Magnetic Field Signals Research Articles

Numerical simulation of pipeline crack detection probe with poly-magnetic structure

The detection and characterization of cracks is one of the key issues in oil and gas transmission pipeline inspection. The weak degree of spatial magnetic field distortion caused by the small size of the crack creates great difficulties for signal extraction. In this paper, we propose an ACM crack detection probe with poly-magnetic structure, and investigate the influence of the core, shield on the detection signal through numerical simulations. The results show that the crack detection probe with the core and shield can effectively improve the distorted magnetic field component in space acquired by the magnetic element, increasing the distorted magnetic field signals in the vertical and horizontal directions by a factor of 2.10 and 1.76 respectively. Verification that ACM probe with poly-magnetic structure can effectively increases the crack-induced magnetic field distortion signal and reduce the probability of misses.

A Novel Method to Achieve Precision and Reproducibility in Exposure Parameters for Low-Frequency Pulsed Magnetic Fields in Human Cell Cultures.

The effects of extremely low-frequency electromagnetic field (ELF-MF) exposure on living systems have been widely studied at the fundamental level and also claimed as beneficial for the treatment of diseases for over 50 years. However, the underlying mechanisms and cellular targets of ELF-MF exposure remain poorly understood and the field has been plagued with controversy stemming from an endemic lack of reproducibility of published findings. To address this problem, we here demonstrate a technically simple and reproducible EMF exposure protocol to achieve a standardized experimental approach which can be readily adopted in any lab. As an assay system, we chose a commercially available inflammatory model human cell line; its response to magnetic fields involves changes in gene expression which can be monitored by a simple colorimetric reporter gene assay. The cells were seeded and cultured in microplates and inserted into a custom-built, semi-automated incubation and exposure system which accurately controls the incubation (temperature, humidity, ) and magnetic-field exposure conditions. A specific alternating magnetic field (<1.0% spatial variance) including far-field reduction provided defined exposure conditions at the position of each well of the microplate. To avoid artifacts, all environmental and magnetic-field exposure parameters were logged in real time throughout the duration of the experiment. Under these extensively controlled conditions, the effect of the magnetic field on the cell cultures as assayed by the standardized operating procedure was highly reproducible between experiments. As we could fully define the characteristics (frequency, intensity, duration) of the pulsed magnetic field signals at the position of the sample well, we were, for the first time, able to accurately determine the effect of changing single ELF-MF parameters such as signal shape, frequency, intensity and duty cycle on the biological response. One signal in particular (10 Hz, duty cycle, rectangular, bipolar, T) provided a significant reduction in cytokine reporter gene expression by in our model cell culture line. In sum, the accuracy, environmental control and data-logging capacity of the semi-automated exposure system should greatly facilitate research into fundamental cellular response mechanisms and achieve the consistency necessary to bring ELF-MF/PEMF research results into the scientific mainstream.

A Symmetrical Quartz-Based Magnetoelectric Sensor for Pico-Tesla Magnetic Field Detection

The magnetic sensor should acquire a high detection ability over a wide low-frequency (LF) band of 1–100 Hz for biomagnetic measurements due to the large LF noise. This work presents a magnetic sensor with a modulation coil based on the tri-layer symmetrical Metglas/Quartz/Metglas laminate for LF magnetic fields detection. The Metglas/Quartz/Metglas laminate was fabricated using a rectangle quartz plate with twenty Metglas foils epoxy glued symmetrically. Additionally, the coil can be used to generate modulation voltage. The limit of detection (LOD) of the fabricated symmetrical magnetoelectric (ME) sensor has been measured and optimized without DC bias via frequency modulation technique. Experimental results demonstrate that the proposed ME sensor can detect a small magnetic field of 11 pT at 1 Hz. Moreover, the Metglas thickness and the modulation voltage also have been optimized and the detection ability of the fabricated sensor has been enhanced with a lower LOD value of 2.7 pT at 1 Hz. This paper provides a symmetrical magnetoelectric sensor using piezoelectric quartz material for LF pico-Tesla magnetic field signals detection. Additionally, the symmetrical sensor without bias can provide a cost-effective and high-performance approach for LF magnetic field detection.

Nondestructive Testing of Coal Mine Wire Ropes Based on Magnetic Sensors

Safety is the first priority in production. The situation is complex in the deep underground of coal mines, and safety accidents often occur. Wire rope is a kind of safety device. With the help of wire rope, the safety of miners can be guaranteed to a certain extent. It is a very important tool for mining production. However, the current detection of coal mine wire rope still relies on the data from the factory, and it is impossible to achieve nondestructive testing in use. This article aims to study the degree of wear of mining wire ropes to ensure the safety of miners as much as possible. According to the characteristics of the wire rope, any defect (rust, broken wire, broken wire, etc.) changes in the cross-sectional area of the wire rope will change the magnetic permeability of the wire rope. With the help of equipment, we can collect data on changes in the magnetic field (MF). Based on this experimental design, the steel wire rope is given an MF, and the magnetic sensor is used to monitor the MF signal and convert it into an electrical signal. According to the collected electrical signal analysis and judgment, the sensor model is constructed, the size and position of the wire rope cross-sectional change are deduced, and the defect of the wire rope is judged. The experimental results in this study show that the magnetic sensor is an effective measure to monitor the nondestructive degree of the wire rope, with a sensitivity of more than 80%.

Aerobic granulation and microbial community succession in sequencing batch reactors treating the low strength wastewater: The dual effects of weak magnetic field and exogenous signal molecule

The application of magneto-biological effects in wastewater treatment has been brought under the spotlight recently. This work explored the dual effects of magnetic field (MF) and exogenous N-hexanoyl-l-homoserine lactone (C6-HSL) on activated sludge granulation. Results showed that exposure to MF and C6-HSL obviously accelerated the aerobic granulation process and promoted the secretion of extracellular polymeric substances, especially polysaccharides, humic acid-like substances, aromatic proteins, and tryptophan-like substrates. Illumina MiSeq sequencing results indicated that the introduction of MF and C6-HSL can increase the diversity and richness of microbial community without antagonism, and the biological basis for rapid granulation process in this study was the enrichment of slow-growing bacteria Candidatus_Competibacter. Besides, the overgrowth of filamentous bacteria Thiothrix could be suppressed due to the presence of MF, improving the stabilities of aerobic granular sludge. This study provides a new understanding of the MF and C6-HSL effects on rapid aerobic granulation when treating the low-strength wastewater.

Development of high precision digital magnetometer

Aiming at the low measurement accuracy of magnetometer, a high stability constant current source circuit is developed to drive indium arsenide Hall sensor, designs a self stabilizing zero preamplifier to pick up the magnetic field signal, and uses a low-noise circuit structure to adaptively adjust the signal amplification to make the magnetic field signal reach the highest signal-to-noise ratio. After analog-to-digital conversion with high-linearity ADC, the least square method is used to correct the nonlinearity caused by the hall sensor, so as to improve the accuracy of the magnetometer in the whole range. Through verification and test, the accuracy of the magnetometer is better than 0.5% within the measuring range of 3T, which meets the requirements of high-precision magnetic field measurement in industrial production.

Modeling and experimental investigation of magnetic anomaly detection using advanced triaxial magnetoelectric sensors

Magnetoelectric (ME) sensors have been proven to have great performance on weak magnetic field detection with high sensitivity, low noise, broad bandwidth and low power consumption. In this work, a self-designed ME detection system consisting of a high-performance triaxial ME sensor was used for magnetic anomaly detection (MAD). As the core sensing element of the ME sensor, the laminated ME composites were made of Metglas laminates and Mn-doped PMN-PT single crystal fibers with in-plane series connection. The noise equivalent magnetic induction (NEB) of the ME sensors were below 6.28pT/Hz1/2 @ 1 Hz, and the limit detection of magnetic field is about 5 × 10−10 T, representing great performance to detect weak magnetic field. An experiment of detecting a real ship was conducted to test the performance of the triaxial ME detection system. To analyze the magnetic anomaly signal induced by the ship, a 3D finite element model (FEM) about the magnetic field distribution of the moving ship is developed. The estimated signals of the scalar total magnetic field and the motion parameters of the ship simulated by the proposed FEM match well with the experimental data, which proves the reliability of the model. The error analysis of the simulation was also discussed in detail. The experimental investigation reveals a promising application of ME sensor in MAD, while the proposed finite element model can be further modified to meet the analysis requirements on the detection of the magnetic anomaly induced by ferromagnetic targets with large dimension.

A high-resolution MEMS magnetoresistive sensor utilizing magnetic tunnel junction motion modulation driven by the piezoelectric resonator

High-sensitivity MEMS magnetoresistive (MR) sensors have attracted ever-increasing attention due to their ability to detect weak magnetic fields, but the resolution is severely limited by the 1/f noise. This paper reports a MEMS MR sensor that can effectively suppress the 1/f noise by modulating the magnetic field signal to the higher frequency region utilizing magnetic tunnel junction vertical motion modulation based on the MEMS piezoelectric cantilever resonator. The magnetic sensitivity can be increased to 2283.3%/mT with a high magnetic gain of 39.3 by integrating the structure-optimized fixed magnetic flux concentrators. The signal-to-noise ratio of the MEMS MR sensor can be improved by three orders of magnitude and the 160 pT/√Hz resolution can be reached. These results make the MEMS MR sensor based on the MTJ motion modulation a competitive candidate in the pico-Tesla magnetic detection.

A Temperature and Magnetic Field-Based Approach for Stator Inter-Turn Fault Detection

Effective fault detection techniques are needed to reduce the maintenance and downtime costs of induction motors. This article presents an approach for stator end-winding inter-turn short-circuit fault detection using a metal-coated fiber Bragg grating (FBG) sensor with 0.5-mm diameter and 10-mm length to monitor the temperature and magnetic field around the end winding. The sensing theory, design, manufacturing, and installation of the sensor are detailed in this article. The nickel coating on the surface of the sensor is formed by electroless plating and electroplating, which makes the sensor sensitive to both temperature and magnetic field. The feasibility of the presented approach has been supported by both simulation and experimental results. The temperature and magnetic field signals are decoupled by filtering, and the experimental data are analyzed in the time-frequency domain. The results show that the inter-turn short-circuit fault can be detected at an incipient stage with 5% shorted turns.

Geophysical surveying for the detection of ferrous-based objects: possibilities for depth estimative combining analytic signal and vertical integral of the anomalous magnetic field

The detection of buried clandestine objects challenges forensic and archeologic search group teams on varying terrains, and variable scales of research. Therefore, the study of controlled buried objects is useful for trainings in geophysical acquisition and processing. In this study, we applied ground survey data for testing the magnetic method at controlled geophysical sites for the location of ordinary objects and firearms. We used data filtering techniques in order to facilitate the location of magnetic targets. Also, we experienced the 3D inversion of analytic signal of the vertically integrated magnetic field (ASVI), for the location of targets in depth. As a result, the study determined the location of four magnetic targets, and a three-dimensional view was constructed from the estimated magnetic susceptibility. We concluded that modeling transformed magnetic data is an affordable technique for application in near-surface investigations. Also, this experiment exemplifies the relevance of magnetic methods for location of excavation sites on the basis of geophysical methods.

A Novel Crack Quantification Method for Ultra-High-Definition Magnetic Flux Leakage Detection in Pipeline Inspection

Cracks that may cause pipeline cracking and leakage become the main risk of in-service pipelines after conventional metal loss defects have been detected. Therefore, it is imperative to develop ultra-high-definition magnetic flux leakage (MFL) detection for cracks. Due to the larger spatial sampling interval of conventional MFL inspections than the crack defect width, sparse sampling will result in problems such as missed detection of crack defects or insufficient signal sampling of crack defect MFL signals. To address the problem, this paper presents a detection topology in which the magnetic field signal is integrated first and then sampled, and it can effectively sample the leakage magnetic field of cracks. Furthermore, a magnetic field spatial integration (MFSI) method is proposed based on the magnetic dipole model, which develops an analytical solution for the depth quantification of crack defects. Using the multi-MFL spatial integral values under different lift offs, iterative equations are constructed, and the numerical solution for the width quantification of crack defects is provided. The finite element simulation and physical experiment are constructed. And, the results show that the proposed MFSI method can realize the quantification of crack size. When the crack defect aspect ratio is greater than 4, the quantization error of the crack depth and width does not exceed 0.7 mm and 0.1 mm, respectively. The robustness of the MFSI method for crack quantification is also discussed and verified. Moreover, based on theoretical analysis and simulation data, this paper concludes that the distribution of cracks MFL signal is width-insensitive, which would cause that classic MFL opening profile recognition methods for metal loss defects are no longer applicable to crack defects. Therefore, the proposed MFSI method is useful and meaningful for crack defect quantification in ultra-high-definition MFL detection.

Alleviation of Residual Vibrations in Hard-Magnetic Soft Actuators Using a Command-Shaping Scheme.

Hard-magnetic soft materials belong to a class of the highly deformable magneto-active elastomer family of smart materials and provide a promising technology for flexible electronics, soft robots, and functional metamaterials. When hard-magnetic soft actuators are driven by a multiple-step input signal (Heaviside magnetic field signal), the residual oscillations exhibited by the actuator about equilibrium positions may limit their performance and accuracy in practical applications. This work aims at developing a command-shaping scheme for alleviating residual vibrations in a magnetically driven planar hard-magnetic soft actuator. The control scheme is based on the balance of magnetic and elastic forces at a critical point in an oscillation cycle. The equation governing the dynamics of the actuator is devised using the Euler–Lagrange equation. The constitutive behaviour of the hard-magnetic soft material is modeled using the Gent model of hyperelasticity, which accounts for the strain-stiffening effects. The dynamic response of the actuator under a step input signal is obtained by numerically solving the devised dynamic governing equation using MATLAB ODE solver. To demonstrate the applicability of the developed command-shaping scheme, a thorough investigation showing the effect of various parameters such as material damping, the sequence of desired equilibrium positions, and polymer chain extensibility on the performance of the proposed scheme is performed. The designed control scheme is found to be effective in controlling the motion of the hard-magnetic soft actuator at any desired equilibrium position. The present study can find its potential application in the design and development of an open-loop controller for hard-magnetic soft actuators.

An Approximate Analytical Model of Surface Cracks in AC Field Measurement Technique

An appropriate modeling technique is critical for the quick analysis of alternating current (ac) field measurements destined for qualitative or quantitative studies of surface defects in conductive materials. Traditional modeling techniques often use the finite-difference method to solve the governing Laplace equation in the crack region, which gives a closed-form solution in the Fourier domain for regions outside the crack. However, these models are complex and only useful for cracks with extremely narrow openings. This article proposes an approximate analytical model that is based on current shunting of parallel circuits and the Biot–Savart law. We assume that the current induced by a high-frequency current-carrying coil is evenly distributed within a very thin layer at the surface of a conductor. In the presence of a defect, the current flows only along the edges and the bottom of the defect. Under these assumptions, the model simplifies the induced current by treating it as due to many current sources of equal amplitude. The magnetic field above the defect can be mathematically described by the linear superposition of these current sources. The proposed model can thus be used to analyze cracks with wider openings. We compare the magnetic-field signals of flat-bottomed cracks of various sizes as obtained by the proposed model and the finite-element method and also explore cracks with complex bottom profiles. The results show that the proposed model produces accurate quantitative and qualitative results for a wider range of defects.

Performance optimization of harmonized flexible printed coils of axial magnetized magnetostrictive patch transducers for pipeline inspection

Currently, different types of magnetostrictive patch transducers (MPT) utilizing high magnetostriction patches, such as iron-cobalt alloys attached to the tested samples, have been proved to be effective electromagnetic acoustic transducers (EMAT). In 2019, an innovative guided wave-based MPT called the harmonized flexible printed coil (HFPC) sensor, consisting of a harmonized flexible printed coil sheet and a magnetized iron-cobalt patch, was proposed to replace conventional MPT. The HFPC sensor exhibits better performance than conventional MPT by generating a uniform magnetic field and triggering stronger signals. On the basis of previous research, this paper reported a newly optimized multilayer HFPC sensor, which considers coil inductance, capacitance, and other related parameters in a fixed-voltage AC power supply environment, which is rarely done by most researchers before. The optimized HFPC parameters were obtained from simulation studies and verified by the experimental investigation, where the performance was improved by 1.68 times compared to the old HFPC-based MPT.

Floquet Spin Amplification.

Detection of weak electromagnetic waves and hypothetical particles aided by quantum amplification is important for fundamental physics and applications. However, demonstrations of quantum amplification are still limited; in particular, the physics of quantum amplification is not fully explored in periodically driven (Floquet) systems, which are generally defined by time-periodic Hamiltonians and enable observation of many exotic quantum phenomena such as time crystals. Here we investigate the magnetic-field signal amplification by periodically driven ^{129}Xe spins and observe signal amplification at frequencies of transitions between Floquet spin states. This "Floquet amplification" allows us to simultaneously enhance and measure multiple magnetic fields with at least one order of magnitude improvement, offering the capability of femtotesla-level measurements. Our findings extend the physics of quantum amplification to Floquet spin systems and can be generalized to a wide variety of existing amplifiers, enabling a previously unexplored class of "Floquet spin amplifiers".

Worldwide Statistical Correlation of Eight Years of Swarm Satellite Data with M5.5+ Earthquakes: New Hints about the Preseismic Phenomena from Space

Nowadays, the possibility that medium-large earthquakes could produce some electromagnetic ionospheric disturbances during their preparatory phase is controversial in the scientific community. Some previous works using satellite data from DEMETER, Swarm and, recently, CSES provided several pieces of evidence supporting the existence of such precursory phenomena in terms of single case studies and statical analyses. In this work, we applied a Worldwide Statistical Correlation approach to M5.5+ shallow earthquakes using the first 8 years of Swarm (i.e., from November 2013 to November 2021) magnetic field and electron density signals in order to improve the significance of previous statistical studies and provide some new results on how earthquake features could influence ionospheric electromagnetic disturbances. We implemented new methodologies based on the hypothesis that the anticipation time of anomalies of larger earthquakes is usually longer than that of anomalies of smaller magnitude. We also considered the signal’s frequency to introduce a new identification criterion for the anomalies. We find that taking into account the frequency can improve the statistical significance (up to 25% for magnetic data and up to 100% for electron density). Furthermore, we noted that the frequency of the Swarm magnetic field signal of possible precursor anomalies seems to slightly increase as the earthquake is approaching. Finally, we checked a possible relationship between the frequency of the detected anomalies and earthquake features. The earthquake focal mechanism seems to have a low or null influence on the frequency of the detected anomalies, while the epicenter location appears to play an important role. In fact, land earthquakes are more likely to be preceded by slower (lower frequency) magnetic field signals, whereas sea seismic events show a higher probability of being preceded by faster (higher frequency) magnetic field signals.

Earth as a transducer for axion dark-matter detection

We demonstrate that ultralight axion dark matter with a coupling to photons induces an oscillating global terrestrial magnetic-field signal in the presence of the background geomagnetic field of the Earth. This signal is similar in structure to that of dark-photon dark matter that was recently pointed out and searched for in [Fedderke et al. Phys. Rev. D 104, 075023 (2021)] and [Fedderke et al. Phys. Rev. D 104, 095032 (2021)]. It has a global vectorial pattern fixed by the Earth's geomagnetic field, is temporally coherent on long timescales, and has a frequency set by the axion mass ${m}_{a}$. In this work, we both compute the detailed signal pattern and undertake a search for this signal in magnetometer network data maintained by the SuperMAG Collaboration. Our analysis identifies no strong evidence for an axion dark-matter signal in the axion mass range $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}18}\text{ }\text{ }\mathrm{eV}\ensuremath{\lesssim}{m}_{a}\ensuremath{\lesssim}7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}\text{ }\text{ }\mathrm{eV}$. Assuming the axion is all of the dark matter, we place constraints on the axion-photon coupling ${g}_{a\ensuremath{\gamma}}$ in the same mass range; at their strongest, for masses $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}\text{ }\text{ }\mathrm{eV}\ensuremath{\lesssim}{m}_{a}\ensuremath{\lesssim}4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}\text{ }\text{ }\mathrm{eV}$, these constraints are comparable to those obtained by the CAST helioscope.

Determining patterns in the generation of magnetic fields when using different arc welding techniques

This paper reports a study into the levels of magnetic fields induced by arc welding equipment in various ways in order to assess their impact on the body of welders. It is known that welders are exposed to a magnetic field of high intensity. Depending on the welding technique and the type of welding equipment, it may exceed the maximum permissible levels (MPL). Note that new Ukrainian sanitary standards for magnetic fields have been introduced, which regulate their levels depending on the frequency range. Therefore, it became necessary to carry out their hygienic assessment according to the new standards in order to devise appropriate methods for protecting welders. To this end, it was required to choose a new generation of devices to determine the intensity of magnetic fields induced by welding equipment. Based on the analysis of the constructed oscillograms and spectrograms of magnetic fields, it was found that semi-automatic welding with a metal electrode in carbon dioxide is characterized by an increased level of magnetic field in the frequency range of 50‒1000 Hz. With automatic arc welding under the flux, there are no excess of the maximum permissible levels of individual harmonics of the magnetic field but there is an excess of the total value of all harmonic components of the magnetic field. Manual arc welding with direct current involving a non-melting electrode in argon is characterized by a moderate level of magnetic field in workplace. During manual arc welding with coated electrodes, the exceeded level of the magnetic field is observed only on the electrode cable itself. It is shown that the spectral composition of the magnetic field signal is determined mainly by the welding technique itself, the peculiarities of arc combustion, and the nature of the transfer of electrode metal in the arc gap, as well as the initial parameters of the power supplies of the welding arc

On the characterization of tidal ocean-dynamo signals in coastal magnetic observatories

Periodic tidal ocean currents induce electric currents and, therefore, magnetic field signals that are observable using spaceborne and ground-based observation techniques. In theory, the signals can be used to monitor oceanic temperature and salinity variations. Tidal magnetic field amplitudes and phases have been extracted from magnetometer measurements in the past. However, due to uncertainties caused by a plentitude of influencing factors, the shape and temporal variation of these signals are only known to a limited extent. This study uses past extraction methods to characterize seasonal variations and long-term trends in the ten year magnetometer time series of three coastal island observatories. First, we assess data processing procedures used to prepare ground-based magnetometer observations for tidal ocean dynamo signal extraction to demonstrate that existing approaches, i.e., subtraction of core field models or first-order differencing, are unable to reliably remove low-frequency contributions. We hence propose low-frequency filtering using smoothing splines and demonstrate the advantages over the existing approaches. Second, we determine signal and side peak magnitudes of the M2 tide induced magnetic field signal by spectral analysis of the processed data. We find evidence for seasonal magnetic field signal variations of up to 25% from the annual mean. Third, to characterize the long-term behavior of tidal ocean dynamo signal amplitudes and phases, we apply different signal extraction techniques to identify tidal ocean-dynamo signal amplitudes and phases in sub-series of the ten-year time series with incrementally increasing lengths. The analyses support three main findings: (1) trends cause signal amplitude changes of up to approx 1~nT and phase changes are in the order of {mathcal {O}}(10^{circ }) within the observation period; (2) at least four years of data are needed to obtain reliable amplitude and phase values with the extraction methods used and (3) signal phases are a less dependent on the chosen extraction method than signal amplitudes.Graphical

Numerical simulation methods for motion-induced eddy current testing signals based on Ar formulation and edge finite elements

In this paper, numerical methods for simulation of the motion-induced eddy current testing (MIECT) signals were developed based on the reduced magnetic vector potential formulation (Ar method) and the edge finite element. According to the principle of the MIECT problem, numerical methods with reference frame referring to the transducer or the inspection object were developed respectively to solve the eddy current and pickup magnetic field signals. In addition, a quasi-static numerical scheme was also adopted to simulate the MIECT problem for inspecting crack along the moving direction. Based on the proposed numerical schemes and the conventional Ar code, numerical programs of the 3 methods were developed and validated for simulating MIECT signals. Through comparing the numerical results and efficiencies of the three simulation schemes each other, the validity of the proposed methods and the corresponding numerical codes were theoretically verified at first. Then, a MIECT experimental system and a prototype probe were developed and the validity of the proposed numerical methods were further proved experimentally. It is found that the moving probe-fixed object method is the most efficient scheme for MIECT signal simulation among the three proposed numerical methods. The numerical methods and codes developed in this paper provide numerical tools for design and optimization of the MIECT probes and testing system used in inspection of rails or wheels system etc, as well as the quantitative defect evaluation based on the MIECT signals through model based inverse analyses.