• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.144-145
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• 2003

A feasibility study on the alternating jet flow under the static electromagnetic field was carried out. When a fluid with electrical conductivity lies in the static electromagnetic field and moves electric current occurs in the fluid. Due to the electromagnetic field and the electric current, lorentz force generates in the fluid, which undergo the 'breaking' effect to the fluid. In order to simulate the complex fluid flow in the magnetic field, electromagnetic and fluid flow analysis need to be solved simultaneously. In the present study, a SOLA (SOLution Algorithm) scheme was used in order to calculate electromagnetic and fluid flow field. Jet flow without an electromagnetic field was compared with analytical solution in order to validate the flow analysis scheme. Effect of jet velocity on the flow pattern down the jet was investigated.

• Transactions of Materials Processing
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• v.8 no.2
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• pp.127-134
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• 1999

This study suggests the practical method which can reduce the lead time of the field trial and design of the dies. The virtual manufacturing, with which the die design is evaluated by computer analysis, reveals the impropriety of a design before die makings. Three methods for reducing the die making process occupying over 60% of the automotive development are like follows: First, the crack and wrinkle occurrence can be prevented by virtually adjusting the blank holding force and drawbead force with a computer simulation. Second, the parts which can not remove the forming defects in spite of the adjustment of forming parameters need to modify the part geometry or punch temporary shape. Third, the simulation before field trial, and field trial simulation can be effectively used in die design.

• Journal of the Korean Ceramic Society
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• v.14 no.4
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• pp.226-229
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• 1977

The infrared absorption spectrum of Synthesized magnesite is shown in the wve number region 2510 and 745cm-1. By using Wilson's GF matrices the force constants' of the Urey-Bradley force field were deterined from the infrared absorption frequencies. For magnesite the stretching force constant K=5.41, the bending force constant H=0.46, the repulsive force constant F=1.97, and the force constant for the out-of-plane vibration fθ=0.65md/Å. For calcite they are K=5.51, H=0.38, F=1.88 and fθ=0.64md/Å.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.4
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• pp.109-117
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• 1993

Force balance method is employed to predict forging information such as forging load, tool pressure and normal stress at the surface of tangential velocity discontinuity. The incipient stages of deformation for the plane strain forging of rectangular billets in V-shaped dies of different semi-angles are analysed. To construct an approximate model for the analysis of deformation by the force balance method in the incipient deformation stages, slip-line field is used. When the deformation mode by slip-line method is the same as that by force balance method, the slip-line method and the force balance method give identical solutions. The effects of die angle, coefficient of friction, billet geometries and deforma- tion characteristics are also investigated. In order to verify the validity of force balance analysis, the rigid-plastic finite element simulation for the various forgig parameters are performed and performed and find to be in good agreement.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.599-604
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• 2000

In order to study unsteady aerodynamic loads on high speed trains passing by each other at the speed of 350km/h, three-dimensional flow fields around trains during the crossing event are numerically simulated using the three-dimensional Euler equations. The Roe's FDS with MUSCL interpolation is employed to simulate wave phenomena properly. An efficient moving grid system based on domain decomposition techniques is developed to analyze the unsteady flow field induced by the restricted motion of a train on a rail. The numerical simulations of the trains passing by on the double-track are carried out to study the effect of the train nose-shape, the train length and the existence of tunnel when the crossing event occur. Unsteady aerodynamic loads side force and drag force-acting on the train during the crossing are numerically predicted and anlayzed. It is found that the strength of the side force mainly depends on the nose-shape, and that of drag force on tunnel existence. And it is observed that the push-pull like impulsive force successively acts on each car and acts in different directions between the neighborhood cars. The maximum change of the impulsive force reaches about 3 tons. These aerodynamic force data are absolutely necessary for the evaluation of the stability of the high speed multi-car train. The results also indicate the effectiveness of the present numerical method for the simulation of unsteady flow field induced by the bodies in the relative motion.

• Journal of Electrical Engineering and Technology
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• v.2 no.2
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• pp.208-215
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• 2007

The significant drawback of the permanent magnet linear synchronous motor (PMLSM) is force ripples, which are generated by the distortion of the stator flux linkage distributions, cogging forces caused by the interaction of the permanent magnet and the iron core and the end effects. This will deteriorate the performance of the drive system in high precision applications. The PMLSM and its parasitic effects are analyzed and modeled using the complex state-variable approach. To minimize the force ripple and realize the high precision control, the components of force ripples are extracted first and then compensated by injecting the instantaneous current to counteract the force ripples. And this method of the PMLSM system is realized by the field oriented control method. In order to verify the validity of this proposed method, the system simulations are carried out and the results are analyzed. The effectiveness of the proposed force ripples reduction method can be seen according to the comparison between the compensation and non-compensation cases.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.36 no.1
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• pp.70-73
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• 2023

To improve superconductor properties, the size of the crystal grains of the superconductor should be adjusted, the amount of electricity flowing through the superconductor should be increased, and the superconductor should be designed to withstand external magnetic fields. It is necessary to control the microstructure so that many flux pinning centers are developed inside the superconductor so that defects are generated physically or chemically, and the micro secondary phase for trapped magnetic flux must be dispersed inside the superconductor. In order to measure the superconducting magnetic force of the superconducting bulk in a simplified manner, the superconducting magnetic force was analyzed using an Nd-Fe-B permanent magnet of 3.80 kG. In particular, by delaying the growth of partially melted Y₂BaCuO₅ particles, we devised a plan to refine Y₂BaCuO₅ particles to effectively improve superconducting magnetic force, and analyzed superconducting magnetic force in a single crystal YBa₂Cu₃O_7-y superconducting bulk using a gauss meter. The melted superconducting bulk traps 80% or more of the applied magnetic field, and can be used as a bulk magnet of high magnetic field magnetization applicable to electric power equipment.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.111.1-111.1
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• 2015

As an alternative way to get sophisticated nanostructures, atomic force microscopy (AFM) has been used to directly manipulate building primitives. In particular, assembly of metallic nanoparticles(NPs) can provide various structures for making various metamolecules. As far, conventionally made polygonal shaped metallic NPs showed non-uniform distribution in size and shape which limit its study of fundamental properties and practical applications. In here, we optimized conditions for deterministic manipulation of ultra-smooth and super-spherical gold nanoparticles (AuNPs) by AFM. [1] Lowered adhesion force by using platinum-iridium coated AFM tips enabled us to push super-spherical AuNPs in linear motion to pre-programmed position. As a result, uniform and reliable electric/magnetic behaviors of assembled metamolecules were achieved which showed a good agreement with simulation data. Furthermore, visualization of near field for super-spherical AuNPs was also addressed using photosensitive azo-dye polymers. Since the photosensitive azo-dye polymers can directly record the intensity of electric field, optical near field can be mapped without complicated instrumental setup. [2] By controlling embedding depth of AuNPs, we studied electric field of AuNPs in different configuration.

• Smart Structures and Systems
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• v.9 no.5
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• pp.427-439
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• 2012

The present paper deals with the analytical solution of a functionally graded piezoelectric (FGP) cylinder in the magnetic field under mechanical, thermal and electrical loads. All mechanical, thermal and electrical properties except Poisson ratio can be varied continuously and gradually along the thickness direction of the cylinder based on a power function. The cylinder is assumed to be axisymmetric. Steady state heat transfer equation is solved by considering the appropriate boundary conditions. Using Maxwell electro dynamic equation and assumed magnetic field along the axis of the cylinder, Lorentz's force due to magnetic field is evaluated for non homogenous state. This force can be employed as a body force in the equilibrium equation. Equilibrium and Maxwell equations are two fundamental equations for analysis of the problem. Comprehensive solution of Maxwell equation is considered in the present paper for general states of non homogeneity. Solution of governing equations may be obtained using solution of the characteristic equation of the system. Achieved results indicate that with increasing the non homogenous index, different mechanical and electrical components present different behaviors along the thickness direction. FGP can control the distribution of the mechanical and electrical components in various structures with good precision. For intelligent properties of functionally graded piezoelectric materials, these materials can be used as an actuator, sensor or a component of piezo motor in electromechanical systems.

• Progress in Superconductivity and Cryogenics
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• v.9 no.3
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• pp.32-36
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• 2007

On the contrary of a conventional motor with very narrow air-gap. it is difficult to calculate the accurate magnetic field distribution and the performance of an air-cored superconducting motor by 2 dimensional analysis. which does not use high permeability material except outer machine shield. This paper aims to do analysis of magnetic field and force distribution from the 3 dimensional modelling of a 1MW class superconducting synchronous motor. Especially. the field coil composed of Bi-2223 high-temperature superconductor and the outer machine shield are modelled by finite element analysis software according to their structures and the self-inductance and Lorentz force are calculated based on the 3 dimensional magnetic field calculation. Moreover. the influence of an important parameter, synchronous reactance, has been analyzed on the machine performances such as voltage variation and output power.