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Keywords = extremely weak magnetic field

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14 pages, 3968 KiB  
Article
Investigating the Coherence Between Motor Cortex During Rhythmic Finger Tapping Using OPM-MEG
by Hao Lu, Yong Li, Yang Gao, Ying Liu and Xiaolin Ning
Photonics 2025, 12(8), 766; https://doi.org/10.3390/photonics12080766 - 29 Jul 2025
Viewed by 138
Abstract
Optically pumped magnetometer OPM-MEG has the potential to replace the traditional low-temperature superconducting quantum interference device SQUID-MEG. Coherence analysis can be used to evaluate the functional connectivity and reflect the information transfer process between brain regions. In this paper, a finger tapping movement [...] Read more.
Optically pumped magnetometer OPM-MEG has the potential to replace the traditional low-temperature superconducting quantum interference device SQUID-MEG. Coherence analysis can be used to evaluate the functional connectivity and reflect the information transfer process between brain regions. In this paper, a finger tapping movement paradigm based on auditory cues was used to measure the functional signals of the brain using OPM-MEG, and the coherence between the primary motor cortex (M1) and the primary motor area (PM) was calculated and analyzed. The results demonstrated that the coherence of the three frequency bands of Alpha (8–13 Hz), Beta (13–30 Hz), and low Gamma (30–45 Hz) and the selected reference signal showed roughly the same position, the coherence strength and coherence range decreased from Alpha to low Gamma, and the coherence coefficient changed with time. It was inferred that the change in coherence indicated different neural patterns in the contralateral motor cortex, and these neural patterns also changed with time, thus reflecting the changes in the connection between different functional areas in the time-frequency domain. In summary, OPM-MEG has the ability to measure brain coherence during finger movements and can characterize connectivity between brain regions. Full article
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28 pages, 21323 KiB  
Article
Modified Grey Wolf Optimizer and Application in Parameter Optimization of PI Controller
by Long Sheng, Sen Wu and Zongyu Lv
Appl. Sci. 2025, 15(8), 4530; https://doi.org/10.3390/app15084530 - 19 Apr 2025
Viewed by 591
Abstract
The Grey Wolf Optimizer (GWO) is a well-known metaheuristic algorithm that currently has an extremely wide range of applications. However, with the increasing demand for accuracy, its shortcomings of low exploratory and population diversity are increasingly exposed. A modified Grey Wolf Optimizer (M-GWO) [...] Read more.
The Grey Wolf Optimizer (GWO) is a well-known metaheuristic algorithm that currently has an extremely wide range of applications. However, with the increasing demand for accuracy, its shortcomings of low exploratory and population diversity are increasingly exposed. A modified Grey Wolf Optimizer (M-GWO) is proposed to tackle these weaknesses of the GWO. The M-GWO introduces mutation operators and different location-update strategies, achieving a balance between exploration and development. The experiment validated the performance of the M-GWO using the CEC2017 benchmark function and compared the results with five other advanced metaheuristic algorithms: the Improved Grey Wolf Optimizer (IGWO), GWO, Whale Optimization Algorithm (WOA), Dung Beetle Optimizer (DBO), and Harris Hawks Optimization (HHO). The performance results indicate that the M-GWO has a better performance than competitor algorithms on all 29 functions in dimensions 30 and 50, except for function 26 in dimension 30 and function 28 in dimension 50. Compared with competitor algorithms, the proposed M-GWO is the most effective algorithm, with an overall effectiveness of 96.5%. In addition, in order to show the value of the M-GWO in the practical engineering field, the M-GWO is used to optimize the PI controller parameters of the current loop of the permanent magnet synchronous motor (PMSM) system. By designing a PI controller parameter optimization scheme based on the M-GWO, the fluctuation of the q-axis current and d-axis current of the motor is reduced. The designed scheme reduces the q-axis fluctuation to around −2~1 A and the d-axis current fluctuation to around −2~2 A. By comparing the current-tracking errors of the q-axis and d-axis under different algorithms, the validity of the optimized parameters of the M-GWO is proved. Full article
(This article belongs to the Section Computing and Artificial Intelligence)
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8 pages, 3660 KiB  
Communication
Role of Minor Ta Substitution on Thermal Behavior and Soft Magnetic Properties of Co-Fe-Mo-Si-B Metallic Glass Ribbon
by Peipei Shen, Yanan Gao, Shuyan Zhang, Hua Chen, Pengfei Wang, Yangzhi Xue, Hongbo Zhou, Danyue Ma and Jixi Lu
Materials 2025, 18(8), 1828; https://doi.org/10.3390/ma18081828 - 16 Apr 2025
Viewed by 442
Abstract
Cobalt-based metallic glasses have sparked intensive attention because of their extraordinary properties. In this work, a series of Co66Fe4Mo2-xTaxSi16B12 (x = 0, 0.5, 1.0, 1.5, 2.0) metallic glass ribbons were [...] Read more.
Cobalt-based metallic glasses have sparked intensive attention because of their extraordinary properties. In this work, a series of Co66Fe4Mo2-xTaxSi16B12 (x = 0, 0.5, 1.0, 1.5, 2.0) metallic glass ribbons were systematically designed to investigate the influence of the minor Ta substitution for Mo on the thermal behavior and magnetic performance. The results reveal that the width of the supercooled liquid region initially increases with Ta content, reaching 98 K at x = 1.0, and subsequently decreases with further Ta addition. It indicates that the Co66Fe4Mo1.0Ta1.0Si16B12 alloy has the optimal glass-forming ability. Moreover, the crystallization onset temperature and crystallization peak temperature of all as-quenched ribbons were improved with the Ta content x increasing to 2.0, which is due to the higher melting temperature of the element Ta (3290 K). In addition, these ribbons exhibit outstanding soft magnetic properties, including ultralow coercivity (Hc < 1.1 A/m) and moderate saturation magnetization, which indicates that these ribbons are suitable for magnetic shielding. These results offer valuable insights into the design of soft magnetic metallic glass. Full article
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22 pages, 5535 KiB  
Article
Computational Modeling of Cardiac Electrophysiology with Human Realistic Heart–Torso Model
by Chen Yang, Yidi Cao, Peilun Li, Yanfei Yang and Min Xiang
Bioengineering 2025, 12(4), 392; https://doi.org/10.3390/bioengineering12040392 - 6 Apr 2025
Viewed by 746
Abstract
The electrocardiogram (ECG) has long been considered the non-invasive gold standard in diagnosing heart diseases. However, its connection with the cardiac molecular biology remains somewhat unclear. Therefore, modeling the electrophysiological behavior of the heart provides an important theoretical complement to clinically observable data. [...] Read more.
The electrocardiogram (ECG) has long been considered the non-invasive gold standard in diagnosing heart diseases. However, its connection with the cardiac molecular biology remains somewhat unclear. Therefore, modeling the electrophysiological behavior of the heart provides an important theoretical complement to clinically observable data. This study employed an electrophysiological model, integrating a bidomain model with the Fitzhugh–Nagumo (FHN) model, to compute an ECG and body surface potential maps (BSPMs). Parameters from previous studies were simulated individually for the cardiac domain. A specific set of parameters was selected based on comparisons of the morphology of the 12-lead ECG. The effect of the heart position relative to the torso on the 12-lead ECG was analyzed using a simplified whole-heart model to approximate the realistic heart position within the torso. Significant waveform changes were observed in leads VIII and aVL, as compared to other leads. This study employed a realistic heart–torso model, in contrast to earlier studies. External stimuli were incorporated into the original electrophysiological model to account for the electrical isolation between the atria and ventricles. The morphology of the simulated 12-lead ECG closely matched that of clinically observed data. Full article
(This article belongs to the Section Biosignal Processing)
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17 pages, 8025 KiB  
Article
Improving the Sensitivity of a Dark-Resonance Atomic Magnetometer
by Hao Zhai, Wei Li and Guangxiang Jin
Sensors 2025, 25(4), 1229; https://doi.org/10.3390/s25041229 - 18 Feb 2025
Viewed by 688
Abstract
The combination of unmanned aerial vehicles and atomic magnetometers can be used for detection applications such as mineral resource exploration, environmental protection, and earthquake monitoring, as well as the detection of sunken ships and unexploded ordnance. A dark-resonance atomic magnetometer offers the significant [...] Read more.
The combination of unmanned aerial vehicles and atomic magnetometers can be used for detection applications such as mineral resource exploration, environmental protection, and earthquake monitoring, as well as the detection of sunken ships and unexploded ordnance. A dark-resonance atomic magnetometer offers the significant advantages of a fully optical probe and omnidirectional measurement with no dead zones, making it an ideal choice for airborne applications on unmanned aerial vehicles. Enhancing the sensitivity of such atomic magnetometers is an essential task. In this study, we sought to enhance the sensitivity of a dark-state resonance atomic magnetometer. Initially, through theoretical analysis, we compared the excitation effects of coherent population trapping (CPT) resonance on the D1 and D2 transitions of 133Cs thermal vapor. The results indicate that excitation via the D1 line yields an increase in resonance contrast and a reduction in linewidth when compared with excitation through the D2 line, aligning with theoretical predictions. Subsequently, considering the impact of various quantum system parameters on sensitivity, as well as their interdependent characteristics, two experimental setups were developed for empirical investigation. One setup focused on parameter optimization experiments, where we compared the linewidth and contrast of CPT resonances excited by both D1 and D2 transitions; this led to an optimization of atomic cell size, buffer gas pressure, and operating temperature, resulting in an ideal parameter range. The second setup was employed to validate these optimized parameters using a coupled dark-state atom magnetometer experiment, achieving approximately a 10-fold improvement in sensitivity. Full article
(This article belongs to the Section Physical Sensors)
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18 pages, 2611 KiB  
Article
TSF-MDD: A Deep Learning Approach for Electroencephalography-Based Diagnosis of Major Depressive Disorder with Temporal–Spatial–Frequency Feature Fusion
by Wei Gan, Ruochen Zhao, Yujie Ma and Xiaolin Ning
Bioengineering 2025, 12(2), 95; https://doi.org/10.3390/bioengineering12020095 - 21 Jan 2025
Cited by 1 | Viewed by 1779
Abstract
Major depressive disorder (MDD) is a prevalent mental illness characterized by persistent sadness, loss of interest in activities, and significant functional impairment. It poses severe risks to individuals’ physical and psychological well-being. The development of automated diagnostic systems for MDD is essential to [...] Read more.
Major depressive disorder (MDD) is a prevalent mental illness characterized by persistent sadness, loss of interest in activities, and significant functional impairment. It poses severe risks to individuals’ physical and psychological well-being. The development of automated diagnostic systems for MDD is essential to improve diagnostic accuracy and efficiency. Electroencephalography (EEG) has been extensively utilized in MDD diagnostic research. However, studies employing deep learning methods still face several challenges, such as difficulty in extracting effective information from EEG signals and risks of data leakage due to experimental designs. These issues result in limited generalization capabilities when models are tested on unseen individuals, thereby restricting their practical application. In this study, we propose a novel deep learning approach, termed TSF-MDD, which integrates temporal, spatial, and frequency-domain information. TSF-MDD first applies a data reconstruction scheme to obtain a four-dimensional temporal–spatial–frequency representation of EEG signals. These data are then processed by a model based on 3D-CNN and CapsNet, enabling comprehensive feature extraction across domains. Finally, a subject-independent data partitioning strategy is employed during training and testing to eliminate data leakage. The proposed approach achieves an accuracy of 92.1%, precision of 90.0%, recall of 94.9%, and F1-score of 92.4%, respectively, on the Mumtaz2016 public dataset. The results demonstrate that TSF-MDD exhibits excellent generalization performance. Full article
(This article belongs to the Section Biosignal Processing)
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11 pages, 1123 KiB  
Article
Simulation Research on Low-Frequency Magnetic Noise in Fe-Based Nanocrystalline Magnetic Shields
by Shuai Kang, Wenfeng Fan, Jixi Lu and Wei Quan
Materials 2025, 18(2), 330; https://doi.org/10.3390/ma18020330 - 13 Jan 2025
Viewed by 791
Abstract
Depending on high permeability, high Curie temperature, and low eddy current loss noise, nanocrystalline alloys, as the innermost layer, exhibit great potential in the construction of cylindrical magnetic shielding systems with a high shielding coefficient and low magnetic noise. This study compares a [...] Read more.
Depending on high permeability, high Curie temperature, and low eddy current loss noise, nanocrystalline alloys, as the innermost layer, exhibit great potential in the construction of cylindrical magnetic shielding systems with a high shielding coefficient and low magnetic noise. This study compares a magnetic noise of 1 Hz, simulated by the finite element method (FEM), of a cylindrical nanocrystalline magnetic shield with different structural parameters based on the measured initial permeability of commercial Fe-based nanocrystalline (1K107). The simulated results demonstrate that the magnetic noise is irrelevant to the pump and probe hole diameter. The magnetic noise of a nanocrystalline cylinder with a fixed length gradually increases with the rise in aspect ratio. The radial and axial magnetic noise of a nanocrystalline cylinder with a fixed diameter can reach optimal values when the aspect ratio is 1.3 and 1.4, respectively. The layer thickness of a nanocrystalline cylinder is negatively correlated to magnetic noise. Additionally, by comparing the 1 Hz magnetic noise of a cylindrical nanocrystalline magnetic shield with varying initial permeability, it can be concluded that an increase in loss factor results in an increase in magnetic noise. These results are useful for the design of a high-performance passive magnetic shield with low magnetic noise. Full article
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17 pages, 4943 KiB  
Article
Cost-Reference Particle Filter-Based Method for Constructing Effective Brain Networks: Application in Optically Pumped Magnetometer Magnetoencephalography
by Yuyu Ma, Xiaoyu Liang, Huanqi Wu, Hao Lu, Yong Li, Changzeng Liu, Yang Gao, Min Xiang, Dexin Yu and Xiaolin Ning
Bioengineering 2024, 11(12), 1258; https://doi.org/10.3390/bioengineering11121258 - 12 Dec 2024
Viewed by 916
Abstract
Optically pumped magnetometer magnetoencephalography (OPM-MEG) represents a novel method for recording neural signals in the brain, offering the potential to measure critical neuroimaging characteristics such as effective brain networks. Effective brain networks describe the causal relationships and information flow between brain regions. In [...] Read more.
Optically pumped magnetometer magnetoencephalography (OPM-MEG) represents a novel method for recording neural signals in the brain, offering the potential to measure critical neuroimaging characteristics such as effective brain networks. Effective brain networks describe the causal relationships and information flow between brain regions. In constructing effective brain networks using Granger causality, the noise in the multivariate autoregressive model (MVAR) is typically assumed to follow a Gaussian distribution. However, in experimental measurements, the statistical characteristics of noise are difficult to ascertain. In this paper, a Granger causality method based on a cost-reference particle filter (CRPF) is proposed for constructing effective brain networks under unknown noise conditions. Simulation results show that the average estimation errors of the MVAR model coefficients using the CRPF method are reduced by 53.4% and 82.4% compared to the Kalman filter (KF) and maximum correntropy filter (MCF) under Gaussian noise, respectively. The CRPF method reduces the average estimation errors by 88.1% and 85.8% compared to the MCF under alpha-stable distribution noise and the KF method under pink noise conditions, respectively. In an experiment, the CRPF method recoversthe latent characteristics of effective connectivity of benchmark somatosensory stimulation data in rats, human finger movement, and auditory oddball paradigms measured using OPM-MEG, which is in excellent agreement with known physiology. The simulation and experimental results demonstrate the effectiveness of the proposed algorithm and OPM-MEG for measuring effective brain networks. Full article
(This article belongs to the Section Biosignal Processing)
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39 pages, 8550 KiB  
Review
Enhancement of Magnetic Shielding Based on Low-Noise Materials, Magnetization Control, and Active Compensation: A Review
by Yijin Liu, Jianzhi Yang, Fuzhi Cao, Xu Zhang and Shiqiang Zheng
Materials 2024, 17(22), 5469; https://doi.org/10.3390/ma17225469 - 8 Nov 2024
Cited by 7 | Viewed by 3926
Abstract
Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic [...] Read more.
Magnetic-shielding technologies play a crucial role in the field of ultra-sensitive physical measurement, medical imaging, quantum sensing, etc. With the increasing demand for the accuracy of magnetic measurement, the performance requirements of magnetic-shielding devices are also higher, such as the extremely weak magnetic field, gradient, and low-frequency noise. However, the conventional method to improve the shielding performance by adding layers of materials is restricted by complex construction and inherent materials noise. This paper provides a comprehensive review about the enhancement of magnetic shielding in three aspects, including low-noise materials, magnetization control, and active compensation. The generation theorem and theoretical calculation of materials magnetic noise is summarized first, focusing on the development of spinel ferrites, amorphous, and nanocrystalline. Next, the principles and applications of two magnetization control methods, degaussing and magnetic shaking, are introduced. In the review of the active magnetic compensation system, the forward and inverse design methods of coil and the calculation method of the coupling effect under the ferromagnetic boundary of magnetic shield are explained in detail, and their applications, especially in magnetocardiography (MCG) and magnetoencephalogram (MEG), are also mainly described. In conclusion, the unresolved challenges of different enhancement methods in materials preparation, optimization of practical implementation, and future applications are proposed, which provide comprehensive and instructive references for corresponding research. Full article
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38 pages, 7399 KiB  
Review
Preprocessing and Denoising Techniques for Electrocardiography and Magnetocardiography: A Review
by Yifan Jia, Hongyu Pei, Jiaqi Liang, Yuheng Zhou, Yanfei Yang, Yangyang Cui and Min Xiang
Bioengineering 2024, 11(11), 1109; https://doi.org/10.3390/bioengineering11111109 - 2 Nov 2024
Cited by 4 | Viewed by 4042
Abstract
This review systematically analyzes the latest advancements in preprocessing techniques for Electrocardiography (ECG) and Magnetocardiography (MCG) signals over the past decade. ECG and MCG play crucial roles in cardiovascular disease (CVD) detection, but both are susceptible to noise interference. This paper categorizes and [...] Read more.
This review systematically analyzes the latest advancements in preprocessing techniques for Electrocardiography (ECG) and Magnetocardiography (MCG) signals over the past decade. ECG and MCG play crucial roles in cardiovascular disease (CVD) detection, but both are susceptible to noise interference. This paper categorizes and compares different ECG denoising methods based on noise types, such as baseline wander (BW), electromyographic noise (EMG), power line interference (PLI), and composite noise. It also examines the complexity of MCG signal denoising, highlighting the challenges posed by environmental and instrumental interference. This review is the first to systematically compare the characteristics of ECG and MCG signals, emphasizing their complementary nature. MCG holds significant potential for improving the precision of CVD clinical diagnosis. Additionally, it evaluates the limitations of current denoising methods in clinical applications and outlines future directions, including the potential of explainable neural networks, multi-task neural networks, and the combination of deep learning with traditional methods to enhance denoising performance and diagnostic accuracy. In summary, while traditional filtering techniques remain relevant, hybrid strategies combining machine learning offer substantial potential for advancing signal processing and clinical diagnostics. This review contributes to the field by providing a comprehensive framework for selecting and improving denoising techniques, better facilitating signal quality enhancement and the accuracy of CVD diagnostics. Full article
(This article belongs to the Section Biosignal Processing)
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11 pages, 3109 KiB  
Article
Far-Detuning Laser Frequency Disturbance Suppression for Atomic Sensor Based on Intrinsic Fiber Fabry–Pérot Cavity
by Guanghui Li, Lihong Duan, Xinxiu Zhou and Wei Quan
Photonics 2024, 11(11), 1027; https://doi.org/10.3390/photonics11111027 - 30 Oct 2024
Viewed by 915
Abstract
The method of laser far-detuned frequency locking is proposed based on a fiber Fabry–Perot cavity which transfers the ultra-stable atomic reference frequency stability to the target laser utilized for atomic sensors. The control transfer function of the closed-loop system is established to elucidate [...] Read more.
The method of laser far-detuned frequency locking is proposed based on a fiber Fabry–Perot cavity which transfers the ultra-stable atomic reference frequency stability to the target laser utilized for atomic sensors. The control transfer function of the closed-loop system is established to elucidate the process of perturbation suppression. It is illustrated that this method is robust against the disturbance to the laser and cavity by controlling the cavity with different parameters. After the long-term experimental test, the stability of the laser frequency locked on the fiber cavity achieves an Allan deviation of 9.9×1011 and the detuning of the nearest atomic frequency resonance point is more than 200 GHz. Its stability and detuning value exceed previous reports. Full article
(This article belongs to the Special Issue Optically Pumped Magnetometer and Its Application)
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22 pages, 2278 KiB  
Review
Perspectives on the Toxic Effects of Micro- and Nanoplastics on the Environment: A Bibliometric Analysis of the 2014 to 2023 Period
by Xianhong Li and Zhonghong Li
Toxics 2024, 12(9), 676; https://doi.org/10.3390/toxics12090676 - 16 Sep 2024
Cited by 4 | Viewed by 2910
Abstract
Over the past decade, micro- and nanoplastics (MNPs) have garnered significant attention due to their frequent detection in and potential toxic effects on the environment and organisms, making them a serious threat to human health. To comprehensively understand the research on MNPs’ toxicity, [...] Read more.
Over the past decade, micro- and nanoplastics (MNPs) have garnered significant attention due to their frequent detection in and potential toxic effects on the environment and organisms, making them a serious threat to human health. To comprehensively understand the research on MNPs’ toxicity, we employed the R language-based Bibliometrix toolkit (version 4.3.0), VOSviewer (version 1.6.11) and CiteSpace (version 6.3.R1) to perform statistical and visual analyses of 3541 articles pertaining to MNPs’ toxicity between 2014 and 2023, which were retrieved from the Web of Science Core Collection (WOSCC) database. The analysis revealed that research related to MNPs’ toxicity has experienced a rapid increase in recent years. China’s particularly prominent influence in the field of MNPs’ toxicity is evidenced by its academic exchanges and the establishment of a mature cooperation system with other countries (regions), such as the USA and Germany. Studies related to MNPs’ toxicity are primarily published in leading journals, including the Science of the Total Environment, Environmental Pollution, and the Journal of Hazardous Materials. The Chinese Academy of Sciences was identified as the leading institution in terms of research on MNPs’ toxicity, contributing 203 papers to the total number of studies published. Keyword co-occurrence and burst analyses indicated that the current research on MNPs’ toxicity mainly focuses on the toxic effects of MNPs on aquatic organisms, the combined toxicity of MNPs and other contaminants, and the toxic effects and mechanisms of MNPs. Future research should integrate computational toxicology and toxicomics to enhance our understanding of MNPs’ toxicity mechanisms and assess the potential health risks posed by atmospheric MNPs. Full article
(This article belongs to the Section Novel Methods in Toxicology Research)
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14 pages, 1065 KiB  
Article
Analysis and Selection of the Optimal Pump Laser Power Density for SERF Co-Magnetometer Used in Rotation Sensing
by Kai Zhang, Linlin Yuan, Ze Cai, Hang Gao, Rui Wang, Pengcheng Du and Xinxiu Zhou
Photonics 2024, 11(9), 835; https://doi.org/10.3390/photonics11090835 - 4 Sep 2024
Cited by 1 | Viewed by 1063
Abstract
This paper systematically studies the output noise model of the K-Rb-21Ne co-magnetometer and proposes the method for determining the optimal pump laser power density. The amplitude-frequency response and the equivalent model for each frequency band are obtained through the transfer function [...] Read more.
This paper systematically studies the output noise model of the K-Rb-21Ne co-magnetometer and proposes the method for determining the optimal pump laser power density. The amplitude-frequency response and the equivalent model for each frequency band are obtained through the transfer function of the co-magnetometer. Based on the established model and considering the power spectral density characteristics of magnetic noise, the output noise equation is formulated. Consequently, the pump laser power density yielding minimal output noise is determined. Both experimental and simulation results indicate that the pump laser power density yielding minimal output noise is greater than the pump laser power density corresponding to the maximum scale factor. Moreover, when the co-magnetometer operates at the pump laser power density corresponding to the minimal output noise, the output noise can be reduced by approximately 25%, and the Allan variance reaches its optimal value. The optimal Allan variance at 180 °C and 190 °C are 0.01395°/h @100 s and 0.01329°/h @100 s, respectively. Therefore, this pump laser power density is designated as the optimal pump laser power density for the co-magnetometer. Finally, simulations are conducted to investigate the variation patterns of the optimal pump laser power density points and the minimum output noise under different density ratios and gas pressures. The theories and methods proposed in this paper provide significant reference value for selecting the optimal pump laser power density and suppressing magnetic noise in co-magnetometers. Full article
(This article belongs to the Special Issue Quantum Enhanced Devices and Instruments for Sensing Applications)
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23 pages, 9514 KiB  
Review
Global Trends and Current Advances in Slow/Controlled-Release Fertilizers: A Bibliometric Analysis from 1990 to 2023
by Xianhong Li and Zhonghong Li
Agriculture 2024, 14(9), 1502; https://doi.org/10.3390/agriculture14091502 - 2 Sep 2024
Cited by 11 | Viewed by 5465
Abstract
Slow/controlled-release fertilizers (SRFs/CRFs) occupy a critical position in agricultural advancement, enhancing productivity and sustainability by regulating nutrient release, improving fertilizer efficiency, reducing pollution, and promoting lasting agricultural progress. To attain an in-depth understanding of the current landscape, hotspots, and development trends in SRF/CRF [...] Read more.
Slow/controlled-release fertilizers (SRFs/CRFs) occupy a critical position in agricultural advancement, enhancing productivity and sustainability by regulating nutrient release, improving fertilizer efficiency, reducing pollution, and promoting lasting agricultural progress. To attain an in-depth understanding of the current landscape, hotspots, and development trends in SRF/CRF research, this study employed the Bibliometrix toolkit in R, VOSviewer, and CiteSpace for the statistical and graphical analysis of pertinent literature in the Web of Science Core Collection (WOSCC) database from 1990 to 2023. In this study, several dimensions were evaluated to assess the research scope and impact, including the quantity of published articles, authorship, citation frequency, keywords, institutional affiliations, publication journals, and source countries. The results indicate a significant increase in scholarly publications related to SRFs/CRFs from 1990 to 2023, totaling 1676 published papers across 77 subject categories. Research activities spanned 69 countries/regions, with China and the USA leading contributions. A total of 1691 research institutions published on SRFs/CRFs, with the University of Florida, the Chinese Academy of Sciences, and China’s Shandong Agricultural University being preeminent. HortScience, Science of the Total Environment, and Communications in Soil Science and Plant Analysis were the top three journals. Keyword co-occurrence and burst analysis disclosed that current research primarily focuses on several key areas: nitrogen (N) use efficiency, the processes of nitrification and denitrification, degradation, the use of phosphate (P) fertilizers, urea, and factors affecting crop growth and quality. The findings revealed several critical areas and trends within the sphere of SRFs/CRFs, with future research specifically directed towards developing cost-effective, efficacious, and environmentally friendly alternatives. Furthermore, future progress will concentrate on addressing the enduring environmental ramifications of SRF/CRF utilization. Full article
(This article belongs to the Section Agricultural Soils)
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10 pages, 3191 KiB  
Article
Magnetic Flux Concentration Technology Based on Soft Magnets and Superconductors
by Yue Wu, Liye Xiao, Siyuan Han and Jiamin Chen
Crystals 2024, 14(8), 747; https://doi.org/10.3390/cryst14080747 - 22 Aug 2024
Cited by 1 | Viewed by 2181
Abstract
High-sensitivity magnetic sensors are fundamental components in fields such as biomedicine and non-destructive testing. Flux concentration technology enhances the sensitivity of magnetic sensors by amplifying the magnetic field to be measured, making it the most effective method to improve the magnetic field resolution [...] Read more.
High-sensitivity magnetic sensors are fundamental components in fields such as biomedicine and non-destructive testing. Flux concentration technology enhances the sensitivity of magnetic sensors by amplifying the magnetic field to be measured, making it the most effective method to improve the magnetic field resolution of magnetic sensors. Superconductors and high-permeability soft magnetic materials exhibit completely different magnetic effects. The former possesses complete diamagnetism, while the latter has extremely high magnetic permeability. Both types of materials can be used to fabricate flux concentrators. This paper compares superconducting and soft magnetic flux concentration technologies through theoretical simulations and experiments, investigating the impact of different structural parameters on the magnetic field amplification performance of superconducting and soft magnetic concentrators. This research is significant for the development of magnetic focusing technology and its applications in weak magnetic detection and other fields. Full article
(This article belongs to the Special Issue Superconductors and Magnetic Materials)
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