scholarly journals A problem of Ulam about magnetic fields generated by knotted wires

2017 ◽  
Vol 39 (8) ◽  
pp. 2048-2070 ◽  
Author(s):  
ALBERTO ENCISO ◽  
DANIEL PERALTA-SALAS
Keyword(s):  
Magnetic Fields ◽  
Magnetic Line ◽  
The Wire

In the context of magnetic fields generated by wires, we study the connection between the topology of the wire and the topology of the magnetic lines. We show that a generic knotted wire has a magnetic line of the same knot type, but that given any pair of knots there is a wire isotopic to the first knot having a magnetic line isotopic to the second. These questions can be traced back to Ulam in 1935.

scholarly journals Information storage in permalloy modulated magnetic nanowires

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guidobeth Sáez ◽  
Pablo Díaz ◽  
Eduardo Cisternas ◽  
Eugenio E. Vogel ◽  
Juan Escrig
Keyword(s):  
Magnetic Material ◽  
Phase Diagram ◽  
Magnetic Fields ◽  
Domain Walls ◽  
Wire Diameter ◽  
Information Storage ◽  
Magnetic Nanowires ◽  
The Wire ◽  
The Stability ◽  
Cylindrical Wire

AbstractA long piece of magnetic material shaped as a central cylindrical wire (diameter $$d=50$$ d = 50 nm) with two wider coaxial cylindrical portions (diameter $$D=90$$ D = 90 nm and thickness $$t=100$$ t = 100 nm) defines a bimodulated nanowire. Micromagnetism is invoked to study the equilibrium energy of the system under the variations of the positions of the modulations along the wire. The system can be thought of as composed of five independent elements (3 segments and 2 modulations) leading to $$2^5=32$$ 2 5 = 32 possible different magnetic configurations, which will be later simplified to 4. We investigate the stability of the configurations depending on the positions of the modulations. The relative chirality of the modulations has negligible contributions to the energy and they have no effect on the stability of the stored configuration. However, the modulations are extremely important in pinning the domain walls that lead to consider each segment as independent from the rest. A phase diagram reporting the stability of the inscribed magnetic configurations is produced. The stability of the system was then tested under the action of external magnetic fields and it was found that more than 50 mT are necessary to alter the inscribed information. The main purpose of this paper is to find whether a prototype like this can be complemented to be used as a magnetic key or to store information in the form of firmware. Present results indicate that both possibilities are feasible.

scholarly journals Information storage in permalloy modulated magnetic nanowires

2021 ◽  
Author(s):  
Guidobeth Sáez ◽  
Pablo Díaz ◽  
Eduardo Cisternas ◽  
Eugenio E. Vogel ◽  
Juan Escrig
Keyword(s):  
Magnetic Material ◽  
Phase Diagram ◽  
Magnetic Fields ◽  
Domain Walls ◽  
Wire Diameter ◽  
Information Storage ◽  
Magnetic Nanowires ◽  
The Wire ◽  
The Stability ◽  
Cylindrical Wire

Abstract A long piece of magnetic material shaped as a central cylindrical wire (diameter d = 50 nm) with two wider coaxial cylindrical portions (diameter D = 90 nm and thickness t = 100 nm) defines a bimodulated nanowire. Micromagnetism is invoked to study the equilibrium energy of the system under the variations of the positions of the modulations along the wire. The system can be thought of as composed of 5 independent elements (3 segments and 2 modulations) leading to 25 = 32 different magnetic configurations. We investigate the stability of the configurations depending on the positions of the modulations. The relative chirality of the modulations has negligible contributions to the energy and they have no effect in the stability of the stored configuration. However, the modulations are extremely important in pinning the domain walls that lead to consider each segment as independent from the rest. A phase diagram reporting the stability of the inscribed magnetic configurations is produced. The stability of the system was then tested under the action of external magnetic fields and it is found that more than 50 mT are necessary to alter the inscribed information. The main purpose of this paper is to find weather a prototype like this can complemented to be used as firmware or magnetic keys. Present results indicate that this is feasible.

scholarly journals Numerical modelling of dynamic resistance in high-temperature superconducting coated-conductor wires

2021 ◽  
Author(s):  
MD Ainslie ◽  
Christopher Bumby ◽  
Zhenan Jiang ◽  
R Toyomoto ◽  
N Amemiya
Keyword(s):  
Magnetic Fields ◽  
Angular Dependence ◽  
Flow Resistance ◽  
Transport Current ◽  
Ac Loss ◽  
Dynamic Resistance ◽  
Coated Conductor ◽  
Superconducting Properties ◽  
Flux Flow ◽  
The Wire

The use of superconducting wire within AC power systems is complicated by the dissipative interactions that occur when a superconductor is exposed to an alternating current and/or magnetic field, giving rise to a superconducting AC loss caused by the motion of vortices within the superconducting material. When a superconductor is exposed to an alternating field whilst carrying a constant DC transport current, a DC electrical resistance can be observed, commonly referred to as ‘dynamic resistance.’ Dynamic resistance is relevant to many potential hightemperature superconducting (HTS) applications and has been identified as critical to understanding the operating mechanism of HTS flux pump devices. In this paper, a 2D numerical model based on the finite-element method and implementing the H-formulation is used to calculate the dynamic resistance and total AC loss in a coated-conductor HTS wire carrying an arbitrary DC transport current and exposed to background AC magnetic fields up to 100 mT. The measured angular dependence of the superconducting properties of the wire are used as input data, and the model is validated using experimental data for magnetic fields perpendicular to the plane of the wire, as well as at angles of 30° and 60° to this axis. The model is used to obtain insights into the characteristics of such dynamic resistance, including its relationship with the applied current and field, the wire’s superconducting properties, the threshold field above which dynamic resistance is generated and the flux-flow resistance that arises when the total driven transport current exceeds the field-dependent critical current, Ic(B), of the wire. It is shown that the dynamic resistance can be mostly determined by the perpendicular field component with subtle differences determined by the angular dependence of the superconducting properties of the wire. The dynamic resistance in parallel fields is essentially negligible until Jc is exceeded and flux-flow resistance occurs.

Angular dependence of giant magneto impedance and magnetic characteristic of Co-based wire in different magnetic field ranges

2014 ◽  
Vol 28 (25) ◽  
pp. 1450197 ◽  
Author(s):  
Reza Mardani ◽  
Ahmad Amirabadizadeh ◽  
Majid Ghanaatshoar
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Angular Dependence ◽  
Hysteresis Loops ◽  
Magnetic Characteristic ◽  
Field Range ◽  
Wire Axis ◽  
Amorphous Wires ◽  
Giant Magneto Impedance ◽  
The Wire

Angular dependence of the giant magneto impedance (GMI), hysteresis loops and magnetization curves have been investigated in amorphous wires with respect to direction and amplitude of the magnetic field in room temperature. The measurements were performed at different orientation angles of the applied magnetic field relative to the wire axis and various magnetic field strengths in moderate (0–200 Oe) and high (0–5000 Oe) ranges. The highest GMI response (500%) and magnetization (100 emu/gr) were found for angles close to the wire axis in high magnetic field range. By increasing the angle from 0°, in moderate external magnetic fields the GMI and magnetization decrease without reaching the saturation. However, in high magnetic fields (~ 5000 Oe) these parameters are nearly constant and almost saturated for all angles. In both magnetic field ranges, increasing the angle of applied field widens the impedance curves.

NOVEL ONE-DIMENSIONAL STATES IN A BENT QUANTUM HALL JUNCTION

2007 ◽  
Vol 21 (08n09) ◽  
pp. 1207-1208 ◽  
Author(s):  
M. GRAYSON ◽  
L. STEINKE ◽  
M. HUBER ◽  
D. SCHUH ◽  
M. BICHLER ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Ohmic Contacts ◽  
Filling Factor ◽  
Quantum Hall ◽  
Electron System ◽  
Wire Length ◽  
Zero Bias ◽  
One Dimensional ◽  
Dc Bias ◽  
The Wire

Using a recently developed crystal growth technique (see Fig. 1), we have succeeded in creating a two-dimensional (2D) electron system that is bent at an atomically sharp angle of 90°1. Naming the two 2D systems after their substrate (S) and precleave (P) facets, we can measure their densities ns and np. In the presence of a tilted magnetic field, this system realizes an abrupt junction between two quantum Hall effect (QH) systems with arbitrary filling factors2νs = nsh/eB cos (θ) and νp = nph/eB sin (θ). When the two filling factors are equal νs = νp, the corner junction represents a multimode wire with the maximum number of forward & reverse moving modes equalling the filling factor ν plus two spin degenerate modes from corner-accumulation wire. The conductance of this bent QH system dI/dV(V) or G(T) can be characterized with four-point measurements. As long as the excitation energy (V or T, respectively) is smaller than the QH gap energy, there is no scattering of electrons away from the wire system to the 2D bulk and the transport is truly one-dimensional. The devices studied here are from 0.4 - 4 mm long with ohmic contacts alloyed on both facets away from the junction. The resulting 1D wire at the corner junction has exhibited metallic, insulating, and critical phases depending on filling factor, with all 1D conductances of order 0.02e2/h or below. The insulating 1D behavior occurs for ν = 1 and ν = 2, and is manifest in a vanishing 1D conductance at low temperatures and low dc voltage biases. Metallic 1D behavior occurs for ν = 1/3 where the conductance rises with decreasing temperature and the dc bias shows a large zero-bias peak in the differential conductivity. The so-called critical behavior has only weak temperature dependence and a weak zero-bias dip in the dc bias voltage dependence. The conductance G at ν = 3 and ν = 4 goes inversely with the wire length L indicating that scattering is distributed equally along the wire length. These observations can be partly explained with Hartree calculations of the bent quantum Hall junction. Low magnetic fields (ν = 3 and 4) are expected to manifest a multimode wire, which provides a basis for understanding the critical phase. Higher magnetic fields (ν = 1 and 2) are expected to open up a gap in the 1D energy spectrum at the corner, resulting in the experimentally observed insulating phase. Alternatively, disorder may also explain the 1D insulating behavior via scaling theory of localization. The highest magnetic fields for the fractional state ν = 1/3 show the remarkable metallic phase which might be explained in terms of an antiwire between counterpropagating ν = 1/3 Luttinger liquid edges which are randomly coupled by electron back-scattering events3.

scholarly journals INFLUENCE OF SUSPENSION OF WIRES ON THE ELECTROMAGNETIC FIELD OF A HIGH-VOLTAGE ELECTRIC TRANSMISSION LINE

2020 ◽  
Vol 2020 (1) ◽  
pp. 221-222
Author(s):  
Dmitriy Seredkin
Keyword(s):  
Electromagnetic Field ◽  
Magnetic Fields ◽  
Transmission Line ◽  
High Voltage ◽  
Software Package ◽  
Power Line ◽  
Electric Transmission ◽  
Electric Transmission Line ◽  
Electric And Magnetic Fields ◽  
The Wire

The conditions of electromagnetic safety on the route of a high-voltage power line are considered, taking into account the sag of the wire. As a result of modeling in the Fazonord software package, it was shown that taking into account the sag of the power line wire causes a significant change in the electric and magnetic fields at a normalized height

scholarly journals On the dependence of magnetic line ratios on time and spatial scales

2008 ◽  
Vol 4 (S259) ◽  
pp. 231-232
Author(s):  
Mikhail L. Demidov
Keyword(s):  
Magnetic Fields ◽  
Spatial Resolution ◽  
Solar Atmosphere ◽  
Solar Disk ◽  
Large Scale ◽  
Spatial Scales ◽  
Spectral Lines ◽  
Magnetic Line ◽  
Made In

AbstractComparison of magnetic fields measurements made in different spectral lines and observatories is an important tool for diagnostics of magnetohydrodynamic conditions in the solar atmosphere. But there is a deficit of information about the dependence of results on detailed position on the solar disk, spatial resolution and time. In this study these issues are discussed in application to the solar large-scale and Sun-as-a-star magnetic fields observations.

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