Influence of different magnetic forces on the effect of colonic anastomosis in rats

BACKGROUND Despite much work having been conducted on magnetic compression anastomo-sis(MCA)in the digestive tract,there are no reports on the influence of magnetic force on the anastomosis.AIM To investigate the effect of different magnetic force magnets on the MCA of the digestive tract.METHODS Two groups of magnets of the same sizes but different magnetic forces were designed and produced.A total of 24 Sprague-Dawley rats were randomly assigned into two groups(powerful magnet group and common magnet group),with 12 rats in each group.Two types of magnets were used to complete the colonic side-to-side anastomosis of the rats.The operation time and magnet discharge time were recorded.The anastomotic specimens were obtained 4 wk after the operation and then the burst pressure and diameter of the anastomosis were measured,and the anastomosis was observed via the naked eye and subjected to histological examination.RESULTS The magnetic forces of the powerful and common magnet groups at zero distance were 8.26 N and 4.10 N,respectively.The colonic side-to-side anastomosis was completed in all 24 rats,and the operation success rate and postoperative survival rate were 100%.No significant difference was noted in the operation time between the two groups.The magnet discharge time of the powerful magnet group was slightly longer than that of the common magnet group,but the difference was not statistically significant(P=0.513).Furthermore,there was no statistical difference in the burst pressure(P=0.266)or diameter of magnetic anastomosis(P=0.095)between the two groups.The gross specimens of the two groups showed good anastomotic healing,and histological observation indicated good mucosal continuity without differences on healing.CONCLUSION In the rat colonic side-to-side MCA model,both the powerful magnet with 8.26 N and the common magnet with 4.10 N showed no significant impact on the anastomosis establishment process or its effect.

Magnetic Field Curves and Magnetic Equipotential Surfaces around Crossing Electrical Wires Replacing Classical Magnetic Field Lines

This article is based on a recent model specifically defining magnetic field values around electrical wires. With this model, calculations of field around parallel wires were obtained. Now, this model is extended with the new concept of magnetic equipotential surface to magnetic field curves around crossing wires. Cases of single, double, and triple wires are described. Subsequent article will be conducted for more general scenarios where wires are neither infinite nor parallel.

Harmonics in the Squirrel Cage Induction Motor,Analytic Calculation Part Ⅱ:Synchronous Parasitic Torques,Radial Magnetic Forces

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forces have been discussed in great detail in the literature,but always separately,for a long time.However,systematization of the phenomenon still awaits.Therefore,it is worth summarizing the completeness of the phenomena in a single study–with a new approach at the same time-in order to reveal the relationships between them.The role of rotor slot number is emphasized much more than before.New formulas derived for both synchronous torques and radial magnetic forces are used for further investigation.It will be shown that both phenomena in subject must be treated together.Formulas will be provided to take into account attenuation.Design guide will be provided to avoid dangerous rotor slot numbers.It will be shown that the generation of synchronous torques and radial magnetic forces do not depend–in this new approach-on the slot combination,but on the rotor slot number itself.

Magnetic domain structures in ultrathin Bi_(2)Te_(3)/CrTe_(2) heterostructures

Chromium tellurium compounds are important two-dimensional van der Waals ferromagnetic materials with high Curie temperature and chemical stability in air,which is promising for applications in spintronic devices.Here,highquality spin-orbital-torque(SOT)device,Bi_(2)Te_(3)/CrTe_(2)heterostructure was epitaxially grown on Al_(2)O_(3)(0001)substrates.Anomalous Hall measurements indicate the existence of strong ferromagnetism in this device with the CrTe_(2)thickness down to 10 nm.In order to investigate its micromagnetic structure,cryogenic magnetic force microscope(MFM)was utilized to measure the magnetic domain evolutions at various temperatures and magnetic fields.The virgin domain state of the device shows a worm-like magnetic domain structure with the size around 0.6μm-0.8μm.Larger irregular-shape magnetic domains(>1μm)can be induced and pinned,after the field is increased to coercive field and ramped back to low fields.The temperature-dependent MFM signals exhibit a nice mean-field-like ferromagnetic transition with Curie temperature around 201.5 K,indicating a robust ferromagnetic ordering.Such a device can be potentially implemented in future magnetic memory technology.

Ion and electron motions in the outer electron diffusion region of collisionless magnetic reconnection

Two-dimensional particle-in-cell simulations are performed to study the coupling between ion and electron motions in collisionless magnetic reconnection.The electron diffusion region(EDR),where the electron motions are demagnetized,is found to have a two-layer structure:an inner EDR near the reconnection site and an outer EDR that is elongated to nearly 10 ion inertial lengths in the outflow direction.In the inner EDR,the speed of the electron outflow increases when the electrons move away from the X line.In the outer EDR,the speed of the electron outflow first increases and then decreases until the electrons reach the boundary of the outer EDR.In the boundary of the outer EDR,the magnetic field piles up and forms a depolarization front.From the perspective of the fluid,a force analysis on the formation of electron and ion outflows has also been investigated.Around the X line,the electrons are accelerated by the reconnection electric field in the out-of-plane direction.When the electrons move away from the X line,we find that the Lorentz force converts the direction of the accelerated electrons to the x direction,forming an electron outflow.Both electric field forces and electron gradient forces tend to drag the electron outflow.Ion acceleration along the x direction is caused by the Lorentz force,whereas the pressure gradient force tends to decelerate the ion outflow.Although these two terms are important,their effects on ions are almost offset.The Hall electric field force does positive work on ions and is not negligible.The ions are continuously accelerated,and the ion and electron outflow velocities are almost the same near the depolarization front.

The Pairing Analysis Improvement of Magnetized Structure in Electromagnetic Bulging Process in Case of Tube with Field Shaper

In the current practical science, the accuracy in the formability of metal alloys being the goal when using electromagnetic forming (EMF) technology, which is a high-speed processing technology that uses Lorentz forces to achieve plastic deformation of sheet metal;according to the previous analysis, the results have shown that in most cases, the Lorentz force acting on the workpiece (metal) is not uniform, there are uneven axial deformations of the metal plates which prevent the rapid advancement of today’s technology. In this article, we presented some advanced analyzes which will lead us to improve the technical solution for the problems of non-uniform axial deformations of the metals in the traditional tube electromagnetic forming technology (EMF). A field shaper is used as a practical forming tool to influence the magnetic field and magnetic pressure distribution, thereby improving the forming ability and result during the electromagnetic forming (EMF) process and we see that induced eddy current control is realized by changing the structural parameters of the magnetic field shaper;which improves the strength and controllability of the magnetic force that acts on the workpiece;thereby a greater radial magnetic pressure can be achieved with field shaper than the case without it;the field shaper regulates the electromagnetic force, the distribution of the magnetic pressure decreases, and the uniform force area of the tube increases which effectively enhances the uniform range of the pipe electromagnetic bulging and the electromagnetic induction coupling between the coil and the metallic workpiece is generally required to produce the Lorentz forces. Using COMSOL Multiphysics® simulation software helped us to accurately represent the real world, simulating multiple physical effects that happened in this model during the process.

Magnetic force distribution and deformation law of sheet using uniform pressure electromagnetic actuator

The distribution of magnetic forces and current on sheet and coil was analyzed in detail according to the structural parameter of the coil which was invalid.The result shows that the current direction based on simulation result agrees with the principles of uniform pressure electromagnetic actuator.The reason for coil failure was proposed.Then the magnetic forces on the sheet were input into an explicit finite element software ANSYS/LS-DYNA to analyze the deformation law of the sheet.

Vibration analysis of maglev three-span rigid frame bridge considering magnetic force

The dynamic interaction between the maglev vehicle and the three-span rigid frame bridge is discussed. With the consideration of magnetic force, the interaction model is developed. Numerical simulations are performed to study the dynamic characteristics of the bridge during vehicle movement along the bridge. The results show that a reasonable value of the linear stiffness ratio of columns to beams is between 2. 0 and 3.0. The dynamic responses of the bridge are aggravated with the decrease in bending rigidity and the increase in vehicle speed and the span ratio of the bridge. It is suggested that a definite way is to control impact coefficients and acceleration in the dynamic design of the bridge. It is unsuitable to adopt the moving load model and the moving mass model in the design. The proposed results can serve in the design of high-speed maglev three-span rigid frame bridges.

Effect of electromagnetic force on melt induced by traveling magnetic field

A new apparatus was designed to measure the electromagnetic force and a computational study of the traveling magnetic field(TMF)and its application to the Ga-In-Sn melt(with low melting point),then the forces on Al,Mg,and Li melt,were simulated. The result show that the electromagnetic force on the melt increases linearly with the increasing length of the melt in the TMF.The TMF-induced Lorentz force increases with increasing frequency,and then decreases.The maximum value is obtained when the current frequency is 160 Hz,over that frequency the force decreases rapidly.When the iron-core is activated,the force increases when the melt closes to the iron-core.The Lorentz forces have inversely-proportional relationships with the electrical resistivity,the dfx/dρdecreases and the dfy/dρincreases with the increasing electrical resistivity(df/dρis the slope of the Lorentz force profile).

Magnetic Microstructures of 2∶17 Type Sm(Co,Fe,Cu,Zr)_z Magnets Detected by Magnetic Force Microscopy

The magnetic microstructures of 2：17 type Sm （Co, Fe, Cu, Zr）z magnets were detected by magnetic force microscopy. Comparing the microstructures of the specimens eoated with and without Ta thin film before and after heat-treatment, it is found that： （a） as a protection layer, Ta coating layer about 20 nm thick can effectively restrain Sm volatilization under high temperature; （b） the stress built in the 2.17 type Sm-Co magnets during specimen preparation only affects some local parts of the domain structures; （c） the magnetic microstructures vary largely for specimens heat-treated at high temperature without Ta film coating due to Sm volatilization. In addition, by comparing with high coercivity Fe-Pt point tips, it is found that the Co-Cr thin-film tips are not suitable for detecting the magnetic microstructures of strong permanent magnets.

Modeling Density and Anisotropy of Energetic Electrons Along Magnetic Field Lines

The electromagnetic wave growth or damping depends basically on the number density and anisotropy of energetic particles as the resonant interaction takes place between the particles and waves in the magnetosphere. The variance of both the number density and anisotropy along the magnetic field line is evaluated systematically by modeling four typically prescribed distribution functions. It is shown that in the case of ＂the positive anisotropy＂ （namely, the perpendicular temperature T⊥ exceeds the parallel temperature T｜｜）, the number density of energetic electrons always decreases with the magnetic latitude for a regular increasing magnetic field and the maximum wave growth is therefore generally confined to the equator where the resonant energy is minimum, and the number density is the largest. However, the ＂loss-cone＂ anisotropy of the electrons with a ＂pancake＂ distribution or kappa distribution keeps invariant or nearly invariant, whereas the ＂temperature＂ anisotropy with a pure bi-Maxwellian distribution or Ashour-Abdalla and Kennel＇s distributions decreases with the magnetic latitude. The results may provide a useful approach to evaluating the number density and anisotropy of the energetic electrons at latitudes where the observation information is not available.

Rectification of magnetic force tracker using neural network inaugmented reality system

Nonlinear errors always exist in data obtained from tracker in augmented reality （AR）, which badly influence the effect of AR. This paper proposes to rectify the errors using BP neural network. As BP neural network is prone to getting into local extrema and convergence is slow, genetic algorithm is employed to optimize the initial weights and threshold of neural network. This paper discusses how to set the crucial parameters in the algorithm. Experimental results show that the method ensures that the neural network achieves global convergence quickly and correctly. Tracking precision of AR system is improved after the tracker is rectified, and the third dimension of AR system is enhanced.

Transcranial magnetic stimulation-induced finger force changes under various finger coordination patterns and target finger force phases

BACKGROUND： The detection of motor evoked potential is utilized to explore neuromuscular finger coordination. The influence of transcranial magnetic stimulation on finger force has been investigated mainly on a single finger, and only time-dependent increased target finger force has been detected in the finger force task. OBJECTIVE： To explore the neural mechanism of finger force coordination in the motor cortex by observing the influence of various finger coordination patterns and patterns of transcranial magnetic stimulation （TMS）-induced finger force changes. DESIGN, TIME AND SETTING： Neurophysiological and behavioral study was performed at the Biomedical Engineering Laboratory of Chongqing University from April to June 2008. PARTICIPANTS： A total of 10 healthy, university students, comprising 5 males and 5 females, aged 21-23 years, voluntarily participated in this study. All participants were right-handed, with normal or corrected vision. Individuals with upper limb complaints or other musculoskeletal disorders were excluded. METHODS： A target force-tracking task was conducted on the index finger, the index and middle fingers, and four fingers （index, middle, ring, and little）, respectively. Target force trace in a single trial consisted of a 6-second ramp phase, a 20-second constant phase, and a 6-second drop phase. During experimentation, an unpredictable single-pulse TMS （120% motor threshold） was applied to the primary motor cortex （M1） in each phase. MAIN OUTCOME MEASURES： Changes in peak force induced by TMS were obtained for each finger pattern during each force-tracking phase. Differences in force changes were tested between different finger pattems with regard to ramp, constant, and drop phases of target force. RESULTS： Under ramp, constant, and drop phases of target force, the increase in magnetic stimulation-induced finger forces changes positively correlated with the number of fingers involved in the force tracking task. The magnetic stimulation-induced force changes from the index finger were less than the combination of the index and middle fingers or all four fingers under the corresponding target force, and the force changes from the combination of the index and middle fingers were less than all four fingers, Le., index finger 〈 index and middle fingers 〈 four fingers. CONCLUSION： Different neuromuscular mechanisms could be involved in finger force production for different finger combination patterns. Results from the present study suggested that independent motor neurons regulated individual finger force production.

Magnetic Force Transmission of a Reciprocating Motion

Magnetic force transmission of a reciprocating motion is studied by theoretical analysis and experiment. A mathematical model for calculating the magnetic force is derived using the theory of equivalent magnetic charges. An experimental rig is constructed to test the transmission and the model is verified by experiment. Effect of the transmission parameters on the magnetic force is analyzed theoretically from the model, and characteristic of the transmission is studied experimentally. Since the transmission is without direct contact between two elements, it is suitable for application in an organism.

Numerical simulation of applied electromagnetic field and electromagnetic force in all-position welding

All-position welding is an important technology in energy sources, chemical, shipbuilding and other industries. When welding current is larger than 200 A, the molten metal tends to flow down due to the force of gravity. In order to ＂push＂ the molten metal into the weld, a new kind of U-frame excitation model, which could produce electromagnetic force to balance the gravity of the molten pool, was designed. The related parameters of the excitation model were simulated by Maxwell 3D, and the relationships between the parameters and the magnetic induction intensity were analyzed. Finally, the electromagnetic force in the molten pool was calculated, and the appropriate parameters of the U-frame excitation model were determined. The results of the simulation verify the feasibility of the all-position welding excitation model.

A New Type of a Magnetic Plane Motor Coupled Mechanical Vibration with Electromagnetic Force

This paper proposes a new magnetic plane motor capable of rotation by the resonance energy of double-cantilever beam model excited by an electromagnetic force. This magnetic plane motor has two double-cantilever models, and the rotational direction is able to change by changing of the vibration mode. Basic characteristics of a prototype for the magnetic plane motor, such as rotational speed, output torque and efficiency were determined experimentally. Experimental results demonstrated that the rotational speed of 8.1 rpm was obtained with output torque of 0.07 Ncm for the magnetic plane motor having double-cantilever model. The output torque characteristics of the magnetic plane motor with two double-cantilever models improved 200 percent compared with double-cantilever model.

Magnetic force improvement and parameter optimization for magnetic abrasive polishing of AZ31 magnesium alloy

The magnetic force acting on workpiece to be machined plays a significantly important role in magnetic abrasive polishing process.But in a case of polishing nonferrous materials,the strength of magnetic force is very low and it leads lower polishing efficiency.The magnesium alloy that has superior mechanical properties for industrial application such as a lightweight and high specific strength is one of the most famous nonferrous materials.An improving strategy of the magnetic force for the AZ31 magnesium alloy installed with a permanent magnet was proposed and experimental verification was carried out.For the proposed strategy,the effect of process parameters on the surface roughness of the AZ31 magnesium alloy was evaluated by a design of experimental method.

A Sensitivity Mapping Technique for Tensile Force and Case Depth Characterization Based on Magnetic Minor Hysteresis Loops

In the nondestructive testing and evaluation area,magnetic major hysteresis loop measurement technology are widely applied for ferromagnetic material evaluation.However the characterization ability of major hysteresis loop measurement technology greatly varies as the evaluated target properties.To solve this limitation,magnetic minor hysteresis loops,which reflect the responses of ferromagnetic material magnetization in a systematic way,is recommend.Inspired by plenty of information carried by the minor loops,the sensitivity mapping technique was developed to achieve the highest sensitivity of minor-loop parameters to the nondestructively evaluated targets.In this study,for the first time,the sensitivity mapping technique is used to measure the tensile force in a steel strand and evaluate the effective case depth in induction-hardened steel rods.The method and procedures for the sensitivity mapping technique are given before experimental detection.The obtained experimental results indicate that the linear correlation between the induced voltage(or the magnetic induction intensity)and the tensile force(or effective case depth)exists at most of the locations in the cluster of minor loops.The obtained sensitivity maps can be used to optimize the applied magnetic field(or excitation current)and the analyzed locations at the minor loops for achieving the highest sensitivity.For the purpose of tensile force measurement,it is suggested that the strand should be firstly magnetized to the near-saturation state and then restored to the remanent state.In this way,the highest sensitivity is obtained as about 15.26 mV/kN.As for the induction-hardened steel rods,the highest sensitivity of magnetic induction intensity to the effective case depth occurs under low magnetic field conditions and the absolute value of the highest sensitivity is about 0.1110 T/mm.This indicates that if the highest sensitivity is required in the case depth evaluation,the induction-hardened steel rods are only required to be weakly magnetized.The proposed sensitivity mapping technique shows the good performance in the high-sensitivity evaluation of tensile force and case depth in ferromagnetic materials and its application scope can be extended to other nondestructive detection fields.

Dynamic Analysis of Axial Magnetic Forces for DVD Spindle Motors

The axial magnetic force, induced by the complicated flux linkage distribution from rotor magnet and stator slotted, is constructed by different relative heights and calculated by 3D finite element method (FEM) to analyze the dynamic characteristics for a DVD spindle motor. The axial magnetic force is designed to provide an axial stiffness, and govern the natural frequency of the dynamic performance. According to the simulation results and experimental measurements, the dynamic behaviors are significantly improved with a variation of relative height of rotor magnet and stator slotted on a DVD spindle motor.

Fast Calculation of Electromagnetic Forces in IPMSMs Under PWM VSI Supply Based on Small-Signal Time-Harmonic Finite Element Method

This paper introduces a novel method for fast calculating the electromagnetic forces in interior permanent magnet synchronous machines(IPMSMs)under pulse width modulation(PWM)voltage source inverter(VSI)supply based on the small-signal time-harmonic finite element analysis(THFEA),which has been successfully utilized for fast calculating the PWMinduced losses in silicon steel sheets and permanent magnets.Based on the small-signal THFEA,the functional relationships between high-frequency harmonic voltages(HFHVs)and corresponding airgap flux densities are established,which are used for calculating the flux density spectra caused by each HFHV in the PWM voltage spectra.Then,the superposition principle is applied for calculating the flux density spectra caused by fundamental currents and all HFHVs,which are converted to the electromagnetic force spectra at last.The relative errors between the force density spectra calculated with the proposed method and those obtained from traditional time-stepping finite element analysis(TSFEA)using PWM voltages as input are within 3.1%,while the proposed method is 24 times faster than the traditional TSFEA.