Residual Flux Research Articles

Residual Magnetic Moment Influences the Features of Fe3s XPS Spectrum: A Case Study

Background: Fe 3sXPS spectrum exhibits doublet peak instead of predicted singlet peak based on spin-orbit coupling theory. This anomalous behavior is considered to be of magnetic origin. However, the effect of residual magnetic moment on the features of Fe3s doublet peak is not understood fully. Objective: This study aims to verify the effect of residual magnetic moment on the spectral features of Fe3s XPS spectrum of magnetic material. Method: As a case study, we have carried out a high-temperature XPS study of the Fe 3s spectrum of magnetic domain aligned (MDA) sample with composition composed of SrFe10.8Al1.2O19. In addition, the XPS data have been compared with the data acquired at different temperatures of magnetic domain non-aligned (MDNA) sample. Results: The results show that the majority peak intensity and minority peak width of Fe 3s spectrum of MDA are smaller than those of the MDNA sample, and they increase systematically with increasing temperature. However, it is noted that the features of Fe3s spectrum of both MDA and MDNA samples completely overlap near and above the Curie temperature, Tc ~ 670K. Discussion: The residual magnetic flux in the MDA sample alters the interaction between 3s electrons and valence 3d spin. In addition, the presence of residual magnetic moment leads to deviation of the escaped electrons from their path, therefore the majority peak intensity of MDA sample becomes smaller than the MDNA sample at below the Curie temperature. Consequently, the spectral features of MDA samples are different than the MDNA samples at below the Curie temperature. Conclusion: The analysis of XPS data suggests that the residual magnetic moment influences the spectral features of the Fe3s spectrum. These results provide evidence that it is important to consider the contribution of the residual magnetic moment while deriving information from the Fe 3s XPS spectrum of the MDA sample.

Magnetic Characterization of the Nugget Microstructure at Resistance Spot Welding

Conventional resistance spot welds are not visible from the outside. Therefore, it is not straightforward to evaluate the joint quality non-destructively. The pulse-echo method of manual ultrasonic is widely used for non-destructive testing. Another option is the passive magnetic flux density testing, which is being developed at Technische Universität Dresden, Germany. The spot weld is magnetized in the normal direction and the residual magnetic flux density is measured on top of the surface of the joint. This method is suitable for spot welds on typical car body steels. Previous investigations show that the magnetic properties of the materials influence the test result. In order to develop this new non-destructive testing method further, it is necessary to know the magnetic properties of the different microstructure regions of a spot weld. This article focuses on methods to measure and evaluate the magnetic properties of these regions, especially of the base material and the weld. Different measuring methods and approaches are presented and compared with each other. Based on the results, recommendations for future measurements for magnetic characterizations are given.

Review of the Observed Energy Flow in the Earth System

The energy budget imbalance at the top of the atmosphere (TOA) and the energy flow in the Earth’s system plays an essential role in climate change over the global and regional scales. Under the constraint of observations, the radiative fluxes at TOA have been reconstructed prior to CERES (Clouds and the Earth’s Radiant Energy System) between 1985 and 2000. The total atmospheric energy divergence has been mass corrected based on ERA5 (the fifth generation ECMWF ReAnalysis) atmospheric reanalysis by a newly developed method considering the enthalpy removing of the atmospheric water vapor, which avoids inconsistencies due to the residual lateral total mass flux divergence in the atmosphere, ensuring the balances of the freshwater fluxes at the surface. The net surface energy flux (Fs) has been estimated using the residual method based on energy conservation, which is the difference between the net TOA radiative flux and the atmospheric energy tendency and divergence. The Fs is then verified directly and indirectly with observations, and results show that the estimated Fs in North Atlantic is superior to those from model simulations. This paper gives a brief review of the progress in the estimation of the observed energy flow in the Earth system, discusses some caveats of the existing method, and provides some suggestions for the improvements of the aforementioned data sets.

Influence of Pre-Tinning Process on Coating Morphology and Interface Structure of Low Carbon Steel Dipped in Molten 6061 Al Alloy

Pre-treated low carbon steel specimens with flux or flux + tin mixture were coated by hot-dip aluminizing process. Al alloy (6061) was melted and hold at 750 °C. Fluxed and pre-tinned low carbon steel samples were dipped in a molten bath for time intervals of 0.5, 1, 2.5 and 3.5 min. Applying double coating processes via tinning-aluminizing techniques facilitated the formation of Fe-Al intermetallic interface and increasing the thickness of homogenous coating layer over the substrate material. The presence of Sn facilitates to great extent the formation of a better interlayer-free bond of residual flux and/or oxides. The fluxed–dipped steel substrates have inhomogeneous distribution of Al alloy coating as well as an interface with residual flux and oxides for dipping time up to 2.5 min. A homogenous distribution with good thickness morphology of the Al alloy coating and homogeneous thin intermetallic interface was achieved for tinned steel substrate at all applied dipping times. The comparison between the pre-tinning and pre-fluxing processes on steel substrates showed a significant effect of tinning over fluxing treatment acting on the thickness layer of Al-coating and interface using a short time dipping. For dipping time up to 2.5 min, the hardness of pre-tinning substrates is greater than that of fluxed ones due to the presence of residual flux and void interface in fluxed steel.

Zero-Mode Inrush Current Characteristics and Zero-Sequence Protection Countermeasure Under Sympathetic Interaction

When the transformer is energized, the three-phase inrush current with the zero-mode component named zero-mode inrush current (ZMIC) will be generated due to the inconsistent saturation of the three-phase iron core. From the on-site waveform record, the ZMIC attenuates very slowly and leads to the zero-sequence zone Ⅲ backup protection malfunction of the upstream transmission line of the transformer. The malfunction expands outages and has an adverse effect on the equipment safety and system stability. To solve this problem, an ZMIC analytical model under the sympathetic interaction considering residual flux, closing angles, transformer types, and other factors is constructed to analyze the characteristics of the ZMIC. Subsequently, a protection countermeasure based on the third harmonic component of the ZMIC to prevent the zero-sequence protection malfunction under the sympathetic interaction is proposed. The countermeasure is simple in principle and only uses the information of its own substation. However, it can deal with various energization and complex failure situations even the situation that the transformer is energized to the minor internal fault effectively. Besides, it is less affected by transition resistance and CT saturation. The effectiveness of countermeasure has been verified by the digital simulations, dynamic physical simulation tests and field wave recording tests.

Numerical Simulation and Analysis of Water and Suspended Sediment Transport in Hangzhou Bay, China

Hangzhou Bay is a large, high-turbidity shallow bay located on the southern side of the Changjiang Estuary, China. The process and dynamic mechanisms of water and sediment transport in the bay are not yet clear. An improved three-dimensional sediment numerical model that combined various dynamic factors was established to simulate and analyze these mechanisms. The residual current cannot properly represent the net water and sediment transport, and the residual unit width water flux (RUWF) and residual unit width sediment flux (RUSF) were used to explain the water and sediment transport. The results of numerical simulations indicate that in summer, the surface RUWF from the Changjiang Estuary near Nanhui Cape flows westward along the coast, in which the major part flows southward to the Zhenhai area, and the small part flows further westward along the north coast and then turns to the south coast and eastward, forming the water transport pattern of north-landward and south-seaward, which is stronger in the spring tide than in the neap tide. The bottom RUWF near Zhenhai flows northward to Nanhui Cape in the neap tide, which is larger in the neap tide than in the spring tide. In the middle and western parts of the bay, the RUWF has the same pattern as the surface water transport and is stronger in the spring tide than in the neap tide. The pattern of RUSF is roughly similar to the water flux transport. During the spring tide, the water and sediment transport fluxes near Nanhui Cape are from the Changjiang Estuary into Hangzhou Bay, but from Hangzhou Bay into the Changjiang Estuary during the neap tide. In the winter, the distributions of RUWF, RUSF, and suspended sediment concentration (SSC) are similar to those in the summer. In addition, the distance of surface water transport westward along the north coast is shorter than that in the summer, the magnitude of the bottom RUWF is smaller than that in the summer due to the weaker salinity gradient, and the bottom RUSF near Nanhui Cape is weaker than that in the summer during the neap tide. The net transect water flux (NTWF) and the net transect sediment flux (NTSF) near Nanhui Cape are from the Changjiang Estuary into Hangzhou Bay during the spring tide; during the neap tide, the NTWF is still from the Changjiang Estuary into Hangzhou Bay, but the NTSF is from Hangzhou Bay into the Changjiang Estuary because the SSC is much higher in the bottom layer than in the surface layer. The dynamic reason for the temporal and spatial variation in RUWF and RUSF is that the barotropic pressure gradient force is larger than the baroclinic pressure gradient force during the spring tide and is the opposite during the neap tide.

Estimation of Depth Direction of Crack by measuring the Residual Magnetic Vector Flux Density around Grains

We suggests an algorithm to estimate the depth direction of fatigue cracks. This algorithm uses the distribution of residual magnetic vector flux density (RMVFD) on the specimen. Magnetic domains are the region with a magnetic moment in the same direction. A grain has several magnetic domains. Domain wall is the boundary of the magnetic domain. Magnetic energy stabilized when no external magnetic field applied. That is, the sum of the total magnetic moments is close to zero. It is because that the magnetic flux densities are canceling each other at both ends of the domain wall. The domain wall moves when an external magnetic field applied. As a result, the magnetic domain, which has the same direction with the external magnetic field, enlarged. This phenomenon is magnetization. The domain wall stops moving when it meets with factors that limit the domain wall movement (FLWM). Here FLWM are dislocations, defects, and crystal boundaries. The magnetic energy is unstable at the end of FLWM in the magnetic hysteresis phenomenon. Other end of FLWM has to have the opposite direction of RMVFD to stabilize the magnetic energy. Thus, there are opposite direction of RMVFD each other around crack or grain boundaries. Three dimensional RMVFD (3-RMVFD) can indicates crack existence and depth direction of crack. To verify this theorem, we prepared fatigue crack specimens with different depth direction. The three dimensional shapes of grains reconstructs at the crack. The RMVFD measured by scanning a 3-axis magnetic sensor. And the 3-RMVFD indicated in each grains around crack. The depth directions of crack and grains could estimated by using the 3-RMVFD.

Analysis of Analytical Magnetic Field and Flux Regulation Characteristics of Axial-Flux Permanent Magnet Memory Machine

Due to the high power density, short axial size, and wide permanent magnet (PM) flux linkage regulation range, an axial-flux PM memory machine (AFPMMM) with hybrid Halbach array is investigated in this article. To solve the problem of magnetic density variation of Halbach array composed of different types of PMs in asymmetric bilateral air-gap structure, the analytical method for calculating the air-gap flux density of AFPMMM is presented through mathematical analysis, which uses cylindrical coordinate system instead of Cartesian coordinate system and is solved by equivalent method, separated variable method, and boundary conditions. The magnetic field generated by the Halbach array is divided into three directions: radial, circumferential, and axial. The analytical model is compared with the finite element method (FEM) simulation results to verify its effectiveness. In addition, an approximate piecewise linear hysteresis model with parallelogram return line is established based on the analytical expression of magnetic field. By applying different pulse currents to change the residual flux density of PM, the flux regulation characteristics of the motor are studied, and it is found that the air-gap flux density of the motor can be smoothly adjusted by continuously changing the pulse current, which plays a positive role in solving the problem of online magnetic regulation of the motor.

Reconstructing the Three-Dimensional Structure of Loop Current Rings from Satellite Altimetry and In Situ Data Using the Gravest Empirical Modes Method

The three-dimensional structure of Gulf of Mexico’s warm-core rings, detaching from the Loop Current, is investigated using satellite altimetry and a large set of ARGO float profiles. Reconstruction of the Loop Current rings (LCRs) vertical structure from sea surface height observations is made possible by the use of the gravest empirical modes method (GEM). The GEMs are transfer functions that associate a value of temperature and salinity for each variable pair {dynamic height; pressure}, and are computed by estimating an empirical relationship between dynamic height and the vertical thermohaline structure of the ocean. Between 1993 and 2021, 40 LCRs were detected in the altimetry and their three-dimensional thermohaline structure was reconstructed, as well as a number of dynamically relevant variables (geostrophic and cyclogeostrophic velocity, relative vorticity, potential vorticity, available potential energy and kinetic energy density, etc.). The structure of a typical LCR was computed by fitting an analytical stream function to the LCRs dynamic height signature and reconstructing its vertical structure with the GEM. The total heat and salt contents and energy of each LCR were computed and their cumulative effect on the Gulf of Mexico’s heat, salt and energy balance is discussed. We show that LCRs have a dramatic impact on these balances and estimate that residual surface heat fluxes of −13 W m−2 are necessary to compensate their heat input, while the fresh water outflow of the Mississippi river approximately compensates for their salt excess input. An average energy dissipation of O [10−10–10−9] W kg−1 would be necessary to balance their energy input.

A Novel Analysis Method for Flatted Single-Layer Interior Permanent Magnet Machines Having Overhang Structure

This study describes a novel analysis method for interior permanent magnet (IPM) machines with an overhang, in which the rotor axial length exceeds that of the stator. Adopting an overhang structure facilitates the achievement of a high torque density per machine volume without increasing the stator size due to the additional magnetic flux of the rotor. However, the use of the three-dimensional (3-D) finite-element method (FEM) is inevitable, which requires substantial computation time and large computer memory to accommodate the overhang effect. Therefore, a new analysis method combined with a lumped magnetic equivalent circuit (MEC) is proposed to overcome the inefficient conventional approach. A new residual flux density can be derived by considering the magnetic flux paths in the overhang structure. Two-dimensional FEM combined with the residual accurately considers the IPM with overhang. The validity of the proposed concept is verified via 3-D FEM using several test models.

A Novel Methodology to Estimate the Nonlinear Magnetizing Characteristic of Single-Phase Transformers Using Minimum Information

This paper presents a novel methodology to estimate the saturation curve parameters of single-phase transformers, using minimum information from inrush and no-load tests. Only the value of the first current peak and the decay time are used from a unique inrush test, and only the third and fifth current harmonics from a unique no-load test. The proposed methodology is based on the existence of a signature for each transformer which can be easily obtained and characterize all possible inrush currents. This is the main contribution of the paper. Different transformers with different parameters have been tested in the laboratory. Experiments and simulations are carried out to validate the methodology. First, the respective no-load and inrush tests are made. Second, the parameters of each transformer are estimated. Third, the performance and accuracy of the proposed methodology are verified by a close agreement between the measured and the estimated saturation curves and between the simulated and the recorded inrush waveforms. Some remarkable advantages of the proposed methodology are: (a) considers the deep saturation, (b) avoids the need to know the residual flux (or to demagnetize the transformer) and the switching angle from the inrush test, and (c) it is computationally straightforward.

Toward on-sky adaptive optics control using reinforcement learning

Context. The direct imaging of potentially habitable exoplanets is one prime science case for the next generation of high contrast imaging instruments on ground-based, extremely large telescopes. To reach this demanding science goal, the instruments are equipped with eXtreme Adaptive Optics (XAO) systems which will control thousands of actuators at a framerate of kilohertz to several kilohertz. Most of the habitable exoplanets are located at small angular separations from their host stars, where the current control laws of XAO systems leave strong residuals. Aims. Current AO control strategies such as static matrix-based wavefront reconstruction and integrator control suffer from a temporal delay error and are sensitive to mis-registration, that is, to dynamic variations of the control system geometry. We aim to produce control methods that cope with these limitations, provide a significantly improved AO correction, and, therefore, reduce the residual flux in the coronagraphic point spread function (PSF). Methods. We extend previous work in reinforcement learning for AO. The improved method, called the Policy Optimization for Adaptive Optics (PO4AO), learns a dynamics model and optimizes a control neural network, called a policy. We introduce the method and study it through numerical simulations of XAO with Pyramid wavefront sensor (PWFS) for the 8-m and 40-m telescope aperture cases. We further implemented PO4AO and carried out experiments in a laboratory environment using Magellan Adaptive Optics eXtreme system (MagAO-X) at the Steward laboratory. Results. PO4AO provides the desired performance by improving the coronagraphic contrast in numerical simulations by factors of 3–5 within the control region of deformable mirror and PWFS, both in simulation and in the laboratory. The presented method is also quick to train, that is, on timescales of typically 5–10 s, and the inference time is sufficiently small (<ms) to be used in real-time control for XAO with currently available hardware even for extremely large telescopes.

Water Circulation and Transport Time Scales in the Beagle Channel, Southernmost Tip of South America

The Beagle Channel is a long and narrow interoceanic passage within the Tierra del Fuego archipelago in the southernmost tip of South America. A high-resolution 3D hydrodynamic model based on the finite elements method was applied to investigate the residual circulation, water fluxes and transport time scales inside this channel. Numerical solutions were analyzed at seasonal time scale and the model results compared with observed ocean data. The circulation pattern is characterized by a west-to-east residual flow with low intensity and low seasonal variability. The water fluxes through the channel were estimated to be, on average, around 12,700 m3/s, with inflow through its western entrance and eastwards outflow mainly through the Mackinlay Strait. The water residence times vary seasonally with basin averages between 36 and 43 days and maximum values between 53 and 95 days. The results provide an overview of the hydrodynamics and water residence times in the Beagle Channel, a unique ecosystem threatened by recent anthropogenic pressures and climate change.

The Low-Redshift Lyman Continuum Survey

Aims. Combining 66 ultraviolet (UV) spectra and ancillary data from the recent Low-Redshift Lyman Continuum Survey (LzLCS) and 23 LyC observations by earlier studies, we form a statistical sample of star-forming galaxies at z ∼ 0.2 − 0.4 with which we study the role of cold interstellar medium (ISM) gas in the leakage of ionizing radiation. We also aim to establish empirical relations between the H I neutral and low-ionization state (LIS) absorption lines with different galaxy properties. Methods. We first constrain the massive star content (stellar ages and metallicities) and UV attenuation by fitting the stellar continuum with a combination of simple stellar population models. The models, together with accurate LyC flux measurements, allow us to determine the absolute LyC photon escape fraction for each galaxy (fescabs). We then measure the equivalent widths and residual fluxes of multiple H I and LIS lines, and the geometrical covering fraction of the UV emission, adopting the picket-fence model. Results. The LyC escape fraction spans a wide range, with a median fescabs (0.16, 0.84 quantiles) of 0.04 (0.02, 0.20), and 50 out of the 89 galaxies detected in the LyC (1σ upper limits of fescabs ≲ 0.01 for non-detections, typically). The H I and LIS line equivalent widths scale with the UV luminosity and attenuation, and inversely with the residual flux of these lines. Additionally, Lyα equivalent widths scale with both the H I and LIS residual fluxes, but anti-correlate with the corresponding H I or LIS equivalent widths. The H I and LIS residual fluxes are correlated, indicating that the neutral gas is spatially traced by the low-ionization transitions. We find that the observed trends of the absorption lines and the UV attenuation are primarily driven by the geometric covering fraction of the gas. The observed nonuniform gas coverage also demonstrates that LyC photons escape through low-column-density channels in the ISM. The equivalent widths and residual fluxes of both the H I and LIS lines strongly correlate with fescabs: strong LyC leakers (highest fescabs) show weak absorption lines, low UV attenuation, and large Lyα equivalent widths. We provide several empirical calibrations to estimate fescabs from UV absorption lines. Finally, we show that simultaneous UV absorption line and dust attenuation measurements can, in general, predict the escape fraction of galaxies. We apply our method to available measurements of UV LIS lines of 15 star-forming galaxies at z ∼ 4 − 6 (plus 3 high-z galaxy composites), finding that these high-redshift, UV-bright galaxies (MUV ≲ −21) may have low escape fractions, fescabs ≲ 0.1. Conclusions. UV absorption lines trace the cold ISM gas of galaxies, which governs the physics of the LyC escape. We show that, with some assumptions, the absolute LyC escape can be statistically predicted using UV absorption lines, and the method can be applied to study galaxies across a wide redshift range, including in the epoch of cosmic reionization.

Air-Gap Permeance and Reluctance Network Models for Analyzing Vibrational Exciting Force of In-Wheel PMSM

There is recognized interest in in-wheel motors for vehicle traction. Studies have gradually focused the design of in-wheel motors on electro-mechanical vibration, subject to the demand of driving comfort. It is crucial to model, analyze, and minimize the air-gap exciting force, the dominant source of vibration. In order to qualitatively and quantitatively study the air-gap vibrational exciting force and evaluate its characteristic for an in-wheel outer-runner permanent magnet synchronous machine (PMSM), this research proposes an air-gap permeance model (APM) and a unique adaptive reluctance network model (ARNM). In the process of motor design, APM is a quick means of determining dominant radial force density (RFD) harmonics and minimizing specific components that may produce considerable vibration. Morphing surface-mounted magnets and nonuniform air-gap length are guided by design optimization which complicates the analysis. Yet, proposed ARNM can account for this geometry variation and handle deformed gap geometry by using modified equation-based local permeance and residual flux. The speed and accuracy of proposed model are verified through the comparison of flux density and force mapping data between the calculation by proposed analytical model and the simulation by finite element tools. A 3-kW prototype is fabricated and tested to explore the effectiveness of ARNM-based performance prediction.

A model of hard-magnetic soft curved beams at large deformation

<p indent="0mm">Magnetic-activated soft materials have shown their considerable advantages such as quick response, remote and reversible control, and programmable shape-shifting, making them promising in functional designs of bionic robots, bionic sensors, grippers, valves and metamaterials. Magnetoactive elastomers (MAEs) (also referred to as magnetic polymer composites (MPCs) or magnetorheological elastomers) are a kind of soft active composites that can respond to magnetic field excitation, which are generally composed of micrometer-scale magnetizable particles (e.g., NdFeB particles) embedded in a soft matrix (e.g., silica gel, hydrogel and shape memory polymer). The matrix acts as a continuum medium transmitting the internal force, while the magnetic particles have the interaction among themselves and with the external magnetic field. Compared with soft magnetic materials which are difficult to achieve robust programming, hard-magnetic materials hold residual magnetic flux density vector that does not change with the external magnetic field. After saturation of magnetization, the interaction with the external magnetic field produces micro torque, and programming the micro torque distribution generated by hard-magnetic particles can further form complex shapes. Owing to the intricate interplay between inherent electromagnetic coupling and geometric nonlinearity, it is still a challenge to model and predict the mechanical behaviors of hard-magnetic soft materials. Most of existing models of hard-magnetic elastomers are based on the assumption that the remanence direction is along the axis, which limits the diversification degree of deformation to some extent. In addition, most hard-magnetic beam models are based on Euler-Bernoulli hypothesis (normal remains normal) by neglecting shear deformations. When the beam becomes thick, the effect of shear deformation may turn out to be significant and cannot be ignored. Here, we develop a nonlinear curved beam model to predict large deformations of hard-magnetic soft elastica. The model follows Timoshenko’s first-order shear deformation theory, by accounting for axis elongation and the constitutive law of hard-magnetic elastomers. A set of ordinary differential governing equations containing seven basic unknowns are deduced theoretically. The model can thus describe shear deformation, axis elongation and curvature change of hard-magnetic soft beams upon large deformation. Combined with boundary conditions, the model can be efficiently solved by using shooting methods. In order to verify the accuracy of our hard-magnetic soft beam model, we compare it with the experiments, finite element simulations, and the Euler-Bernoulli hypothesis-based beam model in the literature, for different directions of applied magnetic field. The results verify and highlight the accuracy and universality of our hard-magnetic soft curved beam model which has higher accuracy and wider application range (applicable to thick beams, thin beams and curved beams) compared to the hard-magnetic thin beam model based on Euler-Bernoulli hypothesis (only considering bending deformations). Besides, we explore the bending and buckling deformations of hard-magnetic soft beams with different length-thickness ratios, under different applied magnetic fields. We reveal that the decrease of length-thickness ratio and of applied magnetic fields can enhance shear effects on deformations of hard-magnetic soft beams. Our model could be used not only to analyze geometrically nonlinear behaviors of hard-magnetic elastomers, but also to guide rational designs of ferromagnetic slender structures and soft continuum robots.

Evoking the snap-through instability in hard-magnetic soft materials: Rapid actuation and giant deformation

In this paper, we break into an appropriate strategy for achieving a rapid actuation and giant deformation in hard magnetoactive elastomers (MAEs). We devise a flat arch with a properly distributed residual magnetic flux field and realize the large deformation by harnessing the snap-through instability. With an ingenious design of the residual magnetic flux field within the arch that has a large slenderness ratio, the applied magnetic field for inducing the onset of instability can be relatively small. Even if the size of the flat arch is up to millimeter level, the applied magnetic field is as small as hundreds of oersted. We also develop a theoretical model for revealing the mechanism of the magnetic-driven instability in hard magnetoactive elastomers. The stress, induced by the coupling between the external magnetic field and the residual magnetic flux field, is transformed into a surface load. We formulate the total energy of the magneto-mechanical system and carry out the first and second variations to study the equilibrium states and their stability. To verify our theoretical predictions, we fabricate the corresponding MAE specimen and observe the tantalizing magneto-mechanical behaviors in the lab. Our theoretical predictions agree with the experimental observations in the case of flat arches of MAEs. This paper is desirable to open new ways of designing multifunctional MAE devices with rapid actuation and giant deformation.

Field‐circuit coupling numerical calculation method of transformer remanence

When the transformer is re-energised, the remanence in the core will cause inrush current, which will have adverse impacts on the power system. In the remanence distribution calculation, not only the hysteresis characteristics of the core, but also the characteristics of the external circuit need to be considered. In this paper, an indirect field-circuit coupling method for calculating transformer remanence distribution is presented. The residual flux density distribution at every point of the iron core, which has not been shown in previous literatures, can be obtained, and also the H-B trajectory of the iron core. In the field calculation, the pseudo-permeability method is modified in order to fit the field separation-based dynamic hysteresis model. The pseudo-permeability method and the initial value estimation method are used to speed up the iteration convergence. Furthermore, in the electric circuit topology used in the calculation, the switching process of the circuit breaker and the capacitance in the circuit are considered, and this has not been tried in the previous remanence calculation method. The remanence results are verified by comparison with the results in the literature. The remanence results can provide a basis for the impact analysis and phase control of the re-energisation.

Study on Two Residual Flux Suppression Strategies of Current Transformer During Automatic Reclosing

After power system short-circuit fault occurs, there is a large amount of residual magnetism in current transformer core, which will lead to wrong operation of connected relay protection and affect its reliability. Based on the direct current method, this paper puts forward two kinds of current transformer residual flux suppression strategies, which are constant voltage variable frequency (CVVF) and variable voltage constant frequency (VVCF), the magnetic flux of the core is gradually reduced by controlling the polarity of the output voltage of the switch module. The principle of residual flux suppression is introduced, and the method of parameter selection is given. The suppression effect of two residual flux suppression strategy is simulated and analyzed by experiment simulation. The results show that the two residual flux suppression strategies can demagnetize the current transformer core during automatic reclosing, but the constant voltage CVVF residual flux suppression strategy is simpler and more efficient.

Experimental Evidence of Intrinsic Current Generation by Turbulence in Stationary Tokamak Plasmas.

High-β_{θe} (a ratio of the electron thermal pressure to the poloidal magnetic pressure) steady-state long-pulse plasmas with steep central electron temperature gradient are achieved in the Experimental Advanced Superconducting Tokamak. An intrinsic current is observed to be modulated by turbulence driven by the electron temperature gradient. This turbulent current is generated in the countercurrent direction and can reach a maximum ratio of 25% of the bootstrap current.Gyrokinetic simulations and experimental observations indicate that the turbulence is the electron temperature gradient mode (ETG). The dominant mechanism for the turbulent current generation is due to the divergence of ETG-driven residual flux of current. Good agreement has been found between experiments and theory for the critical value of the electron temperature gradient triggering ETG and for the level of the turbulent current. The maximum values of turbulent current and electron temperature gradient lead to the destabilization of an m/n=1/1 kink mode, which by counteraction reduces the turbulence level (m and n are the poloidal and toroidal mode number, respectively). These observations suggest that the self-regulation system including turbulence, turbulent current, and kink mode is a contributing mechanism for sustaining the steady-state long-pulse high-β_{θe} regime.