Action Of Pulsed Magnetic Field Research Articles

Effects of pulsed magnetic field on density reduction of high flow velocity plasma sheath

A three-dimensional model is proposed in this paper to study the effect of the pulsed magnetic field on the density distribution of high flow velocity plasma sheath. Taking the typical parameters of plasma sheath at the height of 71 km as an example, the distribution characteristics and time evolution characteristics of plasma density in the flow field under the action of pulsed magnetic field, as well as the effect of self-electric field on the distribution of plasma density, are studied. The simulation results show that pulsed magnetic field can effectively reduce the density of plasma sheath. Meanwhile, the simulation results of three-dimensional plasma density distribution show that the size of the density reduction area is large enough to meet the communication requirements of the Global Position System (GPS) signal. Besides, the location of density reduction area provides a reference for the appropriate location of antenna. The time evolution of plasma density shows that the effective density reduction time can reach 62% of the pulse duration, and the maximum reduction of plasma density can reach 55%. Based on the simulation results, the mechanism of the interaction between pulsed magnetic field and plasma flow field is physically analyzed. Furthermore, the simulation results indicate that the density distributions of electrons and ions are consistent under the action of plasma self-electric field. However, the quasi neutral assumption of plasma in the flow field is not appropriate, because the self-electric field of plasma will weaken the effect of the pulsed magnetic field on the reduction of electron density, which cannot be ignored. The calculation results could provide useful information for the mitigation of communication blackout in hypersonic vehicles.

Effects of Pulsed Magnetic Fields of Different Intensities on Dislocation Density, Residual Stress, and Hardness of Cr4Mo4V Steel

To study the effects of pulsed magnetic fields of different intensities on the dislocation density, residual stress, and hardness of Cr4Mo4V steel, magnetic treatment is conducted at 0, 1.0, 1.3, 1.5, 2.0, and 2.5 T. The dislocation density and residual stress are measured using Electron Backscatter Diffraction (EBSD) and X-ray technique, respectively. The results reveal the dislocation density and compressive residual stress decrease at lower magnetic fields such as 1.0 T and 1.3 T, while they increase at higher magnetic fields such as 2.0 T and 2.5 T. The average value of kernel averaged misorientation (KAM) and compressive residual stress decrease about 10.4% and 15.8%, respectively, at 1.0 T, while they increase about 5.88% and 18.2%, respectively, at 2.5 T. The average value of hardness decreases about 3.5% at 1.0 T, from 817 HV to 787 HV. With the increments of intensities, the hardness of the treated samples increases. The hardness essentially remains unchanged at 2.0 T and 2.5 T. The reason for the dislocation motion under the action of pulsed magnetic fields is discussed.

Preparation and In Vivo Biodistribution of Ultra-Small Superparamagnetic Iron Oxide Nanoparticles with High Magnetic Targeting Response.

The ultra-small superparamagnetic iron oxide (USPIO) particles with high saturation magnetization and good superparamagnetism were prepared by reverse micro-emulsions using novel C16E15 as surfactant, which can reduce magnetic dipole-dipole interaction, hence decreasing the critical blocking temperature (TB). Powder X-ray diffraction (XRD), Infrared spectrum (FT-IR), Transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and Vibrating sample magnetometer (VSM) were used to characterize the magnetic particles. The higher ratio of Fe2+/Fe3+ caused redundant FeO on the USPIO surface. An in vitro approach model for simulating target delivery of USPIO particles to sites of interest was developed to illustrate the relationship between magnetic fluid retention rate and pole distance. In Vivo targeted interception and magnetic targeting bio-distribution of superparamagnetic particles were also investigated simultaneously. The results indicated that the USPIO had high ability for magnetic focusing in mimetic surrounding tissue surrounding blood vessels under the action of pulsed magnetic field. The USPIO nanoparticles will be fundamental in biomedical applications.

On the dynamics of the spin crossover in cobalt octaethylporphyrin molecular magnets in a terahertz pulsed magnetic field

The results of theoretical study of the spin crossover dynamics in the cobalt octaethylporphyrin molecule under the action of an external pulsed magnetic field with an induction of 36.8 T are presented. It is shown that, in the case of the high-spin state, under the action of a pulsed magnetic field, spin switching occurs in the system, and the system is characterized by a large relaxation time. In the case of the low-spin state, the system relaxes rapidly to the ground state. The temperature dependence of the product of the magnetic susceptibility and the temperature has a feature in the vicinity of 40 K related to the transition between spin states.

Study of Thermal Resistance and Mechanical Properties of Thin Sheets of Low-Alloyed Aluminum Al-Cu-Mn and Al-Mg-Si Alloys

The paper investigates a variety of properties of thin aluminum sheets fabricated using physical action of pulsed magnetic fields and weak pulsed current. The possibility of using thermal resistant aluminum alloys parts in aircraft manufacturing, including ones made by forming processes which require sufficiently high plasticity of initial sheets, is widely discussed. Two possible technological options have been tested for manufacturing sheet samples of Al-Cu-Mn and Al-Mg-Si alloys. A set of properties has been investigated (thermal resistance, mechanical properties, specific electrical conductivity, macrostructure of weldability zones, corrosion resistance of alloy samples. Casted workpieces were thermo-mechanically treated by heating and upsetting to 50 – 55 % with consequent hardening and aging. After that workpieces were subjected to multi-cycle rolling up to 0.3x10-3 m. The achieved results demonstrate that after 400 hours of exposure to 250°C, the thermal resistant parameters by tensile strength are higher after the exposure to weak pulsed currents than after the exposure to pulsed magnetic fields. Maximal thermal resistant parameters by tensile strength and maximal electrical conductivity was achieved in 01327+Sc (Al-Mg-Si) alloy. The mechanical properties, corrosion resistance and Erichsen formability parameters were also determined.

Effect of strong magnetic fields on gas adsorption

The effect of strong pulsed magnetic fields on gas adsorption at dielectric surfaces is demonstrated. We describe the experimental technique and the results indicating a considerable increase in the surface concentration of the adsorbed substance under the action of pulsed magnetic fields with an induction amplitude up to 50 T. The increase in the lifetime and stability of the adsorbed layer is observed. It is shown that the effect of magnetically induced sorption is also manifested in the interaction of iodine vapor with the surface of dielectrics.

Effects of Pulsed Magnetic Field on Microsegregation of Solute Elements in a Ni-Based Single Crystal Superalloy

The effects of a pulsed magnetic field (PMF) on the microsegregation of solute elements during directional solidification of a Ni-based single crystal superalloy were experimentally investigated, and the results show that the PMF significantly affects the microsegregation of Al, Ti, Co, Mo and W elements in the alloy. However, the distribution behavior differs for both positive and negative segregation elements. With the PMF, the microsegregation of negative segregation elements, Co and W, was restrained effectively, while that of positive segregation elements, Al, Ti and Mo, was aggravated. A segregation model was established to reveal the distribution mechanism of the elements with PMF. It is considered that, under the action of PMF, the jumping of solute atoms from the liquid phase to solid phase is hindered, but the jumping of solute atoms from the solid phase into liquid phase is promoted during solidification. As a result, the effective distribution coefficient of the solute atoms is reduced, which leads to the reduction of microsegregation of negative segregation elements and aggravation of microsegregation of positive segregation elements.

Investigation of relaxation phenomena in high-temperature superconductors HoBa2Cu3O7−δ at the action of pulsed magnetic fields

Abstract A mechanical method to investigate the stimulated Abrikosov vortex dynamics in superconductors has been used. We found out that pulsed magnetic fields change the path of relaxation processes taking place in vortex matter. The study of the influence of magnetic pulses differing in their durations and amplitudes on the vortex system of the isotropic high-temperature superconductor system HoBa 2 Cu 3 O 7− δ showed the presence of a threshold phenomena. Short duration pulses do not change the path of relaxation processes taking place in vortex matter. When the duration of pulses exceeds some critical value (threshold), then their influence changes the path of relaxation process which is revealed by a stepwise change of the relaxing mechanical moment τ rel . These investigations showed that the time for formatting of the Abrikosov vortex lattice in HoBa 2 Cu 3 O 7− δ is of the order of 20 μs which exceeds by one order of magnitude the time necessary for formation of a single vortex observed in type II superconductors.

Micro-Microvascular Healing: Induction of Angiogenesis and Wound-Healing Factors Using Radiofrequency Pulsed Magnetic Fields (PMF) and Clinical Application

Pulsed magnetic fields (PMF) have been shown to enhance healing of non-unions, fresh fractures, and spine fusion. Additional clinical indications have been reported in double–blind studies for the treatment of avascular necrosis, tendonitis, and osteoarthritis. Radiofrequency PMF of the type utilized in the author's laboratory and clinic have been shown to enhance chronic wound repair and reduce pain and edema. Additionally, radiofrequency PMF signals have been reported to enhance skin blood flow in diabetic individuals. Recently, the author's laboratory has shown that PMF stimulates neovascularization when applied to a transplanted tail arterial loop in a rat model. This was the first time that PMF was shown to promote angiogenesis in an in vivo model. More recently, this study was extended to a rat groin flap model in which PMF was also shown to stimulate angiogenesis and to allow for elevation of a free flap in the rat, purely on the neovascularized skin flap. The mechanism of action of PMF and its clinical use in wound healing, revascularization of organs, use in CNS disorders and CNS trauma that have been developed were discussed.

Investigation of stimulated dynamics of vortex matter in high-temperature superconductors

A simple mechanical method for the investigation of Abrikosov vortex lattice stimulated dynamics in superconductors has been used. By this method we studied the action of pulsed magnetic fields on the vortex lattice and established the resulting change of the course of relaxation processes in the vortex matter in high-temperature superconductors. This method can be used for investigation of phase transitions in vortex matter both high-temperature and exotic superconductors.

Behavior of metastable phases in zirconium ceramics resulting from thermal and magnetic pulse action

The phenomenon of destabilization of metastable phases in zirconium ceramics containing 3 mol.% Y2O3 and their phase transformations caused by the action of weak pulsed magnetic fields on the material are established experimentally. Magnetic pulse treatment of zirconium ceramics results in either destabilization of the tetragonal phase and formation of deformation martensite or reverse transformation from martensite to the tetragonal phase depending on the temperature regime. A possible mechanism of the action of a pulsed magnetic field on the object is suggested that suits the concept of selective action of physical fields on the defect structure of the material.

Action of Pulse Magnetic Field on Molten Metal.

Effect of pulse magnetic field on two-phase zone of crystallizing metal has been investigated by methods of mathematical modelling in reference to vertical continuous casting machine. On the first step of the investigation electromagnetic problem for penetration of pulse magnetic field of cylindrical inductor in depth of liquid metal has been solved and distribution of electromagnetic forces in the melt has been obtained at different time moments. With a view to solve this problem combined method has been proposed. It contains boundary element method for description of field in surrounding air medium with inductor and also finite difference method for solving of the problem in molten metal. On the second step of the investigation with the help of obtained distribution of electrodynamic forces problem for acceleration of the melt has been solved. It is determined the optimal relation for pulse duration (in the case of single pulse), when melt velocity reaches its maximum value. Besides, it is shown that magnetic field may be used with the purpose of effect on crystallization zone through shell of solidified metal.

The action of pulsed magnetic fields on cyclic AMP levels in cultured fibroblasts

Pulsed magnetic fields, similar to those used clinically to promote bone repair, have been applied to cultured fibroblasts obtained from chick embryo tendons and rabbit bone marrow. Cyclic adenosine monophosphate (cAMP) levels were found to be lower in field-treated cultures in response to hormones such as prostaglandin E 2 and isoproterenol, and the fibroblasts appear less sensitive to environmental perturbation prior to hormone incubation. We propose that the adenylate cyclase complex is temporarily inactivated by prolonged exposure to pulsed magnetic fields, and that this effect might be analogous to desensitisation phenomena.

Resistance to deformation of titanium, alloy under the action of strong magnetic fields in the temperature range 293-4.2�K

In order to study the effect of a pulsed magnetic field (MF)on the material deformation mechanisms in the temperature range 293-4.2 K, UMN-10 equipment was used making it possible to carry out specimen testing with application of a pulsed magnetic field with an intensity up to 32.0 MA/m. Practical use of the effect of superconductivity in turbogenerators with a superconducting exciting winding and other devices requires consideration of the effect of powerful electromagnetic fields on the strength and deformation features of structural materials used for their manufacture. The approach described for estimating the effect of a pulsed MF on deformation and failure of metals may be used in working out the strength of elements for cryogenic structures operating under the action of pulsed MF. With repeated action of an MF it is necessary to take account of the capacity of the material to resist thermal cyclic loading.