Interaction Of Magnetic Field Research Articles

Hydrogenic impurity effect on the optical properties of Ga1-xAlxAs quantum wire under terahertz field

In this study, the effect of impurity factor on the optical absorption coefficients, refractive index changes, second harmonic generation, and third-harmonic generation for the intersubband transitions is explored between the electronic states of Ga1-xAlxAs quantum wire initiated by the symmetric parabolic potential. The system is conquered by the presence of an intense electric field, magnetic field, and Rashba spin-orbit interaction. For the linear and non-linear optical absorption coefficients, refractive index, second harmonic generation, and third harmonic generation coefficient, the analytical expressions are obtained with the assistance of the compact density-matrix approach. The arithmetical outcomes illustrate the optical properties are significantly intuitive to the concentration of impurity and can be controlled by this parameter. The variation in the magnitude and position of peaks via impurity factor indicates the opportunity in the mechanism of optical non-linearity in the quantum wire and also, helps in the optical non-linearity tuning which has device application.

An observer design for the flux of line start permanent magnet synchronous motors

The permanent magnet flux is an important model parameter that determines the operation of the line start permanent magnet synchronous motor. It is degraded with operating time due to the permanent magnet demagnetization which is principally caused by the armature magnetic field interaction and operating temperature. This paper introduces an observer design study aimed at estimating the permanent magnet flux of the line start permanent magnet synchronous motor from the measurement of stator currents. Derived from the mathematical description in the dq0 reference frame, a model of the motor with state variables of stator currents, magnetic fluxes and rotor angular frequency is considered. Model analysis and with a new flux variable setting allow an estimation of the rotor flux through the open loops from the stator currents. The observer is then designed with a constant gain for the system with states of stator currents and permanent magnet flux. Simulation confirms the efficiency and robustness of the designed observer.

Critical Current and AC Ripple Loss Analysis of a Global Self-Shielding HTS DC Cable Made of Filament REBCO Tapes

For the high-temperature superconducting dc cable with the same current orientation in every layer, the maximum magnetic field generally arises in the outermost layer. When the cable transmits a large current, the generated strong magnetic field will make the utilization rate of tapes extraordinarily low. The current direction of two neighboring layers in the self-shielding sandwich cable is inverse, which can whittle the magnetic field interaction of each layer, so as to minish the critical current attenuation of REBCO tape. The previous global self-shielding dc cable adjusts the current distribution between layers to homogenize the magnetic field. However, this article proposes a new global self-shielding dc cable made of filament REBCO tapes, which adjusts the current distribution in each layer. The uniformity of magnetic field can be improved further by using filament tapes to wind the cable. In this article, <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>T-A</i></b> formulation is adopted to study the critical current and ac ripple loss of global self-shielding sandwich cables made of filament REBCO tapes in detail. The simulation results demonstrate that the structure made of filament tapes has better performance than the previous global self-shielding structure.

Theoretical analysis of entropy production in exothermic/endothermic reactive magnetized nanofluid flow through curved porous space with variable permeability and porosity

In current analysis, flow of magnetized nanofluids in porous curved stretchable surface with variable characteristics has been inspected by imposing the thermal radiation, and activation energy. The exothermic/endothermic reactive effect is included along with Buongiorno nanofluid model to investigate the thermal performance more extensively. The Lorentz force characteristics that cause the interaction of magnetic field with nanoliquid motion is further investigated. Additionally, production of entropy in the porous curved system because of irreversible process has been considered here. The modeled systems for considered model are firstly transformed into ODEs via appropriate variables and then computed by employing NDSolve technique using tool of Mathematica. Flow fields variation against relevant variables is inspected via tables and sketches. The key outcome of analysis is that, the entropy rate upsurges for higher local inertia parameter, radiation variable and Brinkman number.

Magnetic manipulation of discontinuous ferromagnetic fibers in viscous fluids: Dynamics of single fiber alignment

AbstractThe method of fiber morphology manipulation using magnetic field interaction is proposed for single discontinuous steel fibers dispersed in viscous fluids and subjected to low magnetic fields. The goal of this study was to investigate the fiber behavior under different test conditions. The effects of the fluid viscosity, the fiber aspect ratio and the strength of the magnetic field on the dynamics of fiber alignment were analyzed. In‐plane magnetic alignment tests with a single fiber were carried out to avoid fiber‐fiber interactions and fiber clustering. Based on the experimental results, a model to predict ferromagnetic fiber alignment caused by a static unidirectional magnetic field was provided. Existing models focus on the different torques occurring in the realignment process. The presented model is based on single‐term exponential equations and considers all previously mentioned variables. It is shown that a good agreement between experimental data and fiber realignment predictions for single fibers is achieved.

Loschmidt echo and momentum distribution in a Kitaev spin chain

We investigate the Loschmidt echo in a one-dimensional spin chain having Kitaev-type interaction in constant and kicked magnetic fields. The Loschmidt echo for the initial states having different magnon excitations shows long-time revivals for smaller chains and has short-time revival peaks for the longer chains. The system near the critical point shows peculiarly long-time revival peaks of the Loschmidt echo for relatively larger chains. The presence of a magnon in the initial state affects the Loschmidt echo revival peaks. The momentum distribution function exhibits maxima for a few momenta that are associated with the momentum of the magnon excitation present in the initial states. The probability maxima decay as O(1/N ) with the system size. For the Hamiltonian with kicked magnetic fields, the Loschmidt echo depends on the kick period. For a special kick period, the Loschmidt echo shows no evolution at all irrespective of the system size.

A Self-Similar Approach to Study Nanofluid Flow Driven by a Stretching Curved Sheet

Nano-fluids have considerable importance in the field of thermal development that relates to several industrial systems. There are some key applications in recent construction systems flow, as well as microscale cooling gadgets and microstructure electric gadgets for thermal migration. The current investigation concludes the study of electrically conducting nano-fluid flow and heat transfer analysis in two-dimensional boundary layer flow over a curved extending surface in the coexisting of magnetic field, heat generation and thermal radiation. The small sized particles of copper (Cu) are taken as nanoparticles and water is assumed to be the base fluid. We used quasi-linearization and central difference approximation to numerically solve the system of coupled equations obtained from the partial differential equations (PDEs) by incorporating the concept of similarity. The impacts of non-dimensional parameters on velocity, concentration and thermal profiles have been discussed with the help of suitable graphs and tables. It has been noticed that the velocity decelerated with the effect of the magnetic field interaction parameter. Thermal radiation caused an increase in temperature.

Magnetic field interactions of smartwatches and portable electronic devices with CIEDs - Did we open a Pandora's box?

IntroductionMagnetic interaction of portable electronic devices (PEDs), such as state-of-the art mobile phones, with cardiovascular implantable electronic devices (CIEDs) has been reported. The aim of the study was to quantify the magnetic fields of latest generation smartwatches and other PEDs and to evaluate and predict their risk of CIED interactions.MethodsHigh resolution magnetic field characterization of five smartwatches (Apple Watch 6/7, Fitbit Sense, Samsung Galaxy 3, Withings Scanwatch) was performed using a novel magnetic field camera. Ex vivo measurements of the minimal safety distance (MSD) at which no mode switch can be observed were performed between 11 PEDs and six representative CIEDs.ResultsMaximal 1 mT distances ranged between 10 mm (Withings) and 19 mm (Fitbit and AppleWatch), and 1 mT volumes between 6 cm3 (Withings) and 19 cm3 (Fitbit). All these measures were observed only for the back side of the smartwatches. While most smartwatches with measured 1 mT distance < 15 mm posed low ex vivo interaction within a distance of < 10 mm, PEDs such as electronic pens and in-ear-headphones with measured 1 mT distance > 15 mm showed device interaction up to > 15 mm. Linear regression analysis showed a linear relationship of the MSD with 1 mT distance (B coefficient: 0.46; 95 %-CI: 0.25–0.67, p < 0.001).ConclusionSmartwatches are safer compared to other PEDs such as electronic pens or in-ear headphones with regards to CIED interaction. With a standardized magnetic field camera, the risk assessment of CIED interaction of novel PEDs is feasible.

Antiferromagnet thickness dependence and rotatable spins in exchange biased CoO/Fe films

The emergence of exchange bias and coercivity enhancement has been investigated in epitaxial CoO/Fe films with varied antiferromagnet (AF) thicknesses, even smaller than the critical value where the frozen CoO spins are detectable. Vector magnetometry and first-order reversal curve (FORC) measurements reveal different CoO thickness dependence of the exchange bias and coercivity enhancement, including the evolution of magnetization reversal from a high coercivity, low bias phase due to rotatable CoO moments to a high bias, low coercivity phase due to frozen CoO moments. The AF domain state is found to be metastable, which can be reoriented by external and exchange fields prior to the appearance of frozen spins, pointing to a generic origin of the training effect. Monte Carlo simulations show that the AF anisotropy energy barrier and the rotatable spins induced by magnetic field and exchange interaction at the interface are responsible for the observed effects.

Exploring bosonic and fermionic link models on (3+1)D tubes

Quantum link models (QLMs) have attracted a lot of attention in recent times as a generalization of Wilson's lattice gauge theories (LGT), and are particularly suitable for realization on quantum simulators and computers. These models are known to host new phases of matter and act as a bridge between particle and condensed matter physics. In this article, we study the Abelian $U(1)$ lattice gauge theory in $(3+1)$-d tubes using large-scale exact diagonalization (ED). We are then able to motivate the phase diagram of the model with finite size scaling techniques (FSS), and in particular propose the existence of a Coulomb phase. Furthermore, we introduce the first models involving fermionic quantum links, which generalize the gauge degrees of freedom to be of fermionic nature. We prove that while the spectra remain identical between the bosonic and the fermionic versions of the $U(1)$-symmetric quantum link models in $(2+1)$-d, they are different in $(3+1)$-d. We discuss the prospects of realizing the magnetic field interactions as correlated hopping in quantum simulator experiments.

Magnetic Resonance Imaging Evaluation of a Hearing Protector Device Designed for Neonatal Patients

BackgroundHearing protection for neonates that can be effectively used during magnetic resonance imaging (MRI) examinations is limited. Because MRI-related acoustic noise poses a serious risk to this patient population, a viable option for hearing protection is needed. A new hearing protector device was recently developed specifically for neonates. Because of safety concerns for products used in the MRI setting, the objective of this investigation was to evaluate MRI-related issues for this hearing protector device. In addition, patient tolerance and responses were observed and reported from in a small group of neonates. MethodsThe neonatal hearing protector device (DREAMIES T-M, NEATCap Medical, LLC, Bethlehem, Pennsylvania) was evaluated for magnetic field interactions (translational attraction and torque; 3-Tesla), MRI-related heating (1.5-Tesla/64-MHz and 3-Tesla/128-MHz), and in vitro testing of artifacts (T1-weighed spin echo and gradient echo pulse sequences obtained at 3-Tesla) using standardized test procedures. In addition, seven study subjects wearing the neonatal hearing protector device underwent MRI of the brain. ResultsThere was no translation attraction, no torque, no heating at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz, and no artifacts were observed for the neonatal hearing protector device in the in vitro and study subject observations. The device was easy to apply, stayed in place for the duration of the MRI examination, and was tolerated well by the neonates evaluated. ConclusionsBecause of the benign findings for the MRI tests, along with the materials used to make this device (i.e., nonmetallic and nonconducting), this new neonatal hearing protector device is designated “MR Safe”, which is a medical device that poses no known hazards resulting from exposure to any MRI environment. In the limited number of subjects evaluated during the observational period, the device provided sufficient noise protection enabling neonates to remain undisturbed throughout their scans, resulting in images with little or no motion artifacts and diagnostically acceptable MRI examinations.

Development of a Novel Underactuated Robotic Fish with Magnetic Transmission System

In this study, a robotic fish inspired to carangiform swimmers has been developed. The artifact presents a new transmission system that employs the magnetic field interaction of permanent magnets to ensure waterproofness and prevention from any overload for the structure and the actuating motor. This mechanism converts the rotary motion of the motor into oscillatory motion. Such an oscillating system, along with the wire-driven mechanism of the tail, generates the required traveling wave in the robotic fish. The complete free swimming robotic fish, measuring 179 mm in length with a mass of only 77 g, was able to maintain correct posture and neutral buoyancy in water. Multiple experiments were conducted to test the robotic fish performance. It could swim with a maximal speed of 0.73 body lengths per second (0.13 m/s) at a tail beat frequency of 3.25 Hz and an electric power consumption of 0.67 W. Furthermore, the robotic fish touched the upper bound of the efficient swimming range, expressed by the dimensionless Strouhal number: 0.43 at 1.75 Hz tail beat frequency. The lowest energy to travel 1 meter was 4.73 Joules for the final prototype. Future works will focus on endowing the robot with energy and navigation autonomy, and on testing its potential for real-world applications such as environmental monitoring and animal–robot interaction.

Two-phase bio-nanofluid flow through a bifurcated artery with magnetic field interaction

A modified multiphase flow model is applied for a better understanding of bio-nanofluid (blood containing 4% (w/v) Fe3O4 nanoparticles) flow regimes through a real bifurcated artery. The magnetic field with distinct current intensities (I = 0 – 300 A) was employed to induce the flow features when the wire's source is placed nearby the junction of the asymmetrical branched artery during numerical computation. The finite volume method was used to solve the coupled hemodynamics model. Results show that the pressure, and vorticity profiles increased and fallen gradually with the existence of the magnetic source and further obtained the maximum pressure for the strong current intensity (I = 300 A). The fluctuating vorticity distributions are found along the inner and outer vessel wall as well as the predicted lines created within the simulated domain for the increase of current intensity. The velocity outlines variates steadily, and the local peak velocities are obtained with the increase of the magnetic force. With the increment of the current intensity upto I = 300 A, the flow rate rises progressively for the asymmetric branched vessel, and the opposite scenario is found for the root vessel. The temperature profiles decrease steadily with the increment of the applied current intensity. With the manifestation of the magnetic source, the irregular flow behaviours are found within the asymmetrical bifurcated artery. This modeling investigation could be beneficial for the emergent therapy plan of ample vascular diseases as the magnetic drug targeting system.

Robotic Autonomy for Magnetic Endoscope Biopsy.

Magnetically actuated endoscopes are currently transitioning in to clinical use for procedures such as colonoscopy, presenting numerous benefits over their conventional counterparts. Intelligent and easy-to-use control strategies are an essential part of their clinical effectiveness due to the un-intuitive nature of magnetic field interaction. However, work on developing intelligent control for these devices has mainly been focused on general purpose endoscope navigation. In this work, we investigate the use of autonomous robotic control for magnetic colonoscope intervention via biopsy, another major component of clinical viability. We have developed control strategies with varying levels of robotic autonomy, including semi-autonomous routines for identifying and performing targeted biopsy, as well as random quadrant biopsy. We present and compare the performance of these approaches to magnetic endoscope biopsy against the use of a standard flexible endoscope on bench-top using a colonoscopy training simulator and silicone colon model. The semi-autonomous routines for targeted and random quadrant biopsy were shown to reduce user workload with comparable times to using a standard flexible endoscope.

Theory of magnetic-field effect on trions in two-dimensional materials.

In this work, we present a theoretical method to study the effect of magnetic field on trions in two-dimensional materials. The trion is modeled by a three-particle Schrödinger equation and the magnetic-field interaction is included by means of a vector potential in symmetric gauge. By using a coordinate transformation and a unitary transformation, the trion Hamiltonian can be converted into the sum of a translational term describing the Landau quantization for the trion center-of-mass motion, an internal term describing the trion binding, and a translational-internal coupling term depending linearly on the magnetic-field strength. The trion eigenenergy and wavefunction can then be calculated efficiently by using a variational method, and the quantum numbers of trions in magnetic fields can be assigned. The eigenenergies, binding energies, and correlation energies of three trion branches, which correspond to the ground-state trion and two excited-state trions solved from the trion Hamiltonian in zero magnetic field, are studied numerically in finite magnetic fields. The present method is applied to study the magnetic-field dependence of trion energy levels in hole-doped WSe2 monolayers. The binding energies and correlation energies of positive trions in WSe2 are investigated over a range of magnetic fields up to 25T.

First Light of the Integral Field Unit of GRIS on the GREGOR Solar Telescope

An Integral Field Unit (IFU) based on image slicers has been added to the GREGOR Infrared Spectrograph (GRIS). This upgrade to the instrument makes possible 2D spectropolarimetry in the near-infrared by simultaneously recording the full Stokes profiles of spectral lines (in a given spectral interval) at all the points in the field of view (FOV). It provides high-cadence spectropolarimetric observations at the instrument’s high spatial resolution and high polarization sensitivity at the GREGOR solar telescope. The IFU is ideal for observing the polarized spectrum of fast-evolving solar features at high spatial and spectral resolutions. The high observing cadence opens the possibility of time-series observations. The analysis of observations to this level of accuracy is essential for understanding the complex dynamics and interactions of solar plasma and magnetic fields. The image slicer of the IFU has eight slices of width 100[Formula: see text][Formula: see text]m, covering a total FOV of [Formula: see text]. It was designed and built within the framework of the European projects SOLARNET and GREST, as a prototype for future instruments of the European Solar Telescope (EST) and was integrated into GRIS. After two commissioning campaigns in 2017 and 2018, the IFU was finally installed at the end of September 2018 and offered to all observers who use the telescope.

Laser cluster interaction in ambient magnetic fields for accelerating electrons in two stages without external injection

In the few-cycle pulse regime of laser-cluster interaction (intensity >10^{16},text{ W/cm}^{2}, wavelength > 780 nm), laser absorption is mostly collisionless and may happen via anharmonic resonance (AHR) process in the overdense (cluster) plasma potential. Many experiments, theory and simulation show average absorbed energy per cluster-electron ({mathcal {E}_A}) close to the electron’s ponderomotive energy (U_mathrm {p}) in the collisionless regime. In this work, by simple rigid sphere model (RSM) and detailed particle-in-cell (PIC) simulation, we show enhanced {mathcal {E}_A}approx 30–70U_mathrm {p}—a 15–30 fold increase—with an external (crossed) magnetic field near the electron-cyclotron resonance (ECR). Due to relativistic mass increase, electrons quickly deviate from the standard (non-relativistic) ECR, but time-dependent relativistic-ECR (RECR) happens which also contributes to enhanced {mathcal {E}_A}. Here laser is coupled to electrons in two stages, i.e, AHR and ECR/RECR. To probe further we retrieve the phase-difference Delta psi between the driving electric field and corresponding velocity component for each electron (in PIC and RSM). We find absorption by electron via AHR happens in a very short interval Delta tau for less than half a laser period where Delta psi remains close to pi (necessary condition for maximum laser absorption) and then Delta psi drops to its initial pi /2 (meaning no absorption) after such short-lived AHR. On the contrary, auxiliary magnetic field near the ECR modifies AHR scenario inside the cluster and also helps maintaining the required phase Delta psi approx pi for the liberated cluster-electron accompanied by frequency matching for ECR/RECR for a prolonged Delta tau (which covers 50–60% of the laser pulse through pulse maxima) even after AHR—leading to jump in {mathcal {E}_A}approx 30–70U_mathrm {p}. We note that to realize the second stage of enhanced energy coupling via ECR/RECR, the first stage via AHR is necessary.

The Role of Reconnection in the Onset of Solar Eruptions

Solar eruptive events such as coronal mass ejections and eruptive flares are frequently associated with the emergence of magnetic flux from the convection zone into the corona. We use three-dimensional magnetohydrodynamic numerical simulations to study the interaction of coronal magnetic fields with emerging flux and determine the conditions that lead to eruptive activity. A simple parameter study is performed, varying the relative angle between emerging magnetic flux and a preexisting coronal dipole field. We find that in all cases the emergence results in a sheared magnetic arcade that transitions to a twisted coronal flux rope via low-lying magnetic reconnection. This structure, however, is constrained by its own outer field and so is noneruptive in the absence of reconnection with the overlying coronal field. The amount of this overlying reconnection is determined by the relative angle between the emerged and preexisting fields. The reconnection between emerging and preexisting fields is necessary to generate sufficient expansion of the emerging structure so that flare-like reconnection below the coronal flux rope becomes strong enough to trigger its release. Our results imply that the relative angle is the key parameter in determining whether the resultant active regions exhibit eruptive behavior and is thus a potentially useful candidate for predicting eruptions in newly emerging active regions. More generally, our results demonstrate that the detailed interaction between the convection zone/photosphere and the corona must be calculated self-consistently in order to model solar eruptions accurately.

Near field communication (NFC) device: Evaluation of MRI issues

ObjectiveNear field communication (NFC) is a wireless, short-range, secure communication technology that may be used for healthcare-related applications. An NFC device was recently developed that was intended for implantation in the dorsal fascia, above the interosseous compartment of the hand. This implant uses a ferrite rod to increase the distance of communication between devices. The purpose of this investigation was to evaluate MRI issues for this NFC device using standardized techniques and well-accepted methodology. MethodsThe NFC device (Vivokey Spark 2, Cryptobionic Implant, Vivokey Technologies, www.vivokey.com) was assessed for magnetic field interactions (force and torque) at 3-Tesla, magnetic field interactions according to the simulated intended use of the implant, MRI-related heating at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz, functional change associated with MRI conditions at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz, and artifacts at 3-Tesla. ResultsThe mean deflection angle was 90° ± 0 and torque was “positive”. However, tests evaluating the simulated intended use of the NFC device demonstrated no movement, displacement, or rotational alignment. The highest temperature changes at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz were 1.7 °C and 1.9 °C, respectively. There was no change in the operational capabilities of the NFC device related to the MRI exposures. Artifacts were relatively large in comparison to the size of the NFC device. ConclusionsThe findings indicated that the particular NFC device that underwent evaluation is “MR Conditional” for a patient undergoing MRI at 1.5-Tesla or 3-Tesla, operating the scanner in the Normal Operating Mode (i.e., default whole-body averaged SAR of 2.0-W/kg). Notably, this is the first NFC device evaluated for MRI-related issues.

Design, dynamics, and dissipation of a torsional-magnetic spring mechanism

We present an analytical and experimental study of a torsional magnetic spring where the restoring torque results from magnetic field interactions between rotating and fixed permanent magnets (PMs). The rotating cylindrical PM, called the rotor, is supported on ball bearings between two fixed permanent magnets, called the stators. Perturbing the rotor from its equilibrium angle induces a restoring magnetic torque whose effect ressembles a torsional spring. Along with this restoring effect, dissipation mechanisms arise from structural viscoelasticity, air, electromagnetic damping, and friction in the ball bearings. To investigate dynamic effect of these restoring and dissipation mechanisms, we construct an experimental setup capable of mechanical, electrical, and magnetic measurements. For various rotor–stator gaps in this setup, we validate an analytical model that assumes viscous and dry (Coulomb) damping during the rotor’s free response. Moreover, we force the rotor by an electromagnetic coil into high amplitude oscillations. We observe unusual resonator’s nonlinearity: at large rotorstator gaps, the oscillations are softening; at reduced gaps, the oscillations stiffen-then-soften. The developed reduced-order models capture the nonlinear effects of the rotor-to-stator and the rotor-to-coil distances. These magnetic oscillators are promising for low-frequency electromagnetic signal transmission and for designing magneto-elastic metamaterials with tailorable nonlinearity.