Magnetic Source Research Articles

A Mathematical Study on a Steady MHD Flow in Double Stratification Medium

The detailed analysis on the flow of MHD fluid in double stratification medium across a stretching sheet with exponential permeability is examined in this research. The approximate analytical solution for the governing equations in steady state is found by using a new approximate analytical method called Ananthaswamy-Sivasankari Method (ASM) and Modified Homotopy Analysis Method (MHAM). The approximate analytical expressions for the dimensionless velocity, dimensionless temperature and dimensionless concentration are derived using these methods. The analytical and numerical results (previous work) are compared and there is a good agreement between our analytical results and numerical works. The impacts of several parameters including porosity, magnetic, suction and heat source parameters are shown in graphical representation. The error table for the physical parameter namely Nusselt number for various values of Prandtl number has been provided. Both ASM and MHAM are very useful to solve some other non-linear boundary value problems especially in MHD fluid flow

Nanoparticle shape effects on hydromagnetic flow of Cu‐water nanofluid over a nonlinear stretching sheet in a porous medium with heat source, thermal radiation, and Joule heating

AbstractIn this article, the shape effects of copper‐water nanofluid on magnetohydrodynamic boundary layer flow and heat transfer over a nonlinear stretching sheet in a porous medium under the influence of radiation, a heat source, and Joule heating effects are studied. The primary objective of this study is to determine which shape of nanoparticle is most effective in terms of heat transfer rate and to analyze how nanoparticle shape affects it. The governing PDEs are transformed to ODEs through similarity variables, and the numerical solutions are computed with the help of MATLAB's built‐in bvp4c solver. Plots of the velocity and temperature profiles are shown for various key parameters. The stretching parameter decreases both velocity and temperature, whereas the magnetic parameter, porosity, Eckert number, radiation, and heat source escalate temperature profiles. The heat transfer rate of lamina‐shaped nanoparticles is higher than that of other shapes.

The Correlation of Geothermal Energy Potential Deduced from Aeromagnetic and Aeroradiometric Data of Akiri and Environs, North-Central Nigeria

The aeromagnetic and aeroradiometric data were combined to investigate the geothermal energy potential of Akiri and Environs, North-Central Nigeria. The aeromagnetic and aeroradiometric data were obtained from the Nigerian Geological Survey Agency (NGSA), Abuja. The data consists of nine square map sheets of Wamba, Kwolla, Shendam, Lafia, Akiri, Ibi, Makurdi, Akwana and Wukari. The LANDSAT imagery data of the study area was obtained from the National Centre for Remote Sensing, Jos. The spectral analysis method was applied to aeromagnetic data to obtain the geothermal parameters of the magnetic sources. The results show that the depth-to-top of magnetic sources in the study area ranges between 0.76 and 4.46 km; while the depth-to-centroid ranges between 7.29 and 19.6 km. The depth-to-bottom of magnetic sources corresponds to the Curie point depth (CPD) in the study area which is the depth at which magnetic rocks lose their magnetism. The results show that the CPD varies between 12.70 and 37.22 km, the geothermal gradient varies between 15.58 and 45.67 ◦C/km, and the geothermal heat flow varies between 38.9 and 114.17 mW/m2. Two dimensional structural models were constructed to show the estimated depths at each profile taken. The models show uplifted crust and mantle in some areas due to magmatic intrusions which gave rise to low CPDs (12 to 28 km) which resulted to high geothermal heat flow values (60 to 115 mW/m2). The results show that there are low values of CPD in some areas which indicates that the study area has geothermal energy potential. The study shows that the geothermal energy potential deduced from aeromagnetic data correlates well with the geothermal energy potential deduced from aeroradiometric data.

Magnetic Mode Coupling in Hyperbolic Bowtie Meta-Antennas.

Hyperbolic metaparticles have emerged as the next step in metamaterial applications, providing tunable electromagnetic properties on demand. However, coupling of optical modes in hyperbolic meta-antennas has not been explored. Here, we present in detail the magnetic and electric dipolar modes supported by a hyperbolic bowtie meta-antenna and clearly demonstrate the existence of two magnetic coupling regimes in such hyperbolic systems. The coupling nature is shown to depend on the interplay of the magnetic dipole moments, controlled by the meta-antenna effective permittivity and nanogap size. In parallel, the meta-antenna effective permittivity offers fine control over the electrical field spatial distribution. Our work highlights new coupling mechanisms between hyperbolic systems that have not been reported before, with a detailed study of the magnetic coupling nature, as a function of the structural parameters of the hyperbolic meta-antenna, which opens the route toward a range of applications from magnetic nanolight sources to chiral quantum optics and quantum interfaces.

On the anatomy and structural control of a dyke swarm that fed caldera-forming ignimbrite eruptions

The evolution of eruptive vents related to calderas is not fully understood. We focus on a structural, rock-magnetic and geochemical investigation of a 314 Ma rhyolite dyke swarm associated with the late-orogenic Altenberg–Teplice Caldera, Bohemian Massif, eastern Variscan belt. The whole-rock major element, trace element and Nd–Pb isotope geochemistry along with the published U–Pb zircon geochronology link the extra-caldera dyke swarm with intra-caldera ignimbrites. The magnetic fabrics determined using the anisotropy of magnetic susceptibility are interpreted to record a continuum from magma ascent to emplacement and eruption during sinistral shearing. The latter evidences an interplay with regional tectonics associated with the activity of crustal-scale shear zones. The sinistral kinematics and strike of the dyke swarm, the elongation of caldera intrusive units, and the kinematics of major caldera faults are consistent with the dextral Riedel shear system, where the dykes correspond to antithetic R’ or X shears. Such a kinematic configuration implies that the maximum and minimum principal stresses were oriented roughly north–south and east–west, respectively. The relation between the stress field and the caldera elongation and orientation is not typical. We suggest that a pre-existing mutually perpendicular set of cross-cutting structural lineaments largely controlled the magma chamber and caldera formation. Supplementary material : The whole-rock major, trace element and isotope geochemical tables, magnetic fabrics source data and details of methods are available at https://doi.org/10.6084/m9.figshare.c.6715893

Computational investigation of double non-uniform magnetic field on heat transfer of nanofluid stream along 180-degree elbow pipe

The thermal efficiency of the nanofluid flow along the 180-elbow pipe is investigated under effects of double source of non-uniform magnetic field. To model the nanofluid stream with double magnetic sources, computational fluid dynamic is used. Effects of magnetic intensities and velocity of nanofluid on the hydrodynamic of the chosen model is also investigated in this research. The results of simulation indicate that the vortices are generated near the magnetic field and these vortices extend the thermal layer into the main stream and consequently, thermal efficiency of nanofluid stream is enhanced in 180-degree elbow. The results of various magnetic intensities also show that the increasing the magnetic intensities changes the location of maximum heat transfer from 1st magnetic source to 2nd one.

The High Arctic Large Igneous Province: first seismic-stratigraphic evidence for multiple Mesozoic volcanic pulses on the Lomonosov Ridge, central Arctic Ocean

We use seismic reflection data acquired by an over-winter expedition on drifting sea ice in the central Arctic Ocean to explore a possible spatial and temporal magmatic relation between the sub-bottom geology of part of the deep Arctic Ocean and the Mesozoic volcanic rocks found on the islands and the bordering continental shelf of Franz Josef Land and Svalbard. The new dataset from the North American segment (85–90°N) of the Lomonosov Ridge, central Arctic Ocean documents several Mesozoic volcanic pulses over a distance of c. 600 km along the ridge. This volcanism borders a domain of high magnetic field intensity over the adjacent Alpha Ridge in the deep basin where the magnetic source rocks and recent seismic reflection data indicate extensive Mesozoic magmatism. We suggest that the Mesozoic volcanism on the Lomonosov Ridge in its palaeo-position at the former continental margin north of Franz Josef Land and Svalbard spatially links the Mesozoic magmatic pulses of the continental High Arctic Large Igneous Province (HALIP) of polar Europe to volcanism on the adjacent Alpha Ridge in the deep Arctic Ocean. Increased input of heat to the upper crust on the Lomonosov Ridge enhanced maturation of hydrocarbon source rocks as manifested by the presence of gas or fluid escape pipes restricted to the area of volcanism.

Targeted delivery of therapeutic agents in a healthy and stenosed patient-specific carotid artery using an external magnetic field

In Magnetic Drug Targeting (MDT), an alternative and highly efficient technique to traditional drug delivery methods, therapeutic agents labeled with magnetic particles are transported to a target region using an external magnetic field. A high concentration of agents in the target tissue and their non-dispersion in the body increases treatment efficiency. In this study, targeted delivery of endothelial cells containing magnetic particles in a healthy and stenosed patient-specific carotid artery was studied. The Eulerian-Lagrangian approach was adapted to track the motion of particles and solve fluid equations. The effect of many internal parameters such as plaque morphology (occlusion percentage and the chord length of stenosis) and external parameters such as the strength and the position of the magnetic source, injection time, and the mass of magnetic particles inside each cell on the capture efficiency (CE) of cells was investigated. Results reveal that increasing the mass of magnetic particles in each cell and magnetic field strength enhances the capture efficiency of cells in the target region. Also, shifting the magnetic source location from position 1 (before the carotid sinus) to position 3 (after the carotid sinus) can increase and decrease the number of absorbed cells in the target region and CCA, respectively, both of which are desirable. Investigation of the injection time shows that the CE of cells when injecting in the systole and diastole is approximately the same as their CE when injected in a whole cardiac cycle. For a stenosed carotid artery, the percentage of occlusion is directly related to the CE of cells in the target region. Also, the chord length of stenosis has a direct and inverse relationship with the number of absorbed cells on the plaque surface and in the target region, respectively. Therefore, magnetic particles with higher magnetism or stronger magnetic fields are recommended for the stenosed carotid artery with a more severe occlusion percentage or a longer chord length.

Two-dimensional biaxial magnetic field imaging with millisecond resolution

Multi-axial dynamic magnetic field imaging with femto-Tesla sensitivity paves a promising route for acquiring comprehensive information of the extremely-weak magnetic source. Here we propose a two-dimensional (2D) scanning imaging configuration that can realize rapid biaxial magnetic field measurement. Based on the Bragg diffraction, the configuration utilizes two orthogonally-arranged acousto-optic modulators to scan the probe laser temporally and spatially, realizing a 2D (7 × 7 pixels) magnetic field detection. To solve the multi-axial dynamic magnetic field imaging problem, a non-modulated time-sharing technique is theoretically and experimentally verified. Profiting from the non-modulated biaxial working mode that avoids long demodulation time, the magnetometer realizes millisecond temporal resolution (17.15 ms) for each sensitive axis. Operation in the spin-exchange relaxation-free regime, the single-pixel measurement sensitivity reaches around 2.6 fT/Hz1/2 (y-axis) and 7.5 fT/Hz1/2 (z-axis). Furthermore, weak pump and probe lasers power (500 μW and 350 μW) make it a low-power imaging device.

Design and comparison of electro-permanent magnetic field sources for magnetocaloric heat pumps

We present the results of a comprehensive study of the design, numerical analyses and experimental validation of various electro-permanent magnetic structures that can be used in magnetocaloric refrigeration. Most magnetic field sources currently used in conceptual magnetic cooling devices require moving parts, which produce noise, vibrations and require maintenance. Furthermore, the operating frequency of such magnetic structures is relatively low and limited by aspects of the mechanical construction. Unlike any magnetic structure currently used in a magnetocaloric refrigeration device, the presented structure consists of a hybrid assembly of an electromagnet and a permanent magnet. We report on how different configurations of permanent magnets and the windings of electromagnets, including the air gaps, affect the energy efficiency, the input power and the total mass of the magnetic field source. Some guidelines for future research and the development of electro-permanent magnetic field sources for magnetocaloric refrigeration and heat pumps are presented, supported by information on how such structures can enable higher operating frequencies that could increase the compactness of future magnetocaloric devices.

Heat and Mass Transfer of CNTs Blood-based Casson Nanoliquids MHD Flow over a Rotating Stretchable Disk with Magnetic Field and Heat Source

Carbon nanotubes (CNTs) are being used in nanomedicine as drug delivery systems, particularly for the medical therapy of cancer. The CNTs are initially infused into the blood, which then travels to the tumour via waves generated by the artery walls in the presence of an outside influence, like a magnetic field. This article analyses the study of heat and mass transmission in a blood-based Casson nanoliquid MHD flow using single-wall (SW) and multi-wall (MW) carbon nanotubes (CNTs) on a rotating disc with a heat source and magnetic field effects. The suspension of both kinds of carbon nanotubes is accomplished using Casson blood. The spinning and extending of the disc cause the flow to be formed. The controlling nonlinear PDEs are transformed into nonlinear ODEs, and ODEs are resolved using the Runge-Kutta fourth-order approach in MATLAB's bvp4c package. By means of graphical representation, the effects of different model restrictions are highlighted for the following parameters: momentum, energy transport, concentration, microorganism profiles, drag coefficient, heat and mass transport rates, and motile density number. This study demonstrates that the fluid momentum of a single-walled CNTs-blood Casson nanofluid is relatively less impacted and that the heat profile of this nanofluid is more dominant than that of a multi-walled CNTs-blood nanoliquid. The outcomes further show that with higher levels of the volume fraction of nanoparticles, the friction factor and rate of heat transport are improved.

Aeromagnetic and structural characterization of dyke swarms in southeast Brazil: Evidence for Cenozoic reactivation of the Guapiara lineament, Ponta Grossa Arch

The Guapiara Lineament located on the northern edge of the Ponta Grossa Arch, Southeastern São Paulo state, Brazil, it is an important morphostructural feature defined by dykes oriented in NW-SE direction. The main objective of this work is applying new techniques for enhancing magnetic anomalies of the Guapiara Lineament and other structures, and using aeromagnetic data as support for the analysis of structure reactivation. Aerogeophysical techniques included qualitative and semiquantitative approaches (Euler Deconvolution and Radial Average Spectrum), we used the vertical and horizontal gradients, as well as deep magnetic sources and shallow magnetic sources filters, for an in-depth magnetic-structural characterization that was further correlated with the outcropping geology. We have also applied upward continuation (2000m) in the anomalous magnetic field map which was the basis for applying the Total Horizontal Gradient of the Analytical Signal (TDY), Analytic Signal Amplitude (ASA), Tilt angle (TDR), Total Horizontal Derivative of the Tilt Angle (TDR-THDR) and Tilt Angle of the Horizontal Gradient (TAHG) to improve our interpretations of the regional framework. The magnetic trends of the Guapiara Lineament are superimposed on the NE-SW (e.g.: Cubatão Lineament) and E-W (e.g.: São Sebastião Lineament) anomalies, which are considered structural inheritances of the Proterozoic basement. We report a set of reactivated N40–70W and E-W strike-slip faults showing the same orientation as the mapped magnetic lineaments. Moreover, they seem to be associated to deformational features in the dyke swarm, which was interpreted as evidence of Cenozoic tectonic reactivation.

A Suitable Magnetic Field Source Composed of an HTS Coil and HTS Bulks for Magnetic Drug Delivery System

To realize Magnetic Drug Delivery System (MDDS), it is necessary to reduce the frictional force on the inner surface of the blood vessel and increase the magnetic force in the longitudinal direction of the blood vessel acting on magnetic drugs deep inside the body. In other words, where the magnetic drugs are concentrated, the magnetic flux density gradient in the longitudinal direction of the blood vessel must be large and the magnetic flux density gradient perpendicular to the blood vessel surface must be small. However, creating such a magnetic field distribution with a single magnetic field source is difficult. Therefore, we investigated a magnetic field source configuration method that can increase the magnetic flux density gradient in the longitudinal direction of the blood vessel and decrease the magnetic flux density gradient perpendicular to the blood vessel surface by configuring the magnetic field source with an HTS coil and zero-field-cooled HTS bulks and using the antimagnetic effect of the HTS bulks. We examined the effect of the number of cylindrical HTS bulks on the magnetic force acting on the magnetic drugs. The shielding current field of the HTS bulk had the effect of reducing the magnetic flux density gradient perpendicular to the blood vessel surface and the relative position of the area where the magnetic drugs are concentrated and the shielding current region within the HTS bulk greatly affected the magnetic flux density gradient perpendicular to the blood vessel surface. Based on these results, we examined the effect of the distance between two cylindrical HTS bulks placed inside an HTS coil on the magnetic force acting on the magnetic drugs. The magnetic force in the longitudinal direction of the blood vessel was able to be increased by placing the HTS bulks so that the boundary of the HTS bulk (shielding current region) is near the area directly below the area where the magnetic drugs are concentrated. The distance between the square-column HTS bulks that maximized the magnetic force was longer than that of the cylindrical HTS bulks.

A calibration method of ground-airborne frequency domain electromagnetic receving system based on magnetic source excitation

In the ground-airborne frequency domain electromagnetic detection, the receving system converts the magnetic field signal into an electrical signal representing the magnetic field signal. In order to accurately obtain the relationship between the magnetic field signal and the electrical signal, it is necessary to avoid the influence of environment and other factors on the system accuracy through on-site calibration. This requires high calibration accuracy, simple operation, portable equipment and strong adaptability to the environment. However, the existing calibration methods put forward higher requirements for instruments and environment. For example, the calibration of uniform magnetic field generated by Helmholtz coil needs to shield external magnetic field interference. In this paper, an overall calibration method of measurement system based on magnetic source excitation is proposed to meet the requirements of electromagnetic field accurate measurement in ground-airborne frequency domain. Firstly, based on the electromagnetic measurement method in ground-airborne frequency domain, the overall calibration method and principle of the detection system are introduced. Then, based on the computable standard magnetic field generated by the magnetic source transmitting coil, determine the measured voltage obtained by the receiving system, get the calibration coefficient of the receiving system. At last,the source of standard uncertainty related to calibration is analyzed, and the uncertainty is evaluated. In addition, the method is verified by comparing the calibration results with those obtained by Braunbeck coil calibration.

Noninvasive blood glucose sensing by secondary speckle pattern artificial intelligence analyses.

Diabetes is a prevalent disease worldwide that can cause severe health problems. Accurate blood glucose detection is crucial for diabetes management, and noninvasive methods can be more convenient and less painful than traditional finger-prick methods. We aim to report a noncontact speckle-based blood glucose measurement system that utilizes artificial intelligence (AI) data processing to improve glucose detection accuracy. The study also explores the influence of an alternating current (AC) induced magnetic field on the sensitivity and selectivity of blood glucose detection. The proposed blood glucose sensor consists of a digital camera, an AC-generated magnetic field source, a laser illuminating the subject's finger, and a computer. A magnetic field is applied to the finger, and a camera records the speckle patterns generated by the laser light reflected from the finger. The acquired video data are preprocessed for machine learning (ML) and deep neural networks (DNNs) to classify blood plasma glucose levels. The standard finger-prick method is used as a reference for blood glucose level classification. The study found that the noncontact speckle-based blood glucose measurement system with AI data processing allows for the detection of blood plasma glucose levels with high accuracy. The ML approach gives better results than the tested DNNs as the proposed data preprocessing is highly selective and efficient. The proposed noncontact blood glucose sensing mechanism utilizing AI data processing and a magnetic field can potentially improve glucose detection accuracy, making it more convenient and less painful for patients. The system also allows for inexpensive blood glucose sensing mechanisms and fast blood glucose screening. The results suggest that noninvasive methods can improve blood glucose detection accuracy, which can have significant implications for diabetes management. Investigations involving representative sampling data, including subjects of different ages, gender, race, and health status, could allow for further improvement.

Simulation validation based on emission coil of three-axis square Helmholtz magnetic source

In electromagnetic detection, the received signal strength is largely determined by the transmitter’s signal strength. Therefore, it is necessary to select and design the transmitting coil to meet the requirements of the electromagnetic launching system. To obtain better-transmitting coils, Maxwell is used to establishing square and toroidal coil models for calculation and compare magnetic field intensity and uniformity. To cope with electromagnetic exploration in a complex environment, the electromagnetic field model of the three-axis toroidal coil and square Helmholtz coil is established. The magnetic field simulation results verify that the three-axis square Helmholtz coil has higher emission field intensity under the same excitation condition, which is suitable for electromagnetic exploration.

An artificial intelligence-based pipeline for automated detection and localisation of epileptic sources from magnetoencephalography.

Objective.Magnetoencephalography (MEG) is a powerful non-invasive diagnostic modality for presurgical epilepsy evaluation. However, the clinical utility of MEG mapping for localising epileptic foci is limited by its low efficiency, high labour requirements, and considerable interoperator variability. To address these obstacles, we proposed a novel artificial intelligence-based automated magnetic source imaging (AMSI) pipeline for automated detection and localisation of epileptic sources from MEG data.Approach.To expedite the analysis of clinical MEG data from patients with epilepsy and reduce human bias, we developed an autolabelling method, a deep-learning model based on convolutional neural networks and a hierarchical clustering method based on a perceptual hash algorithm, to enable the coregistration of MEG and magnetic resonance imaging, the detection and clustering of epileptic activity, and the localisation of epileptic sources in a highly automated manner. We tested the capability of the AMSI pipeline by assessing MEG data from 48 epilepsy patients.Main results.The AMSI pipeline was able to rapidly detect interictal epileptiform discharges with 93.31% ± 3.87% precision based on a 35-patient dataset (with sevenfold patientwise cross-validation) and robustly rendered accurate localisation of epileptic activity with a lobar concordance of 87.18% against interictal and ictal stereo-electroencephalography findings in a 13-patient dataset. We also showed that the AMSI pipeline accomplishes the necessary processes and delivers objective results within a much shorter time frame (∼12 min) than traditional manual processes (∼4 h).Significance.The AMSI pipeline promises to facilitate increased utilisation of MEG data in the clinical analysis of patients with epilepsy.

Laser powder bed fusion of anisotropic Nd-Fe-B bonded magnets utilizing an in-situ mechanical alignment approach

Nd-Fe-B bonded magnets are an important class of permanent magnets, employed in many technological sectors. Additive Manufacturing (AM) enables the fabrication of net-shape bonded magnets with complex geometries, allowing to tailor their magnetic stray field specifically for a given application. A crucial challenge is the production of magnetically anisotropic components. Approaches presented in the literature up to now required a post-printing procedure or the complex integration of a magnetic field source into the AM process. Here, we present a technique to fabricate anisotropic bonded magnets via Laser Powder Bed Fusion (LPBF) by utilizing the mechanical alignment of anisotropic particles in a single step, without the need for a magnetic field source. Anisotropic bonded magnets were fabricated using a mixture of anisotropic Nd-Fe-B powder (MQA-38–14) and polyamide-12 (PA12). This magnetic powder consists of ellipsoidal particles, where the easy magnetization axis is distributed perpendicular to their longest side, and the mean aspect ratio of 3:1 can be exploited to generate magnetic texture. Depending on the particle size used as feedstock, the degree of alignment (<cosθ>) can be tailored to a maximum of <cosθ> = 0.78. The fabricated anisotropic bonded magnets exhibited a maximum remanence of Jr = 377 mT and an energy product of (BH)max = 28.6 kJ/m3, respectively.

Evaluation of Geothermal Energy Potential in Parts of the Lower Benue Trough, Nigeria, Using Aeromagnetic Data

Abstract Nine sheets of Regional Aeromagnetic data of parts of Lower Benue Trough were evaluated through the use of Centroid and forward modelling of the spectral peak methods with a view to delineating structures and basin geometry of the Southern (Lower) Benue Trough of Nigeria. Geological cross sections were used to determine the number of anomalies from the residual magnetic map after which the Discrete Fourier Transform method was applied in calculating and computing the depth to the top (Zt), depth to the bottom (Zo), Curie point depth (CPD), geothermal gradient and heat flow. From the results, the depth to the top of the magnetic source ranges between 0.5km and 12.5km with the highest points towards the south - western part of the study area. The depth to the bottom of magnetic source (centroid depth) ranges from 2km to 54km and the highest areas are located towards the north-eastern part of the study area. The geothermal gradient ranged between 21oC/Km to 29.5oC/Km., Ogoja, Oturkpo, and Katsina–Ala are situated within the region of high geothermal gradients (&gt;26.5oC/Km). The heat flow values range from 22mW/M2 to 74 mW/M2 and the areas with the high heat flow values are Makurdi, Ogoja, Gboko and Katsina-Ala. The results also show that the Curie temperature isotherm within the study area is not a horizontal level surface, but it is undulating. The study also identified high sedimentary thickness and considerable geothermal potential which could serve as a basis for hydrocarbon accumulation and geothermal exploitation. Keywords: Geothermal Gradient, heat flow, Crustal Temperature, Geothermal Potentials, Total Magnetic Intensity (TMI).

Utilizing 3D magnetic source imaging with landmark-based features and multi-classification for Alzheimer’s Disease diagnosis

Utilizing 3D magnetic source imaging with landmark-based features and multi-classification for Alzheimer’s Disease diagnosis