Electromagnetic Hybrid Research Articles

Power System Subsynchronous Oscillations Electromagnetic and Electromechanical Transient Hybrid Real-Time Simulation Based on RTDS

In this paper, power system electromagnetic and electromechanical transient hybrid real-time simulation technology is expounded in details, which has advantages of the electromagnetic transient simulation program and electromechanical ones. The more details needed to analyze the dynamic characteristics of power systems are provided by this hybrid simulation technology, and the scale of power system simulated is not limited in the hybrid simulation program. The hybrid simulation program is applied to analyze the power system subsynchronous oscillation problem occurred in a power plant with 4 turbine generators located in the northwestern China. According to the simulation results, it is clear that the stability of generators is threatened by the subsynchronous oscillations caused by capacitor series compensation in the transmission line connecting the power plant and the load center system. In meantime, the effectiveness of the countermeasure is validated simultaneously by the hybrid simulation results.

The relation between ion temperature anisotropy and formation of slow shocks in collisionless magnetic reconnection

We perform a two‐dimensional simulation by using an electromagnetic hybrid code to study the formation of slow‐mode shocks in collisionless magnetic reconnection in low beta plasmas, and we focus on the relation between the formation of slow shocks and the ion temperature anisotropy enhanced at the shock downstream region. It is known that as magnetic reconnection develops, the parallel temperature along the magnetic field becomes large in association with the anisotropic plasma sheet boundary layer ion beams, and this temperature anisotropy has a tendency to suppress the formation of slow shocks. On the basis of our simulation result, we found that the slow shock formation is suppressed due to the large temperature anisotropy near the X‐type region, but the ion temperature anisotropy relaxes with increasing the distance from the magnetic neutral point. As a result, two pairs of current structures, which are the strong evidence of dissipation of magnetic field in slow shocks, are formed at the distance ∣x∣ ≥ 115 λi from the neutral point.

Satellite observations of plasma physics near the magnetic field reconnection X line

[1] Satellite observations near the X line are required to understand electromagnetic energy conversion and particle acceleration resulting from magnetic field reconnection. More than 900 orbits of Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft across the low-latitude dayside magnetopause, involving more than 4000 magnetopause crossings and 5000 h of data, were searched for examples of magnetic field reconnection within a few electron skin depths of the X line. Evidence that the X line was crossed in the best of these events comes from observations of DC electric and magnetic fields, electrostatic and electromagnetic lower hybrid waves, magnetosheath electrons flowing along the separatricies, and a super-Alfvenic electron jet flowing perpendicular to the magnetic field. A dispersion analysis identifies properties of the wave that are in agreement with the experiment. Neither these waves nor the DC electric field were sufficient to account for acceleration of the electron jet. The anomalous drag was not an important source of the observed DC electric field. The observed pressure gradient is a possible candidate for maintaining the electric field.

HYPERS: A unidimensional asynchronous framework for multiscale hybrid simulations

Treatment of disparate timescales remains a major challenge in computational science. Previously we introduced a new asynchronous approach to the explicit time integration of multiscale numerical systems based on partial differential equations and particle techniques – self-adaptive discrete-event simulation (DES). In DES time increments for updates of numerical variables (events) are predicted by imposing small but finite bounds to their changes, and event synchronization requirements are defined with physical rules. The feasibility and superior metrics of DES were demonstrated for several different physical problems in one dimension. Here we extend DES to multiple dimensions by introducing a unidimensional infrastructure for asynchronous simulations on logically uniform meshes. As the first example of this infrastructure we present a new event-driven electromagnetic hybrid code, HYPERS (HYbrid Particle Event-Resolved Simulator). This code is validated in two dimensions against a state-of-the-art time-stepping hybrid code on a numerically challenging problem which describes the interaction between the magnetized plasma flow and a magnetic dipole obstacle. We find that HYPERS achieves significant speedups and remains physically accurate in a broad mesh resolution range, including coarser resolutions where the time-driven code produces numerical artifacts.

초고속 자기부상열차 적용을 위한 초전도 하이브리드 전자석 시작품의 설계

This paper deals with the design and fabrication of prototype superconducting hybrid electromagnet(SH-EM) for EMS (Electromagnetic suspension)-based Maglev. The design requirements are based on the normal conducting EM used in the German high-speed Maglev. From the MMF-Levitation force curves simulated by FEM analysis, the required MMF by superconducting coil is suggested. As an experimental test setup to demonstrate the SH-EM, the experimental SH-EM with HTS coil cooled in <TEX>$LN_2$</TEX> is fabricated. From the expected operating current of the HTS coil, the levitation performance of the SH-EM is estimated.

Saturation characteristics of electromagnetic ion cyclotron waves

[1] Electromagnetic ion cyclotron (EMIC) waves are an integral component of the Earth's dynamic space environment. In order to quantify their effect, it is necessary to know their saturation amplitude, but in modeling studies it is usually the linear growth rate that is calculated and various assumptions need to be made in order to relate this growth rate to the final amplitude of the wave. Here, we perform a comparison of the saturation characteristics of EMIC waves using a 2.5-D electromagnetic hybrid PIC code, with the corresponding linear growth rates calculated with the hot-plasma dispersion solver of the HOTRAY code. We choose a set of values consistent with satellite observations for our nominal case, and explore the parameter space in the neighborhood of this nominal case, by varying the hot proton density and thermal anisotropy. We find that the saturation amplitudes increase monotonically, and the times to saturation decrease monotonically with increasing growth rates, independent of the values of density and anisotropy. Both the saturation amplitude and time to saturation curves can be fit by simple two-parameter models with acceptable errors. This result implies that within the limitations and caveats of the present study, the saturation amplitudes and time to saturation can be predicted with good accuracy based on the linear growth rates alone, which can be used directly in conjunctions with global ring current simulations to model the resultant effects on magnetospheric particles.

Theoretical and FEM analysis of suspension and propulsion system with HTS hybrid electromagnets in an EMS Maglev model

We have been constructed a proto-type electromagnetic suspension (EMS) based maglev vehicle system. The maglev concept utilizes magnetic forces for noncontact suspension, guidance and propulsion. The suspension system with high temperature superconducting (HTS) hybrid electromagnet (EM) is composed of HTS coils and normal coils, which consume little power to keep large suspension gap. The magnetic forces realize to guide the vehicle, propel the vehicle along the guide-way and assist in braking action. The proto-type EMS-based Maglev model is designed to keep the suspension gap of 20mm. This paper presents the theoretical analysis of the maglev vehicle based on the EMS model to obtain the designing parameters for levitation and propulsion forces. The magnetic field distributions of the electromagnetic forces with hybrid EM and propulsion stator coils are analyzed based on three dimension (3D) finite element method (FEM) analysis. From the simulation results, appropriately design parameters of the suspension, guidance and propulsion were obtained.

Oriented growth of magnetite along the carbon nanotubes via covalently bonded method in a simple solvothermal system

Abstract A new type of CNTs/magnetite hybrid material was prepared via covalently bonded method in a simple solvothermal system using FeCl 3 as iron source, ethylene glycol as the reducing agent, and 4-aminophenoxyphthalonitrile-grafted CNTs as templates. The magnetite nanoparticles, with the diameters of 70–80 nm, were self-assembled along the CNTs. The FTIR, UV–vis and DSC revealed that a stable covalent bond between nitriles group and iron ion promoted the oriented growth of magnetite nanoparticles along the CNTs, resulting in good dispersibility and solution storage stability. The magnetic properties measurements indicated that a higher saturated magnetization (70.7 emu g −1 ) existed in the CNTs/magnetite hybrid material, which further enhanced the electromagnetic properties. The magnetic loss was caused mainly by natural resonance, which is in good agreement with the Kittel equation results. The novel electromagnetic hybrid material is believed to have potential applications in the microwave absorbing performances.

초전도 하이브리드 자기부상 마그넷 시스템의 코어 형상 설계 연구

This paper deals with the design on iron-core shape for superconducting hybrid electromagnet (SH-EM). A proto-type SH-EM was developed by Yonsei University. It is the first step study on the fundamental technology for advanced railroad system development. We proposed the method that reduce the number of cooling systems in order to improve operating efficiency of the SH-EM. The results was obtained by changing of iron-core shape were verified by the FEM analysis. This paper can be expected to suggest useful data for an advanced SH-EM.

One-pot solvothermal synthesis of sandwich-like graphene nanosheets/Fe 3O 4 hybrid material and its microwave electromagnetic properties

A novel sandwich-like graphene nanosheets (GNs)/Fe 3O 4 hybrid material was synthesized through a facile one-pot solvothermal method using FeCl 3 as iron source, ethylene glycol as the reducing agent and graphene nanosheets as templates. The Fe 3O 4 nanoparticles, with the average diameters of ca. 40 nm, were self-assembled on the graphene nanosheets through electrostatic attraction and formed sandwich-like nanostructure. The ferromagnetic signature emerged with the saturated magnetization of ~ 72.3 emu g − 1 , and the coercive force of ~ 196.1 Oe at 300 K. The magnetic loss was caused mainly by natural resonance which is in agreement with the Kittel equation. The novel electromagnetic hybrid material is believed to have potential applications in the microwave absorbing performances.

Multiscale quantum mechanics/electromagnetics simulation for electronic devices

The continuous downsizing of modern electronic devices implies the increasing importance of quantum phenomena. As the feature sizes of transistors inch towards 10 nanometer, simulations including quantum effects and atomistic details are inevitable. Here we report a novel hybrid quantum mechanics and electromagnetics (QM/EM) method to model individual electronic components at the nanoscale. QM and EM models are solved in different regions of the system in a self-consistent manner. As a demonstration, we study a carbon nanotube based electronic device embedded in a silicon block. Good agreement is obtained between simulation by QM/EM method and full QM treatment of the entire system.

Three-Dimensional Relativistic Particle-in-Cell Hybrid Code Based on an Exponential Integrator

In this paper, we present a new 3-D full electromagnetic relativistic hybrid plasma code, the hybrid virtual laser plasma laboratory. The full kinetic particle-in-cell method is used to simulate low-density hot plasmas while the hydrodynamic model applies to the high-density cold background plasma. To simulate the linear electromagnetic response of the high-density plasma, we use a newly developed form of an exponential integrator method. It allows us to simulate plasmas of arbitrary densities using large time steps. The model reproduces the plasma dispersion and gives the correct spatial scales like the plasma skin depth even for large grid cell sizes. We test the hybrid model validity by applying it to some physical examples.

Preparation, characterization and electromagnetic properties of carbon nanotubes/Fe3O4 inorganic hybrid material

A novel carbon nanotubes/Fe3O4 inorganic hybrid material was prepared by in situ decomposition of the precursor ferric chloride crystal and CNTs in liquid ethylene glycol. XRD, SEM, TEM, EDS were used to characterize the as-prepared products. Results indicated that the monodispersed magnetite microspheres with the size of about 100nm were uniformly self-assembled along the surface of the carbon nanotubes. The formation of magnetite nanoparticles on CNTs was through an aggregation process of subparticles on the surface of CNTs. The ferromagnetic signature emerged with the saturated magnetization of 60.94emug−1, and the coercive force of 148.59Oe at 300K. The measured relative complex permittivity indicated a high resistivity existence in the CNTs/Fe3O4 inorganic hybrid material. The magnetic loss was caused mainly by natural resonance, which is in good agreement with the Kittel equation results. The novel electromagnetic hybrid material is believed to have potential applications in the microwave absorbing performances.

Contactless Dielectrophoretic Handling of Diamagnetic Levitating Water Droplets in Air

Micromagnets have been reported to successfully levitate picoliter water droplets in air. Manipulation of levitating water droplets is a contamination-free alternative to digital-microfluidic labs-on-chip where droplets are handled in channels or on a substrate. An integrated electromagnetic hybrid device combining dielectrophoretic (DEP) forces to control the position of levitating droplets along a magnetic groove, is proposed. Diamagnetic forces are analytically computed with CADES while Comsol Multiphysics™ (FEM) is used for the DEP forces. Approximations of the `point dipole model' are compared to the Maxwell Stress Tensor method applied on the 3-D model. Based on these results, an electric sequence for polarizing planar parallel Indium Tin Oxide (ITO) electrodes is proposed in order to provide a stable and accurate control of the droplet microposition along the gap. The use of these electrodes as micro-conductors to produce variable magnetic fields for magnetophoretic droplet actuation is considered and compared to DEP actuation.

Effects of process parameters on warm and electromagnetic hybrid forming of magnesium alloy sheets

As the lightest structural metal, magnesium (Mg) is attracting increasing interest from both the industrial and academic fields. Magnesium alloy parts are mainly processed by die casting due to their poor sheet formability at room temperature. Warm forming is a popular method of forming; Mg alloy sheets produced in this manner show excellent formability around 200–400 °C. Electromagnetic forming (EMF) can improve the formability of metal sheets without the need for lubricants. In this paper, a new approach, called warm and electromagnetic hybrid forming (WEMF), is presented. The effects of voltage, capacity, and temperature on the bulging height of Mg alloy sheets are investigated. Results show that the bulging height of Mg sheets increases with moderate discharging energies. Enhancing the discharging voltage is also a more efficient method for increasing bulging height compared to simply increasing the capacity. When the discharging energy is kept constant, the bulging height first decreases (<150 °C) and then increases (>150 °C) from room temperature to 230 °C. The formability of Mg alloy sheets improves with increasing temperature, while the forming efficiency of WEMF decreases under similar conditions.

Hybrid simulations of the plasma environment around Enceladus

The plasma environment around Enceladus is governed by the interaction between the corotating plasma with the body of the moon and the neutral gas associated with Saturn's extended cloud and plumes ejected from its southern polar region. To understand the nature of this interaction, we use 3‐D electromagnetic hybrid simulations that treat ions kinetically through particle‐in‐cell methods and treat the electrons as a charge‐neutralizing fluid. In these simulations, plasma interaction with the neutrals takes place through charge exchange. The results show that plasma absorption by Enceladus forms a tail‐like density cavity behind the moon and a depletion wake which is confined in the direction perpendicular to the magnetic field but extends many Enceladus radii along the magnetic field. Except in the cavity tail, the flow is not slowed by the interaction but is diverted toward the cavity in a symmetric fashion. Interaction of the corotating plasma with the extended neutrals results in the generation of ion cyclotron waves and plasma deceleration to velocities below the corotation speed. The results also show that the extent to which the presence of a plume in the southern pole affects the nature of the interaction depends on its density. For plumes with base densities of ∼106/cm3 (6.5 × 1029 molecules in the plume) or lower we find no significant impacts, while plumes with base densities of ∼107/cm3 and larger are found to greatly impact the interaction region. Specifically, the interaction is no longer symmetric with a density cavity tail in the Northern Hemisphere and a density enhancement tail in the Southern Hemisphere. At base densities of ∼108/cm3, a strong Alfven wing is also generated in the interaction. Preliminary comparisons of the simulations with the Cassini Plasma Spectrometer data during the 12 March 2008 encounter with Enceladus suggest plume base densities of ∼5 × 108/cm3 corresponding to production of ∼4 kg/s of new ions.

Engine operation control for an electromagnetic coupling dual electric machine hybrid electric bus

An electromagnetic coupling dual electric machine hybrid electric bus is investigated. The flywheel and start-motor of the Internal Combustion Engine (ICE), the mechanical clutch and the manual transmission are replaced by Double-electric Machines (DM). The DM work as an electromagnetic clutch and a continuously variable transmission, simultaneously. An Improved Engine Operation Control (IEOC) is proposed to maximise the efficiency of the overall electromagnetic coupling system, in which the ICE efficiency, the DM efficiencies and the battery efficiency are all explicitly taken into account. Simulation results indicate potential fuel economy improvement relative to the traditional control.

Warm electromagnetic lower hybrid wave dispersion relation

Lower hybrid (LH) waves can interact resonantly with both electrons and ions transferring energy between the species. For this reason the properties of LH waves are of interest. Most treatments of LH waves include either electromagnetic (EM) or warm plasma effects but not both. Here a new analytic dispersion relation for LH waves, including both EM and warm plasma effects, is derived and shown to be more consistent than the previous analytic dispersion relations with numerical results. These comparisons show a very good agreement of the real part of the frequency and reasonable agreement of the imaginary part for a wide range of parameters. It is found that ion magnetization effects, which have been neglected in all previous analytic treatments of LH waves, are surprisingly important. When ion magnetization effects become important the continuous LH mode breaks up into a series of segments of ion Bernstein modes.

Determining ion production rates near Saturn's extended neutral cloud from ion cyclotron wave amplitudes

Recent Cassini observations of active venting of water molecules from Enceladus indicate that the moon is the primary source of Saturn's extended neutral cloud. Ionization of the neutrals through charge exchange creates a population of newborn ions with a velocity space distribution, which is highly unstable to the generation of electromagnetic ion cyclotron waves. Cassini observed such ion cyclotron waves, finding spatial and temporal variability in the wave amplitudes throughout the extended neutral cloud region. Since the amount of energy in the ion cyclotron waves is proportional to the number of newborn ions generating them, it is possible to infer the ion production rate in the region. To do so, we use two‐dimensional electromagnetic hybrid (kinetic ions, fluid electrons) simulations to investigate the growth and nonlinear evolution of ion cyclotron waves. We focus on conditions near Enceladus' L shell and compare the simulated and observed ion cyclotron wave amplitudes to estimate the neutral densities and ion production rates. Our simulation results find a relatively linear relation between ion production rate and quasisteady wave energy level (δB2). For conditions near Enceladus' L shell, we find that water group ion production rates of 0.007–0.014/cc/s (which yield wave amplitudes of ∼0.1–0.3 nT) are appropriate. For ion production within an annulus volume from 3.9 to 4 RS, we obtain ion production rates of 3.8 × 1026 to 7.6 × 1026 ions/s or 10.2–20.4 kg/s.

One-dimensional electromagnetic relativistic PIC-hydrodynamic hybrid simulation code H-VLPL (hybrid virtual laser plasma lab)

In this paper we present a new one-dimensional full electromagnetic relativistic hybrid plasma model. The full kinetic particle-in-cell (PIC) and hydrodynamic model have been combined in the single hybrid plasma code H-VLPL (hybrid virtual laser plasma laboratory). The semi-implicit algorithm allows to simulate plasmas of arbitrary densities via automatic reduction of the highest plasma frequencies down to the numerically stable range. At the same time, the model keeps the correct spatial scales like the plasma skin depth. We discuss the numerically efficient implementation of this model. Further, we carefully test the hybrid model validity by applying it to a series of physical examples. The new mathematical method allows to overcome the typical time step restrictions of explicit PIC codes.