• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.4
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• pp.149-156
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• 2022

Magneto-Rheological Fluid (MRF) is a functional fluid in which flow characteristics change into magnetic force due to its magnetic particles. When the semi-active control device does not use MRF for a long time, precipitation of magnetic particles and abnormal control force occur. Thus, Electro Magneto-Rheological Fluid (EMRF), which improves the precipitation of magnetic particles for MRF and exhibits existing control performance, was developed in this study. First, the optimal mix proportion ratio was selected by conducting a precipitation experiment and a controlled force test by varying the content of grease based on the existing MRF components. Also, EMRF was applied to the shear-type damper to evaluate the control performance when applied to the control device. The cylinder-type damper was developed to apply to the structure, and control performance evaluation was conducted. The result confirmed that the precipitation of the magnetic particles was improved, while the damper using EMRF exhibited excellent control performance.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.5
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• pp.182-188
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• 2003

We have demonstrated a fluidic technique for self-assembly of microfabricated parts onto substrate using patterned shapes of magnetic force self-assembled monolayers (SAMs). The metal particles and the array were fabricated using the micromachining technique. The metal particles were in a multilayer structure (Au, Ti, and Ni). Sidewalls of patterned Ni dots on the array were covered by thick negative photoresist (SU-8), and the array was magnetized. The array and the particles were mixed in buffer solution, and were arranged by magnetic force interaction. Binding direction of the metal particle onto Ni dots was controlled by multilayer structure and direction of magnetization. A quarter of total Ni dots were covered by the particles. The binding direction of the particles was controllable, and condition of particles was almost even with the Au surface on top. The particles were successfully arranged on the array.

• Journal of the Korean Magnetics Society
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• v.6 no.5
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• pp.334-339
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• 1996

In order to investigate the influence of the magnetic paticle size and its properties on the particulate magnetic material, we evaluated the dispersion of magnetic particles and the electromagnetic properties in magnetic tape made from the magnetic paints by use of each magnetic particles witch were different from particle size and its propertis. The dispersion of magnetic particles depends on the surface chemical properties rather than particle size. As particle size is smaller, the packing ratio of magnetic particle and the magnetic flux density in tape increase. The output levels in playing back of tape incerase in wide frequency range from 315 Hz to 10 kHz and the noises decrease. It is very important to choose the size, the shape, the surface chemical properties and the magnetic properties of the magnetic particle in producing the high quality magnetic tape.

• Current Optics and Photonics
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• v.2 no.6
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• pp.623-628
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• 2018

Clotting properties of human blood are important clinical information to monitor for patients with platelet and coagulation disorders. Most devices used to diagnose these disorders utilize blood plasma together with tissue factors and $Ca^{{+}{+}}$ additives. In some instruments, magnetic particles were mixed with blood samples and a rotating magnetic field was applied, resulting in the rotation of magnetic particles, which was probed by impinging light. The working principle seems obvious yet had not been investigated in depth. We modeled the collective behavior of light propagating through magnetic needles, aligned in the direction of the rotating external magnetic field, with scattering light analysis software. Simulation results indicated that the scattering pattern undergoes periodic undulations with respect to the slant angle of the magnetic needles. Also provided is a means of extracting meaningful information from the scattering measurement.

• Kyungpook Mathematical Journal
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• v.60 no.4
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• pp.853-867
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• 2020

The aim of this study was to analyze the momentum and heat transfer of a rotating nanofluid with conducting spherical dust particles. The fluid flows over a stretching surface under the influence of an external magnetic field. By applying similarity transformations, the governing partial differential equations were trans-formed into nonlinear coupled ordinary differential equations. These equations were solved with the built-in function bvp4c in MATLAB. Moreover, the effects of the rotation parameter ω, magnetic field parameter M, mass concentration of the dust particles α, and volume fraction of the nano particles 𝜙, on the velocity and temperature profiles of the fluid and dust particles were considered. The results agree well with those in published papers. According to the result the hikes in the rotation parameter ω decrease the local Nusselt number, and the increasing volume fraction of the nano particles 𝜙 increases the local Nusselt number. Moreover the friction factor along the x and y axes increases with increasing volume fraction of the nano particles 𝜙.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.10
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• pp.34-41
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• 2004

A new method to fabricate the fine magnetic abrasives by using mechanical alloying is proposed. The mechanical alloying process is a solid powder process where the powder particles are subjected to high energetic impact by the balls in a vial. As the powder particles in the vial are continuously impacted by the balls, cold welding between particles and fracturing of the particles take place repeatedly during the ball milling process using a planetary mill. After the manufacturing process, fine magnetic abrasives which the guest abrasive particles c lung to the base metal matrix without bonding material can be obtained. The shape of the newly fabricated fine magnetic abrasives was investigated using SEM and its polishing performance was verified by experiment. It is very helpful to finishing the injection mold steel in final polishing stage. The areal ms surface roughness of the workpiece after several polishing processes has decreased to a few nanometer scales.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.316-321
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• 2008

Monodispersed particles of poly(styrene-co-4-vinylpyridine), poly(st-co-4vp) were prepared by soapless emulsion polymerization. Iron oxide was formed on the surface and inside of the poly(st-co-4vp) particles by thermal decompostion of iron pentacarbonyl. The obtained magnetic poly(st-co-4vp) particles was mondispersed and the average size was 250 nm. The magnetic poly(st-co-4vp) particles had 14% of iron oxide, which was identified as $Fe_3O_4$ by XRD. The magnetic poly(st-co-4vp) particles had superparamagnetism according to superconducting susceptometer (SQUID).

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.687-689
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• 1995

Our team works on mixture of hard magnetic materials. As hard magnetic material we used mixture of powders: melt-spun ribbon Nd-Fe-B, ferrite and Alnico. Their different mixtures are basic material for dielectromagnets under our investigation. Main disadvantage of dielectromagnets with Nd-Fe-B alloy powder as a component is a low corrosion resistance. Protection against corrosion is covering dielectromagnets with metallic or organic coating film. The coating film protects dielectromagnets from free particles on the surface and low resistance for mechanical stresses too. The surface of dielectromagnets prepared from mixture of powders if formed by metallic particles - powder of Nd-Fe-B and Alnico, particles of oxide - powder of ferrite and particles of resin - bonding materials. Team work on technology of laying the metallic coating on dielectromagnets prepared from mixture of mentioned powders. Papers show the results of initial investigation on metallic coating technology. It shows influence of type and used technology of the metallic coating film on magnetic properties of dielectromagnets.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.149-153
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• 2001

This paper describes on the fabrication of Fe-Co hydrophilic magnetic fluids from the waste pickling liquor of steel. By adding with HNO$_3$in the waste liquor oxidation is proceeded from Fe$^{3+}$ion at 6$0^{\circ}C$ with air blowing. Ultra-fine Co-ferrite particles with the mean particle size of 50 $\AA$ were produced at pH 12 after adjusting the ratio of Fe$^{3+}$Co$^{2+}$=7/3(wt%) and Fe-Co particles with the mean particle size of 94 $\AA$ were produced by reducing the Co-ferrite particle with H$_2$at the temperature of 50$0^{\circ}C$. After triple adsorption of oleic acid dodecyl benzene sulfonate(D.B.S.) and tetra methyl ammonium(T.M.A.) ions on the surface of Fe-Co particles Fe-Co hydrophilic magnetic fluid was produced by dispersing the Fe-Co particles in ethylene glycol solution. The magnetization of the Fe-Co hydrophilic magnetic fluid increased with increasing the Fe-Co concentration. The magnetic fluid containing 70% (g/cc) Fe-Co showed 73 emu/g in magnetization at the magnetic intensity of 10 kOe.kOe.e.

• Journal of Magnetics
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• v.6 no.3
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• pp.94-100
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• 2001

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. BCC structure of Fe-Co-Ni spherical particles can be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-80$0^{\circ}C$ for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a post heating at $600^{\circ}C$ for 5 hours. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nano-particles in a random arrangement on $Al_2O_3$substrate the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and inter-particle distance.