Effect Of Lorentz Force Research Articles

In situ analysis of copper electrodeposition reaction using unilateral NMR sensor

The uses of high-resolution NMR spectroscopy and imaging (MRI) to study electrochemical reactions in situ have greatly increased in the last decade. However, most of these applications are limited to specialized NMR laboratories and not feasible for routine analysis. Recently we have shown that a bench top, time domain NMR spectrometer can be used to monitor in situ copper electrodeposition reaction and the effect of Lorentz force in the reaction rate. However these spectrometers limit the cell size to the magnet gap and cannot be used with standard electrochemical cells. In this paper we are demonstrating that unilateral NMR sensor (UNMR), which does not limit sample size/volume, can be used to monitor electrodeposition of paramagnetic ions in situ. The copper electrodeposition reaction was monitored remotely and in situ, placing the electrochemical cell on top of the UNMR sensor. The Cu2+ concentration was measured during three hours of the electrodeposition reactions, by using the transverse relaxation rate (R2) determined with the Carr–Purcell–Meiboom–Gill pulse sequence. The reaction rate increased fourfold when the reaction was performed in the presence of a magnetic field (in situ), in comparison to the reactions in the absence of the magnetic field (ex situ). The increase of reaction rate, in the presence of the UNMR magnet, was related to the magneto hydrodynamic force (FB) and magnetic field gradient force (F∇B). F∇B was calculated to be one order of magnitude stronger than FB. The UNMR sensor has several advantages for in situ measurements when compared to standard NMR spectrometers. It is a low cost, portable, open system, which does not limit sample size/volume and can be easily be adapted to standard electrochemical cells or large industrial reactors.

Thermochemical Nonequilibrium 2D Modeling of Nitrogen Inductively Coupled Plasma Flow**supported by Grant-in-Aid for Scientific Research (No. 23560954), sponsored by the Japan Society for the Promotion of Science

Two-dimensional (2D) numerical simulations of thermochemical nonequilibrium inductively coupled plasma (ICP) flows inside a 10-kW inductively coupled plasma wind tunnel (ICPWT) were carried out with nitrogen as the working gas. Compressible axisymmetric Navier-Stokes (N-S) equations coupled with magnetic vector potential equations were solved. A four-temperature model including an improved electron-vibration relaxation time was used to model the internal energy exchange between electron and heavy particles. The third-order accuracy electron transport properties (3rd AETP) were applied to the simulations. A hybrid chemical kinetic model was adopted to model the chemical nonequilibrium process. The flow characteristics such as thermal nonequilibrium, inductive discharge, effects of Lorentz force were made clear through the present study. It was clarified that the thermal nonequilibrium model played an important role in properly predicting the temperature field. The prediction accuracy can be improved by applying the 3rd AETP to the simulation for this ICPWT.

Near-wall measurements of the bubble- and Lorentz-force-driven convection at gas-evolving electrodes

Chemical energy storage systems, e.g., in the form of hydrogen or methanol, have a great potential for the establishment of volatile renewable energy sources due to the large energy density. The efficiency of hydrogen production through water electrolysis is, however, limited by gas bubbles evolving at the electrode’s surface and can be enhanced by an accelerated bubble detachment. In order to characterize the complex multi-phase flow near the electrode, simultaneous measurements of the fluid velocities and the size and trajectories of hydrogen bubbles were performed in a water electrolyzer. The liquid phase velocity was measured by PIV/PTV, while shadowgraphy was used to determine the bubble trajectories. Special measurement and evaluation techniques had to be applied as the measurement uncertainty is strongly affected by the high void fraction close to the wall. In particular, the application of an advanced PTV scheme allowed for more precise fluid velocity measurements closer to electrode. Based on these data, stability characteristics of the near-wall flow were evaluated and compared to that of a wall jet. PTV was used as well to investigate the effect of Lorentz forces on the near-wall fluid velocities. The results show a significantly increased wall parallel liquid phase velocity with increasing Lorentz forces. It is presumed that this enhances the detachment of hydrogen bubbles from the electrode surface and, consequently, decreases the fractional bubble coverage and improves the efficiency. In addition, the effect of large rising bubbles with path oscillations on the near-wall flow was investigated. These bubbles can have a strong impact on the mass transfer near the electrode and thus affect the performance of the process.

Coupled electro-magnetic field & Lorentz force effects in silicon and metal for ESD investigation in transient and harmonic regimes

The purpose of this paper is to present a fully-coupled electro-magnetic field formulation including Lorentz force corrections with the purpose of investigating ESD events in great detail in silicon (FEOL) and the metal stack (BEOL). This study is focused on ESD events in advanced CMOS technology. For specific ESD events, responses, design and topology it is important to take into account all electromagnetic phenomena in the structure. To perform such an accurate study, the first step is to build a powerful tool for the harmonic and transient regime coupling all electric and magnetic fields. Typical ESD structures are simulated to ultimately know the impact of the electro-magnetic field and Lorentz force. The harmonic regime is used for parasitic capacitance extraction and the transient regime for the ESD behaviour. We demonstrate that the simulation tool has a wide range of applicability by giving additional applications.

Variations of magnetocaloric effect and magnetoresistance across RCuGe (R=Tb, Dy, Ho, Er) compounds

RCuGe (R=Tb–Er) compounds have been studied by structural, magnetic, magnetocaloric and magnetotransport measurements. All these compounds are iso-structural and show antiferromagnetic ordering below their Néel temperatures (TN). Except TbCuGe, all the studied compounds show large magnetocaloric effect (MCE), arising due to the field induced metamagnetic transition. They also show a sign reversal of magnetoresistance (MR) with change in temperature or field. The non-monotonic variation of the magnitude of MR is attributed to the competing effects of Lorentz force, changes in the spin disorder scattering and the spin fluctuations.

Anisotropic magnetocapacitance in ferromagnetic-plate capacitors

The capacitance of a parallel plate capacitor can depend on applied magnetic field. Previous studies have identified capacitance changes induced via classical Lorentz force or spin-dependent Zeeman effects. Here we measure a magnetization direction dependent capacitance in parallel-plate capacitors where one plate is a ferromagnetic semiconductor, gallium manganese arsenide. This anisotropic magneto-capacitance is due to the anisotropy in the density of states dependent on the magnetization through the strong spin-orbit interaction.

Nondiagonal graphene conductivity in the presence of in-plane magnetic fields

We study the electron/hole transport in puddle-disordered and rough graphene samples which are subject to in-plane magnetic fields. Previous treatments, mostly devoted to regimes where the electron/hole scattering wavelengths are larger than the surface height correlation length, are based on the use of transport equations with appropriate forms for the collision term. We point out in this work, as a counterpoint, that classical Lorentz force effects, which are expected to hold when the Fermi level is far enough away from the charge neutral point, can be heuristically assessed through disordered Boltzmann equations that contain magnetic-field dependent material derivatives, and keep the zero magnetic-field structure of the collision term. It turns out that the electric conductivity tensor gets a peculiar nondiagonal component, induced by the in-plane magnetic field that crosses the rough topography of the graphene sheet, even if the projected random transverse magnetic field vanishes in the mean. Numerical estimates of the transverse conductivities suggest that they are suitable of observation under conditions which are within the reach of up-to-date experimental methods.

Experimental and theoretical investigations on magnetic and related properties of ErRuSi

We report experimental and theoretical studies of magnetic and related properties of ErRuSi compound. Various experimental techniques such as neutron diffraction, magnetization, magneto-thermal, magneto-transport, optical conductivity have been used to investigate this compound. Neutron diffraction shows ferromagnetic ordering at low temperatures with moments aligned in the ab plane. Neutron diffraction and magnetization data indicate the influence of crystalline electric field effects in the moment at low temperatures. The compound shows good magnetocaloric properties with a low-field adiabatic temperature change of 4.7 K, which is larger than that of many proposed low temperature magnetic refrigerant materials. Magnetoresistance (MR) shows large negative value at 8 K, which changes its sign and increases in magnitude with decrease in temperature and/or increase in field. The positive MR at low temperatures is attributed to the Lorentz force effect. The electronic structure calculations accounting for electronic correlations of the 4 f electrons of Er elucidate the ferromagnetic ordering and effective paramagnetic moment. Interband transitions between the Ru and the Er d states and the Er f states in one spin projection are found to form the main feature of the measured optical conductivity in this compound.

WITHDRAWN: Effect of Lorentz forces on forced-convection nanofluid flow over a stretched surface

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.

A212 電磁超音波共鳴法シミュレーションの実験的検証(OS2 保全・設備診断技術(3))

The electromagnetic acoustic resonance (EMAR) method provides accurate and stable evaluation of thickness of pipes. Wall thickness measurement depend on such as the shape of the pipe. A simulation is necessary to be more reliable thickness assessment. In considering the simulation, it has a problem. The working principle of electromagnetic acoustic transducer (EMAT) caused by the Lorentz force and magnetostrictive effect. It is a complicated operating principles. In order to develop a simulation of EMAT's operating principle by the Lorentz force. The authors verified and compared with the experimental values the validity of analysis in the existing ultrasound analysis.

Dynamics and instability of current-carrying microbeams in a longitudinal magnetic field

Abstract The dynamics and instability of current-carrying slender microbeams immersed in a longitudinal magnetic field is investigated by considering the material length scale effect of the microbeam. On the basis of modified couple stress theory, a theoretical model considering the effect of Lorentz forces is developed to analyze the free vibration and possible instability of the microbeam. Using the differential quadrature method, the governing equations of motion are solved and the lowest three natural frequencies are determined. The obtained results reveal that the electric current and the longitudinal magnetic field tend to reduce the microbeam's flexural stiffness. It is therefore shown that the lowest natural frequencies would decrease with increasing magnetic field parameter. The mode shapes of the microbeam are found to be generally three-dimensional spatial in the presence of the longitudinal magnetic field. It is interesting that buckling instability would concurrently occur in the first mode or in the higher-order modes when the magnetic field parameter becomes sufficiently large.

Variational data assimilation for a forced, inertia-free magnetohydrodynamic dynamo model

Variational data assimilation (4DVar) is a powerful technique for tuning dynamic models to observations, in order not only to forecast future time evolution of the system, but to make inferences about quantities that are otherwise unconstrained by observation. We apply this technique, well-grounded in meteorology and oceanography, to the Earth's core where incompressible fluid motions in an electrically conducting medium are responsible for magnetic field generation. Our dynamic model's momentum equation neglects inertia such that the entire evolution depends only on the structure of the initial magnetic field; time evolution of the system is solely governed by the equation of magnetic induction. Nevertheless the dynamic system encompasses the effects of rotation, Lorentz forces and viscosity and aims to mimic a reasonable force-balance in the Earth's core. Building on the work of Li et al., in order to optimize the data-fit subject to the dynamics, we further develop the mathematical structure of the adjoint equations of the system. We address the feasibility of recovering 3-D spatial properties of the system using only time-varying 2-D observations of different character. Using closed-loop testing, we demonstrate the retrievability of the initial state (and thus the entire trajectory) of the system over convective timescales, when sampling in regions in which magnetic induction dominates over diffusion. The results suggest the possibility of retrieving the entire trajectory of the dynamo system of the Earth using the 400-yr model of secular variation gufm1.

Deflection of a liquid metal jet/drop in a tokamak environment

The interaction of a liquid gallium jet with plasma has been investigated in the ISTTOK tokamak. The jet was observed to remain intact during its interaction with plasma, within a certain length beyond which drop formation was observed. Significant deflection of the jet was detected as soon as plasma production was started. Furthermore, a strong dependency of the deflection magnitude on plasma position was observed that could be correlated with plasma potential gradients. As a means to capture and, possibly, quantify this effect, a preliminary magnetohydrodynamic analysis was performed in order to predict the trajectory of a jet that is traveling inside an electromagnetic field. The effect of Lorentz forces, gravity and pressure drop are accounted for in a unidirectional model that assumes a small jet radius in comparison with the trajectory length. The effect of external electric potential gradients on jet deflection was ascertained in conjunction with the importance of electric stresses in modulating the jet speed and radius. Analysis of the results reported in the ISTTOK experiments identifies the process of jet break-up as a capillary instability. The trajectory of the ensuing droplets is modeled and intensification of the deflection process is predicted in the presence of Lorentz forces.

Nonlinear relative dynamics of Lorentz spacecraft about J2-perturbed orbit

The Lorentz force acted on a charged spacecraft via interaction with planetary magnetic field provides new means of propellantless electromagnetic propulsion. Active modulation of the surface charge allows the spacecraft to perform orbital maneuvers. By assuming the Earth’s magnetic field could be modeled as a tilted dipole that co-rotates with Earth, a nonlinear dynamical model describing the orbital motion of Lorentz spacecraft with respect to J2-perturbed orbit is developed using Lagrangian mechanics. Two potential applications of the proposed model, J2-perturbed Lorentz-augmented spacecraft hovering and Lorentz-propelled rendezvous, are considered in this paper. Fuel-optimal control strategies are designed for hovering, and optimal trajectory of the specific charge of Lorentz spacecraft for propellantless rendezvous that minimizes the consumption of control energy is also derived via Gauss pseudospectral method. To capture the interactive effect of J2 perturbations and Lorentz force on relative motion, comparisons are made between results derived from J2-perturbed model and unperturbed model for both applications. Numerical simulations prove the validity of the proposed relative dynamical model and the applicability of Lorentz force in J2-perturbed spacecraft hovering and rendezvous. Comparisons show that J2 perturbation should be considered when long-term hovering is necessary or more precise rendezvous trajectory is required, especially for low Earth orbit where J2 perturbation is one of the most dominant perturbative forces.

Low Power Nonlinear Active Devices Based on Intrinsic Metal Nonlinearities

In this paper, we report a novel low-power nonlinear plasmonic nanoswitch mainly based on optical nonlinearity of centro-symmetric metals. We consider metal nonlinear terms including electrical and magnetic parts of Lorentz force and convective effect, due to the free electron mobility and Lorentz oscillator for bound electrons. We use hydrodynamic model for free electrons of metal to describe nonlinear terms that play more significant role in the second and third harmonic generation processes. We study the impact of each individual term. Our simulation results show that the convective term is much more effective than the others. We simulate the second harmonic generation of 2-D nanopillar and plasmonic switch by the 2-D finite difference time domain method. The required powers for exciting the intrinsic metal nonlinearities due to the free and bound electrons are less than those of other kinds of nonlinearities such as Kerr effect in dielectrics. In our nanoswitch, fundamental frequency as a pump signal controls each output ports and switching performance.

Evaluation of Reynolds stress MHD turbulence models using decaying homogeneous turbulence

Abstract Direct numerical simulation databases and theoretical analysis for decaying homogeneous turbulent flow in a conducting fluid subjected to an imposed magnetic field are investigated to evaluate the second-order models proposed by Widlund et al. and Kenjeres et al. The case of very small magnetic Reynolds numbers ( Re m ≪ 1 ) is considered in the present work. This case corresponds to the quasi-static approximation, which is well suited for most industrial flows involving liquid metals. The results obtained from our calculations show the performance of the model of Widlund et al. in predicting the Lorentz force effects compared with the model of Kenjeres et al.

Millicharged neutrino with anomalous magnetic moment in rotating magnetized matter

New exact solutions of the modified Dirac equation describing a neutrino with nontrivial electromagnetic properties in extreme background conditions are obtained. Within the quasi-classical treatment the effective Lorentz force that describes the neutrino propagation in the magnetized rotating matter is introduced. We predict the effect of the spatial separation of different types of relativistic neutrinos and antineutrinos (different in flavors and energies) by the magnetized rotating matter of a star. Low energy neutrinos can be even trapped inside the star. We also predict two new phenomena: a new type of the neutrino electromagnetic radiation (termed “Light of (milli)Charged Neutrino”, LCν) and a new mechanism of the star angular velocity shift due to neutrinos escaping the star (termed “Neutrino Star Turning” mechanism, νST). The possible impact of the νST mechanism on a supernova explosion yields a new astrophysical limit on the neutrino millicharge qν<1.3×10−19e0. In addition, the νST mechanism can be also used to explain the origin of pulsar “anti-glitches” and ordinary glitches as well.

Numerical analysis of the attitude stability of a charged spacecraft in the Pitch-Roll-Yaw directions

In this paper, the effect of Lorentz force on the stability of attitude orientation of a charged spacecraft moving in an elliptic orbit in the geomagnetic field is considered. Euler equations are used to derive the equations of attitude motion of a charged spacecraft. The equilibrium positions and its stability are investigated separately in the pitch, roll and yaw directions. In each direction, we use the Lorentz force to identify an attitude stabilization parameter. The analytical methods confirm that we can use the Lorentz force as a stabilization method. The charge-to-mass ratio is the main key of control, in addition to the components of the radius vector of the charged center of the spacecraft, relative to the center of mass of the spacecraft. The numerical results determine stable and unstable equilibrium positions. Therefore, in order to generate optimum charge, which may stabilize the attitude motion of a spacecraft, the amount of charge on the surface of spacecraft will need to be monitored for passive control.

Observation of a Geometric Hall Effect in a Spinor Bose-Einstein Condensate with a Skyrmion Spin Texture

For a spin-carrying particle moving in a spatially varying magnetic field, effective electromagnetic forces can arise due to the geometric phase associated with adiabatic spin rotation of the particle. We report the observation of a geometric Hall effect in a spinor Bose-Einstein condensate with a Skyrmion spin texture. Under translational oscillations of the spin texture, the condensate resonantly develops a circular motion in a harmonic trap, demonstrating the existence of an effective Lorentz force. When the condensate circulates, quantized vortices are nucleated in the boundary region of the condensate and the vortex number increases over 100 without significant heating. We attribute the vortex nucleation to the shearing effect of the effective Lorentz force from the inhomogeneous effective magnetic field.

Magnetic electrodeposition of ZnNi alloy films

Magnetic fields parallel to electrodes were introduced during plating process to obtain ZnNi alloy films from acid baths. Effects of different magnetic intensities on the composition, nucleation magnetism, surface morphology and anticorrosion of ZnNi films were investigated. With the increase in magnetic intensity, deposition rate and nickel contents increased gradually due to magnetohydrodynamic (MHD) effects caused by Lorentz force. It was found that magnetic force Fm in the magnetic electrodeposition process could have a significant effect on the mass transfer to dramatically improve deposition rate. Maximum deposition rate (90 m h−1) was achieved when the magnetic intensity was equal to 1 T. The films were densely covered with typical nodular structure. Films of smaller grain size and smooth surface could be formed under high magnetic intensity as a result of Lorentz force and MHD effects. Moreover, ZnNi films obtained with higher magnetic intensity possessed more positive self-corrosion potential and optimal anticorrosion performance. However, much higher nickel contents in ZnNi films may drop anticorrosion performance.