• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.11
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• pp.856-862
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• 2008

This paper presents the characterization of a continuous magnetophoretic microseparator for separating white and red blood cells from peripheral whole blood cells based on their native magnetic properties. The magnetophoretic microseparator separated the blood cells using a high gradient magnetic separation (HGMS) method without the use of additives such as magnetic beads or probing materials. Experimental results show that the paramagnetic capture mode microseparator can continuously separate out 93.5% of red blood cells and 97.4% of white blood cells from diluted whole blood, and the diamagnetic capture mode microseparator can continuously separate out 89.7% of red blood cells and 72.7 % of white blood cells by using applying an external magnetic flux of 0.2 T using a permanent magnet.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.496-503
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• 2001

The suspension of the optical pickup actuator is damped by the presence of silicone rubber damper bond at its termination. In spite of the presence of it, the actuator still exhibits a strong mechanical resonance which affects its settling time and vibrational characteristics. This resonance can cause errors in reading information from the disk, particularly in high speed CD-ROM and DVD-ROM drives. Ferrofluids are stable colloidal suspensions of sub-micron sized magnetic particles in a carrier liquid. In the actuator design, ferrofluid is applied to the surface of the magnets until the quantity is sufficient to maintain intimate contact with the bobbin/carrier assembly. The fluid is retained in the magnetic field and its viscosity provides the desired mechanical damping to the moving assembly, improving the actuators settling time and vibrational characteristics. Access time is also improved, particularly on warped or eccentric discs.

• Journal of Environmental Science International
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• v.12 no.1
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• pp.41-45
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• 2003

Magnetite powder for kerosene-based ferrofluid was synthesized by air oxidation of waste acid containing $Fe^{2+}$ and $Fe^{3+}$ ions in the pH=11 at $60^{\circ}C$. Stable kerosen-based ferrofluid was prepared by addition of polyoxyethylene nonylphenyl ether(POENPE) to the magnetite containing water. Dispersion mechanism of an addition POENPE to the magnetite was examined by means of the fraction of solid dispersed FT-IR spectrum. And magnetic properties of kerosen-based ferrofluid were examined by method of Vibrating Sample Magnetometer. In order to remove oil on the water surface by an addition of kerosen-based ferrofluid, the optimum conditions were examined.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.37-39
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• 1999

In this paper, the magnetic fluid linear pump is designed. Inside the small tube, magnetic fluid is shielded with thin rubber protector. The magnetic fluid activated by traveling pulses of magnetic field drags the water inside the pump. The iterative algorithm for the shape of magnetic fluid is presented by using nonlinear finite element method and Navier-Stokes equations. The computed curvature of fluid under the magnetic field and the gravitational force is agreed well with photograph image. The dimension and electric configurations of the magnetic linear pump are optimized and the results are compared with measurements.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.684-692
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• 1990

Ultrafine magnetite powder for the ferromagnetic fluid was prepared by an addition of alkaline solution to the solution containing Fe2+ and Fe3+ ions at 6$0^{\circ}C$. The optimum condition of the magnetite synthesis was delineated by examining such various physico-chemical properties as Fe2+/Fe+3 ratio in the powder, phase characteristics, MHC and $\sigma$max. A new scheme for the steric stabilization of colloidal dispersion was proposed using the concept of the buffer group action for the increased interfacial density of the stabilizing moieties at colloid particle/dispersion medium interface. The proposed concept was successfully applied to the preparation of the kinetically stable kerosinebased ferrofluid using Tween and Span as dispersants. In the dispersion of magnetite particles in a kerosine, Tween(polyoxyethylene sorbitan oleate) acts as a primary stabilizer which provides an anchor group, whereas Span(sorbitan oleate) can be classified as a secondary stabilizer which adsorbs on the surface of magnetite particle through the action of the buffer group. Dispersion studies using various quantities of Tween and Span supported the concept of the buffer group action for increased dispersion characteristics of the kerosine based ferromagnetic fluid.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.945-947
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• 1993

This paper presents the numerical algorithm that can obtain the surface configuration of the magnetic fluid seals. The magnetic field is computed by nonlinear finite element method considering the saturation of magnetic fluid and pole piece. The surface equilibrium condition in ferrohydrodynamics are used in algorithm. The influence of the surface configuration on the sealed pressure due to the magnetic, centrifugal and gravitational forces is analyzed and compared with other experimental results.

• Tribology and Lubricants
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• v.13 no.2
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• pp.105-111
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• 1997

This paper deals with an experimental study on the friction torque characteristics of magnetic fluid seals for various oil temperatures, rotating speeds, and vacuum pressures. The friction torque of MFS was measured by high response torque meter. The experimental results show that, as the rotating speed increases, the friction torque of MFS increases and as the oil temperature increases, the friction torque of MFS decreases. Also, the experimental results show that the friction torque of Model-II is 1.73~2.56, 2.0~2.89, 2.0~3.25 times higher than those of Model-I under the atmospheric pressure, vacuum pressure ($10^{-4} and 10^{-6}$ torr), respectively.

• Journal of Biomedical Engineering Research
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• v.14 no.2
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• pp.147-153
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• 1993

In this paper, we studied about the micro pressure transmission system using fluid. For the investigation of feasibility of microhydraulic system, the hydraulic characteristics were examined by using the capillary tube system and the micro cylinder system that consists of a rod and a micro capillary tube. A new hydraulic micro actuator using magnetic fluid and an external magnetic field was also investigated. The results showed that our microhydraulic system has the possibility of power transmission in arbitrary directions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.227-230
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• 2005

The paper presents the identification of dynamic property of a rotor system with a squeeze film damper (SFD) using magnetic fluid. An electromagnet is installed in the inner damper of the SFD. The magnetic fluid is well known as a functional fluid. Its rheological property can be changed by controlling the applied current to the fluid and the fluid can be used as lubricant. Basically, the proposed SFD has the characteristics of a conventional SFD without an applied current, while the damping and stiffness properties change according to the variation of the applied electric current. Therefore, when the applied current is changed, the whirling vibration of the rotor system can be effectively reduced. The clustering-based hybrid evolutionary algorithm (CHEA) is used to identify linear stiffness and damping coefficients of the SFD based on measured unbalance responses.

• Journal of Drive and Control
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• v.15 no.1
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• pp.38-49
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• 2018

This research describes the development model and testing of a hybrid damper which can be applicable to a vehicle suspension. The hybrid damper is devised to improve the performance of a conventional passive oil damper using a magneto-rheological (MR) accumulator which consists of a gas accumulator and a MR device. The level of damping is continuously variable by the means of control in the applied current in a MR device fitted to a floating piston which separates the gas and the oil chamber. A simple MR device is used to resist the movement of floating piston. At first a mathematical model which describes all flows within the conventional oil damper is formulated, and then a small MR device is also devised and adopted to a mathematical model to characterize the performance of the device.