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1/ $f$ noise is one of the main noise sources of magnetoresistance (MR) field sensors, which can cause intrinsic detection limit at low frequency. To suppress this noise, a novel magnetic flux vertical motion modulation (MFVMM) design using micro-electromechanical system flux concentrator (FC) and actuator is proposed in this paper, which can mitigate the 1/ $f$ noise by shifting the measurement frequency to kilohertz range. The proposed MFVMM has high efficiency and simple structure. The magnetic FC and the modulation film of MFVMM were analyzed with a numerical simulation. The simulation results show that the modulation efficiency of MFVMM exceeds 21%. A preliminary prototype sensor based on the multilayered giant MR AA002 and MFVMM was fabricated, and its modulation efficiency achieves 18.8% at a frequency of 7.01 kHz, which exceeds the efficiency of most existing sensors with the other modulation schemes. In addition, the magnetostatic detection ability is improved to 0.44 nT/ $\surd $ Hz. [ABSTRACT FROM AUTHOR]

The accurate measurement of a geomagnetic field is a key technology in geomagnetic navigation. Many magnetic interferential fields on navigation vehicles, such as ferromagnetic parts and electric equipments, will seriously disturb the magnetometer, and thus should be compensated. This paper develops a new magnetic interferential field compensation method using three-axial magnetometer measurements. The method relies on a formulation derived from the difference of the measured geomagnetic magnitude and its true value. The goal is to evaluate the magnetic interferential field parameters first and then compensate the measurements with them. The trust-region method is adopted to evaluate the parameters in the formulation. A simulation is conducted to test the validity of the method. An experiment is designed and implemented on an underwater vehicle. Both simulation and experimental results indicate that vehicle magnetic interferential field can be well compensated with this method. [ABSTRACT FROM PUBLISHER]

• Presents a fatigue assessment method for metal components based on residual stress. • Proposes an evaluation method based on fusion between data-driven and physics. • SDE is used to make the model closer to the fatigue relaxation process. The change of residual stress is complex in the fatigue cycle. The method of evaluating the fatigue state through physical models couldn't express the possibility of residual stress evolution. The data-driven model doesn't conform to the physical evolution law in detail and the most model need large-scale data. In this paper, a probabilistic model based on physical model and Gaussian Process Flow is proposed to describe the fatigue life degradation curve of alloy components in practical production. It could get different evolution paths instead of statistical parameters by Gaussian Process Flow. Different evolution paths are calibrated by Kalman filter, and the model is optimized combined with the physical model. Through a fatigue test for nickel alloy, the proposed model could better describe the evolution relationship between fatigue stress and fatigue cycle under small samples. [ABSTRACT FROM AUTHOR]

The superconductor/magnetoresistance (MR) mixed magnetic sensor, which is composed of a superconducting magnetic flux transformation amplifier (SMFTA) and a MR sensitive element, has extremely great development potential in weak magnetic field detection because of its excellent sensitivity, simple structure and small size. However, it still lacks an effective method to study the spatial distribution of the magnetic field produced by SMFTA. Here, a finite element simulation method was proposed to study the magnetic field amplification effect of the SMFTA. Several factors affecting the magnetic field amplification were studied via this simulation method. Furthermore, mixed magnetic sensors with three typical sizes were successfully fabricated, and the experimentally measured magnifications of the three sensors were basically consistent with the simulation values, demonstrating the reliability of this simulation method. Our works are expected to pave a meaningful way for the SMFTA design and promote the development of superconductor/MR mixed magnetic sensors. [Display omitted] • A simulation method was proposed to study superconducting magnetic flux amplifier. • The spatial distributions of amplified magnetic field can be obtained. • Several key influencing factors were investigated using this method. • The reliability of simulation method was demonstrated experimentally. [ABSTRACT FROM AUTHOR]

Abstract: With the growing interest to use composite materials and honeycomb sandwich panels in industrial fields, much attention is devoted to the development of non-destructive testing (NDT) techniques for the detection and evaluation of defects. In this work, scanning pulsed eddy current (PEC) was investigated and two features, representing the magnetic field intensity and conductivity, were used to characterise the different types of defects in carbon fibre reinforced plastics (CFRP) laminates and honeycomb sandwich panels. The experimental results show that the low energy impact from 4J to 12J, conductive and non-conductive insert defects can be effectively detected and evaluated using the proposed methods. The effectiveness was verified and the advantages of scanning PEC were addressed through comparative studies with flash thermography and shearography. [Copyright &y& Elsevier]

Abstract: With the growing interest to use engineering composite structures, much attention is devoted to the development of non-destructive testing (NDT) techniques for impact evaluation. Eddy current pulsed thermography (ECPT) is an emerging NDT technique, which is firstly investigated for crack evaluation in carbon fiber reinforced plastic (CFRP) in 2011 and the preliminary results have shown the significant potential. However, the research is limited by the experimental conditions. In this work, the detection mechanism for carbon fiber structure and impact are analyzed through theoretic analysis and validated by experimental studies under reflection and transmission modes. Laminates impacted with different energies from 4J to 12J are characterised. The qualitative and quantitative conclusions for impact behavior understanding are outlined, which is helpful to develop the reliable instruments for quality control and in-service inspection of CFRP. [Copyright &y& Elsevier]

Abstract: Magnetic distortions such as eddy-current field and low frequency magnetic field have not been considered in vector compensation methods. A new compensation method is proposed to suppress these magnetic distortions and improve compensation performance, in which the magnetic distortions related to measurement vectors and time are considered. The experimental system mainly consists of a three-axis fluxgate magnetometer (DM-050), an underwater vehicle and a proton magnetometer, in which the scalar value of magnetic field is obtained with the proton magnetometer and considered to be the true value. Comparing with traditional compensation methods, experimental results show that the magnetic distortions can be further reduced by two times. After compensation, error intensity and RMS error are reduced from 11684.013nT and 7794.604nT to 16.219nT and 5.907nT respectively. It suggests an effective way to improve the compensation performance of magnetic distortions. [Copyright &y& Elsevier]

Highlights: [•] Three measurement strategies are designed using nonmagnetic rotation equipment. [•] The influence of calibration strategies are compared and analyzed quantitatively. [•] The generality of calibration parameters with different strategies are tested. [•] Several kinds of calibration algorithms are compared. [•] The accuracy of a MAG3300 magnetometer is improved. [ABSTRACT FROM AUTHOR]

Abstract: The accuracy of three-axis magnetometers is influenced by different scale and bias of each axis and nonorthogonality between axes. One limitation of traditional iteration methods is that initial parameters influence the calibration, thus leading to the local optimal or wrong results. In this paper, a new method is proposed to calibrate three-axis magnetometers. To employ this method, a nonmagnetic rotation platform, a proton magnetometer, a DM-050 three-axis magnetometer and the differential evolution (DE) algorithm are used. The performance of this calibration method is analyzed with simulation and experiment. In simulation, the calibration results of DE, unscented Kalman filter (UKF), recursive least squares (RLS) and genetic algorithm (GA) are compared. RMS error using DE is least, which is reduced from 81.233nT to 1.567nT. Experimental results show that comparing with UKF, RLS and GA, the DE algorithm has not only the least calibration error but also the best robustness. After calibration, RMS error is reduced from 68.914nT to 2.919nT. In addition, the DE algorithm is not sensitive to initial parameters, which is an important advantage compared with traditional iteration algorithms. The proposed algorithm can avoid the troublesome procedure to select suitable initial parameters, thus it can improve the calibration performance of three-axis magnetometers. [Copyright &y& Elsevier]

Abstract: Eddy current, especially pulsed eddy current (PEC), is known as an effective tool to detect defects in aircraft structures. Current PEC defect classification methods require highly trained personnel and the results are usually influenced by human subjectivity. Therefore, automated defect classification is desirable in a PEC instrument. In this work, five eddy current based methods are integrated into an instrument using a universal model and modular structure. Then, a Support Vector Machine (SVM) is used to build the classifier model and predict the type of defect. Principal component analysis (PCA) and independent component analysis (ICA) are investigated for feature extraction and compared for classification results using SVM. Two-layer Al–Mn alloy specimens with four kinds of defects are used for classification. The experimental results show that the proposed methods have great potential for in-situ defect inspection of multi-layer aircraft structures. [Copyright &y& Elsevier]

Abstract: Pulsed eddy current (PEC) thermography has been successfully applied to detect cracks in metal alloy and carbon fibre reinforced plastic (CFRP) in previous works. In these applications, an inductor and infrared camera are on the same side of components, named reflection mode. In this work, the transmission mode, where the inductor and infrared camera are on opposite sides of component is investigated for defect characterisation through the analytical analysis and experimental studies. The studies show that the detection mechanisms for impact and delamination in CFRP are totally different. Carbon structure can be observed on the early stage of heating phase and impact leading to decreasing conductivity can be also detected in heating phase. However, delamination can be characterised using late stage of cooling phase. Combing the detection mechanisms, principal components analysis and independent components analysis, image reconstruction method is used to improve the sensitivity. [Copyright &y& Elsevier]

Abstract: Magnetic tunnel junctions (MTJs) have larger magnetoresistance ratio and higher magnetic sensitivity than other magnetoresistive structures, whereas their 1/f noise is also larger. To reduce the 1/f noise and improve the low frequency detection capability of MTJ sensors, some magnetic flux modulation schemes based on MEMS flux concentrators have been put forward, and several prototypes with gap-changed modulation (GCM) were fabricated by Army Research Laboratory (ARL). Presently, the problem of low magnetic modulation efficiency in GCM is still an obstacle for MTJ sensors with a resolution of pico-Tesla. In this paper, a novel magnetic flux modulation called vertical motion modulation (VMM) is proposed. In VMM, a modulation film driven by a MEMS actuator vibrates vertically above the air gap of the flux concentrator and the MTJs in the air gap detect an AC magnetic field with a DC bias. Theoretically the modulation efficiency of VMM can exceed 30% when the air gap varies from 30μm to 70μm. A preliminary prototype sensor with VMM was fabricated and its modulation efficiency achieves 17.4%. It is expected that the modulation efficiency of MTJ magnetic sensors with VMM can surpass 30% through modifying the sizes and improving the magnetic permeability of modulation films. [Copyright &y& Elsevier]

The sensitivity of Tunnel Magnetoresistance (TMR) sensors is characterized by significant temperature drift and poor sensitivity drift repeatability, which severely impairs measurement accuracy. Conventional temperature compensation techniques are often hindered by low compensation precision, inadequate real-time performance, and an inability to effectively address the issue of poor repeatability in temperature drift characteristics. To overcome these challenges, this paper introduces a novel method for suppressing temperature drift in TMR sensors. In this method, an alternating reference magnetic field is applied to TMR sensors, and the output amplitude at the frequency of the reference magnetic field is calculated to compensate the sensitivity temperature drift in real time. Temperature characteristic tests were conducted in a non-magnetic temperature test chamber, and the results revealed that the proposed method significantly reduced the TMR sensitivity drift coefficient from 985.39 ppm/°C to 59.08 ppm/°C. Additionally, the repeatability of sensitivity temperature characteristic curves was enhanced, with a reduction in root mean square error from 0.84 to 0.21. This approach effectively mitigates temperature-induced sensitivity drift without necessitating the use of a temperature sensor, and has the advantages of real-time performance and repeatability, providing a new approach for the high-precision temperature drift suppression of TMR.

Thermal barrier coating (TBC) of turbine blades can prevent aeroengine damage resulting from high temperature. TBC exhibits a multilayer complex structure of ceramic and bonding layers. The ceramic layer is dielectric, whereas the bonding layer is conductive. Disabling either layer can endanger aircraft safety. Changes in TBC parameters are indicative of failure. This study proposed a neural-network-based method to inverse the three key parameters of TBC simultaneously based on electromagnetic/capacitive dual-module sensor. Thus, this method can be used for monitoring the status of aeroengines. The experimental results revealed that the inversion error of thickness and permittivity of the ceramic layer and the conductivity of the bonding layer is less than 2%. Therefore, the proposed method can satisfy application requirements.

Background: This study assessed operative experiences with common pediatric retroperitoneal tumors invading major blood vessels., Methods: Forty-seven pediatric patients with retroperitoneal tumors were enrolled. They included 22 neuroblastomas, 6 gangliocytomas and 19 Wilms' tumors, and underwent primary surgical resection after vascular skeletonization and manipulations of involved vessels., Results: In the above tumors, the one-stage gross total resection rates of, respectively, 95.45%, 100% and 100% were obtained. There was only one complication, namely post-operational early acute renal failure that recovered with dialysis. There were no deaths., Conclusions: Vascular skeletonization and other vessel manipulations prior to surgery improve the gross total resection rates of pediatric retroperitoneal tumors.