Magnitude Of Magnetic Flux Research Articles

Design, Simulation and Fabrication of a Novel Phage Filter for Pathogens Testing from Large Volumes of Water

In this paper, a phage filter has been developed to capture, concentrate and isolate small numbers of pathogens from large volumes of water. The phage filter consists of a magnetized filter frame and hundreds of phage-coated filter elements made of a magnetostrictive material. ANSYS Maxwell magnetostatic simulations have been conducted on filter designs. A prototype filter frame in the size of 2″ has been made of a PMMA pipe and Permalloy 80 wire. Two permanent magnets were used to generate a uniform magnitude of magnetic flux density and a desired direction of flux vectors to align and hold a high density of filter elements. The filter elements in the size of 4 mm × 0.8 mm × 30 µm were made of Metglas 2826MB ribbon by mechanically dicing. The experimental results were compared with the simulation models to improve the filter design.

Improved magnetorheological honing process for nanofinishing of variable cylindrical internal surfaces

ABSTRACTImproved magnetorheological honing process is developed for nanofinishing of variable cylindrical internal surfaces with better surface integrity. In the present work, finishing performance of existing magnetorheological honing process is enhanced. The present improved process consists magnetorheological honing tool having curved permanent magnet end surfaces. When magnetic field is analyzed using Ansoft Maxwell, the improved magnetorheological honing process results in uniform and higher magnitude of magnetic flux density over its magnetic tool curved end surfaces as compared to the tool having magnetic flat end surfaces. Therefore, an improved magnetorheological honing process has been developed with tool having curved permanent magnet end surfaces. During experimentation, surface roughness values Ra, Rq, and Rz get decreased by 76.28%, 76.67%, and 75.20%, respectively, with improved magnetorheological honing tool having curved end magnetic surfaces, while 47.97%, 46.24%, and 47.08% decreased with tool having flat end magnetic surfaces in same 60 minutes of finishing time. This results in enhancement of finishing performance of the present improved magnetorheological honing process in terms of reduced finishing time and ability to produce good surface integrity. Hence, the present improved magnetorheological honing process performance with tool having curved end magnetic surfaces is found as comparatively better than the finishing tool having flat end permanent magnetic surfaces.

A novel high-density power energy harvesting methodology for transmission line online monitoring devices.

This paper presents a novel energy-harvesting model which takes the primary current, secondary turns, dimension, the magnitude of magnetic flux density B, and the core loss resistance into consideration systematically. The relationship among the potential maximum output power, the dimension of energy harvesting coil (EHC), the load type of EHC, and the secondary turns is predicted by theoretical analysis and further verified by experiments. A high power density harvester is also developed and tested. It is shown that the power density of this novel harvester is 0.7 mW/g at 10 A, which is more than 2 times powerful than the traditional ones. Hence, it could lighten the half weight of the harvester at the same conditions.

Improvement of uniformity in a weakly magnetized inductively coupled plasma

Magnetic fields are applied to inductively coupled plasma (ICP) to achieve high plasma densities using electromagnets. If the magnetic fields are set up such that the magnitude of magnetic flux density on the substrate decreases with both radial and axial distances from the substrate’s center (here after referred to as M-ICP-A), the plasma density increases by 237% compared with that for ICP although the non-uniformity of the plasma density for M-ICP-A (11.1%) is higher than that for ICP (10.9%). As the rate of decrease in the magnitude of magnetic flux density on the substrate increases both radially and axially, the non-uniformity in the plasma density increases further. The increase in the non-uniformity for M-ICP-A was confirmed to arise from the flute instability. To suppress the flute instability, we arranged the magnitude of magnetic flux density on the substrate to increase with increasing distance from the substrate center both radially and axially (here after referred to as M-ICP-V). In this configuration, plasma fluctuations were not observed, hence the plasma density non-uniformity was lowered to 8.1%, although the measured plasma density was higher than that for M-ICP-A. The oxide etch-rate non-uniformity in M-ICP-V (2.5%) was also lower than that for ICP (5.2%) or that for M-ICP-A (21.4%).

Torque Ripple Reduction in an Axial Flux High Temperature Superconducting Motor

The design, construction, and operation of superconducting rotatory machines in an axial flux configuration are strongly dependent on the ability to reduce torque ripple. A new concept is presented in order to maximize the output power optimizing the magnetic flux density within the air gap of a three-phase fully superconducting induction motor. The machine is designed on a basis of bilateral stators distributed around a central rotor. The optimal distribution of magnetic flux and the minimization of torque ripple are resulting from an adequate distribution of motor phases, number of rotor bars, and choice of air-gap thickness. The magnitude of magnetic flux in the air gap is obtained by means of finite-element analysis, and some derived parameters are compared to experimental results. Then, the impact of the design on torque magnitude and torque ripple is discussed.

Simulation of the electron beam in a TEM as a charged particles flux

The behavior of an electron beam in a TEM was simulated as a function of accelerating voltage, excitation current of the lenses and relative permeability of the pole pieces, by the software COMSOL Multiphysics version 4.2a. The results showed a low vertical speed of stray electrons, which were filtered by the diaphragms. Moreover, the plots displayed an increase in the magnetic flux density with the increase of the magnetic permeability of the pole pieces. Furthermore, the outcome indicated that a boost in the magnetic flux density increased the angle of divergent electrons and reduced their vertical speed. Finally, the observations illustrated that the number of electrons at the inlet does not affect the beam overall behavior nor the magnetic flux density magnitude.

Selective handling of droplets in a microfluidic device using magnetic rails

Droplet microfluidics is currently undergoing an explosive development due to its ability to compartmentalize samples in picolitre to nanolitre volumes, transport them without dispersion and perform high-throughput analysis. The precise manipulation of single droplets, however, still requires complex chips, such as microelectrode arrays, or equipment, such as laser-based sorting. We report here a very simple proof of concept of an innovative and active technology which allows the individual manipulation of single droplets. This technology combines ferromagnetic rails and magnetic nanolitre droplets. Ferromagnetic rails are used to locally create magnetic potential wells. When the field is turned OFF, the hydrodynamic drag force transports the magnetic droplets according to the flow velocity profile. By switching ON the magnetic field, droplets experience a magnetic force that affects their trajectory when passing over the magnetized rail. The combination of the drag force exerted by the oil flow and the magnetic force resulting from the magnetized rail leads to a deflection force that guides the droplet along the rail, thus imposing a deterministic trajectory. The magnetic rails networks offer a spatially and temporally addressable guidance and sorting of individual magnetic droplets by synchronizing field activation and droplets positions. Numerical simulations were performed to evaluate spatial distribution of both drag and magnetic forces within the microdevice. The influence of different parameters such as magnetic flux density magnitude, flow rate and orientation of the rail has been investigated. Finally, selective droplet sorting, parking and merging were demonstrated and the monitoring of parallelized enzymatic reactions was performed.

Periodical Oscillation Phenomena Observed in Salt-Water Oscillator Experiments under Small Gravity Conditions

We examined periodical oscillation phenomena that were observed during salt-water oscillator experiments under a small gravity condition. This condition was realized by situating a lower-density gadolinium chloride (GdCl 3) aqueous solution on a higher-density sodium chloride (NaCl) aqueous solution and applying a downward magnetic force. The GdCl 3 solution concentration was 0.15 mol/kg (density ρ=1.03×103 kg/m 3), and the NaCl concentration was varied to (A) 4.35 mol/kg (ρ=1.15×103 kg/m 3), (B) 3.79 mol/kg (ρ=1.12×103 kg/m 3), and (C) 2.49 mol/kg (ρ= 1.09×10 3 kg/m 3). The magnitude of magnetic flux density was varied from 0 to 4.00 T. As the magnetic flux density grew larger, the GdCl 3 solution was pulled downward by the magnetic force, and upward and downward flows were generated simultaneously at the orifice. These flows were accompanied by a periodical, locally thickened part. The thickened part was only observed when the magnetic force magnitude was small in cases (A) and (B). This flow pattern was not observed in case (C), in which a conventional salt-water oscillation was induced instead (C). In this paper we discuss new experimental results in which the oscillation cycles in cases (A) and (B) are strongly associated with the magnitude of the magnetic force and the density difference in the biphase solutions.

Variation of the solar magnetic flux spectrum during solar cycle 23

By using the unique database of Solar and Heliospheric Observatory/Michelson Doppler Imager full disk magnetograms from September 1996 to January 2011, covering the entire solar cycle 23, we analyze the time‐variability of the solar magnetic flux spectrum and study the properties of extended minimum of cycle 23. We totally identify 11.5 million magnetic structures. It has been revealed that magnetic features with different magnetic fluxes exhibit different cycle behaviors. The magnetic features with flux larger than 4.0×1019 Mx, which cover solar active regions and strong network features, show exactly the same variation as sunspots; however, the remaining 82% magnetic features which cover the majority of network elements show anti‐phase variation with sunspots. We select a criterion that the monthly sunspot number is less than 20 to represent the Sun's low activity status. Then we find the extended minimum of cycle 23 is characterized by the long duration of low activity status, but the magnitude of magnetic flux in this period is not lower than previous cycle. Both the duration of low activity status and the minimum activity level defined by minimum sunspot number show a century period approximately. The extended minimum of cycle 23 shows similarities with solar cycle 11, which preceded the mini‐maxima in later solar cycles. This similarity is suggestive that the solar cycles following cycle 23 are likely to have low activity.

Numerical Simulation of Fluid Flow in a Round Bloom Mold with In-Mold Rotary Electromagnetic Stirring

In this article, an electromagnetic field simulation and a flow analysis model are performed to describe the three-dimensional electromagnetic field distribution and the electromagnetically driven flow characteristics in a round-bloom mold with a low-frequency in-mold rotary electromagnetic stirrer. The interaction between the induced flow and the inertial impinging jet from a straight-through submerged entry nozzle (SEN) of the caster is considered. The effects of stirrer current and frequency on the electromagnetic field and the flow in the round-bloom mold are investigated, and a strategy to optimize the stirring parameters is proposed. The results show that the distributions of magnetic flux density and electromagnetic force magnitude are nonuniform in a three-dimensional electromagnetic stirring (EMS) configuration. There exists a significant axial induced component of electromagnetic force. The flow in the in-mold EMS system is characterized by a dominant swirling movement at the transverse sections, coupled with the recirculating flows in the axial direction. An upper recirculation zone and a lower recirculation zone with the reverse melt flowing are found near the strand wall at the axial location close to the middle of the stirrer, and another recirculation zone is formed due to the interference of the induced flow with the jet from SEN. The meniscus surface has a swirl flow, and the meniscus level rises near the bloom strand wall and sinks around the SEN wall. All of these flow features are closely associated with metallurgical performances of the in-mold rotary stirrer. With the increase of stirring current and the decrease of frequency, the magnetic flux magnitude increases. There is an optimum frequency to obtain a peak of electromagnetic force magnitude and maximum tangential velocity. For a mold rotary EMS system, to determine the optimum stirring intensity, it is necessary to make a compromise between a larger tangential velocity and a relatively quiescent meniscus surface.

Study on Magnetic Field for Navigation of Articulated Needle

When the magnetic articulated needle is inserting, the magnetic field which can produce the magnetic force of variable direction is required in order to implement the magnetic navigation in three-dimensional space. The paper puts forward a method for generating three-dimensional magnetic field based on the rotaion and translation of multiple permanent magnets. In this method, multiple permanent magnets form a circumference array. Every permanent magnet can rotate around the spin axis of itself in the array plane and move along the direction vertical to the array plane. Thus, in the array center, a magnetic fied which can produce the uniform magnetic flux density is obtained. The direction of magnetic fied is controllable in three-dimensional space and the magnitude of magnetic flux density is variable in a certain range. The simulations by ANSYS verify the feasibility of the proposed method.

Avoiding singularities in recurrent neural control for induction motors

In this paper, a master–slave synchronization scheme based on parameter identification is proposed to overcome the controller singularity problem that appears when linearization-like techniques are applied in indirect adaptive neural control, like Neural Block Control (NBC). Such a synchronization strategy requires an identifier-like recurrent neural network and an adaptive law to update the neural weights. The proposed adaptive law prevents both, specific adaptive weights zero-crossing and the ‘parameter drift’ phenomenon. NBC consists of two tasks; synchronizing an identifier-like recurrent neural network (slave) with the plant (master) and controlling the system based on the slave model. The effectiveness of the synchronization law is tested using NBC for controlling the angular speed and magnetic flux magnitude of an induction motor. Usingit a priori knowledge about the real plant, a high-order recurrent neural network is proposed as the slave system. Based on the slave neural model, a discontinuous control law is derived, which combines Block Control and Sliding Modes. NBC with the proposed synchronization strategy is tested via simulations, comparing results with a standard parameters adaptive law. Copyright © 2011 John Wiley & Sons, Ltd.

Observation of Magnetization Distribution in Soft Underlayer of Perpendicular Magnetic Recording Media by Electron Holography

The magnetic properties of the soft underlayer (SUL) of perpendicular recording media affect the recording performance significantly. We visualized and quantified the distribution and magnitude of magnetic flux in the recording layer and SULs of perpendicular recording media by electron holography. Pseudo-SULs with different permeability were deposited on the slider of perpendicular recording heads. The SUL with higher permeability produced higher write magnetic flux (B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> ) as compared to the SUL with lower permeability, which results higher overwrite performance. Further, the magnitude profile of B <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> in the SUL thickness direction was different for the two SULs; the magnitude of magnetic flux in SUL is related to the occurrence of adjacent track erasure.

Observing the Magnetization Distribution in the Pseudo Soft Underlayer of Perpendicular Magnetic Recording Media by Electron Holography

We visualized the magnetic flux density of the cross track direction in the pseudo soft underlayer (SUL) of perpendicular magnetic recording media. We deposited a pseudo-SUL on the fabricated slider of a perpendicular magnetic recording head, and used electron holography to visualize and quantify the magnetic flux magnitude and distribution in the pseudo-SUL. We observed the pseudo-SUL magnetized by the write field from the writer pole tip. The magnetic flux magnitude and full width at half maximum increased with an increasing write field. We observed a correspondence between an actual recording situation and the electron holography observation.

Solar-Cycle Characteristics Examined in Separate Hemispheres: Phase, Gnevyshev Gap, and Length of Minimum

Research results from solar-dynamo models show the northern and southern hemispheres may evolve separately throughout the solar cycle. The observed phase lag between the hemispheres provides information regarding the strength of hemispheric coupling. Using hemispheric sunspot-area and sunspot-number data from Cycles 12 - 23, we determine how out of phase the separate hemispheres are during the rising, maximum, and declining period of each solar cycle. Hemispheric phase differences range from 0 - 11, 0 - 14, and 2 - 19 months for the rising, maximum, and declining periods, respectively. The phases appear randomly distributed between zero months (in phase) and half of the rise (or decline) time of the solar cycle. An analysis of the Gnevyshev gap is conducted to determine if the double-peak is caused by the averaging of two hemispheres that are out of phase. We confirm previous findings that the Gnevyshev gap is a phenomenon that occurs in the separate hemispheres and is not due to a superposition of sunspot indices from hemispheres slightly out of phase. Cross hemispheric coupling could be strongest at solar minimum, when there are large quantities of magnetic flux at the Equator. We search for a correlation between the hemispheric phase difference near the end of the solar cycle and the length of solar-cycle minimum, but found none. Because magnetic flux diffusion across the Equator is a mechanism by which the hemispheres couple, we measured the magnetic flux crossing the Equator by examining magnetograms for Solar Cycles 21 - 23. We find, on average, a surplus of northern hemisphere magnetic flux crossing during the mid-declining phase of each solar cycle. However, we find no correlation between magnitude of magnetic flux crossing the Equator, length of solar minima, and phase lag between the hemispheres.

Sinusoidal Behavior of a Dipole Magnetization for Position Sensing Applications

Magnetic position sensing is used in many applications, especially in environments where the sensor is subjected to vibrations, temperature variations, or high humidity. The Hall effect position sensors, due to their simplicity and versatility, are elegant solutions to many application requirements, although the disadvantage are a maximum operating temperature of about 175°C, airgap operation limited to no greater than about 2.5mm and sensitivity to external pressure acting on the sensor package [1]. The need for sensors is growing, for example, in automotive applications, where, in engine control applications, the number of sensors used will increase from about ten in 1995, to more than thirty in 2010 [2]. Magnetic position sensing is based on the measurement of the magnetization pattern of a di-pole, or multi-pole, magnetic ring using a Hall sensor, which shows the variation of the magnetic field density along the circumference of the ring. The ideal magnetic behavior of the permanent magnet ring has a sinusoidal hall-sensor output, which makes it suitable for sensing applications. However, practical measurements show that the sinusoidal behavior sometimes occurs with errors. This paper describes the investigation of these errors by means of mismatch in the magnetization pattern of the di-pole permanent magnet (PM)-ring. The PM-ring yields that the developed magnetic flux is purely sinusoidal, where the geometrical dimensions of the PM-ring influence the magnitude Hall-sensor output voltage level. A deviation in the sinusoidal behavior is influenced by a non-ideal PM-ring by means of varying magnetic flux density magnitude and orientation.

Dynamic Brain Activation Patterns for Face Recognition: A Magnetoencephalography Study

The present study used magnetoencephalography (MEG) to investigate the spatiotemporal profile of neurophysiological activity associated with recognition of recently encountered human faces in seventeen healthy right-handed adults. Activity sources modeled as instantaneous equivalent current dipoles were found in ventral occipito-temporal regions during the early stages of stimulus processing and in lateral temporal cortices during later stages. Hemispheric asymmetries in regional activity were restricted to ventral occipitotemporal areas. The magnitude of magnetic flux originating in these regions was greater in the right hemisphere during the first 350 ms post-stimulus onset. In addition, the duration of neurophysiological activity was greater in the right hemisphere after 600 ms post-stimulus onset. The results indicate right hemisphere predominance in the degree of engagement of neurophysiological processes involved in both the pre- and post-recognition phases of face processing.

Adaptive Finite Element Analysis Using Dynamic Bubble System Taking into Account Magnitude of Magnetic Flux Density

In this paper, a new adaptive method for finite element analysis using dynamic bubble system taking into account magnitude of magnetic flux density is proposed. The error estimation is performed according to the Zienkiewicz and Zhu error norm estimator and using improved solution of the problem instead of the unknown exact values which is both straightforward and computationally cheap. Mesh density is easily controlled by changing the radii of node bubbles that describe the outline of the analysis region according to the previously performed error estimation. The proposed method produce adaptively generated meshes independent of the initial coarse mesh. The final mesh satisfies the user defined relative error of the solution and takes into account the magnetic flux density distribution. The effectiveness of the proposed adaptive method is investigated for 2-D and 3-D magnetostatic field computations. The obtained results show that the proposed method is suitable and very promising for adaptive electromagnetic field analysis.

Power line magnetic flux density quick estimation plots

This paper introduces the method of quick estimation plots to characterize the magnetic flux density associated with power lines. The largest value of the magnetic flux density magnitude and its location along a lateral traverse at or close to ground level can be determined using these quick estimation plots. The plots are available for single circuit (horizontal, vertical and delta) and double circuit (super bundle and low reactance) three phase power line configurations, assuming balanced, symmetrical three phase currents.

In situ measurement of magnetoresistive head transfer curves on a spin stand tester (abstract)

An in situ method of measuring the magnetoresistive (MR) head transfer curves directly on a spin-stand tester is presented. We define the MR head transfer curve as the MR output voltage amplitude versus the magnitude of magnetic flux arising from transitions. To obtain adjustable transition flux magnitude on a spin stand tester, isolated transitions are recorded with write current level varied from zero to saturation. Adjusting the write current level varies the magnetization level difference across a recorded transition, thereby varying the magnetic flux generated by the transitions. At each write current level, the magnitude of the magnetic flux arising from the recorded transitions is measured by the thin film (TF) writer whose response is linear with respect to magnetic flux. At the same time, the MR head output is also measured. By plotting the MR head output as a function of the TF head output, a transfer curve is obtained. The experiments were performed using a film disk (Disk A) of MrT=2 memu/cm2, and a biased MR head. In order to confirm the validity of this method, a thin film disk (Disk B) with magnetic layer thickness gradually varying from one portion of the disk to another was fabricated by adding a shutter in the film deposition process. The MrT value of the film disk fabricated changes from zero to 2 memu/cm2 along a recording track within a revolution. Figure 1 shows the measured outputs of both the MR and TF writer as a function of write current using Disk A. At high write current level, the normalized MR output becomes smaller than the TF output due to head nonlinearity. The MR output as a function of TF output gives the MR head transfer curve. An MR transfer curve can also be measured by the quasistatic dc applied field method, and it has been shown to have good agreement with the medium transition excitation method.1 Using the three different methods, namely the varying write current, varying MrT, and varying dc-field methods, three MR transfer curves are measured and plotted in Fig. 2. Comparing the three transfer curves, excellent agreement is found among these methods in terms of the shape of the transfer curve which reflects amplitude asymmetry and nonlinearity.