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1

Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces  

NASA Technical Reports Server (NTRS)

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

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

2003-01-01

2

Longitudinal magnet forces?  

NASA Astrophysics Data System (ADS)

The Ampere electrodynamics of metallic conductors and experiments supporting it predict that the interaction of a current-carrying wire with its own magnetic field should produce longitudinal mechanical forces in the conductor, existing in addition to the transverse Lorentz forces. The longitudinal forces should stretch the conductor and have been referred to as Ampere tension. In 1964 it was discovered that a current pulse would break a straight copper wire into many fragments without visible melting. A metallurgical examination of the pieces confirmed that the metal parted in the solid state. The same observation has now been made with aluminum wires. In the latest experiments the wire was bent into a semicircle and arc-connected to a capacitor discharge circuit. The arc connections ruled out rupture by Lorentz hoop tension and indicated the longitudinal forces may also arise in circular magnet windings. Explanations of wire fragmentation by thermal shock, longitudinal stress waves, Lorentz pinch-off, bending stresses, and material defects have been considered and found unconvincing. Computed Ampere tensions would be sufficient to fracture hot wires. The Ampere tension would double the hoop tension normally expected in dipole magnets. This should be borne in mind in the design of large dipole magnets contemplated for MHD power generators and railgun accelerators.

Graneau, P.

1984-03-01

3

High resolution switching magnetization magnetic force microscopy  

NASA Astrophysics Data System (ADS)

We introduce switching magnetization magnetic force microscopy based on two-pass scanning atomic force microscopy with reversed tip magnetization between the scans. Within this approach the sum of the scanned data with reversed tip magnetization depicts local van der Waals forces, while their differences map the local magnetic forces. Here we implement this method by fabricating low-momentum magnetic probes that exhibit magnetic single domain state, which can be easily reversed in low external field during the scanning. Measurements on high-density parallel and perpendicular magnetic recording media show enhanced spatial resolution of magnetization.

Cambel, V.; Precner, M.; Fedor, J.; Šoltýs, J.; Tóbik, J.; Š?epka, T.; Karapetrov, G.

2013-02-01

4

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.

5

NTNU Java: Free-Body Force Diagram  

NSDL National Science Digital Library

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

Hwang, Fu-Kwun

2005-02-07

6

Investigating Magnetic Force Fields  

NSDL National Science Digital Library

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

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

2012-03-18

7

Optimizing magnetization orientation of permanent magnets for maximal gradient force  

Microsoft Academic Search

The force exercised on a permanent magnet (PM) in a nonuniform field (gradient force) is dependent on the magnetization orientation of the magnet. In this paper, it is shown theoretically that the gradient force is greatest when the magnetization through the magnet, or at least at its surface, is collinear with the external field. The formulae for calculating the force

Arvi Kruusing

2001-01-01

8

An assessment of body force representations for compressor stall simulation  

E-print Network

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

Kerner, Jonathan (Jonathan H.)

2010-01-01

9

Three-body critical Casimir forces  

E-print Network

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 along their center-to-center axis, 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.

T. Mattos; L. Harnau; S. Dietrich

2014-08-29

10

Modeling forces on the human body  

NASA Astrophysics Data System (ADS)

Several simulations involving the human body, using the simulation software Interactive Physics™, are used to analyze the forces during both static situations and dynamic collisions. The connection of the simulations with the biological sciences and with sports activities should make them appealing to both high school and college-level physics students.

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

1999-11-01

11

Optimizing magnetization orientation of permanent magnets for maximal gradient force  

NASA Astrophysics Data System (ADS)

The force exercised on a permanent magnet (PM) in a nonuniform field (gradient force) is dependent on the magnetization orientation of the magnet. In this paper, it is shown theoretically that the gradient force is greatest when the magnetization through the magnet, or at least at its surface, is collinear with the external field. The formulae for calculating the force between an axis-symmetric optimal magnet and a coaxial axis-symmetric coil are presented. Using the finite element method (FEM), calculations of the magnetic field distribution of an optimal cylindrical magnet and some its approximations are performed. The forces between these magnets and a pancake coil are computed and compared. For a system consisting of a magnet with a height of 1 unit and a diameter of 2 units and magnetization invariant in field and an annular pancake coil with a diameter of 2.4 units, a thickness of 0.2 units, an inner diameter of 0.4 units and a distance from the magnet of 0.2 units, the force on the optimal magnet was 1.44 times greater than the force on an axially magnetized magnet of the same size and magnetization magnitude. The optimal magnetization may be approximated by magnetization inclined at a constant angle to the axis and by a combination of axially and radially magnetized sections. With magnetization at a constant angle to the axis in the axis plane, the force was greatest when the angle was about 45°, being 1.38-fold compared to the force on an axially magnetized magnet. When the magnet was composed of an axially magnetized cylindrical core and a radially magnetized outer ring, the force was greatest when the volume of the core was approximately equal to the volume of the ring, being 1.26-fold compared to the force on an axially magnetized magnet. The optimal magnet and its approximations also provided a reduced stray field. A short review of methods of the fabrication of permanent magnets (PMs) with a continuous variation of the magnetization orientation and with radial magnetization orientation is given. The results of this study can be used to design linear electromagnetic (micro)actuators.

Kruusing, Arvi

2001-09-01

12

Magnetic Force Between Magnetic Nano Probes at Optical Frequency  

E-print Network

Magnetic force microscopy based on the interaction of static magnetic materials was demonstrated in the past with resolutions in the order of nanometers. Measurement techniques based on forces between electric dipoles oscillating at optical frequencies have been also demonstrated leading to the standard operation of the scanning force microscope (SFM). However the investigations of a SFM based on the magnetic force generated by magnetic dipole moments oscillating at optical frequencies has not been tackled yet. With this goal in mind we establish a theoretical model towards observable magnetic force interaction between two magnetically polarizable nanoparticles at optical frequency and show such a force to be in the order of piconewtons which could be in principle detected by conventional microscopy techniques. Two possible principles for conceiving magnetically polarizable nano probes able to generate strong magnetic dipoles at optical frequency are investigated based on silicon nanoparticles and on clusters...

Guclu, Caner; Capolino, Filippo

2014-01-01

13

Assessment of a body force representation for compressor stability estimation  

E-print Network

This thesis presents a methodology for the integration of blade row body forces, derived from axisymmetric and three- dimensional flow fields, for use in the stability analysis of axial compressors. The body force database ...

Patel, Amish A. (Amish Ashok)

2009-01-01

14

136Sn and three body forces  

E-print Network

New experimental data on 2+ energies of 136,138Sn confirms the trend of lower 2+ excitation energies of even-even tin isotopes with N > 82 compared to those with NE2; 6+ -> 4+)) of these nuclei, simultaneously, apart from one whose matrix elements have been changed empirically to produce mixed seniority states by weakening pairing. We have shown that the experimental result also shows good agreement with the theory in which three body forces have been included in a realistic interaction. The new theoretical results on transition probabilities have been discussed to identify the experimental quantities which will clearly distinguish between different views.

M. Saha Sarkar; S. Sarkar

2014-11-10

15

Cryogenic magnetic force microscope M. Rosemana)  

E-print Network

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

Grütter, Peter

16

Magnetic force and work: an accessible example  

NASA Astrophysics Data System (ADS)

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

Gates, Joshua

2014-05-01

17

Static forces in a superconducting magnet bearing  

SciTech Connect

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

Stoye, P.; Fuchs, G. [Institut fuer Festkoerper- und Werkstofforschung, Dresden (Germany)] [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

18

A many-body force decomposition with applications to flow about bluff bodies  

Microsoft Academic Search

The study presents a force theory for incompressible flow about several solid bodies, which enables us to examine the force contribution to each body from individual fluid elements. By employing auxiliary potential functions, we decompose hydrodynamic forces in terms of the unsteadiness of the incoming stream, vorticity within the flow, and surface vorticity on the solid bodies. The usefulness of

Chien-C. Chang; Shih-Hao Yang; Chin-Chou Chu

2008-01-01

19

Development of a body force description for compressor stability assessment  

E-print Network

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

Kiwada, George (George Ford)

2008-01-01

20

Levitation forces in bearingless permanent magnet motors  

Microsoft Academic Search

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

W. Amrhein; S. Silber; K. Nenninger

1999-01-01

21

Three-Body Nuclear Forces from a Matrix Model  

E-print Network

We compute three-body nuclear forces at short distances by using the nuclear matrix model of holographic QCD proposed in our previous paper with P. Yi. We find that the three-body forces at short distances are repulsive for (a) aligned three neutrons with averaged spins, and (b) aligned proton-proton-neutron / proton-neutron-neutron. These indicate that in dense states of neutrons such as cores of neutron stars, or in Helium-3 / tritium nucleus, the repulsive forces are larger than the ones estimated from two-body forces only.

Koji Hashimoto; Norihiro Iizuka

2010-05-24

22

Modeling solar force-free magnetic fields  

NASA Astrophysics Data System (ADS)

A class of nonlinear force-free magnetic fields is presented, described in terms of the solutions to a second-order, nonlinear ordinary differential equation. These magnetic fields are three-dimensional, filling the infinite half-space above a plane where the lines of force are anchored. They model the magnetic fields of the sun over active regions with a striking geometric realism. The total energy and the free energy associated with the electric current are finite and can be calculated directly from the magnetic field at the plane boundary using the virial theorem. In the study of solar magnetic fields with data from vector magnetographs, there is a long-standing interest in devising algorithms to extrapolate for the force-free magnetic field in a given domain from prescribed field values at the boundary. The closed-form magnetic fields of this paper open up an opportunity for testing the reliability and accuracy of algorithms that claim the capability of performing this extrapolation. The extrapolation procedure as an ill-posed mathematical problem is discussed.

Low, B. C.; Lou, Y. Q.

1990-03-01

23

Many-body forces and the cluster decomposition  

Microsoft Academic Search

Direct-interaction dynamics is considered in the relativistic Hamiltonian constraint formalism. It is proven that the Todorov-Komar equations for an N-particle system (N>2) of mutually interacting particles have no solutions that permit interaction if only two-body forces are admitted. The inclusion of many-body forces leads to a system of equations that determines allowed classes of such forces recursively. Starting with given

F. Rohrlich

1981-01-01

24

Levitation forces in bearingless permanent magnet motors  

SciTech Connect

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

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

1999-09-01

25

Development of magnetic force modeling equipment for magnetic levitation system  

Microsoft Academic Search

In this paper, we propose a modeling equipment that obtains every equilibrium point of a magnetic levitation system automatically. To obtain every equilibrium point, we develop an automatic modeling equipment that measures the magnetic force exerted on the levitation object, the coil current of electromagnet, and the distance between the levitation object and the electromagnet. The modeling equipment is composed

Ji-Hyuk Yang; Young-Sam Lee; Oh-Kyu Kwon

2010-01-01

26

Magnetic force control technique in industrial application  

NASA Astrophysics Data System (ADS)

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

Nishijima, S.

2010-11-01

27

Forces on interaction region quadrupoles and dipoles due to a detector solenoid magnet  

Microsoft Academic Search

We will only discuss detector solenoids which have a main component, as well as a radial fringe field component, but no azimuthal component. Both components can produce substantial Lorentz forces on the accelerator magnet coils. In the body of the magnet coils, where the current is only in the ±z direction, the solenoid Bz component generates no force only the

James J. Welch; Gerald F. Dugan

1997-01-01

28

Measuring Ligand-Receptor Unbinding Forces with Magnetic Beads: Molecular Leverage  

E-print Network

Measuring Ligand-Receptor Unbinding Forces with Magnetic Beads: Molecular Leverage Z. Guttenberg, A by a magnetic bead adhered to the membrane. The forces exerted on pinning centers can be deduced using classical) the adhesion proteins are embedded in a soft body (the cell membrane) that is known to deform very considerably

Bausch, Andreas

29

Computing nonlinear force free coronal magnetic fields  

E-print Network

Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.

T. Wiegelmann; T. Neukirch

2008-01-21

30

Treatment of body forces in boundary element design sensitivity analysis  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

31

Magnetic Force and Work: An Accessible Example  

ERIC Educational Resources Information Center

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

Gates, Joshua

2014-01-01

32

Electric and Magnetic Forces: Electric Charges  

NSDL National Science Digital Library

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

National Science Teachers Association (NSTA)

2008-10-30

33

Dynamical friction force exerted on spherical bodies  

E-print Network

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

O. Esquivel; B. Fuchs

2007-04-30

34

Magnetic force microscopy studies of submicron and nanoscale magnet arrays  

NASA Astrophysics Data System (ADS)

Magnetic structure and magnetization reversal of lithographically patterned submicron and nanometer scaled magnets with elliptical, disk, ring shapes, and pseudo spin valve structures, were studied by magnetic force microscopy. Magnetic measurements were performed with a custom built vacuum magnetic force microscopy with in-situ in plane magnetic fields. The MFM has been optimized with a force gradient sensitivity as high as 1 x 10-6 N/m. By using various magnetic tips, operating in different modes, and studying different samples, the effect of the magnetic tip stray field induced distortion of the magnetic state of a submicron sized magnet is presented. Through the systematic study, a method of how to detect and to avoid these irreversible distortions is also presented. A local 'hysteresis loop' technique has been invented to study the abrupt switching behavior of individual elements. In arrays of elongated magnetic particle array, the aspect ratio dependence of the switching indicates that the vortex state can be trapped inside the elements and form an energetic stable state, leading to a broad switching field distribution. In an array of 70 nm wide pseudo spin valve elements, parallel and antiparallel single domain configurations are found. Major and minor hysteresis loops as well as inter-layer coupling are investigated. We found that interlayer coupling leads to switching field variations. In a Permalloy disk array, the vortex state with vortex core singularity is found. The switching mechanism through the nucleation and annihilation processes is demonstrated by the local hysteresis loop. An interdot coupling-induced anisotropic switching is observed. In Permalloy ring structures, a vortex state and an 'onion' state are found. The onion state in permalloy rings with diameters of 5mum is found to be a flux closure state with a head to head domain wall. The switching behavior of these ring elements is found to be domain wall propagation.

Zhu, Xiaobin

35

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

36

A compact high field magnetic force microscope.  

PubMed

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

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

2014-12-01

37

Modeling Forces on the Human Body.  

ERIC Educational Resources Information Center

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

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

1999-01-01

38

Resonance behavior of liquid bridges under axial and lateral oscillating total body forces  

E-print Network

Resonance behavior of liquid bridges under axial and lateral oscillating total body forces M bridges that are magnetically levitated in air against gravity are subjected to either axial or lateral technology and nature. An axially symmetric bridge supported by two equal, coaxial disks at each end

Taylor, Philip L.

39

Microrheology of cells with magnetic force modulation atomic force microscopy.  

PubMed

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

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

2014-04-01

40

Nonlinear gravitational self-force: Field outside a small body  

NASA Astrophysics Data System (ADS)

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

Pound, Adam

2012-10-01

41

Magnet polepiece design for uniform magnetic force on superparamagnetic beads  

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

42

Magnetic force-induced damping effect for magnetic bearing motor  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

43

Integrated Cantilever Loop Probe for Magnetic Resonance Force Microscopy  

Microsoft Academic Search

The measurement of magnetic fields, especially at the nanoscale, has become an issue of considerable interest. Applications include quantum computing, data storage, and magnetic resonance imaging (MRI). At the interface between conventional atomic force microscopy and MRI lies magnetic resonance force microscopy. Radio frequency (RF) waves excite electrons in a sample, and a magnetic cantilever probe can image a slice

Douglas Lagally

2005-01-01

44

Controlling a magnetic force microscope to track a magnetized nanosize particle  

E-print Network

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

Andersson, Sean B.

45

Quantitative measurement of the magnetic moment of individual magnetic nanoparticles by magnetic force microscopy.  

PubMed

The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10(-18) A m(2) under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology. PMID:22730177

Sievers, Sibylle; Braun, Kai-Felix; Eberbeck, Dietmar; Gustafsson, Stefan; Olsson, Eva; Schumacher, Hans Werner; Siegner, Uwe

2012-09-10

46

Quantitative Measurement of the Magnetic Moment of Individual Magnetic Nanoparticles by Magnetic Force Microscopy  

PubMed Central

The quantitative measurement of the magnetization of individual magnetic nanoparticles (MNPs) using magnetic force microscopy (MFM) is described. Quantitative measurement is realized by calibration of the MFM signal using an MNP reference sample with traceably determined magnetization. A resolution of the magnetic moment of the order of 10?18 A m2 under ambient conditions is demonstrated, which is presently limited by the tip's magnetic moment and the noise level of the instrument. The calibration scheme can be applied to practically any magnetic force microscope and tip, thus allowing a wide range of future applications, for example in nanomagnetism and biotechnology. PMID:22730177

Sievers, Sibylle; Braun, Kai-Felix; Eberbeck, Dietmar; Gustafsson, Stefan; Olsson, Eva; Schumacher, Hans Werner; Siegner, Uwe

2012-01-01

47

Boosting oncolytic adenovirus potency with magnetic nanoparticles and magnetic force.  

PubMed

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

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

2010-08-01

48

Magnetic force microscopy applied in magnetic data storage technology  

NASA Astrophysics Data System (ADS)

Microstructured thin-film elements with critical dimensions of 1 ?m or less play an increasingly important role in magnetic components for information technology applications. Devices that are directly based on such microstructures are key components in magnetoelectronics for storage and sensor applications as well as modern concepts which are likely to substitute today's hard disk drives. Basic research on magnetic materials as well as industrial applications create an increasing demand for high-resolution magnetic imaging methods. One such method is magnetic force microscopy (MFM). In spite of considerable achievements, MFM also has some serious shortcomings, which have not been overcome to date. Under normal circumstances, the method yields only qualitative information about the magnetic object and it is difficult to improve the resolution to values below 100 nm. In this paper, we will report on advanced MFM probe preparation, based on electron beam methods, and discuss the possibilities for batch fabrication of such advanced MFM tips. We show that the advanced probes allow high-resolution imaging of fine magnetic structures within thin-film permalloy elements without perturbing them. Additionally, we present high-frequency MFM measurements on a hard disk write head.

Koblischka, M. R.; Hewener, B.; Hartmann, U.; Wienss, A.; Christoffer, B.; Persch-Schuy, G.

49

Body Force Model for the Aerodynamics of Inclined Perforated Surfaces  

E-print Network

Body Force Model for the Aerodynamics of Inclined Perforated Surfaces Juntao Xiong, Andrew Johnson.2514/1.J051699 This is a joint experimental and computational research effort on the aerodynamics aspects of the aerodynamics of wedge FFDs. The following sections present the experimental

Papamoschou, Dimitri

50

Magnetic dynamos in accreting planetary bodies  

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

51

Investigation of many-body forces in krypton and xenon  

SciTech Connect

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

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

1988-10-15

52

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

PubMed Central

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

Neuman, Keir C.; Nagy, Attila

2012-01-01

53

Many-Body Force and Mobility Measurements in Colloidal Systems  

Microsoft Academic Search

We demonstrate a technique for simultaneously measuring each component of the force vectors and mobility tensor of a small collection of colloidal particles based on observing a set of particle trajectories. For a few-body system of micron-sized polymer beads in oil separated by several particle radii, we find that the mobility tensor is well-described by a pairwise Stokeslet model. This

Jason W. Merrill; Sunil K. Sainis; Jerzy Blawzdziewicz; Eric R. Dufresne

2009-01-01

54

Spin-motive force due to a gyrating magnetic vortex.  

PubMed

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

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

2012-01-01

55

On the force on a body moving in a fluid  

NASA Astrophysics Data System (ADS)

It is well-known that freely falling or rising objects and self-propelling bodies shed vorticity. It is then a natural question to ask how to define the forces (drag and lift) experienced by the body in terms of the vorticity distribution in the surrounding fluid and the normal velocity of the body surface, since these define the velocity distribution uniquely. In this paper we outline the answer given by Burgers in an almost forgotten paper from 1920, and point at the close relationship of Burgers's ideas in these matters with those of Sir James Lighthill. The connection with more recent work by Kambe and Howe is established and we briefly discuss related issues concerning "vortex methods" and "vortex sound".

Biesheuvel, Arie; Hagmeijer, Rob

2006-10-01

56

LABORATORY VI MAGNETIC FIELDS AND FORCES  

E-print Network

PROBLEM #1: PERMANENT MAGNETS You have a job working a company that designs magnetic resonance imaging that the different magnet configurations in each figure do not interact with the magnets in the other figures. WARM MAGNETS Lab VI - 3 Before you start, you should review the Warm-up questions for Problem #1

Minnesota, University of

57

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

E-print Network

MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy

Fornberg, Bengt

58

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

NASA Astrophysics Data System (ADS)

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

Bihun, Oksana; Calogero, Francesco

2013-10-01

59

A flow simulation study of protein solution under magnetic forces  

NASA Astrophysics Data System (ADS)

We have developed a superconducting magnet system generating magnetic forces able to compensate gravity and suppress convection of diamagnetic protein solution from which protein crystals precipitate. A simulation model has been proposed to elucidate the motion of protein solutions and search for the optimal conditions of the crystal formation process. This model incorporates general, non-uniform magnetic forces as external forces, while the previous models involve only simple, uniform magnetic forces. The simulation results indicate that the vertical component can suppress the convection of protein solution, while the horizontal component induces minimal convection. We, therefore, need to take into account the both components when considering the formation of protein crystals under magnetic forces.

Okada, Hidehiko; Hirota, Noriyuki; Matsumoto, Shinji; Wada, Hitoshi

2013-02-01

60

Computation of unbalanced radial force in permanent magnet motors  

SciTech Connect

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

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

1998-10-01

61

Effect of permanent-magnet irregularities in levitation force measurements.  

SciTech Connect

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

Hull, J. R.

1999-10-14

62

Superadiabatic Forces in Brownian Many-Body Dynamics  

NASA Astrophysics Data System (ADS)

Theoretical approaches to nonequilibrium many-body dynamics generally rest upon an adiabatic assumption, whereby the true dynamics is represented as a sequence of equilibrium states. Going beyond this simple approximation is a notoriously difficult problem. For the case of classical Brownian many-body dynamics, we present a simulation method that allows us to isolate and precisely evaluate superadiabatic correlations and the resulting forces. Application of the method to a system of one-dimensional hard particles reveals the importance for the dynamics, as well as the complexity, of these nontrivial out-of-equilibrium contributions. Our findings help clarify the status of dynamical density functional theory and provide a rational basis for the development of improved theories.

Fortini, Andrea; de las Heras, Daniel; Brader, Joseph M.; Schmidt, Matthias

2014-10-01

63

Measured force/current relations in solid magnetic thrust bearings  

SciTech Connect

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

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

1997-01-01

64

Power dissipation and magnetic forces and MAGLEV rebars  

SciTech Connect

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

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

1997-03-01

65

An identification method of suspension force and magnetic unbalance pull force parameters in buried-type IPM bearingless motors  

Microsoft Academic Search

A new on-line identification method of suspension force and magnetic unbalance pull force parameters in buried-type IPM bearingless motors has been presented in this paper. The suspension force parameters depend on the current condition, because armature reaction and magnetic saturation in the stator teeth often occur in this type of machines. Moreover, the magnetic unbalance pull force also generates due

Masahide Ooshima; Takeshi Kurokawa; Masashi Sakagami; Akira Chiba; M. Azizur Rahman; Tadashi Fukao

2004-01-01

66

Nonconservative electric and magnetic optical forces on submicron dielectric particles  

SciTech Connect

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

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

2011-03-15

67

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

NASA Astrophysics Data System (ADS)

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

Essén, H.

2011-05-01

68

Whole body postmortem magnetic resonance angiography.  

PubMed

  Computed tomography (CT) and magnetic resonance (MR) imaging have become important elements of forensic radiology. Whereas the feasibility and potential of CT angiography have long been explored, postmortem MR angiography (PMMRA) has so far been neglected. We tested the feasibility of PMMRA on four adult human cadavers. Technical quality of PMMRA was assessed relative to postmortem CT angiography (PMCTA), separately for each body region. Intra-aortic contrast volumes were calculated on PMCTA and PMMRA with segmentation software. The results showed that technical quality of PMMRA images was equal to PMCTA in 4/4 cases for the head, the heart, and the chest, and in 3/4 cases for the abdomen, and the pelvis. There was a mean decrease in intra-aortic contrast volume from PMCTA to PMMRA of 46%. PMMRA is technically feasible and allows combining the soft tissue detail provided by MR and the information afforded by angiography. PMID:22211886

Ruder, Thomas D; Hatch, Gary M; Ebert, Lars C; Flach, Patricia M; Ross, Steffen; Ampanozi, Garyfalia; Thali, Michael J

2012-05-01

69

Electromotive force and huge magnetoresistance in magnetic tunnel junctions.  

PubMed

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

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

2009-03-26

70

Magnetically controllable Casimir force based on a superparamagnetic metametamaterial  

NASA Astrophysics Data System (ADS)

We theoretically investigate the magnetically controllable Casimir force between a parallel metal plate and a superparamagnetic metametamaterial (MMM) plate based on Mie scattering and effective medium theory. A type of MMM composed of superparamagnetic nanoparticles is proposed to fulfill the high frequency magnetic effect to gain Casimir repulsion when interacting with the metal plate. The permeability of such MMM depends on an external magnetic field, which makes it possible to adjust the magnitude of Casimir force. The effects of size, filling ratio, and magnetic property of the superparamagnetic particles on the tuning range are also investigated. Construction of such MMM using the micro/nanofabrication technology is promising to achieve magnetically controllable repulsive Casimir force.

Ma, Junming; Zhao, Qian; Meng, Yonggang

2014-02-01

71

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

72

EXPERIMENTAL BENCHMARKING OF THE MAGNETIZED FRICTION FORCE.  

SciTech Connect

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

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

2005-09-18

73

Forces on a magnet moving past figure-eight coils  

SciTech Connect

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.

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

74

Forces on a magnet moving past figure-eight coils  

SciTech Connect

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.

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

75

Force measurements in magnetic bearings using fiber optic strain gauges  

E-print Network

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

Raymer, Stephen Geoffrey

2012-06-07

76

Fundamental study of phosphor separation by controlling magnetic force  

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

77

Sensitive magnetic force detection with a carbon nanotube resonator  

NASA Astrophysics Data System (ADS)

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

Willick, Kyle; Haapamaki, Chris; Baugh, Jonathan

2014-03-01

78

1/00 E&M forces -1/8 ELECTRIC AND MAGNETIC FORCES  

E-print Network

a fluorescent screen. eVa As the electrons move in the horizontal (x) direction, an electric force may will remain constant. The electrons will move in a circular path of radius R with the force toward the center of electrons by electric and magnetic fields. APPARATUS: Electron beam tube, stand with coils, power supply

Glashausser, Charles

79

Solutions and symmetries of force-free magnetic fields  

SciTech Connect

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.

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

80

Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances  

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

81

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

NASA Astrophysics Data System (ADS)

This paper describes an analytical model for analyzing magnetic forces developed in permanent magnet motors of radial field topology. The slotting effect is taken into consideration by solving the boundary value problem of the air gap field. The solution is expressed in the form of Fourier series with which the analysis of the harmonic contents in the magnetic forces can be readily performed. In particular, the curvature effect or the flux focusing effect in the slot opening regions is taken into consideration. The results of magnetic forces obtained from this model are verified with numerical simulations using the finite element method and experimental results.

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

2008-04-01

82

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

E-print Network

-- e.g. weight (gravitational force), or electric or magnetic force. Surface forces: We can motivate model for some purposes, for instance water waves, flow over weirs, flow around rising, oscillating.* A more sophisticated treatment of surface forces would require us to introduce the stress tensor

Cambridge, University of

83

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

E-print Network

--- e.g. weight (gravitational force), or electric or magnetic force. Surface forces: We can motivate. This is a good model for some purposes, for instance water waves, flow over weirs, flow around rising numbers, on average.* A more sophisticated treatment of surface forces would require us to introduce

Cambridge, University of

84

"Killer App" of Wearable Computing: Wireless Force Sensing Body Protectors for Martial Arts  

E-print Network

"Killer App" of Wearable Computing: Wireless Force Sensing Body Protectors for Martial Arts Ed H of a martial art competition. Our system uses piezoelectric force sensors that transmit signals wirelessly

Chi, Ed Huai-hsin

85

Towards quantitative magnetic force microscopy: theory and experiment  

NASA Astrophysics Data System (ADS)

We introduce a simple and effective model of a commercial magnetic thin-film sensor for magnetic force microscopy (MFM), and we test the model employing buried magnetic dipoles. The model can be solved analytically in the half-space in front of the sensor tip, leading to a simple 1/R dependence of the magnetic stray field projected to the symmetry axis. The model resolves the earlier issue as to why the magnetic sensors cannot be described reasonably by a restricted multipole expansion as in the point pole approximation: the point pole model must be extended to incorporate a ‘lower-order’ pole, which we term ‘pseudo-pole’. The near-field dependence (?R-1) turns into the well-known and frequently used dipole behavior (?R-3) if the separation, R, exceeds the height of the sensor. Using magnetic nanoparticles (average diameter 18 nm) embedded in a SiO cover as dipolar point probes, we show that the force gradient-distance curves and magnetic images fit almost perfectly to the proposed model. The easy axis of magnetization of single nanoparticles is successfully deduced from these magnetic images. Our model paves the way for quantitative MFM, at least if the sensor and the sample are independent.

Häberle, Thomas; Haering, Felix; Pfeifer, Holger; Han, Luyang; Kuerbanjiang, Balati; Wiedwald, Ulf; Herr, Ulrich; Koslowski, Berndt

2012-04-01

86

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

PubMed Central

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

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

2014-01-01

87

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

PubMed

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

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

2014-01-01

88

Forced oscillations in magnetized accretion disks and QPOs  

E-print Network

We propose a new model for these QPOs based on forced oscillations induced in the accretion disk due to the stellar magnetic field. First, it is shown that a magnetized accretion disk evolving in a rotating nonaxisymmetric magnetic field anchored to a neutron star will be subject to three kinds of resonances: a corotation resonance, a Lindblad resonance due to a driving force, and a parametric resonance due to the time varying epicyclic frequencies. In the second part of the paper, we focus on the linear response of a thin accretion disk, developing the density perturbation as the sum of free wave solutions and non-wavelike disturbances. In the last part, we show results of 2D numerical simulations of a simplified version of the accretion disk consisting of a column of plasma threaded by a vertical magnetic field. It is argued that the nearly periodic motion induced in the disk will produce high quality factor QPOs.

J. Pétri

2005-07-06

89

Magnetic force microscopy investigation of the magnetization reversal of permalloy particles at high temperatures  

NASA Astrophysics Data System (ADS)

The magnetization reversal of an array of permalloy particles formed by scanning probe lithography on the silicon dioxide surface has been investigated in the temperature range from room temperature to 800 K. Using scanning magnetic force microscopy and numerical calculations of the magnetic anisotropy field of a particle at different temperatures, it has been shown that an increase in the temperature leads to a decrease in the external magnetic field required to reverse the magnetization direction of the particle. From the obtained results, it has been concluded that the magnetization reversal of the studied particles is accompanied by the formation of an intermediate state with an inhomogeneous magnetization structure.

Nurgazizov, N. I.; Khanipov, T. F.; Bizyaev, D. A.; Bukharaev, A. A.; Chuklanov, A. P.

2014-09-01

90

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

PubMed

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

Geng, Yanan; Wu, Weida

2014-05-01

91

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

PubMed Central

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

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

2012-01-01

92

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

93

Exchange Bias Systems studied by High Resolution Quantitative Magnetic Force  

E-print Network

Exchange Bias Systems studied by High Resolution Quantitative Magnetic Force Microscopy;Abstract It is generally believed that exchange bias (EB) implies the presence of pinned uncompen- sated domains to areas of proportionally higher pin-UCS aligned antiparallel to F-moments. This confirms our

Amrhein, Valentin

94

Magnetic bearing control systems and adaptive forced balancing  

Microsoft Academic Search

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

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

1994-01-01

95

Minimization of cogging force in a linear permanent magnet motor  

SciTech Connect

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

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

1998-09-01

96

Minimization of cogging force in a linear permanent magnet motor  

Microsoft Academic Search

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

P. J. Hor; Z. Q. Zhu; D. Howe; J. Rees-Jones

1998-01-01

97

Electric and Magnetic Forces: Electrostatics and Current Electricity  

NSDL National Science Digital Library

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

National Science Teachers Association (NSTA)

1900-01-01

98

THE MEAN ELECTROMOTIVE FORCE RESULTING FROM MAGNETIC BUOYANCY INSTABILITY  

SciTech Connect

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

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

2011-02-01

99

Magnetization Relaxation and Geometric Forces in a Bose Ferromagnet  

NASA Astrophysics Data System (ADS)

We construct the hydrodynamic theory for spin-1/2 Bose gases at arbitrary temperatures. This theory describes the coupling between the magnetization and the normal and superfluid components of the gas. In particular, our theory contains the geometric forces on the particles that arise from their spin’s adiabatic following of the magnetization texture. The phenomenological parameters of the hydrodynamic theory are calculated in the Bogoliubov approximation and using the Boltzmann equation in the relaxation-time approximation. We consider the topological Hall effect due to the presence of a Skyrmion, and show that this effect manifests itself in the collective modes of the system. The dissipative coupling between the magnetization and the normal component is shown to give rise to magnetization relaxation that is fourth order in spatial gradients of the magnetization direction.

Armaitis, J.; Stoof, H. T. C.; Duine, R. A.

2013-06-01

100

Corroboration of magnetic forces in US Maglev design  

SciTech Connect

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

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

1993-01-01

101

Corroboration of magnetic forces in US Maglev design  

SciTech Connect

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

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

1993-06-01

102

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

SciTech Connect

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

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

2008-12-15

103

Vortex Dislocations and Body Forces in Flow-Structure Interactions  

Microsoft Academic Search

DNS is used in order to simulate 3D flow past stationary, rigid or flexible cylinders subject to forced vibrations (FV) or vortex induced vibrations (VIV). Different flow and structural parameters such as shear rate, Reynolds number, cylinder aspect ratio and end-conditions are investigated in order to examine structural responses and hydrodynamic forces. The relationship of these quantities with the dynamics

Didier Lucor; Constantinos Evangelinos; George Em Karniadakis

1999-01-01

104

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

SciTech Connect

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

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

1995-12-14

105

On the unsteady-motion theory of magnetic forces for maglev  

SciTech Connect

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

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

1996-02-01

106

On the finite volume discretization of discontinuous body force field on collocated grid: Application to VOF method  

Microsoft Academic Search

Discontinuities in the body force field typically appear at the interface of two fluid systems. Modeled with the volume-of-fluid (VOF) and discretized with the finite volume method, the discontinuous body force fields are represented as abruptly variable. In the present study, gravity and continuum surface force (CSF) are considered. Such strongly variable body forces can produce unphysical spikes in the

Jure Mencinger; Iztok Žun

2007-01-01

107

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

PubMed

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

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

2010-11-16

108

Suppression of Magnetic Force Relaxation in a Magnet-High Superconductor System  

Microsoft Academic Search

We have measured that the levitation forces relax at the different order equilibrium positions of a bulk YBaCuO superconductor. In a given symmetrical levitation system, high order equilibrium positions can be obtained by increasing the number of the reversal movements of the magnet; the higher order equilibrium position, the lower the relaxation of the levitation force. This method is confirmed

Xing-Yi Zhang; You-He Zhou; Jun Zhou

2008-01-01

109

Collisionless forced magnetic reconnection in an electron-positron plasma  

SciTech Connect

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.

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

110

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

NASA Astrophysics Data System (ADS)

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.

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

2009-10-01

111

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

NASA Astrophysics Data System (ADS)

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

Fisher, J. K.; Kleckner, N.

2014-02-01

112

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

PubMed

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

Fisher, J K; Kleckner, N

2014-02-01

113

Chiral nuclear forces and many-body applications  

NASA Astrophysics Data System (ADS)

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

Krebs, Hermann

2012-09-01

114

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

SciTech Connect

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

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

1992-04-01

115

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

SciTech Connect

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

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

1992-01-01

116

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

117

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

NASA Technical Reports Server (NTRS)

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

Frankenthal, S.

1977-01-01

118

Distinguishing ferritin from apoferritin using magnetic force microscopy.  

PubMed

Estimating the amount of iron-replete ferritin versus iron-deficient apoferritin proteins is important in biomedical and nanotechnology applications. This work introduces a simple and novel approach to quantify ferritin by using magnetic force microscopy (MFM). We demonstrate how high magnetic moment probes enhance the magnitude of MFM signal, thus enabling accurate quantitative estimation of ferritin content in ferritin/apoferritin mixtures in vitro. We envisage MFM could be adapted to accurately determine ferritin content in protein mixtures or in small aliquots of clinical samples. PMID:25355655

Nocera, Tanya M; Zeng, Yuzhi; Agarwal, Gunjan

2014-11-21

119

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

NASA Astrophysics Data System (ADS)

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

Yu, Jing-Jiang; Garno, Jayne

2012-02-01

120

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

PubMed Central

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

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

2014-01-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

122

Effect of nonharmonic forcing on bluff-body vortex dynamics.  

PubMed

Forced nonharmonic excitation of the two-dimensional flow about a circular cylinder is studied by numerical simulations at mean Reynolds numbers of 180 and 150. Moderate deviations of the forced inflow velocity waveform from a pure harmonic generate different modes of phase-locked vortex formation in the cylinder wake, involving combinations of single and/or pairs of vortices for the same forcing frequency and peak-to-peak amplitude. The dynamical response of the wake oscillator is studied by employing phase portraits of the drag and lift coefficients that display modified limit-cycle behavior due to nonharmonic excitation. It is further shown that changing solely the velocity waveform can incite transition from a quasiperiodic state to a phase-locked state. The findings demonstrate that the wake oscillator is admissible to an infinite number of phase-locked and/or modulated states characterized by a single point on the frequency-amplitude plane. PMID:19518288

Konstantinidis, E; Bouris, D

2009-04-01

123

Bifurcations of a forced magnetic oscillator near points of resonance  

SciTech Connect

We study a forced symmetric oscillator containing a saturable inductor with magnetic hysteresis, approximated by a noninvertible map of the plane. The system displays a Hopf bifurcation to quasiperiodicity, entrainment horns, and chaos. Behavior near points of resonance (weak and strong) is found to correspond well with Arnold's theory. Within an entrainment horn, we observe symmetry breaking, period doubling, and complementary band merging. The symmetry behavior is explained by use of the concept of half-cycle map.

Bryant, P.; Jeffries, C.

1984-07-16

124

On the unsteady-motion theory of magnetic forces for maglev  

SciTech Connect

Motion-dependent magnetic forces are the key elements in the study of magnetically levitated vehicle (maglev) system dynamics. In the past, most maglev-system designs were based on a quasisteady-motion theory of magnetic forces. This report presents an experimental and analytical study that will enhance our understanding of the role of unsteady-motion-dependent magnetic forces and demonstrate an experimental technique that can be used to measure those unsteady magnetic forces directly. The experimental technique provides a useful tool to measure motion-dependent magnetic forces for the prediction and control of maglev systems.

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

1993-11-01

125

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

PubMed

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

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

2013-11-14

126

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

SciTech Connect

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

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

2013-11-14

127

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

SciTech Connect

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

Oberkampf, W. L.

1981-04-01

128

Localized Spectroscopy using a Magnetic Resonance Force Microscope.  

NASA Astrophysics Data System (ADS)

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

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

2006-03-01

129

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

PubMed Central

Cantilevers and optical tweezers are widely used for micromanipulating cells or biomolecules for measuring their mechanical properties. However, they do not allow easy rotary motion and can sometimes damage the handled material. We present here a system of magnetic tweezers that overcomes those drawbacks while retaining most of the previous dynamometers properties. Electromagnets are coupled to a microscope-based particle tracking system through a digital feedback loop. Magnetic beads are first trapped in a potential well of stiffness approximately 10(-7) N/m. Thus, they can be manipulated in three dimensions at a speed of approximately 10 microm/s and rotated along the optical axis at a frequency of 10 Hz. In addition, our apparatus can work as a dynamometer relying on either usual calibration against the viscous drag or complete calibration using Brownian fluctuations. By stretching a DNA molecule between a magnetic particle and a glass surface, we applied and measured vertical forces ranging from 50 fN to 20 pN. Similarly, nearly horizontal forces up to 5 pN were obtained. From those experiments, we conclude that magnetic tweezers represent a low-cost and biocompatible setup that could become a suitable alternative to the other available micromanipulators. PMID:12023254

Gosse, Charlie; Croquette, Vincent

2002-01-01

130

Force-free magnetic fields - Generating functions and footpoint displacements  

NASA Technical Reports Server (NTRS)

This paper presents analytic and numerical calculations that explore equilibrium sequences of bipolar force-free magnetic fields in relation to displacments of their magnetic footpoints. It is shown that the appearance of magnetic islands - sometimes interpreted as marking the loss of equilibrium in models of the solar atmosphere - is likely associated only with physically unrealistic footpoint displacements such as infinite separation or 'tearing' of the model photosphere. The work suggests that the loss of equilibrium in bipolar configurations, sometimes proposed as a mechanism for eruptive solar events, probably requires either fully three-dimensional field configurations or nonzero plasma pressure. The results apply only to fields that are strictly bipolar, and do not rule out equilibrium loss in more complex structures such as quadrupolar fields.

Wolfson, Richard; Verma, Ritu

1991-01-01

131

Effects of magnetic saturation on radial force of bearingless synchronous reluctance motors  

Microsoft Academic Search

The effects of magnetic saturation on radial force production in synchronous reluctance type bearingless motors are discussed. MMFs are calculated and flux densities are derived with approximated magnetic saturation curve. The radial force is almost proportional to the difference of squared flux densities. The maximum radial force is found to be limited by magnetic saturation if motor excitation is high

Akira Chiba; Masahiko Hanazawa; Tadashi Fukao; M. Azizur Rahman

1996-01-01

132

Public Relations Body of Knowledge Task Force Report.  

ERIC Educational Resources Information Center

Lists the initial readings to be codified in the public relations body of knowledge. Categories include foundations of public relations, organizational and managerial context, the communication and relationship context, public relations processes, elements and functions of professional practice, and contexts for professional practice. (MM)

PRSA Task Force

1988-01-01

133

Land use Controls: Can Landowners Force Governmental Bodies to Pay?  

Microsoft Academic Search

A governmental body has the right to regulate owners' use of their land by exercising police powers. However, when such regulation substantially deprives an owner of the use of land, the owner can argue that a taking has occurred. Traditionally, a landowner could seek a declaration that the governmental regulation was unconstitutional and should be enjoined. At times an alternative

Peter J. Shedd

1981-01-01

134

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

Microsoft Academic Search

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

Sl M. KHAN; R. S. Dhaliwal

1976-01-01

135

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

PubMed Central

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

Shapiro, Benjamin

2010-01-01

136

Many-Body Force and Mobility Measurements in Colloidal Systems  

Microsoft Academic Search

We demonstrate a technique for simultaneously measuring each component of the\\u000aforce vectors and mobility tensor of a small collection of colloidal particles\\u000abased on observing a set of particle trajectories. For a few-body system of\\u000amicron-sized polymer beads in oil separated by several particle radii, we find\\u000athat the mobility tensor is well-described by a pairwise Stokeslet model. This

Jason W. Merrill; Sunil K. Sainis; Eric R. Dufresne

2009-01-01

137

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

PubMed Central

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

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

2012-01-01

138

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

139

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

PubMed

In recent years, superparamagnetic nanoparticles (SPNs) have become increasingly important in applications ranging from solid state memory devices to biomedical diagnostic and therapeutic tools. However, detection and characterization of the small and unstable magnetic moment of an SPN at the single particle level remains a challenge. Further, depending on their physical shape, crystalline structure or orientation, SPNs may also possess magnetic anisotropy, which can govern the extent to which their magnetic moments can align with an externally applied magnetic field. Here, we demonstrate how we can exploit the magnetic anisotropy of SPNs to enable uniform, highly-sensitive detection of single SPNs using magnetic force microscopy (MFM) in ambient air. Superconducting quantum interference device magnetometry and analytical transmission electron microscopy techniques are utilized to characterize the collective magnetic behavior, morphology and composition of the SPNs. Our results show how the consideration of magnetic anisotropy can enhance the ability of MFM to detect single SPNs at ambient room temperature with high force sensitivity and spatial resolution. PMID:23149438

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

2012-12-14

140

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

NASA Technical Reports Server (NTRS)

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.

Spreiter, John R

1950-01-01

141

Resonantly Detecting Axion-Mediated Forces with Nuclear Magnetic Resonance  

NASA Astrophysics Data System (ADS)

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

Arvanitaki, Asimina; Geraci, Andrew A.

2014-10-01

142

Resonantly detecting axion-mediated forces with nuclear magnetic resonance.  

PubMed

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

Arvanitaki, Asimina; Geraci, Andrew A

2014-10-17

143

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

NASA Astrophysics Data System (ADS)

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

Jardin, Thierry; Bury, Yannick

2014-06-01

144

Kinesin-microtubule interactions during gliding assays under magnetic force  

NASA Astrophysics Data System (ADS)

Conventional kinesin is a motor protein capable of converting the chemical energy of ATP into mechanical work. In the cell, this is used to actively transport vesicles through the intracellular matrix. The relationship between the velocity of a single kinesin, as it works against an increasing opposing load, has been well studied. The relationship between the velocity of a cargo being moved by multiple kinesin motors against an opposing load has not been established. A major difficulty in determining the force-velocity relationship for multiple motors is determining the number of motors that are moving a cargo against an opposing load. Here I report on a novel method for detaching microtubules bound to a superparamagnetic bead from kinesin anchor points in an upside down gliding assay using a uniform magnetic field perpendicular to the direction of microtubule travel. The anchor points are presumably kinesin motors bound to the surface which microtubules are gliding over. Determining the distance between anchor points, d, allows the calculation of the average number of kinesins, n, that are moving a microtubule. It is possible to calculate the fraction of motors able to move microtubules as well, which is determined to be ˜ 5%. Using a uniform magnetic field parallel to the direction of microtubule travel, it is possible to impart a uniform magnetic field on a microtubule bound to a superparamagnetic bead. We are able to decrease the average velocity of microtubules driven by multiple kinesin motors moving against an opposing force. Using the average number of kinesins on a microtubule, we estimate that there are an average 2-7 kinesins acting against the opposing force. By fitting Gaussians to the smoothed distributions of microtubule velocities acting against an opposing force, multiple velocities are seen, presumably for n, n-1, n-2, etc motors acting together. When these velocities are scaled for the average number of motors on a microtubule, the force-velocity relationship for multiple motors follows the same trend as for one motor, supporting the hypothesis that multiple motors share the load.

Fallesen, Todd L.

145

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

PubMed Central

This paper investigates the accuracy of the resistive-force theory (Gray and Hancock method) which is commonly used for hydrodynamic analysis of swimming flagella. We made a comparison between the forces, bending moments, and shear moments calculated by resistive-force theory and by the more accurate slender-body theory for large-amplitude, planar wave forms computed for a flagellar model. By making an upward empirical adjustment, by about 35%, of the classical drag coefficient values used in the resistive-force theory calculations, we obtained good agreement between the distributions of the forces and moments along the length of the flagellum predicted by the two methods when the flagellum has no cell body attached. After this adjustment, we found the rate of energy expenditure calculated by the two methods for the few typical test cases to be almost identical. The resistive-force theory is thus completely satisfactory for use in analysis of mechanisms for the control of flagellar bending, at the current level of sophistication of this analysis. We also examined the effects of the presence of a cell body attached to one end of the flagellum, which modifies the flow field experienced by the flagellum. This interaction, which is not considered in resistive-force theory, is probably insignificant for small cell bodies, such as the heads of simple spermatozoa, but for larger cell bodies, or cell bodies that have large-amplitude motions transverse to the swimming direction, use of slender-body theory is required for accurate analysis. PMID:262381

Johnson, R E; Brokaw, C J

1979-01-01

146

Constraints of magnetic field which magnetized the Farmington meteorite parant body  

NASA Technical Reports Server (NTRS)

Analysis indicates the following: (1) the parent body of the Farmington meteorite experienced sufficient heating (probably from shock accompanying a major collision occurring 520 million years ago) to erase the record of any magnetization acquired prior to that event; therefore, (2)the observed magnetization in the Farmington meteorite must have been acquired after the collision; and (3)shockproduced magnetization is unlikely, because of the finite cooling time indicated by the burial depth of approximately several meters. The possibility of shock or irradiation-produced magnetizations is proposed as an experimental study, even though neither appears likely to have produced the magnetic field which produced the magnetization in the parent body of the Farmington meteorite.

Rowe, M. W.

1974-01-01

147

Nonlinear forced oscillation in a magnetically levitated system: the effect of the time delay of the electromagnetic force  

Microsoft Academic Search

Vibration analysis is important to explain and control the various kinds of vibration problems in magnetically levitated mechanical\\u000a systems. This study investigates the vibration phenomena of the one-degree-of-freedom magnetically levitated system considering\\u000a the effect of the nonlinearity of the electromagnet. It is difficult to apply the conventional nonlinear analysis techniques\\u000a for the magnetically levitated system, since the magnetic force has

Tsuyoshi Inoue; Yukio Ishida

2008-01-01

148

Calculation of cogging force in a novel slotted linear tubular brushless permanent magnet motor  

Microsoft Academic Search

A finite element\\/analytical based technique for the prediction of cogging force in a novel topology of slotted linear brushless permanent magnet motor has been developed and validated. The various force components, which influence cogging are pre-calculated by the finite element analysis of some basic magnetic structures, facilitate the analytical synthesis of the resultant cogging force. The technique can be used

Z. Q. Zhu; P. J. Hor; D. Howe; J. Rees-Jones

1997-01-01

149

Magnetic evidence for a partially differentiated carbonaceous chondrite parent body  

PubMed Central

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

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

2011-01-01

150

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

ERIC Educational Resources Information Center

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

Onorato, Pasquale; De Ambrosis, Anna

2013-01-01

151

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

E-print Network

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

Paris-Sud XI, Université de

152

The Physical Connection and Magnetic Coupling of the MICE CoolingChannel Magnets and the Magnet Forces for Various MICE OperatingModes  

SciTech Connect

A key issue in the construction of the MICE cooling channel is the magnetic forces between various elements in the cooling channel and the detector magnets. This report describes how the MICE cooling channel magnets are hooked to together so that the longitudinal magnetic forces within the cooling channel can be effectively connected to the base of the experiment. This report presents a magnetic force and stress analysis for the MICE cooling channel magnets, even when longitudinal magnetic forces as large as 700 kN (70 tons) are applied to the vacuum vessel of various magnets within the MICE channel. This report also shows that the detector magnets can be effectively separated from the central MICE cooling channel magnets without damage to either type of magnet component.

Yang, Stephanie Q.; Baynham, D.E.; Fabricatore, Pasquale; Farinon, Stefania; Green, Michael A.; Ivanyushenkov, Yury; Lau, Wing W.; Maldavi, S.M.; Virostek, Steve P.; Witte, Holger

2006-08-20

153

The indirect measurement of biomechanical forces in the moving human body  

NASA Astrophysics Data System (ADS)

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.

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

2006-02-01

154

Impact force measurement of a spherical body dropping onto a water surface.  

PubMed

We propose a method for measuring the impact force of a spherical body dropping onto a water surface. The velocity of the center of gravity of a metal spherical body, in which a cube corner prism is embedded so that its optical center coincides with the center of gravity of the sphere, is accurately measured using an optical interferometer. The acceleration, displacement, and inertial force of the sphere are calculated from the velocity. The sphere is also observed using a high-speed camera. The uncertainty in measuring the instantaneous value of the impact force with a sampling interval of approximately 1 ms is estimated to be 8 mN, which corresponds to 0.8% of the maximum force of approximately 1.0 N. PMID:25085174

Araki, R; Takita, A; Ishima, T; Kawashima, H; Pornsuwancharoen, N; Punthawanunt, S; Carcasona, E; Fujii, Y

2014-07-01

155

Forced three-dimensional magnetic reconnection due to linkage of magnetic flux tubes  

NASA Technical Reports Server (NTRS)

During periods of southward interplanetary magnetic field (IMF) orientation the magnetic field geometry at the dayside magnetopause is susceptible to magnetic reconnection. It has been suggested that reconnection may occur in a localized manner at several patches on the magnetopause. A major problem with this picture is the interaction of magnetic flux ropes which are generated by different reconnection processes. An individual flux rope is bent elbowlike where it intersects the magnetopause and the magnetic field changes from magnetospheric to interplanetary magnetic field orientation. Multiple patches of reconnection can lead to the formation of interlinked magnetic flux tubes. Although the corresponding flux is connected to the IMF the northward and southward connected branches are hooked into each other and cannot develop independently. We have studied this problem in the framework of three-dimensional magnetohydrodynamic simulations. The results indicate that a singular current sheet forms at the interface of two interlinked flux tubes if no resistivity is present in the simulation. This current sheet is strongly tilted compared to the original current sheet. In the presence of resistivity the interaction of the two flux tubes forces a fast reconnection process which generates helically twisted closed magnetospheric flux. This linkage induced reconnection generates a boundary layer with layers of open and closed magnetospheric flux and may account for the brightening of auroral arcs poleward of the boundary between open and closed magnetic flux.

Otto, A.

1995-01-01

156

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

NASA Technical Reports Server (NTRS)

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.

Chung, Paul M.

1961-01-01

157

Three Body Bound State Calculation with Two and Three Body Forces without Partial Wave Decomposition  

Microsoft Academic Search

The Faddeev equation for the three nucleon bound state with including genuine three nucleon forces is solved as function of vector Jacobi momenta without applying partial wave decomposition techniques. The NN as well as the 3N potential are of Malfliet-Tjon type and are also calculated directly as function of vector momenta. When spin degrees of freedom are neglected, the Faddeev

Hang Liu; Charlotte Elster; Walter Gloeckle

2002-01-01

158

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

NASA Technical Reports Server (NTRS)

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

Hartmann, K.

1982-01-01

159

Influences of denucleation on contact force of facet joints under whole body vibration.  

PubMed

To investigate the influence of the injured disc, frequency, load and damping on the facet contact forces of the low lumbar spine on the condition of whole body vibration, a detailed 3-D nonlinear finite element model was created based on the actual geometrical data of embalmed vertebrae of lumbar spine. The denucleation and facetectomy, together with removal of the capsular ligaments was employed to mimic the injury conditions of lumbar spine after surgery. The compression cyclic force was assumed to mimic the dynamic loads of transport vehicles. The results show that the high frequency vibration might increase both of the value and the vibration amplitude of facet contact forces of the lumbar spine under whole body vibration. The nucleus removal may increase significantly the facet contact forces. Although damping can decrease the vibration amplitude of facet contact forces for intact models, it has less effect on the vibration amplitude of facet contact force for the denucleated models. The denucleation of intervertebral discs is more harmful to the facet articulation on the condition of whole body vibration. PMID:17510817

Guo, L-X; Zhang, M; Teo, E-C

2007-07-01

160

Many-body forces and electron correlation in small metal clusters  

Microsoft Academic Search

The many-body decomposition of the interaction energy for BeN and LiN (N=2 to 4) clusters is calculated in two approximations: the self-consistent-field method and the Mo\\/ller-Plesset perturbation theory up to the fourth order. This allows us to estimate the electron-correlation contributions to the many-body forces. The explicit expressions for these contributions in the perturbation theory formalism are obtained. We present

Ilya G. Kaplan; Jorge Hernández-Cobos; Iván Ortega-Blake; Octavio Novaro

1996-01-01

161

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

DOEpatents

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

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

1991-04-09

162

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

DOEpatents

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

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

1991-01-01

163

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

PubMed

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

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

2013-12-01

164

Calculatoin and experimental study of the retracting force for magnetic spring of two types  

E-print Network

Designs for magnetic springs of two types have been proposed, and the methods of calculation of their retracting forces have been developed. Formulas are obtained for the retracting force in the main section of spring force characteristics. Experimental data are in good agreement with the results of theoretical calculations. The force characteristics of the proposed magnetic spring constructions can be varied for a specific application. The derived formulas are verified experimentally. Ways to change the force characteristics of magnetic springs according to specific requirements are demonstrated.

Tsivilitsin, V; Goncharuk, V; Bondar, I

2014-01-01

165

Effect of gender, facial dimensions, body mass index and type of functional occlusion on bite force  

PubMed Central

Objective Some factors such as gender, age, craniofacial morphology, body structure, occlusal contact patterns may affect the maximum bite force. Thus, the purposes of this study were to determine the mean maximum bite force in individuals with normal occlusion, and to examine the effect of gender, facial dimensions, body mass index (BMI), type of functional occlusion (canine guidance and group function occlusion) and balancing side interferences on it. Material and Methods Thirty-four individuals aged 19-20 years-old were selected for this study. Maximum bite force was measured with strain-gauge transducers at first molar region. Facial dimensions were defined by standardized frontal photographs as follows: anterior total facial height (ATFH), bizygomathic facial width (BFW) and intergonial width (IGW). BMI was calculated using the equation weight/height2. The type of functional occlusion and the balancing side interferences of the subjects were identified by clinical examination. Results Bite force was found to be significantly higher in men than women (p<0.05). While there was a negative correlation between the bite force and ATFH/BFW, ATFH/IGW ratios in men (p<0.05), women did not show any statistically significant correlation (p>0.05). BMI and bite force correlation was not statistically significant (p>0.05). The average bite force did not differ in subjects with canine guidance or group function occlusion and in the presence of balancing side interferences (p>0.05). Conclusions Data suggest that bite force is affected by gender. However, BMI, type of functional occlusion and the presence of balancing side interferences did not exert a meaningful influence on bite force. In addition, transverse facial dimensions showed correlation with bite force in only men. PMID:21625746

KOÇ, Duygu; DO?AN, Arife; BEK, Bülent

2011-01-01

166

Induction of electromotive force by an autonomously moving magnetic bot.  

PubMed

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

Sailapu, Sunil Kumar; Chattopadhyay, Arun

2014-02-01

167

The effect of magnet configurations on the levitation force of melt processed YBCO bulk superconductors  

Microsoft Academic Search

The high levitation force of YBCO bulk superconductors makes it possible for many applications such as magnetic bearings, flywheels and magnetic levitation transport systems etc. But for a given superconductor, the levitation forces are much different with different magnetic field distributions. In this paper, many small magnets (10×10×10cm3) with the B=0.5T on the top surface have been selected to investigate

W. M. Yang; L. Zhou; Y. Feng; P. X. Zhang; J. R. Wang; C. P. Zhang; Z. M. Yu; X. D. Tang; W. Wei

2001-01-01

168

Accurate body force integration in boundary methods applied to plane elasticity  

Microsoft Academic Search

A simple and accurate method for evaluating the domain integrals associated with body force effects in plane elasticity problems solved by boundary oriented methods is proposed and evaluated. The method is based on subdividing the elastic region embedded in the infinite plane into triangular sectors formed by the boundary points and a field point at which the effect is desired.

G. Burgess; E. Mahajerin

1996-01-01

169

A Benchmark Calculation for the Nd Scattering with a Model Three-Body Force  

E-print Network

Using the complex energy method, the problem of nucleon-deuteron scattering is solved with a simple three-body force having a separable form. Our results are compared with the results of modern direct two-variable calculations and a good agreement is found. This forms a firm base for other applications of the complex energy method.

Phyu, Aye Mya; Golak, Jacek; Oo, Htun Htun; Witala, Henryk; Gloeckle, Walter

2012-01-01

170

Extraction of user's navigation commands from upper body force interaction in walker assisted gait  

Microsoft Academic Search

BACKGROUND: The advances in technology make possible the incorporation of sensors and actuators in rollators, building safer robots and extending the use of walkers to a more diverse population. This paper presents a new method for the extraction of navigation related components from upper-body force interaction data in walker assisted gait. A filtering architecture is designed to cancel: (i) the

Anselmo Frizera Neto; Juan A Gallego; Eduardo Rocon; José L Pons; Ramón Ceres

2010-01-01

171

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

NASA Astrophysics Data System (ADS)

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

Wright, Sarah; Hickman, Steven; Marohn, John

2008-03-01

172

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

SciTech Connect

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

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

1997-08-06

173

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

174

Design of Feedforward Controller to Reduce Force Ripple for Linear Motor using Halbach Magnet Array with T Shape Magnet  

NASA Astrophysics Data System (ADS)

Recently, in micro/nano fabrication equipments, linear motors are widely used as an actuator to position workpiece, machining tool and measurement head. To control them faster and more precise, the motor should have high actuating force and small force ripple. High actuating force enable us to more workpiece with high acceleration. Eventually, it may provide higher throughput. Force ripple gives detrimental effect on the precision and tracking performance of the equipments. In order to accomplish more precise motion, it is important to make lower the force ripple. Force ripple is categorized into cogging and mutual ripple. First is dependent on the shape of magnets and/or core. The second is not dependent on them but dependent on current commutation. In this work, coreless mover i.e. coil winding is applied to the linear motor to avoid the cogging ripple. Therefore, the mutual ripple is only considered to be minimized. Ideal Halbach magnet array has continuously varying magnetization. The THMA (Halbach magnet array with T shape magnets) is proposed to approximate the ideal one. The THMA can not produce ideal sinusoidal flux, therefore, the linear motor with THMA and sinusoidal commutation of current generates the mutual force ripple. In this paper, in order to compensate mutual force ripple by feedforward(FF) controller, we calculate the optimized commutation of input current. The ripple is lower than 1.17% of actuating force if the commutation current agree with the magnetic flux from THMA. The performance of feedforward(FF) controller is verified by experiment.

Kim, Moojong; Kim, Jinyoung; Lee, Moon G.

175

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

NASA Astrophysics Data System (ADS)

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

Chen, Mao-Wei; Sun, Mao

2014-08-01

176

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

Microsoft Academic Search

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

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

2001-01-01

177

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

178

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

NASA Astrophysics Data System (ADS)

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

Kim, Dong Ki; Lee, Jeong Tae

179

Axial force imparted by a current-free magnetically expanding plasma  

SciTech Connect

The axial force imparted from a magnetically expanding, current-free, radiofrequency plasma is directly measured. For an argon gas flow rate of 25 sccm and an effective rf input power of {approx}800W, a maximum force of {approx}6mN is obtained; {approx}3mN of which is transmitted via the expanding magnetic field. The measured forces are reasonably compared with a simple fluid model associated with the measured electron pressure. The model suggests that the total force is the sum of an electron pressure inside the source and a Lorentz force due to the electron diamagnetic drift current and the applied radial magnetic field. It is shown that the Lorentz force is greatest near the magnetic nozzle surface where the radial pressure gradient is largest.

Takahashi, Kazunori [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Department of Electrical Engineering and Computer Science, Iwate University, Morioka 020-8551 (Japan); Lafleur, Trevor; Charles, Christine; Alexander, Peter; Boswell, Rod W. [Space Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra ACT 0200 (Australia)

2012-08-15

180

Assessment of Influence of Magnetic Forces on Aggregation of Zero-valent Iron Nanoparticles  

PubMed Central

Aggregation of zero-valent nanoparticles in groundwater is influenced by several physical phenomena. The article shortly introduces preceding works in modeling of aggregation of small particles including influence of sedimentation, velocity profile of water, heat fluctuations, and surface electric charge. A brief description of inclusion of magnetic forces into the model of aggregation follows. Rate of influence of the magnetic forces on the aggregation depends on the magnitude of magnetization of the particles, radius of nanoparticles, size of the aggregates, and their concentration in the solution. Presented results show that the magnetic forces have significant influence on aggregation especially of the smallest iron particles.

2011-01-01

181

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

NASA Astrophysics Data System (ADS)

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.

Reunanen, Arttu; Larjola, Jaakko

2005-03-01

182

GravitoMagnetic force in modified Newtonian dynamics  

SciTech Connect

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

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

2013-08-01

183

On the Inertial Force Experienced by a Solid Body Undergoing Rotation about Two Axes  

SciTech Connect

The theory of rigid body motion is used to derive the governing equations, in terms of the Eulerian angles, of a top rotating about two axes. Then, a formula for the 'lifting' component of the net inertial force (as function of the angle of inclination, the top's two angular velocities and its moments of inertia) is derived for a particular motion termed constrained nutation. In a distinguished limit, the critical value of the angle of inclination, i.e., the value for which the vertical component of the net inertial force acting on the top overcomes the weight of the rotating system, is calculated.

Christov, I. C. [Department of Engineering Sciences and Applied Mathematics, Northwestern University Evanston, IL 60208-3125 (United States); Christov, C. I. [Department of Mathematics, University of Louisiana at Lafayette Lafayette, LA 70504-1010 (United States)

2009-10-29

184

Forced oscillations of a body attached to a viscoelastic rod of fractional derivative type  

E-print Network

We study forced oscillations of a rod with a body attached to its free end so that the motion of a system is described by two sets of equations, one of integer and the other of the fractional order. To the constitutive equation we associate a single function of complex variable that plays a key role in finding the solution of the system and in determining its properties. This function could be defined for a linear viscoelastic bodies of integer/fractional derivative type.

Teodor M. Atanackovic; Stevan Pilipovic; Dusan Zorica

2012-07-01

185

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

PubMed

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

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

2010-01-01

186

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

ERIC Educational Resources Information Center

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

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

2013-01-01

187

Full-Body Compliant Human-Humanoid Interaction: Balancing in the Presence of Unknown External Forces  

Microsoft Academic Search

This paper proposes an effective framework of human-humanoid robot physical interaction. Its key component is a new control technique for full-body balancing in the presence of external forces, which is presented and then validated empirically. We have adopted an integrated system approach to develop humanoid robots. Herein, we describe the importance of replicating human-like capabilities and responses during human-robot interaction

Sang-ho Hyon; Joshua G. Hale; Gordon Cheng

2007-01-01

188

Hysteresis loops of individual Co nanostripes measured by magnetic force microscopy  

PubMed Central

High-resolution magnetic imaging is of utmost importance to understand magnetism at the nanoscale. In the present work, we use a magnetic force microscope (MFM) operating under in-plane magnetic field in order to observe with high accuracy the domain configuration changes in Co nanowires as a function of the externally applied magnetic field. The main result is the quantitative evaluation of the coercive field of the individual nanostructures. Such characterization is performed by using an MFM-based technique in which a map of the magnetic signal is obtained as a function of both the lateral displacement and the magnetic field. PMID:21711935

2011-01-01

189

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

E-print Network

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

M. Kohno

2012-09-23

190

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

E-print Network

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

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

2014-01-01

191

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

E-print Network

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

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

2014-06-18

192

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

PubMed Central

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

Beretic, Igor; ?urovic, Marko; Okicic, Tomislav; DOPSAJ, Milivoj

2013-01-01

193

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

PubMed

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

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

2010-01-01

194

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux  

NASA Astrophysics Data System (ADS)

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

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

2002-11-01

195

Investigation of Body Force Effects on Flow Boiling Critical Heat Flux  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

196

Nonlinear force-free modeling of the solar coronal magnetic field  

E-print Network

The coronal magnetic field is an important quantity because the magnetic field dominates the structure of the solar corona. Unfortunately direct measurements of coronal magnetic fields are usually not available. The photospheric magnetic field is measured routinely with vector magnetographs. These photospheric measurements are extrapolated into the solar corona. The extrapolated coronal magnetic field depends on assumptions regarding the coronal plasma, e.g. force-freeness. Force-free means that all non-magnetic forces like pressure gradients and gravity are neglected. This approach is well justified in the solar corona due to the low plasma beta. One has to take care, however, about ambiguities, noise and non-magnetic forces in the photosphere, where the magnetic field vector is measured. Here we review different numerical methods for a nonlinear force-free coronal magnetic field extrapolation: Grad-Rubin codes, upward integration method, MHD-relaxation, optimization and the boundary element approach. We briefly discuss the main features of the different methods and concentrate mainly on recently developed new codes.

T. Wiegelmann

2008-01-18

197

Forces on Interaction Region Quadrupoles and Dipoles Due to a Detector Solenoid Magnet  

NASA Astrophysics Data System (ADS)

Several interaction region accelerator magnets are being built partly or wholly inside a high energy physics detector solenoid field. The forces on the coils due the solenoid field can be very large. Forces due to misalignments, given the proximity of the detector steel, can also be large. In this paper we derive several generally applicable formulae to calculate forces due to the solenoid, discuss symmetries, and evaluate the results for the CESR Phase III interaction region magnets. Forces due to nearby steel were calculated using ANSYS and the results are presented.

Welch, James J.; Dugan, Gerald F.

1997-05-01

198

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

E-print Network

between a permanent magnet (PM) and a high-temperature superconductor (HTSC) is currently a subject to these issuesis to investigate various aspectsof the magnetic force acting betweena PM and a HTSC. While there has for granular HTSCs-sintered materials or composites.`2The HTSC was here modeled as a system consisting

Johansen, Tom Henning

199

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

PubMed

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

Kaidatzis, A; García-Martín, J M

2013-04-26

200

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

Microsoft Academic Search

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

Saleem M. Khan; Ranjit S. Dhaliwal

1977-01-01

201

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

PubMed Central

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

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

2004-01-01

202

Design and construction of a magnetic force microscope  

E-print Network

and interface it with a commercial scanning probe electronics controller with the help of an appropriate force sensor. The MFM head and the force sensor were to be designed to work at low temperatures (down to 4 K) and in high vacuum. During this work, a...

Khandekar, Sameer Sudhakar

2005-08-29

203

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

NASA Astrophysics Data System (ADS)

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

Wetter, Laura; Verosub, Ken; Russell, James

2007-06-01

204

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

NASA Astrophysics Data System (ADS)

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

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

205

Fabrication of magnetic force microscopy probes via localized electrochemical deposition of cobalt  

E-print Network

recording media2 and other magnetic nanostructures.3­5 The resolution of MFM is strongly dependent on individual probes in the fluid cell of a Digital Instruments Multimode atomic force microscope AFM operated

Zettl, Alex

206

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

E-print Network

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

Zutavern, Zachary Scott

2009-06-02

207

Effects of Velocity-Dependent Force on the Magnetic Form Factors of Odd-Z Nuclei  

Microsoft Academic Search

We investigate the effects of the velocity-dependent force on the magnetic form factors and magnetic moments of odd-Z nuclei. The form factors are calculated with the harmonic-oscillator wavefunctions. It is found that the contributions of the velocity-dependent force manifest themselves in the very large momentum transfer region (q ? 4fm-1). In the low and medium q region the contributions of

Tie-Kuang Dong; Zhong-Zhou Ren

2008-01-01

208

Experimental investigations into forces acting during a magnetic abrasive finishing process  

Microsoft Academic Search

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

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

2006-01-01

209

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

Microsoft Academic Search

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

Bharat Bhushan; Ju-Ai Ruan

1993-01-01

210

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

PubMed

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

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

2014-11-01

211

Effective field theory for neutron stars with genuine many-body forces  

NASA Astrophysics Data System (ADS)

The aim of our contribution is to shed some light on open questions facing the high density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role for the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings the concept of naturalness has been adopted. In order to encourage possible new directions of research, we discuss relevant aspects of a 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 Quantum Hadrodynamics (QHD) models found in literature and how we can potentially use our approach to describe new physics for neutron stars. We also show some preliminary results for the equation of state, population profiles and mass-radius relation for neutron stars assuming local charge neutrality and beta equilibrium.

Vasconcellos , C. A. Z.; Gomes, R. O.; Dexheimer, V.; Negreiros, R. P.; Horvath, J.; Hadjimichef, D.

2014-09-01

212

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

213

Three-body force effect on the neutron and proton spectral functions in asymmetric nuclear matter  

NASA Astrophysics Data System (ADS)

We investigate the effect of microscopic three-body forces (TBFs) on the off-shell behavior of the neutron and proton mass operators M?(k,?)=V?(k,?)+iW?(k,?) in asymmetric nuclear matter within the framework of the extended Brueckner-Hartree-Fock approach. We adopt the Argonne V18 two-body potential supplemented with a microscopic TBF as the realistic nucleon-nucleon interaction. At high densities well above the normal nuclear matter density, the TBF turns out to affect significantly the off-shell behavior of both the proton and neutron mass operators. The neutron and proton spectral functions in asymmetric nuclear matter are calculated and discussed. At low densities around and below the normal density, the TBF effect on the spectral functions turns out to be negligibly weak. At high densities well above the saturation density, the TBF is shown to affect noticeably the neutron and proton spectral functions.

Wang, Pei; Zuo, Wei

2014-05-01

214

Effective Field Theory for Neutron Stars with Genuine Many-body Forces  

E-print Network

The aim of our contribution is to shed some light on open questions facing the high density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role for the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings the concept of naturalness has been adopted. In order to encourage possible new directions of research, we discuss relevant aspects of a 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 Quantum Hadrodynamics (QHD) models found in literature and how we can potentially use our approach to describe new physics for neutron stars. We also show some preliminary results for the equation of state, population profiles and mass-radius relation for neutron stars assuming local charge neutrality and beta equilibrium.

Vasconcellos, C A Z; Dexheimer, V; Negreiros, R P; Horvath, J; Hadjimichef, D

2014-01-01

215

Effective Field Theory for Neutron Stars with Genuine Many-body Forces  

E-print Network

The aim of our contribution is to shed some light on open questions facing the high density nuclear many-body problem. We focus our attention on the conceptual issue of naturalness and its role for the baryon-meson coupling for nuclear matter at high densities. As a guideline for the strengths of the various couplings the concept of naturalness has been adopted. In order to encourage possible new directions of research, we discuss relevant aspects of a 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 Quantum Hadrodynamics (QHD) models found in literature and how we can potentially use our approach to describe new physics for neutron stars. We also show some preliminary results for the equation of state, population profiles and mass-radius relation for neutron stars assuming local charge neutrality and beta equilibrium.

C. A. Z. Vasconcellos; R. O. Gomes; V. Dexheimer; R. P. Negreiros; J. Horvath; D. Hadjimichef

2014-02-23

216

Alternating Magnetic Field Forces for Satellite Formation Flying  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

217

Nonlinear force-free modeling of the solar coronal magnetic field  

NASA Astrophysics Data System (ADS)

The coronal magnetic field is an important quantity because the magnetic field dominates the structure of the solar corona. Unfortunately, direct measurements of coronal magnetic fields are usually not available. The photospheric magnetic field is measured routinely with vector magnetographs. These photospheric measurements are extrapolated into the solar corona. The extrapolated coronal magnetic field depends on assumptions regarding the coronal plasma, for example, force-freeness. Force-free means that all nonmagnetic forces like pressure gradients and gravity are neglected. This approach is well justified in the solar corona owing to the low plasma beta. One has to take care, however, about ambiguities, noise and nonmagnetic forces in the photosphere, where the magnetic field vector is measured. Here we review different numerical methods for a nonlinear force-free coronal magnetic field extrapolation: Grad-Rubin codes, upward integration method, MHD relaxation, optimization, and the boundary element approach. We briefly discuss the main features of the different methods and concentrate mainly on recently developed new codes.

Wiegelmann, T.

2008-03-01

218

Recoil curve properties and coercive force decrease ratio in NdFeB sintered magnets  

NASA Astrophysics Data System (ADS)

It is examined that whether a reverse domain and magnetic domain wall exist in a lower demagnetization area than the coercive force and whether the observed demagnetization ratio curve can be explained using the alignment distribution function or not. From measurements of the recoil curve in the low demagnetization field, it was confirmed that minor demagnetization occurred in every demagnetization field and magnets of every grade of coercive force. The alignment distribution of Nd2Fe14B grains was also measured by electron back-scattering diffraction (EBSD). The alignments and the coercive force decrease ratios were calculated using these alignment distributions. These data were compared against the results obtained from magnetization measurements. From EBSD data, it was found that the alignment distributions of magnets used in this experiment were close to a Gaussian distribution. It was also found that there was no difference in the alignment distribution between magnets with Dy and without Dy, even though the coercive force decrease ratios were Dy dependent. The calculated alignments using the alignment distribution functions were close to the values of magnetization measurements. However, it was found that the calculated coercive force decrease ratios were different from the results obtained from magnetization measurement.

Matsuura, Yutaka; Kitai, Nobuyuki; Ishii, Rintaro; Natsumeda, Toshimitsu; Hoshijima, Jun

2013-11-01

219

Influence of an external magnetic field on forced turbulence in a swirling flow of liquid metal  

Microsoft Academic Search

We report an experimental investigation on the influence of an external magnetic field on forced three-dimensional turbulence of liquid gallium in a closed vessel. We observe an exponential damping of the turbulent velocity fluctuations as a function of the interaction parameter N (ratio of Lorentz force over inertial terms of the Navier-Stokes equation). The flow structures develop some anisotropy but

Basile Gallet; Michael Berhanu; Nicolas Mordant

2009-01-01

220

Van der Waals versus dipolar forces controlling mesoscopic organizations of magnetic nanocrystals  

Microsoft Academic Search

The structure, thermodynamics and dynamics in many physical and chemical systems are determined by interplay of short-range isotropic and long-range anisotropic forces. Magnetic nanoparticles dispersed in solution are ideal model systems to study this interplay, as they are subjected to both isotropic van der Waals and anisotropic dipolar forces. Here we show from experiment an abrupt transition of maghemite nanocrystal

Y. Lalatonne; J. Richardi; M. P. Pileni

2004-01-01

221

A low-temperature dynamic mode scanning force microscope operating in high magnetic fields  

E-print Network

-field optical microscope designed for operation at low temperatures.5 In this setup, an optical fiber is glued scanning near field optical microscopy,5,7­10 magnetic force microscopy,11 and acoustic near field as a friction- force sensor. The advantages of these piezoelectric sensors are the availability, the low cost

Ihn, Thomas

222

Influence of Waiting Time on the Levitation Force Between a Permanent Magnet and a Superconductor  

NASA Astrophysics Data System (ADS)

This paper describes the experimental results of the levitation force of single-grained YBaCuO bulk superconductors preparing by the top-seeded melt-growth method with different waiting time tw below an NdFeB permanent magnet. It was found that waiting time has large effects on the zero-field-cooled (ZFC) and field-cooled (FC) levitation force, and the levitation force shows aging characteristics at the liquid nitrogen temperature.

Zhang, Xing-Yi; Zhou, You-He; Zhou, Jun

223

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

Microsoft Academic Search

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

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

2007-01-01

224

Fabrication of 3D Tissue-Like Structure Ussing Magnetite Nanoparticles and Magnetic Force  

Microsoft Academic Search

Novel technologies to establish 3D tissue-like constructs are desired for tissue engineering. In the present study, magnetic force and magnetite nanoparticles were used to construct a layered mesenchymal stem cell (MSC) sheet, a layered cardiomyocyte sheet, and a layered fibroblast sheet involving capillaries. Magnetite cationic liposomes (MCLs) were taken up by the target cells. When a magnet was set under

A. Ito; K. Ino; K. Shimizu; H. Honda; M. Kamihira

2006-01-01

225

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

226

Force.  

ERIC Educational Resources Information Center

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

Gamble, Reed

1989-01-01

227

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

SciTech Connect

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

He, Jianliang; Coffey, H.

1997-08-01

228

Energy Loss by Drag Force of Superconductor Flywheel Energy Storage System With Permanent Magnet Rotor  

Microsoft Academic Search

Energy loss is one of the most important problems for the practical use of superconductor flywheel energy storage (SFES) system. The energy loss of the SFES is mainly caused by drag force induced by magnetic field parts such as the superconductor magnetic bearing (SMB) and permanent magnet (PM)-type motor\\/generator (PMSM\\/G). In this paper, a vertical-shaft-type SFES with journal-type SMB was

Jeong-Phil Lee; Byung-Jun. Park; Young-Hee Han; Se-Yong Jung; Tae-Hyun Sung

2008-01-01

229

Fast magnetic reconnection driven by ponderomotive force in two-beam laser-solid interactions  

SciTech Connect

The magnetic reconnection phenomenon has been repeatedly observed in laser plasmas. A fast magnetic-reconnection model driven by the ponderomotive force was developed to explain the phenomenon in two-beam laser-solid interactions. Properties of the magnetic-reconnection process, such as the reconnection time scale and jet velocity, are obtained with classical values of the Spitzer resistivity. Our results are consistent with experimental measurements.

Liu Sanqiu [Department of Physics, Nanchang University, Nanchang 330047 (China); School of Materials Science and Engineering, Nanchang University, Nanchang 330047 (China); Yang Xiaosong [School of Materials Science and Engineering, Nanchang University, Nanchang 330047 (China); Li Xiaoqing [Department of Physics, Nanjing Normal University, Nanjing 210097 (China)

2011-11-15

230

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

SciTech Connect

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

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

2011-12-31

231

A new method to destruct targeted cells using magnetizable beads and pulsed magnetic force  

Microsoft Academic Search

We investigated a new method to destruct targeted cells using magnetizable beads and pulsed magnetic force. The cells were combined with the beads by an antigen-antibody reaction (cell\\/bead\\/antibody complex), aggregated by a magnet, and stimulated by a magnetic stimulator. The viability of the aggregated and stimulated cell\\/bead\\/antibody complexes was significantly decreased, and the cells were destructed by the penetration of

Mari Ogiue-Ikeda; Yuko Sato; Shoogo Ueno

2003-01-01

232

Guidance force in an infinitely long superconductor and permanent magnetic guideway system  

NASA Astrophysics Data System (ADS)

Guidance force is calculated when a high-temperature superconductor moves laterally on a permanent magnetic guideway. Both the superconductor and the guideway are infinitely long. The dependence of guidance performance upon both geometrical parameters, such as the shape of the superconductor and the guideway, and intrinsic parameters, such as critical current density of the superconductor and uniform magnetization of the guideway, are studied. The results may be helpful to the design and optimization of the superconducting magnetically levitated train system.

Wang, Xiaorong; Ren, Zhongyou; Song, Honghai; Wang, Xingzhi; Zheng, Jun; Wang, Suyu; Wang, Jiasu; Zhao, Yong

2005-02-01

233

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

234

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

NASA Astrophysics Data System (ADS)

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

Garshelis, I. J.; Crevecoeur, G.

2014-05-01

235

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

NASA Technical Reports Server (NTRS)

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

Yang, Wei-Hong

1987-01-01

236

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

PubMed

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

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

2013-04-01

237

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

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

238

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

PubMed

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

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

2015-02-01

239

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

240

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

SciTech Connect

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

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

2011-06-15

241

Magnetic energy dissipation in force-free jets  

NASA Technical Reports Server (NTRS)

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.

Choudhuri, Arnab Rai; Konigl, Arieh

1986-01-01

242

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

PubMed Central

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

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

2013-01-01

243

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

NASA Astrophysics Data System (ADS)

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

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

1998-08-01

244

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

245

Adaptive forced balancing for magnetic bearing control systems  

Microsoft Academic Search

Active magnetic bearings (AMBs) support shafts or rotors without any mechanical contract. They require feedback control for robust stabilization and performance. A problem common to all mechanical systems with rotating shafts, including AMB systems, is the synchronous vibration caused by mass unbalance. Autobalancing compensation causes AMB actuators to spin a rotor about its inertial axis and thus eliminate the centrifugal

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

1992-01-01

246

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

NASA Astrophysics Data System (ADS)

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

Cheng, Bo; Hu, Zheng; Deng, Xinyan

2010-11-01

247

Many-body Interactions in Magnetic Films and Nanostructures  

SciTech Connect

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

Stephen D. Kevan

2012-12-12

248

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

249

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

PubMed Central

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

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

1999-01-01

250

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

PubMed

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

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

2014-02-01

251

Effect of Low-Pass Filtering in Force Calibration of Magnetic Tweezers  

NASA Astrophysics Data System (ADS)

In typical experiments where magnetic tweezers are involved, precise measurement of the magnetic forces is of crucial importance. To achieve this, a widely applied method is to track the bead's Brownian motion trajectory and to calculate the force from its mean-squared-displacement. However, this method does not take into account the fact that the bead-tracking device always has a finite bandwidth, acting effectively as a low-pass filter. The result could be subjected to significant system errors, which overestimates the magnetic force. We analyze the power spectrum of the bead's Brownian motion, and provide a corrected formula to calculate the magnetic force, which is free of system errors induced by limited detection bandwidth. A dsDNA force-extension curve is experimentally measured. The curve is consistent with the WLC model, exhibiting correctness of the new formula. On the other hand, the force given by the traditional method shows significant deviation from the WLC model, which is 3 times larger at most.

Zheng, Hai-Zi; Nong, Da-Guan; Li, Ming

2013-11-01

252

Particle tracks in a cloud chamber: historical photographs as a context for studying magnetic force  

NASA Astrophysics Data System (ADS)

We present a sequence of experiments aimed at exploring magnetic force. The activity sequence was organized into three main phases, each starting from an experiment. The first phase aimed to help students understand the direction and magnitude of the magnetic force experienced by current-carrying wires located in a homogeneous magnetic field; the second referred to the study of magnetic force acting on electrons emitted by a cathode and moving through a homogeneous magnetic field; finally, students were asked to analyse the sub-nuclear particle tracks in cloud and streamer chambers in real experiments, based on the experience they acquired during previous work with digital photographs. The activity sequence was designed for students on introductory physics courses or in advanced high-school classes and was implemented in five high-school classes (approximately 100 students). Our results compared with those reported in the literature indicate that students' understanding of the direction and magnitude of magnetic force improved markedly and that some typical difficulties were overcome.

Onorato, Pasquale; De Ambrosis, Anna

2012-11-01

253

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

PubMed Central

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

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

2006-01-01

254

Forced convection of power-law fluids flow over a rotating nonisothermal body  

SciTech Connect

Presented is an analysis of steady laminar flow of power-law fluids past a rotating body with nonisothermal surfaces. A coordinate transformation combined with the Merk-type series expansion is employed to transform the governing momentum equations into a set of coupled ordinary differential equations. The equations are numerically integrated to obtain the axial and tangential velocity gradients for determining the friction coefficient. For forced convection, a generalized coordinate transformation is used to analyze the temperature field of the power-law flow. Solutions to the transformed energy equations are obtained in the form of universal functions. The heat transfer coefficients in terms of NuRe exp 1/(n + 1) are presented for a rotating sphere. The effects of power-law index, rotation parameter, Prandtl number, and the location of step discontinuity in surface temperature on the local Nusselt number are fully investigated and demonstrated. 13 refs.

Kim, H.W.; Esseniyi, A.J. (Youngstown State Univ., OH (United States))

1993-12-01

255

A Hybrid N-Body Code Incorporating Algorithmic Regularization and Post-Newtonian Forces  

E-print Network

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

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

2008-03-15

256

Improvement of the propulsion force for HTSC-permanent magnet hybrid magnetically levitated carrying system by using the pinned flux of HTSC  

NASA Astrophysics Data System (ADS)

Magnetically levitated carrying system has been developed. In this system, pinning force of high temperature bulk superconductor (HTSC) is used for the levitation and guidance. The magnetic rail is set on the ground, and flux from the magnetic rail is pinned by HTSCs. To increase levitation force, repulsive force of the permanent magnet is used. For the propulsion system, electromagnets are installed on the surface of the magnetic rail. Improvement of the propulsion force is studied. In the previous system, only flux of the permanent magnet of the carrier is used for propulsion. To increase propulsion force, that of the HTSC of the carrier is also used. Using this excitation method, the propulsion force is improved even though total number of the excited coil is the same.

Ikeda, M.; Sasaki, R.; Ueno, T.; Ohashi, S.

257

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

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

258

Effects of Spin Quantum Force in Magnetized Quantum Plasma  

NASA Astrophysics Data System (ADS)

Starting from the governing equations for a quantum magnetoplasma including the electron spin -1/2 effects and quantum Bohm potential, we derive Korteweg-de Vries (KdV) equation of the system of quantum magnetohydrodynamics (QMHD). The amplitude and width of magnetosonic soliton with different parameters in the system are studied. It is found that the normalized Zeeman energy E plays a crucial role, for E >= 1 the amplitude rm? and the width w? of solitary wave all decrease as E increases. That is, the introduction of spin quantum force modifies the shape of solitary magnetosonic waves and makes them more narrower and shallower.

Yang, Xiu-Feng; Jiang, Hong; Qi, Xue-Hong; Duan, Wen-Shan

2011-10-01

259

Forces  

NSDL National Science Digital Library

This page provides the background for a basic laboratory exercise on force. Included is an explanation of force and vector components and an interactive java applet to demonstrate vectors and vector algebra.

Sorokin, Vladimir

2004-11-28

260

Manipulation and sorting of magnetic particles by a magnetic force microscope on a microfluidic magnetic trap platform  

E-print Network

to a magnetic particle that follows the field gradients generated by macroscopic rare-earth magnets that provides a translatable local magnetic field gradient to capture and move magnetic particles with nanometer a magnetic field gradient to pull the magnetic particles away from the solution, thereby leaving the unwanted

Donahue, Michael J.

261

Manipulation and sorting of magnetic particles by a magnetic force microscope on a microfluidic magnetic trap platform  

E-print Network

to a magnetic particle that follows the field gradients generated by macroscopic rare­earth magnets that provides a translatable local magnetic field gradient to capture and move magnetic particles with nanometer a magnetic field gradient to pull the magnetic particles away from the solution, thereby leaving the unwanted

Donahue, Michael J.

262

Operation of a forced two phase cooling system on a large superconducting magnet  

SciTech Connect

This paper describes the operation of a forced two phase cooling system on a two meter diameter superconducting solenoid. The magnet is a thin high current density superconducting solenoid which is cooled by forced two phase helium in tubes around the coil. The magnet, which is 2.18 meters in diameter and 3.4 meters long, has a cold mass of 1700 kg. The two phase cooling system contains less than 300 liters of liquid helium, most of which is contained in a control dewar. This paper describes the operating characteristics of the LBL two phase forced cooling system during cooldown and warm up. The paper presents experimental data on operations of the magnet using either a helium pump or the refrigerator compressor to circulate two phase helium through the superconducting coil cooling tubes.

Green, M.A.; Burns, W.A.; Eberhard, P.H.; Gibson, G.H.; Pripstein, M.; Ross, R.R.; Smits, R.G.; Taylor, J.D.; Van Slyke, H.

1980-05-01

263

Role of Three-Body Forces in Proton and Heavy-Ion Scatterings  

NASA Astrophysics Data System (ADS)

The three-body forces (TBF) effect is known to play an important role on the nuclear saturation property, which can be demonstrated typically in the Brueckner (G-matrix) theory. Recently, we have proposed new complex G-matrix interactions CEG07, from which nucleon-nucleus (NA) and nucleus-nucleus (AA) folding potentials are obtained. The CEG07 G-matrices are derived from the free-space nucleon-nucleon interaction, the Extended Soft Core (ESC) model, including the TBF contributions composed of the three-body repulsive (TBR) and attractive (TBA) components. Using CEG07, we have analyzed the elastic scattering of NA and AA systems. For NA systems, we have tested the optical potentials obtained by the single-folding procedure with CEG07 in the cases of the proton elastic scattering. We have further applied the CEG07 G-matrix to the AA systms in the framework of the double-folding model and analyzed the elastic scattering of complex nuclei systems at E/A = 70 ~ 135 MeV. The TBF (especially TBR) effect is clearly seen in all cases investigated.

Furumoto, Takenori; Sakuragi, Yukinori; Yamamoto, Yasuo

2011-09-01

264

Approximating edges of source bodies from magnetic or gravity anomalies.  

USGS Publications Warehouse

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

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

1986-01-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

266

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

SciTech Connect

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

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

1994-05-01

267

Force  

NSDL National Science Digital Library

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

Brownie, Mrs.

2010-04-07

268

Influence of an external magnetic field on forced turbulence in a swirling flow of liquid metal  

E-print Network

We report an experimental investigation on the influence of an external magnetic field on forced 3D turbulence of liquid gallium in a closed vessel. We observe an exponential damping of the turbulent velocity fluctuations as a function of the interaction parameter N (ratio of Lorentz force over inertial terms of the Navier-Stokes equation). The flow structures develop some anisotropy but do not become bidimensional. From a dynamical viewpoint, the damping first occurs homogeneously over the whole spectrum of frequencies. For larger values of N, a very strong additional damping occurs at the highest frequencies. However, the injected mechanical power remains independent of the applied magnetic field. The simultaneous measurement of induced magnetic field and electrical potential differences shows a very weak correlation between magnetic field and velocity fluctuations. The observed reduction of the fluctuations is in agreement with a previously proposed mechanism for the saturation of turbulent dynamos and wit...

Gallet, Basile; Mordant, Nicolas

2009-01-01

269

Magnetic Resonance Force Microscopy of paramagnetic electron spins at millikelvin temperatures  

E-print Network

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

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

2011-05-17

270

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

271

Development of forced flow cooled current leads for fusion magnets  

NASA Astrophysics Data System (ADS)

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

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

2001-03-01

272

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

E-print Network

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

Navas, David

273

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

NASA Astrophysics Data System (ADS)

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

Farnoush, Somayeh; Manzari, Mehrdad T.

2014-12-01

274

High-Resolution Magnetic Resonance Force Microscopy using Iron Filled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Magnetic Resonance Force Microscopy is able to probe below surfaces to map out spins in a non-destructive manner by measuring the force from the dipolar coupling of a magnetic probe to spins in the sample. We have used low force constant cantilevers with low intrinsic dissipation to obtain 2 spin sensitivity. To obtain better sensitivity one avenue of improvement is to increase the magnetic field gradient from the magnetic probe. Iron-filled carbon nanotubes provide a promising route for very high magnetic field gradient micromagnetic probes; we have successfully attached these iron nanowires to IBM style ultrasoft silicon cantilevers. The smaller size of the tip (15 to 25 nm) allows gradients an order of magnitude greater than micron-sized rare-earth magnets. In addition, iron filled carbon nanotubes have the possibility to lower the non-contact friction by reducing the surface area of the probe close to the sample. Iron filled carbon nanotubes also exhibit high anisotropy fields, a result of the shape anisotropy. This work was supported by The Army Research Office under W911NF-07-1-0305 and the National Science Foundation under DMR-0807093.

Herman, Michael; Banerjee, Palash; Chung Fong, Kin; Pelekhov, Denis; Wolny, Franziska; Muhl, Thomas; Büchner, Bernd; Hammel, Chris

2009-03-01

275

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

E-print Network

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

M. Angeles Perez-Garcia; J. Navarro; A. Polls

2009-04-06

276

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

NASA Technical Reports Server (NTRS)

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

Dress, David A.

1988-01-01

277

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

PubMed

The impulse oscillation system (IOS) has been developed recently to measure respiratory system resistance (Rrs) and reactance (Xrs) at different frequencies up to > or = 25 Hz. IOS has, however, not been validated against established techniques. This study compared IOS with the classical pseudorandom noise forced oscillation technique (FOT) and body plethysmographic airway resistance (Raw) in 49 subjects with a variety of lung disorders and a wide range of Raw (0.10-1.28 kPa x L(-1) x s). Rrs,IOS was slightly greater than Rrs,FOT, especially at lower frequencies, with a mean +/- SD difference at 5-6 Hz of 0.14 +/- 0.09 kPa x L(-1) x s. Comparisons with the wave-tube technique applied on two analogues indicated an overestimation by IOS. Xrs,IOS and Xrs,FOT were very similar, with a slightly higher resonant frequency with IOS than with FOT (mean difference +/- SD 1.35 +/- 3.40 Hz). Raw was only moderately correlated with Rrn,FOT and Rrs-IOS; although the mean differences were small (0.04 +/- 0.14 kPa x L(-1)s for Rrs6,FOT and -0.10 +/- 0.14 kPa x L(-1) x s for Rrs5,IOS), IOS and FOT markedly underestimated high resistance values. In conclusion, the impulse oscillation system yields respiratory system resistance and reactance values similar, but not identical to those provided by the forced oscillation technique. PMID:11589356

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

2001-09-01

278

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

E-print Network

Numerical dosimetry of currents induced in the human body by ELF magnetic fields Riccardo Scorretti, 2010 Abstract Purpose: The classical - a formulations for numerical dosimetry of currents induced dosimetry, formulation, finite element 1 Introduction The fields induced in the human body by ELF

Paris-Sud XI, Université de

279

Contactless grasp of a magnetic particle in a fluid and its application to quantifications of forces affecting its behavior  

NASA Astrophysics Data System (ADS)

In this study, the contactless grasp of a magnetic particle suspended in a fluid at rest or in motion by coil current control, and a method for estimating these forces quantitatively were developed. Four electromagnets were used to apply magnetic fields to magnetic ferrite particles (diameter, 300 nm-300 µm) in a fluid in a vessel. Particle-tracking velocimetry with high-speed image processing was used to visualize the behavior of the magnetic particles in the fluid. In addition, contactless grasp of a magnetic particle using the feedback control was accomplished. Furthermore, by making the magnetic force and the resultant force of the other forces affecting a magnetic particle be in balance, the vertical and horizontal forces affecting the minute magnetic particle, such as the viscous force or the magnetic force between magnetized particles, could be estimated quantitatively from the current in the coil of each electromagnet, without any physical contact with the particle itself. These results constitute useful information for studies on the issues in the handling of micro- or nano-particles.

Tokura, S.; Hara, M.; Kawaguchi, N.; Amemiya, N.

2014-03-01

280

Effect of Annealing on Coercive Force and Remanent Magnetizations in Magnetite  

Microsoft Academic Search

A series of experiments is described in which single crystals of magnetite were annealed under controlled conditions. Structural changes in the magnetite were followed by changes in the magnitudes of coercive force and saturation isothermal remanent magnetization. The structural changes were identified by comparing their activation energies as estimated from the annealing curves with those of known physical processes. It

W. Lowrie; M. Fuller

1969-01-01

281

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

Microsoft Academic Search

Brushless permanent magnet motors have been widely used in home applications and industrial fields. These days, high efficiency and low noise motors are demanded from the view point of environment. Electromagnetic noise and iron loss of the motor are produced by the harmonic fluxes and electromagnetic forces. However, order and space pattern of these have not been discussed in detail.

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

2007-01-01

282

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

E-print Network

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

Bausch, Andreas

283

Calculation of cogging force in a novel slotted linear tubular brushless permanent magnet motor  

SciTech Connect

There is an increasing requirement for controlled linear motion over short and long strokes, in the factory automation and packaging industries, for example. Linear brushless PM motors could offer significant advantages over conventional actuation technologies, such as motor driven cams and linkages and pneumatic rams--in terms of efficiency, operating bandwidth, speed and thrust control, stroke and positional accuracy, and indeed over other linear motor technologies, such as induction motors. Here, a finite element/analytical based technique for the prediction of cogging force in a novel topology of slotted linear brushless permanent magnet motor has been developed and validated. The various force components, which influence cogging are pre-calculated by the finite element analysis of some basic magnetic structures, facilitate the analytical synthesis of the resultant cogging force. The technique can be used to aid design for the minimization of cogging.

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

1997-09-01

284

Estimation of the total magnetization direction of approximately spherical bodies  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

285

High coercive force and large remanent moment magnetic films with special anisotropies (invited)  

NASA Astrophysics Data System (ADS)

Special sputtering methods have been used to synthesize magnetic films that exhibit high intrinsic coercive forces iHc, large remanent moments, and special anisotropies. By special anisotropies we mean that the easy direction of magnetization in various films can be made to be either in or out of the film plane or in a particular direction within the film plane. To achieve high coercive forces in the films it has been necessary to synthesize the films from high iHc rare-earth transition metal systems such as SmCo5, Nd2Fe14B, and several new compounds in the Sm-Ti-Fe system. Films have been synthesized with different crystal textures by varying the sputtering parameters. The magnetic properties observed have been found to be strongly dependent on the film texture. Several possible film scale geometries for electronic applications have been considered.

Cadieu, F. J.

1987-04-01

286

Body armour: the effect of load, exercise and distraction on landing forces.  

PubMed

We investigated the effect of added load and intense exercise on jump and landing performance and ground reaction force (GRF) during landings where attentional demand was varied. Fifty-two males (37 ± 9.2 years, 180.7 ± 6.1 cm, 90.2 ± 11.6 kg, maximal aerobic fitness (VO(?max)) 50 ± 8.5 ml (.) kg(-1 .) min(-1), BMI 27.6 ± 3.1, mean ± s) completed a VO(?max) test. Experimental sessions were completed (?4 days in between) in a randomised counterbalanced order, one while wearing body armour and appointments (loaded) and one without load (unloaded). A vertical jump, a drop landing concentrating on safe touchdown, a drop jump and a drop landing with an attentional distraction were performed. These were repeated 1 min after a 5-min treadmill run. Mean jump height decreased by 12% (P < 0.001) with loading and a further by 6% following the running task. Peak GRFs were increased by 13-19% with loading (P < 0.001) depending on the landing task demands and a further by 4-9% following intense exercise. The distracted drop landing had significantly higher GRFs compared to all other landings. Results demonstrate that added load impacts on jumping and landing performance, an effect that is amplified by prior intense exercise, and distraction during landing. Such increases in GRF apply to police officer performance in their duties and may increase the risk of injury. PMID:24050682

Dempsey, Paddy C; Handcock, Phil J; Rehrer, Nancy J

2014-01-01

287

Do body weight and gender shape the work force? The case of Iceland.  

PubMed

Most studies of the relationship between body weight - as well as its corollary, beauty - and labor-market outcomes have indicated that it is a function of a gender bias, the negative relationship between excess weight or obesity and labor-market outcomes being greater for women than for men. Iceland offers an exceptional opportunity to examine this hypothesis, given that it scores relatively well on an index of gender equality comprising economic, political, educational, labor-market, and health-based criteria. Equipped with an advanced level of educational attainment, on average, women are well represented in Iceland's labor force. When it comes to women's presence in the political sphere, Iceland is out of the ordinary as well; that Icelanders were the first in the world to elect a woman to be president may suggest a relatively gender-blind assessment in the labor market. In the current study, survey data collected by Gallup Iceland in 2002 are used to examine the relationship between weight and employment within this political and social setting. Point estimates indicate that, despite apparently lesser gender discrimination in Iceland than elsewhere, the bias against excess weight and obesity remains gender-based, showing a slightly negative relationship between weight and the employment rate of women, whereas a slightly positive relationship was found for men. PMID:21196135

Asgeirsdottir, Tinna Laufey

2011-03-01

288

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

SciTech Connect

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).

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

2010-01-15

289

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

290

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

E-print Network

An estimate of strong local body forcing and gravity wave radiation based on OH airglow and meteor with an OH airglow imager and the meteor radar at the MU Observatory in Japan. This was a wave breaking event of momentum and energy to play a role in thermospheric dynamics to much higher altitudes than previously

Vadas, Sharon

291

Effects of Rigid Body Collisions and Tide-Forced Drift on Large Tabular Icebergs of the Antarctic  

E-print Network

1 Effects of Rigid Body Collisions and Tide-Forced Drift on Large Tabular Icebergs of the Antarctic ICEBERGS #12;2 Abstract. Following the calving of an iceberg from an ice shelf, many collisions between the new iceberg and the remaining shelf can occur as the iceberg responds to time-varying oceanic

Macayeal, Douglas R.

292

Pressure tensor and heat flux vector for inhomogeneous nonequilibrium fluids under the influence of three-body forces  

E-print Network

Pressure tensor and heat flux vector for inhomogeneous nonequilibrium fluids under the influence the influence of three-body forces. The derivation is based on the method of planes formalism of Todd, Evans for the isotropic pressure, but have negligible influence on the shear stress hence viscosity and heat flux vector

293

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

294

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

SciTech Connect

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

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

1998-09-01

295

Embedding Circular Force-Free Flux Ropes in Potential Magnetic Fields  

NASA Astrophysics Data System (ADS)

We propose a method for constructing approximate force-free equilibria in active regions that locally have a potential bipolar-type magnetic field with a thin force-free flux rope embedded inside it. The flux rope has a circular-arc axis and circular cross-section in which the interior magnetic field is predominantly toroidal (axial). Its magnetic pressure is balanced outside by that of the poloidal (azimuthal) field created at the boundary by the electric current sheathing the flux rope. To facilitate the implementation of the method in our numerical magnetohydrodynamic (MHD) code, the entire solution is described in terms of the vector potential of the magnetic field. The parameters of the flux rope can be chosen so that a subsequent MHD relaxation of the constructed configuration under line-tied conditions at the boundary provides a numerically exact equilibrium. Such equilibria are an approximation for the magnetic configuration preceding solar eruptions, which can be triggered in our model by imposing suitable photospheric flows beneath the flux rope. The proposed method is a useful tool for constructing pre-eruption magnetic fields in data-driven simulations of solar active events. Research supported by NASA's Heliophysics Theory and LWS Programs, and NSF/SHINE and NSF/FESD.

Titov, V. S.; Torok, T.; Mikic, Z.; Linker, J.

2013-12-01

296

Magnetic susceptibility variations in Loess sequences and their relationship to astronomical forcing  

NASA Technical Reports Server (NTRS)

The long, well-exposed and often continuous sequences of loess found throughout the world are generally thought to provide an excellent opportunity for studying long-term, large-scale environmental change during the last few million years. In recent years, the most fruitful loess studies have been those involving the deposits of the loess in China. One of the most intriguing results of that work has been the discovery of an apparent correlation between variations in the magnetic susceptibility of the loess sequence and the oxygen isotope record of the deep sea. This correlation implies that magnetic susceptibility variations are being driven by astronomical parameters. However, the basic data have been interpreted in various ways by different authors, most of whom assumed that the magnetic minerals in the loess have not been affected by post-depositional processes. Using a chemical extraction procedure that allows us to separate the contribution of secondary pedogenic magnetic minerals from primary inherited magnetic minerals, we have found that the magnetic susceptibility of the Chinese paleosols is largely due to a pedogenic component which is present to a lesser degree in the loess. We have also found that the smaller inherited component of the magnetic susceptibility is about the same in the paleosols and the loess. These results demonstrate the need for additional study of the processes that create magnetic susceptibility variations in order to interpret properly the role of astronomical forcing in producing these variations.

Verosub, Kenneth L.; Singer, Michael J.

1992-01-01

297

Non-linear Force-free Modeling Of Coronal Magnetic Fields  

NASA Astrophysics Data System (ADS)

We compare a variety of nonlinear force-free field (NLFFF) extrapolation algorithms, including optimization, magneto-frictional, and Grad-Rubin-like codes, applied to a solar-like reference model. The model used to test the algorithms includes realistic photospheric Lorentz forces and a complex field including a weakly twisted, right helical flux bundle. The codes were applied to both forced "photospheric'' and more force-free "chromospheric'' vector magnetic field boundary data derived from the model. When applied to the chromospheric boundary data, the codes are able to recover the presence of the flux bundle and the field's free energy, though some details of the field connectivity are lost. When the codes are applied to the forced photospheric boundary data, the reference model field is not well recovered, indicating that the Lorentz forces on the photosphere severely impact the extrapolation of the field. Preprocessing of the photospheric boundary does improve the extrapolations considerably, although the results depend sensitively on the details of the numerical codes. When applying the NLFFF codes to solar data, the problems associated with Lorentz forces present in the low solar atmosphere must be recognized: the various codes will not necessarily converge to the correct, or even the same, solution.

Metcalf, Thomas R.; De Rosa, M. L.; Schrijver, C. J.; Barnes, G.; van Ballegooijen, A.; Wiegelmann, T.; Wheatland, M. S.; Valori, G.; McTiernan, J. M.

2007-05-01

298

ENSC 283: Center of Pressure and Hydrostatic Force on a submerged body School of Engineering Science  

E-print Network

surface. Because no shear stress exists in a static fluid, all hydrostatic forces on any element-section. Hence, the force due to weight of the water always produces the same moment referred to the pinpoint how appended weight, , and its lever arm, , are related to resultant force and its lever arm: . . (13

Bahrami, Majid

299

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

SciTech Connect

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

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

2010-07-15

300

Report of the Task Force on SSC Magnet System Test Site  

SciTech Connect

The Task Force on SSC Magnet Systems test Site was appointed by Maury Tigner, Director of the SSC, Phase 1 in August 1984. In brief, the charge asked the Task Force to make a critical evaluation of potential test sites for a major SSC magnet System Test Facility (STF) with regard to: (1) availability of the needed space, utilities, staff and other requirements on the desired time scale; and (2) the cost of preparing the sites for the tests and for operating the facilities during the test period. The charge further suggests that, by virtue of existing facilities and availability of experienced staff, BNL and FNAL are the two best candidate sites and that is therefore appears appropriate to restrict the considerations of the Task Force to these sites. During the subsequent deliberations of the Task Force, no new facts were revealed that altered the assumptions of the charge in this regard. The charge does not ask for a specific site recommendation for the STF. Indeed, an agreement on such a recommendation would be difficult to achieve considering the composition of the Task Force, wherein a large fraction of the membership is drawn from the two contending laboratories. Instead, we have attempted to describe the purpose of the facility, outline a productive test program, list the major facilities required, carefully review the laboratories` responses to the facility requirements, and make objective comparisons of the specific features and capabilities offered.

NONE

1984-10-01

301

Two-body interaction currents and nuclear magnetic moments  

Microsoft Academic Search

The meson-theoretical approach to nuclear interaction currents is considered in the one-meson exchange approximation. Results are presented for two models of charge-symmetric piN coupling: the gamma5 model and the static model. The effect of interaction currents on the nuclear dipole magnetic moment of odd-mass-nuclei with jj closed-shells plus (or minus) one nucleon is calculated within the framework of the pure

Marc Chemtob

1969-01-01

302

Identification of superconducting phases in ceramic particles by magnetic field induced forces using a magnetized wire  

NASA Astrophysics Data System (ADS)

A new equipment for minority phase analysis of superconducting (SC) phases within chemically inhomogeneous ceramic grains using a high gradient magnetic field or field induced effect of torque is presented. Single grains down to 20 ?m are either captured by a magnetized iron wire or identified because of their torque movement in a pulsed magnetic field. An assembly of many hundreds of grains can be investigated for minor quantities of SC phases from 80 K up to room temperature. A maximum field of up to 100-140 mT allows us to reliably identify SC grains and evaluate their SC critical temperatures Tc. Localization of SC grains allows us to extract them for further analysis. Experiments with YBa2Cu3O2-? grains demonstrated that Tc values evaluated in such a way are rather close to those, which are determined by magnetization measurements.

Pérez, Daniel; Hulliger, Jürg

2010-06-01

303

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

Microsoft Academic Search

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

Masatsugu Takemoto; Akira Chiba; Hirofumi Akagi; Tadashi Fukao

2004-01-01

304

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

Microsoft Academic Search

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

Masatsugu Takemoto; Akira Chiba; Hirofumi Akagi; Tadashi Fukao

2002-01-01

305

Force-Free Magnetic Fields Calculated from Automated Tracing of Coronal Loops with AIA/SDO  

NASA Astrophysics Data System (ADS)

One of the most realistic magnetic field models of the solar corona is a nonlinear force-free field (NLFFF) solution. There exist about a dozen numeric codes that compute NLFFF solutions based on extrapolations of photospheric vector magnetograph data. However, since the photosphere and lower chromosphere is not force-free, a suitable correction has to be applied to the lower boundary condition. Despite of such "pre-processing" corrections, the resulting theoretical magnetic field lines deviate substantially from observed coronal loop geometries. - Here we developed an alternative method that fits an analytical NLFFF approximation to the observed geometry of coronal loops. The 2D coordinates of the geometry of coronal loop structures observed with AIA/SDO are traced with the "Oriented Coronal CUrved Loop Tracing" (OCCULT-2) code, an automated pattern recognition algorithm that has demonstrated the fidelity in loop tracing matching visual perception. A potential magnetic field solution is then derived from a line-of-sight magnetogram observed with HMI/SDO, and an analytical NLFFF approximation is then forward-fitted to the twisted geometry of coronal loops. We demonstrate the performance of this magnetic field modeling method for a number of solar active regions, before and after major flares observed with SDO. The difference of the NLFFF and the potential field energies allows us then to compute the free magnetic energy, which is an upper limit of the energy that is released during a solar flare.

Aschwanden, M. J.

2013-12-01

306

MEMS-Based Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer  

NASA Technical Reports Server (NTRS)

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).

Lee, Choonsup; Butler, Mark C.; Elgammal, Ramez A.; George, Thomas; Hunt, Brian; Weitekamp, Daniel P.

2006-01-01

307

Iron filled carbon nanotubes as novel monopole-like sensors for quantitative magnetic force microscopy.  

PubMed

We present a novel ultrahigh stability sensor for quantitative magnetic force microscopy (MFM) based on an iron filled carbon nanotube. In contrast to the complex magnetic structure of conventional MFM probes, this sensor constitutes a nanomagnet with defined properties. The long iron nanowire can be regarded as an extended dipole of which only the monopole close to the sample surface is involved in the imaging process. We demonstrate its potential for high resolution imaging. Moreover, we present an easy routine to determine its monopole moment and prove that this calibration, unlike other approaches, is universally applicable. For the first time this enables straightforward quantitative MFM measurements. PMID:20876975

Wolny, F; Mühl, T; Weissker, U; Lipert, K; Schumann, J; Leonhardt, A; Büchner, B

2010-10-29

308

Study of the leakage field of magnetic force microscopy thin-film tips using electron holography  

NASA Astrophysics Data System (ADS)

Electron holography is applied for the study of the leakage field of thin-film ferromagnetic tips used as probes in magnetic force microscopy. We used commercially available pyramidal tips covered on one face with a thin NiCo film, which were then placed in a high external magnetic field directed along the pyramid axis. Good agreement between simulated and experimental electron phase difference maps allows to measure the local flux from the ferromagnetic tips and therefore to evaluate the perturbation induced by the microprobe stray field on the sample area.

Frost, B. G.; van Hulst, N. F.; Lunedei, E.; Matteucci, G.; Rikkers, E.

1996-03-01

309

The Influence of the Lorentz Force on Line Profiles in Early-Type Magnetic Stars  

NASA Astrophysics Data System (ADS)

We have computed theoretical He I line profiles by means of LTE models for the photosphere of B stars. In these models we have taken into account the effect of the Lorentz force in the equation of hydrostatic equilibrium following the procedure of tet*{Valya}. We analyze the influence of a magnetic field on the line profiles. This mechanism can explain the variations in line profile and the stability of the continuum flux of some He-variable stars. We discuss the determination of abundances in magnetic stars.

Vallverdú, R. E.; Cidale, L. S.; Rohrmann, R. D.

2007-03-01

310

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.

311

Large-scale magnetic field generation by randomly forced shearing waves.  

PubMed

A rigorous theory for the generation of a large-scale magnetic field by random nonhelically forced motions of a conducting fluid combined with a linear shear is presented in the analytically tractable limit of low magnetic Reynolds number (Rm) and weak shear. The dynamo is kinematic and due to fluctuations in the net (volume-averaged) electromotive force. This is a minimal proof-of-concept quasilinear calculation aiming to put the shear dynamo, a new effect recently found in numerical experiments, on a firm theoretical footing. Numerically observed scalings of the wave number and growth rate of the fastest-growing mode, previously not understood, are derived analytically. The simplicity of the model suggests that shear dynamo action may be a generic property of sheared magnetohydrodynamic turbulence. PMID:22243085

Heinemann, T; McWilliams, J C; Schekochihin, A A

2011-12-16

312

Determination of forces in a magnetic bearing actuator - Numerical computation with comparison to experiment  

NASA Technical Reports Server (NTRS)

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.

Knight, J. D.; Xia, Z.; Mccaul, E.; Hacker, H., Jr.

1992-01-01

313

Construction of Multi-layered Cell Sheet Using Magnetite Nanoparticles and Magnetic Force  

Microsoft Academic Search

\\u000a Novel technologies to establish 3D tissue-like constructs are desired for tissue engineering. In the present study, magnetic\\u000a force and magnetite nanoparticles were used to construct a layered mesenchymal stem cell (MSC) sheet, a layered cardiomyocyte\\u000a sheet, and a layered fibroblast sheet involving capillaries. Magnetite cationic liposomes (MCLs), which have a positive surface\\u000a charge, were taken up by the target cells.

Akira Ito; Hiroyuki Honda; Masamichi Kamihira

314

Magnetic force microscopy/current contrast imaging: A new technique for internal current probing of ICs  

SciTech Connect

This invited paper describes recently reported work on the application of magnetic force microscopy (MFM) to image currents in IC conductors [1]. A computer model for MFM imaging of IC currents and experimental results demonstrating the ability to determine current direction and magnitude with a resolution of {approximately} 1 mA dc and {approximately} 1 {mu}A ac are presented. The physics of MFM signal generation and applications to current imaging and measurement are described.

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

1993-09-01

315

Investigation of Force-Freeness of Solar Emerging Magnetic Field via Application of the Virial Theorem to MHD Simulations  

E-print Network

Force-freeness of a solar magnetic field is a key to reconstructing 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 (MHD) 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.

Kang, Jihye

2014-01-01

316

Low-temperature magnetic properties of iron-bearing sulfides and their contribution to magnetism of cometary bodies  

NASA Astrophysics Data System (ADS)

In this study we present a review of low-temperature magnetic properties of alabandite (Fe, Mn)S, daubreelite FeCr 2S 4, pyrrhotite Fe 1-xS and troilite FeS updated with new experimental data. The results indicate that besides FeNi alloys mainly daubreelite with its Curie temperature T C ˜ 150 K and strong induced and remanent magnetizations may be a significant magnetic mineral in cold environments and may complement that of FeNi or even dominate magnetic properties of sulfide rich bodies at temperatures below T C. Comets are known to contain iron-bearing sulfides within dusty fraction and their surfaces are subject to temperature variations in the range of 100-200 K down to the depth of several meters while the cometary interior is thermally stable at several tens of Kelvin which is within the temperature range where alabandite, daubreelite or troilite are "magnetic". Thus not only FeNi alloys, but also sulfides have to be considered in the interpretation of magnetic data from cometary objects such as will be delivered by Rosetta mission. Modeling indicates that magnetic interactions between cometary nucleus containing iron-bearing sulfides and interplanetary magnetic field would be difficult, but not impossible, to detect from orbit. Rosetta's Philae lander present on the surface would provide more reliable signal.

Kohout, Tomáš; Kosterov, Andrei; Haloda, Jakub; Týcová, Patricie; Zbo?il, Radek

2010-08-01

317

Design framework of a teleoperating system for a magnetically levitated robot with force feedback  

NASA Astrophysics Data System (ADS)

Precise works and manipulating micro objects are tough jobs for operators both mentally and physically. To execute these jobs smoothly without feeling wrongness, use of master-slave system is preferable because position and force are able to be scaled up and down as well under the system. In this study we develop a master-slave system where the size of a slave robot is very small and the slave robot is levitated by magnetic forces. In distinction from ordinary master- slave systems, the levitated robot does not get any other contact forces from outside. Thus we introduce a method using an impedance model for constructing the master-slave system. We confirmed the effectiveness of the positioning control algorithm through experiments.

Tsuda, Naoaki; Kato, Norihiko; Nomura, Yoshihiko; Matsui, Hirokazu

2002-02-01

318

Noninvasive Oxygen Partial Pressure Measurement of Human Body Fluids In Vivo Using Magnetic Resonance Imaging1  

Microsoft Academic Search

Rationale and Objectives. The oxygen partial pressure (pO2) of human body fluids reflects the oxygenation status of sur- rounding tissues. All existing fluid pO2 measurements are invasive, requiring either microelectrode\\/optode placement or fluid removal. The purpose of this study is to develop a noninvasive magnetic resonance imaging method to measure the pO2 of human body fluids. Materials and Methods. We

Greg Zaharchuk; Reed F. Busse; Guy Rosenthal; Geoffery T. Manley; Orit A. Glenn; William P. Dillon

319

Robust tracking control of a magnetically suspended rigid body  

NASA Technical Reports Server (NTRS)

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

Lim, Kyong B.; Cox, David E.

1994-01-01

320

Theoretical analysis of ferromagnetic microparticles in streaming liquid under the influence of external magnetic forces  

NASA Astrophysics Data System (ADS)

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.

Brandl, Martin; Mayer, Michael; Hartmann, Jens; Posnicek, Thomas; Fabian, Christian; Falkenhagen, Dieter

2010-09-01

321

Quantitative magnetic resonance analysis and a morphometric predictive model reveal lean body mass changes in migrating Nearctic-Neotropical passerines.  

PubMed

Most studies of lean mass dynamics in free-living passerine birds have focused on Old World species at geographical barriers where they are challenged to make the longest non-stop flight of their migration. We examined lean mass variation in New World passerines in an area where the distribution of stopover habitat does not require flights to exceed more than a few hours and most migrants stop flying well before fat stores near exhaustion. We used either quantitative magnetic resonance (QMR) analysis or a morphometric model to measure or estimate, respectively, the fat and lean body mass of migrants during stopovers in New York, USA. With these data, we examined (1) variance in total body mass explained by lean body mass, (2) hourly rates of fat and lean body mass change in single-capture birds, and (3) net changes in fat and lean mass in recaptured birds. Lean mass contributed to 50% of the variation in total body mass among white-throated sparrows Zonotrichia albicollis and hermit thrushes Catharus guttatus. Lean mass of refueling gray catbirds Dumetella carolinensis and white-throated sparrows, respectively, increased 1.123 and 0.320 g h(-1). Lean mass of ovenbirds Seiurus aurocapillus accounted for an estimated 33-40% of hourly gains in total body mass. On average 35% of the total mass gained among recaptured birds was lean mass. Substantial changes in passerine lean mass are not limited to times when birds are forced to make long, non-stop flights across barriers. Protein usage during migration is common across broad taxonomic groups, migration systems, and migration strategies. PMID:21079970

Seewagen, Chad L; Guglielmo, Christopher G

2011-04-01

322

ON THE STABILITY OF NON-FORCE-FREE MAGNETIC EQUILIBRIA IN STARS  

SciTech Connect

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.

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

323

Template-assisted CoPd nanowire arrays: magnetic properties and FORC analysis.  

PubMed

Highly hexagonally ordered CoPd alloy nanowire arrays were synthesized through electrochemical deposition techniques into the nanopores of anodic alumina membranes used as templates. Two different electrolytes were used for this purpose, one with pH = 4.1 and the other with pH = 7. Under applying different electrodeposition parameters and by adjusting both, the current density and the electrolyte composition, it could be possible make to vary the composition of CoPd alloy nanowires in a wide range. Their composition and morphology were investigated by SEM and EDX. The magnetic properties of the nanowires array have been measured with a VSM as a function of the temperature, ranging from RT down to 50 K, for different CoPd alloy nanowires composition. Also, the temperature influence on the reversible-irreversible magnetization processes related with the magnetization reversal of the CoPd nanowires array has been analyzed by first order reversal curve (FORC) method. PMID:22905524

Vega, V; Rosa, W O; García, J; Sánchez, T; Santos, J D; Béron, F; Pirota, K R; Prida, V M; Hernando, B

2012-06-01

324

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

Microsoft Academic Search

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

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

2003-01-01

325

The design, construction, and calibration of a dynamometer used to measure forces applied by a magnetic bearing to a rotating shaft  

E-print Network

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...

Henderson, Gregory Lane

2012-06-07

326

A comparison of 60 Hz uniform magnetic and electric induction in the human body  

NASA Astrophysics Data System (ADS)

High-resolution computations of induced fields are used to assess equivalent source levels for human exposure to uniform low-frequency electric and magnetic fields. These results pertain to 60 Hz foot-to-head electric excitation of the body in three positions with respect to a ground plane, and to magnetic excitation by three orthogonal source orientations. All computations are based on an anatomically derived human body model composed of 1736 873 cubic voxels with 3.6 mm edges. The data for magnetic excitation are computed using a scalar potential finite difference (SPFD) method, while those for electric excitation are computed using a hybrid method based on the SPFD method coupled with a quasistatic finite difference time domain code. The data are analysed in two ways, using an induced current density threshold of . Firstly, the various field strengths required to produce a whole-body average current density magnitude equal to the threshold are derived for each configuration, and the associated current density levels in various organs and tissues are presented. It is found that the average current density magnitude values in at least one tissue group can be up to 3 (5) times greater than the whole-body average under electric (magnetic) excitation, and that the associated maximum values can be up to 46 (28) times greater than the whole-body average under electric (magnetic) excitation, for at least one source/body configuration. Secondly, the data are analysed from the opposite point of view, in which the source levels required to induce average or maximum induced current density magnitudes at the threshold level in specific tissue groups are determined. Evaluations such as the present one should prove useful in the development of protection standards, and are also expected to aid in the understanding of results from various animal and tissue culture studies.

Dawson, Trevor W.; Caputa, Kris; Stuchly, Maria A.

1997-12-01

327

Magnetism and mineralogy of Almahata Sitta polymict ureilite (= asteroid 2008 TC3): Implications for the ureilite parent body magnetic field  

NASA Astrophysics Data System (ADS)

The Almahata Sitta meteorite is the first case of recovered extraterrestrial material originating from an asteroid that was detected in near Earth space shortly before entering and exploding in the high atmosphere. The aims of our project within the 2008 TC3 consortium were investigating Almahata Sitta's (AS) magnetic signature, phase composition and mineralogy, focussing on the opaque minerals, and gaining new insights into the magnetism of the ureilite parent body (UPB). We report on the general magnetic properties and behavior of Almahata Sitta and try to place the results in context with the existing data set on ureilites and ureilite parent body models. The magnetic signature of AS is dominated by a set of low-Ni kamacites with large grain sizes. Additional contributions come from micron-sized kamacites, suessite, (Cr) troilite, and daubreelite, mainly found in the olivine grains adjacent to carbon-rich veins. Our results show that the paleomagnetic signal is of extraterrestrial origin as can be seen by comparing with laboratory produced magnetic records (IRM). Four types of kamacite (I-IV) have been recognized in the sample. The elemental composition of the ureilite vein metal Kamacite I (particularly Co) clearly differs from the other kamacites (II-IV), which are considered to be indigenous. Element ratios of kamacite I indicate that it was introduced into the UPB by an impactor, supporting the conclusions of Gabriel and Pack (2009).

Hoffmann, Viktor H.; Hochleitner, Rupert; Torii, Masayuki; Funaki, Minoru; Mikouchi, Takashi; Kaliwoda, Melanie; Jenniskens, Peter; Shaddad, Muawia H.

2011-10-01

328

Magnetic Boundary Conditions at Non-Conducting Planetary Bodies: Applications to Ganymede  

NASA Astrophysics Data System (ADS)

The interaction of planetary bodies with their surrounding magnetized plasma can often be described with the magneto-hydrodynamic (MHD) equations, which are commonly solved by numerical models. For these models it is necessary to define physically correct boundary conditions. Many planetary bodies have electrically non-conductive surfaces, which do not allow electric current to penetrate their surfaces. Magnetic boundary conditions, which correctly consider that the associated radial electric current at the planetary surface is zero, are however difficult to implement because they include the curl of the magnetic field. Here we derive new boundary conditions for the magnetic field at non-conducting surfaces by a decomposition of the magnetic field in poloidal and toroidal components and their spherical harmonics expansions. We find that the toroidal part of the magnetic field needs to vanish at the surface of the isolator. For the spectral spherical harmonics coefficients of the poloidal part we derive a Cauchy boundary condition, which includes the Gauss coefficients of a possible intrinsic field. Our non-conducting boundary condition can thus additionally include intrinsic dynamo fields as well as induction fields within electrically conductive subsurface layers such as subsurface oceans. We implement the new boundary condition in the MHD simulation code ZEUS-MP using spherical geometry. We apply these new magnetic boundary conditions to a model for Ganymede's plasma environment. With this model we can describe the in-situ observations by the Galileo spacecraft and Hubble Space Telescope observations of Ganmyede's aurora very well.

Saur, J.; Duling, S.; Seufert, M.; Wicht, J.

2013-12-01

329

Acute effects of whole-body vibration on jump force and jump rate of force development: a comparative study of different devices.  

PubMed

The goal of this study was to compare the acute effects of whole-body vibration (WBV) delivered by 3 devices with different mechanical behavior on jump force (JF) and jump rate of force development (JRFD). Twelve healthy persons (4 women and 8 men; age 30.5 ± 8.8 years; height 178.6 ± 7.3 cm; body mass 74.8 ± 9.7 kg) were exposed to WBV for 15 and 40 seconds using 2 professional devices (power plate [PP; vertical vibration] and Galileo 2000 [GA; oscillatory motion around the horizontal axis in addition to vertical vibration]) and a home-use device [Power Maxx, PM; horizontal vibration]). The JF and JRFD were evaluated before, immediately after, and 5 minutes after WBV. The JF measured immediately after 40 seconds of vibration by the GA device was reduced (3%, p = 0.05), and JRFD measured after 5 minutes of rest after 40 seconds of vibration by the PM device was reduced (12%, p < 0.05) compared with the baseline value. The acute effects of WBV (15 or 40 seconds) on JF and JRFD were not significantly different among the 3 devices. In conclusion, our hypothesis that WBV devices with different mechanical behaviors would result in different acute effects on muscle performance was not confirmed. PMID:22126972

Bagheri, Javad; van den Berg-Emons, Rita J; Pel, Johan J; Horemans, Herwin L; Stam, Henk J

2012-03-01

330

Measurement of the adhesion force between particles for high gradient magnetic separation of pneumatic conveyed powder products  

NASA Astrophysics Data System (ADS)

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.

Senkawa, K.; Nakai, Y.; Mishima, F.; Akiyama, Y.; Nishijima, S.

2011-11-01

331

Comment on 'Casimir force acting on magnetodielectric bodies embedded in media'  

SciTech Connect

It is shown that the Raabe and Welsch [Phys. Rev. A 71, 013814 (2005)] criticism of the Dzyaloshinskii-Lifshitz-Pitaevskii theory of the van der Waals-Casimir forces inside a medium is based on misunderstandings. It is explained why and at which conditions one can use the ''Minkowski-like'' stress tensor for calculations of the forces. The reason why, in my opinion, the approach of Raabe and Welsch is incorrect is discussed.

Pitaevskii, L. P. [Department of Physics, University of Trento and CNR-INFM BEC Center, I-38050 Povo, Trento (Italy)

2006-04-15

332

Estimating three-dimensional orientation of human body parts by inertial/magnetic sensing.  

PubMed

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

Sabatini, Angelo Maria

2011-01-01

333

Estimating Three-Dimensional Orientation of Human Body Parts by Inertial/Magnetic Sensing  

PubMed Central

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

Sabatini, Angelo Maria

2011-01-01

334

Mapping magnetized geologic structures from space: The effect of orbital and body parameters  

NASA Technical Reports Server (NTRS)

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.

Schnetzler, C. C.; Taylor, P. T.; Langel, R. A.

1984-01-01

335

Fully Suspended, Five-Axis, Three-Magnetic-Bearing Dynamic Spin Rig With Forced Excitation  

NASA Technical Reports Server (NTRS)

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.

Morrison, Carlos R.; Provenza, Andrew; Kurkov, Anatole; Montague, Gerald; Duffy, Kirsten; Mehmed, Oral; Johnson, Dexter; Jansen, Ralph

2004-01-01

336

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

NASA Technical Reports Server (NTRS)

Innovative Information Systems (IIS), Inc. is in the process of designing and fabricating a high bandwidth force and moment measuring device (i.e. the Magnetic Thruster Test Stand). This device will use active magnetic suspension to allow direct measurements of the forces and torques generated by the rocket engines of the missile under test. The principle of operation of the Magnetic Thruster Test Stand (MTTS) is based on the ability to perform very precise, high bandwidth force and position measurements on an object suspended in a magnetic field. This ability exists due to the fact that the digital servo control mechanism that performs the magnetic suspension uses high bandwidth (10 kHz) position data (via an eddy-current proximity sensor) to determine the amount of force required to maintain stable suspension at a particular point. This force is converted into required electromagnet coil current, which is then output to a current amplifier driving the coils. A discussion of how the coil current and magnetic gap distance (the distance between the electromagnet and the object being suspended) is used to determine the forces being applied from the suspended assembly is presented.

Stuart, Keith; Bartosh, Blake

1993-01-01

337

A Novel Magnetic Suspension-Force Compensation in Bearingless Induction-Motor Drive With Squirrel-Cage Rotor  

Microsoft Academic Search

This paper presents an improved analysis of magnetic force compensation in a bearingless induction motor with a squirrel-cage rotor. The expressions for air-gap flux linkages are derived. Simulation blocks of suspension force are constructed. A novel control system, which compensates the delay and direction error in suspension force generation for a squirrel-cage rotor, is proposed. The efficacy of the proposed

Taishi Hiromi; Tatsuya Katou; Akira Chiba; M. Azizur Rahman; Tadashi Fukao

2007-01-01

338

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  

NASA Astrophysics Data System (ADS)

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.

Karc?, Özgür; Dede, Münir; Oral, Ahmet

2014-10-01

339

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.  

PubMed

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. PMID:25362401

Karc?, Ozgür; Dede, Münir; Oral, Ahmet

2014-10-01

340

Asymptotic forms for the energy of force-free magnetic field ion figurations of translational symmetry  

NASA Technical Reports Server (NTRS)

It is known from computer calculations that if a force-free magnetic field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution and 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.

Sturrock, P. A.; Antiochos, S. K.; Klinchuk, J. A.; Roumeliotis, G.

1994-01-01

341

Novel System for Bite-Force Sensing and Monitoring Based on Magnetic Near Field Communication  

PubMed Central

Intraoral devices for bite-force sensing have several applications in odontology and maxillofacial surgery, as bite-force measurements provide additional information to help understand the characteristics of bruxism disorders and can also be of help for the evaluation of post-surgical evolution and for comparison of alternative treatments. A new system for measuring human bite forces is proposed in this work. This system has future applications for the monitoring of bruxism events and as a complement for its conventional diagnosis. Bruxism is a pathology consisting of grinding or tight clenching of the upper and lower teeth, which leads to several problems such as lesions to the teeth, headaches, orofacial pain and important disorders of the temporomandibular joint. The prototype uses a magnetic field communication scheme similar to low-frequency radio frequency identification (RFID) technology (NFC). The reader generates a low-frequency magnetic field that is used as the information carrier and powers the sensor. The system is notable because it uses an intra-mouth passive sensor and an external interrogator, which remotely records and processes information regarding a patient's dental activity. This permits a quantitative assessment of bite-force, without requiring intra-mouth batteries, and can provide supplementary information to polysomnographic recordings, current most adequate early diagnostic method, so as to initiate corrective actions before irreversible dental wear appears. In addition to describing the system's operational principles and the manufacture of personalized prototypes, this report will also demonstrate the feasibility of the system and results from the first in vitro and in vivo trials. PMID:23112669

Lantada, Andres Diaz; Bris, Carlos Gonzalez; Morgado, Pilar Lafont; Maudes, Jesus Sanz

2012-01-01

342

Generalized Lorentz Law and the force of radiation on magnetic dielectrics  

NASA Astrophysics Data System (ADS)

The macroscopic equations of Maxwell combined with a generalized form of the Lorentz law are a complete and consistent set; not only are these five equations fully compatible with the special theory of relativity, they also conform with the conservation laws of energy, momentum, and angular momentum. The linear momentum density associated with the electromagnetic field is ?EM(r,t)=E(r,t)×H(r,t)/c2, whether the field is in vacuum or in a ponderable medium. [Homogeneous, linear, isotropic media are typically specified by their electric and magnetic permeabilities ?? ?(?) and ???(?).] The electromagnetic momentum residing in a ponderable medium is often referred to as Abraham momentum. When an electromagnetic wave enters a medium, say, from the free space, it brings in Abraham momentum at a rate determined by the density distribution ?EM(r,t), which spreads within the medium with the light's group velocity. The balance of the incident, reflected, and transmitted (electromagnetic) momenta is subsequently transferred to the medium as mechanical force in accordance with Newton's second law. The mechanical force of the radiation field on the medium may also be calculated by a straightforward application of the generalized form of the Lorentz law. The fact that these two methods of force calculation yield identical results is the basis of our claim that the equations of electrodynamics (Maxwell + Lorentz) comply with the momentum conservation law. When applying the Lorentz law, one must take care to properly account for the effects of material dispersion and absorption, discontinuities at material boundaries, and finite beam dimensions. This paper demonstrates some of the issues involved in such calculations of the electromagnetic force in magnetic dielectric media.

Mansuripur, Masud

2008-08-01

343

A nonlinear eigenvalue problem for self-similar spherical force-free magnetic fields  

NASA Astrophysics Data System (ADS)

An axisymmetric force-free magnetic field B(r, ?) in spherical coordinates is defined by a function r sin ? B ? = Q ( A ) relating its azimuthal component to its poloidal flux-function A. The power law r sin ? B ? = a A | A | 1/ n, n a positive constant, admits separable fields with A = An/(?)rn, posing a nonlinear boundary-value problem for the constant parameter a as an eigenvalue and An(?) 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/(? ,?)rn+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.

Lerche, I.; Low, B. C.

2014-10-01

344

Atomic force microscopy-coupled microcoils for cellular-scale nuclear magnetic resonance spectroscopy  

PubMed Central

We present the coupling of atomic force microscopy (AFM) and nuclear magnetic resonance (NMR) technologies to enable topographical, mechanical, and chemical profiling of biological samples. Here, we fabricate and perform proof-of-concept testing of radiofrequency planar microcoils on commercial AFM cantilevers. The sensitive region of the coil was estimated to cover an approximate volume of 19.4?×?103??m3 (19.4?pl). Functionality of the spectroscopic module of the prototype device is illustrated through the detection of 1? resonance in deionized water. The acquired spectra depict combined NMR capability with AFM that may ultimately enable biophysical and biochemical studies at the single cell level. PMID:24719493

Mousoulis, Charilaos; Maleki, Teimour; Ziaie, Babak; Neu, Corey P.

2013-01-01

345

Cooling a magnetic resonance force microscope via the dynamical back action of nuclear spins  

NASA Astrophysics Data System (ADS)

We analyze the back-action influence of nuclear spins on the motion of the cantilever of a magnetic force resonance microscope. We calculate the contribution of nuclear spins to the damping and frequency shift of the cantilever. We show that, at the Rabi frequency, the energy exchange between the cantilever and the spin system cools or heats the cantilever depending on the sign of the high-frequency detuning. We also show that the spin noise leads to a significant damping of the cantilever motion.

Greenberg, Ya. S.; Il'Ichev, E.; Nori, Franco

2009-12-01

346

Measurement and calculation of levitation forces between magnets and granular superconductors  

NASA Technical Reports Server (NTRS)

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.

Johansen, T. H.; Bratsberg, H.; Baziljevich, M.; Hetland, P. O.; Riise, A. B.

1995-01-01

347

Measurement and calculation of levitation forces between magnets and granular superconductors  

SciTech Connect

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. The authors have studied central features of the mechanics of PM-HTSC systems of simple geometries. Here they 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 using a minimum of model parameters.

Johansen, T.H.; Bratsberg, H.; Baziljevich, M.; Hetland, P.O.; Riise, A.B.

1995-04-01

348

STRUCTURE OF NON-FORCE-FREE MAGNETIC FLUX ROPES IN AN AMBIENT MEDIUM  

SciTech Connect

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.

Chen, James, E-mail: James.Chen@nrl.navy.mil [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375 (United States)

2012-12-20

349

Sub-surface characterization and three dimensional profiling of semiconductors by magnetic resonance force microscopy  

SciTech Connect

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.

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

1996-10-01

350

Laminar Forced Convection Heat Transfer From Isothermal Bodies With Unity Aspect Ratio in Coaxial Air Flow  

Microsoft Academic Search

In this article a semianalytical approach is employed to obtain dimensionless heat transfer correlations for forced convection over three geometries—sphere, cone, and cylinder with unity aspect ratio in laminar axial air flow. The comparison of the present results for a sphere with the previous work shows very good agreement. For example, the average difference between the results of the present

Yaser Hadad; Khosrow Jafarpur

2012-01-01

351

Revolting bodies, hysterical state: women protesting the Armed Forces Special Powers Act (1958)  

Microsoft Academic Search

The Armed Forces Special Powers Act (1958) (AFSPA) has been debilitating for people in Manipur, already struggling with socio-economic and political marginalisation since independence. The consistent erasure of Manipur by an apathetic and forgetful ‘mainland’ India provides the political impetus for anti-state groups demanding autonomy. The people of the state are, however, ambivalent about taking sides, having experienced the violence

Namrata Gaikwad

2009-01-01

352

Flame sheet dynamics of bluff-body stabilized flames during longitudinal acoustic forcing  

E-print Network

, and the kinematic response of the flame to this forcing. The near-field flame features are con- trolled by flame anchoring and the far-field by kinematic restoration. In the near-field, the flame response grows. This behavior is strongly non-linear, resulting in significant variation in far-field flame-sheet response

Lieuwen, Timothy C.

353

Quantitative modeling of forces in electromagnetic tweezers  

PubMed Central

This paper discusses numerical simulations of the magnetic field produced by an electromagnet for generation of forces on superparamagnetic microspheres used in manipulation of single molecules or cells. Single molecule force spectroscopy based on magnetic tweezers can be used in applications that require parallel readout of biopolymer stretching or biomolecular binding. The magnetic tweezers exert forces on the surface-immobilized macromolecule by pulling a magnetic bead attached to the free end of the molecule in the direction of the field gradient. In a typical force spectroscopy experiment, the pulling forces can range between subpiconewton to tens of piconewtons. In order to effectively provide such forces, an understanding of the source of the magnetic field is required as the first step in the design of force spectroscopy systems. In this study, we use a numerical technique, the method of auxiliary sources, to investigate the influence of electromagnet geometry and material parameters of the magnetic core on the magnetic forces pulling the target beads in the area of interest. The close proximity of the area of interest to the magnet body results in deviations from intuitive relations between magnet size and pulling force, as well as in the force decay with distance. We discuss the benefits and drawbacks of various geometric modifications affecting the magnitude and spatial distribution of forces achievable with an electromagnet. PMID:21258580

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

2010-01-01

354

Quantitative modeling of forces in electromagnetic tweezers  

NASA Astrophysics Data System (ADS)

This paper discusses numerical simulations of the magnetic field produced by an electromagnet for generation of forces on superparamagnetic microspheres used in manipulation of single molecules or cells. Single molecule force spectroscopy based on magnetic tweezers can be used in applications that require parallel readout of biopolymer stretching or biomolecular binding. The magnetic tweezers exert forces on the surface-immobilized macromolecule by pulling a magnetic bead attached to the free end of the molecule in the direction of the field gradient. In a typical force spectroscopy experiment, the pulling forces can range between subpiconewton to tens of piconewtons. In order to effectively provide such forces, an understanding of the source of the magnetic field is required as the first step in the design of force spectroscopy systems. In this study, we use a numerical technique, the method of auxiliary sources, to investigate the influence of electromagnet geometry and material parameters of the magnetic core on the magnetic forces pulling the target beads in the area of interest. The close proximity of the area of interest to the magnet body results in deviations from intuitive relations between magnet size and pulling force, as well as in the force decay with distance. We discuss the benefits and drawbacks of various geometric modifications affecting the magnitude and spatial distribution of forces achievable with an electromagnet.

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

2010-11-01

355

Upper body force production after a low-volume static and dynamic stretching.  

PubMed

This study investigated the acute effect of a low-volume static and dynamic stretching on maximal isometric peak force (MIPF), time to maximal isometric force (TMIF), rate of force production (RFP) and average amplitude of the surface EMG (AvgEMG) of the main agonist muscles acting on the bench press maximum isometric force exercise. Thirty subjects were randomly divided into three groups: static stretch (SG: 22.8 ± 5.6 years, 176.6 ± 3.5 cm, 74.4 ± 5.9 kg), dynamic stretch (DG: 21.4 ± 3.9 years, 178.4 ± 7.2 cm, 71.7 ± 8.2 kg) and control group (CG: 20.4 ± 3.6 years, 179.8 ± 5.8 cm, 74.4 ± 9.8 kg). SG performed two 30-s repetitions and DG performed 10 repetitions of each of the two different exercises for the pectoralis major and triceps brachii. The MIPF, TMIF, RFP and AvgEMG of the pectoralis major (sternocostal part) and triceps brachii (long and lateral head) were measured before and immediately after the stretching protocols. A significant decrease in the MIPF from pre- to post-stretching was observed in both SG (p <0.001) and DG (p <0.05). No significant differences were found in the CG for all force parameters. No significant differences in the TMIF and RFP from pre- to post-stretching were found in the three groups. The SG showed a significant (p <0.05) decrease in the AvgEMG of the three muscles, whereas no significant differences were found for the DG and CG. These findings suggest that a low-volume static and dynamic stretching adversely affects efforts of muscle maximal strength of the upper limb muscles studied, but it does not seem to affect TMIF or RFP. PMID:24533497

Leone, D C P G; Pezarat, P; Valamatos, M J; Fernandes, O; Freitas, S; Moraes, A C

2014-01-01

356

Noninvasive Measurements of Magnetic Field Generated by Induced Current within Human Body under Exposure to Very Low Frequency Electromagnetic Fields  

Microsoft Academic Search

We have developed a measurement system for a magnetic field that is generated by the induced ionic current within the human body under exposure to very low frequency electromagnetic fields, and compared the magnetic field strength obtained with those of a magnetomyogram (MMG). The developed system consists of an exposure coil, a magnetic sensor, a lock-in detector, and data acquisition.

Keiji Tsukada; Toshihiko Kiwa

2005-01-01

357

Magnetism on the angrite parent body and the early differentiation of planetesimals.  

PubMed

Angrites are among the oldest known pristine basaltic meteorites and record the earliest stages of planet formation and differentiation. Our paleomagnetic analysis of three angrites found that they record a past magnetic field of approximately 10 microteslas on the angrite parent body extending from 4564 to at least 4558 million years ago. Because the angrite paleomagnetic record extends beyond the expected lifetime of the early circumstellar disk, these paleofields were probably generated internally on the angrite parent body, possibly by an early dynamo in a rapidly formed metallic core. PMID:18974346

Weiss, Benjamin P; Berdahl, James S; Elkins-Tanton, Linda; Stanley, Sabine; Lima, Eduardo A; Carporzen, Laurent

2008-10-31

358

Forced convection of power-law fluids flow over a rotating nonisothermal body  

Microsoft Academic Search

Presented is an analysis of steady laminar flow of power-law fluids past a rotating body with nonisothermal surfaces. A coordinate transformation combined with the Merk-type series expansion is employed to transform the governing momentum equations into a set of coupled ordinary differential equations. The equations are numerically integrated to obtain the axial and tangential velocity gradients for determining the friction

H. W. Kim; A. J. Esseniyi

1993-01-01

359

Nonlinear Force-free Extrapolation of the Coronal Magnetic Field Based on the Magnetohydrodynamic Relaxation Method  

NASA Astrophysics Data System (ADS)

We develop a nonlinear force-free field (NLFFF) extrapolation code based on the magnetohydrodynamic (MHD) relaxation method. We extend the classical MHD relaxation method in two important ways. First, we introduce an algorithm initially proposed by Dedner et al. to effectively clean the numerical errors associated with ? · B . Second, the multigrid type method is implemented in our NLFFF to perform direct analysis of the high-resolution magnetogram data. As a result of these two implementations, we successfully extrapolated the high resolution force-free field introduced by Low & Lou with better accuracy in a drastically shorter time. We also applied our extrapolation method to the MHD solution obtained from the flux-emergence simulation by Magara. We found that NLFFF extrapolation may be less effective for reproducing areas higher than a half-domain, where some magnetic loops are found in a state of continuous upward expansion. However, an inverse S-shaped structure consisting of the sheared and twisted loops formed in the lower region can be captured well through our NLFFF extrapolation method. We further discuss how well these sheared and twisted fields are reconstructed by estimating the magnetic topology and twist quantitatively.

Inoue, S.; Magara, T.; Pandey, V. S.; Shiota, D.; Kusano, K.; Choe, G. S.; Kim, K. S.

2014-01-01

360

Classical formulations of the electromagnetic self-force of extended charged bodies  

NASA Astrophysics Data System (ADS)

Several formulations of the classical electrodynamics of charged particles, as have been developed in the course of the twentieth century, are compared. The mathematical equivalence of the various dissimilar expressions for the electromagnetic self-force is demonstrated explicitly by deriving these expressions directly from one another. The new connections that are established present the previously published results on a common basis, thereby contributing to a coherent historical picture of the development of charged particle models.

Smorenburg, P. W.; Kamp, L. P. J.; Luiten, O. J.

2014-09-01

361

Effects of a Circulating-water Garment and Forced-air Warming on Body Heat Content and Core Temperature  

PubMed Central

Background: Forced-air warming is sometimes unable to maintain perioperative normothermia. We therefore compared heat transfer, regional heat distribution, and core rewarming of forced-air warming with a novel circulating-water garment. Methods: Nine volunteers were each evaluated on two randomly ordered study days. They were anesthetized and cooled to a core temperature near 34°C. The volunteers were subsequently warmed for 2.5 hours with either a circulating-water garment or forced-air cover. Overall, heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Average arm and leg (peripheral) tissue temperatures were determined from 18 intramuscular needle thermocouples, 15 skin thermal flux transducers, and “deep” arm and foot thermometers. Results: Heat production (? 60 kcal/h) and loss (?45 kcal/h) were similar with each treatment before warming. The increase in heat transfer across anterior portions of the skin surface was similar with each warming system (?65 kcal/h). Forced-air warming had no effect on posterior heat transfer whereas circulating-water transferred 21 ± 9 kcal/h through the posterior skin surface after a half hour of warming. Over 2.5 h, circulating-water thus increased body heat content 56% more than forced air. Core temperatures thus increased faster than with circulating water than forced air, especially during the first hour, with the result that core temperature was 1.1 ± 0.7°C greater after 2.5 h (P < 0.001). Peripheral tissue heat content increased twice as much as core heat content with each device, but the core-to-peripheral tissue temperature gradient remained positive throughout the study. Conclusions: The circulating-water system transferred more heat than forced air, with the difference resulting largely from posterior heating. Circulating water rewarmed patients 0.4°C/h faster than forced air. A substantial peripheral-to-core tissue-temperature gradient with each device indicated that peripheral tissues insulated the core, thus slowing heat transfer. PMID:15114200

Taguchi, Akiko; Ratnaraj, Jebadurai; Kabon, Barbara; Sharma, Neeru; Lenhardt, Rainer; Sessler, Daniel I.

2005-01-01

362

Rigid-body rotation of an electron cloud in divergent magnetic fields  

NASA Astrophysics Data System (ADS)

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.

Fruchtman, A.; Gueroult, R.; Fisch, N. J.

2013-07-01

363

Clinical examination or whole-body magnetic resonance imaging: the Holy Grail of spondyloarthritis imaging  

PubMed Central

Whole-body magnetic resonance imaging allows acquisition of diagnostic images in the shortest scan time, leading to better patient compliance and artifact-free images. Methods of clinical examination of the anterior chest wall joints vary between physician groups and consideration of the rules of rib motion is suggested. The type of joint and its synovial lining may also aid imaging/clinical correlation. This well-written study by experts in the field with a standardized design and methodology allows good scientific analysis and suggests the advantages of whole-body magnetic resonance imaging in anterior chest wall imaging. Selection of clinical examination criteria and specific joints may have had an influence on the study results and the lack of association reported. PMID:22380535

2012-01-01

364

Hysteresis force loss and damping properties in a practical magnet superconductor maglev test vehicle  

NASA Astrophysics Data System (ADS)

In order to investigate the feasible application of a permanent magnet-high-temperature superconductor (PM-HTS) interaction maglev system to a maglev train or a space vehicle launcher, we have constructed a demonstration maglev test vehicle. The force dissipation and damping of the maglev vehicle against external disturbances are studied in a wide range of amplitudes and frequencies by using a sine vibration testing set-up. The dynamic levitation force shows a typical hysteresis behavior, and the force loss is regarded as the hysteresis loss, which is believed to be due to flux motions in superconductors. In this study, we find that the hysteresis loss has weak frequency dependence at small amplitudes and that the dependence increases as the amplitude grows. To analyze the damping properties of the maglev vehicle at different field cooling (FC) conditions, we also employ a transient vibration testing technique. The maglev vehicle shows a very weak damping behavior, and the damping is almost unaffected by the trapped flux of the HTSs in different FC conditions, which is believed to be attributed to the strong pinning in melt-textured HTSs.

Yang, Wenjiang; Liu, Yu; Wen, Zheng; Chen, Xiaodong; Duan, Yi

2008-01-01

365

Forced Magnetic Reconnection at an X-point: A Fully Kinetic Study  

NASA Astrophysics Data System (ADS)

We will present electromagnetic Particle-In-Cell (PIC) simulation of the current sheet formation and resulting magnetic reconnection at an X-point of an initially potential field closed by conducting wall boundaries. The reconnection we study is driven by forcing that is far from the initial separatrices and is slow compared to a characteristic Alfvén speed. The effects of two types of forcing will be investigated separately: (i) convergent flows at two opposite boundaries, and (ii) enhanced pressure gradient in two spatial domains on opposite sides of the initial separatrix. For both cases, we will present the time dependence of the reconnecting electric field (suitably normalized), energy partitioning, and dependence on system size. Our results will be compared with fluid simulations of the same setup to seek suitable closure relation with necessary kinetic effects in the fluid models. This challenge problem is carried out under the auspices of a Focus Team in the NASA Living With a Star Targeted Research and Technology Program.; Reconnecting electric field Ey in the case of forcing by boundary convergent flows. Change of sign of Ey is observed. Note that the value shown is unnormalized and that if normalized by upstream B and outflow velocity, the value can be of order 0.1. ; The out-of-plane current along two axes passing the X-point at two times. The signs are opposite for the two times. The length of the current sheet is in tens of di while the width is about 1di.

Wang, L.; Bhattacharjee, A.; Bessho, N.; Germaschewski, K.

2012-12-01

366

Magnetic resonance imaging in the evaluation of vaginal foreign bodies in a young girl  

Microsoft Academic Search

A 7-year-old girl with foul-smelling, bloody vaginal discharge for more than 2 years was initially suspected of suffering\\u000a from vaginal foreign bodies. Although plain radiography revealed no abnormal findings in the pelvis, magnetic resonance imaging\\u000a (MRI) showed multiple low intensity objects and an intact vaginal wall. Four plastic toys were removed with forceps under\\u000a general anesthesia. MRI is supposed to

M. Kihara; N. Sato; H. Kimura; M. Kamiyama; S. Sekiya; H. Takano

2001-01-01

367

Current sheet scattering and ion isotropic boundary under 3-D empirical force-balanced magnetic field  

NASA Astrophysics Data System (ADS)

determine statistically the extent to which current sheet scattering is sufficient to account for the observed ion isotropic boundaries (IBs) for <30 keV ions, we have computed IBs from our 3-D empirical force-balanced magnetic field, identified IBs in FAST observations, and investigated the model-observation consistency. We have found in both model and FAST results the same dependences of IB latitudes on magnetic local time, ion energy, Kp, and solar wind dynamic pressure (PSW) levels: IB moves to higher latitudes from midnight toward dawn/dusk and to lower latitudes as energy increases and as Kp or PSW increases. The model predicts well the observed energy dependence, and the modeled IB latitudes match fairly well with those from FAST for Kp = 0. As Kp increases, the latitude agreement at midnight remains good but a larger discrepancy is found near dusk. The modeled IBs at the equator are located around the earthward boundary of highly isotropic ions observed by Time History of Events and Macroscale Interactions during Substorms at midnight and postmidnight, but with some discrepancy near dusk under high Kp. Thus, our results indicate that current sheet scattering generally plays the dominant role. The discrepancies suggest the importance of pitch angle scattering by electromagnetic ion cyclotron waves, which occur more often from dusk to noon and are more active during higher Kp. The comparison with the observed IBs is better with our model than under the nonforce-balanced T89, indicating that using a forced-balanced model improves the description of the magnetic field configuration and reinforces our conclusions regarding the role of current sheet scattering.

Yue, Chao; Wang, Chih-Ping; Lyons, Larry; Liang, Jun; Donovan, Eric F.; Zaharia, Sorin G.; Henderson, Michael

2014-10-01

368

Nature of stability of Mg 4 and many-body forces  

Microsoft Academic Search

The precise ab initio calculations of the tetramer Mg4 were performed at the all-electron CCSD(T)\\/aug-cc-pVQZ level. The dissociation energy in respect to all possible dissociation channels at different levels of accuracy, from SCF till CCSD(T), but with the same large basis set, was calculated. Except the SCF method, in all approximations Mg4 was found stable. The many-body decomposition of the

C. C. Díaz-Torrejón; F. Espinosa-Magaña; Ilya G. Kaplan

2010-01-01

369

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

Microsoft Academic Search

The comparative study of the interaction energy and its many-body decomposition for Be4, Mg4, and Ca4 at the all-electron CCSD(T)\\/aug-cc-pVQZ level is performed. For study of dependence of the binding energy and the orbital population on the cluster size the corresponding dimers and trimers were also calculated at the same level of theory. In comparison with weakly bound dimers, the

C. C. Díaz-Torrejón; Ilya G. Kaplan

2011-01-01

370

Quench Propagation Kinetics Within ‘Iseult\\/INUMAC’ Whole Body 11.7 T MRI Magnet Shielding Coils  

Microsoft Academic Search

In the framework of the French-German consortium Iseult\\/INUMAC, focused on very-high-magnetic-field molecular imaging, the development of an 11.7 T whole body MRI magnet has been launched in 2006. This magnet is mainly composed of one wet and cryostable main coil and two fully impregnated coils that shield the magnetic field in order to meet the security requirements on the fringe

F. P. Juster; C. Berriaud; P. Fazilleau

2010-01-01

371

On Fully Developed Channel Flows: Some Solutions and Limitations, and Effects of Compressibility, Variable Properties, and Body Forces  

NASA Technical Reports Server (NTRS)

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.

Maslen, Stephen H.

1959-01-01

372

Scaling of maximum velocity, body force, and power consumption of dielectric barrier discharge plasma actuators via particle image velocimetry  

NASA Astrophysics Data System (ADS)

This study presents Particle Image Velocimetry (PIV) measurements of the induced flow characteristics generated by single dielectric barrier discharge (DBD) actuators in quiescent conditions. The primary aim is to establish accurate empirical trends for model development on both the maximum induced velocity and body force with voltage and consumed power. The results reveal a power law variation for the maximum velocity at low voltages which is followed by an asymptotic behavior. In contrast, the body force is characterized by two power law regions. The power law exponent is shown to be a function of the dielectric thickness, frequency and dielectric constant. Reducing the former or increasing the latter two result in a higher coefficient and lower voltage at which the trend changes. The onset of the second region occurs at a Re ˜ 100 (based on the maximum velocity, um, and corresponding half height, y1/2) and is characterized by a velocity profile which no longer agrees with the laminar profile of Glauert whilst moving increasingly towards the turbulent case. Phase locked PIV measurements show that as the voltage increases the peak momentum transfer shifts from the middle of the AC cycle to the latter end of the forward stroke. Lissajous plots of um? against the corresponding x location and plasma length ?x demonstrate that the peak momentum transfer remains relatively fixed in space as the voltage and plasma length increase.

Murphy, J. P.; Kriegseis, J.; Lavoie, P.

2013-06-01

373

COMPARISON OF FORCE-FREE CORONAL MAGNETIC FIELD MODELING USING VECTOR FIELDS FROM HINODE AND SOLAR DYNAMICS OBSERVATORY  

SciTech Connect

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.

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

374

Librational motion of asymmetric rolling bodies and the role of friction force  

E-print Network

We designed a very simple asymmetric rolling spool and we studied it experimentally, in the librational regime, by using a video camera and video analysis software. Comparison of experimental results and theoretical analysis allows addressing critical aspects related both to the characteristic of the oscillatory anharmonic motion of the system and to the role of friction forces in determining it. For that reasons the asymmetric rolling spool can be presented to undergraduate students as an interesting case study where to apply their physics knowledge to understand the behavior of real objects.

Onorato, P; Mascheretti, P; De Ambrosis, A

2014-01-01

375

Magnetic force microscope study of antiferromagnet-ferromagnet exchange coupled films  

NASA Astrophysics Data System (ADS)

Magnetic microstructure in micron and submicron size elements made of bilayer antiferromagnet-ferromagnet (AFM/FM) (AFM: NiMn, PtMn, and IrMn; FM: NiFe and CoFe) exchange coupled polycrystalline films have been studied using a magnetic force microscope. AFM/FM elements with various thickness of FM layer (50-500 A) have been examined and compared with nonexchange biased FM elements of the same size, shape, and thickness. Micromagnetic structures observed in AFM/FM elements with thick (>200 A) FM layer indicated that, in addition to unidirectional anisotropy, the AFM layer induces uniaxial anisotropy in a FM layer. Bilayers with a NiMn or PtMn AFM layer exhibited higher induced uniaxial anisotropy than ones with IrMn. In the elements with a thin (<100 A) FM layer and NiMn or PtMn as an AFM layer, a local switching of the magnetization direction under an external applied field has been observed. The size of the "switched" areas depends on the material and thickness of the FM and AFM layers. No local switching, just slight rippling of magnetization in the FM, was observed in the samples with an IrMn AFM layer. The results can be explained using either the model of thermally activated switching of AFM grains or the model of induced uniaxial anisotropy at the AFM/FM interface suggesting local variations of induced uniaxial anisotropy. In both models, the in-plane exchange in the FM layer has to be taken into account.

Pokhil, Taras; Song, Dian; Linville, Eric

2002-05-01

376

Magnetism  

NSDL National Science Digital Library

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.

Team, University C.

2007-12-12

377

Equilibrium points and stability under effect of radiation and perturbing forces in the restricted problem of three oblate bodies  

NASA Astrophysics Data System (ADS)

This paper presents a generalized problem of the restricted three body studied in Abdul Raheem and Singh with the inclusion that the third body is an oblate spheroidal test particle of infinitesimally mass. The positions and stability of the equilibrium point of this problem is studied for a model in which the primaries is the binary system Struve 2398 (Gliese 725) in the constellation Draco; which consist of a pair of radiating oblate stars. It is seen that additional equilibrium points exist on the line collinear with the primaries, for some combined parameters of the problem. Hence, there can be up to five collinear equilibrium points. Two triangular points exist and depends on the oblateness of the participating bodies, radiation pressure of the primaries and a small perturbation in the centrifugal force. The stability analysis ensures that, the collinear equilibrium points are unstable in the linear sense while the triangular points are stable under certain conditions. Illustrative numerical exploration is given to indicate significant improvement of the problem in Abdul Raheem and Singh.

Singh, Jagadish; Haruna, Sunusi

2014-01-01

378

Decay Characteristics of Levitation Force of YBCO Bulk Exposed to AC Magnetic Field above NdFeB Guideway  

NASA Astrophysics Data System (ADS)

The superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the nonuniformity of the magnetic field along the movement direction above the NdFeB guideway is inevitable due to the assembly error and inhomogeneity of the material property of the NdFeB magnet. So it is required to study the characteristics of levitation force of the bulks affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we will study the characteristics of the levitation force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet is used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experimental results, it has found that the levitation force is decreasing with the application of the AC external magnetic field, and the decay increasing with the amplitude of the applied magnetic field and is almost independent of the frequency.

Liu, Minxian; Lu, Yiyun; Wang, Suyu; Ma, Guangtong

2011-04-01

379

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

E-print Network

We self-consistently derive the magnetic energy and relative magnetic helicity budgets of a three-dimensional linear force-free magnetic structure rooted in a lower boundary plane. For the potential magnetic energy we derive a general expression that gives results practically equivalent to those of the magnetic Virial theorem. All magnetic energy and helicity budgets are formulated in terms of surface integrals applied to the lower boundary, thus avoiding computationally intensive three-dimensional magnetic field extrapolations. We analytically and numerically connect our derivations with classical expressions for the magnetic energy and helicity, thus presenting a so-far lacking unified treatment of the energy/helicity budgets in the constant-alpha approximation. Applying our derivations to photospheric vector magnetograms of an eruptive and a noneruptive solar active regions, we find that the most profound quantitative difference between these regions lies in the estimated free magnetic energy and relative magnetic helicity budgets. If this result is verified with a large number of active regions, it will advance our understanding of solar eruptive phenomena. We also find that the constant-alpha approximation gives rise to large uncertainties in the calculation of the free magnetic energy and the relative magnetic helicity. Therefore, care must be exercised when this approximation is applied to photospheric magnetic field observations. Despite its shortcomings, the constant-alpha approximation is adopted here because this study will form the basis of a comprehensive nonlinear force-free description of the energetics and helicity in the active-region solar corona, which is our ultimate objective.

M. K. Georgoulis; Barry J. LaBonte

2007-06-27

380

Cryogenic analysis of forced-cooled, superconducting TF magnets for compact tokamak reactors  

SciTech Connect

Current designs for compact tokamak reactors require the toroidal- field (TF) superconducting magnets to produce fields from 10 to 15 T at the winding pack, using high-current densities to high nuclear heat loads (greater than 1 kW/coil in some instances), which are significantly greater than the conduction and radiation heat loads for which cryogenic systems are usually designed. A cryogenic system for the TF winding pack for two such tokamak designs has been verified by performing a detailed, steady-state heat-removal analysis. Helium properties along the forced-cooled conductor flow path for a range of nuclear heat loads have been calculated. The results and implications of this analysis are presented. 12 refs., 6 figs.

Kerns, J.A.; Slack, D.S.; Miller, J.R.

1988-10-25

381

Cryogenic analysis of forced-cooled, superconducting TF magnets for compact tokamak reactors  

NASA Astrophysics Data System (ADS)

Current designs for compact tokamak reactors require the toroidal-field (TF) superconducting magnets to produce fields from 10 to 15 T at the winding pack, using high-current densities to high nuclear heat loads (greater than 1 kW/coil in some instances), which are significantly greater than the conduction and radiation heat loads for which cryogenic systems are usually designed. A cryogenic system for the TF winding pack for two such tokamak designs has been verified by performing a detailed, steady-state heat-removal analysis. Helium properties along the forced-cooled conductor flow path for a range of nuclear heat loads have been calculated. The results and implications of this analysis are presented.

Kerns, J. A.; Slack, D. S.; Miller, J. R.

1988-10-01

382

Analysis of adipose tissue distribution using whole-body magnetic resonance imaging  

NASA Astrophysics Data System (ADS)

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.

Wald, Diana; Schwarz, Tobias; Dinkel, Julien; Delorme, Stefan; Teucher, Birgit; Kaaks, Rudolf; Meinzer, Hans-Peter; Heimann, Tobias

2011-03-01

383

Nonlinear Force-Free Modeling of Coronal Magnetic Fields Part I: A Quantitative Comparison of Methods  

NASA Astrophysics Data System (ADS)

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).

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

384

Magnetically operated check valve  

NASA Astrophysics Data System (ADS)

A magnetically operated check valve is disclosed having, in one aspect, 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.

Morris, Brian G.; Bozeman, Richard J., Jr.

1993-03-01

385

The dust motion inside the magnetized sheath - The effect of drag forces  

SciTech Connect

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.

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

386

Collapsing of Thick-Walled Cylinders Using Electro-Magnetic Driving Forces  

NASA Astrophysics Data System (ADS)

The Thick-Walled Cylinder technique, reported in the literature, uses explosive loading to enforce collapsing of the cylindrical sample. This experimental set-up has been established as a controlled and repeatable technique to create and study multiple adiabatic shear bands. Searching to establish a simpler experimental platform to perform large sets of experiments, we have designed an Electro-Magnetic (EM) set-up for the collapsing of thick walled cylinders. The EM set-up is based on a pulsed current generator using a capacitor bank system. The specimen is an assembly of coaxial cylinders, where the inner and outer cylinders, each attached to an opposite pole, are short-circuited. Upon discharge, a high current flows through the cylinders, in opposite directions, creating repulsive magnetic forces between them. This work presents the design procedure of the specimens using numerical simulations and some experimental results for SS304L thick-walled samples, using this set-up. The spatial distribution of the multiple adiabatic shear bands in these experiments is in good agreement with that reported in the literature for the explosive driven experiments with a similar material.

Lovinger, Zev; Rikanati, Avi; Rittel, Daniel; Rosenberg, Zvi

2009-06-01

387

The three-body problem with short-range forces: renormalized equations and regulator-independent results  

E-print Network

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

Afnan, I R; Phillips, Daniel R.

2004-01-01

388

The three-body problem with short-range forces: renormalized equations and regulator-independent results  

E-print Network

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

I. R. Afnan; Daniel R. Phillips

2003-12-05

389

Connecting Neutron Star Observations to Three-Body Forces in Neutron Matter and to the Nuclear Symmetry Energy  

E-print Network

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 using polytropes and a quark matter model, and we show that our results do not change strongly upon variation of the lower boundary density where these polytropes begin. Neutron star observations offer an important constraint on a coefficient which is directly connected to the strength of the three-body force in neutron matter, and thus some theoretical models of the three-body 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.

A. W. Steiner; S. Gandolfi

2011-10-18

390

Averaging out magnetic forces with fast rf-sweeps in an optical trap for metastable chromium atoms  

E-print Network

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.

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

391

Nonlinear Force-Free Magnetic Field Extrapolations: Comparison of the Grad Rubin and Wheatland Sturrock Roumeliotis Algorithm  

NASA Astrophysics Data System (ADS)

We compare the performance of two alternative algorithms which aim to construct a force-free magnetic field given suitable boundary conditions. For this comparison, we have implemented both algorithms on the same finite element grid which uses Whitney forms to describe the fields within the grid cells. The additional use of conjugate gradient and multigrid iterations result in quite effective codes.

Inhester, Bernd; Wiegelmann, Thomas

2006-05-01

392

Influence of experimental methods on crossing in magnetic force-gap hysteresis curve of HTS maglev system  

NASA Astrophysics Data System (ADS)

The crossing in magnetic levitation force-gap hysteresis curve of melt high-temperature superconductor (HTS) vs. NdFeB permanent magnet (PM) was experimentally studied. One HTS bulk and PM was used in the experiments. Four experimental methods were employed combining of high/low speed of movement of PM with/without heat insulation materials (HIM) enclosed respectively. Experimental results show that crossing of the levitation force-gap curve is related to experimental methods. A crossing occurs in the magnetic force-gap curve while the PM moves approaching to and departing from the sample with high or low speed of movement without HIM enclosed. When the PM is enclosed with HIM during the measurement procedures, there is no crossing in the force-gap curve no matter high speed or low speed of movement of the PM. It was found experimentally that, with the increase of the moving speed of the PM, the maximum magnitude of levitation force of the HTS increases also. The results are interpreted based on Maxwell theories and flux flow-creep models of HTS.

Lu, Yiyun; Qin, Yujie; Dang, Qiaohong; Wang, Jiasu

2010-12-01

393

Calculations of magnetic states and minimum energy paths of transitions using a noncollinear extension of the Alexander-Anderson model and a magnetic force theorem  

NASA Astrophysics Data System (ADS)

Calculations of stable and metastable magnetic states as well as minimum energy paths for transitions between states are carried out using a noncollinear extension of the multiple-impurity Alexander-Anderson model and a magnetic force theorem which is derived and used to evaluate the total energy gradient with respect to orientation of magnetic moments—an important tool for efficient navigation on the energy surface. By using this force theorem, the search for stable and metastable magnetic states as well as minimum energy paths revealing the mechanism and activation energy of transitions can be carried out efficiently. For Fe monolayer on W(110) surface, the model gives magnetic moment as well as exchange coupling between nearest and next-nearest neighbors that are in good agreement with previous density functional theory calculations. When applied to nanoscale Fe islands on this surface, the magnetic moment is predicted to be 10% larger for atoms at the island rim, explaining in part an experimentally observed trend in the energy barrier for magnetization reversal in small islands. Surprisingly, the magnetic moment of the atoms does not change much along the minimum energy path for the transitions, which for islands containing more than 15 atom rows along either [001] or [11¯0] directions involves the formation of a thin, temporary domain wall. A noncollinear magnetic state is identified in a 7×7 atomic row Fe island where the magnetic moments are arranged in an antivortex configuration with the central ones pointing out of the (110) plane. This illustrates how the model can describe complicated exchange interactions even though it contains only a few parameters. The minimum energy path between this antivortex state and the collinear ground state is also calculated and the thermal stability of the antivortex state estimated.

Bessarab, Pavel F.; Uzdin, Valery M.; Jónsson, Hannes

2014-06-01

394

Evolution of a Magnetic Flux Rope and its Overlying Arcade Based on Nonlinear Force-free Field Extrapolations  

NASA Astrophysics Data System (ADS)

Dynamic phenomena indicative of slipping reconnection and magnetic implosion were found in a time series of nonlinear force-free field (NLFFF) extrapolations for the active region 11515, which underwent significant changes in the photospheric fields and produced five C-class flares and one M-class flare over five hours on 2012 July 2. NLFFF extrapolation was performed for the uninterrupted 5 hour period from the 12 minute cadence vector magnetograms of the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory. According to the time-dependent NLFFF model, there was an elongated, highly sheared magnetic flux rope structure that aligns well with an H? filament. This long filament splits sideways into two shorter segments, which further separate from each other over time at a speed of 1-4 km s-1, much faster than that of the footpoint motion of the magnetic field. During the separation, the magnetic arcade arching over the initial flux rope significantly decreases in height from ~4.5 Mm to less than 0.5 Mm. We discuss the reality of this modeled magnetic restructuring by relating it to the observations of the magnetic cancellation, flares, a filament eruption, a penumbra formation, and magnetic flows around the magnetic polarity inversion line.

Jing, Ju; Liu, Chang; Lee, Jeongwoo; Wang, Shuo; Wiegelmann, Thomas; Xu, Yan; Wang, Haimin

2014-03-01

395

Radial force and speed detection for improved magnetic suspension in bearingless motors  

Microsoft Academic Search

In this paper, radial forces and speeds are detected and used in negative feedback loops to enhance damping factors and response speed in bearingless induction motors. Radial forces and speeds are calculated from the detected radial force fluxes. Both radial force and torque generating fluxes are detected from search coil fluxes wound around stator teeth. The effectiveness on improving damping

Akira Chiba; Koji Kiryu; M. Azizur Rahman; Tadashi Fukao

2006-01-01

396

Control of natural convection in non- and low-conducting diamagnetic fluids in a cubical enclosure using inhomogeneous magnetic fields with different directions  

Microsoft Academic Search

A magnetization force caused by an inhomogeneous magnetic field is a body force and acts on both paramagnetic and diamagnetic fluids. Most practically important fluids are diamagnetic. In this paper, the magnetic effect on natural convection in non- and low-conducting diamagnetic fluids is numerically investigated, focusing on the effects of the direction of magnetization force and the dependence of Ra.

L. B. Wang; Nobuko I. Wakayama

2002-01-01

397

Application of small-angle neutron scattering to the study of forces between magnetically chained monodisperse ferrofluid emulsion droplets  

SciTech Connect

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.

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

398

Effect of the size of GdBCO-Ag secondary magnet on the static forces performance of linear synchronous motors  

NASA Astrophysics Data System (ADS)

Bulk high temperature superconductor magnets (HTSMs) have a higher flux-generating capability compared to conventional permanent magnets (PMs). These materials potentially can be used in high temperature superconducting (HTS) linear synchronous 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 of the secondary HTSM on the static performance (thrust force and normal force) of a LSM. In order to obtain high-field HTSM as the secondary, single grain bulk GdBCO-Ag superconductors of diameter 20 mm, 30 mm and 40 mm, which have higher Jc and trapped fields than YBCO superconductors, were used in this device for the first time following application by the same optimized magnetization condition. It was found that both thrust and normal forces increase and saturate with the increasing size of the HTSM secondary at the small size range, and then potentially distort when the physical size of the HTSM secondary approaches the pole pitch of the linear three-phase primary windings of the LSM. Furthermore, more experiments of a larger-sized multi-seeded HTSM secondary, confirmed that the relationship between the HTSM secondary size and the pole pitch of the primary is an important factor for achieving higher thrust and normal forces. It is suggested that the multi-pole HTSM secondary will be more beneficial to future HTS LSM designs since the single-pole HTSM secondary size should be equal to or smaller than the stator pole pitch in the paper.

Zheng, Jun; Shi, Yunhua; He, Dabo; Jing, Hailian; Li, Jing; Deng, Zigang; Wang, Suyu; Wang, Jiasu; Cardwell, David A.

2014-11-01

399

Erratum: Casimir interaction between two magnetic metals in comparison with nonmagnetic test bodies [Phys. Rev. B 88, 155410 (2013)  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

400

Estimating whole body intermuscular adipose tissue from single cross-sectional magnetic resonance images  

PubMed Central

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

Ruan, Xiang Yan; Gallagher, Dympna; Harris, Tamara; Albu, Jeanine; Heymsfield, Steven; Kuznia, Patrick; Heshka, Stanley

2009-01-01

401

Large Eddy Simulations of forced ignition of a non-premixed bluff-body methane flame with Conditional Moment Closure  

SciTech Connect

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)

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

402

Study of the branching domain structures in epitaxial films of yttrium iron garnet by end face magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The distribution of the magnetization vector on the free surface and end (cleaved facet) of thick epitaxial yttrium iron garnet films has been studied by the scanning magnetic-force microscopy method. Volume fractal-like branching of the domain structure has been found at the interface of the film and the free space with the refinement of the formed partial branches of the stripe (labyrinth) domains. Triangular closing domains have been observed at the interface between the film and the substrate. Direct experimental proof of the existence of the static horizontal Bloch lines within the stripe domain walls has been obtained.

Lisovskii, F. V.; Mansvetova, E. G.; Temiryazeva, M. P.; Temiryazev, A. G.

2013-01-01

403

Numerical evaluation of 60 Hz magnetic induction in the human body in complex occupational environments.  

PubMed

Exposure to 60 Hz non-uniform magnetic fields is evaluated using realistic configurations of three-phase current-carrying conductors. Two specific scenarios are considered, one involving a seated worker performing cable maintenance in an underground vault with conductors carrying 500 A root-mean-square (rms) per phase, and the other involving a standing worker during inspection of a 700 MW generator with conductors carrying 20000 A (rms) per phase. Modelling is performed with a high-resolution (3.6 mm) voxel model of the human body using the scalar potential finite difference (SPFD) method. Very good correspondence is observed between various exposure-field measures, such as the maximum, average, rms and standard deviation values, and the associated induced field measures within the whole body and various organs. The exposure fields produced by the lower currents in the vault conductors result in correspondingly low current densities induced in human tissues. Average values are typically below 0.2 mA m(-2). On the other hand, the average exposure related to the inspection of the generator isophase buses is about 1.5 mT at a distance of 1.2 m from the conductors. This field induces organ average current densities in the range of 2-8 mA m(-2), and peak (maximum in voxel) values above 10 mA m(-2). A comparison with uniform field exposures indicates that induced fields in organs can be reasonably well estimated from the accurately computed exposure fields averaged over the organs and the organ dosimetric data for uniform magnetic fields. Furthermore, the non-uniform field exposures generally result in lower induced fields than those for the uniform fields of the same intensity. PMID:10232812

Dawson, T W; Caputa, K; Stuchly, M A

1999-04-01

404

Body position can be monitored in 3D using miniature accelerometers and earth-magnetic field sensors  

Microsoft Academic Search

Objectives: The study and diagnosis of movement disorders can be improved by monitoring body position simultaneously with the EMG.Methods: We developed a monitor of the 3-dimensional (3D) orientation of body parts that can be applied in long-term ambulatory recordings in the daily life of a patient. The 3D sensor combines miniature sensors for earth's gravity and magnetism. It measures 60×50×10

Bob Kemp; Ad J. M. W. Janssen; Bob van der Kamp

1998-01-01

405

Estimation of changes in dynamic hydraulic force in a magnetically suspended centrifugal blood pump with transient computational fluid dynamics analysis.  

PubMed

The effect of the hydraulic force on magnetically levitated (maglev) pumps should be studied carefully to improve the suspension performance and the reliability of the pumps. A maglev centrifugal pump, developed at Ibaraki University, was modeled with 926 376 hexahedral elements for computational fluid dynamics (CFD) analyses. The pump has a fully open six-vane impeller with a diameter of 72.5 mm. A self-bearing motor suspends the impeller in the radial direction. The maximum pressure head and flow rate were 250 mmHg and 14 l/min, respectively. First, a steady-state analysis was performed using commercial code STAR-CD to confirm the model's suitability by comparing the results with the real pump performance. Second, transient analysis was performed to estimate the hydraulic force on the levitated impeller. The impeller was rotated in steps of 1 degrees using a sliding mesh. The force around the impeller was integrated at every step. The transient analysis revealed that the direction of the radial force changed dynamically as the vane's position changed relative to the outlet port during one circulation, and the magnitude of this force was about 1 N. The current maglev pump has sufficient performance to counteract this hydraulic force. Transient CFD analysis is not only useful for observing dynamic flow conditions in a centrifugal pump but is also effective for obtaining information about the levitation dynamics of a maglev pump. PMID:19894088

Masuzawa, Toru; Ohta, Akiko; Tanaka, Nobuatu; Qian, Yi; Tsukiya, Tomonori

2009-01-01

406

The implications of three-dimensional mesh generation on the calculation of mechanical forces in magnetic devices  

Microsoft Academic Search

The implications of the methods used in mesh generation for force calculation in three-dimensional magnetic device analysis are discussed. Virtual-work and single-solution methods are compared, and the usefulness of the element topological information is considered. It is concluded that because the virtual work approach is somewhat independent of the meshing system used and the coenergy values may be derived easily

D. A. Lowther; B. Forghani; S. McFee

1990-01-01

407

Evaluation of a quantitative magnetic resonance imaging system for whole body composition analysis in rodents  

PubMed Central

We evaluated the EchoMRI-900 combination rat and mouse quantitative magnetic resonance (QMR) body composition method in comparison to traditional whole-body chemical carcass analysis (CCA) for measurements of fat and fat-free mass in rodents. Live and postmortem QMR fat and lean mass measurements were obtained for lean, obese and outbred strains of rats and mice, and compared with measurements obtained using CCA. A second group of rats was measured before and after 18 h food or water deprivation. Significant positive correlations between QMR and CCA fat and lean mass measurements were shown for rats and mice. While all live QMR fat and lean measurements were more precise than CCA for rats, values obtained for mice significantly differed from CCA for lean mass only. QMR performed post-mortem slightly overestimated fat and lean values relative to live QMR but did not show lower precision than live QMR. Food deprivation reduced values for both fat and lean mass; water deprivation reduced estimates of lean mass only. In summary, all measurements using this QMR system were comparable to those obtained by CCA, but with higher overall precision, similar to previous reports for the murine QMR system. However, postmortem QMR measurements slightly overestimated live QMR values, and lean and fat mass measurements in this QMR system are influenced by hydration status and animal size, respectively. Despite these caveats, we conclude that the EchoMRI QMR system offers a fast in vivo method of body composition analysis, well correlated to but with greater overall precision than CCA. PMID:20057373

Nixon, JP.; Zhang, M; Wang, C; Kuskowski, M; Novak, CM; Levine, JA; Billington, CJ; Kotz, CM

2010-01-01

408

Fully suspended, five-axis, three-magnetic-bearing dynamic spin rig with forced excitation  

Microsoft Academic Search

A significant advancement in the dynamic spin rig (DSR), i.e., the five-axis, three-magnetic-bearing DSR, is used to perform\\u000a vibration tests of turbomachinery blades and components under rotating and non-rotating conditions in a vacuum. The rig has\\u000a three magnetic bearings as its critical components: two heteropolar radial active magnetic bearings and a magnetic thrust\\u000a bearing. The bearing configuration allows full vertical

C. R. Morrison; A. Provenza; A. Kurkov; G. Montague; K. Duffy; O. Mehmed; D. Johnson; R. Jansen

2005-01-01

409

Monocoil reciprocating permanent magnet electric machine with self-centering force  

NASA Technical Reports Server (NTRS)

A linear reciprocating machine has a tubular outer stator housing a coil, a plunger and an inner stator. The plunger has four axially spaced rings of radially magnetized permanent magnets which cooperate two at a time with the stator to complete first or second opposite magnetic paths. The four rings of magnets and the stators are arranged so that the stroke of the plunger is independent of the axial length of the coil.

Bhate, Suresh K. (Inventor); Vitale, Nicholas G. (Inventor)

1989-01-01

410

DYNAMICAL BEHAVIOR OF FLYWHEEL ROTOR SUSPENDED BY HYSTERETIC FORCE OF HTSC MAGNETIC BEARING  

Microsoft Academic Search

Recently, the application of high-Tc superconductor to a magnetic bearing has reached the second stage in some institutes and companies. The static stability of the levitation has already been established. However, the dynamic stability is still under research because the non-linear magnetic characteristics of HTSC and the permanent magnet system are not sufficiently understood. In this paper, the dynamic behavior

Takashi Hikihara; Hitoshi Adachi; FRANCIS C. MOON; Yoshisuke Ueda

1999-01-01

411

The attenuation of the levitation force of HTS bulk exposed to AC magnetic field on the above NdFeB guideway  

NASA Astrophysics Data System (ADS)

In the present High Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So it is required to study the characteristics of levitation force of the HTS bulk affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which AC magnetic field generated by an electromagnet is used to simulate the time-varying magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC field, and the attenuation is increased with the amplitude of the AC field, but the attenuation is almost independent of the frequency the AC magnetic field.

Liu, Minxian; Wang, Yan

2012-01-01

412

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

NASA Astrophysics Data System (ADS)

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 reflectometry with micromagnetic simulations. With the first method, lateral dimension of domains with alternative magnetization directions normal to the surface and separated by domain walls in 20-nm-thick CoCrPt films were determined in good agreement with micromagnetic simulations. Quantitative analysis of data on reflectometry shows that domain walls consist of a Bloch wall in the center of the thin film, which is gradually transformed into a pair of Néel caps at the surfaces. The width and in-depth thickness of the Bloch wall element, transition region, and Néel caps are found consistent with micromagnetic calculations. A complex structure of domain walls serves to compromise a competition between exchange interactions, keeping spins parallel, magnetic anisotropy orienting magnetization normal to the surface, and demagnetizing fields, promoting in-plane magnetization. It is shown that the result of such competition strongly depends on the film thickness, and in the thinner CoCrPt film (10 nm thick), simple Bloch walls separate domains. Their lateral dimensions estimated from neutron scattering experiments agree with micromagnetic simulations.

Navas, David; Redondo, Carolina; Badini Confalonieri, Giovanni A.; Batallan, Francisco; Devishvili, Anton; Iglesias-Freire, Óscar; Asenjo, Agustina; Ross, Caroline A.; Toperverg, Boris P.

2014-08-01

413

Measurement of Casimir force with magnetic materials Alexandr Banishev, Chia-Cheng Chang, Umar Mohideen Department of Physics and Astronomy, University of California, Riverside, USA  

NASA Astrophysics Data System (ADS)

The Casimir effect is important in various fields from atomic physics to nanotechnology. According to the Lifshitz theory of the Casimir force, the interaction between two objects depends both on their dielectric permittivity and magenetic permeability. Thus the role of magnetic properties on the Casimir force is interesting particularly due to the possibility of a reduction the Casimir force. In this report we will present the results of a Casimir force measurement between a magnetic material such as nickel coated on SiO2 plate and a Au-coated sphere.

Banishev, Alexandr; Chang, Chia-Cheng; Mohideen, Umar

2012-02-01

414

Forces and Motion  

NSDL National Science Digital Library

Explore the forces at work when you try to push a filing cabinet. Create an applied force and see the resulting friction force and total force acting on the cabinet. Charts show the forces, position, velocity, and acceleration vs. time. View a Free Body Diagram of all the forces (including gravitational and normal forces).

Simulations, Phet I.; Reid, Sam; Podelefsky, Noah; Loeblein, Trish; Perkins, Kathy

2010-10-01

415

Pulsatile Flow of Couple Stress Fluid Through a Porous Medium with Periodic Body Acceleration and Magnetic Field  

Microsoft Academic Search

Pulsatile flow of blood through a porous medium has been studied under the influence of periodic body acceleration by considering blood as a couple stress, incompressible, electrically conducting fluid in the presence of magnetic field. An exact solution of the equation of motion is obtained by applying the Laplace and finite Hankel transforms. The expressions for axial velocity, flow rate,

V. P. Rathod; Shakera Tanveer

416

The error of L5/S1 joint moment calculation in a body-centered non-inertial reference frame when the fictitious force is ignored.  

PubMed

In ergonomics studies, linked segment models are commonly used for estimating dynamic L5/S1 joint moments during lifting tasks. The kinematics data input to these models are with respect to an arbitrary stationary reference frame. However, a body-centered reference frame, which is defined using the position and the orientation of human body segments, is sometimes used to conveniently identify the location of the load relative to the body. When a body-centered reference frame is moving with the body, it is a non-inertial reference frame and fictitious force exists. Directly applying a linked segment model to the kinematics data with respect to a body-centered non-inertial reference frame will ignore the effect of this fictitious force and introduce errors during L5/S1 moment estimation. In the current study, various lifting tasks were performed in the laboratory environment. The L5/S1 joint moments during the lifting tasks were calculated by a linked segment model with respect to a stationary reference frame and to a body-centered non-inertial reference frame. The results indicate that applying a linked segment model with respect to a body-centered non-inertial reference frame will result in overestimating the peak L5/S1 joint moments of the coronal plane, sagittal plane, and transverse plane during lifting tasks by 78%, 2%, and 59% on average, respectively. The instant when the peak moment occurred was delayed by 0.13, 0.03, and 0.09s on average, correspondingly for the three planes. The root-mean-square errors of the L5/S1 joint moment for the three planes are 21Nm, 19Nm, and 9Nm, correspondingly. PMID:23768468

Xu, Xu; Faber, Gert S; Kingma, Idsart; Chang, Chien-Chi; Hsiang, Simon M

2013-07-26

417

Effect of self-consistent magnetic field on plasma sheet penetration to the inner magnetosphere under enhanced convection: RCM simulations combined with force-balance magnetic field solver  

NASA Astrophysics Data System (ADS)

Transport of plasma sheet particles into the inner magnetosphere is strongly affected by the penetration of the convection electric field, which is the result of the large-scale magnetosphere-ionosphere electromagnetic coupling. This transport, on the other hand, results in plasma heating and magnetic field stretching, which become very significant in the inner plasma sheet (inside 20 RE). We have previously run simulations with the Rice Convection Model (RCM) to investigate how the earthward penetration of convection electric field, and therefore plasma sheet population, depends on plasma sheet boundary conditions. Outer boundary conditions at r ~20 RE are a function of MLT and interplanetary conditions based on 11 years of Geotail data. In the previous simulations, Tsyganenko 96 magnetic field model (T96) was used so force balance between plasma pressure and magnetic fields was not maintained. We have now integrated the RCM with a magnetic field solver (Liu et al., 2006) to obtain the required force balance in the equatorial plane. We have run the self-consistent simulations under enhanced convection with different boundary conditions in which we kept different parameters (flux tube particle content, plasma pressure, plasma beta, or magnetic fields) at the outer boundary to be MLT-dependent but time independent. Different boundary conditions result in qualitatively similar plasma sheet profiles. The results show that magnetic field has a dawn dusk asymmetry with field lines being more stretched in the pre-midnight sector, due to relatively higher plasma pressure there. The asymmetry in the magnetic fields in turn affects the radial distance and MLT of plasma sheet penetration into the inner magnetosphere. In comparison with results using the T96, plasma transport under self-consistent magnetic field results in proton and electron plasma sheet inner edges that are located in higher latitudes, weaker pressure gradients, and more efficient shielding of the near-Earth convection electric field (since auroral conductance is also confined to higher latitudes). We are currently evaluating the simulated plasma sheet properties by comparing them with statistical results obtained from Geotail and THEMIS observations.

Gkioulidou, M.; Wang, C.; Lyons, L. R.; Wolf, R. A.

2010-12-01

418

Forced Magnetic Reconnection at an X-point: Particle-In-Cell and Ten-Moment Extended MHD Simulations  

NASA Astrophysics Data System (ADS)

We will present comparative numerical studies of current sheet formation and forced magnetic reconnection at an X-point, beginning from a potential field. The problem will be simulated by the fully kinetic Particle Simulation Code (PSC) [1] and an extended ten-moment MHD code Gkeyll [2] that retains important kinetic physics, particularly, electron inertia and full electron/ion pressure tensors. Our goals are to investigate the similarities and differences between the two models, and to seek suitable parameterization of kinetic effects in the fluid models. The simulation domain is restrained in 2-D and is closed by conducting wall boundaries. The reconnection is forced by in-plane flows imposed on two opposite boundaries, where the forcing flows converge at the two boundary centers, and are slow compared to the characteristic Alfvén speed. We will compare results on the time-dependence of the reconnecting electric field (suitably normalized), as well as the structure of current sheets from PSC, Gkeyll, and an MHD code, varying ion-to-electron mass ratio and domain size. This study is carried out under the auspices of a Focus Topic in the NASA Living With a Star Targeted Research and Technology Program. [1] Fox, W., A. Bhattacharjee, and K. Germaschewski. "Magnetic reconnection in high-energy-density laser-produced plasmas." Physics of Plasmas 19 (2012): 056309. [2] Hakim, Ammar H. "Extended MHD modelling with the ten-moment equations." Journal of Fusion Energy 27.1-2 (2008): 36-43.

Wang, L.; Bessho, N.; Bhattacharjee, A.; Germaschewski, K.; Hakim, A.

2013-12-01

419

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

E-print Network

because it provides superior access to the sample mounted on a mechanical cantilever by the optical fiber- nance imaging MRI .1,2 Following the initial success of an electron spin resonance ESR MRFM experiment,3 of the various magnetic fields necessary for magnetic resonance and the requirement that the optical fiber

Hammel, P. Chris

420

Influence of three-body forces and anharmonic effects on the zero-point energy of rare-gas crystals  

Microsoft Academic Search

The stabilization of the fcc structure of the heavier rare-gas crystals is mainly due to the zero-point energy (ZPE) calculated at the harmonic level with two-body contributions only. We evaluate the influence of the anharmonic contributions on the ZPE within the Einstein approximation. For the influence of the three-body contributions we develop an analytic three-body potential fitted to coupled-cluster ab

Krzysztof Rosciszewski; Beate Paulus

2002-01-01

421

Regional proton magnetic resonance spectroscopy patterns in dementia with Lewy bodies.  

PubMed

Magnetic resonance spectroscopy (MRS) characteristics of dementia with Lewy bodies (DLB) Alzheimer's disease (AD) and cognitively normal controls were compared. DLB (n = 34), AD (n = 35), and cognitively normal controls (n = 148) participated in a MRS study from frontal, posterior cingulate, and occipital voxels. We investigated DLB patients with preserved hippocampal volumes to determine the MRS changes in DLB with low probability of overlapping AD pathology. DLB patients were characterized by decreased N-acetylaspartate/creatine (NAA/Cr) in the occipital voxel. AD patients were characterized by lower NAA/Cr in the frontal and posterior cingulate voxels. Normal NAA/Cr levels in the frontal voxel differentiated DLB patients with preserved hippocampal volumes from AD patients. DLB and AD patients had elevated choline/creatine, and myo-Inositol/creatine in the posterior cingulate. MRS abnormalities associated with loss of neuronal integrity localized to the occipital lobes in DLB, and the posterior cingulate gyri and frontal lobes in AD. This pattern of MRS abnormalities may have a role in differential diagnosis of DLB and in distinguishing DLB patients with overlapping AD pathology. PMID:24468473

Graff-Radford, Jonathan; Boeve, Bradley F; Murray, Melissa E; Ferman, Tanis J; Tosakulwong, Nirubol; Lesnick, Timothy G; Maroney-Smith, Mandie; Senjem, Matthew L; Gunter, Jeffrey; Smith, Glenn E; Knopman, David S; Jack, Clifford R; Dickson, Dennis W; Petersen, Ronald C; Kantarci, Kejal

2014-06-01

422

Magnetic Resonance Spectroscopy in the Diagnosis of Dementia with Lewy Bodies  

PubMed Central

Dementia with Lewy bodies (DLB) is considered to be the second most frequent primary degenerative dementing illness after Alzheimer's disease (AD). DLB, together with Parkinson's disease (PD), Parkinson's disease with dementia (PDD) belong to ?-synucleinopathies—a group of neurodegenerative diseases associated with pathological accumulation of the ?-synuclein protein. Dementia due to PD and DLB shares clinical symptoms and neuropsychological profiles. Moreover, the core features and additional clinical signs and symptoms for these two very similar diseases are largely the same. Neuroimaging seems to be a promising method in differential diagnosis of dementia studies. The development of imaging methods or other objective measures to supplement clinical criteria for DLB is needed and a method which would accurately facilitate diagnosis of DLB prior to death is still being searched. Proton magnetic resonance spectroscopy (1H-MRS) provides a noninvasive method of assessing an in vivo biochemistry of brain tissue. This review summarizes the main results obtained from the application of neuroimaging techniques in DLB cases focusing on 1H-MRS. PMID:25110697

Magierski, Radoslaw; Sobow, Tomasz

2014-01-01

423

Modeling muscle activity to study the effects of footwear on the impact forces and vibrations of the human body during running.  

PubMed

A previously developed mass-spring-damper model of the human body is improved in this paper, taking muscle activity into account. In the improved model, a nonlinear controller mimics the functionality of the Central Nervous System (CNS) in tuning the mechanical properties of the soft-tissue package. Two physiological hypotheses are used to determine the control strategies that are used by the controller. The first hypothesis (constant-force hypothesis) postulates that the CNS uses muscle tuning to keep the ground reaction force (GRF) constant regardless of shoe hardness, wherever possible. It is shown that the constant-force hypothesis can explain the existing contradiction about the effects of shoe hardness on the GRF during running. This contradiction is emerged from the different trends observed in the experiments on actual runners, and experiments in which the leg was fixed and exposed to impact. While the GRF is found to be dependent on shoe hardness in the former set of experiments, no such dependency was observed in the latter. According to the second hypothesis, the CNS keeps the level of the vibrations of the human body constant using muscle tuning. The results of the study show that this second control strategy improves the model such that it can correctly simulate the effects of shoe hardness on the vibrations of the human body during running. PMID:19883916

Zadpoor, Amir Abbas; Nikooyan, Ali Asadi

2010-01-19

424

Influence of three-body forces and anharmonic effects on the zero-point energy of rare-gas crystals  

NASA Astrophysics Data System (ADS)

The stabilization of the fcc structure of the heavier rare-gas crystals is mainly due to the zero-point energy (ZPE) calculated at the harmonic level with two-body contributions only. We evaluate the influence of the anharmonic contributions on the ZPE within the Einstein approximation. For the influence of the three-body contributions we develop an analytic three-body potential fitted to coupled-cluster ab initio data. Both the anharmonic and three-body contributions change the absolute value of the ZPE, but have no influence on the fcc-hcp energy difference.

Ro?ciszewski, Krzysztof; Paulus, Beate

2002-09-01

425

Development of many-body polarizable force fields for Li-battery components: 1. Ether, alkane, and carbonate-based solvents.  

PubMed

Classical many-body polarizable force fields were developed for n-alkanes, perflouroalkanes, polyethers, ketones, and linear and cyclic carbonates on the basis of quantum chemistry dimer energies of model compounds and empirical thermodynamic liquid-state properties. The dependence of the electron correlation contribution to the dimer binding energy on basis-set size and level of theory was investigated as a function of molecular separation for a number of alkane, ether, and ketone dimers. Molecular dynamics (MD) simulations of the force fields accurately predicted structural, dynamic, and transport properties of liquids and unentangled polymer melts. On average, gas-phase dimer binding energies predicted with the force field were between those from MP2/aug-cc-pvDz and MP2/aug-cc-pvTz quantum chemistry calculations. PMID:16553446

Borodin, Oleg; Smith, Grant D

2006-03-30

426

Excitation of forced ion acoustic waves, large plasma sheets, and magnetic field fluctuations over Gakona, Alaska  

E-print Network

Two research subjects: (1) excitation of "forced ion acoustic waves", and (2) "simultaneous excitation of plasma density fluctuations and geomagnetic field fluctuations" are reported in my M.S. thesis. The data was acquired ...

Cohen, Joel (Joel A.)

2009-01-01

427

Driving force of ultrafast magnetization dynamics This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Driving force of ultrafast magnetization dynamics This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2011 New J. Phys. 13 123010 (http n ­ a c c e s s j o u r n a l f o r p h y s i c s New Journal of Physics Driving force of ultrafast

Aeschlimann, Martin