Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces
NASA Technical Reports Server (NTRS)
Guevorkian, Karine; Wurzel, Sam; Mihalusova, Mariana; Valles, Jim
2003-01-01
At Brown University, we are developing the use of magnetic body forces as a means to simulate variable gravity body forces on biological systems. This tool promises new means to probe gravi-sensing and the gravi-response of biological systems. It also has the potential as a technique for screening future systems for space flight experiments.
Probing Gravitational Sensitivity in Biological Systems Using Magnetic Body Forces
NASA Astrophysics Data System (ADS)
Valles, James; Guevorkian, Karine; Wurzel, Samuel; Mihalusova, Mariana
2003-03-01
We have commissioned a superconducting solenoid based apparatus designed to exert strong magnetic body forces on biological specimens and other organic materials in ambient environmental conditions for extended periods. In its room temperature bore, it can produce a maximum magnetic field-field gradient product of 16 T^2-cm-1 which is sufficient to levitate frog embryos Xenopus Laevis[1]. We will discuss how we are applying these magnetic body forces to probe the known influences of gravitational forces on frog embryos and the swimming behavior of Paramecium Caudatum. In the process, we will describe a novel method for measuring the diamagnetic susceptibilities of specimens such as paramecia.
Interaction Forces Between Multiple Bodies in a Magnetic Field
NASA Technical Reports Server (NTRS)
Joffe, Benjamin
1996-01-01
Some of the results from experiments to determine the interaction forces between multiple bodies in a magnetic field are presented in this paper. It is shown how the force values and the force directions depend on the configuration of the bodies, their relative positions to each other, and the vector of the primary magnetic field. A number of efficient new automatic loading and assembly machines, as well as manipulators and robots, have been created based on the relationship between bodies and magnetic fields. A few of these patented magnetic devices are presented. The concepts involved open a new way to design universal grippers for robot and other kinds of mechanisms for the manipulation of objects. Some of these concepts can be used for space applications.
NASA Astrophysics Data System (ADS)
Sugiura, T.; Ogawa, S.; Ura, H.
2005-10-01
Characteristics of high- Tc superconducting levitation systems are no contact support and stable levitation without control. They can be applied to supporting mechanisms in machines, such as linear-drives and magnetically levitated trains. But small damping due to noncontact support and nonlinearity in the magnetic force can easily cause complicated phenomena of nonlinear dynamics. This research deals with nonlinear oscillation of a rigid bar supported at its both ends by electro-magnetic forces between superconductors and permanent magnets as a simple modeling of the above application. Deriving the equation of motion, we discussed an effect of nonlinearity in the magnetic force on dynamics of the levitated body: occurrence of combination resonance in the asymmetrical system. Numerical analyses and experiments were also carried out, and their results confirmed the above theoretical prediction.
Friar, J.L.
1982-01-01
Three-body forces are defined and their properties discussed. Evidence for such forces in the trinucleon bound states and scattering reactions is reviewed. The binding energy defects of the trinucleon bound states, the /sup 3/He charge density, the Phillips line for doublet n-d scattering lengths, and three-nucleon breakup reactions are discussed, together with the possible influence of three-body forces on these observables.
S. M. Kalebin
1988-01-01
Torsion installation with magnetic suspension of test bodies for detection of small forces is considered. Installation application for verification of equivalence of inertial and gravitational mass in the case of test body incidence on the Earth (Etvesh experiment) and in the case of their incidence on the Sun (Dicke experiment) is discussed. The total mass of test bodies, produced in
Cruz-Pol, Sandra L.
10/2/13 1 Magnetic Forces, Materials and Devices INEL 4151 ch 8 Dr. Sandra Cruz/10/spintronics-discover-could-lead-to- magnetic-batteries.php Applica'ons Motors Transformers MRI=ľH= magnetic field density H=magnetic field intensity Force can be due to: ˇ B on moving
The swim force as a body force.
Yan, Wen; Brady, John F
2015-07-29
Net (as opposed to random) motion of active matter results from an average swim (or propulsive) force. It is shown that the average swim force acts like a body force - an internal body force. As a result, the particle-pressure exerted on a container wall is the sum of the swim pressure [Takatori et al., Phys. Rev. Lett., 2014, 113, 028103] and the 'weight' of the active particles. A continuum description is possible when variations occur on scales larger than the run length of the active particles and gives a Boltzmann-like distribution from a balance of the swim force and the swim pressure. Active particles may also display 'action at a distance' and accumulate adjacent to (or be depleted from) a boundary without any external forces. In the momentum balance for the suspension - the mixture of active particles plus fluid - only external body forces appear. PMID:26154729
An Observation of Body Force Distributions in Electric Machines
Hong Soon Choi; Young Sun Kim; Joon Ho Lee; Il Han Park
2007-01-01
It is required to calculate the electromagnetic forces at the distributed parts of electric machines for the prediction of performance. In this paper, the body force distribution of electric machines such as surface permanent magnet and interior permanent magnet is presented and discussed for the first time using the recently developed body force calculation methods which are based on the
Casimir force on amplifying bodies
Agnes Sambale; Dirk-Gunnar Welsch; Stefan Yoshi Buhmann; Ho Trung Dung
2009-02-23
Based on a unified approach to macroscopic QED that allows for the inclusion of amplification in a limited space and frequency range, we study the Casimir force as a Lorentz force on an arbitrary partially amplifying system of linearly locally responding (isotropic) magnetoelectric bodies. We demonstrate that the force on a weakly polarisable/magnetisable amplifying object in the presence of a purely absorbing environment can be expressed as a sum over the Casimir--Polder forces on the excited atoms inside the body. As an example, the resonant force between a plate consisting of a dilute gas of excited atoms and a perfect mirror is calculated.
Magnetic Exchange Force Microscopy
NASA Astrophysics Data System (ADS)
Schwarz, Alexander; Kaiser, Uwe; Schmidt, Rene; Wiesendanger, Roland
Magnetic exchange force microscopy is a novel noncontact atomic-force microscopy based technique to image the arrangement of magnetic moments at surfaces with atomic resolution using sharp magnetic tips. Recent results obtained with iron coated silicon tips on two magnetically different antiferromagnetic surfaces are reviewed: NiO(001), an insulator, where the spin-carrying d-electrons are localized and interact via superexchange and Fe/W(001), a metal with delocalized spin-carrying d-electrons. The experimental findings are discussed with respect to the tip configuration, the role of an applied magnetic field, the magnitude of the magnetic signal as well as the interplay between chemical and magnetic forces.
Passeri, Daniele; Dong, Chunhua; Reggente, Melania; Angeloni, Livia; Barteri, Mario; Scaramuzzo, Francesca A; De Angelis, Francesca; Marinelli, Fiorenzo; Antonelli, Flavia; Rinaldi, Federica; Marianecci, Carlotta; Carafa, Maria; Sorbo, Angela; Sordi, Daniela; Arends, Isabel WCE; Rossi, Marco
2014-01-01
Magnetic force microscopy (MFM) is an atomic force microscopy (AFM) based technique in which an AFM tip with a magnetic coating is used to probe local magnetic fields with the typical AFM spatial resolution, thus allowing one to acquire images reflecting the local magnetic properties of the samples at the nanoscale. Being a well established tool for the characterization of magnetic recording media, superconductors and magnetic nanomaterials, MFM is finding constantly increasing application in the study of magnetic properties of materials and systems of biological and biomedical interest. After reviewing these latter applications, three case studies are presented in which MFM is used to characterize: (i) magnetoferritin synthesized using apoferritin as molecular reactor; (ii) magnetic nanoparticles loaded niosomes to be used as nanocarriers for drug delivery; (iii) leukemic cells labeled using folic acid-coated core-shell superparamagnetic nanoparticles in order to exploit the presence of folate receptors on the cell membrane surface. In these examples, MFM data are quantitatively analyzed evidencing the limits of the simple analytical models currently used. Provided that suitable models are used to simulate the MFM response, MFM can be used to evaluate the magnetic momentum of the core of magnetoferritin, the iron entrapment efficiency in single vesicles, or the uptake of magnetic nanoparticles into cells. PMID:25050758
Tunneling magnetic force microscopy
NASA Technical Reports Server (NTRS)
Burke, Edward R.; Gomez, Romel D.; Adly, Amr A.; Mayergoyz, Isaak D.
1993-01-01
We have developed a powerful new tool for studying the magnetic patterns on magnetic recording media. This was accomplished by modifying a conventional scanning tunneling microscope. The fine-wire probe that is used to image surface topography was replaced with a flexible magnetic probe. Images obtained with these probes reveal both the surface topography and the magnetic structure. We have made a thorough theoretical analysis of the interaction between the probe and the magnetic fields emanating from a typical recorded surface. Quantitative data about the constituent magnetic fields can then be obtained. We have employed these techniques in studies of two of the most important issues of magnetic record: data overwrite and maximizing data-density. These studies have shown: (1) overwritten data can be retrieved under certain conditions; and (2) improvements in data-density will require new magnetic materials. In the course of these studies we have developed new techniques to analyze magnetic fields of recorded media. These studies are both theoretical and experimental and combined with the use of our magnetic force scanning tunneling microscope should lead to further breakthroughs in the field of magnetic recording.
Mathematical model of magnetically interacting rigid bodies
Stanislav Zub
2008-01-01
Dynamics of two bodies, which interact by magnetic forces, is considered. The model of inter- action is built on quasi-stationary approach for electroma gnetic field, and symmetric tops with different moments of inertia of the bodies are considered. The general form of the interaction energy is discovered for the case of coincidence of mass and magnetic symmetries. Since the energy
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.
Shi, Xing; Lin, Guang
2014-11-01
To model the sedimentation of the red blood cell (RBC) in a square duct and a circular pipe, the recently developed technique derived from the lattice Boltzmann method and the distributed Lagrange multiplier/fictitious domain method (LBM-DLM/FD) is extended to employ the mesoscopic network model for simulations of the sedimentation of the RBC in flow. The flow is simulated by the lattice Boltzmann method with a strong magnetic body force, while the network model is used for modeling RBC deformation. The fluid-RBC interactions are enforced by the Lagrange multiplier. The sedimentation of the RBC in a square duct and a circular pipe is simulated, revealing the capacity of the current method for modeling the sedimentation of RBC in various flows. Numerical results illustrate that that the terminal setting velocity increases with the increment of the exerted body force. The deformation of the RBC has significant effect on the terminal setting velocity due to the change of the frontal area. The larger the exerted force is, the smaller the frontal area and the larger deformation of the RBC are.
Three-Body Forces from n-BODY Inversion
NASA Astrophysics Data System (ADS)
Gavin, E. J. O.; Fiedeldey, H.; Sofianos, S. A.
Within the context of the lowest order approximation to the calculation of the n-body bound state in the Hyperspherical Harmonic Expansion Method, the hypercentral potential may be determined from n-body spectral data. Previously, we showed how the two-body force can be determined exactly from the hypercentral potential in the absence of three-body forces. In this paper, we investigate to what extent the three-body force can be determined if the two-body force is assumed to be known. For this purpose, a three-quark system is considered.
G J Mathews; M Meixner; J P Olson; I-S Suh; T Kajino; T Maruyama; J Hidaka; C-Y Ryu; M-K Cheoun; N Q Lan
2013-03-01
We summarize several new developments in the nuclear equation of state for supernova simulations and neutron stars. We discuss an updated and improved Notre-Dame-Livermore Equation of State (NDL EoS) for use in supernovae simulations. This Eos contains many updates. Among them are the effects of 3- body nuclear forces at high densities and the possible transition to a QCD chiral and/or super-conducting color phase at densities. We also consider the neutron star equation of state and neutrino transport in the presence of strong magnetic fields. We study a new quantum hadrodynamic (QHD) equation of state for neutron stars (with and without hyperons) in the presence of strong magnetic fields. The parameters are constrained by deduced masses and radii. The calculated adiabatic index for these magnetized neutron stars exhibit rapid changes with density. This may provide a mechanism for star-quakes and flares in magnetars. We also investigate the strong magnetic field effects on the moments of inertia and spin down of neutron stars. The change of the moment of inertia associated with emitted magnetic flares is shown to match well with observed glitches in some magnetars. We also discuss a perturbative calculation of neutrino scattering and absorption in hot and dense hyperonic neutron-star matter in the presence of a strong magnetic field. The absorption cross-sections show a remarkable angular dependence in that the neutrino absorption strength is reduced in a direction parallel to the magnetic field and enhanced in the opposite direction. The pulsar kick velocities associated with this asymmetry comparable to observed pulsar velocities and may affect the early spin down rate of proto-neutron star magnetars with a toroidal field configuration.
Magnetic Force Microscopy in Liquids.
Ares, Pablo; Jaafar, Miriam; Gil, Adriana; Gómez-Herrero, Julio; Asenjo, Agustina
2015-09-01
In this work, the use of magnetic force microscopy (MFM) to acquire images of magnetic nanostructures in liquid environments is presented. Optimization of the MFM signal acquisition in liquid media is performed and it is applied to characterize the magnetic signal of magnetite nanoparticles. The ability for detecting magnetic nanostructures along with the well-known capabilities of atomic force microscopy in liquids suggests potential applications in fields such as nanomedicine, nanobiotechnology, or nanocatalysis. PMID:26150330
Exploring Effective Three-body Forces
Alexander Volya
2008-09-30
Topics related to the construction, phenomenological determination, and effects of the effective three-body forces within the traditional nuclear shell model approach are discussed. The manifestations of the three-body forces in realistic nuclei in the 0f7/2 and 1s0d shell model valence spaces are explored.
Three-body forces and the trinucleons
Friar, J.L.
1987-01-01
Three-body forces are discussed in the context of classical, atomic, solid-state and nuclear physics. The basic theoretical ingredients used in the construction of such forces are reviewed. Experimental evidence for three-nucleon forces and an overview of the three-nucleon bound states are presented. 53 refs., 9 figs.
2 DYNAMICS 2.1 Surface vs. body forces, and the concept of pressure
Cambridge, University of
-- e.g. weight (gravitational force), or electric or magnetic force. Surface forces: We can motivate, or collapsing bubbles, and most of the flow field around streamlined bodies like aircraft. *Viscous forces.* A more sophisticated treatment of surface forces would require us to introduce the stress tensor
Magnetic Resonance Force Microscope Development
Hammel, P.C.; Zhang, Z.; Suh, B.J.; Roukes, M.L.; Midzor, M.; Wigen, P.E.; Childress, J.R.
1999-06-03
Our objectives were to develop the Magnetic Resonance Force Microscope (MRFM) into an instrument capable of scientific studies of buried structures in technologically and scientifically important electronic materials such as magnetic multilayer materials. This work resulted in the successful demonstration of MRFM-detected ferromagnetic resonance (FMR) as a microscopic characterization tool for thin magnetic films. Strong FMR spectra obtained from microscopic Co thin films (500 and 1000 angstroms thick and 40 x 200 microns in lateral extent) allowed us to observe variations in sample inhomogeneity and magnetic anisotropy field. We demonstrated lateral imaging in microscopic FMR for the first time using a novel approach employing a spatially selective local field generated by a small magnetically polarized spherical crystallite of yttrium iron garnet. These successful applications of the MRFM in materials studies provided the basis for our successful proposal to DOE/BES to employ the MRF M in studies of buried interfaces in magnetic materials.
LABORATORY V MAGNETIC FIELDS AND FORCES
Minnesota, University of
of the magnetic field for various combinations of bar magnets, and to draw vector diagrams (field maps) for eachLABORATORY V MAGNETIC FIELDS AND FORCES Lab V - 1 Magnetism plays a large part in our modern world problems, you will map magnetic fields from different sources and use the magnetic force to deflect
Magnetic nanowire based high resolution magnetic force microscope probes
Qin, Lu-Chang
Magnetic nanowire based high resolution magnetic force microscope probes G. Yang Department-resolution magnetic force microscope probes using preformed magnetic nanowires. Nickel and cobalt nanowires produced are characterized. Š 2005 American Institute of Physics. DOI: 10.1063/1.2043237 Magnetic force microscopy MFM
Magnetic Force in an Electrolyte
NASA Astrophysics Data System (ADS)
Kire, Marián; Jeková, Zuzana
2007-01-01
Various ways of demonstrating the magnetic force on moving charged particles have been described in the physics teaching literature.1-4 Here we describe a simple experiment to demonstrate the magnetic force in an electrolyte. All you need for this experiment is a glass dish (d ? 8 cm), two copper ring electrodes (d1 ? 2 cm, d2 ? 7.5 cm), a solenoid with an iron core (ours has N = 600 turns, R ? 9 ?, rated for 2 A), a dc power supply, copper sulfate solution (approximately 20 g of copper sulfate/100 ml of water), connecting wires, and an overhead projector. A similar experimental setup was developed5 by E. Morgan using a salt solution and a bar magnet with zinc or copper electrodes. The setup we describe is both very simple and easily viewed using an overhead projector.
Three-body critical Casimir forces
NASA Astrophysics Data System (ADS)
Mattos, T. G.; Harnau, L.; Dietrich, S.
2015-04-01
Within mean-field theory we calculate universal scaling functions associated with critical Casimir forces for a system consisting of three parallel cylindrical colloids immersed in a near-critical binary liquid mixture. For several geometrical arrangements and boundary conditions at the surfaces of the colloids we study the force between two colloidal particles in the direction normal to their axes, analyzing the influence of the presence of a third particle on that force. Upon changing temperature or the relative positions of the particles we observe interesting features such as a change of sign of this force caused by the presence of the third particle. We determine the three-body component of the forces acting on one of the colloids by subtracting the pairwise forces from the total force. The three-body contribution to the total critical Casimir force turns out to be more pronounced for small surface-to-surface distances between the colloids as well as for temperatures close to criticality. Moreover, we compare our results with similar ones for other physical systems such as three atoms interacting via van der Waals forces.
Investigation of a cuboidal permanent magnets force exerted on a robotic capsule
Yang, Wanan; Tang, Chengbing; Qin, Fengqing
2014-01-01
To control and drive a robotic capsule accurately from outside a patients body, we present a schema in which the capsule enclosing the imaging device, circuits, batteries, etc is looped by a permanent magnet ring that acts as an actuator. A cuboidal permanent magnet situated outside the patients body attracts or pushes the magnet ring from different directions to make the capsule move or rotate. A mathematic model of attractive or repulsive force that the cuboidal magnet exerts on the magnet ring is presented for accurate calculation of force. The experiments showed that the measuring force was in agreement with the theoretical one, and the relations between the dimensions of the cuboidal magnet and force are useful to produce a cuboidal magnet with optimal shape to get appropriate force. PMID:25170283
2 DYNAMICS 2.1 Surface vs. body forces, and the concept of pressure
Cambridge, University of
--- e.g. weight (gravitational force), or electric or magnetic force. Surface forces: We can motivate, oscillating, or collapsing bubbles, and most of the flow field around streamlined bodies like aircraft numbers, on average.* A more sophisticated treatment of surface forces would require us to introduce
Control of bubbles in fluids by using magnetic buoyancy forces
NASA Astrophysics Data System (ADS)
Wakayama, Nobuko I.
1999-07-01
Magnetic force, i.e., magnetization force is body force and the function of density, and it is possible to induce buoyancy and convection similarly to the gravitational one. Magnetization force under 1D magnetic field gradient is generally shown by the product of density (p), mass magnetic susceptibility (xg), magnetic field strength (H) and its gradient (dH/dy). Several experiments to control bubbles by using magnetic buoyancy forces were conducted under microgravity as follows: (1) Magnetic transport of bubbles: In pure water and glycerol/water mixture which are diamagnetic, the magnetic buoyancy force caused by a strong permanent magnet could transport bubbles toward a stronger magnetic field and to fix bubbles at the maximum point of magnetic strength. The transporting velocity was found to decrease with decreasing the radius of bubbles and increasing the viscosity. (2) Collision and fusion of two bubbles: It is almost impossible to observe the collision of bubbles clearly on the earth. the technique of magnetic control of bubbles nd microgravity condition made this observation possible. (3) Magnetic support of chemical reaction to produce bubbles (2H2O2-->O2+2H2O on Pt catalyst). When small O2 bubbles were removed from the surface of catalyst by magnetic buoyancy force, the decomposition reaction was observe to continue smoothly even under microgravity. On the other hand, in the absence of the magnet, the reaction was observed to stop under microgravity. Thus, the present study suggest the potential of using magnetic buoyancy forces to control bubbles in space experiments.
Forces in magnetic fluids subject to stationary magnetic fields
M. d'Aquino; G. Miano; C. Serpico; W. Zamboni; G. Coppola
2003-01-01
The problem of magnetic forces in magnetizable fluids is discussed and classical formulas for volume force density (Kelvin, Helmholtz) are reviewed. The general problem of hydrostatic equilibrium of a magnetic liquid subject to magnetic field is formulated. On the basis of this formulation, the displacement of a linear magnetic fluid subject to the field produced by sheet-shaped coils is numerically
Astrophysical Gas Dynamics: Magnetic Forces 1/59 Characterisation of Magnetic Forces
Bicknell, Geoff
Astrophysical Gas Dynamics: Magnetic Forces 1/59 Characterisation of Magnetic Forces 1 Introduction The momentum equation (1) contains pressure gradient terms and gravitational force terms that we are familiar Dynamics: Magnetic Forces 2/59 of the following is to come to a better physical understanding of what
Assessment of a body force representation for compressor stability estimation
Patel, Amish A. (Amish Ashok)
2009-01-01
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 ...
Magnetic force and optical force sensing with ultrathin silicon resonator
NASA Astrophysics Data System (ADS)
Ono, Takahito; Esashi, Masayoshi
2003-12-01
In this article, we demonstrated magnetic and optical force measurements using an ultrathin silicon cantilever down to 20 nm or 50 nm in thickness. The cantilever was heated in an ultrahigh vacuum for enhancing the Q factor and a magnetic particle was mounted at the end of the cantilever using a manipulator. The vibration was measured by a laser Doppler vibrometer and its signal was fed to an opposed metal electrode for electrostatic self-oscillation. An application of a magnetic field with a coil exerted a force to the magnetic material, which results in the change of the resonant frequency. However, the change in the mechanical properties of the cantilever, due to mechanical instability and temperature variation, drifts the resonance peak. Force balancing between the magnetic force and an electrostatic force in the opposite phase can minimize the vibration amplitude. From the electrostatic force at the minimum point, the exerted force can be estimated. A magnetic moment of 4×10-20 J/T was measured by this method. The same technique was also applied to measure the optical force of 10-17 N, impinging on the cantilever by a laser diode.
Force sensor using changes in magnetic flux
NASA Technical Reports Server (NTRS)
Pickens, Herman L. (Inventor); Richard, James A. (Inventor)
2012-01-01
A force sensor includes a magnetostrictive material and a magnetic field generator positioned in proximity thereto. A magnetic field is induced in and surrounding the magnetostrictive material such that lines of magnetic flux pass through the magnetostrictive material. A sensor positioned in the vicinity of the magnetostrictive material measures changes in one of flux angle and flux density when the magnetostrictive material experiences an applied force that is aligned with the lines of magnetic flux.
M. Saha Sarkar; S. Sarkar
2014-11-10
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 N 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.
A force calibration standard for magnetic tweezers
NASA Astrophysics Data System (ADS)
Yu, Zhongbo; Dulin, David; Cnossen, Jelmer; Köber, Mariana; van Oene, Maarten M.; Ordu, Orkide; Berghuis, Bojk A.; Hensgens, Toivo; Lipfert, Jan; Dekker, Nynke H.
2014-12-01
To study the behavior of biological macromolecules and enzymatic reactions under force, advances in single-molecule force spectroscopy have proven instrumental. Magnetic tweezers form one of the most powerful of these techniques, due to their overall simplicity, non-invasive character, potential for high throughput measurements, and large force range. Drawbacks of magnetic tweezers, however, are that accurate determination of the applied forces can be challenging for short biomolecules at high forces and very time-consuming for long tethers at low forces below 1 piconewton. Here, we address these drawbacks by presenting a calibration standard for magnetic tweezers consisting of measured forces for four magnet configurations. Each such configuration is calibrated for two commonly employed commercially available magnetic microspheres. We calculate forces in both time and spectral domains by analyzing bead fluctuations. The resulting calibration curves, validated through the use of different algorithms that yield close agreement in their determination of the applied forces, span a range from 100 piconewtons down to tens of femtonewtons. These generalized force calibrations will serve as a convenient resource for magnetic tweezers users and diminish variations between different experimental configurations or laboratories.
May the Magnetic Force Be with You
NSDL National Science Digital Library
VU Bioengineering RET Program, School of Engineering,
After a demonstration of the deflection of an electron beam, students review their knowledge of the cross-product and the right-hand rule with example problems. Then they study the magnetic force on a charged particle, compared to the electric force. Provided lecture material covers the motion of a charged particle in a magnetic field with respect to the direction of the field. Finally, students apply these concepts to understand the magnetic force on a current carrying wire. Through the associated activity, students further explore the force on a current carrying wire.
Verifying Magnetic Force on a Conductor
ERIC Educational Resources Information Center
Ganci, Salvatore
2011-01-01
The laboratory measurement of the magnetic force acting on a straight wire of length "l" carrying a current of intensity "i" in a magnetic field "B" is usually made using current balances, which are offered by various physics apparatus suppliers' catalogues. These balances require an adequate magnet and commonly allow only the measurement of the
Hydrodynamic Forces on Submerged Rigid Bodies -Steady Flow
Thomann, Enrique
Hydrodynamic Forces on Submerged Rigid Bodies - Steady Flow Ronald B. Guenther +#3; Department are derived for computing hydrodynamic forces on a sub- merged rigid body under the assumption the far #12;eld behavior of the pressure, the stress vector and either the inertial force term
Calculation of electromagnetic forces for magnet wheels
Ogawa, Kokichi; Horiuchi, Yoko; Fujii, Nobuo
1997-03-01
The characteristics of magnet wheels for magnetic levitation and linear drives are investigated by using a three-dimensional computer simulation. Magnet wheels levitate by revolving permanent magnets over a conducting plate, in which the eddy currents are induced. The thrust is also produced by making the torque unbalance. This paper deals with the ``partial overlap type`` magnet wheels, producing the lift force and the thrust. The magnetic flux density and eddy currents are examined for the 4-pole and the 2-pole structures.
Magnetic force and work: an accessible example
NASA Astrophysics Data System (ADS)
Gates, Joshua
2014-05-01
Despite their physics instructors arguments to the contrary, introductory students can observe situations in which there seems to be compelling evidence for magnetic force doing work. The counterarguments are often highly technical and require physics knowledge beyond the experience of novice students, however. A simple example is presented which can illustrate that all may not be what it seems when energy transfer and the magnetic force are involved. Excel and Python simulations of the process are also provided.
Body forces and pressures in elastic models of the myocardium.
Pierce, W H
1981-01-01
Tension strands are introduced to represent active myocardial fibers. They create one body force proportional to the divergence of the tension-direction vector, and a second equal to the tension divided by the radius of curvature. Explicit solutions to isotropic linearly elastic tensor equations with these body forces are found for the radially-symmetric, linearly-isotropic, elastic spherical heart with arbitrary radial body force. They confirm experiments showing supraluminal intramural pressures. Such pressures may affect coronary perfusion. A tension strand model which is a reasonable compromise between actual myofibrillar geometry and analytical simplicity is the iso-oblique, terminating, nonintersecting model. The body force from that or any other axially symmetric body force can be the forcing term for equations in which the heart is modeled as a thin, ellipsoidal, elastic membrane. PMID:7213931
LABORATORY VI MAGNETIC FIELDS AND FORCES
Minnesota, University of
Lab VI - 1 LABORATORY VI MAGNETIC FIELDS AND FORCES Magnetism plays a large role in our world for the differences as you go through the problems in this lab. In this set of laboratory problems, you will map motion. PREPARATION: Before coming to lab you should be able to: ˇ Add fields using vector properties
Magnetic forces produced by rectangular permanent magnets in static microsystems.
Gassner, Anne-Laure; Abonnenc, Mélanie; Chen, Hong-Xu; Morandini, Jacques; Josserand, Jacques; Rossier, Joel S; Busnel, Jean-Marc; Girault, Hubert H
2009-08-21
Finite element numerical simulations were carried out in 2D geometries to map the magnetic field and force distribution produced by rectangular permanent magnets as a function of their size and position with respect to a microchannel. A single magnet, two magnets placed in attraction and in repulsion have been considered. The goal of this work is to show where magnetic beads are preferentially captured in a microchannel. These simulations were qualitatively corroborated, in one geometrical case, by microscopic visualizations of magnetic bead plug formation in a capillary. The results show that the number of plugs is configuration dependent with: in attraction, one plug in the middle of the magnets; in repulsion, two plugs near the edges of the magnets; and with a single magnet, a plug close to the center of the magnet. The geometry of the magnets (h and l are the height and length of the magnets respectively) and their relative spacing s has a significant impact on the magnetic flux density. Its value inside a magnet increases with the h/l ratio. Consequently, bar magnets produce larger and more uniform values than flat magnets. The l/s ratio also influences the magnetic force value in the microchannel, both increasing concomitantly for all the configurations. In addition, a zero force zone in the middle appears in the attraction configuration as the l/s ratio increases, while with a single magnet, the number of maxima and minima goes from one to two, producing two focusing zones instead of only one. PMID:19636467
Research into Orbital Motion Stability in System of Two Magnetically Interacting Bodies
Stanislav Zub
2011-01-01
The stability of the orbital motion of two long cylindrical magnets interacting exclusively with magnetic forces is described. To carry out analytical studies a model of magnetically interacting symmetric tops [1] is used. The model was previously developed within the quasi-stationary approach for an electromagnetic field based on the general expression of the energy of interacting magnetic bodies [2]. A
Three-body nuclear forces from a matrix model
NASA Astrophysics Data System (ADS)
Hashimoto, Koji; Iizuka, Norihiro
2010-11-01
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 Helium3/ tritium nucleus, the repulsive forces are larger than the ones estimated from two-body forces only.
Three-body forces and neutron star structure
NASA Astrophysics Data System (ADS)
Zhou, X. R.; Burgio, G. F.; Lombardo, U.; Schulze, H.-J.; Zuo, W.
2004-01-01
We calculate the nucleonic equation of state within the Brueckner-Bethe-Goldstone formalism using the Argonne ?18 two-body interaction and a three-body interaction. We adopt two different three-body forces: the phenomenological Urbana IX model and a microscopic meson-exchange force including nucleon virtual excitations and nucleon-antinucleon excitations. We compare their respective predictions regarding the structure of neutron stars, in particular the mass-radius relation.
Development of magnetic force modeling equipment for magnetic levitation system
Ji-Hyuk Yang; Young-Sam Lee; Oh-Kyu Kwon
2010-01-01
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
7/15 Force current 1/7 FORCE ON A CURRENT IN A MAGNETIC FIELD
Gustafsson, Torgny
7/15 Force current 1/7 FORCE ON A CURRENT IN A MAGNETIC FIELD PURPOSE: To study the force exerted in a magnetic field B, it experiences a magnetic force, called the Lorentz force, F qvBsin , (1) which results in motion along a curved path. If the charge is an electron confined in a conducting wire, it travels only
One-Piece Force-Transducer Body
NASA Technical Reports Server (NTRS)
Meyer, R. A.
1986-01-01
Rugged unit designed to operate in severe environment. Forcetransducer body designed for measurement of loads on specimens tested in hydrogen gas at temperatures up to 2,000 degree F (1,090 degree C). Body has symmetrical radial-shear-beam configuration and machined in one piece from bar stock.
Magnetic force control technique in industrial application
NASA Astrophysics Data System (ADS)
Nishijima, S.
2010-11-01
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.
Nuclear Matter EOS with a Three-body Force
A. Lejeune; U. Lombardo; W. Zuo
2001-02-15
The effect of a microscopic three-body force on the saturation properties of nuclear matter is studied within the Brueckner-Hartree-Fock approach. The calculations show a decisive improvement of the saturation density along with an overall agreement with the empirical saturation point. With the three-body force the symmetry energy turns more rapidly increasing with density, which allows for the direct URCA process to occur in $\\beta$-stable neutron star matter. The influence of the three-body force on the nuclear mean field does not diminish the role of the ground state correlations.
Magnetic Micro Actuator Using Interactive Force between Magnetic Elements
NASA Astrophysics Data System (ADS)
Hatama, Kenji; Tsumori, Fujio; Xu, Yang; Kang, Hyungoo; Osada, Toshiko; Miura, Hideshi
2012-06-01
In micro electro mechanical system (MEMS) field, there have been used many kinds of actuators. Among them, the magnetic actuator has some advantages. As magnetic micro actuators do not need electric wiring for energy supply, the structure can be simple and be downsized easily. However, the magnetic force would be very small with downsizing, which is the main problem for conventional magnetic actuators. We propose a new type actuator using magnetic interaction force between magnetic elements to solve this matter. This actuator can work even if it gets smaller, because the interaction force is dominant in a microscopic region. We fabricated the actuator by a casting process with photolithography using the SU-8 resist material. Then, the structure was fabricated by casting the mixture of poly(dimethylsiloxane) (PDMS) and a magnetic powder material. The beam type actuator works successfully and also shows interesting behavior. We can control the behavior of this actuator by changing the arrangement of magnetic elements on the structure. We also show theoretical evaluation of the deformation of the present actuator.
A study of two-body forces in fluidization
Kashiwa, B. A.; Rauenzahn, Rick M.
2004-01-01
The effect of two-body forces on the structure of dynamic waves in fluidized beds is studied, with particular emphasis on expansion waves. Averaged equations of motion are used for the study, so the media appear to be interpenetrating continua. Both inertial and viscous two-body effects are considered for incompressible materials fluidized by an incompressible fluid. Inertial effects are included in the averaged momentum exchange force, using exact (classical) results for the potential flow generated by the motion of one submerged body relative to another body. Viscous effects are represented, in the limit of zero relative Reynolds number, by solutions to Stokes equations for the two-body problem. For simple one-dimensional motion the inertial force is repulsive always, giving a positive compressibility to the dispersed field total density; the force is of such a magnitude that the single-pressure continuum equations are unconditionally hyperbolic. The corresponding 1-D viscous force is attractive when the bodies move apart, and therefore introduces a negative compressibility to the dispersed field. Competition between the two-body inertial and viscous forces ultimately determines the nature of dynamic waves in a given fluidization system.
Magnetic Force and Work: An Accessible Example
ERIC Educational Resources Information Center
Gates, Joshua
2014-01-01
Despite their physics instructors' arguments to the contrary, introductory students can observe situations in which there seems to be compelling evidence for magnetic force doing work. The counterarguments are often highly technical and require physics knowledge beyond the experience of novice students, however. A simple example is presented
Thermodynamic properties of nuclear matter with three-body forces
NASA Astrophysics Data System (ADS)
Somŕ, V.; Bo?ek, P.
2009-08-01
We calculate thermodynamic quantities in symmetric nuclear matter within the self-consistent Green's functions method including three-body forces. The thermodynamic potential is computed directly from a diagrammatic expansion, implemented with the CD-Bonn and Nijmegen nucleon-nucleon potentials and the Urbana three-body forces. We present results for entropy and pressure up to temperatures of 20 MeV and densities of 0.32fm-3. While the pressure is sensitive to the inclusion of three-body forces, the entropy is not. The unstable spinodal region is identified and the critical temperature associated to the liquid-gas phase transition is determined. When three-body forces are added we find a strong reduction of the critical temperature, obtaining Tc?12MeV.
Thermodynamic properties of nuclear matter with three-body forces
V. Soma; P. Bozek
2009-04-07
We calculate thermodynamic quantities in symmetric nuclear matter within the self-consistent Green's functions method including three-body forces. The thermodynamic potential is computed directly from a diagrammatic expansion, implemented with the CD-Bonn and Nijmegen nucleon-nucleon potentials and the Urbana three-body forces. We present results for entropy and pressure up to temperatures of 20 MeV and densities of 0.32 fm^-3. While the pressure is sensitive to the inclusion of three-body forces, the entropy is not. The unstable spinodal region is identified and the critical temperature associated to the liquid-gas phase transition is determined. When three-body forces are added we find a strong reduction of the critical temperature, obtaining T_c ~ 12 MeV.
Resonance behavior of liquid bridges under axial and lateral oscillating total body forces
Taylor, Philip L.
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
A compact high field magnetic force microscope.
Zhou, Haibiao; Wang, Ze; Hou, Yubin; Lu, Qingyou
2014-12-01
We present the design and performance of a simple and compact magnetic force microscope (MFM), whose tip-sample coarse approach is implemented by the piezoelectric tube scanner (PTS) itself. In brief, a square rod shaft is axially spring-clamped on the inner wall of a metal tube which is glued inside the free end of the PTS. The shaft can thus be driven by the PTS to realize image scan and inertial stepping coarse approach. To enhance the inertial force, each of the four outer electrodes of the PTS is driven by an independent port of the controller. The MFM scan head is so compact that it can easily fit into the 52mm low temperature bore of a 20T superconducting magnet. The performance of the MFM is demonstrated by imaging a manganite thin film at low temperature and in magnetic fields up to 15T. PMID:25189114
Modeling Forces on the Human Body.
ERIC Educational Resources Information Center
Pagonis, Vasilis; Drake, Russel; Morgan, Michael; Peters, Todd; Riddle, Chris; Rollins, Karen
1999-01-01
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)
Forces and moments on a slender, cavitating body
Hailey, C.E.; Clark, E.L.; Buffington, R.J.
1988-01-01
Recently a numerical code has been developed at Sandia National Laboratories to predict the pitching moment, normal force, and axial force of a slender, supercavitating shape. The potential flow about the body and cavity is calculated using an axial distribution of source/sink elements. The cavity surface is assumed to be a constant pressure streamline, extending beyond the base of the model. Slender body approximation is used to model the crossflow for small angles of attack. A significant extension of previous work in cavitation flow is the inclusion of laminar and turbulent boundary layer solutions on the body. Predictions with this code, for axial force at zero angle of attack, show good agreement with experiments. There are virtually no published data availble with which to benchmark the pitching moment and normal force predictions. An experiment was designed to measure forces and moments on a supercavitation shape. The primary reason for the test was to obtain much needed data to benchmark the hydrodynamic force and moment predictions. Since the numerical prediction is for super cavitating shapes at very small cavitation numbers, the experiment was designed to be a ventilated cavity test. This paper describes the experimental procedure used to measure the pitching moment, axial and normal forces, and base pressure on a slender body with a ventilated cavity. Limited results are presented for pitching moment and normal force. 5 refs., 7 figs.
Experimental studies of the magnetized friction force
Fedotov, A. V.; Litvinenko, V. N.; Gaalnander, B.; Lofnes, T.; Ziemann, V.; Sidorin, A.; Smirnov, A.
2006-06-15
High-energy electron cooling, presently considered as an essential tool for several applications in high-energy and nuclear physics, requires an accurate description of the friction force which ions experience by passing through an electron beam. Present low-energy electron coolers can be used for a detailed study of the friction force. In addition, parameters of a low-energy cooler can be chosen in a manner to reproduce regimes expected in future high-energy operation. Here, we report a set of dedicated experiments in CELSIUS aimed at a detailed study of the magnetized friction force. Some results of the accurate comparison of experimental data with the friction force formulas are presented.
Experimental studies of the magnetized friction force.
Fedotov, A V; Gĺlnander, B; Litvinenko, V N; Lofnes, T; Sidorin, A; Smirnov, A; Ziemann, V
2006-06-01
High-energy electron cooling, presently considered as an essential tool for several applications in high-energy and nuclear physics, requires an accurate description of the friction force which ions experience by passing through an electron beam. Present low-energy electron coolers can be used for a detailed study of the friction force. In addition, parameters of a low-energy cooler can be chosen in a manner to reproduce regimes expected in future high-energy operation. Here, we report a set of dedicated experiments in CELSIUS aimed at a detailed study of the magnetized friction force. Some results of the accurate comparison of experimental data with the friction force formulas are presented. PMID:16906990
Degen, Christian
Frequency domain multiplexing, using an actively damped micromechanical cantilever, is used to detect multiple force signals simultaneously. The measurement principle is applied to magnetic resonance force microscopy to ...
Nonlinear gravitational self-force: Field outside a small body
NASA Astrophysics Data System (ADS)
Pound, Adam
2012-10-01
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 bodys 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 bodys 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.
NASA Astrophysics Data System (ADS)
Zheng, Yangdong; Yoshimura, Satoru; Egawa, Genta; Zheng, Fu; Kinoshita, Yukinori; Saito, Hitoshi
2015-08-01
A pulsed magnetic field magnetic force microscope (PMF-MFM) is developed for evaluation of the magnetic properties of nano-scale materials and devices, as well as the characteristics of MFM tips. We present the setup of the PMF-MFM system, and focus on the evaluation of a FeCo soft magnetic tip by PMF-MFM. We find a new theoretical method to calculate tip magnetization curves (M-H curves) using MFM phase signals. We measure the MFM phase and amplitude signals for the FeCo tip during the presence of the pulsed magnetic fields oriented parallel and antiparallel to the initial tip magnetization direction, and acquire the tip coercivity H c ~ 1.1?kOe. The tip M-H curves are also calculated using the MFM phase signals data. We obtain the basic features of the tip magnetic properties from the tip M-H curves.
Stability of semicircularly arched force-free magnetic fields
NASA Astrophysics Data System (ADS)
Hu, You-qiu
1995-02-01
Based on the energy principle, this paper derives a general form of the energy integral of semicircularly arched force-free magnetic fields andproves that all semicircularly arched force-free magnetic fields are definitely stable.
Many-body effects for critical Casimir forces
T. G. Mattos; L. Harnau; S. Dietrich
2013-01-28
Within mean-field theory we calculate the scaling functions associated with critical Casimir forces for a system consisting of two spherical colloids immersed in a binary liquid mixture near its consolute point and facing a planar, homogeneous substrate. For several geometrical arrangements and boundary conditions we analyze the normal and the lateral critical Casimir forces acting on one of the two colloids. We find interesting features such as a change of sign of these forces upon varying either the position of one of the colloids or the temperature. By subtracting the pairwise forces from the total force we are able to determine the many-body forces acting on one of the colloids. We have found that the many-body contribution to the total critical Casimir force is more pronounced for small colloid-colloid and colloid-substrate distances, as well as for temperatures close to criticality, where the many-body contribution to the total force can reach up to 25%.
Magnetic Forces and DNA Mechanics in Multiplexed Magnetic Tweezers
Dekker, Cees
provides a scalable solution for parallel tracking of the xyz-positions of many beads simultaneously. We. Citation: De Vlaminck I, Henighan T, van Loenhout MTJ, Burnham DR, Dekker C (2012) Magnetic Forces and DNA in real time by tracking the xyz-position of the paramagnetic bead using video microscopy, thereby
Magnet polepiece design for uniform magnetic force on superparamagnetic beads
Fallesen, Todd; Hill, David B.; Steen, Matthew; Macosko, Jed C.; Bonin, Keith; Holzwarth, George
2010-01-01
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 300600 mT and constant gradients of 67 T?m over a sample space of 0.5×4 mm2 in the focal plane of the microscope and 0.05 mm along the microscope optic axis. Within this space the maximum force on a 2.8 ?m diameter Dynabead was 12 pN with a spatial variation of approximately 10%. Use of the magnet in a biophysical experiment is illustrated by showing that gliding microtubules propelled by the molecular motor kinesin can be stopped by the force of an attached magnetic bead. PMID:20687745
Magnetic Resonance Force Microscopy Detected Long-Lived Spin Magnetization
Chen, Lei; Longenecker, Jonilyn G.; Moore, Eric W.; Marohn, John A.
2015-01-01
Magnetic resonance force microscopy (MRFM), which combines magnetic resonance imaging with scanning probe microscopy together, is capable of performing ultra-sensitive detection of spin magnetization. In an attempt to observe dynamic nuclear polarization (DNP) in an MRFM experiment, which could possibly further improve its sensitivity towards a single proton spin, a film of perdeuterated polystyrene doped with a nitroxide electron-spin probe was prepared. A high-compliance cantilever with a 4 ?m diameter magnetic tip was brought near the film at a temperature of 7.3 K and in a background magnetic field of ~0.6 T. The film was irradiated with 16.7 GHz microwaves while the resulting transient change in cantilever frequency was recorded in real time. In addition to observing the expected prompt change in cantilever frequency due to saturation of the nitroxides electron-spin magnetization, we observed a persistent cantilever frequency change. Based on its magnitude, lifetime, and field dependence, we tentatively attribute the persistent signal to polarized deuteron magnetization created via transfer of magnetization from electron spins. Further measurements of the persistent signals dependence on the cantilever amplitude and tip-sample separation are presented and explained by the cross-effect DNP mechanism in high magnetic field gradients. PMID:26097251
Magnetic force-induced damping effect for magnetic bearing motor
NASA Astrophysics Data System (ADS)
Wang, Chien-Chang; Yao, Y. D.; Chang, Yu-Hsiu; Tung, Pi-Cheng; Xiao, Ren-Bin
2005-05-01
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.
Discreteness noise versus force errors in N-body simulations
NASA Technical Reports Server (NTRS)
Hernquist, Lars; Hut, Piet; Makino, Jun
1993-01-01
A low accuracy in the force calculation per time step of a few percent for each particle pair is sufficient for collisionless N-body simulations. Higher accuracy is made meaningless by the dominant discreteness noise in the form of two-body relaxation, which can be reduced only by increasing the number of particles. Since an N-body simulation is a Monte Carlo procedure in which each particle-particle force is essentially random, i.e., carries an error of about 1000 percent, the only requirement is a systematic averaging-out of these intrinsic errors. We illustrate these assertions with two specific examples in which individual pairwise forces are deliberately allowed to carry significant errors: tree-codes on supercomputers and algorithms on special-purpose machines with low-precision hardware.
Magnetic dynamos in accreting planetary bodies
NASA Astrophysics Data System (ADS)
Golabek, Gregor; Labrosse, Stéphane; Gerya, Taras; Morishima, Ryuji; Tackley, Paul
2013-04-01
Laboratory measurements revealed ancient remanent magnetization in meteorites [1] indicating the activity of magnetic dynamos in the corresponding meteorite parent body. To study under which circumstances dynamo activity is possible, we use a new methodology to simulate the internal evolution of a planetary body during accretion and differentiation. Using the N-body code PKDGRAV [2] we simulate the accretion of planetary embryos from an initial annulus of several thousand planetesimals. The growth history of the largest resulting planetary embryo is used as an input for the thermomechanical 2D code I2ELVIS [3]. The thermomechanical model takes recent parametrizations of impact processes [4] and of the magnetic dynamo [5] into account. It was pointed out that impacts can not only deposit heat deep into the target body, which is later buried by ejecta of further impacts [6], but also that impacts expose in the crater region originally deep-seated layers, thus cooling the interior [7]. This combination of impact effects becomes even more important when we consider that planetesimals of all masses contribute to planetary accretion. This leads occasionally to collisions between bodies with large ratios between impactor and target mass. Thus, all these processes can be expected to have a profound effect on the thermal evolution during the epoch of planetary accretion and may have implications for the magnetic dynamo activity. Results show that late-formed planetesimals do not experience silicate melting and avoid thermal alteration, whereas in early-formed bodies accretion and iron core growth occur almost simultaneously and a highly variable magnetic dynamo can operate in the interior of these bodies. [1] Weiss, B.P. et al., Science, 322, 713-716, 2008. [2] Richardson, D. C. et al., Icarus, 143, 45-59, 2000. [3] Gerya, T.V and Yuen, D.J., Phys. Earth Planet. Int., 163, 83-105, 2007. [4] Monteux, J. et al., Geophys. Res. Lett., 34, L24201, 2007. [5] Aubert, J. et al., Geophys. J. Int., 179, 1414-1428, 2009. [6] Safronov, V.S., Icarus, 33, 3-12, 1978. [7] Davies, G.F., in: Origin of the Earth, ed. H.E. Newsom, J.H. Jones, Oxford Un. Press, 175-194, 1990.
Control of the Casimir Force Using Semiconductor Test Bodies
G. L. Klimchitskaya; U. Mohideen; V. M. Mostepanenko
2011-04-09
We describe experimental and related theoretical work on the measurement of the Casimir force using semiconductor test bodies. This field of research started in 2005 and several important and interesting results have already been obtained. Specifically, the Casimir force or its gradient were measured in the configuration of an Au-coated sphere and different semiconductor surfaces. It was found that the force magnitude depends significantly on the replacement of the metal with a semiconductor and on the concentration of charge carriers in the semiconductor material. Special attention is paid to the experiment on the optical modulation of the Casimir force. In this experiment the difference Casimir force between an Au-coated sphere and Si plate in the presence and in the absence of laser light was measured. Possible applications of this experiment are discussed, specifically, for the realization of the pulsating Casimir force in three-layer systems. Theoretical problems arising from the comparison of the experimental data for the difference Casimir force with the Lifshitz theory are analyzed. We consider the possibility to control the magnitude of the Casimir force in phase transitions of semiconductor materials. Experiments on measuring the Casimir force gradient between an Au-coated sphere and Si plate covered with rectangular corrugations of different character are also described. Here, we discuss the interplay between the material properties and nontrivial geometry and the applicability of the proximity force approximation. The review contains comparison between different experiments and analysis of their advantages and disadvantages.
Chiral nuclear dynamics with three-body forces
J. W. Holt; N. Kaiser; W. Weise
2011-11-25
We review recent progress in implementing high-precision chiral two- and three-body forces in nuclear many-body systems beyond light nuclei. We begin with applications to finite nuclei, which we study through the nuclear shell model and self-consistent mean field theory. We then turn our attention to infinite nuclear matter treated within the framework of Landau's theory of normal Fermi liquids.
NASA Astrophysics Data System (ADS)
Liu, Dongzi; Mo, Kangxin; Ding, Xidong; Zhao, Liangbing; Lin, Guocong; Zhang, Yueli; Chen, Dihu
2015-09-01
A bimodal magnetic force microscopy (MFM) that uses an external magnetic field for the detection and imaging of magnetic thin films is developed. By applying the external modulation magnetic field, the vibration of a cantilever probe is excited by its magnetic tip at its higher eigenmode. Using magnetic nanoparticle samples, the capacity of the technique which allows single-pass imaging of topography and magnetic forces is demonstrated. For the detection of magnetic properties of thin film materials, its signal-to-noise ratio and sensitivity are demonstrated to be superior to conventional MFM in lift mode. The secondary resonance MFM technique provides a promising tool for the characterization of nanoscale magnetic properties of various materials, especially of magnetic thin films with weak magnetism.
How to Classify Three-Body Forces -- and Why
NASA Astrophysics Data System (ADS)
Griesshammer, Harald W.
2007-10-01
To add 3-body forces when theory and data disagree is untenable when predictions are required. For the ``pion-less'' Effective Field Theory at momenta below the pion-mass, I provide a recipe to systematically estimate the typical size of 3-body forces in all partial waves and orders, including external currents [1]. It is based on the superficial degree of divergence of the 3-body diagrams which contain only two-body forces and the renormalisation-group argument that low-energy observables must be insensitive to details of short-distance dynamics. Na"ive dimensional analysis must be amended as the asymptotic solution to the leading-order problem depends for large off-shell momenta crucially on the partial wave and spin-combination considered. The typical strength of most 3-body forces turns out weaker than expected, demoting many to high orders. As application, the thermal cross section of nd->t? bears no new 3-body force [2], besides those fixed by the triton binding energy and nd scattering length in the triton channel: 0.485(LO)+0.011(NLO)+0.007(NNLO) ];mb=[0.503ą0.003];mb, converges and compares well with data, [0.509ą0.015];mb. Potential models list [0.490.66];mb, depending on the 2-nucleon potential and inclusion of the ?(1232). [1] H.W. Grießhammer: Nucl. Phys. A760 (2005) 110 [2] H. Sadeghi, S. Bayegan and H.W. Grießhammer: Phys. Lett.B643 (2006), 263.
Unbalanced magnetic forces in rotational unsymmetrical transverse flux machine
Salwa Baserrah; Keno Rixen; Bernd Orlik
2010-01-01
The torque and unbalanced magnetic forces in a small flux concentrating permanent magnet transverse flux machine (FCPM-TFM) in segmented compact structure, which are the resultants of the tangential; axial and normal magnetic forces, respectively, are in general influenced by pole-teeth-winding configuration. The paper calculates the torque and unbalanced magnetic forces using finite element (FE-) method by solving Maxwell stress tensor
A high performance magnetic force microscope
NASA Astrophysics Data System (ADS)
Valera, M. S.; Farley, A. N.
1996-01-01
We have constructed a high performance magnetic force microscope optimized for operation in the force gradient detection mode. The instrument incorporates a novel differential heterodyne interferometer that has a high immunity to microphonics and interference. The detection limit of the interferometer is limited by the intrinsic thermal noise of the cantilever sensor. Positioning and scanning of the sample is undertaken by a monolithic flexure stage driven by piezoelectric actuators. The stage incorporates capacitance sensors which are used to linearize the motion of the stage via a closed loop control system. The linearity achieved is better than 1% (full scale) with a positioning stability of 1 nm (rms). Recorded bit patterns in longitudinal media and domains in an AC-demagnetized Co/Pt multilayer have been studied.
Dust Transport And Force Equilibria In Magnetized Dusty DC Discharges
Land, Victor [FOM Institute for Plasma Physics Rijnhuizen, Association Euratom-Fom (Netherlands); Thomas, Edward Jr.; Williams, Jeremaiah [Plasma Sciences Laboratory, Auburn University (United States)
2005-10-31
We have performed experiments on magnetized dusty Argon DC discharges. Here we report on the characterization of the plasma- and the dustparameters and on the response of the dust particles and the plasma to a change in the magnetic configuration inside the discharge. Finally, we show a case in which the balance of forces acting on the dust particles differs from the classical balance (in which the electrostatic force balances the downward force of gravity). In this case the electrostatic force acts as a downward force on the dust particles. From observations we will argue that the ion drag force might be the force that balances this downward electrostatic force.
Magnetic resonance imaging of the body
Higgins, C.B.; Hricak, H.
1987-01-01
This text provides reference to magnetic resonance imaging (MRI) of the body. Beginning with explanatory chapters on the physics, instrumentation, and interpretation of MRI, it proceeds to the normal anatomy of the neck, thorax, abdomen, and pelvis. Other chapters cover magnetic resonance imaging of blood flow, the larynx, the lymph nodes, and the spine, as well as MRI in obstetrics. The text features detailed coverage of magnetic resonance imaging of numerous disorders and disease states, including neck disease, thoracic disease; breast disease; congenital and acquired heart disease; vascular disease; diseases of the liver, pancreas, and spleen; diseases of the kidney, adrenals, and retroperitoneum; diseases of the male and female pelvis; and musculoskeletal diseases. Chapters on the biological and environmental hazards of MRI, the current clinical status of MRI in comparison to other imaging modalities, and economic considerations are also included.
Sandwell, David T.
- 1 - http://topex.ucsd.edu/body_force/ Response of an Elastic Half Space to an Arbitrary 3-D Vector Body Force (Copyright 2002, Bridget R. Smith and David T. Sandwell) We wish to calculate the displacement vector u(x,y,z) on the surface of the Earth due to a vector body force at depth. The approach
Collision of viscoelastic bodies: Rigorous derivation of dissipative force.
Goldobin, Denis S; Susloparov, Eugeniy A; Pimenova, Anastasiya V; Brilliantov, Nikolai V
2015-06-01
We report a new theory of dissipative forces acting between colliding viscoelastic bodies. The impact velocity is assumed not to be large to neglect plastic deformations in the material and propagation of sound waves. We consider the general case of bodies of an arbitrary convex shape and of different materials. We develop a mathematically rigorous perturbation scheme to solve the continuum mechanics equations that deal with both displacement and displacement rate fields and accounts for the dissipation in the bulk of the material. The perturbative solution of these equations allows to go beyond the previously used quasi-static approximation and obtain the dissipative force. The derived force does not suffer from the inconsistencies of the quasi-static approximation, like the violation of the third Newton's law for the case of different materials, and depends on particle deformation and deformation rate. PMID:26087916
Collision of viscoelastic bodies: Rigorous derivation of dissipative force
Denis S. Goldobin; Eugeniy A. Susloparov; Anastasiya V. Pimenova; Nikolai V. Brilliantov
2015-01-13
We report a new theory of dissipative forces acting between colliding viscoelastic bodies. The impact velocity is assumed not to be large, to avoid plastic deformations and fragmentation at the impact. The bodies may be of an arbitrary convex shape and of different materials. We develop a mathematically rigorous perturbation scheme to solve the continuum mechanics equation that deals with both displacement and displacement rate fields and accounts for the dissipation in the bulk of the material. The perturbative solution of this equation allows to go beyond the previously used quasi-static approximation and obtain the dissipative force. This force does not suffer from the physical inconsistencies of the latter approximation and depends on particle deformation and deformation rate.
Three-Body Forces and Neutron-Rich Exotic Nuclei
NASA Astrophysics Data System (ADS)
Otsuka, Takaharu; Suzuki, Toshio
2013-08-01
Physics of three-body forces in connection to exotic nuclei will be discussed. Three-nucleon forces (3NF), especially Fujita-Miyazawa 3NF, are shown to be the key for the solution to the long-standing problem of oxygen drip line, which deviates from basic trend towards the stability line. Three-body forces produce repulsive modifications to effective interaction between valence neutrons, and make the ground states less bound. The oxygen drip line is then located at the right place. The relation to the neutron matter is presented. Applications to Ca isotopes will be presented. The shell evolution due to the 3NF depicts the raising of single-particle energies and the widening of splitting among the orbits. This is in contrast to the so-called shell quenching. The 2+ levels are calculated for Ca isotopes, suggesting about the same sub-magic structure for N = 32 and 34.
Fluctuations of the van der Waals attraction force between macroscopic bodies
Kogan, A. S. (Aleksandr Semenovich)
2003-01-01
The tliccry of the fluctuations of the van der Waals (vdW) attractive force between macroscopic bodies is developed. A general equation for the spectral density of the fluctuating surface Maxwell stress (force per unit mea.) in va,cuurn nea,r the surface of a body is derived under the assumption that, inside the bodies, the random La.ngevin sources of the electric and magnetic fields (charges, polarizations, currents) are Gaussian. This spectral density of stress is an integral over frequencies of a sum of terms each of which is a product of Fourier amplitudes of two field components' correlation functions. For metallic bodies, the contribution of free electrons to the vdW force (at frequencies up to the frequency of electron scattering) is calculated. This contribution to the force and its noise grows with temperature. Application of noiseless voltage to two interacting metals across the vacuum gap between them generates an additional force noise. This additional noise is proportional to the volta.ge squared and to the spectral density of the random electric field at the frequency of noise measurement. The theoretical qualitative conclusions are in good agreement with experirncnts.
Convolution approach for analysis of magnetic forces in electrical machines
R. Rothe; M. van der Giet; K. Hameyer
2010-01-01
Purpose The purpose of this paper is to present a method for analyzing higher magnetic force harmonics in electrical machines based on electromagnetic finite element simulation. Design\\/methodology\\/approach Sampling of air gap field solution data allows for a Fourier decomposition of magnetic forces and flux densities. A two-dimensional convolution gives insight into the spectral decomposition of forces responsible for
Force-moment line element method for flexible slender bodies in Stokes flow.
Jiang, H; Yang, B
2013-09-01
The hydrodynamics of flexible slender bodies in Stokes flow is studied by taking into account the fluid-structure interaction through both forces and coupled moments. The fluid subjected to line sources of forces and moments is described by using integral equations. Meanwhile, the flexible slender body is modeled using finite beam elements. The two sides are linked through interfacial continuity conditions. Upon discretization, it results in a higher-order line element method for efficient and accurate solution of slender-body hydrodynamics. Four examples are presented to demonstrate the validity and efficiency of the present method: (a) hydrodynamics of a flexible slender rod subjected to a torque at one end, (b) hydrodynamics of a flexible slender rod subjected to a bending moment at one end, (c) hydrodynamics of a flexible slender rod subjected to a cyclic force, and (d) hydrodynamics of a flexible slender rod with a magnetized head within a rotating magnetic field. Examples (a) and (b) may serve as benchmark solutions and examples (c) and (d) show how planar and spiral waves can be excited in a slender body. PMID:24125384
Magnetic forces associated with bursty bulk flows in Earth's magnetotail
NASA Astrophysics Data System (ADS)
Karlsson, Tomas; Hamrin, Maria; Nilsson, Hans; Kullen, Anita; Pitkänen, Timo
2015-05-01
We present the first direct measurements of magnetic forces acting on bursty bulk flow plasma in the magnetotail. The magnetic forces are determined using Cluster multispacecraft measurements. We analyze 67 bursty bulk flow (BBF) events and show that the curvature part of the magnetic force is consistently positive, acting to accelerate the plasma toward Earth between approximately 10 and 20 RE geocentrical distances, while the magnetic field pressure gradient increasingly brakes the plasma as it moves toward Earth. The net result is that the magnetic force accelerates the plasma at distances greater than approximately 14 RE, while it acts to decelerate it within that distance. The magnetic force, together with the thermal pressure gradient force, will determine the dynamics of the BBFs as they propagate toward the near-Earth tail region. The determination of the former provides an important clue to the ultimate fate of BBFs in the inner magnetosphere.
6/2015 E&M forces-1/8 ELECTRIC AND MAGNETIC FORCES
Gustafsson, Torgny
of electrons by electric and magnetic fields. APPARATUS: Electron beam tube, stand with coils, power supply6/2015 E&M forces-1/8 ELECTRIC AND MAGNETIC FORCES PURPOSE: To study the deflection of a beam by a "Helmholtz coil". In the first part of the experiment we will study just the magnetic deflection
Force generation by orthodontic samarium-cobalt magnets.
von Fraunhofer, J A; Bonds, P W; Johnson, B E
1992-01-01
The use of samarium-cobalt (Sm-Co) magnets for light force application is a relatively new concept in orthodontic tooth movement. This study reports on the forces generated by these magnets. Magnets were attached to aluminum rods mounted in a universal testing machine. The magnets were initially separated by 10 mm were moved toward each other at 2.5mm/min in repulsion or attraction, depending upon the magnetic pole orientation. The magnets were also positioned initially in contact and then moved apart at a rate of 2.5mm/min, again producing repulsion or attraction, depending upon the pole orientation. The Sm-Co magnets exhibit very large forces when in close approximation but forces decrease markedly at separations greater than 2mm. The force, P, generated between magnets is determined by their separation, d, and follows the relationship P = dn. At magnet separations of 0 to 2mm, the exponent n is equal to -0.4; at separations of 2mm to 7mm, exponent n equals -2.1 for both attraction and repulsion. Thus the classic Coulomb law of magnetic force was followed only at magnet separations of greater than 2mm. Force-separation behavior and the high cost of these magnets may not justify their routine clinical use. PMID:1416238
May the Magnetic Force Be with You
ERIC Educational Resources Information Center
Wilcox, Jesse; Richey, Lindsey R.
2012-01-01
Although most elementary students have had experiences with magnets, they generally have misconceptions about magnetism (Driver et al. 1994; Burgoon, Heddle, and Duran 2010). For example, students may think magnets can attract all metals or that larger magnets are stronger than smaller magnets. Students often confuse magnets with magnetic
Science in a Box. Magnets III: Force Fields.
ERIC Educational Resources Information Center
Learning, 1992
1992-01-01
Presents ideas to help elementary school educators teach their students about magnetic force fields by observing how iron filings line up around magnets. The article lists materials needed and offers a student page with suggested student activities. (SM)
Nuclear matter equation of state and three-body forces
Mansour, H. M. M.; Algamoudi, A. M. A. [Cairo University, Physics Department, Faculty of Science (Egypt)
2012-04-15
The energy per particle, symmetry energy, pressure, and free energy are calculated for symmetric nuclear matter using BHF approach with modern nucleon-nucleon CD-Bonn, Nijm1, Argonne v{sub 18}, and Reid 93 potentials. To obtain saturation in nuclear matter we add three-body interaction terms which are equivalent to a density-dependent two-nucleon interaction a la Skyrme force. Good agreement is obtained in comparison with previous theoretical estimates and experimental data.
Boal, David
Demonstration: levitating globe comparing a magnetic force with the force of gravity; Geiger interaction - gravity. Gravity As you know from high school physics, the gravitational force between two. This functional form is identical to that of Newton's law for gravity: ˇthe force is proportional to the product
Gravito-Magnetism in one-body and two-body systems: Theory and Experiments.
O'Connell, Robert F.
and lunar-laser ranging measurements (which actually involve three bodies). Two-body systems inevitablyGravito-Magnetism in one-body and two-body systems: Theory and Experiments. R. F. O (rotation) effects in binary systems. A detailed discussion is given of the two-body Kepler problem and its
On the force on a body moving in a fluid
NASA Astrophysics Data System (ADS)
Biesheuvel, Arie; Hagmeijer, Rob
2006-10-01
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".
Nuclear Three-Body Force from the Nijmegen Potential
NASA Astrophysics Data System (ADS)
Li, Z. H.; Lombardo, U.; Schulze, H.-J.; Zuo, W.
2008-02-01
A nuclear three-body force based on the meson-exchange approach is constructed using the same meson parameters and the exponential form factors as in the Nijmegen potential, involving four kinds of important mesons, ?, ?, ?, and ? [f0(975) and ?(760)]. For the 2?-exchange three-nucleon component, we adopt the new expansion strength constants a, b, c consistent with the contemporary ?N-scattering data base and the corresponding dipole form factor. An effective two-body interaction is derived by averaging out the third nucleon, and is self-consistently used together with the Nijmegen potential in the Brueckner-Hartree-Fock approximation. The empirical nuclear matter saturation properties are reproduced very well. At higher density the equation of state becomes rather stiff due to the strong repulsion from the (?, ?)-N three-body contribution.
Performance enhancement of a Lorentz force velocimeter using a buoyancy-compensated magnet system
NASA Astrophysics Data System (ADS)
Ebert, R.; Leineweber, J.; Resagk, C.
2015-07-01
Lorentz force velocimetry (LFV) is a highly feasible method for measuring flow rate in a pipe or a duct. This method has been established for liquid metal flows but also for electrolytes such as saltwater. A decrease in electrical conductivity of the medium causes a decrease of the Lorentz force which needs to be resolved, affecting the accuracy of the measurement. We use an electrical force compensation (EFC) balance for the determination of the tiny force signals in a test channel filled with electrolyte solution. It is used in a 90°-rotated orientation with a magnet system hanging vertically on its load bar. The thin coupling elements of its parallel guiding system limit the mass of the magnets to 1?kg. To overcome this restriction, which limits the magnetic flux density and hence the Lorentz forces, a weight force compensation mechanism is developed. Therefore, different methods such as air bearing are conceivable, but for the elimination of additional horizontal force components which would disturb the force signal, only compensation by lift force provided by buoyancy is reasonable. We present a swimming body setup that will allow larger magnet systems than before, because a large amount of the weight force will be compensated by this lift force. Thus the implementation of this concept has to be made with respect to hydrodynamical and mechanical stability. This is necessary to avoid overturning of the swimming body setup and to prevent inelastic deformation. Additionally, the issue will be presented and discussed whether thermal convection around the lifting body diminishes the signal-to-noise ratio (SNR) significantly or not.
Solvable Many-Body Models of Goldfish Type with One-, Two- and Three-Body Forces
NASA Astrophysics Data System (ADS)
Bihun, Oksana; Calogero, Francesco
2013-10-01
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? ?.
2005-01-01
Journal of Magnetism and Magnetic Materials 286 (2005) 324328 Light-free magnetic resonance force volumes in a wide variety of materials. Unlike conventional magnetic reso- nance techniques for Physical Sciences, College Park, MD, USA Available online 4 November 2004 Abstract Magnetic resonance force
MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS B. Fornberg,2
Fornberg, Bengt
MAGNETIC FIELD CONFINEMENT IN THE SOLAR CORONA. I. FORCE-FREE MAGNETIC FIELDS N. Flyer,1 B Axisymmetric force-free magnetic fields external to a unit sphere are studied as solutions to boundary value to the formation of an azimuthal rope of twisted magnetic field embedded within the global field, and to the energy
Estimation of axial compressor body forces using three-dimensional flow computations
Reichstein, Georg A
2009-01-01
This thesis presents an examination of body force distributions in a single stage low speed compressor. The body force distributions are developed using two different computational procedures, an axisymmetric streamline ...
Lateral restoring force on a magnet levitated above a superconductor
NASA Technical Reports Server (NTRS)
Davis, L. C.
1990-01-01
The lateral restoring force on a magnet levitated above a superconductor is calculated as a function of displacement from its original position at rest using Bean's critical-state model to describe flux pinning. The force is linear for small displacements and saturates at large displacements. In the absence of edge effects the force always attracts the magnet to its original position. Thus it is a restoring force that contributes to the stability of the levitated magnet. In the case of a thick superconductor slab, the origin of the force is a magnetic dipole layer consisting of positive and negative supercurrents induced on the trailing side of the magnet. The qualitative behavior is consistent with experiments reported to date. Effects due to the finite thickness of the superconductor slab and the granular nature of high-Tc materials are also considered.
Computation of unbalanced radial force in permanent magnet motors
Salon, S.J.; Howe, M.; Slavik, C.J.; DeBortoli, M.J.; Nevins, R.J.
1998-10-01
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.
A potential MRI hazard: forces on dental magnet keepers.
Gegauff, A G; Laurell, K A; Thavendrarajah, A; Rosenstiel, S F
1990-09-01
The objective of this study was to determine the forces on dental prosthetic magnet keepers, with a view to assessing the potential for patient injury during magnetic resonance imaging (MRI). Four pre-formed keepers and one castable keeper alloy were tested. Magnetizations and high field susceptibilities were determined for each of the five specimens using data from a vibrating sample magnetometer. The magnetic field intensity with respect to distance from the main magnet coil was obtained from the manufacturer (1-5 tesla General Electric Signa Imaging System). A plot of force versus distance from the main coil and the maximum force at the magnet portal was determined for each specimen. The maximum forces ranged from 0.12-0.24 N for the pre-formed keepers and 3.67 MNm-3 for the castable alloy. It was concluded that the risk of patient injury by displacement is minimal, if the keepers are properly attached to supporting structures. PMID:2231158
Kelvin force in a layer of magnetic fluid
Adrian Lange
2002-04-09
The Kelvin force in a layer of magnetic fluid subjected to a homogeneous magnetic field and local heating is studied. The study is motivated by the question about the corresponding Kelvin force density [M. Liu, Phys. Rev. Lett., 2762 (2000)]. It is shown that the usual and the newly proposed formulation of the Kelvin force are entirely equivalent. It is only when approximations are introduced that differences arise.
Varying the effective buoyancy of cells using magnetic force
NASA Astrophysics Data System (ADS)
Guevorkian, Karine; Valles, James M.
2004-06-01
We introduce a magnetic force buoyancy variation (MFBV) technique that employs intense inhomogeneous magnetic fields to vary the effective buoyancy of cells and other diamagnetic systems in solution. Nonswimming Paramecia have been suspended, forced to sediment and driven to rise in solution using MFBV. Details of their response to MFBV have been used to determine the magnetic susceptibility of a single Paramecium. The use of MFBV as a means by which to suspend cell cultures indefinitely is also described.
Three-body forces and the limit of oxygen isotopes.
Otsuka, Takaharu; Suzuki, Toshio; Holt, Jason D; Schwenk, Achim; Akaishi, Yoshinori
2010-07-16
The limit of neutron-rich nuclei, the neutron drip line, evolves regularly from light to medium-mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced in shell-model calculations derived from microscopic two-nucleon forces. Here, we present the first microscopic explanation of the oxygen anomaly based on three-nucleon forces that have been established in few-body systems. This leads to repulsive contributions to the interactions among excess neutrons that change the location of the neutron drip line from (28)O to the experimentally observed (24)O. Since the mechanism is robust and general, our findings impact the prediction of the most neutron-rich nuclei and the synthesis of heavy elements in neutron-rich environments. PMID:20867759
Three-Body Forces and the Limit of Oxygen Isotopes
Otsuka, Takaharu [Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); Center for Nuclear Study, University of Tokyo, Hongo, Tokyo 113-0033 (Japan); National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan, 48824 (United States); Suzuki, Toshio [Department of Physics, College of Humanities and Sciences, Nihon University, Sakurajosui 3, Tokyo 156-8550 (Japan); Holt, Jason D.; Schwenk, Achim [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Akaishi, Yoshinori [RIKEN Nishina Center, Hirosawa, Wako-shi, Saitama 351-0198 (Japan)
2010-07-16
The limit of neutron-rich nuclei, the neutron drip line, evolves regularly from light to medium-mass nuclei except for a striking anomaly in the oxygen isotopes. This anomaly is not reproduced in shell-model calculations derived from microscopic two-nucleon forces. Here, we present the first microscopic explanation of the oxygen anomaly based on three-nucleon forces that have been established in few-body systems. This leads to repulsive contributions to the interactions among excess neutrons that change the location of the neutron drip line from {sup 28}O to the experimentally observed {sup 24}O. Since the mechanism is robust and general, our findings impact the prediction of the most neutron-rich nuclei and the synthesis of heavy elements in neutron-rich environments.
Effects of three-body forces in the 3 H bound state
Knutson, Lynn
ARTICLES Effects of three-body forces in the 3 H bound state L. D. Knutson Physics Department function obtained with the pair-correlated hyperspherical harmonic method are presented for a variety of three-body force models. In each calculation the strength of the three- body force is adjusted
Response of a Viscoelastic Layered Half-space to an Arbitrary 3-D Vector Body Force
Sandwell, David T.
Response of a Viscoelastic Layered Half-space to an Arbitrary 3-D Vector Body Force (Copyright 2003 elastic half-space to an arbitrary 3-D vector body force [Smith and Sandwell, 2003], we now wish to extend that our solutions will be prepared in the Fourier domain. The method follows: i.) Develop the body force
The force exerting on cosmic bodies in a quaternionc field
V. Majernik
2003-09-03
The expression of a time-dependent cosmological constant $\\lambda \\propto 1/t^2$ is interpreted as the energy density of a special type of the quaternionic field. The Lorenz-like force acting on the moving body in the presence of this quaternionic field is determined. The astronomical and terrestrial effects of this field are presented, and the ways how it can be observably detected is discussed. Finally, a new mechanism of the particle creation and an alternative cosmological scenario in the presence of the cosmic quatertionic field is suggested.
Many-Body Force and Mobility Measurements in Colloidal Systems
Jason W. Merrill; Sunil K. Sainis; Jerzy Blawzdziewicz; Eric R. Dufresne
2009-12-22
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 stands in contrast to the electrostatic interactions, which were found to deviate significantly from a pairwise model. The measurement technique presented here should be simple to extend to systems of heterogeneous, non-spherical particles arranged in arbitrary 3D geometries.
MAGNETIC HELICITY OF SELF-SIMILAR AXISYMMETRIC FORCE-FREE FIELDS
Zhang Mei; Flyer, Natasha; Low, Boon Chye
2012-08-10
In this paper, we continue our theoretical studies addressing the possible consequences of magnetic helicity accumulation in the solar corona. Our previous studies suggest that coronal mass ejections (CMEs) are natural products of coronal evolution as a consequence of magnetic helicity accumulation and that the triggering of CMEs by surface processes such as flux emergence also have their origin in magnetic helicity accumulation. Here, we use the same mathematical approach to study the magnetic helicity of axisymmetric power-law force-free fields but focus on a family whose surface flux distributions are defined by self-similar force-free fields. The semi-analytical solutions of the axisymmetric self-similar force-free fields enable us to discuss the properties of force-free fields possessing a huge amount of accumulated magnetic helicity. Our study suggests that there may be an absolute upper bound on the total magnetic helicity of all bipolar axisymmetric force-free fields. With the increase of accumulated magnetic helicity, the force-free field approaches being fully opened up with Parker-spiral-like structures present around a current-sheet layer as evidence of magnetic helicity in the interplanetary space. It is also found that among the axisymmetric force-free fields having the same boundary flux distribution, the one that is self-similar is the one possessing the maximum amount of total magnetic helicity. This gives a possible physical reason why self-similar fields are often found in astrophysical bodies, where magnetic helicity accumulation is presumably also taking place.
In vivo implant forces acting on a vertebral body replacement during upper body flexion.
Dreischarf, Marcel; Albiol, Laia; Zander, Thomas; Arshad, Rizwan; Graichen, Friedmar; Bergmann, Georg; Schmidt, Hendrik; Rohlmann, Antonius
2015-02-26
Knowledge about in vivo spinal loads is required for the identification of risk factors for low back pain and for realistic preclinical testing of spinal implants. Therefore, the aim of the present study was to measure the in vivo forces on a vertebral body replacement (VBR) during trunk flexion and to analyze in detail the typical relationship between trunk inclination and spinal load. Telemeterized VBRs were implanted in five patients. In vivo loads were measured 135 times during flexion while standing or sitting. The trunk inclination was simultaneously recorded. To reveal elementary differences between flexion while standing and sitting, the force increases at the maximal inclination, as compared to the upright position, were also determined. Approximately 90% of all standing trials showed a characteristic inclination-load relationship, with an initial increase of the resultant force followed by a plateau or even a decrease of the force at an inclination of approximately 33°. Further flexion to the average maximal inclination angle of 53° only marginally affected the implant loads (~450N). Maximal forces were measured during the return to the initial standing position (~565N). Flexion during standing led to a greater force increase (~330N) than during sitting (~200N) when compared to the respective upright positions. The force plateau at greater inclination angles might be explained by abdominal load support, complex stabilization of active and passive spinal structures or intricate load sharing within the implant complex. The data presented here aid in understanding the loads acting on an instrumented lumbar spine. PMID:25640900
NASA Astrophysics Data System (ADS)
Lee, C. J.; Jang, G. H.
2008-04-01
This paper investigates the distortion of magnetic field of a brushless dc (BLDC) motor due to deformed rubber magnet. Global or local deformation of rubber magnet in the BLDC motor is mathematically modeled by using the Fourier series. Distorted magnetic field is calculated by using the finite element method, and unbalanced magnetic force is calculated by using the Maxwell stress tensor. When the rubber magnet is globally or locally deformed, the unbalanced magnetic force has the frequencies with the first harmonic and the harmonics of slot number ą1. However, the harmonic deformation with multiple of common divisor of pole and slot does not generate unbalanced magnetic force due to the rotational symmetry.
Classical diamagnetism, magnetic interaction energies, and repulsive forces in magnetized plasmas
NASA Astrophysics Data System (ADS)
Essén, H.
2011-05-01
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.
On the resistive diffusion of force-free magnetic fields
NASA Technical Reports Server (NTRS)
Low, B. C.
1980-01-01
Reid and Laing (1979) conjectured on the general behavior of resistive force-free magnetic fields in a slab model following a numerical study. However, the basic properties of resistive force-free magnetic fields had been established previously. Some results from the previous work are extended to show that the conjecture of Reid and Laing is incorrect. A general analytic treatment of the problem provides the correct physical properties that Reid and Laing were unable to deduce from their numerical solutions. A criticism is also given of the results presented in another numerical study treating cylindrical resistive force-free magnetic fields, by the same authors.
Power dissipation and magnetic forces and MAGLEV rebars
Zahn, M.
1997-03-01
Concrete guideways for proposed MAGLEV vehicles may be reinforced with electrically conducting and magnetizable steel rebars. Transient magnetic fields due to passing MAGLEV vehicles will then induce transient currents in the rebars leading to power dissipation and temperature rise as well as Lorentz and magnetization forces on the rebars. In order to evaluate if this heating and force on the rebars affects concrete life and performance, analysis is presented for an infinitely long conducting and magnetizable cylinder in imposed uniform axial or transverse magnetic fields. Exact and approximate solutions are presented for sinusoidal steady state and step transient magnetic fields inside and outside the cylinder, the induced current density, the vector potential for transverse magnetic fields, the time average dissipated power in the sinusoidal steady state, and the total energy dissipated for step transients. Forces are approximately calculated for imposed magnetic fields` with a weak spatial gradient. The analysis is applied to representative rebar materials.
Microscopic Energy Current Field with Multi--body Force in Hamiltonian System
Atsushi Ito; Hiroaki Nakamura
2006-08-08
Microscopic energy current can be derived from microscopic energy field localized only in particle positions. If the energy current is applied to classical molecular dynamics, it is expected to become a new information. However, multi-body force except two-body force causes obscurity when multi-body interaction energy is localized. In the present study, our new method enables to determine the localization of the multi--body interaction energy. We obtain the energy current between particles by the law of the multi--body force corresponding to Newton's third law on two--body force.
Nonconservative electric and magnetic optical forces on submicron dielectric particles
Gomez-Medina, Raquel; Nieto-Vesperinas, Manuel; Saenz, Juan Jose
2011-03-15
We present a study of the total force on a small lossless dielectric particle, which presents both an electric and magnetic response, in a optical vortex wave field. We show that the force is a simple combination of conservative and nonconservative steady forces that can rectify the flow of magnetodielectric particles. In a vortex lattice the electric-magnetic dipolar interaction can spin the particles either in or out of the whirl sites leading to trapping or diffusion. Specifically, we analyze force effects on submicron silicon spheres in the near infrared, proving that the results previously discussed for hypothetical magnetodielectric particles can be observed for these Si particles.
Experimental studies of protozoan response to intense magnetic fields and forces
NASA Astrophysics Data System (ADS)
Guevorkian, Karine
Intense static magnetic fields of up to 31 Tesla were used as a novel tool to manipulate the swimming mechanics of unicellular organisms. It is shown that homogenous magnetic fields alter the swimming trajectories of the single cell protozoan Paramecium caudatum, by aligning them parallel to the applied field. Immobile neutrally buoyant paramecia also oriented in magnetic fields with similar rates as the motile ones. It was established that the magneto-orientation is mostly due to the magnetic torques acting on rigid structures in the cell body and therefore the response is a non-biological, passive response. From the orientation rate of paramecia in various magnetic field strengths, the average anisotropy of the diamagnetic susceptibility of the cell was estimated. It has also been demonstrated that magnetic forces can be used to create increased, decreased and even inverted simulated gravity environments for the investigation of the gravi-responses of single cells. Since the mechanisms by which Earth's gravity affects cell functioning are still not fully understood, a number of methods to simulate different strength gravity environments, such as centrifugation, have been employed. Exploiting the ability to exert magnetic forces on weakly diamagnetic constituents of the cells, we were able to vary the gravity from -8 g to 10 g, where g is Earth's gravity. Investigations of the swimming response of paramecia in these simulated gravities revealed that they actively regulate their swimming speed to oppose the external force. This result is in agreement with centrifugation experiments, confirming the credibility of the technique. Moreover, the Paramecium's swimming ceased in simulated gravity of 10 g, indicating a maximum possible propulsion force of 0.7 nN. The magnetic force technique to simulate gravity is the only earthbound technique that can create increased and decreased simulated gravities in the same experimental setup. These findings establish a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.
ANALYSIS OF THE MAGNETIZED FRICTION FORCE.
FEDOTOV, A.V.; BRUHWILER, D.L.; SIDORIN, A.O.
2006-05-29
A comprehensive examination of theoretical models for the friction force, in use by the electron cooling community, was performed. Here, they present their insights about the models gained as a result of comparison between the friction force formulas and direct numerical simulations, as well as studies of the cooling process as a whole.
Magnetic levitation of metamaterial bodies enhanced with magnetostatic surface resonances
Urzhumov, Yaroslav; Bingham, Chris; Padilla, Willie; Smith, David R
2011-01-01
We propose that macroscopic objects built from negative-permeability metamaterials may experience resonantly enhanced magnetic force in low-frequency magnetic fields. Resonant enhancement of the time-averaged force originates from magnetostatic surface resonances (MSR) which are analogous to the electrostatic resonances of negative-permittivity particles, well known as surface plasmon resonances in optics. We generalize the classical problem of MSR of a homogeneous object 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.
Controlling a magnetic force microscope to track a magnetized nanosize particle
Andersson, Sean B.
of the MFM and prove that this trajectory converges to a neighborhood of the magnetic particle. The viability1 Controlling a magnetic force microscope to track a magnetized nanosize particle Dimitar Baronov of the magnetic particle induces a shift in the phase of oscillation of the tip of the MFM. We present a nonlinear
Estimating the magnetic penetration depth using constant-height magnetic force
Grütter, Peter
Estimating the magnetic penetration depth using constant-height magnetic force microscopy images to determine the relative value of the magnetic penetration depth to within 1020% using an uncalibrated tip to obtain an absolute value of with similar accuracy. The magnetic penetration depth is one
Integrals of Motion for Planar Multi-Body Formations with Internal Forces
Peck, Mason A.
Integrals of Motion for Planar Multi-Body Formations with Internal Forces Michael C. Norman of such a force potentially complicates the analysis of these systems, inte- grals of motion still exist, AIAA Member. 1 of 19 Integrals of Motion for Planar Multi-Body Formations with Internal Forces #12;~q
Structure Preserving Approximations of Conservative Forces for Application to Small-Body Dynamics
Hirani, Anil N.
Structure Preserving Approximations of Conservative Forces for Application to Small-Body Dynamics traditional methods for complex force evaluations near small irregular bodies. Such methods also hold the promise of simplifying the inclusion of experimental data to update the force model. However, the cubetree
LABORATORY V MAGNETIC FIELDS AND FORCES
Minnesota, University of
in a uniform magnetic field and describe its motion. PREPARATION: Read Serway & Jewett: Chapter 22, sections 1 with the magnets in the other figures. WARM-UP Read Serway & Jewett: sections 22.1, 22.2. 1. Make a sketch of all
Force measurements in magnetic bearings using fiber optic strain gauges
Raymer, Stephen Geoffrey
2000-01-01
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...
A model for quantum jumps in magnetic resonance force microscopy
G. P. Berman; F. Borgonovi; V. I. Tsifrinovich
2005-01-01
We propose a simple model which describes the statistical properties of quantum jumps in a single-spin measurement using the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. Our computer simulations based on this model predict the average time interval between two consecutive quantum jumps and the correlation time to be proportional to the characteristic time of the magnetic
Chem. Rev. 1994, 94, 1975-1997 1975 Many-Body Effects in Intermolecular Forces
Elrod, Matthew J.
Chem. Rev. 1994, 94, 1975-1997 1975 Many-Body Effects in Intermolecular Forces Contents Matthew J, such that many relevant pair potential energy surfaces are now obtainable by inversion of experi- mental data to the actual many-body experimental result. Therefore, the study of many-body forces generally demands very
Extending the range for force calibration in magnetic tweezers.
Daldrop, Peter; Brutzer, Hergen; Huhle, Alexander; Kauert, Dominik J; Seidel, Ralf
2015-05-19
Magnetic tweezers are a wide-spread tool used to study the mechanics and the function of a large variety of biomolecules and biomolecular machines. This tool uses a magnetic particle and a strong magnetic field gradient to apply defined forces to the molecule of interest. Forces are typically quantified by analyzing the lateral fluctuations of the biomolecule-tethered particle in the direction perpendicular to the applied force. Since the magnetic field pins the anisotropy axis of the particle, the lateral fluctuations follow the geometry of a pendulum with a short pendulum length along and a long pendulum length perpendicular to the field lines. Typically, the short pendulum geometry is used for force calibration by power-spectral-density (PSD) analysis, because the movement of the bead in this direction can be approximated by a simple translational motion. Here, we provide a detailed analysis of the fluctuations according to the long pendulum geometry and show that for this direction, both the translational and the rotational motions of the particle have to be considered. We provide analytical formulas for the PSD of this coupled system that agree well with PSDs obtained in experiments and simulations and that finally allow a faithful quantification of the magnetic force for the long pendulum geometry. We furthermore demonstrate that this methodology allows the calibration of much larger forces than the short pendulum geometry in a tether-length-dependent manner. In addition, the accuracy of determination of the absolute force is improved. Our force calibration based on the long pendulum geometry will facilitate high-resolution magnetic-tweezers experiments that rely on short molecules and large forces, as well as highly parallelized measurements that use low frame rates. PMID:25992733
Fundamental study of phosphor separation by controlling magnetic force
NASA Astrophysics Data System (ADS)
Wada, Kohei; Mishima, Fumihito; Akiyama, Yoko; Nishijima, Shigehiro
2013-11-01
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.
Sensitive magnetic force detection with a carbon nanotube resonator
Willick, Kyle; Haapamaki, Chris; Baugh, Jonathan
2014-03-21
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.
EXPERIMENTAL BENCHMARKING OF THE MAGNETIZED FRICTION FORCE.
FEDOTOV, A.V.; GALNANDER, B.; LITVINENKO, V.N.; LOFNES, T.; SIDORIN, A.O.; SMIRNOV, A.V.; ZIEMANN, V.
2005-09-18
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.
Force Measurements in Magnetic Suspension and Balance System
NASA Technical Reports Server (NTRS)
Kuzin, Alexander; Shapovalov, George; Prohorov, Nikolay
1996-01-01
The description of an infrared telemetry system for measurement of drag forces in Magnetic Suspension and Balance Systems (MSBS) is presented. This system includes a drag force sensor, electronic pack and transmitter placed in the model which is of special construction, and receiver with a microprocessor-based measuring device, placed outside of the test section. Piezosensitive resonators as sensitive elements and non-magnetic steel as the material for the force sensor are used. The main features of the proposed system for load measurements are discussed and the main characteristics are presented.
A Model for Quantum Jumps in Magnetic Resonance Force Microscopy
G. P. Berman; F. Borgonovi; V. I. Tsifrinovich
2004-02-09
We propose a simple model which describes the statistical properties of quantum jumps in a single-spin measurement using the oscillating cantilever-driven adiabatic reversals technique in magnetic resonance force microscopy. Our computer simulations based on this model predict the average time interval between two consecutive quantum jumps and the correlation time to be proportional to the characteristic time of the magnetic noise and inversely proportional to the square of the magnetic noise amplitude.
Magnetic force microscopy sensors using iron-filled carbon nanotubes
Winkler, Andreas; Muehl, Thomas; Menzel, Siegfried; Kozhuharova-Koseva, Radinka; Hampel, Silke; Leonhardt, Albrecht; Buechner, Bernd
2006-05-15
Probes for magnetic force microscopy (MFM) were prepared by pinning iron-filled multiwall carbon nanotubes to conventional scanning force microscopy probes. These nanotube MFM probes reveal a great potential for high spatial resolution of both topography and magnetic stray field. The ends of the high aspect ratio iron nanowires within the nanotubes can be considered as stationary effective magnetic monopole moments which opens the possibility of quantitative stray field measurements in a straightforward manner. The carbon shells around the iron nanowires provide wear resistance and oxidation protection.
Magnetic forces in high-Tc superconducting bearings
NASA Technical Reports Server (NTRS)
Moon, F. C.
1991-01-01
In September 1987, researchers at Cornell levitated a small rotor on superconducting bearings at 10,000 rpm. In April 1989, a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu307. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.
A magnetic gradient induced force in NMR restricted diffusion experiments
Ghadirian, Bahman; Stait-Gardner, Tim; Castillo, Reynaldo; Price, William S.
2014-03-28
We predict that the phase cancellation of a precessing magnetisation field carried by a diffusing species in a bounded geometry under certain nuclear magnetic resonance pulsed magnetic field gradient sequences results in a small force over typically micrometre length scales. Our calculations reveal that the total magnetisation energy in a pore under the influence of a pulsed gradient will be distance-dependent thus resulting in a force acting on the boundary. It is shown that this effect of the magnetisation of diffusing particles will appear as either an attractive or repulsive force depending on the geometry of the pore and magnetic properties of the material. A detailed analysis is performed for the case of a pulsed gradient spin-echo experiment on parallel planes. It is shown that the force decays exponentially in terms of the spin-spin relaxation. The proof is based on classical electrodynamics. An application of this effect to soft matter is suggested.
Thermal Casimir Force between Magnetic Materials
G. L. Klimchitskaya; B. Geyer; V. M. Mostepanenko
2009-11-21
We investigate the Casimir pressure between two parallel plates made of magnetic materials at nonzero temperature. It is shown that for real magnetodielectric materials only the magnetic properties of ferromagnets can influence the Casimir pressure. This influence is accomplished through the contribution of the zero-frequency term of the Lifshitz formula. The possibility of the Casimir repulsion through the vacuum gap is analyzed depending on the model used for the description of the dielectric properties of the metal plates.
Thermal Casimir Force Between Magnetic Materials
NASA Astrophysics Data System (ADS)
Klimchitskaya, G. L.; Geyer, B.; Mostepanenko, V. M.
2010-04-01
We investigate the Casimir pressure between two parallel plates made of magnetic materials at nonzero temperature. It is shown that for real magnetodielectric materials only the magnetic properties of ferromagnets can influence the Casimir pressure. This influence is accomplished through the contribution of the zero-frequency term of the Lifshitz formula. The possibility of the Casimir repulsion through the vacuum gap is analyzed depending on the model used for the description of the dielectric properties of the metal plates.
Magnetic forces in high-T(sub c) superconducting bearings
NASA Technical Reports Server (NTRS)
Moon, F. C.
1990-01-01
In September 1987 research at Cornell levitated a small rotor on superconducting bearing at 10,000 rpm. In April 1989 a speed of 120,000 rpm was achieved in a passive bearing with no active control. The bearing material used was YBa2Cu3O7. There is no evidence that the rotation speed has any significant effect on the lift force. Magnetic force measurements between a permanent rare-earth magnet and high T(sub c) superconducting material versus vertical and lateral displacements were made. A large hysteresis loop results for large displacements, while minor loops result for small displacements. These minor loops seem to give a slope proportional to the magnetic stiffness, and are probably indicative of flux pinning forces. Experiments of rotary speed versus time show a linear decay in a vacuum. Measurements of magnetic drag forces of a magnetic dipole over a high-T(sub c) superconducting disc of YBCO show that the drag force reaches a constant value, independent of the speed. Dampling of lateral vibrations of levitated rotors were measured which indicates that transverse flux motion in the superconductor will create dissipation. As a result of these force measurements, an optimum shape for the superconductor bearing pads which gives good lateral and axial stability was designed. Recent force measurements on melt-quench processed superconductors indicate a substantial increase in levitation force and magnetic stiffness over free sintered materials. As a result, application of high-T(sub c) superconducting bearings are beginning to show great promise at this time.
Detecting the gravitational sensitivity of Paramecium caudatum using magnetic forces
NASA Astrophysics Data System (ADS)
Guevorkian, Karine; Valles, James M., Jr.
2006-03-01
Under normal conditions, Paramecium cells regulate their swimming speed in response to the pN level mechanical force of gravity. This regulation, known as gravikinesis, is more pronounced when the external force is increased by methods such as centrifugation. Here we present a novel technique that simulates gravity fields using the interactions between strong inhomogeneous magnetic fields and cells. We are able to achieve variable gravities spanning from 10xg to -8xg; where g is earth's gravity. Our experiments show that the swimming speed regulation of Paramecium caudatum to magnetically simulated gravity is a true physiological response. In addition, they reveal a maximum propulsion force for paramecia. This advance establishes a general technique for applying continuously variable forces to cells or cell populations suitable for exploring their force transduction mechanisms.
Solutions and symmetries of force-free magnetic fields
Tassi, E.; Pegoraro, F.; Cicogna, G.
2008-09-15
New analytical results concerning force-free magnetic fields are presented. A number of examples of exact solutions for two-dimensional nonlinear force-free fields described by the Liouville equation are shown. These include classical solutions, such as, the Gold-Hoyle field and the force-free Harris sheet as special cases. The connection between these solutions and the Lie point symmetries of the Liouville equation is illustrated. Lie point symmetries of the equation describing force-free magnetic fields in helical symmetry in cylindrical geometry are also investigated and an infinitesimal generator that, in the vicinity of the cylinder axis, makes it possible to transform purely radially dependent solutions into helically symmetric solutions, is found. Finally we point out the existence of a formal analogy between the equations for the vector potential components of a class of force-free fields and the equations of motion of a charged particle in a magnetic field. This analogy makes it possible to transfer known results from the theory of the motion of a charged particle, into the context of force-free magnetic fields. Explicit examples of such application are given.
Cryogenic magnetic force microscope M. Rosemana)
Grütter, Peter
, in fields of 08 T. The system uses a fiber optic interferometer to measure cantilever deflections as feedthroughs for electrical connections, the optical fiber, and pumping lines for a turbomolecular vacuum pump positioners, capable of operation in high magnetic fields, perform in situ tip and fiber approaches
Many-body forces, isospin asymmetry and dense hyperonic matter
R. O. Gomes; V. Dexheimer; S. Schramm; C. A. Z. Vascconcellos
2015-04-10
The equation of state (EoS) of asymmetric nuclear matter at high densities is a key topic for the description of matter inside neutron stars. The determination of the properties of asymmetric nuclear matter, such as the symmetry energy ($a_{sym}$) and the slope of the symmetry energy ($L_0$) at saturation density, has been exaustively studied in order to better constrain the nuclear matter EoS. However, differently from symmetric matter properties that are reasonably constrained, the symmetry energy and its slope still large uncertainties in their experimental values. Regarding this subject, some studies point towards small values of the slope of the symmetry energy, while others suggest rather higher values. Such a lack of agreement raised a certain debate in the scientific community. In this paper, we aim to analyse the role of these properties on the behavior of asymmetric hyperonic matter. Using the formalism presented in Ref. (R.O. Gomes et al 2014}, which considers many-body forces contributions in the meson-baryon coupling, we calculate the EoS of asymmetric hyperonic matter and apply it to describe hyperonic matter and hyperon stars.
Many-body forces, isospin asymmetry and dense hyperonic matter
Gomes, R O; Schramm, S; Vascconcellos, C A Z
2015-01-01
The equation of state (EoS) of asymmetric nuclear matter at high densities is a key topic for the description of matter inside neutron stars. The determination of the properties of asymmetric nuclear matter, such as the symmetry energy ($a_{sym}$) and the slope of the symmetry energy ($L_0$) at saturation density, has been exaustively studied in order to better constrain the nuclear matter EoS. However, differently from symmetric matter properties that are reasonably constrained, the symmetry energy and its slope still large uncertainties in their experimental values. Regarding this subject, some studies point towards small values of the slope of the symmetry energy, while others suggest rather higher values. Such a lack of agreement raised a certain debate in the scientific community. In this paper, we aim to analyse the role of these properties on the behavior of asymmetric hyperonic matter. Using the formalism presented in Ref. (R.O. Gomes et al 2014}, which considers many-body forces contributions in the ...
Many-body central force potentials for tungsten
NASA Astrophysics Data System (ADS)
Bonny, G.; Terentyev, D.; Bakaev, A.; Grigorev, P.; Van Neck, D.
2014-07-01
Tungsten and tungsten-based alloys are the primary candidate materials for plasma facing components in fusion reactors. The exposure to high-energy radiation, however, severely degrades the performance and lifetime limits of the in-vessel components. In an effort to better understand the mechanisms driving the materials' degradation at the atomic level, large-scale atomistic simulations are performed to complement experimental investigations. At the core of such simulations lies the interatomic potential, on which all subsequent results hinge. In this work we review 19 central force many-body potentials and benchmark their performance against experiments and density functional theory (DFT) calculations. As basic features we consider the relative lattice stability, elastic constants and point-defect properties. In addition, we also investigate extended lattice defects, namely: free surfaces, symmetric tilt grain boundaries, the 1/2<1?1?1>{1?1?0} and 1/2<1?1?1> {1?1?2} stacking fault energy profiles and the 1/2<1?1?1> screw dislocation core. We also provide the Peierls stress for the 1/2<1?1?1> edge and screw dislocations as well as the glide path of the latter at zero Kelvin. The presented results serve as an initial guide and reference list for both the modelling of atomically-driven phenomena in bcc tungsten, and the further development of its potentials.
Visualization and characterization of prolamellar bodies with atomic force microscopy.
Grzyb, Joanna M; Solymosi, Katalin; Strza?ka, Kazimierz; Mysliwa-Kurdziel, Beata
2013-09-15
Prolamellar bodies (PLBs) isolated from etiolated wheat seedlings were studied with the use of atomic force microscopy (AFM), transmission electron microscopy (TEM) and fluorescence spectroscopy. With AFM, PLBs were seen as spherical structures about 1-2?m in diameter, more elastic than mica and poly-l-lysine substrate. TEM analyses confirmed that PLBs of wheat leaf etioplasts also had an average diameter of appr. 1?m. Illumination induced the photoreduction of photoactive protochlorophyllide (Pchlide), i.e. Pchlide bound to protochlorophyllide oxidoreductase, which was shown in fluorescence spectra. The photoreduction was followed by the disruption of PLB structures, which started with the enlargement of PLB spheres and then their fragmentation into small balls as seen with AFM. Light-induced vesicle formation and the outgrowth of lamellar (pro)thylakoid membranes on the PLB surface were also confirmed by TEM analyses, and resulted in the apparent enlargement of the PLB diameter. The blue-shift of the fluorescence emission maximum of chlorophyllide observed for PLBs at room temperature after Pchlide photoreduction was completed within 25min. However, structural changes in PLBs were still observed after the completion of the blue-shift. The incubation of PLBs in darkness with HgCl2 also resulted in PLB enlargement and a loosening of their structure. AFM provides a unique opportunity to observe PLBs at a physiological temperature without the necessity of fixation. PMID:23777838
Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient
Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo
2014-01-01
Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971
Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient.
Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo
2014-01-01
Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient. PMID:25365971
Spinmotive force due to motion of magnetic bubble arrays driven by magnetic field gradient
NASA Astrophysics Data System (ADS)
Yamane, Yuta; Hemmatiyan, Shayan; Ieda, Jun'ichi; Maekawa, Sadamichi; Sinova, Jairo
2014-11-01
Interaction between local magnetization and conduction electrons is responsible for a variety of phenomena in magnetic materials. It has been recently shown that spin current and associated electric voltage can be induced by magnetization that depends on both time and space. This effect, called spinmotive force, provides for a powerful tool for exploring the dynamics and the nature of magnetic textures, as well as a new source for electromotive force. Here we theoretically demonstrate the generation of electric voltages in magnetic bubble array systems subjected to a magnetic field gradient. It is shown by deriving expressions for the electric voltages that the present system offers a direct measure of phenomenological parameter ? that describes non-adiabaticity in the current induced magnetization dynamics. This spinmotive force opens a door for new types of spintronic devices that exploit the field-gradient.
Switching Magnetization Magnetic Force Microscopy An Alternative to Conventional Lift-Mode MFM
NASA Astrophysics Data System (ADS)
Cambel, Vladimír; Greguová, Dagmar; Eliá, Peter; Fedor, Ján; Kosti?, Ivan; Ma?ka, Ján; Ballo, Peter
2011-01-01
In the paper we present an overview of the latest progress in the conventional lift-mode magnetic force microscopy (MFM) technique, achieved by advanced MFM tips and by lowering the lift height. Although smaller lift height offers improved spatial resolution, we show that lowered tip-sample distance mixes magnetic, atomic and electric forces. We describe an alternative to the lift-mode procedure - Switching Magnetization Magnetic Force Microscopy [SM-MFM], which is based on two-pass scanning in tapping mode AFM with reversed tip magnetization between the scans. We propose design and calculate the magnetic properties of such SM-MFM tips. For best performance the tips must exhibit low magnetic moment, low switching field, and single-domain state at remanence. The switching field of such tips is calculated for Permalloy hexagons.
Tunable Casimir forces by means of the external magnetic field
Wang Jing; Zhang Xiangdong; Pei Shouyong; Liu Dahe [Department of Physics, Beijing Normal University, Beijing 100875 (China)
2006-04-15
We have theoretically investigated the tuning of Casimir forces by means of an external magnetic field. We have found that the Casimir force between two homogeneous slabs can be tuned by the external field in two ways. One is to add cap layers to the two dielectric slabs. The other is to insert a new dielectric layer into the cavity made of the two slabs. Since the dielectric constants of the materials used as the cap layers or the inserted layers depend on the external magnetic field, the Casimir force can be modified significantly by the external magnetic field. Our results show that it is possible to control the Casimir interaction in the fabrication of materials by an external field.
NASA Astrophysics Data System (ADS)
Yang, Yong
2008-12-01
In an actual levitation system composed of high temperature superconductors (HTSs) and permanent magnets (PMs), the levitating bodies may traverse in arbitrary directions. Many previous researchers assumed that the levitating bodies moved in a vertical direction or a lateral direction in order to simplify the problem. In this paper, the vertical and lateral forces acting on the PM are calculated by the modified frozen-image method when a PM above an HTS traverses in arbitrary directions. In order to study the effects of the movement directions on the vertical and lateral forces, comparisons of the forces that act on a PM traversing in a tilted direction with those that act on a PM traversing in a vertical direction or a lateral direction have been presented.
Using Magnetic Forces to Probe the Gravi-response of Swimming Paramecium
NASA Astrophysics Data System (ADS)
Guevorkian, Karine; Valles, James M., Jr.
2004-03-01
Paramecium Caudatum, a single celled ciliate, alters its swimming behavior when subjected to different gravity environments (e.g. centrifugation and micro-gravity). To dissect the mechanisms behind this gravi-response and that of other biological systems, we are developing the use of magnetic body forces as a means of creating a rapidly tunable, simulated variable gravity environment. Since biological materials are weakly diamagnetic, we must subject them to intense inhomogeneous magnetic fields with characteristic field-field gradient products on the order of 16 T^2/cm. We will describe experiments on Paramecium Caudatum in which we adjust their net buoyancy with magnetic forces and measure the resulting changes in their swimming behavior.
NASA Astrophysics Data System (ADS)
Batista, L.; Rabe, U.; Hirsekorn, S.
2013-01-01
The formation of a cementite phase influences significantly the macroscopic mechanical and magnetic properties of steels. Based on a correlation between mechanical and magnetic properties, mechanical properties as well as the morphology and content of the cementite phase can be inspected by electromagnetic non-destructive testing methods. The influence of the carbon content on bulk magnetic properties of unalloyed steels is studied on a macroscopic scale by hysteresis loop and Barkhausen noise measurements. The micro- and nanostructure is investigated by atomic force microscopy and magnetic force microscopy. Surface topography images and magnetic images of globular cementite precipitates embedded in a ferrite matrix are presented. The size, shape, and orientation of the precipitates influence the domain configuration. Applied external magnetic fields cause magnetization processes mainly in the ferrite matrix: Bloch walls move and are pinned by the cementite precipitates. The correlation between the microscopic observations and macroscopic magnetic properties of the material is discussed.
Design and optimization of force-reduced high field magnets
NASA Astrophysics Data System (ADS)
Rembeczki, Szabolcs
High field magnets have many important applications in different areas of research, in the power industry and also for military purposes. For example, high field magnets are particularly useful in: material sciences, high energy physics, plasma physics (as fusion magnets), high power applications (as energy storage devices), and space applications (in propulsion systems). One of the main issues with high-field magnets is the presence of very large electromagnetic stresses that must be counteracted and therefore require heavy support structures. In superconducting magnets, the problems caused by Lorentz forces are further complicated by the fact that superconductors for high field applications are pressure sensitive. The current carrying capacity is greatly reduced under stress and strain (especially in the case of Nb 3Sn and the new high temperature superconductors) so the reduction of the acting forces is of even greater importance. Different force-reduced magnet concepts have been studied in the past, both numerical and analytical methods have been used to solve this problem. The developed concepts are based on such complex winding geometries that the realization and manufacturing of such coils is extremely difficult and these concepts are mainly of theoretical interest. In the presented research, a novel concept for force-reduced magnets has been developed and analyzed which is easy to realize and therefore is of practical interest. The analysis has been performed with a new methodology, which does not require the time consuming finite element calculations. The developed computer models describe the 3-dimensional winding configuration by sets of filaments (filamentary approximation). This approach is much faster than finite element analysis and therefore allows rapid optimization of concepts. The method has been extensively tested on geometries of force-reduced solenoids where even analytical solutions exist. As a further cross check, the developed computer codes have been tested against qualified finite element codes and found to be in excellent agreement. The developed concept of force-reduced coils is directly applicable to pulsed magnets and a conceptual design of a 25 Tesla magnet has been developed. Although no experimental proof was possible within the scope of this research, there is strong evidence to believe that the developed concept is also applicable to superconducting magnets operating in a constant current mode.
Body Force Produced by Plasma Actuator Using PIV and Pressure Measurements
Liu, Feng
Body Force Produced by Plasma Actuator Using PIV and Pressure Measurements Xuanshi Meng1 , Yushuai Liu5 and Shijun Luo6 University of California, Irvine, CA 92697-3975, America The body force-Stokes equations and the measured velocity and pressure distributions in order to study the contribution
PAMM header will be provided by the publisher Magnetic Force Formulae for Magnets at Small Distances
Popovic, Nikola
-continuous vector field which is trivially extended to the entire space R3 , i.e., mA = mAA. Let HA be the magnetic and denote with HAB the magnetic field generated by m := mA + mB. The experimental idea which drives bothPAMM header will be provided by the publisher Magnetic Force Formulae for Magnets at Small
Localization and removal of ferromagnetic foreign bodies by magnet.
Cakir, Bari?; Akan, Mithat; Yildirim, Serkan; Aköz, Tayfun
2002-11-01
Foreign bodies should be removed from wounds during the primary wound management stage whenever possible. Metallic fragments can be identified and localized by conventional radiography, computed tomography, sonography, x-ray image intensifier, or electromagnetic metal detector. Locating metallic objects may still cause problems for the surgeon during the removal procedure. Detection and removal of superficial ferromagnetic fragments (iron, nickel, and cobalt) by a magnet is possible. In the literature the authors found no report about using the magnet for this purpose. Having conferred with the manufacturer KANAT (Istanbul, Turkey), the authors used a magnet made of neodymium. The power of the magnet was 12,000 gauss. It was cylindrical and 1.3 x 0.8 cm in diameter. This method was used in 6 patients successfully for localization and removal of ferromagnetic foreign bodies. Use of a magnet is an easy and cost-effective method that does not require education and specific staff. PMID:12439024
Local nonlinear rf forces in inhomogeneous magnetized plasmas
Chen, Jiale; Gao, Zhe
2014-06-15
The local nonlinear forces induced by radio frequency (rf) waves are derived in inhomogeneous magnetized plasmas, where the inhomogeneity exists in the rf fields, in the static magnetic field as well as in the equilibrium density and temperature. The local parallel force is completely resonant, but a novel component dependent on those inhomogeneities is obtained as the result of the inhomogeneous transport of parallel resonant-absorbed momentum by the nonlinear perpendicular drift flux. In the local poloidal force, the component induced by the inhomogeneity of rf power absorption is also confirmed and it can be recognized as the residual effect from the incomplete cancellation between the rate of the diamagnetic poloidal momentum gain and the Lorentz force due to the radial diffusion-like flux. The compact expression for radial force is also obtained for the first time, whose nonresonant component is expressed as the sum of the ponderomotive force on particles and the gradients of the nonresonant perpendicular pressure and of the nonresonant momentum flux due to the finite temperature effect. Numerical calculations in a 1-D slab model show that the resonant component dependent on the inhomogeneities may be significant when the ion absorption dominates the resonant wave-particle interaction. A quantitative estimation shows that the novel component in the parallel force is important to understand the experiments of the ion-cyclotron-frequency mode-conversion flow drive.
N-body nuclear forces at short distances in holographic QCD
Hashimoto, Koji; Nakatsukasa, Takashi [RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Iizuka, Norihiro [Theory Division, CERN, CH-1211 Geneva 23 (Switzerland)
2010-05-15
We provide a calculation of N-body (N{>=}3) nucleon interactions at short distances in holographic QCD. In the Sakai-Sugimoto model of large-N{sub c} massless QCD, N baryons are described by N Yang-Mills instantons in 5 spacetime dimensions. We compute a classical short-distance interaction Hamiltonian for N't Hooft instantons. This corresponds to N baryons sharing identical classical spins and isospins. We find that genuine N-body nuclear forces turn out to vanish for N{>=}3, at leading order. This suggests that classical N-body forces are always suppressed compared with 2-body forces.
Magnetoelectric force microscopy based on magnetic force microscopy with modulated electric field.
Geng, Yanan; Wu, Weida
2014-05-01
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
Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays
NASA Astrophysics Data System (ADS)
Lin, Yi-Chia; Kramer, Corinne M.; Chen, Christopher S.; Reich, Daniel H.
2012-02-01
In this paper, the use of magnetic nanowires for the study of cellular response to force is demonstrated. High-aspect ratio Ni rods with diameter 300 nm and lengths up to 20 ?m were bound to or internalized by pulmonary artery smooth muscle cells (SMCs) cultured on arrays of flexible micropost force sensors. Forces and torques were applied to the cells by driving the nanowires with AC magnetic fields in the frequency range 0.1-10 Hz, and the changes in cellular contractile forces were recorded with the microposts. These local stimulations yield global force reinforcement of the cells traction forces, but this contractile reinforcement can be effectively suppressed upon addition of a calcium channel blocker, ruthenium red, suggesting the role of calcium channels in the mechanical response. The responsiveness of the SMCs to actuation depends on the frequency of the applied stimulation. These results show that the combination of magnetic nanoparticles and micropatterned, flexible substrates can provide new approaches to the study of cellular mechanotransduction.
Low temperature behavior of magnetic domains observed using a magnetic force microscope
Chung, S. H.; Shinde, S. R.; Ogale, S. B.; Venkatesan, T.; Greene, R. L.; Dreyer, M.; Gomez, R. D.
2001-06-01
A commercial atomic force microscope/magnetic force microscope (MFM) was modified to cool magnetic samples down to around 100 K under a high vacuum while maintaining its routine imaging functionality. MFM images of a 120 nm thick La{sub 0.7}Ca{sub 0.3}MnO{sub 3} film on a LaAlO{sub 3} substrate at low temperature show the paramagnetic-to-ferromagnetic phase transition. Evolution of magnetic domains and magnetic ripples with decreasing temperature are also observed near the edge of a 20 nm thick patterned Co film on a Si substrate. {copyright} 2001 American Institute of Physics.
A basic inverse problem in the magnetic force microscopy of linear magnetic materials
NASA Astrophysics Data System (ADS)
Coffey, Mark W.
1997-10-01
A fundamental inversion problem for the magnetic force microscopy (MFM) of a semi-infinite linear magnetic material is formulated. Magnetostatic conditions are assumed so that a magnetic scalar potential can be employed. Using a point-dipole MFM tip, a unique layer-dependent magnetic permeability 0266-5611/13/5/008/img1 can be recovered from one-dimensional force measurements. The inversion procedure uses a wavenumber-dependent kernel function K(k). These results describe the use of MFM data to extract a material property as a function of depth.
Magnetic Force Calculation Between Thin Coaxial Circular Coils in Air
Slobodan I. Babic; Cevdet Akyel
2008-01-01
We present new and fast procedures for calculating magnetic forces between thin coaxial circular coaxial coils in air. The results are expressed in semianalytical form in terms of the complete elliptical integrals of the first and second kind, Heuman's Lambda function, and a term that must be solved numerically. These expressions are accurate and simple to use for several practical
Minimization of cogging force in a linear permanent magnet 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
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.
THE MEAN ELECTROMOTIVE FORCE RESULTING FROM MAGNETIC BUOYANCY INSTABILITY
Davies, C. R.; Hughes, D. W. E-mail: d.w.hughes@leeds.ac.uk
2011-02-01
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.
First-Order Reversal Curve (FORC) analysis of chondrule magnetism
NASA Astrophysics Data System (ADS)
Emmerton, S.; Muxworthy, A. R.
2009-12-01
We report a rock magnetic study of the magnetic properties of chondrules from the Allende and Mokoia carbonaceous chondritic meteorites. To characterise the magnetic carriers, we have made detailed magnetic hysteresis analysis including FORC measurements. We have also conducted isothermal acquisition unmixing analysis. We have determined the ancient magnetic field intensities (paleointensities) recorded by the two meteorites. As these chondrules are highly susceptible to chemical alteration on heating, we have employed two non-heating methods of determining the ancient field intensity: (1) the calibrated REM method and (2) the newly developed Preisach-based approach that determines absolute paleointensities. Allende has been extensively studied but this is the first paleointensity estimate for the Mokoia meteorite.
Direct Forced Evaporative Cooling in Permanent Magnetic Microtraps
Mohammadi, Amir; Pariz, Aref
2010-01-01
We propose two simple permanent magnetic micro-structures for creating single Ioffe-Pritchard magnetic microtraps. Direct forced evaporative cooling of neutral atoms without using spin flips can be implemented in these microstructures to attain Bose-Einstein condensation (BEC). A BEC critical temperature of $\\sim 10 \\mu$K is numerically obtained for $^{87}$Rb atoms in the atom chips. A bias magnetic field is used to vary the depth of the trap, frequencies and the minimum of the potential. Even without the external magnetic field, it is possible to hold ultracold atoms in the microtraps. Therefore, after achieving the BEC in the atom chips, the bias magnetic field can be slowly removed to increase the trap barrier heights for more efficiently holding the Bose-Einstein condensate.
Formation of Force-Free Magnetic Helix as Astrophysical Jets
NASA Astrophysics Data System (ADS)
Li, H.; Lovelace, R. V. E.; Colgate, S. A.
2000-10-01
Powerful narrow jets from many active galaxies might arise from twisting magnetic fields threading a differentially rotating accretion disk around a black hole. We model the formation of astrophysical jets by numerically solving the Grad-Shafranov equation with axisymmetry. An initial flux distribution is set up on a Keplerian disk, which is regarded as perfectly conducting and massive. We use the differential rotation of the disk as the input control parameter and calculate the current on each flux surface self-consistently. Since the greatest winding of the flux surfaces takes place at the smallest radius, we show that most of the magnetic energy is concentrated near the disk axis, resulting in the formation and strong collimation of force-free magnetic helix. Furthermore, we show that the increasing differential winding gives an axially growing magnetic tower. We discuss how these results might explain the distribution of magnetic fields in galaxy clusters. (Supported by the DOE.)
Magnetic Study of Paris Meteorite: a Partially Differentiated Parent Body?
NASA Astrophysics Data System (ADS)
Cournčde, C.; Gattacceca, J.; Rochette, P.; Zanda, B.
2011-12-01
The Paris meteorite is a unique carbonaceous CM chondrite find with almost no traces of terrestrial weathering [1]. Contrary to others CM chondrites, that contain abundant magnetite formed during aqueous alteration on their parent body, Paris is characterized by the coexistence of magnetite and abundant metallic Fe-Ni. We conducted a magnetic study (magnetic properties and paleomagnetism) of several oriented samples of this meteorite, with masses ranging from several mg up to 17 g. Preliminary rock magnetism results confirm that Paris has a magnetic mineralogy that is notably different from that of other CM chondrites, with a dominant FeNi metal, and minor magnetite. This corroborate that Paris suffered less aqueous alteration than other CM chondrites. Anisotropy of magnetic susceptibility shows that Paris is also one of the most anisotropic CM chondrite, and that it has a homogeneous fabric at least at the centimeter-scale. The comparison of the remanent magnetization obtained for metal-rich and magnetite-rich samples may have provided constraints on the magnetic fields present before and after accretion respectively. Unfortunately, paleomagnetic data show that the meteorite has been exposed to strong artificial magnetic field (magnet), precluding the study of the possible soft natural magnetization carried by FeNi. However, a high-coercivity magnetization is still preserved in the meteorite. It is homogeneous in direction and intensity at the scale of the meteorite. We interpret it as a pre-terrestrial component acquired on the parent body in a field on 3 ą 1 ?T (estimated with the method described in [2]). In view of its coercivity (up to 120 mT) we suppose that this magnetization is carried by fine-grained magnetite (although thermal and chemical demagnetization experiments are needed to confirm this hypothesis). In this case, because crystallization of magnetite likely occurred several Myr after the formation of the solar system [3], i.e. after the possible existence of strong solar and nebular magnetic fields, the paleofield had to be generated by the parent body. In view of its intensity, this paleofield may have been an internally generated field, pointing to a partially differentiated parent body with a convecting metallic core. Such process has recently been proposed for the parent body of CV chondrites [4, 5]. [1] Zanda et al., 2010. Meteoritics Planetary Sci., 45, 222-222. [2] Gattacceca and Rochette, 2004. EPSL, 227, 377-393 [3] Petitat and Gounelle, 2010. LPSC, abstract #1673. [4] Carporzen et al., 2011. Proc. National Acad. Sci., 108, 6386-6389. [5] Elkins-Tanton et al., 2011. Earth Planet . Sci. Lett., 305, 1-10.
Corroboration of magnetic forces in US Maglev design
Coffey, H.; He, J.; Wang, Z.
1993-01-01
Four System Concept Definition (SCD) contractors to the National Maglev Initiative (NMI) developed conceptual designs of maglev systems in 1991--1992. The objective of the work reported here was to perform independent calculations of the magnetic forces and fields of these four systems to assess the reasonableness'' of the results presented to the government. Commercial computer software was used for computing forces in the system employing nonlinear ferromagnetic materials and for some calculations of induced eddy current effects in finite-sized systems. Other cases required the use of models developed at ANL and verified by experiment, or in a few cases, new computer programs that have not been validated by experiment. The magnetic forces calculated by the contractors were found to be credible in every case evaluated. The stray fields were also found to be in reasonable agreement with those calculated by the contractors, but, for lack of spice, are not reported here.
Corroboration of magnetic forces in US Maglev design
Coffey, H.; He, J.; Wang, Z.
1993-06-01
Four System Concept Definition (SCD) contractors to the National Maglev Initiative (NMI) developed conceptual designs of maglev systems in 1991--1992. The objective of the work reported here was to perform independent calculations of the magnetic forces and fields of these four systems to assess the ``reasonableness`` of the results presented to the government. Commercial computer software was used for computing forces in the system employing nonlinear ferromagnetic materials and for some calculations of induced eddy current effects in finite-sized systems. Other cases required the use of models developed at ANL and verified by experiment, or in a few cases, new computer programs that have not been validated by experiment. The magnetic forces calculated by the contractors were found to be credible in every case evaluated. The stray fields were also found to be in reasonable agreement with those calculated by the contractors, but, for lack of spice, are not reported here.
Three-axis force actuator for a magnetic bearing
NASA Technical Reports Server (NTRS)
Gondhalekar, Vijay (Inventor)
1998-01-01
This invention features a three-axis force actuator that axially, radially and rotatably supports a bearing member for frictionless rotation about an axis of rotation generally coincident with a Z-axis. Also featured is a magnetic bearing having such an actuator. The actuator includes an inner member, a magnetic member and a pole assembly having a ring member and four pole extending therefrom. The poles are equi-angular spaced from each other and radially spaced about the Z-axis. The inner member extends along the Z-axis and is a highly magnetic permeable material. The magnetic member is formed about the inner member outer surface, extends along the Z-axis and is configured so one magnetic pole polarity is located at its outer surface and the other polarity pole is located at its inner surface. Preferably, the magnetic member is a radially magnetized permanent magnet. The inner surface of the ring member is magnetically coupled to the magnetic member and a face of each pole is coupled to the bearing member. The magnetic member, the pole assembly, the inner member and the bearing member cooperate to generate a magnetic field that radially and rotatably supports a rotating member secured to the bearing member. The actuator further includes a plurality of electromagnetic coils. Preferably, a coil is formed about each pole and at least 2 coils are formed about the inner member. When energized, the electromagnetic coils generate a modulated magnetic field that stabilizes the rotating member in the desired operational position.
On unsteady-motion theory of magnetic force for maglev systems.
Chen, S. S.; Zhu, S.; Cai, Y.; Energy Technology
1995-12-14
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.
Disentangling the magnetic force noise contribution in LISA Pathfinder
NASA Astrophysics Data System (ADS)
Armano, M.; Audley, H.; Auger, G.; Baird, J.; Binetruy, P.; Born, M.; Bortoluzzi, D.; Brandt, N.; Bursi, A.; Caleno, M.; Cavalleri, A.; Cesarini, A.; Cruise, M.; Danzmann, K.; Diepholz, I.; Dolesi, R.; Dunbar, N.; Ferraioli, L.; Ferroni, V.; Fitzsimons, E.; Freschi, M.; Gallegos, J.; García Marirrodriga, C.; Gerndt, R.; Gesa, L. I.; Gibert, F.; Giardini, D.; Giusteri, R.; Grimani, C.; Harrison, I.; Heinzel, G.; Hewitson, M.; Hollington, D.; Hueller, M.; Huesler, J.; Inchauspé, H.; Jennrich, O.; Jetzer, P.; Johlander, B.; Karnesis, N.; Kaune, B.; Korsakova, N.; Killow, C.; Lloro, I.; Maarschalkerweerd, R.; Madden, S.; Mance, D.; Martín, V.; Martin-Porqueras, F.; Mateos, I.; McNamara, P.; Mendes, J.; Mendes, L.; Moroni, A.; Nofrarias, M.; Paczkowski, S.; Perreur-Lloyd, M.; Petiteau, A.; Pivato, P.; Plagnol, E.; Prat, P.; Ragnit, U.; Ramos-Castro, J.; Reiche, J.; Romera Perez, J. A.; Robertson, D.; Rozemeijer, H.; Russano, G.; Sarra, P.; Schleicher, A.; Slutsky, J.; Sopuerta, C. F.; Sumner, T.; Texier, D.; Thorpe, J.; Trenkel, C.; Tu, H. B.; Vitale, S.; Wanner, G.; Ward, H.; Waschke, S.; Wass, P.; Wealthy, D.; Wen, S.; Weber, W.; Wittchen, A.; Zanoni, C.; Ziegler, T.; Zweifel, P.
2015-05-01
Magnetically-induced forces on the inertial masses on-board LISA Pathfinder are expected to be one of the dominant contributions to the mission noise budget, accounting for up to 40%. The origin of this disturbance is the coupling of the residual magnetization and susceptibility of the test masses with the environmental magnetic field. In order to fully understand this important part of the noise model, a set of coils and magnetometers are integrated as a part of the diagnostics subsystem. During operations a sequence of magnetic excitations will be applied to precisely determine the coupling of the magnetic environment to the test mass displacement using the on-board magnetometers. Since no direct measurement of the magnetic field in the test mass position will be available, an extrapolation of the magnetic measurements to the test mass position will be carried out as a part of the data analysis activities. In this paper we show the first results on the magnetic experiments during an end- to-end LISA Pathfinder simulation, and we describe the methods under development to map the magnetic field on-board.
Single Molecule Magnetic Force Detection with a Carbon Nanotube Resonator
NASA Astrophysics Data System (ADS)
Willick, Kyle; Walker, Sean; Baugh, Jonathan
2015-03-01
Single molecule magnets (SMMs) sit at the boundary between macroscopic magnetic behaviour and quantum phenomena. Detecting the magnetic moment of an individual SMM would allow exploration of this boundary, and could enable technological applications based on SMMs such as quantum information processing. Detection of these magnetic moments remains an experimental challenge, particularly at the time scales of relaxation and decoherence. We present a technique for sensitive magnetic force detection that should permit such measurements. A suspended carbon nanotube (CNT) mechanical resonator is combined with a magnetic field gradient generated by a ferromagnetic gate electrode, which couples the magnetic moment of a nanomagnet to the resonant motion of the CNT. Numerical calculations of the mechanical resonance show that resonant frequency shifts on the order of a few kHz arise due to single Bohr magneton changes in magnetic moment. A signal-to-noise analysis based on thermomechanical noise shows that magnetic switching at the level of a Bohr magneton can be measured in a single shot on timescales as short as 10 ?s. This sensitivity should enable studies of the spin dynamics of an isolated SMM, within the spin relaxation timescales for many available SMMs. Supported by NSERC.
Ball lightning as a force-free magnetic knot
Ranada; Soler; Trueba
2000-11-01
The stability of fireballs in a recent model of ball lightning is studied. It is shown that the balls shine while relaxing in an almost quiescent expansion, and that three effects contribute to their stability: (i) the formation in each one during a process of Taylor relaxation of a force-free magnetic field, a concept introduced in 1954 in order to explain the existence of large magnetic fields and currents in stable configurations of astrophysical plasmas; (ii) the so called Alfven conditions in magnetohydrodynamics; and (iii) the approximate conservation of the helicity integral. The force-free fields that appear are termed "knots" because their magnetic lines are closed and linked. PMID:11102074
The magnetic mirror force in plasma fluid models
NASA Technical Reports Server (NTRS)
Comfort, R. H.
1988-01-01
In the past decade, there have been several attempts to include the magnetic mirror force in the equation of motion for a plasma in a fluid formalism. In the process, some confusion has been evident regarding when and how this should be done. This problem has been addressed in the literature, but these treatments appear to have been forgotten or misunderstood. The mathematical arguments are summarized so that the physical consequences are readily perceived. It is shown that for an isotropic plasma fluid, in the direction parallel or anti-parallel to a magnetic field, the forces associated with a diverging magnetic field cancel out. Only for anisotropies in the fluid properties does the diverging field influence the plasma dynamics.
Consistent nucleon-nucleon potentials and three-body forces
NASA Astrophysics Data System (ADS)
Li, Z. H.; Lombardo, U.; Schulze, H.-J.; Zuo, W.
2008-03-01
We construct microscopic three-nucleon forces consistent with the Bonn and Nijmegen two-nucleon potentials, and including ?, Roper, and nucleon-antinucleon excitations. Recent results for the choice of the meson parameters are discussed. The forces are used in Brueckner calculations and the saturation properties of nuclear matter are determined.
Energy buildup in sheared force-free magnetic fields
NASA Technical Reports Server (NTRS)
Wolfson, Richard; Low, Boon C.
1992-01-01
Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.
Horizontal radial magnetic inversion for retrieving 3D geologic bodies
NASA Astrophysics Data System (ADS)
Oliveira, V. C., Jr.; Barbosa, V. C.
2013-05-01
We present a new 3D method for inverting magnetic data to retrieve the geometry of isolated geologic bodies whose uniform magnetization and depth to the top are prescribed by the interpreter. This method uses a 3D interpretation model consisting of a set of right prisms that are juxtaposed in the vertical direction of a right-handed coordinate system. Each prism has a horizontal cross-section defined by a polygon with a fixed number of vertices that are equally spaced from 0° to 360° and described by polar coordinates referred to an origin inside the polygon. Each prism has a uniform and known magnetization and thickness. Our inversion method estimates the radii associated with the vertices of the polygon and the horizontal coordinates of the origin of each prism. The estimated radii of the ensemble of prisms vertically stacked recover the 3D geologic source. Our method recovers stable and geologically meaningful solutions by using a wide variety of constraints that are designated by the interpreter with the aim of introducing information about the shape of the body. We applied our method to the noise-corrupted synthetic data (grey scale map in Fig. 1a) produced by the simulated body shown in Fig. 1b (black wire-frame body). The results confirmed the potential of our method to retrieve the shape and to infer the depth of the simulated source (black wire-frame body in Fig. 1b). The estimated source is shown in Fig. 1b (grey prisms) and produces the predicted data shown in Fig. 1a (dashed-white lines).; Fig. 1 - Application to synthetic data. (a) Noise-corrupted magnetic anomaly (grey scale map) and predicted data (dashed-white lines). (b) Simulated body (black wire-frame body) and estimated body (grey prisms).
Edge effects on forces and magnetic fields produced by a conductor moving past a magnet
Mulcahy, T.M.; Hull, J.R.; Almer, J.D. ); Rossing, T.D. )
1992-01-01
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.
Edge effects on forces and magnetic fields produced by a conductor moving past a magnet
Mulcahy, T.M.; Hull, J.R.; Almer, J.D.; Rossing, T.D.
1992-04-01
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.
Dilation of force-free magnetic flux tubes. [solar magnetic field profiles
NASA Technical Reports Server (NTRS)
Frankenthal, S.
1977-01-01
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.
On transition from Alfvén resonance to forced magnetic reconnection
Luan, Q.; Wang, X.
2014-07-15
We revisit the transition from Alfvén resonance to forced magnetic reconnection with a focus on the property of their singularities. As the driven frequency tends to zero, the logarithmic singularity of Alfvén resonance shifts to the power-law singularity of forced reconnection, due to merging of the two resonance layers. The transition criterion depends on either kinetic effects or dissipations that resolve the singularity. As an example, a small but finite resistivity ? is introduced to investigate the transition process. The transition threshold is then obtained as the driven frequency reaches a level of ?O((?/k){sup 1/3})
NASA Astrophysics Data System (ADS)
Yu, Jing-Jiang; Garno, Jayne
2012-02-01
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
NASA Technical Reports Server (NTRS)
Martin, E. Dale
1961-01-01
A study is made of the steady laminar flow of a compressible viscous fluid in a circular pipe when the fluid is accelerated by an axial body force. The application of the theory to the magnetofluidmechanics of an electrically conducting gas accelerated by electric and magnetic fields is discussed. Constant viscosity, thermal conductivity, and electrical conductivity are assumed. Fully developed flow velocity and temperature profiles are shown, and detailed results of the accelerating flow development, including velocity and pressure as functions of distance, are given for the case where the axial body force is constant and for the case where it is a linear function of velocity. From these results are determined the pipe entry length and the pressure difference required.
Analytical equation of state with three-body forces: Application to noble gases
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
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.
NASA Astrophysics Data System (ADS)
Li, Xiang; Li, Zhenghua; Pan, Deng; Yoshimura, Satoru; Saito, Hitoshi
2014-05-01
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.
Fisher, J. K.; Kleckner, N.
2014-01-01
Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging. PMID:24593368
NASA Astrophysics Data System (ADS)
Fisher, J. K.; Kleckner, N.
2014-02-01
Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.
Trapped scattering with three incident channels and the evaluation of the three-body forces
NASA Astrophysics Data System (ADS)
Bao, C. G.
2010-11-01
A design of trapped scattering is proposed and related theoretical calculation is performed to evaluate the weak three-body interactions among neutral atoms and molecules. Different from traditional experiments of scattering, the design has three incident channels; three-body collisions would occur in a trap repeatedly, and the number of collisions can be controlled. Hence, the effect of each collision can be accumulated and eventually enlarged. Therefore the design is particularly suitable for the cases with very weak interactions. Results of the calculation demonstrate that, once the two-body force of a species has been known, information on the three-body force can be thereby obtained.
Effect of guideway discontinuities on magnetic levitation and drag forces
Rossing, T.D.; Korte, R.; Hull, J.R. )
1991-11-15
Transients in the lift and drag forces on a NdFeB permanent magnet were observed as the magnet passed over various discontinuities in a rotating aluminum disk at velocities of 4 to 25 m/s. For full cuts in the disk, the amplitude of the lift and drag transients and the wave form of the drag transient depend on the width, and the amplitudes are much larger than for partial cuts. The use of a backing plate to join two cut segments is ineffective.
Distinguishing ferritin from apoferritin using magnetic force microscopy
NASA Astrophysics Data System (ADS)
Nocera, Tanya M.; Zeng, Yuzhi; Agarwal, Gunjan
2014-11-01
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.
Biomechanics of pressure ulcer in body tissues interacting with external forces during locomotion.
Mak, Arthur F T; Zhang, Ming; Tam, Eric W C
2010-08-15
Forces acting on the body via various external surfaces during locomotion are needed to support the body under gravity, control posture, and overcome inertia. Examples include the forces acting on the body via the seating surfaces during wheelchair propulsion, the forces acting on the plantar foot tissues via the insole during gait, and the forces acting on the residual-limb tissues via the prosthetic socket during various movement activities. Excessive exposure to unwarranted stresses at the body-support interfaces could lead to tissue breakdowns commonly known as pressure ulcers, often presented as deep-tissue injuries around bony prominences or as surface damage on the skin. In this article, we review the literature that describes how the involved tissues respond to epidermal loading, taking into account both experimental and computational findings from in vivo and in vitro studies. In particular, we discuss related literature about internal tissue deformation and stresses, microcirculatory responses, and histological, cellular, and molecular observations. PMID:20415590
Evolving nuclear many-body forces with the similarity renormalization group
Jurgenson, E. D.; Navratil, P.; Furnstahl, R. J. [Lawrence Livermore National Laboratory, P. O. Box 808, L-414, Livermore, California 94551 (United States); Lawrence Livermore National Laboratory, P. O. Box 808, L-414, Livermore, California 94551, USA and TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, V6T 2A3 (Canada); Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)
2011-03-15
In recent years, the Similarity Renormalization Group has provided a powerful and versatile means to soften interactions for ab initio nuclear calculations. The substantial contribution of both induced and initial three-body forces to the nuclear interaction has required the consistent evolution of free-space Hamiltonians in the three-particle space. We present the most recent progress on this work, extending the calculational capability to the p-shell nuclei and showing that the hierarchy of induced many-body forces is consistent with previous estimates. Calculations over a range of the flow parameter for {sup 6}Li, including fully evolved NN + 3N interactions, show moderate contributions due to induced four-body forces and display the same improved convergence properties as in lighter nuclei. A systematic analysis provides further evidence that the hierarchy of many-body forces is preserved.
Force analysis of magnetic bearings with power-saving controls
NASA Technical Reports Server (NTRS)
Johnson, Dexter; Brown, Gerald V.; Inman, Daniel J.
1992-01-01
Most magnetic bearing control schemes use a bias current with a superimposed control current to linearize the relationship between the control current and the force it delivers. For most operating conditions, the existence of the bias current requires more power than alternative methods that do not use conventional bias. Two such methods are examined which diminish or eliminate bias current. In the typical bias control scheme it is found that for a harmonic control force command into a voltage limited transconductance amplifier, the desired force output is obtained only up to certain combinations of force amplitude and frequency. Above these values, the force amplitude is reduced and a phase lag occurs. The power saving alternative control schemes typically exhibit such deficiencies at even lower command frequencies and amplitudes. To assess the severity of these effects, a time history analysis of the force output is performed for the bias method and the alternative methods. Results of the analysis show that the alternative approaches may be viable. The various control methods examined were mathematically modeled using nondimensionalized variables to facilitate comparison of the various methods.
A spaceship with a thruster - one body, one force
Dudley, S C; Dudley, Scott C.; Serna, Mario A.
2004-01-01
A spaceship with one thruster producing a constant magnitude force is analyzed for various initial conditions. This elementary problem, with one object acted upon by one force, has value as a challenge to one's physical intuition and in demonstrating the benefits and limitations of dimensional analysis. In addition, the problem can serve to introduce a student to special functions, provide a mechanical model for Fresnel integrals and the associated Cornu spiral, or be used as an example in a numerical methods course. The problem has some interesting and perhaps unexpected features.
A 4-Tesla superconducting whole-body magnet for MR imaging and spectroscopy
Vetter, J.; Ries, G.; Reichert, T.
1988-03-01
Since January 87 a 4 tesla MR magnet with a 1.25 m diameter warm bore is in operation at the Siemens Research Laboratories. The magnet weighing 10 tons is part of a whole-body MR device devoted to in-vivo research studies at magnetic fields significantly higher than 2 tesla; the highest field strength presently used in standard MR whole-body systems. The stored energy of the adiabatically stable six-coil system is 39 MJ at 4 tesla. The rated current is 376 A. Superconducting and resistive shim-coils together with iron shims reduce the bare magnet inhomogeneity of 100 ppm down to less than 5 ppm in a 50 cm diameter spherical volume. The magnet operates in persistent mode with the current leads retracted. The field drift is less than 3 x 10/sup -8//h. A small helium refrigerator is used to cool both the two radiation shields of the cryostat and the current leads and to reliquify the evaporating helium gas. Results of coil design, analysis of forces and stresses, quench protection, cryostat design and magnet operation are reported.
A magnetic force spring and its application in driver's seat suspension
Xiaomei Xu; Sihong Zhu
2010-01-01
To improve the ride comfort of the off-road vehicles a magnetic force spring was designed and its characteristic curves were researched. Based on the magnetic force spring and the conventional passive seat suspension a magnetic force seat suspension was constructed and its dynamic characteristics and the adjustability of its equivalent stiffness were experimentally studied. Research results show that the dynamic
Boundary force method for analyzing two-dimensional cracked bodies
NASA Technical Reports Server (NTRS)
Tan, P. W.; Raju, I. S.; Newman, J. C., Jr.
1986-01-01
The Boundary Force Method (BFM) was formulated for the two-dimensional stress analysis of complex crack configurations. In this method, only the boundaries of the region of interest are modeled. The boundaries are divided into a finite number of straight-line segments, and at the center of each segment, concentrated forces and a moment are applied. This set of unknown forces and moments is calculated to satisfy the prescribed boundary conditions of the problem. The elasticity solution for the stress distribution due to concentrated forces and a moment applied at an arbitrary point in a cracked infinite plate are used as the fundamental solution. Thus, the crack need not be modeled as part of the boundary. The formulation of the BFM is described and the accuracy of the method is established by analyzing several crack configurations for which accepted stress-intensity factor solutions are known. The crack configurations investigated include mode I and mixed mode (mode I and II) problems. The results obtained are, in general, within + or - 0.5 percent of accurate numerical solutions. The versatility of the method is demonstrated through the analysis of complex crack configurations for which limited or no solutions are known.
Unsteady Aerodynamic Forces on a Slender Body of Revolution in Supersonic Flow
NASA Technical Reports Server (NTRS)
Bond, Reuben; Packard, Barbara B.
1961-01-01
Linearized slender-body theory is applied to the computation of aerodynamic forces on an oscillating, or deforming, body in supersonic flow. The undeformed body is a body of revolution and the deformed body is represented by movement of a line through the centers of the cross sections which are assumed to remain circular. The time dependence is based on sinusoidal motion. For a body of vanishing thickness the slender-body theory yields the apparent mass approximation as it is obtained for incompressible crossflow around a cylinder. Both linearized slender-body theory and the apparent mass approximation are used to calculate the pitching-moment coefficients on a rigid slender body with a parabolic arc nose cone, and these coefficients are compared with some experimental results.
Duration of magnetic field(s) acting on meteorite parent body(s)
NASA Technical Reports Server (NTRS)
Rowe, M. W.
1974-01-01
An overview is presented on the efforts being made to estimate the time that the magnetic field(s) existed and acted on meteorite parent bodies. The basic premise is that if a sample exhibits a low K-Ar age, it is the requisite amount of Ar-40. This assumption is applied to a preliminary analysis of the Farmington chondrite.
Separation of each torque component on parts of electric machine using magnetic force density
Hong Soon Choi; Joon Ho Lee; Il Han Park
2005-01-01
For the mechanical structure design of electric machines, each force component on the parts of an electric machine need to be separated. In this paper, a separation scheme of each torque component is presented. It is based on the magnetic force density analysis of the general formulation of equivalent magnetic charge method and Lorentz force density. The force density analysis
Constraints of magnetic field which magnetized the Farmington meteorite parant body
NASA Technical Reports Server (NTRS)
Rowe, M. W.
1974-01-01
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.
a General Formula for Calculating Forces on a 2-D Arbitrary Body in Incompressible Flow
NASA Astrophysics Data System (ADS)
Pan, L. S.; Chew, Y. T.
2002-01-01
In the present paper, a general integral equation is presented to calculate the forces exerted on a two-dimensional (2-D) body of arbitrary shape immersed in unsteady, incompressible flows. By finding the general solutions of a set of Laplace equations with particular boundary conditions, the equation can be simplified to produce a simplified formula for calculating the forces. The simplified formula consists of three parts, representing contributions from different physical phenomena: added mass force and/or inertial force in inviscid flow, the force caused by the deformation of fluid and viscosity and the force caused by the convection of fluid with nonzero circulation. It can be applied to any 2-D arbitrary body in viscous or inviscid, steady or unsteady incompressible flow. As the formula excludes either temporal derivatives of velocity or spatial derivatives of vorticity in the flow field, the numerical errors contained in the numerical solution of velocity and vorticity fields will not be magnified, and therefore the resulting force calculated is more accurate. Most importantly, the formula presents an alternative method for obtaining the added mass of a 2-D body of arbitrary shape accelerating in a fluid. For bodies of simple shape, such as a circle, ellipse and plate, the added masses predicted using the present method are in agreement with that obtained by conventional methods. For bodies of complex shape, the present method only requires the calculation of the first two coefficients of the conformal transformation and cross-sectional area.
Forces on a magnet moving past figure-eight coils
Mulcahy, T.M.; He, J.; Rote, D.M. ); Rossing, T.D. . Dept. of Physics)
1993-11-01
Considerable attention has been given to the magnetic levitation of vehicles over guideways consisting of periodically-spaced conducting coils. Examples of proposed guideway configurations include arrays of independent coils (''loop track''), interconnected coils (''ladder track''), two layers of coils (double-layer ''null-flux'' track), and figure-eight coils (single-layer ''null-flux'' track). Typically, widely-separated superconducting magnets are mounted in the vehicle. A system that achieves both lift and guidance from vertical figure-eight coils in the guideway sidewalls has been developed in Japan. This system, when well designed, can have a very large lift-to-drag ratio. The authors conducted an experimental and theoretical investigation of the lift, drag, and guidance forces on a permanent magnet moving close to various arrays of figure-eight coils. The measured time-histories of the forces provide a basis for the evaluation of electrodynamic models and codes developed to analyze the magnetic levitation of vehicles using the discrete suspension coils of the null-flux type. Good correlation was found between the experimental data and the predictions of the code COIL GDWY. The authors report some of the results and discuss their application to the design of maglev systems.
Localized Spectroscopy using a Magnetic Resonance Force Microscope.
NASA Astrophysics Data System (ADS)
Moresi, Giorgio; Lin, Qiong; Mouaziz, Schahrazede; Hunkeler, Andreas; Degen, Christian; Meier, Urban; Brugger, Juerger; Meier, Beat
2006-03-01
The Magnetic Resonance Force Microscope (MRFM) constitutes a promising next-generation magnetic resonance detection device at room temperature. A MRFM observes nuclear (or electron) spin magnetization as a force, which occurs when a paramagnetic sample is polarized in inhomogeneous static magnetic field (10E5 T/m) and a high frequency drives the cantilever on-resonance by a cyclic adiabatic modulation, which make able to measure T1 rho. In this contribution, we combine the MRFM with spin-echo spectroscopy to add spectral resolution to NMR signals of micro-scale objects at room temperature. First experimental spectra recorded with the amplitude detection technique from a sample of barium chlorate monohydrate and ammonium sulfate single crystals mounted on a non commercial cantilever show resolution of 2?m and a sensitivity of 10E13 spins. The new microscope, which uses the frequency detection down to m-Hz resolution and the annealed non-commercials cantilevers, which have Q factor up to 250000 at room temperature, improve the sensitivity to 10E9 spins. This new setup and a new measurement technique should make able to measure T1.
Public Relations Body of Knowledge Task Force Report.
ERIC Educational Resources Information Center
PRSA Task Force
1988-01-01
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)
Force-free magnetic fields - Generating functions and footpoint displacements
NASA Technical Reports Server (NTRS)
Wolfson, Richard; Verma, Ritu
1991-01-01
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.
NMR Spectroscopy for Thin Films by Magnetic Resonance Force Microscopy
Won, Soonho; Saun, Seung-Bo; Lee, Soonchil; Lee, SangGap; Kim, Kiwoong; Han, Yunseok
2013-01-01
Nuclear magnetic resonance (NMR) is a fundamental research tool that is widely used in many fields. Despite its powerful applications, unfortunately the low sensitivity of conventional NMR makes it difficult to study thin film or nano-sized samples. In this work, we report the first NMR spectrum obtained from general thin films by using magnetic resonance force microscopy (MRFM). To minimize the amount of imaging information inevitably mixed into the signal when a gradient field is used, we adopted a large magnet with a flat end with a diameter of 336??m that generates a homogeneous field on the sample plane and a field gradient in a direction perpendicular to the plane. Cyclic adiabatic inversion was used in conjunction with periodic phase inversion of the frequency shift to maximize the SNR. In this way, we obtained the 19F NMR spectrum for a 34?nm-thick CaF2 thin film. PMID:24217000
Chen, Christopher S.
Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays.1088/0957-4484/23/7/075101 Probing cellular traction forces with magnetic nanowires and microfabricated force sensor arrays Yi. These local stimulations yield global force reinforcement of the cells' traction forces, but this contractile
Vadas, Sharon
hypothesized earlier that the zonal mean body force required to close the mesospheric jets is sporadic in time and Vincent, 1987; Tsuda et al., 1990; Holton, 1983; Roble and Ridley, 1994; Hamilton et al., 1995]. This drag force is sufficiently large to close the mesospheric jets and reverse the latitudinal gradient
Gravito-magnetism of an extended celestial body
NASA Astrophysics Data System (ADS)
Panhans, Michel; Soffel, Michael H.
2014-12-01
Einstein's general relativity predicts that the intrinsic rotation of an astronomical body leads to a general-relativistic contribution to its gravitational field. One of the consequences of general relativity is the so called Lense-Thirring effect, which has been a subject of many theoretical and experimental investigations during the last decades. In this article the model of a rigidly rotating, homogeneous, oblate spheroid will be analyzed with respect to its gravito-magnetic properties beyond the Lense-Thirring contribution to its gravitational field. As a consequence, a scalar, gravito-magnetic potential containing all the information about the spheroid's gravito-magnetic field will be derived. Based upon these results, general-relativistic effects like the gravito-magnetic gyroscope precession and the so called G-clock effect in the vicinity of the rotating spheroid will be treated with post-Newtonian accuracy.
Three-body forces and proton-rich nuclei.
Holt, J D; Menéndez, J; Schwenk, A
2013-01-11
We present the first study of three-nucleon (3N) forces for proton-rich nuclei along the N=8 and N=20 isotones. Our results for the ground-state energies and proton separation energies are in very good agreement with experiment where available, and with the empirical isobaric multiplet mass equation. We predict the spectra for all N=8 and N=20 isotones to the proton dripline, which agree well with experiment for 18Ne, 19Na, 20Mg and 42Ti. In all other cases, we provide first predictions based on nuclear forces. Our results are also very promising for studying isospin symmetry breaking in medium-mass nuclei based on chiral effective field theory. PMID:23383896
Three-Body Forces and Proton-Rich Nuclei
Holt, Jason D [ORNL; Menendez, J. [Technische Univ. Darmstadt/GSI Helmholtzzentrum fur Schweionenforschung, Germany; Schwenk, A. [GSI-Hemholtzzentrum fur Schwerionenforschung, Darmstadt, Germany
2013-01-01
We present the first study of three-nucleon (3N) forces for proton-rich nuclei along the N 8 and N 20 isotones. Our results for the ground-state energies and proton separation energies are in very good agreement with experiment where available, and with the empirical isobaric multiplet mass equation. We predict the spectra for all N 8 and N 20 isotones to the proton dripline, which agree well with experiment for 18Ne, 19Na, 20Mg and 42Ti. In all other cases, we provide first predictions based on nuclear forces. Our results are also very promising for studying isospin symmetry breaking in medium-mass nuclei based on chiral effective field theory.
Magnetic evidence for a partially differentiated carbonaceous chondrite parent body
Carporzen, Laurent; Weiss, Benjamin P.; Elkins-Tanton, Linda T.; Shuster, David L.; Ebel, Denton; Gattacceca, Jérôme
2011-01-01
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 Allendes magnetization was acquired over several million years (Ma) during metasomatism on the parent planetesimal in a > ? 20 ?T field up to approximately 910 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.
Nonlocal Properties of Dynamical Three-Body Casimir-Polder Forces
Rizzuto, L.; Passante, R.; Persico, F.
2007-06-15
We consider the three-body Casimir-Polder interaction between three atoms during their dynamical self-dressing. We show that the time-dependent three-body Casimir-Polder interaction energy displays nonlocal features related to quantum properties of the electromagnetic field and to the nonlocality of spatial field correlations. We discuss the measurability of this intriguing phenomenon and its relation with the usual concept of stationary three-body forces.
A magnetic force microscopy study of the magnetic reversal of a single Fe nanowire.
Wang, T; Wang, Y; Fu, Y; Hasegawa, T; Li, F S; Saito, H; Ishio, S
2009-03-11
The magnetization reversal properties of a single 60 nm diameter Fe nanowire were investigated with an in-field magnetic force microscope (MFM). MFM images were observed in a successively decreasing applied field, at various angles between the applied field and the nanowire axis. The results show that the magnetization undergoes a sharp reversal at various angles. When the applied field deviates from the nanowire axis, before complete magnetization reversal, a coherent rotation of magnetic moments inside the nanowire and a stable vortex state at the end of the nanowire are exhibited. The angle dependence of the switching field can be closely described by a curling model, despite the fact the magnetization reversal process is not identical to this model. PMID:19417535
Dynamic force-induced direct dissociation of protein complexes in a nuclear body in living cells.
Poh, Yeh-Chuin; Shevtsov, Sergey P; Chowdhury, Farhan; Wu, Douglas C; Na, Sungsoo; Dundr, Miroslav; Wang, Ning
2012-01-01
Despite past progress in understanding mechanisms of cellular mechanotransduction, it is unclear whether a local surface force can directly alter nuclear functions without intermediate biochemical cascades. Here we show that a local dynamic force via integrins results in direct displacements of coilin and SMN proteins in Cajal bodies and direct dissociation of coilin-SMN associated complexes. Spontaneous movements of coilin increase more than those of SMN in the same Cajal body after dynamic force application. Fluorescence resonance energy transfer changes of coilin-SMN depend on force magnitude, an intact F-actin, cytoskeletal tension, Lamin A/C, or substrate rigidity. Other protein pairs in Cajal bodies exhibit different magnitudes of fluorescence resonance energy transfer. Dynamic cyclic force induces tiny phase lags between various protein pairs in Cajal bodies, suggesting viscoelastic interactions between them. These findings demonstrate that dynamic force-induced direct structural changes of protein complexes in Cajal bodies may represent a unique mechanism of mechanotransduction that impacts on nuclear functions involved in gene expression. PMID:22643893
Calculation of Magnetic Helicity in a Force-Free Field
NASA Astrophysics Data System (ADS)
Updike, A. C.; Pevtsov, A.
2002-12-01
One of the goals of solar physics is to understand the solar dynamo. By studying the nature of magnetic helicity, we are studying the solar magnetic field driven by the dynamo. We used chromospheric magnetographs in the Ca II line (8543 Ĺ) and EIT images in the Fe XII line (195 Ĺ) to determine the degree of twist in the magnetic field. Using this degree of twist and the known magnetic energy for a given active region, we were able to measure the magnetic helicity in this force-free region. Over a period of three years (August 1996 to November 1998), we studied 37 active regions. We found a 73% hemispheric preference in the sign of the helicity - in the northern hemisphere, 70% of the active regions exhibited negative helicity; in the southern hemisphere, 76.5% of the active regions exhibited positive helicity. Our observations agree with earlier studies of the sign of helicity, which used vector magnetograms and studies of quiescent filiments.
Studies of coercive force of permanent magnet materials
NASA Astrophysics Data System (ADS)
Wallace, W. E.
1984-01-01
Permanent magnets were prepared by sintering on-stoichiometry Sm2Co17 and Sm2Co17 doped Fe,Mn,Zr and Hf. Coercive forces subscript i H subscript C were low, less than 1 kOe. Although doping increases anisotropy field, it does not enhance subscript i H subscript C except for Mn as dopant. In this case, doping increases subscript i H subscript C about two-fold. In these systems subscript i H subscript C seems to be nucleation-controlled. It is postulated that nucleation occurs at the oxidized surface where anisotropy is weak or negative. Surfaces were investigated by Auger spectroscopy with results consistent with the postulated mechanism. To test for effects of surface roughness, powders were washed with acid. No increase in subscript i H subscript C was observed. Samples ground under pentane and liquid nitrogen showed no significant difference in subscript i H subscript C. Oxygen content was about 3000 ppm by weight in the finished magnets. Results suggest that coercive force of the so-called 2-17 magnets (which are actually 2-phase mixtures of components with 1:5 and 2:17 stoichiometry, originates with the component having 1:5 stoichiometry.
Voigt, A; Christ, S; Klein, M
2008-07-01
The aim of this study was to determine which combination of differently designed magnetic abutments provides the best retention for an auricular prosthesis. The withdrawal forces of eight combinations of abutments were measured and results compared. There was a significantly higher withdrawal force in arrangements containing three magnets over only two. The highest withdrawal force was found in the combination of one telescopic magnet and two large spherical magnets (median: 7.69 N), whereas two telescopic magnets alone showed the lowest withdrawal force (3.41 N). The use of two conical magnets increased retention slightly, but the median retention force remained the same (3.41 N). The commonly used combination of two small spherical magnets and one telescopic magnet showed the lowest retention of combinations consisting of three magnets (4.94 N). There seems to be no difference in median withdrawal force if a conical magnet instead of a telescopic magnet is used. The withdrawal force at a 45 degrees angle was about 10% higher than the vertical force but the difference was not significant. The rupture force needed to tear the magnet completely out of the silicone was 240.6-519.7 N (mean 331.74 N) and therefore over 10 times higher than magnetic retention. PMID:18440779
S. Q. Yang; D. E. Baynham; P.. Fabricatore; S.. Farinon; M. A. Green; Y.. Ivanyushenkov; W. W. Lau; S. M. Maldavi; S. P. Virostek; H.. Witte
2007-01-01
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
Clock field in arrayed magnetic logic gates with a magnetic force microscope tip
NASA Astrophysics Data System (ADS)
Nomura, H.; Imanaga, Y.; Hiratsuka, Y.; Nakatani, R.
2012-08-01
A magnetic logic gate (MLG), which is based on magnetic quantum dot cellular automata (MQCA), is capable of NAND/NOR logic operations. By arranging MLGs in a two-dimensional periodic array, a highly functional circuit can be created. However, NAND/NOR gates are difficult to form into a two-dimensional periodic arrangement. Here, we propose NOT/AND/ORs gate based on MLGs, which can be arranged in a two-dimensional periodic array. To demonstrate logic operations, we performed numerical simulations based on the macro-spin model. To execute logic operation in the arrayed structure, we used the stray field from a magnetic force microscope tip.
Resonantly Detecting Axion-Mediated Forces with Nuclear Magnetic Resonance
NASA Astrophysics Data System (ADS)
Arvanitaki, Asimina; Geraci, Andrew A.
2014-10-01
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.
Gravity and magnetic modeling of granitic bodies in Central Portugal
NASA Astrophysics Data System (ADS)
Machadinho, Ana; Figueiredo, Fernando; Pereira, Alcides
2015-04-01
A better understanding of the subsurface geometry of the granitic bodies in Central Portugal is the main goal of this work. The results are also relevant for the assessment of the geothermal potential of the same region. The study area is located in the Central Iberian Zone where the Beiras granite batholith outcrops. These variscan granitoids were emplaced into the "Complexo Xisto-Grauváquico" (CXG), a thick and monotonous megasequences of metapelites and metagreywackes. This metasedimentary sequence is affected by the Variscan deformation phases and a late Proterozoic to Cambrian age has been generally assumed for this rocks. The granitoids in the region are attributed to the magmatic activity associated to the post-collisional stages of the Variscan orogeny during the D3 stage. The granitic bodies in the study area are considered syn-D3 and late to post-D3. To achieve the goal of the research, magnetic and gravimetric surveys where performed in order to obtain the Bouguer and magnetic anomalies. All the standard corrections were applied to the gravimetric and magnetic data. Considering and integrating all the available geological data and physical proprieties (density and magnetic susceptibility) the mentioned potential fields were simultaneously modeled. In this way it was possible to characterize the subsurface geometry of the granitic bodies in the studied region. The modeling results show that the regional tectonic setting controls the geometry of the granitic bodies as well as the structure of the host CXG metasedimentary sequence. Through the modeling of the potential field the overall geometry, average and maximum depths of the granitic bodies in the study area was obtained. Some late to post-D3 plutons outcrop in spatial continuity and as they have similar ages, a common feeding zone is assumed as the most likely scenario. The sin-D3 pluton is more abrupt and vertical, suggesting the presence of a fault contact with the late-D3 pluton. According to the developed study the areas with higher geothermal potential for EGS applications are located over the sectors where the granitic bodies have the greater thickness.
Many-body forces and stability of the alkaline-earth tetramers
NASA Astrophysics Data System (ADS)
Díaz-Torrejón, C. C.; Kaplan, Ilya G.
2011-03-01
The comparative study of the interaction energy and its many-body decomposition for Be 4, Mg 4, and Ca 4 at the all-electron CCSD(T)/aug-cc-pVQZ level is performed. For study of dependence of the binding energy and the orbital population on the cluster size the corresponding dimers and trimers were also calculated at the same level of theory. In comparison with weakly bound dimers, the binding energy in trimers and, especially, in tetramers drastically increases; e.g., E b/ N in Be 3 is 7 times larger and in Be 4 is 18.4 times larger than in Be 2. This sharp increase is explained as a manifestation of many-body forces. As follows from the many-body decomposition, the tetramers, and trimers as well, are stabilized by the three-body forces, whereas the two- and four-body forces are repulsive. The attractive contribution to the three-body forces has a three-atom electron exchange origin. The latter benefits the promotion of ns-electrons to np-orbitals. The natural bond orbital (NBO) population analysis reveals a relatively large np-population in trimers and tetramers (in Be 4 it is equal to 2p 0.44). The population of the valence np-orbitals leads to the sp-hybridization providing the covalent bonding.
Self-forces on extended bodies in electrodynamics
Abraham I. Harte
2006-01-20
In this paper, we study the bulk motion of a classical extended charge in flat spacetime. A formalism developed by W. G. Dixon is used to determine how the details of such a particle's internal structure influence its equations of motion. We place essentially no restrictions (other than boundedness) on the shape of the charge, and allow for inhomogeneity, internal currents, elasticity, and spin. Even if the angular momentum remains small, many such systems are found to be affected by large self-interaction effects beyond the standard Lorentz-Dirac force. These are particularly significant if the particle's charge density fails to be much greater than its 3-current density (or vice versa) in the center-of-mass frame. Additional terms also arise in the equations of motion if the dipole moment is too large, and when the `center-of-electromagnetic mass' is far from the `center-of-bare mass' (roughly speaking). These conditions are often quite restrictive. General equations of motion were also derived under the assumption that the particle can only interact with the radiative component of its self-field. These are much simpler than the equations derived using the full retarded self-field; as are the conditions required to recover the Lorentz-Dirac equation.
Lower body predictors of glenohumeral compressive force in high school baseball pitchers.
Keeley, David W; Oliver, Gretchen D; Dougherty, Christopher P; Torry, Michael R
2015-06-01
The purpose of this study was to better understand how lower body kinematics relate to peak glenohumeral compressive force and develop a regression model accounting for variability in peak glenohumeral compressive force. Data were collected for 34 pitchers. Average peak glenohumeral compressive force was 1.72% ą 33% body weight (1334.9 N ą 257.5). Correlation coefficients revealed 5 kinematic variables correlated to peak glenohumeral compressive force (P < .01, ? = .025). Regression models indicated 78.5% of the variance in peak glenohumeral compressive force (R2 = .785, P < .01) was explained by stride length, lateral pelvis flexion at maximum external rotation, and axial pelvis rotation velocity at release. These results indicate peak glenohumeral compressive force increases with a combination of decreased stride length, increased pelvic tilt at maximum external rotation toward the throwing arm side, and increased pelvis axial rotation velocity at release. Thus, it may be possible to decrease peak glenohumeral compressive force by optimizing the movements of the lower body while pitching. Focus should be on both training and conditioning the lower extremity in an effort to increase stride length, increase pelvis tilt toward the glove hand side at maximum external rotation, and decrease pelvis axial rotation at release. PMID:25734579
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
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.
The influence of gravitational body force in meteoritic chondrule and lunar glass formation
NASA Technical Reports Server (NTRS)
Budka, P. Z.
1984-01-01
The effects of gravitational body force must be considered in the formation of extraterrestrial materials such as meteoritic chondrules and lunar glasses. Solidification experiments conducted in microgravity as well as g values greater than Earth's gravitational force have demonstrated that gravitational force can have profound and sometimes unexpected effects upon the way materials solidify and, therefore, upon their physical and mechanical properties. Solutal, thermal and sedimentation effects differ from those experienced on Earth. Because buoyancy forces are reduced, materials of different densities may remain in close proximity. The spherical morphology of chondrules and many lunar glasses may reflect the tendency for free floating liquids to form spherical droplets in a microgravity environment, a form which minimizes surface energy. Under these conditions, surface energy forces dominate gravity forces. The formation of two common chondrule textures, barred and radiating chondrules, can be explained using observations from glass science.
Leu, Tzong-Shyng "Jeremy"
, this side force may be as large as the normal force acting on the slender body. In this paper, experimental- ferent roll angles of a cone-cylinder slender body. Aerodynamic force measurement results indicate of the incidence plane toward weak vortex side direction). Significant changes are noticed from the surface
The effect of power law body forces on a thermally-driven flow between concentric rotating spheres
NASA Technical Reports Server (NTRS)
Macaraeg, M. G.
1985-01-01
A numerical study is conducted to determine the effect of power-law body forces on a thermally-driven axisymmetric flow field confined between concentric co-rotating spheres. This study is motivated by Spacelab geophysical fluid-flow experiments, which use an electrostatic force on a dielectric fluid to simulate gravity; this force exhibits a (1/r)sup 5 distribution. Meridional velocity is found to increase when the electrostatic body force is imposed, relative to when the body force is uniform. Correlation among flow fields with uniform, inverse-square, and inverse-quintic force fields is obtained using a modified Grashof number.
The effect of power-law body forces on a thermally driven flow between concentric rotating spheres
NASA Technical Reports Server (NTRS)
Macaraeg, M. G.
1986-01-01
A numerical study is conducted to determine the effect of power-law body forces on a thermally-driven axisymmetric flow field confined between concentric co-rotating spheres. This study is motivated by Spacelab geophysical fluid-flow experiments, which use an electrostatic force on a dielectric fluid to simulate gravity; this force exhibits a (1/r)sup 5 distribution. Meridional velocity is found to increase when the electrostatic body force is imposed, relative to when the body force is uniform. Correlation among flow fields with uniform, inverse-square, and inverse-quintic force fields is obtained using a modified Grashof number.
G. H. Jang; N. K. Park; C. I. Lee; J. H. Chang; S. W. Jeong; D. H. Kang
2008-01-01
This paper investigates the characteristics of the magnetic force and the torque in the conventional rotatory two-phase transverse flux machine (TFM) by using the three-dimensional finite element method. This research shows that the unbalanced magnetic force is one of the dominant excitation forces in this machine, and it proposes a TFM with symmetric multipair cores in which each stator core
How Can Magnetic Forces Do Work? Investigating the Problem with Students
ERIC Educational Resources Information Center
Onorato, Pasquale; De Ambrosis, Anna
2013-01-01
We present a sequence of activities aimed at promoting both learning about magnetic forces and students' reflection about the conceptual bridge between magnetic forces on a moving charge and on a current-carrying wire in a magnetic field. The activity sequence, designed for students in high school or on introductory physics courses, has been
Radiation-Reaction Force on a Small Charged Body to Second Order
NASA Astrophysics Data System (ADS)
Moxon, Jordan; Flanagan, Eanna
2015-04-01
In classical electrodynamics, an accelerating charge emits radiation and experiences a corresponding radiation reaction force, or self force. We extend to greater precision (higher order in perturbation theory) a previous rigorous derivation of the electromagnetic self force in flat spacetime by Gralla, Harte, and Wald. The method introduced by Gralla, Harte, and Wald computes the self-force from the Maxwell field equations and conservation of stress-energy, and does not require regularization of a singular point charge, as has been necessary in prior computations. For our higher order compuation, it becomes necessary to adopt an adjusted definition of the mass of the body to avoid including self-energy from the electromagnetic field sourced during the history of the body. We derive the evolution equations for the mass, spin, and center of mass position of an extended body through second order using our adjusted formalism. The final equations give an acceleration dependent evolution of the spin (self-torque), as well as a mixing between the extended body effects and the acceleration dependent effects on the overall body motion.
Single Protein Molecule Mapping with Magnetic Atomic Force Microscopy
Moskalenko, Andriy V.; Yarova, Polina L.; Gordeev, Sergey N.; Smirnov, Sergey V.
2010-01-01
Abstract Understanding the structural organization and distribution of proteins in biological cells is of fundamental importance in biomedical research. The use of conventional fluorescent microscopy for this purpose is limited due to its relatively low spatial resolution compared to the size of a single protein molecule. Atomic force microscopy (AFM), on the other hand, allows one to achieve single-protein resolution by scanning the cell surface using a specialized ligand-coated AFM tip. However, because this method relies on short-range interactions, it is limited to the detection of binding sites that are directly accessible to the AFM tip. We developed a method based on magnetic (long-range) interactions and applied it to investigate the structural organization and distribution of endothelin receptors on the surface of smooth muscle cells. Endothelin receptors were labeled with 50-nm superparamagnetic microbeads and then imaged with magnetic AFM. Considering its high spatial resolution and ability to see magnetically labeled proteins at a distance of up to 150 nm, this approach may become an important tool for investigating the dynamics of individual proteins both on the cell membrane and in the submembrane space. PMID:20141762
Magnetic Force Microscopy of Superparamagnetic Nanoparticles for Biomedical Applications
NASA Astrophysics Data System (ADS)
Nocera, Tanya M.
In recent years, both synthetic as well as naturally occurring superparamagnetic nanoparticles (SPNs) have become increasingly important in biomedicine. For instance, iron deposits in many pathological tissues are known to contain an accumulation of the superparamagnetic protein, ferritin. Additionally, man-made SPNs have found biomedical applications ranging from cell-tagging in vitro to contrast agents for in vivo diagnostic imaging. Despite the widespread use and occurrence of SPNs, detection and characterization of their magnetic properties, especially at the single-particle level and/or in biological samples, remains a challenge. Magnetic signals arising from SPNs can be complicated by factors such as spatial distribution, magnetic anisotropy, particle aggregation and magnetic dipolar interaction, thereby confounding their analysis. Techniques that can detect SPNs at the single particle level are therefore highly desirable. The goal of this thesis was to develop an analytical microscopy technique, namely magnetic force microscopy (MFM), to detect and spatially localize synthetic and natural SPNs for biomedical applications. We aimed to (1) increase MFM sensitivity to detect SPNs at the single-particle level and (2) quantify and spatially localize iron-ligated proteins (ferritin) in vitro and in biological samples using MFM. Two approaches were employed to improve MFM sensitivity. First, we showed how exploitation of magnetic anisotropy could produce a higher, more uniform MFM signal from single SPNs. Second, we showed how an increase in probe magnetic moment increased both the magnitude and range up to which the MFM signal could be detected from a single SPN. We further showed how MFM could enable accurate quantitative estimation of ferritin content in ferritin-apoferritin mixtures. Finally, we demonstrated how MFM could be used to detect iron/ferritin in serum and animal tissue with spatial resolution and sensitivity surpassing that obtained using conventional biochemical assays. We envisage these advancements will allow MFM to serve as a novel biosensing technique to spatially localize iron/ferritin in small aliquots of clinical samples (i.e. serum) and in tissue biopsies at the ultra-sensitive and ultra-structural level. We also discuss how future work incorporating our advancements could lead to the development of a novel indirect MFM technique, which could enable high-throughput analysis of SPNs for biomedical applications.
Couple compensation of magnetic forces of transverse flux linear induction motor
Kwang Suk Jung
2005-01-01
The magnetic force across the air-gap between primary and secondary in linear induction motor is for the most part constrained by bearing or linear guide. But, the existence of normal or levitation force gives us a possibility to drive the linear motor stably without the bearing. However, as the normal force depends inevitably and strongly on the thrust force, it
The software for the calculations of force-free magnetic fields in solar active regions
Jian Chen; Yuanzhang Lin; Xiaolei Wei
1989-01-01
A set of software for the numerical calculations of constant force-free magnetic fields in solar active regions is given. Chiu-Hilton's representation is taken as the resolution of equations for a force-free field.
Three-Body Forces Produced by a Similarity Renormalization Group Transformation in a Simple Model
Bogner, S K; Perry, R J
2007-01-01
A simple class of unitary renormalization group transformations that force hamiltonians towards a band-diagonal form produce few-body interactions in which low- and high-energy states are decoupled, which can greatly simplify many-body calculations. One such transformation has been applied to phenomenological and effective field theory nucleon-nucleon interactions with success, but further progress requires consistent treatment of at least the three-nucleon interaction. In this paper we demonstrate in an extremely simple model how these renormalization group transformations consistently evolve two- and three-body interactions towards band-diagonal form, and introduce a diagrammatic approach that generalizes to the realistic nuclear problem.
Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)
1991-01-01
The present invention identifies several configurations of conducting elements capable of 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, M.L.; Mueller, F.M.; Smith, J.L.
1991-04-09
The present invention identifies several configurations of conducting elements capable of storing extremely high magnetic fields for the purpose of energy storage or for other uses, wherein forces experienced by the conducting elements and the magnetic field pollution produced at locations away from the configuration are both significantly reduced over those which are present as a result of the generation of such high fields by currently proposed techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency. 15 figures.
Wing and body motion and aerodynamic and leg forces during take-off in droneflies.
Chen, Mao Wei; Zhang, Yan Lai; Sun, Mao
2013-12-01
Here, we present a detailed analysis of the take-off mechanics in droneflies performing voluntary take-offs. Wing and body kinematics of the insects during take-off were measured using high-speed video techniques. Based on the measured data, the inertia force acting on the insect was computed and the aerodynamic force of the wings was calculated by the method of computational fluid dynamics. Subtracting the aerodynamic force and the weight from the inertia force gave the leg force. In take-off, a dronefly increases its stroke amplitude gradually in the first 10-14 wingbeats and becomes airborne at about the 12th wingbeat. The aerodynamic force increases monotonously from zero to a value a little larger than its weight, and the leg force decreases monotonously from a value equal to its weight to zero, showing that the droneflies do not jump and only use aerodynamic force of flapping wings to lift themselves into the air. Compared with take-offs in insects in previous studies, in which a very large force (5-10 times of the weight) generated either by jumping legs (locusts, milkweed bugs and fruit flies) or by the 'fling' mechanism of the wing pair (butterflies) is used in a short time, the take-off in the droneflies is relatively slow but smoother. PMID:24132205
A microscopic approach to Casimir and Casimir-Polder forces between metallic bodies
Pablo Barcellona; Roberto Passante
2015-03-09
We consider the Casimir-Polder interaction energy between a metallic nanoparticle and a metallic plate, as well as the Casimir interaction energy between two macroscopic metal plates, in terms of the many-body dispersion interactions between their constituents. Expressions for two- and three-body dispersion interactions between the microscopic parts of a real metal are first obtained, both in the retarded and non-retarded limits. These expressions are then used to evaluate, a compare each other, the overall two- and three-body contributions to the macroscopic Casimir-Polder and Casimir force, by summing up the contributions from the microscopic constituents of the bodies (metal nanoparticles), for two geometries: metal nanoparticle/half-space and half-space/half-space, where all the materials are assumed perfect conductors. In the case of nanoparticle/half-space, our results fully agree with those that can be extracted from the corresponding macroscopic results, and explicitly show the non-applicability of the pairwise approximation for the geometry considered. In both cases, we find that, while the overall two-body contribution yields an attractive force, the overall three-body contribution is repulsive. Also, they turn out to be of the same order, consistently with the known nonapplicability of the pairwise approximation. The issue of the rapidity of convergence of the many-body expansion is also briefly discussed.
A microscopic approach to Casimir and Casimir-Polder forces between metallic bodies
NASA Astrophysics Data System (ADS)
Barcellona, Pablo; Passante, Roberto
2015-04-01
We consider the Casimir-Polder interaction energy between a metallic nanoparticle and a metallic plate, as well as the Casimir interaction energy between two macroscopic metal plates, in terms of the many-body dispersion interactions between their constituents. Expressions for two- and three-body dispersion interactions between the microscopic parts of a real metal are first obtained, both in the retarded and non-retarded limits. These expressions are then used to evaluate the overall two- and three-body contributions to the macroscopic Casimir-Polder and Casimir force, and to compare them with each other, for the two following geometries: metal nanoparticle/half-space and half-space/half-space, where all the materials are assumed perfect conductors. The above evaluation is obtained by summing up the contributions from the microscopic constituents of the bodies (metal nanoparticles). In the case of nanoparticle/half-space, our results fully agree with those that can be extracted from the corresponding macroscopic results, and explicitly show the non-applicability of the pairwise approximation for the geometry considered. In both cases, we find that, while the overall two-body contribution yields an attractive force, the overall three-body contribution is repulsive. Also, they turn out to be of the same order, consistently with the known non applicability of the pairwise approximation. The issue of the rapidity of convergence of the many-body expansion is also briefly discussed.
Identification of human-generated forces on wheelchairs during total-body extensor thrusts
Singhose, William
Identification of human-generated forces on wheelchairs during total-body extensor thrusts Seong extensor thrust experienced by wheelchair users with neurological disorders may cause injuries via impact during unconstrained extensor thrust events is of great importance in developing more comfortable
Levitation force on a permanent magnet over a superconducting plane: Modified critical-state model
Yang, Z.J.
1997-08-01
The authors consider a model system of a permanent magnet above a semi-infinite superconductor. They introduce a modified critical-state model, and carry out derivations of the levitation force acting on the magnet. A key feature of the modification allows the current density to be less than the critical value. The theoretical results show an exponential relationship between the force and the distance. Analytical expressions are developed for permanent magnets in the form of a point dipole, a tip of a magnetic force microscope, and a cylindrical magnet. In the latter case, the exponential relationship has been observed in numerous experiments but without previous interpretation.
Effect of three-body forces on response functions in infinite neutron matter
D. Davesne; J. W. Holt; A. Pastore; J. Navarro
2014-11-12
We study the impact of three-body forces on the response functions of cold neutron matter. These response functions are determined in the random phase approximation (RPA) from a residual interaction expressed in terms of Landau parameters. Special attention is paid to the non-central part, including all terms allowed by the relevant symmetries. Using Landau parameters derived from realistic nuclear two- and three-body forces grounded in chiral effective field theory, we find that the three-body term has a strong impact on the excited states of the system and in the static and long-wavelength limit of the response functions for which a new exact formula is established.
Effect of three-body forces on response functions in infinite neutron matter
Davesne, D; Pastore, A; Navarro, J
2014-01-01
We study the impact of three-body forces on the response functions of cold neutron matter. These response functions are determined in the random phase approximation (RPA) from a residual interaction expressed in terms of Landau parameters. Special attention is paid to the non-central part, including all terms allowed by the relevant symmetries. Using Landau parameters derived from realistic nuclear two- and three-body forces grounded in chiral effective field theory, we find that the three-body term has a strong impact on the excited states of the system and in the static and long-wavelength limit of the response functions for which a new exact formula is established.
NASA Astrophysics Data System (ADS)
Bomont, J. M.; Bretonnet, J. L.
2002-06-01
Recently, we proposed a new self-consistent integral equation to obtain the pair correlation function of simple fluids in the case of pairwise additive forces [J. Chem. Phys. 114, 4141 (2001)]. Here this integral equation is applied to predict the structural and thermodynamic properties of xenon at supercritical temperatures and low densities, with the aim of examining the possible effect of the three-body dispersion forces. The validity of our extended integral equation is tested against molecular dynamics, and the results are compared to recent small-angle neutron scattering measurements [Formisano et al. Phys. Rev. E 58, 2648 (1998)] and thermodynamic properties. The good agreement found between semianalytic calculations and simulation or experimental results of the structural and thermodynamic properties gives clear indication of the efficiency of the use of our integral equation conjugated with an effective pair potential consisting of the Aziz-Slaman two-body potential plus the Axilrod-Teller three-body potential.
Wing/body kinematics measurement and force and moment analyses of the takeoff flight of fruitflies
NASA Astrophysics Data System (ADS)
Chen, Mao-Wei; Sun, Mao
2014-08-01
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).
Three-body recombination for electrons in a strong magnetic field: Magnetic moment
Robicheaux, F. [Department of Physics, Auburn University, Auburn, Alabama 36849-5311 (United States)
2006-03-15
Using a classical Monte Carlo method, we have computed the three-body recombination (two free electrons and a proton scattering into one free electron and a hydrogen atom, e+e+p{yields}H+e) in strong magnetic fields. The proton is fixed in space but the electrons are allowed their full, three-dimensional motion. We investigate recombination for temperatures and fields similar to those used in recent experiments that generated antihydrogen. The present rate is compared to that when the electrons' motion is given by the guiding center approximation, validating previous results at low temperature and demonstrating the breakdown of this approximation at higher temperature. Unlike the B=0 case, strong B gives preferential recombination to atoms with positive magnetic moment. Also, the canonical angular momentum in the field direction is often negative even when the magnetic moment is negative. Both results affect the trapping of antihydrogen using spatially dependent magnetic fields.
Kumar, Dinesh; Bhattacharyya, R. [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India)] [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)] [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)
2013-11-15
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.
NASA Astrophysics Data System (ADS)
Kiselev, N. S.; Dragunov, I. E.; Neu, V.; Rößler, U. K.; Bogdanov, A. N.
2008-02-01
Recently synthesized magnetic multilayers with strong perpendicular anisotropy exhibit unique magnetic properties including the formation of specific multidomain states. In particular, antiferromagnetically coupled multilayers own rich phase diagrams that include various multidomain ground states. Analytical equations have been derived for the stray field components of these multidomain states in perpendicular multilayer systems. In particular, closed expressions for stray fields in the case of ferromagnetic and antiferromagnetic stripes are presented. The theoretical approach provides a basis for the analysis of magnetic force microscopy (MFM) images from this class of nanomagnetic systems. Peculiarities of the MFM contrast have been calculated for realistic tip models. These characteristic features in the MFM signals can be employed for the investigations of the different multidomain modes. The obtained results are applied for the analysis of multidomain modes that have been reported earlier in the literature from experiments on [Co/Cr]Ru superlattices.
Revealing bending and force in a soft body through a plant root inspired approach
Lucarotti, Chiara; Totaro, Massimo; Sadeghi, Ali; Mazzolai, Barbara; Beccai, Lucia
2015-01-01
An emerging challenge in soft robotics research is to reveal mechanical solicitations in a soft body. Nature provides amazing clues to develop unconventional components that are capable of compliant interactions with the environment and living beings, avoiding mechanical and algorithmic complexity of robotic design. We inspire from plant-root mechanoperception and develop a strategy able to reveal bending and applied force in a soft body with only two sensing elements of the same kind, and a null computational effort. The stretching processes that lead to opposite tissue deformations on the two sides of the root wall are emulated with two tactile sensing elements, made of soft and stretchable materials, which conform to reversible changes in the shape of the body they are built in and follow its deformations. Comparing the two sensory responses, we can discriminate the concave and the convex side of the bent body. Hence, we propose a new strategy to reveal in a soft body the maximum bending angle (or the maximum deflection) and the externally applied force according to the body's mechanical configuration. PMID:25739743
Revealing bending and force in a soft body through a plant root inspired approach
NASA Astrophysics Data System (ADS)
Lucarotti, Chiara; Totaro, Massimo; Sadeghi, Ali; Mazzolai, Barbara; Beccai, Lucia
2015-03-01
An emerging challenge in soft robotics research is to reveal mechanical solicitations in a soft body. Nature provides amazing clues to develop unconventional components that are capable of compliant interactions with the environment and living beings, avoiding mechanical and algorithmic complexity of robotic design. We inspire from plant-root mechanoperception and develop a strategy able to reveal bending and applied force in a soft body with only two sensing elements of the same kind, and a null computational effort. The stretching processes that lead to opposite tissue deformations on the two sides of the root wall are emulated with two tactile sensing elements, made of soft and stretchable materials, which conform to reversible changes in the shape of the body they are built in and follow its deformations. Comparing the two sensory responses, we can discriminate the concave and the convex side of the bent body. Hence, we propose a new strategy to reveal in a soft body the maximum bending angle (or the maximum deflection) and the externally applied force according to the body's mechanical configuration.
Revealing bending and force in a soft body through a plant root inspired approach.
Lucarotti, Chiara; Totaro, Massimo; Sadeghi, Ali; Mazzolai, Barbara; Beccai, Lucia
2015-01-01
An emerging challenge in soft robotics research is to reveal mechanical solicitations in a soft body. Nature provides amazing clues to develop unconventional components that are capable of compliant interactions with the environment and living beings, avoiding mechanical and algorithmic complexity of robotic design. We inspire from plant-root mechanoperception and develop a strategy able to reveal bending and applied force in a soft body with only two sensing elements of the same kind, and a null computational effort. The stretching processes that lead to opposite tissue deformations on the two sides of the root wall are emulated with two tactile sensing elements, made of soft and stretchable materials, which conform to reversible changes in the shape of the body they are built in and follow its deformations. Comparing the two sensory responses, we can discriminate the concave and the convex side of the bent body. Hence, we propose a new strategy to reveal in a soft body the maximum bending angle (or the maximum deflection) and the externally applied force according to the body's mechanical configuration. PMID:25739743
Hailey, C.E.; Clark, E.L.; Cole, J.K.
1991-01-01
High-speed water-entry is a very complex, dynamic process. As a first attempt at modeling the process, a numerical solution was developed at Sandia National Laboratories for predicting the forces and moments acting on a body with a steady supercavity, that is, a cavity which extends beyond the base of the body. The solution is limited to supercavities on slender, axisymmetric bodies at small angles of attack. Limited data were available with which to benchmark the axial force predictions at zero angle of attack. Even less data were available with which to benchmark the pitching moment and normal force predictions at nonzero angles of attack. A water tunnel test was conducted to obtain force and moment data on a slender shape. This test produced limited data because of waterproofing problems with the balance. A new balance was designed and a second water tunnel test was conducted at Tracor Hydronautics, Inc. This paper describes the numerical solution, the experimental equipment and test procedures, and the results of the second test. 8 refs., 11 figs.
Force production mechanisms of a tangential jet on bodies at high alpha
NASA Technical Reports Server (NTRS)
Font, G. I.
1992-01-01
This work explores the mechanisms by which tangential slot blowing creates forces on a body at a high angle of attack. The study is conducted numerically by solving the three-dimensional, compressible-flow Navier-Stokes equations. A tangent-ogive cylinder configuration is used with the blowing slot located both on the nose and on the cylindrical part of the body. The angle of attack used is 30 deg., the Mach no. is 0.2 and the Reynolds no., based on diameter, is 52,000. Several conclusions were made concerning the physical mechanisms by which the jet interacts with the ambient flowfield to produce a side force: (1) A centrifugal force component is created at the wall due to the momentum of the jet being forced to follow the curvature of the surface. (2) A large amount of vorticity is added to the flowfield by the jet. In the region of the slot, the vorticity has the effect of inducing circulation around the body. Downstream of the slot, the vorticity alters the strength of the nose vortices. (3) The position of the nose vortices can be altered to the jet changing the location of separation. And (4), the jet has the ability to excite unstable behavior producing a global change in the character of the flow.
Role of three-nucleon forces and many-body processes in nuclear pairing
J. D. Holt; J. Menendez; A. Schwenk
2013-06-11
We present microscopic valence-shell calculations of pairing gaps in the calcium isotopes, focusing on the role of three-nucleon (3N) forces and many-body processes. In most cases, we find a reduction in pairing strength when the leading chiral 3N forces are included, compared to results with low-momentum two-nucleon (NN) interactions only. This is in agreement with a recent energy density functional study. At the NN level, calculations that include particle-particle and hole-hole ladder contributions lead to smaller pairing gaps compared with experiment. When particle-hole contributions as well as the normal-ordered one- and two-body parts of 3N forces are consistently included to third order, we find reasonable agreement with experimental three-point mass differences. This highlights the important role of 3N forces and many-body processes for pairing in nuclei. Finally, we relate pairing gaps to the evolution of nuclear structure in neutron-rich calcium isotopes and study the predictions for the 2+ excitation energies, in particular for 54Ca.
Flow and Force Equations for a Body Revolving in a Fluid
NASA Technical Reports Server (NTRS)
Zahm, A F
1930-01-01
Part I gives a general method for finding the steady-flow velocity relative to a body in plane curvilinear motion, whence the pressure is found by Bernoulli's energy principle. Integration of the pressure supplies basic formulas for the zonal forces and moments on the revolving body. Part II, applying this steady-flow method, finds the velocity and pressure at all points of the flow inside and outside an ellipsoid and some of its limiting forms, and graphs those quantities for the latter forms. Part III finds the pressure, and thence the zonal force and moment, on hulls in plane curvilinear flight. Part IV derives general equations for the resultant fluid forces and moments on trisymmetrical bodies moving through a perfect fluid, and in some cases compares the moment values with those found for bodies moving in air. Part V furnishes ready formulas for potential coefficients and inertia coefficients for an ellipsoid and its limiting forms. Thence are derived tables giving numerical values of those coefficients for a comprehensive range of shapes.
Microscopic nuclear equation of state with three-body forces and neutron star structure
NASA Astrophysics Data System (ADS)
Baldo, M.; Bombaci, I.; Burgio, G. F.
1997-12-01
We calculate static properties of non-rotating neutron stars (NS's) using a microscopic equation of state (EOS) for asymmetric nuclear matter, derived from the Brueckner-Bethe-Goldstone many-body theory with explicit three-body forces. We use the Argonne AV14 and the Paris two-body nuclear force, implemented by the Urbana model for the three-body force. We obtain a maximum mass configuration with Mmax = 1.8 M_? (Mmax = 1.94 M_?) when the AV14 (Paris) interaction is used. They are both consistent with the observed range of NS masses. The onset of direct Urca processes occurs at densities n >= 0.65 fm(-3) for the AV14 potential and n >= 0.54 fm(-3) for the Paris potential. Therefore, NS's with masses above M(Urca) = 1.4 M_? for the AV14 and M(Urca) = 1.24 M_? for the Paris potential can undergo very rapid cooling, depending on the strength of superfluidity in the interior of the NS. The comparison with other microscopic models for the EOS shows noticeable differences.
Research into Orbital Motion Stability in System of Two Magnetically Interacting Bodies
Stanislav Zub
2011-01-17
The stability of the orbital motion of two long cylindrical magnets interacting exclusively with magnetic forces is described. To carry out analytical studies a model of magnetically interacting symmetric tops [1] is used. The model was previously developed within the quasi-stationary approach for an electromagnetic field based on the general expression of the energy of interacting magnetic bodies [2]. A special role in the investigation of the stability of orbital motions is played by the so-called relative equilibria [3], i.e. the trajectories of the system dynamics which are at the same time one-parameter subgroups of the system invariance group. Nowadays their stability is normally investigated using two similar approaches -- energy-momentum and energy-Casimir methods. The most suitable criterion for the system stability investigation was formulated in the theorem of [4]; this stability criterion successfully generalizes both the methods mentioned above and covers the Hamiltonian formalism based on Poisson structures [1]. The necessary and sufficient conditions for the circular orbit stability are derived from this theorem.
Development of a Force Measurement Device for Lower-Body Muscular Strength Measuring of Skaters
NASA Astrophysics Data System (ADS)
Kim, Dong Ki; Lee, Jeong Tae
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.
A GLRT AND BOOTSTRAP APPROACH TO DETECTION IN MAGNETIC RESONANCE FORCE MICROSCOPY
Moura, José
A GLRT AND BOOTSTRAP APPROACH TO DETECTION IN MAGNETIC RESONANCE FORCE MICROSCOPY PeiJung Chung, USA moura@ece.cmu.edu ABSTRACT Magnetic resonance force microscopy (MRFM) is a tech- nology that will potentially enable microscopy of molecules and proteins at atomicscale detail. Physicists are pursuing MRFM
Transport of particles by magnetic forces and cellular blood flow in a model microvessel
Freund, Jonathan B.
Transport of particles by magnetic forces and cellular blood flow in a model microvessel J. B in oscillating shear flow Phys. Fluids 23, 111901 (2011) Pair collisions of fluid-filled elastic capsules://pof.aip.org/authors #12;PHYSICS OF FLUIDS 24, 051904 (2012) Transport of particles by magnetic forces and cellular blood
Computation of trunk muscle forces, spinal loads and stability in whole-body vibration
NASA Astrophysics Data System (ADS)
Bazrgari, B.; Shirazi-Adl, A.; Kasra, M.
2008-12-01
Whole-body vibration has been indicated as a risk factor in back disorders. Proper prevention and treatment management, however, requires a sound knowledge of associated muscle forces and loads on the spine. Previous trunk model studies have either neglected or over-simplified the trunk redundancy with time-varying unknown muscle forces. Trunk stability has neither been addressed. A novel iterative dynamic kinematics-driven approach was employed to evaluate muscle forces, spinal loads and system stability in a seated subject under a random vertical base excitation with ą1 g peak acceleration contents. This iterative approach satisfied equations of motion in all directions/levels while accounting for the nonlinear passive resistance of the ligamentous spine. The effect of posture, co-activity in abdominal muscles and changes in buttocks stiffness were also investigated. The computed vertical accelerations were in good agreement with measurements. The input base excitation, via inertial and muscle forces, substantially influenced spinal loads and system stability. The flexed posture in sitting increased the net moment, muscle forces and passive spinal loads while improving the trunk stability. Similarly, the introduction of low to moderate antagonistic coactivity in abdominal muscles increased the passive spinal loads and improved the spinal stability. A trade-off, hence, exists between lower muscle forces and spinal loads on one hand and more stable spine on the other. Base excitations with larger peak acceleration contents substantially increase muscle forces/spinal loads and, hence, the risk of injury.
Measurement and calculation of forces in a magnetic journal bearing actuator
NASA Technical Reports Server (NTRS)
Knight, Josiah; Mccaul, Edward; Xia, Zule
1991-01-01
Numerical calculations and experimental measurements of forces from an actuator of the type used in active magnetic journal bearings are presented. The calculations are based on solution of the scalar magnetic potential field in and near the gap regions. The predicted forces from single magnet with steady current are compared with experimental measurements in the same geometry. The measured forces are smaller than calculated ones in the principal direction but are larger than calculated in the normal direction. This combination of results indicate that material and spatial effects other than saturation play roles in determining the force available from an actuator.
Magnetic levitation force measurement on high [Tc] superconducting ceramic/polymer composites
Unsworth, J.; Du, Jia; Crosby, B.J. ); Macfarlane, J.C. )
1993-01-01
An experimental study of magnetic levitation force for 0--3 and 3--3 superconducting ceramic/polymer composites is presented. A simple, inexpensive force versus distance measurement technique is described. The measurements of force against distance or magnetic field show strong hysteretic behavior, which is similar to the sintered superconductor ceramics and is consistent with the hysteresis in magnetization of superconductor. The volume fraction dependence and sample thickness dependence of the levitation forces are also studied for 0--3 composites. Results suggest that the new composite materials are most suitable for levitation applications.
On the Inertial Force Experienced by a Solid Body Undergoing Rotation about Two Axes
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
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.
Test bodies and naked singularities: is the self-force the cosmic censor?
Enrico Barausse; Vitor Cardoso; Gaurav Khanna
2010-12-17
Jacobson and Sotiriou showed that rotating black holes could be spun-up past the extremal limit by the capture of non-spinning test bodies, if one neglects radiative and self-force effects. This would represent a violation of the Cosmic Censorship Conjecture in four-dimensional, asymptotically flat spacetimes. We show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities.
Test bodies and naked singularities: is the self-force the cosmic censor?
Barausse, Enrico; Cardoso, Vitor; Khanna, Gaurav
2010-12-31
Jacobson and Sotiriou showed that rotating black holes could be spun up past the extremal limit by the capture of nonspinning test bodies, if one neglects radiative and self-force effects. This would represent a violation of the cosmic censorship conjecture in four-dimensional, asymptotically flat spacetimes. We show that for some of the trajectories giving rise to naked singularities, radiative effects can be neglected. However, for these orbits the conservative self-force is important, and seems to have the right sign to prevent the formation of naked singularities. PMID:21231640
Orthodontic magnets. A study of force and field pattern, biocompatibility and clinical effects.
Bondemark, L
1994-01-01
Magnetic forces have been incorporated into orthodontic mechanics during recent years. However, the biocompatibility of magnet alloys and the possible risk of harmful or unusual reactions in tissues exposed to static magnetic fields have been characterized as inconsistent and often contradictory. It has also been questioned whether magnetic forces have significant advantages over traditional mechanics. The present series of studies aimed to analyse the force and field properties, the biocompatibility and the clinical effects of rare earth magnets as well as to compare the efficiency of tooth movement between magnets and another force system. Samarium-cobalt magnets for molar distalization were tested in experimental models for force and field properties. The cytotoxicity of different magnet alloys (rare earth types) as well as of clinically used and recycled magnets was assessed by two in vitro methods, the millipore filter method and an extraction method. The effect of static magnetic fields on human gingival tissue and dental pulp was examined histologically for alterations in cell pattern and cell morphology. The effects of using repelling samarium-cobalt magnets for simultaneous distalization of maxillary first and second molars were analysed in individuals with Class II malocclusion. The efficiency of molar distalization was also intra-individually compared between repelling magnets and superelastic NiTi-coils in individuals with Class II malocclusion and deep bite. The magnet forces decreased approximately with the reciprocal square of the separation distance between the magnets. No fatigue of force over time could be seen. The static magnetic fields were weak and had a limited extent and the flux density dropped exponentially in all directions with increased distance from the magnets, implying a small exposure area when the magnets are used clinically. Rare earth magnets showed good biocompatibility, particularly coated magnets. However, uncoated samarium-cobalt magnets showed significant cytotoxicity. It was also found that stainless-steel-coated samarium-cobalt magnets could be recycled with maintained good biocompatibility. After exposure to static magnetic fields, normal clinical and histological conditions in the human gingival tissue and normal histological features in the human dental pulp were found. Repelling magnets were effective in producing maxillary molar distalization but some side effects like anchorage loss and molar tipping were found. The superelastic coils were shown to be even more efficient than the repelling magnets for maxillary molar distalization in individuals with Class II malocclusion and deep bite. PMID:7801229
Axial force imparted by a current-free magnetically expanding plasma
Takahashi, Kazunori; Lafleur, Trevor; Charles, Christine; Alexander, Peter; Boswell, Rod W.
2012-08-15
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.
First-Principles Theory of van der Waals Forces between Macroscopic Bodies
NASA Astrophysics Data System (ADS)
Yannopapas, Vassilios; Vitanov, Nikolay V.
2007-09-01
We present a first-principles method for the determination of the van der Waals interactions for a collection of finite-sized macroscopic bodies. The method is based on fluctuational electrodynamics and a rigorous multiple-scattering method for the electromagnetic field. As such, the method takes fully into account retardation, many-body, multipolar, and near-fields effects. By application of the method to the case of two metallic nanoparticles, we demonstrate the breakdown of the standard 1/r2 distance law as the van der Waals force decays exponentially with distance when the nanoparticles are too close or too far apart.
Testing for three-body quark forces in L=1 excited baryons
Pirjol, Dan
2010-01-01
We discuss the matching of the quark model to the effective mass operator of the 1/Nc expansion using the permutation group S_N. As an illustration of the general procedure we perform the matching of the Isgur-Karl model for the spectrum of the negative parity L=1 excited baryons. Assuming the most general two-body quark Hamiltonian, we derive two correlations among the masses and mixing angles of these states which should hold in any quark model. These correlations constrain the mixing angles and can be used to test for the presence of three-body quark forces.
Nuclear pairing from bare interaction: Two and three-body chiral forces
Finelli, Paolo [Physics Department, University of Bologna, Via Irnerio 46, 40126 Bologna (Italy); INFN, Section of Bologna, Viale Berti Pichat 6/2, 40127 Bologna (Italy)
2012-10-20
In a recent paper the {sup 1}S{sub 0} pairing gap in isospin-symmetric nuclear matter and finite nuclei has been investigated starting from the chiral nucleon-nucleon potential at the N{sup 3}LO order in the two-body sector and the N{sup 2}LO order in the three-body sector. To include realistic nuclear forces in RHB (Relativistic Hartree Bolgoliubov) calculations we relied on a separable representation of the pairing interaction. In this paper we would like to show recent results concerning isotonic chains with N= 28,50,82.
Increasing of thrust force in transverse flux machine by permanent-magnet screen
Do Hyun Kang
2005-01-01
This paper proposes a basic model and an analytical study of the transverse flux machines using permanent-magnet (PM) shields to increase the thrust force. By improving the magnetic field distribution in the electrically excited transverse flux linear motor (TFE-LM), the rare-earth PM shields provide an increase of the thrust force. Analytical equations are developed to predict the thrust force and
Nonlinear force-free modeling of the solar coronal magnetic field
Wiegelmann, Thomas
compared to unity (b = 2 m0 p/B2 (1). In lowest-order nonmagnetic forces like pressure gradient and gravity current density and m0 the permeability of vacuum. Equation (1) implies that for force-free fieldsNonlinear force-free modeling of the solar coronal magnetic field T. Wiegelmann1 Received 30 March
Friction force microscopy study of lubricant thin films on thin-film magnetic recording media
Ichiro Fujiwara; Takahiro Kamei; Koichi Tanaka
1995-01-01
The microscopic frictional properties of lubricant thin films on thin-film magnetic recording media [metal-evaporated (ME) tape] were investigated with a friction force microscope in order to understand the intrinsic frictional properties of the lubricant on the ME tapes. We propose the microscopic effective friction coefficient, the friction force normalized by the normal force based on the JKR theory, of the
Vadas, Sharon
An estimate of strong local body forcing and gravity wave radiation based on OH airglow and meteor, and that the resulting local forcing of the mean flow represents a vigorous source of secondary gravity waves] and Vadas et al. [2002] have called attention to the potential for localized gravity wave forcing to result
ERIC Educational Resources Information Center
Savinainen, Antti; Makynen, Asko; Nieminen, Pasi; Viiri, Jouni
2013-01-01
Earlier research has shown that after physics instruction, many students have difficulties with the force concept, and with constructing free-body diagrams (FBDs). It has been suggested that treating forces as interactions could help students to identify forces as well as to construct the correct FBDs. While there is evidence that identifying
Cellular effects of magnetic nanoparticles explored by atomic force microscopy.
Mao, Hongli; Li, Jingchao; Duli?ska-Molak, Ida; Kawazoe, Naoki; Takeda, Yoshihiko; Mamiya, Hiroaki; Chen, Guoping
2015-08-11
The investigation of subtle change of cells exposed to nanomaterials is extremely essential but also challenging for nanomaterial-based biological applications. In this study, atomic force microscopy (AFM) was employed to investigate the effects of iron-iron oxide core-shell magnetic nanoparticles on the mechanical properties of bovine articular chondrocytes (BACs). After being exposed to the nanoparticles even at a high nanoparticle-concentration (50 ?g mL(-1)), no obvious difference was observed by using conventional methods, including the WST-1 assay and live/dead staining. However a significant difference of Young's modulus of the cells was detected by AFM even when the concentration of nanoparticles applied in the cell culture medium was low (10 ?g mL(-1)). The difference of cellular Young's modulus increased with the increase of nanoparticle concentration. AFM was demonstrated to be a useful tool to identify the subtle change of cells when they were exposed to nanomaterials even at a low concentration. PMID:26261856
GravitoMagnetic force in modified Newtonian dynamics
Exirifard, Qasem
2013-08-01
We introduce the Gauge Vector-Tensor (GVT) theory by extending the AQUAL's approach to the GravitoElectroMagnetism (GEM) approximation of gravity. GVT is a generally covariant theory of gravity composed of a pseudo Riemannian metric and two U(1) gauge connections that reproduces MOND in the limit of very weak gravitational fields while remains consistent with the Einstein-Hilbert gravity in the limit of strong and Newtonian gravitational fields. GVT also provides a simple framework to study the GEM approximation to gravity. We illustrate that the gravitomagnetic force at the edge of a galaxy can be in accord with either GVT or ?CDM but not both. We also study the physics of the GVT theory around the gravitational saddle point of the Sun and Jupiter system. We notice that the conclusive refusal of the GVT theory demands measuring either both of the gravitoelectric and gravitomagnetic fields inside the Sun-Jupiter MOND window, or the gravitoelectric field inside two different solar GVT MOND windows. The GVT theory, however, will be favored by observing an anomaly in the gravitoelectric field inside a single MOND window.
Forced-Convection Extinction of a Diffusion Flame Sustained by a Charring Body
GEORGE CARRIER; FRANCIS FENDELL; PHILLIP FELDMAN; STANTON FINK TRW
1982-01-01
The subsonic isobaric forced-convective flow of air past a pyrolyzing, char-forming body outgassing combustible fuel vapor is examined; the goal is to seek a generalized approach toward establishing approximate criteria for extinction of burning. A Shvab-Zeldovich formulation (incorporating, inter alia, a one-step irreversible exothermic finite-rate chemical reaction) is adopted to describe the gas-phase burning of initially unmixed reactants. For specificity,
Campanella, H; Jaafar, M; Llobet, J; Esteve, J; Vázquez, M; Asenjo, A; del Real, R P; Plaza, J A
2011-12-16
We report on a new approach for magnetic imaging, highly sensitive even in the presence of external, strong magnetic fields. Based on FIB-assisted fabricated high-aspect-ratio rare-earth nanomagnets, we produce groundbreaking magnetic force tips with hard magnetic character where we combine a high aspect ratio (shape anisotropy) together with strong crystalline anisotropy (rare-earth-based alloys). Rare-earth hard nanomagnets are then FIB-integrated to silicon microcantilevers as highly sharpened tips for high-field magnetic imaging applications. Force resolution and domain reversing and recovery capabilities are at least one order of magnitude better than for conventional magnetic tips. This work opens new, pioneering research fields on the surface magnetization process of nanostructures based either on relatively hard magnetic materials-used in magnetic storage media-or on materials like superparamagnetic particles, ferro/antiferromagnetic structures or paramagnetic materials. PMID:22107927
Rouge, Clémence; Lhémery, Alain; Ségur, Damien
2013-10-01
An electromagnetic acoustic transducer (EMAT) or a laser used to generate elastic waves in a component is often described as a source of body force confined in a layer close to the surface. On the other hand, models for elastic wave radiation more efficiently handle sources described as distributions of surface stresses. Equivalent surface stresses can be obtained by integrating the body force with respect to depth. They are assumed to generate the same field as the one that would be generated by the body force. Such an integration scheme can be applied to Lorentz force for conventional EMAT configuration. When applied to magnetostrictive force generated by an EMAT in a ferromagnetic material, the same scheme fails, predicting a null stress. Transforming body force into equivalent surface stresses therefore, requires taking into account higher order terms of the force moments, the zeroth order being the simple force integration over the depth. In this paper, such a transformation is derived up to the second order, assuming that body forces are localized at depths shorter than the ultrasonic wavelength. Two formulations are obtained, each having some advantages depending on the application sought. They apply regardless of the nature of the force considered. PMID:24116402
Pull-in control due to Casimir forces using external magnetic fields
R. Esquivel-Sirvent; M. A. Palomino-Ovando; G. H. Cocoletzi
2009-07-13
We present a theoretical calculation of the pull-in control in capacitive micro switches actuated by Casimir forces, using external magnetic fields. The external magnetic fields induces an optical anisotropy due to the excitation of magneto plasmons, that reduces the Casimir force. The calculations are performed in the Voigt configuration, and the results show that as the magnetic field increases the system becomes more stable. The detachment length for a cantilever is also calculated for a cantilever, showing that it increases with increasing magnetic field. At the pull-in separation, the stiffness of the system decreases with increasing magnetic field.
Transient body force effects on the dryout and rewet of a heated capillary structure
NASA Astrophysics Data System (ADS)
Reagan, Michael K.
1994-04-01
A transient, one-dimensional numerical code was developed to model the liquid flow in a non-uniformly heated, axial square groove. The groove was subjected to transient body forces up to approximately 0.51 m/s sq. Axial variation in meniscus levels, shear stress and heat transfer between the groove wall and the liquid, axial conduction through the liquid, evaporation and body forces were accounted for in the model. Dryout and rewet of the groove were allowed; the front location was determined using conservation of mass and linear extrapolation. A physical experiment was performed with a stainless steel plate into which eight square grooves were machined. Ethanol was used as the working liquid. One end of the plate was tilted relative to the other end and this tilt was varied with time, thereby providing the transient body force. The depth of the ethanol in the groove, and the dryout and rewet front locations, were experimentally measured. Within the uncertainty of the measurements, the numerical results from the code predicted the correct movement of liquid within the groove structure and also the correct position of the dryout and rewet fronts.
Thrust Force of Novel PM Transverse Flux Linear Oscillating Actuators With Moving Magnet
Qinfen Lu; Minghu Yu; Yunyue Ye; Youtong Fang; Jianguo Zhu
2011-01-01
This paper investigates the thrust forces of two novel permanent magnet transverse flux linear oscillating actuators (TFLOAs), one with moving magnet and the other moving both magnet and iron core, for pump and compressor drives. Different from the conventional linear actuators, the lamination construction of the TFLOAs is similar to that of a normalrotating motor, which is easy to stack.
Scaling of forced magnetic reconnection in the Hall-magnetohydrodynamic Taylor Richard Fitzpatrick
Fitzpatrick, Richard
to greatly accelerate the rate of magnetic reconnection. In the linear Hall-MHD regime, the peak. Plasmas 21, 020703 (2014); 10.1063/1.4865378 Gyro-induced acceleration of magnetic reconnection PhysScaling of forced magnetic reconnection in the Hall-magnetohydrodynamic Taylor problem Richard
Real-Time Control of Humanoid Robots Considering External Forces on Upper Part of the Body
NASA Astrophysics Data System (ADS)
Inomata, Kentaro; Shigemori, Yo; Uchimura, Yutaka
Recently, the demand for the practical use of service robots has risen significantly because of acceleration of demographic aging, and a humanoid robot is one of the promising form factors of service robots. When a humanoid robot is used by a human in a real environment, the robot needs to be designed by taking into account the various external forces that act on the robot. Thus far, most of the walking humanoid robots have been mainly controlled by the conventional ZMP method to maintain a stable walking posture. However, the conventional ZMP method can not be used to handle the various external forces that act on the upper part of the humanoid robot body. To overcome these problems, in this paper, we propose a novel control method, which we called 3DZMP and pZMP, for a humanoid robot to react to the external force on the upper part of the body. The 3DZMP is defined as the point in three-dimensional space at which the moment about all axes is zero. 3DZMP can prevent the rotation of a humanoid robot. The pZMP is defined as the point corresponding to the orthographic projection of the 3DZMP on a plane. pZMP is used to evaluate the stability of 3DZMP. We implemented the proposed method on a prototype robot and verified that the robot gained the capability to react to external forces that could not be handled by the conventional ZMP method.
Stability of the Taylor-Couette flow under a radial thermoelectric body force
NASA Astrophysics Data System (ADS)
Yoshikawa, Harunori; Mutabazi, Innocent; Crumeyrolle, Olivier; Meyer, Antoine
2013-11-01
A circular Couette flow developed between coaxial two infinite-length cylinders is considered in the case where only the inner cylinder is rotating. A radial temperature gradient and a radial electric field are applied to the flow, their coupling resulting in the dielectrophoretic body force density. This thermoelectric force can stabilize and destabilize the flow, depending on the heating direction. The critical Taylor number, wavenumber and frequency are determined for a wide range of control parameters. The mechanism behind the instability will be discussed. A circular Couette flow developed between coaxial two infinite-length cylinders is considered in the case where only the inner cylinder is rotating. A radial temperature gradient and a radial electric field are applied to the flow, their coupling resulting in the dielectrophoretic body force density. This thermoelectric force can stabilize and destabilize the flow, depending on the heating direction. The critical Taylor number, wavenumber and frequency are determined for a wide range of control parameters. The mechanism behind the instability will be discussed. This work benefited from a financial support from CNES (French Space Agency), the CPER-Haute Normandie under the program THETE and from the FEDER.
Pai, C N; Shinshi, T; Shimokohbe, A
2010-01-01
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
Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths
A. Ekström; G. R. Jansen; K. A. Wendt; G. Hagen; T. Papenbrock; S. Bacca; B. Carlsson; D. Gazit
2014-06-18
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.
Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths
Ekström, A; Wendt, K A; Hagen, G; Papenbrock, T; Bacca, S; Carlsson, B; Gazit, D
2014-01-01
We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems, and compute Gamow-Teller transitions in carbon-14, oxygen-22 and oxygen-24 using consistent two-body currents. We compute spectra of the daughter nuclei nitrogen-14, fluorine-22 and fluorine-24 via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q^2 ~ 0.84-0.92 of the axial-vector coupling. The half life of carbon-14 depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current.
Effects of Three-Nucleon Forces and Two-Body Currents on Gamow-Teller Strengths
NASA Astrophysics Data System (ADS)
Ekström, A.; Jansen, G. R.; Wendt, K. A.; Hagen, G.; Papenbrock, T.; Bacca, S.; Carlsson, B.; Gazit, D.
2014-12-01
We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems and compute Gamow-Teller transitions in 14C O,2422 using consistent two-body currents. We compute spectra of the daughter nuclei 14N and F,2422 via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q2?0.84 - 0.92 of the axial-vector coupling. The half-life of 14C depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current.
Effects of three-nucleon forces and two-body currents on Gamow-Teller strengths.
Ekström, A; Jansen, G R; Wendt, K A; Hagen, G; Papenbrock, T; Bacca, S; Carlsson, B; Gazit, D
2014-12-31
We optimize chiral interactions at next-to-next-to leading order to observables in two- and three-nucleon systems and compute Gamow-Teller transitions in 14C and (22,24)O using consistent two-body currents. We compute spectra of the daughter nuclei 14N and (22,24)F via an isospin-breaking coupled-cluster technique, with several predictions. The two-body currents reduce the Ikeda sum rule, corresponding to a quenching factor q2?0.84-0.92 of the axial-vector coupling. The half-life of 14C depends on the energy of the first excited 1+ state, the three-nucleon force, and the two-body current. PMID:25615316
Roetenberg, Daniel; Luinge, Henk J; Baten, Chris T M; Veltink, Peter H
2005-09-01
This paper describes a complementary Kalman filter design to estimate orientation of human body segments by fusing gyroscope, accelerometer, and magnetometer signals from miniature sensors. Ferromagnetic materials or other magnetic fields near the sensor module disturb the local earth magnetic field and, therefore, the orientation estimation, which impedes many (ambulatory) applications. In the filter, the gyroscope bias error, orientation error, and magnetic disturbance error are estimated. The filter was tested under quasi-static and dynamic conditions with ferromagnetic materials close to the sensor module. The quasi-static experiments implied static positions and rotations around the three axes. In the dynamic experiments, three-dimensional rotations were performed near a metal tool case. The orientation estimated by the filter was compared with the orientation obtained with an optical reference system Vicon. Results show accurate and drift-free orientation estimates. The compensation results in a significant difference (p < 0.01) between the orientation estimates with compensation of magnetic disturbances in comparison to no compensation or only gyroscopes. The average static error was 1.4 degrees (standard deviation 0.4) in the magnetically disturbed experiments. The dynamic error was 2.6 degrees root means square. PMID:16200762
NASA Astrophysics Data System (ADS)
Jang, G. H.; Park, N. K.; Lee, C. I.; Chang, J. H.; Jeong, S. W.; Kang, D. H.
2008-04-01
This paper investigates the characteristics of the magnetic force and the torque in the conventional rotatory two-phase transverse flux machine (TFM) by using the three-dimensional finite element method. This research shows that the unbalanced magnetic force is one of the dominant excitation forces in this machine, and it proposes a TFM with symmetric multipair cores in which each stator core of phases A and B is divided into two and the divided cores are disposed symmetrically to cancel the unbalanced magnetic force of each phase of a TFM. However, symmetric multipair cores of a TFM may reduce the winding space of coil which results in the reduction of torque and power. This research performs the optimization of teeth-slot configuration of the stator to overcome this shortcoming. It shows that the unbalance magnetic force of a TFM can be effectively eliminated without sacrificing torque or power by introducing symmetric multipair cores.
Investigation of Body Force Effects on Flow Boiling Critical Heat Flux
NASA Technical Reports Server (NTRS)
Zhang, Hui; Mudawar, Issam; Hasan, Mohammad M.
2002-01-01
The bubble coalescence and interfacial instabilities that are important to modeling critical heat flux (CHF) in reduced-gravity systems can be sensitive to even minute body forces. Understanding these complex phenomena is vital to the design and safe implementation of two-phase thermal management loops proposed for space and planetary-based thermal systems. While reduced gravity conditions cannot be accurately simulated in 1g ground-based experiments, such experiments can help isolate the effects of the various forces (body force, surface tension force and inertia) which influence flow boiling CHF. In this project, the effects of the component of body force perpendicular to a heated wall were examined by conducting 1g flow boiling experiments at different orientations. FC-72 liquid was boiled along one wall of a transparent rectangular flow channel that permitted photographic study of the vapor-liquid interface at conditions approaching CHF. High-speed video imaging was employed to capture dominant CHF mechanisms. Six different CHF regimes were identified: Wavy Vapor Layer, Pool Boiling, Stratification, Vapor Counterflow, Vapor Stagnation, and Separated Concurrent Vapor Flow. CHF showed great sensitivity to orientation for flow velocities below 0.2 m/s, where very small CHF values where measured, especially with downflow and downward-facing heated wall orientations. High flow velocities dampened the effects of orientation considerably. Figure I shows representative images for the different CHF regimes. The Wavy Vapor Layer regime was dominant for all high velocities and most orientations, while all other regimes were encountered at low velocities, in the downflow and/or downward-facing heated wall orientations. The Interfacial Lift-off model was modified to predict the effects of orientation on CHF for the dominant Wavy Vapor Layer regime. The photographic study captured a fairly continuous wavy vapor layer travelling along the heated wall while permitting liquid contact only in wetting fronts, located in the troughs of the interfacial waves. CHF commenced when wetting fronts near the outlet were lifted off the wall. The Interfacial Lift-off model is shown to be an effective tool for predicting the effects of body force on CHF at high velocities.
Huang, Chen-Yu; Wei, Zung-Hang
2015-01-01
Concentric magnetic structures (ring and square) with domain wall (DW) pinning geometry are designed for biological manipulation. Magnetic beads collection was firstly demonstrated to analyse the local magnetic field generated by DWs and the effective regions to capture magnetic targets of size 1 ?m. Primary mouse embryonic fibroblasts (MEFs) are magnetically labeled by internalizing poly (styrene sulfonic acid) stabilized magnetic nanoparticles (PSS-MNPs) and then are selectively trapped by head-to-tail DWs (HH DWs) or tail-to-tail DWs (TT DWs) to be arranged into linear shape or cross shape. The morphologies and the nuclear geometry of the cells growing on two kinds of concentric magnetic structures are shown to be distinctive. The intracellular magnetic forces generated by the local magnetic field of DWs are found to influence the behaviour of cells. PMID:26270332
Magnetic Levitation Force Measurement System at Any Low Temperatures From 20 K To 300 K
NASA Astrophysics Data System (ADS)
Celik, Sukru; Guner, S. Baris; Coskun, Elvan
2015-03-01
Most of the magnetic levitation force measurements in previous studies were performed at liquid nitrogen temperatures. For the levitation force of MgB2 and iron based superconducting samples, magnetic levitation force measurement system is needed. In this study, magnetic levitation force measurement system was designed. In this system, beside vertical force versus vertical motion, lateral and vertical force versus lateral motion measurements, the vertical force versus temperature at the fixed distance between permanent magnet PM - superconducting sample SS and the vertical force versus time measurements were performed at any temperatures from 20 K to 300 K. Thanks to these measurements, the temperature dependence, time dependence, and the distance (magnetic field) and temperature dependences of SS can be investigated. On the other hand, the magnetic stiffness MS measurements can be performed in this system. Using the measurement of MS at different temperature in the range, MS dependence on temperature can be investigated. These measurements at any temperatures in the range help to the superconductivity properties to be characterized. This work was supported by TUBTAK-the Scientific and technological research council of Turkey under project of MFAG - 110T622. This system was applied to the Turkish patent institute with the Application Number of 2013/13638 on 22/11/2013.
Levitation force and magnetic stiffness in bulk high-temperature superconductors
Chang, P.Z.; Moon, F.C. ); Hull, J.R.; Mulcahy, T.M. )
1990-05-01
Levitation forces between a small permanent magnet and a disk of bulk high-temperature superconductor at 77 K were measured as a function of vertical separation for disks of composition Y-Ba-Cu-O, Ag/Y-Ba-Cu-O, (Pb,Bi)-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O. The forces were highly hysteretic; however, for all samples, on the initial descent of the magnet toward the disk, the force was unique, independent of magnet speed, and varied approximately as the negative exponential of the separation distance. Magnetic stiffness, associated with minor hysteresis loops, was found to be approximately proportional to the levitation force, and nearly independent of magnet configuration and superconductor composition.
Scaling the energy conversion rate from magnetic field reconnection to different bodies
California at Berkeley, University of
Scaling the energy conversion rate from magnetic field reconnection to different bodies F. S. Mozer reconnection is often invoked to explain electromagnetic energy conversion in planetary magnetospheres, stellar in these bodies, it is important to understand energy conversion as a function of magnetic field strength
Fouchard, Jonathan; Bimbard, Célian; Bufi, Nathalie; Durand-Smet, Pauline; Proag, Amsha; Richert, Alain; Cardoso, Olivier; Asnacios, Atef
2014-01-01
Cell shape affects proliferation and differentiation, which are processes known to depend on integrin-based focal adhesion (FA) signaling. Because shape results from force balance and FAs are mechanosensitive complexes transmitting tension from the cell structure to its mechanical environment, we investigated the interplay between 3D cell shape, traction forces generated through the cell body, and FA growth during early spreading. Combining measurements of cell-scale normal traction forces with FA monitoring, we show that the cell body contact angle controls the onset of force generation and, subsequently, the initiation of FA growth at the leading edge of the lamella. This suggests that, when the cell body switches from convex to concave, tension in the apical cortex is transmitted to the lamella where force-sensitive FAs start to grow. Along this line, increasing the stiffness resisting cell body contraction led to a decrease of the lag time between force generation and FA growth, indicating mechanical continuity of the cell structure and force transmission from the cell body to the leading edge. Remarkably, the overall normal force per unit area of FA increased with stiffness, and its values were similar to those reported for local tangential forces acting on individual FAs. These results reveal how the 3D cell shape feeds back on its internal organization and how it may control cell fate through FA-based signaling. PMID:25157134
NASA Technical Reports Server (NTRS)
Tan, Choon-Sooi; Suder, Kenneth (Technical Monitor)
2003-01-01
A framework for an effective computational methodology for characterizing the stability and the impact of distortion in high-speed multi-stage compressor is being developed. The methodology consists of using a few isolated-blade row Navier-Stokes solutions for each blade row to construct a body force database. The purpose of the body force database is to replace each blade row in a multi-stage compressor by a body force distribution to produce same pressure rise and flow turning. To do this, each body force database is generated in such a way that it can respond to the changes in local flow conditions. Once the database is generated, no hrther Navier-Stokes computations are necessary. The process is repeated for every blade row in the multi-stage compressor. The body forces are then embedded as source terms in an Euler solver. The method is developed to have the capability to compute the performance in a flow that has radial as well as circumferential non-uniformity with a length scale larger than a blade pitch; thus it can potentially be used to characterize the stability of a compressor under design. It is these two latter features as well as the accompanying procedure to obtain the body force representation that distinguish the present methodology from the streamline curvature method. The overall computational procedures have been developed. A dimensional analysis was carried out to determine the local flow conditions for parameterizing the magnitudes of the local body force representation of blade rows. An Euler solver was modified to embed the body forces as source terms. The results from the dimensional analysis show that the body forces can be parameterized in terms of the two relative flow angles, the relative Mach number, and the Reynolds number. For flow in a high-speed transonic blade row, they can be parameterized in terms of the local relative Mach number alone.
FORCE-FREENESS OF SOLAR MAGNETIC FIELDS IN THE PHOTOSPHERE Q1 Y.-J. Moon,1,2
is that the magnetic fields above the solar photosphere are force- free, implying that there is no net magnetic forces It is widely believed that solar magnetic fields are force-free in the solar corona but not in the solar photo are not so far from force-free as conventionally regarded. As a good example of a linear force-free field,Q4
A many-body dissipative particle dynamics study of forced water-oil displacement in capillary.
Chen, Chen; Zhuang, Lin; Li, Xuefeng; Dong, Jinfeng; Lu, Juntao
2012-01-17
The forced water-oil displacement in capillary is a model that has important applications such as the groundwater remediation and the oil recovery. Whereas it is difficult for experimental studies to observe the displacement process in a capillary at nanoscale, the computational simulation is a unique approach in this regard. In the present work, the many-body dissipative particle dynamics (MDPD) method is employed to simulate the process of water-oil displacement in capillary with external force applied by a piston. As the property of all interfaces involved in this system can be manipulated independently, the dynamic displacement process is studied systematically under various conditions of distinct wettability of water in capillary and miscibility between water and oil as well as of different external forces. By analyzing the dependence of the starting force on the properties of water/capillary and water/oil interfaces, we find that there exist two different modes of the water-oil displacement. In the case of stronger water-oil interaction, the water particles cannot displace those oil particles sticking to the capillary wall, leaving a low oil recovery efficiency. To minimize the residual oil content in capillary, enhancing the wettability of water and reducing the external force will be beneficial. This simulation study provides microscopic insights into the water-oil displacement process in capillary and guiding information for relevant applications. PMID:22133087
Nonlinear force-free modeling of the solar coronal magnetic field
T. Wiegelmann
2008-01-18
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.
Magnetic levitation force of semi-infinite type-II superconductors
Coffey, M.W.
1995-10-01
The levitation force acting on a point magnetic dipole above a semi-infinite type-II superconductor in both the Meissner and mixed states is studied. A formalism is developed for axisymmetric problems using London theory. The magnetostatic interaction energy and corresponding force can be put into closed form for such problems for arbitrary height of the magnetic point source. The results for stray fields have ready application to magnetic-force microscopy (MFM) with point probes. The results are useful for a range of experiments including the low-temperature MFM imaging of vortices and decoration measurements. Special cases include earlier results and previous approximations are obviated.
Low-frequency transient electric and magnetic fields coupling to child body.
Ozen, S
2008-01-01
Much of the research related to residential electric and magnetic field exposure focuses on cancer risk for children. But until now only little knowledge about coupling of external transient electric and magnetic fields with the child's body at low frequency transients existed. In this study, current densities, in the frequency range from 50 Hz up to 100 kHz, induced by external electric and magnetic fields to child and adult human body, were investigated, as in residential areas, electric and magnetic fields become denser in this frequency band. For the calculations of induced fields and current density, the ellipsoidal body models are used. Current density induced by the external magnetic field (1 microT) and external electric field (1 V/m) is estimated. The results of this study show that the transient electric and magnetic fields would induce higher current density in the child body than power frequency fields with similar field strength. PMID:17526911
NASA Astrophysics Data System (ADS)
Zhang, Zhen-Rong; Liu, Hong; Han, Bao-Shan
2002-06-01
The domain structure of (PtCoPt)/Si multilayers in the dc demagnetized state has been investigated by magnetic force microscopy. The domain structure is found to change dramatically as the thickness of the non-magnetic Si sublayer (tSi) increases. Together with the analysis of magnetic properties, the variation of the domain period indicates that the domain wall energy decreases. Using the model developed by Draaisma and de Jonge, the domain wall energy is obtained.
Kaidatzis, A; García-Martín, J M
2013-04-26
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
Dependence of the Black Body Force on Spacetime Geometry and Topology
Muniz, C R; Cunha, M S; Landim, R R; Filho, R N Costa
2015-01-01
In this manuscript we compute the corrections to the black body force due to spacetime geometry and topology. This recently discovered attractive force on neutral atoms is caused by the thermal radiation emitted from black bodies and here we investigate it in systems with spherical and cylindrical symmetries. For some astrophysical objects we find that the corrected force is greater than the flat case, showing that this kind of correction can be quite relevant when curved spaces are considered. Then we consider four cases: The Schwarzschild spacetime, the non-relativistic infinity cylinder, and both the static and stationary cosmic strings. For the spherically symmetric case we find that two corrections appear: One due to the gravitational modification of the temperature and the other due to the modification of the solid angle subtended by the atom. We apply the found results to a typical neutron star and to the Sun. For the cylindrical case, which is locally flat, no gravitational correction to the temperatu...
Quantitative magnetic resonance (QMR) measurement of changes in body composition of neonatal pigs
Technology Transfer Automated Retrieval System (TEKTRAN)
The survival of low birth weight pigs in particular may depend on energy stores in the body. QMR (quantitative magnetic resonance) is a new approach to measuring total body fat, lean and water. These measurements are based on quantifying protons associated with lipid and water molecules in the body...
Dual-body magnetic helical robot for drilling and cargo delivery in human blood vessels
NASA Astrophysics Data System (ADS)
Lee, Wonseo; Jeon, Seungmun; Nam, Jaekwang; Jang, Gunhee
2015-05-01
We propose a novel dual-body magnetic helical robot (DMHR) manipulated by a magnetic navigation system. The proposed DMHR can generate helical motions to navigate in human blood vessels and to drill blood clots by an external rotating magnetic field. It can also generate release motions which are relative rotational motions between dual-bodies to release the carrying cargos to a target region by controlling the magnitude of an external magnetic field. Constraint equations were derived to selectively manipulate helical and release motions by controlling external magnetic fields. The DMHR was prototyped and various experiments were conducted to demonstrate its motions and verify its manipulation methods.
Lorentz force time-optimal transfer trajectory design in Jovian magnetic field
NASA Astrophysics Data System (ADS)
Zhang, Zhiguo; Gong, Shengping; Li, Junfeng
2015-02-01
In this paper, the Lorentz force in Jupiter's magnetic field is used to design the transfer trajectory between Galileo moons' Lagrange points. The equatorial orbits of charged spacecraft in three-body axis-aligned nontilted-dipole magnetic field model are analyzed and the results show that the libration point L1 and L2 become nearer or further away from Europa with the variable size and polarity of the charge. The bang-bang charge control with the variable size and polarity of the charge can be used to change orbit's direction and shape. Analytical and numerical iteration methods give the fast and accurate bang-bang charge control to send the spacecraft to the L2 point of Europa, respectively. Finally, two numerical methods, the indirect and direct methods, give the time-optimal charge controls which are similar to but different from the semi-revolution variable polarity control maneuver. The optimal results achieve the final position and the flight angle at the same time, and need less time and less magnitude of charge compared with the numerical iteration method.
Chen, Qian Nataly; Ma, Feiyue; Xie, Shuhong; Liu, Yuanming; Proksch, Roger; Li, Jiangyu
2013-07-01
Accurate scanning probing of magnetic materials at the nanoscale is essential for developing and characterizing magnetic nanostructures, yet quantitative analysis is difficult using the state of the art magnetic force microscopy, and has limited spatial resolution and sensitivity. In this communication, we develop a novel piezomagnetic force microscopy (PmFM) technique, with the imaging principle based on the detection of magnetostrictive response excited by an external magnetic field. In combination with the dual AC resonance tracking (DART) technique, the contact stiffness and energy dissipation of the samples can be simultaneously mapped along with the PmFM phase and amplitude, enabling quantitative probing of magnetic materials and structures at the nanoscale with high sensitivity and spatial resolution. PmFM has been applied to probe magnetic soft discs and cobalt ferrite thin films, demonstrating it as a powerful tool for a wide range of magnetic materials. PMID:23720016
Linear stability of a circular Couette flow under a radial thermoelectric body force.
Yoshikawa, H N; Meyer, A; Crumeyrolle, O; Mutabazi, I
2015-03-01
The stability of the circular Couette flow of a dielectric fluid is analyzed by a linear perturbation theory. The fluid is confined between two concentric cylindrical electrodes of infinite length with only the inner one rotating. A temperature difference and an alternating electric tension are applied to the electrodes to produce a radial dielectrophoretic body force that can induce convection in the fluid. We examine the effects of superposition of this thermoelectric force with the centrifugal force including its thermal variation. The Earth's gravity is neglected to focus on the situations of a vanishing Grashof number such as microgravity conditions. Depending on the electric field strength and of the temperature difference, critical modes are either axisymmetric or nonaxisymmetric, occurring in either stationary or oscillatory states. An energetic analysis is performed to determine the dominant destabilizing mechanism. When the inner cylinder is hotter than the outer one, the circular Couette flow is destabilized by the centrifugal force for weak and moderate electric fields. The critical mode is steady axisymmetric, except for weak fields within a certain range of the Prandtl number and of the radius ratio of the cylinders, where the mode is oscillatory and axisymmetric. The frequency of this oscillatory mode is correlated with a Brunt-Väisälä frequency due to the stratification of both the density and the electric permittivity of the fluid. Under strong electric fields, the destabilization by the dielectrophoretic force is dominant, leading to oscillatory nonaxisymmetric critical modes with a frequency scaled by the frequency of the inner-cylinder rotation. When the outer cylinder is hotter than the inner one, the instability is again driven by the centrifugal force. The critical mode is axisymmetric and either steady under weak electric fields or oscillatory under strong electric fields. The frequency of the oscillatory mode is also correlated with the Brunt-Väisälä frequency. PMID:25871198
Linear stability of a circular Couette flow under a radial thermoelectric body force
NASA Astrophysics Data System (ADS)
Yoshikawa, H. N.; Meyer, A.; Crumeyrolle, O.; Mutabazi, I.
2015-03-01
The stability of the circular Couette flow of a dielectric fluid is analyzed by a linear perturbation theory. The fluid is confined between two concentric cylindrical electrodes of infinite length with only the inner one rotating. A temperature difference and an alternating electric tension are applied to the electrodes to produce a radial dielectrophoretic body force that can induce convection in the fluid. We examine the effects of superposition of this thermoelectric force with the centrifugal force including its thermal variation. The Earth's gravity is neglected to focus on the situations of a vanishing Grashof number such as microgravity conditions. Depending on the electric field strength and of the temperature difference, critical modes are either axisymmetric or nonaxisymmetric, occurring in either stationary or oscillatory states. An energetic analysis is performed to determine the dominant destabilizing mechanism. When the inner cylinder is hotter than the outer one, the circular Couette flow is destabilized by the centrifugal force for weak and moderate electric fields. The critical mode is steady axisymmetric, except for weak fields within a certain range of the Prandtl number and of the radius ratio of the cylinders, where the mode is oscillatory and axisymmetric. The frequency of this oscillatory mode is correlated with a Brunt-Väisälä frequency due to the stratification of both the density and the electric permittivity of the fluid. Under strong electric fields, the destabilization by the dielectrophoretic force is dominant, leading to oscillatory nonaxisymmetric critical modes with a frequency scaled by the frequency of the inner-cylinder rotation. When the outer cylinder is hotter than the inner one, the instability is again driven by the centrifugal force. The critical mode is axisymmetric and either steady under weak electric fields or oscillatory under strong electric fields. The frequency of the oscillatory mode is also correlated with the Brunt-Väisälä frequency.
Walker, Thomas K., III
2009-01-01
This thesis presents a methodology for development of a body force database, from design conditions to flows below the stall point, for compressor stability analysis. The methodology is based on two-dimensional blade element ...
NASA Astrophysics Data System (ADS)
Zhang, Junfang; Todd, B. D.
2004-03-01
We present a derivation of the pressure tensor and heat flux vector for inhomogeneous fluids under the influence of three-body forces. The derivation is based on the method of planes formalism of Todd, Evans, and Daivis [Phys. Rev. E 52, 1627 (1995); 51, 4362 (1995)]. Our derivation is validated against nonequilibrium molecular dynamics simulations of a confined fluid acted upon by a two-body Barker-Fisher-Watts force coupled with the Axilrod-Teller three-body force. Our method of planes calculations agree perfectly with the equivalent mesoscopic route of integrating the momentum and energy continuity equations directly from the simulation data. Our calculations reveal that three-body forces have an important consequence for the isotropic pressure, but have negligible influence on the shear stress (hence viscosity) and heat flux vector (hence thermal conductivity) for a confined simple fluid.
Magnetic Force Driven Nanogenerators as a Noncontact Energy Harvester and Sensor
Wang, Zhong L.
Magnetic Force Driven Nanogenerators as a Noncontact Energy Harvester and Sensor Nuanyang Cui Supporting Information ABSTRACT: Nanogenerator has been a very important energy harvesting technology through nanogenerator (CLNG), which avoids the direct contact between nanogenerator and mechanical movement source
Constraint Force Equation Methodology for Modeling Multi-Body Stage Separation Dynamics
NASA Technical Reports Server (NTRS)
Toniolo, Matthew D.; Tartabini, Paul V.; Pamadi, Bandu N.; Hotchko, Nathaniel
2008-01-01
This paper discusses a generalized approach to the multi-body separation problems in a launch vehicle staging environment based on constraint force methodology and its implementation into the Program to Optimize Simulated Trajectories II (POST2), a widely used trajectory design and optimization tool. This development facilitates the inclusion of stage separation analysis into POST2 for seamless end-to-end simulations of launch vehicle trajectories, thus simplifying the overall implementation and providing a range of modeling and optimization capabilities that are standard features in POST2. Analysis and results are presented for two test cases that validate the constraint force equation methodology in a stand-alone mode and its implementation in POST2.
Quantum Monte Carlo calculations of neutron matter with chiral three-body forces
Tews, I; Gezerlis, A; Schwenk, A
2015-01-01
Chiral effective field theory (EFT) enables a systematic description of low-energy hadronic interactions with controlled theoretical uncertainties. For strongly interacting systems, quantum Monte Carlo (QMC) methods provide some of the most accurate solutions, but they require as input local potentials. We have recently constructed local chiral nucleon-nucleon (NN) interactions up to next-to-next-to-leading order (N$^2$LO). Chiral EFT naturally predicts consistent many-body forces. In this paper, we consider the leading chiral three-nucleon (3N) interactions in local form. These are included in auxiliary field diffusion Monte Carlo (AFDMC) simulations. We present results for the equation of state of neutron matter and for the energies and radii of neutron drops. In particular, we study the regulator dependence at the Hartree-Fock level and in AFDMC and find that present local regulators lead to less repulsion from 3N forces compared to the usual nonlocal regulators.
The Role of Three-Nucleon Forces and Many-Body Processes in Nuclear Pairing
Holt, Jason D. [Technische Univ. Darmstadt/GSI/UTK/ORNL; Menendez, J. [Technische Univ. Darmstadt/GSI Helmholtzzentrum fur Schweionenforschung, Germany; Schwenk, A. [Technische Univ. Darmstadt/GSI Helmholtzzentrum fur Schweionenforschung, Germany
2013-01-01
We present microscopic valence-shell calculations of pairing gaps in the calcium isotopes, focusing on the role of three-nucleon (3N) forces and manybody processes. In most cases, we find a reduction in pairing strength when the leading chiral 3N forces are included, compared to results with lowmomentum two-nucleon (NN) interactions only. This is in agreement with a recent energy density functional study. At the NN level, calculations that include particle particle and hole hole ladder contributions lead to smaller pairing gaps compared with experiment. When particle hole contributions as well as the normal-ordered one- and two-body parts of 3N forces are consistently included to third order, we find reasonable agreement with experimental three-point mass differences. This highlights the important role of 3N forces and manybody processes for pairing in nuclei. Finally, we relate pairing gaps to the evolution of nuclear structure in neutron-rich calcium isotopes and study the predictions for the 2+ excitation energies, in particular for 54Ca.
Verification of a Constraint Force Equation Methodology for Modeling Multi-Body Stage Separation
NASA Technical Reports Server (NTRS)
Tartabini, Paul V.; Roithmayr, Carlos; Toniolo, Matthew D.; Karlgaard, Christopher; Pamadi, Bandu N.
2008-01-01
This paper discusses the verification of the Constraint Force Equation (CFE) methodology and its implementation in the Program to Optimize Simulated Trajectories II (POST2) for multibody separation problems using three specially designed test cases. The first test case involves two rigid bodies connected by a fixed joint; the second case involves two rigid bodies connected with a universal joint; and the third test case is that of Mach 7 separation of the Hyper-X vehicle. For the first two cases, the POST2/CFE solutions compared well with those obtained using industry standard benchmark codes, namely AUTOLEV and ADAMS. For the Hyper-X case, the POST2/CFE solutions were in reasonable agreement with the flight test data. The CFE implementation in POST2 facilitates the analysis and simulation of stage separation as an integral part of POST2 for seamless end-to-end simulations of launch vehicle trajectories.
Nuclear Pairing from Two-body Microscopic Forces: Analysis of the Cooper Pair Wavefunctions
Finelli, P; Holt, J W
2014-01-01
In a recent paper we studied the behavior of the pairing gaps $\\Delta_F$ as a function of the Fermi momentum $k_F$ for neutron and nuclear matter in all relevant angular momentum channels where superfluidity is believed to naturally emerge. The calculations employed realistic chiral nucleon-nucleon potentials with the inclusion of three-body forces and self-energy effects. In this contribution, after a detailed description of the numerical method we employed in the solution of the BCS equations, we will show a preliminary analysis of the Cooper pair wavefunctions.
Nuclear pairing from two-body microscopic forces: analysis of the Cooper pair wavefunctions
NASA Astrophysics Data System (ADS)
Finelli, P.; Maurizio, S.; Holt, J. W.
2015-05-01
In a recent paper [1] we studied the behavior of the pairing gaps ?F as a function of the Fermi momentum kF for neutron and nuclear matter in all relevant angular momentum channels where superfluidity is believed to naturally emerge. The calculations employed realistic chiral nucleon-nucleon potentials [2, 3] with the inclusion of three-body forces and self-energy effects. In this contribution, after a detailed description of the numerical method we employed in the solution of the BCS equations, we will show a preliminary analysis of the Cooper pair wavefunctions.
Nuclear Pairing from Two-body Microscopic Forces: Analysis of the Cooper Pair Wavefunctions
P. Finelli; S. Maurizio; J. W. Holt
2014-11-27
In a recent paper we studied the behavior of the pairing gaps $\\Delta_F$ as a function of the Fermi momentum $k_F$ for neutron and nuclear matter in all relevant angular momentum channels where superfluidity is believed to naturally emerge. The calculations employed realistic chiral nucleon-nucleon potentials with the inclusion of three-body forces and self-energy effects. In this contribution, after a detailed description of the numerical method we employed in the solution of the BCS equations, we will show a preliminary analysis of the Cooper pair wavefunctions.
Cluster variational method for nuclear matter with the three-body force
Takano, M.; Togashi, H.; Yamamuro, S.; Nakazato, K.; Suzuki, H. [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 Japan and Department of Physics and Applied Physics, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Department of Physics and Applied Physics, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo 169-8555 (Japan); Department of Physics, Faculty of Science and Technology, Tokyo University of Science, Yamazaki 2641, Noda, Chiba 278-8510 (Japan)
2012-11-12
We report the current status of our project to construct a new nuclear equation of state (EOS), which may be used for supernova numerical simulations, based on the cluster variational method starting from the realistic nuclear Hamiltonian. We also take into account a higher-order correction to the energy of the nuclear three-body force (TBF). The nuclear EOSs with and without the higher-order TBF correction at zero temperature are very close to each other, when parameters are readjusted so as to reproduce the empirical saturation data.
2D PIC Simulations of Collisionless Magnetic Reconnection for a Force-Free Current Sheet
NASA Astrophysics Data System (ADS)
Wilson, F.; Neukirch, T.; Hesse, M.
2014-12-01
We will present some results of two-dimensional particle-in-cell simulations of magnetic reconnection, starting from a recently found collisionless force-free current sheet equilibrium (for the force-free Harris sheet). A number of features will be discussed, such as the time evolution of the electron pressure tensor, magnetic and electric fields, current density, and reconnection rate. These features are compared with those from a Harris sheet plus guide field simulation.
Motion of small bodies in general relativity: foundations and implementations of the self-force
NASA Astrophysics Data System (ADS)
Pound, Adam
2010-06-01
Extreme mass-ratio inspirals, in which solar-mass compact bodies spiral into supermassive black holes, are an important potential source for gravitational wave detectors. Because of the extreme mass-ratio, one can model these systems using perturbation theory. However, in order to relate the motion of the small body to the emitted waveform, one requires a model that is accurate on extremely long timescales. Additionally, in order to avoid intractable divergences, one requires a model that treats the small body as asymptotically small rather than exactly pointlike. Both of these difficulties can be resolved by using techniques of singular perturbation theory. I begin this dissertation with an analysis of singular perturbation theory on manifolds, including the common techniques of matched asymptotic expansions and two-timescale expansions. I then formulate a systematic asymptotic expansion in which the metric perturbation due to the body is expanded while a representative worldline is held fixed, and I contrast it with a regular expansion in which both the metric and the worldline must be expanded. This results in an approximation that is potentially uniformly accurate on long timescales. The equation of motion for the body's fixed worldline is determined by performing a local-in-space expansion in the neighbourhood of the body. Using this local expansion as boundary data, I construct a global solution to the perturbative Einstein equation. To concretely characterize orbits, I next devise a relativistic generalization of the Newtonian method of osculating orbits. Making use of this method and two-timescale expansions, I examine the utility of adiabatic approximations that can forgo an explicit calculation of the force.
NASA Astrophysics Data System (ADS)
Phophongviwat, Teeraphon
Transformer noise is of increasing environmental concern so continued efforts are being made by electrical steel and transformer producers to satisfy users by reducing the noise. Magnetostriction and magnetic forces are the main causes of transformer core noise and vibration. Understanding of the relationship from the core material to core structure and core vibration to core noise can help the design of low noise transformer cores. The most appropriate parameter for investigating the relationship between noise and vibration is sound pressure (in the unit of Pascals) in the frequency domain because it is not A-weighted. In this study, the side surfaces of transformer cores were found to emit higher noise than front and top surfaces at low magnetic induction. When the magnetic induction was increased, the effect of magnetic force increased and caused the front surfaces to emit higher noise. For three phase three limb transformer cores, the front surface of the middle limb generated higher noise than the outer limbs due to the effect of T-joint. However this does not translate higher noise level because of the phase difference of the vibration between the limbs. Due to this A-weighted sound power level of three phase, three limb transformer cores were shown to be lower than single phase transformer cores, although at the same cross sectional area and core window size the three phase cores has larger size.. A model, developed to separate the effects of magnetostriction and magnetic forces on transformer core vibration, showed that at low induction, magnetostriction is more significant than magnetic forces. The magnetic forces become more significant than magnetostriction when the induction is increased. Magnetostriction primarily depends on material and stress but magnetic forces principally depend on core building. Louder noise can be generated from a core built with low magnetostriction material than higher magnetostriction if the building tolerances are worse. The effect of magnetic forces on transformer core vibration can be reduced by using a bonding technique..
Donato Bini; Thibault Damour
2014-09-24
Tidal interactions have a significant influence on the late dynamics of compact binary systems, which constitute the prime targets of the upcoming network of gravitational-wave detectors. We refine the theoretical description of tidal interactions (hitherto known only to the second post-Newtonian level) by extending our recently developed analytic self-force formalism, for extreme mass-ratio binary systems, to the computation of several tidal invariants. Specifically, we compute, to linear order in the mass ratio and to the 7.5$^{\\rm th}$ post-Newtonian order, the following tidal invariants: the square and the cube of the gravitoelectric quadrupolar tidal tensor, the square of the gravitomagnetic quadrupolar tidal tensor, and the square of the gravitoelectric octupolar tidal tensor. Our high-accuracy analytic results are compared to recent numerical self-force tidal data by Dolan et al. \\cite{Dolan:2014pja}, and, notably, provide an analytic understanding of the light ring asymptotic behavior found by them. We transcribe our kinematical tidal-invariant results in the more dynamically significant effective one-body description of the tidal interaction energy. By combining, in a synergetic manner, analytical and numerical results, we provide simple, accurate analytic representations of the global, strong-field behavior of the gravitoelectric quadrupolar tidal factor. A striking finding is that the linear-in-mass-ratio piece in the latter tidal factor changes sign in the strong-field domain, to become negative (while its previously known second post-Newtonian approximant was always positive). We, however, argue that this will be more than compensated by a probable fast growth, in the strong-field domain, of the nonlinear-in-mass-ratio contributions in the tidal factor.
NASA Astrophysics Data System (ADS)
Lee, C. I.; Jang, G. H.
2009-04-01
Uneven magnetization of permanent magnets (PMs) is one of the major sources of unbalanced magnetic force and torque ripple, which excite a brushless dc (BLDC) motor. This paper investigates the frequency contents of the back electromotive force (BEMF) due to the unevenly magnetized PMs in a BLDC motor. The magnetic field of a BLDC motor is solved by using the finite element method, and the BEMF is calculated by differentiating the flux linkage with respect to time. The characteristics of BEMF are investigated by using the spectral analysis. Magnetic flux density of the ideally magnetized PMs has the harmonics of the pole-pair number, but unevenly magnetized PMs generate the additional harmonics. This research shows numerically and experimentally that the frequency components of the BEMF are determined by the least common multiple between the frequency contents of magnetic flux density from the PMs and the slot number per phase. It also shows that the magnetized status of the PMs of a BLDC can be noninvasively identified by monitoring the frequencies and the amplitudes of BEMF.
Urethral foreign body: removal of degraded magnetic spheres using Hartmann ear forceps.
Chung, Paul H; Traylor, Janelle; Baker, Linda A
2014-11-01
Lower urinary tract foreign bodies have been reported in both children and adults. It is helpful for urologists to review foreign body case reports to become familiar with alternative approaches for removal that may prove helpful during challenging cases. To our knowledge, we describe for the first time a degraded rare-earth magnet within the body and use of Hartmann ear forceps to remove a foreign body from the urethra under cystoscopic guidance through a limited urethrotomy. PMID:25443938
Observations on high-anisotropy single crystals using a combined Kerr/magnetic force microscope
NASA Astrophysics Data System (ADS)
Rave, W.; Zueco, E.; Schäfer, R.; Hubert, A.
1998-01-01
A magnetic force sensor was integrated into the objective revolver of an optical polarization microscope. The instrument was tested on a wedge-shaped Co single crystal and on branched NdFeB domains. The combination of force and Kerr microscopy on identical domains gives access to a new interpretation of MFM contrasts. Three contrast mechanisms are proposed to interpret the observations.
Many-body Interactions in Magnetic Films and Nanostructures
Stephen D. Kevan
2012-12-12
We describe results supported by DOE grant DE-FG02-04ER46158, which focused on magnetic interaction at surfaces, in thin films, and in metallic nanostructures. We report on three general topics: 1) The Rashba spin splitting at magnetic surfaces of rare earth metals, 2) magnetic nanowires self-assembled on stepped tungsten single crystals, and 3) magnetic interaction in graphene films doped with hydrogen atoms.
Measured force on elongated bodies in a simulated low-Earth orbit environment
NASA Astrophysics Data System (ADS)
Maldonado, C. A.; Ketsdever, A. D.; Gimelshein, S. F.
2014-12-01
An overview of the development of a magnetically filtered atomic oxygen plasma source and the application of the source to study low-Earth orbit drag on elongated bodies is presented. Plasma diagnostics show that the magnetic filter plasma source produces atomic oxygen ions (O+) with streaming energies equivalent to the relative orbital environment of approximately 5eV and can supply the appropriate density for LEO simulation. Previous research has demonstrated that momentum transfer between ions and metal surfaces is equivalent to the momentum transfer expected for neutral molecules with similar energy, due to charge exchange occurring prior to momentum transfer. Total drag measurements of aluminum cuboid geometries of varying length to diameter ratios immersed in the extracted plasma plume are presented as a function of streaming ion energy.
Linear force-free magnetic fields for solar extrapolation and interpretation
NASA Technical Reports Server (NTRS)
Gary, G. Allen
1989-01-01
This paper discusses the interconnection of the various linear force-free magnetic field formulations, the specific phenomenological and topological parameters of these formulations, and their usefulness. Particularly, the limitations and usefulness of linear force-free fields are discussed. Specific field configurations are related to magnetographic interpretation. The relationship of the integral and Fourier procedures is shown explicitly. The physical interpretation of linear force-free fields is shown by analytic models and from the Marshall Space Flight Center solar vector magnetograms.
Fayol, D; Frasca, G; Le Visage, C; Gazeau, F; Luciani, N; Wilhelm, C
2013-05-14
Magnetic forces induce cell condensation necessary for stem cell differentiation into cartilage and elicit the formation of a tissue-like structure: Magnetically driven fusion of aggregates assembled by micromagnets results in the formation of a continuous tissue layer containing abundant cartilage matrix. PMID:23526452
Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits
Campbell, Ann. N. (13170-B Central SE #188, Albuquerque, NM 87123); Anderson, Richard E. (2800 Tennessee NE, Albuquerque, NM 87110); Cole, Jr., Edward I. (2116 White Cloud NE, Albuquerque, NM 87112)
1995-01-01
A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits.
Magnetic force microscopy method and apparatus to detect and image currents in integrated circuits
Campbell, A.N.; Anderson, R.E.; Cole, E.I. Jr.
1995-11-07
A magnetic force microscopy method and improved magnetic tip for detecting and quantifying internal magnetic fields resulting from current of integrated circuits are disclosed. Detection of the current is used for failure analysis, design verification, and model validation. The interaction of the current on the integrated chip with a magnetic field can be detected using a cantilevered magnetic tip. Enhanced sensitivity for both ac and dc current and voltage detection is achieved with voltage by an ac coupling or a heterodyne technique. The techniques can be used to extract information from analog circuits. 17 figs.
H Seidel; R Blüthner; B Hinz
2001-01-01
Objective. To predict forces acting on the spine during whole-body vibration for a variety of boundary conditions body mass, height and posture.Design. Representative anthropometric data and models for an upright, relaxed and bent forward sitting posture were used to derive model families with 30 variants of a finite-element model.Background. A given exposure to whole-body vibration can cause a variable
Wang, Wencui; Bottauscio, Oriano; Chiampi, Mario; Giordano, Domenico; Zilberti, Luca
2013-04-01
The paper proposes and discusses a boundary element procedure able to predict the distribution of the electric field induced in a human body exposed to a low-frequency magnetic field produced by unknown sources. As a first step, the magnetic field on the body surface is reconstructed starting from the magnetic field values detected on a closed surface enclosing the sources. Then, the solution of a boundary value problem provides the electric field distribution inside the human model. The procedure is tested and validated by considering different non-uniform magnetic field distributions generated by a Helmholtz coil system as well as different locations of the human model. PMID:22899216
A long-lived coronal X-ray arcade. [force-free magnetic field analysis
NASA Technical Reports Server (NTRS)
Mcguire, J. P.; Tandberg-Hanssen, E.; Krall, K. R.; Wu, S. T.; Smith, J. B., Jr.; Speich, D. M.
1977-01-01
A large, long-lived, soft X-ray emitting arch system observed during a Skylab mission is analyzed. The supposition is that these arches owe their stability to the stable coronal magnetic-field configuration. A global constant alpha force-free magnetic field analysis, is used to describe the arches which stayed in the same approximate position for several solar rotations. A marked resemblance is noted between the theoretical magnetic field configuration and the observed X-ray emmitting feature.
Guidance force in an infinitely long superconductor and permanent magnetic guideway system
NASA Astrophysics Data System (ADS)
Wang, Xiaorong; Ren, Zhongyou; Song, Honghai; Wang, Xingzhi; Zheng, Jun; Wang, Suyu; Wang, Jiasu; Zhao, Yong
2005-02-01
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.
Magnetic damping forces in figure-eight-shaped null-flux coil suspension systems
He, Jianliang; Coffey, H.
1997-08-01
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.
NASA Astrophysics Data System (ADS)
Pankoke, S.; Buck, B.; Woelfel, H. P.
1998-08-01
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 spineespecially in the three lower vertebraehas 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.
Messina, Riccardo [LNE-SYRTE, Observatoire de Paris, CNRS UMR 8630, UPMC, 61 avenue de l'Observatoire, F-75014 Paris (France); Antezza, Mauro [Universite Montpellier 2, Laboratoire Charles Coulomb UMR 5221, F-34095, Montpellier (France); CNRS, Laboratoire Charles Coulomb UMR 5221, F-34095, Montpellier (France)
2011-10-15
We study the radiative heat transfer and the Casimir-Lifshitz force occurring between two bodies in a system out of thermal equilibrium. We consider bodies of arbitrary shape and dielectric properties, held at two different temperatures and immersed in environmental radiation at a third different temperature. We derive explicit closed-form analytic expressions for the correlations of the electromagnetic field and for the heat transfer and Casimir-Lifshitz force in terms of the bodies' scattering matrices. We then consider some particular cases which we investigate in detail: the atom-surface and the slab-slab configurations.
On the force relaxation in the magnetic levitation system with a high-Tc superconductor
NASA Astrophysics Data System (ADS)
Smolyak, B. M.; Zakharov, M. S.
2014-05-01
The effect of magnetic flux creep on the lift force in a magnet/superconductor system was studied. It was shown experimentally that in the case of real levitation (when a levitating object bears only on a magnetic field) the suspension height and consequently the lift force did not change over a long period of time. When the levitating object is fixed for some time (i.e. a rigid constraint is imposed on it), the levitation height decreases after removal of the external constraint. It is assumed that free oscillations of the levitating object slow down the flux creep process, which is activated when these oscillations are suppressed.
Magnetic Circuit Model of PM Motor-Generator to Predict Radial Forces
NASA Technical Reports Server (NTRS)
McLallin, Kerry (Technical Monitor); Kascak, Peter E.; Dever, Timothy P.; Jansen, Ralph H.
2004-01-01
A magnetic circuit model is developed for a PM motor for flywheel applications. A sample motor is designed and modeled. Motor configuration and selection of materials is discussed, and the choice of winding configuration is described. A magnetic circuit model is described, which includes the stator back iron, rotor yoke, permanent magnets, air gaps and the stator teeth. Iterative solution of this model yields flux linkages, back EMF, torque, power, and radial force at the rotor caused by eccentricity. Calculated radial forces are then used to determine motor negative stiffness.
NASA Astrophysics Data System (ADS)
Gómez-Medina, R.; García-Cámara, B.; Suárez-Lacalle, I.; Froufe-Pérez, L. S.; González, F.; Moreno, F.; Nieto-Vesperinas, M.; Sáenz, J. J.
2011-10-01
Nanospheres made of non-magnetic materials are shown to present non-conventional scattering properties similar to those previously reported for somewhat hypothetical magnetodielectric particles. We find a wide window in the near-infrared, where light scattering by lossless submicrometer semiconductor nanospheres is fully described by their induced electric and magnetic dipoles. The interference between electric and magnetic dipolar fields is shown to lead to anisotropic angular distributions of scattered intensity, including zero backward and almost zero forward scattered intensities at specific wavelengths. Optical forces, arising in the intersection region of two standing waves, lead to a complex force field that can rectify the flow of magnetodielectric particles.
NASA Astrophysics Data System (ADS)
Garshelis, I. J.; Crevecoeur, G.
2014-05-01
Non oriented silicon steels are widely used within rotating electrical machines and are assumed to have no anisotropy. There exists a need to detect the anisotropic magnetic properties and to evaluate the local changes in magnetic material properties due to manufacturing cutting processes. In this paper, the so called moving magnet hyteresis comparator is applied to non destructively detect directional variations in coercive force in a variety of local regions of rotor and stator laminations of two materials commonly used to construct induction motors cores. Maximum to minimum coercive force ratios were assessed, varying from 1.4 to 1.7.
Magnus force and the inertial properties of magnetic vortices in weak ferromagnets
NASA Astrophysics Data System (ADS)
Zvezdin, A. K.; Zvezdin, K. A.
2010-08-01
The Magnus force (gyroscopic force) acting on magnetic vortices (Bloch lines) within domain boundaries in weak ferromagnets is discussed. A general formula is derived for the Magnus force in weak ferromagnets. The Magnus force is found to be nonzero for most types of domain boundaries and is determined by the average sublattice magnetization and the constants for the Dzyaloshinsky interaction and the exchange interaction between sublattices. Generalized expressions are obtained for the effective Lagrange and Rayleigh functions in weak ferromagnets taking their vortex structure into account. The question of the vortex mass, which has been found to be on the order of m*10-14g/cm in YFeO3, is discussed. The dynamic flexure of domain boundaries when moving vortices are present is analyzed. A formula is derived for the magnetic field dependence of the velocity of a vortex in a motionless domain boundary.
DNA Micromanipulation Using Novel High-Force, In-Plane Magnetic Tweezer
NASA Astrophysics Data System (ADS)
McAndrew, Christopher; Mehl, Patrick; Sarkar, Abhijit
2010-03-01
We report the development of a magnetic force transducer that can apply piconewton forces on single DNA molecules in the focus plane allowing continuous high precision tethered-bead tracking. The DNA constructs, proteins, and buffer are introduced into a 200?L closed cell created using two glass slides separated by rigid spacers interspersed within a thin viscoelastic perimeter wall. This closed cell configuration isolates our sample and produces low-noise force-extension measurements. Specially-drawn micropipettes are used for capturing the polystyrene bead, pulling on the magnetic sphere, introducing proteins of interest, and maintaining flow. Various high-precision micromanipulators allow us to move pipettes and stage as required. The polystyrene bead is first grabbed, and held using suction; then the magnetic particle at the other end of the DNA is pulled by a force created by either two small (1mm x 2mm x 4mm) bar magnets or a micro magnet-tipped pipette. Changes in the end-to-end length of the DNA are observable in real time. We will present force extension data obtained using the magnetic tweezer.
Comparison of seat belt force-limiting methods using the MADYMO multi-body/finite element program.
Sieveka, E M; Kent, R W; Crandall, J R
2001-01-01
Belt force can be limited by a device in the belt retractor hardware or with force-limiting as an integral part of the webbing force/strain properties. In this research, MADYMO multi-body/finite element models of a 50th percentile Hybrid-3 male passenger in an airbag-equipped 4-door mid-size sedan were set up to compare occupant injury response under loading 1) from a baseline standard (non-force-limiting) belt system, 2) from a retractor-based force-limiting system, and 3) from a webbing-based force-limiting system. Chest acceleration was similar for the two force-limiting designs but the peak was approximately 10% greater for the standard belt. The magnitude of the head acceleration was similar for all three belts while the duration of these accelerations was much narrower for the force-limiting belts. Chest compression was similar for both force-limiting methods, and was about 60% less than the standard belt case. Compared to the baseline system and the retractor-based system, webbing-based force-limiting allowed greater pelvic excursion and a corresponding increase in femur force. It is concluded that webbing-based force limiting has some potential for reducing head and chest responses but these reductions must be evaluated with respect to other considerations such as submarining potential, non-frontal impact response, and future concepts like programmable force limiting. PMID:12214345
Phase Diagrams of Forced Magnetic Reconnection in Taylor's Model
Comisso, L; Waelbroeck, F L
2015-01-01
Recent progress in the understanding of how externally driven magnetic reconnection evolves is organized in terms of parameter space diagrams. These diagrams are constructed using four pivotal dimensionless parameters: the Lundquist number $S$, the magnetic Prandtl number $P_m$, the amplitude of the boundary perturbation $\\hat \\Psi_0$, and the perturbation wave number $\\hat k$. This new representation highlights the parameters regions of a given system in which the magnetic reconnection process is expected to be distinguished by a specific evolution. Contrary to previously proposed phase diagrams, the diagrams introduced here take into account the dynamical evolution of the reconnection process and are able to predict slow or fast reconnection regimes for the same values of $S$ and $P_m$, depending on the parameters that characterize the external drive, never considered so far. These features are important to understand the onset and evolution of magnetic reconnection in diverse physical systems
Forced MHD turbulence in a uniform external magnetic field
NASA Technical Reports Server (NTRS)
Hossain, M.; Vahala, G.; Montgomery, D.
1985-01-01
Two-dimensional dissipative MHD turbulence is randomly driven at small spatial scales and is studied by numerical simulation in the presence of a strong uniform external magnetic field. A behavior is observed which is apparently distinct from the inverse cascade which prevails in the absence of an external magnetic field. The magnetic spectrum becomes dominated by the three longest wavelength Alfven waves in the system allowed by the boundary conditions: those which, in a box size of edge 2 pi, have wave numbers (kx' ky) = (1, 1), and (1, -1), where the external magnetic field is in the x direction. At any given instant, one of these three modes dominates the vector potential spectrum, but they do not constitute a resonantly coupled triad. Rather, they are apparently coupled by the smaller-scale turbulence.
Pricoupenko, Ludovic
2011-06-15
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.
Measurement of internal forces in superconducting accelerator magnets with strain gauge transducers
Goodzeit, C.L.; Anerella, M.D.; Ganetis, G.L.
1988-01-01
An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the compressive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made with a new system that eliminates sources of errors due to spurious resistance changes in interconnecting wiring and solder joints. The design of the transducers and their measurement system is presented along with a discussion of the method of compensation for thermal and magnetic effects, methods of calibration with typical calibration data, and measured effect in actual magnets of the thermal stress changes from cooldown and the Lorentz forces during magnet excitation. 13 figs., 1 tab.
Measurement of internal forces in superconducting accelerator magnets with strain gauge transducers
Goodzeit, C.L.; Anerella, M.D.; Ganetis, G.L.
1989-03-01
An improved method has been developed for the measurement of internal forces in superconducting accelerator magnets, in particular the compressive stresses in coils and the end restraint forces on the coils. The transducers have been designed to provide improved sensitivity to purely mechanical strain by using bending mode deflections for sensing the applied loads. Strain gauge resistance measurements are made with a new system that eliminates sources of errors due to spurious resistance changes in interconnecting wiring and solder joints. The design of the transducers and their measurement system is presented along with a discussion of the method of compensation for thermal and magnetic effects, methods of calibration with typical calibration data, and measured effects in actual magnets of the thermal stress changes from cooldown and the Lorentz forces during magnet excitation.
qPlus magnetic force microscopy in frequency-modulation mode with millihertz resolution
Wastl, Daniel; Giessibl, Franz J
2012-01-01
Summary Magnetic force microscopy (MFM) allows one to image the domain structure of ferromagnetic samples by probing the dipole forces between a magnetic probe tip and a magnetic sample. The magnetic domain structure of the sample depends on the alignment of the individual atomic magnetic moments. It is desirable to be able to image both individual atoms and domain structures with a single probe. However, the force gradients of the interactions responsible for atomic contrast and those causing domain contrast are orders of magnitude apart, ranging from up to 100 Nm?1 for atomic interactions down to 0.0001 Nm?1 for magnetic dipole interactions. Here, we show that this gap can be bridged with a qPlus sensor, with a stiffness of 1800 Nm?1 (optimized for atomic interaction), which is sensitive enough to measure millihertz frequency contrast caused by magnetic dipoledipole interactions. Thus we have succeeded in establishing a sensing technique that performs scanning tunneling microscopy, atomic force microscopy and MFM with a single probe. PMID:22428108
Approximating edges of source bodies from magnetic or gravity anomalies.
Blakely, R.J.; Simpson, R.W.
1986-01-01
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
A portable Halbach magnet that can be opened and closed without force: The NMR-CUFF
NASA Astrophysics Data System (ADS)
Windt, Carel W.; Soltner, Helmut; Dusschoten, Dagmar van; Blümler, Peter
2011-01-01
Portable equipment for nuclear magnetic resonance (NMR) is becoming increasingly attractive for use in a variety of applications. One of the main scientific challenges in making NMR portable is the design of light-weight magnets that possess a strong and homogeneous field. Existing NMR magnets can provide such magnetic fields, but only for small samples or in small regions, or are rather heavy. Here we show a simple yet elegant concept for a Halbach-type permanent magnet ring, which can be opened and closed with minimal mechanical force. An analytical solution for an ideal Halbach magnet shows that the magnetic forces cancel if the structure is opened at an angle of 35.3° relative to its poles. A first prototype weighed only 3.1 kg, and provided a flux density of 0.57 T with a homogeneity better than 200 ppm over a spherical volume of 5 mm in diameter without shimming. The force needed to close it was found to be about 20 N. As a demonstration, intact plants were imaged and water (xylem) flow measured. Magnets of this type (NMR-CUFF = Cut-open, Uniform, Force Free) are ideal for portable use and are eminently suited to investigate small or slender objects that are part of a larger or immobile whole, such as branches on a tree, growing fruit on a plant, or non-metallic tubing in industrial installations. This new concept in permanent-magnet design enables the construction of openable, yet strong and homogeneous magnets, which aside from use in NMR or MRI could also be of interest for applications in accelerators, motors, or magnetic bearings.
Extraction of user's navigation commands from upper body force interaction in walker assisted gait
2010-01-01
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 high-frequency noise caused by vibrations on the walker's structure due to irregularities on the terrain or walker's wheels and (ii) the cadence related force components caused by user's trunk oscillations during gait. As a result, a third component related to user's navigation commands is distinguished. Results For the cancelation of high-frequency noise, a Benedict-Bordner g-h filter was designed presenting very low values for Kinematic Tracking Error ((2.035 ą 0.358)ˇ10-2 kgf) and delay ((1.897 ą 0.3697)ˇ101ms). A Fourier Linear Combiner filtering architecture was implemented for the adaptive attenuation of about 80% of the cadence related components' energy from force data. This was done without compromising the information contained in the frequencies close to such notch filters. Conclusions The presented methodology offers an effective cancelation of the undesired components from force data, allowing the system to extract in real-time voluntary user's navigation commands. Based on this real-time identification of voluntary user's commands, a classical approach to the control architecture of the robotic walker is being developed, in order to obtain stable and safe user assisted locomotion. PMID:20687921
Magnetic Field, Force, and Inductance Computations for an Axially Symmetric Solenoid
NASA Technical Reports Server (NTRS)
Lane, John E.; Youngquist, Robert C.; Immer, Christopher D.; Simpson, James C.
2001-01-01
The pumping of liquid oxygen (LOX) by magnetic fields (B field), using an array of electromagnets, is a current topic of research and development at Kennedy Space Center, FL. Oxygen is paramagnetic so that LOX, like a ferrofluid, can be forced in the direction of a B field gradient. It is well known that liquid oxygen has a sufficient magnetic susceptibility that a strong magnetic gradient can lift it in the earth's gravitational field. It has been proposed that this phenomenon can be utilized in transporting (i.e., pumping) LOX not only on earth, but on Mars and in the weightlessness of space. In order to design and evaluate such a magnetic pumping system, it is essential to compute the magnetic and force fields, as well as inductance, of various types of electromagnets (solenoids). In this application, it is assumed that the solenoids are air wrapped, and that the current is essentially time independent.
Principle and Basic Characteristics of a Hybrid Variable-Magnetic-Force Motor
NASA Astrophysics Data System (ADS)
Sakai, Kazuto; Kuramochi, Satoru
Reduction in the power consumed by motors is important for energy saving in the case of electrical appliances and electric vehicles (EVs). The motors used for operating these devices operate at variable speeds. Further, the motors operate with a small load in the stationary mode and a large load in the starting mode. A permanent magnet motor can be operated at the rated power with a high efficiency. However, the efficiency is low at a small load or at a high speed because the large constant magnetic force results in substantial core loss. Furthermore, the flux-weakening current that decreases the voltage at a high speed leads to significant copper loss and core loss. Therefore, we have developed a new technique for controlling the magnetic force of a permanent magnet on the basis of the load or speed of the motor. In this paper, we propose a novel motor that can vary the magnetic flux of a permanent magnet and clarify the principle and basic characteristics of the motor. The new motor has a permanent magnet that is magnetized by the magnetizing coil of the stator. The analysis results show that the magnetic flux linkage of the motor can be changed from 37% to 100% that a high torque can be produced.
Long-lived magnetism from solidification-driven convection on the pallasite parent body.
Bryson, James F J; Nichols, Claire I O; Herrero-Albillos, Julia; Kronast, Florian; Kasama, Takeshi; Alimadadi, Hossein; van der Laan, Gerrit; Nimmo, Francis; Harrison, Richard J
2015-01-22
Palaeomagnetic measurements of meteorites suggest that, shortly after the birth of the Solar System, the molten metallic cores of many small planetary bodies convected vigorously and were capable of generating magnetic fields. Convection on these bodies is currently thought to have been thermally driven, implying that magnetic activity would have been short-lived. Here we report a time-series palaeomagnetic record derived from nanomagnetic imaging of the Imilac and Esquel pallasite meteorites, a group of meteorites consisting of centimetre-sized metallic and silicate phases. We find a history of long-lived magnetic activity on the pallasite parent body, capturing the decay and eventual shutdown of the magnetic field as core solidification completed. We demonstrate that magnetic activity driven by progressive solidification of an inner core is consistent with our measured magnetic field characteristics and cooling rates. Solidification-driven convection was probably common among small body cores, and, in contrast to thermally driven convection, will have led to a relatively late (hundreds of millions of years after accretion), long-lasting, intense and widespread epoch of magnetic activity among these bodies in the early Solar System. PMID:25612050
Magnetic energy dissipation in force-free jets
NASA Technical Reports Server (NTRS)
Choudhuri, Arnab Rai; Konigl, Arieh
1986-01-01
It is shown that a magnetic pressure-dominated, supersonic jet which expands or contracts in response to variations in the confining external pressure can dissipate magnetic energy through field-line reconnection as it relaxes to a minimum-energy configuration. In order for a continuous dissipation to occur, the effective reconnection time must be a fraction of the expansion time. The dissipation rate for the axisymmetric minimum-energy field configuration is analytically derived. The results indicate that the field relaxation process could be a viable mechanism for powering the synchrotron emission in extragalactic jets if the reconnection time is substantially shorter than the nominal resistive tearing time in the jet.
NASA Astrophysics Data System (ADS)
Somŕ, V.; Bo?ek, P.
2008-11-01
We present spectral calculations of nuclear matter properties including three-body forces. Within the in-medium T-matrix approach, implemented with the CD-Bonn and Nijmegen potentials plus the three-nucleon Urbana interaction, we compute the energy per particle in symmetric and neutron matter. The three-body forces are included via an effective density dependent two-body force in the in-medium T-matrix equations. After fine tuning the parameters of the three-body force to reproduce the phenomenological saturation point in symmetric nuclear matter, we calculate the incompressibility and the energy per particle in neutron matter. We find a soft equation of state in symmetric nuclear matter but a relatively large value of the symmetry energy. We study the the influence of the three-body forces on the single-particle properties. For symmetric matter the spectral function is broadened at all momenta and all densities, while an opposite effect is found for the case of neutrons only. Noticeable modification of the spectral functions are realized only for densities above the saturation density. The modifications of the self-energy and the effective mass are not very large and appear to be strongly suppressed above the Fermi momentum.
Fundamental Forces Two categories of forces
Hennon, Christopher C.
Fundamental Forces Two categories of forces: 1) Body forces Forces whose magnitudes change slightly as the distance between interacting bodies increases Example Gravitational force 2) Surface forces Result from molecular (small-scale) interactions along surface elements. Independent
NASA Astrophysics Data System (ADS)
Lee, Injae; Choi, Haecheon
2015-01-01
We present an immersed boundary (IB) method for the simulation of flow around an elastic slender body. The present method is based on the discrete-forcing IB method for a stationary, rigid body proposed by Kim, Kim and Choi (2001) [25]. The discrete-forcing approach is used to relieve the limitation on the computational time step size. The incompressible Navier-Stokes equations are implicitly coupled with the dynamic equation for an elastic slender body motion. The first is solved in the Eulerian coordinate and the latter is described in the Lagrangian coordinate. The elastic slender body is modeled as a thin and flexible solid and is segmented by finite number of thin blocks. Each block is moved by external and internal forces such as the hydrodynamic, elastic and buoyancy forces, where the hydrodynamic force is obtained directly from the discrete forcing used in the IB method. All the spatial derivative terms are discretized with the second-order central difference scheme. The present method is applied to three different fluid-structure interaction problems: flows around a flexible filament, a flapping flag in a free stream, and a flexible flapping wing in normal hovering, respectively. Computations are performed at maximum CFL numbers of 0.75-1. The results obtained agree very well with those from previous studies.
Resolving sub-cellular force dynamics using arrays of magnetic microposts
NASA Astrophysics Data System (ADS)
Reich, Daniel
2010-03-01
The biological response of cells to mechanical forces is integral to both normal cell function and the progression of many diseases, such as hypertensive vascular wall thickening. This likely results from the fact that mechanical stresses can directly affect many cellular processes, including signal transduction, gene expression, growth, differentiation, and survival. The need to understand the relationship between applied forces and the mechanical response of cells as a critical step towards understanding mechanotransduction calls for tools that can apply forces to cells while measuring their contractile response. This talk will describe an approach that simultaneously allows local mechanical stimulation of the adherent surface of a cell and spatially resolved measurement of the local force fields generated throughout the cell in response to this stimulation. Cells are cultured on the top surfaces of arrays of micrometer-scale posts made from a flexible elastomer (PDMS), and the contractile forces generated by an adherent cell bend the posts. Measurements of the displacement of each post allow the contractile force field of the cell to be mapped out with sub-cellular precision. To apply forces to cells, rod- shaped magnetic nanoparticles are embedded in some of the posts so that externally applied magnetic fields selectively deform these ``magnetic posts,'' thereby exerting tunable local, mechanical stresses to the adherent surface of attached cells. Alternatively, magnetic particles bound to or internalized by the cell may be employed to apply forces and torques to the cell. With either approach, measuring the deflection of the surrounding non-magnetic posts probes the full mechanical response of the cell to these stresses. Results that illustrate the temporal dynamics and spatial distribution of the non-local response of fibroblasts and smooth muscle cells to local stresses will be discussed.
A hybrid N-body code incorporating algorithmic regularization and post-Newtonian forces
NASA Astrophysics Data System (ADS)
Harfst, S.; Gualandris, A.; Merritt, D.; Mikkola, S.
2008-09-01
We describe a novel N-body code designed for simulations of the central regions of galaxies containing massive black holes. The code incorporates Mikkola's `algorithmic' chain regularization scheme including post-Newtonian terms up to PN2.5 order. Stars moving beyond the chain are advanced using a fourth-order integrator with forces computed on a GRAPE board. Performance tests confirm that the hybrid code achieves better energy conservation, in less elapsed time, than the standard scheme and that it reproduces the orbits of stars tightly bound to the black hole with high precision. The hybrid code is applied to two sample problems: the effect of finite-N gravitational fluctuations on the orbits of the S-stars, and inspiral of an intermediate-mass black hole into the Galactic Centre.
Hassel, C.; Stienen, S.; Roemer, F. M.; Meckenstock, R.; Dumpich, G.; Lindner, J. [Fachbereich Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, 47048 Duisburg (Germany)
2009-07-20
Magnetic domain walls are created in a controllable way in transversally magnetized epitaxial Fe wires on GaAs(110) by approaching a magnetic force microscope (MFM) tip. The electrical resistance-change due to the addition of these domain walls is measured. The anisotropic magnetoresistance as well as the intrinsic domain wall resistance contribute to the resistance-change. The efficiency of this procedure is proven by MFM images, which are obtained subsequent to the domain wall creation at a larger sample-to-probe distance. The contribution of the anisotropic magnetoresistance is calculated using micromagnetic calculations, thus making it possible to quantify the intrinsic domain wall resistance.
NASA Astrophysics Data System (ADS)
Gómez-Medina, R.; García-Cámara, B.; Suárez-Lacalle, I.; Froufe-Pérez, L. S.; González, F.; Moreno, F.; Nieto-Vesperinas, M.; Sáenz, J. J.
2012-10-01
Nanospheres made of non-magnetic materials are shown to present non-conventional scattering properties similar to those previously reported for somewhat hypothetical magnetodielectric particles. We find a wide window in the near-infrared, where light scattering by lossless submicrometer semiconductor nanospheres is fully described by their induced electric and magnetic dipoles. The interference between electric and magnetic dipolar fields is shown to lead to anisotropic angular distributions of scattered intensity, including zero backward and almost zero forward scattered intensities at specific wavelengths. Interesting new consequences for the corresponding optical forces are derived from the interplay, both in and out of resonance, between the electric- and magnetic-induced dipoles.
Aspiration from the vitreous of a non-magnetic foreign body.
Chawla, H B; Coleiro, J A; Jonasson, F
1978-11-01
A non-magnetic vitreal foreign body was aspirated from over the macula through the pars plana. The surgeon guided a blunt needle towards the foreign body while watching both with the binicular indirect ophthalmoscope. His assistant's tentative suction movements with an attached syringe drew the foreign body up into the needle without risking a retinal perforation. Visual recovery was complete. It is suggested that aspiration might be the procedure of choice for such small visible intraocular fragments. PMID:718819
Resonance motions of a nonsymmetric rigid body in a rotating magnetic field
NASA Astrophysics Data System (ADS)
Eropkina, T. A.
1984-12-01
In earlier studies (Martynenko, 1973, 1980), the stability of resonance stationary rotations of a rigid body in a magnetic field has been analyzed for dynamically symmetric and arbitrary bodies. Here, an analysis is presented for a body with an arbitrary ellipsoid of inertia whose angular velocity is close to the rotational velocity of the field. Averaged equations describing the behavior of the slow variables of the problem with allowance for resonance effects are obtained.
Morphology and Dynamics of Lithospheric Body Force Instabilities: Sheets, Drips and In-Between
NASA Astrophysics Data System (ADS)
Beall, A.; Moresi, L. N.
2014-12-01
Foundering of the Earth's lithosphere, and consequent energy and mass flux across the upper boundary layer and mantle interface, is driven locally by gravitational body forces. The related instabilities are usually classified as having sheet-like or drip-like morphologies. The former is associated with whole lithosphere (subduction) or delamination type foundering such as suggested for beneath the southern Sierra-Nevada and the Colorado Plateau, the latter to classic Rayleigh-Taylor instability below an upper layer, suggested to have occurred beneath the Tibetan Plateau and North Island, New Zealand. This dichotomy is non-trivial; classification of phenomena into one or the other is often debated and is difficult to infer from observables. The two morphologies are most likely end-members. Here I refine the dynamics driving morphology selection as a function of rheological lamination and boundary layer Rayleigh number in 2D and 3D, using the finite-element particle-in-cell code Underworld. I explore the influence of morphology on mass flux, topography and crustal deformation as well as deviation from classic 2D scalings. Additionally, tectonic displacement interference with instability development is discussed using basic 3D shear-box style models. By quantifying and describing the theoretical instability dynamics which could result in a plausible range of morphological expressions, I aim to build a general framework which can be paired to the discussion involving firstly, the recognition of varied styles of body force instabilities in the modern Earth and rock record and secondly, to what degree pattern selection impacts boundary layer mass and energy flux.
Thin-foil magnetic force system for high-numerical-aperture microscopy
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
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
ERIC Educational Resources Information Center
Gamble, Reed
1989-01-01
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)
Magnetic Evidence for a Partially Differentiated Carbonaceous Chondrite Parent Body
Shuster, David L.
The textures of chondritic meteorites demonstrate that they are not the products of planetary melting processes. This has long been interpreted as evidence that chondrite parent bodies never experienced large-scale melting. ...
Structure formation by a fifth force: N-body versus linear simulations
Li Baojiu; Zhao Hongsheng
2009-08-15
We lay out the frameworks to numerically study the structure formation in both linear and nonlinear regimes in general dark-matter-coupled scalar field models, and give an explicit example where the scalar field serves as a dynamical dark energy. Adopting parameters of the scalar field which yield a realistic cosmic microwave background (CMB) spectrum, we generate the initial conditions for our N-body simulations, which follow the spatial distributions of the dark matter and the scalar field by solving their equations of motion using the multilevel adaptive grid technique. We show that the spatial configuration of the scalar field tracks well the voids and clusters of dark matter. Indeed, the propagation of scalar degree of freedom effectively acts as a fifth force on dark matter particles, whose range and magnitude are determined by the two model parameters ({mu},{gamma}), local dark matter density as well as the background value for the scalar field. The model behaves like the {lambda}CDM paradigm on scales relevant to the CMB spectrum, which are well beyond the probe of the local fifth force and thus not significantly affected by the matter-scalar coupling. On scales comparable or shorter than the range of the local fifth force, the fifth force is perfectly parallel to gravity and their strengths have a fixed ratio 2{gamma}{sup 2} determined by the matter-scalar coupling, provided that the chameleon effect is weak; if on the other hand there is a strong chameleon effect (i.e., the scalar field almost resides at its effective potential minimum everywhere in the space), the fifth force indeed has suppressed effects in high density regions and shows no obvious correlation with gravity, which means that the dark-matter-scalar-field coupling is not simply equivalent to a rescaling of the gravitational constant or the mass of the dark matter particles. We show these spatial distributions and (lack of) correlations at typical redshifts (z=0,1,5.5) in our multigrid million-particle simulations. The viable parameters for the scalar field can be inferred on intermediate or small scales at late times from, e.g., weak lensing and phase space properties, while the predicted Hubble expansion and linearly simulated CMB spectrum are virtually indistinguishable from the standard {lambda}CDM predictions.
Zhu, Suming; Zhu, Huangqiu
2015-07-01
The control accuracy and dynamic performance of suspension force are confined in the traditional bearingless permanent magnet slice motor (BPMSM) control strategies because the suspension force control is indirectly achieved by adopting a closed loop of displacement only. Besides, the phase information in suspension force control relies on accurate measurement of rotor position, making the control system more complex. In this paper, a new suspension force control strategy with displacement and radial suspension force double closed loops is proposed, the flux linkage of motor windings is identified based on voltage-current model and the flexibility of motor control can be improved greatly. Simulation and experimental results show that the proposed suspension force control strategy is effective to realize the stable operation of the BPMSM. PMID:25840676
Gravo-Magnetic force in the MOND regime
Exirifard, Qasem
2013-01-01
We derive the gravomagnetic field in the dark matter and Modified Newtonian Dynamics (MOND) paradigms before showing that the the gravomagnetic force at the edge of a galaxy can be in accord with only one of them. We further notice that MOND alters the Lens-Thirring precession of a gyroscope in the semi-lagrange point of the Sun-Jupiter system. Near future technology may enable us to measure this anomaly.
Petrichenko, O; Erglis, K; C?bers, A; Plotniece, A; Pajuste, K; Béalle, G; Ménager, Ch; Dubois, E; Perzynski, R
2013-01-01
We synthesize giant magnetic liposomes by a reverse-phase evaporation method (REV) using a new self-assembling Cationic Pyridine Amphiphile (CPA) derived from 1,4-dihydropyridine as liposome-forming agent and a magnetic ferrofluid based on ?-Fe(2)O(3) nanoparticles. Having in view the potential interest of CPA in targeted transport by magnetic forces, the mechanical elastic properties of such bilayers are here directly investigated in vesicles loaded with magnetic nanoparticles. Bending elastic modulus K(b) ? 0.2 to 5k(B)T and pre-stress ? ? 3.2 to 12.10(-6) erg/cm(2) are deduced from the under-field deformations of the giant magnetic liposomes. The obtained K(b) values are discussed in terms of A. Wurgers's theory. PMID:23359032
Stetten, George
tool, because it permits both pulling and pushing at a smaller tip, which a magnet based pre-load force and stabilization system to permit both push and pull forces at the tip to be measured proximally within the handle
Magnetic field sensor based on the Ampere's force using dual-polarization DBR fiber laser
NASA Astrophysics Data System (ADS)
Yao, Shuang; Zhang, Yang; Guan, Baiou
2015-08-01
A novel magnetic field sensor using distributed Bragg reflector (DBR) fiber laser by Ampere's force effect is proposed and experimentally demonstrated. The key sensing element, that is the dual-polarization DBR fiber laser, is fixed on the middle part of two copper plates which carry the current. Ampere's force is applied onto the coppers due to an external magnetic field generated by a DC solenoid. Thus, the lateral force from the coppers is converted to a corresponding beat frequency signal shift produced by the DBR laser. The electric current sensing is also realized by the same configuration and same principle simultaneously in an intuitive manner. Good agreement between the theory calculation and the experimental results is obtained, which shows a good linearity. This sensor's sensitivity to the magnetic field and to the electric current finally reaches ~258.92 kHz/mT and ~1.08727 MHz/A, respectively.
NASA Astrophysics Data System (ADS)
Xiao, Jing; Ray Chaudhuri, Ritesh; Seo, Sang-Woo
2015-10-01
This paper demonstrates a fluidic assisted heterogeneous integration of optical thin-film device using surface tension as driving force and magnetic field as guiding force. Thin-film devices can be auto-aligned and integrated using surface tension onto their predesigned locations on a host substrate due to minimization of interfacial energy. By inserting a layer of nickel (Ni) into device metallization step, magnetic force was employed to increase mobility and contact probability of thin-film devices to their binding sites on the host substrate. A thin-film gallium arsenide (GaAs) inverted Metal-Semiconductor-Metal (MSM) photodetector (PD) has been successfully integrated onto a silicon host substrate with the proposed integration approach. The influence of the nickel layer to the PD performance was also investigated. Due to the self-assembly capability and thin-film format of the device, the proposed method has potential for wafer-scale implementation and is compatible with the matured silicon-based CMOS technology. This is a critical step towards a scalable manufacturing process to create advanced photonic/optoelectronic systems that are low-cost, compact, high performance, and complex in multi-material functionality.
Ramírez-Salgado, J. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Domínguez-Aguilar, M.A., E-mail: madoming@imp.mx [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Castro-Domínguez, B. [University of Tokyo, Department of Chemical System Engineering, Faculty of Engineering Bldg. 5, 7F 722, 7-3-1 Hongo, Bunkyo-ku, Tokyo 1138656 (Japan); Hernández-Hernández, P. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Newman, R.C. [University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Toronto M5S 3E5 (Canada)
2013-12-15
The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite was detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a ghosted effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA.
Magnetic tracking of acoustic radiation force-induced micro-order displacement.
Pavan, Theo Z; Almeida, Thiago W J; Carneiro, Antonio Adilton O
2011-05-01
The dynamic behavior of a rigid magnetic sphere induced by an acoustic radiation force was investigated. The sphere was suspended in water in a simple pendulum configuration. The drag force acting on the pendulum during its motion was considered to follow a modified Stokes law for a low Reynolds number, accounting for phenomena related to its oscillatory movement. Steady forces of long (a few seconds) and short (a few milliseconds) durations were used. The movement of the magnetic sphere was tracked using a magnetoresistive sensor. From the new equilibrium position of the sphere in response to the long-duration static radiation force, the amplitude of this force was estimated. To assess the water viscosity, the relaxation movement after the acoustic force had stopped was fitted to a harmonic-motion model. Based on the results for the acoustic force and water viscosity, a theoretical profile of the sphere's micro-order displacement as a function of time caused by short-duration acoustic radiation force agreed well with experimental results. PMID:21622046
Estimation of the total magnetization direction of approximately spherical bodies
NASA Astrophysics Data System (ADS)
Oliveira, V. C., Jr.; Sales, D. P.; Barbosa, V. C. F.; Uieda, L.
2014-09-01
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.
Navas, David
Ferromagnetic domain patterns and three-dimensional domain-wall configurations in thin CoCrPt films with perpendicular magnetic anisotropy were studied in detail by combining magnetic force microscopy and polarized neutron ...
Characteristics and computer model simulation of magnetic damping forces in maglev systems
He, J.L.; Rote, D.M.; Chen, S.S.
1994-05-01
This report discusses the magnetic damping force in electrodynamic suspension (EDS) maglev systems. The computer model simulations, which combine electrical system equations with mechanical motion equations on the basis of dynamic circuit theory, were conducted for a loop-shaped coil guideway. The intrinsic damping characteristics of the EDS-type guideway are investigated, and the negative damping phenomenon is confirmed by the computer simulations. The report also presents a simple circuit model to aid in understanding damping-force characteristics.
Effect of size on levitation force in a magnet/superconductor system
Yang, Z.J.; Hull, J.R.
1996-03-01
We consider a model system consisting of an infinitely long magnetic dipole line placed symmetrically above an infinitely long superconducting strip. Using the Meissner effect of superconductors, we derive analytical expressions of the levitation forces acting on the dipole line. At lowest-order approximation, we discuss the possible application of our model system to estimate the upper limit of the levitation forces in some magnetic bearing systems. In one example, the model correctly calculated the vertical vibration frequency of an experimental superconducting bearing.
Magnetic force systems in orthodontics. Clinical results of a pilot study.
Blechman, A M
1985-03-01
In this report, the initial results of magnetic force systems as applied to clinical orthodontics are presented. More particularly, the article describes the use of operator-controlled, small, permanent magnets for intermaxillary and intramaxillary mechanics. In addition to generating a force of sufficient intensity and duration, which is controlled by the operator, other advantages also became apparent. Good three-plane vector control independent of patient cooperation were observed in two patients. Both patients reported no discomfort during treatment. Extensive additional clinical testing is currently being conducted. PMID:3856394
NASA Astrophysics Data System (ADS)
Cristache, Cristian; Valiente-Blanco, Ignacio; Diez-Jimenez, Efren; Alvarez-Valenzuela, Marco Antonio; Pato, Nelson; Perez-Diaz, Jose Luis
2014-05-01
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.
Magnetic Resonance Force Microscopy of paramagnetic electron spins at millikelvin temperatures
A. Vinante; G. Wijts; O. Usenko; L. Schinkelshoek; T. H. Oosterkamp
2011-12-07
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.
Derivation of a pion-rho' exchange three-body force and application to the trinucleon system
NASA Astrophysics Data System (ADS)
Robilotta, M. R.; Filho, M. P. Isidro
1984-02-01
The pion-rho exchange three-body force is derived by means of lagrangians which are approximately invariant under chiral and gauge transformations. The leading contribution to the potential arises from a seagull diagram, which corresponds to forces that are dominantly repulsive and comparable to those due to the exchange of two pions. The qualitative features of our results are analysed by means of plots of the energy of the trinucleon system.
NASA Astrophysics Data System (ADS)
Klein, Olivier
2013-03-01
In this talk, we will discuss how magnetic-resonance force microscopy, can provide quantitative measurement of the power emitted by a spin-transfer nano-oscillator, consisting of a normally magnetized Py|Cu|Py circular nanopillar, excited both in the autonomous and forced regimes.[2] From the power behavior in the subcritical region of the autonomous dynamics, one obtains a quantitative measurement of the threshold current and of the noise level. Their field dependence directly yields both the spin torque efficiency acting on the thin layer and the nature of the mode which first auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. We will then demonstrate that the observed spin-wave spectrum in the forced regime critically depends on the method of excitation. While the spatially uniform radio-frequency (RF) magnetic field excites only the axially symmetric modes having azimuthal index l = 0 , the RF current flowing through the nano-pillar, creating a circular RF Oersted field, excites only the modes having azimuthal index l = + 1 .[3] It is then demonstrated that in order to phase lock this auto-oscillating mode, the external source must have the same spatial symmetry as the mode profile, i.e., a uniform microwave field must be used rather than a microwave current flowing through the nanopillar. In this talk, we will discuss how magnetic-resonance force microscopy, can provide quantitative measurement of the power emitted by a spin-transfer nano-oscillator, consisting of a normally magnetized Py|Cu|Py circular nanopillar, excited both in the autonomous and forced regimes.[2] From the power behavior in the subcritical region of the autonomous dynamics, one obtains a quantitative measurement of the threshold current and of the noise level. Their field dependence directly yields both the spin torque efficiency acting on the thin layer and the nature of the mode which first auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. We will then demonstrate that the observed spin-wave spectrum in the forced regime critically depends on the method of excitation. While the spatially uniform radio-frequency (RF) magnetic field excites only the axially symmetric modes having azimuthal index l = 0 , the RF current flowing through the nano-pillar, creating a circular RF Oersted field, excites only the modes having azimuthal index l = + 1 .[3] It is then demonstrated that in order to phase lock this auto-oscillating mode, the external source must have the same spatial symmetry as the mode profile, i.e., a uniform microwave field must be used rather than a microwave current flowing through the nanopillar. This research was partially supported by the French Grant Spinnova (ANR-11-NANO-0016)
Teodorescu, C.; Young, W. C.; Swan, G. W. S.; Ellis, R. F.; Hassam, A. B.; Romero-Talamas, C. A. [University of Maryland, College Park, Maryland 20742 (United States)
2010-08-20
Interferometric density measurements in plasmas rotating in shaped, open magnetic fields demonstrate strong confinement of plasma parallel to the magnetic field, with density drops of more than a factor of 10. Taken together with spectroscopic measurements of supersonic ExB rotation of sonic Mach 2, these measurements are in agreement with ideal MHD theory which predicts large parallel pressure drops balanced by centrifugal forces in supersonically rotating plasmas.
Focal transcranial magnetic stimulation and response bias in a forced-choice task
J. P. Brasil-neto; A Pascual-Leone; J Valls-Solé; L G Cohen; M Hallett
1992-01-01
The effects of transcranial magnetic stimulation were studied on the performance of a warned, forced-choice response time task by normal adults. The task consisted of extension of the index finger in response to the click produced by the discharge of the magnetic coil (go-signal). The subjects were asked to choose the right or left finger only after the go-signal was
Probing the Magnetic Forces in fcc-Fe(001) Films by Means of Surface Phonon Spectroscopy
Benedek, G.; Hulpke, E.; Steinhoegl, W.
2001-07-09
Helium atom scattering experiments on Fe films of a few monolayers grown on a Cu(001) substrate demonstrate that (a) in a magnetic film the interatomic magnetic forces can be directly probed from the temperature dependence of the Rayleigh wave frequency across the Curie temperature, and (b) the Rayleigh wave velocity and the topmost interlayer spacing, measured as a function of the film thickness, show a simultaneous 10% reduction at 3 to 4monolayers -- an indication of large magnetostrictive effects.
The dependence of the helicity bound of force-free magnetic fields on boundary conditions
Mei Zhang; Natasha Flyer
2008-05-13
This paper follows up on a previous study showing that in an open atmosphere such as the solar corona the total magnetic helicity of a force-free field must be bounded and the accumulation of magnetic helicity in excess of its upper bound would initiate a non-equilibrium situation resulting in an expulsion such as a coronal mass ejection (CME). In the current paper, we investigate the dependence of the helicity bound on the boundary condition for several families of nonlinear force-free fields. Our calculation shows that the magnitude of the helicity upper bound of force-free fields is non-trivially dependent on the boundary condition. Fields with a multipolar boundary condition can have a helicity upper bound ten times smaller than those with a dipolar boundary condition when helicity values are normalized by the square of their respective surface poloidal fluxes. This suggests that a coronal magnetic field may erupt into a CME when the applicable helicity bound falls below the already accumulated helicity as the result of a slowly changing boundary condition. Our calculation also shows that a monotonic accumulation of magnetic helicity can lead to the formation of a magnetic flux rope applicable to kink instability. This suggests that CME initiations by exceeding helicity bound and by kink instability can both be the consequences of helicity accumulation in the corona. Our study gives insights into the observed associations of CMEs with the magnetic features at their solar surface origins.
NASA Astrophysics Data System (ADS)
Lee, Jinmo; You, Donghyun
2013-01-01
A fully-implicit ghost-cell immersed boundary method for simulations of flow over complex moving bodies on a Cartesian grid is presented. The present immersed boundary method is highly capable of controlling the generation of spurious force oscillations on the surface of a moving body, thereby producing an accurate and stable solution. Spurious force oscillations on the surface of an immersed moving body are reduced by alleviating spatial and temporal discontinuities in the pressure and velocity fields across non-grid conforming immersed boundaries. A sharp-interface ghost-cell immersed-boundary method is coupled with a mass source and sink algorithm to improve the conservation of mass across non-grid conforming immersed boundaries. To facilitate the control for the temporal discontinuity in the flow field due to a motion of an immersed body, a fully-implicit time-integration scheme is employed. A novel backward time-integration scheme is developed to effectively treat multiple layers of fresh cells generated by a motion of an immersed body at a high CFL number condition. The present backward time-integration scheme allows to impose more accurate and stable velocity vectors on fresh cells than those interpolated. The effectiveness of the present fully-implicit ghost-cell immersed boundary method coupled with a mass source and sink algorithm for reducing spurious force oscillations during simulations of moving body problems is demonstrated in a number of test cases.
Constraints on magnetic energy and mantle conductivity from the forced nutations of the earth
NASA Technical Reports Server (NTRS)
Buffett, Bruce A.
1992-01-01
The possibility of a presence of a conducting layer at the base of the mantle, as suggested by Knittle and Jeanloz (1986, 1989), was examined using observations of the earth's nutations. Evidence favoring the presence of a conducting layer is found in the effect of ohmic dissipation, which can cause the amplitude of the earth's nutation to be out-of-phase with tidal forcings. It is shown that the earth's magnetic field can produce observable signatures in the forced nutations of the earth when a thin conducting layer is located at the base of the mantle. The present theoretical calculations are compared with VLBI determinations of forced nutations.
Sniadecki, Nathan J.
the motion of the body is termed as Kinematics and if it deals with the forces causing motion also, is called MECHANICS Dynamics. The dynamics dealing with the problems without referring to the forces causing
Magnetic imaging of vortices and inhomogeneity in Ba(Fe,Co)2As2 by magnetic force microscopy
NASA Astrophysics Data System (ADS)
Wu, Weida; Park, S.; Li, Linjun; Li, Yongkang; Chen, Hang; Cao, Guanghan; Xu, Zhu'an
2009-03-01
Single crystals of BaFe2-xCoxAs2 synthesized by FeAs flux method were studied by variable temperature magnetic force microscopy (VT-MFM). The nominal Co doping concentrations range from underdoped region (x0.1) to optimum doped region (x0.2) of the superconducting dome. Sharp superconducting transitions (1K) indicate good sample quality. Individual Abrikosov vortices were visualized by VT-MFM below Tc at low magnetic field. The temperature dependence of vortex configuration indicates a strong pinning effect, which is supported by Bean-model behaviorootnotetextC.P. Bean, PRL, 8, 250 (1962). observed at high magnetic field. Results of magnetic inhomogeneity of underdoped samples will be discussed.
Gravito-Magnetism in one-body and two-body systems: Theory and Experiments
R. F. O'Connell
2009-09-12
We survey theoretical and experimental/observational results on general-relativistic spin (rotation) effects in binary systems. A detailed discussion is given of the two-body Kepler problem and its first post-Newtonian generalization, including spin effects. Spin effects result from gravitational spin-orbit and spin-spin interactions (analogous to the corresponding case in quantum electrodynamics) and these effects are shown to manifest themselves in two ways: (a) precession of the spinning bodies per se and (b) precession of the orbit (which is further broke down into precessions of the argument of the periastron, the longitude of the ascending node and the inclination of the orbit). We also note the ambiguity that arises from use of the terminology frame-dragging, de Sitter precession and Lense-Thirring precession, in contrast to the unambiguous reference to spin-orbit and spin-spin precessions. Turning to one-body experiments, we discuss the recent results of the GP-B experiment, the Ciufolini-Pavlis Lageos experiment and lunar-laser ranging measurements (which actually involve three bodies). Two-body systems inevitably involve astronomical observations and we survey results obtained from the first binary pulsar system, a more recently discovered binary system and, finally, the highly significant discovery of a double-pulsar binary system.
NASA Technical Reports Server (NTRS)
Tadesse, T.; Wiegelmann, T.; Gosain, S.; MacNeice, P.; Pevtsov, A. A.
2014-01-01
Context. The magnetic field permeating the solar atmosphere is generally thought to provide the energy for much of the activity seen in the solar corona, such as flares, coronal mass ejections (CMEs), etc. To overcome the unavailability of coronal magnetic field measurements, photospheric magnetic field vector data can be used to reconstruct the coronal field. Currently, there are several modelling techniques being used to calculate three-dimensional field lines into the solar atmosphere. Aims. For the first time, synoptic maps of a photospheric-vector magnetic field synthesized from the vector spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) are used to model the coronal magnetic field and estimate free magnetic energy in the global scale. The free energy (i.e., the energy in excess of the potential field energy) is one of the main indicators used in space weather forecasts to predict the eruptivity of active regions. Methods. We solve the nonlinear force-free field equations using an optimization principle in spherical geometry. The resulting threedimensional magnetic fields are used to estimate the magnetic free energy content E(sub free) = E(sub nlfff) - E(sub pot), which is the difference of the magnetic energies between the nonpotential field and the potential field in the global solar corona. For comparison, we overlay the extrapolated magnetic field lines with the extreme ultraviolet (EUV) observations by the atmospheric imaging assembly (AIA) on board the Solar Dynamics Observatory (SDO). Results. For a single Carrington rotation 2121, we find that the global nonlinear force-free field (NLFFF) magnetic energy density is 10.3% higher than the potential one. Most of this free energy is located in active regions.
Magnified Spin-Motive Forces in MRAM Magnetic Tunnel Junctions
NASA Astrophysics Data System (ADS)
Barnes, Stewart
2014-03-01
In the Slonczewski 2005 theory for spin-torque-transfer (STT) of a magnetic tunnel junction (MTJ) the tunnelling magneto resistance (TMR) and Gilbert damping parameter ? are of key importance. However the observed critical voltage from the switching of STT-MRAM implies a ? ten times that measured by ferromagnetic resonance (FMR). In addition the TMR is strongly voltage dependent while the STT effect is not. This along with the weak dependence of the critical current on switching direction are inconsistent with the tunnelling model and have never been properly explained. Here will be described a circuit model based upon SU(2) theory for a MTJ for which the basic SMF of about 10 ?V is magnified to a 200mV shift between the parallel P and anti-parallel AP branches of the IV characteristic. It is implied that the TMR has for origin an SMF.
Computational analysis of wake structure and body forces on marine animal research tag
NASA Astrophysics Data System (ADS)
Rosanio, Matthew; Morrida, Jacob; Green, Melissa
2013-11-01
The Acousounde 3B marine animal research tag is used to study the relationship between the sounds made by whales and their behaviors, and ultimately to improve whale conservation efforts. In practical implementation, some researchers have attached external GPS Fastloc devices to the top surface of the tag, in order to accurately record the position of the whales throughout the deployment. There is a need to characterize the flow over the tag in order to better understand the body forces being exerted on it and how wake turbulence could affect noise measurements. The addition of the GPS Fastloc exacerbates both of these concerns, as it complicates the hydrodynamics of the device. Using CFD techniques, we were able to simulate the flow over the tag with a GPS attachment at multiple yaw angles. We used Pointwise to construct the mesh and Fluent to simulate the flow. We have also used flow visualization to experimentally validate our computational results. It was found that the GPS has a minimal effect on the wake of the tag at a 0 degree offset from the freestream flow. However, at increasing offset angles, the presence of the GPS greatly increased the amount of wake turbulence observed. The Acousounde 3B marine animal research tag is used to study the relationship between the sounds made by whales and their behaviors, and ultimately to improve whale conservation efforts. In practical implementation, some researchers have attached external GPS Fastloc devices to the top surface of the tag, in order to accurately record the position of the whales throughout the deployment. There is a need to characterize the flow over the tag in order to better understand the body forces being exerted on it and how wake turbulence could affect noise measurements. The addition of the GPS Fastloc exacerbates both of these concerns, as it complicates the hydrodynamics of the device. Using CFD techniques, we were able to simulate the flow over the tag with a GPS attachment at multiple yaw angles. We used Pointwise to construct the mesh and Fluent to simulate the flow. We have also used flow visualization to experimentally validate our computational results. It was found that the GPS has a minimal effect on the wake of the tag at a 0 degree offset from the freestream flow. However, at increasing offset angles, the presence of the GPS greatly increased the amount of wake turbulence observed. Performed work while undergrad at Syracuse.
NASA Astrophysics Data System (ADS)
Hercik, David; Auster, Hans-Ulrich; Heinisch, Philip; Richter, Ingo; Glassmeier, Karl-Heinz
2015-04-01
Minor bodies in the solar system, such as asteroids and comets, are important sources of information for our knowledge of the solar system formation. Besides other aspects, estimation of a magnetization state of such bodies might prove important in understanding the early aggregation phases of the protoplanetary disk, showing the level of importance of the magnetic forces in the processes involved. Meteorites' magnetization measurements suggest that primitive bodies consist of magnetized material. However, space observations from various flybys give to date diverse results for a global magnetization estimation. The flybys at Braille and Gaspra indicate possible higher magnetization (~ 10-3 Am2/kg), while flybys at Steins and Lutetia show no significant values in the global field change illustrating low global magnetization. Furthermore, the interpretation of remote (during flybys) measurements is very difficult. For correct estimates on the local magnetization one needs (in the best case) multi-point surface measurements. Single point observation has been done by NEAR-Shoemaker on 433 Eros asteroid, revealing no signature in magnetic field that could have origin in asteroid magnetization. Similar results, no magnetization observed, have been provided by evaluation of recent data from ROMAP (Philae lander) and RPC-MAG (Rosetta orbiter) instruments from comet 67P/Churyumov-Gerasimenko. The ROMAP instrument provided measurements from multiple points of the cometary surface as well as data along ballistic path between multiple touchdowns, which support the conclusion of no global magnetization. However, even in case of the in-situ on surface observations the magnetization estimate has a limiting spatial resolution that is dependent on the distance from the surface (~ 50 cm in case of ROMAP). To get information about possible smaller magnetized grains distribution and magnetization strength, the sensor shall be placed as close as possible to the surface. For such observations the next ideal candidate mission is Hayabusa-II with its Mascot lander equipped with fluxgate magnetometer. The small-sized lander shall deliver the magnetometer within centimeters from the surface, providing measurements on multiple points thanks to a hopping ability. The mission has been recently launched (December 2014) and is aiming to a C-type asteroid 1999 JU3 to reach it in 2018. The results will hopefully add some piece of information to the still unclear question of minor solar system bodies magnetization.
Electric Charge and Magnetic Flux on Rotating Black Holes in a Force-Free Magnetosphere
Hyun Kyu Lee; Chul H. Lee; Maurice H. P. M. van Putten
2001-02-13
The electric charge on rotating black holes is calculated to be ~ BJ in the force-free configuration of Ghosh (2000), with a horizon flux of ~ BM^2. This charge is gravitationally weak for B ~ 10^{15} G, so that the Kerr metric applies. Being similar to the electric charge of a magnetar, both electric charge and magnetic flux should be, in sign and order of magnitude, continuous during stellar collapse into a black hole. Extraction of the rotational energy from newly formed black holes may proceed by interaction with the magnetic field. Keywords:black hole physics --magnetic fields
Magnetic force microscopy of epitaxial magnetite films through the Verwey transition
NASA Astrophysics Data System (ADS)
Lee, A. K. H.; Jayathilaka, P. B.; Bauer, C. A.; Monti, M. C.; Markert, J. T.; de Lozanne, A.; Miller, Casey W.
2010-10-01
Magnetic force microscopy was performed on 300 nm thick magnetite films grown epitaxially on MgO (001) at temperatures ranging from well below to well above the Verwey transition temperature, TV. Frequency shift images were acquired at different locations on the sample as temperature was increased through the Verwey transition. The magnetic domain features are persistent at all temperatures, which indicates that the domains are pinned across the phase transition, probably due to antiphase boundaries. An enhancement of magnetic contrast below TV indicates the moments tilt out of the plane below TV, which is corroborated by superconducting quantum interference device magnetometry.
Edge detection of magnetic body using horizontal gradient of pseudogravity anomaly
NASA Astrophysics Data System (ADS)
Alamdar, K.; Ansari, A. H.; Ghorbani, A.
2009-04-01
Potential field methods are used extensively in mineral exploration. These methods also are used as reconnaissance method in oil and gas exploration. In Contrast with gravity anomaly the magnetic surveying produces dipolar anomaly which is caused complicated interpretation rather than gravity anomaly. The observation magnetic anomaly in each location other than magnetic poles has displacement rather than causative body. Several methods are used to overcome to this problem such as reduction to the pole (RTP) that an asymmetric anomaly is converted to symmetrical anomaly. Boundary analysis is another method to distinguish causative magnetic body from observed magnetic data directly. One of the applicable methods in boundary detection of local scale magnetic anomaly is total gradient of pseudogravity anomaly. In this method, pseudogravity anomaly is calculated in the first step. Pseudogravity converts the magnetic field into gravity field that would be observed if the magnetization distribution were to be replaced with an identical density distribution. This filter is a linear filter that is created in the frequency domain. Poisson's relationship between magnetic and gravity potential can be used for magnetic and gravity anomaly transformation to each other. Pseudogravity transformation is done in 3 steps (1) Fourier transform of magnetic data to frequency domain. (2) Multiplying the result of step (1) on to pseudogravity filter expression. (3) Inverse Fourier transform to space domain. It is a useful technique for the interpretation of major magneto- tectonic provinces as it simplifies anomaly patterns and focuses on large scale features rather than local details. After this process the horizontal gradient of calculated pseudogravity anomaly is computed and mapped in surveying scale. In this image maximum value of total horizontal gradient determines magnetic body edge. In this work we applied this method to synthetic magnetic data from prismatic model and also in magnetic data from Gol-Gohar mining area from Iran. This area is one of the iron ore in Iran and located in 1:250000 map in Neyriz geological block. For implementation the described method to studied area observation magnetic anomaly was transformed to pseudogravity anomaly at the first step. Then horizontal gradient of this anomaly was calculated and mapped. Maximum value of horizontal gradient of psedogravity as form of two bands located in magnetic anomaly trend direction. Field observations show an iron vein with 30m width that using described technique as a boundary detection method, confirms this feature. Keywords: Magnetization, Edge detection, Reduction to the pole, pseudogravity, Poisson's relationship, Horizontal gradient, Gol-Gohar.
Student understanding of the direction of the magnetic force on a charged particle
NASA Astrophysics Data System (ADS)
Scaife, Thomas M.; Heckler, Andrew F.
2010-08-01
We study student understanding of the direction of the magnetic force experienced by a charged particle moving through a homogeneous magnetic field in both the magnetic pole and field line representations of the magnetic field. In five studies, we administer a series of simple questions in either written or interview format. Our results indicate that although students begin at the same low level of performance in both representations, they answer correctly more often in the field line representation than in the pole representation after instruction. This difference is due in part to more students believing that charges are attracted to magnetic poles than believing that charges are pushed along magnetic field lines. Although traditional instruction is fairly effective in teaching students to answer correctly up to a few weeks following instruction, especially for the field line representation, some students revert to their initial misconceptions several months after instruction. The responses reveal persistent and largely random sign errors in the direction of the force. The sign errors are largely nonsystematic and due to confusion about the direction of the magnetic field and the execution and choice of the right-hand rule and lack of recognition of the noncommutativity of the cross product.
C. J. de Ruiter; R. M. van der Linden; M. J. A. van der Zijden; A. P. Hollander; A. de Haan
2003-01-01
. Whole-Body vibration (WBV) may lead to muscle contractions via reflex activation of the primary muscle spindle (Ia) fibres.\\u000a WBV has been reported to increase muscle power in the short term by improved muscle activation. The present study set out\\u000a to investigate the acute effects of a standard WBV training session on voluntary activation during maximal isometric force\\u000a production (MVC)
Majda, Marcin
Antibody-Antigen Equilibria in a Field of Magnetic Forces: Design of Reagentless Biosensors in diameter) to a sensor surface. The individual tethers consist of either double stranded DNA or antibody-antigen complex and are designed to selectively detect either specific ssDNA or antigenic proteins, respectively
Magnetic levitation force and penetration depth in type-II superconductors
Xu, J.H.; Miller, J.H. Jr.; Ting, C.S. )
1995-01-01
The superconducting levitation force [ital F] acting on a magnet placed above a type-II superconductor in both Meissner and mixed states is calculated as a function of temperature, based upon the London model. A simple relationship between the levitation force and the London penetration depth [lambda] is found. In particular, in the limit of [ital a]/[lambda][much gt]1, where [ital a] is the separation between the magnet and the superconductor, [ital F] varies linearly with [lambda], regardless of the shape of the magnet. The temperature dependences of [lambda] and [ital F] are examined for various superconducting pairing states, including [ital s]-wave, [ital d]-wave, and [ital s]+[ital id] states. It is found that, at low temperatures, both [lambda] and [ital F] show an exponential temperature dependence for [ital s]-wave, linear-[ital T] for [ital d]-wave, and [ital T][sup 2] dependence in a wide low-temperature range for the [ital s]+[ital id] state with a dominant [ital d]-wave component. The magnetic force microscope (MFM) is proposed to accurately measure the temperature-dependent levitation force. It is shown that the microscopic size of the MFM tip enables one to obtain the intrinsic temperature-dependent penetration depth of a single grain, in spite of the overall quality of the superconducting sample.
A low-temperature dynamic mode scanning force microscope operating in high magnetic fields
Ihn, Thomas
scanning near field optical microscopy,5,710 magnetic force microscopy,11 and acoustic near field system. The 4 He pumping line and the He-recovery line are plastic pipes which are suspended together with all electrical connections to the cryostat from additional elastic ropes. Vibrations from the 4 He
Nonideal evolution of nonaxisymmetric, force-free magnetic fields in a magnetar
Alpha Mastrano; Andrew Melatos
2008-04-25
Recent numerical magnetohydrodynamic calculations by Braithwaite and collaborators support the `fossil field' hypothesis regarding the origin of magnetic fields in compact stars and suggest that the resistive evolution of the fossil field can explain the reorganisation and decay of magnetar magnetic fields. Here, these findings are modelled analytically by allowing the stellar magnetic field to relax through a quasistatic sequence of nonaxisymmetric, force-free states, by analogy with spheromak relaxation experiments, starting from a random field. Under the hypothesis that the force-free modes approach energy equipartition in the absence of resistivity, the output of the numerical calculations is semiquantitatively recovered: the field settles down to a linked poloidal-toroidal configuration, which inflates and becomes more toroidal as time passes. A qualitatively similar (but not identical) end state is reached if the magnetic field evolves by exchanging helicity between small and large scales according to an $\\alpha$-dynamo-like, mean-field mechanism, arising from the fluctuating electromotive force produced by the initial random field. The impossibility of matching a force-free internal field to a potential exterior field is discussed in the magnetar context.
NASA Astrophysics Data System (ADS)
Fukushige, Toshiyuki; Taiji, Makoto; Makino, Junichiro; Ebisuzaki, Toshikazu; Sugimoto, Daiichiro
1996-09-01
We have developed a parallel, pipelined special-purpose computer for N-body simulations, MD-GRAPE (for "GRAvity PipE"). In gravitational N- body simulations, almost all computing time is spent on the calculation of interactions between particles. GRAPE is specialized hardware to calculate these interactions. It is used with a general-purpose front-end computer that performs all calculations other than the force calculation. MD-GRAPE is the first parallel GRAPE that can calculate an arbitrary central force. A force different from a pure 1/r potential is necessary for N-body simulations with periodic boundary conditions using the Ewald or particle-particle/particle-mesh (P^3^M) method. MD-GRAPE accelerates the calculation of particle-particle force for these algorithms. An MD- GRAPE board has four MD chips and its peak performance is 4.2 GFLOPS. On an MD-GRAPE board, a cosmological N-body simulation takes 6O0(N/10^6^)^3/2^ s per step for the Ewald method, where N is the number of particles, and would take 24O(N/10^6^) s per step for the P^3^M method, in a uniform distribution of particles.
A calculation method for levitating force of AC magnetic levitation system
Fujita, H.; Masukawa, S.; Sakui, M.; Takayasu, Y.
1982-01-01
With the progress in the linear motor, various kinds of magnetic levitating devices, most of them driven by dc current, are under study. In this paper, a simple magnetic levitating device driven by ac current is proposed. In this device, the cylindrical air gap is excited by an ac current and a thin nonmagnetic conducting ring is put into the air gap. The levitating force exerted on the ring is produced by the current induced in the ring by the ac magnetic flux. The current induced in the ring changes the flux density distribution and the phase of magnetic flux. The authors propose in this paper a method to calculate the flux density distribution and magnetic flux phase.
ON THE FORCE-FREE NATURE OF PHOTOSPHERIC SUNSPOT MAGNETIC FIELDS AS OBSERVED FROM HINODE (SOT/SP)
Tiwari, Sanjiv Kumar
2012-01-01
A magnetic field is force-free if there is no interaction between it and the plasma in the surrounding atmosphere, i.e., electric currents are aligned with the magnetic field, giving rise to zero Lorentz force. The computation of various magnetic parameters, such as magnetic energy (using the virial theorem), gradient of twist of sunspot magnetic fields (computed from the force-free parameter {alpha}), and any kind of extrapolation, heavily hinges on the force-free approximation of the photospheric sunspot magnetic fields. Thus, it is of vital importance to inspect the force-free behavior of sunspot magnetic fields. The force-free nature of sunspot magnetic fields has been examined earlier by some researchers, ending with incoherent results. Accurate photospheric vector field measurements with high spatial resolution are required to inspect the force-free nature of sunspots. For this purpose, we use several vector magnetograms of high spatial resolution obtained from the Solar Optical Telescope/Spectro-Polarimeter on board Hinode. Both the necessary and sufficient conditions for force-free nature are examined by checking the global and local nature of equilibrium magnetic forces over sunspots. We find that sunspot magnetic fields are not very far from the force-free configuration, although they are not completely force-free on the photosphere. The umbral and inner penumbral fields are more force-free than the middle and outer penumbral fields. During their evolution, sunspot magnetic fields are found to maintain their proximity to force-free field behavior. Although a dependence of net Lorentz force components is seen on the evolutionary stages of the sunspots, we do not find a systematic relationship between the nature of sunspot magnetic fields and the associated flare activity. Further, we examine whether the fields at the photosphere follow linear or nonlinear force-free conditions. After examining this in various complex and simple sunspots, we conclude that, in either case, photospheric sunspot magnetic fields are closer to satisfying the nonlinear force-free field approximation.
NASA Astrophysics Data System (ADS)
de Groot, L. V.; Fabian, K.; Bakelaar, I. A.; Dekkers, M. J.
2014-12-01
Obtaining reliable estimates of the absolute palaeointensity of the Earth's magnetic field is notoriously difficult. Many methods to obtain paleointensities from suitable records such as lavas and archeological artifacts involve heating the samples. These heating steps are believed to induce 'magnetic alteration' - a process that is still poorly understood but prevents obtaining correct paleointensity estimates. To observe this magnetic alteration directly we imaged the magnetic domain state of titanomagnetite particles - a common carrier of the magnetic remanence in samples used for paleointensity studies. We selected samples from the 1971-flow of Mt. Etna from a site that systematically yields underestimates of the known intensity of the paleofield - in spite of rigorous testing by various groups. Magnetic Force Microscope images were taken before and after a heating step typically used in absolute palaeointensity experiments. Before heating, the samples feature distinct, blocky domains that sometimes seem to resemble a classical magnetite domain structure. After imparting a partial thermo-remanent magnetization at a temperature often critical to paleointensity experiments (250 °C) the domain state of the same titanomagnetite grains changes into curvier, wavy domains. Furthermore, these structures appeared to be unstable over time: after one-year storage in a magnetic field-free environment the domain states evolved into a viscous remanent magnetization state. Our observations may qualitatively explain reported underestimates from technically successful paleointensity experiments for this site and other sites reported previously. Furthermore the occurrence of intriguing observations such as 'the drawer storage effect' by Shaar et al (EPSL, 2011), and viscous magnetizations observed by Muxworthy and Williams (JGR, 2006) may be (partially) explained by our observations. The major implications of our study for all palaeointensity methods involving heating may be evident.
Fictitious forces and simulated magnetic fields in rotating reference frames.
Klink, W H; Wickramasekara, S
2013-10-18
We show that the Wigner-Bargmann program of grounding nonrelativistic quantum mechanics in the unitary projective representations of the Galilei group can be extended to include all noninertial reference frames. The key concept is the Galilean line group, the group of transformations that ties together all accelerating reference frames, and its representations. These representations are constructed under the natural constraint that they reduce to the well-known unitary, projective representations of the Galilei group when the transformations are restricted to inertial reference frames. This constraint can be accommodated only for a class of representations with a sufficiently rich cocycle structure. Unlike the projective representations of the Galilei group, these cocycle representations of the Galilean line group do not correspond to central extensions of the group. Rather, they correspond to a class of nonassociative extensions, known as loop prolongations, that are determined by three-cocycles. As an application, we show that the phase shifts due to the rotation of Earth that have been observed in neutron interferometry experiments and the rotational effects that lead to simulated magnetic fields in optical lattices can be rigorously derived from the representations of the loop prolongations of the Galilean line group. PMID:24182238
FORC diagram study of magnetostatic interactions in 2D longitudinal arrays of magnetic wires
NASA Astrophysics Data System (ADS)
Nica, Mihai; Stancu, Alexandru
2015-10-01
The switching behavior of magnetic wires in 2D-longitudinal arrays is systematically analyzed with the first-order reversal curve (FORC) diagram method. The magnetostatic interactions in these systems are more difficult to calculate compared with the 2D-perpendicular arrays in which the global interaction effect is dominated by the demagnetizing mean-field interactions. The geometrical parameters of the magnetic structure can transform the magnetic system from one dominated by demagnetizing interactions to one dominated by the magnetizing interactions. We have found a structure in which the FORC distribution is symmetrical which indicate zero-mean field interaction. This compensated structure was studied at the level of the individual wire switchings and we show that in this case the switching field fluctuates around the intrinsic coercivity of the wire. In this particular case the switching field distribution obtained from the FORC diagram is identical with the distribution of the coercivities of the non-interacting wires. However, the system behavior is still not completely in agreement with the Classical Preisach Model. A comparison between the behavior of three systems with magnetizing, demagnetizing and compensated mean-field interactions is also presented and the results are discussed.
On the numerical computation of nonlinear force-free magnetic fields. [from solar photosphere
NASA Technical Reports Server (NTRS)
Wu, S. T.; Sun, M. T.; Chang, H. M.; Hagyard, M. J.; Gary, G. A.
1990-01-01
An algorithm has been developed to extrapolate nonlinear force-free magnetic fields from the photosphere, given the proper boundary conditions. This paper presents the results of this work, describing the mathematical formalism that was developed, the numerical techniques employed, and comments on the stability criteria and accuracy developed for these numerical schemes. An analytical solution is used for a benchmark test; the results show that the computational accuracy for the case of a nonlinear force-free magnetic field was on the order of a few percent (less than 5 percent). This newly developed scheme was applied to analyze a solar vector magnetogram, and the results were compared with the results deduced from the classical potential field method. The comparison shows that additional physical features of the vector magnetogram were revealed in the nonlinear force-free case.
Calculation of cogging force in a novel slotted linear tubular brushless permanent magnet motor
Zhu, Z.Q.; Hor, P.J.; Howe, D.; Rees-Jones, J.
1997-09-01
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.
Gravitational self-force in a Schwarzschild background and the effective one-body formalism
Damour, Thibault [Institut des Hautes Etudes Scientifiques, 35, route de Chartres, 91440 Bures-sur-Yvette (France)
2010-01-15
We discuss various ways in which the computation of conservative gravitational self-force (GSF) effects on a point mass moving in a Schwarzschild background can inform us about the basic building blocks of the effective one-body (EOB) Hamiltonian. We display the information which can be extracted from the recently published GSF calculation of the first-GSF-order shift of the orbital frequency of the last stable circular orbit, and we combine this information with the one recently obtained by comparing the EOB formalism to high-accuracy numerical relativity data on coalescing binary black holes. The information coming from GSF data helps to break the degeneracy (among some EOB parameters) which was left after using comparable-mass numerical relativity data to constrain the EOB formalism. We suggest various ways of obtaining more information from GSF computations: either by studying eccentric orbits, or by focusing on a special zero-binding zoom-whirl orbit. We show that logarithmic terms start entering the post-Newtonian expansions of various (EOB and GSF) functions at the fourth post-Newtonian level, and we analytically compute the first logarithm entering a certain, gauge-invariant 'redshift' GSF function (defined along the sequence of circular orbits).
Navier-Stokes Computations of Longitudinal Forces and Moments for a Blended Wing Body
NASA Technical Reports Server (NTRS)
Pao, S. Paul; Biedron, Robert T.; Park, Michael A.; Fremaux, C. Michael; Vicroy, Dan D.
2004-01-01
The object of this paper is to investigate the feasibility of applying CFD methods to aerodynamic analyses for aircraft stability and control. The integrated aerodynamic parameters used in stability and control, however, are not necessarily those extensively validated in the state of the art CFD technology. Hence, an exploratory study of such applications and the comparison of the solutions to available experimental data will help to assess the validity of the current computation methods. In addition, this study will also examine issues related to wind tunnel measurements such as measurement uncertainty and support interference effects. Several sets of experimental data from the NASA Langley 14x22-Foot Subsonic Tunnel and the National Transonic Facility are presented. Two Navier-Stokes flow solvers, one using structured meshes and the other unstructured meshes, were used to compute longitudinal static stability derivatives for an advanced Blended Wing Body configuration over a wide range of angles of attack. The computations were performed for two different Reynolds numbers and the resulting forces and moments are compared with the above mentioned wind tunnel data.
Navier-Stokes Computations of Longitudinal Forces and Moments for a Blended Wing Body
NASA Technical Reports Server (NTRS)
Pao, S. Paul; Biedron, Robert T.; Park, Michael A.; Fremaux, C. Michael; Vicroy, Dan D.
2005-01-01
The object of this paper is to investigate the feasibility of applying CFD methods to aerodynamic analyses for aircraft stability and control. The integrated aerodynamic parameters used in stability and control, however, are not necessarily those extensively validated in the state of the art CFD technology. Hence, an exploratory study of such applications and the comparison of the solutions to available experimental data will help to assess the validity of the current computation methods. In addition, this study will also examine issues related to wind tunnel measurements such as measurement uncertainty and support interference effects. Several sets of experimental data from the NASA Langley 14x22-Foot Subsonic Tunnel and the National Transonic Facility are presented. Two Navier-Stokes flow solvers, one using structured meshes and the other unstructured meshes, were used to compute longitudinal static stability derivatives for an advanced Blended Wing Body configuration over a wide range of angles of attack. The computations were performed for two different Reynolds numbers and the resulting forces and moments are compared with the above mentioned wind tunnel data.
Paleo-Magnetic Field Recorded in the Parent Body of the Murchison Meteorite
NASA Astrophysics Data System (ADS)
Kletetschka, G.; Páchová, H.
2014-12-01
Murchison meteorite is a carbonaceous chondrite containing small amount of chondrules, various inclusions, and matrix with occasional porphyroblasts of olivine and/or pyroxene. We applied magnetic efficiency method (Kletetschka et al 2005, Kohout et al, 2008) in order to get the demagnetization spectra for several randomly oriented fragments of Murchison meteorite. Our method detected not only viscous magnetization removable in low fields, but also very persistent magnetizations in all meterorite fragments. Data suggest that magnetic carriers within the Murchison meteorite were grown in a paleofield of 450 - 850 nT. Meteorite record in other fragments contains an existence of antipodal fields that may be tied to an event of magnetic reversal within the nebular magnetic field or parent asteroid body. Other meteorites show stable record over its entire spectrum, giving magnetic paleofield of 1100 - 1900 nT. Magnetic record in Murchison meteorite comes from magnetite, pyrrhotite and Iron Nickel alloy. Pyrrhotite is suggested to be the main carrier of the paleofield in Murchison. Iron-Nickel alloy generate observable zigzag pattern when magnetically saturated. Kletetschka, G., Kohout, T., Wasilewski, P., and Fuller, M. D., 2005, Recognition of thermal remanent magnetization in rocks and meteorites, The IAGA Scientific Assembly, Volume GAI10: Toulouse, IAGA, p. IAGA2005-A-00945. Kohout, T., Kletetschka, G., Donadini, F., Fuller, M., and Herrero-Bervera, E., 2008, Analysis of the natural remanent magnetization of rocks by measuring the efficiency ratio through alternating field demagnetization spectra: Studia Geophysica Et Geodaetica, v. 52, no. 2, p. 225-235.
NASA Astrophysics Data System (ADS)
Karci, Ozgur; Celik, Umit; Oral, Ahmet; NanoMagnetics Instruments Ltd. Team; Middle East Tech Univ Team
2015-03-01
We describe a novel method for excitation of Atomic Force Microscope (AFM) cantilevers by means of radiation pressure for imaging in an AFM for the first time. Piezo excitation is the most common method for cantilever excitation, but it may cause spurious resonance peaks. A fiber optic interferometer with 1310 nm laser was used both to measure the deflection of cantilever and apply a force to the cantilever in a LT-AFM/MFM from NanoMagnetics Instruments. The laser power was modulated at the cantilever`s resonance frequency by a digital Phase Lock Loop (PLL). The force exerted by the radiation pressure on a perfectly reflecting surface by a laser beam of power P is F = 2P/c. We typically modulate the laser beam by ~ 800 ?W and obtain 10nm oscillation amplitude with Q ~ 8,000 at 2.5x10-4 mbar. The cantilever's stiffness can be accurately calibrated by using the radiation pressure. We have demonstrated performance of the radiation pressure excitation in AFM/MFM by imaging a hard disk sample between 4-300K and Abrikosov vortex lattice in BSCCO single crystal at 4K to for the first time.
NASA Astrophysics Data System (ADS)
Vrijsen, N. H.; Jansen, J. W.; Compter, J. C.; Lomonova, E. A.
2013-07-01
A measurement method is presented which identifies the magnetic hysteresis effects present in the force of linear reluctance actuators. The measurement method is applied to determine the magnetic hysteresis in the force of an E-core reluctance actuator, with and without pre-biasing permanent magnet. The force measurements are conducted with a piezoelectric load cell (Kistler type 9272). This high-bandwidth force measurement instrument is identified in the frequency domain using a voice-coil actuator that has negligible magnetic hysteresis and eddy currents. Specifically, the phase delay between the current and force of the voice-coil actuator is used for the calibration of the measurement instrument. This phase delay is also obtained by evaluation of the measured force and flux variation in the E-core actuator, both with and without permanent magnet on the middle tooth. The measured magnetic flux variation is used to distinguish the phase delay due to magnetic hysteresis from the measured phase delay between the current and the force of the E-core actuator. Finally, an open loop steady-state ac model is presented that predicts the magnetic hysteresis effects in the force of the E-core actuator.
Vrijsen, N H; Jansen, J W; Compter, J C; Lomonova, E A
2013-07-01
A measurement method is presented which identifies the magnetic hysteresis effects present in the force of linear reluctance actuators. The measurement method is applied to determine the magnetic hysteresis in the force of an E-core reluctance actuator, with and without pre-biasing permanent magnet. The force measurements are conducted with a piezoelectric load cell (Kistler type 9272). This high-bandwidth force measurement instrument is identified in the frequency domain using a voice-coil actuator that has negligible magnetic hysteresis and eddy currents. Specifically, the phase delay between the current and force of the voice-coil actuator is used for the calibration of the measurement instrument. This phase delay is also obtained by evaluation of the measured force and flux variation in the E-core actuator, both with and without permanent magnet on the middle tooth. The measured magnetic flux variation is used to distinguish the phase delay due to magnetic hysteresis from the measured phase delay between the current and the force of the E-core actuator. Finally, an open loop steady-state ac model is presented that predicts the magnetic hysteresis effects in the force of the E-core actuator. PMID:23902095
Removal of Maxillary Sinus Metallic Foreign Body Like a Hand Sewing Needle by Magnetic Iron
Qin, Xiurong; Ma, Yingwei
2014-01-01
ABSTRACT Metallic foreign bodies are rarely found in the maxillary sinus, and usually they have a dental origin. Two main surgical approaches are currently used for the removal of foreign bodies in the maxillary sinus: the bone flap and the endoscopic sinus techniques. However, the treatment is not only surgical removal. We are reporting one case of foreign body like a hand sewing needle entered into the maxillary sinus through an unusual route carious deciduous molar tooth. It was diagnosed by three-dimensional images from cone-beam computed tomography (CBCT) and removed by a simple procedure, with magnetic iron, thereby avoiding the risk of damage to a large portion of the alveolar bone near the maxillary sinus. How to cite this article: Shao L, Qin X, Ma Y. Removal of Maxillary Sinus Metallic Foreign Body Like a Hand Sewing Needle by Magnetic Iron. Int J Clin Pediatr Dent 2014;7(1):61-64. PMID:25206242
Bipolar solar magnetic fields. Behaviors resulting from a nonlinear force-free equation
NASA Astrophysics Data System (ADS)
Tautz, R. C.; Lerche, I.
2015-09-01
Aims: Understanding magnetic fields in the solar corona is closely related to the complex nature of the often nonlinear differential equations describing such structures. Based on the ansatz of force-free fields, a class of solutions is derived and discussed that allows for axisymmetric bipolar magnetic fields. Methods: Allowed dipolar solutions for self-similar axisymmetric force-free magnetic fields use the formalism of a Grad-Shafranov equation involving the vector potential. For separable solutions involving poloidal fields decaying radially as r-n, there are no dipolar field structures for the decay index n ? 1 . Results: In the domain n < 1 dipolar field structures are possible in restricted ranges of the angular coordinate ? depending on the value for n. Outside of the restricted domains there are no dipolar solutions, but there can be multipole solutions. The limiting case of the parameter n ? 0 has been discussed previously, so that now the full regime 0 ? n < ? is covered.
High-force NdFeB-based magnetic tweezers device optimized for microrheology experiments.
Lin, Jun; Valentine, Megan T
2012-05-01
We present the design, calibration, and testing of a magnetic tweezers device that employs two pairs of permanent neodymium iron boron magnets surrounded by low-carbon steel focusing tips to apply large forces to soft materials for microrheology experiments. Our design enables the application of forces in the range of 1-1800 pN to ?4.5 ?m paramagnetic beads using magnet-bead separations in the range of 0.3-20 mm. This allows the use of standard coverslips and sample geometries. A high speed camera, custom LED-based illumination scheme, and mechanically stabilized measurement platform are employed to enable the measurement of materials with viscoelastic moduli as high as ?1 kPa. PMID:22667631
NASA Astrophysics Data System (ADS)
McVitie, S.; Ferrier, R. P.; Scott, J.; White, G. S.; Gallagher, A.
2001-04-01
In this article we present results and analysis from measurements of the field distributions from standard magnetic force microscope tips. These measurements are made using Lorentz microscopy and tomographic reconstruction techniques with the field reconstructed in a plane situated about 50 nm from the end of the magnetic force microscope (MFM) tip; this corresponds approximately to the sample plane in the MFM. By examination of the experimental results and comparison with simulated field distributions from point and extended charge distributions, we conclude that the magnetization configuration of the tip is best represented by an extended charge distribution and that the point pole approximation represents only, at best, the central part of the field distribution.
Foulhoux, L. . Marine Advanced Techniques Section); Bernitsas, M.M. . Dept. of Naval Architecture and Marine Engineering)
1993-05-01
Complete expressions are derived for the inertia forces and moments acting on a small body in a six-degree-of-freedom motion in a three-dimensional unsteady flow in an unbounded ideal fluid. The far-field approximation of the body motion is represented by a series of multipoles located at the origin of the body. Unsteady terms are expanded in a dual series to the multipole series. Lagally integrals are expressed in terms of multipoles as well, by using Legendre polynomial expansions. New inertia force expressions are derived by truncating the multipole series after the quadrupoles. Corresponding terms for moments are also developed. The derived formulas are still compact enough for engineering applications. Many practical problems involving fixed and oscillating cylinders, piles, and risers are studied numerically. Comparisons to the Morison equation formulation prove that the nonlinear convective terms are not negligible in multidimensional relative flows.
Critical speeds and forced response solutions for active magnetic bearing turbomachinery, part 1
NASA Technical Reports Server (NTRS)
Keesee, J.; Rawal, D.; Kirk, R. Gordon
1991-01-01
The prediction of critical speeds and forced response of active magnetic bearing turbomachinery is of great interest due to the increased use of this new and promising technology. Calculating the system undamped critical speeds and forced response is important to all those who are involved in the design of the active magnetic bearing system. An extended Jeffcott model which was used as an approximate solution to a more accurate transfer matrix procedure is presented. Theory behind a two-degree-of freedom extended Jeffcoat model is presented. Results of the natural frequency calculation are shown followed by the results of the forced response calculation. The system response was predicted for two types of forcing. A constant magnitude excitation with a wide frequency variation was applied at the bearings as one forcing function. The normal unbalance force at the midspan was the second source of excitation. The results of this extended Jeffcott solution gives useful design guidance for the influence of the first and third modes of a symmetric rotor system.
NSDL National Science Digital Library
Mrs. Brownie
2010-04-07
Instructions: This is a webquest designed to help students understand force. It is specifically meant to teach the idea that the greater the force applied to an object the greater the change in speed or direction of the object depending on the mass. This is also known as Newton's Second Law of Motion. Lets Learn about Force! For this project your students will understand force. They will use Newton's second law to solve the problem presented. UT Core Curriculum: Science 3rd Grade. Standard 3- Students will understand the relationship between the force applied to an object and resulting motion of the ...
Attosecond Electro-Magnetic Forces Acting on Metal Nanospheres Induced By Relativistic Electrons
NASA Astrophysics Data System (ADS)
Lagos, M. J.; Batson, P. E.; Reyes-Coronado, A.; Echenique, P. M.; Aizpurua, J.
2014-03-01
Swift electron scattering near nanoscale materials provides information about light-matter behavior, including induced forces. We calculate time-dependent electromagnetic forces acting on 1-1.5 nm metal nanospheres induced by passing swift electrons, finding both impulse-like and oscillatory response forces. Initially, impulse-like forces are generated by a competition between attractive electric forces and repulsive magnetic forces, lasting a few attoseconds (5-10 as). Oscillatory, plasmonic response forces take place later in time, last a few femtoseconds (1- 5 fs), and apparently rely on photon emission by decay of the electron-induced surface plasmons. A comparison of the strength of these two forces suggests that the impulse-like behavior dominates the process, and can transfer significant linear momentum to the sphere. Our results advance understanding of the physics behind the observation of both attractive and repulsive behavior of gold nano-particles induced by electron beams in aberration-corrected electron microscopy. Work supported under DOE, Award # DE-SC0005132, Basque Gov. project ETORTEK inano, Spanish Ministerio de Ciencia e Innovacion, No. FIS2010-19609-C02-01.
Greg Zaharchuk; Reed F. Busse; Guy Rosenthal; Geoffery T. Manley; Orit A. Glenn; William P. Dillon
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
Magnetic irreversibility and pinning force density in the Ti-V alloys
NASA Astrophysics Data System (ADS)
Matin, Md.; Sharath Chandra, L. S.; Chattopadhyay, M. K.; Meena, R. K.; Kaul, Rakesh; Singh, M. N.; Sinha, A. K.; Roy, S. B.
2013-04-01
We present a study of critical current density estimated through dc magnetization measurements in the superconducting alloys Ti60V40 and Ti70V30. The magnetization is irreversible below the irreversibility field (BIrr), which is different from the upper critical field for the alloys. Additionally, the alloys are found to exhibit a peak effect in magnetization below the upper critical field. The critical current densities of the alloys estimated from the magnetization results decrease strongly with increasing magnetic field. The pinning force density follows a universal scaling relation with respect to the magnetic field divided by the BIrr. The field dependence of the pinning force density is analyzed in terms of the size of the grains of the main ? phase, the possible presence of dislocation arrays within the grains of the main phase, the presence of additional metallurgical phases, and the configuration of the grain boundaries in the system. The temperature dependence of critical current density is also analyzed within the framework of existing theories.
N. S. Kiselev; I. E. Dragunov; V. Neu; U. K. Rößler; A. N. Bogdanov
2008-01-01
Recently synthesized magnetic multilayers with strong perpendicular anisotropy exhibit unique magnetic properties including the formation of specific multidomain states. In particular, antiferromagnetically coupled multilayers own rich phase diagrams that include various multidomain ground states. Analytical equations have been derived for the stray field components of these multidomain states in perpendicular multilayer systems. In particular, closed expressions for stray fields in
Hollerbach, John M.
3-D Force Control on the Human Fingerpad Using a Magnetic Levitation Device for Fingernail Imaging of Mechanical Engineering University of Utah ABSTRACT This paper demonstrates fast, accurate, and stable force. The primary application of this force control is for the automated calibration of a fingernail imaging system
NASA Technical Reports Server (NTRS)
Groom, Nelson J.
1997-01-01
The expanded equations for torque and force on a cylindrical permanent magnet core in a large-gap magnetic suspension system are presented. The core is assumed to be uniformly magnetized, and equations are developed for two orientations of the magnetization vector. One orientation is parallel to the axis of symmetry, and the other is perpendicular to this axis. Fields and gradients produced by suspension system electromagnets are assumed to be calculated at a point in inertial space which coincides with the origin of the core axis system in its initial alignment. Fields at a given point in the core are defined by expanding the fields produced at the origin as a Taylor series. The assumption is made that the fields can be adequately defined by expansion up to second-order terms. Examination of the expanded equations for the case where the magnetization vector is perpendicular to the axis of symmetry reveals that some of the second-order gradient terms provide a method of generating torque about the axis of magnetization and therefore provide the ability to produce six-degree-of-freedom control.
Robust tracking control of a magnetically suspended rigid body
NASA Technical Reports Server (NTRS)
Lim, Kyong B.; Cox, David E.
1994-01-01
This study is an application of H-infinity and micro-synthesis for designing robust tracking controllers for the Large Angle Magnetic Suspension Test Facility. The modeling, design, analysis, simulation, and testing of a control law that guarantees tracking performance under external disturbances and model uncertainties is investigated. The type of uncertainties considered and the tracking performance metric used is discussed. This study demonstrates the tradeoff between tracking performance at low frequencies and robustness at high frequencies. Two sets of controllers were designed and tested. The first set emphasized performance over robustness, while the second set traded off performance for robustness. Comparisons of simulation and test results are also included. Current simulation and experimental results indicate that reasonably good robust tracking performance can be attained for this system using multivariable robust control approach.
Simulation of four-body interaction in a nuclear magnetic resonance quantum information processor
Wen-Zhang Liu; Jin-Fu Zhang; Gui Lu Long
2007-04-10
Four-body interaction plays an important role in many-body systems, and it can exhibit interesting phase transition behaviors. Historically it was the need to efficiently simulate quantum systems that lead the idea of a quantum computer. In this Letter, we report the experimental demonstration of a four-body interaction in a four- qubit nuclear magnetic resonance quantum information processor. The strongly modulating pulse is used to implement spin selective excitation. The results show a good agreement between theory and experiment.
A Non-Linear Force-Free Field Model for the Solar Magnetic Carpet
NASA Astrophysics Data System (ADS)
Meyer, Karen; Mackay, D.; van Ballegooijen, A.; Parnell, C.
2013-07-01
The magnetic carpet is defined to be the small-scale photospheric magnetic field of the quiet-Sun. Recent high resolution, high cadence observations have shown that although small-scale, the magnetic carpet is far from 'quiet', it is continually evolving in a complex and dynamic manner. I will present a two-component model for the dynamic evolution of the Sun's magnetic carpet. The first component is a 2D model for the photospheric evolution of the small-scale solar magnetic field, that reproduces many observed parameters. The basic evolution of magnetic elements within the model is governed by a supergranular flow profile. In addition, magnetic elements may evolve through the processes of emergence, cancellation, coalescence and fragmentation. The synthetic magnetograms produced by the 2D model are then applied as photospheric boundary data to drive the continuous evolution of a 3D non-linear force-free coronal field. We studied the resultant complex, small-scale coronal magnetic field, in particular the energetics of the field.
A comparison of 60 Hz uniform magnetic and electric induction in the human body
NASA Astrophysics Data System (ADS)
Dawson, Trevor W.; Caputa, Kris; Stuchly, Maria A.
1997-12-01
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.
Effect of repulsive and attractive three-body forces on nucleus-nucleus elastic scattering
Furumoto, T.; Sakuragi, Y.; Yamamoto, Y. [Department of Physics, Osaka City University, Osaka 558-8585 (Japan); Department of Physics, Osaka City University, Osaka 558-8585, Japan and RIKEN Nishina Center, RIKEN, Wako, Saitama 351-0198 (Japan); Physics Section, Tsuru University, Tsuru, Yamanashi 402-8555 (Japan)
2009-10-15
The effect of the three-body force (TBF) is studied in nucleus-nucleus elastic scattering on the basis of Brueckner theory for nucleon-nucleon (NN) effective interaction (complex G matrix) in the nuclear matter. A new G matrix called CEG07 proposed recently by the present authors includes the TBF effect and reproduces a realistic saturation curve in the nuclear matter, and it is shown to well reproduce proton-nucleus elastic scattering. The microscopic optical potential for the nucleus-nucleus system is obtained by folding the G matrix with nucleon density distributions in colliding nuclei. We first analyze in detail the {sup 16}O+{sup 16}O elastic scattering at E/A=70 MeV. The observed cross sections are nicely reproduced up to the most backward scattering angles only when the TBF effect is included. The use of the frozen-density approximation (FDA) is essentially important to properly estimate the effect of the TBF in nucleus-nucleus scattering. Other prescriptions for defining the local density have also been tested, but only the FDA prescription gives a proper description of the experimental cross sections as well as the effect of the TBF. The effects of the three-body attraction and the {omega}-rearrangement term are also analyzed. The CEG07 interaction is compared with CDM3Y6, which is a reliable and successful effective density-dependent NN interaction used in the double-folding model. The CEG07 G matrix is also tested in the elastic scattering of {sup 16}O by the {sup 12}C, {sup 28}Si, and {sup 40}Ca targets at E/A=93.9 MeV, and in the elastic scattering of {sup 12}C by the {sup 12}C target at E/A=135 MeV with great success. The decisive effect of the TBF is clearly seen also in those systems. Finally, we have tested CEG07a, CEG07b, and CEG07c for the {sup 16}O+{sup 16}O system at various energies.
NASA Astrophysics Data System (ADS)
Kishore, G. V. K.; Kumar, Anish; Chakraborty, Gopa; Albert, S. K.; Rao, B. Purna Chandra; Bhaduri, A. K.; Jayakumar, T.
2015-07-01
Nickel base Ni-Cr alloy variants are extensively used for hardfacing of austenitic stainless steel components in sodium cooled fast reactors (SFRs) to avoid self-welding and galling. Considerable difference in the compositions and melting points of the substrate and the Ni-Cr alloy results in significant dilution of the hardface deposit from the substrate. Even though, both the deposit and the substrate are non-magnetic, the diluted region exhibits ferromagnetic behavior. The present paper reports a systematic study carried out on the variations in microstructures and magnetic behavior of American Welding Society (AWS) Ni Cr-C deposited layers on 316 LN austenitic stainless steels, using atomic force microscopy (AFM) and magnetic force microscopy (MFM). The phase variations of the oscillations of a Co-Cr alloy coated magnetic field sensitive cantilever is used to quantitatively study the magnetic strength of the evolved microstructure in the diluted region as a function of the distance from the deposit/substrate interface, with the spatial resolution of about 100 nm. The acquired AFM/MFM images and the magnetic property profiles have been correlated with the variations in the chemical compositions in the diluted layers obtained by the energy dispersive spectroscopy (EDS). The study indicates that both the volume fraction of the ferromagnetic phase and its ferromagnetic strength decrease with increasing distance from the deposit/substrate interface. A distinct difference is observed in the ferromagnetic strength in the first few layers and the ferromagnetism is observed only near to the precipitates in the fifth layer. The study provides a better insight of the evolution of ferromagnetism in the diluted layers of Ni-Cr alloy deposits on stainless steel.
Fan, Zheyong; Wang, Hui-Qiong; Zheng, Jin-Cheng; Donadio, Davide; Harju, Ari
2015-01-01
We derive expressions of interatomic force and heat current for many-body potentials such as the Tersoff, the Brenner, and the Stillinger-Weber potential used extensively in molecular dynamics simulations of covalently bonded materials. Although these potentials have a many-body nature, a pairwise force expression that follows Newton's third law can be found without referring to any partition of the potential. Based on this force formula, a stress applicable for periodic systems can be unambiguously defined. The force formula can then be used to derive the heat current formulas using a natural potential partitioning. Our heat current formulation is found to be equivalent to most of the seemingly different heat current formulas used in the literature, but to deviate from the stress-based formula derived from two-body potential. We validate our formulation numerically on various systems descried by the Tersoff potential, namely three-dimensional silicon and diamond, two-dimensional graphene, and quasi-one-dimen...
NASA Astrophysics Data System (ADS)
Fan, Zheyong; Pereira, Luiz Felipe C.; Wang, Hui-Qiong; Zheng, Jin-Cheng; Donadio, Davide; Harju, Ari
2015-09-01
We derive expressions of interatomic force and heat current for many-body potentials such as the Tersoff, the Brenner, and the Stillinger-Weber potential used extensively in molecular dynamics simulations of covalently bonded materials. Although these potentials have a many-body nature, a pairwise force expression that follows Newton's third law can be found without referring to any partition of the potential. Based on this force formula, a stress applicable for periodic systems can be unambiguously defined. The force formula can then be used to derive the heat current formulas using a natural potential partitioning. Our heat current formulation is found to be equivalent to most of the seemingly different heat current formulas used in the literature, but to deviate from the stress-based formula derived from two-body potential. We validate our formulation numerically on various systems described by the Tersoff potential, namely three-dimensional silicon and diamond, two-dimensional graphene, and quasi-one-dimensional carbon nanotube. The effects of cell size and production time used in the simulation are examined.
Light-induced dynamics in the Lorentz oscillator model with magnetic forces
Fisher, W. M.; Rand, S. C. [Applied Physics Program, University of Michigan, Ann Arbor, Ann Arbor, Michigan 48109 (United States)
2010-07-15
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.
Ferromagnetic resonance imaging of Co films using magnetic resonance force microscopy
Suh, B.J.; Hammel, P.C.; Zhang, Z.; Midzor, M.M.; Roukes, M.L.; Childress, J.R.
1998-07-01
Lateral one-dimensional imaging of cobalt (Co) films by means of microscopic ferromagnetic resonance (FMR) detected using the magnetic resonance force microscope (MRFM) is demonstrated. A novel approach involving scanning a localized magnetic probe is shown to enable FMR imaging in spite of the broad resonance linewidth. We introduce a spatially selective local field by means of a small, magnetically polarized spherical crystallite of yttrium iron garnet (YIG). Using MRFM-detected FMR signals from a sample consisting of two Co films, we can resolve the {approximately}20 {mu}m lateral separation between the films. The results can be qualitatively understood by consideration of the calculated spatial profiles of the magnetic field generated by the YIG sphere. {copyright} {ital 1998 American Vacuum Society.}
Vadas, Sharon
Compressible f-plane solutions to body forces, heatings, and coolings, and application to the primary, f-plane compressible solutions to local, interval, 3-D horizontal and vertical body forces, and heat/cooling consists of dipoles at z 150200 km and a heating at z 240260 km. We find that the compressible solutions
Secondary breakup of axisymmetric liquid drops. I. Acceleration by a constant body force
NASA Astrophysics Data System (ADS)
Han, Jaehoon; Tryggvason, Grétar
1999-12-01
The secondary breakup of liquid drops, accelerated by a constant body force, is examined for small density differences between the drops and the surrounding fluid. Two cases are examined in detail: a density ratio close to unity (?d/?o=1.15, where the Boussinesq approximation is valid) and a density ratio of ten. A finite difference/front tracking numerical technique is used to solve the unsteady Navier-Stokes equations for both the drops and the surrounding fluid. The breakup is controlled by the Eötvös number (Eo), the Ohnesorge number (Oh), and the viscosity and density ratios. If viscous effects are small (small Oh), the Eötvös number is the main controlling parameter. In the Boussinesq limit, as Eo increases the drops break up in a backward facing bag, transient breakup, and a forward facing bag mode. At a density ratio of ten, similar breakup modes are observed, with the exception that the forward facing bag mode is replaced by a shear breakup mode. Similar breakup modes have been seen experimentally for much larger density ratios. Although a backward facing bag is seen at low Oh, where viscous effects are small, comparisons with simulations of inviscid flows show that the bag breakup is a viscous phenomenon, due to boundary layer separation and the formation of a wake. At higher Oh, where viscous effects modify the evolution, the simulations show that the main effect of increasing Oh is to move the boundary between the different breakup modes to higher Eo. The results are summarized by "breakup maps" where the different breakup modes are shown in the Eo-Oh plane for different values of the viscosity and the density ratios.
Report of the Task Force on SSC Magnet System Test Site
NONE
1984-10-01
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.
ERIC Educational Resources Information Center
Carruthers, Rebecca; de Berg, Kevin
2010-01-01
Seventeen Grade Six students were divided into small groups to study the concept of forces in the context of magnets and their properties. The researcher, a pre-service primary school teacher, encouraged the students into conversation about magnets and it was found that, without hesitation, they talked about their prior experience of magnets. The
Asymptotic analysis of force-free magnetic fields of cylindrical symmetry
NASA Technical Reports Server (NTRS)
Sturrock, P. A.; Antiochos, S. K.; Roumeliotis, G.
1995-01-01
It is known from computer calculations that if a force-free magnetic-field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution, and, in the process, the energy of the field increases progressively. Analysis of a simple model of force-free fields of cylindrical symmetry leads to simple asymptotic expressions for the extent and energy of such a configuration. The analysis is carried through for both spherical and planar source surfaces. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.
Rogers, Hunter B.; Anani, Tareq; Choi, Young Suk; Beyers, Ronald J.; David, Allan E.
2015-01-01
Realizing the full potential of magnetic nanoparticles (MNPs) in nanomedicine requires the optimization of their physical and chemical properties. Elucidation of the effects of these properties on clinical diagnostic or therapeutic properties, however, requires the synthesis or purification of homogenous samples, which has proved to be difficult. While initial simulations indicated that size-selective separation could be achieved by flowing magnetic nanoparticles through a magnetic field, subsequent in vitro experiments were unable to reproduce the predicted results. Magnetic field-flow fractionation, however, was found to be an effective method for the separation of polydisperse suspensions of iron oxide nanoparticles with diameters greater than 20 nm. While similar methods have been used to separate magnetic nanoparticles before, no previous work has been done with magnetic nanoparticles between 20 and 200 nm. Both transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis were used to confirm the size of the MNPs. Further development of this work could lead to MNPs with the narrow size distributions necessary for their in vitro and in vivo optimization. PMID:26307980
Magnetic force driven nanogenerators as a noncontact energy harvester and sensor.
Cui, Nuanyang; Wu, Weiwei; Zhao, Yong; Bai, Suo; Meng, Leixin; Qin, Yong; Wang, Zhong Lin
2012-07-11
Nanogenerator has been a very important energy harvesting technology through directly deforming piezoelectric material. Here, we report a new magnetic force driven contactless nanogenerator (CLNG), which avoids the direct contact between nanogenerator and mechanical movement source. The CLNG can harvest the mechanical movement energy in a noncontact mode to generate electricity. Their output voltage and current can be as large as 3.2 V and 50 nA, respectively, which is large enough to power up a liquid crystal display. We also demonstrate a means by which a magnetic sensor can be built. PMID:22681509
MEMS-Based Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer
NASA Technical Reports Server (NTRS)
Lee, Choonsup; Butler, Mark C.; Elgammal, Ramez A.; George, Thomas; Hunt, Brian; Weitekamp, Daniel P.
2006-01-01
Nuclear Magnetic Resonance (NMR) spectroscopy allows assignment of molecular structure by acquiring the energy spectrum of nuclear spins in a molecule, and by interpreting the symmetry and positions of resonance lines in the spectrum. As such, NMR has become one of the most versatile and ubiquitous spectroscopic methods. Despite these tremendous successes, NMR experiments suffer from inherent low sensitivity due to the relatively low energy of photons in the radio frequency (rt) region of the electromagnetic spectrum. Here, we describe a high-resolution spectroscopy in samples with diameters in the micron range and below. We have reported design and fabrication of force-detected nuclear magnetic resonance (FDNMR).
Estimating Three-Dimensional Orientation of Human Body Parts by Inertial/Magnetic Sensing
Sabatini, Angelo Maria
2011-01-01
User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) space. Although they are a promising choice as wearable sensors under many respects, the inertial and magnetic sensors currently in use offer measuring performance that are critical in order to achieve and maintain accurate 3D-orientation estimates, anytime and anywhere. This paper reviews the main sensor fusion and filtering techniques proposed for accurate inertial/magnetic orientation tracking of human body parts; it also gives useful recipes for their actual implementation. PMID:22319365
Estimating three-dimensional orientation of human body parts by inertial/magnetic sensing.
Sabatini, Angelo Maria
2011-01-01
User-worn sensing units composed of inertial and magnetic sensors are becoming increasingly popular in various domains, including biomedical engineering, robotics, virtual reality, where they can also be applied for real-time tracking of the orientation of human body parts in the three-dimensional (3D) space. Although they are a promising choice as wearable sensors under many respects, the inertial and magnetic sensors currently in use offer measuring performance that are critical in order to achieve and maintain accurate 3D-orientation estimates, anytime and anywhere. This paper reviews the main sensor fusion and filtering techniques proposed for accurate inertial/magnetic orientation tracking of human body parts; it also gives useful recipes for their actual implementation. PMID:22319365
Large-Scale Magnetic Field Generation by Randomly Forced Shearing Waves
NASA Astrophysics Data System (ADS)
Heinemann, T.; McWilliams, J. C.; Schekochihin, A. A.
2011-12-01
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.
Magnetic dipole super-resonances and their impact on mechanical forces at optical frequencies.
Liberal, Ińigo; Ederra, Ińigo; Gonzalo, Ramón; Ziolkowski, Richard W
2014-04-01
Artificial magnetism enables various transformative optical phenomena, including negative refraction, Fano resonances, and unconventional nanoantennas, beamshapers, polarization transformers and perfect absorbers, and enriches the collection of electromagnetic field control mechanisms at optical frequencies. We demonstrate that it is possible to excite a magnetic dipole super-resonance at optical frequencies by coating a silicon nanoparticle with a shell impregnated with active material. The resulting response is several orders of magnitude stronger than that generated by bare silicon nanoparticles and is comparable to electric dipole super-resonances excited in spaser-based nanolasers. Furthermore, this configuration enables an exceptional control over the optical forces exerted on the nanoparticle. It expedites huge pushing or pulling actions, as well as a total suppression of the force in both far-field and near-field scenarios. These effects empower advanced paradigms in electromagnetic manipulation and microscopy. PMID:24718235
LeBlanc, M
1990-01-01
Present body-powered upper-limb prostheses use a cable control system employing World War II aircraft technology to transmit force from the body to the prosthesis for operation. The cable and associated hardware are located outside the prosthesis. Because individuals with arm amputations want prostheses that are natural looking with a smooth, soft outer surface, a design and development project was undertaken to replace the cable system with hydraulics located inside the prosthesis. Three different hydraulic transmission systems were built for evaluation, and other possibilities were explored. Results indicate that a hydraulic force transmission system remains an unmet challenge as a practical replacement for the cable system. The author was unable to develop a hydraulic system that meets the necessary dynamic requirements and is acceptable in size and appearance. PMID:10149042
Hypervelocity impacts and magnetization of small bodies in the Solar System
NASA Technical Reports Server (NTRS)
Chen, Guangqing; Ahrens, Thomas J.; Hide, Raymond
1995-01-01
The observed magnetism of asteroids such as Gaspra and Ida (and other small bodies in the solar system including the Moon and meteorites) may have resulted from an impact-induced shock wave producing a thermodynamic state in which iron-nickel alloy, dispersed in a silicate matrix, is driven from the usual low-temperature, low-pressure, alpha, kaemacite, phase to the paramagnetic, epsilon (hcp), phase. The magnetization was acquired upon rarefaction and reentry into the ferromagnetic, alpha, structure. The degree of remagnetization depends on the strength of the ambient field, which may have been associated with a Solar-System-wide magnetic field. A transient field induced by the impact event itself may have resulted in a significant, or possibly, even a dominant contribution, as well. The scaling law of Housen et al. (Housen, K. R., R. M. Schmidt, and K. A. Holsapple 1991) for catastrophic asteroid impact disaggregation imposes a constraint on the degree to which small planetary bodies may be magnetized and yet survive fragmentation by the same event. Our modeling results show it is possible that Ida was magnetized when a large impact fractured a 125 +/- 22-km-radius protoasteroid to form the Koronis family. Similarly, we calculate that Gaspra could be a magnetized fragment of a 45 +/- 15 km-radius protoasteroid.
NASA Technical Reports Server (NTRS)
Knight, J. D.; Xia, Z.; Mccaul, E.; Hacker, H., Jr.
1992-01-01
Calculations of the forces exerted on a journal by a magnetic bearing actuator are presented, along with comparisons to experimentally measured forces. The calculations are based on two-dimensional solutions for the flux distribution in the metal parts and free space, using finite but constant permeability in the metals. Above a relative permeability of 10,000 the effects of changes in permeability are negligible, but below 10,000 decreases in permeability cause significant decreases in the force. The calculated forces are shown to depend on the metal permeability more strongly when the journal is displaced from its centered position. The predicted forces in the principal attractive direction are in good agreement with experiment when a relatively low value of permeability is chosen. The forces measured normal to the axis of symmetry when the journal is displaced from that axis, however, are significantly higher than predicted by theory, even with a value of relative permeability larger than 5000. These results indicate a need for further work including nonlinear permeability distributions.
Imaging Carbon Nanotubes in High Performance Polymer Composites via Magnetic Force Microscope
NASA Astrophysics Data System (ADS)
Lillehei, Peter T.; Park, Cheol; Rouse, Jason H.; Siochi, Emilie J.
2002-12-01
Application of carbon nanotubes as reinforcement in structural composites is dependent on the efficient dispersion of the nanotubes in a high performance polymer matrix. The characterization of such dispersion is limited by the lack of available tools to visualize the quality of the matrix/carbon nanotube interaction. The work reported herein demonstrates the use of magnetic force microscopy (MFM) as a promising technique for characterizing the dispersion of nanotubes in a high performance polymer matrix.
Imaging Carbon Nanotubes in High Performance Polymer Composites via Magnetic Force Microscope
NASA Technical Reports Server (NTRS)
Lillehei, Peter T.; Park, Cheol; Rouse, Jason H.; Siochi, Emilie J.; Bushnell, Dennis M. (Technical Monitor)
2002-01-01
Application of carbon nanotubes as reinforcement in structural composites is dependent on the efficient dispersion of the nanotubes in a high performance polymer matrix. The characterization of such dispersion is limited by the lack of available tools to visualize the quality of the matrix/carbon nanotube interaction. The work reported herein demonstrates the use of magnetic force microscopy (MFM) as a promising technique for characterizing the dispersion of nanotubes in a high performance polymer matrix.
Calculation of the induced currents and forces for a hybrid magnetic levitation system
Albertz, D.; Dappen, S.; Henneberger, G.
1997-03-01
This paper presents the calculation of the induced currents and forces for a 3D non-linear eddy current field problem with ferromagnetic moving conductors. The {rvec A}, V-{rvec A} formulation is used in combination with four different gauging methods to stabilize the solution process. To consider non-rectangular shapes of geometries tetrahedral elements were employed. The computation procedure is applied to a hybrid magnetic levitation system of a contactless and frictionless conveyance system.
Many-Body Electrostatic Forces between Colloidal Particles at Vanishing Ionic Strength
NASA Astrophysics Data System (ADS)
Merrill, Jason W.; Sainis, Sunil K.; Dufresne, Eric R.
2009-09-01
Electrostatic forces between small groups of colloidal particles are measured using blinking optical tweezers. When the electrostatic screening length is longer than the interparticle separation, forces are found to be non-pairwise-additive. Both pair and multiparticle forces are well described by the linearized Poisson-Boltzmann equation with constant potential boundary conditions. These findings may play an important role in understanding the structure and stability of a wide variety of systems, from micron-sized particles in oil to aqueous nanocolloids.
Niranjan Sahoo; D. R. Mahapatra; G. Jagadeesh; S. Gopalakrishnan; K. P. J. Reddy
2003-01-01
A miniature three-component accelerometer balance system for measuring the fundamental aerodynamic force coefficients over blunt bodies has been designed, fabricated and tested in the Indian Institute of Science hypersonic shock tunnel HST2 at a nominal Mach number of 5.75. The model and the balance system are supported by rubber bushes, thereby ensuring unrestrained free-floating conditions of the model in the
NASA Astrophysics Data System (ADS)
Savinainen, Antti; Mäkynen, Asko; Nieminen, Pasi; Viiri, Jouni
2013-06-01
Earlier research has shown that after physics instruction, many students have difficulties with the force concept, and with constructing free-body diagrams (FBDs). It has been suggested that treating forces as interactions could help students to identify forces as well as to construct the correct FBDs. While there is evidence that identifying interactions helps students in quantitative problem solving, there is no previous research investigating the effect of a visual-representation toolan interaction diagram (ID)on students ability to identify forces, and to construct the correct FBDs. We present an empirical study conducted in 11 Finnish high schools on students (n=335, aged 16) taking their first, mandatory, introductory physics course. The study design involved groups of students having heavy, light, or no use of IDs. The heavy and light ID groups answered eight pairs of ID and FBD questions in various physical contexts and the no ID group answered two of the eight FBD questions. The results indicate that the heavy ID group outperformed both the light and the no ID groups in identifying forces and constructing the correct FBDs. The analysis of these data indicates that the use of IDs is especially beneficial in identifying forces when constructing FBDs.
Magnetic Tweezers-Based Force Clamp Reveals Mechanically Distinct apCAM Domain Interactions
Kilinc, Devrim; Blasiak, Agata; OMahony, James J.; Suter, Daniel M.; Lee, Gil U.
2012-01-01
Cell adhesion molecules of the immunoglobulin superfamily (IgCAMs) play a crucial role in cell-cell interactions during nervous system development and function. The Aplysia CAM (apCAM), an invertebrate IgCAM, shares structural and functional similarities with vertebrate NCAM and therefore has been considered as the Aplysia homolog of NCAM. Despite these similarities, the binding properties of apCAM have not been investigated thus far. Using magnetic tweezers, we applied physiologically relevant, constant forces to apCAM-coated magnetic particles interacting with apCAM-coated model surfaces and characterized the kinetics of bond rupture. The average bond lifetime decreased with increasing external force, as predicted by theoretical considerations. Mathematical simulations suggest that the apCAM homophilic interaction is mediated by two distinct bonds, one involving all five immunoglobulin (Ig)-like domains in an antiparallel alignment and the other involving only two Ig domains. In summary, this study provides biophysical evidence that apCAM undergoes homophilic interactions, and that magnetic tweezers-based, force-clamp measurements provide a rapid and reliable method for characterizing relatively weak CAM interactions. PMID:22995484
Cha, Y.S.; Hull, J.R.; Mulcahy, T.M.; Rossing, T.D. )
1991-11-15
A series of experiments measuring the levitation force between a permanent magnet (PM) and a high-temperature superconductor (HTS) and between pairs of PMs, coupled with finite-element calculations of the forces and fields, has identified factors that influence the levitation force. The self-demagnetizing factor within the HTS and, to some extent, within the PM has a profound effect on magnetic pressure. For large HTSs with strong flux-pinning, the demagnetizing effect of the diamagnetic image of the PM is substantial. For short distances between the HTS and PM, compression of magnetic flux produces a dependence on PM diameter.
NASA Astrophysics Data System (ADS)
Prajapati, R. P.
2013-01-01
The Jeans instability of self-gravitating dusty plasma with polarization force is investigated considering the effects of magnetic field, dust temperature and radiative condensation. The condition of Jeans instability and expression of critical Jeans wave number are obtained which depend upon polarization force and dust temperature but these are unaffected by the presence of magnetic field. The radiative heat-loss functions also modify the Jeans condition of instability and expression of critical Jeans wave number. It is observed that the polarization force and ratio of radiative heat-loss functions have destabilizing while magnetic field and dust temperature have stabilizing influence on the growth rate of Jeans instability.
Nonlinear force-free magnetic fields. [quasi-steady state evolution of astrophysical fields
NASA Technical Reports Server (NTRS)
Low, B. C.
1982-01-01
The nonlinear properties of force-free magnetic fields are reviewed with particular reference to the mechanisms for the sudden release of stored energy in flares during the quasi-steady evolution of solar fields. It is shown that in the solar atmosphere, force-free fields with a nonconstant scalar function in the field equations are more likely to occur than those with a constant scalar function, and the nonlinear properties of these fields may give rise to many interesting physical effects. Consideration is then given to two possible mechanisms of field evolution: a model in which a force-free field in a medium of infinite electrical conductivity evolves in response to slowly changing boundary conditions brought about by photospheric motions in the solar active region, and a model in which a field in a medium of small finite electrical conductivity evolves in response to the slow Ohmic dissipation of the electric current.