Change Of Magnetic Flux Research Articles

Detection of blood coagulation in an extracorporeal circuit using magnetic and absorbance properties

In extracorporeal circulation, intra-circuit blood coagulation can lead to serious problems. However, intra-circuit coagulation cannot be monitored in real-time and is only intermittently monitored by measuring the activated clotting time (ACT). As blood clotting progresses in a circuit, the color of the blood turns from bright red to dark red. And, changes in blood coagulation can be detected using devices with optical sensors because the absorbance is likely to change as blood coagulates. However, the absorbance may also increase when oxygen partial pressure is altered by artificial lungs. Thus, there is a need for a device that is not affected by blood oxygenation. Therefore, we used a magnet and a flux meter to assess changes in the magnetic force with blood coagulation. Thus, there is a need for a device that is not affected by blood oxygenation. Therefore, we used a magnet and a flux meter to assess changes in the magnetic force with blood coagulation. Measurements were made at different flux intensities to capture the magnetic flux changes during blood coagulation. Blood (100 ml) was stored in a beaker. Calcium chloride (CaCl2: 0.2 ml) was then added to the beaker to promote coagulation. Blood from the beaker was drawn into a syringe and set in the magnetic flux measurement fixture, and a magnet was fixed on top of the syringe for 24 min. The flux meter readings increased as the blood coagulated. The results suggest that it is possible to capture magnetic flux density changes during the process of blood coagulation. From the above may lead to the development of a device that monitors coagulation in extracorporeal circuits in real time by monitoring two aspects of the coagulation process: absorbance and magnetic flux density.

Phase matching of electromagnetic wave on moving interface

Due to the boundary conditions of electromagnetic fields and phase matching of electro magnetic waves on interface being the basis to drive the Snell’s laws and Fresnel’s laws, they are also crucial for the analysis of electromagnetic wave propagation in a moving medium. There are mainly two methods to derive the boundary conditions of electromagnetic fields on moving interface. One of them is to use the kinematic integral form, yet this method is based on the classical time-space, and the other is based on the relativistic transformation, the boundary conditions are derived from the scaling effect with geometric method, or from the principle of relativity directly. However, the first one has a form the same as the form obtained by using the kinematic integral form, while the second one obtains a different form. At the same time, the phase matching of electromagnetic wave on moving interface is only discussed by Galileo transformation, however this is unreasonable, because of the relativistic effect cannot be ignored here. Therefore, it is necessary to reexamine the boundary conditions of electromagnetic fields and phase matching of electromagnetic wave on moving interface. Herein, firstly, the relativistic transformation formula of the unit normal vector of moving surface is derived from the surface equation and principle of relativity. Secondly, the boundary conditions of electromagnetic fields on moving interface are given based on the relativistic transformation formula and the non-relativistic transformation formula of the unit normal vector and electromagnetic fields, which show that the boundary conditions of electromagnetic fields on moving interface under the relativistic case and the non-relativistic case have the same form. This is not accidental but definite, because the change of flux of electromagnetic fields, like the change of magnetic flux, from the induction of electromagnetic filed is the same as that from the variation of surface element. Thirdly, the phase matching of electromagnetic wave on moving interface is given based on the relativistic transformation formula of the unit normal vector and the phase matching of electromagnetic wave on resting interface. In the problem of light incident on a homogeneous medium moving at a constant velocity in vacuum or air, using the phase matching of electromagnetic wave on moving interface, the same results can be easily obtained through other methods. The discussion in this study belongs to classical electrodynamics with no quantum effects considered, but the results will provide some conveniences for theoretically analyzing electromagnetic communication, remote sensing and telemetering.

Measurement of Magnetic Flux Density Changes in Mode I Interlaminar Fracture in Magnetostrictive Fiber–Embedded Glass Fiber-Reinforced Polymer Composites

As sensor materials for structural health monitoring (SHM, a nondestructive test for the continuous evaluation of the conditions of individual structural components and entire assemblies), magnetostrictive materials, piezoelectric materials, and optical fibers have attracted significant interest. In this study, the mode I interlaminar fracture load and crack self-detection potential of glass fiber-reinforced polymer (GFRP)–embedded magnetostrictive Fe–Co fibers were investigated via double cantilever beam testing. The results indicated that by controlling the amount of Fe–Co fibers introduced into GFRP, the number of Fe–Co fibers could be reduced without compromising the performance of GFRP. Furthermore, the magnetic flux density increased significantly with crack propagation, indicating that the magnetic flux density change could determine crack propagation.

Comprehensive assessment of the quality of laminated core of electrical machines by the high-frequency induction-vibration method

In this work, the problem of assessing the quality of active parts of electric machines, in particular charged magnetic conductors, is considered. The essential diagnostic indicators of the actual state of the recruitment core were determined, namely specific losses during remagnetization and weakening of package pressing, which are associated with increased losses, decreased efficiency, violation of the thermal regime, etc. induction-measuring module for determining the level of inter-sheet insulation breakdown and the growth of losses in the core. It is recommended when loosening for small-sized magnetic conductors, impregnation of the weakened area with adhesive varnish and subsequent drying with a compressed core. Also, for cores of a small diameter, between the pressure washer and the extreme sheets of the core, drive textolite wedges every 2...4 teeth. When the pressing of the cores of large electric machines, in which the pressing is carried out by tension pins, is weakened, the pins are tightened. A two-dimensional field mathematical model of a charged magnetic core package was developed in order to estimate the distribution of the electromagnetic field and eddy currents and losses at different frequencies from 50 Hz to 10 kHz. It is proposed to use the analysis of the transient process when the magnetic flux changes in the magnetic circuit. To simplify the measuring scheme, it is proposed to use the process of switching the current in the excitation winding. With the help of the developed model, the calculation of transient modes was carried out on the example of the studied magnetic circuit. As an object of research, a mock-up of a stacked magnetic core was used, which is a set package of magnetic steel sheets used in magnetic cores of dry transformers of small and medium power. In order to combine the two methods, an installation was developed that allows checking the quality of pressing and the quality of inter-sheet insulation at the same time.

Electric Power Generated from Magnetic Nanofluid Droplets Sliding upon Superslippery Surfaces.

An enduring challenge in the field of electric power generation employing magnetic nanofluids pertains to the inherent issue of solid-liquid adhesion, which results in random residue deposition of magnetic nanofluids on solid substrates during motion. Superslippery surfaces, characterized by their exceptional repellent properties and ultralow adhesion characteristics toward an extensive spectrum of fluids, offer an effective approach to ameliorate the aforementioned adhesive problem. Herein, it is demonstrated that electric power can be generated through the sliding of magnetic nanofluid droplets on superslippery surfaces. The electric power generation can be attributed to the change in magnetic flux caused by the magnetic nanofluid droplet passing or leaving a bottom coil associated with a magnet. By tailoring system parameters, such as the volume of the magnetic nanofluid or the vibration speed, the resulting maximal current can exceed 6 μA. An integrated device, featuring enclosed superslippery inner surfaces, can be securely attached to the arm of a volunteer, allowing for the conversion of mechanical energy into electricity. When the volunteer's arm moves, the electrical energy generated by the device can be utilized to light an LED lamp bead. The proposed strategy using superslippery surfaces facilitates low-adhesion transport of magnetic nanofluids, presenting an alternative solution to the development of next-generation solid/liquid energy harvesting devices.

Evaluation of Magnetic Flux Density Change for Vibration Energy Harvesting: Comparison Between Direct and Indirect Measurements

Evaluation of Magnetic Flux Density Change for Vibration Energy Harvesting: Comparison Between Direct and Indirect Measurements

Electromagnetic load evaluating and optimizing approach of the blanket system during VDEs considering halo current

In most scenarios, the vertical displacement event (VDE) represents the most extreme electromagnetic (EM) event within the tokamak device. The significant EM loads experienced during this event have the potential to compromise the structural stability of in-vessel components. This study investigates the EM loads on the water-cooled ceramic breeder blanket system of China Fusion Engineering Test Reactor (CFETR) using finite element analysis methods in two characteristic events: hot-VDE and cold-VDE. The study discusses the EM load effects resulting from changes in magnetic flux and induced electromotive force, respectively, with a specific focus on halo currents. The results reveal that, with similar current quech time, the difference in EM load on the blanket system during the VDEs primarily depends on the halo currents. When the electrical connection of the back supporting structure (BSS) is open, the halo current path within the blanket system and vacuum vessel (VV) changes, and a substantial portion of the halo current in the blanket system is conducted to the VV via the BSS. Consequently, a portion of the EM load on the blankets and BSS is transferred to the VV due to the transfer of halo current. Inspired by this, the conceptual use of ‘shunts’ is proposed to provide a dedicated circuit for shunting halo currents away from critical device components, such as the VV and blankets. This approach allows for the sharing of EM loads caused by halo currents and reduces the threat posed by halo currents to the structural integrity of these essential components.

Effect of the Static Magnetic Fields on the Circadian Rhythm in Arabidopsis thaliana

The influence of geomagnetic field on various biological processes is certainly an interesting research field, and more work is beingperformed across the globe. However, the impact of varying magnetic flux density on plant circadian rhythms has not yet beencompletely investigated. Different researchers have mostly focused their attention on the molecular workings of circadian rhythms invarious plant systems and the circadian architecture of transcriptomes under varying conditions. The present investigation evaluatedthe influence of variable geomagnetic field on the expression of genes that are under the control of circadian rhythm, and checkedwhether the expression pattern of these genes with respect to time (circadian nature) under different magnetic flux density changesor not in Arabidopsis seedlings. This study examined the impact of varying magnetic flux densities on the mRNA expression levels ofsix genes in Arabidopsis thaliana during the final 33 hours of their total 120 hour growth period. A. thaliana seedlings were subjectedto four distinct magnetic flux densities (0, 25, 50, and 90 μT), and the abundance of transcripts for chlorophyll a/b binding protein 4,the large subunit of RuBisCO, rubisco activase, chalcone synthase, porphobilinogen synthase, and phytoene dehydrogenase genes wasexamined. While the present study’s findings lend credence to the idea that the aforementioned genes are differentially expressed inresponse to changes in magnetic flux density, it also proved that the circadian nature of these genes was largely unaffected, with theirexpression pattern remaining largely unaltered regardless of the strength of the magnetic field.

Parametric Studies of the EU DEMO Central Solenoid

The Central Solenoid (CS) is at the core of the EU DEMO tokamak, and has a strong impact on the tokamak design and the overall machine size. By ramping its current, the CS generates a change of magnetic flux, which initiates the plasma, and induces and controls the plasma current. In the context of the conceptual design studies for DEMO coordinated by EUROfusion, the Swiss Plasma Center has developed a simple pre-dimensioning methodology, assuming uniform current density in the solenoid winding pack, and considering the use of Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn and REBCO. The effects of grading of the superconductor and structural steel are also discussed. Since the CS for the EU DEMO will experience tens of thousands of charge/discharge cycles during its lifetime, mechanical fatigue considerations are taken into account. The proposed methodology has been used for the preliminary design of the CS winding pack, and for a number of parametric analyses in the context of the integrated physics and engineering studies for the EU DEMO machine (identifying the relationship between key performance parameters of the solenoid, such as the generated magnetic flux and the fatigue lifetime).

Electromagnetic Induction: Unraveling Faraday's Laws and Their Applications in Generators and Transformers

This study delves into the fundamental principles of electromagnetic induction, as proposed by Michael Faraday, and their applications in generators and transformers. Through a series of carefully designed experiments, the relationship between changing magnetic fields and induced electromotive force (emf) is systematically explored. The collected data, aligned with theoretical expectations, reaffirms Faraday's laws, showcasing the direct link between varying magnetic fields and induced emf. A graphical representation further illustrates the linear relationship between the rate of change of magnetic flux and induced emf, in accordance with Faraday's Second Law. The implications of these findings extend to the functioning of generators and transformers, highlighting the role of electromagnetic induction in converting mechanical energy to electricity and facilitating energy transfer. While potential sources of error are acknowledged, the successful experimental validation of Faraday's laws enriches our understanding of electromagnetism's core principles and their real-world applications.

Performance enhancement of electromagnetic vibration energy harvesters via bi-stable structure based on MEMS 3D coils

In this study, we conducted a systematic exploration of a micro-electromagnetic vibration energy harvester with a bi-magnet structure and microelectromechanical systems 3D coils. First, we establish a physical model of stiffness and damping characteristics based on the superposition principle for the bi-magnet structure which has also been verified experimentally. Then, we investigate the influence of magnet gap and air gap on the stiffness and the magnetic flux change rate, mainly focusing on the distance and the potential barrier between the two potential wells. Finally, we fabricate and assemble the bi-magnet VEH prototype and tested the output performance under 1 and 6g excitation, which correspond the intra-well vibration and inter-well vibration, respectively. The tested results show that under 1g excitation, the prototype can output 155.38 μW power with 32 Hz half-power bandwidth and 4939.06 μW·Hz integrated power, which are obviously higher than those for mono-magnet under same excitation. When the excitation raises to 6g, the output power is improved to 362.98 μW with the half power bandwidth and integrated power enhanced to 56 Hz and 9289.96 μW·Hz, respectively. The tested results also prove that the structure proposed in this study can significantly enhance the output performance compared with a mono-magnet structure and other published data.

Effect of Laminated Core Body Size on Motor Magnetic Properties

The magnetic characteristics of electromagnetic steel sheets used for motors are evaluated under ideal sinusoidal excitation. However, in actual equipment driving, excitation by pulse-width modulation (PWM) waves is the mainstream method. Therefore, it is necessary to clarify how the magnetic properties used in motors are changed by sinusoidal excitation and inverter excitation. To clarify the magnetic properties of the laminated core by inverter excitation, samples with different core sizes were prepared and the effects on the magnetic properties were then investigated. The magnetic properties were measured by changing only the input voltage VDC while maintaining the carrier frequency and modulation factor constant. As the results, the iron loss values of the small, medium, and large samples with inverter excitation were 6.05, 9.58, and 11.62 W/kg, respectively. The iron losses of the small, medium, and large toroidal cores with inverter excitation increased by 124.9, 256.1, and 332.0%, respectively, compared with the iron loss of each toroidal core with sinusoidal excitation. The larger the body, the higher the required voltage and iron loss. It can be inferred that a larger amount of energy was required to excite a larger toroidal core. This was because the change in magnetic flux density per unit time of the large toroidal core was greater than that of other cores. This indicates that the large toroidal core generated larger eddy currents than other cores. Therefore, it is possible to say that large toroidal cores generate greater eddy current losses than other cores.

NOVEL TECHNIQUE FOR INTRAOCULAR FOREIGN BODY REMOVAL: Magnetized Disposable Microforceps. A Systematic Approach and First Clinical Result.

To verify whether disposable microforceps can be magnetized to atraumatically attract and then grasp intraocular foreign bodies. An effective magnetization protocol was developed. The clinical relevance was tested, and a first practical application was performed. The magnetic flux density (MFD) of a bar magnet and an electromagnet was measured. Steel screws were used to determine the magnetization protocol. Disposable microforceps was magnetized, MFD generated at the tip was measured, and the weight that can be lifted was tested. Foreign body removal with such forceps was performed. The electromagnet MFD was much higher than the bar magnet. The most effective magnetization protocol was to pass the screw from the end along the shaft and back over the electromagnet. Magnetized microforceps had a 7.12 mT change in MFD at the tip. Steel balls up to 87 mg could be lifted in buffered saline solution. In clinical use, the intraocular foreign body could be attracted and grasped safely. Disposable microforceps can be easily and inexpensively magnetized. The achievable MFD is clinically relevant to attract typical intraocular foreign bodies. An electromagnet is best suited for this purpose. With such prepared forceps, foreign bodies can be attracted atraumatically and grasped securely.

Pulsed Eddy Current Sensor for Cascade Electrical Conductivity and Thickness Estimation in Nonferrous Metal Plates

This paper presents a pulsed eddy current (PEC) sensor design for cascade electrical conductivity and thickness estimation in non-ferrous metal plates. With a single excitation coil design, the combined change in magnetic flux density caused by the excitation coil and the induced eddy current (EC) in the test plate is detected by a compact anisotropic magneto-resistive (AMR) sensor. The effects of the varying input pulse width are discussed with both numerical simulations in commercial finite element analysis (FEA) software and experimental results, and the time-domain characteristics of the responses are analyzed in relation to the properties of the test plates. It is revealed that the electrical conductivity can be gauged based on the peak value of the short pulse response, and with a known electrical conductivity value, plate thickness can be subsequently derived with the rise time of the long pulse response. A cascade estimation process is therefore proposed to calculate the parameters sequentially by adopting hybrid input signals with both short and long input pulses. Verified by the FEA results, this cascade estimation process was then experimentally validated with a prototype of the PEC sensor.

Parametric study on circularly abrupt magnetic flux density changes of electromagnetic energy harvesters via simulation

Energy harvesting has long been widely studied. In this paper, we systematically investigate the output performances of rotating electromagnetic energy harvesters (EMEHs) with different magnetic pole pairs and coil parameters via simulations. Different numbers of magnetic pole pairs obviously affect the abrupt magnetic flux density (MFD) change and the further output voltage. Hence, we set up finite element (FEM) models of proposed harvesters to compare the output voltage under different numbers of the magnetic pole pairs p in the same coil parameters conditions. Subsequently, to further study how the coil parameters affect the voltage and power of EMEHs, we conduct simulations using different coil heights h and wire diameters d with the same magnet array. The results of the magnet simulation indicate that in a certain volume, EMEHs yield a maximal output voltage of about 12.2 V in the case of p=4. In the best contrast, EMEHs produce a peak output power of about 26.36 W under the excitation of 180 rad/s. This study will be of great significance in improving power in the field of harvesting electromagnetic energy.

A Sensor for the Ultraweak DC Current Covered by Strong AC Currents

In the field of insulation monitoring of high-voltage power equipment, the dc leakage current is an important indicator to evaluate the insulation state. However, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> -level dc leakage currents are usually mixed with mA-level power-frequency ac currents, bringing obstacles to the accuracy of the dc measurement. In this regard, a new magnetic modulator with a suppressing structure is proposed. Based on the fact that Lenz law only keeps valid for a changing magnetic flux, the ac suppressing structure is developed to enclose the original magnetic modulator. Then, the factors of the suppression structure’s performance, including weakening the ac magnetic flux and reducing the dc measurement sensitivity, have been analyzed. And the performance is found to be closely related to the magnet dimensions, the magnetic permeability, and the suppressing winding turns. Finally, the improved prototype current sensor for the converter transformer valve side bushing has been developed, and experiments are conducted to verify its dc accuracy and ac suppressing performance.

Investigation of the Three-Dimensional Hybrid Casson Nanofluid Flow: A Cattaneo-Christov Theory.

We consider the Casson hybrid nanofluid (HN) (ZnO + Ag/Casson fluid) that flows steadily along a two-directional stretchable sheet under the influence of an applied changing magnetic flux and is electrically conducting. The basic Casson and Cattaneo-Christov double diffusion (CCDD) formulations are used for the simulation of the problem. This is the first study on the analysis of the Casson hybrid nanofluid by using the CCDD model. The use of these models generalize basic Fick's and Fourier's laws. The current produced due to the magnetic parameter is taken into consideration by using the generalized Oham law. The problem is formulated and then transformed to a coupled set of ordinary differential equations. The simplified set of equations is solved using the homotopy analysis method. The obtained results are presented through tables and graphs for various state variables. A comparative survey in all the graphs is presented for the nanofluid (ZnO/Casson fluid) with the HN (ZnO + Ag/Casson fluid). These graphs depict the effect of various pertinent parameters, like Pr, M, Sc, γ, Nt, m, Nb, δ1, and δ2, varying values over the flow. The Hall current parameter m and stretching ratio parameter γ show increasing trends for the velocity gradient, while the magnetic parameter and the flux of mass depict opposite trends for the same profile. The increasing values of the relaxation coefficients show an opposite trend. Furthermore, the ZnO + Ag/Casson fluid shows a good performance in the transfer of heat and thus can be used for cooling purposes to increase the efficiency of the system.

A self-sensing intelligent soft pneumatic actuator with soft magnetic structures

Many achievements for soft pneumatic actuators (SPAs) are made in the structure design and application demonstration. However, few studies focus on their mechanical sensing which is significant toward autonomous and intelligent soft robots. Herein, a self-sensing intelligent soft pneumatic actuator (SISPA) is developed by integrating a sensing layer that is silicone rubber/NdFeB composite twined with a varnished wire. The induced voltage is generated with the bending deformation of the sensing layer. Experimental results show that the induced voltage rises with the increasing mass fraction of magnetic powders, turns of the varnished wire, and thicknesses and widths of the composite. The bending deformation of the SISPA is also investigated experimentally and numerically. The bending angle of the SISPA reaches 225.5° with an applied pressure of 40 kPa, which is 92.68% of that of the SPA without embedding the sensing layer. The effect of the four parameters of the sensing layer on the bending deformation is investigated as well. In conclusion, the sensing layer has a slight effect on the bending deformation of the SISPA. Based on the experimental data, we find that there is a linear relationship between the bending angle and magnetic flux change. So the relation of the bending deformation and output voltage is formulated approximatively. Finally, an intelligent bionic hand is developed by utilizing the SISPA, which outputs different signals according to diverse gestures. Therefore, the proposed SISPA can be an attractive candidate involving accuracy control and intelligent soft robots.

Development of a Magnetic/Eddy-Current Sensing System For Simultaneous Estimation of Electrical Conductivity and Thickness in Non-Ferrous Metal Plates

This article presents the development of a nonferrous–metal magnetic/eddy-current (NFM-M/EC) sensing system for simultaneous estimation of electrical conductivity and thickness in nonferrous metal plates. The distributed current source (DCS) method models the axisymmetric magnetic/eddy-current fields for the sensor design. An anisotropic magnetoresistive sensor is used to detect the change in magnetic flux density caused by the induced eddy currents in the test plates. The frequency-mapping method for sweep frequency measurements is numerically validated. Calibration between the model and experimental data by the mesh refinement method is introduced to improve the accuracy of estimations efficiently. The DCS method is verified numerically by comparing it with finite-element analysis. The proposed sensing system design is tested on four different materials with varying thicknesses. Accurate estimations in experiments substantiate the NFM-M/EC sensing system as a new alternative for nondestructive detection.

Stress monitoring capability of magnetostrictive Fe–Co fiber/glass fiber reinforced polymer composites under four-point bending

Many structural health monitoring (SHM) techniques have been investigated for damage detection in woven glass fiber reinforced polymer (GFRP) laminates. Recently, the GFRP composites integrated with sensors have received attention because the composite material can transmit information about the structural condition during operation. Magnetostrictive materials are considered as feasible candidates to realize the contactless SHM techniques by exploiting the Villari effect, but the theoretical modeling to correlate a magnetostrictive response with structural conditions is a critical issue. In this study, the analytical procedure considering the mechanics of materials and electromagnetism was proposed to model the magnetic induction by the Villari effect of magnetostrictive GFRP laminates under bending. The magnetostrictive Fe–Co fiber/GFRP composites were then developed, and the four-point bending tests were carried out to evaluate the fabricated composites’ stress monitoring capability. The magnetic flux density behavior corresponded to the bending stress fluctuation. The maximum magnetic flux density change was 70.7 mT subjected to the peak bending stress of 158 MPa. The analytical solutions showed reasonable agreement with the experimental results. The applied stress and measured magnetic flux density were correlated by the theoretical models. Thus, these results suggest an important step in realizing the novel contactless SHM technique utilizing magnetostrictive materials.