We evaluate, using exact general formulas, the flux-metric and magnetometric demagnetizing factors, N/sub f,m/, of a rectangular prism dimensions 2a/spl times/2b/spl times/2c with susceptibility /spl chi/=0 factor, N, an ellipsoid semiaxes a, b. c along axis. The results as functions longitudinal transverse dimension ratios are listed in tables plotted figures. three special cases b/spl Gt/(ca)/sup 1/2/, Lt/(ca)/sup a=b analyzed together case, to quantitatively show validity approximate...

Abstract Magnetic iron oxide particles are widely used as contrast agents to improve the sensitivity of magnetic resonance imaging (MRI). Their efficiency in MRI is usually quantified by transverse relaxivity ( r 2 ) solution. Herein, we synthesized a series magnetite nanocrystal clusters (MNCs) with ultra‐high polyol process and studied relationship between size MNCs. The sizes MNCs can be tuned over wide range from 13 179 nm. MNC suspensions function cluster was analyzed compared...

High temperature superconducting (HTS) armature windings have the potential for increasing electric loading of a synchronous generator due to their high current transport capacity, which could increase power density an HTS rotating machine. In this work, novel prototype with stator and permanent magnet rotor has been developed. It basic structure four poles six slots. The winding was constructed from double-pancake race-track coils 44 turns each. designed deliver 2.5 kW at 300 rpm. A...

From a theoretical analysis based on an energy minimization procedure and the critical-state model, authors analyze levitation of infinitely long superconductor above permanent magnets with different arrangements. A discussion optimum geometries showing large force good stability is presented from model results.

The fundamental complex susceptibilities χ=χ′−jχ″ are calculated from the symmetric critical-state hysteresis loops M(H) for an infinitely long hard superconductor with a rectangular cross section 2a×2b (a≤b). For model, Bean, Kim, exponential law, and triangular-pulse local-internal-field-dependent critical-current densities Jc(Hi) chosen. results of χ′ χ″ given as functions field amplitude Hm normalized to full-penetration Hp, sample dimensional ratio a/b, p parameter that characterizes Hi...

A numerical model based on the critical-state approximation and a magnetic-energy minimization procedure is presented to simulate levitation of system composed two isolated infinitely long superconductors levitating over permanent-magnet guideways. Three different sets magnetic guideways are simulated compared with experimental tests linear superconducting bearing for prototype real vehicle. In spite complexity guideway design, serves as first approach calculate vertical force these...

The force and stability of a levitating system consisting an infinitely long superconductor different arrangements parallel permanent magnets are theoretically analyzed for two cooling processes, field zero-field cooling, by using model based on the critical-state magnetic energy minimization procedure. authors find that near magnets, one can obtain improved lateral as compared to case cooling.

A large decrease in transport current density has been observed high-temperature superconducting films for increasing film thickness. In this work we theoretically explain the nature and ubiquitous presence of so-called thickness effect by analyzing self-field created currents superconductor, assuming a realistic field-dependent critical-current Jc. This knowledge can help finding ways to improve films.

The current–voltage curve and transport ac loss of a second-generation HTS tape with ferromagnetic NiW substrate brass stabilizer are measured. It is found that the up to two orders magnitude larger than what expected by power-law E(J) determined increases increasing frequency. Modeling results show overly large contributed in strip enhanced magnetic hysteresis substrate, frequency-dependent occurs layer covering but not itself as assumed previously. associated currents eddy currents, it has...

We present a systematic theoretical study of current profiles, magnetic field lines, and hysteresis ac loss in linearly arranged arrays rectangular superconducting strips subjected to transport current. Results are obtained by means numerical calculations assuming the critical-state model with constant critical density. Because finite filament thickness coupling effects considered, we can provide some useful hints as how arrange filaments order reduce actual tapes.

Levitation force is studied in a two-dimensional system consisting of an infinitely long superconductor immersed the magnetic field created by different arrangements parallel permanent magnets, based on critical-state model using energy minimization procedure. Results force, stability, and losses levitation process this are analyzed.

The levitation force and stability of superconducting devices are strongly dependent on both the geometry dimensions components cooling process superconductor. In this work we study these effects in levitating systems consisting an infinitely long superconductor a guideway different arrangements parallel permanent magnets. Using model based critical-state magnetic-energy minimization procedure, taking into account demagnetization fields, analyze influence parameters system such as width...

Important modifications on the magnetization loops of superconductor have been observed in superconductor-ferromagnet hybrids due to effects ferromagnetic components, which can be used for tuning critical-current density Jc desirable values. Here, a model based an energy minimization procedure is presented analyze complex interaction between and ferromagnets. We show how geometry orientation ferromagnets chosen shifting position peaks appearing positive or negative applied fields, and,...

Fluxmetric and magnetometric demagnetizing factors Nf Nm have been calculated using a finite-element method for rectangular prism 2a×2b×2c with susceptibility χ=−1, in the completely shielded state. Assuming field is applied along c dimension, results are plotted tabulated as functions of their aspect ratios c∕a b∕max[c,a].

The levitation force and stability in a superconductor-magnet system with maglev geometry are studied as function of the critical-current density superconductor, from realistic model based on minimizing magnetic energy. Results show that although is an increasing Jc, overhigh Jc may result instability. Therefore, optimum superconductor for given should be intermediate value which depends dimensions field magnet.

The demagnetization problem for a hollow sphere of inner radius a, outer b, and material susceptibility χ is solved analytically. As a/b increases from 0 to 1, the magnetometric demagnetizing factor N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> decreases 1/3 when > <; 0. In limit = 1 as -1 ∞. fluxmetric xmlns:xlink="http://www.w3.org/1999/xlink">f</sub> has negative minimum -3/4. These features are explained conceptually...

Complex ac susceptibility of magnetic colloids nanospheres, each consisting Fe3O4 nanoparticles densely and uniformly embedded in a polystyrene matrix, is measured as function frequency. A data analysis based on model the directly size distribution shows that spherical aggregate carries small residual moment, whose average basically independent sphere size. The mentioned assumes spheres undergo rotational Brownian motions obeying Debye’s theory Néel magnetization rotations. discussion made...

There is an intense research in maglev technology for providing convenient and safe transportation. In particular, several projects are being carried out worldwide -particularly Germany, Brazil, China- constructing full-scale trains. They based on the levitation of superconducting pellets over magnetic guideways. The optimization their geometrical parameters properties both parts become very important. Theoretical simulations capturing essential physics a useful tool understanding improving...

A phenomenological model has been developed for interpreting the magnetic properties of hard type-II superconductors. By means a volume and surface supercurrent density, this considers effects bulk flux pinning, thermal equilibrium magnetization, barrier. Based on model, several difficult problems concerning explanation hysteresis loop susceptibility data high-${\mathit{T}}_{\mathit{c}}$ superconducting grains are solved. Our work demonstrates presence surface-barrier effect in Accordingly,...

Perpendicular ac susceptibility of a superconducting long tape defined by magnetic moment and determined inductively flux is calculated using Brandt's technique from power-law dependence electric field on sheet current density. The requirements χ measurements to the experimental setup procedure are discussed based calculation results.