Induced Research Articles

Analysis and Design of Adjustable-Gap Double-Side Axial Flux Permanent Magnet Hysteresis Damper

In this paper, a novel adjustable gap double-side axial flux permanent magnet hysteresis damper (AGDSAPHD) is proposed, of which the torque can be adjusted by changing the air gap and the magnetic field angle between the upper and lower stators at the same time. To analyze and design, a modified vector Jiles-Atherton (JA) hysteresis model is used for simulating the magnetic flux distribution and the hysteresis torque of AGDSAPHD. The eddy currents in the AGDSAPHD are analyzed, which have a great influence on the output torque when the rotational speed is fast. A splitting method used in the rotor of the AGDSAPHD is proposed to reduce the effect of eddy currents. The heat distribution of the AGDSAPHD is calculated to determine its slip power and operating mode. A prototype is built and tested to verify the reliability of the analysis. The experiments prove that the modified vector JA model has high computational accuracy in calculating the hysteresis effects of the AGDSAPHD. A splitting method used in the rotor can greatly reduce the eddy current torque. AGDSAPHD has a greater torque adjustment range and better temperature stability than the traditional one.

On the potential of eddy current characterization of the ferritic content of recovered 316L powders after LaserPowder bed fusion fabrication

An original container was designed to measure the ferritic content of powder batches by the Eddy Current (EC) technique. As opposed to the standard X-Ray Diffraction (XRD) or Electronic BackScatter Diffraction (EBSD) methods, the EC measurements can be implemented on powder batches of significant sizes, say a hundred grams or so. Using a methodology based on the multiple recycling of an initially ferrite-free virgin powder, it was shown that the EC signals are sensitive to the ferritic content of the recovered powder. On the other hand, in the frequency range scanned by the sensor, the EC signals are virtually independent on the oxygen concentration within the tested powder.

A multisensor approach coupled with multivariate statistics and geostatistics for assessing the status of land degradation: The case of soils contaminated in a former outdoor shooting range

Soil contamination in outdoor shooting ranges (OSRs) is a major threat for human health, particularly when, after the end of activities, the land is used for recreational areas or agricultural production. The status of land degradation of an OSR in southern Italy was assessed using a multisensor approach. It was based on: i) proximal sensors, including electromagnetic induction (EMI) for measuring soil electrical conductivity (ECa) and magnetic susceptibility (MSa), γ-ray spectrometry for K, eU and eTh analyses and ultrasonic penetrometry detecting cone index (CI) data representative of soil's strength, ii) field surveys on soil thickness (ST), and iii) laboratory analyses of potentially-toxic-elements (PTEs) by portable X-ray fluorescence spectrometry and polycyclic aromatic hydrocarbons (PAHs) by gas-chromatography. Spatial variability of measurements was modelled and mapped using geostatistical methods. The most densely measured covariate (i.e., the ECa of the topsoil) was used within kriging with external drift to improve the PTEs predictions. The PTEs maps were complemented by maps of spatial uncertainty. A robust multivariate principal component analysis (rPCA) was applied to proximal sensor and laboratory data and allowed to identify associations of PAHs, lead, CI with the topsoil ECa along the first component (PC1), highlighting the correlation between land anthropogenic effects and EMI measures; while the association between the ST (estimating the depth of underground travertine hard-layers) and the bottom soil ECa and MSa along the second component (PC2) evidenced the influence of soil stratigraphy on the EMI measures. This study demonstrates that the simultaneous use of different proximal sensors associated with laboratory analysis can allow to assess and model the spatial variability of the land degradation status of an OSR, including soil compaction, organic and inorganic contamination. The correlation between EMI data with the PTEs content highlights the potential of this technique in the field of soil contamination.

FreeGSNKE: A Python-based dynamic free-boundary toroidal plasma equilibrium solver

We present a Python-based numerical solver for the two-dimensional dynamic plasma equilibrium problem. We model the time evolution of toroidally symmetric free-boundary tokamak plasma equilibria in the presence of the non-linear magnetohydrodynamic coupling with both currents in the “active” poloidal field coils, with assigned applied voltages, and eddy currents in the tokamak passive structures. FreeGSNKE (FreeGS Newton–Krylov Evolutive) builds and expands on the framework provided by the Python package FreeGS (Free boundary Grad–Shafranov). FreeGS solves the static free-boundary Grad–Shafranov (GS) problem, discretized in space using finite differences, by means of Picard iterations. FreeGSNKE introduces: (i) a solver for the static free-boundary GS problem based on the Newton–Krylov (NK) method, with improved stability and convergence properties; (ii) a solver for the linearized dynamic plasma equilibrium problem; and (iii) a solver for the non-linear dynamic problem, based on the NK method. We propose a novel “staggered” solution strategy for the non-linear problem, in which we make use of a set of equivalent formulations of the non-linear dynamic problem we derive. The alternation of NK solution steps in the currents and in the plasma flux lends this strategy an increased resilience to co-linearity and stagnation problems, resulting in favorable convergence properties. FreeGSNKE can be used for any user-defined tokamak geometry and coil configuration. FreeGSNKE's flexibility and ease of use make it a suitably robust control-oriented simulator of plasma magnetic equilibria. FreeGSNKE is entirely written in Python and easily interfaced with Python libraries, which facilitates machine learning based approaches to plasma control.

Study on the as-cast microstructure and mechanical properties of 35CrMo steel based on electric field control

Herein, the effect of current on the solidification microstructure and properties of 35CrMo structural steel has been studied. The effect of an electric field on the solidification structure of an ingot was investigated by immersing two parallel electrodes into the free surface of molten steel. Using the interaction between the current and melt as well as the Lorentz force generated by its own induced magnetic field, the whole region of the melt was covered with an eddy current. The numerical simulation of the ingot solidification process has been carried out and its influence on the inner flow field during the ingot solidification control process discussed. The results showed that an applied electric field caused turbulence inside the ingot, which drove the molten alloys to rotate and stir, refined the solidification structure, reduced the solidification defects, such as shrinkage cavity and segregation, and increased from 549.9 MPa at the top edge of the ingot and 411.4 MPa at the middle edge to 560.2 and 510.2 MPa, respectively. In addition, the electric field made the hardness and strength of each part of the ingot more uniform and improved the quality of its rigidity for the steel production process.

Applications of geophysical methods in agriculture and their potential in Vietnam

Geophysical methods are very popular in Vietnam and have been applied for several decades in deep-earth investigations such as geological mapping, mineral resource searching, and especially oil and gas exploration. In the world, they have proven to be great tools in agriculture as well for soil characterization and monitoring thanks to their notable advantages including rapid data acquisition, large data coverage, high data density, non-destructive and inexpensive survey implementation. However, in Vietnam, the applications of geophysical methods in agriculture have received little attention probably due to the lack of suitable equipment and data processing techniques. This article gives an overview of popular geophysical methods being applied in agriculture in several countries to characterize and monitor soil properties such as moisture, salinity, density, texture, structure, porosity, etc. The main uses of each method are summarized, and relevant publications are given for reading recommendations with the aim of suggesting similar applications in Vietnam. Accordingly, Ground Penetrating Radar (GPR) and Electromagnetic Induction (EMI) are the most versatile with minimum field crew for data acquisition. They should be prioritized to try in Vietnamese agriculture. Since EMI equipment is not currently available in Vietnam, only a GPR test survey was implemented in the Agricultural Academy experimental field by the authors of Hanoi University of Mining and Geology. The preliminary result shows that the biggest challenge is to find reliable techniques to accurately infer soil properties from measured geophysical parameters, which have no explicit relationship with soil properties. Noise suppression is another problem that needs to be addressed to ensure sufficient data quality.

THE ELECTROMAGNETIC FIELD AT THE FLAT SURFACE OF CONDUCTING BODY CAUSED BY BASIC SOURCES OF A NON-UNIFORM EXTERNAL FIELD

The purpose of the work is to obtain the expressions for the intensities of the electric and magnetic components of electromagnetic field at the action of two types of the basic sources of external field located near conducting half-space, where the eddy currents flow. The basic sources are the rectilinear current of infinite length, parallel to the interface between the dielectric and conducting media, and the magnetic moment, oriented along normal to the interface. The solution for electromagnetic field at surface between the media is applied. It is valid for strong skin effect in the form of expansion into an asymptotic series. Each term of the series is proportional to the derivative of corresponding order of external field components. This allows taking into account the external field non-uniformity. It is shown that the mathematical models with ideal skin effect have limited application. Then it is necessary to use more correct mathematical models for non-uniform field and a bounded depth of skin layer. The obtained expressions for electromagnetic field at the action of the basic sources of non-uniform external field allow us to use the principle of superposition to determine the field distributions in electromagnetic systems with more complex three-dimensional configuration. References 25, figures 5.

Intelligent Method for Corrosion Detection and Quantification in Aircraft Lap Joints Using Pulsed Eddy Current

Nondestructive evaluation using pulsed eddy current (PEC) has remarkable capabilities for the detection and characterization of hidden corrosion in multilayer structures. Previous works proposed maximum peak value, time-to-peak, and time-to-zero crossing of PEC signals for hidden corrosion detection. In practice, there are two important noise sources: probe liftoff and interlayer gap. These noise sources disable the aforementioned components in defect detection and classification. This paper delivers a new intelligent method for detection and classification of corrosion defects in two-layer structures at the presence of gap and liftoff. Application independent component analysis and principal component analysis to PEC signals for features extraction and Fisher’s linear discriminant method for classification provide an automatic material loss characterization in multilayer structures. Comparing the results with conventional methods based on PEC signals shows the importance of post-processing methods in the detection and quantification of corrosion.

A topical reappreasal on use of repetitive Transcranial Magnetic Stimulation in elderly patients with postischemic stroke statuses - a systematic literature review

Abstract: Introduction: Stroke is a cerebrovascular disease with an impressive potential of disabil-ity, (multi)morbidity, and mortality among elderly patients. After stroke, a series of seque-lae represents a dynamic challenge for rehabilitation, especially for improving motor, cognitive and depressive disorders (1,2). Repetitive Transcranial Magnetic Stimulation (rTMS) is a non-invasive, painless, neuromodulations and neurostimulation method, which uses electromagnetic induction to administer repeated trains of pulses, with thera-peutic, diagnostic and research purposes (3–5). Method: We performed a systematic literature review of the related literature using a widely international accepted method - Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA)(6), by searching, filtering, and selecting profile documen-tary material. Combinations/syntaxes of keywords were searched in the following interna-tional databases: Elsevier(7), PubMed(8), PMC(9), PEDro(10), in ISI indexed journals by Web of Knowledge/Science(11) during 1/01/2019-31/12/2021. Besides the 9 articles selected to enhance our related knowledge base we have also used some works freely identified in the literature. Results and discussions: 9 articles satisfied all the previous filtering criteria/ PRISMA steps and were selected for qualitative and detailed analysis. The benefits of rTMS, aiming to bring further insight into the responsiveness of motor deficit, depression, and cognitive impairment of the treatment, and through the favorable dynamic progress of the scores of the quantification scales used: HAMD-17/ HDRS, Hamilton Depression Scale; MMSE, Mini-Mental State Examination; MoCA, Montreal Cognitive Assesment; SCWT, Stroop Color-Word Interference Test; WAIS, Wechsler Adult Intelligence Scale; NIHSS, National Institutes of Health Stroke Scale; Barthel Index Score; ADL, Activities of Daily Living; mRS, modified Rankin Scale; FIM, Functional Independence Measures. Conclusions: Through this systematic review, we wish to present the perspective of the successful use of rTMS among elderly patients. We also intend for this work to be the start-ing point in the development of a doctoral study, which will include post-stroke sequelae, such as motor deficits, depressive and cognitive disorders, and through which we will strengthen scientific confidence in the tolerability and effectiveness of this type of stimula-tion for this segment of age.

Scientific and Technical Basis for the Development of an Induction Heating Unit for Milk Pasteurization

Introduction. Induction heating is a preferred heating technique for industrial, medical and consumer systems, because it has a number of advantages over traditional heat transfer methods. The advantages include energy efficiency, heating rate, safety of operation, cleanliness of the process, low metal consumption, simple design, and precise control of the temperature of the heated raw materials. An induction heating unit is especially important for farms involved in processing of milk and producing milk-based products. Aim of the Study. The study is aimed at developing a prototype unit for long-term pasteurization of milk using a container heated by induction currents and at selecting optimal operating conditions for the developed prototype unit. Materials and Methods.There was used 3D modeling in the KOMPAS-3D computeraided design system to develop the main components of a milk pasteurization prototype unit with induction heating. The container for raw materials, stirrer and lid are made of stainless steel AISI 304 and AISI 430. The inductor is a frame made of polymer material with a litz wire arranged in a spiral manner. The body of the prototype unit is made of aluminum composite material. The developing and debugging of the electronic circuit of the prototype unit power part was carried out with the use of the design program Proteus 7.10. The microcontroller Mega 2560 was used to make the power part of the electromagnetic induction generation unit. The controlled temperature was monitored by using the waterproof temperature sensor DS18B20. A thermal imager was used to visualize the propagation of the thermal field over the surface of the container walls. Results. The structure diagram of the developed prototype unit with induction heating for long-term pasteurization of milk is presented. The article gives grounds to the use of the necessary elements and actuators in the unit for pasteurization of milk in a container heated by induction currents. There are presented a diagram of the developed power part for the prototype unit and the results of testing it when heating containers made of various materials. An algorithm has been developed to control the operation and PID regulation of the milk pasteurization in an experimental unit with the use the Raspberry Pi microcomputer. The graphs of transient processes when changing the coefficients of PID temperature control are presented. Discussion and Conclusion. When testing the induction heating principle on stainless steels of different compositions, it has been concluded that for the efficiency of heating the container, there is required a ferromagnetic steel pad welded on top of the main container made of food-grade stainless steel. The developed system of inductors made it possible to create a prototype unit with two heating zones depending on the volume of processed raw materials that is important for small farms engaged in processing milk and producing milk-based products.

Numerical investigation into turbulent drag reduction via the application of pufferfish spine-inspired cone microstructures in Suboff models

The effective reduction of seawater drag is pivotal in enhancing the speed and minimizing the energy consumption of submarines, which has significant implications in the fields of energy and defense. Surface bionics has emerged as one of the leading techniques for drag reduction. Current research primarily focuses on replicating the groove-like structures observed on shark skins and the flexible properties of dolphin skins. However, the application of cone microstructures on submarine surfaces remains relatively underexplored. In this study, a novel arrangement of bionic drag-reducing microstructures is employed to modify the turbulence structure surrounding the submarine by incorporating bionic cone microstructures at both the front and rear ends of the submarine. Numerical simulations were performed using the SST k-ω turbulence model to evaluate the impact of these frontal microstructures on drag reduction under varying Reynolds numbers, spacings, and positions, as well as the tail microstructures’ effect at different Reynolds numbers, heights, and circumferential separation angles. The findings reveal that positioning microstructures at the submarine’s head increases the drag reduction rate proportionally with the distance from the apex, displaying an inverse relationship between spacing and drag reduction rate. Conversely, an increase in cone separation angle at the tail leads to a decrease in the overall drag reduction rate. At the same time, an inverse proportionality is observed between cone height and drag reduction rate. This suggests that cone microstructures play a dual role: mitigating friction drag greatly and augmenting pressure drag, thereby achieving overall drag reduction. Moreover, these cone microstructures disrupt eddy currents within the boundary layer surrounding the submarine, restraining the propagation of turbulent momentum transfer in both the head and tail regions. This research not only pioneers a novel drag reduction strategy for underwater vehicles but also sparks new avenues for their optimized surface design.

A lift-off measurement and compensation method based on a comprehensive EMAT-PEC probe

In the field of industrial testing, lift-off fluctuations of the probe are inevitable, leading to unstable signals and inconsistent detection results, especially in electromagnetic acoustic transducer (EMAT). Besides, EMAT has a low energy utilization, since the induced pulsed eddy current (PEC) is not fully utilized during the transduction process. To address these issues, this paper proposes a novel composite detection method which is able to measure the lift-off based on PEC and compensate for the lift-off effect on EMAT using a designed comprehensive EMAT-PEC probe. A finite element (FE) model of the EMAT consisting of a permanent magnet and a type of butterfly coil is established, and the spatial distribution of the PEC density induced by the butterfly coil is analyzed. Based on this, comparison of the effectiveness among different EMAT-PEC probe configurations for lift-off detection is implemented, and an optimal EMAT-PEC probe with a compact structure is designed. This probe is capable of obtaining both EMAT signal and PEC signal synchronously through a single excitation, ensuring the accuracy and efficiency of the compensation process. The blind test is then performed to simulate the random lift-off fluctuation, and the experimental results demonstrate that the relative errors of the measured lift-off and the compensated peak amplitudes of EMAT signals are all less than 7%, verifying the effectiveness of the method. For industrial applications, based on the developed method, a probe array with different lift-off combinations is designed to simplify the calibration process, and an application in probe inclination detection is introduced, proving the method has good application foreground.

Mapping saltwater intrusion via Electromagnetic Induction (EMI) for planning a Managed Aquifer Recharge (MAR) facility in Maltese Island

In coastal areas, saltwater intrusion causes a depletion of the resource by reducing potable and irrigation freshwater supplies and causing severe deterioration of groundwater quality. This trend is observed in Pwales Valley, in the North part of Malta where the management of water resources plays a crucial role for the environmental sustainability of the area, given the importance of intensive agricultural activity along this valley. In order to tackle such phenomenon, actions or adaptation measures against climate change are strongly required. For example, Managed Aquifer Recharge (MAR) is an increasingly important water management strategy to maintain, enhance and secure stressed groundwater systems and to protect and improve water quality. To accurately plan a Managed Aquifer Recharge scheme, it is crucial to define a hydrogeological model of the studied area, with the use of traditional hydrogeological measurements and innovative unconventional techniques. In recent years, Electromagnetic Induction measurements, based on induction of em fields, have been increasingly used for investigating the saltwater intrusion dynamics due to their high sensitivity to the salinity. In the study area of Pwales Valley, a Managed Aquifer Recharge scheme is being planned and, for this aim, a hydrogeological model has been developed through an Electromagnetic Induction survey. More than 20,000 apparent electrical conductivity (ECa) data were collected to generate a quasi 3D high-resolution model of electrical conductivity of the Pwales Valley. The results highlighted the spatial extension of the tongue-shape salt water intrusion from east to west along the valley, as well as some geological-hydrogeological peculiarities such as the thickness of the salt wedge and the irregular top surface of the bottom impermeable layer, otherwise undetectable with other direct techniques at the field scale resolution. The approach was confirmed to be a useful tool for an effective hydrogeological characterisation, essential for planning adaptation measures to a changing climate, such as the implementation of a Managed Aquifer Recharge scheme.

Characteristics of Electric Field Induced by Oscillating Metal Underwater Vehicle

To analyze the induced electric field characteristics generated by the rotation and shaking of underwater metal vehicles, a mathematical model of the induced electric field generated by the underwater metal vehicles was derived using Faraday’s electromagnetic induction law. A mathematical model of the induced electric field on the electrode pairs of metal vehicles shaking in different coordinate system planes was established through in-depth analysis. Based on this, a three-component output model of the induced electric field output by the three-axis sensor was obtained when the measurement system was shaking at all three angles. At a constant speed, the induced electric field interference output by the measurement system is a static signal. The value of the static electric field is proportional to the vehicle’s speed and the value of the geomagnetic field, and the value of each component is related to the direction of movement and the value of the geomagnetic field component. The simulation results show that when the navigation body is moving at a constant speed, the induced electric field is a static electric field with a magnitude of mV/m. In a stable state, the induced electric field noise generated by changes in pitch, roll, and heading sway is at the nV/m level and does not have a significant impact on detection. The correctness of the theoretical model has been verified through experiments on offshore speedboat platforms, and it is feasible to use metal navigation bodies for ship electric field detection.

Stochastic Optimization of an Electric Bus Dynamic Wireless Charging System

The Electric Bus Dynamic Wireless Charging (EB-DWC) system is a bus charging system that enables electric buses to receive power wirelessly from ground-based electromagnetic induction devices. In this system, how to optimally configure the charging infrastructures while considering the unpredictable nature of bus movement is a great challenge. This paper presents an optimization problem for an EB-DWC system in urban settings, addressing stochastic elements inherent in the vehicle speed, initial charging state, and dwell time at bus stops. We formulate a stochastic planning problem for the EB-DWC system by integrating these uncertainties and apply Monte Carlo sampling techniques to effectively solve this problem. The proposed method can improve the system’s robustness effectively.

Development and fusion of NDT classifiers for defect detection on underwater structures

Vessel hull inspection is a complex and labor-intensive task, motivating the utilization of data fusion from complementary nondestructive testing (NDT) techniques to boost reliability and reduce detection uncertainties. In this study, an underwater robot equipped with three NDT systems – monocular RGB camera, eddy current (ECT), and ultrasound (UT) – is employed to assess a 12.7 mm thick ASTM-A36 carbon steel plate with artificially induced defects – coating loss, crack, pitting, and generalized corrosion. A classifier is developed for each NDT system for defect classification. Mask R-CNN is used for the camera data, achieving a mean average precision of 67.7% across three defect classes. A multilayer perceptron is used to classify the ECT data into six defect types and the non-defective class, attaining an accuracy of 98.8% on the test set. For UT data, a rule-based classifier based on A-scan-derived features distinguishes four defect classes. Subsequent to spatial synchronization, these classifier outputs are fused at the decision level, where redundancies between the camera and ECT classifiers are eliminated. Their outcomes are concatenated with the UT classifier results, culminating in a comprehensive detection map capable of representing eleven distinct defect classes. The classifiers and fusion are evaluated on a novel plate with unseen artificial defects. The camera and UT classifiers excel in detecting all classes for which they were specifically trained. In contrast, ECT exhibits a more limited capability, detecting only 21% of the specified defect classes. The findings underscore the potential of NDT data fusion to enhance inspection reliability by minimizing redundancies and extending the detection range.

Electromagnetic and Thermal analysis of an Intra-layer no-insulation coil during Quench

The intra-layer no-insulation (LNI) layer-wound REBCO coil has been widely studied for its excellent high thermal stability in the research of nuclear magnetic resonance superconducting magnets. Due to the complex structure of the LNI layer-wound coil and the numerous factors that affect thermal stability, its quench characteristics are not clear. In this paper, a numerical multiphysics coupling model is established to study the transient electromagnetic and thermal behaviors of the LNI layer-wound coil during quench. The results indicate that temperature follows the diffusion law, while the currents evolve through electrical connection and electromagnetic induction. Due to the high contact resistance, the azimuthal current and axial current vary almost in units of the entire coil layer. The direction of the radial current upstream of the turn where a quench occurs is positive due to the bypassing behavior, while the radial current direction is negative downstream. The insulation material inside the LNI layer-wound coil strongly affects the quench propagation. When its thickness decreases, the equivalent radial thermal conductivity increases, thereby increasing the quench propagation velocity and current peak, and shortening the duration of the current response during quench.

Errors in average strength estimates of sedimentary rock masses 
 in South Yakutia based on geometric induction sounding data

The probabilistic model developed to describe the engineering and geological conditions for the operation of buildings and infrastructure in the city of Neryungri has been verified. The model is a power-function equation which correlates, by regression relationships, laboratory-determined compressive strength of saturated frozen sandstone samples with attenuation of the high-frequency harmonic field of a vertical magnetic dipole in warm permafrost composed of sandstone. The attenuation values were obtained by geometric electromagnetic induction sounding at a frequency of 1.125 MHz. The model verification was conducted at a fixed frequency on a section of the Amur-Yakutsk Railway located at a significant distance from Neryungri. The railway here is underlain by low-temperature dolomite masses. The statistical analysis indicates that the relative errors of the dolomite saturated strength estimates from the geometric EM induction data with a 73.0% probability do not exceed 20%. With this level of accuracy close to that of laboratory tests according to GOST 25100–2020, it is reasonable to suggest that the probabilistic model can be used region-wide in southern Yakutia to predict saturated strength of foundation materials composed of sandstone and dolomite. It can provide an effective solution for market-based construction and mining industries, as increasing anthropogenic and climatic impacts are anticipated to cause thawing and saturation of sedimentary rock masses.

Research on the heating effect evaluation of the electromagnetic induction heating system at low temperature based on the electrochemical-thermal coupling model

The extremely fast electromagnetic induction heating system (EIHS) was recently introduced to improve the poor charge and discharge performance of lithium-ion batteries (LiBs) at low temperature. In this work, aimed to investigate the heating effect of EIHS, the accurate electrochemical-thermal coupling model, validated against the charging capacity calibration with various C-rates and HPPC tests at different environments, was developed in depth to reflect the electrochemical and heat transfer behaviors of the LiB exposed to external cool air during the electromagnetic induction heating process. When the copper coil was subjected to a sinusoidal alternating current (SAC) excitation at 10 A, 3 kHz, the LiB can be warmed up to 293.15 K from 243.15 K within 742 s with an even heat generation inside the LiB. The impact of the SAC parameters on the needed heating time was illustrated with time maps, a series of contours suggested that the heating velocity increase with the increase of both the amplitude and frequency. As compared with the low-temperature state, the internal resistance had a more than 3-fold decrease, which can improve the discharging voltage platform and terminal voltage output, thus increasing the pulse power and usable capacity. Neither noticeable capacity retention difference before and after the heating cycles nor obvious capacity loss discrepancy between the normal charge-discharge and heating cycle tests was found at the end of the 200 heating cycles, so the EIHS can achieve a good tradeoff among temperature rising effect, working behaviors and LiB cycle lifespan, which had a considerable potential to enhance the applicability of EVs (electric vehicles) in frigid weather. Moreover, a better heat transfer condition, higher material thermal conductivity and lower specific heat capacity play an important positive role on the improvement of temperature rising performance.

Formulation of energy loss due to magnetostriction to design ultraefficient soft magnets

The mechanism of energy loss due to magnetostriction in soft magnetic materials was analytically formulated, and our experiments validated this formulation. The viscosity of magnetic materials causes the resistive force acting on magnetic domain walls through strain due to magnetostriction, and magnetic energy is eventually dissipated by friction even without eddy currents. This energy loss mechanism explains the frequency dependence of the excess loss observed in the experiments, and the excess loss is dominated by the contribution of magnetostriction when the magnetostriction constant exceeds approximately 20 ppm. The random anisotropy model was extended by considering the effect of local magnetostriction as a correction to the magnetocrystalline anisotropy. The effect of magnetostriction was considerably suppressed by the exchange-averaging effect. The estimated effective random magnetoelastic anisotropy for nanocrystalline α-Fe reached as low as 18.6 J/m3, but this static effect could not explain the high excess loss at high frequencies observed in the experiments. The results of this research could provide new design criteria for high-performance soft magnetic materials based on low magnetostriction to reduce the excess loss.