the muscle force; and the environment produces reaction forces back on the body. The actual motion is an emergent property of these interactions. To examine the roles of body stiffness, muscle activation, and fluid environment for swimming animals, a computational model of a lamprey was developed. The model uses an immersed boundary framework that fully couples the Navier-Stokes equations of fluid dynamics with an actuated, elastic body model. This is the first model at a Reynolds number appropriate for a swimming fish that captures the complete fluid-structure interaction, in which the body deforms according to both internal muscular forces and external fluid forces. Results indicate that identical muscle activation patterns can produce different kinematics depending on body stiffness, and the optimal value of stiffness for maximum acceleration is different from that for maximum steady swimming speed. Additionally, negative muscle work, observed in many fishes, emerges at higher tail beat frequencies without sensory input and may contribute to energy efficiency. Swimming fishes that can tune their body stiffness by appropriately timed muscle contractions may therefore be able to optimize the passive dynamics of their bodies to maximize peak acceleration or swimming speed. PMID:21037110

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

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

    SciTech Connect

    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

    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.

  1. Assessing the ability of first-order reversal curve (FORC) diagrams to unravel complex magnetic signals

    Microsoft Academic Search

    Adrian R. Muxworthy; James G. King

    2005-01-01

    (1) First-order reversal curve (FORC) diagrams for mixtures of different magnetic phases and bimodal distributions have been measured to examine the efficiency of the FORC method at unraveling complex magnetic signals. The FORC distributions for various magnetic minerals, including magnetite, maghemite, hematite, and goethite, and their linear additivity are assessed. Mixtures containing only hard magnetic minerals like hematite or goethite,

  2. Assessing the ability of first-order reversal curve (FORC) diagrams to unravel complex magnetic signals

    Microsoft Academic Search

    Adrian R. Muxworthy; James G. King; David Heslop

    2005-01-01

    First-order reversal curve (FORC) diagrams for mixtures of different magnetic phases and bimodal distributions have been measured to examine the efficiency of the FORC method at unraveling complex magnetic signals. The FORC distributions for various magnetic minerals, including magnetite, maghemite, hematite, and goethite, and their linear additivity are assessed. Mixtures containing only hard magnetic minerals like hematite or goethite, which

  3. Design and construction of a magnetic force microscope

    E-print Network

    Khandekar, Sameer Sudhakar

    2005-08-29

    compared to the previous designs. Some of the anticipated system specifications are: 1) room temperature scanning range of 175?? 175 ??m, 2) low temperature scanning range between 35-50 ??m, 3) smallest detectable magnetic force in the range of one pN and 4...

  4. Comparison of simulation and experiment on levitation force between GdBCO bulk superconductor and superconducting magnet

    NASA Astrophysics Data System (ADS)

    Araki, S.; Nagashima, K.; Seino, H.; Murakami, T.; Sawa, K.

    2009-10-01

    High temperature bulk superconductors have significant potential for various engineering applications such as a flywheel energy storage system. This system is expected to decrease the energy loss by using bulk superconductors for the bearing. Recently, the authors have developed a new superconducting magnet to realize large levitation force. In this system, the axial component of magnetic field is canceled each other but the radial component of magnetic field expects to be enhanced. Thus, it was expected that the large levitation force can be realized and its time relaxation will be decreased. And in the previous paper, the levitation force and its time relaxation were measured under the various conditions by using this new magnet. But it is difficult to consider what phenomenon has happened in the bulk from only experimental results. In addition the quantitative evaluation cannot be done only by the experimental results, for example, the influence of the magnetic field penetration and magnetic distribution around a bulk superconductor on the maximum force and so on. Thus, in this paper, the authors simulated the levitation force of bulk superconductor by using ELF/MAGIC, which is a three-dimensional electromagnetic analytical software. In the simulation the bulk was considered as a rigid body and the simulation was executed under the same conditions and model with the experiment. The distribution of magnetic field and the levitation force were obtained and discussed.

  5. On the unsteady-motion theory of magnetic forces for maglev

    SciTech Connect

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

    1996-02-01

    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.

  6. Height and body composition determine arm propulsive force in youth swimmers independent of a maturation stage.

    PubMed

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

    2014-09-29

    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

  7. Corroboration of magnetic forces in US Maglev design

    SciTech Connect

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

    1993-01-01

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

  8. Corroboration of magnetic forces in US Maglev design

    SciTech Connect

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

    1993-06-01

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

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

    PubMed Central

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

    2014-01-01

    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

  10. Three-axis force actuator for a magnetic bearing

    NASA Technical Reports Server (NTRS)

    Gondhalekar, Vijay (Inventor)

    1998-01-01

    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.

  11. Single Molecule Magnetic Force Detection with a Carbon Nanotube Resonator

    NASA Astrophysics Data System (ADS)

    Willick, Kyle; Walker, Sean; Baugh, Jonathan

    2015-03-01

    Single molecule magnets (SMMs) sit at the boundary between macroscopic magnetic behaviour and quantum phenomena. Detecting the magnetic moment of an individual SMM would allow exploration of this boundary, and could enable technological applications based on SMMs such as quantum information processing. Detection of these magnetic moments remains an experimental challenge, particularly at the time scales of relaxation and decoherence. We present a technique for sensitive magnetic force detection that should permit such measurements. A suspended carbon nanotube (CNT) mechanical resonator is combined with a magnetic field gradient generated by a ferromagnetic gate electrode, which couples the magnetic moment of a nanomagnet to the resonant motion of the CNT. Numerical calculations of the mechanical resonance show that resonant frequency shifts on the order of a few kHz arise due to single Bohr magneton changes in magnetic moment. A signal-to-noise analysis based on thermomechanical noise shows that magnetic switching at the level of a Bohr magneton can be measured in a single shot on timescales as short as 10 ?s. This sensitivity should enable studies of the spin dynamics of an isolated SMM, within the spin relaxation timescales for many available SMMs. Supported by NSERC.

  12. Disentangling the magnetic force noise contribution in LISA Pathfinder

    NASA Astrophysics Data System (ADS)

    Armano, M.; Audley, H.; Auger, G.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Bursi, A.; Caleno, M.; Cavalleri, A.; Cesarini, A.; Cruise, M.; Danzmann, K.; Diepholz, I.; Dolesi, R.; Dunbar, N.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E.; Freschi, M.; Gallegos, J.; García Marirrodriga, C.; Gerndt, R.; Gesa, L. I.; Gibert, F.; Giardini, D.; Giusteri, R.; Grimani, C.; Harrison, I.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hueller, M.; Huesler, J.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johlander, B.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C.; Lloro, I.; Maarschalkerweerd, R.; Madden, S.; Mance, D.; Martín, V.; Martin-Porqueras, F.; Mateos, I.; McNamara, P.; Mendes, J.; Mendes, L.; Moroni, A.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Prat, P.; Ragnit, U.; Ramos-Castro, J.; Reiche, J.; Romera Perez, J. A.; Robertson, D.; Rozemeijer, H.; Russano, G.; Sarra, P.; Schleicher, A.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J.; Trenkel, C.; Tu, H. B.; Vitale, S.; Wanner, G.; Ward, H.; Waschke, S.; Wass, P.; Wealthy, D.; Wen, S.; Weber, W.; Wittchen, A.; Zanoni, C.; Ziegler, T.; Zweifel, P.

    2015-05-01

    Magnetically-induced forces on the inertial masses on-board LISA Pathfinder are expected to be one of the dominant contributions to the mission noise budget, accounting for up to 40%. The origin of this disturbance is the coupling of the residual magnetization and susceptibility of the test masses with the environmental magnetic field. In order to fully understand this important part of the noise model, a set of coils and magnetometers are integrated as a part of the diagnostics subsystem. During operations a sequence of magnetic excitations will be applied to precisely determine the coupling of the magnetic environment to the test mass displacement using the on-board magnetometers. Since no direct measurement of the magnetic field in the test mass position will be available, an extrapolation of the magnetic measurements to the test mass position will be carried out as a part of the data analysis activities. In this paper we show the first results on the magnetic experiments during an end- to-end LISA Pathfinder simulation, and we describe the methods under development to map the magnetic field on-board.

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

    SciTech Connect

    Oberkampf, W. L.

    1981-04-01

    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.

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

    SciTech Connect

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

    2010-11-15

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

  15. Energy buildup in sheared force-free magnetic fields

    NASA Technical Reports Server (NTRS)

    Wolfson, Richard; Low, Boon C.

    1992-01-01

    Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.

  16. THE NEGATIVE EFFECTIVE MAGNETIC PRESSURE IN STRATIFIED FORCED TURBULENCE

    SciTech Connect

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

    2012-04-20

    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.

  17. Effects due to body-forces and body-couples in the interior of a micropolar elastic half-space

    Microsoft Academic Search

    Sl M. KHAN; R. S. Dhaliwal

    1976-01-01

    Summary A general solution of the equilibrium equations is obtained for a half-space with a stress-free boundary and arbitrary but axisymmetric distribution of body-forces and body-couples in the interior of the half-space. Few particular cases have been investigated in detail. The stresses, displacements and rotation have been obtained at the boundary of the half-space. Numerical results have been displayed graphically

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    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.

  19. Ferromagnetic Resonance Imaging with Magnetic Resonance Force Microscopy

    NASA Astrophysics Data System (ADS)

    Pelekhov, Denis

    2009-03-01

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

  20. Collisionless forced magnetic reconnection in an electron-positron plasma

    SciTech Connect

    Hosseinpour, M.; Vekstein, G. [Jodrel Bank Center for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom)

    2008-02-15

    Collisionless forced magnetic reconnection in an electron-positron plasma, where the mechanism of the magnetic field breaking is inertia of plasma particles, is considered. The model under analytical investigation is the so-called Taylor problem: a tearing stable slab plasma equilibrium with a magnetic field reversal is subjected to a small-amplitude boundary perturbation that drives magnetic reconnection at the neutral surface within the plasma. It is shown that forced collisionless reconnection has a direct analogy with its collisional (resistive) counterpart investigated by T. S. Hahm and R. M. Kulsrud [Phys. Fluids 28, 2412 (1985)], with the role of the inverse Lundquist number S{sup -1}<<1 of the resistive magnetohydrodynamics now being played by the normalized inertia skin depth d{identical_to}(c/{omega}{sub p}a)<<1 ({omega}{sub p} is the electron-positron plasma frequency, and a is a width of the plasma slab). The transition between the collisionless and resistive regimes of forced reconnection is also considered.

  1. Effective 2-body interaction based on Extended-Skyrme force

    SciTech Connect

    Resler, D.A.; Bloom, S.D. [Lawrence Livermore National Laboratory, CA (United States); Moszkowski, S.A. [UCLA, CA (United States)

    1993-10-01

    Basing the effective nucleon-nucleon force in nuclei on the experimental global parameters of nuclei over the mass, range of {sup 4}He to nuclear matter has been under study for many years. In this work, we emphasize the global constraints of binding energy, size, and the Hartree-Fock (saturation) condition for {sup 4}He, {sup 16}O, and {sup 40}Ca. For symmetric nuclear matter, we also include the effective mass and the incompressibility. We are parameterizing the effective nucleon-nucleon interaction using the form of the Extend-Skyrme force which includes a finite-range density dependence. For {sup 4}He, we have found that we must go beyond the mean-field approximation. This will be discussed along with the results of large-basis shell model calculations using the Extended-Skyrme force.

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

    PubMed Central

    Fisher, J. K.; Kleckner, N.

    2014-01-01

    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

  3. Magnetic Force Driven Nanogenerators as a Noncontact Energy Harvester and Sensor

    E-print Network

    Wang, Zhong L.

    Magnetic Force Driven Nanogenerators as a Noncontact Energy Harvester and Sensor Nuanyang Cui Supporting Information ABSTRACT: Nanogenerator has been a very important energy harvesting technology through directly deforming piezoelectric material. Here, we report a new magnetic force driven contactless

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

    PubMed Central

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

    2012-01-01

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

  5. Effect of guideway discontinuities on magnetic levitation and drag forces

    SciTech Connect

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

    1991-01-01

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

  6. On the unsteady-motion theory of magnetic forces for maglev

    SciTech Connect

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

    1993-11-01

    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.

  7. Extended-body approach to the electromagnetic self-force in curved spacetime

    E-print Network

    Javier Molina Sanchez; Eric Poisson

    2007-01-05

    We offer a novel derivation of the electromagnetic self-force acting on a charged particle moving in an arbitrary curved spacetime. Our derivation is based on a generalization from flat spacetime to curved spacetime of the extended-body approach of Ori and Rosenthal. In this approach the charged particle is first modeled as a body of finite extension s, the net force acting on the extended body is computed, and the limit s -> 0 is taken at the end of the calculation. Concretely our extended body is a dumbbell that consists of two point charges that are maintained at a constant spacelike separation s. The net force acting on the dumbbell includes contributions from the mutual forces exerted on each charge by the field created by the other charge, the individual self-forces exerted on each charge by its own field, and the external force which is mostly responsible for the dumbbell's acceleration. These contributions are added up, in a way that respects the curved nature of the spacetime, and all diverging terms in the net force are shown to be removable by mass renormalization. Our end result, in the limit s -> 0, is the standard expression for the electromagnetic self-force in curved spacetime.

  8. 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...

  9. Muscle force redistributes segmental power for body progression during walking

    Microsoft Academic Search

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

    2004-01-01

    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,

  10. A Force-Feedback Algorithm for Adaptive Articulated-Body Dynamics Simulation

    E-print Network

    Redon, Stephane - NRIA Grenoble

    and Stephane Redon i3D - GRAVIR - INRIA Abstract-- This paper introduces a novel algorithm for haptic.g. virtual coupling [1]), force-feedback algorithms often have to be tailored to the objects being haptically rendered (e.g. rigid or articulated bodies, deformable bodies, fluids, etc.). In partic- ular, haptics

  11. Convective motion and transfer of force by many-body hydrodynamic interaction

    Microsoft Academic Search

    B. U. Felderhof; R. B. Jones

    1987-01-01

    We consider hydrodynamic interactions between N rigid bodies of arbitrary shape immersed in an incompressible fluid. When the bodies are carried along by an incident flow without exerting forces or torques on the fluid then their translational and rotational velocities are linearly related to the incident flow velocity by convection kernels. In the absence of an incident flow, but with

  12. Apparatus having reduced mechanical forces for supporting high magnetic fields

    DOEpatents

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

    1991-01-01

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

  13. Three-Body Forces and Proton-Rich Nuclei

    SciTech Connect

    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

    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.

  14. Noncontact Friction and Force Fluctuations between Closely Spaced Bodies

    SciTech Connect

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

    2001-08-27

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

  15. The Aerodynamic Forces on Slender Plane- and Cruciform-Wing and Body Combinations

    NASA Technical Reports Server (NTRS)

    Spreiter, John R

    1950-01-01

    The load distribution, forces, and moments are calculated theoretically for inclined slender wing-body combinations consisting of a slender body of revolution and either a plane or cruciform arrangement of low-aspect-ratio pointed wings. The results are applicable at subsonic and transonic speeds, and at supersonic speeds, provided the entire wing-body combination lies near the center of the Mach cone.

  16. Three-Dimensional Force Measurement and Control of a Flux-Path Control Magnetic Suspension

    Microsoft Academic Search

    Munehiro Furutachi; Shunsuke Inaba; Yuji Ishino; Masaya Takasaki; Takeshi Mizuno

    2008-01-01

    In the flux-path control magnetic suspension system, the force acting on a floator is controlled by moving a control plate made of ferromagnetic material, which is located between the permanent magnet and the floator. In this paper, the three-dimensional attractive forces acting on the floator were measured with a manufactured force sensor. The force actuating in the vertical direction is

  17. Force-free magnetic fields - The magneto-frictional method

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  18. Effect of three-body forces on response functions in infinite neutron matter

    NASA Astrophysics Data System (ADS)

    Davesne, D.; Holt, J. W.; Pastore, A.; Navarro, J.

    2015-01-01

    We study the impact of three-body forces on the response functions of cold neutron matter. These response functions are determined in the random phase approximation from a residual interaction expressed in terms of Landau parameters. Special attention is paid to the noncentral part, including all terms allowed by the relevant symmetries. Using Landau parameters derived from realistic nuclear two- and three-body forces grounded in chiral effective field theory, we find that the three-body term has a strong impact on the excited states of the system and in the static and long-wavelength limit of the response functions for which a new exact formula is established.

  19. Localized Spectroscopy using a Magnetic Resonance Force Microscope.

    NASA Astrophysics Data System (ADS)

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

    2006-03-01

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

  20. Gravito-magnetism of an extended celestial body

    NASA Astrophysics Data System (ADS)

    Panhans, Michel; Soffel, Michael H.

    2014-12-01

    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.

  1. The stochastic design of force-minimized compact magnets for high-field magnetic resonance imaging applications

    Microsoft Academic Search

    Stuart Crozier; Christopher J. Snape-Jenkinson; Larry K. Forbes

    2001-01-01

    New designs for force-minimized compact high-field clinical MRI magnets are described. The design method is a modified simulated annealing (SA) procedure which includes Maxwell forces in the error function to be minimized. This permits an automated force reduction in the magnet designs while controlling the overall dimensions of the system. As SA optimization requires many iterations to achieve a final

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

    E-print Network

    Lande, Brian Jacob

    2010-01-01

    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

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

    Microsoft Academic Search

    T. Nomura; T. Satow; M. Ashkin

    1988-01-01

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

  4. The rate of separation of magnetic lines of force in a random magnetic field.

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.

    1973-01-01

    The mixing of magnetic lines of force, as represented by their rate of separation, as a function of distance along the magnetic field, is considered with emphasis on neighboring lines of force. This effect is particularly important in understanding the transport of charged particles perpendicular to the average magnetic field. The calculation is carried out in the approximation that the separation changes by an amount small compared with the correlation scale normal to the field, in a distance along the field of a few correlation scales. It is found that the rate of separation is very sensitive to the precise form of the power spectrum. Application to the interplanetary and interstellar magnetic fields is discussed, and it is shown that in some cases field lines, much closer together than the correlation scale, separate at a rate which is effectively as rapid as if they were many correlation lengths apart.

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

    PubMed

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

    2014-01-01

    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. PMID:25145681

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

    PubMed

    Voigt, A; Christ, S; Klein, M

    2008-07-01

    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

  7. Magnetic domains and domain walls in pseudo-single-domain magnetite studied with magnetic force microscopy

    Microsoft Academic Search

    Taras G. Pokhil; Bruce M. Moskowitz

    1997-01-01

    Magnetic domain and domain wall structures in pseudo-single-domain grains (5-20 gm) of magnetite (Fe304) were studied using magnetic force microscopy. Many of the observed micromagnetic features can be explained by the magnetostatic effects of surfaces and grain edges and interactions within and between walls. Domain walls were frequently subdivided into 1-3 opposite polarity segments separated by Bloch lines, although some

  8. Magnetic domains and domain walls in pseudo-single-domain magnetite studied with magnetic force microscopy

    Microsoft Academic Search

    Taras G. Pokhil; Bruce M. Moskowitz

    1997-01-01

    Magnetic domain and domain wall structures in pseudo-single-domain grains (5-20 mum) of magnetite (Fe3O4) were studied using magnetic force microscopy. Many of the observed micromagnetic features can be explained by the magnetostatic effects of surfaces and grain edges and interactions within and between walls. Domain walls were frequently subdivided into 1-3 opposite polarity segments separated by Bloch lines, although some

  9. Film Condensation with and Without Body Force in Boundary-Layer Flow of Vapor Over a Flat Plate

    NASA Technical Reports Server (NTRS)

    Chung, Paul M.

    1961-01-01

    Laminar film condensation under the simultaneous influence of gas-liquid interface shear and body force (g force) is analyzed over a flat plate. Important parameters governing condensation and heat transfer of pure vapor are determined. Mixtures of condensable vapor and noncondensable gas are also analyzed. The conditions under which the body force has a significant influence on condensation are determined.

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

    NASA Technical Reports Server (NTRS)

    Dress, David A.

    1989-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Nakashima, Motomu; Satou, Ken; Miura, Yasufumi

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

  12. The indirect measurement of biomechanical forces in the moving human body

    NASA Astrophysics Data System (ADS)

    Cluss, Melanie; Laws, Kenneth; Martin, Natalie; Nowicki, T. Scott; Mira, Allan

    2006-02-01

    Inexpensive experimental techniques now exist for indirectly measuring forces within the moving human body. These techniques involve nontrivial applications of basic physical principles, have practical uses, and are appropriate for undergraduate experimentation. A two-dimensional video motion analysis is used to find the accelerations of various parts of the body, and anatomical geometry is used to determine specific biomechanical forces and torques. The simple movement of a dancer landing from a vertical jump is analyzed through the use of a theoretical model of the leg to find the forces in the tendons attached to the knee. It is shown that these forces can be sufficiently large to lead to injury if jumps are performed repetitively.

  13. Resonantly detecting axion-mediated forces with nuclear magnetic resonance.

    PubMed

    Arvanitaki, Asimina; Geraci, Andrew A

    2014-10-17

    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

  14. Nuclear magnetic resonance force microscopy with a microwire rf source

    SciTech Connect

    Poggio, M.; Degen, C. L.; Rettner, C. T.; Mamin, H. J.; Rugar, D. [IBM Research Division, Almaden Research Center, 650 Harry Rd., San Jose, California 95120 (United States) and Center for Probing the Nanoscale, Stanford University, 476 Lomita Hall, Stanford, California 94305 (United States); IBM Research Division, Almaden Research Center, 650 Harry Rd., San Jose, California 95120 (United States)

    2007-06-25

    The authors use a 1.0 {mu}m wide patterned Cu wire with an integrated nanomagnetic tip to measure the statistical nuclear polarization of {sup 19}F in CaF{sub 2} by magnetic resonance force microscopy. With less than 350 {mu}W of dissipated power, the authors achieve rf magnetic fields over 4 mT at 115 MHz for a sample positioned within 100 nm of the 'microwire' rf source. A 200 nm diameter FeCo tip integrated onto the wire produces field gradients greater than 10{sup 5} T/m at the same position. The large rf fields from the broadband microwire enable long rotating-frame spin lifetimes of up to 15 s at 4 K.

  15. Gravity and magnetic modeling of granitic bodies in Central Portugal

    NASA Astrophysics Data System (ADS)

    Machadinho, Ana; Figueiredo, Fernando; Pereira, Alcides

    2015-04-01

    A better understanding of the subsurface geometry of the granitic bodies in Central Portugal is the main goal of this work. The results are also relevant for the assessment of the geothermal potential of the same region. The study area is located in the Central Iberian Zone where the Beiras granite batholith outcrops. These variscan granitoids were emplaced into the "Complexo Xisto-Grauváquico" (CXG), a thick and monotonous megasequences of metapelites and metagreywackes. This metasedimentary sequence is affected by the Variscan deformation phases and a late Proterozoic to Cambrian age has been generally assumed for this rocks. The granitoids in the region are attributed to the magmatic activity associated to the post-collisional stages of the Variscan orogeny during the D3 stage. The granitic bodies in the study area are considered syn-D3 and late to post-D3. To achieve the goal of the research, magnetic and gravimetric surveys where performed in order to obtain the Bouguer and magnetic anomalies. All the standard corrections were applied to the gravimetric and magnetic data. Considering and integrating all the available geological data and physical proprieties (density and magnetic susceptibility) the mentioned potential fields were simultaneously modeled. In this way it was possible to characterize the subsurface geometry of the granitic bodies in the studied region. The modeling results show that the regional tectonic setting controls the geometry of the granitic bodies as well as the structure of the host CXG metasedimentary sequence. Through the modeling of the potential field the overall geometry, average and maximum depths of the granitic bodies in the study area was obtained. Some late to post-D3 plutons outcrop in spatial continuity and as they have similar ages, a common feeding zone is assumed as the most likely scenario. The sin-D3 pluton is more abrupt and vertical, suggesting the presence of a fault contact with the late-D3 pluton. According to the developed study the areas with higher geothermal potential for EGS applications are located over the sectors where the granitic bodies have the greater thickness.

  16. Radiation-Reaction Force on a Small Charged Body to Second Order

    NASA Astrophysics Data System (ADS)

    Moxon, Jordan; Flanagan, Eanna

    2015-04-01

    In classical electrodynamics, an accelerating charge emits radiation and experiences a corresponding radiation reaction force, or self force. We extend to greater precision (higher order in perturbation theory) a previous rigorous derivation of the electromagnetic self force in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self-force from the Maxwell field equations and conservation of stress-energy, and does not require regularization of a singular point charge, as has been necessary in prior computations. For our higher order compuation, it becomes necessary to adopt an adjusted definition of the mass of the body to avoid including self-energy from the electromagnetic field sourced during the history of the body. We derive the evolution equations for the mass, spin, and center of mass position of an extended body through second order using our adjusted formalism. The final equations give an acceleration dependent evolution of the spin (self-torque), as well as a mixing between the extended body effects and the acceleration dependent effects on the overall body motion.

  17. Influence of Polarization Force on Jeans Instability of Magnetized Dusty Plasma

    NASA Astrophysics Data System (ADS)

    Prajapati, R. P.; Chhajlani, R. K.

    2011-11-01

    We investigate the Jeans instability of self-gravitating magnetized dusty plasma including the effect of polarization force on the massive charged dust grains. The basic dusty magnetohydrodynamic (MHD) equations are constructed considering the effect of magnetic field, gravitational force and polarization force. A general dispersion relation and condition of Jeans instability is obtained using normal mode analysis. It is found that polarization force modifies the condition of Jeans instability but it is unaffected due to magnetic field. The polarization force has destabilizing while magnetic field has stabilizing influence on the growth rate of Jeans instability.

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

    Microsoft Academic Search

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

    2008-01-01

    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

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

    Microsoft Academic Search

    Yoshifumi Amemiya; Shigeru Ohkuma

    1977-01-01

    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

  20. Magnetotelluric anomalies, computed over models having high magnetic permeability bodies

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    Microsoft Academic Search

    Han He; Huaning Wang

    2008-01-01

    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

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

    ERIC Educational Resources Information Center

    Onorato, Pasquale; De Ambrosis, Anna

    2013-01-01

    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…

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

    E-print Network

    Paris-Sud XI, Université de

    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 cleanliness of operation and better resistance to wear and tear. Ironless motors feature two magnetic tracks

  4. 3-D Analytical Calculation of the Torque and Force Exerted Between Two Cuboidal Magnets

    Microsoft Academic Search

    Hicham Allag; Jean-Paul Yonnet

    2009-01-01

    Most of the systems working by magnet interactions can be calculated by superposition of the interactions between parallelepiped elementary magnets. Each elementary magnet is submitted to a force and a torque. By 3-D fully analytical calculation, up to now, only the force components problem has been solved. It was published for the first time in 1984. Until now, the torque

  5. Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic force microscopy, and micromagnetic simulations

    E-print Network

    Metlushko, Vitali

    Frustrated magnetic vortices in a triad of permalloy rings: Magneto-optical Kerr effect, magnetic October 2005; published 28 March 2006 The field dependent magnetization of three mutually touching permalloy rings were investigated by means of the magneto-optical Kerr effect, magnetic force microscopy

  6. Magnetic fields produced by steady currents in the body.

    PubMed Central

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

    1980-01-01

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

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed

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

    2013-12-01

    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

  9. A microscopic approach to Casimir and Casimir-Polder forces between metallic bodies

    NASA Astrophysics Data System (ADS)

    Barcellona, Pablo; Passante, Roberto

    2015-04-01

    We consider the Casimir-Polder interaction energy between a metallic nanoparticle and a metallic plate, as well as the Casimir interaction energy between two macroscopic metal plates, in terms of the many-body dispersion interactions between their constituents. Expressions for two- and three-body dispersion interactions between the microscopic parts of a real metal are first obtained, both in the retarded and non-retarded limits. These expressions are then used to evaluate the overall two- and three-body contributions to the macroscopic Casimir-Polder and Casimir force, and to compare them with each other, for the two following geometries: metal nanoparticle/half-space and half-space/half-space, where all the materials are assumed perfect conductors. The above evaluation is obtained by summing up the contributions from the microscopic constituents of the bodies (metal nanoparticles). In the case of nanoparticle/half-space, our results fully agree with those that can be extracted from the corresponding macroscopic results, and explicitly show the non-applicability of the pairwise approximation for the geometry considered. In both cases, we find that, while the overall two-body contribution yields an attractive force, the overall three-body contribution is repulsive. Also, they turn out to be of the same order, consistently with the known non applicability of the pairwise approximation. The issue of the rapidity of convergence of the many-body expansion is also briefly discussed.

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

    Microsoft Academic Search

    B. K. Rao

    1984-01-01

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

  11. 2 DYNAMICS 2.1 Surface vs. body forces, and the concept of pressure

    E-print Network

    Cambridge, University of

    which n points. If the fluid as a whole is at rest (i.e. at rest apart from the molecular­scale motions§2 DYNAMICS §2.1 Surface vs. body forces, and the concept of pressure We need to distinguish#ects tend to cancel rather than add up. If the fluid as a whole is at rest, then the cancellation

  12. 2 DYNAMICS 2.1 Surface vs. body forces, and the concept of pressure

    E-print Network

    Cambridge, University of

    . If the fluid as a whole is at rest (i.e. at rest apart from the molecular-scale motions), then the pressure§2 DYNAMICS §2.1 Surface vs. body forces, and the concept of pressure We need to distinguish to cancel rather than add up. If the fluid as a whole is at rest, then the cancellation is complete because

  13. Modifications of single-particle properties in nuclear matter induced by three-body forces

    E-print Network

    V. Soma; P. Bozek

    2008-11-25

    Within the self-consistent Green's functions formalism, we study the effects of three-body forces on the in-medium spectral function, self-energy and effective mass of the nuclear matter constituents, analyzing the density and momentum dependence.

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

    Microsoft Academic Search

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

    2011-01-01

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

  15. Magnetic force microscopy observation of sensitized Inconel 600

    NASA Astrophysics Data System (ADS)

    Takaya, Shigeru; Suzuki, Takayuki; Uchimoto, Tetsuya; Miya, Kenzo

    2002-05-01

    An application of magnetic force microscopes (MFM) is proposed to the characterization of sensitized Inconel 600 alloy with submicron order accuracy. The magnetic microstructures of Inconel 600 sensitized at 620 °C for various heat treatment periods were observed by means of a MFM. MFM images show semicontinuous morphologies of the magnetizations near and at grain boundaries. The absolute value of the MFM signal, the phase shift between the oscillation of the cantilever and the piezoelectric actuator, at the grain boundary increases at first and then decreases with increasing heat treatment time, while the full width at half maximum about the MFM signals across the grain boundary increases continuously. These results coincide with the fact that the chromium content decreases at first due to production of the chromium carbide and then increase slightly due to the change in the activities of carbon and chromium near the grain boundaries. This method is useful because MFMs enable very high spatial resolution observations with minimal sample preparation and relatively easy operations.

  16. Magnetic resonance force microscopy and a solid state quantum computer.

    SciTech Connect

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

    2001-01-01

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

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

    PubMed Central

    2010-01-01

    Background As the strategy for tissue regeneration using mesenchymal stem cells (MSCs) for transplantation, it is necessary that MSCs be accumulated and kept in the target area. To accumulate MSCs effectively, we developed a novel technique for a magnetic targeting system with magnetically labeled MSCs and an external magnetic force. In this study, we examined the effect of an external magnetic force on magnetically labeled MSCs in terms of cell adhesion and proliferation. Methods Magnetically labeled MSCs were plated at the bottom of an insert under the influence of an external magnetic force for 1 hour. Then the inserts were turned upside down for between 1 and 24 hours, and the number of MSCs which had fallen from the membrane was counted. The gene expression of MSCs affected magnetic force was analyzed with microarray. In the control group, the same procedure was done without the external magnetic force. Results At 1 hour after the inserts were turned upside down, the average number of fallen MSCs in the magnetic group was significantly smaller than that in the control group, indicating enhanced cell adhesion. At 24 hours, the average number of fallen MSCs in the magnetic group was also significantly smaller than that in control group. In the magnetic group, integrin alpha2, alpha6, beta3 BP, intercellular adhesion molecule-2 (ICAM-2), platelet/endothelial cell adhesion molecule-1 (PECAM-1) were upregulated. At 1, 2 and 3 weeks after incubation, there was no statistical significant difference in the numbers of MSCs in the magnetic group and control group. Conclusions The results indicate that an external magnetic force for 1 hour enhances cell adhesion of MSCs. Moreover, there is no difference in cell proliferation after using an external magnetic force on magnetically labeled MSCs. PMID:20152029

  18. Magnetic microposts as an approach to apply forces to living cells

    E-print Network

    Chen, Christopher S.

    Magnetic microposts as an approach to apply forces to living cells Nathan J. Sniadecki*, Alexandre, 2007) 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

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

    E-print Network

    Ritort, Felix

    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 to investigate the forces and motions associated with biological molecules and enzymatic activity. The most

  20. Body-Centered-Cubic Ni and Its Magnetic Properties

    NASA Astrophysics Data System (ADS)

    Tian, C. S.; Qian, D.; Wu, D.; He, R. H.; Wu, Y. Z.; Tang, W. X.; Yin, L. F.; Shi, Y. S.; Dong, G. S.; Jin, X. F.; Jiang, X. M.; Liu, F. Q.; Qian, H. J.; Sun, K.; Wang, L. M.; Rossi, G.; Qiu, Z. Q.; Shi, J.

    2005-04-01

    The body-centered-cubic (bcc) phase of Ni, which does not exist in nature, has been achieved as a thin film on GaAs(001) at 170 K via molecular beam epitaxy. The bcc Ni is ferromagnetic with a Curie temperature of 456 K and possesses a magnetic moment of 0.52±0.08?B/atom. The cubic magnetocrystalline anisotropy of bcc Ni is determined to be +4.0×105 ergs·cm-3, as opposed to -5.7×104 ergs·cm-3 for the naturally occurring face-centered-cubic (fcc) Ni. This sharp contrast in the magnetic anisotropy is attributed to the different electronic band structures between bcc Ni and fcc Ni, which are determined using angle-resolved photoemission with synchrotron radiation.

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

    PubMed

    Chen, Youping

    2006-02-01

    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

  2. Power generation from human body motion through magnet and coil arrays with magnetic spring

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Wang, Yufeng; Kim, Eun Sok

    2014-02-01

    This article presents a hand-held electromagnetic energy harvester which can be used to harvest tens of mW power level from human body motion. A magnet array, aligned to a coil array for maximum magnetic flux change, is suspended by a magnetic spring for a resonant frequency of several Hz and is stabilized horizontally by graphite sheets for reducing the friction. An analytical model of vibration-driven energy harvester with magnetic spring through magnet and coil arrays is developed to explore the power generation from vibrations at low frequency and large amplitude. When the energy harvester (occupying 120 cc and weighing 180 g) is placed in a backpack of a human walking at various speeds, the power output increases as the walking speed increases from 0.45 m/s (slow walking) to 3.58 m/s (slow running), and reaches 32 mW at 3.58 m/s.

  3. Influence of body posture and gravitational forces on shear wave propagation in the skin.

    PubMed

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

    2001-01-01

    The body posture and gravitational forces govern in part the intrinsic skin tensile strength because they influence the orientation of the dermal fibre networks. Our objective was to assess changes in shear wave propagation in the skin according to the body posture and orientation of the gravitational forces. The study was performed in 30 middle-aged women with a normal body mass index. The Reviscometer was used to assess the mechanical wave propagation on the volar forearm in extension or flexion. Similar measurements were made on the supra-areolar region of the breast when the trunk was in the horizontal or vertical position. Four measurements were made in each of 4 directions at given angles with regard to the body axis. The device gave reproducible data. Shear wave propagation was influenced by the body posture. The intra-individual variability in shear wave velocity according to the directions of measurements increased when the tissues were in a relaxed position. Skin tensile anisotropy increased in a relaxed body posture. Shear wave propagation may be a convenient non-invasive tool to better identify the natural skin tension lines in the skin, thus refining the orientation of incision during cutaneous surgery. PMID:11306851

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

    DOEpatents

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

    1991-04-09

    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.

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

    SciTech Connect

    Yang, Z.J.

    1997-08-01

    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.

  6. General{relativistic free decay of magnetic elds in a spherically symmetric body.

    E-print Network

    General{relativistic free decay of magnetic elds in a spherically symmetric body. K.{H. Radler, H The decay of a magnetic eld penetrating a compact spherical electrically conducting body and continuing in its nonconducting surroundings is sys- tematically studied. The body, considered as a rough model

  7. Control of a three-dimensional magnetic force generated from a magnetic navigation system to precisely manipulate the locomotion of a magnetic microrobot

    NASA Astrophysics Data System (ADS)

    Nam, J. K.; Jeon, S. M.; Lee, W. S.; Jang, G. H.

    2015-05-01

    We propose a method to generate a three-dimensional (3D) magnetic force to manipulate a magnetic microrobot in various environments by using a magnetic navigation system. The proposed method is based on the control of the magnetic force with respect to the change in the magnetization direction of the microrobot and an external magnetic flux gradient. We derived the nonlinear constraint equations which can determine the required direction of the uniform magnetic fields and magnetic gradients to generate the 3D magnetic force of a microrobot. The solutions of the equations were calculated using a geometrical analysis of the equations without any singular point. The proposed methodology was verified on 3D planar environments considering gravitational force, and we also conducted an experiment in a 3D water-filled tubular environment to verify the possibility of the clinical application in human blood vessels.

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  9. Flow and Force Equations for a Body Revolving in a Fluid

    NASA Technical Reports Server (NTRS)

    Zahm, A F

    1930-01-01

    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.

  10. 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)

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

    2014-07-01

    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.

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

    SciTech Connect

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

    1997-08-06

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

  12. Magnetic force microscopy study of magnetization reversal in sputtered FeSiAl(N) films

    SciTech Connect

    Lo, C. C. H.; Snyder, J. E.; Leib, J.; Chen, R.; Kriegermeier-Sutton, B.; Kramer, M. J.; Jiles, D. C.; Kief, M. T.

    2001-03-01

    The magnetization reversal in a series of rf-sputtered FeSiAl(N) films has been studied using magnetic force microscopy. A system has been developed which has the capability to image domain structure while an in-plane magnetic field is applied in situ. All films exhibited a stripe domain structure in zero applied field which was indicative of a perpendicular component of domain magnetization which alternates in sign. All films showed a similar sequence of magnetization processes: on reducing the applied field from saturation a fine stripe domain structure nucleated and then coarsened as the field was decreased to zero. Local switching of domain contrast was observed along the steepest part of the hysteresis loop as the perpendicular component reversed. As the reverse field was increased toward saturation, the stripe domains disintegrated into smaller regions. This observation is consistent with an interpretation that the domain magnetization rotated locally into the sample plane. The saturation field and the film stress exhibited similar trends with nitrogen partial pressure. The results suggest that the perpendicular anisotropy that caused the formation of the stripe domain structure could be induced by the film stress via magnetoelastic coupling.

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

    SciTech Connect

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

    2010-11-12

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

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

    NASA Astrophysics Data System (ADS)

    Zou, Jibin; Li, Xuehui; Lu, Yongping; Hu, Jianhui

    2002-11-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

  16. The application of magnetic force differentiation for the measurement of the affinity of peptide libraries

    NASA Astrophysics Data System (ADS)

    Shang, Hao; Kirkham, Perry M.; Myers, Tina M.; Cassell, Gail H.; Lee, Gil U.

    2005-05-01

    A new method has been developed for measuring the binding affinity of phage displayed peptides and a target protein using magnetic particles. The specific interaction between the phage displayed peptides and the target protein was subject to a force generated by the magnetic particle. The binding affinity was obtained by analyzing the force-bond lifetime.

  17. Electromagnetic Forces on a Metal Disk in an Alternating Magnetic Field

    Microsoft Academic Search

    Samir Basu; K. D. Srivastava

    1969-01-01

    Many fast-acting electromechanical devices utilize the repulsion forces produced on a metal disk subjected to a transient magnetic field. Coupled circuit theory yields a simple expression for this force in terms of an equivalent inductance. The equivalent inductance, however, is difficult to evaluate by theoretical and\\/or experimental methods when the metal disk is very close to the magnet coil. A

  18. Novel gradient coil set with canceled net thrust force for nuclear magnetic resonance applications

    Microsoft Academic Search

    Labros S. Petropoulos; Michael A. Morich

    1995-01-01

    The interaction of the spatially varying main field components of a Magnetic Resonance Imaging (MRI) system with the currents of a gradient coil set generates axial and transverse Lorentz forces. In this paper, a novel technique for designing minimum inductance gradient coils with zero net axial and lateral Lorentz force is presented. Design examples are given for a short magnet

  19. Comparison of magnetic forces for IPM and SPM motor with rotor eccentricity

    Microsoft Academic Search

    Kyung-Tae Kim; Kwang-Suk Kim; Sang-Moon Hwang; Tae-Jong Kim; Yoong-Ho Jung

    2001-01-01

    The permanent magnet motor is often the most important element in many precision rotor applications and also a frequent source of vibration and acoustic noise. The eccentricity between stator and rotor is inevitably introduced during manufacturing process, such as mass unbalance, shaft bow and bearing tolerances. This paper investigates radial force density and magnetic unbalanced force for IPM and SPM

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

    NASA Astrophysics Data System (ADS)

    G, Ravi; Goyal, Vidhi

    2012-10-01

    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.

  1. Stresses in case-bonded solid-propellent rocket motors under transverse body-force loading

    Microsoft Academic Search

    R. Reid Parmerter

    1969-01-01

    The stresses in rocket motors generated by transverse body forces during storage, shipping or in flight maneuvers become increasingly\\u000a significant as motor size increases. An 8-ft-diam centrifuge was used to study these stresses in photoelastic models made\\u000a from Hysol 4485. The models were 5.4-in. diameter, with an internal star-shaped boundary which was free, and an external circular\\u000a boundary enclosed in

  2. Effectiveness of nonequilibrium closures for the many body forces in concentrated colloidal dispersions

    Microsoft Academic Search

    R. A. Lionberger; W. B. Russel

    1997-01-01

    Here we present a theory for predicting the effect of interparticle interactions on the nonequilibrium dynamics of concentrated colloidal dispersions. A configuration-space conservation equation for the pair density P2 provides a fundamental basis for calculating the nonequilibrium microstructure; however, it includes pairwise additive three-body couplings. The resulting forces depend on the three-particle distribution function, necessitating an additional equation to completely

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

    PubMed

    Rouge, Clémence; Lhémery, Alain; Ségur, Damien

    2013-10-01

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

  4. Application of superconductivity for magnetic force control in medical and industrial fields

    NASA Astrophysics Data System (ADS)

    Nishijima, S.

    2008-09-01

    The magnetic force control technique has expanded the applied field with developing a superconductivity because a high magnetic field and a high magnetic field gradient can be produced using the superconducting magnet. The magnetic force control technique has been applied to industrial fields such as recycling of abrasives, removing ferromagnetic particles from powdered products and purifying waste water. The technique is also applied to the drug delivery system as the medical application. Open gradient of magnetic separation was used for the recycling of the abrasives in wasted slurry from solar battery factory. For the removing the ferromagnetic particles from powdered products the magnetic filters were designed not to be blocked with the aggregated powder. In the water purification system, the superconducting high gradient magnetic separation was employed. For the magnetic drug delivery system the superconducting bulk magnet was used to navigate the nanometer-sized ferromagnetic particles in the blood vessel.

  5. Investigation of Ferromagnetic Microstructures by Local Hall Effect and Magnetic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Nitta, Junsaku; Schäpers, Thomas; Heersche, Hubert B.; Koga, Takaaki; Sato, Yuuki; Takayanagi, Hideaki

    2002-04-01

    We have investigated the magnetization process of NiFe micro-magnets, using fringing field induced local Hall effect (LHE) and magnetic force microscopy (MFM). Although the LHE reflects information only from the edge of micro-magnets, the MFM observation supports the conclusion that a rapid jump in the Hall resistance implies a sharp switching of the magnetization. The width dependence of coercive field Hc for NiFe micro-magnets obtained from LHE measurement is well reproduced by numerical calculations. The good agreement between the LHE experiment and the model calculation shows that a LHE device provides useful information on the magnetization process in micro-magnets.

  6. Radial forces in a centrifugal compressor; Experimental investigation by using magnetic bearings and static pressure distribution

    NASA Astrophysics Data System (ADS)

    Reunanen, Arttu; Larjola, Jaakko

    2005-03-01

    The volute of a centrifugal compressor causes a non-uniform pressure distribution which leads to a radial force on the impeller. This force was measured using magnetic bearings. In addition, the radial force was estimated using the static pressure distribution measured at the impeller outlet. The impeller force was found to be the highest at choke, the lowest at the design flow and moderate at stall. The radial force determined from the pressure measurements was only slightly different from the force obtained from the bearing measurements. The rotational speed was seen to affect the force to some extent.

  7. The Geometry of Halo and Lissajous Orbits in Circular Restricted Three Body Problem with Drag Forces

    E-print Network

    Pal, Ashok Kumar

    2014-01-01

    In this article we determine the effect of radiation pressure, Poynting-Robertson drag and solar wind drag on the Sun-(Earth-Moon) restricted three body problem. Here, we take the bigger body Sun as a bigger primary, and Earth+Moon as a smaller primary. With the help of perturbation technique we find the Lagrangian points, and see that the collinear points deviate from the axis joining the primaries, whereas the triangular points remain unchanged in their configuration. It is also found that Lagrangian points move toward the Sun when radiation pressure increases. We have also analyzed the stability of the triangular equilibrium points and found that they are unstable due drag forces. Moreover, we have computed the halo orbits in the third-order approximation using Lindstedt-Poincar$\\acute{e}$ method and found the effect of the drag forces. According to this prevalence, the Sun-(Earth-Moon) model is used to design the trajectory for spacecraft traveling under the drag forces. keywords:Restricted three body pro...

  8. Generalized Landau Lifshitz Gilbert equation for uniformly magnetized bodies

    NASA Astrophysics Data System (ADS)

    Serpico, C.; Mayergoyz, I. D.; Bertotti, G.; d'Aquino, M.; Bonin, R.

    2008-02-01

    We consider generalized Landau-Lifshitz-Gilbert (LLG) deterministic dynamics in uniformly magnetized bodies. The dynamics take place on the unit sphere ?, and are characterized by a vector field v tangential to ?. By using Helmholtz decomposition on ?, it is proven that v is uniquely defined by two potentials ? and ?. Potential ? can be identified with the free energy of the system, while ? describes non-conservative interactions of the system with the environment. The presence of ? modifies the usual energy balance of LLG dynamics. Instead of purely relaxation dynamics we may have steady injection of energy through non-conservative interactions. The implications of the new form of the energy balance are discussed in detail.

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

    SciTech Connect

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

    2005-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Inomata, Kentaro; Shigemori, Yo; Uchimura, Yutaka

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

  11. An optimal direct thrust force control for interior Permanent Magnet Linear Synchronous Motors incorporating field weakening

    Microsoft Academic Search

    M. Abroshan; K. Malekian; J. Milimonfared; B. A. Varmiab

    2008-01-01

    This paper presents an optimum direct thrust force control for interior permanent magnet linear synchronous motor (PMLSM) over wide velocity range in which the maximum thrust force per ampere (MTPA) strategy is used below the base velocity and field weakening strategy is used above the base velocity. Using MTPA strategy, copper losses is minimized in constant force region, and using

  12. Measurement of the gradient of the Casimir force between a nonmagnetic sphere and a magnetic plate

    E-print Network

    Banishev, A A; Klimchitskaya, G L; Mostepanenko, V M; Mohideen, U

    2012-01-01

    We measured the gradient of the Casimir force between an Au sphere and a plate made of ferromagnetic metal (Ni). It is demonstrated that the magnetic properties influence the force magnitude. This opens prospective opportunities for the control of the Casimir force in nanotechnology and for obtaining Casimir repulsion by using ferromagnetic dielectrics.

  13. Measurement of the gradient of the Casimir force between a nonmagnetic sphere and a magnetic plate

    E-print Network

    A. A. Banishev; C. -C. Chang; G. L. Klimchitskaya; V. M. Mostepanenko; U. Mohideen

    2012-05-04

    We measured the gradient of the Casimir force between an Au sphere and a plate made of ferromagnetic metal (Ni). It is demonstrated that the magnetic properties influence the force magnitude. This opens prospective opportunities for the control of the Casimir force in nanotechnology and for obtaining Casimir repulsion by using ferromagnetic dielectrics.

  14. Effects of Three-Nucleon Forces and Two-Body Currents on Gamow-Teller Strengths

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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 14C O,2422 using consistent two-body currents. We compute spectra of the daughter nuclei 14N and F,2422 via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q2?0.84 - 0.92 of the axial-vector coupling. The half-life of 14C depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current.

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

    E-print Network

    Ekström, A; Wendt, K A; Hagen, G; Papenbrock, T; Bacca, S; Carlsson, B; Gazit, D

    2014-01-01

    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.

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

    PubMed

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

    2014-12-31

    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 14C and (22,24)O using consistent two-body currents. We compute spectra of the daughter nuclei 14N and (22,24)F via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q2?0.84-0.92 of the axial-vector coupling. The half-life of 14C depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current. PMID:25615316

  17. Force-range correction in the three-body problem: Application to three-nucleon systems

    SciTech Connect

    Efimov, V. (Institute for Nuclear Theory, HN-12, and Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States))

    1991-12-01

    A leading correction to the zero-range theory is considered for three-body systems. The correction is linear in the force range {ital r}{sub 0}. An explicit expression is obtained for this correction for the case of correlation between the three-body binding energy and the particle-pair scattering length, as well as for the practically interesting case of correlation between the triton binding energy and the neutron-deuteron doublet scattering length. The correction for the neutron-deuteron quartet scattering length is also found. Physics of the correction involves a modification of the effective long-range interaction 1/{ital R}{sup 2}, which arises in the three-body systems under the conditions of the zero-range theory, by a singular correction {ital r}{sub 0}/{ital R}{sup 3}.

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

    SciTech Connect

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

    2012-05-01

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

  19. Self-gravitating Body with an Internal Magnetic Field. I. New Analytical Equilibria

    NASA Astrophysics Data System (ADS)

    Aly, J.-J.; Amari, T.

    2012-05-01

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

  20. Investigation of Body Force Effects on Flow Boiling Critical Heat Flux

    NASA Astrophysics Data System (ADS)

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

    2002-11-01

    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.

  1. Effects of adding whole body vibration to squat training on isometric force/time characteristics.

    PubMed

    Lamont, Hugh S; Cramer, Joel T; Bemben, Debra A; Shehab, Randa L; Anderson, Mark A; Bemben, Michael G

    2010-01-01

    Resistance training interventions aimed at increasing lower-body power and rates of force development have produced varying results. Recent studies have suggested that whole-body low-frequency vibration (WBLFV) may elicit an acute postactivation potentiation response, leading to acute improvements in power and force development. Potentially, the use of WBLFV between sets of resistance training rather than during training itself may lead to increased recruitment and synchronization of high-threshold motor units, minimize fatigue potential, and facilitate the chronic adaptation to resistance exercise. The purpose of this study was to determine the effects of applying TriPlaner, WBLFV, prior to and then intermittently between sets of Smith machine squats on short-term adaptations in explosive isometric force expression. Thirty recreationally resistance trained men aged 18-30 were randomly assigned to 1 of 3 groups: resistance training only (SQT, n = 11), resistance plus whole-body vibration (SQTV, n = 13), or active control (CON, n = 6). An isometric squat test was performed prior to and following a 6-week periodized Smith machine squat program. Whole-body low-frequency vibration was applied 180 seconds prior to the first work set (50 Hz, 2-4 mm, 30 seconds) and intermittently (50 Hz, 4-6 mm, 3 x 10 seconds, 60 seconds between exposures) within a 240-second interset rest period. Subjects were instructed to assume a quarter squat posture while positioning their feet directly under their center of mass, which was modified using a handheld goniometer to a knee angle of 135 +/- 5 degrees . Instructions were given to subjects to apply force as fast and as hard as possible for 3.5 seconds. Isometric force (N) and rates of force development (N.s(-1)) were recorded from the onset of contraction (F(0)) to time points corresponding to 30, 50, 80, 100, 150, and 250 milliseconds, as well as the peak isometric rate of force development (PISORFD), and rate of force development to initial peak in force (RFDinitial). Repeated measures analysis of variance and analysis of covariance revealed no significant group by trial interactions for isometric rate of force development (ISORFD) between 0-30, 0-50, 0-80, 0-100, 0-150, and 0-250 milliseconds and PISORFD (p > 0.05). A significant group x trial interaction was seen for RFDinitial with SQTV >CG (p = 0.04, mean difference 997.2 N.s(-1)) and SQTV >SQT (p = 0.04, mean difference 1,994.22 N.s(-1)). Significant trial by covariate interactions (week one measures for ISORFD) and main effects for trial were observed for ISORFD between 0-80, 0-100, 0-and 150 milliseconds; PISORFD; and RFDinitial (p < 0.01). A significant trial effect was seen for Finitial (%) when expressed as a relative percentage of maximal voluntary contraction (MVC) (MVC = 100%) (p = 0.015; week 1 > week 7, mean difference, 5.82%). No significant differences were seen for any other force variables from the onset of contraction to MVC between weeks 1 and 7 (p > 0.05). The data suggest that there was a significant benefit afforded by adding WBLFV to a short-term resistance training protocol with regard to "explosive" strength expression. The addition of vibration prior to and between sets of resistance exercise may be a viable alternative to vibration applied during resistance exercise when trying to improve "explosive" isometric strength. PMID:19924007

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed Central

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

    2014-01-01

    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

  4. Effects due to body-forces and body-couples in the interior of a micropolar elastic half-space—I

    Microsoft Academic Search

    Saleem M. Khan; Ranjit S. Dhaliwal

    1977-01-01

    A general solution of the equilibrium equations is obtained for a half-space with a fixed boundary and arbitrary but axisymmetric distribution of body forces and body couples in the interior of the half-space. Few particular cases have been investigated in detail. The stresses have been obtained at the boundary and the displacements have been obtained in the interior of the

  5. Study of magnetic and multiferroic oxides by scanning force microscope

    NASA Astrophysics Data System (ADS)

    Chuang, Tien-Ming

    The first part of this dissertation introduces the techniques for scanning force microscope (SFM) that we use to investigate our samples. A compact design for a low-temperature SFM is presented in the second part. A fiber-optic interferometer is used as cantilever deflection sensor. The tip-sample coarse approach and lateral tip positioning are performed by piezoelectric positioners in situ. The microscope has been operated at temperatures between 6K and 300K and could be incorporated with an 8 Tesla superconducting magnet in out-of-plane direction. Our homemade SFM is also capable of scanning in multi-modes. The second and third part focused on our results of two different samples: a multiferroic polycrystalline (EuMnO 3)0:5(YMnO3)0:5 sample and a colossal magnetoresistive (CMR) manganite La0:60Ca0:40MnO 3 thin film grown on NdGaO3(001) substrate.

  6. GravitoMagnetic force in modified Newtonian dynamics

    SciTech Connect

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

    2013-08-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

    We present a theoretical calculation of the pull-in control in capacitive microswitches actuated by Casimir forces using external magnetic fields. The external magnetic fields induce an optical anisotropy due to the excitation of magnetoplasmons 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 the increasing magnetic field.

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

    E-print Network

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

    2009-07-13

    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.

  9. Phase combination for self-cancellation of magnetic force in undulators

    NASA Astrophysics Data System (ADS)

    Kinjo, Ryota; Tanaka, Takashi

    2014-12-01

    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.

  10. Characterization of the Weld Regions within Duplex Stainless Steels using Magnetic Force Microscopy

    Microsoft Academic Search

    B. Gideon; L. Ward; K. Short

    Standard metallography and optical microscopy are well established techniques for the characterization of duplex stainless steels (DSS), which consist of approximately 50% ferrite and 50% austenite. Recently, the use of atomic and magnetic force microscopies (AFM and MFM respectively) have been employed to differentiate between magnetic and non magnetic phases in materials. Such techniques would be valuable to identify different

  11. Visualization and quantification of magnetic nanoparticles into vesicular systems by combined atomic and magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Dong, C.; Corsetti, S.; Passeri, D.; Rossi, M.; Carafa, M.; Pantanella, F.; Rinaldi, F.; Ingallina, C.; Sorbo, A.; Marianecci, C.

    2015-06-01

    We report a phenomenological approach for the quantification of the diameter of magnetic nanoparticles (MNPs) incorporated in non-ionic surfactant vesicles (niosomes) using magnetic force microscopy (MFM). After a simple specimen preparation, i.e., by putting a drop of solution containing MNPs-loaded niosomes on flat substrates, topography and MFM phase images are collected. To attempt the quantification of the diameter of entrapped MNPs, the method is calibrated on the sole MNPs deposited on the same substrates by analyzing the MFM signal as a function of the MNP diameter (at fixed tip-sample distance) and of the tip-sample distance (for selected MNPs). After calibration, the effective diameter of the MNPs entrapped in some niosomes is quantitatively deduced from MFM images.

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

    NASA Astrophysics Data System (ADS)

    Duermann, Christoph; Wurm, Gerhard; Kuepper, Markus

    2013-10-01

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

  13. Magnetic microposts as an approach to apply forces to living cells.

    PubMed

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

    2007-09-11

    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

  14. Safety Implications of High-Field MRI: Actuation of Endogenous Magnetic Iron Oxides in the Human Body

    PubMed Central

    Dobson, Jon; Bowtell, Richard; Garcia-Prieto, Ana; Pankhurst, Quentin

    2009-01-01

    Background Magnetic Resonance Imaging scanners have become ubiquitous in hospitals and high-field systems (greater than 3 Tesla) are becoming increasingly common. In light of recent European Union moves to limit high-field exposure for those working with MRI scanners, we have evaluated the potential for detrimental cellular effects via nanomagnetic actuation of endogenous iron oxides in the body. Methodology Theoretical models and experimental data on the composition and magnetic properties of endogenous iron oxides in human tissue were used to analyze the forces on iron oxide particles. Principal Finding and Conclusions Results show that, even at 9.4 Tesla, forces on these particles are unlikely to disrupt normal cellular function via nanomagnetic actuation. PMID:19412550

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

    E-print Network

    Walker, Thomas K., III

    2009-01-01

    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 ...

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

    PubMed

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

    2015-03-01

    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. PMID:25871198

  17. Quantum Monte Carlo calculations of neutron matter with chiral three-body forces

    E-print Network

    I. Tews; S. Gandolfi; A. Gezerlis; A. Schwenk

    2015-07-20

    Chiral effective field theory (EFT) enables a systematic description of low-energy hadronic interactions with controlled theoretical uncertainties. For strongly interacting systems, quantum Monte Carlo (QMC) methods provide some of the most accurate solutions, but they require as input local potentials. We have recently constructed local chiral nucleon-nucleon (NN) interactions up to next-to-next-to-leading order (N$^2$LO). Chiral EFT naturally predicts consistent many-body forces. In this paper, we consider the leading chiral three-nucleon (3N) interactions in local form. These are included in auxiliary field diffusion Monte Carlo (AFDMC) simulations. We present results for the equation of state of neutron matter and for the energies and radii of neutron drops. In particular, we study the regulator dependence at the Hartree-Fock level and in AFDMC and find that present local regulators lead to less repulsion from 3N forces compared to the usual nonlocal regulators.

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

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

    SciTech Connect

    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

    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.

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

    Microsoft Academic Search

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

    2009-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Hamadeh, A.; de Loubens, G.; Naletov, V. V.; Grollier, J.; Ulysse, C.; Cros, V.; Klein, O.

    2012-04-01

    Using a magnetic-resonance force microscope (MRFM), the power emitted by a spin-transfer nano-oscillator consisting of a normally magnetized Py|Cu|Py circular nanopillar is measured both in the autonomous and forced regimes. From the power behavior in the subcritical region of the autonomous dynamics, one obtains a quantitative measurement of the threshold current and of the noise level. Their field dependence directly yields both the spin torque efficiency acting on the thin layer and the nature of the mode which first auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. From the MRFM behavior in the forced dynamics, it is then demonstrated that in order to phase lock this auto-oscillating mode, the external source must have the same spatial symmetry as the mode profile, i.e., a uniform microwave field must be used rather than a microwave current flowing through the nanopillar.

  2. Aspiration from the vitreous of a non-magnetic foreign body

    Microsoft Academic Search

    H. B. Chawla; J. A. Coleiro; F. Jonasson

    1978-01-01

    A non-magnetic vitreal foreign body was aspirated from over the macula through the pars plana. The surgeon guided a blunt needle towards the foreign body while watching both with the binicular indirect ophthalmoscope. His assistant's tentative suction movements with an attached syringe drew the foreign body up into the needle without risking a retinal perforation. Visual recovery was complete. It

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

  4. Stability in a rhomboidal 5-body problem with generalized central forces

    NASA Astrophysics Data System (ADS)

    Marchesin, Marcelo; Vidal, Claudio

    2013-10-01

    We consider a system of five mass points r1, r2, r3, and r4 with masses m1 = m2 = m and m_3= m_4= tilde{m} moving about a single massive body r0 with mass m0 at its center which is assumed to be the origin of the coordinates system. We assume that the central body r0 makes a generalized force on the four mass points and that such a force is generated by a Manev's type potential, i.e., characterized by a potential of the form 1/r+? /r^2, on the other hand is assumed that the attraction between the bodies r1, r2, r3, and r4 is of the Newtonian type. This model represents several cases, for instance, when the central body is a spheroid or a radiating source. First, we prove the existence of three different relative rhomboidal solutions, and its (central) configuration is as follows: (1) the rhombus is a square and all primaries have equal masses; (2) the rhombus is not a square but all masses are equal; and (3) the rhombus is not a square and the pairs of primaries have different masses. The first two cases present two parameters: ?, the radiation or the oblateness coefficient and m = ? the common mass of the primaries. In the third case, the only parameter to be considered is ? since it can be shown that in this case both m and tilde{m} depend on ?. Second, we study the stability of these solutions. We determine the values of the parameters (?, ?) for which the square solution is spectrally stable and we prove that the rhomboidal solutions are unstable in the Lyapunov sense in the other two situations.

  5. Dual-body magnetic helical robot for drilling and cargo delivery in human blood vessels

    NASA Astrophysics Data System (ADS)

    Lee, Wonseo; Jeon, Seungmun; Nam, Jaekwang; Jang, Gunhee

    2015-05-01

    We propose a novel dual-body magnetic helical robot (DMHR) manipulated by a magnetic navigation system. The proposed DMHR can generate helical motions to navigate in human blood vessels and to drill blood clots by an external rotating magnetic field. It can also generate release motions which are relative rotational motions between dual-bodies to release the carrying cargos to a target region by controlling the magnitude of an external magnetic field. Constraint equations were derived to selectively manipulate helical and release motions by controlling external magnetic fields. The DMHR was prototyped and various experiments were conducted to demonstrate its motions and verify its manipulation methods.

  6. Numerical dosimetry of currents induced in the human body by ELF magnetic fields

    E-print Network

    Paris-Sud XI, Université de

    Numerical dosimetry of currents induced in the human body by ELF magnetic fields Riccardo Scorretti by ELF magnetic fields requires that the source field is provided through a vector potential. We present experimental measurements, as there is no need for a magnetic vector potential. Keywords: ELF, numerical

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

    SciTech Connect

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

    1988-01-01

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

  8. Study of ac-plane Magnetic Microstructure of Fe3GeTe2 Using Magnetic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Leon Brito, Neliza; Bauer, Eric D.; Ronning, Filip; Thompson, Joe D.; Movshovich, Roman

    2015-03-01

    In the quest to develop design principles governing high performance rare earth-free ferromagnets our group has focused on materials where electronic correlations and crystal environment lead to high magnetic anisotropy. The present study concentrates its efforts on one of these materials, the layered itinerant ferromagnet Fe3GeTe2, which has a high degree of magnetic anisotropy and an easy magnetization direction along the c-axis. Magnetic force microscopy was used to observe the ground state magnetic microstructure of the a-c plane, and its evolution in an external magnetic field along the b-axis. We built a ``surface magnetization loop'' based on the MFM data from -5 Tesla to +5 Tesla. We will discuss our results in view of the bulk magnetization data obtained with a superconducting quantum interference device magnetometer. Work at LANL was performed under the auspices of the U.S. DOE and supported by the LDRD program.

  9. Quantitative assessment of pinning forces and magnetic penetration depth in NbN thin films from complementary magnetic force microscopy and transport measurements

    Microsoft Academic Search

    T. Shapoval; H. Stopfel; S. Haindl; J. Engelmann; D. S. Inosov; B. Holzapfel; V. Neu; L. Schultz

    2011-01-01

    Epitaxial niobium nitride thin films with a critical temperature of Tc=16 K and a thickness of 100 nm were fabricated on MgO (100) substrates by pulsed laser deposition. Low-temperature magnetic-force-microscopy (MFM) images of the supercurrent vortices were measured after field cooling in a magnetic field of 3 mT at various temperatures. The temperature dependence of the penetration depth has been

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

    E-print Network

    Zutavern, Zachary Scott

    2009-06-02

    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...

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

    PubMed

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

    2013-07-01

    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

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

    NASA Astrophysics Data System (ADS)

    Wetter, Laura; Verosub, Ken; Russell, James

    2007-06-01

    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.

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

    Microsoft Academic Search

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

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    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.

  15. Experimental investigations into forces acting during a magnetic abrasive finishing process

    Microsoft Academic Search

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

    2006-01-01

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

  16. Magnetic field effects in the Casimir force between two parallel anti-ferromagnetic slabs

    NASA Astrophysics Data System (ADS)

    Palomino-Ovando, M.; Kinto-Ramírez, H.; Cocoletzi, Gregorio H.

    2008-03-01

    We study the Casimir force F between two parallel anti-ferromagnetic slabs taking into account an external magnetic field in the Voigt configuration. Using a frequency and magnetic field dependent magnetic permeability tensor and a frequency independent dielectric permittivity, to describe the slabs, we calculate the Casimir force using non-normal incidence reflectivity of the electromagnetic waves in the free space between the slabs. We determine the Casimir force by performing two-dimensional calculations. F is investigated as a function of the layer thickness d, the vacuum gap width L between slabs, and the external magnetic field strength H. Features of F as function of the external field include the presence of sharp dips and peaks, which appear in the vicinity of the resonance frequency, and are consequences of the interaction of the external magnetic field with the electron spin. In addition, an external field may diminish F, which is an important effect not found in any other system.

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

    PubMed

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

    2014-11-01

    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

  18. Three-Dimensional Force Measurement and Control of a Flux-Path Control Magnetic Suspension

    NASA Astrophysics Data System (ADS)

    Furutachi, Munehiro; Inaba, Shunsuke; Ishino, Yuji; Takasaki, Masaya; Mizuno, Takeshi

    In the flux-path control magnetic suspension system, the force acting on a floator is controlled by moving a control plate made of ferromagnetic material, which is located between the permanent magnet and the floator. In this paper, the three-dimensional attractive forces acting on the floator were measured with a manufactured force sensor. The force actuating in the vertical direction is measured with the load cell built in the sensor. The force actuating in the horizontal direction is measured with the plate springs with strain gauges. These measurements clarify the relations between the positions of the control plates and the three-dimensional attractive forces. In addition, stable suspension and three-dimensional positioning were achieved by applying PD control. Several dynamic characteristics were measured in both the vertical and horizontal directions.

  19. Scattering-matrix approach to Casimir-Lifshitz force and heat transfer out of thermal equilibrium between arbitrary bodies

    SciTech Connect

    Messina, Riccardo [LNE-SYRTE, Observatoire de Paris, CNRS UMR 8630, UPMC, 61 avenue de l'Observatoire, F-75014 Paris (France); Antezza, Mauro [Universite Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34095, Montpellier (France); CNRS, Laboratoire Charles Coulomb UMR 5221, F-34095, Montpellier (France)

    2011-10-15

    We study the radiative heat transfer and the Casimir-Lifshitz force occurring between two bodies in a system out of thermal equilibrium. We consider bodies of arbitrary shape and dielectric properties, held at two different temperatures and immersed in environmental radiation at a third different temperature. We derive explicit closed-form analytic expressions for the correlations of the electromagnetic field and for the heat transfer and Casimir-Lifshitz force in terms of the bodies' scattering matrices. We then consider some particular cases which we investigate in detail: the atom-surface and the slab-slab configurations.

  20. A STUDY OF FORCE IN A STEADY MAGNETIC FIELD WITH ASYMPTOTIC BOUNDARY CONDITIONS

    Microsoft Academic Search

    Saul PASARE

    In this paper there is performed a comparative study of the force that acts over a mobile coil pierced by current when it is placed in an external steady magnetic field. Firstly the determination of force is performed through analytic calculations and by experiments over a physical model from the Faculty of Electrotechnics, University of Craiova. The determined values are

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

    Microsoft Academic Search

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

    2002-01-01

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

  2. Topology-based inequalities and inverse problems for near force-free magnetic fields

    Microsoft Academic Search

    P. Robert Kotiuga

    2004-01-01

    We review a conjecture characterizing the knotting of current paths arising as solutions to an inverse problem involving near force-free magnetic fields. Results about the nonexistence of solutions involving force-free fields supported in a finite domain are then considered, as are explicit constructions of force-free solutions in unbounded domains. This shows why truncating solutions defined on unbounded domains has proven

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

    PubMed

    Vanderburgh, Paul M; Crowder, Todd A

    2006-08-01

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

  4. Many-body Interactions in Magnetic Films and Nanostructures

    SciTech Connect

    Stephen D. Kevan

    2012-12-12

    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.

  5. Magnetization of a warm plasma by the nonstationary ponderomotive force of an electromagnetic wave

    SciTech Connect

    Shukla, Nitin; Shukla, P. K.; Stenflo, L. [Department of Physics, Umeaa University, SE-90187 Umeaa (Sweden); Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Department of Physics, Linkoeping University, SE-58183 Linkoeping (Sweden)

    2009-08-15

    It is shown that magnetic fields can be generated in a warm plasma by the nonstationary ponderomotive force of a large-amplitude electromagnetic wave. In the present Brief Report, we derive simple and explicit results that can be useful for understanding the origin of the magnetic fields that are produced in intense laser-plasma interaction experiments.

  6. Magnetic force microscopy and cross-sectional transmission electron microscopy of carburised surfaces

    Microsoft Academic Search

    K. J Stevens; A Parbhu; J Soltis

    2004-01-01

    Magnetic force microscopy has been used to determine the origin and spatial distribution of changes in magnetic properties of an HPM alloy carburised by exposure in an ethylene production furnace. In higher activity carburising atmospheres at 400–800 °C, metal dusting can occur in which the exposed surface becomes carburised to such an extent that the tube alloy pits and literally

  7. The Lorentz forces on an electrically conducting sphere in an alternating magnetic field

    Microsoft Academic Search

    Udaya B. Sathuvalli; Yildiz Bayazitoglu

    1996-01-01

    A method to calculate the Lorentz force on an electrically conducting sphere placed in an arbitrary sinusoidally varying magnetic field is developed. The crux of this method lies in expressing the external magnetic held and the eddy current density in the sphere in terms of a “source function” of the current sources and a “skin depth dependent function”. The general

  8. Scaling of forced magnetic reconnection in the Hall-magnetohydrodynamic Taylor problem

    E-print Network

    Fitzpatrick, Richard

    Scaling of forced magnetic reconnection in the Hall-magnetohydrodynamic Taylor problem Richard-dimensional, incompressible, zero guide-field, nonlinear Hall-MHD magnetohydrodynamical simulations are used to investigate magnetohydrodynamical MHD theory is capable of accounting for magnetic reconnection, but generally predicts reconnection

  9. Magnetic force microscopy of epitaxial magnetite films through the Verwey transition

    Microsoft Academic Search

    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

    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

  10. The Relationship of Body Weight and Clinical Foot and Ankle Measurements to the Heel Forces of Forward and Backward Walking

    PubMed Central

    Albensi, Raymond J.; Nyland, John; Caborn, David N.M.

    1999-01-01

    Objective: To compare and contrast the relationships of selected static clinical measurements with the heel forces of forward and backward walking among healthy high school athletes. Design and Setting: Single-group, cross-order-controlled, repeated-measures design. All data were collected in a high school athletic training room. Subjects: Seventeen healthy high school student-athlete volunteers. Measurements: We performed static clinical measurements of the foot, ankle, and knee using handheld goniometers. We used a metric ruler to assess navicular drop and a beam balance platform scale to measure body weight. Mean peak heel forces were measured using F-scan insole force sensors. Data were sampled for 3 5-second trials (50-Hz sampling rate). Mean peak heel forces were determined from 3 to 5 consecutive right foot contacts during forward and backward walking at approximately 4.02 to 4.83 km/h (2.5 to 3.0 mph). Subjects wore their own athletic shoes and alternated their initial walking direction. Results: Forward stepwise multiple regression analyses revealed that body weight, navicular drop, and standing foot angle predicted mean peak heel forces during forward and backward walking. Conclusions: Heel forces during forward and backward walking increase as body weight and navicular drop magnitude increase, and they decrease as standing foot angle increases. Subtle differences in foot, ankle, and knee joint postures and kinematics can affect heel forces even among normal subjects. Injury and protective bracing or taping may further affect these heel forces. PMID:16558581

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

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

    PubMed

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

    2014-08-01

    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

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

    DOEpatents

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

    1995-11-07

    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.

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

    DOEpatents

    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

    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.

  15. Alternating Magnetic Field Forces for Satellite Formation Flying

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

  16. Subsurface characterization and three dimensional profiling of semiconductors by magnetic resonance force microscopy

    Microsoft Academic Search

    P. C. Hammel; G. Moore; M. Roukes; Zhenyong Zhang

    1996-01-01

    This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project successfully developed a magnetic resonance force microscope (MRFM) instrument to mechanically detect magnetic resonance signals. This technique provides an intrinsically subsurface, chemical-species-specific probe of structure, constituent density and other properties of materials. As in conventional magnetic resonance

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

    SciTech Connect

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

    2011-12-31

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Garshelis, I. J.; Crevecoeur, G.

    2014-05-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Minteer, Timothy M.

    2015-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    McAndrew, Christopher; Mehl, Patrick; Sarkar, Abhijit

    2010-03-01

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

  4. In medium T-matrix for nuclear matter with three-body forces - binding energy and single particle properties

    E-print Network

    V. Soma; P. Bozek

    2008-08-21

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

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

    SciTech Connect

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

    2008-11-15

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

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

    SciTech Connect

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

    1988-01-01

    An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the compressive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made with a new system that eliminates sources of errors due to spurious resistance changes in interconnecting wiring and solder joints. The design of the transducers and their measurement system is presented along with a discussion of the method of compensation for thermal and magnetic effects, methods of calibration with typical calibration data, and measured effect in actual magnets of the thermal stress changes from cooldown and the Lorentz forces during magnet excitation. 13 figs., 1 tab.

  7. 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)

    Dress, David A.

    1988-01-01

    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.

  8. Force-distance relation and properties of repelling Sm-Co5 magnets in orthodontic clinical use: an experimental model.

    PubMed

    Bondemark, L; Kurol, J

    1992-08-01

    In recent years, magnets and magnetic forces have been suggested as an alternative to traditional orthodontic devices such as elastics, springs and wires. The purpose of this study was to analyze the reliability and the output of forces for prefabricated orthodontic repelling Sm-Co5 magnets and the force conditions for the magnets after 5 months of maximal loading. The test-machine consisted of a jig where the tested pair of repelling magnets was mounted close to the clinical situation. With a cylindrical strain gauge transducer, a micrometer screw, a bridge-amplifier, and a Mingograph jet recorder, force-distance diagrams were constructed. The force-distance diagrams showed that the force-distance curve was hyperbolic and that the mean force when the magnetic pole faces were almost in contact with each other was 214.9 g, SD 13.42 g. The variation of magnetic force between different Sm-Co5 magnets was 6-9%. The difference in force before and after 5 months of maximal loading of the magnets was not significant. The test results indicate that with proper handling of the forces according to the new force diagrams, the system is reliable for orthodontic use. PMID:1439528

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

    NASA Astrophysics Data System (ADS)

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

    2005-01-01

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

  10. Many-body Forces in the Equation of State of Hyperonic Matter

    NASA Astrophysics Data System (ADS)

    Gomes, R. O.; Dexheimer, V.; Schramm, S.; Vasconcellos, C. A. Z.

    2015-07-01

    In this work we introduce an extended version of the formalism proposed originally by Taurines et al. that considers the effects of many-body forces simulated by nonlinear self-couplings and meson–meson interaction contributions. In this extended version of the model, we assume that matter is at zero temperature, charge neutral, and in beta-equilibrium, considering that the baryon octet interacts by the exchange of scalar–isoscalar (?, {? }*), vector–isoscalar (?, ?), vector–isovector (\\varrho ), and scalar–isovector (?) meson fields. Using nuclear matter properties, we constrain the parameters of the model that describe the intensity of the indirectly density dependent baryon–meson couplings to a small range of possible values. We then investigate asymmetric hyperonic matter properties. We report that the formalism developed in this work is in reasonable agreement with experimental data and also allows for the existence of massive hyperon stars (with more than 2 {M}? ) with small radii, compatible with astrophysical observations.

  11. Conformal coating of particles in microchannels by magnetic forcing

    NASA Astrophysics Data System (ADS)

    Tsai, Scott S. H.; Wexler, Jason S.; Wan, Jiandi; Stone, Howard A.

    2011-10-01

    We present a co-flow microfluidic method to coat paramagnetic beads with a thin layer of fluid as the beads are pulled across a liquid-liquid interface by an external magnetic field. We show that the coating thickness can be controlled by the magnitude of the flow speed. Also, the number of beads aggregated within a single coating can be adjusted by varying the strength of the magnetic field or the liquid-liquid interfacial tension.

  12. The Inverse-Cube Law of Magnetic Forces

    NSDL National Science Digital Library

    2012-08-03

    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).

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

    NASA Astrophysics Data System (ADS)

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

    2011-01-01

    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.

  14. Morphology and Dynamics of Lithospheric Body Force Instabilities: Sheets, Drips and In-Between

    NASA Astrophysics Data System (ADS)

    Beall, A.; Moresi, L. N.

    2014-12-01

    Foundering of the Earth's lithosphere, and consequent energy and mass flux across the upper boundary layer and mantle interface, is driven locally by gravitational body forces. The related instabilities are usually classified as having sheet-like or drip-like morphologies. The former is associated with whole lithosphere (subduction) or delamination type foundering such as suggested for beneath the southern Sierra-Nevada and the Colorado Plateau, the latter to classic Rayleigh-Taylor instability below an upper layer, suggested to have occurred beneath the Tibetan Plateau and North Island, New Zealand. This dichotomy is non-trivial; classification of phenomena into one or the other is often debated and is difficult to infer from observables. The two morphologies are most likely end-members. Here I refine the dynamics driving morphology selection as a function of rheological lamination and boundary layer Rayleigh number in 2D and 3D, using the finite-element particle-in-cell code Underworld. I explore the influence of morphology on mass flux, topography and crustal deformation as well as deviation from classic 2D scalings. Additionally, tectonic displacement interference with instability development is discussed using basic 3D shear-box style models. By quantifying and describing the theoretical instability dynamics which could result in a plausible range of morphological expressions, I aim to build a general framework which can be paired to the discussion involving firstly, the recognition of varied styles of body force instabilities in the modern Earth and rock record and secondly, to what degree pattern selection impacts boundary layer mass and energy flux.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

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

    E-print Network

    Microscope to Track a Magnetized Nanosize Particle Dimitar Baronov, Student Member, IEEE, and Sean B moving in three dimensions using a mag- netic force microscope (MFM). The stray magnetic field, we in- troduce a feedback control law that steers the tip of a magnetic force microscope (MFM

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

    Microsoft Academic Search

    Masato Akamatsu; Mitsuo Higano; Yoshio Takahashi; Hiroyuki Ozoe

    2005-01-01

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

  18. Design and construction of a magnetic force microscope 

    E-print Network

    Khandekar, Sameer Sudhakar

    2005-08-29

    means reducing the intensity of MFM signal. The better way is to apply a voltage bias between the tip and the sample.9 The absolute value of this force is much greater than van der Waals force which becomes negligible. The value of the bias... to be equivalent to the physical length of the tip in most cases). 2. AC mode MFM This is also called as far-field MFM. Here the vibrating cantilever is held on the order of hundreds of angstroms from the sample surface. In this region, both the absolute...

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  20. An Effective Theory for Nuclear Matter with Genuine Many-Body Forces

    NASA Astrophysics Data System (ADS)

    Vasconcellos, César A. Z.; Horvath, Jorge; Hadjimichef, Dimiter; Gomes, Rosana O.

    Nuclear science has developed many excellent descriptions that embody various properties of the nucleus, and nuclear matter at low, medium and high densities. However, a full microscopic understanding of nuclear systems is still lacking. The aim of our theoretical research group is to shed some light on such challenges and particularly on open questions facing the high density nuclear many-body problem. Here we focus our attention on the conceptual issue of naturalness and its role in shaping the baryon-meson phase space dynamics in the description of the equation of state (EoS) of nuclear matter. In particular, in order to stimulate possible new directions of research, we discuss relevant aspects of a recently developed relativistic effective theory for nuclear matter with natural parametric couplings and genuine many-body forces. Among other topics we discuss in this work the connection of this theory with other known effective QHD models of the literature and its potentiality in describing a new physics for dense matter.

  1. Magnetic evidence for a partially differentiated carbonaceous chondrite parent body

    E-print Network

    Weiss, Benjamin P.

    demagnetization, rock magnetic, and paleoin- tensity measurements on 71 mutually oriented bulk subsamples of Allende sample AMNH5056 (approximately 10-cm diameter and 8-mm thick slab surrounded by fusion crust (4, 9, 10), the HC magnetization is unidirectionally oriented throughout the meteorite's interior

  2. Magnetic resonance imaging for the in vivo determination of body composition in animal science

    Microsoft Academic Search

    U. Baulain

    1997-01-01

    Magnetic resonance imaging (MRI) is a diagnostic tool, originally developed for human medicine. It generates cross-sectional images of nearly all parts of the body with a high contrast between soft tissues. In animal science it has been utilized predominantly as an in vivo technique for the determination of body composition. The process of scanning live animals and especially the choice

  3. Structural responses of cells to intracellular magnetic force induced by superparamagnetic iron oxide nanoparticles

    PubMed Central

    Shen, Han; Tong, Sheng; Bao, Gang; Wang, Biao

    2014-01-01

    In this paper, we study the effects of intracellular force on human umbilical vein endothelial cells. We generated intracellular force on endothelial cells under different magnetic fields using the cell uptake of superparamagnetic iron oxide nanoparticles. Cell responses to intracellular force were observed using fluorescent microscopy. Our results indicated that nanoparticles were taken up by the cell by endocytosis and were deposited in lysosomes. Nanoparticles and lysosomes inside the cell could be relocated by the application of a magnetic force. The intracellular magnetic force could also be used to accelerate cell migration by adjusting the magnetic fields and giving the cell free culture space. No cytotoxicity of nanoparticles was found in our experiments. By comparing intracellular relocalization with migration of the whole cell, we obtained a better understanding of the self-defence mechanisms of cells based on their mechanical properties. Based on the promising mechanical properties and low cytotoxicity of our magnetic nanoparticles, their potential applications in cytomechanics and cell patterning are discussed. PMID:24336693

  4. Aspiration from the vitreous of a non-magnetic foreign body.

    PubMed Central

    Chawla, H. B.; Coleiro, J. A.; Jonasson, F.

    1978-01-01

    A non-magnetic vitreal foreign body was aspirated from over the macula through the pars plana. The surgeon guided a blunt needle towards the foreign body while watching both with the binicular indirect ophthalmoscope. His assistant's tentative suction movements with an attached syringe drew the foreign body up into the needle without risking a retinal perforation. Visual recovery was complete. It is suggested that aspiration might be the procedure of choice for such small visible intraocular fragments. Images PMID:718819

  5. Magnetic energy dissipation in force-free jets

    NASA Technical Reports Server (NTRS)

    Choudhuri, Arnab Rai; Konigl, Arieh

    1986-01-01

    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.

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

    PubMed

    Punyabrahma, P; Jayanth, G R

    2015-02-01

    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

  7. VARIFORC: a powerful FORC analysis tool specially suited to environmental magnetic applications

    NASA Astrophysics Data System (ADS)

    Egli, Ramon

    2015-04-01

    VARIFORC is a new tool for the analysis of first-order reversal curves (FORC), especially developed for the highly demanding applications typically occurring in environmental magnetism (e.g. quantitative magnetic component unmixing in weak samples). The currently unique capabilities of VARIFORC are illustrated with examples where the magnetic signature of authigenic minerals (e.g. magnetofossils) is isolated from other magnetic contributions associated with detrital or aeolian inputs in pelagic carbonates. Life demonstrations at the poster stand are possible. VARIFORC is freely available at http://www.conrad-observatory.at/cmsjoomla/de/download.

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

    NASA Astrophysics Data System (ADS)

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

    We study radiative activity of magnetic white dwarf undergoing torsional vibrations about axis of its own dipole magnetic moment under the action of Lorentz restoring force. It is shown that pulsating white dwarf can convert its vibration energy into the energy of magneto-dipole emission, oscillating with the frequency equal to the frequency of Alfvén torsional vibrations, provided that internal magnetic field is decayed. The most conspicuous feature of the vibration energy powered radiation in question is the lengthening of periods of oscillating emission; the rate of period elongation is determined by the rate magnetic field decay.

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

    PubMed

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

    2013-06-01

    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

  10. Particle diffusion and energization in Arnold-Beltrami-Childress force-free helical magnetic fields

    NASA Astrophysics Data System (ADS)

    Dasgupta, B.; Holguin, F.; Ram, A. K.; Mitra, D.

    2013-10-01

    It has long been considered that the cosmic magnetic fields in regions of low plasma pressure and large currents, such as in interstellar space and gaseous nebulae, are force-free in the sense that the Lorentz force vanishes. The Arnold-Beltrami-Childress (ABC) field is an example of a force-free helical magnetic field. The ABC magnetic field lines exhibit a complex and varied structure and can be chaotic. The motion of charged particles in regions of spatially chaotic ABC magnetic field lines displays a variety of dynamical behavior depending on the particle's energy and its initial direction of motion with respect to the local magnetic field vector. Particles started on chaotic magnetic field lines do not necessarily follow chaotic orbits. A class of particles executes periodic motion. For steady-state ABC fields the particles diffuse in space. For time-dependent ABC fields the particles gain energy for extended time periods-the mean kinetic energy has a power-law behavior in time. We present results on the dynamics of particles, and on their spatial diffusion and velocity space energization in ABC fields. It has long been considered that the cosmic magnetic fields in regions of low plasma pressure and large currents, such as in interstellar space and gaseous nebulae, are force-free in the sense that the Lorentz force vanishes. The Arnold-Beltrami-Childress (ABC) field is an example of a force-free helical magnetic field. The ABC magnetic field lines exhibit a complex and varied structure and can be chaotic. The motion of charged particles in regions of spatially chaotic ABC magnetic field lines displays a variety of dynamical behavior depending on the particle's energy and its initial direction of motion with respect to the local magnetic field vector. Particles started on chaotic magnetic field lines do not necessarily follow chaotic orbits. A class of particles executes periodic motion. For steady-state ABC fields the particles diffuse in space. For time-dependent ABC fields the particles gain energy for extended time periods-the mean kinetic energy has a power-law behavior in time. We present results on the dynamics of particles, and on their spatial diffusion and velocity space energization in ABC fields. Supported by DoE, NSF, European Research Council, and Swedish Research Council.

  11. Magnetic Evidence for a Partially Differentiated Carbonaceous Chondrite Parent Body

    E-print Network

    Shuster, David L.

    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. ...

  12. Magnetic Force Microscopy Imaging of Current Paths R. Yongsunthon1

    E-print Network

    Williams, Ellen D.

    that of a control Cr/Au region which was unaffected by the ion beam processing. MFM imaging of an ion-implant patterned line shows current deflection around the implant region. INTRODUCTION We have previously, with typical commercial MFM tips, such as the Digital Instruments MESP- HM tip, the magnetic film coats

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

    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.

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

    SciTech Connect

    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

    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.

  15. Magnetic field sensor based on the Ampere's force using dual-polarization DBR fiber laser

    NASA Astrophysics Data System (ADS)

    Yao, Shuang; Zhang, Yang; Guan, Baiou

    2015-05-01

    A novel magnetic field sensor using distributed Bragg reflector (DBR) fiber laser by Ampere's force effect is proposed and experimentally demonstrated. The key sensing element, that is the dual-polarization DBR fiber laser, is fixed on the middle part of two copper plates which carry the current. Ampere's force is applied onto the coppers due to an external magnetic field generated by a DC solenoid. Thus, the lateral force from the coppers is converted to a corresponding beat frequency signal shift produced by the DBR laser. The electric current sensing is also realized by the same configuration and same principle simultaneously in an intuitive manner. Good agreement between the theory calculation and the experimental results is obtained, which shows a good linearity. This sensor's sensitivity to the magnetic field and to the electric current finally reaches ~258.92 kHz/mT and ~1.08727 MHz/A, respectively.

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

    NASA Astrophysics Data System (ADS)

    Kim, Byung I.

    2012-05-01

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

  17. Atomic-resolution single-spin magnetic resonance detection concept based on tunneling force microscopy

    NASA Astrophysics Data System (ADS)

    Payne, A.; Ambal, K.; Boehme, C.; Williams, C. C.

    2015-05-01

    A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single-electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy system noise. The results show that the approach could provide single-spin measurement of electrically isolated qubit states with atomic spatial resolution at room temperature.

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

    E-print Network

    Navas, David

    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 ...

  19. Critical conditions for magnetic instabilities in force-free coronal loops

    Microsoft Academic Search

    A. W. Hood; E. R. Priest

    1981-01-01

    Ideal MHD stability theory is studied in order to gain an understanding of the effect of line-tying on an ideal MHD plasma before adding further complexities, and necessary and sufficient conditions are derived for the stability of force-free magnetic loops in the solar corona. The force-free basic state is discussed, and linear stability equations are derived. Attention is given to

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

    NASA Astrophysics Data System (ADS)

    Klein, Olivier

    2013-03-01

    In this talk, we will discuss how magnetic-resonance force microscopy, can provide quantitative measurement of the power emitted by a spin-transfer nano-oscillator, consisting of a normally magnetized Py|Cu|Py circular nanopillar, excited both in the autonomous and forced regimes.[2] From the power behavior in the subcritical region of the autonomous dynamics, one obtains a quantitative measurement of the threshold current and of the noise level. Their field dependence directly yields both the spin torque efficiency acting on the thin layer and the nature of the mode which first auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. We will then demonstrate that the observed spin-wave spectrum in the forced regime critically depends on the method of excitation. While the spatially uniform radio-frequency (RF) magnetic field excites only the axially symmetric modes having azimuthal index l = 0 , the RF current flowing through the nano-pillar, creating a circular RF Oersted field, excites only the modes having azimuthal index l = + 1 .[3] It is then demonstrated that in order to phase lock this auto-oscillating mode, the external source must have the same spatial symmetry as the mode profile, i.e., a uniform microwave field must be used rather than a microwave current flowing through the nanopillar. In this talk, we will discuss how magnetic-resonance force microscopy, can provide quantitative measurement of the power emitted by a spin-transfer nano-oscillator, consisting of a normally magnetized Py|Cu|Py circular nanopillar, excited both in the autonomous and forced regimes.[2] From the power behavior in the subcritical region of the autonomous dynamics, one obtains a quantitative measurement of the threshold current and of the noise level. Their field dependence directly yields both the spin torque efficiency acting on the thin layer and the nature of the mode which first auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. We will then demonstrate that the observed spin-wave spectrum in the forced regime critically depends on the method of excitation. While the spatially uniform radio-frequency (RF) magnetic field excites only the axially symmetric modes having azimuthal index l = 0 , the RF current flowing through the nano-pillar, creating a circular RF Oersted field, excites only the modes having azimuthal index l = + 1 .[3] It is then demonstrated that in order to phase lock this auto-oscillating mode, the external source must have the same spatial symmetry as the mode profile, i.e., a uniform microwave field must be used rather than a microwave current flowing through the nanopillar. This research was partially supported by the French Grant Spinnova (ANR-11-NANO-0016)

  1. Global constant-alpha force-free magnetic fields and coronal structures

    NASA Technical Reports Server (NTRS)

    Nakagawa, Y.; Wu, S. T.; Tandberg-Hanssen, E.

    1978-01-01

    Nakagawa's (1973) general formulation of constant-alpha global force-free magnetic fields is used to examine the topological characteristics of axisymmetric constant-alpha fields with specific reference to solar EUV, XUV, and X-ray structures observed from Skylab. The theoretical formulation is briefly summarized, and topological characteristics of the field lines are analyzed. The results are compared with X-ray observations of a large coronal arch and white-light observations of a coronal transient. It is concluded that global-scale force-free magnetic fields are present in the solar atmosphere and that their topological characteristics differ significantly from those of potential fields.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

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

    Microsoft Academic Search

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

    1992-01-01

    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

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

    SciTech Connect

    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

    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.

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

    Microsoft Academic Search

    Weichung Yeih

    2006-01-01

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

  6. An estimate of strong local body forcing and gravity wave radiation based on OH airglow and meteor radar observations

    E-print Network

    Vadas, Sharon

    An estimate of strong local body forcing and gravity wave radiation based on OH airglow and meteor July 2001; accepted 14 December 2001; published 25 May 2002. [1] Airglow measurements of gravity wave ability to quantify gravity wave dynamics at mesopause altitudes. We consider here an event observed

  7. Magnetic Effects on Thickness of Adsorbed Layer in Aqueous Solutions Evaluated Directly by Atomic Force Microscope.

    PubMed

    Higashitani; Oshitani

    1998-08-15

    The short-range interaction force between a mica surface and an AFM probe tip in electrolyte solutions was measured by atomic force microscopy (AFM) to directly evaluate the thickness of the adsorbed layer on the surface. The magnetic effects were estimated by comparing the thickness in the magnetized solution with that in nonmagnetized solution. It was found that (i) the magnetic exposure thickens the adsorbed layer on the surface in electrolyte solutions, (ii) the magnetic effects are easily destroyed by the external disturbance, (iii) there exists a memory in the magnetic effects, which remains for at least a day, (iv) the magnetic effects appear mostly in the solutions of structure-disordering cations, such as Cs+, Rb+, and K+, and (v) the results are consistent with those obtained in preceding macroscopic experiments. It is hypothesized from these results that the water molecules weekly bound around the structure-disordering ions are quasistabilized and structured by the magnetic exposure and that the magnetic thickening of the adsorbed layer is caused by the adsorption of those structured ions on the surface. Copyright 1998 Academic Press. PMID:9698416

  8. Novel electro-magnetic test facility for the calibration of a propulsor fluctuating force module

    NASA Astrophysics Data System (ADS)

    Schofield, N.; Lonsdale, A.; Hodges, A. Y.

    2004-05-01

    The testing of scale model propulsors is an essential part of any marine propulsion design process. The fluctuating force module (FFM) is a self-contained, instrumented propulsor drive system designed to be an integral part of a scaled propulsor test facility. This paper describes a novel electro-magnetic test facility which provides a static axial thrust of 0-1kN and triaxial dynamic forces of 0.3-3Nrms, at frequencies of 80-800Hz, to an equivalent propulsor mass rotating at speeds of 0-900rpm, in order to calibrate the FFM force measurement systems.

  9. Whole-body magnetic resonance imaging: emerging applications.

    PubMed

    Colleran, Gabrielle C; Moynagh, Michael R; Tavernaraki, Katarina; Shelly, Martin J; Eustace, Stephen J; Kavanagh, Eoin C

    2010-03-01

    Beyond established roles in the assessment of skeletal metastatic disease, in muscle diseases and in myeloma, WBMRI has the potential to offer many further valuable clinical applications. This article presents an overview of emerging clinical applications of WBMRI emphasizing its role in the assessment of musculoskeletal ailments, ranging from the assessment of arthropathy through to body composition research. PMID:20229441

  10. Wake dynamics past a curved body of circular cross-section under forced cross-flow vibration

    NASA Astrophysics Data System (ADS)

    de Vecchi, A.; Sherwin, S. J.; Graham, J. M. R.

    2009-05-01

    Three-dimensional numerical simulations are presented of flow past a curved body at a Reynolds number of 100. The geometry consists of a circular cross-sectioned body, whose centreline axis is prescribed by a quarter ring with a horizontal extension. This plane of curvature of the body is aligned to the free-stream flow direction such that the outer part of the ring is the body's stagnation face (convex configuration). The bluff body is forced to sinusoidally vibrate in the cross-flow direction at different amplitudes and frequencies. The resulting vortex shedding is strongly influenced by the curvature of the body. Within the lock-in region for a straight cylinder, the shedding past the convex body exhibits a 2S mode for all the pairs of input parameters tested; outside this region, a “weak” form of shedding with two pairs of counter-rotating vortices per cycle occurs in the top part of the body. At lower amplitudes of oscillation and frequencies below the Strouhal value for a straight cylinder, dislocations are found in the near wake: these generally occur in the middle of the curved part of the body, at an angle of approximately 45 from the top plane, regardless of the amplitude of oscillation. However, at very low amplitudes, an increase in the input frequency is found to influence the spanwise position of the dislocations by shifting them towards the top sections. The wake dynamics and force distribution are associated with the relative importance of the different regions of the curved geometry: the top region, nearly perpendicular to the inflow and therefore comparable to a straight cylinder, and the lower region with the horizontal extension, which is parallel to the inflow direction and hence behaves similarly to a slender body. The influence of the force contributions from these regions and their different nature determine the occurrence of dislocations in the wake, as well as their position along the span. The energy transfer mechanism, which determines whether the body is excited or damped by the flow, is also affected by this balance: at very low amplitudes the top part undergoes a lift force due to vortex shedding, which is strong enough to overcome the dampening effect from the horizontal extension used in this case and therefore provides a positive energy transfer from the fluid to the structure.

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

    NASA Astrophysics Data System (ADS)

    Katou, Tatsuya; Chiba, Akira; Fukao, Tadashi

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

  12. Effect of Body Force on Forced-Convection in the Thermal Entrance Region of Symmetrically or Asymmetrically Cooled Vertical Channel with the Air Upward-Flow

    NASA Astrophysics Data System (ADS)

    Naito, Etsuro; Nagano, Yasutaka

    A numerical investigation has been conducted to study the effect of body force on forced-convection of air upward-flow in the thermal entrance region between vertical parallel plates with the constant wall temperature. The governing equations based on the usual Boussinesq approximation are solved for two thermal conditons of parallel plates: one wall cooled with the other wall insulated; and both walls cooled in the same uniform states. The results are discussed in conjunction with those of uniform irrotational velocity. Numerically predicted friction factors and local Nusselt numbers are compared with their counterparts for pure forced convection. For use in practical applications, correlation equations are developed for the friction factors and the local Nusselt numbers.

  13. Magnetism of Minor Bodies in the Solar System: From 433 Eros, passing Braille, Steins, and Lutetia towards Churyumov-Gerasimenko and 1999 JU3.

    NASA Astrophysics Data System (ADS)

    Hercik, David; Auster, Hans-Ulrich; Heinisch, Philip; Richter, Ingo; Glassmeier, Karl-Heinz

    2015-04-01

    Minor bodies in the solar system, such as asteroids and comets, are important sources of information for our knowledge of the solar system formation. Besides other aspects, estimation of a magnetization state of such bodies might prove important in understanding the early aggregation phases of the protoplanetary disk, showing the level of importance of the magnetic forces in the processes involved. Meteorites' magnetization measurements suggest that primitive bodies consist of magnetized material. However, space observations from various flybys give to date diverse results for a global magnetization estimation. The flybys at Braille and Gaspra indicate possible higher magnetization (~ 10-3 Am2/kg), while flybys at Steins and Lutetia show no significant values in the global field change illustrating low global magnetization. Furthermore, the interpretation of remote (during flybys) measurements is very difficult. For correct estimates on the local magnetization one needs (in the best case) multi-point surface measurements. Single point observation has been done by NEAR-Shoemaker on 433 Eros asteroid, revealing no signature in magnetic field that could have origin in asteroid magnetization. Similar results, no magnetization observed, have been provided by evaluation of recent data from ROMAP (Philae lander) and RPC-MAG (Rosetta orbiter) instruments from comet 67P/Churyumov-Gerasimenko. The ROMAP instrument provided measurements from multiple points of the cometary surface as well as data along ballistic path between multiple touchdowns, which support the conclusion of no global magnetization. However, even in case of the in-situ on surface observations the magnetization estimate has a limiting spatial resolution that is dependent on the distance from the surface (~ 50 cm in case of ROMAP). To get information about possible smaller magnetized grains distribution and magnetization strength, the sensor shall be placed as close as possible to the surface. For such observations the next ideal candidate mission is Hayabusa-II with its Mascot lander equipped with fluxgate magnetometer. The small-sized lander shall deliver the magnetometer within centimeters from the surface, providing measurements on multiple points thanks to a hopping ability. The mission has been recently launched (December 2014) and is aiming to a C-type asteroid 1999 JU3 to reach it in 2018. The results will hopefully add some piece of information to the still unclear question of minor solar system bodies magnetization.

  14. Many-body forces in the equation of state of hyperonic matter

    E-print Network

    R. O. Gomes; V. Dexheimer; S. Schramm; C. A. Z. Vasconcellos

    2014-11-18

    In this work we introduce an extended version of the formalism proposed originally by Taurines et al. that considers the effects of many-body forces simulated by non-linear self-couplings and meson-meson interaction contributions. In this extended version of the model, we assume that matter is at zero temperature, charge neutral and in beta-equilibrium, considering that the baryon octet interacts by the exchange of scalar-isoscalar ($\\sigma$,$\\,\\sigma^*$), vector-isoscalar ($\\omega$,$\\,\\phi$), vector-isovector ($\\varrho$) and scalar-isovector ($\\delta$) meson fields. Using nuclear matter properties, we constrain the parameters of the model that describe the intensity of the indirectly density dependent baryon-meson couplings to a small range of possible values. We then investigate asymmetric hyperonic matter properties. We report that the formalism developed in this work is in agreement with experimental data and also allows for the existence of massive hyperon stars (with more than $2M_{\\odot}$) with small radii, compatible with astrophysical observations.

  15. Gravitational self-force in a Schwarzschild background and the effective one-body formalism

    SciTech Connect

    Damour, Thibault [Institut des Hautes Etudes Scientifiques, 35, route de Chartres, 91440 Bures-sur-Yvette (France)

    2010-01-15

    We discuss various ways in which the computation of conservative gravitational self-force (GSF) effects on a point mass moving in a Schwarzschild background can inform us about the basic building blocks of the effective one-body (EOB) Hamiltonian. We display the information which can be extracted from the recently published GSF calculation of the first-GSF-order shift of the orbital frequency of the last stable circular orbit, and we combine this information with the one recently obtained by comparing the EOB formalism to high-accuracy numerical relativity data on coalescing binary black holes. The information coming from GSF data helps to break the degeneracy (among some EOB parameters) which was left after using comparable-mass numerical relativity data to constrain the EOB formalism. We suggest various ways of obtaining more information from GSF computations: either by studying eccentric orbits, or by focusing on a special zero-binding zoom-whirl orbit. We show that logarithmic terms start entering the post-Newtonian expansions of various (EOB and GSF) functions at the fourth post-Newtonian level, and we analytically compute the first logarithm entering a certain, gauge-invariant 'redshift' GSF function (defined along the sequence of circular orbits).

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

    SciTech Connect

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

    2010-03-15

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

  17. First Use of Synoptic Vector Magnetograms for Global Nonlinear, Force-Free Coronal Magnetic Field Models

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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 threedimensional magnetic fields are used to estimate the magnetic free energy content E(sub free) = E(sub nlfff) - E(sub pot), 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.

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

    PubMed

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

    2012-11-01

    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

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

    E-print Network

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

    2001-02-13

    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

  20. Force

    NSDL National Science Digital Library

    Mrs. Brownie

    2010-04-07

    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 ...

  1. Magnified Spin-Motive Forces in MRAM Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Barnes, Stewart

    2014-03-01

    In the Slonczewski 2005 theory for spin-torque-transfer (STT) of a magnetic tunnel junction (MTJ) the tunnelling magneto resistance (TMR) and Gilbert damping parameter ? are of key importance. However the observed critical voltage from the switching of STT-MRAM implies a ? ten times that measured by ferromagnetic resonance (FMR). In addition the TMR is strongly voltage dependent while the STT effect is not. This along with the weak dependence of the critical current on switching direction are inconsistent with the tunnelling model and have never been properly explained. Here will be described a circuit model based upon SU(2) theory for a MTJ for which the basic SMF of about 10 ?V is magnified to a 200mV shift between the parallel P and anti-parallel AP branches of the IV characteristic. It is implied that the TMR has for origin an SMF.

  2. ON THE FORCE-FREE NATURE OF PHOTOSPHERIC SUNSPOT MAGNETIC FIELDS AS OBSERVED FROM HINODE (SOT/SP)

    SciTech Connect

    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

    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.

  3. Investigation of the Casimir interaction between two magnetic metals in comparison with nonmagnetic test bodies

    E-print Network

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

    2014-03-23

    We present the complete results for the dynamic experiment on measuring the gradient of the Casimir force between magnetic (Ni-coated) surfaces of a plate and a sphere. Special attention is paid to the description of some details of the setup, its calibration, error analysis and background effects. Computations are performed in the framework of the Lifshitz theory at nonzero temperature with account of analytic corrections to the proximity force approximation and of surface roughness using both the Drude and the plasma model approaches. The theory of magnetic interaction between a sphere and a plate due to domain structure of their surfaces is developed for both out-of-plane and in-plane magnetizations in the absence and in the presence of spontaneous magnetization. It is shown that in all cases the magnetic contribution to the measured force gradients is much smaller than the total experimental error. The comparison between experiment and theory is done using the rigorous statistical method. It is shown that the theoretical approach taking into account dissipation of free electrons is excluded by the data at a 95% confidence level. The approach neglecting dissipation is confirmed by the data at more than 90% confidence level. We prove that the results of experiments with Ni-Ni, Ni-Au and Au-Au surfaces taken together cannot be reconciled with the approach including free electrons dissipation by the introduction of any unaccounted background force, either attractive or repulsive.

  4. Magnetic resonance force microscopy quantum computer with tellurium donors in silicon.

    PubMed

    Berman, G P; Doolen, G D; Hammel, P C; Tsifrinovich, V I

    2001-03-26

    We propose a magnetic resonance force microscopy (MRFM)-based nuclear spin quantum computer using tellurium impurities in silicon. This approach to quantum computing combines well-developed silicon technology and expected advances in MRFM. Our proposal does not use electrostatic gates to realize quantum logic operations. PMID:11290066

  5. Antibody-Antigen Equilibria in a Field of Magnetic Forces: Design of Reagentless Christopher F. Monsona

    E-print Network

    Majda, Marcin

    Antibody-Antigen Equilibria in a Field of Magnetic Forces: Design of Reagentless Biosensors of an analyte with two-component molecular tethers attaching superparamagnetic microspheres (4 microns-antigen complex and are designed to selectively detect either specific ssDNA or antigenic proteins, respectively

  6. Measurement of Local Viscoelasticity and Forces in Living Cells by Magnetic Tweezers

    E-print Network

    Bausch, Andreas

    Measurement of Local Viscoelasticity and Forces in Living Cells by Magnetic Tweezers Andreas R measured the viscoelastic properties of the cytoplasm of J774 macrophages with a recently developed circuit, we measured the shear elastic modulus, the effective viscosities, and the strain relaxation time

  7. Study of electric fields parallel to the magnetic lines of force using artificially injected energetic electrons

    NASA Technical Reports Server (NTRS)

    Wilhelm, K.; Bernstein, W.; Whalen, B. A.

    1980-01-01

    Electron beam experiments using rocket-borne instrumentation will be discussed. The observations indicate that reflections of energetic electrons may occur at possible electric field configurations parallel to the direction of the magnetic lines of force in an altitude range of several thousand kilometers above the ionosphere.

  8. Transport of particles by magnetic forces and cellular blood flow in a model microvessel

    E-print Network

    Shapiro, Benjamin

    geometry on blood flow patterns in curved vessels Phys. Fluids 24, 031902 (2012) Dynamics of microcapsulesTransport of particles by magnetic forces and cellular blood flow in a model microvessel J. B to the streamwise-asymmetric orientation of the flowing blood cells. In essence, the cells act as low

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

    Microsoft Academic Search

    Zhiqian Chen; Mutuwo Tomita; Shinji Doki; Shigeru Okuma

    2003-01-01

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

  10. Nonideal evolution of nonaxisymmetric, force-free magnetic fields in a magnetar

    E-print Network

    Alpha Mastrano; Andrew Melatos

    2008-04-25

    Recent numerical magnetohydrodynamic calculations by Braithwaite and collaborators support the `fossil field' hypothesis regarding the origin of magnetic fields in compact stars and suggest that the resistive evolution of the fossil field can explain the reorganisation and decay of magnetar magnetic fields. Here, these findings are modelled analytically by allowing the stellar magnetic field to relax through a quasistatic sequence of nonaxisymmetric, force-free states, by analogy with spheromak relaxation experiments, starting from a random field. Under the hypothesis that the force-free modes approach energy equipartition in the absence of resistivity, the output of the numerical calculations is semiquantitatively recovered: the field settles down to a linked poloidal-toroidal configuration, which inflates and becomes more toroidal as time passes. A qualitatively similar (but not identical) end state is reached if the magnetic field evolves by exchanging helicity between small and large scales according to an $\\alpha$-dynamo-like, mean-field mechanism, arising from the fluctuating electromotive force produced by the initial random field. The impossibility of matching a force-free internal field to a potential exterior field is discussed in the magnetar context.

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

    Microsoft Academic Search

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

    2007-01-01

    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

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

    Microsoft Academic Search

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

    1994-01-01

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

  13. Self-Assembled DNA Structures for Molecular Force Measurement: A Magnetically Actuated Approach

    NASA Astrophysics Data System (ADS)

    Armstrong, M.; Lauback, S.; Miller, C.; Peace, C.; Castro, C.; Sooryakumar, R.

    2015-03-01

    Understanding molecular forces is important to comprehend many of the underlying properties of molecular machines and biological processes. The relevant forces in these cases often lie in the picoNewton range, and thus experiments on individual biomolecules must integrate techniques capable of measuring such forces. A mechanical system to measure molecular forces associated with interacting DNA strands is being developed by using self-assembled DNA nanostructures and super-paramagnetic beads. The DNA nanostructure consists of single-stranded DNA molecules which can be folded into a precise compact geometry using hundreds of short oligonucleotides, i.e., staples, via programmed molecular self-assembly. These nanostructures can be polymerized into micron-scale filaments. By functionalizing the filament ends with bispecific conjugate staples, the structure can be attached to a surface as well as labeled with magnetic beads in order to apply a force on the system. External magnetic fields provide the means to maneuver and manipulate the magnetically labeled DNA structures. Preliminary findings associated with the DNA constructs and their manipulation lay the groundwork to establish real-time control of DNA nanodevices with micromanipulation.

  14. Optimal Rotations of Deformable Bodies and Orbits in Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Avron, J. E.; Gat, O.; Kenneth, O.; Sivan, U.

    2004-01-01

    Deformations can induce rotation with zero angular momentum where dissipation is a natural “cost function.” This gives rise to an optimization problem of finding the most effective rotation with zero angular momentum. For certain plastic and viscous media in two dimensions the optimal path is the orbit of a charged particle on a surface of constant negative curvature with a magnetic field whose total flux is half a quantum unit.

  15. Particle Energization in a Chaotic Force-free/Non-Force-free Magnetic field

    NASA Astrophysics Data System (ADS)

    Li, X.; Dasgupta, B.; Li, G.

    2014-12-01

    Force-free field is believed to be a reasonable description of the quiet sun and a good approximation for low-beta plasma, like the lower region of solar corona. This field is similar to ABC field, which has been demonstrated to be chaotic. Here, we study the particle transport behavior in this field. We are particularly interested in particle energization if there is an electric field, which can be introduced by turbulent motion of plasma parcels. We expect a second order Fermi acceleration. Different spectra for turbulent motions are used, and particles with various mass-to-charge ratio are investigated. This process can provide a seed population generation mechanism for CME-driven shocks.

  16. Radiation pressure excitation of Low Temperature Atomic Force & Magnetic Force Microscope (LT-AFM/MFM) for Imaging

    NASA Astrophysics Data System (ADS)

    Karci, Ozgur; Celik, Umit; Oral, Ahmet; NanoMagnetics Instruments Ltd. Team; Middle East Tech Univ Team

    2015-03-01

    We describe a novel method for excitation of Atomic Force Microscope (AFM) cantilevers by means of radiation pressure for imaging in an AFM for the first time. Piezo excitation is the most common method for cantilever excitation, but it may cause spurious resonance peaks. A fiber optic interferometer with 1310 nm laser was used both to measure the deflection of cantilever and apply a force to the cantilever in a LT-AFM/MFM from NanoMagnetics Instruments. The laser power was modulated at the cantilever`s resonance frequency by a digital Phase Lock Loop (PLL). The force exerted by the radiation pressure on a perfectly reflecting surface by a laser beam of power P is F = 2P/c. We typically modulate the laser beam by ~ 800 ?W and obtain 10nm oscillation amplitude with Q ~ 8,000 at 2.5x10-4 mbar. The cantilever's stiffness can be accurately calibrated by using the radiation pressure. We have demonstrated performance of the radiation pressure excitation in AFM/MFM by imaging a hard disk sample between 4-300K and Abrikosov vortex lattice in BSCCO single crystal at 4K to for the first time.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    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.

  18. Paleo-Magnetic Field Recorded in the Parent Body of the Murchison Meteorite

    NASA Astrophysics Data System (ADS)

    Kletetschka, G.; Páchová, H.

    2014-12-01

    Murchison meteorite is a carbonaceous chondrite containing small amount of chondrules, various inclusions, and matrix with occasional porphyroblasts of olivine and/or pyroxene. We applied magnetic efficiency method (Kletetschka et al 2005, Kohout et al, 2008) in order to get the demagnetization spectra for several randomly oriented fragments of Murchison meteorite. Our method detected not only viscous magnetization removable in low fields, but also very persistent magnetizations in all meterorite fragments. Data suggest that magnetic carriers within the Murchison meteorite were grown in a paleofield of 450 - 850 nT. Meteorite record in other fragments contains an existence of antipodal fields that may be tied to an event of magnetic reversal within the nebular magnetic field or parent asteroid body. Other meteorites show stable record over its entire spectrum, giving magnetic paleofield of 1100 - 1900 nT. Magnetic record in Murchison meteorite comes from magnetite, pyrrhotite and Iron Nickel alloy. Pyrrhotite is suggested to be the main carrier of the paleofield in Murchison. Iron-Nickel alloy generate observable zigzag pattern when magnetically saturated. Kletetschka, G., Kohout, T., Wasilewski, P., and Fuller, M. D., 2005, Recognition of thermal remanent magnetization in rocks and meteorites, The IAGA Scientific Assembly, Volume GAI10: Toulouse, IAGA, p. IAGA2005-A-00945. Kohout, T., Kletetschka, G., Donadini, F., Fuller, M., and Herrero-Bervera, E., 2008, Analysis of the natural remanent magnetization of rocks by measuring the efficiency ratio through alternating field demagnetization spectra: Studia Geophysica Et Geodaetica, v. 52, no. 2, p. 225-235.

  19. Critical speeds and forced response solutions for active magnetic bearing turbomachinery, part 1

    NASA Technical Reports Server (NTRS)

    Keesee, J.; Rawal, D.; Kirk, R. Gordon

    1991-01-01

    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.

  20. Meta-Stable Magnetic Domain States That Prevent Reliable Absolute Palaeointensity Experiments Revealed By Magnetic Force Microscopy

    NASA Astrophysics Data System (ADS)

    de Groot, L. V.; Fabian, K.; Bakelaar, I. A.; Dekkers, M. J.

    2014-12-01

    Obtaining reliable estimates of the absolute palaeointensity of the Earth's magnetic field is notoriously difficult. Many methods to obtain paleointensities from suitable records such as lavas and archeological artifacts involve heating the samples. These heating steps are believed to induce 'magnetic alteration' - a process that is still poorly understood but prevents obtaining correct paleointensity estimates. To observe this magnetic alteration directly we imaged the magnetic domain state of titanomagnetite particles - a common carrier of the magnetic remanence in samples used for paleointensity studies. We selected samples from the 1971-flow of Mt. Etna from a site that systematically yields underestimates of the known intensity of the paleofield - in spite of rigorous testing by various groups. Magnetic Force Microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. Before heating, the samples feature distinct, blocky domains that sometimes seem to resemble a classical magnetite domain structure. After imparting a partial thermo-remanent magnetization at a temperature often critical to paleointensity experiments (250 °C) the domain state of the same titanomagnetite grains changes into curvier, wavy domains. Furthermore, these structures appeared to be unstable over time: after one-year storage in a magnetic field-free environment the domain states evolved into a viscous remanent magnetization state. Our observations may qualitatively explain reported underestimates from technically successful paleointensity experiments for this site and other sites reported previously. Furthermore the occurrence of intriguing observations such as 'the drawer storage effect' by Shaar et al (EPSL, 2011), and viscous magnetizations observed by Muxworthy and Williams (JGR, 2006) may be (partially) explained by our observations. The major implications of our study for all palaeointensity methods involving heating may be evident.

  1. Quantitative magnetic resonance (QMR) method for bone and whole-body-composition analysis

    Microsoft Academic Search

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

    2003-01-01

    Objective: to evaluate the applicability, precision, and accuracy of the new EchoMRI quantitative magnetic resonance (QMR) method for in-vitro bovine bone analysis and in-vivo whole-body-composition analysis of conscious live mice. Research methods and procedures: bovine tibia bone samples were measured by QMR and dual-energy X-ray adsorptiometry (DEXA). Repeated measures of whole-body composition were made using live and dead mice with

  2. Magnetic resonance and computed tomography imaging of a carotid body tumor in a dog.

    PubMed

    Kromhout, Kaatje; Gielen, Ingrid; De Cock, Hilde E V; Van Dyck, Kristof; van Bree, Henri

    2012-01-01

    A 5-year-old castrated male Labrador Retriever was presented to a referring veterinarian for a swelling in the neck region. Based on the results of histopathology, a carotid body tumor, was diagnosed. The dog was referred to a medical imaging unit for further staging and follow up. This report describes the magnetic resonance (MR) and computed tomographic (CT) appearance of a carotid body tumor. PMID:22507757

  3. Effects of local and core body temperature on grip force modulation during movement-induced load force fluctuations

    Microsoft Academic Search

    Stephen S. Cheung; Luke F. Reynolds; Mark A. B. Macdonald; Constance L. Tweedie; Robin L. Urquhart; David A. Westwood

    2008-01-01

    Impaired manual functioning often occurs when the hands are exposed to cold temperatures, but the underlying mechanism is\\u000a not clearly understood. Tactile feedback is thought to provide important information during object manipulations in order\\u000a to scale and regulate grip forces; however, topical anaesthetic-induced tactile sensation impairments may not realistically\\u000a simulate the systemic neuromuscular impairment of the whole hand that could

  4. Three-wire magnetic trap for direct forced evaporative cooling Shengwang Du1,* and Eun Oh2

    E-print Network

    Du, Shengwang

    Three-wire magnetic trap for direct forced evaporative cooling Shengwang Du1,* and Eun Oh2 1 potential for direct forced evaporative cooling of neutral atoms without using induced spin, 03.75.Be, 85.85. j Traditionally, forced evaporative cooling has been the only way to achieve gaseous

  5. Three-dimensional force microscope: A nanometric optical tracking and magnetic manipulation system for the biomedical sciences

    Microsoft Academic Search

    J. K. Fisher; J. R. Cummings; K. V. Desai; L. Vicci; B. Wilde; K. Keller; C. Weigle; G. Bishop; R. M. Taylor; C. W. Davis; R. C. Boucher; E. Timothy O'Brien; R. Superfine

    2005-01-01

    We report here the development of a three-dimensional (3D) magnetic force microscope for applying forces to and measuring responses of biological systems and materials. This instrument combines a conventional optical microscope with a free-floating or specifically bound magnetic bead used as a mechanical probe. Forces can be applied by the bead to microscopic structures of interest (specimens), while the reaction

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

    PubMed

    Rogachevskii, Igor; Kleeorin, Nathan

    2003-09-01

    An effect of sheared large-scale motions on a mean electromotive force in a nonrotating turbulent flow of a conducting fluid is studied. It is demonstrated that in a homogeneous divergence-free turbulent flow the alpha effect does not exist, however a mean magnetic field can be generated even in a nonrotating turbulence with an imposed mean velocity shear due to a "shear-current" effect. A mean velocity shear results in an anisotropy of turbulent magnetic diffusion. A contribution to the electromotive force related to the symmetric parts of the gradient tensor of the mean magnetic field (the kappa effect) is found in nonrotating turbulent flows with a mean shear. The kappa effect and turbulent magnetic diffusion reduce the growth rate of the mean magnetic field. It is shown that a mean magnetic field can be generated when the exponent of the energy spectrum of the background turbulence (without the mean velocity shear) is less than 2. The shear-current effect was studied using two different methods: the tau approximation (the Orszag third-order closure procedure) and the stochastic calculus (the path integral representation of the solution of the induction equation, Feynman-Kac formula, and Cameron-Martin-Girsanov theorem). Astrophysical applications of the obtained results are discussed. PMID:14524884

  7. ESR-MRI Using Low-Temperature Magnetic Resonance Force Microscopy

    NASA Astrophysics Data System (ADS)

    Tsuji, Shigenori; Fujimoto, Tatsuya; Yoshinari, Yohsuke; Inomata, Kohsuke

    2008-03-01

    The low-temperature operation of Magnetic Resonance Force Microscopy (MRFM) leads to a significantly better signal-to-noise ratio (SNR) than at room temperature, because of an increase of the spin magnetization and a reduction of the thermo-mechanical noise of the cantilever. We have built a low-temperature equipment, which is capable of operating in vacuum at liquid helium temperature. Our setup employed the sample-on-cantilever design at present. A magnetic needle with 100 ?m in diameter was placed on a stage to generate magnetic field gradient 11.3 G/?m at the magnetic field 714 G. The 3D closed-loop stage based on slip-stick principle allows a 200 x200 x200 ?m^3 scan range with 50 nm resolution. The experimental results of the 2D magnetic resonance force map carried out on diphenylpicrylhydrazil (DPPH) at T = 14 K are shown and an improvement of the SNR by 154 compared with the results at room temperature is confirmed. The 2D reconstructed images will be shown as well.

  8. NONLINEAR FORCE-FREE MAGNETIC FIELD FITTING TO CORONAL LOOPS WITH AND WITHOUT STEREOSCOPY

    SciTech Connect

    Aschwanden, Markus J., E-mail: aschwanden@lmsal.com [Lockheed Martin Advanced Technology Center, Solar and Astrophysics Laboratory, Org. ADBS, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304 (United States)

    2013-02-15

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

  9. The hydrodynamic forces encountered by aquatic animals affect their energetic requirements and therefore their body

    E-print Network

    and therefore their body morphology and swimming patterns. Steller sea lions rely on swimming to travel (Romanenko, 1995). Unlike these undulatory swimmers, sea lions swim with an essentially rigid body and move estimate of the drag for rigid-body swimmers (Webb, 1975; Blake, 1983), such as actively swimming sea lions

  10. Robust tracking control of a magnetically suspended rigid body

    NASA Technical Reports Server (NTRS)

    Lim, Kyong B.; Cox, David E.

    1994-01-01

    This study is an application of H-infinity and micro-synthesis for designing robust tracking controllers for the Large Angle Magnetic Suspension Test Facility. The modeling, design, analysis, simulation, and testing of a control law that guarantees tracking performance under external disturbances and model uncertainties is investigated. The type of uncertainties considered and the tracking performance metric used is discussed. This study demonstrates the tradeoff between tracking performance at low frequencies and robustness at high frequencies. Two sets of controllers were designed and tested. The first set emphasized performance over robustness, while the second set traded off performance for robustness. Comparisons of simulation and test results are also included. Current simulation and experimental results indicate that reasonably good robust tracking performance can be attained for this system using multivariable robust control approach.

  11. A Non-Linear Force-Free Field Model for the Solar Magnetic Carpet

    NASA Astrophysics Data System (ADS)

    Meyer, Karen; Mackay, D.; van Ballegooijen, A.; Parnell, C.

    2013-07-01

    The magnetic carpet is defined to be the small-scale photospheric magnetic field of the quiet-Sun. Recent high resolution, high cadence observations have shown that although small-scale, the magnetic carpet is far from 'quiet', it is continually evolving in a complex and dynamic manner. I will present a two-component model for the dynamic evolution of the Sun's magnetic carpet. The first component is a 2D model for the photospheric evolution of the small-scale solar magnetic field, that reproduces many observed parameters. The basic evolution of magnetic elements within the model is governed by a supergranular flow profile. In addition, magnetic elements may evolve through the processes of emergence, cancellation, coalescence and fragmentation. The synthetic magnetograms produced by the 2D model are then applied as photospheric boundary data to drive the continuous evolution of a 3D non-linear force-free coronal field. We studied the resultant complex, small-scale coronal magnetic field, in particular the energetics of the field.

  12. Observation of force-detected nuclear magnetic resonance in a homogeneous field

    PubMed Central

    Madsen, L. A.; Leskowitz, G. M.; Weitekamp, D. P.

    2004-01-01

    We report the experimental realization of BOOMERANG (better observation of magnetization, enhanced resolution, and no gradient), a sensitive and general method of magnetic resonance. The prototype millimeter-scale NMR spectrometer shows signal and noise levels in agreement with the design principles. We present 1H and 19F NMR in both solid and liquid samples, including time-domain Fourier transform NMR spectroscopy, multiple-pulse echoes, and heteronuclear J spectroscopy. By measuring a 1H-19F J coupling, this last experiment accomplishes chemically specific spectroscopy with force-detected NMR. In BOOMERANG, an assembly of permanent magnets provides a homogeneous field throughout the sample, while a harmonically suspended part of the assembly, a detector, is mechanically driven by spin-dependent forces. By placing the sample in a homogeneous field, signal dephasing by diffusion in a field gradient is made negligible, enabling application to liquids, in contrast to other force-detection methods. The design appears readily scalable to ?m-scale samples where it should have sensitivity advantages over inductive detection with microcoils and where it holds great promise for application of magnetic resonance in biology, chemistry, physics, and surface science. We briefly discuss extensions of the BOOMERANG method to the ?m and nm scales. PMID:15326302

  13. An Acoustic Model for a Permanent Magnet Machine: Modal Shapes and Magnetic Forces

    Microsoft Academic Search

    Dirk Verdyck; Ronnie J. M. Belmans

    1994-01-01

    The magnetic field inside a machine is to a large extent responsible for the mechanical excitation of the stator structure, generating vibrations and thus, audible noise. The current numerical techniques allow an easy calculation of the magnetic field. Unfortunately, the step to the mechanical excita- tion of the stator is difficult to make, because of the numerical errors occurring when

  14. Connecting neutron star observations to three-body forces in neutron matter and to the nuclear symmetry energy.

    PubMed

    Steiner, A W; Gandolfi, S

    2012-02-24

    Using a phenomenological form of the equation of state of neutron matter near the saturation density which has been previously demonstrated to be a good characterization of quantum Monte Carlo simulations, we show that currently available neutron star mass and radius measurements provide a significant constraint on the equation of state of neutron matter. At higher densities we model the equation of state by using polytropes and a quark matter model. We show that observations offer an important constraint on the strength of the three-body force in neutron matter, and thus some theoretical models of the three-body force may be ruled out by currently available astrophysical data. In addition, we obtain an estimate of the symmetry energy of nuclear matter and its slope that can be directly compared to the experiment and other theoretical calculations. PMID:22463511

  15. Study of magnetism in Ni-Cr hardface alloy deposit on 316LN stainless steel using magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.

    2015-07-01

    Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.

  16. Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy

    SciTech Connect

    Suh, B.J.; Hammel, P.C.; Zhang, Z. [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Condensed Matter and Thermal Physics, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Midzor, M.M.; Roukes, M.L. [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States)] [Condensed Matter Physics, California Institute of Technology, Pasadena, California 91125 (United States); Childress, J.R. [University of Florida, Gainesville, Florida 32611 (United States)] [University of Florida, Gainesville, Florida 32611 (United States)

    1998-07-01

    Lateral one-dimensional imaging of cobalt (Co) films by means of microscopic ferromagnetic resonance (FMR) detected using the magnetic resonance force microscope (MRFM) is demonstrated. A novel approach involving scanning a localized magnetic probe is shown to enable FMR imaging in spite of the broad resonance linewidth. We introduce a spatially selective local field by means of a small, magnetically polarized spherical crystallite of yttrium iron garnet (YIG). Using MRFM-detected FMR signals from a sample consisting of two Co films, we can resolve the {approximately}20 {mu}m lateral separation between the films. The results can be qualitatively understood by consideration of the calculated spatial profiles of the magnetic field generated by the YIG sphere. {copyright} {ital 1998 American Vacuum Society.}

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

    PubMed Central

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

    2012-01-01

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

  18. Effects of the field dependent Jc on the vertical levitation force between a superconductor and a magnet

    Microsoft Academic Search

    Gang Li; Meng Jun Qin; Hua Kun Liu; Shi Xue Dou

    2003-01-01

    The vertical levitation force between a superconductor disk (SC) and a permanent magnet disk (PM) has been calculated from first principles using different Jc(B) relationships of the magnetic field. Based upon the first principles, the current distribution inside the SC induced by the applied inhomogeneous magnetic field generated by the PM and the field profiles have been calculated with a

  19. Modeling of a linear PM Machine including magnetic saturation and end effects: maximum force-to-current ratio

    Microsoft Academic Search

    Henk Polinder; Johannes G. Slootweg; Martin J. Hoeijmakers; John C. Compter

    2003-01-01

    The use of linear permanent-magnet (PM) actuators increases in a wide variety of applications because of their high force density, robustness, and accuracy. These linear PM motors are often heavily loaded during short intervals of high acceleration, so that magnetic saturation occurs. This paper models saturation and end effects in linear PM motors using magnetic circuit models. The saturating parts

  20. The Use of Magnets for Introducing Primary School Students to Some Properties of Forces through Small-Group Pedagogy

    ERIC Educational Resources Information Center

    Carruthers, Rebecca; de Berg, Kevin

    2010-01-01

    Seventeen Grade Six students were divided into small groups to study the concept of forces in the context of magnets and their properties. The researcher, a pre-service primary school teacher, encouraged the students into conversation about magnets and it was found that, without hesitation, they talked about their prior experience of magnets. The…

  1. Scaling the energy conversion rate from magnetic field reconnection to different bodies

    SciTech Connect

    Mozer, F. S.; Hull, A. [Space Sciences Laboratory, University of California, Berkeley, California 94720 (United States)

    2010-10-15

    Magnetic field reconnection is often invoked to explain electromagnetic energy conversion in planetary magnetospheres, stellar coronae, and other astrophysical objects. Because of the huge dynamic range of magnetic fields in these bodies, it is important to understand energy conversion as a function of magnetic field strength and related parameters. It is conjectured theoretically and shown experimentally that the energy conversion rate per unit area in reconnection scales as the cube of an appropriately weighted magnetic field strength divided by the square root of an appropriately weighted density. With this functional dependence, the energy release in flares on the Sun, the large and rapid variation of the magnetic flux in the tail of Mercury, and the apparent absence of reconnection on Jupiter and Saturn, may be understood. Electric fields at the perihelion of the Solar Probe Plus mission may be tens of V/m.

  2. A Sound Mind in a Sound Body: That's the Philosophy behind This Classical Greek Magnet School.

    ERIC Educational Resources Information Center

    Natale, Jo Anna

    1992-01-01

    Central City High School, Kansas City, Missouri, has found its identity in the past. As part of comprehensive desegregation program, this magnet school offers its students classical Greek program that, like ancient Greek civilization, calls for as much attention to body as to mind. The costly Olympic athletic program and classical Greek curriculum…

  3. An accelerometer balance system for measurement of aerodynamic force coefficients over blunt bodies in a hypersonic shock tunnel

    Microsoft Academic Search

    Niranjan Sahoo; D. R. Mahapatra; G. Jagadeesh; S. Gopalakrishnan; K. P. J. Reddy

    2003-01-01

    A miniature three-component accelerometer balance system for measuring the fundamental aerodynamic force coefficients over blunt bodies has been designed, fabricated and tested in the Indian Institute of Science hypersonic shock tunnel HST2 at a nominal Mach number of 5.75. The model and the balance system are supported by rubber bushes, thereby ensuring unrestrained free-floating conditions of the model in the

  4. Rotordynamic forces acting on a centrifugal open impeller in whirling motion by using active magnetic bearing

    NASA Astrophysics Data System (ADS)

    Nagao, N.; Eguchi, M.; Uchiumi, M.; Yoshida, Y.

    2013-03-01

    Rotordynamic forces acting on a centrifugal open impeller of a rocket engine turbopump were measured using a rotordynamic test stand controlled by active magnetic bearings. The tangential rotordynamic force ft had a small constantly negative value in the measured range. The direct stiffness K had a positive value under various test conditions. In general, direct stiffness K of a closed impeller had a negative value because of the Bernoulli effect. In the case of open impellers, the Bernoulli effect is speculated to be smaller because the absence of a front shroud makes K positive.

  5. Searching for spin-dependent short-range forces using nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Geraci, Andrew; Arvanitaki, Asimina

    2014-05-01

    Axions are particles predicted to exist in order to explain the apparent smallness of the neutron electric dipole moment. While also being a promising candidate for dark matter, in tabletop experiments axions can mediate novel macroscopic forces between matter objects. I will describe a new method for detecting short-range forces from axion-like particles based on nuclear magnetic resonance in hyperpolarized Helium-3. The method can potentially improve previous experimental bounds by several orders of magnitude and can probe deep into the theoretically interesting regime for the QCD axion. Supported in part by NSF-PHY 1205994.

  6. Asymptotic analysis of force-free magnetic fields of cylindrical symmetry

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Antiochos, S. K.; Roumeliotis, G.

    1995-01-01

    It is known from computer calculations that if a force-free magnetic-field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution, and, in the process, the energy of the field increases progressively. Analysis of a simple model of force-free fields of cylindrical symmetry leads to simple asymptotic expressions for the extent and energy of such a configuration. The analysis is carried through for both spherical and planar source surfaces. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

  7. Does using a visual-representation tool foster students' ability to identify forces and construct free-body diagrams?

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

    Earlier research has shown that after physics instruction, many students have difficulties with the force concept, and with constructing free-body diagrams (FBDs). It has been suggested that treating forces as interactions could help students to identify forces as well as to construct the correct FBDs. While there is evidence that identifying interactions helps students in quantitative problem solving, there is no previous research investigating the effect of a visual-representation tool—an interaction diagram (ID)—on students’ ability to identify forces, and to construct the correct FBDs. We present an empirical study conducted in 11 Finnish high schools on students (n=335, aged 16) taking their first, mandatory, introductory physics course. The study design involved groups of students having heavy, light, or no use of IDs. The heavy and light ID groups answered eight pairs of ID and FBD questions in various physical contexts and the no ID group answered two of the eight FBD questions. The results indicate that the heavy ID group outperformed both the light and the no ID groups in identifying forces and constructing the correct FBDs. The analysis of these data indicates that the use of IDs is especially beneficial in identifying forces when constructing FBDs.

  8. Investigation of the Casimir force between metal and semiconductor test bodies

    E-print Network

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

    2005-07-08

    The measurement of the Casimir force between a large gold coated sphere and single crystal silicon plate is performed with an atomic force microscope. A rigorous statistical comparison of data with theory is done, without use of the concept of root-mean-square deviation, and excellent agreement is obtained. The Casimir force between metal and semiconductor is demonstrated to be significantly different than between two similar or dissimilar metals.

  9. Many-Body Electrostatic Forces between Colloidal Particles at Vanishing Ionic Strength

    Microsoft Academic Search

    Jason W. Merrill; Sunil K. Sainis; Eric R. Dufresne

    2009-01-01

    Electrostatic forces between small groups of colloidal particles are measured\\u000ausing blinking optical tweezers. When the electrostatic screening length is\\u000asignificantly larger than the particle radius, forces are found to be\\u000anon-pairwise additive. Both pair and multi-particle forces are well described\\u000aby the linearized Poisson-Boltzmann equation with constant potential boundary\\u000aconditions. These findings may play an important role in understanding

  10. Transient body force effects on the dryout and rewet of a heated capillary structure. Doctoral thesis, January 1990-April 1994

    SciTech Connect

    Reagan, M.K.

    1994-04-01

    A transient, one-dimensional numerical code was developed to model the liquid flow in a non-uniformly heated, axial square groove. The groove was subjected to transient body forces up to approximately 0.51 m/s sq. Axial variation in meniscus levels, shear stress and heat transfer between the groove wall and the liquid, axial conduction through the liquid, evaporation and body forces were accounted for in the model. Dryout and rewet of the groove were allowed; the front location was determined using conservation of mass and linear extrapolation. A physical experiment was performed with a stainless steel plate into which eight square grooves were machined. Ethanol was used as the working liquid. One end of the plate was tilted relative to the other end and this tilt was varied with time, thereby providing the transient body force. The depth of the ethanol in the groove, and the dryout and rewet front locations, were experimentally measured. Within the uncertainty of the measurements, the numerical results from the code predicted the correct movement of liquid within the groove structure and also the correct position of the dryout and rewet fronts.

  11. Estimating Three-Dimensional Orientation of Human Body Parts by Inertial/Magnetic Sensing

    PubMed Central

    Sabatini, Angelo Maria

    2011-01-01

    User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) space. Although they are a promising choice as wearable sensors under many respects, the inertial and magnetic sensors currently in use offer measuring performance that are critical in order to achieve and maintain accurate 3D-orientation estimates, anytime and anywhere. This paper reviews the main sensor fusion and filtering techniques proposed for accurate inertial/magnetic orientation tracking of human body parts; it also gives useful recipes for their actual implementation. PMID:22319365

  12. Mapping magnetized geologic structures from space: The effect of orbital and body parameters

    NASA Technical Reports Server (NTRS)

    Schnetzler, C. C.; Taylor, P. T.; Langel, R. A.

    1984-01-01

    When comparing previous satellite magnetometer missions (such as MAGSAT) with proposed new programs (for example, Geopotential Research Mission, GRM) it is important to quantify the difference in scientific information obtained. The ability to resolve separate magnetic blocks (simulating geological units) is used as a parameter for evaluating the expected geologic information from each mission. The effect of satellite orbital altitude on the ability to resolve two magnetic blocks with varying separations is evaluated and quantified. A systematic, nonlinear, relationship exists between resolution and distance between magnetic blocks as a function of orbital altitude. The proposed GRM would provide an order-of-magnitude greater anomaly resolution than the earlier MAGSAT mission for widely separated bodies. The resolution achieved at any particular altitude varies depending on the location of the bodies and orientation.

  13. Estimating three-dimensional orientation of human body parts by inertial/magnetic sensing.

    PubMed

    Sabatini, Angelo Maria

    2011-01-01

    User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) space. Although they are a promising choice as wearable sensors under many respects, the inertial and magnetic sensors currently in use offer measuring performance that are critical in order to achieve and maintain accurate 3D-orientation estimates, anytime and anywhere. This paper reviews the main sensor fusion and filtering techniques proposed for accurate inertial/magnetic orientation tracking of human body parts; it also gives useful recipes for their actual implementation. PMID:22319365

  14. Gradient-induced acoustic and magnetic field fluctuations in a 4T whole-body MR imager

    Microsoft Academic Search

    Yuhua Wu; Blaine A. Chronik; Chris Bowen; Chris K. Mechefske; Brian K. Rutt

    2000-01-01

    Both the acoustic and magnetic fluctuation frequency response functions for a Siemens AS25 body gradient coil inside a 4 Tesla whole-body MR system were measured and analyzed in this study. In an attempt to correlate the acoustic noise inside the gradient coil with magnetic field oscillations, triangular and trap- ezoidal gradient impulses of varying amplitudes and widths were used to

  15. Coercivity map in perpendicular media investigated by using in situ magnetic force microscopy

    NASA Astrophysics Data System (ADS)

    Bai, J.; Saito, H.; Ishio, S.

    2004-11-01

    The spatial distribution of coercivities in a CoCrPt-SiO2 granular perpendicular magnetic recording medium was measured by using in situ magnetic force microscopy. The coercivity map that shows the spatial distribution of coercivities was obtained at 1kOe intervals in the medium. The "local" coercivities within microscopic areas of less than 100nm square were evaluated with a good reproducibility. Measuring coercivity map will become a technique for investigating the influence of the spatial distribution of coercivities on the medium noise in perpendicular recording.

  16. Magnetic force driven nanogenerators as a noncontact energy harvester and sensor.

    PubMed

    Cui, Nuanyang; Wu, Weiwei; Zhao, Yong; Bai, Suo; Meng, Leixin; Qin, Yong; Wang, Zhong Lin

    2012-07-11

    Nanogenerator has been a very important energy harvesting technology through directly deforming piezoelectric material. Here, we report a new magnetic force driven contactless nanogenerator (CLNG), which avoids the direct contact between nanogenerator and mechanical movement source. The CLNG can harvest the mechanical movement energy in a noncontact mode to generate electricity. Their output voltage and current can be as large as 3.2 V and 50 nA, respectively, which is large enough to power up a liquid crystal display. We also demonstrate a means by which a magnetic sensor can be built. PMID:22681509

  17. MEMS-Based Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer

    NASA Technical Reports Server (NTRS)

    Lee, Choonsup; Butler, Mark C.; Elgammal, Ramez A.; George, Thomas; Hunt, Brian; Weitekamp, Daniel P.

    2006-01-01

    Nuclear Magnetic Resonance (NMR) spectroscopy allows assignment of molecular structure by acquiring the energy spectrum of nuclear spins in a molecule, and by interpreting the symmetry and positions of resonance lines in the spectrum. As such, NMR has become one of the most versatile and ubiquitous spectroscopic methods. Despite these tremendous successes, NMR experiments suffer from inherent low sensitivity due to the relatively low energy of photons in the radio frequency (rt) region of the electromagnetic spectrum. Here, we describe a high-resolution spectroscopy in samples with diameters in the micron range and below. We have reported design and fabrication of force-detected nuclear magnetic resonance (FDNMR).

  18. Investigation of force-freeness of a solar emerging magnetic field via application of the virial theorem to magnetohydrodynamic simulations

    NASA Astrophysics Data System (ADS)

    Kang, Jihye; Magara, Tetsuya

    2014-12-01

    Force-freeness of a solar magnetic field is a key to reconstructing the invisible coronal magnetic structure of an emerging flux region on the Sun where active phenomena such as flares and coronal mass ejections frequently occur. We have performed magnetohydrodynamic simulations which are adjusted to investigate force-freeness of an emerging magnetic field by using the virial theorem. Our focus is on how the force-free range of an emerging flux region develops and how it depends on the twist of a pre-emerged magnetic field. As an emerging flux region evolves, the upper limit of the force-free range continuously increases while the lower limit is asymptotically reduced to the order of a photospheric pressure scale height above the solar surface. As the twist becomes small the lower limit increases and then seems to be saturated. We also discuss the applicability of the virial theorem to an evolving magnetic structure on the Sun.

  19. Determination of forces in a magnetic bearing actuator - Numerical computation with comparison to experiment

    NASA Technical Reports Server (NTRS)

    Knight, J. D.; Xia, Z.; Mccaul, E.; Hacker, H., Jr.

    1992-01-01

    Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and free space, using finite but constant permeability in the metals. Above a relative permeability of 10,000 the effects of changes in permeability are negligible, but below 10,000 decreases in permeability cause significant decreases in the force. The calculated forces are shown to depend on the metal permeability more strongly when the journal is displaced from its centered position. The predicted forces in the principal attractive direction are in good agreement with experiment when a relatively low value of permeability is chosen. The forces measured normal to the axis of symmetry when the journal is displaced from that axis, however, are significantly higher than predicted by theory, even with a value of relative permeability larger than 5000. These results indicate a need for further work including nonlinear permeability distributions.

  20. The design, construction, and calibration of a dynamometer used to measure forces applied by a magnetic bearing to a rotating shaft 

    E-print Network

    Henderson, Gregory Lane

    1994-01-01

    A force measurement dynamometer has been constructed which will be the primary instrument used to measure the dynamic forces applied by a magnetic bearing to a rotating shaft. The dynamometer consists of two force measurement assemblies, named...

  1. Equilibrium force balance and eruptive instabilities in solar-relevant laboratory magnetic flux ropes

    NASA Astrophysics Data System (ADS)

    Myers, C. E.; Yamada, M.; Belova, E. V.; Ji, H.; Yoo, J.; Jara-Almonte, J.

    2013-10-01

    Quasi-statically driven line-tied magnetic flux ropes are studied in the context of storage-and-release eruptions in the solar corona. The Magnetic Reconnection Experiment (MRX) facility is utilized to produce these arched low- ? flux ropes. Detailed in situ magnetic measurements and supporting MHD simulations permit quantitative analysis of the plasma behavior. We find that the orientation of the applied potential magnetic field arcade with respect to the flux rope footpoints (i.e., the electrodes) is key. With an arcade that is aligned parallel to the footpoints, force free currents induced in the expanding flux rope modify the pressure and tension in the arcade to produce a confined, quiescent discharge and a saturated kink instability. In an obliquely aligned arcade, on the other hand, a sigmoidal equilibrium forms that can dynamically erupt. Both the kink instability and the torus instability are studied as candidate eruptive mechanisms--the latter by varying the vertical gradient of the potential field arcade. New 2D magnetic measurements of these equilibrium and eruptive features facilitate comparisons to solar observations and modeling. Quasi-statically driven line-tied magnetic flux ropes are studied in the context of storage-and-release eruptions in the solar corona. The Magnetic Reconnection Experiment (MRX) facility is utilized to produce these arched low- ? flux ropes. Detailed in situ magnetic measurements and supporting MHD simulations permit quantitative analysis of the plasma behavior. We find that the orientation of the applied potential magnetic field arcade with respect to the flux rope footpoints (i.e., the electrodes) is key. With an arcade that is aligned parallel to the footpoints, force free currents induced in the expanding flux rope modify the pressure and tension in the arcade to produce a confined, quiescent discharge and a saturated kink instability. In an obliquely aligned arcade, on the other hand, a sigmoidal equilibrium forms that can dynamically erupt. Both the kink instability and the torus instability are studied as candidate eruptive mechanisms--the latter by varying the vertical gradient of the potential field arcade. New 2D magnetic measurements of these equilibrium and eruptive features facilitate comparisons to solar observations and modeling. This research is supported by DoE Contract Number DE-AC02-09CH11466 and by the Center for Magnetic Self-Organization (CMSO).

  2. Parallel rf Force Driven by the Inhomogeneity of Power Absorption in Magnetized Plasma Zhe Gao,1,2,* Jiale Chen,2

    E-print Network

    Parallel rf Force Driven by the Inhomogeneity of Power Absorption in Magnetized Plasma Zhe Gao,1 Jersey 08543, USA (Received 8 February 2013; published 6 June 2013) A nonlinear parallel force can no integrated force over a plasma volume, this force can redistribute momentum parallel to the magnetic field

  3. Nonlinear generation of large-scale magnetic fields in forced spherical shell dynamos

    SciTech Connect

    Livermore, P. W.; Hughes, D. W.; Tobias, S. M. [Department of Applied Mathematics, University of Leeds, Leeds LS2 9JT (United Kingdom)

    2010-03-15

    In an earlier paper [P. W. Livermore, D. W. Hughes, and S. M. Tobias, ''The role of helicity and stretching in forced kinematic dynamos in a spherical shell'', Phys. Fluids 19, 057101 (2007)], we considered the kinematic dynamo action resulting from a forced helical flow in a spherical shell. Although mean field electrodynamics suggests that the resulting magnetic field should have a significant mean (axisymmetric) component, we found no evidence for this; the dynamo action was distinctly small scale. Here we extend our investigation into the nonlinear regime in which the magnetic field reacts back on the velocity via the Lorentz force. Our main result is somewhat surprising, namely, that nonlinear effects lead to a considerable change in the structure of the magnetic field, its final state having a significant mean component. By investigating the dominant flow-field interactions, we isolate the dynamo mechanism and show schematically how the generation process differs between the kinematic and nonlinear regimes. In addition, we are able to calculate some components of the transport coefficient {alpha} and thus discuss our results within the context of mean field electrodynamics.

  4. Magnetic field-induced currents in the human body in proximity of power lines

    SciTech Connect

    Stuchly, M.A.; Zhao, S. [Univ. of Victoria, British Columbia (Canada). Dept. of Electrical and Computer Engineering] [Univ. of Victoria, British Columbia (Canada). Dept. of Electrical and Computer Engineering

    1996-01-01

    Electric currents induced due to 60 Hz magnetic fields in a human body placed in a close proximity of various high voltage transmission lines are computed. A realistic model of the human body from the anatomical and electrical point of view with resolution of 1.3 cm for the body and 0.665 cm for the head is used. The computations are performed using the impedance method. Three representative configurations of high voltage transmission lines, namely 500 kV, 138 kV and 25 kV are analyzed. The results indicate that the maximum current densities of the order of 0.2 {micro}A/cm{sup 2} can be induced in a lineman working on a 500 kV line (0.5 m away from closest conductors). A good correlation can be seen between the computed magnetic field in the location of the human body and the induced current densities. The induced currents computed here and estimated from measured magnetic fields in various power line environments are compared to those for typical home and office exposures, including appliances.

  5. Two Means by which Magnetized Cosmic Bodies can Seed the Universe with Life

    NASA Astrophysics Data System (ADS)

    Belian, R. D.

    2013-01-01

    There is currently much interest in the source of life on Earth and whether other objects in the Solar System or other planetary systems contain life. In my view, there are two dominant themes. First and maybe the oldest is that life developed in the seas of the Earth itself and developed out of a random conglomeration of chemicals, conditions and events. The second view is that life developed somewhere in the universe and somehow migrated to the Earth. Indeed, a good deal of effort goes into looking for "Earth" like (habitable) planets around other stars. One prevalent idea is that in environments that are similar to what we have on the Earth, life could develop spontaneously anywhere in the universe - maybe even life that is similar to that on Earth. In this paper, I suggest that magnetized cosmic bodies can seed the universe with life, in the form of spores or viruses (and likely other microorganisms). Firstly, life can be transported from any life bearing planet to other cosmic bodies by the actions of what are called magnetic substorms. Secondly, I suggest that life can 'leak' from near Earth, or other magnetized cosmic bodies, environments onto the Interplanetary Magnetic Field to be swept away by that field.

  6. Resonance behavior of liquid bridges under axial and lateral oscillating total body forces

    E-print Network

    Taylor, Philip L.

    bridges that are magnetically levitated in air against gravity are subjected to either axial or lateral of acoustically trapped bubbles in water and in sea water (Asaki and Marston 1995). Thus, one advantage of the technique of time-varying magnetic levitation is that problems associated with the influence of the outer

  7. Temporal and preparation effects in the magnetic nanoparticles of Apis mellifera body parts

    NASA Astrophysics Data System (ADS)

    Chambarelli, L. L.; Pinho, M. A.; Abraçado, L. G.; Esquivel, D. M. S.; Wajnberg, E.

    Magnetic nanoparticles in the Apis mellifera abdomens are well accepted as involved in their magnetoreception mechanism. The effects of sample preparation on the time evolution of magnetic particles in the honeybee body parts (antennae, head, thorax and abdomen) were investigated by Ferromagnetic Resonance (FMR) at room temperature (RT), for about 100 days. Three preparations were tested: (a) washed with water (WT); (b) as (a), kept in glutaraldehyde 2.5% in 0.1 M cacodylate buffer (pH 7.4) for 24 h and washed with cacodylate buffer (C); (c) as (a), kept in glutaraldehyde 2.5% for 24 h and washed with glutaraldehyde 2.5% in cacodylate buffer (GLC). The four body parts of young and adult worker presented magnetic nanoparticles. The Mn 2+ lines are observed except for the antennae spectra. The high field (HF) and low field (LF) components previously observed in the spectra of social insects, are confirmed in these spectra. The HF line is present in all spectra while the LF is easily observed in the spectra of the young bee and it appears as a baseline shift in spectra of some adult parts. The HF intensity of the abdomen is commonly one order of magnitude larger than any other body parts. This is the first systematic study on the conservation of magnetic material in all body parts of bees. The results show that the time evolution of the spectra depends on the body part, conserving solution and bee age. Further measurements are necessary to understand these effects and extend it to other social insects.

  8. Theoretical analysis of ferromagnetic microparticles in streaming liquid under the influence of external magnetic forces

    NASA Astrophysics Data System (ADS)

    Brandl, Martin; Mayer, Michael; Hartmann, Jens; Posnicek, Thomas; Fabian, Christian; Falkenhagen, Dieter

    2010-09-01

    The microsphere based detoxification system (MDS) is designed for high specific toxin removal in extracorporeal blood purification using functionalized microparticles. A thin wall hollow fiber membrane filter separates the microparticle-plasma suspension from the bloodstream. For patient safety, it is necessary to have a safety system to detect membrane ruptures that could lead to the release of microparticles into the bloodstream. A non-invasive optical detection system including a magnetic trap is developed to monitor the extracorporeal venous bloodstream for the presence of released microparticles. For detection, fluorescence-labeled ferromagnetic beads are suspended together with adsorbent particles in the MDS circuit. In case of a membrane rupture, the labeled particles would be released into the venous bloodstream and partly captured by the magnetic trap of the detector. A physical model based on fluidic, gravitational and magnetic forces was developed to simulate the motion and sedimentation of ferromagnetic particles in a magnetic trap. In detailed simulation runs, the concentrations of accumulated particles under different applied magnetic fields within the magnetic trap are shown. The simulation results are qualitatively compared with laboratory experiments and show excellent accordance. Additionally, the sensitivity of the particle detection system is proofed in a MDS laboratory experiment by simulation of a membrane rupture.

  9. Molecular dynamics simulation of Lorentz force microscopy in magnetic nano-disks

    NASA Astrophysics Data System (ADS)

    Dias, R. A.; Mello, E. P.; Coura, P. Z.; Leonel, S. A.; Maciel, I. O.; Toscano, D.; Rocha, J. C. S.; Costa, B. V.

    2013-04-01

    In this paper, we present a molecular dynamics simulation to model the Lorentz force microscopy experiment. Experimentally, this technique consists in the scattering of electrons by magnetic structures in surfaces and gases. Here, we will explore the behavior of electrons colliding with nano-magnetic disks. The computational molecular dynamics experiment allows us to follow the trajectory of individual electrons all along the experiment. In order to compare our results with the experimental one reported in literature, we model the experimental electron detectors in a simplified way: a photo-sensitive screen is simulated in such way that it counts the number of electrons that collide at a certain position. The information is organized to give in grey scale the image information about the magnetic properties of the structure in the target. Computationally, the sensor is modeled as a square matrix in which we count how many electrons collide at each specific point after being scattered by the magnetic structure. We have used several configurations of the magnetic nano-disks to understand the behavior of the scattered electrons, changing the orientation direction of the magnetic moments in the nano-disk in several ways. Our results match very well with the experiments, showing that this simulation can become a powerful technique to help to interpret experimental results.

  10. The effects of exposure to a 1.5-tesla magnetic field on intravitreous metallic foreign bodies in rabbits

    Microsoft Academic Search

    Cheryl Cullen; Edward Kendall; Jie Cui; Kevin Colleaux; Bruce Grahn

    2002-01-01

    Background: The study was performed to determine (1) whether intravitreous ferromagnetic foreign bodies (FBs) are sufficiently mobile in a magnetic field to induce acute injury in vivo, and (2) whether the length of time from implantation of the intravitreous FB affects mobility. Methods: A 3 mm 2 0.72 mm magnetic FB (MFB) and a non-magnetic metallic FB (NMFB) of similar

  11. Magnetic reconnection in a force-free plasma: Simulations of micro- and macroinstabilities

    NASA Astrophysics Data System (ADS)

    Nishimura, Kazumi; Gary, S. Peter; Li, Hui; Colgate, Stirling A.

    2003-02-01

    Two-and-one-half-dimensional particle-in-cell plasma simulations are used to study the stability of a force-free sheet pinch equilibrium, in which currents flow parallel to the sheared magnetic field and the plasma is uniform. The magnetic shear drives a long wavelength, electromagnetic tearing instability, whereas a sufficiently large current may excite a shorter wavelength electrostatic electron/ion instability. This latter instability heats electrons locally, which causes the formation of a new configuration with inhomogeneous electron density and temperature which, in turn, enhances the growth of the tearing mode. Both instabilities lead to conversion of magnetic energy into plasma particle energy, but only the tearing mode leads to significant reconnection.

  12. ON THE STABILITY OF NON-FORCE-FREE MAGNETIC EQUILIBRIA IN STARS

    SciTech Connect

    Duez, V.; Braithwaite, J. [Argelander Institut fuer Astronomie, Universitaet Bonn, Auf dem Huegel 71, D-53111 Bonn (Germany); Mathis, S., E-mail: vduez@astro.uni-bonn.d [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/SAp Centre de Saclay, F-91191 Gif-sur-Yvette (France)

    2010-11-20

    The existence of stable magnetic configurations in white dwarfs, neutron stars, and various non-convective stellar regions is now well recognized. It has recently been shown numerically that various families of equilibria, including axisymmetric mixed poloidal-toroidal configurations, are stable. Here we test the stability of an analytically derived non-force-free magnetic equilibrium resulting from an initial relaxation (self-organization) process, using three-dimensional magnetohydrodynamic simulations: the obtained mixed configuration is compared with the dynamical evolution of its purely poloidal and purely toroidal components, both known to be unstable. The mixed equilibrium shows no sign of instability under white noise perturbations. This configuration therefore provides a good description of magnetic equilibrium topology inside non-convective stellar objects and will be useful to initialize magneto-rotational transport in stellar evolution codes and in multi-dimensional magnetohydrodynamic simulations.

  13. Effects of three-body forces on the maximum mass of neutron stars in the lowest-order constrained variational formalism

    NASA Astrophysics Data System (ADS)

    Goudarzi, S.; Moshfegh, H. R.

    2015-05-01

    The equation of state of neutron star matter is calculated within the lowest order constrained variational (LOCV) method using different two-body interactions and an Urbana type three-body force. The core of the neutron star is modelled by ? -stable matter. The corresponding neutron star mass-radius relations are presented and the effect of using a three-body interaction on the maximum gravitational mass of the star is also discussed. It is shown that including the three-body force generally increases the maximum gravitational mass.

  14. Forces

    NSDL National Science Digital Library

    The representation depicts what forces are and how they can change the motion and shape of objects in an animated slide show. This resource also includes an interactive test and review of the material, and can be downloaded for offline use.

  15. Geometry of halo and Lissajous orbits in the circular restricted three-body problem with drag forces

    NASA Astrophysics Data System (ADS)

    Pal, Ashok Kumar; Kushvah, Badam Singh

    2015-01-01

    In this paper, we determine the effect of radiation pressure, Poynting-Robertson drag and solar wind drag on the Sun-(Earth-Moon) restricted three-body problem. Here, we take the larger body of the Sun as a larger primary, and the Earth+Moon as a smaller primary. With the help of the perturbation technique, we find the Lagrangian points, and see that the collinear points deviate from the axis joining the primaries, whereas the triangular points remain unchanged in their configuration. We also find that Lagrangian points move towards the Sun when radiation pressure increases. We have also analysed the stability of the triangular equilibrium points and have found that they are unstable because of the drag forces. Moreover, we have computed the halo orbits in the third-order approximation using the Lindstedt-Poincaré method and have found the effect of the drag forces. According to this prevalence, the Sun-(Earth-Moon) model is used to design the trajectory for spacecraft travelling under drag forces.

  16. Measurement of the adhesion force between particles for high gradient magnetic separation of pneumatic conveyed powder products

    NASA Astrophysics Data System (ADS)

    Senkawa, K.; Nakai, Y.; Mishima, F.; Akiyama, Y.; Nishijima, S.

    2011-11-01

    In the industrial plants such as foods, medicines or industrial materials, there are big amount of issues on contamination by metallic wear debris originated from pipes of manufacturing lines. In this study, we developed a high gradient magnetic separation system (HGMS) under the dry process by using superconducting magnet to remove the ferromagnetic particles. One of the major problems of dry HGMS systems is, however, the blockage of magnetic filter caused by particle coagulation or deposition. In order to actualize the magnetic separation without blockage, we introduced pneumatic conveyance system as a new method to feed the powder. It is important to increase the drag force acting on the sufficiently dispersed particles, which require strong magnetic fields. To generate the strong magnetic fields, HGMS technique was examined which consists of a magnetic filter and a superconducting solenoid magnet. As a result of the magnetic separation experiment, it was shown that the separation efficiency changes due to the difference of the cohesive property of the particles. On the basis of the result, the adhesion force which acts between the ferromagnetic particles and the medium particles used for the magnetic separation was measured by Atomic Force Microscope (AFM), and cohesion of particles was studied from the aspect of interparticle interaction. We assessed a suitable flow velocity for magnetic separation according to the cohesive property of each particle based on the result.

  17. Lean body mass correction of standardized uptake value in simultaneous whole-body positron emission tomography and magnetic resonance imaging.

    PubMed

    Jochimsen, Thies H; Schulz, Jessica; Busse, Harald; Werner, Peter; Schaudinn, Alexander; Zeisig, Vilia; Kurch, Lars; Seese, Anita; Barthel, Henryk; Sattler, Bernhard; Sabri, Osama

    2015-06-21

    This study explores the possibility of using simultaneous positron emission tomography-magnetic resonance imaging (PET-MRI) to estimate the lean body mass (LBM) in order to obtain a standardized uptake value (SUV) which is less dependent on the patients' adiposity. This approach is compared to (1) the commonly-used method based on a predictive equation for LBM, and (2) to using an LBM derived from PET-CT data. It is hypothesized that an MRI-based correction of SUV provides a robust method due to the high soft-tissue contrast of MRI.A straightforward approach to calculate an MRI-derived LBM is presented. It is based on the fat and water images computed from the two-point Dixon MRI primarily used for attenuation correction in PET-MRI. From these images, a water fraction was obtained for each voxel. Averaging over the whole body yielded the weight-normalized LBM. Performance of the new approach in terms of reducing variations of (18)F-Fludeoxyglucose SUVs in brain and liver across 19 subjects was compared with results using predictive methods and PET-CT data to estimate the LBM.The MRI-based method reduced the coefficient of variation of SUVs in the brain by 41??± 10% which is comparable to the reduction by the PET-CT method (35??± 10%). The reduction of the predictive LBM method was 29??± 8%. In the liver, the reduction was less clear, presumably due to other sources of variation.In conclusion, employing the Dixon data in simultaneous PET-MRI for calculation of lean body mass provides a brain SUV which is less dependent on patient adiposity. The reduced dependency is comparable to that obtained by CT and predictive equations. Therefore, it is more comparable across patients. The technique does not impose an overhead in measurement time and is straightforward to implement. PMID:26020722

  18. Lean body mass correction of standardized uptake value in simultaneous whole-body positron emission tomography and magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Jochimsen, Thies H.; Schulz, Jessica; Busse, Harald; Werner, Peter; Schaudinn, Alexander; Zeisig, Vilia; Kurch, Lars; Seese, Anita; Barthel, Henryk; Sattler, Bernhard; Sabri, Osama

    2015-06-01

    This study explores the possibility of using simultaneous positron emission tomography—magnetic resonance imaging (PET-MRI) to estimate the lean body mass (LBM) in order to obtain a standardized uptake value (SUV) which is less dependent on the patients' adiposity. This approach is compared to (1) the commonly-used method based on a predictive equation for LBM, and (2) to using an LBM derived from PET-CT data. It is hypothesized that an MRI-based correction of SUV provides a robust method due to the high soft-tissue contrast of MRI. A straightforward approach to calculate an MRI-derived LBM is presented. It is based on the fat and water images computed from the two-point Dixon MRI primarily used for attenuation correction in PET-MRI. From these images, a water fraction was obtained for each voxel. Averaging over the whole body yielded the weight-normalized LBM. Performance of the new approach in terms of reducing variations of 18F-Fludeoxyglucose SUVs in brain and liver across 19 subjects was compared with results using predictive methods and PET-CT data to estimate the LBM. The MRI-based method reduced the coefficient of variation of SUVs in the brain by 41??± 10% which is comparable to the reduction by the PET-CT method (35??± 10%). The reduction of the predictive LBM method was 29??± 8%. In the liver, the reduction was less clear, presumably due to other sources of variation. In conclusion, employing the Dixon data in simultaneous PET-MRI for calculation of lean body mass provides a brain SUV which is less dependent on patient adiposity. The reduced dependency is comparable to that obtained by CT and predictive equations. Therefore, it is more comparable across patients. The technique does not impose an overhead in measurement time and is straightforward to implement.

  19. Towards an on-chip platform for the controlled application of forces via magnetic particles: A novel device for mechanobiology

    NASA Astrophysics Data System (ADS)

    Monticelli, M.; Albisetti, E.; Petti, D.; Conca, D. V.; Falcone, M.; Sharma, P. P.; Bertacco, R.

    2015-05-01

    In-vitro tests and analyses are of fundamental importance for investigating biological mechanisms in cells and bio-molecules. The controlled application of forces to activate specific bio-pathways and investigate their effects, mimicking the role of the cellular environment, is becoming a prominent approach in this field. In this work, we present a non-invasive magnetic on-chip platform which allows for the manipulation of magnetic particles, through micrometric magnetic conduits of Permalloy patterned on-chip. We show, from simulations and experiments, that this technology permits to exert a finely controlled force on magnetic beads along the chip surface. This force can be tuned from few to hundreds pN by applying a variable external magnetic field.

  20. How Should One Optimize Nonlinear Force-Free Coronal Magnetic Field Extrapolations from SDO/HMI Vector Magnetograms?

    NASA Astrophysics Data System (ADS)

    Wiegelmann, T.; Thalmann, J. K.; Inhester, B.; Tadesse, T.; Sun, X.; Hoeksema, J. T.

    2012-11-01

    The Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) provides photospheric vector magnetograms with a high spatial and temporal resolution. Our intention is to model the coronal magnetic field above active regions with the help of a nonlinear force-free extrapolation code. Our code is based on an optimization principle and has been tested extensively with semianalytic and numeric equilibria and applied to vector magnetograms from Hinode and ground-based observations. Recently we implemented a new version which takes into account measurement errors in photospheric vector magnetograms. Photospheric field measurements are often affected by measurement errors and finite nonmagnetic forces inconsistent for use as a boundary for a force-free field in the corona. To deal with these uncertainties, we developed two improvements: i) preprocessing of the surface measurements to make them compatible with a force-free field, and ii) new code which keeps a balance between the force-free constraint and deviation from the photospheric field measurements. Both methods contain free parameters, which must be optimized for use with data from SDO/HMI. In this work we describe the corresponding analysis method and evaluate the force-free equilibria by how well force-freeness and solenoidal conditions are fulfilled, by the angle between magnetic field and electric current, and by comparing projections of magnetic field lines with coronal images from the Atmospheric Imaging Assembly (SDO/AIA). We also compute the available free magnetic energy and discuss the potential influence of control parameters.

  1. [Data base for body surface potential maps of normal populations--normal data base by the Japanese Circulation Society Task Force Committee on Criteria for Body Surface Mapping].

    PubMed

    Ikeda, K

    1995-01-01

    In order to evaluate the normal ranges of the body surface potential maps, data from normal healthy subjects were compiled by the Japanese Circulation Society Task Force Committee on Criteria for Body Surface Mapping (Chairman: Shoji Yasui, Nagoya National Hospital). The subjects met all the following criteria; (1) normal physical findings; (2) no heart or lung diseases; (3) no hypertension (160/90 mmHg); (4) normal 12-lead electrocardiogram; (5) normal chest roentgenogram (may be omitted in children); (6) normal findings in exercise test in subjects 40 years of age or older; and (7) no major morbidity. Body surface mapping data were recorded by use of 87-lead mapping systems, HPM-5100, HPM-6500, and VCM-3000 (Fukuda Denshi, and Chunichi Denshi), or 128-lead mapping systems Cardiovision (Tokyo Technological University-Teijin), and Cardiomap (Gakken). To construct the database, each original set of body surface mapping data was copied to an MS-DOS file. Data recorded by a 128-lead mapping system was transformed into an 87-lead system data. Next, each individual data was transformed into a file of common format with a header containing clinical information, and the onset and offset of each electrocardiographic waves. From these secondary files, mean and standard deviation of each electrocardiographic lead were calculated for instantaneous voltages of P wave, QRS wave, and ST-T; time integrals of P, QRS, and QRST; and ventricular activation time, to subgroups divided age and gender. All these data were stored in a optical disk, and also mean and standard deviation for subgroups were stored in a set of floppy disks.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7897857

  2. Standing and sitting motion of inverted pendulum type assist robot using whole-body motion with force control

    NASA Astrophysics Data System (ADS)

    Jeong, SeongHee; Takahashi, Takayuki

    2007-12-01

    This paper describes quick and stable standing and sitting motion of an inverted pendulum type robot by wholebody motion including force control. The whole-body motion is achieved by controlling composite center of gravity of the robot, and damping force control of a wrist-roller is employed to assure the stability of inverted pendulum control on a contact situation with the ground. Motion planning of standing and sitting based on the proposed control method is also proposed. Standing and sitting motion using the proposed motion control and motion planning is simulated with a dynamic simulator, ODE(Open Dynamics Engine). From the simulation results, it was confirmed that the robot successively realized the standing and sitting motion quickly and stably.

  3. Radiation of plasma waves by a conducting body moving through a magnetized plasma

    NASA Technical Reports Server (NTRS)

    Barnett, Alan; Olbert, Stanislaw

    1986-01-01

    A theory is presented describing energy loss due to radiation of plasma waves by a conducting body moving through a magnetized plasma, which makes it possible to estimate the total power radiated at all frequencies. Using energy conservation and a source current deduced by physical reasoning, numerical predictions were made for the power radiated. It was found that radiation is produced at all frequencies for which one of the plasma modes has zero phase velocity in some direction.

  4. A preliminary morphometric magnetic resonance imaging study of regional brain volumes in body dysmorphic disorder.

    PubMed

    Rauch, Scott L; Phillips, Katharine A; Segal, Ethan; Makris, Nikos; Shin, Lisa M; Whalen, Paul J; Jenike, Michael A; Caviness, Verne S; Kennedy, David N

    2003-01-20

    Morphometric magnetic resonance imaging (MRI) was used to compare regional brain volumes in eight women with body dysmorphic disorder (BDD) and eight healthy comparison subjects. The BDD group exhibited a relative leftward shift in caudate asymmetry and greater total white matter vs. the comparison group. Findings with respect to the caudate nucleus are consistent with both the conceptualization of BDD as an obsessive-compulsive spectrum disorder, and the 'striatal topography model' of obsessive-compulsive disorders. PMID:12589879

  5. The Magnetization of Face-Centred Cubic and Body-Centred Cubic Iron + Nickel Alloys

    Microsoft Academic Search

    J. Crangle; G. C. Hallam

    1963-01-01

    Magnetizations of single phase binary iron+nickel alloys have been measured and Bohr magneton numbers p estimated for body-centred cubic alloys with 0 to 32.3 at. % of nickel and for face-centred cubic alloys with 31 to 80 %. Initially p increases at the rate 1.1 ± 0.1 mu_B per nickel atom in iron-rich b.c.c. alloys. In the f.c.c. phase p

  6. Force-free equilibria of magnetized jets. [pressure confined extragalactic radio hydromagnetics

    NASA Technical Reports Server (NTRS)

    Koenigl, A.; Choudhuri, A. R.

    1985-01-01

    Force-free equilibrium configurations of magnetic-pressure-dominated magnetized supersonic jets confined by slowly varying external pressure are investigated analytically. For the case where internal dissipation mechanisms are active, the lowest-energy field configuration is found to be the superposition of an axisymmetric mode and a helical mode with a wavelength equal to 5 times the jet radius, and the pressure below which the nonaxisymmetric mode becomes energetically favorable is given as 2700 times the product of the 4th power of the magnetic helicity per unit length and the -6th power of the magnetic flux. A model of the total and polarized emission of such a configuration is developed and applied to the extended well-collimated astronomically resolved jet NGC 6251. The model is shown to reproduce significant features such as transverse oscillations of the ridge line, width oscillations and emission knots, the projected magnetic-field configuration, oscillations of the degree of polarization, and the distribution of the Faraday rotation measure.

  7. Current sheet formation in a sheared force-free-magnetic field. [in sun

    NASA Technical Reports Server (NTRS)

    Wolfson, Richard

    1989-01-01

    This paper presents the results of a study showing how continuous shearing motion of magnetic footpoints in a tenuous, infinitely conducting plasma can lead to the development of current sheets, despite the absence of such sheets or even of neutral points in the initial state. The calculations discussed here verify the earlier suggestion by Low and Wolfson (1988) that extended current sheets should form due to the shearing of a force-free quadrupolar magnetic field. More generally, this work augments earlier studies suggesting that the appearance of discontinuities - current sheets - may be a necessary consequence of the topological invariance imposed on the magnetic field geometry of an ideal MHD system by virtue of its infinite conductivity. In the context of solar physics, the work shows how the gradual and continuous motion of magnetic footpoints at the solar photosphere may lead to the buildup of magnetic energy that can then be released explosively when finite conductivity effects become important and lead to the rapid dissipation of current sheets. Such energy release may be important in solar flares, coronal mass ejections, and other eruptive events.

  8. Lorentz Force on Sodium and Chlorine Ions in a Salt Water Solution Flow under a Transverse Magnetic Field

    ERIC Educational Resources Information Center

    De Luca, R.

    2009-01-01

    It is shown that, by applying elementary concepts in electromagnetism and electrochemistry to a system consisting of salt water flowing in a thin rectangular pipe at an average velocity v[subscript A] under the influence of a transverse magnetic field B[subscript 0], an electromotive force generator can be conceived. In fact, the Lorentz force

  9. Fully Suspended, Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig With Forced Excitation

    NASA Technical Reports Server (NTRS)

    Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Montague, Gerald; Duffy, Kirsten; Mehmed, Oral; Johnson, Dexter; Jansen, Ralph

    2004-01-01

    The Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig, a significant advancement in the Dynamic Spin Rig (DSR), is used to perform vibration tests of turbomachinery blades and components under rotating and nonrotating conditions in a vacuum. The rig has as its critical components three magnetic bearings: two heteropolar radial active magnetic bearings and a magnetic thrust bearing. The bearing configuration allows full vertical rotor magnetic suspension along with a feed-forward control feature, which will enable the excitation of various natural blade modes in bladed disk test articles. The theoretical, mechanical, electrical, and electronic aspects of the rig are discussed. Also presented are the forced-excitation results of a fully levitated, rotating and nonrotating, unbladed rotor and a fully levitated, rotating and nonrotating, bladed rotor in which a pair of blades was arranged 180 degrees apart from each other. These tests include the bounce mode excitation of the rotor in which the rotor was excited at the blade natural frequency of 144 Hz. The rotor natural mode frequency of 355 Hz was discerned from the plot of acceleration versus frequency. For nonrotating blades, a blade-tip excitation amplitude of approximately 100 g/A was achieved at the first-bending critical (approximately 144 Hz) and at the first-torsional and second-bending blade modes. A blade-tip displacement of 70 mils was achieved at the first-bending critical by exciting the blades at a forced-excitation phase angle of 908 relative to the vertical plane containing the blades while simultaneously rotating the shaft at 3000 rpm.

  10. Rigid-body rotation of an electron cloud in divergent magnetic fields

    SciTech Connect

    Fruchtman, A. [H.I.T.—Holon Institute of Technology, Holon 58102 (Israel)] [H.I.T.—Holon Institute of Technology, Holon 58102 (Israel); Gueroult, R.; Fisch, N. J. [Princeton Plasma Physics Laboratory, Princeton University, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, New Jersey 08543 (United States)

    2013-07-15

    For a given voltage across a divergent poloidal magnetic field, two electric potential distributions, each supported by a rigid-rotor electron cloud rotating with a different frequency, are found analytically. The two rotation frequencies correspond to the slow and fast rotation frequencies known in uniform plasma. Due to the centrifugal force, the equipotential surfaces, that correspond to the two electric potential distributions, diverge more than the magnetic surfaces do, the equipotential surfaces in the fast mode diverge largely in particular. The departure of the equipotential surfaces from the magnetic field surfaces may have a significant focusing effect on the ions accelerated by the electric field. The focusing effect could be important for laboratory plasma accelerators as well as for collimation of astrophysical jets.

  11. From: The Student Budget Sustainability Task Force To: The Wesleyan Student Body

    E-print Network

    Royer, Dana

    choice of the given options. Second, need aware admissions is morally undesirable since it deviates from;2 Priorities Committee. We analyzed budget documents and conducted research on relevant peer institutions, gaining a thorough understanding of the issues at hand. After educating ourselves, the Task Force met

  12. Method for locating a small magnetic object in the human body

    SciTech Connect

    Kaufman, L.; Williamson, S.J.; Ilmoniemi, R.J.; Weinberg, H.; Boyd, A.D.

    1988-02-29

    A piece of a thin acupuncture needle lodged under the right scapula of a patient could not be found in surgical procedures accompanied by studies of 30 standard x-ray images. To locate it, the authors mapped the magnetic-field component normal to a plane lying above the object, using a superconducting quantum interference device (SQUID). Assuming that the needle could be modeled as a magnetic dipole, the authors were able to infer its lateral position, depth, orientation, and magnetic moment. With this information, directed CT scans, high-resolution x-ray films, and the subsequent surgical removal of the needle proved that it could be located in the body with an accuracy of about three millimeters.

  13. Effect of wind, current and non-linear second order drift forces on a moored multi-body system in an irregular sea

    Microsoft Academic Search

    Y. Inoue; M. R. Islam; M. Murai

    2001-01-01

    A study is made on the slowly varying oscillation of a moored multi-body system in wind, current and waves. Linear potential theory is used to describe the fluid motion and three dimensional source technique is applied to obtain the transfer function of drift forces in waves, which is used to obtain the slowly varying drift forces in horizontal plane for

  14. Baseband Detection of Bistatic Electron Spin Signals in Magnetic Resonance Force Microscopy (MRFM)

    E-print Network

    Yip, C; Rugar, D; Fessler, J A; Yip, Chun-yu; Hero, Alfred O.; Rugar, Daniel; Fessler, Jeffrey A.

    2003-01-01

    In single spin Magnetic Resonance Force Microscopy (MRFM), the objective is to detect the presence of an electron (or nuclear) spin in a sample volume by measuring spin-induced attonewton forces using a micromachined cantilever. In the OSCAR method of single spin MRFM, the spins are manipulated by an external rf field to produce small periodic deviations in the resonant frequency of the cantilever. These deviations can be detected by frequency demodulation followed by conventional amplitude or energy detection. In this paper, we present an alternative to these detection methods, based on optimal detection theory and Gibbs sampling. On the basis of simulations, we show that our detector outperforms the conventional amplitude and energy detectors for realistic MRFM operating conditions. For example, to achieve a 10% false alarm rate and an 80% correct detection rate our detector has an 8 dB SNR advantage as compared with the conventional amplitude or energy detectors. Furthermore, at these detection rates it co...

  15. A simple approach to the First Order Reversal Curves (FORC) of two-phase magnetic systems

    NASA Astrophysics Data System (ADS)

    Panagiotopoulos, I.

    2011-08-01

    The features that commonly appear in the First Order Reversal Curves (FORC) of magnetic composites, consisting of a hard and a soft phase, are reproduced by a simple mean-field approach in the limit of weak coupling. In this case the features corresponding to each phase are distinct and the effect of the interactions appears as biasing field on the soft phase and a coercivity reduction of the hard one. Interactions produce additional twin (positive/negative) interference features in the region of the (H, HR) FORC diagram where there is a strong dependence on H through the soft phase and on HR through the hard phase. The slope and the intensity of these twin features depend on interaction strength.

  16. Asymptotic forms for the energy of force-free magnetic field ion figurations of translational symmetry

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Antiochos, S. K.; Klinchuk, J. A.; Roumeliotis, G.

    1994-01-01

    It is known from computer calculations that if a force-free magnetic field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution and the energy of the field increases progressively. For configurations of translationalsymmetry, it has been found empirically that the energy tends asymptotically to a certain functional form. It is here shown that analysis of a simple model of the asymptotic form of force-free fields of translational symmetry leads to and therefore justifies this functional form. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

  17. Design of a self-aligned, wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with 10 nm magnetic force microscope resolution

    SciTech Connect

    Karc?, Özgür [NanoMagnetics Instruments Ltd., Hacettepe - ?vedik OSB Teknokent, 1368. Cad., No: 61/33, 06370, Yenimahalle, Ankara (Turkey); Department of Nanotechnology and Nanomedicine, Hacettepe University, Beytepe, 06800 Ankara (Turkey); Dede, Münir [NanoMagnetics Instruments Ltd., Hacettepe - ?vedik OSB Teknokent, 1368. Cad., No: 61/33, 06370, Yenimahalle, Ankara (Turkey); Oral, Ahmet, E-mail: orahmet@metu.edu.tr [Department of Physics, Middle East Technical University, 06800 Ankara (Turkey)

    2014-10-01

    We describe the design of a wide temperature range (300 mK-300 K) atomic force microscope/magnetic force microscope with a self-aligned fibre-cantilever mechanism. An alignment chip with alignment groves and a special mechanical design are used to eliminate tedious and time consuming fibre-cantilever alignment procedure for the entire temperature range. A low noise, Michelson fibre interferometer was integrated into the system for measuring deflection of the cantilever. The spectral noise density of the system was measured to be ~12 fm/?Hz at 4.2 K at 3 mW incident optical power. Abrikosov vortices in BSCCO(2212) single crystal sample and a high density hard disk sample were imaged at 10 nm resolution to demonstrate the performance of the system.

  18. The electromagnetic self-force on a charged spherical body slowly undergoing a small, temporary displacement from a position of rest

    E-print Network

    V. Hnizdo

    2000-05-12

    The self-force of classical electrodynamics on a charged "rigid" body of radius R is evaluated analytically for the body undergoing a slow (i.e., with a speed velectromagnetic field, which has been the subject of a recent controversy.

  19. Solutions of the Helmholtz equation with boundary conditions for force-free magnetic fields

    NASA Technical Reports Server (NTRS)

    Rasband, S. N.; Turner, L.

    1981-01-01

    It is shown that the solution, with one ignorable coordinate, for the Taylor minimum energy state (resulting in a force-free magnetic field) in either a straight cylindrical or a toroidal geometry with arbitrary cross section can be reduced to the solution of either an inhomogeneous Helmholtz equation or a Grad-Shafranov equation with simple boundary conditions. Standard Green's function theory is, therefore, applicable. Detailed solutions are presented for the Taylor state in toroidal and cylindrical domains having a rectangular cross section. The focus is on solutions corresponding to the continuous eigenvalue spectra. Singular behavior at 90 deg corners is explored in detail.

  20. Magnetic force microscopy of colossal magneto-resistive materials and superconductors

    NASA Astrophysics Data System (ADS)

    Lu, Qingyou

    Using a home-built low temperature piezo-driven magnetic force microscope (LT-PD-MFM), we have studied the magnetic domain behaviors in colossal magneto-resistive (CMR) thin films, the vortex behavior in high TC superconducting (HTCS) thin films as well as the localized penetration depth in a Yttrium(1)Barium(2)Copper(3)Oxygen(7) single crystal. We have obtained MFM images of domains in CMR films for temperatures from close to TC to far below TC. Domains behave differently for these two temperature zones. Well below TC, neighboring domains exhibit strong interdomain coupling. External magnetic fields can split domains more easily than rearrange them. As temperature increases, domain interactions become weaker with a reduced magnetization, and are subject to moving, splitting or merging. They are still traceable in the presence of a sample scratch. As temperature drops from TC, domains increase in magnetization. The weak interdomain interactions and high fluctuations make domain tracing impossible if there are no topographic defects. Sample scratches tend to pin domains for T ˜ TC. Current flow in CMR films can split domains. This splitting can be both reversible and irreversible when current is turned on and off. Lattice mismatch between a CMR film and a substrate leads to a stress that results in smaller domains. The magnetization of these smaller domains does not cancel out, resulting in "large-scale" domains if detected from a longer distance from the sample. Images of superconducting vortices in BSSCO films show that they grow with temperature, which is compared with the theory. The theory fits our experimental data well. We also measured the gradient of the levitation force between a magnetic tip and a superconducting single crystal as a function of the tip-sample distance. A series of these measurements were performed at different temperatures. By comparing these data with the theory in which the penetration depth lambda and the TC are parameters to be determined by least-squared fitting, we obtained the local penetration depth lambdaLoc(T) and T C,Loc. We find that the temperature behavior of lambdaLoc(T) is comparable to lambdaBulk(T) measured by another group, but TC,Loc = 83.2 K is substantially lower than TC,Bulk = 92 K measured by SQUID.

  1. Measurement and calculation of levitation forces between magnets and granular superconductors

    NASA Technical Reports Server (NTRS)

    Johansen, T. H.; Bratsberg, H.; Baziljevich, M.; Hetland, P. O.; Riise, A. B.

    1995-01-01

    Recent developments indicate that exploitation of the phenomenon of magnetic levitation may become one of the most important near-term applications of high-T(sub c) superconductivity. Because of this, the interaction between a strong permanent magnet(PM) and bulk high-T(sub c) superconductor (HTSC) is currently a subject of much interest. We have studied central features of the mechanics of PM-HTSC systems of simple geometries. Here we report experimental results for the components of the levitation force, their associated stiffness and mechanical ac-loss. To analyze the observed behavior a theoretical framework based on critical-state considerations is developed. It will be shown that all the mechanical properties can be explained consistently at a quantitative level wing a minimum of model parameters.

  2. Long-lived magnetism from inner core solidification on small planetary bodies

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Paleomagnetic measurements of meteorites suggest that many asteroids generated their own magnetic activity during the early solar system, with the majority of measured meteorite classes appearing to have recorded dynamo fields. Despite this apparent near ubiquity of magnetic activity among small planetary bodies, many of the most fundamental aspects of this activity remain enigmatic. Crucially, both the temporal evolution and the processes capable of generating small body magnetic activity are yet to be gleaned from paleomagnetic measurements. This information has been central in understanding the dynamic and thermochemical evolution of our planet, and equivalent information from asteroids could help illuminate the evolution of matter in our solar system. Here, we present time-resolved records of the magnetic activity generated on the main-group pallasite parent body inferred from X-ray photoemission electron microscopy (XPEEM) images of the metal matrix within the Imilac, Esquel, Brenham and Marjalahti pallasite meteorites. This metal cooled at <10 K/Myr, which permitted a unique nanostructure known as the cloudy zone (CZ) to form. The CZ is an excellent paleomagnetic recorder, and formed over a distance of ~10 µm over tens of millions of years. By spatially resolving the magnetism of this nanostructure using XPEEM, we infer both the direction and intensity of the field experienced by the CZ of these meteorites. All four meteorites recorded unidirectional fields. The Brenham and Marjalahti meteorites recorded relatively weak fields with intensities of >20 µT over a period of ~4 - 10 Myr. The Imilac meteorite recorded a stronger field between 120 - 130 µT over a period of <10 Myr. The Esquel meteorite initially recorded a field of ~80 µT, which then weakened over time down to a plateau at ~30 µT, before decreasing further down to ~0 µT. By comparing experimental cooling rates to those predicted from planetary cooling models, the Brenham and Marjalahti meteorites are expected to have recorded the magnetic activity shortly before core solidification, and the Imilac and Esquel meteorites are expected to have recorded the magnetic activity associated with the early and later stages of this process, respectively. Dynamo field intensities predicted from empirical scaling relationships suggest that the Imilac meteorite experienced a dipolar dynamo field generated by compositional convection associated with the early stages of bottom-up core solidification. The Esquel meteorite appears to have experienced a dipolar-multipolar transition (intensity decrease), multipolar regime (plateau at ~30 µT), and the cessation of dynamo activity associated with the near-completion of core solidification (decrease down to ~0 µT). The weak fields experienced by the Brenham and Marjalahti are consistent with a period of dynamo activity quiescence prior to inner core growth. Solidification-driven convection is yet to be associated with small bodies, but given its efficiency, likely lead to convection across the majority of bottom-up solidifying cores in these bodies, implying a widespread, intense and long-lived epoch of magnetic activity among small bodies during the early solar system.

  3. Effect of Body Structure on Skill Formation in a Force Precision Task Mimicking Cello Bowing Movement

    NASA Astrophysics Data System (ADS)

    Ogihara, Naomichi; Yamazaki, Nobutoshi

    To elucidate the skill formation mechanism in a complex force precision task mimicking cello bowing movements, three-dimensional joint orientations and changes in bowing force are measured for 2 novice and 2 expert subjects. A rigid link model of the human upper limb is constructed in order to calculate changes in joint moment, potential energy and structural inductivity of motion during bowing, and the motions are compared kinetically. Results show that the novices generate low-in-potential energy bowing motion, but not suitable for skillful control of the bow. In contrast, the experts can fulfill a task requirement by skillfully coordinating the musculo-skeletal system, but the motion is not easy as that of the novices. It is suggested that the transition from a novice to an expert may be difficult due to the ease in the initially generated motion, which obstructs the search for the optimal skillful motion.

  4. On Fully Developed Channel Flows: Some Solutions and Limitations, and Effects of Compressibility, Variable Properties, and Body Forces

    NASA Technical Reports Server (NTRS)

    Maslen, Stephen H.

    1959-01-01

    An examination of the effects of compressibility, variable properties, and body forces on fully developed laminar flow has indicated several limitations on such streams. In the absence of a pressure gradient, but presence of a body force (e.g., gravity), an exact fully developed gas flow results. For a liquid this follows also for the case of a constant streamwise pressure gradient. These motions are exact in the sense of a Couette flow. In the liquid case two solutions (not a new result) can occur for the same boundary conditions. An approximate analytic solution was found which agrees closely with machine calculations.In the case of approximately exact flows, it turns out that for large temperature variations across the channel the effects of convection (due to, say, a wall temperature gradient) and frictional heating must be negligible. In such a case the energy and momentum equations are separated, and the solutions are readily obtained. If the temperature variations are small, then both convection effects and frictional heating can consistently be considered. This case becomes the constant-property incompressible case (or quasi-incompressible case for free-convection flows) considered by many authors. Finally there is a brief discussion of cases wherein streamwise variations of all quantities are allowed but only a such form that independent variables are separable. For the case where the streamwise velocity varies inversely as the square root distance along the channel a solution is given.

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

    Microsoft Academic Search

    I. R. Afnan; Daniel R. Phillips

    2004-01-01

    We discuss effective field theory treatments of the problem of three\\u000aparticles interacting via short-range forces. One case of such a system is\\u000aneutron-deuteron scattering at low energies. We demonstrate that in attractive\\u000achannels the renormalization-group evolution of the 1+2 scattering amplitude\\u000amay be complicated by the presence of eigenvalues greater than unity in the\\u000akernel. We also show that

  6. STRUCTURE OF NON-FORCE-FREE MAGNETIC FLUX ROPES IN AN AMBIENT MEDIUM

    SciTech Connect

    Chen, James, E-mail: James.Chen@nrl.navy.mil [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

    2012-12-20

    The structure of non-force-free equilibrium magnetic flux ropes in an ambient medium of specified pressure p{sub a} is studied. A flux rope is a self-organized magnetized plasma structure consisting of a localized channel of electric current and the magnetic field arising from this current. An analytic method is developed to obtain one-dimensional equilibrium solutions satisfying c {sup -1} J Multiplication-Sign B - {nabla}p = 0 subject to the requirements that (1) all physical quantities be nonsingular and continuous, (2) pressure p(r) be physically admissible-real and non-negative, and (3) the magnetic field profile have ''minimum complexity''. The solutions are shown to be characterized by two parameters, B{sup *}{sub t}{identical_to} B-bar{sub t}/(8{pi}p{sub a}){sup 1/2} and B*{sub p} {identical_to} B{sub pa} /(8{pi}p{sub a} ){sup 1/2}, where B-bar{sub t} is the toroidal (axial) field averaged over the cross-sectional radius a and B{sub pa} is the poloidal (azimuthal) field at the edge of the current channel (r = a). The physical constraint on pressure defines equilibrium boundaries in the B*{sub t}-B*{sub p} space beyond which no physical solutions exist. The method is illustrated with a number of families of solutions governed by distinct physical constraints. The force-free limit with p{sub a} {ne} 0 is investigated and is found to be characterized by plasma {beta} = {infinity}. The local Alfven speed V{sub A} and plasma {beta} are computed. The results are scale-invariant.

  7. Magnetically operated check valve

    NASA Technical Reports Server (NTRS)

    Morris, Brian G. (inventor); Bozeman, Richard J., Jr. (inventor)

    1994-01-01

    A magnetically operated check valve is disclosed. The valve is comprised of a valve body and a movable poppet disposed therein. A magnet attracts the poppet to hold the valve shut until the force of fluid flow through the valve overcomes the magnetic attraction and moves the poppet to an unseated, open position. The poppet and magnet are configured and disposed to trap a magnetically attracted particulate and prevent it from flowing to a valve seating region.

  8. Whole-body magnetic resonance imaging in children: state of the art*

    PubMed Central

    Teixeira, Sara Reis; Elias Junior, Jorge; Nogueira-Barbosa, Marcello Henrique; Guimarães, Marcos Duarte; Marchiori, Edson; Santos, Marcel Koenigkam

    2015-01-01

    Whole-body imaging in children was classically performed with radiography, positron-emission tomography, either combined or not with computed tomography, the latter with the disadvantage of exposure to ionizing radiation. Whole-body magnetic resonance imaging (MRI), in association with the recently developed metabolic and functional techniques such as diffusion-weighted imaging, has brought the advantage of a comprehensive evaluation of pediatric patients without the risks inherent to ionizing radiation usually present in other conventional imaging methods. It is a rapid and sensitive method, particularly in pediatrics, for detecting and monitoring multifocal lesions in the body as a whole. In pediatrics, it is utilized for both oncologic and non-oncologic indications such as screening and diagnosis of tumors in patients with genetic syndromes, evaluation of disease extent and staging, evaluation of therapeutic response and post-therapy follow-up, evaluation of non neoplastic diseases such as multifocal osteomyelitis, vascular malformations and syndromes affecting multiple regions of the body. The present review was aimed at describing the major indications of whole-body MRI in pediatrics added of technical considerations. PMID:25987752

  9. Analysis of adipose tissue distribution using whole-body magnetic resonance imaging

    NASA Astrophysics Data System (ADS)

    Wald, Diana; Schwarz, Tobias; Dinkel, Julien; Delorme, Stefan; Teucher, Birgit; Kaaks, Rudolf; Meinzer, Hans-Peter; Heimann, Tobias

    2011-03-01

    Obesity is an increasing problem in the western world and triggers diseases like cancer, type two diabetes, and cardiovascular diseases. In recent years, magnetic resonance imaging (MRI) has become a clinically viable method to measure the amount and distribution of adipose tissue (AT) in the body. However, analysis of MRI images by manual segmentation is a tedious and time-consuming process. In this paper, we propose a semi-automatic method to quantify the amount of different AT types from whole-body MRI data with less user interaction. Initially, body fat is extracted by automatic thresholding. A statistical shape model of the abdomen is then used to differentiate between subcutaneous and visceral AT. Finally, fat in the bone marrow is removed using morphological operators. The proposed method was evaluated on 15 whole-body MRI images using manual segmentation as ground truth for adipose tissue. The resulting overlap for total AT was 93.7% +/- 5.5 with a volumetric difference of 7.3% +/- 6.4. Furthermore, we tested the robustness of the segmentation results with regard to the initial, interactively defined position of the shape model. In conclusion, the developed method proved suitable for the analysis of AT distribution from whole-body MRI data. For large studies, a fully automatic version of the segmentation procedure is expected in the near future.

  10. Whole-body magnetic resonance imaging in children: state of the art.

    PubMed

    Teixeira, Sara Reis; Elias Junior, Jorge; Nogueira-Barbosa, Marcello Henrique; Guimarães, Marcos Duarte; Marchiori, Edson; Santos, Marcel Koenigkam

    2015-01-01

    Whole-body imaging in children was classically performed with radiography, positron-emission tomography, either combined or not with computed tomography, the latter with the disadvantage of exposure to ionizing radiation. Whole-body magnetic resonance imaging (MRI), in association with the recently developed metabolic and functional techniques such as diffusion-weighted imaging, has brought the advantage of a comprehensive evaluation of pediatric patients without the risks inherent to ionizing radiation usually present in other conventional imaging methods. It is a rapid and sensitive method, particularly in pediatrics, for detecting and monitoring multifocal lesions in the body as a whole. In pediatrics, it is utilized for both oncologic and non-oncologic indications such as screening and diagnosis of tumors in patients with genetic syndromes, evaluation of disease extent and staging, evaluation of therapeutic response and post-therapy follow-up, evaluation of non neoplastic diseases such as multifocal osteomyelitis, vascular malformations and syndromes affecting multiple regions of the body. The present review was aimed at describing the major indications of whole-body MRI in pediatrics added of technical considerations. PMID:25987752

  11. Sub-surface characterization and three dimensional profiling of semiconductors by magnetic resonance force microscopy

    SciTech Connect

    Hammel, P.C.; Moore, G.; Roukes, M.; Zhenyong Zhang

    1996-10-01

    This is the final report of a two-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project successfully developed a magnetic resonance force microscope (MRFM) instrument to mechanically detect magnetic resonance signals. This technique provides an intrinsically subsurface, chemical-species-specific probe of structure, constituent density and other properties of materials. As in conventional magnetic resonance imaging (MRI), an applied magnetic field gradient selects a well defined volume of the sample for study. However mechanical detection allows much greater sensitivity, and this in turn allows the reduction of the size of the minimum resolvable volume. This requires building an instrument designed to achieve nanometer-scale resolution at buried semiconductor interfaces. High-resolution, three-dimensional depth profiling of semiconductors is critical in the development and fabrication of semiconductor devices. Currently, there is no capability for direct, high-resolution observation and characterization of dopant density, and other critical features of semiconductors. The successful development of MRFM in conjunction with modifications to improve resolution will enable for the first time detailed structural and electronic studies in doped semiconductors and multilayered nanoelectronic devices, greatly accelerating the current pace of research and development.

  12. Zero-point energy differences and many-body dispersion forces

    Microsoft Academic Search

    E. A. Power; T. Thirunamachandran

    1994-01-01

    The fully retarded dispersion interaction potentials, including many-body interactions, among neutral molecules are found in a systematic way. The method used relates the total zero-point energy of all the electromagnetic modes with the spectral sum of a linear operator. The difference between the zero-point energies with and without the molecules present is given as a contour integral. From the value

  13. Long-range forces: atmospheric neutrino oscillation at a magnetized detector

    SciTech Connect

    Samanta, Abhijit, E-mail: abhijit.samanta@gmail.com [Ramakrishna Mission Vivekananda University, Belur Math, Howrah 711 202 (India)

    2011-09-01

    Among the combinations L{sub e}-L{sub ?}, L{sub e}-L{sub ?} and L{sub ?}-L{sub ?} any one can be gauged in anomaly free way with the standard model gauge group. The masses of these gauge bosons can be so light that it can induce long-range forces on the Earth due to the electrons in the Sun. This type of forces can be constrained significantly from neutrino oscillation. As the sign of the potential is opposite for neutrinos and antineutrinos, a magnetized iron calorimeter detector (ICAL) would be able to produce strong constraint on it. We have made conservative studies of these long-range forces with atmospheric neutrinos at ICAL considering only the muons of charge current interactions. We find stringent bounds on the couplings ?{sub e?,e?} ?< 1.65 × 10{sup ?53} at 3? CL with an exposure of 1 Mton·yr if there is no such force. For nonzero input values of the couplings we find that the potential V{sub e?} opposes and V{sub e?} helps to discriminate the mass hierarchy. However, both potentials help significantly to discriminate the octant of ?{sub 23}. The explanation of the anomaly in recent MINOS data (the difference of ?m{sub 32}{sup 2} for neutrinos and antineutrinos), using long-range force originated from the mixing of the gauge boson Z' of L{sub ?}-L{sub ?} with the standard model gauge boson Z, can be tested at ICAL at more than 5? CL. We have also discussed how to disentangle this from the solution with CPT violation using the seasonal change of the distance between the Earth and the Sun.

  14. Time Evolution of Force-Free Parameter and Free Magnetic Energy in Active Region NOAA 10365

    NASA Astrophysics Data System (ADS)

    Valori, G.; Romano, P.; Malanushenko, A.; Ermolli, I.; Giorgi, F.; Steed, K.; van Driel-Gesztelyi, L.; Zuccarello, F.; Malherbe, J.-M.

    2015-02-01

    We describe the variation of the accumulated coronal helicity derived from the magnetic helicity flux through the photosphere in active region (AR) NOAA 10365, where several large flares and coronal mass ejections (CMEs) occurred. We used SOHO/MDI full-disk line-of-sight magnetograms to measure the helicity flux, and the integral of GOES X-ray flux as a proxy of the coronal energy variations due to flares or CMEs. Using the linear force-free field model, we transformed the accumulated helicity flux into a time sequence of the force-free parameter ? accounting for flares or CMEs via the proxy derived from GOES observations. This method can be used to derive the value of ? at different times during the AR evolution, and is a partial alternative to the commonly used match of field lines with EUV loops. By combining the accumulated helicity obtained from the observations with the linear force-free theory, we describe the main phases of the emergence process of the AR, and relate them temporally with the occurrence of flares or CMEs. Additionally, a comparison with the loop-matching method of fixing alpha at each time independently shows that the proposed method may be helpful in avoiding unrealistic or undetermined values of alpha that may originate from an insufficient quality of the image used to identify coronal loops at a given time. For the relative intensity of the considered events, the linear force-free field theory implies that there is a direct correlation between the released energy on the one hand and the product of the coronal helicity with the variation of ? due to the event on the other. Therefore, the higher the value of the accumulated coronal helicity, the smaller the force-free parameter variation required to produce the same decrease in the free energy during the CMEs.

  15. Magnetism

    NSDL National Science Digital Library

    University Corporation for Atmospheric Research Windows to the Universe team

    2007-12-12

    This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

  16. Nonlinear Alfvén wave dynamics at a 2D magnetic null point: ponderomotive force

    NASA Astrophysics Data System (ADS)

    Thurgood, J. O.; McLaughlin, J. A.

    2013-07-01

    Context. In the linear, ? = 0 MHD regime, the transient properties of magnetohydrodynamic (MHD) waves in the vicinity of 2D null points are well known. The waves are decoupled and accumulate at predictable parts of the magnetic topology: fast waves accumulate at the null point; whereas Alfvén waves cannot cross the separatricies. However, in nonlinear MHD mode conversion can occur at regions of inhomogeneous Alfvén speed, suggesting that the decoupled nature of waves may not extend to the nonlinear regime. Aims: We investigate the behaviour of low-amplitude Alfvén waves about a 2D magnetic null point in nonlinear, ? = 0 MHD. Methods: We numerically simulate the introduction of low-amplitude Alfvén waves into the vicinity of a magnetic null point using the nonlinear LARE2D code. Results: Unlike in the linear regime, we find that the Alfvén wave sustains cospatial daughter disturbances, manifest in the transverse and longitudinal fluid velocity, owing to the action of nonlinear magnetic pressure gradients (viz. the ponderomotive force). These disturbances are dependent on the Alfvén wave and do not interact with the medium to excite magnetoacoustic waves, although the transverse daughter becomes focused at the null point. Additionally, an independently propagating fast magnetoacoustic wave is generated during the early stages, which transports some of the initial Alfvén wave energy towards the null point. Subsequently, despite undergoing dispersion and phase-mixing due to gradients in the Alfvén-speed profile (?cA ? 0) there is no further nonlinear generation of fast waves. Conclusions: We find that Alfvén waves at 2D cold null points behave largely as in the linear regime, however they sustain transverse and longitudinal disturbances - effects absent in the linear regime - due to nonlinear magnetic pressure gradients.

  17. Modeling of induced current into the human body by low-frequency magnetic field from experimental data

    Microsoft Academic Search

    Riccardo Scorretti; Noël Burais; Laurent Nicolas; Alain Nicolas

    2005-01-01

    The induced currents into the human body by a low-frequency magnetic field are computed using three-dimensional finite elements and a special ?-A formulation. This magnetic field is generated by a real (possibly unknown) power system. The stray field is characterized by an equivalent multipole, fitted from some local measurements of the field, which is a good compromise between accuracy and

  18. Developing Nuclear Magnetic Resonance Force Microscopy (NMRFM) as an Electronic Probe of Nanoscale Condensed Matter Systems

    NASA Astrophysics Data System (ADS)

    Paster, Jeremy W.; Tennant, Daniel M.; Mozaffari, Shirin; Markert, John T.

    2015-03-01

    The investigation of NMR via magnetic force coupling in a large field gradient has led to vast improvements in spatial resolution over the conventional inductive method. It has been demonstrated that nanoscale force sensors could be scaled to distinguish a single nuclear spin, assuming experimental noise can be minimized and other specious force signatures stifled. Accordingly, there are many efforts aimed at repurposing NMR for 3D imaging on the atomic scale. In addition to proof-of-concept experiments aimed at separately resolving some of the eventual experimental barriers to atomic resolution, some of us have directed our attention to using NMR to probe the electronic environment in larger condensed matter systems which are not well suited for other scanning probe microscopy techniques and which are prohibitively small for inductive NMR detection. Previously, we proposed using NMRFM to probe superconducting transitions in microcrystals. In parallel, we revamped our investigation of thin films to explore two-dimensional conducting interfaces between insulating oxides. Presented here is a survey of the technical impediments as well as current strategies for unlocking this exciting potential for NMRFM, as a tool to investigate sub-surface electronic transport in microscale and nanoscale condensed matter systems.

  19. COMPARISON OF FORCE-FREE CORONAL MAGNETIC FIELD MODELING USING VECTOR FIELDS FROM HINODE AND SOLAR DYNAMICS OBSERVATORY

    SciTech Connect

    Thalmann, J. K.; Tiwari, S. K.; Wiegelmann, T., E-mail: thalmann@mps.mpg.de [Max-Plank-Institut fuer Sonnensystemforschung, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany)

    2013-05-20

    Photospheric magnetic vector maps from two different instruments are used to model the nonlinear force-free coronal magnetic field above an active region. We use vector maps inferred from polarization measurements of the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) and the Solar Optical Telescope's Spectropolarimeter (SP) on board Hinode. Besides basing our model calculations on HMI data, we use both SP data of original resolution and scaled down to the resolution of HMI. This allows us to compare the model results based on data from different instruments and to investigate how a binning of high-resolution data affects the model outcome. The resulting three-dimensional magnetic fields are compared in terms of magnetic energy content and magnetic topology. We find stronger magnetic fields in the SP data, translating into a higher total magnetic energy of the SP models. The net Lorentz forces of the HMI and SP lower boundaries verify their force-free compatibility. We find substantial differences in the absolute estimates of the magnetic field energy but similar relative estimates, e.g., the fraction of excess energy and of the flux shared by distinct areas. The location and extension of neighboring connectivity domains differ and the SP model fields tend to be higher and more vertical. Hence, conclusions about the magnetic connectivity based on force-free field models are to be drawn with caution. We find that the deviations of the model solution when based on the lower-resolution SP data are small compared to the differences of the solutions based on data from different instruments.

  20. Eruption triggering of giant magma bodies by internal versus external forcing: A rhyolite-MELTS study

    NASA Astrophysics Data System (ADS)

    Carley, T. L.; Gualda, G. A.; Ghiorso, M. S.; Miller, C. F.

    2012-12-01

    Silicic volcanism, particularly supereruptions, raises questions about the mechanisms by which magma bodies destabilize and erupt. Are external events necessary to initiate an eruption of a large silicic system, or is possible for internal processes (crystallization, volatile exsolution) to destabilize a system and drive it to erupt? If external triggers are critically important to prompting eruption, are all felsic magma bodies equally prone to erupt? To respond to these questions, we use rhyolite-MELTS (Gualda et al. 2012) to investigate the pre-eruptive chemical evolution and the resultant changes to physical properties of giant (super-eruptive) felsic magma bodies. Simulations are conducted using pumice and glass compositions from the Peach Spring (Southwestern USA) and the Bishop (California USA) Tuffs, two giant high-silica rhyolite deposits. In our simulations, we vary initial pressure (150-350 MPa in 50 MPa intervals), volatile content (initial water ranging from 1-7 wt. %), mode of crystallization (equilibrium vs. fractional), and rheology of the magma reservoir (isobaric vs. isochoric vs. transitional). We run simulations through as much of the crystallization interval as possible, but focus on the first ~50 wt. % crystallization, most relevant for volcanic systems. In all simulations, we observe near-invariant behavior when the system becomes saturated in quartz, two feldspars and a fluid phase, from which point crystallization is essentially isothermal. Prior to the near-invariant, crystallization leads to gradual changes in bulk properties (e.g., < 1% volume decrease over 50 °C), which effectively results in modest pressure changes within the magma body (i.e., ~10 MPa). Upon reaching the near-invariant, the bulk properties change abruptly (e.g., > 5% volume increase in 0.1 °C), causing significant overpressurization of the magma body. The magnitude of this overpressurization (i.e. 10s to 100s of MPa depending on system conditions) is sufficient to exceed the yield strength of the country rocks, effectively making eruption possible independent of any external triggers. Our simulations reveal that the Peach Spring and Bishop Tuff magmatic systems represent two contrasting types of behavior. In the Bishop case, only ~5-25 wt.% of crystallization over a short temperature interval (~30 °C cooling) is needed to reach near-invariant behavior, making it plausible that crystallization led to eruption without external triggers. This is consistent with the lack of evidence for interaction of Bishop magma with mafic magmas. In the Peach Spring case, 30-70 wt. % crystallization over a much longer temperature interval (~60-130 °C cooling) is needed for the system to reach the near-invariant. Given that Peach Spring pumice and fiamme are characterized by <30 wt. % crystals, it seems unlikely that crystallization alone led to eruption, suggesting the action of an external trigger in promoting eruption. This is consistent with evidence for significant heating and mush remobilization preserved in intracaldera Peach Spring rocks. Our results show that phase-equilibria constrains whether a magma system is likely to destabilize itself and erupt as a result of overpressurization by closed-system crystallization and volatile exsolution.

  1. Molecular interference in antibody-antigen interaction studied with magnetic force immunoassay.

    PubMed

    Dorokhin, D; van IJzendoorn, L J; de Jong, A M; Nieto, L; Brunsveld, L; Orsel, J G; Prins, M W J

    2015-09-25

    Molecular interferences are an important challenge in biotechnologies based on antibody-antigen interactions, such as sandwich immunoassays. We report how a sandwich immunoassay with magnetic particles as label can be used to probe interference by surfactants. Surfactants are often used to improve the performance of immunoassays, however the surfactants can affect the involved proteins and the mechanism of action of surfactant molecules on the antibody-antigen system is mostly unknown. As an example, we investigated molecular interference by a nonionic surfactant (Pluronic F-127) in a cardiac troponin (cTn) sandwich immunoassay with two monoclonal antibodies. The influence of the surfactant below the critical micelle concentration (0.00-0.04%) on dissociation properties was quantified in a magnetic tweezers setup, where a force is applied to the molecules via magnetic particle labels. The force-dependent dissociation curves revealed the existence of two distinct cTn-dependent bond types, namely a weak bond attributable to non-specific binding of cTn, and a strong bond attributable to the specific binding of cTn. The dissociation rate constant of the strong bonds increased with the surfactant concentration by about a factor of two. Circular dichroism spectroscopy data showed that the nonionic surfactant influences the conformation of cTn while not noticeably affecting the two monoclonal antibodies. This suggests that the surfactant-induced increase of the dissociation rate of the specific sandwich-type cTn binding may be related to a conformational change of the antigen molecule. The described methodology is an effective tool to study the influence of surfactants and other interferences on assays based on protein interactions. PMID:25676839

  2. A multipole accelerated desingularized method for computing nonlinear wave forces on bodies

    SciTech Connect

    Scorpio, S.M.; Beck, R.F. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Naval Architecture and Marine Engineering

    1996-12-31

    Nonlinear wave forces on offshore structures are investigated. The fluid motion is computed using an Euler-Lagrange time domain approach. Nonlinear free surface boundary conditions are stepped forward in time using an accurate and stable integration technique. The field equation with mixed boundary conditions that result at each time step are solved at N nodes using a desingularized boundary integral method with multipole acceleration. Multipole accelerated solutions require O(N) computational effort and computer storage while conventional solvers require O(N{sup 2}) effort and storage for an iterative solution and O(N{sup 3}) effort for direct inversion of the influence matrix. These methods are applied to the three dimensional problem of wave diffraction by a vertical cylinder.

  3. Quantitative analysis of the magnetic domain structure in polycrystalline La(0.7)Sr(0.3)MnO3 thin films by magnetic force microscopy.

    PubMed

    Li, Zhenghua; Wei, Fulin; Yoshimura, Satoru; Li, Guoqing; Asano, Hidefumi; Saito, Hitoshi

    2013-01-14

    The nanoscale magnetic domain structure of the polycrystalline La(0.7)Sr(0.3)MnO(3) granular thin films was imaged with a developed magnetic force microscopy technique by simultaneously detecting both the perpendicular and in-plane components of magnetic field gradients during the same scan of the tip oscillation. The characteristics of both the perpendicular and in-plane magnetic field gradient at the grain edges or the nonmagnetic grain boundary phase for LSMO films were demonstrated and can be used to evaluate the magnetic domain structure and magnetic isolation between neighboring grains. A two dimensional signal transformation algorithm to reconstruct the in-plane magnetization distribution of the polycrystalline LSMO thin films from the measured raw MFM images with the aid of the deconvolution technique was presented. The comparison between the experimental and simulated MFM images indicates that the magnetic grains or clusters are in the single domain (SD) or multi-domain (MD) state with the magnetic moments parallel or anti-parallel to the effective magnetic field of each grain, possibly due to the need for minimizing the total energy. The quantitative interpretation of the magnetic domain structure indicates that the large magnetoresistance in the studied LSMO films is mainly due to tunnel effect and scattering of conducted electrons at the nonmagnetic grain boundary phase related to the different configurations of magnetic domain states between neighboring grains. PMID:23183628

  4. Hybrid Wing Body Model Identification Using Forced-Oscillation Water Tunnel Data

    NASA Technical Reports Server (NTRS)

    Murphy, Patrick C.; Vicroy, Dan D.; Kramer, Brian; Kerho, Michael

    2014-01-01

    Static and dynamic testing of the NASA 0.7 percent scale Hybrid Wing Body (HWB) configuration was conducted in the Rolling Hills Research Corporation water tunnel to investigate aerodynamic behavior over a large range of angle-of-attack and to develop models that can predict aircraft response in nonlinear unsteady flight regimes. This paper reports primarily on the longitudinal axis results. Flow visualization tests were also performed. These tests provide additional static data and new dynamic data that complement tests conducted at NASA Langley 14- by 22-Foot Subsonic Tunnel. HWB was developed to support the NASA Environmentally Responsible Aviation Project goals of lower noise, emissions, and fuel burn. This study also supports the NASA Aviation Safety Program efforts to model and control advanced transport configurations in loss-of-control conditions.

  5. Convergence of the hyperspherical-harmonics expansion with increasing number of particles for bosonic systems. II. Inclusion of the three-body force

    NASA Astrophysics Data System (ADS)

    Timofeyuk, N. K.

    2015-04-01

    This paper presents a numerical convergence study of a hyperspherical-harmonics expansion for binding energies of a system of 4 ?N ?728 helium atoms using a phenomenological soft attractive two-body He-He potential and a repulsive three-body force aimed at compensating for the absence of the two-body repulsive core. Earlier calculations with such a potential have shown an improved convergence when N increases from four to six. The present study reveals that the improved convergence occurs only for a limited range of N determined by the range of the three-body repulsion. For a soft repulsive three-body force, the convergence is fast for N ?20 , while for a short-range three-body repulsion it deteriorates at N ?10 . The reasons for this deterioration are discussed. The range of the three-body force also determines the binding energy behavior with N , and it is also responsible for binding the excited states. The long-range force binds all first excited 0+ states but strongly underbinds the systems of N helium atoms at large N . The short-range force does not bind the first 0+ states for A ?7 but gives better predictions of binding energies as compared to the calculations of other authors though overestimating them. Some options to improve both the description of the binding energies and the convergence of the hyperspherical-harmonics expansion using phenomenological forces are discussed. It is pointed out that a fast convergence is very much needed for the reliable predictions of states with nonzero angular momentum, examples of which are also given.

  6. Investigation of the effect of high magnetic field on the MnBi\\/Mn 1.08Bi phase transformation in Mn–Bi alloys by measuring the magnetic force in gradient magnetic field

    Microsoft Academic Search

    X. Li; Z. M. Ren; Y. Fautrelle

    2006-01-01

    Owing to the change in magnetic susceptibility while the phase transformation occurs, a new method is suggested to determine the phase transformation temperature by measuring the temperature at which the magnetic force changes abruptly in a gradient magnetic field. The MnBi\\/Mn1.08Bi phase transformation temperature in a high magnetic field is measured by this method and the result indicates that the

  7. EFFECT OF POLARIMETRIC NOISE ON THE ESTIMATION OF TWIST AND MAGNETIC ENERGY OF FORCE-FREE FIELDS

    SciTech Connect

    Tiwari, Sanjiv Kumar; Venkatakrishnan, P.; Gosain, Sanjay; Joshi, Jayant [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313 001 (India)], E-mail: stiwari@prl.res.in, E-mail: pvk@prl.res.in, E-mail: sgosain@prl.res.in, E-mail: jayant@prl.res.in

    2009-07-20

    The force-free parameter {alpha}, also known as helicity parameter or twist parameter, bears the same sign as the magnetic helicity under some restrictive conditions. The single global value of {alpha} for a whole active region gives the degree of twist per unit axial length. We investigate the effect of polarimetric noise on the calculation of global {alpha} value and magnetic energy of an analytical bipole. The analytical bipole has been generated using the force-free field approximation with a known value of constant {alpha} and magnetic energy. The magnetic parameters obtained from the analytical bipole are used to generate Stokes profiles from the Unno-Rachkovsky solutions for polarized radiative transfer equations. Then we add random noise of the order of 10{sup -3} of the continuum intensity (I {sub c}) in these profiles to simulate the real profiles obtained by modern spectropolarimeters such as Hinode (SOT/SP), SVM (USO), ASP, DLSP, POLIS, and SOLIS etc. These noisy profiles are then inverted using a Milne-Eddington inversion code to retrieve the magnetic parameters. Hundred realizations of this process of adding random noise and polarimetric inversion is repeated to study the distribution of error in global {alpha} and magnetic energy values. The results show that (1) the sign of {alpha} is not influenced by polarimetric noise and very accurate values of global twist can be calculated, and (2) accurate estimation of magnetic energy with uncertainty as low as 0.5% is possible under the force-free condition.

  8. A nonlinear eigenvalue problem for self-similar spherical force-free magnetic fields

    SciTech Connect

    Lerche, I. [Institut für Geowissenschaften, Naturwissenschaftliche Fakultät III, Martin-Luther Universität, D-06099 Halle (Germany); Low, B. C. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307 (United States)

    2014-10-15

    An axisymmetric force-free magnetic field B(r, ?) in spherical coordinates is defined by a function r?sin??B{sub ?}=Q(A) relating its azimuthal component to its poloidal flux-function A. The power law r?sin??B{sub ?}=aA|A|{sup 1/n}, n a positive constant, admits separable fields with A=(A{sub n}(?))/(r{sup n}) , posing a nonlinear boundary-value problem for the constant parameter a as an eigenvalue and A{sub n}(?) as its eigenfunction [B. C. Low and Y. Q Lou, Astrophys. J. 352, 343 (1990)]. A complete analysis is presented of the eigenvalue spectrum for a given n, providing a unified understanding of the eigenfunctions and the physical relationship between the field's degree of multi-polarity and rate of radial decay via the parameter n. These force-free fields, self-similar on spheres of constant r, have basic astrophysical applications. As explicit solutions they have, over the years, served as standard benchmarks for testing 3D numerical codes developed to compute general force-free fields in the solar corona. The study presented includes a set of illustrative multipolar field solutions to address the magnetohydrodynamics (MHD) issues underlying the observation that the solar corona has a statistical preference for negative and positive magnetic helicities in its northern and southern hemispheres, respectively; a hemispherical effect, unchanging as the Sun's global field reverses polarity in successive eleven-year cycles. Generalizing these force-free fields to the separable form B=(H(?,?))/(r{sup n+2}) promises field solutions of even richer topological varieties but allowing for ?-dependence greatly complicates the governing equations that have remained intractable. The axisymmetric results obtained are discussed in relation to this generalization and the Parker Magnetostatic Theorem. The axisymmetric solutions are mathematically related to a family of 3D time-dependent ideal MHD solutions for a polytropic fluid of index ??=?4/3 as discussed in the Appendix.

  9. Whole-body isometric force/torque measurements for functional assessment in neuro-rehabilitation: platform design, development and verification

    PubMed Central

    Mazzoleni, Stefano; Toth, Andras; Munih, Marko; Van Vaerenbergh, Jo; Cavallo, Giuseppe; Micera, Silvestro; Dario, Paolo; Guglielmelli, Eugenio

    2009-01-01

    Background One of the main scientific and technological challenges of rehabilitation bioengineering is the development of innovative methodologies, based on the use of appropriate technological devices, for an objective assessment of patients undergoing a rehabilitation treatment. Such tools should be as fast and cheap to use as clinical scales, which are currently the daily instruments most widely used in the routine clinical practice. Methods A human-centered approach was used in the design and development of a mechanical structure equipped with eight force/torque sensors that record quantitative data during the initiation of a predefined set of Activities of Daily Living (ADL) tasks, in isometric conditions. Results Preliminary results validated the appropriateness, acceptability and functionality of the proposed platform, that has become now a tool used for clinical research in three clinical centres. Conclusion This paper presented the design and development of an innovative platform for whole-body force and torque measurements on human subjects. The platform has been designed to perform accurate quantitative measurements in isometric conditions with the specific aim to address the needs for functional assessment tests of patients undergoing a rehabilitation treatment as a consequence of a stroke. The versatility of the system also enlightens several other interesting possible areas of application for therapy in neurorehabilitation, for research in basic neuroscience, and more. PMID:19878556

  10. A 3-axis optical force\\/torque sensor for prostate needle placement in Magnetic resonance imaging environments

    Microsoft Academic Search

    Hao Su; Gregory S. Fischer

    2009-01-01

    The work presented in this paper has been performed in furtherance of developing an MRI (Magnetic resonance imaging) compatible fiber optical force sensor. In this paper, we discuss the design criteria and sensing principle of this optical sensor for monitoring forces in the 0-20 Newton range with an sub-Newton resolution. This instrumentation enables two degrees-of-freedom (DOF) torque measurement and one

  11. The multiscale coarse-graining method. IX. A general method for construction of three body coarse-grained force fields

    NASA Astrophysics Data System (ADS)

    Das, Avisek; Andersen, Hans C.

    2012-05-01

    The multiscale coarse-graining (MS-CG) method is a method for constructing a coarse-grained (CG) model of a system using data obtained from molecular dynamics simulations of the corresponding atomically detailed model. The formal statistical mechanical derivation of the method shows that the potential energy function extracted from an MS-CG calculation is a variational approximation for the true potential of mean force of the CG sites, one that becomes exact in the limit that a complete basis set is used in the variational calculation if enough data are obtained from the atomistic simulations. Most applications of the MS-CG method have employed a representation for the nonbonded part of the CG potential that is a sum of all possible pair interactions. This approach, despite being quite successful for some CG models, is inadequate for some others. Here we propose a systematic method for including three body terms as well as two body terms in the nonbonded part of the CG potential energy. The current method is more general than a previous version presented in a recent paper of this series [L. Larini, L. Lu, and G. A. Voth, J. Chem. Phys. 132, 164107 (2010)], 10.1063/1.3394863, in the sense that it does not make any restrictive choices for the functional form of the three body potential. We use hierarchical multiresolution functions that are similar to wavelets to develop very flexible basis function expansions with both two and three body basis functions. The variational problem is solved by a numerical technique that is capable of automatically selecting an appropriate subset of basis functions from a large initial set. We apply the method to two very different coarse-grained models: a solvent free model of a two component solution made of identical Lennard-Jones particles and a one site model of SPC/E water where a site is placed at the center of mass of each water molecule. These calculations show that the inclusion of three body terms in the nonbonded CG potential can lead to significant improvement in the accuracy of CG potentials and hence of CG simulations.

  12. Design of a magnetic force exciter for a small-scale windmill using a piezo-composite generating element

    NASA Astrophysics Data System (ADS)

    Luong, Hung Truyen; Goo, Nam Seo

    2011-03-01

    We introduce a design for a magnetic force exciter that applies vibration to a piezo-composite generating element (PCGE) for a small-scale windmill to convert wind energy into electrical energy. The windmill can be used to harvest wind energy in urban regions. The magnetic force exciter consists of exciting magnets attached to the device's input rotor, and a secondary magnet that is fixed at the tip of the PCGE. Under an applied wind force, the input rotor rotates to create a magnetic force interaction to excite the PCGE. Deformation of the PCGE enables it to generate the electric power. Experiments were performed to test power generation and battery charging capabilities. In a battery charging test, the charging time for a 40 mAh battery is approximately 1.5 hours for a wind speed of 2.5 m/s. Our experimental results show that the prototype can harvest energy in urban areas with low wind speeds, and convert the wasted wind energy into electricity for city use.

  13. Direct current force sensing device based on compressive spring, permanent magnet, and coil-wound magnetostrictive/piezoelectric laminate.

    PubMed

    Leung, Chung Ming; Or, Siu Wing; Ho, S L

    2013-12-01

    A force sensing device capable of sensing dc (or static) compressive forces is developed based on a NAS106N stainless steel compressive spring, a sintered NdFeB permanent magnet, and a coil-wound Tb(0.3)Dy(0.7)Fe(1.92)/Pb(Zr, Ti)O3 magnetostrictive?piezoelectric laminate. The dc compressive force sensing in the device is evaluated theoretically and experimentally and is found to originate from a unique force-induced, position-dependent, current-driven dc magnetoelectric effect. The sensitivity of the device can be increased by increasing the spring constant of the compressive spring, the size of the permanent magnet, and/or the driving current for the coil-wound laminate. Devices of low-force (20 N) and high-force (200 N) types, showing high output voltages of 262 and 128 mV peak, respectively, are demonstrated at a low driving current of 100 mA peak by using different combinations of compressive spring and permanent magnet. PMID:24387458

  14. Synthesis of cobalt ferrite nanocrystallites by the forced hydrolysis method and investigation of their magnetic properties

    NASA Astrophysics Data System (ADS)

    Hanh, N.; Quy, O. K.; Thuy, N. P.; Tung, L. D.; Spinu, L.

    2003-04-01

    Cobalt ferrite powder has been synthesized by the forced hydrolysis method in 1,2-propanediol. The particles, having a cubic spinel structure, are nanocrystallites with a mean diameter of 4 nm with almost equiaxial shapes and a narrow size distribution. These particles are superparamagnetic at room temperature and ferrimagnetic at temperatures below the blocking temperature of about 180 K. A remarkable shift of the blocking temperature with frequency was observed in the AC susceptibility measurements. The calculated value of anisotropy constant at 0 K, KA(0)=5.36×10 7 erg/cm 3, is higher than that in the bulk material. The saturation magnetization and the coercivity measured at 5 K are 75 emu/g and 10.3 kOe, respectively.

  15. Use of a magnetic force exciter to vibrate a piezocomposite generating element in a small-scale windmill

    NASA Astrophysics Data System (ADS)

    Truyen Luong, Hung; Goo, Nam Seo

    2012-02-01

    A piezocomposite generating element (PCGE) can be used to convert ambient vibrations into electrical energy that can be stored and used to power other devices. This paper introduces a design of a magnetic force exciter for a small-scale windmill that vibrates a PCGE to convert wind energy into electrical energy. A small-scale windmill was designed to be sensitive to low-speed wind in urban regions for the purpose of collecting wind energy. The magnetic force exciter consists of exciting magnets attached to the device’s input rotor and a secondary magnet fixed at the tip of the PCGE. The PCGE is fixed to a clamp that can be adjusted to slide on the windmill’s frame in order to change the gap between exciting and secondary magnets. Under an applied wind force, the input rotor rotates to create a magnetic force interaction that excites the PCGE. The deformation of the PCGE enables it to generate electric power. Experiments were performed with different numbers of exciting magnets and different gaps between the exciting and secondary magnets to determine the optimal configuration for generating the peak voltage and harvesting the maximum wind energy for the same range of wind speeds. In a battery-charging test, the charging time for a 40 mA h battery was approximately 3 h for natural wind in an urban region. The experimental results show that the prototype can harvest energy in urban regions with low wind speeds and convert the wasted wind energy into electricity for city use.

  16. Nonlinear Force-Free Modeling of Coronal Magnetic Fields Part I: A Quantitative Comparison of Methods

    NASA Astrophysics Data System (ADS)

    Schrijver, Carolus J.; De Rosa, Marc L.; Metcalf, Thomas R.; Liu, Yang; McTiernan, Jim; Régnier, Stéphane; Valori, Gherardo; Wheatland, Michael S.; Wiegelmann, Thomas

    2006-05-01

    We compare six algorithms for the computation of nonlinear force-free (NLFF) magnetic fields (including optimization, magnetofrictional, Grad Rubin based, and Green's function-based methods) by evaluating their performance in blind tests on analytical force-free-field models for which boundary conditions are specified either for the entire surface area of a cubic volume or for an extended lower boundary only. Figures of merit are used to compare the input vector field to the resulting model fields. Based on these merit functions, we argue that all algorithms yield NLFF fields that agree best with the input field in the lower central region of the volume, where the field and electrical currents are strongest and the effects of boundary conditions weakest. The NLFF vector fields in the outer domains of the volume depend sensitively on the details of the specified boundary conditions; best agreement is found if the field outside of the model volume is incorporated as part of the model boundary, either as potential field boundaries on the side and top surfaces, or as a potential field in a skirt around the main volume of interest. For input field (B) and modeled field (b), the best method included in our study yields an average relative vector error E n = < |B-b|>/< |B|> of only 0.02 when all sides are specified and 0.14 for the case where only the lower boundary is specified, while the total energy in the magnetic field is approximated to within 2%. The models converge towards the central, strong input field at speeds that differ by a factor of one million per iteration step. The fastest-converging, best-performing model for these analytical test cases is the Wheatland, Sturrock, and Roumeliotis (2000) optimization algorithm as implemented by Wiegelmann (2004).

  17. Clinical value of whole-body magnetic resonance imaging in health screening of general adult population

    PubMed Central

    Tarnoki, David Laszlo; Tarnoki, Adam Domonkos; Richter, Antje; Karlinger, Kinga; Berczi, Viktor; Pickuth, Dirk

    2015-01-01

    Background Whole-body magnetic resonance imaging (WB-MRI) and angiography (WB-MRA) has become increasingly popular in population-based research. We evaluated retrospectively the frequency of potentially relevant incidental findings throughout the body. Materials and methods 22 highly health-conscious managers (18 men, mean age 47±9 years) underwent WB-MRI and WB-MRA between March 2012 and September 2013 on a Discovery MR750w wide bore 3 Tesla device (GE Healthcare) using T1 weighted, short tau inversion recovery (STIR) and diffusion weighted imaging (DWI) acquisitions according to a standardized protocol. Results A suspicious (pararectal) malignancy was detected in one patient which was confirmed by an endorectal sonography. Incidental findings were described in 20 subjects, including hydrocele (11 patients), benign bony lesion (7 patients) and non-specific lymph nodes (5 patients). Further investigations were recommended in 68% (ultrasound: 36%, computed tomography: 28%, mammography: 9%, additional MRI: 9%). WB-MRA were negative in 16 subjects. Vascular normal variations were reported in 23%, and a 40% left proximal common carotid artery stenosis were described in one subject. Conclusions WB-MRI and MRA lead to the detection of clinically relevant diseases and unexpected findings in a cohort of healthy adults that require further imaging or surveillance in 68%. WB-MR imaging may play a paramount role in health screening, especially in the future generation of (epi)genetic based screening of malignant and atherosclerotic disorders. Our study is the first which involved a highly selected patient group using a high field 3-T wide bore magnet system with T1, STIR, MRA and whole-body DWI acquisitions as well. PMID:25810696

  18. Application of the drag force method to evaluate magnetic property degradation near the cut edges of electrical steels

    NASA Astrophysics Data System (ADS)

    Garshelis, Ivan J.; Crevecoeur, Guillaume; Tollens, Stijn P. L.; Dupre, Luc

    2011-04-01

    The increase in hysteresis loss associated with the altered microstructure and residual stress fields in regions near the cut edges of electrical steels is investigated by means of drag force measurements. Measurements are made using relatively narrow magnets on samples of two grades of nonoriented steels cut by laser or mechanical processes. Largest drag forces, hence losses, are consistently found in slow laser cut samples, smallest drag forces with fast laser cut samples, and moderately higher losses in mechanically cut samples. These results are consistent with other measurement methods.

  19. Baseband Detection of Bistatic Electron Spin Signals in Magnetic Resonance Force Microscopy (MRFM)

    E-print Network

    Chun-yu Yip; Alfred O. Hero; Daniel Rugar; Jeffrey A. Fessler

    2003-08-20

    In single spin Magnetic Resonance Force Microscopy (MRFM), the objective is to detect the presence of an electron (or nuclear) spin in a sample volume by measuring spin-induced attonewton forces using a micromachined cantilever. In the OSCAR method of single spin MRFM, the spins are manipulated by an external rf field to produce small periodic deviations in the resonant frequency of the cantilever. These deviations can be detected by frequency demodulation followed by conventional amplitude or energy detection. In this paper, we present an alternative to these detection methods, based on optimal detection theory and Gibbs sampling. On the basis of simulations, we show that our detector outperforms the conventional amplitude and energy detectors for realistic MRFM operating conditions. For example, to achieve a 10% false alarm rate and an 80% correct detection rate our detector has an 8 dB SNR advantage as compared with the conventional amplitude or energy detectors. Furthermore, at these detection rates it comes within 4 dB of the omniscient matched-filter lower bound.

  20. The dust motion inside the magnetized sheath - The effect of drag forces

    SciTech Connect

    Pandey, B. P. [Department of Physics and Astronomy, Macquarie University, Sydney, New South Wales 2109 (Australia); Samarian, A.; Vladimirov, S. V. [School of Physics, University of Sydney, New South Wales 2006 (Australia)

    2010-08-15

    The isolated charged dust inside the magnetized plasma sheath moves under the influence of the electron and ion drag force and the sheath electrostatic field. The charge on the dust is a function of its radius as well as the value of the ambient sheath potential. It is shown that the charge on the dust determines its trajectory and dust performs the spiraling motion inside the sheath. The location of the turning spiral is determined by the number of negative charge on the dust, which in turn is a function of the dust radius. The back and forth spiraling motion finally causes the dust to move in a small, narrow region of the sheath. For a bigger dust particle, the dust moves closer to the sheath presheath boundary suggesting that the bigger grains, owing to the strong repulsion between the wall and dust, will be unable to travel inside the sheath. Only small, micron-sized grains can travel closer to the wall before repulsion pushes it back toward the plasma-sheath boundary. The temporal behavior of the spiraling dust motion appears like a damped harmonic oscillation, suggesting that the plasma drag force causes dissipation of the electrostatic energy. However, after initial damping, the grain keeps oscillating although with much smaller amplitude. The possible application of the present results to the ongoing sheath experiments is discussed.

  1. Vertically polarizing undulator with the dynamic compensation of magnetic forces for the next generation of light sources

    NASA Astrophysics Data System (ADS)

    Strelnikov, N.; Trakhtenberg, E.; Vasserman, I.; Xu, J.; Gluskin, E.

    2014-11-01

    A short prototype (847-mm-long) of an Insertion Device (ID) with the dynamic compensation of ID magnetic forces has been designed, built, and tested at the Advanced Photon Source (APS) of the Argonne National Laboratory. The ID magnetic forces were compensated by the set of conical springs placed along the ID strongback. Well-controlled exponential characteristics of conical springs permitted a very close fit to the ID magnetic forces. Several effects related to the imperfections of actual springs, their mounting and tuning, and how these factors affect the prototype performance has been studied. Finally, series of tests to determine the accuracy and reproducibility of the ID magnetic gap settings have been carried out. Based on the magnetic measurements of the ID Beff, it has been demonstrated that the magnetic gaps within an operating range were controlled accurately and reproducibly within ±1 ?m. Successful tests of this ID prototype led to the design of a 3-m long device based on the same concept. The 3-m long prototype is currently under construction. It represents R&D efforts by the APS toward APS Upgrade Project goals as well as the future generation of IDs for the Linac Coherent Light Source (LCLS).

  2. Physiologic and dosimetric considerations for limiting electric fields induced in the body by movement in a static magnetic field.

    PubMed

    Jokela, Kari; Saunders, Richard D

    2011-06-01

    Movement in a strong static magnetic field induces electric fields in a human body, which may result in various sensory perceptions such as vertigo, nausea, magnetic phosphenes, and a metallic taste in the mouth. These sensory perceptions have been observed by patients and medical staff in the vicinity of modern diagnostic magnetic resonance (MR) equipment and may be distracting if they were to affect the balance and eye-hand coordination of, for example, a physician carrying out a medical operation during MR scanning. The stimulation of peripheral nerve tissue by a more intense induced electric field is also theoretically possible but has not been reported to result from such movement. The main objective of this study is to consider generic criteria for limiting the slowly varying broadband (<10 Hz) electric fields induced by the motion of the body in the static magnetic field. In order to find a link between the static magnetic flux density and the time-varying induced electric field, the static magnetic field is converted to the homogeneous equivalent transient and sinusoidal magnetic fields exposing a stationary body. Two cases are considered: a human head moving in a non-uniform magnetic field and a head rotating in a homogeneous magnetic field. Then the electric field is derived from the magnetic flux rate (dB/dt) of the equivalent field by using computational dosimetric data published in the literature for various models of the human body. This conversion allows the plotting of the threshold electric field as a function of frequency for vertigo, phosphenes, and stimulation of peripheral nerves. The main conclusions of the study are: The basic restrictions for limiting exposure to extremely low frequency magnetic fields recommended by the International Commission on Non-Ionizing Radiation Protection ICNIRP in 1998 will prevent most cases of vertigo and other sensory perceptions that result from induced electric fields above 1 Hz, while limiting the static magnetic field below 2 T, as recently recommended by ICNIRP, provides sufficient protection below 1 Hz. People can experience vertigo when moving in static magnetic fields of between 2 and 8 T, but this may be controlled to some extent by slowing down head and/or body movement. In addition, limiting the static magnetic field below 8 T provides good protection against peripheral nerve stimulation. PMID:22004933

  3. ANALYSIS AND NUMERICAL SIMULATION OF MAGNETIC FORCES BETWEEN RIGID POLYGONAL BODIES.

    E-print Network

    Popovic, Nikola

    and physical analysis of magnetoelastic phenomena is a topic of ongoing research. Different formulae have been corresponding real-life experiments. 1. Introduction The analysis and modeling of magnetoelastic phenomena

  4. Gaussian approximation and single-spin measurement in magnetic resonance force microscopy with spin noise

    SciTech Connect

    Raghunathan, Shesha; Brun, Todd A. [Center for Quantum Information Science and Technology, Communication Sciences Institute, Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089 (United States); Goan, Hsi-Sheng [Department of Physics and Center for Theoretical Sciences, National Taiwan University, Taipei 10617, Taiwan (China); Center for Quantum Science and Engineering, National Taiwan University, Taipei 10617, Taiwan (China)

    2010-11-15

    A promising technique for measuring single electron spins is magnetic resonance force microscopy (MRFM), in which a microcantilever with a permanent magnetic tip is resonantly driven by a single oscillating spin. The most effective experimental technique is the oscillating cantilever-driven adiabatic reversals (OSCAR) protocol, in which the signal takes the form of a frequency shift. If the quality factor of the cantilever is high enough, this signal will be amplified over time to the point where it can be detected by optical or other techniques. An important requirement, however, is that this measurement process occurs on a time scale that is short compared to any noise which disturbs the orientation of the measured spin. We describe a model of spin noise for the MRFM system and show how this noise is transformed to become time dependent in going to the usual rotating frame. We simplify the description of the cantilever-spin system by approximating the cantilever wave function as a Gaussian wave packet and show that the resulting approximation closely matches the full quantum behavior. We then examine the problem of detecting the signal for a cantilever with thermal noise and spin with spin noise, deriving a condition for this to be a useful measurement.

  5. Averaging out magnetic forces with fast rf-sweeps in an optical trap for metastable chromium atoms

    E-print Network

    Q. Beaufils; R. Chicireanu; A. Pouderous; W. de Souza Melo; B. Laburthe-Tolra; E. Maréchal; L. Vernac; J. C. Keller; O. Gorceix

    2007-11-05

    We introduce a novel type of time-averaged trap, in which the internal state of the atoms is rapidly modulated to modify magnetic trapping potentials. In our experiment, fast radiofrequency (rf) linear sweeps flip the spin of atoms at a fast rate, which averages out magnetic forces. We use this procedure to optimize the accumulation of metastable chomium atoms into an optical dipole trap from a magneto-optical trap. The potential experienced by the metastable atoms is identical to the bare optical dipole potential, so that this procedure allows for trapping all magnetic sublevels, hence increasing by up to 80 percent the final number of accumulated atoms.

  6. Estimating whole body intermuscular adipose tissue from single cross-sectional magnetic resonance images

    PubMed Central

    Ruan, Xiang Yan; Gallagher, Dympna; Harris, Tamara; Albu, Jeanine; Heymsfield, Steven; Kuznia, Patrick; Heshka, Stanley

    2009-01-01

    Estimating whole body intermuscular adipose tissue from single cross-sectional magnetic resonance images. Intermuscular adipose tissue (IMAT), a novel fat depot linked with metabolic abnormalities, has been measured by whole body MRI. The cross-sectional slice location with the strongest relation to total body IMAT volume has not been established. The aim was to determine the predictive value of each slice location and which slice locations provide the best estimates of whole body IMAT. MRI quantified total adipose tissue of which IMAT, defined as adipose tissue visible within the boundary of the muscle fascia, is a subcomponent. Single-slice IMAT areas were calculated for the calf, thigh, buttock, waist, shoulders, upper arm, and forearm locations in a sample of healthy adult women, African-American [n = 39; body mass index (BMI) 28.5 ± 5.4 kg/m2; 41.8 ± 14.8 yr], Asian (n = 21; BMI 21.6 ± 3.2 kg/m2; 40.9 ± 16.3 yr), and Caucasian (n = 43; BMI 25.6 ± 5.3 kg/m2; 43.2 ± 15.3 yr), and Caucasian men (n = 39; BMI 27.1 ± 3.8 kg/m2; 45.2 ± 14.6 yr) and used to estimate total IMAT groups using multiple-regression equations. Midthigh was the best, or near best, single predictor in all groups with adjusted R2 ranging from 0.49 to 0.84. Adding a second and third slice further increased R2 and reduced the error of the estimate. Menopausal status and degree of obesity did not affect the location of the best single slice. The contributions of other slice locations varied by sex and race, but additional slices improved predictions. For group studies, it may be more cost-effective to estimate IMAT based on one or more slices than to acquire and segment for each subject the numerous images necessary to quantify whole body IMAT. PMID:17053107

  7. Compressible f-plane solutions to body forces, heatings, and coolings, and application to the primary and secondary gravity waves generated by a deep convective plume

    NASA Astrophysics Data System (ADS)

    Vadas, S. L.

    2013-05-01

    We derive the analytic, linear, f-plane compressible solutions to local, interval, 3-D horizontal and vertical body forces, and heat/coolings in an isothermal, unsheared, and nondissipative atmosphere. These force/heat/coolings oscillate at the frequency â and turn on and off smoothly over a finite interval in time. The solutions include a mean response, gravity waves (GWs), and acoustic waves (AWs). The excited waves span a large range of horizontal/vertical scales and frequencies ?. We find that the compressible solutions are important for GWs with vertical wavelengths |?z|>(1 to 2)×??if the depth of the force/heat/cooling is greater than the density scale height ?. We calculate the primary GWs excited by a deep convective plume, ray trace them into the thermosphere, and calculate the body force/heat/coolings which result where the GWs dissipate. We find that the force/heat/cooling amplitudes are up to ˜40% smaller using the compressible (as compared to the Boussinesq) GW spectra. For a typical plume, the force/heat/coolings are deeper than ? and have maximum amplitudes of ˜0.2 to 0.6 m/s2and ˜0.06 to 0.15 K/s for solar maximum to minimum, respectively. The heat/cooling consists of dipoles at z˜150-200 km and a heating at z˜240-260 km. We find that the compressible solutions are necessary for calculating the secondary GWs excited by these thermospheric force/heat/coolings.

  8. The magnetic field, force and inductance of the system consisting of a thin ellipsoidal coil and a ferromagnetic ellipsoid

    Microsoft Academic Search

    Jan Purczynski; Pawel Rolicz; Ryszard Sikora

    1975-01-01

    The method of separation of variables has been applied to determine the magnetic field of the system consisting of a thin\\u000a ellipsoidal coil and a ferromagnetic ellipsoid of revolution. The inductance and the force acting between the coil and the\\u000a ellipsoid are also examined.

  9. Optimal Design to Increase Thrust Force in ElectroMagnetic Linear Actuator for Fatigue and Durability Test Machine

    Microsoft Academic Search

    Yul-Kyu Son; Yong-Min You; Byung-Il Kwon

    2011-01-01

    This paper introduces the Halbach array and an optimal design process to effectively increase thrust force and decrease the yoke volume in electro-magnetic linear actuator for fatigue and durability test machine. The finite element method is used for dynamic response analysis of the thrust, velocity and displacement. In the optimal design process, sampling points are chosen by Latin hypercube sampling

  10. Effect of the size of GBCO-Ag secondary magnet on the static forces performance of linear synchronous motors

    E-print Network

    Zheng, Jun; Shi, Yunhua; He, Dabo; Jing, Hailian; Li, Jing; Deng, Zigang; Wang, Suyu; Wang, Jiasu; Cardwell, David A.

    2014-01-01

    motors (LSMs) as superconducting secondary magnets, what will result in a reduced volume and weight as well as in higher force density and efficiency of these devices when compared to conventional PMs. The focus of this paper is on the effect of size...

  11. A New Magnetic-Field Electron-Irradiation Treatment for Producing Low-Coersive-Force Rectangular Hysteresis Loops in Supermalloy

    Microsoft Academic Search

    D. I. Gordon; R. S. Sery

    1964-01-01

    True magnetic-annealing effects, i. e., hysteresis loops with high remanence and rectangularity, with no increase in coercive force, can be induced in flat ring samples of bulk .015 cm thick polycrystalline Supermalloy at low temperatures by a new electron-radiomagnetic treatment. This treatment is possible because radiation produces vacancies in excess of the thermal equilibrium number, and this excess of vacancies

  12. Do the Billecocha normal faults (Ecuador) reveal extension due to lithospheric body forces in the northern Andes?

    NASA Astrophysics Data System (ADS)

    Ego, F.; Sébrier, M.; Carey-Gailhardis, E.; Beate, B.

    1996-11-01

    Active compressional and transcurrent structures are widely reported for the entire northern Andes, whereas there is no clear evidence of extensional tectonics in that region. In contrast, both active compressional and extensional structures occur extensively in the Central Andes. Extensional tectonism in the central Andes occurs mainly in high plateaus of large wavelength (? 100 km), and is interpreted to have resulted from the effect of compensated high topography at the lithospheric scale. The observation of Holocene normal faults on the low wavelength (? 15 km) Billecocha high plateau in the northern Ecuadorian Andes raises a problem. Could the lithospheric body forces be the cause of the normal faulting in a chain with a mean altitude of ? 2800 m? Compared to the central Andes, where normal faulting is widely distributed across the chain, normal faulting on the Billecocha plateau is concentrated in a restricted 4-km-wide zone. In addition, normal faulting does not extend further than a few kilometres eastward, where compressive structures have been observed. Considering the local character of the extension, body forces at the lithospheric scale cannot be responsible for this normal faulting, and thus we can preclude a significant lowering of the magnitude of ?Hmax in the northern Andes with respect to the central Andes. Analysis of these normal faults shows that normal faulting occurred between 10,000 yr and 6000 yr B.P. In addition, the relationship between the geometrical parameters (vertical throw and rupture length) of the major normal fault differs significantly from that given empirically by methods based on scale laws. In such a case, the Billecocha normal faults are unlikely to have a tectonic origin. Various local processes (e.g., gravity gliding, "sackung") that may be possible are contemplated for triggering the normal faulting. In addition, a theoretical simple 2-D model is proposed in where local conditions peculiar to the plateau (structure, glaciation) and the surrounding areas are taken into account. In this model, normal faulting occurs by shearing along the planes of weakness (bedding planes) in response to the elastic rebound of the fluid-saturated plateau, which prevailed after the last glaciation.

  13. An improved computational technique for calculating electromagnetic forces and power absorptions generated in spherical and deformed body in levitation melting devices

    Microsoft Academic Search

    Jin-Ho Zong; Julian Szekely; E. Schwart

    1992-01-01

    An improved computational technique for calculating the electromagnetic force field, the power absorption, and the deformation of an electromagnetically levitated metal sample is described. The technique is based on the volume integral method but represents a substantial refinement: the coordinate transformation employed allows the efficient treatment of a broad class of rotationally symmetrical bodies. Compound results are presented to represent

  14. Providing haptic feedback in robot-assisted minimally invasive surgery: a direct optical force-sensing solution for haptic rendering of deformable bodies.

    PubMed

    Ehrampoosh, Shervin; Dave, Mohit; Kia, Michael A; Rablau, Corneliu; Zadeh, Mehrdad H

    2013-01-01

    This paper presents an enhanced haptic-enabled master-slave teleoperation system which can be used to provide force feedback to surgeons in minimally invasive surgery (MIS). One of the research goals was to develop a combined-control architecture framework that included both direct force reflection (DFR) and position-error-based (PEB) control strategies. To achieve this goal, it was essential to measure accurately the direct contact forces between deformable bodies and a robotic tool tip. To measure the forces at a surgical tool tip and enhance the performance of the teleoperation system, an optical force sensor was designed, prototyped, and added to a robot manipulator. The enhanced teleoperation architecture was formulated by developing mathematical models for the optical force sensor, the extended slave robot manipulator, and the combined-control strategy. Human factor studies were also conducted to (a) examine experimentally the performance of the enhanced teleoperation system with the optical force sensor, and (b) study human haptic perception during the identification of remote object deformability. The first experiment was carried out to discriminate deformability of objects when human subjects were in direct contact with deformable objects by means of a laparoscopic tool. The control parameters were then tuned based on the results of this experiment using a gain-scheduling method. The second experiment was conducted to study the effectiveness of the force feedback provided through the enhanced teleoperation system. The results show that the force feedback increased the ability of subjects to correctly identify materials of different deformable types. In addition, the virtual force feedback provided by the teleoperation system comes close to the real force feedback experienced in direct MIS. The experimental results provide design guidelines for choosing and validating the control architecture and the optical force sensor. PMID:24156342

  15. Large Eddy Simulations of forced ignition of a non-premixed bluff-body methane flame with Conditional Moment Closure

    SciTech Connect

    Triantafyllidis, A.; Mastorakos, E. [Hopkinson Laboratory, Department of Engineering, University of Cambridge, Cambridge CB2 1PZ (United Kingdom); Eggels, R.L.G.M. [Rolls Royce Deutschland, Blankenfelde-Mahlow (Germany)

    2009-12-15

    Large Eddy Simulations (LES) of forced ignition of a bluff-body stabilised non-premixed methane flame using the Conditional Moment Closure (CMC) turbulent combustion model have been performed. The aim is to investigate the feasibility of the use of CMC/LES for ignition problems and to examine which, if any, of the characteristics already observed in related experiments could be predicted. A three-dimensional formulation of the CMC equation was used with simple and detailed chemical mechanisms, and sparks with different parameters (location, size) were used. It was found that the correct pattern of flame expansion and overall flame appearance were predicted with reasonable accuracy with both mechanisms, but the detailed mechanism resulted in expansion rates closer to the experiment. Moreover, the distribution of OH was predicted qualitatively accurately, with patches of high and low concentration in the recirculation zone during the ignition transient, consistent with experimental data. The location of the spark relative to the recirculation zone was found to determine the pattern of the flame propagation and the total time for the flame stabilisation. The size was also an important parameter, since it was found that the flame extinguishes when the spark is very small, in agreement with expectations from experiment. The stabilisation mechanism of the flame was dominated by the convection and sub-grid scale diffusion of hot combustion products from the recirculation zone to the cold gases that enter the burner, as revealed by analysis of the CMC equation. (author)

  16. Design of superconducting magnetic bearings with high levitating force for flywheel energy storage systems

    Microsoft Academic Search

    Z. Xia; Q. Y. Chen; K. B. Ma; C. K. McMichael; M. Lamb; R. S. Cooley; P. C. Fowler; W. K. Chu

    1995-01-01

    Hybrid superconducting magnetic bearing (SMB), using YBCO high temperature superconductors (HTS) coupled with permanent magnets, has been implemented into a flywheel energy storage (FES) system prototype. The hybrid SMB design uses permanent magnets to levitate the rotor weighing 19 kg and superconductors to stabilize the inherently unstable magnet-magnet interactions. The SMB bearings are brought into action under convenient field-cooled conditions.

  17. Design and development of scanning eddy current force microscopy for characterization of electrical, magnetic and ferroelectric properties with nanometer resolution

    NASA Astrophysics Data System (ADS)

    Nalladega, Vijayaraghava

    This dissertation describes the design and development of a new high-resolution electrical conductivity imaging technique combining the basic principles of eddy currents and atomic force microscopy (AFM). An electromagnetic coil is used to generate eddy currents in an electrically conducting material. The eddy currents induced in the sample are detected and measured with a magnetic tip attached to the AFM cantilever. The interaction of eddy currents with the magnetic tip-cantilever is theoretically modeled. The model is then used to estimate the eddy current forces generated in a typical metallic material placed in induced current field. The magnitude of the eddy current force is directly proportional to the electrical conductivity of the sample. The theoretical eddy current forces are used to design a magnetic tip-cantilever system with appropriate magnetic field and spring constant to facilitate the development of a high-resolution, high sensitivity electrical conductivity imaging technique. The technique is used to experimentally measure eddy current forces in metals of different conductivities and compared with theoretical and finite element models. The experimental results show that the technique is capable of measuring pN range eddy current forces. The experimental eddy current forces are used to determine the electrical resistivity of a thin copper wire and the experimental value agrees with the bulk resistivity of copper reported in literature. The imaging capabilities of the new technique are demonstrated by imaging the electrical conductivity variations in a composite sample and a dual-phase titanium alloy in lift mode AFM. The results indicate that this technique can be used to detect very small variations in electrical conductivity. The spatial resolution of the technique is determined to be about 25 nm by imaging carbon nanofibers reinforced in polymer matrix. Since AFM is extensively used to characterize nanomaterials, the newly developed technique is used to characterize metallic nanoparticles. The results showed for the first time that it is possible to image helicons in nanometallic particles at low electromagnetic frequencies using an AFM. The theoretical analysis of the helicons in nanostructured materials is presented using the concept of effective mass of electrons. The primary objective of the research work reported in this dissertation is to develop a high-resolution electrical conductivity imaging system. However, the interaction of induced currents with different materials gives rise to different interaction forces. If an appropriate probe and an imaging mode are used, different material properties can be characterized using the same experimental setup. Therefore, in this study, magneto-acoustic, magnetic and dielectric properties of materials placed in induced current fields are studied. The modifications necessary to image these properties are discussed in detail. The advantages, limitations and applications of the new methodology are discussed.

  18. Equilibrium of magnetic fields with arbitrary interweaving of the lines of force. I - Discontinuities in the torsion

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1986-01-01

    Consideration is given to the static force-free equilibrium of a magnetic field in which all of the lines of force connect without knotting between parallel planes. The field is formed by continuous deformation from an initial uniform field, and is conventiently described in terms of the scalar function psi, which is the stream function for the incompressible wrapping and interweaving of the lines of force. Local compression and expansion of the lines of force is described in terms of the scalar function Phi. Equilibrium in the field requires satisfaction of two independent equations which cannot be accomplished without the full freedom of both psi and Phi. It is shown that discontinuities in the torsional characteristics of the lines occur when psi is predetermined by an arbitrary pattern. Discontinuities in the winding pattern of the lines can lead to discontinuities in the associated current sheets.

  19. Three-dimensional force microscope: A nanometric optical tracking and magnetic manipulation system for the biomedical sciences

    NASA Astrophysics Data System (ADS)

    Fisher, J. K.; Cummings, J. R.; Desai, K. V.; Vicci, L.; Wilde, B.; Keller, K.; Weigle, C.; Bishop, G.; Taylor, R. M.; Davis, C. W.; Boucher, R. C.; O'Brien, E. Timothy; Superfine, R.

    2005-05-01

    We report here the development of a three-dimensional (3D) magnetic force microscope for applying forces to and measuring responses of biological systems and materials. This instrument combines a conventional optical microscope with a free-floating or specifically bound magnetic bead used as a mechanical probe. Forces can be applied by the bead to microscopic structures of interest (specimens), while the reaction displacement of the bead is measured. This enables 3D mechanical manipulations and measurements to be performed on specimens in fluids. Force is generated by the magnetically permeable bead in reaction to fields produced by external electromagnets. The displacement is measured by interferometry using forward light scattered by the bead from a focused laser beam. The far-field interference pattern is imaged on a quadrant photodetector from which the 3D displacement can be computed over a limited range about the focal point. The bead and specimen are mounted on a 3D translation stage and feedback techniques are used to keep the bead within this limited range. We demonstrate the system with application to beads attached to cilia in human lung cell cultures.

  20. Application of small-angle neutron scattering to the study of forces between magnetically chained monodisperse ferrofluid emulsion droplets

    SciTech Connect

    Jain, Dr Nirmesh [University of Sydney, Australia] [University of Sydney, Australia; Liu, Dr C K [Institute of Materials research and Engineering, A-STAR, Singapore] [Institute of Materials research and Engineering, A-STAR, Singapore; Hawkett, Dr B. S. [University of Sydney, Australia] [University of Sydney, Australia; Warr, G. G. [University of Sydney, Australia] [University of Sydney, Australia; Hamilton, William A [ORNL] [ORNL

    2014-01-01

    The optical magnetic chaining technique (MCT) developed by Leal-Calderon, Bibette and co-workers in the 1990 s allows precise measurements of force profiles between droplets in monodisperse ferrofluid emulsions. However, the method lacks an in-situ determination of droplet size and therefore requires the combination of separately acquired measurements of droplet chain periodicity versus an applied magnetic field from optical Bragg scattering and droplet diameter inferred from dynamic light scattering (DLS) to recover surface force-distance profiles between the colloidal particles. Compound refractive lens (CRL) focussed small-angle scattering (SANS) MCT should result in more consistent measurements of droplet size (form factor measurements in the absence of field) and droplet chaining period (from structure factor peaks when the magnetic field is applied); and, with access to shorter length scales, extend force measurements to closer approaches than possible by optical measurements. We report on CRL-SANS measurements of monodisperse ferrofluid emulsion droplets aligned in straight chains by an applied field perpendicular to the incident beam direction. Analysis of the scattering from the closely spaced droplets required algorithms that carefully treated resolution and its effect on mean scattering vector magnitudes in order to determine droplet size and chain periods to sufficient accuracy. At lower applied fields scattering patterns indicate structural correlations transverse to the magnetic field direction due to the formation of intermediate structures in early chain growth.