Constant Magnetic Flux Research Articles

Quantum transport of massless Dirac fermions through wormhole-shaped curved graphene in presence of constant axial magnetic flux

In this work, we have studied the spin-dependent quantum transport of charged fermion on (2+1)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(2+1)$$\\end{document}-dimensional spacetime, whose spatial part is described by a wormhole-type geometry in the presence of constant axial magnetic flux. Choosing the solutions of the Dirac equation associated with real energy and momentum, we explored the spin-dependent transmission probabilities and giant magnetoresistance (GMR) through a single layer of wormhole graphene with an external magnetic field, using the transition matrix (T-Matrix) approach. The spin-up and spin-down components within the A and B sublattices of graphene in the matrix of 4×1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$4\ imes 1$$\\end{document} wave function are coupled to each other due to the wormhole structure and the magnetic field. We have found that transport properties strongly depend on the magnetic field, incident energy, and geometric parameters of the system. We observed that the transmission probability increases as the radius of the wormhole increases, and the length of the wormhole decreases. The higher energies lead to a decrease in the transmission probabilities of particles. Furthermore, we observed that the probability of the spin-flip effect is almost larger than that of the non-spin-flip effect, illustrating that electrons lose their spins during transmission. These findings highlight the complex and interesting behavior of wormhole graphene in the presence of external magnetic fields and suggest that these nano structures can have potential applications in electronic and spintronic devices.

Analysis of Fine Fault Electrothermal Characteristics of Converter Transformer Reduced-Scale Model

Converter transformer is the key equipment in UHVDC transmission. If a local overheating fault occurs, it will inevitably form a local hot spot on the core, winding or other structural parts. Among these faults, multipoint grounding and interlaminar short circuit faults account for 30–50% of core accidents. The continuous overheating of 150–250 °C will cause ablation on the silicon steel sheet, which will destroy the insulation material and reduce the insulation performance. In severe cases, it will cause thermal expansion, resulting in local deformation or displacement of the core. Considering the scale of size and temperature parameters, the scale model of converter transformer is established based on the principle of constant magnetic flux density. By using the homogenization theory, the scaled model under multipoint grounding and interlaminar short circuit fault is simulated by electromagnetic heat. First, the single-phase four-column model of the core is established according to the scaled principle, and the core is refined. Secondly, taking the refined model as the research object, the magnetic thermal coupling simulation and analysis are carried out under multi-point grounding and interlaminar short circuit fault, and the magnetic density, eddy current loss and temperature distribution on each lamination are obtained. Finally, the correctness of the simulation is verified by the one-dimensional eddy current loss analytical equation, which provides a reference for the local overheating problem of converter transformers.

Chiral magnets from string theory

Chiral magnets with the Dzyaloshinskii-Moriya (DM) interaction have received quite an intensive focus in condensed matter physics because of the presence of a chiral soliton lattice (CSL), an array of magnetic domain walls and anti-domain walls, and magnetic skyrmions, both of which are important ingredients in the current nanotechnology. In this paper, we realize chiral magnets in type-IIA/B string theory by using the Hanany-Witten brane configuration (consisting of D3, D5 and NS5-branes) and the fractional D2 and D6 branes on the Eguchi-Hanson manifold. In the both cases, we put constant non-Abelian magnetic fluxes on higher dimensional (flavor) D-branes, turning them into magnetized D-branes. The O(3) sigma model with an easy-axis or easy-plane potential and the DM interaction is realized on the worldvolume of the lower dimensional (color) D-branes. The ground state is the ferromagnetic (uniform) phase and the color D-brane is straight when the DM interaction is small compared with the scalar mass. However, when the DM interaction is larger, the uniform state is no longer stable and the ground state is inhomogeneous: the CSL phases and helimagnetic phase. In this case, the color D-brane is no longer straight but is snaky (zigzag) when the DM interaction is smaller (larger) than a critical value. A magnetic domain wall in the ferromagnetic phase is realized as a kinky D-brane. We further construct magnetic skyrmions in the ferromagnetic phase, realized as D1-branes (fractional D0-branes) in the former (latter) configuration. We see that the host D2-brane is bent around the position of a D0-brane as a magnetic skyrmion. Finally, we construct, in the ferromagnetic phase, domain-wall skyrmions, that is, composite states of a domain wall and skyrmions, and find that the domain wall is no longer flat in the vicinity of the skyrmion. Consequently, a kinky D2-brane worldvolume is pulled or pushed in the vicinity of the D0-brane depending on the sign of the skyrmion topological charge.

Nonlinear Interaction of Magnetoacoustic Modes in a Quasi-Isentropic Plasma Flow

The nonlinear interaction of magnetoacoustic waves in a plasma is analytically studied. A plasma is an open system. It is affected by the straight constant equilibrium magnetic flux density forming constant angle with the wave vector which varies from 0 till π. The nonlinear instantaneous equation which describes excitation of secondary wave modes in the field of intense magnetoacoustic perturbations is derived by use of projecting. There is a diversity of nonlinear interactions of waves in view of variety of wave modes, which may be slow or fast and may propagate in different directions. The excitation is analysed in the physically meaningful cases, that is: harmonic and impulsive exciter, oppositely or accordingly directed dominant and secondary wave modes.

Mass spectrum in a six-dimensional SU(n) gauge theory on a magnetized torus

We examine six-dimensional SU(n) gauge theories compactified on a two-dimensional torus with a constant magnetic flux background to obtain a comprehensive low-energy mass spectrum. We introduce general background configurations including the magnetic flux and continuous Wilson line phases, consistent with classical equations of motion. Under the standard gauge fixing procedure, the complete mass spectrum in low-energy effective theory for the SU(n) case is newly presented without imposing restrictions on the gauge fixing parameter. Our analysis confirms the inevitable existence of tachyonic modes, which neither depend on the background configurations of Wilson line phases nor are affected by the gauge fixing parameter. Masses for some low-energy modes exhibit dependence on the gauge fixing parameter, and these modes are identified as would-be Goldstone bosons that are absorbed by massive four-dimensional vector fields. We discuss the phenomenological implications associated with stabilization or condensation of the tachyonic states. Various mass spectra and symmetry-breaking patterns are expected with flux backgrounds in the SU(n) case. They are helpful for constructing phenomenologically viable models beyond the standard model, such as gauge-Higgs unification and grand unified theories.

Topology in the space-time scaling limit of quantum dynamics

We investigate the role of topology in the space-time scaling limit of quantum quench dynamics, where both time and system size tend to infinity at a constant ratio. There, while the standard topological characterization relying on local unitary transformations becomes ill defined, we show how a different dynamical notion of topology naturally arises through a dynamical winding number encoding the linear response of the Berry phase to a magnetic flux. Specifically, we find that the presence of a locally invisible constant magnetic flux is revealed by a dynamical staircase behavior of the Berry phase, whose topologically quantized plateaus characterize the space-time scaling limit of a quenched Rice-Mele model. These jumps in the Berry phase are also shown to be related to the interband elements of the DC current operator. We outline possible experimental platforms for observing the predicted phenomena in finite systems.

Pulse Frequency Modulated Interleaved Boost-Integrated LC Series Resonant Converter With Frequency-Free Designed Transformer

In this article, we propose a novel interleaved boost-integrated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> series resonant converter, in which the series resonant tank is located on the secondary side. Moreover, the input and output of the interleaved boost unit are in series directly, which is helpful to reduce the voltage stress of the output filter capacitor of boost unit. With the proposed pulse frequency modulation, except for that the output voltage can be controlled as constant under different input voltages, another feature is that the high-frequency transformer design is related to the series resonant frequency instead of the switching frequency. Hence, the proposed converter can operate under a very wide switching frequency range with a constant maximum magnetic flux density. The zero voltage switching and zero current switching can be achieved for all switches diodes. Finally, a 500-W prototype with a switching frequency range from 60 to 200 kHz is built to verify the operation principles of the proposed converter and modulation.

A Magnetically Controlled Current Transformer for Stable Energy Harvesting

The magnetically controlled current transformer (MCCT) is proposed to harvest stable energy from the magnetic field induced by the transmission-line fluctuating current. Compared with the conventional current transformer (CT), the advance of the proposed MCCT originates from the so-called constant magnetic flux control, which is achieved by connecting an electronic load on the secondary side of MCCT, and adjust the load impedance to make it equivalent to the corresponding resistive-capacitive impedance for magnetization or demagnetization. Furthermore, the working principle and the excitation characteristic of the MCCT system have been analyzed using the equivalent magnetic circuit and equivalent circuit methods. In addition, the details of the electronic load circuit and control system of the MCCT are presented in this paper, and the stability of the system is verified using logarithmic criterion and total harmonic current distortion (THDi) analysis. Finally, the co-simulation and experimental results show that MCCT can produce a stable output power of 13 W in the range of 50–500 A current fluctuations, demonstrating that the proposed magnetic energy harvester is capable of a high conversion efficiency and output stability.

Investigation of MHD natural convective flow of optically thick medium-radiating CNT Casson nanofluid over an infinite flat plate with reference to Caputo fractional derivative: As an application to water purification

In this article, the application of Caputo fractional operators of order α, α∈ (0,1) has been studied. Heat transmission near the surface of a vertical plate in the flow of optically thick radiating Casson nanofluid along with mass diffusion in the presence of heat source/sink and constant magnetic flux is investigated. In the fluid problem, an H2O-based Casson nanofluid with carbon nanotube (CNTs) suspensions is investigated. The non-dimensionalized governing PDEs have been solved analytically via the combination of Fourier-sine and Laplace transform techniques and closed form of solutions are attained for the velocity, temperature, and concentration fields in terms of the Mittag-Leffler function. The physical behavior of the significant parameters has been scrutinized graphically. As a result, it is identified that the concentration, temperature, and velocity curves escalate drastically with the raising values of the fractional quantity α due to the alteration in mass, thermal, and momentum boundary layers with higher values of time t. When t>1, the species level in the fluid along with the fluid temperature and velocity rises with the fractional quantity α and decelerates when 0<t<1. Further analysis reveals that as the magnetic field is strengthened, the flow curves decelerate rapidly. Also, tables have been presented to show the influence of the controlling physical quantities on the friction drag and heat transmission rate.

Magnetohydrodynamics (MHD) Induced Slip Flow of a Non-Newtonian Fluid through Circular Microchannels

The present numerical analysis reveals the nature of non-Newtonian fluid flow through circular microchannels under slip boundary conditions. The power law has been used for the simulation of the fluid flow, which considers a steady, laminar, incompressible non-Newtonian fluid acted upon by a constant, externally applied magnetic field. The flow is axisymmetric and slip boundary conditions are applied in the near wall. A constant magnetic flux has been applied on the wall boundary to analyze the effect of magnetic field on Xanthan solution in formic acid, a type of non-Newtonian fluid having electrical conductivity. Using control volume method of finite difference scheme, a set of dimensionless governing differential equations defining the behavior of the fluid flow in the microchannel under an externally applied magnetic field, has been solved using slip boundary conditions to understand the effect of magnetic field on slip induced flow of non-Newtonian fluids. The results have depicted that the magnetic field affects both the centerline velocity and slip velocity but it is more prominent for the centerline velocities. The main objective of this research is to study the flow of non-Newtonian fluid, Xanthan through a circular microchannel and its corresponding behavior when flow boundary conditions are applied to interpret the characteristics under an externally applied magnetic field. The results obtained from this present study will find its application in the area of the flow of ferrofluids and biofluids.&#x0D; HIGHLIGHTS&#x0D; &#x0D; Most of the bio fluids and ferrofluids are non-Newtonian in nature and it is required to control these fluids when they pass through microchannels of modern devices&#x0D; Analysis conducted to find out the flow behaviour of non-Newtonian fluids through circular microchannels when they are exposed to externally applied magnetic fields&#x0D; Slip flow occurs in the fluid flow and an externally applied magnetic field controls the flow patterns by affecting slip velocity and centerline velocity which introduces extra flow in the microchannel. The results are helpful for better understanding of the flow of ferrofluids and bio fluids through circular microchannels&#x0D; &#x0D; GRAPHICAL ABSTRACT

Influence of Gamma Radiation on the Damping Property of Magnetorheological Elastomer.

Magnetorheological elastomer (MRE) is a kind of smart material, whose mechanical property can be controlled by the external magnetic field quickly and reversibly. The damping property of MRE is one of the most concerned properties when designing MRE based devices. In this work, the influence of gamma radiation on the damping property of MRE was investigated. Six different exposures of gamma radiation were applied to the MRE samples. The highest gamma radiation dose was up to 1 × 105 Gy(Si), which can cover most of the engineering application scenarios. The influence of gamma radiation on the damping-strain relation and the damping-magnetic-field relation were studied. The probable mechanisms were discussed in detail. It is found that the gamma radiation does not affect the variation trend of loss factor of MRE with increasing strain amplitude or magnetic flux density. But it affects the variation trend of the maximum change of strain-induced or magnetic-field-induced loss factor of MRE. Besides, with constant strain and constant magnetic flux density, the loss factor of MRE shows w-shape variation trend with increasing gamma radiation dose. It is considered to be resulted from the combined action of the intrinsic damping and the interfacial friction damping of MRE.

Design and simulation of a binary full adder based on quantum rings

In this paper, a binary full adder circuit is designed with eight quantum rings where each ring is threaded by a magnetic flux which is an odd multiple of half of the magnetic flux quantum. The quantum rings are divided into two categories with four rings connected to each other in parallel. They are attached symmetrically to two semi-infinite one-dimensional metallic electrodes , and three gate voltages are applied as three inputs of the full adder. The Hamiltonian of the system is approximated by the tight-binding method, and the calculations are performed by using Green's function formalism. The current-voltage characteristics are obtained for different values of applied gate voltages in the strong and weak-coupling strengths between the quantum rings and source and drain electrodes. The results are in accordance with the truth table of a binary full adder and show this quantum circuit behaves as a binary full adder. • This work proposes a binary full adder consisting of eight quantum rings where a constant magnetic flux is passing through each of them. • The designed full adder with eight quantum rings is divided into two separate parts (Sum and Carry-out) which are connected symmetrically to the source and drain electrodes. • The values of the applied gate voltages are considered as the full adder inputs and the electric current is the output of the system. • The output current of the proposed circuit based on the system input voltages is in accordance with the truth table of a binary full adder.

Micromagnetic and Microstructural Characterization of Ferromagnetic Steels in Different Heat Treatment Conditions

The paper addresses the investigation of microstructures from AISI 52100 and AISI 4140 in hardened as well as in quenched and tempered conditions. The specimens are compared in terms of their magnetic hysteresis and their microstructural and mechanical properties. Material properties were determined by hardness, microhardness, and X-ray diffraction measurements. Two different approaches were used to characterize magnetic properties via a hysteresis frame device, aiming, on the one hand, to record the magnetic hysteresis with established proceedings by setting a constant magnetic flux and, on the other hand, by offsetting a constant field strength to facilitate reproducibility of the results with other micromagnetic measurement systems. Comparable differences in both the micromagnetic and the mechanical material properties could be determined and quantified for the specifically manufactured specimens. The sensitivity of the magnetic hysteresis and, determined from that, the relationship between magnetic flux and magnetic field strength were confirmed. It was shown that a consistent change in hysteresis shape from hardened to high temperature tempered material states develops and that this change allows the characterization of different materials without the need to adjust magnetization parameters. Repeatedly, an increase in remanence with decreasing hardness was found for both test approaches. Likewise, a decreasing coercivity and increasing maximum magnetic flux could be detected with decreasing retained austenite content. The investigated correlations should thus contribute to the calibration of comparable measurement systems through the holistic characterized specimens.

Control Algorithm for Parallel Connected Offshore Wind Turbine Generators

A control algorithm for Parallel Connected Offshore Wind Turbines with permanent magnet synchronous Generators (PCOWTG) is presented in this paper. The algorithm estimates the optimal collective speed of turbines based on the estimated mechanical power of wind turbines without direct measurement of wind speed. In the proposed topology of the wind farm, direct-drive Wind Turbine Generators (WTG) is connected to variable low-frequency AC Collection Grids (ACCG) without the use of individual power converters. The ACCG is connected to a variable low-frequency offshore AC transmission grid using a step-up transformer. In order to achieve optimum wind power extraction, the collective speed of the WTGs is controlled by a single onshore Back to Back converter (B2B). The voltage control system of the B2B converter adjusts voltage by keeping a constant Volt/Hz ratio, ensuring constant magnetic flux of electromagnetic devices regardless of changing system frequency. With the use of PI pitch compensators, wind power extraction for each wind turbine is limited within rated WTG power limits. Lack of load damping in offshore wind parks can result in oscillatory instability of PCOWTG. In this paper, damping torque is increased using P pitch controllers at each WTG that work in parallel with PI pitch compensators.

Influence of the shape of the input pulses on the characteristics of hybrid electromagnetic system with magnetic flux modulation

Introduction. Nowadays, the accelerated development of materials and technologies and the finding of new ones is a prerequisite for the improvement of well-known electromagnetic constructions used in various devices, as well as for the development of new ones. New construction of hybrid electromagnetic system with magnetic flux modulation (HEMSMM) is studied. The construction is composed of: ferromagnetic frame with air gaps, input and output coils and permanent magnets. Two input coils connected to the pulsed power supply are used to change the path of the generated by the permanent magnets constant magnetic flux. Input pulses with different shapes are applied to the input coils and signals in the output coils are obtained and compared. The main purpose of the work is to find the shape of the input pulses which leads to higher output power in comparison with the other shapes. Methods. Finite element method and COMSOL software is used for computer modelling of the proposed construction, where coupled electromagnetic field – electric circuit analysis is carried out. Results. A mathematical and numerical 3D model of new HEMSMM construction is realised and studied. The model allows to calculate and compare power efficiency of the studied device, when input pulses with different shapes are applied. Practical value. The developed computer model enables the study of the HEMSMM and other electromagnetic devices at different operating modes. It can be further improved and used in the search for optimal parameters of a particular electromagnetic device.

Ultrasonic welding of magnetic hybrid material systems \u2013316L stainless steel to Ni/Cu/Ni-coated Nd2Fe14B magnets

The performance of electric sensors is continuously improving due to the demands of modern vehicles and electronic devices. Magnetic sensors are used in a wide field of applications. However, handling and mounting the typical high-performance rare earth permanent magnets are challenging due to their brittleness. A constant magnetic flux is a key property of the magnetic setup in many devices. State-of-the-art adhesive bonding of magnets in devices can cause problems due to the low durability and viscous behaviour of adhesive polymers, as the magnet may change its position and hence, the magnetic flux distribution in the magnetic setup changes.Ultrasonic welding is a powerful technique to join hybrid material systems quickly and reliably, providing high joint strength, even for brittle materials such as glasses, ceramics and rare earth permanent magnets. The latter is being investigated in this work for the first time. The ultrasonic welding process was adapted to join 316L stainless steel, representing potential components of magnetic devices, to Ni/Cu/Ni-coated Nd2Fe14B. In addition to directly joined steel/magnet-hybrids, ductile aluminium and nickel interlayers were used in order to enhance the joint strength.Process parameters were developed and evaluated considering the resulting shear strength of the joints. The highest shear strength of 35 MPa was achieved for 316L/Nd2Fe14B and 316L/Al/Nd2Fe14B, which is more than twice the shear strength of adhesively bonded joints of up to 20 MPa, according to the literature. The functional performance of the hybrid material systems, evaluated by the magnetic flux density of the hybrid material systems was the highest for directly bonded joints, and those with a nickel interlayer, which did not show any losses in comparison to the single magnet in its initial state. Joints with an aluminium interlayer showed losses of 3% and adhesively bonded joints showed losses of 7% of the magnetic flux density.In summary, the results of this work indicate that ultrasonic welding is a suitable technique to improve the production process and performance of magnetic devices.

Scattering of charged fermion to two-dimensional wormhole with constant axial magnetic flux

Scattering of charged fermion with (1+2)-dimensional wormhole in the presence of constant axial magnetic flux is explored. By extending the class of fermionic solutions of the Dirac equation in the curved space of wormhole surface to include normal modes with real energy and momentum, we found a quantum selection rule for the scattering of fermion waves to the wormhole. The newly found momentum–angular momentum relation implies that only fermion with the quantized momentum k=m'/asqrt{q} can be transmitted through the hole. The allowed momentum is proportional to an effective angular momentum quantum number m' and inversely proportional to the radius of the throat of the wormhole a. Flux dependence of the effective angular momentum quantum number permits us to select fermions that can pass through according to their momenta. A conservation law is also naturally enforced in terms of the unitarity condition among the incident, reflected, and transmitted waves. The scattering involving quasinormal modes (QNMs) of fermionic states in the wormhole is subsequently explored. It is found that the transmitted waves through the wormhole for all scenarios involving QNMs are mostly suppressed and decaying in time. In the case of QNMs scattering, the unitarity condition is violated but a more generic relation of the scattering coefficients is established. When the magnetic flux phi =mhc/e, i.e., quantized in units of the magnetic flux quantum hc/e, the fermion will tunnel through the wormhole with zero reflection.

Magnetic and Transient Temperature Field Simulation of Plate–Plate Magnetorheometer Using Finite-Element Method

This article presents a numerical simulation of a plate–plate magnetorheometer using the finite-element method. In this design of the rheometer, the electromagnetic coil generates a high and a constant magnetic-flux density (1.1 T at 3 A coil current) along the radius of the magnetorheological (MR) region. A uniform magnetic-flux density is distributed over the area of the MR region due to which there are no effects of magnetic-flux gradients on the MR properties. The other benefit of the proposed design is the reduction of electromagnetic heating effects on the MR sample. A uniform temperature generated in the MR region is 299 K due to the electromagnetic coil at 3 A current and 1.1 T magnetic-flux density after 30 min, while the maximum temperature caused due to electromagnetic coil heating is about 337 K around the coil. The temperature generated due to the slippage of MR fluid is 306 K at the same operating conditions. Thus, this design of the magnetorheometer minimizes the total temperature generated due to the electromagnetic coil and slippage in the MR region. Finite–element simulation involves magnetostatic, laminar fluid flow, and heat transfer analysis.

Исследование режимов и работы синхронных машин с массивным ротором

The article presents a procedure for analyzing the performance of a frequency controlled induction machine in the case of using a scalar control algorithm with keeping the power losses in the machine itself to a minimum and maintaining constant overlood capacity and magnetc flux. The essence of the proposed procedure consists in combining the calculated values of machine parameter obtained from its mathematical model in the case of using frequency control with the analytical expressions characterizing the power loss components. As a result, it becomes possible to determine not only the total power losses in a frequency controlled induction machine, but also shanges in its other operating parameters, the reactive powerabsorbed from the being the most important one of them. It has been found that with these parameters, i.e., the total power losses in the machine and the absorbed reactive power duly taken into account, in is most expedient to use a control algorithm maintaining constant overloading capacity and magnetic flux at a constant torque on the machine shaft. With the machine shaft torque being of a windage type as determined from the power losses taken in combination with the absorbed reactive power, the best performance is achieved in using the machine control law maintaining its constant averloading capacity: kus=kn kfs wr.

Charged fermion in two-dimensional curved spaces of constant Gaussian curvature with constant magnetic flux

We investigate the behavior of spin-1/2 particles (electron and positron) confined to the Gaussian curvature surfaces. For the non-negative Gaussian curvatures, we present the preliminary results in cylindrical and spherical cases. To be specific we use the deformed hyperbolic solutions to obtain eigenvalues of the Dirac equation in the presence of an axial gauge field. Our results demonstrate the quantized energy and eigenstates of fermion. The quantization of energy depends on the spin-orbit coupling and the Landau quantization. The imaginary energy is obtained from the negative Gaussian curvatures. It is interpreted as the quasi normal mode (QNM). The angular momentum of fermion is shifted by addition of the constant magnetic flux. The fermion behaves like boson when the flux is half-integer.