Magnetic Plate Research Articles

A Mechanical Antenna With Frequency Multiplication and Phase Modulation Capability

This article reports on a novel direct frequency multiplication and phase modulation (PM) scheme for mechanical antennas operating at the very-low-frequency band (3-30 kHz) and lower. This antenna is intended as a transmitter for underwater and underground communication applications. In mechanical antennas, instead of using signal generators to drive the antenna for radiation, the radiation is induced by accelerating (rotating) electric charges or permanent magnets. One important challenge for mechanical antennas is to find an approach to modulate the information signal with sufficient bandwidth. We propose a novel PM scheme by rotating a permanent magnet which is sandwiched between two pairs of orthogonal bow-tie shape high- μ magnetic material plates. By moving the angular position of the magnetic plates, it is shown that the phase and amplitude of the EM signal can be modulated. The amplitude modulation is significant and this provides an additional important feature, which allows the antenna to generate higher harmonics of the rotation frequency, and thereby it facilitates radiation at a much higher frequency than the rotational frequency of the magnet. Hence, higher range and more radiated power can be achieved. Here, the performance of proposed mechanical antenna with its PM and frequency multiplication capability is first verified analytically and through numerical simulations using ANSYS Maxwell. Then, a prototype of the antenna is fabricated with the aid of low cost 3-D-printing technology and its performance is measured. Measurements are in good agreement with the simulation predictions.

Energy Scavenging From Low Frequency Vibrations Through a Multi-Pole Thin Magnet and a High-Aspect-Ratio Array Coil

The challenges of developing a micro electromagnetic power generator are to increase the flux density from the thin permanent magnet and reduce the resistance of the micro high-winding-density coil. To overcome these challenges, we propose a novel MEMS power generator for low-frequency-vibration energy harvesting employing a 16-poles thin magnet plate and a high-aspect-ratio spiral micro array coil. Transient magnetic analysis has proved that the multi-pole magnet thin plate (8.9 × 8.9 × t0.5 mm) magnetized by laser assisted heating helps increase the output power from the generator compared with the unidirectional one. The high-aspect-ratio spiral micro array coil (width: 80 µm, thickness: 160 µm, total turns: 144) fabricated by the combination of multilayer SU-8 micro moldings, copper plating, and silver paste screen printing is beneficial for increasing coil density and reducing resistance, thus improving output power. The vibration experiment showed that in terms of no consideration of spring and guideway structure, when the magnet is directly vibrated by an actuator, the induced voltage, generated power, and power density were 1.63 mV, 0.12 µW and 1.03 µW/cm3, respectively at an excitation frequency of 10 Hz with an amplitude of 2 mm. When a 3D-printed cantilever beam was adopted as the spring and guideway structure for the resonant prototype, the counterparts were 8.48 mV, 3.34 µW and 5.22 µW/cm3, respectively at 38 Hz and 2 mm excitation (corresponding to a vibration acceleration peak of 11.6 g).

An analytical solution to the problem of a cup-cored coil located over a conducting plate with a hole

Pot-core coils are utilised in eddy current non-destructive testing (NDT) to detect defects in conducting materials. In this paper, an analytical solution to the problem of a cup-cored coil placed over a three-layer plate with an inner hole is obtained. Using the truncated region eigenfunction expansion (TREE) method, expressions for the magnetic vector potential of the filamentary coil, and final formulae for the impedance of the cylindrical coil, are derived. These formulae make it possible to model conducting magnetic and non-magnetic plates with an internal hole, a surface hole, a subsurface hole and a through hole. The final expressions in a closed form are implemented in MATLAB. The calculation results are verified using finite element method (FEM) models created with COMSOL Multiphysics, Finite Element Method Magnetics (FEMM) and Ansys Maxwell software packages. Very good agreement for the coil impedance components is obtained within the whole studied frequency range of 1 kHz to 100 kHz.

Nonlinear Vibrations of Embedded Nanoplates Under In-Plane Magnetic Field Based on Nonlocal Elasticity Theory

AbstractNonlinear vibrations of the orthotropic nanoplates subjected to an influence of in-plane magnetic field are considered. The model is based on the nonlocal elasticity theory. The governing equations for geometrically nonlinear vibrations use the von Kármán plate theory. Both the stress formulation and the Airy stress function are employed. The influence of the magnetic field is taken into account due to the Lorentz force yielded by Maxwell's equations. The developed approach is based on applying the Bubnov–Galerkin method and reducing partial differential equations to an ordinary differential equation. The effect of the magnetic field, elastic foundation, nonlocal parameter, and plate aspect ratio on the linear frequencies and the nonlinear ratio is illustrated and discussed.

Preparation of ZnO layer for solar cell application

Abstract Zinc Oxide has important role in solar cell as it may enhance the absorption of light into the device and improve the electrical transportation. In the present work, we have used drop casting approach to fabricate the nanocrystalline ZnO film on a glass substrate. Zinc acetate dehydrate and ethanol were used as a starting material and solvent, respectively. The zinc oxide solution was prepared by using a magnetic hot plate with a magnetic stirrer. X-Ray Diffraction (XRD) and UV–Visible were employed to characterize structure and optical properties of the as-deposited film. The XRD results confirm the nanocrystalline structure of the deposited ZnO films. From the UV–visible analysis it was observed that the optical transmittance form the ZnO film is around 80% in the wave length range from 400 nm − 1100 nm and it exhibited the energy band gap to be 3.10 eV.

Modeling of magnetic shape memory alloy plates for pressure sensor application

This article investigates the basis for pressure sensor application based on the magnetic shape memory effect in membranes. Von Karmans nonlinear terms are considered in strain–displacement relationships of thin films, and a new method is presented for solution of large deflections of thin films with arbitrary boundary condition. In this study, the equations of motion of magnetic shape memory alloys are extended. In pressurized membranes, the complex distribution of mechanical stress can cause the martensitic reorientation, which is the underlying mechanism for sensing applications in magnetic shape memory alloys. To examine the obtained model, the governing equations of magnetic shape memory alloys are solved for clamped thin films and results are compared with experimental data. Demonstrating good agreement with experimental data, the presented model can be used for analysis of magnetic shape memory alloy–based smart structures. In this article, the deflection profile of the uniformly loaded thin films is determined with different boundary conditions. Furthermore, the center deflection of magnetic shape memory alloy membrane under different magnetic bias field is simulated. The results of simulation can be used for designing a membrane-based pressure sensor using magnetic shape memory alloys.

Magnetizing Technique for Permanent Magnets in IPM Motor Rotors Using HTS Bulk Magnet

A unique activation technique for permanent Nd-Fe-B magnets which were embedded in the rotors of interior permanent magnet (IPM) motors has been developed as a magnetizing tool with use of high temperature superconducting (HTS) bulk magnet. The experimental and numerical simulation studies were conducted to evaluate the magnetic field-trapping performances of the rotor of air-conditioner compressor in the hybrid-type automobiles. The sample rotor containing six demagnetized permanent magnet plates were exposed in the intense static magnetic fields above the magnetic pole which contained the bulk magnet generating over 4 T. As a result, the sample magnets were perfectly magnetized in the static magnetic field. The precise simulation on the flux distribution in the rotor clarified that it is important to make the flux direction in the rotor core and the easy magnetization axis of PM identical. We convinced this activation technique should enable us to promote the degrees of freedom of motor designing and its processing.

The effect of magnetorheological fluid and aerodynamic damping on the flutter boundaries of MR fluid sandwich plates in supersonic airflow

The present study deals with aeroelastic stability analysis of sandwich plates, containing magnetorheological fluid as the core layer, subjected to the supersonic airflow. The classical plate theory, Hamilton's principle and linear first-order piston theory have been employed to extract the governing equations of motion of the structure. The assumed mode method is used to solve the derived equations and identify the instability region of the sandwich plate. In order to demonstrate validity of the proposed solution, an experiment on a cantilever sandwich plate consisting of polyethylene terephthalate (PET) as the face layers and MR fluid (MRF 132DG) as the core layer is conducted. In this study, the primary attention is focused on the effect of MR fluid and aerodynamic damping on the stability of the MR sandwich plates. Furthermore, the effect of magnetic flux, boundary conditions and plate parameters on the flutter boundaries of the sandwich MR plates are investigated. The results highlight the significance of MR fluid and aerodynamic damping in the flutter suppression of the sandwich plate structures, in a wide range of aerodynamic pressure.

Detection of mixing ratio of binary-mixture particles based on a principle of magnetic separation conducted in a microgravity area

Translation of binary-mixture particles composed of solid CO2 and graphite were observed in an area of static magnetic-field that monotonically decreased in one direction, and magnetic susceptibility χmix of individual particle was determined from the observed relationship between translating velocity and field intensity. Using the variance of χmix value, mixing ratio f of graphite was speedily estimated without consuming the particle; here published χ values of solid CO2 and graphite were used in the estimation, and mass measurement of particle was unnecessary. In the experiment, the translated particles were quietly released in an area of microgravity produced by a short shaft with a height of 180 m (duration< 0.5 s), and the magnetic field was supplied by a pair of small Nd magnetic plate. The detection of f was based on a principle which realized magnetic separation of ordinary diamagnetic and paramagnetic particles at low field intensity. The experimental results confirm the efficiency of the energy conservation law proposed for the field-induced translation at a reduced temperature of T∼200 K. By improving the present apparatus, binary-mixture particles can be magnetically separated according to the sequence of their f value, and a histogram of f is speedily obtained from the population of separated particles. Such histogram will provide direct information to estimate the formation process of the binary-mixture particles, especially in various onsite missions on the terrestrial surface as well in the outer solar system.

Exploring the Effectiveness of a Complex Coating Technique for Use the Smallest Parts of Advanced Powertrain Fuel System

The objective is to develop the complex coating technique with high quality and homogeneity of coating for spherical parts with diameter of 2 ∼ 4 mm and stable mass production shall be secured with consideration of coating material, process and jig design. Silicon oxide-diamond like carbon (SiO-DLC) complex coating chemistry is expected to enhance the high temperature stability as opposed to DLC. Currently, the spherical part is first welded and then assembled with other parts, finally they are coated with DLC. However in this manner, the maximum charging in one coating batch is limited due to the very big size of the whole component which increases cost. Therefore the spherical part is to be coated before welding. Overall, reactive sputtering with high precision fixturing and masking technique resulted in the best overall properties for modern powertrain fuel system. The jig design was optimized with consideration of coating properties (height, width, thickness, inserting distance) and spherical parts were fixed at the jig with magnet plate. Coating material and process were determined with several trials. In conclusion the PVD+PACVD coated parts is developed and coatings with high quality, homogeneity and 30,000 inserting amount are secured. Coated parts are minimum 100 % more durable than non-coated parts.

Research on the Method of Suppressing the End Detent Force of Permanent Magnet Linear Synchronous Motor Based on Stepped Double Auxiliary Pole

Permanent magnet linear synchronous motors have the advantages of high thrust density, high acceleration, high speed, and high efficiency, which are widely used in CNC lathes, lithography machines, rail transportation, etc. In high-speed, high-precision servo control systems, detent force fluctuation caused by end effect can easily cause problems such as speed fluctuation, mechanical vibration and electromagnetic noise, which affect the servo performance of permanent magnet linear synchronous motors. Aiming at the detent force fluctuation caused by the end effect of permanent magnet linear synchronous motor, this paper proposes a stepped double auxiliary pole method. The method has a good suppression effect on the end normal force fluctuation and the end thrust fluctuation, which improves the servo performance of the permanent magnet linear synchronous motor in the high-precision servo system. In the traditional methods of suppressing the fluctuation of end detent force, two common methods are using a magnetic isolation aluminum plate and optimizing the auxiliary pole size. The former needs a magnetic isolation aluminum plate to connect the auxiliary pole and the primary mover. Therefore, it needs to add the connection device to connect those three parts. The connection device complicates the auxiliary pole part and increases manufacturing difficulty. The latter does not change the manufacturing process, but in the early design process, the optimum size of the auxiliary needs to be considered. Compared with these two methods, the one proposed in this paper avoids the complex structure of magnetic isolation aluminum plate, the stepped double auxiliary pole is integrated with the primary mover. Moreover, it has a fixed structure with optimum size. Therefore, the method in the paper does not change the manufacturing process, improves the strength of the initial pole structure, and reduces design period. Finally, the finite element analysis by ANSYS was performed to illustrate the correctness and effectiveness of the method.

Analysis of structure factors affecting suspension force of permanent magnet system with variable magnetic flux path control

To solve the problem of reduction of suspension force of permanent magnet system with variable magnetic flux path control, according to the structure of the system, suspension principle of the permanent magnet system with variable magnetic flux path control and the generation principle of the load torque, the influence of the mechanical structure of the system on the suspension force is analyzed by changing part of parameters of the system structure. The results show that the existence of magnetic isolation plate is the main reason for the decrease of suspension force, the permanent magnet ring can be thickened to 11.91 mm, the annular gap can be reduced to 1 mm, thickness of the “F” shaped magnetizer can be increased to 9 mm to increase the suspension force.

Twisting and tweezing the spin wave: on vortices, skyrmions, helical waves, and the magnonic spiral phase plate

Spin waves are the low-energy excitations of magnetically ordered materials. They are key elements in the stability analysis of the ordered phase and have a wealth of technological applications. Recently, we showed that spin waves of a magnetic nanowire may carry a definite amount of orbital angular momentum components along the propagation direction. This helical, in addition to the chiral, character of the spin waves is related to the spatial modulations of the spin-wave phase across the wire. It, however, remains a challenge to generate and control such modes with conventional magnetic fields. Here, we make the first proposal for magnetic spiral phase plate by appropriately synthesizing two magnetic materials that have different speeds of spin waves. It is demonstrated with full-numerical micromagnetic simulations that despite the complicated structure of demagnetization fields, a homogeneous spin wave passing through the spiral phase plate attains the required twist and propagates further with the desired orbital angular momentum. While excitations from the ordered phase may have a twist, the magnetization itself can be twisted due to internal fields and forms what is known as a magnetic vortex. We point out the differences between both types of magnetic phenomena and discuss their possible interaction.

Extending service life of hall thrusters: recent progress and future challenges

Hall thrusters are widely applied to space propulsion missions because of characteristics such as high specific impulse, great thrust-to-power ratio, high efficiency, and simple structure. Because the scope of space missions using Hall thrusters has expanded, a higher total impulse is required to extend a north–south station-keeping mission to an orbit transfer mission, requiring Hall thrusters with improved lifetimes. Existing research shows that improving the anti-sputtering capacity of the discharge channel and significantly reducing the ion energy and flux bombardment on the wall of the discharge channel are the best measures to improve the lifetime of Hall thrusters. This study summarizes the lifetime restraining factors of Hall thrusters and analyzes the magnetic shielding technology, wall-less technology, aft-magnetic technology, and cylindrical Hall thruster technology to reduce ion energy and flux bombardment on the discharge-channel wall, adopting low-sputtering yield materials to reduce the wall erosion rate, which can improve the lifetime of Hall thrusters. This paper also identifies the limitations of each technology, such as the erosion of magnetic poles (MS) and ceramic cover plates (CHT), larger plume divergence angle (wall-less), hard-to-select aft-magnetic degree (aft-magnetic technology), low compactness, and great porosity (graphite material), providing a reference for further research.

Spin-Wave Resonance in (Fe0.82Ni0.18)/V Nanostructure

We have studied the transmission of millimeter-range electromagnetic waves through (Fe0.82Ni0.18)/V nanostructure. The dependences of the transmission coefficient in the external magnetic field have been measured. The curves have a minimum caused by energy absorption under the ferromagnetic resonance conditions at frequencies 26–35.6 and 37–38 GHz. In a narrow frequency interval near 36 GHz, a complex pattern of resonance phenomena associated with ferromagnetic and spin-wave resonances is observed. We have calculated the field dependence of the transmission coefficient. It has been established that the model of a homogeneous magnetic metal plate used in calculations makes it possible to reproduce some features of resonant changes in the transmission coefficient, which are induced by ferromagnetic and spin-wave resonances.

Design, construction and characterisation of a novel nanovibrational bioreactor and cultureware for osteogenesis

In regenerative medicine, techniques which control stem cell lineage commitment are a rapidly expanding field of interest. Recently, nanoscale mechanical stimulation of mesenchymal stem cells (MSCs) has been shown to activate mechanotransduction pathways stimulating osteogenesis in 2D and 3D culture. This has the potential to revolutionise bone graft procedures by creating cellular graft material from autologous or allogeneic sources of MSCs without using chemical induction. With the increased interest in mechanical stimulation of cells and huge potential for clinical use, it is apparent that researchers and clinicians require a scalable bioreactor system that provides consistently reproducible results with a simple turnkey approach. A novel bioreactor system is presented that consists of: a bioreactor vibration plate, calibrated and optimised for nanometre vibrations at 1 kHz, a power supply unit, which supplies a 1 kHz sine wave signal necessary to generate approximately 30 nm of vibration amplitude, and custom 6-well cultureware with toroidal shaped magnets incorporated in the base of each well for conformal attachment to the bioreactor’s magnetic vibration plate. The cultureware and vibration plate were designed using finite element analysis to determine the modal and harmonic responses, and validated by interferometric measurement. This helps ensure that the vibration plate and cultureware, and thus collagen and MSCs, all move as a rigid body, avoiding large deformations close to the resonant frequency of the vibration plate and vibration damping beyond the resonance. Assessment of osteogenic protein expression was performed to confirm differentiation of MSCs after initial biological experiments with the system, as well as atomic force microscopy of the 3D gel constructs during vibrational stimulation to verify that strain hardening of the gel did not occur. This shows that cell differentiation was the result of the nanovibrational stimulation provided by the bioreactor alone, and that other cell differentiating factors, such as stiffening of the collagen gel, did not contribute.

Effect of the Number of ME Elements on Capture Rate of a Small Number of Pathogens in the Prototype of Phage Filter with a Comparison of Rocking Method

Foodborne illness is a frequent public health problem because there is potential for food to be contaminated by pathogens at any point from farms to the dinner tables. Each year, the cost of foodborne illness in the U.S. is enormous. The direct and indirect costs associated with foodborne illness are more than $15.6 billion per year. For rapid detection of foodborne pathogens, Magnetoelastic (ME) biosensor is one of the methods to detect pathogens on food surface and liquids. As the multistate outbreak caused by Romaine lettuce contamination in 2018, current microbiological testing methods, required by Food and Drug Administration (FDA)’s Bacteriological Analytical Manual (BAM), shows shortages. According to the requirement, a new method, named 3D bio-molecular filter, was developed to capture, concentrate, and isolate a small number of pathogens in large volume of liquid streams. The filter consists of ME filter elements, a pair of permanent magnetic plates, and testing glass tube. ME filter elements are magnetically held and arrayed in a testing glass tube. The target pathogen in a large volume of liquid will be capture by ME filter elements when a large volume of liquid passes through. A prototype of a compact edition was developed in this paper to support this method. The device consists of high magnetic plates, which provide uniform high magnetic force to hold ME filter elements, and a square glass tube to pass through the liquid with target pathogen. In this work, E2 phage is immobilized on ME filter elements to capture, concentrate, and isolate Salmonella Typhimurium in processing water. Two different methods to capture Salmonella, rocking method and 3D biomolecular filter method, are compared. The capture rate and effects of the number of ME filter elements on Salmonella capture efficiency will be discussed.

Sensitive current sensor based on Fe73.5Cu1Nb3Si13.5B9/Pb(Zr,Ti)O3 composite with a tunable magnetic flux concentrator.

This paper presents a sensitive current sensor based on magnetoelectric composite Fe73.5Cu1Nb3Si13.5B9/Pb(Zr,Ti)O3 with a tunable magnetic concentrator. The concentrator with a movable magnetic plate can enable the DC bias magnetic field (Hdc) to become tunable to meet the needed optimal Hdc of Fe73.5Cu1Nb3Si13.5B9/Pb(Zr,Ti)O3 and to reduce the magnetoresistance of the magnetic loop. Furthermore, the sensor's resonant frequency is adjustable to improve the sensitivity for measuring current at different frequencies. From experiments, the proposed sensor has a sensitivity of ∼246.71 mV/A and a linearity of ∼0.98% at 50 Hz current. The results indicate that the proposed current sensor is ideally suited for current-monitoring.

Photobiomodulation by dual-wavelength low-power laser effects on infected pressure ulcers.

The aim of this study was to evaluate the effects of photobiomodulation (PBM) by dual-wavelength low-power lasers on the healing and bacterial bioburden of pressure ulcer (PU) models. Twenty-five male Swiss mice were divided into five equal groups. Ischemia reperfusion cycles were employed to cause PU formation by the external application of magnetic plates. Immediately after wounding, a suspension of Pantoea agglomerans was applied at the base of all the wounds of the infected groups, using a calibrated pipette. PBM (simultaneous emission at 660 and 808nm, 142.8J/cm2, in continuous wave emission mode) was applied to the PUs for 14 sessions. The animals were euthanized 14days after PU induction, and their tissues were analyzed for wound contraction and reepithelialization, epidermis thickness, bacterial survival, and IL-1β and IL-10 mRNA level evaluations. The PU areas appeared larger in the mice from the infected groups than in those in the laser group 4days after PU induction and presented incomplete reepithelialization 14days after PU induction. However, the PBM accelerated the wound healing in the infected + laser group compared with the infected group 11 and 14days following the PU induction. The infected and irradiated PUs exhibited a thinner neo-epidermis than those in the infected group, and the bacterial survival decreased in the laser group; the relative expression IL-1β mRNA levels demonstrated an increasing tendency while the relative expression IL-10 mRNA levels demonstrated a decreasing tendency in the infected + laser and laser groups. These results suggest that PBM improves healing by killing or inhibiting bacteria in PUs as well as by accelerating the wound healing, resulting in tissue repair.

Phthalates and Bisphenol-A Determination and Release from Different Beverage Plastic Containers by Dispersive Liquid-Liquid Microextraction and GC-IT/MS Analysis

Phthalates and bisphenol-A are molecules widely used in packaging because they increase the plastic malleability and workability but they show the tendency to migrate or dissociate from plastics. Recently, researchers raised the alarm to have found their traces in water samples of plastic bottles left at high outdoor temperatures for a long time. The paper would like to show a simple, sensitive, and reproducible method for the simultaneous determination of phthalates and bisphenol-A in drinking water, based on the dispersive liquid-liquid microextraction followed by gas chromatography-mass spectrometry analysis. The dispersion is favored by means of ultrasonic bath and stirring magnetic plate, without dispersive solvent. The method presents an average R2 0.993 in the range 10–5000 ng mL-1, a limit of detection below 1.2 ng mL-1, and a limit of quantification below 7.7 ng mL-1. The release of such compounds from different beverage containers (6 plastic bottles, 6 canteens, and 3 newborn feeding bottles) has been analyzed. The release kinetics from the bottles are studied over 2 months, whereas over 6 h for the other containers. Only 2 compounds have been found in a plastic bottle and in a canteen bottle, with concentrations ranging between 24 and 117 ng mL-1.