Interaction Of Magnetic Field Research Articles

Исследование фазовых переходов в системах с конкурирующими взаимодействиями в магнитном поле методом компьютерного моделирования

Исследование фазовых переходов в системах с конкурирующими взаимодействиями в магнитном поле методом компьютерного моделирования

Mathematical modeling of the interaction of magnetic fields of red blood cells

The article discusses the movement of red blood cells along narrow capillaries with a diameter less than the diameter of the red blood cell. The erythrocyte membrane in the narrow capillary performs a tank-treating motion with a frequency reaching several tens of revolutions per second. Electric charges located on the surface of an erythrocyte move together with the erythrocyte membrane and create a magnetic field in the surrounding space. A two-dimensional model of the movement of red blood cells along narrow capillaries is developed. Various options were considered: either neighboring red blood cells rotate in one direction, or in different directions. With different options, different distributions of the magnetic field strength are obtained. Calculations of the magnetic field were carried out at various distances between red blood cells and the speed of rotation of the erythrocyte membrane. It was shown that at distances between red blood cells less than two capillary diameters, the influence of neighboring red blood cells can be neglected (the difference is less than 3%).

Mars' Ionospheric Interaction With Comet C/2013 A1 Siding Spring's Coma at Their Closest Approach as Seen by Mars Express

AbstractOn 19 October 2014, Mars experienced a close encounter with Comet C/2013 A1 Siding Spring. Using data from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) on board Mars Express (MEX), we assess the interaction of the Martian ionosphere with the comet's coma and possibly magnetic tail during the orbit of their closest approach. The topside ionospheric electron density profile is evaluated from the altitude of the peak density of the ionosphere up to the MEX altitude. We find complex and rapid variability in the ionospheric profile along the MEX orbit, not seen even after the impact of a large coronal mass ejection. Before closest approach, large electron density reductions predominate, which could be caused either by comet water damping or comet magnetic field interactions. After closest approach, a substantial electron density rise predominates. Moreover, several extra topside layers are visible along the whole orbit at different altitudes, which could be related to different processes as we discuss.

Thermomagnetic Behavior of a Ferrimagnet of High Spins: Monte Carlo Analysis

We investigate some critical phenomena of a Ising ferrimagnetic system on a square lattice with spins $Q=\pm 7/2, \pm 5/2, \pm 3/2$ , and ±1/2 in a $B$ sublattice and spins $S=\pm 5/2, \pm 3/2$ , and ±1/2 in a $A$ sublattice in presence of an $h'$ external magnetic field, such that $Q$ and $S$ are the nearest-neighbors ferrimagnetically coupled. Using Monte Carlo simulations, we calculate the finite-temperature phase diagrams of magnetization, specific heat, and magnetic susceptibility of the model. The system is defined by a Hamiltonian $(\mathcal {H})$ that contains ferromagnetic next-nearest-neighbors interactions between $S$ spins ( $J'_{2}$ ), as well as external magnetic field and anisotropy interactions at each point of lattice. For a defined range of parameters in $\mathcal {H}$ , the system exhibits discontinuities in their physical variables and spin compensation behaviors. In the planes $J'_{2}-k_{\mathrm{ B}}T'$ and $h'-k_{\mathrm{ B}}T'$ , we analyze the relationship between the critical, compensation, and discontinuous phase transition temperatures with the external magnetic field and the next-nearest-neighbors interaction between $S$ spins. We found that the existence of discontinuous phase transition depends on the strengths of $h'$ and $J'_{2}$ .

The effects of electron-phonon coupling and magnetic field on charge structure factors of armchair graphene nanoribbons

We present the behaviors of both dynamical and static charge susceptibilities of undoped armchair graphene nanoribbon using the Green’s function approach in the context of Holstein model Hamiltonian. Specially, the effects of magnetic field and electron-phonon coupling strength on the plasmon modes of armchair graphene nanoribbon are investigated via calculating correlation function of charge density operators. Random phase approximation has been implemented to find the interacting dynamical charge susceptibility. The electrons in this systems interacts with each other by mediation of dispersionless Holstein phonons. Our results show the increase of electron phonon coupling strength leads to decrease intensity of charge collective mode. Also the frequency position of the collective mode tends to higher frequencies with electron phonon coupling. We also show that the frequency positions of plasmon mode of armchair nanoribbon are not affected by the increase of magnetic field. Furthermore the number of collective excitation mode increases with ribbon width in the presence of electron-phonon interaction. Finally the temperature dependence of static charge structure factor of armchair graphene nanoribbon is studied. The effects of magnetic field, ribbon width and electron-phonon interaction on the static structure factor are addressed in details.

HHR impact on 3D radiative stretched flow of Cu-H2O nanofluid influenced by variable magnetic field and convective boundary condition

In an attempt to the influence of homogenous and heterogeneous reactions, variable magnetic field and thermal radiation on three-dimensional flow of an incompressible nanofluid over an exponential stretching sheet subject to convective boundary condition has been analyzed. In view of enhancement of heat transfer capability of nanofluids, effective implementation of Patel model is carried in the current study. The transformed governing differential equations are solved using fourth-order Runge-Kutta method along with shooting technique and secant method is employed for better approximation. The significant outcome of the present computational study is that the magnetic field interaction impedes the fluid motion leading to diminution of the wall shear stresses (axial as well as transverse) and homogenous and heterogeneous parameters belittle the fluid concentration appreciably.

Synergy of CT and MRI in detecting trajectories of lodged bullets in decedents and potential hazards concerning the heating and movement of bullets during MRI

The purpose of this study was to assess the value of magnetic resonance imaging (MRI) in addition to computed tomography (CT) in gunshot wound cases with bullets or pellets lodged inside the head. In this context, the potential heating and movement of the lodged bullets were additionally investigated using animal models. Eleven forensic cases of penetrating gunshot wounds underwent CT and MRI. The data of each imaging modality were reviewed according to the following relevant characteristics: bony lesion at the entrance, intracranial bone fragments, intracranial metal fragments, gunshot residues, the wound channel and the severity of metal artifacts. Four-point Likert scales were used for the assessment. The heating of projectiles and their magnetic field interactions with the static magnetic field were assessed using animal models. MRI presented major advantages in cases with transversal trajectories and non-ferromagnetic bullets compared to CT. In general, MRI enabled a clear visualization of the wound channel and gunshot-related soft tissue injuries. An image fusion of CT and MRI datasets demonstrated the individual strengths of both modalities. Radio frequency (RF)-induced heating due to bullets lodged inside the brain tissue was invalidated. The likelihood of ferromagnetic projectile migration inside brain tissue is low. MRI of decedents with a bullet lodged inside their heads is viable and provides a valuable supplement to CT. The in situ, noninvasive depiction of the wound channel and gunshot-related soft tissue injuries on MRI can contribute to the knowledge of wound ballistics.

MRI safety and imaging artifacts evaluated for a cannulated screw used for guided growth surgery

ObjectivePercutaneously-placed cannulated screws are the implant of choice for treatment of skeletal deformity associated with growing children that have spastic cerebral palsy (CP). These patients often require MRI examinations throughout their childhood to evaluate associated comorbidities and frequently for research protocols. There are concerns related to the use of MRI when metallic implants are present. Therefore, this study characterized MRI safety and imaging artifacts for a cannulated screw commonly used for guided growth. MethodsStandardized and well-accepted in vitro techniques were used to evaluate a cannulated screw (4.5 mm diameter x 50 mm length, 316 L stainless steel) for MRI issues. Static magnetic field interactions (i.e., translational attraction and torque) and artifacts were tested at 3-Tesla. Radiofrequency-related heating was assessed at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz using relatively high levels of RF energy (whole-body averaged specific absorption rates of 2.7 W/kg and 2.9-W/kg, respectively). Artifacts were determined using T1-weighted, spin echo and gradient echo pulse sequences. ResultsThe cannulated screw exhibited minor magnetic field interactions (14° deflection angle, no torque). The highest temperature changes at 1.5-Tesla/64-MHz and 3-Tesla/128-MHz MRI were 2.1 °C and 2.4 °C, respectively. The maximum artifact size on a gradient echo sequence extended 20 mm relative to the dimensions of the implant. ConclusionsThe in vitro tests performed on the cannulated screw indicated that there were no substantial concerns with respect to the use of 1.5- and 3-Tesla MRI. Therefore, a patient with this cannulated screw can safely undergo MRI by following specific conditions to ensure safety.

On the field-induced transport of magnetic nanoparticles in incompressible flow: Modeling and numerics

By methods from non-equilibrium thermodynamics, we derive a class of nonlinear pde-models to describe the motion of magnetizable nanoparticles suspended in incompressible carrier fluids under the influence of external magnetic fields. Our system of partial differential equations couples Navier–Stokes and magnetostatic equations to evolution equations for the magnetization field and the particle number density. In the second part of the paper, a fully discrete mixed finite-element scheme is introduced which is rigorously shown to be energy-stable. Finally, we present numerical simulations in the 2D-case which provide first information about the interaction of particle density, magnetization and magnetic field.

Quasinormal modes of magnetized black hole

We investigate charged, massive scalar field around static, spherically symmetric black hole immersed into an external asymptotically uniform magnetic field $B$. It is shown that for given multipole number $\ell$ there are $2\ell+1$ numbers of modes due to the Zeeman effect appearing by an interaction of the external magnetic and charged scalar fields introducing an effective mass of the scalar field $\mu_{\rm eff}=\sqrt{\mu^2-mqB}$ where $m$ is the azimuthal number and $q$ is the charge coupling constant. We calculate threshold value of effective mass in which quasinormal modes are arbitrarily long lived and beyond that value quasinormal modes vanish. In the case of $m qB<0$ quasinormal modes are longer lived with larger oscillation frequencies. Whenever, magnetic and massive scalar fields satisfies condition $\mu_{\rm eff}^2<0$, an instability appears, i.e., if $qB>0$ or $qB<0$ there is an instability for the values of azimuthal number $m>\mu^2/qB$ or $m<\mu^2/qB$, respectively.

Mechanical feedback analysis of a ferrofluid-based module with 2D dynamic traveling waves for tactile display application

With the advances of human-machine systems, tactile displays have become one of the important features for modern products. Tactile feedback can increase working efficiency and help humans to explore new environments or objects by the sense of touch. This study used a 3 × 3 electromagnet array and a ferrofluid bladder to build a tactile display module, which can create smooth and continuous real-time 2-D dynamic traveling waves. The interactions of magnetic fields between electromagnets in the array were used to control the directions of the magnetic lines of force to create different graph patterns. Our user test showed that the overall tactile perception rate was 74% for the 2-D dynamic graph patterns generated using the ferrofluid-based tactile display module.

Spin-orbit interaction and snake states in a graphene p-n junction

We study a model of a $p$-$n$ junction in single-layer graphene in the presence of a perpendicular magnetic field and spin-orbit interactions. By solving the relevant quantum-mechanical problem for a potential step, we determine the exact spectrum of spin-resolved dispersive Landau levels. Close to zero energy, we find a pair of linearly dispersing zero modes, which possess a wave-vector-dependent spin polarization and can be regarded as quantum analogous of spinful snake states. We show that the Rashba spin-orbit interaction, in particular, produces a wave vector shift between the dispersions of these modes with observable interference effects. These effects can in principle provide a way to detect the presence of Rashba spin-orbit interaction and measure its strength. Our results suggest that a graphene $p$-$n$ junction in the presence of strong spin-orbit interaction could be used as a building block in a spin field-effect transistor.

The Eddy Current Method of Alloy Drill Pipes Wall Thickness Evaluation: Impact Analysis

The dependences of the surface eddy current probe added voltage at the interaction of the probe magnetic field with an aluminum pipe from the following main interference factors are determined: the pipe wall thickness, the gap between the probe and the surface of the pipe, the electrical conductivity of the material, the curvature of the pipe wall, the presence of areas with a smooth thickness change of the wedge character and a local spherical thinning, axis misalignment with respect to the pipe surface, the lateral misalignment of the probe axis. The problem is solved with the help of the finite element method (FEM). These data are consistent with the experimental results.

Assessment of magnetic field interactions, radiofrequency, and radiation‐induced heating of Zr implants in 7 T MR scanner

Assessment of magnetic field interactions, radiofrequency, and radiation‐induced heating of Zr implants in 7 T MR scanner

Dynamics of a pair of ellipsoidal microparticles under a uniform magnetic field

Under a uniform magnetic field, magnetic particles tend to form chains, clusters or columns due to particle–particle interactions. Non-spherical magnetic particles dispersed in a liquid medium show different rheological properties. However, there is a lack of knowledge about the fundamental mechanism of particle–particle interactions of non-spherical particles under a uniform magnetic field. In this work, we numerically investigate the particle–particle interactions and relative motions of a pair of paramagnetic elliptical particles by using direct numerical simulations to create two-dimensional models that resolve the magnetic and flow fields around the finite-sized particles. The modeling is based on the finite element method and arbitrary Lagrangian–Eulerian approach with full consideration of particle–fluid–magnetic field interaction. The effects of initial position and aspect ratio of the particles are investigated. The results show that the particles spend much more time under global reorientation than local magneto-orientation. Larger initial relative angles and distances, and larger aspect ratios, tend to require more time to form a stable chain. The particle–particle interactions and relative motion of a pair of elliptical particles in this study provide insights into the particle alignment and chaining processes under uniform magnetic fields, which are closely related to the response of magneto-rheological fluids to magnetic fields.

A Novel Electromagnetic Testing Method Based on the Magnetic Field Interaction

The traditional magnetic flux leakage (MFL) method with a single magnetic excitation source has been widely used in engineering practice but fails in long-range (long liftoff distance of the sensor from the surface of the tested object) defect detection, especially when the liftoff distances increase. Thus, we propose a novel electromagnetic testing method based on the magnetic field interaction between the primary magnetic induction field and the secondary field of MFL. The principles of the new method are first introduced, and the method is compared with the common MFL methods; this comparison indicates that the new method has the capabilities of long-range defect detection and signal strength enhancement. Furthermore, a series of simulations and analyses demonstrates that the proposed method is more efficient in defect detection, particularly when the induction magnet is a diamagnetic material, which is independent of the coercive force. Finally, experiments and comparisons were conducted to verify the feasibility and reliability of our proposed method in the long-range defect detection. All results show that the novel method has great promise in widely practical applications in the future.

HTS Bulk Experiments Performed for and Under Space Conditions

In the shadow of dominant long-length high-temperature superconductors bulk HTS show a considerable effort of magnetic engineering application. Bulk HTS are capable of providing easily magnetic fields of several tesla, levitates self- stabilized mirrors or measuring instruments, and can be used as a passive magnetic shield. By simulating space conditions we have been investigated the possible degradation of YBCO material under 160 MeV proton irradiation at a radiative dose of 10-20 krad. We report the successful preparation of an HTS bearing cosmic background radiation, the fabrication and testing of a bulk superconducting device operating in the Columbus laboratory of the International Space Station (ISS). The Magvector/MFX experiment operates the last four years at the ISS. It measures the interaction of a YBCO HTS with the Earth magnetic field using sensitive flux gate sensors in μT level. Laboratory shielding results are given. Dependent on the bulk conductivity at T>T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> and T<;T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> the Earth magnetic field interaction causes distortions of the surrounding electromagnetic (EM) field. Possible benefits of HTS bulk devices on applications in space will be discussed.

Quantum coherence of the spin-1 system under an XY spin chain with three-spin interaction

We investigate the performance of quantum coherence and nonlocal advantage of quantum coherence (NAQC) for the central spin-1 system which couple to an XY spin chain with three-spin interaction in a transverse magnetic field. For the case that the central spin system couple weakly to the spin chain, both quantum coherence and NAQC endure sudden change around the critical point of quantum phase transitions when the three-spin interaction is switched off. While there is three-spin interaction, the performances of quantum coherence and NAQC indicate that the critical point has been shifted away from its ordinary position. Therefore, quantum coherence and NAQC can be used to detect the critical point of quantum phase transitions of the XY spin chain for the weak-coupling case. However, three-spin interaction has no obvious effect on the dynamics of quantum coherence and NAQC for the strong-coupling case.

Investigation of the Arc Characteristics of Switching DC Arcs on Hydrogen Containing Gas Mixtures

The characteristics of switching DC current arcs in hydrogen containing gas mixtures under pressure were investigated using a model chamber. The switching device consists of an electro-mechanic double breaker unit with copper contacts. High-speed imaging and spectroscopy were used to observe and to characterize the switching arc. The experiments indicate how the dynamic interaction of an external magnetic field with a high-pressure discharge causes an elongation and twisting of the arc-channel and consequently a voltage increase. Comparative measurements with and without external magnetic field indicate a strong influence of this factor. Cu and N lines together with strongly broadened H lines were observed.

Analysis of Electromagnetohydrodynamic Stagnation Point Flow of Nanofluid Over a Nonlinear Stretching Sheet with Variable Thickness

ABSTRACTPresent study explores stagnation point flow of nanofluid towards a nonlinear stretching sheet of variable thickness in the presence of electromagnetic field and convective heating. The effect of viscous dissipation and Joule heating are also taken into consideration. Novel concept of non-linear radiative heat flux is also considered. The nanofluid is inspired by Lorentz force which is instigated from the interaction of magnetic and electric fields. Using similarity transformation, the governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations and then solved numerically by fourth order Runge-Kutta method along with shooting technique. The velocity, temperature and nanoparticle concentration profiles are plotted and analysed corresponding to various pertinent flow parameters. Also, the skin friction and rate of heat and mass transfers at the surface are computed and explained in detail. It is observed that higher wall thickness parameter results in the reduction of velocity, temperature and nanoparticle concentration when velocity power index is less than unity and opposite effect is observed when velocity power index is greater than unity. Due to intensification of electric field, nanofluid velocity is getting retarded and thereby resulting in enhancement of fluid temperature and nanoparticle concentration.