Direction Of Magnetic Flux Research Articles

Development of Ti-Coated Ferromagnetic Needle, Adaptable for Ablation Cancer Therapy by High-Frequency Induction Heating

To develop a novel ablation therapy for human solid cancer, the heating properties of a ferromagnetic carbon steel rod and a prototype Ti-coated needle using this carbon steel rod, were investigated in several high-frequency outputs at 300 kHz. In the former, the heating property was drastically different among the three inclination angles (θ = 0°, 45° and 90°) relative to the magnetic flux direction as a result of the shape magnetic anisotropy. However, the effect of the inclination angles was completely eliminated in the latter. It is considered that the complete non-oriented heating property relative to the magnetic flux direction allows the precise control of the ablation temperature during minimally invasive thermotherapy without a lead-wire connected to a fiber-optic thermometer. This newly designed Ti-coated device will be suitable for clinical use combined with its superior biocompatibility for ablation treatments using high-frequency induction heating.

Heat generation ability in AC magnetic field of needle‐type Ti‐coated mild steel for ablation cancer therapy

PurposeThe purpose of this paper is to develop a ferromagnetic needle adaptable for a novel ablation cancer therapy; the heat generation ability of the mild steel rod embedded into the Ti‐tube having a different thickness was investigated in a high‐frequency output at 300 kHz.Design/methodology/approachThe outer diameter and length of the Ti‐tubes were 1.8 and 20 mm, respectively, while the inner diameter was varied from 1.6 to 0 mm. The mild steel rod was embedded in a Ti‐tube for preparing the needle‐type specimen. Their heat generation ability was examined by changing the inclination angle to the magnetic flux direction in a high‐frequency coil.FindingsWhen the thickness of the Ti surrounding the mild steel rod was as low as 0.1 mm, the heat generation ability was drastically different among the three inclination angles (θ=0°, 45°, and 90°) to the magnetic flux direction due to the effect of the shape‐induced magnetic anisotropy. However, the effect of the inclination angle was almost eliminated in the specimen surrounded by the 0.4 mm thick Ti, suggesting that the non‐oriented heat generation property is achieved for the needle‐type mild steel rod coated with Ti having the optimum thickness.Originality/valueThe prototype ablation needle having a complete non‐oriented heat generation ability was fabricated to use in subsequent animal experiments. It is considered that the newly designed Ti‐coated device is useful in ablation treatments using a high‐frequency induction heating.

Modification of BN nanosheets and their thermal conducting properties in nanocomposite film with polysiloxane according to the orientation of BN

A facile technique was developed to modify boron nitride (BN) nanosheets with iron oxides in order to fabricate highly-oriented polysiloxane/BN nanosheet composite films and their thermal properties were evaluated according to the orientation of BN. The surfaces of the BN nanosheets were modified with iron oxide nano particles by chemical vapor deposition, and their one-dimensional arrangement with variation of BN content was controlled under a magnetic field. The homogeneous suspension of BN nanosheets and pre-polymers of polysiloxane was cast on a glass spacer, and subjected to a magnetic field before the mixture was crosslinked. X-ray diffraction, transmission electron microscopy, and superconducting quantum interference device measurements were employed to identify the phases and amounts of iron oxide nano particles deposited on the BN nanosheets. The results revealed that the modified BN nanosheets were aligned either horizontally or vertically to the film plane, depending on the direction of magnetic flux with high anisotropy. The transmittance and thermal conductivity of the nano composite films were improved due to the orientation of the BN nanosheets inside the polymer matrix.

Facile orientation of unmodified BN nanosheets in polysiloxane/BN composite films using a high magnetic field

Composite films consisting of highly oriented boron nitride (BN) nanosheets in polysiloxane were fabricated without modifying the BN surface by applying a high magnetic field generated by a superconducting magnet. The hexagonal BN nanosheets were dispersed by sonication in a prepolymer mixture of polysiloxane. The homogeneous suspension was then cast on a polyamide spacer of microscale thickness and a magnetic field was applied before the mixture became crosslinked. The BN nanosheets in the polysiloxane were aligned with high anisotropy either parallel or perpendicular to the composite film plane depending on the magnetic flux direction. The fabricated composite films exhibited enhanced thermal conductivity by controlling the anisotropy of the BN nanosheets in the film. The mechanisms for rotation of BN nanosheets and heat diffusion across the composite film are discussed.

Defect characterisation based on pulsed eddy current imaging technique

The pulsed eddy current (PEC) technique is an emerging electromagnetic method, which is widely applied to detect defects in the field of nondestructive testing and evaluation (NDT&E). This paper studied the PEC imaging technique to identify and evaluate the corrosion type of defects. Based on PEC probe consisting of a rectangular exciting coil and an induction pick-up coil, the C-scan imaging technique is researched and analyzed in two directions (magnetic induction flux and exciting current). The averaging method and wavelet transform are used to de-noise the response PEC signals. Experiment results have shown that the corrosion type of defect can be identified effectively by particular character based on rectangular exciting coil in both directions, and that the results in direction of magnetic induction flux are more effective than those in direction of exciting current. Defect characterisation is carried out based on the C-scan image. The defects are discriminated to surface defect by selecting the rising time as the feature and the sizing of defects are preliminarily obtained based on the imaging results. To sum up, the PEC imaging technique is an effective means to evaluate the corrosion type of defects, which can be extended to the characterisation of complex defects.

MAGNETOHYDRODYNAMIC MODELING FOR A FORMATION PROCESS OF CORONAL MASS EJECTIONS: INTERACTION BETWEEN AN EJECTING FLUX ROPE AND AN AMBIENT FIELD

We performed magnetohydrodynamic simulation of a formation process of coronal mass ejections (CMEs), focusing on interaction (reconnection) between an ejecting flux rope and its ambient field. We examined three cases with different ambient fields: no ambient field, and cases with dipole field of two opposite directions which are parallel and anti-parallel to that of the flux rope surface. As a result, while the flux rope disappears in the anti-parallel case, in other cases the flux ropes can evolve to CMEs and show different amounts of rotation of the flux rope. The results imply that the interaction between an ejecting flux rope and its ambient field is an important process for determining CME formation and CME orientation, and also show that the amount and direction of magnetic flux within the flux rope and the ambient field are key parameters for CME formation. Especially, the interaction (reconnection) plays a significant role to the rotation of the flux rope, with a process similar to "tilting instability" in a spheromak-type experiment of laboratory plasma.

Defect edge identification with rectangular pulsed eddy current sensor based on transient response signals

The Pulsed Eddy Current (PEC) testing is an increasingly emerging nondestructive testing & evaluation (NDT&E) technique. The main purpose of this study is to improve the performance of defect edge identification of C-scan imaging technique utilizing the rectangular PEC sensor. When sensor scans along the defect, peak waves of response signals always present a crest and a trough in direction of magnetic induction flux, while present different shapes in direction of exciting current. The maximum and minimum values of peak waves in direction of magnetic induction flux are corresponding to the moment of sensor entering and leaving the length edge of defect, which provides us a way to evaluate the length edge of defect. To evaluate the width edge of defect, we obtain and analyze the C-scan imaging results in direction of magnetic induction flux. For improving the identification of width edge of defect, we proposed news features from response signals and differential response signals. Experiment results have shown that the width edge of defects on surface can be identified effectively by selecting and normalizing the appropriate features in time domain. Therefore, both length edge and width edge of defect can be evaluated effectively in direction of magnetic induction flux. The rectangular PEC sensor is helpful for C-scan imaging inspection technique and has a good prospect in field of nondestructive testing & evaluation.

Defect classification based on rectangular pulsed eddy current sensor in different directions

Pulsed eddy current (PEC) testing is a new emerging and effective electromagnetic non-destructive testing (NDT) technique. The main purpose of this study is to identify surface defects and sub-surface defects using features-based rectangular pulsed eddy current sensor. The further study of PEC rectangular sensor proposed in author's previous work has been made to classify the different types of defects in specimen. In different directions of sensor scanning, peak waves of pick-up coil are studied. We find that when sensor is on different position against the defect, peak waves of response signals present the same shape in direction of magnetic induction flux, while present different shapes in direction of exciting current. Experiment results have shown that the different classes of defects can be identified and classified effectively by selecting the rising time as the time domain feature in both directions. For improving the performance of defect classification, two new features from differential response signal are proposed to classify different types of defects combined with rising time. One is called as crossing time; the other is differential time to peak. The blind test is carried out and the results show that the new features are effective to classify the defects.

Effect of molecular structure on extrudate swell behavior for different thermoplastic melts in an electro‐magnetized die

AbstractThe extrudate swell ratio of five different thermoplastic melts flowing in a constant shear rate rheometer having a capillary die with and without application of magnetic field was studied. The effects of the magnetic flux direction and density, die temperature, and wall shear rate on the extrudate swell and flow properties were investigated. The experimental results suggested that an increasing wall shear rate increased the swelling ratio for the polystyrene (PS), LLDPE, and PVC melts, but the opposite effect was observed for the ABS and PC melts. The extrudate swell ratio for the PS, ABS, PC, and LLDPE melts decreased with increasing die temperature, the effect being reversed for the PVC melt. Thermoplastic melts having high benzene content in the side‐chain and exhibiting anisotropic character were apparently affected by the magnetic field, the extrudate swell ratio increasing with magnetic flux density. The effect of the magnetic field on the extrudate swell ratio decreased in the order of PS → ABS → PC. The extrudate swell ratio for the co‐parallel magnetic field system was slightly higher than that for the counter‐parallel magnetic field system at a high magnetic flux density. POLYM. ENG. SCI., 47:270–280, 2007. © 2007 Society of Plastics Engineers.

New method of characterization of magnetoelastic properties of amorphous ring cores

New method of characterization of magnetoelastic properties of amorphous ring cores is presented. The uniform compressive stresses are applied to the core perpendicular to the magnetic flux direction using special backings. The magnetoelastic properties of the amorphous Fe 78 Si 13 B 9 ring core were investigated by the described method. The effect of stress up to 30 MPa is presented.

A new coil configuration of a linear DC motor to improve thrust

The purpose of this study was to develop a linear DC motor capable of generating greater thrust. A new type of coil configuration consisting of magnetic and non-magnetic wires was proposed. The magnetic wire enhances the magnetic flux density in the magnetic circuit, and the non-magnetic wire controls the direction of magnetic flux in the magnetic wire. Electric current is applied to the magnetic wire.The software simulation showed that the averaged magnetic densities of the magnetic wire and of nonmagnetic wire, just above the magnet, were 0.615T and 0.075T, respectively. The thrust of the linear DC motor improved approximately 30% comparison with the conventional linear DC motor consisting of copper wired coil only at the same power supply.The measured thrust of the prototype linear DC motor showed approximately 80% against the estimated thrust because of differences between the analysis model and the actual form.Suitable width ratio between the magnetic wire and the non-magnetic wire, and reasonable clearance between outer diameter of coil and inner diameter of outer yoke were estimated.

Dynamo simulation and palaeosecular variation models

In this paper we examine the simulation results of a fully nonlinear, three–dimensional dynamo and obtain inferences useful in the study of present and past geomagnetic field. This approach has importance because of the limitation in the available data of the real magnetic field: the present field is known with a high accuracy, but the time covered is only a small fraction of the time constant inherent to the geodynamo, while palaeomagnetic data provide data for a long time–span, but they are of poor quality and are distributed quite irregularly both in space and time. Thus, we compare what we see from the external field of the dynamo model with the features established or conjectured for the present or palaeomagnetic fields. We show that some of the statistical properties of the magnetic field generated by dynamo models compare well with those of the real magnetic field: dominance of the axial dipole, similar power in each degree of the harmonic at the core surface, nearly normal distribution of Gauss coefficients, and the lack of correlation among their variations. Differences were observed in other features, such as drift in the azimuthal direction and concentration of magnetic flux in small patches at the core surface. They can be attributed to either the shortness of the observational period, or to the difference in the resolution of the models, which suppresses small–scale features far below the level of the observation.

磁場配向で作製したＭｎ‐Ｚｎフェライトの磁気特性

Acicular manganese zinc ferrite fine particles were made from the as raw materials of acicular α-FeOOH, Mn(C5H7O2)3, and Zn(C5H7O2)2. These fine particles were oriented with the long axis in parallel to the magnetic flux direction by a magnetic field of 7 kOe. The fine particles were then formed into thin, multi-layered toroidal cores. The green bodies were sintered at 1200°C for 6 hours in air, then cooled in a nitrogen atmosphere. The crystals of sintered manganese zinc ferrites were strongly oriented to the direction of the (110) plane of the spinel; this plane was formed along the upper plane of toroidal cores. The crystal growth behavior was similar to that of a manganese zinc ferrite single crystal of the (110) plane. The initial permeability of crystal-oriented manganese zinc ferrites was 2120. The sample exhibited good high-frequency magnetic properties.

Fabrication of double rectangular type FeTaN film inductors

A double rectangular spiral inductor is fabricated using FeTaN films. The inductor is composed of internal coils sandwiched by magnetic layers. Characteristics of inductor performance are investigated with an emphasis on planarization of magnetic films. In the absence of the planarization process, the grating topology of upper magnetic films over the coil arrays degrades the soft magnetic properties and the inductor performance. It also induces a uniaxial magnetic anisotropy with the easy axis aligned to the magnetic flux direction. This alignment prevents the upper magnetic films from contributing to the total induction. Glass bonding is a viable method for achieving a completely planar inductor structure. The planar inductor with glass bonding shows excellent performance: inductance of 1.1 /spl mu/H, Q factor of 7 (at 5 MHz), and a DC current capability up to 100 mA.

Effect of the magnetic flux direction on LEC GaAs growth under magnetic field

The two-dimensional temperature distributions of B 2O 3 and molten GaAs interface were directly investigated under both horizontal (H-MLEC) and vertical (V-MLEC) magnetic field applied liquid-encapsulated Czochralski technique. The crystal shape becomes ellipsoid under H-MLEC growth without seed rotation, while it becomes round under V-MLEC condition even without seed rotation. A H-MLEC crystal shows very strong striation contrasts and periodic stripes were observed by X-ray transmission topography. On the other hand, a V-MLEC grown crystal shows very weak contrasts. The V-MLEC technique is found superior to H-MLEC for growing the homogeneous crystals.

Anisotropy of DC magnetostriction in cold-rolled electrical sheets of Goss texture

The maximum differences are found to exist between the directions [100] and [110], and not between [100] and [111]. A similar relation occurs also for the coercive force. Anisotropy of magnetostriction is brought about by the sheet crystalline structure and texture. The phenomenon has been analyzed qualitatively. It was found that the elongation depended on the magnetic flux direction and the degree of texture.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The electrochemical asymmetric reduction of α-keto acids in the magnetic fields

It was found that mandelic or lactic acid, which was produced by the electrolytic reduction of phenylglyoxylic or pyruvic acid in the magnetic fields of 980–1680 Gauss, was dextrorotatory. The optical yield increased proportionally to the magnetic flux density. The electrochemical asymmetric reduction occurred when the direction of magnetic flux was parallel to the normal of the surface of mercury electrode. The same results were obtained if the magnet was placed upside down, that is, north and south poles were replaced reversely. No rotatory power appeared when the magnetic flux was directed horizontally. In the case of phenylglyoxylic acid reduction, the maximum optical yield was 21% under the conditions of pH 3.8, 10°C, 1680 Gauss and the controlled potential with −1.25 V vs sce. Pyruvic acid was similarly reduced to form excessive l-isomer when the electrolysis was carried out at pH 4.4, 25°C, 1680 Gauss and −1.3 V vs sce.

Application of the anisometric method for determining polar curves of induction, apparent core loss, and core loss in cold-rolled electrical sheets of Goss texture

A method of determining directional properties of electrical sheets of Goss texture is presented. The method is new and very useful for the purpose of calculating magnetic circuits. In order to determine directional properties of sheets it is necessary to make use of the Epstein test with reference to a sample sheared in the rolling direction as well as of anisotropy curves determined by means of an anisometer on samples of a disk shape. The proposed method makes it possible to limit the number of labor-consuming measurements taken in the Epstein test on samples sheared at many angles as well as to examine tapes of random width. Empirical relations between anisotropy of induction \DeltaB , apparent core losses \DeltaV , core losses \DeltaP , and parameters of the anisotropy curve J_{\perp} = f(\varphi) are given. Curves approximating the results obtained experimentally are provided. The proposed method of determining magnetic characteristics makes it possible to draw a polar figure, i.e., a curve illustrating changes of some magnetic properties according to the magnetic flux direction. Experiments covering transformer plates and dynamo sheets of varying orientation and metallurgical composition prove the correctness of applying the described method.