• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.233-240
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• 1996

Analyses of the viscous and end effects on electromagnetic (EM) pumps of annular linear induction type for the sodium coolant circulation in Liquid Metal Fast Breeder Reactors have been carried out based on the MHD laminar flow analysis and the electromagnetic field theory. A one-dimensional MHD analysis for the liquid metal flowing through an annular channel has been performed on the basis of a simplified model of equivalent current sheets instead of three-phase currents in the discrete primary windings. The calculations show that the developed pressure difference resulted from electromagnetic and viscous forces in the liquid metal is expressed in terms of the slip, and that the viscous loss effects are negligible compared with electromagnetic driving forces except in the low-slip region where the pumps operate with very high flow velocities comparable with the synchronous velocity of the electromagnetic fields, which is not applicable to the practical EM pumps. A two-dimensional electromagnetic field analysis based on an equivalent current sheet model has found the vector potentials in closed form by means of the Fourier transform method. The resultant magnetic fields and driving forces exerted on the liquid metal reveal that the end effects due to finiteness of the pump length are formidable. In addition, a two-dimensional numerical analysis for vector potentials has been performed by the SOR iterative method on a realistic EM pump model with discretely-distributed currents in the primary windings. The numerical computations for the distributions of magnetic fields and developed pressure differences along the pump axial length also show considerable end effects at both inlet and outlet ends, especially at high flow velocities. Calculations of each magnetic force contribution indicate that the end effects are originated from the magnetic force caused by the induced current ( u x B ) generated by the liquid metal movement across the magnetic field rather than the one (E) produced by externally applied magnetic fields by three-phase winding currents. It is concluded that since the influences of the end effects in addition to viscous losses are extensive particularly in high-velocity operations of the EM pumps, it is necessary to find ways to suppress them, such as proper selection of the pump parameters and compensation of the end effects.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1675-1682
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• 2017

This paper deals with three dimensional orientation estimation algorithm for an attitude and heading reference system (AHRS) based on nine-axis inertial/magnetic sensor signals. In terms of the orientation estimation based on the use of a Kalman filter (KF), the quaternion is arguably the most popular orientation representation. However, one critical drawback in the quaternion representation is that undesirable magnetic disturbances affect not only yaw estimation but also roll and pitch estimations. In this paper, a sequential direction cosine matrix-based orientation KF for AHRS has been presented. The proposed algorithm uses two linear KFs, consisting of an attitude KF followed by a heading KF. In the latter, the direction of the local magnetic field vector is projected onto the heading axis of the inertial frame by considering the dip angle, which can be determined after the attitude KF. Owing to the sequential KF structure, the effects of even extreme magnetic disturbances are limited to the roll and pitch estimations, without any additional decoupling process. This overcomes an inherent issue in quaternion-based estimation algorithms. Validation test results show that the proposed method outperforms other comparison methods in terms of the yaw estimation accuracy during perturbations and in terms of the recovery speed.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2214-2218
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• 2007

The effects of bath temperature on electrochemical behavior, alloy composition, crystallographic structure, morphology and the magnetic properties of electrodeposited Co-Pt-W(P) films were investigated. Electrochemical studies show that alloy electrodeposition has been shifted to more positive potentials and the critical time for nucleation decreased as electrolyte temperature increased. As the temperature increased from 40 oC to 80 oC, tungsten content in the deposit increased, while phosphorus content decreased. The films deposited at T = 40 oC exhibited soft magnetic properties. However, electrodeposited at T = 70 oC, the films exhibited hard magnetic properties. It is also demonstrated that higher temperature more than 70 oC could weaken hard magnetic properties. XRD results indicated that the deposits obtained at 50 oC-70 oC showed enhancement of [00.1] P.O. (preferred orientation) with the bath temperature, which resulted in the stronger perpendicular magnetic anisotropy.

• Journal of Radiation Industry
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• v.10 no.4
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• pp.193-198
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• 2016

Perfusion magnetic resonance image of biological mechanism are independent of magnetic field strength in hyper acute ischemic stroke. 3.0 T magnetic field, however, does affect the SNRs (signal to noise ratio) and artifacts of PMRI (perfusion magnetic resonance image), which basically will influence the quantitative of PMRI. In this study, the effects of field strength on PMRI are analyzed. The effects of the diseases also are discussed. PMRI in WM(white matter), GM (gray matter), hyper acute ischemic stroke were companied with 1.5 T and 3.0 T on SNR. PMRI also was compared to the SI difference after setting ROI(region of interest) in left and right side of the brain. In conclusion, the SNRs and SI of the 3.0 T PMRI showed higher than those at 1.5 T. In summary, PMRI studies at 3.0 T is provided significantly improved perfusion evaluation when comparing with 1.5 T.

• Journal of Magnetics
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• v.5 no.1
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• pp.19-22
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• 2000

The effects of a hard-biased Held on the magnetic and magnetoresistive properties of a crossed spin-valve head are investigated by computer simulation with particular emphasis on the asymmetry of the output signal. The spin-valve considered in this work is NiMn (25 nm)/NiFe (2.5 m)/Cu (3 nm)/NiFe (5.5 m), with a length of 1500 m and a width of 600 nm. A simple model is used where each magnetic layer consists of a single domain, and the magnetoresistance is a function of the angle between the magnetization directions of the two magnetic layers. The ideal crossed spin-valve structure is not realized with the present model and magnetic parameters, but the deviation from ideality is decreased by the hard-biased field. This results in the improvement of the linearity of the output signal with the use of the bias field. The magnetoresistance ratio and magnetoresistive sensitivity, however are reduced. The magnetic properties including the magnetoresistance are found to be strongly affected by magnetostatic interactions, particularly the inter-layer magnetostatic field.

• Journal of the Korean Society of School Health
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• v.24 no.1
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• pp.23-32
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• 2011

Purpose: This study was to examine the effects of magnetic therapy applying the principal of Sa-am Acupuncture on menstrual cramps and dysmenorrhea in high school students. Methods: A quasi-experimental nonequivalent control group, pre- and post-test design was used. Participants were 60 female high school students living in S city, 30 in the experimental group and 30 in the control group. Data were collected from February to August 2008. Magnetic therapy was performed three days before menstruation for three menstrual cycles. Results: Magnetic therapy significantly reduced menstrual cramps and dysmenorrhea. There was a significant difference in menstrual cramps and dysmenorrhea between the experimental and control groups. Conclusion: Magnetic therapy may be an effective nursing intervention in reducing menstrual cramps and dysmenorrhea.

• Advances in nano research
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• v.14 no.5
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• pp.475-493
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• 2023

In the context of nonclassical nonlocal strain gradient elasticity, this article studies the free and forced responses of functionally graded material (FGM) porous nanoplates exposed to thermal and magnetic fields under a moving load. The developed mathematical model includes shear deformation, size-scale, miscorstructure influences in the framework of higher order shear deformation theory (HSDT) and nonlocal strain gradient theory (NSGT), respectively. To explore the porosity effect, the study considers four different porosity models across the thickness: uniform, symmetrical, asymmetric bottom, and asymmetric top distributions. The system of quations of motion of the FGM porous nanoplate, including the effects of thermal load, Lorentz force, due to the magnetic field and moving load, are derived using the Hamilton's principle, and then solved analytically by employing the Navier method. For the free and forced responses of the nanoplate, the effects of nonlocal elasticity, strain gradient elasticity, temperature rise, magnetic field intensity, porosity volume fraction, and porosity distribution are analyzed. It is found that the forced vibrations of FGM porous nanoplates under thermal and live loads can be damped by applying a directed magnetic field.

• Journal of the Korean Magnetic Resonance Society
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• v.1 no.2
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• pp.71-78
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• 1997

The magnetic anisotropy effects of peptide group in structured protein on proton chemical shift have been investigated using trialanine modeling. The structure dependent part of chemical shift of C${\alpha}$H of the second amino acid residue was assumed to come purely from the magnetic anisotropy effects of C=O and C-N bonds of peptide in the direct neighborhood and thus to be dependent on and $\psi$ angle of this dipeptide. A set of dipeptide models with different and $\psi$angles were generated and from these models the chemical shift values were calculated using known algorithm to emphasize the role of parameters used in the equation. Comparison of sets of different parameters resulted in an optimized parameters which could reproduce the statistical chemical shift values observed in proteins with respect ot the secondary conformation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.876-883
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• 2007

The magnetic flux leakage(MFL) type nondestructive testing(NDT) method is widely used to detect corrosion, defects and mechanical deformation of the underground gas pipelines. The object pipeline is magnetically saturated by the magnetic system with permanent magnet and yokes. Hall sensors detect the leakage fields in the region of the defect. The defects are sometimes occurred in group. The accuracy of the detecting signals in this defect cluster become lowered because of the complexity of the defect cluster. In this paper, the effects of the multi -defects are analyzed. The detecting signals are computed by 3-dimensional finite element method and compared with real measurement. The results say that, rather than the size of the defects, the effects of the relative position of the multi-defects are very important on the detecting signals.

• Journal of the Korean Ceramic Society
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• v.14 no.2
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• pp.78-81
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• 1977

The effects of variation in composition and the addition of small amount of the rare-earth oxides La2O3, CeO2 and Sm2O3 on the magnetic properties of Mn-Zn system ferrites, 0.5MnO.0.5ZnO.(1＋0.1X) Fe2O3(X=-1, 0, 1, 2), were investigated in the range of frequencies of 0.1~100 kHz. It was shown that the magnetic permeability of the specimens with the composition Mn 0.5 Zn 0.5 Fe2O4 was maximum in the Mn-Zn system ferrites, and that the addition of a small amount of the rare-earth oxides to the composition 0.5 MnO.0.5ZnO.0.9 Fe2O3 caused the sharp increase of magnetic permeability and the decrease of the loss factors.